a
o

a
m
o

a

MANUAL OF THE INFUSORIA.

VOLUME I.

"Our little systems have their day,

They have their day and cease to be ;
They are but broken lights of Thee,
And Thou, O Lord, art more than they."

TENNYSON, In Memoriam.

MANUAL OF THE INFUSORIA:

INCLUDING A DESCRIPTION OF ALL KNOWN

FLAGELLATE, CILIATE, AND TENTACULIFEROUS PROTOZOA,

BRITISH AND FOREIGN,

AND AN ACCOUNT OF THE

ORGANIZATION AND AFFINITIES OF THE SPONGES.

BY

W. SAVILLE KENT, F.L.S., F.Z.S., F.R.M.S.,

FORMERLY ASSISTANT IN THE NATURAL HISTORY DEPARTMENTS OF THE BRITISH MUSEUM.

VOLUME I.

LONDON:

DAVID BOGUE, 3 ST. MARTIN'S PLACE,

TRAFALGAR SQUARE, W.C.

I88o-l88l.

TO

THOMAS HENRY HUXLEY, LL.D., F.R.S.,

TO WHOM THE AUTHOR IS INDEBTED FOR MANY MARKS OF PERSONAL KINDNESS

AND WORDS OF ENCOURAGEMENT

DURING THE PREPARATION OF THIS TREATISE;

AND TO WHOSE TEACHING IN THE LECTURE-ROOM AND LABORATORY HE IS CHIEFLY

BEHOLDEN FOR HIS QUALIFICATION
TO ENTER AS A HUMBLE LABOURER UPON THE ARENA OF SCIENTIFIC INVESTIGATION,

THIS 'MANUAL OF THE INFUSORIA' is GRATEFULLY

PREFACE.

IT is now some ten years since the author, then but a recruit in the ranks
of practical microscopists, elected to concentrate his attention upon the
group of organisms that form the subject of this treatise. At a very early
period of his investigations, formidable obstructions to substantial progress
in the course mapped out, presented themselves in connection not only
with the very backward condition of the literature of this country relating
to this topic, but by reason also of the exceedingly wide and scattered area
of Continental bibliography that had to be explored and sifted before it
was possible to arrive at any adequate idea of the state of contemporary
knowledge concerning almost any given type that might be the subject of
examination. It was the recognition of, and continual contact with these
difficulties that suggested to the author the advantages that would accrue
both to himself and all English-speaking microscopists, from the compilation
of a treatise, brought up to date, that should contain a concise description
of the innumerable species known to science whose descriptions were dis-
tributed throughout many scattered sources, and that led to the efforts,
now carried into execution, to supply this desideratum.

It was in the first instance suggested that this Manual should be based
upon the same lines as the, at the time, only other English treatise devoted
to the subject, ' A History of the Infusoria/ by Andrew Pritchard, the fourth
and last edition of which was published so long since as the year 1861 ;
that it should include in a similar manner an account of the several distinct
groups of microscopical organisms known as the Rotifera, Desmidiaceae,
Diatomaceae, and other Protophytes which form, as being a reproduction
of Ehrenberg's ' Infusionsthiere/ so conspicuous a feature of Mr. Pritchard's
book. It soon became apparent, however, that to compass so compre-
hensive a task with any degree of efficiency would extend the size of this
treatise far beyond convenient limits, and that indeed more than sufficient
material for a work on the same scale as the one above-named had
accumulated in connection with the Infusoria in the most limited and
restricted sense as represented by the Flagellate, Ciliate, and Tentacu-
liferous Protozoa.

Those readers and subscribers, therefore, who at first sight may

I L I H 3

viii PREFACE.

experience some disappointment at the relatively narrow scope of this
work, will, the author trusts, find on a closer acquaintance with it, sufficient
compensation in the vastly extended assemblage of forms here included
within the ranks of the true Infusoria as compared with that dealt with in
any pre-existing treatise. The most notable accessions in this connection
are undoubtedly associated with the class Flagellata, hitherto occupying in
our text-books a very uncertain status upon the border-land of the animal
and vegetable kingdoms, but which is now shown to include an infinitely
varied series of unquestionable animal forms. All these Flagellata, to
which the author has devoted special attention, are of exceedingly minute
size, requiring the highest magnifying powers of modern construction for
their correct interpretation. The majority of the Flagellate types figured
and described in this treatise, indeed, not only represent the outcome of
the most recent research, but may be regarded also as a first instalment of
the almost inexhaustible harvest that awaits the garnering of the industrious
investigator. It is hoped that this work may in this manner constitute
a fresh basis of departure, and supply an incentive towards the acquisition
of a yet truer and more comprehensive knowledge of the diversified
and exquisitely beautiful representatives of this, excepting to the initiated,
practically invisible world.

For the general Biologist, to whom for the most part the Infusorial
series represents but a single scarcely noteworthy link in the grand scheme
of organic nature, it has been the endeavour of the author to demonstrate
that there yet remain in connection with this group certain side issues of
the highest interest and importance. Should he combine with his general
knowledge of the morphology and embryology of the more highly organized
Metazoic animals, a practical acquaintance with that remarkable order here
figured and described at length under the title of the Choano-Flagellata,
he will scarcely fail to recognize the close bond of affinity that subsists
between these Infusoria and the Sponges, however much the last named
organisms may be apparently modified in the direction of a Metazoic
formula. In connection, again, with the innumerable varieties of ciliated
embryos of the Annelida, Echinodermata, Mollusca, and other Invertebrate
series, there is, as indicated in the opening pages of Vol. II., ample scope
for speculation with respect to the by no means improbable derivation of
these higher organisms from Infusoria Ciliata, of which, in their embryonic
condition, they are indeed, in so many cases, the most remarkable possible
homotypes.

Some apology is perhaps due from the author on account of the very
considerable interval that has elapsed since the first announcement of this
work and its ultimate publication, as also for the delay that has intervened

PREFACE. IX

between the issue of the first part in October 1880, and the concluding
number in June 1882. With respect to that first named, it may be stated
that the publication, dated November 1878,* of Stein's ' Infusionsthiere '
Abth. III. Heft I, devoted to the Flagellata, occasioned an almost complete
recasting of the manuscript referring to this group, then ready for the press,
the work involved being greatly increased through the fact that the
diagnoses and descriptions of the species figured being reserved by Stein
for an as yet unpublished volume, the onus of forming diagnoses from
these figures for the many new forms illustrated, devolved upon the author.
Since, again, the publication of Part I. of this Manual in October 1880, the
energy of Continental investigators in this department of Biology has been
so marked that it became requisite, at the risk of some slight delay, to
make suitable provision both in the text and plates of the later numbers
of the treatise for the record of their discoveries. No more substantial
illustration of this circumstance could perhaps be afforded than by a
reference to Part VI., devoted chiefly to the class Tentaculifera, in which
it will be found that no small space is occupied by the description and
illustration of many new and interesting species described by Maupas so
recently as November 1881, the same number including the results of the
author's yet later personal investigation of the remarkable type Dendrosoma
radians. Such inconvenience therefore as subscribers may have sustained
in consequence of its tardier issue, they will, the author hopes, consider
to some extent counterbalanced by the considerable augmentation and
continuation literally up to date of the subject-matter of this treatise.

Having during the progress of this work received from numerous
English and American sources an intimation that a few suggestions
respecting the apparatus and means employed by the author for the
effectual investigation of the more minute Flagellate Infusoria would be
greatly appreciated, he has much pleasure in submitting, in connection with
PI. LI., an illustration, with accompanying explanation, of a simple method
whereby, with the least expenditure of manipulative energy, the best results
may be readily obtained. For his first acquaintance wjth this method, as
also for the kind permission to make the present use of the same, the
author's thanks are due to Mr. E. M. Nelson, F.R.M.S., one of our
leading and most experienced experts in the use of the higher powers of
the compound microscope.

The pleasing task yet devolves upon the author of tendering his
grateful acknowledgments to the officers of the libraries of the various
scientific societies, including more especially those of the Royal, Linnean,
and Zoological Societies, as also of the Royal College of Surgeons, for their

* Not received in England till January 1879.

X PREFACE.

ready and valuable assistance in working out the voluminous and, in many
cases, exceedingly intricate bibliography of the present subject. He has
also to record his high appreciation of the accurate and highly artistic
manner in which Mr. W. Rhein has reproduced on stone the drawings for
the plates committed to his care.

For an abundant supply of living material for investigation, much of
which has been utilized in the record of new data, and for the illustration
of this Manual, the best thanks are due from the author to Mr. Thomas
Bolton of Birmingham, and to Mr. John Hood of Dundee.

Lastly, but not leastly, the author has to acknowledge his great indebt-
edness to the Council of the Royal Society, through whose recommendation
a grant from the Government Fund for the Promotion of Scientific Research
has been on several occasions allotted him, thus assisting him with the
means of obtaining the necessary costly microscopical apparatus, and of
devoting that time to original research, without which the prolonged
investigations recorded in this treatise, more especially in connection with
the Flagelliferous Infusoria, could scarcely have been accomplished.

LONDON, May 1882.

MANUAL OF THE INFUSORIA.

CHAPTER I.

INTRODUCTORY— GENERAL HISTORY OF THE INFUSORIA FROM THE TIME
OF THEIR DISCOVERY BY LEEUWENHOEK IN 1675 TO THE YEAR 1880.

INAPPRECIABLE individually to the unaided vision, the countless hosts of
the Infusorial world, more familiar perhaps to the popular mind under
the designation of animalcules, or animalcula, surround us literally on
every side. They abound in the full plenitude of life alike in the running
stream, the still and weed-grown pond, or the trackless ocean. Nay,
more, as demonstrated in a future page,* every dew-laden blade of
grass supports its multitudes, while in their semi-torpid encysted or
sporular state they permeate as dust the atmosphere we breathe, and
beyond question form a more or less considerable increment of the very
food we swallow. Yet again, and apparently as the inevitable corollary of
the last-named circumstance, they occur abundantly as parasites within the
viscera or vital fluids of the representatives of almost every higher organic
group. Essentially dependent on a liquid medium for the exhibition of
their vital functions, there is practically, the simple conditions of air and
moisture being granted, no limit to the area of their distribution, no field
so barren but will yield its quota of strange and varied forms to the
industrious explorer. For the professional biologist and the dilettante
investigator alike, the members of this intangible and yet omnipresent
group of organisms present a fascination unshared by any other section of
the organic world. Their very intangibility and practically inexhaustible
variety — each improvement and augmentation of the penetrating power of
the optical appliances yet employed enabling us to discover, as in the sister
science of astronomy, " fresh fields and pastures new " for exploration — no
doubt represent important factors in this power of fascination, though
by no means the most influential ones. With the Infusoria we encounter
not only the as yet known most minute, but also the most elementary and
simply formed productions of the Creator's handiwork, though, for all that,
none the less complete and excellently finished. Among the Infusoria,

* See p. 140.

2 INTRODUCTION.

making a free adaptation of the admirable thesis propounded by the illus-
trious Oken, we find in their primeval shape the very bricks and mortar
out of which the entire superstructure of the organic world has been
erected. So early as the year 1805, long before the conception of the
unicellular nature of the Infusoria by Theodor von Siebold, this astute
philosopher, the co-originator with Goethe of the vertebrate theory of
the skull, had enunciated the opinion that the infusorial animalcules
consisted of simple cells or vesicles, and formed the protoplasmic basis
from whence all higher organisms were fashioned or evolved, and into
which condition of simple cells or vesicles these same higher organisms
were again resolved by the process of dissolution. The divine fiat, " Dust
thou art, and unto dust thou shalt return," thus received unconsciously at
the hands of Oken a practical and truly remarkable illustration. Finally,
among the world of Infusoria we arrive at that dim boundary line, too
subtle and obscure for arbitrary definition, that separates, or more correctly
blends into one harmonious whole, the two departments of the animal and
vegetable worlds ; and here, moreover, with all reverence be it said, we
approach, if anywhere, the confines of the organic and inorganic, and are
brought face to face with that already half-lifted veil behind which lies,
waiting to reward our patient search, the very clue to the deep mystery of
Life itself.

Postponing to a succeeding chapter a detailed account of the structural,
developmental, and other vital phenomena pertaining to the Infusoria, as
made manifest by the light of modern investigation, it has been decided
that some space in the first instance might be advantageously devoted to a
brief epitomization of the more important epochs in the history of these
minute organisms, as accumulated step by step from the time of their earliest
discovery. As a matter of necessity, man's acquaintanceship with the puny
members of this organic group has been comparatively short, and is co-ex-
tensive only with the invention and practical application of the microscope.
None of the myriad forms — though in some few instances conspicuous in
their concrete state or discernible individually by the unassisted vision, as
mere moving points — yield up the secret of their separate organization and
life-history without the aid of that most invaluable and indispensable
auxiliary to biological discovery. In like manner, our present advanced,
though still far from perfect knowledge, of the Infusoria has been acquired
by slow degrees, and contemporaneously with the improvements made upon
that instrument, each successive stage of progress achieved in this direction
representing, indeed, but a reflex of the higher perfection of the appliances
placed from time to time at the disposal of the histologist through the
augmented skill of the optician. It is much to be regretted that authentic
evidence is wanting that can identify with absolute certainty the first
inventor of the microscope, or rather of those simple spheres of glass
or doubly convex lenses, mostly home made, employed over two centuries
ago, with which in the hands of the earliest investigators, as presently

LEEUWENHOEtfS OBSERVATIONS. 3

related, such truly astonishing results were obtained, and out of which
the highly perfected optical instruments of the present day have, by slow
and tedious steps, been finally elaborated. Fontana, of Naples, Cornelius
Drebell, the Dutchman, and Zacharius Jansen and son, fellow-country-
men of Drebell, have thus alike been respectively credited by different
authorities with this distinction. However this may be, it is at all events
generally conceded that the microscope, in its simplest form, was first
brought into public notice in or about the year 1619. Regarded at this
early date in the mere light of an ingenious and interesting toy, little or no
promise was then given of the important r61e in the onward march of
science it was afterwards destined to fulfil. Nearly half a century, indeed,
elapsed before its aid was invoked for the systematic exploration of the
hidden mysteries of nature. With the exception, perhaps, of the Italian
philosopher Petrus Borellus, our own countryman Dr. Robert Hooke,
author in the year 1665 of the famous ' Micrograph i a Illustrata,' claims the
first place in the ranks of scientific microscopic investigators. The dis-
covery of the minute organic beings that form the special subject of this
treatise, fell, however, a few years later to the lot of the illustrious Dutch-
man Antony van Leeuwenhoek. The accounts of the animalcules first
observed, as given by Leeuwenhoek and a few other investigators who,
animated by his example, towards the close of the seventeenth century
devoted their attention to the further exploration of this fascinating and
then newly opened field for discovery, possess intrinsically such high classic
interest, and display, notwithstanding the simple and imperfect character
of the optical appliances employed, so keen an insight into, and appreciation
of, the structural features and phenomena of the various forms encountered,
that quotations from the same, with a faithful reproduction of their original
quaint style of diction, are herewith appended in extenso. Leeuwenhoek's
earliest contribution to the literature of this subject necessarily takes the
first place upon the list, and is found embodied in the 'Philosophical
Transactions,' vol. xii. No. 133, for the year 1677. The title of his first
record and associated account of the various species therein described runs
as follows : —

" Observations communicated to the Publisher by Mr. Antony van Leeuwenhoek, in
a Dutch letter of the gth of October, 1676, here Englished, concerning little
animals observed in Rain, Well, Sea, and Snow Water, as also in Water wherein
Pepper had lain infused."

OBSERVATION I.

"In the year 1675 I discovered living creatures in rain-water which had stood
but four days in a new earthen pot, glased blew within. This invited me to view this
water with great attention, especially those little animals appearing to me ten
thousand times less than those represented by Mons. Swammerdam, and by him called
water-fleas or water-lice, which may be perceived in the water with the naked eye.
The first sort by me discovered in the said water, I divers times observed to consist
°f 5> 6, 7, or 8 clear globules, without being able to discover any film that
held them together, or contained them. When these animalcula or living atoms

B 2

4 BIBLIOGRAPHY.

did move, they put forth two little horns, continually moving themselves ; the place
between these two horns was flat, though the rest of the body was roundish, sharpen-
ing a little towards the end, where they had a tayle, near four times the length of the
whole body, of the thickness (by my microscope) of a spider's web ; at the end of
which appear'd a globul, of the bigness of one of those which made up the body ;
which tayl I could not perceive, even in very clear water, to be mov'd by them.
These little creatures, if they chanced to light upon the least filament or string, or
other such particle, of which there are many in the water, especially after it hath
stood some days, they stook entangled therein, extending their body in a long round,
and striving to dis-entangle their tayle ; whereby it came to pass, that their whole body
lept back towards the globul of the tayle, which then rolled together serpent-like, and
after the manner of copper or iron-wire that having been wound about a stick, and
unwound again, retains those windings and turnings. This motion of extension and
contraction continued a while ; and I have seen several hundreds of these poor little
creatures, within the space of a grain of gross sand, lie cluster'd together in a few
filaments.

" I also discovered a second sort, the figure of which was oval, and I imagine their
head to stand on the sharp end, these were a little bigger than the former. The
inferior part of their body is flat, furnished with divers incredibly thin feet, which
moved very nimbly and which I was not able to discern till after several Observa-
tions. The upper part of the body was round, and had within 8, 10, or 12
globuls, where they were very clear. These little animals did sometimes change their
figure into a perfect round, especially when they came to lie on any dry place. Their
body was also very flexible ; for as soon as they hit against any the smallest fibre or
string, their body was bent in. which bending presently also jerked out again. When I
put any of them in a dry place, I observ'd, that changing themselves into a round,
their body was raised pyramidal-wise with an extant point in the middle, and having
lain thus a little while with a motion of their feet, they burst asunder, and globuls
were presently diffus'd and dissipated, so that I could not discern the least thing of
any film, in which the globuls had doubtless been inclosed : And at this time of
their bursting asunder I was able to discover more globuls than when they were
alive.

" But then I observ'd a third sort of little animals, that were twice as long as
broad, and to my eye yet eight times smaller than the first. Yet for all this, I
thought I discerned little feet, whereby they moved very briskly, both in a round and
streight line.

" There was further a fourth sort, which were so small that I was not able to give
them any figure at all. These were a thousand times smaller than the eye of a big
louse ; For I judge, the axis of the eye of such a louse to be more than ten times
as long as the axis of any of the said little creatures. These exceeded all the
former in celerity. I have often observ'd them to stand still as 'twere upon a point,
and then turn themselves about with that swiftness, as we see a top turn round, the
circumference they made being no bigger than that of a small grain of sand, and
then extending themselves streight forward, and by and by lying in a bending
posture.

OBSERV. II.

"The 26. May it rained hard ; the rain growing less I caused some of the rain-
water, running down from the house top, to be gathered in a clean glass, after it had
been washed two or three times with the water. And in this I observed some few
very little living creatures, and seeing them, I thought they might have been pro-
duced in the leaden gutters in some water that had there remained before.

OBSERV. III.

" On the same day, the rain continuing, I took a great porcelain-dish, and
exposed it to the free air upon a wooden vessel, about a foot and a half high, that
so no earthy parts, from the falling of the rain-water upon that place, might be

LEEUWENHOEICS OBSERVATIONS. 5

spattered or dashed into the said dish. With the first water that fell into the dish,
I washed it very clean, and then flung the water away, and receiv'd fresh into it, but
could discern no living creatures therein ; only I saw many irregular terrestrial parts
in the same. The 3oth of May, after I had, ever since the 26th, observ'd every day
twice or thrice the same rain-water, I now discovered some but very few, exceeding
little animals, which were very clear. The 3ist of May, I perceived in the same
water more of those animals, as also some that were somewhat bigger. And, I
imagine, that many thousands of these little creatures do not equal an ordinary grain
of sand in bigness : And comparing them with a cheese-mite, to be like that of a bee
to a horse : For, the circumference of one of these little animals in water, is not so
big as the thickness of a hair in a cheese-mite.

OBSERV. IV.

" June Qth, having received, early in the morning, some rain-water in a dish,
as before, and poured it into a very clean wine-glass, and exposed it about 8 of the
clock in the morning to the air, about the height of the third story of my
house, to find, whether the little animals would appear the sooner in the water,
thus standing in the air : Observing the same accordingly the loth of June,
I imagin'd I saw some living creatures therein ; but because they seem'd to be but
very few in number, nor were plainly discernible, I had no mind to trust to this
observation. The nth of the same month, seeing this water move in the glass from
a stiff gale of wind (which had blown for thirty-six hours without intermission,
accompanied with a cold, that I could very well endure my winter-cloaths,) I did
not think I should then perceive any living creatures therein ; yet viewing it atten-
tively, I did, with admiration, observe a thousand of them in one drop of water,
which were of the smallest sort, that I had seen hitherto.

OBSERV. V.

" The Qth of June I put of the same rain-water in a very clean wine-glass on my
counter of study, and viewing the same, I perceived no living creatures in it.

"The loth of June, observing the mentioned rain-water, which now had stood
twenty-four hours in my study, I noted some few very small living creatures in
which by reason of their extreme minuteness I could see no figure, and among the
rest I discovered one that was somewhat greater, of an oval figure. Note, that when
I say I have viewed the water, I mean, that I have viewed only three, four, or five
drops of the water, which I also flung away.

" The nth of June, looking upon the water afresh, I saw the said little creatures
again, but there were then but very few of them.

'•The 1 2th, I saw them as the day before; besides I took notice of one figured
like a mussel-shell, with its hollow side downwards, and it was of a length equal
to the eye of a louse.

OBSERV. VI.

"The i ;th of this month of June it rained very hard ; and I catched some of
that rain-water in a new porcelain-dish, which had never been used before, but found
no living creatures at all in it, but many terrestrial particles, and, among others,
such as I thought came from the smoak of smith's coals and some thin thrids, ten
times thinner than the thrid of a silk-worm, which seemed to be made up of globuls ;
and where they lay thick upon one another, they had a green colour. The 26th,
having been eight days out of town, and kept my study shut up close, when I was
come home and did view the said water, I perceived several animalcula, that were
very small, and herewith I desisted from making at this time any further observations
of rain water.

" Mean time, this town of Delft being very rich in water and we receiving from
the river Maase fresh water, which maketh our water very good ; I viewed this water
divers times, and saw extream small creatures in it, of different kinds and colours;
and even so small, that I could very hardly discern their figures : But some were

6 BIBLIOGRAPHY.

much bigger, the describing of whose motion and shape would be too tedious :
this only I must mention here, that the number of them in this water was far less
than that of those found in rain-water ; for I saw a matter of twenty-five of them in
one drop of this town-water, that was much. In the open court of my house I have
a well which is about 15 foot deep, before one comes to the water. It is encompassed
with high walls, so that the sun, though in Cancer, yet can hardly shine much upon
it. This water comes out of the ground, which is sandy, with such a power, that
when I have laboured to empty this well, I could not so do it but there remained
ever a foot's depth of water in it. This water is in summer time so cold, that you
cannot possibly endure your hand in it for any reasonable time. Not thinking at
all to meet with any living creatures in it (it being of a good taste and clear), looking
upon it in September of the last year, I discovered in it a great number of living
animals, very small, that were exceeding clear, and a little bigger than the smallest
of all that I ever saw ; and I think, that in a grain weight of this water there were
above 500 of these creatures, which were very quiet and without motion. In the
winter I perceived none of these little animals, nor have I seen any of them this
year before the month of July, and then they appeared not very numerous, but in
the month of August I saw them in great plenty.

"July 27, 1676, I went to the sea-side at Schevelingen, the wind coming from the
sea with a very warm sun-shine ; and viewing some of the water very attentively, I
discovered divers living animals therein. I gave to a man, that went into the sea
to wash himself, a new glass bottle, bought on purpose for that end, intreating him,
that being on the sea, he would first wash it well twice or thrice, and then fill it full
of the sea water ; which desire of mine having been complied with, I tyed the bottle
close with a clean bladder, and coming home and viewing it, I saw in it a little
animal that was blackish, looking as if it had been made up of two globuls. This
creature had a peculiar motion, after the manner as when we see a very little flea
leaping upon a white paper ; so that it might very well be called a water-flea ; but
it was by far not so great as the eye of that little animal which Dr. Swammerdam
calls the water-flea. I also discovered little creatures therein, that were clear, of
the same size with the former animal which I first observed in this water, but of an
oval figure, whose motion was serpent-like. I took notice of a third sort, which
were very slow in their motion : Their body was of a mouse-colour, clear towards
the oval point ; and before the head, and behind the body there stood out a sharp
little point angle-wise. This sort was a little bigger. But there was yet a fourth
sort somewhat longer than oval. Yet of all these sorts there were but a few of
each, so that in a drop of water I could see sometimes but three or four, sometimes
but one.

" Observations of water, wherein whole Pepper had layn infused several dayes.

" i. I having several times endeavoured to discover the cause of the pungency
of pepper upon our tongue, and that the rather because it hath been found, that
though pepper had layn a whole year in vinegar, yet it retained its full pungency ; 1
did put about \ of an ounce of whole pepper in water, placing it in my study, with
this design, that the pepper being thereby rendered soft, I might be enabled the
better to observe what I proposed to myself. The pepper having layn about 3
weeks in the water, to which I had twice added some snow-water, the other water
being in great part exhaled ; I looked upon it the 24. of April 1676, and discovered
in it, to my great wonder, an incredible number of little animals of divers kinds ;
and among the rest some that were 3 or 4 times as long as broad ; but their whole
thickness did, in my estimation, not much exceed that of the hair of a louse. They
had a very pretty motion, often tumbling about and sideways ; and when I let the
water run off from them, they turned as round as a top, and at first their body
changed into an oval, and afterwards, when the circular motion ceased, they
returned to their former length.

"The 26th of April I took 2\ ounces of snow-water, which was almost three
years old, and which had stood either in my cellar or study in a glass bottle well

LEEUWENHOEK'S OBSERVATIONS. J

stopped. In it I could discover no living creatures : And having poured some of it
into a porcelain thea-cup, I put therein half an ounce of whole pepper, and so I
placed it in my study. Observing it daily until the 3rd of May, I could never
discover any living thing in it ; and by this time the water was so far evaporated,
and imbibed by the pepper, that some of the pepper-corns began to lye dry. This
water was now very thick of odd particles ; and then I poured more snow-water to
the pepper, until the pepper-corns were cover'd with water half an inch high.
Whereupon viewing it again the 4th and 5th of May, I found no living creatures in
it ; but the 6th I did very many, and these exceeding small ones, whose body seemed
to me twice as long as broad ; but they moved very slowly and often round ways.

" The 7th I saw them yet in far greater numbers.

" The loth I put more snow-water to the pepper, because the former was again
so exhaled, that the pepper-corns began to dry again.

"The 1 3th and i4th I saw the little creatures as before ; but the i8th the water
was again so dryed away, that it made me pour in more of it. And the 23rd I
discovered, besides the aforesaid little animals, another sort, that were perfectly
oval, and in figure like cuckow-eggs. Me thought the head of them stood on the
sharp end : their body did consist, within, of 10, 12 or 14 globuls, which lay separate
from one another. When I put these animalcula in a dry place, they then changed
their body into a perfect round and often burst asunder, and the globuls, together
with some aqueous particles, spread themselves everywhere about, without my being
able to discern any other remains. These globuls, which in the bursting of these
creatures did flow asunder here and there, were about the bigness of the first very
small creatures. And though as yet I could not discern any feet in them, yet
me thought, they must needs be furnished with very many, seeing that the smallest
creatures, which I said before to be very plentiful in the water, and lay sometimes
more than 100 of them on one of the oval creatures, were by the motion made in
the water by the great ones (though to my eye they seem'd to lye still) driven away
by them as we blow a feather from our mouth. Of the same oval creatures I never
could discover any very little ones, how attentive soever I was to observe them.

"The 24th of May observing this water again, I found in it the oval little
animals in a much greater abundance. And in the evening of the same day, I
perceived so great a plenty of the same oval ones, that 'tis not one only thousand
which I saw in one drop ; and of the very small ones, several thousands in one drop.*

"The 25th I saw yet more oval creatures : and the 26th I found so vast a plenty
of these oval creatures, that I believe there were more than 6 or 8000 in one drop,
besides the abundance of those very little animals whose number was yet far greater.
This water I took from the very surface ; but when I took up any from beneath, I
found that not so full of them by far. Observing that these creatures did augment
into vast numbers, but not being able to observe them increase in bigness, I began
to think whether they might not in a moment, as 'twere, be composed or put
together : But this speculation I leave to others. The 26th of May at night, I
discovered almost none of the little creatures, but saw some with tayls, of which I
have spoken heretofore, to have seen them in rain-water : But there drove in the
water throughout an infinity of little particles, like very thin hairs, only with this
difference, that some of them were bent.

" May the 26th, I took about ^ of an ounce of whole pepper, and having
pounded it small, I put it into a thea-cup with z\ ounces of rain-water upon it, stirring
it about, the better to mingle the pepper with it, and then suffering the pepper to
fall to the bottom. After it had so stood an hour or two, I took some of the water,
before spoken of, wherein the whole pepper lay, and wherein were so many several
sorts of little animals ; and mingled it with this water, wherein the pounded pepper
had lain an hour or two, and observed that when there was much of the water of
the pounded pepper, with that other, the said animals soon died, but when little they
remained alive."

* " This phenomenon and some of the following ones seeming to be very extraordinary, the author
hath been desired to acquaint us with his method of observing, that others may confirm such
observations as these."

8 BIBLIOGRAPHY.

Although it is scarcely possible to fix with certainty the specific identity
of the numerous animalcules enumerated by Leeuwenhoek in the foregoing
" Observations '' in various instances, the characters recorded are so well
defined as to clearly indicate the generic group to which the organism de-
scribed should be relegated. Taking, for example, the first form encoun-
tered by him in rain-water, having a globular body with two little anterior
horns and a long thread-like tail, which under certain conditions contracted
into a spiral form, there can be no question that this type represents some
species of Vorticella, or bell-animalcule, and is apparently identical with the
form now known by the distinctive title of Vorticella microstomum. While
the recorded presence of the two anterior " horn-like processes " appears at
first sight to represent a somewhat anomalous structural characteristic,
this seeming incongruity vanishes on applying to it the standard of a
slightly later acquired knowledge of the members of this infusorial group,
and through which medium it is at once made evident that the appendages
above referred to as seen by Leeuwenhoek represented merely the imper-
fectly defined optical aspect of the lateral edges of the characteristic peri-
stomal fringe of cilia. As a remarkable illustration of the manner in which
"history repeats itself" even in the annals of scientific discovery, it may be
here noted that a precisely similar error of interpretation is associated by
Mr. H. J. Carter, close upon two centuries later, in his figure and description of
the flagellate organism described in this volume under the name of Salpingceca
Carteri (see PI. VI. Fig. 39). The characteristic membranous collar dis-
tinctive of this type and its allies, which occupies a position corresponding
with that of the ciliary wreath of a Vorticella, is so exceedingly transparent
as to be distinctly visible only with the aid of the highest magnifying
powers of the modern compound microscope. The structure as observed by
Mr. Carter with inadequate magnification, displayed simply its two lateral
peripheries, assuming under such conditions the aspect of two projecting
ear-like processes, and under which latter designation they are chronicled in
the description quoted. The second oval form described by Leeuwenhoek
as furnished on the under side with divers incredibly thin feet, and having
a soft flexible body capable of assuming a variety of figures, would appear
to be a species of Oxytricha, while in the little animal like a mussel-shell,
having also on its under side little feet, recorded in the course of his fifth
Observation, is at once recognized a form closely allied to, if not specifically
identical with the cosmopolitan type Stylonychia mytilus. It is well worthy
of note, that while Leeuwenhoek in this first recorded account of the
members of the infusorial world more usually associates with them the
vague terms of little animals or creatures, he employs for them at the
commencement of his discourse that of " animalcula," or, in English,
animalcules, generally adopted in conjunction with that of the Infusoria
by the majority of later writers. In his observations of various species
discovered by him 'in an infusion of pepper we finally find the origin of the
burning question of the possible "spontaneous generation " of these minute

SIfi E. KING, 1693. JOHN HARRIS, 1696. 9

beings, and which, while not entirely accepted by Leeuwenhoek, is conceived
and tossed by him as a very apple of discord to posterity.*

The period intervening between this first discovery of the Infusoria by
Leeuwenhoek, and his further contribution to the literature of the same
subject in the year 1703, is signalized by the corroboration of that autho-
rity's observations, and an extension of our knowledge of the group, at the
hands of several of our own countrymen, among whom have to be more
especially mentioned the names of Sir E. King, John Harris, and Stephen
Gray. In each case the results obtained by these early investigators are
recorded in the pages of the ' Philosophical Transactions,' and in connec-
tion with one contribution, that of Sir E. King, is to be found the first
published illustration of infusorial life. The form thus represented was
obtained in an infusion of pepper, and appears to be identical with the
Enchclys arcuata of Ehrenberg. This authority also places on record the
results of the experimental application of certain chemical and other sub-
stances to living animalcules, a subject which will be found referred to
at greater length in the section devoted to this special topic. The account
of John Harris's investigations contained in the ' Philosophical Transac-
tions' for the year 1696, embodies the earliest description given of Euglena
I'iridis, and some remarkably shrewd and philosophic speculations as to the
manner in which Infusoria were so rapidly and unaccountably developed.
These latter were altogether opposed to the then newly-conceived theory of
spontaneous generation, and, as hereafter shown, add their weight to the
evidence which has been since adduced in a similar direction. Mr. Harris's
description of Euglena and certain other associated forms, that first men-
tioned being evidently a species of Anguillula, and the second a Rotifer,
probably R. vulgaris, is as follows : —

" On July yth, 1694, I examined a small drop of rain-water that had stood in a
gally-pot in my window for about two months. In the thick part of the drop — for
the water from whence I took it had contracted a thickish skum — I found two sorts
of animals as a kind of eels like those in vinegar. I saw here also an animal like a
large maggot, which would contract itself up into a spherical figure, and then stretch
itself out again ; the end of the last appeared with a forceps like that of an earwig ;
and I could plainly see it open and shut its mouth, from whence air-bubbles would
frequently be discharged. Of these I could number about four or five, and they
seemed to be busie with their mouths as if in feeding. April 27th, 1696. With a
much better microscope I examined some rain-water that had stood uncovered a
pretty while, but had not contracted any such thick and discoloured a skum as that
before mentioned had. A little thin white skum, that like grease began to appear on

* In association with the discoveries of Leeuwenhoek here recorded, it is worthy of remark that
a cabinet of the microscopes, to the number of twenty-six, as self-constructed and employed by that
investigator, and consisting of simple doubly convex lenses, were originally presented by him to the
Royal Society of England, but have long since been lost sight of. The latebt tidings of them would
appear to be furnished by Mr. Henry Baker, who in his work, 'The Microscope Made Easy,' pub-
lished in the year 1 785, attests to having had these glasses under examination away from the Society's
premises and at his own private icsidence. The recovery of such precious heirlooms, and the recon-
signment of the same to their former custody, or among the series of optical instruments belonging
to the Royal Microscopical Society, where perhaps they would be even more highly prized, is a
consummation most devoutly to be wished, and may possibly be helped forward by this notice.

10 BIBLIOGRAPHY.

the surface, I found to be a. congeres of exceeding small animalcula of different
shapes and sizes. At the same time I look't on a small drop of the green surface of
some puddle-water, which stood in my yard ; this I found to be altogether composed
of animals of several shapes and magnitudes. But the most remarkable were those
which I found gave the water that green colour, and were oval creatures, whose
middle was of a grass green, but each end clear and transparent. They would
contract and dilate themselves, tumble over and over many times together, and then
shoot away like fishes. Their head was at the broadest end, for they still moved
that way. They were very numerous, but yet so large, that I could distinguish them
very plainly, with a glass that did not magnify very much.

"April agth, 1696. I found another sort of creatures in the water (some of which
I had kept in a window, in an open glass). They were as large as three of the
other, with the green border about their middles, but these were perfectly clear and
colourless. Then also examining more accurately the belts or girdles of green that
were about the animals, mentioned above, I found them to be composed of globules,
so like the rowes or spawn of fishes, that I could not but fancy that they served for the
same use in the little creatures : For I found now since April 27. many of them with-
out anything at all of that green belt or girdle ; others with it very much and that
unequally diminished, and the water filled with a vast number of small animals,
which before I saw not there, and which I now looked on as the young animated
frye, which the old ones had shed. I continued looking on them at times for two
days, during which time the old ones with the green girdles decreased more and
more ; and at last I could not see one of them so encompassed, but they were all
clear and colourless from end to end.

"May 1 8th, 1696. I look't in some of the surface of puddle-water which was
blewish, or rather of a changeable colour, between blew and red. In a large
quantity of it I found a prodigious number of animals, and of such various bignesses,
that I could not but admire their great number and variety ; but among these were
none with those girdles before-mentioned, either of green, or any other colour. I then
also examined the surface of some other puddle-water, that look't a little greenish ;
and this I found stockt with such an infinite number of animals, that I yet never
saw the like anywhere but in the Genitura masculina of some creatures. Among
these there were many of a greenish colour ; but they all moved about so strangely
swift, and were so near to each other, that tho' I tried my eyes, I could not distin-
guish whether the green colour were all over their bodies, or whether it were only
round their middle in girdles, as before, but from the roundness of their figure and
their smallness, I judge that they chiefly consisted of the young animated spawn of the
kind of animals mentioned already. I found that the point of a pin dipt in spittle
would presently kill them all; as I suppose it will other animalcula of this
kind."

The interest attached to the writings upon this same subject of Stephen
Gray, published also in the same volume of the ' Philosophical Transac-
tions' for the year 1696, is connected most prominently with the discovery
made by this early investigator, that particles contained within a simple
sphere of glass, or animalcules contained in a corresponding globule of water,
become when viewed under favourable conditions more powerfully magnified
than with the assistance of any ordinary bi-convex lens. Several varieties
of animalcules were described by Stephen Gray, as examined by him with
this most simple optical apparatus, among them being a form, appa-
rently the Halteria grandinella of Dujardin, in association with which he
places on record the earliest account of what, while interpreted by him as
a possible act of generation, was more probably an instance of the more
ordinary phenomenon of transverse fission. A brief abstract, in his own

STEPHEN GRA Y, 1696. LEEUWENHOEK, 1703. IJ

words, of Stephen Gray's account of his discoveries in these several direc-
tions is herewith subjoined : —

" I know not well how at this time to account for this strange phenomenon, that
an object should be placed so far within the focus of a spherule, as to be within the glass,
and yet seen distinctly to the eye so near it ; but since by matter of fact, I found it was
so, I made this inference, and concluded, that if I conveyed a small globule of water
to my eye, and that there were any opacous or less transparent particles than the
water therein, I might see them distinctly.

" Exp. 4. Having by me a small bottle of water, which I knew to have in it some
of those minute insects, which the deservedly famous observator Mr. Leeuwenhoek dis-
covered, by the help of excellent microscopes. Having seen them with the common
glass microscopes, and with the first aqueous, as above mentioned, I poured a few drops
of this water on the table, and taking a small portion thereof on a pin, I laid it on the
end of a small piece of brass wire, of about one-tenth of an inch diameter. I con-
tinued to lay on two or three portions of water, till there was formed somewhat more
than an hemispherule of water ; then keeping the wire erect, I applied it to my eye,
and standing at a proper distance from the light, I saw them and some other irre-
gular particles, as I had predicted, but most enormously magnified ; for whereas they
are scarce discernible by the glass microscopes, or the first aqueous one, within the
globule, they appeared not much different both in their form, nor less in magnitude
than ordinary peas. They cannot well be seen by daylight except the room be
darkened, after the manner of the famous dioptrical experiment, but most distinctly
by candle-light; they may be very well seen by the full moon light, and the pin
sometimes takes up the water round enough to shew its objects distinct.

" The insects I have yet this way observed, are of two sorts, globular and ellipti-
cal : I shall first describe the former. They are of a globular form, they are but a little
less transparent than the water they swim in ; they have sometimes two dark spots
diametrically opposite, but these are rarely seen ; there are sometimes two of these
globular insects sticking together ; where they are joined 'tis opacous, possibly they may
be in the act of generation ; they have a twofold motion, a swift progressive irregular
one, and at the same time a rotation on their axes at right angles to the diameter
that has the dark spots, but this is seen only when they move slowly. They are
almost of an incredible minuteness. Mr. Leeuwenhoek is moderate enough in his com-
putation, when he tells us * he saw insects in water, so small, that 30,000 could not
more than equal a coarse sand ; but I believe it will seem a paradox to him, when
one that tells him so shall at the same time say, that he can see them by only
applying the bare eye, to a portion of water wherein they are contained."

In the year 1703 Leeuwenhoek contributed to the 'Philosophical Trans-
actions ' an account of several species of animalcules observed by him on
the roots of duckweed obtained from the River Maes at Delf-haven in
Holland, which was accompanied by woodcut illustrations of the various
forms encountered. Among them are especially conspicuous a species of
Vorticella, apparently V. nebulifera, and a tube-dwelling variety allied to,
if not identical with Vaginicola crystallina. In addition to the true Infusoria
above named, Leeuwenhoek figured and described for the first time the Fresh-
water Polyp (Hydra) and a large sedentary Rotifer most nearly resembling
Limnias ceratophylli. The majority of these types are represented as
adherent to a single rootlet of duckweed, having interspersed among them
several acicular diatoms (Fragillaria), and a few other exceedingly minute
stalked particles referred to by him as " little flower-like figures," and which

* ' Phil. Trans.,' No. 213, p. 198.

1 2 BIBLIOGRAPHY.

are undoubtedly minute sedentary Flagellata, such as Spumella or Oiko-
monas.

The issue of the ' Philosophical Transactions ' following upon the
one containing the foregoing figures and descriptions, is conspicuous for
the insertion, at the hands of an anonymous writer, of an account of
a considerable number of infusorial forms obtained from an infusion of
pepper. The type first described by Leeuwenhoek, Vorticella micro-
stomnm or putrinum, is here figured for the first time, as also Paramcciiun
aurelia showing its characteristic ciliation, a species of Euplotes, Enchelys,
Oxytricha, and a variety of other animalcules whose identity cannot so
easily be determined. Among the delineations given of the Enplotes, one
example represents an animalcule dividing by transverse fission, and is
referred to in the accompanying text as a probable example of copulation.
The highest interest attached to this early contribution to microscopic
literature is, however, associated with the fact that it embodies a remarkably
clear and graphic account of several species of the exceedingly minute
and low-organized Phytozoa, Vibrio and Spirillum — briefly referred to by
Leeuwenhoek in the preceding quotations as " an infinity of little particles
like very thin hairs which drove through the water " — which is accompanied
by illustrations of the types observed, equal both in execution and the
scale of magnification employed to those produced by workers in this same
field of research for more than a century later. The apparatus, nevertheless,
at the disposal of this early investigator was the single-lensed instrument
only manufactured by Mr. Wilson, but out of which he testifies to having
succeeded in obtaining a magnification of no less than 640 diameters. In
recognition of their attenuate serpentine form and movements, this dis-
coverer proposed to confer upon the hair-like bodies just referred to the
distinctive title of " Capillary Eels." A brief abstract of this anonymous
author's original and earliest recognizable description of these exceptionally
minute and highly interesting organisms is here appended. After submit-
ting an account of the instrument employed and various forms observed by
him in his infusion of pepper, he continues : —

" One sort I never discovered till but three or four days ago. These are very
long slender worms, of which my pepper-water is prodigiously full. They are all of
the same thickness, but their lengths are very different, some twice and some thrice as
long as others, and at a medium I judge the proportions of their length to their breadth
at least as 50 to i. To the largest magnifiers they look like threads of horse -ha;r,
(to a naked eye), from a quarter to three-quarters of an inch long, and their motion
is equable and slow and generally they wave their bodies but little in their progres-
sion, though sometimes they make greater undulations. But what is more remark-
able, they swim with the same facility both backward and forward, so that I can-
not distinguish at which end the head is, and I have seen the same worm go
forward with one end, and back again with the other end foremost about twenty
times together. And sometimes they will (like leeches) fix one end on the glass
plate (on which I lay the water), and move the loose part of their body round
about very oddly. These I take leave to call Capillary Eels, and I have given you
as well as I could a representation of their appearance to a great magnifier, in the
several postures I have seen them swim.

HENRY BAKER, 1742, 1753. 13

"Oct. 6th, 1702. I thought those which I called capillary eels had been
peculiar to pepper-water, but have since observed the same (tho' but few) in some
standing water which drained from an horse dunghill. Among these the prettiest
object was a great number of a kind of eels which appear most distinctly when the
water is almost dry, which make brisk shoots, and have a pretty wriggling motion ;
they are of different lengths, and are about the thickness of what I^call capillary
eels."

Among the contributors to our knowledge of infusorial life during the
earlier half of the eighteenth century the names of Louis Joblot, Henry
Baker, and Abraham Trembley hold a p: eminent position. Joblot, author
in the year 1718 of a large treatise upon microscopes and the forms
of microscopic animals to be found in various artificial infusions, was
unfortunately led, through his possession of a more than ordinarily romantic
imagination, to embellish very considerably his descriptions and drawings
of the various types observed, these latter being in many instances moulded
by his facile pen into the similitude of satyrs' heads, and other monstrosities
having no existence in the plain and solid ground of fact. Henry Baker's
work, 'The Microscope Made Easy,' published in the year 1742, while
embracing a general account of all the various forms of microscopes in use
up to that date, and of subjects suitable for examination with the aid of
that instrument, includes in addition, a description with figures of many
forms of animalcules discovered by himself in organic infusions. This
special subject is, however, treated still more extensively in his subsequent
volume, 'Employment for the Microscope,' published in the year 1753.
In this last-named treatise is to be found the first printed account, accom-
panied by an easily recognizable figure, of the species now well known
by the title of the Swan Animalcule, Lacrymaria olor, and upon which
Mr. Baker conferred the name of the " Proteus." Of this he writes : —

" Having one evening been examining of the slime-like matter taken from the side
of a glass jar, in which small fishes, water-snails, and other creatures had been kept
alive two or three months, by giving them fresh water frequently, I was diverted with
the sudden appearance of a little creature whose figure was entirely new to me,
moving about with great agility, and having so much seeming intention in all its
motions, that my eyes were immediately fixed upon it with admiration. Its body
in substance and colour resembled a snail's ; the shape thereof was somewhat ellip-
tical, but pointed at one end, whilst from the other a long, slender and finely pro-
portioned neck stretched itself out, and was terminated with what I judged to be an
head, of a size perfectly suitable to the other parts of the animal. In short, without
the least fancy, which is ever carefully to be guarded against in the use of the
microscope, the head and neck, and indeed the whole appearance of the animal,
had no little resemblance to that of a swan : With this difference, however, that its
neck was never raised above the water, as the neck of a swan is, but extended
forwards, or moved from side to side, either upon the surface of the water, or in a
plane nearly parallel to the surface thereof. It swam to and fro with great vivacity,
but stopped now and then for a minute or two, during which time its long neck
was usually employed, as far as it could reach, forwards, and on every side, with a
somewhat slow but equable motion, like that of a snake, frequently extending thrice
the length of its body, and seemingly in search of food. I could discern no eyes,
nor any opening like a mouth in what appears to be the head ; but its actions
plainly prove it an animal that can see ; for notwithstanding multitudes of different

1 4 BIBLIOGRA PHY.

animalcules were swimming about in the same water, and its own progressive motion
was very swift, it never struck against any of them, but directed its course between
them, with a dexterity wholly unaccountable, should we suppose it destitute of
sight."

Henry Baker's speculations concerning the probable origin of animalcules
in hay and other infusions will be referred to in a future chapter.

Abraham Trembley's name, while most famous in association with his
remarkable discoveries concerning the extraordinary recuperative properties
after mutilation possessed by the fresh-water polypes, Hydra vulgaris and
viridis, has also to be included in the list of contributors to our early
knowledge of the Infusoria. In the course of his investigations and expe-
riments upon the more highly organized forms just mentioned, he was the
first to encounter many of the larger Stentors or trumpet-animalcules, and
regarding them as structurally allied to the latter, described them in the
' Philosophical Transactions ' for 1744 under the respective titles of the white,
blue, and green funnel- or tunnel-like polypes. Through a prolonged study of
these forms Trembley made himself familiar with, and recounted at length,
the peculiar oblique manner in which they subdivide, the mode in which
the new head and oral aperture is formed upon the posterior segment, and
a new caudal prolongation upon the anterior one, being related with such true
and exhaustive detail as to leave but little to be added in this connection
by later investigators. Under the title of " Clustering Polypes " this
authority also figured and described several varieties of Epistylis, notably
E.flavicans, relating precisely the manner in which by constant and even
longitudinal subdivision and prolongation of the supporting pedicle the
branched compound colony is built up. This premised affinity of the trumpet-
animalcules with the polypes suggested by Trembley received the full
approbation of the father of systematic natural history, the immortal and
illustrious Linnaeus, by whom they were included in the tenth edition of his
famous ' Systema Naturae,' published in the year 1758, under the title of
Hydra stentorea.

Five years later, 1763, we find for the first time the term "Infusoria"
introduced for the distinction of the minute beings that form the subject
of this treatise. M. F. Ledermuller, of Nuremberg, to whom must be
awarded the credit of creating this highly suggestive title, which has since
been almost universally adopted, employed it in the first instance for
the distinction of all those microscopically minute animals discovered by
himself and earlier investigators in water in which hay had been for some few
days previously steeped. This new title he further proposed to extend to
all the microscopical forms of animal life inhabiting infusions and putrid
liquids, including also those discovered in stagnant rain-water nearly a
century previously by Leeuwenhoek ; the Stentors were, nevertheless, left by
him in the position among the polypes assigned to them by Linnaeus and
Trembley. The names of Rosel, 1755, Wrisberg, 1765, and Pallas, 1766, may
be mentioned among the more prominent contributors to our earliest know-

O. F. MULLER, 1773-1786. 15

ledge of the larger forms of animalcules, chiefly Vorticellidae and Stentoridae,
preceding the appearance of what to the present day holds rank as the
earliest standard work that embodies a complete and systematic account of
the members of the infusorial world. Reference is here made to the
'Animalcula Infusoria' of Otho Friedrich Miiller, a posthumous quarto
volume published in the year 1786, containing no less than fifty plates and
367 pages of letterpress devoted to the description and illustration of close
upon three hundred species, fluviatile and marine, investigated and drawn
from the life by this indefatigable worker during a period extending over
no less than twenty years.

This early pioneer in the then terra incognita of the Protozoic
sub-kingdom had already in his 'Vermium terrestrium et fluviatilium
succincta Historia,' ' Zoologica Danicae Prodromus,' and ' Zool. Dan. Icones,'
published respectively in the years 1773, 1776, and 1779, given descriptions
and illustrations of a large number of these numerous types, to all of which
he attached distinctive generic and specific titles in conformity with Linnaeus'
then newly-introduced binomial system of nomenclature ; each of these
compilations, however, possess but minor value compared with the work
first quoted. To this latter, one is justified, indeed, in conceding as important
a status, as compared with all preceding literature upon the subject, as is sub-
sequently commanded by C. G. Ehrenberg's classic volume, ' Die Infusions-
thierchen,' published a little over half a century later. As might be anticipated,
O. F. Muller embraces in his 'Animalcula Infusoria' numerous minute
organisms that find no place in the infusorial group as at present constituted,
although in this respect he trespasses but slightly from the path subse-
quently pursued by Ehrenberg. In all, Muller institutes seventeen generic
denominations, the whole of which are still in use, and only one, his genus
Cercaria, being founded upon forms not admitted into Ehrenberg's system
of classification, while another, his genus Vibrio, embraces in addition to
many common forms of Bacteria, Vibrio, and Spirillum, as now recognized,
various examples of the microscopic hair-worms or Anguillulce. The several
species of Stentor were now recognized as members of the same infusorial
series, and transferred to his somewhat comprehensive genus, Vorticella. As
a necessary consequence of the very imperfect instruments available for
investigation at this early date, little more than a rough general outline of
the species examined, and no details of their internal organization, are
usually recorded, while in many of the types figured the cilia are but repre-
sented in part, or even altogether omitted. A reproduction of O. F. Muller's
generic subdivisions and earliest proposed scheme of classification of the
Infusoria will be found in the chapter hereafter devoted to this special
subject.

In the long interval intervening between the publication of Muller's ' Ani-
malcula Infusoria ' and the appearance of Ehrenberg's world-famed treatise,
a considerable number of investigators occupied themselves in the study of
these minute organisms, but without achieving any very notable results.

1 6 niBLIOGRAPHY.

Bonnet, Goezc, Gleichcn, Eichorn, Spallanzani, and Schranck, towards the
termination of the eighteenth, and Treviranus, Oken, Dutrochet, Nitzsch,
and Bory de St. Vincent, during the commencement of the present century,
are among the more conspicuous of these. Gleichen's name, perhaps,
deserves special notice, he being the first to demonstrate, through the admix-
ture of finely comminuted carmine with the water, the capacity of Infusoria
to appropriate this and other solid substances as food. Spallanzani detected
within the body-plasma of various species the bubble-like pulsating space or
spaces afterwards denominated contractile vesicles, while the presence of an
internal, more solid, gland-like structure, the nucleus or endoplast, and the
capacity of many to increase by longitudinal or transverse subdivision were
familiar to the majority of these observers. Examples of these last-named
phenomena were, indeed, figured and described by Miiller, and had, as already
intimated, been observed long previously by Trembley in association with the
Stentors or trumpet-animalcules. Dutrochet, in the year 1812, achieved a
progressive step by the recognition of the essential distinction of all the
species referred by O. F. Miiller to the genus Brachionus ; these were
shown to exhibit a much higher organization than the ordinary Infusoria,
possessing well-developed internal organs, and a much more complex type
of external contour, and were now distinguished for the first time by the
title of Rotiferae or wheel-animalcules. This distinction, pointed out by
Dutrochet, was recognized by Lamarck and Cuvier in their respective
classifications of the animal kingdom, the Infusoria as embodied in Cuvicr's
scheme including all of Miiller's types, subdivided into two leading orders,
the one including the more complex Rotiferae, and the other the appa-
rently structureless and homogeneous animalcules. These latter were,
indeed, accepted by Cuvier and all leading authorities up to the year 1830
as the simplest forms of animal life, exhibiting a degree of organization
most appropriately compared with mere specks of animate jelly variously
modified in external shape.

With the last-named date commenced an entirely new era in the his-
tory of the Infusoria. For fourteen years previously Christian Gottfried
Ehrenberg had been devoting studious attention to the investigation of
the lowest grades of vegetable and animal life, the matured fruits of
which now took the scientific world completely by surprise. He at this
time commenced the publication of his various essays, seeking to demon-
strate that the Infusoria, notwithstanding their minute size, possessed a
degree of organization as perfect and complex as that of the higher
animals, which culminated in the year 1838 in the production of his
world-famed history of the Infusoria, ' Die Infusionsthicrchen als Volkom-
mene Organismen.' This magnificent folio treatise, embodying no less
than 532 pages of letterpress and an accompanying atlas of 64 coloured
plates, including several hundred specific forms delineated for the most
part with a life-like exactitude, will ever remain a lasting memorial of the
unflagging industry and talent of this most indefatigable investigator.

EHRENBERG, 1836. 17

Notwithstanding the comparative imperfection of the optical appliances
at his disposal, it may indeed with justice be said that Ehrenberg's
figures, so far as they relate to contour and broad superficial details of
structure, are scarcely to be improved upon, and considerably excel, in
execution, the delineation of the same forms included in many more
modern treatises. Ehrenberg, like Miiller, associated together under the
collective title of the Infusoria a vast assemblage of minute animal and
vegetable organisms, a small section only of which finds its equivalent under
the same classificatory term in its more modern and restricted sense. In
addition to the true Infusoria he still retained the Rotifera, or wheel-
animalcules, the descriptions and illustrations of these monopolizing over
one-third of the text and plates of his entire volume, while a very con-
siderable portion of the remainder is occupied with the description and
delineation of the essentially vegetable Desmidiaceae and Diatomaceae, to
which are also added many forms of Rhizopoda and unicellular plants
other than the Bacillaria.

It was to the residual portion, that alone coincides with the tribe Infu-
soria as at present recognized, that Ehrenberg attributed the possession
of a highly complex internal structure, whose chief feature was further
described as consisting of a large number of pedunculate bubble-like
stomach-cavities associated with one another in a clustered form. The most
weighty testimony relied on by Ehrenberg in support of this theory was
derived from his repetition and extension of the experiments of Gleichen,
by whom it was demonstrated that carmine, indigo, or other pigmentary
matter suspended in the water was freely devoured. After passing through
the oral aperture this coloured matter was found to become collected in
small spherical bubble-like masses, variously distributed throughout the
body-substance or parenchyma, and without apparently taking the pains
to assure himself that these vacuoles occupied a permanently fixed
position, Ehrenberg assumed that such was the case, and assigned to
each vacuole the significance of a distinct food-receptacle or stomach ; it
was with special reference to these supposed numerous stomach-cavities
that the title of the Polygastrica was adopted by him for the dis-
tinction of this particular group. Ehrenberg's conception of the high and
complex organization of his so-called Polygastrica, however, by no means
ended here. The transparent vacuole possessing the property of contracting
rhythmically, first observed by Spallanzani, conjointly with the still more
universally recognized gland-like nucleus or endoplast, were pronounced to
be integral parts of the male generative organs, the former representing a
seminal vesicle, and the latter a seminal gland or testis. The minute
granular corpuscles distributed more or less abundantly throughout the
substance of the body were declared to be eggs, which after fecundation
from the seminal vesicle were discharged through the anal aperture or
vent. The possession by these Polygastrica of a complex muscular,
nervous, and blood-circulating system was likewise insisted on, though no

C

1 8 BIBLIOGRAPHY.

proof in these latter instances was brought forward ; the coloured eye-like
pigment specks conspicuous in Euglena, Ophryoglena, and various other
types, were finally regarded by him as highly differentiated visual organs.

Ehrenberg's evidence in support of his many-stomached or polygastric
theory was built on too insecure a foundation to stand the test of contem-
porary investigation, and before which, indeed, the entire superstructure
of his most ingeniously conceived digestive, neural, haemal, and repro-
ductive systems was speedily demolished.

The first and most prominent authority to call in question the accuracy
of Ehrenberg's interpretations was M. Felix Dujardin, who, firstly in various
contributions to the ' Annales des Sciences Naturelles,' extending through
the years 1835-38, and later in a special treatise devoted to this subject,
' Histoire Naturelle des Infusoires,' 1841, brought forward evidence that
threw an entirely new light on the organization of the members of this
group. Through an investigation, in their living state, of various representa-
tives of the minute marine shell-forming organisms upon which D'Orbigny,
in the year 1826, conferred the distinctive title of Foraminifera, Dujardin
discovered that their internal structure was far more simple than had been
previously conjectured. Guided only by an acquaintance with the empty
shells or tests of these minute beings, and taking into account their
predominating nautiloid form and chambered character, D'Orbigny and
his contemporaries concluded that their fabricators exhibited a correspond-
ingly high degree of organization, and described them as diminutive
representatives of the Cephalopodous order of the Mollusca. Dujardin,
examining various Mediterranean forms belonging chiefly to the genera
Cristellaria, Miliola, and Vorticialis, speedily determined that their living
occupants could lay claim to no such exalted position, being found by him
to possess no distinct organs or differentiated tissues, but in their place
a simple transparent gelatinous body, capable of extending fine thread-
like prolongations of its substance in every direction, by means of which
they adhered to and crept over submerged objects. Dujardin likewise
discovered in both salt and fresh water minute organisms possessing
similarly extensile gelatinous bodies and still more simple, unchambered,
and mostly corneous tests, upon which he conferred the generic names
of Gromia and Eugtyphia. Between these several types and Ehrenberg's
test-inhabiting polygastric genera Arcella and Difflugia, and the still more
simple shell-less Amcebce, Dujardin soon recognized that there subsisted the
closest affinity, and separating them from all other forms, instituted for
their reception, in reference to their peculiar mode of locomotion by root-
like extensions of their body-substance, the class title of the Rhizopoda.
Dujardin further conferred upon the plastic, gelatinous, and apparently
homogeneous body-substance of these Rhizopoda the distinctive name of
"sarcode," and finally sought to demonstrate that in all those infusorial
forms described by Ehrcnberg as exhibiting a polygastric type of structure,
their body-substance possessed a similar simple gelatinous or sarcode

F. DUJARDIN, 1841. T. VON SIEBOLD, 1845. 19

consistence, although, through the superaddition of a denser external
membrane, they were incapable of emitting thread- or root-like pseudo-
podic processes. No trace of a muscular or nervous system could be
detected by this authority, while the non-existence of the complex digestive
apparatus described by Ehrenberg was effectually demonstrated. On
feeding Vorticellae and other animalcules with carmine, in accordance with
the plan adopted by Gleichen and Ehrenberg, Dujardin found that the
food-particles, after their reception at the oral aperture, were not retained
in definite and permanently fixed stomach-sacculi, but after aggregation
into small spheroidal masses were passed backwards into the body-sarcode
or parenchyma, and there freely circulated until digestion or rejection at
the anal aperture. The somewhat similar and characteristic independent
circulation of the inner sarcode or parenchyma of Paramecium bursaria
and Vaginicola crystallina was also recorded for the first time by Dujardin.
The contractile organ, first discovered by Spallanzani, and interpreted by
Ehrenberg as belonging to the reproductive system, was pronounced by
this investigator to be a mere vacuolar space situated close to the surface,
apparently fulfilling a respiratory function by the continual absorption and
expulsion of water.

This simple interpretation of the organization of the Infusoria arrived
at by Dujardin, in opposition to that of Ehrenberg, soon gained powerful
adherents. Among the more noteworthy authorities who also by their
independent and almost contemporaneous researches, arrived at conclusions
coinciding with those of Dujardin and antagonistic to the polygastric
theory, may be mentioned the names of Meyen and Focke. Thuret and
Unger, again, from a botanical point of view, indicated the close correspon-
dence of the zoospores of Ckara, Vaucheria, and various confervoid algae
with the monadiform animalcules referred by Ehrenberg to the genera
Chlamydomonas, Phacelomonas, and Microglena. The most decisive advance
made towards the elucidation of the true structure and affinities of the In-
fusoria, following upon Dujardin's investigations, was, however, accomplished
by Carl Theodor von Siebold. It was this biologist who, in his ' Text-book
of Comparative Anatomy/ published in the year 1845, first enunciated the
theory, anticipated to some extent by Oken, Schleiden and Schwann,
that the representatives of the Infusoria were unicellular organisms. Each
separate animalcule possessed, in his opinion, the value only of a simple
cell, of which the central gland-like organ observed by so many previous
authorities, was now for the first time declared to be homologous with an
ordinary cell-nucleus, and described under a like distinctive title. The
contractile spaces or vesicles were further interpreted by Siebold as possess-
ing a circulatory or cardiac function. The simple sarcodic nature of the body-
substance of the Infusoria, first pointed out by Dujardin, was fully recog-
nized by this authority, and all the organisms possessing such a simple
unicellular structure were assembled together as the representatives of
an independent sub-kingdom of the Invertebrata, upon which he conferred

C 2

20 BIBLIOGRAPHY.

the suggestive title of the Protozoa. These Protozoa Siebold further
divided into the two subordinate classes of the Rhizopoda and Infusoria,
the former corresponding with the same section as similarly named by
Dujardin, and including all those forms whose locomotion was accomplished
by the extension of lobate or filiform processes or pseudopodia, while the
latter embraced those in which cilia or flagelliform appendages fulfilled
a similar function. The distinction between the Ciliate and Flagellate
sections of the Infusoria was also fully recognized by this investigator, who,
however, conferred upon them titles differing from those now recognized.
The Ciliata only being regarded by him as possessing a distinct oral
aperture, were denominated the " Stomatoda," and the supposed entirely
mouthless flagellate animalcules, the " Astomata." Siebold, by his creation
of the sub-kingdom Protozoa, acceptation of the Infusoria as simple
sarcode organisms possessing individually the morphological value of a
simple cell, and restriction of the Infusoria to the Ciliate and Flagellate
members of the Protozoa, practically initiated that definition of the boun-
daries and organization of the class that receives the most powerful support
at the present day, and is closely adhered to by the present author.

As might be anticipated, a universal concession to Siebold's unicellular
interpretation of infusorial organization was by no means granted at the
period of its announcement to the scientific world. Although the polygastric
hypothesis, in the sense rendered by Ehrenberg, was speedily rejected,
there have not been wanting those who from that earlier date up to the
present time have sought to associate with these microscopic beings a
complex type of structure, and to demonstrate their affinities with many of
the more highly organized invertebrate sub-kingdoms. Among the first
opponents of Siebold in this direction the names of Eckard and Oscar
Schmidt are the most prominent. Both founded their arguments against
the unicellular theory partly from their independent observation of the
development of embryos from within the interior of the body-substance of
Stentor c&ruleus and polymorphic, while the latter more especially sought
to demonstrate the close affinity of the higher ciliate animalcules with the
Turbellarian group of the sub-kingdom Annuloida. O. Schmidt's indication
of this supposed affinity was brought about by his discovery in Paramecium
aurelia and Bursaria (Panophrys] flavicans of a subcuticular layer of minute
rod-like bodies — now familiarly known (as trichocysts) to be developed in
many infusorial forms — similar to those met with in various Turbellaria
and lower Annelides. He further discovered that the contractile vesicle in
various animalcules communicated with the outer water, a fact which at
once suggested to his mind the probable correspondence of this structure
with the water-vascular system of the last-named higher zoological groups.
These results of O. Schmidt's researches bring us to 'the year 1849,
a date memorable for the appearance on the field of that accom-
plished investigator to whom we are most indebted for our present
knowledge of the morphology and development of the infusorial animal-

FRIEDRICH STEIN, 1849-1854. 21

cules, and from whom also we have received that scheme of classification
of the Ciliate section of the class that obtains the widest recognition at the
present day, and is mainly adopted in this volume. It is almost super-
fluous to add that the authority here referred to is none other than
Friedrich Ritter von Stein, who, after his first contribution to the literature
of this subject in the year first named, may be said thenceforward, and up
to the present day, to have made a life-study of the history, habits, and
organization of the representatives of this highly interesting group. The
earliest published results of this eminent observer are specially remarkable
for their association with a theory relating to the development of the
Vorticellidae, which commanded at the time almost as large a share of atten-
tion and adverse criticism as followed upon Ehrenberg's polygastric inter-
pretations. Instead of accepting Acineta and its numerous allies, collected
together in this treatise under the title of the Tentaculifera, as animalcules
possessing an independent history and organization, Stein was led, through
their frequent occurrence in company with certain species of Vorticellidae,
and by his observation of the production by some Acineta of Vorticella-
like ciliated embryos, to regard these organisms as developmental con-
ditions only of the latter. In accordance with this interpretation, the
Podophryafixa of Ehrenberg was pronounced by Stein * to be a transitional
or acinete phase of Vorticella microstoma ; Acineta mystacina, that of
Vaginicola crystallina ; and the form here included under the name of
Podophrya lemnarum as a similar condition of Opercularia nutans. Addi-
tional instances in support of this Acineta theory were brought forward by
Stein in the ' Zeitschrift fur Wissenschaftliche Zoologie' for February 1852,
its most extensive application and amplification being, however, embodied
in his separate treatise ' Die Infusionsthiere auf ihre Entwickelunggeschichte,'
published at Leipzig in the year 1854. This volume, notwithstanding the
fact that its associated Acineta theory was shortly after disputed, and
ultimately abandoned by Stein himself, still constitutes what may be
almost regarded as a monograph of the Vorticellidae and Tentaculiferous
section of the Infusoria. In addition to embodying the most accurate
account and delineations of the form, structure, and developmental pheno-
mena of numerous representatives of these groups that had yet appeared,
similar details concerning various Holotrichous types were likewise included;
the multiplication of Colpoda cucullulus, through encystment and the sub-
division of its substance into two, four, or eight spore-like bodies, as
amply described later on, being among the most important of these supple-
mentary data thus recorded. The supposed relationship of the twelve or
more acinete types described by Stein to an equivalent number of Peritricha,
including representatives of the genera Vorticella, Epistylis, Opercularia,
Zoothamnium, Cothurnia, Vaginicola, Spirochona, and Ophrydium, is re-
ferred to at length in the descriptions hereafter given of the Acinetae as
independent organisms.

* Wiegmann's ' Archiv fur Naturgeschichte,' 1849.

22 BIBLIOGRAPHY.

Contemporaneously with the earlier publications of Stein as above
recorded, mention must be made of the work of Maximilian Perty, ' Zur
Kentniss kleinster Lebensformen/ published at Bern in the year 1852.
This treatise, like the earlier ones of Miiller and Ehrenberg, embraces
an account, with illustrations, of a heterogeneous assemblage of micro-
scopic aquatic beings, including Rotifera, Rhizopods, and Bacillaria in
addition to the ordinary Infusoria. These latter are, however, together
with the Rhizopoda, separated by Perty from the associated animal and
vegetable organisms, and collated together as distinct classes of a sub-
kingdom, essentially identical with the Protozoa of Von Siebold, but
upon which he conferred the new title of the Archezoa. The class of
the Infusoria is further divided by Perty into the two orders of the
Ciliata and Phytozoida, the former comprising all the ordinary ciliate
animalcules, and the latter flagellate organisms generally, whether of an
animal or vegetable nature. The innumerable infusorial forms figured and
described by Perty were collected by himself entirely in the vicinity of the
Bernese Alps, and embrace many new species, some of which have not been
since met with, while a few, such as his Eutreptia viridis and Mallomonas
Plosslii, are delineated in this present volume after examination, for the first
time, with the higher magnifying powers of the compound microscope in
its present comparatively perfected state. Taken as a whole, Perty's illus-
trations of the Infusoria, and of his Ciliata in particular, are exceedingly
rough and unsatisfactory, being inferior in many respects to those previously
given by Ehrenberg, and not to be compared with the contemporaneous
ones of Stein. The view taken by this author with reference to the organiza-
tion and internal structure of the Infusoria, is distinguished by its opposition
to both the unicellular one of Siebold and the polygastric one of Ehrenberg.
In place of these, Perty substituted the interpretation that these microscopic
beings are composed of an aggregation of separate cells, none of which
have attained their complete development, but remain indistinguishably
united with each other. He thus, as presently related, anticipated to some
extent the views adopted by Max Schultze in the same direction. The
presence of any nervous, muscular, or other complex organization he
entirely denied, as also that of a distinct internal parenchyma, the body
being described by him as composed wholly of simple contractile substance.
The thickly ciliated cuticular surface of Stentor and other forms he never-
theless compared to the ciliated epithelium of more highly differentiated
organic types.

The first onslaught upon the Acineta theory enunciated about this
date by Stein, was delivered by Johannes Lachmann, who, in Miiller's
'Archives ' for the year 1856, adduced testimony strongly in favour of the
independent organization oi Acineta and its allies, showing the character-
istic manner in which they preyed upon other Infusoria, and their mode of
reproduction through the separating of a portion of the central nucleus or
endoplast. Corroborative evidence of a still more conclusive character, and

CLAPAREDE AND LACHMANN, 1858-1860. 23

which indeed finally established the claim of these remarkable animalcules
to hold rank as the members of a distinct order of the Infusoria, was
brought forward by the last-named investigator in conjunction with Edouard
Claparede, in three extensive essays, published in volumes v. to vii. of the
' Memoires de 1'Institut Genevois/ extending over the years 1858 to 1860.
These three memoirs, derived from the joint work of the above authori-
ties, both co-workers in the laboratories, and disciples of the eminent
Johannes M tiller, form, as issued more recently in a single volume, the well-
known ' Etudes sur les Infusoires et les Rhizopodes,' containing collectively
over seven hundred pages of text, and thirty-seven quarto plates, constantly
referred to in these pages, and which holds rank as one of the most complete
and important contributions to the literature of the present subject as yet
extant. That portion of the volume above quoted which relates more
especially to the organization of the Acinetae, proving the same to be
entirely independent of the Vorticellidae, and thus reversing the verdict of
Stein, is embodied chiefly in the so-called third part of the ' Etudes.'
Actually, however, this section of the work was published the first of all, its
substance being included in the conjoint prize essay communicated to the
Paris Academy of Sciences in February of the year 1855. The scheme
of classification adopted by Claparede and Lachmann is submitted in its
fully extended state later on, but may be briefly referred to here as
comprising the ordinary infusorial orders of the Ciliata and Flagellata, two
smaller groups of similar value being, however, instituted, the one entitled the
Suctoria for the reception of Acineta, Podophrya, and all corresponding forms
in which prey was seized and incepted through the medium of tubular and
suctorial tentacle-like appendages, while that of the Cilio-flagellata was
proposed by the same authorities for the distinction of Peridinium and
various associated types which have as locomotive organs a girdle or other
supplementary series of fine vibratile cilia, in addition to one or more
flagellate appendages.

Claparede and Lachmann's interpretation of the organization and
affinities of the Infusoria, for which, however, the first-named writer would
appear to be chiefly responsible, is altogether opposed to the unicellular
one of Von Siebold. While conceding to these organisms a separate and
even the lowest position in the animal scale, they proposed to regard them as
approximated most nearly, on the one hand, to the Ccelenterata, and on
the other, more remotely, to the lower Annelids. In accordance with
the views of these Geneva anatomists, the Infusoria were, in short, repre-
sented as possessing a well-defined body-wall, the softer internal area
enclosed and bounded by which constituted an equally distinct chyme-
filled somatic or gastric cavity. A very considerable accession to the
number of known forms of animalcules, and more especially as relates to
the previously little studied marine types, e. g. genera Freia (Follicularid),
Tintinnus, and Peridinium, was effected through the indefatigable labours
of Claparede and Lachmann, while the evidence accumulated by them

24 BIBLIOGRAPHY.

respecting the developmental phenomena of the class in general is of the
utmost value.

The same decade, conspicuous for the substantial progress effected
towards a more accurate and extensive knowledge of the Infusoria at
the hands of Stein, Claparede, and Lachmann, includes divers other
names which, although not similarly associated with the authorship of
separate treatises, hold a deservedly high place in the annals of infusorial
literature. That of Balbiani is especially noteworthy in this direction, he
having been the first, in the year 1858, to announce that the hitherto
supposed longitudinal fission of Paramecium aurelia and various other
animalcules, was not an act of division at all, but one of genetic or sexual
union, attended with complex internal changes, as detailed at length in the
chapter devoted to an account of the reproductive phenomena of this class.

Max Schultze's name, though more intimately connected with the
history of the Rhizopodous section of the Protozoa, demands notice
here, he having in the years 1860 and 1861 developed and modified
to a marked extent the unicellular theory of the Infusoria first origi-
nated by Von Siebold. By this author the frequent absence from,
and non-essentiality of, a bounding membrane or distinct cell-wall to
many lower unicellular protozoic structures, was especially insisted on,
the probability also being suggested that many, such as Actinosphcerium
EicJwrnii, and others possessing a multiplicity of nucleus-like structures,
were composed of a greater or less number of wall-less cells indistinguishably
amalgamated with each other. Further, Max Schultze in his demonstration
that the soft plastic contents only, independently of an outer bounding
wall, constitute the very essence or essential factor of cell organization,
proposed to distinguish this soft and contractile substance by the charac-
teristic title of " protoplasm " in contradistinction to that of " sarcode,"
introduced in a somewhat similar but narrower sense some years pre-
viously by Dujardin. With this author there also originated the brilliant
and fortunate conception that the cell-contents of all animal and vegetable
organisms were composed of a similar simple protoplasmic basis, such
forms again, in their simplest expression, as in an Amceba, consisting of
a mere animated speck or lump of undifferentiated protoplasm. Max
Schultze's interpretation concerning the probable composite structure of
certain Rhizopoda and Radiolaria received substantial confirmation at the
hands of Ernst Haeckel, in his magnificent monograph of the Radiolaria,
published in the year 1862.

Stein, already mentioned as having in the year 1854 published an
important work devoted more especially to the organization of the Vorti
cellidae and their supposed associated Acinetce, gave abundant evidence
of continued activity in the same field by the production, in the year 1859,
of the first volume of the folio series still in course of progress, having as its
aim the description and illustration of all known infusorial forms. In this
volume Stein carried into practical application the new system of classifica-

F. STEIN, 1859. R. M. DIES ING, 1848-1866. 25

tion of the higher or Ciliate section of the Infusoria first introduced by him a
few years previously,* and which has since been generally adopted as the
most natura1 and convenient scheme yet proposed. In accordance with
this, the ciliate animalcules were divided, with reference to the character
and distribution of their cilia, into the four subordinate orders of the
Holotricha, Heterotricha, Hypotricha, and Peritricha ; this special volume, in
addition to including a complete summary of the biography and organiza-
tion of the Infusoria as known up to that date, constituting an exhaustive
account or monograph of the Hypotrichous section. The position conceded
to the Infusoria by Stein in this treatise is that of the highest group of the
Protozoa, though, taken individually, a more complex type of organization
is assigned to them than is involved with the unicellular interpre-
tation of Von Siebold. The characteristic contractile vesicle, with its
frequently associated radiating canals, more particularly, is here accepted
as formerly by O. Schmidt and Claparede and Lachmann as indicative
of a more or less remote relationship with the Turbellaria and lower
Annelids.

The interval intervening before the issue, in the year 1867, of Stein's
second volume of his 'General History of the Infusoria,' bore substantial fruit
through the researches of Balbiani and T. W. Engelmann in the direction
of that more extended knowledge of the developmental phenomena of the
class referred to at length in a succeeding chapter. The number of known
infusorial forms was also considerably enriched, and their structure accu-
rately described and delineated by the authority last quoted and many
other able investigators, among whom the names of A. Quennerstedt,
H. J. Carter, Frederick Cohn, J. D'Udekem, and A. Wrzesniowski, are
especially conspicuous.

In association with the period now under consideration the novel
interpretation of the affinities of the Infusoria and proposed subdivision of
the group introduced by R. M. Diesing, may be suitably referred to. In
accordance with the views of this author, the sub-kingdom of the Protozoa,
as instituted by Von Siebold, possessed no real existence, the entire assem-
blage of forms included in it representing simply lower or imperfectly
developed conditions of various more highly organized animal groups. The
Rhizopoda and Foraminifera were thus held by Diesing, following the views
of D'Orbigny, to be degraded headless Mollusca, the majority of the Ciliata
and mouth-bearing Flagellata to be lower worms, while the Vorticellidae
and Stentors, with reference to the closely approximated location of
their oral and anal apertures, were referred to the Polyzoa, and collected
into a group upon which he conferred the title of the Bryozoa Anopisthia.
This breaking up of the class of the Infusoria and distribution of its
members among various other Invertebrate sub-kingdoms, while first
proposed by Diesing in the year 1848, received its full development in
his ' Systema Helminthum, Order Prothelmintha/ and ' Revision der

* ' Sitzung. der konigl. Bohmischen Gesellschaft der Wissenschaften,' Oct. 1857.

2 6 BIBLIOGRA PHY.

Prothelminthen,' published respectively in the years 1850, 1865, and
1866. These last-named contributions constitute practically a synopsis,
with accompanying diagnoses, of all the infusorial forms then known,
exclusive of the Vorticellidae and Stentoridae, the chief value of which
undoubtedly depends upon their very complete bibliographic references.
In no case does Diesing appear to have personally acquainted himself with
even a single example of the numerous types epitomized, his diagnoses
being framed entirely upon the descriptions given by their original
discoverers, and whose errata are also necessarily reproduced. Thus,
accepting the dictum of Ehrenberg, all the Flagellata are erroneously
represented as possessing a distinct oral aperture, Volvox, Pandcrina, and
other undoubted mouthless Phytozoa even being included in the category.
Viewed as a whole, Diesing divides his so-called order of the Prothelmintha
into the two sub-orders of the Mastigophora and Amastiga, the same
corresponding respectively, exclusive of exceptions above named, with the
Flagellate and Ciliate divisions of the Infusoria first instituted by Von
Siebold. The Flagellata, or Mastigophora, are further separated by him
into the two sections of the Atrichosomata and Trichosomata, the latter
group including only the Peridinidae and other allied forms possessing
cilia in addition to the characteristic flagella, and therefore corresponding
with the order of the Cilio-Flagellata as comprehended in this volume.
The two sectional titles of the Holotricha and Hypotricha introduced by
Stein are made by this author to include all his recognized representatives
of the Amastiga or Ciliata. A considerable number of new generic names,
established some with, and some without, substantial grounds, were, as
hereafter frequently attested to, founded by Diesing on various of the older
specific forms.

Here mention may be most appropriately made of the one complete
book devoted to the organization of the Infusoria that had so far, or has
since up to the publication of this present volume, issued from the British
press. This work, 'A History of the Infusoria,' by Andrew Pritchard,
which in the year 1861 arrived at its fourth enlarged and revised edition,
the first appearing in the year 1834, can, however, in no way be cited as an
independent treatise, it constituting merely an excellent and abbreviated
transcript of the technical descriptions of all so-called infusorial forms
published up to the year 1858, and included chiefly in the works of
Ehrenberg, Perty, and Dujardin. The views of these and other contem-
poraneous authorities are fully enunciated, and the whole series of forms
described made to amalgamate with the system of classification adopted
by Ehrenberg in his ' Die Infusionsthierchen.' No original views, no trace
of original research, nor any record of newly discovered species, are con-
tained in this volume, which must therefore be considered rather as a
compilation than as an independent work. As such, and in connection with
the state of our knowledge at that time, its utility was unquestionable,
and more especially to the general working microscopist, since its scope,

ANDREW PRITCHARD, 1861. H. JAMES-CLARK, 1868. 27

corresponding with that of Ehrenberg's opus magnum, includes not only
the Infusoria proper, but also the several entirely unrelated groups of the
Diatomaceae, Desmidiaceae, Confervaceae, and many Rhizopods, Radiolaria,
and even Acari. It is scarcely to be wondered at that, placed in front of
so vast and heterogeneous an assemblage of organic forms, the author
should have called in extraneous assistance, and hence it is we find the
names of J. T. Arlidge, W. Archer, J. Ralfs, and W. E. Williamson — all
high authorities on one or other of the several groups separate from
the true Infusoria — associated as coadjutors in the fourth edition of
Mr. Pritchard's work.

Stein's second volume, issued, as already mentioned, in the year 1867,
constitutes a monograph of the Heterotrichous order of the Ciliata, and forms
a worthy companion to the one previously published, the series of types
included in this section being delineated and described with an accuracy and
exhaustiveness of detail hitherto unapproached. This monograph embodies,
in addition to the above-mentioned more special subject-matter, data of the
highest importance concerning the general organization and reproductive
phenomena of the Infusoria, and is also notable for containing a formal
abandonment, with some slight reservation, of his original theory asso-
ciated with the Acineta, and acknowledgment of the claim of these animal-
cules to the independent position assigned to them by Claparede and
Lachmann. This reservation, as above intimated, was manifested by Stein's
continued adhesion to the opinion that certain infusorial types, e. g. Stentor,
Stylonychia, and Urostyla, commenced their existence within the parent
body as minute ovate or subspheroidal embryos, with or without cilia, and
possessing in addition a greater or less number of retractile tentaculiform
appendages corresponding with those of the ordinary Acinetae. These
supposed embryos of the associated Ciliata are, however, now shown to
be minute parasites, referable chiefly to Claparede and Lachmann's genus
Sphcerophrya.

The following year (1868) commands a conspicuous position in the
bibliography of the present subject, through its association with the dis-
covery by Professor H. James- Clark, of the Agricultural College of Penn-
sylvania, U.S.A., of certain Flagellate Infusoria exhibiting an entirely new
type of structure, accompanied by his simultaneous announcement that all
sponges consist essentially of colonial aggregations of similar Flagellate
animalcules. Three years later, 1871, the present author had the good
fortune to encounter the greater portion of H. James-Clark's types, and
several new but closely allied forms, upon this side of the Atlantic, and
having since selected this group as the subject of special attention, has so
augmented its original numbers and demonstrated their distinctive features
as compared with the more ordinary Flagellata, as to have felt justified
in establishing for them a new order, upon which it is here proposed to
bestow the title of the Choano-Flagellata. Pursuing the path indicated by
Professor Clark with reference to the structure and zoological position of

28 BIBLIOGRAPHY.

the sponges, the result of the author's investigations has, as recorded in the
chapter hereafter devoted to this special subject, been the accumulation of
additional data of the most substantial character in support of the pre-
viously suggested affinities.

Among the numerous contributors towards a more extended knowledge
of the Infusoria as yet unreferred to, may be mentioned, more especially in
association with the Ciliata, the names of Wrzesniowski, Richard Greeff,
and Edouard Everts, and with the Flagellata, that of L. Cienkowski.
Among the former Greeff is exceptionally prominent, he being led, through
his discovery in the Vorticellidae of a more complex pharyngeal apparatus
and muscular system — hereafter described — than had hitherto been attri-
buted to them, to adopt a Ccelenterate interpretation of infusorial structure
closely identical with that first enunciated by Claparede and Lachmann.
Cienkowski's investigations are especially interesting, as being productive of
a masterly account of the structure and developmental history of Noctiluca,
which is definitely shown by him to be intimately related to the more
ordinary Flagellata.

Associated with those that take a prominent position within the present
decade as expositors of the structure and affinities of the Infusoria, Professor
Ernst Haeckel's name is eminently noteworthy. In his admirable essay,
"Zur Morphologic der Infusorien," published in the 'Jenaische Zeitschrift,'
Bd. vii. Heft 4, for the year 1873, this gifted biologist brings forward,
beyond question, the most powerful evidence in support of the unicellular
composition of these protozoic organisms adduced since the first conception
of the theory by Carl von Siebold, in the year 1845. The lucid exposition
given by him of the general morphology, reproduction, and developmental
aspects of the higher Infusoria, may be further said to constitute one of
the most complete accounts of this interesting group yet produced. It
must be noted here, however, that Professor Haeckel in his essay admits
to the rank of true Infusoria those representatives of the class only that
are here collated under the title of the Ciliata, the equally or even more
abundant and important class of the Flagellata being dismissed as con-
taining an association of doubtful forms, chiefly referable to the vegetable
kingdom. The great progress that has been made since the date of this
essay in our knowledge of the last-named group will no doubt, however,
exert its influence, and reconcile Professor Haeckel to its occupation of a
position in the animal scale contiguous to that conceded in his earlier
classificatory systems to the Ciliata.

Comparatively insignificant as has hitherto been the sum of contribu-
tions to our knowledge of infusorial life and structure by English investi-
gators, and as is conspicuously evidenced on reference to the Bibliogra-
phical list appended to this volume, a brilliant exception is furnished in
connection with the names of Messrs. W. H. Dallinger and J. Drysdale,
whose joint investigations are recorded in various numbers of the ' Micro-
scopical Journal ' extending through the years 1873 to 1875. The chief

DALLINGER AND DRYSDALE, 1873-1875. E. DE FROMENTEL, 1876. 2Q

interest and value attached to the results achieved by these joint workers
is accomplished through their having struck upon and most successfully
followed up an entirely new channel of discovery. Employing the highest
and most perfectly constructed modern powers of the compound microscope,
and concentrating upon their task an amount of energy and patience
scarcely before equalled, Messrs. Dallinger and Drysdale directed their
attention to unravelling the mystery so long associated with the incon-
ceivably rapid production of low flagellate organisms or monads in organic
infusions, and more especially such as are so abundantly produced in fish
macerations. Taking turn by turn at the microscope, and patiently watch-
ing the same forms from hour to hour and day to day, the entire life-history
of numerous species of these most minute organisms was now revealed for
the first time. Not only was it found that these animalcules increased to
an indefinite extent by the familiar phenomena of longitudinal and trans-
verse fission, but also that under certain conditions two or even more
individuals of the same species would become intimately united, the result
of this fusion or coalescence being the formation of encystments, whose
contents broke up into a greater or less number of spore-like bodies, which
speedily developed into the parent type. In some cases these reproductive
spores were so excessively minute as to defy individual detection under
a magnifying power of no less than 15,000 linear, their presence being in-
dicated only by their presenting as they escaped en masse from the investing
envelope the aspect of a fluid possessing a slightly higher refractive index
than the surrounding water. The power to withstand great vicissitudes of
temperature — in some cases even up to and beyond boiling point, and pari
passu the practical indestructibility of these monad spores — was also proved
by these investigators ; the facts elicited as a whole, affording some of the
most important evidence yet educed towards the solution of the much-
vexed question of spontaneous generation, and in demonstration of the
dominance of the inexorable law of " like begetting like " among even these
most minute and humble members of the organic world. The special
bearing of Messrs. Dallinger and Drysdale's evidence upon these highly
interesting points receives extensive notice in a future chapter.

Among the more recent literary productions bearing upon the subject
of the Infusoria, brief allusion must be here made to the ' fetudes sur les
Microzoaires ou Infusoires proprement dits,' published by E. de Fromentel
in the year 1876. The expectations raised by a first glance at this
portly volume and its thirty quarto plates receive a somewhat severe
shock on proceeding to a more intimate acquaintance. This writer is
apparently entirely ignorant of the work achieved in the same field by
Stein, Engelmann, and other modern German investigators, their names not
being so much as mentioned throughout the whole course of his treatise.
With scarcely an exception, his entire series of diagnoses of the innumerable
forms, new and old, are so vague and indefinite as to be scarcely in advance
of the necessarily incomplete ones given last century by O. F. M tiller,

30 BIBLIOGRAPHY.

while the numerous figures accompanying these descriptions will in most
instances scarcely compare favourably with those handed down to us by
Perty and Dujardin. Taken as a whole, it is but too evident that De
Fromentel's volume is published prematurely, the author possessing but the
most superficial acquaintance with his subject. As a consequence, and
notwithstanding the fact that many new forms of high interest are embodied
in his volume, the reader closes De Fromentel's book regretting the fine
opportunity lost and that so much valuable space and expenditure of
time should have been bestowed upon a work so inadequately representing
our present comparatively advanced knowledge of infusorial morphology.

A few names only are now wanting to conclude this list. With the
exception of Stein's most recently issued volume, 'Der Organismus der
Infusionsthiere/ Abth. iii. Heft I, 1878, containing a general account of the
Flagellata, with twenty-four magnificently executed plates — referred to
at length in the introductory portion of Chapter VII., no works of primary
importance remain to be enumerated. At the same time various authorities,
through the exhaustive investigation of special representatives of the in-
fusorial world, have considerably extended our knowledge and appreciation
of the structure and affinities of the group as a whole, contributing largely
towards the establishment of that solid basis of practical evidence from
whence future exploration must depart. Hertwig, Biitschli, Sterki, Ernst
Zeller, Wrzesniowski, Mereschkowsky, and C. Robin are more especially
deserving of mention in this last-named category, their respective publica-
tions receiving due notice in both the subsequent Bibliographic list and in
association with the systematic descriptions of those specific types that
formed the more immediate subject of their investigation.

This chapter may be concluded with the citation of one other prominent
and most worthy name. John Tyndall, the talented physicist and contri-
butor to the 'Philosophical Transactions' for the years 1876 and 1877 °f
two most important papers treating upon the optical deportment of the
atmosphere in relation to the phenomena of putrefaction, and upon the vital
persistence of putrefactive and infective organisms, has beyond question,
through his most carefully conducted experiments and philosophic deduc-
tions, as hereafter reported in extenso, furnished some of the most crucial
evidence yet adduced towards the subversion of the now well-nigh aban-
doned doctrine of Heterogeny, or, in other words, the production of
Infusoria and other lowly organized animal and vegetable types out of
inorganic elements.

CHAPTER II.

THE SUB-KINGDOM PROTOZOA.

THE contents of the preceding chapter constitute a brief chronological
summary of the more important advances gained in our knowledge of the
Infusoria from the date of their first discovery by Leeuwenhoek up to the
present time. A comprehensive survey of the organization and affinities of
the members of this zoological group, as illumined by the light of recent
research, has now to be proceeded with.

As an initial step in this direction, a short space must, however, be first
devoted to a consideration of that larger subdivision of the animal kingdom,
of which as a whole the Infusoria are most generally and here definitively
accepted as a constituent group or groups. This subdivision, the Protozoa
of Von Siebold, or Archezoa of Max Perty, has undergone much modi-
fication at the hands of biologists since its first institution in the year 1845.
Great diversity of opinion exists, even at the present day, with respect to
the delimitations both of its own borders and those of the minor sections
and orders into which it may be most conveniently and naturally sub-
divided. As here accepted, the sub-kingdom Protozoa may be defined
as embracing all those forms of life referable to the lowest grade of the
animal kingdom, whose members are for the most part represented by
organisms possessing the histologic value only of a single cell, or of a con-
geries or colonial aggregation of similar independent unicellular beings.
In such cases as Opalina and other multinucleate forms, in which from the
compound character of the nuclear or endoplastic element the organism
would appear to be composed of several cells, these cells are indistinguish-
ably fused with each other, and have not allocated to them separate func-
tions or properties as in all more highly organized multicellular animals or
Metazoa.

The essential body-substance of all Protozoa consists of apparently
homogeneous, or more or less conspicuously granular, slime-like sarcode or
protoplasm, all organs of locomotion or prehension consisting of simple
or variously modified prolongations of this element. The food-substances
ingested by the Protozoa may be incepted by a single well-defined oral
orifice or cytostome, or there may be a plurality of such apertures. Among
the Rhizopoda and many Flagellata, on the other hand, such material may
be indefinitely received at any point of the periphery, while in yet a fourth
series, chiefly endoparasitic — such as the Opalinidae — there is no oral

32 A MANUAL OF THE INFUSORIA.

aperture, definite or distributed, the zooid absorbing through the surface of
its integument the nutritious liquid pabulum in which it is constantly
immersed. In their development the Protozoa exhibit a tendency to increase
chiefly by the process of binary subdivision or gemmation, or through
the breaking up of the entire body into a number of sporular elements,
which may or may not be preceded by the conjugation or zygosis of two
or more individual zooids or units. No sexual elements developed sepa-
rately, and corresponding with the ova or spermatozoa of higher animals,
occur among the Protozoa, and in no case is there associated with the
developmental phenomena of this sub-kingdom the formation of a multi-
cellular germinal layer or blastoderm, the fundamental origin and ground-
work of all tissue structures in the more highly organized animal groups
or Metazoa.

The earliest subdivision of the Protozoa into secondary sections or
orders as initiated by Von Siebold partook, as related in the preceding
chapter, of the simplest possible character. All the types then known were
separated by this author into the two subordinate groups of the Rhizopoda
and Infusoria, the former characterized by the pseudopodous, and the
latter by the ciliate or flagelliform character of the locomotive append-
ages. Correlated with the systems of the present day, this proposed
primary subdivision of the Protozoa still finds many advocates, an identical
plan, though in different wording, being indeed adopted by Professor
Huxley in his 'Anatomy of Invertebrated Animals,' 1878, p. 76, and in
which it is suggested that all Protozoa may be conveniently distinguished
as Myxopods and Mastigopods. These two correspond so precisely and
respectively, with reference to their locomotive appendages, with the Rhizo-
poda and Infusoria as instituted by Von Siebold, that but little advantage is
to be gained apparently by the proposed exchange. With reference to the
latter of these two terms, it is further worthy of remark that it coincides to
a considerable extent, in both sound and the sense implied, with the
Mastigophora of R. M. Diesing.

Following out the further subdivision of the two foregoing primary
sections of the Protozoa into secondary groups or orders which has up to
the present time found most extensive support, the first — that of the
Rhizopoda, or Myxopoda — is found to include the Amcebina, Foraminifera,
and Radiolaria, while the second — that of the Infusoria, or Mastigopoda —
embraces in a similar manner, and in accordance more especially with the
classification-scheme introduced byMessrs. Claparede and Lachmann, the four
orders of the Ciliata, Cilio-Flagellata, Flagellata, and Suctoria. For this last
group — that of the Suctoria — Professor Huxley has proposed to substitute
the very appropriate title of the Tentaculifera, recent investigation having
shown that the more customary suctorial organs may be replaced by simply
prehensile and non-suctorial tentacles. By some, the small endoparasitic
group of the Gregarinidae is reckoned to constitute a third and distinct class
of the Protozoa, but it is evident that we have here a degraded group of the

AFFINITIES OF THE SPONGIDA. 33

ordinary Rhizopoda most nearly allied to the Amcebina, which exhibit a
like modification of structure with relation to the latter as is presented
by the Opalinidae with respect to the ordinary Ciliata. The much-vexed
question of the zoological position and affinities of the Spongida or Porifera
has necessarily to be considered in association with the delimitation of the
sub-kingdom Protozoa. Formerly the members of this important section
were regarded mostly as forming either a subordinate group of the Rhizo-
poda, or an independent class of the Protozoa. More recently, however,
there has been a tendency to exclude the sponges entirely from the Protozoic
sub-kingdom, and to assign to them a position more nearly approximating
that of the Ccelenterata, or zoophytes and corals, among the more highly
organized tissue-constructed animals or Metazoa. Professor Ernst Haeckel,
the most powerful supporter and also the originator of this proposed
innovation, has based his arguments in favour of such transfer chiefly upon
his own peculiar interpretation of the structure and developmental phe-
nomena of those bodies, the swarm-gemmules or so-called ciliated larvae,
hereafter described, by which the local distribution of special sponge
species is periodically effected. Taking on trust this developmental inter-
pretation of Ernst Haeckel, many leading biologists have committed
themselves to a similar exclusion of the Spongida from the Protozoa,
and it is thus that in Professor Huxley's recently quoted work — which
must be accepted as the latest and most important exposition of Inverte-
brate anatomy in this country — a like allocation of this much-debated
group to the Metazoic section of the animal kingdom is upheld. Postponing
for a future chapter a complete summary of the grounds upon which an
interpretation entirely opposed to that advocated by Professor Haeckel is
adopted in this volume, it will suffice for present purposes to state that a
considerable interval devoted to a careful investigation of the structural and
developmental phenomena of the sponges and Protozoa generally has
resulted in the arrival by the present author at the opinion that — (i) these
phenomena accord essentially and entirely with those presented by the
typical Protozoa ; (2) that there is no formation of a germinal layer or true
tissue structure in any period of their development ; and (3) that the posi-
tion of the Spongida among the Protozoa is most nearly allied to that
Infusorial group here distinguished by the title of the Choano-Flagellata,
and out of which, by the process of evolution, there is substantial reason
to presume they were primarily derived.

Proceeding with the consideration of the subdivision of the Protozoa into
subordinate classes and orders, it has been further found, in association with
the investigations above referred to, that the older and primary groups of
the Rhizopoda and Infusoria, or of the Myxopoda and Mastigopoda, as
more recently proposed, by no means allow of as clear and natural a
grouping of their various orders as it is possible to submit, while it is still
less efficacious for the indication of the many complex affinities that
undoubtedly subsist between one and another, or, as it is often found,

D

34 THE SUB-KINGDOM PROTOZOA.

between one and many of these orders. The inadequacy of the several
systems hitherto proposed for the fulfilment of these last-named require-
ments, as also an outline of one closely corresponding with that here
introduced, were respectively recognized and provided for by the author
in association with the paper entitled ' A Monograph of the Gymnozoidal
Discostomatous Flagellata, with a Proposed New Scheme of Classification
of the Protozoa/ communicated to the Linnaean Society on the 2ist of
June, 1877, and referred to at some length in the 'Annals and Magazine of
Natural History' for January 1878.* In accordance with the scheme then
proposed, and as now submitted in its more extended form with certain
amendments, the fundamental basis upon which the subdivision of the
Protozoa into primary groups or sections is founded, bears relation not so
much to the varied character of the locomotive or prehensile appendages
possessed by the representatives of this sub-kingdom as to the nature of
the oral apparatus or systems subordinated to the function of food-
ingestion. Comparing small things with great, this morphological element
yields indeed as convenient and sound a basis for taxinomical diagnosis as
is afforded by the oral systems of the higher Invertebrata or the dental
formulae of the mammalian class.

Following out this newly proposed plan of subdivision, it will be found
that the entire series of the sub-kingdom Protozoa range themselves into
four natural and readily distinguished groups or sections. In the first,
most lowly organized, and with reference to its subordinate subdivisions or
orders most numerically abundant of these several groups, an oral orifice
in the literal sense of the term has no existence, food being incepted
indifferently at any point of the periphery or general surface of the body.
This most simple or elementary type of structure of the Protozoa is best
illustrated by such familiar examples as A mceba and Actinophrys, the various
representatives of the Foraminifera, and certain Flagellata such as Spumella
and Anthophysa. For the distinction of these most simply organized forms,
characterized by the indefinite or generally diffused character of their oral
or introceptive area, the divisional title of the PANTOSTOMATA is here
adopted in place of that of the Holostomata originally proposed in the
earlier communications by the present author as above mentioned. This
latter term, while scarcely conveying the sense intended, possesses the
disadvantage of having been previously employed for the distinction of a
group of the Mollusca. Next in the ascending scale a group of the
Protozoa is met with, in which though differentiation has not proceeded
so far as to arrive at the constitution of a distinct oral aperture, the
inception of food-substances is limited to a discoidal area occupying the
anterior extremity of the body, and is associated with the special food-
arresting apparatus described in detail later on. To this section of the
Protozoa are naturally relegated all the minute collar-bearing flagellate
animalcules first discovered by Professor H. James-Clark, of which so

* Mr. Saville Kent, " Observations upon Professor Ernst Haeckel's Group of the Physemaria
and on the Affinities of the Sponges."

PRIMARY SUBDIVISIONS— A UTHOKS S YSTEM. 3 5

many new species are figured and described in this volume, and also the
entire assemblage of the sponges or Porifera. For this group, and with
reference to the characteristic discoidal configuration of the introceptive
area, the title of the DiSGOSTOMATA, as previously proposed, is still retained.
In the third section of the Protozoa, as here defined, the highest degree of
organization is arrived at. Here alone, and for the first time, a single
simple or often highly differentiated oral aperture or true mouth is met
with, for which reason the group appropriately commands the title of the
EUSTOMATA. Associated with this section are found the majority of those
organisms that collectively constitute the class Infusoria in the more
modern acceptation of the term, it embracing the majority of the Ciliata,
the Cilio-Flagellata, and such Flagellata as Euglena and Chilomonas,
in which the presence of a distinct and circumscribed oral aperture has
been clearly demonstrated. With the fourth and remaining natural Pro-
tozoic section, the oral or inceptive apparatus exhibits a remarkable and
highly characteristic structural modification. This is not, as in the pre-
ceding groups, restricted to a definite area, nor is it associated indefinitely
with the entire general surface of the creature's body. In place of this, a
variable and usually considerable number of flexible retractile tentacle-like
organs radiate from diverse irregularly disposed or definite regions of the
periphery, each of which subserves as a tubular sucking-mouth, or for the
purposes of grasping food. The representatives of this section, including
the so-called suctorial animalcules of Claparede and Lachmann, or Tenta-
culifera of Professor Huxley, may be literally described as many-mouthed,
and appropriately designated the POLYSTOMATA.

A tabular view of these four sections of the Protozoa as above defined,
with their included classes, orders, and characteristic genera, is herewith
annexed. Upon examining this table it will be apparent that the
secondary subdivisions or classes of the Protozoa, as therein defined, by
no means coincide precisely with those more comprehensive and funda-
mental sections or groups into which the sub-kingdom may, as just
proposed, be primarily divided. Thus, within the section of the Panto-
stomata are found comprised the whole of the class Rhizopoda, and a
portion only of the Flagellata. The remainder of this last-named class
falls partly within the section of the Discostomata, which so far as known
includes Flagelliferous Protozoa only, and partly within the more highly
differentiated group of the Eustomata ; while within the boundaries of the
latter section are included, in addition to the Stomatode Flagellata, the
entire class of the Ciliata. It is in point of fact altogether impossible in
any such arbitrary and necessarily artificial, lineally arranged table to
adequately and intelligibly illustrate the innumerable cross-relationships
or lines of evolution that undoubtedly connect these various orders and
classes with one another. The special diagrammatic scheme given on the
page succeeding that of the tabular view, has therefore been constructed
by the writer with the purpose of as far as possible indicating, with the
following explanation, the more obvious of these affinities : —

D 2

THE SUB-KINGDOM PROTOZOA.

TABULAR VIEW OF THE SECTIONS, CLASSES, ORDERS, AND TYPICAL GEM.K A
OF THE SUB-KINGDOM PROTOZOA.

Sections.

A.

PANTOSTOMATA.

Ingestive area diffuse.

B.

DISCOSTOMATA.
Ingestive area discoidal,
not constituting a dis-
tinct mouth.

C.

EUSTOMATA.

Ingestive area taking

the form of a single

distinct mouth.

D.

and multiple.

Classes. Orders.

Genera.

I. Amoebina

. . Amccba.

2. Gregarinida

. . Grcgariiia.

I. RHIZOPODA.
Appendages pseudo-
podic, lobate or
radiate.

3. Arcellinida
4. Foraminifera

.. Gromia, Arcella.
.. Rotalia, Nummulina.

5. Labyrinthulida ..

. . Labyrinthula.

6. Radiolaria

. . Actinophrys, Collosphara.

f 7. Mycetozoa

.. j£thalium, Didymhim.

8. Trypanosomata . .

. . Trypanosoma.

9. Rhizo-Flagellata

. . Mastigamceba, Podostoma.

10. Radio-Flagellata

. . Aclinomonas, Eueliitonia.

II. FLAGELLATA.

II. Flagellata-Pantostomata

.. Spumella, Anthophysa.

Appendages <
flagelliform.

12. Choano-Flagellata .. ..iCodosiga, Salping&ca,
(vel Discostomata-Gymnozoida) I Protospongia.

13. Spongida

.. iHalisarca, Graittia,

*

(vel Discostomata-Cryptozoida) \ Spongilla.

/

14. Flagellata-Eustomata

.. Euglena, Noctihtca.

ki5. Cilio-Flagellata

.. PeridiniumtHeteromastix.

/1 6. Holotricha..

. . Paramecium.

III. C I LI AT A.

Appendages ciliate.

17. Heterotricha
1 8. Hypotricha

.. Stentor, Spirostomum.
.. Euplotes, Oxytricha.

\

^19. Peritricha

.. Vortuella, Ophrydium.

(IV. TENTACULIFERA. ( 20. Actinaria
Appendages
tentaculate. ( 21. Suctoria

.. Ephelota.
., Acineta, Dendrosoma.

AUTHORS PHYLOGENETIC SCHEME.

37

DIAGRAMMATIC SCHEME : — SHOWING RELATIONSHIPS, AND PRESUMED
PHYLOGENY, OR LINES OF EVOLUTION, OF SECTIONS, CLASSES, AND
ORDERS OF THE SUB-KINGDOM PROTOZOA.

JHTSTQJMiSM.

38 THE SUB-KINGDOM PROTOZOA.

Referring to the foregoing diagrammatic scheme, it will be observed that
the four primary sections of the PANTOSTOMATA, DISCOSTOMATA, POLY-
STOMATA, and EUSTOMATA, including their more important classes and
orders as embodied in the preceding table, are circumscribed by a broader
and double circular line. Making use of a convenient metaphor, these
circular sections with their varied contents may be compared to so many
planetary systems or constellations, all derivable from one common centre
and indicating at the points where their peripheries are made to intersect,
their mutual relationship to, and interdependence on each other. The centre
of the entire series and common source from whence, through the process of
evolution, all the various types, orders, and classes of the Protozoa have
probably through a more or less extensive epoch of time developed, is
undoubtedly to be found among the most simply organized Pantostomata,
finding there its typical embodiment in the amoeban order, the hypothetic
primeval ancestor of which may, for convenience' sake, appropriately
receive the generic name of Protamceba. Accepting this last-named
generic type as the common basis for departure, the dotted lines radiating
outwards from it exhibit, so far as it is possible to predicate, the various
directions apparently traversed by the several phylogenetic lines or tracks
of evolution before their arrival at the more complex and outlying
members of the series. Selecting that phylogenetic line connecting the
central or amoeban group with the most highly differentiated Eustomata
typified by the class Ciliata, as a first example in illustration of this
proposed scheme, the following explanation may be submitted. The
first cycle of development in this direction, exhibiting a transition from
the Rhizopodal or Myxopodous towards the Flagelliform or Mastigopodous
structural type, is evidently embodied in the group or order of the
Trypanosomata. An Amceba flapping through the water, or other in-
habited fluid, through the medium of a flattened, crest-like and undu-
lating extension of its lateral margin, constitutes to all intents and pur-
poses a representative Trypanosoma. Although among the few known
members of this series a flagellate appendage is not as yet perfectly
developed, such organ may be said to exist in its most pristine and
rudimentary condition in the tag-like prolongation of one extremity of
the body that constitutes so important a characteristic of the species
Trypanosoma sanguinis, as more recently figured by Professor E. Ray
Lankester, and reproduced in PI. I. Figs. I and 2 of this volume.
The lateral crest-like* extension which represents the most prominent
characteristic of this order, carries with it an equally, if not still more
important significance. A similar structure associated with the title of an
undulating crest or membrane, is constantly recurring among the more
Jiighly organized groups of both the Flagellate and Ciliate Protozoa, and
undoubtedly takes its origin from this source. As illustrations in this
direction, reference may be made to the supplementary undulating mem-
branes that form a permanent characteristic of certain species of the genera
Trichonwnas, Hexamita, and Conchonema, among the Flagellata ; and of

FLA CELL A TA -PA NTOS TO MA TA ; FLA CELL A TA-EUS TO MA TA. 39

Lembtis, Condylostoma, and Spirochona, among the Ciliate class of the
Protozoa. Furthermore, as recorded by the author in the systematic
portion of this treatise, the characteristic adoral fringe of certain higher
Ciliata, such as Stentor and Euplotes, is developed through the splitting
up of a similar primary undulating membrane.

In the next cycle of advance, as exemplified in the order of the Rhizo-
Flagellata, the several genera, Mastigamceba, Rhizomonas, and Podostoma,
while retaining the general characteristics of repent or floating Amoeba,
have superadded a distinct flagellum, and undoubtedly constitute the root-
forms of several leading sections of the Protozoa hereafter referred to.
The retraction of the pseudopodic processes of the Rhizo-Flagellata, with
the retention of the flagellum and capacity to incept food at any point
of the periphery, is alone required to perfect the passage to the next
succeeding order, that of Flagellata-Pantostomata. In this group we find
a considerable diversity in the number and character of the flagellate
appendages, this organ being single in such simple types as Monas and
Bodo, double in Spumella and A nthophysa, while in others such as Tetramitus,
Hexamita, and Lophomonas, the number is very considerably increased. It
is among the Polymastigous section of this order, somewhere near Lopho-
monas, that the remarkable compound marine type Magosphtzra planula,
PI. I. Figs. 12-17, upon which Professor Haeckel has proposed to found a
new class group entitled the Catallacta, should apparently be placed. A
special feature of Magospkcera, as described by Haeckel, is exhibited by
its tendency to revert to a repent amoeboid phase pending the process
of encystment and reproduction. A similar disposition is, however, as
hereafter shown, shared by the majority of the Pantostomata.

In proceeding to the next group or order in the direct line of evolu-
tion, the boundary line that circumscribes the class of the Pantostomata is
necessarily traversed, and the associated forms, while still characterized
by the possession of one or more flagellate appendages, exhibit their
higher grade of organization through the development of a well-defined
oral aperture. This order, upon which is here conferred the title of the
Flagellata-Eustomata, embraces among its more familiar genera the types
Euglena, Astasia, Noctiluca, and Anisonema. The interesting order of the
Cilio-Flagellata, including chiefly the Peridiniidae and a few aberrant
forms such as Heteromastix and Mallomonas, are alone wanting to make
the phylogenetic line from Amoeba to the most highly specialized class
of the Protozoa, that of the typical Ciliata, entirety complete. Arriving
at the termination of this evolutionary line or phylum, it is requisite
to make a passing reference only to the group of the Opalinidae, which,
although possessing no oral aperture, are plainly retrograde forms of
Holotrichous Ciliata, exhibiting, by reason of their endoparasitic habits, a.
similar loss of this otherwise essential organ of nutrition as obtains in
the corresponding parasitic Cestoidea among the Annelidous, or the
Rhizocephala among the Crustaceous sections of the Invertebrata.

Returning once more to the Amcebina, and following out the line that

40 THE SUB-KINGDOM PROTOZOA.

terminates in the Tentaculifera, the first important divergence from the
preceding track is encountered on arriving at the newly instituted order of
the Radio-Flagellata. This small group, to which at present are referred
the four genera, Actinomonas, Spongocyclia, Spongasteriscus, and Euchitonia,
may be said to retain the same relationship with respect to the ordinary
Radiolaria as subsists between the Rhizo-Flagellata and various other
orders of the Pantostomata. In the form Actinomonas, figured and
described for the first time in this volume, PI. I. Figs. 7, 8, and 18, the
permanent possession of a terminal vibratile flagellum alone distinguishes
it from a stalked Heliozoidal Radiolarian such as Actinolophus in its naked
phase, and with which type it was presumed at first sight to be identical.
Inversely, it needs only the withdrawal of the radiating pseudopodia, with
the retention of the flagellum, to produce the Pantostomatous Flagellate
genus Oikomonas. The primary derivation of the entire Radiolarian order
from the Flagelliferous section of the Pantostomata is clearly indicated in
association with the embryonic conditions of its representatives, and all of
which, so far as at present known, exhibit a Pantostomatous Flagellate
structure. The direct metamorphosis of such a simple flagellate zooid
into the Radiolarian type Actinophrys, as recently observed by the author,
will be found recorded in the systematic description of the Radio-Flagellata,
and is illustrated at PI. I. Figs. 9-11.

The passage from the extensive group of the Radiolaria with its sub-
sections of the Heliozoa, Monocyttaria, and Polycyttaria, onward to the
Tentaculifera, appears at first sight to be somewhat obscure. As shown,
however, in the chapter devoted specially to their description, the Tenta-
culifera, as now known, form among themselves two natural subordinate
groups or orders : the one, that of the Suctoria, being distinguished by the
sucker-like form and function of the radiating tentacles ; while in the other,
that of the Actinaria, these appendages closely resemble ordinary pseudo-
podia, being simply adhesive, and in some instances, e. g. Ephelota, invertile.
The transition from the Radiolaria to the Tentaculifera is apparently
accomplished through this last-named group, such types as Zooteira
and Actinolophus on the one hand, and Ephelota and ActinocyatJnis
on the other, representing the most conspicuous connecting forms. The
Tentaculifera, in their highest phase of development, exhibit several note-
worthy peculiarities. The embryos do not, as with most Radiolaria, take a
flagelliferous or monadiform contour, but are, while mouthless, more or less
thickly ciliate. The ciliation in the different genera and species, moreover,
varies considerably, the several more important deviations in this respect
exhibiting a remarkable conformity with the three types of ciliation that
characterize the three leading orders of the ordinary Ciliata, as distinguished
by the respective titles of the Holotricha, Hypotricha, and Peritricha. On
account of this last-named circumstance, it may be reasonably inferred that
some genetic relationship subsists between the two sections of the Poly-
stomata and Eustomata, this probable affinity being indicated in the

CHOANO-FLAGELLATA; MYCETOZOA. 41

accompanying diagrammatic plan by the intersection of the circles enclosing
the respective groups. A speculation as to the possible affinities of the
Tentaculifera in a totally independent direction is recorded in the chapter
devoted more especially to the general organization of the Infusoria.

The line of evolution or phylogeny from the Amcebina to the Dis-
costomatous class of the Protozoa, remains to be traced. The direct
relationship of the highest and most complex factor in this section, that of the
Spongida, to the more simple Choano-Flagellata, as illustrated by the genera
Codosiga, Salpingcsca, and other recently discovered types, is, as explained
in Chapter V., devoted to the organization of the sponges, too obvious to
need extensive comment here. As there demonstrated, the representatives
of this last-named organic group can be regarded only as specialized,
colonial stocks of similar collar-bearing Flagellata living immersed within
a channelled and collectively exuded common gelatinous matrix or cyto-
blastema, and whose substance is more usually strengthened by calcareous
or siliceous spicula, or a network of horny matter. As demonstrated
by the present author in the chapter cited, the separate zooids or units
of both the Spongida and simpler Choano-Flagellata exhibit in their
developmental phenomena the closest possible affinity. These originate
chiefly in either case from mouthless monadiform flagellate germs, thus
exhibiting their phylogenetic relationship with thePantostomatous Flagellata,
while the adult zooids revert at will to the condition of either Rhizo-
Flagellata or simple A mcebcz. In certain species of Salpingcsca, as hereafter
described, e. g. 6". ampJwridium, new zooids are shown to originate as
amcebiform gemmules separated by division from the parent animalcule,
thus completing the retracement of the line to the central or primitive
ancestral stock.

In the foregoing diagrammatic scheme the line of evolution of the
Spongida is made to abut upon or traverse the group of the Myxomycetes
or Mycetozoa. The reasons for adopting this course require brief explana-
tion. Formerly, and by some even yet regarded as a low order of fungi,
or as a special group of organisms intermediate between animals and plants,
which exhibit at one epoch of their life all the vital characteristics of the
former, and at another those of the latter kingdom, their admission into
the Protozoic galaxy or system will no doubt encounter objection. The
evidence most recently and independently eliminated by L. Cienkowski* and
Dr. A. de Bary,t concerning the structure and life-history of this most
remarkable group, establishes, however, beyond question their purely
animal nature. The Mycetozoa, in common with all ordinary representa-
tives of the Protozoa, originate from minute sporuloid bodies which escape
from the spore case as monadiform animalcules having a soft, plastic body-
substance, a single terminal flagellum, contractile vesicle, and endoplast

* L. Cienkowski, "Zur Entwickelungsgeschichte der Myxomyceten." Pnngsheim's Jahrbiicher,
Bd. iii., Hft. 2 and 3, 1862.

t A. de Bary, 'Die Mycetozoen. Ein Beitrag zur Kenntniss der Niedersten Organismen.'
Leipzig, 1864.

42 THE SUB-KINGDOM PROTOZOA.

or nucleus, being thus in no way distinguishable from the typical repre-
sentatives of the ordinary Flagellata-Pantostomata, as met with in the
genus Monas. By-and-by these monadiform zooids become more sluggish,
subside to the bottom of the inhabited fluid medium, and for a while
retaining their flagella, creep about after the manner of a Mastigam&ba,
incepting in the same way solid food-particles at any point of the periphery.
The zooids in this condition may be said to represent the adult form
of the Rhizo-Flagellata. Sooner or later the flagella are withdrawn, and
an entirely amoeboid condition is assumed. These amoeboid zooids,
encountering their fellows in the course of their wanderings, at once co-
alesce with them, and form at length by their amalgamated numbers and
increase of size through the incessant increment of food, those conspicuously
large masses of gelatinous consistence, characteristic of the so-called animal
phase of the Myxomycetan, technically known as the " plasmodium."
This plasmodium, exhibiting diverse forms in various species, may be
found creeping over wet tan, rotten wood, or decaying leaves in the
similitude of a colossal Amceba, or, taking a reticulate form, spreads
itself over the surface of these substances, and presents under such con-
ditions the aspect of the mycelia of various fungi. Examined with the
microscope, all trace of the multicellular or multizooidal origin of the
plasmodium is found to have disappeared, the entire mass exhibiting the
character of homogeneous granular sarcode. A greater or less number
of rhythmically pulsating contractile vesicles are discernible at various
points, and a distinct circulatory motion or cyclosis of the granular
plasma, sometimes in a single and sometimes in contrary directions,
is exhibited within the deeper substance of the plasmodium. This
phenomenon of cyclosis is most readily observed in those forms, like
Didymium serpula, in which the plasmodium assumes a reticulate or
much ramified mycelium-like outline, the motile currents of sarcode
under such conditions closely corresponding with those common to the
pseudopodic reticulations and ramifications of the Foraminifera and
Labyrinthulina. Following upon the plasmodium state, the highly charac-
teristic so-called vegetable phase is now arrived at. In this condition
animal vitality is apparently entirely suspended, the aspect being usually
that of a minute Gasteromycetous fungus, mostly stalked, and with a
spheroidal, ovate, or urn-shaped capitulum or sporangium. The outer wall
of this capitulum is more or less coriaceous, and is found interiorly to be
densely packed with spore-like bodies, mostly held together by a dense
network of delicate anastomosing fibres of a horn-like consistence. By
the dehiscence of a cup-like lid or the disintegration of the walls of the
sporangium, the contained spores are eventually liberated and repeat the
metamorphoses just described. It is upon the external likeness to certain
fungi of the quiescent sporangia of the Myxomycetes, as developed from
the plasmodium, that the arguments in favour of the vegetable nature
of these singular organisms have been chiefly based.

MYCETOZOAj LABYRINTHULIDA. 43

From the foregoing brief recapitulation of the developmental history of
this group it is evident, however, that we have here a quiescent or resting
phase preceding sporular reproduction corresponding on a compound and
enlarged scale with the simple encapsuled or sporocyst state of the more
ordinary Protozoa known as encystment. In both the formation of the
gigantic compound plasmodium and in the development therefrom of the
characteristic sporangia, these Myxomycetes exhibit certain phenomena
singularly suggestive of a more or less remote affinity with the sponges.
In these latter also the initial term takes the form of spore-developed
uniflagellate monads, which, uniting in social colonies, form a gelatinous
mass corresponding closely with the plasmodial element of the former
group. In the fine horny network usually contained with the spores within
the sporangium developed by the mature plasmodium, a substance is pro-
duced singularly resembling the fine horn-like elements or keratose fibre of
certain sponges, while, what is still more remarkable, in certain forms
spicule-like bodies composed of carbonate of lime are also developed within
the substance of the walls of the sporangium, or so-called " peridium," that
accord substantially in outline with the stellate siliceous spicula of the
Tetthyidae and other familiar sponge-groups. In illustration of the apparent
close approximation of the Mycetozoa to the Spongida and other flagellate
Protozoa, as here presumed, the lower half of Plate XI. of this volume,
with its accompanying descriptions, has been devoted to a reproduction of
some of the more characteristic figures given by de Bary and Cienkowski
in the works quoted, that would appear to substantially support the
author's views.

Two or three orders of the Protozoa, included within the section of
the Pantostomata and indicating apparently an independent derivation
from the central ancestral stock, have yet to be mentioned. That of the
Labyrinthulida, as- typified in Cienkowski's genus Labyrinthula, exhibits in
its normal and adult condition a more or less extensively ramified or reticu-
late sarcode expansion upon submerged objects, corresponding to a consi-
derable degree with the finely branched plasmodia of certain of the
Myxomycetes last described. This expansion, however, does not appear to
be derived from, or to be associated at any date of its existence with flagel-
liferous zooids, while an additional element in the form of minute ovate
or spindle-shaped bodies, travelling in the directions assumed by the
characteristic currents of circulation or cyclosis, is to be observed. In this
last-named feature the constituent sarcode exhibits a close correspondence
with that of the test-inhabiting Foraminifera, and the natural position of
the group, as indicated in the diagram, would appear to be midway between
the latter order and that of the Myxomycetes. The derivation of the
Foraminifera themselves from the Amcebina, through such types zsArcella,
Lieberkuhnia, and Gromia, is too patent to require prolonged notice. Of the
small supplementary group of the Gregarinidae, it remains to be remarked
that it exhibits a similar type of degradation or retrograde development in

44 THE SUB-KINGDOM PROTOZOA.

association with the Amoebina as is presented by the Opalinida with
relation to the normal Ciliata. All pass an endoparasitic condition within
the viscera of other animals, and derive their sustenance through the direct
imbibition or endosmosis of the juices of the selected host through their
cuticular surface.

While the foregoing sketch suffices to indicate the leading aspects and
characteristics of the Protozoic sub-kingdom generally, and to explain the
view of the derivation and affinities of the various orders adopted by the
author of this volume, a few other points demand brief attention. Among
these, reference has yet to be made to the undoubtedly close relationship
which subsists between the lowest members of the Protozoic sub-kingdom
and the unicellular members of the vegetable world, and to the opinions
maintained in this direction by recent authorities of note. The difficulty of
indicating a clear line of demarcation that shall arbitrarily separate certain
unicellular cryptogamic plants or Protophyta from the unicellular animals or
Protozoa, has long been recognized, and even at the present day cannot be
said to have obtained its final solution. It is, indeed, scarcely to be antici-
pated that any such result should be arrived at, since here, as between many
other arbitrarily defined so-called natural classes and subdivisions of the
animal and vegetable worlds, modern discovery is unceasingly revealing
the existence of intermediate forms that, filling up the pre-existing lacunae,
further demonstrate the harmonious continuity of the entire organic series.
Taxonomy, or classification, through this consideration, is necessarily reduced
to a purely empirical and constantly progressive status, to an artificial
means for the demarcation of those boundaries or landmarks most clearly
conspicuous to our appreciation, that system recommending itself most,
and having the most lasting duration, whose foundations are established
upon the most simple and natural basis.

Failing to eliminate such a natural or artificial boundary line as shall
serve to decisively mark out the apparently intersecting zones of animal
and vegetable life, one of the foremost biologists of the age, Professor
Ernst Haeckel, has elected to establish yet a third kingdom of the organic
world, to which he has relegated not only all dubious types, but also
many concerning whose animal or vegetable nature not so much as a doubt
exists. This proposed new organic kingdom, denominated by its founder
the " Protista," is, with the exception of the Ciliata, Spongida, and Ten-
taculifera, made to include all the members of the Protozoa embraced m
the previously submitted scheme, and in addition to these, the assemblage
of undoubted vegetable organisms forming the tribe of the Diatomaceae.
This attempt to cut the Gordian knot by the interpellation of a third
and intermediate kingdom, is by no means happy. Even if this latter
possessed in itself the elements of stability, the difficulty would be in no
ways lessened, but simply augmented, as there \vould be now two lines
of demarcation, one between the Protista and vegetable forms, and the
other between the Protista and the animal series, to be defined in place

GROUPS PROTISTA AND MONERA. 45

of the pre-existing single one. The Protista, however, as a group separate
from both the animal and vegetable kingdoms, has no real existence,
there not being, with the exception of the Diatomaceae, a single family or
generic type included in Haeckel's tabular view of his new kingdom that
cannot with tolerable, if not absolute certainty, be referred to the former of
these two sections.

As a subordinate group of the Protista, Professor Haeckel has further
proposed to found the class of the " Monera " for the reception of all those
types, externally corresponding with ordinary Rhizopoda and Radiolaria,
in which as yet the possession of a distinct endoplast or nucleus has
not been demonstrated, and which are consequently regarded by him as
exhibiting an essentially lower type of structure. The progress of modern
scientific discovery has, however, so curtailed the boundaries of this
supposed Moneran class, that further exploration in the same direction
bids fair to deprive its illustrious founder of all interest in it beyond
that of an empty title. Up to a very recent date the members of the
extensive and important order of the Foraminifera were presumed to exhibit
this specially simple structural type, and were in consequence relegated
by Haeckel to, and formed the most important constituent of, his class
Monera. Following Haeckel's lead, such a position among the so-called
Monera is allotted to the Foraminifera in Professor Huxley's 'Anatomy of
the Invertebrata,' though in a supplement to the same work (p. 658), the
discovery of distinct nuclei in many genera of this order by the independent
investigations of Schultze and Biitschli is alluded to as carrying with it the
necessity of their withdrawal from this position.* A similar demonstration
of the possession of nucleolar structures in the few remaining organisms
relegated to this group will not improbably result from their further careful
examination, with the assistance of the special treatment resorted to in the
case of the Foraminifera. Finally, it is altogether questionable whether the
presence or absence of a nucleus or endoplast can be accepted as furnishing
a distinct and reliable character even for specific diagnosis. This structure,
as shown at greater length in the chapter devoted to the organization of
the Infusoria, is evidently in many instances an accompaniment only of the
matured and reproductive phase.

Dismissing as entirely unnecessary and untenable, the proposed sub-
stitution by Professor Haeckel of an intervening kingdom of the Protista,
it has been elected here to fall back upon the old lines, and to indicate as
nearly as may be, the most salient features of distinction adopted, though
perhaps somewhat arbitrarily, in this volume for the separation of the
animal and vegetable series. The purpose of this treatise being the
description and exposition of the structure and life-history of those

* The presence of nucleus-like bodies in the Foraminiferal type Halyphysema Tumanowiczii,
Bwbk. (Squamulina scapula, Carter) has likewise been noted and figured by the present author in an
article on the nature and affinities of this species, published in the ' Annals and Magazine of Natural
History ' for July 1878 ; such discovery being confirmed by Professor E. Ray Lankester's subsequent
investigation of this form reported in the ' Quarterly Journal of Microscopical Science ' for October
1879.

46 THE SUB-KINGDOM PROTOZOA.

microscopic organisms only which exhibit easily recognized animal charac-
teristics, some one or more tangible clues to such facile recognition have
to be enumerated. The primary basis for such distinction here selected is,
as in the case of the landmarks enumerated for the convenient subdivision
of the Protozoic sub-kingdom itself, associated with the phenomena of nutri-
tion. Excepting in a few small aberrant groups, distinguished mostly by
their endoparasitic mode of existence, and possessing in consequence an
abnormal and retrograde type of structure, all those forms referable to the
animal section of the series, exhibit in a conspicuous and readily verified
manner, their capacity to ingest solid particles of food, and their depend-
ence upon such solid food ingestion for the growth and display of their
various vital functions. Among the more highly organized Protozoa,
a special organ of ingestion or oral aperture forms a characteristic and
permanently recognizable structural feature, while in others there is no such
special organ, the food being incepted indifferently at any part of the
periphery, the actual process of its seizure and ingestion, or the recognition
of the presence of externally derived pabula within the substance of the
parenchyma or endoplasm being in these instances requisite for the satis-
factory determination of the question. In those low-organized unicellular
plants, on the other hand, which at first sight, on account of their closely
corresponding form and motile properties are apparently indistinguishable
from their animal congeners, the act of food injection is never witnessed,
nor is its presence to be detected within their inner substance. Nutrition
here, as among the higher ranks of the vegetable kingdom, is effected by
the absorption of the requisite pabulum in a purely liquid state.

With relation to its chemical aspect, the composition of the nutrient
matter assimilated respectively by animal and vegetable organisms is found
again to be essentially distinct. All animal forms at present known are
absolutely dependent on other proteaceous, or, so to say, " ready manu-
factured" organic matter for their food supply. Plants, on the other
hand, while in a few exceptional cases, such as the so-called " insectivorous
species " and certain fungi, capable of sustaining life on similar formed
protein, manufacture this substance themselves out of the crude material
distributed in the liquid or gaseous condition in the fluids which they
imbibe. Plants thus fulfil the r61e of builders up or constructors from the
inorganic of organic materials, while animals are, without exception, the
consumers or breakers down of this same substance.

Accessory to the very important nutritive feature of distinction above
submitted, there remain yet certain other characteristics that may be cited
as of supplemental though subordinate utility in predicating the animal
or vegetable nature of a given low-typed organism. Chief among these,
and having a psychological rather than a physiological bearing upon this
question, has to be mentioned the characters afforded by the respective
modes of locomotion exercised by the separate representatives of these two
groups in a like fluid medium. It is necessarily only between the fla^ellum-

DISTINCTION BETWEEN PROTOZOA AND PROTOPHYTES. 47

bearing members of these latter, including in the plant series the indepen-
dent unicellular Protophytes, and the so-called zoospores or antherozooids of
Algae and Confervae, and in the animal one chiefly the Pantostomatous and
some Eustomatous Flagellata, that a difficulty in determination is likely to
arise. To one accustomed, however, by a long practical acquaintance with the
characteristic motions of these minute beings, there is at once recognizable a
certain, so to say, method in the manner of the locomotion associated with
the animal organism which is under no circumstances encountered in the
case of the plant. In the latter instance, citing as examples the motile
phases of Volvox, Chlamydomonas, or Protococcus, it will be found that they
swim, as it were, blindfold through the water, stumbling and striking
against their fellow forms or any other object that may be opposed
to their aimless course. In the animal types, on the contrary, as illus-
trated by a Euglena, Monas, or Heteromita, there is no such absence of
purpose in their movements ; tentative, well-controlled progress in various
directions, and intelligent deviations, or, as it were, tackings backwards or
to either side being continually displayed. Objects lying in their path are,
again, carefully passed over or avoided, similar conduct being likewise
observable in their encounter with comrades of the same or diverse species.
Under these latter conditions there is often, moreover, exhibited a distinct
appreciation of the society of their associates, this phenomenon being more
especially alluded to in connection with the two forms described hereafter
under the respective names of Heteromita ludibunda and Chloraster marina.
One other accessory character, scarcely yet, perhaps, sufficiently investi-
gated for recording as an undeviating diagnostic feature of distinction, is
connected with the presence or absence of the rhythmically expanding
and contracting space, sometimes single and sometimes multiple, situated
at various points — such position in a given specific form being invariably
definite — within the cortical substance of the organism, and designated
the contractile vesicle or vacuole. Among the representatives of the animal
series, this structure, excepting in certain Opalinidae, would appear to be
constantly present, while in vegetable forms it would seem to be as invariably
absent. From the explanation of the character and functions of this special
organ or structure given in the succeeding chapter, it is reasonable to
predicate that it is an accompaniment only of animal organization. As
there shown, this pulsating vessel is continually replenished from the fluid
element imbibed by the organism with the solid food-particles, or through
the ciliary or otherwise produced currents, the same fluid often travelling
towards and debouching into the vessel in question by well-defined canal-
like channels. According to some observers, including Stein, contractile
vesicles are common also to several undoubted plant forms, such as Volvox
and Protococcus. The closest investigation in this direction on the author's
part, and as accomplished with the aid of a magnifying power of I- or 2000
diameters — which renders these structures distinctly visible in organisms of
far more minute size — has, however, entirely failed to substantiate the

48 THE SUB-KINGDOM PROTOZOA.

presence of any such periodically contracting vesicles in the aforesaid and
other allied types, though in many of these, irregularly formed and per-
manently conspicuous vacuoles or inter-parenchymal spaces, having no
fixed location nor rhythmically contractile motions, were found to occur.
These observations having been confirmed by repeated and most careful
examination of the two generic types just named, the presence or absence
of a contractile vesicle is now definitely accepted by the author as affording
a ready means of distinguishing between unicellular animal and vegetable
organisms. In those instances in which the possession of a contractile
vesicle has been attributed to Volvox globator, as by Busk * and other inves-
tigators, it would appear probable that either Uroglena, Syncrypta, or some
other of the several Volvox-like animal organisms formed the subject of
observation.

* ' Transactions of the Microscopical Society,' p. 35, 1852.

( 49 )

CHAPTER III.

NATURE AND ORGANIZATION OF THE INFUSORIA.

PROCEEDING to the more immediate consideration of the special group or
groups of organisms that form the subject-matter of this volume, it is in the
first place scarcely requisite to observe that the title of the Infusoria as
employed from the date of its earliest introduction up to the present time
has carried with it a most wide and indeterminate meaning. Formerly
utilized for the distinction of almost every microscopically minute aquatic
organism, whether belonging to the animal or vegetable series, it is found
to embrace for the most part in its more modern application several highly
differentiated classes or sections of the sub-kingdom Protozoa, and in some
cases, even yet, organisms whose true position should undoubtedly be among
the representatives of the vegetable world. In accordance with the views
held by the present author, the Infusoria as a group, even when restricted to
forms exhibiting a decided animal organization only, scarcely possesses an
intrinsic or coherent status, embracing as it does, though incompletely,
representatives of all four of the primary natural sections of the Protozoa
that have been previously enumerated. Adapted, however, as closely as
possible to meet existing exigency, this same group or legion, as it may
be conveniently denominated, corresponds as here embodied most closely
with those three classes of the Protozoa included in the preceding tabular
view of this sub-kingdom under the titles of the Flagellata, Ciliata, and
Tentaculifera. In other words, it comprehends, with the exception of
the typical Rhizopoda and two subordinate Flagellate orders of the
Spongida and Mycetozoa, the whole of the representatives of the Protozoa.
But for the limits of space at command, the first, if not the second, of these
two last-named orders would likewise have been admitted and described
in extenso on equal terms with their associated groups ; its individual repre-
sentatives, as explained at length in Chapter V., conforming in all essential
structural and developmental details with those of that special order here
distinguished by the name of the Choano-Flagellata. From the evidence
already submitted, it is clearly apparent that the Infusoria, from whichever
point of view selected, can be regarded as irregularly gathered excerpts
only from that primary subdivision of the animal kingdom known as the
Protozoa, and that no correct estimate of the affinities nor definition of the
characters of its multitudinous representatives can be accomplished apart
from their consideration as constituent integers of this one harmonious

E

5O ORGANIZA TION OF THE INFUSORIA.

whole, as indicated in the diagrammatic plan and tabular view given in the
preceding chapter. In order to meet present requirements, it has been
found desirable, nevertheless, to institute the following definition of the
Infusoria ; this, while according as far as possible with the broader prin-
ciples of the above-named scheme, includes all, and those only, of the
numerous and exceedingly diverse forms described in this volume.

DEFINITION OF THE LEGION INFUSORIA.

Protozoa furnished in their adult condition with prehensile or locomotive appen-
dages, that take the form of cilia, flagella, or of adhesive or suctorial tentacula, but
not of simple pseudopodia; zooids essentially unicellular, free-swimming or sedentary ;
naked, encuirassed, loricate, or inhabiting a simple mucilaginous matrix ; single, or
united in colonial aggregations, in which the individual units are distinctly recog-
nizable ; not united and forming a single gelatinous plasmodium, as in the Myce-
tozoa, nor immersed within and lining the internal cavities of a complex proto-
plasmic and mostly spiculiferous or other skeleton-forming cytoblastema, as in the
Spongida, Food-substances incepted by a single distinct oral aperture, by several
distinct apertures, through a limited terminal region, or through the entire area of
the general surface of the body. Increasing by simple longitudinal or transverse
fission, by external or internal gemmation, or by division — preceded mostly by the
assumption of a quiescent or encysted state — into a greater or less number of sporular
bodies. Sexual elements, as represented by true ova or spermatozoa, entirely absent,
but two or more zooids frequently coalescing as an antecedent process to the
phenomena of spore-formation.

The annexed plan of the further subdivision of the Infusoria into its
component sections, classes, and orders is necessarily an abbreviation only
of the tabular view of the Protozoa given at page 36, supplemented in the
present instance, however, with a brief summary of the more essential
diagnostic characters.

The general Morphology, Organography, ./Etiology, Distribution, Repro-
ductive Phenomena, and all other features associated with the group of the
Infusoria as here defined may now be examined in detail, and under their
respective headings.

MORPHOLOGY.

Unicellular Nature of the Infusoria.

As implied in the definitions of the Protozoic sub-kingdom generally,
and of the Infusorial legion in particular, already submitted, any repre-
sentative zooid or individual unit of the group now under consideration
possesses according to the views supported by the author the morphological
value only of a simple cell. This interpretation, originating in its substantial
form with Carl Theodor von Siebold in the year 1845, was beyond doubt
foreshadowed many years previously by Lorenz Oken, received further
amplification at the hands of Schleiden and Schwann, and represents at the
present date the most generally accepted estimate of the organization of
the members of this class. From a very early period up to the present
time, however, there have not been wanting authorities of more or less
considerable eminence who have advocated on behalf of the Infusoria a

AUTHORS CLASSIFICATORY TABLE.

TABULAR VIEW OF THE SECTIONS, CLASSES, AND ORDERS OF THE
LEGION INFUSORIA.

Sections

A.

PANTOSTOMATA.
Oral or inceptive area dis-
tributed over the entire
cuticular surface.

B.

DISCOSTOMATA.
Inceptive area limited to
a discoidal anterior
region, but not consti-
tuting a true mouth.

c.

EUSTOMATA.
Inceptive area taking the
form of a distinct
mouth.

D.

POLYSTOMATA.

Inceptive areas distinct

and multiple.

Classes.

I. Flagellata.

Appendages
flagelliform.

Orders.

I. TRYPANOSOMATA.

RHIZO-FLAGELLATA.

RADIO.FLAGELLATA.

Flagellum rudi mentary, \
supplemented byanun->
dulating membrane . . J

Flagellum supplemented 1
by lobate pseudopodia . . I

Flagellum supplemented!
by ray-like pseudopodia j

Simply flagelliferous, no}

pseudopodic appen-> 4. FLAGELLATA-PANTOSTOMATA.
dages ........ J

Flagellum issuing fromj ^ CHOANO-FLAGELLATA

CX- (vel DISCOSTOMATA-GYMNOZOIDA)

tensile membrane

Flagellum single o\\
multiple, no auxiliary
cilia !

6. FLAGELLATA-EUSTOMATA.

II. Ciliata.

Appendages taking'
the form of cilia.

Flagellum associated witrA
more or less numerous > 7. CILIO-FLAGELLATA.
auxiliary cilia . . . . J

Cilia distributed over the"!
entire surface of the body, > 8. HOLOTRICHA.
similar in character . . J

Cilia distributed through-}
out, oral series of larger) 9. HETEROTRICHA.

Cilia usually more or lessj
diverse, confined to thel HYPOTRICHA.
ventral surface of thef
body

Cilia not generally distri-

buted, mostly limited to

ii. PERITRICHA.

III. Tentaculifera. ( Tentacles

( sive
Appendages |

tentaculate. \ Tentacles suctorial

a conspicuous circular or
spiral adoral wreath

simply adhe-1

?I2. ACTINARIA.

13. SUCTORIA.

E 2

52 ORGANIZATION OF THE INFUSORIA.

comparatively complex type of structure altogether at variance with the
foregoing unicellular conception. Enumerated in chronological order, the
first interpretation attributing a complex and multicellular structural type
to these organisms was advanced by C. G. Ehrenberg, who in the year
1830 enunciated his celebrated Polygastric theory. In accordance with
Ehrenberg's interpretation, the Infusoria, including both the simpler Flagel-
late and more highly differentiated Ciliate representatives of the series,
were, as previously stated, distinguished by the possession of a variable
number of distinct stomach-cavities, and of glandular and sensory organs
of various descriptions, the affinities of the group as a whole being deemed
by him as most nearly approximate to that of the Annelida. Founding
their arguments upon a basis altogether independent of Ehrenberg's
remarkable hypothesis, several authorities have since held the Ciliate
division of the Infusoria to exhibit similar affinities with the lower or Tur-
bellarian worms, the names of Oscar Schmidt and Diesing being most
eminently conspicuous in this direction. According to the views of the
last-named taxonomist, however, the Peritrichous group of the Ciliata
exhibited a type of structure more nearly approaching that of the Polyzoa,
Diesing's interpretation in this connection being likewise independently
maintained by the elder Agassiz. The most powerful opposition to the
unicellular nature of the Infusoria, such opposition being based upon the
supposed nearer conformance of their structure to that of the Ccelenterata
or zoophytes, is undoubtedly found in the conjoint writings of Claparede
and Lachmann. A corresponding Ccelenterate interpretation of the affinities
of this group, as illustrated more especially by the organization of the Vorti-
cellidae, has been quite recently advocated by Richard Greeff.

Among those authorities who, while contesting the unicellular nature of
the Infusoria as advocated by Von Siebold, have substituted for it no definite
and compensating alternative interpretation, may be mentioned the names
of Perty, Lieberkuhn, and to a considerable extent also Stein. The crucial
test respecting the disputed unicellular or multicellular structure of the
infusorial body is undoubtedly, however, to be found associated with the
phenomena of development. As pointed out more especially by Professor
Haeckel in his ' Morphologic der Infusorien,' published in the year 1873, the
entire life-history of an Infusorium, taken even in its most exalted grade of
development, as represented by the higher Ciliata, is an epitomization only
of the life-history of a simple cell. By the various modes of fission or
duplicative division common to all representatives of the class, the infusorial
zooid multiplies itself in a manner precisely corresponding with what obtains
in the augmentation of the ultimate elements of all cellular structures.
Again, in those more rarely observed, but still very generally occurring
phenomena of sporular or internal gemmule-production, the sporoid body
or embryo commences life as an undoubted simple cell, and retains this
same morphological simplicity for the remainder of its existence. At
no epoch of its history, from its pristine germination to its ultimate

UNICELL ULAR NA TURE. 5 3

dissolution, is there any appearance of a multicellular constitution, or in the
former instance, more especially, the formation of a distinct germinal layer
or blastoderm, the one essential feature and index of all the multicellular
animals or Metazoa. It is true nevertheless, although the circumstance
has apparently as yet attracted but little notice, that many infusorial forms
belonging both to the Ciliate and Flagellate sections of the group, exhibit
in connection with that mode of reproduction characterized by the resolution
of the primary cell or zooid into a number of sporular bodies, an aspect and
plan of organization in no ways to be distinguished from the moruloid or
primary segmental condition of the ovum of the Metazoa. Beyond this
stage, however, the analogy, or, if it exists, the homology, entirely ceases ;
for whereas, in the Infusorium or Protozoon, each segment or unicellular
component of the pseudo-morula becomes metamorphosed into a distinct
and independent being, in the Metazoon, this primary independence is
almost immediately obliterated through the recasting or reconstruction out
of the primary segmental elements, or morula, of the true multicellular
embryo with its characteristic inner and outer germinal layers or primordial
tissues. In the case of the sponges, as shown later on, and notwithstanding
the deceptiveness of external appearances, the production of similar pseudo-
morulae are associated both with the growth of the free-swimming swarm-
gemmules or so-called ciliated larvae, and also with the development in
certain types of the characteristic ciliated chambers, or, as they are more
usually designated, the ampullaceous sacs of the adult sponge.

Taking for granted that all infusorial structures possess a unicellular
morphologic value only, the very extensive range of complexity compatible
with such simple organization, as exhibited by the representatives of
the Infusoria, has now to be considered. Among the majority of the
older biologists, and with many even at the present day, the conception
of a single histologic cell, or of an independent unicellular organism, differs
widely from the one that is here advocated. With the former it was, and is,
held, firstly, that such a simple cell or unicellular organism must have a
differentiated bounding membrane, the cell-wall or primordial utricle ; and
secondly, that the same must contain a central denser and more highly
refractive mass, or nucleus, which may or may not be associated with a still
more minute segregated mass, the nucleolus. As demonstrated, however,
by the later school of biologists, and among whom Professor Haeckel's
name occupies a pre-eminent position, neither a distinct cell-wall nor
a differentiated central nucleus forms an essential or invariable element
of cell-organization, be such cell either an independent being, or unit,
or an integral constituent only of a compound tissue. In accordance
with the results of more modern investigation, the intrinsic value or
potentiality of such a cell-structure resides neither in the cell-wall nor
in the nucleus, but in the simple protein matter indifferently denomi-
nated sarcode or protoplasm, of which the cell-body is built up. With
reference to the more or less highly differentiated organization of cell-

54 ORGANIZATION OF THE INFUSORIA.

structures and single-celled organisms, Professor Haeckel has recently pro-
posed to introduce a special code of terminology. In connection with this he
confers upon all those cells, or so-called plastids, in which no nucleus or
nucleus-like structure is present, the title of simple cytodes, reserving that of
true cells for those alone in which such a structure is distinctly represented.
Both of these are again recognized by this authority as including two minor
groups of equal value, distinguished by the presence or absence of a
bounding membrane or cell-wall ; the naked and membrane-bounded
cytodes he has denominated respectively gymnocytodes and hullcytodes,
and the nucleated cells in a similar manner, Urzellen or gymnocyta, and
Hullzellen or lepocyta. This separation of the nucleated and non-nucleated
unicellular structures generally, as applied to independent unicellular or
Protozoic organisms in particular, forms the basis upon which Professor
Haeckel has, as previously stated, proposed to establish his non-nucleated
class-group of the Monera. In recognition of this same distinction, Professor
Huxley, in his 'Anatomy of the Invertebrata,' has subdivided the Protozoa
into the two groups of the Monera and Endoplastica ; the former corre-
sponding with the group of the same name as established by Haeckel,
and the latter including that remaining great majority of the Protozoa in
which an endoplastic or nucleus-like structure is distinctly visible. Such
a distinction is, nevertheless, adopted by this author as a matter only of
temporary convenience, he freely expressing his doubts as to whether it
will stand the test of extended investigation. The outcome of such research
since the publication of Professor Huxley's volume, has indeed fully
justified the characteristic caution displayed by this eminent biologist ;
several of the more important groups of the so-called Monera, including
more especially the Foraminifera, being now found to consist of nucleated
structures conforming in all essential details with that larger section of the
Protozoa from which it has been proposed to separate them. In accordance
with the opinion maintained by the author of this volume, and as already
intimated in the preceding chapter, the Monera, as a distinct class, has no
substantial claim for retention, all the representatives of the Protozoa being
held to possess a nucleus, or its equivalent, in their fully matured condition.
In their earliest and immature state this important structure, the nucleus,
is undoubtedly, however, often absent, the Protozoon, under such condi-
tions only, conforming in structure with Professor Haeckel's diagnosis
of a simple cytode or Moneron. That a unicellular animal may, on the
other hand, be entirely destitute of a differentiated bounding membrane, or
cell-wall, is abundantly evident. All such peripheral differentiation is
clearly conspicuous for its absence in the whole of that section of the
Protozoa here distinguished by the title of the Pantostomata, and in which
food-substances are incepted indifferently at any point of the periphery.
As already indicated in the preceding chapter, this simplest and homo-
geneous type of protoplasmic structure, the inseparable corollary of the
Pantostomatous organism, is found associated with by far the larger portion

UN 1C ELL ULA R NA TURE. 5 5

of the entire sum of Protozoic structures, and embraces among the Infusoria
proper, as here comprehended, no less than four out of the total of thirteen
orders that make up the series.

Although the unicellular nature of the Infusoria is here fully accepted
and maintained, it has yet to be admitted that in a considerable number of
instances such unicellularity has become somewhat obscure. This is
more especially observable among the order of the Ciliata, where we find
several representatives of the Opalinidae possessing an almost indefinite
number of nucleus-like structures, a like complexity in this respect being
also exhibited by the TracJielophyllum apiculatum of Claparede and Lach-
mann, and a few other Holotricha. Among the Hypotrichous order of the
Ciliata, the nucleus is, again, rarely single, being more usually represented
in duplicate. Other forms, such as Loxophyllum meleagris may be further
quoted as illustrative of examples in which the nucleus exhibits a condition
of modification midway between the two previously quoted series. This
frequently recurring composite character of the nucleus has been seized
upon by those who are unwilling to concede to the Infusoria the nature and
position of unicellular structures, as affording substantial evidence in support
of their objections. No single cell or unicellular organism, in their opinion,
can possess more than a single nucleus, and where there is a multiplicity of
such structures there must, they maintain, likewise be multicellularity ! As
explained more at length, however, later on, this structure, the nucleus, as
encountered among independent Protozoic organisms, presents an amount
of variation and complexity not met with in simple tissue cells, exhibit-
ing more especially in the present connection a capacity to subdivide
within, and independently of its surrounding protoplasm and peripheral
cell-wall, where such exists. The distinction in both aspect and properties
of the nucleus, as thus viewed, from its normal condition as the single
central and essential constituent of a simple tissue cell, is so obvious that
doubts have been naturally expressed as to whether the so-called nucleus
of the infusorial body can be regarded as the precise equivalent of the
structure that takes the same name in the latter instance. It has been
further elected by Professor Huxley, in face of these doubts, to confer
upon the nucleus, or its seeming equivalent as associated with Protozoic
structures, the distinctive title of the " endoplast," and which title is accepted
and for the future mainly adopted throughout this treatise.

The fundamental unicellular structure of Protozoic or infusorial
organisms is masked in a yet entirely opposite direction, the obscurity
arising in this instance from the imperfect separation of the zooids
produced through the ordinary process of duplicative division. Familiar
examples of this type of modification are afforded by the compound colo-
nies of the Flagellata AnthopJiysa and Codosiga, and various Vorticellidae,
such as Zoothamnium and Carchesium, in all of which a greater or less
number of the divided zooids remain intimately united with one another
through the continuity of their supporting pedicles. In all of these

56 ORGANIZATION OF THE INFUSORIA.

examples it is nevertheless a matter of no difficulty to recognize the vital
independence and essentially unicellular significance of each zooid produced
by the binary subdivision of its predecessor. The entire colony stock, in
either of the above-named or cognate cases, represents, in fact, the sum total
of the process of segmentation of an original single cell. The only instances
in which, so far as is at present known, there would appear to be a complete
obliteration of the boundary lines that normally separate each unicellular
element or vital area, is encountered in that singular type Dendrosoma
radians belonging to the group of the Tentaculifera. In this we find
a common repent stolon throwing up numerous trunks, which give rise
to lateral branchlets that terminate each in a fascicle of suctorial tentacles
similar to those borne by an ordinary Acineta. It can scarcely be main-
tained that we have here a simply unicellular organism ; each tentaculiferous
branchlet is without doubt the equivalent of a typical Podophrya, or Acimta
that has arisen from the longitudinal subdivision of a preceding zooid, and
with which it has remained intimately and indissolubly connected. Through
the process of imperfectly separated terminal gemmation, a somewhat
parallel compound body is produced in the allied genus Ophryodendron,
and more particularly in the new form here described under the name of
Ophryodendron tmilticapitata. The Podophrya gemmipara of Cienkowski
exhibits temporarily, during its characteristic reproductive state, a com-
pound condition closely identical with that presented by the normal phase
of the last-named species. In each of these last-named instances the
derivation of the colony stock from a single primary cell or plastid, is self-
evident, and notwithstanding the obliteration, or rather non-development,
in the case of Dendrosoma, of all boundary lines between the individual
zooids, their essential unicellular significance remains conspicuous.

INTERNAL AND EXTERNAL DIFFERENTIATION.
Cuticular Elements or Ectoplasm.

The infusorial body in its simplest type of development exhibits a
structural composition substantially corresponding with that of the lowest
organized tissue cell or plastid, as defined in a previous page. There is no
distinct bounding membrane or cell-wall, and no means of discriminating
between the soft, semifluid constituents of the interior and exterior
regions ; it is throughout, and apart from the nucleus or endoplast, one con-
tinuous mass of granular, but otherwise homogeneous and undififerentiated
protoplasm. The greater portion of the members of the several orders of
the Pantostomata must be referred to this category. In the next step of
advance, the outer or peripheral border of the protoplasmic mass, while not
assuming the character of a distinct cell-wall or so-called cuticle, presents,
as compared with the inner substance of that mass, a slightly more solid
type of composition. The somewhat denser external layer may in this
instance be conveniently denominated the " ectoplasm " and the softer inner

CUTICULAR ELEMENTS. 57

substance the " endoplasm." The possession of this slightly denser ectoplastic
in place of a distinct cuticular layer is evidenced in certain Pantostomata
and in many Eustomatous Flagellata and Discostomata, which, while
usually exhibiting a more or less characteristic normal outline, can revert
at will to a pseud-amceboid and repent state, progressing then through the
aid of variously modified pseudopodic prolongations. The possession of
a well-differentiated cuticular layer, while regarded usually as the special
attribute of the Ciliata, is common also to many Flagellata, being among
these latter most conspicuously represented in such genera as Euglena,
Anisonema, and Polytoma.

The development of a simple external or bounding membrane in
addition to an immediately subjacent firmer ectoplasm, commonly
styled under such circumstances the cortical layer, by no means, how-
ever, exhausts the cuticular organization of the Infusoria. As demon-
strated by Professor Haeckel, it is possible, among the most highly or-
ganized representatives of this class, to recognize no less than four
distinct layers or elements exterior to the soft, semifluid, central endo-
plasm, the same taking from without inwards the following plan of
construction and arrangement. Outermost of all occurs that perfectly
hyaline homogeneous layer with which the name of the true cuticle is most
appropriately associated. It represents the formed, and consequently life-
less, cell-wall of ordinary plant and animal tissues, and is as an independent
structure most readily distinguished in such a type as Vorticella, where,
in addition to forming the outer envelope of the body proper, it is con-
tinued downwards, and constitutes the external, structureless, hyaline and
elastic sheath of the characteristic retractile stalk. It is this structureless
and transparent external layer, again, which enters into the composition of
the more or less indurated dorsal shield or investing cuirass of Ettplotes and
Peridinium ; while it is out of this same element, though as a secondary
product, that we find derived the hardened cases or loricse of Vaginicola,
Tintinnus, and other Heterotricha and Peritricha. Immediately beneath
the hyaline external cuticle is encountered, without exception, throughout
that large section that takes its name from its characteristic ciliary organs,
that comparatively firm, homogeneous, highly elastic and contractile layer,
of which the cilia, or their variously modified representatives in the form of
setae, styles, or uncini, are the direct products or appendages, and which
latter necessarily perforate the external cuticle in order to be brought in
contact with the surrounding fluid. With reference to the special func-
tion of this element, Haeckel has proposed to confer upon it the title of
the ciliary layer. Beneath this last-named layer is found developed in
certain of the more highly organized Ciliata, though by no means with
a large number, that peculiar hyaline and highly contractile fibrillate
structure which fulfils for these unicellular organisms functions analogous
with those performed by the muscular tissues of the Metazoa. In
recognition of the special properties of this last-named element, it is

58 ORGANIZATION OF THE INFUSORIA.

referred to indifferently as the muscular or myophan layer, the latter
one finding most favour with Professor Haeckel. Among the types
in which this myophan layer is most conspicuously developed, may
be mentioned the genus Stentor, in which it takes the form of closely
set, longitudinally arranged, thread-like fibrillae ; Spirostomtim, in which
fibrillae of similar aspect exhibit an oblique or spiral plan of disposition ;
and Vorticella, in which it forms a finely longitudinally striate or fibrillate
sheet that invests the entire body, and is continued in a condensed and
thread-like form down the centre of the pedicle, constituting the motile
or contractile element of that structure. According to the recent investi-
gations of Ernst Zeller, the cortical layers of the various species of Opalina
are found under treatment with hydrochloric acid, as shown at PL XXVI.
Fig. 9, to consist of closely approximated oblique or longitudinally-disposed
muscle-like fibrillae, though these latter by no means possess the highly con-
tractile properties of the myophan element as represented in the preceding
forms. The fourth and remaining elemental layer to be mentioned having,
as far as is yet known, a somewhat limited distribution, is that associated
with the production of the minute rod-like bodies possessing in some
forms an apparently urticating, and in others a simply tactile property,
distinguished by the name of trichocysts. The authority last quoted
proposes to distinguish this as a separate trichocyst layer, though whether
it possesses a sound claim for such distinction is at present somewhat
doubtful, there being forms among the Flagellata, as for example the genus
Raphidomonas, in which trichocysts are abundantly represented inde-
pendently of any specially differentiated deeper cuticular layer. The genera
Paramecium, A mphileptus, Prorodon, and Nassula yield examples in which
these peculiar structures, described at length further on, may be most
advantageously examined.

Internal Elements or Endoplasm.

In the majority of the Infusoria the central substance of the body,
here denominated the endoplasm, but frequently also distinguished by
the titles of the chyme-mass or parenchyma, — though not in this latter
instance to be confounded with the similarly-named element of multicel-
lular structures, — consists of a more or less fluid, clear or granular, but
otherwise undifferentiated protoplasm. This endoplasm in most instances
maintains a persistent or inappreciably varying status, but in a few others
exhibits more or less constant molecular or circulatory motions, which in
exceptional cases, such as Paramecium bursaria, may even assume an
aspect and amount of regularity analogous in many respects to the cell-
circulation or cyclosis of certain plants. The endoplasmic element does not,
however, at all times present the simple homogeneous aspect portrayed
in the foregoing paragraph. In a few exceptional types, such as Trache-
lius ovum, and Loxodes rostrum, though still more notably in Noctihtca
and its allies, the entire substance of the internal protoplasm is so divided

EXCRETED ELEMENTS.

59

by the intercalation of variously developed vacuolar spaces as to assume
a more or less complete reticulate or network-like character. Within the
ramifications of this central network, the granular sarcode with the enclosed
food-substances may or may not exhibit more or less regular circulatory
movements, the general appearances and attendant phenomena here, as in
the instances above cited, approximating again in a marked manner to
those which may be observed in various plants. Such a composition
and associated phenomena are, as pointed out by Professor Allman in
his recent Presidential Address to the British Association (Sheffield,
1879), especially observable in those plant cells with large sap-cavities,
met with in the stinging hairs of nettles, and other vegetable hairs, the
internal lining of which projects into the enclosed sap-cavity thin proto-
plasmic strings or filaments ; these, fusing with one another in various
directions, form an irregular network, along which under a high power of
the microscope a slow current of granules may be witnessed. As rightly
observed by Professor Allman, the vegetable cell with its surrounding
wall of cellulose is comparable under such conditions in all essential points
with a closely imprisoned Rhizopod ; the likeness, however, between a
highly vacuolate infusorium and such an internally modified vegetable cell
is still more striking.*

Among the examples in which the central endoplasm has been observed
to exhibit motions other than circulatory, reference may be more especially
made to the type first described by Ehrenberg under the title of Monas
vivipara, here referred to the genus Spumella, and in which the entire body-
substance within the periphery exhibits under high magnification an active
vibratory motion of its enclosed granules that corresponds most closely
with the purely mechanical or " Brownian movements " of finely divided
inorganic particles.

Excreted Elements.

Under the above heading have to be assembled all those excreted pro-
ducts whose function it is to provide an external protective envelope for the
defence of the enclosed animalcules, and the majority of the variously
modified pedicles and other fulcra for support possessed by certain of the

* An independent observation in a similar direction has recently fallen within the author's expe-
rience, the type in question being the elegant marine diatom Isthmia eitervis. The unicellular frus-
tules of this species, collected and examined in the living state at Teignmouth, Devonshire, in July
1879, were found to exhibit an exceedingly remarkable internal structure. The characteristic olive-
brown cell-contents or endochrome was found to be collected for the most part into a more or less
extensive central spheroidal mass, from which radiating and frequently branched granular thread-
like prolongations of the same substance extended to and united with the periphery. Submitted to
high magnifying power (700 diameters) both the central mass of endochrome and its radiating pro-
longations were shown to be composed of an aggregation of minute brown ovate or spindle-shaped
corpuscles immersed in or held together by a colourless and more fluid plasma. In the radiating
and reticulate extensions from the central mass these corpuscles were sometimes quiescent, but more
often were seen travelling in slow and regular order to and fro between the centre and the periphery ;
the general aspect under these conditions corresponded so nearly with the characteristic granule
circulation of certain Foraminifera and other Rhizopoda that it was difficult to realize that it wa> a uni-
cellular plant and not a Protozoon under examination. In the most actively moving cells almost the
whole of the ovate corpuscles were deployed upon, and in motion along, the radiating filaments, while
in the most quiescent examples both filaments and corpuscles were withdrawn into the central mass.

60 ORGANIZA TION OF THE INFUSORIA.

attached or sedentary species. Among the former are necessarily included
those variable and often exceedingly beautiful vase-like or tubular structures
upon which the titles of sheaths or loricae are most usually conferred, and
likewise those investments of simple mucus subservient in a similar manner
as a dwelling house for the habitation and protection of the one or many
animalcules who are engaged in its construction. Within the category of
"excreted structures" have also most essentially to be included those
hermetically closed indurated cysts or envelopes exuded by almost every
known type of animalcule under certain uncongenial conditions, and also
very frequently as an accompaniment of the phenomena of binary division
or sporular reproduction. The excreted structures pertaining to these
last-named special purposes possessing an altogether independent signifi-
cance, they are treated of separately later on under the respective titles
of " encystment " and " sporular multiplication."

In all of the foregoing cases it is evident that the secreted structure is the
direct product of exudation or simple separation from the external layer or
ectoplasm of the contained animalcule, and is indeed in many instances
scarcely to be distinguished from the outermost or true cuticular element of
the several layers of the ectoplasm already described at length. Instances
in which the closest affinity may be said to subsist between these two
structures are afforded by, and specially referred to, in the account given
of the members of the genus Lagenophrys and of Opercularia nutans. In
its simplest form, and yet at the same time partaking of the character
of an independent exuded structure, the secreted envelope has a purely
gelatinous consistence, and corresponds essentially in nature and aspect
with the exuded mucilage that constitutes the common envelope of various
bacterial growths in the characteristic " glcea " phase of their existence, and
is similarly associated with many other low-organized plants or Phytozoa.
Instances among the higher or Ciliate group of the Infusoria, in which a
simple mucilaginous investment takes the place of an indurated sheath or
lorica, are of comparatively rare occurrence, the genera Ophrydium, Ophio-
nella, C/uztospira, and certain species of Stentor, yielding the most prominent
exceptions. Among the Flagellata such mucilaginous investments, and more
especially when pertaining to colonial or sociably aggregated types, are far
more frequent, such genera as Uroglena, Protospongia, Spongomonas, and
Phalansterium being especially noteworthy in this direction. The transition
from a simple gelatinous sheath to a comparatively hardened test or lorica
is very gradual, and is well exemplified among the members of the genus
Salpingceca, in several of which, as, for example, S. ampulla, the development
of the highly characteristic lorica from a primary simple mucilaginous exu-
dation has been attentively observed. The composition of the loricae
throughout the various orders and families of the infusorial class is found to
exhibit a very uniform character, being represented in most cases in its
matured state by a more or less brittle material, having an apparently chiti-
nous consistence. In the majority of instances these loricae are perfectly

EXCRETED ELEMENTS. 6 1

transparent, permitting a free view of their enclosed constructors, but in some
few, and notably in association with the genera Cothurnia, Vaginicola, and
their allies, the loricae assume with age a deep chestnut hue, and are more
or less completely opaque. Certain of the representatives of the foregoing
group are further distinguished by their possession of a supplementary
simple operculum or more complex valvular structure, which, upon the
withdrawal of the animalcule, closes the aperture of the lorica, and effec-
tually protects the animalcule from molestation from without. The greatest
diversity in form exhibited by the protective cases or loricae of the infuso-
rial animalcules is undoubtedly met with among the more simply organized
Flagellate section. Here we have several families, as, for example, the
Trachelomonadidae, Dinobryonidae, and Salpingaecidae, notable for the diver-
sity of contour exhibited by the domiciliary structures secreted ; those
appertaining to the one last named being particularly worthy of mention,
as including forms which vie for elegance in outline with the classic vases
and amphorae of ancient Greece. Within this family, and also in that of
the Dinobryonidae, more complex loricate types occur than among any as
yet known Ciliata, many loricse in such instances remaining united to one
another, and forming more or less extensive branching structures, highly
suggestive of the horny and chambered polyparies of the Sertularian zoo-
phytes and Polyzoa ; for these last-named aggregations of ordinary simple
loricae the distinctive title of " zoothecia " has been adopted by the author.
Although it mostly happens that the texture of the lorica is purely horn-
like or chitinous, it is sometimes found, as in Codonella, and among certain
members of the genus Tintinmis, that a more or less considerable amount
of sand-grains or other extraneous particles are incorporated within its
substance. In a still more limited series of types, e. g. the genus Dictyo-
cysta, sharing with Tintinnus a pelagic habitat, the shell or lorica is purely
siliceous, variously perforate or fenestrate, and, in the absence of its charac-
teristic occupant, is scarcely to be distinguished from the elegantly latticed
siliceous shells of certain Polycystinae. As mentioned in the account given
of that family group, there are strong grounds for suspecting that the
investing cuirass of certain pelagic Peridiniadae is likewise of a siliceous
nature.

The investing loricae of the Infusoria represent by no means the entire
sum of the structures produced by excretion. Among both the Ciliata and
Flagellata are found compound tree-like growths or " zoodendria," that
exhibit a highly complex type of organization. Reference is more especially
made here to such an excreted compound pedicle as occurs in Anthophysa
vegetaus, a full account of the formation and mode of development of which
is placed on record in connection with the account given of that species.
In this particular type it was shown by experiment that the ramifying
supporting stalk is built up by excretion, from the posterior region of the
associated animalcules, of the residual particles of the substances first in-
cepted for nutrient purposes mingled with some amount of cohesive mucus,

62 ORGANIZATION OF THE INFUSORIA.

or so altered by deglutition as to present a homogeneous, horn-like con-
sistence ; each fine longtitudinal stria recognizable in the branching stalk
under normal conditions, indicating, again, the integral portion contributed
towards the formation of the whole by the separate members of the
terminal uvella-like colony. In certain other recently discovered forms,
as, for example, Stein's new genera Rhipidodendron and Cladomonas, a more
or less extensively branching tubular structure or " zooaulon " is built up,
into the composition of which, in the first-named genus more especially,
many hundred tubules not unfrequently enter. Each of these separate
tubules represents in either case the excreted product of the single animal-
cule or zooid which is found occupying its distal extremity, and which is
undoubtedly formed in a manner corresponding closely with that of the
pedicle of Anthophysa, though in this instance the excretion of digested
particles and mucus takes place throughout the greater portion of the area
of the periphery, instead of being limited only to the posterior region of
the body.

Encystment.

The phenomenon of encystment or cyst-development, briefly referred
to in a preceding page, represents so important a factor in the life-history
of the infusorial animalcules as to demand separate and extended notice.
As there intimated, this encysting process is found to exhibit many dis-
tinct and independent phases. In the first, and most general of these,
encystment may be defined as a mere conservative act resorted to by
any independent infusorium in the presence of conditions unfavourable
to its welfare, such as the change of temperature, or the drying up of the
surrounding water, or other inhabited medium. In this simply " protective
encystment," as instanced by Paramecium, Trachelius, and other free-swim-
ming types, the animalcule loses its accustomed activity, and settling down
in some chosen spot becomes, after a short duration of purely rotatory
movements, perfectly quiescent. The cilia now gradually disappear,
the animalcule at the same time contracts into a more or less perfect
spheroidal form, and exudes from its entire periphery a soft, mucilaginous
envelope, at first visible only as a delicate bounding line, but which harden-
ing by degrees assumes the nature of a transparent, membranous or shelly
capsule. Although in most instances these protective cysts present a simple
spheroidal contour and smooth homogeneous surface, several prominent
deviations are to be found. Thus in some instances this cyst or capsule
is double-walled, the exterior wall being, as shown by Auerbach in the case
of Oxytridia pellionella, soft and granular, and the inner one membranous
and elastic. In Stentor caruleus, again, the cyst (PL XXIX. Fig. 15)
is flask-shaped, and provided at its upper extremity with a close-fitting
operculum-like lid. In Euplotes charon, as shown by Stein, this same struc-
ture presents numerous longitudinally disposed, serrated, crest-like elevations,
which communicate to the capsule a somewhat melon-shaped outline. A

ENCYSTMENT. 63

corresponding type of form with certain modifications, the areas between
the longitudinal ridges being transversely striate or otherwise ornamented,
is common to the encystments of various Vorticellidae, while a somewhat
similar one, having the elevated crests transversely placed, recurs in the
Acinete type Podophrya fixa. In many species, such as Stylonychia pustu-
lata and Pleurotricha lanceolata, the exterior surface of the spheroidal cyst
is closely studded with more or less irregular papilliform elevations. In
all these instances of simple or protective encystment, the animalcule upon
the return of favourable conditions assumes once more its normal aspect,
and, breaking through the walls of its temporary prison-house, resumes
its customary active habits. It is undoubtedly to the possession of this
simple self-protective faculty that the extensive distribution and prolonged
vitality of many infusorial forms is mainly due. Where the ponds, ditches,
or other tracts of fluid containing such animalcules become entirely dried up,
these latter run no risk of extermination. Throwing out around them their
transparent envelopes, they remain in a quiescent or torpid state until the
reappearance of the previous congenial surroundings, or, taken up by the
passing breeze, are wafted away in the form of dust until conditions are
encountered corresponding sufficiently with those under which they origi-
nally flourished.

The encystment of the second order to be mentioned is of comparatively
rare occurrence, and, instead of being associated with a simple conservative
function, is an accompaniment of, or rather the prelude to, the phenomenon
of multiplication by binary division, and may for this reason be most
appropriately denominated " duplicative encystment." The preliminary
manifestations and aspect of the constructed cyst correspond essentially
with those recorded of the simply protective form ; but the animalcule
enclosed within its capsule, instead of resolving itself into a quiescent and
inert mass, divides itself by the ordinary mode of increase by transverse
fission, the two halves shortly after making their exit through the walls
of the cyst, smaller in size, but in all other respects corresponding struc-
turally with the single pre-existing zooid. Encystment of this special
type, in conjunction with other noteworthy data, has been observed by
Claparede and Lachmann of the Holotrichous form Amphileptus meleagris.
As recorded in detail later on, this animalcule is essentially predatory in
its habits, and is addicted to preying upon the stationary and defenceless
zooids of the Vorticellidan genus Epistylis, in the same manner that the
Myxopod Vampyrella feeds upon the frustules of the Diatom Gomphonema.
In a like manner also, having gorged itself to satiety, the devouring
A mphilepttis builds its cyst on the apex of the supporting stem of its latest
victim, and there undergoes the metamorphosis above described. Duplica-
tive encystment is recorded by Stein of Glaucoma scintillans, and in accord-
ance with the observations of that authority occurs also in Colpoda cucullulus,
in combination with that variety of the process next described.

The third, and remaining form of encystment to be enumerated, closely

64 ORGANIZA TION OF THE INFUSORIA.

approaches in many instances the one last mentioned, while in others it
exhibits widely distinct features. Like the preceding, it is connected with
the phenomena of reproduction, but the encysted animalcule multiplies
itself not merely by the process of binary fission, but by the subdivision of
the encapsuled mass into a greater or less number of spore-like bodies
which, after a more or less prolonged quiescent state, develop to the
parent form. This type of encystation may be most appropriately
denominated "sporular encystment," and the cyst or capsule secreted
in such instances, a " sporocyst." Details of this special mode of multi-
plication are given in the section devoted to the subject of reproduction,
and it is only requisite here to indicate one important point in which such
sporular encystment departs widely from both of the preceding kinds.
In each of these latter the cyst or capsule produced is the product of a
primarily single and independent animalcule, but in the one now alluded
to it very frequently, though not invariably happens, that such a cyst is
the product of two primarily amalgamated or conjugated zooids. In certain
cases, even, as, for example, Heteromita uncinata, as many as three or four
conjugated animalcules build up the characteristic sporocyst. This special
sporular form of encystment is, with but few exceptions, limited to the
Flagellate class of the Infusoria.

Locomotive and Prehensile Appendages.

All of the variously modified appendages possessed by the several
orders of the Infusoria, used indifferently for the purposes of locomotion or
prehension, are to be regarded as mere extensions of the body-protoplasm ;
sometimes, as in most Flagellata, they are produced directly from the ex-
ternal surface of the ectoplasm, and in others, as the Ciliata, from the deeper
or cortical layer of that element. In certain Tentaculifera the characteristic
tentacle-like appendages would seem to originate in close proximity to the
central or endoplasmic region. With the exception of the organs last
mentioned, which would appear to most nearly represent specialized modi-
fications of the pseudopodia of the Radiolaria, the transition from one to
the other of the several types of appendages borne is most distinct and
gradual. In this manner, flagella can be characterized only as isolated and
more or less elongate cilia ; while the divers forms of setse, styles, and uncini
possessed most abundantly by the Ciliate section of the series, can be regarded
as variations only, in separate directions, of similar simple cilia. Viewed
from an independent standpoint, and as is requisite for the purposes of
technical diagnosis, the term of " cilia " may be conveniently restricted to
such short, slender, vibratile appendages as constitute the ordinary loco-
motive organs of a Paramecium, or the more or less convolute adoral ciliary
wreath of a Vorticella. With the name of "setae" are to be associated the
slender, hair- like, more or less flexible but non- vibratile appendages that
clothe the entire body of a Pleuronema, that are developed girdle-wise, and
fulfil a special leaping function in the genus Halteria, or that in an isolated

LOCOMOTIVE AND PREHENSILE APPENDAGES, 65

form constitute a hair-like caudal termination in the genera Uronema and
Urotricha. " Styles " and "stylate appendages," differing from the organs
referred to the last-named category in their greater comparative bulk and
thickness, are most abundantly represented among the Hypotrichous sub-
order of the Ciliata, being developed in well-defined groups or series on the
ventral aspect of such genera as Oxytricha and Stylonychia, and being
represented as a single terminal caudal style among the members of the
family Dysteriadae. Of uncini, which also occur chiefly among the
Oxytrichidae, it may be said that, except for their usually shorter and
curved or claw-like shape, they coincide entirely in character and function
with the ordinary stylate structures, and act in combination with them as
most efficient ambulatory organs. It is undoubtedly among the members
of this family group that the cilia attain their highest and most luxuriant
development, in many species all of the four typical variations of these
appendages being borne by a single individual. Here, too, in certain
species, such as Stylonychia pustulata, S. mytilus, and Euplotes patella,
we find the styles and setae departing altogether from their ordinarily
simple character, and assuming a more or less branched and often elegantly
feathered or fimbriate character. Furthermore, as recently pointed out by
Sterki, the adoral series of cilia among these Infusoria differ considerably
from vibratile cilia of the ordinary type. These modified cilia are much
flattened or compressed, and appropriately receive from him the distinc-
tive title of " membranellae."

In addition to the cilia and their various modifications as above enume-
rated, there have to be included in the list of locomotive and prehensile
appendages now under consideration, the diverse forms of membranes,
some vibratory or undulating and others quiescent, which, either as isolated
structures or in combination with cilia or flagella, compass or assist in com-
passing the objects more usually relegated exclusively to one or other of
these last-named structures. As has been previously submitted (see p. 38),
an undulating membrane may be regarded from a developmental aspect as
the root or primal form only of the adoral fringe of cilia ; in certain other
directions, however, it develops an entirely independent type of structure.
Commencing with the lowly organized Trypanosomata, where it is found
to constitute the sole organ of progression, it makes its next appearance
as a supplementary locomotive organ in the Flagellate genera Trichomonas
and certain species of Hexamita. By far the most remarkable development
of a membraniform appendage in connection with the Flagellate section of
the Infusoria, is undoubtedly represented by the singular infundibular mem-
branous expansion or "collar," with its characteristic circulating currents,
distinctive of the order here distinguished by the title of the Choano-
Flagellata, and met with elsewhere throughout the entire organic series
only in association with the class Spongida, whose intimate relationship
with these Flagellata is thus indubitably established. The marvellous
mechanism of this collar-like membrane, and its utility in combination with

F

66 ORGANIZATION OF THE INFUSORIA.

the centrally enclosed flagellum as a most efficient snare for the capture of
food-substances, will be found fully discussed in the systematic description
of this special group. Among the Ciliata, an equal or even greater vari-
ation in the form and functions of their membraniform appendages may
be enumerated. In one remarkable type, Torquatella, referred, however,
with some diffidence to the Ciliata, a terminal frill or collar-like expansile
and contractile membrane represents the only organ of locomotion and
prehension. In Pleuronema, Uronema, and Baonidium, a delicate hood-
shaped membrane is let down in front of the mouth when the animalcule
is feeding, forming thus a bag-like trap, into which food-particles are
swept by the adoral ciliary currents. In Lembus and Proboscella the same
purpose is accomplished by the assistance of a more or less prolonged
crest-like membrane, which is produced from the anterior extremity
alongside of the adoral groove to the ventrally located oral aperture. As
a supplementary element to the ordinary adoral fringe of cilia, a band-like
undulating membrane is of constant occurrence in association with the
Heterotrichous and Hypotrichous genera, Condylostoma, Blepharisma, Ony-
chodromus, and Stylonychia, while in Euplotes patella, and in various species
of the genus Stentor, the adoral fringe itself commences its existence as a
similar simple band-like membrane. In the Holotrichous family of the
Ophryoglenidae, again, embracing some dozen genera, all of the members
are characterized by the possession of a small flap or clapper-like mem-
brane, which is enclosed within, or projects to a less or greater distance
beyond the oral fossa.

It is obvious that the locomotive and prehensile appendages of the
Tentaculifera, including Acineta and its allies, depart widely in form and
function from those pertaining to the more ordinary Ciliate and Flagellate
groups, approaching more nearly in this respect the pseudopodia of the
Radiolaria. This affinity is more especially apparent in such types as
Ephelota trold and Hemiophrya gemmipara, in the former of which none,
and in the latter a portion only, of the tentacle-like organs exhibit the more
frequent tubular and suctorial character, being simply prehensile, and in
some instances invertile. In the genus OpJiryodendron the single or several
extensile proboscidiform tentacula, with their associated terminal fibrillae,
exhibit a complex type of structure whose true significance yet requires
elucidation. Notwithstanding, however, the humble Radiolarian affinities
apparently indicated by the most simply organized members of this group,
it has yet to be borne in mind that the embryonic forms of all the species,
as yet investigated, are more or less completely clothed with fine vibra-
tile cilia, a circumstance which would seem to betoken an adult type of
organization in advance even of that possessed by the permanently ciliate
group usually accepted as representing the highest section of the Protozoic
sub-kingdom. The more important bearings of the organization of the
Tentaculifera in this connection will be again referred to.

ORAL APERTURE. 67

Oral Aperture or Cytostome.

It is necessarily only in connection with the members of the Eusto-
matous section of the Infusoria, including the three orders of the Flagellata-
Eustomata, Cilio-Flagellata, and Ciliata, that a true oral aperture — or, as
Haeckel designates it in contradistinction to the oral opening of the multi-
cellular animals, a " cytostome " — is met with, food-substances in the
remaining sections being incepted indifferently over the whole or a more
or less widely dispersed area of the peripheral surface. Where, as above
indicated, such a distinct oral aperture is represented, a considerable amount
of variation is found to subsist with relation to its contour and associated
structure. With the great majority, the oral aperture takes the form only
of a simple orifice, or of a tubular passage, through which direct inter-
communication is established between the surrounding medium and the
inner or deeper endoplasmic region of the animalcule's body. Most
frequently this oral aperture is permanently conspicuous, but not un-
frequently, as in the genera Dinomonas and Trichoda, it happens that this
structure is to be detected only at the moment when food is being swal-
lowed, its lateral walls at all other times closing so completely upon each
other as to leave no passage visible. As might be anticipated, when the
walls of the oral passage are loose and elastic, as in the above-named types,
this orifice is capable of great distension, the food mass devoured being
frequently but little inferior in size to the body of its captor. The first
manifestation of a complex organization in connection with the oral aper-
ture is indicated by a simple thickening or induration of the lining wall ;
this thickening in certain types, such as TracJielophylhim apiculatum, takes
the form of well-developed longitudinal rugae, while in others, such as
Chilomonas paraineciuin> this region has been lately shown by Biitschli to
be both longitudinally and transversely plicate. Among the majority of
the Dysteriadae, as also in association with many of the Prorodontidae,
a distinct corneous tube, that may be isolated from the surrounding body-
plasma, is substituted for the simple indurated oral passage characteristic
of the last-named series ; this structural type leads again directly to that
considerable assemblage of forms in which, in place of such a simple
corneous tube, a tubular fascicle of rod-like teeth or stylets is enclosed
within, but remains at the same time capable of protrusion at will beyond,
the oral fossa, and is employed by the animalcule for the purpose of
grasping and engulphing its accustomed prey. This special type of oral
armature is, so far as it is at present known, possessed only by the Ciliate
section of the Infusoria, occurring, however, in three out of the four
leading groups or orders of this division, as represented by the genera
Prorodon and Nassula among the Holotricha, Chilodon and Phascolodon
among the Hypotricha, and apparently in the solitary case of Polykrikos in
the group of the Peritricha.

F 2

68 ORGANIZATION OF THE INFUSORIA.

The most remarkable type of oral armature possessed by the series of
organisms now under consideration is, undoubtedly, met with in the Dystcria
armata of Professor Huxley, in which the simple corneous tube or tubular
rod-fascicle of its nearest associates is, as fully recorded in the description
given of this specific form, replaced by a series of corneous plates and
styles of such diverse and complex character that considerable doubt was
entertained at the date of its discovery as to whether the organism might
not be more correctly relegated to the section of the Rotifera. Following
upon the oral aperture, it not unfrequently happens that a secondary tubular
passage, conveniently though incorrectly termed the " pharynx " — it being in
no way homologous with that structure as developed in Metazoic organisms
— penetrates still deeper into the substance of the central endoplasm,
and serves as a channel for the conduct of incepted food-substances to this
region. An example of such a prolonged pharyngeal passage, its distal
termination at the same time exhibiting a somewhat remarkable hook-like
curvature, characterizes Cohn's genus Helicostomum. In many instances,
such as Climacostomum and the type last named, this pharyngeal prolonga-
tion is entirely smooth throughout, while in others, such as Nyctotherus and
Metopus, it is more or less distinctly ciliate. The most complex form of
oral and pharyngeal organization is, however, met with in certain of the
Peritrichous representatives of the Ciliata. Here, as demonstrated by Greeff,
more especially in the cases of Epistylis flavicans d&&plicatilist the prolonged
and thickly ciliated pharynx is followed by an almost equally long but
exceedingly slender and non-ciliate tubular canal, or so-called " oesophagus,"
whose distal termination is suspended freely in the central fluid endo-
plasm. At the point of junction of the pharynx with the above narrower
canal-like prolongation this latter structure exhibits a peculiar bulb-like
dilatation into which the food-particles fall after their passage through
the wider superior portion, and are there moulded into the characteristic
pellet-like masses which are to be seen regurgitating through the sub-
stance of the body. The foregoing type of oral and cesophageal organization
has been recently shown by Wrzesniowski to obtain in Ophrydium versatile,
and is apparently common to all the members of the Vorticellidan family.
In the genus Didinium, the inner lining of the oral region can be protruded
to a considerable distance, after the manner of a proboscis, for the purpose
of food-capture ; a like, though somewhat less pronounced, structural
modification is met with in Mesodinitim.

Anal Aperture or Cytopyge.

The results of recent investigation have tended to demonstrate that a
distinct anal aperture, or as Haeckel denominates it the "cytopyge," for
the discharge of faecal substances, exists in at least all of the Eustomatous
section of the Infusoria, while in not a few of the Pantostomata, such a
distinct aperture is, although not distinctly developed, most clearly fore-

CONTRACTILE VESICLES. 69

shadowed. Among these latter, reference may be made more especially
to such types as Anthophysa vegetans and Oikomonas obliquus, in both of
which the excrementitious particles are rejected at the posterior region
of the body, and are in the former instance intimately interwoven with the
substance of the branching stem. Even among the Ciliata, where this
organ attains its most pronounced development, it is, except during the
passage of rejectamenta, rarely conspicuous. An exception to the above
rule is, however, afforded by the members of the genus Nyctotherus, where
it is permanently recognizable as a posteriorly located thick-walled,
tubular passage, that penetrates to a considerable distance into the sub-
stance of the body. As pointed out by Professor Huxley, * the tract
along which the food passes in this Infusorium is so circumscribed
through the delimitation of the pharynx, anal passage, and very short
intermediate area of fine granular endosarc or endoplasm, that it may be
not inappropriately described as possessing a rudimentary intestinal canal.
In common with Nyctotherus, the anal orifice is more usually terminal or
subterminal, but may, as in Stentor or Follicularia, have a lateral location,
or as in the large group of the Vorticellidae, it may open upon the
anterior extremity in close vicinity to the oral aperture.

Contractile Vacuole or Vesicle.

In close association with the anal or excretory aperture — the functions
of which it in many instances would seem to assist in performing — has
to be described that early recognized organ, sometimes single and some-
times multiple, presenting in the generality of species the aspect of a
clear, rhythmically expanding and 'contracting spheroidal space, most
generally distinguished by the title of the " contractile vesicle." A very
considerable diversity of opinion has been, and is even yet, maintained
with relation to the true structure and function of this very important
organ. By Ehrenberg it was first described as a spermatic gland ;
Spallanzani and Dujardin attributed to it a respiratory function ; Lieber-
kuhn and Claparede and Lachmann recognized in it a rudimentary heart
or circulatory organ ; while in accordance with the views of Stein and
Oscar Schmidt, the functions discharged by it are excretory and correspond
most nearly with that of the renal organ of the higher animals, and the
excretory water-canals of the Turbellaria. As maintained more recently
by Professor Haeckel, it seems, however, most reasonable to infer that the
functions performed by the contractile vesicle of the Infusoria partake of
a twofold character, being both respiratory and excretory. One of the most
important points for consideration in the determination of the functions
of this organ, is the long-disputed question as to whether or not it main-
tains a free communication with the outer water. By the majority of
earlier and many recent writers, including among the latter Claparede
* ' Invertebrate Anatomy,' p. 105.

7<D ORGANIZATION OF THE INFUSORIA.

and Lachmann, it has been affirmed that no such intercommunication
exists, and that the organ consequently partakes of the character of a
closed vessel. Among the first to arrive at a contrary decision and to
declare that the contents of this vacuole were at the time of collapse
or "systole" discharged externally, may be mentioned the names of
Oscar Schmidt and Mr. H. J. Carter, strong confirmatory evidence in
the same direction being likewise contributed by Professor E. Ray
Lankester, in his " Remarks on Opalina and its Contractile Vesicles," pub-
lished in the 'Quarterly Microscopical Journal' for the year 1870. Since
that date testimony has been forthcoming from a variety of sources
establishing beyond question the existence of the intercommunication
above indicated, its precise pore-like character being further described and
figured by Wrzesniowski in association with the genera Enchelyodon and
Dendrocometes. In the last-named type, furthermore, a delicate tubular
canal has been found to proceed from the spheroidal vesicle and to
penetrate the thick cuticular investment. A second disputed point, almost
equal in its consequence and bearings to the preceding, was for a long while
connected with the precise structure of the contractile vesicle, and more
especially as to whether or not it possessed a distinct bounding membrane.
By Ehrenberg, Siebold, Claparede and Lachmann, and also by Mr. Carter,
the presence of such a definite wall or bounding membrane to this vesicle
has been maintained ; a contrary view, however, being advocated by Dujardin,
Perty, Stein, and the majority of recent investigators. In accordance with
the opinion of these latter, no such bounding membrane exists, the vesicle in
this respect presenting no higher structural differentiation than the various
non-contractile or irregularly contractile vacuoles or lacunae that occur so
abundantly in the protoplasmic element of both animal and vegetable
cells. The non-possession by the contractile vesicle of any bounding
membrane is now amply proved through the tendency exhibited by this
structure in certain species to split up into a variable number of minor
vesicles, which may again unite in an irregular manner with one another.
This phenomenon has been especially demonstrated by Wrzesniowski
in connection with the Holotrichous type Trachelophyllum apiculatum.
The non-occupation by the contractile vesicle of this species of a perma-
nently fixed position has likewise been elicited by this authority, he having
observed that during the discharge of faecal matter from the terminal anal
aperture the vacuole is forced backwards to a very considerable extent to
permit of its free passage.

The constant and free intercommunication of the contractile vesicle with
the outer water or other inhabited fluid medium, and the composition of
this structure as a mere rhythmical pulsating vacuole or lacuna in the
cortical layer of the ectoplasm, possessing no distinct bounding membrane,
being here accepted as fully established, further details with relation to the
functions and more prominent variations it assumes in various infusorial
types may be proceeded with. In its simplest form, and as represented

CONTRACTILE VESICLES. 71

in the majority of the Infusoria, the contractile vesicle exhibits at the
period of its fullest expansion or " diastole," a merely spheroidal contour,
and becoming entirely lost to view at the moment of collapse or " systole."
The time occupied between the consecutive pulsations of this organ is
found, under normal conditions, to present a constant average among
individuals of the same species, varying from a few seconds only in certain
forms to over sixty or even one hundred seconds in other types. Un-
doubtedly, in many cases the characters afforded by the pulsations of this
vesicle yield a useful accessory feature for specific diagnosis, and the regis-
tration of such characteristics, in connection with the technical description
of each specific form, would be of value. Passing on to the more complex
phases of this structure, reference may first be made to those types in which
the otherwise simply spheroidal contractile vesicle is supplemented with
two or more lateral sinuses or lacunae, the contents of which flow together
immediately upon the contraction or systole of the central vacuole and
assist materially in the re-expansion of this central part. An instance in
which two symmetrically bilateral accessory sinuses are combined with
a central vesicle, exhibiting in this case a broadly pyriform outline, has
been ascertained by the author to occur in Urocentrum turbo, a similar modi-
fication being likewise characteristic of the homomorphic species Calceola
(Peridiniitm] cypripedium of Professor H. James-Clark. Examples in which
a greater and variable number of similar lateral or peripheral sinuses are
found along with the central vesicle, imparting to it under certain conditions
a characteristic rosette-shaped configuration, are afforded by such forms as
Follicularia ampulla, Trachelophyllum apiculatum, and Didinium nasutum. It
is, however, in such types as Paramecium aurelia and Ophryoglena flava that
this special modification of the contractile vesicle attains its most complex
development. Here, it is found that the supplementary sinuses present a
narrower or more linear contour, and exhibit, as a consequence of their
radiate plan of disposition around the central vacuole, an elegant and highly
characteristic stellate aspect. In Paramecium there are usually from five
to seven or eight of such radiating sinuses, while in the case of OpJiryoglena,
Lieberkuhn has reported the existence of no less than thirty. Examined
carefully with the assistance of the higher powers of the microscope, it has
moreover been demonstrated by the authority last quoted, and also by
Mr. Carter, that these lateral sinuses extend as slender radiating and
frequently branching canals throughout the entire cortical layer. A still
more conspicuous canal-like system that anastomoses with a main or
central contractile vacuole, may obtain. This special type of organization,
while occurring in a considerable number of infusorial forms, is perhaps
most prominently illustrated by the various representatives of the genus
Stentor. Here, the main and spheroidal dilatation of this organ is situated a
little below the peristomal ciliary wreath, to the left hand of the ventral
aspect, and closely adjacent to the anal aperture. From this spheroidal
dilatation, as first pointed out by Lachmann, a single long and more or less

72 ORGANIZATION OF THE INFUSORIA.

tubular, canal-like diverticulum extends, inferiorly, down the left side of the
animalcule to within a short distance of the adherent foot ; while another
similar canal, departing from the superior region of the same vacuole,
extends in an annular form round the entire circumference of the peristome.
As recently demonstrated by Wrzesniowski, an almost identical configura-
tion of the contractile vesicle occurs in Ophrydium versatile, an anterior
annular canal without the posterior diverticulum obtaining also in several
other Vorticellidae. Among the numerous examples in which the contractile
vesicle takes the form of a simple lateral canal-like prolongation, exhibiting
the normal spheroidal dilatation at its point of discharge, with occasionally
one or more minor bulbous dilatations at various portions of its course,
may be mentioned more especially such genera as Spirostomum, LoxopJiyl-
lum, and Climacostomum. In a yet more considerable assemblage of species
the contractile vesicular system is remarkable for what may be denominated
its dispersed type of representation. With these, instead of presenting a
simple, well-defined centre, with perhaps one or more associated canal-
like diverticula, a variable and often indefinite number of similar indepen-
dently pulsating vacuoles are developed at various separate points. It is
thus that in Paramecimn and Panophrys two such separated pulsating
centres occur ; in Chilodon, Chlamydodon, and many Acinetidae, simple
spheroidal contractile vacuoles, varying in number from three or four
only to as many as twenty, are variously and mostly irregularly distributed
throughout the cortical substance ; while in a few rarer instances, such as
Bursaria truncatella, Trachelius ovum, and the Prorodon margaritifera of
Claparede and Lachmann, these independent contractile centres are so
abundant as to be almost past enumeration. One other characteristic
modification of the compound contractile vacuolar system is exemplified
by AmpJiileptus gigas and certain Opalinidae, in which an even serial or
linear distribution of these vesiculae is exhibited. In all the examples
above cited the animalcules named belong to the Ciliate section of the
infusorial class. A plurality of contractile centres is not unfrequently,
however, associated with the representatives of the Flagellata. Examples
in connection with this group are yielded by the important order of the
Choano-Flagellata, among whose members two or more comparatively
large posteriorly located contractile vesicles are almost invariably pre-
sented, while in certain species of Oikomonas and Anisonema, two equal-
sized and in the former case alternately pulsating vacuoles have been
observed by the present author. In Anisonema acinus and Entosiphon
sulcatum, Stein, again, has indicated in his recently published volume
that the normally single and subspheroidal contractile vesicle develops, at
diastole, lobate peripheral sinuses, which impart to the entire structure a
rosette-like aspect resembling that already referred to in connection with
various Ciliata.

Such being the most prominent external configurations of the contractile
vesicle, in both its simple and compound type of development, it yet remains

NUCLEUS OR ENDOPLAST. 73

to indicate the more important function in the economy of the infusorial
body that it may be predicated to fulfil. Beyond doubt, the leading
function of the contractile vesicular system is excretory, in the getting
rid of the comparatively vast amount of fluid constantly brought into
the body through the ciliary or other currents in combination with the
incepted food-material. As is conspicuously evident when watching the
feeding process in a Vorticella or other highly organized Infusorium, each
spheroidal pellet or isolated fragment of incepted pabulum, regurgitated
through the yielding endoplasm, is enclosed within an equal or even
more extensive mass of water, and which liquid, without some special
outlet for its discharge, would soon accumulate to an extent incompatible
with the well-being of the animalcule. In this relation, the contractile
vesicle with its tributary canaliculi and lacunae, clearly visible in certain
instances and doubtless existing in all, enacts the part of a highly ela-
borate and efficient drainage system, collecting the superabundant fluid
from every part of the body-plasma, and discharging it after its reception
into the single or several more or less spheroidal, reservoir-like centres
beyond the cuticular periphery. That the considerable quantity of water
thus brought constantly into intimate contact with the body-plasma, and as
it were circulated throughout every portion of its substance, plays an
important rdle in the reoxygenization of its molecular constituents, and thus
fulfils a rudimentary respiratory function, may be likewise consistently pre-
mised, as also that by the time this same water has circulated through the
animalcule's tissues, and has debouched into the reservoir or contractile
vesicle from which it is eventually discharged, its chemical composition has
become materially altered through both the loss of oxygen and the incre-
ment of carbonic acid and other waste material. It is possible that the pale
pink hue, mostly prevalent in the contents of the expanded vesicle, owes its
presence to such chemical reaction, and it presents at any rate a point
worthy of future investigation.

Vacuolar spaces possessing no rhythmically pulsating properties, some-
times constant in position, at others sharing in the movements of the paren-
chyma, and not unfrequently exhibiting slowly contractile motions which
terminate in their permanent obliteration, are constantly met with among
the Infusoria. In some few instances this vacuolation, as more fully related
at page 58, is developed to such an extent that the entire endoplasmic
substance presents a mere trabecular or network-like appearance. This
extreme type is especially prominent in the Flagellate group of the Nocti-
lucidae, and attains a closely parallel degree of development in the Ciliate
forms TracJielius ovum and Loxodes rostrum.

Nucleus or Endoplast, and Nucleolus or Endoplastule.

These important organs, while possessing a stronger claim for consi-
deration, perhaps, in that section specially devoted to the description of
the reproductive structures and phenomena, represent in themselves such

74 ORGANIZA TION OF THE INFUSORIA.

highly characteristic elemental factors, and exhibit among the various
members of the class such varied characters and configuration, that their
independent treatment is rendered necessary. The morphological corre-
spondence of the nucleus or endoplast, as it occurs among the simplest
and lowest organized Infusoria, with the nucleus or cytoblast of the ordinary
animal or vegetable tissue-cell, is so conspicuously obvious as to render
extended comment needless. Among the higher representatives of this
group, it, nevertheless, manifests so wide a divergence in various direc-
tions from this simple and primitive condition as to render desirable
the employment of some equally appropriate but at the same time suffi-
ciently distinctive and independent title. This widely felt desideratum
has been happily recognized and provided for by Professor Huxley, whose
recently introduced term of the " endoplast " in place of that of the nucleus
when applied to Infusoria or other Protozoic structures is, as previously
related, adopted by the author. The simplest representative type of
the infusorial endoplast, and the one which corresponds most closely with
the nucleus of the ordinary organic cell, is met with most abundantly
among the Flagellate section of the series, but is also represented in not a
few of the higher Ciliata. In this initial phase of development it exhibits
a simply spheroidal contour, and may or may not enclose a central endo-
plastule, the homologue of the histologic nucleolus. The first step towards
a departure from this primitive condition is manifested by the tendency of
the endoplast, as illustrated by the Flagellate genus Euglena and its allies,
to lose the spheroidal and to assume a more or less ovate outline. A still
more attenuate and somewhat sausage-like configuration is exhibited by the
endoplast appertaining to the Ciliate genera Balantidium and Nyctotherus,
a further element of divergence being here introduced, however, through the
fact that the endoplastule or so-called nucleolus is not contained within the
substance of the endoplast, but is adherent exteriorly to its lateral peri-
phery : this special phenomenon, entirely opposed to what obtains with
reference to the nucleolus of the ordinary tissue-cell, occurs repeatedly
among the Infusoria. The most pronounced development of the elongate
type of endoplast is found associated with the Peritrichous group of the
Vorticellidae, and where in many cases it assumes a remarkably attenuate,
ribbon-like aspect. Such a ribbon-like or almost filiform configuration of
the endoplast is more especially characteristic of the genus Ophrydiiun,
and is also represented, though in a less marked degree, in the Hetero-
trichous form Bursaria truncatclla. In intimate connection with the band-
or ribbon-like type above described, has to be enumerated that branched
variety of this structure common to many of the Suctorial Infusoria, or
Acinetidae, and also that modification of the elongate form of the endoplast,
similarly band-like in the earlier stages of its development, but which in the
mature condition of its existence exhibits a more or less uniform series of
constrictions or strangulations. In its most characteristic phase of develop-
ment, as prominently illustrated by the genera Stentor, Condylostoma, and

NUCLEUS OR ENDOPLAST. 75

Spirostomitm, these constrictions of the endoplast are so evenly developed as
to impart to it the aspect of a symmetrical moniliform or necklace-like
structure, that may be composed, as shown by Stein in the case of Spirosto-
mum ambiguum, of no less than twenty-five or thirty ovate or bead-like
segments. Although, as hereafter shown, each ovate element of this elongate
endoplast becomes ultimately separated and represents the germ or embryo
of a new zooid, any distinct separation between them is rarely recognizable
during the normal and mature condition of the animalcule, each consecutive
fragment being, for the most part, joined closely and intimately to the one
next adjacent. In occasional instances, however, it may be observed that
certain of these ovate or bead-like constituents are separated for intervals
equal to about one-half of their total length, such interval being bridged
over by a slender thread-like connecting filament. This special form of
endoplastic configuration, occurring as an exception to the evenly monili-
form type of the several last-named genera, is found to foreshadow or pre-
typify in a very feeble manner the normal and persistent characteristic of
certain other species. Special reference is made here to the endoplastic
structure demonstrated by Wrzesniowski to obtain in Loxodes rostrum
and LoxopJiyllum meleagris. Under ordinary conditions, the endoplastic
system appears to be represented in these types by a number of nodular
bodies, either ovate or spherical, distributed irregularly throughout the
cortical substance. Examining the same with the aid of reagents and the
higher powers of the microscope, it was found, however, by this author
that all of these endoplastic nodules were united to one another by a
slender and transparent connecting filament — or, as it may be conveniently
denominated, a " funiculus " — the distances between each constituent nodule,
and consequent length of the connecting thread, in the case of Loxophyllum,
often exceeding by many times the length of the nodules.

One important modification of endoplastic development, as yet unreferred
to, is presented by those species in which this special structure actually
exhibits the isolated fragmentary or multiple configuration apparently,
but not really, existing in the two last-named forms. The endoplast,
in this multiple or compound type of organization, is further found to pre-
sent as considerable a series of variation as is associated with that of the
contractile vesicle in its multiple condition previously described. Thus, in
a large series of animalcules, embracing more especially the members of the
Hypotrichous family of the Oxytrichidae, this structure is invariably repre-
sented by two elongate-ovate endoplasts, the one usually situated a little in
advance of, and the other a little posterior to, the centre line or transverse axis
of the animalcule's body. In yet a few other forms belonging to this
family group, such as the Onychodromus grandis of Stein, there are normally
four such endoplastic elements, these, however, not unfrequently being
doubled again through the redivision or fission of each component element.
From this simple manifestation of the compound endoplastic formula, every
phase of gradation is encountered, until at length, and notably in certain

76 ORGANIZATION OF THE INFUSORIA.

species of Opalina, as recently demonstrated by Engelmann and Ernst
Zeller, the number of endoplastic elements almost exceeds computation, and
takes the form of exceedingly minute spheroidal corpuscles associated with
a central endoplastule distributed everywhere throughout the substance of
the cortex. It is almost needless to remark that in each of these com-
pound phases the infusorial endoplast differs essentially from the ordinary
tissue nucleus, which is there invariably represented in its simple and
single form. By those who contest the unicellular organization of the
Infusoria, this frequent occurrence of a multiplicity of endoplastic elements
has, as previously observed, been referred to as yielding the strongest
evidence of multicellular structure. Such testimony is, however, entirely
neutralized when correlated with the fact that this element has to be
regarded as differing essentially in a variety of aspects from the nucleus
of the simple histologic cell, one of the more important of these being
its capacity to multiply indefinitely within, and independently of, the
circumambient cell-wall or its equivalent. In connection with this phenome-
non, and as more fully explained in the section devoted to the reproduc-
tive features of the class, the infusorial endoplast, in both its attenuate
band-like, and compound aspect, has to be regarded in the light of a
specialized proliferous stolon, adapted for the production under certain con-
ditions of a greater or less number of embryonic zooids, and as a supplement
to that more normal mode of increase by duplicative division or fission
which resembles the only reproductive faculty possessed by the ordinary
tissue-cell. One feature of importance presented by the infusorial endoplast
remains to be enumerated. In accordance with the results of the most recent
investigation, and in connection with which the names of Greeff and Biitschli
have especially to be mentioned, it has been demonstrated beyond question
that in its more complex form this structure is enclosed within a delicate
and hyaline bounding membrane or pellicle, which may, perhaps, be most
appropriately compared, physiologically and so far as its structureless
nature is concerned, with the similarly transparent and structureless pellicle
ensheathing the constituent elements of ordinary muscular tissue, known
as the " sarcolemma." It is apparently of this hyaline supplemental
envelope alone that the slender and transparent filamentous cords, or
funiculi, are composed that hold in union with one another the otherwise
disjointed fragments of the compound endoplast, as represented in the
genera Loxodes and Loxophyllum.

That marked disparity of aspect and significance recorded of the infu-
sorial endoplast, as compared with the ordinary histologic nucleus, is found
to extend likewise to the nucleolus or endoplastule. In all ordinary tissue-
cells this special structure is found to constitute an integral and essential
constituent of the nucleus, of which organ it presents the appearance
merely of a central, more solid, and opaque spheroidal fragment. With the
majority of the Flagellata and some few Ciliata, such as Pleiironema and its
allies, and many of the Chilodontidae, a similar contour and relationship

NUCLEOLUS OR ENDOPLASTULE. 77

with the associated nucleus or endoplast is maintained ; but among the
greater portion of the representatives of this last-named group an altogether
different plan of arrangement is found to obtain. The nucleolus or endo-
plastule is, in these, no longer immersed within the substance of the nucleus or
endoplast, but attached to its external periphery, or, it may be, completely
isolated from it. Familiar instances of such simple lateral attachment of the
endoplastule are afforded by the genera Paramecium, Balantidium, and
Nyctotherus ; this phenomenon, however, attains its most conspicuous
development among the Oxytrichidae and other Hypotricha, in which the
endoplast, as before stated, is usually represented in duplicate, and each
independent element accompanied by a sometimes adherent and sometimes
detached, minute, oval endoplastule. In Stylonychia mytilus, mostly pending
the process of multiplication by binary subdivision, two or even three endo-
plastular fragments are sometimes found associated with a single endoplastic
element. The most abnormal conditions and aspect of the endoplastule
are perhaps, however, developed in the Hypotrichous form Loxodes rostrum,
and in which, as shown by Wrzesniowski, the endoplastic system is repre-
sented by a dozen or more spheroidal elements, held in intimate union
with each other, but at distant intervals, by a connecting thread-like cord.
Within the centre of each of these spheroidal fragments a distinct central
endoplastule was made visible through the employment of reagents ; while,
in addition, a supplementary but external series of similar endoplastule-like
bodies was found attached, in some instances singly to the external surface
of the endoplast, and sometimes to the connecting cord or funiculus. In
that series of Infusoria including chiefly the Vorticellidae and Stentoridae,
in which the endoplast presents a ribbon-shaped or band-like outline,
the endoplastular element is mostly represented by scattered granular frag-
ments, one or more of which become enclosed within each of the segmental
portions into which the endoplast becomes separated during the process of
reproduction by internal gemmation, described later on. The several
interpretations concerning the true significance of the endoplastule, as
advocated by different authorities, being more fully discussed in the
section devoted to the reproductive manifestations of the class, it suffices to
add here that where this structure is developed externally to, or separate
from, the accompanying endoplast, recent investigation has not yielded
evidence in support of its fulfilling the part of a male generative organ or
testis, as hitherto generally supposed, but rather indicates that its nature
and import are essentially identical with those of the endoplast itself, and
whose place and functions it ultimately supplies.

An approximate estimate of the innumerable modifications of the
endoplast and endoplastule of the infusorial body as now enumerated may
be obtained on reference to the supplementary plate (PI. XLIX.) devoted
especially to the illustration of these and kindred structures.

78 ORGANIZATION OF THE INFUSORIA.

Colouring Matters.

Under the above denomination necessarily fall those pigmentary sub-
stances which in their diffused state impart, in many instances, a supple-
mentary characteristic and easily recognized feature of distinction, and also
those anteriorly located coloured corpuscles, of diverse size and number, so
conspicuously represented in the families of the Euglenidae and Chloro-
monadidae. To these latter structures, on account of their aspect and
position, a visual function was not unnaturally attributed by the earlier
authorities, Ehrenberg first figuring and describing them as veritable optic
organs, while at the present day they retain the title of eye-like pigment-
spots. It is now, however, generally conceded that these characteristic
structures are altogether innocent of the exalted function first assigned
them, and that their true structure and composition are merely oleaginous
or pigmentary, according essentially with the isolated coloured corpuscles
possessed by numerous undoubted unicellular plants or Protophytes. The
unessential nature of these bodies, and the entire absence from them of all
the phenomena usually exhibited by so complex and highly organized a
structure as an eye, is amply demonstrated by the exceedingly variable
conditions under which they make their appearance, even among individuals
of the same species. Thus, while in Euglena viridis one such characteristic
eye-like pigment-spot represents the normal development, two or even
three such corpuscles not unfrequently occur, while in yet a third series
it may be entirely suppressed. Although these characteristic pigment-
corpuscles are most abundantly represented among the members of the
Flagellata, they occur occasionally among the Ciliate section, as promi-
nently illustrated in the genus Ophryoglena, while according to Claparede
and Lachmann, such a structure is likewise present in the earlier and free-
swimming condition of Freia (Follicularia) elegans. The Flagellate genus
Distigma would seem to be the only type among the Infusoria in which
two pigmentary corpuscles are persistently developed, in all other forms a
single one only being normally present. Excepting in the case of Ophryo-
glena, in which the pigment-spot is almost black, a brilliant crimson or
scarlet hue is found to predominate. No trace of these supplementary
coloured corpuscles have been yet recorded in association with the
representatives of the Tentaculifera.

Colouring matter in a diffused state, or as forming an integral element
of the entire body-substance, while not very generally developed, constitutes
in certain types a conspicuous and highly characteristic feature. The
Flagellate group of the Euglenidae, distinguished for the brilliant green
hue of the entire subcuticular parenchyma, affords perhaps the most pre-
eminent examples of such diffuse coloration. The chlorophylloid nature of
the pigmentary matter, or " endochrome " as it may be appropriately
designated in these instances, is so evident that its presence has long been

COLOURING SUBSTANCES. 79

held to indicate their essentially vegetable nature, and but for the recent
demonstration by Stein and the present author, of a well-developed oral
aperture and accompanying capacity to ingest solid food, would yet furnish
a solid argument in support of such interpretation. Between the green
colouring matter of an Euglena and that of a Palmellaceous plant or
protophyte, such as Protococcus, there would appear to be absolutely
no distinction, the same substances in both cases exhibiting, furthermore,
a tendency, at a certain epoch of their existence, to assume a more or
less conspicuous red or crimson tint. This last-named phenomenon is
especially characteristic of the type figured and described by Ehrenberg
under the title of Astasia (Euglena} sanguined, the rapid change of colour
from green to red in which has doubtless given rise in many instances
to the legendary accounts in rural districts of the conversion of standing
water into blood, and has even been suggested by Ehrenberg as yielding
an intelligible interpretation of that mysterious "turning of the waters
into blood," which distinguished the visitation of the first Egyptian
plague. Green colouring matter closely allied to, if not absolutely identical
with the chlorophyll of vegetable organisms, is found, though in a more
distinctly granular or less diffuse state, in many other infusorial groups.
Instances in this connection are afforded by various Peridinia, but espe-
cially by Paramecium chrysalis, in which the greater part of the chlorophyll-
like endoplasmic granules exhibit, as previously related, a characteristic
circulatory motion. In the green variety of Stentor polymorphic it has
been shown by Professor E. Ray Lankester that the absorption-bands
yielded on examination with the microspectroscope, correspond closely
with those given by the green colouring matter of Hydra viridis and
Spongilla, and indicate the presence of an essentially chlorophylloid body.
Various other species of Stentor are also remarkable for the brilliant
colouring of their inner parenchyma, the pigmentary matter being distri-
buted in a granular form throughout its substance, and exhibiting in some
cases, such as 5. castaneus, under a high magnifying power, two distinct and
easily recognized tints. The most anomalous hue yet recorded is, perhaps,
associated with Stentor cceruleus, in which the dispersed pigment-granules
are of a brilliant and intense blue. Submitted to spectroscopic analysis, the
absorption-bands yielded by the bodies of this species, either singly or en
masse, were found, by the author above quoted, to differ so remarkably
from those of any other known organic substance, that he has proposed to
distinguish it by the suggestive title of "stentorin." *

In a number of animalcules, equalling if not exceeding what may be
termed the chlorophyllaceous series, the parenchyma is found to yield a
colouring matter — mostly diffuse, as in the green colour of an Euglena —
the fundamental hue of which is brown, but varies from pale amber or
orange to a deep olive. In this latter instance the aspect of the pigmentary
matter closely approaches that of " diatomin " or the essential olive-brown

* "On Blue Stentorin," E. Ray Lankester, 'Quart. Journal Micro. Science,' April 1873.

80 ORGANIZA TION OF THE INFUSORIA.

colouring matter of the Diatomaceae ; while in the pale and more decidedly
yellow examples, a nearer approximation is perhaps made to " phyco-
chrome," or to the yellow colouring matter of various lower algae. Among
the most conspicuous examples of this yellow and brown-coloured series
may be mentioned the majority of the Cilio-Flagellate group of the
Peridiniidae, and a very considerable proportion of the Tentaculifera or
AcinetidcTe: Similar yellow or olive pigment matter is likewise met with
among a large number of typical Flagellata, such as Dinobryon, Microglctia,
and Chrysopyxis, but is remarkable in all these types for its limitation to
two lateral band-like areas — a circumstance which has been accepted by
the author as justifying their collection into the single family group here
distinguished by the title of the Chloromonadidae.

As illustrations of Ciliate forms in which the colouring hue presents
abnormally marked features, reference may be made more especially to the
Leucophrys (Holophryd) sanguined of Ehrenberg, in which the parenchyma is
of a bright crimson colour, and Nassula ornata, in which numerous vesiculse
of a brilliant violet tint are found distributed throughout the same element.
In this latter instance, however, the colouring matter does not represent
an essential constituent of the body-substance, but is due to a reaction
of the associated juices upon the ingested food-material. An interest-
ing example of the occurrence of fine granular matter, differing in colour
from the surrounding protoplasm, is yielded by the Monas (Spumella) vivi-
para of Ehrenberg, in which such granules are exceedingly minute, of a
bright red hue, and exhibit a constant vibratory and apparently purely
mechanical or "Brownian" movement. Minute coloured granules of a
brilliant crimson hue are also found embedded in the contractile element
of the stem of Vorticella picta.

Although possessing no claim for consideration as supplementary
colouring substance, it may be most appropriately remarked here that in
all of the exceedingly minute collar-bearing monads, or Choano-Flagellata,
a pale glaucous or fluorescent hue prevails, that assists materially in
the recognition of their presence, even where the magnifying power
employed is insufficient to render the characteristic membranous collar
clearly visible. A similar pale green or glaucous tint is exhibited also
by many species of Bacteria, and would appear to represent the predomi-
nating refractive index of abnormally minute protoplasmic bodies.

Accessory Structures — Trichocysts.

First in importance among the supplementary and non-essential ele-
ments associated with the Infusorial economy, have to be described those
remarkable bodies, recurring under a variety of aspects and conditions,
known as " trichocysts." These structures exist in their most characteristic
form in the very cosmopolitan species Paramecium aurelia, taking there
the form of minute and exceedingly slender rod-like bodies, or fibrillae,

TRICHOCYSTS. 8 1

crowded together and distributed in an even layer immediately beneath

the cuticle throughout the whole extent of the cortex, their disposition with

respect to the external periphery being everywhere perpendicular. Under

certain conditions, including the application of artificial stimuli, such as

weak acetic acid, these trichocysts become suddenly elongated, and their

distal ends piercing the overlying cuticle stand out like fine, stiff, hair-like

setae, beyond the cilia, around the entire circumference of the animalcule,

frequently becoming entirely separated from their base of attachment.

The names of Ehrenberg and Oscar Schmidt are most usually associated

with the earliest discovery of these special structures, the first-named

authority having recorded their presence in Bursaria (Panophrys) vernalis

so long ago as the year 1832, and in which connection they are figured and

described as minute prismatic rod-like bodies embedded beneath the cilia

in the body-substance. By Oscar Schmidt, in the year 1849, similar rod-like

bodies were reported to occur in Bursaria (Panophrys) leucas, and Para-

mecium aurelia, their close correspondence with the rod-like bodies possessed

by various Turbellaria being indicated. It has been recently elicited,

however, by the present author that the existence of these trichocysts in

Paramecium aurelia was discovered, and their characteristic aspect when

extended figured and described, by our distinguished countryman John Ellis,

more than a century ago, and at a time when microscopical science was

quite in its infancy. With the imperfect magnifying apparatus employed

by this investigator it was not possible to recognize the fine vibratile cilia

by which the ordinary motions of the animalcule are accomplished, a

circumstance which led him to attribute such a special function to the

bodies in question ; this, however, in no way detracts from his merit as

their first discoverer. Ellis's account of these trichocysts being of high

intrinsic as well as classic interest, its reproduction in extenso is herewith

appended. After recording his discovery of the locomotive organs, or cilia

which he denominates " minute fins," in various species of Infusoria, which

he sagaciously compares with the natatory organs or cilia then- recently

described by Linnaeus as characteristic of the Ccelenterate genus Beroe,

he proceeds to say : —

" I have lately found out, by mere accident, a method to make their fins (cilia)
appear very distinctly, especially in the larger kind of animalcula, which are common
to most vegetable infusions, such as the Terebrella (Paramecium) ; this has a longish
body, with a cavity or groove at one end, like a gimlet. By applying a small stalk
of the horseshoe geranium, G. zonale, Linn., fresh broken, to a drop of water in
which these animalcules are swimming, we shall find that they become torpid
instantly, contracting themselves into an oblong-oval shape, with their fins extended
like so many bristles all round their bodies ; the fins are in length about half the
diameter of the middle of their bodies. Before I discovered this experiment, I tried
to kill them by different kinds of salts and spirits, but though they were destroyed
by this means, their fins were so contracted that I could not discover them in the
least. After lying in this state of torpidity two or three minutes, if a drop of clean
water is applied to them, they will recover their shape and swim about immediately,
rendering their fins again invisible."

82 ORGANIZATION OF THE INFUSORIA.

From the foregoing account, as it appears in the ' Philosophical Transac-
tions/ vol. lix., for the year 1769, there cannot be the slightest doubt that the
bristle-like " fins," made suddenly to appear by the application of the acrid
geranium juice, are identical with the fine setaceous trichocysts characteristic
of the species described on a preceding page, any doubts that might exist
upon this subject being at once dissipated on reference to the characteristic
illustrations of the animalcule accompanying Ellis's description, and em-
bodied in Table VI., Fig. 5, a, b, c, and d of the volume quoted. In the
above connection John Ellis has, however, not only to be accredited with the
first discovery of these supplementary structures, but, through the applica-
tion of the special means by which he effected such discovery, he takes
rank as one of the first to make successful use of reagents, now so widely
employed in the elucidation of the more minute histology of the Infusoria.
In this direction, nevertheless, and as recorded at page 1 14, Ellis was to
some extent anticipated by another Englishman, Sir Edmund King, at so
early a date as the year 1693.

The demonstration of the precise nature of trichocysts, and the con-
nection with them of their now generally recognized and characteristic title,
belongs to a comparatively recent epoch. In this instance also, however, an
Englishman is to the fore, such demonstration and titular denomination
having been accomplished at the hands of the present distinguished
President of the Linnean Society, Professor G. J. Allman, who, in the
'Journal of Microscopical Science' for the year 1855, described at consider-
able length the more minute characters and phenomena presented by these
bodies as met with in Bursaria (Panophrys) Icucas. Here, as recorded by
him in the publication quoted, the trichocysts, now so-called for the first
time, were found to exhibit the aspect of minute fusiform bodies embedded
thickly and on a perpendicular plan of arrangement, as in the manner already
described of Paramecium. Under external irritation, such as the drying
away of the surrounding water, the application of acetic acid, or forcible
compression, they became similarly and suddenly transformed into long,
fine, hair-like filaments or setae, which projected from the whole periphery.
The rapidity with which the transformation from the fusiform to the
filamentous condition was effected, combined with the greater minuteness
and transparency of the objects examined, hindered for a considerable
while the recognition of the exact manner in which the process was
accomplished. At length, by carefully crushing examples and isolating the
trichocysts in their normal and fusiform condition, it was found that these
latter, after the lapse of a few seconds, became all at once changed with
a peculiar jerk, as if by the sudden release of some previous state of
tension, and assumed through this change a minute spheroidal shape.
After remaining in this condition for two or three seconds longer, a spiral
filament was next observed to become rapidly evolved from the sphere,
apparently through the rupture of a previously confining membrane, the
filament winding itself with such rapidity that the eye could scarcely

TRICHOCYSTS. 83

follow it, and being finally extended straight and rigid on the field of the
microscope, under the form of -.a very fine and attenuate acicular crystal.
In their most completely extended state these bodies were found to consist
of an elongate .and rigid spiculum-like moiety, acutely pointed at one
extremity and continuous at the opposite end into an excessively fine
filiform appendage, less than half the length of the spiculum ; this second
portion was usually observed to be bent at an angle upon the first, and
to be more or less curved at its free end. The considerable structural
resemblance that subsists between the trichocysts of the Infusoria as
just described, and the cnidae or thread-cells of the Ccelenterata or
Zoophyte class, was at the time recognized by Professor Allman, and the
circumstance has been cited on various occasions as producing strong
evidence against the more recently advocated unicellular nature of the
Infusoria. The non-validity of this argument is, however, at once made
manifest on regard being given to the fact that the thread-cells, even as
they occur among the Ccelenterata, do not possess the independent
morphologic value of simple cells, many such being frequently enclosed
within the bounding membrane of a single cellular element, and of which
they are therefore to be regarded as the secreted product. In other words,
as maintained by Professor Allman, " the formative Ccelenterate cell may in
this respect be compared with the entire body of the Infusorium." Accord-
ing to Biitschli, the trichocysts in certain forms, including a species of
Nassula, emit a filament at each extremity of the previously enclosing
capsule instead of at one end only, as in the more normal case last
described. This investigator has suggested that such a double emission
is probably exhibited by the trichocysts of all Infusoria, and which
in that case affords a means of distinction between these latter and the
genuine thread-cells of the Ccelenterata ; this hypothesis has not, however,
been confirmed by more recent investigation. The trichocysts of abnormal
size, exhibiting an entirely irregular distribution, reported by Biitschli of
Polykrikos Swartzii, are apparently, as explained in the account given of
the species, accidentally engulphed thread-cells only of some neigh-
bouring Ccelenterate organism. Although more generally trichocysts
occur, as in the cases of Paramecium and Ophryoglena, as an even and
crowded series beneath the entire cuticular surface, in others, such as
Litonotus and Loxophylhim, they present a limited and definite plan
of distribution. Thus, in the former genus they form a conspicuous
linear series confined entirely to the ventral aspect of the proboscidiform
anterior prolongation, while in certain representatives of the latter they
exhibit a partly linear and partly fasciculate arrangement. Although with
but few exceptions the special bodies now under consideration are entirely
limited to the Ciliate section of the Infusoria, Stein has recently shown that
the Monas (Raphidomonas) semen of Ehrenberg possesses these structures
variously distributed throughout the cortical region, but most abundantly
along the anterior border, while a doubtful case of their occurrence in a

G 2

84 ORGANJZA TION OF THE INFUSORIA.

marine Acinete form has been recorded by Lachmann. Opinions with respect
to the functions of the trichocysts of the Infusoria are not entirely in accord,
some relegating to them, as with the thread-cells of the Ccelenterata, an
offensive and defensive, and others a simply tactile property : the balance
of evidence would appear to be in favour of the former interpretation.

Amylaceous Corpuscles.

Those bodies of an apparently amylaceous or starch-like nature, included
under the above title, possess a very limited distribution, occurring, so far
as is at present known, only among the Flagellata and in relationship
with the family of the Euglenidae, already cited as most conspicuously
distinguished for the possession of eye-like pigment-spots. In the genus
Englena, which is especially remarkable for the development of these
structures, they are found, moreover, to present a distinct and varied form
in the separate species, which consequently derive from their posses-
sion supplementary characteristics of some value for specific diagnosis.
The more ordinary contour of these amylaceous corpuscles is oblong or
elongate-quadrate, but varies in such types as Euglena acus and E. deses
to bacillate, or even acicular. In some forms, such as E. spirogyra and
E. oxyurus, there are more usually only two such corpuscles, one at each
extremity, of large size, and exhibiting a more opaque centre and pellucid
external zone, while in the two first-named types they are more generally
numerous, and present a homogeneous and semi-opaque consistence. In
certain instances they appear to multiply by division within the animalcule's
body, and, contrary to the structures previously described, appear to lie
loose within the central endoplasmic element, instead of being enclosed
inside the cortical layer or ectoplasm. The precise nature and significance of
these peculiar bodies have yet to be elucidated.

Decomposition or Diffluence.

Some remarkable phenomena connected with the manner in which, under
various uncongenial conditions, the soft sarcode bodies of the Infusoria
become more or less rapidly disintegrated, require brief notice. Artificially,
through the addition to the water of a little ammonia or other reagent,
or naturally, by permitting the same water to evaporate, certain species
possessing a non-indurated integument, such as the representatives of the
genera Oxytricha, Trichoda, and Enchclys, may be observed to fall bodily
to pieces, or, decomposition commencing at one point gradually spreads
throughout the entire organism, granular or globular portions becoming
successively detached, until at length the entire body has been as it were
consumed. At any point, however, by the addition of a fresh supply of
oxygenated water, this action of decomposition may be permanently
arrested, and the animalcule, or such larger portion or portions of it

BINARY DIVISION. 85

that remain, redevelop within the course of a few hours to the size and
form of the normal zooid. In Vorticella, Paramecium, and other hard-
skinned Infusoria a closely similar phenomenon of decomposition is mani-
fested under like conditions through the extension at various points of the
cuticle of globules of sarcode, this process, if not artificially or otherwise
arrested, continuing until the entire endoplasm has become dissipated.
Among the more minute monadiform animalcules a parallel form of disin-
tegration is preceded by the assumption of an entirely irregular and mostly
amrebiform contour, closely corresponding with such as accompanies the
processes of fusion or encystment ; the type Monas diffluens, figured and
described later on, affords a suitable example of this last-named phase.
Collectively, the very appropriate name of " diffluence " has been applied
by Dujardin to these several closely identical modes of decomposition here
enumerated. Similar phenomena, however, as they occur among' the
Ciliata were long before observed by O. F. Muller, who described them
under the several titles of " molecular effusion " and " dissolution." In
certain exceptional instances, including notably Halteria grandinella and
its allies, an apparent modification of the process of diffluence is exhibited
by the animalcule bursting suddenly to fragments in its mid career, without
any accompanying visible causes of irritation.

REPRODUCTIVE PHENOMENA.
Binary Division or Fission.

This mode of reproduction represents not only the earliest recognized
and most widely distributed, but undoubtedly that also by which under
normal conditions the specific infusorial form is most abundantly propa-
gated. As in all of the manifold structural aspects previously discussed, the
infusorial! body reproduces, with diverse modifications, the structural and
functional features only of a simple cell, so likewise this special mode of
multiplication is found to be a mere reflex of the ordinary reproductive
phenomena exhibited by the cellular elements or units of all higher tissue
structures. In these, from the most simple to the most complex, the
increase in size or growth of the tissue is effected through the indefinite
increase by binary or duplicative division of the specific type of cells of
which it is composed. The astonishingly rapid growth of certain cellular
tissues or structures, through such constantly repeated binary division of
the constituent cells, is too familiar for recapitulation, and almost equally
extraordinary figures are attained in connection with the multiplication
of the independent unicellular bodies of the Infusoria through this simple
process. Thus, Ehrenberg long since computed that in the case of Stylonychia
mytilus, no less than one million of independent beings were derived through
the simple and repeated fission of a single zooid in the course of ten days,
while in that of Paramecium aurelia, he reckoned that as many as 268

86 ORGANIZATION OF THE INFUSORIA.

millions might be similarly developed within the space of a single month.
Substantial evidence of the prodigious numbers that may be produced
by this simple reproductive mode is afforded by the various species be-
longing to both the Ciliate and Flagellate sections of Infusoria that
are characterized by their sedentary and colonial mode of growth, each
colony-stock under such conditions representing the sum total of the
repeated binary subdivision of a primary single unicellular zooid. Ophry-
dium versatile constructs in such a manner aggregated masses, derived
primarily from a single animalcule, that vary in size from that of a walnut
to a child's head, while Epistylis grandis similarly produces on submerged
plants, or the walls of an aquarium, what appear to the unassisted vision
as homogeneous slime-like masses of many feet in extent. Correspond-
ingly derived colonial aggregations, though on a somewhat smaller scale,
are encountered among the several Flagellate genera Dendromonas, Spongo-
monas, Phalansterium, and A nthophysa, while in the group of the Spongida,
that must be regarded as peculiarly modified colonial aggregations of
such Flagellate types as Codosiga and Phalansterium, a composite struc-
ture is produced by a chiefly though not entirely similar process, which
in many cases far exceeds in bulk the extensive colonies of the several
Ciliate forms first quoted.

The phenomena of multiplication by binary division or fission are found
to manifest several characteristic modifications. With the majority of species
such division takes a cross-wise or transverse direction, a groove or con-
striction making its appearance towards the centre of the body, and
becoming gradually deeper and deeper, until at length the anterior and
posterior halves become entirely separated from one another, each swimming
off as an independent animalcule, and such organs as might be wanting
to either separated moiety becoming rapidly developed. In a somewhat
smaller, but still pretty considerable assemblage of types, the process
of fission is manifested in a precisely opposite or longitudinal direction.
Such a plan of multiplication is more essentially characteristic of the large
group of the Vorticellidae, and those representatives of the Flagellata, in
which, as with many of the former, a compound tree-like colony-stock is
built up. Illustrations among these latter are especially afforded by such
genera as Codosiga, Dendromonas, and Rhipidodendron. The compound
zoothecium of Dinobryon, while at first sight apparently constructed by
means of a similar reproductive formula, is the product of transverse
fission, each anteriorly separated zooid utilizing the wall of the lorica it
quits as the fulcrum of attachment of its own independently constructed
domicile. The most remarkable modification of longitudinal fission is
perhaps furnished by the collared Flagellate genus Desmarella, and in
which the variable number of zooids developed by this process remain
laterally attached in such a manner as to form a more or less elongate
necklace-like series. In the genus Vorticella and its allies, as hereafter
recorded, the process of fission is always preceded by the closing up and

EXTERNAL GEMMATION. 87

entire obliteration of the primary oral system, two new ones subsequently
appearing in its place.

In a third, but comparatively very small number of Infusorial forms,
neither a transverse nor longitudinal mode of fission is met with, but
one that takes an entirely oblique direction. The Ciliate genera Stentor
and Lagenophrys, and the new Flagellate type described in this volume
under the title of Anchomonas sigmoides, are among the most noteworthy
examples of this somewhat aberrant process. Although it usually happens
that all of these various phenomena of multiplication by simple binary
division now enumerated are accomplished during the active life of the
animalcule, it not unfrequently happens that a quiescent or encysted con-
dition, as described at page 63, is specially entered upon for the fulfilment
of this purpose. Illustrations of this developmental phase are afforded
by Amphileptus meleagris, Otostoma Carteri, Etiglena viridis, and many
other Flagellata. The appearances exhibited in certain of these cases
more nearly coincide, however, with the sporular conditions discussed later
on. In all instances, it would seem that the duplication of the in-
fusorial body by the process of binary division is, as with the similar
multiplication of the cells of ordinary tissue structures, accompanied, or
rather preceded as an initial act, by the subdivision of the nucleus or endo-
plast. Other organs, such as the contractile-vesicle and oral or anal structures
and appendages, are not so divided, but are independently developed in
that moiety in which previous to subdivision they were unrepresented.

External and Internal Gemmation.

The phenomenon of reproduction by " external gemmation," although
represented in tolerable abundance among the present organic group, occurs
by no means so generally as was formerly supposed. Up to within a com-
paratively recent date that larger or smaller bud-like body, not unfrequently
found attached to the lateral periphery of various members of the Vorti-
cellidae, and also the secondary pendent zooid, which, while first attached
to, finally breaks away from the parental stem, were premised to be
examples of such gemmation. In both of these cases, however, the so-called
gemmule is derived through a modification of the process of binary fission,
previously described, from an ordinary zooid, though in the former instance
the association is fortuitous, and, as hereafter shown, has a peculiar
significance. Instances of true external gemmation are, nevertheless,
afforded by such types as Spirochona, and apparently also Lagenopkrys
among the Ciliata, while among the Tentaculifera, Hemiophrya (Podophrya)
gcinmipera and the various species of OpJiryodendron, more especially
O. multicapitata, supply prominent examples of this phenomenon. In
the majority of the cases mentioned it has been recently demonstrated that
a diverticulum of the endoplast accompanies the outgrowth of the body-
substance, forming the characteristic bud, and becomes separated off and

88 ORGANIZATION OF THE INFUSORIA.

enclosed within the latter on its detachment from the parent stock. The
most remarkable modification of external gemmation is afforded perhaps
by certain Opalinidae, in which, as exemplified by the A noplophrya prolifera
of Claparede and Lachmann, a long series of buds are developed simulta-
neously at the posterior extremity, and become successively detached from
the parent zooid after the manner of the buds or " proglottides " of a
cestoid worm. A highly remarkable modification of the process of external
gemmation is exhibited by the Flagellate type Noctiluca miliaris. Here,
as demonstrated more especially by the recent investigations of Cienkowski,
the entire subcuticular protoplasm becomes broken up into nodular
fragments which are protruded upon the external surface under various
conditions of disposition, and are finally liberated from the parent sphere as
simple monadiform bodies.

" Internal gemmation " in its most typical condition may be described as
a modification only of the previous process. As in the latter case a portion
of the endoplast is separated off and enclosed within a portion of the
parent substance, but the gemmule or so-called embryo thus produced
is retained within the parental body until matured, in place of remaining
affixed to its outer wall. Such typical internal gemmation is most abun-
dantly represented among the Tentaculifera, as instanced by the more
ordinary Acinetce, and various species of Podophrya and Dendrocometes.
A modification of this form of internal gemmation is also undoubtedly
represented among those numerous types of the Ciliata, such as Stentor,
Spirostomum, and many Vorticellidae in which embryos or, more correctly
speaking, internal gemmules become separated from the more or less
elongate endoplast, which may be properly characterized in this con-
nection as an internal proliferous stolon. In all of these last-named
cases it is, however, necessary to remark that the internal gemmules so
formed are constructed entirely from the substance of the endoplast, and
contain no fragment of the surrounding body-substance. In that peculiar
form of reproduction recently recorded by Stein of various Euglenidae,
Anisonemidae, and other Flagellata, in which young are produced through
the enlargement and subdivision of the endoplastic element into one or
more germinal masses, the phenomena manifested closely correspond with
those last related, but at the same time lead the way to that more general
mode of propagation among the Flagellata which is next described.

Spornlar Multiplication.

Under the above-named denomination are correlated by the author all
those reproductive phases connected with the assumption by the individual
animalcule of a quiescent or encysted condition, accompanied by the subse-
quent partition of the entire primitive mass into a greater or less number
of spore-like bodies. In those instances in which the sporuloid bodies so
produced may be easily reckoned, and do not exceed the numbers of two,

SPORULAR MULTIPLICATION. 89

four, eight, sixteen, or thirty-two, they may be appropriately termed
" macrospores," while in those instances in which there is an excess of this
last-named number, and may be described as innumerable, they may be con-
veniently denominated " microspores." In extreme cases many thousands
of these last-named bodies may be included within the parent capsule or
" sporocyst," their individual calibre being so minute as to be inappreciable
even with the highest constructed powers of the compound microscope.
Whether microspores or macrospores, each segmented particle ultimately
develops to the parent form. The demonstrated existence to any consider-
able extent of this sporular form of multiplication is connected with the
results of the most recent investigation, many of the facts testifying to
the universal prevalence of such phenomenon being now published, indeed,
for the first time. Among the higher orders of the class Infusoria sporular
reproduction is comparatively rare, being as yet almost unknown among the
groups of the Tentaculifera, while in that of the Ciliata a few stray
instances can alone be cited. It is in that lower section of the class dis-
tinguished by the flagelliform character of their locomotive appen-
dages that spore -formation attains its most vigorous development, it
representing among these, in fact, in many instances the most general
and prolific form of propagation. Quoting those few instances in which
spore-production in its true sense occurs among the Ciliata, mention may
be made of Colpoda cuculhilus, in which, as demonstrated by Stein many
years since* — though then reported as cases of simple encystment — the
encapsuled zooids became divided into two, four, or eight spore-like bodies
or macrospores, each having a separate membranous investment; these
give exit to animalcules of smaller size, but which in other respects preserve
all the characteristics of the parent form. Phenomena closely corresponding
with those related of Colpoda have also been observed by Mr. Carter in
the Holotrichous genus Otostoma, and still more recently by the author
previously quoted in connection with Prorodon teres and Panophrys flava.
The only instance as yet placed on record in which an encysted Ciliate
animalcule becomes divided into segments so numerous as to fall within
the denomination of microspores is afforded by the type recently described
by Fouquet under the title of Ichthyopthiriits multifiliis, the encapsuled
zooid in this instance dividing up into at least several hundred spore-like
fragments. The products of these spores, when first excluded from their
cyst or capsule, differ considerably from the parent animalcule, but by
degrees acquire an identical aspect and character. Arriving at the Flagellate
section of the infusorial class, the difficulty is rather to indicate types in
which a sporuloid phase does not more or less frequently intervene. In
consequence of the searching scrutiny that has been directed of late years
upon this previously all but neglected group, the life-histories and repro-
ductive phenomena of its members are in many instances more completely
known than that of the more highly organized Ciliata.

* 'Die Infusionsthiere,' 1854.

90 ORGANIZATION OF THE INFUSORIA.

The investigator, to whom credit is due for first demonstrating the
sporiparous mode of multiplication among the Flagellata, and for indi-
cating with reference to such peculiarity the close approach made by this
group to the Palmellaceae and other Protophytes, is without doubt Pro-
fessor L. Cienkowski, who in the year 1865* figured and described at
length such "sporular multiplication in connection with his Monas (Heter-
omitd) amyli, various species of his newly founded genus Pseudospora,
and several types of ordinary Rhizopoda. Although he discovered such
developmental phenomena, Cienkowski, however, scarcely attributed to
them the interpretation here adopted, the quiescent or encysted condition
and transitional amoeboid phases being treated by him as more essential
and characteristic than the motile flagelliform bodies issuing from the spores,
named by him " zoospores," and which certainly represent the typical
form of expression of the species in its most mature condition. Not only,
however, did Cienkowski recognize the respective natatory or flagel-
liform, amoeboid or repent, and quiescent or sporular conditions of the
above-named types, but he also witnessed the conjugation or coalescence in
several instances of two or more zooids during the amoeboid stage, and the
construction by them of a single sporocyst. In connection with this last-
named phenomenon, he sagaciously recognized the close approach made to
the construction of the compound plasmodium of the Myxomycetes, at
that time the subject of special observation by de Bary and himself,
and to a certain extent, also, anticipated the more prominent points in
the life-history of certain monadiform species revealed a few years later
through the painstaking investigations of our own countrymen, Messrs.
Dallinger and Drysdale. Full details of the somewhat varying phenomena
presented by the diverse types examined by these two authorities
being recorded in connection with the systematic descriptions of the
Flagellata given further on, and among which may be more especially
cited such forms as Monas Dallingerii, Ccrcomonas typica, and Heteromita
itncinata, it will suffice here to indicate that Messrs. Dallinger and Drysdale
established in every instance the interpolation among the ordinary mode
of multiplication by binary division of a spore-producing phase, accom-
panied by the assumption of the individual zooid of a resting or encysted
state. Preceding such encystment a transitory repent amoeboid condition
was usually exhibited, and was in most instances accompanied by the
coalescence of two or more such amoeboid units. In certain cases the
sporular bodies so produced were of such a size and number as to fall
under the category of macrospores, while in a few others they were of such
excessive minuteness and corresponding numbers as to defy individual
definition with the magnifying power of 15,000 diameters brought to bear
upon them with the aid of a ^V~mch objective. These three leading phases
in the life-history of a Monad, as above enumerated, and which may be
respectively denominated the active flagelliferous, the transitory amoeboid,

* 'Arch. f. Mik. Anat.,' Bd. i.

GENE TIC REP ROD UCTION. 9 1

and the quiescent sporocyst states, the first yielding the essential and
specific form, are now found to obtain throughout the majority of the
Flagellata. Simultaneously with, and in many instances anterior to, the
publication of Messrs. Dallinger and Drysdale's researches, corresponding
phenomena had been observed and duly recorded by the present author in
relation with the representatives of the Choano-Flagellata or collar-
bearing section, and other more simply organized Flagellata. Like results
have also accompanied his more recent investigations, while confirmatory
evidence in the same direction is abundantly afforded in the magnificent
volume devoted to the illustration of the Flagellata generally, lately pub-
lished by Professor Stein. As examples of the persistence of the three
above-named characteristic phases in the group of the Choano-Flagellata,
reference may be more especially made to the systematic descriptions and
accompanying figures of such species as Salpingceca amphoridium, S. fusi-
formis, and Codosiga botrytis, in all of which the transitory amoeboid phase
is particularly remarkable. In all those Eustomatous Flagellata which,
like Phacus and Anisonema, possess an indurated cuticle, the assumption
of an amoeboid condition would not be possible, and the animalcule pre-
vious to encystment and spore development merely loses its flagella, and
assumes a quiescent state. In Euglena and its allies, including Eutreptia,
the animalcules exhibit a transitory amcebiform, or, more correctly, a
gregarine-like repent state immediately preceding the process of encyst-
ment. With the representatives of the two last-named genera it is further
worthy of note that the initial condition of existence on emerging from
the spore is likewise amcebiform and non-flagelliferous. Among the Choano-
Flagellata this earliest stage is simply flagellate or monadiform, there
being no trace of the characteristic collar, while in a larger series, including
the majority of the Pantostomata, such initial phase, in all but size,
corresponds essentially with the parent zooid.

Sexual or Genetic Reproduction.

Sexual reproduction in the broad acceptation of the term as belonging
to the propagative phenomena of the higher animals or Metazoa, or, as
up to within a comparatively recent date maintained by Balbiani and
others to obtain among the members of the higher Ciliate section of Infu-
soria, and in either case involving the concourse of true and independently
developed sexual cellular elements — ova and spermatozoa — remains, so
far as it concerns all or any members of the class or classes now under
discussion, entirely undemonstrable. Nor, the essentially unicellular nature
or value of the infusorial organism, as here advocated, being once firmly
and incontestably established, can a contrary verdict be anticipated !
Notwithstanding, however, the apparently uncompromising verdict pro-
nounced in the foregoing sentence, it will presently be shown that these
Protozoic organisms, in essence if not in fact, fulfil a r61e of reproduction

92 ORGANIZATION OF THE INFUSORIA.

that corresponds most closely with this important function as it is met
with in all Metazoic or multicellular structures. As already maintained
in the description of that more common phase of multiplication which
takes the form of constantly repeated binary division, the Infusoria
through such mode of increase merely repeat in a separate and inde-
pendent manner that process of cell-multiplication which characterises the
normal growths of all tissue structures. By-and-by, however, in the case of
the Metazoon or tissue organism, an epoch is arrived at when the com-
ponent cells cease to exhibit their previous duplicative energy, the conse-
quence being the gradual decay and ultimate dissolution or death of the
entire organism. But for the interposition of a special and more or less
periodical regenerative act, this termination of the life of the individual
would also, sooner or later, involve the extinction of the race or species.
Such a regenerative act, and the further survival of the race, is, however,
here accomplished through the fusion or union of one of that congeries of cells
out of which the compound organism is composed with one other exteriorly
derived cell liberated from another organism or congeries of cells pertaining
to the same specific type. The result of such fusion between these two,
denominated respectively the germ-cell and sperm-cell, or, in other words,
the ovum and spermatic cell or element, is the capacity conferred upon the
former of once more proceeding with the duplicative process, and repeating
that cycle of cell-aggregation or tissue-construction followed by the parent
organism. In a precisely similar manner, the infusorial body, after repeated
duplicative multiplication, arrives at a condition in which the strain or
race is too exhausted for the further maintenance of this process, and
without the intervention of some supplementary regenerative operation
would become extinct. By, however, the coalescence or fusion of one of
these individual cells or animalcules with an elemental cell or animalcule
derived from a neighbouring race or strain, the capacity to continue the
duplicative process is revived, and the further duration of the race secured.
The two animalcules thus uniting with one another correspond to all intents
and purposes with the coalescing germ-cell and sperm-cell, or ovum and
spermatozoon of the higher tissue organisms, the only essential point of
divergence being in the subsequent changes manifested ; the organism in
the latter instance exhibits a tendency to build out of the cells amassed
by the duplicative process, more or less complex coherent tissues, while in
the former each cell so produced maintains a separate and independent
existence.

Among the extensive series of types included in the infusorial classes, the
phenomenon of " conjugation," " fusion," or " zygosis," as it is variously called,
and which undoubtedly represents the sexual or genetic reproductive process
of the higher animals in its most simplified or elementary form of expression,
exhibits certain well-defined modifications. With the majority of the more
highly organized Ciliata, such conjugation has to be denominated, as com-
pared with the form next described, transient and incomplete, being, as

GENETIC REPRODUCTION. 93

illustrated by the generic type Paramecium, accompanied by the following
manifestations. Two previously independent and free-swimming zooids
meeting one another, become locked together through the close applica-
tion and apparently intimate union or coalescence of their two oral or ventral
surfaces, the aspect presented by the united couple coinciding closely with
that of longitudinal fission as it occurs among many familiar types, and for
which simple reproductive process it was originally mistaken by Ehrenberg
and other early writers. This process of conjugation or fusion has in the
present species been observed to extend over a period of five or six days,
the two united animalcules swimming about in the interim with an amount
of ease and activity scarcely inferior to that exhibited by the single and
independent zooids. The genera Bursaria, Blepharisma, Chilodon, Cyrto-
stomum, and many other forms, exhibit conjugative .phenomena closely
identical with those presented by Paramecium, while in Stylonychia it would
appear, according to Engelmann, that both the transient and the complete
form of conjugation may be met with among individuals of the same species.
In the normally stationary or attached genus Stentor the conjugative process
is also transient, the contiguous animalcules, according to Balbiani, becoming
temporarily united by their anteriorly located oral areas. A similar tran-
sient conjugative act has likewise been reported to obtain among the
members of the genus Podophrya, but, as shown by the author in the case
of P. mollis, such apparent act is not unfrequently attributable to the less
complex process of multiplication by binary division.

The form of conjugation to be next enumerated is characterized by
its complete and permanent duration. Two animalcules or zooids in this
case become, as it were, so completely melted or welded together, that
their previous individuality is entirely obliterated. Among the Ciliate
section of the Infusoria, this special complete or entire conjugative phase
is almost exclusively restricted to the Peritrichous family of the Vorticellidae,
but recurs occasionally in alternation with the partial or transient one in
Stylonychia and other Hypotricha. The most prominent development of
this permanent or complete type is undoubtedly met with in the Flagellate
section of the series throughout the whole of which, as at present known,
it would appear to constitute the one and only conjugative process.
Most usually, among these Flagellata, this complete conjugative act
is accompanied with the assumption by the coalescing individuals of
an outline entirely at variance with the normal specific aspect. The
flagella or other appendages are in this instance entirely withdrawn,
and pseudopodic processes, like those of an Amoeba or Actinophrys,
extended for locomotive or prehensile purposes from various parts of the
periphery. Succeeding such conjugation among the Flagellata, it most
usually happens that the sporular reproductive phase, described on a pre-
ceding page, is immediately entered on, though that such conjugation is
not imperatively associated with this spore-production has been demon-
strated by the present author, in connection with Heteromita angustata, and

94 ORGANIZATION OF THE INFUSORIA.

various other species. As elicited by the recent investigations of Messrs.
Dallinger and Drysdale, it occasionally happens that the coalescence of three
or four or more metamorphosed or amcebiform Flagellate animalcules takes
the place of the more ordinary conjugation of two zooids only. In this
latter instance, as illustrated by the biflagellate type Heteroviita uncinata, a
close approximation is made towards that multiple coalescing process by
which out of a number of similarly metamorphosed or flagellate zooids
the compound amcebiform plasmodium of the Mycetozoa is built up ; a
modification of this phenomenon would also, as hereafter shown, appear to
accompany the construction of the compound locomotive gemmules, or
so-called " ciliated larvae " of the Spongida.

While the interpretation of the sexual or genetic reproductive phenomena
of the Infusoria embodied in the earlier portion of this present section
adapts itself most nearly to the data elicited by the most recent investiga-
tors, among whom the names of Engelmann and Butschli are especially
noteworthy, it by no means represents the one regarded with the greatest
favour prior to the publication of the discoveries of these authorities, nor
even yet, perhaps, the one at the present day most extensively maintained.
From almost the earliest epoch of their history, the probable propagation of
infusorial animalcules by a sexual or genetic process analogous to that
which obtains among the higher animals has now and again been suggested.
Such an interpretation was thus, though inaccurately, attributed by Sir
Edmund King, in the year 1693, to the ordinary process of transverse fission
witnessed by him in a species of Euplotes, while O. F. Miiller, in his
' Animalcula Infusoria,' 1786, figured and described that conjugative process
or genetic union of Paramecium aurelia since generally admitted, so far as
the external features are concerned, to be substantially correct.

Passing over, for the present, that far-fetched and long since abandoned
hypothesis advanced by Ehrenberg, in which the contractile vesicle was
regarded as a spermatic reservoir engaged in the continued fecundation of
closely associated ova, the far more practicable and intelligent one origi-
nating with Balbiani in the year 1858 may be cited. By this accomplished
investigator it was at the foregoing date first pointed out that the hitherto
supposed instances of longitudinal fission, as figured and described by
Ehrenberg, of Paramecittm bursaria and other free-swimming Ciliata, had
nothing to do with such a duplicative process, but were indicative of a
genetic union or conjugation between two individual zooids. Balbiani
further maintained that the nucleus and nucleolus during such conjugative
process became transformed into veritable sexual organs, of which the
nucleus or endoplast, dividing up into a number of spheroidal fragments,
performed the function of an " ovary," and the nucleolus or endoplastule in
the same way, after first assuming a longitudinally striate aspect, and then
separating into a number of rod-like spermatic elements, fulfilled that of a
testis or "seminal capsule." During the process of conjugation, lasting in
this species, according to Balbiani, five or six days, the nucleoli or seminal

GENETIC REPRODUCTION. 95

capsules were respectively exchanged, the so-called ovules in each ani-
malcule being thus mutually fertilized on a plan corresponding with that
exhibited by the Helicidae and other monoecious Gasteropoda. These
phenomena of fusion or genetic union, first reported of Paramecium, were
recorded by the same observer as occurring in a variety of animalcules,
and were soon, so far as the external circumstances were concerned, found
to obtain very generally, but under varied conditions, the union being
sometimes transitory and in others permanent, throughout the whole
infusorial class. Among the authorities who, after devoting themselves
specially to the investigation of this organic group, have arrived at con-
clusions confirming the discoveries of Balbiani, and have relegated to the
nucleus and nucleolus the same respective genetic functions, may be men-
tioned the names of Kolliker, Stein, Claparede, and Lachmann, and, in a
slightly modified manner, also Mr. Carter. This last-named author, how-
ever, previous to the discoveries of Balbiani,* attributed the production of
spermatic elements to the nucleus, and that of germs or ovules to the
general body-substance.

An examination may now be made of those recent discoveries of Engel-
mann and Biitschli which have resulted in the introduction of an entirely
new train of thought respecting the reproductive properties of the Infu-
soria. After a prolonged and independent research, these two authors
have, while admitting the conjugative process, been compelled to reject in
toto Balbiani's interpretation assigning to the endoplast and endoplastule
respectively the functions of an ovary and testis. The characteristic
striated aspect exhibited by the endoplastule during conjugation is de-
clared by them to be in no way connected with the production of spermatic
elements, but to represent the normal aspect of both this structure and
the nucleolus of the ordinary tissue-cell prior to the act of subdivision.
Nuclei, in both animal and vegetable cells, are further maintained by them,
and confirmed by the observations of Hertwig and Strassburger, to fre-
quently exhibit a similar striated appearance and general likeness to the
so-called " seminal capsules " of the Infusoria. Briefly epitomized, the
general conclusions arrived at by Biitschli with reference to the conjugative
process of the Infusoria are as follows : — During such process the original
nucleus or endoplast in both animalcules breaks up into a number of
fragmentary portions, and becomes lost among the endoplasm or general
body-sarcode. By-and-by an entirely new endoplast is constructed through
the gradual assemblage and union with each other of fragmentary particles
having a similar general derivation, this newly found endoplast being single
and common to the two in such instances as Vorticella, where conjugation
or fusion is complete and permanent, while two or more, according to the
normal number, are reproduced where such conjugation is, as in Paramecium,
partial and transient. In the case of Stylonychia mytilus it is further affirmed

* H. J. Carter, " Notes on the Freshwater Infusoria of Bombay," ' Ann. and Mag. Nat. Hist.,'
Ser. ii. Nos. civ. and cv. 1856.

96 ORGANIZATION OF THE INFUSORIA.

by Biitschli that the endoplast of each individual divides, during conjuga-
tion, into four fragments, which, becoming rounded into a form corresponding
with the so-called "ovules" of Balbiani, are cast out of the body as "waste
matter." The same destiny is likewise attributed by him to one out of the
four fragments into which the endoplastule becomes divided — two remaining
to represent the normal complement of these structures, and the residual
one assuming first a more considerable volume and transparent aspect, and
ultimately redividing and constituting the two new nuclei or endoplasts.
The endoplastules in all cases preceding subdivision assumed a fusiform
shape and striated character, but in no instance was an interchange of these
structures between two conjugated animalcules witnessed, as was affirmed
to take place by Balbiani. Qualitatively, the endoplastules of the Infusoria
are regarded by Biitschli as differing in no way from the endoplasts, and
into which latter, in accordance with his observations, they not unfrequently
develop. The idea that embryos are developed independently from the
endoplast is entirely rejected by this author, the significance attached by
him to this structure being simply that of the nucleus of an ordinary animal
or vegetable cell. The only reproductive faculty conceded to the Infusoria
by Butschli is that of division or gemmation, the conjugative act being
associated by him only with the conference of renewed power or vital
energy for the continuation of the dividing process. The superficial
analogy existing between the complete conjugative process, as exhibited in
the genus Vorticella, with the union of the ovum and spermatozoon of the
higher animals, is accorded by this author, but hermaphroditism or sexual
differentiation, as a constant and essential feature of the representatives of
this organic group, is entirely denied. The unicellular nature of the
Infusoria is necessarily maintained, in the most thoroughgoing and forcible
interpretation of the term, in connection with Biitschli's foregoing exposition
of the reproductive features.

Engelmann's latest independent investigations in this direction, while
resulting — contrary to his earlier researches — in an entire acquiescence with
the views of Butschli, so far as the reconstructive properties of the endoplast
and the total rejection of the embryonic theory are concerned, exhibit certain
points of difference. Thus, although the nucleus or endoplast is regarded
by him in most instances as the equivalent simply of the nucleus of the
histologic cell, this same structure is in certain cases, such as Stylonycliia
and Euplotes, interpreted as representing a female element, while the
accompanying nucleoli or endoplastules are further stated to be exchanged
between two conjugating individuals, and held to exert a possible fecun-
dating influence in the building up of the new nucleus. In the case of
Vorticella, where conjugation or zygosis is complete, the usually smaller
detached zooid, whether derived by fission or gemmation, that encounters
and buries itself in the substance of a larger sessile individual, is regarded
as a male zooid, and the latter sessile one as the female ; in this sense the
Vorticellidae and other types exhibiting similar phenomena are deemed to

GENETIC REPRODUCTION. 97

be essentially hermaphrodite. Conjugation under any circumstance is,
however, interpreted by Engelmann as productive of a mere revitalizing
or rejuvenating power, enabling the unicellular organism to continue its
normal mode of multiplication by binary division. During all conjugative
processes, the disintegration and subsequent reconstruction of the endo-
plastic element, and the assumption by the endoplastule of a striated
aspect, reported by Biitschli, is entirely corroborated.

While inclined to acquiesce with the views of Engelmann and Biitschli
now briefly recorded, so far as their interpretation of the conjugative pro-
cess is concerned, and, as previously intimated, to attribute to this process
a chiefly revitalizing or rejuvenating function as implying the most logical
possible interpretation of the reproductive phenomena exhibited by uni-
cellular organizations, the present author is not prepared to follow these
authorities in that part of their argument which involves the disassociation
of the endoplast with any function beyond that possessed by the nucleus of
an ordinary tissue-cell, or to deny to the Infusoria any faculty of repro-
duction beyond that of binary division. The one alternative is most
intimately, and indeed inseparably, involved with the other, and in this
connection sufficient consideration has certainly not been granted by
Biitschli and Engelmann to the results practically, and not merely
theoretically, obtained by other workers in the same field. That the
endoplast does, under certain conditions, exhibit phenomena entirely
distinct from those presented by the simple histologic nucleus, and that
the Infusorial organism can propagate its kind by means other than those
of simple fission, has been already demonstrated in the section devoted to
external and internal gemmation, and is conspicuously manifested in such
types as Hemiophrya gemmipara among the Acinetidse, in which ramifying
diverticula of the endoplast ascend into the anterior bud-like extensions of
the body-substance and become separated off, and enclosed within the same,
when the latter are severed from the parent organism ; phenomena of
an essentially similar kind are likewise presented by the gemmiparous
Acineta mystacina and various species of the genus Spirochona. There
is, further, no sufficient reason for doubting the accuracy of the obser-
vations first made by Eckhard in the year 1846, and since confirmed and
extended by Claparede and Lachmann, concerning the production of
internal embryos in Stentor cceruleus and polymorphic, these embryos being
developed individually from a single element or node of the characteristic
moniliform endoplast. Where such embryos have been reported, Engel-
mann and Biitschli have dismissed them as merely externally derived
parasitic forms, mostly Acinetae, referable to the genus Spkaropkrya of
Claparede and Lachmann, synonymous with Engelmann's genus Endo-
sph(zra. Such in many cases they undoubtedly are, and notably in those
supposed embryonic forms associated by Stein with the several types
Stentor polymorphic, Bursaria truncatella, and Stylonychia mytilus /_. these
unmistakable parasitic forms represent, however, but a small and altogether

II

98 ORGANIZA TION OF THE INFUSORIA.

unimportant minority. Undoubted evidence of the production of embryos
through the breaking up of the substance of the endoplast is afforded, in
addition to the instances already cited, by Haeckel, in his account and
illustrations of the pelagic form Codonella campanella, and by Balbiani, in
connection with his most recent investigations of the Miillerian type
Didinium nasutum. In the genus Euglena and its allies, the production of
embryos through the increment in size and splitting up of the substance of
the endoplast has been amply demonstrated by Stein and Carter, and
is confirmed also by the observations of the present author. As a last
illustration of this production of germs or embryos through the subdivision
of the endoplastic element, may be cited Professor Allman's account of
the development of a species of Epistylis, communicated to the meeting of
the British Association, held at Brighton in the year 1875. In this case
individuals possessing a normal development of the ordinary band-like
endoplast were observed to undergo encystment, the enclosing membrane
becoming after the lapse of a few days so opaque as to preclude a clear
view of its contents. Upon breaking the capsule open, however, it was
found that the endoplast had increased prodigiously at the expense of
the surrounding plasma, presenting the aspect of a long and much con-
voluted cord, while in still more advanced phases this cord-like endoplast
had separated into a number of ciliated and free-swimming germs whose
contour, as in the case of Didinium nasutum, most closely resembled the
adult form of Trichodina (Halteria) grandinella. Reproductive phenomena,
closely corresponding with those just described, have been recently reported
by Everts of Vorticella nebulifera.

Before finally dismissing the subject of the production of embryos from
the substance of the endoplast, a protest must undoubtedly be lodged
against Biitschli's assertion that the fragments into which it becomes
separated during or after conjugation, are merely cast out of the body as
waste matter. Such an unprofitable destiny is not usually found associated
with so essential a structure, and in place of the purely negative evidence
adduced, it is equally probable, and far more logical, to presume that
these detached fragments represent germs which ultimately develop to
the parent forms, as in the case of the endoplastic fragments of Stentor,
Vorticella, Euglena, and other types already alluded to. Whether or
not the conjugation or fusion of two individual animalcules exerts a direct
influence upon the sporular or gemmiparous reproductive phases, in addition
to the more ordinary binary segmental one, is as yet scarcely determ in-
able, though that in the first-named case it commonly, if not more usually,
precedes spore-production is made evident through the investigations of
Messrs. Dallinger and Drysdale, added to those of the present author, in
connection with a considerable number of Flagellata.

With respect to the actual act of conjugation, fusion, or zygosis, as it is
variously denominated, it is worthy of remark that where such conjugation
is complete and permanent, as in the family of the Vorticellidae, and so far

ZOOLOGICAL AFFINITIES. 90

as known, in all the members of the Flagellata, the coalescing units are
frequently of diverse size and contour, the one larger and more rounded, and
the other smaller and more attenuate. The inference to be derived from this
circumstance, combined with the fact that in the conjugative process the
smaller unit mostly, if not invariably, becomes absorbed by or immersed
within the substance of the larger, is unavoidable. The larger unit takes the
place of the female element, and in itself figuratively and physiologically
represents the monocellular unimpregnated ovum ; the smaller one to an
equivalent degree is identical with the male element or spermatozoon, and
through its union with the female one communicates to the latter that re-
vivifying influence expressed through a capacity to prolong the reproductive
function, and whether that function takes the form of binary division, gem-
mation, or spore-production, the dioecious generative type may certainly
be said to be represented in its most elementary condition. With those
animalcules, on the other hand, such as Paramecium and Bursaria, in which
conjugation is simply transient and incomplete, and where both conjugative
factors meet and part on equal terms, both the male and female elements,
if such are represented, are necessarily united in each individual zooid, and
the generative system is as distinctly and essentially hermaphrodite or
monoecious.

Affinities of the Infusoria to the Higher Zoological Groups.

Among the very extensive, and in some respects heterogeneous, assem-
blages of animal forms associated in this volume under the comprehensive
title of the Infusoria there is necessarily encountered a series of races or
types that not only differ very widely from one another, but which occupy,
so far as it is possible to predicate, a very different rank or position with
relation to the outlying representatives of the organic series. Being ac-
cepted, as already explained, as simple unicellular organisms or Protozoa,
no comparisons possessing a homologic value can necessarily be instituted
between the Infusoria and any members of the more highly organized and
multicellular Metazoa. It remains, however, to be shown that, while no
such direct homological comparisons can be established, there permeates
throughout the ranks of this extensive group a substratum of superficial
or homoplastic resemblances whose existence it is impossible to ignore.
Regarded from this point of view, the Infusoria will be found, like an archi-
tect's puny and homogeneous clay or plaster model, to, as it were, anticipate
and pre-typify the elaborate edifice of multiple and diverse materials
afterwards erected or eliminated from this same" primary simple plan.
In yet another direction it is likewise capable of demonstration that
a very considerable number of infusorial animalcules foreshadow or typify
in a corresponding manner, in either their isolated or socially aggregated
condition, the separate or associated cellular elements out of which the
higher tissue-structures or Metazoic organisms are built up. The like-
ness in this last instance is necessarily far more substantial than in the

H 2

100 ORGANIZATION OF THE INFUSORIA.

preceding case, and, as the comparisons instituted are as between cell
and cell or equivalent appendages of such cells, all likenesses of this
description may in the strictest parlance be termed homologous resem-
blances. Some of the more prominent examples that fall within this
last-named category may be first enumerated. Commencing with the
Infusorial group, in its simplest or most lowly organized condition, or in the
first place descending yet a step lower, and selecting a simple Rhizopodous
Protozoon, such as an Amoeba, it is impossible not to recognize that we have
here the morphological equivalent or homologue of a tissue-cell in its most
elementary condition, as represented by a colourless blood-, lymph-, or
ganglionic-corpuscle. The likeness in this instance is, furthermore, not
simply one of form ; in the case of the blood- and lymph-corpuscles, reptant
movements accomplished by the extension and contraction of pseudopodic
appendages, and similar to those of the independent Rhizopod, are also
freely manifested. It is from such a similar simple repent amcebiform body
that many of the flagelliferous members of the Infusorial class take their
origin, as demonstrated by the author in the case of Euglena, Eutreptia, and
many Choano-Flagellata, while the retrogression to such a simple elemental
type is a familiar phenomenon among the representatives of this same section
immediately antecedent to the process of either encystment or coalescence.
Proceeding with an examination of the flagelliferous section of the Infusoria
in its normal conditions of development, we find at the bottom of the series
the curious genus Trypanosoma distinguished in the case of T. EbertJd by
a long attenuate body, around which is spirally disposed a most delicate
frill-like membrane, whose active vibrations fulfil the function of locomotion.
It is a remarkable fact that an essentially similar type of structure charac-
terizes the exceptionally shaped monocellular spermatozoons of Triton,
Bombinator, and other tailed and tailless Amphibia, as originally figured
by Wagner and Leuckart, Unker, and Von Siebold. Spermatozoa in their
normal and most familiar form consist merely of a more or less rounded
anterior extremity or head, and a dependent flagelliform appendage or tail,
and have been recently compared by Professor Huxley * to a simple cell
of which the larger and more solid anterior part represents the nucleus,
and the dependent tail only the very fully developed and much attenuated
peripheral protoplasm. This more normal and simple form of the sper-
matozoal element is abundantly represented in the class now under con-
sideration. Such simple uniflagellate types as Monas and Petalomonas
exhibit in their adult state of development a type of structure essentially
corresponding with that of an ordinary spermatozoon, while the Heteromita,
the majority of the Choano-Flagellata, and numerous Eustomatous
Flagellata commence their existence as simple uniflagellate spermatozoon-
like organisms. In the case of Heteromita lens, as also in that of the
swarm-gemmules of the flagelliferous Spongozoa, it is, moreover, noteworthy
that in their initial condition of free-swimming existence the individual

* Biological Lectures, South Kensington, Session 1879-80.

ZOOLOGICAL AFFINITIES. IOI

unicellular zooids are aggregated together in clusters, closely resembling
the sperm-bundles of various higher animals, the same being similarly
derived from the repeated cleavage or fission of a primarily single unit.
Illustrations of the homoplastic likeness that subsists between certain
Infusoria and the more complex forms of spermatozoidal structures are
afforded by the Heteromitce in their adult and bi-flagellate condition, in
which they resemble in a remarkable manner the so-called " zoospores "
or " antherozooids " of various cryptogamic plants, while in the Poly-
mastigous forms Pyramimonas and Chloraster the modification presented
is almost identical with that which obtains in the spermatic elements of
Homarus and other Podophthalmous Crustacea.

The next recurring structural homotype in the ascending scale as repre-
sented by independent Infusorial organisms with relation to the differentiated
elements of a compound tissue-structure, is met with in the remarkable
multiflagellate type discovered by Professor Haeckel, and which has re-
ceived from him the title of Magospkcera. In this instance the isolated zooids
of the normally compound globose colony present a somewhat elongate
pyriform contour, and bear at their truncate, anterior extremities a number
of long whip-like' appendages or flagella. A type of structure in all ways
comparable with the zooids of Magosphcera is repeated in the ciliated
epithelium-cells of all higher tissue organisms, from which, compared
separately, they are scarcely to be distinguished. One more illustration
in connection with the present line of comparison remains to be cited.
Many Flagellata, such as Spongomonas, Phalansterium, and Uroglena, are
distinguished for their excretion of a glairy gelatinous matrix, within
the substance of which the separate units multiply by the process of
binary segmentation, and gradually extend the limits of their common
domicile. A similar building up by excretion of a common gelatinous
matrix, and the extension of the boundaries of the mass by repeated fission
within the same, is the essential characteristic of the cartilage cells of
both Vertebrata and Invertebrata. The comparison here instituted is, how-
ever, still more striking in the case of Nostoc and other allied plants. In
these latter the condition of simple nucleated cells, imbedded like those of
cartilage cells in the midst of a common gelatinous matrix, is generally
exhibited, while in that of the Infusoria it obtains only during the
duplicative process.

As might have been anticipated, it is among the lower or flagelliferous
section of the Infusoria only that are encountered those forms that find their
counterpart in the component elements of the higher tissue-structures now
enumerated ; in a similar manner it will be found that those homoplastic
prototypes of certain Metazoic organisms, taken as a whole, exist only
among the ranks of the more highly differentiated Ciliate and Tentaculi-
ferous divisions of the group.

Before proceeding, however, to an enumeration of these more highly
differentiated homoplasts, it has to be shown that both the Flagellate and

102 ORGANIZATION OF THE INFUSORIA.

Ciliate sections of the Infusoria share between them one typical develop-
mental phase, which is usually regarded as an essential factor only of the
Metazoa. Among all these organisms the first developmental step exhibited
by the simple unicellular reproductive cell or ovum is the division of its mass
by the process of segmentation or repeated binary fission, the secondary
result of which subdivision is the production of a more or less spheroidal
aggregation of simple cells or blastomeres, upon which has been bestowed,
in reference to its mulberry-like aspect, the characteristic title of a " Morula."
Such a Morula is, however, not limited to the Metazoa. As demonstrated
in the chapter devoted to the reproductive phenomena of the Infusoria,
certain Ciliata, such as Colpoda, Otostoma, and IchtJiyophthirius, and an innu-
merable host of the Flagellata, exhibit in their developmental cycles an
essentially corresponding embryonic type. In no point can the segmented
cell-mass or Morula of the Metazoon and Protozoon be distinguished, and it
is only in the succeeding phases of development that the distinction becomes
apparent. Through the disintegration or falling to pieces of the Protozoic
Morula, each individual cell or segmented element mostly commences an
independent existence, while in that of the Metazoon they remain perma-
nently united and initiate new and complex metamorphoses. Exceptional
and highly instructive instances among the Protozoa, in which the Morula
condition may be said to be retained as the characteristic adult life form,
are afforded by the subspheroidal colony-stocks of Magospk&ra, Symira,
and Syncrypta, and in a modified manner also by the spheroidal clusters or
"ccenobia" of Anthophysa vegetans, Codosiga botrytis, and other sedentary
types. The compound Radiolaria, Collosphtzra and Sph&rosoum, &c., may
also probably be correctly interpreted as modifications of the moruloid
type. Although any direct comparison between the Protozoic and Meta-
zoic organisms beyond this Morula stage would be inconsistent, certain
most remarkable homoplastic resemblances invite attention. Commencing
with the lowest order of the Ciliate group, and selecting as an illustration
one of the mouthless Opalinidae, it will be at once recognized that there
is here presented a form which, on a simplified and monocellular scale, most
distinctly foreshadows or epitomizes the structural type exhibited by the
so-called "Planula," or ciliated larva, developed by Metazoic organisms,
as the direct outcome of the embryonic Morula already described. Like
a typical Opalina, these Planulae are characterized by the possession of a
more or less ovate body, which is covered throughout its surface with fine
vibratile locomotive cilia. In neither case is there any trace of an oral
aperture, so that both animals may be described as closed, externally
ciliated sacs. In the Planula this closed sac is composed of multicellular
elements, arranged in two distinct superimposed layers, the ectoderm and
endoderm, while in Opalina the entire homoplastic counterpart is fashioned
out of a single cell. It is a significant fact, however, that in this latter
instance the organism has been recently demonstrated to be multi-
nucleate, a fact in itself suggestive of latent or potential multicellular com-

ZOOLOGICAL AFFINITIES. 103

position. In the same way that the Opalinidae may be said to foreshadow
the Planula type of organization, it might be suggested that the ordinary
stomatode Ciliata, and more especially the multinucleate species, anticipate
the next progressive developmental phase of the Metazoic embryo, as
represented by the typical "Gastraea" or "Gastrula." The only advance
in organization exhibited by this last-named type as compared with the
Planula is, that intercommunication between the central cavity and the
outer world is now effected through the breaking away of the apical ex-
tremity of the primitive closed sac, this apical perforation or " cytostome "
constituting the primitive mouth or oral aperture.

As a rule, the Ciliate Infusorium develops, in addition to an oral orifice, a
second or anal aperture, but in many it is not distinctly represented ; in these
the conformity to the Gastraea type is necessarily all the more complete. By
Professor Haeckel, to whom the scientific world is chiefly indebted for
the discovery of the three several "Morula," "Planula," and "Gastrula"
developmental phases of the Metazoic series, it has been suggested that,
in accordance with the laws of evolution, these successive transitory phases
doubtless represent the permanent conditions of as many primitive and
pre-existing Metazoic organisms, to which might be attached for convenience
the hypothetic titles of " Arche-Morula," " Arche-Planula," and "Arche-
Gastrula." From the foregoing data it is very evident, however, that such
archetypes are even yet in existence, and may be successfully sought for
among the representatives of the Protozoa.

Entering now upon an examination of those few instances in which
representatives of the Infusoria appear to pre-typify, not embryonic or
transient, but fully matured conditions of certain lower Metazoa, attention
may be first directed to those forms, such as Paramecium and Ophryoglena,
in which the subcuticular layer abounds with the minute evertile structures
known as trichocysts. As already pointed out many years previously by
Kolliker, Oscar Schmidt, and other authorities, the correspondence between
such types and certain of the lower Annelida or Turbellaria is, so far as
the general form and the possession and disposition of their trichocysts is
concerned, most conspicuous, so that on a simple monocellular scale these
Infusoria may be said to foreshadow or pre-typify these simple Annelids. It
has been suggested by Louis Agassiz, and also by Diesing, that the typical
Vorticellidae, with their closely approximated oral and anal apertures and
well-developed pharyngeal tube, indicate a considerable conformance with
the fundamental organism of the Polyzoa — the last-named authority, indeed,
transferring this section of the Infusoria to that series. In its originally
implied sense it is necessarily impossible to maintain such a proposed
affinity, but in a more remote manner, regarding such animalcules as
modifications of unicellular zooids in the direction indicated, it may perhaps
be accepted. While, as already intimated, Paramecium and its allies
would appear to pre-typify the Turbellaria, another more lowly organized
group of the Ciliata exhibits an entirely distinct and highly interesting

IO4

ORGANIZA TION OF THE INFUSORIA.

affinity. The group in question is that of the Opalinidae. The simpler
members of this section have been already compared with embryonic
Planulae, but in certain of the more highly modified representatives of the
family the homoplastic resemblance to the similarly endoparasitic tape-
worms or Cestoidea is most marvellous. Both are distinguished for the
entire absence of an oral or anal aperture, and are in this respect imperforate
saccular bodies. Both occasionally develop horny hooklets or an acetabu-
late appendage at the anterior extremity wherewith to ensure a permanent
adhesion to the internal viscera of the host infested. Both, moreover, share
in common a special mode of reproduction, which, while it recurs among the
higher Annelida, is met with nowhere else among the Protozoa. Reference
is here made to that peculiar form of terminal gemmation exhibited by the
Opalina (A noplophryci) prolifcra of Claparede and Lachmann, and several
other allied forms, and in which a long series of buds or segments are
produced at the posterior extremity, and become successively liberated,
like the segments or " proglottids " of an ordinary tape-worm.

The affinities, real or apparent, of one important section of the Infusoria,
that of the Tentaculifera, remain to be discussed. At first sight, this
group, including Acineta and its allies, would seem to stand by itself and
to present no special homoplastic points of agreement with any Metazoic
type. It is proposed here, however, to show that in more respects than
one these suctorial animalcules epitomize most conspicuously, though on
a simple unicellular scale, the structural plan of the lower Hydrozoa.
To illustrate this resemblance, the Hydroid Polypite in its simplest
form, as represented by the so-called " Dactylozooids " recently dis-
covered by Mr. H. N. Moseley,* to play so important a part in the life-
economy of Millepora, Stylaster, and other coral-building Hydrozoa, may
be selected. Such a Dactylozooid or Polypite presents the aspect of
a long, slender, sinuous body, provided with numerous simple or knobbed
tentacles, but is entirely devoid of any mouth or stomach. The function of
these Polypites is simply to seize food and convey it to the mouth-bearing
polypes or " gastrozooids." There can be little doubt, however, that these
rudimentary or secondary Polypites represent the primary and independent
zooids of some more ancient stock, and the question naturally arises how
in such a case did they ingest food ? In reply, it may be submitted that all
that is needed is a perforation of the extremity of each separate tentaculum,
such as normally exists in many Ccelenterata, combined with the capacity of
incepting food at these orifices. It is this slight modification, furthermore,
that is alone required to produce an organism fundamentally corresponding
with that of an ordinary suctorial Acineta, and whose only means of com-
munication with the outer world is similarly through perforations of the
extremities of its prehensile tentacles. In one genus of the Acinetidae,
Hemiophrya, it is further worthy of remark that certain of the tentacles only,
and those the inner ones, are devoted to the ingestive function, while those
* II. N. Moseley, "On the Structure of Millepora," 'Phil. Trans. Roy. Soc.,' vol. clxvii. (1877).

ZOOLOGICAL AFFINITIES. 105

forming the peripheral series are simply prehensile, and catch and convey
food to the central ones.

Should a type be discovered possessing, in addition to the peripheral
or prehensile series, only one central ingestive tentacle, in place of the three
or four that more usually obtain, and which would consequently occupy
that position in relation to Hemiophrya that is maintained by Rhyncheta
with respect to Podophrya, there would be undoubtedly presented an
organism directly comparable with an ordinary gustatory Hydroid Polypite.
The homoplastic correlation of the Tentaculifera with the Hydrozoa can
be still further extended. In the compound type Dendrosoma radians,
for example, we meet for the first time, and, as far as yet known, with the
only existing instance among the Protozoa in which is produced a decum-
bent creeping stolon and an erect branching stalk, essentially analogous
with the so-called creeping " hydrorhiza " and erect " hydrocaulus," which
form the common " ccenosarc " of the ordinary Hydroid Zoophytes. The
phenomena of development in this group yield yet another highly
suggestive co-ordination in a similar direction. As previously stated, the
larval condition of the Ccelenterata generally, including the Hydrozoa, is
a free-swimming, mouthless, ciliated sac, named a Planula, with which
certain of the Opalinidre have been indirectly compared. It is a note-
worthy fact that the larval condition of the Tentaculifera is also in all
cases a free-swimming and mouthless ciliated sac entirely different from
the parent organism, whose cilia become similarly obliterated on the
assumption of the normal sedentary state.

In addition to the foregoing enumeration of the several apparent homo-
plastic affinities here suggested as subsisting between the various sections of
the Infusoria with relation to certain Metazoa, or to the more simple
elements of the same, the morphologic relationship or position of these
several groups or sections with respect to each other remains to be
summarized. The main lines or phyla of evolution, from the lowest and
most simplified factors in the series as represented by such types as
Mastigamceba or Monas, by diversely branching and frequently intercalat-
ing tracks, up to the highest members of the class, has been already dis-
cussed at length, and diagrammatically illustrated in a preceding chapter.
The more intricate question, however, as to which special group or sub-
order of the Infusoria generally, or of the Ciliata and Tentaculifera in
particular, claims precedence as exhibiting the most highly differentiated
structural type, has yet to be decided. More usually this most advanced
position has been conceded to the Peritrichous sub-order of the Ciliata,
including chiefly the Vorticellidae, whose higher structural plan is held
to be manifested through the reduction and concentration of the ciliary
appendages so as to form a simple circular or spiral adoral wreath. Viewed
also with respect to the closely approximated positions of the oral and anal
apertures, and to the high organization of the pharyngeal apparatus, the
evidence would appear to be altogether in favour of the Peritricha.

106 ORGANIZATION OF THE INFUSORIA.

In certain important points, nevertheless, it will be found that another
sub-order, that of the Hypotricha, commends itself equally as a candidate for
recognition. It is, for instance, undoubtedly among the representatives of
the genera Stylonychia, Euplotes, and other Oxytrichidae that we find the
most elaborate differentiations of the Ciliate type, certain of the numerous
and diversely modified groups of appendages being severally set apart for
the accomplishment of the special functions of food-collection, natation, and
even ambulation. Such forms, although not indicating any homoplastic
affinity, as in the previously cited cases, with the Metazoic series, un-
doubtedly represent the as yet known most highly specialized type of a
simple unicellular animal or Protozoon, and exhibit in this respect, as
compared to the other sections of the Ciliata, a type of organization
parallel to that which obtains among the higher Insecta with relation to
the Annelidous or Myriapodous groups of the Arthropoda. It is not,
however, in either of these more highly specialized divisions that the phylum
of evolution onwards and towards the yet higher groups of the organic
world is to be sought. Such differentiated types represent merely the
most advanced and terminal series of an entirely divergent and independent
branch or outgrowth from the parent stock. In yet another point, the
Hypotrichous sub-order of the Ciliata would seem to lay claim to a higher
grade of organization than that possessed by the Peritricha. In their
phenomena of reproduction the processes of conjugation, as exhibited by
these two sections, are conspicuously distinct, being in the case of the
Peritricha complete and permanent, as with the Flagellata and lower
Protophytes, while with the Oxytrichidae, and also certain Holotricha, such
as Paramecium, the conjugative act is only transitory, the two conjugated
individuals finally separating and renewing their independent existence.
The approximation in the latter instance towards the genetic reproductive
process of the Metazoic series, and in the former case towards the simpler
vegetative one known as " zygosis," as it occurs among the lower plants,
is self-suggestive, and affords an additional element for consideration in
summing up the evidence in favour of the higher organization of these
respective groups.

The apparent affinities of the Tentaculiferous class of the Infusoria
with reference to the Metazoic series has been already discussed, but not so
those that obtain between the Tentaculifera and the Ciliate division of the
same group. Excepting for the data yielded by the phenomena of develop-
ment, no direct relationship indeed would seem to subsist between the two,
neither cilia, flagella, nor any recognizable modifications of those appendages
being characteristic of the adult forms. In place of such organs these
animalcules possess suctorial or prehensile tentacula, which, as explained
at length on a previous page, more closely approach, in their simplest
condition, the extensile ray-like pseudopodia of Actinophrys and other
Radiolaria. The free-swimming larvae or embryos of all Tentaculifera
are, nevertheless, characterized by the possession of a more or less com-

DIS TRIE UTION. \ O 7

plete covering of cilia. These cilia are found in different genera and
species to exhibit three separate plans of distribution, which are further
remarkable as coinciding essentially with those three patterns of ciliary
distribution exhibited by the three Ciliate orders of the Holotricha, Peri-
tricha, and Hypotricha. Thus, the simple forms Urnula epistylidis, and
Acineta linguifera, furnish examples of Holotrichous ciliated embryos ;
Podopkrya fixa and P. cyclopum, Peritrichous ; while in those of Dendro-
cometes paradoxa, Ophryodendron abietimim, and Hemiophrya gemmipara,
such ciliation essentially corresponds with that of the Hypotrichous series.
Paying due regard, therefore, to the morphologic axiom that the embryonic
history of the higher species foreshadows or epitomizes the adult state or
states of others lower in the organic scale, the deduction is unavoidably
arrived at that the Tentaculiferous group of animalcules represents a series
of organisms occupying a position morphologically higher than that of
any of the Ciliata, and all of the leading divisions of which latter are
passed through or structurally represented by the Tentaculifera during their
earlier or embryonic state. It is a further noteworthy fact that the em-
bryos presenting a Holotrichous pattern of ciliation are met with in asso-
ciation with the simplest representatives of the Acinetidae, while in the most
complex ones, such as Hemiophrya and Ophryodendron, it assumes the
Hypotrichous type. This last-named circumstance may be cited as further
correlative testimony towards the evidence already adduced in support of
the higher organization of the Hypotricha as compared with the Peritricha.
The innumerable intercalating relationships and affinities that serve to
bind together and unite in one harmonious whole the several orders of the
Ciliata, are discussed at length in connection with the preliminary defini-
tions given of each respective subdivision of the class.

Taking the evidence now submitted in its complete form, and having
regard to the innumerable intricacies exhibited in the organization and
development of the class Tentaculifera, the position of the highest factor
in the Protozoic sub-kingdom is herewith accorded to it, and the antici-
pation at the same time submitted, that future investigation will serve to
establish on a still more substantial basis the affinities between this group
and the more elementary factors of the Hydrozoic series.

Distribution of the Infusoria.

Although, taken as a whole, and as already intimated in general terms
in the opening paragraph of this volume, the Infusoria exhibit practically no
limit to their distribution, it will be found on a closer examination that many
out of the various groups, families, and genera present a certain fixed order
of diffusion. Among these, some may exclusively inhabit salt water, and
others fresh, the several secondary conditions of both these latter elements,
whether fresh or stagnant, being also productive of special forms or types.
Water in its various conditions, as above indicated, by no means represents,

108 ORGANIZATION OF THE INFUSORIA.

however, the total limit of infusorial dissemination ; several groups are
distinguished for their exclusively endoparasitic habits, the alimentary
and circulatory systems of various Vertebrata and Invertebrata, including
that of man himself, being often the unconscious entertainers of infusorial
guests. As the result of the most recent investigation, one considerable
group is found associated with offensively putrid fish and other animal
macerations, while in a totally opposite direction, as discovered by the
present author, and recorded in the chapter devoted to the subject of
Spontaneous Generation, the limpid water of condensed dew or falling
rain as it settles on the grass provides a microcosm for the maintenance
of a still more extensive series.

Passing in brief review several of the more abnormal habitats now
enumerated or recorded in the succeeding chapters, those infusorial
organisms distinguished for their salt-water predilections may be first
noticed. Although as yet our knowledge of the marine species of Infusoria
may be said to be but imperfect, many generic and family groups may
be cited as belonging almost entirely if not exclusively to this category.
Commencing with the higher Ciliate division, the free-swimming pelagic
forms Tintinnus, Codonella and Dictyocysta, and the sedentary type Follicu-
laria, are especially prominent. In the last-named genus, a single fresh-
water species, F. Bottom, has, however, been quite recently discovered. Other
genera, such as Lembus, Metacystis, and Blepharisma, while essentially
marine, are more notably littoral or stagnant sea- water types. To this
last-named group have also to be referred the two Hypotrichous family
divisions of the Chlamydodontidae and Ervilliidae, and the three separate
genera Styloplotes, Uronychia, and Epiclintes. Among the Cilio-Flagellata, the
genus Ceratium is almost entirely marine ; C. longicorne and C. kumaonense
being the only known fluviatile forms, while the allied genera Prorocentrum,
Amphidinium, and Dinophysis are exclusively pelagic. Noctiluca and Lepto-
discus may be selected from the Flagellate section as the most conspicuous
pelagic types, the several genera, Glyphyidium, A nchonema, and Conchonema,
being in a similar manner characteristic of sea-water in its stagnant or
putrid state. The section of the Tentaculifera is pretty evenly balanced
between salt and fresh water habitats; two genera, OpJiryodendron and
Ephelota, are, however, so far as known, exclusively marine. Although
the foregoing generic and family groups are here quoted as typically
characteristic of the marine infusorial fauna, they are by no means cited as
constituting an exhaustive summary. It will be further found that a very
considerable percentage of the more ordinary fluviatile types of the Ciliata
have likewise their marine representatives, and as familiar examples of
which may be mentioned the greater number of genera of the exten-
sive family groups of the Vorticellidae, Oxytrichidae, and Euplotidae, not
a few species among these, indeed, such as Ophrydium versatile and
Uronema marinum, being notable for their indifferent salt and fresh water
habitat.

DISTRIBUTION. IOQ

In an enumeration of those animalcules whose distribution pertains
to neither of the two last-named elements, but is for the most part
inextricably interwoven with that of various more highly organized animal
types, upon whose vital juices they are dependent for their existence,
the most prominent position has undoubtedly to be awarded to the
mouthless Opalinidae. All of the various specific and generic types of
this important family group are found leading an endoparasitic existence
within the alimentary canals, in some instances of various Amphibia, such
as newts, frogs, and toads, and in others of various aquatic Annelida, these
latter being in several instances marine. Among the Peritricha, the two
genera Opkryoscolex and Entodinium are notable for- their limitation to
the stomachal cavities of various ruminants, while the Heterotrichous form
Balantidium coli honours the rectal passage of the human subject with
its presence. Other species belonging to the last-named genus, as also
its near allies Plagiotoma and Nyctotherus, limit their attentions in a
similar manner to various worms and other lower Invertebrata. The two
generic types Conchophthirus and Ptychostomum form noteworthy examples
of the parasitic series, being both found inhabiting the mucilaginous
body-slime of various terrestrial Mollusca. The more recently discovered
IchtJiyopJitkirius multifiliis is remarkable for its attachment to the cuticular
surface of young trout, and often causes severe losses to the French fish
cultivators by reason of its depredations.

Although the Tentaculiferous section of the Infusoria yields but few
examples of endoparasitism, one single genus, Sphcerophrya, is characterized
by its passing the earlier stages or chief portion of its existence within the
internal substance or endoplasm of various other animalcules. The Flagelli-
ferous section of the class yields, so far as endoparasitic habits are con-
cerned, a series of examples little inferior in extent and interest to that of
the Ciliata. It is to the ranks of this group that have to be assigned the
actively motile organisms recently discovered by Mr. T. R. Lewis in the
blood of healthy rats, and described hereafter under the title of Herpemonas
Lewisi. One species of Trichomonas has as yet been found only in fluid
obtained from the human vagina. Bodo urinarins inhabits human urine,
while the several species of Lophomonas infest the intestinal tracts of the
cockroach and other Insecta. The two specific forms here referred to the
order of the Trypanosomata undoubtedly represent the Flagellate Protozoa
in their most rudimentary condition, and are respectively inhabitants of
the blood of frogs and other Amphibia, and the rectal passages of ducks,
geese, and other domestic poultry. As intimated in the systematic de-
scription of these types, it is possible that they represent developmental
conditions of the same organism.*

Apart from the large number of Infusoria that exhibit ecto- and
endoparasitic habits, it will be found that a very considerable series, while

* An extensive notice of the essentially parasitic representatives of the Infusoria is embodied in
an article contributed by the present author to the ' Popular Science Review ' for October 1880.

! I0 ORGANIZATION OF THE INFUSORIA.

invariably attached to other living organisms, are not maintained at the
expense of the essential juices of these latter, but simply occupy with
respect to them the position of co-lodgers or messmates. The very
appropriate title of "commensals" has been recently employed by Prof.
P. van Beneden to distinguish those organisms among the higher Metazoic
series which pass a similar co-associated, non-hurtful, and often mutually
dependent existence, and that of " commensalism " for the distinction of
the peculiar pseudo-parasitic life habits which they exhibit. As might be
anticipated, the phenomenon of commensalism is exhibited among the
Infusoria chiefly by those types that lead a fixed or sedentary existence,
and is notably conspicuous among the Peritrichous Vorticellidae. From
these may be selected as examples various species of the several genera
Epistylis, Zoothamnium, Opercularia, Cothurnia, Scyphidia, and Spirochona,
a very large number of which are found in company only with certain
species of aquatic Insecta, Crustacea, or Mollusca.

As free or unattached messmates or commensals, reference may be more
especially made to the family of the Urceolariidae, including Trichodina
pediculus, notable for its intimate relationship with the fresh-water Hydra,
and which position it shares with the Hypotrichous form Kerona polypornui.
Other animalcules of the same family, exhibiting closely corresponding
habits, are rep'resented by the two genera Urceolaria and Trichodinopsis ,
while a near ally, Licnophora, has been found as yet as a commensal only of
certain marine Planarians. The genus Ophryodendron, among the Tenta-
culifera, furnishes in the two species O. sertularia and O. multicapitata
marked examples of pseudo-parasitic life, the former being a common
guest of both Sertularian zoophytes and the little hairy crab Porcellana
platycheles, while the latter, recently discovered by the author, has as yet
been found attached only to the limbs and carapace of a species of sessile-
eyed crustacean. Descending to the division of the Flagellata, commen-
salism, so far as is at present known, would appear to be most abundantly
represented among the mostly sedentary collar-bearing section of the
Choano-Flagellata, where it is further noteworthy that the majority are
found attached, as commensals, to the peduncles or loricae of other higher
Infusoria. In this manner Salpingoeca minuta is found in society with the
flagellate type Dinobryon sertularia, while Salpingoeca convallaria grows on
Epistylis anastatica, and Monosiga Steinii on Vorticella convallaria and
Epistylis plicatilis, itself a commensal of the common pond-snail.

While the foregoing summary of some of the more abnormal areas of
distribution of the Infusoria subserves the purpose of indicating to the
student and collector of this group of beings the localities in which to seek
with success for certain specific or generic types, a brief space devoted to
an enumeration of the most favoured habitats of the non-aberrant types
will probably be welcome. In this direction it need scarcely be indicated
that weedy ponds, and slowly running water, containing an abundance of
aquatic plants, present both the most accessible and most remunerative

DISTRIBUTION. I I £

hunting grounds. Arrived here, the collector should be careful to secure
more especially portions of all the more finely divided plants, such as
MyriopJiyllum and Ceratophyllum, these affording favourite fulcra of attach-
ment for the sedentary species belonging both to the Ciliate and Flagellate
sections of the class, and being especially suited in consequence of their
slender contour for subdivision and transference to the glass slide or
zoophyte trough for examination. Living plants, however, by no means
exhaust the category of material to be secured. Dead leaves, from adjacent
trees, that have fallen into the water, and are passing rapidly into decay,
are often covered on their lower surfaces with the extensive slime-like
colonies of Vorticella campanula or Epistylis grandis. Specimens of the
almost always numerously represented Entomostraca, Cyclops and Cantho-
camptus, or higher crustacean forms such as Asellus and Gammartis, as
likewise all larvae of aquatic Insects, Mollusca, and even Annelida, should
be brought home and diligently examined, for some one or more of the
many parasitic or pseudo-parasitic species recently referred to. The
family of the Daphniadae or " water-fleas," as exceptions, are rarely the
entertainers of infusorial guests.

Ponds of smaller pretensions, presenting only a superficial layer of
duckweed, or stagnant ditches with a surface of brilliant green or other
coloured slime, may always be visited with advantage. In the latter
instance, some representative of the social Euglenidse, or possibly Peri-
diniidae, is usually to be encountered ; while in the former one the pendent
rootlets of the floating duckweed will in most cases be found to support a
perfect forest-growth of Vorticellcs and other Infusoria. Restlessly wander-
ing among the floating leaves of this gregarious plant, numerous Oxytri-
chidae, Tracheliidae, and not unfrequently Urocentrum turbo will reward
research, while the interstices of the decaying leaves may be examined for
examples of the singular genera Stichotricha and Chcetospira. In the ponds
of our metropolitan parks and commons that so abound with various
aquatic Ranunculi, the various species of brilliantly coloured Stentors
or "trumpet-animalcules" are commonly met with, their social colonies
often forming thin coloured incrustations on the minutely divided leaflets
of the plants in question that are conspicuously visible to the unassisted
eye. Lastly, in connection with fresh-water habitats, the upland ponds and
marshes abounding with Sphagnum, Drosera, and other bog-plants, are rich
hunting grounds that have as yet been but very imperfectly examined, and
may be expected to yield a rich infusorial fauna to the investigator. As
the result, indeed, of a few brief hours recently spent by the author on the
outskirts of Dartmoor, the two new and highly remarkable Flagellate types,
described later on under the titles of Rhipidomonas Huxleyi and Spongomonas
saccuhis, were obtained.

For the collector sojourning at the seaside, an almost equally unexplored
hunting ground is thrown open. Some of the most prolific habitats in
this instance are afforded by the living polyparies of the Hydrozoa and

112 ORGANIZATION OF THE INFUSORIA.

Polyzoa that may be gathered at low-water mark or dredged from the
sea-bottom. These in almost all instances produce an abundant harvest
of Zoothamnium alternans and other attached Vorticellidas, Acinetidae, and
Flagellata, being in this respect far more prolific than the neighbouring sea-
weeds, though certain of the finer divided varieties of these will be found
to yield their characteristic types. Many free-swimming species may be
secured by a careful surface-skimming of the smaller rock-pools, and more
especially such as are invaded by the sea only during the spring tides and
are left undisturbed through the intervening intervals. As in pond collect-
ing, the innumerable small Crustacea, Annelids, and other animal organisms
with which the sea abounds, should be carefully examined for parasitic
forms. For the capture of the less familiar pelagic types, including repre-
sentatives of the families of the Noctilucidae, Peridiniidae, Dictyocystidae, and
Tintinnidae, the use of a boat and muslin towing-net must be resorted to.

Concerning the geographical distribution of the Infusoria, we cannot
be said at present to possess anything approaching a comprehensive know-
ledge. The infusorial fauna of but few countries or even districts has
as yet been thoroughly investigated, while whole continents remain of
which it may be said that absolutely nothing whatever is known. From
such data as are at present available, nevertheless, and as might be antici-
pated with reference to organisms occupying so humble a position in the
organic scale, it is made manifest that generic, and in many cases even
specific, forms exhibit a most diffuse and practically cosmopolitan area of
distribution. Thus, a number of types belonging to identical or indis-
tinguishable specific forms are found to occur on the European continenti
in England, North America, and the neighbourhood of Bombay. Arctic,
temperate, and tropic climes yield, so far as at present explored, no more
widely divergent types than are to be encountered within adjacent districts.
Even the marine species as a rule exhibit no clear and well-defined demar-
cation, for the most part including the same generic and in not a few
instances specific sorts identical with those obtained from fresh water.

Of the dissemination of Infusoria in time, or in other words their geolo-
gical distribution, there is, as a necessary consequence of their mostly soft
and perishable nature, scarcely a trace preserved. The hard coverings or
loricae of a few species have, however, been recognized by Ehrenberg in
the Cretaceous deposits, and referred by him to the genera Ch<ztotypJila and
Ceratium. The siliceous loricae of the Peritrichous genus Dictyocysta occur
also in company with the pelagic Polycistina of the Tertiary formations,
and there can be but little doubt that the Infusoria in their simplest
condition represent one, if not the most ancient, of the stock-forms of the
organic series. Accepting, in fact, the Spongida as representatives of
the Choano-Flagellata, a subject-matter which is fully discussed in a suc-
ceeding chapter, the Flagellate section of the infusorial series is distinctly
traceable through every marine deposit from the present day back to the
Cambrian and even the Laurentian section of the Palaeozoic epoch.

PRESER VA TION. I 1 3

Preservation of Infusoria.

Up to within the last few years no attempts aiming at the preservation
of Infusoria in a condition approaching that which they exhibit in their
living state appear to have been successful. Ehrenberg and other early
investigators succeeded by careful desiccation in securing some shadowy
semblance of the pristine form of a few Ciliata, such as Paramecium and
Pleuronema, but for histologic purposes it is scarcely requisite to state
that types so preserved are practically worthless. Such progress has,
however, been made within the last half of the present decade in the
discovery of reagents and preservative fluids for the treatment of all organic
tissues, that the securing of permanent slides of the majority of infusorial
types is at the present day a mere matter of manipulation. That medium
which lays claim to the foremost position in the ranks for the conservation
of animalcules in their normal state, is undoubtedly osmic acid. Previously
utilized as an ordinary histologic reagent, it was first recommended to the
author by Professor Huxley in the year 1877 for the purpose now under
consideration, and is at the present time very generally employed. Applied
either in the form of vapour or as a solution in distilled water, having a
strength of from one to two per cent, the results obtained are most remark-
able. All structures, such as cilia, cirrhi and flagella, the internal endoplast,
and in Euglena and its allies the colours also, are preserved, the animal-
cules, excepting for the absence of motion, being scarcely distinguishable
from the living organisms. With certain of the more exceptionally
contractile forms, such as Stentor and Oxytricha, it is, as recommended
by M. A. Certes, better that the osmic acid should be employed in the
direct form by placing a drop of the solution on the covering glass before
laying the latter upon the slide containing the Infusoria ; this plan indeed
has been found by the author to be the most effectual and simple of appli-
cation in the majority of instances. For the Vorticellcs the employment
of a more concentrated solution of the acid than the one above mentioned
is recommended. As pointed out by M. Raphael Blanchard,* and also by
M. Certes, colouring reagents, such as haematoxylin, eosin, and picro-
carmine,t may be advantageously used in combination with osmic acid,
and assist greatly in developing the presence and form of the nucleus or
endoplast. The animalcules thus killed may be fastened down as per-
manent preparations, without the addition of any other preservative, and
afford valuable material for future reference and comparison. It will be
found that the smallest and most delicate flagelliferous species are equally
amenable to this course of treatment, preserving their flagella, and even,
in the case of the Choano-Flagellata, their delicate sarcode collars, in a
life-like form. As attested to in a succeeding chapter, the employment

* ' Rev. Internal. Sci.,' iii. 1879.

t In using this medium, the addition of one part of glycerine and one part of distilled water is
recommended by M. Certes.

I 14 ORGANIZATION OF THE INFUSORIA.

by the author of this medium for the investigation and preservation of the
similar collar-bearing sponge-monads has been attended with the most
satisfactory results. In addition to osmic acid, divers other conservative
reagents, accompanied with variable success, have been recently introduced.
Among these may be mentioned rectified pyroligneous acid, a drop or two
of which may be applied in the same manner as the medium last described.
Also, a concentrated solution of iodine prepared according to the formula
prescribed in Huxley and Martin's 'Elementary Biology,' and embodied in
the appended footnote.* The least portion of this fluid added to that
containing the Infusoria has been found by the author to act in a manner
almost identical with that related of osmic acid, and in some instances even
more efficiently. This medium possesses the additional advantage of
yielding no deleterious exhalations, which have to be carefully guarded
against in the use of osmic acid. An equally efficient and entirely harm-
less medium for the preservation of Infusoria is, according to M. G. du
Plessis,t afforded by a saturated solution of permanganate of potash ; this
last-named chemical being recommended by another authority % in com-
bination with chromic oxydichloride acid in the proportions of 25 per cent,
chromic acid, 5 per cent, permanganate, and 50 per cent, water. Staining
agents, such as the anilin blue or diamond fuchsin, in proportionate parts
of, in the first place, one part of the anilin solution to 200 parts of dis-
tilled water, plus 800 parts of pyroligneous acid, are reported to act
well in the resolution of otherwise obscure endoplastic structures. A
i per cent solution of acetic acid is also of important use for this purpose,
but on account of its corrosive properties is not available as a medium for
conservation.

In many instances, and more especially for the preservation of the
retractile-stalked simple and compound Vorticellidae, the employment by
the author of very weak dilute spirit, about one part of spirit to ten of
water, has been attended with the most successful results, the stems re-
taining under such treatment their stalks in every condition of contraction
and expansion, and their ciliary discs everted as in life. According to
Mr. J. E. Lord,§ the pelagic type Noctiluca miliaris may be preserved by
mounting in cells filled simply with pure sea-water.

Sir John Ellis's claim for notice as one of the earliest employers of
reagents in the investigation of infusorial organisms, the medium utilized
being the acrid juice of geranium leaves, has been already mentioned at
page 82. Brief reference was at the same time made to the still earlier
experiments, in a similar direction, instituted by Sir Edmund King, details
of the methods and materials he resorted to being, however, reserved for
enumeration under the present heading. Such earliest authentic record, as
contributed by Sir E. King to the ' Philosophical Transactions,' No. 283,

* " Prepare a saturated solution of potass'c iodide in distilled water ; saturate this solution with
iodine ; filter ; dilute to a brown sherry colour."
t ' Science-Gossip,' March 1879.
j T. C. in ' Science-Gossip,' May 1879. § ' Science-Gossip,' No. 173, 1879.

ME THODS OF INVES TIG A TION. I I 5

for the year 1693, embodies the following highly interesting data. Having
recorded the results of the application to Infusoria, with a needle's point, of
various substances producing no very important effects, he says — " Tincture
of salt of tartar (tartaric acid?} put with them in the same manner kills
them more immediately, but yet they will be first so sick or so affected,
call it what you please, as you may see by a surprising convulsive motion,
they will grow faint and languid apace, and you may see them fall to the
bottom of the drop upon your object plate, dead but in their own shape
that they were in before you applied your needle, and will neither be flat
as with spirit of vitrol, nor cylindrical as with common salt liquor ; but lie
dead in the same shape as before you put in your needle with the salt of
tartar. — Sack will kill them, but not so speedily as the other liquors."

Methods of Investigation.

To the working microscopist a hint or two will probably prove accept-
able with reference to the mechanical means that may be most advan-
tageously resorted to in the investigation of the structure and life-histories
of the more minute, and comparatively unfamiliar, representatives of the
Infusorial series. These, as typified by the several orders of the class
Flagellata, necessarily demand in conjunction with the high-power object-
glasses that are indispensable for their correct appreciation, more delicate
methods of manipulation.

A chief obstacle encountered in the employment of these short-focussed
lenses presents itself at the outset in the matter of penetration. However
thin may be the covering glass employed, it rarely fulfils the needs of the
investigator, and mostly causes both inconvenience and loss of time on
account of its extreme brittleness. Where the objects under examination
are attached to more solid substances, such as the stems of water plants,
this rigidity and brittleness of the covering glass hampers progress in a most
provoking manner, and materially restricts the limits of clear vision. The
unsuitability of ordinary covering glasses for the special investigations here
alluded to, was long since recognized by the present author, and a substitute
provided that has been productive of the most satisfactory results. The
material utilized for this purpose was no other than the one extensively
employed, previous to the introduction of specially prepared glass, for the
permanent mounting of microscopic objects. This substance, represented
by ordinary talc as extensively used for gaselier shades, may with a little
practice be split into laminae of such extreme tenuity that they may be
blown away with the lightest breath, while for perfect evenness and trans-
parency they will compare favourably with the finest manufactured glass.
With the employment of these talc-films the investigation of Infusoria with
the TV, ?V> or even the ^-'mch objectives becomes a comparatively easy task.
The material in question possesses the further considerable advantages of
bending readily and permitting the object-glass to be brought close down

I 2

I 1 6 ORGANIZATION OF THE INFUSORIA.

on the more remote objects in the microscopic field, while it may be cut
with the scissors to any required -size or shape.

In the investigation of the Flagellata, or indeed of any Infusoria in
which it is sought to arrive at an accurate knowledge of the life or develop-
mental history of any given type, it is desirable that the same individual
zooid or animalcule should be continuously examined. An important
mechanical obstacle that has to be overcome in the conduct of such con-
tinuous investigation, which may extend over many hours or days, results
from the rapid evaporation of the water or other fluid from beneath the
covering glass, combined with the necessity of keeping it constantly
replenished. Various mechanical appliances for accomplishing the desired
end have been introduced by Recklinghausen, Leuckart, and other Con-
tinental workers, none of these, however, being equal in efficiency to that
employed by Messrs. Dallinger and Drysdale, during their famous
" Researches into the Life-history of the Monads," figured and described in
the 'Monthly Microscopical Journal' for March 1874. The illustrations
given of this apparatus with accompanying explanations are reproduced
in the plate devoted to mechanical appliances at the end of the atlas to
this volume, and may be thus briefly described. It consists firstly of
a plain glass stage, about the one-tenth of an inch thick, fitted so as to
slide on in place of the ordinary sliding stage of the microscope. From
the left-hand anterior border of this stage a projecting arm is produced
which carries a socket for the reception of a small glass reservoir about
I \ or 2 inches deep. The glass stage being too thick to work through with
an achromatic condenser and high powers, a circular aperture of sufficient
size is cut through it, and a piece of thin glass cemented on its upper
surface. A piece of blotting-paper is now cut coinciding in form with the
glass stage, but slightly smaller, and with a tongue-like projection that lies
along the projecting arm and dips down into the glass reservoir. A
circular aperture of larger size than the covering glass employed is cut
out of the centre of this paper, such aperture, where a £-inch cover is
made use of, being preferentially the \\ of an inch. The foundation of the
moist chamber is now complete, and it only remains to provide the
bounding walls. This Messrs. Dallinger and Drysdale accomplish by
means of a piece of glass tubing, about i^ inch in diameter, cut to f inch
in length. Across one end of this tubing a thin sheet of caoutchouc is
next firmly stretched and securely tied, and a small hole perforated in its
centre. The tubing with its free edge, which should be carefully ground, is
now placed concentrically upon the glass stage, over the aperture in the
blotting-paper, and the object-glass racked down upon the perforation in
the caoutchouc. The caoutchouc should be sufficiently thin to offer no
impediment to the action of the fine adjustment, while it at the same time
clasps the object-glass firmly round its central perforation and in combination
with the lowermost or free edge resting on the blotting-paper, constitutes a
practically air-tight chamber. Everything is now in working action and it

METHODS OF INVESTIGA TION. 1 1 ^

only remains to add the material to be examined and to fill the reservoir
with water. The water from the reservoir soaking through the bibulous
paper keeps the air-tight chamber constantly moist, and evaporating faster
from its contained free circular edge, prevents loss of moisture from beneath
the covering glass. The water in the reservoir will maintain the moist
chamber in the above conditions for many days and will require replenish-
ing only at distant intervals.

Where uninterrupted observation is not demanded, but simply the
chronicling of the more important developmental phases of some sedentary
or encysted type, and where in the interim the microscope is probably
required for the examination of other objects, it will be found convenient
to transfer the slides containing the animalcules to an ordinary moist
chamber which may be extemporized out of a tumbler or small bell-glass
inverted upon a plate containing a few folds of well-saturated bibulous
paper. By a registration with a graduated scale on the mechanical stage,
or by a rough drawing of the bearings of the type to be re-examined with
relation to surrounding objects, it may be with facility refound for sub-
sequent observation. An efficient moist chamber for the same purpose,
and, as is often needed, for the transfer of a slide containing living Infusoria
from place to place, is ready to hand in the shape of an ordinary wide-
mouthed pomatum bottle, with some moistened blotting-paper at the
bottom ; the height inside being a little over three inches allows the cork to
be thrust down upon the slide, thus keeping it firmly in one position.

The ingenious chambers constructed by Professor Tyndall for the
reception of test-tubes in connection with his experiments on atmospheric
germs, fully described in the succeeding chapter, and illustrated side by side
with Messrs. Dallinger and Drysdale's apparatus, at PL L., offer special
facilities for the effectual isolation and continued examination of specific
infusorial types.

CHAPTER IV.

SPONTANEOUS GENERATION.

THE solution of the yet smouldering, and but a few years since fiercely
incandescent, question of " spontaneous generation " is so inextricably bound
up with an extensive knowledge and correct appreciation of the vital
phenomena of the microscopic beings that form the subject of this volume,
that it is felt by the author that a grave error of omission would be com-
mitted were not a few pages set apart for its consideration. Spontaneous
generation, " generatio tzquivoca" or as it is now more widely designated
" abiogenesis," is by no means an invention of to-day or yesterday. It
dates back to the classic times of Plutarch, Virgil, and Aristotle, by which
three brilliant leaders and expositors of the world's highest wisdom it was
seriously maintained that eels grew out of mud, bees from putrefying flesh,
and rats through the vitalizing properties of the sun's rays, without any
intervening parental agency. Spontaneous generation as enunciated at
the present day is the same in essence if not in fact as when evolved and
launched upon the seething waters of scientific controversy over two
thousand years ago. Then as now, or now as then, the point sought to be
established by its exponents was or is, that organic beings can be and are
under certain conditions generated or newly created out of dead organic
or purely inorganic material, independently of any pre-existent parent,
egg» or germ. With the revival of the arts and scientific culture which
distinguished the latter half of the seventeenth century, the theory of spon-
taneous generation as applied to the grosser forms of animal life, and
accepted as an article of creed from the days of antiquity, was attacked
and finally disposed of through the labours of such careful investigators
as Redi, Reaumur, and Schwammerdam. By the first-named of these
authorities, more especially, the maggots found in putrid meat and hitherto
supposed to be generated spontaneously, were shown by a combination
of careful experiment and inductive reasoning to be the progeny only of
flies which had previously deposited their eggs upon it. Reasoning from
the constantly observed presence of flies round decaying meat previous
to the appearance of the maggots, Redi concluded that these winged insects
were the progenitors of the same, and took steps to prove it. Placing meat
in a jar and covering it so carefully with paper that flies could not obtain
access to it, he found that although putrefaction set in, no maggots were
developed, while at the same time these organisms appeared abundantly in

RED I; TUBERVILLE NEEDHAM. 119

similar jars of meat left purposely uncovered. Substituting fine gauze for
the paper coverings, the flies were soon attracted by the emanating odour,
but being unable to get at the meat deposited their eggs upon the gauze,
and out of which eggs minute maggots were then seen to develop. This
very simple experiment by which Redi proved his case, carries with it, as
presently shown, a most practical and important bearing upon the question
of spontaneous generation in the modern acceptation of the term. The
weapon, however, that proved of the greatest service at about this same
epoch in breaking down the ancient superstitions concerning the spontaneous
generation of highly organized animals, was undoubtedly the microscope,
now utilized for the first time in unravelling the mysteries of nature.

With this instrument in the hands of Leeuwenhoek, Robert Hooke,
Hartsoeker, and other early labourers, it was soon discovered that the hitherto
deemed doubtful or spontaneously multiplying species propagated their
kind perpetually through the medium of impregnated seeds or eggs, after
the manner of the larger and more familiar types, and the idea of spon-
taneous generation, so far as such organisms was concerned, was banished
to oblivion. The agency, however, which thus achieved the overthrow
of this theory in one direction, paved the way for its re-establishment
in another, and as it at first seemed, on an apparently far more sure and
substantial basis.

Among the most important revelations of the hitherto invisible and
unknown world made known with the assistance of the microscope, was
undoubtedly the discovery by Leeuwenhoek, in the year 1676, of the micro-
scopic beings that form the subject-matter of this volume. The abundant
confirmation of this discovery and the intense interest manifested on all
sides in so newly indicated and fascinating a field of research, necessarily
entailed a speedy recognition of the extraordinary rapidity with which these
minute organisms multiplied, and also of their appearance suddenly in vast
numbers under auspices totally at variance with the propagative phenomena
of all previously known organic forms. None of the then familiar laws of
organic reproduction sufficing to explain these several phenomena, the mind
naturally reverted to that interpretation of the "incomprehensible" initiated
by the philosophers of antiquity, and stamped such abnormal manifestations
with the brand of the miraculous.

As indicated in a preceding chapter, the theory of abiogenesis or spon-
taneous generation, as applied to the minute animalcules produced so
abundantly in infusions, took its origin as a possible hypothesis with their
first discoverer, and was upheld with more or less force by Gleichen, Joblot,
and O. F. Miiller. The first, however, to mould this somewhat vague
idea into shape and to formulate out of it that definitive doctrine con-
cerning the spontaneous production of the lowest organisms that with
varying fortune has commanded adherents thenceforward up to the present
time, was undoubtedly our own countryman Tuberville Needham, who in
his ' New Microscopical Discoveries,' printed in the year 1745, and various

120 SPONTANEOUS GENERATION.

subsequent publications, declared that infusorial animalcules were directly
and spontaneously engendered from more highly organized bodies in a state
of putrefaction. This bold declaration was entirely approved by Buffon,
who further maintained that with respect to these organisms such a mode
of generation was not only the most frequent and universal, but also in all
probability the most ancient.

Such being the definite position taken up by the advocates of spon-
taneous generation, it was not long before it was vigorously assailed, the
controversy that ensued surpassing probably in acrimony and the extent
of its duration that of any yet brought within the area of scientific polemics.
The earliest authority to declare himself opposed to this doctrine and to
submit an intelligible interpretation of the apparently anomalous conditions
of growth and reproduction of infusorial organisms, is usually held to be
the Abbe Lazzaro Spallanzani, of Pavia, who in the year 1765 enun-
ciated the opinion that such animalcules were propagated through the
medium of minute germs constantly present in the atmosphere, and
which fructified or developed immediately they came in contact with
the conditions suitable for their growth furnished by artificial or other
infusions. The atmospheric "germ theory," attributed to Spallanzani, can
boast, however, of a far more remote antiquity. Seventy years prior to
the time of Spallanzani (1696), an Englishman, John Harris, whose name
as one of the earliest observers of infusorial life has been previously
quoted, contributed to the ' Philosophical Transactions ' a suggestion con-
cerning the generation of these minute beings that is now, almost two
centuries later, found to represent the true position of the case more nearly
than any of the manifold interpretations brought forward between that date
and the present time. In the course of his observations upon the subject
of infusorial animalcules, embodied in the foregoing communication, the
following paragraph occurs : —

" How such vast numbers of animals can be as it were at pleasure, produced,
without having recourse to equivocal generation, seems a very great difficulty to
account for. But the solving of it that way makes short work of the matter (for
'tis easie enough to say they are bred there by putrefaction), yet the asserting
equivocal generation seems to me to imply more absurdities and difficulties than
perhaps may appear at first sight, i wish therefore that this matter would a while
imploy the thought of some ingenious and inquisitive man. In the mean time I've
conjectured that these animalcula may be produced by one or both of the following
ways. I. I have thought that the eggs of some exceeding small insects, which are
very numerous, may have been laid or lodged in the plica? or rugae of the coats of
the grain by some kinds that inhabit the same as their proper places. For that
insects of the larger kinds do frequently thus deposite their eggs on the flowers and
leaves of plants, has been often experimented ; and 'tis very probable that the smaller
or microscopical insects do the same. Now these being washed out of the seeds, by
their immersion in water, may rise to the surface and there be hatched into those
animals which we see so plentifully to abound there. II. Or the surface of the
water may arrest the straggling eggs of some microscopical insects that were perhaps
about in the air, and being fitted and prepared for the purpose, by the infusion of
proper grain, or a proportionable degree of heat, may compose so proper a nidus

JOHN HARRIS ; SPALLANZANI. l 2 r

for them, that they may by the warmth of the sun be easily hatched into living
creatures .... and perhaps sometimes both these circumstances, and others of the
like nature, concur for their production."

Making due allowances for John Harris's conception of Infusoria as the
product or offspring of microscopically minute insects, it is astonishing to
find how closely his two suggestions of their being primarily attached in the
form of eggs to the rugae and plicae of the surfaces of the vegetable sub-
stances experimented on, or of their falling from the atmosphere and
germinating in such suitable liquid nidus as may present itself, coincide
with the actual distribution of infusorial eggs or spores as demonstrated by
the most recent research.

Proceeding to an enumeration of the results obtained by the many
"ingenious and inquisitive men" who, following the recommendation of
John Harris, did "imploy their thoughts" upon the subject of infusorial
propagation, it has to be further recorded of Spallanzani that he initiated
the experiment of filling flasks with organic infusions, and after hermeti-
cally sealing their apertures and boiling their contents, showed that no
life was generated in them, however long they remained in their closed
condition. The Genevan naturalist Bonnet, the intimate friend of Spal-
lanzani, adopting the same line of argument, proceeded so much further as
to declare that all substances both organic and inorganic were permeated
with these infinitely minute germs, and that these germs were in some cases
able to resist the highest temperatures. This latter property ascribed to
the organic germs was the outcome of certain exceptional cases in which,
in infusions boiled and confined in flasks in the manner above indicated,
living organisms were found both by himself and Spallanzani to make
their appearance.

This point of the controversy being arrived at, the subject attracted
such general attention that the whole world of science may be said to have
divided itself into two hostile camps, the one supporting Needham's and
Buffon's, and the other Spallanzani's and Bonnet's hypotheses. As
rallying titles or noms de guerre that should serve to distinguish the
adherents of these two respective camps, that of " heterogenists " was
generally associated with the supporters of abiogenesis, or who, as the
word implies, advocated the heterogenetic or spontaneous generation of
the organisms under dispute ; that of " panspermists " being applied with
corresponding significance to those followers of Spallanzani who attri-
buted the rapid propagation and distribution of Infusoria to the universal
presence of their germs in the surrounding air. Among the many doughty
champions who, as successors to Needham, distinguished themselves for
their ardent devotion to the cause of abiogenesis or heterogeny during
the earlier portion of the nineteenth century, have more especially to be
placed on record the names of Lamarck, Oken, Bory de St. Vincent, and
Dujardin. On the side of the "panspermists," on the other hand, appear
during the same epoch those of Paul Gervais, Schwann, Schultze, and

I 2 2 SPONTANEOUS GENERA TION.

Ehrenberg. Lamarck, one of the most fervent advocates of heterogeny,
in his celebrated 'Philosophic Zoologique' (Paris, 1809), freely declared
that all bodies were constantly undergoing mutations of form, some passing
continually from the state of the inorganic into the organic, and others
reverting from the living to the inanimate condition. Nature was further
represented as thus exhibiting one continuous evolutionary cycle, and with
the aid of heat, light, moisture, and electricity, as producing new organisms
by direct or spontaneous generation at the initial or root terms of both the
animal and vegetable kingdoms.

Almost contemporaneously with this pronunciamento of Lamarck
appeared also Lorenz Oken's celebrated * Lehrbuch der Naturphilosophie,'
in which, in addition to further expounding his views initiated in the year
1805 concerning the fundamental construction of all living bodies out of
vesicular or cellular elements that found their equivalents in the inde-
pendent and simple vesicular bodies of infusorial animalcules, he declared
himself most strongly in favour of " spontaneous generation." Oken's
remarkable enunciation of these two separate principles in their mutual
or interdependent aspect is thus expressed in the treatise above quoted : —

" The first organic points are vesicles. The organic world has for its basis an
infinity of vesicles. — The mucous primary vesicle may in a philosophical sense be
aptly called an infusorium. — If the organic fundamental substance consist oi infusoria,
so must the whole organic world originate from infusoria. Plants and animals can
only be metamorphoses of infusoria. — This being granted, so also must all organiza-
tions consist of infusoria, and during their destruction dissolve into the same.
Every plant, every animal is converted by maceration into a mucous mass; this
putrefies, and the moisture is stocked with infusoria. — Putrefaction is nothing else
than a division of organisms into infusoria, and reduction of the higher to the
primary life. — Organisms are a synthesis of infusoria. Their generation is none
other than an accumulation of infinitely numerous mucous points or infusoria. In
these the organisms have not been at once wholly and perfectly depicted as on the
smallest scale, nor contained in a state of performation ; but they are only infusorial
vesicles, that by different combinations assume different forms, and grow up into
higher organisms.

" As the whole of nature has been a successive fixation of aether, so is the
organic world a successive fixation of infusorial mucous vesicles. The mucus is the
aether, the chaos for the organic world. The semen of all animals consists also of
infusoria; the same may be said of the vitellus. — Every generation commences
d priori or from the beginning. The organic substance must again be dissolved
into the original chaos or mucus if anything new should originate. — Out of an
organic menstruum only can a new organism proceed, but not one organism out of
the other. A finished or perfect organism cannot gradually transform itself into
another. — The generative juices, or semen and vitellus, are none other than the
total organism reduced to the primary menstruum. — Physically regarded also, every
individual originates only from the absolute, but no one out of the other. The
history of generation is a retrogression into the absolute of the organic, or the
organic chaos-mucus, and a new evolution from the same. — This development from
mucus is only applicable, however, to the generation of the perfect organisms, but
not to the origin of the organic body, or the infusorial mass. The former originate
only from an organic mass that has been already formed ; but the infusorial mass, as
constituting the organic primary bodies, cannot have originated in the same way.
It was and must originate directly from the inorganic. From whence can the
organic have otherwise proceeded? — The infusorial mucus-mass originated at the

LORENZ OK EN; EHRENBERG. 123

moment when the earth's metamorphosis was at an end, and at the moment when
the planet succeeded in so bringing together and identifying all the elementary
processes, that they were all together or at one and the same time in every point. —
This origin of the organic primary bodies I designate generatio originaria, creation. —
But infusorial vesicles can also originate by mere division of larger organic carcases,
and these can again originate as well through the combination of these secondary
as of the primitive vesicles, or as it were by coagulation only. I nominate this
generation generatio cequivoca. — There are only two kinds of generation in the world,
the creation proper and the propagation that is sequent thereupon, or the generatio
originaria and secondaria. — No organism has been consequently created of larger
size than an infusorial point. No organism is, nor has one ever been, created,
which is not microscopic. Whatever is larger has not been created, but developed."

Wild, fanciful, and bordering on the very verge of " idiotic inspiration,"
as Oken's utterances in connection with the above and kindred physiological
problems have been most generally pronounced, our wondering admiration
must, so far as the present subject-matter is concerned, certainly be
accorded to the creations of this most original and master mind. Notwith-
standing the inability to reconcile his views of the constant recurrent
or spontaneous generation of Infusoria out of inorganic matter with our
present more perfected knowledge of the vital phenomena of the class, his
conception of the morphologic value and significance of the infusorial body
with relation to organic life in general, and compound or tissue-forming
organisms in particular, has certainly anticipated in a most clear and striking
manner the views expounded as original by many eminent physiologists
who have succeeded him. Giving Oken his due, to him most certainly must
be accredited the origination of the cellular theory subsequently introduced
by Schleiden and Schwann ; for what otherwise than the equivalents of cells,
the ultimate factors of all organic bodies as recognized at the present date,
are Oken's " first organic points," or " mucous primary vesicles " ? By his
comparison of the infusorian body with such a simple mucus-vesicle or cell,
he anticipates again that conception of the same adopted by Von Siebold
and Kolliker, and confirmed by the most recent investigation, while in his
interpretation of all higher organisms as compound agglomerations of
infusorial bodies, or their equivalents, and in his declaration that organic
life must have originated with these simple infusorial types, out of which
again by a process of development, and not through independent creation,
the higher forms have been constructed, is most naturally foreshadowed
that grand doctrine of evolution with which the names of Lamarck and
Darwin are so honourably associated.

Returning to the more legitimate subject of discussion, that of " spon-
taneous generation," notice must now be taken of the arguments advanced
by the leading and contemporary partisans of the opposite or panspermist
persuasion. Ehrenberg, one of the most ardent espousers of this latter cause,
based his objections to the spontaneous form of reproduction on the many
new facts concerning the organography of the Infusoria elicited through
his special investigations, and which included, in his own estimation, the
discovery of reproductive organs and the production of ova corresponding

I 2 4 SPONTANEO US GENERA TION.

with those of the higher animals,' and which circumstance he declared ren-
dered the addition of an independent or spontaneous mode of growth
entirely superfluous. Evidence of a far more substantial nature, and which
was held at the time to be utterly subversive of the cause of the heterogenists,
was that produced by Schultze and Schwann in the years 1836 and 1837.
The former of these demonstrated that organic infusions after boiling might
be exposed to the action of the atmospheric air for many months without
developing living animalcules, provided such air passed first through con-
centrated sulphuric acid, which was pronounced by Schultze to destroy
or devitalize the air-suspended germs. The results obtained by Schwann
and the means employed were precisely identical, excepting that calcined
air was substituted by him in place of sulphuric acid. An important con-
clusion arrived at by this investigator, as a necessary corollary of the above
results, was, that the putrefaction of organic bodies was entirely dependent
on the associated growth and multiplication within their substance of
minute organisms, such as Infusoria and their allies.

Helmholtz in the year 1843, and Schroder in various contributions pub-
lished between the years 1854 and 1859, accumulated additional evidence
in favour of the panspermists, and towards demonstrating that the animal-
cules developed in infusions originated mainly, if not entirely, from pre-
existing atmospheric germs. Among the more noteworthy experiments
of Helmholtz, it was shown that a putrefying infusion, and one sterilized
by boiling, might be divided from each other by means of a thin membrane
only, so that the liquid masses of the two might freely intermingle through
the processes of exosmosis and endosmosis without the latter one becoming
tainted, as it indubitably did if the smallest portion of the putrescent fluid
was added to it in its concrete form. The unavoidable conclusion derived
from this experiment was that the germs existed in the putrescent infusion
as actual very minute and solid particles that could not pass like the asso-
ciated fluids through the intervening membrane. Following out this same
line of demonstration, Schroder further showed that simple plugs of cotton-
wool inserted in the necks of flasks containing organic infusions sterilized
by boiling, sufficed as efficient filters for the exclusion of organic germs,
and for the indefinite maintenance of the liquid in the sterilized condition.
This last-named experiment is now commonly repeated ; flasks of steril-
ized putrescible fluid being at the present moment on view at the South
Kensington Biological Laboratory, which have remained for many years
with a similar simple cotton plug guarding their contents from the invasion
of organic germs and accompanying putrefaction.

Notwithstanding the almost overwhelming amount of evidence now
adduced in contravention of the hitherto extensively upheld doctrine of
spcntaneous generation, a new champion of its cause was soon to the fore-
front, and one who has almost down to the present day laboured with all
his force and much ingenuity to prove his case. This new leader of the
heterogenists was no other than Dr. F. A. Pouchet, the accomplished

POUCHET ; PASTEUR. 125

Director of the Rouen Natural History Museum. In the year 1847 Pouchet
had already demonstrated that the multiplication of Infusoria by the
process of fission was by no means so common as was ordinarily supposed,
and that the astonishingly rapid increase of their numbers could not be
accounted for by such simple means. It was not, however, until the year
1859 that he brought forward that new interpretation of their developmental
phenomena with which his name is most eminently associated. In accord-
ance with the representations of this author, the most important factor in
the production of animalcules, independent of parental agency, or in other
words by spontaneous generation, was the filmy or gelatinous skin or
pellicle, that within a greater or less interval is commonly developed on the
surface of putrefying infusions. According to Pouchet this superficial
pellicle, designated by him the pseudo-membrane, or "proligerous mem-
brane," was the matrix, produced through the decomposition or breaking
down of pre-existing organisms, in which egg-like bodies were generated
de novo and developed into various species of Infusoria. The idea of
the germs existing in the atmosphere in sufficient quantities to produce
their normal and remarkably rapid development, as held by the pan-
spermists, was rejected by Pouchet as not only untenable, but ridiculous,
he reasoning that if such abundance obtained, they would visibly interfere
with the clearness of the atmosphere and produce masses comparable with
the clouds themselves.

The arguments of Pouchet were not destined to remain long unchal-
lenged. In the following year, 1860, M. Pasteur, the eminent chemist of the
Parisian Conservatoire, entered the lists on behalf of the panspermists, and
after several years of animated controversy with Pouchet and his partisans,
accompanied by the most patient and ingenious experiments, achieved
results that most completely turned the tables upon the heterogenists.
Among the more prominent and positive of these must be mentioned
Pasteur's actual collection of floating organic germs, mingled with inorganic
particles from the atmosphere, and which sown by him in sterilized infusions,
were found to develop the ordinary infusorial animalcules in abundance.
It was further demonstrated by the same investigator that the atmo-
spheric germs in question were by no means so evenly and abundantly
distributed as the panspermists had previously maintained. Thus, while
sterilized infusions became immediately affected, and crowded with animal-
cules, when exposed to the grosser and comparatively impure atmosphere
of large towns, or other thickly peopled districts, he showed by direct
experiment that the same infusions bore the ordeal of exposure to the clear
and moteless atmosphere of the Alpine glaciers without exhibiting the
slightest alteration or trace of organic life. Transporting his experimental
flasks to the pure and tranquil air of those subterranean vaults or " cata-
combs " for which Paris is so famous, a similar exemption from organic
change was observed. In a still more complete and precise manner, Pasteur
also repeated and confirmed the experiments of Schwann and Schroder

126 SPONTANEOUS GENERATION.

already mentioned, and in the long run produced so complete and logical a
chain of evidence in support of the atmospheric dissemination of infusorial
germs, and their derivation from similar antecedent parents, that his views
were accepted by the Paris Academy as definitely solving the long contested
problem in favour of the panspermists.

Banished from France, the doctrine of heterogeny or abiogenesis has
yet once again, and probably for the last time, found a staunch advocate in
England, the land of its birth, where, however, as presently demonstrated,
such reappearance has been associated with an even more disastrous defeat
than that administered at the hands of M. Pasteur. The English champion
and recognized leader in these latter days of the forlorn hope of heterogeny,
Dr. H. Charlton Bastian, entered the public arena in that capacity early in
1870. Already, in January of that year, Professor Tyndall approaching
the subject from an entirely independent standpoint, had, as hereafter
recorded, declared himself entirely in favour of Pasteur's panspermic inter-
pretation, and it was with the view of refuting the arguments of both of
these investigators that Dr. Bastian took up the gauntlet.

Divested of all irrelevant matter, the evidence elicited through his
independent experiments was productive of two new arguments, which
without doubt, had they remained uncontroverted, would have once more
secured a substantial victory for the cause he advocated. In the first place,
Dr. Bastian declared that he had succeeded in obtaining growths of bacteria,
and other organic germs, from infusions remaining in hermetically closed
flasks, from which almost the whole of the air had been expelled by boiling.
As at this period of the controversy it was a mutually accepted axiom of
heterogenists and panspermists alike that living matter in no shape or form
could survive exposure to the temperature of boiling water, 212° Fahr., it
necessarily followed that both this axiom and Dr. Bastian's results being
substantiated, the organisms developed in the infusions after ebullition were
the product of de novo or spontaneous generation. In the second place, he
declared that all the evidence yet adduced since the date of its first
announcement, concerning the existence of germs of invisible or ultra-
microscopic minuteness in the atmosphere, springing from and developing
to a known parental or specific type, was entirely negative, and as a
necessary sequence totally unreliable and unworthy of credence. These
two points of contention raised by the partisans of heterogeny through
Dr. Bastian, viz. the unproduced proof of, firstly, the absolute existence
of these prederived ultra-microscopic germs, and secondly, the capacity
of such germs to withstand a temperature of 212° Fahr., represent the
last tenable position held by the adherents of the doctrine of spontaneous
generation, and with the carrying of that position, so far as its serious enter-
tainment by the reasoning and scientific mind is concerned, this doctrine
undoubtedly receives its final death-blow.

The two missing links in the otherwise strong chain of evidence ad-
duced by the panspermists, and indicated in the preceding paragraph, have

PROFESSOR TYNDALL. 127

now to be supplied. Their production has necessarily, and as a guarantee
of their reliability, to be the joint product of several independent workers,
and those names which must ever remain memorably associated with their
forging, are those of Professor Tyndall and Messrs. Dallinger and Drysdale.
As a humble labourer at the eleventh hour only, seeking for and obtaining
evidence of an independent character corroborative of the important results
achieved by the foregoing authorities, the author of the present volume is,
as presently shown, also in a position to subscribe his name as an additional
witness for the panspermists.

Commencing with the achievements of Professor Tyndall in this special
field of research, it has first to be related that his earliest association with
the subject of spontaneous generation was the result of a happy accident.
In the course of those physical investigations for which his name is so justly
famous, he happened, while experimenting on the subject of radiant heat
in relation to the gaseous form of matter, to require air that was completely
free from all extraneous or floating matter, however fine. The passage
of the same through alkalis, acids, alcohols, and ethers, was found insufficient
to produce the purity desired ; but on the other hand, air filtered through
cotton-wool, air kept free from agitation sufficiently long to allow the floating
particles to subside, air in a calcined state, or obtained from the deeper
cells of the human lungs, proved to be effectually cleansed from all such
floating substances and to be in every way suited for the purposes required.
A delicate and certain method of testing atmospheres to ensure their
requisite purity was also devised by Professor Tyndall. This ready test
was found to be presented by a concentrated beam of the oxyhydrogen or
electric lamp. Surrounding objects being in darkness, such a beam thrown
across the ordinary atmosphere revealed its track in a similar manner, but
to a still more intense degree, as a sunbeam shining through a minute
aperture of a closed window-shutter ; wherever it passed it either threw up
vividly distinctly moving dust, or presented a turbid or foggy aspect, through
the reflection or scattering of light of the myriads of invisibly minute
particles with which the same air was laden. Passing a similar beam
through air purified in either of the manners above recorded, no such
interruption of its course occurred, and from one end to the other of the
traversed space its route was dark, and entirely indistinguishable from the
surrounding and unilluminated atmosphere.

It presently occurred to Professor Tyndall that the important results
obtained by Schwann, Schroder, and Pasteur, and other notable pansper-
mists, concerning the sterility of certain exposed infusions, were intimately
associated with those pure and moteless optic conditions of the atmosphere
last described. Put to the test, this inference was verified beyond his most
sanguine expectations. The ordinary infusions of turnip, hay, and other
organic substances were prepared in tubes, and after boiling left to their
fate in carefully closed chambers of ingenious construction, whose air con-
tents, after two or three days allowed for subsidence, were shown by the

I 2 8 SPONTANEO US GENERA TION.

electric beam to be entirely pure and moteless. Other tubes containing
a like infused material, prepared under precisely similar conditions, were
placed in the ordinary air immediately adjacent to but outside the last-
named chambers, and the result awaited. It was this : In the course
of three or four days the tubes outside the chamber became turbid and
swarming with Bacteria and other organisms, while those in the inside were
as clear and sterile as on the day of preparation, and furthermore remained
in the same sterile and pellucid state for several months. At the end
of this period a door in the chamber wall was opened, so as to allow the
ingress of the ordinary atmosphere, and within three days after such
exposure they too became affected and swarming with bacterial life. One
logical inference only was to be derived from these results. The Bacteria
and other microscopic forms were abundantly present in their germinal
state in that ordinary and dust-laden atmosphere on the outside of the
closed chamber, and indicated their presence by falling into and freely
developing in the suitable nidus provided for them in the exposed tubes.
In the still, optically pure, and what may be correctly termed "empty,"
atmosphere of the closed chambers they were, on the other hand, entirely
absent, though all the while, as the sequel demonstrated, beating against
the outside of the door and ready to rush in by millions to carry out their
work of infection and destruction immediately the portal was thrown open.
Varying his experiments in every conceivable form, a like ultimate result
was arrived at. Thus, since leading heterogenists had declared that a high
temperature was most suited for the production of de novo generation, and
especially one approximating that of 115° Fahr., tubes, with infusions as
before mentioned, were maintained at this temperature in one of the com-
partments of the Turkish Baths, Jermyn Street, for nine days without any
trace of life appearing. To meet, again, the argument that certain organic
infusions were more productive than others of spontaneously generated life,
well-nigh the entire catalogue of animal and vegetable substances used in
domestic economy, and including among the former beef, mutton, hare,
rabbit, kidney, liver, fowl, pheasant, grouse, haddock, sole, salmon, cod,
turbot, mullet, herring, whiting, eel, and oyster ; and among the latter
hay, turnips, potatoes, oatmeal, tea, coffee, hops, &c., were ransacked and
severally experimented upon by Professor Tyndall, but with the same
result. So long as the infusions were kept in pure and moteless air, so
long did they remain pellucid and free from the slightest trace of bacterial
or other life, but in all cases on exposure to the ordinary dusty and germ-
laden atmosphere, they became, within three or four days at the outside,
swarming with organic forms. A small pinch of dust from the laboratory
floor, or a dip on a needle's-point from a previously infected infusion, was
in either case found sufficient to inoculate the sterile tubes confined in the
moteless chamber, though the time occupied in the development of the
moving organisms in these two respective cases presented conspicuous
points of divergence. Where the inoculation was produced through a

PROFESSOR TYNDALL. I 29

needle-dip from an already affected tube the resulting contagion was almost
immediate, while where dust was supplied in its dry form, two days mostly
elapsed before any indication of such inoculation made its appearance. The
sagacious explanation of these phenomena, given by Professor Tyndall, was
that the dust supplied contained only germs in a desiccated state, which
necessarily required a set time, or "period of latency," to expire before
they displayed their vital properties ; while in those taken from the fluid
medium, these vital properties were already in their full force, permitting
the organisms to increase and multiply from the first moment of their
contact with the sterile liquid.

One interesting experiment bearing upon the phenomenon last described
requires mention. A certain mineral solution, containing in proper propor-
tions all the substances which enter into the composition of Bacteria, was
found after inoculation with the least speck of liquid containing living
Bacteria, to be always swarming and turbid with such organisms within a
space of twenty-four hours ; while a small pinch of laboratory dust added to
the same fluid, and containing the germs in their desiccated condition,
remained in contact with the fluid with impunity for many weeks. Bacteria
in their living and moist condition, and those in their desiccated state, were
thus shown to possess highly differentiated developmental properties.
Another fact of importance, elicited by Professor Tyndall, bears reference
to the want of uniformity in the distribution of bacterial and other germs in
any given atmosphere. This was demonstrated through the preparation of
large trays, contrived to hold as many as from sixty to one hundred tubes
of infusions side by side, and on the same level. All of these exposed to
dust-laden air were infallibly, after a greater or less duration of time, teem-
ing with living organisms, but the order of their affection or inoculation was
found to differ considerably, intervals of several days not unfrequently
elapsing between the inoculation of closely contiguous tubes. A consider-
able difference was likewise found to obtain, under such conditions, in the
character of the developed matter, Bacteria of different species, fungoid
growths, and other organisms, variously and irregularly preponderating.
Professor Tyndall happily explains these phenomena by comparing the
aerial distribution of microscopic germs to the cloud-patches visible in a
mottled sky ; all parts of the landscape, as represented by the tray of tubes,
being overshadowed in turn by these patches, but in no definite or regular
sequence. It has been pointed out by Professor Huxley, that a closely
corresponding simile was originally employed by Ehrenberg, who as an
exponent of the atmospheric distribution of Infusoria, either as eggs or in
their encysted state, likened the non-uniformity of their occurrence under
such conditions to irregularly alternating days of sunshine and heavy
downpour. As shown already, however, at page 120, the atmospheric germ
theory originated with John Harris, more than a century prior even to the
time of Ehrenberg.

That the atmosphere in its purest state may be entirely free from organic

K

I3r-> SPONTANEOUS GENERATION.

germs, had already been demonstrated by M. Pasteur through exposing
infusions with perfect immunity from infection, to the open air of the
Mer de Glace, which experiment, with precisely identical results, was
repeated by Professor Tyndall in the vicinity of the Bel Alp at an elevation
of 7000 feet above the sea, in July of the year 1877. Respecting the
capacity of Bacteria and atmospheric germs to resist exposure to abnormal
elevations of temperature, he found the widest divergence to obtain in
materials derived from different sources or in different conditions of vitality.
Where the fully developed and vitally active organisms were experimented
on, contact with boiling water, or sometimes a temperature considerably
below ebullition, was found sufficient to deprive them of life, but where the
desiccated germinal matter was operated on, the results were as a rule
entirely reversed. In some few instances these germs were so tender
as to succumb to boiling for a term of five minutes, or even less, while in
extreme cases they were found sufficiently obstinate to survive a similar
ordeal of no less than eight hours' duration. As regards their respective
" death-points," or limit of heat-resistance, Professor Tyndall suggests that
the infusorial germs of the atmosphere might be conveniently classified under
the following heads : " Killed in five minutes ; not killed in five minutes,
but killed in fifteen ; not killed in fifteen minutes, but killed in thirty ; not
killed in thirty minutes, but killed in an hour ; not killed in an hour, but
killed in two hours ; not killed in two, but killed in three hours ; not killed
in three, but killed in four hours." Several cases of survival after four, five,
six, and even eight hours' boiling were met with, and as he further remarks,
there is no valid warrant for fixing upon eight hours as the final limit.

The germinal dust obtained from long preserved, and thoroughly desic-
cated, hay was in all instances found to yield the most obstinately resisting
material, and the presence of a truss of hay anywhere in the vicinity of the
germinal matter experimented on, always constituted an important factor
in its reduction by boiling to a condition of sterility. Notwithstanding,
however, the great resistant property possessed by a large number of these
germs, Professor Tyndall has shown that even the most obstinate can
be sterilized or killed if certain precautions are taken in their treatment.
These consist of setting aside the infusion containing them, after ebullition,
in a warm room for a period of ten or twelve hours, then raising it again to,
and maintaining it for a short interval at, the boiling point, repeating the
process with similar intervals of rest several successive times. By these
means the germs as they approach their point of final development are
successively killed off in the order of their resistance, and the liquid is in the
end completely sterilized.

The special chambers improvised by Professor Tyndall for the conduct
of the experiments above recorded recommend themselves so strongly,
on account of their simplicity of form and efficiency in action, both for
further experiments in a similar direction, and for the cultivation of Infu-
soria generally, that an illustration of one constructed to hold six test-

PROFESSOR TYNDALL. 131

tubes, as given by its talented inventor, is embodied in the plate at the end
of the Atlas devoted to mechanical appliances. This simply constructed
apparatus consists of a square wooden chamber or box, having a glass
front, side windows, and back-door. Through the bottom of the chamber
test-tubes pass, packed air-tight, with their open ends protruding for about
one-fifth of their length into the chamber. Provision is made through
sinuous glass tubings for the free access of air from without, but through
which, on account of their sinuous form, no germinal or other dust obtains
admission to the central chamber. The top of the chamber is perforated
by a circular hole two inches in diameter, and closed air-tight by a sheet
of indiarubber. This is pierced in the middle by a pin, and through the
pin-hole is pushed the shank of a long pipette, ending above in a small
funnel. The shank also passes through a stuffing-box of cotton-wool,
moistened with glycerine ; so that, tightly clasped by the rubber and wool,
the pipette is not likely in its motions up and down to carry any dust
into the chamber. The four legs upon which the chamber is elevated are
of sufficient height to permit of the application of a spirit-lamp, or other
heat-generator, to the bases of the depending test-tubes.

Proceeding now to an examination of the more important data bearing
upon the subject of spontaneous generation, obtained through the investiga-
tions of Messrs. Dallinger and Drysdale, it must be mentioned, in the first
place, that the evidence elicited through their researches was arrived at from
an entirely different standpoint, and, in the second place, that it fills up an
important hiatus held by the heterogenists to be present in the chain of
evidence adduced by Professor Tyndall. Notwithstanding that the only
reasonable and inevitable inference to be drawn from the results of his
experiments was that infusorial germs of exceeding minuteness were ever
present in the ordinary atmosphere, and ready to germinate in the first
suitable fluid medium with which they came in contact, it has been urged
by his opponents that there is no direct proof of the actual presence of
these countless ultra-microscopic germs, and that his evidence is therefore
of an entirely negative character. But, to those who are well versed
in the life-phenomena of this special class of organisms, the connection
between the impalpable germinal dust gathered by Professor Tyndall from
the laboratory floor or revealed by the electric beam, and the crops of
animated beings produced out of it when sown in the sterilized fluid,
is inductively as certain as that the celestial nebulae, as yet unresolved into
their ultimate elements by the telescope, consist of star-aggregations similar
to those of the nearer and more familiar constellations.

Fortunately for the cause of the panspermists, this one weak joint in
their armour, if such may be said to have been left open — this one little
loophole for doubt, out of which the heterogenists have attempted at the
eleventh hour to make good their untenable position — has now to be
finally closed up. The propagation of infusorial organisms by germs or
spores of ultra-microscopic minuteness, has been definitely and most

K 2

132 SPONTANEOUS GENERATION.

conclusively demonstrated by Messrs. Dallinger and Drysdale, in their
accounts of the life-history of various species of monads, contributed chiefly
to the 'Monthly Microscopical Journal' during the years 1873 to 1875, and
as described hereafter, systematically, under the specific headings of Monas
Dallingeri, Cercomonas typica, and Heteromita rostrata and uncinata. As
there recorded, the spores or germs of these animalcules, when first released
by the rupture of their enclosing cyst,, are of such extreme minuteness
as to defy individual resolution with a 3Vinch objective and associated
magnifying power of no less than 15,000 diameters, appearing in the
aggregate under such conditions as a faintly granular fluid, having a re-
fractive index scarcely distinguishable from the surrounding water. As
germination and development progress, each individual spore, however,
passes within the range of vision, and by degrees assumes the determinate
size, form, and characteristics of the parent organism. The record of
these reproductive phenomena of the monads in question was brought
forward at the time simply as a newly discovered and interesting chapter
in their life-history. Later on, however, Mr. Dallinger published in the
'Monthly Microscopical Journal' for December 1876, the results of his
further investigations of these minute organisms, in which, through corre-
lating his own discoveries with those of Professor Tyndall, he obtained
some most important results.

Drying up the residual portion of a maceration or infusion containing a
certain known form of monad, he had already shown that the light, porous,
papier-mache-like substance resulting from such desiccation might be
saved, like the seeds of a plant, and used for propagating the species at
will in any suitable sterilized putrescible fluid. Working on this basis,
an infusion of haddock's head, containing in abundance the so-called
" Springing Monad" (Heteromita rostrate?) and the Calycine Monad (Tetra-
mitus rostratus) in the spore-producing stage, was gradually evaporated,
then raised to a temperature of 150° Fahr., or 10° above that required to
kill the adult form, and so reduced to a porous and highly friable condition.
A small portion of this dried material, reduced to powder, was now diffused
in an experimental chamber like those employed by Professor Tyndall,
and the condensed beam of an oxyhydrogen lime-light being transmitted
through the windows, its path within the chamber was more brilliantly
marked than on the outride, indicating the preponderating existence therein
of the spore-containing or germinal dust. This was now allowed to settle
for a space of four hours and a half, when the lime-light still demonstrated,
though in a less marked manner, the presence of the suspended dust. Ten
small glass dishes, each partially filled with a sterilized fluid, were then
introduced into the chamber, four of them being covered with projecting
glass lids, mechanically movable, without opening the door of the chamber,
and smeared with glycerine, to prevent the disturbance of any previously
settled germs. At. the end of twenty-four hours the lids were removed
from the four covered vessels, and the whole now left undisturbed for

DALLINGER AND DRYSDALE. 133

four days. The six vessels left uncovered from the commencement being
successively examined, were found in every instance to be abundantly
peopled with both of the two monad forms present in the evaporized
infusion, and developed from the germs diffused as dust through the air of
the experimental chamber. Two days later a similar examination was
made of the four remaining vessels which had remained covered, and with
somewhat different results. In all these the Springing Monad was abun-
dantly developed, but the Calycine form was found in only one of the
receptacles, and then in very small numbers.

At first, this result appeared perplexing, but it occurred to Mr. Dallinger
that the spores or germs of the last-named type, as in the case of the adult
monad, were considerably larger than those of the former, and had, on account
of their greater specific gravity, fallen to the bottom of the chamber before
the removal of the covers from the four vessels last examined, and had thus
been excluded from developing ; this inference was fully substantiated by a
repetition of the experiment with certain modifications. On this occasion, the
material used was the desiccated residuum of an infusion containing abun-
dantly, in its sporiform condition, the simple uniflagellate type, Monas Dallin-
geri, the smallest species yet met with by him, and whose adult length did not
exceed the i-4OOOth or i-45ooth part of an English inch. The spores or
germs produced by this animalcule were correspondingly minute, and it was
consequently surmised that they would remain floating in the still air of the
experimental chamber long after the subsidence of the germs of the larger
types, and develop in vessels placed there for their reception at a later date.
Finely pulverized and intimately mixed with material containing the larger
Calycine Monad (Tetramitus rostratus] having an adult length of ^^ to
•nrW> these most minute germs were dispersed as before in a prepared
chamber. At the end of four hours and a half, nine small glass basins
were introduced, three of them remaining open and six being temporarily
covered. At the end of twenty-four hours two of these covered vessels were
exposed to the air of the chamber, and at the expiration of forty-two hours
the remaining four were similarly exposed. After each set had been left
undisturbed for five days they were examined with the following results.
The first three (without covers) contained both descriptions of monads
in every drop out of the sixty examined. The next two, uncovered at the
end of twenty-four hours, were found in every instance to contain the
smaller uniflagellate monad in abundance, but the larger one in a single
drop only out of the total of sixty examined. In the remaining four
vessels, uncovered after a lapse of forty-two hours, the result was that
the smaller type was found abundantly in every drop, while the larger one
was entirely absent. Finally, after the removal from the chamber of these
last four, four more vessels of sterilized putrescible fluid were put in their
places, to ascertain if any of the germs of the same type yet remained
suspended in the air ; but on examination five days later it was found
that not a trace even of this most minute flagellate species was present

134 SPONTANEOUS GENERATION.

in either one of the four vessels, their germs being thus demonstrated to
have entirely subsided.

In addition to the highly suggestive evidence adduced through these
several experiments, in demonstration of the persistency of form, and enor-
mous capacity for atmospheric diffusion, possessed by these monads, their
ultra-microscopic spores or germs are now shown to possess varying degrees
of ponderosity, and it would seem by no means beyond the range of possi-
bility, by further research, and having regard especially to the length of
time occupied in the subsidence of a given type, to ascertain, by comparison
with some larger and measurable variety, the exact or approximate dimen-
sions of those germs, as yet lying beyond the defining powers of our most
perfected microscopes, but instantly revealed by the searching electric beam,
and which may be cultivated at will in an appropriate fluid medium.

In addition to the very important bearings upon the question of spon-
taneous generation embodied in the foregoing researches, Mr. Dallinger's
name demands notice also with reference to some most important experiments
conducted alone, and in combination with Dr. Drysdale, for the purpose of
ascertaining the power of resisting high temperatures possessed by these
lower forms of life in both their adult and sporular or germ condition.
These experiments entirely confirmed Professor Tyndall's observations,
and possessed, moreover, the additional advantage that a given and varying
thermal death-point, or limit of heat-resistance, was now associated for
the first time with fixed and specific monad types. Following out this
line of investigation, it was thus shown that the spores of Tetramitus
rostrata could successfully resist a temperature of 250° Fahr. (12 i°C.), those
of Dallingeria Drysdali 220°, those of Cercomonas typica 260°, while in the
case of Heteromita rostrata and H. uncinata they passed unscathed through
a temperature of no less than 300° Fahr., or 148° C, which represents the
highest limit that has as yet been obtained. It was further ascertained that
a somewhat different result accrued according to whether the heat was
applied in a wet or dry form, the spores in certain instances exhibiting
a difference of as much as 10° Fahr. in this respect, and the highest
being resisted when applied in the dry condition. The adult and active
monads, having their constituent sarcode or protoplasm in a soft and semi-
fluid state, in all cases succumbed to the comparatively low temperature,
as an approximate limit, of 140° Fahr., and in many instances to one con-
siderably lower even than this.

Some results of the author's personal investigations have now to be
submitted, which tend, from an entirely independent point of view, towards
the solution of the question now under discussion. Respecting Professor
Tyndall's highly valuable testimony, it has been, and may yet be, objected
by the partisans of heterogeny that his atmospheric germs are purely hypo-
thetical and intangible, not having been actually seen by him, nor, what
is more important, being so far connected with any recognized specific
form of infusorial life. The evidence adduced by Messrs. Dallinger

A UTHOKS INVESTIGA TIONS. 1 3 5

and Drysdale may also be cavilled at as deficient of the necessary proofs,
inasmuch as the various species with which their researches are connected
are peculiar to certain putrefying animal macerations only, and cannot
therefore be said to fairly represent those types common to organic infusion
generally, with which the phenomena of de novo generation have been held
more especially to obtain.

Now, among these, infusion of hay has from the earliest date of the
discovery of Infusoria, and the promulgation of the doctrine of spontaneous
generation, been recognized as the most productive material for the artificial
development of these minute beings, and as the one in which such presumed
de novo or spontaneous generation is most prominently manifested. So
far, this seeming special potentiality of macerated hay has not been made
the subject of rigid and exhaustive inquiry, while the evidence recorded
by Professor Tyndall concerning the extraordinary heat-resisting and in-
fective properties of hay-derived germs in their concrete form, is no doubt
accepted by the heterogenists as simply testifying to the possession by
this material of such potentiality. If, however, the disciples of heterogeny
flatter themselves that from this last uninvaded vantage-ground they may
peradventure be able to withstand and bring discomfiture upon the ad-
vancing hosts of their opponents, the panspermists, they are destined to
signal disappointment.

Within the last two years the animalcules produced so abundantly in
hay-infusions have been the object of the author's special investigation,
many of the new species described in the systematic portion of this volume
being, indeed, the outcome of such research. Hitherto the infusorial types
commonly observed in hay-infusions have been of comparatively large
size, belonging to the higher order of the Ciliata, and pertaining to such
genera as Paramecium, Colpoda, Cyclidium, Oxytricha, and Vorticella.
These, however, represent numerically but an insignificant minority com-
pared with the vast hosts of flagellate forms which abound in a hay-infusion
during the earlier days of its maceration. In such infusions, watched from
day to day, and produced from hay obtained from different localities, the
number of types presenting themselves in tolerably regular sequence was
found to be perfectly marvellous. Foremost among the generic groups
putting in their appearance must be mentioned that of Heteromita, frequently
represented simultaneously by three or four species, and including more
especially the Heteromita (Manas) lens of O. F. Muller, H. caudata, and
H. gracilis. Other genera, such as Oikomonas, Dinomonas, Petalomonas,
Rhabdomonas, Ampkimonas, Monas proper, Cryptomonas, Hexamita, and
Gymnodinium, contribute likewise an almost equally considerable contin-
gent ; while Bacteria in their characteristic motile and quiescent states are
invariably present, and furnish an abundant and ever ready pabulum for
their more highly organized animal consociates.

The question presented to the author for solution was, from whence
were derived all these myriad organisms, frequently produced in such

136 SPONTANEOUS GENERATION.

abundance as to literally jostle each other for room in every drop of water
extracted for examination? The heterogenists, including notably MM.
Pouchet and Pennetier, have asserted that the highest Ciliate types present
in hay-infusions, such as Colpoda and Vorticclla, are generated de novo out
of the filmy pellicle, or so-called " proligerous membrane," that in the course
of a few days makes its appearance upon the surface of the liquid. This
proligerous membrane, again, is further represented to be formed from the
accumulated dead and floating bodies of Monads, Bacteria, and Vibrios,
that first appeared in the infusion, and to constitute a kind of primordial
stroma or pseud-ovary, out of the granular constituents of which, through
coalescence at various points of the component particles, true eggs are
developed, giving birth to such Ciliata as sooner or later appear upon
the scene. The Monads themselves are treated as primary motile mole-
cules, occupying a place midway between the organic and inorganic, and
possessing motile properties most nearly corresponding with the molecular
or Brownian motions of minute inorganic particles. The spontaneous
derivation of these Monads from the dead and disintegrated particles of
the macerated hay is regarded as too obvious to need discussion. It has
been positively ascertained by the author, however, that these minute
beings are derived from spores which literally encrust with their countless
numbers the stalks and blades of the vegetable matter ; these again being
the product of pre-existing monad forms, whose active life was passed in
close association with the green and growing hay under the circumstances
hereafter narrated.

In order to arrive at a comprehensive insight into the life-phenomena
and progressive developmental manifestations of the special group of infu-
sorial animalcules now under consideration, hay from different localities
was placed in maceration and examined continuously, from its first contact
with the fluid medium, for periods varying in duration from a few days only
to several weeks. The water added to the hay was of the purest possible
description, and was frequently boiled for some time to prevent the intro-
duction of extraneous germs. In all instances, the results obtained were
broadly and fundamentally the same, and differed only with respect to
the specific types found living together in the separate infusions. Even
here, however, the general dominance of two or more special forms was
notably apparent. Commencing with the first wetting and simultaneous
examination of any given sample, spores of different sizes were found
congregated in countless numbers, and in various orders of distribution,
throughout the surfaces of the vegetable tissues. The majority of these
spores were excessively minute, spherical, of the average diameter of the
l-2O,oooth part of an English inch, and required necessarily the employment
of the highest powers of the compound microscope for the correct registra-
tion of their characteristic form and size. Sometimes these spores were to
be observed collected in definite spherical heaps, but more often they were
scattered in irregular-shaped patches, such patches being often again more

A UTHORS INVESTIGA TIONS. 1 3 7

or less confluent, and thus forming collections of considerable extent. A
large number of these spores were likewise to be seen, detached from
their original adhesions, freely floating in the water, or collected in masses,
upon the peripheries of the small air-bubbles that had here and there
become entangled between the slide and the covering glass. In this latter
instance the spores exhibited a thicker and more opaque bounding wall,
and manifested, as in the case of lycopodium powder, the power of resisting
for some time the hydrostatic or wetting action of the water ; this property
had already been suspected by Professor Tyndall to be possessed by
these minute bodies, but had not previously been practically demonstrated.

The hay within from four to six hours after maceration revealed, on
examination of a small fragment, a considerable alteration in the character
and comportment of the associated spores. Hitherto these had displayed
no signs of motion, a uniform stillness reigning throughout the entire
expanse of the microscopic field. Now, however, among the numbers that
had become detached from their original adhesion to the vegetable matter,
the majority exhibited an active vibratory motion that at first sight was
scarcely to be distinguished from the characteristic " Brownian movements."
The size of these motile spores corresponded with that of the quiescent
ones, not exceeding the i-2O,oooth of an inch in diameter, and without
recourse to the highest magnifying power and the most careful adjust-
ment of the illumination, it was not found possible to ascertain by what
means their locomotion was accomplished. Examined successively with
the -tV, 7>V> and 7V inch objectives of Messrs. Powell and Lealand, it was
at length satisfactorily determined that each individual spore or body was
furnished with a single, long, slender, whip-like organ or flagellum, whose
active vibrations propelled the spherical body through the water. These
minute motile corpuscles exhibited, in fact, at this early stage of their
development a type of organization in all ways comparable with that of the
simply uniflagellate genus Monas.

A highly characteristic feature of these moving spores remains to be
mentioned. Although vast numbers of them were to be seen careering
singly through the water, a very considerable proportion were united to
each other in irregular clusters consisting of from two or three to as many
as a dozen, or, as still more generally occurred, from two to as many as
eight of them were joined laterally, so as to form floating moniliform or
necklace-like aggregations corresponding in general aspect and mode of
attachment with the normal moniliform colonies of the collared flagellate
type Desmarella moniliformis, hereafter figured and described. If watched
for a sufficient time, these clustered and serial aggregations were observed
to become disintegrated, each separate corpuscle thenceforward maintain-
ing an independent existence. In consequence of the characteristic aggre-
gate forms primarily exhibited by this special species, it has been further
found possible to definitely identify it with one of the types of animal-
cules described by O. F. Mliller in the year 1786, and upon which he

138 SPONTANEOUS GENERATION.

conferred the name of Monas lens. As figured and described by this author,
the above-named species is distinguished in its more minute form by the
two conditions of aggregation just enumerated, his illustrations of them
being necessarily on a very small scale, and no trace being indicated or
discernible with the instruments at his disposal of the characteristic loco-
motive flagella.

The further development of the separated monadiform corpuscles has
yet to be traced. Following the assumption of the independent motile
condition, an increment in the size of the constituent body, and with it a
duplication of the locomotive appendage, was observed. Within twelve
hours from the first submersion of the hay, many of these bodies had
increased to twice their original size, measuring now the i-io,oooth part
of an inch in diameter, and possessed in addition to a vibratile appen-
dage a second flagellum which trailed posteriorly when the animalcule
swam through the water, or held it anchored at will to the vegetable
debris or other substances contained in the infusion. Retaining their
spheroidal form and two associated flagella, they still continued to increase
in bulk, until, at the end of twenty-four hours, the field was more or less
crowded with biflagellate animalcules having an average diameter of from
the i-3OOOth to the i-25OOth part of an inch, and exhibiting in their
adult state all the characteristics of an ordinary Heteromita. To make the
history complete, these adult Heteromitce were observed to increase
abundantly by simple fission, as also more rarely to unite or coalesce, the
product of such fusion being the assumption by the united zooids of a
quiescent or encysted state, followed by the breaking up of the combined
mass into a heap of minute sporular bodies corresponding with those just
described, and which, like them, were subsequently released and recom-
menced their developmental cycle under the form of similar irregularly
clustered or chain-like aggregations. Heteromita lens, however, represented
but one, though perhaps the most constant and abundantly ^developed,
out of a number of monad forms that were produced in the various
macerations of hay examined, all of which existed, and were for the most
part recognizable, in their sporular condition attached to the external
surface of the vegetable tissues at the time of their immersion.

Such other spores of various descriptions were found abundantly
scattered among those of the type just described, most of them, as in the
case of Heteromita caudata and Oikomonas mutabilis, being of considerably
larger dimensions than, and sometimes, as in the first of these two instances,
presenting a contour altogether distinct from, the simply spheroidal spores
of H. lens. In the last two instances the sporular bodies were produced
by the subdivision of the parent animalcule into four, eight, or sixteen
segments only, and thus conformed in character with the type designated
" macrospores " in the account given of the reproductive phenomena of
the Infusoria. In that of Heteromita lens, on the other hand, these cor-
responding bodies were so numerous and minute as to baffle computation,

AUTHOR'S INVESTIGATIONS. 139

and laid claim in a corresponding manner to the appellation of " micro-
spores." In yet other instances the encysted monads were observed to
give exit to spores of such excessive minuteness, that, as in the case of
several types described by Messrs. Dallinger and Drysdale, they were not
individually recognizable as they escaped from the parent cyst, but pre-
sented in the aggregate, as viewed with the highest magnifying power,
the aspect only of a viscid granular fluid, having a refractive index
scarcely higher than that of the surrounding water. The recurrence of the
various monad forms just enumerated by no means, however, exhausts
the evidence of latent or pre-existing life found accompanying well-nigh
every fragment of hay examined. The spores of fungi occurred in abun-
dance, and also ciliate Infusoria, such as Vorticella, Colpoda, and Trichoda,
in their resting or encysted state, while Bacteria were never absent. These
latter, as time progressed, developed their several motile, gloea,'and fila-
mentous phases, and were repeatedly, with the assistance of the ^ -inch
objective, demonstrated to increase by means of minute internally pro-
duced spores, after the manner of the co-associated monads. Some idea
of the conditions under which the spores and encystments of the various
animalcules present themselves in connection with hay-fibres, as viewed
with a high magnifying power, may be arrived at on reference to the upper
portion of PI. XL, which, with its accompanying explanation, is devoted to
the special illustration of this topic.

From the foregoing detailed account of the life-history of one special
monad type, and of the circumstances under which the spores of this and
other species are found primitively attached to the macerated hay, there
would appear to be little left to prove the utter untenability of the argu-
ments adduced by the heterogenists in favour of the de novo generative
properties of this material. One important link in the chain, neverthe-
less, remains to be filled up. So far it has not been shown under what
circumstances these countless multitudes of spores became originally
deposited upon, and attached to, the dried hay fibre, and such an absence
of definite demonstration might be interpreted by the heterogenists in
favour of their having been developed there spontaneously. Of the larger
Ciliate species it has been frequently suggested that they are derived from
animalcules carried by river inundations on to the low-lying meadow lands,
and which have remained attached in their encysted state to the grass on
the retreat of the overflowing waters. Such an interpretation, however,
necessarily implies a local and restricted distribution only, and in no way
accounts for the unexceptional and cosmopolitan distribution of Infusoria
and their germs upon hay derived from whatever source. Neither, again,
does the vast quantity, and definite disposition of the spores with rela-
tion to their vegetable matrix, allow of the alternative that they have
simply fallen from the surrounding atmosphere, and which, in point of
fact, can be no more regarded as their native or parental element than it
is that of the floating thistle-down.

140 SPONTANEOUS GENERATION.

The mode of distribution of these infusorial spores upon the hay-fibres
indicated, in characters too clear to be mistaken, that all the essential
conditions of their life-cycle had been passed in close connection with it.
This interpretation was arrived at inductively, and its correctness was
recently put to the test, with the following remarkable results. On Satur-
day, October the loth, 1879, a day of intense fog, the author gathered
grass, saturated with dew, from the Regent's Park Gardens, the Regent's
Park, and the lawn of the Zoological Gardens, and submitted it to micro-
scopical examination, without the addition of any supplementary liquid
medium. In every drop of water examined, squeezed from the grass or
obtained by its simple application to the glass slide, animalcules in their
most active condition were found to be literally swarming, the material
derived from each of the several named localities yielding, notwithstanding
their close proximity, a conspicuous diversity of types. Heteromita lens
and H. caudata were in all three instances abundantly present, as also
minute actively motile Bacteria. Other types, such as Vorticella infusionmn,
Dinomonas vorax, Hexamita inflata, Trepomonas agilis, and Phylloniitus
undulans, to say nothing of a host of unidentified spores and encystments,
occurred variously distributed among the three examined samples of dew-
laden grass, but even these by no means exhausted the list of living forms.
Two species of Rotifera, Rotifer vulgaris and Theorus vernalis, numerous
Amoeba, AngitillulcB, and various diatoms, chiefly motile Naviculce, contri-
buted their quota towards the host of active living organisms that were
found peopling more especially the lower and decaying regions of the dew-
moistened vegetation, the collection as a whole being undistinguishable
from the ordinary microscopic fauna of a roadside pond.

The data elicited through the observations just recorded carry with
them an important and far-reaching significance. In addition to the
conclusive proof herewith afforded of the primary origin of germs in hay,
Infusoria and other minute forms of aquatic life were thereby demon-
strated to possess an area of active vital distribution hitherto undreamt
of. Water in its stable and concrete form is no longer, as hitherto
presumed, a requisite concomitant of such vital energy. The smooth-
shaven lawn, park-land, and meadow are each and all one vast teeming
city, peopled by its myriads of tiny inhabitants, heedlessly crushed
under foot in our daily walks abroad. Securely housed in their spore-
membranes or encystments, these microscopic beings slumber undisturbed
and unconsciously throughout the dry, dusty summer days, awaiting, how-
ever, only the fall of the evening dew, or passing shower, to cast off the
frail cerements that enclose them, and to re-awake to active sentient life.
The mode or conditions of existence of the animalcules thus found so
plentifully on the dew-, or rain-moistened grass, are obvious. As already
stated, they are encountered most abundantly on the lowermost blades,
coloured brown or yellow, upon which the finger of decay has already set
its stamp. Here, in fact, is a plentiful banquet ever set in order for them,

A UTHORS INVESTIGA TIONS. 1 4 1

closely identical in character with the artificially prepared infusions of hay,
and other vegetable substances, which are so speedily attended by their
myriad guests. Their purpose in life, as in the case of the animalcules
inhabiting artificial infusions, is to break down and convert into new
protoplasmic matter this otherwise waste product. To maintain the balance
here, however, and to check the too rapid increase of the herbivorous
monads, we find other types, such as Dinomonas and various Ciliata,
answering to the Carnivora among the various higher animal sub-kingdoms,
developed side by side with and feeding in turn upon the plant-eating
species.

The general conclusions deducible from the long array of evidence now
produced with respect to the question of "spontaneous generation," or
" abiogenesis," may now be briefly summarized. From every line of inquiry
investigated, one and the same answer is invariably returned. Life in its
most humble and obscure form, be it existent as impalpable germinal dust
floating in the atmosphere, or shaken from a truss of hay, or manifested in
its more active state as the minute monads, bacteria, and other organisms
developed in infusions, tells everywhere the same unvarying tale. Traced
backwards to its origin, or forwards to its ultimate development, each
type is found by patient search to be derived, not de novo out of dead or
inorganic elements, but from a specific parental form identical in all respects
with itself, and whose life-cycle is as true and complete as that, even, of
man himself.

To the scientific mind the conception that organic matter was primarily
eliminated, or in other words created, out of the inorganic, is forced home
as a natural and logical conclusion, and also that this transition may be a
process of every day occurrence. So far, however, as such recurring or de
novo generation is exhibited by the types of organic life dealt with in
this volume, or at present known, there is no longer left a loophole for
doubt. The evidence from all sides, revealed by the exhaustive light of
recent research, proves conclusively that in all these cases, down to the
lowest monad and bacterium, the reproduction of their kind, formerly
supposed to be altogether fortuitous and irregular, conforms in every essential
particular with that of the highest members of the organic series.

Accepting, in point of fact, the infusorial or protozoic spore as the
physiological, though not morphological, equivalent of the ovum of all
higher animals, or Metazoa, Harvey's once famous, but since discarded,
aphorism " Omne vivum ex ovo," is found, so far as human knowledge has
as yet penetrated, to dominate with equal force from one extremity to the
other of nature's chain. To assert, however, that we have penetrated to
and laid bare the ultimate and finite confines of the organic realm, would
be an arrogant and altogether illogical assumption : a vast terra incog-
nita of organic forms may still remain to be explored. As yet, the latest
investigations of physiologists have pushed so far forward as to acquire an
approximate, though by no means exhaustive, knowledge of the " cellular "

142 SPONTANEOUS GENERATION.

as manifested by unicellular and multicellular products. Unicellular pro-
ducts, however, there are ample grounds for maintaining, are susceptible
of differentiation to an almost unlimited extent, such differentiation being
essentially "molecular" In the same manner that unicellular organisms
are now shown to correspond with the essential or primary elements
out of which all multicellular organisms are built up, so is it within the
region of possibility that entities yet exist which in a parallel manner find
their morphological equivalent in the constituent elements of unicellular
beings, and whose composition may be therefore correctly described as
simply molecular. Practically, such molecular organic entities exist in the
individually invisible or ultra-microscopic germs, discharged in a semifluid
state from the encystments of many monads. The embryonic condition of
one form typifying the adult state of one lower in the organic scale, is of
almost undeviating recurrence in the scheme of nature, and the conception,
therefore, of beings possessing in their highest state of development a corre-
sponding germinal, and yet ultra-microscopic or molecular condition, follows
as a natural and almost unavoidable deduction. It is, logically, within the
realms of the molecular alone, if anywhere, that the transition from the
inorganic to the organic is to be sought. Elsewhere, throughout the entire
range of cellular structures, the phenomena of reproduction are distinct and
uniform, rendering entirely untenable and nugatory their correlation with
the doctrine of abiogenesis.

One final, though indirect, result of the rigid scrutiny to which the
monads, and other low unicellular organisms, have been submitted in order
to solve the mystery of their generation, remains to be recorded. As conclu-
sively proved by Professor Tyndall, Dallinger and Drysdale, Cohn, Kiihne,
and other investigators, such organisms in their germinal or sporular state
can successfully resist exposure to temperatures that prove fatal to any other
more highly organized structures, even up to and beyond the boiling-point
of water. So far, therefore, as they are brought in contact with the ordinary
conditions of the earth's surface they are practically indestructible. Nay
more ! as suggested by Professor Tyndall, there is no reasonable pretext for
assuming that there are not germs capable of resisting far higher tempera-
tures than those which have been hitherto subjected to experiment. Hence,
among all known organic forms, the Infusoria and their allies alone would
appear to possess the power of weathering the cataclysmic changes of the
universe, and, secure from all influences of heat and cold, of migrating
in safety through interplanetary space.

( 143 )

CHAPTER V.

NATURE AND AFFINITIES OF THE SPONGES.

IT is proposed to devote the present chapter to an extensive discussion of
that near relationship of the sponges to certain of the Infusoria Flagellata;
briefly referred to on several occasions in the course of the preceding
pages. This affinity is found, indeed, upon an impartial examination of
the data here collected, to be so comprehensive and thoroughgoing as to
render absolutely unavoidable the correlation of this group with the typical
representatives of the flagellate Protozoa. Those differences which do
exist between the two groups are, in point of fact, far less essential than
those which obtain between many of the subordinate sections of the ordinary
Ciliate and Flagellate Infusoria ; such being the case, the present work
could not be considered complete if it did not embrace a more or less
extensive account of the fundamental plan of organization, at least, of the
Spongida. Strictly speaking, the sponges, throughout all their wealth of
form and organization, are here accepted as Mastigophorous Protozoa, and
it is on account only of the limited space at disposal, that their full specific
enumeration and description, on a scale corresponding with that allotted to
the more typical representatives of the Flagellate Infusoria, is here omitted.
Under existing circumstances, it is found possible to submit a brief sketch
only of those broad fundamental characters which either unite with, or
distinguish the members of the sponge-tribe from their nearest allies,
supplementing them with the author's personal interpretation of those
somewhat obscure structural and developmental points which have been
held by other authorities to indicate an affinity in a different direction.
For, although it is confidently anticipated that the evidence now brought
forward must materially assist in securing to the sponges, eventually, a
general recognition of their intimate relationship to the Choanophorous
section of the Flagellate Infusoria, it can by no means be said that such an
affinity is at the present date universally recognized. On the contrary,
the balance of contemporaneous scientific opinion favours the relegation
of this organic group to the division of the Metazoa, though upon grounds
which, plausible as they seem to be upon the surface, are fundamentally
purely artificial and untrustworthy.

In order to arrive at a position permitting a thoroughgoing and
impartial appreciation of the very voluminous and conflicting evidence
that has been amassed with reference to the much debated affinities of

144 NATURE AND AFFINITIES OF THE SPONGES.

the sponges, it is, before all things, desirable to commence with an exami-
nation of the earlier periods of their intelligibly recorded history, and
thence to trace forwards, link by link, those consecutively recorded data
which have led up to the present controversial position of the question.

As an initial step in this direction, it is worthy of remark that the
conclusive demonstration of the very animal nature of the Spongida has
only been accomplished within the present generation ; for while originally
premised by Marsigli at the commencement of the eighteenth century,
and subsequently advocated by Ellis and Solander, Montagu, and Lamarck,
it was left to Grant, Bowerbank, Carter, Lieberkuhn, and Dujardin within
these later limits to produce the actual proofs of their animal organization.
Among the investigators just enumerated, the name of our fellow-country-
man Dr. Grant may be specially singled out, as the authority who first
discovered the characteristic ciliary action in sponges, as also the existence
of the remarkable free-swimming ciliated reproductive bodies described at
length later on. That of Felix Dujardin, however, has to be still more
prominently mentioned, he having been the first to indicate that relation-
ship between these organisms and the more ordinary Flagellate Protozoa,
which with some modification is here supported. In the course of his
'Histoire des Infusoires,' published in the year 1854, this author devotes
two brief pages to the nature and organization of the group now under
consideration. Tearing to pieces a living fresh-water sponge (Spongilla
lacustris), he there records that the constituent living particles will be
found, on submission to microscopical examination, singly or united in'
groups, either floating in the water or adherent to the glass slide, and
that for the most part these constituents are furnished with long vibratile
filaments or flagella, similar in character to those possessed by the simplest
Flagellate Infusoria or monads. These same constituent particles, he,
moreover, observed to throw out lobe-like expansions or pseudopodia, and
to creep about after the manner of amoebae. This phenomenon, while
possessed by the floating ones, is more especially marked in those which
adhere to the surface of the glass, and in which the vibratile flagella had
become withdrawn or obliterated. He also briefly alluded to the ciliated
reproductive bodies of Spongilla and various marine sponges, and the group
as a whole he declared to exhibit a type of organization comparable to
associated colonies of Infusoria, possessing the united characteristics of
both monads and amcebae. Respecting the horny fibres and siliceous or
calcareous spicules secreted by the various tribes of sponges, Dujardin
suggested that they are analogous respectively to the branching and some-
what horn-like supporting stalk of such monads as Anthophysa, and to the
siliceous and calcareous tests presented by the ordinary Rhizopoda.

. By Mr. Carter, in November of the same year 1854,* the announce-
ment was made of the discovery, in Spongilla, of so-called zoosperm-like
bodies, these, however, as he afterwards admitted, representing the ordinary

* 'Ann. and Mag. Nat. Hist.,' vol. xiv. ser. ii.

NATURE AND AFFINITIES OF THE SPONGES. 145

polymorphic and flagellate cells first noticed by Dujardin. To a like cate-
gory must undoubtedly also be relegated the so-called "spermatic elements,"
described by Professor Huxley in the 'Annals of Natural History' for the
year 1851. Lieberkuhn* corroborated and added considerably to the
details of the structure and life-history of Spongilla made known by
Dujardin, and elicited much new evidence concerning the occurrence in
this type of the motile ciliated germs, in addition to the more ordinarily
occurring non-motile and so-called "seed-like bodies," first discovered by
Dr. Grant, in association with various marine species, and merely recorded
by Dujardin, on the authority of M. Laurent, as existing in Spongilla.
Following upon Lieberkuhn's discoveries, must be recorded the very
important contributions respecting the ultimate structure of the closely
allied Indian species of Spongilla, contributed by Mr. Carter to the
'Annals and Magazine of Natural History,' during the years 1857 and
1859. In the first of these contributions, the entire life-history, from the
indurated " seed-like body " up to the adult state, was successfully traced
out, and many entirely new facts respecting the more minute histology of
the sponge organism elicited. Among these it was demonstrated that the
essential living constituents of the sponge-body were represented by the
ciliated monad-like elements first described by Dujardin, and that they
exhibited a very definite mode of arrangement. Under normal conditions,
Mr. Carter found that the monad cells were congregated together so as to
form a single and even layer within the interior of small spherical chambers
excavated within the sarcode or mucilaginous basal substance of the
sponge, and to which chambers he applied the term of "ampullaceous sacs."
The additional name of ovi-cells was also given to these chambers in their
earlier condition, from his having observed their development out of a
pre-existing ovule-like or granular mass, this latter first passing into the
normal, small, monociliated and unciliated sponge-cells which then spread
over the interior surface of the so-called ovi-cell, each with its cilium
directed inwards, and so leaving a cavity in the centre which finally became
connected with the nearest adjacent afferent canal.

The origin of these " ampullaceous sacs," by a process of development
corresponding to the growth and segmentation of an. ordinary ovum, is,
as hereafter shown, entirely confirmed by the investigations of the present
author. Mr. Carter further demonstrated the capacity of both the ciliated
and unciliated sponge-cells of the ampullaceous sacs to take in solid
food in the form of minute granules of carmine distributed in the surround-
ing water, as also the possession by these individual bodies of contractile
vacuoles and nucleus-like granules. Taken as a whole, the animal nature
of Spongilla was now proved beyond further question, and its composition
maintained to consist essentially of polymorphic monadiform or amoeba-like
elements, closely corresponding with ordinary monads and amoebae, the
former being aggregated together in definite order within the structureless

* Miiller's ' Archiv,' Bd. i., 1856.

L

146 NATURE AND AFFINITIES OF THE SPONGES.

jelly-like sarcode, that formed the groundwork or substratum of the
sponge-body. Within the central substance of this sponge-body, and 'also
in the superficial part, called by Mr. Carter the investing membrane, were
found scattered the innumerable amoeba-like non-flagellate cells, as also the
characteristic spicules of the species, which were reported to be secreted
by the amoeboid elements. Finally, the entire sponge-body was shown
to be brought into intimate relationship with the external water, firstly, by
a series of pore-like apertures opening or closing at will in the investing
membrane, and communicating through the afferent canals with the am-
pullaceous sacs ; and secondly, by another series of tubular channels, the
efferent canals, which originating in the deeper substance of the sponge,
united with each other, and finally debouched upon the large excurrent
apertures or " oscula."

As a result chiefly of the very exhaustive evidence concerning the
ultimate structure of Spongilla elicited through Mr. Carter's investigations
as here briefly epitomized, the position of the sponges among the ranks
of the Protozoa, and as specialized and colonial aggregations of amoeboid
and monadiform Protozoic beings, became almost universally accepted.
It is at the same time worthy of notice, that Mr. Carter hinted at the
possible correspondence of the ciliated sponge-chambers or ampullaceous
sacs with the stomach-cavities of the simplest polyps, certain Planariae,
and other organisms in which the cavities receiving the injected food are
also lined with cilia. In January 1859, Mr. Carter contributed a further
communication to the journal already named, recording new data of interest
relative to the form and structure of the essential monadiform sponge-cells,
though at the same time he temporarily modified his previous views con-
cerning the character of the ampullaceous sacs. The most important point
that requires notice relates to the circumstance that he here described and
figured in association with certain of the larger ciliate or monadiform
sponge-cells, the existence of two " spines " or " ear-like points," which he
figured and described as projecting to an even distance on either side of
the base of the single whip-like cilium. A possible spermatozoic character
of these so-called "spiniferous cells" was at first suggested by Mr. Carter,
but subsequently abandoned through his demonstration of their capacity
to take in solid nutriment. The special interest attached to the discovery
by Mr. Carter of these spiniferous elements will shortly become apparent.

The earliest complete treatise of importance demanding notice bearing
upon the structure and organization of sponges, is the first volume of
Dr. Bowerbank's ' Monograph of the British Spongiadae,' published by the
Royal Society in the year 1864. Vast, however, as is the mass of material
embodied in this and the two subsequent volumes of this work (1866 and
1874), it relates almost entirely to the structure and organization of sponges
in their dried or preserved condition, and is of practical value only for the
purposes of specific identification. In such preserved specimens, as there
described, the essential vital elements now under discussion had become

NATURE AND AFFINITIES OF THE SPONGES. 147

completely metamorphosed or obliterated. Excepting, in fact, his notice
of the several observations of Grant, Dujardin, Carter, and Lieberkuhn,
concerning the presence and disposition of the monociliated sponge-cells,
Dr. Bowerbank's only personal record of their definite recognition is asso-
ciated with the calcareous type Grantia compressa, of which species he
figures and describes their characteristic tesselated plan of arrangement.
In their isolated condition the separate flagellate elements are so delineated
as to resemble the spermatic cells of ordinary vertebrate animals, having a
small ovate body and a long and comparatively thick terminal flagellum.

With the year 1866, an important epoch in the elucidation of the
structure and affinities of the Spongida was inaugurated. In June of that
year was published in a condensed form in the ' Proceedings of the Boston
Society of Natural History,' the results of a prolonged and painstaking
investigation instituted by Professor H. James-Clark, of the Agricultural
College of Pennsylvania, U.S.A., with reference to the ultimate form and
composition of the monociliated cells of a calcareous sponge most nearly
allied to the Leucosolenia botryoides of Bowerbank, and having respect to
their close correspondence with the individual zooids or units of certain
new forms of Flagellate Infusoria which he had recently discovered and
then described for the first time. This important communication, with
accompanying plates, appeared in extenso in the ' Memoirs ' of the above-
named society, vol. i. plate iii., for the year 1868. The essential feature of
the new and special forms of Flagellata here introduced, numbering in all
four species, and referred to the then two newly instituted genera Codosiga
and Salpingceca, consisted of the fact that all of their representatives were
provided at the free anterior extremity with a delicate funnel-shaped ex-
pansion of the sarcode, possessing an extraordinary amount of plasticity,
which in its normal condition of expansion surrounded the base of the
flagellum.

Upon this newly discovered and remarkable structural element Professor
Clark bestowed the appropriate title of the " collar," and as " collared " or
" collar-bearing " monads, the animalcules then and since discovered sharing
a corresponding structure, are now generally known. Turning his atten-
tion to the ultimate ciliated elements of the calcareous sponge just
mentioned, Professor Clark at once recognized that when viewed with a
sufficiently high magnifying power they exhibited a type of organization
precisely identical with that which obtained in the independent collar-bearing
monads, possessing like these a similar film-like, extensile and contractile,
collar-like membrane, enclosed terminal flagellum, posteriorly located con-
tractile vesicles, and all other details characteristic of an isolated monad
of his newly established genus Codosiga or Salpingceca. As indicated by
Professor Clark, any one previously acquainted with the structure of
Codosiga, but not with the sponge, would without doubt, in describing
merely the congregated monads of the latter, pronounce them to be colonial
and massive growths of the previously named simple Flagellata. The other

L 2

148 NATURE AND AFFINITIES OF THE SPONGES.

elements recognized by Professor Clark as entering into the composition
of the complete sponge-body, manifesting its differentiation from such a
simple monad colony as Codosiga, were, in the first place, an externally
placed and excessively hyaline, glairy, gelatinous matrix, upon the internal
surface of which the characteristic flagellate cells were embedded, and
secondly, the spicular bodies found immersed within the substance of this
glairy matrix, and by which latter element he considered them to be
secreted. Upon this common matrix he conferred the title of the cyto-
blastematous layer, or " cytoblastema," in contradistinction to the internal
pavement-like one composed of collar-bearing units, and which he desig-
nated the monadigerous layer. The spiculae themselves he represented as
directly comparable with the horn-like loricae secreted, or rather excreted,
as protective coverings by such genera as Cothurnia, Salpingceca, and other
ordinary Infusoria.

It was at once recognized by Professor Clark that the so-called spini-
ferous elements of Spongilla, figured and described by Mr. Carter in the
year 1859, were closely identical with what had been observed by himself
in Leucosolenia, and that the two "spines" or "ear-like" points recorded by
the former authority, represented actually the right and left profiles of a
similar subcylindrical membranous collar. Mr. Carter's observation of these
" spine-bearing " cells in a limited number of instances only is satisfactorily
accounted for by Professor Clark's record of the facility and rapidity with
which when disturbed this membranous collar is completely withdrawn
into the general substance of the body-sarcode. With reference to the
food-incepting phenomena of the sponge-monads, Professor Clark was not
able to arrive at a definite conclusion. Presuming, nevertheless, from his
assumed discovery of a distinct oral aperture in Codosiga and other
Flagellata, close to the base of the flagellum, he was led to predicate the
existence of a similarly located one in the case of the sponge-monads. As
hereafter shown, however, Professor Clark's inferences concerning the nature
and position of the oral aperture in both the independent and associated
collared monads, have not been confirmed. Summing up the results of his
discoveries, the views maintained by Professor H. James-Clark with refer-
ence to the position and affinities of the sponges were, that these organisms
must be regarded as compound colonial forms of Flagellata, whose units, in
the case of Leucosolenia, exhibited a type of structure essentially similar
to that of Codosiga and Salpingceca, but might possibly in other instances
more closely approximate to that of Monas (Spumella) Bicosceca or
A nthophysa.

The entirely new light brought to bear upon the much vexed question
of the affinities of the sponges, and the influence upon the scientific mind
it was calculated to exert, through the important discoveries of Professor
Clark, were doomed, for a time at least, to be thrown into the back-
ground, if not altogether set aside, in consequence of the almost contem-
poraneous introduction upon the scene of a yet more novel, and for the

NATURE AND AFFINITIES OF THE SPONGES. 149

disciples of the doctrine of evolution, a far more fascinating interpretation
of the structure and relationship of these organisms.

The following year, that of 1869, was signalized in the annals of the
scientific world by the publication of Professor Ernst Haeckel's brilliant
disquisition in the 'Jenaische Zeitschrift,' Bd. v. 1869 (reprinted in the
'Annals' for January and February, 1870), in which this talented author
announced, in the most emphatic terms, that the sponges were more nearly
related to the corals, or Anthozoarian Ccelenterata, than to any other
organized beings, and that the position hitherto assigned to them among the
Protozoa was fallacious, and could no longer be maintained. Practically,
in the advancement of this theory, Haeckel may be said to have merely
resuscitated and clothed in a new and attractive garb the moribund one
that, first originating with Ellis and Pallas, was still more extensively
developed by Leuckart, but rejected by the verdict of subsequent in-
vestigators. This supposed affinity, as advocated by Leuckart and his
predecessors, was, however, one only of broad external isomorphic or homo-
plastic resemblances. In accordance with their views, each efferent or
oscular area in a compound sponge-body was regarded as the equivalent
of an individual polyp of a coral stock, minus in each instance the
characteristic tentacles, stomachal sac, and internal mesenteries and septa
that distinguish the representatives of the corals. Summing it up, such a
likeness as evoked by Leuckart on the part of the sponges with respect to
the corals may, borrowing a dramatic simile, be aptly compared to the
play of ' Hamlet,' minus the king of Denmark. Professor Haeckel, how-
ever, disinterring and infusing new breath into Leuckart's abandoned con-
ception, claimed for it a far wider and more deeply reaching significance.
It was insisted upon by the illustrious biologist of Jena that not only a
general external or homoplastic resemblance existed between the organic
groups in question, but that the internal structure and histological organiza-
tion of the two also coincided. Following out this line of argument, it was
represented that the nutritive canal system of the sponges was both homo-
logous and analogous with the gastrovascular system of the corals ; that
both the corals and the sponges were characterized by the possession of
similar distinct external and internal cellular layers, or ectoderm and
entoderm ; and that the adult organisms were derived in either case from
similar primitive diploplastic ciliated larvae, planulce and gastrulce, these
again being developed from ordinary segmented ova.

As may have been anticipated, this bold conception of Professor
Haeckel's inaugurated for the sponges an era of most close and rigid
investigation not yet ended, which has already resulted in a mass of
evidence that has added vastly to our previous knowledge of the ultimate
composition of these structures. None of this testimony, however, can be
said to confirm precisely that interpretation of the structural or develop-
mental phenomena insisted upon by Haeckel. In the majority of instances,
indeed, it is entirely subversive of his theory. Among the earliest of

150 NATURE AND AFFINITIES OF THE SPONGES.

the several protests against the views submitted by Professor Haeckel,
reference may be made to the communications contributed by the present
author to the 'Annals of Natural History' for March and August 1870.
The subject on these occasions was approached more entirely from
the Ccelenterate point of view, the writer being at that time officially
occupied in the study, identification, and arrangement of the series of
corals, recent and fossil, contained in the Natural History Department
of the British Museum. Arguing from such a standpoint, it was sought
to demonstrate that between the alimentary systems of the two groups
in question there was nothing whatever in common ; that the single,
well-defined gastrovascular aperture in a coral, subservient both for the
processes of ingestion and excretion, was in no ways comparable to the
multifarious canal-system through which, upon every side of its periphery,
the sponge-body received its nutriment, and that the assumption by
Professor Haeckel of a distinct ectoderm and endoderm in the structural
elements of a sponge was by no means clearly demonstrated. His claim
of a distinct personality for each oscular area of a sponge-body was
likewise contested, and an adhesion given generally to that Protozoic
interpretation of the sponge question, then supported in the text-books of
Huxley, Carpenter, and other English authorities, and manifested by the
investigations of Lieberkuhn, Bowerbank, and Carter, and especially
through the more recent investigations of Professor H. James-Clark
already quoted. Evidence of a still more substantial nature, tending in
the same direction, and emanating from one of the earliest and first
authorities in this country upon sponge organization, has next to be
noticed.

In October 1871, Mr. H. J. Carter contributed to the 'Annals of
Natural History ' the announcement of his identification, in all of the
numerous marine siliceous and calcareous sponge types recently examined
by him, of a structure essentially corresponding with that which he
previously described as obtaining in Spongilla, and generally indicated
their nonconformity with the Coelenterate plan of organization insisted on
by Professor Haeckel. As interpreted by Mr. Carter, the " ampullaceous
sacs," or other ciliated systems, represented the only essential portion of
the sponge structure, the remaining elements compared with these being
entirely subsidiary. One especially weak point in Professor Haeckel's
argument was further pointed out in his remarks concerning the sexuality
of the sponges. In none out of the hundreds of Calcispongiae examined
by him with the microscope, Haeckel says, could he detect a trace of
fecundatory male elements or zoospermia, and that therefore the bodies
subserving the purposes of reproduction constantly present cannot be
designated true sexual eggs or ova, but asexual germ-cells or "spores."
These spores, or so-called ova, in all the sponges he investigated, Professor
Haeckel, moreover, declared to be perfectly naked and destitute of mem-
brane, like the flagellate cells from which they proceed ; furthermore, he

NATURE AND AFFINITIES OF THE SPONGES. 151

reported that in all the sponges examined by him he had never found any
trace of a membrane or true cell-membrane on the cells, and that therefore
all sponge structures were composed of naked cells or " gymnocytodes." As
indicated by Mr. Carter, this sporidular interpretation of the reproductive
phenomena advocated by Professor Haeckel was in itself completely sub-
versive of the theory he attempted to substantiate, and, as the very essence
and starting-point of which, the existence of true and normally fecundated
ova, represents an indispensable condition for the evolution of the two
primitive germinal layers having the significance of an ectoderm and endo-
derm in the ordinary and restricted acceptation of the terms. Finally, Mr.
Carter directed attention to the recent discoveries of Professor H. James-
Clark as indicative probably of the true direction in which the affinities of
the sponges are to be sought.

Practically following up this clue, Mr. Carter, in the ' Annals ' for July
of the year 1871, produced a still more important contribution towards the
elucidation of the structure and affinities of the sponges. On this occasion
he announced that by renewed investigations, with increased magnifying
power, he was enabled to entirely confirm Professor Clark's discoveries
concerning the peculiar collar-like structures possessed by the mono-
flagellate sponge-cells, and stated that it is out of such collared mono-
flagellate elements that sponge organisms are more essentially constructed.
While the material supplying Mr. Carter with this important confirmatory
evidence was chiefly derived from the calcareous type Grantia com-
pressa, other species, such as Grantia (Sycon) ciliata, Leticonia nivea, and
Clathrina stilpJmrea, were found to yield substantially parallel testimony.
Those elements of Spongilla described by himself, in the year 1859, as
flagellate cells with ear-like or spine-like points, were also now recognized
as indicating the same fundamental structural form in the fresh-water
species. On one point only did Mr. Carter dissent essentially from the
views of Professor Clark, namely, with reference to the mode of food-
inception. While the last-named author attributed to the collar-bearing
sponge-cells, and also to the independent collared flagellate types Codosiga
and Salpingceca, the possession of a distinct mouth — not actually discerned,
but supposed to be situated within the collar, close to the base of the
flagellum — Mr. Carter was inclined, in consequence of the exceedingly vari-
able or polymorphic properties of these sponge-cells, to infer that they
engulfed food at any point of their periphery after the manner of amoebae.
With respect to the highly conspicuous polymorphic features of these
essential sponge-cells, he further considered that they were to be regarded
rather as forms intermediate between Rhizopoda and Infusoria-Flagellata
than as typical Infusoria as interpreted by Professor Clark ; preferentially,
perhaps, they were to be accepted as a distinct and independent Protozoic
group, whose component units or individuals might be appropriately desig-
nated sponge-animals or Spongozoa.

Before the close of the same year, 1871, additional but unfortunately for

152 NATURE AND AFFINITIES OF THE SPONGES.

science, the latest evidence in this direction, a few months prior only to
his much-to-be-lamented decease, was produced by Professor Clark him-
self. Already, in 'Silliman's American Journal' for February 1871, he
had drawn attention to Cienkowski's new social monad genus Phalanstc-
rium, and indicated its apparent close affinity to the collared types Codosiga
and Salpingoeca discovered by himself, but from which they differed most
essentially in the less conspicuous development of the characteristic collar,
and in their social or colonial occupation of a common gelatinous matrix.
This latter point more especially was cited as indicative of a still more
intimate relationship with the sponges than that presented by the two last-
named genera. Professor Clark further placed on record in the same serial
the results of his recent investigations into the ultimate structure of the
American Fresh-water Sponge, Spongilla arachnoides J.-Clk., the results
confirming substantially, and adding considerably to, the data elicited through
his previous examination of the marine calcareous type Leucosolenia botry-
oides. In this fresh-water form, however, the characteristic collared flagellate
cells were found occupying definite spherical excavated chambers, corre-
sponding with those described by Mr. Carter of Spongilla alba under the
name of ampullaceous-sacs, which received from Professor Clark the equi-
valent title of the " monad chambers." Taken in its entirety, the sponge-
body of this species was declared to be composed of the three following
distinct and well-marked elements : Firstly, of a common, glairy, gelatinous
basis, within which all the remaining constituents were embedded, and
which he designated the cytoblastema. Although presenting the same
characteristic consistence throughout, this glairy cytoblastema exhibited a
separation into two distinct regions, the one consisting of a thin superficial
stratum, stretched out on the points of the larger externally projecting
spicula, after the manner of a tent-canvas extended upon the ends of its
supporting poles. Within this peripheral cytoblastematous layer, designated
by Professor Clark in its separate form the " investing membrane," there was
no trace to be found of the monad-chambers. These latter, which consti-
tuted the second and most important structural element, were confined
entirely to the deeper and comparatively solid substratum of the cytoblas-
tema, and which he therefore distinguished, with relation to its contents, as
the " monadigerous layer." The third and remaining essential element recog-
nized by Professor Clark consisted of the innumerable amoebiform cells or
bodies scattered more or less abundantly throughout the substance of the
cytoblastema, and most conspicuously visible, in consequence of the absence
of the monad-chambers, in the thin superficial stratum or so-called investing
membrane. These amcebiform cells were distinguished by Professor Clark
merely by the name of the " cell-elements " of the cytoblastema, but, for
convenience, may be appropriately designated the " cytoblasts " or
" cytodes." Like simple cytodes, they were shown, as also pointed out by
Professor Haeckel, to possess no distinct cell-wall, and, unless specially
focussed for, were scarcely to be distinguished from the cytoblastema in

NATURE AND AFFINITIES OF THE SPONGES. 153

which they were embedded. Seen under the most favourable auspices, their
substance was demonstrated to be slightly granular, and that they con-
tained a subcentral, spherical, and more highly refractive nucleus or
endoplast. The contours presented by these cytoblastic bodies varied
greatly, ranging from simply ovate to every variety of irregular and jagged
outline, and their periphery often taking the form of more or less prolonged
caudiform projections, directly comparable with the pseudopodic appen-
dages of a typical Amoeba. In addition to these three essential elements,
e. g. the transparent structureless " cytoblastema," the " collared monads,"
and the polymorphic amcebiform " cytoblasts," one conspicuous but non-
essential structural element, as represented by the supporting or strength-
ening siliceous spicula, remains to be mentioned. The spicula in the
sponge in question were of two sorts, large and small, and were found
in either case to be confined exclusively to the cytoblastematous layer, and
not to intrude into the monad-chambers ; while the larger ones penetrated
into the deeper substratum of this element, the smaller ones occurred only
in the more attenuate peripheral region, and were evidently built up or
secreted by the cytoblastema or its enclosed amcebiform cytoblasts. The
exclusion here made of the secreted spicula from the category of essential
elements, while a departure from the course taken by Professor Clark, is
justified by the fact that sponges exist — e. g. the Myxospongiae, including
Halisarca and its allies — in which, while all the other three elements
are fully represented, spicula or skeletal structures of any kind are entirely
absent.

Among the data of importance recorded by Professor Clark concerning the
organization of the separate collar-bearing elements of the monad-chambers
or ampullaceous sacs, has to be particularly mentioned that he demonstrated
in this type most definitely the possession by each monad of two or more
conspicuously developed and evenly pulsating contractile vesicles. The
location of these vesicles was found to be more towards the posterior
extremity of the body, their systole and diastole being further described as
on the whole extremely slow, but very distinct, if sufficient patience was
used to watch them fixedly and without interruption. The last third
portion of the act of systole differed in being considerably more abrupt,
the vesicle appearing only at such time to contract suddenly. This latter
circumstance, taken together with the constant position of the vesicles, is
cited by Professor Clark as sufficing to rebut the inference that might
otherwise be arrived at, and as actually insisted on by Professor Haeckel,
that these vesicles were simply irregular protoplasmic vacuoles, such as
occur among undoubted protophytes and various ordinary tissue-cells.
Comparing the arguments adduced by Professor Haeckel, in favour of the
Ccelenterate affinities of the sponges, with the actual structural composition
of Spongilla and Leucosolcnia, elicited by his own special investigations,
Professor Clark finally arrived at the decision that the attempted parallel-
ism between the two groups must utterly fail, the relationship of the

154 NATURE AND AFFINITIES OF THE SPONGES.

sponges to certain Flagellate Protozoa being, on the other hand, so distinct
and decisive as to forbid their logical inclusion among the representatives
of any other organic class.

The year 1872 is, perhaps, more notable that any in the entire annals
of sponge biography through the publication of Professor Haeckel's truly
magnificent work of labour and art, if nothing more, entitled 'A Monograph
of the Calcispongiae.' This treatise, as its name denotes, embraced an
exhaustive account of every known form and variety of sponge charac-
terized by the possession of a skeleton composed of spicules of carbonate
of lime, and of which the little white Grantia compressa of our own
coast affords a familiar example. The chief interest of this monograph,
however, depends upon the fact that it is made the vehicle of Professor
Haeckel's more matured views concerning the near relationship affirmed
by him to subsist between the sponges and the corals, and which he now
sought, by means of the sponge-group monographed, to establish on a
more firm and solid basis. This remarkable work has in other words
to be regarded as embodying the veritable consummation of his then
newly conceived and now world-familiar "Gastraea" theory, having as
its aim the demonstration that all animal forms, from the sponges up
to the Vertebrata, emanate in their developmental history from one
single stock-form or phylum, upon which the common title of a "gastrula"
is conferred. This gastrula, as formulated by Haeckel, is constructed
fundamentally upon the same type as the advanced condition of the
embryonic planula, having an ovate body composed of two even, separate
cellular layers, the ectoderm and endoderm, and a central primitive
stomach-cavity or archenteron, which communicates at one extremity
with the outer world by a primitive oral orifice. From this identity of
the bilaminate gastrula in representatives of the most various animal
stocks, from the sponges to the Vertebrata, Haeckel, to quote his own
words, deduced the common descent of these various animal phyla from
a single unknown stock-form, his hypothetical gastraea, which was con-
structed on a plan essentially corresponding with the above-described
typical gastrula. As a first step towards the successful correlation of his
gastraea theory with the group of organisms now under consideration, it
necessarily devolved upon Professor Haeckel to refute the more recent
interpretations, still adhered to by many authorities, which relegated the
sponges to the lowermost or Protozoic section of the organic series. At
the least, it was to be expected that this eminent author would devote
some little space to the serious discussion of the new and very im-
portant facts concerning the ultimate structure of sponges and suggestive
affinities elicited through the investigations of Professor H. James-Clark
and Mr. Carter. In place of this, no consideration whatever is given
to their discoveries, which are brusquely dismissed with the comment that
neither one nor the other of these authorities have any conception of
the essence of the cell-theory. The present author is visited, for his

NATURE AND AFFINITIES OF THE SPONGES. 155

temerity in having dared to call in question the soundness of the suggested
Coelenterate affinities of the sponges, with a far more substantial share
of the learned professor's attention. " Mr. Saville Kent's attacks " upon
his theory are finally summed up as incapable of refutation, since he
" neither understands the arguments brought forward, nor is in general
sufficiently acquainted with the structure and development of zoophytes
and sponges." — The endeavour is here made to show that Mr. Saville Kent
has since that time devoted his best energies to rectifying the omission in
his education pointed out by Professor Haeckel, the outcome of his humble
efforts in this direction being, however, scarcely conducive perhaps to the
firmer establishment of that authority's hypothesis. — The most crushing
shafts of Haeckel's sarcasm are undoubtedly directed against an accidental
misrendering or misinterpretation, on the author's part, of some of the more
abstruse questions of homology and analogy propounded as subsisting
between the representatives of the two groups in question. Whatever may
have been the error in this direction, the very important and significant fact
remains that Professor Haeckel's exposition of the Ccelenterate affinities of
the sponges, embodied in his ' Monograph of the Calcispongiae,' is charac-
terized by a complete abandonment of that position which he had formerly
maintained with so much vehemence, and by a repudiation of that very
homology he had formerly insisted on, and which was especially disputed by
the present author. In order to make this significant contradiction clear, it
is necessary merely to quote and compare Haeckel's oracular utterances of
the two respective years 1869 and 1872. In his first notable essay, 'On
the Organization of the Sponges and their Relationship to the Corals,' he
says : —

" Certain sponges differ from certain corals only by a less degree of histological
differentiation, and especially by the want of urticating organs. The most essential
peculiarity of the organization of sponges is their nutritive canal system, which is
both homologous with, and analogous to, the so-called coelenteric vascular system, or
gastrovascular apparatus of the Ccelenterata."

In his 'Monograph of the Calcispongise,' Bd. i. p. 461, his recantation,
modestly interred in an unobtrusive footnote, runs as follows : —

" Whereas the near relation of the sponges to the corals, to which I formerly gave
particular prominence, is to be understood only as an analogy, not as an homology,
I thought at that time that I found in the radiate structure of the Sycones (Grantia
(Sycon) ciliatd) an essential morphological point of comparison with the corals ; but
the developmental history of the radial tubes of the Sycones, with which I only
became acquainted subsequently, has convinced me that these are not homologous
with the perigastric radial chambers of the corals."

Having abandoned his former line of defence, Professor Haeckel
depends mainly, in the monograph now under discussion, upon making
good his position with relation to the suggested affinities through the
evidence he adduces with respect to the developmental phenomena of the
Calcispongiae. The radial aquiferous system of the adult sponge, originally

156 NATURE AND AFFINITIES OF THE SPONGES.

paraded with so much tfclat, when put to the test was, to use a familiar
expression, found incapable of " holding water " ; it now remains to be
seen whether Professor Haeckel's new arguments were based upon a
more firm foundation. The one essential point brought forward on this
occasion relates to the composition and significance of those ciliated and
motile reproductive bodies common to all sponges, first discovered by Dr.
Grant, and noticed by various subsequent observers, but whose true struc-
ture and import have not yet been exhaustively investigated. In accord-
ance with Professor Haeckel's interpretations, these bodies, or " ciliated
larvae," as they have since been more commonly designated, abundantly
developed throughout the representatives of the Calcispongiae, were all
referable to one common plan, with regard both to external configuration
and internal histologic composition. This common plan, as now enun-
ciated, manifested itself externally in the possession of an evenly ovate
or subpyriform contour, the broader end representing the anterior pole,
as exhibited by the body in its condition of natation. Except at one
point, the entire peripheral surface of these bodies was clothed with long
vibratile cilia, each cilium originating from the centre of a minutely circum-
scribed polygonal area, to each of which was assigned the morphologic value
of a single cell. The exceptional region referred to, over which the cilia did
not extend, was limited to the anterior pole, from which point an axial
canal was described as leading from the external surface to a central body-
cavity. Round the outer edge of this apical opening were stationed a circu-
lar border of larger subspheroidal non-ciliated cells, which represented the
externally protruding units of a layer of similar cells that lined in a single
and continuous series the entire surface of the hollow internal cavity with
which the apical aperture was continuous. Taken thus in optical longi-
tudinal section, these bodies, as interpreted by Professor Haeckel, or
borrowing from his own illustrations, as represented at Fig. 2 in the
adjoining woodcut, presented the aspect of an ovate sac composed of two
separate, and histologically distinct, external and internal cellular layers,
the outer one being composed of more minute subcylindrical and radially
disposed monociliate cells, and the inner one of a correspondingly simple
layer of much larger subspheroidal and non-ciliated cells. This sac-shaped
bilaminated structure Professor Haeckel denominated a "gastrula," and
represented it to be the ground or stock-form from which all sponges
were primarily developed. It was further insisted that the outer or so-
called " dermal lamina " of this bilaminated structure represented a true
external dermal layer or ectoderm, and the inner or so-called "gastral
lamina" a true entoderm, as obtains in all ordinary Metazoic organisms.
Launching out into the regions of hypothesis, Professor Haeckel claimed
for his so-called " gastrula " a far-reaching and most important significance.

" I regard the gastrula," Haeckel says, " as the most important and significant
embryonic form in the whole animal kingdom. It occurs among the sponges, the
Acalephae, the Annelida, Echinodermata, Arthropoda, Mollusca, and the Vertebrata

NATURE AND AFFINITIES OF THE SPONGES.

157

as represented by Amphioxus. In all these representatives of the most various
animal stocks, the gastrula preserves exactly the same structure. From this
identity of the gastrula in representatives of the most various animal stocks, from the
sponges to the Vertebrata, I deduce, in accordance with the biogenetic fundamental
law, a common descent of the animal phyla from a single unknown stock-form,
gastraea or archegastrula, which was constructed essentially like the gastrula."

Speculating still further with reference to this newly-detected keystone,
Haeckel maintained that the primary stock-form of all the sponges must
have been an attached, bilaminate, gastrula-like organism, in all ways com-

FIG. i.

FIG. 2.

Hypothetical Ciliated Larva or so-called " Gastrula " of a Calcareous Sponge, Levcvlmis echinus
Hkl., as viewed, Fig. i, superficially, and Fig. 2 in longitudinal section. In Fig. 2 an imaginary central
gastric cavity, having a terminal but non-existing oral aperture and imaginary lining of subspheroidal
eudodermal cells, is represented. In Fig. i the most anteriorly developed cells of this imaginary endodermic
layer are projecting around the hypothetic oral aperture. — After Haeckel, Monograph of the Calcispongue,
pi. xxx. figs. 8 and 9, 1872.

parable with this typical " archegastrula," possessing a simple, double-
walled, sac-shaped body, with a central stomachal cavity, terminal oral
aperture, and no porous system. Should the walls be strengthened with
spicula, such a type might be designated Prosycum, or, in its still more
simplified form without any spicula, ArcJiespongia. Such a typical hypo-
thetic A rchespongia, though not actually known to exist, Haeckel anticipated
to probably possess a close ally in the singular form first described by Dr.
Bowerbank under the title of Haliphysema Tumanowiczii. Haeckel's later
and most ingenious exploits with this self-selected type will receive due
notice presently.

Summing up the deductions and speculations concerning the affinities
and significance of the so-called sponge-larva or gastrula, just enumerated,
it is almost impossible to overrate the important and far-reaching issues
involved in Professor Haeckel's interpretation of this developmental struc-
ture. Presuming his interpretation to have been substantiated, and to have

158 NATURE AND AFFINITIES OF THE SPONGES.

received the confirmation of the many investigators who have subsequently
devoted themselves to the study of this special zoologic group, the Metazoic
organization and affinities of the sponges, as insisted upon by Haeckel,
would undoubtedly have been established upon a firm basis. If, on the
other hand, such investigation proved the existence of important errors in
the interpretation rendered, neither the intimated affinity of the sponges,
nor any of the many side-inferences and deductions connected with and
interdependent upon such interpretation, possess further value. As a matter
of fact, the crucial test applied has been productive of the most unlooked-
for results, for, not only has it been shown that errors do exist, but that
these are of such a radical and fundamental nature that the inference is
most reluctantly arrived at that Haeckel, carried away in his ardent pursuit
of the Metazoic archetype, has lost for the time his power of discrimina-
tion between matters of fact and hypothesis, and so evolved from his own
inner consciousness those details that are wanting to complete and perfect
his theory. This at any rate is the most charitable construction to place
on the extraordinary discrepancies found to exist between even the broad
structural characteristics of his so-called sponge-gastrula as reported by
himself, and as since found to exist in fact by a number of independent
witnesses. Without entering now into a precise and extensive account of
the data elicited, it will suffice at present to state that on all sides, as
demonstrated by the independent investigations of Metschnikoff, Oscar
Schmidt, Barrois, F. E. Schulze, H. J. Carter, and the present author, it has
been made evident that a reproductive body having the form and organiza-
tion of the so-called gastrula or ciliated larva, as attributed by Haeckel
to the Spongida, and reproduced in the foregoing woodcut, has no real
existence, and that his representation of such a structure is entirely at fault
in the following cardinal points. In the first place, this ciliated body never
does possess two distinctly marked cellular layers comparable to a true
ectoderm and endoderm ; in the second place, there is neither a distinct
gastric cavity nor an intercommunicating apical, oral, or other aperture as
required for the confirmation of Haeckel's dictum ; while, finally, the anterior
and posterior poles have, as compared with what exists in nature, been
exactly reversed in order to make them conform with his particular require-
ments. This latter circumstance is made obvious from the fact that in all
instances, in both his figures and descriptions, the larger cells, which do
frequently, but not invariably, occur in connection with these bodies, are
stationed by him at the anterior, or his so-called " oral extremity," while
in reality they are located at the posterior one. Taken altogether, it is
clearly evident that the so-called " sponge-gastrulae," described and figured
over and over again in Professor Haeckel's ' Monograph,' are an entire
myth, and that the superstructure of the gastraea theory, so far as it rests
upon this basis, is entirely worthless. From this it is also clear that a very
considerable portion of Professor Haeckel's artistically executed plates in
the monograph in question are utterly untrustworthy and worse than use-

NATURE AND AFFINITIES OF THE SPONGES. 159

less, since, accepting as infallible the representations of so high an authority,
these entirely imaginary figures with their accompanying definitions have
been already extensively reproduced as proven facts in many recent text-
books of biology.* The glaring unreliability of Professor Haeckel's repre-
sentations, in this special connection, necessarily justifies more than cus-
tomary precaution in accepting as Gospel fact his evidence in other
directions, wherever room is left for entertaining the slightest reasonable
doubt. A case altogether to the point is afforded by his representations
of the spermatozooids of various sponge species, in Plates I, 7, 9, 1 1, 25, and
48 of his monograph. Scarcely three years previously, Haeckel, as already
stated, declared that sponges were asexual and sporiparous, and that the
careful examination by himself of hundreds of specimens had satisfied him
that spermatic elements were entirely wanting throughout the class. As
pointed out by Mr. Carter, the admission was in itself fatal to his Metazoic
or gastraea theory as applied to the sponges, spore production being an
essential property of Protozoic organisms only, and the union of true sexual
elements, ova and spermatozoa, being of unvarying occurrence throughout
all the higher or Metazoic groups. Tacitly, Professor Haeckel evidently
acknowledged the trenchant force of Mr. Carter's argument. At any rate it
is an interesting and significant fact that so-called true spermatozoa were
found ready to hand and produced in abundance in Haeckel's succeeding
essay on the affinities of the sponges. The celerity with which these
missing elements were discovered in profusion, directly their presence was
shown to be essential for the sustenance of his Metazoic theory, and in
face of his previously declared incapacity to recognize them after a most
exhaustive investigation, when not specially wanted, a few months earlier,
is in itself a suspicious circumstance. It is just possible that these sup-
posed spermatozoa may represent in some instances a misinterpretation
of certain earlier conditions of the ordinary flagellate cells ; but in one
special case,t in which the actual fructification of a sponge ovum by sper-
matic bodies is delineated, it is difficult to resist the conclusion that the
learned professor's fertile imagination — as in the case of the gastric cavity,
oral aperture, and endodermic cell-layer of his sponge-gastrula — has risen
to the occasion and kindled into being forms and features possessing no
tangible existence.

Before proceeding to an examination of the evidence towards an
elucidation of the precise structure and affinities of the sponges, accu-
mulated through other independent sources, one later contribution of
Professor Haeckel's demands brief notice. Reference is here made to his
separate brochure ' Studien zur Gastraea-theorie,' published in the year 1877.
While devoted generally to the exposition of his latest and most matured
views upon the gastraea theory, it is specially worthy of notice as the

* E.g. "Development of Sponge, Ascetta primordialis," in Prof. Huxley's 'Manual of the
Invertebrata,' p. 112, fig. vi.

t 'Monograph of the Calcispongiae,' pi. 48, fig. 6.

l6o NATURE AND AFFINITIES OF THE SPONGES.

channel selected by him for the introduction to the scientific world of what
appeared to be an entirely new and remarkable little group of organisms.
Professor Haeckel had previously declared, in his ' Monograph of the
Calcispongiae,' his belief that the so-called " gastrula " or " ciliated larva "
of a sponge typified the permanent and adult condition of some pre-
existing type which might be appropriately designated an archegastrula,
and that probably a very close approach to this hypothetic archetype was
furnished by the supposed little sponge-form first described by Dr. Bower-
bank under the title of Haliphysema Tttmanowiczii. In the ' Biologische
Studien ' Haeckel announces, as the results of his most recent personal
investigation, the discovery of a series of forms generically identical for
the most part with this type ; that his former anticipations were fully
verified ; and that in Haliphysema, and its allies, the true archetype of all
sponges and the entire Metazoic series was at length forthcoming. As
interpreted by Haeckel, Haliphysema was declared to be simply an attached
sac-like " gastrula," having a simple central gastric cavity, terminal orifice,
and imperforate body-wall composed of two closely apposed inner and
outer cellular layers, the former one or entoderm being made up of flagel-
late cells, corresponding with those of the ciljated chambers of the ordinary
Spongida, and the outer or ectoderm being constructed out of coalescent
non-ciliate cells, and in all ways corresponding with his so-called syncytial
element of the more complex sponges. No spicula or other endoskeletal
structures were secreted by these Haliphysemata, but the external layer or
" syncytium " possessed the faculty of appropriating and building up a
variously modified and protective test, or exoskeletal covering, out of sand-
grains, sponge-spicules, or any other suitable adventitious particles found
in its vicinity. For the reception of the various types described the new
group-title of the Physemaria was created, its members being announced
by Haeckel to belong properly neither to the sponges nor to the zoo-
phytes, but to represent in themselves an independent order which more
nearly approached the hypothetic root-form of all Metazoa, his so-called
" gastraea," than any yet discovered organic type.

The various species, five in all, referred to the genus Haliphysema were
severally distinguished by the form and composition of their respective
tests or exoskeletal elements, one among these, H. globigerina, being
specially remarkable in having its test built up entirely of the shells of
Rhizopods, such as Globigerina, Rotalia, Orbulina, Textnlaria, and various
Radiolarians, collectively indicative of a deep-sea habitat. A second generic
group was referred by Haeckel to the Physemarian order, under the
new name of Gastrophysema. Of the two species referred to this genus
the one received the title of Gastrophysema dithalamium, while the other,
G. scopula, was identified with an organism described by Mr. Carter in the
year 1870 under the name of Squamulina scopula, and referred by that
investigator to the group of the Foraminifera. The only essential external
difference presented by Gastrophysema, as compared with Haliphysema, was

NATURE AND AFFINITIES OF THE SPONGES. l6l

afforded by the character of the test, which in the former instance consisted
of two or more intercommunicating chambers in place of the single one
only possessed by the last-named type. Concerning the internal structure and
significance of the interconnecting cavities in Gastrophysema, however, a far
different and most remarkable interpretation was arrived at. The different
chambers were in fact declared by Haeckel to be set apart for the per-
formance of special and independent functions. Affirming that ciliated
bodies or gastrulae, similar to those of the sponges, were found only in the
proximal or basal of the two chambers of G. dithalamium, he relegated to
this cavity the function of reproduction, and bestowed upon it the special
title of the " brood-chamber " or " uterus." The succeeding or anterior of
the two cavities he declared to be a true stomach, communicating with the
external world through the medium of the terminal aperture designated
by him the mouth. The list of structural complexity, however, by no
means ended here. Among the ordinary flagellate cells of the so-called
stomach-cavity, Haeckel observed, or affirms to have observed, certain ovate
cells of a special nature, pronounced by him to be of a glandular character ;
these he accordingly figured and described as gland-cells, " Driisenzellen."

Had Professor Haeckel's observations and interpretations concerning this
newly introduced group of the Physemaria been confirmed, Haliphysema
would undoubtedly have to be accepted as a sponge structure in its simplest
known form, while in Gastrophysema a complexity of organization would be
superadded forbidding its correlation with either the sponges or the ordinary
Coelenterata. As a matter of fact, however, the evidence more recently
adduced has tended to raise the gravest doubts concerning the very existence
even of such an organic group as the so-called Physemaria of Professor
Haeckel.

Haliphysema Tumanowiczii and Gastrophysema (Squamulind) scopula have
both been proved to be varieties of one form, and instead of a simple sponge,
as first described by Dr. Bowerbank, to be an arenaceous or test-bearing
foraminiferal type. This interpretation, first suggested by Mr. Carter, has
been fully established by the present author in a paper, with accompanying
illustrations, published in the ' Annals and Magazine of Natural History '
for July 1878. The account and illustrations there given were derived from
the examination of living specimens collected in the Channel Islands, and
which in their healthy condition exhibited their true nature by the emission,
from the terminal aperture of their tests, of extensive reticulate pseudopodia
exhibiting circulatory currents, comparable in all ways to those of the
ordinary Foraminifera. By a careful investigation of that portion of the
organism contained within the test, it was likewise shown that there was no
trace whatever of a lining layer of flagellate cells, as asserted by Professor
Haeckel, all, throughout, being simple homogeneous or more or less granular
sarcode. A similar Foraminiferal interpretation has been arrived at by
Professor Mobius, with respect to a new species, Haliphysema capitulatum,
examined by him in the living state at the Mauritius, and in which pseudo-

M

1 62 NATURE AND AFFINITIES OF THE SPONGES.

podia were seen issuing in a corresponding manner from the single terminal
aperture of the spiculiferous test. This confirmation, to which the author's
attention was directed, after the publication of his communication to the
'Annals,' appeared in the 'Versammlung d. deutschen Naturforscher in
Hamburg,' p. 115, for the year 1876. Evidence corroborating still more
strongly the results above recorded, was published, however, in the ' Quar-
terly Journal of Microscopical Science ' for October 1879, in which Professor
E. Ray Lankester, after a most exhaustive examination of duplicate speci-
mens of Haliphysema Ttimanowiczii remitted him by the author from Jersey,
in both the living and preserved condition, entirely supports the forami-
niferal interpretation, and indicates the necessity of Professor Haeckel pro-
ducing some satisfactory explanation of the very antagonistic statements
now on record, for which he is responsible, with reference to Haliphysema
and its allies.

Possibly, as suggested by the present author, isomorphic forms may
exist having the external contour of a Haliphysema and the histologic
internal structure of a simple sponge ; but the evidence in this direc-
tion is up to the present time altogether opposed to such a supposition.
Analyzing, in fact, the by no means extensive list of Professor Haeckel's
Physemarian genera, Haliphysema and Gastrophysema, scarcely a single type
is left him wherewith to demonstrate the existence of such isomorphism.
Thus out of his five species of Haliphysema, H. echinoides is undoubtedly,
as already pointed out by Mr. Norman, the young condition of the
Tethyadan sponge first described in its young and stalked condition by
Professor G. Percival Wright, under the name of Wyville-Thomsonia
Wallichii* next described by the present author in the adult state as
Dorvillia agariciformis,\ and finally by Sir Wyville Thomson, as one
of the trophies of the ' Lightning ' and ' Porcupine ' expedition, under
the name of Tisiphonia agariciformis. Haliphysema Ttimanowiczii and
H. ramulosa are identified as undoubted Foraminifera. H. globigerina has
been examined by Haeckel as dead, spirit-preserved examples only,
and consequently under conditions in which the characters attributed by
him to the typical forms would not be recognizable.

Of the genus Gastrophysema, G. scopula is demonstrated to be a Fora-
minifer identical with Haliphysema Tumanowiczii, and it so happens that
H. primordiale and G. ditJtalamium are now alone left to vindicate the
claims of the Physemaria for further scientific recognition. Even here
the resemblance in every particular — setting aside the hypothetic and the
utterly untenable " uterine " and " glandular " differentiations — coincides so
closely with all the broad external features of some one or other of the
numerous polymorphic forms of the one-, two-, three-, four-, or many-
chambered spiculiferous tests of Haliphysema Tumanowiczii, that, unless
Professor Haeckel can produce substantial testimony of their independent,

* 'Quarterly Journal of Microscopical Science,' vol. x., January 1870.
t 'Monthly Microscopical Journal,' December 1870.

NATURE AND AFFINITIES OF THE SPONGES. 163

and in that case amazingly remarkable isomorphism, the erasure of their
names from scientific nomenclature, and also that of the entire Physema-
rian order, will be rendered unavoidable. Most unfortunately for Professor
Haeckel, the context of his essay under discussion upon the gastraea theory
in general, and upon the group of the Physemaria in particular, so abounds
with direct negations and manipulations of known facts in order to adapt
them to the requirements of his own hypotheses, that the verdict arrived
at by the most impartial students of this question must inevitably tend to
cast discredit upon his representations even where the same are possibly
correct. It is thus not a little surprising to find reproduced as the larval
type of Haliphysema in this essay, the self-same erroneous accounts and
diagrammatic illustrations of his so-called " gastrula-larva " of the sponges,
first formulated in his ' Monograph of the Calcispongiae,' and submitted at
page 157 of this volume.

The same inversion of the anterior and posterior apices and accompany-
ing fallacious allocation of a gastric cavity, oral aperture, and evenly
developed external and internal cellular layers, is once more repeated,
the larval forms of the Physemaria being made to correspond with a like
altogether hypothetic formula. The histologic characters of the essential
collar-bearing flagellate cells of the sponge-body, assumed to be shared
by Haliphysema and its allies, are again materially reduced in order to
make them conform more nearly to the plan of ordinary tissue-cells, and
with the morphologic and functional value of which they are alone accredited.
Professor H. James-Clark and Mr. Carter had already shown that these
peculiar flagellate sponge-cells exhibited a very significant Protozoic
feature in the possession of two or more posteriorly located, rhythmically
pulsating, contractile vesicles. In his 'Monograph of the Calcispongiae,'
Professor Haeckel grudgingly conceded and figured a single posterior
vacuole, but denied to it the property of rhythmical contraction, affirming
that it was a mere non-persistent and unessential lacuna developed in the
protoplasmic substance of the cell. In that advanced exposition of the
gastraea theory, however, embodied in his 'Biologische Studien' for the
year 1877, the contractile vesicle, or protoplasmic lacuna, is improved
altogether off the morphologic landscape, and the essential flagellate
sponge-cell now appears with a simply nucleated but otherwise undiffer-
entiated protoplasmic body. In two instances only does Haeckel make
any concession to the antagonistic results arrived at by contemporary
explorers in the same field of research, while even here these results are
with a little tension made subservient to his special views. In the first
place, the evidence since adduced not being confirmatory of his diploblastic
interpretation of the sponge embryo, as produced by the delamination of
the interior from the outer cellular layer, he now declared that essentially
the same results were obtained, and the same form constructed, by the
process of invagination. In the second place, the researches, more espe-
cially, of Oscar Schmidt, having elicited the fact that in many instances

M 2

1 64 NATURE AND AFFINITIES OF THE SPONGES.

these ciliated bodies, as produced by the Calcispongiae, exhibited an ex-
ternal conformation entirely different from his so-called "gastrulae,"
Haeckel accounted for the inconsistency by declaring that in these special
instances the embryonic form was represented by a distinct biogenetic
type, which might be conveniently denominated an "amphiblastula."

Passing on from the foregoing brief record of the peculiar interpretations
maintained by Professor Haeckel, with reference to the structure and
affinities of the sponges, attention may now be directed to the facts
elicited in this connection by the light of most recent research, including
those adduced through the investigations of the present author. As
an inevitable consequence of the very authoritative declarations of Pro-
fessor Haeckel in favour of the Ccelenterate affinities of the sponges, and
seeming coincidence of the evidence brought forward with these emphatic
statements, the bias of late years has been altogether in the direction of
substantiating their Metazoic nature, and of reconciling, with this end in
view, the very conflicting structural and developmental data exhibited
by the different members of this highly important group. Most note-
worthy in this direction is that line of interpretation followed by Metschni-
koff, Barrois, and F. E. Schulze, by whom, in both the adult and embryo
sponge, the existence of three cellular layers, ectoderm, endoderm, and
mesoderm, are distinctly recognized. In conformity with such interpreta-
tions, the ectoderm in the adult organism consists of a superficial layer of
flattened, simply nucleated cells, closely approximated to each other, and
agreeing to a considerable extent with the so-called "syncytium" of
Professor Haeckel, this external element being also produced inwards, and
lining the cavities of the aquiferous system. The special collared flagellate
cells that line the so-called ciliate chambers are accepted as entodermic
elements, while to the mesoderm is relegated the remaining interstitial
portion, upon which chiefly devolves the secretion of the spicula or other
skeletal structures.

In opposition to the widely supported Metazoic view founded by
Professor Haeckel, adhesion is given in this treatise to that interpreta-
tion of the structure and affinities of the sponges that first originated
with Professor H. James-Clark, and indicated their close relationship to
the then small and insignificant little group of Flagellate Protozoa, first
introduced to scientific notice by himself, and here described in a greatly
extended form under the title of the Choano-Flagellata or Discostomata-
Gymnozoida. The immense wealth of material that has been accumulated,
both in the direction of the more minute structure of the sponges, and in
the extension of our acquaintance with the above special group of Flagellate
Protozoa and their allies, since the death of Professor Clark, is found on
examination to support the views here adopted to the fullest possible
extent. Already, in the 'Annals and Magazine of Natural History' for
January and August 1878, and in the 'Popular Science Review' for April
of the same year, the leading features of this advocated affinity have been

NATURE AND AFFINITIES OF THE SPONGES. 165

submitted at considerable length. With this evidence, however, has now to
be amalgamated the results of more recent research, as educed both by the
author's personal researches and those of contemporaneous investigators.

Commencing with the general structural features of an adult sponge,
as met with throughout the several more important groups into which
the class Spongida is most naturally divided, it will be found that in
any one of them, the three elements, demonstrated through the inves-
tigations of Professor Clark, constitute the actual and essential com-
ponents of the sponge-body. These three, the collar-bearing flagellate
monads, the hyaline and mucous-like cytoblastema, and the included
amceba-like cytoblasts, will be invariably found in every sponge, more
generally with superadded skeletal structures, and often with a greater or
less proportional preponderance or reduction of the first, second, or third of
the essential elements enumerated, but in no instance presenting an entire
absence of any one of them. Out of these three elements, again, it is
beyond question that the first-named, or collar-bearing flagellate monads,
lay claim to the foremost position in the sponge economy, and that the two
remaining ones are, as compared with them, entirely subsidiary. Separating
the collar-bearing units from those two subordinate elements, as shown
more especially at PI. VIII., and comparing them with the independent
collar-bearing flagellate monads, figured in Pis. II. to VI., the close
identity of the two cannot possibly fail to be recognized. This likeness,
furthermore, is found to be not merely general and superficial, but to extend
to every point that may be enumerated. Neither is such likeness common
and unimportant, or comparable to such as is usually found between
ordinary tissue-cells, or to more practically illustrate the case, to such
as exists between an amoeba and a leucocyte or white blood-corpuscle.
Amcebiform cells, indistinguishable in their isolated condition from ordi-
nary amcebae, recur again and again as the constituent or associated
elements of the organic tissues of both vertebrate and invertebrate
animals. That special modification of a simple cell, however, exemplified
by the independent collared monads or Choano-Flagellata, and precisely
reflected in the essential elements of the sponge-body, finds its counter-
part nowhere else throughout the entire range of organic nature. While
these two can be correlated and shown to harmonize with each other in
every detail, it becomes self-evident that all attempts to co-ordinate either
of them with any other structures are rendered nugatory, and are, in point
of fact, attempts to compare that which is altogether uncomparable. In
what manner the collar-bearing monads differ essentially from all other
known unicellular structures, is explained at length in the section devoted
to the systematic description of their order. Briefly, however, it may now
be stated that the all-important distinction here insisted on is connected
with that peculiar structure the " collar " and its accompanying functions. As
demonstrated by the author, this " collar " is not a mere funnel-shaped
expansion of inert sarcode, as might be inferred from the earliest accounts

1 66 NATURE AND AFFINITIES OF THE SPONGES.

given of it, but it practically represents the most actively motile and
important element in the animalcule's economy. During life, in its typical
fully-extended state, a continuous stream of fine granular protoplasm
is ever flowing up the exterior and down the interior surface of the
collar, in all ways identical with the protoplasmic circulation or cyclosis
exhibited in the extended pseudopodia of the Foraminifera and other Rhizo-
poda. In other words, this structure with its circulatory currents might be
described as a peculiarly modified funnel-shaped pseudopodium. By direct
observation the author has further demonstrated that the collar, with its
characteristic currents, is an exquisitely contrived trap for the arrest and
capture of its customary food, which, driven by the action of the centrally
enclosed flagellum against the outer margin of the collar, adheres to it,
and passes with the onflowing protoplasmic stream into the animalcule's
body. The whole nutrient process, with its associated circulatory currents,
as exhibited by an animalcule of the solitary genus Monosiga, will be at
once comprehended on reference to the coloured illustration given in the
frontispiece. Now, what has been described and delineated of the inde-
pendent collar-bearing type Monosiga and its allies, is found to obtain with
full force, and in the very minutest detail, in the essential collar-bearing
flagellate units of a sponge -body. The collar there exhibits the same
circulatory motions and is subservient, in the self-same way, as a trap for
the capture of food-particles ; the body, as already intimated, exhibits the
same posteriorly located rhythmically pulsating contractile vesicles, the
same central spheroidal nucleus or endoplast, and presents, furthermore,
the most closely identical reproductive phenomena. The essential collar-
bearing sponge-monads, or Spongozoa, as they have been appropriately
designated by Mr. Carter, are, in fact, to all intents and purposes, collar-
bearing Flagellate Protozoa, differing only from Codosiga, Salpingceca,
Desmarella, and the various other genera included in this volume under
the denomination of the Choano-Flagellata, in their special colonial mode
of aggregation, and in the accessory and non-essential elements more
usually, but not invariably, added in the form of skeletal structures.

An additional character, indicative of the close identity in all functional
manifestations that exists between the sponge-monads and the indepen-
dent collared types, remains to be mentioned. In the descriptions given
of these latter, attention is frequently directed to the extreme plasticity
of the individual animalcules, and the facility with which the funnel-
shaped collar and flagellum is retracted at will, pseudopodium -like
extensions of the body-sarcode projected, and the most polymorphic
aspects exhibited. Examples of such metamorphoses, as presented by
the loricate type Salpingceca amphoridium, may be seen at PI. V. Figs.
5-8, and also in many other figures illustrative of this genus, and the
illoricate Codosiga and Monosiga, in the several plates devoted to this
interesting group. Among the collared monads of the more complex
sponge-stock, not only an equal, but a far higher degree of plasticity

NATURE AND AFFINITIES OF THE SPONGES. 167

is presented. The component sarcode of the monad's body in this latter
case is apparently of thinner or more fluid consistence, permitting of rapid
and protean changes of form on the slightest irritation or other stimulus.
Thus, when a dissection is made of any living sponge, such as Grantia
compressa, it is found requisite to examine rapidly with the microscope
in order to witness the constituent monads with their collars and flagella
in the normal condition of extension ; otherwise, within the space of a few
minutes, these organs are, one or both, more or less completely retracted,
and their former possessors creeping about the field, or remaining congre-
gated in clusters under conditions that render them indistinguishable from
ordinary Flagellate monads, or simple amoebae. In this latter instance,
they are, indeed, identical in all respects with the amcebiform zooids or
cytoblasts scattered throughout the common gelatinous central matrix or
cytoblastema of the sponge-body. The more conspicuous modifications
of form assumed at will by the collared sponge-monads, either with the
collar and flagellum extended with the former organ alone, or with both
of these two retracted, will be found abundantly illustrated in Figs. 2-38
of PI. VIIL, devoted especially to the histology of the Spongida. Among
them two or three examples occur which deserve particular notice. Thus,
at Fig. 17 of the plate quoted, is represented an individual monad which,
after the retraction of the collar and flagellum, has thrown out innumer-
able long slender pseudopodia, which convey to it an appearance highly
suggestive of that of the Radiolarian type Actinophrys. Other examples,
exhibiting in a less degree the same plan of metamorphosis, are also
delineated in connection with the groups or isolated examples numbered
respectively 12, 14, 15, 16, 20, and 24. In Figs. 29, 30, 31, a modification in
an entirely different direction is shown. Here, with the collars and flagella
entirely withdrawn, as before, slender pseudopodia are emitted from the peri-
phery, terminating in distinctly capitate extremities which recall to mind the
specialized suctorial tentacles of the Acinetidae. Recovering from the disturb-
ing influence which has brought about any of the various metamorphoses
above enumerated, the emitted pseudopodia or lobate sarcode extensions
are, after a while, drawn in, and the normal form with the extended collar
and flagellum again assumed. At Fig. 18 of PL VIII. will be found
examples of such sponge-monads, which after a short tenure of a vagrant
amoeboid condition, have reattached themselves to a minute spiculum of the
parent sponge, and resumed the customary aspect of the typical Spongozoa.
Were it not explained that these readherent collared monads belonged
to a sponge-stock, it would be impossible to distinguish them from the
representatives of such independent collared animalcules as Monosiga
Steinii, represented at PI. IV. Fig. 12. The collared sponge-monads, thus
reattached, soon throw out around them a thin investing film of hyaline
cytoblastema, as shown at Figs. 19, 21, and 22, and are thus capable,
without any other extraneous assistance, of either repairing a mutilated
sponge-stock, or of building up an entirely new one. With reference to

1 68 NATURE AND AFFINITIES OF THE SPONGES.

the feeding capacities of the sponge-monads, it may be here noted, that
the phenomena of nutrition are precisely identical with those exhibited
by the independent collared species, the selected pabulum being arrested by
the hyaline collar and carried with its circulating current into the body
of the animalcule. Examples are given at PI. VIII. Figs. 9 and 19, in
which the bodies of the neighbouring sponge-monads are rilled with ingested
and artificially administered carmine particles. Such functions of nutrition
are, however, not confined to the collared zooids ; the amoebiform units
or cytoblasts being equally capable, as shown at Fig. 41 of the same plate,
of ingesting solid pabulum.

Examining the matter more closely, it has now to be shown that even
the special differences already cited as indicating a distinction between the
Spongida, independent collared monads, and ordinary Infusoria, are scarcely
more substantial than those found to exist between the more conspicu-
ously divergent representatives of the same groups or orders of the last-
named section. Taking, in illustration of this analogy, the very familiar
group of the Vorticellidae, we find in Vorticella, or more correctly, in the
stiff-stalked form Rhabdostyla and in the compound type Epistylis, the
precise analogues of the solitary collared type Monosiga and the social
genus Codosiga. Proceeding yet a step further, the slime- immersed colonial
type Ophrydium is beyond doubt comparable in a like manner to the
colonial slime-immersed genus Phalansterium. Beyond this it is not
possible, as yet, to institute a direct comparison, but, supposing that a
genus of colonial slime-immersed Vorticellidae should be discovered in
which the animalcules, instead of projecting directly into the surrounding
water through the peripheral surface of their common matrix, as obtains in
Ophrydium, were enclosed within chambers which communicated with each
other, and with the outer water, by a system of interconnecting canals ;
supposing also that all the spores, germs, encystments, or other repro-
ductive products remained embedded and developed to maturity within
the common matrix, a type of the Vorticellidae would be produced pre-
senting a parallel to Ophrydium precisely identical with what actually
exists between the most simple known sponge and Phalansterium*

With the assistance of Plates VII. to X. it is now proposed to draw

* At the eleventh hour, while going to press, the author has had the good fortune to light upon
a new and highly interesting representative of the independent collared series, that illustrates in
a yet more decisive manner the close relationship of this group to the Spongida. The type in
question, represented at PI. X. Figs. 20-30, and hereafter described under the title of Protospongia
Haeckeli, agrees with Phalansterium, so far as the zooids are immersed within a common gelatinous
matrix or zoocytium. The characteristic collars are, however, fully developed in place of being
rudimentary as in the last-named genus, while the inhabited gelatinous matrix is perfectly trans-
parent and homogeneous instead of densely granular. Within their matrix the zooids were observed
to assume various metamorphic amoeboid conditions, to multiply both by the process of binary
subdivision and by the partition of their entire mass into sporular elements. The resultants of
the last reproductive process commence their active existence as simple, minute, uniflagellate
monads, which project, as shown at Fig. 22 b b, from the periphery of the zoocytium side by
side with the adult collared units. This interesting species which, in its mature condition, corre-
sponds in a most remarkable and significant manner with a fragment of cytoblastema, with its
enclosed collared zooids, amcebiform cytoblasts, and sporular elements, of any typical sponge-
form, was obtained by the author in July 1 880, in water brought from the lake in Kew Gardens.

NATURE AND AFFINITIES OF THE SPONGES. 169

attention to the more important structural features exhibited by the leading
subdivisions of the Spongida, and especially to those points in which their
close relationship to the independent collar-bearing monads figured in
the five preceding plates is most prominently shown. As already stated,
the collared cells or essential Spongozoa of any given sponge-body are
invariably found lining special chambers excavated within the common,
structureless, mucilaginous basis or cytoblastema which enters more or less
considerably into its composition. These special chambers, again, are
found in different sponges to exhibit a considerable diversity of contour,
but, on the whole, to conform to two distinct and widely differentiated
plans. In one of them it is found that the collared cells more or less com-
pletely line the entire internal cavities of the sponge, including both the
afferent and efferent canal-systems. Such a type of structure, as is most
prominently developed among the section of the Calcispongiae, is illustrated
in the sectional views given at PI. VII. Figs. 3 and 4, of the interstitial
canal-system and disposition of the characteristic collared monads or Spon-
gozoa in the familiar British species Grantia compressa. At Fig. 3 a general
view is given of the segment of a complete transverse section of this sponge,
showing the characteristic disposition of the interstitial loculi with their
monad linings around the common cloaca, while at Fig. 4 one complete and
another incomplete loculus is considerably enlarged, proving the essential
correspondence of the contained monads with the independent forms figured
in the preceding plates. In the series belonging to the second structural
plan, the collared cells, instead of being distributed more or less generally
throughout the entire internal canal-system, are confined to certain sphe-
roidal chambers excavated within the substance of the sponge body, these
chambers being brought freely into relation with the external water through
the agency of both the afferent and efferent canals. It was upon these
spheroidal chambers, as first discovered in Spongilla, that Mr. Carter con-
ferred the title of " ampullaceous sacs," by which name, together with that
of "ciliated chambers," they have since been most familiarly known. A
similar ampullaceous disposition of the collar-bearing cells is found to obtain
among a very extensive series, if not throughout the majority of the Spon-
gida, including, in fact, all the known members of the Myxospongia, the
greater part of the Siliceospongia, and in accordance with the representa-
tions given by Professor Haeckel, the family of the Leuconidae among the
Calcispongiae. The highly characteristic aspect presented by the collared
monads or Spongozoa, as grouped upon this principle, will be found deli-
neated at PL VII. Figs. I and 2, and PL IX. Figs. I, 3, and 12, and is
remarkable for the elegant clustered or grape-like appearance presented
by the monad aggregations with their interconnecting canal-systems. In
Fig. i of PL VII. is reproduced the portion of a section of the non-
spiculiferous sponge Halisarca lobularis as delineated by F. E. Schulze,
while at Fig. 2 is represented a somewhat similar section of the siliceous
type Esperia sp., as observed by the author.

I 70 NATURE AND AFFINITIES OF THE SPONGES.

Deferring for a while the more minute account of the structure and
significance of these monad-lined chambers, brief attention may be directed
to certain other broad external features superficially recognizable in the
various more highly differentiated sponge groups. As previously stated,
in every known variety of sponge three essential elements are invariably
present, namely, the collar-bearing flagelliferous cells, the mucilaginous
cytoblastema, and the amcebiform cytoblasts, to which other accessory or
non-essential elements may, or may not, be added. The relative propor-
tions in which these three essential elements exist among the several
sections of the Spongida, present some important differences. Among the
simplest known sponge forms, as represented by the genus Halisarca, in
which these elements occur in their pure and simple condition without
any addition of spicula, horny fibres, or other skeletal structures, and where,
as just stated, the collar-bearing monads exhibit the ampullaceous plan
of arrangement, it will be observed, on further reference to the illustration
quoted (PL VII. Fig. I.) that this special system by no means occupies
a largely predominating portion of the entire sponge body, a very consi-
derable part consisting of the common gelatinous matrix or cytoblastema
and its enclosed amcebiform cytoblasts. With the majority of the Siliceo-
spongiae, including those forms which have, either with or without siliceous
spicules, a horny or keratose skeleton, an almost identical predominance of
these elements is met with. Among the more characteristic representatives
of the Siliceospongiae, however, including the species of Esperia delineated
at PI. VII. Fig. 2, a highly characteristic modification is presented. In
such as these the cytoblastema is especially remarkable for its extremely
thin and pellucid consistence, this being particularly noticeable in the
superficial or peripheral region, where it is supported canopy wise, or after
the manner of a tent-covering, from the light and efficient scaffold-work
furnished by the projecting spicula. A similar type of structure is, as first
pointed out by Professor Clark, highly characteristic of the fresh-water genus
Spongilla. That combination remaining to be described, in which the pro-
portions of the three primary structural elements exhibit a marked diver-
gence from those just noticed, is most conspicuously developed in the
section of the Calcispongiae, and, with the exception of the Leuconidae,
would appear to be essentially characteristic of that group. As already
stated, the collared cells in this section are characterized by their diffuse
plan of distribution, the entire surface of the internal chambers and passages
being more or less completely lined with them. In correlation with this
distribution of the collared cells, it is found that the cytoblastema is, as
compared with those elements, reduced to its minimum, being indeed super-
ficially, as exhibited in the sections of Grantia compressa in Figs. 3 and 4
of PI. VII., altogether inconspicuous.

A closer examination of those special points by which, in accordance
with the author's views, the close affinity of the Spongida with the inde-
pendent collar-bearing Discostomata is held to be substantiated, may now

NATURE AND AFFINITIES OF THE SPONGES. 171

be proceeded with. As previously maintained, between the separate collar-
bearing monads of any of the independent Choano-Flagellata and the special
collar-bearing cells that constitute the one essential element of all sponge
structures, there is absolutely no recognizable distinction in form, structure,
and function. The body with its nucleus or endoplast, multiple contractile
vesicles, and appendages as represented by the characteristic collar and
enclosed flagellum, so precisely accord with each other as to defy individual
identification, a circumstance which will be at once recognized on comparing
these collared elements in their isolated or aggregated form, as abundantly
illustrated in the Plates VII. to X. and II. to VI., devoted respectively
to the morphology of the Spongida and that of the independent collared
monads. The likeness, however, does not end, but practically only com-
mences here, for, as it has now to be shown, all the phenomena of
reproduction and development are likewise reducible to a corresponding
type.

In order to fully comprehend and appreciate the full force of this
relationship, it is requisite only to place still more intimately en rapport,
the life-phenomena of the collar-bearing sponge-monads and those of the
independent Choanophorous and ordinary Flagellate Protozoa. That the
thin, structureless cytoblastema forming the common gelatinous matrix
which encloses and more or less completely conceals the collar-bearing
monads of the sponge-body, is the equivalent of the common gelatinous
matrix of such genera as Phalansterium and Spongomonas, or, reverting to
a still more familiar ciliate infusorial type, that of Ophrydium, is imme-
diately apparent, and is similarly, as hereafter shown, the direct product
by exudation of the included zooids. By Professor Haeckel this common
gelatinous element in sponge structures is denominated the "syncytium,"
and treated of as an independent tissue-layer formed by so intimate a
coalescence of independent constituent cells that their nuclei only are to be
discerned. That a syncytium, however, in the sense assumed by Haeckel,
does not exist, is abundantly proved by the testimony accumulated from a
variety of sources ; what he embodies under this title represents in point
of fact both of those fundamental elements which receive in this volume
the titles of the " cytoblastema " and " cytoblasts." It is to the existence
and significance of the last-named elements that attention has now to be
directed. The characteristic aspect of the cytoblasts — which occur as
amoebiform bodies of variable size and contour, variously distributed and
more or less completely immersed within the substance of the cytoblas-
tema—is delineated at PI. VII. Fig. 2 c and PI. VIII. Figs. 41 to 43. Like
Amoeba, they are constantly undergoing a change of outline, and may also
be observed to shift their position from one part to another of the inhabited
matrix or cytoblastema. Oftentimes their long, slender pseudopodia, radi-
ating towards those of their neighbours, unite together, forming under
such conditions a complex network which presents, as a whole, as shown at
Fig. 43, a remarkable resemblance to ganglionic corpuscles ; these highly

172 NATURE AND AFFINITIES OF THE SPONGES.

differentiated metazoic tissue-elements they may be said, in fact, to typify
in both form and function.

It is undoubtedly through the stimulus received and transmitted by
the cytoblasts that the characteristic contractions and expansions of the
oscula, and other portions of the sponge-body, are accomplished. Strictly,
however, these elements perform a more general function than that of
simple nerve-ganglia, they being in addition the direct motor agents in
the contraction and expansion of the general cytoblastema, and thus fulfil-
ling the part of both nerve- and muscle-fibres. The independent existence
and characteristic aspect and functions of the cytoblasts were first pointed
out by Lieberkuhn,* his observations being since abundantly confirmed by
the independent researches of Carter, H. James Clark, F. E. Schulze, and
many other investigators, including the author.

At first sight, the connection between these amcebiform cytoblasts and
the more essential collar-bearing zooids is scarcely obvious and has not as
yet, apparently, been even so much as suspected by any other authority.
To arrive at a comprehension of their true significance it is only necessary,
however, to refer to the life and developmental phenomena presented by
the independent collared monads and Flagellate Infusoria generally. Here,
both the primary and terminal conditions of the typical flagellate zooids
are frequently characterized by the exhibition of a similar amoeboid aspect,
as is abundantly shown in the accounts and illustrations given of the life
and developmental phases of the genera Codosiga, Salpingceca, Monas,
Oikomonas, Euglena, Eutreptia, Heteromita, and a host of other forms
described in this volume. The capability of the adult collared and flagel-
liferous spongozoa to take upon themselves a similar amcebiform character
has been observed repeatedly by the author, as illustrated in a large number
of figures contained in PI. VIII., which is confirmed by the observations of
Carter, F. E. Schulze, and other recent investigators, including even Pro-
fessor Haeckel himself.f The amcebiform elements of a sponge-stock
cannot therefore be consistently regarded even as independent structures.
To all intents and purposes they are the mere larval or metamorphosed
phases of the typical and essential collar-bearing zooids; the distinctive
title of cytoblasts, as here adopted, being conferred upon them only as a
matter of convenience. Where, as frequently occurs, the amoebifonn
bodies are of comparatively colossal size, the coalescence of a greater or
less number of the ordinary cytoblasts has undoubtedly taken place, the
phenomena in this instance being directly comparable with the building
up of the huge amcebiform " plasmodia " of the Mycetozoa, or with the
coalescence of a number of metamorphosed amcebiform elements as ex-
hibited by the simple Flagellate types Heteromita nncinata and H. amyli.
The import of the amoeba-like masses thus constructed is likewise in all
instances identical ; each such aggregate mass ultimately producing, by

* " Ueber das contractile Gewebe der Spongien." Miiller's ' Archives,' pp. 74-86, 1867.
t See 'Monograph of the Calcispongise,' Taf. 25, fig. 6 : " Vier Geisselzellen welche sich in
amoeboide Zellen verwandelt haben." Also, PI. VIII. Figs. 32 to 35 of this work.

NATURE AND AFFINITIES OF THE SPONGES. 173

segmentation, a swarm of unicellular flagellate zooids resembling those
from whence they derived their origin.

The very important phenomenon of spore-production by sponges, com-
parable in every way with that exhibited so abundantly among the ordinary
Infusoria, and which places in a still more prominent light their close
connection with the typical Flagellata and Protozoa generally, has now
to be described. While the occurrence of spores in various sponge-
types had been noted so long since as the year 1874, its first record was
contained in a communication made by the author to the Linnean Society
in June 1877 ; further reference to this phenomenon, with accompanying
illustrations, being likewise published in the author's " Notes on the Embry-
ology of Sponges," contributed to the 'Annals and Magazine of Natural
History' for August 1878. Since that time, however, much additional
material has been amassed in demonstration of this special mode of repro-
duction, and more especially in connection with various sponge forms
collected and examined by the author at Teignmouth, Devonshire, in the
summer of 1879.

The types thus recently examined in the living state included more
especially Grantia compressa, Grantia (Sycon) ciliatum, Leucosolenia
botry aides, and Leucosolenia (Ascettd) coriacea, among the calcareous
forms, and Halichondria punicea, H. incrustans, and a species of Esperia
belonging to the siliceous series. All of these were found to yield
sporular bodies in abundance, their most profuse development being,
however, afforded by the calcareous type Leucosolenia coriacea. Here
symmetrically rounded masses, irregular patches, or more or less isolated
spores, of a yellow or light brown hue, were found scattered literally in
thousands throughout the substance of the cytoblastema and in various
stages of development. In their earliest observed condition, in which the
spore-aggregations form compact spheroidal masses, these masses mea-
sured in diameter the i-i3OOth, and the individual spores that only of the
i-75OOth, part of an English inch. Bringing to bear upon them the high
magnifying power of 2500 diameters, as obtained with a -^-'mch objective
by Powell and Lealand, it was discovered that at a very early period of
their development, that is in all that had arrived at twice their first
noted bulk, each spore possessed a single long vibratile flagellum, and
corresponded precisely in aspect with the initial phases of many of the
simple monad types hereafter figured and described. Moreover, as
liberated by dissection from their natural position in the cytoblastema of
the parent sponge, these sporular bodies, with their vibrating flagella,
were set free in the surrounding water singly, in twos or threes, or in
larger social aggregations that singularly resembled the early phases of
development of Monas (Heteromita] lens, described at page 137, and
delineated at PI. XL Figs. 8-13. Not unfrequently, again, these motile
spore-aggregations were of considerably larger size, and retained their
primitive spheroidal form. Illustrations of all of these various conditions

I 74 NATURE AND AFFINITIES OF THE SPONGES.

of spore-production, as observed in Leucosolenia coriacea, are given at
PL X. Figs. 1-7, while, for the purposes of future reference and comparison,
sections of this sponge and the other species named, exhibiting similar
reproductive features, were preserved with osmic acid and other suitable
media.

As a substantial proof of the derivation of these variously formed
spore-masses from the typical collar-bearing units, examples were observed,
as represented at PL X. Figs, la and 2b, in which these zooids had with-
drawn their characteristic collars and flagella and assumed a quiescent
or encysted state, while in closely adjacent examples they had become
resolved into the spore-masses under discussion. Near these again,
the spore-masses in their disintegrated state, or higher developmental
phases, were found, as shown at Fig. 2, d d, scattered through the sub-
stance of the thin, transparent cytoblastema. In one point only was the
character of the spore-masses, as now examined with the highest available
magnifying power, found to differ from that assigned to them in their
earlier record already quoted. At that time, in the case of Leucosolenia
botryoides, a delicate capsular investment or sporocyst was presumed to
exist. No trace of such an investing element could, however, be detected
in L. coriacea. The entire body of the collared sponge-monad, after
assuming a quiescent state, divides by segmentation into a mass of
characteristic microspores, and these falling asunder, become distributed
throughout the hyaline cytoblastema. It might have been suggested, and
was indeed at first anticipated by the author, that the spore-masses, as here
figured and described, might have been derived from some protozoon or
protophyte which had established itself as a parasite or commensal within
the canal-system of the sponge-body. The unmistakable import of these
structures as integral constituents of the latter, is, however, abundantly
demonstrated by their undeviating recurrence and mode of distribution in
the sponge-body, even when obtained from the most remote localities.

In this connection it has to be recorded that spore-masses, presenting
the same form, size, and character, have been encountered by the author
without any exception in examples of Leucosolenia coriacea, personally
collected and examined in the living state, derived from Teignmouth,
Ansty's Cove, Falmouth, and other points on the Devonshire and Cornish
coasts, and also from various stations in the Channel Islands. Corro-
borative evidence relating to this species has likewise been recently
obtained from an independent and altogether unexpected source. In
vol. iii. page 8, of Dr. Bowerbank's ' Monograph of the British Spongiadae,'
1874, bodies of a precisely similar character, though connected with a
different title, are described as occurring in specimens of this sponge col-
lected in Shetland and remitted, preserved in spirit, to the author by the
Rev. A. M. Norman. Dr. Bowerbank's account of these spores is as follows : —

" On examining the sponge microscopically I found it contained an abundance
of gemmules. They were exceedingly numerous on the inner surface of the dermal

NATURE AND AFFINITIES OF THE SPONGES. 175

membrane. Their form was either spherical or slightly oval ; they were of a nut-
brown colour, and filled with numerous spherical molecules, which were distinctly
visible with a power of 700 linear. One of the largest of the gemmules measured
1-1119 inch in diameter, and the molecules within did not exceed 1-15000 inch in
diameter. This gemmule had all the appearance of being in a fully developed con-
dition. The greater portion of the other gemmules were much smaller ; one, of
about the average size, measured 1-1705 inch in diameter."

Unfortunately no figures are given of these bodies, but there is scarcely
room for doubt that the spore-masses figured and described in this volume,
and the so-called " gemmules " with their " molecular contents," as observed
by Dr. Bowerbank, represent the same structures. Apparently the last-
named authority attributed to these molecular or sporular aggregations
the possession of a distinct investing cellular membrane, his interpretation
thus according with the impression first conveyed to the author when
examining them with inadequate magnifying power. In yet another
calcareous type Dr. Bowerbank has placed on record his observation of
somewhat similar spore-like bodies. In his account of Leucosolenia
(Ascortis) lacunosa* he writes : —

" The whole surface of the interior of the fistulse and central cloacal cavity is
abundantly furnished with circular nucleated cells varying in diameter from 1-5454
inch to 1-3000 inch; they are regularly disposed, and are seldom more than about
the length of their diameter distant from each other. The nuclei occupy from one-
third to about two-thirds of the diameter of the interior of the cell, and neither in it,
nor in the cell surrounding it, is there any appearance of granules. I could not
detect any of these cells in the dried specimen of the same species, nor have I ever
seen similar cells in any other calcareous sponge. It is difficult, in the present limited
state of our knowledge of this tribe of sponges, to determine the import of these
bodies in the economy of the sponge, but it is most probable they are reproductive
organs."

Correlated with the evidence just submitted in connection with the allied
type L. coriacea, there is every reason to believe that here also spores of a
closely identical type exist. Much evidence substantiating the very general
occurrence of spores among the Spongida may be further adduced from
the more recent publications of various Continental spongologists, though
no such interpretation of the structures observed would so far appear to
have presented itself to the minds of these investigators. Thus in his
" Untersuchungen iiber Hexactinelliden," t W. Marshall figures and de-
scribes spore-like granules as occurring separately or in spherical masses
within the substance of the undifferentiated sarcode or cytoblastema of a
species of Holtenia. C. Barrois, " Embryologie de quelques Sponges de
la Manche,"t figures as peculiar granular cells, perhaps spermatozoa, of a
species of Isodictya, subspheroidal and more or less elongate aggregations
of spore-like bodies held together by thread-like transparent chords. This
identical, type has been encountered abundantly by the author on the Jersey
coast, and was independently observed to exhibit a similar peculiarity. The

* 'Mon. Brit. Spong.,' vol. ii., 1866. f ' Zeit. Wiss. Zool.,' Bd. xxv., 1875.

\ ' Ann. de Sc. Nat. Zool.,' 1876.

I 76 NA TURE AND AFFINITIES OF THE SPONGES.

••
whole cytoblastemic element in this species is remarkably tenacious or

glutinous, and is drawn out in long strings, like bird-lime, when the sponge
is broken apart ; the granular cells observed by Barrois are evidently the
spore-masses held together in the withdrawn glutinous threads of the invest-
ing cytoblastema. The so-called "sperm-balls," figured by F. E. Schulze,
in relation with the genus Halisarca* would appear also to belong to
the same category. The abundantly distributed subspheroidal groups of
so-called coloured corpuscles figured and described by this last-named
authority as imparting the characteristic yellow tint to the keratose type
Aplysina aerophoba, \ correspond remarkably with the yellow or light
brown spores of Leucosolenia coriacea. Lastly, Metschnikoff's valuable
" Spongologische Studien " J embraces abundant testimony in a corre-
sponding direction, and as is made evident at PI. X. Figs. 8 and 9 of the
present treatise, reproducing his illustrations of the so-called " mesoderm "
elements of the genus Siphonochatina.

In anticipation of the argument that may be advanced by the adherents
of the Metazoic interpretation of sponge structures, to the effect that the
sporular bodies here figured and described, represent spermatic or male
reproductive elements, it is only requisite to point still more emphatically
to the fact that these spores distributed broadcast throughout the substance
of the cytoblastema may, as ascertained by the author, be met with and
traced onwards through every intermediate size and stage, from the single
spheroidal spore up to the adult collared monads or amoebiform cytoblasts ;
the derivation of these spores through the splitting up into a granular or
sporular mass of the entire substance of the matured collar-bearing zooids
being correspondingly substantiated. Their phenomena of production and
cycle of development are, in fact, in all ways identical with those that obtain
among the typical Choano-Flagellata and ordinary Flagellata, and in all
of which the spores derived by a similar segmentation of the parent body
develop first a simple monadiform or amoeboid phase, and after arriving at
the adult state revert once more to the amcebiform condition, become
quiescent, and are again resolved into minute spores. In the sponge, all
these transformations and developmental processes take place within the
substance of the cytoblastema, which constitutes a suitable nidus for them
essentially corresponding with the gelatinous matrix or zoocytium of
Ophrydium, P halansterium, and Protospongia.

While the evidence so far submitted suffices to indicate the close
connection of the Spongida with the typical Infusoria - Flagellata, and
also explains, in connection with the phenomena last described, the manner
in which the general sponge-body is, by ever progressing internal spore-
production, rapidly increased in size, certain other important features
connected with their reproduction remain to be recorded. Although
the scattering of the spores through, and their development within, the

* ' Zeit. Wiss. Zool.,' Bd. xxviii., 1877. f Ibid., Bd. xxx., 1878.

\ Ibid., Bd. xxxii., 1879.

NATURE AND AFFINITIES OF THE SPONGES. 177

substance of the cytoblastema contributes largely towards the augmentation
of the common colony, it evidently does not provide for the more remote
dispersion of the species. This is effected in an entirely distinct manner.
In many cases, such as that of the common fresh-water Spongilla, such a
desired result is partly brought about by the production of encapsuled
gemmules, or so-called " seed-like bodies " at the time of the decadence
and disintegration of the parent stock. Practically, the development of
these reproductive bodies may be said to represent on a large scale a
modified process of encystment closely corresponding with the production
of sporangia among the Mycetozoa described on a preceding page. As
winter approaches, the zooids forming the parent colony assume an
amoeboid state and coalescing in spheroidal groups, secrete around them
a common spiculiferous capsule, within which they remain in a torpid or
quiescent state, until revivified by the return of spring and its accompany-
ing congenial temperature. A singular inversion of this phenomenon
obtains among the Spongilla of tropic countries, and in which, as recorded
by Mr. Carter of certain types occurring in the neighbourhood of Calcutta,
the production of gemmules, or entrance upon a hibernating or quiescent
state is resorted to (identically with that of many tropic fishes, such as
Lepidosiren] as a protective provision against the summer droughts, when
the tanks and reservoirs that they customarily inhabit are dried up.

The quiescent or hibernating gemmules, however, play but a minor part
in the local distribution of the species compared with the actively motile
reproductive bodies produced as offgrowths by sponges of apparently every
denomination during their period of luxuriant growth. With these motile
bodies, indeed, the quiescent or hibernating gemmules are in no ways com-
parable, they representing more correctly composite modifications of the
temporary " protective encystments " of the ordinary Infusoria. As true
reproductive gemmules only are here recognized those free-swimming
bodies, the so-called " ciliated-larvae," or " ciliated sponge-embryos," first
discovered by Grant and Lieberkuhn, upon the correct interpretation of
which the minds of biologists within these latter days have been so
diligently exercised. It is upon these seemingly anomalous reproductive
structures, moreover, that Professor Haeckel has, as already stated,
conferred the distinctive title of gastrula, and sought to demonstrate
the conformance of the Spongida to the Metazoic type. Without recapitu-
lating the altogether erroneous interpretations first published, and quite
recently maintained, by Haeckel concerning the form and structure of these
bodies, reproduced, rather as an admonition and warning than for the pur-
poses of edification, in the woodcut illustration with its accompanying
description at page 157, a brief examination of the more reliable data accu-
mulated through the independent investigations of Metschnikoff, Oscar
Schmidt, F. E. Schulze, Barrois, and other recent authorities may be
proceeded with. While one and all of them are unanimous in condemn-
ing, as entirely fallacious and untrustworthy, that special bilaminate and

N

178 NATURE AND AFFINITIES OF THE SPONGES.

sac-shaped structural type attributed by Haeckel to the so-called ciliated
embryos, the Haeckelian interpretation of the Mctazoic affinities of the
sponges has exerted so widespread an influence, and obtained such favour,
that every point has been strained on all sides to reduce these reproductive
structures, one way or another, to the Metazoic formula.

Unfortunately for these authorities, however, the one dissentient party
to this seemingly plausible and, so far as the sponges are concerned, most
honourable correlation is encountered in the very object of their solicitous
attention. The ciliated sponge-embryo — or, as shown later on, it may be
more appropriately denominated the " ciliated sponge-gemmule " — stub-
bornly resists interpretation as the exact analogue of any one of the various
embryonic types prevalent among the Metazoa, and seems indeed to derive
a pleasurable satisfaction from the exhibition of a varying type of structure,
possessing by turns some shadowy semblance of all, but actually conforming
in no single instance to any one of them. Sometimes, in fact, not only in
the same order, or in the same family, but in the same genus, in the same
species, and even in the same individual sponge-colony, an entire series of
diversely constructed reproductive bodies may be met with.

Abundant illustration is afforded of the more important variations of
form and structure found to obtain among the free-swimming sponge-
gemmules, by the figures numbered 22 to 36 of PI. IX., derived partly
from the author's personal investigation, and partly from the published
contributions of the various authorities previously quoted. Examined atten-
tively, it will become apparent that this entire series exhibits, with various
intermediate gradations, what may be denominated three fundamental
plans of structural differentiation. Thus, in the first of these, as shown
in Figs. 22, 23, and 36, such plan presents the simplest possible expression,
the so-called body-wall of the more or less ovate body consisting of a
simple and even layer of columnar cells, each giving origin peripherally
to a single elongate cilium or flagellum. In the second series, Figs. 27
and 29, an entirely distinct and more complex plan is exhibited. Here, the
cellular components of the anterior and posterior regions of the gemmule
differ in both size and structure ; those of the former being columnar, and
bearing flagella as in those of the first series, while in the latter they
are very much larger, usually more or less spheroidal, and entirely devoid
of flagellate appendages. The third and highest state of complexity is
arrived at in Fig. 30, where a new element is superadded in the form of
a central zone of smaller rounded cells, interposed between the anterior
columnar and posterior spheroidal series. It is scarcely to be wondered
that the energies of talented biologists have been taxed to their uttermost
to reconcile such entirely diverse structures with the typical developmental
formulae of the Metazoic embryo. By none of these, as yet, can such
identification be claimed to have been successfully established ; nor, on
examining more closely the very discordant interpretations that have been
suggested by different authorities with relation even to gemmules found

NATURE AND AFFINITIES OF THE SPONGES. 179

in the same specific type, would there seem to be much prospect of arrival
at a more definite result.

The Metazoic nature of the sponges, in deference to the authoritative
dictum of Professor Haeckel, being accepted d priori as an article of creed,
it has been rendered necessary to indicate, in one and all of those diverse
so-called ciliated sponge-embryos, the existence of the two primary and
absolutely essential constituents of the Metazoic embryo, the ectoderm
and endoderm, as produced by the segmentation and subsequent meta-
morphosis of a primitive unicellular impregnated ovum. Deferring for a
while the consideration of the presumed identity of this earliest or initial
phase, it may be first observed that the structural type, out of the three
respective series just enumerated, which has been accepted as conforming
itself most conveniently to the Metazoic formula, is exhibited by that one
in which the apical pole or segment of the reproductive body is composed
of more minute columnar flagellate cells, and the opposite one of larger
but simply subspheroidal elements. Here, as typically represented in the
calcareous sponge, Grantia compressa (PI. IX. Fig. 27), there certainly, at
first sight, appears to be a remarkable structural correspondence with the
segmented holoblastic ovum of the Mammalia, Amphibia, and various fishes,
including Amphioxus, and numerous higher Invertebrata in which one-half
of the primitive ovum, dividing more rapidly and abundantly, becomes con-
verted into numerous minute columnar blastomeres, and the opposite half,
Dividing more slowly and less extensively, into fewer larger and sub-
spheroidal blastomeres. Out of these two elemental series, distinguished
respectively as the epiblast and hypoblast, the future ectoderm and endoderm
are subsequently developed, the former from the minute columnar blas-
tomeres or epiblast, and the latter from the larger blastomeres or hypoblast.
The identity of the segmentation process in the Metazoic embryo and in
the so-called sponge-larva being so far regarded as complete, the apparent
corresponding factors in either case have also been accepted as homologous
ectodermic and endodermic elements. Supposing, for the time, that these
two structural elements could be consistently correlated, what should be
the next step ?

In the Metazoic embryo it invariably happens that either by the
invagination or falling inwards, as in Amphioxus, upon the primitive
central segmentation cavity or archenteron of the hypoblast or endodermic
element, or by the encroachment upon or growing over the latter, as in
the Amphibia, of the epiblast or ectodermal element, it comes to pass that
the endoderm is enclosed within the ectoderm, and a bilaminate structure
is produced roughly resembling the double-walled sac-like body or so-called
" gastrula " of Professor Haeckel. The outer lamina or wall of this sac-
like body is now the ectoderm, the inner one, closely applied to it, the
endoderm. The central cavity most usually enclosed within these layers
represents the primitive alimentary tract or archenteron, and the aperture
placing the latter in communication with the outer world the primitive anal

N 2

l8o NATURE AND AFFINITIES OF THE SPONGES.

aperture or blastopore. The question at issue is whether similar or equi-
valent developmental steps are traceable in the ciliated sponge-gemmule ?
F. E. Schulze, writing of Sycandra raphanus in the year 1875, deposes that
there are, giving in demonstration the figures reproduced at PI. IX. Fig. 33.
The same authority reports, however, as the result of a more recent investi-
gation of this species, an entirely opposite plan of structure. According to
his later interpretation,* it is not the larger and apparent endodermic blas-
tomeres that become invaginated or enclosed within the more minute
ectodermal elements, but, as indicated at Fig. 34 of the same plate, the
latter that sink down into, and are enclosed by, the former. By Metschni-
koff, a second chronicler of the developmental phases of this identical species,
the so-called ciliated larvae are described as presenting, in addition to the
ordinary form having dissimilar hemispheres of large, subspheroidal, non-
flagelliferous, and more minute columnar flagellate cells, examples that are
made up entirely of flagellate columnar elements, which, however, towards
the basal region, are of somewhat larger size. This slight modification of
the first of the three structural types enumerated in a preceding page, as
observed by Metschnikoff, of Sycandra raphanus, represents the dominant
form found in other closely allied calcareous species, as also in the
Myxospongiae and the majority of the Siliceospongiae, where the charac-
teristic amphiblastuloid type previously considered is not known to occur.
This so to say homoblastic embryonic form, produced by the entire and even
segmentation of the primitive so-called ovum, and exhibiting in its charac-
teristic state the structure and condition only of a monoblastic or simple
single-cell-walled morula, with a more or less extensive segmentation cavity,
does not subsequently, by direct or indirect invagination, as occurs with the
monoblastic morulae of the Metazoa, attain to the higher diploblastic formula ;
it cannot therefore be consistently compared with the typical and charac-
teristic diploblastic embryo of any Metazoic organism. Nevertheless, various
more or less arduous attempts have been made to demonstrate that even
in this simpler monoblastic reproductive body, the essential Metazoic
elements, " ectoderm," " endoderm," and in some cases even " mesoderm,"
are substantially represented.

By some, including Professor Haeckel, it has been suggested that the
endoderm is indirectly produced through the process of delamination,
instead of that of invagination, as most usually obtains. Such an interpre-
tation, however, is entirely upset by some highly remarkable results of
recent investigation. It has been shown, in fact, by Oscar Schmidt, f with
relation to the calcareous type Ascetta primordialis, that the elements usually
accepted as representing the endoderm are produced neither by delamina-
tion nor by invagination, but creep into the central segmentation cavity
as separate and independent amcebiform units from the circumjacent
so-called ectodermal layer, of which latter they are the metamorphosed

* 'Zeitschrift fur Wissenschaftliche Zoologie, ' Bel. xxxi., 1878.
t ' Archiv fiir Mikroskopische Anatomic,' Bd. xiv., 1877.

NATURE AND AFFINITIES OF THE SPONGES. 181

constituents. Sooner or later, the segmentation cavity becomes filled up
with these metamorphosed, or, as Oscar Schmidt has denominated them,
"wandering cells," which breaking their way through the posterior pole,
ultimately appear as a projecting heap in this region, and thus convey to
the entire organism an aspect closely corresponding with the normal
amphiblastuloid type. It is through the medium of these projecting meta-
morphosed cells that the young sponge becomes fixed to its selected
fulcrum of support, and that the further development onward to the charac-
teristic adult sponge-stock is initiated. Some of the most characteristic
representations of the phenomena last described, as given by Oscar Schmidt,
will be found reproduced at PL IX. Figs. 36-38. The remarkable and
important data, first elicited by the last-named authority, have been entirely
confirmed by the later researches of Metschnikoff, * in connection with both
Ascett.i primordialis and various other widely separated sponge-forms. Pro-
ceeding still further, however, this investigator maintains that in these types
not only the so-called endodermic, but special mesodermic (spiculiferous)
elements are likewise produced by a similar developmental process.

The task of reconciling all of the various developmental formulae now
enumerated as exhibited by diverse, or, it may be, by even a single sponge
type, with one or any of those that typically characterize the Metazoic
embryo, -is obviously almost hopeless : it now remains to be seen whether
or not more substantial progress in the interpretation of the affinities of
the sponges by means of the so-called ciliated larvae can be accomplished
in a totally distinct direction. Presuming that the account given by
F. E. Schulze of Sycandra raphanus represented the typical and constant
form and process of development — though practically such is very far from
the case — Mr. T. M. Balfour, one of our leading authorities in this country
on embryologic matters, has quite recently, January 1879, contributed to
the ' Quarterly Journal of Microscopical Science •' the results of his own
analysis of the evidence so far adduced. The verdict he arrives at, while
not proceeding to the full length advocated by the author of this volume, is
noteworthy for its marked bias in a similar direction, and for its deviation
in an essential manner from that Metazoic interpretation hitherto most
generally acquiesced in by Continental biologists.

Mr. Balfour's expressed views in this connection are so important as to
demand quotation in extenso. After enumerating the chief features of the
developmental history of Sycandra raphanus as last reported by F. E.
Schulze, he thus proceeds : —

" The first point in the development of Sycandra which deserves notice is the
character of the free-swimming larva. The peculiar larval form, with one half of
the body composed of amoeboid granular cells, and the other of clear ciliated cells,
is nearly constant among the Calcispongiae, and widely distributed in a modified
form amongst the Fibrospongias and Myxospongise. Does this larva retain the
characters of an ancestral type of the Spongida, and if so, what does its form mean ?

'Zeitschrift Wissenschaftliche Zoologie,' Bd. xxxii., 1879.

1 82 NATURE AND AFFINITIES OF THE SPONGES.

It is, of course, possible that it has no ancestral meaning, but has been secondarily
acquired. I prefer myself to think that this is not the case, more especially as
it appears to me that the characters of the larva may be plausibly explained by
regarding it as a transitional form between the Protozoa and Metazoa.

" According to this view, the larva is to be considered as a colony of Protozoa —
one half of the individuals of which have become differentiated into nutritive forms,
and the other half into locomotor and respiratory forms. The granular amoeboid
cells represent the nutritive forms, and the ciliated cells represent the locomotor and
respiratory forms. That the passage from the Protozoa to the Metazoa may have
been effected by such a differentiation is not improbable on d priori grounds, and
fits in very well with the condition of the free-swimming larva of the Spongida.

" While the above view seems fairly satisfactory for the free-swimming stage of
the larval sponge, there arises in the subsequent development a difficulty which at
first sight seems fatal to it. This difficulty is the invagination of the ciliated cells
instead of the granular ones. If the granular ones represent the nutritive individuals
of the colony, they, and not the ciliated cells, ought most certainly to give rise to
the lining of the gastrula cavity, according to the generally accepted views of the
morphology of the Spongida.

"The suggestion which I would venture to put forward in explanation of this
paradox involves a completely new view of the nature and functions of the germinal
layers of the adult sponges. It is as follows : — When the free-swimming ancestor of
the Spongida became fixed, the ciliated cells by which its movements used to be
effected must have to a great extent become functionless ; at the same time the
amoeboid nutritive cells would need to expose as large a surface as possible. In
these two considerations there may, perhaps, be found a sufficient explanation of
the invagination of the ciliated cells and the growth of the amoeboid cells over them.
Though respiration was, no doubt, mainly effected by the ciliated cells, it is impro-
bable that it was completely localized in them ; but the continuation of their function
was provided for by the formation of an osculum and pores. The ciliated collared
cells which line the ciliated chambers, or in some cases the radial tubes, are
undoubtedly derived from the invaginated cells; and if there is any truth in the
above suggestion, the collared cells in the adult sponge must be mainly respiratory,
and not digestive, in function, while the normal epithelial cells which cover the
surface of the sponge, and in most cases line the greater part of the passages
through its substance, must carry on the digestion. If the reverse is the case, the
whole theory falls to the ground. It has not, so far as I know, been definitely made
out where the digestion is carried on. Lieberkuhn would appear to hold the view
that the amoeboid lining cells of the passages are mainly concerned with digestion,
while Carter holds that digestion is carried on by the collared cells of the ciliated
chambers. If it is eventually proved by actual experiments in the nutrition of
sponges that digestion is carried on by the general cells lining the passages, and not
by the ciliated cells, it is clear that neither the ectoderm nor entoderm of sponges
will correspond with the similarly named layers in the Ccelenterata and the Metazoa.
The invaginated entoderm will be the respiratory layer, and the ectoderm the diges-
tive and sensory layer ; the sensory function being probably mainly localized in the
epithelium on the surface, and the digestive one in the epithelium lining the passages.
Such a fundamental'difference in the germinal layers between the Spongida and the
other Metazoa would necessarily involve the creation of a special division of the
Metazoa for the reception of the former group."

It is very clear, after a perusal of Mr. Balfour's views as above
enunciated, that the claims of the Spongida for admission into the ranks of
the typical Metazoa, and more especially for correlation with the Ccelen-
terata, as advocated by Professor Haeckel, rests upon the most shallow and
insecure foundation. It is likewise evident that in Mr. Balfour's estimation
the sponges retain a close kinship with the Protozoa, and are at the outside

NATURE AND AFFINITIES OF THE SPONGES. 183

an intermediate group between the Protozoic and Metazoic sections.
Proceeding yet further, it is maintained by the present author that the
structure and relationship of the Spongida is altogether Protozoic, and that
the phenomena exhibited by the life and developmental history of the
ciliated reproductive bodies now under discussion are, equally with the
structural composition of the adult sponge, reducible to and capable of
correct interpretation only in association with a Protozoic standard.

Before proceeding to an examination of the evidence that can be
adduced in support of this declaration, a passing note may be made of one
or two of the points involved in Mr. Balfour's argument. In the first
instance, the so-called larval sponge form distinguished by Haeckel by the
title of an " amphiblastula," and consisting of one hemisphere of amoeboid,
and the other of flagellate cells, cannot, as Mr. Balfour suggests, be
accepted as the typical and ancestral form of these bodies, it occurring
only, and then not persistently, in the group of the Calcispongia:: ; a still
simpler type having all the cellular constituents alike in form and cha-
racter, and thus presenting a closer structural conformance to a simple
vesicular morula, is mostly dominant. The important issue at stake,
recognized by Mr. Balfour, relating to the digestive functions of the
amoeboid and flagellate elements of both the adult and embryo sponge, can
fortunately be completely disposed of, and in such a manner as, on Mr.
Balfour's own admission, demonstrates that neither the so-called ectoderm
nor endoderm of Spongida will correspond with the similarly named layers
in the Ccelenterata and other Metazoa. Nutrition and digestion are, in
fact, accomplished by both the collared flagellate and the amoeboid cells, a
circumstance which would require for their strict correlation with the
equivalent Metazoic elements, the possession of nutritive functions by both
the ectodermal and endodermal layers.

Passing now to a consideration of the interpretation of these special
reproductive sponge structures maintained in this volume, it may be
affirmed to be substantially identical with that submitted by the author in
the 'Annals and Magazine of Natural History' for August 1878, previously
embodied in the communication made to the Linnean Society in June
1877, and as extensively confirmed by subsequent investigation. The fact
of the case is, that in almost every one of the accounts and illustrations
given by contemporaneous authorities, that which may unhesitatingly be
pronounced to represent the most important and significant structural
element in these reproductive bodies, has been persistently ignored. The
omission referred to is the fundamental composition of the free-swim-
ming sponge-embryos of collared flagellate zooids, in all ways identical
with those that line the interstitial cavities, and constitute the essential
factors of the adult sponge. The so-called ciliated sponge-larva is, it is
here maintained, in its typical phase of development, not an individual
germ or larva, but a motile swarm-gem mule, consisting of a more or less
ovate colonial aggregation of typical collared zooids, as shown at PI. IX.

184 NATURE AND AFFINITIES OF THE SPONGES.

Figs. 24 and 25, which represent phases of these reproductive structures, as
observed by the author in the common calcareous sponge Grant ia comprcssa.
The collars left out — and it is admitted that without much care and patience
in examination they are, like the collars of the independent collared monads
and Spongozoa, most difficult to recognize — the structure accords completely
with that vesicular, moruloid embryonic type so abundantly figured and
described by Oscar Schmidt, F. E. Schulze, and Metschnikofif. Neither of
these biologists appear to have detected the existence of that important
element, the collar. That such a structure, however, positively exists, does
not rest only upon testimony submitted by the present author, it being
substantially confirmed by the independent investigation of Barrois, and
even Haeckel. The former of these two authorities indicates, though
feebly, the possession of collars by the motile reproductive gemmules of
Halisarca lobularis, while Professor Haeckel still more clearly denotes their
existence in his representations of his so-called ciliated larvae or gastrulae
of the calcareous sponges Leuculmis echinus and Sycyssa Huxleyi. With
both Haeckel and Barrois, however, the collared cells have apparently no
significance beyond that of ordinary ciliated epithelium, the special function
of the funnel-shaped collar, and its import with relation to both the sponge-
monads and the entire order of independent organisms described in this
volume under the title of the Choano-Flagellata, being as yet unrecognized.
It is not only in connection with the simpler moruloid type of the
ciliated sponge-gemmule that its fundamental composition out of typical
collar-bearing zooids is made manifest. A like interpretation applies with
equal force to that seemingly more complex amphiblastuloid type upon
which an agreement with the Metazoic embryologic formula has been most
powerfully upheld. This may be demonstrated in connection with the
identical sponge-form, Grantia compressa, cited in the previous instance.
As shown at PI. IX. Figs. 26-29, tn's amphiblastuloid reproductive body
may, furthermore, present three very distinct developmental phases. It may,
as in the first instance, Fig. 26, exhibit typical collared cells in the posterior
or basal hemisphere, and simply flagellate ones in the anterior one ; in
a second case, Fig. 27, the basal elements may be simply amoeboid and
the anterior flagellate, this representing indeed the characteristic condition
under which the amphiblastuloid type has been most extensively figured
and described. A modification of this type, in which the basal amcebiform
units project irregularly from the periphery, is shown at Fig. 29. In the
third and remaining form, Fig. 28, the basal elements are also amoeboid,
but the anterior ones, in place of being simply flagellate, bear also charac-
teristic hyaline collars. These three are, in fact, progressional phases only
of one and the same fundamental amphiblastuloid type, the latter again
being an unevenly developed variation only of the simpler and homogene-
ously constructed moruloid form. In the moruloid type, Figs. 22 to 25, the
development of the collared units has progressed evenly throughout the
entire series, while in the three amphiblastuloid ones above enumerated, it

NATURE AND AFFINITIES OF THE SPONGES. 185

exhibits various phases of unevenness which may be thus explained. In all
three, the posterior half has developed considerably in advance of the
anterior one, but exhibits in the first figure its typical composition of collar-
bearing monads ; in the other two, on the other hand, the posterior basal
elements have passed from the collar-bearing to the amoeboid state, and
coalesced more or less extensively with each other. In a like manner, the
elements of the anterior half in both of the Figs. 26 and 27 represent the
immature and simply flagellate phases of the collared zooids, but which in
Fig. 28 have acquired their characteristic adult form. The life-history and
various developmental phases of the free-swimming ciliated sponge-gem-
mules are, in fact, epitomizations only of the phenomena already described
of the collared zooids of the adult sponge-stock. Here, as there, the
essential constituents, or collared zooids, of the colonial aggregation, com-
mence life as simple flagellate units, which, after attaining their typical
adult form, assume successively an amoeboid and quiescent state, and give
rise by minute sporular subdivision to a further progeny of collared zooids.
As a clear indication of the common origin and significance of both the
moruloid and amphiblastuloid sponge-gemmules, with their various modifi-
cations, it needs only to be recorded that every one of these seemingly
distinct structures has been met with by the author in a single sponge-
stock of Grantia compressa, and also in Leucosolenia botryoides and Grantia
(Sycori) ciliatum, as obtained both in the Channel Islands in the years
1877-8, and on the South Devon and Cornish coast in 1879. From
the last examined examples, furthermore, sections containing these
gemmules in abundance, treated with osmic acid, have been successfully
preserved for permanent reference and comparison. It is, moreover,
in connection with the first-named sponge-form (Grantia compressa}
that Barrois has reported the occurrence of that variety of the amphi-
blastuloid gemmule, in which a ring of intermediate non-flagellate cells
are developed equatorially between the typical flagellate and amoeboid
series. The latter elements, as shown at PI. IX. Fig. 30, are of somewhat
abnormal size, and, as in many other of the examples figured, are far too
large to have represented individually a primarily single collared zooid.
This phenomenon, as also that of the presence of the equatorial girdle of
smaller cells in the example cited, admits of simultaneous explanation.
The equatorial girdle, in fact, may be interpreted as representing an anterior
ring of amoeboid cells metamorphosed from the typical collared units at a
slightly later date than those of the posterior area, and which latter have
become still more obscurely transformed and increased in size, though
lessened in number, by coalescence. It is by a similar process of retro-
gression to an amoeboid type, and the more or less extensive union or
coalescence of amoeboid zooids that the ciliated gemmules themselves
originate.

In addition to the various symmetrically constructed moruloid and
amphiblastuloid modifications of the ciliated sponge-gemmule already

1 86 NATURE AND AFFINITIES OF THE SPONGES.

enumerated, it has yet to be recorded that it very commonly happens that
these structures present an altogether irregular and asymmetrical contour.
Illustrations of such irregular formations, as figured by Oscar Schmidt, of
Grantia (Sycandrd) compressa, and as observed by the author, will be found
reproduced at PI. IX. Figs. 32 and 35. Such asymmetrically developed
gemmules may retain fundamentally the moruloid or amphiblastuloid
structural type, being in the one case composed entirely of similar and in
the other case of dissimilar constituents. The fact that these various
irregularly formed gemmules are by no means of rare occurrence, may
be accepted as furnishing supplementary evidence in demonstration of the
non-correspondence of these sponge-gemmules, or so-called ciliated larvae,
with the embryos of the typical Metazoa, and in which latter organic
series the production of asymmetrical germs is quite exceptional. One of
the strongest arguments furnished in support of the essentially Protozoic
significance of these reproductive bodies is, undoubtedly, afforded by the
independently contributed testimony of Oscar Schmidt and Metschnikoff,
by both of whom it is shown that in the case of Ascetta primordialis,
the component flagellate elements of the moruloid gemmule assume
quite independently an amoeboid condition, and retiring separately into
the central segmentation cavity, undergo their further metamorphoses.
Ultimately, these separately retreating amoebiform units completely fill
up the central cavity, and burst through the posterior region of the
ciliated body, project at this extremity, and so produce in a roundabout
manner a pseudo-amphiblastula. It will be at once recognized that
while this peculiar developmental phenomenon of the sponge-gemmule
exhibited by Ascetta primordialis, is altogether opposed to anything that
obtains among the Metazoic series, it is at once reconcilable with a
Protozoic interpretation. With their near allies the simple flagellate or
collared monads, e.g. Phalansterhim,Spongomonas, and Protospongia, parallel
phenomena, including the assumption by the adult zooids of an amoeboid
state, and their retreat within the common gelatinous cytoblastema-like
matrix, or zoocytium, represents the normal reproductive process.

The highly important evidence that demonstrates the thoroughgoing
Protozoic affinities of the sponge with relation to the primary origin and
development within the parent sponge-stock of the free-swimming ciliated
gemmules, has yet to be submitted. The initial condition of these repro-
ductive structures, as conceded unanimously by the independent testimony
of every investigator, takes the form of an amcebiform body, varying in size
from the i-3OOOth to the i-2OOth of an English inch, and presents a con-
siderable likeness to the primary condition of an ordinary ovum. With,
however, the interpretation of the significance and subsequent evolution of
this amcebiform structure that is most generally advocated, the author has
to declare himself entirely at issue. In accordance with this more widely
accepted view, the amcebiform body is a true ovum, developed separately
and independently in the interstitial substance of the sponge, and after-

NATURE AND AFFINITIES OF THE SPONGES. 187

wards fecundated by spermatozoa independently generated within the
same sponge-body.

Had such a process of production and development been actually
substantiated, the Metazoic affinities of the Spongida would undoubtedly be
capable of considerable development, but, as a matter of fact, no substan-
tial proof of the existence of any such process has been as yet adduced.
The evidence available for the gauging of this important question favours,
on the other hand, an entirely opposite conclusion. It is here maintained,
indeed, as first suggested in the author's communication to the 'Annals of
Natural History' for July 1878, that the amoeboid oviform bodies are not
independent products of the adult sponge-stock, but simply retromorphosed
collar-bearing zooids that have retreated within the cytoblastema, and
assumed, as is common to them after passing their matured collar-bearing
stage, an amceboid condition. It is these amoeboid units that through
coalescence with their fellows attain by degrees the comparatively colossal
proportions they present in their most advanced phase of development, and
then by the process of segmentation produce the characteristic moruloid or
amphiblastuloid ciliated gemmule. There is in this process of evolution no
concourse of male and female or true ova and spermatozoa as occurs among
the Metazoa, but the phenomena exhibited are in all ways identical with
those that obtain among the most simple Flagellate Infusoria, such as
Monas and Heteromita, in which the typical flagellate zooids, passing the
zenith of their adult condition, enter into an amceboid state, and coalescing
in pairs, or even socially, give rise by segmentation to a new generation of
flagellate units. On a yet larger scale, and in a manner more closely
corresponding with what obtains among the Spongida, identical phenomena,
as described at page 42, are encountered in the group of the Myxomycetes
or Mycetozoa. The only fundamental point that distinguishes the segmen-
tation process in the two groups of the Spongida and ordinary Flagellata
is that, whereas in the more simple Flagellata the products of such
segmentation are scattered apart throughout the inhabited fluid medium,
and maintain an independent existence, in that of the sponge-gemmule
these flagellate units are intimately bound to one another at the time of
their exodus from the parent colony-stock, and remain associated within
their subsequently developed common gelatinous matrix or cytoblastema for
the whole term of their existence. Substantial corroboration of the opinion
here maintained that the reproductive sponge-gemmules, or so-called
ciliated larvae, are the product of the coalescence or fusing with one
another of a large number of metamorp~hosed collared zooids, and that
they are not independently generated after the manner of true ova, is
afforded by the circumstances under which they are naturally met with
in the tissues of the parent sponge-stock. In this connection, both in
accordance with the author's experiences, and as distinctly shown in the
figures given by all the more notable investigators of this organic group, it
is invariably found that these bodies are, as shown at PI. VII. Fig. I,

I 88 NATURE AND AFFINITIES OF THE SPONGES.

produced first in the deeper and consequently older portion of the sponge-
stock, and that where abundantly developed they monopolize its interstitial
substance to the exclusion of the ampullaceous sacs or other combinations
under which the collared zooids may be characteristically distributed.
These latter have, in fact, after attaining maturity, assumed the amoeboid
state, and, abandoning their normal position, coalesced extensively with
one another after the manner of various ordinary Flagellata, the outcome
of this process being the more or less regular segmentation of the united
mass and production of the characteristic ciliated gemmule. Regarded
from such a point of view, this ciliated reproductive structure is in no sense
an egg, or its derivative, but represents a coherent aggregate of monadiform
swarm-spores, or, as it may be most appropriately denominated, a " swarm-
gemmule."

In addition to the characteristic ciliated reproductive bodies or swarm-
gemmules just described, there remain to be discussed certain other complex
bodies, generated within the interstitial sponge-substance, that, as first
suggested by Mr. Carter, take their origin by an essentially identical
developmental process. The structures here referred to are the so-called
" ampullaceous sacs " or spheroidal ciliated chambers characteristic of Hali-
sarca, the greater portion of the keratose and siliceous sponge-forms, and
some few calcareous species. It has been ascertained by the author in the
case of Halisarca Dujardinii, a species of Isodictya, and various other types,
that these structures are also, as shown at PI. IX. Figs. 4-9, originally
developed from the segmentation of a primitive amoeboid body produced,
as in the former instance, by the coalescence of more or fewer metamor-
phosed collared zooids. Such segmentation is in this instance, however,
entirely even, and results in the production of a perfectly spheroidal moruloid
body having a somewhat extensive central segmentation cavity. The only
difference that characterizes the more advanced condition of the ampul-
laceous sacs is manifested by the fact, that while in the case of the free-
swimming ciliated gemmules the constituent collared zooids are so de-
veloped that their collars and flagella are directed peripherally or away
from the central segmentation cavity, in the case of the ampullaceous sacs
they take an opposite direction, their flagella and collars being projected
into this cavity. As with the ciliated gemmules, the component zooids,
before acquiring their characteristic collars, present a simply flagellate con-
dition, their aspect at such stage being represented at PI. IX. Fig. 11.
Immediately prior to this simply ciliate condition the individual units are
amcebiform and non-flagelliferous, and held together circumferentially by
a thin film of structureless cytoblastema ; often, as shown at PI. IX. Fig. 10,
they are considerably isolated. In their more matured state the collared
zooids cohere laterally to one another, and, excepting at the afferent and
efferent apertures, present no break or interruption. Taken in optical
section, so as to avoid these openings, a matured and typical ampullaceous
sac presents, in fact, the exceedingly elegant and symmetrical structural

NATURE AND AFFINITIES OF THE SPONGES. 189

form illustrated by Fig. I of the plate just quoted. Isolating some half-
dozen cell-units from this complete section, as shown at PI. IX. Fig. 2, a
monad aggregation is produced that corresponds in a most remarkable
manner with the characteristic moniliform colony-stocks of the free-swimming
marine collared type Desmarella moniliformis, S. K., represented at PI. II.
Fig. 30, a fresh-water variety of which genus has been since figured by
Professor Stein under the title of Codonodesmus phalanx. The symmetrical
pattern of the ampullaceous sacs just described is, however, by no means
persistent. In many sponges a greater or less number of these primitively
spheroidal chambers, abutting upon one another, coalesce together, and so
form altogether irregularly shaped cavities that may ultimately be of very
considerable extent.

In his ' Spongiologische Studien ' * Metschnikoff has quite recently
drawn attention to certain structural elements in Halisarca Dujardinii
that have hitherto escaped notice. These structures, upon which he bestows
the name of " rosette-cells," consist of small subspheroidal groups of cells,
usually eight or sixteen, that are developed independently within the inter-
stitial substance of the adult sponge, and also within the central cavity of
the free-swimming ciliated gemmules, in this latter case being the product,
by segmentation, of the metamorphosed and increeping zooids from the
peripheral region. Some of the more characteristic representatives given
by Metschnikoff of these rosette-cells are reproduced at PI. IX. Figs. 15-17,
the two last of these exhibiting the existence of flagellate appendages.
It so happens that these newly-reported rosette-cells supply, most oppor-
tunely, an important link in the organization of certain Spongida, recognized
by the author some years since, but which, pending the production of
corroborative evidence, has not hitherto been brought forward. Closely
identical cell-aggregations have been thus observed in a variety of sponge-
forms, being found more especially abundant, however, in blood-red examples
of the same type, Halisarca Dujardinii, collected on the Jersey coast and
examined in the living state in the month of February 1878. At this time
of the year none of the characteristic ciliated swarm-gemmules were
present ; but in cutting sections, numbers of spheroidal uvella-like groups
of typical collared monads were liberated, and were likewise observed
united to the cytoblastema, entering largely, in combination with the ampul-
laceous sacs, under such conditions into the formation of the general sub-
stance of the sponge-stock. While in their- most typical and matured con-
dition the constituent zooids of these independent rosette-shaped groups were
provided with collars and flagella, and in all respects resembled those
lining the ampullaceous sacs, in less matured examples they were simply
flagellate, and in still earlier conditions possessed no appendages whatever,
the larger examples being then indistinguishable from the morula-like cell-
aggregates out of which the ampullaceous sacs are themselves developed.
There can be but little doubt that these structures observed in the Channel

* 'Zeitschrift flir Wissenscha'tliche Zoologie,' Bd. xxxii., 1879.

1 90 NATURE AND AFFINITIES OF THE SPONGES.

Islands examples, and as exhibited in their various developmental phases
at PL IX. Figs. 18-21, are identical with the so-called rosette-cells lately
described by Metschnikoff ; the descriptions and delineations of them -as
given by him being, however, deficient in one important point — that of the
possession by each constituent unit, in its matured condition, of the charac-
teristic collar. This oversight is, however, altogether what might have been
expected when it is found on examining his text and plates illustrating
the histology of various calcareous and siliceous sponge-forms, that that
important structure is not, except in one doubtful instance, either figured
or alluded to.

The true significance of the special rosette-like aggregations remains
to be discussed. Their derivation through the coalescence and segmenta-
tion of a greater or less number of amcebiform units, as in the case of the
larger ciliated gemmules, and that of the ampullaceous sacs, was ascertained
by the author, their close correspondence with the former of these two struc-
tures being thus made especially apparent. Their only distinction from the
ciliated gemmules subsists, in fact, in their much smaller size, through being
derived from the fusion of a small number of zooids only, and their retention
of a spheroidal uvella-like contour, without any development, by separation
from each other, of an extensive cleavage cavity. It would seem to be by
no means improbable that the rosette-shaped aggregations, thus derived
from the fusion and segmentation of a smaller number of the typical
collared cells, represent in the one direction a more primitive form of the
ciliated reproductive gemmule, and in another the more primitive mode of
grouping of the typical collared zooids in the colonial sponge-stock. As
already stated, and as shown at PL IX. Fig. 21, these spheroidal groups
were found attached to and projecting from the cytoblastema into the
adjacent canal-systems in the case of Halisarca, and contributed largely, in
combination with the ampullaceous sacs, to the composition of the general
substance of the compound body. It is quite probable that sponge-forms
exist, or have existed, in which such a disposition alone of the collar-bearing
zooids represents the normal and characteristic type of structure. A close
approach to this has in fact already been observed by the writer in con-
nection with a siliceous-spiculed sponge, further investigation, however,
being desirable for its complete exposition. Should anticipations in this
direction be confirmed, it will certainly admit of a yet closer approxi-
mation of the sponges to the independent Flagellate Infusoria than is now
attempted. For in such a case, a sponge-stock having its essential collared
zooids so disposed that they project simply in the form of uvella-like
clusters into the interstitial canal-system, and whose motile reproductive
bodies consist simply of similar, but detached, uvelloid clusters, would in
all ways be comparable to a colony of Codosiga botrytis or Anthophysa
vegetans, in which, instead of developing a branching stem, the spheroidal
clusters or "ccenobia" of associated zooids extended around them, and

NATURE AND AFFINITIES OF THE SPONGES. 191

remained immersed within, a common gelatinous matrix, or " zoocytium,"
such as actually exists in the several genera Spongomonas, P/ialansterium,
and Ophrydium, taking there the place of a dendritic pedicle. In Anthophysa
vegetans, furthermore, as shown at PI. XVIII. Figs. 2, 4, 5, the propagation
of the species by the detachment of entire uvelloid masses corresponding
essentially with the rosette-like clusters of Halisarca, is well substantiated.
A still more pertinent comparison in this direction may, however, be insti-
tuted between the rosette-gemmules of Halisarca Dnjardinii delineated at
PI. IX. Figs. 19 and 20, and the monad aggregate of Codosiga botrytis
reproduced from Stein's drawings at PI. IV. Fig. 6.

Summing up the entire evidence now submitted with reference to the
structural and developmental phenomena of the Spongida, and correlating
it with that embodied in this volume relative to those of the independent
Choano-Flagellata and other Flagellate Protozoa, scarcely a shadow of
doubt even is admissible concerning the intimate and thoroughgoing relation-
ship that subsists between one and the other. The primary and essential
element of the apparently complex sponge-stock is the assemblage of
collared flagellate zooids that inhabit its interstitial cavities under various
plans of distribution. Individually, these collared zooids correspond, struc-
turally and functionally, in every detail with the separate collared units of
such genera as Codosiga, Salpingceca, and Protospongia. The collar in either
case presents the same structure and functions, exhibits the same circu-
latory currents or cyclosis, and acts in a precisely similar manner as a trap
for the capture of food. The body contains an identical centrally located
spheroidal nucleus or endoplast, and a corresponding, posteriorly located,
series of rhythmically pulsating contractile vesicles. The developmental and
reproductive phenomena are also strictly parallel. Both originate as simple
amoebae or simple flagellate monads exhibiting no trace, in their earliest
developmental phase, of the subsequently acquired characteristic collar.
Both again, after passing matured age, withdraw their collar and flagellum,
and assume an amoeboid state. Then, coalescing or not with their fellows,
they enter upon a quiescent or encysted condition, and breaking up into a
greater or fewer number of sporular bodies, provide for the further existence
and distribution of the species. Among the independent collared types this
sporular progeny, except in Protospongia and Phalansterium, is scattered
through the surrounding water, while in the sponge they are retained
within the common gelatinous matrix, or cytoblastema, and assist in the
extension of the common colony. More exceptionally, for the purpose of
securing the local distribution of the species, the coalescing amcebiform
zooids of the sponge-stock, derived from the metamorphosed collared
zooids, form by repeated segmentation a pseud-embryo, or so-called ciliated
larva, of considerable size, whose cell-constituents when analyzed are found
to consist of typical collared zooids, resembling those from whence they
previously originated, and presenting similarly in their earliest phase of

1 92 NATURE AND AFFINITIES OF THE SPONGES.

existence a simply flagellate structural type. In their most characteristic
form, these reproductive bodies or cell-aggregates consist of a uniform
series of collared zooids, but by irregular growth one half may arrive
at or pass maturity in advance of the other, the product then being a
compound structure presenting a close correspondence with that phase of
development of the Metazoic ovum known as the amphiblastula. Since,
however, these bodies are in no way comparable with the Metazoic ovum —
not being the product of the concourse of true sexual elements — the above
likeness is simply homoplastic, and the body as a whole, consisting as it
does of an aggregation of numerous independent zooids, may be most
appropriately denominated a " swarm-gemmule." While no direct approach
to the production of a similar compound gemmule occurs among the
typical Infusoria-Flagellata, as at present known, something much akin
to it obtains in the protophytic type Volvox globator, which liberates
from its interior, free-swimming gemmules that take the form of spherical
aggregations of biflagellate daughter-cells. In their isolated state, on the
other hand, the svvarm-gemmules of the sponge-stock are directly com-
parable with the free-swimming subspheroidal colony-stock of the flagellate
Infusoria Synura, Syncrypta, and Uroglena, or with the attached subsphe-
roidal clusters of Codosiga and Anthophysa.

In certain respects, as already pointed out at page 41 et seq., a very
remarkable and suggestive analogy in the direction of the Spongida is
furnished by the Protozoic group of the Myxomycetes or Mycetozoa.
Here we find the essential elements consisting primarily of independent
flagellate zooids possessing a spheroidal endoplast, contractile vesicles,
taking in solid nutriment, and presenting other characters in common with
the ordinary Flagellata. Passing their matured flagellate condition these
now assume an amoebiform condition and coalescing in large numbers, as in
the case of the Spongozoa, form a colossal amcebiform mass, the plasmo-
dium, not unlike the cytoblastema of a sponge with its amcebiform contents,
out of which by a species of encystment the characteristic fungus-like
sporangia are developed. These sporangia are to a considerable extent
comparable with the hibernating encystments or so-called " gemmules "
of Spongilla and other sponges, and subsequently, through the process
of segmentation, become resolved into innumerable minute spores, which
again give birth to a host of flagellate monadiform zooids resembling those
from whence they originally sprang. It is further remarkable and sugges-
tive of some distant affinity with the Spongida, that the network of fine
interlacing threads, or " capillitium," that frequently binds the enclosed
spores together, closely corresponds with the fine horny fibre of the
keratose sponge-series ; while in the substance of the outer wall or '• peri-
dium " of the sporangia of some Mycetozoa, such as Didymium nigripes and
D. serpula (see PI. X. Figs. 30 and 31), calcareous deposits resembling
sponge spicula are developed.

It is clearly manifest that in a very singular manner, and to a marked

NATURE AND AFFINITIES OF THE SPONGES. 193

extent, the developmental phenomena of the Spongida are productive of
composite structures, the swarm-gemmules or so-called ciliated larvae,
which bear the closest superficial resemblance to the segmented ovum and
primary form and disposition of the component blastomeres of the Metazoic
embryo. Penetrating beneath this superficial likeness, however, the points
of analogy are found to diverge and vanish altogether. No Metazoic em-
bryo, and no Metazoic structure, whatever, is distinguished by the posses-
sion of collared flagellate cells, with their attendant properties and functions,
as found to exist respectively in these ciliated reproductive bodies, in the
essential monadiform constituents of the adult sponge, and among the inde-
pendent Discostomatous Flagellata. It is this one important histologic
element, the collared cell with its attendant physiologic functions, that
so closely unites together the two sections of the Spongida and indepen-
dent Discostomata or Choano-Flagellata, while it isolates them at the same
time from the members of every other organic group. Were the interstitial
canals and chambers of the sponge-stock lined with cells possessing no
contractile vesicles, bearing simply flagella, or corresponding with ordinary
ciliated epithelium, and yet capable of ingesting solid food-matter, the
grounds for removing this organic section into the Metazoic series would
apparently be based on a surer foundation and some analogy would be
presented with the simpler Hydrozoa and many Turbellaria, where, as
shown by Kolliker and Kleinenberg, the endoderm cells lining the ali-
mentary canal develop long flagella or pseudopodic processes, and it
would appear, engulf food-substances after the manner of Amoeba.
Even here, however, the hypothetical analogy would be entirely delu-
sive, the matured sponge-stock being the sum total, not of the concourse
of sexual elements, but of the essentially Protozoic process of spore-
development.

In the fashioning of the motile ciliated gemmules, or pseud-embryos,
upon the plan of the Metazoic morula and amphiblastula, and in the
peculiar arrangement and separation of the constituent flagellate and
amoeboid factors of the adult sponge, nature would certainly seem to have
marshalled her forces preparatory to crossing the border from the Protozoa
to the Metazoa, and so far as a transitional group between the two series
can be predicated, it is probably realized in the section of the Spongida.
The step, as a complete one, however, is by no means accomplished in this
group. As is at once made manifest by a closer insight, the sponges
remain in every detail of structure, function, and development, typical and
thoroughgoing Protozoa. Their position in, and affinities among, the
several groups of this sub-kingdom are evidently close to, and inseparable
from, that of the naked and independent Discostomata or Choano-Flagel-
lata, and which, having due regard to the clearly defined laws of organic
evolution, must be recognized as the ancestral progenitors or archetypes of
all sponge-forms. The phylogeny or backward passage, again, from these
independent collared types to the simpler monadiform Flagellata, is made

O

194 NATURE AND AFFINITIES OF THE SPONGES.

apparent not only in the matured condition of such a form as Phalansterium
— where the collar is rudimentarily developed — but also in the ontogeny
or individual life-history of all other collar-bearing zooids, and which,
whether they belong to the simple and independent Choano-Flagellata or
to the interstitial system of a complex sponge-stock, commence existence
as similar collarless uniflagellate monads.

( 195 )

CHAPTER VI.

SYSTEMS OF CLASSIFICATION OF THE INFUSORIA ADOPTED BY VARIOUS
AUTHORITIES FROM THE TIME OF O. F. MULLER TO THE PRESENT DATE.

CONSIDERABLE advantage being derived from an examination and compa-
rison of the various systems of taxonomy or classification that have at
different epochs been adopted with relation to the assemblage of organisms
described in this treatise, the more important are herewith submitted in
extenso.

Commencing with the earliest essay at such systematic tabulation, as
included by O. F. M tiller in his ' Animalcula Infusoria ' published in the
year 1786, and reproduced at page 199, one is at once struck by the im-
portant influence that was exerted in its formulation by the then rudimen-
tary condition of the optical appliances at the disposal of this authority.
Thus, the entire series of seventeen genera embraced in his scheme are
separated into two leading groups or sections distinguished by their exhi-
bition or not of distinct locomotive appendages as viewed with the imperfect
microscopes of that day. It is now well known, however, that every one of
these, with the single exception of Proteus, possesses either well-developed
cilia or flagella. That exceptional type, with the five Mtillerian genera
Volvox, Vibrio, Gonium, Cercaria, and Brachionus, are necessarily eliminated
from the several classes and orders of the Infusoria as comprehended at the
present day, the remaining eleven, though considerably limited in their
significance, being still retained. The number of specific types included
in Miiller's system, deducting the Rotiferae, Phytozoa, and other extraneous
forms, closely approaches two hundred.

With Ehrenberg's ' Die Infusionsthiere,' a far more extended series of
organisms, and corresponding elaboration of the classificatory system adopted
(see pages 200 and 201), is introduced. The supposed possession by all typical
Infusoria of a distinct oral aperture and numerous gastric cavities, is, as
stated in a previous chapter, the foundation-stone of his system, subordi-
nate to which the presence or, as in the case of Mtiller's system, presumed
absence of locomotive appendages, the character of these appendages, and
location of the oral and excretory apertures, receives attention. The
number of true infusorial forms included in Ehrenberg's magnificent treatise
may be set down as approximating three hundred and fifty, which are
included in sixteen family and eighty generic groups.

Felix Dujardin's ' Histoire des Zoophytes Infusoires,' published in the

O 2

CLASSIFICATION OF THE INFUSORIA.

year 1841, is mostly notable for the distinction given to the Flagellate
section of the Infusoria, many members of which, bearing new generic titles,
were now for the first time figured and described with considerable accu-
racy. These Flagellata, while included in Order III. of his classificatory
system given at page 202, were not, however, invested with any specially
distinctive title.

C. T. Von Siebold's scheme, reproduced at page 203, bearing the date
of 1845, and already referred to at length at page 20, is chiefly remarkable
for its subdivision of the Infusoria into the two primary groups of the
Astomata and Stomatoda ; the former including the Opalinidae and all
the Flagelliferous types, and the latter all the ordinary Ciliata.

The next system demanding notice is that of Maximilian Perty, em-
bodied in his work ' Zur Kenntniss kleinster Lebensformen,' published in
the year 1852. In this treatise marked progress is made upon the classifi-
catory schemes previously noticed. The entire series of infusorial forms
are included in one primary sub-kingdom designated the Archezoa — in
all essential respects synonymous with the Protozoa of Von Siebold — and
its representatives separated into the primaiy sections of the Filigera or
Phytozoida and Ciliata, which practically correspond with the Flagellate
and Ciliate subdivisions as recognized at the present day. Twenty-six
family and one hundred generic groups are comprehended in Perty's classifi-
catory table (see pages 203 and 204), the number of species incorporated
falling short, however, of that made known by Ehrenberg.

Claparede and Lachmann's extensive work, 'Etudes sur les Infu-
soires,' published as a complete treatise in 1868, but which had previously
appeared as separate contributions to the 'Memoirs of the Institute of
Geneva' during the years 1858 to 1860, next demands attention. In
this for the first time we find the Infusoria definitely restricted to the
limits within which they are circumscribed in this volume, the leading sub-
divisions of the entire series included closely corresponding also, as shown
at page 205, with those here accepted as affording the most convenient
and natural arrangement. By promoting, in point of fact, the three orders
of the Infusoria distinguished by these authorities by the titles of the
Flagellata, Suctoria, and Ciliata, to the rank of classes, retaining meanwhile
their fourth group of the Cilio-Flagellata as a subordinate order only of
the class Flagellata, the main basis of arrangement of the extensive series
of forms noticed in this treatise is at once arrived at. It is to be re-
gretted that Messrs. Claparede and Lachmann did not bestow upon the
ordinary Flagellate division the same attention which they gave to the
three remaining groups. But two or three forms only referable to this
important section are described, the order as recognized by them not being
even so much as tabulated. The most important improvements upon the
earlier classificatory schemes accomplished by Messrs. Claparede and Lach-
mann, consist of the introduction of the two groups of the Suctoria and
Cilio-Flagellata, the former being compounded chiefly of forms previously

CLASSIFICATION OF THE INFUSORIA. 197

maintained by Stein to be metamorphic conditions of various Vorti-
cellidae, while the latter one comprised only the family group of the
Peridiniidae.

The classification of Diesing, a compiler and not an independent inves-
tigator, of the present group of organisms, is reproduced (see page 206 et
seq.) so far only as relates to the Flagellate series, he exhibiting a keener
appreciation of their most salient diagnostic characters than had been dis-
played by any previous authority. Taking on trust the dictum of Ehren-
berg, this writer, unfortunately, fell into the error of ascribing to every
member of this group the possession of a distinct oral aperture, which
structure is abundantly shown in this manual to have no definite existence
among a very considerable series. Diesing's peculiar views respecting the
affinities of certain of the Ciliata and Protozoa generally have been referred
to at length at page 25 of Chapter I.

Professor Stein's system, which may be cited as representing the most
advanced views of Continental biologists with reference to the classification
and taxonomy of this highly interesting organic group, demands more
extensive notice. In its concrete form, as reproduced at pages 209 and 210,
such a tabulated list has not yet appeared, it being composed of the scheme
relating to the Ciliata only, embodied by Stein in the second volume of his
'Organismus der Infusionsthiere,' published in the year 1867, to which is
prefixed the list of families with included genera contained in the preface
to his recently issued volume, illustrative of the Flagellata, published at the
close of the year 1878. As previously remarked, no diagnoses or descrip-
tive accounts of the numerous families, genera, or species so abundantly and
admirably figured in this volume have as yet appeared, nor is any attempt
made to subdivide the series as a whole into subordinate sections or orders.
Critical remarks can consequently under present circumstances be passed
only upon his proposed family grouping of the respective genera. In this
connection, exception is here taken, in the first instance, to Stein's admission
among the ranks of the Flagellate Infusoria of the several family groups
of the Volvocina, Chlamydomonadina, and Hydromorina, whose represen-
tatives, with one or two exceptions, must undoubtedly, as first insisted by
Von Siebold, be referred to the vegetable kingdom. Their claim for admis-
sion to Stein's scheme is, while the inevitable sequence of the very shallow
basis upon which he considers the proof of their animal organization to be
substantiated — that only of the possession of a nucleus and contractile
vesicle — by no means supported by the verdict of such modern authorities
as Cohn, Sachs, and Pringsheim, by all of whom Volvox and its allies more
especially are relegated without hesitation among the lower Algals or Pal-
mellaceae. The broad distinction insisted upon by these writers as subsist-
ing between unicellular plants and animals is identical with that already
submitted by the author at page 36 et seq., namely — the capacity of such
animal forms to incept and digest food-matter in its solid state, and the cor-
responding absence of such an ingestive faculty in all vegetable organisms.

I 98 CLASSIFICA TION OF THE INFUSORIA.

With scarcely an exception, none of the generic types included in Stein's
three family groups just cited possess this ingestive property, and are
consequently here refused admission within the essentially zoologic section
of the Infusoria.

With reference to the remaining twelve Flagellate family groups included
in Stein's classificatory system, some few, such as those of the Dendromo-
nadina, Spongomonadina, Craspemonadina, Bikcecida, and Chrysomonadina,
beyond doubt contain genera that exhibit well-marked natural affinities.
Others, such as his Monadina, Astasiae, and Scytomonadina, comprise the
most incongruous elements, mouthed and mouthless, uniflagellate, biflagel-
late, and multiflagellate animalcules being indifferently intermingled.
Phalansterinin, a uniflagellate collared monad, is interpolated amongst the
otherwise natural biflagellate group of the Spongomonadina, and with which,
excepting for the secretion of a similar gelatinous zoocytium, the animal-
cules possess nothing in common. Poteriodendron, again, while represented
in the figures given and accompanying index as possessing a collar homo-
logous with that of Codosiga and its allies, but somewhat differently situated,
instead of being placed among the Craspemonadina, is included in the family
group of the Bicoscecidse. Stein's apparently inconsistent location of Pote-
riodendron is nevertheless important, since it entirely supports the views
concerning this type expressed on a succeeding page, and where it is held
by the author to be actually a biflagellate organism closely allied to
Bicosccca and synonymous with the Dinobryon petiolatum of Dujardin and
the Stylobryon petiolatum of De Fromentel. The separation of the two
genera Epipyxis and Dinobryon from all the other generic groups of the
Chrysomonadina, with which in structure they fundamentally agree, is
entirely artificial.

The scheme proposed by Stein for the subdivision into groups or orders
of the Ciliate section of the Infusoria, such orders being distinguished by
the titles of the Holotricha, Heterotricha, Hypotricha, and Peritricha, leaves,
so far as our present knowledge extends, nothing to be desired, and is
cordially adopted in the present work.

The system introduced by the author, and adopted for the purposes of
classification and taxonomy throughout this treatise, alone awaits notice. Its
chief features of distinction, as connected with the several schemes previously
enumerated, are naturally connected with the class Flagellata, upon which
the author's attention has for many years past been more exclusively con-
centrated. The result of such investigation has been the discovery of forms
differing so widely from the previously known representatives of this group,
that the introduction of new distinctive titles having the value of Orders,
and carrying with them as thoroughgoing a significance as the foregoing
ordinal appellations of the class Ciliata, has been rendered necessary. The
broad grounds upon which these new orders are established — chiefly based
upon the modifications exhibited by the oral system and appendicular struc-
tures— have been already discussed in Chapters II. and III., and are also

MULLERS CLA SSI PICA TOR Y S YSTEM. 1 99

succinctly indicated in connection with the abbreviated diagnoses of the
subordinated family and generic groups in the tabular forms prefixed to the
succeeding descriptive accounts of each more important group. So far as
practical, the family names given in the systems of the earlier authorities
quoted have been retained, with the simple adaptation of their terminal
syllables in conformance with the recommendations of the British Associa-
tion contained in their " Rules for Zoological Nomenclature " issued in the
year 1878. In face, nevertheless, of the vast augmentation of specific types
collected from every available source, many of them now figured and
described in this volume for the first time, a corresponding increase of the
number of family and generic titles has been unavoidable. Taken in their
entirety, no less than nine hundred infusorial species, distributed among
about eighty family and three hundred generic groups, are embraced by
the author's system, being a sum total of more than double the number
included in any previous treatise.

O. F. MULLER, ' Animalcula Infusoria,' 1786.

INFUSORIORT7M DIVISIO METHODICA.

I. ORGANIS EXTERNIS NULLIS.

* Crassiuscula.

Gen. i. MONAS : punctiforme.
„ 2. PROTEUS : mutabile.
„ 3. VOLVOX : sphaericum.
„ 4. ENCHELIS : cylindricum.
„ 5. VIBRIO : elongatum.

** Membranacea.

Gen. 6. CYCLIDIUM : ovale.
„ 7. PARAM^CIUM : oblongum.
„ 8. KOLPODA : sinuatum.
„ 9. GONIUM : angulatum.
„ 10. BURSARIA : cavum.

II. ORGANIS EXTERNIS.

* Nuda.

Gen. i. CERCARIA : caudatum.
„ 2. TRICHODA: crinitum.
,, 3. KERONA : corniculatum.

Gen. 4. HIMANTOPUS : cirratum.
„ 5. LEUCOPHRA : ciliatum undique.
„ 6. VORTICELLA : ciliatum apice.

** Test& tecta.
Gen. 7. BRACHIONUS : ciliatum apice.

2OO

EHRENBERGS CLASSIFICATORY SYSTEM.

<$

FAMILY.
Monadina.

«

Vibrionia.

Clostcrina.

Astasiaa.

Dinobryina.
. Amcebcea.

Arcdlina.
Bacillaria.

Cydidina.

PeridincRa.

Vorticellina.
, Ophry 1ina

i 1 .< . -i <

1 11 11 ill
1 Ililtli

i— i

H3 K

>

>

•— <

HH S

X X

>— i

< — i

j ^
3 """*

Kj ^ HH HH lj J-J 1-4 »-5

j^j ^ HH i— ' ^ n jxj M

> >

HH

^ K^^t^K^XO^
rS ^ t^ rS rS S^

HH

. «2

' rt
y
°C

c

O

' 2f

' O

HH

^

* *

• &

*

'

CO

t-^.

rt

.

»

<U

bO 'bo

i

t

H->

O

g

en

•S 2

I— t •

• C

: Ǥ

<U

;

(3 oo

;

: •

: : : : J :

w

p4

_o

'•u

fl*
c/5 /-**

H

o |

"rt o t*^

•M C^H 1) •

ffl :

; o

3 -B

£3

*"ijQ M

.

. 4

: : o ja : : C •

^^

EH

u,

rt O

ci

C O

C <U p

ro

•3

bo 1>

T3

'55 <u

- > .^

00

Ci|

<L>

.

.

.

. .

M

o

^*

bo ^

Q-i

o

^o ^*^

•>

****

8

op D

j5

2 2

o ^ °

<u

CO

(\\

5

"To

•

•

0 0

•

•

•

; • rQ 2 • t« ;

0)

W

to

T3

•> ' >-> ^

1

i— i

^

£ -S

aS

cJ bO

k • X •' f% 19 •

c/l

a
_o

t— 1 U

< -1

o bo

_o -r3

2 bC
bO _C

bO •S

_C
bo

11

" -| J ' .a 2

^2

hM O

'§ '^

2 :>

.2

I

'.

rO O
£3 J-i

•

•

* '^* ^ * /» O

q

o 3

J Q

(X) •— •

O CJ rt

• OH o_ ^* C •

G. EHRENBERG, '

S TWENTY-TW
( Fission com- (

plete. j
Fission incom- (

. X
5 G

5 o
c "3

*-> "y

"ft M

_— -~

c/5

(A

1 Illoricate

j Loricate . .

>. &l

c o

ri "^

II

S'bb
•^ .2

O 'in

I

•

; ;

• • * § • .§ g •

ja J w ^

• 3 . bo bO •

• 'S $ * .2 .2 *

05 03

. . -5 -5 . S S .

« • 3 3 « to 01 .

Jo g §
. <5 S . PH PH

oj

ffi

.

PH •<

.

,

H

±i

ft

'"—

•

0

CO

2

^«^-

I

2

^ changeal
f Illoricate

1

i Loricate

1 Illoricate

1 Loricate

Illoricate
Loricate

O O O -

OdS ft Q n
.-H O .rt O ..5 O

»i -r* »•« T1 *-" T!

.2 o .2 o ^ o

HH t—5 HH 1-1 HH 1-3

0

g

— vx

4-> •— J

rt "13 ?^

1

6

B
0
t

a

-a -c^

S-i

o 5
«2>

T3

1

'M -^

<A s-^. o> is

S ^ -S tny^-N C^

^s^ «^« ^^

%>k 2 t-H %i "^ JO
fcnW.'a B w * '"-b

-

R

i ">3

V .t« <H IH ^" S *> ^

E

a
c
2

°0^

f**±

0

§

P

ftoos; (Uu-x; '-'<.

^a§ ^e^ 2,3
i&a J~ £~

H ^ <

_j>

"

oT

u

.2

*$

S3
'w "1

tn

%>

<D *^J

<J •g

s

^ .s i

/-N

rri

js "«

EHRENBERG'S CLASSIFICATORY SYSTEM. 2OI

EHRENBERGIAN GENERA INCLUDED IN THE FOREGOING SYNOPSIS.

FAMILY.

I. MONADINA .

II. CRYPTOMONADINA

III. VOLVOCINA .

IV. VlBRIONIA . .

V. CLOSTERINA

VI. ASTASI^EA ..
VII. DlNOBRYINA

VIII. AMCEB^A ..

IX. ARCELLINA . .

X. BACILLARIA . .

XI. CYCLIDINA ..

XII. PERIDIISLEA . .

XIII. VORTICELLINA

XIV. OPHRYDINA
XV. ENCHELIA

XVI. COLEPINA ..

XVII. TRACHELINA

XVIII. OPHRYOCERCINA
XIX. ASPIDISCINA

XX. COLPODEA ..
XXI. OXYTRICHINA
XXII. EUPLOTINA .

Genus i, Monas ; 2, Uvella ; 3, Polytoma ; 4, Micro-
glena; 5, Phacelomonas ; 6, Glenomorum ;
7, Doxococcus ; 8, Chilomonas ; 9, Bodo.

„ i, Cryptomonas ; 2, Ophidomonas ; 3, Proro-
centrum ; 4, Lagenella ; 5, Cryptoglena ;

6, Trachelomonas.

» r> Gyges ; 2, Pandorina; 3, Gonium ; 4, Syn-
crypta; 5, Synura ; 6, Uroglena; i,Eudo-
rina ; 8, Chlamydomonas ; 9, Spharosira ;
10, Volvox.

„ i, Bacterium; 2, Vibrio; 3, Spirochata ,•
4, Spirillum ; 5, Spirodiscus.

„ i, Closterium.

„ i, Astasia ; 2, Amblyophis ; 3, Euglena ;
4, Chlorogonium ; 5, Colacium ; 6, Z>/-
stigma.

„ i, Epipyxis ; 2, Dinobryon.

,, i, Amoeba.

„ i^Difflugia', 2,Arcella; 3, Cyphidium.

„ (DESMIDIACE^;) ; (DFATOMACE^;); Acineta.

„ i, Cyclidium; 2,Pantotrichum ; 3, Chtetomonas.

„ i, Chatotyphla; 2, Chcetoglena ; 3, Peridinium ;
4, Glenodinium.

„ i, Stentor ; 2, Trichodina ; 3, Urocentrum ;
4, Vorticella ; ^Carchesium; 6, Epistylis ;

7, Opercularia; 8, Zoothamnium.

„ i, Ophrydium; 2, Tintinnus ; 3, Vaginicola ;
4, Cothurnia.

„ i, Enchelys ; 2, Disoma ; 3, Actinophrys ; 4, 7h-
chodiscus ; 5, Podophrya ; 6, Dendrosoma ;
7, Trichoda; 8, Lacrymaria ; 9, Leuco-
phrys ; 10, Holophrya; n, Prorodon.

„ i, Coleps.

„ i, Trachdivf ; 2,Loxodes; $,Bursaria; ^Spi-
rostomum; 5, Phialina ; 6, Glaucoma;
7, Chilodon; 8, Nassula. •

„ i, Trachelocerca.
„ i, Aspidiscus.

„ i, Colpoda; 2, Paramecium; 3, Amphileptus ;
4, Uroleptus ; 5, Ophryoglena.

„ i, Oxytricha ; 2, Ceratidium ; 3, Kerona ;
4, Urostyla; 5, Stylonychia.

„ i , Discocephalus ; 2, Himantophorus ; 3, Chlamy-
dodon; 4, Euplotes.

202 DUJARDIWS CLASSIFICATORY SYSTEM.

F. DUJARDIN, ' Histoire des Zoophytes Infusoires,' 1841.

SECTION I. ASYMMETRICA.

Order I. INFUSORIA WITHOUT VISIBLE LOCOMOTIVE APPENDAGES.

Family i. VIBRIONINA : Gen. Bacterium, Vibrio, Spirillum (Spirochata Ehr., Spiro-
discus Ehr.).

Order II. INFUSORIA PROVIDED WITH VARIABLE EXPANSIONS.
„ 2. AMCEBINA : Gen. Amoeba.
„ 3. RHIZOPODA: QzK.ArceUa(CyphidiumT8n:.},Difflugia,Trinema,Euglypha,

Gromia, Miliola, Cristdlaria, Vortirilialis.
„ 4. ACTINOPHRYINA : Gen. Actinophrys (Peritricha Bory, Podophrya Ehr.),

Acineta, Dendrosoma.

Order III. INFUSORIA PROVIDED WITH ONE OR MORE FLAGELLIFORM

APPENDAGES.

Family 5. MONADINA : Gen. Monas, Cydidium, Cercomonas, Amphimonas, Trepo-

monas, Chilomonas, Hexamita, Heteromita (Bodo Ehr.), Trichomonas,

Uvdla (Polytoma Ehr.), Anthophysa.
„ 6. VOLVOCINA : Gen. Volvox, Pandorina (Eudorina Ehr.), Gonium (Pectora-

lina Bory), Uroglena (Syncrypta Ehr.).
„ 7. DINOBRYINA : Gen. Dinobryon, Epipyxis.
„ 8. THECAMONADINA : Gen. Trachdomonas (Chcetotyphla Ehr., Chatoglena

Ehr.), Cryptomonas (Cryptoglena,'Ehr.), P/iacus, Crumenula,Prorocentrum,

Disdmis (Chlamydomonas Ehr.), Anisonema, Plceotia, Oxyrrhis.
„ 9. EUGLENINA : Gen. Peranema, Astasia, Euglena (Raphanella Bory, Ambly-

ophis Ehr., Chlorogonium Ehr.), Colacium, Distigma, Zygoselmis, Hdero-

nema, Polysdmis.
„ 10. PERIDININA : Gen. Peridinium (Glenodinium Ehr.), Ceratium.

Order IV. CILIATE INFUSORIA.

„ 1 1. ENCHELINA : Gen. Acomia, Gastrochata, Enchelys, Alyscum, Uronema.
„ 12. TRICHODINA : Gen. Trichoda, Trachelius, Acineria, Pdecida, Dileptus.
„ 13. KERONINA : Gen. Halteria, Oxytricha (Uroleptus Ehr., Urostyla Ehr.),

Kerona (Stylonychia Ehr.).
„ 14. PLCESCONINA : Gen. Plcesconia (Euplotes Ehr., Discocephalus Ehr.,

Himantophorus Ehr.), Chlamydodon, Diophrys, Coccudina, Aspidisca,

Loxodes.

„ 15. ERVILINA : Gen. Ervilia, Trochilia.
,, 1 6. LEUCOPHRYINA : Gen. Spathidium, Leucophrys, Opalina.
„ 17. PARAMECINA : Gen. Lacrymaria (Straulema Bory, Phialina Ehr.), Pleuro-

nema, Glaucoma, Kolpoda, Paramedum, Amphileptus, Loxophyllum,

Chilodon, Panophrys, Nassula, Holophrya, Prorodon.
„ 1 8. BURSARINA: Gen. Plagiotoma, Ophryoglena, Bursaria, Spirostoma, Kondylo-

stoma.

„ 19. URCEOLARINA : Gen. Stentor, Urceolaria, Ophrydium, Urocentrum.
„ 20. VORTICELLINA : Gen. Scyphidium, Epistylis, Opercularia, Vorticdla,

Vaginicola.

SECTION II. SYMMETRICA.
Genus Coleps.

CLASSIFICATORY SYSTEMS OF SIEBOLD AND OF PERTY. 203
C. T. VON SIBBOLD, 'Lehrbuch der Vergleichenden Anatomic,' 1845.

Class INFUSORIA.

ORDER I. ASTOMA (no oral aperture).

Family i. ASTASI^EA : Gen. Amblyophis, Euglena, Chlorogonium.
„ 2. PERIDIN^EA : Gen. Peridinium, Glenodinium.
„ 3. OPALIN^EA : Gen. Opalina.

ORDER II. STOMATODA (with a distinct oral aperture).

„ 4. VORTICELLINA : Gen. Stentor, Trichodina, Vorticella, Epistylis, Car-
chesium.

„ 5. OPHRYDINA : Gen. Vaginicola, Cothurnia.

„ 6. ENCHELIA : Gen. Actinophrys, Leucophrys, Prorodon.

„ 7. TRACHELINA: Gen. Glaucoma, Spirostomum, Trachelius, Loxodes, Chilo-
don, Phialina, JBursaria, Nassula.

„ 8. KOLPODEA : Gen. Kolpoda, Paramecium, Amphileptus.
,, 9. OXYTRICHINA: Gen. Oxytricha, Stylonychia, Urostyla.
„ 10. EUPLOTA : Gen. Euplotes, Himantophorus , Chlamydodon.

MAXIMILIAN PERTY, ' Kleinster Lebensformen,' 1852.

Sub-Kingdom ARCHEZOA.
Class INFUSORIA.

SECTION I. PHYTOZOIDIA (Filigera).

Family i. UINOBRYINA : Dinobryon.

„ 2. VOLVOCINA: Syncrypta,Voh'ox,Spharosira,Pandorina,Synaphia,Gonium,
Hirmidium.

„ 3. MONADINA : Heteromitus, Ampkimonas, Tetramitus, Trichomonas, Mallo-
monas, Pleuromonas, Trepomonas, Spiromonas, Cercomonas, Monas,
Menoidium, Chromatium, Acari&um, Polytoma, Uvel/a, Anthophysa.

,, 4. AsTASiiE : £ug/e/ia, Astasia, Peranema, Colacium, Eutreptia, Chloro-
gonium, Zygoselmis, Dinema.

„ 5. THECOMONADINA : Chatotyphla, Trypemonas, Chonemonas.

,, 6. CRYPTOMONADINA : Cryptomonas, Phacotus, Anisonema, Phacus, Lepo-

cindis
„ 7. PERIDINIDA : Ceratium, Glenodinium, Peridinium.

2 04 PER TV'S CLASS I PICA TOR Y SYS TEM.

SECTION II. CILIATA (non-vibratile, slightly contractile cilia).
Family 8. ACTINOPHRYINA : Actinophrys, Podophrya, Acineta.

A. METABOLICA (highly contractile and changeable in form).
„ 9. OPHRYOCERCINA : Trachelocerca, Lacrymatia.

B. M ONI MA (contractile, but without jerking action or alteration of contour).

„ 10. COLEPINA : Coleps.

„ ii. EUPLOTINA : Euplotes, Himantophorus, Coccudina, Aspidisca.

„ 12. COBALINA : Alastor, Plagiotoma, Leucophrys, Opalina.

„ 13. OXYTRICHINA : Stichotriclia, Mitophora, Oxytricha, Urostyla, Cerona.

„ 14. TRACHELINA : Trachelius, Harmodirus, Amphileptus, Loxophyllum,
Dilepfus, Pelecida, Loxodes.

„ 15. TAPINIA : Acropisthium, Acomia, Trichoda, Cyclidium, Boeonidium, Opis-
thiotricha,) Siagontherium, Megatricha.

„ 1 6. APIONIDINA : Ptyxidium, Colobidium^ Apionidium.

„ 17. CINKTOCHILINA : Glaucoma, Cinetochilum.

„ 1 8. DECTERIA : Cyclogramma, Chilodou, Nassula, Prorodon, Habrodon.

„ 19. APHTHONIA: Pleuronema.

„ 20. HOLOPHRYINA : Holophrya, Enchefys, Spathidium.

„ 21. PARAMECIINA : Ophryoglena, Panophrys, Parameeium, Blepharisma,
Colpoda.

„ 22. BURSARINA : Bursarid.

C. SPASTIC A (contractile, form changeable, with a jerking action).

„ 23. URCEOLARINA : Stentor, Spirostomum, Canomorpha, Urocentrum.

„ 24. OPHRYDINA : Ophrydium.

„ 25. VORTICELLINA : Vorticella, Scyphidia, Epistylis.

„ 26. VAGINIFERA : Vaginicola, Cothurnia.

CLAPAREDE AND LACHMANWS CLASSIFICATORY SYSTEM.

CLAPAREDE AND LACHMANN, 'Etudes sur les Infusoires,' 1858-1860.

ORDER I. FLAGELLATA. (Not tabulated.)

ORDER II. CILIO-FLAGELLATA.

Family i. PERIDININA : Ceratium, Peridinium, Dinophysis, Amphidinium, Proro-
centrum.

ORDER III. SUCTORIA.

„ 2. ACINETINA : Podophrya, Spharophrya, Trichophrya, Acineta^ Solenophrya,
Dendrosoma, Dendrocometes, Ophryodendron.

ORDER IV. CILIATA.

„ 3. HALTERINA : Strombidium, Halteria.
„ 4. COLEPINA : Coleps,

„ 5. TRACHELINA : Loxophyllum, Amphilepttts, Trachelius, Loxodes, Trichopus,
Chilodon, Nassula, Prorodon, Enchelyodon, Urotricha, Holophrya,
Enchelys, Trachdophyllum, Phialina, Lacrymaria.

„ 6. DYSTERINA : ffux!eya, (Egyria, Dysferia, Iduna.

,, 7. COLPODINA : Glaucoma, Pleuronema, Cydidium, Colpoda, Paramedum.

„ 8. BURSARINA : Ophryoglena, Bursaria, Frontonia, Metopus, Lembadium,
Balantidium, Kondylostoma, Plagiotoma, Spirostomum, Leucophrys,
Stentor, Freia, Chcetospira.

„ 9. TINTINNODEA : Tintinnus.

,, 10. OXYTRICHINA: Aspidisca, Campy lopus, Schizopus, Euplotes, Stylonychia,
Stichochata, Oxytricha.

,, ii. UROCENTRUM : Urocentrum.

„ 12. VORTICELLINA : Trichodina, Lagenophrys, Vaginicola, Cothurnia, Ophry-
dium, Gerda, Scyphidia, Epistylis, Zoothamnium, Carchesium, Vorticella,
(Spirochond).

2 06 DIES ING'S CLA SSI PICA TOR Y SYS TEM.

R. M. DIESING, 'Revision der Prothelminthen.' Abtheilung Mastigophoren, 1865.

Sub-Order MASTIGOPHORA.

TRIBUS I. MASTIGOPHORA ATRICHOSOMATA (Corpus nudum}.

Fam. I. MONADINEA.
Sub-Fam. I. Monadinea baud loricata.

* ACERCOMONADINEA (Corpus ecaudatuni).
t Os terminate (Acrostomata).

MONOMASTIGA (Flagellum ununi).

Animalcula monima.

Gen. Monas, Uvella, Anthophysa, Micro-
glena, Glenouvella.

Animalcula metabolica.
Gen. Peranema, Amblyophis, Coladum.

DIMASTIGA (Flagella duo).
Gen. Isomita, Dimastix, Glenomorum, Trepanomonas.

TETRAMASTIGA (Flagella quatuor).

Animalcula monima. Animalcula metabolica.

Pyramimonas. Polyselmis.

POLYMASTIGA (Flagella 6, 10, out numeroso).
Gen. Chloraster, Spondylomorum, Phacelomonas, Lophomonas.

\\ Os inpagina ventrali (Hypostomata).
MONOMASTIGA.

Animalcula monima. I Animalcula metabolica.

Gen. Plagiomastix. Gen. Pyronema.

DIMASTIGA.

Animalcula monima.

Gen. Heteromita, Chilomonas, Polytoma,
Glenopolytoma.

Animalcula metabolica.
Gen. Zygoselmis, Heteroncrna.

Genera insufficienter cognita, Gorgostomum, Doxococcus, Menoidium.

** CERCOMONADINEA (Corpus caudatum).

t Os terminate (Acrostomata},

MONOMASTIGA.

Animalcula monima.
Gen. Bodo, Thaumas, Dicercomonas.

Animalcula metabolica.
Gen. Astasia, Euglena.

DIESINGS CLASSIFICATORY SYSTEM. 207

DlMASTIGA.

Animalcula monima. Animalcula metabolica.

Gen. Amphimonas. Gen. Chlorogonium.

ft Os in pagina ventrali (Hypostomatd).
Gen. Trichomonas.

Sub-Fam. II. Monadinea loricata.

t Os terminate (Acrostomata).

a. CORPUS LOR ICO INSTRUCTUM.

MONOMASTIGA.

Animalcula monima.
Gen Cryptomonas, Petalomonas, Ophi-

Animalcula metabolica.
Gen. Lepocinctis.

domonas, Crumenula.

DlMASTIGA.

Gen. Diseeraa, Diplotricha, Anisonema, Cryptoglena.

TETRAMASTIGA.
Gen. Phacotus, Carteria.

/3. CORPUS URCEOLO CIRCUMDATUM.
MONOMASTIGA.

Animalcula monima.

Gen. Lagenella, Trachelomonas, Chato-
typhla, Chcetoglena.

Animalcula metabolica.
Gen. Dinobryon.

Genus insufficienter cognitum, Epipyxis,

DlMASTIGA.

Gen. Chonemonas.

tt Os inferum (Hypostomata).
Gen. Oxyrrhis,

Fam. II. VOLVOCINEA.
* VOLVOCINEA EC A UD ATA.

MONOMASTIGA.

Corpus urceolo indusum vel lacerna involutum.
Gen. Pandorina, Eudorina, Syncrypta.

2O8 DIESINGS CLASSIFICATORY SYSTEM.

DlMASTIGA.

Syncecesium subglobosum.
Gen. Stephanosphczra, Glceococcus^ Chlamydomonas, Chlamydococcus, Volvox.

Syncecesium tabulare.
Gen. Gonium, Glenogonium.

Genus insufficienter cognitum, Trochogonium.

Syncecesium lineare.
Gen. Hirmidium.

** VOLVOCINEA CAUDATA.
Gen. Uroglena.

Genus insufficienter cognitum, Synura.

TRIBUS II. MASTIGOPHORA TRICHOSOMATA (Corpus ciliatum).
Fam. III. MALLOMONADINEA.

Sub-Fam. I. Mallomonadinea haud loricata.
Gen. Mallomonas.

Sub-Fam. II. Mallomonadinea loricata.
Gen. Prorocentrum.

Fam. IV. PEBIDINEA.
t Os terminate (Acrostomatd).

MONOMASTIGA.

Gen. Heteroaulax, Gonyaulax, Glenoaulax.

ft Os in pagina ventrali (Hypostomata).

MONOMASTIGA.

* Lorica suleo transversali antrorsum vel retrorsum collocate.
Gen. Proaulax, Amphidinium, Dinophysis.

** Lorica sulco transversali in medio fere corporis collocato.
Gen. Peridinium, Glenodinium.

DlMASTIGA.

Gen Dimastigoaulax.

S TEIN'S CLA SSIFICA TOR Y S Ki TEM. 209

F. STEIN, 'Organismus der Infusionsthiere,' Abtheilung III. (Flagellata), Heft i,

1878.

Class I. FLAGELLATA.

Family i. MONADINA : Cercomonas, Monas, Goniomonas, Bodo, Phyllomitus, Tetra-
mitus, Trepomonas, Trichomonas, Hexamita, Lophomonas, Platytheca.

,, 2. DENDROMONADINA : Dendromonas, Cephalothamnium, Anthophysa.

„ 3. SPONGOMONADINA : Cladomonas, Rhipidodendron, Spongomonas, Phalan-
sterium,

„ 4. CRASPEMONADINA : Codonosiga, Codonocladium, Codonodesmus, Salpingceca.
,, 5. BIKCECIDA : Bikceca, Poteriodendron.
„ 6. DINOBRYINA : Epipyxis, Dinobryon.

„ 7. CHRYSOMONADINA : Coelomonas, Raphidomonas, Microglena, Chrysomonas,
Uroglena, Syncrypta, Synura, ffymenomonas, Sty lochry sails, Chrysopyxis.

„ 8. CHLAMYDOMONADINA : Polytoma, Chlamydomonas, Chlamydococcus, Pha-
cotus, Coccomonas, Tetraselmis, Gonium.

„ 9. VOLVOCINA : Eudorina, Pandorina, Stephanosphczra, Volvox.

„ 10. HYDROMORINA : Chlorogonium, Chlorangium, Pyramidomonas, Chloraster,
Spondylomorum.

„ ii. CRYPTOMONADINA : Chilomonas, Cryptomonas, Nephroselmis.

„ 12. CHLOROPELTIDEA : Cryptoglena, Chloropeltis, Phacus.

„ 13. EUGLENIDA : Euglena, Colacium, Ascoglena, Trachdomonas.

„ 14. ASTASI^EA : Eutreptia, Astasia, Hetcronema, Zygoselmis, Perancma.

„ 15. SCYTOMONADINA : Scytomonas, Petalomonas, Menoidium, Atractonema^
Phialonema, Sphenomonas, Tropidocyphus, Anisonema, Colponcma,
Entosiphon.

P

2 I O ^ TEIWS CLASS I PICA TOR Y S YSTEM.

F. STEIN, 'Organismus der Infusionsthiere,' Heft 2, 1867.

Class II. CILIATA.

ORDER I. HOLOTRICHA.

Family i. OPALININA : Opalina, Hoplophrya, Anoplophrya, Haplophrya (Disco-
phrya).

„ 2. TRACHELINA : Amphilcptus, Loxophylhnn, Loxodes, Trachelius, Dileptus.
„ 3. ENCHELINA : Trachelophyllum, Trachcloccrca, Phialina, Lacrymaria, Enchc-

lyodon, Enchelys, Coleps, Plagiopogon, Perispira, Urotricha, Actinobolus,

Holophrya, Prorodon.

„ 4. PARAMUECINA : Sub-Fam. a, Paramaecina : Cyrtostomum, Nassula (Lio-
siphon, Cyc/ogramma,Acidophorus),Parama:aiim, Colpoda, Ptychostomnm,
Conchophthirus , Isotricha. Sub-Fam. b, Leucophryina : Colpidium,
Leucophrys, Panophrys.

„ 5. CINETROCHILINA : Ophryoglena, Glaucoma, Cinetrochilum, Pleurochili-
dium, Trichoda, Cydidium, Plagiopyla, Pleuronema, Lembadion.

ORDER II. HETEROTRICHA.

„ i. BURSARINA : Plagiotoma, Metopus, Nyctotherus, Balantidium, Bursaria,

„ 2. STENTORINA : Freia, Stentor.

„ 3. SPIROSTOMEA : Climacostomum, Spirostomum, Blepharisma, Condylostoma.

ORDER III. HYPOTRICHA.

„ i. PERITROMINA : Peritromus.

„ 2. CHLAMYDODONTA : Chilodon, Opisthodon, Trichopus, Phascolodon, Chlainy-
dodon, Scaphidiodon.

„ 3. ERVILIINA (Duj.) : Huxleya, Trochilia, Ervilia (Dysteria, Iduna).

„ 4. ASPIDISCINA (Ehr.) : Aspidisca.

„ 5. EUPLOTINA (Ehr.) : Uronychia, Styloplotes, Euplotes.

„ 6. OXVTRICHINA : Urostyla, Epidintes, Kerona, Stichotricha, Uroleptus,
Gastrostyla, Pleurotricha, Onydiodromus, Stylonychia, Oxytricha, Psilo-
tricha.

ORDER IV. PERITRICHA.

„ i. HALTERINA (C. & L.) : Strombidium, Halteria.

„ 2. TINTINNODEA (C. & L.) : Tintinnopsis, Tintinnus.

„ 3. CYCLODINEA : Mesodinium, Didinium, Urocentrum.

„ 4. GYROCORIDA : Gyrocorys.

„ 5. URCEOLARINA: Trichodinopsis, Trichodina, Urceolaria.

„ 6. VORTICELLINA (Ehr.) : Astylozoon, Gerda, Scyphidia, Vorticdla, Carche-
sium, Zootfiamnium, Epistylis, Opercularia.

„ 7. OPHRYDINA (Ehr.) : Ophrydium, Vaginicola, Cothurnia, Lagenophrys.

„ 8. SPIROCHONINA : Spirochona.

„ 9. OPHRYOSCOLECINA : Entodinium, Ophrycscolex.

A UTHOKS CLASSIFICA TOR Y S YSTEM. 2 1 1

CLASSIFICATORY SYSTEM ADOPTED IN THIS VOLUME.

Sub-Kingdom PROTOZOA.
Legion INFUSORIA.

Class I. FLAGELLATA vel MASTIGOPHORA.

Order I. TRYPANOSOMATA.

Genus I, Trypanosoma.

Order II. RHIZO-FLAGELLATA.

Genus I, Mastigamceba ; 2, Reptomonas ; 3, RJusomonas ; 4, Podostoma.

Order III. RADIO-FLAGELLATA.

FAMILY.

I. ACTINOMONADID^L : Genus I, Actinomonas .

II. EUCHITONID^: : Genus I, Euchitonia ; 2, Spongocyclia ; 3, Spong-
asteriscus.

Order IV. FLAGELLATA-PANTOSTOMATA.

I. MON ADIDAS: Genus i, Monas ; 2, Scytomonas ; 3, Cyathomonas ;
4, Leptomonas ; 5, Ophidomonas ; 6, Herpetomonas ; 'j.Ancyromonas.

II. PLEUROMONADID^E : Genus i, Pleuromonas ; 2, Merotricha.

III. CERCOMONADID./E : Genus i, Oikomonas ; 2, Bodo ; 3, Cercomonas.

IV. CoDONCEClDyE : Genus I, Codonceca ; 2, Platytheca.

V. DENDROMONADID/E : Genus i, Physomonas ; 2, Cladonema; i,Den-
dromonas ; 4, AntJiopJiysa ; 5, Ccphalothamnium.

VI. BlKCECID^: : Genus i, Hedraophy sa ; 2, Bicosceca ; 3, Stylobryon.

VII. AMPHIMONADID/E : Genus I, Goniomonas ; 2, A mphimonas ; 3, Delta-
monas.

VIII. SPONGOMONADID^E : Genus i, Cladomonas ; 2, Rhipidodendron ;
3, Spongomonas ; 4, Diplomita.

P 2

212 A UTHOKS CLA SSI PICA TOR Y S YS TEM.

FAMILY.

IX. HETEROMITID^: : Genus I, Heteromita ; 2, Colponema ; 3, Spiro-
monas ; 4, Phyllomitus.

X. TREPOMONADID^E : Genus i, Trepomonas.
XI. POLYTOMID^: : Genus I, Polytoma.
XII. PSEUDOSPORID^I : Genus I, Pseudospora.

XIII. SPUMELLID^E : Genus i, Spumella.

XIV. TRIMASTIGID^E : Genus i, Callodictyon ; 2, Trichomonas ; 3, Dal-

lingeria ; 4, Trimastix.

XV. TETRAMITID/E : Genus i, Tetramitus ; 2, Tetraselmis ; 3, Chlo-
raster.

XVI. HEXAMiTiDyE : Genus i, Hexamita.
XVII. LOPHOMONADID^: : Genus i, Lophomonas.
XVIII. CATALLACTID/E : Genus i, Magosphara.

Order V. CHOANO-FLAGELLATA vel FLAGELLATA-DISCOSTOMATA.

Section I. DlSCOSTOMATA-GYMNOZOIDA.

I. CODONOSIGID^: : Genus i, Monosiga ; 2, Codosiga ; 3, Astrosiga ;
4, Desmarella.

II. SALPINGCECID,£ : Genus i, Salpingceca; 2, Lagenceca ; 3, Polyoeca.
III. PHALANSTERIID^E : Genus i, PJialansterium ; 2, Protospongia.

Section II. DISCOSTOMATA-SARCOCRYPTA (Spongida).

Order VI. FLAGELLATA-EUSTOMATA.

I. PARAMONADlD^i : Genus i,Paramonas ; 2, Petalomonas ; $,Atrac-
tonema ; 4, Phialonema ; 5, Menoidium.

II. ASTASIAD^E : Genus i, Astasia ; 2, Colpodella.

III. EUGLENlDyE: Genus i, Etiglena ; 2, Amblyophis ; 3, Phacus ;

4, Chloropeltis ; 5, Trachelo monas ; 6, Raphidomonas ; 7, Ccelo-
monas ; 8, Ascoglena ; 9, Colacium.

IV. NOCTILUCID^E : Genus I, Noctiluca ; 2, Leptodiscus.

V. CHRYSOMONADID^E : Genus I, Chloromonas ; 2, Chrysomonas ;
3, Microglena ; 4, Cryptomonas ; 5, Nephroselmis ; 6, Stylo-
chrysalis ; 7, Uvella ; 8, Chlorangium ; 9, Hymenomonas ;
10, Chrysopyxis ; u, Epipyxis ; 12, Dinobryon ; 13, Synura ;
14, Syncrypta ; 15, Uroglena.

A UTHOR'S CLA SSI PICA TOR Y S YSTEM. 2 1 3

FAMILY.

VI. ZYGOSELMID^: : Genus I, Eutreptia ; 2, Zygoselmis ; 3, Distigma ;
4, Cryptoglena ; 5, Sterromonas ; 6, Dinomonas.

VII. CHILOMONADID^; : Genus i, Chilomonas ; 2, Oxyrrhis.
VIII. ANISONEMID^ : Genus I, Heteronema ; 2, Diplomastix ; 3, Aniso-

nema ; 4, Entosiphon.
IX. SPHENOMONADIDA: : Genus i, Sphenomonas.

Order VII. CILIO-FLAGELLATA.

I. PERIDINIID;E : Genus i, Hemidinium ; 2, Gymnodiniuin ; 3, Melo-
dinium ; 4, Glenodinium ; 5, Peridinium ; 6, Ceratium ;
7, Dinophysis ; 8, A mphidinium ; 9, Prorocentrum ; 10, Dima-
stigoaulax.

II. HETEROMASTIGID^: : Genus i, Heteromastix.

III. MALLOMONADID^E : Genus i, Mallomonas.

IV. STEPHANOMONADID.E ; Genus i, Stephanomonas ; 2, Asthmatos.
V. TRICHONEMID^E : Genus i, Trichonema ; 2, Mitophora.

Class II. CILIATA vel TRICHOPHORA.

Order I. HOLOTRICHA.

I. PARAMCECIID/E : Genus i, Paramaecium ; 2, LoxocepJialns ; 3, Placus ;
4, Conchophthirus.

II. PRORODONTID^E : Genus i, Prorodon ; 2, Nassula ; 3, Cyrto-
stomum ; 4, IsotricJia ; 5, Holophrya ; 6, Otostoma ; 7, Heli-
costoma.

III. TRACHELOPHYLLID^;: Genus i, Trachelophyllum ; 2, Enchelyodon ;

3, Urotricha.

IV. COLEPID^E: Genus i, Coleps ; 2, Plagiopogon ; 3, Polykrikos.

V. ENCHELYID^E: Genus i, Enchelys ; 2, Metacystis ; 3, Perispira ;

4, AnopJirys ; 5, Colpoda ; 6, Tillina.

VI. TRACHELOCERCID/E : Genus i, Trachelocerca ; 2, Lachrymaria ;
3, Phialina ; 4, Maryna ; 5, Lagynis ; 6, Chcenia.

VII. TRACHELIID^I : Genus i, TracJiclius ; 2, A mphileptus ; 3, Loxo-
phyllnm.

VIII. ICHTHYOPHTHIRIID^ : Genus i , Ichthyophthirius.

214 A UTHORS CLASS I PICA TOR Y SYS TEM.

FAMILY.

IX. OPHRYOGLENID^E : Genus \,Ophryoglena; 2, Panophrys ; $,Cydo-
tricha ; 4, Trichoda ; 5, Lembadion ; 6, Leucophrys ; 7, Colpi-
dium ; 8, Plagiopyla ; 9, Meniscostomum ; 10, Chasmatostomum ;
1 1, Pleurochilidium.

X. PLEURONEMID^E : Genus i,Pleuronema; 2,Cyclidium; $,Uronema;
4, Bceonidium.

XI. LEMBID^E: Genus I, Lembus ; 2, Proboscella.

XII. TRICHONYMPHID^; : Genus I, Trichonympha ; 2, Pyrsonema ;

3, Dinonympha.

APPENDIX.

XIII. OPALINID^: : Genus I, Opalina ; 2, Anoplopkrya ; 3, Discophrya ;

4, Hoplitophrya.

Order II. HETEROTRICHA.

I. BURSARIID^E: Genus i, Bursaria; 2, Bursarella ; 3, Balantidium ;
4, Nyctotherus; 5, Metopus ; 6, Metopides ; 7, Plagiotoma.

II. SPIROSTOMID^E : Genus I, Condylostoma ; 2, Blcpharisma ; 3, S//-
rostomum ; 4, Climacostomum.

III. STENTORID.E: Genus I, Stentor ; 2, Follicularia ; 3, Chatospira.

IV. TlNTINNOD^E : Genus I, Tintinnus ; 2, Tintinnidiiim ; 3, Vasicola ;

4, Strombidinopsis.

V. TRICHODINOPSID^E : Genus i, Trichodinopsis.

VI. CODONELLID^E : Genus I, Codonella ; 2, Tintinnopsis.
VII. CALCEOLID^E: Genus i, Calceolus.

Order III. PERITRICHA.
I. TORQUATELLID^L : Genus i, Torquatella.
II. DlCTYOCYSTlD^L : Genus i, Dictyocysta.

III. ACTINOBOLID/E : Genus i, Actinobolus.

IV. HALTERIID^E : Genus I, H alter ia ; 2, Strombidium ; 3,

dinium ; 4, Acarella ; 5, Arachnopsis ; 6, Didinium.

V. GYROCORID^E: Genus i, Gyrocoris ; 2, Urocentrum.

VI. URCEOLARIID^E : Genus i, Trichodina ; 2, Urceolaria ; 3,
chata ; 4, Licnophora.

VII. OPHRYOSCOLECID^; : Genus i, Opkryoscolex ; 2, Entodinium ;

3, Astylozoon.

A UTHOKS CLASS I PICA TOR Y S YSTEM. 2 1 5

FAMILY.

VIII. VORTICELLID^; : Sub-Fam. I., VORTICELLINA : Genus i, Gerda,
2, Scyphidia ; 3, Spirochona ; 4, Stylochona ; 5, Rhabdostyla ;
6, Pyxidium ; 7, Vorticella ; 8, Carchesium ; 9, Zoothamnium ;
10, Epistylis ; 1 1, Opercularia. Sub-Fam. II., VAGINICOLINA :
Genus I, Vaginicola ; 2, Thuricola; 3, Cothurnia ; 4, Pyxicola ;
5, Stylocola ; 6, Platycola ; 7, Lagenophrys. Sub-Fam. III.,
OPHRYDINA : Genus I, Ophionella ; 2, Ophrydium.

Order IV. HYPOTRICHA.

I. LlTONOTlD^E : Genus I, Litonotus.

II. CHLAMYDODONTID/E : Genus i, Phascolodon ; 2, Chilodon ;

3, Loxodes ; 4, Opisthodon ; 5, Chlamydodon ; 6, Scaphiodon.

III. DYSTERIAD^E : Genus i, Iduna ; 2, Dysteria ; 3, Cypridium ;

4, ^Egyria ; 5, Trochilia ; 6, Huxley a ; 7, Trichopus.

IV. PERITROMID^; : Genus i, Peritromus.

V. OXYTRICHID^E : Genus i, Psilotricha ; 2, Kerona ; 3, Tricho-
gaster ; 4, Urostyla ; 5, Onychodromus ; 6, A mphisia ; 7, Holo-
sticha ; 8, Plagiotricha ; 9, Epiclintes ; 10, Stichocluzta ;
n, Stichotricfia ; 12, Strongyliditim ; 13, Uroleptus ; 14, Stylo-
nethes ; 15, Allotricha; 16, Pleurotricha ; 17, Gastrostyla ;
1 8, Opisthotricha ; 19, Oxytricha ; 20, His trio ; 21, Actinotricha ;
22, Stylonychia.

VI. EUPLOTID^E: Genus i, Aspidisca (Glaucoma; Microthorax) ; 2,
Urony cilia ; 3, Euplotes ; 4, Styloplotes.

Class III. TENTACULIFERA.
Order I. TENTACULIFERA-STTCTOBJA.

I. RHYNCHETID^: : Genus i, Rhynclieta; 2, Urnula.

II. ACINETID^L: Genus i, Trichophrya; 2, Podophrya\ 3, Hemiophrya' ;
4, Soletwphrya; 5, Acineta.

III. DENDROCOMETID^ : Genus i, Dendrocometes.

IV. DENDROSOMID^; : Genus i, Dendrosoma.

Order II. TENTACTJLIFEEA-ACTINARIA.

I. EPHELOTID^E: Genus i,Ephelota; 2, Actinocyathus.
II. OrilRYODENDRID^L : Genus i, Ophryodendron ; 2, Acetiuopsis.

( 216 )

CHAPTER VII.

SYSTEMATIC DESCRIPTION OF THE INFUSORIA FLAGELLATA.

Class I. FLA GELLA TA .

ANIMALCULES bearing one, two, or more long, lash-like flagella, which
mostly represent the sole organs of progression, but are occasionally
supplemented by cilia, pseudopodia, or other locomotive or prehensile
appendages. Oral or ingestive system varying in character ; definite, diffuse,
or indistinct. One or more contractile vesicles almost invariably represented.
Multiplying rapidly by binary fission and by the subdivision of their entire
body-mass into sporular elements. The sporular reproductive process
often preceded by the complete fusion or conjugation of two or more adult
zooids.

The title of the Flagellata, as distinctive of a large and important series of infu-
sorial types, was employed almost simultaneously by Johannes Miiller and F. Cohn
about the year 1853 ; it is practically synonymous with that of the Filigera introduced
one year previously by M. Perty, and with the Mastigophora of R. M. Diesing.

Although thus receiving their characteristic name at a comparatively recent date,
the members of this class were known to the majority of the earlier writers, being
abundantly figured and described in the works of O. F. Miiller, and C. G. Ehrenberg,
while a first intelligible record of their existence is undoubtedly contained in
Mr. John Harris's account of little fish-like animals (Euglena viridis) communicated
to the ' Philosophical Transactions ' for the year 1696, reproduced at pages 9 and
10. By these earlier authorities, however, the flagelliform organs were almost
altogether overlooked, and it was not until the employment of more perfected
instruments having a comparatively high magnifying power, at the hands of
Felix Dujardin and Maximilian Perty, that these appendages were extensively
recognized as representing the essential organs of locomotion, or their number,
character, and mode of insertion made use of for the purpose of generic diagnosis.
Much even then remained to be discovered with relation to their more minute
organization. While Ehrenberg had declared that all these flagellate organisms
possessed a distinct mouth, and in most instances numerous gastric cavities,
Dujardin made the entire absence of an oral aperture a leading distinction of the
Order III. or Flagelliferous section of his ' Zoophytes Infusoires.' So much
uncertainty has prevailed, again, respecting the claims of the Flagellata for recogni-
tion as animal organisms — their external shape and mode of locomotion correspond-
ing so closely with those of many undoubted unicellular plants or Protophytes, and
with the spermatic elements, " antherozooids " or " zoospores," of the higher Crypto-
gamia — that almost down to the present time biologists have refused to admit them
among the ranks of the typical Infusoria. The more perfect insight into the structure
and life-history of the representatives of this class, obtained by the assistance of the
higher magnifying glasses of recent construction, has, however, practically revealed
in them the existence of an entirely new world of mieroscopic organisms, possessing
the most evident animal attributes, and exhibiting with relation to each other an even

CLASS FLAG ELLA TA. 2 I 7

more extensive range of structural variation than is met with among the hitherto
more familiar Ciliate section of the Infusorial series.

The foremost place amongst those who by their original investigations have con-
tributed most substantially towards our more correct knowledge of this previously
comparatively neglected group, must undoubtedly be awarded to Professor Stein in
connection with the recently published third volume, Part I., of his magnificent folio
series devoted to the description and illustration of infusorial organization. As he
himself justly remarks, this volume represents the most important of the three now
issued, it dealing exclusively and on the most liberal and comprehensive scale with
the class now under consideration. So far, however, Stein's volume is complete
with reference only to the illustrations contained in the twenty-four magnificently
executed plates, the one hundred and fifty-four pages of text that precede them
being devoted chiefly to an exhaustive review of the work achieved by earlier
investigators, with relation to both flagellate animal and vegetable organisms, and to
a discussion of the claims of the innumerable forms he figures for comprehension
among the animal series. A full description of the types there illustrated is reserved for
a much looked forward to, but as yet unpublished, second part.* All the species
delineated by Stein in the treatise quoted are represented as seen under the high
magnification of from 600 to 1200 diameters and upwards, and which is indeed
absolutely requisite for gaining a correct estimate of the often highly complex
organization of these exceptionally minute beings. As now shown by Stein, numbers
of these Flagellata possess not only a well-developed oral aperture, but frequently in
addition an extensive pharyngeal dilatation, and in some cases even a buccal or
pharyngeal armature comparable to that found in various higher Ciliata. Among
the more important features of Stein's work may be also mentioned his comprehen-
sion of numerous types belonging to the collared series, first discovered by Professor
H. James-Clark — here included in the order Choano-Flagellata, and his acquiescence,
through such discovery, with the views maintained by Professor Clark, and supported
by the author, respecting the affinities of the sponges. The limits assigned to the
>Flagellata by Professor Stein differ essentially from those recognized in this treatise.
As already notified at page 197, the fundamental basis upon which he establishes this
class relates merely to the presence of a nucleus and contractile vesicle, without any
reference to food-ingesting properties, the result of such lax definition being the
admission of such types as Volvox, Gonium, Protococcus (Chlamydococcus), and
numerous other forms of whose essential vegetable affinities there is scarcely room
for doubt. It is indeed contested by the author (see page 47) whether the types
just enumerated possess contractile vesicles ; the inability to detect such structures
in numberless examples investigated with the greatest care, being accepted as a
conclusive proof of their vegetable nature.

A conspicuous feature of the reproductive phenomena of the Flagellata
is manifested by the tendency of almost all the forms to multiply, in addition
to the ordinary process of binary fission, by encystment and the subsequent
breaking up of their entire body-mass into sporular elements, such mode of repro-
duction being precisely parallel with what obtains among the unicellular plants or
Protophytes. Sometimes the spores so produced are few in number and of
conspicuous size, meriting the title, as here applied to them, of " macrospores " ; while
in other instances they are altogether innumerable, and of such minute calibre as to
defy individual definition, even with the assistance of the highest magnifying powers
of the compound microscope ; the sporular bodies under such conditions being
appropriately designated " microspores." It is further worthy of notice that the
production of microspores is more usually preceded by the genetic union or
coalescence of two, or it may be many, independent zooids, while that of macro-

* As a consequence of the present unfinished condition of Stein's monograph, the diagnoses
of the innumerable new generic and specific types it embodies, given in this manual, have been
framed by the author on the broad characters only indicated in Stein's drawings. The many
deficiencies in these diagnoses which must necessarily exist can be supplied only at the hands of the
original discoverer of the forms figured.

218

ORDER TRYPANOSOMATA.

spores commonly follows upon the simple encystment of a single animalcule. The
recognition of these important reproductive phenomena is chiefly due to the recent
painstaking investigations of Messrs. Dallinger and Drysdale, whose researches in
this direction are fully recorded in the descriptive accounts given of Monas
Dallingerii, Cercomonas typica, Tetramitus rostrata, Dallingeria Drysdali, and several
species of Heteromtta.

With reference to the variously modified characters of the oral system, and of the
locomotive and supplementary appendages, the class of the Flagellata may be con-
veniently subdivided into primary sections or Orders as below : —

A.

Ingestive area diffuse.

B.

Ingestive area discoidal,
limited to the anterior
region ; no true mouth.

C.

Ingestive area

constituting a true and

distinct mouth.

Flagellum rudimentary, sup-
plemented by an undu-
lating membrane .. ..

Flagellum supplemented byl
lobate pseudopodia . . . . /

Flagellum supplemented by)
ray-like pseudopodia . . J

Flagella representing the sole)
organs of locomotion . . /

Flagellum issuing from the
centre of a collar-like ex-
tensile membrane

Flagellum not supplemented)
by cilia /

Flagellum supplemented by
a more or less highly de-
veloped ciliary system

ORDER I. TRYPANOSOMATA.

II. RHIZO-FLAGELLATA.

III. RADIO-FLAGELLATA.

IV. FLAGELLATA-PANTOSTOMATA.

V. CHOANO-FLAGELLATA.

VI. FLAGELLATA-EUSTOMATA.

VII. CILIO-FLAGELLATA.

Order I. TRYPANOSOMATA, S. K.

Animalcules flattened or lamellate, one or more of the lateral borders
forming a frill-like undulating membrane by the vibrations of which
progress is effected ; one extremity sometimes attenuate and somewhat
resembling a flagellum. Oral or ingestive area undefined.

Two species only, representing but a single genus, can be as yet referred to
this newly established order. So far as it can be at present determined, these two
endoparasitic types would seem to lie at the base of all the succeeding more typical
sections of the Infusoria Flagellata and Ciliata. Although no positive flagellum is
present, the growth of such an organ is evidently foreshadowed in the slender tag-
like appendage of Trypanosoma sanguinis, while, on the other hand, the undulating
membranous border, constituting the essential organ of locomotion, may without
hesitation be regarded as closely, if not absolutely, homologous with the similar
undulating frill-like border present in the earlier developmental phases of Sttntor,
Euplotes, and other higher Ciliate types, and which eventually splits up to form the
characteristic adoral fringe.

GENUS I. TRYPANOSOMA, Gruby.

F" Animalcules free-swimming, compressed ; one side produced as a thin,
undulating, frill-like border ; the anterior extremity sometimes produced as
a long tag-like or flagellate appendage. No distinct oral aperture.

Occurring in the blood of Amphibia, and within the intestinal viscera of
domestic poultry.

GENUS TRYPANOSOMA. 219

Trypanosoma sanguinis, Gruby. PL. I. FIGS, i AND 2.

Body compressed, semilunate, twisted ; the convex border membranous
and undulating, with its margin deeply toothed ; the posterior extremity of
the body portion pointed and curved inwards, the opposite one produced
into a long tag- or tail-like appendage which almost equals in length the
remainder of the body ; surface of the body coarsely striate longitudinally ;
endoplasm or parenchyma slightly granular ; endoplast ovate, central.
Dimensions, 1-600".

HAB. — Blood of the frogs, Rana esciilenta and R. temporaria.

This species was first introduced to scientific notice by Gruby, who described
and bestowed upon it the name here given in the ' Comptes Rendus ' for November
1843. More recently this animalcule has been figured by Professor E. Ray
Lankester in the ' Quarterly Journal of Microscopical Science' for October 1871,
under the title of Undulina ranarum, its identity with Grub/s type being, however,
subsequently admitted.

Professor Lankester's account given of the characteristic aspect and movements
of this singular animalcule, in the serial quoted, is as follows : — " In making examina-
tions of the blood of frogs, I have now and then met with the interesting little
parasite drawn in the woodcut. When I first saw it, in some blood from a frog last
summer, I took it for a very active white blood-corpuscle, since it is a very little
smaller than one of the red corpuscles of the frog's blood. On using, however, a
higher power (No. ioa immersion, of Hartnack), I made out its infusorial nature,
though, on account of the great activity of its movements, I was long uncertain as
to the nature of its locomotive organs. Numerous specimens occurred in the blood
of a frog (Rana esculenta), examined at Leipzig in March last, and by the use of a
small quantity of acetic acid vapour I was able to kill the little creature without
injuring it, and then to make out its structure. It was seen to be a minute pyriform
sac, with the narrower end bent round on itself somewhat spirally, and the
broader end spread out into a thin membrane, which exhibited four or five folds,
and was produced on one side into a very long flagellum. The wall of the sac was
striated coarsely, as in Opalina ; and the direction of the striae on the two sides of the
sac, as seen one through the other, showed that the small end of the sac was twisted
as well as bent over on itself. A pale, clear nucleus and a very few granules were
also seen. In life the broad membrane undulates vigorously in a series of waves, the
flagellum taking part, and presents then a deeply toothed appearance. The move-
ments produced by the activity of this membrane tend to urge the animal in a wide
circle. The opposite extremity of the sac twists and untwists itself to a small
extent also during life. The series of waves of the undulating membrane are not
incessantly in one direction ; after a certain time they change to the opposite
direction, and then resume their original direction, an alternation of from right to left,
and from left to right being kept up. When minute traces of acetic acid vapour are
passed into the gas-chamber where this infusorian is, it soon becomes affected ; the
undulations become deranged, starting from both ends simultaneously and meeting
in the middle, and at length ceasing."

Trypanosoma Eberthi, S. K. PL. I. FIGS. 3-6.

Body flattened, and semilunate when at rest, its convex membraniform
border serrated or presenting a beaded aspect ; straight, lanceolate, and
pointed at each extremity when in motion, not produced at either end into
a tag-like prolongation ; the membranous border often spirally convolute

2 20 ORDER RHIZO-FLA GELLA TA.

around the thicker central portion, the entire body assuming under such
conditions an auger-like aspect. Length 1-1760".

HAB. — The intestinal viscera of various domestic poultry.

It is proposed to distinguish, under the above title, the organism figured and
described by Dr. J. Eberth in Siebold and Kolliker's ' Zeitschrift ' for the year 1861,
p. 98, as a new infusorial form inhabiting the intestinal viscera — chiefly the caecum
and ileum — of ducks, geese, and other domestic poultry. No name is there bestowed
upon it, and its accordance to a considerable extent with the Trypanosoma sanguinis
of Gruby, and Amoeba rotatoria of Meyer is acknowledged. Its distinction from
Gruby's type is clearly manifested, however, by the entire absence of the anterior
filamentous or tag-like appendage which forms so conspicuous a characteristic of
that species, and which is so prominently figured in Professor Lankester's more
recent delineation here reproduced. If the above-named structure in T. sangui?ris is
to be regarded as the analogue or rudiment of a true flagellum, it would appear
almost desirable to create a new generic title for the reception of the present more
simple form. On the other hand, however, a further investigation may not impos-
sibly demonstrate that both this and the preceding type are but transitional phases
of the same specific form, which, in common with many higher endoparasitic
organisms, requires the association of two distinct hosts for the full development of
its life-cycle, and exhibits under each condition an altogether distinct aspect. In
this manner it may be proved hereafter, though only submitted now as a suggestion,
that the flagellum- or filament-bearing Trypanomonas sanguinis, as found in the
blood of the frog, represents the adult condition of the more minute T. Ebcrthi,
which would probably be swallowed by the amphibians or their tadpoles, in com-
pany with the discharged faeces of the water-fowl. Or again, though this seems
less likely, T. sanguinis may represent the larval condition, which being devoured
with its host, the frog, by the water-fowl, may develop in the intestine of the latter
to T. Eberthi.

Yet another interpretation may be suggested relative to the true nature and
significance of the present species of Trypanosoma. It is, as already stated at page
100, a noteworthy fact that the spermatic elements of many Amphibia correspond
structurally in a remarkable manner with the representatives of the present species
as figured by Eberth. The long, slender bodies of such spermatozoa are, as first
pointed out by Wagner and Leuckhart in the year 1837, and as still more fully
demonstrated by C. T. Von Siebold,* supplemented throughout their length by a
delicate frill-like border, developed straight along or in a spiral manner around it
throughout the whole extent or greater part of its total length. Quite recently it has,
moreover, been shown by Mr. Heneage Gibbes,f that the spermatozoa of the
Mammalia possess also, though in a less developed degree, corresponding supple-
mentary membranes. The high import attaching itself to this structural feature of
Amphibian spermatozoa just described is obvious. It necessarily renders it quite
possible that the form discovered by Dr. Eberth, and here provisionally accepted as
an independent infusorial species, may ultimately prove to be the spermatic elements
of frogs and other Amphibia, which, as commonly happens, have been devoured by
the water-fowl, and retained their vitality while passing through its viscera.

Order II. RHIZO-FLAGELLATA, S. K.

Animalcules progressing by means of pseudopodic extensions of their
sarcode after the manner of the ordinary Rhizopoda, but bearing at the same
time one or more flagellate appendages ; oral or ingestive area diffuse.

* "Ueber undulirender Membranen," 'Zeit. Wiss. Zool.,' Bd. ii., 1850.

t "On the Structure of the Vertebrate Spermatozoon," 'Quart. Jour. Mic. Sci.,' No. Ixxvi.,
Oct. 1879.

GENUS MASTIGAMCEBA . 221

The some half a dozen species as yet known that may be consistently referred
to this order, intimately connect with each other the two classes of the' Rhizopoda,
as represented by the Amoebina, and the typical Infusoria-Flagellata. In accordance
with the number and character of their flagelliform and pseudopodic appendages
they admit of the following generic grouping : —

GENERA OF RHIZO-FLAGELLATA.

Flagellum single, / RePent
anteriorly situated.

Sedentary, with radiating digitiform prolongations .. ,, 3. Rhizomonas.
Flagella multiple, inconstant in number and position , , 4. Podostoma.

GENUS I. MASTIGAMCEBA, Schulze.

Animalcules repent, amoeba-like, changeable in form, emitting pseudo-
podia from all parts of the periphery, the anterior extremity bearing a single,
long, non-retractile, lash-like flagellum.

Mastigamceba aspera, Schulze. PL. I. FIG. 21.

Body when extended oval, depressed, pointed anteriorly ; pseudopodia
cylindrical, unbranched, digitiform, diverging in somewhat regular order
from the lateral margins of the periphery, those at the posterior extremity
of the body shorter than the others, emitting extremely fine ray-like sar-
codic projections, similar to those of A mceba (Pelomyxd) villosa ; flagellum
issuing from the pointed anterior extremity, about equal in length to the
body ; entire external surface, including more especially the pseudopodia,
beset with exceedingly minute refringent rod-like structures which commu-
nicate to it a hispid aspect. Contractile vesicles two in number, situated
near the posterior extremity. A subspheroidal endoplast-like structure
developed anteriorly ; endoplasm enclosing numerous reddish - yellow
spherules and colourless granules. Length of body 1-150".

HAB. — Pond water.

Excepting for its smaller size and the presence of the anteriorly developed
flagellum, the representatives of this species correspond in a remarkable manner
with the Dinamceba mirabilis of Dr. Joseph Leidy, as recently figured in his magni-
ficent monograph of the Freshwater Rhizopods of North America.

Mastigamceba simplex, S. K. PL. I. FIG. 30.

Body when extended usually widest and rounded at the anterior extre-
mity, tapering posteriorly ; pseudopodia irregular in shape, simple, lobate,
or furcately branched, not differentiated from one another as in M. aspera,
usually directed backwards ; flagellum antero-terminal, about twice the
length of the body ; external surface entirely smooth ; contractile vesicle

222 ORDER RHIZO-FLAGELLATA.

anteriorly situated ; endoplast spherical, subcentral ; endoplasm trans-
parent, colourless. Length of body 1-2000".
HAB. — Pond water.

Deprived of its terminal flagellum, this species would seem closely to agree both
in aspect and size with the Amoeba lacerata of Dujardin. Like that form, the pseudo-
podia are altogether irregular in shape, and present a laciniate or ragged out-
line. The movements of this animalcule in the water are tolerably active, it creeping
rapidly forwards over the surface of submerged objects by the continual rolling to the
front of the granular contents of the body-sarcode in a manner identical with what
obtains among the ordinary amoebae ; the long, whip-like flagellum is at the same time
vigorously flourished in advance or thrust around in every direction, as though
seeking for suitable food-substances. These latter when met with, are whipped
backwards by the action of the flagellum, and striking against some portion of the
periphery of the body, are at once engulfed by the soft yielding sarcode. On one
occasion an example was observed dragging a Navicula almost equalling itself in size
by an abnormal thread-like extension of one of its pseudopodia, as shown in the
illustration given. The Protozoon figured and described by Biitschli under the title
of " eine geisseltragender Rhizopode," * is apparently almost identical with this form ;
but the pseudopodia, in accordance with his illustrations, are smaller and more
slender, and the flagellum, in comparison, is considerably longer.

Mastigamceba monociliata, Carter, sp. PL. I. FIGS. 22 AND 23.

Body amoeboid, variable in form; pseudopodal extensions irregularly
lobate, the posterior extremity having a brush-like villous tuft, anterior
flagellum equalling the body in length. Dimensions unrecorded.

HAB. — Fresh water. Bombay, H. J. C.

This species is briefly described by Mr. H. J. Carter f as a new species of
Amoeba, upon which he proposes to confer the title of Amoeba monodliata. From
Mastigamoeba simplex, which it most nearly resembles, it may be distinguished by
the tuft of villi at the posterior extremity.

Mastigamoeba ramulosa, S. K. PL. I. FIGS. 19 AND 20.

Body when extended elongate-ovate, about one and a half times as long
as broad ; the entire peripheral surface bearing subequal shortly branched
pseudopodic prolongations, neither these nor the general surface of thj
body having secondary hispid pseudopodia ; flagellum exceeding the body
in length ; endoplast spherical, subcentral ; contractile vesicle posteriorly
located. Length 1-400".

HAB. — Marsh water.

This animalcule has as yet been met with by the author on one occasion
only, being then found in marsh-water from the neighbourhood of Le Marais,
Jersey, associated with the Ciliate types Spirostomum ambiguum and Litonotus fasriata.
The conspicuously branched character of the abundant pseudopodia serves to dis-
tinguish it readily from either of the preceding species, and communicates to it as
a whole an aspect suggestive of a minute Nudibranch, such as Eolis or Dendro-
notus. Like these molluscs, the little animalcule, under any disturbing influence,

* 'Zeit. Wiss. Zool.,' Bd. xxx. Heft 2, 1878. f 'Ann. Nat, Hist.,' Jan. 1864.

GENUS REPTOMONAS. 22$

immediately contracts into a subspheroidal contour, as shown in PI. I. Fig. 20.
It was observed that the granule circulation, conspicuously indicated in the central
substance of the body-sarcode, did not extend into the branched pseudopodic
extensions, neither on any occasion were these last-named appendages withdrawn
entirely within the periphery.

Doubtful Species.

The free-swimming flagellate amoebae, described by Tatem in the ' Monthly Micro-
scopical Journal' for June 1869, appeared at first sight to require a position in or
adjacent to the genus Mastigamceba, but the result of a recent investigation into
the life-history of innumerable Pantostomatous Flagellate species, has inclined the
author to regard the forms there figured and described as merely metamorphosed
amoeboid phases of some such type as Monas fluida.

GENUS II. REPTOMONAS, S. K.
(Latin, repto, to creep ; monas.)

Animalcules repent, but slightly changeable in form, bearing a single
anterior flagellum ; locomotive pseudopodia produced only from the
repent or ventral surface.

The limitation of the pseudopodia to the ventral region, and the conservation by
the body, taken as a whole, of a persistent contour, distinguish this genus from
Mastigamceba, which it otherwise closely approaches.

Reptomonas caudata, S. K. PL. I. FIGS. 31-33.

Body monadiform, elongate-ovate, somewhat inflated posteriorly ;
flagellum slender, exceeding the body in length, produced from the apex
of the narrower and slightly pointed anterior extremity ; a long, trailing,
caudiform pseudopodium continued backwards from the posterior end of
the ventral surface, and numerous similar but smaller pseudopodia emitted
irregularly from the whole surface of this region ; contractile vesicle single,
situated near anterior extremity ; endoplast spherical, subcentral. Length,
exclusive of caudal pseudopodium, 1-1200" to 1-750".
;, HAB. — Hay infusions, and among naturally decaying grass.

This as yet single discovered species of the newly instituted genus Reptomonas
was obtained by the author in tolerable abundance from a hay infusion made at
St. Heliers, Jersey, in February 1879, a closely similar, if not absolutely identical,
specific type having also been met with among wet grass gathered in the Regent's
Paric m October of the same year, and under the circumstances narrated at length
at page 140. During progression the anterior extremity of the animalcule is usually
elevated in the manner shown at PI. I. Fig. 31, the flagellum meanwhile vibrating
vigorously in all directions in search of food. On one occasion, as delineated at
Fig. 33, a Bacterium thrown by the vibrations of this organ against the anterior
margin was at once secured by an outflowing wave of the peripheral sarcode, and
rapidly passed into the interior of the body. In many respects the animalcule here
described presents a considerable resemblance to the Cercomonas crassicauda of
Dujardin, as reproduced from Stein's work at PL XIV. Figs. 15 and 16. That type,
however, in common with all the representatives of the genus Cercomonas as here
accepted, is a free-swimming or natatory, and not a repent form.

224 ORDER RHIZO-FLA CELL A TA .

GENUS III. RHIZOMONAS, S. K.

(Greek, rhiza, root; monas.)

Animalcules monadiform, adherent to submerged objects by root-like
pseudopodic extensions of the posterior region ; the anterior extremity
bearing a single lash-like flagellum.

Rhizomonas verrucosa, S. K. PL. I. FIGS. 26 AND 27.

Body subspheroidal, its general surface bearing throughout even sized,
conical pseudopodic elevations whose length nearly equals one-half the
diameter of the body ; similar but somewhat longer conical pseudopodia
produced from the posterior extremity, and rooting the animalcule to the
selected point of attachment ; flagellum slender, its length equalling twice
the diameter of the body ; contractile vesicle single, subspherical ; endo-
plast not observed. Diameter 1-1500".

HAB. — Hay infusions.

This remarkable form was obtained by the author from the hay infusion that
yielded Reptomonas caudata. In its normal and fixed condition the vibrations of
the flagellum are so rapid and powerful as to maintain the entire body in a state of
active tremor — after the manner of the wings of many moths when hovering —
thus rendering it exceedingly difficult to recognize its true form and proportions.
This energetic motion becomes, however, even yet more pronounced when, either
voluntarily or through a disturbance of the infusion, the animalcule is set free in
the surrounding water. Under these circumstances it tumbles over and over or to
and fro in apparently the most aimless and excited manner, allowing but an occa-
sional and momentary distinct glimpse of either its body or flagellum. In very
many instances it was observed that the attached animalcules, either singly or in
associated groups of three or four, were immersed within a granular mucilaginous
sheath apparently exuded from their own bodies, and out of which the long, powerful
flagella alone projected. Such a solitary en sheathed zooid is delineated at PI. I.
Fig. 26.

GENUS IV. PODOSTOMA, Claparede & Lachmann.

Animalcules amceba-like, changeable in form, emitting pseudopodic
prolongations, the free extremities of which are capable of further extension
into long, thread-like, and actively motile flagella.

The single species upon which this genus is founded represents the most perfect
known gradational form between the two classes of the Rhizopoda and Infusoria-
Flagellata. Unlike Mastigamceba, to which the second place in this category may
be allotted, the lash-like organ or flagellum is constant neither in its presence
or position, but shares with the pseudopodia the capacity of being emitted from or
withdrawn into the substance of the body at any point of the periphery ; two or
more of these organs may, moreover, be simultaneously extended from a single
animalcule, while in Mastigamceba the flagellum is single and persistent as regards
both its position and existence.

ORDER RA DIO-FLA CELL A TA. 225

Podostoma filigerum, C. & L. PL. I. FIGS. 28 AND 29.

Body repent or freely floating, highly polymorphic, almost spherical
when contracted, substellate with attenuate pseudopodic prolongations
when extended ; the distal terminations of the pseudopodia produced as
long, thread-like, vibratile flagella, which are capable of contracting in a
spiral manner, or of being entirely withdrawn into the substance of the
pseudopodium ; contractile vesicle single, endoplast distinct, subspheroidal.
Length of extended body 1-500".

HAB. — Fresh water, among aquatic plants.

Overlooking the presence of the flagellate appendages, this animalcule, as
remarked by Claparede and Lachmann, closely resembles in its stellate condition
the Amoeba radiosa of Ehrenberg, while at other times, in its contracted state, it
might be as easily mistaken for A. diffluens. Any food-particle arrested by one
of the flagellate appendages is immediately withdrawn with the latter into the
substance of the pseudopodium that carries it, a slight depression momentarily
marking the point of entrance. Biitschli,* while recently proposing to identify
Ehrenberg's Atnczba radiosa with this type, has sought to demonstrate that the
radiating pseudopodia of the former are capable of similar attenuate prolongation
in the form of flagella. An intimate acquaintanceship with the Amoeba named inclines
the author, however, to regard the two as distinct, and that Biitschli must have
had Claparede and Lachmann's type, and not Ehrenberg's, under examination. In
the latter species, however finely attenuate may be the extensions of the pseudo-
podia, they never assume the form and functions of vibratile and spirally contractile
flagella. This decision is entirely confirmed by an examination of the exhaustive
figures and accompanying description of Amoeba radiosa embodied in Professor
Leidy's monograph of the North American Rhizopoda, previously quoted.

Order III. RADIO-FLAGELLATA, S. K.

Animalcules emitting numerous ray-like pseudopodia, after the manner
of the Radiolaria, and provided at the same time with one or more
flagellate appendages ; no distinct oral aperture. Mostly marine.

The several genera referred to this newly instituted Order of the Flagellata
form two natural and well-differentiated groups. In the one — that of the
Euchitonidae — we find types which, except for the presence of the characteristic
flagellum, are not to be distinguished from the ordinary representatives of that
typical Radiolarian group known as the Polycystinae ; while in the second one — that
of the Actinomonadidae — are presented forms that most intimately unite the more
typical flagellate monads with the Heliozoan group of the same Radiolarian class.
Since it is now demonstrated of all the other leading groups of the Radiolaria
so far investigated, that their initial conditions take the form of simply flagellate
monadiform zoospores, it may be consistently predicated that in the two above-
named family divisions is permanently retained that primitively developed locomotive
organ which among the more ordinary Radiolaria becomes aborted at an early
epoch of their existence.

The direct metamorphosis, observed by the author, of a flagelliferous zooid
into an adult Radiolarian type of structure, as exemplified in the genus Actinophrys,
will be found illustrated at PI. I. Figs. 9-11. As first observed, see Fig. 9, the
monadiform germ closely corresponded in appearance with the Peranema g/obitlosa

* " Beitrage zur Kenntniss der Flagellaten," ' Zeit. Wiss. Zool.,' Bd. xxx., 1878.

Q

226 ORDER RADIO-FLAGELLATA.

of Dujardin. In the midst of its natatory course it was observed to project blunt
digitiform processes from all sides of the periphery, as shown at Fig. 10. Its
motions now became more sluggish, the flagellum was completely withdrawn,
and then suddenly, as though by magic — the bursting of a rocket or other firework
affording perhaps the most suitable comparison — fine ray-like pseudopodia were
shot out in every direction, and the animalcule was at once metamorphosed into
a typical Actinophrys. According to Cienkowski, the monadiform germs or so-
called "zoospores" of the Radiolarian type Collosphcera spinosa, Hkl., are furnished
with two subequal flagellate appendages. An account of Cienkowski's investiga-
tions in this connection, translated from the German, is published in the ' Quarterly
Journal of Microscopical Science,' vol. xi., No. xliv., 1871.

FAMILIES AND GENERA OF RADIO-FLAGELLATA.

Fam. I. Aetinomonadidce. \
Animalcules naked, no I Animalcules free-swimming or attached posteriorly\ , , ..

exoskeleton or central [ by a thread-like pedicle }l. Actinomonas.

capsule.

' Test external to capsule with cyclic chambers . . 2. Euchitonia.
Fam. II. Euchitonida.

Animalcules with a

siliceous test or lorica,

and an indurated central

capsule.

{External trabecular lattice-work)
more or less evenly ovate . .
External trabecular lattice-work) Oi
forming arm-like processes . . H Congas tenscus.

Fam. I. ACTINOMONADID-ffi, S. K.

Animalcules ovate or spheroidal, fixed or freely motile, entirely naked,
possessing neither an indurated test nor a central capsule ; fine ray-like
pseudopodia projecting from all parts of the periphery, supplemented at
one point by a long vibratile flagellum.

GENUS I. ACTINOMONAS, S. K.
(Greek, atfis, ray ; monas.)

Animalcules ovate or spherical, uniflagellate, free-swimming, or attached
posteriorly by a temporarily developed thread-like pedicle ; endoplasm
soft and plastic, emitting ray-like pseudopodia from all points of the
periphery ; food-particles attracted by the vibrations of the flagellum, and
then seized by the pseudopodia and introduced into the substance of the
body at any part of its circumference ; endoplast and contractile vesicles
usually conspicuous.

The two species upon which the new genus Actinomonas is here founded
represent some of the most remarkable and interesting types of the class Flagel-
lata. Divested of their radiating pseudopodia, there is nothing to distinguish them
from the typical members of the genus Oikomonas, while by the retention of the
pseudopodia and removal only of the terminal flagellum, a form is produced scarcely
distinguishable from the stalked Radiolarian recently described by F. E. Schulze under
the title of Actinolophus pedunciilatus. Through this generic type, in fact, the two
Protozoic groups of the Radiolaria and the Infusoria-Flagellata would appear to be
as effectually bridged as are the last-named group and the ordinary Rhizopoda by
the several genera, Mastigamceba, Rhizomonas, Reptomonas, and Podostoma.

GENUS ACTINOMONAS. 227

Actinomonas mirabilis, S. K. PL. I. FIG. 18.

Body subspherical or ovate, seated on a slender pedicle, which usually
equals two or three times the diameter of the body ; endoplasm trans-
parent, slightly granular ; flagellum very long and slender, extended rigidly
and arcuately in advance ; pseudopodia equalling in length the diameter
of the body, very numerous, radiating from all points of the periphery ;
contractile vesicles two in number, situated close to each other in the
posterior region of the body ; endoplast spherical, subcentral. Diameter
1-2000".

HAB. — Salt water.

Several examples of this interesting type were met with at St. Heliers, Jersey, in
May of the year 1878, in a jar of sea- water preserved for some weeks, containing
various protozoa and hydroid zoophytes collected on the adjacent coast. At first
sight the aspect presented by these animalcules so closely resembled that of the
ordinary members of the genus Spumella or Oikomonas, with, perhaps, some little
extra haziness around the peripheral margin, that they were nearly passed over as
such, and it was not until the aid of a more powerful object-glass was brought to
bear upon them that their true nature became apparent. It was then demonstrated
that the hitherto hazy environment of the periphery of the body consisted of fine,
closely-set, slender pseudopodia radiating in every direction, agreeing in form and
structure with those of Actinophrys^ Actinolophus, or any other typical Radiolaria,
and subservient to a closely similar function. Through its possession of a long
terminal flagellum, however, Actinomonas possesses considerable advantages over
such a type as Actinolophus. While the last-named form has to wait patiently for
the advent of food-particles within grasping reach of its tenacious pseudopodia,
Actinomonas, by the vibrations of its flagellate appendage, draws towards it all such
substances floating in the vicinity, and throws them back among the pseudopodic
processes, by which they are immediately seized and dragged into the substance of
its body. The capture and ingestion of food-matter in this manner, at all parts of
the circumference, were witnessed on several occasions. Physiologically, the ex-
tended peripheral pseudopodia of Actinomonas are closely analogous to the exten-
sile sarcode collar of the Choano-Flagellate order hereafter described, a similar
trap-like function, in combination with the flagellum, being common also to that
diversely modified pseudopodic structure. The developmental and reproductive
phenomena of this remarkable type have yet to be determined.

Actinomonas pusilla, S. K. PL. I. FIGS. 7 AND 8.

Body subspheroidal ; pedicle equal to, or very slightly exceeding in
length, the diameter of the body ; flagellum slender, extended rigidly and
arcuately from the apical extremity ; pseudopodia equalling in length the
diameter of the body, projected from all parts of the periphery, much
less numerous than in the preceding species. Diameter of body 1-3250".

HAB. — Salt water.

This species may be distinguished from the preceding by its more minute size,
the shorter comparative length of the pedicle, and the considerably less numerical
development of the radiating pseudopodia. It was obtained in some abundance in
sea-water containing Zoothamnium dichotomum attached to Fuci, remitted to the
author by Mr. Thomas Bolton from the Birmingham Aquarium in February of the
present year (1880). It was observed that the specimens often attached themselves
to the neighbouring vegetable debris by several radiating pseudopodia simultaneously,

Q 2

228 ORDER RADIO-FLA GELLA TA.

as shown at Fig. 8, as well as by the temporarily modified posterior one that
usually fulfilled the office of a pedicle. Disengaging themselves from their single
or several points of attachment, the animalcules were frequently seen to swim freely
in the water with great rapidity after the manner of Oikomonas or Spumella.

Fam. II. EUCHITONTD-ffi, S. K.

Animalcules free-floating, secreting a variously constructed canccllate
siliceous test or lorica, which is distinguished by the invariable presence of
a central differentiated capsule ; ray-like pseudopodia extending from all
parts of the periphery, supplemented anteriorly by a comparatively large
and well-developed flagellate appendage. Entirely pelagic.

As the members of this family possess characters that unite them more intimately
with the typical Radiolaria than with the ordinary Flagellata, a description of each
specific form is not included in this treatise, but a brief diagnosis only of a charac-
teristic representative of each generic group.*

GENUS I. EUCHITONIA, Haeckel.

Test siliceous, consisting of a flattened, biconvex, cyclically chambered,
central capsule, with radially developed projecting arms, which are dis-
posed in the same plane and chambered cyclically in correspondence with
the central disc ; the interspaces between the radiating arms filled in by
a loose, unsymmetrical, siliceous network.

Euchitonia Virchowii, Hkl. PL. I. FIG. 24.

Central capsule discoidal, with from two to three concentric chamber-
cycles ; radiating prominences three in number, their length slightly
exceeding the diameter of the central disc, the two* anterior slightly
narrower than the single isolated median posterior one, and basally
united ; cyclical chambers, of which the radiating arms are composed,
varying from four to six in number ; flagellum massive, equalling or
exceeding the length of the test, projecting from the angle between the
two anterior arms. Diameter of the central capsule 1-375".

HAB. — Pelagic : Messina.

In addition to the foregoing type, as many as six other specific forms are referred
by Haeckel to the genus Euchitonia, in his magnificent monograph ' Die Radio-
larien,' Berlin, 1862, under the respective titles of E. -Bcskmanni, E. Gcgenbauri,
E, Krohnii, E. Muelleri, E. Leydigii, and E. Koellikeri.

GENUS II. SPONGOCYCLIA, Haeckel.

Test siliceous, consisting of a central capsule composed of concentric
and symmetrical chamber-cycles, surrounded by an irregular, sponge-like
lattice-work of siliceous trabeculae, this sponge-like lattice-work not deve-
loped peripherally into distinct arm-like processes.

* Professor St. George Mivart recognizing the important distinction furnished by the presence
of flagella in the three genera included in this family division, has proposed ('Linnean Society's
Journal,' vol. xiv., No. 74, 1878) to separate them from the ordinary Radiolaria as a distinct section
of the " Flagellifera."

GENUS SPONGASTERISCUS. 229

Spongocyclia charybdsea, Hkl. PL. I. FIG. 25.

General contour of test escutcheon-shaped, flattened and angular ante-
riorly, slightly widest centrally, tapering and obtusely pointed at the
posterior extremity ; central capsule composed of from seven to fourteen
concentric chamber-cycles, its diameter equalling one-half of the entire
test ; flagellum stout, exceeding the length of the test, projecting from the
centre of the anterior border. Length 1-72".

HAB. — Pelagic: Messina.

Additional species, figured and described by Haeckel, are distinguished by the
respective titles of Spongocyclia cycloides, S. elliptica, S. orthogona, and S. scyllcea.

GENUS III. SPONGASTERISCUS, Haeckel.

Test siliceous, consisting of a central discoidal capsule composed of
concentric and symmetrical chamber-cycles, surrounded by an irregular
trabeculate siliceous lattice-work, as in Spongocyclia, but which, in place of
being simply subcircular or escutcheon-shaped, is developed into distinct
angular arm-like processes, which lie in the same plane as the flattened
central disc.

Spongasteriscus quadricornis, Hkl.

Central capsule circular, flattened, composed of from eight to sixteen
concentric chamber-cycles, radiating arm-like processes four in number,
subequal, triangular, forming two basally united pairs at the anterior and
posterior regions, their length equal to one-third of the diameter of the
central disc ; flagellum projecting from the notch between the anterior pair
of angular processes. Diameter of central disc 1-96".

HAB. — Pelagic : Messina.

One additional species is described by Haeckel under the title of Spongasteriscus
tctraceras.

Order IV. FLAGELLATA-PANTOSTOMATA, S. K.

Animalcules simply flagelliferous, having in their characteristic adult
state no supplementary lobate or ray-like pseudopodic appendages ; oral
or ingestive area entirely undefined, food-substances being incepted in-
differently at all points of the periphery.

Among the typical Infusoria-Flagellata, this order may be said to represent the
lowest and least specialized, it being directly allied through the small group of the
Rhizo-Flagellata, previously described, with the Amoeban order of the Rhizopoda.
Many of the generic and specific forms at present referred to this section must be
regarded as occupying therein a purely provisional position, it not being improbable
that the animalcules, upon further acquaintance, may be found to possess a distinct
oral aperture, and thus demand transfer to the succeeding order of the Flagellata-
Eustomata. While again, in a very considerable number of instances, the ingestion
of food-substances at all points of the periphery has been directly observed, it would
seem highly probable that where neither this phenomenon nor the presence of an

230

SCHEDULE OF FAMILIES AND

.i Q «•» S s;

i 1 111

hlllli

°«$*s-i-^

Ancyromonas.

Plcuromonas.
Merotricka.

Oikomonas.
Bodo.

, Cercomonas.

, Codonceea.
. Platytheca.

Physomonas.

!

^

^ « 1
8 -^ "^
Ifl

^ ^ -1
1 ^^ ^3 tj

f 3
S §

Stylobryon.

Goniomonas.

Amphimonis.
Dcltomonas.

•* d co 4 ^<>

r^ 00 ON

o -

-

« ^H

>n

id

, — ••

i l*** OQ ON

d «
N N

N

M

*„

$ »'! a

£ <E o J)

P, -*-»

rt 5

• "7 ctj I — j - 1

9

'•a.ai'a '
: § g8 jr .

.y d ^ 8 3
•§.- " « « 'S

4)

1

T S^S

• .£? 2 rt MM

|

8*1 o a'g^j
2 S D a* S

"o a! c .S E .S/3

PH PH 3 4_» O J3
4* T *r*

1 : :

it retractile .
it non-retracti

:

: :

oodendrium f

• C H •« £2

:|||||

'S -5 S-TJ £f
c c ° c 2

fl) Oj flJ M O H

^ T3 -Cjii -S §

15 8 8-° 8J

i

4)

"o

cu

c
o

:

"o

•3 .
&•

"S . 'S i2 _ w o

1° : :

W H

41 4)

•

u

X1

N N N

•

0,

rt

rD D £* CU ^ *0

to "3 y .^ c1

o E o "-1 £? o

so r :
g

1 1

T3

0

1

: :

"o

•

p ,

•a

0

_=

g s "2 g s

.Sa ^3.S 3

iS ^

o
(J

d

4)

3

_a-

*s

I « i 1 1 fi-

: :

•i -i

5

•

y

r- •!- O "i - —

!•§ 2 S-S

en en

^

2
o

•^ t>

o c •-« cu "o

••

3 3

rt

jj

7;^

i|

<y Pj ^_> qj j-

^ T ,

•fl

u

-a g

<; <; 3 en o-.

4)

O 0

Lg

-_J

's

^

'O O *rt

S
u

•
* o

^ 'to

T7' ^^r

"to : •
_a

t£ tO

c c

y

1

i

jj

O O w *^ O
*- 0 « £ 0

N 'Tj qj M

^o

o

XI

£ O

O

j

>fc»t*- CJ til **^

C

b

if J 1

0)

i

's '§

J J

tO

T)
B

c4

1

"3-2 ^^ 2

6 § 6 « §

•

_o
5

-v-

^ s 'i S

?^ • •

*? *£

S

13 "

-•

'S

•a -a c.S-

•

•^

1

'

0 fe >

V J

rf3
H3 <n

<U 1>

.s

« g

•d

<

B

rt

t

'? .2 >,

?

tf "S

A

c

b

Tl

C

*

>» s

II

w "*

ill

n3 o IT*

Attached or :
Attached or !

•i

s

\ Loricate, ere
t Lorica decun

'Solitary, attai

lllll

•§_B |^ S
<! rt S

./

1 Loricae solita

Loricae unitei

Free-swimmi

Sedentary

» Q

,

"*x^ ^

*•

V

^— —

— -v

i IH •

CJ ^

rt

*^*

r^ Ci G S

c

g

c

cS 0 C

•

O 'o W rf

c

. 'n?

.~

S 8 "8 ba

o

'?

H £ g

FAMILY.
/

I. MONADID^:.
Animalcules naked, usually
swimming ; flagellum termini
pedicle or caudal appendage.

II. PLEUROMONADIDyE.
Animalcules naked, tailless
gellum lateral or ventral.

III. CERCOMONADID>E.
Animalcules naked, with a

like caudal filament.

IV. CODONCECIDJE.

I Animalcules loricate.

V. DENDROMONADID^:.

Animalcules illoricate, with i
lique frontal border ; mostly
and constructing tree-like zo
dria ; flagella unequal, one Ion,
one short.

VI. BlKCECID^E.
Animalcules inhabiting
loricse, front border oblique

fl

OS

to

a

4)

o
B

i

*> ti

S O

VII. AMPHIMONADID^.
Animalcules naked, free-s

ming, or attached singly and pi
nently by the posterior extremi
by a tail-like filament; flagella

S ^ "to

OH .S

en <! g

OS 3

H O 13
^ >2 bo

<0 E

GENERA OF FLAGELLATA-PANTOSTOMATA.

231

Cladomonas.
Rh ipidodendrt

Spongomonas.
Diplomita.

, Heteromita.
, Colponema.
, Spiromonas.
. Phyllomttus.

Trepomonas.

Polytoma.

i

I

, Callodktyon.
Trichomonas.
Dallingeria.
Trimastix.

Tetramitus.
Tetraselmis.
Chloraster.

Hexamita.

!
t

, Magosphara.

<o t-- oo cf\

CO CO CO co

to

CO

CO

CO

OO O\ O «

CO CO Tf •<$•

N CO ^

*

*

^

•5 1

is 1 :

*

•

'

•

•

*

rt >-> g

a. o . o .

.

.

v a • N

55 « i_,

•

•

*

•

*

g 2 -1 .

(U

0)

B
B

B

'S '§1 1

: 8 : '

G

• tx :

.

,

t

.

a ' '
e- . .

o • •

i-i

V

1

B

.

0 § X °

11

2

a

•a

1

tn

0

N ^ ^3 w :

« 8 | :

:

1,

0)
0,

• '• § M

"o • •

O

:

§*

0 0 .> 0 3,

^o

PQ a

(X

Ul

13

& ^ § 'So--
"3 g *{ 8f S

o *•" .

O Q >•> •

:

1

:

I

• • rt '2

• >-c e

o .£

4)

^O

:

S"

•JQ >° aj " '"'

-.3 2

•^

U

. tao 5

*M '^ ^

In

H H 1 cT

1 ^ '&, :

T3

IM

O

•s

r§"

: : _B t/i

9 fS Q

O

OH

:

9

— r — B J

OJ rt T3" ;

<u
Is

M

a

o

: »1*

1/5 •" <c
"3 "3 »-

O

o

"o

r. 11

O £ ctf

E

6

1

^

1

a.

§

:1 II

"3 "3 3

22^

J

'§
5

1

"3

inhabiting a bi
• zoothecium .

inhabiting a co
inhabiting sepa

S T3 *^

O M • -

a

1

•a
1

rt

polymorphic, e

rt

1

"rt

jella vibratile
vibratile, one (
m vibra- J Fre
ailing .. \Ent

'2 '3 ,j>

a
: B

0

: flagella vibrat

!
1

1

united in sphei

</) cJ </)</)

D »— « QJ 1>

'•§ g |

2

•

8

z

rt _rt ^3 •"

a ^

_o

s

£

Bi 11

^•gj -^

B

S

"3

o

1

£ §> Si ^

I1 ^

<a

' -g

•a

0

1

!* 11

'2-- 23

13 £ 13
tjo_2 ba

1

Ji
D

1

-a

3

3
•3

JJ^ TO rt •*-*

^ ^f
^ S B '•w

i i

§

Lj

O

•a

B
•3

•a

'

i— i

^

<

^

<! H O

-.

^

^

VIII. SPONGOMONADID^E.
Animalcules symmetrically ovate,
ostly social and secreting variously (
odified protective coverings ; fla-
:lla of even length.

IX. HETEROMITID^.
Animalcules naked, free-swim-
ing, or temporarily attached by '
e posterior flagellum.

X. TREPOMONADID^.
Animalcules free-swimming, en-
ely unsymmetrical.

XI. POLYTOMID^;. \
Animalcules ovate, free-swim-

ing, with an indurated external '
.velope, multiplying by endoge- 1
»us subdivision. J

XII. PsEUDOSPORIDy<E.
Animalcules repent and natatory,
gella even.

XIII. SPUMELLIDyE. 1

Flagella three in number, diverse,
ie long and two short.

XIV. TRIMASTIGIDJE. ,
lagella three in number, subequal.

XV. TETRAMITID^E.
Flagella four or five in number.

XVI. HEXAMITIDyE. \

Flagella six in number. j

XVII. LOPHOMONADID^E.

Flagella numerous, animalcules
litary.

XVIII. CATALLACTID^;.
Flagella numerous, animalcules
rming social colony-stocks.

2 a So

23

»

2 S a

CO

CB

0

S

«

£

<! t;

< .2

<J "°

E"* • o

E-| p .2

S ^ S

OH g

U

^ C/5 O

o "^ ^

•fl

5^ ^ rt

H§ -5

^ >-3 ^

B

^ fl ^

^ /* \ •-"•

rt Q i*

P-C Q. t/J
"^ M

U

232 ORDER FLAGELLATA-PANTOSTOMATA.

oral aperture has been detected, e. g. Hcrpetomonas, Polytoma, Hexamita, and Tricho-
monas. that the animalcules derive their nutriment, as in the case of the Opalinidae,
by the direct absorption, at all points, of the proteaceous material held in solution in
the fluid media they inhabit. Whether this latter be the haemal or perivisceral fluid
of a higher animal, an animal maceration, or a vegetable infusion, protein in its con-
centrated and more or less diffused condition is invariably present, and its direct
absorption under such circumstances by the contained unicellular animalcules would
be strictly analogous to the alimentary process as performed by the individual cell-
units of the intestinal tract of all the more highly organized Metazoa. These
being>, in fact, live continually immersed within a, so to say, ready prepared bath of
nutritive broth, and require no display of energy beyond the passive one of assimila-
tion or endosmosis for the satisfying of their creature wants. So far, a group of
Flagellata presenting the physiological characteristics here submitted, has been
entirely overlooked, its representatives being simply collated with the ordinary
mouthed or mouthless species. Even Stein, in his recently published monograph,*
erroneously represents such unmistakable Pantostomatous forms as Oikomonas,
Spumc//a, and Anthophysa as possessing a well-defined oral aperture.

'1 he Flagdlata-Piintostomata, in common with the order of the Eustomata, maybe
conveniently divided into three minor sections or sub-orders, with reference to the
number of flagellate appendages, as indicated in the foregoing schedule.

A.— PANTOSTOMATA-MONOMASTIGA
(one flagellum only).

Fam. I. MONADIDJE, Ehrenberg.

Animalcules naked or illoricate, entirely free-swimming ; flagellum
single, terminal ; no distinct oral aperture ; an endoplast or nucleus and
one or more contractile vesicles usually present.

GENUS I. MONAS, Muller.

Animalcules free-swimming, exceedingly minute, globose, ovate, or
elongate, plastic and unstable in form, possessing no distinct cuticular
investment ; flagellum single, terminal ; food-substances incepted at all
parts of the periphery, not provided with a distinct mouth ; a nucleus or
endoplast and one or more contractile vesicles mostly conspicuous ; multi-
plying by longitudinal or transverse fission, or by encystment and the sub-
division of the entire substance of the body into a less or greater number
of sporular elements.

Inhabiting salt and fresh water, especially abundant in infusions.

In the genus Monas, as here delimited, are included the simplest known forms
of the typical Infusoria-Flagellata. Its specific representatives exhibit, so far as at
present discernible, no higher degree of organization than that of mere specks of
more or less granulate and vacuolar nucleated protoplasm, and possess as a locomotive
appendage a single thread-like vibratile flagellum. 1 heir extreme simplicity of contour,
combined with their very minute size and apparent absence of all readily appre-
ciable differential characteristics, necessarily renders it an exceedingly difficult task to
discriminate between the innumerable so-called species that have from time to time
been referred to this genus. A large proportion of these latter are without doubt

1 Infusionsthiere, ' Abth. Hi., 1878: Der Flagellaten.

GENUS MONAS. 233

simply varieties of the same type, transitional or larval conditions of other Flagellate
Infusoria or Radiolaria, which commence their existence as similar simple uni-
fligellate beings, or it may be the initial or zoospore phases of Algae, Palmellaceae,
or other Protophytic plants. Such being granted, it is only in a provisional sense,
and until their correct status shall have been decided by the light of more modern
investigation, that the majority of the specific forms collated under the present
generic title are admitted to this volume. Of those four or five types alone that are
placed first on the list can it be said that sufficient is known to permit of their recog-
nition as distinct and independent beings, and it is upon these few only that the
amended diagnosis of the genus, as here given, is constructed. While thus obliged
to leave a considerable number of species in an undecided and probational position,
the main object aimed at by the author will, it is hoped, be accomplished, and the
genus Monas be established upon a secure and substantial footing.

By the earlier writers, every animalcule whose dimensions were so minute that it
presented under the highest magnifying powers then available the aspect of a mere
motile speck, was consigned to this genus, while by even the most recent investigators
an almost equally incongruous assemblage of microscopic beings is similarly dealt with.
Thus Cienkowski, in his recent accounts of monadiform organisms, includes under this
same generic title both uniflagellate and biflagellate animalcules ; Stein, again, in his
recently published volume of plates, without detailed descriptions, of the Infusoria-
Flagellata, delineates as typical representatives of the genus Monas those triflagellate,
voluntarily attached, or free-swimming forms out of which, upon ample grounds,
Cienkowski formulated some years previously the genus Spumella. Typical members
of the present genus, as here defined, are in the same work referred by Stein to
the genus Cercomonas ; a step in the right direction being at the same time accom-
plished by his elimination of the stomatode forms Monas grandis, M. semen, and
M. ochracea of Ehrenberg, and creation for the same of the independent genera
Ccelomonas, Raphidomonas^ and Chrysomonas.

Particular and accurate attention should, above all things, be directed, in the
future investigation of these minute beings, to the manner in which food-matter is
ingested, it being only those entirely free-swimming, uniflagellate forms which aie
capable of incepting such pabulum at all parts of their periphery, after the manner
of an Amaba, or which, as is probably the case of Monas Dallingeri, absorb
nutriment in a fluid form through the same generally diffused area, that can rightly
lay claim to the present generic title.

Monas Dallingeri, S. K. PL. XIII. FIGS. 1-9.

Body ovate, rounded posteriorly, the anterior extremity more pointed
and slightly curved, surface smooth ; flagellum from one to one and a half
times the length of the body, flexible throughout when young, rigid towards
the base in older specimens ; no endoplast or contractile vesicle as yet
detected. Locomotion straight and uniform, without jerking or irregularity.
Length 1-4500" to 1-4000".

HAB. — Fish macerations.

The author has much pleasure in connecting with this species the name of the
authority who, in conjunction with Dr. J. Drysdale, has contributed so largely to our
knowledge of the minute organisms now under consideration. In their published
' Researches into the Life-history of the Monads,' already quoted at pages 29
and 133, this particular form is figured and described * under the title of the simple
" uniflagellate " or " multiple-fission " monad, and was obtained in great abundance
in a maceration of cod's head three months old. Its life-cycle, as worked out by
these indefatigable investigators, yields to none in the interest and completeness of

* 'Monthly Microscopical Journal,' vol. xi., No. Ixii., 1874.

234 ORDER FLAGELLATA-PANTOSTOMATA.

the phenomena elicited, and represents, indeed, the only member of the genus Monas
par excellence, as here recognized, with whose entire developmental manifestations
we are at present conversant.

The reproductive phenomena of this particular species, as reported by Messrs.
Dallinger and Drysdale, may be briefly epitomized as follows. The extraordinarily
rapid multiplication of this type being unaccounted for by the ordinary process
of transverse fission, or by the production of minute spores requiring time to
develop to maturity, a further investigation elicited that under certain conditions
there intervened a supplementary process of fission, by which as many as from
thirty to sixty individuals of appreciable size were produced from a previously
single zooid. The indications given by an individual about to increase by this
multiple mode of fission were its adoption, first, of a somewhat rounded outline,
then of a more irregular and slightly amoeboid form, and finally of a simple
spheroidal contour. In this last condition only, the flagellum disappeared, and the
animalcule entered upon a perfectly quiescent or encysted state. Patiently watched
with an amplification of about 3000 diameters, a cruciform mark or constriction
was observed to appear suddenly, dividing the sphere into four equal portions
(PL XIII. Fig. 3), other divisional lines quickly following, until the entire body was
partitioned by deep curved indentures with innumerable segments. An active
whirling motion of the sarcode then ensued, lasting from ten to as many as seventy
minutes, and at the end of this period it broke up into numerous sausage-shaped
bodies as shown at Fig. 5. These now exhibited a quick writhing motion upon each
other, which lasted for a space of seven to thirty minutes, the whole mass finally fall-
ing to pieces or detaching itself separately as uniflagellate monads, identical in shape,
though of smaller size, with the original or parent animalcules. No separate investing
membrane or indurated cyst was at any time associated with this process of multipli-
cation, the separate segments being held together until the time of their final libera-
tion by mere cohesion of their constituent sarcode. Reproduction by spores, pro-
duced by the genetic union or coalescence and encystment of two individuals, was
likewise ascertained by Messrs. Dallinger and Drysdale to play an important part in
the developmental life-cycle of this form. The zooids upon whom this special and
more important mode of propagation devolves are of slightly larger size and more
rounded outline than the ordinary forms ; the anterior extremity, or that nearest to
the flagellum, is also conspicuously and coarsely granulate.* Moving among the
smaller animalcules, they fix themselves to one of these as shown at Fig. 7, and the
two swim about joined to one another for a considerable interval. The smaller
monad is at length completely absorbed into the substance of the larger one, whose
movements now become sluggish, and terminate in its assumption of a slightly
flattened subspherical and encysted state (Fig. 8). The encystments, after remaining
quiescent for about thirty-six hours, open slowly, liberating, as shown at Fig. 9, what
appears to be merely a glairy fluid, differing slightly in density only from the surround-
ing water. Examined with the highest available amplifying glasses — that is, a -^-inch
objective, with a magnifying power of from 2500 to 15,000 diameters, no granular
composition indicating the presence of spores could be detected in the discharged
fluid, but in about seven hours after its emission minute points, hitherto too small for
detection, made their appearance, and rapidly increased in size. Movements in
these granular points were detected in the course of the next five hours, and soon
after this they swam off, corresponding in all respects, except for their slightly smaller
size, with the typical monads from whence they originally sprang.

Monas fluida, Duj. PL. XIII. FIGS. 10-18.

Body soft and semifluid, exceedingly variable in shape ; its most
regular contour elongate-ovate or subcylindrical, with the length equal to
about three times the diameter, but more frequently widest anteriorly,

* By accident the artist has omitted to reproduce the more coarsely granular aspect of the
anterior region.

GENUS MONAS. 235

tapering towards the opposite extremity, and there prolonged in an attenuate
tail-like manner, the sarcode of this tail-like prolongation often ragged in
outline or irregularly branched ; flagellum flexible throughout, equalling the
body in length ; contractile vesicle posteriorly located ; endoplast con-
spicuous, spherical, subcentral. Length of elongate-ovate zooids 1-1500".
HAB. — Vegetable infusions.

The species agreeing with the foregoing diagnosis, and, so far as it is possible to
determine, identical with the Monas fluida of Dujardin, has been obtained abundantly
by the author from hay infusions in fresh water. It usually makes its appearance on
the fourth day of maceration, and is often for the next day or two the most abundant
and dominant type, finally succumbing, however, in its turn to the onslaughts of its
more powerful congeners Dinomonas vorax and tuberculatus hereafter described.
The varieties of contour assumed by this remarkably plastic monad are too numerous
for description ; but a few of the more prominent of these are illustrated in the
accompanying figures. In the most attenuate example the entire length of the
body, including the tail-like prolongation, is equal to seven or eight times its
greatest breadth. The characteristic plasticity of the sarcode of this type would
seem in all instances to attain its highest development at the posterior extremity ;
on many occasions individuals were observed to adhere by this region to the glass
object-carrier, and to become drawn out into an attenuate shape by the mere force
of the capillary currents induced by the partial evaporation of the water. In this
method of adhesion the species may be said to advance a step towards the develop-
ment of a temporarily adhesive pedicle as obtains in the genus Oikomonas. Not
unfrequently the anterior extremity is abruptly or obliquely truncate, the animalcule
in the latter instance, when a subcylindrical contour is preserved, presenting an
appearance, excepting for the absence of the secondary flagellum, closely correspond-
ing with that of Chilomonas. The inception of particles of indigo at various points
of the periphery was frequently observed, as also the coalescence of two animalcules,
and the assumption by both these and by the solitary zooids of an encysted state.
The Monas sucdssa of Perty, characterized by its ragged and not unfrequently
bifurcate posterior border, is possibly identical with this species. On altogether
insufficient grounds Diesing has proposed to elevate this last-named type, as described
by Perty, into a new genus, conferring upon it the title of Dicercomonas.

Monas ramulosa, Stein, sp. PL. XIII. FIGS 22-24.

Body elongate, subcylindrical, widest posteriorly, tapering and conical at
the anterior extremity, three or four times as long as broad, the entire
peripheral surface frequently produced into a greater or less number of
attenuate lobate or digitiform prolongations ; flagellum as long or longer
than the body ; contractile vesicle spherical, posteriorly located, sometimes
subdivided into three or four smaller vacuoles ; endoplast subcentral or
anteriorly situated ; endoplasm granulate. Length 1-650" to 1-325".

HAB. — Fresh water.

This animalcule is figured, but not described, in Stein's recent work ' Infusions-
thiere,' Abth. iii., 1878, under the name Cercomonas ramulosa; but as in no one of
the examples delineated is an indication given of the caudal filament which so essen-
tially characterizes the last-named genus as here amended, its transfer to the present
one has been decided on. In some respects the general contour and remarkable
modification of the cuticular surface approximate this type to the Monas fluida of
Dujardin ; but the prolongations of the surface of the periphery take a more definite
digitate appearance. Should this species, in common with many other members of

236 ORDER FLAGELLATA-PANTOSTOMATA.

the group, pass through a repent phase of existence, its correspondence under such
conditions with the members of the Rhizo-flagellate genus Mastigamceba of Max
Schulze must be eminently conspicuous.

Monas obesa, Stein, sp. PL. XIII. FIGS. 20 AND 21.

Body elongate, subcylindrical, widest and rounded posteriorly, attenuate
and conically pointed anteriorly, about three times as long as broad,
the periphery usually produced at variable points into one or more attenu-
ately pointed, rectilinear, pseudopodal prolongations ; flagellum equal to or
exceeding the length of the body ; endoplast located in the median line
towards the anterior extremity ; contractile vesicle spherical, posteriorly
situated, sometimes divided into two secondary vesiculae ; endoplasm
coarsely granular. Length 1-650". HAB. — Fresh water.

This species is figured by Stein,* under the title of Cercomonas obesa; but is
evidently, as in the case of his Cercomonas ramulosa, correctly referable to the present
generic group. In addition to the two examples figured by him as possessing
respectively one and two posteriorly, but not terminally, developed pseudopodal
prolongations, a third specimen, as reproduced at Fig. 20, is represented with an
anterior conical prolongation only that projects close to the insertion of the fla-
gellum. To some extent the body-contour of this type corresponds with that of
Sterromonas formicina, represented at PL XXIV. Figs. 39 and 40.

Monas irregularis, Perty. PL. XIII. FIG. 19.

Body more or less globular, hyaline; flagellum slender throughout,
mostly curved at its distal extremity, over twice the length of the body ;
contractile vesicles two in number, minute, situated close to the lateral
border ; endoplast distinct, located centrally towards the anterior extremity.
Length 1-2500" to 1-1250". Hab. — Pond water.

The animalcule figured, and briefly alluded to by Cienkowski under the above
title,f is here provisionally accepted as the type of this species. The specific form
upon which Perty originally conferred this name, while corresponding in general
contour and proportions, is represented as not unfrequently exhibiting capillary or
angular peripheral extensions. This phase possibly represents the typical amceboid
condition assumed previous to the act of encystment and multiplication by segmen-
tation. In one of Cienkowski's figures the retention of a large particle of food
within a vacuole at the posterior extremity is clearly indicated.

Monas parasitica, Cienkowski, sp.

Body irregularly ovate, rounded anteriorly, smooth and transparent ;
flagellum very long and slender, more or less curved, three or four times
longer than the body ; contractile vesicles two or three in number, anteriorly
situated ; endoplast central, spherical. Length i-iooo".

HAB. — Fresh water.

Described by Cienkowski as Pseudospora parasitica. In its normal free-swimming
and flagellate condition this species frequently exhibits posterior lobate extensions
of the periphery ; the amoeboid phase preceding encystment is of short duration.

Infusionsthiere,1 Abth. iii., 1878. f ' Archiv fur Mik. Anat.,' Bd. i., 1865.

GENUS MONAS. 237

The body occupies but a small space within the membranous envelope of the cyst,
and breaks up into numerous sporular fragments, the indigestible residue of the
incepted food-particles being cast aside within the cavity of the cyst

Monas nitellarum, Cienk., sp.

Body minute, globose ; flagellum very slender and attenuate, six or seven
times as long as the body ; encystment spherical, double walled. Diameter
1-2500". HAB. — Fresh water, among decaying matter.

Synonymous with the Pseudospora nitellarum of Cienkowski.

Monas concava, Duj.

Body circular, meniscoidal, concave on one side and convex on the
other, thin centrally, the margin tumid ; flagellum long and slender, vibrating
throughout its length. Diameter 1-2000". HAB. — Marsh water.

It is impossible to decide whether this and the three following species referred
by Dujardin * to the genus Monas, belong to that generic group as here constituted,
or whether they do not represent imperfectly observed or imperfectly developed
animalcules of other Flagellata. Their admission here must consequently be
regarded as entirely provisional.

Monas elongata, Duj.

Body elongate, nodular, flexible, and changeable in form, vacuolate ;
flagellum long and slender. Length 1-1250".
HAB. — Putrid infusions with marsh water.

Monas attenuata, Duj.

Body ovoid, tapering at the two extremities, nodular and vacuolate ;
flagellum thick at its base, continuous with the pointed apical extremity.
Length 1-1500". HAB. — Putrid marsh water.

Dujardin intimates that a slightly more pronounced development of the posterior
extremity would necessitate the allotment of this form to the genus Cercomonas.

Monas oblonga, Duj.

Body oblong, irregular, tuberculate, enclosing numerous vacuoles ;
flagellum distinct, somewhat thickened at the base. Length 1-3000" to
1-1600". HAB. — Vegetable infusions.

Monas varians, Duj.

Body oblong, tapering anteriorly, its substance soft and glutinous,
exceedingly plastic and changeable in form. Length 1-800" to 1-625".
HAB. — Ditch water.

Monas constricta, Duj.

Body elongate, four or five times as long as broad, blunt, and rounded
posteriorly, narrower and often constricted in the centre. Length 1-1250".
HAB. — Infusions of gelatine with chlorate of potash.

* 'Histoire des Zoophytes Infusoires,' Paris, 1841.

238 ORDER FLAGELLATA-PANTOSTOMATA.

This species is probably identical with the form described further on under the
title of Sterromonas formirina, the second flagellum being of such small size as to
have easily evaded the resolving capacities of the magnifying lenses at Dujardin's
disposal. At the same time, another species — Oikomonas mutabili* — presents in
its free-swimming condition a somewhat similar elongate and constricted contour.

Monas Oberhauserii, Fres.

Body cylindrical, rounded at each extremity, hyaline, faintly carmine-
coloured, enclosing a variable number of intensely crimson globules ;
flagellum apparent only through the movements of the animalcule, which
are rotatory and tumbling. Length 1-2000" to 1-1150".

HAB. — Sulphur spring at Frankfort.

This monad is probably identical with the M. Okeni of Ehrenberg. The
M. bipunctata of Fresenius, found under similar conditions, but of smaller size, with
an elongate-oval figure, and enclosing one or more red points at each extremity,
apparently represents an earlier stage only of this form. The Monas truncata of
Fresenius, possessing two flagellate appendages, has been selected by Stein as the
type of the new genus Goniomonas.

Monas lamellula, Miiller.

Body minute, compressed, diaphanous, two or three times as long as
broad ; flagellum long and undulating ; movements forward in a zigzag
manner. Length 1-2000." HAB. — Salt water.

Originally described by O. F. Miiller as a marine form, but reported to De
Fromentel, also from fresh water.

In accordance with the views of the author, both this and the ten succeeding
specific types — embodied by De Fromentel in his ' Etudes sur les Microzoaires,'
Paris, 1876, and identified by him on the most slender grounds with the species
bearing the same titles first described by O. F. Miiller, Ehrenberg. and Dujardin —
might be advantageously consigned to the appended list of " Doubtful species " In
no single instance are the characters given sufficiently explicit for their absolute
identification as typical representatives of the genus Monas.

Monas Kolpoda, Ehr.

Body convex on one side, flattened on the other, the anterior extremity
pointed and bearing a long flagellum ; parenchyma enclosing green
granules ; movement oscillating. Length 1-1600". HAB. — Fresh water.

The above diagnosis, as recently given by De Fromentel, scarcely agrees with
the original one of Ehrenberg, who characterizes this species as oval or egg-shaped,
having a length of 1-7200" only.

Monas ovalis, Ehr.
Body ovate, colourless ; motion tremulous. Length 1-9600".

De Fromentel describes this species as differing from M. deses only in its absence
of colour and the less development of the flagellum. Ehrenberg gives as its habitat
the water from the fresh-water mussel, Anodon.

GENUS MONAS. 239

Monas gibbosa, Duj.

Body oblong or spheroidal, the surface having irregular distensions and
gibbosities ; flagellum long and undulating, usually springing from a
narrowed anterior region of the body. Length 1-2500".

This type was encountered by Dujardin in an infusion of gelatine, in company
with Monas lens, and of which, as he remarks, it possibly represents an altered con-
dition or variety. De Fromentel refers a form to this species agreeing with it in
general contour, but having the cuticular surface striate and granular, and with a
conspicuous lateral contractile vesicle.

Monas globulus, Duj.

Body subglobose, compressed and pointed anteriorly, constant in form ;
flagellum springing from the narrower anterior end ; surface smooth or
faintly granulate. Length 1-1700". HAB. — Salt water.

Dujardin describes this form as differing from Monas (Hderomitd) lens in the
more spherical form of its body, and in the absence of the superficial tuberosities
which frequently distinguish that species. De Fromentel reports the same type from
fresh water.

Mouas mica, Miiller.

Body oval, inconstant in form, tapering anteriorly, transparent, coarsely
granulate ; movement slow and oscillating. Length 1-1200".
HAB. — Fresh water.

This species is recognized under the above title by Miiller, Ehrenberg, and
De Fromentel.

Monas vinosa, Ehr.

Body globular; colour wine-red; motion tremulous. Length 1-12000"
to 6000". HAB. — Vegetable infusions.

The Monas rnbra of De Fromentel, of equally minute dimensions, and thus
characterized : " Body rounded, furnished with a long and relatively thick flagellum ;
colour bright red ; motion slow and tremulous," is apparently identical with the
above form. Both are, however, probably rightly referable to the Palmellaceae or
Protophytes.

Monas nodosa, Duj.

Body irregularly oblong, tapering posteriorly ; the frontal margin trun-
cate ; flagellum springing from the centre of this truncate border ; surface
nodular. Length 1-2000". HAB. — Salt water.

De Fromentel ascribes to this species a fresh-water habitat.

Monas viridis, Duj.

Body spherical, one half transparent, the other green ; flagellum long
and slender ; living socially. Diameter 1-2000". HAB.— Fresh water.

This species is probably the motile spore of some Algal. Dujardin refers it with
doubt to the genus, but De Fromentel has thought fit to retain it.

240 ORDER FLAGELLATA-PANTOSTOMATA.

Monas depressa, From.

Body elongate, the two extremities rounded ; the ventral side flattened,
the dorsal one convex ; flagellum always directed beneath. Length 1-1600".
HAB. — Fresh water.
This is probably a species of Petalomonas.

Monas sphaerica, From.

Body irregularly spherical; surface granulate, enclosing minute red
corpuscles ; flagellum slender, about three times the length of the body ;
contractile vesicle conspicuous, postero-lateral. Diameter i-iooo".

HAB. — Fresh water.

This species is almost the only representative of the genus satisfactorily delineated
by De Fromentel, its larger size permitting, with the magnification of 400 diameters
customarily employed by him in his investigation of these minute organisms, a
tolerably fair appreciation of its form and structure. No details are appended
as to the special conditions or circumstances under which it was encountered, but it
would seem not altogether improbable that it represents the motile form of the
trimastigate type Spumella vivipara.

Monas ovata, From.

Body* oval, widest posteriorly ; transparent, with yellow granulations
towards the posterior extremity ; the anterior end pointed and hyaline ;
flagellum long, slender, and undulating. Length 1-2000".

HAB. — Fresh water.

Doubtful Species.

The Monas crepusculum of Miiller and Ehrenberg, represented by minute
spherical points only, under a magnification of 800 diameters, and the M.punctum and
pulvisculus of the same authorities, figured in De Fromentel's recent work,* cannot be
admitted as independent species, being indistinguishable from the early germinating
conditions of numerous other larger animalcules. 'I he following species of the
older writers, reproduced by Pritchard,f are in most instances too ill-defined for future
identification, but may be added to complete the list : —

M. erubescens, Ehr., spherical, rose-coloured; motion slow and continuous;
diameter 1-1728". HAB. — Saltwater.

M. enchelys, Ehr., colourless ; motion slow, continuous. In marsh water, i-i 200"
to 1-960".

M. umbra, Ehr., ovate, colourless ; motion rapid. Among fresh Confervae.
1-2400".

M. hyalina, ovate, colourless ; active, seems to leap or jump. In stale water.
1-6000" to 1-2880".

M. gliscens, ovate, colourless ; motion gliding. In infusions of stinging-nettle.
1-4500".

M. eylindrica, solitary, elongate, colourless; motion revolving. In salt water.
1-1150".

M. Okeni, elongate, red ; motion revolving, vibratory ; social. In running water.
1-2300".

M. sodalis, conical, colourless ; social. In water-butts. 1-700".

* De Fromentel, 'Etudes sur les Microzoaires,' Paris, 1876.

t ' A History of the Infusoria,' by Andrew Pritchard, 4th ed. 1860.

GENUS C YA THOMONA S. 241

M. simplex, spindle-shaped, colourless ; motion gliding or rotatory. In water of
the Nile and at Berlin. 1-1720".

M. inanis, fusiform, colourless; motion vacillating. In stagnant and foul
water. 1-3600".

M sdntillans, fusiform; very active, motion vacillating. Among fresh-water
Confervas. 1-6000" to 1-4600".

M. Dumalii (described by Dujardin as possessing two flagella, and therefore
referable to the Dimastigous group), of a deep red colour ; in vast numbers in the
salt-marsh water of the Mediterranean, to which they give a deep blood-colour.

M prodigiosa, a minute red monad, producing the blood-like spots occasionally
appearing in bread and other farinaceous substances. (Cohn asserts this organism
to be a Vibrio, and not a Monas.)

M. astasioides, Pty., of variable form, often with one or two longitudinal lines and
a central vacuole. 1-1340".

M. piscatorum, irregularly oval, pointed anteriorly ; colourless ; flagellum short,
scarcely i^ times the length of the body; movements sluggish. 1-1400".

M sucdssa, oval ; usually truncate, rarely pointed behind ; colourless, with large
vacuoles ; flagellum twice the length of the body ; movement active and revolving.
In fresh pond water. 1-1800".

M, cordata, cordate as seen on one side, oval and truncate on another, rounded
anteriorly, hyaline or granulate; swims fast, with an oscillating motion, seldom
revolving ; flagellum difficult to discern, more than double the length of the body.
In pond water. 1-1140" to 1-1080".

M. urceolaris, small, urceolate, obliquely emarginate in front ; colourless ; flagel-
lum indicated only by movement produced in the water ; motion slow. In running
streams. 1-2640".

The Monas excavata of Perty, having two filaments, is not referable to this
present genus, and the M. rotulus, farcimen, and hilla of the same authority are
most probably the zoospores of Palniellaceae or higher Algae.

GENUS II. SCYTOMONAS, Stein.

Animalcules free-swimming, ovate, persistent in form, having a simple
terminal flagellum ; no distinct oral aperture.

This genus represented by a single minute species, figured but not yet described
at length by Stein, differs from Monas only in its persistent shape and accompanying
greater rigidity of the peripheral or ectoplasmic layer.

Scytomonas pusilla, Stein. PL. XIII. FIGS. 41 AND 42.

Body elongate-ovate or pyriform, narrowest anteriorly, about twice as
long as broad ; flagellum equalling or slightly exceeding the length of the
body ; contractile vesicle single, situated a little in advance of the centre of
the body. Length 1-1600".

HAD. — Fresh water. Dividing by longitudinal fission.

GENUS III. CYATHOMONAS, De Fromentel.

Animalcules free-swimming, ovate or cylindrical ; abruptly truncate or
excavate at the anterior margin ; a single long flexible flagellum projecting
from the centre of this truncate area ; contractile vesicle usually conspicuous ;
increasing by longitudinal fission ; no distinct oral aperture.

The genus Cyathomonas has been instituted by De Fromentel (' Microzoaires,'
1876) for the reception of certain flagellate types, differing from Monas only in the

R

242 ORDER FLAGELLATA-PANTOSTOMATA.

abruptly truncate or excavate contour of the frontal border. No details respecting
the mode of inception of food are recorded, and, in the absence of all evidence as
to the existence of a distinct mouth, it appears desirable to retain the genus among
those forms most closely allied to it structurally, in which food-particles are known
to be ingested at all points of the periphery. The several species described are
very briefly characterized, the descriptions and accompanying drawings being the
result of an examination with a magnifying power of 400 diameters only, which is
altogether insufficient for the full and exhaustive investigation of these minute
beings.

Cyathomonas turbinata, From.

Body elongate, turbinate, about twice as long as broad ; the posterior
extremity pointed, the anterior border truncate ; flagellum somewhat short,
not exceeding the length of the body ; parenchyma transparent, granulate ;
dividing by longitudinal fission. Length 1-1200". HAB. — Freshwater.

Cyathomonas spissa, From. PL. XIII. FIGS. 46 AND 47.

Body elongate-ovate, or subcylindrical, about twice as long as broad,
pointed posteriorly, widest in the centre, and slightly narrowing again at
the truncate anterior margin ; flagellum short ; contractile vesicle situated
laterally in the anterior third of the body ; parenchyma granular ; dividing
by longitudinal fission. Length of body 1-2000". HAB. — Fresh water.

The difference between this form and Cyathomonas turbinata, From., appears to
be too slight for specific separation. The figures given closely correspond with one
another, the contractile vesicle indicated in the present variety affording, indeed, the
only mark of distinction.

Cyathomonas viridis, From.

Body subcylindrical, about twice as long as broad, rounded posteriorly,
the anterior border truncate ; flagellum long and slender ; parenchyma
green, and granulate. Length 1-2000". HAB. — Fresh water.

Cyathomonas alba, From.

Size and contour identical with that of C. viridis, but the parenchyma
hyaline and less granular. This and the preceding form are evidently
varieties only of one species.

Cyathomonas lychnus, From.

Body hemispherical, truncate anteriorly ; posterior and peripheral
portion coloured green, the anterior border hyaline ; flagellum long and
slender. Diameter 1-3000". HAB. — Fresh water.

Cyathomonas turbo, From. PL. XIII. FIG. 48.

Body top-shaped, tapering and pointed posteriorly, the anterior border
truncate ; flagellum very long and undulating, three or four times the
length of the body ; parenchyma granulate ; contractile vesicle antero-
lateral. Length of body i-i 600". HAB. — Freshwater.

GENUS LEPTOMONAS. 243

Cyathomonas emarginata, From.

Body elongate, subcylindrical, slightly tapering posteriorly, the anterior
border truncate, notched or emarginate on one side ; flagellum long and
slender, nearly twice the length of the body ; parenchyma clear yellow,
with red granules interspersed ; contractile vesicle conspicuous, situated in
the posterior third of the body. Length of body i-iooo".

HAB. — Fresh water.

Cyathomonas elongata, From.

Body elongate, about two and a half times as long as broad, tapering
posteriorly, slightly constricted immediately behind the truncate anterior
border; flagellum long and slender; parenchyma clear yellow, enclosing
a few red granules ; contractile vesicle situated in the .posterior third of the
body. Length 1 800". HAB. — Fresh water.

The distinction between this and the preceding type is apparently insufficient for
their specific separation.

GENUS IV. LEPTOMONAS, S. K.
(Greek, leptos, slender ; monas.)

Animalcules free-swimming, persistent in shape, elongate fusiform or
aciculate, bearing a single long undulating flagellum at the anterior
extremity ; no distinct oral aperture yet detected.

The above generic title combined with the following specific one is here intro-
duced for the reception of the monoflagellate animalcule figured and briefly described,
without any name, by O. Biitschli in the ' Zeitschrift fur Wissenschaftliche Zoologie,'
Bd. xxx. Hft. ii., for January 1878. While corresponding with the ordinary repre-
sentatives of the genus Monas in its simple monoflagellate type of structure, it is to
be distinguished from them by its persistent acicular form. From what little is at
present known of it, it is almost impossible to decide whether this organism possesses
a sound claim to the separate generic distinction here accorded it, or whether it is
not the developmental phase of some other flagellate species. It was originally
proposed to employ the generic title of Rhaphimonas —with referen :e to its acicular
contour — for the distinction of this specific form. The contemporary adoption of
the almost identical one of Raphidomonas by Stein, in connection with the Monas
semen of Ehrenberg, has, however, made it desirable to substitute a new name for
the present form. By accident, the previously selected title has been employed by
the author in an article on parasitic Infusoria contributed to the ' Popular Science
Review' for October 1880.

Leptomonas Butschlii, S. K. PL. XIII. FIGS. 25 AND 26.
Body elongate fusiform, pointed at each extremity, but most attenuate
posteriorly, eight or nine times as long as broad ; flagellum nearly twice the
length of the body ; a contractile vesicle situated at a short distance from
the anterior extremity, and a little behind this a dark, granular, nucleus-like
body. Length 1-2250".

HAB. — Parasitic, within the intestinal tract of the Nematozoon Trilobus
gracilis,

R 2

244 ORDER FLAGELLATA-PANTOSTOMATA.

This species was found by Biitschli in considerable quantities in the intestinal
tract of the above-named host ; some freely detached, and others united to one
another in clusters by their posterior extremities. Their movements when liberated
into the surrounding water, were swift and vigorous.

GENUS V. OPHIDOMONAS, Ehr.

Animalcules free-swimming, very elongate, thread-like or vermicular,
persistent in shape but more or less spirally curved ; a single flagellum at
the anterior extremity ; parenchyma usually enclosing numerous refringent
corpuscles.

The single species referred to this genus by Ehrenberg in his ' Infusionsthiere,'
under the title of Ophidomonas jenensis, but without any accompanying illustration,
was represented as a loricated animalcule. In a more recent publication, however,*
he gives an illustration of both this and a second presumed form of the same genus,
O. sanguinca, which by no means supports such an interpretation. The close
correspondence in general contour of the members of this genus with those of
Vibrio or Spirillum is at first sight very striking ; the larger size and presence of
a flagellum at the anterior extremity only of the thread-like body in the case of
C. jenensis, afford, nevertheless, substantial marks of distinction. The motions
of these organisms in the living state are furthermore entirely distinct from those
of Spirillum and its allies, the body being drawn through the water after the manner
of the ordinary Flagellata by the vibrations of the single anterior flagellum, while
with the Spirilla the posterior flagellum represents the organs of locomotion, and
propels the body in advance. The existence of an endoplastic or contractile vesicular
system remains to be demonstrated, as also whether or not solid food-particles can
be ingested.

Ophidomonas jenensis, Ehr. PL. XIII. FIGS. 27 AND 28.

Body elongate, vermicular, obtusely rounded at each extremity, more
or less spirally twisted ; about one-twelfth as broad as long ; flagellum
undulating, nearly equalling one-half of the body in length ; colour olive-
brown, enclosing one or more rows of clear refringent corpuscles. Length
1-570". HAB. — Spring water. Increasing by transverse fission.

Ophidomonas sanguinea, Ehr.

Body very long, slender, and flexible ; about twenty-four times as long
as broad ; parenchyma usually transparent, and enclosing minute brilliant
crimson corpuscles, sometimes suffused with a paler tint of the same colour.
Length 1-570". HAB. — Pond and brackish water.

Although reported by Ehrenberg as an inhabitant of brackish water, examples
according in all essential points with the type of this species, as figured by that
authority, have been obtained by the author in pond water. Such personal acquaint-
ance with it has, however, given rise to the opinion that this organism is in no
way related to the preceding form, but represents rather the filamentous con-
dition of a Spirillum closely, if not absolutely, identical with the organism figured and
described by Messrs. P. Geddes and J. Ewart in the ' Proceedings of the Royal
Society,' p. 482, pi. xi. fig. 4, 1878. No flagellate appendages could be discovered
with the comparatively low magnifying power then at disposal, and its movements

' Abhandl. Berlin Akad.,' 1862.

GENUS HERPETOMONAS. 245

as observed were more repent than natatory, being chiefly confined to worm-like
writhings among the vegetable debris in which it was discovered. All the speci-
mens met with by the author possessed the perfectly transparent parenchyma
with the enclosed brilliant crimson corpuscules distinctive of the species. The
form figured and referred to this type by Cohn (reproduced by T. Jeffrey Bell,
'Quart. Jour. Mic. Sc.,' pi. xx., 1876) is altogether distinct, and an undoubted
Vibrio with a long flagelhim at each extremity. A far greater likeness exists, on
the other hand, between Ehrenberg's original drawings of Ophidomonas sanguined
and the " linear filaments of Bacterium rubescens" figured by Professor E. Ray
Lankester in a subsequent number of the same journal.

GENUS VI. HERPETOMONAS, S. K.
(Greek, herpeton, snake ; monas.)

Animalcules free-swimming, elongate or vermicular, highly flexible ;
the posterior extremity often the most attenuate, but not constituting a
distinct caudal appendage ; flagellum single, terminal ; contractile vesicle
usually conspicuous. Habits mostly endoparasitic.

This new genus is instituted for the reception of the form figured by Stein,
' Infusionsthiere,' Abth. iii., 1878, under the title of Cercomonas muscce-domesticce,
and identified by that authority with the Bodo musca-domestica of Burnett and the
Cercomonas muscarum of Leidy. The entire absence of a distinct caudal filament
serves, however, at once to distinguish it from the typical representatives of either
of the two last-named genera, and approximates it the more nearly to Leptomonas
or Ophidomonas. A second minute form recently discovered by Mr. T. R. Lewis in
the blood of rats is provisionally referred to this generic group.

Herpetomonas muscse-domesticse, Burnett sp. PL. XIII. FIGS. 29-34.

Body vermicular, highly flexible and polymorphic, usually thickest
centrally and tapering to a sharp point at each extremity, from ten to
twenty times as long as broad ; flagellum equalling or slightly exceeding
the body in length, thick at its base and becoming gradually more attenuate
towards the distal end ; parenchyma granular ; contractile vesicle single,
located near the anterior extremity; endoplast inconspicuous. Length
1-650" to 1-430".

HAB. — Intestine of common house-fly, Musca domestica.

The synonyms of this species have been recorded in the preceding diagnosis of
the genus. According to the recent figures, with their descriptive indices given by
Stein, a more marked flexibility of the body, permitting the animalcule to assume
various snake-like and other contorted shapes, is especially characteristic of the
younger and smaller zooids.

Herpetomonas Lewisi, S. K. PL. XIII. FIGS. 35-40.

Animalcules exceedingly minute, attenuate and vermicular under
normal conditions, but highly polymorphic and capable of assuming a
variety of contours ; flagellum single, terminal, two or three times the length
of the extended body ; no contractile vesicle, endoplast, or other internal
differentiation as yet detected. Length 1-1500".

HAB. — The blood of Indian rats.

246 ORDER FLAGELLATA-PANTOSTOMATA.

The circumstances under which the animalcules distinguished by the fore-
going title were first discovered by Mr. T. Richards Lewis, are so graphically
described by himself in the ' Quarterly Journal of Microscopical Science ' for
January 1879, tnat an abstract in extenso from that serial is herewith submitted.
Having been directed by the Indian Government to prosecute inquiries respecting
the Spirillum of Bombay fever, he remarks : — " Whilst doing this I had occasion to
examine the blood of a considerable number of animals, and eventually (July 1877)
detected organisms in the blood of a rat, which at first sight I took to be of
the nature either of vibrions or spirilla. The blood, when transferred to the
microscope, appeared to quiver with life, but for some considerable time nothing
could be detected to account for this animated condition, as the blood-corpuscles
were somewhat closely packed. On diluting the blood with a half per cent, solution
of salt, motile filaments could be seen rushing through the serum and tossing the
blood-corpuscles about in all directions. Their movements were of a more undu-
latory character than are the movements of spirilla, and the filaments were thicker, and
more of a vibrionic aspect. They were pale, translucent beings, without any trace of
visible structure or granularity ; but as their movements were so rapid, exact informa-
tion as to their microscopical characters could not be ascertained at the time. The
slides were, therefore, placed under a bell-glass until these should diminish.

" On the following morning the activity of the filaments was much less. Their
movements were more restricted and more undulatory in character, and the blood-
corpuscles, having become somewhat agglutinated, had apparently squeezed out the
organisms, so that the latter occupied the serum-areas of the preparations. After
watching their movements for some time under a Hartnack's No. 9 immersion
objective, it was observed that every now and then blood-corpuscles, some con-
siderably distant from any visible motile filament, would suddenly quiver. On
carefully arranging the light it was eventually observed that this movement was due
to the existence of a very long and exceedingly fine flagellum, apparently a posterior
flagellum, as the organisms seemed generally to move with the thicker end forwards,
the flagellum being seen following it, and lashing the fluid during the moment it
remained in focus. I have not been able to detect any flagellum at the opposite
end. They may sometimes be kept alive for two or three days, but generally the
greater portion will have died within twelve or twenty-four hours ; and not only
have died, but also disappeared from view.

" When very carefully watched, the plasma constituting the thicker portion of their
substance may be seen suddenly to swell out at certain places, sometimes so as to
divide the ' body ' into two parts ; at other times two or three such constrictions and
dilatations may be detected, the dilatations being possibly observable only on one
side. At other times they assume an arrow-shaped aspect ; occasionally something
like granularity may be observed before their disappearance, but not a trace of them
is left after their disintegration. It seems as though they had been dissolved in the
serum in which they were found. I have examined the blood of a great number of
rats for the purpose of ascertaining what proportion of them contains these organisms
in their blood, and find that of those specially examined for this purpose, their
existence was demonstrated in 29 per cent. Sometimes, however, the number
detected were very few, not more than one or two in a slide, but in the greater
number of cases they were very numerous, every slide containing several hundreds."

Mr. Lewis further remarks that the nearest approach to a description of these
haematozoa met with by him is contained in O. F. Biitschli's account of a flagellate
parasite obtained from the intestinal canal of the free nematode Trilobus gracilis.*
He -also gives quotations from Dr. Bastian's 'Beginnings of Life,' where, on the
authority of Dr. Gros, minute worms or " vermicules " are recorded to have been
observed in the blood of a field-mouse in such numbers as to cause the blood to
present an animated aspect, as also that the blood of the mole has been found
to exhibit a similar phenomenon. It is a remarkable circumstance that the rats

* This form has been previously figured and described under the title of Lfplomonas Biitscklii.

GENUS ANCYROMONAS. 247

affected with these minute parasites occupied a restricted portion only of the pre-
mises on which they were first discovered. One point especially worthy of remark,
as recorded by Mr. Lewis, has reference to the position of the flagellum. If, as he
is inclined to maintain, this organ is produced from the posterior extremity, and
propels instead of draws the animalcule through the inhabited serum, we have
presented a structural and functional feature without parallel among the other
representatives of these Protozoa flagellata, the recognition of which would demand
the creation of a distinct generic and family group for the reception of these
singular organisms. The correspondence of these animalcules, this last-named
interpretation of the flagellum being correct, with the spermatozoa or male genetic
elements of ordinary Metazoic animals, is most remarkable, and not unnaturally
affords a foundation for the suggestion that further investigation may possibly
demonstrate their identity with the discharged spermatic elements of the minute
Nematodes, Micro-filariae, or other Metazoic endoparasitic forms known to flourish
amid the same surroundings.

GENUS VII. ANCYROMONAS, S. K.

(Greek, ancyra, anchor; monas.)

Animalcules ovate or elongate, free-swimming or adherent at will ;
flagellum single, trailing, adhesive or anchorate at its distal extremity,
vibratile throughout the remainder of its length ; endoplast and contractile
vesicle conspicuous.

The single type referred to this genus is of much interest, it combining in its
single trailing filament the functions of both the trailing and vibratile flagella of
such genera as Heteromita or Anisonema. It is further remarkable as corresponding
in its mature form with the earlier or larval condition of the representatives of these
two last-named generic types, in the former of which more especially (see Heteromita
rostrata and H. uncinatd) it has been demonstrated by Messrs. Dallihger and Drysdale
that the trailing or anchorate flagellum is the first to make its appearance, and
continues for a while the sole organ of locomotion.

Ancyromonas sigmoides, S. K. PL. XIII. FIGS. 49-53.

Body persistent in form, gibbously ovate or sigmoidal, about three times
as long as broad, the anterior extremity pointed and recurved ventrally, the
posterior one sometimes rounded, but more often shortly pointed and
slightly recurved in an opposite direction ; flagellum continuous with the
recurved anterior extremity, reflected backwards or ventrally, about twice
the length of the body, the distal extremity adhesive or anchorate, the
remaining portion vibratile or undulating ; endoplast spherical, subcentral ;
contractile vesicle situated close to the anterior extremity. Length 1-5000"
to 1-4000".

HAB. — Salt water, among decaying Fucus. Increasing by oblique fission
and by encystment and breaking up of the body into spores.

This species was obtained at St. Heliers, Jersey, in September 1878, in vast quan-
tities, among a mucilaginous exudation from fronds of the seaweed Fucus siliquosa
that had been macerated in sea-water for the space of one week. As first seen
with a magnification of 800 diameters only, the author was inclined to anticipate
that the long, reflected and adherent flagellum was only one of two flagellate appen-
dages, and that another finer vibratile one was stationed at the anterior extremity
which would thus identify the animalcule with the typical representatives of the genus

248 ORDER FLAGELLATA-PANTOSTOMATA.

Heteromita. A more careful investigation, however, aided by the employment of a
^Jg-inch objective with a magnification of from 2500 to 5000 diameters, conclusively
demonstrated that no other flagellate appendage existed, and that the single one
present fulfilled in a remarkable manner the functions performed in Heteromita by two
such organs. In the free-swimming animalcules, which were less numerous than the
adherent ones, progression was effected in a straight line, accompanied by an oscillat-
ing motion, the single flagellum trailing in the rear like the posterior one of Heteromita,
but slowly undulating throughout its length, and accomplishing by its vibrations the
advancement made. In the temporarily adherent forms, fixed to the glass object-
carrier or fragments of vegetable debris by the adhesive extremity of the same flagel-
lum, a similar undulating action of the remaining length of this organ was apparent,
this undulating action causing the entire organism to oscillate slowly up and down
(see PI. XIII. Fig. 50), and inducing at the same time a current to set in towards the
animalcule's body. Viewed in profile, the motile flagellum seen just beneath the
ventral surface of the body, presented at times an appearance closely corresponding
with that of a minute undulating membrane ; the body, however, in the next minute
tilting away from the flagellum, exhibited its true nature. The phenomena attend-
ing the process of fission in this species were further observed to be somewhat
abnormal. This takes place obliquely, the first indication of the1 impending process
being a lengthening out of the body, accompanied by the greater prolongation of the
more or less pointed posterior extremity until it attains a curvature, though in a
reversed direction, corresponding with that of the anterior end, and develops at its
apex a flagellum similar in all ways to the anterior one originally possessed. No
trace of segmentation, however, has as yet made its appearance, and the animalcule
remains riding at anchor or floats through the water, presenting (as shown at
PI. XIII. Fig. 51) a symmetrically sigmoidal contour closely identical with
that of Trepomonas agilis, as seen from a lateral point of view (see PI. XIX.
Fig. n), the two similar flagella divergent from each recurved point assisting to
complete this likeness. Presently a faint oblique line makes its appearance,
extending from above the median point of the dorsal surface of the original
animalcule, downwards and backwards to behind the median point of the ventral
region. This faint line gradually increases in the clearness of its delineation, and
soon assumes the aspect of a distinct groove, which gradually deepens until the
anterior and posterior halves become separated from one another as two precisely
similar and undistinguishable units. Both bear the characteristic reflected flagellum,
and likewise the central endoplast and antero-terminal contractile vesicle, these
respective structures having also made their appearance previous to the commence-
ment of the fissive process, the former by the segmentation of the original endoplast,
and the latter by independent development. The encystment of zooids which
previously exhibited an irregular amoeboid phase, and the subdivision of these into
eight or sixteen macrospores, giving rise to animalcules similar in shape to, but of
much smaller size than the adults, have been observed, but not as yet the coal-
escence or genetic union of two or more units, and the breaking up of their united
masses into more minute and abundant microspores.

Fam. II. PLEUROMONADID-2E, S. K.

Animalcules naked or illoricate, entirely free-swimming, flageilum single,
lateral or ventral ; no distinct oral aperture.

GENUS I. PLEUROMONAS, Perty.

Animalcules free-swimming, kidney-shaped, bearing a single vibratile
flagellum which projects from the centre of the concave ventral side ; no
distinct oral aperture.

GENUS MEROTRICHA. 249

Monadiform beings, coinciding in form with the representatives of the genus
Pleuromonas, as formulated by Max Perty, have been met by the author on several
occasions. Seeing, however, that similar forms represent the earlier or larval con-
ditions of other Flagellate organisms, such as Salpin^ceca fusiformis and Anthophysa
vegetans, the present retention of this genus must be regarded as entirely provisional.
It is, further, by no means improbable that the type P. jaculans, upon which the genus
has been founded, is identical with the Heteronema (Bodd) saltans of Ehrenberg, and
which, in addition to exhibiting similar leaping movements, appears under insufficient
magnifying power to possess a single flagellum only.

Plenromonas jaculans, Pty. PL. XIII. FIGS. 43 AND 44.

Body kidney-shaped, colourless, slightly granulate ; flagellum about three
times the length of the body. Movements eccentric, jerking and leaping.
Length 1-6000" to 1-3160". HAB. — Stale water and infusions.

The Pleuromonas granulosa of De Fromentel thus characterized :— Body ovoid,
granular, rounded posteriorly, the anterior extremity attenuate, sharply recurved ;
flagellum proceeding from the apex of the anterior extremity, and often folded
between the recurved portion and the body ; parenchyma granulate ; contractile
vesicles two in number, posteriorly situated. Length 1-800" — cannot be generally
associated with P. jaculans, and would seem to either represent the type of a new
genus, or possibly an imperfectly observed Heteromita.

GENUS II. MEROTRICHA, Mereschkowski.

Animalcules free-swimming, persistent in form, more or less ovate ;
flagellum single, issuing from a pit-like depression of the ventral surface ;
parenchyma enclosing trichocyst-like corpuscles. HAB. — Fresh water.

Merotricha bacillata, Mereschk. PL. XIII. FIG. 45.

Body evenly ovate or elliptical, one and a half times as long as broad ;
ventral depression with associated flagellum situated at a short distance
from the anterior extremity ; a sheaf-shaped fascicle of rod-like trichocysts
occupying a median position at the anterior extremity; cuticular surface
entirely smooth ; endoplasm coloured green ; contractile vesicle situated
immediately behind the fascicle of trichocysts. Dimensions unrecorded.

HAB. — Fresh water : Lake Onega, Mereschkowski.

This species, described by C. von Mereschkowski, in company with many newly
discovered Protozoic types,* is of special interest, it representing one of the very few
Flagellate animalcules in which the presence of trichocysts has been recorded.

Fam. III. CERCOMONADID^S, S. K.

Animalcules naked, free-swimming or adherent, provided with a per-
manent or temporarily developed caudal filament ; vibratile flagellum
single, terminal ; no distinct oral aperture.

* " Studien iiber Protozoan des Nordlichen Russland," ' Archiv f. Mikrosk. Anatomic.' Bd. xvi.,
1878.

250 ORDER FLAGELLATA-PANTOSTOMATA.

GENUS I. OIKOMONAS, S. K.
(Greek, eoika, resembling ; monas.)

Animalcules exceedingly minute, plastic and unstable in form, ovate,
globular, or elongate, sometimes free-swimming and sometimes attached by
a temporarily developed thread-like prolongation of the posterior extremity
of the body ; flagellum single, anteriorly located, subservient when swimming
to the purpose of locomotion and in the attached condition to bringing food-
particles within reach, these incepted at any portion of the periphery ; con-
tractile vesicle and endoplast usually conspicuous.

HAB. — Fresh and salt water, abundant in infusions.

This new generic title is introduced for the reception of all those uniflagellate
species that correspond precisely in their free-swimming state .with those of the preced-
ing genus Monas, but which possess in addition the faculty of attaching themselves at
will to foreign bodies through the medium of a thread-like extension of the sarcode
of the posterior end of the body. Preferring again to pursue a nomadic life, this
extemporized pedicle is withdrawn into the substance of the parenchyma, and the
animalcules swim away under conditions and appearances identical with those pre-
sented during their previous wandering state. As a necessary consequence, an
acquaintanceship of some duration is in most instances absolutely requisite for the
precise determination as to which of the two genera, Monas or Oikomonas, certain
animalcules should be referred. In their more typical fixed or stalked condition
the identification of the representatives of the last-named genus presents no difficulty ;
but the same zooid, as hereafter shown, sometimes exhibits in its nomadic state an
aspect so entirely divergent from the fixed one, that unless the passage from the one
to the other has been actually witnessed, their specific relationship would not so much
as be suspected. With the typical form Oikomonas mutabilis, here introduced, has
naturally to be included the Monas termo of Professor H. James-Clark, recently
demonstrated by that authority * to possess a stalked as well as a free-swimming
condition. The possession of a single flagellum only instead of one long and one or
two shorter ones, serves to distinguish Oikomonas respectively from the two genera
Physomonas and Spumella.

Oikomonas mutabilis, S. K. PL. XIII. FIGS. 55-64.

Body plastic and variable in form — in the attached condition — symmetri-
cally ovate, pyriform, or subspherical, seated on a slender pedicle about
equal to the body in length — in the free-swimming condition — changing
from spherical or ovate to an elongate contour, about three times as long as
broad, with a rounded and wider posterior extremity, a slightly constricted
central portion, and a bluntly pointed and somewhat truncate anterior
border ; flagellum long and slender, inserted at the apical extremity, when
swimming held arcuately and apparently rigidly in advance ; parenchyma
colourless, more or less granular, enclosing anteriorly a spherical endoplast,
and posteriorly two contractile vesicles. Dimensions of subspherical
attached body 1-1500" ; length of elongate free-swimming zooids 1-750".

HAB. — Vegetable infusions in fresh water ; gregarious ; motion in the
water straight and even.

* 'Memoirs Boston Soc. Nat. Hist.,' vol. i., part iii., 1868.

GENUS OIKOMONAS. 251

This species has been obtained abundantly in a maceration of hay in spring
water, in which at times it absolutely swarmed. The relationship of the elongate
free-swimming zooids to the sedentary ovate or subspheroidal ones, was not
for a long while determined, the former being indeed chronicled in the author's
note-book as elongate nomadic monads, most nearly resembling the Monas
constricta of Dujardin, and representing probably an early and monoflagellate
condition only of the species described later on under the name of Sterromonas
formicina. The identity of the two was demonstrated while examining a group of
stalked individuals that had become isolated within a small space in the glass slide,
through the gradual evaporation of the water. As this space became still more
limited by the encroachment of air the animalcules apparently took alarm. Detach-
ing themselves, the pedicle contracted and disappeared within the posterior
protoplasmic substance, the body became at once less broadly ovate, and assumed
within a few seconds the elongate contour, with a slightly constricted central region
identical with the free-swimming types before observed. In this elongate form the
monads swam round and round the confines of the liquid space, now less than
the diameter of the field of the TVinch objective, vainly seeking a pathway for
escape, and were ultimately dried up. This identity of the locomotive and fixed
forms being once discovered, the further verification of the fact proved a com-
paratively easy task, the transformation being observed not only of the fixed to the
free-swimming type, but that also of the latter to the sedentary one. In this
instance the animalcule became attached by an irregularly-shaped mucilaginous
extension of the posterior extremity, which gradually assumed a slender and thread-
like aspect accompanied by a shortening and thickening of the outline of the body.
The rigid extension of the flagellum in both the attached and motile phases of
this species imparts to it, in the latter instance, a stiffness of motion in the water,
corresponding closely with that of Sterromonas, with which it was at first supposed
to be identical. This apparent stiffness is shown by the application of reagents,
or when the animalcules become exhausted through the want of oxygen, to be a
mere optical aspect, the rotation of the distal end of the flagellum being then
conspicuous, while the whole organ as death approaches loses its seeming rigidity,
and becoming flexible, feebly undulates throughout its length. Reproduction by
the longitudinal fission of detached ovate examples of this species, accompanied
by a division of the conspicuous spherical endoplast, has been noticed, as also the
encystment and the breaking up of the encysted zooids into spore-like bodies.
Young individuals of elongate, conical outline, with a truncate anterior end and
rigidly projecting flagellum, which exhibited a similar stiff comportment during
natation, occurred abundantly among the adult animalcules. The smaller of these
immature forms measured about one quarter only of the length of the full-grown
specimens, every gradation in size from the one to the other being traceable. The
ingestion of food during the sedentary condition at different points of the periphery
was frequently observed.

Oikomonas termo, J.-Clk. sp. PL. XIII. Fi -s. 78-80.

Body ovate or subspherical, somewhat compressed, rounded posteriorly,
free-swimming, or attached by a thread-like pedicle of variable length ; the
anterior margin notched or emarginate and exhibiting a projecting lip-like
angle ; flagellum springing from the notch produced by the lip-like promi-
nence extended rigidly in advance and slightly curved, about twice the
length of the body ; parenchyma colourless, more or less granular ; con-
tractile vesicle posteriorly located ; endoplast spherical, subcentral. Length
of body 1-5000" to 1-3000". HAB. — Fresh water and vegetable infusions.

This species, regarded by Professor H. James-Clark (/. c. p. 306) as probably
identical with the Monas termo of Miiller and Ehrenberg, is referred by O. Biitschli

252 ORDER FLAGELLATA-PANTOSTOMATA.

to the genus Spumella of Cienkowski. The absence, however, of the two shorter
flagella at once demonstrates the necessity of their generic separation.

It is in connection with this form that Professor James-Clark has sought to demon-
strate the existence of a distinct mouth, which, in consequence of his having witnessed
the entrance of food at this spot on many occasions, he maintained to be situated
between the base of the flagellum and the lip-like prominence. O. Biitschli again has
more recently advocated the recognition of the lip-like prominence as the recipient
of the food-substances that are thrown backwards against the body by the vibratile
action of the flagellum. On repeated occasions, however, the author has satisfied
himself that the ingestive area has no such restricted limits, but that it is distributed
throughout the entire peripheral surface, from any point of which, if a food-particle
strikes it, a film of sarcode flows out to seize it. It is at the same time requisite to
observe that in the majority of instances these particles are thrown back with such
precision as to fall upon the lip-like prominence or other portion of the anterior
border, a prolonged observation of the same animalcule being usually requisite for
the detection of those more exceptional instances in which it impinges upon, and is
engulphed by, the lateral or posterior region. The contractile vesicle and endoplast
in this species, in accordance with Biitschli's observations, lay close by side of
one another towards the anterior border of the body. Professor James-Clark,
however, gives a more posterior location to the last-named structure, a similar posi-
tion being distinctive of the examples observed and here figured by the author.
When swimming, this species glides along smoothly in a straightforward direction,
propelled by the whirling motion of the distal extremity of the flagellum, which
otherwise presents that rigid arcuate aspect which characterizes the fixed condi-
tion ; the body varies to no appreciable extent in this locomotive form from the
more typical sedentary phase. The Monas neglecta of James-Clark, separated
from M. (Oikomonas) termo by that authority on account of the more active pulsation
and slightly more anterior location of the contractile vesicle, and by the greater length
and more sigmoid flexure of the anterior flagellum, but agreeing in all other essential
details with the present species, while referable to the genus Oikomonas, appears
to possess almost too slender a claim for independent specific recognition.

Oikomonas obliquus, S. K. PL. XIII. FIG. 72.

Body subspherical, rounded posteriorly, with a strongly developed
conical anterior lip-like prominence; flagellum about three times the length
of the body, projecting from the notch produced by the abrupt rising of the
anterior lip, rigid and slightly arcuate, deflected at an angle of about 45°
from the perpendicular axis of the body ; pedicle slender, about equal to
the body in length ; parenchyma very clear and transparent. Greatest
length 1-7500". HAB. — Pond water.

Although somewhat resembling Oikomonas termo, this species may be readily
distinguishable from that form by its exceedingly minute size and the remarkably
oblique flexure of the flagellum. This organ in both the latter and preceding
type is continuous at its base with the axial line of the body, but becomes slightly
curved in the distal portion of its course ; here, however, we find it bent aside
from its point of origin at an angle of no less than forty-five degrees. In connec-
tion with this species a remarkable phenomenon was observed relating to the
inceptive capacities and subsequent method of getting rid of effete and unassi-
milated food-particles. Finely pulverized carmine was voraciously swallowed by
the monads, and in many instances in such a quantity that the entire parenchyma
became filled with small spherical aggregations of this pigment, leaving no space for
further importations. It was now determined to ascertain in what manner the
indigestible portions would be disposed of; this after a little patient waiting was
fully revealed. Piece by piece these effete rejectamenta were released from the

GENUS OIKOMONAS. 253

posterior extremity of the body close to its juncture with the pedicle, and falling
to the ground, formed around the base of this structure a small heap, which at the
end of half an hour — the little monad still continuing to incept fresh particles
— had accumulated to dimensions equal to and in some cases larger than its own
body. The possession by this species of a definite excretory area, not sufficiently
limited to be called an aperture, was thus demonstrated, and is of interest, with
relation to the somewhat similar but more highly complex excretory phenomena
exhibited by the compound type Anthophysa vegetans hereafter described.

Oikomonas Steinii, S. K. sp. PL. XIII. FIGS. 65-70.

Body in its motile condition very variable, spheroidal, ovate or elongate,
in the sedentary state more or less regularly pyriform and attached by the
tapering posterior extremity, which is not sufficiently prolonged as to con-
stitute a distinct pedicle ; flagellum undulating, not extended rigidly or in
an arcuate form, equalling the body in length ; contractile vesicle single,
subcentral, endoplast posteriorly located. Length 1-1500".

HAB. — Vegetable infusions.

The above title is here proposed for the form figured by Stein in his recently
published volume under the name of Cercomonas termo, and presumed to be identical
with the Monas termo of Muller and Ehrenberg. It being, however, entirely
separate from the type previously connected with that title by Professor Clark,
it becomes incumbent to introduce a new one for its distinction. Whether or not
the present form or Professor Clark's species represents precisely the animalcule
upon which Muller and Ehrenberg conferred the particular title of Monas termo, it
is next to impossible to determine, there being, in addition to these, a whole host of
monadiform beings that present, under a similar comparatively low magnifying power,
an aspect identical with that reported by the earlier authorities of the type in ques-
tion. The new species next described, exhibits, in both habits and external form,
broad general features that, without the employment of a high objective, entirely
coincide with those of the present species, and is, therefore, quite as probably
identical with the Miillerian or Ehrenbergian type.

Oikomonas Steinii is, according to Stein's illustrations here reproduced,
eminently social, assembling in clusters upon the surface of the Bacteria-films or
vegetable debris contained in the infusions that give it birth. One of the alto-
gether irregular contours that may be assumed at will by the adult zooids of this
species is represented at PI. XIII. Fig. 67. In their younger and more minute
condition they present, as shown at Figs. 69 and 70, a much more regular ovate
contour, the posterior extremity being sometimes acutely pointed. Stein's proposed
reference of this type to the genus Cercomonas is, however, by no means justified, no
structure taking the form of a permanent tail-like appendage being exhibited in
any of his accompanying figures.

Oikomonas rostratum, S. K. PL. XIII. FIGS. 73-77.

Body evenly ovate or pyriform in its free-swimming condition ; gibbously
ovate with a wider central region in the attached state, the anterior ex-
tremity usually rostrate and curved ventrally, the posterior one attached
immediately to the object of support, or so attenuated as to form a more
or less distinct pedicle, this pedicle never exceeding and rarely equalling
the entire length of the animalcule's body ; flagellum extended obliquely
and rigidly from the curved anterior end, equalling the body in length;

254 ORDER FLAGELLATA-PANTOSTOMATA.

contractile vesicles two in number, subcentral ; endoplast posteriorly located.
Length 1-2000" to 1-1500".

HAB. — Hay infusions in both salt and fresh water.

While agreeing considerably, both in general habits and external contour, as seen
under moderate amplification, with O. Steinii, last described, this species may be
readily distinguished from that type, on closer examination, by the recurved and
rostrate form of the anterior extremity, the rigid and arcuate flexure of the flagellum,
the presence of two contractile vesicles, and the frequent though not invariable de-
velopment of a more or less distinct pedicle. The type was obtained by the author
in equal abundance in hay infusions in both salt and fresh water, experimented with
in the months of January and February, at St. Heliers, Jersey, in the year 1879.
Examples in the latter medium appeared at the end of the first, while those in the
salt water were not observed until the end of the second week. When crowded
together in their attached state on the finer vegetable fibres and other debris, with
their bodies swaying to and fro and their anterior beak-like extremities and flagella
maintained in an active condition of elevation and depression, they present (as
shown at PI XIII. Fig. 73) a most grotesque resemblance to a group of little
birds bowing and chattering to one another. Figures 74 and 76 of the same plate
indicate the very considerable latitude of motion which the rostrum and accom-
panying flagellum possesses. The ingestion of solid food-particles at various points
of the periphery was observed on numerous occasions, as also the formation by
these animalcules of smooth spheroidal encystments.

'

Oikomonas quadratum, S. K. PL. XIII. FIG. 71.

Body variable in shape, in its most typical sedentary condition,
irregularly quadrate or subpyriform, tapering and attenuate posteriorly,
attached to the chosen fulcrum of support by an attenuate thread-like
pedicle equal to or exceeding the length of the body ; flagellum very long,
curved or flexuose, twice or thrice the length of the body ; parenchyma
transparent, finely granular ; contractile vesicle single, situated towards the
anterior border ; endoplast subcentral. Length 1-1500".

HAB. — Pond water.

This species was obtained in November 1871 on Anacharis in pond water
containing Codosiga botrytis, Anthophysa vegetans, and other ordinary fresh-water
Flagellata. It is readily distinguished from the preceding species by the great
attenuation of the posterior region and marked quadrate contour frequently exhibited
by the entire body. In the social group represented at PI. XIII. Fig. 71, the
example occupying the ' lowermost position to the extreme left, illustrates most
conspicuously this characteristic quadrate outline. In the two examples marked
a and b the ingestion of food-substances at opposite points of the periphery, as
observed by the author, is delineated. The contour adopted by the animalcule in
its free-swimming condition has not as yet been recorded.

GENUS II. BODO, Ehrenberg.

Animalcules ovate or elongate, free-swimming or temporarily attached,
exceedingly plastic and changeable in form, the anterior extremity having
a single vibratile flagellum, the posterior one prolonged into an attenuate
and persistent caudal filament ; no distinct oral aperture ; occurring mostly
as endoparasites within the intestinal viscera of various Vertebrates and
Invertebrates.

GENUS BO DO. 255

The genus Bndo, as originally instituted by Ehrenberg, included an heterogeneous
assemblage of Flagellata, some with and some without a conspicuous caudal
prolongation or filament, while in almost all the existence of an anterior flagellate
appendage was entirely overlooked. Out of the total of eight species enumerated
and figured by this authority in his grand work ' Die Infusion sthiere,' there can
be but little doubt that his Bodo sodalis is identical with the Spumella vulgaris
of Cienkowski, and his B, grandis with a species of Anisonema or Heteromita,
The residual forms, while for the most part too imperfectly figured and described
for identification, include nevertheless two conspicuous species which, having
formed the subject of investigation of various later authorities, are found to yield
sufficiently well-marked characters for generic diagnosis, and are consequently
here retained as typical representatives of the genus. The two in question are the
Bodo intestinalis and B. ranarum of Ehrenberg as hereafter described, and around
which may be grouped a considerable number of animalcules that appear to exhibit
a fundamental correspondence in all essential points with the terms submitted in the
foregoing diagnosis. In no instance, as yet, has the inception of solid food by
any representative of the genus Bodo been actually witnessed, although one species,
B. julidis, described by Professor Leidy, would appear, so far as may be decided
on by his drawings, to be capable of incepting such solid food-particles on its lateral
border, and therefore probably at all parts of its periphery. It is by no means
improbable, however, that in the majority of instances, and in a manner correspond-
ing to that of the Opalinidae, these endoparasitic animalcules assimilate the nutrient
intestinal juices of their hosts by direct absorption or endosmosis, and are thus
independent of a special oral area. A further investigation into the alimentary
capacities and more intimate structural details of the various members of this genus
is much to be desired.

From the genus jCercomonas of Dujardin, with which in many respects it most
closely corresponds, Bodo, as here delimited, is to be distinguished by the capacity
and general tendency possessed by its representatives of forming a temporary or
permanent adhesion to neighbouring objects through the medium of its persistent
caudal prolongation ; Cercomonas, while similarly caudate, is entirely free-swimming.
The distinction between these two genera as here constituted is therefore precisely
parallel to that which obtains between the two generic groups Monas and Oikomonas.
With Oikomonas in its attached condition, the members of the present generic group
still more closely coincide, their distinction in this instance being manifested, how-
ever, by their retention of the caudal filament in both their free and attached
conditions.

Stein, in his volume of the Flagellata, figures as representatives of the genus
Bodo, various species of Heteromita and Amphimonas, as defined by Dujardin, these
two last-named genera being consequently though without sufficient grounds sup-
pressed. Typical members of the genus Bodo as here constituted do not appear
as yet to have fallen within the cognizance of this authority.

Bodo intestinalis, Ehr. PL. XIV. FIG. 14.

Body colourless, transparent, elongate-ovate, conical or clavate, rounded
anteriorly, attenuate and pointed posteriorly, about three times as long
as broad ; tail-like filament about equalling the body in length. Length
1-1700".

HAB. — Intestinal viscera of various frogs, toads, and tailed Amphibia.

The examples referred, to this species, figured and described by Perty under the
title of Cercomonas intestinalis, and found in the intestine of Triton cristatus, are
represented with a caudal filament two or three times as long as the body. It
possibly represents a distinct variety. Professor Leidy has obtained the same

256 ORDER FLAGELLATA-PANTOSTOMATA.

species from the rectum of the American toad, Bufo americanus. The Monas
intcstinalis of Dujardin, discovered among the excrement of Triton palmipes, is
apparently also synonymous with this type.

Bo do ranarum, Ehr.

Body colourless, transparent, subovate, about twice as long as broad,
pointed at each extremity, but more so posteriorly; caudal filament shorter
than the body. Length 1-1440".

HAB. — Intestinal mucus of various frogs and toads.

The habitat of this species being identical with the preceding, suggests the
possibility of its being merely a transitional condition of it. Its specific distinc-
tion is at the same time recognized by Perty, Schmarda, and Diesing.

Bodo hominis, Davaine sp.

Body pyriform, anterior flagellum much longer than the body ; caudal
filament rigid, nearly equalling it in length. Length 1-2500".

HAB. — The human intestine, found associated wit: fhe foecal evacuations
of cholera patients and in typhoidal affections ; in the latter instance the
animalcules are usually of smaller size ; occasionally also abundantly in
the gelatinous excreta of infants.

This type is identical with the Cercomonas hominis of Davaine referred to in
Leuckart's ' Menschlichen Parasiten,' Bd. i. p. 143, 1863.

Bodo helicis, Leidy sp. PL. XIV. FIGS. 12 AND 13.

Body exceedingly plastic and changeable in form, elongate-ellipsoid,
fusiform, or ovate ; caudal filament equal to or exceeding the body in length ;
anterior flagellum short; parenchyma colourless, finely granular, enclosing
an anterior and posterior vesicula, representing probably the imperfectly
observed endoplast and contractile vesicle. Length 1-1500" to 1-1200".

HAB. — Copulatory tubes of various land-snails, Helicidce.

This species was originally described under the generic title of Cryptobia and
Cryptoicus by Professor Leidy, but has since been referred to Ehrenberg's genus
Bodo by Diesing. Among the numerous examples represented in the woodcut
accompanying Professor Leidy's original description, several of the animalcules, as
shown at Fig. 13, exhibit lateral protuberances with enclosed particles, which have
apparently been engulphed laterally in the same manner that food-substances are
ingested by the genera Oikomonas, Spiimdla, and other Pantostomata.

Bodo julidis, Leidy. PL. XIV. FIGS. 1-3.

Body changeable in form, globose, oval, or pyriform ; caudal filament
twice the length of the body, capable of active movements and frequently
twisted at its extremity in a loop-like manner ; parenchyma translucent
greenish, slightly granular, enclosing one or two large spherical vacuoles,
and numerous minute ones. Diameter 1-3000".

HAB. — The large intestine of Julus marginatus.

GENUS BODO. 257

According to Professor Leidy, this species occurs often in numbers which must
be estimated by millions, within the intestinal canal of the above-named Myriapod,
its companion in such rubitat being the ciliate animalcule Njdotherus velox.

Bodo colubrorum, Hammerschmidt.

Body hyaline, ovato-lanceolate ; anterior flagellum longer than the body,
the caudal filament of about equal length. Length 1-3450" to 1-2880".
HAB. — Cloaca of the common snake, Tropidonotus natrix,

Bodo lymnaei, Stiebel sp PL. XIV. FIGS. 9-11.

Body hyaline, changeable in shape, more usually pyriform ; caudal
filament equalling the body in length, anterior flagellum scarcely as long.
Length 1-1200". HAB. — Viscera of the pond-snail, Lymnaus stagnalis.

Although first referred to the present genus by Diesing, this form was previously
described by Stiebel, Karsch, and Ecker as a species of Cercomonas, The pheno-
mena of encystment of this type have been recorded at some length by the last-named
authority.* On examining the dead and opaque eggs of the mollusc above named,
many of them were found to be densely packed with minute cysts having a diameter
of from 1-500" to 1-350" ; these bursting, gave birth to swarms of monadiform germs,
which speedily acquired the form and dimensions of the parent zooids. While thus
observing the development of the motile zooids from the indurated encystments,
Ecker does not appear to have witnessed the production of these cysts by the adult
animalcules. Taking into consideration the disparity in size between the motile
zooids and the cysts, there are, nevertheless, substantial grounds for anticipating
that these comparatively large sporocysts are produced through the coalescence of a
considerable number of monadiform units. Ecker' s representation of a character-
istic cyst with the liberated germs is reproduced at PI. XIV. Fig. ir.

Bodo melolonthse, Leidy.

Body spherical, caudal filament equal in length to the diameter of the
body. HAB. — Intestine of the American cockchafers, Melolontha quercina
and M. brunnea.

Bodo muscarum, Leidy.

Body elongate, caudal filament four or five times longer than the body,
often enclosing a nucleus-like structure. Length 1-2160".

HAB. — Occurring in immense quantities within the intestine of the
common house-fly, Musca domestica.

This species is probably identical with the Ctrcomonas musca-domestiea, as figured
by Stein, and here referred to the new genus Herpetomonas.

Bodo maximus, Schmarda. PL. XIV. FIGS. 4-6.

Body elongate-pyriform or clavate, rounded anteriorly, attenuate and
pointed posteriorly, from two to three or four times as long as broad ; caudal

* A. Ecker, "Zur Entwicklungsgeschichte der Infusorien,'' ' Zeitschrift fur Wissenschaftliche
Zoologie,' Bd. Hi., 1851.

S

258 ORDER FLA GELLA TA-PANTOSTOMA TA.

filament equal to or double the length of the body ; usually enclosing a
conspicuous central vacuole. Length 1-600" to 1-420".
HAB. — Fresh water : Alexandria, Schmarda.

Excepting for its large size, the characters of this species, as described and
figured by Schmarda,* closely correspond with those of Bodo intestinalis. No
indication of an anterior flagellum is given by that authority, though such doubtless
exists. In several instances two or three individuals are represented in Schmarda's
drawings, as reproduced at PL XIV. Fig. 5, grouped upon a single stem-like
caudal filament; this circumstance, taken with its non-parasitic habit, makes it
rather doubtful whether this type is a true representative of the genus Bodo.

Bodo urinarius, Hassall. PL. XIV. FIGS. 7 AND 8.

Body plastic and variable in shape, subglobose, ovate, or clavate, in the
latter instance widest and rounded anteriorly ; a flagellum equal in length
to the extended body projecting from each extremity. Length of body
i-iooo". HAB. — Urine of the human subject.

An abstract of the description of this species, as communicated by Dr. Hassall
to the 'Lancet' for November 1859, is herewith appended. The animalcules in
question (B. urinarius) are about i-iooo" in length and 1-3000" in breadth,
presenting when living and active a rounded or oval form and granular aspect, not
unlike that of a delicate mucous corpuscle; sometimes they are broader at one end,
and are furnished with one, but usually two, long lashes or cilia produced from
opposite extremities, and with which they move themselves with great rapidity.
The rounded or oval forms most constant when the animalcules are first placed in a
drop of urine beneath the microscope, gradually, as the fluid evaporates, assume a
flattened and somewhat twisted outline, their motions becoming more sluggish, and
death soon following. It is when they are thus dying or just dead that the
flagella become most conspicuous, these organs during their active state being
indistinguishable. Not unfrequently the animalcules attach themselves posteriorly
to the glass object-carrier, and thus remain for a considerable time swaying to and
fro like an inflated balloon held down by cords. Multiplication by longitudinal
fission was frequently observed, the animalcules undergoing this process presenting
as they swam about the appearance of two conjugated individuals. The species
was observed to become developed in alkaline urine containing much animal
matter, and which had been freely exposed to the air. On their first appearance
they are equally diffused throughout the bulk of liquid, but after multiplying to a
considerable extent collect upon the surface, and form there a greasy-looking scum.
Indigo mixed with the urine apparently expedited their further development in
great multitudes. In all cases — about fifty — in which the presence of this animalcule
was detected the urine was either feebly acid or alkaline, and the subject exhibited
symptoms of weakness and debility.

GENUS III. CERCOMONAS, Dujardin.

Animalcules entirely free-swimming, ovate, globular, or elongate, more or
less plastic, developing a single long flagellum at the anterior extremity of
the body, and a similar or dissimilar caudal filament at the opposite or
posterior extremity ; no distinct oral aperture.

HAB. — Fresh water and infusions.

* 'Denkschrift d. k. Akad. d. Wiss. Wien,' 1850.

GENUS CERCOMONAS. 259

The Cercomonas figured and described without a specific name by Messrs.
Dallinger and Drysdale in the 'Monthly Microscopical Journal' for August 1873
is here adopted as the type-form of the present genus, it so far, representing the
only species of whose distinct individuality, as derived from a knowledge of its
entire life-cycle, we can be absolutely certain. There can be but little doubt that
many of the species on which the title of Cercmnonas was first conferred by Dujardin
are transitional conditions of other genera, such as Monas, Oikomonas, Amphimonas,
and Heteromita, those only being consequently here retained whose characters accord
substantially with the foregoing diagnosis, and which have been described with suffi-
cient distinctness for future identification. In none of the forms yet known are any
details recorded respecting the manner in which food is ingested, but it may at the
same time be predicted that if a distinct mouth existed in the species so carefully
investigated by Messrs. Dallinger and Drysdale it would scarcely have escaped
attention. In one of the figures given by Stein of his Cercomonas longicauda, a green
vegetable corpuscle is represented as enclosed within the endoplasmic substance,
but no indication is given of any special inceptive area. The essentially free-
swimming habits of the type-form here described at once distinguishes it from the
somewhat similar tailed but adherent members of the genus Bodo.

Cercomonas typicus, S. K. PL. XIV. FIGS. 22-30.

Body ovate, rounded posteriorly, pointed and slightly curved anteriorly,
surface smooth ; flagellum long and slender, about twice the length of the
body ; posterior filament usually shorter than the flagellum. Length
1-3500". HAB. — Fish macerations.

This form is identical with the " Cercomonad " described by Messrs. Dallinger
and Drysdale in the above-named Journal. Its multiplication by the several
processes of coalescence, encystment, and resolution of the amalgamated zooids
into spores of infinitesimal minuteness, similar to those already described of Monas
Dallitigerii, was accurately determined. Rapid increase by the more simple
process of transverse fission was likewise abundantly observed ; the time occupied
by a zooid in thus dividing itself into two was ascertained in an average of forty
cases to be exactly four minutes and forty seconds. Adult individuals preparing
to conjugate or coalesce with one another assume the amcebiform condition repre-
sented at PI. XIV. Figs. 23 and 24; they then, with the aid of their extemporized
pseudopodia, creep about, retaining for a while their flagellate appendages, and
present under such conditions an aspect not unlike that of the Rhizo flagellate form
Mastigamatba simplex. Two of these amceboid zooids coming in contact fuse
intimately with one another, and losing their flagella become transformed into a
smooth, quiescent cyst, from which myriads of almost imperceptible spores are
subsequently liberated.

Cercomonas longicauda, Duj. PL. XIV. FIGS. 17-20.

Body elongate-ovate, fusiform, flexible, terminating posteriorly in a long,
undulating, tail-like filament, about twice the length of the body ; anterior
flagellum slender, usually shorter ; contractile vesicle single, laterally
located ; endoplast spherical, subcentral. Length of body 1-2700".

HAB. — Vegetable infusions.

This species being figured with fuller details by Stein in the third volume of
his ' Infusionsthiere,' has permitted the addition of those data concerning the relative
positions of the endoplast and contractile vesicle which are wanting in Dujardin's
diagnosis. In one of the illustrations given by the first-named authority the animalcule
is represented in profile, and in a creeping state, presenting under such conditions a

S 2

260 ORDER FLAGELLATA-PANTOSTOMATA.

considerable resemblance to the permanently repent form Reptomonas caudata, pre-
viously described. In another example, delineated by Professor Stein, the animalcule
encloses within the substance of its parenchyma a recently-devoured spore-like
corpuscle. Multiplication by longitudinal fission, preceded by the development, in
the first instance, of a second anterior flagellum and caudal filament, is likewise
represented in Stein's figures here reproduced.

Cercomonas crassicauda, Stein. PL. XIV. FIGS. 15 AND 16.

Body elongate-ovate, from two to two and a half times as long as broad,
its substance granulate ; caudal filament usually very thick at its base,
tapering to a fine point at its distal end, about equal in length to the
body ; anterior flagellum finer and longer than the caudal filament ; con-
tractile vesicles two or three in number, located near the anterior extremity ;
endoplast subcentral. Length of body 1-930".

HAB. — Fresh water and infusions.

The animalcule according with the above diagnosis and accompanying
illustrations, while referred by Stein * to the Cercomonas crassicauda of Dujardin,
appears scarcely to conform with the animalcule upon which this title was originally
conferred. The species as described by the last-named writer is said to correspond
closely in general appearance with Monas lens, and is regarded as a probable
transient phase of that type. It is further spoken of as attaching itself at
will by its posterior extremity, which then becomes drawn out in a tail-like
manner, and is again absorbed into the substance of the parenchyma on its
resumption of a free-swimming state. It is evident that we have here a form
closely related to one of the several species of the newly-introduced genus Oikomonas,
and an animalcule, so far as it is possible to decide in the absence of any explanatory
text, entirely distinct from the Cercomonas crassicauda of Friedrich Stein. In several
of the examples figured by this last authority, lobate or more or less attenuate
pseudopodal prolongations are, as shown at PI. XIV. Fig. 16, protruded from around
the base of the caudal filament, representing probably the amoeboid phase preceding
encystment or genetic union.

Cercomonas globulus, Duj.

Body subglobose, somewhat pointed anteriorly, surface slightly tuber-
cular ; flagellum and posterior filament subequal in length, two or three
times as long as the body, the former more slender and undulating, the
latter stiff. Length of body 1-2000". HAB. — Marsh water.

Cercomonas fusiformis, Duj.

Body fusiform, inflated centrally, tapering at the two extremities ;
flagellum and posterior filament long and slender. Length of body
1-1700". HAB. — Infusions of moss.

Cercomonas cylindrica, Duj. PL. XIV. FIG. 21.

Body elongate-cylindrical, about four times as long as broad, tapering
posteriorly, surface smooth ; flagellum and posterior filament slender,
equalling the body in length. Length of body 1-2500".

HAB. — Infusions of moss.

* ' Infusionsthiere,' Abth. iii., 1878.

GENUS CODONCECA. 261

Doubtful Species.

The Cercomonas detracta, C. viridis, C. lacryma, C. acuminata, C. truncata, and
C. lobata of Dujardin would appear in a similar manner to represent transitional or
amoeboid phases of other monadiform types. The Cercomonades intestinalis, curvata,
•vorticellaris, ranarum and facula of Perty are apparently for the most part referable
to the genus Bodo of Ehrenberg, and in no instance conform with the amended
diagnosis of the genus here adopted. Stein's recently figured Cercomonas termo
(Oikomonas Steinii), C. musca-domestica, C. ramulosa and C. obesa exhibit, in no
instance, that essential characteristic of a true representative of the genus Cercomonas,
as manifested by the possession of a persistent caudal filament ; these three types
are here distributed among the two genera Herpetomonas and Monas proper.

Fam. IV. CODONOECID^J, S. K.

Animalcules inhabiting a horny sheath or lorica ; flagellum single,
terminal ; no distinct oral aperture.

GENUS I. CODONOECA, James-Clark.

Animalcules solitary, uniflagellate, inhabiting an erect pedicellate lorica,
to the bottom of which they are fixed in a sessile manner, and not attached
to the same by a secondary flexible pedicle. HAB. — Salt and fresh water.

This genus was established by Professor H. James-Clark for the reception of a
single species, differing most essentially from JBicosceca in the absence of the
flexible pedicle, which in the latter genus unites the animalcule with the base or
fundus of the lorica, and by its possession of a single flagellum only. To the single
marine species first discovered by Professor Clark, a second, fresh-water type is
here added.

Codonceca costata, Jas.-Clk. PL. XIV. FIG. 53.

Lorica campanulate, divided by a constriction into two regions ; the
basal third obconical, tapering gradually towards its junction with the
pedicle, the anterior two-thirds bulging out abruptly but narrowing again
slightly towards the terminal aperture ; the inflated portion sulcated
longitudinally by about twenty or thirty equal furrows, which impart a
scalloped aspect to the anterior margin ; pedicle equal in length to the
lorica, somewhat uneven. Contained animalcule elongate - ovate, the
posterior end rounded, half filling the narrower proximal third of the lorica,
the anterior end somewhat pointed ; flagellum vibratile, projecting con-
siderably beyond the orifice of the lorica ; colour dingy yellow. Length of
lorica 1-1500". HAB. — Saltwater.

The singular form and elegant sculpturing of the lorica of this species in some
respects agrees with that of the collared monad Salpingoeca ampulla, hereafter
described. But a single example of this type has been so far met with by the
author, and in that instance an empty lorica only, attached to sea-weed obtained
from the Crystal Palace aquarium.

Codonceca inclinata, S. K. PL. XIV. FIG. 54.

Lorica simply ovate, not sulcate longitudinally, attached obliquely to a
pedicle of twice its length. Contained animalcule ovate, occupying the

262 ORDER FLA GELLA TA-PANTOSTOMA TA.

posterior two-thirds of the cavity of- the lorica ; the flagellum projecting
considerably beyond its aperture. Length of lorica 1-1650".
HAB. — Pond water.

The length of the pedicle and its oblique mode of attachment to the lorica,
serve to distinguish this type from any other flagellate form here described. It
was at first regarded by the author as a species of Bicosceca, with the animalcule in
a semi-contracted state, and was so described in the ' Monthly Microscopical
Journal' for December 1871. The sessile mode of attachment of the zooid to the
bottom of its lorica, added to the presence of a single flagellum only, indicates,
however, the necessity of referring it to the present genus.

GENUS II. PLATYTHECA, Stein.

Animalcules solitary, ovate, enclosed within a depressed, laterally
attached or decumbent lorica ; flagellum single, terminal, projecting
through the orifice of the lorica.

Platytheca micropora, Stein. PL. XIII. FIG. 54.

Lorica ovate, depressed, transparent, not quite one and a half times as
long as broad, rounded and widest posteriorly, tapering towards the anterior
border and there perforated by an exceedingly minute pore-like orifice
through which the flagellum of the enclosed animalcule is protruded ; body
of animalcule depressed pyriform, pointed anteriorly, scarcely filling one-half
of the cavity of the lorica ; one or more contractile vesicles situate near
the anterior extremity ; endoplast posteriorly located. Length of lorica
1-1200". HAB. — Fresh water.

This animalcule, while figured by Stein in the recently published volume of his
4 Infusionsthiere,' is referred to in the accompanying index as a somewhat doubtful
Flagellate type, the flagellum not exhibiting the usual characteristic vibratile
movements, and presenting the aspect rather of a fine setum or pseudopodium.
The examples delineated were found attached to the superficial cells of the roots of
duckweed (Lemna). Division by fission is shown to take place within the cavity of
the comparatively capacious lorica.

B.— PANTOSTOMATA-DlMASTIGA.

Fam. V. DENDROMONADID-2E, Stein.

Animalcules illoricate, mostly sedentary, with a more or less obliquely
truncate anterior border, caused by the lip-like projection of one of its
lateral angles ; rarely solitary, usually attached singly or in groups to
the extremities of a variously-branching pedicle or zoodendrium ; flagella
two in number, unequal, one long and one short, inserted close to each
other towards the centre of the anterior border ; parenchyma transparent,
granular ; endoplast and one or more contractile vesicles usually con-
spicuous, the latter mostly posteriorly located ; no distinct oral aperture,
food being incepted indifferently at all parts of the periphery ; increasing
by longitudinal subdivision.

GENUS PHYSOMONAS. 263

The representatives of the Dendromonadidae present collectively a type of modifi-
cation closely analogous to that which obtains among the more highly organized
Peritrichous family group of the Vorticellidae. Here as there, while some few are
distinguished by their solitary habits, the large majority are conspicuous for the
extensive tree-like colony-stocks produced by their associated numbers. These,
indeed, frequently present in miniature so striking a resemblance to the tree-like
colony-stocks of Epistylis and other compound Vorticellidae that, in the absence
of magnifying power sufficient for the demonstration of their true nature, they
have frequently been described as diminutive forms or earlier growths of such
higher Ciliata. The probable derivation of the more complex dendritic forms, such
as Anthophysa and Dendromonas, from such a primary solitary type as Physomonas,
and through such a simply aggregated stock-form as Cladonema, can scarcely be
doubted, the fundamental contour and structure of the individual animalcules,
as manifested by the oblique lip-like anterior border and flagella of diverse lengths,
throughout this natural family group being identical.

GENUS I. PHYSOMONAS, S. K.
(Greek, physa, bladder ; monas.)

Animalcules solitary, occasionally free-swimming, but normally attached
by a slender, flexible, posteriorly developed, thread-like pedicle ; body sub-
spheroidal, anterior border obliquely truncate, provided with a projecting
lip-like prominence ; flagella two in number, unequal, one long and one
short ; endoplast and one or more contractile vesicles mostly conspicuous ;
no distinct oral aperture, food being incepted at all parts of the periphery.
Inhabiting fresh or salt water. Increasing by longitudinal fission and by
the subdivision of the entire body into spores.

Physomonas socialis, S. K. PL. XIV. FIGS. 37-45.

Body subglobose, transparent and slightly granular, obliquely truncate
anteriorly ; primary flagellum two or three times the length of the body,
secondary one less than one-half the length of the primary one ; pedicle
slender and flexible, equalling in length the larger flagellum ; contractile
vesicles largely developed, two in number, contracting and expanding alter-
nately, located side by side a little behind the median line ; endoplast
spherical, subcentral. Diameter of body 1-5000" to 1-2500".

HAB. — Pond water with decaying vegetable matter. Increasing by
longitudinal fission, and by encystment and the breaking up of the body
into spores.

It was originally suspected that this species was either a mere variety QiSpumella
guttula, having but one short secondary flagellum, or that the last-named type
represented the present form immediately antecedent to the process of fission, and
when the development of supplementary flagella gives the earliest indication of the
approaching change. It has, however, been met with by the author on so many
occasions, and is found to exhibit persistently such important and fundamental
differences with relation to both its structural and reproductive features, as to
necessitate its recognition as both a distinct specific and generic form. Such
structural differences are conspicuously manifested, in addition to the character
furnished by the flagella, in the less perfectly spheroidal or globose condition of the
body, and in its possession of two largely developed contractile vesicles in place of
the single one characteristic of 6". guttula ; there is, further, no trace of the linear

264 ORDER FLAGELLATA-PANTOSTOMATA.

granular band or groove near the anterior extremity, erroneously supposed by Stein
and Cienkowski to represent a distinct oral aperture. In its free-swimming con-
dition, again, the present type usually exhibits but little alteration of its sedentary
shape, while S. guttiila is subject under like conditions to the most protean
metamorphoses. With respect to the reproductive process, both Stein and
Cienkowski accord in attributing to S. guttula the production of endogenous spore-
masses formed from an isolated central portion of the animalcule, while in Physo-
monas socialis, as here shown, the entire body-mass becomes split up to produce
the sporular elements.

Detailing at length the more important features of the reproductive phenomena
of the present type, as observed by the author, it may be remarked that, in addition
to the ordinary process of longitudinal fission, the encystment of animalcules, accom-
panied or not by the coalescence of two zooids, and succeeded by the breaking
up of the encysted body into comparatively large macrospores, has been witnessed,
as also the escape of these latter as simple uniflagellate monadiform germs closely
corresponding in contour with the type upon which Perty has instituted the genus
Plenromonas, already described. Various phases of this reproductive process will
be found delineated at PI. XIV. Figs. 43-45. As there shown, the animalcules
mostly remain attached to their pedicles throughout these transformations, the last-
named structure indeed losing its vitality and becoming as rigid and indurated as
the peripheral wall of the encystment. The example indicated by the letter c in the
group delineated at Fig. 43, is of especial interest, it indicating by the two pedicles
that support the single cyst, that this latter structure has been formed by the coales-
cence of two zooids in their attached condition : the two others (a and b) close to
this are as evidently the result of solitary encystment. As made apparent by the
principal group illustrative of this species (Fig. 37), it may be described as eminently
social, numbers being usually found crowded together on the vegetable debris
obtained from those localities which it favours, and these exhibiting by their com-
bined restless movements as they sway to and fro on their slender elastic pedicles
— their vibrating flagella producing strong currents in the surrounding water — a
scene of animation that is scarcely rivalled by the social groups of the larger and
more highly organized representatives of the Ciliata. Although the adult zooids
of the same colony correspond in size, a considerable difference is found to subsist
between those derived from separate localities. The two extremes in this respect
are recorded in the foregoing diagnosis ; an intermediate calibre, that of 1-3000",
would, however, appear to be most common.

The binary character of the contractile vesicle in this species was determined
on numerous occasions, but is necessarily difficult to recognize unless the animal-
cules face the observer in such a way that the two vesicles are placed side by
side, and not one in front of the other. On first examining this type, and
mastering the details of its organization and reproductive phenomena, in the
year 1871, the writer was disposed to identify it with the Bodo socialis of Ehren-
berg. The present specific title is even now retained with reference to the proba-
bility of such identity. A species of Physomonas, closely agreeing with the present
form, but having the body more globular and with that anteriorly emarginate
aspect caused by the greater extension of one side of the anterior border less marked,
has been obtained by the author in sea-water, at St. Heliers, Jersey : this type or
variety may be provisionally distinguished by the title of Physomonas marina. The
characters afforded by the flagella, together with the dimensions of the body, coincide
precisely with those of P. socialis.

GENUS II. CLADONEMA, S. K.
(Greek, klados, branch ; nema, thread.)

Animalcules forming social colony-stocks, irregularly pyriform, with an
obliquely truncate anterior border, attached singly to the extremities of a
perfectly flexible, hyaline, slender and thread-like, branching pedicle ;

GENUS DENDROMONAS. 265

flagella two in number, one long and one short ; endoplast and one or more
contractile vesicles usually conspicuous ; no distinct oral aperture, food being
incepted at all parts of the periphery. Inhabiting fresh water.

The representatives of this genus differ only from those of Physomonas, in that
the resultants of division by longitudinal fission, instead of being cast off as free-
swimming animalcules, remain adherent by their slender thread-like pedicles, and
which, taken in the aggregate, present necessarily a more or less regular dichotomous
plan of growth.

Cladonema laxa, S. K. PL. XVII. FIGS. 5-7.

Bodies irregularly pyriform, compressed, the anterior border widest,
obliquely truncate; attached separately to the extremities of a slender,
flexible, thread-like, irregularly-dichotomously branching pedicle ; con-
tractile vesicle posteriorly located ; endoplast spherical, subcentral. Length
of bodies 1-3250".

HAB. — Pond water, on Myriophylhim. Colony-stocks including from
three or four to as many as twenty or more zooids.

This species was first briefly described by the author, with an accompanying figure,
in the ' Monthly Microscopical Journal ' for December 187 1, under the title of Antho-
physa laxa; the isolated instead of clustered mode of attachment of the animalcules
to their pedicle, added to the flexible, thread-like aspect and consistence of this
structure, distinguishes it, however, so conspicuously from the representatives of
either the genus Anthophysa or other allied forms described in this treatise, that a
new generic title has been created for its reception. Except for the somewhat more
elongate contour of their bodies, the colony-stocks of the present form might be
aptly compared to a number of zooids of Physomonas socialis, with their flexible
thread-like pedicles intimately united. The process of multiplication by longitudinal
fission, as shown at PI. XVI. Fig. 6, and also that of the ingestion of solid food-
particles at various points of the periphery, may be observed with great facility in the
somewhat large and distinctly isolated zooids of this species. At Fig. 7 of the plate just
quoted, an example is given of food-inception towards the posterior region of the
lateral border. As originally figured and described, this species was reported as
forming colony-stocks of three or four zooids only. More luxuriant examples,
including as many as twenty or more animalcules, remitted by Mr. Thomas Bolton,
of Birmingham, have, however, since been examined, and have supplied the material
for the accompanying illustration.

GENUS III. DENDROMONAS, Stein.

Animalcules irregularly pyriform, the anterior border obliquely truncate,
stationed singly at the extremities of an erect, rigid, perfectly hyaline and
homogeneous, variously branching pedicle or zoodendrium ; flagella two in
number, one long and the other short ; endoplast and one or more contrac-
tile vesicles usually conspicuous ; no distinct oral aperture, food-substances
being incepted at all parts of the periphery. Inhabiting fresh water.

The rigid and erect composition and mode of growth of the pedicle in this genus
distinguish its representatives from those of Cladonema, The hyaline and homo-
geneous consistence of the pedicle, added to the solitary disposition of the zooids,
serves to separate it from Anthcphysa.

266 ORDER FLAGELLATA-PANTOSTOMATA.

Dendromonas virgaria, Weisse sp. PL. XVII. FIGS. 1-4.

Bodies irregularly and obliquely pyriform, compressed ; zoodendrium
erect, slender, evenly dichotomous ; contractile vesicles two in number,
posteriorly situated ; endoplast spherical, subcentral. Length of bodies
1-3250". Height of zoodendrium 1-130".

HAB. — Pond water. Over one hundred zooids frequently included in
a single colony-stock.

This species was briefly described by the author, though without an accompanying
illustration, in the 'Monthly Microscopical Journal' for December 1871 under the
title of Anthophysa Bennetti. It being, however, evidently identical with the form
referred by Stein in his recently published volume — in connection with the present
generic name — to the Epistylis virgaria first described by Weisse, such prior
specific title is now substituted. There can further be little doubt that the type
figured by Stein himself in ' Wiegmann's Archives' for the year 1849, here repro-
duced at PI. XVII. Fig. 2, as the probable young condition of Epistylis anastatica,
represents likewise the species now under discussion. Among all of the numerous
stock-building pedicellate varieties of the Flagellata figured and described in this
treatise, few perhaps excel the present one in the exuberance of growth and graceful
symmetry of the erect, branching zoodendrium. The associated colony-stocks of
this species have been frequently observed by the author in such abundance on the
finely divided leaves of Myriophyllum and other water plants, as to present the aspect
of a perfect forest growth of tiny crystal trees, each terminal leaflet replete with life,
and quivering with the combined vibratory action of their flagella. The separate
animalcules of Dendromonas virgaria correspond essentially with those of Anthophysa
vcgetans, and need an equally high microscopic power for their satisfactory examina-
tion. As recently figured by Stein, a much more angular outline is given to their
bodies than was presented by those observed by the author, while a single contractile
vesicle only is delineated by this authority stationed close to the anterior border.
It is possible, under such circumstances, that the two represent distinct varieties.
Examples of this species have been recently remitted to the author by Mr. John
Hood, of Dundee.

Dendromonas pusilla, Schmarda sp. PL. XVII. FIG. 8.

Bodies ovate, stationed singly at the extremities of an irregularly
branching, paniculate zoodendrium. Length of bodies 1-3000", of branch-
ing zoodendrium 1-160". HAB. — Fresh water.

This species is figured and described by Schmarda * under the title of Epistylis
pusilla. His delineation given, here reproduced, represents the animalcule as seen
under a magnification altogether inadequate for the exhibition of the flagellate or
other appendages which the zooids severally possessed, these being consequently
represented as simply ovate and entirely naked. There can be but little doubt
that the type thus figured represents a stock-building flagellate animalcule nearly
allied to Dendromonas virgaria, from which, however, it differs in the comparatively
irregular plan of subdivision exhibited by the erect zoodendrium.

GENUS IV. ANTHOPHYSA, Bory.

Animalcules obliquely pyriform, attached in clusters to the extremities
of a rigid or slightly flexible, granular and opaque, not hyaline and homo-
geneous, simple or more or less branching pedicle or zoodendrium ; flagella
* ' Denkschrift d. Konig. Acad. Wien,' 1850.

GENUS ANTHOPHYSA. 267

two in number, one considerably longer than the other; no distinct mouth,
food being incepted at any point of the periphery ; an endoplast and one
or more contractile vesicles usually conspicuous. Inhabiting fresh water.

Anthophysa vegetans, Miiller sp.
PL. XVII. FIGS. 13-26, AND PL. XVIII. FIGS. i-io.

Bodies irregularly pyriform, obliquely truncate anteriorly, slightly com-
pressed ; attached in rosette-like clusters of fifty or sixty or more zooids
to the terminations of an irregularly branching, and in the more robust
condition erect, dark brown, longitudinally striate, horn-like pedicle ; this
pedicle in weakly or overgrown examples simply granular and highly
flexuose ; contractile vesicles two or more in number, posteriorly located ;
endoplast spherical, subcentral. Length of bodies 1-4000" to 1-3500".

HAB. — Fresh water, abundant.

Among the earlier writers there has been a general tendency to confound the
animalcules of this species — first described by Miiller under the title of Volvox
•vegetans, but since more generally known by Bory's title of Anthophysa Mulleri —
with Uvella, this view being even reproduced and adhered to in Pritchard's ' History
of the Infusoria,' ed. iv., 1861, and yet more recently in De Fromentel's ' FJtudes sur les
Microzoaires.' Such widespread but mistaken opinion as to the affinities of Antho-
physa has no doubt arisen from the considerable resemblance in mere outward form
subsisting between the detached rosette-like clusters, or " coenobia " as they are desig-
nated by Stein, of the present species and the permanently free-floating spheroidal
colonies of the genus Uvella and its allies. Ehrenberg indeed, regarding the floating
clusters and attached colony-stocks as independent organisms, conferred upon the
latter the title of Epistvlis vegetans and on the former that of Uvella uva and U. chama-
morus. The Uvella-like aspect of the floating clusters is nevertheless purely superficial,
the individual zooids exhibiting, on closer examination, an essentially distinct type of
structure. In further illustration of the diversity of opinion that originally prevailed
concerning the nature and affinities of Anthophysa, it may be mentioned that Bory
de St. Vincent referred it to that doubtful organic group " le regne Psychodiaire"
proposed by him for the reception of all such types as appeared, with the means
then at disposal for their investigation, to form an intermediate link between the
animal and vegetable kingdoms.*

By M. Kiitzing Anthophysa vegetans was regarded as a true plant or aquatic
fungus of which the branching stem represented the mycelium, and the terminal
groups of monads the reproductive bodies or zoogonidia. Viewing it from this
aspect this authority placed it among other fungi, and conferred upon it the generic
name of Stereonema. That the branching stems or zoodendria of this social monad
bear a strong likeness to the mycelium of certain cryptogamic types, is not to be
denied, more especially as this portion of the organism, usually of a rusty brown
hue, is frequently found thickly encrusting aquatic plants without presenting any trace
of the clusters of animalcules which in the perfect condition terminate, and originally
constructed, each compound branchlet, but subsequently falling away have left but
the naked stalks. This circumstance, as explained by Claparede and Lachmann,
who unfortunately only succeeded in obtaining the species in such imperfect state,
doubtless gave rise to Kiitzing's opinion of its fungoid character, he accepting the
naked branching stalk as the primary portion destined to produce, as an aftergrowth,

* Bory, by the establishment of this transitional organic group, may be said to have completely
anticipated Haeckel in his comparatively recent creation of a propose! kingdom of the Protista,
already referred to at page 44.

268 ORDER FLAGELLATA-PANTOSTOMATA.

the groups of monads or so-called " zoogonidia." This would necessarily be the case
if Anthophysa was a plant ; on the contrary, however, the stem here, and in all the
true animal forms, is produced secondarily from the bodies of the animalcules, and
in the present instance in a highly interesting manner. Both Dujardin and Cohn
are among those who at an early date decided, on the grounds just stated, upon
the animal nature of this organism. Still more recently this type has been made
the subject of investigation by Professor H. James-Clark.* As in the case of Monas
(Oikomonas}, Codosiga, and other Flagellate types treated of in his memoir, that
authority advocates for this animalcule the possession of a distinct mouth, and goes
so far as to indicate in his accompanying figures the exact position of the supposed
oral aperture, namely, on the anterior truncate edge immediately beneath the rostrum
or projecting lip-like border, and at the base of the two flagella. There is no doubt
that more frequently than otherwise the food-particles thrown back by the action of
the flagella do impinge upon this anterior truncate border, and are thus engulfed
somewhere near the point just indicated. Prolonged observation on the part of
the author has nevertheless elicited that not unfrequently the food-particles strike
against other portions of the surface of the body, and are then immediately entrapped
by an outflowing film of sarcode in a manner similar to that recorded in this
treatise of Oikomonas, Spumella, Physomonas, Amphimonas, and numerous other
Pantostomata.

Although advancing so strong, but undoubtedly mistaken an opinion upon the
food-assimilating function of Anthophysa vegetans, Professor Clark is altogether silent
respecting the opposite and compensating function, of the rejection or evacuation
of the digested refuse. Neither has that authority been altogether felicitous in his
interpretation concerning the nature and development of the supporting pedicle, which,
as presently shown, is intimately connected with the process of defecation. Upon this
latter point he thus expresses himself: "As to the development of the stem, I
think it quite certain that it grows out of the posterior end of the body. The best proof
of this is that I have frequently found a monad nearly sessile upon a clear spot, and
attached by a very short, faint, film-like thread. From this size upward, I have no
difficulty in finding abundant examples as gradually increasing in diameter as they
did in length ; this furnishing a pretty strong evidence that the stem grows under the
influence of its own innate powers, and is not therefore a deposit emanating from the body
of the monad, except perhaps, as far as it may be nourished by a fluid circulating
within its hollow core." Professor James-Clark was much mistaken in thus ascribing
to the stem of Anthophysa an innate power of growth independent from that of the
bodies of the monads. The function of getting rid of waste and digested particles
and that of building up the pedicle are in fact co-ordinate ; this supporting stem
being almost entirely composed of the food-particles cast out from the parenchyma
or endoplasm after the monads have extracted from them such nutritive qualities as
they possessed on their first inception. We have here indeed a phenomenon pre-
cisely parallel in kind, though differing slightly in degree, from what has been already
recorded on a previous page of Oikomonas obliquus, concerning which species it
was shown, that the food-particles were, after the extraction of their nutritive pro-
perties, passed out at the posterior extremity of the body, and accumulated in a
heap round the base of the pedicle.

The more minute structure and actual mode of the growth of the stem of
Anthophysa vegetans, as ascertained by the author's recent investigations, may now
be considered. Under ordinary conditions this pedicle or zoodendrium is somewhat
flattened, tapering and narrowest at its fixed or proximal extremity, gradually
increasing in diameter as it approaches its junction with the terminal mulberry-like
group of monads. If the colony is an old one this pedicle is usually divided into
three or four branches, the extremity of each branch bearing its monad cluster.
The colour of the stem, where it has been formed some time, is a dark rusty brown
changing into amber colour, and finally becoming quite diaphanous as it approaches

' Mem. Boston Soc. Nat. Hist.,' vol. i., part 3, 1868.

GENUS ANTHOPHYSA. 269

and is fused with the conjoined posterior extremities of the monad groups. In this
region, moreover, the consistence of the pedicle is so soft and flexible that it allows
the attached group of monads to gyrate or spin freely backwards and forwards
upon its stalk in response to the active vibrations of the innumerable flagella. Not
unfrequently, owing to diminution in quantity and quality of the building material
used in the fabrication of the stem, it becomes incapable of further supporting these
actively motile groups, and snapping through, sets them free in the form of those
simply spheroidal clusters so closely resembling superficially the permanently free
spheroidal colonies of Uvella or Synura, with which they were originally confounded.
Examples of such free-floating clusters or " ccenobia," as delineated respectively by
O. F. Miiller and Friedrich Stein, are given at PI. XVII. Fig. 15, and PI. XVIII.
Figs. 2, 4, and 5. The substance of the adult stem of Anthophysa vegetans is
apparently at first sight horn-like and homogeneous, and similar to that out
of which the loricse and pedicles of many higher Infusoria are composed.
Usually a nature akin to chitine is ascribed to this substance, but its affinity is
probably much nearer to that of keratose or keratine, the basal substance of the
skeletal framework of the fibrous or horny sponges. The comparatively firm con-
sistence of the adult pedicles of the present species readily accounts for their long
duration, they being frequently met with even after the monads have died away or
become dispersed. Examined more minutely, it is found that the pedicle of
Anthophysa vegetans, in place of being homogeneous, is, as shown in PL XVII.
Figs. 1 6 to 1 8, striated longitudinally, the number of striae increasing with the pro-
longation and corresponding greater diameter of the stem, but not themselves under-
going any alteration in their respective diameters.

By feeding a colony of these animalcules with pulverized carmine the significance
of the stem with its mode of growth and striated structure became at once apparent.
The administered pigment was so greedily ingested, that within a few minutes the
body of each monad was gorged with brilliant particles, which regurgitated freely
within the body-sarcode after the manner of the food-pellets in Codosiga or Vorticella.
It was not long, however, before the discovery was made that there was little or
no nutritive matter in this pigmentary substance, and its rejection thereupon com-
menced. This was effected entirely at the posterior extremity, or point of union
with the pedicle, of each independent animalcule. In this species each member of
the large spheroidal cluster radiates from the same terminal point of a single
branchlet, and thus the separate contributions of rejected particles proceeding from
each individual, become concentrated at their point of exit into one united stream.
A change, however, now came over the aspect of the pedicle itself, for the particles
of discarded material, instead of falling away as waste, and accumulating round the
base of the pedicle as was observed of Oikomonas obliqttus, were actually utilized as
material out of which to build up and prolong it. The amber colour and striated
appearance which had previously characterized this structure disappeared, and the
pedicle now continued increasing rapidly in length, composed entirely of particles
of carmine bound together by a small admixture of glutinous material passed
from the monads' bodies. So rapidly and abundantly indeed were the carmine-
particles received and discharged, that within half an hour the pedicle of one
group had nearly doubled its former length, and continued growing at the
same rate until a very abnormal and striking effect was produced. The general
aspect of an example of Anthophysa vegetans with such an artificially constructed
stem is illustrated at PI. XVII. Fig. 18, and in which instance the whole of the
pedicle from the point a represents the portion that was produced in the space
of half an hour. In other instances the process of assimilating the carmine was
carried on for a still longer interval, the result in such cases being that, missing its
customary strength, the pedicle bent upon itself, forming a loose, flexible loop as
shown at Fig. 19. Under ordinary conditions the growth of the pedicle is a much
slower process, the pabulum out of which it is built not being usually so abundant,
and consisting of more easily digested animal and vegetable particles, which
weld together into a more compact and homogeneous mass. The stem-producing
property of Anthophysa under such ordinary conditions may in fact be compared

2 70 ORDER FLAGELLATA-PANTOSTOMATA.

with that of some highly finished machine, into one end of which the raw and
heterogeneous material is flung to issue at the opposite extremity a perfected and
homogeneous fabric. On first passing away from the monad's body this stem is
perfectly soft and glutinous, it gradually hardening and acquiring its dark brown
hue with exposure to the water. It is only after this prolonged exposure, more-
over, that the longitudinal striae previously described make their appearance,
such striae again obviously representing the outlines of the individual contributions
of each separate monad towards the common fabric, and these separate elements
become fused with one another during their pristine soft and plastic state. The
ordinary method of increase of the monad clusters of this species, namely by
rapid longitudinal fission of the individual zooids, assists materially in demon-
strating the opinion here expressed, as to the significance of the strias, for as the
stem grows longer and the monads continue to multiply in number the longitudinal
striae become also correspondingly more numerous. That there is a permanent
hollow core in this structure, as has been maintained by James-Clark, is certainly
not supported by the results of the author's investigations. That new-formed
part of the stem near its point of junction with the terminal monad group, no
doubt exhibits a firmer consistence exteriorly where it comes into direct contact
with the water, but this distinction is only temporary and becomes entirely obliterated
as the stem increases in age and strength.

Multiplication by longitudinal fission, as already indicated, represents an ordinary
method of increase in these animalcules ; a primary single monad dividing inde-
finitely, after the manner of Codosiga or Epistylis, until from the single individual
which laid the foundation of the colony, one or more mulberry-like clusters are
formed numbering respectively some fifty or sixty individual zooids. Now and then,
these terminal clusters break away, and forming new attachments develop compound
clusters similar to those from whence they originally sprang. Doubtless, however,
there is another more complex method of increase manifested by this species,
analogous to what has been already observed of numerous other Flagellata,
obtained through the genetic union of two or more individual zooids, and followed
by the production of innumerable independent germs or spores. Although up to
the present time no direct evidence of such a sporular mode of reproduction is
forthcoming, the following phenomena, observed by the author, may possibly serve
as a clue towards the supply of this, as yet, missing link in the life-history of the
species.

In the month of August 1871, the examination of a leaf of Myriophyllum led
to the detection of an oval body adhering to it, closely resembling the egg of some
free-swimming Rotiferae, as represented at PI. XVII. Fig. 20. Movements being
in progress within this body, promising the early release of its contents, attention
was specially concentrated upon it. Only a short interval had elapsed, however,
before it became evident that the transparent shell contained innumerable independent
organic particles in place of the single multicellular germ of an ordinary egg. As time
progressed these separate particles began to exhibit violent ebullition-like move-
ments as though endeavouring to break through the prison wall that encircled them.
At the end of half an hour a rift suddenly appeared at one extremity, and a second
inner investing membrane was protruded funnel-wise through the aperture, as shown
at Fig. 21. The energetic or, so to say, excited motions of the imprisoned particles
became now greatly augmented, till at length bursting in its turn (Fig. 22), this
second inner capsule let loose into the surrounding water a countless swarm of
minute, reniform, uniflagellate animalcules. These monadiform germs, which pre-
sented a remarkable resemblance to the somewhat similarly developed progeny of
Fhysomonas socialis, and also to the adult form of the Pleuromonas jaculans of Perty,
enjoyed their free roving condition for but a brief interval. Within a few minutes
after their escape they became sluggish in their movements, and settling down on
the surface of the glass slide withdrew their flagella and changed their shape from
reniform to spherical, as shown at Fig. 25. In this quiescent state these spheroidal,
and apparently encysted, bodies remained for the next twelve hours, when an accident
occurred which interrupted the further investigation of their life-history in so

GENUS ANTHOPHYSA.

direct a manner as had been intended. The damp growing-cell in which these
organisms were confined, unfortunately became dry during an absence of more
than a day's duration. Although everything contained in the cell was completely
desiccated, abundant traces were left, nevertheless, of what had taken place previous to
the evaporation of the water. At each spot which had been carefully noted as the
point of attachment of the quiescent or encysted monads, was a minute, dark brown,
striated, branching stem, corresponding in all ways with the characteristic pedicle
of Anthophysa vegetans. The process of drying up had necessarily removed every
trace of the animalcules whose presence would have still more satisfactorily esta-
blished the connection between the monadiform products of the original egg-like
cyst and the colonies of the species named ; the evidence of the branching and
striated stems was, however, so substantial as to leave little, if any, doubt of their
relationship. How this original ovate cyst, assuming that it belonged to Antho-
physa vegetans, was originally produced, remains to be determined. Judging from
its comparatively large size it would appear to be most reasonable to surmise
that it was formed by the coalescence of an entire colony or spheroidal terminal
cluster of the flagelliferous monads, which after encystment broke up into abundant
smaller uniflagellate locomotive germs, which made their escape under the conditions
just related. A parallel fusion of numerous zooids succeeded by encystment and
breaking up of their united masses into numerous spore-like bodies, is afforded in
the life-history of the monad first described and figured by Messrs. Dallinger and
Drysdale, as the "Hooked Monad," and which finds a place in this volume under the
title of Heteromita uncinata. Phenomena closely identical are also presented in that
mode of multiplication among the sponge-monads manifested by the production
of the swarm-gemmules or so-called ciliated larvae described in Chapter V.

Some slight additional testimony in favour of the above-suggested interpretation
of the developmental phenomena of Anthophysa vegetans is afforded by the illustra-
tions of this species given in Stein's recently published work. Among his excellent
illustrations of this type — the more important of which are reproduced in PL XVIII. of
this treatise — a representation is given (see Fig. 6) of a normally detached spheroidal
cluster or " coenobium," whose constituent monads have become separated from one
another, and protrude from their posterior regions tail-like pseudopodal prolongations.
At Figs. 7 and 8 of the same plate are represented similarly derived isolated monads
that have assumed a conspicuously amcebiform contour. In some instances, as
shown at Fig. 9, it would appear that these amoebiform zooids attached themselves
separately and lay the foundation of new colonies, but it would seem also highly
probable that under such condition they, in common with various other Flagellata,
coalesce together and produce sporocysts similar to the one just described.

The highly distinctive longitudinally striate aspect of the branching stem of Antho-
physa vegetans is not definitely indicated in any of Stein's figures, and it is further note-
worthy that the example selected by him as illustrating the normal stock-form of this
interesting species (see PI. XVIII. Fig. i) represents that lax and attenuate structural
type indicating either the absence of congenial nutriment, or that the colony has
outgrown its strength and lacks vital energy sufficient for the production of its
customarily erect and comparatively massive zoodendrium. De Fromentel, in his
' Etudes sur les Microzoaires,' figures a like emaciated colony-stock. An almost
precisely parallel deviation from a normally erect to a lax and decumbent growth-
form, is afforded by the Peritrichous type, Epistylis flavicans, whose branched
zoodendrium, while stiff and erect in its earlier and most robust condition, presents
later on that loose and weakly structural form upon which Ehrenberg and other
earlier authorities, regarding it as a distinct variety, have conferred the separate
specific title of Epistylis grandis. In the original delineation of the species given by
O. F. Miiller, under the title of Volvox vegetans* reproduced at PI. XVII. Figs. 13
and 14, the more ordinary rigid and erect growth-form of the branching pedicle
is represented. Brightwell, in his 'Infusorial Fauna of Norfolk,' 1848, figures this

' Animalcula Infusoria,' 1786.

272 ORDER FLA GELLA TA-PANTOSTOMA TA .

species in an intermediate or semi-erect condition under Ehrenberg's name otEpistylis
vegetans.

Anthophysa socialis, From. sp. PL. XVII. FIGS. 9-11.

Bodies broadly ovate, abruptly truncate anteriorly, attached in clusters
of about eight zooids only to the extremity of a simple, thick, and evenly
granular pedicle. Length of separate zooids 1-3000"; height of supporting
pedicle i-iooo" to 1-750".

HAD. — Fresh water, on Confervae.

The above specific title is adopted for the distinction of the flagellate organism
imperfectly figured and described by De Fromentel * under the name of Pycno-
bryon socialis. Biitschli has already proposed to identify it with Anthophysa vegctans,
but the more broadly ovate contour of the animalcules, which exhibit a perfectly
straight instead of an obliquely truncate anterior border, added to the simple and
coarsely granular character of the supporting pedicle, distinguish it in a marked
manner from that species. The presence of the secondary and shorter flagellum
characteristic of the present genus, was not recognized by De Fromentel ; the
magnification of 400 diameters only, employed by him in his examination of this
and kindred Flagellata, being inadequate for its detection. The form figured by the
same writer at pi. ix. fig. n of the work quoted, and referred with some doubt to
the present type, is evidently a young colony of Codosiga botrytis. Biitschli's repre-
sentation of Anthophysa vegetans, reproduced at PI. XVII. Fig. n, is apparently
identical with the present animalcule and can certainly not be accepted as a typical
example of the last-named species.

GENUS V. CEPHALOTHAMNIUM, Stein.

Animalcules obliquely pyriform, attached in groups to the extremities
of an erect, rigid, hyaline and homogeneous, more or less extensively
branching pedicle or zoodendrium ; flagella two in number, one long and
one short ; endoplast and one or more contractile vesicles usually con-
spicuous. Inhabiting fresh water.

The representatives of this genus while corresponding, in the form and structure
of the individual monads and their mode of groupment, with those of Anthophysa,
are to be distinguished from them by the stiff, hyaline, and homogeneous composi-
tion of the supporting pedicle.

Cephalothamnium csespitosa, S. K. sp.
PL. XVII. FIGS. 27-32, AND PL. XVIII. FIGS. 33-35.

Animalcules somewhat variable in shape, mostly irregularly and obliquely
pyriform, attached in clusters of from two or three to as many as six or eight
to the summit of a simple or sparsely divided pedicle ; pedicle rarely
exceeding the height of the individual animalcules. Length of separate
bodies 1-5000".

HAB. — Fresh water, attached to a species of Cyclops.

This animalcule was first figured and described by the author under the title of
Anthophysa caspitosa in a communication made to the Linnean Society in June
1877, and nas rnore recently received, at the hands of Stein, the name of Cephalo-

* 'Microzoatres,' pp. 212 and 337, pi. ix. fig. 10, and xxvi. fig. 9.

GENUS CEPHALOTHAMNIUM. 273

thainnium cydopum. While readily adopting Stein's proposed generic designation,
the author's earlier conferred specific one is here retained. Superficially examined,
the dense clusters of this specific type, as first met with, presented a considerable
resemblance to the gregarious colonies of Deltomonas cydopum described on a
succeeding page. A nearer investigation, however, revealed the presence of the
common supporting stem or pedicle. In no instance was this supporting pedicle
found to exceed in height the length of a single animalcule's body, while in most
cases it scarcely attained to one half that altitude. While usually perfectly simple,
the larger colony-stocks occasionally exhibit a rudimentary branching of the pedicle
towards the summit, none so far met with by the author, however, presenting so
distinct a development of secondary branches as is indicated in Stein's figure repro-
duced at PL XVIII.

Examined separately, the zooids of this species were found to present a consi-
derable range of variation in their form and general aspect, their component sarcode
exhibiting a more plastic or less firm consistence than in those of the Dendro-
monadidae previously described. Here, too, for the first time among the representa-
tives of this family group, examples were observed in which the flagella were entirely
retracted, and short pseudopodium-like processes projected from either one portion
or the general surface of the body. Phases of this amoebiform condition, as repre-
sented at PL XVII. Figs. 30 and 31, correspond in a remarkable manner with the
analogous amoebiform condition of the collared monad Codosiga botrytis delineated
at PL II. Fig. 25. This metamorphosed state is no doubt intimately connected with
the process of reproduction. The somewhat abnormal process of multiplication by
transverse fission, resulting in the product of a free-swimming zooid, was observed
on one occasion, and is represented at PL XVII. Fig. 32. This species has been
obtained by the writer attached to a species of Cydops taken from ponds on
Wandsworth Common.

Cephalothamnmm cuneatum, S. K. PL. XVII. FIG. 12.

Bodies subtriangular or cuneiform, compressed, attached in clusters of
about eight zooids to a slender, rectilinear, simple, or sparsely bifurcating
pedicle. Length of bodies 1-2500".

HAB. — Pond water, on a species of Cyclops.

Examples of this species have been met with on one occasion only on the
Entomostracon mentioned, obtained from a pond near Acton. The most luxuriant
specimen presented only the single bifurcation of the pedicle, as represented in the
accompanying illustration. The larger size and more regular cuneiform contour of
the animalcules, combined with the comparatively greater and more symmetrical
development of the pedicle, distinguish this form from A. caspitosa with which it is
otherwise most nearly related.

Fam. VI. BIKCECID^, Stein.

Animalcules sedentary, ovate or pyriform, with a usually more or less
projecting anterior lip-like prominence, solitary or colonially associated,
secreting separate horny sheaths or loricae, which are mostly stalked ;
flagella terminal, two in number, one long and one short ; parenchyma
transparent ; no distinct oral aperture ; endoplast and one or more con-
tractile vesicles usually conspicuous ; increasing by transverse subdivi-
sion and by the separation of the body into a mass of sporular elements.
Inhabiting fresh and salt water.

T

274 ORDER FLAGELLATA-PANTOSTOMATA.

The animalcules relegated to this family group closely coincide with those of
the Dendromonadidae last described, but are to be distinguished from them by their
secretion of horny loricne and normally transverse mode of fission ; the relationship
of these two groups is consequently closely parallel with that which subsists between
the naked and loricate sections of the Vorticellidse.

GENUS I. HEDR^OPHYSA, S. K.

(Greek, hedraios, sessile ; physa, bladder.)

Animalcules solitary, irregularly ovate, possessing a more or less con-
spicuous anterior lip-like prominence, inhabiting horny sheaths or loricae,
which are attached in a sessile manner, without an intermediate pedicle,
to subaquatic objects ; flagella two in number, unequal, one long and one
short, originating close to each other near the centre of the anterior border.

The representatives of this genus differ from those of Bicosoeca merely in the
absence of a supporting pedicle to the lorica. A single species, inhabiting salt
water, has as yet been observed.

Hedraeophysa bulla, S. K. PL. XVIII. FIG. 24.

Lorica subglobose, bubble-like, anterior aperture of small dimensions ;
animalcule occupying the greater portion of the cavity of the lorica,
attached in a sessile manner to its bottom ; height of lorica 1-4000".

HAB. — Salt water.

A single example only of this species has been so far met with, being then
obtained by the author attached to Conferva from- sea-water collected at St. Heliers,
Jersey.

GENUS II. BICOSCECA, James-Clark.

Animalcules solitary, more or less ovate, with a projecting anterior lip-
like prominence, inhabiting simple, pedicellate, horny loricae, to the bottom
of which they are attached by a thread-like contractile ligament or peduncle;
flagella two in number, unequal, one long and one short ; an endoplast and
one or more contractile vesicles usually conspicuous ; no distinct oral aper-
ture, food being incepted at all points of the periphery. Increasing by
transverse fission and by the subdivision of the body into spores.

As first described by Professor H. James-Clark, the members of this genus were
represented as possessing a single vibratile flagellum only. The existence of a
comparatively minute' secondary one has, however, been clearly demonstrated by the
author on innumerable occasions, and in connection with a variety of specific types.
The homologue of a secondary flagellum has been supposed by Professor Clark to
exist in B. lacustris in the posterior eccentrically developed contractile ligament
which fixes the animalcule to the bottom of its lorica, and which in such case he
maintains favours the interpretation of Bicostxca as a thecated Heteromita or Aniso-
n cm a permanently affixed in its sheath by the trailing or gubernaculate flagellum.
That Bicosceca originates from a motile Heteromitous zooid is shown by the author
in the following descriptions of B. lacustris and B. pociilum ; but the accompanying
demonstration of the existence of two vibratile flagella, in addition to the contractile
ligament, during the more normal sedentary conditions of these species, entirely
negatives Professor Clark's hypothesis. In Bicosoeca pocillum, more especially, the

GENUS BICOSCECA. 275

primary origin of the contractile pedicle as an altogether independent tail-like
prolongation of the posterior region is clearly manifested. Stein* substitutes the
title of Bikceca for this genus as more etymologically correct.

Bicosoeca lacustris, J.-Clk. PL. XVIII. FIGS. 13-19.

Lorica elongate-ovate, widest posteriorly, a little over twice as long as
broad, supported on a pedicle which nearly equals it in length ; animalcule
when extended projecting beyond the aperture of the lorica, produced
anteriorly in the form of a projecting lip-like prominence, attached
posteriorly to the bottom of the lorica by an eccentrically developed,
thread-like, contractile ligament ; flagella uneven, one long and one short,
the longer one when retracted rolled spirally within the cavity of the
lorica ; contractile vesicles two or three in number, posteriorly situated ;
endoplast spherical, subcentral. Length of lorica 1-2500".

HAB. — Pond water ; abundant.

This species represents, undoubtedly, one of the most widely distributed members
of the Flagellata, it having been met with by the author in more or less abundance
on weeds from almost every sample of pond-water examined. The presence of
the second and comparatively very short flagellum is difficult to determine without
the employment of a high magnifying power of the microscope (800 diameters and
upwards) and a careful manipulation of the illuminating agency. In the descriptions
illustrative of this type, indeed, as originally given by H. James-Clark, or more
subsequently by Stein or Biitschli, a single long flagellum only is reported to exist.
The possession of a minute supplementary appendage has, however, been repeatedly
corroborated, and more recently* with the advantage of verification by an indepen-
dent witness. Even where not distinctly visible, its presence is clearly indicated by
the tremulous motion of the particles in the vicinity of the much attenuated lip-like
prominence, and behind which process of the anterior region this smaller flagellum
is frequently more or less completely concealed. The posterior and retractile
thread-like ligament securing the animalcule to its lorica in this species is inserted
eccentrically, and towards the ventral aspect— a circumstance, however, which is
distinctly shown only when a lateral view, as indicated at PL XVIII. Fig. 19,
is presented. On retreating into its lorica, this thread-like ligament or peduncle is
folded tightly on itself, while the longer of the two flagella, as shown at Fig. 17,
is thrown into an elegant spiral coil, reminding the observer of the spirally retracted
proboscis of a butterfly. The ingestion of food-particles has been observed to take
place indifferently at all points of the exposed anterior border, against which region
they are cast by the vibrating motions of the long flagellum, the shorter appendage
apparently assisting in making further secure the food-substances brought within
reach by the longer one.

The most general method of reproduction exhibited by Bicosoeca lacustris, in
common with the other representatives of the same genus, is that of multiplica-
tion by transverse fission. Preceding such duplicative process, the body of the
animalcule, growing to nearly twice its normal size, almost completely fills the
cavity of the lorica ; a transverse furrow then makes its way across the centre,
increasing in depth until the anterior moiety becomes completely separated from
the hinder one, and is liberated into the outer water. Within the course of a
few minutes, the posterior portion, which is left attached to the contractile pedicle,
develops two new flagella, and has assumed a contour in every way identical with
that which the animalcule originally possessed. The detached anterior half issuing
from the aperture of the lorica, immediately takes upon itself the form and habits
of a free-swimming zooid, altogether unlike the parent, and most nearly resembling

* ' Infnsionsthiere,' Abth. iii., 1878.

T 2

276 ORDER FLAGELLA TA-PAATOSTOMATA.

some representative of Dujardin's genus Heteromita. The anterior extremity
of the body retains its pointed rostrum, and likewise the two flagella; but the
function of these two organs becomes materially altered. Formerly the longer of
the two flagella was apparently the most actively employed ; this, however, is
now left trailing in the rear, while the shorter one is advanced to the front,
and, vigorously vibrating, constitutes the motive or propelling power. The move-
ments of the animalcule during this free-swimming condition are, however, by no
means regular, nor of long duration. After tumbling about in an aimless sort of
manner for a little while — say half an hour — it meets with some surface suitable
for attachment, and fixing itself to it, gradually develops a lorica, pedicle, and all
other parts that characterize the parent form. In all such instances, where this
interesting growth from a detached zooid has been observed, it is worthy of remark
that the attachment was effected and the pedicle produced at that extremity whicli
previously bore the flagella, these organs being absorbed and developed anew at the
opposite or distal extremity. The peculiar aspect and movements of the free-
swimming zooids of Bicosceca lacustris distinguish them readily from typical Het&o-
mita or other independent forms, while their presence in the water affords a sure
indication of the close vicinity of the adult sedentary animalcules from whence,
by fission, they were originally derived. Not unfrequently Bicosceca lacustris has
been observed by the author in a quiescent and apparently encysted state within
its lorica; while still more recently an example has been met with — PI. XVIII.
Fig. 1 8 — in which the former contents of the lorica were broken up into numerous
spore-like bodies. Empty loricae are of frequent occurrence, and are evidently of
considerable consistence. Although such a phenomenon has not yet been observed,
it is highly probable that the free-swimming monads liberated by the process of
transverse fission, occasionally coalesce with one another, or with one of the fixed
examples, and thus give rise to the sporular encystments, in a manner identical with
what is now known to obtain among so many of the ordinary illoricate Flagellata.
A first record of the occurrence of this species on this side of the Atlantic, embody-
ing a figure illustrating the existence of two flagella — the second flagellum being
there described as a shorter stylate appendage — was communicated by the author to
the 'Monthly Microscopical Journal' for December 1871.

Bicosoeca gracillipes, J.-Clk. PL. XVIII. FIGS. 21 AND 22.

Lorica subcylindrical, slightly everted at the aperture, tapering towards
its junction with the pedicle, about three and a half times as long as broad ;
pedicle twice the length of the lorica ; enclosed animalcule elongate-oval,
usually entirely enclosed within the cavity of the lorica ; contractile vesicle
subcentral. Length of lorica 1-2000", of contained animalcule 1-4000".

HAB. — Salt water.

This species was obtained by the author in September 1872, attached to seaweeds
and Polyzoa collected at Bognor, Sussex. The example represented at PI. XVIII.
Fig. 22, differs from the more typical form of growth in the shorter comparative
length of the pedicle which supports the lorica, and in the more exsert character of
the contained zooid.

Bicosceca tenuis, S. K. PL. XVIII. FIG. 23.

Lorica elongate-ovate or subfusiform, nearly three times as long as
broad, tapering equally at each extremity ; pedicle scarcely one-half the
height of the lorica ; animalcule with an attenuate anterior lip-like projec-
tion, slightly exsert anteriorly. Length of lorica 1-3000" to 1-2500".

HAB.— Salt water.

GENUS BICOSCECA. 277

This species has been obtained on filamentous algae and Sertularian zoophytes at
St. Heliers, Jersey, and likewise at Bognor, Sussex. Both the lorica and contained
animalcule, while presenting a considerable resemblance to the common fresh-water
type B. lacustris, are to be distinguished from the same by their more attenuate
contour. The development of this type from a naked P/iysomonas-like form has been
observed, the subsequently produced lorica first appearing as a mere bubble-like
film round the anterior margin of the animalcule's body.

Bicosceca pocillum, S. K. PL. XVIII. FIGS. 25-29.

Lorica cup-shaped or subcylindrical, rounded posteriorly, the anterior
margin abruptly truncate, neither everted or constricted, varying in height
from one and a half to two or three times its greatest breadth ; pedicle
short, rarely half as high as the lorica ; animalcule subovate or calceo-
late, rounded posteriorly, the antefior margin excavate, produced on one
side as a broad, flattened, lip-like process, occupying from one-third to
one-half of the cavity of the lorica ; posterior retractile ligament equalling
the body in length ; contractile vesicle posteriorly situated ; endoplast
spherical, subcentral. Length of lorica 1-2500" to 1-1500", of contained
animalcule 1-3250".

HAB. — Salt water attached to the polyparies of hydroid zoophytes
and polyzoa.

This species was obtained abundantly by the author at St. Heliers, Jersey, in the
summer of the year 1878. It may be readily distinguished from all the preceding
members of the genus by the rounded and subcalceolate contour of the animalcule
and the plain cup-like or subcylindrical shape of the protective sheath. Multipli-
cation by transverse fission was frequently observed, the free-swimming zooid
produced by this process presenting a somewhat variable but highly distinctive
form. In certain instances — PL XVIII. Fig. 27 — the posterior region of the body
was symmetrically rounded, as in the parent monad, but in others (Fig. 28) drawn out
in an attenuated tail-like manner. The longer or primary flagellum under these free-
swimming conditions was always extended in advance, causing by its undulations an
even motion in a straightforward direction, while the shorter and secondary
flagellum, about half the length of the primary one, was reflected ventrally, and
trailed in the rear in a manner that imparted to the animalcule, as in the case of the
similar motile zooid of Bicosozca laeustris, a close resemblance to the members of
the genus Heteromita. Encountered in this free-swimming condition only, the
animalcule would, indeed, without the slightest inconsistence, be referred to the last-
named genus. The motile animalcules, after a brief nomadic existence, were observed
to attach themselves, and to gradually develop, by exudation, their transparent
loricse. In the fixed condition immediately preceding the secretion of this protective
structure, or in which the body had developed only its thread-like pedicle, as shown
at PL XVIII. Fig. 29, the general form and structure correspond, to all appearances,
with those of a typical representative of the genus Physomonas. The developmental
history of this type is thus shown to exhibit three widely distinct phases, each of
them being characteristic successively of the normal or adult condition of the three
distinct Flagellate genera Heteromita, Physomonas, and finally Bicosceca. There is
doubtless a still earlier and more simple monoflagellate condition resulting from the
breaking-up of the parent body into spores, to be discovered. The ingestion of
food at various parts of the periphery was frequently observed.

Examples of this species have been recently received by the author, in company
with other marine Infusoria, from Mr. Thomas Bolton's microscopical studio.

278 ORDER FLAGELLATA-PANTOSTOMATA.

GENUS III. STYLOBRYON, De Fromentel.

Animalcules social, inhabiting a compound polythecium, composed of
separate horny loricae united to one another, or to a common pedicle,
through the medium of slender independent footstalks ; bodies ovate
with a projecting lip-like anterior border, affixed to the bottom of their
loricae by a contractile thread-like peduncle ; flagella two in number,
uneven, one long and one short, the former rolled spirally when retracted ;
parenchyma transparent and homogeneous. Increasing by transverse
subdivision and by the resolution of the body into spores.

HAB. — Fresh water.

Stylobryon petiolatum, Duj. sp. PL. XXIII. FIGS. 17-30.

Component loricae of polythecium wineglass-shaped, widest and slightly
everted anteriorly, tapering towards and conically pointed at the posterior
extremity, from one and a half to three times as long as broad ; united
to each other by pedicles which, while subequal in the same polythecium,
vary in diverse colony-stocks from less than one-half to three or four
times the length of a single lorica ; pedicles produced for some little
distance within the cavity of their associated loricae, and forming bases of
attachment for the enclosed zooids ; animalcules plastic and changeable in
shape, irregularly ovate, with one of the antero-lateral angles projecting
in a lip-like manner, occupying about one-half of the cavity of the loricae,
united to it posteriorly by a contractile thread-like peduncle ; flagella two
in number, one long and one short, inserted at the base of the anterior lip-
like prominence, the longer one coiled spirally when retracted ; contractile
vesicle single, posteriorly located ; endoplast spherical, subcentral. Length
of loricae 1-800" to 1-500".

HAB. — Pond water, multiplying by transverse fission and by the sub-
division of the entire body into spores.

This animalcule was first described by Dujardin under the title of Dinobryon
petiolatum, the generic one here given being conferred upon it by De Fromentel, who
figures and describes it in his ' Microzoaires ' as Stylobryon insignis. There can
further be but little doubt that the species figured by Stein in his recently published
volume under the name of Poteriodendron petiolatum represents the same form, and
this notwithstanding there are certain remarkable structural features accredited to it
by this authority which, if fully substantiated, would necessitate its recognition as an
entirely distinct organic type. According to Stein, the loricae, while corresponding
entirely in their contour and mode of union as defined in the above diagnosis,
contain animalcules possessing one flagellum only, but which bear in the anterior
region and to one side of the flagellum a supplementary membraniform expansion,
resembling in a less conspicuously developed degree the funnel-shaped collar of
the Choano-Flagellata. Having, however, had the opportunity of examining an
extensive series of examples of the form now under discussion obtained from diverse
localities, the author has arrived at the conclusion that so far as the presence of a
collar-like structure is concerned, Stein has misinterpreted the actual facts of the
case. In no instance could any such independent organ be detected ; but in place
of this it was observed that the anteriorly developed lip-like prominence occupied

GENUS STYL OBR YON. 279

a conspicuous position, and might with ease be identified with the looked-for
"collar." A reference to the plate illustrative of this type, in which at Figs. 27
and 28 are reproduced out of Stein's work two colony-stocks with their reputed
collars, and at Figs. 17-23 delineations of aggregated colonies and isolated zooids
in various aspects and conditions, as observed by the author, will at once make
clear the ground of such identification. In Figs. 19 and 20 especially, where a
front and profile view is given of an animalcule under the high magnifying power
of 1500 diameters, it will be at once seen that the more attenuated sarcode sub-
stance entering into the composition of the anterior lip-like prominence necessarily
presents in juxtaposition to the denser mass of the body proper the appearance of
an independent hyaline organ. Such an aspect and correlated type of structure is
by no means, however, restricted to the type now being considered, but is more or
less prominent throughout all the members of both the present family and that of
the preceding one of the Dendromonadidce. The presence of the shorter of the two
flagella, overlooked by Stein, is not easy to detect in living examples, but is shown
distinctly in specimens killed with osmic acid.

As indicated in the figures given by the authority just quoted, the compound
polythecium, built up of the more or less numerous separate and independent loricae,
exhibit a very considerable range of variation. Thus sometimes, as in Figs. 18 and
27, the loricae may be so closely approximated that the pedicles as independent
elements are almost completely subordinated, while in other cases, as at Figs. 17
and 28, these structures may equal or considerably exceed the length of the loricae.
The exceptionally long-stalked variety illustrated in the first of these two figures,
was obtained by the author from a pond in the neighbourhood of Prestwich, Man-
chester, in November 1875 ; more ordinary examples of this species have been
collected both in the vicinity of London and at St. Heliers, Jersey. An excep-
tionally fine specimen preserved with osmic acid, and obtained from one of the
water-fowl ponds in the Zoological Gardens, Regent's Park, has been recently placed
at the author's disposal by Mr. L. Dreyfus. The zoothecium embraces over one
hundred loricae, united by short pedicles as in the example figured at PI. XXIII.
Fig. 27. Among this group furthermore were included several loricae in which the
bodies of the animalcules had become divided up into sporular elements, these in
some instances being entirely enclosed within and in others partly discharged from
the apertures of the loricae. Examples of such spore-bearing loricae are represented
at Figs. 24 and 25, as also isolated spores more highly magnified at Fig. 26.

Stylobryon (Poteriodendrori) petiolatum, considered with the aid of the hitherto
unrecorded structural details here submitted, must undoubtedly be regarded as a
compound modification only of the form Bicosceca lacustris, previously described.
It is a noteworthy circumstance, in this connection, that Stein himself, while
advocating so distinct an interpretation of its structural features, admits it in his
classification scheme to the same- family group as Bicosceca, while Biitschli * figures
and describes it — without indicating the presence of a second flagellum — as a
probable compound example only of the last-named species.

While going to press, October 1880, the author has received luxuriant colony-
stocks of this species from the neighbourhood of Dundee, through Mr. John Hood,
in company with an interesting Melicertan, apparently new to science.

Stylobryon epistyloides, S. K. PL. XVIII. FIG. 32.

Loricae evenly ovate, about twice as long as broad, attached by short
secondary peduncles, in social clusters of from two or three to six or
eight zooids, to the summit of a simple, straight, rigid pedicle ; anterior
extremity of animalcules prolonged into a lip-like prominence, projecting
slightly beyond the orifice of the loricae. Length of loricae 1-2000", of
contained animalcules 1-3250". HAB. — Fresh water.

* " Beitrage zur Kenntniss der Flagellaten," ' Zeit. Wiss. Zool.,' Bd. xxx., 1878.

280 ORDER FLAGELLATA-PANTOSTOMATA.

The colonies of this species closely resemble a number of zooids of Bicosceca
lacustris grouped together at the extremity of a common rigid pedicle. This
supporting stem is itself of variable dimensions, being sometimes only half as long
as, but more often considerably exceeding in length the ovate loricae. The com-
pound groups of this species are apparently produced by the repeated longitudinal
fission of a primary naked zooid of abnormal size, the formation and induration of
the loricae being accomplished subsequently. Examples of this type have been
obtained from both Wandsworth Common and a pond near Acton. It was
originally referred by the author to the genus Dinobryon, and is figured in connection
with that generic title in the ' Popular Science Review' for April 1878.

Fam. VII. AMPHIMONADID^:, S. K.

Animalcules naked, free-swimming, or sedentary and adherent by a
prolongation of the posterior extremity or by a distinctly developed
caudal filament ; flagella two in number, terminal, of equal size ; no distinct
oral aperture, food-substances being incepted at all points of the periphery.

The even development of the two flagella serves to distinguish the representatives
of this family group from those of the Dendromonadidae.

GENUS I. GONIOMONAS, Stein.

Animalcules free-swimming, persistent in shape, the anterior border
obliquely truncate, having at the apex of the projecting angle two subequal
and closely approximated flagella ; multiplying by longitudinal fission.

HAB. — Fresh water.

This generic group is instituted by Stein * for the reception only of the Monas
truncata of Fresenius.

Goniomonas truncata, Fres. sp. PL. XIV. FIGS. 31-33.

Body ovate, compressed, from one and a half to three times as long as
broad, rounded posteriorly, the anterior border abruptly and obliquely
truncate, with a sharply pointed and projecting anterior angle ; flagella
short, of uniform size, scarcely equalling the body in length, inserted at the
apex of the projecting angle ; parenchyma transparent, granular, enclosing
near the anterior border a transversely placed, dark, band-like body ; con-
tractile vesicle situated on the shorter lateral border, a little behind the
band-like body ; endoplast located near the centre of the opposite or longer
lateral border. Length 1-2500" to i-iooo". HAB. — Fresh water.

This species, synonymous with the Monas truncata of Fresenius, f has been
recently encountered by both Biitschli and Stein, the former regarding it as. a
migrant member of the genus Spumella, to which he has provisionally relegated it,
while the latter, as already mentioned, has instituted the present generic title for
its reception. By both of these authorities has the anterior band-like body, first
delineated by Fresenius, been observed, but is in either case evidently diversely

* ' Infusionsthiere,' Abth. iii., 1878.

t " Beitrage zur Kenntniss Mikroskopischer Organismen," 'Abhandl. d. Senckenbergischen
Naturforschenden Gesellschaft,' Frankfort, 1858.

GENUS A MPHIMONA S. 281

interpreted. Biitschli remarks that under a high magnifying power it exhibits a
granular formation, and is apparently homologous with the eye-like pigment-spot of
Euglena and other Flagellata, while in Stein's figures, unfortunately accompanied
by no descriptive text, the same initial (b) is set against it that is employed in a
neighbouring form Spumella guttula — distinguished by the possession of a similar
granular pig-nent-band— for the indication of a presumed oral furrow. -The pre-
sence of ingested food-matter within the substance of the parenchyma is figured
and alluded to by Professor Stein, and is probably incepted indifferently at all parts
of the periphery. The movements of this type are reported by Biitschli to be rapid
and uninterrupted ; in some minute examples, however, recently examined by the
author, the locomotion was observed to be weak, tremulous, and subject to constant
interruption.

GENUS II. AMPHIMONAS, Dujardin.

Animalcules of spherical, ovate, or irregular outline, plastic and change-
able in shape, attached posteriorly by a slender, non-contractile, thread-
like filament : flagella two in number, equal in length and character ; food
incepted at any portion of the periphery ; contractile vesicle and endoplast
usually conspicuous.

Out of the three species of this genus enumerated by Dujardin, the one,
Amphimonas caudata, is referable to the genus Heteronema, while the other two,
A. dispar and A. brachiata, are exceedingly doubtful forms that might represent the
motile condition of various biflagellate types. The two new species here introduced
adapt themselves so well, however, to the broad characters of the genus as first
established by Dujardin, that it seems desirable, with some slight amendment, to
retain his generic title of Amphimonas for them in preference to constructing
a new one, which would otherwise be necessary. As here characterized, the
representatives of this genus correspond on the one hand with those of P/iysomonast
from which they are to be distinguished by their possession of two equal-sized
flagellate appendages, and on the other with those of Deltomonas, which while
possessing similar flagellate organs, attach themselves bodily to the chosen fulcrum
of support without the intermedium of a filamentous pedicle. Perty, in referring a
single form to the genus Amphimonas under the title of A. exi/is, evidently associated
with Dujardin's generic group an interpretation closely corresponding with the one
here adopted. Diesing, in his ' Conspectus dispositionis familiarum et generum,'
has merged the several species of Hexamita of Dujardin in the genus Amphimonas^
though upon what grounds it is difficult to comprehend, the animalcules of that
generic type being multiflagellate and, as hitherto recorded, free-swimming forms,
presenting no resemblance whatever to the fixed biflagellate monads now under
consideration.

Amphimonas globosa, S. K. PL. XIV. FIGS. 55-59.

Body subspherical, attached posteriorly by a slender, flexible, filamentous
pedicle, equal in length to about three times its own diameter ; flagella
"even, inserted close to one another in the centre of the anterior border,
twice the length of the body, vibrated in an irregular undulating manner ;
parenchyma hyaline, vacuolar ; contractile vesicles two in number, situated
a little behind the median line ; endoplast spherical, subcentral. Diameter
of body 1-2000". HAB. — Pond water with Myriophyllum.

The considerably larger size of this animalcule serves to distinguish it at once
from Physomonas sodalis with which, when first seen, it is perhaps liable to be

282 ORDER FLAGELLATA-PANTOSTOMATA.

confounded. On closer examination it is, morever, found to entirely want the
emargination of the anterior border characteristic of that species, this region in
the present form being perfectly smooth and even. Lastly, and more importantly,
the characters afforded by the flagella separate it decisively from either the last-
named or any superficially corresponding type. Neither of these organs, which are
of equal length, are extended in that rigid arcuate manner characteristic of the single
longer flagellate appendage of either P/iysomonas, Spumella, or Oikomonas, but are
vigorously lashed and vibrated now on one side and then on the other, as in
Diplomita, describing a maze of convolutions not easy for the eye to follow ; the
body of the animalcule meanwhile sways to and fro or floats up and down at the
end of its flexible pedicle as light as a child's air-ball at the end of its restraining
string. Food-particles, seized by the extremities of the extended flagella, are thrown
back against the body, the thin yielding sarcode opening and spreading out to
engulf them at whatever point upon which they may happen to impinge. An
interesting example of food-ingestion, as observed by the author, will be found
represented at PL XIV. Figs. 56-59. The ingested morsel, a large Bacillus, was
first captured end-on, a transparent film of sarcode flowing out to invest it, the
captured prey was then brought crosswise along the anterior border of the animal-
cule, and finally bent up and tucked away within the inner substance of the little
creature's body. At Fig. 550 an example is delineated in the act of ingesting a
minute particle on its lateral border. Spherical pedicellated encystments, corre-
sponding closely with those described of Physomonas communis, but of larger size,
have been observed in the neighbourhood of the present species, and apparently
belonged to it

Amphimonas divaricans, S. K. PL. XIV. FIG. 66.

Body irregular in form, widest transversely, rounded posteriorly, the
anterior margin abruptly and obliquely truncate, its two lateral angles
unequally produced as conical prolongations ; flagella corresponding in
length and character, borne respectively by the apex of the two anterior
angular extensions, equal in length to twice the diameter of the body ;
pedicle slender, straight, nearly equal to the flagella in length. Height of
body 1-10,000", greatest width 1-8500". HAB. — Salt water.

This remarkably minute monad has as yet been met with on one occasion only,
a group of two or three individuals being then found attached to conferva filaments
from a jar of sea-water containing various polyzoa and hydroid zoophytes, obtained
at St. Heliers, Jersey. The flagella, stationed at the termination of the conical
anterior prolongations, one of which is produced to twice the height of the other,
exhibited great activity, whirling round and round in a circular manner, and at the
same time presenting a somewhat sinuous outline. The parenchyma was colourless
and slightly granular, and a vacuolar space, which probably represented the con-
tractile vesicle, being visible towards the posterior extremity. The exceedingly
small dimensions of this form necessitated the employment of a magnifying power
of no less than 2000 diameters for the satisfactory recognition of the external
characters here recorded.

Amphimonas exilis, Perty.

Body conical or wedge-shaped, attenuate posteriorly, the anterior border
truncate, sometimes emarginate ; flagella long and slender, issuing close to
one another from the centre of the anterior border, equal in size, twice the
length of the body ; parenchyma colourless, motion oscillating. Length of
body 1-2 1 80". HAB. — Stale marsh-water.

GENUS DEL TO MO N A S. 283

Perty detected on one occasion the presence of a posterior thread-like filament,
and upon which slender evidence only the species is here provisionally retained in
the genus Amphimonas.

GENUS III. DELTOMONAS, S. K.
(Greek A ; monas.)

Animalcules variable in form, subtriangular or wedge-shaped, attached
by an attenuate prolongation of the posterior extremity of the body, which
does not, however, assume the character of a distinct pedicle or caudal
filament ; flagella two in number, of equal length ; no distinct oral aperture.
Inhabiting fresh water.

The animalcules of this genus, while corresponding with those of Amphimonas
in their fixed habits, and in the possession of two subequal anterior flagella, are to
be distinguished from them by their direct mode of attachment, without the inter-
medium of a specially differentiated pedicle.

Deltomonas cyclopum, S. K. PL. XIV. FIGS. 60-65.

Body exceedingly plastic and variable in shape, most usually elongate-
clavate, triangular, or wedge-shaped, somewhat compressed, widest and
truncate anteriorly, tapering gradually towards the attached posterior
extremity ; flagella similar in size and character, equalling the body in
length, springing from the lateral angles of the truncate anterior border ;
parenchyma colourless, granular ; contractile vesicle conspicuous, situated
a little in advance of the centre of the body; endoplast spherical, subcentral.
Length of extended body 1-3000".

HAB. — Pond water. Multiplying mostly by longitudinal, rarely by
transverse fission, and by the breaking-up of the body-mass into spores.

This Flagellate type was found in the month of January 1877, literally encrusting
with its multitudes the carapace and limbs of specimens of a species of Cyclops taken
from a horsepond in the neighbourhood of Ashby-de-la-Zouch. The various contours
presented by different animalcules of the same colony are almost too numerous for
description. Simply ovate, clavate, symmetrically or obliquely pyriform, are among
a few of the leading variations from the typical triangular shape exhibited, these
variations depending more or less on the state of development or extension of the
individual zooids, as also upon the aspect in which they are presented to the view
of the observer. The species increases rapidly by longitudinal fission, the first
indication given of this process being the appearance of two flagella in place of one
only at each of the anterior angles (see PI. XIV. Fig. 63), this being speedily
followed by the gradual cleavage through the centre, from above downwards, of the
entire body-substance. The two zooids produced by this process of multiplication,
although usually completely separated, remain near to one another on the same
fulcrum of support, and in this way a single individual speedily produces an extensive
and closely aggregated colony. Not unfrequently instances have been met with in
which the units produced in this manner were collected in little clusters of four or
more individuals, the bases of which, if not organically united, sprang apparently
from the same point of attachment, as shown at Fig. 62. On more rare occasions
the phenomenon of transverse fission was likewise witnessed, the divided anterior
portion swimming off as a Heteromitous biflagellate monad destined either to lay the
foundation of a new community in a more remote district, or not improbably to aid

284 ORDER FLAGELLATA-PANTOSTOMATA.

in compassing the still more rapid multiplication of the species by a genetic fusion
with another individual, followed by the breaking-up of the united zooids into spore-
like elements. That a sporular mode of increase does occur in connection with
this form, was fully demonstrated by the discovery occasionally, among the others,
of pyriform encysted individuals, in which the whole body-substance was divided
into minute oval bodies as shown at Figs. 64 and 65, such metamorphosed animal-
cules evidently representing the characteristic sporocyst stage recorded of numerous
other flagellate types described in this treatise.

Fam. VIII. SPONGOMONADID^S, Stein.

Animalcules symmetrically ovate ; usually social, invariably secreting
an external protective covering, which may take the form of horny loricae,
a gelatinous, more or less granular zoocytium, or an arborescent tubular
zoothecium ; flagella two in number, of equal length ; no distinct oral
aperture. Inhabiting fresh water.

The representatives of this family group are to be distinguished from those
of the Dendromonadidae or Bikoecidae — with which their supporting or protective
fabrics most nearly correspond — by the symmetry of their bodies and the equal
development of the two flagella. The majority of forms included are remarkable
for the considerable and often visibly conspicuous size attained by their compound
colony-stocks.

GENUS I. CLADOMONAS, Stein.

Animalcules ovate, with two anteriorly inserted, equal-sized- flagella,
living in social colonies, dividing by longitudinal fission, and building up a
tubular and more or less regular, dichotomously branching zoothecium ;
the tubular branches not united to one another in a fasciculate manner, but
remaining distinct throughout their length, and enclosing each at its distal
end a single zooid ; the basal end of each tubule sometimes separated
from the preceding one by a distinct joint or dissepiment ; zooids possessing
no distinct oral aperture. Inhabiting fresh water.

The independence or non-fasciculate arrangement of the tubular branches of
the zoothecium of this genus distinguishes it from that of Rhipidodcndron, next
described, with which it otherwise substantially corresponds. The form and struc-
ture of the enclosed animalcules are in both instances closely identical.

Cladomonas fruticulosa, Stein. PL. XVIII. FIGS, n AND 12.

Zoothecium arborescent, erect, branching in the same plane, the separate
ramifications short, rarely exceeding twice the length of the zooids, straight
or flexuose ; the bodies of the zooids evenly ovate, usually projecting for
about half-way beyond the orifices of their respective tubules ; flagella equal
to ©r exceeding twice the length of the body; contractile vesicle con-
spicuous, subcentral. Length of bodies 1-3000", height of zoothecium
1-300". HAB. — Fresh water.

The two colonies of this species figured by Stein,* here reproduced, differ
remarkably, the tubular ramuscules in one example being perfectly straight, and

1 Infusionsthiere,' Abth. iii., 1878.

GENUS RHIPIDODENDRON. 285

divaricating at an approximately uniform angle of 45°, while in the second and
larger specimen these, while branching in the same plane, curve about in an alto-
gether irregular manner. It is possible that this less regularly constructed tenement
represents an instance in which the food supply had been less plentiful, the tubular
fabric excreted losing through such a cause — as in the branching stalk Q{ Anthophysa
vegetans — its characteristic more erect and rigid bearing. In this comparatively
irregular example, there would also appear to be an entire absence of the dissepi-
ments or joint-like structure developed at each point of bifurcation in the more
symmetrical and rigid form. The adult colonies of this species, according to Stein's
figures, contain from but ten to fourteen zooids ; the tubules, immediately succeeding
the act of longitudinal fission of the enclosed zooids and preceding the further
development and bifurcation of the ramuscule, necessarily enclose two animalcules.

GENUS II. RHIPIDODENDRON, Stein.

Animalcules ovate, with two anteriorly inserted, attenuate and equal-
sized vibratile flagella, living in social colonies, and building up a flabellate
or dendriform aggregation or zoothecium of closely approximated granular
tubules, the cavities of which are separately inhabited by a single zooid ;
contractile vesicle and endoplast conspicuous ; no distinct oral aperture.
Inhabiting fresh water.

Rhipidodendron splendidum, Stein. PL. XVI. FIGS. 1-3.

Aggregated tubules of the colony-stock forming an erect, compressed,
flabelliform, profusely branching zoothecium ; animalcules evenly ovate or
elliptical, usually occupying the distal extremity of these tubules, their
flagella only projecting into the surrounding water ; flagella of equal size,
about twice the length of the body ; contractile vesicle and endoplast
situated close to each other a little behind the centre of the body ; paren-
chyma transparent, granular. Length of zooids 1-2000", height of adult
zoothecium 1-75". HAB. — Fresh water.

The plate devoted by Professor Stein to the illustration of this most remarkable
type* may be justly described as forming the gem of the entire series contained in
his recently issued and important work. The innumerable members of the extensive
colony-stock build up an aggregated structure that may be compared most appro-
priately with the similarly fan-shaped, tubular polyparies of the Cyclostomatous Poly-
zoon Tubulipora flabellaris. As suggested by Stein, it would seem just possible that
the Aporca ambigua, described by J. W. Bailey in vol. ii. of the ' Smithsonian Con-
tributions' for 1850 as a doubtful algoid or stalked infusorial product, is identical
with this type ; this earlier name, in the event of such identity being substan-
tiated, will necessarily take precedence of Stein's. So far as it is possible to decide
in the absence of full descriptive details, the ramifying tubular zoothecium of this
interesting species would seem to be homologous with the solid branching pedicle or
zoodendrium of Anthophysa vegetans, its tubular instead of solid character resulting
through its secretion or excretion from the entire periphery of the individual animal-
cules, instead of from their posterior extremity only. As delineated by Stein, the
consistence of this excreted zoothecium exhibits a distinct granular aspect, and is,
in accordance with the accompanying explanation, of a rust-brown hue. In the
larger example figured by this authority, and here reproduced, PI. XVI. Fig. i,

* 'Infusionsthiere,' Abth. iii. Taf. iv., 1878.

286 ORDER FLA GELLA TA-PANTOSTOMA TA.

on a slightly reduced scale, there are no less than two hundred tubules bound together
in the flabelliform zoothecium, about one-half of these only, however, being occupied
by their minute fabricators.

Rhipidodendron Huxleyi, S. K. PL. XVI. FIGS. 4-9.

Aggregated tubules forming a spreading, bush-like, rust-brown, dichoto-
mously branching, granular zoothecium, each separate branchlet of which
is normally composed of four laterally united tubules ; animalcules
elongate-ovate, about twice as long as broad, scarcely projecting beyond
the apertures of their respective tubules ; flagella of equal size, twice the
length of the body, inserted close to one another at the anterior extremity.
Length of zooids 1-4000", diameter of adult bush-like zoothecium i-io".

HAB. — Bog water.

This second species of the genus Rhipidodendron represents one of the latest
acquisitions chronicled in this treatise, it having been collected by the author in
September 1879 at Lustleigh Cleave, on the borders of Dartmoor, S. Devon; the
same bog water yielding also the two new forms hereafter described under the titles
of Spongomonas sacculus and Monosiga longicollis.

From the preceding type the present species may be at once distinguished by
the attenuate form of growth of the zoothecium, only four tubules, as a rule, instead
of a large and indefinite number, being bound up together in each separate ramus-
cule. The manner in which this more symmetrically branching zoothecium is con-
structed, is made apparent by reference to the diagrammatic illustration given at
PI. XVI. Fig. 8. As there shown, all four of the monads inhabiting the primitive
four- chambered ramuscule divide by longitudinal fission simultaneously and abreast
of one another, the result being the production of eight in place of the preceding
four ; the lateral pressure thus brought to bear within the comparatively confined
space causes each equal moiety of four zooids to diverge slightly from the other,
and these continuing independently the fabrication of their granular sheath, pro-
duce, at more or less regular intervals, the characteristic bifurcation of the entire
mass. The absence of symmetrical subdivision of the zoothecium in R. splcndiJmn
is explained by the fact that the component tubules are congregated in rows two or
three deep, the monads evidently not separating persistently in the same plane as
obtains in the present type. The rust-brown, bush-like zoothecia of this species
were produced abundantly, in close proximity to those of Spongomonas sacculus, on
the sides of the bottle of water brought from the locality quoted, remaining so
attached and forming conspicuous objects to the unaided vision for several weeks.
Fragmentary branches of the zoothecia of a species identical with, or closely allied to,
the present form, but exhibiting less regularity in the combination of the individual
tubules and plan of bifurcation, have been recently received by the author from
Mr. J. Levick, of Birmingham.

GENUS III. SPONGOMONAS, Stein.

Animalcules evenly ovate or spheroidal, provided with two equal-sized,
anteriorly inserted, vibratile flagella ; living in social colonies, and forming
by excretion a common domicile, which takes the form of a variously
modified gelatinous or semi-granular zoocytium, within which they remain
constantly immersed, their flagella only protruding into the outer water ;
contractile vesicle and endoplast usually conspicuous ; no distinct oral
aperture. Inhabiting fresh water. Increasing by longitudinal fission and
by the subdivision of the entire body into sporular elements.

GENUS SPONGOMONAS. 287

This genus is founded by Stein * upon the Phalansterium intestinum of Cien-
kowski, two new and highly characteristic species being added. The desirability
of separating this type from the monoflagellate Phalansterium consociatum of the
last-named writer, had been recognized by the author previous to the publication of
Stein's volume, and he had allotted to it in the manuscript of this work, then in the
printer's hands, the new generic title of Gleomonas. The animalcules of Spongomonas
correspond essentially in general form and structure with those of Rhipidodendron
and Cladomonas, differing only in the character of the common supporting and
protective element they collectively excrete, which here takes the form of a gelatinous
and more or less granular zoocytium, closely analogous to the common slime-sheath
produced by Ophrydium in the section of the Ciliata.

Spongomonas intestinalis, Cienk. sp. PL. XI. FIGS. 11-14.

Gelatinous zoocytium or common investing matrix presenting a slender,
attenuate, more or less irregularly convolute, thread-like contour ; contained
animalcules ovate or subglobose ; flagella similar in size and character,
twice the length of the body, protruding for almost their entire length
beyond the periphery of the zoocytium ; contractile vesicle single, lateral ;
endoplast spherical, subcentral. Length of zooids 1-3000", diameter of
thread-like matrix 1-250" to 1-125".

HAB. — Pond water with Anthophysa and Dinobryon.

As already stated, this species was primarily included by Cienkowski in his
newly established genus, Phalansterium.^ The more luxuriant colony-stocks may
attain, according to this same authority, a length of as much as three centimetres,
forming, under such circumstances, conspicuous objects to the unaided vision.
These extensive colonies are produced by continuous fission and sporular subdivision
from a single primary individual, accompanied by the secretion or exudation by
each monad so produced, of mucus and rejectamenta, towards the building-up of the
common gelatinous slime-sheath. The free ingestion of particles of indigo, at
apparently no distinct oral aperture, is recorded by Cienkowski. The more explicit
details of the form, structure, and mode of subdivision of the monads, supplied by
Stein's recent illustrations, are reproduced in the accompanying plate. As there
shown, a single zooid, by encystment and segmentation, becomes divided into two,
four, or eight sporular elements.

Spongomonas discus, Stein. PL. XI. FIG. 10.

Zoocytium discoidal, flattened, gelatinous, and highly granular ; ani-
malcules subspheroidal ; flagella two or three times the length of the body.
Dimensions 1-3200". . HAB. — Fresh water.

The zoothecium of this species corresponds closely in general form with that t>f
Phalansterium consociatum, but does not exhibit the radiating or chambered sub-
division of its structure characteristic of that type. Stein is somewhat uncertain
which of these two represents the originally described Monas consociata of Fresenius,
but the possession by each animalcule of a single flagellum only, is so clearly indicated
in the figures given by that authority, as to leave but little doubt as to the correct-
ness of Cienkowski's interpretation. Many individuals in the group figured by
Stein, here reproduced, have withdrawn their flagella and become separated into

* ' Infusionsthiere,' Abth. iii., 1878.

t L. Cienkowski, " Ueber Palmellaceen und einige Flagellaten," ' Archiv f. Mik. Anat.,' Bd. vi.
Heft 4, 1870.

288 ORDER FLAGELLA TA-PANTOSTOMA TA.

two or four macrospores within spheroidal cavities of the gelatinous zoothecium
previously occupied by the parent zooids.

Spongomonas uvella, Stein. PL. XI. FIGS. 15 AND 16.

Animalcules ovate, nearly twice as long as broad, forming an erect,
lobulate zoocytium, which tapers posteriorly into a short, slender, and almost
stalk-like point of attachment ; expanding distally into a variable number
of closely associated ovate lobules, each of which is inhabited by a separate
zooid ; flagella rarely exceeding twice the length of the bodies, mostly less.
Length 1-2100", height of zoocytium 1-500". HAB. — Fresh water.

The largest colony-stock of this species figured by Stein and here reproduced,
contains about a dozen zooids only. No indication is given of spore-production,
after the manner of the two preceding types.

Spongomonas sacculus, S. K. PL. XI. FIGS. 17-23.

Zoocytium granular, rust-brown colour, subglobose or sacculate, pendant,
many individual zooids crowded within each saccular diverticulum of the
common mass ; the social colony-stock produced forming in its entirety a
conspicuous object to the unaided vision ; animalcules elongate-ovate, twice
as long as broad ; flagella about twice the length of the bodies ; contractile
vesicle lateral ; endoplast ovate, central. Length of zooids 1-3250", of
adult saccular zoocytium 1-25" to |". HAB. — Bog water.

This species was obtained by the author in September 1879, m bog water col-
lected at Lustleigh Cleave, S. Devon, in company with Rhipidodendron Huxleyi. As
first encountered it was passed over as mere flocculent inorganic debris adherent
to the sides of the glass receptacle, and it was only by the accidental inclusion
of a fragment with the examined specimens of the last-named type, that its presence
and true nature were elicited. Once recognized, its existence in corresponding or
even greater abundance than Rhipidodendron became apparent, and data of interest
concerning its structural characteristics and rapidity of growth were placed on
record. In this last connection, more especially, it was found, by taking diurnal
measurements, that a colony-stock which on a given day presented in its total bulk
the size only of a grain of millet-seed, or a diameter of 1-25", might within three
days so increase in calibre as to form a subpyriform pendulous sac, equalling or
slightly exceeding the length of half an inch. From this point the zoocytium
usually became disintegrated, and, falling away piecemeal, liberated the contained
monads into the surrounding water under conditions favourable, no doubt, for the
establishment of new colonies. A delineation of the contours of such a colony-stock,
as observed at the commencement and termination of three consecutive days, is
reproduced at PI. XI. Figs. 18 and 19.

When examined with a high magnifying power, a conspicuous feature of the
zoocytium of this type, shared, however, not only by the remaining members of this
genus, but being in a less degree characteristic also of the more substantial zoo-
thecia and zoocytia of Rhipidodendron, Phalansterium, and apparently Cladomonas,
is manifested by the exceedingly regular distribution and even size of the granular
particles distributed through its substance, and which add so materially to its con-
sistence. In the present instance, these granular elements, taken separately, are
of a roughly spheroidal shape, having a diameter of about one-tenth of the length of
the associated monads, or the i-3o,oooth of an inch, and exhibit by transmitted light a
pale amber hue. So densely are these minute particles packed together within the
transparent and mucilaginous element of the zoocytium, that they represent at

GENUS DIPLOMITA. 289

least one-half of the total bulk of this structure, imparting to it, by their dense
aggregation, the rich chestnut-brown or tawny hue characteristic of the entire organism,
as seen even with the unassisted vision. The interpretation of the nature and origin
of these minute coloured granules is undoubtedly to be found connected with the
phenomena of excretion, and of which they are as much the direct product as is the
branching stem or zoodendrium of Anthophysa vegetans, described in a previous
page. In its more robust state of growth, the excreted elements in that species are
welded together so as to produce one tolerably homogeneous, longitudinally striate
stem ; but in its more weakly condition, or when the food-material supplied is not
sufficiently soluble, the excreted refuse is deposited and built into the substance of
the stalk as two distinct elements, partly mucous and partly granular. It is this
more abnormal condition, as seen in Anthophysa, that represents the normal one
of Spongomonas, and apparently also that of the several previously-named Flagellate
genera in which the mucilaginous and granular constituents are as persistently
distinct. In Rhipidodendron and Cladomonas, however, the separate granular and
mucilaginous elements, while plainly visible in the external wall of the zoothecium,
are more closely amalgamated, and present an almost complete homogeneous
consistence in the interior or lining layer of each tubule, the structure in its integrity
thus acquiring that greater solidity which permits of its assumption of an erect
dendritic contour.

The zooids of Spongomonas sacculus were observed to divide by transverse fission,
the temporary retraction of the flagella and the lengthening and segmentation of the
ovate endoplast constituting the preliminary act to such duplicative process.
Sporular subdivision, as recorded of S. intestinum, has not as yet been detected. The
distinction of this type from Spongomonas uvella, its apparent nearest ally, is mani-
fested, independently of the comparatively colossal proportions it attains, by the
crowded distribution of the monads within each lobe or saccular dilatation of the
compound zoocytium, those in the last-named type occupying each a separately
projecting chamber.

GENUS IV. DIPLOMITA, S. K.
(Greek, diploos, double ; mifos, thread.)

Animalcules solitary, evenly ovate, attached by a thread-like retractile
ligament to the bottom of a simple, pedicellate, horny lorica ; flagella two in
number, similar in length and character ; the front margin not produced in a
lip-like manner; a rudimentary eye-like pigment-spot often present in the
anterior region ; no distinct oral aperture. Inhabiting fresh water.

The as yet single known representative of this genus, while resembling Bicosoeca
in the form of the lorica and its mode of attachment within the same, exhibits in
the character of the flagella and general features of the contained animalcule, so
close a conformity to the zooids of Spongomonas and its allies, that it is here referred
to the same family group.

Diplomita socialis, S. K. PL. XVIII. FIGS. 30 AND 31.

Lorica evenly ovate, about twice as long as broad, attached by a short
pedicle ; animalcules with two long terminal flagella of equal length, occu-
pying a little more than one-half of the cavity of the lorica, slightly exsert
from the aperture of this structure when extended ; contractile vesicle
posteriorly located ; endoplast spherical, subcentral ; parenchyma trans-
parent, homogeneous ; a minute, eye-like pigment-spot situated near the
anterior extremity. Length of lorica 1-1675" \ colour pale brown, or amber.

HAB. — Pond water.

u

2QO ORDER FLAGELLATA-PANTOSTOMATA.

The lorica in this species so closely resembles that of Bicosceca lacustris, that when
empty, except for its larger size, it might be easily mistaken for it. The structure of
the enclosed animalcule is, however, altogether distinct. In place of the one Jong
and one short flagellum, there are here two long, equal-sized flagella, which lash the
water vigorously in every direction, instead of being extended rigidly in an arcuate
form with the extreme point alone vibrating, as obtains in the single long appendage
of Bicosceca. There is likewise no distinct lip-like projection or rostrum, as in that
type, the anterior border being evenly rounded. Where found, this animalcule
usually occurs in considerable numbers, completely covering the filaments of
Conferva or other aquatic objects, as shown in PL XVIII. Fig. 31. The
colour of the lorica in Diplomita is deeper than has as yet been observed in any other
representative of the Pantostomatous group, presenting usually in adult examples a
pale brown or amber hue. This circumstance may be cited as additional evidence
in indication of its near affinity to the generic forms with which it is here corre-
lated, but which in place of secreting separate loricae, build up similarly coloured
zoothecia or zoocytia. In all the examples so far examined, a bright spot, cor-
responding apparently with the so-called eye-speck of Euglena, Dinobryon, and other
Flagellata, was conspicuous towards the anterior extremity. This type was first
figured and briefly described by the author under the title of Bicosceca svciatis, in the
' Monthly Microscopical Journal' for December 1871.

Fam. IX. HETEROMITIDJE, S. K.

Animalcules naked, free-swimming or temporarily attached ; flagella
two in number, the more anterior appendage, " tractellum," locomotive and
vibratile, the posterior one, " gubernaculum," usually trailing and adherent ;
no distinct oral aperture.

The representatives of this family correspond closely in their general form,
habits, and character of the flagella with those of the Stomatode Anisonemidae, but
differ from them owing to the total absence of a distinct oral aperture, food-ingestion
being accomplished at diverse points of the periphery. The appropriate titles of a
"gubernaculum" and "tractellum," proposed respectively by Professors H. James-
Clark and E. Ray Lankester for the distinction of the peculiar modified trailing
flagellum and the ordinary vibratile appendage characteristic of the Heteromitidae
and other Flagellata, are here cordially adopted. A fuller reference to this subject
is made in the account given hereafter of the family Anisonemidae.

GENUS I. HETEROMITA, Dujardin.

Animalcules free-swimming or temporarily attached, ovoid, globular, or
elongate, plastic and changeable in shape, having no differentiated cuticular
investment ; flagella two in number, originating close to each other at the
anterior or antero-ventral extremity of the body, the foremost, tractellum,
directed in advance and constantly vibrated, the more posterior one, guber-
naculum,usually trailing, or adherent by its distal extremity ; food ingested
at any portion of the periphery, possessing no distinct mouth. Inhabiting
fresh and salt water, very abundant in animal and vegetable infusions.

Dujardin instituted this genus for the reception of those flagellate forms which,
while agreeing with Heteronema and Anisonema in their external contour, are to be
distinguished from them by the absence of a distinct cuticular investment. By
many later writers this distinction has been considered insufficient for generic sepa-
ration. A prolonged and careful investigation of numerous representatives of this
genus has, however, enabled the author to point out a second and even more important
correlative differentiation. Reference is here made to the ingestive functions, which

GENUS HETEROMITA. 291

in Heteromita correspond with those of Oikomonas, Amphimonas, Physomonas, and
other Flagellata previously described, as manifested by the capacity to incept food at
any portion of the periphery. Both Anisonema and Heteronema in this respect
offer a much more highly advanced structural type, each of these possessing, as
demonstrated by Biitschli and Stein, a distinct oral aperture and pharyngeal tract.

In Stein's recently published volume several species of Heteromita are referred
to the genus Bodo ; the last-named generic title, however, does not adapt itself to the
forms included under the same denomination in this treatise, or as comprehended
in it by other recent authorities.

The presumed resemblance between certain members of this genus and the so-
called zoospores of the parasitic fungus Peronospora infestans will be found discussed
in connection with the descriptive account of Heteromita lens,

Heteromita lens, Mviller sp. PL. XV. FIGS. 1-17.

Body exceedingly soft and plastic, susceptible of considerable alteration
of contour, usually subglobose, peach-shaped, or more or less ovate with a
slightly narrower anterior extremity ; flagella equal in size, very slender
and flexible throughout, about twice the length of the body ; endoplast
spherical, subcentral ; contractile vesicle posteriorly situated. Length
1-5000" to 1-3250".

HAB. — Vegetable infusions in both fresh and salt water.

This species, here identified with the Monas lens of Miiller, occurs in vast
abundance in hay infusions in both fresh and salt water, being usually, indeed, the
first form to make its appearance in such artificial macerations. By continued and
repeated examinations, the life-cycle and developmental manifestations of this type
have been successfully traced, and are found to correspond broadly with those of
the two species studied by Messrs. Dallinger and Drysdale, next described.

The results of the author's recent investigation of this form may be thus briefly
summarized : — So soon as within twelve hours after placing the hay to macerate, the
ordinary spring water used had become slightly discoloured, and on examination was
found to contain, in addition to Bacteria, numerous excessively minute monadiform
beings, spherical in shape, measuring the i-2o,oooth part of an inch only in their
diameter. These minute organisms, as shown at PI. XV. Figs. 11-14, occurred
singly or united in groups or short moniliform clusters, and propelled themselves
through the water with an oscillating motion by the means of single, anteriorly
developed, vibratile flagella. These motile organs necessarily required the most
careful adjustment of the illuminating agency for their detection, and were often
made manifest only by the movements of the particles in the surrounding water
induced by their vibrations. At this early stage of their growth the monadiform
units might, in their isolated condition, be identified with the Monas punctum or
pulvisculus of Ehrenberg, or with any other of the simple globular forms of the
genus Monas, that are so minute as to have received at the hands of their first
discoverers no more definite description than that of mere moving points. The
moniliform or aggregated clusters, on the other hand, delineated at Figs, n, 12,
and 14, so essentially and unmistakably correspond with the younger and more
minute conditions of Monas lens, as depicted by O. F. Miiller in Table i. fig. 1 1 of
his ' Animalcula Infusoria' (1786), that the author has not the slightest hesitation in
identifying them with his species. A closer investigation of fragments of the hay
undergoing maceration revealed the presence of crowds of minute quiescent
sporiform bodies identical in size with the motile units, and as which they were later
on seen to detach themselves and swim away. These quiescent spores were found
scattered more or less thickly over the entire surface of the hay, and were in many
instances massed together in small symmetrical spheroidal heaps. The growth
in the maceration of the motile monadiform units just described, proceeded so rapidly

U 2

292 ORDER FLA GELLA TA-PANTOSTOMA TA.

that within the course of only a few hours the entire field of the microscope, as
supplied from the most minute dipping, was found crowded with adult zooids corre-
sponding in form, size, and structure with the terms of the foregoing diagnosis.

In their most characteristic adult state the animalcules of Heteromita lens are
normally subspherical or peach-shaped, as represented at PI. XV. Fig. i, but are
subject to considerable individual variation. An ovoid form with a somewhat nar-
rower anterior extremity (Fig. 2), on the symmetrical side, and an irregular, almost
amcebiform contour (Fig. 3) on the unsymmetrical one, represent the most constant
departures from the typical subspheroidal shape that have to be recorded. The
greater portion of these monads were to be seen, as soon as the excitement ensuing
upon their transference to the glass slide had subsided, temporarily attached, or
as it were anchored, to the glass or vegetable debris through the medium of the
hinder flagellum, or gubernaculum, and upon which the body oscillated, as though
on a pendulum, through the constantly vibratory action of the anterior appendage.
Many others were, however, swimming freely in the water, in some instances trailing
their posterior or guberaaculate flagellum in the rear, and flourishing the anterior one
in advance, while in others both flagella were directed anteriorly, their joint vibratory
action assisting in the task of locomotion. These last-named examples, however,
would appear to represent animalcules which had either passed or not yet arrived at
their complete development. Division by longitudinal fission, as also the coalescence
or fusion of the adult monads (Figs. 7 and. 8), were frequently observed, likewise the
subsequent encystment and breaking up of the intimately amalgamated zooids into
minute spores corresponding precisely in form and size with those from which,
as already shown, they originally sprang. In addition to this genetic mode of re-
production, multiplication by the simple encystment and splitting into four, eight, or
sixteen segments or macrospores of the single zooids, was likewise authenticated,
each such subdivided portion possessing two flagella, and, except for its more minute
size, corresponding entirely with the parent animalcules at the time of its liberation
into the surrounding water; the more conspicuous features of this reproductive
process are represented at Figs. 15-17 of the same plate. Investigations pursued
simultaneously with the vegetable material of a like nature macerated in sea-water
instead of fresh, were attended by a similar first arrival of a monad perfectly agreeing
in form and in its developmental cycle with the present species, excepting that the
size was slightly smaller and the endoplasm apparently a little more dense and
compact. This slight variation in size and consistence may be reasonably attributed
to the higher specific gravity of the fluid medium employed. The Heteromita gramdum
of Dujardin, characterized by its spherical granulate body and two equal, slender
flagella — diameter 1-2250", hab. salt water — is probably identical with this marine
variety of H. lens.

A feature of interest relating to the life-history of the present species that
remains to be recorded, bears reference to the conduct of the animalcules under
conditions inauspicious to their well-being, and which may be regarded as a modi-
fication of the process of diffluence. Thus if confined in quantities between the
ordinary slide and cover-glass without a renewal of liquid medium, the oxygen
apparently gets insufficient to support life comfortably, the movements of the
animalcules grow weaker and more sluggish, and presently losing their capacity of
fixing or anchoring themselves by their trailing flagellum, they float freely in the
water, and are carried passively in whichever direction the capillary currents produced
by the evaporation of the water may set in. Sometimes the normal spheroidal or
ovate contour is retained for a considerable interval, but more usually the peripheral
wall appears to entirely lose its customary more firm consistence, and the whole
body-sarcode becomes projected in various directions, after the manner of ragged and
irregularly developed pseudopodia. As the animalcule drifts helplessly along, these
improvised pseudopodia often adhere tenaciously to the slide or other object,
arresting its further progress, the aspect manifested under such conditions being
represented at PI. XV. Fig. 4. With a renewal of fresh oxygenated water the
animalcules speedily reassume their pristine symmetry and activity, while by a
further withholding of this important element complete dissolution soon terminates

GENUS HETEROMITA. 293

the scene. Additional details respecting the discovery of this species both in its adult
and sporular conditions, in intimate connection with both hay and growing grass, are
recorded at page 136 et seq., of Chapter IV. (see also upper portion of PI. XI.)
devoted to the subject of Spontaneous Generation.

So remarkable a likeness subsists between the so-called biflagellate " zoospores "
of the potato-fungus, Peronospora infestans, figured by Mr. Worthington Smith in the
' Monthly Microscopical Journal' for September 1876, and the typical adult zooids
of Hetromita lens as here figured and described, that the author is unable to repress
a suspicion that these presumed zoospores actually represent examples of the present
cosmopolitan animalcule. Not only are the sizes of the bodies and the various
shapes assumed absolutely identical, but even the presence of an endoplast and
contractile vesicle, which occupy precisely similar relative positions, is clearly though
unconsciously indicated in Mr. Smith's drawings. The abundant and almost
invariable development of H. lens in connection with decaying foliage and other
vegetable matters derived from well nigh every source, renders it not only possible but
highly probable that the spores of these animalcules were imported with the potato
leaves that formed the subject of Mr. Worthington Smith's investigation, freely
developing side by side with the germs of the cryptogamic plant, and during their
quiescent states so closely resembling them that their distinct nature and independent
origin escaped detection.

Heteromita rostrata, S. K. PL. XV. FIGS. 18-28.

Body elongate-ovate, somewhat inflated posteriorly, the anterior ex-
tremity pointed and usually slightly recurved towards the ventral aspect ;
flagella equally slender, the anterior vibratile flagellum from one and a half
to twice the length of the body, the posterior one, or gubernaculum, longer
than the preceding, contracting, when the animalcule is attached, in a
loose spiral coil ; contractile vesicle mostly conspicuous, situated close to
the anterior extremity ; endoplast located near the opposite or posterior
extremity. Length of body 1-3000".

HAB. — Putrefying fish macerations.

The above title is here conferred upon the species figured and described by
Messrs. Dallinger and Drysdale * under the name of the " Springing Monad," the
springing action suggesting the name being caused by the rapid coiling and un-
coiling of the longer anchoring or gubernaculate flagellum in its fixed condition.
A similar leaping motion through the contraction of the gubernaculum being
common to various other species of the genus Heteromita, the technical name here
adopted has been conferred upon it more particularly with relation to the peculiar
beak-like or rostrate contour of the anterior extremity of the body. The develop-
mental and reproductive phenomena of this form as carefully followed out by its
discoverers, correspond broadly with those of the many other monadiform animal-
cules they examined. Multiplication by the ordinary process of longitudinal fission
represents the commonest and most conspicuous mode of increase, the two flagella,
as shown at PL XV. Fig. 19, participating in the duplicative process. Certain
animalcules, however, assume a spherical quiescent state and split obliquely or
transversely into halves, each such divided portion swimming away in a form not
distinguishable from the typical zooids. Further tracing these motile units, it was
found that they did not attach themselves by their anchoring flagella, but wandered
about until they came in contact with the ordinary sedentary monads, and with which
they immediately coalesced. The ultimate result of this genetic fusion was the
production of triangular encystments, which subsequently dehiscing at their three

* ' Monthly Microscopical Journal,' Dec. 1873.

294 ORDER FLAGELLATA-PANTOSTOMATA.

angles, liberated countless spores of infinitesimal dimensions. A space of ten hours
was occupied in the attainment by these almost invisible spores of the typical adult
form and size, these germinal products passing, in their onward growth, through a
phase in which a single flagellum, and that the posterior or anchoring one, alone
was visible. The illustrations given by Messrs. Dallinger and Drysdale of this
interesting genetic reproductive process are reproduced at PL XV. Figs. 22-28.
An adult monad, presenting the essential characteristics of the half-developed
monoflagellate condition of Heteromita rostrata, recently discovered by the author
in salt water, has been previously figured and described under the title of Ancyro-
monas marina.

Heteromita uncinata, S. K. PL. XV. FIGS. 29-41.

Body smooth, ovate, rounded posteriorly, narrower and slightly curved
towards the ventral aspect anteriorly ; anterior vibratile flagellum short,
scarcely exceeding one-half of the length of the body, recurved or hooked
at its extremity, posterior or trailing flagellum more than twice the length
of the body ; contractile vesicle conspicuous, situated near the narrower
anterior end ; endoplast at the opposite extremity. Length 1-4000" to
1-3000".

HAB. — Fish macerations in an advanced state of putrefaction.

The foregoing specific name is here proposed for the type figured and described
by Messrs. Dallinger and Drysdale * under the title of the " Hooked Monad." Its
developmental cycle, as successfully traced by these gentlemen, differs considerably
in its details from that of the form last described. Transverse fission, preceded
usually by the assumption of a semi-amoeboid condition of the subdividing ani-
malcule, constitutes the most simple mode of increase. The more important genetic
mode of reproduction was found, however, to consist of the intimate amalgamation
not only of two, but often of as many as four or even six individual zooids, the
result of such fusion being the production of a larger or smaller spheroidal cyst, from
which active monadiform germs of appreciable size, and in many instances already
furnished with a single (the posterior) flagellum, were subsequently liberated. This
monad is described as progressing rapidly through the water by a series of jerks or
springs, which follow each other in constant succession, and are coincident with the
movements of the hooked flagellum ; no mention is made of its anchoring itself by
the longer and trailing one, though this appendage is doubtless used for such a
purpose. The so-called " snapping eyelid " alluded to by Messrs. Dallinger and
Drysdale, undoubtedly represents the characteristic contractile vesicle, and in those
instances where the anterior flagellum is described as having a knob or knot at its
free extremity the animalcule is apparently engaged in withdrawing the organ into
the substance of its body previous to the assumption of an amoeboid condition and
ultimate encystment.

The phenomenon of the compound coalescence or genetic union of a plurality
of zooids, attested to by the authorities here quoted, in connection with Heteromita
vncinata, is of especial interest, on account of the circumstance that a practically
identical process of compound coalescence productive of sporular elements or their
equivalents on a comparatively colossal scale obtains in the two groups of the
Myxomycetes or Mycetozoa and the Spongida.

In neither of the two species of Heteromita, just described, and for whose discovery
•and life-history we are indebted to the painstaking researches of Messrs. Dallinger
and Drysdale, has any intimation whatever been as yet given respecting their
alimentary functions. Had a distinct oral orifice existed, or had the inception

Monthly Microscopical Journal,' Jan. 1874.

GENUS HETEROMITA. 295

of solid food-particles at any point been directly observed, testimony to this effect
would undoubtedly have been placed on record. Since, however, both in their
illustrations and descriptive text all evidence of food-ingestion or of a food-ingesting
aperture is conspicuous for its absence, there is substantial ground for premising
that these lowly organized beings derive their sustenance after the manner of the
Opalinidae, by the direct imbibition, at all parts of their periphery, of the proteaceous
nutritive fluids within which they are constantly immersed.

Heteromita ovata, Duj. PL. XV. FIGS. 65 AND 66.

Body ovate, narrower anteriorly ; surface smooth ; endoplasm slightly
granulate ; anterior or terminative flagellum slender, two or three times
longer than body, flexible throughout; posterior or anchoring flagellum four
times the length of the body, and twice the thickness of the anterior
one ; contractile vesicle conspicuous, situated near the anterior extremity.
Length of body i-iooo" to 1-700".

HAB. — River water with aquatic plants.

A form agreeing structurally with the terms of the foregoing diagnosis has been
met with by the author in pond water, its increase by longitudinal fission, and the
inception of food at various points of the periphery being also observed.

An animalcule presumed to be identical with this species but having a depressed
lenticular contour with a plane ventral and convex dorsal surface, is figured by
Stein under the name of Bodo ovatus, his drawings of it being represented in
the accompanying plate. As there indicated, no less than three minute spheroidal
contractile vesicles are stationed at the anterior extremity, the endoplast being
located close behind them in the middle line. The two flagella as delineated by
Stein are very slender and subequal in both length and thickness.

Heteromita globosa, Stein sp. PL. XV. FIGS. 61-64.

Body somewhat variable in shape, more usually subspheroidal or
elliptical, surface coarsely granulate ; flagella slender, subequal in length
and thickness, two or three times the length of the body, inserted ventrally ;
contractile vesicle single, situated close to the centre of the right lateral
border ; endoplast spherical, located in the median line towards the anterior
extremity. Length of body 1-2500" to i-iooo".

HAB. — Pond water.

This species is figured by Stein * in association with the title of Bodo globosus.
An apparently identical form has been recently met with by the author in pond
water from the neighbourhood of Birmingham, remitted by Mr. Levick. Numbers
were crowded together within the carapace of a dead rotifer, Noteus, feasting upon
its contents under conditions analogous to those reproduced from Stein's drawings
at PL XV. Fig. 64, the pabulum in this instance being however the cell-contents
of a fragment of (Edogonium. When thus collected within a small space, the dis-
tinction between the vibratile and trailing flagellum is not apparent, both appendages
being deployed in advance and exhibiting an irregular undulatory motion. Except
for their larger size and coarse granulation, the animalcules of this species coincide
considerably in general form and proportions with those of Heteromita lens. The
contractile vesicle, among other points of distinction, may be cited, however, as
occupying a more anterior position.

* ' Infusionsthiere,' Abth. iii., 1878.

296 ORDER FLA GELLA TA-PANTOSTOMA TA.

Heteromita exigua, Perty.

Body oval or spheroidal, transparent ; flagella about three times the
length of the body, one projecting in front, the other trailing. Length
1-7200" to 1-4800".

HAB. — Turf water, in the Bernese Alps. Movements oscillating.

It is almost impossible to decide from the brief account given by Perty, whether
this species is an independent form or only the young of another animalcule.

Heteromita pusilla, Perty.

Body elongate-ovate, subcylindrical, more or less constricted centrally,
sometimes emarginate posteriorly ; flagella from two to two and a half
times the length of the body ; endoplasm slightly granulate ; movements
oscillating. Length 1-3600" to 1-2160".

HAB. — Stagnant water with Conferva.

Heteromita amyli, Cienkowski sp.

Body elongate-fusiform, pointed at each extremity, seven or eight times
as long as broad ; flagella fine, subequal, not quite as long as the body.
Length 1-600". HAB. — Pond water with decaying Nitella.

This species, originally described by Cienkowski under the name of Monas
amyli* must necessarily be separated from the genus Monas on account of its pos-
sessing two flagellate appendages. The comportment and proportions of these organs
in accordance with that writer's drawings, correspond furthermore so closely with
those of the ordinary representatives of the present genus, that it appears desirable to
retain it in the same. The assumption of an amoeboid phase accompanied by the
extension of slender ray-like pseudopodia was witnessed, as also the fusion or
coalescence of numerous animalcules into a single mass during their amoeboid state
after the manner of Heteromita uncinata previously described. The result of this
conjugative process was the formation of a spheroidal cyst, the contents of which
split up into innumerable fragments to be subsequently released as monadiform germs.
The presence of a spherical endoplast and one or more contractile vesicles was
noted during the amoeboid phase. Excepting that this animalcule is not reported to
possess the faculty of assuming a spirally twisted contour, its general form and
proportions correspond closely with those of the Heteromita (Spiromonas) angiistata
of Dujardin hereafter described.

Heteromita sulcata, Mereschk.

Body somewhat variable in form, more or less oval or cylindrical, about
twice as long as broad, the hinder extremity rounded or evenly truncate, the
anterior border obliquely truncate ; the dorsal surface traversed throughout
by three or four parallel longitudinal furrows or striations ; flagella slender,
subequal in size, the posterior or trailing one slightly the longer, not twice
the length of the body ; contractile vesicle single, of large size, situated
close to the insertion of the flagella. Dimensions unrecorded.

HAB. — Fresh water : Northern Russia (Mereschkowski t).

* " Beitrage zur Kenntniss der Monaden," ' Archiv fur Mikroskopische Anatomic,' Bd. i., 1865.
t " Studien iiber Protozoen des Nordlichen Russland," ' Archiv fur Mikroskopische Anatomic,'
Bd. xvi., 1878.

GENUS COLPONEMA. 297

Heteromita adunca, Mereschk. PL. XV. FIG. 44.

Body oval, rounded posteriorly, sharply pointed and curved to one side
anteriorly, nearly three times as long as broad ; cuticular surface entirely
smooth ; endoplasm transparent, finely granular ; flagella slender, inserted
at the anterior extremity, the vibratile appendage slightly longer than the
body, the trailing one exceeding twice that length ; contractile vesicle
conspicuous, situated in the anterior body-half. Length 1-4000".

HAB. — Salt water from the White Sea ; on the surface of infusions
(Mereschkowski). Movements quick, tremulous, in a zigzag manner.

Heteromita cylindrica, Mereschk.

Body cylindrical, evenly rounded at both extremities, twice as long as
broad ; cuticular surface entirely smooth ; endoplasm finely granulate ;
flagella slender, the anterior one equalling the body in length, the posterior
one about twice as long ; contractile vesicle single, subcentral, very large.
Length 1-700". HAB. — Salt water: White Sea (Mereschkowski).

GENUS II. COLPONEMA, Stein.

Animalcules free-swimming, persistent in shape, irregularly ovate, the
anterior extremity pointed and curved to one side, the ventral surface with
a broad, subcentral, longitudinal groove or channel ; flagella two in number,
the one vibratile and the other trailing, the former inserted at the base of
the anterior projection, and in front of the oral aperture, the latter produced
from towards the centre of the ventral groove.

Colponema loxodes, Stein. PL. XV. FIGS. 45 AND 46.

Body gibbously ovate or subsigmoidal, about twice as long as broad,
the anterior extremity pointed, curved towards the left, the posterior
extremity more bluntly pointed, sometimes straight and sometimes curved
towards the right, thus giving the body a sigmoidal outline ; ventral groove
very wide in the anterior region, narrowing as it approaches the posterior
termination ; flagella slender, subequal, exceeding the body in length ;
endoplasm transparent, granular ; contractile vesicle spherical, centrally
located ; endoplast indistinct. Length 1-900". HAB. — Fresh water.

The figures of this singular form, as here reproduced, without descriptive details,
are alone published by Stein in his recently issued volume. In the lateral flexure
of the anterior region it somewhat resembles the Heteromita adunca of Meresch-
kowski.

GENUS III. SPIROMONAS, Perty.

Animalcules free-swimming or temporarily attached, soft and plastic,
flattened or compressed, twisted spirally on their long axis, bearing two
anteriorly inserted subequal flagella, one of which is adherent at will.
Inhabiting infusions and water with decomposing organic matter.

298 ORDER FLAGELLATA-PANTOSTOMATA.

The genus Spiromonas, as comprehended in this treatise, includes the Cyclidium
distortum of Dujardin and Spiromonas volubilis of Perty, to which is added a~ third
very distinct species apparently identical with the Heteromita angustata of the
first-named investigator, whose developmental phenomena have been recently traced
by the author. The two previously mentioned forms have been regarded by some
authorities as possibly representing transitional conditions only of Monas lens, but
such an interpretation cannot be entertained in face of the data here recorded
concerning the entire life of that species. The members of this genus, as
originally described by Dujardin, are represented as having a single flagellum only,
while Perty indicates the possession of no appendage whatever. The comparatively
inferior quality of the optical appliances at the disposal of these earlier investigators,
however, amply accounts for such an oversight.

Spiromonas distortum, Duj. sp. PL. XX. FIG. 23.

Body oval, compressed and nodular, with thickened tuberculate
margins, twisted irregularly on its longitudinal axis in a single spire.
Length i-iooo".

HAB. — Fresh water containing decomposing animal matter.

This species, which is described by Dujardin under the name of Cyclidium
distortum, is represented as bearing a single long and slender flagellum at its
anterior extremity, though probably a second one exists. The young zooids were
observed by him to be simply discoidal, the spiral flexure being characteristic only
of the adult animalcules.

Spiromonas volubilis, Perty.

Body leaf-like, compressed, rounded at both extremities, twisted longi-
tudinally in a single spire ; surface smooth, the margins not thickened or
tuberculate. Length 1-1300".

HAB. — Stale water with decomposing matter in suspension.

Spiromonas angustata, Duj. sp. PL. XV. FIGS. 49-60.

Body elongate, linear, compressed, more or less pointed at the two
extremities, five or six times as long as broad, twisted spirally or in a
screw-like manner on its longitudinal axis ; flagella slender, subequal,
inserted close to each other at the apex of the anterior extremity, equalling
the body in length, both directed forwards and vibratile when the ani-
malcule is swimming, the inferior one sometimes used for the temporary
attachment of the animalcule ; contractile vesicle posteriorly located ;
endoplast inconspicuous. Length of body 1-2500".

HAB. — Vegetable infusions.

The animalcule as above characterized and here identified with the Heteromita
angustata of Dujardin, was obtained abundantly by the author at St Heliers, Jersey,
in an infusion of hay with spring water at the end of three weeks' maceration.
Although the elongate, screw-like form, with two or three spiral twists, represents
the normal aspect of the adult individuals in their free-swimming state, a very
considerable range of variation occurs among the units of a large series. This
individual variation is dependent not only on the phase of development of the
separate monads, but also on the condition of rest or activity that may at the time
predominate. In common with Spiromonas distortum, the young of this species

GENUS PHYLLOMITUS. 299

show no trace of the spiral convolutions which distinguish the adults, but are
simply elongate and compressed ; later on a single spiral flexure is developed, and
it is not until the most mature and active natatory condition is arrived at that its
characteristic highly convoluted contour is attained. In that intermediate phase
in which the animalcules exhibit but one spiral twist, the body is comparatively
short, about three times as long as broad, with rounded extremities, and presents
a considerable resemblance to Pertys Spiromonas volubilis, last described. A pro-
longed investigation of this species elicited that it possesses a temporarily fixed as
well as an active swimming stage, the animalcules at such time attaching themselves
by the extremity of the posterior of the two flagella, and fishing in the surrounding
water with the anterior one, after the manner of an ordinary Heteromita or Aniso-
nema. It was further observed that under these conditions the spiral convolutions
were relaxed, sometimes one only being represented, and in others disappearing
altogether. On becoming detached and resuming the free-swimming state the
spirally convolute contour is again adopted. At the end of a few hours almost the
whole adult individuals of the colony under examination were seen to assume an
amoeboid phase, and to crawl actively over the surface of the glass by the aid of their
pseudopodia. Some of these coming in contact with their fellows immediately fused
or coalesced, forming subsequently spherical encystments which later on broke up
into minute spore-like bodies. The single zooids likewise formed similar but smaller
encystments, and dividing by multiple fission into two or four segments only, were
subsequently liberated as units resembling the unconvolute earlier stages of the
parent monads. The motion through the water of the adult animalcules is regular
and even, consisting of progress in a straight line, the body turning on its long axis
in a screw-like manner, both flagella actively vibrating in advance. In the younger
examples the movements are eccentric and vacillating, the animalcules first advanc-
ing straight forward for a short distance, and then turning round and returning to
the point from whence they started. Their motion in this respect somewhat resembles
that of various species of Vibrio or Spirillum, The so-called Bodo grarilis, merely
figured by Stein in his recently published volume, without a word of explanatory text,
must undoubtedly be regarded as a synonym of this species.

GENUS IV. PHYLLOMITUS, Stein.

Animalcules free-swimming, variable in form, more or less ovate ;
flagella two in number, produced from the anterior extremity, unequal in
length and united to one another throughout their basal portion ; no
distinct oral aperture.

The single species referred to this genus is figured without an accompanying
description in Stein's recently issued volume, the present diagnosis of both that
species and the present newly instituted generic group having to be framed from
his delineations.

Phyllomitus undulans, Stein. PL. XV. FIGS. 47 AND 48.
Body elongate-ovate, variable in form, three or four times as long as
broad ; sometimes straight and rounded, and sometimes sharply pointed and
recurved posteriorly ; flagella united basally for a distance exceeding one-
half of the length of the body, forming in this region a ligulate or strap-like
prolongation, the shorter flagellum produced separately but a little distance
beyond the distal termination of this ligulate prolongation, the longer one
fine and undulating continued for a length exceeding that of the entire
body ; the anterior extremity of the ventral region immediately beneath the
insertion of the flagella exhibiting an oval excavation ; endoplast anteriorly

300 ORDER FLAGELLATA-PANTOSTOMATA.

situated; contractile vesicle not clearly indicated. Length 1-1200" to
1-914". HAB. — Fresh water.

The form of the body in this species accords closely with that of the Tetramitus
desdssus of Perty, it exhibiting a similar indifferently rounded or sharply pointed
posterior conformation, and a corresponding excavation beneath the insertion of
the flagella ; the peculiar character of these last-named organs distinguishes it
conspicuously from any representative of the Flagellata hitherto described. Although
not indicating the existence of a well-defined contractile vesicle, Stein delineates in
his several figures of this animalcule a vesicular-like structure near the posterior
extremity, upon which, in the accompanying index, the title of an anal aperture is
conferred.

Fam. X. TREPOMONADID-ffi, S. K.

Animalcules naked, free-swimming, entirely asymmetrical ; flagella two
in number, separately inserted ; no distinct oral aperture.

GENUS I. TREPOMONAS, Dujardin.

Animalcules free-swimming, exceedingly unsymmetrical in shape, plastic
and highly flexible ; irregularly oval, from a dorsal aspect ; thickened poste-
riorly, with two anterior, slender, recurved, wing-like lobes as seen in lateral
view ; sigmoidal with reversed and pointed extremities viewed apically ;
flagella two in number, alike in form and character, produced from the
extremity of each of the lateral lobate processes ; contractile vesicle and
endoplast conspicuous ; no distinct oral aperture ; movements very rapid,
gyratory. Inhabiting stagnant water with decomposing organic matter.

Trepomonas agilis, Duj. PL. XIX. FIGS. 1-14.

Body, from a dorsal view (Fig. 12), irregularly oval, broadish anteriorly,
more slender and slightly curved posteriorly, with a longitudinal fold
towards the left side; in lateral view (Fig. 10), somewhat tongue-shaped,
thickest and rounded posteriorly, expanding anteriorly into two symme-
trical, laminate, wing-like lobes, which are reflexed backwards to about the
centre of the body and terminate each in a single long vibratile flagellum.
Apical aspect (Fig. li) broadly sigmoidal, with a thin hyaline border con-
necting the recurved points with the thicker body portion ; the flagella
continuous from the recurved points; endoplasm transparent, enclosing
foreign granules ; contractile vesicle postero-terminal ; endoplast anteriorly
situated. Length of body 1-1125".

HAB. — Marsh water with decaying vegetable substances.

The extraordinarily diverse aspects presented by this animalcule as seen from
various points of view, taken together with its minute size and exceedingly active
movements in the water, has hitherto presented %an almost insurmountable obstacle
to its accurate description and delineation. O. Biitschli,* making a careful investi-
gation of this interesting type with the highest available magnifying power and the
use of reagents has, however, clearly demonstrated its correct structure and contour,
the foregoing diagnosis being framed from his excellent figures and description. The

* " Beitrage zur Kenntniss der Flagellaten," 'Zeit. Wiss. Zool.,' Band xxx. Heft 2, Jan. 1878.

GENUS POLYTOMA. 301

researches of this author establish the accuracy of Dujardin's original anticipation
that the animalcule possessed two flagella proceeding from the extremities of the
recurved lobate processes, although by Perty, Fresenius, and more recently by De
Fromentel, a single flagellate appendage only is reported. The figures given by these
last-named authorities, representing this form as caliper-shaped or bifid posteriorly,
with a single median anterior flagellum, is now shown to be an imperfect interpre-
tation of the lateral view given at PL XIX. Fig. 10. By Diesing Trepomonas
agilis is described as possessing a terminal oral aperture ; but Biitschli, while
noting the presence in the endoplasm of enclosed foreign particles, entirely failed to
discover the existence of such a structure. Under these circumstances it seems
desirable to refer this type, at all events provisionally, to the Pantostomatous section of
the Flagellata, the food-particles observed being probably incepted at any point of
the periphery. A circulation or cyclosis of the inner substance of the endoplasm is
recorded of this form by Biitschli, and has been witnessed by the author, which
corresponds broadly with that which obtains in the higher Ciliate type Faramecium
bursaria. Two animalcules joined to one another posteriorly by a slender, fila-
mentous extension of the body-sarcode, representing an advanced phase of the
process of longitudinal fission, was observed on one occasion. The correspondence
that subsists between the contour of this type, as seen in lateral aspect, Fig. n, and
the fission-stage of Ancyromonas sigmoides (see PL XIII. Figs. 51 and 52), is highly
remarkable.

Stein, in his recently issued volume, gives a very exhaustive series of illustrations
of the polymorphic contours presented by Trepomonas agilis under varying conditions
of attitude or flexure, the more important of which are here reproduced. The
young of this type are, in accordance with the same authority, provided with three
or four long, slender flagella, presenting under such conditions the appearances
delineated at PL XIX. Figs. 13 and 14.

Fam. XI. POLYTOMID-2B, S. K.

Animalcules symmetrical, free-swimming or temporarily adherent,
illoricate, but with a more indurated membraniform cuticular envelope ;
flagella terminal, two in number, of equal size ; no distinct oral aperture ;
multiplying by endogenous subdivision.

GENUS I. POLYTOMA, Ehrenberg.

Animalcules biflagellate, free-swimming or temporarily adherent, more or
less ovate, persistent in shape, possessing a distinct investing membrane;
flagella of equal length, projecting from the anterior extremity ; contractile
vesicles and endoplast conspicuous, inhabiting water containing decomposing
animal matter. Increasing by endogenous multiple fission and by the pro-
duction of macro- and micro-spores. No distinct oral aperture.

The type-form of this genus, the Polytoma uvella of Ehrenberg or Monas iiva of
Miiller, is evidently identical with the so-called " biflagellate or acorn-monad "
figured and described by Messrs. Dallinger and Drysdale in the ' Monthly Micro-
scopical Journal' for December 1874. A considerable difference of opinion has
existed as to whether Polytoma, as represented by this type, should be rightly referred
to the animal or vegetable kingdom, the balance of evidence being now, however,
entirely in favour of the first alternative. There is no secretion of chlorophyll
within the endoplasm as in the ordinary phytozoa, and the investing membrane
refuses to become blue under the action of iodine, as it would if composed of
cellulose. Ehrenberg further reports that the animalcules will ingest coloured
matter, such as indigo, and figures artificially fed examples in his work. This last
circumstance, combined with the constant presence of conspicuously developed

302 ORDER FLAGELLATA-PANTOSTOMATA.

contractile vesicles, demonstrates the entire compliance of these organisms with the
formula adopted at the commencement of this work for the distinction of all typical
Infusoria.

Polytoma uvella, Ehr. PL. XV. FIGS. 67-78.

Body ovate or oblong, equally rounded at the two extremities, or
slightly more pointed at the anterior one, invested by a delicate hyaline
membranous cuticle ; flagella inserted close to one another at the anterior
extremity, of equal size, exceeding the body in length, having apparently a
small bead-like or fusiform inflation at their point of origin, such ap-
pearance being produced by a minute loop-like basal flexure ; this basal
region of the flagella, soft and adhesive, enabling the animalcules to
attach themselves at will to foreign objects ; contractije vesicles two in
number, anteriorly situated ; endoplast central, spherical ; endoplasm of the
posterior half of the body usually more coarsely granulate. Length of body
1-1200" to i -800".

HAB. — Fish and other animal macerations.

In describing the form, as quoted overleaf, under the title of " the biflagellate or
acorn-monad," Messrs. Dallinger and Drysdale appear to have been unaware of its
identity with the Polytoma uvella of Ehrenberg, and of the results of Schneider's and
Perty's investigations. These last-named authorities, while by no means supplying
a complete and exhaustive account of its reproductive history, assist materially
in the interpretation of certain phenomena, which have been left unexplained by
our fellow countrymen. As first made known by Schneider, and since shown by
Messrs. Dallinger and Drysdale, the animalcules increase rapidly by a process of
multiple fission, caused by the first dividing into two, and then into four, eight, or
even sixteen segment-masses of the entire protoplasmic mass enclosed within the
external hyaline cuticular membrane, and quite independently of that structure.
These divided portions assume the shape and aspect of the parent monad, the flagella
often perforating and protruding through the cuticle of the latter, as shown at
PI. XV. Fig. 73. The organism now swims about with its contained young for a
longer or less duration of time as an apparently compound organism. — It was
this pseudo-compound phase, indeed, that Ehrenberg regarded as the normal one,
and upon which he conferred its characteristic title of Polytoma. Subsequently, each
of these subdivided portions breaking through the investing membrane of the parent
monad, assumes an independent existence, leaving the latter as an empty and
lifeless cyst While the products of this multiple fission process may continue
increasing in a similar manner for many generations and without the intervention of
the coalescence or genetic union of two zooids, it has been shown by Messrs.
Dallinger and Drysdale that there is yet another mode by which the perpetuation of
the species is asexually accomplished. In certain examples under examination it was
observed by these authorities that the posterior portion of the body was almost filled
with granular masses of protoplasm, which conveyed to this region a roughened
acorn-cup-like aspect as compared with the smooth and hyaline anterior portion ;
carefully watching them it was found that in the midst of their swiftly moving course
these acorn-like zooids would suddenly discharge the entire contents of the posterior
region as separate granular fragments into the surrounding water, as shown at
Fig. 75. Each of these fragments thus liberated was amorphous in form, more or
less agglomerated and perfectly transparent. Examined attentively with the aid of a
magnification of 2500 diameters and upwards, minute dots were next seen to
make their appearance in these granules, which increasing in size, exhibited active
vibratory movements and were ultimately released as minute bacterium-like bodies.
The growth of these liberated particles within a space of four or five hours to
monads identical in size and structure with the parent form, was subsequently

GENUS POLYTOMA. 303

ascertained. A third or true genetic form of reproduction dependent on the intimate
fusion or coalescence of two individuals followed by encystment and the breaking up
of the amalgamated zooids into countless almost invisible spores (see PI. XV.
Figs. 77 and 78), as already described of Monas Dallingert, Cercomonas typicus, and
Heteromita rostrata, completes the life-cycle of this remarkable species as observed
by these indefatigable investigators.

A few structural peculiarities of this type referred to by Messrs. Dallinger and
Drysdale, demand brief notice. The so-called "snapping eye-spots" situated in the
anterior region of this form, and reported to be present in many other monads
examined by them, though they failed to determine their precise import and function,
represent undoubtedly the characteristic contractile vesicles already recognized by
Schneider and other earlier writers. Under certain conditions the two anterior
flagella were further pronounced by these investigators to be replaced or supple-
mented by two knob-like structures, mounted on slender pedicles, and to which
phase of the monad they therefore applied the title of the " clubbed condition."
It was at first supposed that this condition was intimately connected with some
special reproductive process, the question ultimately, however, being left undecided.
Schneider, nevertheless, had previously maintained that the knob-like processes
represented the flagella as withdrawn or shortened previous to encystment. Even
under normal conditions the existence of fusiform or pear-shaped inflations of the
bases of the flagella is recorded, these inflations being further interpreted as playing
an important part in the function of natation, and as possessing apparently a
muscular property. The swimming motions of Polytoma are described by Messrs.
Dallinger and Drysdale as very graceful and swallow-like ; the flagella being thrown
out in the manner of a swimmer's arms and made to meet at the posterior end of the
monad ; these appendages can likewise, they report, be used in various other ways,
producing a rolling-forward motion, a gyrating horizontal one, or even a longitudinal
revolution.

Quite recently, January 1880, the author had the opportunity of examining
living samples of Polytoma uvella as developed abundantly in animal macerations
at the Biological Laboratory, South Kensington. The data thus independently
derived have thrown an entirely unexpected light on the phenomena previously
recorded, concerning the so-called knob-like or pyriform inflations at the base of the
flagella, as observed by Schneider and Messrs. Dallinger and Drysdale. It has been
definitely ascertained by both the examination of living monads and of examples
killed with iodine and osmic acid, that what these authorities took for independent
knob-like or fusiform developments are actually minute loop-like flexures of the
basal region of the flagella, as shown in Figs. 67-69 of Plate XV. The substance
of the flagella throughout this region is softer and more adhesive than in the
remainder of their length, and it is by this loop-like flexure that the animalcules
attach themselves to the glass or other neighbouring objects as first observed by
Schneider, and may thus ride securely anchored, during the passage around them of
even a considerably forcible current. It is certainly a very remarkable circumstance
that this capacity of attaching themselves, so abundantly displayed in the specimens
recently examined, should have entirely escaped the many hours' observation of Messrs.
Dallinger and Drysdale, who have described them only as motile or free-swimming
animalcules. In both the examples examined by the author on the occasion quoted,
and still more recently, it was observed, indeed, that the attached condition is the
more normal one, but few, unless purposely disturbed, exhibiting their natatory
properties two minutes after their transfer to the field of the microscope. The
existence of the loop-like flexures at the bases of the flagella, discovered by the
author, explains readily the several apparently anomalous features concerning the
type, noticed in the accounts given by previous investigators ; thus the so-called
" clubbed " condition of the animalcule, as reported by them, was repeatedly recog-
nized, but was demonstrated to be the optical image, produced under high magnifica-
tion, of the basal portion of the flagellum with its loop-like flexure only being in focus.
Under slightly modified conditions, again, the loop-like flexures and the remaining
length of the flagella being clearly visible, the divarication of this latter portion may

304 ORDER FLAGELLATA-PANTOSTOMATA.

be at such an angle that, as shown at Plate XV. Fig. 67, the basal flexure and terminal
portion may appear to be separate structures, the former presenting an independent
knob-like aspect. Lastly, where the distal lengths of the flagella and their basal
flexures are both in focus, and apparently continuous with each other, these flexures
may be coiled so closely beneath the anterior region of the animalcule's body, as to
present the aspect of fusiform or pyriform inflations of the basal region of the
flagella, as first interpreted by the two authorities here quoted. When the animalcules
are treated with osmic acid or iodine, they roll over and over helplessly in the water,
every portion of their organization being brought successively into focus, and the true
significance of the previously imperfectly observed phenomena, as here explained ,
may easily be verified. Figs. 68 and 69 of the accompanying plate are delineated
from examples submitted to this treatment. The two anterior so-called " snapping
eye-like structures " reported by Messrs. Dallinger and Drysdale of this type, were
immediately identified by the author with the normally developed and highly
characteristic contractile vesicles.

Stein includes a long series of figures of this species in his recently published
volume, the same, however, apparently containing but little that is new. One or more
dark, granular, eye-like pigment-spots are shown in some, but not in all, of these
figures, such spots being moreover located indifferently in separate animalcules at
either the anterior or posterior extremity of the body. No indication of the charac-
teristic loop-like flexure of the flagella or of the possession by the animalcules of
a capacity to attach themselves, as 'here recorded, is given in Stein's figures or
accompanying index.

The two forms described by Perty under the respective names of Polytoma
ocellata and P, virens, cannot be regarded as otherwise than local or transitional
variations of P. uvella. Diesing, nevertheless,* has proposed to institute a new generic
and specific title, Glenopolytoma typicum for that variety, P. ocellata, in which a red
pigment-spot is present at the anterior extremity.

Fam. XII. PSETJDOSPORnXffi, S. K.

Animalcules naked, repent or natatory ; flagella two in number, of even
size ; no distinct oral aperture.

GENUS I. PSEUDOSPORA, Cienkowski.

Animalcules free-swimming or repent, plastic and changeable in form,
typically more or less ovate or globose ; the anterior extremity bearing
two long, equal-sized flagella ; food incepted at any point of the periphery ;
endoplast and contractile vesicles conspicuous.

The Pseudospora volvods only of Cienkowski is retained in the present genus,
the two other forms, referred to it by that authority under the titles of Pseudospora
parasitica and P. nitdlarum, being in no way distinct from the ordinary members of
the genus Monas, to which they are here referred. Food-particles would appear to
be incepted at any point of the periphery, otherwise the features afforded by the
plasticity of the body-sarcode and character of the flagella correspond considerably
with those exhibited by the stomatode genus Zygosdmis.

Pseudospora volvocis, Cienk. PL. XV. FIGS. 42 AND 43.

Body ovate or globose, often amoebiform ; flagella fine, equal in size,
exceeding the body in length ; contractile vesicles minute, three in number,
scattered ; endoplast spherical, subcentral. Length 1-1250".

HAB. — Fresh water, as a parasite of Volvox globator.

* ' Revision der Prothelminthen," 1866.

GENUS SPUMELLA. 305

According to Cienkowski * this species plunders the contents of Volvox globator
in a manner somewhat identical with that pursued by Colpodella pugnax with relation
to Chlamydomonas pulvisculus. Boring its way through the outer envelope of that
protophyte, it creeps about on its inner surface, gradually devouring all the green
cellular elements and daughter-cells. During the process it presents a semi-
amoeboid aspect, but retains the two long natatory flagella; under these auspices
it would seem to exhibit more affinity with the genus Mastiganuxba, and might
therefore perhaps be appropriately relegated to the order of the Rhizo-Flagellata.
Subsequently the flagella are completely withdrawn and the animalcule forms a
double-walled encystment, the further development of which was not followed.

C. — PANTOSTOMATA-POLYMASTIGA

(Flagellate appendages three or more in number).

ram. xin. SPUMELLID^EJ, s. K.

Animalcules naked, free-swimming or attached ; flagella terminal, three
in number, unequal, one long and two short ; no distinct oral aperture.

GENUS I. SPUMELLA, Cienkowski.

Animalcules minute, sometimes free-swimming but normally attached
by a slender thread-like pedicle, more or less spherical or ovate in their
sedentary state, but exceedingly plastic and changeable in shape in their
free-swimming condition ; flagelliferous system consisting of one long and
two short rudimentary flagella which originate close to each another near
the centre of the anterior border ; endoplast and one or more contractile
vesicles usually conspicuous ; no distinct oral aperture, solid food-particles
being incepted at all parts of the periphery. Inhabiting fresh and salt
water, and abundant in infusions.

Those forms only are retained as representatives of the "present genus that
correspond structurally with the Spumella vulgaris of Cienkowski \ (Monas guttula
Ehr.), characterized by the possession of one long and two comparatively minute
flagellate appendages. The monoflagellate types referred to it by O. Biitschli, under
the titles of Spumella termo and S. neglecta, are necessarily relegated to the generic
group Oikomonas, with whose representatives, as also with those of Physomonas and
Amphimoiias, except strict attention is paid to the character of the flagelliferous
elements, the several species of Spumella are liable to be confounded.

Spumella guttula, Ehr. sp. PL. XIV. FIGS. 46-52.

Body perfectly globose in its sedentary condition, ovate, pyriform or
elongate in its free-swimming state ; flagellate appendages consisting of one
long and two very short rudimentary flagella, the former extended rigidly
and arcuately, the latter tremulous ; endoplasm transparent, finely granulate,
enclosing near the anterior border a short, straight, linear, pigmentary, or
more densely granular band ; contractile vesicle single, located near the

* "Beitrage zur Kenntniss der Monaden," ' Archiv f. Mikroskopische Anatomic,' Bd. i., 1865.
t " Ueber Palmellaceen und einige Flagellaten," ' Archiv f. Mikroskopische Anatomic,' Bd. ii.,
1870.

306 ORDER FLA GELLA TA-PANTOSTOMA TA.

centre of the lateral periphery ; endoplast situated in the median line,
towards the anterior extremity. Diameter of spheroidal zooids 1-2500".
HAS. — Pond water.

Stein * proposes to identify this type with both the Monas guttula of Ehrenberg
and the more recently introduced Spumella vulgaris of Cienkowski. It would seem
just possible that the first-named identification is correct, but no mention is made
by Ehrenberg of its most characteristic fixed existence and attachment by a special
caudal filament, and which would undoubtedly, if recognized, have influenced that
authority to relegate the animalcule to his caudate genus Bodo. Stein agrees with
Cienkowski in allotting to this form the presence of two minute supplementary
flagella at the base of the more conspicuous axial one ; he further figures what he
interprets to be the genetic union between a normal sedentary, and a minute motile
zooid, the latter attaching itself to one side of the larger one, and becoming absorbed
into its substance, the phenomena corresponding with those exhibited during the
genetic union of the larger sedentary and minute migrant zooids of Vorticdla,
first discovered by this same authority and described later on. In specimens of
this type, recently examined by the author, obtained in pond water containing
Acineta mystacina and Salpingceca gracilis, the presence of the one long and two
rudimentary flagella was fully certified, as also the existence of the linear furrow-like
mark near the anterior border, interpreted by Stein and Cienkowski as representing
a distinct oral aperture. That no such ingestive function can be assigned to it was
however conclusively demonstrated through the witnessing on numerous occasions
'of the inception of solid food-particles at the most diverse regions of the periphery.
As in the case of Oikomonas, Amphimonas, Anthophysa, and numerous other Panto-
stomatous Flagellata already described, such food-inception was manifested by the
temporary rupture of the peripheral wall of the animalcule's body at whatever
point against which the food-particle was thrown by the flagellum, accompanied by
the simultaneous outflow of the softer inner sarcode which enveloped and secured
the welcome morsel. Under such circumstances there can be but little doubt that
this so-called oral furrow is, as in the case of Goniomonas truncata, as interpreted
by Biitschli, a mere linear granular deposition corresponding morphologically with
the red or other coloured pigment-spots common to Euglena and various ordinary
Flagellata. Such a granular pigmentary interpretation entirely accords with the
decision arrived at by the author in connection with the present species, after care-
fully submitting it to the highest available magnifying power. It would seem to
be by no means improbable that Stein's representation of the presumed coalescence
of a minute free-swimming zooid with a larger sedentary one, as here reproduced,
Plate XIV. Fig. 49, might be more accurately interpreted as an example of the
ingestion of a foreign food-particle at the lateral periphery.

Spumella vivipara, Ehr. sp. PL. XIV. FIGS. 34-36.

Body when attached usually obovate, widest and rounded anteriorly,
tapering to a point at its posterior extremity; exceedingly plastic and
changeable in shape, ovate, spheroidal, or elongate in its free-swimming
state ; one long axial and two short lateral flagella ; endoplasm transparent,
enclosing innumerable constantly vibrating refringent corpuscles ; a short
linear pigment-band or furrow-like mark situated close to the anterior
border ; pedicle short, scarcely equalling the body in length ; contractile
vesicle single, located near the centre of the lateral border; endoplast
median, anteriorly situated. Length i-iooo" to 1-620".

HAB. — Fresh water and infusions.

* ' Infusionsthiere,' Abth. iii., 1878.

GENUS CALLODICTYON. 307

This species, originally described by Ehrenberg under the title of Monas vivifara,
is distinguished more particularly by the presence of the innumerable moving cor-
puscles enclosed within the substance of the endoplasm, and which were mistaken by
that authority for its living progeny. Stein, who has recently figured it in connec-
tion with the same name, has added the fuller details of the flagella, mode of attach-
ment, and positions of the endoplast and contractile vesicle here recorded. The
author has recently encountered an animalcule closely resembling the present form
in hay infusions, it being of the same size and enclosing similar motile corpuscles
within the endoplasm ; the endoplast was, however, in these instances, situated to
the rear of the contractile vesicle. The ingestion of food was observed on numerous
occasions, a film of sarcode being thrown out at such times and enveloping the
captured particle. This film was projected indifferently from various parts of the
anterior border, and sometimes simultaneously from two separate portions of the
periphery. In no instance could the linear pigment-band or so-called oral ledge or
furrow, as indicated in Stein's drawings, be detected, and which circumstance,
together with the variation in the position of the endoplast, favours the opinion
that we have in this last-named instance a closely allied but specifically distinct
variety.

Tarn. XIV. TRIMASTIGrlD-ffi, S. K.

Animalcules naked, free-swimming or temporarily adherent ; flagella
three in number, equal or subequal, inserted close to one another; no
distinct oral aperture.

GENUS I. CALLODICTYON, Carter.

Animalcules naked, entirely free-swimming, more or less ovate but
plastic and somewhat variable in form ; endoplasm highly vacuolar or
cancellate, presenting a reticulate appearance ; flagella three in number,
similar in size and character, originating close to each other near the centre
of the anterior border ; no distinct oral aperture, all parts of the periphery
being equally capable of incepting food-substances.

Callodictyon triciliatum, Carter. PL. XIX. FIGS. 16-19.
Body subpyriform, straight or slightly curved, from one and a half to
twice as long as broad, widest anteriorly, tapering towards the posterior
end, which is sometimes sharply and sometimes obtusely pointed and
bifid at its extremity ; flagella slender, equal in length to about one-half
that of the body, inserted within a small depression in the centre of the
anterior border ; endoplasm transparent, divided up by innumerable equal-
sized spherical vacuoles so as to present a reticulate or cellular aspect ;
endoplast spherical, anteriorly situated ; no distinct contractile vacuole.
Length 1-770". HAB.— Fresh water with Euglence : Bombay (H. J. C.).

This singular animalcule is figured and described under the above title in
Mr. Carter's account of the " Fresh- and Salt-water Rhizopoda of England and
India," in the 'Annals of Natural History' for April 1865. Its plastic nature,
and capacity of incepting food at any portion of its periphery, as in the case of
Amoeba, has induced this authority to refer the type to the section of the Rhizopoda,
but it is very evident that its rightful position is among that newly instituted Panto-
stomatous division of the Infusoria Flagellata as delimited in this treatise. The
voracity of this type, as evidenced by its discoverer, is very remarkable, organisms

X 2

3 O8 ORDER FLA CELL A TA -PA NTOS TO MA TA .

equal to or even exceeding itself in size being indiscriminately seized and pressed
within the substance of its yielding reticulate body-sarcode. In one instance, Mr.
Carter figures a large Cremenula thus incepted, while in another, PL XIX. Fig. 17,
the animalcule has enclosed the central portion of a filament of Osrillatoria, the two
ends of which are protruding from the opposite poles of the creature's body. Although
the evenly vacuolar or reticulate character of the parenchyma or endoplasm of
Callodictyon would appear to find no exact counterpart among the ordinary repre-
sentatives of its class, a near approach in this respect obtains in Noctiluca and
Lepfodiscus among the Stomatode Flagellate forms, and in Trachdius and Loxodes
among the Ciliata. Such an open vacuolar character of the parenchyma would seem
to obviate the necessity for a contractile vesicle, the presence of which structure
Mr. Carter was unable to detect.

GENUS II. TRICHOMONAS, Donne".

Animalcules free-swimming, soft and plastic, ovate or subfusiform,
bearing at the anterior extremity two long subequal flagella, a third
supplementary one depending from the posterior extremity ; a toothed or
lobate undulating membrane developed down one lateral border, which
presents under insufficient magnifying power the aspect of a fringe of
cilia ; no distinct oral aperture. Habits endoparasitic.

The illustrations of Trichomonas batrachorum given by Stein in the third volume
of his ' Infusionsthiere,' though unaccompanied by any descriptive text, have necessi-
tated not only the formulation of a new generic diagnosis, but also the transfer of
the genus from the monomastigate to the polymastigate section of the Flagellata.
As originally described by Donnd and embodied in the works of Dujardin and Perty,
Trichomonas was represented as possessing a single anteriorly situated flagellum
only, supplemented on one lateral border by a conspicuous fringe of cilia. As now
shown by Stein, in the case at all events of the above-named species, there are no
less than three flagellate appendages, while the presumed lateral fringe of cilia is
found to be a delicate notched undulating membrane, closely resembling the
membraniform border that constitutes the sole organ of locomotion in the genus
Trypanosoma. An oral aperture, or rather the presumed position of such a structure,
is indicated in one of Stein's figures, though by no means with sufficient distinctness
to permit of the acceptance of the organism as an undoubted stomatode type. Such
being the case, its provisional retention among the ordinary Pantostomata has been
decided on.

Trichomonas batrachorum, Perty. PL. XIX. FIGS. 30-32.

Body subfusiform, widest centrally, pointed at each extremity, but most
attenuate posteriorly, two or three times as long as broad ; two long slender
flagella produced from the apex of the anterior extremity, a similar single
one apparently originating at a little distance from the posterior termination ;
a more or less conspicuous toothed or lobate undulating membrane developed
down one lateral border, and a raised keel-like line down the opposite one ;
endoplast anteriorly located ; contractile vesicle situated at a short distance
from the posterior extremity. Length 1-2000" to 1-640".

HAB. — Intestinal canal of the common frog and toad.

The above diagnosis and accompanying illustrations of this species are drawn
up and reproduced from the excellent figures of the type included in Stein's lately
issued volume. In the absence of the forthcoming descriptive text, one or two

GENUS DALLINGERIA. 309

points have to remain undecided, these relating chiefly to the character and number
of the flagella. In one instance as many as three, but in all others only two of
these appendages are produced from the anterior extremity. It is also somewhat
difficult to decide whether the so-called posterior flagellum is actually developed
from this region, or is merely a reflexed member of a single anteriorly inserted
series.

Trichomonas vaginalis, Duj. PL. XIX. FIGS. 33 AND 34.

Body irregularly ovate, tuberculate, soft and plastic, and changeable in
shape, often adherent by a gelatinous tail-like prolongation of the posterior
extremity of the body ; flagellum thicker at its base, fine and slender ante-
riorly, two or three times the length of the body, supplemented apparently
by a lateral fringe of large and conspicuous cilia ; endoplasm vacuolate.
Length of body 1-2500". HAB. — Vaginal mucus.

This species was first observed in decomposed human vaginal mucus by M.
Donnd, he communcating the circumstance to Dujardin. The zooids occurred in
aggregated groups or as isolated individuals which readily adhered to the glass
object-carrier, or other fulcrum of support, by a glutinous prolongation of the
posterior extremity, their movements when so attached being oscillating. It has
been suggested by some authorities that the objects thus observed by Donnd were
merely singly detached or agglomerated cells of ordinary ciliated epithelium ; the
possession, however, of a distinct flagellate appendage, as indicated in Dujardin's
drawings, would seem, pending further investigation, to justify its provisional in-
clusion among the members of the present organic group. Neither the diagnosis
here given of either this or of the succeeding species is to be accepted as complete,
they being constructed from the very imperfect descriptions and figures placed on
record by investigators who had not optical appliances suitable for their exhaustive
examination. With such assistance it will probably be found that, as in Trichomonas
batrachorum, the apparent lateral fringe of cilia is in reality an undulating membrane,
and that the single flagellate appendage hitherto observed is supplemented by others
of like kind.

Trichomonas limacis, Duj.

Body ovoid, smooth, pointed at each extremity; flagellum slender
throughout, about twice the length of the body ; a lateral fringe of cilia
apparently extending from the base of the flagellum more than half-
way to the posterior extremity ; endoplasm vacuolar ; movements active,
rotating on its axis. Length of body 1—1650".

HAB. — Intestinal tract of Limax agrestris.

GENUS III. DALLINGERIA, S. K.

(Nora, prop., Dallinger.)

Animalcules free-swimming, more or less ovate, persistent in form,
having a single antero-terminal, and two oppositely placed lateral flagella,
the latter adhesive at their distal extremities, permitting the zooid to
temporarily anchor itself to any chosen spot after the manner of Heteromita
and A nisonema. Endoplast conspicuous ; no distinct oral aperture. Inha-
biting animal macerations.

This new genus is established for the reception of the animalcule figured and
described by the Rev. W. H. Dallinger, in a memoir published in the ' Proceedings

310 ORDER FLAGELLATA-PANTOSTOMATA.

of the Royal Society' for May 1878, as a "minute septic organism," no technical
name being given nor any attempt being made to identify it with any previously
described form. It being the only type, among the many so painstakingly in-
vestigated by Mr. Dallinger, in company usually with Dr. Drysdale, that repre-
sents both a new generic and specific form, the author derives much pleasure from
bestowing upon it technical titles that shall serve to perpetuate their names in
connection with this group of organisms.

As in the case of the numerous other monadiform beings referred to in this
volume which have formed the subject of that authority's investigations, the entire
life-cycle, as hereafter related, has been traced out. So far as can be at present
determined, this special type would appear to exhibit a close affinity with the repre-
sentatives of the genus ffeteromita, from which, however, it is at once distinguished
by the presence of two lateral instead of a single ventral anchoring filament. No
reference being made to the existence of a distinct oral aperture or the presence of
incepted food-granules, it must be provisionally assumed that the animalcule feeds
by endosmosis, after the manner of the Opalinidse, upon the nutritive fluids in
which it takes up its residence.

Dallingeria Drysdali, S. K. PL. XIX. FIGS. 35-41.

Body elongate-ovate, about three times as long as broad, widest and
rounded posteriorly, constricted centrally, the anterior region abruptly
narrowed and neck-like; flagella subequal, long and slender, about twice
the length of the body, the two lateral ones produced on each side
immediately behind the narrower neck-like region ; endoplast posteriorly
located. Length of body 1-4000". HAB. — Animal macerations.

The life-history of this species, as traced by the Rev. W. H. Dallinger, accords
broadly with that of Monas Dallingeri, Heteromita rostrata, and other flagellate
types upon which he and Dr. Drysdale conjointly have so successfully concentrated
their attention. Multiplication by fission represents the normal and most common
mode of increase. This process is preceded in the first instance by the splitting of the
anterior flagellum (see Plate XIX. Fig. 37), the line of segmentation extending thence
through the longitudinal axis of the body, including the subdivision of the endoplast, the
missing lateral filament being reproduced by the attenuation of the sarcode film which
lastly unites the eventually separated bodies. A period of from four to seven minutes
is occupied in the completion of this act of fission, which may be repeated at intervals
of three minutes for the duration of an hour. During the next two hours the same
process proceeds at intervals of from seven to ten minutes, while after this, fission is
more rare and sluggish and interrupted by irregular intervals varying from twenty to
as much as forty minutes. The phenomenon of longitudinal fission may, in this
manner, be continued, commencing with a newly developed individual, for a space
of from five to seven hours, when death most usually ensues. Much more rarely, on
an average of three cases out of nine, however, it was found that the monads at the
end of about three hours of continuation of this cleavage process, underwent a com-
plete metamorphosis. In these instances the two lateral flagella contracting, first
assume a knotted or clubbed aspect, and the body, losing its normal ovoid form,
becomes irregularly lobate around the margin and semi-amoeboid. The two lateral
flagella are ultimately entirely withdrawn, and the body, assuming a still more regu-
larly ovate contour than it originally presented, being without the central constriction,
progresses through the water as a simple monoflagellate organism, in all ways
identical with the ordinary representatives of the genus Monas. The endoplast
meanwhile increases largely in its proportions, and occupies a more posterior location,
while, in addition, a belt-like granular zone makes its appearance, encircling the exact
centre of the body, as shown at PI. XIX. Fig. 38.

GENUS DALLINGERIA. 3 1 1

Swimming among the ordinary triflagellate members of the species the
metamorphosed monads were observed to attach themselves to one of these, the
two then swimming off and becoming by degrees completely fused with one another ;
all the flagella were now entirely retracted, the conjoined bodies exhibiting first an
irregularly lobate or amoeboid aspect, and finally a quiescent encysted state. The
cysts thus formed, Fig. 39, were of an elongate-ovate or fusiform shape, and
apparently devoid of all structure. After an interval of from three to five hours
the cysts were seen to burst or collapse, releasing a cloud of exquisitely minute
spores, hardly appreciable, and then only as the most minute specks, under a
magnification of 5000 diameters. In five hours after their emission from the cyst the
sporular elements grew to the size and contour of the parent form, the first traces of
the characteristic lateral flagella having made their appearance as minute points at
the end of the first two hours, before any movements had commenced, and while
each individual appeared under the magnification quoted as but little more than a
mere elongate speck. The habits of the animalcule as related by Mr. Dallinger are
remarkable. When swimming it progresses through the water rapidly, in a direct
line or in graceful curves, arresting, however, or reversing its course abruptly at any
moment. On these occasions, one or both of the two lateral flagella are brought
into action, and extended in an arm-like manner in place of remaining closely
adpressed to the side with their free extremities trailing, as is more usual when
a straight uninterrupted path is pursued. In all these movements the animalcule
apparently exhibits a complete volitional control over the movements of these
flagellate appendages and in the determination of its course.

The highly characteristic sedentary condition of the adult form remains to be
described. Like Heteromita, Anisonema, and other Flagellata, this type, as already
mentioned, temporarily anchors itself at will to any chosen spot, its moorings, however,
being rendered doubly secure by the utilization, for this purpose, of the two lateral
flagella in place of the single gubernaculate one employed by the foregoing forms.
In this " anchored " condition the animalcule still exhibits vigorous movements, which
are of a most remarkable character. In Anisonema, motion when at anchor consists,
in its most actively motile state, of a swaying to and fro of the body only, after the
manner of a pendulum. In Dallingeria, according to its discoverer, it takes the
form of a rapid springing up and down, much as in Heteromita rostrata, the two
adherent flagella being thrown, on the return of the body, into two spiral coils, which
are once more relaxed by the upward spring. In the performance of these
evolutions the body describes in the course of its descent the arc of a circle, striking
with great rapidity and proportionate force, hammerwise, upon the point represented
by the outstretched limit of reach of the anchoring flagella. It is further affirmed
that this hammering action is always manifested in presence of decomposing organic
matter, the blows being levelled against it with the apparent purpose of breaking up
this material, and evidently contributing to or hastening such a result. Should the
animalcule be found to possess an oral aperture, or other means of appropriating in
a substantial form the fruits of its Vulcanic labours, this interpretation of its move-
ments might be accepted, but in the absence of any such demonstration the author
is scarcely prepared to regard its reported pulverizing accomplishments as other than
fortuitous.*

Experiments, conducted with great skill and care by Mr. Dallinger, in order to

* In the accompanying illustration the letters a and b of Fig. 35 denote the positions succes-
sively maintained by a zooid with relation to its base of attachment, through the coiling and
uncoiling of the lateral flagella. By accident, the ruptured cyst discharging spores, Fig. 40, is placed
at the point upon which the body of the animalcule would strike on the full extension of the spirally
coiled appendage ; repeated blows delivered in this fashion would doubtless have the effect of breaking
the cyst and scattering the| spores in the manner indicated. It might be suitably suggested as an
alternative to the food-pulverizing interpretation arrived at by Mr. Dallinger, that the characteristic
movements of these animalcules are intimately connected with such an artificial liberation and dis-
tribution of these spores.

3 I 2 ORDER FLA CELL A TA -PANTOS TO MA TA .

ascertain the respective thermal death-points of the adult monad and its spores,
elicited that the former succumbed at a fluid temperature of 142° Fahr., while the
spores successfully resisted the very considerable one of 220° Fahr. of fluid heat, and
the still higher one of 248° Fahr. if submitted to dry heat.

GENUS IV. TRIMASTIX, S. K.
(Greek, treis, three ; mastix, lash.)

Animalcules naked, entirely free-swimming, more or less ovate or
pyriform, with a laterally produced membranous border ; flagella three in
number, anteriorly inserted, one vibratile directed in advance, two reflected
and trailing posteriorly ; endoplast and contractile vesicle conspicuous ; no
distinct oral aperture.

, Trimastix marina, S. K. PL. XIX. FIGS. 24-26.

Body subpyriform, rounded and inflated posteriorly, the pointed and
attenuate anterior extremity curved slightly towards the ventral aspect ; the
lateral border produced on the right-hand side, extending from the anterior
to the posterior extremity; flagella subequal in size and character, about twice
the length of the body, the anteriorly directed flagellum vibratile throughout
its length, one of the reflected ones free, the other retained towards its
centre by the angle formed between the body-wall and lateral membrane,
its length between this region and its point of insertion at the apical extre-
mity constantly vibratile ; contractile vesicle anteriorly located ; endoplast
spherical, adjacent to the posterior extremity. Length 1-1425".

HAB. — Salt water with decaying vegetation.

This species was obtained by the author in November 1878, at St. Heliers,
Jersey, in a vessel of sea-water containing Fuel in an advanced state of decomposi-
tion, a thick Bacterial pellicle in the gelatinous or "zooglcea" condition being
present on the surface. While the general form, number, and disposition of the
*' flagella correspond to some extent with those of Dallingeria, it differs conspicuously
from that and all other types hitherto described in the development of the
remarkable lateral border, and in the peculiar comportment of one of the posteriorly
reflected flagella with relation to it. As first seen, it was premised that the anterior
portion of this appendage was an independent undulating membrane, analogous
to that possessed by Trypanosoma or Trichomonas, but its continuity with the
portion produced beyond the posterior extremity was ultimately traced. The
membranous lateral border, imparting to the animalcule a scroll-like aspect, or more
correctly, perhaps, that of a convoluted shell, is of comparatively firm consistence,
and was not observed to exhibit any variation in its contour. Although not repre-
sented in any previously known member of the Flagellata, a somewhat similar
lateral membranous expansion occurs in the Holotrichous forms Lembus and Probo-
scdla. It was supposed that the vibratile portion of the reflected flagellum might be
connected with the office of conducting food-particles to a distinct oral aperture.
No such orifice, however, was observed, nor the inception of food-substances at
any part of the periphery.

Fam. XV. TETRAMITID-ffi, S. K.

Animalcules naked, entirely free-swimming ; flagella usually four,
rarely five, in number, inserted close to one another, near the centre of the
anterior border ; no distinct oral aperture.

GENUS TETRAMITUS. 313

GENUS I. TETRAMITUS, Perty.

Animalcules naked, free-swimming, plastic and changeable in form,
usually more or less conical and tapering posteriorly, with a truncate anterior
margin ; flagella four in number, inserted close to each other at some point
of the frontal border. No distinct oral aperture ; contractile vesicle and
endoplast conspicuous. HAB. — Stale water and organic infusions.

This genus was instituted by Perty, ' Kleinster Lebensformen,' 1852, for the
reception of two closely allied forms, Tetramitus restrains and T. descissus. By
several authors, including more notably Diesing and Biitschli, it has been assumed
that the genera Pyramimonas of Schmarda and Chlor aster of Ehrenberg, include
all the essential characteristics of the later one instituted by Perty, and which conse-
quently possesses no claim for recognition. A reference to Schmarda's original
figures and description of his type-form of the genus Pyramimonas, fortified by an
intimate acquaintance with a closely-allied species, has fully satisfied the author,
however, that the animalcules investigated and described by Perty represent an
entirely distinct generic form, his title being consequently retained in this treatise.
This decision, previously arrived at, has been entirely endorsed in Stein's recently
published volume, and in which, indeed, all three genera, Tetramitus, Chloraster,
and Pyramimonas, are admitted.

Tetramitus restrains, Perty. PL. XIX. FIGS. 42-48.

Body soft and plastic, subpyriform, compressed, tapering and attenuate
posteriorly, the frontal border abruptly truncate, with a small spout-like
projection at its lower angle ; a shallow groove extending from this point
towards the posterior extremity; flagella subequal, slender and flexible
throughout, exceeding the body in length, inserted into the small conical
projection of the truncate frontal border ; contractile vesicles two in number,
situated close to each other near the base of the flagella ; endoplast oval,
central. Length of body i-iooo" to 1-900".

HAB. — Standing water and animal macerations.

This species, representing the Tetramitus rostratus of Perty and Fresenius, and
the Pyramimonas rostrata of Diesing, is beyond doubt identical with the so-called
" Calycine Monad," figured and described by Messrs. Dallinger and Drysdale
in the ' Monthly Microscopical Journal' for May 1871. Its life-history, as elicited
by the investigations of these authorities, coincides broadly with that of Heteromita
rostrata, described on a previous page. Multiplication by longitudinal fission,
accompanied by the temporary assumption of a softer semi-plastic state, repre-
sents the ordinary mode of increase, and has been already recorded by Perty. In
this process the subdivision of the cone bearing the four flagella takes its share, the
two newly developed zooids possessing at the time of separation only two flagellate
appendages ; these however subsequently divide rapidly in half, and thus secure to
the animalcule its full complement. The more important phenomena of increase,
through the genetic union of two animalcules followed by encystment and the break-
ing up of the amalgamated bodies into dust-like spores, was successfully traced through
its various phases. In a space of nine hours the minute dust-like spores attained
the characteristic aspect of the parent monads, and were simply slightly inferior to
them in size. The individual zooids preparatory to and during the act of coalescence
assume an altogether irregular and remarkable contour (see PI. XIX. Figs. 44 and
45). The anterior portion bearing the four vibratile flagella alone retains its original
outline, the whole posterior portion of the body protruding bluntly lobate pseudo-

3 1 4 ORDER FLA GELLA TA-PANTOSTOMA TA.

podic processes by the aid of which it is enabled to creep about after the manner of
an Amoeba. Messrs. Dallinger and Drysdale further add that when in this amoeboid
condition they rapidly devour such living or dead Bacteria as they may chance to
come across, ingesting them as Amoeba do at any point of their periphery.
The two rhythmically opening and closing so-called " eye-like spots " referred
to by these same writers as being constantly present at the anterior extremity
of the animalcules, evidently represent the contractile vesicles common to almost
all members of the Flagellata. Perty and Fresenius indicate the existence of a single
large vesicle only at its anterior end ; but the two, as shown by Messrs. Dallinger
and Drysdale, are situated so close to each other as to naturally appear as one only,
unless an extremely high magnifying power is employed. Perty's description
and illustrations of the process of longitudinal fission differ to a slight extent from
that reported by Messrs. Dallinger and Drysdale, he having observed on various
occasions that the four new flagella are developed before the partitioning into
halves of the original animalcule, and which is thus provided for a short interval
with eight of these appendages. The young of this species, as recently figured
by Stein, possess a very attenuate contour, as shown at PI. XIX. Figs. 47 and 48,
more closely resembling in this respect the adult form of Tetramitus dcscissus.

Tetramitus descissus, Perty. PL. XIX. FIGS. 49 AND 50.

Body elongate, slightly curved, conical or wedge-shaped, plastic and
somewhat variable in form, the posterior extremity mostly tapering and
pointed, sometimes obtusely rounded ; the anterior half of the body
obliquely truncate or excavate on its concave or ventral side ; flagella
subequal, slender, inserted close to one another at the anterior margin
of the frontal excavation ; contractile vesicle single, located near the
posterior extremity ; endoplast central, spherical. Length of body
1-1800". HAB. — Stagnant water with decomposing organic matter.

This animalcule, originally described by Perty under the above title, is apparently
identical with the flagellate form recently investigated by O. Biitschli, and referred by
him, while retaining Perty's specific name, to the genus Pyramimonas. There are
nevertheless one or two points in Biitschli's account which do not exactly correspond
with Perty's figures and description, though such differences as exist may be possibly
attributable to mere local variation. Thus the flagella, while described by the earlier
authority as being equal to or longer than the body, are represented by Biitschli as
only half that length. The obliquely truncate anterior border bearing these flagella
is likewise described and figured by the same authority as extending backwards on
the ventral side to a much further distance than is shown by Perty.

These distinctions, if further substantiated, may necessitate the future introduction
of two separate specific titles in place of the one here employed. The sarcode
substance of this variety is apparently more plastic and liable to variations of outline,
under normal conditions, than that of Tetramitus rostratus. No details have yet
been recorded respecting the phenomena of reproduction. Representations of this
species closely corresponding with those given by Biitschli are included in Stein's
recently published volume.

Tetramitus sulcatus, Stein. PL. XIX. FIGS. 26 AND 27.

Body obtusely pyriform or subcordate, widest and rounded anteriorly,
tapering towards and bluntly pointed at the posterior extremity, about one
and a half times as long as broad ; a deep groove traversing the entire
length of the centre of the ventral side and imparting to the posterior
extremity, as seen from beneath, a bilobate contour; flagella four in number,

GENUS TETRASELMIS. 315

of equal length, inserted close together in the centre of the anterior border ;
endoplast and contractile vesicle located side by side near the same anterior
margin ; parenchyma granular, soft and plastic. Length 1-700".
HAB. — Fresh water.

The form of the body of this species, with its bilobate terminal extremity, accords
closely with that of the Callodictyon triciliatum of Carter, the number and disposition
of the flagella, and shape also of the body, excluding the median groove and
posterior bifurcation, approaching that of Tetraselmis. In both of the last-named
structural characters it differs considerably from the two preceding species, and would
seem almost to lay claim to a separate generic title. In the figures only of this type
included in Stein's recently published work, the enclosure within the body of solid
food-particles is delineated, but no indication is given of a distinct oral aperture ;
probably, as in Callodictyon, these are incepted at any point of the periphery.

GENUS II. TETRASELMIS, Stein.

Animalcules free-swimming, solitary, contained within a transparent
membranous lorica ; four flagella of similar size and character inserted at the
anterior extremity ; endoplasm coloured green, usually enclosing an eye-
like pigment-spot.

Tetraselmis cordiformis, Carter sp. PL. XIX. FIGS. 28 AND 29.

Lorica somewhat heart-shaped, widest and emarginate anteriorly,
rounded and slightly narrower posteriorly; body of animalcule only partially
or almost completely fitting the cavity of the lorica, coloured green
throughout ; flagella inserted close to each other in the centre of the ante-
rior margin and thence protruded through the aperture of the lorica ; eye-
like pigment-spot situated near the centre of the lateral border ; a large
vacuolar dilatation lying immediately beneath the insertion of the flagella ;
contractile vesicles two in number, located one on each side of this area ;
endoplast located in the median line, a short distance to the rear of the
contractile vesicles ; the posterior region of the body often containing from
one to three or more solid corpuscles of an apparently amylaceous nature.
Length of lorica 1-933". HAB. — Fresh water.

This species was first described by Mr. Carter * under the title of Cryptoglena
cordiformis, and has been rightly recognized by Stein as representing an independent
generic form. On one occasion Mr. Carter observed an example that had become
encysted and broken up into a number of sporular bodies. The more complete
diagnosis of the structural characters of the type here submitted is rendered with
the aid of the illustrations of the species given by Professor Stein.

GENUS III. CHLORASTER, Ehrenberg.

Animalcules free-swimming, somewhat variable in form, subfusiform,
angular, or prismatic ; the anterior border bearing a central vibratile
flagellum surrounded by four long, recurved, hair-like or setose flagellate
appendages ; endoplasm coloured green, frequently enclosing a red eye-like
pigment ; no distinct oral aperture. HAB. — Salt and fresh water.

* ' Annals of Natural History,' 1858.

3 1 6 ORDER FLA GELLA TA-PANTOSTOMA TA.

The genus Chloraster, as 'here recognized, includes, in addition to the Chloraster
gyrans of Ehrenberg, the Pyramimonas of Schmarda, and a third salt-water form
recently obtained by the author in the Channel Islands. The close affinity of all
three, and the undesirability of separating them into two generic groups, is made
manifest on reference to the figures of both Ehrenberg's and Schmarda's types, as
included in Stein's recently published work, and reproduced at PL XIX. As
previously intimated, it has been proposed by Diesing and Biitschli to relegate the
representatives of the genus Tetramitus also to that of Chloraster, or rather to Pyra-
mimonas as defined by Schmarda, but it is evident from the comparatively complete
data now made known concerning these respective groups that they exhibit nothing
in common with each other, and cannot consistently be united.

Chloraster gyrans, Ehr. PL. XIX. FIGS. 21 AND 22.

Body subfusiform, widest centrally, pointed at each extremity, about
twice as long as broad ; the central region sometimes produced into
four symmetrical lobate processes, which stand out at right angles to the
long axis of the body ; flagella five in number, of equal length, produced
from the pointed anterior extremity ; endoplasm green, enclosing anteriorly
an eye -like pigment-speck. Length 1-632". HAB. — Fresh water.

The delineations of this type are reproduced from the figures given in Stein's
recently published volume.*

Chloraster tetrarhynchus, Schmarda sp. PL. XIX. FIG. 20.

Body pyramidal or conical, truncate and widest anteriorly, the opposite
extremity more or less pointed, longitudinally carinate down the central
line at each of the four lateral angles ; four long, recurved, setose flagella
issuing from a papilla-like prominence in the centre of the anterior border,
a long vibratile flagellum projecting from the centre of the reflected seta ;
colour green ; movements swift, in a straight line or rotatory. Length
1-780" to 1-720". HAB. — Fresh water : near Vienna (Schmarda).

No indication is given by Schmarda, in either his drawings or description, of the
central vibratile flagellum characteristic of both the preceding and the succeeding
species ; this organ is, however, so difficult to detect without the use of reagents
and the most perfect magnifying glasses that it may have naturally escaped his
attention. In some instances, as likewise in the case of C. agilis, the more normal
quadrate contour of the body of the animalcule is exchanged for a rounded sub-
conical or shortly fusiform outline. No coloured eye-like pigment-spot appears
to be present in this type. Mr. Carter, in a manuscript note-book kindly placed
at the author's disposal, has figured an organism with four radiating seta-like
appendages at the anterior extremity, obtained by him from a well at Bombay, that
is apparently closely allied to if not identical with this species. It having been
collected in company with Cladophora fracta, Mr. Carter has suggested, in absence
of further evidence, that the form may represent the motile zoospore-like elements
of that algal ; the appearance of both this and the following form, indeed, so closely
approximates such reproductive structures, that but for the characteristic and
evidently independent movements exhibited by C. agilis, circumstances would have
apparently justified the relegation of this genus to the vegetable series.

In the accompanying figure given of this species, reproduced from Stein, there

' Infusionsthiere,' Abth. iii., 1878.

GENUS CHLORASTER. 3 1 7

are no less than eight setose appendages delineated, representing apparently the
number developed preparatory to the process of longitudinal fission.

Chic-raster agilis, S. K. PL. XIX. FIG. 15.

Body conical or subtriangular in profile, widest and truncate anteriorly,
gradually tapering towards the posterior extremity, which is sometimes
bluntly and sometimes sharply pointed; exhibiting in transverse view a
quadrate outline with four symmetrically developed, projecting, keel-like
angles ; central vibratile flagellum slender, as long as the body, pro-
duced from a papilliform or pyramidal prominence that arises from the
centre of the frontal border ; four fine, flexible, setose flagella originating
close to the base of the central flagellum, which they equal in length, and
recurved towards the posterior extremity of the body ; endoplasm pale
transparent green, with a colourless central space, a faint red eye-like
pigment-spot usually present near one of the angles of the anterior border.
Length of body 1-2500". HAB. — Salt water.

This species, distinguishable from the preceding by its diminutive size and salt-
water habitat, was obtained in some abundance in an infusion of hay in sea-
water at St. Heliers, Jersey. It was first observed after the vegetable matter had
been macerating for a space of about four weeks, and was probably imported
originally with the water in the sporular condition. At first the author was disposed
to identify it generically, if not specifically, with the Plceotia vitrea of Dujardin : his
description of this form, however, in which it is described as possessing two
flagella only, one of which is vibrated in advance and the other trailed behind and
adherent at will, demonstrates the place of that species to be close to Heteromita
or Anisonema, and nowhere near the present type. Like Oxyrrhis, this species
exhibits a restless and active condition, in which it darts about too swiftly almost
for the eye to follow, and a sedentary one, in which the body remains perfectly
quiescent, and apparently angles for food with its extended vibratory flagellum.
The four accessory, reflected, but flexible, hair-like setae, although motionless during
the quiescent state, are probably brought into active use in the natatory condition, it
being difficult otherwise to account for the rapidity with which it, as it were, shoots
along in a straight line from one resting-point to another.

The number of the setose flagella, as also the exact contour of the body,
whether triangulate or quadrate, proved for a considerable while a difficult point to
decide, but was finally settled by the addition to the water of dilute osmic acid,
which at once killed the animalcules without altering their shape, and thus made
clear the characters embodied in the foregoing diagnosis and accompanying figure.
Neither the existence of a contractile vesicle, of a definite oral aperture, nor the
inception of solid food, has as yet been determined in this species. The apparent
control over their motions in the water exhibited by these little beings demands brief
notice, and fully proves their claim for admission as representatives of the animal
series. In a drop of water containing several examples of this species, it was noticed
that if one animalcule in its swift nomadic career passed near another, possibly
striking it with one of its extended setae, the one so disturbed immediately started in
pursuit, several often joining in the chase, and gambolling together in a manner
corresponding with what is hereafter related of the Holotrichous Ciliate type
Cyclidiitm glaucoma. In a similar manner it was also observed that they would
congregate together in that part of the field most brilliantly illuminated by the aid
of the achromatic condenser, when illuminated by artificial light. In addition to
the faint red pigment-spot usually present at the anterior end, an oval, darkish-
green, nucleus-like body was frequently noticed towards the posterior extremity.

3 1 8 ORDER FLAGELLA TA-PANTOSTOMA TA.

Fam. XVI. HEXAMITID^J, S. K.

Animalcules naked, free-swimming or temporarily adherent ; flagella
six in number ; no distinct oral aperture.

GENUS I. HEXAMITA, Dujardin.

Animalcules naked, free-swimming or temporarily adherent ; elongate-
ovate or subfusiform, but more or less plastic and variable in shape ; the
posterior extremity bearing two long, flexible, adhesive, caudal flagella ; four
long vibratile flagella produced from the anterior border ; endoplast and
contractile vesicle usually conspicuous ; no distinct oral aperture. Inhabit-
ing stagnant water and the intestinal viscera of Amphibia. Increasing by
longitudinal fission.

Up to a comparatively recent date much doubt prevailed respecting the exist-
ence of the hexaflagellate animalcules, imperfectly described and connected with
the present generic title by Dujardin so long since as the year 1841.* Within the
last few years, however, various specific types have been rediscovered and subjected
to minute examination by Stein, Biitschli, and the present author, their place as
highly remarkable representatives of the Infusoria Flagellata being through such
investigation fully established. Among the data of note concerning the vital pheno-
mena of these singular animalcules, recorded for the first time in this volume, may
be mentioned their demonstrated capacity to lead a temporarily attached, in addition
to a natatory existence, as described in association with the two specific types
H. intestinalis and H. inflata. Although Stein has indicated in one of his drawings
the position of a presumed oral aperture, no trace of any such distinct inceptive area
has so far been detected by the author. Pending, consequently, the production
of more decisive evidence in this direction, it has been decided to relegate the
members of this generic group to the section of the Pantostomata.

Hexamita intestinalis, Duj. PL. XIX. FIGS. 60-62.

Body subfusiform, widest towards the anterior region, tapering and
pointed posteriorly, two or three times as long as broad, frequently with
one or two longitudinal dorsal sulci ; all six flagellate appendages similar
in size, equalling or exceeding the length of the body, the two posterior
trailing flagella inserted close to each other at the pointed posterior
extremity, the four anterior vibratile flagella originating in like manner
from the anterior or apical extremity ; contractile vesicle anteriorly located ;
endoplast spherical, subcentral. Length 1-2000" to 1-1500".

HAB. — Alimentary canal of Tritons and Batrachia.

This species is illustrated by a large series of figures in Stein's recently pub-
lished volume, and has been obtained and examined in considerable abundance by
the author from frogs dissected at Professor Huxley's biological laboratory, South
Kensington, during the winter session of 1879 and 1880. In none of the illustrations
given by the first-named authority is, however, any indication given of the character-
istic habit manifested by the animalcules to attach themselves by their posterior
flagella, as observed by the author of both this and the species next described. When

* F. Dujardin, 'Histoire des Zoophytes Infusoires,' Paris, 1841.

GENUS HEX A MIT A. 319

first transferred to the stage of the microscope, they, like Polytoma, usually rush wildly
about the field, conveying the impression that they are entirely free-swimming. After a
short interval, however, their movements get less excited, and they finally affix them-
selves to the glass slide, or any neighbouring organic debris, by their adherent
posterior flagella, while the four anterior appendages are vibrated actively in the
surrounding liquid medium, in the manner indicated at PL XIX. Fig. 61. The
exact number, character, and point of insertion of the flagella may be readily
substantiated during this attached condition, though with even greater facility on
killing the little creatures by the application of a small drop of iodine or osmic acid.
The extreme flexibility of these animalcules is frequently manifested in both their
natatory and sedentary conditions, the body being frequently flexed to such an extent
that the anterior and posterior extremities almost touch. In the figures of Hexamita
intestinalis, recently published by Stein, two examples are represented as possessing
a delicate, denticulate, frill-like membrane on each side of the anterior border, one
of these, as represented at PI. XIX. Fig. 62, exhibiting in addition numerous elon-
gate papillose projections in the posterior region, which are pronounced in the
index to be merely adherent Bacteria. No such frill-like border could be detected
in any of the examples examined by the author, and it would seem highly probable
that both this structure and the Bacteria-like appendages represent peculiarly modi-
fied pseudopodic expansions of the body-sarcode of the animalcule preparatory to
the assumption of an encysted state. Similar slender papillose pseudopodia are
shown in this volume to be emitted under like circumstances by the zooids of
Codosiga botrytis and Cephalothamnium c&spitosa. The young of this species,
according to Stein's figures, possess only two anteriorly inserted vibratile flagella,
while the general contour of the body is more attenuate than that of the adults.

Among the numerous examples recently examined by the author, zooids were
not unfrequently observed, in which the posterior region was distinctly cleft or
bifurcated, after the manner of the succeeding species. This circumstance, added
to the fact of the identity of the habitats of the free-swimming H. inflata and the
Amphibia that harbour H. intestinalis, not unnaturally raises a doubt as to whether
these two presumed distinct types may not ultimately prove to be free-swimming,
and endoparasitic phases of the same specific form.

Hexamita inflata, Duj. PL. XIX. FIGS. 56-59.

Body oblong or subquadrangular, emarginate or bifid posteriorly,
plastic and changeable in form, varying from one and a half to two or three
times as long as broad, the two caudal trailing flagella produced as tail-like
prolongations of each limb of the posterior bifurcation, the four anterior
vibratile flagella originating close to one another in the centre of the
anterior border ; contractile vesicle anteriorly located ; endoplast sub-
central. Length 1-2500" to 1-1200".

HAB.— Pond water with decomposing organic matter and in vegetable
infusions.

Independently of its distinct habitat, this species is to be distinguished from the
preceding form by its broader contour and the conspicuous emargination of the pos-
terior region. It has recently been figured by both Stein and Biitschli, and has also
been obtained by the author from both marsh-water and from an infusion of decaying
flowers, its companions in each instance being Trepomonas agilis, and in the latter
one also Vorticella infusionum. Like Hexamita intestinalis, it has been frequently
observed to affix itself by the two caudal flagella, the anterior appendages being
meanwhile deployed and vibrated actively in the surrounding water, with the
apparent object of drawing suitable food-particles within reach of the body. The
animalcules under this temporarily affixed condition were found on several occasions

3 20 ORDER FLA GELLA TA-PANTOSTOMA TA.

to exhibit a remarkable peculiarity of deportment, which, though subsequently
observed, has not as yet been recorded of the preceding type. The adhesion in
these instances was effected only by the extreme distal terminations of the caudal
flagella, and the animalcule, extended to its full length at their extremity, rotated
rapidly backwards and forwards on its long axis. The two caudal flagella were thus
alternately twisted upon each other in converse directions, while the four anterior
appendages performed, in unison with this reversible gyratory motion, graceful and
devious curves around the creature's body ; the aspect of an animalcule engaged in
such active exercise is represented at PI. XIX. Fig. 59. As already suggested by the
author in an article on " Parasitic Infusoria," contributed to the ' Popular Science
Review' for October 1880, it would seem highly probable that the form described
by Professor Leidy under the title of Trichonympha agilis — referred provisionally in
this treatise to the Holotrichous order of the Ciliata — represents some species of
Hexamita, imperfectly observed by him under the conditions just related. The
simile invoked by this authority in connection with Trichonympha, that of ballet-
dancers having long cords suspended from their shoulders, which whirled around
them in mazy undulations as they danced, by no means inaptly represents the
characteristic aspect of the members of the present genus during their attached
gyratory phase of existence here recorded.

The adhesive character of the caudal flagella of Hexamita is often manifested
by the animalcules picking up flocculent matter or other debris with these appen-
dages, and dragging it with them as they swim through the water. This pheno-
menon is indicated in the delineation by Stein, without explanatory notes, reproduced
at Fig. 58 of the plate just quoted, and has been frequently witnessed by the author.
In addition to its more ordinary sedentary condition, the present type has also
been observed by the author to creep and bore its way through the gelatinous
zooglcea-scum collected on the surface of vegetable infusions, the body at such
times assuming the most protean contours, and closely resembling that of an Amceba.
Hexamita inflata is figured by Biitschli as having six vibratile flagella, in addition to
the caudal pair, inserted at remote distances upon the lateral periphery. This
representation of their disposition is apparently derived from an error of interpreta-
tion, otherwise, if eight flagella in all were actually present, the example had evidently
developmented a supplementary pair, preparatory to the process of longitudinal
subdivision. Such an octoflagellate example, reproduced from Stein's volume, is
delineated at PI. XIX. Fig. 57 ; but in this case the supplementary pair is developed
at the posterior extremity, which has become doubly emarginate or quadrifid.

Hexamita rostrata, Stein. PL. XIX. FIG. 55.

Body fusiform, broad and inflated centrally, with a conical or rostrate
anterior prolongation, and a still longer and attenuate caudal termination,
the total length about equal to twice the central breadth ; flagella long,
slender, and of equal size, the four anterior ones inserted close to each other
at the apex of the anterior prolongation, the two posterior appendages
similarly approximated at the end of the caudal extension ; contractile
vesicle posteriorly situated ; endoplast not indicated. Length 1-640".

H AB . — U nrecorded.

This species is shown by Stein's figures to correspond closely with H. intestinalis,
but may be distinguished from the same by the distinct prolongations of the anterior
and posterior regions of the body. In general contour, as delineated by Stein, this
type may be said to correspond singularly with that of the apterous insect Lepisma,
the proportions and locations of the two sets of flagella agreeing in a remarkable
manner with the antennary and caudal filaments of that arthropod.

GENUS L OPHOMONAS. 3 2 I

Hexamita nodulosa, Duj.

Body oblong, with three or four longitudinal nodular rows, the two
lateral of which are extended posteriorly, imparting to this region a
bifurcate aspect ; caudal flagella produced from the posterior bifurca-
tions ; vibratile flagella four in number, long and slender, projecting from
the anterior margin. Length 1—2000" to 1-1500".

HAB. — Pond water with decomposing animal matter.

This species, as yet observed only by Dujardin, is most probably, as suggested
by Biitschli, a variety merely of fl. inflata.

Fam. XVII. LOPHOMONADID^E, S. K.

Animalcules naked, solitary, and free-swimming, bearing a tuft of flagella
at the anterior extremity ; no distinct oral aperture.

GENUS I. LOPHOMONAS, Stein.

Animalcules free-swimming, somewhat plastic and varying in form,
spherical, ovate, or fusiform, bearing at the anterior extremity a crescent-
shaped fascicle of long, slender flagella ; endoplast sometimes distinct ; con-
tractile vesicle not yet recognized ; inhabiting the intestinal tract of various
Insecta.

This genus was first instituted by Stein, in the year 1860,* for the reception of a
singular form obtained by him from the intestinal canal of the common cockroach,
Blatta (Periplaneta) orientalis. The same type has been since met with under similar
conditions by O. Biitschli, who has further described a second well-marked species.
The tuft-like fascicle of flagella at the anterior extremity, forming the leading
characteristic of the members of this genus, consists of so thick an aggregation of
these vibratile appendages, as to convey to the individual zooids the aspect almost
of certain Ciliata, such as Strombidium.

Lophomonas blattarum, Stein. PL. XIX. FIGS. 52-54.

Body somewhat variable in form, ovate or subspherical, surface smooth ;
the frontal margin slightly narrowed, abruptly truncate ; flagella issuing in
a dense brush-like tuft from the frontal border, the central ones longest,
directed straight forward, equal to or exceeding the length of the body, the
lateral ones shorter, gradually diminishing in size, reflected outwards;
an indistinct vesicular space posteriorly located ; endoplast spherical,
situated in the median line near the anterior extremity. Length of body
1-825".

HAB. — Intestine of the common cockroach, Blatta ^Periplaneta) orientalis.

The accounts given by Stein and Biitschli of this animalcule, while agreeing in
general details with one another, differ slightly in some minor points. Stein, for
instance, has described the examples examined by him as of a rounded sub-
spherical shape, whereas those forming the subject of Biitschli's investigations were,
for the most part, of elongate-oval form ; the rounder outline being chiefly associated

' Sitz. der konig. bohm. Ges. Wiss."

322 ORDER FLA GELLA TA-PANTOSTOMA TA.

with younger individuals. This slight disparity of contour, Biitschli suggests, may
be possibly accounted for by the fact that Stein turned his examples into pure water,
a medium which, proving uncongenial to their habits, may have resulted in their
assumption of a more contracted shape. Using himself a solution of the white of
egg, he preserved the animalcules in a healthy and normal state for a space of
twenty-four hours and upwards. The presence of food-particles within the sub-
stance of the endoplasm has been observed by both of the authorities quoted, Stein
further reporting the possession of a narrow, crescentic oral aperture at the anterior
extremity. The existence of such a structure is, however, not confirmed by the
investigation of Biitschli. The food-particles ingested are usually collected together
in the posterior half of the body, leaving the anterior moiety clear and transparent ;
the expulsion of effete matter at the posterior extremity was on one occasion wit-
nessed by Biitschli. Not unfrequently this investigator observed that the body-
plasma of the posterior end was drawn out in a tail-like manner ; his illustration
given of this phenomenon being at the same time connected with one of the rounder
or younger individuals, would seem to indicate that in this earlier stage the sarcode
of the body presents that greater amount of viscosity or ductility which is common to
the young, and in some instances to the adults also, of the more simple monadine
types. The first step towards the process of increase by fission has been observed,
but not the complete act. In one of these suspected instances there was an appear-
ance as of fine cilia at the posterior extremity of the body. The movements of the
flagella-fascicle of this animalcule are somewhat complex, the central bundle of
straight and longer ones undulating together rhythmically, while the shorter and
reflected lateral ones vibrate independently.

Lophomonas striata, Biitschli. PL. XIX. FIG. 51.

Body variable in shape, mostly subfusiform, with an attenuate and
pointed posterior extremity, but sometimes ovate and rounded in this
region ; anterior border abruptly and somewhat obliquely truncate ;
flagella-fascicle brush-like, similar to that of L. blattarum, but somewhat
shorter in proportion to the length of the body ; the entire external surface
distinctly and obliquely striate ; contractile vesicle and endoplast not
yet observed. Length 1-800".

HAB. — Intestine of Blatta (Periplaneta) orientalis.

Although the characters of this animalcule appear sufficiently distinct for separate
specific recognition, Biitschli entertains some doubt whether it may not ultimately
be found to represent a transitional condition only of L. blattarum. The two,
while tenanting the same specific host, were, however, usually found inhabiting
separate individuals, and did the present form represent a developmental phase only
of the other, it would scarcely have escaped Stein's notice. The substance of the
parenchyma in this type or variety would appear to be much more homogeneous than
in the form last described. A clear vacuolar space was on one occasion noticed near
the anterior extremity, but no trace of an endoplast or nucleus could be detected.

Leydig has briefly referred, in his anatomical description of the mole-cricket,
Gryllotalpa, to a globose animalcule bearing a lateral tuft of undulating hairs, that
inhabits the intestinal tract of that insect. As remarked by Biitschli, it is highly
probable that this organism represents another species of Lophomonas, as also
that this genus has numerous other representatives distributed among the Ortho-
pterous order of the Insecta.

Fam. XVIII. CATALLACTID-ffi, S. K.

Animalcules coherent in social clusters, their anterior and exposed
border clothed with long vibratile flagella ; no distinct oral aperture.

GENUS MAGOSPH^RA. 323

GENUS I. MAGOSPH^RA, Haeckel.

Animalcules free-swimming, united in social clusters, joined to each
other centrally by an inward extension of their prolonged posterior
extremities, the anterior or exposed margin of each animalcule clothed
with long vibratile flagella ; endoplast and contractile vesicle conspicuous,
increasing by the subdivision into sporular elements of a single encysted
zooid. Inhabiting salt water.

Professor Haeckel * has proposed to create a special and independent class of
his sub-kingdom of the Protista, which he denominates the Catallacta, for the
reception of the as yet single known type bearing the above generic title, dis-
covered by himself on the coast of Norway. It is evident, however, that the
structure, life history, and developmental features of this organism, as reported by
himself, accord so closely with those of all the ordinary representatives of the
Infusoria Flagellata, as recorded in this volume, that any such complete isolation of
this particular type is altogether artificial and uncalled for. Individually examined,
the zooids of Magosphara correspond remarkably with those of the endoparasitic
type Lophomonas, last described, and if encountered separately under like con-
ditions would undoubtedly be relegated to the same multiflagellate genus. Their
coherence in spheroidal clusters, again, and maintenance of a free-swimming
existence, find precise parallels in such genera as Synura, Syncrypfa, and Uroglena,
while the ultimate assumption by the zooids of an amoeboid phase and subdivision
into sporular elements are common to the majority, if not to the entire section of the
Pantostomatous Flagellata. Mostly, among the ordinary Flagellata, the resultants of
such a process of multiple fission or sporular subdivision become scattered asunder
throughout the surrounding water ; a like more or less permanent coherence of the
subdivisional derivatives is nevertheless maintained by the three last-named genera,
and, with certain modifications, recurs in those motile reproductive products of the
sponges, the " swarm-gemmules " or so-called " ciliated larvae," discussed at length
in Chapter V., and which are there shown to consist similarly of ovate or sub-
spheroidal aggregations of flagellate animalcules. The only essential distinction
manifested by the several types just quoted consists of the fact that in these latter
the constituent zooids of the spheroidal or ovate masses are monoflagellate or
biflagellate, while in those of the present generic group they are polyflagellate.
While thus reluctantly compelled to ignore Professor Haeckel's claim on behalf of
Magosph&ra of a title carrying with it the comprehensive significance he would
attach to it, his denomination of the same, slightly modified so as to reduce its
import to that only of a family name, is here preserved.

Magosphsera planula, Haeckel. PL. I. FIGS. 12-17.

Bodies pyriform, forming spheroidal clusters, united to each other
centrally by an attenuate inward prolongation of their posterior
extremities, the interstices between being filled in by a common gela-
tinous matrix or zoocytium, the anterior margin truncate flattened,
the antero-lateral borders polyhedral through mutual pressure ; flagella
equalling one-half of the length of the body, developed from the entire
exposed anterior surface ; endoplast spherical, situated in the median line
towards the anterior extremity ; contractile vesicle single, subcentral.
Diameter of adult sphere-masses 1-320".

HAB. — Salt water, Norwegian coast.

* " Die Catallacten, eine neue Protistengruppe," ' Jenaische Zeitschrift,' Bd. vi., 1870.

Y 2

324 ORDER CHOANO-FLAGELLATA.

The development of this interesting form, as reported by Haeckel, may be
thus summarized. The earliest or initial condition is represented by a single
spherical, egg-like body, containing a large central nucleus or endoplast and enclosed
nucleolus or endoplastule immersed within structureless transparent protoplasm, and
surrounded by a denser investing membrane, as shown at PI. I. Fig. 1 6 ; the nucleus
divides by fission into two equal halves, accompanied by a similar segmentation of
the circumjacent protoplasm, each section of which now envelops a single nucleus.
By a repetition of this process, similar to that of ordinary yolk-cleavage, four, eight,
sixteen, and finally thirty-two nucleated cleavage-spheres or daughter-cells are pro-
duced, and the segmentation is completed. The thirty-two bodies resulting from
this segmentation begin now to exhibit amoeboid movements within the investing
pellicle, and emit from their surface small, irregular pseudopodic processes ; these
gradually become longer and thinner, ultimately presenting the form of attenuate
vibratile flagella. United in a single spherical mass these bodies rotate slowly
within their membranous prison, which at length bursts asunder, leaving the com-
pound colony to swim away freely in the surrounding water, under the characteristic
adult aspect detailed in the foregoing diagnosis, and delineated at PI. I. Fig. 12.
Sooner or later this compound body falls to pieces, the individual zooids assume an
amoeboid form (Fig. 15), and it is believed become encysted and once more
repeat the cycle. During their active aggregated life the zooids ingest food
apparently at any part of their exposed anterior border, there being no distinct
oral aperture, and likewise during their amoeboid condition through any portion of
their periphery.

Apart from the true affinities and significance of Magosph&ra previously dis-
cussed, the singular resemblance in general form, size, and plan of ciliation of the
separate zooids to the constituent elements of ciliated epithelium will at once
suggest itself to the practical physiologist. A coherent spherule of such epithelial
cells indeed, excepting for the absence of the contractile vesicles, would be in-
distinguishable from a colony-stock of Magosphara plamda, as originally described
and delineated by Professor Haeckel.

Order V. CHOANO-FLAGELLATA, S. K.

OR FLAGELLATA-DISCOSTOMATA.

Animalcules exceedingly minute, highly polymorphic and variable in
form, usually exhibiting in their most normal and characteristic phase a
symmetrically ovate, pyriform, or clavate outline ; a single long, lash-like
flagellum produced from the centre of the anterior border, the base of which
is embraced by a delicate, hyaline, extensile and retractile, collar-like
expansion of the body-sarcode ; the collar in its extended condition infundi-
buliform or wineglass-shaped, when contracted subcylindrical or conical,
exhibiting in its expanded state a distinct circulating current or cyclosis
of its finely granular substance ; ingestive area discoidal, food-substances
being brought in contact with the expanded collar through the vibratory
action of the flagellum, first carried up the outside and then down the inside
of this structure with the circulating sarcode current, and finally received
into the substance of the body anywhere within the circular area circum-
scribed by its base ; faecal or waste products discharged at any point within
the same discoidal space ; a distinct spheroidal endoplast with a contained
endoplastule and two or more contractile vesicles usually conspicuous.

SECTION L DISCOSTOMATA-GYMNOZOIDA. 325

Inhabiting salt and fresh water. Increasing by longitudinal or transverse
fission and by encystment and subdivision of the entire body into sporular
elements.

Section L DISCOSTOMA TA-GYMNOZOIDA.

Collared monads free-swimming or sedentary, loricate or illoricate^
solitary or colonially associated, never in the latter instance completely
immersed or hidden within special chambers in a common gelatinous matrix
or cytoblastema, but either entirely naked or with their distal regions
freely exposed to the surrounding water.

The extensive and remarkably beautiful series of Flagellate organisms com-
prehended under the present sectional title may be said to represent the fruits of
the most recent microscopic research. The immunity from discovery and
taxonomy which they have for so long previously enjoyed is undoubtedly due to
their excessive minuteness, the largest individual zooid in the entire group not
exceeding in length the i-ioooth part of an English inch, while in the majority of
instances the much smaller calibre of the i~3oooth" obtains. The rapid progress made
by opticians, however, within the last few years, in the production, at a moderate
cost, of object-glasses of high magnifying power, has placed in the hands of the
histologist the key to an entirely new organic world, and of which the present
group furnishes, perhaps, a not altogether inappropriate illustration.

The earliest intelligible record given concerning the existence of the seiies of
minute organisms here referred to the newly established order of the Choano-Flagellata,
and distinguished in all instances by their possession of the delicate, collar-like organ
which encloses with its base the single terminal flagellum, must undoubtedly be
associated with the name of the late Professor H. James-Clark, of the Agricultural
College of Pennsylvania, U.S.A., who in June 1866 communicated to the Boston
Society of Natural History a detailed account, with copious illustrations, of four
American forms discovered by himself as inhabitants partly of salt and partly of
fresh water. Previous to this date such authorities as Ehrenberg and Stein had
certainly figured and described one or two species of the genus Codosiga as minute
varieties or early growths of representatives of the Peritrichous genus Epistylis,
while Fresenius had gone so far as to recognize in the form now known as Codosiga
botrytis the flagelliferous character of the component zooids, and also the possession
by them of a truncate hyaline projection of the anterior border that may be readily
identified at the present day with the distinct collar-like organ that characterizes all
members of this group. Prior even to the time of Ehrenberg a record of the
existence of these minute Flagellate organisms is to be met with, some members of the
genera, Monosiga or Salpingceca being in all probability represented by the so-called
" squamulae adhaerentes " figured by O. F. Miiller, and even referred to by Leeuwen-
hoek as being found attached to the pedicles of Vorticella (Carchesiuni) polypinum
and V. (Epistylis) anastatica. The names of those who have to be accredited
with the confirmation and further extension of the comparatively recent discoveries
of Professor Clark are as yet but few in number. The pleasant experience of being
the first upon this side of the Atlantic to recognize types belonging to the same
category, partly identical with and partly differing from those made known by that
authority, and to generally substantiate that interpretation of their structure which
he had first submitted, fell to the lot of the present author.

A notice of such discovery, with illustrations and brief diagnoses of the several
forms observed, was communicated to the meeting of the Royal Microscopical Society
held on November ist, 1871, and was published in the following, December, number of
the ' Monthly Microscopical Journal.' From that date forward the author's attention
has been more especially concentrated upon this highly interesting organic group,
the result of such investigation being the registration of over three-quarters out of
the total number of fifty or more species now known to science, and described in

326 ORDER CHOANO-FLAGELLATA.

this treatise. The greater number of this series were already known to the author
in the year 1877, and formed the subject of a communication, accompanied by an
extensive set of plates, read in abstract at the meeting of the Linnaean Society on
June 2 ist, 1877. While, however, it was subsequently decided to reserve all com-
plete textual and illustrative details for primary publication in the present manual,
a general summary of the contents of this communication was given in three
articles published respectively in the ' Annals and Magazine of Natural History ' for
January and August 1878, and in the 'Popular Science Review' for April of the
same year. As an accompaniment to the article in this last-named periodical, entitled
" A New Field for the Microscopist," were produced furthermore two plates con-
taining upon a reduced scale delineations, with their technical names attached, of
all the newly discovered species embraced in the larger communication made to the
Linnaean Society, so as to secure for them a priority of nomenclature pending the
appearance of the present treatise. Since the publication of these several papers
a recognition of the collared monads has been accomplished by the German
authorities, Professors F. Stein and O. Biitschli, the former more especially in
his ' Infusionsthiere,' Bd. iii. Heft i, produced in November 1878, containing
illustrations, of which the textual descriptions yet await publication, of some
half a dozen varieties distinct from those first discovered by Professor Clark, or
included in the author's earlier communication of the year 1871. Butschli's obser-
vations were confined to three or four specific forms identical with types pre-
viously examined by Professor Clark or the author. Still later, M. Charles
Robin, in the 'Journal de 1'Anatomie et de la Physiologic ' for November 1879,
has placed on record the results of his investigation of the single type Codosiga
botrytis, bringing to a conclusion the enumeration of the literature concerning this
highly interesting group of the Flagellata so far accumulated. By no one of these
several authorities, however, has there as yet been produced any attempt at a full
interpretation of the remarkable and important functional properties pertaining to
the delicate funnel-shaped sarcode expansion or " collar " common to all the
members of this organic series. By both Professor Clark and Biitschli it has been
maintained that an oral aperture is present, the former indicating its position as
within the area circumscribed by the collar, and at the base of the flagellum, while
Biitschli, in the case of Codosiga botrytis, has somewhat more vaguely defined it as
appertaining to special vacuolar areas developed at different points of the periphery
external to the base of the expanded collar. The intimate correlation of this last-
named structure with the process of food-inception, appears to have altogether escaped
recognition by these investigators.

What the precise import of the "collar" is, and in what manner it is con-
nected with the ingestive functions, had been ascertained by the present author so
far back as the year 1871, and is indirectly referred to in the paper then com-
municated to the Royal Microscopical Society, already quoted. Full details, with
explanatory illustrations, were, however, reserved for comprehension in the more
exhaustive account of this remarkable group of animalcules produced six years later,
and were also extensively set forth, with accompanying figures, in the two articles
bearing upon this subject, published in the months of January and April 1878. A
slightly amended quotation in extenso from the later of these two publications, in
conjunction with the coloured frontispiece of this manual, may be advantageously
produced on the present occasion in illustration of the structural and functional
properties and peculiarities of the organ now under consideration : — " Specifically,
this delicate hyaline organ, the ' collar,' is of such extreme tenuity, that its true form
and nature can be demonstrated only by a very careful adjustment of the achromatic
condenser or other accessory illuminating apparatus employed, and is even then
exhibited to greater advantage by supplying the animalcule under examination with
artificial food, such as carmine or indigo. Under the conditions last mentioned, it
will be found that the collar consists of a transparent infundibuliform film of sarcode
that may be protruded from and withdrawn at will into the general substance of the
monad's body, in the same manner as the sarcode prolongations or pseudopodia of
an Amceba or other Rhizopod. As in the pseudopodia of certain Rhizopods, such

SECTION I. DISCOSTOMATA-GYMNOZOIDA. 327

as the Foraminifera, it will moreover be found that, notwithstanding the extreme
tenuity of the sarcode film, a circulation of its substance is being constantly
maintained, flowing upwards on the outside, over the distal edge or rim, and
downwards on the inner surface, at the base of which it again comes in contact
and merges with the protoplasmic substance of the body. This wineglass-like film
of sarcode doubtless acts as an efficient branchial or respiratory organ, but such by
no means represents its most important function. In conjunction with the centrally
enclosed flagellum it constitutes a most admirably contrived trap or snare for the
capture and retention of the animalcule's food. Whirling round with inconceivable
rapidity, the last-named organ, the flagellum, creates a strong centrifugal current in
the water, setting in from behind towards the direction of its own apex, and bringing
with it all such tiny organic particles as do not possess sufficient weight or power to
stem its tide.* But for the outstretched collar, these would simply hurry with the
stream past the monad's body and out of reach. Not for them, however, so easy a
passing of the rapids ! In the midst of their swift career they strike against the
almost impalpable film of sarcode of which the organ is composed, and to this they
adhere as tenaciously as a snared bird to a lime-daubed twig or an incautious fly to
a spider's web. Then slowly, almost imperceptibly, the captive atoms are carried
along with the circulating current of the collar's substance up the outside and down
the inside until, on reaching the base of its inner surface, they are engulfed within
the sarcode substance of the monad's body. The food-particles after ingestion are
gradually accumulated into spherical agglomerations, and then regurgitated through
the body under conditions nearly identical with those exhibited by such a higher
infusorial type as Vorticella. The indigestible residua are eventually liberated from
the area, limited by the base of the collar, within which they primarily gained access."
The highly characteristic aspect of an animalcule that has fed upon and become
gorged with carmine particles in the manner previously suggested, is delineated in the
frontispiece of this treatise, which represents an animalcule of Monosiga gracilis S. K.,
viewed with the enormous magnification of 8000 diameters, as obtained by a ^Vmcn
object-glass and C ocular, supplied to the author by Messrs. Powell and Lealand.
The arrows placed in various positions serve to indicate the direction of the current
induced by the active rotation of the flagellum, and also the course described by
the carmine particles after striking upon and becoming adherent to the extended
collar. Even where the magnifying power employed is not sufficient to exhibit the
cyclosis of the collar substance, the addition of carmine or indigo, in a granular
form, to the water containing the animalcules is highly advantageous, since the
particles having a tendency to accumulate upon the distal rim of the structure, as
shown in the frontispiece, define its contour with an amount of perspicuity
obtainable under no ordinary conditions. Most usually, in point of fact, as seen
even with adequate magnification, this highly important organ, the collar, is visible
only in the optically denser regions represented by the two lateral peripheries, taking
the apparent shape then of two linear or setaceous appendages projecting one on
either side of the centrally located flagellum. As such apparently simply linear or
setose structures, the lateral peripheries of the characteristic collar have indeed been
delineated by both earlier and more modern investigators. Examples of monads
having their true structure thus only partially revealed, are abundantly furnished by
the illustrations reproduced from the authorities referred to, given at Plate II. Figs.
12, 16, 19, 20, and 21, PL V. Figs. 32 and 33, and PI. VI. Fig. n. The figure
last quoted is of especial interest, since it represents a form included by Mr. Carter

* This seemingly anomalous direction of the current induced by the motion of the flagellum
may be simply and practically illustrated and explained by inserting a stick through a ring and
giving them a swift rotatory action, the free or distal end being made to describe the larger circle.
Although the stick may be elevated perpendicularly, the ring will travel from the base to its apex,
thus demonstrating the centrifugal nature of the force engendered. Such a more abnormal rotatory
flagellum will act as a "pu/settum" (see p. 416), driving the body, if detached, backwards through
the water. In all ordinary Flagellata the motions of the flagellum are simply undulatory, producing
currents in an opposite direction, or towards its base of attachment, and the appendage acting as a
" tractellum" drags the body after it, if detached, in a straightforward course.

328 ORDER CHOANO-FLAGELLATA.

in his note-book so long ago as the year 1857, under the designation of an
" animalcule with ear-like processes," and which has been since recognized by him as
a species closely allied to the Salpingceca amphoridium of Professor H. James-Clark.

The more exact morphological significance of that special organ, the " collar,"
remains to be discussed. Having due regard to the circulatory currents or cyclosis
manifested by the sarcode substance of which it is composed, there can scarcely be
room for doubt that this structure finds its precise homologue in the pseudopodia of
the Foraminiferous group of the Rhizopoda, and in which a similar circulation or
cyclosis of the constituent sarcode is exhibited. Its extreme mobility and plasticity,
allowing it at will to be contracted from a widely expanding infundibular contour to
a subcylindrical or truncate conical outline, as first recognized by Clark, and shown
in many of the accompanying illustrations, or further to be withdrawn entirely into the
substance of the body, is of itself indicative of a close relationship with the group just
designated. The collar may, in fact, be most appropriately compared in this connec-
tion to a funnel-shaped aggregation of the single anteriorly protruded pseudopodic
fascicle of some Monothalamous Foraminifer such as Lagena or Miliola, or it may
be supposed that such a type has developed a single subcylindrical anterior pseudo-
podium, whose substance has become hollowed out centrally, so as to produce a
tubular or infundibuliform contour. In either case the central flagellum may be
regarded as a supplementary appendage, whose presence alone secures the group of
the Choano-Flagellata from being placed among, or closely adjacent to, such typical
Rhizopoda.

Comparatively small as is the number of species that have so far been referred to
this Discostomatous or collared Flagellate section, the multiplicity of forms presented
by them is truly remarkable. Still more noteworthy, however, in this connection,
is the extraordinary similarity that subsists between these various modifications
and conditions of growth, as here exhibited, and those found to obtain among the
more highly organized Peritrichous group of the Vorticellidae. Like these latter,
the great majority of its members pass a sedentary existence, and are similarly
distinguished under such conditions for their solitary, or social and dendritic habits
of growth, for their secretion and occupation of distinct horny loricae, or for their
colonial aggregation within a common gelatinous matrix or zoocytium. Compared
in detail with one another, the isolated representatives of the genus Monosiga may
aptly be likened to those of Vorticella or Rhabdostyla, Codosiga to Epistylis or
Opercularia, Salpingceea to Vaginicola or Cothurnia, while in Phalansterium and
Protospongia the conditions presented find their precise parallel in Ophrydium.
It would seem by no means unreasonable, indeed, to regard these diversely modi-
fied Flagellata as the lineal ancestors or archetypes of the Peritrichous series,
and it has been already suggested, by Gruber * that the funnel-shaped collar of the
present Flagellate series finds its morphological counterpart in the delicate trans-
parent membrane lying within the peristome of many ordinary Vorticellidae, and
which seen in profile presents the aspect of a setose appendage. A still closer
approximation is, however, undoubtedly found in E. Ray Lankester's anomalous
genus Torquatclla, where an extensile and contractile collar-like membrane takes
the place of the normal circular fringe of cilia. As demonstrated in various
instances in the course of this treatise, the primitive condition of the adoral fringe
or wreath of cilia is that of a simple membranous band or expansion ; and accepting
the phenomena thus exhibited by the life-history of the zooid or individual as in
all probability indicative of the developmental cycle or phylogeny of the group or
order, it may be consistently inferred that the Peritrichous series originated from a
stock or phylum in which the now highly specialized adoral ciliary wreath was repre-
sented by a simple infundibuliform membranous expansion. While the genus Torqua-
tella affords substantial evidence in favour of this interpretation, still more important
testimony in the same direction is perhaps yielded by the two Cilio-flagellate types
Stephanomonas and Asthmatos. Both of these, while possessing an anteriorly located

* ' Zeitschrift fiir Wissenschaftliche Zoologie,' Bd. xxxi., 1879.

GENUS MONOSIGA. 329

circular fringe of cilia, are furnished in addition with a long terminal flagellum, the
relationship maintained between these diversely modified appendages being identical
with that subsisting between the collar and its centrally enclosed flagellum in the
flagellate group now under discussion. If, indeed, future investigation were to reveal
that the initial condition of the ciliary wreath in these two generic types took, as in
other cases, the form of a simple membranous expansion, these animalcules, during
such earlier epoch of their existence, would be altogether indistinguishable from the
representatives of the ordinary Choano-Flagellata. In Asthmatos it is further note-
worthy that the cilia comprising the adoral wreath are of an unstable and fugitive
nature, being capable of protrusion and retraction after the manner of pseudopodia
within the substance of the body-sarcode. This particular attribute of the appendages
in question may be also cited as substantially supporting the affinity here inferred,
a similar but even more conspicuously pronounced Rhizopodal attribute being
exhibited by the morphologically corresponding or homologous appendage possessed
by the collared monads.

As already briefly related at page 80, the animalcules belonging to this highly
interesting Flagellate order are remarkable for their pale glaucous green or fluorescent
hue, such colour assisting materially in the recognition of their presence even when
the magnifying power employed is insufficient for the detection of their characteristic
collar, with its enclosed flagellum.

The leading demarcations of the family and generic groups of the independent or
Gymnozoidal section of the collared Flagellata or Discostomata adopted in this
volume are set forth in the accompanying Table.

FAMILIES AND GENERA OF CHOANO-FLAGELLATA.

SECTION I. DISCOSTOMATA-GYMNOZOIDA.
FAMILY. GENUS.

I. CoDONOSiGlDjE. / [ Solitary, stalked or sessile . . I. Monosiga.

Animalcules naked, se- Attached.. .. j United socially on a common J2 Codosi

creting neither a lorica / ( pedicle /

nor a gelatinous syn- I -p. ,.•„,• mrn- „ / United in stellate clusters .. 3. Astrosiga.

cytium. I ling \ United in chain-like series .. 4. Desmarella.

II. SALPINGCECID^E.
Animalcules secreting
horny loricse.

III. PHALANSTERIID^;.

Animalcules secreting a
gelatinous zoocytium ;
forming extensive so-
cial colonies.

Lorica solitary (Sedentary.. 5. Salpingaca.

3 \ Free-swimming 6. Lagenceca.

Loricae united socially and forming a branching "1 _ „ ,
polythecium .. .. *>^. Polyaca.

Collar rudimentary 8. Phalansterium.

Collar well developed 9. Protospongia.

Fam. I. CODONOSIGID-a:, S. K.

Animalcules free-swimming or attached, solitary or socially united,
entirely naked, secreting neither independent loricae nor gelatinous zoo-
cytia ; collar well developed, encircling the base of the single terminal
flagellum ; contractile vesicles two or three in number, posteriorly located ;
endoplast spherical, subcentral.

GENUS I. MONOSIGA, S. K.
(Greek, monos, solitary ; siga, silence.)

Animalcules solitary, illoricate, of ovate or spheroidal contour, but some-
what plastic and changeable in shape, sessile or attached through the
medium of a simple rigid pedicle ; bearing anteriorly a well-developed

330 ORDER CHOANO-FLAGELLATA.

membranous collar and single centrally enclosed flagellum ; contractile
vesicles two or three in number, posteriorly located ; endoplast spheroidal,
subcentral. Inhabiting salt and fresh water. Increasing by transverse
fission, and by the breaking up of the entire body-mass into sporular
elements.

This newly established generic group comprehends the simplest known represen-
tatives of the Choano-Flagellate order. All its members, while agreeing essentially
in structure with the isolated zooids of the previously discovered genera Codosiga and
Salpingceca, are to be distinguished from the former by their eminently solitary
mode of growth, and from that of Salpingaca by the entire absence of a protective
sheath or lorica. With relation to the compound type Codosiga, Monosiga may be
said to occupy a position similar to that which subsists between the solitary Peritri-
chous genus Vorticella and the compound forms Carchcsium and Epistylis. In all
the species here enumerated it has been observed that the body-sarcode is of much
softer and more plastic consistence than obtains in either Codosiga or most other
generic representatives of the same order ; owing to this circumstance it is found
that while each specific type preserves a more normally maintained characteristic
form, the separate zooids are subject to considerable individual variation. A like
plasticity, developed, however, to a more extensive degree, is especially distinctive
of the aggregated collared monads of all sponge-stocks, and which, examined in
their isolated condition as shown at PI. VIII. Figs. 2-7, 10, 18, and 20, might
easily be mistaken for members of the present genus. A distinctive feature per-
taining to the developmental phenomena of Monosiga as compared with Codosiga, is
afforded by their transverse in place of longitudinal plan of subdivision ; the anteriorly
produced resultant of such process of segmentation swims off as a simple collarless
uniflagellate monad, and forms an independent attachment.

A. — PEDICLE ABSENT, RUDIMENTARY, OR NON-PERSISTENT.
Monosiga angustata, S. K. PL. II. FIGS. 31 AND 32.

Body very attenuate, clavate or subcylindrical, about four times as long
as broad, attached by its more slender posterior extremity, without the
intermedium of a pedicle; endoplast spherical, subcentral; contractile
vesicles two in number, posteriorly located. Length of body 1-2500".

HAB. — Fresh water, solitary.

Only two or three examples of this elegant little animalcule have been as
yet observed, being then discovered attached to examples of a species of Cyclops
obtained from a pond on Wandsworth Common. The earlier condition of this
type, prior to the development of the characteristic collar, represented at PI. II.
Fig. 32, is remarkable for its conspicuous resemblance to the undeveloped and
elongate collarless monads of a motile sponge-gemmule, as illustrated in various
figures of PL IX.

Monosiga consociatum, S. K. PL. IV. FJGS. 19-21.

Body ovate or pyriform, widest posteriorly, about one and a half times
as long as broad, attached sessilely or through the intermedium of a short
rudimentary pedicle ; endoplast spherical, subcentral ; contractile vesicles
two in number, posteriorly located. Length of body 1-4000" to 1-3500".

HAB. — Fresh water, gregarious.

The zooids of this species are not unlike those of the persistently stalked marine
M. ovata, but are of even more plastic consistence. Although a short pedicle was

GENUS MONOSIGA. 331

occasionally observed, the majority of examples were fixed directly to the water-
weed without any such intermedium. This diverse character of the mode of attach-
ment of the individual zooids finds its parallel in the loricated type Salpingceca
amphoridium, where also a short pedicle may or may not be developed. A colony
of this species was first discovered attached to decaying leaves of Valisneria from
a fresh-water aquarium, and has been subsequently met with clustered in a similar
social manner upon the carapace of a species of Cyclops taken from a mill-pond
in St. Peter's Valley, Jersey.

At Figs. 20 and 21 of PL IV. two zooids are represented which, having with-
drawn their collars and flagella, have assumed a semi-amcebiform contour, while the
endoplasm has become highly vacuolar.

Monosiga Steinii, S. K. PL. IV. FIG. 12.

Body elongate-ovate or subfusiform, widest centrally, tapering evenly
towards each extremity, about twice as long as broad, attached imme-
diately by its pointed posterior termination to the chosen fulcrum of
support ; collar nearly equalling the body in height ; contractile vesicle
single, posteriorly situated ; endoplast inconspicuous. Length of body
I- 1 600".

HAB. — Fresh water, attached to the pedicle of Vorticella convallaria.

Some half a dozen zooids of this species are figured by Stein * as doubtful phases
of Codosiga botrytis, attached to the contractile stalk of a single example of the
Vorticellidan above named. The even fusiform contour of the body, and entire
absence of a pedicle, serve to distinguish this type from M. brevipes, which it other-
wise most nearly resembles. A species apparently identical with this form has
been recently observed by the author attached to the branching pedicle of Epistylis
plicatilis.

Monosiga fusiformis, S. K. PL. IV. FIG. 1 7.

Body elongate-fusiform, widest centrally, tapering and attenuate at each
extremity, about three times as long as broad, fixed by the posterior
extremity without any intermediate pedicle ; contractile vesicles two in
number, posteriorly located; endoplast subcentral. Length 1-2500".

HAB. — Pond water, gregarious.

Examples of this species were found congregated upon the carapace and ovisacs
of a species of Cyclops obtained from one of the water-fowl ponds in the Zoological
Gardens, Regent's Park, in May 1879. Its more attenuate contour and crowded
habit of growth distinguish it from Monosiga Steinii.

B. — PEDICLE CONSPICUOUSLY AND PERSISTENTLY DEVELOPED.
Monosiga gracilis, S. K. PL. II. FIG. 3, and FRONTISPIECE.

Body elongate-ovate, broadest anteriorly, attenuate posteriorly, about
two and a half times as long as broad, seated on a pedicle of from three to
four times the length of the body, distal extremity of the pedicle retaining
its original plastic state for a length nearly equalling that of the body.
Length 1-4000". HAB. — Salt water.

This species was obtained by the author in November 1875, attached to the
stems of hydroid zoophytes and sea-weeds from the Manchester Aquarium, and also

' Infusionsthiere,' Abth. iii., 1878.

332 ORDER CHOANO-FLAGELLATA.

growing on similar organisms taken direct from the sea at Bognor, Sussex, in Sep-
tember 1872. In the examples derived from the last-named locality, the bodies of
the animalcules presented a somewhat more rounded outline than those obtained at
Manchester, both, however, agreeing in that essential plastic character of the distal
region of the pedicle referred to in the foregoing diagnosis. The elegant wineglass-
shaped collar in this type attains a greater comparative altitude than has been observed
of any other member of this group, its total height not unfrequently equalling twice
that of the body. It is at the same time of such extreme tenuity as to be scarcely
visible throughout its entire length without recourse to the artificial feeding
process described in the introductory remarks upon the group (see p. 326). Such
feeding process at once shows up the outline of the hyaline organ with marvellous
distinctness, and may be advantageously adopted in all cases where the contour of
this structure is difficult to determine. An example of this species has been selected
for the illustration given, in the frontispiece, of the ingestive phenomena exhibited
by the animalcules of this order, the characteristic collar being somewhat fore-
shortened for want of space.

Monosiga ovata, S. K. PL. II. FIGS. 33-35.

Body subject to considerable variation in its proportions, normally
inversely egg-shaped or obovate, broadest posteriorly, seated upon a rigid
pedicle of a length equal or subequal to that of the body. Length of body
1-5000" to 1-3500". HAB. — Salt water.

The normal contour of the body of this species closely resembles that of
Monosiga gracilis with the proportions reversed, e. g. the broader region being the
end next to the pedicle instead of the one forming the free or distal extremity.
The pedicle is also proportionally much shorter and rigid throughout its entire
length. Representatives of this species frequently occur in which the form of the
body differs considerably from the above and typical state, the outline then
assumed being considerably more elongate and almost subcylindrical. These
elongate zooids, as shown at PI. II. Fig. 35, are sometimes slightly constricted
towards the centre, and point probably to a phase preparatory to multiplication by
transverse fission. The examples supplying this description were found, in company
with Monosiga gracilis, attached to filamentous marine algae collected at Bognor,
Sussex, in September 1872.

Monosiga globosa, S. K. PL. II. FIGS. 4-6.

Body subspheroidal, attached to a very long, straight, and slender
pedicle, whose total length equals four or five times that of the diameter of
the body. Dimensions of body 1-4000". HAB. — Fresh water.

The globular contour of the body and, in fully developed zooids, the great
proportional length of the supporting pedicle, distinguish this type from any of
the various species here described. Propagation by transverse fission, or by the
separating off from the anterior extremity of monoflagellate free-swimming gemmules,
has been frequently observed ; the zooid so liberated, after passing a short nomadic
existence, attaches itself by its posterior extremity, and developing a pedicle and
collar, grows to the parent form. Such a separated monadiform zooid, with its
primitively attached state, is represented at PI. II. Figs. 5 and 6.

Monosiga brevipes, S. K. PL. II. FIGS. 7-9.

Body in its more normal state symmetrically ovate or elliptical, the
posterior and anterior extremities being equally and obtusely pointed ;

GENUS CODOSIGA. 333

pedicle rigid and very short, not exceeding half the length of the body.
Length of body 1-3000" to 1-2500". HAB. — Fresh water.

The zooids of this species have been encountered by the author abundantly
attached to the pedicles of the higher Infusorial types, Vorticella nebulifera,
V. campanula, Epistylis flavicans, and Carchesium polypinum. They not improbably
represent the so-called " squamulae adhaerentes " referred to at page 325, first met with
under similar conditions by O. F. Miiller. As in Monosiga ovata, the form of the
body is subject to considerable variations of contour. PI. II. Fig. 8 thus illustrates an
example in which the anterior extremity is so considerably prolonged as to impart
to the animalcule a flask- like or bottle-shaped outline, while on other occasions, as
at Fig. 9, the two apices may be so retracted as to produce an almost spheroidal
shape. The pedicle, though short, is always distinctly developed, a circumstance
which serves to distinguish this type from Monosiga Steinii.

Monosiga longicollis, S. K. PL. IV. FIG. 18.

Body flask-shaped, rounded and widest posteriorly, produced anteriorly
in an attenuate neck-like manner, rather over twice as long as broad ; pedicle
short, one-quarter the length of the body. Length of body 1-2500".

HAB. — Bog water, gregarious.

This type, which exhibits persistently a flask-shaped contour closely correspond-
ing with that occasionally presented by Monosiga brevipes, was discovered by the
author in September 1879, attached in social groups to the branching zoothecium of
Rhipidodendron Huxleyi, previously described.

GENUS II. CODOSIGA, James-Clark.

Animalcules illoricate, spherical or ovate, attached socially to the ter-
minations of a simple or variously branching, fixed and rigid pedicle or
zoodendrium ; collar well developed, enclosing the single terminal flagellum ;
contractile vesicles conspicuous, two or more in number, posteriorly located ;
endoplast anterior or subcentral ; multiplying by longitudinal fission and by
encystment and subdivision into spores. Inhabiting salt and fresh water.

To the single fresh-water representative of this genus, the Codosiga pulcherrima
of Professor H. James-Clark, since identified with the imperfectly observed Epistylis
botrytis of Ehrenberg, nine well-marked additional forms have been added by the
author. Some of these inhabit salt and some fresh water, while all are readily
distinguishable from each other by the form of growth of the supporting stem,
or by the varying contours of the individual zooids. The branching colony-stocks
of Codosiga, viewed with an insufficient amount of magnification, correspond so
closely in their general mode of growth with those of Epistylis, that many of
them encountered without a knowledge of their true nature, by both earlier and
comparatively recent investigators, have been regarded as either immature or
exceedingly minute species of that genus. Stein has preferred in his lately
published work to alter the designation of this generic group from Codosiga to
Codonosiga, upon the ground that the etymology of the first title as introduced
by Professor Clark is not perfectly correct. Adhering, however, to the recom-
mendations of the British Association,* to the effect that all scientific titles must
be regarded simply as proper names, without regard to their strict etymological
construction, and that when once conferred it is desirable that they should be
permanently retained, Stein's proposed alteration has not been adopted in this
manual.

* ' Rules of Zoological Nomenclature,' ed. 1878.

334

ORDER CHOANO-FLAGELLATA.

Codosiga botrytis, Ehr. sp. PL. II. FIGS. 22-29, and PL. IV. FIGS. 6-10.

Bodies smooth and transparent, symmetrically ovate, more attenuate
posteriorly, about one and a half times as long as broad ; from two or three
to as many as twenty or more zooids, attached to the extremity of a
straight, slender, simple, rigid pedicle, whose height equals four or five times
the length of the body; their junction with this structure effected through
the medium of a slender flexible extension of the posterior region, which
frequently presents the aspect of a distinct secondary footstalk ; contractile
vesicles two or three in number, posteriorly located ; endoplast spherical,
situated in the median line in advance of the centre of the body. Length
of body, exclusive of the collar, 1-2500" to 1-2000", the collar when ex-
tended equalling the body in height. HAB. — Fresh water, gregarious.

It being now universally admitted that this species — first described in an
intelligible and exhaustive form by the late Professor H. James-Clark, under the
name of Codosiga pulcherrima — is identical with the Epistylis botrytis of Ehrenberg,
and Anthophysa solitaria of Bory and Fresenius, the specific title conferred upon it
by the earliest of these several investigators must necessarily take precedence of the
otherwise eminently suitable one proposed by the American authority. Among
the numerous specific forms of the genus Codosiga enumerated in this volume,
the present type represents the one most generally distributed. Since first meeting
with it in the neighbourhood of London in the year 1871, it has been obtained by
the author from innumerable stations throughout the country. Where once found,
it is, moreover, usually abundant, being eminently sociable in its habits, and not
unfrequently, as shown at PL II. Fig. 29, covering with a miniature forest-like
growth the thread-like filaments of various aquatic Confervae; the finely divided
leaves of Myriophyllum spicatum form likewise a favourable fulcrum of support for
this most elegant little species. At first sight it would appear that each separate
ovate zooid springs immediately from the rigid pedicle, but a closer examination
shows that each of these possesses a short, independent footstalk, which is, moreover,
flexible and endowed with the vitality of the body proper. This fact may be clearly
demonstrated by the observation of animalcules undergoing the process of longi-
tudinal fission, and at which times it will be seen that the short flexible footstalk
shares in the subdivision. As shown at Fig. 24, both the flagellum and the mem-
branous collar participate in the longitudinal subdivision of the zooid, the latter
structure during the process being conically contracted.

During the author's earlier acquaintance with this animalcule examples were
frequently met with in which the entire surface of the body bristled with slender
rod-like projections, which were at first regarded as foreign bacterium-like organisms
accidentally entangled in the peripheral sarcode. Later on, however, it was deter-
mined that these structures were organically connected with the animalcule's body.
It was then thought that the individuals exhibiting this peculiarity belonged to a
separate species, and they were consequently figured and briefly described in the
' Monthly Microscopical Journal' for December 1871, under the title of Codosiga
echinata. It has since been ascertained by the author that this supposed specific
variety is an amcebiform condition of C. botrytis previous to its passing into
an encysted state ; the short rod-like processes corresponding indeed with the
retractile pseudopodia temporarily developed under like circumstances by Salpingoeca
amphoridium, or other ordinary Flagellata. Sometimes, as shown at PI. II. Fig. 26,
these rod-like radiating pseudopodia are developed while the collar is fully expanded,
but more often both this structure and the flagellum are entirely withdrawn into
the substance of the body, which then presents the aspect delineated at Fig. 25.
Upon this amoeboid phase ensues an encysted condition in which the entire
cuticular surface becomes indurated, and the enclosed endosarc breaks up into a

GENUS CODOSIGA. 335

number of spore-like bodies, as shown at Fig. 27. It is not improbable that
previous to this encysting process, conjugation with other free-swimming animalcules
is effected ; but such a genetic union has not up to the present time been witnessed
by the author, but is reported by Stein.

Biitschli, who has recently examined this form,* is disposed to maintain that
food is ingested outside the membranous collar, through vesicular extensions that
may be developed at any point close to its base. This interpretation, however,
together with the original separate mouth theory advanced by Professor Clark,
becomes quite untenable when set side by side with the evidence recently adduced
relative to the nature and function of the collar, and as explained at length in
the introductory notice of this group. Although normally only two spherical con-
tractile vesicles, as represented by Bxitschli, are to be observed in the posterior
extremity of the body, as many as three are not unfrequently to be found, though,
as explained by Professor Clark, this is more usual in examples about to increase by
longitudinal fission. The systole and diastole of each of these vesicles, as observed
by the author, occupy a duration of 60'" ; Professor Clark, however, gives only half
this time. The adherent bacteria interpretation, now abandoned, but formerly
connected by the author with the echinate or amoeboid state of this animalcule, is
adopted independently by Biitschli in the publication quoted. Stein likewise figures
an example in his recently issued volume, with a similar bacterial explanation, and
also an instance in which the genetic union of a smaller free-swimming zooid
with a solitary sedentary one is apparently in process of accomplishment. In
both of these last-named instances, reproduced at PL IV. Figs. 9 and 10, it would
seem probable, however, that the types figured are referable to the solitary genus
Monosiga rather than to the colonially associated one now under consideration.
Attention may be especially directed to the remarkable similarity that subsists
between a luxuriant and subspheroidal colony-stock of Codosiga botrytis, as repro-
duced from Stein's work, at PL IV. Fig 6, and the subspheroidal or rosette-shaped
gemmules, consisting of similar closely aggregated collared monads, developed by
the sponge Halisana lobularis, delineated at PL IX. Fig. 20. The addition of a
pedicle is alone required in this latter instance to render the two monad aggregates
indistinguishable.

Dr. Charles Robin has very recently t figured a supposed variety of Codosiga
botrytis in which the characteristic collar is replaced by four rigid cirrhate processes.
It is quite evident, however, that this presumed distinct variety represents merely
that modified condition common to all members of the Choano-Flagellata, and
specially referred to and illustrated in the description given of Salping&ca amphori-
diu»i, in which, the collar being withdrawn, simple pseudopodic extensions take its
place. There can further be but little doubt that the form obtained from the
Victoria Docks, figured and described by the author of this treatise in the ' Monthly
Microscopical Journal ' for May 1869, under the title of Acineta socialis, and com-
pared at the time with the Epistylis botrytis of Ehrenberg, is identical with a similarly
modified condition of the present species. Polymorphic tentacle-like processes
approximating more closely to the pseudopodia of an ordinary Rhizopod than to
the characteristic appendages of a true Acineta, were distinctly observed, and their
presence accepted as rendering the relegation of the type to the order of the
Suctoria entirely provisional.

Codosiga umbellata, Tatem sp. PL. IV. FIGS. 1-5.

Bodies gibbously ovate, rather over twice as long as broad, clustered in
groups of from four to eight individual zooids at the terminations of a rigid
tripartite, bi-tripartite, or occasionally quadripartite branching pedicle or
zoodendrium. Length of bodies 1-1250". Total length of branching pedicle

* ' Zeitschrift fiir Wissenschaftliche Zoologie,' Bd. xxx., Heft 2, 1878.
t ' Journal de 1'Anatomie et Physiologic,' Nov. and Dec. 1879.

336 ORDER CHOANO-FLAGELLATA.

eight or ten to twenty times that of the body of a single zooid. Contractile
vesicles and endoplast as in C. botrytis. HAB. — Fresh water.

This species, first figured and briefly described by the author under the above title
in the ' Monthly Microscopical Journal' for December 1871, represents, both as
regards the dimensions of the individual zooids and the size and proportion of the
branching pedicle, the largest, and at the same time one of the most symmetrically
developed members of this notably elegant genus so far discovered. An adult
colony, inclusive of the branching pedicle, not unfrequently attains a total height of as
much as the i-62nd part of an English inch, and is therefore easily recognized with
a comparatively low power of the microscope. It is almost beyond doubt a variety
of this species that is figured and described by Mr. Tatem in the ' Transactions of
the Royal Microscopical Society' for the year 1868, as a new type of Epistylis, and
which he proposes to distinguish by the title of Epistylis umbellatus. The magnifi-
cation of 300 diameters only, employed by Mr. Tatem, was not sufficient to enable
him to recognize the hyaline collar and flagellum surmounting the distal extremity
of each animalcule's body, but that he did not prove the existence of true cilia is
equally apparent on reference to his figures, where in place of the continuous ciliary
wreath characteristic of the ordinary Epistylids, a mere suspicion only of such
structure is indicated at the two antero-lateral margins, and which may be easily
identified with the imperfectly seen outline in profile of the transparent infundibu-
late collar. The dimensions, again, of the individual animalcules and branching
pedicle of Mr. Tatem's supposed Epistylis accord so closely with those of the species
now under discussion, that there can be but little uncertainty as to the near, if not
absolute, identity of the two forms, and on this account Mr. Tatem's proposed
specific title is here retained, and his own name associated with the nomenclature
of the species. The method in which the symmetrically branched pedicle of Codosiga
umbellata is produced is not very readily comprehended. The example figured by
Mr. Tatem would seem to afford an instance of a quadripartite branching variety,
but the tripartite one is the more prevalent. It might have been anticipated that
this quadripartite type would have been the most frequent as the resultant of
a single zooid twice divided by longitudinal fission, the four individuals thus pro-
duced then making a new start afterwards to repeat the process. The figure
supplied by Mr. Tatem in fact shows four individuals at the extremity of each of
the sixteen branchlets of the pedicle, a circumstance which exactly bears out such an
interpretation. In all cases examined by the author, however, the pedicle was
either tripartite or bi-tripartite (see PL IV. Figs, i and 3), the termination of each
branchlet bearing, moreover, a considerable number of collared zooids. The
foregoing explanation is therefore altogether inapplicable in these instances, and it
remains an open question whether this distinct order of growth is not possibly
indicative of a separate specific organization. Not having, however, as yet met
with the quadripartite form figured by Mr. Tatem, and thus obtained an opportunity
of instituting the necessary comparisons, the testimony so far elicited is here
accepted in favour of their specific identity, and they are here distinguished
as varietal forms only of Codosiga umbellafa. In the more frequent tripartite and
bi-tripartite pedicle of this specific type, it might in another direction be not inappro-
priately suggested that we find foreshadowed the same potential energy that pro-
duces in connection with the essentially similar collar-bearing monads of certain
calcareous and siliceous sponge-forms their characteristic tripartite or bi-tripartite
spicula. In addition to obtaining examples of Codosiga umbellata from various
localities near London, the author has also received it growing upon Anacharis
from the neighbourhood of Stourbridge, Worcestershire, in company with Oper-
cularia nutans and other Infusorial forms remitted by Mr. Thomas Bolton.

Various altogether irregular stock-forms of this species are figured by Stein in
his recently published volume, one of the more prominent of these being repro-
duced at PL IV. Fig. 5. That authority has further conferred upon the present
species the distinct generic name of Codonodadium, with reference evidently to the
branched character of the supporting pedicle. The transition, however, from the

GENUS CODOSIGA. 337

forms in which the zooids are almost, but not quite, sessilely attached to the summit
of the primary stalk, as in C. botrytis, to those in which the latter structure is con-
spicuously branched, as in C. umbellata, and as shown by such types as C. pyriformis,
C. grossulariata, and C. candelabrum, hitherto unknown to Stein, is however so
gradual that an independent generic title in the present instance cannot be con-
sistently maintained.

In examples of Codosiga umbellata examined by the author while going to press
— November 1880, received from Mr. John Hood, of Dundee — a phenomenon -has
been observed not previously recorded of any other representative of the present
Flagellate order. These having been submitted to somewhat undue pressure, threw
out around their bodies a hyaline film of sarcode, which imparted to them the aspect
of being enclosed within independent sheaths or loricag, ultimately retracting both their
collars and flagella. This pressure being removed, the bodies resumed their accus-
tomed shape and the flagella and collars were again extended. In the delineations
of Codosiga botrytis given by O. Biitschli, one abnormal example, figured and
described as possessing a delicate viscid case, apparently represents a closely parallel
condition of metamorphosis.

Codosiga allioides, S. K. PL. II. FIGS, i AND 2.

Animalcules as in C. botrytis, but associated upon a multicapitate pedicle
or zoodendrium, the main stem developing from one point as many as ten
secondary branches of equal length, at the extremities of which the animal-
cules are grouped in subsessile social clusters ; contractile vesicles and
endoplast conspicuous. Length of bodies 1-1650". Secondary stalks
six or seven times, and primary stalk over twelve times the length of the
supported zooids. HAB. — Fresh water.

The umbellate zoodendrium of this variety exhibits a plan of ramification that
corresponds substantially with the floral umbel of the genus Allium and its allies
among vegetable types, and upon which account the present specific title has been
adopted. In another direction this species may be said to present the appearance of
a number of colony-stocks of Codosiga botrytis, united at the bases of their respective
pedicles to one common main rachis. In the single example that has yet been met
with, there were no less than ten of these branches bearing each from three to six or
seven animalcules. The length of each secondary stalk was rather longer in pro-
portion than the single one of C. botrytis, while the main rachis measured a little over
twice the length of the secondary ones. A corresponding diversity in size also subsists
between the individual zooids of this type and those of C. botrytis, the latter being
considerably smaller. The single specimen here figured and described was found
growing on Nitella taken from a pond in the neighbourhood of London, supplied to
the author by Mr. William Gay, F.R.M.S. From Codosiga umbellata, with the
irregular growth-form of which, as reproduced from Stein's work at PI. IV. Fig. 5,
it to some extent agrees, the present species may be readily distinguished by the
lax and undulating instead of rigid and rectilinear character of the supporting
pedicle.

Codosiga cymosa, S. K. PL. III. FIGS. 3-7.

Zooids symmetrically ovate, stationed separately, upon short inde-
pendent footstalks, at the extremities of a cymose or corymbiform, pro-
fusely branching pedicle or zoodendrium. Length of bodies 1-5000", of main
rachis 1-500" to 1-250". HAB. — Salt water.

The number of animalcules included in a single colony-stock of Codosiga cymosa
exceeds that of any other species of the genus yet discovered, the luxuriantly branch-
ing pedicle not unfrequently supporting, as shown in the accompanying plate, as

z

338 ORDER CHOANO-FLAGELLATA.

many as, or more than, one hundred individual zooids. With the exception of
C. pyriformis, it is further the only example, out of the nine known species of
the genus, that has been found in salt water, though doubtless future investigation
will reveal the existence of many additional forms. The species as here figured and
described was met with in November 1875, attached in great abundance to the
empty cells of Polyzoa and Sertularian zoophytes, taken from the marine tanks of
the Manchester Aquarium, at that time in the author's charge. As these zoophytes
were in the first instance derived from various remote localities, it is not possible to
fix the exact station on the British coast-line from whence they were originally
imported. The branching pedicle or zoodendrium of Codosiga cymosa varies con-
siderably in different colonies ; where a large number of zooids are present the
characteristic corymboid type is predominant, and the colony-stock as a whole con-
siderably resembles in external contour the corymbiform flower-spike or panicle of
the sea-lavender (Statice limonium). PI. III. Fig. 7, represents an abnormal
growth of this species in which the complete colony-stock presents in the arrange-
ment of its constituent zooids an aspect highly suggestive in miniature of the zoarium
of the polyzoic genera Aulopora or Hippothoa. This growth-form is produced by the
abnormal mode of gemmation. Usually the tree-like colony is formed by the
irregular dichotomous branching of the pedicle, the primary animalcules at the base
of these branches becoming obliterated or losing their individuality by their onward
growth. In this instance, however, each new bud, in taking its origin from the base
of its predecessor, has left the preceding one intact, while at the same time the
gemmation is much more sparse, and the pedicle to each individual is unusually
prolonged. As shown at Fig. 4, it mostly happens that all the animalcules com-
posing one large colony-stock, are so disposed as to face in the same direction, a
formula of growth remarkable for its symmetry and elegance. At PI. III. Fig. 6a
will be found delineated a zooid in which the collar is retracted and the body, after
throwing around it a hardened cyst-like investment, has divided itself into two equal
parts. This no doubt represents the initial stage of a further breaking up of the
entire body into sporular elements. As shown at Fig. 50, there appears to be a
tendency in this species to occasionally produce zooids of abnormal size. This
phenomenon is probably also connected with the function of reproduction, and is
suggestive of the like development, for reproductive purposes, of animalcules of
abnormal size, which obtains in the genus Zoothamnium, among the higher Peritri-
chous Infusoria.

Codosiga grossularia, S. K. PL. II. FIGS. 10 AND n.

Zooids subspheroidal, attached in small clusters, through the inter-
medium of short independent pedicles, to a simple or sparsely branching
main rachis. Length and diameter of bodies of animalcules 1-2500" ; height
of main rachis five or six to ten times the length of the supported zooids,
secondary branchlets not equalling or but slightly exceeding their diameter.

HAB. — Fresh water.

This species may be easily recognized by the globose form of the bodies of the
separate zooids, all the remaining representatives of the genus hitherto met with
exhibiting a more or less ovate outline. The main stem remains undivided for
a considerable distance, and is sinuous, as in C. alloides. The secondary subdivisions
of the pedicle rarely exceed in length the diameter of a single animalcule, and
being given off in close proximity to one another, impart to the complete colony-
stock a considerable resemblance to a small bunch of currants. This species is
of rare occurrence, two or three isolated examples only having been so far met
with. At Plate II. Fig. n a colony-stock of three zooids only is represented, which
are protruding digitiform pseudopodia from their lateral peripheries in a manner cor-
responding to that which has been previously recorded of C. botrytis. The examples

GENUS CODOSIGA. 339

furnishing this description were obtained by the author from a pond in the North
London district supplied from the New River Waterworks.

Codosiga candelabrum, S. K. PL. III. FIGS. 8 AND 9.

Zooids elongate, gibbously ovate, from two and a half to three times as
long as broad, forming small erect clusters and attached by secondary foot-
stalks of their own altitude to the extremity of a pedicle of almost twice
that height. Length of bodies 1-2000".

HAB. — Fresh water, on Entomostraca.

This type was obtained in March 1876, from the fresh-water dykes in the
neighbourhood of Great Yarmouth, Norfolk, all the specimens then examined being
found attached to the ovisacs and limb-joints of a species of Cyclops. In form and
size the individual zooids correspond closely with those of Codosiga umbellata, the
shortness of the primary pedicle, the length of the secondary ones, and the erect
position maintained by the animalcules with relation to their supporting stem, dis-
tinguish it at once, however, from either the adults or from a young colony of that
species, for which it might possibly at first sight be mistaken. Except for the small
number of animalcules included in one colony-stock, four being the greatest number
that has been yet observed, this species in miniature recalls to mind the higher
Infusoria Epistylis digitalis, or E. anastatica, found growing with it on the same
Entomostracon.

Codosiga pyriformis, S. K. PL. II. FIG. 14.

Zooids subpyriform, attached in small clusters by distinct rigid foot-
stalks, which equal their own bodies in length, to the apex of a long, simple,
and slightly sinuous primary pedicle. Length of bodies 1-4000".

HAB. — Salt water.

This type closely approaches the cosmopolitan fresh-water species C. botrytis,
previously described. In addition, however, to its salt-water habitat and the broader
contour of the animalcules, it may be readily distinguished from that species by the
more attenuate and less rigid growth of the primary pedicle, by the greater length of
the secondary ones, and the in general more erect position assumed by the indi-
vidual zooids ; this latter feature is a necessary accompaniment of the comparatively
rigid consistence of the short secondary pedicles which immediately support the
animalcules. It would seem to be not altogether improbable that the so-called
variety of Codosiga botrytis recently figured and described by C. Robin, characterized
by similarly developed secondary footstalks, represents the type now under considera-
tion. This supposition receives substantial support from the circumstance that,
although no habitat is recorded, the majority of accompanying infusorial types
described by him are essentially inhabitants of salt water.

The examples of Codosiga pyriformis examined by the author were obtained
growing abundantly on the deserted polyparies of Hydroid zoophytes and Polyzoa
received from Brighton.

Codosiga furcata, S. K. PL. II. FIGS. 15-19.

Zooids shortly and obtusely ovate, attached singly or in pairs by foot-
stalks of about their own length to a short and irregular, furcately branching
pedicle. Length of bodies 1-3300", height of primary pedicle rarely ex-
ceeding that of a single zooid. HAB. — Fresh water.

This species may be readily distinguished from all the preceding forms by the
character of the pedicle which commences branching at a short distance only from

Z 2

340 ORDER CHOANO-FLAGELLATA.

its origin. So far but a single colony of two animalcules has been met with by
the author, but there can be little doubt that it is identical with that uncertain form
figured by Stein in his ' Die Infusionschiere auf ihre Entwickelunggeschichte,' 1854, as
probably the young condition of one of the branching Vorticellidae, or rather as an
Acineta-phase, which he at that time believed preceded the perfect ciliated state of
those more highly organized Infusoria. The magnifying power employed by Stein
revealed only the two lateral margins of the transparent collar, which thus resembled
the semi-withdrawn suctorial fascicles of various typical Acineta.

As many as ten zooids are comprised by Stein in the largest colony-stock he
illustrates. The single specimen encountered by the author was obtained from a
pond near South Norwood, London, in June 1877.

Codosiga Steinii, S. K. PL. II. FIG. 20.

Zooids evenly ovate, stationed singly, or during the process of sub-
division in pairs, at the extremities of a slender, dichotomously branching
pedicle or zoodendrium. Length of bodies 1-3000" ; primary, secondary
and succeeding subdivisions of the pedicle mostly equalling about twice the
length of the supported zooids. HAB. — Fresh water.

The above specific title is conferred upon the animalcule figured by Stein in
' Wiegman's Archives,' Taf. ii. fig. 36, 1849, as the probable young of Epistylis
nutans;* these figures indicating, however, by the presence of the setum-like
process on each side of the anterior border, the possession of an imperfectly observed
but characteristic collar. In the illustrations of this form referred to and here repro-
duced, as many as fourteen zooids, in various processes of development, are repre-
sented upon the branching colony. The interspace between the basal attachment
and first division of the pedicle, as also those between its subsequent ramifications,
vary from the same to that of about twice the length of the body of the separate
zooids ; this more extended proportionate distance maintained between the ramifica-
tions of the pedicle readily distinguishes the species from Codosiga furcata, with
which the contour of this structural element most closely coincides.

Codosiga assimilis, S. K. PL. II. FIG. 21.

Zooids few in number, ovate or subpyriform, stationed singly at the
extremities of a branching pedicle, the main rachis of which, equal to
about four times the length of the zooids' bodies, is straight and simple,
dividing then in a dichotomous manner, and forming short ramifications
not exceeding the length of the animalcule's body. Length of these latter
1-1800". HAB. — Fresh water.

This type is likewise figured by Stein, in company with the two preceding forms,
as a probable early condition of Epistylis nutans, the mode of growth of the pedicle,
and proportionately larger size of the animalcules, indicating, however, its specific
distinctness. Pritchard, in reproducing Stein's figure, has proposed to identify it
'.vith the Epistylis (Codosiga) botrytis of Ehrenberg, but the compound ramification
of the distal region of the pedicle demonstrates its non-correspondence with that
simply pedicellate type. In this last named feature the pedicle of Codosiga assimilis
agrees more closely with that of C. grossularia, while the contour of the zooids
nearly resembles that of the marine Codosiga pyriformis. These latter are at the
same time of considerably larger dimensions than those of either of the last-named
varieties.

By accident, the illustration of this species has been included in the index to
PI. II. as a second example of C. Steinii.

* See also Pritchard's 'Infusoria,' pi. xxvii. fig. 22.

GENUS ASTROSIGA— DESMARELLA. 341

GENUS III. ASTROSIGA, S. K.

(Greek, astron, star; siga, silence.)

Animalcules naked, free-swimming, united by their posterior extremities
so as to form compound stellate or subspheroidal clusters ; anterior region
bearing a single long terminal flagellum, whose base is encircled by a well-
developed, extensile and contractile, hyaline collar.

Astrosiga disjuncta, From sp. PL. II. FIGS. 12 AND 13.
Zooids fusiform, tapering posteriorly, and there united to one another
by the attenuated and almost pedicle-like elongations of the body-substance
of this region. Length of zooids i-i 600". HAB. — Freshwater.

The new generic title conferred upon this species has been established by
the author for the reception of the form figured and described by De Fromentel * as
a species of Uvella. In his description, which is most meagre, and also in his
illustration, each unit is represented as bearing three short flagella, which, from their
position and direction, it is evident represent a central flagellate appendage and the
two lateral margins of the hyaline infundibulate collar of a typical collared animalcule,
as seen under inadequate magnification. The figure given by De Fromentel is repro-
duced at PL II. Fig. 12, as also another representation, Fig. 13, slightly enlarged
from this, with the anterior margin of the collar, which escaped that authority's
notice, alone filled in. The example figured represents a stellaeform colony composed
of five zooids only, but doubtless much larger ones exist. Taken collectively, the
colony-stocks of this specific type present a close resemblance to the monad-clusters
of Codosiga botrytis separated from their common footstalk and floating freely in the
water after the manner of the detached monad aggregates or " coenobia " of
Anthophysa vegetans. The more attenuate contour of the constituent monads of
Astrosiga at the same time precludes the inference that might otherwise be arrived
at, that it represents a detached colony of the first-named species.

GENUS IV. DESMARELLA, S.K.

(Dim. of Greek desmos, chain.)

Animalcules naked, free-swimming, forming compound colonies, and
united to one another by their lateral surfaces, without the intermedium of
a pedicle or other supplementary element. Flagellum single, terminal, its
base encircled by a well-developed, extensile and contractile, hyaline
collar.

This and the preceding genus constitute the only free-swimming compound
colony forms of the Choano-Flagellate order as yet discovered, though further
investigation will probably lead to the recognition of as large a number of varieties
as are here shown to obtain among the sedentary species.

Desmarella moniliformis, S. K. PL. II. FIG. 30.

Zooids symmetrically ovoid, arranged in single chain-like series, each
colony-stock containing from two to as many as eight individual units ;
endoplast spherical, subcentral ; contractile vesicles two or more in number,
posteriorly located. Length of individual zooids 1-4000".

HAB. — Salt water.

* 'Etudes sur les Microzoaires,' Paris, 1876.

342 ORDER CHOANO-FLAGELLATA.

Examples of this specific type have been obtained in considerable abundance
both in sea-water from the fish-house at the Zoological Gardens, Regent's Park,
during the month of April 1877, and since then in water from the open sea at St. Heliers,
Jersey. Propelled by the rapid motion of their flagella, the floating colonies of this
species pass through the water with such rapidity that it is difficult to retain them
in the field of view when a high power of the microscope is being used, and it is
only when naturally at rest, or the animalcules become entangled among sur-
rounding substances, that their true structure can be satisfactorily determined. The
mode of growth of this type seems to indicate that the moniliform colony is pro-
duced by the successive longitudinal fission of the primary individuals, though the
process has not yet been directly observed. In the larger colonies the perfect chain
of animalcules usually assumes a rounded crescentic outline. The individual zooids
appear to possess a more indurated cuticular surface than is met with in any other
representative of this group, and up to the present time no trace of a plastic or
amoeboid condition has been detected. The contractile vesicles are, as with the
more ordinary members of this order, posteriorly located. The remarkable resem-
blance that subsists between a colony of this specific form and the portion of a single
segment of the collar-bearing zooids of the " ampullaceous sacs " of certain sponge-
forms will be made apparent on comparing the illustration given of this species with
PL IX. Fig. 2 representing such an isolated fragment of the ampullaceous sac of the
spiculeless sponge Halisarca Dujardinii.

Small colonies of this species, consisting of from two to four laterally united
zooids only, have been quite recently, November 1880, detected by the author in
sea-water, remitted with living Polyzoa by Mr. Thomas Bolton from the Aston
Aquarium, Birmingham.

Desmarella phalanx, Stein sp.

Zooids resembling those of Desmarella moniliformis, forming similar
floating chain-like colonies, but inhabiting fresh water.

This species is figured by Stein* under the designation of Codonodesnms phalanx.
While its fresh-water habitat renders it probable that the form is specifically distinct
from the type last described, there can be no doubt as to their generic identity.
Since, however, the title introduced by the author has been already made use of
in connection with illustrations and textual reference on two occasions prior to
the appearance of Stein's volume, t such previously proposed one necessarily takes
the precedence. In one of the chain-like colony-stocks of the present type, figured
by Stein, no less than eleven zooids are laterally united, while in another, consisting
of eight animalcules, the group is in process of division into two smaller aggregates
of four units each. Stein apparently entertains doubts as to whether this species
represents a permanent and independent stock-form, he having connected with the
generic and specific titles introduced by him a provisional significance only.

Fam. II. SALPINGCECIDJE, S. K.

Animalcules secreting and inhabiting independent or socially united
protective sheaths or loricae, which are either free-floating or attached, in a
sessile manner or through the medium of a distinct pedicle, to aquatic
objects ; flagellum single, terminal, encircled laterally by a well-developed
membranous collar; contractile vesicles usually two or more in number,
posteriorly located ; endoplast subcentral. Inhabiting salt and fresh
water.

* ' Infusionsthiere,' Abth. iii., November 1878.

t ' Popular Science Review,' April 1878, and ' Ann. Nat. Hist.,' August 1878.

GENUS SALPINGCECA.

GENUS I. SALPINGCECA, James-Clark.

343

Animalcules solitary, plastic and variable in form, secreting and
inhabiting a fixed, chitinous, transparent sheath or lorica ; the lorica
either sessile or mounted on a more or less distinctly developed pedicle ;
mostly freely movable within and not attached permanently to the lorica,
but sometimes united to it posteriorly through the intermedium of a
pedicle-like extension of the body-sarcode, or through the medium of several
pseudopodic prolongations ; contractile vesicles conspicuous, two or more in
number. Inhabiting salt and fresh water. Increasing usually by transverse,
rarely by longitudinal fission and by subdivision into spores.

The animalcules of this genus correspond in form and aspect with those of
Codosiga and Monosiga, indicating in the great plasticity of their sarcode, as also in
their isolated mode of growth, their more close affinity with the latter. The
diversely shaped and elegant transparent loricse secreted and inhabited by the
numerous members of the genus Salpingxca, readily distinguish them from those of
the preceding groups. Pursuing that comparison between these lowly organized
types and the higher infusorial forms which has been previously instituted, Salpin-
gceca may be said to exhibit a relationship towards Monosiga analogous to that which
subsists between the loricated genera Cothurnia or Vaginicola and the simple illori-
cate genus Vorticella. Professor James-Clark, who first established the present
generic group, introduced three forms as claimants for admission to it. All of these
have been met with by the author in British waters, while upwards of twenty forms
new to science are here added to them. The process of alimentation in Salpingosca
corresponds exactly with what has been described of Codosiga or Monosiga, there
being no distinct mouth as at first presumed by Professor Clark, but the inceptive
or oral area being common to the whole region enclosed by the membranous collar,
and the ingested food-particles being captured with the assistance of this structure.
Propagation by transverse fission, as in Monosiga, as also by the breaking up of
the body into sporular elements, has been satisfactorily determined in connection
with several specific types.

A. — PEDICLE ABSENT, RUDIMENTARY, OR EXCEPTIONALLY

DEVELOPED.

Salpingceca amphoridium, J.-Clk. PL. V. FIGS. 1-9.

Lorica sessile, flask-shaped, rounded at the base, produced anteriorly
into a long, narrow neck, aperture of the neck slightly everted; con-
tained zooid adapting itself to the shape of the lorica, inflated pos-
teriorly and developed anteriorly into a slender neck-like portion ; con-
tractile vesicles three or four in number, posteriorly located ; endoplast
spherical, subcentral. Length of lorica, including the neck, 1-3350" to
1-2500" ; diameter of the expanded base 1-4000".

HAB. — Fresh water, attached gregariously to Confervae and other
aquatic plants.

Var. a. — Same as the above, but the lorica mounted on a very short and
rudimentary pedicle.

This animalcule appears to be the most abundant and widely distributed repre-
sentative of the collar-bearing Flagellate order so far discovered. First introduced

344 ORDER CHOANO-FLAGELLATA.

to the notice of the scientific world by Professor H. James-Clark,* it has been met
with by the author in incredible numbers coating the filaments of various confervoid
algae and other water plants taken from numerous widely separated localities. A
tolerable idea of the gregarious habits of this Flagellate animalcule, as manifested
under favourable conditions, maybe gained by reference to PL V. Fig. i, representing
the portion only of a colony attached to a single cell of one of the filamentous
algae viewed with a magnifying power of about 600 diameters. The lorica, which
throughout Salpingaea and the three succeeding genera furnishes as a rule the only
safe and reliable means of arriving at a satisfactory diagnosis of the species, is in
this particular instance strongly suggestive of a Florence flask, or the more familiar
caraffe that forms the necessary adjunct of the domestic toilet-table. With these
it likewise vies in its crystalline transparency, which thus freely permits a clear and
uninterrupted view of its living occupant.

The contained zooid itself, whose hardened exudation has built up its crystal
cell, closely corresponds with that of a Codosiga or Monosiga, but exhibits a still
greater amount of plasticity and tendency to alter its shape than has been observed in
either of those two genera. The animalcule, which after secreting its lorica lies entirely
free within it, occupies in its normal condition about one-half of its cavity, as repre-
sented at PI. V. Fig. 2, the film-like collar and flagellate appendage projecting beyond
the distal expansion of the neck of the lorica. It frequently happens, however, that
the sarcode body occupies a considerably larger portion than one-half of the cavity of
its lorica, and it is under these conditions that the animalcule usually exhibits its
most characteristic polymorphic properties. At such times the hyaline collar
disappears, having been altogether withdrawn into the substance of the body ; the
flagellum is soon retracted in a similar manner, and the whole animalcule thus
becomes to all appearance one homogeneous mass of protoplasm. On arriving at
this stage, or even before the absorption of the flagellum, however, this little speck of
sarcode, apparently cramped and confined by the walls of its domicile, has com-
menced to protrude or bubble over, as it were, from the orifice of the lorica, the
sarcode thus projected exhibiting remarkably diverse contours. Figs. 5 to 7 of the
plate representing this species serve to illustrate the more typical modifications that
may be assumed under the above conditions by the extended sarcode. Fig. 5, for
instance, represents a phase in which, the collar being retracted, the flagellum still
remains intact, and projects from a lobe-like extension of the excurrent sarcode. At
Fig. 7 the flagellum is entirely withdrawn, and the mass of protruding sarcode, greatly
increased in bulk, is separated into numerous digitate prolongations, imparting to the
animalcule a general aspect strongly suggestive of an example of the loricated Rhizo-
pod Difflugia, with its pseudopodia extended, and of which genus, had it been only
encountered in this stage, it might have been consistently accepted as a minute species.
Fig. 6 represents a third variety of the many -protean forms assumed by this animal-
cule, and in which the projecting sarcode is split up into innumerable fine divisions
after the manner of the pseudopodia of the genus Gromia. We have in this
instance, probably, a phase exhibiting an abnormal disintegration of the hyaline
collar previous to its complete absorption, and corresponding in kind, though exceeding
it in degree, to that one reported by C. Robin of Codosiga bo fry (is, in which, as already
related, the collar was replaced by four processes resembling setae. The import
of the foregoing singular modification of the sarcode of Salpingceca ainphoridium
does not however culminate in its mimetic resemblance to certain ordinary Rhizo-
pods. There is undoubtedly correlated with this phenomenon one of the most
important phases of the animalcule's reproductive functions. It has indeed been
ascertained by repeated observation on the part of the present author, that the
redundant mass of sarcode extruded from the interior of the lorica under the
various forms described, is ultimately severed from the parent mass, and after a
short lease of liberty reattaches itself and becomes developed into a collared zooid
resembling that from whence it sprang. The parent animalcule, after this budding
or practically transverse fission process, diminished considerably in size, assumes its

* ' Memoirs of the Boston Society of Natural History,' vol. i., 1868.

GENUS SALPINGCECA.

345

pristine contour, and developing a new hyaline collar and flagellum, is not to be dis-
tinguished from the ordinary zooids with which it is associated. That portion of
the sarcode which is extruded and breaks away in the manner just described, is
found in the case of the species now under discussion, to uniformly assume a persis-
tent and highly characteristic shape. This, as shown at PI. V. Figs. 8 and 9, may be
compared to that of a minute, stellate, free-swimming Amoeba corresponding closely
with the type described by Dujardin under the title of Amceba radiosa, but of much
smaller comparative proportions and with shorter pseudopodia. In close proximity
to the larger colonies of this species, minute, floating, stellate, amoeboid zooids,
identical in form with those whose detachment has been actually observed, are
almost invariably met with, these at the same time retaining a marked resem-
blance to the phase assumed by the sarcode when issuing from the lorica as shown
at Fig. 7, allowing for that slight contraction and general pulling together of its sub-
stance which ensue upon its detachment from the parent mass.

Professor James-Clark, in his original account of this species, attributes to it a
distinct oral and anal aperture, lying somewhere near the base of the flagellum.
This interpretation of its alimentary apparatus has, however, as in the case of all
other members of the Choano-Flagellata, to be finitely dismissed. Carmine, when
administered, was intercepted and ingested under circumstances and in a manner
absolutely identical with what has been already described at page 326 of Monosiga
gradlis, while digested particles were observed to pass out in a similar manner
from any part of the area confined by the base of the hyaline collar. Professor
Clark further describes the flagellum as usually assuming a rigid and arcuate deport-
ment ; this aspect, however, is only the optical impression imparted at first sight
through its exceedingly rapid revolution, an explanation which is satisfactorily con-
firmed by introducing carmine and watching the course of the currents produced
in the manner already detailed. The duration of time occupied between the systole
and diastole of each of the three or four conspicuous contractile vesicles situated at
the lower extremity of this animalcule's body, average, in accordance with the
author's observations, from thirty to fifty seconds. The duration of time between
the expansion and contraction of these special vesicles, appears to differ consider-
ably among allied members of the same genus, and furnishes probably a supplementary
character for specific diagnosis.

While inspecting the manuscript note-books kindly placed at the author's disposal
by Mr. Carter, a drawing has been noticed which beyond doubt represents several
examples of a species closely allied to the present one, though, so far as can be judged
from the comparatively low power of magnification employed in their delineation,
the necks of the loricae would appear, proportionately, to be considerably shorter.
The drawing quoted, indicating by the short diverging lines at the apex of each lorica
the presence of the characteristic collar and central flagellum, is with Mr. Carter's
permission reproduced at PL III. Fig. i. Beyond the registration of their having
been obtained from fresh water at Bombay in the year 1855, no written details are
preserved. The Chytridium ampullaceum of Braun * presents a remarkable super-
ficial resemblance in both form and habits of growth to the minute Flagellate type
now under discussion. No trace, however, of the flagellum or collar-like appendage, as
distinctly marked in the preceding instance, is exhibited in the illustrations quoted,
but merely a short conical projection beyond the orifice of the flask-shaped lorica,
somewhat resembling a minute pseudopodic protrusion, but which may at the same
time be the conical operculum of a genuine Chytridium. Stein, in his recently
published volume,! appears inclined to identify the present form with Braun's type,
and at the same time associates with the title of Salpingoeca amphoridium an elongate
form altogether distinct from the one originally figured and described by Professor
H. James-Clark. Upon this more elongate type the author has consequently con-
ferred in this volume the new name of Salpingoeca Steinii. None of the various
polymorphic phases of the present species, as here figured and described, appear
to have been noted by Professor Stein.

* 'Abhl. Berl. Akad.,' Taf. v. figs. 24-26, 1855. f 'Infusionsthiere,' Abth. iii., 1878.

346 ORDER CHOANO-FLAGELLATA.

Examples in which, as at PL V. Fig. 3, the lorica is mounted on a very short or
rudimentary pedicle, are not unfrequently met with among the more ordinary sessile
specimens.

Salpingceca fusiformis, S. K. PL. V. FIGS. 27-31.

Lorica sessile, subfusiform or vase-shaped, widest centrally, tapering
equally towards the two extremities, but expanding again anteriorly into a
somewhat prolonged and everted neck ; contained animalcule flask-shaped,
as in 5. amphoridium, but of larger size. Length of lorica 1-1600".

HAB. — Fresh water, solitary.

The elegant vase-like contour of the lorica of this species readily distinguishes
it from the preceding form. Though tapering gradually to a slender point at the
posterior or proximal extremity, it has not yet been found in any instance to develop
a distinct pedicle, as not unfrequently occurs with Salpingxca amphoridium. It is,
furthermore, much less plentiful than that species, and must be described as of
solitary rather than gregarious habits. The withdrawal of the flagellum and collar,
and the exudation of the sarcode, in a manner parallel to that already described of
S. amphoridium, have been repeatedly observed. One of the more prominent
phases of these protean changes will be found illustrated by Fig. 28 of PI. V.,
in which instance the superabundant sarcode is exuding in the shape of an irregular
lobate process, while in Fig. 27, representing the same zooid as observed fifteen
minutes later, and in which the excurrent sarcode has broken away, the animalcule
has once more assumed its normal shape and condition, the body now filling little
more than half of the cavity of the lorica. Still more recently, April 1877, an
example of multiple fission or breaking up of the parent zooid into spore-like
bodies, preceded by retraction within its lorica and a process of encystment, has
been observed. Fig. 31 represents an interesting phase of this process, in which
the numerous monoflagellate zooids, the result of such a sporular mode of repro-
duction, are issuing from the aperture of the lorica. The pulsations of the contractile
vesicle in this species occur at longer intervals than in S. amphoridium, a period of
from eighty to one hundred seconds being, as so far observed, the average time
occupied between the systole of each individual vesicle.

O. Biitschli* has recently described an animalcule identical with the present
form under the name of Salpingceca Clarki : the present title, bestowed upon it in the
author's communication to the Linnsean Society in June 1877, quoted also in the
'Annals of Natural History' for January 1878, necessarily, however, takes precedence
of this later one.

Salpingceca Steinii, S. K. PL. V. FIGS. 10-12.

Lorica sessile, subfusiform or vase-shaped, about two and a half times
as long as broad, attenuate and pointed posteriorly, tapering towards the
anterior region, but expanding again and forming an everted neck ;
contained zooid flask-shaped, with an inflated basal and attenuate neck-
like portion occupying about one-half of the cavity of the lorica ; con-
tractile vesicles two or more in number, posteriorly located ; endoplast
spherical, subcentral. Length of lorica 1-600".

HAB. — Fresh water, forming gregarious rosette-shaped clusters.

This species, figured by Stein f as synonymous with the Salpingoeca amphoridium
of H. James-Clark, is evidently a perfectly distinct type, whose more elongate lorica

* ' Zeitschrift fur Wissenschaftliche Zoologie,' Bd. xxx., 1878.
t 'Infusionsthiere,' Abth. iii., 1878.

GENUS SALPINGCECA. 347

accords so closely with that of S. fusiformis, previously described, that but for its
marked gregarious habits of growth it would be difficult to distinguish it from that
species. By Stein, it is represented as forming more or less considerable stellate
or rosette-shaped clusters upon the branching pedicle or zoodendrium of the
Peritrichous type Epistylis anastatica ; it has recently been met with by the author
forming similar clusters on the retractile pedicles of Vorticella nebulifera, collected in
the neighbourhood of Acton. The author has much pleasure in associating with
this species the name of its eminent discoverer.

Salpingceca minuta, S. K. PL. III. FIGS. 10-12.

Lorica sessile, ovate or conical, rounded and widest basally, tapering
evenly towards the apical extremity, but not prolonged in a neck-like
manner ; the anterior aperture not everted. Length of lorica 1-4000".

HAB. — Fresh water, attached to the loricae of other flagellate animal-
cules ; solitary or sparsely scattered.

This diminutive type has up to the present time been met with attached only
to the conjoint loricae or polythecium of the minute Flagellate form Dinobryon
sertularia, hereafter described, and under which conditions it has been obtained
in tolerable abundance. On account of its extremely small size, the body within
the lorica frequently not exceeding in length the 6oooth part of an English inch,
a more than ordinarily high power is required for its satisfactory examination.
An interesting process of gemmation similar to that recorded of two former species
has been observed also in this pigmy representative of the genus. At Fig. 12 of
PL III. an example is afforded of a zooid with the sarcode flowing out of the aperture
of the lorica, the flagellum being as yet unretracted, while at Fig. 10, which repre-
sents two animalcules growing upon an empty cell of Dinobryon sertularia, a small
rounded body attached below and indicated by the letter a, is evidently the result
of the budding-oif of one of these zooids, requiring but a brief interval for its
development into the characteristic parent form.

Salpingceca pyxidium, S. K. PL. III. FIG. 16.

Lorica sessile, obovate, attached by the more pointed posterior ex-
tremity, the larger and distal end slightly involute round the edge of the
minute terminal aperture; contained animalcule subglobose, filling the
anterior half of the cavity of the lorica. Length of lorica 1-4000".

HAB. — Fresh water, solitary.

The dimensions of the lorica of this species correspond closely with those of
S. minu/us, in shape it is likewise conical, but the proportions are exactly reversed,
the free end being considerably the larger. The aperture also does not occupy the
whole of the anterior border as in all the species hitherto described, but only a
small central portion, while the margin surrounding it is involute, thus imparting to
the lorica, as seen in optical longitudinal section, a somewhat heart-shaped contour.
A single example only of this species has been so far met with.

Salpingceca amphora, S. K. PL. V. FIG. 13.

Lorica vase-shaped, attenuate posteriorly, having a neck-like con-
striction near the anterior margin, the greatest width being immediately
beneath this region ; no pedicle. Length of lorica 1-2000".

HAB. — Fresh water, solitary.

348 ORDER CHOANO-FLAGELLATA.

In the shape of the lorica this species most nearly resembles the pediculate
marine variety 5. urceolata, delineated in the same plate. The only example yet
found was attached to the carapace of the Entomostracon Diaptomus castor obtained
from a pond on Wandsworth Common in April 1877.

Salpingoeca cylindrica, S. K. PL. VI. FIG. 37.

Lorica sessile, subcylindrical, slightly widest posteriorly, about one and
a half times as long as broad ; contained animalcule elongate-ovate, attached
by its posterior extremity to the bottom of the lorica, its distal end level
with the orifice of this structure. Length of lorica 1-3250".

HAB. — Fresh water, solitary.

The simple subcylindrical lorica of this species agrees most nearly with that
of the marine form Salpingoeca petiolatum, and may be said at the same time to
correspond closely in miniature with that of many of the sessile Peritrichous
Vaginicolce. The only example yet observed was found upon Conferva taken
from a pond near Acton.

Salpingoeca Carter!, S. K. PL. VI. FIG. 39.

Lorica flask-shaped, the neck very attenuate, exceeding in length the
bulbose posterior portion. Total length 1-3000".
HAB. — Fresh water : Bombay (H. J. C).

The above specific name is here introduced for the reception of the form
originally figured and described by Mr. H. J. Carter* under the title merely of a
" Bell-shaped Infusorium." As more recently recognized by him, the affinity of
this variety with the Salpingoeca amphoridium of James-Clark is very close, but the
greater proportional length of the lorica, as shown by comparison of the figures
of the two forms in question, indicates the necessity of conferring upon it a new
specific title. The illustration by Mr. Carter, here reproduced, seems to indicate
that the body of the lorica is joined to the object upon which it grows, through
the medium of a narrowed prolongation of its substance, presenting the aspect of
a peculiarly modified and expanded footstalk. The type-example of this species
was found on Conferva in the fresh-water tanks of Bombay.

Salpingoeca (?) Wallichi, S. K. PL. V. FIGS. 23 AND 24.

Lorica irregularly pyriform or flask-shaped, inflated posteriorly, terminat-
ing anteriorly in a narrow neck, growing upon or immersed within the shell-
substance of Globigerince and other Foraminifera. HAB. — Salt water.

This type was originally described by Dr. Wallichf under the title of "externally
opening pyriform cavities within the shell-substance of Globigerince" It is here intro-
duced as a probable representative of the genus Salpingoeca, with some amount of
diffidence, the living constructor of the pyriform loricae or cavities not having so far
been observed, and the bodies in question having been hitherto regarded by their
discoverer, and also by Dr. Carpenter, J as essential structural elements of the
exogenously developed shell-substance of the organisms with which they are found
associated. As such hypothetical structural elements, they are interpreted on the
one hand by Dr. Carpenter as being produced through the invasion from without

* 'Ann. Nat. Hist.,' vol. viii. p. 9, pi. ii. fig. 42, 1871.

t ' The North Atlantic Seabed,' 1862, and 'Deep Sea Researches on the Biology of Globi-
gerina,' 1876.

\ "On the Nature of the Seabottom procured by H.M.S. Challenger" ' Proc. Roy. Soc '
1875-

GENUS SALPINGCECA. 349

inwards of portions of the normal sarcodic investment of the shell, and by Wallich
as the product of shell-secretion round extruded masses of sarcode. Comparison
of these structures, however, as figured by Dr. Wallich and here reproduced, with
the loricae of various Salpingcecce, such as S. amphoridium or S. minuta, reveals so
remarkable a similarity of outline and correspondence in size, that the conclu-
sion has been arrived at by the author that the two represent similar elements.
Such being the case, it would appear that these loricae are developed upon the
shell-surface of the Foraminifera at an early stage of their growth, becoming, as
this covering thickens, gradually surrounded and immersed within it, much in
the way as certain Mollusca and Cirripedes, e.g. Magilus and Pirgoma, are found
embedded within the hard calcareous sclerobase of madrepores or stony corals.
Should the interpretation of these minute flask-shaped parasitic bodies, as here
suggested, be correct, a further careful investigation may be expected to reveal
their presence attached to and standing out independently from the external surface
of Globigerina in their earlier, thin-shelled, floating state.

Salpingceca petiolata, S. K. PL. III. FIG. 26.

Lorica sessile, subcylindrical, about twice as high as broad, rounded
posteriorly, the oral aperture not everted ; contained zooid cylindrical, its
length equal to about two-thirds of that of the lorica, to the bottom of which
it is affixed by a slender thread-like pedicle. Height of lorica 1-1700".

HAB. — Salt water, solitary or scattered.

This species has been obtained by the author in some quantity at St. Heliers,
Jersey, in sea-water containing Polyzoa and hydroid zoophytes obtained from the
adjacent coast, which had been left standing in open jars for some months. While
the lorica corresponds chiefly with that of the fresh-water S. cylindrica, the contained
animalcule differs essentially in its possession of a slender pedicle. Several examples
were met with in which the zooids had entered upon an encysted condition within
their loricae. All traces of the collar, flagellum, and pedicle had, under these con-
ditions, disappeared, the body being contracted into a simply ovate form within the
furthest recess of its transparent domicile. It will possibly be desirable later on to
establish a new generic title for those species at present retained in the genus
Salpingceca in which the animalcule is affixed, as in the present instance, within its
lorica through the medium of a separate thread-like pedicle.

Salpingceca ampulla, S. K. PL. III. FIGS. 17-21.

Lorica sessile, narrow and ovate beneath, expanding superiorly in an
inflated, balloon-like manner, the external surface frequently exhibiting
even longitudinal sulci or striations ; animalcule, including the hyaline
collar, entirely enclosed within the lorica, and attached to the bottom of this
structure through the intermedium of a slender thread-like pedicle; the
smaller posterior portion of the lorica enveloping the body, and the balloon-
shaped anterior one the expanded collar of the contained animalcule.
Length of lorica 1-1250", of animalcule's body 1-4000".

HAB. — Salt water.

This very beautiful variety is readily distinguished from all other representatives
of the genus Salpingceca hitherto described, both on account of the remarkable shape
of the lorica, and from the fact that the whole of the animalcule, including even
the flagellum and hyaline collar, is completely enclosed within that structure.
This last-named feature, which is shared to some extent by the stalked form
Salpingceca campanula, might in fact be considered as of almost sufficient im-

350 ORDER CHOANO-FLAGELLATA.

portance to warrant the creation, on behalf of this particular type, of a new and
independent generic title. The gradual formation of the very elegant lorica by
the enclosed animalcule, as also the development of the latter from a detached
and simple uniflagellate monadiform gemmule, has been observed and will be
found represented in the several figures illustrative of this species. The primary
condition of this lorica, PL III. Fig. 19, is a mere film-like mucilaginous exudation
from the general surface of the animalcule's body, altogether devoid of that
symmetry of form which subsequently characterizes it. From this immature and
plastic condition it is gradually moulded by the action of the flagellum and collar
into the intermediate condition represented at Fig. 21, and thence by degrees into
the permanent adult shape. Immediately this last stage is attained the lorica at
once hardens, and acquires such a density as to considerably outlast the life of the
animalcule by which it is built up. Loricae left empty through the death of their
original inhabitants, as shown at PI. III. Fig. 18, are of frequent occurrence. The
longitudinal sulci which characterize certain of the adult and vacated loricae are
altogether absent in others, a circumstance which may perhaps be hereafter deemed
sufficient for separating the two as distinct species ; both were, however, so closely
associated with one another that they are for the present regarded as mere varieties.
At Fig. iga of the plate just quoted will be found represented one of the mona-
diform free-swimming germs of Salpingoeca ampulla which has just attached itself
to the half-perfected lorica of a zooid of the same species. Within two minutes
after such attachment it was observed to develop a rudimentary collar and commence
the formation of its protective sheath, as shown at Fig. 20. This type was originally
discovered by the author growing on algae and zoophytes taken from the tanks of
the Manchester Aquarium in May 1874, and has been since found (Feb. 1877)
in considerable abundance, under similar conditions, in sea-water brought from
Brighton.

Salpingceca cornuta, S. K. PL. VI. FIGS. 33-36.

Lorica vaginate or sheath-shaped, elongate, from seven to ten or twelve
times as long as broad, arcuate or flexuose, tapering posteriorly and
gradually widening as it approaches the anterior border, the anterior
margin widest but not conspicuously everted ; animalcule plastic and
variable in form, elongate, subcylindrical or flask-shaped, occupying about
one-fifth of the length of the lorica, often attached to it posteriorly by one
or more filamentous or pseudopodic extensions of the body-sarcode. Length
of lorica 1-400" to 1-300", of the contained animalcule 1-1250".

HAB. — Salt water.

The great proportionate length of the lorica in this type, combined with the
capacity possessed by the enclosed zooid of emitting posteriorly one or more
pseudopodic processes, by which at will it attaches itself to the lateral walls of
the lorica, distinguish it in a marked manner from all of the previously described
representatives of the present genus. PI. VI. Figs. 33 and 36 serve to illustrate
the more important modifications of this abnormal method of attachment. In
the latter of these, Fig. 36, the single attenuate pseudopodal prolongation is so
thread-like and elastic as to present the aspect and possess all the attributes of
a veritable retractile pedicle, permitting the animalcule to extend itself to the
orifice or to withdraw suddenly within the cavity of its transparent domicile,
after the manner of Bicososca or Dinobryon. In the former example, Fig. 33, ex-
amined on the same occasion, the animalcule was found to retain or alter its
position in its lorica through the medium of no less than three of these sarcode
extensions, each of which, however, had a more irregular pseudopodium-like
appearance than in the last variety. In numerous instances, again, zooids
were seen in which no trace whatever of adherent processes could be detected.

GENUS SALPINGCECA. 351

The shape of the lorica, apart from the salt-water habitat, of this type, at once
suffices to distinguish it from Salpingoeca gracilis, which it in some respects slightly
resembles. The investing sheath has never as yet been found perfectly straight as
in that species, but always has one or more graceful curvatures; this, combined
with its evenly increasing diameter, communicates to this structure a contour closely
resembling the graceful curving horns of certain antelopes, and has suggested the
specific title given.

Upon one occasion, Fig. 33, a lorica was found having a bifurcation at its
distal extremity, each of the separate tubular terminations being occupied by a
single zooid. Whether this example was the product through fission of a single
primary individual, or was derived through the attachment of an independent
gemmule to a half-formed lorica, could not at the time be satisfactorily ascertained ;
the former alternative would, however, appear most probable. The animalcules of
Salpingoeca cornuta, while frequently presenting the subcylindrical shape most
characteristic of S. gracilis, is subject, through the great plasticity of its substance,
to a very extensive range of variation. Not unfrequently it assumes that soda-water-
bottle or clavate shape, with an attenuate anterior extremity, characteristic of various
other members of the same generic group, while on other occasions again (Fig. 35)
it has been observed with these proportions exactly reversed, the posterior end
being the narrower one of the two, and the characteristic collar and flagellum being
developed from the larger one. Examples of this species were first obtained growing
on Polyzoa and hydroid zoophytes gathered at Bognor, Sussex, in September 1872,
as also more recently (October 1875) from the tanks of the Manchester Aquarium.

Salpingceca tuba, S. K. PL. VI. FIG. 38.

Lorica sessile, subcylindrical, rounded posteriorly, slightly constricted
anteriorly, the frontal margin somewhat everted; enclosed animalcules mostly
flask-shaped, with a rounded and inflated posterior and narrower neck-like
anterior region, occupying one-half or the greater portion of the cavity of
the lorica ; sometimes subcylindrical and attached by their posterior extre-
mities to the bottom of this structure ; collar largely developed, equalling
the body in height. Length of bodies 1-4000" to 1-2000".

HAB. — Salt water, social.

This species was obtained by the author in September 1879, attached in social
clusters to zoophytes and marine Conferva collected at St. Heliers, Jersey. But for
its smaller size and salt-water habitat it might have been identified with the sessile
variety of Salpingoeca gracilis represented at PI. VI. Fig. 32. Additional points may,
however, be cited that seem to indicate its distinctness from that form. The con-
tained animalcules always occupy at least one-half of the cavity of their respective
loricae, and not uncommonly its entire length, being under such conditions
attached by their posterior extremities to the bottom of their domiciles, as indicated
in the example to the extreme left in the group shown at Fig. 38. When freely
suspended within their loricae they almost invariably assume an attenuate flask-
shaped contour, corresponding closely with that frequently exhibited by Salpingoeca
cornuta, but never presented by S. gracilis.

Salpingceca gracilis, J.-Clk. PL. VI. FIGS. 25-32.

Lorica elongate, vaginate or subcylindrical, straight, five or six times
as long as broad, sometimes rounded, in other instances more or less
attenuate or even pedunculate posteriorly, the anterior margin slightly
everted, somewhat constricted beneath this region ; contained animalcule
subcylindrical elongate, occupying from one-fourth to one-third of the total

352 ORDER CHOANO-FLAGELLATA.

length of the lorica; contractile vesicles two in number, posteriorly
situated. Length of lorica 1-800" to 1-500", of body of contained
animalcule 1-2000" to i-iooo".

HAD. — Fresh water, occurring singly or in small groups of three or four
individuals.

The figures illustrating this species, contributed by Prof. H. James-Clark to the
Memoirs of the Boston Society of Natural History for the year 1868, convey but an
inadequate idea of the very considerable variation in contour that may be assumed by
the protective lorica, he in all instances delineating and describing that form in which
the posterior extremity is so attenuate as to constitute a veritable pedicle, as shown
at PI. VI. Figs. 26 and 27. Although frequently met with in the condition that
has been alone encountered by the American authority, the examination of many
hundred examples by the present author has elicited the fact that in at least British
waters this very attenuated form is more exceptional, the majority tapering but
moderately as in the example represented at Fig. 28 of PL VI. or being evenly
rounded in this region as at Fig. 32. This species, in common with S. amphoridium,
appears to be almost universally distributed, examples having been found attached
mostly to confervoid algae, obtained from numerous widely separated stations, some-
times occurring as solitary samples, and in other instances in little closely approxi-
mated clusters of three or four individuals, as in the figure last referred to. These
social groups are the product by repeated transverse fission or gemmation of
a single primary zooid in the manner indicated in Figs. 28 and 29, and as more
fully described in connection with the marine type Salpingceca inquillata. The
motile zooid or germ derived from this fissive process presents, in the first instance,
a simple monadiform aspect, as shown at Fig. 30, and fastening itself close to the
base of the parent lorica, speedily acquires all the essential characters of the adult
organism. Encysted examples exhibiting a more or less advanced stage of segmen-
tation, as shown at Fig. 31, are of frequent occurrence. Stein, in his recently
published volume, connects with the present title examples only having a distinct
peduncular posterior prolongation ; the intermediate variety, as reproduced from his
work at Fig. 24, being distinguished by the title of Salpingceca vaginicola.

B. — PEDICLE PERSISTENT, CONSPICUOUSLY DEVELOPED.
Salpingceca marina, J.-Clk. PL. III. FIGS. 13-15, AND PL. V. FIG. 34.

Lorica ovate, inflated and widest posteriorly, tapering evenly towards
the aperture at the opposite or anterior extremity, mounted on a straight
or irregularly curved pedicle, which equals or slightly exceeds the lorica in
height ; animalcule adapting itself to the shape of the lorica, and almost
filling it. Length of lorica 1-4000" to 1-3250".

HAB. — Salt water, attached to the hydrothecae of Sertularian zoophytes,
solitary.

In Salpingaca amphoridium and S. grarilis the occasional or more abnormal
occurrence of a very short or more or less conspicuously developed pedicle, has
been already alluded to ; with S. marina, however, we arrive at a group of forms
in which a pedicle is constantly present, and usually of considerable length. But
for this feature being inconstant in the two above-named species, it might have
been desirable to create a new generic title, for either the pedicellate or non-
pedicellate series, equivalent in value to Cothurnia and Vaginicola among the
higher Ciliate types. These exceptional instances, however, serve well to illustrate
the unreliability of such characters for the purposes of classification. The specimens
of Salpingoeca marina as first described and figured by Prof. H. James-Clark, agree
in all respects with those obtained by the author in British waters, with the

GENUS SALPINGCECA. 353

exception that in the former instance the pedicle possesses a more or less curved
outline, while in those personally observed, this structure has been invariably per-
fectly straight ; the shape and size of the lorica and all other details of importance
accord, however, so harmoniously, that the two forms can scarcely be regarded
otherwise than as local varieties of one and the same specific type. The lorica
itself very closely approaches in shape that of the fresh-water and non-pedicellate
species Salpingceca minuta, being like that, conical, or as Professor Clark sug-
gests, resembling a Florence-flask with the neck cut short. The examples of this
species examined were found in some profusion, in the first instance, attached
to various Sertularian zoophytes gathered near low-water mark at Bognor, Sussex,
and more recently under similar circumstances at St. Heliers, Jersey. An animal-
cule is represented at PI. V. Fig. 34, in which the collar and flagellum being
retracted, pseudopodic processes are extended from the anterior region in a manner
closely resembling what has already been recorded of S. amphoridiwn. An early
developmental phase previous to the production of the lorica, and in which the
zooid is not to be distinguished from an ordinary stalked example of the genus
Monosiga, is represented at PL III. Fig. 13.

Salpingceca longipes, S. K. PL. VI. FIG. 7.

Lorica ovate, truncate at the anterior border, slightly tapering pos-
teriorly, mounted on a long, straight, slender pedicle, which equals four
or five times its length ; contained animalcule shortly ovate, occupying
the anterior two-thirds of the cavity of the lorica. Length of lorica
1-2500". HAB. — Salt water, solitary or in scattered groups.

The great length of the pedicle compared with the lorica, and the very simple
contour of this latter structure, render this species easy of recognition. The con-
tained animalcule, adapting itself to the shape of the lorica, is almost globular, and
devoid of that narrow anterior prolongation pertaining to the more ordinary repre-
sentatives of the genus, and which conveys to them a bottle-like contour. Examples
furnishing the material for this description were discovered by the author, in November
1873, attached to Conferva and Polyzoa growing in the Brighton Aquarium.

Salpingceca urceolata, S. K. PL. V. FIGS. 14-16.

Lorica urceolate, conical, gradually tapering towards its junction with
the pedicle, inflated in a shoulder-like manner anteriorly, and then suddenly
constricted and forming a short and somewhat contractile neck ; contained
zooid flask-shaped, inflated posteriorly, with a narrow neck-like anterior
portion ; pedicle straight and rigid, equal to or slightly exceeding the lorica
in height. Length of lorica 1-2000". HAB. — Salt water, solitary.

This species was obtained by the author in company with S. marina, but in
less abundance, at Bognor, Sussex, in September 1872 ; the elegant pitcher-like
shape of the lorica at once distinguishes it from the preceding or any other stalked
representative of the genus that has been discovered, with the exception, perhaps,
of S. ringens. From this latter form, however, it differs in the greater narrowness of
the neck-like region, which is further remarkable for its elasticity, expanding and
contracting considerably in accordance with the movements of the animalcule. In
the deserted loricae, which were frequently observed, the contraction, as shown at
PL V. Fig. 1 6, attains its utmost limit.

Salpingceca teres, S. K.

Lorica attenuate, conical or subfusiform, widest anteriorly, about four
times as long as broad ; pedicle straight, slightly exceeding the lorica in

2 A

354 ORDER CHOANO-FLAGELLATA.

length ; enclosed animalcule elongate-ovate, occupying one-half of the
cavity of lorica. Length of lorica 1-2500". HAB. — Salt water, solitary.

A single example only of this species has as yet been met with, being then
obtained in company with 6". inquillata and S. curvipes on zoophytes originally
brought from Brighton. Excepting for its smaller size, the lorica in its form and
proportions corresponds so closely with that of the long-stalked variety of the fresh-
water Salpingaca gracilis, as delineated at PI. VI. Fig. 27, that its separate
illustration has been omitted.

Salpingceca tintinnabulum, S. K. PL. V. FIGS. 21 AND 22.

Lorica bell- or cup-shaped, somewhat variable in its proportions, widest
and everted at its anterior margin, the width usually nearly equal to
the total length ; pedicle varying from a less length to twice the length of
the lorica ; contained animalcule pyriform, tapering posteriorly, attached
to the bottom of its lorica by an attenuate prolongation of the body-
substance. Length of the lorica 1-3250".

HAB. — Salt water, solitary.

This animalcule was obtained somewhat abundantly from sea-water derived from
the Brighton Aquarium, containing sponges and Ascidians in a semi-decayed state.
The variable length of the rigid pedicle forms a conspicuous feature of this species.
At PI. V. Fig. 22 the encysted condition of an example of the short-stalked variety
is represented.

Salpingceca ringens, S. K. PL. V. FIGS. 17 AND 18.

Lorica tapering posteriorly, one and a half times as long as broad,
ovate for the two-thirds forming its central and posterior portions, the
anterior third expanding outwards abruptly, the greatest width being
at the front margin. Pedicle straight, equal in length to the lorica ;
enclosed animalcule flask-shaped, attenuate anteriorly. Length of lorica
1-2000". HAB. — Salt water, solitary.

The lorica of this species presents a certain resemblance to that of both
S. inquillata and 6". urceolata. From the latter of these it may, however, be at once
distinguished by the greater breadth and abrupt widening out of its anterior border,
and by the non-contractility of the walls of this region ; a similar widening out of
the anterior region, together with the shorter and broader proportions of the lorica,
generally distinguishing it in a like manner from S. inquillata ; added to this, the
enclosed animalcule in the present instance is altogether distinct in shape, being in
its normal condition flask-shaped or pyriform, instead of simply ovate. A perfectly
quiescent or encysted condition of the animalcule, probably pending the propagation
of the species by multiple fission, after the manner already described of Salpingceca
fusiformis, was observed, and is represented at PL V. Fig. 18. This variety was
found attached to sea-weed imported to the fish-house of the Zoological Gardens
from Weymouth in April 1877.

Salpingoeca inquillata, S. K. PL. VI. FIGS. 1-6.

Lorica elongate-ovate, tapering posteriorly, widest in the centre, slightly
everted at the anterior margin, about twice as long as broad ; contained
animalcule simply ovate, occupying about one-half of the cavity of the

GENUS SALPINGCECA. 355

lorica ; pedicle straight and rigid, equalling or exceeding the length of the
lorica. Length of lorica 1-2500".

HAB. — Salt water, solitary or scattered.

This little animalcule was obtained abundantly in February 1877 in sea- water
from Brighton in company with S. curvipes, with which the shape of its lorica
somewhat corresponds. It is at once to be distinguished from that form, however,
by the much greater length of the pedicle and by the entire absence of the curvature
of either this element or the posterior extremity of the lorica. The shape of the
anterior extremity of the protective sheath is subject to individual variation, being
often so narrowed as to communicate to the whole a subfusiform contour. The
phenomena of multiplication by transverse fission, as observed by the author, possess
much interest. The most prominent successive phases of this process are illustrated
at PI. VI. Figs. 2-5. In the first condition observed, as represented by Fig. 5, the
body of the animalcule had become divided by a median constriction into two equal
subspherical portions, the upper one still retaining the characteristic hyaline collar
and flagellum, tilted, however, to one side, while from the anterior surface of the
posterior segment there was projected a slender pseudopodic extension of the
sarcode. In the next stage, Fig. 2, the filamentous flagellum of the anterior half
was the only appendage visible, the collar having become entirely absorbed. This
flagellum was shortly after withdrawn in a similar manner, the succeeding meta-
morphosis exhibited being delineated at Fig. 4. Here the anterior and posterior
halves had separated considerably from one another, but at the same time remained
connected by a thin cylindrical film of sarcode, which constituted for the time being
a representation of the hyaline collar, but common to both of the imperfectly seg-
mented moieties. Ultimately the lower or posterior half assumed the entire possession
of the newly developed hyaline collar, while the anterior one, detaching itself
completely, drifted away as a simple plastic sphere of sarcode. The last stage,
prior to the ultimate separation of the two halves, is shown at Fig. 3. A recently
attached collarless zooid, derived by the process of segmentation as just described,
and in the act of constructing, by exudation, its characteristic lorica, is seen
at PI. VI. Fig. 6.

Salpingoeca curvipes, S. K. PL. V. FIG. 19.

Lorica somewhat attenuate, nearly three times as long as broad, widest
in the centre and at the expanded anterior margin, slightly constricted
between these two areas, the tapering posterior extremity slightly curved ;
pedicle short, not more than half the length of the lorica, joining in the
line of curvature characteristic of the posterior extremity of that structure ;
contained animalcule ovate, occupying one-half of the cavity of the lorica.
Length of lorica 1-2500".

HAB. — Salt water, solitary.

The protective sheath of this very elegant little species is easily recognized by its
elongate outline and the graceful curve shared by both the short pedicle and its own
posterior extremity. It has been found sparingly in company with many other
representatives of the same order attached to the hydrothecae of Sertularian and
other zoophytes procured from Brighton.

Salpingoeca napiformls, S. K. PL. V. FIGS. 25 AND 26.

Lorica napiform or turbinate, depressed, widest centrally, pointed
posteriorly and further produced as a short, rigid pedicle, the anterior region
constricted, forming a narrow and slightly everted neck ; contained animal-

2 A 2

356 ORDER CHOANO-FLAGELLATA.

cule flask-shaped, flattened, occupying the greater portion of the cavity of
the lorica. Height of lorica, without the pedicle, 1-3250", diameter across
the centre equal to or exceeding this dimension.
HAD. — Salt water, gregarious.

This species was obtained by the author at St. Heliers, Jersey, in June 1877,
clustered in profusion upon various filamentous marine algae under conditions closely
parallel with those already related of the more cosmopolitan fresh-water type,
Salpingceca amphoridium. The depressed napiform contour of the lorica of this
species isolates it completely from any of the preceding forms.

Salpingceca infusionum, S. K. PL. VI. FIGS. 8-16.

Lorica simply ovate, not everted anteriorly, about one and a half times
as long as broad, mounted on a short, straight pedicle, varying from a
similar length to twice the length of the lorica ; contained animalcule
evenly ovate, occupying from one-half to two-thirds of the cavity of the
lorica. Length of lorica, without pedicle, 1-3000" to 1-2500".

HAB. — Salt water, more especially abundant in vegetable infusions
compounded with that medium ; solitary or scattered.

This species has been obtained by the author in remarkable profusion in
connection with those experimental infusions of hay in salt water, productive of
Monas (Heteromita) lens, Dinomonas vorax, Dinomonas tuberculata, and Sterro-
monas formicina, described elsewhere in this volume. Its earliest appearance,
and then in a larval and immature form, was first noticed on the fourth day
succeeding the setting aside of the hay to macerate, while after that date it con-
stituted for some weeks one of the most characteristic and abundant Flagellate
types. Through the artificial cultivation of this animalcule in the manner indi-
cated, an intimate acquaintance has been made with the more important and
highly interesting phases of its life-history. The earliest stage in this life-cycle,
in common with that of the majority, or in all probability of all its congeners, is a
simple, spherical, spore-like body measuring, in this case, the i-io,oooth of an inch in
diameter; from this spore there is developed a minute spherical monadiform body
bearing a single lash-like flagellum at its apical pole. This monadiform germ speedily
assumes a symmetrically ovate shape, and as it pursues its nomadic course through
the water might be readily regarded as a typical representative of the genus Monas.
Delineations of such earlier migratory developmental phases of this species are given
at PI. VI. Figs. 10 and 16, the germ in the former instance, while precisely similar in
character, being derived from the process of transverse fission. A little later this vagrant
monad, finding a site suited to the requirements of its adult sedentary existence,
anchors itself by its posterior extremity, and speedily develops from this region a
delicate hair-like pedicle, as shown at Fig. n. There is as yet no appearance of
the characteristic collar, the stalked monad with its single terminal flagellum pre-
senting at this epoch of its ontogeny a striking likeness to the sedentary states of the
representatives of the genus Oikomonas. While under examination the missing
collar gradually makes its appearance as a film-like extension of the anterior
substance of the sarcode, while the pedicle, at first short, gradually lengthens and
acquires a rigid consistence. The animalcule, however, see Figs. 12 and 13, by no
means possesses as yet a sound claim for admission into the present generic group.
The external protective sheath or lorica remains to be developed, and pending the
production of that structure, the immature monad corresponds to all appearances
with the members of the illoricate collar-bearing genus Monosiga. A few brief
minutes suffice now, however, for the development of this last-named essential
element, and with it the assumption by the animalcule of its complete specific
features as described in the introductory diagnosis, and depicted at Fig. 8.

GENUS SALPINGCECA. 357

The successive phases of the life-history of this species as here enumerated, and
fully illustrated in the accompanying plate, show that, inclusive of the mature con-
dition, the animalcule exhibits consecutively the characteristics of no less than four
well-defined generic types of the Infusoria-Flagellata, commencing with the most
simple type of all, as furnished by the genus Monas, and passing thence through
those of Oikomonas and Monosiga to its characteristic adult one of Salpingceca. The
completion of the entire life-cycle by the encystment of the adult animalcule, followed
by its resolution into numerous spore-like bodies, Fig. 15, similar to that from
which it originally sprang, was ultimately observed. The contour of the lorica of
Salpingoeca infusionum corresponds most nearly with that of S. longipes, its propor-
tionately shorter pedicle, however, readily distinguishing it from that type.

Salpingoeca campanula, S. K. PL. IV. FIG. n.

Lorica goblet- or bell-shaped, scarcely longer than broad, the basal region
narrower, conically pointed, the anterior two-thirds expanding abruptly
and in a marked manner in comparison with the first-named area, the
anterior border widest, but not everted ; pedicle equalling the length of the
lorica ; contained zooid symmetrically ovate, occupying and projecting
slightly beyond the conical basal area ; the fully expanded collar enclosed
entirely within the wider anterior area of the cavity of the lorica, the
flagellum extending for about half its length beyond its anterior border ;
contractile vesicles two in number, posteriorly located ; endoplast spherical,
subcentral. Length of lorica 1-800". HAB. — Salt water, solitary.

The single example of this specific type so far observed was discovered by the
author attached to the carapace of an amphipodous crustacean allied to Gammarus,
at St. Hellers, Jersey, in February 1878. The form of the lorica coincides con-
siderably with that of the Codonceca costata of Professor Clark, and also, omitting the
pedicle, to a certain extent with that of Salpingceca ampulla, previously described, as
manifested by the complete enclosure of both the body of the zooid and its character-
istic collar within the cavity of the lorica, and by the adaptation of this last-named
element to the contours of these conjoint structures.

Salpingceca convallaria, Stein. PL. IV. FIGS. 13-16.

Lorica vase-shaped or campanulate, pointed posteriorly, inflated and
widest a little behind the median line, slightly constricted anteriorly,
scarcely one and a half times as long as broad ; pedicle very slender,
usually about one-third of the height of the lorica ; animalcule filling the
greater portion of the cavity of the lorica, the collar equalling the body in
height, protruding almost entirely from the orifice of the lorica ; contractile
vesicles multiple, posteriorly situated ; endoplast anterior, subcentral.
Length of lorica 1-1600" to i-iooo".

HAB. — Fresh water, attached to the branching pedicle of Epistylis
digitalis.

The walls of the lorica in this species are described by Stein in his index to the
figures given,* as being remarkably soft and plastic. Excepting for the thick pedicle
and more constricted anterior border, it would appear to closely resemble the minute

' Infusionsthiere,' Abth. iii., 1878.

358 ORDER CHOANO-FLAGELLATA.

imperfectly observed Flagellate organisms recorded by Greeff as adhering in numbers
to the pedicle of Epistylis flavicans, and reproduced from his drawings at PI. III.
Figs. 22-24. According to Stein, this type multiplies within its lorica by longitudinal
instead of transverse fission, a phenomenon distinctly observed as yet of no other
representative of the genus.

Salpingceca oblonga, Stein. PL. VI. FIGS. 20-23.

Lorica pedicellate, elongate-ovate or subfusiform, widest a little behind
the median line, tapering gradually towards each extremity, nearly two
and a half times as long as broad ; pedicle varying in length from one
half to nearly twice the length of the lorica ; animalcule usually occupying
the two anterior thirds of the cavity of the lorica, leaving the posterior
one vacant ; collar equalling the body in height ; contractile vesicles
multiple, posteriorly situated ; endoplast anteriorly located. Length of
lorica 1-1200" to 1-950". HAB.— Fresh water.

In some of the examples figured by Stein,* including the delineation reproduced
at PI. VI. Fig. 23, the animalcules have apparently entered into a spheroidal encysted
state within the cavity of their lorica, the orifice of the same being closed by a lid-
like secretion. In another instance (see Fig. 22) two zooids are drawn, which
are explained by Stein in the index as illustrating an abnormal instance of longi-
tudinal fission, but which would seem quite as probably to represent the process of
fusion or genetic union between a larger sedentary and a smaller illoricate motile
zooid, or even an advanced phase of transverse fission closely resembling that of
Salpingceca inquillata shown at PI. VI. Fig. 5.

Salpingceca Clarkii, Stein. PL. VI. FIGS. 17-19.

Lorica elongate flask-shaped, from two to three times as long as
broad, slightly inflated and rounded posteriorly, tapering gradually
towards the anterior extremity, terminating in an attenuate, scarcely
everted neck ; pedicle straight, moderately stout, usually equalling the
lorica in length; animalcule nearly or entirely filling the cavity of the
lorica ; contractile vesicles multiple, posteriorly situated ; endoplast sub-
central. Length of lorica 1-1200".

HAB. — Fresh water, attached gregariously to the carapace of the rotifer
Philodina hirsuta Ehr.

In conferring the above title upon this form, Stein t appears to have overlooked
the fact that the same name had been previously proposed by Biitschli for a distinct
species of the same genus. As, however, Biitschli's type has been shown to corre-
spond with the Salpingceca fusiformis still earlier described by the author, Stein's
title, to avoid a further change of name, is in the present instance, though somewhat
irregularly, retained. In the chief figure of this species given by Stein no less than
forty individuals are represented crowded upon the projecting snout of the above-
named rotifer. One example among the isolated individuals he delineates has
withdrawn its collar and protruded its sarcode beyond the orifice of the lorica in
a bubble-like manner, while in another instance a thread-like pedicle connects the
body of the animalcule with the bottom of its protective sheath. Both of these
more abnormal cases are reproduced at PL VI. Figs. 18 and 19.

1 Infusionsthiere,' Abth. iii., 1878. f Ibid.

GENUS LAGENOECA. 359

Salpingoeca Boltoni, S. K.

Lorica pedunculate, elongate-conical, the anterior border widest, slightly
everted, tapering and acuminately pointed posteriorly, from two to two
and a half times as long as broad ; pedicle straight and slender, equalling
or exceeding twice the length of the lorica ; enclosed animalcule symme-
trically ovate or subcylindrical, occupying one-half of the cavity of the
lorica, sometimes affixed to it by a thread-like prolongation of the posterior
region of the body. Length of lorica 1-1250", of contained zooid 1-2500".

HAB. — Fresh water, solitary.

This species represents the first-fruits of the more extended acquaintanceship
with this interesting order of the Flagellata acquired through the publication of
the plates illustrative of all the previously known forms, in the first part of this
Manual, in October 1880. Its discovery is due to Mr. Thomas Bolton, who having
detected it attached to Myriophyllum from his aquaria, failed to identify it precisely
with any of the species figured in Plates II. to X. of this treatise, and remitted
examples to the author. So far as the external contour of the lorica, and the pro-
portionate length of the supporting pedicle are concerned, it most nearly resembles
the marine Salpingoeca inquillata, represented at PI. VI. Figs. 1-6. Apart from its
fresh-water habitat, it may be distinguished from that type, however, by its con-
siderably larger size and the greater proportionate length of the pedicle, which is
surpassed by that alone of ,5. longipes,

A few weeks previous to Mr. Bolton's independent discovery of this species
(September 1880) the author met with examples undoubtedly referable to the same
type on vegetable debris derived from the Victoria regia tank in Kew Gardens, and
it has since propagated abundantly in a window aquarium containing Aponogeton,
Myriophyllum, Ceratophyllum, and other aquatic plants in a vigorous state of growth.
On one occasion an example was observed in which the animalcule was attached to
the side of its lorica by a contractile thread-like prolongation of the sarcode of its
posterior region, in a manner resembling that already described of Salpingoeca cornu-
tum. A rough delineation of this species is contained, at letter c, in the pen-and-
ink sketch executed by the author for Mr. Bolton, included in his advertisement
to subscribers bound up with Part II. of the Manual, published in November 1880,
this sketch being further reproduced as a lithographic plate in Part I. of the ' Northern
Microscopist,' announced for January 1881. No fitter illustration of the abundant
distribution of the Flagellate Infusoria can perhaps be cited than the drawing just
referred to, in which no less than three varieties of collared monads and two
sedentary Pantostomatous species are, as observed by the author, grouped upon a
small portion of a leaflet of Myriophyllum spicatum.

GENUS II. LAGENCECA, S. K.

(Greek, lagenos, flask ; oikeo, to inhabit.)

Solitary, collar-bearing, flagellate animalcules, resembling those of
Salpingoeca, but secreting and inhabiting a freely detached protective sheath
or lorica.

The members of this genus, of which but a single species has as yet been dis-
covered, may be said to occupy that position with reference to the more ordinary
stationary Choanophorous Flagellata that is held by the higher Ciliata Dictyocysta or
Tintinnus with relation to the sedentary representatives of the primary groups to
which they respectively belong.

360 ORDER CHOANO-FLAGELLATA.

Lagenoeca cuspidata, S. K. PL. III. FIG. 25.

Lorica amber-coloured, flask-shaped, compressed, widest posteriorly and
there ornamented with one long axial and four shorter, subequal and
evenly disposed, peripheral, mucronate spines ; contained animalcule flask-
shaped, inflated posteriorly, produced anteriorly in a neck-like manner,
protruding some little distance beyond the orifice of the lorica, filling
posteriorly the greater portion of the cavity of this structure. Length of
lorica 1-4000". HAB. — Pond water.

The single example of this species hitherto encountered was discovered by the
author in December 1871 in pond water containing Codosiga botrytis, Salpingaca
amphoridium, and Bicosoeca lacustris. The contained zooid, apart from its lorica,
was indistinguishable both in form and size from that of Salpingceca amphoridium,
the anterior, and in this case protruding, collar-bearing region being in the same
way narrowly prolonged in a neck-like form, although there was in this instance
no corresponding conformity in the shape of the lorica. This assumption of a
clavate or flask-shaped outline in the zooid independent of a similar one in the
contour of the lorica, appears to be of common occurrence among the members of
the Salpingoecidae. The lorica itself was of a pale amber colour and ornamented at its
base with five sharply pointed projecting spines, conveying to the observer an aspect
remarkably suggestive of one of the many varieties of flask-shaped shells distinctive
of the genus Lagena among the Foraminifera. Although so scantily represented
in the present treatise, it is highly probable that a more extended investigation will
demonstrate a greatly varied and extensive distribution of free-swimming loricate
types referable to this generic group.

GENUS III. POLYCECA, S. K.

(Greek, polys, many; oikeo, to in \ bit.)

Collar-bearing, flagellate, loricate animalcules, similar to those of Salpin-
gceca, but forming by the serial conjunction of their respective loricae a more
or less extensive branching colony-stock or polythecium.

This genus bears the same relation to Salpingceca that Codosiga does to Monosiga,
being the compound expression through the continued fission without complete
separation of the preceding simpler types. Only one species, an inhabitant of salt
water, has been so far discovered.

Polyoeca dichotoma, S. K. PL. III. FIGS. 27, 28, AND PL. V. FIG. 20.

Loricae of polythecium urceolate, pedicellate, tapering posteriorly, slightly
constricted at a distance of one-third of the total length from the anterior
margin, and then widening out to their greatest diameter ; pedicles of each
separate lorica straight, slender, varying from the same to two or three times
the length of the latter structure ; contained animalcules ovate, occupying
respectively about one-half of the cavities of the loricae ; contour of poly-
thecium subdichotomous, each zooid usually giving rise by transverse fission
to two new ones which attach themselves to opposite sides of the parent
lorica. Length of separate lorica 1-2500". HAB. — Saltwater.

The compound polythecium of this very elegant and as yet single known represen-
tative of the genus Polyoeca may be most aptly compared to a number of zooids of

GENUS PHALANSTERIUM. 361

Salpingceca inquillata, whose loricse are united to one another in systematic order
through the medium of their respective pedicles. As shown in the accompanying
figures, the more general dichotomous mode of gemmation in this species admits of
some slight modifications. Thus at PI. III. Fig. 28, the colony, after starting on
the typical plan, is continued on each side in a uniserial order, while at Fig. 20 of
Plate V., representing the largest colony of this species as yet met with, the right-
hand resultant of the primary zooid gives origin to no less than two individuals at
each anterior angle. Each of these, however, as is evident from the simple structure
of the pedicle in its proximal region, commenced as single animalcules, these, at a
short distance from the parent, dividing a second time by longitudinal fission.

This highly interesting form was found attached to the hydroid zoophytes and
Polyzoa obtained in May 1874 from the Crystal Palace Aquarium. As with various
other types described in this manual derived from the tanks of large public aquaria,
it is impossible to predicate from what portion of the coast-line it was originally
imported. The correspondence of the polythecium of this species, with reference both
to its general mode of growth and to the contour of the individual loricae, with that
of the biflagellate fresh-water type Stylobryon (Poteriodendroti) petiolatum is worthy of
remark.

Fam. III. PHALANSTERIID^J, S. K.

Animalcules solitary or social, more or less ovate, bearing a single
terminal flagellum, the base of which is encircled by a rudimentary and per-
manently contracted, or by a well-developed and widely extensile mem-
branous collar ; excreting and inhabiting a simple or complex mucilaginous
protective sheath or zoocytium.

Compared with the preceding Choano-Flagellata, the members of this family
group may be said to maintain a relationship corresponding with that which sub-
sists between the Peritrichous genus Ophrydium, and such typical Vorticellidae as
Vorticella, Epistylis, and Vaginicola. At the same time, the new investing element
or zoocytium now introduced is undoubtedly both morphologically and physiologically
identical with the common mucilaginous matrix or cytoblastema which enters so
largely into the composition of all sponge structures, and which is similarly excreted
and inhabited by colony-stocks of corresponding collared flagellate monads. By
this family group of the Phalanstcriidtz the two sections of the Discostomata-
Gymnozoida or naked collared monads, and the Discostomata-Sarcocrypta or slime-
immersed collared monads as represented by the Spongida, are beyond question
effectually bridged.

GENUS I. PHALANSTERIUM, Cienkowski.

Animalcules normally symmetrically ovate but more or less plastic and
variable in form, bearing a single terminal flagellum, whose base is enclosed
by a conical, non-extensile, hyaline collar ; endoplast and one or more con-
tractile vesicles usually conspicuous ; producing extensive colonies through
multiplication within a variously modified common gelatinous matrix or
zoocytium ; the flagella only projecting beyond the zoocytium into the
outer water.

As originally founded by Cienkowski,* the genus Phalansterium was made to
include two entirely distinct flagellate forms, one of which, P. intestinum, possessing
two flagelliform appendages, has been selected by Stein as the type of the previously

1 Archiv fiir Mikroskopische Anatomic,' Bd. vi., 1870.

362 ORDER CHOANO-FLAGELLATA.

described genus Spongomonas. The single species left out of these two, to which
another is now added by Stein, was recognized by Cienkowski as exhibiting a
peculiar beak-like modification of the anterior region, into which the base of the
single flagellum is inserted. Professor James-Clark was the first to indicate the
probable homology of this beak-like prominence with the collar-like organ dis-
covered by him in connection with the two generic forms Codosiga and Salpingceca,
his inference being entirely substantiated by Stein's later illustrations. As shown in
the figures reproduced from this authority, the collar-like organ or its homologue in
the present genus, so far as observed, never exhibits that expanded funnel-shaped
contour which is seen in all the Choano-Flagellata previously described, but exhibits
rather that conical form with a wider basal or proximal, and narrower contracted
distal region, that characterizes them in their retracted state. Whether or not a cir-
culating current or cyclosis of the sarcode substance of this reduced and rudimentary
form of collar developed in Phalansterium, is maintained, remains to be demon-
strated.

As first pointed out by Professor H. James-Clark, the habit exhibited by the
members of this genus of exuding and socially inhabiting a common gelatinous
matrix or .zoocytium, approximates them more nearly than any previously known
members of the independent collared Flagellata to the important group of the
Spongida. An advance in this direction is nevertheless accomplished in the recently
discovered Flagellate type upon which the new generic title of Protospongia is here
conferred.

Phalansterium consociatum, Fres. sp. PL. XII. FIGS. 5-9.

Common gelatinous matrix or zoocytium depressed, discoidal or shield-
shaped, more or less granular, divided by radiating dissepiments into
separate subtriangular or tubular areas representing the chambers within
the zoocytium primarily constructed by the individual zooids ; contained
zooids elongate-ovate or pyriform, from one and a half to twice as long as
broad ; collar conical, having the appearance of an anteriorly developed
beak-like process, about one-third the length of the body ; contractile
vesicles two in number, posteriorly located ; endoplast spherical, subcentral.
Length of zooids 1-2500", diameter of discoidal zoocytium 1—420".

HAB. — Fresh water.

This species was originally described by Fresenius* under the title of Monas
consociatum, its relegation to the present generic group being accomplished, as already
remarked, by Cienkowski. The zooids in their encysted condition, as reported by
this authority, exhibit, as shown at PI. XII. Fig. 8, a somewhat peculiar contour,
being subspheroidal with three longitudinal keel-like ridges, one of which is produced
in a mucronate manner at the two apices. According also to this observer, fission
in this type takes place longitudinally, or in a direction contrary to that which, as
indicated by Stein, obtains in the species next described.

Phalansterium digitatum, Stein. PL. XII. FIGS. 1-4.

Animalcules plastic and variable in form, ovate or elliptical, one and a
half to three times as long as broad, building up an erect, lobate, palmate,
or digitiform, subdichotomously branching, coarsely, granular zoocytium ;
terminations of the branches hollow, inflated, and subcylindrical, with large
circular distal apertures, containing each a single or, after fission, two

* ' Beitrage zur Kenntniss Mikroskopischer Organismen,' Frankfort, 1858.

GENUS PROTOSPONGIA. 363

separate animalcules ; flagellum attenuate, two or three times the length
of the body, conical collar embracing its base for about a distance of one-
eighth of its total length ; contractile vesicles two in number, posteriorly
situated, endoplast spherical, subcentral. Length of zooids 1-1500", altitude
of branching zoocytium 1-60". HAB. — Freshwater.

Only in the most luxuriant and fully grown examples does the zoocytium of this
species present the profusely branched contour delineated at Fig. i of the accom-
panying plate, and which, in this instance, may be appropriately compared
with the gelatinous polyzoarium of the marine polyzoon Alcyonidium gelatinosum.
As a contrast to this, it frequently exhibits a but slightly elevated lobulate aspect
closely approaching that of Spongomonas uvella, every phase of gradation occurring
between these two extremes. Multiplication in the present type is, according to
Stein, effected by transverse fission. Neither this nor the preceding form appear so
far to have been discovered in British waters.

GENUS II. PROTOSPONGIA, S.K.

(Greek, protos, first; spoggos, sponge.)

Animalcules normally ovate or pyriform, but more or less plastic and
variable in contour, bearing a single terminal flagellum whose base is
embraced by a well-developed, extensile and contractile, funnel-shaped
collar ; forming extensive colony-stocks, excreting and inhabiting a
common mucilaginous matrix or zoocytium, within the substance of which
the bodies remain constantly immersed, the collars and flagella only being
projected into the surrounding water ; endoplast and one or more contractile
vesicles usually conspicuous ; increasing by binary fission and by the sub-
division of their entire body-mass into sporular elements.

This new generic group is established for the reception of a single recently
discovered Flagellate type which corresponds with Phalansterium in so far as that the
animalcules excrete, and live more or less completely immersed within, a common
mucilaginous matrix or zoocytium. An important distinctive feature is, however,
to be noted in the fact that the collar, in place of being rudimentary and having
a permanently conical and contracted aspect, attains to its full development, being
capable of contraction and expansion, exhibiting circulatory currents, and in all ways
corresponding with the normal condition of this structure as existing in the
preceding families of the Codonosigidae and Salpingcecidae, and throughout the entire
section of the Spongida.

The importance of the position occupied by the typical representative of this
genus with relation to the last-named group, that of the sponges, can scarcely be
over-estimated, and is fully explained in its succeeding specific description. With
reference to the relationship indicated, this interesting type is herewith dedicated
to, and specially commended to the notice of, the illustrious evolutionist of Jena.

Protospongia Haeckeli, S. K. PL. X. FIGS. 20-30.

Zooids more or less ovate or pyriform, but exceedingly plastic and
variable in shape, from one and a half times to twice as long as broad,
sometimes pointed and more attenuate posteriorly, these proportions in
other instances being precisely reversed, often assuming an altogether
irregular amcebiform contour, the flagella and collars under such conditions
being entirely retracted ; collar when fully extended equalling or even

364 ORDER CHOANO-FLAGELLATA.

exceeding the length of the body ; contractile vesicles two in number,
posteriorly located ; endoplast spherical, subcentral ; common mucilaginous
matrix or zoocytium exceedingly transparent, forming a more or less ex-
tensive film-like expansion on the surface of the water or over submerged
objects, containing from six to eight to as many as fifty or sixty or more
zooids. Length of zooids 1-3000". HAB. — Fresh water.

This very interesting form was obtained by the author so recently as July 1880,
in water containing Myriophyllum, and other aquatic plants, brought from the lake
in Kew Gardens. While detected in some few instances growing upon this vegeta-
tion, the more luxuriant colony-stocks were discovered forming faintly granular, film-
like expansions on the glass or the surface of the water after some days' isolation in
a shallow glass receptacle. Until the existence as an independent structure of the
entirely transparent or very faintly granular zoocytium was definitely determined, it
was presumed that the collared monads that excrete this element were colonies
only of a species of Monosiga such as M. sodalis, that had developed upon the
surface of a bacterial film or other foreign organic mucilage. The isolation of colony-
stocks and the registration of the constantly augmented dimensions of this zoocytium
pari passu with the increase in number of the contained zooids, speedily demon-
strated, however, the incorrectness of this first inference. The import of this film-
like excretion being thus determined, the close affinity of the type to Cienkowski's
genus Phalansterium was immediately recognized. Compared with that organism,
it at the same time exhibited several important features of distinction, the chief of
these being the well developed, in place of the rudimentary condition, of the terminal
collar and the exceedingly hyaline instead of coarsely granular mucilaginous
zoocytium. The collars in this type agreed essentially, in fact, in form and function,
with those of the several genera Monosiga, Codosiga, and Salpingocca previously
described. This rudimentary condition of the collar and accompanying coarsely
granular condition of the zoocytium in Phalansterium, and the transparency of this
zoocytial element in Protospongia, conjoined with a well-developed collar, are
correlations that evidently admit of a logical explanation. In allied forms possessing
similar well-developed collars it has been demonstrated by the author that all effete
matters are cast out within the discoidal area circumscribed by the base of the
structure, and hence in Protospongia they would be thrown out beyond the periphery
of the zoocytium, and could not possibly get entangled in its substance. In
Phalansterium, on the other hand, where the collar exists as a rudimentary structure
only, no such terminal liberation of the waste products can take place, but instead
of this are probably got rid of through the general peripheral surface, as occurs in
Rhipidodendron and Spongomonas, and further becoming, as in these genera, incor-
porated within the substance of the zoocytium. This interpretation is entirely
supported by the illustrations of the genus Phalansterium recently published by
Stein, in which this common mucilaginous matrix is depicted as enclosing uni-
formly distributed coarse granular corpuscles identical in appearance with those
that undoubtedly represent faecal rejectamenta in the two previously cited genera.

The instability of contour and extreme plasticity of the constituent sarcode are
more marked in the zooids of Protospongia Haeckeli than in any other animalcule of
the Choano-Flagellate order so far examined. On the slightest disturbance the collars
and flagella are withdrawn, and an altogether irregular amoebiform aspect assumed,
as shown at a, a, a, a, in PI. X. Figs. 20 and 21. The binary fission of the zooids
during the assumption of a similar amoeboid state, as in Monosiga and Salpingoeca,
was frequently observed, as also their subdivision into larger or smaller sporular
elements, as at 22 a and 20 s of the same plate. The development of these sporular
bodies to the characteristic collared state was likewise traced, their initial condition
being that of simple uniflagellate monads, which, taking up a position in the
zoocytium adjacent to the adult zooids, as shown at PI. X. Fig. 22 bb, speedily
acquire the parent form. The establishment of new colony-stocks by similar but
single monoflagellate germs was likewise witnessed. In its initial condition such a

SECTION II. DISCOSTOMATA-SARCOCRYPTA. 365

founder of the future colony, PL X. Fig. 26, was scarcely to be distinguished from
an ordinary representative of the genus Oikomonas, it being entirely naked, attached
by a prolongation of its posterior extremity, and possessing merely a single terminal
flagellum. The collar being next developed, the animalcule for a while was
indistinguishable from such a member of the genus Monosiga as M. Steinii, while
finally, a thin mucilaginous film being thrown out around its body, see Fig. 27, the
appearance presented was that of an early condition of Salpingceca ampulla, as
delineated at PL III. Figs. 19 and 20. From this stage onwards, two or more
zooids being now included within the mucilaginous matrix, as shown at Figs. 24 and
25, the characteristic aspect of the genus Protospongia as here defined is permanently
assumed. In many of the smaller colony-stocks, as illustrated by Figs. 21 and 23,
clear traces remain of their derivation through the quadruple plan of segmentation
of a single primary unit.

By far the most interesting point connected with the structural and developmental
features of this type remains to be discussed. As previously intimated, it is, so
far as known, the nearest concatenating form between the respective groups of
the ordinary Choano - Flagellata and the Spongida. Furthermore, it may be
consistently accepted as furnishing a stock-form from which by the process of
evolution all sponges were primarily derived. A comparison of the figures illustrative
of this species with those included in this treatise relating to the organography of
the class Spongida, is alone needed to make clear this postulate. On making such
comparison it will be at once recognized that typical colony-stocks of Protospongia,
as shown at PL X. Figs. 20, 21, 22, correspond in a most remarkable manner
with a fragment of the mucilaginous cytoblastema, with its incorporated collared
monads, amoebiform cytoblasts, and sporular elements of any ordinary sponge-stock,
and more especially with that of such a non-spiculiferous type as Halisarca Dujardinii
or H. lobularis. It needs indeed but a slight modification of the disposition of the
zooids of Protospongia, to such an extent that in place of protruding on the external
surface of the mucilaginous zoocytium, they should debouch upon saccular invagina-
tions of this matrix, to produce what would have to be accepted as an undoubted
though very rudimentary sponge-stock. The establishment of free intercommunica-
tion between these saccular monad aggregates through the means of tubular canals,
is alone wanted to further transform such a sponge-stock into a typical representative
of the genus Halisarca.

In all minor structural and developmental details the zooids of the Protospongia
Haeckeli accord essentially with the simpler, naked, Choano-Flagellata previously
described ; but in their extreme plasticity, in their excretion and occupation of a
common gelatinous matrix, and in the retention of the more ordinary reproduc-
tive products within this matrix, this specific type unmistakably manifests its near
affinity to the group of the Spongida.

Section II. DISCOSTOMATA-SARCOCRYPTA
(or SPONGIDA).

Collared monads structurally resembling those of the Discostomata-
Gymnozoida, but hidden or immersed within variously modified inter-
communicating chambers of a common gelatinous matrix or cytoblastema,
which may or may not be strengthened by supplementary skeletal ele-
ments.

The necessity of accepting the sponges as peculiarly modified colony-stocks
of collared flagellate Infusoria, which correspond in every essential detail with
the simpler or independent types previously described, is abundantly demonstrated
in Chapter V., devoted to that special group of organisms, and is indeed self-
evident on examination and comparison of the plates in this volume numbered II.
to VI. and VII. to X. devoted respectively to the organization of the sponges and

366 ORDER FLAGELLATA-EUSTOMATA.

to that of the preceding less complex organic series. As there made clear, the
only substantial distinction found to subsist between the Spongida and the inde-
pendent collared Flagellata is manifested by the circumstance that, while in the
latter instance the characteristic collared monads are naked, and more or less
completely exposed to view, they are in the case of the Spongida associated to-
gether and completely concealed within specialized excavations of a common
gelatinous matrix, the zoocytium or cytoblastema. Hence the two groups are here
accepted as co-ordinate sections of the same primary subdivision of the Protozoa,
which, as intimated on a preceding page, may be conveniently distinguished by the
respective titles of the Discostomata-Gymnozoida and the Discostomata-Sarcocrypta.
So far the social types Phalansterium and Protospongia are the nearest annec-
tant forms between these respective groups, though in all probability such small
hiatus as yet exists will be still more effectually obliterated by the results of future
investigation.

The further subdivision of the Spongida into minor sections or sub-orders may be
most conveniently accomplished with reference to the nature of their skeletal
elements, as below.

Sub-Order I. MYXOSPONGI^E ., .. No accessory skeletal elements.

,, II. CALCISPONGI^E .. .. Skeletal elements represented by calcareous spicula.

,, III. SILICOSPONGI^: .. .. Skeletal elements consisting of siliceous spicula.

„ IV. KERATOSPONGI^: .. .. Skeletal elements consisting of horny fibre.

A systematic description of the multitudinous representatives of the Spongida
not falling within the scope of the present manual, students desiring to familiarize
themselves with their more minute histologic characteristics are referred to the
complete works or separate pamphlets of Bowerbank, Carter, Oscar Schmidt, Ernst
Haeckel, F. E. Schulze, W. Marshall, and numerous other authorities quoted in the
bibliographical list appended to this treatise. In all instances the collared monads,
as here described, constitute the one constant and primary factor of the living
sponge-stock, the various plans upon which these are grouped together, and more
especially the nature and mode of disposition of the skeletal elements, mostly but
not universally developed, affording the readiest clue to their generic and specific
identification.

Order VI. FLAGELLATA-EUSTOMATA, S. K.

Animalcules possessing one or more flagelliform appendages but no
locomotive organs in the form of cilia ; a distinct oral aperture or
cytostome invariably developed ; multiplying by longitudinal or transverse
fission or by the subdivision of a whole or part of the body-substance into
sporular elements.

The number of forms that have to be included in this highest section of the
typical Flagellata has been largely increased through the lately published researches of
Professor Stein. Previously, the entire group of the Flagellata, including even the
simplest monads, had certainly been accredited by Ehrenberg with the possession of
a true oral aperture ; his dictum in this connection being accepted by other more
recent writers, including Diesing and Pritchard. This attribution to them of so
high a structural differentiation was nevertheless, in the majority of instances, purely
inferential, being deduced simply from the recognized presence of ingested food-
particles within the body-sarcode of the animalcules examined. As demonstrated,
however, in this treatise, there exists a very considerable series of forms, scarcely to be
distinguished in their broad external characters from the one now about to be intro-
duced, in which solid food-particles, while freely ingested, do not obtain access through
a specially differentiated oral aperture, but are taken in indifferently at all points of

SECTION A. EUSTOMATA-MONOMASTIGA. 367

the periphery. This series, already described, has received from the author the
self-suggestive appellation of the Flagellata-Pantostomata.

Among those instances in which the conclusions arrived at by Ehrenberg con-
cerning the presence of a true mouth have been substantiated by the results of
modern investigation, reference may be more especially made to the Monas grandis
and semen of the last-named authority, now included by Stein with his new generic
groups Coelomonas and Raphidomonas, and to the two important family series of
the Euglenidad and Chrysomonadidse as here circumscribed. Several structural,
functional, and developmental phenomena, in addition to those furnished by the
ingestive faculties, may be cited as indicative of the higher position in the organic
scale occupied by the Eustomatous Flagellate group now under discussion. Among
these it may be mentioned that the constituents of the body exhibit as a rule a
far more well-defined separation into external and internal sarcode layers, or
ectoplasm and endoplasm, than is encountered among the ordinary Pantostomata ;
the former element, or ectoplasm, often indeed has both the appearance
and all the attributes of a true cuticle. In rarer instances, again, such as Phacus,
Oxyrrhis, and Entosiphon, the external envelope may become so indurated
as to constitute a veritable cuirass as commonly met with amongst the members
of the higher Infusoria- Ciliata. Correlated with this firmer development of the
ectoplasmic or cuticular element, it is further found that the members of the
Eustomata rarely exhibit that plasticity and unstability of contour so generally
characteristic of the Pantostomata, and which manifests itself most conspicuously
in that order by the tendency of the animalcules to assume at will — though more
frequently in connection with the processes of genetic union or encystment — an
altogether irregular repent amoeboid phase. Concerning the developmental pheno-
mena of these two parallel groups, it is further worthy of note that while among the
Pantostomata sporular reproduction is almost invariably accompanied, as in the
lower Phytozoa, by the splitting up of the entire substance of the body — thus involv-
ing the death or extinction of the pre-existing zooid or individual — among the
Eustomata, as exemplified by the Euglenidae, Chrysomonadidae, and Anisonemida?,
such sporular bodies are more frequently developed from the endoplast alone, or
as entirely independent endogenous reproductive elements, the parent zooids, after
giving birth to these, continuing their individual existence. Phenomena of a like
nature, but exemplified by an exogenous mode of spore or germ production, is also
exhibited by Noctiluca, and is in all instances indicative of a higher grade of
organization than is found to obtain among the Pantostomata or other Flagellata
previously described.

A tabular view of the families and genera of the Flagellata-Eustomata, as
defined in this volume, is herewith annexed. While, as there shown, the entire
series may for convenience be separated into the two sections of the Eustomata-
Monomastiga and Eustomata-Dimastiga, these respective subdivisions are completely
bridged in the very natural family group of the Chrysomonadidas by such types as
Chloromonas, Chrysomonas, and Microglena.

Section A . E US TO MA TA-MONOMASTIGA

(Flagellum single).
Fam. I. PARAMONADID-ffi, S. K.

Animalcules entirely free-swimming, more or less persistent in form,
bearing a single terminal flagellum ; endoplasm transparent, colourless,
more or less granular ; oral aperture distinct, situated near the base of the
flagellum.

The presence of a distinct oral aperture alone distinguishes the representatives
of this family from those of the Pantostomatous group of the Monadidse previously

368

ORDER FLA CELL A TA-EUS TO MA TA .

O
H
co
^
W

W
O

-
K
w
O

.

S

g

. Paramonas.

-1

1

. Atractonemi

. Phialonema.

. Menoidium.

. Astasia.
. Colpodella.

<•> .^

if i !

V W •• -£r

t^ ^ ft, G

Traehelomo*

Raphidomon
Ccelomonas.

Ascoglena.
Colacium.

Noctiluca.
Leptodiscus.

w

ri

fi

rt-

w>

VO *•»

00 0\ C) «

M

CO Tf

vo VO

^ 06

:

;

•

•

8 : a a : i :

.

.

a. o

'•3 2 c

•

.

• •

£f i- u

13 g ... O t>

•

•

•

. •

3 . S • 'C a

B fc

H * *3 a • fc i>

o 2 ^5 S e

:

:

:

: ;

«§ •? S =

:

:

: :

wg, •§ § S § S.

c wi s « c - «

•> § ° 8 5«y

t5™ 0 0 G £^

f =

[u

o
c

MH Z 3 !>

w :

• *QJ

.
a,

. ' ^ '

>,

• bjO

rt

>,^ C <SJ

•2 "3 « a,

o

12

^

:

- :

U ii

o :

8 §

KS <^-2

'S.
2

1 |

I

8 2

1 :

~

" E^

e o

«J _!,

^> fl»

*J U

& °

£? 4;
rt o

TJ

7j

8 |

<n a

S 1

^

D

•c

5 '5!

i3 d

D C

SO
0

3

§

'C o

Me

•-« >^

M

H ^

o

a. 5

e or spheroidal

ompressed

i, subcylindrical

:

or ensiform . .

a. *

H

1 « e

P 4) §

o w-2
c F tS

if I
*«•

With an abnor-
mally dilated
pharyngeal
cavity.

Solitary, inhabi
Grouped sociall

"> S

^-T ""
rt O

"O C
'3 j.
6j rt

ts

U

e

.22

n 2

^

— ^ —

— y .

^ ^

\t

^o

rt

3 5,

cx *3

o

o

<—

C

•*-* i-*

.

•

jfi w

( Symmetrically

Much flattened

J

o

V

•8

0.

rt

•3

i

[ Compressed, lu

With a distinct
No distinct pha

£

Sedentary . .

Animalcules sul
' Animalcules dis

[. PARAMONADID^E.

nalcules free-swimming, J
•sistent in form ; endo- 1

plasm colourless.

II. ASTASIADjE.
lalcules highly metabolic; '
mdoplasm colourless.

III. EUGLENIDjE.
imalcules mostly highly ,
etabolic ; endoplasm

loured brilliant green.

>

[V. NOCTILUCID^:.
oplasm highly vacuolar
ticulate, phosphorescent.

• — \j

& v

c E

Q

'w cl>

<*

Z

<

C »-

<j H c1

3 n *a

< O g |

W 0 5g

t> ^ rt°

W P FT

FAMILIES AND GENERA OF FLAGELLATA-EUSTOMATA. 369

S

5

8 -5"

'-5

g

a

-S.

* • I*

S

Chloromoiu

Chrysomon
Microglena

. Cryptomon
Nephroselm

Stylochrysa

Uvella.
Chlorangiu

S

S

i

4

Chrysopyxl
Epipyxis.

(•I

1 «
q ^

Syncrypta.
Uroglena.

Eutreptia.

j jf •§ i i 4 § l l J

•gg^oSSS^gg^^,
1 f - f 1 1 i i I J I

^ -s b -S •£ ^§ v S *• * i!

Sphenomon

NH

to

a

H «

§

™ R

d «

N ro

to to

-*•
to

"""""^"""^^

vo

U

<u

• ^

-3
• %

rt 13

<u

bfl §

•

S ***

o oj
'C

« 3

£ cu

'

'

ft i3

*

<U

° C'

FO rt

s ^

Su

brf ^2

« J

D a
*T t-i

S2 ^
2 a.

:

to %
•9 5

to cJ

C/I

S £

"S i
^ 8

:

0

!

w *

CJ <U

c t:

»

•

Animalcules persistent in shape

INo distinct phar
With a distinct ]

(Free- Flagella' inserted beneath a h
swim-
ming. Flagella inserted in a lateral

fS

'u

•3

<L>

CX

T3

;§o

rt
0

-s

X

55
<

— X

3 bjO

73 .3

W "fl

.5 c

rt 2

« t

(U O

•s •§.

3 1

." in

2 *

•S §
g- E,

a -

•8 I
•3 2

& O

3

"o

o
en

| Free-swimming

Solitary j j Body free within the im
( Sedentary s
( United to lorica by a th

Forming a compound branching zoot
Social .
United in free-floating spheroidal clu

Zooids closely approximated without independe
Zooids not directly united, possessing independei

( Endoplasm coloured brilliant green .

Naked j Endoplasm transparent, Entirely ft
I granular Free-swim

Loricate, free-swimming
Flagella diverse, one long and one short ..
Flagella equal or subequal
rically labiate
ly excavate
Cuticle elastic, highly metabolic
Not metabolic, simply soft and plastic
Pharynx distinct, but not protrusible
Pharynx protrusible as a separate horny tube .

or more longitudinal keel-like ridges

—

-% •

__ c " -- -- • -

3

i
I
|

r2

1

1

<u

flagella :
:d within a
szoocytium.

£ £ d 3? o g" %%

1 ?! II *i Hi

I M- 3 J «.§ 'ia§

£

tui

1

d

O

1'

i

I

o

o 2§
^ s s

H 1

to

s Si I I :§l Isi

S 11 I 1 I8 'g*

£ S(/)CH> £ 3

I

"o

(X!
— ' -v

«• S/} ' «* v

<u u

. O lH

•2

£3 1/1

« S . . « TJ . o ^ ,,5

I

i
i

V. CHRYSOMONADID^E
Endoplasm enclosing tw
laterally-disposed olive o
vellow oitrment-bands.

Flagellate appendages, w

but rare exceptions, two
number, of similar or dive
length.

dll IHI §10

1! 11 IJH 1

H» JS£S S° g H f^S3 A

^•o^^ S'CuC |-|^?2

^8 >||8 >^|| ><

EJ < g -1 =*

Animalcules prismatic, pt
sietent in shape ; two vibra
*, flagella, one long and one sh

f~* o ^2

^ E-I Cud

PQ

o^<g

H 2 o

en g £

"— ' O t"1

•

W M ^

2 B

3 70 ORDER FLA CELL A TA-E US TO MA TA .

described, and with which, so far as external contour only is concerned, they in
many instances exhibit the closest possible correspondence.

GENUS I.' PARAMONAS, S.K.
(Greek, para, close to ; monas.)

Animalcules free-swimming, ovate or globular, uniflagellate, more or
less persistent in shape, incepting food-substances through a distinct oral
aperture which is situated anteriorly at the base of the flagellum.

The above generic title is here instituted for the reception of several forms re-
ferred to the genus Monas by De Fromentel,* but which are declared by him to possess
a distinct oral aperture. A still larger number of the species hitherto relegated to
the same generic group will probably have to be transferred irf a similar manner to
this present one, as soon as a more perfect knowledge of their minute struc-
ture and life-history shall have been gained. Owing to the greater density, though
not absolute rigidity, of their cuticular investment, the representatives of the
genus Paramonas, in addition to possessing a distinct oral aperture, are further
characterized by their comparatively persistent shape. These features, taken
collectively, secure for them a distinction from the members of the genus Monas,
similar to that which is further on shown to subsist between the otherwise super-
ficially corresponding generic types Heteromita, Heteronema, and Anisonema. The
genus Petalomonas of Stein, represented by the Cyclidium abscissum, and possibly
also the C. nodulosum and C. crassum of Dujardin, necessarily approaches most
closely to Paramonas. As, however, the flattened and leaf-like contour of the body
is insisted on as a leading characteristic of Stein's genus, it is requisite to establish
an independent one for the globular or ovate forms included under the present
title.

Paramonas globosa, From. sp. PL. XX. FIG. i.

Body spherical, transparent, enclosing red granules ; contractile vesicle
subcentral ; oral aperture conspicuous, situated at the base of the flagellum.
Length 1-2400". HAB. — Fresh water.

Identical with the Monas globosa of De Fromentel.

Paramonas ovum, From. sp.

Body ovate, transparent, coarsely granulate ; flagellum constantly
vibrating ; mouth situated close to the base of this organ. Length 1-1500".
HAB. — Fresh water.

The Monas ovum of De Fromentel.

Paramonas stellata, From. sp. PL. XX. FIG. 2.

Body ovate or spherical ; endoplasm green and granulate ; oral aperture
apical, stellate ; flagellum long and fine, constantly vibrating. Length
1-1500". HAB. — Freshwater.

Both this and the succeeding species, characterized by De Fromontel as having
their endoplasmic substance coloured green, are referred provisionally only to the
genus Paramonas, If such coloured matter represents a permanent constituent,

* 'Etudes sur les Microzoaires,' Paris, 1876.

GENUS PETALOMONAS. 371

and not incepted food-substance, they are referable probably to the family groups
of the Euglenidae or Chrysomonadidae. The present type was originally included
by De Froraentel in the genus Monas.

Paramonas deses, Ehr. sp.

Body oblong, rounded at the two extremities, colour bright green,
ora^aperture distinct, situated at the base^of the flagellum, the latter organ
long and undulating; contractile vesicle central. Length 1-1200".

HAB. — Fresh water ; solitary.

Identical with the Monas deses of Ehrenberg and De Fromentel.

GENUS II, PETALOMONAS, Stein.

Animalcules free-swimming, ovate, depressed, with a single long vibratile
flagellum ; cuticular surface indurated, often carinate ; oral aperture distinct,
situated close to the base of the flagellum.

Stein first founded this genus upon the Cyclidium absdssum of Dujardin, to which,
in his recently published work,* several distinct forms are added. Dujardin's
generic title of Cyclidium having been previously employed by Ehrenberg for certain
ciliate animalcules, cannot be retained among the Flagellata.

Petalomonas abscissa, Duj. sp. PL. XX. FIGS. 5 AND 6.

Body subtriangular or irregularly ovate, flattened and leaf-like, slightly
pointed anteriorly, the posterior margin somewhat truncate, the dorsal
surface traversed longitudinally with one or occasionally two keel-like
elevations ; parenchyma transparent, slightly granular ; flagellum slender
throughout, about twice the length of the body, directed rigidly in advance,
and vibrating only at its anterior extremity ; movements slow and even ;
multiplying by longitudinal subdivision. Length 1-900".

HAB. — River water.

While the subtriangular outline indicated in the accompanying figures represents
the more typical contour of this species, Stein's illustrations show that examples
occur in which the posterior border is evenly rounded as in P. mediocanellata, while
more rarely the lateral borders may be irregularly contorted, or two keel-like
elevations are developed on the dorsal surface.

Petalomonas mediocanellata, Stein. PL. XX. FIG. 3.

Body flattened, resembling an apple-pip in shape, acuminately pointed
anteriorly, rounded and widest posteriorly, about twice as long as broad, a
straight narrow groove or channel extending down the median line of the
ventral surface from the oral aperture nearly to the posterior border;
flagellum equalling or slightly exceeding the length of the body; contractile
vesicle situated towards the anterior extremity at the left-hand side of the
median groove, the endoplast located further back on the opposite side of
this same channel. Length 1-700". HAB. — Fresh water.

* ' Infusionsthiere,' Abth. iii., 1878.

2 B 2

372 ORDER FLAG ELLA TA-E US TOMATA.

Petalomonas sinuata, Stein. PL. XX. FIG. 4.

Body flattened, obtusely pointed anteriorly ; the posterior margin widest,
singly or doubly emarginate, its two lateral angles prolonged outwards, no
median ridge or channel, but a short oblique groove produced from the
oral aperture towards the right-hand border ; flagellum nearly equalling
twice the length of the body ; endoplast and contractile vesicle as in
P. mediocanellata. Length 1-800".

HAB. — Fresh water, dividing by longitudinal fission.

Petalomonas ervilia, Stein. PL. XX. FIG. 7.

Body flattened, elongate, ovate or elliptical, slightly pointed anteriorly,
twice as long as broad ; the ventral surface with a broad groove or channel
that extends along the left lateral border from the anterior to the posterior
extremity ; flagellum exceeding the length of the body ; contractile vesicle
and endoplast situated as in the preceding species, the former sometimes
presenting a compound aspect. Length 1-580". HAB. — Fresh water.

Doubtful species.

The Cyclldium nodulosum and crassum of Dujardin are probably referable to
the genus Petalomonas, but the presence of an oral aperture in these forms has yet
to be demonstrated. Their brief diagnostic characters, as given by Dujardin, are
herewith appended.

Cyclidium (Petalomonas?} nodulosum, Duj. — Body flat, discoidal, nodular
and vacuolate, movements slow. Length 1-500".

HAB. — River water, with Myriophyllum.

Cyclidium (Petalomonas ?) crassum, Duj. — Body thick and rounded at the
edges; flagellum thickest at the base, slightly undulating; movements
active and in a zigzag direction. Length 1-1700". HAB. — Ditch water.

A small animalcule, as represented at PI. XX. Figs. 8 and 9, has been recently
obtained by the author from hay infusions, whose position would appear to be
among or closely adjacent to the representatives of the genus Petalomonas. Their
contour, while persistent, is less flattened than that of the more normal species
previously described, and was observed to vary considerably in different individual
zooids. In most instances, as at Fig. 8, the animalcules were symmetrically ovate,
as in P. abscissum, but somewhat more elongate and less flattened, without any
groove or keel-like ridge, while more rarely they were altogether irregular and
nodulate, as shown at Fig. 9. The average length of these animalcules did not
exceed 1-2500".

The mode of progress through the water normally exhibited by this type is
peculiar, and may assist perhaps in the substantiation or otherwise of its claim for
admission to the generic group wherein it is here relegated, though unfortunately
no data have as yet been published concerning the characteristic comportment of
the several species already enumerated. Such locomotion in the present instance
was always accomplished steadily forwards and in a straight line, the body and
terminal flagellum being depressed at the angle indicated in the accompanying
illustrations; the distal end only of this last-named appendage was maintained
in a state of vibration, and was thrust here and there over the surface of the
slide or surrounding debris, apparently in search of food. Not unfrequently the

GENUS A TRA C TONE MA . 373

animalcules effect a momentary adherence by the distal region of this flagellum, and
swinging their bodies round upon it as though on a pivot, direct their course in an
opposite direction. It is provisionally proposed to distinguish this species by the
name of Petalomonas irregularis. The presence of a distinct oral aperture has not
as yet been definitely certified.

GENUS III. ATRACTONEMA, Stein.

Animalcules free-swimming, persistent in shape, fusiform or elongate ;
flagellum single, terminal ; oral aperture at the base of the flagellum,
followed by a distinct tubular pharynx, the posterior termination of which
apparently communicates freely with the contractile vesicle ; endoplast
subcentral ; endoplasm transparent, finely granular. Inhabiting fresh water.

Atractonema teres, Stein. PL. XX. FIGS. 10-12.

Body elongate fusiform, widest centrally, attenuately pointed at each
extremity, four or five times as long as broad ; flagellum slender, vibratile,
equalling the body in length ; posterior termination of the pharynx, and
communicating contractile vesicle almost joining the central spheroidal endo-
plast ; endoplasm finely granular, often enclosing between the endoplast
and posterior termination a discoidal amylaceous corpuscle. Length 1-640".

HAB. — Fresh water, dividing by longitudinal fission ; movements, repent
and rotatory.

In accordance with the index to Stein's figures,* the representatives of this
species swim freely through the water or creep, head downwards, with the attenuate
oral region applied to the surface of the objects traversed. In some of the examples
delineated, see PI. XX. Fig. 12, the flagellum has disappeared, and the central
endoplast become enlarged and broken up into spore-like bodies.

GENUS IV. PHIALONEMA, Stein.

Animalcules free-swimming, persistent in form, more or less flask-shaped ;
oral aperture terminal, dilated, bearing on one side a single flagellum,
succeeded by a curved tubular pharyngeal dilatation, which is produced
backwards to or beyond the centre of the body; endoplasm transparent
granular ; contractile vesicle and endoplast distinct. Inhabiting fresh
water.

Phialonema cyclostomum, Stein. PL. XX. FIGS. 13 AND 14.

Body flask-shaped, somewhat gibbous, about three times as long as
broad, widest centrally, pointed posteriorly, with a neck-like anterior pro-
longation, the extremity of which is obliquely truncate, and forms a circular,
thick-bordered, expanded rim around the oral excavation ; curved tubular
pharynx, often produced backwards to within a short distance of the
posterior extremity, its distal end much dilated ; cuticular surface usually
obliquely striate, but these striae occasionally replaced by a few spirally
disposed projecting ribs ; flagellum short, vibratile, nearly equalling the body

* ' Infusionsthiere,' Abth. iii., 1878.

374 ORDER FLAGELLATA-EUSTOMATA.

in length ; endoplast subcentral ; contractile vesicle situated towards the
anterior extremity, and to one side of the pharynx. Length 1-500".
HAB. — Fresh water.

The animalcules of this species, in addition to swimming freely in the water,
creep over the surfaces of submerged objects, with their oral region applied to the
same, much in the same manner as Atractonema. An approach to the repent
mode of progression exhibited by these two last-described generic forms would
appear to be foreshadowed in the species provisionally referred by the author to the
genus Petalomonas, under the name of P. irregularis, and in which the distal ex-
tremity of the flagellum persistently maintains a close relationship with the surface
of the ground or objects traversed.

GENUS V. MENOIDIUM, Perty.

Animalcules free-swimming, persistent in form, lunate or ensiform, com-
pressed, bearing a single terminal flagellum, at the base of which is situated
the oral aperture, followed by a minute tubular pharynx ; endoplasm trans-
parent, granular ; contractile vesicle and endoplast conspicuous, the former
situated close to the termination of the pharynx. Inhabiting fresh water ;
movements oscillating or rotatory.

Menoidium pellucidium, Pty. PL. XX. FIGS. 15 AND 16.

Body lunate, compressed, four to six times as long as broad, with a
more thickened, convex ventral, and concave dorsal border, most attenuate
anteriorly, its superior edge sometimes developed above the oral aperture as
a projecting tooth-like spine ; flagellum slender, equalling the body in
length ; endoplasm transparent, more or less granular, usually containing
one or more large ovate amylaceous corpuscles ; contractile vesicle, appa-
rently communicating with the termination of the pharynx ; endoplast
subcentral. Length 1-600" to 1-400". HAB. — Fresh water.

The general form of the body of this animalcule may be compared to that of a
minute transparent Closterium. As originally figured and described by Perty, the
terminal flagellum is not represented, and its existence only suspected. Stein * is
the first who has published an amplified delineation of its contour and component
structure, the chief details of which the author is in a position to corroborate,
having recently, November 1878, encountered the species in marsh water obtained
from the neighbourhood of St. Heliers, Jersey. In none of the examples as yet
examined, however, was detected the anterior tooth-like projection characteristic
of the majority of Stein's figures, while in all cases the endoplasm exhibited a feature
previously unnoticed. In Stein's delineations the granulation of this element
presents no definite plan of distribution, and is diversely developed in different indi-
viduals. In those personally investigated, the granulation was confined entirely to
the posterior region of the body, and consisted of innumerable minute spherical
corpuscles of uniform size, as shown at PI. XX. Fig. 15. In most of these there
was a single large, elliptical, subcentral, amylaceous corpuscle ; but in some instances,
as in Stein's figures, two or more smaller ones. An exceptional specimen exhibited
an inflated and almost cylindrical in place of the usually compressed body contour.
Dead examples occasionally occur in which the flagellum has disappeared, but the
animalcule still retains its distinct tubular pharynx, thus demonstrating the indurated
character of the walls of this structure.

* ' Infusionsthiere," Abth. Hi., 1878.

GENUS AST ASIA. 375

Fam. II. ASTASIAD-ZE, S. K.

Animalcules mostly free-swimming, exceedingly plastic and variable in
form, bearing a single terminal flagellum ; oral aperture distinct ; endoplasm
colourless.

GENUS I. ASTASIA, Ehr.

Animalcules free-swimming, ovate or elongate, very elastic and change-
able in form, metabolic, invested by a distinct cuticula ; flagellum single,
projecting from the more attenuate anterior extremity ; oral aperture
situated close to the base of the insertion of the flagellum, highly extensile,
continued into a long, straight, tubular pharyngeal tract ; endoplasm
transparent, enclosing incepted granules, but not assimilating chlorophyll
or other coloured matter ; contractile vesicle and endoplast distinct. In-
habiting fresh and salt water.

Considerable difficulty has usually attended the separation of the members of
this genus from those of Euglena, a circumstance that must be attributed to the
imperfection of the distinctive characters of the two genera as first laid down by
Ehrenberg, accompanied by his inclusion under the same generic heading of animal-
cules belonging to each of the two types. Adopting, nevertheless, the distinctions
first pointed out by Dujardin, and since recognized by Carter and other later writers,
it becomes evident that the genera Euglena and Astasia are not only easily distinguish-
able, but appertain to two widely distinct family groups. In accordance with their
respective diagnoses formulated in this volume, it will be found that while in external
contour and in the remarkable elasticity of the endoplasmic element with its invest-
ing cuticula the two generic types bear a considerable superficial resemblance, a
strongly marked structural differentiation is developed immediately beneath. One
of the most important distinctions that thus presents itself pertains to the characters
of the ingestive or buccal apparatus. In Astasia this consists of a large, widely
dilatable but simple aperture, continued backwards into a clearly defined pharyngeal
tract, through which food-particles of a considerable size are readily transported. In
Euglena, on the other hand, the oral aperture, while correlated with a peculiar
modification of the anterior extremity of the body, is not dilatable or continuous
with a distinct pharyngeal tract, and is capable of incepting food- particles of the
minutest comparative dimensions only. The distinction subsisting between the
consistence of the endoplasm or parenchyma in the two genera is even more easily
appreciated. In Astasia this structural element consists of clear and apparently
homogeneous sarcode, similar to that encountered among all the more ordinary
transparent Flagellata, coloured matter, if present, remaining distinctly isolated,
and clearly exhibiting its extraneous derivation ; neither in Astasia is there ever
represented that coloured pigmentary corpuscle, the so-called "eye-spot" of the
earlier authors, which, although of uncertain value for the purposes of specific dis-
crimination, is broadly characteristic of the group to which Euglena appertains.
The endoplasm throughout all the representatives of the last-named genus is further
conspicuous for its brilliant colouring, this colouring matter not being held tem-
porarily in suspension, but being most intimately incorporated or assimilated with
the substance of the endoplasm.

Dujardin has proposed to separate from the genus Astasia certain species in
which the body was of a more globular shape, and the terminal flagellum thicker
and more rigid at its base, proposing for them originally the title of Pyronema, and
afterwards that of Peranema. Out of the two representative forms of this genus
described by that authority, however, one, P. protracta, is now recognized to be
identical with Ehrenberg's Trachelius (Astasia} trichophora, while his P. globulus

376 ORDER FLAGELLATA-EUSTOMATA.

has been demonstrated by the present author to be a transitional condition only of a
Radiolarian closely allied to, if not identical with, Actinophrys sol (see p. 225).
Stein, for reasons as yet unexplained, figures in his recently published volume,* as
members of the genus Astasia, biflagellate animalcules corresponding most nearly
with the forms upon which Dujardin has conferred the name of Heteronema, while
the typical representative of the present genus, the Astasia ( Traehdius) trichophora
of Ehrenberg, is referred to Dujardin's genus Peranema, which, as just shown,
possesses no sound claim for retention.

Astasia trichophora, Ehr. sp. PL. XX. FIGS. 17-21.

Body highly metabolic, variable in shape, more usually irregularly
pyriform or clavate, widest posteriorly and tapering gradually towards the
pointed anterior extremity, the posterior end sometimes with a short caudi-
form prolongation ; flagellum thick and cord-like, about one and a half times
longer than the body ; contractile vesicle situated anteriorly, closely
adjacent to the centre of the pharyngeal track ; endoplast spherical, central,
of large size; endoplasm clear and transparent. Length of body 1-1200"
to 1-370". HAB. — Marsh and stagnant water.

This animalcule was first described under the title of Trachelius trichophonts by
Ehrenberg, who mistook the thick cord-like flagellum for an attenuate neck-like
prolongation of the body, similar to that met with in the ciliated genera Lacrymaria,
Aniphileptus, and Trachelius. Claparede was the first to indicate its rightful position,
but not before it had been redescribed by Dujardin under the titles of both Peranema
protracta and Astasia limpida. The varieties of contour assumed by this form are
indeed so manifold and protean, that it seems highly probable that many, if not the
majority, of species hitherto referred to the genus are merely slightly modified
expressions of this single type. In its movements, which are of two kinds, repent
and natatory, the body is at one moment perfectly symmetrical and perhaps almost
cylindrical, while during the next it is writhing in amoeba-like contortions, and,
compared with its former aspect, almost unrecognizable. These contortions, as
already remarked by H. James-Clark, do not consist, as in Am&ba, of an actual
outflowing of the substance of the sarcode or parenchyma, but from an exceedingly
variable puckering of the cuticular surface, always accompanied by a more or less
longitudinal contraction of the body. This is most clearly apparent when the
animalcule becomes doubled on itself by an abrupt retrogressive motion.

Professor Clark f has proposed to demonstrate that the occasionally conspicuous
caudiform prolongation of the posterior extremity of the body of this species is the
rudimentary homologue of the trailing flagellum, or, as he has termed it, the "guber-
naculum " of Anisonema and other biflagellate types. Its thoroughly inconstant and
fugacious character, however, scarcely favours this interpretation. Although the
possession by the representatives of the genus Astasia of a distinct terminal oral
aperture has been recognized since the time of Ehrenberg, the connection with this
structure of a distinct indurated pharynx or so-called buccal tube was first recognized
and described by Mr. H. J. Carter in his notes on the Infusoria of Bombay, pub-
lished in the ' Annals of Natural History ' for August-September 1856, his observations
in this direction being abundantly confirmed by the later investigations of Stein and
Biitschli. Mr. Carter, in the publication just referred to, has adopted for this species
Dujardin's name of Astasia limpida. An illustration of the extreme elasticity pos-
sessed by the oral aperture of this type is furnished by one of Butschli's figures, in
which an animalcule is represented as incepting a spherical organism, apparently a
monad, whose diameter considerably exceeds that of its own body. A corresponding
extensibility of the oral aperture is encountered in the biflagellate type Dinotnonas,

* ' Infusionsthiere,' Abth. iii., 1878. t 'Mem. Bost. Soc. Nat. Hist.,' 1868.

GENUS AST A SI A . 377

described later on. The contractile vesicle of Astasia trichophora has been shown
by Butschli to exhibit a somewhat complex character, the water discharged in the
act of systole being partly driven into smaller lateral diverticula, as obtains in
Entosiphon and certain species of Anisonema, and as also observable in Paramecium
and many higher Ciliata. Multiplication by fission in this species takes a longitudinal
direction. The presence of endogenously developed germs, as represented at
PI. XX. Fig. 1 8, has been recorded by Mr. Carter.

Astasia contorta, Duj.

Body colourless, semi-transparent, flexible and contractile, sub-
cylindrical, widest in the centre, bluntly pointed at the two extremities ;
the surface of the cuticle obliquely and closely striate, so as to impart to it
a twisted aspect. Length 1-425". HAB. — Salt water.

A second marine species described by Dujardin under the name of Astasia
tnflata, having the cuticular surface obliquely striate in a similar manner, and the same
approximate dimensions, but with a more ovoid body, is apparently a variation only
of A. contorta.

Astasia flavicans, Ehr.

Body extensile, conical or subcylindrical, rounded anteriorly, with a
short, blunt, tail-like posterior prolongation ; parenchyma enclosing yellowish
granules. Length of body 1-430". HAB. — Ditch-water.

Astasia pusilla, Ehr.

Body colourless, extensile, conical, largest and rounded posteriorly, and
with a short pointed posterior prolongation ; flagellum twice the length of
the body. Length of body 1-1440" to 1-400". HAB. — Ditch-water; social.

This and the preceding are apparently variations only of the same form, and
are, as already remarked by Carter, closely allied to if not identical with the Astasia
(Trachelius) trichophora of Ehrenberg and A. limpida of Dujardin.

Astasia longifilis, Perty.

Body persistent in form, hyaline, enclosing pale-green granules, the
anterior half exhibiting a longitudinal plait or furrow; flagellum at least
three times the length of the body. Length i-iooo".

Doubtful Species.

A number of fresh-water species have recently been added to the genus Astasia
by De Fromentel,* but are in the majority of cases too ill-defined for re-identification.
The figures accompanying his descriptions might at the same time do duty in most
instances for one or other of the protean phases of Astasia trichophora. A slightly
amended translation of Fromentel's diagnoses of such forms only as seem to possess
appreciable distinctive characters is herewith appended.

Astasia utriculus, From. — Body flask-shaped, inflated at the base and
rounded at the summit ; flagellum inserted somewhat on one side of the
neck-shaped anterior portion. Length 1-800". His Astasia cucurbita, of
similar size and shape, is apparently .identical with this form.

* ' Etudes sur les Microzoaires,' Paris, 1876.

378 ORDER FLAGELLATA-EUSTOMATA.

Astasia deformis, From. — Body hyaline, with irregular digitate expan-
sions; contractile vesicles posteriorly situated. Length 1-600".

Astasia turbo, From. — Body top-shaped, with a dilated, somewhat
flattened central portion, and attenuate anterior and posterior regions ;
parenchyma finely granulate ; flagellum long and slender. Length
1-400".

Astasia fusif or mis, From. — Body fusiform, attenuate at the two extre-
mities ; contractile vesicle conspicuous, posteriorly situated. Length
1-600".

Astasia crassa, From. — Body highly contractile, subspherical, often
changing its form, but retaining an attenuate, tail-like, posterior prolon-
gation ; flagellum long and slender ; parenchyma white and granular.
Length 1-700".

Astasia regularis, From. — Body regularly oval, slightly flattened on one
side ; pharyngeal tract conspicuous ; parenchyma enclosing coloured granules.
Length i-iooo".

The Trachelius dendrophilus of Ehrenberg* — "body ovate, subacute at each
extremity, proboscis flagelliform, slender and pointed, more than twice the length of
the body. Length 1-3456"." Found among moss from trees, with habits like those
of Trachelius (Astasia} trichophora — is apparently a minute representative of the
present genus.

GENUS II. COLPODELLA, Cienkowski.

Animalcules free-swimming or adherent, ovate or elongate, bearing a
single anterior terminal flagellum, at the base of which is a suctorial oral
aperture ; contractile vesicle and endoplast conspicuous. Habits predatory,
preying upon various minute Phytozoa, the cell-walls of which they perforate,
and abstract the contents.

In contour and in the character of the single flagellate appendage the repre-
sentatives of this genus are scarcely to be distinguished from those of Monas or
Paramonas, and might, unless observed in the act of feeding, be relegated to one of
these two genera.

Colpodella pugnax, Cienk. PL. XX. Fig. 22.

Body somewhat variable in form, its most characteristic shape elongate,
semilunate, pointed at each extremity, with a flat ventral and convex dorsal
border ; flagellum equalling or slightly exceeding the body in length ; con-
tractile vesicle single, circular, situated close to the ventral border at a short
distance from the posterior extremity ; endoplast spherical, anteriorly
located. Length 1-2000".

HAB. — Fresh water, preying upon Chlamydomonas pulvisculus.

According to Cienkowski \ the zooids of Colpodella pugnax, after fully satis-
fying their hunger by the extraction of the cell-contents of one or more speci-
mens of the above-named protophyte, become encysted, and the enclosed bodies
split up into eight or more sporular elements. These subsequently make their

* 'Ber. Akad. Berlin,' 1853.

t ' Archiv fur Mikroskopischer Anatomic,' Bd. i., 1865.

GENUS EUGLENA. 379

escape from the cysts in a form identical with that of the parent, but of smaller
size. Not unfrequently, as shown at PI. XX. Fig. 22, two or three Colpodella fasten
themselves simultaneously to a single Chlamydomonas, and perforating its body-
wall, rapidly reduce it to an empty shell. No instance of the coalescence or fusion
of two or more individual zooids has as yet been recorded, but in all probability
occasionally takes place.

Fam. III. EUGLENTD-ffi, Stein.

Animalcules free-swimming or sedentary, naked or loricate, solitary or
united in social colonies ; flagellum single, terminal ; oral aperture distinct ;
endoplasm usually coloured brilliant green, more rarely red, through the
assimilation of chlorophyllaceous substances, often enclosing several highly
refracted corpuscles of an apparently starch-like or amylaceous nature ; one
or more brightly coloured eye-like pigment-specks frequently developed at
the anterior extremity; contractile vesicle and endoplast conspicuous, the
former usually located close to the anterior border. Multiplying by longi-
tudinal and transverse fission, by the subdivision of the entire body-
substance into sporular elements, and by the development of independent
germinal bodies out of the substance of the endoplast.

The members of this highly characteristic and very natural family group are
readily recognized in connection with the brilliant coloration — the prevailing hue
being green — of the endoplasmic elements, which under normal conditions more
or less conspicuously distinguishes every one of the considerable number of
generic and specific types as herewith comprised. The common occurrence within
the body-substance of variously shaped corpuscles of considerable size and of an
apparent amylaceous or starch-like nature, as also the endogenous mode of repro-
duction, manifested by the enlargement and subdivision of the central endoplast
or nucleus, yield supplementary distinctive features of importance. With respect to
the amylaceous corpuscles, it is worthy of remark that in the case of those of elongate
rectangular contour developed in Euglena deses, Dujardin has attributed to them the
nature of crystals of sulphate of lime.

GENUS I. EUGLENA, Ehrenberg.

Animalcules free-swimming, more or less fusiform or elongate, exceed-
ingly flexible and changeable in shape ; bounded by an elastic and highly
contractile cuticulum, terminating posteriorly in a more or less deve-
loped tail-like prolongation ; endoplasm usually tinged bright green or
red through the assimilation of chlorophyll or other colouring matter ;
flagellum single, slender and flexible throughout, issuing from an anterior
funicular, notch-like excavation, at the bottom of which a minute oral
aperture is situated ; contractile vesicle and endoplast conspicuous ; one or
more distinct eye-like pigment-spots usually present at the anterior extre-
mity. Inhabiting fresh, stagnant, and brackish waters ; solitary, or occurring
in such numbers on the surface of the water as to impart to it a highly
characteristic feature, even as seen with the unaided vision. Increasing by
longitudinal fission, and by the production of germs through the subdivision
of the endoplast or of the entire mass of the internal parenchyma.

In their general contour and extreme flexibility, which permits them at wiU to
assume the most varied and protean shapes, the members of the genus Euglena so

380 ORDER FLAGELLATA-EUSTOMATA.

closely correspond with those of Astasia that the two have been usually included in
the same family. By Ehrenberg, indeed, the presence or absence of the so-called
coloured eye-speck was regarded as representing the only distinctive feature, the
natural sequence to such an artificial distinction being that many forms have been
referred by him to the genus Astasia which properly belong to the one now under
consideration. Dujardin was the first to point out the unreliable character of
Ehrenberg's proposed diagnosis, substituting for it the distinctions here maintained,
afforded by the coloured or transparent consistence of the endoplasm. This last-
named characteristic may still be adopted as furnishing a safe and speedy means of
distinguishing between the representatives of the two respective genera, although, as
will be presently shown, much more important structural differences exist. The
colouring matter of Euglena — most usually green and apparently partaking of the
nature of chlorophyll — which invariably, under normal conditions, enters to a greater
or less extent into the composition of the endoplasmic layer of the various species,
is, as already intimated in the account given of the genus Astasia, not scattered in
an irregular granular manner, as in numerous other infusorial forms, denoting by
such a distribution its foreign nature and temporary lodgment only, but permeates
its substance so completely as to be inseparable from it under the highest magnify-
ing power, and remaining as intimately amalgamated with it when, as described
later on, it breaks up within the integument into germinal masses. In this manner
the endoplasm of Euglena is, as it were, indeed, more or less completely stained
with the characteristic hue peculiar to the species.

The possession by Euglena of a distinct oral aperture, and its capacity, of incept-
ing solid particles of ^food through this orifice, have not up to a recent date been
clearly demonstrated. Stein, however,* in the year 1867, went so far as to attribute
the office of such a structure to the notch-like anterior cleft of Amblyophis, and which
he described as being followed by a distinct pharyngeal tract ; a similar interpretation
was also arrived at by him with reference to the smaller anterior notch of Euglena,
though in no instance was the passage of food-particles directly determined. Still
later,t this authority has represented a tubular oral aperture as pertaining to all of
the members of this family group as here comprised. The apparent absence of a
distinct oral apparatus and ingestive capacity, taken together with the green hue of
the body-plasma, previously induced most modern authorities, including Mr. Carter,
to deny to the representatives of Euglena and its allies the rank of animal or-
ganisms, they referring them rather to the division of the Protophyta or lower
unicellular plants. The present author's views, to within a comparatively recent
date, harmonized with this decision, but a still later and more exhaustive examina-
tion of the type form of the genus, E. viridis, made in April 1877, has resulted in
the adoption of an entirely opposite opinion. Keeping animalcules of this species
for a prolonged interval in water with finely pulverized carmine, and submitting
them to a magnification of 800 diameters and upwards, the passage into their
bodies at the anterior extremity of exceedingly fine particles of this pigment was
repeatedly observed, as also the accumulation, in various parts of the body-substance,
of small globular aggregations of the particles ingested. Hitherto this anterior
region in Euglena has been represented as exhibiting a bilabiate aspect, and the
flagellum as a thread-like extension of the upper of the two lip-like prominences.
With the aid of the high magnifying power employed on this occasion, it was, how-
ever, clearly shown that the inner surfaces of these lip-like prominences actually
represented the upper and lower boundary walls of a conical or infundibular excava-
tion or vestibulum, the innermost recess of which fulfils the office of an oral
aperture by permitting the free passage of exceedingly minute food-particles. This
infundibular cleft, the walls of which are so thin and transparent as to require
the aid "of the highest powers of the microscope for their satisfactory delineation,
are at once suggestive of the infundibular, collar-like, pre-oral expansion of the
Choanophorous order of the Flagellata Codosiga, Salpingceca, &c., and may not

' Infusionsthiere,' Abth. ii., 1867. t Ibid., Abth. iii., 1878.

GENUS E UGLENA . 381

improbably be to some extent homologous with it. The flagellum was in all cases
demonstrated to take its origin within the interior and close to the bottom of the
infundibuliform excavation.

Euglena viridis, Ehr. PL. XX. FIGS. 29-51.

Body elongate, subcylindrical or fusiform, exceedingly flexible and
variable in shape, mostly rounded anteriorly, and with a short, transparent,
conically pointed, tail-like posterior prolongation ; cuticular surface faintly
striate obliquely ; endoplasm usually entirely bright green, but sometimes
changing to dark orange or red ; flagellum slender, exceeding the body in
length, a red pigment-spot generally present at the anterior extremity ;
contractile vesicle situated at the anterior extremity, close to the coloured
pigment-spot ; endoplast, spherical, subcentral. Length 1-600" to 1-140".

HAB. — Pond and stagnant water, on the surface of which it frequently
occurs in vast shoals.

The aspects presented by this animalcule under various developmental or
external conditions are so numerous and diverse as to have led to its description by
the earlier writers under several specific titles. There can be little doubt that the
Euglena snnguinea of Ehrenberg, having the same external form, but of a blood-red
colour, or variegated with red and green, represents one of the matured phases of
the species now under consideration, while the E. hyalina of the same authority
illustrates a still less well-marked variation, in which, through probably the absence
of suitable food-material, the endoplasm is almost completely transparent. It is
maintained by Perty that the Amblyophis viridis of Ehrenberg — which has received
a separate generic title on account merely of the rounded instead of pointed and
more tail-like posterior extremity — is also a variation only of Euglena viridis, it
occurring in company with the normal animalcules, and according to him being
reproduced directly from them. As the latter generic distinction is, however, allowed
by more recent writers, including more especially Stein, it appears desirable to retain
it in this treatise.

Endogenous multiplication, manifested by the diyision of the entire coloured
inner substance of Euglena vii idis into germs of variable number and subfusiform
or irregular contour, as shown at PI. XX. Figs. 36 and 37, and in a manner
most nearly resembling that already recorded of Polytoma uvella, was observed
by the present author in connection with the observations relating to the oral
apparatus previously described, as also encystment, attended sometimes by and
sometimes without the coalescence of two individual zooids. The result of the
process of encystment, as shown at PI. XX. Figs. 49 and 50, was the breaking up
of the entire protoplasmic body-contents into numerous globular spore-like bodies,
which were ultimately released as small, green, creeping amrebae, Fig. 51, pos-
sessing at this early stage no trace of the flagellum, oral aperture, or pigment-
spot which were subsequently acquired. The fusiform zooids produced by the
subdivision of the internal substance of the motile Euglence appear on the contrary
to be furnished in most instances with both a flagellum and eye-speck, on bursting
through the investing membrane of the parent cell ; this observation is further con-
firmed by the investigations of both Kolliker and Mr. Carter. In addition to the
reproductive form of encystment just described, Euglena is in the habit, upon the
drying up of the ponds or ditches that contain it, of assuming a sphejical form and,
throwing around itself a gelatinous envelope which becomes gradually indurated,' of
remaining in this quiescent state until the return of genial conditions. In this
manner the temporarily encysted Euglence often form film-like expansions of con-
siderable extent, and have been mistaken for independent forms of Algae. Microcystis
olivacea and M. Noltii, as also the Protococcus turgidus and P. chalybius of Kiitzing,
are thus now regarded as representing variable phases of this resting condition of

382 ORDER FLAGELLA TA-EUSTOMA TA.

Euglena viridis. The existence of the contractile vesicle in this species, and its
rhythmical though slow pulsations, were distinctly authenticated on repeated occa-
sions. In various instances there appeared to be two of these organs situated close
to one another near the anterior eye-like pigment-spot In demonstration of the
unreliability of the characters afforded by the last-named structure, Dujardin figures
an example in which no less than three of these coloured bodies are present, while
instances not unfrequently occur in which it is altogether absent.

Stein, in his recently published work,* has given very copious illustrations of
this cosmopolitan species. From them are here reproduced his delineations of
a mode of reproduction that has not been previously recorded. This, as shown at
Figs. 39-41 of PL XX., is brought about by the abnormal growth and enlargement
of the endoplast, which next breaks up into innumerable spore-like bodies that
are finally liberated during the life of the animalcule as minute monadiform germs.
A similar process of reproduction is likewise attributed by this same authority
to the genus Trachelomonas. Encysted conditions resulting in the subdivision of
the entire body-mass into sporular bodies, as delineated by Stein, are reproduced at
Figs. 44-48, while simple fission, as it occurs in the temporarily encysted state, is
represented at Fig. 43. Fission during the motile life of this animalcule takes place
in a longitudinal direction.

An interesting local variety of Euglena viridis has been recently described by
Mr. M. H. Robson, of Newcastle-upon-Tyne, in ' Science Gossip ' for October 1879,
in which the distal extremity of the flagellum presents an inflated knob-like aspect,
as shown at PI. XX. Fig. 29. Possibly such modification of this important organ
represents a phase preliminary to its entire withdrawal, and antecedent to the
entrance of the animalcule upon the encysted or resting state.

Euglena spirogyra, Ehr. PL. XX. FIGS. 27 AND 28.

Body elongate, sub-cylindrical, seven or eight times as long as broad when
extended ; slightly truncate anteriorly, the posterior extremity produced as
a transparent, ensiform, tail-like prolongation ; cuticular surface ornamented
with even closely approximated oblique rows of minute bead-like elevations ;
colour bright green, yellow, or brown ; endoplasm usually containing two
large ovate or elliptical amylaceous bodies, between which the ovate or
subspheroidal endoplast is located ; contractile vesicle situated at the
anterior extremity immediately behind the scarlet eye-like pigment-spot.
Length 1-240" to 1-120". HAB. — Fresh water, solitary.

According to Mr. Carter, the obliquely striate aspect of this and other species
of Euglena is occasioned by the presence beneath the cuticle of a layer of pointed
sigmoid fibrillae. The examination of numerous living examples of this type by
the present author, with the aid of a magnifying power of 800 diameters, has,
however, failed to reveal any such complex structure, though, on the other hand,
the entire surface of the cuticle was shown to be traversed by oblique rows of
closely approximated bead-like prominences ; the peripheral margin of the body
presented at the same time a finely crenulate aspect, demonstrating that the bead-
like appearance was a structural reality, and not a mere optical appearance. A
similar beaded pattern of the cuticular layer, though of a more open character, is
furthermore characteristic of the figures of this species as given by Stein. In
addition to the central nucleus or endoplast, two large obliquely disposed elliptical
or subcylindrical amylaceous corpuscles, situated, the one a little in front of, and the
other shortly behind, the centre of the body, as shown at PL XX. Fig. 27 a a,
were usually observed. The contractile vesicle, as in E. viridis, is located imme-
diately to the rear of the eye-like pigment spot.

' Infusionsthiere,' Abth. iii., 1878.

GENUS EUGLENA. 383

Euglena oxyuris, Schmarda. PL. XX. FIG. 26.

Body elongate, subcylindrical, or ligulate, eight or nine times as long as
broad when extended, often spirally contorted, terminating posteriorly in
a long, slightly curved, spur-like, caudal prolongation ; cuticular surface
obliquely striate ; amylaceous corpuscles cylindrical or elliptical, often very
numerous; colour green. Length 1-130". HAB. — Freshwater.

The simple oblique striation of the cuticular surface, and less conspicuous deve-
lopment of the caudal spine, serve to distinguish this type from E. spirogyra.
The figure here given of the species, reproduced from Stein's drawings, represents
an animalcule in its more abnormal contorted condition.

Euglena deses, Ehr. PL. XX. FIGS. 52 AND 53.

Body elongate, vermicular, cylindrical, fifteen to twenty times as long
as broad, acutely pointed posteriorly when extended, but capable of assuming
the most protean contours ; cuticular surface smooth ; colour green ; amyla-
ceous corpuscles acicular. Length 1-760" to 1-240".

HAB. — Pond water, among Lemnse.

The figures here given are reproduced from Stein's recently published volume ;
that represented at Fig. 53 is described in the index as a young non-flagelliferous
example, whose locomotion is effected by peristaltic movements of the body.
According to Ehrenberg, this species never swims, but confines its motions to
sluggish creeping and twisting.

Euglena acus, Ehr. PL. XX. FIGS. 24 AND 25.

Body very slender and elongate, from seven or eight to ten or twelve
times as long as broad, tapering towards both extremities, the anterior
end abruptly truncate, the posterior one acuminately pointed ; cuticular
surface smooth ; colour bright green ; a red eye-like pigment-spot usually
developed ; contractile vesicle conspicuous, anteriorly situated ; amylaceous
corpuscles numerous, elongate rectangular. Length 1-5/0" to i-uo".

HAB. — Fresh and brackish water.

Quite recently, November 1880, the author has received examples of this species
from the neighbourhood of Birmingham through Mr. Thomas Bolton. The speci-
mens thus examined yielded an average length of 1-150", and were remarkable for
the fact that, excepting for the anteriorly developed eye-like pigment-spot, their
body-substance was perfectly transparent — a circumstance attributable probably to
their having been for a long while deprived of their ordinary food-material. All
the examples were exceedingly attenuate, their greatest central breadth usually
scarcely exceeding that of the truncate anterior border. Their deportment in the
water, unlike that of most representatives of the genus Euglena, was remarkably
stiff. On rare occasions only were they observed to flex their bodies to the extent
represented at PI. XX. Fig. 25, while in no instances did they exhibit protean
contractions and expansions as attested to in other of Stein's recent delineations.
Such metamorphic properties are apparently, in accordance with the index to his
figures, manifested chiefly by the older zooids. A number of examples were
observed with their more attenuate posterior extremities affixed to the glass slide or
accompanying organic debris, the movements of their flagella under such conditions
causing their stiff acicular bodies to revolve in circles as though on a pivot. Not
unfrequently a number of zooids becoming attached in this manner close to each

384 ORDER FLAGELLATA-EUSTOMATA.

other, recalled to mind the group of Leptomonas Biltschlii represented at PI. XIII.
Fig. 25. In all the examples a greater or less number of rectangular attenuate
amylaceous corpuscles were clearly discerned.

Euglena rostrata, Ehr.

Body elongate, conical, tapering posteriorly, and terminating in a short
tail-like process, the anterior extremity bent in a beak-like manner ; colour
green. Length 1-500". HAB. — Pond water.

Euglena geniculata, Duj.

Body elongate, subcylindrical, more or less even throughout, flexible,
but slightly contractile, with an obliquely directed tail-like prolongation ;
cuticular surface smooth, colour green ; red pigment-spot conspicuous.
Length 1-200" to 1-170". HAB. — Pond and river water.

This species may be distinguished from E. spirogyra, which it most nearly
approaches, by the smooth surface of the cuticle and the obliquely directed caudal
ter mination.

Euglena fusiformis, Carter. PL. XX. FIG. 58.

Body shortly fusiform, about one and a half times as long as broad,
obtusely pointed at each extremity, the anterior one faintly bilabiate ; no
posterior tail-like prolongation ; colour rich green ; endoplast central,
situated between two refractive, nucleated, cell-like structures, which extend
round the body equatorially ; contractile vesicle and eye-like pigment-
spots anteriorly located ; parenchyma a rich green colour ; motion rotatory
and oscillating. Length 1-700".

HAB. — Fresh-water tanks, Bombay.

This species should probably be included in the genus Amblyophis. The
Euglena zonalis of Carter, somewhat resembling it, is referred by Stein to the genus
Chloropeltis.

Euglena agilis, Carter. PL. XX. FIG. 64.

Body somewhat flask-shaped, inflated and widest posteriorly, attenuate
anteriorly ; a short, blunt, caudal prolongation sometimes present, but not
essential ; multiplying in its active condition by longitudinal and trans-
verse fission, and in its passive or encysted one by crucial or by linear
segmentation; colour green; movements very active. Length 1-600".

HAB. — Brackish water, Bombay.

This species, described by Mr. H. J. Carter in his ' Notes on the Fresh-water Infu-
soria of the Island of Bombay,' * is remarkable for its occasional linear mode of
segmentation, briefly referred to in the foregoing diagnosis, the cyst-like envelope
that encloses the segmented fragments being so transformed, PL XX. Fig. 64, as
to assume an elongate subcylindrical contour. The germs, four in number, produced
by this fissive process are each provided with a red eye-like pigment. A somewhat
parallel linear mode of segmentation of the encysted animalcules has been reported
by Claparede and Lachmann of the Cilio- Flagellate genus Peridinium, and are
represented at PI. XXV. Figs. 49 and 50.

Ann. and Mag. Nat. Hist.,' Aug. and Sept. 1856.

GENUS AMBLYOPHIS. 385

Euglena tuba, Carter. PL. XX. FIGS. 54 AND 55.

Body fusiform, subcylindrical, fish-shaped ; obtuse and bilabiate an-
teriorly, terminating posteriorly in a short, pointed, tail-like prolongation ;
eye-like pigment-spot and contractile vesicle anteriorly situated ; colour
green. Length 1-300". HAB. — Fresh water, Bombay : social.

Although this animalcule in its normal free-swimming condition presents no
important distinction from Euglena viridis, it exhibits in its quiescent or encysted
state a highly characteristic deviation. In this condition, according to its dis-
coverer, the animalcules produce by exudation, as shown at PI. XX. Fig. 55, a common
reticulate, transparent, gelatinous basis, within the tubular ramifications of which they
secrete individually a flask-shaped cyst or lorica, having a round inflated basal
portion and a long tubular neck, the apical extremity of which is dilated like the
mouth of a trumpet. The relationship between the free-swimming animalcules
and these flask-shaped encystments cannot be said to be definitely determined.
Although not mentioned in the original description of this form,* Mr. Carter has
personally informed the author that the motile and encysted conditions were not
observed in direct connection with one another, but that the tank from which
they were taken, while found on one occasion to yield the free-swimming Etiglentz
in abundance, produced in the place of these, when visited a few days later, a com-
plete surface-stratum of the encysted structures immersed in their gelatinous network.
The contour of these cysts, with their elongate necks and everted apertures, is so
distinct from what is met with among the members of the ordinary Euglenidae, but
at the same time corresponds so remarkably with that of the flask-shaped loricse of
the collared monad Salpingozca ampJwridium and its allies, that the author is half
inclined to suspect that a further investigation may elicit that this presumed encysted
state of Euglena tuba is in no way connected with the free-swimming animalcules
observed by Mr. Carter, but represents the quiescent condition of an as yet unde-
scribed type of the Choano-Flagellate order. Should these premises prove correct,
this organism will constitute a new generic type of the group indicated, corre-
sponding closely with the mucous inhabiting Phalansterium, but representing in
itself a most interesting departure in the direction of the sponges.

Euglena — Supplementary.

The Euglena ovum of Ehrenberg is now referred by Stein to the genus Chloro-
peltis, and the E. pyrum and longicauda of the same authority to that of Phacus.
The Euglena mucronata of Perty, with its pointed tail and finely striped cuticle, is
scarcely to be distinguished from E. spirogyra, while the E. obscura of Dujardin
would seem to represent a variety only of E. viridis. De Fromentel has introduced
into his work, \ as new species of Eugiena, several forms, all of which, however,
might be referred to E. viridis, and differ from each other only in minor points of
contour and coloration. The reproduction of these names with their diagnoses
would serve only to further burden and embarrass the synonymy of the genus.

GENUS II. AMBLYOPHIS, Ehrenberg.

Animalcules uniflagellate, free-swimming, elongate, flexible and
changeable in form, rounded posteriorly, never exhibiting a tail-like pro-
longation of this region ; endoplasm coloured green ; an anterior eye-like
pigment-spot usually present ; the front margin apparently bilabiate, in-
dicating the presence of an oral aperture resembling that of Euglena, this
sometimes followed by a distinct pharyngeal tract.

* ' Ann. and Mag. Nat. Hist.,' April 1869. t 'Etudes sur les Microzoaires,' Paris, 1876.

2 C

386 ORDER FLAGELLATA-EUSTOMATA.

In accordance with the views of Perty and other writers, the type of this genus
represents merely a tail-'ess variety of Euglena viridis; its generic and specific dis-
tinctness is, however, maintained by Stein.

Amblyophis viridis, Ehr. PL. XX. FIG. 63.

Body elongate, subcylindrical or compressed, rounded posteriorly, highly
flexible, eight or ten times as long as broad when extended ; the anterior
margin obliquely truncate, transparent, apparently bilabiate, perforated by
the oral aperture and succeeding tubular pharyngeal tract, the remaining
endoplasm coloured bright green ; a red eye-like pigment-spot usually
present ; endoplast central, subspherical, several rod-like amylaceous cor-
puscles generally developed. Length 1-2 10" to 1-140".

HAB. — Pond and stagnant water, in company with Euglena viridis.

Amblyophys segyptiaca, Schmarda.

Body elongate, rounded and widest posteriorly when extended, oval or
spherical when contracted ; flagellum equalling the body in length ; eye-
like pigment-spot conspicuous ; colour dull green. Length, 1-480" to
1-360". HAB. — Fresh water, Egypt. (Schmarda.*)

GENUS III. PHACUS, Dujardin.

Animalcules free-swimming, persistent in form, mostly compressed and
leaf-like, terminating posteriorly in a sharp-pointed tail-like prolongation ;
oral aperture terminal, not projecting, followed by a distinct tubular pharynx,
giving origin to a single long, vibratile flagellum ; cuticular surface indurated ;
endoplasm coloured green, usually enclosing anteriorly an eye-like pigment-
spot ; contractile vesicle large, subspheroidal, situated close to the eye-like
pigment-spot; endoplast conspicuous, frequently modified as in Euglena,
and forming by subdivision one or more large oval sporosacs. Inhabiting
fresh water.

The several forms referred to this genus by Dujardin were originally described
by Ehrenberg as species of Euglena, from which they differ essentially in their
persistent form and in the more or less indurated consistence of their cuticular layer,
which often remains as an empty shell after the dissolution of the enclosed contents.

Phacus pleuronectes, Mull. sp. PL. XXI. FIGS. 2-5.

Body obovate, compressed, leaf-like, one and a half times as long as
broad, caudal prolongation about one-quarter the length of the body,
directed obliquely towards the dorsal aspect ; cuticular surface smooth, or
presenting a faintly striate appearance only in its empty state ; endoplasm
bright green, often enclosing a large, central, spheroidal, amylaceous cor-
puscle ; endoplast spherical, posteriorly located ; contractile vesicle con-
tiguous to the eye-like pigment-spot, frequently exhibiting irregularly
developed lateral lacunae. Length 1-1200" to 1-480".

HAB. — Stagnant water.

* ' Denkschrift der Kaiser. Akad. der Wiss. Wien,' 1854.

GENUS CHLOROPELTIS. 387

This species was originally described by O. F. Miiller under the title of Cercaria
plcuronect's, it was transferred to that of Euglena by Ehrenberg, and to the present
one of Phacus by Dujardin. Examples figured in Stein's recently published volume
are represented as containing three or four large ovate sporosacs, his " Keimsacken,"
or the so-called " glaire-cells " of Mr. H. J.' Carter, each of these enclosing an
endoplastule in an apparently unaltered state.

Phacus triqueter, Ehr. sp. PL. XXI. FIG. i.

Body ovate, compressed, leaf-like, having a raised keel-like elevation
produced down the centre of the right-hand side, presenting in transverse
section a triquetrous contour ; caudal prolongation one-fourth or one-third
the length of the body, acuminately pointed, directed obliquely towards
the .dorsal aspect ; cuticular surface finely but distinctly striate longitudi-
nally. Length 1-580". HAB. — Fresh water, amongst Lemruz.

Identical with the Euglena triqueter of Ehrenberg.

Phacus pyrum, Ehr. sp. PL. XXI. FIG. 10.

Body subfusiform or pyriform, about twice as long as broad, continued
posteriorly as a straight acuminate tail-like prolongation which equals or
slightly exceeds in length one-half of the preceding body portion ; cuticular
surface coarsely and obliquely sulcate. Length 1-1200" to 1-864".

HAB. — Pond water.

First figured and described by Ehrenberg under the title of Euglena pyrum.

Phacus longicaudus, Ehr. sp. PL. XXI. FIGS. 6 AND 7.

Body ovate, compressed and leaf-like, often contorted or twisted upon
its axis, from one and a quarter to twice as long as broad ; produced
posteriorly as an acuminate, mostly straight, but sometimes irregularly
curved caudal prolongation, which nearly equals the body in length ;
cuticular surface finely striate longitudinally. Length 1-480" to 1-120".

HAB. — Fresh water.

As explained by Stein in his index to the figures given of this species,* it is enabled
to change from the more normal flattened form to the screw-like or spirally twisted
contour, though in consequence of the comparatively hardened consistence of the
cuticle the process is very slow and gradual. In its power to alter in any way
its external configuration, this type differs essentially from the preceding species,
and may be said in consequence to occupy an intermediate position between the
typical members of the two genera Euglena and Phacus. The animalcule was
originally referred by Ehrenberg to the first-named genus.

GENUS IV. CHLOROPELTIS, Stein.

Animalcules free-swimming, persistent in shape, more or less ovate,
usually compressed, terminating posteriorly in an acuminate tail-like
prolongation ; oral aperture terminal, situated at the extremity of a short,
conical, snout-like prolongation, giving origin to a single, long, vibratile

* ' Infusionsthiere,' Abth. iii., 1878.

2 C 2

388 ORDER FLAGELLATA-EUSTOMATA.

flagellum, succeeded posteriorly by a slender pharyngeal passage; endoplasm
coloured green, generally enclosing an anterior eye-like pigment-spot ;
contractile vesicle and endoplast conspicuous. Inhabiting fresh water.

So far as it is possible to determine from the figures, with their accompanying
indices, given by Stein,* the members of this genus are to be distinguished from
those of Phacus by the presence only of the conical anterior prolongation which is
perforated at its apex by the oral aperture. In all other respects the two appear to
essentially agree.

Chloropeltis hispidula, Eichwald sp. PL. XXI. FIGS. 8 AND 9.

Body broadly ovate, compressed, nearly as broad as long ; caudal pro-
longation straight or slightly curved, equalling one-third of the length of
the body ; cuticular surface longitudinally ribbed, each rib thickly hispid
throughout ; an anterior eye-like pigment-spot usually developed ; the
contractile vesicle situated close to the termination of the pharyngeal
passage, and apparently communicating with it ; endoplast ovate, posteriorly
located. Length 1-500". HAB. — Fresh water.

The general contour of the body of this species coincides remarkably with the
flattened and longitudinally ribbed fruit of various Umbelliferous plants, and more
especially perhaps with that of the common parsnep, Pastinaca ; it was originally
described by Eichwald \ as a species of Euglena. As figured in Stein's recent
work, the number of longitudinal hispid ribs is shown to vary considerably in
different individuals. In some there are only half-a-dozen upon each flattened side,
while in others there may be as many as or more than twice that number.

Chloropeltis ovum, Ehr. sp. PL. XXL FIGS. 11-13.

Body somewhat variable in form, mostly symmetrically elliptical and
cylindrical, but sometimes subspheroidal or subfusiform ; caudal prolonga-
tion short, acuminate ; cuticular surface usually finely striate in an oblique
but more exceptionally in a longitudinal direction ; anterior conical projec-
tion conspicuously developed ; endoplasm often enclosing two large or
four smaller, circular, bilaterally corresponding, amylaceous corpuscles-
Length 1-1500" to 1-640". HAB. — Fresh water.

This species was first described by Ehrenberg under the title of Euglena ovum.
Stein proposes to identify the more attenuate, fusiform variety with the Euglena
zonalis of Mr. Carter.

GENUS V. TRACHELOMONAS, Ehrenberg.

Animalcules monoflagellate, plastic and changeable in form, enclosed
within a free-floating, ovate or spheroidal, indurated sheath or lorica, the
anterior extremity of the lorica perforated by a minute aperture, through
which in its normal condition the single flagellum only is protruded ; oral
aperture terminal, followed by a distinct pharyngeal passage endoplasm
coloured green, with usually a red pigment-spot at the anterior extremity ;
contractile vesicle single, spherical, located near the anterior pigment-spot.
Mostly inhabiting fresh water.

* ' Infusionsthiere,' Abth. iii., 1878. t ' Infusoria Russlands,' 1847.

GENUS TRACHELOMONAS. 389

It has quite recently been shown by Stein * that the animalcules of this genus
correspond essentially with those of Euglena, and from the representatives of which,
indeed, they are distinguished only by their possession of a variously shaped indurated
lorica. In accordance with the more recent researches of this authority, the three
Ehrenbergian genera, Lagenella, Chcetotyphla, and Chcetoglena must also be merged
with Trachelomonas, these several forms exhibiting merely slight modifications in the
contour of the loricae that possess simply a specific value. As first described by
Ehrenberg, the lorica, in both Chcctotyphla and Chcztoglena, is reported to be siliceous,
but is evidently, as in the more normal Trachelomonads, simply corneous, but at the
same time of an exceedingly brittle and almost shell-like consistence. Lagenella was
separated by Ehrenberg from Trachelomonas with reference merely to the neck-
like prolongation of the minute terminal aperture, but which may be variously
developed or even almost entirely suppressed in individuals of the same species.
While under ordinary circumstances the bodies of the animalcules of this genus are
entirely enclosed within their ovate or spheroidal loricae, their lash-like flagella only
protruding, it was originally observed by Perty, and more recently by Stein, that
under certain conditions they contrive to squeeze through the minute anterior
aperture, the extruded body under such circumstances presenting the aspect of
a normal Euglena. This feat, comparing the large size of the animalcule's body
with the minute diameter of the orifice of the lorica, appears, as remarked by
Stein, to be as difficult of achievement as the passage of the proverbial camel through
the eye of a needle. The various phases of this process as delineated by him,
and reproduced at PL XXI. Figs. 15 and 22, serve to demonstrate the almost
amoeboid plasticity of the endoplasm and overlying cuticle. In many species the
lorica is remarkable for its red or crimson hue, this tint, however, being conspicuous
only as concentrated at the periphery, where it appears as a brilliantly coloured
ring or band around the bright green endoplasm of the enclosed animalcule.
Multiplication through the liberation from the parent body of a multitude of minute
monoflagellate germs has been observed by Stein in several species of the genus.

Trachelomonas volvocina, Ehr. PL. XXI. FIGS. 14-16.

Lorica spheroidal, entirely smooth, aperture usually level with the
adjacent wall but sometimes produced so as to form a minute cylindrical,
projecting neck ; periphery presenting the aspect of an encircling crimson
ring. Length i-iooo" to 1-860".

HAB. — Fresh water, amongst Conferva.

In one example of this species as figured by Stein, the tubular neck is produced
into the interior cavity of the lorica, which in consequence resembles in contour
the shell of the Foraminiferous genus Entosolenia ; reference to this abnormal form
will no doubt appear with the forthcoming descriptive text. In other figures, here
reproduced, the egress of the animalcule through the minute aperture of the lorica
and the liberation from the body of the parent of a swarm of monociliated germs
are depicted.

Trachelomonas mgulosa, Stein. PL. XXI. FIG. 17.
Lorica spheroidal, resembling that of T. volvocina, excepting that its entire
external surface is finely wrinkled ; anterior aperture plane or slightly pro-
minent. Length 1-1080". HAB. — Fresh water.

Trachelomonas lagenella. Stein. PL. XXI. FIGS. 18 AND 19.
Lorica colourless, oval or elliptical, nearly one and a half times as
long as broad, the anterior and posterior extremities even, sometimes

* ' Infusionsthiere,' Abth. iii., 1878.

390 ORDER FLA CELL A TA-E US TO MA TA .

subquadrate, its surface entirely smooth ; the anterior aperture produced as
a short, tubular, obliquely projecting neck. Length 1-1200" to 1-750".
HAB. — Fresh water.

This species is identified by Stein with the Lagenella euchlora of Ehrenberg, and
should apparently retain the specific title conferred upon it by the last-named
authority. One example, PI. XX. Fig. 19, as represented by Stein, has assumed
a quiescent condition within its lorica, and become divided into two equal
spheroidal moieties.

Trachelomonas cylindrica, Ehr. PL. XXI. FIG. 20.

Lorica elongate, cylindrical, about three times as long as broad, entirely
smooth, anterior aperture plane or produced as a short tubular neck ;
colour crimson or purple. Length i-iooo". Hab. — Fresh water.

The Trachelomonas nigricans of Ehrenberg, coinciding in general form, but
having the lorica coloured a deep reddish or blackish brown, is regarded by Perty
as an older condition only of the present species.

Trachelomonas hispida, Pty. sp. PL. XXI. FIGS. 21-23.

Lorica evenly ovate or elliptical, from a little over one and -a half to
nearly two and a half times as long as broad, the entire surface finely and
evenly hispid ; anterior aperture plane or forming a short cylindrical neck ;
walls of peripheral border scarlet or crimson. Length 1-1150" to 1-600".

HAB. — Fresh water.

This species is identified by Stein with the Chatoglena volvodna of Ehrenberg and
with the Chonemonas hispida and C. Schrankii of Max Perty. It is necessary to remark,
however, that the enclosed animalcule is represented by Perty as having two long,
equal-sized flagella, as in Eutreptia, instead of a single one as figured by the first-
named writer. The lorica of this type is susceptible of a very considerable range of
variation, it, in addition to the two contours mentioned in the foregoing diagnosis,
being sometimes supplemented, as in T. caudata and T. acuminata, with a short,
conical, tail-like prolongation. The empty shell has been observed by both Stein
and Perty to be finely striate obliquely in cross directions, the intersection of these
lines communicating to the entire structure a reticulate appearance.

Trachelomonas eurystoma, Stein. PL. XXI. FIG. 27.

Lorica ovate, bluntly pointed posteriorly, about one and a half times
as long as broad, surface smooth, anterior aperture comparatively wide,
slightly projecting, its edges crenulate. Length 1-812".

HAB. — Fresh water.

Trachelomonas armata, Ehr. sp. PL. XXI. FIG. 25.

Lorica broadly ovate or elliptical, about one and a quarter times as long
as wide ; ten or twelve long claw-like spines projecting from the posterior
margin, and a number of short conical ones sometimes disposed around
the short tubular anterior aperture ; the intervening area smooth ; the free
edge of the short neck-like projection sometimes finely toothed ; colour
brown. Length, excluding the posterior spines, 1-650".

HAB. — Fresh water.

GENUS RAPHIDOMONAS. 391

This animalcule is identified by Stein with both the Chtztotyphla armata and
C. aspera of Ehrenberg. As in many other species of the genus, the lorica presents
a wide range of individual variation, this being manifested most prominently in con-
nection with the more or less extensive development of the spinous processes.

Trachelomonas caudata, Ehr. sp. PL. XXI. FIG. 24.

Lorica elongate-ovate or flask-shaped, two or three times as long as
broad, tapering posteriorly and further produced into an acuminate tail-like
process, the anterior aperture developed in a neck-like manner, its free
margin everted and deeply toothed ; the entire surface, exclusive of the
anterior and posterior prolongations, finely and densely hispid. Length
1-864" to 1-480". Hab. — Fresh water.

This species is identified by Stein with the Chcetoglena caudata of C. G. Ehrenberg.

Trachelomonas bulla, Stein.

Lorica elongate-ovate, from two and a half to three times as long as
broad, produced anteriorly into a conical, neck-like prolongation ; the
surface entirely smooth or beset with minute hispid points which are both
finer and less thickly distributed than in T. hispida and T. caudata. Length
1-500" to 1-430". HAB. — Fresh water.

Trachelomonas acuminata, Schm. sp. PL. XXL FIG. 26.

Lorica obovate or flask-shaped, inflated and widest posteriorly, supple-
mented in that region by an acuminate and somewhat irregular tail-like
process, the anterior extremity produced into a cylindrical, moderately
large, obliquely-truncate, neck-like prominence, the surface entirely smooth
throughout. Length 1-500". HAB. — Fresh water.

This animalcule was originally described by Schmarda under the title of Lagenella
acuminata, and is refigured and referred to the present generic group by Stein.

Doubtful Species.

Pritchard's ' Infusoria ' includes the briefest possible diagnosis of two additional
species of Trachelomonas as follows, and without any reference to their original
describers : —

" T. areolata, globose, surface areolated.

" T. aspera, similar to the preceding, but its surface covered with rough points."

GENUS VI. RAPHIDOMONAS, Stein.

Animalcules free-swimming, monoflagellate, moderately contractile ; oral
aperture terminal, conducting to a well - defined pharyngeal chamber ;
cuticular layer enclosing a large number of variously distributed trichocysts ;
contractile vesicle and endoplast conspicuous ; colour green.

This genus is founded by Stein on the Monas semen of Ehrenberg ; excepting
for the presence of numerous and variously distributed trichocysts it closely
resembles Ccelomonas.

392 ORDER FLAGELLATA-EUSTOMATA.

Raphidomonas semen, Ehr. sp. PL. XX. FIGS. 60-62.

Body elongate-ovate, flexible and somewhat variable in form, usually
rounded and widest anteriorly, tapering and slightly attenuate posteriorly,
from two and a half to three times as long as broad ; flagellum scarcely
equalling the body in length, issuing from the anterior oral fossa ; pharyngeal
chamber subtriangular or lunate, transversely placed ; contractile vesicle
single, anteriorly situated ; endoplast large, ovate, subcentral ; endoplasm
green ; trichocysts most abundant along the anterior margin. Length 1-575"
to 1-400".

HAB. — Marsh water, among decaying Sphagnum ; movements sluggish,
vacillating.

As originally described by Ehrenberg under the title of Monas (?) semen, this
species is distinguished by the presence of a peculiar triquetrous structure beneath
the frontal border, by the enclosure within its substance of numerous minute spicular
bodies, and by its apparent possession of fine vibratile cilia. As now shown by
Stein * the first-named structure represents a capacious subtriangular pharyngeal
excavation, which communicates with the oral aperture and is homologous with the
still more conspicuous spheroidal one possessed by Cozlomonas grandis ; the pre-
sumed cilia he has further demonstrated to coincide with the anteriorly placed tricho-
cysts in their exserted state, as shown at PL XX. Fig. 61. In their more normal
retracted condition these trichocysts — coinciding with Ehrenberg's spicular bodies —
present the aspect of simple minute bacillar bodies which underlie, as an even and
closely set row, the entire frontal border, and are found distributed irregularly and
in various degrees of abundance throughout the remaining body area. Although
not taking the form of evenly distributed lines in the last-named region, they appear
from Stein's figures to maintain mostly a uniform longitudinal disposition. Meresch-
kowski's genus Merotricha, see p. 249, would appear to represent the only other
Flagellate animalcule to which the existence of trichocysts has been accurately
demonstrated, though, in accordance with the recent investigations of O. Biitschli,
there is reason for believing that analogous structures are possessed also by
Chilomonas paramecium. In neither instance, however, have they been shown to
possess a distinct capacity of extension and retraction, as is recorded by Stein of
Raphidomonas.

GENUS VII. CCELOMONAS, Stein.

Animalcules free-swimming, monoflagellate, highly contractile and vari-
able in form, having a distinct anterior oral aperture, which conducts to a
capacious subspheroidal pharyngeal chamber ; endoplast and contractile
vesicle conspicuous, no trichocysts. Inhabiting fresh water.

This genus is founded by Stein t on the Monas grandis of Ehrenberg, its dis-
tinctive feature being the capacious pharyngeal chamber, usually filled with a fluid
substance, that follows upon the well-developed oral cleft. While a somewhat
similar pharyngeal excavation is developed in both Raphidomonas and Microglena,
it does not in either of these latter types attain the proportions characteristic
of the present genus. More correctly, perhaps, this so-called "body-cavity," or
" Leibes/iohle" as it is designated by Stein in his index to the various figures given,
may be compared with the vestibular fossa of Vorticclla and other Peritricha, the
resemblance in contour between these structures being more particularly pro-
minent in the type previously described under the title of Raphidomonas semen.

Infusionsthiere,' Abth. iii., 1878. f Ibid.

GENUS COLACIUM. 393

Coelomonas grandis, Ehr. sp. PL. XX. FIG. 59.

Body highly contractile and variable in form, regularly or irregularly
elongate-ovate or subspheroidal, pharyngeal dilatation occupying nearly
the entire anterior half of the body ; flagellum short, not equalling the
body in length ; cuticular layer enclosing innumerable golden-green
chlorophyll-granules ; contractile vesicle single, anteriorly situated ; endo-
plast spheroidal, subcentral. Length 1-430".

HAB. — Marsh water ; movements sluggish.

This species, as previously intimated, is identical with the Monas grandis of
Ehrenberg.

GENUS VIII. ASCOGLENA, Stein.

Animalcules solitary, monoflagellate, highly elastic and changeable in
shape, enclosed within a sessile tubular or flask-shaped lorica, to the bottom
of which they adhere by the posterior extremity ; endoplasm coloured
green, enclosing an anterior eye-like pigment-spot ; oral aperture and
contractile vesicle as in Euglena. Inhabiting fresh water.

The representatives of this genus may be described as Ettglence which secrete
and inhabit sessilely attached loricae and hold in their family group a position
corresponding with that occupied by Vaginicola as compared with Vorticdla among
the Vorticellidae, or that of Salpingceca with relation to Monosiga among the Choano-
Flagellata.

Ascoglena vaginicola, Stein. PL. XXI. FIGS. 28 AND 29.

Lorica erect, tubular, subcylindrical, rounded and widest posteriorly,
tapering gradually towards the anterior aperture, about three times as long
as broad, its consistence finely granular with a somewhat more transparent
anterior border ; animalcule clearly visible through the walls of the lorica,
Euglena-like and highly contractile, its distal extremity when extended
reaching to the anterior aperture ; dividing within the lorica by transverse
fission. Height of lorica 1-640". HAB. — Fresh water.

GENUS IX. COLACIUM, Ehrenberg.

Animalcules monoflagellate, exhibiting two distinct phases of existence,
the one free-swimming and the other sedentary : in the motile stage solitary,
highly elastic and changeable in form, and in all essential details corre-
sponding with simple free-swimming Euglencz ; in the sedentary stage affixed
socially, mouth downwards, to a simple stalk or to the extremities of a more
or less elevated branching pedicle or zoodendrium, which is produced by
the repeated longitudinal fission of a single primary zooid ; endoplasm
coloured green, enclosing an anterior eye-like pigment-spot ; oral system,
endoplast, and contractile vesicle, as in Euglena. Inhabiting fresh water.

The several species referred to the genus Coladum, as originally instituted by
Ehrenberg, are not represented as possessing any distinct flagelliform appendage,
though the presence of one or more such organs was suspected by him through the

394 ORDER FLAGELLATA-EUSTOMATA.

observation of almost constantly recurring currents in the surrounding water. The
practical demonstration of the possession by these animalcules of a single terminal
flagellum, of their enjoyment of a solitary free-swimming and social colony-building
existence, and of their entire structural correspondence during the former phase with
the zooids of the genus Euglena, was arrived at by the author in the winter of the year
1877, in connection with the Colacium stentorinum, in part, of Ehrenberg, and the new
species here described under the title of C. Steinii. The observations then made are
substantially confirmed by Stein's figures and accompanying indices, illustrating other
allied species, published in November 1878. Certain points observed by the author
have, however, apparently escaped the attention of Professor Stein, and are now
recorded for the first time. Chief among these it must be mentioned that in no
instance does that authority indicate the possession of a flagellum by any members
of the sedentary colony-stocks, the animalcules, according to his figures, after their
first attachment losing this organ, and their offspring produced by repeated longi-
tudinal fission of the primarily attached zooid, which remains affixed to the extremities
of the branching pedicle, not developing any flagellate appendage. As shown,
however, in the author's account and illustrations of the species quoted, the flagella
are developed, though difficult to detect, by both the motile and sedentary zooids,
disappearing through absorption as a preliminary only to the act of encystment
and sporular reproduction.

The two cycles of existence manifested in the representatives of this genus find,
with the exception of Chlorangiwn, no parallel among the entire class of the Infusoria.
As in both the sedentary and motile conditions the reproductive faculties would
appear to be represented — the power of multiplying by ordinary fission being retained
by the natatory zooids — this generic group may be further cited as undoubtedly
yielding a novel instance of the interesting phenomenon of the alternation of gene-
ration. Whether genetic reproduction, accomplished by the conjugation of two
independent zooids, obtains during the sedentary or natatory phases, is an interest-
ing problem that yet awaits solution. The remarkable fixation of the locomotive
zooids of Colacium by their oral end, and development into stalked sedentary
organisms, in which the characteristics of theSr natatory phase are almost completely
masked, will scarcely fail to recall to mind the singular and somewhat parallel
metamorphoses exhibited by the Cirrhipede Crustacea.

Colacium arbuscula, Stein. PL. XXI. FIG. 33.

Sedentary zooids elongate-ovate, about twice as long as broad when
extended, shortly pyriform or subglobose when contracted, grouped at about
the same level at the extremities of a slender, erect, smooth and even,
dichotomously branching pedicle, the basal stem of which equals or con-
siderably exceeds the height of an extended zooid, the secondary and
succeeding ramifications being shorter ; parenchyma enclosing comparatively
few largish ovate chlorophyll-corpuscles. Length of bodies i-icoo" to
1-800"; height of adult colonies 1-250".

HAB. — Fresh water, on Rotifera.

The examples of this species figured by Stein* are represented as attached to
the Rotifer Anuraa fissa of Mr. P. H. Gosse. No less than two adult colonies,
bearing respectively six and eight zooids, and four smaller ones, are thus shown
growing upon one specimen of this minute rotifer, whose movements in the water
must have been much impeded by the accession of a living burden whose total bulk
considerably exceeded that of its own body. No illustrations are given or references
made to the free-swimming zooids of this type.

'Infusionsthiere,' Abth. iii., 1878.

GENUS COLACIUM. 395

Colacium calvum, Stein. PL. XXI. FIGS. 30-32.

Sedentary zooids elliptical or oblong, about two and a half times as
long as broad, of even width throughout, scarcely rounded and almost
square at the two extremities, elevated at an even altitude upon a very
short, thick pedicle, the main stem and subsequent subdivisions of which do
not equal a total height of one-half that of a single zooid ; motile zooids
highly contractile and variable in form, usually widest anteriorly ; endo-
plasm, with the exception of a clear, cap-like, longitudinally striate, anterior
area, enclosing numerous, minute, spherical chlorophyll-corpuscles, each
with a central nucleus-like point ; contractile vesicle large, communicating
freely with the tubular pharynx ; endoplast conspicuous, situated in the
median line at a distance of one-third of the length of the body from the
posterior extremity. Length of sedentary zooids 1-500".

HAB. — Fresh water, mostly forming small colonies of two or four
zooids only.

Colacium vesiculosum, Ehr. PL. XXI. FIGS. 34-38.

Sedentary zooids subfusiform, about two and a half times as long as
broad, tapering towards each extremity, but more attenuate posteriorly
when extended, pyriform and widest anteriorly when contracted, seated at
the same level at the summit of a short, slender, and often transversely
wrinkled, branching pedicle, the entire height of which scarcely equals one-
half of that of an extended zooid ; motile zooids Euglena-like, variable in
form. Chlorophyll-corpuscles of endoplasm oval, numerous and equally
distributed. Length of sedentary zooids 1-800".

HAB. — Fresh water, on Cyclops and other Copepodous Crustacea ; colony-
stocks including from two to eight animalcules.

Colacium Steinii, S. K. PL. XXL FIGS. 39-41.

Sedentary zooids elongate-ovate, about two and a half times as long as
broad when extended, globose, pyriform, or subnapiform, with an inflated
central and conically projecting anterior and posterior prolongation when
contracted ; pedicle branching irregularly or subdichotomously, bearing the
zooids at different heights and attaining an altitude equal to two or three
times that of an extended animalcule ; motile zooids Euglena-like, variable
in form ; endoplasm enclosing numerous, evenly distributed, ovate chloro-
phyll-corpuscles. Length of sedentary zooids 1-900".

HAB. — Fresh water, on a species of Cyclops.

In the general contour of the extended zooids and comparative altitude of the
supporting pedicle, this species corresponds considerably with C. arbusculum. It
may be distinguished from it, however, by the more or less irregular instead of even
dichotomous divarication of the secondary branches and by the elevation of the
animalcules at diverse instead of corresponding heights. During their contracted
state the napiform contour referred to in the diagnosis is of common occurrence,
but does not, from Stein's figures, appear to be assumed by either of the preceding
types. While this last-named contour is the most characteristic, innumerable other

396 ORDER FLA GELLA TA-EUSTOMA TA.

shapes are from time to time assumed, the parenchyma and cuticle being remark-
ably soft and plastic, and the animalcules, as observed by the author, being exceed-
ingly restless, continually elongating or shortening their outline, and twisting to and
fro upon their pedicles. As previously intimated, it was in connection with this
species that the possession of flagellate appendages by the sedentary zooids was
determined. On several occasions these sedentary individuals were seen to detach
themselves from the branching pedicle and swim freely in the water after the manner
of Euglena:, while in other instances they were observed to absorb their flagella and
form ovate encystments whose enclosed contents broke up into innumerable spore-
like bodies. The rupture of these encystments and the liberation of their contents
as simple non-flagellate germs were likewise witnessed. The author is inclined to
believe that the Colacium stentorinum of Ehrenberg embraces two distinct forms, one
with short, acuminate branches and attenuate, fusiform, biflagellate, sedentary zooids
of a dull green hue, corresponding with the Chlorangium stentorinum of Stein, and
another with bluntly ovate, bright green, uniflagellate animalcules forming variously
shaped bush-like growths, that corresponds probably with the present species. The
examples of Colacium Steinii, as here figured and described, were found on a species
of Cyclops taken from a pond near Acton in December 1877.

Supplementary Species.

An animalcule most nearly resembling Colacium calvum in external shape, but of
much more minute size — the length of the sedentary zooids not exceeding the
1-1300", and. that of the extended natatory ones the i-iooo" — has been recently
obtained by the author attached to the carapaces and limbs of a species of Cyclops
inhabiting pond-water from brickfields near Shepherd's Bush, London. In no case,
however, out of the numbers so far examined, was more than a single animalcule
found attached to one pedicle. The contour of these sedentary examples, while
quadrate, was, moreover, much more irregular, the distal or free margin being much
broader than the proximal one or that which is united to the pedicle. More usually
from two to four scarlet eye-like pigment-spots were developod in place of the single
one characteristic of the species previously described, while the chlorophyll-cor-
puscles were of much larger proportionate size, and leaving comparatively small
interspaces in the exposed periphery. Pending further investigation it is proposed
to provisionally distinguish this type by the title of Colacium multoculata. The
possession of a flagellum by the sedentary zooids was amply demonstrated.

Fam. IV. NOCTILTJCID-ffi, S. K.

Animalcules free-swimming, bounded by a distinct external membrane
or cuticle, the contained endoplasm highly vacuolar, forming a variously
modified protoplasmic network ; oral aperture distinct, associated with a
single vibratile flagellum, to which may be added a prolonged tentaculiform
appendage. Habits pelagic, often phosphorescent.

Professor Haeckel * has proposed to elevate the most prominent and, up to within
a comparatively recent date, only known generic form referable to the present family
group, to the rank of a separate order of the Protozoa, or rather of his so-called
" Protista, " to be designated the Cysto-Flagellata. The affinities of the type in
question, Noctiluca, with the more ordinary representatives of the Stomatode Flagel-
lata are, however, so obvious that any such isolation of it cannot be consistently
maintained. A closely identical reticulate character of the endoplasmic layer, chiefly
distinctive of this form, is met with among various ciliate and flagellate Infusorial
types, including such genera as Trachdius, Loxodes, and Callodictyon, while the non-
essentiality of the caudiform tentaculate appendage is demonstrated by its entire
absence in Hertwig's recently discovered and closely allied genus Leptodiscus.

* 'Natiirliche Schopfungsgcschichte,' Berlin, 1868.

GENUS NOCTILUCA. 397

GENUS I. NOCTILUCA, Suriray.

Animalcules free-swimming, subspherical, consisting of a smooth, hyaline
investing pellicle and an internal protoplasmic mass, which radiating in
every direction from the centre of the body, spreads itself in a thin
peripheral layer over the inner surface of the bounding membrane ; the
oral aperture situated at the base of a subcentral infundibulate pit-like
depression, the single slender vibratile flagellum originating from within its
cavity ; a supplementary long, flexible, and elastic tentaculiform appendage
arising close to and overhanging the oral fossa. Endoplast conspicuous ;
no contractile vesicle as yet observed. HAB. — Salt water.

It has been suggested that the tentacle-like appendage in this generic type finds
its homologue in the frequently larger trailing flagellum or gubernaculum of
Anisonema and its allies, and under which circumstances the rightful position of the
form would be among the Dimastigous section of the present group. Having
respect, however, to the new generic group Lcptodiscw, in which there is no such
appendage, the author is disposed rather to regard this last-named structure as an
entirely adventitious growth. Further investigation may not improbably establish
a bond of affinity between Noctiluca and the correspondingly pelagic Peridiniidae,
certain of which, such as Gymnodinium, are devoid of an investing cuirass, while
many are notable in a like manner for their phosphorescent properties.

Notiluca miliaris, Suriray. PL. I. FIGS. 34-44.

Body hyaline, peach-shaped, somewhat compressed, with a distinct
meridional groove ; oral fossa situated at one extremity of the meridional
groove, having on one side a hard, tooth-like, projecting ridge, close to one
end of which the vibratile flagellum takes its origin ; tentaculate appendage
transversely striate, its length about equal to the diameter of the body ; a
narrow ridge or rod-like induration of the cuticular membrane extending in
a straight line from the aboral extremity of the meridional groove through
about one-third of the circumference of the body, and there terminating
abruptly. Endoplast oval, subcentral. Diameter 1-80" to 1-20".

HAB. — Pelagic, cosmopolitan ; eminently phosphorescent.

As remarked by Professor Allman, there is perhaps no one of the phosphorescent
animals as yet known to science that possesses such highly luminous properties as
Noctiluca miliaris. To the presence of this animalcule in countless myriads upon
the upper stratum of the water on calm summer nights is due especially that diffused
form of phosphorescence that is more essentially characteristic of temperate latitudes.
Under the most favourable of these conditions the waves falling upon the strand
leave as they retreat a glittering carpet of scintillating points, the oars of the
passing boat seem to dip as it were into molten silver, while on the high seas the
waste of waters churned into foam by the revolving screw or paddles of the steam-
vessel leaves in its wake a broad luminous track as far as the eye can reach. A
glassful of water taken from the surface of the sea at such times immediately reveals
the origin of this wonderful phenomenon ; here and there will be seen floating
minute, bladder-like, transparent spheres, resembling as nearly as possible small
granules of boiled sago, and which exhibit on closer investigation with the micro-
scope, the structural characters given in the foregoing diagnosis. Irritated by
agitation in any shape or form they at once respond by, as it were, angry flashes
of silvery greenish light, and it is to the coruscations in their aggregate condition of

39$ ORDER FLAGELLATA-EUSTOMATA.

millions of these minute bodies that the several phenomena above recounted are pro-
duced. One other manifestation of pelagic phosphorescence dependent upon the
presence in countless numbers of this same tiny protozoon, may be suitably recorded
in these pages. By those accustomed to a seafaring life, the sight on nights when
the luminosity of the sea is most conspicuous, of fish following or darting away
from the sides of the vessel, apparently themselves aglow with phosphoric light,
and leaving behind them, in accordance with their size, a more or less conspicuous
luminous path in the murky waters, is frequently recorded. It is commonly sup-
posed that such form of luminosity is emitted by the fish themselves, but on closer
investigation it will be found that this also is due to the presence of the animal-
cules now under discussion, and which are disturbed into a sudden display of their
phosphoric properties by the passage of the fish through their midst. This light is
reflected as from a mirror by the glistening scales of the larger animal, while the
Noctilucce remain scintillating for some few moments in the path through which the
fish has passed, thus producing the more or less conspicuous tracks of light which
are left in its wake.*

The special seat of the phosphorescent properties of Noctiluca miliaris is pre-
sumed to be the peripheral protoplasmic layer lying immediately beneath the surface
of the cuticle. This supposition is favoured by adding a small drop of alcohol to
the water containing a living specimen while examined under the microscope. In
place of the momentary flash of light emitted under ordinary disturbance, the little
creature now exhibits its luminosity with the fullest intensity for several seconds.
At the end of that time it commences to gradually disappear, and before becoming
finally extinct with the life of the animalcule, presents the aspect of a mere luminous
ring upon the dark background of the field of the microscope. This last phe-
nomenon is pointed out by Professor Allman as indicating that the phosphoric
properties are confined to the peripheral portion, the light when the annular
appearance is presented having become so weak as to be appreciable only towards
the edges of the projected sphere, and where necessarily a greater depth of the
luminous stratum lies in the direction of vision. On the other hand, there appears
to be no appreciable differentiation between the protoplasmic stratum beneath the
cuticle and the central or radiating portions, and it is difficult to reconcile this
fact with the presumed limitation of the phosphoric property. It would seem an
open question, indeed, whether the last peripheral scintillations of the dying
Noctiluca are not directly comparable with the phenomena exhibited by a burning
paper in which the flame, having no longer any pabulum to support its volume,
leaves upon its departure a multitude of coruscating sparks which, animated by a
mysterious and irresistible centrifugal force, hurry or creep out as it were from the
centre and become extinct only on reaching the periphery. If the substance of the
charred paper reflected and transmitted instead of absorbed light, as is apparently
the case with the smooth cuticle of Noctiluca, the last appearance presented in this
instance also, presuming the paper was circular, would be that of a luminous ring.

The process of reproduction in Noctiluca has been successfully followed by Cien-
kowski.| Transverse fission after the manner common to almost all the Infusoria,
attended by an enlargement and division of the central nucleus or endoplast, is of
common occurrence. During this process the animalcule retains its normal contour
or assumes a spheroidal or semi-encysted form, in which all traces of the tentacle,
tooth-like process and cilium, and meridional groove entirely disappear, presenting,
indeed, under such circumstances so distinct an aspect as to have been frequently and
even quite recently (vide infra) mistaken for a separate organism. In connection with
this spheroidal condition, a process of multiplication is recorded by Cienkowski that
has not been previously observed. In this instance the central endoplast disappears
and the protoplasmic contents of the cyst, collecting to one spot on its inner surface,

* A fuller reference to this special form of marine phosphorescence, as witnessed by the author
in the Bay of Biscay, is contained in an article on " Phosphorescence in Fish," published in ' Nature,'
vol. vii., for the year 1872.

f ' Archiv f. Mikroskopische Anatomic,' Band vii. Heft ii., 1871, and Band ix. Heft i., 1872.

GENUS NOCTILUCA. 399

become separated by binary segmentation into at first two and then consecutively
four, eight, sixteen, thirty-two, or more masses in a manner corresponding precisely
with what has been previously described of many ordinary Flagellata. The cuticular
surface next becomes nodular to adapt itself to the contour of the subjacent segment-
masses, and these at length penetrating through the cuticle, remain attached for a
short while on its external surface, developing there a long flagelliform appendage,
and become ultimately detached as simple monadiform germs. The germs or
daughter-cells, thus developed, are usually aggregated in a discoidal or cake-like
form at one pole of the exterior surface, as shown at PI. I. Figs. 35 and 37, but
sometimes take a more loosely reticulate arrangement, Fig. 36, or may form an
equatorial girdle around the parent envelope. A considerable variety of contour is
exhibited by these germs. In their most typical aspect, PI. I. Figs. 39 and 40, they
are somewhat conical, with a rostrum-like process — which apparently represents
the rudimentary condition of the subsequent rod-like induration of the cuticle — are
divided by an annular groove into an anterior and posterior region, and have a
short, tongue-like appendage and a long, flexible, lash-like flagellum. In another
and probably earlier state the germ is a simple spheroidal sac with or without
the lash-like flagellum, Figs. 37 and 38.

The conjugation of adult N'octilucce in either their normal or spheroidal state has
been frequently observed, and is manifested in the first instance by the close apposi-
tion of their respective oral surfaces. The tentaculiform appendages are then cast
off, the two endoplasts become united by a bridge of endoplasm, and the two bodies
gradually coalescing, Fig. 44, are within the space of five or six hours indissolubly
fused together. This process, though evidently requisite for the occasional rejuvena-
tion of the reproductive functions, is apparently not a necessary precedent to each
reproductive act. The recuperative properties possessed by this animalcule are
somewhat remarkable ; a crushed or otherwise mutilated zooid withdraws its flagel-
lum, and after contracting into an irregular protoplasmic mass, develops a fresh
cuticular investment, while the smallest portion of sarcode, separated from the
parent, is capable of growing into a perfect zooid. The food of Noctiluca consists
chiefly of the floating Diatomaceae which occur in such abundance upon the upper
stratum of the ocean, numerous varieties of which will frequently be found entangled
within the internal radiating protoplasmic network. Elaborate and masterly accounts
of the leading structural features of this highly interesting type, which have served as
a basis for the foregoing technical diagnosis, have been contributed by Professors
T. H. Huxley and G. J. Allman to the ' Journal of Microscopical Science ' for the
years 1855 and 1872.

There can be but little doubt that the organism figured by Professor Sir Wyville
Thompson in the 'Proceedings of the Royal Society,' vol. xxiv., pi. 21, 1876, as
a new diatom under the title of Pyrocystis pseudonoctihica — his illustration of the
same being reproduced at PI. I. Fig. 45 — represents the normal encysted condition
of Noctiluca miliaris as previously described by numerous investigators, and notably
by Johannes Miiller, as translated in the 'Journal of Microscopical Science' for
1855. The account there given runs as follows : — " These encysted bodies consti-
tuted the principal luminous animalcules observed at Messina in the autumn of 1853.
Free Noctiluccz at that season were not seen there; and in 1849 the same kind of
encysted bodies were very common at Nice. The cyst is a perfectly transparent,
spherical capsule, with a light-bluish brilliancy at the edge, and appearing like the
egg-membrane of some Crustacea. Within the cyst is lodged a body in all respects
resembling Noctiluca miliaris, except that at this time no vibratile filament can be
perceived. The Noctiluca-Vke. creature fills the cyst more or less entirely, though
occasionally it is much smaller. In this condition the animalcules are luminous
without being agitated." Professor Wyville Thompson's second species, distin-
guished by the title of Pyrocystis fusiformis (PI. I. Fig. 54), represents apparently a
similar quiescent phase of Leptodiscus medusoides, next described. It is a remark-
able circumstance, and one perhaps not altogether worthy of congratulation, that,
excepting for a passing notice of the occurrence of Peridiniiclae in certain latitudes,
the very existence even of the important and highly interesting organic group

400 ORDER FLAGELLATA-EUSTOMATA.

described in this treatise, was completely ignored by the talented staff of the ' Chal-
lenger' expedition, its representatives indeed, when encountered, as in the present
instance, being unrecognized and referred to the vegetable series. It is to be hoped
that the opportunities for acquiring a further knowledge of the morphology and
distribution of the hitherto little known or altogether unchronicled pelagic Infusoria
will not be neglected in the future scientific expeditions of a like kind that may be
organized by this country. It may be confidently anticipated that in this field
alone new and interesting forms remain to be discovered, that surpass in number and
variety the by no means inconsiderable series that are already known to science.

GENUS II. LEPTODISCUS, Hertwig.

Animalcules free-swimming, more or less flattened or discoidal, having,
as in Noctiluca, a hyaline investing pellicle and an internal, radiating or
reticulate, protoplasmic layer ; oral aperture situated at the base of a
tubular pit-like excavation ; a long, lash-like, vibratile flagellum issuing from
the entrance to the adoral fossa ; no supplementary tentaculate appendage ;
endoplast conspicuous ; no contractile vesicle as yet detected.

HAB. — Pelagic.

R. Hertwig,* the original discoverer of the single known member of this genus,
is inclined to regard it as the type of a family distinct from Noctiluca. The various
structural details, excepting for the absence of the transversely annulate tentaculate
appendage, correspond however so closely with those of the latter type that its
complete separation from it seems scarcely justified.

Leptodiscus medusoides, Hertwig. PL. I. FIGS. 46-53.

Body very much flattened, meniscoidal and orbicular, highly flexible,
thickest in the centre and gradually tapering towards the periphery ; oral
fossa subcentral, opening on the convex surface, descending obliquely
through the entire thickness of the body to the protoplasmic lining of the
opposite bounding membrane ; flagellum slender, vibratile, its length equal
to less than one-fourth of the diameter of the disc, inserted close within
the entrance to the oral fossa ; endoplast oval, subcentral, consisting of a
larger granular and smaller transparent region ; a number of minute,
spherical, oil-like globules immediately underlying the upper and convex
cuticular layer. Diameter of largest individual 1-4".

HAB. — Pelagic : Messina.

The close resemblance of the adult zooids of this singular species to minute jelly-
fish (Medusae) is very remarkable, their large size, as represented without the aid of
magnifying power at PL I. Figs. 46 and 47 further supporting this analogy. Hertwig
figures as the supposed young of Leptodiscus some organisms that differ altogether
from the parent. These bodies, PL I. Figs. 52 and 53, are of more elongate
outline, flattened and somewhat cushion-shaped, with a central, transversely annular
constriction ; there is no flagellate or other appendage, the endoplast is central,
oval, and granulate throughout, and represents the point from whence the internal
protoplasmic reticulations chiefly radiate, as in the adult form. The mode of
natation in these hypothetic non-adult zooids is exceedingly remarkable, being
effected, according to Hertwig, by the alternate contractions of the internal proto-
plasmic radii on each side of the central annular constriction, this contraction in

* " Ueber Leptodiscus medusoides ," ' Jenaische Zeitschrift,' Bd. xi., Nov. 1877.

GENUS CHLOROMONAS. 401

each instance being so complete that the side affected by it presents a temporary
aspect of complete collapse. This locomotive phenomenon, taken together with the
very distinctive contour and structure of the organism as a whole, differs so essenti-
ally from Leptodiscus medusoides in its normal state that it is almost impossible to
repress the suspicion that this more minute organism will eventually prove to belong
to an independent and perfectly distinct pelagic type.

Section B.—EUSTOMATA-DIMASTIGA.
Fam. V. CHRYSOMONADID.S3, S. K.

Animalcules bi-flagellate, rarely monoflagellate, social or solitary, free-
swimming or adherent, naked, loricate, or immersed within a common
mucilaginous matrix or zoocytium ; endoplasm always containing two
lateral, occasionally green, but more usually olive-brown or yellow, differ-
entiated pigment-bands ; one or more supplementary eye-like pigment-
spots frequently present.

The considerable series of genetic types assembled in this newly proposed family
group are at once recognized by the presence of the characteristic lateral pigment-
bands, these elements being here held to be of such primary import as to over-
ride the fact that in the first three genera described a single flagellum only has as
yet been detected. The colour-bands in question, in addition to their distinctive
tint, are apparently of firmer consistence than the surrounding transparent proto-
plasm, and bear a very considerable resemblance to the endochrome or colouring
matter of the Diatomaceae. The development of these pigment-bands, though
constant among zooids of the same species, varies considerably among different
generic and specific forms, being symmetrical or unsymmetrical, and produced
either in whole or in part only down the lateral borders of the animalcule's body.
While until recently the affinities of these animalcules were accepted as closely
approximate to that of Volvox, Protococcus, and other undoubted Protophytes, the
most recent researches of Stein, in combination with the independent investigations
of the present author, have substantiated in many instances — as, for example, the
genera Dinobryon, Uroglena, and Chrysomonas — their undoubted animal organiza-
tion. So far as at present known, all the members of this family are inhabitants of
fresh water.

GENUS I. CHLOROMONAS, S. K.
(Greek, chloros, green ; monas.)

Animalcules more or less ovate, solitary, free-swimming, persistent in
shape, flagellum single, terminal ; endoplasm enclosing two differentiated
lateral pigment-bands, and usually an anterior eye-like pigment-spot.

This new genus is instituted for the distinction of the form identified by Stein
with the Cryptoglena pigra of Ehrenberg, but which, as presently explained, differs
essentially from the typical Cryptoglentz in the possession of the characteristic colour-
bands and of a single flagellate appendage.

Chloromonas pigra, Ehr. sp. PL. XXII. FIGS, i AND 2.

Body ovate or conical, somewhat compressed, pointed posteriorly, the
cuticular surface indurated and presenting sharpened or keel-like lateral
borders ; pigment-bands bright green, extending evenly on each side
throughout the length of the body ; eye-like pigment-spot immersed within

2 D

402 ORDER FLAGELLATA-EUSTOMATA.

the substance of the anterior region of one of the lateral bands ; oral
aperture situated close to the flagellum, continued into a distinct though
minute, tubular pharynx ; contractile vesicle single, conspicuously developed,
located centrally close to the termination of the pharynx ; endoplast
occupying the median line near the pointed posterior extremity. Length
1-3000". HAB. — Pond water ; movements slow.

This species is identical with the Cryptoglena plgra of Ehrenberg and Stein, its
departure from the type of the last-named genus being made manifest more especially
by the two characteristic lateral colour-bands and by the possession of a single
flagellum only. By the addition of a second flagellate appendage the present
type would be rendered eligible for inclusion in the genus Cryptomonas, and would
be scarcely distinguishable from the young of C. ovata, as shown at PI. XXII.
Fig. 1 8.

GENUS II. CHRYSOMONAS, Stein.

Animalcules free-swimming, illoricate, more or less ovate or elongate,
but flexible and changeable in form ; flagellum single, produced from the
centre of the anterior border ; oral aperture conspicuous, not followed
by a distinct pharyngeal dilatation ; endoplasm enclosing two lateral
coloured bands and an anteriorly situated eye-like pigment-spot ; con-
tractile vesicle and endoplast conspicuous. Inhabiting fresh water.

This genus is founded by Stein * on the Monas flavicans of Ehrenberg. Except-
ing for the absence of the characteristic pharyngeal excavation, it would seem to
closely approach Microglena.

Chrysomonas flavicans, Ehr. sp. PL. XXII. FIGS. 8 AND 9.

Body soft and plastic, variable in form, usually more or less elongate-
ovate or subcylindrical, three or four times as long as broad ; flagellum
single, scarcely equalling the body in length ; endoplasm enclosing two
anteriorly produced lateral colour-bands, which do not extend to the posterior
extremity, and a single eye-like pigment-spot ; contractile vesicle single or
double, spheroidal, and of large size, situated immediately beneath the
insertion of the flagellum ; endoplast minute, spherical, subcentral. Length
1-1720" to l-6oo". HAB. — Ditch water.

In the figures of this species given by Stein one example is represented as having
devoured a Navicula almost equalling itself in length, and another with two incepted
Chlamydomonads. Multiplication, following upon a quiescent or encysted condition
as delineated by the same authority, exhibits highly interesting phenomena, one
zooid forming, as seen at PL XXII. Fig. 9, a spheroidal granular matrix, within
which it divides, by repeated longitudinal fission, into as many as sixteen units,
bearing under such conditions a considerable likeness, excepting for the absence
of flagella, to the characteristic spheroidal colony-stocks of Syncrypta and Uroglena.

Chrysomonas ochracea, Ehr. sp. PL. XXII. FIGS. 3-7.

Body variable in form, ovate, elongate or subglobose ; endoplasm clear,
ochreous yellow ; colour-bands centrally located, a single eye-like pigment-

* 'Infusionsthiere,' Abth. iii., 1878.

GENUS MICROGLENA. 403

spot usually developed ; flagellum single, equalling or exceeding the length
of the body ; contractile vesicle single, anteriorly situated. Length 1-600"
to 1-1200". HAB. — Fresh water.

This minute species is referred by Stein, with some doubt, to the Monas ochracea
of Ehrenberg. Multiple fission within a comparatively large spheroidal cyst or
capsule, closely corresponding with the reproductive process recorded of the type
last described, as figured by the same authority, is reproduced at PI. XXII.
Figs. 5 and 7.

GENUS III. MICROGLENA, Ehrenberg.

Animalcules free-swimming, illoricate, plastic and changeable in form,
usually more or less ovate or elongate ; oral aperture distinct, anteriorly
placed, communicating with a dilated pharyngeal cavity ; flagellum single,
terminal ; endoplasm green or yellow, enclosing two supplementary longi-
tudinally placed coloured bands and one or more eye-like pigment-spots ;
contractile vesicle and endoplast conspicuous. Inhabiting fresh water.

Microglena punctifera, Ehr. PL. XXII. FIG. 10.

Body somewhat variable in form, elongate-oval or obconical, widest and
rounded anteriorly, tapering and bluntly pointed at the posterior extremity,
about twice as ' long as broad ; flagellum attenuate, vibratile, issuing from
the oral aperture, scarcely equalling the body in length ; pharyngeal cavity
capacious, subspheroidal or pyriform ; endoplasm yellow, the two lateral
coloured bands produced through the entire length of the body ; two minute
red eye-like pigment-spots at the anterior extremity ; contractile vesicles
numerous, spheroidal, four or six in number, located around the border of
the pharyngeal excavation ; endoplast ovate, subcentral. Length 1-620"
to 1-500''. HAB. — Fresh water.

The diagnosis of this species, and also of the genus Microglena, is here amended
in accordance with the figures given by Stein in the recently issued volume of his
' Infusionsthiere.' The following form not having apparently fallen under the notice
of this authority, has associated with it an imperfect description formulated only upon
the figures and brief description originally given by Ehrenberg.

Microglena monadina, Ehr.

Body shortly ovate or subspheroidal, evenly rounded at each extremity ;
flagellum equalling the body in length ; endoplasm brilliant green, enclosing
a single, anteriorly situated, scarlet, eye-like pigment-spot ; pharyngeal
excavation capacious ; endoplast (?) band-like, subcentral. Length 1-2400"
to 1-720". HAB. — Pond water ; movements rotatory.

A very distinct band-like structure, apparently corresponding with the ovate
endoplast of the preceding type, is indicated by Ehrenberg in the various figures
given of this species, as also a large anterior pharyngeal excavation. By Pritchard it
is recorded as occurring among slimy water plants in the neighbourhood of Hamp-
stead and Finchley.

2 D 2

404 ORDER FLA GELLA TA-EUSTOMA TA.

GENUS IV. CRYPTOMONAS, Ehrenberg.

Animalcules free-swimming, illoricate, persistent in form, more or less
ovate or elongate ; flagella two in number, subequal, issuing from beneath
a prominent, anterior, lip-like process ; oral aperture conspicuous, opening
close to the base of the flagella, continued backwards as a distinct tubular
pharynx; endoplasm enclosing two lateral, longitudinally placed colour-
bands ; contractile vesicle and endoplast conspicuous. Inhabiting fresh
water.

The animalcules of this genus, excepting for the presence of the endoplasmic
colour-bands, correspond in form and structure with those of Chilomonas.

Cryptomonas ovata, Ehr. PL. XXII. FIGS. 16-18.

Body elongate-ovate, compressed, usually narrowest and sometimes
recurved towards the dorsal aspect posteriorly, about three times as long as
broad ; oral aperture large ; pharyngeal passage conspicuous, tubular, con-
tinued backwards beyond the centre of the body ; colour-bands bright green,
mostly developed on the dorsal and ventral aspects throughout the entire
length of the body ; contractile vesicle situated immediately above the
commencement of the pharynx; endoplast posteriorly located. Length
1-600" to 1-400". HAB. — Fresh water, amongst Conferva.

As shown by Stein's figures,* here reproduced, PI. XXII. Fig. 18, the young of
this species differ from the adults in possessing a flexible body and an acuminately
pointed, recurved posterior extremity ; the characteristic colour-bands are also limited
during the earlier stages of growth to two green, subcentral, ovate corpuscles, which
gradually assume a band-like outline as growth progresses, and finally extend through-
out the length of the body. In those adult individuals which possess a recurved
posterior region, it is explained by Stein that the cuticular surface has become
indurated while retaining more nearly the external contour of the embryonic stage ;
these more exceptional examples which present a somewhat sigmoid flexure, have
been described by Ehrenberg as a distinct species under the title of Cryptomonas
curvata.

Cryptomonas erosa, Ehr. PL. XXII. FIGS. 19-21.

Body elongate-ovate, compressed, about twice as long as broad, the
posterior extremity bluntly rounded, recurved slightly towards the ventral
aspect ; pharyngeal tube scarcely produced to the centre of the body ;
colour-bands light green ; contractile vesicle and endoplast as in C. ovata.
Length 1-960". HAB. — Fresh water, among Conferva.

This species may be distinguished from C. ovata by its shorter proportional
length, smaller size, and ventral curvature of the posterior extremity. By Stein's
figures it is shown to divide by longitudinal fission after the manner of Chilomonas.
The nucleus or endoplast in both this and the preceding type exhibits reproductive
phenomena corresponding with those presented by Euglena and Phacus. By con-
centration, around this structure, of the substance of the endoplasm, or through

1 Infusionsthiere,' Abth. iii., 1878.

GENUS NEPHROSELMIS—STYLOCHRYSALIS. 405

the extension of its own outer wall, it assumes a comparatively enormous size.
Taking an ovate form it often — as shown at PL XXII. Fig. 19 n — occupies more
than half of the cavity of the parenchyma, and ultimately divides by repeated fission
into innumerable minute germs or microspores. By Stein this reproductive structure
is denominated the germ-sac or germ-sphere ("Keimkugel"), but may perhaps be
more appropriately distinguished as the sporosac.

GENUS V. NEPHROSELMIS, Stein.

Animalcules solitary, illoricate, free-swimming ; flagella two in number,
of diverse size, issuing from the centre of one of the lateral borders;
endoplasm enclosing two lateral pigment-bands. Inhabiting fresh water.

Nephroselmis olivacea, Stein. PL. XXII. FIGS. 11-13.

Body subreniform, the dorsal border convex, the ventral one concave ;
the two flagella of unequal length, inserted close to each other in the centre
of the concave ventral surface ; coloured pigment-bands extending through-
out the lateral peripheries ; contractile vesicle situated close beneath the
insertion of the flagella, two denser and apparently amylaceous corpuscles
in the dorsal or posterior region. Greatest length or diameter of bodies,
i-iooo". HAB. — Fresh water.

In form, the animalcules of this species would seem to closely resemble those
of the Pleuromonas of Perty, but are to be distinguished from them by the possession
of an oral aperture, two flagella, and distinct pigment-bands. Practically, the sub-
reniform contour of this type may be said to be produced by the thrusting-in of the
anterior border of an ordinary ovate animalcule accompanied by the compensating
dilatation of the lateral peripheries. An example of multiplication by longitudinal
fission is represented in Stein's drawings of this species.

GENUS VI. STYLOCHRYSALIS, Stein.

Animalcules not secreting a protective lorica, attached separately to
foreign objects through the medium of a stiff non-elastic pedicle ; flagella
two in number, subequal ; endoplasm enclosing two lateral pigment-bands.
Inhabiting fresh water.

Stylochrysalis parasita, Stein. PL. XXII. FIG. 22.

Body ovate, somewhat pointed at each extremity ; supporting pedicle
varying from the same length to twice the length of the body ; lateral
pigment-bands evenly developed ; contractile vesicle single, posteriorly
located. Length of body, without pedicle, 1-2500".

HAB. — Pond water, attached to Etidorina elegans.

In the examples of this species as yet simply figured and not described by Stein,
one animalcule is delineated as undergoing the process of multiplication by transverse
fission, while in all the zooids a structure which may be an eye-like pigment-spot or
an oral dilatation is placed at the anterior extremity.

406 ORDER FLAGELLATA-EUSTOMATA.

GENUS VII. UVELLA, Ehrenberg.

Animalcules united by their posterior extremities and forming social,
free-swimming, spheroidal colonies, the individual zooids not enclosed
within a membranous lorica, nor the colony as a whole immersed within a
common gelatinous matrix or zoocytium ; flagella two in number, subequal ;
endoplasm containing two lateral colour-bands ; an eye-like pigment-spot
present or absent. HAB. — Fresh water.

The non-possession of a separate membranous investment or lorica by the
animalcules of this genus serves to distinguish it from Synura.

Uvella virescens, Ehr. PL. XXII. FIGS. 24-26.

Bodies elongate-ovate or clavate, their united posterior extremities
attenuate and stalk-like ; flagella equal or subequal, exceeding the body
in length ; lateral pigment-bands bright yellowish-green, extending on
each side through almost the entire length of the body ; no conspicuous
eye-like pigment-speck ; contractile vesicles two in number, posteriorly
located ; endoplasm subcentral ; colony-stocks containing from five or six
to as many as seventy or eighty zooids. Length of bodies 1-2000".

HAB. — Pond water.

The posterior location of the contractile vesicles, independently of the absence of
separate loricae, serves at once to distinguish the zooids of this species from those of
Synura uvella, with which in their aggregate condition they may otherwise be readily
confounded. The endoplast, although not distinctly exhibited under ordinary
conditions, is, according to Biitschli,* at once denned by the application of Beale's
carmine. Encysted individuals possessing a delicate or irregular outer coat and a
denser internal one, were encountered by this authority both in connection with the
motile colonies and with the isolated animalcules. Longitudinal fission according
with that of the ordinary Flagellata was likewise noticed.

GENUS VIII. CHLORANGIUM, Stein.

Animalcules more or less ovate, persistent in shape, exhibiting two
distinct phases of existence, the one motile and the other sedentary ; in
the former instance possessing two evenly developed, anteriorly inserted,
vibratile flagella ; in the latter condition non-flagelliferous, attached in social
groups, mouth downwards, to a common pedicle ; endoplasm enclosing two
lateral colour-bands ; contractile vesicle and endoplast conspicuous.

This genus is instituted by Stein for the reception of the Colacium stetitorinum
of Ehrenberg, which he reports as differing from the several species of Colacium
previously described in the possession by the motile zooids of two flagellate appen-
dages, a more or less firm and non-contractile cuticula, and in the development of
two lateral coloured pigment-bands. Probably, as demonstrated by the present
author in the case of Colacium Steinii, it will be ultimately shown that the flagella
here also are retained during the sedentary condition.

'Studien iiber Flageliaten," ' Zeitschrift fur Wissenschaftlicher Zoologie,' Bd. xxx., 1878.

GENUS HYMENOMONAS.

Chlorangium stentorinum, Ehr. sp. WOODCUT, FIGS. 1-7.

407

Bodies elongate-ovate or subfusiform, about three times as long as
broad ; flagella terminal, subequal, not so long as the body ; endoplasmic
colour-bands bright green, produced throughout the whole extent of the
two lateral borders, one of these including near its distal end an obscure
eye-like pigment-spot ; contractile vesicle situated at the anterior ex-
tremity, close to the insertion of the flagella ; endoplast spherical, sub-
central, attached during the sedentary condition to a short, simple, or
slightly branching pedicle, in groups of from two or three to ten or twelve
zooids. Length of zooids 1-1150".

HAB. — Pond water, on various Entomostraca.

Chlorangium ttentortKum, Ehr. sp. — i. Free-swimming biflagellate zooid ; c v, contractile vesicle ; e, eye-like
pigment-spot ; », nucleus or endoplast. 2. Encysted zooid attached by a stalk-like prolongation of its anterior extre-
mity. 3 and 4. Encysted zooids, with body-substance separated respectively into two and four segment-masses.
5. Further developed stage of the preceding example, in which the four segment masses having burst the cyst wall,
remain attached distally to the parent pedicle ; at a, residual portion of the primary cyst. 6. Adult sedentary colony-
stock, produced through the further subdivision of the zooids represented in the preceding figure. 7. Single encysted
zooid, whose body-mass has become subdivided into minute sporular elements. (After Stein, X 480.)

This species was first described by Ehrenberg under the title of Stentor (fypygmaus,
but is relegated in his subsequent work, ' Die Infusionsthierchen,' to the genus
Colacium. The grounds upon which it has been found necessary to separate it
from this last-named' generic group, have been already indicated. The growth of
the sedentary arborescent colony-stocks of this animalcule are produced, according
to Stein's recently published volume, and as shown in the accompanying woodcut,
by the endogenous subdivision of a primary attached zooid, whose cuticle finally
bursting exposes the internally developed units, each with its anterior extremity
firmly attached to the extremity of the parent pedicle. A portion of the posterior
region of the parent cuticle frequently remains for a considerable interval embracing
the base of the common stock and presenting, as seen in profile, Fig. 50, the aspect
of two lateral setose processes. Sporular multiplication, in which encysted zooids
attached singly to their pedicles become divided up into a number of minute micro-
spores, as shown at Fig. 7, is also placed on record by the authority just quoted.
A distinct oral aperture has apparently as yet not been detected, but probably
exists and corresponds with that possessed by Colacium.

GENUS IX. HYMENOMONAS, Stein.

Animalcules solitary, free-swimming, secreting a more or less flexible
lorica ; flagella two in number, subequal ; lateral pigment-bands con-
spicuously developed ; no eye-like speck ; contractile vesicles anteriorly
located. Inhabiting fresh water.

408 ORDER FLAGELLATA-EUSTOMATA.

The possession of a flexible investing sheath or lorica and two flagellate
appendages chiefly distinguishes this generic group from Chrysomonas.

Hymenomonas roseola, Stein. PL. XXII. FIGS. 14 AND 15.

Lorica ovate or ellipsoidal, soft and flexible, crenulate throughout its
periphery, and assuming diverse contours in accordance with the change of
form of the enclosed animalcule. Body of animalcule entirely filling the
lorica, two yellow-brown pigment-bands extending evenly throughout the
lateral margins. A large spheroidal fat-like or amylaceous body usually
present in the posterior region ; two contractile vesicles and a large vacuolar
non-contractile space, possibly a pharyngeal sac, situated at the anterior
extremity; no eye-like pigment-speck. Length of lorica 1-850".

HAB. — Fresh water.

GENUS X. CHRYSOPYXIS, Stein.

Animalcules solitary, ovate or spheroidal, non-contractile, inhabiting a
sessilely attached lorica, but not united to the same by a thread-like pedicle ;
flagella two in number, of equal length, produced from the centre of the
frontal margin, this last-named region rounded and without any projecting
lip -like prominence ; endoplasm enclosing two lateral colour-bands, but no
eye-like pigment-spot. Inhabiting fresh water.

The animalcules of this genus are distinguished from those of Epipyxis by their
two equal-sized flagella, persistent form, and the absence of the connecting pedicle
between the body and the lorica. The single species referred to it is further
remarkable for the peculiar spur-shaped prolongations of the posterior border of the
lorica, and which penetrating in a root-like manner into the cell-wall of the Conferva
to which they are usually attached, retain a close hold upon the same.

Chrysopyxis bipes, Stein. PL. XXII. FIGS. 28 AND 29.

Lorica ovate or shortly flask-shaped, rounded and widest posteriorly,
with a narrow circular anterior orifice, the length but slightly exceeding the
greatest breadth, two diverging and acuminate spur-like prolongations
developed from the posterior border, these penetrating and hidden within
the cellular substance of the plant to which it is attached ; animalcules
subspheroidal, occupying the posterior half of the cavity of the lorica, the
two flagella projecting to a considerable distance beyond its orifice, di-
verging widely from one another ; colour-bands brownish, produced
throughout the two lateral borders ; contractile vesicles one or two in
number, posteriorly situated ; dividing by longitudinal fission. Length of
lorica 1-1600".

HAB. — Fresh water, attached gregariously to confervoid algae.

In his illustration of this species, Stein* indicates the presence of a presumed
oral aperture at the anterior extremity, close to the insertion of the two flagella.
Like Epipyxis utriculus the species is eminently social in its habits, a number of
individuals usually occurring crowded together upon a single cell of a Mougcotia or
other confervoid algal.

* 'Infusionsthiere,' Abth. iii., 1878.

GENUS EPIPYXIS—DINOBRYON. 409

GENUS XL EPIPYXIS, Ehrenberg.

Animalcules contractile, ovate or pyriform, inhabiting solitary, sessilely
attached, erect, transparent loricae, to the bottom or sides of which they are
affixed by a contractile thread-like prolongation of the posterior extremity ;
flagella two in number, one short and the other long ; endoplasm enclosing
two longitudinal colour-bands and an anterior eye-like pigment-spot.
Inhabiting fresh water.

The animalcules of this genus correspond essentially in general form and
structure with those of Dinobryon, and are distinguished from them only by their
secretion of solitary attached loricae in place of a compound branching polythecium.

Epipyxis utriculus, Ehr. PL. XXII. FIGS. 30-33.

Lorica elongate-conical or subcylindrical, abruptly truncate or slightly
everted anteriorly, widest centrally, tapering and attenuately pointed pos-
teriorly, about four times as long as broad ; enclosed animalcule elongate-
ovate or pyriform, occupying about one-half of the cavity of the lorica,
tapering, and continued as a thread-like pedicle posteriorly, the anterior
border developed on one side as a small, conical, projecting lip ; eye-like
pigment-spot minute ; contractile vesicle anteriorly situated, endoplast
subcentral. Length of lorica 1-640". HAB. — Fresh water on Conferva.

The loricae of this species, with their enclosed inhabitants, so closely resemble the
separate thecae and animalcules of Dinobryon sertularia that Stein originally held
them to be early growths only of that form. In the third volume of his ' Infusions-
thiere ' he, however, recognizes their independent status and fully illustrates their
varied aspects and habits. In some of the empty loricae figured by this authority,
a delicate reticulate pattern is spread over the entire surface, and apparently in-
dicates the presence of contained sporular bodies, or the traces of their previous
existence ; multiplication by fission is effected in a somewhat oblique direction.
Though usually found attached in some numbers to the filaments of CEdogonium and
other water-plants, the loricae are in most instances conspicuously isolated from one
another, but sometimes occur, as shown at PI. XXI. Fig. 31, in small closely set
fasciculi. The species has been recently obtained by the author in the neighbour-
hood of Ashby-de-la-Zouch.

GENUS XII. DINOBRYON, Ehrenberg.

Animalcules bi-flagellate, having one long and one short flagellum,
attached by a posterior contractile ligament within the individual cells or
loricse of a compound branching polythecium ; the polythecium constructed
through the successive terminal gemmation of the primary zooids; endoplasm
containing two lateral colour-bands and usually an anteriorly situated eye-
like pigment-spot. Inhabiting fresh water.

Dinobryon sertularia, Ehr. PL. XXII. FIGS. 34-40.

Constituent cells or loricae of polythecium obconical, narrowest and
tapering posteriorly, evertile at the mouth, slightly constricted a little
beneath the anterior border, joined to each other without intermediary

410 ORDER FLAGELLATA-EUSTOMATA.

or separate pedicles. Animalcules elongate-ovoid, not exsert, attached to
the bottom of their respective lorica by a transparent elastic ligament.
Eye-like pigment-speck conspicuous. Length of separate loricae 1-1200",
of contained animalcules 1-2000". HAB. — Pond water.

This species, which may be regarded as the typical representative of the genus
Diitobryenjvi& received the attention of numerous authorities since its first discovery
by Ehrenberg. By no one of these, however, Stein and Biitschli excepted, does
its structure and affinities appear to have been correctly apprehended, a circum-
stance doubtless explained by the extreme minuteness of the individual animalcules
and the consequent necessity of employing the highest available magnifying powers
for their satisfactory determination. Hitherto this form has been regarded and
described as a uniflagellate type much resembling Euglena, and from which alone it
was chiefly distinguished by its compound protective lorica. Professor H. James-
Clark, apparently without a previous acquaintance with the type, refers to it, in
the course of his remarks on the genus Codonceca, as a " calyculated Euglenian."

The first results that attended the author's examination of this elegant species,
in the year 1871, with a sufficient amplifying power, was the detection of two flagella,
one long and the other considerably shorter, in place of the single appendage pre-
viously ascribed to it, while it was at the same time elicited that the animalcules were
attached to the base of their respective lories; through the medium of a separate
retractile ligament. Those two points at once establish the near relationship that
exists between this form and the genus Epipyxis. The compound colony-stocks of
Dinobryon sertularia are frequently met with containing no fewer than fifty to sixty
separate loricae, which are so united to one another as to present as a whole a
remarkable resemblance in miniature to the polyparies of certain of the Polyzoa or
Sertularian Zoophytes. The adult colonies thus constructed are usually found pro-
gressing through the water with a rolling action and considerable velocity, being
propelled by the rapid vibration of the innumerable flagella. In its younger state
it is however an essentially sedentary form, the primary zooid with its investing
lorica being attached to some fulcrum of support, as in other ordinary pedicellate
types here described. As the colony develops, the lower or primary cells become
atrophied, much in the same manner as the lower portion of the branch of a
madreporic coral, and these deserted cells being unable to bear the weight of the
superincumbent mass, snap off", and thus release the colony into the surrounding
water under those conditions which are most usually met with. No process of
reproduction in Dinobryon sertularia has been yet observed in addition to the
ordinary one of oblique fission, as in Epipyxis. The resultant of such fission, how-
ever, in most cases, instead of swimming off to form the foundation of a new settle-
ment, attaches itself just beneath the margin of the aperture of the parent lorica,
and then builds up a corresponding domicile. This process in the course of a few
generations results in the formation of the elegant compound polythecium charac-
teristic of the adult colony.

Both Biitschli and Stein have recently recorded the production by this animalcule
of spherical encystments, as represented at PI. XX. Figs. 38-40 ; it is a remarkable
fact, however, that the well-developed posterior ligament or footstalk, by the con-
traction of which the zooids are enabled to retreat rapidly to the further confines of
their loricae, has not been distinctly recognized in this species by either of these
authorities. The oral aperture, according to Stein, is immediately adjacent to the
point of insertion of the two flagella and scarcely to be distinguished from the eye-
like pigment-speck.

Dinobryon stipitatum, Stein. PL. XXII. FIG. 41.

Loricae elongate, trumpet-shaped, widest and slightly everted anteriorly,
tapering, attenuate, and acuminately pointed posteriorly, the Jotal length
equalling seven or eight times the greatest breadth ; zooids elongate-ovate,

GENUS SYNURA. 4 1 1

occupying the anterior half of the cavity of the lorica, attached to the side-
wall of the same by a thread-like prolongation of the posterior region ;
primary flagellum exceeding the body in length and three times longer
than the secondary one ; eye-like pigment-spot conspicuous ; contractile
vesicle situated a little in advance, and the endoplast a little to the rear of
the centre of the body. A large, subspheroidal, fat-like amylaceous cor-
puscle located near the posterior extremity. Length of loricae, 1—300".
HAB. — Fresh water.

The great proportional length and attenuate posterior terminations of the loricje
of this species, as figured by Stein,* distinguish it conspicuously from the preceding
type. This elongate outline of the posterior region is so marked as to almost
acquire the character of an independent pedicle, while the contour of each inde-
pendent lorica, as a whole, may be appropriately compared with that of a post-horn.

Dinobryon juniperinum, Eichwald. PL. XXII. FIG. 23.
Cells of polythecium evenly ovate or fusiform, not everted at the anterior
border but tapering equally towards each extremity, joined to one another
without the intermedium of a stalk-like prolongation ; the entire colony
consisting of a straight median line of the constituent cells, from the
anterior borders of each of which three cells originate, one directed straight
forwards and continuing the main rachis, and one other on each side of this
median one, which become further developed into oblique lateral branchlets,
these latter subdivisions frequently giving rise to secondary oblique off-
shoots. HAB. — Fresh water. Dimensions unrecorded.

The compound polythecium of this species only is figured and described by
Eichwald in his ' Infusorienkunde Russlands,' 1847, no reference being made to the
inhabiting animalcules. The evenly ovate shape of the individual cells and the
symmetrical rectilinear mode of growth of the general colony, distinguish it in a
marked manner from D. sertularia.

Doubtful Species.

A description of two additional species of the genus Dinobryon is included in
Pritchard's ' Infusoria,' p. 547, the characteristics of which, however, as here repro-
duced, are almost too vague for reidentification.

Dinobryon (?) sociale, Pr. — " Small ; enveloped in a shell of a simply
conical shape, truncated at the mouth. Developed in the form of a shrub-
like polypary. In fresh water. 1-860" ; cluster 1-280"."

Dinobryon gracile, Pr. — Less branching (fruticose), lorica slightly con-
stricted at the middle, aperture truncated. Animalcule 1-2080".

The Dinobryon petiolatum of Dujardin is transferred by the author of this treatise
to De Fromentel's genus Stylobryon, and is evidently identical with both the
6". insignis of that writer and with the Poteriodendrum petiolatum of Stein.

GENUS XIII. SYNURA, Ehrenberg.

Animalcules free-swimming, united in subspheroidal social clusters,
each zooid contained in a separate membranous sheath or lorica, the
posterior extremities of which are confluent ; flagella two in number,
* ' Infusionsthiere,' Abth. iii., 1878.

4 1 2 ORDER FLA CELL A TA-E US TO MA TA .

subequal ; endoplasm containing two lateral pigment-bands, one or more
coloured eye- specks usually developed. Inhabiting fresh water.

Known only by the figures and descriptions of Ehrenberg, the single type-form
of this genus has been regarded as an entirely doubtful species, and, together
with Syncrypta and Uro'glena, been even discarded by Mr. Carter as spermatic or
developmental phases of the vegetable types Volvox or Sph&rophrya. As recently
shown by Stein, however, this form possesses a sound claim for independent recog-
nition. It is further demonstrated by this authority that Ehrenberg was wrong in
assigning to the spheroidal colonies the possession of a common gelatinous matrix,
as in Syncrypta and Uroglena, in addition to the individual loricae. What Ehrenberg
took for such an element were probably the minute, thickly set, filamentous or spinous
processes, now made known by Stein to be developed throughout the external
surfaces of the loricae of the type in question, but which are to be recognized as
distinct structures only when the organism is examined with the aid of an exceedingly
high magnifying power. The presence of two flagella, eye-specks, colour-bands, and
other histologic details, are also for the first time demonstrated by this authority.

Synura uvella, Ehr. PL. XXIII. FIGS, i and 2.

Loricae pyriform, tapering posteriorly, sometimes prolonged in a stalk-
like manner, their external surface beset with evenly developed spinous
processes ; contained animalcules almost entirely filling the cavities of the
loricae, their posterior extremity produced towards and adherent to the
bottom of the same ; flagella subequal, eye-like pigment-specks minute,
two in number, sometimes absent ; a large vacuolar space, apparently
representing a pharyngeal dilatation, developed at the anterior extremity ;
colour-bands produced equally throughout the length of the two lateral
borders ; contractile vesicles two or three in number, posteriorly located ;
endoplast situated in the middle line, immediately behind the two eye-like
specks. Length of individual loricae 1-740" ; diameter of spheroidal colonies
1-350" to 1-200", these latter often consisting of as many as eighty zooids.

HAB. — Pond water.

' Stein regards the type figured by him as the eyeless variety of this species,
PI. XXIII. Fig. i, as identical with the Uvella virescens of Ehrenberg. Biitschli,
however,* figures and describes as representing this last-named organism an entirely
distinct form in which there is no lorica with its spinous processes and no conspicuous
pharyngeal dilatation, such species being here accepted as typifying the genus Uvella.
Stein has further proposed to unite with this organism the Mallomonas Plosslii of Max
Perty, which he regards as isolated individuals of Synura uvella, with the setose or
spinous processes of their loricae greatly produced. Mallomonas is, however, an
entirely distinct monoflagellate animalcule, having, as demonstrated by the author's
description and illustrations elsewhere submitted, nothing in common with the
Chlpromonadidse.

Doubtful Species.

Under the title of Rhodczssa grimselina, Perty figures and describes, apart from
Uvella virescens, a species apparently belonging to this same genus Synura. No
reference to a distinct lorica is given, but the margin of each body is reported to be
distinctly and finely crenulate. Except for two evenly developed bright green lateral
pigment-bands the body-substance is entirely transparent. The crenulation exhibited
represents probably the periphery of a separate lorica. The type was obtained by

Zeitschrift fxtr Wissenschaftliche Zoologie,' Bel. xxx., 1878.

GENUS S YNCR YPTA. 413

Perty in bog water on the Grimsel Alps. The length of the individual zooids is
given as 1-840" to 1-600", and the diameters of the united colonies as 1-180".
These colony-stocks contain from three or four to as many as thirty zooids ; the
spheroidal mass formed, according to his delineations reproduced at PL XXII.
Fig. 27, being very irregular.

GENUS XIV. SYNCRYPTA, Ehrenberg.

Animalcules free-swimming, illoricate, united socially by their posterior
extremities in spheroidal or rosette-shaped clusters, the whole colony-stock
being immersed within a granular, gelatinous matrix or zoocytium, beyond
the periphery of which the flagella alone project ; flagella two in number,
subequal ; lateral colour-bands conspicuously developed ; one or more
eye-like pigment-specks usually present.

Previous to the publication of Stein's recently issued volume, the position of the
single specific form referred by Ehrenberg to this genus was very doubtful ; Du-
jardin regarded it as closely allied to or identical with Cryptomonas, while Mr. Carter
declared it to be the spermatic form of Volvox or Spharophrya. As more thoroughly
investigated by Stein, it is, however, now shown to be an independent type most
nearly allied to Uroglena, but differing from that genus in the close approximation,
without any intermediate spaces or contractile pedicles, of the zooid clusters, and
through the possession by the animalcule of two eye-specks instead of a single one.

Syncrypta volvox, Ehr. PL. XXIII. FIG. 3.

Bodies ovate, tapering posteriorly, and there united together so as to
form rosette-shaped colonies of four, eight, sixteen, or thirty zooids ; the
investing zoocytium granular, and somewhat dense ; flagella two in number,
subequal ; colour-bands evenly developed, of a brownish^ hue, extending
throughout the two lateral borders ; eye-like pigment-specks two in
number, one stationed at the anterior extremity of each of the two colour-
bands ; the contractile vesicle located a little behind the eye-specks and
in the clear space between the colour-bands. Length of individual zooids
1-2500", diameter of social colonies, including gelatinous zooglcea, 1-570".

HAB. — Pond water.

As originally figured and described by Ehrenberg, the zooids of this colonial
form are represented as possessing a single flagellum only, but Stein in his recently
published illustrations of the Flagellata records the existence of two, as also of the
eye-specks and contractile vesicles, which had not been detected by Ehrenberg.
Stein is not very clear in his delineation of the relative length of the two flagella, in
some cases they being delineated as equal and in others as diverse in length. The
balance of evidence is, however, seemingly in favour of their uneven development,
such proportions obtaining in Dinobryon, Epipyxis, Uroglena, and all other members
of this family group that have been examined by the present author with the aid of
the highest magnifying powers. It is a further significant fact that in this instance,
as also in most others in which two uneven-sized flagella actually exist, Ehrenberg has
represented a single one only, the smaller of the two having no doubt been beyond
the defining capacity of his instruments. In the protophytes Volvox and Chlamydo-
tnorias, on the other hand, where the two flagella are of even length and calibre, this
authority has as invariably assigned to them their true character and proportions.

414 ORDER FLAGELLATA-EUSTOMATA.

GENUS XV. UROGLENA, Ehrenberg.

Animalcules enclosed socially within a subspheroidal gelatinous matrix
or zoocytium, to the centre or deeper substance of which they are united
through the medium of slender, thread-like, highly contractile, posteriorly
developed prolongations ; in their normal or extended condition the anterior
borders of the individual animalcules impinging upon or projecting slightly
beyond the periphery of the zoocytium, but capable at will, through the
contractions of the filiform posterior prolongations, or pedicles, of being with-
drawn entirely within its substance ; flagella two in number, of diverse
size ; endoplasm enclosing two distinct lateral colour-bands, and usually one
or more eye-like pigment-spots. Inhabiting fresh water.

Uroglena volvox, Ehr. PL. XXIII. FIGS. 4-15.

Colony-stocks subspherical or more or less asymmetrical ; bodies pyri-
form, the anterior border rounded, somewhat obliquely truncate, taper-
ing posteriorly, and thence continued backwards in the form of a long,
slender, hyaline, and highly contractile thread-like prolongation ; lateral
pigment-bands yellowish-green, of uneven length ; eye-like spot single,
situated anteriorly and in the median line, close to the base of the two
flagella ; flagella of conspicuously diverse size ; contractile vesicles two in
number, located close together near the centre of one of the lateral borders ;
a large ovate and apparently amylaceous corpuscle mostly developed
towards the posterior half of the body. Length of bodies I— 1200", average
diameter of social colony-stocks 1-90". HAB. — Pond water.

This type, in common with Syncrypta, Synura, and other socially aggregated
Chloromonadidae, has been usually regarded as a doubtful form probably representing
an imperfect or transitional condition only of the protophytes Volvox or Sp/uzrosira.
Quite recently, however, it has been shown by both Biitschli and Stein, to be an
independent organism exhibiting, with relation to the form and characters of the
individual zooids, an entire conformance with the several other generic types com-
prised in the Chrysomonadidae. Examples of this species were likewise remitted to
the author during the month of June 1879, by Mr. H. E. Forrest and Mr. Thomas
Bolton, from the neighbourhood of Birmingham, the result of such a personal
acquaintance with it being the discovery of various supplementary structural and
developmental phenomena here recorded for the first time. More especially in this
connection may be mentioned the establishment of the possession by the zooids of
a posteriorly developed thread-like pedicle, first imperfectly observed and inter-
preted by Ehrenberg as a simple tail-like prolongation, but entirely overlooked by
both Stein and Biitschli. This structure is, in fact, so slender and transparent as to
require a high magnifying power, 600 to 800 diameters, and the nicest adjustment of
the illumination for the demonstration of its existence. Such conditions being
secured, however, its presence is conspicuously apparent both in living examples and
in specimens treated with osmic acid and permanently preserved. Under the latter
auspices, indeed, this special structure may perhaps be most readily identified,
though its contractile properties and complete conformity with the contractile pedicles
of Dinobryon and Epipyxis are recognizable only in the living state.

Among the data observed by the author with reference to the reproductive
phenomena, it has to be recorded that zooids were abundantly found withdrawn
into the common matrix or zoocytium, devoid of flagella, and presenting every step

GENUS UROGLENA. 415

of gradation from a simply quiescent but non-encapsuled stage up to subdivision into
two, four, or eight spheroidal segment-masses or sporular elements. These spores
becoming distributed throughout this common gelatinous matrix, speedily acquire
the adult forms and characters, and are in most instances provided with the two
lateral colour-bands and eye-like pigment-spot at or immediately succeeding their
earliest appearance. In the majority of the specimens examined this mode of re-
production was alone observed, and is chiefly to be seen in the two colony-stocks
delineated at PL XXIII. Figs. 4 and 5. Not unfrequently, however, examples were
met with which enclosed supplementary spheroidal structures, having a diameter of
two or three times that of the bodies of the adult zooids, three of these being
included in the colony-stock illustrated by Fig. 4. On making a closer investiga-
tion it was found that these supplementary structures consisted of aggregations of
spore-like bodies contained within a hard and glass-like transparent membrane or
sporocyst, which exhibited its brittle consistence by rupture under artificial pressure
into a number of angular fragments, as shown at PL XXIII. Figs. 10 and n. The
sporular elements thus liberated from their indurated capsules were, found to possess
two entirely distinct dimensions, being in the one instance, Fig. n, of compara-
tively large size, the i-6oooth of an inch in diameter, while in the second case,
Fig. 10, they did not exceed the i-2o,oooth of an English inch. Not improbably,
however, these smaller sporular bodies represent a further segmented phase only of
the larger ones, and in both instances they are so minute as to merit the designation
of " microspores " in contradistinction to that of " macrospores," which may be
appropriately applied to the structures derived from the simple segmentation into
two, four, or eight sporular elements of the ordinary unencapsuled zooids, as
previously described. The precise import of these encapsuled sporular elements
has not yet been determined ; but from the proportionate size of their investing
sporocysts it may be consistently predicated that they were primarily derived through
the conjugation or genetic union of two or more ordinary zooids, while their encap-
suled state would seem further to denote that surviving the disintegration of the
parent colonies, and probably the drying up of the water with the summer drought,
they secure the permanent preservation of the species.

With reference to the retention and development of the larger and naked
sporular elements of Uroglena within the common gelatinous matrix of the parent
colony, the similarity of the phenomena to what obtains among the co-ordinate
section of the Spongida, and as related at length in a preceding chapter, is at once
made manifest. Additional testimony in this direction has to be recorded. The
author has on several occasions observed within the parent colonies the presence
of smaller spheroidal aggregations, apparently corresponding with the " daughter-
spheres" of Volvox or Eudorina, but which, in the event of further corrobora-
tion, may be found to possess a still more important significance. These are, in
fact, directly comparable with the ciliated gemmules or so-called ciliated larvae
of the sponges as they occur in their simplest state, and consist in a like manner
of a vesicular moruloid structure, built up of a single stratum of closely approximated
flagellate zooids. In a similar way these daughter-spheres of Uroglena provide for the
more extensive local dissemination of the species, while the ordinary zooids by simple
sporular segmentation contribute towards the enlargement of the parent colony.
There can be but little doubt that, as in the case of the daughter-spheres of Volvox
and the ciliated gemmules of the Spongida, these corresponding structures in Uroglena
are derived from the primitive coalescence of a considerable number of single cells
or zooids. Though this process has not as yet been directly observed, it may be
predicated by their occupation of an area towards the periphery corresponding with
that normally held by some half a dozen or more of the ordinary animalcules.

Although a single contractile vesicle only is attributed to the zooids of Uroglena
by Biitschli, while such a structure is entirely absent in Stein's latest delineations of
this species, two alternately contracting ones situated towards the centre of one
lateral border have been distinctly seen by the present author. Some amount of
doubt has hitherto existed as to whether the gelatinous matrix in which the zooids
of Uroglena are immersed, is continuous to the centre of the common spheroidal

416 ORDER FLAGELLATA-EUSTOMATA.

mass, or whether this central space is simply fluid ; Butschli inclines to the last-
named alternative, having, he says, observed diatoms and other foreign bodies moving
freely in this position. The present author is, however, disposed to maintain that
this matrix persists throughout, being most fluid centrally and becoming gradually
denser as the peripheral region is approached. In both living and preserved
examples no trace whatever could be detected of distinctly differentiated internal
and external zones.

From Volvox, Syncrypta, Synura, and various other free-floating animal and
vegetable Flagellate types, for which the colony-stocks of Uroglena volvox are some-
what liable to be mistaken, an easily recognized superficial feature of distinction is
afforded by the general contour of the colony-masses, which rarely exhibit that
perfect spherical symmetry which characterizes the several first-named forms.

Fam. VI. ZYGOSELMID-ffi, S. K.

Animalcules solitary, free-swimming or repent ; flagella two in number,
similar in character, both vibratile; endoplasm sometimes coloured green,
but not enclosing differentiated lateral pigment-bands ; oral aperture
distinct, terminal ; one or more eye-like pigment-specks frequently present.
Mostly inhabiting fresh water.

GENUS I. EUTREPTIA, Perty.

Animalcules free-swimming or repent, plastic and changeable in form,
ovate or elongate ; oral aperture terminal, funicular ; flagella two in
number, vibratile, of equal size, issuing from the terminal oral fossa ;
endoplasm coloured a brilliant green, enclosing an anterior eye-like
pigment-spot ; contractile vesicle anteriorly situated ; endoplast subcentral.
Inhabiting fresh water.

Excepting for the possession of two equal-sized flagella and the exhibition of the
peculiar peristaltic movements presently described, the as yet single known repre-
sentative of this genus corresponds essentially with Euglena.

Eutreptia viridis, Pty. PL. XXI. FIGS. .54-59.

Body soft and plastic, exceedingly variable in form, its more normal
contour when swimming pyriform, broadest and widest anteriorly, with
an attenuate and pointed caudal prolongation, at other times elongate
and subcylindrical, subfusiform, napiform, or variously constricted, often
repent, creeping over the surface of submerged objects by active peristaltic
contractions ; flagella slender, equalling the body in length ; eye-like
pigment-spot conspicuous, scarlet ; contractile vesicle located close to the
last-named structure ; endoplast spherical, subcentral. Length 1-240".

HAB. — Pond water.

Since the discovery and description of this animalcule by Max Perty in 1852, it
does not appear to have fallen beneath the observation of any other investigator and
has been more usually regarded as an imperfectly recorded phase of some one of the
various species of Euglena. As such it is dismissed by Stein in the third volume
of his ' Infusionsthiere,' and until quite recently this verdict was accepted by the
present author. So late as February 1879 this type has, however, been encountered
in considerable numbers in pond water from near the village of Samares, Jersey,

GENUS Z YGOSELMIS. 4 1 ^

such discovery justifying its reinstatement as a well-marked generic form. In addition
to the two long, equal, vibratile flagella, which were in all normal conditions distinctly
seen, the peculiar and rapid peristaltic movements exhibited by the animalcule during
its repent state, distinguish it in a marked manner from the various species otEuglena
and approximate it more nearly in this respect with the members of the genus
Distigma or the essentially repent protozoic type Gregarina. In the examples
examined, it was noted that very soon after their transfer to the object-slide they
abandoned their natatory for the repent mode of progress, which is possibly the
more general and congenial. Encysted conditions were frequently observed, and
also the breaking up of the contents of the encysted zooids into innumerable sporular
bodies which were subsequently liberated in the form of minute, green, non-flagellate
amoebae, these phenomena corresponding with those already recorded of Euglena
viridis. Prior to their acquirement of the typical adult state, it is worthy of note
that the amoebiform germs possess a single flagellate appendage only, being under
such conditions altogether indistinguishable from minute Euglena.

As compared with Perty's original figures, the animalcules of Eutreptia were not
observed during their natatory state to assume so attenuately pyriform a contour
as he delineates, the pointed caudal prolongation in the Jersey specimens rarely
exceeding one-half of the length of the inflated body-portion, while in the former
case it frequently equals or even exceeds this region in length. Perty's so-called
variety unifilis of this species represents apparently the young condition only, as
above described.

GENUS II. ZYGOSELMIS, Dujardin.

Animalcules highly metabolical and variable in form, swimming with
the aid of two unequally developed flagellate appendages, which issue from
the pointed anterior extremity ; oral aperture at the base of these flagella,
followed by a distinct tubular pharynx ; endoplasm transparent, granular ;
no eye-like pigment-specks. Inhabiting fresh water.

In their constantly changing form, the animalcules of this genus may be most
appropriately regarded as biflagellate Astasia. Butschli has proposed to identify
the type species Z. nebulosum with Chilomonas paramecium, an animalcule, however,
with which, excepting for its possession of two flagellate appendages, it can scarcely
be said to share a single point in common.

Zygoselmis nebulosa, Duj. PL. XXI. FIGS. 52 AND 53.

Body variable, ovate, globular, or pyriform, changing its form slowly
from one to the other, endoplasm densely granulate ; cuticular surface
finely striate obliquely ; flagella of conspicuously diverse length. Length
of body 1-1250" to 1-500". HAB. — Pond water.

Stein records the existence of a distinct oral aperture and pharyngeal passage
at the base of the two flagella, and delineates an example in his recently published
volume, reproduced at PI. XXI. Fig. 53, whose body is abnormally distended
through the ingestion of two comparatively large diatom frustules. The animalcule
at Fig. 59, bearing three flagellate appendages, is, as explained by Stein, about to
divide by longitudinal fission. Dujardin, who appears to have observed this type
on one occasion only, describes it as incessantly changing its form as it swims through
the water, after the manner of an Astasia.

Zygoselmis insequalis, Perty.

Body hyaline, colourless, slowly assuming various shapes ; one flagellum
somewhat shorter than the other ; parenchyma sometimes filled with clear
green granules ; movements sluggish. Length 1-840".

2 E

41 8 ORDER FLAGELLATA-EUSTOMATA.

The difference between this and the preceding species appears to be only one of
size, and almost too slight for separate distinction.

GENUS III. DISTIGMA, Ehrenberg.

Animalcules free-swimming, highly elastic and changeable in form ;
flagella terminal, two in number, one long and one short, both vibratile ; oral
aperture close to the base of the flagella, succeeded by a long, tubular
pharyngeal passage; endoplasm transparent, usually enclosing two ante-
riorly developed, minute, eye-like pigment-spots ; contractile vesicle and
endoplast conspicuous.

Distigma proteus, Ehr. PL. XXI. FIGS. 46-51.

Body highly metabolic, scarcely ever presenting the same contour, usually
more or less elongate, with irregular constrictions and distensions ; longer
flagellum nearly equalling the body in length, the shorter one scarcely
one-quarter that length ; endoplasm transparent, enclosing numerous dark-
coloured refringent corpuscles whose positions are constantly shifting from
one extremity to the other in accordance with the peristaltic motions of the
body ; two minute, blackish, eye-like pigment-spots usually developed at
the anterior extremity ; tubular pharynx slender, greatly prolonged ; con-
tractile vesicle conspicuous, located close to the termination of the pharynx ;
endoplast ovate, subcentral. Length 1-580" to 1-240".

HAB. — Pond water, among Lemnce.

Stein * refers this species to the genus Astasia, here and elsewhere more generally
retained for the reception only of certain monoflagellate types. He further pro-
poses, in his index to the figures given, to identify the countless protean forms
assumed by this animalcule with the Proteus tenax of O. F. Miiller and Distigma
proteus et tenax, Astasia flavicans et pusilla, and Monas punctum of Ehrenberg ;
these last three hypothetic species being more especially identified with the earlier
stages of its growth. In neither of the two first-named forms did Ehrenberg detect
the presence of any flagellate appendage, and it was assumed by him that such
do not exist ; the movements of the animalcule were further described by this
authority as simply repent and peristaltic. As shown by Stein, however, it is only
the older zooids that lose their flagella and lead a repent life, the younger and more
normal ones possessing two conspicuous but unequal sized flagella, as indicated
in the preceding diagnosis. This elder creeping phase corresponds evidently with
the amoeboid one assumed by the majority of the Flagellata as a preliminary
step to the act of coalescence or encystment. The peculiar peristaltic movements
exhibited by the representatives of this species, both during their natatory and repent
states, coincide closely with those that characterize the Gregarinada, and are, with
the exception of Eutreptia, met with nowhere else among the Infusoria. The
Proteus tenax of O. F. Miiller, while greatly resembling the repent phase of the present
species in outward form, is possibly, from the description given of the parenchyma —
" pellucid and filled with black granules " — a species of Gregarina, identical probably
with the one infesting various species of Cyclops, and not unfrequently found free
in the water containing this abundantly distributed Entomostracon. As such an
independent Gregarine type Stein has indeed previously recognized it, describing
itt under the title of Monocystis tenax. The Distigma uiridis of Ehrenberg would

1 Infusionsthiere,' Abth. iii., 1878. f Ibid., ii., 1867, pp. 7 and 8.

GENUS CRYPTOGLENA. 419

appear to be identical or closely allied to the Eutreptia viridis of Perty, previously
described.

The author has quite recently, November 1880, received specimens of this inter-
esting animalcule, Distigma proteus, from Mr. Thomas Bolton, its companions in
the sample of pond water forwarded being Spirostomum feres, Paramcedum chrysalis,
Astasia trichophora, and Eugkna acus. The various protean forms reproduced from
Stein's work in the accompanying plate were abundantly exhibited during their
natatory condition by the examples examined, each change of contour being accom-
panied by the rapid flowing from one extremity to the other of the endoplasmic
corpuscles in the manner indicated in the foregoing diagnosis.

Yet a week later the author has had remitted him, through the same agency, a
small phial absolutely teeming with the young eyeless condition of this animalcule,
as delineated at Figs. 49-5 1 of PI. XXI. These were found to be much more per-
sistent in shape than the adult zooids. While observed during the first four days to
change their form at more or less frequent intervals, it was noted towards the end of
the fifth and sixth days that they generally assumed a compressed spirally twisted
contour. The diagonal striation of the cuticle in two directions, as represented in
Stein's figure (PI. XXI. Fig. 49), was conspicuously developed in almost every
instance. The correspondence, in both size and contour, of the young Distigma
with Dujardin's Zygoselmis nebulosa is certainly very close, and suggests the proba-
bility of their proving to be synonymous. While going to press, the animalcules are
enjoying their active natatory existence, but owing probably to the absence of their
customary food, have scarcely increased in size, their average length, as when first
received, ranging from 1-800" to 1-500".

GENUS IV. CRYPTOGLENA, Ehrenberg.

Animalcules free-swimming, solitary, plastic and changeable in form,
enclosed within a rigid membranous sheath or lorica ; flagella two in
number, subequal ; endoplasm coloured green throughout ; an anteriorly
located eye-like pigment-speck usually developed.

The representatives of this genus were considered by Dujardin to be so closely
related to Cryptomonas and the Phytozoon Chlamydococcus as to forfeit claim to
independent recognition, this verdict being coincided with by Pritchard. The author
of this treatise is, nevertheless, disposed to regard the type species, Cryptoglena
conica of Ehrenberg, as a well-marked independent form, most closely allied to the
genus Eutreptia, and occupying towards it a position corresponding to that which
subsists between the two genera Euglena and Trachelomonas. The Cryptoglena
lenticularis of Carter* is evidently a species of Chlamydococcus, while his C. cordata
has been transferred by Stein to the new genus Tetraselmis ;

Cryptoglena conica, Ehr. PL. XXL FIG. 42.

Lorica elongate-ovate or obconical, somewhat truncate anteriorly, more
or less pointed posteriorly, sometimes slightly curved ; body of animalcule
occupying the two anterior thirds of the cavity of the lorica ; flagella two
in number, evenly developed ; endoplasm bluish green; a conspicuous
scarlet eye-like pigment-spot developed at the anterior extremity; two
more opaque, ovate, and apparently amylaceous corpuscles frequently
present in the posterior region. Length, including lorica, i-iioo".

HAB. — River water.

According to Ehrenberg the animalcules of this species progress forward rapidly
in the direction of their longitudinal axis, and if interrupted in their course, spring or

* 'Annals of Natural History,' Oct. 1858.

2 E 2

420 ORDER FLA GELLA TA-EUSTOMA TA.

leap briskly to one side. The Cryttoglena ccemleus of the same authority is evidently
an illoricate type not referable to the present generic group, and whose true relation-
ship is as yet doubtful. The form figured by both Ehrenberg and Stein under the
name of Crypt»g!ena pigra is here made the type of the new genus Chloromonas.

Cryptoglena angulosa, Carter. PL. XXI. FIGS. 43-45.

Lorica oblong, angular, and compressed, truncate, but with a short pro-
jecting neck on the anterior margin, the posterior border rounded ; in
lateral view the anterior and posterior borders curved in opposite directions
and exhibiting a sigmoid outline ; body of enclosed animalcule occupying
the greater portion of the lorica, but leaving free a conspicuous peripheral
border ; flagella equal in size ; two contractile vesicles situated close to
each other at the anterior extremity; a red eye-like pigment -spot located
on one side of the periphery ; from one to four amylaceous corpuscles
usually developed towards the posterior extremity. Length of lorica
i- 1080". HAB. — Fresh-water lakes in the island of Bombay.

The encysted state of this species was observed by Mr. Carter,* as also its sub-
division under such conditions into two and four sporular bodies, these latter being
ultimately liberated, by the dehiscence of the old lorica, which becomes smooth and
dilated, as zooids of smaller size, but corresponding in all other respects with the
parent form. The movements of this animalcule are described by its discoverer as
being directed forwards, but in an exceedingly irregular line.

GENUS V. STERROMONAS, S. K.
(Greek, sferros, stiff; monas.)

Animalcules free-swimming, elongate, more or less persistent in form
bearing two flagella of diverse size at the anterior extremity, the longer
of which is extended arcuately and stiffly in advance, while the shorter
one is actively vibratile and flexible throughout ; oral aperture indistinct ;
endoplasm transparent, granular ; no eye-like pigment-specks ; contractile
vesicle and endoplast conspicuously developed.

Sterromonas formicina, S. K. PL. XXIV. FIGS. 40-42.

Body elongate, gibbous, nearly three times as long as broad, inflated
and widest posteriorly, narrower in the centre, slightly widening again
anteriorly, both the anterior and posterior margins obliquely truncate or
angular as seen in profile ; flagella inserted close to one another near the
centre of the frontal border, the longer one equalling the body in length,
directed stiffly in advance, arcuate at its distal termination, the shorter one
less than half the length of the other, flexible and tremulous throughout ;
endoplasm transparent, enclosing numerous granules of irregular form
and size ; endoplast spherical, subcentral ; contractile vesicle posteriorly
located. Length of body 1-2000" to 1-1250".

HAB. — Vegetable infusions in salt and fresh water.

* ' Annals and Magazine of Natural History,' 1859.

GENUS DINOMONAS. 421

The animalcule, as above characterized, presents in profile an aspect so strikingly
suggestive of the body of an ant, with its gibbously inflated posterior and constricted
central portion, that a specific title indicative of this likeness is herewith conferred
upon it. The generic name of Sterromonas, from oreppos, rigid or unbending, bears
reference again to the stiff movements in the water of this as yet single known
representative of the genus, and which are chiefly induced by the constantly rigid
extension of the longer flagellum. Even when altering its course, the animalcule
swings round on its axis, as though on a swivel, without visibly bending its body or
this organ in the slightest degree, and which thus seems to more closely resemble
a stiff seta than a flagellate appendage. At the same time it would appear that
this structure is motile at its free extremity, in a swift vibratory manner as in the
Pantostomatous genera Spumclla and Oikomonas. In addition to its normal leisurely
progress in a straight line, apparently accomplished by the tremulous motions
of the shorter flagellum, this animalcule occasionally darts across the field with
remarkable rapidity, and it is probable that under these circumstances, the longer,
arcuate flagellum constitutes the chief organ of propulsion. The species possesses
prominent adaptive capacities, appearing in equal abundance in artificial infusions
of hay in both fresh and salt water. The latter medium, indeed, seemed to prove
the more congenial, it attaining in this one only, the larger dimensions of 1-1250"
cited in the foregoing diagnosis. An example was observed in one instance to form
a spherical encystment, such entrance upon a quiescent condition being preceded
by the assumption of an irregular amoeboid shape. The aspect of the zooids of
this species considerably resembles that of the natatory conditions of Oikomonas
mutabilis, represented at PL XIII. Figs. 57 and 58. Its smaller size, persistency of
shape, and possession of two flagella readily distinguish it, however, from that type.

Under the title of " Flagellaten-rhizopodenartige Protozoen " O. Biitschli has
described and figured* a flagellate organism which must perhaps be accepted as a
second species of the genus Sterromonas. The contour of this organism in dorsal view
is more symmetrical than that of S. formicinus, being subcylindrical, with a slightly
narrower anterior extremity; the frontal border is obliquely truncate, a spherical endo-
plast is stationed at the anterior extremity, and the contractile vesicle is adjacent to
the centre of the right-hand border; the endoplasm is more evenly and finely granulate
than in the form just described. Biitschli indicates a single long and apparently
stiff, arcuate flagellum at the apical extremity, but it is quite possible a second
shorter one exists, which has been overlooked. This form was found in water with
decomposing organic substances, in company with Anthophysa vegetans and other
flagellate types; the length given is 0-03 mm., or about i'8oo". Observing an
example assume an amoeboid state, accompanied by the extension of pseudopodic
processes, Biitschli has adopted this amoebiform condition as the mature and adult
one, regarding the flagellate monad as its larval or zoospore-like phase. This
amoeba-like type he further proposes to identify with the Nuclearia simplex of Cien-
kowski. It is evident, however, that this amcebiform organism represented merely
that transitory condition of the flagellate monad preceding encystment common to
so many members of the Flagellate class, and that it is the flagellum-bearing zooid
that must be regarded as the typical expression of the species. Presuming that
this animalcule is generically related to S.forwianus, it is here proposed to distinguish
it provisionally by the title of Sterromonas Butschlii.

GENUS VI. DINOMONAS, S. K.

(Greek, deinos, terrible ; monas.)

Animalcules free-swimming, ovate or pyriform, soft and plastic, but
not metabolic ; flagella two in number, equal or subequal in length, vibra-
tile, inserted close to each other at the anterior extremity ; endoplasm
transparent, granular ; no eye-like pigment-spot ; oral aperture very expan-

* ' Zeitschrift fiir Wissenschaftliche Zoologie,' Jan. 1878, p. 269, pi. xiii. fig. 22a.

422 ORDER FLAGELLATA-EUSTOMATA.

sive, located at the anterior extremity immediately beneath the insertion of
the flagella, visible only at the time of food ingestion, not supplemented
by a distinct pharyngeal passage ; feeding voraciously on other flagellate
types, which they swallow whole. Inhabiting vegetable infusions.

This genus is instituted for the reception of two species corresponding with one
another both in their broad external features and in their active predatory habits.
This latter characteristic, combined with the equal size of the flagella and their
comparative persistency of contour, serves to distinguish them from Zygoselmis, with
which they otherwise to a considerable extent agree.

Dinomonas vorax, S. K. PL. XXIV. FIGS. 46-48.

Body persistent in shape, subpyriform, widest and rounded posteriorly,
pointed anteriorly and slightly curved towards the ventral aspect, about two
and a half times as long as broad, surface smooth ; flagella slender, vibratile,
subequal, exceeding the body in length; oral aperture exceedingly elastic,
conspicuous only during the passage of food ; endoplasm finely granulate ;
endoplast spherical, subcentral ; contractile vesicle posteriorly located.
Length of body 1-1600".

HAB. — Infusions of hay in fresh and salt water.

This species was obtained by the author at St. Heliers, Jersey, in February 1878,
in an infusion of hay in spring water on the eighth day of its maceration. For the
next three or four days it constituted the most abundantly developed type, but at the
end of this period it disappeared as suddenly as it came, and was not again seen in
the infusion. A precisely identical animalcule was found in a contemporaneously
prepared hay infusion in salt water on the eleventh day of its maceration, and
was correspondingly fugacious. The habits of this species are eminently preda-
tory, the greater portion of its time being spent in hunting down and devouring
such other flagellate forms as may happen to be present. A few of them, enclosed
in a glass slide with a crowd of Heteromita lens, Monas fluida, &c., were observed to
rush in among these smaller animalcules where they congregated in zones near the
margin of the glass cover, reappearing presently with a captured monad grasped by
its sharply pointed distal extremity. Remaining motionless for a few seconds, this
captured prey was gradually absorbed, a wide, elastic oral aperture, not previously
visible, opening and expanding to receive it, and the chase being then renewed after
other victims. In this manner five or six of the smaller monads were successively
devoured in a very short space of time, and it was consequently not long before
these weaker types succumbed and altogether disappeared before the aggressive
inroads of the new intruders. Thus was illustrated in this humblest path of organic
life the persistence and immutability of that law of the " survival of the fittest " now
recognized as regulating the distribution of the most highly developed sentient
beings, and upon which the welfare and stability even of nations is dependent. The
movements of Dinomonas vorax, when not occupied in the pleasures of the chase, at
which times it darts about hither and thither with great rapidity, consist of an even
motion in a straight line, the snout-like anterior extremity being directed obliquely
downwards, while the two flagella are vibrated actively in advance. In the younger
and smaller examples, as shown at PI. XXIV. Fig 46, the body is considerably
narrower, or more attenuate in proportion to its length,

Dinomonas tuberculatus, S. K. PL. XXIV. FIGS. 43-45.

Body irregularly ovate, somewhat variable in form, but not metabolic,
most usually more attenuate posteriorly, the ventral border flattened, the

GENUS CHILOMONAS. 423

dorsal one convex ; endoplasm very clear and transparent, enclosing
nodular corpuscles of irregular shape and size, many of these located on
or close to the surface, and imparting to it a tuberculate aspect ; flagella
subequal, the anterior slightly the longer, exceeding the body in length ',
endoplast spherical, subcentral ; contractile vesicle posteriorly situated.
Length of body 1-250x3".

HAB. — Vegetable infusions in both salt and fresh water.

This form was obtained by the author in equal abundance in the hay infusions in
both salt and fresh water productive of the preceding type. It is worthy of remark,
however, that while in the salt-water infusion this species preceded D. vorax by a
few days in its advent, the reverse happened in the case of the fresh-water one.
Although in their predacious habits, and in the manner of chasing and incepting
their food, the two species closely correspond with each other, their external appear-
ances are altogether diverse. The smooth, persistent, subpyriform shape of the variety
last described is here replaced by a contour which, while more frequently irregularly
ovate, with a slightly pointed posterior extremity, as represented at PI. XXIV.
Figs. 44 and 45, may in other instances be produced at this region into a long
tail-like process, as shown at Fig. 43, which communicates to it a singular rat-like
contour. On the other hand, it not unfrequently assumes an almost perfectly
spheroidal shape. The habits of this species appear to be slightly more omni-
vorous than those of Dinomonas vorax, for in addition to its ordinary diet of smaller
monads, which are seized and swallowed in a manner similar to that already
related of the last-named type, long bacillar-like filaments, as shown at Fig. 45, are
not unfrequently ingested. Multiplication by longitudinal fission was observed on
several occasions, as likewise the formation of spherical encystments.

Fam. VII. CHILOMONADID-ffi, S. K.

Animalcules free-swimming or temporarily adherent, illoricate ; oral
aperture conspicuously developed, communicating to the anterior border a
bilabiate or excavate appearance ; flagella two in number, both vibratile or
undulating in the natatory state, but one of them coiled upon itself when
the zooid is at rest, adherent through a greater or less portion of its length,
and used for the purpose of temporarily anchoring it to submerged objects ;
endoplasm transparent, granular ; no eye-like pigment-spot. Inhabiting
salt and fresh water.

The most important distinction of this family group as here defined, is afforded
by the anchoring faculty possessed by one of the two flagella, this feature to
some extent approximating it toward the Anisonemidae next described. In none
of the representatives of this last-named group, however, does the anchoring
flagellum exhibit that characteristic coiled contour so conspicuous in the present
instance. Furthermore, the anchoring flagellum in Chilomonas and its allies is
vibratile and subservient to the purpose of locomotion, in place of being trailed
motionlessly in the rear, as obtains among the succeeding group. A modification of
the flagella, in which loop-like coils for the purpose of attachment are developed at
the base of each appendage, has been already recorded in connection with the genus
Polytoma.

GENUS I. CHILOMONAS, Ehrenberg.

Animalcules free-swimming, ovate or elongate, not metabolic but plastic
and subject to considerable alteration in form, the anterior extremity
obliquely truncate, projecting superiorly, and presenting the aspect of a

424 ORDER FLAGELLATA-EUSTOMATA.

prominent upper lip ; oral aperture distinct, opening on the anterior truncate
border, followed by a conspicuous pharyngeal tract ; flagella two in number,
subequal, both vibratile, the one spirally coiled and anchoring the animal-
cule to submerged objects when at rest ; contractile vesicle usually at the
anterior extremity ; endoplast conspicuous ; increasing by longitudinal
fission. Inhabiting salt and fresh water.

By the earlier investigators it was left as a matter of considerable doubt whether
the members of this genus possessed a single flagellate organ only, or two of these
appendages ; Ehrenberg favouring the latter and Dujardin the former of these
alternatives. More recent investigation has established the accuracy of Ehrenberg's
anticipation. Diesing, premising that the animalcule described by these respective
authorities under the title of Chilomonas faratncedum included two distinct types,
has proposed to separate Dujardin's supposed monoflagellate variety under the title
of Plagiomastix, associating with it the doubtful Chilomonas obliqua of the same
writer and the Pleuromonas jaculans of Perty. Such a generic group, however, based
upon Dujardin's misinterpretation of the characters of the flagella, has no just claim
for recognition. Perty's Pleuromonas jaculans, on the other hand, is an entirely
distinct infusorial form. As now known, the representatives of the genus Chilomonas
correspond remarkably in general contour with those of Cryptomonas, previously
described, and are to be distinguished from them only by the absence of the lateral
pigment-bands which so conspicuously characterize that generic form, in common
with all the other members of the Chrysomonadidae.

Chilomonas paramseeium, Ehr. PL. XXIV. FIGS. SI^ND 52.

Body plastic, elongate-ovate, about two and a half times asS<^ig as
broad, widest anteriorly, tapering to a rounded point posteriorly, and
usually curved slightly towards the dorsal aspect ; cuticular surface smooth ;
endoplasm transparent, colourless, enclosing numerous large spheroidal cor-
puscles ; anterior border obliquely truncate, oral aperture situated in the
centre of this border ; the two flagella inserted at the apical extremity
immediately beneath the lip-like prominence, subequal in size, not so long
as the body ; pharyngeal tract narrow and elongate, continuous with the
central axis of the body through nearly half its length, finely striate longi-
tudinally ; contractile vesicle situated at a little distance from the margin
of the lip-like frontal prominence ; endoplast spherical, located at a
distance of one-third of the entire length of the body from the posterior
extremity. Length 1-1125" to 1-650". HAB. — Vegetable infusions.

O. Biitschli * regards this species as identical with both the Chilomonas gramilosa
and Zygoselmis nebulosa of Dujardin, and further proposes to unite with it the animal-
cule next described under the name of Chilomonas cylindrica. That the last-named form
is, however, essentially distinct is presently demonstrated, while Zygoselmis, as already
shown, belongs to a separate family group. The species now under consideration
occurs abundantly in vegetable infusions, and yields many points of interest. Treated
with acetic acid, Biitschli found that the animalcules threw out on every side ray-
like prolongations mingled with minute granular bodies whose nature would seem
most closely to approach the trichocysts of the higher Ciliata. He was however
unable to detect any trace of these structures in the living individuals. When isolated
on a glass slide for investigation the animalcules quickly lose their normal contour,
become more and more spherical, finally bursting and breaking up. Increase by

* 'Zeitschrift fur Wissenschaftliche Zoologie,' Bd. xxx., Jan. 1878.

GENUS CHILOMONAS. 425

longitudinal fission was frequently observed. The two flagella of this species, when
the animalcule is at rest, are described by Biitschli as being folded loosely across one
another, as represented at PI. XXIV. Fig. 51.

Quite recently (August 1879), the author has had an opportunity of examining
this animalcule, and while able to confirm Butschli's more general account of its
structure, has elicited certain data concerning the comportment and insertion of the
flagella that have necessitated a slight modification of the diagnosis previously pre-
pared. In no instance was it made clear that these organs were inserted otherwise
than close to one another, immediately beneath the lip-like prominence, while at the
same time the lower of the two, when the animalcule was at rest, was thrown into
a loose spiral coil in the same manner as the homologous appendage of the genus
Oxyrr/iis, and being used in a similar manner as an organ of attachment. A turn of
this coil, issuing from behind the profile of the animalcule, often presented the appear-
ance of a distinct and separately inserted flagellum, and it is probably upon such a
deceptive optical aspect that Biitschli has based his interpretation of the remote
insertion of the flagella in this species. In addition to the likeness to Oxyrrhis,
conveyed by the convolute disposition of the flagellum in question, the movements
of Chilomonas paramcedum in the water accord to a considerable extent with those of
the last-named type. These consist, in a similar way, of an intensely active condition
in which the animalcule rushes to and fro, though with the anterior end foremost,
at a speed too rapid almost for the eye to follow, while at the next moment it comes
as it were abruptly to anchor, with its body perfectly quiescent and one flagellum
thrown into a coil and adherent to the glass slide or covering glass, while the other
maintains a vibratory motion.

The figures of this species included in Stein's recently published volume * accord
substantially with those given by O. Biitschli, his interpretation of the insertion of the
flagella, however, being identical with that maintained by the present author.

Chilomonas cylindrica, Ehr. sp. PL. XXIV. FIG. 50.

Body moderately persistent in form, elongate, subcylindrical, straight,
about three and a half times as long as broad ; endoplasm yellowish-
brown, enclosing irregularly scattered granules; anterior border obliquely
emarginate ; the oral aperture excentral, continuous with a short, wide
reticulate pharyngeal tract, which extends backwards along the ventral
margin to about one-quarter of the entire length of the body ; the two
flagella inserted close to one another above the oral aperture ; contractile
vesicle situated immediately above the pharyngeal passage ; endoplast
spherical, located at a short distance from the posterior extremity. Length
of body 1-500", and less.

HAB. — Pond water, and amongst decaying vegetation.

This species would appear to be synonymous with the Cryptomonas cylindrica of
Ehrenberg and the Cryptomonas polymorpha, in part, of Perty, though, as already
intimated, Butschli has figured and described it as a variety only of Chilomonas para-
mczcium. Setting aside details of external contour, which are subject to variation, the
structural characteristics of the two are, however, essentially distinct. The position
of the oral aperture in this species is eccentric instead of central, the pharyngeal
tract follows the same eccentric course and is much shorter and wider. The
substance of the endoplasm of the two is likewise distinct, the symmetrically granular
pattern being replaced in the present form by a yellow coloured stroma described by
Butschli as consisting of two even parallel layers continuous throughout the body
and separated from one another by a clear linear interspace- this circumstance,

* 'Infusionsthiere,' Abth. iii. Heft i., 1878.

426 ORDER FLAGELLATA-EUSTOMATA.

indeed, seems almost to justify the transference of this specific type to the genus
Cryptomonas. The trichocyst-like structures are apparently confined entirely to
C.paramcEcium, and are probably associated with the symmetrically arranged granular
bodies just referred to. It has further to be remarked that the two do not occur
together, the present form being obtained mostly in ponds and standing water, and
the one previously described in artificial infusions. The sizes of the two animal-
cules are likewise too divergent to support the opinion of their identity.

Chilomonas amygdalum, S. K. PL. XXIV. FIG. 49.

Body elongate-ovate, almond-shaped, somewhat curved towards the
ventral aspect, from three to four times as long as broad ; flagella sub-
equal, exceeding the body in length ; endoplasm transparent, granular.
Length 1-2000". HAB. — Salt water.

This species was obtained abundantly by the author at St. Heliers, Jersey, in
November 1878, in the sea-water containing decaying sea-weed productive of Trinema
marina, previously described. Its movements when swimming are very active and
restless, mostly rotatory, the animalcules being further observed to chase and feed
voraciously, after the manner of Dinomonas, upon the vibrions and smaller monads
contained in the same water. When at rest it anchored itself by a spiral coil of the
posterior of the two flagella, as recorded of C.paramczcium. Multiplication by longi-
tudinal fission, similar to that which obtains in the last-named type, was frequently
witnessed.

GENUS II. OXYRRHIS, Dujardin.

Animalcules free-swimming, persistent in form, ovate or conical*
obliquely and unevenly emarginate or excavate anteriorly ; flagella two in
number, inserted close to each other within the frontal emargination, one
of them entirely vibratile, the other coiled spirally and used as an organ of
attachment during a state of quiescence, lashed to and fro and driving
the animalcule backwards through the water during natation ; oral aperture
situated in the frontal emargination close to the insertion of the flagellum ;
endoplasm transparent. Inhabiting sea water.

There can be but little doubt that the Glyphidium marinum of Fresenius * and
Cohnf is genetically if not specifically identical with the species previously introduced
by Dujardin under the title of Oxyrrhis marina, and which earlier conferred generic
title, in accordance with the laws of zoological nomenclature, must necessarily take
precedence of the later one. The affinities of this generic type, in consequence of
the hitherto imperfect knowledge of its structural details, have not as yet been so
much as indicated, but from what is now known of this and other Flagellata, its
relationship to Chilomonas, last described, is clearly evident. Two species belong-
ing to that genus, C. paranuzaum and C. amygdalum, have been ascertained by the
author to present a closely corresponding coiled arrangement of the inferior flagellum;
while in both, the smaller notch-like anterior oral emargination may be regarded as
identical with the larger and asymmetrical one of Oxyrrhis. A chief difficulty
hitherto pertaining to the correct interpretation of this animalcule relates to the
inability of previous writers, Dujardin excepted, to recognize in the smooth rounded
extremity, the posterior region, and in the obliquely emarginate one the anterior
one, the true import of these being entirely masked in consequence of the remark-

'Die Infusorien des Seewasseraquarium der Zoologische Garten, Frankfurt,' 1865.
t " Neue Infusorien in Seeaquarium," ' Zeitschrift fur Wissenschaftliche Zoologie,' Bd.

xvi., 1866.

GENUS OXYRRHIS. 427

able retrogressive motions of the species in its more active state. No one, neverthe-
less, would dream, on similar grounds, of correlating with the tail end of a cuttle-
fish or lobster the functions of a cephalic region, simply because that extremity is
directed foremost during natation.

In connection with the retrogressive motions of Oxyrrhis, it is worthy of remark
that it is the only free-swimming infusorial type, at present known, in which a flagellate
appendage serves, as in that of a spermatozoon or a Bacterium, the purpose of
propelling in place of drawing the body through the water. Professor E. Ray
Lankester (see Family ANISONEMID^E) has proposed to confer upon such an organ
of propulsion the distinctive title of a " pulsellum."

Oxyrrhis marina, Duj. PL. XXIV. FIGS. 53-61.

Body conical or helmet-shaped, subcylindrical, rounded posteriorly, the
anterior margin obliquely and unsymmetrically notched or emarginate, the
notch being produced further backwards on the left side, the superior angle
of the same region more or less conically prolonged ; flagella long and
slender, issuing from the posterior extremity of the oblique frontal emargi-
nation ; oral aperture elastic, capable of incepting food-particles of con-
siderable size ; endoplasm transparent, enclosing food-globules and vacuolar
spaces, its external surface smooth ; contractile vesicle anteriorly located.

Length of body 1-900" to 1-500". HAB. — Salt water.

The or'ginal description of this species, as given by Dujardin* and herewith
reproduced in abstract, appears at first sight scarcely reconcilable with the type
indicated in the foregoing diagnosis.

" Body colourless, subcylindrical, rounded posteriorly, the anterior border
emarginate, produced superiorly into a long, conical point, external surface
rugose ; flagella three or four in number, produced laterally from the bottom
of the anterior emargination. Length 1-500". HAB. — Saltwater?

The species, as above described, was obtained by Dujardin in salt water from the
Mediterranean containing Ulva, which had been kept standing fcjr many months.
The considerable number of flagellate appendages accredited to the type by its
discoverer, and as delineated in his original illustration of the type, reproduced at
PI. XXIV. Fig. 53, constitutes a feature of distinction which would appear to establish
the claim of the present form to a separate specific or even generic title. It is
evident, however, that Dujardin's presumed three or four flagella represent only the
optical aspect of the two appendages now shown to exist, when thrown into their
characteristic convolutions, as presently described. The irregular rugosity of the
external surface of the body, again attested to in Dujardin's diagnosis, and as
evidenced by his accompanying illustrations, coincides with the appearance merely
of the miscellaneous mass of food-material usually accumulated within it. A more
detailed account of the results of the author's investigation of this flagellate form, as
examined in abundance at St. Heliers, Jersey, both in water brought direct from
the sea and in long-standing hay infusions compounded with the same medium, may
now be proceeded with.

It was not until examples had been killed with the aid of osmic acid and sub-
mitted to a magnification of 800 diameters, that the precise number and character
of the flagellate appendages, as here recorded, were accurately determined. Under
these auspices it was shown that these were two in number, similar in character,

* ' Histoire des Zoophytes Infusoires,' Paris, 1841.

428 ORDER FLAGELLATA-EUSTOMATA.

slender throughout, and equal to from one and a half to twice the length of the
body in their completely extended state, which they usually assumed under the
influence of this reagent. Aided by the experience of a post mortem examination,
it was not so difficult to recognize their character and relative position in the living
examples. In the more easily examined stationary condition one of these flagella,
which may be termed the superior one, is thrown backwards in an arcuate fashion
over the dorsal border. The second or inferior flagellum meanwhile remains coiled
in a spiral form close against the entrance to the oral aperture, and with its distal
extremity only protruding and attached to the surface of the slide or cover-glass.
Vibratory action, serving the purpose of entrapping food, belongs apparently, chiefly
if not exclusively, to the first-named appendage, which usually during the sedentary
condition exhibits rapid vibratile movements throughout its distal region. These
vibratory motions, combined with the convolute disposition assumed by both flagella,
frequently impart to the animalcule an appearance of possessing several shorter
filaments, and thus invalidate the interpretation originally connected with the
number of these appendages as given by Dujardin. When swimming actively from
one spot to another, or rushing about as it is accustomed to do when disturbed, the
animalcule is driven backwards through the water by means of the flagellum
that remains comparatively inactive and affixed to the ground during the stationary
condition, but which is now stretched out anteriorly to its full extent and
vigorously lashed from side to side, causing the body to rotate upon its axis alter-
nately from right to left and left to right as motion in a backward direction is
effected. The primary or vibratile flagellum during natation appears to be coiled still
more closely and completely within the pre-oral excavation. Particles of carmine
were eagerly incepted by the specimens under examination, their favourite food being
however the various smaller monads and algae spores contained abundantly in the
same infusion, and which were brought within reach during the sedentary condition
of the animalcule by the rapid vibratory motions of the primary flagellum. These,
though nearly equal in diameter to their own bodies, were swallowed whole, the
loop-like convolutions of the basal portion of the inferior flagellum apparently
aiding in pushing these food-substances into the oral cavity. Various vacuolar
spaces and more solid spherical bodies were frequently observed within the other-
wise clear endoplastic substance, one of the former towards the anterior extremity
and immediately above the oral excavation representing apparently the contractile
vesicle, its pulsatory properties not however being very vigorously manifested.
During life, and for a considerable time after death by a natural process, the external
cuticle of this animalcule appears to possess a considerable amount of rigidity, being
often found, indeed, in the latter case as a mere shell devoid of all trace of the
endoplasm and flagellate appendages, and exhibiting under such conditions, as
shown at PL XXIV. Figs. 58 and 59, a sharp and clear outline of its peculiar unsym-
metrically angular form. Under the treatment of dilute osmic acid the entire body
however rapidly disintegrates, first assuming a rounded or spherical outline and then,
as it were, melting gradually away. Increase by transverse fission, Fig. 57, is the
only form of reproduction as yet positively ascertained to occur.

As already intimated, the Glyphidium marinum of Fresenius is beyond doubt
identical with the present species. The examples referred to this type, figured
by Cohn, also entirely harmonize with the form here introduced, excepting that the
body is slightly shorter in proportion to the width and more evenly rounded pos-
teriorly. The character of the flagella, while more accurately appreciated by
Fresenius, is not fully elicited by either of these authorities ; in some instances two
flagella are figured, but in others a single one only is represented. The oral aperture
is further described and figured by Cohn (see PL XXIV. Fig. 29) as apparently
supplemented by a projecting, undulating, lip-like membrane, such structure being
here readily identified with the optical aspect only of the loop-like convolution of the
inferior flagellum.

ORDER FLAGELLATA-EUSTOMATA. 429

Fam. VIII. ANTSONEMID.E3, S. K.

Animalcules ovate or elongate, free-swimming or temporarily adherent ;
flagella two in number, the anterior one or "tractellum" locomotive and
vibratile, the posterior one or " gubernaculum " used for steering or trailed
inactively in the rear during natation, adherent or anchorate by its pos-
terior extremity in the sedentary condition ; oral aperture distinct, mostly
associated with a well-defined tubular pharynx ; endoplasm transparent,
granular. Inhabiting salt and fresh water.

The representatives of this well-defined family group exhibit a type of structure
and habits of life strictly analogous to those already recounted of the Heteromitidag,
the one highly important differential feature being that a well-defined and often
complex oral apparatus takes the place of the indefinite and dispersed inceptive area
characteristic of that family. This oral apparatus in certain members of the Aniso-
nemidae is so complex as to approach the formula typical of Nassula and various
other Holotrichous and Hypotrichous Ciliata, and there can be little doubt that
these animalcules must be regarded as occupying the foremost position among the
Stomatode Flagellata. A further development of the Anisonematous structural type
towards the Ciliate division of the Infusoria is afforded by Professor Clark's genus
Heteromastix, hereafter described, and in which an adoral fringe of cilia is added to
the two flagella.

The peculiar modification of the Flagellate appendages of the Anisonemidae, shared
likewise by the Pantostomatous Heteromitidae, see p. 290, and the Cilio-flagellate
type Heteromastix just quoted, invites more extended attention. The desirability of
introducing a suitable term for the distinction of the posterior or trailing flagellum
used for the purpose of temporarily anchoring the animalcule to submerged
objects, or rudder- wise for the guidance of its course during natation in these
various types, was first recognized by Professor H. James-Clark,* who proposed to
distinguish such appendage by the appropriate title of a " gubernaculum." Irrespec-
tive of the distinction just alluded to, it has been more recently pointed out by
Professor E. Ray Lankester \ that even among uniflagellate organisms the single
flagellum may exercise two totally distinct functions, and merits in each case a
separate appellation. Thus, among all ordinary Flagellata such as Monas, Euglena,
and Astasia, the vibratory motion of the single flagellum draws the animalcule
after it through the water. The appendage possessing such a tractive function
Professor Lankester has proposed to distinguish by the title of a " tractellum." In
other flagellate organisms, as illustrated most familiarly by ordinary spermatozoa
and Bacteria, the filamentous appendage or appendages fulfils an entirely opposite
mission, its motions propelling the body in front of it through the liquid medium.
Where it thus acts as an organ of propulsion the authority last quoted confers upon
it the name of a " pulsellum." Among the free-swimming monoflagellate Infusoria
as at present known, where the locomotive appendage without exception fulfils
during natation the role of a tractellum, its recognition by such title in contra-
distinction to a propelling organ or pulsellum is uncalled for. With the biflagellate
types, however, exhibiting a differentiation of their two appendages corresponding
with that presented by the group now under consideration, Professor Lankester's
term as applied to the anterior locomotive flagellum, and as distinctive of the trailing
flagellum or gubernaculum of Professor Clark, becomes highly useful, and is here
unhesitatingly adopted.

An exceptional instance among the Dimastigous Flagellata, in which one
appendage acts as a pulsellum or organ of propulsion, is afforded by • Oxyrrhis
marina, described at pp. 427 and 428. Artificially detached zooids of the

* 'Memoirs of the Boston Society of Natural History,' 1878.
t Biological Lectures, University College, London, 1876.

430 ORDER FLAGELLATA-EUSTOMATA.

normally sedentary collared monads Codosiga, Salpingceca, &c., have likewise been
observed by the author to exhibit retrogressive natatory movements, a circumstance
which might indeed be consistently predicated in connection with the motion of the
flagellum and the direction of the current it engenders, as described at length at
P- 327-

GENUS I. HETERONEMA, Dujardin.

Animalcules free-swimming, ovate or elongate, highly elastic and
metabolic ; flagella two in number, produced from the anterior extremity,
the one vibratile, the other trailing and adherent ; oral aperture distinct,
situated close to the base of the flagella, usually followed by a well-defined
pharyngeal tract ; endoplasm transparent, granular. Inhabiting salt and
fresh water.

As originally instituted by Dujardin, the genus Heteronema included but one
imperfectly denned specific type, H. marina, which has been usually regarded as
exhibiting too close a resemblance to Anisonema or Heteronrita to merit independent
recognition. Two other well-defined specific forms are added to this genus by
Stein in his recently published volume which, while conforming with Dujardin's
original definition, manifest their distinctness from Anisonema, Heteromita, and other
superficially corresponding genera in their extreme mutability of form, or in other
words highly metabolic character.

Heteronema acus, Ehr. sp. PL. XXIV. FIGS. 14 AND 15.

Body in extension attenuate fusiform, widest a little behind the centre,
tapering towards and sharply pointed at each extremity, eight or ten times
as long as broad ; flagella slender, unequal, the anterior one, or tractellum,
extended rigidly in advance, equalling the body in length, the trailing
one, or gubernaculum, about half that length ; contractile vesicle situated
close to the anterior extremity ; a large, oval, endoplast-like structure in the
centre of the widest portion of the body ; endoplasm finely granulate.
Length of body 1-600" to 1-300".

HAB. — Fresh water : Europe and Bombay.

The form as defined in the foregoing diagnosis and accompanying illustra-
tions, is identified by Stein with the Astasia acus of Ehrenberg, and referred
to its present rightful position. An animalcule presenting a precisely similar
external contour and metabolic properties, is likewise figured as " an Astasia
with two filaments " in one of the note-books kindly placed at the author's disposal
by Mr. H. J. Carter, such animalcule having been encountered by that authority at
Bombay in the year 1856. In one of the delineations made by Mr. Carter its
body is so contracted upon itself that the diameter considerably exceeds the
total length, the two anterior and posterior extremities projecting as mere points
from the flattened and almost discoidal central region of the body. A similar
turbinate or rotulate shape is commonly exhibited among the multitude of protean
configurations presented by Euglena and Astasia, or by the isomorphic Cilio-
Flagellate genus Heteromastix.

Heteronema globuliferum, Ehr. sp. PL. XXIV. FIGS. 16 AND 17.

Body highly metabolic and changeable in shape, mostly elongate-ovate
or pyriform when extended, with a truncate or rounded posterior, and a
narrower pointed anterior extremity, two or three times as long as broad ;

GENUS DIPLOMASTIX. 43 [

vibratile flagellum, or tractellum, about twice the length of the body in full
extension, the trailing one, or gubernaculum, shorter and more slender ; oral
aperture distinct, continued as a long, tubular pharynx ; endoplasm trans-
parent, granular ; cuticular surface sometimes faintly striate obliquely ;
contractile vesicle situated close to the termination of the pharyngeal tube ;
endoplast oval, subcentral. Length 1-650". HAB. — Fresh water.

The species associated by Stein with the above title is identified by that
authority with the Trachelius globulifer of Ehrenberg and the Peranema globulosa of
Dujardin. A form, however, more precisely according with the last-named type
as examined by the author has been demonstrated, as recorded at page 225, to be a
developmental phase only of the Heliozoon, Actinophrys sol.

Heteronema marina, Duj.

Body oblong, irregularly inflated posteriorly, narrower at the anterior
extremity, about twice as long as broad ; cuticular surface obliquely striate ;
vibratile flagellum slender, equalling the body in length, trailing one much
thicker and longer. Length 1-420". HAB. — Salt water.

This species was obtained by Dujardin from sea-water at Cette that had been
kept standing for a fortnight.

Heteronema pusillum, Perty sp.

Body transparent, very elastic and changeable in shape, subglobose, ovate,
or elongate-pyriform at will, mostly the latter ; the two flagella developed
froni the apex of the more usually pointed anterior extremity, very long
and slender, the anterior one two or three times the length of the body, the
trailing one rather shorter. Length 1-840" to 1-768". Movements straight
forward, oscillating. HAB. — Fresh water.

This species, described by Perty under the title of Dinema pusillum, is referred
with some doubt to the present genus, being not improbably a Heteromita.

GENUS II. DIPLOMASTIX, S.K.

Animalcules ovate or elongate, free-swimming or temporarily adherent,
plastic and variable in form, but not metabolic ; flagella two in number,
one vibratile, the other trailing and adherent ; oral aperture well defined,
situated at the base of the flagella ; endoplasm colourless. Inhabiting
salt and fresh water.

This new generic title is necessarily instituted for the distinction of those
Anisonematous forms holding an intermediate position between- A nisonema and
Heteronema. This is manifested by their possession of an ectoplasmic layer, which
while sufficiently soft and plastic as to permit the animalcules to assume slowly
and under special conditions diverse individual contours, never exhibits that high
degree of elasticity and contractility productive of rapid and protean changes of
contour as met with in the last-named generic type. On the other hand, it
is never so firm and indurated as obtains in Anisonema. Two of the species here
described have been recently referred by Stein to the genus Bodo of Ehrenberg,
but evidently possess nothing in common with the representatives of that generic
group as recognized in this volume or associated with that title by most recent
authorities.

432 ORDER FLAGELLATA-EUSTOMATA.

Diplomastix caudata, Duj. sp. PL. XXIV. FIGS. i-io.

Body variable in form, gibbously ovate, sometimes rounded, but more
usually tapering and bent obliquely upwards posteriorly, the anterior
extremity sharply pointed or rostrate, curved towards the ventral aspect ;
flagella slender, subequal, exceeding the body in length, inserted close
to each other at the apex of the rostrate process; contractile vesicle
located near the anterior extremity ; endoplast subcentral ; endoplasm
transparent, finely granular. Length 1-1500" to 1-500".

HAB. — Pond water and organic infusions in both salt and fresh water.

This species is figured without an accompanying description, in Stein's recent
volume,* under the title of Bodo caudata Stein, and with the associated synonym
of Amphimonas caudata of Dujardin, a type again which is regarded by this last-
named authority as probably identical with the Bodo saltans of Ehrenberg. The
present author agrees with Stein in the recognition of this Ehrenbergian species
as a totally distinct form, and has arrived at the conclusion that there are
no less than three specific types closely resembling in general aspect the one
now under consideration, but which exhibit under more minute examination easily
apprehended distinctive features. All of these occur abundantly in hay and other
vegetable infusions, and have recently formed the subject of special investigation.
The present type, JD. caudata, may be at once recognized by its larger size and
movements in the water, which consist chiefly of steady progress forwards in a
straight line for a more or less considerable distance, the rostrum directed down-
wards and rooting as it were among the organic debris, while the body sways to
and fro with a rapid vacillating or hitching action, such mode of locomotion is quite
distinct from the leaping or constantly reversed or tacking motion of the two smaller
types next described under the titles of Diplomastix affinis and D. saltans. Com-
pared with this last-named form, the contractile vesicle is also found to occupy an
exactly inverse position.

The more conspicuous individual diversities of contour exhibited by the
present species are amply illustrated in the accompanying figures ; it is at the same
time worthy of remark that the author has found the shorter and posteriorly rounded
shape, PI. XXII. Fig. i, connected always with the earliest appearance of this
form, the more or less attenuate caudal prolongation, as shown at Figs. 2 and 3,
not making its appearance until the third or fourth day after the advent of the
animalcule in any quantity upon the field. This attenuate extension of the posterior
extremity would seem in the present type to take the place of the more irregular
pseudopodic processes, emitted mostly from the same region, in many Pantosto-
matous forms antecedent to the act of coalescence or encystment. Both of these
phenomena have been abundantly observed, as also the breaking up of the encysted
zooids into four or eight oval macrospores which shortly develop flagella and assume
the form and characteristic movements of their parents. It was also found that the
macrospores so produced were plentifully developed on the dried hay when first
placed to macerate (see PI. XL Fig. 2 <:), lying scattered in little heaps, without
any common investing envelope, among the ridges and sinuosities of the surface
of the separate blades or stalks. The motile zooids derived from these spores
did not make their appearance until the fourth day of maceration, and remained
then for upwards of a month as one of the most abundantly represented types
in the infusion, sometimes crowding the field of view to the exclusion of all other
forms.

By Stein this animalcule is figured as possessing a distinct tubular oral aperture
situated immediately beneath the recurved rostrum. Athough the inception of
food was observed at this point, the author has not yet succeeded in detecting any

1 Infusionsthiere," Abth. iii., 1878.

GENUS DIPLOMASTIX. 433

such permanently visible aperture. According to this last-named authority this type
would seem also to possess the same predatory habits as Cienkowski's monoflagellate
genus Colpodella, he in certain of his figures representing examples extracting and
swallowing the nutrient protoplasm of a species of Chlamydomonas, while in another
instance as many as eight animalcules have fastened to and are feasting, like so many
rats, upon the body of a large Colpoda cucullulus. The example figured by Stein
as illustrating one zooid preying in a similar manner upon another individual
of its own species, is evidently a misinterpretation of the first stage of coalescence
or genetic union, in which, as frequently observed by the author, see PL XXIV.
Fig. 4, one animalcule fixes itself by its rostrum to the dorsal region of its selected
mate, the substance of the two becoming gradually amalgamated. Although
obtained in hay-infusions simultaneously prepared from both salt and fresh water,
it was found by the author to develop far more abundantly in the latter medium.

Diplomastix caudata may be said to be one of the most ubiquitous repre-
sentatives of the Flagellate series, it putting in its appearance wherever decaying
organic matter, animal or vegetable, may be found.

Diplomastix affinis, S. K. PL. XXIV. FIG. 13.

Body gibbously ovate, the posterior extremity rounded, or pointed and
bent towards the ventral aspect, the anterior end rostrate and recurved in
the same direction ; flagella of uniform size, slender, exceeding the body in
length ; contractile vesicle single, posteriorly situated ; endoplast spherical,
subcentral. Length 1-1500" to 1-1200".

HAB. — Hay-infusions in salt and fresh water.

The smaller size, persistent ventral curvature of the posterior extremity, and
location of the contractile vesicle, serve to distinguish this species from the
preceding, to which may be added the still more easily recognized and distinct
mode of locomotion. In D. caudata this, as already described, consists chiefly
of progress through the water in a straight line for a considerable distance, accom-
panied by a peculiar vacillating or hitching gait ; a similar vacillating action is
noticeable in the present type, but the animalcule never maintains its straight course
for a long distance, it bringing itself up suddenly and with a jerking motion every
few seconds through the adhesion of the trailing flagellum or gubernaculum, and
then starting off, like a ship tacking, in a different direction. Frequently also it
remains anchored by its gubernaculum, and fishes steadily with its extended anterior
flagellum or tractellum after the manner of an ordinary Hcteromita or Anisonema,
This sedentary phase has not so far been observed in D. caudata. Develop-
mental phenomena similar to those recorded of the last-named species were observed
of the present type, and it was further found that it multiplied with equal rapidity
in hay-infusions in both fresh and salt water.

Diplomastix saltans, Ehr. sp. PL. XXIV. FIGS, n AND 12.

Body irregularly ovate, rounded posteriorly, with a convex dorsal and
concave ventral surface, the anterior extremity pointed, more or less curved,
often presenting a notched or bilabiate aspect ; the trailing appendage, or
gubernaculum, longer and stouter than the vibratile flagellum, or tractellum,
nearly twice the length of the body, the two inserted at some little distance
from the anterior extremity ; contractile vesicles two in number, anteriorly
situated ; endoplast subcentral. Length 1-1600" to 1-900".

HAB. — Vegetable infusions.

This species is distinguished from the preceding by the notched or bilabiate
contour of the anterior extremity and by the more posterior insertion of the flagella,

2 F

434 ORDER FLAGELLATA-EUSTOMATA.

Its habits are mostly sedentary, the animalcules remaining attached or anchored
in social clusters by the temporary adhesion of their gubernacula, and briskly
springing to and fro to the full length of their "tether" in various directions. By
Ehrenberg this species was first described under the title of Bodo saltans, the
same name accompanying the illustrations which alone are given in Stein's recently
issued work.

GENUS III. ANISONEMA, Dujardin.

Animalcules ovate, free-swimming or temporarily attached, persistent
in form, having a more or less indurated cuticular investment ; oral aper-
ture distinct, usually followed by a well-defined pharyngeal tract ; anal
aperture postero-terminal ; flagellate appendages two in number, of diverse
function, originating close to one another on the ventral surface, the ante-
rior filament, or tractellum, extended in advance, vibratile, subserving
the purposes of locomotion and the capture of food, the posterior flagel-
lum, or gubernaculum, trailing in the rear, distally adherent, non-vibratile,
utilized during natation as a rudder and also for temporarily attaching the
animalcule, cable-wise, to foreign objects ; contractile vesicles and endo-
plast conspicuously developed; multiplying by longitudinal fission, and
by the production of internal germ-masses. Inhabiting fresh and salt
water, and infusions.

By many recent writers it has been proposed to merge both Heteromita and
Heteronema in the present genus, upon the supposition that the softer consistence of
the external envelope and contained body-substance in these types represents merely
a slightly more marked difference of degree, insufficient for the purposes of generic
diagnosis. As demonstrated, however, on a previous page, Heteromita is a perfectly
distinct, though isomorphic form, of much lower organization, having no distinct oral
aperture, and belonging necessarily to the same Pantostomatous primary group as
Monas, Spumella, and Anthophysa. Heteronema, on the other hand, manifests its dis-
tinctness from the present genus by the extreme plasticity of its cuticular invest-
ment and extraordinary metabolic properties. Evidence supporting the opinion
that the members of the genus Anisonema possessed a distinct oral aperture was
first adduced by Professor H. James-Clark * who, while unable to demonstrate the
exact position of this aperture in A. grande, distinctly saw food -particles pass
in at the anterior extremity. This authority likewise suspected the existence of an
anal aperture at the posterior end of the body, such anticipation being entirely
confirmed by the investigations of the present author, which are again further
corroborated by Stein. The determination of the precise position and structure
of the oral aperture, with its accompanying well-defined pharyngeal tract, has been
recently accomplished by both Stein and O. Butschli.

Anisonema grande, Ehr. sp. PL. XXIV. FIGS. 26-30.

Body ovate or oblong, depressed, the dorsal surface slightly convex, the
ventral one flat, or more or less concave, rounded posteriorly, narrower and
pointed anteriorly, about twice as long as broad ; cuticular investment
smooth and indurated ; flagella originating at a little distance from one
another close to the anterior extremity, the anterior vibratile flagellum, or
tractellum, slender, scarcely equalling the body in length, the trailing
flagellum, or gubernaculum, three or four times the length of the other,
* 'Memoirs Boston Soc. Nat. Hist.,' 1868.

GENUS ANISONEMA. 435

usually considerably thicker towards the base ; oral aperture adjacent to
the origin of the posterior flagellum, communicating with a short, tubular
pharyngeal tract ; contractile vesicle single, situated behind or a little to
the left of the oral aperture ; endoplast spherical or ovate, located on the
right-hand side towards the posterior extremity. Length 1-1250" to 1-900".
HAB. — Pond water, amongst Conferva.

This typical species of the genus, more generally known by Dujardin's name of
Anisonema acinus, and recently figured and described by Professor Clark as Anisonema
concavum, is identified by Stein with the Bodo grandis of Ehrenberg, whose primarily
conferred specific title necessarily takes the precedence of all others. The motions
of this animalcule in the water, typifying also those of the genus generally, are very
characteristic, but at the same time closely resemble those of the ordinary members
of the genus Heteromita previously described. Progress through the water consists
chiefly of a smooth, gliding motion in a straight line, the shorter anterior flagellum,
or tractellum, being projected and vibrating in advance, while the long posterior one,
or gubernaculum, as it is designated by Professor Clark, trails cable-wise, like a
boat dragging its anchor, in the rear. This even locomotion is occasionally varied
by a laborious hitching gait, accompanied by a swinging of the animalcule from
side to side, while now and then the body is brought up sharply and propelled in
an opposite direction, through the adhesion to the ground, and simultaneous
loosely spiral contraction, of the trailing gubernaculum. The locality proving
auspicious and the food-supply plentiful, the little animalcule often fixes itself by
the distal extremity of the last-named organ and rides gracefully at anchor, fishing
vigorously with its extended tractellum, detaching itself after a short interval, and
progressing as before in search of a new pasture-ground.

The aspect of this species as seen in profile is subject to considerable variation
according to the point of view taken, and in consequence of the asymmetrical
development of the ventral excavation. Its most characteristic concavo-convex or
meniscoid contour is best illustrated when seen end-on from behind, as represented
at PI. XXIV. Fig. 26. The ventral excavation, so conspicuous under these con-
ditions, is shown to be abruptly and obliquely deepened on its left-hand border,
which thus appears to be recurved over it, while it narrows off gradually on the
right-hand one. It is this character of the ventral furrow that imparts to the
animalcule a meniscoid contour as seen only from the right-hand side, a view from
the opposite or left-hand one yielding the simpler plano-convex shape that has been
more frequently ascribed to it. As shown by Biitschli, individuals vary somewhat
in their dorsal contour, the ovate or " pip-shaped " outline being sometimes
replaced by a shorter, broader, and almost elliptical form. Increase by longitudinal
fission has been observed in this species by various investigators, the two flagella
destined for the new zooid often being developed at the anterior extremity of
the primary individuals prior to the commencement of the dividing process. At
this stage, PL XXIV. Fig. 27, the animalcule has the appearance of possessing
two or three vibratile anterior flagella, and a single or double trailing one. De
Fromentel,* supposing it to represent a new type, has figured and described this
transitional condition under the title of Diplomita insignis, while he confers that of
Heteromita crassa upon the ordinary biflagellate condition of the same animalcule, f
Stein, in his recently published volume, \ represents the anteriorly located con-
tractile vesicle as having frequently a rosette-like aspect through the association of
smaller lateral lacunae, and also the development, within the central endoplasm, of

* ' Etudes sur les Microzoaires,' Paris, 1876.

t This earlier though fruitless employment of the term Diplomita by De Fromentel had escaped
the author's attention when proposing the same title for the biflagellate animalcule described at
p. 289. It being desirable to substitute a new generic name for this altogether distinct form, that of
Difloselmis is herewith given in exchange.

J ' Infusionsthiere,' Abth. iii., 1878.

2 F 2

436 ORDER FLAGELLATA-EUSTOMATA.

two large ovate germ-masses, modified apparently from a single pre-existing en lo-
plast. Illustrations of these special features as observed by Stein are reproduced
at Figs. 28 and 29 of the accompanying plate. This more complex modification of
the contractile vesicle, while of rare occurrence among the Flagellata, will be found
to recur repeatedly with the more highly differentiated Ciliata described in the
succeeding volume.

Anisonema truncatum, Stein. PL. XXIV. FIGS. 24 AND 25.

Body elongate, obconical or subtriangular, widest and truncate an-
teriorly, tapering gradually towards the posterior extremity, rather over
twice as long as broad ; trailing flagellum about twice the length of the
body, the vibratile one slender, not one-half as long as the preceding ; paren-
chyma coarsely granular ; contractile vesicle situated close to the termina-
tion of the short, tubular pharynx ; endoplast elongate ovate, located
posteriorly near the left lateral border. Length 1-600".

HAB. — Fresh water.

Anisonema ludibundum, S. K. PL. XXIV. FIGS. 35 AND 36.

Body elliptical, very slightly depressed, somewhat narrower, but rounded
at the anterior extremity, cuticular surface smooth ; parenchyma trans-
parent, granulate ; flagella equally slender, about one and a half times the
length of the body, inserted at some little distance from the anterior
extremity ; contractile vesicles two in number, located side by side above
the point of insertion of the flagella ; anal aperture distinct, postero-
terminal. Length 1-2500". HAB. — Vegetable infusions, gregarious.

This species was obtained by the author in some abundance from a flower-vase
in which the plants had been left until their stems were in an advanced state of
decomposition. Viewed in profile the body is seen to be much thicker than either
of the precedifig species, from which it also differs in its considerably smaller size,
in the possession of two conspicuous contractile vesicles, and in the more rear-
ward insertion of the flagella. A number of animalcules were generally found in
close proximity, attached by their gubernacula and vigorously fishing with their
extended anterior flagella or tractella. Ever and anon a single individual would, in
the course of its oscillations, come in contact with a neighbour, causing it to
rebound against its fellows, stimulating those also into abnormal action ; the whole
colony thus aroused would whirl about for some seconds, apparently in sport with each
other, and in a manner comparable to flies playing, or to that recorded further on
of the Ciliate type Cydidium glaucum. Effete granular matter was distinctly
observed passing out at the posterior extremity of one of the zooids, as shown
at PL XXIV. Fig. 35.

Anisonema intermedium, S. K. PL. XXIV. FIGS. 37-39.

Body oval, depressed, slightly narrower anteriorly, surface smooth ; in
lateral view thicker posteriorly, and gradually narrowing towards the
anterior end ; the ventral surface flat or slightly concave ; flagella inserted
close to the anterior extremity, equally slender, about twice the length of
the body. Length 1-2000". HAB. — Sea water.

The contour of this animalcule as seen in profile, together with its minute size
and salt-water habitat, appears to justify its recognition as a distinct species. A

GENUS ENTOSIPHON. 437

refringent ovate body, apparently the endoplast, was detected in one example
close to the centre of the left-hand border, and a clear vacuolar space near the
posterior extremity, which may have been the contractile vesicle, and which would
in that case be situated in a position precisely opposite to that of the previously
described species. Mingled with the ordinary forms, smaller flattened ovate
zooids, attached by the pointed anterior end by a long anchoring flagellum, and
having as yet no second vibratile one, were observed ; these, as delineated at
PI. XXIV. Fig. 38, apparently represented an earlier and larval condition of the
adult individuals, though their growth to the same has yet to be determined. As
shown in the account given of Heteromita rostrata and H. uncinata, a similar mono-
flagellate larval condition obtains also in that isomorphic genus.

Anisonema (?) griseolum, Perty sp.

Body elongate-ovoid, twice as long as broad, narrower posteriorly ;
flagella equal, not much exceeding the body in length ; endoplasra
granular, greyish brown. Length 1-250".

HAB. — Pond water ; movements slow, mostly rotatory.

This species, described and figured by Perty under the title of Dinema griseolum,
and referred by Diesing to the genus Heteronema, does not appear to have been
met with by any recent investigator. Its dimensions exceed those of any other
representative of the present genus yet recorded, the rotatory motion attested to by
Perty is also abnormal.

Doubtful Species.

De Fromentel * has bestowed new names on several forms included by him in
the genus Heteromita, held by him, in common with many other writers, to be the
equivalent of the genera Heteromita, Heteronema, and Anisonema of Dujardin.
Certain of these possibly belong to Anisonema, but are too vaguely figured and
described in most instances for reidentification. His Heteromita (Anisonema ?) gibbosa,
characterized by its oval dorsal contour and gibbous enlargement of the posterior
extremity as seen in profile, with a thicker trailing flagellum, equalling twice the
length of the body, is the only one out of these it is desirable to retain. No dimen-
sions or details as to habitat are given with his description, though if drawn to the
same scale as most of the other figures in his plate, its length would be about the
i-ioooth part of an inch. The Heteromita crass a of the same writer is beyond
doubt identical with the Anisonema acinus of Dujardin.

The magnification of 400 diameters only, employed by De Fromentel for the
delineation and description of the Flagellate forms treated of in his book, is
altogether inadequate for their successful or even serious investigation.

GENUS IV. ENTOSIPHON, Stein.

Animalcules free-swimming, persistent in shape, more or less ovate,
usually compressed, the cuticular surface indurated ; flagella two in number,
the one trailing and the other vibratile, inserted close to each other near
the oral fossa ; oral aperture terminal, followed by a distinct tubular
pharynx, the walls of which are indurated and capable of protrusion in,
the form of a horny tube beyond the anterior margin ; endoplasm trans-
parent, granular ; contractile vesicle and endoplast conspicuous. Inhabiting
fresh water.

This genus is founded by Stein \ on the Anisonema sulcata of Dujardin ; the.
essential feature distinguishing it from the ordinary members of the genus Anisonema

* ' Etudes sur les Microzoaires,' 1876, t 'Infusionsthiere,' Abth. iii., 1878.

438 ORDER FLAGELLATA-EUSTOMATA.

being the possession of a separately protrusible pharyngeal tube, apparently of a
corneous nature, and comparable to that met with in Prorodon, Nassula, Chilodon,
and many other Ciliata.

Entosiphon sulcatus, Duj. sp. PL. XXIV. FIGS. 31-34.

Body oval, depressed, slightly narrower anteriorly, the frontal border
obliquely notched on the left-hand side ; the dorsal and ventral surfaces
usually traversed by four or five longitudinal furrows ; flagella equally
slender, inserted at a little distance from each other, slightly to the left and
close to the anterior notch, the posterior appendage or gubernaculum two
or three times the length of the body, the anterior vibratile one usually
shorter ; pharynx tubular, extending in a median line from the oral aperture
at the anterior extremity through nearly three-quarters of the entire length
of the body, independently exsertile ; contractile vesicle single, situated a
little behind the insertion of the flagella and to the left of the pharyngeal
tube ; endoplast spherical, located posteriorly towards the centre of the
left-hand border. Length of body 1-1250". HAB. — Pond water.

The cuticular sulci, obliquely notched contour of the anterior border, and
enormous development of the pharyngeal tube, together with its protrusible properties,
serve to distinguish this type from the various species of Anisonema with which it
was originally included by Dujardin. Longitudinal fission, commencing at the
anterior extremity and separating the body into two equal moieties, has been observed
in this species by both Stein and Biitschli, the animalcule, preparatory to such
process, developing two additional flagella. The young zooids, according to Stein,
are perfectly smooth and pointed at each extremity. The contractile vesicle is
represented by this last authority as often exhibiting a rosette shape similar to
that of Anisonema grandis, while a large ovate germ-mass may in like manner be
developed from the pre-existing simple spheroidal endoplast. After the death of
the animalcule the indurated cuticle, with the enclosed horny pharyngeal tube,
resists decay for a considerable interval, presenting under such conditions the aspect
delineated at PL XXIV. Fig. 34.

Fam. IX. SPHENOMONADID-ffi, S. K.

Animalcules free-swimming, persistent in shape, cuticular surface
indurated ; flagella two in number, one long and one short, both vibratile
and extended anteriorly ; oral aperture succeeded by a distinct tubular
pharynx ; endoplasm colourless, granular ; endoplast and contractile vesicle
conspicuous.

GENUS I. SPHENOMONAS, Stein.

Animalcules free-swimming, persistent in shape, subfusiform, angular
or facetted ; flagella terminal, two in number, one long and the other short,
both extended and vibratile ; oral aperture situated at the base of the
flagella, followed by a distinct tubular pharynx, the distal end of which
usually communicates with the contractile vesicle ; endoplasm transparent,
granular.

This generic group, as here defined, is made to include the genus Tropidocyphus
of Stein, in addition to that of Sphenomonas as constituted by that authority ; the

ORDER CILIO-FLAGELLATA. 439

distinction between the two specific forms only as yet relegated to these respective
genera being apparently too slight for generic separation. Excepting for the
presence of the second shorter flagellum these animalcules would appear to corre-
spond chiefly with those of the monoflagellate form Petalomonas.

Sphenomonas quadrangularis, Stein. PL. XXIV. FIGS. 21-23.

Body subfusiform, or quadrangular, twice as long as broad, widest
centrally and tapering towards each extremity, divided by four oppositely
placed, longitudinal, keel-like ridges, so as to form a quadrate outline in
transverse optical section ; longer flagellum stout, nearly twice the length of
the body, shorter one slender, scarcely one-quarter the length of the pre-
ceding ; endoplast subcentral ; parenchyma transparent, often enclosing a
large, ovate, apparently amylaceous body ; contractile vesicle confluent with
distal end of the tubular pharynx. Length 1-600".

HAB. — Fresh water ; dividing by longitudinal fission.

Sphenomonas octocostatus, Stein sp. PL. XXIV. FIGS. 18-20.

Body symmetrically ovate or subfusiform, compressed, about one and a
half times as long as broad, the posterior extremity pointed, the anterior
one deeply notched or emarginate ; cuticular surface ornamented with
eight longitudinal and sometimes obliquely twisted keel-like ridges ; both
flagella slender, the longer one about twice the length of the body, the
smaller one about one-quarter the length of the preceding ; endoplasm
coarsely granular ; contractile vesicle situated close to but not confluent with
the posterior termination of the tubular pharynx ; endoplast subcentral, reni-
form, often developing into a large ovate germ-mass. Length 1-400".

HAB. — Fresh water.

This species is figured by Stein * under the title of Tropidocyathus octocostatus ;
in the absence of full descriptive details it appears, however, to accord so closely in
all essential points with the type last described, that it has been thought desirable to
include it in the same genus. The addition to the Sphenomonas quadrangularis of four
intervening longitudinal ridges and the emargination of the anterior border are alone
required to produce, in accordance with Stein's figures, an animalcule absolutely
identical with the present form. The encysted condition of this species, as
shown at PL XXIV. Fig. 20, presents a remarkable resemblance to the carinated
seed of an umbelliferous plant, such as Petroselinum or Coriandrum.

Order VII. CILIO-FLAGELLATA, C. & L.

Animalcules free-swimming, locomotive appendages consisting of one
or more lash-like flagella, and a supplementary more or less highly developed
ciliary system ; oral aperture usually distinct.

As first instituted by Claparede and Lachmann,f this order included only the
several genera forming the single family group of the Peridiniidae. The results
of more recent investigation have, however, rendered it necessary to extend its

* 'Infusionsthiere,' Abth. iii., 1878.

t ' Etudes sur les Infusoires,' Geneva, 1858.

440

ORDER CILIO-FLAGELLATA.

Hemidinium.

Gymnodinium.

Melodinium.

Glenodinium.
Peridinium.

Ceratium.

Dinophysis.
Amphidinium.

Prorocentrum.

Dimastigoaula:

Heteromastix.

Mallomonas.

i

s

Asthmatos.

Trichonema.

i

I

**

cJ

ro

•&• w»

*

t^- QO

*

0

-

ci

I?

-

^

^

:

.— *—

c •

i rt

a, "S

1

:

:

:

:

:

:

•3

1 2

:

: :

:

i
0

j

:

:

:

:

:

•9

'fS '•*

J3 ^

*U1 V*

t/1

<L)

jV

eu°

" C4

I/) W»

8|

1

.

.

;

;

;

u

" ri

""•5 S

2 2

0

'bo

rt

£~

1 s

'3 '3
u u

M

: :

;

1

:

:

:

:

:

t/J

"

-

.

<ri

_H

1)

V

c/} c

-j

'o

.

^0

;

?

:

:

jELLAT,

( Cilia descril

Cilia formir

s .

H
§ u

8 'So

CS

r No hora-lik
processes.

1

t With horn-li

^j

'S. '•

1 1

o
S

in
•f

1 and horned,

y metabolic

persistent in

anretractile

retractile . .

0

1

itent in form

*~s

i

[

-1

i t

2 g

i

§

i

1

1

S
I

S

s
S

<u

a,

O P

1

c </>

V

6

sz;-|

I

w 2

1 1

o

m

W

|

m

o

M

E

$

3

pq

V 1 '

»j

V

a

a

u

1,

'Go

E

I"

'So a

M

rf

'fl

o

rt

"d

J- y

11

H
V

1
1

| .

1

s

CJ

C

U

C

o .

1

d

1

a

I

B

I

13
1

rt
tt>

.S

S!
§

1
^

u

^J

"H.

&

O

*T

(^

rt

£

2
i!

H

.3

o

i

Q

S

•8

0

i

3

g

M

nd a distinct ciliary (

i. II. HETEROMASTK

trailing flagellum, cil

n. III. MALLOMONAE

rminal ; body clothed

IV. STEPHANOMON.

reduced from the cent

AM. V. TRICHONEMI

"s
e

0

£

rt

S

I

ra

£

0

o

K

V
4)

S

rt

Pi

h

£

"•EL,

H

ji^^-j

y

'to

•2

H

rt •*

•

(3

D*

PH

<c 'So

o>

•§

•

I— J
1

g

S

1

1

i

-J-
S/3

fS

s

a

o
•«

£

o

fjtj

a

^

4>

0

5

51

ORDER CILIO-FLAGELLATA. 441

boundaries for the admission of diverse other types which maintain under variously
modified conditions the characteristics of the two larger sections of the Flagellata-
Eustomata and ordinary Ciliata, and thus intimately connect together these, at first
sight, seemingly altogether independent groups. In illustration of a few of the more
prominent relationships that are established between the two series of the typical
Flagellata and Ciliata through the intermedium of the present order, it may be sub-
mitted that the retraction of the single flagellum is alone needed, in the genera
Stephanomonas and Asthmatos, to convert these types into simple Peritricha resembling
Strombidium, though in the case of Asthmatos it is worthy of remark that the con-
stituent elements of the terminal tuft of cilia are so long as to partake almost of the
nature of flagella, thus conveying to the animalcules an aspect closely corresponding
with that of the multiflagellate type Lophomonas. In Trichonema and Mitophora a
similar suppression of the single flagellate appendage would transform these animal-
cules into simple Holotricha ; while in the case of Heteromastix, where the flagella
constitute the most important organs of locomotion, it requires only the obliteration
of the adoral ciliary fringe to produce a typical representative of the simply flagellate
genus Heteronema. The affinities of the important family group of the Peridiniidae
are discussed at length in connection with the description given of that earliest
recognized and typical section of the Cilio-Flagellata.

K. M. Diesing, in his ' Revision der Prothelminthen,' * distinguishes this Cilio-
Flagellate order of the Infusoria by the title of the Mastigophora Trichosomata.

An analytical key to the various families and genera of the Cilio-Flagellata, as
here delimited, is given on the opposite page.

Fam. I. PERIDINTIDJE, Ehr.

Animalcules free-swimming, persistent in form, sometimes naked, but
mostly invested by an indurated carapace or cuirass ; flagellum usually
single, ciliary system constituting a more or less perfectly developed zone-
like girdle ; oral aperture distinct ; an eye-like pigment-spot frequently
developed. Inhabiting salt and fresh water, often highly phosphorescent.
Increasing by fission and by subdivision into sporular elements.

The representatives of this highly characteristic family group are readily distin-
guished by the girdle-like disposition of the cilia which supplement the customarily
single, but in one instance double flagellate appendage. It is further found that
the body is with but few exceptions enclosed within a densely indurated carapace
or cuirass, which is itself frequently composed of a greater or less number of poly-
gonal and often elegantly sculptured facets. By far the larger number of species
are inhabitants of salt water, agreeing in this respect with the pelagic Noctilucce^
with which they further correspond, in many instances, by the exhibition of brilliant
phosphoric properties. Excepting for the presence of the equatorial ciliary girdle it
may be further noted that in such a non-encuirassed form as Gymnodinium the
resemblance of external contour to that of Noctiluca is so conspicuous — including
the possession in each case of a corresponding and apparently homologously
developed non-ciliated vertical or ventral groove — that it would not seem incon-
sistent to anticipate that forms will yet be met with that still more closely connect
these two types with one another. In no representative of the Peridiniidae,
however, as yet examined, has the internal body-substance or endoplasm been
observed to exhibit that peculiar vacuolar or reticulate character so eminently dis-
tinctive of the Noctilucidse. In the possession, more especially by the fresh-water
members of this group, of a frequently brilliant scarlet eye-like pigment-spot,
combined with the pervading green or other coloured hue of the general body-sub-
stance, some distant affinity with the family of the Euglenidae would seem to be

* ' Sitz. der Kaiser. Akad. der Wiss. Wien,' 1865.

442 ORDER CILIO-FLAGELLATA.

maintained. In common with these simpler Flagellata, it is further noteworthy that
they often occur in such prodigious numbers as to impart a distinct tint to the water
they inhabit Interesting data connected with this last-named circumstance will be
found recorded in the descriptions hereafter given of Peridinium sanguineum and
Melodinium uberrimum.

GENUS I. HEMIDINIUM, Stein.

Animalcules free-swimming, persistent in form, but not encuirassed ;
flagellum single, supplemented by an adoral fringe of cilia which is
developed in a groove that extends half-way only round the circumference
of the body, and at one extremity of which groove the oral aperture is

located.

Hemidinium nasutum, Stein.

Body much compressed, somewhat kidney-shaped, the left border
straight, the right one convex ; the equatorial, semicircular, ciliated furrow
continued obliquely backwards from the ventral towards the dorsal region of
the left body-half; the anterior moiety of the ventral surface further dis-
tinguished by a faintly impressed vertical groove, the bottom of which gives
origin to the single flagellum ; endoplast roundish, located in the hinder
body-half. Dimensions unrecorded.

HAB. — Fresh water ; colour yellow.

This as yet single known representative of the genus Hemidinium is briefly
described without accompanying figures in the text of Stein's recently published
volume.* The oral aperture, though not directly observed, was adjudged to be located
close to the ventral extremity of the semicircular ciliated groove, while the capacity
of assimilating solid nutriment was fully proved by the presence of incepted green
corpuscles of considerable size. The integument in this type is reported by Stein to
be of firm consistence, and although not indurated and differentiated to such an
extent as to partake of the nature of a cuirass or carapace, exhibits a marked
contrast in this respect to the comparatively soft and yielding cuticular surface of
Gymnodinium.

GENUS II. GYMNODINIUM, Stein.

Animalcules free-swimming, more or less persistent in form, but not
encuirassed ; cilia forming a continuous fringe along the interior of a
transverse groove or furrow which completely encircles the equatorial
region of the body, a second non-ciliated groove produced mesially on the
ventral surface from the transverse furrow towards the anterior or apical
extremity ; oral aperture and the insertion of the single, long, lash-like
flagellum located ventrally, in close vicinity to the juncture of the transverse
and longitudinal grooves. Inhabiting salt and fresh water.

This genus is instituted by Stein \ for the reception of several forms, including
notably the as yet very imperfectly observed Peridinium fuscum and pulvisculus of
Ehrenberg and the Peridinium monadicum and P. corpusculum of Perty, in which the
body and locomotive appendages/while according with those of the ordinary Peridinia,
differ from these in the entire absence of an indurated cuticular investment or cuirass.
As a consequence of this naked and comparatively soft consistence of the external

Infusionsthiere,' Abth. iii., 1878. t Ibid.

GENUS GYMNODINIUM. 443

envelope, the animalcules assume after death various irregular shapes, and speedily
undergo complete disintegration. As indicated by Stein, Gymnodinium may be
regarded as the ground or stock form of the various more complex representatives
of the Peridiniidae.

Gymnodinium fuscum, Ehr. sp. PL. XXV. FIGS. 17 AND 18.

Body oval, slightly compressed, rounded posteriorly, acuminately pointed
anteriorly, nearly twice as long as broad ; surface smooth, colour light brown ;
no eye-like pigment-spot Length 1-430" to 1-280". HAB. — Fresh water.

In the figures of this species, as given by Ehrenberg in connection with the
title of Peridinium fuscum, and here reproduced, the flagellate appendage was
apparently overlooked, while the vertical as well as the transverse groove is
represented as bordered with cilia. The presumed example of longitudinal fission
delineated by the same authority (see PI. XXV. Fig. 18), is regarded by Stein
as an advanced phase of the process of fusion or genetic union between two
previously independent zooids, which he has frequently observed to take place under
similar auspices in connection with the species next described.

Gymnodinium pulvisculus, Ehr. sp. PL. XXV. FIGS. 19 AND 20.

Body subspheroidal, slightly trilobate, surface smooth ; flagellum con-
spicuous, two and a half times as long as the body ; colour light brown or
greenish-yellow. Length 1-2300" to 1-1150".

HAB. — Amongst Conferva with Chlamydomonas pulvisculus, often in
great numbers.

As represented in Ehrenberg's figures of this species, coloured matter is freely
incepted. Perty reports the presence of an eye-like pigment-spot in the anterior
body-half, but such a structure is not indicated in Ehrenberg's original drawings and
descriptions. The process of conjugation or fusion has been observed by Stein, who
identifies with this phenomenon the representations of presumed longitudinal fission
given by Ehrenberg.

Gymnodinium corpusculum, Perty sp.

Body ovate or elliptical, segments very unequal, the posterior one con-
siderably the smaller ; flagellum conspicuous, about twice the length of the
body ; no eye-like pigment-spot ; enclosing variously coloured granules.
Length 1-1120". HAB. — Fresh water, among Marchantia polymorpha.

Described by Perty * under the title of Peridinium corpusculum.

Gymnodinium monadicum, Perty sp.

Body ovate or subspheroidal, segments unequal, the hinder one being
considerably the smaller of the two ; eye-like pigment-speck distinct, sub-
central ; flagellum conspicuous, two or three times as long as the body ;
endoplasm colourless, enclosing green food-corpuscles. Length 1-1120".

HAB. — Pond water.

This species was reported by Perty from the Bernese Alps. Stein \ has encoun-
tered an apparently identical form in the neighbourhood of Prague, recording of it

' Zur Kenntniss kleinster Lebensformen,' Berne, 1852.
t ' Infusionsthiere,' Abth. iii., 1878.

444 ORDER CILIO-FLAGELLATA.

that the body is transparent or bluish-white, with a sharply denned red eye-like pig-
ment-speck, a long flagellum, and very delicate ciliary girdle ; the body was usually
observed to contain a greater or less number of devoured Chlamydomonas monad ina.
By a careful examination a round light spot was detected near the point of junction
of the characteristic equatorial and longitudinal body grooves, which apparently
betokened the oral aperture; the long flagellum was inserted close to this oral
fossa. Stein had previously provisionally conferred upon this type the name of
Peridinium vorticella, but recognizes in his most recently published volume its
probable identity with Perty's type.

Gymnodinium marinum, S. K. PL. XXV. FIGS. 60 AND 61.

Body subspheroidal or trilobate from the dorsal or ventral aspect,
kidney-shaped, with a convex dorsal, and concave ventral surface, as seen
in profile ; flagellum conspicuous, its length equalling twice the diameter
of the body ; endoplasm transparent, usually enclosing numerous spheroidal
corpuscles ; oral aperture distinct. Diameter i-iooo". HAB. — Salt water.

This species was obtained abundantly by the author in an infusion of hay in sea-
water made at St. Heliers, Jersey, in February 1879, an^ after tne expiration of
just one month from the first preparation of the maceration. The motions of the
animalcule in the water were rapid and oscillating, and its habits eminently predatory,
closely resembling those of Dinomonas. As observed of the two species of the last-
named genus, it was continually engaged in chasing and devouring the smaller Hetero-
tnita and other monads contained in the same infusion, its oral aperture during the
engulfment of its captured prey, as shown at PI. XXV. Fig. 61, being expanded
and conspicuously indicated. It would seem just possible that the Peridinium monas
of Ehrenberg, briefly described as " very small, obtuse, without horns, remarkably
social. Diameter 1-1728". Hab. Baltic Sea," may be identical with this species.

Gymnodinium Lachmanni, S. K. PL. XXV. FIGS. 58 AND 59.

Body elliptical, twice as long as broad, equatorial groove very oblique ;
endoplasm transparent, enclosing spheroidal corpuscles. Length 1-600".
HAB. — Salt water.

This species is simply recorded by Claparede and Lachmann as a minute Peri-
dinium, encountered in salt water on the coast of Norway. Its relationship to the
other members of the present genus is obvious, though at the same time it differs,
in its greater proportionate length and in the conspicuously oblique direction of the
equatorial groove, from the marine form previously described.

Gymnodinium roseolum, Schmarda sp. PL. XXV. FIG. 53.

Body elliptical ; segments uneven ; flagellum indistinct ; colour pale
pink ; enclosing an eye-like pigment-spot. Length 1-720".
HAB. — Fresh water.

Described by Schmarda * as a species of Glenodinium. Incepted Chlamydo-
monads and other food-material were observed by its discoverer.

The Peridinium inerme, a minute subspheroidal form (PI. XXV. Fig. 54), and
the Peridinium incequale, having conspicuously narrow segments, of the same writer,
are apparently identical with the Gymnodinium monadicum and G. corpusculum
previously described.

* " Zur Naturgeschichte Egyptens," ' Denkschrift der Kaiser. Akad. der Wiss. Wien, 1854.'

GENUS MELODINIUM. 445

GENUS III. MELODINIUM, S. K.
(Greek, melon, a peach ; dine, a vortex.)

Animalcules naked, persistent in form but not encuirassed, having a
central equatorial ciliated groove, and a second shorter longitudinal furrow-
extending from the transverse one towards the apical extremity ; flagellum
single, issuing from a depression in the ventral groove ; entire surface of the
body ciliated, as well as the annular furrow ; coloured stigma present or
absent.

This new genus is provisionally established for the reception of the Peridiniutn
uberrimum of Professor Allman, characterized by the distribution of vibratile cilia
throughout the whole extent of its cuticular surface, and by the consequent absence of
an indurated carapace or cuirass. It is at the same time not altogether impossible
that future investigation may demonstrate this animalcule to be a shell-less develop-
mental condition of certain ordinary Peridinia, Claparede and Lachmann having
shown that a shell-less or non-encuirassed state is common to the earlier phases of
many of these latter. In the interim, nevertheless, it appears to be desirable to
institute an independent generic name for a type whose characters differ so widely
from those of the genus with which it has been hitherto associated.

Melodinium uberrimum, Allman sp. PL. XXV. FIGS. 34 AND 35.

Body subspheroidal, having a transverse annular furrow and a supple-
mentary vertical groove developed oji the ventral surface, which extends
from the centre of the annular furrow to the apical extremity ; entire
cuticular surface finely ciliate ; endoplast conspicuous, ovate, subcentral ; a
red eye-like pigment-spot usually present in the apical region. Length
l-iooo" to 1-500"; colour reddish brown.

HAB. — Fresh water, ponds in the Phoenix Park, Dublin ; gregarious.

As already notified, this species is synonymous with the Peridinium uberrimum of
Professor Allman, first described in the ' Quarterly Journal of Microscopical Science,'
p. 21, for the year 1855. In its broader details it would seem to correspond closely
with the animalcule figured and described by Claparede and Lachmann (See PL XXV.
Fig. 5) as a possible shell-less or transitional condition of an ordinary Peridinium, such
as P. tabulatiim. At the same time no trace of an entire ciliary clothing is mentioned
or figured by these writers, but which may nevertheless have been too fine to attract
notice with the magnifying power employed.

Some estimate of the essentially gregarious habits of this animalcule may be
arrived at in connection with the following abstract of Professor Allman's original
record. Speaking at the Dublin Academy, in June 1854, he remarked, — that for the
three previous weeks the brown colour assumed by the water in the large ponds in
the Phoenix Park was owing to the presence of prodigious numbers of a species of
Peridinium, this colour being sometimes uniformly diffused through the water, and at
others being collected in dense clouds varying from a few to upwards of one hundred
square yards in extent. Later on, the coloration of the ponds brought about by
the agency of these minute organisms had much increased in density ; by the Qth of
July the water was so deep a brown that a white disc, half an inch in diameter, was
invisible when plunged to a depth of from three to six inches, while a copious
exit stream, constantly flowing away from the ponds, presented a similar deep brown
hue. In many places the animalcules had descended from the surface, and were
found congregated in immense masses near the bottom of the water; in these
instances they had, for the most part, assumed a quiescent or encysted state, the

446 ORDER CILIO-FLAGELLATA.

flagellum and cilia having disappeared, and the body being contracted within the
centre of an external hyaline envelope. Multiplication by transverse fission, as
represented at PI. XXV. Fig. 35, is the only mode of reproduction that was
observed by Professor Allman, though doubtless the encysted state, in common with
that of all ordinary Flagellata — see also Peridinium sanguineum — is accompanied by
the breaking up of the body into sporular elements.

GENUS IV. GLENODINIUM, Ehrenberg.

Animalcules free-swimming, encuirassed, body separated by a transverse
or equatorial ciliated furrow into two equal or subequal portions, a more or
less conspicuous non-ciliated groove produced from the ventral aspect
of the equatorial furrow towards the apical extremity ; cuirass consisting of
two equal or subequal segments, which invest and correspond with the
anterior and posterior halves of the body, leaving bare the equatorial and
longitudinal grooves, not further subdivided into polygonal facets ; oral
aperture and insertion of the flagellum located on the ventral aspect near the
junction of the two grooves; endoplasm often, but not invariably, enclosing
a coloured eye-like pigment-spot. Inhabiting salt and fresh water.

As first instituted by Ehrenberg, this genus was made to include all those forms
of Peridinium and its allies that were distinguished by the possession of an eye-like
pigment-spot. As shown, however, by Claparede and Lachmann, and other recent
observers, this proposed feature of distinction is, as in the genus Euglena, inconstant
even among representatives of the same species, and cannot therefore be made the
basis of generic diagnosis. Quite recently, however, Stein * has pointed out that
among the animalcules referred to the genus Glenodinium by the authority first-named,
there occurs one, G. cinctum, which differs from all its co-associated types in the
smooth and undivided character of the two segments of the cuirass, and that this
distinctive characteristic is likewise shared by other animalcules previously rele-
gated to the genus Peridinium. For these he proposes collectively to retain the
generic name of Glenodinium, introduced by Ehrenberg, and it is with a similar
significance included in this volume.

Glenodinium cinctum, Ehr. PL. XXV. FIGS. 27-29.

Body ovate or elliptical, about twice as long as broad, entirely smooth
and homogeneous ; cuirass composed of two even anterior and posterior
segments only, and not of separate plates or facets ; a red eye-like pigment-
spot present or absent, when developed large and crescentic, subcentral ;
colour light brown. Length 1-570''. HAB. — Fresh water.

This species is identical with the Glenodinium cinctum of Ehrenberg, but not with
the Peridinium cinctum of that same authority ; this latter form, as presently explained,
representing examples only of P. tabulatum, in which an eye-like pigment-spot is
conspicuously developed. The encysted state of this animalcule has been observed
by Claparede and Lachmann, a condition of the same, with the valves of the cuirass
falling asunder, being delineated at PL XXV. Fig. 29.

Glenodinium acuminatum, Ehr. PL. XXV. FIGS. 21 AND 22.

Body ovate or spheroidal, slightly trilobate ; cuirass smooth, terminating
posteriorly in a short acuminate point; colour brownish yellow. Length
1-570". HAB. — Salt water, highly phosphorescent.
* 'Infusionsthiere,' Abth. iii., 1878.

GENUS PERIDINIUM. 447

GENUS V. PERIDINIUM, Ehrenberg.

Animalcules free-swimming, encuirassed ; body divided by a transverse
ciliated furrow into two equal or subequal moieties ; a second, shorter, non-
ciliated groove produced from the centre of the ventral aspect of the
equatorial furrow towards the apical extremity ; cuirass consisting of two
primary anterior and posterior segments, which are further subdivided into
a variable number of smaller smooth or variously sculptured polygonal
facets ; flagellum single, inserted close to the oral aperture near the junction
of the equatorial and vertical furrows; a coloured eye-like pigment-spot
frequently developed. Inhabiting salt and fresh water.

The genus Peridinium, as here constituted, embraces most representatives of
the genera Peridinium and Glenodinium of Ehrenberg, but from out of both of which,
as previously explained, are eliminated and associated with the last-named title those
forms only in which the cuirass or carapace is composed of two simple undivided seg-
ments. The ciliary groove and wreath of Peridinium and its allies, although usually
described as forming an uninterrupted girdle around the centre of the animalcule's
body, is shown by Claparede and Lachmann to deviate more or less conspicu-
ously from so simple circuitous a course. As made apparent more especially by
those observers in connection with the marine form Peridinium spintferum (see
PL XXV. Fig. 15), the left extremity or limb of this ciliary girdle takes its origin
from a point considerably in advance of the precise centre of the ventral surface, and
after obliquely encircling the dorsal region of the animalcule's body, terminates again
in the middle line of the ventral aspect, but at a point as much to the rear of the
same imaginary centre ; the right and left limbs of the groove, with its accompanying
cilia, lie consequently on two distinct levels. A similar deviation of the course of
the equatorial groove and ciliary girdle is in a less marked degree — being some-
times scarcely perceptible — shared by all the representatives of the several genera,
Peridinium, Glenodinium, and Ceratium, Another characteristic common also to
the majority of these closely allied encuirassed forms, is the presence on the
ventral surface, and immediately opposite the anteriorly produced non-ciliated
vertical furrow, of a deep inlet or emargination in the substance of the posterior
segment of the cuirass, which consequently leaves the body of the animalcule
naked and exposed. It is within or in the immediate vicinity of this circumscribed
area that the oral aperture would appear to be situated, though its existence has
not yet been so clearly demonstrated as in the case of Gymnodinium. Imme-
diately above, and in advance of this emargination, will be found inserted the single
long flagelliform appendage.

Although the reproductive phenomena of the present genus, and of the Peridiniidse
in general, have not as yet been completely elucidated, some important data in this
connection have been recorded, through the joint work of Messrs. Claparede and
Lachmann. Encystment has been observed by these authorities to take place in a
large number of forms and under diverse conditions; segmentation on a more
or less extensive scale being in many cases the direct product of the process. In
some instances, as shown at PI. XXV. Figs. 4, 10, and 29, encystment is effected
within the normal carapace or cuirass, and is not attended by any supplementary
metamorphoses. Other instances were observed, however, in which the cuirass of the
typical motile zooid being cast off, a new and continuous cyst, comparable in all
ways to that produced by the ordinary Flagellate and Ciliate Infusoria, was secreted.
The animalcule, pending the secretion of this second envelope, temporarily maintains
a naked phase of existence, which is, as shown at PI. XXV. Fig. 5, directly compar-
able to the permanent form of Gymnodinium. This variety of encystment is some-
times, as among the ordinary Infusoria, associated only with the temporary retreat
or hibernation of the animalcule, or it may have as its object the further propagation

448 ORDER CILIO-FLAGELLATA.

of the species. Under these last conditions the cyst produced is mostly found
to exhibit a peculiar modification of contour. In place of being subspheroidal
or ovate, as obtains under ordinary conditions, one or both of the extremities are
prolonged into an attenuate, curved, and acuminate point. These recurved points
in the latter instance being produced in the same plane, the result is a crescentic
or lunate-shaped cyst, somewhat resembling in shape the Desmid Closterium.
Examples of these lunate or subcrescentic cysts are reproduced from Claparede and
Lachmann's drawings at PI. XXV. Figs. 47, 48, and 49, 50; those in the two former
instances representing a marine, and in the two latter ones a fresh-water type, whose
specific identity could not in either case, unfortunately, be precisely determined. The
delineation given at Fig. 49 is of special interest, since in that instance the primarily
enclosed single zooid has become metamorphosed by linear or serial segmentation into
no less than eight sporular elements or daughter-cells, having each the characteristic
trilobate contour of the parent, but wanting the investing carapace ; they are in fact at
this early phase of their development indistinguishable from the members of the genus
Gynmodinium, previously described, and with which they are thus shown to be inti-
mately and phylogenetically related. It is further noteworthy, in this connection,
that the assumption of a similar and comparatively simple Gymnodinium phase is
frequently resorted to by the animalcules of the present genus as a preliminary to
the process of encystment, while it is only under such temporarily naked state that
increase by fission, or genetic union, can be accomplished. This assumption by the
members of the genus Peridinium of an alternating encuirassed and naked state con-
siderably enhances the difficulty of determining which forms possess a sound claim
for relegation to the genus Gymnodinium, and it is necessarily only those types
which are found to persistently maintain the naked condition that can be allotted to
this group.

Peridinium tabulatum, Ehr. sp. PL. XXV. FIGS. 1-5 AND 55-57.

Body ovate or subcircular as seen in dorsal or ventral view, much
flattened or depressed, with a convex dorsal and concave ventral surface, as
seen in lateral aspect ; cuirass composed of numerous polygonal facets,
which individually exhibit under high magnification a delicate reticulate
structure ; colour yellowish green or brown ; one or more red eye-like pig-
ment-spots frequently but not invariably developed. Length 1-570" to
1-430". HAB. — Fresh water ; gregarious.

This species, originally described by Ehrenberg as a species of Glenodinium,
is one of the most cosmopolitan members of the present genus, and frequently
occurs in pond-water in such abundance as to impart to the water its own charac-
teristic rust-brown hue. A considerable amount of variation is found to obtain in
the contour of the two apical poles of the cuirass of this species in examples derived
from diverse localities. Sometimes, as shown at PI. XXV. Fig. i., both of these
poles are uniformly smooth and rounded ; more often, however, it is found that the
facets of the anterior segment of the cuirass project apically in such a manner as to
impart a notched or shortly bifurcate aspect to the anterior border, and so prepare
the way to the closely parallel but more decided horn-like projections in this region
that are found in Ceratium divergens. Examples with a rounded posterior and
distinctly notched anterior pole are delineated at Figs. 55-57. A still more
complex modification of the cuirass is included in the representations of this species
given by Ehrenberg, in some of which, as reproduced at PL XXIV. Fig. 2, the
posterior segment is likewise produced apically into three or four acuminate points.
The number of large polygonal plates or facets reckoned by Stein to enter into the
composition of the two segments of the cuirass in this species, is no less than
twenty-one, sometimes more, and of which fourteen to sixteen belong to the anterior
and seven to the posterior moiety; added to this, he says, are smaller linear or band-

GENUS PERIDINIUM. 449

like indurations, which bound the equatorial and vertical furrows. The elegant
sculpturing of the larger polygonal and usually five- or six-sided facets, may be most
readily examined in connection with the empty or disintegrated carapaces that are
usually found abundantly distributed in the water that supplies the living zooids.
A delineation of such a highly magnified single 'facet is given at Fig. 3. The encyst-
ment of this species within its cuirass has been observed by Claparede and Lach-
mann, as also the naked Gymnodinium-Vke. phase, both of these conditions being
reproduced from their drawings at Figs. 4 and 5. In examples examined by the
author, a long curved band-like endoplast or nucleus, similar to that commonly met
among the Vorticellidce, has been occasionally observed, one such distinctly nucleated
specimen being represented at Fig. 56. The species has been obtained by the author
in profusion from various localities in the suburbs of London, and has also been
received from the neighbourhood of Birmingham, through Mr. Thomas Bolton.

Very recently, November 1880, the author has received this animalcule in com-
pany with other Flagellata, through Mr. John Hood, from the neighbourhood of
Dundee. The chief interest attached to such consignment is connected with the fact
that many lunate encystments, corresponding essentially with those first described of
an unknown form by Claparede and Lachmann, and represented at PI. XXV. Figs.
49 and 50, were detected among the sedimentary matter at the bottom of the phial in
which they were transmitted. The contents of these cysts, which were usually
divided into two equal moieties, exhibited the same rust-brown hue as the motile
zooids. There can be but little doubt that the similar shaped encystments in the
figures quoted belong to the present very widely distributed species.

«

Peridinium apiculatum, Ehr. sp. PL. XXV. FIGS. 6 AND 7.

Body oval, depressed ; cuirass composed of large polygonal reticulate
facets, the edges of which are finely hispid and separated from one another
by clear, smooth intervals ; colour yellowish-green ; an eye-like pigment-
spot of oblong form usually present. Length 1-570" to 1-350".

HAB.— Fresh water.

This species was described by Ehrenberg under the title of Gymnodinium apicu-
/afitm, and does not so far appear to have been encountered by any other authority.
Stein is inclined to regard it only as a variety or older phase of Peridinium
tabulation.

Peridinium reticulatum, C. & L. PL. XXV. FIG. 41.

Body ovoid ; cuirass composed of numerous minute, smooth, polygonal
facets, equatorial furrow obliquely developed ; colour brown. Length
1-570". HAB. — Salt water : Norwegian coast (C. & L.).

Peridinium spiniferum, C. & L. PL. XXV. FIGS. 15 AND 16

Body ovoid, rounded posteriorly ; cuirass composed of large polygonal
facets ; two closely approximated spines developed at the apical extremity
of the anterior segment ; transverse furrow very oblique, forming an elongate
spire. Length 1-620".

HAB. — Salt water ; Norwegian coast (C. & L.).

Peridinium splendor-maris, Ehr.

Cuirass ovate or subglobose, transparent, facetted, cribrate or granular,
neither apiculate nor provided with horn-like processes ; margins of the

2 G

450 ORDER CILIO-FLAGELLATA.

transverse groove projecting, and presenting laterally the aspect of tooth-
like processes ; facets developed on each side of equatorial furrow, five in
number. Diameter 1-1152" to 1-480".

HAB. — Salt water : Naples. Highly phosphorescent.

In contour this species would appear to closely resemble the smooth variety of
the fresh-water Peridinium tabulatum.

Peridinium chilophsenum, Ehr.

Cuirass subglobose, hornless, its surface smooth, neither facetted nor
punctate ; equatorial furrow distinct, its margins presenting laterally the
appearance of projecting teeth ; oral fossa narrow, curved. Diameter
1-648".

HAB. — Salt water : entrance of Davis Straits, and Iceland, with sound-
ings from a depth of 1158 feet.

Peridinium sanguineum, Carter.

Body subcircular, paraboloidal or kite-shaped, compressed, sulcate
ventrally ; equatorial groove deep, its upper border distinctly ciliate ; cuirass
faintly facetted over the anterior or conical half, the posterior or rounded
half entirely smooth ; an eye-like pigment-spot and endoplast usually
conspicuous. Length i-H2o"to 1-700".

HAB. — Salt-water pools, and in the sea on the shores of the Island of
Bombay. Movements waddling, the small end forwards and the long
flagellum floating behind ; colour changing successively from green or
golden yellow to brown and vermilion or minium red.

This species, described by Mr. H. J. Carter in an article on " The Red Colouring
Matter of the Sea round the Shores of the Island of Bombay," contributed to the
' Annals of Natural History ' for April 1858, is of special interest in connection with
the light it throws upon the phenomena frequently observed, but not previously
explained in a satisfactory manner, concerning the sudden assumption by the sea, or
other waters, of a blood-red hue. According to Mr. Carter, this animalcule, during
the earlier and active phase of its existence, is green and translucent, reflecting little
or no light, the colouring matter out of which its body-substance is composed being
akin to or identical with the chlorophyll of plants. Gradually, as the time approaches
for it to assume its quiescent or encysted state, a number of semi-translucent, refrac-
tive oil-globules are secreted within the interior ; the green colour now disappears
and a bright red one takes its place, mixing with the oil, and thus the animalcules
become visible to the naked eye, the whole portion of the sea charged with them
acquiring a deep vermilion hue. This colour is so prominently developed under
these conditions that in the sea-water pools left by the reflux of the tide on the
shores of the Island of Bombay, such pools present to the uninitiated the appearance
of having had a quantity of vermilion or minium thrown into them. An examina-
tion of this water under a microscope shows, however, that the red colours are
entirely due to the Peridinia. The vermilion hue now arrived at only lasts a few
days ; the animalcules assembling together become individually encapsuled, and in
this state float on the surface or sink to the bottom. Duplicative subdivision now
takes place within the capsules or encystments, each animalcule by such process
becoming divided into two or four equal fragments, which are subsequently
liberated by the bursting of the cyst. In other, rarer instances, it is affirmed by Mr.
Carter that a litter of ciliated monads may be developed in a distinct cell within the

GENUS PERIDINIUM.

451

ordinary capsule, such brood being the product of a true act of generation (con-
jugation), or the final formative effort of the protoplasm.

Many earlier records of the observation of phenomena connected probably with
the presence of an animalcule identical with, or allied to, Peridinium sanguineutn*KQ
quoted by Mr. Carter. Thus, Charles Darwin * observed an apparently identical
animalcule which coloured the sea red, a degree south of Valparaiso. Salt, in
his ' Voyage to Abyssinia,' mentions the presence of animalcules in the Red Sea,
which produced the red colour characteristic of those waters during the day, and
became luminous at night by agitation after the manner of numerous other Peridinia.
Olafsen and Povelsen are further cited as having recorded, so long since as 1 694, of
the sea on the shores of Iceland, that during the daytime it was as red as blood, and in
the night apparently as though on fire. Mr. Carter finally suggests the high probability
that the plague of Egypt — manifested by the apparent turning of all the waters into
blood, in which the fish in the river died, and the river stank, and the Egyptians
could not drink of the water of the river — may be consistently interpreted in con-
nection with an abnormal development of an animalcule allied to this species.
Such interpretation is further supported by facts connected with the discoloration
of the sea, that Dr. Buist recorded in the ' Proceedings of the Bombay Geological
Society' for the year 1855. On the 27th of October 1849 it was observed by that
authority that the water at Ponbunder, on the coast of Khattywar, was changed from
the usual tint to a deep red, emitting a most foul smell ; the fish were speedily all
destroyed, and were washed upon the beach in large quantities. It was conjectured
by the narrator that the phenomenon was owing to some submarine eruption of mud,
but the locality being one in which red water produced by the presence of animal-
cules is extremely common, the cataclysmic interpretation suggested is scarcely
warranted. The offensive effluvium exhaled by waters in which Peridinia and
lower Protophytes have developed in large quantities is personally testified to by
Mr. Carter in the case of a Peridinium obtained by him from a fresh-water tank at
Bombay, and where he says it not only " turned the water quite brown, but imparted
a smell and insipid taste to it, which almost rendered it undrinkable." He further
cites the case of a little algal, Aphanizomenon flos-aquce, frequently developed under
like conditions in the same fresh-water tanks, which often not only " renders the
water undrinkable, but produces an intolerable stench by its putrefaction."

It may be suitably mentioned in connection with the foregoing data that
Ehrenberg, in the ' Monatsbericht der Berliner Akademie ' for the year 1853,
records the fact that during the remarkable cholera epidemic prevalent throughout
Europe in the year 1848, two flagellate organisms, Chloraster gyrans and Spondylo-
morum quaternarium, were so abundantly developed in the water-tanks in the streets
of Berlin as to render the fluid completely green and unfit to drink. If not the
direct cause of zymotic disease, there can be but little doubt that an abnormal
development of these and kindred lowly organized beings in ordinarily potable
water indicates that such fluid has been contaminated by the accession of extraneously
derived organic matter to an extent making it not only unsuitable, but highly
deleterious for human consumption.

Peridinium sequalis, S. K. PL. XXV. FIG. 14.

Body symmetrically bi-conoidal, widest in the centre, tapering evenly
at an angle of about 67° towards the anterior and posterior extremities,
both of which terminate in two or more short, pointed cusps; equatorial
zone of cilia broad and evenly developed ; a second furrow of equal breadth
proceeding from the centre of the equatorial one towards the anterior pole;
measurement between the two poles scarcely exceeding that of the width ;
endoplast conspicuous, band-like. Dimensions unrecorded.

HAB. — Salt-water.

* 'Journal on board H.M.S. Beagle,' pp. 17, 18.

2 G 2

452 ORDER CILIO-FLAGELLATA.

The above title is here conferred on the species of Peridinium figured and briefly
described, without a name attached, by Dr. von Willemoes-Suhm in the ' Zeitschrift
fur Wissenschaftliche Zoologie,' Bd. xxi. p. 303, and Taf. xxxi., 1871. The even and
elegant symmetry of its form distinguishes it conspicuously from all other known
species of the genus. The character or even existence of the flagellum appears to
have escaped the notice of its discoverer.

GENUS VI. CERATIUM, Schrank."

Animalcules free-swimming, encuirassed, body divided by a central
ciliated furrow into two equal or subequal portions, a second shorter, non-
ciliated groove extending from the centre of the ventral aspect of the
equatorial furrow towards the anterior pole ; cuirass consisting of two equal
or subequal segments, separated by the equatorial groove, which may
or may not be subdivided into secondary plates or facets ; one or both of
these segments produced into more or less conspicuous horn-like prolonga-
tions ; flagellum single, inserted close to the oral aperture at or near the
junction of the equatorial and longitudinal furrows ; eye-like pigment-speck
rarely developed. Inhabiting salt and fresh water.

The representatives of this genus, while formerly included in that of Peri-
dinium^ are conveniently separated and distinguished by the presence of the more
or less conspicuously developed horn-like extensions of the cuirass. The close
affinity of the two genera is at the same time abundantly demonstrated by such an
intermediate or annectant form as Ceratium divergens, which practically possesses
but a slightly more differentiated modification of the cuirass than obtains in the
more normal variety of Peridinium tabulatum. The larger number of species of this
genus are pelagic, many of them being noted for their phosphorescent properties.
An interesting feature connected with certain of these pelagic types is the marked
isomorphic resemblance presented by the cuirasses with their long, divergent, horn-
like prolongations, to other floating organisms with which they are associated. In this
manner the attenuately prolonged, triradiate cuirass of Ceratium tripos (var. macroceros)
finds its countertype not only in the skeletal framework of the floating larva or
" Pluteus " of various Echinodermata, but in the larval or free-floating " zosea "
conditions of many of the highly organized Podophthalmous Crustacea, such as
Porcellana, in which a like production of the chief skeletal element, the carapace,
into three attenuate horn-like prolongations many times longer than the body, is
encountered. An even more astonishing mimetic resemblance subsists, however,
between the above-named species of Ceratium and the larval forms, the nauplii, or
so-called " Archezoa" (Dohrn) of the Cirripede Lepas fasriculattis as figured by Dr.
R. von Willemoes-Suhm in the ' Philosophical Transactions,' pi. i., for the year 1876.
Here three long, serrated, spinous processes are developed in the same order and
maintain the same preponderating proportions with relation to the central body, the
superficial resemblance indicated being so complete that under a low magnifying
power the essentially distinct nature of the two organisms would scarcely be detected.
Finally, the four-horned Ceratium longicorne is obtained in company with a Rotifer
(Anurea longispina) characterized by the possession of great spinous processes that
attain a similar proportionate length, and decussate in the same order from the
surface of its carapace. The utility of these arm-like appendages, giving their
possessors greater buoyancy and marked fitness for a pelagic or floating existence,
is obvious ; their coincidence of plan in four such very divergent organic groups
being at the same time most remarkable.

* 'Fauna Boica,' 1793.

GENUS CERATIUM. 453

A. — HORN-LIKE PROCESSES SHORTER THAN THE BODY.
Ceratium divergens, Ehr. sp. PL. XXV. FIGS. 8-13.

Cuirass rhomboidal, widest centrally, attenuate and acuminate posteriorly,
the anterior extremity armed with two short, straight, pointed horns, each
of them having a tooth-like process at the basal portion of their inner
margin. Diameter 1-576".

HAB. — Salt water : Baltic Sea. Colour yellow.

This animalcule was first described by Ehrenberg under the title of Peridinium
divergens. Claparede and Lachmann regard the P. depressum of Bailey (PL XXV.
Figs. 12 and 13) as identical with this species. These same authorities, as shown in
the figures here reproduced, have observed the species in both its encysted and
naked or Gymnodinium phases of existence. The contour of the empty cuirass, as
shown at Figs. 8 and 9, presents a remarkably elegant facetted crystalline aspect.

In the ' Monatsbericht der Berliner Akademie' for the year 1854 Ehrenberg has
described, under the title of P. divergens var. reniforme, a modification of the present
form characterized by a somewhat wider reniform contour of the cuirass, the posterior
extremity being further produced as a short, obtusely pointed, stylate process.

Ceratium Michaelis, Ehr. sp. PL. XXV. FIG. 23.

Cuirass ovate, having two short, straight, anterior and one postero-
terminal, subcylindrical, horn-like processes, the extremities of which are
abruptly truncate ; surface entirely smooth. Length 1-570".

HAB. — Salt water. Highly phosphorescent ; colour yellow.

The truncate termination of the horns, in addition to the absence of tooth-like
processes at the base of the two anterior ones, distinguishes this form from C. divergens,
which it otherwise most nearly resembles.

Ceratium tridens, Ehr.

Cuirass resembling that of C. Michaelis and C. divergens, bearing three
acute frontal horns, the posterior extremity attenuate, surface granular.
Length 1-576". HAB. — Salt water : Baltic Sea. Colour yellow.

Ceratium bicorne, Schmarda sp. PL. XXV. FIG. 62.
Cuirass ovate or subspheroidal, having two anteriorly developed horn-
like processes only, the one taking the form of a straight, axial, acuminate
point, the second antero-lateral, curved, and spur-like, equal in length to
about one-half of the length of the body. Length 1-1080" to 1-840".
Colour brick red. HAB. — Salt water.

Ceratium pyrophorum, Ehr.

Cuirass ovate or subspherical, with two little acuminate points at the
anterior extremity ; surface delicately areolate and granular. Length
1-570" to 1-480".

HAB. — Baltic Sea, near Kiel, and also as a fossil in the flints" of the
chalk formation from the neighbourhood of Brighton and Gravesend.

454 ORDER CILIO-FLAGELLATA.

Ceratium delitiense, Ehr.

Cuirass ovate or subspheroidal, with a single median, lateral, short,
acuminate process. Length 1-430" to 1-280".
HAB. — Fossil in the chalk flints of Delitzsch.

The inclusion of this species among the representatives of the present genus, or
indeed, in the Protozoic sub-kingdom, is necessarily probational.

B. HORN-LIKE PROCESSES AS LONG OR LONGER THAN THE BODY.
Ceratium tripos, Mull. sp. PL. XXV. FIGS. 24, 33, AND 36.

Body somewhat triangular, truncate in front and tapering posteriorly,
the anterior segment of the cuirass bearing two long, laterally developed,
recurved, horn-like processes, and the posterior one a single, similarly
long or longer and straight median process ; the edges of these processes
usually more or less denticulate. Length of body, including the horns,
1-140" ; without the horns, 1-430".

HAB. — Salt water. Colour yellow ; highly phosphorescent.

This species, originally described by O. F. Miiller under the title of Cercaria
tripos, is subject to great individual variation, and more especially with respect
to the proportionate size, and angle of divergence from the body, of the horn-
like processes. Two of the more prominent of these variations, indeed, originally
received a separate specific description at the hands of Ehrenberg, under the
respective titles of Peridinium macroceros and P. arcticum. Briefly epitomized,
Ceratium tripos and its two leading varieties may be thus distinguished : —

C. tripos (normal form}, PI. XXV. Fig. 33. — The two anterior horns much shorter
than the posterior one, about equal to the body in length, arched backwards in such
a manner that, if continued, their points would cross the hinder and median
process ; the margin of anterior horns finely and indistinctly denticulate.

Var. a. (P. macroceros, Ehr.), PL XXV. Fig. 24. — All three horns very long and
slender, the two antero-lateral ones usually the longer, sometimes exceeding six
times the length of the body, produced first in advance of the body, the right one more
so than the left, and then curved round and continued backwards in a straight line
and at an angle of divergence from the posterior and terminal horn ; denticulation
of the margin of the two anterior processes more distinct than in the normal form.

Var. /? (P. arcticum, Ehr.), PI. XXV. Fig. 36. — Horns subequal, very thick,
about twice the length of the body, all three curved, strongly and uniformly denticu-
late ; the two antero-lateral horns not produced in advance, reflected backwards at a
divergent angle.

Although, seen separately, the three above varieties would seem to lay claim to
separate specific recognition, it will be found that every gradation of form connecting
the one with the other occurs among examples from the same locality. At the
same time it has been observed that while the normal form of Ceratium tripos is
most abundant in the vicinity of Bergen, the variety a, macroceros, predominates on
the west coast of Norway, while the variety /?, arcticum, occurs most numerously in
the more northerly latitude of Spitzbergen. The eminent phosphoric properties
attributed to the species by Ehrenberg and Michaelis have not been confirmed by the
researches of Claparede and Lachmann. According to Dr. Pringsheim, a species
closely resembling C. tripos occurs in fresh water in the neighbourhood of Berlin.

The author has recently received from Dr. Wm. J. Gray, F.R.M.S., a sample of
" surface skimmings " collected by Count Castracane in the neighbourhood of Fano,
in the Adriatic, that is particularly rich in Peridiniidae, Ceratium tripos being the most
abundant type, and five other forms, Ceratium fusus, Ceratium divergens, Ceratium
eugrammum, Prorocentrum micans, and Dinophysis caudata, being more or less sparingly

GENUS CERATIUM, 455

represented. Of C. tripos the variety macroceros is most plentiful, the majority of
examples being remarkable for the extreme length and slenderness of their arm-like
processes, which in this respect not unfrequently exceed the proportions given at
PI. XXV. Fig. 24. Every gradation from this attenuate variety to the more typical
condition, Fig. 33, was encountered, but in no instance the thick-armed variety
arcticum, whose appendages are apparently specially adapted to preserve the equili-
brium of the animalcule in the colder and consequently denser waters of the Arctic
seas. An interesting structural feature was elicited in connection with the author's
examination of this type. In specimens mounted in the usual manner for future
observation the median posterior process was shown to be composed of four
longitudinal segments ; these under pressure became separated from one another
throughout the greater portion or even their entire length, presenting under such
conditions the aspect of a fascicle of four rigid, distally divergent setae. This
opportunity of becoming personally acquainted with the typical pelagic repre-
sentative of the genus Ceratium was also utilized by the author for the solution
of the moot question concerning the composition of its exceedingly brittle indu-
rated carapace or cuirass. It had been previously suggested by Mr. Charles
Stewart, of St. Thomas's Hospital, with reference to the accredited capacity of
this element to withstand incineration, that it was probably of a siliceous nature,
such opinion being endorsed by the author in an account given in the ' Midland
Naturalist ' for May 1880, of various marine Infusoria collected off the coast of Corn-
wall. The views there expressed, based only on unsupported testimony, are now
entirely discarded, for, on putting the matter to the test by heating examples on
talc over a spirit-lamp, it was found that they speedily shrivelled up, and ultimately
disappeared, while the more delicate siliceous diatom-frustules and sponge-spicules
scattered beside them remained intact. The possibility of the carapaces of these
Ceratia being composed of silex was thus disproved, and no grounds are left for
supposing that their composition is other than corneous or chitinous, as obtains in the
carapaces, loricag, or capsular elements of all the more familiar infusorial species.
Yet additional testimony in support of the view now advocated is afforded by the
fact that the remains of several reputed species of Ceratium, C. pyrophorum and
C. delitiense, have been obtained as fossils in flints belonging to the cretaceous
formation. It is a well-known fact to geologists that silica in its first state of com-
bination is entirely eliminated from these deposits, and is present only in its recom-
bined and concrete form. It may be hence consistently maintained that the Ceratia
met with in the chalk could not have possessed siliceous tests.

Ceratium furca, Ehr. sp. PL. XXV. FIG. 31.

Cuirass subtriangular, longitudinally striate, bearing three horn-like
processes, the two antero-lateral ones directed straight forwards, not
exceeding the body in length ; the median posterior process straight and
slender, twice the length of the anterior ones. Entire length 1-120".

HAB. — Salt water. Colour yellow.

Claparede and Lachmann include in this species both the Peridinium furca and
P. lincatum of Ehrenberg. The dimensions of the last-named type are however
so much smaller, 1-380" only, that it seems highly probable that the two are distinct.
The present form, according to the last-named authority, is eminently phosphor-
escent. Although usually regarded as entirely marine, M. Werneck has reported
the occurrence of an apparently identical species in fresh water in the vicinity of
Salzburg.

Ceratium biceps, C. & L.

Cuirass subtriangular, striate longitudinally, bearing three horn-like
processes, neither of which exceed the length of the body, the two anterior

456 ORDER CILIO-FLAGELLATA.

ones directed forwards in a straight line, one longer than the other, closely
approximated at their bases. Length 1-120".
HAB. — Salt water : Norwegian coast (C. & L.).

This species most closely approaches C. furca, and is not improbably a variation
only of that type ; provisionally, it may be distinguished from that form by the
shorter proportions of the horn-like processes, neither of which exceed the length of
the body, and by the close proximity of the two anterior ones, which seem to spring
from a common base.

Ceratium fusus, Ehr. sp. PL. XXV. FIG. 40.

Cuirass elongate-fusiform, armed with two horn-like processes only, each
of these about three times the length of the body, and produced in the
same plane respectively from the anterior and posterior segments of the
cuirass ; the posterior process usually straight, the anterior one slightly
curved. Length 1-120" to 1-90".

HAB. — Salt water. Colour yellow ; highly phosphorescent.

Identical with Ehrenberg's Peridinium fusus. Claparede and Lachmann remark
that the customary third horn-like process, though not conspicuously represented, is
often present in the form of a short spine or slight protuberance, near the base of
the single developed anterior horn. Examples of this species were obtained by the
author off Falmouth in July 1879, m connection with the summer excursion of the
Birmingham Natural History Society. A distinct ovate endoplast was observed in a
crushed, spirit-preserved specimen.

Ceratium candelabrum, Ehr. sp.

Contour of cuirass resembling that of Ceratium furca ; body depressed,
greatly dilated, its surface areolate and cribrate, the equatorial furrow
straight, the anterior border oblique ; the three horn-like processes produced
abruptly from the body portion, the basal horn about twice the length of
the body, the two anterior ones unequal, neither of them exceeding one-sixth
the length of the basal process, their surfaces ornamented with unevenly
developed parallel rows of asperities. Total length 1-120".

HAB. — Salt water : Adriatic. Colour yellowish-brown.

Ceratium lineatum, Ehr. sp.

Contour of cuirass resembling that of Ceratium furca but of smaller
size ; its surface ornamented with punctate longitudinal striae, about twelve
such striae being included in the half exposed to view. Total length 1-384".

HAB. — Sea water : Newfoundland.

Ceratium eugrammum, Ehr. sp.

Contour somewhat resembling that of C. furca or C. lineatum ; surface of
cuirass longitudinally striate, the intervals cribrate, not areolate ; body
conical, tapering gradually into the straight, posterior or basal, horn-like
process, which equals the body in length ; the two frontal processes of
unequal length, both shorter than the body. Total length 1-180".

HAB. — Salt water : Adriatic, with phosphorescent water.

GENUS CERATIUM, 457

Examples of this species, having an average length of i-ioo," are abundantly
contained in the sample of surface skimmings from Fano, in the Adriatic, collected
by Count Castracane, and placed at the author's disposal by Dr. Wm. Gray. In
some, but not all instances, it was observed that the surfaces of the horn-like
processes were distinctly serrated.

Ceratium seta, Ehr. sp.

Cuirass bicornate, resembling C. fusus, but longer and more slender ;
body fusiform, slightly inflated centrally, the anterior portion of this region
notched, its posterior one tapering gradually into the basal horn-like
process ; both horns slender, setaceous, straight, or lunately curved, their
extremities truncate, their surfaces roughened or asperate, the front one
mostly the longer, often three times the length of the body. Total length
1-120" to 1-72".

HAB. — Salt water : Adriatic, with phosphorescent water.

Ceratium trichoceros, Ehr. sp.

Cuirass with three elongate, setaceous, horn-like processes, the single
posterior process straight, truncate, over six times as long as the ovate or
subglobose central portion, the two anterior ones recurved, obtusely pointed,
exceeding eight times the length of the central body, all distinctly asperate ;
equatorial groove obliquely directed, parallel with the anterior border of the
cuirass ; colour yellowish-brown. Length of body, without horns, 1-864" '>
total length 1-120" to 1-96".

HAB. — Salt water : Adriatic (September).

Excepting for its minute size, this species, briefly characterized by Ehrenberg in
the ' Monatsbericht Berliner Akademie ' for the year 1859, does not appear to differ
materially from the slender-armed variety of C. tripos previously recorded.

Ceratium longicorne, Perty. PL. XXV. FIG. 26.

Cuirass bearing four horn-like processes, of which three, one longer
median and two shorter antero-lateral ones, are produced from the anterior,
and one long median process from the posterior segment ; entire surface
of cuirass and horn-like processes finely and evenly asperate ; a red eye-like
pigment-spot frequently developed at the anterior extremity of the body.
Length 1-120" to 1-90". HAB. — Fresh water.

This species, while first associated by Perty with the above-named title, was after-
wards identified by him with the Ceratium macroceras of Schrank, and under which
designation it is figured and described in his ' Kleinster Lebensformen,' in the year
1852. That name, however, so closely approaches the previously introduced
C. macroceros distinctive of the marine three-horned variety so named by Ehrenberg,
that the retention of Perty's later title in the present instance has been decided on.
A characteristic feature by which this form may be immediately distinguished from
every marine or fresh-water representative of the genus Ceratium described in this
volume, is afforded by the profuse development of the horn-like appendages of the
cuirass, no other type as yet encountered possessing more than three such processes.
The distribution of the animalcule, as with various other forms of Peridiniidae, may
be described as cosmopolitan. First reported from Germany and the Bernese Alps

458 ORDER CILIO-FLAGELLATA.

by Schrank and Perty, a type indistinguishable from it was obtained in the neigh-
bourhood of Calcutta, in September 1859, by Major, now Colonel, Stuart- Wortley,
as shown by delineations of the same supplied by him to Mr. Carter, copies of
which are in possession of the author. Quite recently again, August 1879, examples
according in all essential details with the Bernese and Indian form, have been
received by the author through Mr. J. Levick and Mr. Thomas Bolton, from the
Olton Reservoir near Birmingham. In the specimens personally examined, it was
found that the surfaces of the body and each of the four horn-like prolongations
were distinctly asperate. Such ornamentation, although not recorded of the Con-
tinental or Indian examples, may have existed, but escaped the notice of their
recorders in consequence of the employment of insufficient magnifying power; or,
as in the case of C. tripos, it may be the outcome only of local influences.

An interesting circumstance connected with the discovery of this type in British
waters is connected with the fact that a Rotifer, Anurea longispina, also new to this
country,* was simultaneously met with, in which long spinous processes, similar in
number, proportions, and plan of disposition, are developed from the surface of the
carapace. The interesting Entomostracon Leptodora hyalina, hitherto unknown to
Britain, was likewise derived from the same locality.

Ceratium Kumaonense, Carter. PL. XXV. FIG. 25.

Cuirass subtriangular, with two anterior and one posterior straight and
massive horn-like processes ; one of the anterior horns axially directed
and, together with the posterior one, equalling the body in length ; the
second or antero-lateral horn produced obliquely, not half the length of the
other two ; all three of these processes finely and evenly serrated. Colour
reddish -brown. Entire length 1-125".

HAB. — Fresh water.

This species, described by Mr. Carter in the ' Annals and Magazine of Natural
History,' vol. vii. 1871, was obtained in the lakes of Kumaon, Hindostan, at an eleva-
tion of from 4000 to 6500 feet above the sea-level, occurring there in such abundance
that the ordinary blue colour of the water was temporarily turned by their presence
to rusty red. From Ceratium furca, with which it rriost nearly corresponds, this
type is to be distinguished by the serration and the shorter proportional lengths of
the horn-like processes.

GENUS VII. DINOPHYSIS, Ehrenberg.

Animalcules encuirassed, having a transverse annular ciliated furrow
close to the posterior extremity, and joining this .on the ventral surface
a raised longitudinal perpendicular crest consisting of two membranous
plates, from the groove between which a single long flagellum takes its
origin. Inhabiting salt water.

It was first supposed by Ehrenberg that the animalcules referred by him to this
genus were most nearly allied to the Ophrydinae (Ophrydium and Vaginicola) though he
afterwards assigned them to their true places as here indicated. At the same time
the position and character of the cilia and flagellate appendage were not determined
or represented by him, although he predicated their existence in consequence of the
movements they exhibited. Claparede and Lachmann, to whom we are indebted
for a more accurate definition of the genus, and who have added to it many new
specific forms, fancifully compare the contour of its representatives to small lidded

* J. Levick on a new Rotifer, 'Midland Naturalist,' October, 1879.

GENUS DINOPHYSIS. 459

jugs ; adopting this simile, the inflated anterior portion is likened to the body of
the jug, the narrow discoidal part behind the annular furrow to the lid, and the
perpendicular membranous crest to the handle.

Dinophysis atlantica, Ehr.

Cuirass ovate, urceolate ; its surface densely shagreened, posterior
segment operculum-like, dilated, ventral plates with transverse decurrent
linear thickenings. Length 1-432". HAB. — Salt water : Newfoundland.

Excepting for its larger size this species is described by Ehrenberg * as correspond-
ing closely with Dinophysis Michaelis.

Dinophysis acuta, Ehr.

Cuirass ovate, acuminate posteriorly, the anterior margin plane, its
surface granulate. Length 1-576".

HAB. — Salt water : Baltic Sea, near Kiel (Ehr.).

As originally figured and described by Ehrenberg, f the anterior and posterior
extremities have been reversed in both this and the succeeding species, D. Michaelis.

Dinoflhysis Michaelis, Ehr.

Cuirass ovate, rounded posteriorly, the anterior border plane, slightly
wider ; surface granulate. Length 1-576".

HAB.— Salt water : Baltic Sea, near Kiel (Ehr.).

Dinophysis norvegica, C. & L. PL. XXV. FIG. 42.

Body compressed, pitcher-shaped, rounded anteriorly, the posterior
segment reduced to a simple concave plate ; the dorsal and anterior margin
supplemented by a thin, longitudinally striate and sometimes denticulate,
keel-like crest, which tapers off on the ventral side towards the abrupt
termination of the raised ventral plates ; ventral plates strengthened by
three transverse linear thickenings ; surface of cuirass coarsely shagreened.
Length 1-400". HAB. — Norwegian coast (Claparede & Lachmann).

Dinophysis ventricosa, C. & L.

Body compressed, pitcher-shaped, ventricose, the anterior extremity
frequently pointed, the posterior segment represented by a simple concave
plate ; no supplementary crest on the dorsal margin ; ventral plates with
three transverse linear thickenings ; surface of the cuirass coarsely
shagreened. Length 1-400".

HAB. — Salt water : Norwegian coast (C. & L.).

Dinophysis acuminata, C. & L. PL. XXV. FIG. 43.

Body compressed, pitcher-shaped, rounded anteriorly, more considerably
inflated on the dorsal side, supplemented at the antero-ventral angle with

* ' Monatsbericht Berliner Akademie,' 1854.
t ' Abhandl. d. Akad. Berlin,' 1839 and 1840.

460 ORDER CILIO-FLAGELLATA.

a projecting claw-like point ; no dorsal crest ; the posterior segment
rudimentary, consisting of a very narrow concave plate ; ventral plates
strengthened by one or two linear thickenings ; surface of cuirass finely
shagreened. Length 1-550".

HAB. — Salt water : Norwegian coast (Claparede & Lachmann).

Dinophysis rotundata, C. & L.

Body inflated, compressed, transverse annular furrow set further forward
than in D. acuminata, the posterior segment being in consequence of pro-
portionally larger size, its margin convex ; surface of cuirass coarsely
shagreened ; no keel-like dorsal crest ; ventral plates with two transverse
linear thickenings. Length 1-500". HAB. — Norwegian coast (C. & L.).

Dinophysis ovata, C. & L. PL. XXV. FIG. 43^.

Body ovate, compressed, two closely approximated spine-like processes
developed at the anterior extremity, the posterior segment convex, cap-
shaped ; surface of the cuirass finely shagreened ; no keel-like dorsal crest ;
ventral plates extending along two-thirds of the ventral border, strengthened
by two linear thickenings. Length 1-625".

HAB. — Salt water : Norwegian coast (C. & L.).

Dinophysis Isevis, C. & L.

Body suborbicular, compressed, surface of cuirass entirely smooth ;
ventral plates produced throughout almost the entire length of the ventral
border, strengthened with three linear thickenings ; posterior segment con-
spicuously developed, its margin slightly convex ; no dorsal crest. Length
1-400". HAB. — Salt water : Norwegian coast (C. & L.).

Dinophysis arctica, Mereschk.

Body broadly flask-shaped, inflated and widest anteriorly, contracted
posteriorly, scarcely one and a half times as long as broad ; ventral crest
largely developed, angular, and obliquely truncate anteriorly, traversed by
three transverse lines ; surface of cuirass finely shagreened throughout.
Length 1-600". HAB. — Salt water: White Sea (Mereschkowsky).

This species closely approaches D. lavis, but is to be distinguished from that
form by its smaller size, the shagreened character of the cuirass, and by the
diverse contour of the ventral plates.

Dinophysis caudata, S. K.

Body suburceolate, the region behind the transverse annular furrow con-
sisting of an inflated, urceolate, basal portion and an abruptly narrowed,
subcylindrical, ventrally curved, anterior prolongation ; a smooth, narrow
ridge produced along the dorsal border of the inflated portion of the posterior
segment, and on the opposite or ventral margin of the same region two
conspicuously developed fin-like ventral plates ; ventral plates angular,

GENUS AMPHIDINIUM—PROROCENTRUM. 461

equalling in breadth one-half of the diameter of the body, traversed by two
or three spine-like linear thickenings ; the entire surface of the posterior
segment distinctly shagreened ; the anterior segment concave, operculum-
like, dilated, its margins delicately striate in a longitudinal direction.
Length 1-212". HAB. — Saltwater: Adriatic.

This species has been obtained sparingly among the material originally collected
at Fano, in the Adriatic, by Count Castracane, and recently placed at the author's
disposal by Dr. Wm. J. Gray, F.R.M.S. From all the species previously described
it may be distinguished by the distinct narrower prolongation of the anterior
segment, which is, as it were, added on to the ordinary ventricose body of D.
norvegica or D. acuminata, and contributes substantially to its total length. The
ventral plates are also of much larger comparative size, resembling, in connection
with the two or three perpendicular spine-like linear thickenings, the elevated
dorsal fin of some Acanthophrygian fish. The smooth narrow ridge developed
along the dorsal margin of the body is undoubtedly homologous with the elevated
crest distinctive of this region in D. norvegica.

GENUS VIII. AMPHIDINIUM, C. & L.

Animalcules encuirassed, having a transverse annular, ciliated furrow
situated at the posterior extremity, as in the genus Dinophysis, the pos-
terior segment being in a similar manner almost entirely atrophied ; the
longitudinal ventral furrow, out of which the flagellum springs, represented
only towards the anterior extremity, and not joining the transverse annular
one ; no salient ventral plates. Inhabiting salt water.

Amphidinium operculatum, C. & L. PL. XXV. FIGS. 44-46.

Body oval, depressed, the ventral side slightly flattened, the dorsal one
convex ; posterior segment rudimentary, operculum-like ; the larger anterior
portion frequently containing a central dark brown structure, possibly the
endoplast, with radiating prolongations ; surface of cuirass entirely smooth.
Length 1-503". HAB. — Salt water : Norwegian coast (C. & L.).

Claparede and Lachmann found in company with the normal animalcules, as
above described, smaller perfectly transparent examples, having in some instances a
pyriform, and in others an almost orbicular contour; these they regard as mere
younger conditions of this species.

GENUS IX. PROROCENTRUM, Ehrenberg.

Animalcules encuirassed, cuirass consisting of a single continuous piece,
not divided as in the preceding genera by a transverse annular furrow ;
a stiff spine or tooth-like process usually developed at the anterior extremity
close to the insertion of the single flagellum. Inhabiting salt water.

Prorocentrum micans, Ehr. PL. XXV. FIGS. 37-39.

Cuirass oval, compressed, pointed posteriorly, the ventral border
flattened, the dorsal one convex, the anterior margin truncate, armed near

462 ORDER CILIO-FLAGELLATA.

the dorsal angle with a tooth-like process; surface of cuirass apparently
smooth in the living state, exhibiting delicate transverse striae when
isolated by maceration ; colour bright yellow. Length 1-430".
HAB. — Salt water.

According to Ehrenberg this species is highly phosphorescent. Claparede and
Lachmann have however failed to confirm the observations of the German authority.

Prorocentrum lima, Ehr.

Cuirass ovate, inflated and rounded posteriorly, becoming gradually
narrower towards the anterior region ; the anterior border slightly emarginate ;
surface sparsely asperate. Diameter 1-1152" to 1-864".

HAB. — Salt water, Adriatic. Colour yellowish-brown.

Doubtful Species.

The minute Prorocentrum viridis of Ehrenberg, reported to be of ovate or sub-
orbicular form with a rounded posterior and shortly pointed anterior extremity,
enclosing green granules, length i-noo", inhabiting the Baltic, is insufficiently
characterized for identification as a representative of this genus.

GENUS X. DIMASTIGOAULAX, Diesing.

Animalcules free-swimming, encuirassed, traversed by an equatorial
ciliated furrow ; flagella two in number, issuing from the same point of
origin in the equatorial groove; cuirass extended into horn-like pro-
longations.

Excepting for the presence of the two flagella, the as yet single known represen-
tative of this genus corresponds in form and structure with those of Ceratium.

Dimastigoaulax cornutum, Ehr. sp. PL. XXV. FIGS. 51 AND 52.

Cuirass compressed, quadrilateral, the dorsal surface convex, the ventral
one concave ; the anterior segment bearing two nearly straight horn-like
processes, and the posterior a single short median one, neither of them
exceeding one-half of the diameter of the body ; flagella subequal,
equalling or surpassing the body in length. Length 1-280" to 1-140".

HAB. — Fresh water; colour brown or slightly green.

This species, which is synonymous with the Peridinium cornutum of Ehrenberg,
Ceratium hirudinella of Dujardin, and Ceratium cornutum of Claparede and Lachmann,
has been selected by Diesing * as the type of the present genus on the strength of the
evidence concerning its possession of two flagella, yielded through the investigations
of Lieberkuhn and Claparede and Lachmann. It must be at the same time noted
that this evidence is by no means conclusive; the last-named authorities, while
figuring two flagella in the drawing, as here reproduced, were by no means certain
as to their existence, and did not feel justified, under such circumstances, in
connecting the species with a new generic title. The Peridinium Carolinianum,
found by Mr. J. W. Bailey at Grahamsville, South Carolina, and described under
the foregoing title in the ' Smithsonian Contributions to Knowledge ' for December
1850, is apparently identical with this type.

'Revision der Prothelminthen," ' Sitz. der Kaiser. Akad. der Wiss. Wien,' 1865.

GENUS HETEROMASTIX:. 463

In addition to his institution of the new genus Dimastigoaulax for the reception of
the species last described, Diesing, /. c., has further proposed to subdivide the family
of the Peridiniidse as here denned into several other subordinate genera. The
definitions submitted not, however, being the outcome of his personal acquaintance
with the organisms treated upon, but being based chiefly on the imperfect descrip-
tions of various earlier authorities, are not considered sufficiently reliable for adoption
in this treatise. An estimate of Diesing's proposed innovations in this direction may
be gathered from the fact that a new genus, Heteroaulax, is proposed by him for the
reception of the animalcules here included under the titles of Gymnodinium fuscum,
Peridinium (Glenodiniuni) inerme, and Glenodinium acuminata. That of Gonyaulax
for Peridinium spiniferum, that of Glenoaulax for Gymnodinium (Glenodiniuni) cequale,
and that of Proaulax for Gymnodinium corpusculum. At the same time the ordinary
horned and hornless representatives of the two genera Ceratium and Peridinium are
retained under the last-named generic title, while the genus Glenodinium is left in
the position originally assigned to it by Ehrenberg, the altogether unstable character
of the presence of an eye-like pigment-spot being cited as distinguishing it from
Peridinium.

Fam. II. HETEROMASTIGID-ffi, S. K.

Animalcules free-swimming, bearing one vibratile and one trailing
flagellum, these appendages being supplemented by an adoral fringe of
cilia ; oral aperture distinct, anteriorly located.

GENUS I. HETEROMASTIX, J.-Clk.

Animalcules naked, free-swimming, ovate or elongate, highly plastic and
changeable in form, metabolic ; flagella two in number, inserted close
together at the anterior extremity, one directed in advance, locomotive and
vibratory, utilized as a tractellum, the other one trailing in the rear,
gubernacular or anchorate ; a fringe of cilia extending on the ventral surface
from the point of insertion of the flagella towards the posterior extremity ;
endoplasm frequently enclosing a coloured eye-like pigment-spot ; oral
aperture situated close to the base of the two flagella.

Heteromastix proteiformis, J.-Clk. PL. XXIV. FIGS. 70 AND 71.

Body highly contractile, changeable in form, mostly elongate fusiform
or lanceolate, with a more pointed anterior extremity ; flagella long and
stout, the anterior one, or tractellum, vibratile, about twice the length
of the extended body, the trailing flagellum or gubernaculum about half
this length ; supplementary cilia produced along a longitudinal groove
which extends backwards on the ventral surface from the insertion of the
flagella through about one-half of its entire length; a red eye-like spot
usually present at the anterior extremity. Length of body 1-500".

HAB. — Fresh water.

This remarkable form, figured and described by Professor H. James-Clark in the
Memoirs of the Boston Society of Natural History for the year 1868, is among the most
interesting representatives of the Cilio-Flagellate group. With a flexible polymorphic
body most closely resembling that of an Astasia or EugZena, exhibiting likewise the
coloured pigment-spot of the latter genus, it possesses the two differentiated flagella,

464 ORDER CILIO-FLAGELLATA.

the one trailing and the other extensile and vibratile, of Anisonema, Heteromita, or
Heteronema. Superimposed on this we find an anterior adoral fringe of well-
developed cilia, the animalcule thus constituted representing an intermediate con-
dition or annectant type between the above-mentioned simpler Flagellata and the
more highly organized Ciliata. Upon this accessory ciliated fringe there appears,
according to Professor Clark's description, to devolve the chief task of locomotion,
the extended and longer anterior flagellum being used more exclusively as a tentative
and prehensile organ. As reported by this authority, the animalcule furthermore
displays much intelligence in the use of its tactile flagellum, turning and twisting it
about, and feeling with it in every direction with as much seeming consciousness as is
shown by an elephant in the control of its proboscis. No details concerning the posi-
tion or existence of a contractile vesicle or endoplast have yet been recorded, nor any
data relating to the phenomena of development and reproduction. Professor James-
Clark has unfortunately omitted to mention whether the endoplasm of this interest-
ing species is coloured green or transparent. , It structural affinities being evidently
nearest to Heteromma, it might be anticipated, in correlation with their structure,
that this element is colourless. At the same time, the development of an anterior
eye-like pigment-spot is more commonly associated with the chlorophyllaceous
forms.

Fam. III. MALLOMONADIDJE, S. K.

Animalcules free-swimming, bearing a single long,' terminal flagellum ;
entire cuticular surface covered with long, flexible, setose cilia.

GENUS I. MALLOMONAS, Perty.

Animalcules free-swimming, oval or elliptic, persistent in shape ; cuti-
cular surface indurated, clothed with long, non- vibratile, hair-like setae ; a
single long vibratile flagellum produced from the anterior extremity ;
contractile vesicle indistinctly developed. Inhabiting fresh water.

Mallomonas Plosslii, Perty. PL. XXIV. FIGS. 72 AND 73.

Body ovate or elliptical, slightly narrower anteriorly ; cuticular surface
finely shagreened or crenulate, thickly clothed with fine, hair-like setae,
whose length is less than that of the body ; flagellum long and slender,
retractile ; endoplasm vacuolar, amber colour or greenish yellow ; contractile
vesicle indistinct, posteriorly located. Length of body i-iooo" to 1-900".

HAB. — Marsh water.

Having, in February 1878, obtained an animalcule from marsh-water from Le
Marais, Jersey, which is undoubtedly identical with the Mallomonas Plosslii of
Perty, the author is enabled to furnish a more accurate description and delinea-
tion of this singular form than has been hitherto supplied. Turning attention
first to the cuticular investment, its indurated character has been clearly demon-
strated through the discovery in abundance in the same water of the empty
skins, either nearly whole or in fragments with angular fractures, as left after
the decay of the living contents. To these cuticular fragments the hair-like seta?
were likewise attached, in a more or less perfect state, indicating not only their
rigid and durable consistence, but also their original derivation from this cuticle and
not from the underlying endoplasm, as was at first suspected by an examination of
living examples only. Perty's testimony respecting the apparently crenulated aspect
of the peripheral border was fully confirmed and explained by the employment of a
high magnifying power, when it was shown that the whole surface of the cuticle is

GENUS MALLOMONAS. 465

ornamented or shagreened with closely approximated hemispherical elevations, each
of which forms a basis of support to the overlying seta. In this respect the cuticular
investment of Mallomonas exhibits a structure corresponding closely with that
of many Holotrichous Ciliata, in which the cilia or setae spring from similar
hemispherical cuticular elevations, the cuticle however, in most instances, remaining
soft and plastic. Examined in the living state the animalcules were found to exhibit
diverse phases of comportment. Sometimes they remained quiescent, with the flagel-
lum entirely retracted within the perforation or oral cleft at the anterior extremity
of the hardened cuticle, while at other times this organ was extended and rapidly
undulated or vibrated. In the former of these instances the quiescent animalcule
with its extended setae and retracted flagellum, except for its colour, presents an
aspect closely similar to that of the Holotrichous Cychdium glaucoma. On abandoning
this quiescent for a motile state, the hitherto erectly extended setae are, as the
animalcule progresses in an even, straightforward course through the water, reflected
backwards, as shown at PI. XXIV. Fig. 73. At first it seemed as though the little
creature possessed an active control over these appendages, and could erect or
depress them at will. The subsequent determination, however, of the relationship
subsisting between the setae and the indurated cuticle, as already described,
precludes such an interpretation, and it is evident that this reflection of the
setae must be accounted for simply by their yielding before the pressure of the
water during locomotion.

The interior parenchyma or endoplasm of the specimens examined was found to
consist of an apparently homogeneous, clear, greenish-yellow plasma, one or two
slowly contracting vacuoles within the same being detected towards the posterior
extremity of the body. Other vacuolar spaces, of a non-contractile order, were
scattered irregularly throughout its substance. By Perty the animal or vegetable
nature of Mallomonas was left undecided. Although the inception of food-particles
was not witnessed, the evident control exerted by this organism in its movements
leaves no doubt as to its true animal nature.

Stein * has attempted to identify Mallomonas Plosslii with the disintegrated and
metamorphosed zooids of Synura uvella. Such an identification, however, in face
of the evidence here brought forward," cannot be maintained. Mallomonas
proper never possesses but a single flagellum, while the characteristic setae exhibit
a uniform size and symmetrical plan of disposition altogether distinct from that
pertaining to the metamorphosed zooids of Uvella, as figured by this authority.

Supplementary Species.

Fresenius f has figured and described an animalcule which he refers to this form,
which on further investigation will probably prove to be a second species. The
hair-like setae in this type are represented as fully equal in length to or longer than
the body, and comparatively few, thirty being the greatest number counted by him,
while considerably less are given in his figures ; the two anterior of these are,
however, described as being usually directed forwards, like antennae, on each side
of the flagellum. It is proposed to provisionally distinguish this animalcule by the
title of Mallomonas Fresenii. A delineation of this species or variety, reproduced
from the figures of Fresenius, is given at PI. XXIV. Fig. 74.

Fam. IV. STEPHANOMONADID-ffi, S. K.

Animalcules free-swimming, bearing a single terminal flagellum, the
base of which is embraced by a brush-like fascicle or uninterrupted circular
wreath of cilia.

* ' Infusionsthiere,' Abth. iii., 1878.

t ' Beitrage zur Kenntniss mikroskopischer Organismen,' Frankfort, 1858.

2 H

466 ORDER CILIO-FLAGELLATA.

Divested of their flagellate appendages, the as yet but little known representatives
of this small family group would bear a marked resemblance to such free Peritricha
as Strombid'nnn and Halteria, and it is not improbable that the transition or line of
evolution from the Flagellata to the above-named group of the Ciliata is accom-
plished in this direction.

GENUS I. STEPHANOMONAS, S. K.

Animalcules free-swimming, more or less ovate, bearing a crown or
wreath of cilia at the anterior extremity of the body, from the centre
of which a single persistent flagellum takes its origin ; the remaining
surface of the cuticle entirely smooth.

This genus is instituted for the form referred with some doubt by De Fromentel *
to the genus Trichomonas under the title of T. locellus ; the symmetrical, crown-
like disposal of the cilia and single flagellate appendage at the anterior end of the
body serve at once, however, to distinguish it from all the members of that generic
group. It is possible that the Asthmatos ciliaris of Salisbury is identical with, or
closely allied to this same form, though in that type both the flagellum and cilia
appear to be much more fugacious in character.

Stephanomonas locellus, From. sp. PL. XXIV. FIG. 69.

Body ovate or pyriform, truncate and slightly narrower anteriorly ;
about twice as long as broad, the posterior region rounded and inflated ;
ciliary wreath symmetrical, encircling the anterior border ; flagellum thickest
towards the base, scarcely exceeding the length of the body ; endoplasm
transparent, granular. Length 1-800". HAB. — Fresh water.

This species, as above intimated, is identical with the Trichomonas locellus of
De Fromentel. The Trichomonas minima of the same writer, somewhat resembling
the present form, but of apparently considerably smaller size, and in which the
central flagellum was not distinctly observed, represents possibly a second species
of the genus Stephanomonas. De Fromentel's Trichomonas hirsuta, with non-vibratile
cilia clothing the entire cuticular surface, is apparently more closely related to his
own Trichomma hirsuta, presently described.

GENUS II. ASTHMATOS, Salisbury.

Animalcules free-swimming, ovate or spherical, bearing a terminal crest
or brush-like fascicle of long, vibratile, retractile cilia, which is supplemented
by a central, long, extensile flagellum or proboscis-like process ; the
remaining cuticular surface naked, soft and plastic, permitting the body to
assume various outlines.

The aspect of the as yet single known species of this genus, as described and
figured by Dr. Salisbury in Hallier's ' Zeitschrift fur Parisitenkunde,' Bd. iv. 1873,
conforms so closely, when the flagellum or so-called proboscis is retracted, with such
Ciliata as Strombidium or Mesodinium, that it was at first proposed to refer the type
to the Peritrichous order. The supplementary appendage named, however, agrees
so essentially in nature with that of an ordinary but somewhat thickened flagellum,
and the cilia themselves possess in their retractile capacity so distinct and it may be

* ' Etudes sur les Microzoaires,' Paris, 1876.

GENUS ASTHMA TOS. 467

said less permanent a character than is met with among the Peritricha, that its refer-
ence to the present intermediate group, sharing the characters of both the Ciliate and
Flagellate infusorial orders, seems desirable. Both the central flagellum and
surrounding fascicle of cilia would seem to manifest in their capacity of retraction
and temporary obliteration a certain correspondence with the similarly retractile
flagellum and associated collar of the order of the Discostomata, which has been
already briefly referred to, see p. 329, in connection with that group.

Asthmatos ciliaris, Salisbury. PL. XXIV. FIGS. 62-64.

Body usually ovate or subspherical, but plastic and changeable in form ;
anterior fascicle of cilia brush-like, long and flexible, the length of the
constituent cilia, when fully extended, equalling that of the body ; flagellate
appendage usually central, but sometimes developed toward one side of the
anterior border, thick at its base, and gradually tapering to the apical
extremity, exceeding the length of the body when fully extended ;
endoplasm finely granular, enclosing one or more vacuolar spaces or
nucleolar bodies. Length 1-1200".

HAB. — Occurring as a parasitic form in the mucous fluid of the eyes,
nose, and throat of the human subject.

This remarkable animalcule is described by its discoverer, Dr. J. H. Salisbury,
in the publication above quoted, as constituting the essential cause of certain forms
of hay-fever, which he proposes to distinguish as " infusorial catarrh and asthma."
This decision is arrived at by him, not through the detection of the animalcule in
connection with a single instance only of the above affection, but from its invariable
presence in large quantities in as many as sixty cases successfully treated by him,
extending over a period of six years, and in all of which instances the recovery of
the patient speedily followed the application of remedies causing the death of the
animalcules. The diagnosis of the disease, as given by Dr. Salisbury, may be thus
abbreviated : The ailment first attacks the mucous surfaces of the eyes and nose,
causing a free secretion of tears, and frequently intense paroxysms of sneezing.
From the nasal passages the affection extends to the fauces, larynx, trachea, and to
the larger and smaller bronchi; burning heat and irritation, accompanied by
violent coughing, attend its arrival at the first-named locality, while upon, reach-
ing the larger bronchi the symptoms exhibited are very similar to those of
"catarrhal fever." Finally invading the smaller bronchi and air-cells, asthmatic
symptoms predominate, associated with intense suffering, which is more particularly
aggravated by exposure to the night or evening air. Relief was invariably afforded
and a speedy cure effected in even the most distressing cases by the frequent
inhalation, every hour or two, of a solution of either carbolic acid, tincture ferri
chloride, sulphuric, hydrochloric, or nitric acids, the solution in either case being
sufficiently weak to avoid irritation during the inhalement. Two grains of quinia
sulphate every four hours, or twenty drops of tincture ferri chloride in a glass of water
morning, noon, and night, further accelerated the recovery of the patient. The
sputa or mucus from the affected parts, examined before and after the first
inhalation, demonstrated the presence in the former instance of the animalcules in
an actively motile state, while in the latter instance they were mostly dead or
motionless, and speedily succumbed to further applications of the remedy. In
connection with the more ordinary and milder form of hay-fever, occurring usually
during the latter end of May and through June, accompanied by violent sneezing
and painful inflammation with the corrosive discharge from the nasal mucous
membrane, Professor Helmholtz * has detected the presence within the nasal

* See ' Nature,' May I4th, 1874.

468 ORDER CILIO-FLAGELLATA.

secretion of innumerable vibrio-like bodies, not observable at other times ; these
were readily destroyed and the hay-fever symptoms cured by administration three
times daily, with a nose-douche, of weak solution (i'8oo) of sulphate of quinine.
The best effects were obtained through applying the solution in a tepid form.

The manner in which Asthmatos ciliaris reproduces its kind is, in accordance
with Dr. Salisbury's account, somewhat remarkable. A single young one at a
time is, he relates, developed inside the parent, and is when mature discharged
posteriorly through the body-wall of the latter. His woodcut illustration of this
liberation of the newly formed animalcule, reproduced at PI. XXIV. Fig. 64,
would seem, however, to represent an instance of ordinary transverse fission similar
to that exhibited by Halteria or Strombidium, and in which the body, becoming
elongate, is constricted centrally, the constriction being accompanied by the growth
of a new circlet of cilia. The newly produced zooids are described as being much
more active than the older ones, rolling from side to side in an oscillating manner,
while the movements of the parents are chiefly tremulous or vibratory.

So recently as November 1880, the author's attention has been directed by
Dr. Joseph Leidy to a communication concerning this singular organism contri-
buted by him to the ' American Journal of Medical Science,' p. 85, for the year
1879. In this communication the claim of Asthmatos for recognition as an
independent protozoic structure is not admitted, Dr. Leidy expressing himself
satisfied that the so-called animalcules, as first described by Dr. Salisbury, represent
merely detached ciliated epithelial cells from the air-passages, more or less modified
by the catarrhal affection. This decision he arrives at not merely from an
analysis of Dr. Salisbury's description and accompanying figures, but — having
been himself affected by an autumn catarrh for many years — through an intimate
acquaintance with an apparently identical organism produced abundantly in his
own person, which he unhesitatingly identifies with ordinary or more or less
deformed ciliated epithelial cells. While the evidence submitted by Dr. Leidy
is here accepted as strongly supporting this epithelial interpretation, one or two
points connected with Dr. Salisbury's original description of Asthmatos leave room
for justifiable doubts as to whether or not two distinct organisms have been
examined by these respective observers. Thus, the production of young from the
parent's body, or, as it is here interpreted, the phenomenon of transverse fission
accompanied by the development of a posterior ciliary circlet, recorded by
Dr. Salisbury, is altogether at variance with the ordinary comportment of detached
epithelial cells; added to which it must be observed that in none of the numerous
figures given by Dr. Leidy is any indication given of the so-called proboscis or
flagellate appendage which constituted an essential feature of the innumerable
examples examined by Salisbury. It may be further mentioned, that reference is
made by Dr. Leidy to a communication, entitled ' Rhizopods (Asthmatos ciliaris} a
cause of Disease,' published by Dr. Ephraim Cutter, of Boston, in the ' Virginia
Medical Monthly' for November 1878, and in which this last-named authority
having, in company wth Professor P. F. Reinsch of Erlangen, examined numberless
examples, arrives at the conclusion that the organism is a Protozoon allied to
Actinophrys, referring the more precise identification of its nature and position to
Dr. Leidy. That infusorial animalcules exist which correspond in all essential
points with the isolated cellular elements of ciliated epithelium, is abundantly
manifested in such isomorphic types as Magosphczra planula and Lophomonas
blattarum, which forms again, excepting for the presence of the more ordi-
narily developed flagellate appendage, the Asthmatos ciliaris of Dr. Salisbury closely
resembles.

Fam. V. TRICHONEMIDJE, S. K.

Animalcules free-swimming, bearing a single terminal flagellum, the
remainder of the cuticular surface more or less completely clothed with
cilia.

GENUS TRICHONEMA—MITOPHORA. 469

The members of this group, as typified by the genus Trichonema of De
Fromentel * may be said to bridge over the gap between the ordinary Flagellata
and Holotrichous Ciliata, in the same manner as the Stephanomonadidce connect
them with the Peritricha. In the absence of the flagellum the animalcule in
question would scarcely be distinguished from a minute Trachelophyllutn or other
representative of the Holotrichous order.

GENUS I. TRICHONEMA, De Fromentel.

Animalcules free-swimming, more or less ovate, elastic and changeable
in form, bearing a single flagellum at the anterior extremity ; the entire
cuticular surface clothed with short cilia ; oral aperture distinct, situated at
the base of the flagellum.

Trichonema hirsute, From. PL. XXIV. FIGS. 65 AND 66.

Body when extended subpyriform or ovate, most usually rounded and
inflated posteriorly, narrower and attenuate anteriorly, contracting to an
almost globular form ; endoplasm hyaline, granular ; flagellum long and
slender, about twice the length of the body, rigid at its base, very flexible
and undulating at its distal extremity ; cuticular cilia short and apparently
non-vibratile ; oral orifice represented by an obliquely oval excavation,
situated at the base of the flagellum ; contractile vesicle posteriorly located.

Length 1-800". HAB. — Fresh water.

GENUS II. MITOPHORA, Perty.

Animalcules free-swimming, persistent in shape, elongate-ovate or
pyriform, bearing a single terminal flagellum which is supplemented by a
lateral or more or less complete peripheral fringe of vibratile cilia.

In the single type referred to this genus by Perty, a considerable range of varia-
tion is, in accordance with his accompanying figures, exhibited in the development of
the accessory cilia. In some instances these appendages are represented as forming
a short lateral fringe only, while in others they constitute an almost complete
peripheral series. It would seem, indeed, not altogether improbable that these cilia
entirely clothe the cuticular surface as in Trichonema, from which generic type it
would then be distinguished only by its persistent shape.

Mitophora dubia, Perty. PL. XXIV. FIGS. 67 AND 68.

Body clavate or pyriform, sometimes curved, from two to three times
as long as broad ; flagellum produced from the thicker of the two
extremities, sometimes with a knob-like distal termination ; lateral ciliary
fringe conspicuous, variably developed ; endoplasm enclosing green granules.
Length 1-450". HAB. — Fresh water ; movements slow and rotatory.

Some uncertainty is attached to the identification of the anterior and posterior
regions of this animalcule, Perty correlating with the latter the extremity bearing
the flagelliform appendage. In one of his figures, however, a notch-like excavation
is indicated close to this organ, and this not improbably represents an imperfectly
observed oral aperture.

* ' Etudes surles Microzoaires,' Paris, 1876.

APPENDIX TO VOL. I.

THE MYXOMYCETES OR MYCETOZOA.

AT pages 41 to 43 and 193 of this volume (published in Parts I. and II., October
and November, 1880), the Myxomycetes or Mycetozoa have been somewhat exten-
sively referred to as exhibiting, in accordance with the researches of De Bary and
Cienkowski, so close an affinity with the typical Flagellate Infusoria that they cannot
be consistently retained in their old place among the Gasteromycetous Fungi, but
must be advanced to a position among the Protozoa at no very remote distance from
the group Spongida. In the pages of ' Grevillea,' for December 1880, the editor,
Dr. M. C. Cooke, has, as a mycologist, lodged a somewhat strong protest against the
proposed transfer, arguing that more substantial evidence than a mere citation of
these continental authorities is required to prove the animal nature of these
organisms. In the 'Popular Science Review' for April 1881,* the author has, in a
re'sumd of the structural and developmental features of the Myxomycetes, fully
replied upon all the points raised by Dr. Cooke, and added to the evidence pre-
viously adduced the record of a recent personal investigation of the developmental
phenomena of several Myxomycetan types, including more especially the Physarum
tussilaginis of Berkeley and Broom,f originally discovered in this country by
Mr. Thomas Brittain of Moss-side, Manchester, and to whom the author is indebted
for the receipt of authenticated specimens. The results obtained through the
careful cultivation of the spores of this species have so fully confirmed and added
to the testimony first submitted by De Bary and Cienkowski, that the author is
prepared, even more confidently than hitherto, to support the animal interpretation
of their nature and affinities. A brief abstract of the developmental data recorded
by the author in connection with this species is herewith reproduced.

The spores in question — primarily enclosed in a depressed sessile sporangium
having a delicate membranous wall studded with minute stellate spiculae % — were
sown in distilled water on ordinary slides, covered with thin glass, and kept when not
under direct examination in a moist chamber. So soon as within seven hours after
wetting them, or indeed directly following their deposition on the slide, an examin-
ation revealed the companionship of innumerable quiescent Bacteria, with a more or
less abundant sprinkling of spores other than those of Physarum, and of consider-
ably smaller size. The spores specially sown, having a diameter of 1-2000" to
1-1500", were found, under high magnification, to consist of an outer wall of con-
siderable thickness, finely echinulate externally, and exhibiting, by transmitted light,
a dark amber or chitinous coloration. The protoplasmic contents rarely entirely
filled the outer shell, but remained separated from it by a greater or less number of
angular interstices. A central spheroidal nucleus, with a contained nucleolus, one
or more large refringent corpuscles, and numerous smaller granules, represented the
sum-total of the recognizable internal elements. By the end of the second day
active life had already dawned upon the scene. Bacteria were swiftly propelling
themselves to and fro in all directions ; one or two biflagellate monads, Heteromitce,
whose development was subsequently traced from certain of the smaller spores above
mentioned, glided slowly along, dragging their posterior flagella, " gubernacula,"
cablewise behind them. Sparsely scattered amongst the spores of the Myxomy-

* "The Myxomycetes or Mycetozoa; Animals or Plants?" by W. Saville Kent, F.L.S., &c.,
' Pop. Sci. Rev.,' New Series, vol. v. No. xvii. pi. iii. and iv., 1881.

t 'Ann. Nat. Hist.,' p. 139, Feb. 1856. J ' Pop. Sci. Rev.,' pi. iv. figs. 30-35.

APPENDIX. 471

cetan were presently observed isolated hyaline protoplasmic spheres having the
same diameter and structure as the contents of the spore-cases, just described. In
a little while the exit of one of these hyaline spheres from the echinulate spore-cases
was witnessed, and the relationship between the two substantially established.

By the termination of the third day, these protoplasmic spheres had much
increased in number, some of them exhibiting feeble amoeboid movements. An
additional factor had, however, now appeared upon the scene in the form of a
vermicular monadiform organism, having a length of 1-1250" to i-iooo", and
which progressed somewhat clumsily through the water revolving on its longitudinal
axis. A spheroidal nucleus, with its enclosed nucleolus, was observable towards
the anterior extremity, and a single rhythmically contracting vesicle at the opposite
region of the body. The derivation of these monadiform beings, from the extruded
protoplasmic spheres, was immediately suspected, and the correctness of this
inference soon substantiated. Selecting an isolated and recently extruded sphere,
it was carefully watched. For a considerable interval the newly released germ
confined its signs of vitality to a feeble expansion and contraction of its peripheral
margin, and to the rhythmical pulsations of its contractile vesicle, which, with the
spheroidal endoplast, were clearly discernible. As time progressed, alterations in
contour were more strongly manifested, though without the germ moving away from
the scene of its birth. At length an altogether elongate amoeboid, or vermiform
aspect predominated, the nucleus or endoplast being shifted to one extremity and
the contractile vesicle occupying the other. Then, all at once, a flickering at one
end indicated the development of a flagellate appendage, which in a few seconds
became distinctly visible. The vibratile motion of this organ soon caused the body
to oscillate, and presently lifting it from its hitherto prone position, it was launched
into the surrounding water a free-swimming, elongate monad. During the next
few days, similar monadiform germs were developed abundantly from the spores in
all parts of the field, and the next step in their ontogeny fully certified. It was found,
in fact, that the free-swimming condition of the germs was but of brief duration, and
subservient, apparently, only to their local distribution. Within a day or two,
the monadiform beings once more betook themselves to a repent mode of existence,
the flagella being for a while retained, communicating to them a remarkable likeness
to the repent flagelliferous animalcules heretofore described under the generic titles
of Mastigamxba and Reptomonas. The flagella being next completely withdrawn, the
organisms became undistinguishable from ordinary Amcebce, and continued to creep
about the field by broad, ovate extensions of their periphery.

An important point yet remained to be solved. De Bary and Cienkowski had
declared that during both their monadiform and subsequent amoeboid phases the
Myxomycetes ingested and subsisted on solid food. This evidence has been
regarded by some writers as extremely doubtful, while by others it has been
emphatically denied. A simple experiment, however, soon demonstrated that these
two authorities were again completely in the right. Examples, more especially of
the repent amoeboid units, had been previously observed, whose bodies contained
vacuoles more or less completely filled with ingested Bacteria, which, being produced
in numbers prior to the hatching out of the Physarum germs, provided for the
Mycetozoa an abundant and ready set feast The common test of adding pulverized
carmine to the water, was speedily followed by its free ingestion by both the
natatory monads and the repent amcebiform units, the former incepting it chiefly
towards the anterior region of the body, and the latter indifferently at any point of
their periphery. As in the case of Bacteria, the smaller particles of pigmentary
matter, after inception, were usually collected together within spheroidal vacuoles
of the endoplasm, and maintained there the same molecular movements they
exhibited in their free condition. The larger particles, on the other hand, remained
distributed as more or less distinctly isolated fragments. For the next few weeks,
these amoeboid organisms continued to feed and increase in size, and were fairly
started on their way towards the succeeding chapter in their ontogeny, viz. their
production, through coalescence, of the comparatively colossal but still amcebiform
" plasmodia," out of which the spore-receptacles or sporangia are finally evolved.

472

APPENDIX.

The points concerning the development and nutritive phenomena of the Myxomy-
cetes thus verified through personal investigation, are accepted by the author as
affording the strongest confirmation of his views previously expressed, to the effect
that these organisms have nothing whatever to do with Fungi, but are rightly refer-
able to the Protozoic division of the animal series. Among these, their correlation
may be accomplished with the utmost ease, their entire life-cycle, indeed, being
precisely parallel in kind, though differing in degree, with what obtains among the
ordinary Flagellate Infusoria. A primary flagelliferous phase, an intermediate repent
amoeboid condition, and a final encysted sporiferous state, these three represent the
normal life-cycle of either a Myxomycetan or a simple monadiform animalcule.
The only distinction manifested on the part of the Myxomycetes, and that, as just
stated, being one only of degree, and not of kind, consists in the fact that the
final act, that of encystment, and the resolution of the body into spores, is in this
group accomplished by a mass of coalescing or conjugating units, which conse-
quently produce a relatively colossal spore-receptacle or sporangium — the so-called
Fungus — while in the case of the typical Flagellata it is an isolated monad, or two
or a few conjugated units only, that build up the relatively minute, but otherwise
morphologically and physiologically identical reproductive structure.

In every structural detail, and in every successive stage of their life-history, the
Myxomycetes or Mycetozoa, from their first exit from the spore until their final
resolution into similar reproductive elements, may be consistently correlated with
the typical Protozoa, and with them alone. While in their compound aggrega-
tion, their production of a horny rete or capillitium, and frequent excretion of spicular
elements, a departure is made in the direction of the Sponges, the simply flagellate
condition of the spore-derived units, and the capacity possessed by them to ingest
food-substances at all parts of their periphery, demonstrate their nearest affinity
with the simple Flagellata Pantostomata, and of which they may be accepted as
representing the most complex factors.

This decision arrived at by the author concerning the affinities of the Myxomy-
cetes receives additional and highly substantial support in connection with the
description, by Surgeon-major D. D. Cunningham, of the life phenomena of certain
microscopic organisms developed in the intestinal canal and faecal evacuations of
man, cows, and other animals, recorded in the ' Quarterly Journal of Microscopical
Science' for April 1881.* Under the title of Protomyxomyces coprinarius, is therein
described an organism which, while presenting an infinity of polymorphic expres-
sions, is reducible in a like manner to the three component terms common to
the two groups of the Myxomycetes and ordinary monads, and which, indeed,
as intelligently recognized by Dr. Cunningham, occupies a position precisely
midway between these two series. With the typical Myxomycetes, Protomyxomyces
agrees in so far as that the usually relatively large sporangium represents the
final disintegration into spores of a multitude of closely associated amoeboid
elements, surrounded by a common membranous envelope studded with organic
granules, these amoeboid elements having again commenced existence as simple
flagellate monads — Dr. Cunningham's so-called "zoospores." From the typical
Myxomycetes, on the other hand, Protomyxomyces differs in that the amoeboid
beings thus building up the compound sporangium do not coalesce intimately with
one another so as to form a common plasmodium, but, while closely approximated,
remain individually distinct, each amoeboid unit separating into an independent
spore-mass after the manner of the typical Flagellata.

* First published as an Appendix to the " Fifteenth Annual Report of the Sanitary Commission
of the Government of India."

END OF VOL. I.