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NATURAL HISTORY

OF THE

UNE ED STATES.

CONTRIBUTIONS

THE NATURAL HISTORY

UNITED STATES OF AMERICA.

BY

LOUIS AGASSIZ.

SECOND MONOGRAPH.

IN FIVE PARTS.—I. ACALEPHS IN GENERAL.—II. CTENOPHORZ.—III. DISCOPHORA.—IV. HYDROIDZ.
—V. HOMOLOGIES OF THE RADIATA;-WITH FORTY-SIX PLATES.

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LID LL Eo BROWN CAND @COMP ANY.

LONDON: DRY BNR. & CO.
1860.

Entered according to Act of Congress, in the year 1860, by
LOUIS AGASSIZ,
In the Clerk’s Office of the District Court for the District of Massachusetts.

_—

CAMBRIDGE:

ALLEN AND FARNHAM, PRINTERS.

PREFACE.

Wuite most readers seeking comprehensive information may have had their attention
drawn to the generalizations contained in the first part of this work, the naturalists who
have studied the second and third parts may have noticed that the subjects under consider-
ation there are treated in a different manner from that generally adopted in similar investi-
gations. Confident that what have been called our classifications are in reality the various
readings of a system which truly exists im nature, I have endeavored to show, that, in
arranging their systems, zodlogists have unconsciously followed great natural relations in the
animal kingdom, and that what they have supposed to be their invention was only their
instinctive perception of an order which unites under a consistent plan all the isolated facts
studied by them. My first step in the attempt to demonstrate this proposition was to collect
all the facts relating to our science and to compare them carefully with the systems, testing
the one by the other. By the coincidence of the two I hope to have proved that the Power
which originated the facts must also have originated the ideas expressed in the systems; and
that the latter are true only so far as they adhere to the great system of Nature from which
they have been transcribed. The first monograph, limited to a single Order, afforded, how-
ever, a meagre field for such a demonstration; though it was broad enough to allow of
the attempt without modifying too much the usual mode of treatment of such subjects.
But finding, after many years’ application of that method in my own investigations, that,
far from complicating my studies, I only derived daily additional facilities in tracing the
manifold relations which unite all kinds of natural groups among animals, I have resolved
upon combining, through the presentation of a whole Class, the description of the facts, with
a critical analysis of their meaning, as far as they have a bearing upon classification. How
successful the attempt has been, time will show.

In selecting the class of Acalephs for such an experiment on a larger scale, I was influ-
enced by the circumstance that these animals had attracted my special attention for many

years past; and that, being particularly familiar with them, it was easy for me to treat

vl PREFACKH.

them as known quantities. Besides this, they afforded in themselves a rich field for extensive
comparisons with numerous other classes, with which some of their number had been asso-
ciated at different times. And again, their remarkable modes of development could not
fail to bring to a test the value of the changes which they undergo during their growth
for the purpose of ascertaining the affinities and relative rank of animals. The circumstance
that the study of this class has received less attention in America than any other, had
also much weight with me, as it gives me an opportunity of making our students more
intimately acquainted with those naturalists, who, in Europe, have given a new aspect to
Zoblogy since the days of Cuvier, and who, not being ornithologists, entomologists, or
conchologists, are hardly known here as they should be; for it is much to be regretted,
that, with the Anglo-Saxons, Zotlogy has now become too much a descriptive or too much
a speculative science.

To the general reader the first part of this volume may be of some interest, inasmuch
as it presents a general account of the progress of Zodlogy since the time of Aristotle to
the present day with special reference to the class of Acalephs, including, besides, such
generalizations as may be deduced from a comparison of these animals with the repre-
sentatives of other classes. ‘To the professional naturalist I venture to recommend the
second part as containing additional information respecting the structure of the Ctenophorie
not to be found in previous contributions to their natural history, and I ask especial
attention to the discussions in which the value of the natural groups admitted in that
Order is considered in detail.

In the preparation of this part of my work I have received much valuable assistance
from my friend and colleague, Professor H. J. Clark, who has traced with me, for more
than nine years, the metamorphoses of our Acalephs, and especially those of the Hydroids ;
besides which he has investigated for himself some special points of their structure, which are
noticed as his contributions in the proper place: but I would particularly call attention to
the description of the lasso-cells of the Ctenophore on page 237, and to the investigation
of the structure of the eye of our Aurelia, which will be published in the next volume,
and the illustrations of which, drawn by him, Pls. XIb, and XI*., are issued with this
volume.

Most of the plates were drawn from nature and on stone by Mr. Sonrel; and it is
but justice to him to say, that I do not know representations of Acalephs executed with
greater accuracy, patience, and skill. Only those fully conversant with the whole range
of our literature on this subject can do complete justice to their great merit; and I can
truly say, that, without the aid of his persevering zeal, I could not have accomplished
what I aimed at in this volume.

I have, further, derived much assistance in my work from the liberality of the Smith-

sonian Institution, in lending me books not to be found in the libraries of Boston and

PREFACE. vil

Cambridge. The collection of scientific periodicals of the Smithsonian Institution is un-
questionably the largest on this continent, and but for the wise policy of Prof. Henry, the
enlightened head of that establishment, the naturalists of America could not at this time
make any investigations involving historical researches. Next to the Smithsonian Institution
I have to mention the Academy of Natural Sciences in Philadelphia, the library of which
has acquired the highest importance for naturalists, through the liberality with which Dr.
Wilson has supplied its wants.

The Museum of Comparative Zodlogy in Cambridge contains specimens of all the
Acalephs described in this work which could be preserved. And I would take this oppor-
tunity to say, that, with proper care, a much larger number of these animals may be
preserved in a state fit for study than is generally supposed. Valuable speciinens were
sent to me by Professor J. Leidy, collected by him in Long Island Sound and along the
shores of the Middle States, some of which he has himself described in his contributions
to the Marine Faune of Rhode Island and New Jersey. Others, from the same localities,
were presented to me by Mr. Samuel Powel of Philadelphia, among which I would
especially mention the Cordylophora described by Prof. Leidy. To my friend Theodore
Lyman I am indebted for fine specimens of several Hydroids of the Bay of Boston, and
to Mr. William Stimpson for others from the eastern shores of the Northern States. To
my friend 'T. G. Cary, and to my son Alexander Agassiz, who have enriched the Museum
of Cambridge with immense collections from California, I owe many specimens of Acalephs
from the west coast of North America. Captain W. H. A. Putnam, of Salem, to whom
our Museum is indebted for the most valuable collections from the Indian and Pacific
Oceans, has brought me a number of Medusee and Hydroids from the East Indies and
from the Gulf Stream, which, after years, are still in a good state of preservation. To
Mr. John MeCrady I am indebted for an early communication of his contributions to the
history of the Acalephs of South Carolina. I would add also, that in the Aquarial
Gardens of Boston I have frequently had opportunities of observing many of our Hydroids
and Meduse in a fine state of preservation.

It is but proper, that, in leaving this volume to speak for itself, I should also mention
the facilities constantly afforded me by the publishers for making it as worthy as possible
of the extensive patronage it has received.

LOUIS AGASSIZ.
CAMBRIDGE, October 31, 1860.

TABLE GF CONTENTS.

Je pad ciel Oh oad Ls

ACALEPHS IN GENERAL:

CHCA R TBR es ale

HISTORY OF OUR KNOWLEDGE OF THE ACALEPHS.

Section 1. Period of Aristotle and the Roman natu- | Section 3. The naturalists of the eighteenth century. —

ralists. — We find unquestionable evidence in Aristotle’s Linneus gives character and importance to the study
History of Animals that he knew the Radiates now of Natural History, by the publication of the “ Sys-

called Acalephs by systematic writers, though this name tema Nature.” His pupils and followers explore the

was applied by the ancient Greeks to the Actiniz as p- 13-18.
Pliny added

nothing to the information of his predecessors, except

world in every direction.

well as to the Acalephe of zoologists. Section 4. The systematic writers and anatomists. —In
the beginning of the nineteenth century the Acalephs
a few remarks on the movements of the Meduse.
p: 3-7.

SECTION 2.

begin to be made the subject of special investigations.
Péron and LeSueur, and, twenty-five years later, Esch-
The naturalists of the sixteenth and seven- scholtz, mark two great epochs in this progress. p. 18-27.

teenth centuries. — Rondelet is the chief investigator of | Srcrron 5. Embryological researches upon Acalephs. —

SECTION 1.

this period; his observations on Medus disclose the
same accuracy of observation and the same penetration
as his other investigations on all the natural productions
of the Mediterranean. Gessner deserves to be studied
chiefly on account of his great erudition, and Rondelet

for his deep insight into the relations of animals. p. 7-12.

The investigations which have led to the knowledge
of the modes of reproduction and growth of the Aca-
lephs are among the most interesting ever made by
naturalists. Sars and Steenstrupp are most prominent
among the discoverers in this field, and, next to them.

Siebold, Dalyell, and Dujardin. p. 28-35.

CHAP ESR sh T:.

ACALEPHS AS A CLASS.

the class. — The study of the structure of animals, unless
combined with a knowledge of their mode of develop-

VOL. I. B

Mode of determining the natural limits of

SECTION 2.

ment and of their homologies, is not sufficient to trace
the natural limits of the classes. p. 36-40.

The different animals referred to the type

x TABLE OF CONTENTS.

of Radiates.— The great diversity of opinions among
naturalists respecting the relations of the lower animals
to one another, has chiefly arisen from a confusion of
ideas as to what constitutes aflinity or analogy. p.
41-64. j
Section 3. The classes of Radiata.—'There are only
three classes among Radiata, the Polyps, the Acalephs,
and the Echinoderms; and these are characterized by
the different modes of execution of the plan of their
p- 64-72.
Section 4,

type.
Morphology and nomenclature. — Natural
range of homologies with reference to the necessity
of introducing new names when new ideas are dis-
cussed, and, if possible, of establishing a connection be-
tween the nomenclature and the objects under con-
sideration. p. 73-87.

Section 5. Individuality and specific difference among

Acalephs. —Importance of studying the question of

individuality in connection with that of the limitation

of species, p. 88-99. Darwin’s views on the origin
of species considered from this side of the question,
note p. 89.

Section 6. Natural limits of the class of Acalephs. —

Though gradually extended farther and farther, the

limits of this class have not yet been sufficiently ex-

all the
to) at.

animals which
p. 99-113.

Gradation among Acalephs. — Simple as the

panded to include are now

believed to belong
Section 7.

structure of the Acalephs is, it is sufficiently compli-

cated readily to point out the relative rank of the
p. 113-124.

Succession of Acalephs.— The order of suc-

different types belonging to the class.
SECTION 8.

cession of the Acalephs in geological times can thus

far only be traced in one of their types, the Tabulata,

through a long series of formations. p. 125-129.
Section 9. Classifications of Acalephs.— Before the
beginning of this century, nothing was done towards
classifying the Acalephs. Lamarck first unites together
the majority of their representatives; then follow the
classifications of Péron and LeSueur, of Cuvier, of
Schweigger, of Goldfuss, of Chamisso and Eysenhardt,
of Latreille, of Eschseholtz, of DeBlainville, of Oken,
of Brandt, of Lesson, of Forbes, of Liitken, and of
Milne-Edwards. More recently embryological researches
have greatly influenced the views of naturalists re-
specting the affinities of the Acalephs, and there have
appeared new classifications proposed by Vogt, Kolli-
ker, Leuckart, Gegenbaur, MeCrady, and Huxley.
The study of the homologies is likely to modify

these views anew. p. 129-102.

Pah Dei.

CTENOPHORA.

CHAPTER

CTENOPHORE

SecTION 1. Structural features of the Ctenophore in
general. — Special homologies traced among all Acalephs,
in order to show the peculiarities of the structure of
the Ctenophore. Natural attitudes and normal position

of the Acalephs. p. 155-173.

A

IN GENERAL.

Secrion 2. Subdivisions of Ctenophore forming sub-
orders. — Critical analysis of the systematic value of
the different names under which the different kinds of
natural groups observed among <Acalephs have been

designated. p. 174-186.

TABLE OF CONTENTS.

X1

CEHVAGR Tne Res Lol.

THE

Secrion 1. Family characters in general among Cteno-
phore. — As in all classes of the animal kingdom, the
natural families of the Acalephs, and those of the Cte-
nophore in particular, are characterized by particular
patterns of form, determined by structural features
bearing upon form. p. 187-190.

Section 2. The natural families of the Ctenophore

Eurystome.— Three families may be distinguished in

this sub-order: the Beroidw proper, the Neseide, and

the Rangiide. p. 190-193.

NATURAL FAMILIES OF THE CTENOPHORZ.

Section 3. The natural families of the Ctenophore Sacca-
te. — This sub-order embraces also three natural families :
the Mertenside, the Cydippide, and the Callianiride,
p- 193-198; while the Cestidw, p. 198, constitute a
sub-order by themselves. p. 292.
Section 4. The natural families of the Ctenophore Lo-
bate. — Five families may now be distinguished in this
sub-order: the Euramphide, the Bolinide, the Mne-

miide, the Calymmide, and the Ocyroide. p. 199-202.

CAEPAC PA TEE Ree Tals.

NORTH AMERICAN

Section 1. The genus Pleurobrachia and its species. —

Natural limits of the genus. Its form and structure ;
the bulk of the body consists of gigantic cells; their
arrangement; the locomotive flappers; the circulation
of fluids; the tentacular apparatus; the lasso-cells of
the tentacles illustrated by Prof. HW. J. Clark; other
203-248.

The genus Bolina and its species ; with remarks

structural details. p.
SECTION 2.

on allied genera. — Characters of the genus; comparison

with Pleurobrachia; the ambulacral tubes and the loco-

motive flappers have not the same extent; the whole

chymiferous system and its ramifications differ in differ-

ent types of Ctenophore, p. 249-269. Genus Mnemi-
opsis, p. 269.

CTENOPHOR.

Section 3. The genus Idyia and other true Beroids. —
The

Description of the species

Difference between Beroe and Idyia as genera.

species belonging to each.

most common along our coast. Its structure, p- 270.
Idyopsis, p. 288.

Section 4. Tabular view of the Ctenophore known at
present. — Systematic enumeration of all the Ctenopho-
re thus far described, with their principal synonymes,
p- 289-296.

Section 5. Geographical distribution of the Ctenophore.

—First attempt to define the faune of the sea by

the Ctenophoree found in different parts of the world;

distinction between faunw and zoological zones. p.

297-301.

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PART I.

ACALEPHS IN GENERAL.

VOL-) Ill: 1

AC ieee ENG ENE RAL.

Cw TER Eins 2:

HISTORY OF OUR KNOWLEDGE OF THE ACALEPHS.

SHO TTrON <1;
PERIOD OF ARISTOTLE AND THE ROMAN NATURALISTS.

Tr is one of the most instructive studies to trace the efforts of the human
mind in its successive attempts to understand the phenomena of Nature. This
study is particularly attractive when it is pursued in connection with a subject
which has taxed the ingenuity of man for a long series of ages; and it may well
be said, that, except Astronomy, no other field affords so much material for such
investigations as Zodlogy, on account of the early attention paid by philosophers
to the study of animated beings. From Aristotle to this day we have an uninter-
rupted series of writers who have recorded their views of the nature of animals, and
thus enable us to ascertain what successive steps have been made towards a more
extensive acquaintance with, and a more accurate appreciation of, the nature, the
affinities, the structure, and the mode of development, of the whole animal kingdom.
And while thus following up the long record of the progress of human knowledge
in this direction, an attentive observer cannot fail to be struck with the similarity
noticeable between the earlier views presented by the older writers on these topics,
and the impression he himself is likely to have received when contemplating for
the first time the same objects. Not less striking is the coincidence between the
sum total of the information gradually obtained in course of time, and the suc-

cessive steps made by those who have approached these studies without a previous

4 ACALEPHS IN GENERAL. Parr I.

acquaintance with the labors of their predecessors. The study of the Acalephs,
under which name naturalists now include the so-called jelly-fishes or sea-blubbers
or sun-fishes, and the animals allied to them, affords a striking example of this corre-
spondence between the gradual progress every one must make who attempts to
understand their nature, and the successive stages of the science relating to these
animals as recorded in the works of the authors of past ages. When we first
observe a jelly-fish, it appears like a moving fleshy mass, seemingly destitute of
organization ; next, we may observe its motions, contracting and expanding,

it floats near the surface of the water. Upon touching it, we may feel the burning

while

sensation it produces upon the naked hand, and perhaps perceive also that it has a
central opening, a sort of mouth, through which it introduces its food into the interior.
Again, we cannot but be struck with their slight consistency, and the rapidity with
which they melt away when taken out of the water. But it is not until our
methods of investigation are improved; and when, after repeated failures, we have
learned how to handle and treat them, that we begin to perceive how remark-
able and complicated their internal structure is ;— it is not until we have become

acquainted with a large number of their different kinds, that we perceive how greatly

diversified they are;— it is not until we have had an opportunity of tracing their
development, that we perceive how wide the range of their class really is ;— it 1s

not until we have extended our comparisons to almost every type of the animal
kingdom, that we can be prepared to determine their general affinity, the natural
limits of the type to which they belong, the distinctive characteristics of their class,
the gradation of their orders, and the peculiarities that may distinguish their families,
their genera, and their species. We cannot, therefore, expect to find, in the older
writers upon Zovlogy, any thing like a natural classification of these animals. Even
Aristotle, whose keen mind has thrown so much light at such an early period upon
the natural affinities of the higher animals, has failed entirely to recognize the rela-
tions which exist between them and the star-fishes and sea-urchins. All that he,
and other naturalists, up to a very recent period, tell us about them, amounts to
little more than the first impression they make on those who see them for the first
time, without attempting to compare them with other animals.

For this reason I have thought it desirable to introduce a brief account of all
that has been written upon the subject of Acalephs, as far as the condition of the
libraries in this part of the world will permit it, not only with a view of thus
recapitulating the successive stages of our knowledge of these beings, and comparing
them with our daily experience in attempting to unravel all the mysteries connected
with their history, but also with a hope of accounting for the very questionable
terminology used at present by all naturalists m describmg the parts of these

singular beings.

Cuap. I. HISTORY OF THE ACALEPHS. 5

The earliest accounts extant, relating to Acalephs, are contained in a few passages
of the History of Animals by Aristotle; but these are very meagre, and show that
the great Greek philosopher had no very clear idea either of their affinities or of
their structure.’ He speaks of them under three names; calling them, in some of his
passages, Acalephe, in others, Knide, and in another, Pneumones. <A careful com-
parison of all the passages in which these animals are mentioned, shows that the
names of Acalephee and Knide were probably applied to Actinie and to Medusx
indiscriminately, and that Aristotle himself did not distinguish these animals accu-
rately, or, at least, did not know in what their essential differences consist, for, speak-
ing of Acalephe as well as of Knida, he only says that there are two kinds, one of
which is attached to the rocks, while the other may free itself and seek its food
by night; which seems to indicate that he believed the free Meduse to be at times
attached like the Actiniw, and capable of freemg themselves at will, or that the

Actiniw, freemg themselves, become Meduse.2 Taking into consideration, however,

1 The best edition of the Zodlogical works of
Aristotle is that of lo. GorrLop ScHNEIDER; Aris-
totelis de Animalibus Historia, Lib. X., Grace and
Latine, Lipsizw, 1811, 4 vols. 8vyo. The best trans-
lation is that of Dr. Fr. Srrack into German:
Aristoteles Naturgeschichte der Thiere iibesetzt und
mit Anmerkungen begleitet, Frankfurt am Main,
1816, 1 vol. 8vo. The French translation by Camus,
Paris, 1783, 2 vols. 4to., is less accurate. There
is no good English translation.

2 As the account which Lesson gives of the
views of Aristotle relating to Medusa, in his Hstocre
Naturelle des Zodphytes: Acalephes, Paris, 1843, is
far from accurate, I deem it necessary to introduce
here a literal translation of all the passages of the
original text relating to that subject.

The name Acalephe appears in six different pas-
sages in Aristotle. First, in Book I. Chap. I. See.
6, when, speaking of the habits and functions of
animals, he says, that “there are some which get
their food in the water, and are unable to live out of
it; they do not, however, take in either air or water,
as the Acalephe and the Ostrea.” Next, in See. 8,
speaking of the ability of animals to change their
place, he says, “some both attach and detach them-
selves, as a genus of the so-called Acalephx, for

some of these, detaching themselves by night, go

about to feed.” In Book IV. Chap. VI. See. 4 and
5, when speaking of the structure of the marine
animals, he mentions that “there is also the genus
of the Acalephe, which is peculiar; they cling to
the rocks, like some of the shell fishes, but oecasion-
ally free themselves. They have no shell, but their
whole body is fleshy, and they feel, and seize the
hand approaching them, and then hold it, as the
Polypus” (which is the Octapus of modern system-
atic writers) “does with its feelers, in such a manner
as to cause the flesh to swell. They have the mouth
in the middle, and live from the rocks as from a
shell” (which probably means that the rocks afford
them the same protection as the shell gives to the
oyster). “If any one of the small fishes falls in their
way, they hold to it, as to the hand; so also if any
thing eatable falls in their way, they devour it, and
one genus frees itself and feeds upon scallops and
sea-urchins, whenever any thing falls in its way.
They seem to have no visible excrements, but in this
they resemble the plants. There are two genera of
Acalephx, one of which is smaller and more eatable,
the other large and hard, like those found about
Chalcis. During the winter their flesh is firm,
wherefore they are caught, and are eatable; during
summer they perish, for they become soft, and, if

touched, are easily torn, and cannot be taken off at

6 ACALEPHS

IN GENERAL.

Part I.

all that is said about Acalephe and Knide, it would seem as if the name of Knidx

applied more particularly to Medusx, as these are the only ones of which he seems

to have known that they possessed burning properties, the nature of which could

not have been very clearly understood by him, for he says, when speaking of the

Sea Scolopendra (probably some Nereis), that it does not bite with the mouth, but pro-

duces with the whole body a painful sensation like that caused by the Knide.

The

description he gives of the Acalephx applies particularly well to the Actiniaw, and but

for the statement that they free themselves could not be applied to any Medusa. Of

the Pneumon, he only states, that they are formed out of themselves.

Neither Pliny? nor Aelian nor Oppian nor Galenus, nor the writers of the middle

all; and, suffering from the heat, they retire further
In Book VIII. Chap. I. Sec. 5,

when, speaking of the

among the rocks.”
intensity of life and_ its
gradations, he considers the marine shells and the
Ascidians as intermediate between the higher ani-
mals and plants. “The transition from them to the
animals is uninterrupted, as has been said before ;
as to some of those in the sea, one might doubt
whether they are animals or plants, for they are
attached, and many of them, when separated, are
destroyed. In some, the nature of the body is
fleshy, as in the so-called Tethya (our Ascidians)
and the genus of the Acalephe. The sponge, how-
ever,” he adds, “is entirely like the plants”; and in
Chap. III. Sec. 3, he says that “the Acalephw live
upon whatever small fishes fall in their way, and
that they have the mouth in the middle, which is
most evident in the largest ones. They have also,
like the oyster, an opening where the food passes
out, and this is upward. In a general way the
Acalephw resemble the internal fleshy part of the
oyster, and it uses the rock as a shell.”

First, in Book
V. Chap. XIV. Sec. 1, where it says that “the

Knide and the Sponges, which are found in the

The name IKnide occurs twice.

clefts of the rocks, though without a shell, multiply
There are,

however, two genera of Knidwe: one in the hollows,

in the same way as the shell fishes.

which never frees itself from the rocks; and another,
living upon flat, smooth bottom, which detaches itself
And in Book IX.
Chap. XXV. See. 4, when speaking of the sea-

snakes, he says of the Sea Scolopendra (our Nereis),

and moyes from place to place.”

that “when it has swallowed the hook, it turns itself
inside out until it expels the hook, and then turns
itself back again; it does not bite with the mouth,
but its whole body produces a painful sensation, like
that of the Knide.”

The name Pneumon occurs but onee (Book V.
Chap. XHI. See. 10), when, speaking of the repro-
duction and growth of animals, he only says that the
so-called Pneumon “is formed from itself,” meaning
that it is spontaneously generated. From this
passage it could hardly be inferred that Aristotle
designated an Acalephe under the name of Pneu-
mon. But when we consider how the Grecian
colonies were scattered along the shores of the
Mediterranean, and that the name Pulmo Marinus
was early applied to the large Rhizostoma of the
Mediterranean, and even figured under that name
by Mathioli; that the Rhizostoma may aptly be
compared to a floating lung; and further, that
this largest Medusa of the Mediterranean is com-
monly called Poumon de Mer by the French fisher-
men, — the conclusion is irresistible, that, if thes Latin
and French names are not a translation of the Greek
“Pneumon,” this name is likely to have been given
to that large Medusa for the same reason for which
the French call it sea-ling. It is singular, however,
that Rondelet, who first represented the Rhizosto-
ma, should have failed to recognize it as the Pneu-
mon of the Greeks, and applied the name to a
compound Ascidian.

1 The best edition of the Natural History of
Pliny is that published in Paris in 1828 by Lemaire,

under the supervision of Ajasson de Grandsagne :

Cuap. I. HISTORY OF THE ACALEPHS. 7

ages, added any important information to that already contained in Aristotle ; and
we must come down to the sixteenth century, before we find authors who have
observed Meduse in nature, and given rude outlines of their external appearance.
Among them Bélon and Rondelet deserve particular mention, for they were the
first who published wood-cuts representing several species of Actinizw and Acalephe ;
and, though their knowledge of these animals is not more accurate than that of
Aristotle, a new era in the natural history of animals begins with them and

Gessner.

SHC LRLON Pi:

THE NATURALISTS OF THE SIXTEENTH AND SEVENTEENTH CENTURIES.

The connection between the extraordinary impulse which the natural sciences
received in the second half of the sixteenth century, and the preceding momentous

Caii Plini secundi Historie Naturalis libri xxxvii.
The third part, devoted to Zodlogy, contains notes
and dissertations by G. Cuvier.

Most of what is contained in Pliny respecting the
Acalephs (Lib. ix. cap. 45) is compiled from Aris-
totle, though it appears from his description, that he
must have observed these animals himself, as he
mentions the manner in which they move about,
and seize their prey. As the name Zodphytes has
been applied to the lower animals by most writers
on natural history since Pliny, it is not out of
place to mention here, that that word was first used
by Sextus Empiricus, and no doubt suggested by
a passage of Aristotle quoted above (note on p. 6),
in which the gradation from the higher animals to
the plants is alluded to. But, far from constituting
a progress in science, that designation introduced
only confusion, or at least served to propagate a
false impression that there were living beings truly
partaking at the same time of the nature of ani-
mals and plants. Nothing can be further from the
truth than to ascribe such a view to Aristotle as
his commentators Gaza and Budeus have done ;
for, though Aristotle alludes to a gradation among
animals, and to a sort of transition from them to
the plants, which he considers as inanimate, he no-

where regards those animals which are immovable,

like plants, as ambiguous in their character, but
everywhere speaks of them as living animals, and
alludes to the Sponges as plants. These erroneous
notions have been entertained for nearly two thou-
sand years, until Peyssonel demonstrated the ani-
mal nature of the expanded individuals of these
so-called Zodphytes, in which some of his prede-
cessors had fancied they saw real flowers.

1 The readers who may wish for more informa-
tion respecting the progress of science during this
and the following periods, in which the natural
history of the Acalephs made comparatively less
advance than that of other classes, are referred
to G. Cuvier, Histoire des sciences naturelles
depuis leur origine jusqu’’ nos jours, Paris, 1841—
1845, 5 vols. 8vo., and Histoire des progres des
sciences naturelles depuis 1789 jusqu’i nos jours,
Paris, 1829, 4 vols. 8vo.— DeBiaINvILLE, His-
toire des sciences de Vorganisation et de leurs pro-
gres, Paris, 1847, 3 vols. 8vo.— Also, Sprx Ge-
schichte und Beurtheilung aller Systeme in der
Zoologie nach ihrer Entwickelungsfolge von Aris-
toteles bis auf die gegenwiirtige Zeit. Niiremberg,
1811, 1 vol. 8vo., and for the middle ages in
particular: Povucurt, Histoire des sciences natu-

relles au moyen age, Paris, 1853, 1 vol. 8yo.

8 ACALEPHS IN GENERAL. Parr

historical events, is not difficult to trace. The establishment of the Mahometans
in Spain, and, some centuries later, the Crusades, had brought the West imto direct
contact with the East, where the Arabs had kept alive the traditions of Greek
learning, and the foundation of the great universities of Europe in the twelfth and
thirteenth centuries was the result of the intellectual impulse which this intercourse
aroused. The institution of the mendicant orders, which were established at the
same time, and whose office was chiefly to teach, stimulated this activity still
further ; while the overthrow of the Byzantine Empire, in the middle of the
fifteenth century, sent westward many of the most learned Greeks of that age.
Then came the Reformation, with its all-embracimg discussions upon the most im-
portant problems of mental activity,—the introduction of the arts of printing and
engraving, multiplying a thousand-fold the imfluence of thought,—the invention of
eunpowder and of fire-arms, bringmg brute force under the control of intellectual
energy and foresight, — the discovery of America, and of a passage into the Pacific
Ocean around the Cape of Good Hope and the southern extremity of America,
opening new worlds to the investigations of the learned.

The extraordinary activity then prevailing manifested itself in the most. striking
manner also among those whose inclination tended towards the study of nature, and
of man as an intellectual being. Besides philosophy and mathematics, we see human
anatomy taught in the public schools, and extending its influence over the investi-
gations of the whole animal kingdom; so that the great anatomists of the sixteenth
century, Vesalius, Fallopius, Eustachius, Fabricius ab Aquapendente, and Harvey, had
their peers among the naturalists in Wotton, Bélon, Salviani, Rondelet, Gessner,
Aldrovandi, and Fabio Colonna. Among these, we are chiefly mdebted to Rondelet
for contributions to the natural history of the Acalephs. He was, indeed, not only
better acquainted with the inhabitants of the Mediterranean than all his prede-
cessors, but he knew them even more accurately than any naturalist that lived
before the present century. Professor of Anatomy in the University of Montpelier,
where he had the best opportunity for studying the marine animals of the Mediter-
ranean, he has published a work upon the fishes inhabiting that sea, which chal-
lenges our admiration even now;' and if his account of the soft-bodied animals is
far inferior to his descriptions of the other types of the animal kingdom, it is simply
to be ascribed to the mode of investigating which has too long prevailed, and from
which even some of the living naturalists are not yet altogether free,— that of
removing the animals to be examined from their natural element in order to

describe them. While there is hardly a naturalist at present who does not know

1 Guiz. Ronpevetir libri de piscibus marinis, 17th book is devoted to the Acalephs, which he calls

Lugduni, 1554, 1 vol. fol. The 14th Chap. of the Urtice (nettles).

CuAr. I. HLSTORY “OF THE ACATE PHS. 9

that neither Polyps nor Acalephs nor Mollusks will exhibit their natural appearance
when taken out of the element in which they live, it is still to be lamented that
both the star-fishes and sea-urchins are everywhere represented as they appear when
taken out of the water, and all their soft appendages, so numerous and diversified, are
drawn in or so contracted and collapsed as no longer to give the slightest idea of
their natural beauty. Like Aristotle, Rondelet still unites the Actinia and Acalephe
under the name of sea-nettles (Urtica marine), distinguishing the former as the
fixed sea-nettles and the latter as the free sea-nettles. Even Cuvier, in his earlier
works, allows these animals to remain together, though it was he himself who. sepa-
Rude

as are the illustrations published by Rondelet, it is hardly possible to mistake in his

rated them afterwards, for the first time, as members of two distinct classes.

fifth species the Rhizostoma of Cuvier, although the disk is too small and the arms
too straight, and in the sixth the Chrysaora of Péron, although Linnzus refers
that figure to the Aurelia aurita.

In the writings of Aristotle a single part of the Acalephe is distinguished by

name, — the mouth, which occupies the centre of the body, of which nothing is stated

except that it is fleshy. The passage already quoted from Pliny (Lib. EX. ch. 45)
speaks of leaves (“ac praenatante pisciculo frondem suam spargit”), no doubt meaning
by frons the thin, expanded margin of the disk, and the appendages about the mouth,
which he considers as a root (“ora ei in radice esse traduntur”), thus carrying out
a comparison of these beings with plants. Rondelet, on the contrary, vindicates
especially their animal nature when he says, that since they alternately expand and
contract their blade, which serves as feet, and since they absorb food through the
mouth and thus show themselves provided with the senses of touch and taste, which
are essential to the animal life, he considers them as imperfect animals, and not as
Zobphytes, as Pliny does. Speaking of the small sea-nettle, which is his first species,
he mentions its short tentacles, and its resemblance to the large intestine, thus dis-
tinctly pointing to the genus Actinia, of which, he says, there are several varieties,
some green, some blue, some blackish, with blue, yellow, or red spots. His second
species seems to be a Tubulibranchiate Annelid, for he says it bites. His third species
is another Actinia, with which he confounds the ASquorea of the Mediterranean.’

* Tn my next Monograph I shall have an oppor-
tunity of representing the North American Echi-
noderms as they appear in life.

* Cum igitur Urtice frondem suam, que pedum
vice est, modo dilatent modo contrahant, cum ore
cibum accipiant, id est, cum tactu gustuque, qui duo
sensus ad yitam animalium sunt necessarii, pradite
sint, non inter Zoophyta, ut Pliuius, sed inter animalia

VOL. Il. 2

non omnino perfecta, eas numerabimus. Rondeletius,
Lib. XVII. p. 527.

® Tt can hardly excite surprise to find, that, with
as little knowledge as Rondelet possessed upon the
subject of Acalephs in general, he should have con-
founded a Medusa and an Actinia, especially when it
is remembered that the numerous radiating tubes of

the /Equorea give it a greater resemblance to an

10 ACALEPHS IN GENERAL. Pang I.

The fourth species is unmistakably the Actinia senilis. Speaking of the fifth species,
which is the Rhizostoma, he compares the disk to a hat, and the eight pendant
appendages to the feet of the Octopus. Of the sixth species, he says that the
four feet may be compared to Acanthus leaves.’

Gessner, in his great Natural History of the Animals, has followed Rondelet for the
Acalephe, as he did for most of the other productions of the Mediterranean; and also
copied his figures and those of Bélon, adding only such remarks as exhibit his vast
erudition, but in no way a better acquaintance with the animals themselves?

It has been a source of constant delight for me, while perusing the works of the
earlier naturalists, to sympathize with the genial spirit and the earnestness that
pervade their writings, so free from egotism, and animosity against their fellow-students.
Their devotion to their studies is equal to the spirit of reverence with which they
look upon nature; and it is disgraceful to our age, that we must contrast with such
dispositions the ill-will, the jealousies, the quarrels for priority, and the profanation,
which pervade the discussions of certain modern authors. Moreover, in a systematic
point of view, the great naturalists of the sixteenth century deserve to be studied
more fully than they have been thus far. It is astonishing, for instance, to see
how near Rondelet, in discussing the views of Aristotle upon the affinities of animals,
came to perceiving their true affinities, and their natural classification under four great
types. In the Ist Chapter of the 17th Book of his great work, “ De Piscibus Marinis,”
after describing the fishes of the Mediterranean, he says, that having thus deseribed
the Enwina,— that is, the animals provided with blood,—he now proceeds to describe
the Anaima, among which he distinguishes the Malakia in contradistinction to the S#leo-
derma. These Malakia are the Cephalopoda, to which unfortunately the Medusx are
added on account of the appendages around the mouth, which were compared by
him to the feelers of the cuttle-fish. In Book 18th he treats of the Crustacea under
the name of Malakostraca, and distinguishes from them the Ostrakoderma, or shell fishes,

Actinia than any other Medusa has; but that he did 2 An interesting notice of the life and writings

confound the two is plain from the following words :
“Saxis aliquando hewret, aliquando soluta vagatur.”
The purple color of the AEquorea may also have con-
tributed to mislead him.

1 Tlere, then, we have for the first time the word
pileus (hat) introduced to designate the disk of the
Medusex, an expression that has been retained by
most later writers, while some zodlogists have sub-
stituted for it the name of wnbrella, or disk; while
the word feet stands for the appendages around the
mouth, to which the name arms was afterwards

more generally applied.

of Gessner, by Cuvier, may be found in the Biogra-
phie universelle, vol. 17, and in the Histoire des
sciences naturelles, vol. 2, p. 835. I would gladly
also refer to the notice by Blainyille in his Histoire
des sciences de lorganisation; but that chapter is so
interwoven with jesuitical insinuations as to be utterly
unpalatable to a sober thinker. The chapter on
Acalephe in the Historia animalium of Gessner is
contained in Book 4, De piscium et Aquatilium ani-
mantium natura, page 1239, published in Ziirich in
1558. — Bélon’s book, de Aquatilibus, Lib. IL, was

printed in Paris in 1553,

Cuar. I. HISTORY OF THE ACALEPHS. il

associating erroneously, however, the sea-urchins with the former. But again, in the
second part of his work, which appeared one year later than the first, discussing the
characteristics of the Ostrakoderma, or Conchifera, and comparing them to the Lntoma,
In this

arrangement, Rondelet is already as far advanced as Lamarck, who separates the

or Insects, he unites the bivalve and univalve shells into one great division.
Cephalopoda as a distinct class from the Conchifera. With reference to the Lntoma,
or Insects, which he characterizes as animals having incisions above or below or on
both sides and no bony parts, he unites the Worms and the Amnelids with a small
Crustacean, and associates also the Star-fishes and Holothurizw with them, a combination
which even Oken has thought natural.

Among the other naturalists of the sixteenth and those of the seventeenth century,
there are a few more who deserve to be mentioned as contributors to the natural
history of the Acalephs. Matthioli, for instance, while commenting upon the plants
of Dioscorides! introduces some remarks upon Acalephs and other Zodphytes of
which he gives wood-cuts. In part second of the same work, published in 1555,
there is a figure of a Beroid Medusa, in a short paragraph “De Cucumere marino,”
p. 131; and another of the “Eschara,” p. 133. Wotton, also,’ speaking of Zodphytes,
mentions the sea-lungs and sea-nettles; and, somewhat later, Aldrovandi, in his gigan-
tic Cyclopedia of Natural History, published in fourteen large volumes, folio, partly
by himself and partly from his papers after his death, mentions also some of these
animals, without, however, adding any thing that would throw new light upon their
nature. The same may be said of the work of Jonston.* It would lead me too far
were I to attempt here to give ever so short an account of the rather indifferent
notices relating to Acalephs that are scattered in the writings of the other natural-
ists of this period. It may suffice to quote their works, and refer the reader to the

originals» One remark, however, applies to most of them, and characterizes the spirit

1 Marrurort (P. A.), Commentarii in sex libros
Dioscoridis de medica materia; adjectis magnis ac
novis Plantarum ace Animalium iconibus, ete, Ve-
netiis, 1554, fol. fig. — Compare also CasALPInus
(A.), De plantis Libri XVI. Florentiis, 1583, 4to.

2 Worton (Epw.), De differentiis Animalium,
Libri X. Parisiis, 1552, fol.

8 Atprovanpr (UL.), Historia Naturalis, Bo-
nonix, 1599-1640, 14 vols. fol. fig.

4 Jonston (J.), Historia Naturalis de Exan-
guibus aquaticis Libri IV. Francofurti ad Moenum,
1650, fol. fig. — Book IV. p. 72 is devoted to the
Zodphytes in general, among which he includes, with

Rondelet, the Actiniw and Meduse, the Holothurie,

the Ascidiz, and the Haleyonoid Polyps. His figures
are copied from Bélon, from Rondelet, from Aldro-
vandi, and from Matthioli.

5 Satvianr (Hrer.), Aquatilium animalium His-
toria, Roma, 1554, fol. fig. —Imrrrato (FERR.),
Historia naturale, nella quale si tratta della diversa
condizione de Minere, Pietre preziose e altre curio-
siti, con varie istorie di Plante e Animali, Napoli,
1559, fol. — Ciusrus (Car.),

decem, quibus Animalium, Plantarum aromatum

Exoticorum libri

aliorumque peregrinorum fructuum historia deseri-
buntur, Anvers, 1605, fol. fig. — Coronna (F8.),
Aquatilium et terrestrium aliquot animalium alia-

rumque naturalium rerum observationes, Rome,

12 ACALEPHS IN GENERAL. Parr I.

of the age.

fo)

They are full of discussions upon the animals known to the ancients,
mixed up with a few original observations, showing plainly the influence exercised by
the revival of letters even upon the cultivators of science.

The naturalists of the second half of the seventeenth century gradually turn their
attention more exclusively to nature, and are less engrossed by mere questions of
erudition. This salutary change is no doubt owing to the influence of the discovery
of America, and the progress of navigation around the Cape of Good Hope and in
Asia, upon the study of Natural History. The animals and plants brought back to
Europe by travellers, and still more the observations published by physicians and
naturalists who explored the new world, must early have impressed on every one the
conviction, that the productions of these countries could not be illustrated by refer-
ences to the writers of past ages. No expedition contributed more powerfully to
strengthen this impression, and to extend the range of human knowledge respecting
the animals and plants of foreign lands, than that of Count Maurice of Nassau to the
Brazils. The work of Maregrave,) who was naturalist to that expedition, remained
until the beginning of this century the principal source of information respecting
the animals of South America; but it contains nothing relating to Acalephs. Du-

3

tertre® and Martens*® have only a few remarks about them, while Boccone’s *

investigations relate chiefly to the Corals. At home, both naturalists and zoblogists,
as well as philosophers generally, apply themselves with increased zeal to the
investigation of minute objects and abstruse questions requiring improved methods
of study; and, of course, the advance made in one branch leads to new researches
in other branches, so that it may well be said, that there never was a time when
the aspirations of men for knowledge were higher and more intense than during
This birth to the

academies founded with a special view to the promotion of experimental researches.

this period. intellectual movement naturally gave scientific

The principal of these academies were, that of the Lyncei in Rome, the Philosophical
Society in London, the Academia Nature Curiosorum in Germany, and the Académie

des Sciences in Paris.

1616, 4to.— Scitia (AGost.), La vana speculatione Brasilixe Libri VIIL, a Joh. de Laét in ordinem

Though

desingarata del senso, Napoli, 1670, 4to. fig.
many of the works quoted are insignificant for the
study of Acalephs, their value is very great in other
respects. Scilla, for instance, opens that series of
investigations upon fossil remains which has made
The works of Clu-

sius, Matthioli, and Czsalpinus, are essentially botan-

Palxontology a distinct science.

ical, and that of Salviani is entirely ichthyological.

1 Marcorave (G.), Historia Rerum Naturalium

digesti, Lugduni-Batayorum, 1648, fol. fig.

* Durertre (J. Barr.), Histoire générale des
Antilles, ete., Paris, 1656-1671, 4 vols. 4to.

® Marrens (Fr.), Spitzbergische und Groénliin-
dische Reise-Beschreibung, im Jahr 1671, Mam-
burg, 1675, 4to. fig.

! Bocconr (P. Siry.), Recherches et obser-
vations (histoire naturelle touchant Je Corail, ete.,

Paris, 1670, 12mo. fig.

Cuap. I. HISTORY OF THE ACALEPHS. 13

Sa Cele Orne LT.

THE NATURALISTS OF THE EIGHTEENTH CENTURY.

5 continue their work during this period in

Travellers! observers,” and compilers
nearly the same spirit as towards the close of the preceding century, with this
It is

no longer the mere existence of curious animals and plants which attracts the atten-

difference only, that the field of inquiry is gradually enlarging and extending.

tion: a desire of appreciating their relations to one another has evidently taken hold
of the naturalists, and this aspiration reaches soon a climax in the publication of the
“ Systema Nature,’ the great work of this age, and the foundation of the lasting
fame of Linnaeus.

Though Linneus himself added comparatively little to the general stock of infor-
mation respecting the Acalephs, he had, nevertheless, as great an influence in preparing
the way for their systematic arrangement as in other classes of the animal king-
dom, by extending to them his bmominal nomenclature. Yet, in the “ Systema
Nature” the members of the class of Acalephs are so far removed from one another

as to show that Linneus did not even dream of the true relations that unite the

1 Rumenius (G. Ey.), D’Amboinsche Rariteit-
kammer, behelzende eene Beschryvinge van aller-
hande 200 Weeke als harde Schaalvischen, ete.,
Amsterdam, 1705, fol. fig. —Stoane (Hans), A
Voyage to the Islands of Madeira, Barbados, Nieves,
St. Christopher’s, and Jamaica, with the Nat. Hist.
of the last of these Islands, ete., London, 1707-1725,
2 vols. fol. fig. — Tournrerorr (Jos. Pirron pr),
Relation @un Voyage du Levant, Paris, 1717, 2 vols.
Ato. fig. — Frurite (Lovrs), Journal d’observations
faites sur les cdtes orientales de ?Amérique et dans
les Indes occidentales, Paris, 1714, 2 vols. 4to. fig. —
Journal @observations faites dans la nouvelle Espagne
et aux iles de l’Amérique, Paris, 1725, 4to.—
Brown (Parr.), The Civil and Natural History
of Jamaica, ete., London, 1756, fol. fig.

* Marsiaur (L. F.), Brieve Ristretto del Saggio
fisico intorno alla Storia del Mare, Venezia, 1711, 4to.
fig. (French by. Leclerc), Histoire physique de la
Mer, Amsterdam, 1725, fol. fig. — Rtaumur (R.

Ant. pb), Observations sur la formation du Corail

et des autres productions appelées Plantes picrreuses,
Mém. Acad. Se. Paris, 1727. — Caressy (Mark).
Natural History of Carolina, Florida, and the Ba-
hama Islands, ete., London, 1731-1743, 2 vols. fol.
fig. col.; Appendix, London, 1748, fol. — Prancus
(Janus), De Conchis mints notis in Littore Arimi-
nensi, Venetiis, 1739, 4to. fig.; edit. altera Rome,
1760, 4to. fig.—Jussiru (Bern. DE), Examen de
quelques productions marines qui ont été mises au
nombre des Plantes, et qui sont Pouvrage d’une sorte
d'Insecte de mer, Mém. Ac. Se. Par. 1742, p. 290.

fic. — Baxer (H1.), Essays on the Natural History
of the Polyps, London, 1743, 8vo. fig.
8 Bester (M. R.), Rariora Musei Besleriani

que olim Bas. et M. R. Besler collegerunt, ete. Com-
mentatio illustrata 4 J. Hl. Lochner, Niirmnberg.
1716, fol. —Srsa (Axz.), Locupletissimi Rerum
naturalium Thesauri accurata Descriptio et Iconi-
bus artificiosissimis per universam Physices his-
toriam (Lat. et Gall.), Amstelodami, 1734-1765, 4

vols. fol. fig.

14 ACALEPHS IN GENERAL.

Parr I.

Meduse proper with the Siphonophoree and the Hydroids." Nevertheless, the share
of attention bestowed upon the Acalephs is steadily increasing, and many valuable
contributions to their history appear during this period; nay, several investigators
begin to study with special care these and other soft-bodied animals, as well as the
lower animals generally. The extraordinary disclosures of Trembley respecting the
fresh-water Hydra? and the discovery of the animal nature of the Corals by Peys-
sonnel,’ had a great and lasting influence upon the progress of our knowledge of the
lower animals; and even now their investigations are constantly alluded to as the
starting points of a better era in the natural history of the Radiates. The paper

of Réaumur upon Rhizostoma, and Plancus’s delineation of the Marsupialis, were soon
> ] ;

followed by Gronoyius’s#

6

figures of many others; Bohadsch’s

1 The history of the successive editions of the
Systema Nature is instructive, on account of the
progress Linneus himself has made in fixing for-
ever the nomenclature of Natural History. The
first edition consisted of a single folio sheet, and has
been republished by Ant. L. A. Fee in 1830, in
Paris; the last edition published by Linnwus him-
self is the twelfth, printed in Stockholm in 1767, in
3 vols. Svo.

2 TremBLey (Apr.), Mémoires powr servir &
Vhistoire dun genre de Polypes d’eau douce, & bras
en forme de cornes, Leyde, 1744, 4to. fig.

(J. A. pr), Traité du Ceorail,

toy. Soe. London, 1755, vol. 47, p.

8 PrEYSSONNEL
ete., Phil. Tr.
445. The history of the views entertained at differ-
ent periods respeeting the nature of the Corals
truly illustrates the progress of Natural History.
At first considered as stones by Boccone (see note
4, p. 12) and Woodward (An Essay towards a Nat-
ural History of the Earth, London, 1695), they
were regarded as plants by Marsigli (see note
2, p. 13), who was the first to observe, in 1706,
what he called the flowers of the Coral. These
supposed flowers, which are the individual polyps
of the Coral stock, were at once considered as
proving the vegetable character of the Coral, and
even the greatest botanist of that time, Bernard de
Jussieu, shared this view, until he had an oppor-
tunity of

Peyssonnel’s statements. Réaumur opposed Peys-

verifying for himself the accuracy of

illustrations of several Meduse ; Baster’s® descriptions and

remarks upon Beroe, with a figure; Chanvallon’s

sonnel so pertinaciously that the extensive work
of this accurate and ingenious observer never was
published (see Flourens in Ann. des Se. Nat.
2d ser. vol. 9, p. 354), and only an abstract of it
appeared in the Transactions of the Royal Society
of London. Had the whole been printed at once,
naturalists would have known a century sooner, that
the animals of the Stony Corals are homologous to
the Actinize and Acalephs, for Peyssonnel does not
hesitate to call them by the same name, Orties,
Urticw, though he also applies to them the name
of Insects. The same volume of the Transactions
of the Royal Society in which an abstract of Peys-
sonnel’s work was published, also contains, p. 95,
an interesting paper by Donati, entitled “ New
Discoveries relating to the History of Coral.”

* Gronovius (L. Tu.).

Zoophylacium

His chief work is the

Gronovianum, exhibens Animalia,
Quadrupeda, Amphibia, Pisces, Insecta, Vermes,
Mollusca, Testacea et Zodphyta que in Museo suo
adservavit atque descripsit.

1763-1781, fol. fig.; but for the Acalephs consult

Lugduni-Batavorum,

his Observationes de Animalibus aliquot marine
aqux innatantibus, atque in littoribus Belgicis obviis,
in Acta Helvetica, 1760, vol. 4.

5 Baster (Jos), Opuscula subseciva, observa-
tiones miscellaneas de Animaleculis et Plantis qui-
busdam marinis eorumque ovariis et seminibus con-
Harlem, 1759-1765, 2 vols. 4to. fig.

® Bomapsen (J. B.), De quibusdam Animalibus

tinentia.

Cuap. I. HISTORY OF THE ACALEPHS. 15

description of the Physalia? (which ought to be remembered in connection with
the illustrations of Patrick Brown already quoted); Dana’s* dissertation upon marine
animals: and Slabber’s delineations of several Medusw.? Besides these, the more
general works of Donati’ Hughes? Hill, Kalm,’ Pontoppidan, and Borlase,’ also
mention incidentally different kinds of Acalephs. The book of Borlase contains
the first descriptions ever published of the Medusx of the British coast accompa-
nied with figures that may be recognized.

Notwithstanding this accumulation of observations, the real information respecting
Meduse thus far brought together is still scanty and disconnected. It consists
chiefly of isolated facts without connecting links; and, though the modes of obsery-
ing and describing are fast improving, we must pass on through another half

century before we find naturalists applying to the study of Acalephs .the accurate

methods to which Zodlogy owes its present condition.

Pallas” and Forskal™ are the

first who give fuller descriptions of Medusze and attempt to distinguish their parts

marinis eorumque proprietatibus vel nondum vel
minus notis, ete., Dresdw, 1761, 4to. fig.

1 CHANVALLON (TurB. DE), Voyage & la Mar-
tinique, contenant diyerses observations sur la Phy-
sique, Histoire naturelle, ?Agriculture, les moeurs
et les usages de cette ile, Paris, 1763, 4to.

2 Dana (J. P. M.), Dissertation sur les diffé-
rences que présentent certains animaux marins
connus sous la dénomination d’Ortie marine. Mise.
Taurin, III. p. 206.— Description une espéce de
Meéduse, in Rozier, Journal de Physique, Indroduct.
plies pay 14s

5 Strasser (Marr.), Naturkundige Vergusti-
gingen, Haarlem, 1778, 4to.

* Donati (ViTAt.), Saggio della Storia naturale
marina dell’ Adriatico, Venezia, 1750, 4to. fiz. French
translation: Essai sur VHistoire Naturelle de la
mer Adriatique, La Haye, 1758, 4to. fig.

° Huaues (Grirrirm), The Natural History of
Barbados, London, 1750, fol. fig. — A letter con-
cerning a Zoéphyton somewhat resembling the
Flower of Marigold, Phil. Trans. XLII. p. 590, fig.

° Hirt (J.), A Natural History of Animals,
containing Descriptions of the Birds, Beasts, Fishes,
Insects, and of the several Classes of Animaleula
visible only by the assistance of microscopes, Lon-
don, 1752, fol. fig.

7 Kato (Perer), En Resa til Norra America,

Stockholm, 1753-1761, 5 vols. 8vo. English trans-
lation: Travels in North America, containing its
Natural History, ete, transl. by J. R. Forster,
Warr. and Lond. 1770, 1771, 3 vols. 8vo.

8 Ponrorripan (Eric), Norviges Natural His-
torie, ete., Kidbenhayn, 1761-1753, 2 vols. 4to. fig.
English: The Natural History of Norway, Lon-
don, 1755, fol.

® Boriase (Witt.), The Natural History of
Cornwall, Oxford, 1758, fol. fig.

1% PatLas (PeTrer Srmon), Miscellanea Zoo-
logica, quibus nove imprimis atque obscura Ani-
malium species describuntur, ete., Hags-Com., 1766,
Ato. fig. — Spicilegia Zoologica, Berolini, 1767-

red

1780; 14 Fascie. 4to. fig.; German translation
by E. G. Baldinger: Naturgeschichte merkwiir-
diger Thiere, ete. Berlin, 1769-1778, 10 vols.
4to. fig. — Elenchus Zoophytorum, sistens Generum
adumbrationes generaliores et Specierum cognitarum
succinctas deseriptiones, cum selectis auctorum Syno-
nymis, Hagw-Com., 1766, 8yo.

1 Forskat (P.), Descriptiones Animalium,
Avium, Amphibiorum, Piscium, Insectorum, Ver-
mium, que in Itinere orientali observavit; edidit
C. Niebuhr, Hafniw, 1775, 4to.—Icones Rerum
naturalium quas in Itinere orientali depingi curavits

ed. C. Niebuhr, Hafniw, 1776, 4to.

16 ACALEPHS IN GENERAL.

Parr I.

with scientific precision; and their followers, O. F. Miiller* and O. Fabricius,? contrib-
ute many valuable additions. Thus far, whenever illustrations had been added to the
descriptions of animals, they were chiefly wood-cuts, or engravings printed in_ black.
But in the year 1776, O. F. Miiller began the publication of a series of truly mag-
nificent colored plates, paimted and engraved by his brother, which appeared in
successive numbers under the title of Zoblogia Danica. This work forms an era in
Natural History, and has set an example, to which we are indebted for all the
costly and ever improving colored illustrations of this kind during the last eighty
years. To this day the Zodlogia Danica is indispensable to the student of marine
animals, It contains a considerable number of good figures of Acalephs, including
true Medusw, Beroids, and Hydroids. Henceforward, the number of Medusse known
is not only much larger than before, but they are described with much greater
fulness and nicety. At the same time, the investigations of Spallanzani® upon the
most delicate problems in the structure of animals excited universal attention by the
extraordinary disclosures to which they led. Cook’s voyages also stimulated inquiries
into the animals of every part of the globe; and Banks, Solander, and Forster, who
had made the voyage round the world with the great English captain, describe,

with the codperation of Ellis, the most remarkable natural productions brought home

1 Mttier (O. Fr.), Zodlogie Danice Pro- della Generazione di Needham e Buffon, Modena,
dromus, seu Animalium Danie et Norvegia indi- 1765, 4to. French translation by Regley: Nou-
genorum characteres. nomina, ete., Hafnie, 1776, velles Recherches sur les Deécouvertes micro-

8vo. — Zoologia Danica, seu Animalium Dani et scopiques et la Geénération des Corps organisés,

Norvegie rariorum Descriptiones et Historia, Hat-
niw et Lipsiw, 1779-1784, 2 vols. 8vo., and Hafniw,
1788-1806, 4 vols. fol. fig., with additions by <Abil-
gaard, Ifolten, Vahl, and J. Rathke.

* Fapricius (0.), Fauna Groenlandica, syste-
matice sistens Animalia Groanlandix occidentalis,
hactenus indagata, Hafnia et Lipsia, 1780, 8vo. fig.
This work is particularly important to the naturalists
of New England, as it contains the first descriptions
of many marine animals found on our own coasts.

8 SpALLANZANI (LaAz.), Prodromo di un opera
sopra le Riproduzioni animali, Modena, 1768, dto.
French translation by Bonnet: Programme ou
Précis Wun Ouvrage sur les Reproductions animales,
Geneve, 1768, 8vo. English translation: An Essay
on Animal Reproductions, ete., London, 1769, 8yvo.
Latin edition: Prolusio Operis de Animalibus mi-
croscopio visibilibus, Mutinw, 1770, 4dto.—Sagegio di

Osservazioni microscopiche, concernenti il Sistema

London et Paris, 1769, 2 vols. 8vo. fig. — Lettera
sulla Feeondazione artifiziale, e sull’ Elettriciti. delle
Torpedini; Opuse. Scelt. 1785. — Risultati di Es-
perienze sopra la Riproduzione della Testa nelle
Lumache terrestri; Mem. Soe. Ital. I. ps ool: die
p. 906, fig. — Sopra gl’ Animali delle Infusioni,
e sui nuovi Pensamenti, in proposito di Needham ;
Giorn. (Ital. TI. — Lettera relativa X diverse Pro-
duzioni marine; Opuse. Scelt. VII.—Opuscoli di

Fisica animale e vegatibile, Modena, 1776, 2 vols.

8vo. fig.; Venezia, 1782, 5 vols. 8vo. French
translation by Senebier: Opuscules de Physique

animale et végcétale, ete., Geneve, 1777; Paris, 1787,

2 vols. 8vo. English Translation, London, 1784,

2 vols. 8vo. — Dissertazioni di Fisica animale e vege-

tabile, Modena, 1780, 2 vols. German translation :

Abhandlungen iiber einige Gegenstiinde aus der

animalischen und vegetabilischen Naturkunde, Leip-

zig, 1778, 2 vols. 8vo.

-

Cuar. I. HISTORY OF THE ACALEPHS. 17

by these expeditions. Cavolini’ investigates the minute animals of the Mediter-
ranean, Pennant? those of the coast of England, Forskal and Lifling® those of the
Red Sea and of New Spain, Swartz* those of the Antilles, Modeer’ those of the
Northern Ocean, Scopoli® and Olivi’ those of the Adriatic, and Macri® those of the
Bay of Naples. Everywhere, stimulated by the influence of their great teacher, we
find the pupils of Linnzeus foremost in this race for knowledge. The harvest of Aca-
lephs is, however, still scanty; and the works of Pallas, Forskal, O. F. Miiller, and O.
Fabricius, are the only ones deserving now special attention, and this chiefly on
account of the influence their accurate descriptions had upon the progress of that
branch of Zodlogy. Pallas, in his Zodlogical Miscellanies, published in 1776, is the

first who gives accurate figures of Hydroids, without suspecting, however, that they

have the least relation to the Meduse proper.

The use of the microscope having become more frequent, objects are not only

examined with more care and accuracy than before, but also frequently magnified,

so as to give a more satisfactory view of their parts.

The treatise of Ellis? on

Corallines is, in that respect, a master-work, to this day indispensable to the student

of the Hydroids; and next to it must be ranked the work of Cavolini.

The last quarter of this century is marked by various compilations of the labors

1 Cavorinrt (Fin.), Memorie per servire alla
Storia dei Polipi marini, Napoli, 1785, 4to. fig. Ger-
man translation by W. Sprengel: Abhandlungen
iiber Pflanzenthiere des Mittelmeeres, Niirnberg,
1813, 4to. fig. — Nuove Ricerche sulle Gorgonie e
sulle Madrepore, Napoli, 1785, 4to. fig. German
translation by Zimmermann, Berlin, 1792, 8vo.—
Memoria sulla Generazione dei Pesci e dei Gran-
chi, Napoli, 1787, 4to. German translation by Zim-
mermann: <Ahhandlung iiber die Erzeugung der
Fische und der Krebse, Berlin, 1792, 8vo. fig.

* Pennant (Tuomas), British Zodlogy, Lond.
1761, 1 vol. fol.; 1768-1769, 3 vols. 8vo.; 103 ad-
ditional plates, 1770; 1776-1777, 4 vols. 8vo.;
1812, 4 vols. 8vo.

® Lortinc (Perer), Iter hispanicum; eller
Resa til spanska Liinderna uti Europa, och America,
Stockholm, 1768, 8vo. fig. German translation by
Al. B. Kolpin: Reise nach den spanischen Liin-
dern, Berlin, 1776, 1 vol. Svo. fig.

4 Swartz (OLor), Medusa unguiculata och Ac-
tinia pusilla upptiickta och beskrifna, Vet. Acad.
Handl. 1788, p. 198.

VOL. III.

oo

5 Moprrr (Apoirn), Om Sliigtet Sjokalf, Me-
dusa, in Svenska Vetenskaps Academiens Nya
Handlingar, Vol. XII. 1791.

° Scorotr (J. Anv.), Introductio ad Historiam
naturalem, sistens genera Lapidum, Plantarum et
Animalium, ete., in tribus divisa, subinde ad leges
Nature, Prage, 1777, 8vo.— Anni historico-natu-
rales, IV. Lipsiw, 1769-1772, 5 vols. 8vo.

7 Oxivi (Gius.), Zoologia Adriatica, ossia Cata-
logo raggionato degli Animali del Golfo e delle
Lagune di Venezia, Bassano, 1792, 4to. fig.

® Macri (Say.), Nuove Osservazioni intorno
la Storia naturale del Polmone marino degli Anti-
chi, Napoli, 1779, 12mo.

® Extis (J.), An Essay towards a Natural His-
tory of the Corallines and other Marine Productions
of the like kind, commonly found on the coasts of
Great Britain and Ireland, ete., London, 1755, 4to.
fiz. French translation: Essai sur ’Histoire Natu-
relle des Corallines, ete., LaHaye, 1758, 4to. fig.
German translation: Versuch einer Naturgeschichte
der Korall-Arten und anderer solcher Meerkorper,
1764, 4to. fig.

Ts
Niirnberg,

18 ACALEPHS IN GENERAL. Parr I.

of preceding years. Several works give such résumés; but they only serve to
brmg more glaringly to light the deficiency of the information upon which a natural
system might be built. The fullest of these compilations is the thirteenth edition
of the Systema Nature of Linnaeus, published between the years 1783 and 1793
by J. Fr. Ginelin’ Another is the Encyclopédie Méthodique, published by an
association of naturalists in Paris in 201 vols. 4to., between the years 1782) and
1852, with a view of presenting a complete eyclopedia of all that was known at
the time in every branch of Natural History. The Acalephs were compiled by
Bruguiere. Nearly all the illustrations published by earlier observers are here
reproduced, but nothing new is added. These publications have lost their merit
now, and can only be used as books of easy reference to the scattered descriptions
and figures of previous writers.

Besides the publication of these systematic cyclopedias, we have also to notice
the scientific dictionaries of the time, which aimed at giving similar, though more
condensed, accounts of the knowledge of their age? but did not add much to the
real progress of science. Not so with the proceedings and transactions of learned
societies ;° for in their volumes we find innumerable original papers in which the
discoveries of the day are recorded, and amone them, here and there, some notices
bearing more or less directly upon the natural history of the Acalephs. The most

important of them have already been quoted.

SO PLON “lV.
THE SYSTEMATIC WRITERS AND ANATOMISTS.
With the beginning of the nineteenth century opens another era in the history

of Acalephs. Now, for the first time, are successful attempts made to combine sys-

tematically the investigations of the past, and every year adds new materials to

1 Guevin (J. Fr.), Car. a Linné Systema Na- those of the Royal Society of London, of the Aca-
ture per Regna tria Natura, ete., editio decima demia Nature Curiosorum, and of the Academy of
tertia, aucta et reformata, Leipzig, 1788-1793, 7 Sciences of Paris. The former are published under
vols. 8vo. the title of Philosophical Transactions of the Royal

2 VaLMonT DE GBomanre, Dictionnaire raisonné Society, the latter as Mémoires de I’Académie des
universel histoire naturelle, Paris, 1765-1768, 5 Sciences de Paris, and those of the Academia Na-
vols. 8vo.; 2e édit. 1768, 1769, 12 vols. 8vo.; 35e ture Curiosorum appeared, first under the title Mis-
édit. 1775, 6 vols. 8vo.; 4e edit. Lyon, 1791, 15 cellanea, next as Ephemerides, and afterwards as
vols. 8vo. Acta, and are now continued as Nova Acta Aca-

® The most valuable of these transactions are demizv Cwsareo-Leopoldine Natura Curiosorum.

HISTORY OF THE ACALEPHS. 19

Cuape. I.

the edifice. Thus far all the Discophoree, whether covered-eyed or naked-eyed, had
been placed in one and the same genus, and even the Ctenophors were associated
with them. Only a few species of Siphonophore were referred to other genera:
but then these were not placed in close proximity with the Meduse proper, and
the Hydroids were unhesitatingly referred to the class of Polyps, or at least arranged
among them. The whole number of genera distinguished among the animals now
referred to the class of Acalephs amounted only to thirteen in 1801; namely, Beroe
Brown, Medusa L., Physalia Lamrk. (first called Arethusa by P. Brown, then Physalis
by Osbeck and Salacia by Linnaeus), Velella Lamrh., and Porpita Lamrk. (first called
Phyllodoce and Thalia by P. Brown), Gleba Brug., Physophora Forsk., Lucernaria
Mill, Hydra L., Coryne Gartn., Tubularia Z., Sertularia Lani. Millepora L.

Owing to the greater number of Meduse now known, imcluding species from
distant parts of the world, and also to the discovery of numerous animals more
or less closely allied to them, it has become necessary to institute comparisons
between the animals of this class and the representatives of other classes, which
This is therefore truly the age of Comparative

were not even suggested before. @
Natural History; and a new science, Comparative Anatomy, arises with it, by the
eigantic labors of the scientific hero of modern times.

Péron and LeSueur! open this period with investigations upon a far greater
number of species of Acalephs than had been observed by all the investigators of
former ages taken together. Engaged as naturalists in the expedition of Captain
Baudin to the South Seas during the first four years of this century, they had
the fullest opportunities of examining these animals alive; and LeSueur, with incom-
parable skill, reproduced their delicate appearance in a series of colored plates, so
magnificent and of such costly execution, that to this day a small part of them
only have been published. But these illustrations were deposited in the library
of the Jardin des Plantes in Paris, and have been extensively used by French
They

are referred to, and partly copied by, de Blainville in his Manuel dActinologie.

naturalists who have written upon Acalephs during the last thirty years.

1 Peron (FR.) et LeSurevr (C. A.), Voyage
de découvertes aux Terres Australes, pendant les
années 1800-1804, Paris, 1807-1816, 3 vols. 4to. fig.
— Histoire générale et particulicre de tous les Ani-
maux qui composent la famille des Méduses, Ann.
Mus. XIV. p. 218.— Tableau des Caracteres géné-
riques et spécifiques de toutes les especes de
Méduses connues jusqu’a ce jour. Ann. Mus. XIV.
p- 325.—Sur les Méduses du genre Equorée, Ann.
Mus. XV. p. 41.— LeSueur by himself published

two papers relating to the Acalephs and allied ani-
mals: Mémoire sur quelques nouvelles especes
@Animaux Mollusques and Radiaires recueillies dans
la Méditerranée pres de Nice, Journal de Physique,
vol. 77, p. 119, and Mémoire sur Vorganisation des
Pyrosomes et sur la place qwils doivent occuper
dans une classification naturelle, Journal de Phy-
sique, vol. 80, p. 413. He was the first to suggest
that the Siphonophore are compound animals, — an

opinion now almost universally admitted.

20 ACALEPHS IN GENERAL.

Parr I.

Lesson used them while preparing his Prodrome dune Monographie des Méduses
and his Histoire naturelle des Acaléphes; and Milne-Kdwards has caused some to
be engraved for the new illustrated edition of Cuvier’s Régne Animal.’ The pub-
lications of Bory de St. Vincent* and of Tilesius,? which next follow, are interesting
as furnishing the first mdications upon the Diphyes; while those of Scoresby,’ Otto,’
VanHasselt,? Eichwald,” DeHaan? Guilding,’ Piet," Baird," Woodward,” von Olfers,!
Meyen," Patterson,” Forbes, Goodsir" and Hyndman," add new species to our lists,
Bose’s'® Natural History of the

Worms also contains some valuable remarks. On account of his residence upon

and new facts respecting species already known.

our southern coasts, the works of Bose are interesting to American naturalists.
While Péron and LeSueur and their successors were thus steadily enlarging the

range of our knowledge by special investigations, the systematic writers of this period

began to perceive more and more clearly the general affinities of these animals ;

1 Cuvier (G.), Le

apres son organisation, pour servir de base & PHis-

Reene animal distribué

toire naturelle des animaux, et d’introduction 4 ?Ana-
tomie comparée ; Edition accompagnée de planches
gravées, par une réunion de disciples de Cuvier,
publice par Fortin, Masson & Co., Paris, Svo. since
1856. The volume containing the <Acalephs is
edited by Milne-Edwards.

2 Bory BE Sarnt-Vincenr (J. B. G.), Voyage
dans les quatre principales iles des mers d’ Afrique,
Paris, 1504, 3 vols. Svo. avee atlas.

® Truestus (W. G.), Naturhistorische Friichte
der ersten kaiserlich-russischen Weltumseglung, Pe-
tersburg, 1813, Ato.

4 Scorespy (W.), An Account of the Arctic
Regions, Edinburgh, 1820, 2 vols. 8yo. fig.

®° Orro (Ap. W.), Conspectus animalium quo-
rumdam maritimorum nondum = editorum, Vratis-
laviw, 1821, dto. fig. — Beschreibung einiger neuer
Mollusken und Zoophyten, N. Act. Nat. Cur. XI.
2, p. 273, fig.; Isis, 1824, VI. p. 626.

® VanTassett, Ueber Physalia, Brief an Prof.
VanSwindern, Isis, 1823, p. 1413.

7 Ercuwatp (Ep.), Observationes nonnull
cirea fabricam Physaliw, Mém. Acad. Petersb. 1824,
IX. p. 455.

® DeHaan (W.), Verhandeling over de Rang-
schikking der Velellen, Porpiten und Physalien,

Bijdrag Natuur. Wetens, 1827, Il. p. 489.

* GuiLpInG (Lansp.), Mollusca Caribbaeana,
if

Zool. Journ. 1827, II. p. 403.

Piet, Description de la grande Physale et
dune curieuse espece de Médusaire, trouvées sur
les edtes de Bretagne, Lye. Armor. XII. p. 189.

1 Barrp (Dr.), On the Luminousness of the
Sea, Mag. Nat. Hist. 1830, III.

® Woopwarp (Sam.), On the Luminosity of
the Sea, Mag. Nat. Hist. 1831, IV. p. 285.

% Von Otrers, Ueber die grosse Seeblase,
Physalia Arethusa, und die Gattung der Seeblasen
derlin, 1851.

4 Mryen (F. J.), Beitriige zur Zoologie; N.
Act. Nat. Cur. XVI. suppl. I. 1834.

15 PATTERSON

im Alleemeinen. Ak. Wiss.

(Rover), Deseription of the

Cydippe pomiformis (Beroé ovata, Flem.), with
Notice of an apparently undescribed Species of Bo-
lina, also found on the Coast of Ireland, Proce. Roy.
Trish Acad. 18

339, p. 237.

1 RForses (Epw.), Contributions to British
Actinology, An. and Mag. Nat. Hist. 1841, VII.
p- 81.— Forpes (Epw.) and Goopsir (J.), On
the Corymorpha nutans, Ann. and Mag. Nat. Iist.
1840, V. p. 309.

™ Wynpman (G. C.), On the Occurrence of the
genus Diphya on the Coast of Ireland; Ann. and
Mag. Nat. Hist. 1841, VII. p. 164.

1 Bosc (L. A. G.), Histoire naturelle des Vers,

Paris, 1802, 18mo. 3 vols. fig.

HISTORY OF THE ACALEPHS. a1

Cuap. I.

and the works of Cuvier! Blumenbach, Duméril,? Lamarck,* Oken,? Goldfuss,® and
Schweiger, suggest successive improvements in their classification. There remains,
however, so much uncertainty respecting the general characteristics of the different

groups of Radiates or Zoophytes, that naturalists disagree even as to the classes

that should be referred to this type.

worms and the

to the Articulata, and the second to his Microzoaires.

the Actinie with the Acalephs, while he afterwards separates them.#

Cuvier, for imstance, unites the Intestinal

Infusoria with the Radiates, while DeBlainville refers the first

Cuvier also at first unites

Even the

limits between the Radiates and the lower Mollusks are ill-defined, so that Sa-

1 Cuvier (GrorGe), Tableau élémentaire de
VHistoire naturelle des animaux, Paris, 1798, Svo.
fiz. — Le Regne animal distribué d’aprés son organi-
sation, pour servir de base & VHistoire naturelle
des animaux et @introduction & PAnatomie comparée,
Paris, 1817, 4 vols. 8vo. fig.

2 Brumensacn (J. Fr.), Handbuch der Natur-
geschichte, Gétting. 1779, 8vo. fig.; Gotting. 1825
(11th ed.), Manuel

@Histoire Naturelle, Paris, 1805, 2 vols. 8vo. fig.

French transl. by Artaud,

5 Dumirit (A. M. C.), Zoologie analytique, ou
Méthode naturelle de Classification des Animaux,
Paris, 1806, 8vo.

4 Lamarck (J. B. pr), Histoire naturelle des
animaux sans vertebres, présentant les caracteres
généraux et particuliers de ces animaux, leur dis-
tribution, ete., Paris, 1815-1822, 7 vols. 8vo.; (See.
édit. augmentée de notes par MM. Desnayers et
Mitnre-Epwarps), Paris, 1835-1843, 10 vols. 8vo.
— His Cours de Zoologie is also important.

° Oxen (Lor.), Lehrbuch der Naturgeschichte,
Weimar, 1816, 2 vols. Svo.— Allgemeine Natur-
geschichte, Stuttgart, 1855-1842, 14 vols. 8vo. fig.

° Gotpruss (G. A.), Handbuch der Zoologie,
Niirnberg, 1820, 2 vols. 8vo.

7 Scuweicer (A. Fr.), Handbuch der Natur-
geschichte der skelettlosen ungegliederten Thiere,
Leipz. 1820, 8vo.

books of that period.

One of the most valuable text-
It is full of original obser-
vations.

* At the time Cuvier characterized the Acalephx
as a distinct class among Radiata in the first edition

of the Regne Animal, published in 1817, the great

French naturalist included among them the Ace-
tinix, now generally referred to the class of Polypi.
To this class he himself removed them in the second
edition of that important work. It is a remarkable
circumstance, that no advance was made towards
a natural classification of the Acalephs from the
days of Aristotle to the period when Savieny,
Schweiger, Cuvier, and others attempted to improve
In the first

edition of the Regne Animal we find the same

our knowledge of the lower animals.

distinction introduced among the Acalephs, between
the free and the fixed Acalephs, which Aristotle had
adopted ; whilst a number of animals which must
be united with the Acalephs are still left among
the Polyps, as they were centuries before. From
the beginning, then, the class of the Acalephe was
far from being circumscribed within natural limits ;
and we shall presently see, that it has required
the indefatigable investigations of some of the ablest
observers for about a century, before the natural
affinities of the animals belonging to this class were
fully appreciated. It is one of the most instructive
lessons for a student of nature to trace the grad-
ual progress of the discoveries which have led to
the views now prevailing respecting these animals,
as they involve discussions upon all the funda-
mental principles of Zodlogy. Instead, therefore,
of giving only the results of my own studies of
the Acalephs, I will attempt, in this work, to trace
also this successive growth of our present knowl-
edge, with the special view of teaching the young
naturalists of America how to proceed in their

own researches.

22 ACALEPHS IN GENERAL. Parr I:

vigny’s’ admirable researches upon compound <Ascidians may be said to have

to}

contributed largely to the progress of the natural history of Acalephs. The same

is true of the papers of Chamisso? and Cuvier?

upon the Salpx. The attempt of

Latreille * to characterize the natural families of the animal kingdom did nothing

towards improving the classification of the Acalephs; but Van der Hoeven gave a

,

good account of what was then known about them. In the special Faun of Risso®

and Fleming,’ there is much to be gleaned. The paper of Rang*® deserves especially

¢
to be noticed, as it is very important for the study of the Beroids.

The interest excited by the success attending a combination of political objects
with scientific explorations in the voyage of Captain Baudin soon led other powers
to imitate the example of the French government, and the result has been a series

of invaluable contributions to science. The most important of these scientific

exploring expeditions are as follows: that of Admiral Krusenstern, with Langsdorf

and Tilesius as naturalists;’ the two voyages of Captain Kotzebue,! with Chamisso

and Exschscholtz as naturalists; then the voyage of Captain Freycinet" in the Uranie

1 Savieny (Jures-Chsarn), Mémoires sur les Zoology, by the Rey. W. Clark, Cambridge, 1856-

animaux sans vertebres, Paris, 1816, 2 vols. Svo. 1858, 2 vols. 8vo. fig. This is the best modern

See also the great work upon Egypt published by
order of Napoleon after the memorable campaign
of 1798.

* Cuamisso (ALBERTUS DE) Ev EyseENHARDT
(C. G.), De Animalibus quibusdam e classe Vermi-
um Linneana, in circumnavigatione terra, auspi-
cante comite N. Romanzorr, duce Orr. pe Korze-
BUE, ann. 1815-1818 peracti, observatis. Act. N,
Nat. Cuy. 1819, 4to.

® Cuvier (G.), Mémoire sur les halides et
les Biphores, Ann. du Mus. 1804, IV. p. 560,—
Mémoire sur les Ascidies, Mém. du Mus. 1815, IT.
p- 10. Both these papers are reprinted in Mc-
moires pour servir & lTistoire et & Anatomie des
Mollusques, Paris, 1817, 4to. fig.

* LarreitteE (P. A.), Familles naturelles du
Reene animal, exposces suecessivement et dans un
ordre analytique, avee Vindication de leurs

Paris, 1825, 8vo.

genres,

®* Van ber Horven (Jonan.), Tabula Reeni
animalis, additis Classium Ordinumque characteri-
bus, Lugd.-Bat., 1828, fol. — Handbock der Dier-
kunde, Delft, 1827, 8vo.; Rotterdam, 1828, 3d edit.,
Handbook of

2 vols. 8vo.— English translation :

text-book of special Zodlogy.

® Risso (A.), Histoire naturelle des principales
productions de l'Europe méridionale, particulitrement
de celles des environs de Nice et des Alpes mari-
times, Paris, 1826, 5 vols. Svo. fig.

7 Freminc (Joun), A History of British Ani-
mals, exhibiting their Descriptive Characters, Edin-
burgh, 1828, 8vo.— The Philosophy of Zoology,
London, 1822, 2 vols. Svo.

5 Rana (SANvER), Etablissement de la famille
des Beéroides dans Vordre des Acalephes libres, et
Description de deux genres nouveaux qui lui
appartiennent, Mém, Soe. Hist. n. Par. IV. p. 166,
fig.; Férussac, Bull. 1829, 17, p. 141.

® See note 3, p. 20.

" Korzebur (Orro), Voyage pittoresque autour
du monde, sur le brick le Rurick, en 1815-1818,
Paris, 1821-1823, fol. — Neue Reise um die Welt
in den Jahren 1825-1826, Weimar, 1830, 2 vols.
8vo. fig.

1 Frevorner (L. pe), Voyage autour du monde
sur les corvettes ’Uranie et la Physicienne, pendant
les années 1817-1820, Paris, 1824, 8 vols. 4to. and

4 vols. atl. fol.

Cuar. I. HISTORY OF THE ACALEPHS. 93

and Physicienne, with Quoy and Gaimard? as naturalists; that of Captain Duperrey ?
in the Coquille, with Lesson and Garnot® as naturalists; the two voyages of Captain
Dumont dUrville,t the first in the Astrolabe with Quoy and Gaimard, and_ the

second in the Astrolabe and Zélée with Hombron and Jacquinot, as naturalists ;

that of Captain LaPlace® in the Favorite, with Eydoux and Baume as naturalists ;

that of Captain Vaillant? in the Bonite, with Eydoux and Souleyet as naturalists ;

and that of Captain Dupetit-Thouars *

in the Venus.

These publications are truly

admirable in their execution, and that of the Astrolabe particularly important for the

Acalephs.

and in England can fairly be placed by the side of them.’

The more recent exploring expeditions fitted out by the United States

In this connnection

it is fitting to remember the great works of Humboldt, the scientific expedition

to Egypt, those in Morea and Algiers, and the many more recent explorations in

almost every part of the world.

1 Quoy er Gararp, Zoologie du Voyage de
l'Uranie, sous les ordres du CarrTaAIne FREYCINET,
de 1817 & 1820, Paris, 1824, 4to. atl. fol.

2 Durerrey (L. J.), Voyage autour du monde
sur la corvette la Coquille, pendant les années
1822-1825, Paris, 1828, 6 vols. 4to. and 4 vols.
atl. fol.

8 Lesson (R. P.) er Garnor (P.), Zoologie
du Voyage autour du monde exécuté sur la Corvette
la Coquirte par L. Durerrey commandant de
YExpédition, pendant les années 1822-1825, Paris,
1829, 2 vols. 4to. atl. fol.

4 Dumont-p’UrRVILLE (J.), Voyage autour du
monde et & la recherche de la Pérouse, sur la
corvette ’Astrolabe, pendant les années 1826-1829,
Paris, 1830, et suiv., 6 vols. 8vo. Atl. fol. — Voyage
au Pole Sud and dans l’Océanie sur les corvettes
lV Astrolabe et la Zélée, pendant les années 1837-
1840, Paris, 34 vols. 8vo. atl. fol.

5 Quoy ET Gaimarp, Zoologie du Voyage de
l’Astrolabe, sous les ordres du Carrrainr Dumont
D’'URVILLE, pendant les années 1826-1829, Paris,
1830-1833, 5 vols. 8vo. atl. fol. — Observations
Zoologiques faites a bord de lAstrolabe en Mai
1826, dans le Détroit de Gibraltar, Ann. Se. n.
1827, X. pp. 5, 172, 225, fig.

6 LaPriace (C. P. Tu.), Voyage autour du

monde par les mers de l’Inde et de la Chine, sur

la corvette la Favorite, pendant les années 1830-
1852, Paris, 1835-18359, 5 vols. 8vo. Histoire
naturelle, vol. 5, par Eydoux et Baume.

7 VAILLANT, Voyage autour du monde, sur la
corvette la Bonite, pendant les années 1856 et
1837, Paris, 1838 et suiv. Zoologie par Eydoux
et Souleyet, 2 vols. Syo. et atl. fol.

8 Dupetit-Tnovars, Voyage autour du monde
sur la frégate la Vénus pendant les années 1837-
1839, Paris, 1840, et suiv. 10 vols. 8vo. atl. fol.
Zoologie par Isid. Geoffrey St. Hilaire et Valen-
ciennes, 1 vol. 8vo. et atl. fol.

®* Bevtcuer (E.), Narrative of a Voyage round
the World in the Sulphur, 1836-1842, London, 1845,
2 vols. 8vo.— The Zodlogy of the Voyage of the
Sulphur, by R. B. Hinds, London, 1845, 2 vols.
4to. — Narrative of the Voyage of the Samarang
among the Islands of the Eastern Archipelago, 1843—
1846, London, 1848, 2 vols. 8vo.— The Zodlogy
by Adams and Reeve. — Firzroy (Roserr), Pro-
ceedings of the Beagle’s Second Voyage to South
America, 1831-1836, London.— The Zodlogy of
the Voyage of the Beagle, edited and super. by
Ch. Darwin, London, 1839-1845, 5 vols. 4to. —
Wires (Cu.), Narrative of the United States Ex-
ploring Expedition during the Years 1838-1842,
Philadelphia, 1845, 3 vols. 8vo.— The Zoology,

Zoophytes, and Crustacea, by J. D. Dana.

24 ACALEPHS IN GENERAL. Parr I.

In the year 1829, Esechscholtz,) who had made two voyages round the world
with Captain Kotzebue, published his system of the Acalephs, the most important
work yet published upon this class, as it embodies not only the results of all the
investigations of his predecessors, but presents, with great fulness and precision,
origmal investigations made by himself upon all the members of this class now
referred to it, with the sole exception of the Hydroids. The figures, though mere

outlines, are invaluable for their aceuracy. In the following year DeBlainville
published a general account of the Zodphytes, in which the Acalephs occupy a large
place; but it can hardly be said to mark a progress in our science, notwithstanding
the many additions it contains in the details, for De Blainville? has been led in
the classification to make changes which are unjustifiable, and to remove from

among the Acalephs a large number of genera which undoubtedly belong to this
g : 2

class.

The more recent publications of systematic importance are those of Mertens?

Brandt,’ and Lesson ;° and with the latter ends fairly the period of the purely

descriptive history of Acalephs.

1 Escuscnoitz (Fr.), System der Acalephen,
eine ausfiihrliche Beschreibung aller medusenartigen
Strahlthiere, Berlin, 1829, 4to. with fourteen plates.
Eschscholtz made two voyages round the world,
the first in 1815-1818 as physician on board the
brig Rurick under the command of Captain Otto
von Jxotzebue, while Chamisso was naturalist to
the expedition.
to the report of this voyage. The results of the
second voyage, in the years 1825-1826, on board
the Predpriaetié sloop of war, under the command
of the same distinguished seaman, are particularly
interesting to American naturalists, as, during a
prolonged stay upon the north-west coast of this
continent, Eschscholtz visited California, and discoy-
ered a great many curious animals peculiar to our
western Fauna, which are described for the first
time in the “ Zoologischer Atlas, enthaltend Abbild-
ungen und Beschreibungen neuer Thierarten, wiih-
rend des Flottcapitains vy. Kotzebue’s 2ter Reise um
die Welt, von Dr. Friedr. Eschscholtz, Berlin, 1829—
1833, in 5 Hefte,” the last of which was edited by
Rathke, after the author’s death. The name of
Eschscholtz is familiar to every lover of flowers, in
the elegant plant that now adorns our gardens and

which bears his name, the Eschscholtzia of California.

There are, still, many papers published at a later

The scientific results of the first voyage of Kotzebue
were in part published by Chamisso and Eysenhardt
in N. Act. Nat. Cur. X. 1821.

* Brainvitte (HW. D. pr), Article Zoophytes
in Nouveau Dictionnaire histoire naturelle, Paris,
1850. Republished under the title of Manuel
d’Actinologie, Paris, 1854, 2 vols. 8vo. fig.

®* Mertens (H.), Beobachtungen iiber die Be-
roéartigen Acalephen, Mém. Acad. Pétersb. 1833.

* Branpor (J. F.), Ausfiihrliche Beschreibung
der yon C, IH. Mertens beobachten Schirmquallen,
ete., Petersb. 1858, dto. fig. col., Mém. Acad. Pét.
scr. 6, 11. Also Prodromus, ete. 1835.

5 Lesson, Ilistoire naturelle des Zoophytes, Aca-
léphes, Paris, 1845, 1 vol. Svo. fig. — Centurie
Zoologique, Paris, 1850, 8vo. fig. — Tableau de la
famille des Zoophytes Béroides, Ann. Se. Nat. V.
p- 254, 1856. Translated in Proc. Zool. Soe.
III. p. 2.— Prodrome @une Monographie des Mé-
duses, in-dto. de 62 pages, Rochefort, juin, 18357.
Edw. Forbes questions the existence of this work ;
but it was really published, in the shape of auto-
graphed sheets, of which, however, a very small
number of copies were issued. I myself used it
when preparing the Nomenclator Zoologicus. The

copy I saw belongs to Duméril.

Cuap. I. HISTOR Ys OR DE Hee AGA HPT Ss.

bo

5

date, which, however, contain so little concerning the structure or embryonic deyelop-
ment of the Acalephs, that they may fairly be enumerated here. Such are Peach’s
Observations on the Luminosity of the Sea;’ Liitken’s® classification of the Meduse ;
Miiller’s* Medusee

Catharina; Alders’s® new British Hydroids, and Catalogue of the Zoidphytes of North-

Forbes and Goodsir’s® description of new species; F. of Santa
umberland ; Gould’s enumeration of those of Massachusetts ;° Sars’s, and Leuckart’s
Contributions to those of the Mediterranean ;* Gosse’s Rambles along the British
shores,* ete.; the Dictionnaire des Sciences Naturelles, the Dictionnaire Classique,”
Ersch and Gruber’s Eneyclopiidie,” the Isis of Oken, the Annales des Sciences Natu-
relles, the Archiv fiir Naturgeschichte, the Zeitschrift fiir wissenschaftliche Zodlogie,
Miiller’s Archiv, the Annals and Magazine of Natural History; and the innumerable
smaller periodical publications, and proceedings of learned societies of our time,
should also be consulted. Enough is now known of the Acalephs to show, that,
since they undergo the most extraordiary changes during their life, the history
of no one species can be considered as satisfactory before it has been traced in
all its conditions. Henceforth, mere descriptions of isolated forms can have but
a very limited interest. The time when it could be thought sufficient merely to
draw up a diagnosis, in order to characterize a species, is indeed gone for the
Acalephs, and, I trust, for other classes of animals also. This great change in the
requirements of our science was chiefly brought about by the investigations related
in the next section.

1 Peacu (Cu. W.), Observations on the Lumi-
nosity of the Sea, with Descriptions of the several
Objects which cause it, Ann. and Mag. Nat. Hist.
1850, VI. p. 425.

* LtrKen (C. F.), Ueber die systematische Grup-
pirung der Medusen, Vidensk. Meddels. 1849-1850,
p- 15. I only know this paper from the abstract
in Arch. f. Naturg. 1854, XX. p. 424.

® Forbes (Epw.) and Goopsir (J.), On some
remarkable marine Invertebrata, new to the British
Seas, Trans. Roy. Soe. Edinb. 1851, XX. p. 307.

4 MULver (Fr.), Zwei neue Quallen von Santa
Catharina (Brasilien), Abh. Nat. Ges. Halle, 1859,
Viemps

5 AtpEeR (Jos.), Notice of some new Genera
and Species of British Hydroid Zoophytes, Ann.
and Mag. Nat. Hist. 1856, XVIII. p. 353 and 439.
— Catalogue of the Zoophytes of Northumberland
and Durham, Trans. Tyneside Natur. Club; in ab-
p-. 242.

VOL. III. 4

stract in Mier. Journ. V.

®° Goutp (A. A.), Report on the Invertebrata
of Massachusetts, Boston, 1841, 8vo.
7 Sars (M.), Bidrae til kundskaben om Middel-

havets Littoral-Fauna, Reisebemiirkninger fra Ita-

lien, Christiania, 1857, 8vo. Abstracts of it may be
found in Arch. Naturg. 1858, II. p. 156 and 163.
— Levoxanrr (R.), Beitriige zur Kenntniss der Me-
dusenfauna von Nizza, Arch. Naturg. 1856, I. p. 1.

* Gosse (Tu. H.), Naturalist’s Rambles on the
Devonshire Coast, London, 1853, 1 vol. Svo. fig. —
Tenby, a Sea-side Holiday, London, 1856, 1 vol.
Svo. fig.

® Dictionnaire des Sciences Naturelles, publie

par les Professeurs du Jardin du Roi, Paris et
Strasbourg, 1816-1829, 60 vols. 8vo. fig.
Dictionnaire Classique d’Histoire naturelle,

etc., Paris, 1824-1830, 17 vols. 8vo.

1 Erscu (J. 8.) und Gruser (J. G.), Allge-
meine Encyclopiidie der Wissenschaften, Leipzig,
1818 und folg. 4to.

26 ACALEPHS IN GENERAL. Parr I.

The harvest to be gathered for the history of Acalephs from the works of
anatomists of preceding periods would be so meagre that I have not even alluded
to them thus far; though, with reference to some particular points of their structure,
and especially those bearing upon their reproduction, it will be necessary hereafter
to return to a consideration of the methods applied in their investigations by the
great anatomists and physiologists of the eighteenth century, in order to trace the
connection between the progress of our knowledge of the lower animals and the
general progress of Zoblogy as a science. We owe to Cuvier the first anatomical
description of a Medusa;' and next to this paper, those of Tilesius? Eysenhardt,
Giide,t Baer? and Delle Chiaje,° deserve a special notice. — Exschscholtz,’ in his clas-
sical treatise on Acalephs, gives the first summary of the anatomy of these animals,
and this is soon followed by Mertens’s* investigations of the Beroids; Brandt's?
descriptions of the Medusxe of Mertens, with numerous anatomical details; and the
more special illustrations of Ehrenberg” on the organization of the Meduse of the

1

German Ocean; Milne-Edwards’s" masterly observations on various Acalephs ; Grant ”

on Beroe; R. Wagner® on the structure of Pelagia; Costa,'? Hollard,” and Krohn”

1 Cuvier (G.), Sur Vlorganisation de quelques
Meéduses, Bull. Soc. Philom. p. 69, Paris, 1800.

2 TinEstos es (W. .G.), Natur-
geschichte der Medusen, N. Act. Nat. Cur, XV.

2, p. 247, fig., contains magnificent figures.

deitriige zur

8 Eysennarpr (C. W.), Zur Anatomie und
Naturgeschichte der Quallen, N. Act. Nat. Cur. X.
p. 375, fig., contains a very elaborate anatomy of
the Rhizostoma Cuvieri.

4 Gape (Ilene. M.), Beitriige zur Anatomie
und Physiologie der Medusen, Berl. 1816, Svo.

5 Barr (Pror. K. E. v.), Ueber Medusa aurita,
Meckel’s Arch. VIII. p. 569.

® Dette Curase (Str.), Memorie sulla Storia e
Notomia degli Animali senza vertebre del Regno
di Napoli, Nap. 1825-1830, 4 vols. 4to. fig. —
Deserizione et Notomia degli Animali invertebrati
della Sicilia citeriore, ete., Nap. 1841-1844, 6 vols.
4to.; 2 vols. fig.

7 See note 1, p. 24.

8 See note 3, p. 24.

® See note 4, p. 24.

10 EnrRenBerG (C. G.), Die Akalephen des
rothen Meeres und der Organismus der Medusen
der Ostsee, Ak. Wiss. Berlin, 1856, 4to. fig.

U Mitne-Epwarps (II.), Observations sur la
structure de la Méduse marsupiale ou Charybdée
marsupiale de Péron et LeSueur, Ann. Se. Nat.
1835, vol. 28, p. 248, fig. — Observations sur la
structure et les fonctions de quelques Zoophytes,
Mollusques et Crustacés des Cotes de France, Ain.
Se. Nat. 2de sér. 1541, vol. 16, p. 193, fig. — Ann.
Se. Nat. 5e sér. 1857, vol. 7, p. 285. — Recherches
Anatomiques et Zoologiques faites pendant un voy-
age sur les cdtes de la Sicile, Paris, 1844, 4to. fig.
vol. 1, p. 57. The last paper gives full descriptions
of the gastrovascular system.

2 Grant (R. E.), On the Nervous System of
Beroe Pileus, Trans. Zool. Soc. I. p. 9, fig.

18 Wacner (R.), Ueber den Bau der Pelagia
noctiluca und die Organisation der Medusen, Leip-
zig, 1841, fol. fig.; also in Icones Zootomicx, ete.,
Leipzig, 1541, fol.

4 Costa (O. G.), Note sur l'appareil vasculaire
de la Vélelle, Ann. Se. Nat. 2de sér. 1841, vol.
16, p. 187, fig.

1 Toitarp (II.), Recherches sur lorganisation
des Vélelles, Ann. Se. Nat. 3e sér. 1845, vol. III.

© Kroun (A.), Ueber die Anwesenheit cigen-
thiimlicher Luftkaniile bei Velella und Porpita, Arch.
Naturg. 1848, vol. 1, p. 30.

HISTORY OF THE ACALEPHS. 27

Cuap. I.
on Velella; Philippi! on Physophora; Ecker and Leydig on Hydra ;? Allman on
Cordylophora ;? Quatrefages on Physalia ;* Huxley’s Anatomy and Affinities of the
Meduse ;°> my own contributions to the natural history of the Acalephs of North

America ;® and the works and papers of Will’ Sars,> Forbes? Leuckart, Vogt,"

Killiker}?” Gegenbauer,” and Schultze.¥

embryology of the Acalephs will be enumerated in the next section.

The papers relating more especially to the

General

accounts of the structure of the Acalephs may be found in most text-books on

Comparative Anatomy, especially in the more recent ones.”

1 Puiriprr1 (R. A.), Ueber den Bau der Phy-
sophoren und eine neue Art derselben; Miiller’s
Arch. 1843, p. 58, fig.

2 Eoxer (At.), Zur Lehre vom Bau und Leben
der kontractilen Substanz der niedersten Thiere,
Basel, 1848, 4to. fig. — Lrypia (F.), Einige Bemer-
kungen iiber den Bau der Hydren, Miiller’s Arch.
1854, p. 270.

® Arpman (G.J.), On the Anatomy and Physi-

olosy of Cordylophora, Phil. Trans. Roy. Soe. 1853,
vol. 143, p. 367.

4 Quarreraces (A. DE), Mémoire sur Vorgani-
sation des Physales, Ann. Se. Nat. de sér. 1854,
vol. 2.

5 Huxvey (Tu. H.), On the Anatomy and Affini-
ties of the Family of the Medusz, Phil. Trans. Roy.
Soc. 1849, p. 413. — On the Anatomy of Physalia,
Proe. Linn. Soe. 1848.— Observations upon the
Anatomy of the Diphydw, and the Unity of Organi-
zation of the Diphyde and Physophoride, Proc.
Linn. Soc. 1849.— Report on the Structure of the
Acalephs; Brit. Assoc. for Ady. Se. 1851. — Ueber
die Sexual Organe der Diphyden und Physophoriden ;
Miiller’s Arch. 1851.— The Oceanic Hydrozoa; a
Description of the Calycophorid and Physophoride
observed during the Voyage of Hl. M. 8. Rattle-
snake; Ray Society, London, 1859, fol. fig.

6 Acassiz (L.), Contributions to the Natural
History of the Acalephe of North America, Parts
I. and IL; Amer. Acad. Arts and Se. vol. IV.
1850.

TOWittis (J
Beschreibung und Anatomie der Akalephen, Leip-
zig, 1844, dto. fig.

G. Fr.), Hore tergestine oder

® Sars (M.), Fauna littoralis Norvegiw, Christi-
ania, 1846 and 1856, fol. fig.

®° Forses (Epw.), Monograph of the British
Naked-eyed Meduse; Ray Society, London, 1847,
fol. fig.

10 Leuckart (R.), Ueber den Bau der Phy-
salien und Siphonophoren, Zeitsch. f. wiss. Zool.
1851, vol. 3. — Zoologische Untersuchungen, 1853,
Ato. fig. — Zur niihern Kenntniss der Siphonophoren
von Nizza, Arch. Naturg. 1854, I. p. 249.— Also
Frey und Levcxart, Beitriige zur Kenntniss wir-
belloser Thiere, Braunschweig, 1847, 4to. fig.

1 Voar (C.), Ueber die Siphonophoren, Zeitsch.
f. wiss. Zool. 1852, vol. 3, p. 522. — Untersuchungen
iiber Thierstaaten, Frankfurt, 1851, Svo. fig. —
Recherches sur les animaux inférieurs de la Meédi-
terrannée ; Premier Mémoire, sur les Siphonophores
de la mer de Nice, Geneve, 1854, 4to. fig.

2 Kotter (A.), Die Schwimmpolypen oder
Siphonophoren von Messina, Leipzig, 1853, fol. fig.

13 GEGENBAUER (C.), Beitriige zur nihern Kennt-
niss der Schwimmpolypen (Siphonophoren) Zeitsch.
f. wiss. Zool. 1854, vol. 5, p. 285, and p. 442.
Bemerkungen iiber die Randkérper der Medusen,
Miiller’s Arch. 1856, p. 230. — Studien iiber Organi-
sation und Systematik der Ctenophoren, Arch.
Nature. 1856, I. p. 163.— Versuch eines Systems
der Medusen, mit Beschreibung neuer oder wenig
gekannter Formen; Zeitsch. f. wiss. Zool. 1857,
vol. 8, p. 202.

M Scuuttze (Max.), Ueber den Bau der Gallert-
scheibe bei den Medusen, Miiller’s Arch. 1856,
p- dll.

1 See notes to pages 26 and 27 of the first

28 ACALEPHS IN GENERAL. Parr I.

Sar e ImMEO N “v4
EMBRYOLOGICAL RESEARCHES UPON ACALEPHS.

The history of the successive steps which have led to a full knowledge of the
reproduction and mode of development of the Medusx exhibits some of the most
interesting features in the annals of scientific discoveries, on account of the pecu-
arity of the facts brought to light im the course of the investigation not only,
but also because the progress has been so very slow and gradual that it discloses,
more clearly than most other subjects, the care, the patience, and the unrelenting

perseverance, with which natural phenomena ought to be traced, in order to secure

satisfactory results.

As I have already enumerated the numerous papers relating to the Embryology

fo)

of Acalephs in another part of this work,’ I shall limit myself here to a_ brief

volume of this work; to which may be added:
Cotpstream (Joun), Article Acalepha in Todd’s
Cyclop. of Anat. and Phys. 18535, 8vo.; | MILNE-
Epwarps Lecons sur la Physiologie et Anatomie
comparce de homme et des animaux, Paris, 1857—
(V.), Icones Zoo-
tomice, mit Original-Beitriigen von Allman, Gegen-
bauer, Huxley, Kolliker, Miiller, Schultze, Siebold,

und Stein, Leipzig, 1857, fol.; and GrGENBAUER

1859, 4 vols. Svo.— Carus

(C.), Grundziige der vergieichenden Anatomie, Leip-
zig, 1809, 1 vol. 8vo.

1 See vol. 1, p. 69. To the works there quoted
may be added: Hassatn (A. H.), Catalogue of
Trish Zoéphytes, Ann. and Mag. Nat. Hist. 1841,
vol. 8. —Sreenstrur (J. J. Su.), Untersuchungen
uber das Vorkommen des IJlermaphroditismus in
Diinischen yon Dr. C. F.
1846, 4to. fig. — Van

BenepeEN (P. J.), Un mot sur le mode de repro-

der Natur. aus dem
Hornschuch. Greifswald,
duction des animaux inférieurs, Bulletins Acad.
Roy. de Belgique, 1847.— Rei (Jon), Obser-
vations on the Development of the Medusw, Ann.
and Mag. Nat. Hist. 1848, vol. 1, p. 25.— GiLrs
(Epw.) and Crarke (W. B.), A few Remarks

upon a Species of Zodphyte discovered in the New

Docks of Ipswich, Ann. and Mag. Nat. ist. 1849,
vol. 4, p. 26.—Mtrier (J.), Archiv fiir Anat.
und Phys. 1852, p. 32, (in the paper on the origin
of shells in Holothuria.) — Tompson (W.), On
the Analogy between the Processes of Reproduction
in the Plant and in the Hydroid Zoiphyte, Ann.
and Mag. Nat. Hist. 1854, XIV. p. 315.— Bur-
MEISTER (II.), Zoonomische Briefe, Leipzig, 1856,
See vol. 1, p. 189.— Pracu (C. W.),
Notice of a curious Metamorphosis in a Zodphyte-
like animal, Edinb. New Phil. Journ. 1856, yol. 4.

—Sars (M.), Einige Worte iiber die Entwickelung

2 vols. 8vo.

der Medusen, Wiegmann’s Archiv of Naturg. 1857,
(Sm Jonn G.), On the
Zoophytes, Edinb. New
Phil. Journ. 1834, vol. 17, and 1836, vol. 21.—

I. p. 117. — Daryeiy

Propagation of Scottish

GEGENBAUER (K.), Zur Lehre yom Generations-
wechsel und der Fortpflanzung bei Medusen und
Polypen, Wiirzburg, 1854, 8vo. fig. — Wrienr (J.
J.), On the Reproduction of Cydippe pomiformis,
Edinb. New Phil. Journ. 1856, vol. 4, p. 85.—
Observations on British Zoéphytes, Edinb. New
Phil. Journ. 1857-1859. — On Hydractinia echinata,
1857, Edinb. New Ph. Journ. — Gossr (Tn. I1.),

Naturalist’s Rambles on the Devonshire Coast, Lon-

HISTORY

(Cie, IE OF THE ACALEPHS. 29

narrative of the successive steps which have furnished us with a connected account
The first facts
relating to the history of the earlier stages of development of the most common

of the extraordinary modes of reproduction of this class of animals.

Jelly-fish of the European seas, the Aurelia aurita, were observed by Sars, and
related by him in a paper published in 1829," and more fully illustrated in a
subsequent work, issued in 1835, which opens a new era in the natural history
of the Acalephs. The fundamental discoveries made by Sars were afterwards
generalized by Steenstrup, and presented to the world in a most unexpected con-
nection with other genetic phenomena which had remained entirely unintelligible.
The first paper of Sars contains only descriptions of animals not noticed before ;°
but among them are those found in the sequel to represent the transitory stages
in the growth of the common Medusa. These are here described as Seyphistoma

and Strobila; the first being considered as a distinct genus of Polyps, the second as

don, 1853, 8vo. fig. — Kronn (A.), Ueber die Natur
des kuppelférmigen Anhanges am Leibe von Phil-
lirhoé bucephalum, Arch. Naturg. 1853, I. p. 278.
—McCravy (J.), Deseription of Oceania nutricula,
and the Embryological History of a singular Medusan
Larva found in the cavity of its Bell; Proc. Elliott
Society, Charleston, S. C., 1857.— Gymnopthalmata
of Charleston Harbor, Proc. Elliott Society, Charles-
ton, §. C., 1858. — On the Development of two
Species of Ctenophorx found in Charleston Harbor,
Proc. Elliott Society, Charleston, S. C., 1859.—
Artman (G. J.), On the Structure of the Repro-
ductive Organs of certain Hydroid Polyps, Proe.
Roy. Soc. Edinb. 1858.— Additional Observations
on the Morphology of the Reproductive Organs in
the Hydroid Polyps, Proc. Roy. Soc. Edinb. 1858.
— Semper (C.), Ueber die Entwickelung der Eucha-
ris multicornis, Zeitsch. f. wiss. Zool. 1858, vol. 9,
p. 234, fig.

1 The first paper of Sars appeared in 1829,
under the title of Bidrag til Séedyrenes Natur-
af M. Sars, Cand. Theol.

med sex illuminerede Steentryktafler, Svo. Bergen,

historie Forste-Haefte,

1829. At that time Sars was still “ Candidatus
Theologie.” An abridged translation of this paper,

with a reproduction of the plates, was published in
Oken’s Isis for 1833, p. 221. I myself have never
seen the original, and I find that most writers have

quoted the investigations related in this paper as

bearing the date of 1853; but this is erroneous:
The paper contained in the Isis of 1833 was not
forwarded to Oken by Sars, but is simply a trans-
lation of the paper of 1829, with a few introductory
remarks by Thienemann.

2 Sars (M.), Beskrivelser og Jagttagelser over

nogle merkelige eller nye i Havet ved den Ber-

genske Kyst levende Dyr af Polypernes, Aca-
lephernes, Radiaternes, Annelidernes og Mollus-
kernes Classer, ete., Bergen, 1835, 4to. with 15
plates. I am indebted for a copy of this rare work

to my friend Professor Eschschricht of Copenhagen.
As it may not be easily accessible to naturalists in
this country, I would mention that abstracts of its
contents may be found in the Isis of Oken for 1837,
p- 354, in the Annales d’Anatomie, ete., II. p. 81,
and in Wiegmann’s Archiv fur Naturgeschichte,
1836, 2d vol. p. 197. What relates to Acalephs
may be found p. 197-200.

8 T avoid intentionally, whenever I can, the use
of the expression new, as applied to animals not
known before to naturalists; for, besides the impro-
priety of applying the word new to what has only
been unnoticed before, I find that students of Pale-
ontology are much puzzled in ascertaining whether
that expression, when applied to fossils, means a
newly discovered species, or one belonging to the

more recent geological formations.

50 ACALEPHS IN GENERAL. Part I.

a peculiar genus of Acalephs, and both as distinct from all the other genera of
Polyps and Meduse known at that time. The genus Scyphistoma is considered
as intermediate between Hydra and Coryne; Scyphistoma filicorne, the only species
described, is characterized as having twenty-four to thirty-two tentacles, the mouth
as being retractile and protractile, and the body as annulate. This last mdication
shows, that the Scyphistoma first observed by Sars was on the point of passing
to the Strobila condition. The genus Strobila is thus described: Animalia nune
sumplicia et libera, nune plura invicem conjuncta, alterum scilicit super alterum
positum, ita ut seriem forment, cujus extremitas infima pedunculo brevi est affixa,
singulum animal disci formam referens, supra paullulum convexum, subtus coneavum,
margo disci in radios plures divisa. Os subtus maxime prominens tetragonum. One
species, Strobila octoradiata: Margo disci in radios octo dichotomos divisa. When
free, these dises are said to move like small Meduse. The eight small ocelli between
the lobes of the eight rays were correctly observed, and compared to those of the
Medusa (Aurelia) aurita and Medusa (Cyanea) capillata. Thienemann, who furnished
the abstract for the Isis, suggests that Sars should ascertain whether this is not the
embryonic state of some Medusa. Sars himself considered Strobila as establishing

1

a transition between the fixed Zodphytes and the Medusxe, while Ehrenberg? mis-

g
took it for a Lucernaria in the process of transverse division.

In his later work, published in 1835, Sars gives a more detailed account of
the Strobila, and shows that the animal he had described as a distinct genus under
the name of Scyphistoma is simply an earlier stage in the development of the
Strobila, and that the free dises of the Strobila are themselves closely allied to the
animals deseribed by Eschscholtz as Ephyra, a genus referred by the latter to the
Acalephxe cryptocarpe. This is illustrated by figures, on his Pl. 5d. These observa-
tions establish beyond the possibility of a doubt the fact, that extraordinary changes
take place in animals that were at first considered to be Polyps, and the growth of
which ends in the production of animals belonging unquestionably to the class of
Meduse. In a later note, Sars declares? that he has satisfied himself that the
Ephyra-like Medusa arising from his Strobila is a younger state of the common
Medusa (Aurelia) aurita, without, however, furnishing the evidence of this assertion,
which is still questioned by Wiegmann.’

In 1841, Sars takes the whole matter up again, and in a masterly paper* demon-

1 EnrenperG (C. G.), Die Akalephen des ® Wiegmann’s Archiv fiir Naturgeschichte, 1837,
rothen Meeres und der Organismus der Medusen vol. 2, p. 276.
der Ostsee, Berlin, 1856, p. 52. 4 Sars (M.), Ueber die Entwickelung der Me-
? Wiegmann’s Archiv fiir Naturgeschichte, 1837, dusa aurita und der Cyanea eapillata, Wiegmann’s

vol. 1, p. 406. Archiv fiir Naturgeschichte, 1841, vol. 1, p. 9-34,

Cuar. 1. HISTORY OF THE ACALEPHS. 3]

strates beyond the possibility of a doubt, that the Scyphistomas are the offspring
of Meduse; that they are transformed into Strobile, which produce Ephyroid
Meduse ; and that the latter end their life as Medusa aurita and Cyanea capillata.
All these facts are illustrated by beautiful figures. He begins by showing that the
free disks of his Strobila are the young Medusa (Aurelia) aurita. He next instances
facts showing the similarity of the development of Cyanea capillata with that of
Aurelia aurita; and then describes his attempts to raise the eggs of the Medusa,
m which he succeeded so far as to show that Scyphistomas are developed from
eges laid by both these Medusxe, and thus closes the cycle of the investigation
undertaken with the view of ascertaming the normal connection of all these animal
forms. There can no longer be any doubt that they are genetically linked together,
even though the transformation has not been watched through all its stages in one
and the same specimen. The difficulty of keeping them alive for a sufficient time
in confinement makes it impossible to obtain that kind of evidence. But as far as
the closest similarity of the forms watched in confinement with those observed in
their natural element is sufficient to trace their mutual dependence, the evidence
is satisfactory and conclusive.

The investigations of Sars had scarcely begun to be noticed in Germany when
Siebold proceeded to trace the earliest stages of the formation of these animals.”
His object was partly to revise the observations of Ehrenberg upon the structure
of the Aurelia aurita, and partly to study the development of its eggs. To him
we are indebted for the first accurate observations respecting the segmentation of
the egg, and the formation of the embryo. Siebold clearly perceived the connection
of the facts he had observed with those seen by Sars, yet a direct transition of
the young from the state to which he had traced it to that observed by Sars
was not seen by him.

The successive discoveries of Sars, combined with the investigations of von
Siebold, had already led to a full knowledge of the characteristic features of the
mode of development of the Medusze, when Steenstrup took up this subject; and

yet this ingenious observer gave a new impulse to the investigation of the Aca-
2d, The base of

pl. 1-4.—A French translation, by Dr. Young, in Wiegm. Arch. 1841, I. p. 20.

appeared in the Annales des Sciences naturelles,
2d series, 1841, vol. 16, p. 321.

1 There are, however, two assertions in this
paper with which I cannot coincide: Ist, the re-
versal of the young embryo when it becomes attached.
Notwithstanding the objections of Sars, Siebold was
right in what he said of the formation of the

mouth, though he gave it up afterward. See note

the Strobila, after the Ephyre are freed, does not
die, as Sars states. Dalyell is correct when he
affirms that they survive, and that tentacles reappear.

2 Srepotp (C. Tu. von), Beitriige zur Natur-
geschichte der wirbellosen Thiere ; Neueste Schrif-
ten der naturforschenden Gesellschaft in Danzig.

vol. 3d, No. 2, Danzig, 1839.

32 ACALEPHS IN GENERAL. Parr IL.

lephs, by the wnexpected views under which he presented the facts recorded by
his predecessors, so much so that a new era may be dated from the publication
of his littke work, for the history of the Acalephs not only, but also for the
invertebrate animals in general. The whole aim of Steenstrup’s investigations is
fully expressed in the title of his work, “On the alternation of generations.” ! He
expresses himself upon that poimt very clearly and in very few words, in_ his
preface: “The substance of this paper is the fundamental idea expressed by alter-
nation of generations. It is a remarkable, and, thus far, unexplained phenomenon

e to be

o

of nature, that an animal brings forth a brood neither similar, nor growin
similar, to the parent, but differing from it, and producing by itself another brood,
that returns to the form and relations of the mother animal, in such a manner
that a mother animal does not rear the like of itself, but reappears only in its
descendants of the second or third or a following generation; and this appears
always, in different animals, in a definite generation, and with definite intermediate
generations.”

Next to Sars and Steenstrup, Sir John Dalyell has been most successful in tracing
the phenomena here alluded to. This author, whom Ed. Forbes, with his quick
appreciation of every kind of merit in others, justly calls the Spallanzani of Scot-
land, has done more for the elucidation of the early history of the Medusxe than
any other writer, although, from want of method in his descriptions and owing to
his disregard of the modern systematic forms of presenting such subjects, his obser-
vations are only intelligible upon very careful perusal, and not available for a
connected study of the gradual growth and successive phases of their development.
For instance, it has not occurred to Sir John Dalyell, that what he calls “Hydra

tuba” may be the offspring of several distinct venera of Meduse, and so he con-
’ to) to)

' Streenstrur (Jou. Jaretrus Sa.), Ueber den consider as a simple metamorphosis of a larva,
Generationswechsel, oder die Fortpflanzung und but as the metamorphosis of a new generation
Entwickelung durch abwechselnde Generationen, derived from the progeny of a Medusa. He goes
iibersetzt von C. Hl. Lorenzen, Copenhagen, 1842, even so far as to consider this mode. of repro-

8vo. fig. English translation by George Busk, pub- duction as a case parallel to that of Salpa, first

lished by the Ray Society: On the Alternation of observed by Chamisso, and to vindicate the aceu-

Generations, London, 1845, Svo. fig. Although the racy of the investigations of the genial poet. Thus

question of alternate generations is for the first
time distinetly raised by Steenstrup, and presented
by him as a phenomenon occurring not only among
Radiates, but also among Mollusks and Articulates,
it would be doing injustice to Sars not to remember,
that, as far as the Medusmw are concerned, he had
already correctly appreciated the character of the

development of Aurelia aurita, which he does not

the groundwork upon which the theory of alternate
generations could be reared is already laid out by
(Wiegmann’s Archiv, 1541,

vol. 1, p. 28), “It is, therefore, not the larva, or

Sars, when he says

the individual hatched from the ege, that develops
into a perfect Acaleph, but the brood arising from

this larva by transverse division.”

Cuap. I. HISTORY OF THE ACALEPHS. 33

founded the history of at least two different genera; for I have no doubt, that,
while the Hydra tuba, represented by him in his great work on “ Rare and Remark-
able Animals of Scotland,’ Vol. I, Pl. XIIL, is the offspring of Aurelia aurita, the
forms which he represents under the same name, Pl. XIV., are the offspring of
Chrysaora, and those of Pl. XIX. are perhaps derived from Cyanea capillata.

In 1854, John Graham Dalyell! (afterwards Sir John) describes, under the name
of Hydra tuba, an animal which is identical with Sars’s Seyphistoma, already men-
tioned and figured by the latter in his paper of 1829; but Dalyell mentions many
particulars, which seem to have for a long time remained unknown to other natu-
ralists. He says that this animal is very voracious, and that it multiplies by
budding, the buds remaining united to the base of the parent by a ligament,
until this is ruptured as the embryo withdraws to establish itself independently.
A single specimen had eighty-three descendants in thirteen months. Sars did not
observe the budding before the year 1856,? and he did not see the buds separate
and grow independently, as Dalyell did, and as I have done myself. In a subse-
quent paper,’ Dalyell describes his further experiments with Hydra tuba up to 1836.
He kept a colony of these animals alive, with their descendants, during six years,
and numbers attained maturity. They fed rapaciously, grew and bred successive
generations at all seasons of the. year. In February and March he observed a
pendulous flexible prolongation, of an inverted conical form, on the face or disk of
some of these Hydras (the Strobila of Sars), developing gradually into twenty or
thirty successive strata, broadening outwards, which, when more mature, were liber-
ated, and swam at large in the water (the Ephyroid Medusa of Sars). He also
considers them as Medusarix, and gives good figures of one of them, figs. 2 and
3, p. 94.
of his observations of the year 1856, Wiegmann, for instance, says,’

Later authors have failed to do justice to Sir John Dalyell. Speaking
that they
contain so much that is enigmatical, that they require to be repeated and explained
by other naturalists. Surely his own ignorance of the facts observed by Dalyell,

the accuracy of which has been fully borne out, did not justify such a rebuke.

1 On the Propagation of Scottish Zobphytes,
Edinb. New Philos. Journ. 1854, vol. 17, page 411,
and Report British Association for Adv. of Sci-
ence, 1834, p. 598. An abstract appeared in Fro-
riep’s Notizen. The name of Dalyell is misspelled
in the Edinburgh New Philosophical Journal, and
stands as Dalzell; under which name the author
became known in Germany, and is quoted again
and again in Wiegmann’s Arch. for 1834, vol. 1,

p. 803 and 306, and for 1837, vol. 2, p. 192.

or

VOL. III.

? Wiegmann’s Archiv, 1841, vol. 1, p. 24.

* Further Illustrations of the Propagation of
Scottish Zobphytes, Edinburgh New Philosophical
Journal, 1836, vol. 21, p. 88; fully translated into
German in Froriep’s Notizen, vol. 50, No. 6, and
in abstract in Wiegmann’s Archiy, 1837, vol. 2, p.
278. The Isis of 1838 contains also abstracts of
Dalyell’s papers.

* Archiv, fiir Naturgeschichte 1837, 2d_ vol.

p- 278.

34 ACALEPHS IN GENERAL. Parr I.

Sars, again, speaks of them as partly confirmatory of his own, when, of course, the
earlier observation was the original one, and the later ones should be considered
as confirmations. The budding of the polypoid state of Strobila had been known
to Dalyell for years before it had even been noticed by Sars. Dalyell already
knew, in 1836, what Sars was still ignorant of in 1841, and, what seems hardly
to be generally known even now, though it is certainly true, that the base of the
Strobila resumes the form of the original Scyphistoma after the Strobila has dissolved
itself into free Ephyre.

But all these so-called “Hydra tuba” are not one and the same animal.

They
are the early stages of development of the different kinds of covered-eyed Medusx
which oceur on the coast of Scotland, and the development of which presents similar
phases. However, while Dalyell confounds in this manner the progeny of all the
Steganophthalms of the vicimity of Edinburgh, his very mistake shows the more
plainly how similar are the earlier stages of development of these different
species of Meduse.

It is much to be regretted, that the facts so carefully and patiently traced by
Sir John Dalyell, for so many suecessive years, should not have earher attracted
the general attention of the investigators of Acalephs; for his work contains satis-
factory information upon many points, which were afterwards discussed as if no
observations had yet been made respecting them. Not less is it to be regretted,
that Sir John Dalyell was not more fully acquainted with the investigations of Sars

and of von Siebold. Had he known their import, his own results would have been

much sooner incorporated into the history of these animals, while they would also

have acquired more precision and directness in his own mind. As it happened, the

highly important labors of Dalyell have remained almost unnoticed until recently,

and have failed to exercise the influence they might have had upon the progress

of seience.

generations had been

Various facts bearmg upon the phenomena of alternate

oO

observed among Hydroids by Ehrenberg,’ Loven,? Nordmann, VanBeneden,' and

1 Enrenpera (C. G.), Die Korallenthiere des 1859, vol. 9, p. 704. This account is too short

rothen Meeres physiologisch untersucht und systema- to be at all satisfactory.
tisch verzeichnet, Berlin, 1834, 4to. 4 VanBenepen (P. F.), Mémoire sur les Cam-

2 LOVEN

(S. L.), Beitrag zur Kenntniss der
Gattung Campanularia und Syncoryne, Wiegmann’s
Arch. 1837, vol. 1, p. 249.

8 NorpMANN (AL. v.), Sur les changements que
Lage apporte dans la manitre d’étre des Campanu-

laires ; Comptes-Rendus de Acad. des Se. Paris,

panulaires de Ja cote d’Ostende, considérées sous le
rapport physiologique, embryogénique et zoologique ;
Ann. Se. Nat. 2e sér. 1843, vol. 20, p. 350, et
Meém. Ac. Brux. 1845, vol. 17, 4to. fig.
sur Tembryogénie des Tubulaires, ete. Mém. Acad.

Brux. 1544, 4to. fig.

Mémoire

Cuap. I. HISTORY OF THE ACALEPHS. 35
Quatrefages,’ without leading to conclusive results, when Dujardin turned his atten-

tion to the subject, and published two most important papers? describing the
formation of genuine Medusz from Hydroids; and thus establishing beyond question
a genetic relation between animals of another family which had thus far been
considered as belonging to different classes. Dujardin’s investigations had a great
influence in establishing the correctness of the views of Sars and Steenstrup, and
in extending the range of our knowledge of the alternate generations; for, not only
did he trace the development of several Meduse from Hydroid Polyps, but he even
saw the eggs of the free Medusxe derived from Hydroids reproduce their Hydroids.
His second paper is accompanied by many beautiful figures, which add greatly to
the clearness of his descriptions, and have forced the facts more directly upon the
attention of naturalists.

Henceforward the study of the Acalephs is pursued in a new light and with
broader views. The investigation of their affinities, their structure, and their mode
of development, forms a part of their history; and their classification is modified

accordingly, and gradually brought nearer and nearer. to nature.

1 QuaTREPFAGES (A. pr), Mémoire sur la Syn- veau genre de Médusaires (Cladonema) provenant

hydre parasite (Synhydra parasites), nouveau genre
de Polype voisin des Hydres; Ann. Sc. Nat. 2de
sér. 1843, vol. 20, p. 230.

2 Dusarpin (FEL.), Observations sur un nou-

de la métamorphose des Syncorynes; Ann. Se. Nat.
2de sér. 1843, vol. 20, p. 870.— Mémoire sur le
développement des Médusaires et des Polypes Hy-

draires; Ann. Se, Nat. 8e sér. 1845, vol, 4, p. 257,

CHAPTER SECOND.

ACALEPHS AS A CLASS.

SECTION I.

MODE OF DETERMINING THE NATURAL LIMITS OF THE CLASS.

Arter what has been said, in the first volume of this work, respecting systems

in Zovlogy, it is hardly necessary to repeat here, that no arbitrary arrangement

of animals can ever constitute a natural classification. Were it

Fig. 1.

not so, every naturalist might present an arrangement suited to

feeling of appropriateness in the minds of
class of Acalephs, however, has presented

particular difficulties to systematic writers ;

and it is not too much to say, that there

PELAGIA CYANELLA,
Pér. and LeS.
aa Umbrella. mm Mouth animals belonging to this type, who agree in
tentacles, or arms; the pro- = . = 7
longation of the angles of their arrangement of them. Nay, the lim-
the mouth. —¢¢ Marginal = ‘

tentacles its of this class are by no means clearly

are no two naturalists, conversant with the

determined ; for, while some unite under that name only the
free moving gelatinous Radiata (%y. 1), others would asso-
ciate with them a number of pedunculated individuals and
fixed communities of animals somewhat allied to Polyps (fy.
.

2), and actually united with Polyps by some naturalists.
gain, some refer to the class of Polyps all the compound

Co)

his individual views, and for which he would have as much
authority as any one else. The absurdity of such a view, when
clearly stated, is at once obvious. And yet most classifications

have no better foundation for their details than a vague

their authors. The

Hypractinra porycrina, Ag.
aa Sterile individuals. —d Fertile
individual, producing male Me-
duse.—d Clusters of male Me-
dusw.—oo Proboseis, with the
mouth at the apex. —¢ Elongated
tentacles of the sterile individu-
als; in the fertile one 6, they are
simple knobs upon the proboscis 0.

Crap. IT. LIMITS OF THE CLASS. 37

communities of free-moying gelatinous animals, the Siphonophore (fy. 5), which

others consider as genuine Acalephs, while some do not hesitate to unite all

Acalephs and Polyps in one single division. On the other ae
hand, we have lately seen a part of the Acalephs, the Cteno- WZ

od

phoree (Figs. 4, 5, 6, and 7), removed from that class, and
referred to the type of Mollusks.

Such conflicting views could not be entertained by so
many and such eminent naturalists, did not almost imsuper-
able difficulties obstruct our attempts to trace the truth. I

know only one way to overcome these obstacles, and to attain
It is to test the affinities

of all these animals by the standard of what is known of their

<A YounG PHysopHora,

greater precision on this subject. (Copied from Gegenbauer.)

e Buds of swimming bells.— 6b So-

called tentacles; lower } so called
5 . n . Polyp.— cc Feelers with lasso

mode of development, in the manner done before with full cus —; airsic.

success for other classes; taking at the same time into account the homologies of

their parts, as far as they can be ascertained. Embryology has, indeed, become

Boutna ALATA, Ag.
(Seen from the broad side.)

aand f Long rows of locomotive fringes. —
gandh Short rows of locomotive fringes.
—o Central black speck (eye-speck ?). —
ito m Triangular digestive cavity.—7 to 0
Funnel-like prolongation of the main cay-
ity.—wv Chymiferous tube of the tenta-
cular apparatus.—m Tentacular appa-
ratus on the side of the mouth. —rr Ear-
like lobe, or auricles, in the prolongation
of the short rows of locomotive fringes.
—tt Prolongation of the vertical chymife-
rous tubes. —nn The same tubes turning
upwards.— xa Bend of the same tubes.
—zz Extremity of the same tubes meet-
ing with those of the opposite side. —w
Recurrent tube anastomozing with those
of the auricles.

the key-note to the knowledge of the closer affinities among animals.

BoLrva ALATA, Ag.
(Seen from the narrow side.)

ab Long rows of locomotive fringes.—c hk
Short rows of locomotive fringes. —o Cen-
tral black speck (eye speck ?).—z7 Upper
end of the digestive cavity. —7 too Fun-
nel-like prolongation of the main cavity of
the body.—m toz Digestive cavity. —rr
Auricles. —m Mouth.—t t Prolong-
ation of the vertical chymiferous tubes.
—nn The same turning upwards, — x x
Bend of the same tubes. —z Anastomosis
of the two longitudinal tubes ¢¢t. —ww
Recurrent tube, anastomozing with those
of the auricles. — A comparison of this fig-
ure with Fig. 4 gives a distinct idea of the
relative position of the digestive cavity 9
to 7, and the chymiferous tubes of the ten-
tacular apparatus v.

Fig. 6.

te d
[POH

v
bed / SS. 0
Han VE ay

\

kh yok
Borsa ALATA, Ag.
(Seen from above.)

o Central black speck (eye speck ?). —abef
Long rows of locomotive fringes. —cdgh
Short rows of locomotive fringes. — rr
Auricles. —ss Cireumscribed area of the
upper end of the body.

7m >

BouinA ALATA, Ag.
(Seen from below.)
m Mouth. —rr Auricles. —t¢tt Prolonga-
tion of the vertical chymiferous tubes. —
zz Anastomosis of these tubes.

Granting,

for instance, that anatomy alone could have settled the question of the true affini-
ties of the Barnacles with Crustaceans, I hardly believe, that, but for our knowledge
of their embryology, naturalists would ever have dared to consider them merely
as a group of the natural division of Entomostraca, which they really are. But

for our knowledge of the mode of development of toads and frogs, their close

38 ACALEPHS:AS/A CLASS. Parr iL

affinity to Salamanders and to Ichthyoid-Batrachians could never have been de-
termined with the same precision; but for our knowledge of the development of
the Comatule, that family would for ever have remained associated with the Star-
fishes; and it seems to me that the inference is unavoidable, that the various
modes of development of the Acalephs, as far as their embryology has already
been traced, must afford the surest clue to the natural affinities of these animals,
and, perhaps, furnish a standard also by which we may determme to what group
certain polyp-like Radiata, alternately placed among Polyps and among Acalephs,
truly belong. Should their special homologies comceide with the indications fur-
nished by their embryology, all doubts on this point would seem to be removed ;
for, if the conclusions arrived at in those types of the animal kingdom which are
now best known have any analogy with the phenomena observed in other types,
we should be able to trace special homologies between all the representatives of
the class of Acalephs, in the same manner as between all Insects, or between all
Mammals.

In this way, it would scarcely seem difficult to determine whether those ani-
mals which have been at different times referred to the class of Acalephs and to
that of Polyps truly belong to the one or the other, if the Polyps and Acalephs
indeed constitute two classes, or if not, to demonstrate satisfactorily that they
should form but one class. Again, all the representatives of the different classes
of one branch are found to agree in their general homologies, as far as they have
been thoroughly studied,— the Fishes with the Reptiles, Birds, and Mammals; the
Insects with the Crustaceans and Worms; and the Acephala with the Gasteropods
and Cephalopods. On the other hand, should there be any animals, thus far re-
ferred to the class of Acalephs or to that of Polyps, which do not agree in their
general homologies with the true Polyps and the true Acalephs and Echinoderms,
we should not hesitate to remove them from the type of Radiates. Thus we may
also settle the question, whether the Ctenophor are true Radiates or Mollusks, as
Quoy and Voet have maintained.

In order to avoid any hasty conclusions, let us examine successively all the
leading representatives of every group that may have been associated with either
the Acalephs or the Polyps, both with reference to their homologies and their mode
of development. Beginning with the Meduse proper (Pl. IIL, IV. V., VL, VIL,
VIIL, TX., XIL, XIIL, and XIV.), we find them to be animals which move freely,
presenting an hemispheric gelatinous disk, in the centre of which a digestive sac is
hollowed out. From the margin hang numerous filaments, and the central opening
is surrounded by four larger appendages. From the central cavity arise many tubes
radiating towards the periphery, where they anastomoze. The essential feature of

this structure consists in the central cavity hollowed out of a contimuous mass,

Car. IT. LIMITS OF THE CLASS. 9

ee)

which is traversed along its lower surface by radiating tubes. It requires but. little
familiarity with the Meduse ‘to know that the marginal fringes vary greatly in
number, as well as in structure; some being hollow, while others are solid. These
appendages are not even present in all Meduse; for neither the Rhizostomata nor
the Cassiopeiw nor the Cephez have them. The central opening presents also
marked differences in its outward termination. In some it has a simple rim, while
in others, four or more prominent angles may extend outward and assume the
shape of very complicated appendages. But in no Medusa is the margin of the
central opening inverted into the digestive cavity.

Not so with the Actinie (/%. 8) and the other Actinoid Polyps. Here the
walls of the body, whether soft, or hardened by calcareous
deposits, enclose a wide cavity, which is divided by radiating
partitions into a number of chambers, communicating freely

with the so-called tentacles or marginal frmees. The central
to) fo)

opening does not communicate directly with the main cavity

of the body, but leads into a distinct digestive sac, suspended — Acrixta_ marcrvara, LeSueur.
é x 9 : ava a (Contracted and the tentacles
in the main cavity. It is as if the upper part of the hollow drawn in.)

aa Base of the animal.— Opening of

cylindrical body had been turned into the cavity below, its “tye aisestivesac

uding into the main
cavity of the body. —cc Opening lead-

ing from one radiating partition into

edge hanging free and open in that cavity, though capable

& . 7 — S, nya tae _— = : <s a fed Be the other. This opening is homologous
of closing by contraction. We have here, then, two distinct cine cireularchymaifurous tubsor the
Tl ‘ naked-eyed Medusw. — e ¢ e Radiating

1e partitions. —// Bunches of eggs hang-

types; but they are homologous in all their parts.

ing from the inner margin of the

outer wall of the Actimiz corresponds to the gelatinous disk siting partitions —e One of the

as . . large:
of the Medusz, only that the centre of its outer surface is 9 4.)

tacles.—s Digestive sac.

diating partitions, to which
ive sac is attached. —o Ten-

so constructed as to enable these animals to attach them-
selves by it, while in the Meduse it is uniformly rounded off, and affords no point
of attachment. The marginal fringes of the Actiniz correspond to the marginal
fringes of the Meduse, only that in the Medusee they communicate directly with the
marginal circular tube, and through this with the radiating tubes, while in Actinic
they open directly into the radiating chambers. The radiating tubes of the Meduse
correspond, it is true, to the radiating chambers of the Actiniw; but in Actinixe these
chambers open freely for their whole length into the centre of the main cavity of
the body, while in the Meduse the radiating tubes are closed cylinders, opening
only at their inner end into the main cavity. The central opening leads, in both,
into the main cavity of the body; but in Meduse the margin of that opening is
turned outward, and may be prolonged into large appendages, between the inner
surfaces of which a cavity is formed leading into the main cavity, while in the
Actinie the outer margin of the central opening is turned inward and extends to
a considerable length into the main cavity, so that the inner surface of the sac so

formed corresponds to the outer surface of the wall of the main cavity; and it is

40 ACALEPHS AS A CLASS. Part I.

this body wall, and not the mouth, which is surrounded by radiating appendages
outside of the central opening.

This comparison is in itself sufficient to show, that, while every part in a
Medusa is homologous to every part in an Actinia, these homologies are only
general homologies; that is, indications that these two animals belong to the same
branch of the animal kingdom, but that special homologies cannot be traced
between them. The body of the Actinia has a flat disk at the lower end, which,
though contiguous with the outer wall, differs from it so much as to constitute
a base of attachment entirely wanting in the Medusa. The upper part of the
lateral walls of the Actinia is thinned in a manner which forms a sort of cir-
cular neck below the fringes, facilitating the mversion of the whole margin towards
the centre in a manner impossible to the Medusa. The central opening of the
Actinia is not circumscribed by the margin of the upper part of the walls of the
body, but that margm is turned inward; while in the Medusa it hangs free,
outward. The radiating hollow spaces are limited in Actinia by radiating partitions,
the imier margin of which is free, and suspended vertically in the main cavity ;
while in the Medusa, what may be compared to the partitions of the Actinia is
a continuous gelatmous mass, between which simple tubes are left, communicating
only through narrow openings with the central cavity, or in other words, the
homologous parts of the Actinia and Medusa exhibit a structure special to each.

We find the same special homologies in all the Actinoid Polyps. They all have
a cylindrical body with a central cavity, divided into chambers by radiating par-
titions, marginal frmges communicating with these chambers, and a digestive cavity
hanging free into that cavity below the central opening; while im all Meduse
we find the same continuous gelatinous body with a simple central cavity and
radiating tubes, and a margin of the central opening turned outward. Now, if the
classes of each branch of the animal kingdom, as has been shown in the first
volume of this work, are natural divisions exhibiting the same plan of structure,
but built respectively in different ways and with different means, we have, in
Actinia and in Medusa, the types of two distinct classes; and it only remains for us
to examine what are the natural limits of these classes, and what different kinds
of animals belong to each. I hold, however, that the preceding remarks are in

themselves sufficient to show that it is an exag

(=)

geration of their affinities to unite,

as Leuckart has done, and as most German naturalists now do, the Polyps and

Acalephs in one and the same great division under the name of Czlenterata.!

1 Leuckart (R.), Ueber die Morphologie, und Thiere, Braunschweig, 1848, 8vo. p. 15. Full of

die Verwandtschafts-Verhiiltnisse der wirbellosen original investigations and suggestions.

Cuar, I. THE DIFFERENT RADIATA. Al

S HCe kOUN TT:
THE DIFFERENT ANIMALS REFERRED TO THE TYPE OF RADIATA.

I shall presently show that all the true Polyps and all the true Acalephs may
naturally be grouped with the two characteristic representatives of their respective
classes, alluded to in the preceding section; and that, in connection with the Echi-
noderms, they constitute one of the four great types of the animal kingdom,
characterized by a peculiar plan of their structure, founded upon the idea of radi-
ation; and that the anatomical differences exhibited by the Echinoderms do not
justify us in considermg them as a distinct type The latter are, in reality, only
another class of Radiata, as a comparison of any of the flat Echinoids, such as
the Echinarrachnius, with an ordinary Medusa, say the Aurelia, readily shows ;
Echinus being, as it were, a Medusa, the soft disk of which is charged with lme-
stone particles. But before proceeding to demonstrate these propositions, it is
proper to take a glance singly at all the different beings which, at different times,
have been associated with or removed from the Radiata.

Whether considered as a distinct type, or simply as a class of the Radiata,
the Echinoderms, as a natural group, are now very generally circumscribed within
the same limits by all naturalists. The question, long agitated among zodlogists,
whether the Sipunculoids should be associated with the true Echinoderms or referred
to the class of Worms, has finally been settled in favor of their complete removal,

9

by the investigations of the late lamented J. Miiller? We may henceforth con-
sider as Echinoderms all the radiated animals provided with an ambulacral system,
and need not for the present enter into a farther consideration of their structure
and general affinities, but leave them out of consideration until we attempt to trace
the general homologies, which, in connection with their mode of development, bind
these animals indissolubly with the Acalephs and Polyps as a separate class of the
type of Radiata.

The natural limits of the class of Acalephs cannot be considered as settled,

1 The separation of the Echinoderms from the
other Radiates, as a distinct type, was first pro-
posed by Leuckart in the work quoted on the
preceding page. This distinction has been adopted
by Kélliker, and by Gegenbauer in his recent excel-
lent text-book of Comparative Anatomy. To me,
however, such a division of the Radiates into two

VOL. Ill. 6

types seems unjustifiable, since the consideration of
the complication of their structure is surely a feat-
ure subordinate to the idea of their plan of struct-
ure; and the mode of execution of a plan should
not be confounded with the plan itself.

2 Ueber den Bau der Echinodermen, Ak. d.
Wiss. Berlin, 1854.

42 ACALEPHS IN GENERAL. Parr B

since Quoy’ and Vogt? would remove the Beroids not only from that class, but
even from the type of Radiata, and refer them to the lower Mollusks in’ the
vicinity of the Ascidians. It seems hardly credible, that the author of an exten-
sive and highly valuable monograph upon the swimming Ascidians? should enter-
tain such an opinion, Every idea of typical plans of structure, as a guide in the
general classification of the animal kingdom, must be given up by those who would
associate animals that are so distinctly radiated as the Ctenophore with others in
which the bilateral type is so evident as in the Tunicata, and place them in an
intermediate position between the latter and the Bryozoa. A general comparison
will be sufficient to show that the Ctenophore or Beroid Medusxe are truly
Radiata. This may best be seen in our Idyia (/%. 9), where the central mouth,

Fig. 9. surrounded by a circular tube, leads into a vast digestive
cavity, above which arise two horizontal tubes, each dividing
into four branches. These branches follow the surface of the
cylindrical, shehtly compressed walls of the animal, and unite
again with the circular tube encircling the mouth. On the
outer surface of the body extend eight vertical rows of flap-
pers, whose upper ends converge to a central knob at the

summit of the animal. The rows of flappers, the hollow tubes,

jovi nasonee the central mouth, the rosette at the summit, every essential

Anal opening. —} Lateral radi- feature in the structure of these animals, is as strictly radi-

ating tube. —c Circular tube. —
defh Vertical rows of locomo-

ated as in any other Radiata in which indications of a bilateral

tive fringes. —¢ The locomotive
fringes seen in profile.

arrangement are subordinate to the general plan of radiation.
These subordinate features in the genus Idyia consist of two additional radiating
tubes along the sides of the animal, in the flattening of the digestive cavity which
exists also in all the Polyps, and in the eccentric position of the double anus.
This eccentricity of the terminal end of the alimentary canal occurs, however, in
the majority of Echinoderms, as well as in the Ctenophorx, only that im Echi-
noderms the anus is simple. But the Ctenophore are not only radiated; they,
in fact, are radiated after the fashion of the other Acalephs, and ought to remain
associated with the common Medusie, as they have been ever since Cuvier distin-
guished these animals as a class.

The special homologies of the Ctenophore and true Meduse are most. striking.

A comparison with Aurelia will at once show this. From the main cavity arise,

1 Quoy et Gaimarp, Voyage de lAstrolabe, ® Voar (C.), Recherches sur les animaux in-
Zoologie, vol. 4, p. 36. férieurs de la Méditerranée; 2d. Mémoire, sur les
2 Voar (C.), Zoologische Briefe, Frankfurt a. M., Tuniciers nageants de la mer de Nice, Mém. de

1851, vol. 1, p. 254. VInstitut national genevois, Geneve, 1854, vol. 2.

Cuap. IT. THE DIFFERENT RADIATA. 4

[Se

in opposite directions, two main stems of the chymiferous tubes. Each of these
divides into two forks, which in their turn are subdivided again, so that each stem
ends in four branches opening into four vertical tubes, extending without farther
ramifications to the lower margin of the animal; and all this with only such differ-
ences in the number of branches as occur between different genera among genuine
Meduse. We have even in Idyia, in the two simple tubes that follow the flattened
sides, a close resemblance to the arrangement prevailing in Aurelia, where straight,
simple tubes alternate with those that are subdivided.

These facts may be sufficient to show that the Ctenophorase cannot be separated
from the ordinary bell-shaped Meduse; yet when we come to examine the
characteristics of the orders in the class of Acalephs, we shall trace those
homologies farther, and also show how the structure of all the Ctenophore, even
of those differmg most from the type of Idyia, such as Cestum, Lesueuria,
Bolina, and Pleurobrachia, is strictly homologous to that of Idyia in all their
peculiarities.

Among the Discophore there exists also a great diversity; and I shall compare
closely all their different types, when examining the natural limits of that order.
Suffice it to say here, that the Rhizostomes, which have been represented as widely
differing from the others in the structure of their mouth, differ only in so far that
the edges of the four pendent branches of the central peduncle — which are free
for their whole length in Aurelia, Chrysaora, Pelagia, and Cyanea, and form four
channels leading to a central opening, the so-called mouth, that opens into the
main cavity —are soldered together for their whole length in Rhizostoma, Cephea,
and Cassiopeia, leaving only here and there small openings between their folds,
through which a less bulky food passes in the same way as in the common Meduse,
along the channels thus formed, into the main cavity of the body. The homology
is perfect, the only difference being that the edges of these four appendages coalesce,
instead of remaining open. (See Pl. XIII. and XIV.)

Before the mode of reproduction of the so called naked-eyed Medusxe was known
as it now is, no question could be raised as to their affinity; and they were simply
referred to the order of Discophore. But since many of them have been ascer-
tained to arise from buds formed upon the stem, or between the tentacles, of the
crown of the so-called Hydroid Polyps, the question now is, whether their association
with the ordinary Discophore in one and the same order is true to nature or not;
and further, what should be the position in a natural system of the Hydroids
themselves, which, before these discoveries, were unhesitatingly associated with the
ordinary Polyps. Does this show that genuine Polyps produce genuine Medusa,
to be considered as distinct animals; or that the Hydroids, with their respective

Medusz, are only alternate modes of existence of the same being? Or does it follow

44 ACALEPHS IN GENERAL. Papal

from these facts, that the classes of Polyps and Medusz must be united into one ?
That there is a considerable difference between the Meduse arising as buds from
Hydroids and the other Discophore appears plainly from the fact, that Eschscholtz
has already separated them into two groups, calling the former Discophoree Crypto-
carpe, and the latter Discophora Phanerocarpe; while Forbes, grouping them in
a similar manner, calls the former Gymnophthalmata and the latter Steganophthal-
mata, and Gegenbauer, Craspedota and Acraspeda. This distinction, it is true, is
mainly founded upon differences in the structure of the ovaries and spermaries,
of the eye-specks of the margin of the disc, and of the radiating tubes, which
are much fewer in the naked-eyed Meduse, and generally simple; but now the
striking peculiarity of their mode of reproduction may be added to separate them
with more precision.

It is important here to remark, that the so-called Hydro-Meduse have generative
organs only in their Medusa state, and that the Hydroids themselves show no sign
of sexuality; for I shall show hereafter that what has been considered as sexual
organs in some Hydroids are themselves Medusi, differing simply from the ordi-
nary naked-eyed Medusxe in not separating from the Hydroid stem upon which they
bud. The Hydroids appear, then, as a kind of larval condition of the Hydro-Me-
duse ; and, in my opinion, can no more be considered as genuine Polyps, than the
wormlike larve of Insects can be considered as genuine Worms. For, just as by
a series of transformations the worm-like young of the Insect pass into the state
of perfect Insects, so also are the Hydroids a state of the naked-eyed Medusie
preceding the maturity of the latter, and standing in a definite relation to them,
even though that relation be not exactly the same as that which exists between
the Insect larva and the perfect Insect. The Hydroids are no more a distinet
group of animals than the larve of Insects, and while they bear a certain resem-
blance to Polyps, they can no more be united with the Polyps than the larva
of Insects with the Worms, except in as far as they belong to the same branch;
for the Worms, as a class, stand in the same relation to the Crustacea and Insects

Fig. 10. as the Polyps to the Acalephs and Echinoderms. The struct-

r,t ural peculiarities that essentially distinguish the Insects from

the Worms appear already in their larve, which are provided
with traches as well as the perfect Insects. And so also is

the structure of the Hydroids a Medusa structure (/%y. 10),

Campanvranra, expanded. and not a Polyp structure. The margin of the mouth spreads

a Axis of the body. —b Calyx.—
c and d Digestive cavity. —o
Mouth. —¢t?t¢ Tentacles.

outward, and is not inverted to form a digestive cavity distinct
from the main cavity of the body. Moreover, the main cavity
of the body in the Hydroid has no radiating partitions, as that of the Polyps has ;

and this is true of all Hydroids without exception. Those from which the Medusz

Cuap. II. THE DIFFERENT RADIATA. 45

buds are not freed have no more the special structure of the Polyps described
above, than those which produce free Medusex.

Whether we consider their special structure or their genetic relation to certain
Medusx, the Hydroids must be associated in close connection with the Medusve
proper; while their peculiar mode of reproduction, and
the greater simplicity of their structure when compared
to that of the covered-eyed Medusx, show that they form
a distinct group in that class. This will be still more
evident, should I succeed in showing that all Hydroids
produce, in the same way, Meduse buds; even though
these Medusxe do not in all of them separate from the
mother stem to lead an independent life. The family

of Tubulariz is most interesting in that respect, because,

while they all agree in their Hydroid state, there are
i Hyxsocopon pROLIFER, Ag.
some, among them the genus Hybocodon (/¥g. 11), for a stem of a single nyara.—o Its mouth sur-
: , a B F rounded with tentacles. —?ft Its marginal
instance, in which the buds (Fig. 11 dd, and Fig. 12), tentactes—ada The most advanced of its
A 5 _ Medusz buds.
though at first not differing from those of other kinds,

become free and lead an independent life as distinct, sexual, naked-eyed Medusx

(figs. 13, 14). In others, such as Tubularia proper, Thamnoenidia, and Parypha, the

3
Medusa bud of
HyBocopon PROLIFER, Ag.

a Base of attachment to the Hydra stock.
—o Proboseis.—ec Circular chymife-
rous tube.—6 Radiating chymiferous
tube. — dt Proliferous Medusa with
its single tentacle. —¢ Single tentacle
of the primary Medusa. — Neare An-
other small proliferous Medusa-bud,
and several others upon the main radi-
ating tube of the proliferous Medusa
dt, between the letters d and t; ex-
hibiting a striking analogy to Siphono-
phore.

Free Medusa of
Hypocopon PROLIFER, Ag.

The largest vertical tube being
seen in profile. At first sight this
Medusa resembles much the Steen-
struppia of Forbes; yet it differs ge-
nerically.

v Proboscis. —r o Radiating tubes. — s

Circular tube.—t Tentacle.—m Buds

of Medusz, proliferous from the base of
the single tentacle.

Free Medusa of
Hypocopon PpROLIFER, Ag.
Facing the largest chymiferous
tube, from the lower end of which
hangs the single tentacle, with many
small proliferous Medusz buds.

a Point of attachment before its separa-
tion from the Hydra stock. — be Radi-
ating or vertical chymiferous tubes, ¢
pointing to the circular tube. —¢ Ten-
tacle.—/ Bunch of proliferous Meduse
buds. —e Rows of epithelial cells form-
ing distinct bands at the surface.—o
Proboscis.

Meduse buds produce new Hydroids without freeing themselves; and yet these
Medusxe buds show all the characteristic features of genuine naked-eyed Meduse.
In Tubularia proper, for instance (Vol. 4, Pl. XXIV. and XXVI, figs. 3 and 4),
they have four radiating tubes with a pendent proboscis and a circular tube, but

hardly a trace of tentacles; while in other genera these characters are variously

46 ACALEPHS IN GENERAL. Parr I.

combined. Thamnocnidia (Vol. 4, Pl. XXII.) has four distinct tentacles and a large.
proboscis, but neither radiating nor circular tubes. Parypha (Vol. 4, Pl XXIIL)
also has tentacles, but of a very different form, and a large
proboscis, but no chymiferous tubes.

In the family of Campanulariw, the Hydroids seem to differ
greatly from the Tubulariz, the stem being horny, and the
bell-shaped animal surrounded by a horny bell; but a micro-

scopic examination of the surface of the stem, and even of

the bell, of all Hydroids, shows that the only difference in the

outer layer of the animal consists in the thickness of that

hyaline layer which in Campanularia and Sertularia becomes
Trocnoryxis, Ag.
New genus of Campanularix.

2a Common basis of thecommunity. the naked eye as a sort of horny sheath enclosing all the

—b Fertile Hydra.—cd Stems of

so firm as to assume permanent forms and to be visible to

sterile Hydre.—eg SterileHyare soft parts, while in Tubularia it is soft and flexible. This once
expanded. — f Secondary sterile
He : : :
ce hesrtdiae understood, the difference between a Campanularia (/%g. 15)
and a Tubularia head is only such as we should expect between members of differ-
ent families, — they differ in form only. Yet there is another distinction to be made
ek among them. The individuals of the same
ig. 16. 5
community, united upon the same stem but
arisme from different axes, exhibit marked

differences among themselves: the larger

number, which have all the same form, re-
FreE Mepusa of the Cam- . ; : ee a

panularia represented in main for ever sterile (Fig. 15, ¢ d@), while oth-

Fig. 16. It is represented

here with the margin of the

ers, of a different form, produce buds along

disc and the tentacles raised, eS rite are ci ay _ 1 2
Fertice Hypna of while the proboscis is pen. their internal proboscis (Hig NG eit, a
Ca anularia. : Sg 6 . “ a rp a 2 as ‘ Q ae
ampanularia dent. Its adult state is de- ad, of, ge a’, di \ which in due time free
a Base of attachment. —b Ca- scribed in the Contributions 7
lyx.—e secushee Apes male to the Nat. Hist. of the Aca- themselves and swim
Be a ae lephs, under the name of : a Fig. 18.
CE oa et ON Thaumantias. off as distinct Meduse
older. [have frequently seen ean ; , 4 7
these buds freeing themselves c Mouth and proboscis. —oo0 1° ea Mate te fay a
papgpcrie reine te ramniee Radiating chymiferous tubes. (Fig. if ‘ ). it his Is, for
Fie. 17 Zz —ee Eyes.—¢t Tentacles. . Fi z . : \G/
ot instance, the case with Mhae
ia
Thaumantias and Tiaropsis, which are only the free Meduse Oy Ss
ee . . i eGo
of different genera of Campanularians. The same is the case, Wy
z 1

again, with the Sertularians (/%y. 18), which produce other

= rp ’ DyNAMENA Faprici, Ag.

kinds of free Meduse. One of the most common Ser-
With these facts before us, there can be no doubt left te Mydroids of our coast.

abe Single individuals; that occu-

in the mind of any unprejudiced observer, that, even though ying the cell) isentirely, and that

in cell c partly, expanded.

the Hydroids from which arise many of the naked-eyed Me-
dus thus far described have not yet been ascertained, and though many Hydroids

are known the Meduse of which have not yet been identified, enough is clearly

Cuap. II. THE DIFFERENT RADIATA. 47

understood of the relations of Hydroids and naked-eyed Meduse to show that there
is a genetic connection between them all, and such an identity in the essential
structure of the Hydroids on one side and the naked-eyed Meduse on the other,
that the view which represents the Hydroids as true Polyps must be for ever
banished from our science. This would be none the less true even should it appear
that the genuine Polyps form part of a larger division, embracing also the Hydroids
with the naked-eyed Meduse; for such a comprehensive division would still have
to be subdivided into secondary groups, no one of which could include at the same
time true Polyps and Hydroids, without conflicting with their natural affinities.
A few more words upon the Sertularians and Campanularians and their free
Meduse will set this matter at rest. A sterile head of Campanularia (7%. 10,
and 15 ed), which is so strictly homologous to Sertularia or Dynamena (Fy. 18)
that a comparison between the two is superfluous, shows a bell-shaped body, in
every respect identical with that of a Tubularia or Hybocodon (7%. 11). It has
a row of feelers around its margin like the latter, only the feelers are more
active, and capable of being drawn in more completely. The floor stretched across
the wider part of the bell is open in the centre, where we find the oral aperture.
The only difference in these parts between Campanularia and Tubularia is, that the
centre of this floor rises, in Tubularia, in the shape of a proboscis, while in Cam-

panularia it may only be raised to a small extent, but is at the same time capable

Fig. 20. Fig. 21.

Medusa bud of
CORYNE MIRABILIS, Ag.

The bud represented here sepa-
rately, with its base of attachment
a cut through, is younger than
that represented in its natural con-
nection in fig. 19 d. The free
Medusa is represented Fig. 21, and
described as Sarsta mirabilis in the
Contributions to the Nat. Hist. of
the Acalephs.

CoRYNE MIRABILIS, Ag.
Hydra with a Medusa bud. The
buds when freed become Sarsiz.
See fig. 21.

The free Medusa, Sarsra, of

a Base of attachment to the Hydra
CORYNE MIRABILIS, Ag.

a Stem of the Hydra. —v Its club-shaped i ue
stock. —o Proboscis.—b Radiating

body. —o Its mouth.—?¢¢ Tentacles s 2 ete P
Y chymiferous tubes. —t¢ Tentacles. o Proboscis.—b Vertical chymiferous
scattered over the body.—d Medusa A i‘ e
bud tube.—c Circular tube. —ee Dia-
phragm. —?t¢ Tentacles.

of greater expansion and contraction. There is in that respect no greater differ-
ence between Campanularia and Tubularia as Hydroids, than between Sarsia (Figs.

19 d, 20, and 21) or Hybocodon (Figs. 12, 13, and 14) as naked-eyed Meduse and

48 ACALEPHS IN GENERAL. Part I.

Thaumantias (7%. 17) or Melicertum (/’gs. 22, and 25), which are respectively the
‘free Meduse of a Coryne (/%y. 19), a Tubularian (F%g. 11), a Campanularian (/%gs. 10
and 16), and a Sertularian (/%y. 18). And if we compare the Coryne with the Tubu-
laria, the only essential difference we notice is, that while in Tubularia the feelers
are arranged in a whorl around the
base of the proboscis, in Coryna
they are scattered all over the
proboscis.

There is only one more group

of animals that has been associated

adi Bare with the Meduse. I mean the
MrpusaA CAMPANULA, Fabr.

(A species of Melicertum —§ Acalénhes hydrostatiques of Cuvier,
Oken, seen in profile.) - is (plik

The free Medusa ofavery Called Siphonophore by Eschscholtz oes
common Sertularian Hy- ; ; ; ; MeEpusA CAMPANULA, Fabr.
droid of the North Ameri. Nd the more recent writers. From
can coast.

(A species of Melicertum Oken, seen from
the time they became first known eve)
: The free Medusa of a very common Sertu-

the vertical chymiferous tubes. throueh the descriptions of Forsk Al larian Hydroidof the Atlantic coast of North
—m Mouth.—a Disc. = America.

t Tentacles. —o Ovaries, along

and the splendid illustrations of

m Mouth.—oo Ovaries along the vertical chy-
miiferous tubes.—t¢tt Tentacles,

LeSueur, they have always been considered as allied
to the Medusx, until recently Kélliker has associated them with the Polyps under
the name of swimming Polyps, Polypi Nechalei. An opinion expressed without
hesitation by so eminent- an investigator as Kélliker requires the most careful
examination. To arrive at a satisfactory result on this critical point, it is neces-
sary, in the first place, to consider the fact, that the so called swimming Polyps, the
Siphonophoree of most authors, are compound animals,—that is to say, communities
of individuals organically connected in a manner similar to the community that
exists between the numerous individuals of a Coral stock or of a Hydroid_ stock.
But this is not all. The individuals so connected in these communities have no
more the same appearance than those of the communities formed by certain Hy-
droids; and that we may be the better prepared to appreciate the extraordinary
extent to which different individuals of the same community may differ in a stock
of so called swimming Polyps, it may be well to consider beforehand the extent
of the differences we observe between the individuals of similar stocks among
genuine Polyps, as well as among Hydroids.

In a Polyp community the rule is, that all the individuals of the same stock
resemble one another in every respect, differing slightly in size, and, it may be,
as in the confluent species, in the number of mouths, circumscribed by a con-
tinuous series of tentacles, as for instance in Meandrina, Diploria, Gyrophyllia,
Manicina, ete. In some of the Madrepores, however, and especially in those which

produce numerous distinct branches, there is a greater difference, each branch

te.

Cuap. If. THE DIFFERENT RADIATA. 49

terminating with a larger Polyp, which is perfectly symmetrical; while the individuals
which stand upon the sides of the branches are not only smaller but at the same
time one-sided, the broader and more prominent side being turned outward, and
the tentacles on that side being also larger than those turned toward the com-
mon axis.

Among the Hydroids, as among the Polyps, we find those in which the com-
munities are formed by identical individuals differing, perhaps slightly, in size.
This is the case in the families to which the genera Tubularia (Vol. IV., Pl. XXIV.)
and Coryne (Pl XVII, XVIII, and XIX.) belong. But there are others, in which
we find, either constantly or at least at certain seasons, two kinds of individuals,
differing not only im size, but also in form, and still farther in the presence or
absence of tentacles, one kind being always sterile, while the other produces Medusz
buds that may be freed. This is the case with the Campanularians (/%gs. 10, 15, 16,
and 17) and the Sertularians (/¥gs. 18, 22, and 23). In the Plumularians, the differ-

ences are still more marked; for besides the fertile indi-

Fig. 24.

viduals there are several kinds of sterile individuals,
grouped together in various clusters, the smaller ones
being attached around the large ones. Finally, there
is a genus—Hydractinia (gs. 24 and 25)—which, among
the Hydroids, exhibits the greatest range of difference
thus far observed between the individuals of the same

species. For in this genus we have, in the first place,

two kinds of communities: one (/%g. 25) in which the

fertile individuals produce only male Medusxe, and another Hypractinta rorycuina, Ag.

@ Sterile individual, —é Fertile individual pro-

gas mine whichy the; fertile: individuals. produce sonlly «7 jicing matenseause 2's vetale Meare

Pp 2 . p . containing advanced m f¢ht Cluster

Fig. 25. fei nale Meduse. Aga In, the fertile of female Medusse with 1 lvanced egers. —
. a = ] ; Is . ] 2 l ki ] ; f ; o Peduncle of the mouth with short globular

Malyviduais mM ot 1 KInNdS O com- tentacles. — ec Individuals with globular ten-

oe ae ne: : RAR ' 9) tacles, upon which no Medusz have as yet ap-

munities have tentacles (Figs. 24 0 eased oily drome wie Tuer vatealceasy

dropped.

and 25 6, 0) entirely different from
those of the sterile individuals. The sterile individuals (/%ys.
24 a and 25 a) differ also greatly among themselves, some being

slender and almost thread-like; others slender, but with a dis-

tinct proboscis and a whorl of tentacles; others short, widening
HE DERCTINGS, POLY CHINAS Se pecreditiyz upward, and assuming almost the form of a trumpet-
aa Sterile individuals. —d Fertile ° h :

individual, producing male Me- mouth. All these individuals differ not only In their form
dusaz.—d Clusters of male Me- hs

dus. —o00 Proboscis, with the and complication, but also in their color, so that we have in

mouth at the apex. —¢t Elongated 5 . —: .

tentacles of the sterile ingividu- this genus about as great a diversity of individuals in one

als; in the fertile one >, they are F . : . , ate

simple knobs upon the proboscis o. community, as 1s observed in the most complicat ed Siphe N0-
phore. The only difference between the two groups consists in this: that while all

VOL. III. Uf

50 ACALEPHS IN GENERAL. Parr I.

compound communities of ILydroids are attached to the ground, those of Siphono-
phore are free; but this is not a character exclusively peculiar to them, for among
the Polyps we have also free communities belonging to the same order as others
that are immovably attached to the ground. Such are the genera Renilla, Penna-
tula, Virgularia, Veretillum, ete. which are inseparable from the genera Gorgonia,
Aleyonium, Xenia, Tubipora, ete., or at least belong to one and the same order.
In these locomotive Haleyonoids the individual Polyps are identical among them-
selves, but grouped together in the most diversified ways, varying in that respect
quite as much among themselves as the fixed Haleyonoids. In Pennatula and
Virgularia they form regular rows upon the two sides of a feather-like stem, in
Veretillum they are scattered around a cylindrical stem, in Renilla they are
arranged in symmetrical lines upon the surface of a kidney-shaped disk. And yet
these communities move and act as one individual. I have frequently seen Renilla,
which is our only genus of free Halcyonoid Polyps, move slowly about in the sand,
its stem buried in a vertical position with the disk spread horizontally.
Now, if I have succeeded in showme that, by their structure, the so-called
Hydroid Polyps are not Polyps, but Acalephs, and if I should also succeed in
Fig. 26. showing that the different kinds of individuals forming the
communities of Siphonophors have the same structure as
the Hydroids, and present everywhere, in all their parts,
special homologies with the Hydroid Polyps and naked-eyed
Medusx, without even exhibiting one of the peculiar char-
acteristics which distinguish the true Polyps from the Hy-
droids, I should then have proved that the Siphonophorz are
really Hydroid Acalephs, and not Polyps, as Koélliker believes
them to be. The evidence thus adduced would be an
additional reason for keeping the true Polyps, the so-called
Anthozoa, by themselves, in a distinct class.
Let us therefore compare more in detail the different
kinds of Siphonophore with the different kinds of Hydroids
and naked-eyed Meduse. Beginning with Physalia (/%y. 26),

it is not difficult to perceive that the various kinds of

appendages which hang from the floating air-bag of that

animal may be compared to the heterogeneous individuals

wees

of an inverted Hydractimia. ‘ancy the channelled layer
PuysaLiA Aretuusa, Til. Ls io i
a Blunt end of the air sac, supporting which forms the attached base of Hydractinia to be swollen
the whole community, at which the 6 . .
youngest buds may be found. —b Open mto a large oblong bag, and the comparison may be CaAr-
end of the air sac.—e Crest of the air 4 . . P ° “7
sac.—m Bunches of single individu. ried even into the details; for the essential difference
als. — 7 Tentacle contracted. —¢t¢ Ten-

tacles of the largest kind extended. between these two genera does not so much consist in a

Cuap. II. THE DIFFERENT RADIATA. al

difference of the individuals forming these communities, as in the form of the
basis to which the individuals are attached. In Physalia that basis is a_ sae,
inverted upon itself, the inner bag of which, opening externally, is filled with air ;
the intervening cavity, communicating with the open bases of the pendent indi-
viduals, contains a greater or less quantity of fluid. Now, suppose the air-bag to
be turned inside out, there would be formed a large and simple hose, containing
liquid that may be pressed into the individuals attached to it, or to which the
individuals may add by pouring their fluid contents into the bag. In Hydractinia,
the narrow anastomozing tubes, in the basis of attachment of the polymorphous
individuals of the community, may be compared to this hose of the Physalia, only
that they are branching. But as a number of individuals arise from each of
these stems, we may just as well consider their basis as a single tube; and then
the only difference between Hydractinia and Physalia would be the narrowness of
the tube of the former, and the great width of that of the latter. But reduce
the diameter of the one or swell the cavity of the other, and all difference dis-
appears, especially if we suppose them both floating or both attached. It may
be that the crest of the Physalia, with its many chambers, carries the homology
with the anastomozing tubes of the Hydractinia still farther.
As to the various kinds of individuals forming these communities, we find first in
Physalia the numerous so-called suckers, or Polyps (figs. 27 66 and 28 66), correspond-
Fig. 21. ing to the larger trumpet-like individuals of Fi
the Hydractinia community (Pl XVI. Fig.
la, 1d). These suckers, very numerous,
and also much diversified among themselves,
are genuine Hydroids. I have seen them

feeding greedily upon small fishes, and

gorging themselves to such a degree that

the silvery scales of their prey could be Beneh O8 Hy dria: of

distinctly seen through their distended P#¥s*h4 Sxernusa, Til.

- is os In various states of contrac-
Bunch of single Hydre and walls. But these so-called “Polyps” have _ tion and expansion.

clusters of Meduse of Puiry- F :

SALI Arernusa, Til. nothing of the polyp structure about them,

bb The Iydre, with their tenta- C : . o) 8 nae ia .
cles ce.—-da The bunches or either radiating partitions dividing their

Medusz.

a The hollow base of attachment
of the whole bunch, communi-
cating freely with the chymifer-
ous cavity of the air sac. —b bb
Single Hydra.—cc Tentacles

internal cavity, nor tentacles opening di-
rectly into radiating chambers, nor an inverted sac hanging in that cavity; on
the contrary, the edge of their oral opening is turned outward as in all Hydroids.
They are, in fact, Hydroids of the simpler kind, but not so simple as some of
the individuals of the Hydractinia communities; for though they have no whorl
of tentacles around their mouth, they have at least one very long and very com-

plicated tentacle. Of these tentacles there are two kinds,—larger ones connected

59 ACALEPHS IN GENERAL. Part I.

with the larger so-called Polyps, and smaller ones connected with the smaller imdi-
viduals (7%. 28 ¢¢). These two kinds of individuals seem to be always distinct, and
some of them never even gape at their outer end. The individuals of these two
kinds form large clusters, small communities as it were, connected with the larger
community. There is a third kind of individuals, smaller than either (Fig. 27 dd),
which are fertile, and upon the neck of which arise numerous Meduse buds, pre-
senting all the characters of the naked-eyed Meduse; that is, having, like them,
four radiating tubes and a circular tube (fv. 29 dd). These Meduse form clusters

Fig. 28 so similar to the bunches of Meduse that

Fig. 30.

hang from the genuine Tubularia, that they
might easily be mistaken one for the other
(4g. 30). (Compare Pl XXIV. fig. 1 with

Fig. 29.) Here, then, is a Siphonophorous

community, im every respect similar to a

Bunch of Meduse of
Puysania Areruusa, Til.

Bunch of Medusz of
TuBULARIA CouTHouyt, Ag.
In various stages of develop- kinds of Hydroids, from some of which are @ Common axis.—add Mature

ment. “ Medusve, already withering.

produced Medusze buds, as in ordinary Hy-

Hydroid community, consisting of various

a Common hollow base of attach-
ment of the whole bunch, com-

municating with theehymiferons Olds. The fact that in Physalia these Medusse buds do not
ie cea ae ee separate from the community but wither upon the stock from
ais which they arise, is not peculiar to this group of animals; since
we have already seen, that, in the family of Tubulariz, we have those that produce
free Medusw, the genus Hybocodon and others, the genera Tubularia (f%y. 50),
Thamnocnidia, and Parypha, the Medusxe of which do not separate from their
parent stock. These facts are in themselves sufficient to show that the Physalia

community does not consist of aggregated Polyps, but of aggregated Hydroids; and

that in a natural classification they cannot be referred to any other order than the
Hydroids, though in that order they constitute a distinct family.

The idea of considerme the Meduse buds of these communities as the sexual
organs of the Hydroids is not admissible; for we have seen that these buds may
become independent and free, and that in due time they acquire themselves distinct
sexual organs, some individuals being provided with ovaries the eggs of which
undergo all the changes through which ordinary eggs pass until new individuals are
formed in them, while other individuals are provided with spermaries which at the
time of spawning are filled with spermatic particles. Now, unless sexual organs
can themselves have distinct sexual parts of both sexes, all these so-called sexual
organs of the Hydroids must be considered as naked-eyed Meduse, which are not
freed from their parent stock as is the case with others.

Velella and Porpita consist of compound communities like Physalia, only that

here the diversity of the Hydroids attached to a common base is not so ereat.
GD 7

Cuap. II. THE DIFFERENT RADIATA. 53

there being, in fact, only two kinds of individuals: the sterile ones, among which
that occupying the centre of the community is larger than the others, lke the
top animal of the Madrepores, and around it, clustered together, a large number of

smaller ones; and outside, the large fertile

Fig. 32.

Fig. 31.

individuals (Fg. 32) from which Meduse buds
arise that become free, and are very simt-

lar to the common Oceania among the

naked-eyed Meduse. This, at. least, is the

Veventa morte, Bose» = Gas in Velella (Figs. 31 and 32), as I

m So-called mouth —aa So-called

kentacles: shall show hereafter more fully. Meanwhile

the wood-cut below (2%. 33) represents an Oceania-like Medus:
Single so-called tentacle of

that freed itself, with many others, from the larger fertile Vererta muriea, Bose,

Bearing Medusie buds d d.— a

individuals of the common Velella of the ee taanienten ieee
7. th : . ¢ d of tk entacle.

Gulf of Mexico, represented in Fig. 31. The =“ ne

individuals forming the communities known as Velella and Por-

pita have no more the structure of Polyps than those of the

Physalia. They are genuine Hydroids.

If from these we pass to the Diphyidw, we notice a long
Free Medusa of
VELELLA mutica, Bose.

o Proboseis. —» Kadiatingehs- Jaye elongated, bell-shaped individuals, com-

miferous tube. —c Circular

string of heterogeneous individuals suspended from one or two
Fig. 34.
pai monly called the swimming-bells, and gen-
erally considered as organs destined to move the whole com-
munity (Figs. 34 and 35). But I believe that this view is not
ae correct, but that, on the contrary, these
so-called swimming-bells are themselves
distinct individuals of one kind connected

with smaller individuals of other kinds,

forming together a community composed

Gareouanta Fittrormts, Lenck. of very heterogeneous elements. The
Diphyes quadrivalvis, Gegenb. i ‘ ° : 1
( Copied from Gegenbauer.) invaluable investigations of Gegenbauer

ab Anterior and posterior swimming-
bells. —c String of twin individuals.
—d Feelers with lasso cells.—e
Cacal termination or base of the
connecting tube or axis.

upon the development of Diphyes seem
to me to leave no doubt upon this point; n

Dienyes SieBoLpi, Koll.
for he has observed the whole develop- (Copied from Killiker.)

ab Anterior and posterior swim-

ment of the egg of one of these animals, showing thas: TG WA peniette ease vot the

axis of the community. —¢

process of segmentation of the egg terminates in the FOUN BIGOT meee ratfatis cr the community,

n se ; a % 2 : with young buds. —d d Fully
of one of these so-called swimming-bells. Now, the product of Bevelbpod nds; with, hele

. : fe S.
the egg, whatever it may be, cannot be a mere organ. It is an
unquestionably a young animal; and that animal, as represented by Gegenbauer, is a

genuine naked-eyed Medusa. It has the four characteristic radiating tubes, a circular

54 ACALEPHS IN GENERAL. Pann

tube, and even the inverted rim of the margin of the bell so constant in naked-eyed
Meduse (/%. 56); and though no mouth is described, I can hardly suppose that it is

wanting. The radiating tubes imply the circulation of a fluid,

Fig. 36.

and that fluid is in all naked-eyed Medusee derived from the
surrounding medium, and introduced either through a proboscis
or through a cruciate opening in the centre leading into the

radiating tubes. The fact that in Staurophora’ IT have found

an immense mouth where none was suspected, leads me to
Embryo of
Dirnyes SresBoupi, Koll.
(Copied from Gegenbauer.) bells of the Siphonophore generally, must have such an oral
e Remnant of the embryonal body. . .
—a Swimming-bell developed Opening, Which has probably not been remarked only because

from the embryonal body.

suppose that this young Diphyes and the so-called swimming-

such an opening would not be looked for in what was sup-
posed to be a mere organ. Yet, considering the strict homology between the
open Polyps, so called, and the closed sacs mixed with them in Physalia, and like
them provided with tentacles, it may be that the swimming-bells are not open
externally, and only communicate with the main axis.

Be this as it may, the swimming-bells of the Diphyidse cannot be compared
to the swimming-bag of the Physalia, which, as we have seen, is the common
base of all the Hydroids of that community; nor is it homologous to the so-
called swimming apparatus of the Physophoridw. The only part in these different
communities really identical in all Siphonophore is the canal marked e in Figs. 34
and 39, along which hang the heterogeneous individuals of the community in Diphyi-
dx, Physophoridx, and Physalide; in the same manner as the many individuals of
the common Hydroids are attached to their hollow axis. In Diphyes proper there
exist, generally, two so-called swimming-bells of nearly the same size, though ocea-
sionally but one is observed, and in others the lower one appears sometimes so
much smaller than the upper one, that, taking these facts in comection with the
facts observed by Gegenbauer respecting the origin of the first swimming-bell from
an egg, it is natural to infer that the second swimming-bell arises from the main
tube of the first, and gradually enlarges to the same size; in the same manner
as in the proliferous naked-eyed Medusx (Figs. 12, 18, and 14), in which one of the
four radiating tubes becomes the basis of attachment of numerous lateral bells. It
is farther to be observed, that the pendent string of Diphyes, with its numerous
individuals, is only a continuation of that same tube which connects the two swim-
ming-bells, and that the individuals attached to it arise also as buds from it. But
here we perceive a variety of parts which require our special attention.

The individuals described as Polyps, or suckers, in Diphyes, are as it were

? Acassiz (L.), Contributions to the Natural History of the Acalephs, Part. I. p. 300.

Crap. I. THE DIFFERENT RADIATA. 55

protected by a flattened, scale-like, gelatinous body (4. 37 a a), and between the

scale and the Polyp hangs a complicated tentacle, ¢d. These

Fig. 37.

individuals I consider to be identical with the Hydroids of
the Physalia, the so-called Polyp representing the proboscis, as
we observe it in Coryne and Clava, only that each is pro-

vided with a single tentacle and surrounded by a protecting

scale. Now, if I am not greatly mistaken, that protecting

scale must be considered as a sort of bell, analogous to that Two twin individuals of the
. . : 7 pendent string of the com-

of Campanularia, but gelatinous, and split open on one side; munity of
é Dirnyes Srenotpu, Kill.
and the so-called sexual organs (Fig. 37 m) of these so-called pose eae

aa The so-called scales. —06b The

Polyps are genuine Meduse buds, with a proboscis, four radi- — socalled Polyps. —m The’ so-

. Z called sexual capsule.—c Ex-

ating tubes, and a circular tube, with a diaphragm around the SI iy pe a LIL
d Feeler contracted.

rim, exactly as in naked-eyed Meduse, producing eggs or sper-
matic cells upon the proboscis, according to the male or female character of
the different individuals, exactly in the same manner as in Sarsia or Hippocrene.

We have, then, in a Diphyes community, three kinds of individuals.’ First,
one or two, or sometimes three, Medusoid individuals at the base of the stock;
secondly, a large number of more Hydroid-like individuals hanging connected with
the pendent string, but differing from the common Hydroids in having an open,
gelatinous, somewhat Medusoid bell, commonly called scale; and, thirdly, arising
from the base of the proboscis of these Hydroids, genuine Meduse buds that are
either male or female, and which can no more be considered as the sexual organs
of these so-called Polyps, than those of the types already considered, since they
are themselves provided either with an ovary or a spermary.

The Diphyes community presents another peculiarity, highly important with
reference to a correct appreciation of the Medusoid character of the genuine
Hydroids. In most of these, we find that every individual consists chiefly of a
bell-shaped or trumpet-shaped or club-shaped sac, with tentacles around the central
opening, or upon its sides or around its base, comparable, indeed, in every respect,
to the proboscis of the naked-eyed Meduse as it exists in Sarsia. But though
the body of the individual Hydroids appears more or less bell-shaped, as in Tubu-
laria and still more in Campanularia, yet that bell is not hyaline and gelatinous
like the bell of the Medusxe proper, while the so-called scale of the Diphyes is
so, thus forming a sort of transition to the so-called swimming-bells, in which the
radiating and circular tubes are fully developed, as in ordinary Medusie, but at the

expense of the proboscis, which is wanting. This would at once explain why the

1 For illustrations of this and the following bauer, Huxley, Kélliker, Leuckart, and Vogt, quoted

families I would refer to the papers of Gegen- page 27, notes 5, 10, 11, 12, and 13.

ACALEPHS IN GENERAL. Part I.

On
f=)

Hydroids proper have no radiating tubes, while their Medusze buds have them
fully developed. I suppose the case to be this: That a perfect Medusa has two
distinct structural elements, the disk or bell with its radiating tubes, and the pro-
boscis with the mouth, and that in Hydroid communities the different individuals
present one or the other of these two elements, singly developed or more or less
combined; while their Medusx# buds have always the characteristic features of per-
fect Medusx, and are always sexual, whereas the Hydroids are never so, whether
the proboscidal or the bell element be the more prominent. If this be true, then
the characteristic feature of a Diphyes community consists in the more Medusoid
character of some of its Hydroids, while the more numerous individuals resemble
the common Hydroids more, and, like those, produce the sexual Meduse buds. We
have already seen, in the family of Tubularie (p. 45), analogous combinations of
characters; some of the fertile buds of these Hydroids being more Medusoid in
their structure than others.

The peculiarities of the genus Abyla (Calpe) seem to confirm this view. We
have here also, as in most Diphyes, two so-called swimming-bells, only that the
first is much smaller and less Medusa-like than the second, and that the so-called
Polyps of the pendent string are not protected by simple scales, but by a cap
resembling the first swimming-bell, with this additional peculiarity, that the tentacles
are more or less removed from the base of the Polyps.

The genus Praya is very closely allied to the genus Diphyes, but its two swim-
ming-bells are placed side by side, and the pendent string consists of Hydroids
with a distinct helm-shaped bell, from which arise the Meduse buds. This string
of twin individuals, one of which is a Hydroid with a helm-shaped bell and
another a genuine Medusa, has been described as a string of single individuals,
the Medusa buds being considered as their sexual organ, but with as little pro-
priety as in the genuine Diphyide, for these buds again are themselves sexual.
The so-called single individuals of all Diphyide are not single beings, but twins,
one of which is Hydroid, and the other Medusoid, in its structure; and these twins
drop together and swim about freely as independent individuals.

In the genus Vogtia, the so-called swimming-bells have a quadrangular shape,
somewhat like a contracted Staurophora, and though no radiating tubes have been
described in them, I doubt not that they will be found when sought for. Below
the pyramid of these Medusoid Hydre, there are a few simple, sucker-like Hydroids,
and from the lower part of the axis arise the sexual Meduse buds, with enormous
proboscides, covered either with eggs or spermatic cells, projecting far out of the
Medusa bell, as is sometimes the case with those Sarsias that are not detached
from their stem. (Pl XVIL Figs. 15, 14, 15, and 16.) In the genera Hippopodius

and Elephantopus, which are certainly distinct, though frequently considered as

Cuap. II. THE DIFFERENT RADIATA.

if

On

synonyms, the swimming-bells are boat-shaped, and their radiating tubes winding,
as in Galeolaria among the Diphyide. In the genus Athorybia, the swimming-
bells have the shape of arched ribs; and, though no radiating tubes have
been described in them, I doubt not that they will be found, unless there
exist here, as in Tubularia, various combinations of the more Hydroid or more
Medusoid features. In the genus Apolemia, the swimiming-bells resemble those of
Physophora, and the Hydroids are arranged in clusters, hanging at intervals, along
the main axis.

The genus Physophora, with its double row of bottle-shaped swimming-bells,
approaches more nearly Hippopodius and Vogtia than Agalmopsis and Forskalia; for
the sucker-like Hydra are few (/g. 38), at the base of the axis, as in Vogtia,
and the Medusxe buds form small bunches. In Agalmopsis,
on the contrary, there is below the double row of heart-
shaped swimming-bells a long string of large Hydroids, pro
vided with protecting scales and furnished with tentacles,
and their sexual Meduse buds form small bunches, suspended

at considerable intervals between them. In Forskalia, finally,

the more or less quadrangular swimming-bells, arranged in

several rows, form a long cone, from which hang two kinds e
of Hydroids, one protected by, and the other without, scales; Youne Puysornora,

(Copied from Gegenbauer.)
and it is from the cluster of the latter that arise the male — , guasof swimming bells.—bd So-
and female Medusx buds. Esrunpecanatastac 78) 2 ae

It is plain, from this rapid survey of the Siphonophore, < mie as
that, with the exception of Physalia, Vellella, and Porpita, which consist of Hydroids
only, they all agree in having a set of more or less numerous Medusw-like Hy-
droids at the base of their common axis; and that from the prolongation of this
axis arise other Hydroids, either altogether resembling the common Hydroids, without
a bell, or protected by a scale-like open bell, in a measure intermediate between
Meduse and Hydroids; and that, finally, all produce Meduse buds. These Meduse
buds mostly wither upon the community, though in some they free themselves in
the shape of twin individuals composed of a Hydroid and a Medusa, which have
been described as distinct genera, under the names of Eudoxia, Aglaisma, ete.

It follows from all this, that while the Siphonophore must be united with the
Hydroids proper in one order, on account of the identity of their structure and
of the similarity in the degree of complication of that structure, the types of this
order in which the community consists of more Medusa-like Hydra, such as the
Physophoride and Diphyide, must constitute a sub-order by themselves ; Physalia,
another sub-order, on account of the peculiarity of structure of the common base of
the community; Velella and Porpita, another, for similar reasons; and the true

VOL. III. 8

8 ACALEPHS IN GENERAL. Parr I.

On

Hydroids, a fourth: unless we separate at once the Sertularians with their horny
stem and bell as a sub-order, distinct from the Tubularians, with their soft Hydroids,
which seems to be the more appropriate course. Diphyide and Physophoridee may
require to be subdivided in the same way.

Now that the investigations of Olfers, Leuckart, Quatrefages, and Huxley, have
made us as fully acquainted with the structure of Physalia as we are with that
of the other Siphonophore, it is hardly worth while to recall the opinion of
DeBlainville upon these animals, as it is evident from his description, that he could
never have entertained such views about them, had he ever had an opportunity
of studying them for himself. DeBlainville considered Physalia as a single animal,
which he referred to the type of Mollusks in connection with the Heteropod
Gasteropods, considerme the crest of the bladder of Physalia as its foot, similar
to that of these Gasteropods, and the pendent appendages as gill-like organs similar
to those of the Dorsibranchiate, while he describes the opening of the bladder as
their mouth. But I myself have had repeated opportunities for examining Physalia
alive, and this examination has left no doubt on my mind that it constitutes a
compound community of a great variety of individuals, presenting all the characters
of true Hydroids.

It is important here to remark, that this great discrepancy in the opinions
expressed respecting the affinities of these animals was in a measure owing, either
to an insufficient acquaintance with their true structure, as was no doubt the case
with Blainville when he referred Physalia to the type of Mollusks, and with Vogt
when he referred the Ctenophore to the same type, or to a want of familiarity
with the other objects associated with them, as is no doubt the case with the
German authors, who, from a want of opportunity of examining Corals alive, have
so generally united the Hydroids and Siphonophore with the Polyps. It is a
remarkable circumstance, that the naturalists who have known the Polyps best, as
Milne-Edwards and Dana, never thought of associating the Siphonophore with them,
though they were equally acquainted with both, and though we owe to Milne-
Edwards in particular, some of the most minute investigations extant upon the
Siphonophore. As to the Hydroids, though they are associated by Milne-Edwards
with the Polyps, he considers them as forming by themselves a natural division
in that class, coequal with the Haleyonoids and <Actinoids; while Dana goes one
step farther in the right direction, by uniting the Haleyonoids and <Actinoids in
one natural division, to which he opposes the Hydroids as another division of
equal value. But even this position Dana has lately abandoned, and he now
unites the Hydroids with the true Acalephs; so that it may be truly said, that,
in proportion as our knowledge of the Siphonophore, the Hydroids, and the Polyps,

has gradually advanced, naturalists have perceived more and more distinctly the

Cuar. II. THE DIFFERENT RADIATA.

Or
cro)

fundamental differences which distinguish the
Polyps from the Acalephs, and at the same
time incline more and more towards uniting
the Hydroids as well as the Siphonophore
with the genuine Acalephs. Incidentally, I

would also remark that I entertain no doubt

LUCERNARIA, LPG DENSE respecting the Hydroid affinities of Lucer-
Seen in profile. Seen froi above. 2 ; a 5
a Peduncle. — b Tentacular m Mouth.—cc Ovaries. — nharla (Figs. 39 and 4()). Moreover, their
bunches. bb Tentacular bunches.

resemblance to the young Meduse is very
great (Figs. 41, 42, and 43), especially during the incipient stage of their Strobila
state of development.

Fig. 41. Fig. 42.

« Uy =o x
ny,

RNS

a

Scyphostoma of Strobila of
AvuRELMIA FLAVIDULA, Pér. & Les. AURELIA FLAVIDULA, Pér, & LeS. Ephyra of
In this stage of growth, Aurelia is a Scyphostoma reproduced at the base AURELIA FLAVIDULA, Pér. & LeS.-
simply a Hydroid. of a Strobila 44, all the disks of which ¢ Mouth.—ee Eyes.—oo Ovaries. —

have dropped off but the last. raga Men taculanapaces:

The types referred to the class of Polyps are not less diversified than those
referred to the class of Acalephs; nor do the different writers upon that subject
agree more closely in the views which they entertain respecting their affinities.
The type which has always been considered as forming the bulk of the class of
Polyps is that of the Corals. The Actiniw have been by turns associated with
them, and separated from them. As we have already seen, the Hydroids have
also, for a long time, been united with them by all naturalists, until doubts arose
respecting the correctness of this combination, in consequence of the discovery of
alternate generations among them. Besides these we find, farther, the Bryozoa
united with the Polyps even to this day by many naturalists ; though the re-

searches of Milne-Edwards and Audouin,' published more than twenty years ago,

1 Epwarps (H. Mitne) et Avupouin (J. V.), 1840, VI. p. 5; 1841, VIII. p. 321; and 1842,

Recherches sur les animaux sans vertebres faites IX. p. 193. The opinion that the Bryozoa are
aux iles Chausey, Ann. Se. Nat.’ II. p. 20. — not Polyps, but a low type of Mollusks, had al-
Milne-Edwards alone published more extensive ac- ready been expressed by K. E. v. Baer, in 1827,
counts of those observations: Recherches Anato- in his Beitriige zur Kenntniss der niedern Thiere,
miques, Physiologiques, et Zoologiques sur les Nova Acta Academie Nature Curiosorum, Vol.

Polypes; Ann. Sc. Nat. 2de sér. 1838, IV. p. 321; XUIL

60 ACALEPHS IN GENERAL. Parr I.

might have satisfied any unprejudiced investigator that they are not Polyps, nay,
not even Radiata, but a kind of low Mollusks.’

What are commonly called Corals are communities of individuals possessing a
solid frame, but of the most heterogeneous structure, and having no common
character except the solidity of their frame. The moment we take into account
the anatomical structure of the beings forming such communities, we must distinguish
several kinds of Coral stocks. First, those which are uniformly calcareous, formed
by genuine Polyps allied to the Actiniw. In fact these Coral stocks differ from
the Actiniz only by the presence of solid deposits in the walls of their body.
Such are the Astraans and Madrepores, all of which have, like the Actinis, numer-
ous simple tentacles, and a digestive cavity hanging below the mouth, as well as
radiating partitions projecting into the main cavity of the body, and to which the
ovaries and spermaries are suspended. Secondly, on account of the similarity in
the organization of their individuals, we would unite, as another group of Corals,
the various solid stocks formed by Haleyonoid Polyps. Some of them are caleare-
ous, like the Actinoids, the Red Coral, for instance ; others are horny, the Gorgonie ;
and others consist of calcareous tubes, such as Tubipora. The Corals of these Hal-
eyonoid Polyps are, it is true, far more diversified than those of the Actinoids, though
there seems to be much less difference between the animals themselves than among
the latter. They all have eight fringed tentacles, and agree fully in this respect, as
well as in their general structure, with those Haleyonoids which have no solid
frame at all, as the genera Halecyonium and Renilla, or only a simple horny rod
in their axis, as Virgularia and Pennatula.

On account of the special homologies of the Actinoids and Haleyonoids, there
can be no doubt that these two types of Polyps belong to one and the same
natural group, as Dana has first shown. They all have vertical radiating partitions
dividing the main cavity of the body into chambers, which communicate freely
with the cavity of the tentacles; in all, the ovaries and spermaries are found
hanging freely from the free inner edge of these partitions, and in all there is
a distinct digestive sac suspended in the upper part of the main cavity of the
body. They are, in one word, strictly homologous to the Actiniw, the structure
of which we have considered more fully above.

Among the Stony Corals generally referred to the Actinoid Polyps there is one

1 Siebold in his Text-book of Comparative Anat- has not yet been found. 3ut, surely, dilateral
omy, and Kolliker in his Schwimmpolypen, referred animals with an alimentary canal open at both
to above, (p. 27, note 12,) still unite the Bryozoa with extremities and bent in a plane dividing the body
the Polyps. Iélliker is particularly explicit on that into equal halves can no longer be associated with
point, and believes that the expression by which Polyps, which are built upon a plan characterized

Mollusks and Radiates may be clearly distinguished by radiation around a vertical axis.

Car. IL. THE DIFFERENT RADIATA. 61

type, belonging to the order of Tabulata of Milne Edwards (igs. 44, 45, and 46),
formed by animals entirely different from the true Actinoids, and closely allied,

as I shall show hereafter, to the genus Hydractinia, constituting a third type of

Fig. 44. Fig. 45.

MiLLerora Atcrcornis, Lmk.

A branch of the Coral of that Minuerora aucicornts, Lmk.

name, natural size. The little pro- MILLEPORA ALCICORNIS, Lmk. T ti fen hof
ae ransverse section of a branch 0
Jections along the edge are meant Magnified view of the extended iherGomleinclinerniied

for the extended Polyps. _ They are Polyps or Hydroids of the same . Ein, .
extremely shy and delicate, and Gormletonle aa ES of the Hydroids, with their suc-
never show themselves again after : Cosety Og Hors pau te, Very Guiticulcyeg
Seach E b fale t aa Smaller Hydroids.—b Larger Hy- obtain sections of the pits occupied
SLL AAS MALS RSE) ISLS ea droid, m its mouth, ¢ its tentacles. by the smaller Hydroids.

of the water.

Coral stocks, which, on account of its Hydroid affinities, must be united with the
class of Acalephs. Moreover, these Corals differ greatly from those of the Actinoid
Polyps. The pits into which the animals retreat have a horizontal floor extending
from wall to wall, and these floors are built successively one above the other,
as the animal rises, the radiating partitions never extending vertically through
successive floors. Not so with the Actinoid Polyps, in which the radiating par-
titions extend from the top to the bottom of the pit, while the horizontal floors,
if they exist, extend only from one radiating partition to the other.

Among Bryozoa we find a fourth type of Corals. These Bryozoa are constructed
on a totally different plan, and exhibit a perfect bilateral symmetry; for even the
whorl of feelers which surrounds the mouth is not circular, but, like a horseshoe,
presents two symmetrical halves. From the mouth arises an alimentary canal,
extending in the longitudinal axis of the body, which bends itself im the same
plane, and, extending again forward, opens below the mouth. There is here no
sign of the characteristic partitions and chambers of the true Polyps, nor of the
vadiating and circular tubes of the true Acalephs: so that we need not even take
into consideration their bilateral structure, in order to satisfy ourselves that their
true position cannot be either with the Polyps or with the Acalephs; while their
relation to the Ascidians and Brachiopods, and especially to the latter, is so close
as to place it beyond question now, that their true affinities are with the Mol-
lusks, and not with the Radiates.

I shall hereafter have an opportunity of showing that the comparative simplicity
of these animals is no evidence of any relation to the Polyps. The primary

question to be decided, in considering the true relations of animals, is not one of

62 ACALEPHS IN GENERAL.

Part I

complication of structure,’ which determines the orders in a class, but one of plan,

which stands even above the consideration upon which classes are founded, and
determines the four great branches into which the whole animal kingdom is
divided. As to the Coral stocks formed by Bryozoa, they vary greatly, being
calcareous in some, as in Eschara; horny in others, as for imstance in Acha-
marchis; and in others again, as in Haleyonidium or Holodactylus, altogether gela-
tinous. Moreover, these Bryozoan Coral stocks never exhibit in the cells oceupied
by the animals, those radiating lamelle so characteristic of the Coral stocks of the
Actinoids. On the contrary, these cells, into which the animals may withdraw
and conceal themselves entirely, are perfectly smooth, and the opening through
which the animal is protruded presents uniformly a transverse, oblong, or crescent-
shaped aperture, similar to the gaping opening between the valves of a Lingula,
or the half-open shells of any other Brachiopod, with which they are much more
closely allied than would at first appear. These cells are external, and do not form
a part of the body-wall of the animal, as do the radiating pits of the Actinoids.
The so-called arms of the Brachiopods are truly homologous to the marginal fringes
of the Bryozoa, between the branches of which the mouth is placed in both. — It
is therefore evident, that, notwithstanding the high authority of some of our best
anatomists, the Bryozoa must be removed altogether, not only from the Polyps,
but also from the type of Radiata, and referred to that of the Mollusks. The
presence of a Coral stock in most of them can no longer have the slightest weight
in determining their affinities; since we have already seen that there is a kind
of Coral stock, the Millepora, formed by certain Hydroids of the same type as Sertu-
laria and Campanularia, or, rather, closely allied to Hydractinia, which truly belong
to the Acalephs; and since, among the genuine Polyps themselves, we find Corals
so diversified as those of the Astraans and Madrepores, of Gorgonias and the Red
Coral, and of Tubipora. Under these circumstances, it must be selfevident that
the name of Corals can no longer be applied to designate a natural group of

animals, but only certain modes of association of animals belonging to very different

1T have already insisted upon this point in those who consider the Worms as a distinct branch

the first volume of this work (p. 145), and in the
chapter on Embryological Systems (p. 220). Baer
was the first to establish a clear distinction between
the degree of perfection in the structure of animals
and the plan upon which that structure is built, a
distinetion which Cuvier had not reached when he
allowed the Intestinal Worms to remain among the

Radiata on account of the simplicity of their strue-

ture. The same confusion remains in the minds of

of the animal kingdom, and associate with them the
Rotifera and even the Bryozoa. With reference to
the Bryozoa and Polyps it is essential to remember,
that, though the body in both may be called a sac,
in Polyps this sae is a radiating sac, while in Bry-
ozoa it is a bilateral sac; i. e., the one is built upon
one plan and the other upon another plan. In
Polyps the fundamental idea is radiation, in Bryo-

zoa bilateral symmetry.

Cuar. IL THE DIFFERENT RADIATA. 63
types. The discovery that the Millepora is a genuine Hydroid, and not at all
allied to the Actinoids, makes a farther revision of all these Stony Corals, the animals

This
is especially the case with Pocillopora (Pl. XV. Fig. 14°), which, from the structure

of which have not yet been sufficiently investigated, particularly desirable.

of the Coral stock itself, I am now satisfied, must also be referred to the Hydroids
with Millepora.!| I believe the same also to be the case with Seriatopora (Pl XY.
Figs. 15 and 15°).

There is a fifth type of Coral stocks, still more remote in its structure from
the Polyps, which, as long as all Corals were considered to be Polyps, was, with
IT allude to the

them to the Polyps, Lamarck assumed that there

the rest, referred to that class. so-called Corallines and the

When

existed animals of a very soft nature upon their surface; which, however, could

referring

Nullipores. g
not retreat into distinct cells, and therefore left no mark of their existence upon
the dried Coral stock. But since these Corallines have been more carefully ex-
amined, no trace of such animals has been observed; and, to say the least, their
animal nature has become very questionable. For my own part, I entertain no
doubt, that, as the investigations of Decaisne? first showed, they are neither more
nor less than genuine Alge with a tissue largely loaded with calcareous particles,
and may fairly be designated under the name of Limestone Alge. They are
true plants of the lowest type, forming, in consequence of the large amount of
lime they contain, Coral stocks of no small importance in the economy of the
Coral reefs. It is by their agency, since they are capable of sustaining their life
even when not permanently under water, that the crest of the Coral reef is raised
above the level of low-water mark; and the growth of some of their representatives
is so extensive that the exposed part of a large number of the islands of the
Florida reef is almost entirely composed of the fragments of these calcareous
sea-weeds. I have seen large slabs of rock, used in the construction of the foun-
dations of Fort Jefferson, upon the Tortugas Islands, composed entirely of the joints

of these calcareous sea-weeds, which were so distinct as to be recognized with ease.

1 As the structure of the Coral stock of the 2 DecatsNE (J.), Essais sur une classification

Tabulata of Milne-Edwards presents in all the same
general features, it is highly probable that the whole
order will have to be referred to the class of Aca-
lephs. I am farther inclined to believe, that the
Rugosa will share the same fate. Their typical
structure seems to be a combination of the char-
acteristies of Lucernaria and the Strobila state of
the higher Discophorw. A section of Strombodes

recalls at once the appearance of a Strobila.

des Algues et des Polypes calciferes, Ann. Se. Nat.
2de sér. 1842, XVII. p. 297.— Mémoire sur les
Corallines ou Polypiers caleiferes, Ann. Sc. Nat.
2de sér. 1842, XVIII. p. 96.

Vegetable Kingdom, London, 1853, 1 vol. 8vo. p.

See also LinpLey,

23.— Ktrzinc, Phycologia Generalis. — Harvey, a
Manual of the British Marine Alge, London, 1848,
p- 103. Schweiger already refers the Corallines to
the Alga.

64 ACALEPHS IN GENERAL. Panels

It is evident that these Corallines ought to be eliminated from the class of Polyps,
since their vegetable nature is proved.

There are a few more animals which have been referred to the class of Polyps,
such as the Lucernaria, the Eleutheria, and the fresh-water Hydra,’ about the affini-
ties of which I shall have more to say hereafter, when considering in detail the
Hydroids and their alternate generations. I leave them aside for the present, as,
on account of their small number of representatives, their position in the natural
system can in no way affect the natural limits of the classes of Acalephs and
Polyps. I shall also take occasion to present some considerations upon the affinities
of the Rugosa,? a type entirely unknown at the present day, but the representatives
of which are found, in large numbers, in the oldest stratified rocks forming part of

So long is it since the Tunicata were removed from among

°

the crust of our globe.
the Zoiphytes, that there is hardly a naturalist living who may remember the time
when they were confounded with Polyps. I need not, therefore, insist here upon

their affinities with the Mollusks.

eile TT ON Edius

THE CLASSES OF RADIATA.
We have thus far considered the various types of animals, chiefly with the
view of ascertaining which among them are true Radiata and which are not; and
it appears plainly, even from this rapid sketch, that while the Ctenophor, the
Medus proper, the Siphonophore, the Hydroids, the Haleyonoids, and the Actinoids,
are truly radiated animals, this is not the case with the Bryozoa, which properly
belong to the type of Mollusks, nor with the Corallines, which are genuine Plants.

oO

1 Milne-Edwards refers the genus Hydra to the called Carduella, showing, more distinctly perhaps

same class, to which he refers also the Anthozoa, than Lucernaria proper, the Acalephian character

the Tabulata, and the Rugosa, which he calls Zo-
antharia, separating, however, the genus Hydra, as a
distinet sub-class; Leuckart, on the contrary, places
it among the Ilydroids proper. Many important
papers have lately been published upon the structure

While

this page was in the printers’ hands I received No.

of this type, but with conflicting results.

31 of the Quarterly Journal of Microscopical Sci-
ence for April, 1860, in which I find Prof. Allman’s

description of a new genus of Lucernarioid Hydroids,

of this family, on one hand, and also its affinity
to the Rugosa, as well as to the embryonic forms of
the higher Discophore.

2 Tf, as I believe, not only the Tabulata, but
also the Rugosa, belong to the Acalephs, the exist-
ence of this class upon our globe, instead of be-
ginning in the Jurassic period, dates from the
earliest geological ages characterized by the presence
of organized beings. Thus far the oldest Acaleph

known, was a Medusa from Solenhofen.

Cuap. II. THE CLASSES OF RADIATA. 65

The question, however, now arises, whether all these radiated animals form a type
distinct from the Echinoderms, as Leuckart would have it; or constitute two classes
of the type of Radiata, coequal with the Echinoderms, as Cuvier represented them ;
or three classes, as Owen and Ehrenberg admit; or any other number of classes.

In uniting the Acalephs and Polyps into one primary division distinct from the
Echinoderms, Leuckart has overlooked the general homologies which unite the
Echinoderms with the Acalephs and the Polyps, and has paid no attention to the
Acalephian character of the embryo of a large number of Echinoderms. There
is no feature more striking in all these animals, in the Polyps and Acalephs on
the one side and the Echinoderms on the other, than the radiated arrangement of
their parts. A comparison of Echinarachnius with Polyclonia and Aiquorea, and of
the latter with Actinia, can leave no doubt upon this question; and since all
Polyps can easily be reduced to the type of Actinia, as well as all Acalephs to
that of Zquorea and all Echinoderms to that of Echinarachnius or of Asterias,
it must be admitted that the plan of structure is the same in all these animals.
They are built upon the idea of radiation; that is to say, all their organs are
arranged around a centre, at which the mouth is placed, and diverge towards the
periphery, to converge again at an opposite pole. But this is not the whole: all the
organs of this structure are homologous. The chambers between the radiating
partitions of the Actinia correspond to the radiating tubes of A%quorea, and these,
again, to the ambulacral system of the Kchinoderms; and the marginal tentacles of
the Actinix correspond to the marginal tentacles of the Acalephs, and appear as
ambulacral tubes in the Echinoderms, under the various forms of seeming gills
around the mouth of Echinoids, or of seeming gills in the rosette of Clypeaster,
or of branching tentacles and ambulacral suckers in the Holothurians. The iden-
tity of all these parts I shall have an opportunity of showing hereafter.

The central cavity, in open communication with the radiating chambers in
Polyps, is closed in Acalephs, and communicates only through narrow openings with
the radiating tubes; while in Echinoderms there arises a distinct alimentary canal,
which is, however, still in direct communication with the ambulacral system through
a network of anastomoses, about which I shall also have more to say hereafter.
The ocelli at the base of the tentacles, which in Polyps are mere pigment cells,
appear like modified tentacles in the higher Medusz, while they are still connected
with real tentacles in the lower ones; in Echinoderms they appear again, in the
same relation with the ambulacral system and the terminal odd ambulacral sucker,
as they are with the tentacles in Acalephs. The sexual organs are upon the sides
of the radiating cavities; that is, upon the edge of the partitions in the Polyps,
upon the sides of the radiating tubes in the Acalephs, and alternating with the
ambulacra in Echinoderms,—everywhere in a homologous position and_ relation.

VOL. II. 9

66 ACALEPHS IN GENERAL. Parr L

Leaving aside, for the present, some farther complication in the structure of Echi-
noderms, which we shall consider more fully in the latter part of this monograph,
it can, finally, be said, that the Echinoderms are Acalephoid animals, the body-
wall of which is loaded with limestone. Lamarck had truly perceived this close
affinity between the Acalephs and Echinoderms when he united them into one
great division under the name of Radiaires to the exclusion of the Polyps, calling
the Acalephs “ Radiaires Mollasses,’ and the Echinoderms “ Radiaires Echinodermes.”
In thus closely combining these two types into one class, however, he committed
an error similar to that of Leuckart, who united the Polyps with the Acalephs
in one larger group, from which he excludes the Echinoderms. But the reference
already made to the homology of their structure is in itself sufficient to show that
Polyps, Acalephs, and Echinoderms are constructed upon the same plan, and ought
therefore to be united in one and the same primary division, for which the name
of Radiata, proposed by Cuvier, seems to be the most appropriate. This once
settled, the question of the subdivision of the Radiata imto classes becomes com-
paratively easy.

I take it for granted, that the distinction I have attempted to make! between
the plun of structwe in animals and the mode of execution of the plan is, if not
admitted by other naturalists, at least fully understood by them; and upon this
basis I now propose to discuss the limitation of the classes of Radiata. Admitting
the plim of structure to be the criterion by which the primary groups of animals
are distinguished, we have seen that Echinoderms cannot be separated from the
other Radiates, since they differ only in structural complications, but not in the
plan of their structure. Admitting, next, that the mode of execution of a given
plan of structure constitutes the essential difference between classes, we haye now
to consider in what way the idea of radiation (upon which the plan of structure
of the Radiates is founded) is carried out in different types of this branch of the
animal kingdom, and with what means their body is built up; and this will furnish
us with a key to find the natural limits of their classes.

The leading characteristics which distinguish the Polyps, the Acalephs, and the
Echinoderms, are so obvious that it is only necessary here to allude to their
most prominent features, in order to show that they are essentially different in
their anatomical structure, though built upon the same plan. In Polyps, the body
has the form of a sac, from the inner surface of which project radiating partitions,
leaving an open space in the centre, however, which is the main cavity of the
body. This central cavity is in free communication with the radiating chambers

enclosed between the radiatmg partitions, for the whole height of the body. In

1 See Vol. 1 of this work, pp. 137 and 145.

Cuap. II. THE CLASSES OF RADIATA. 67

the upper part of the radiating cavity formed by the body-walls arise laterally
more or less numerous hollow tentacles, which are also in direct and free com-
munication with the radiating chambers. In fact, the tentacles are simply lateral
diverticles of the upper part of the chambers. The centre of the upper part of
the sac is widely open, but that opening, generally called the mouth, is not the
open edge of the sac; it is the result of the inversion of the upper central part
of the body-wall, the outer surface of which, in consequence of this bending inward,
becomes internal, and forms what is commonly called the stomach. An accurate
idea of this structure may be formed by comparing the sac of a Polyp to a bottle,
the neck of which should be turned outside in, and expanded into another sac
concentric to the body. This pendent sac, or stomach, is open at the bottom, and
this opening leads into the main cavity of the body. The lower opening of the
digestive cavity is, therefore, properly speaking, the outer opening of the body-wall,
The habit of Actinie, of

turning this so-called stomach inside out, affords an excellent opportunity to trace

and strictly homologous to the mouth of the Acalephs.

this homology, when it becomes plain that the opening commonly called mouth
in Polyps in no way corresponds to the mouth of the Acalephs. It is equally
plain, from such a comparison, that the so-called stomach of the Polyps is not any
more homologous to the so-called stomach of the Acalephs. This stomach of the
Acalephs can only be homologized with the open space in the centre of the main
cavity of the Polyps, with which the radiating chambers stand in the same re-
lation and communication as the radiating tubes of the Acalephs to their so-called
stomach. The fluid circulating through the so-called gastero-vascular system of the
Acalephs is chyme, and nothing but chyme mixed with water, as I have shown
in my contributions to the Natural History of the Acalephs of North America,
Part I. page 263.

These facts are in themselves sufficient to distinguish the Polyps under all
circumstances, not only from the higher Acalephs, but also from the Hydroids, in
which the structure is as essentially Acalephian as in the Meduse proper. For
many years past I have insisted upon these differences, and I truly wonder that
there are still naturalists who do not see how completely distinct the structural
type of the Polyps is from that of the Acalephs. In my lectures on Comparative
Embryology,’ delivered in the winter of 1848 and 1849, I have already shown, not
only how the Hydroids differ from the Polyps, but also how the Hydroids agree

? Twelve Lectures on Comparative Embryology,
delivered before the Lowell Institute, in Boston, in
December and January, 1848-1849, Boston, 1849,

8vo. fig. pp. 42 and 43. See also my paper “On

the Structure and Homologies of Radiated Animals,
with Reference to the Systematic Position of the
Hydroid Polyps,’ Proc. Amer. Ass. of Se. Cam-
bridge, 1849, p. 389.

lor)
[e/e)

ACALEPHS IN GENERAL. Part I.

in their structure with the true Meduse. This agreement is complete ; and there
is no room left for a distinction between Hydroids and Meduse, any more than
for a reunion of Polyps and Hydroids.

The essential structural peculiarity of the Acalephs, as a class, consists in the
presence of a central cavity, hollowed in the mass of the body, without radiating
partitions, but with an external central opening, the edge of which is turned out-
ward and more or less prolonged, in the shape of oral appendages or fringes.
Tentacular appendages may also exist outside of this central opening, or so-called
mouth, or may be wanting; but when they do exist, their cavity, if they are
hollow, communicates only indirectly, through radiating tubes, with the main cavity
of the body, the radiating tubes themselves uniting with a circular tube that
follows the outline of the periphery. This is certainly an essentially different
structure from that of the Polyps. Again, while the Polyps are always sexual
animals, and frequently hermaphrodites in their adult age, the Hydroids are uni-
formly destitute of sexual organs, but produce, by budding, an alternate generation,
the individuals of which, like ordinary Medusa, are always, when adult, either male
or female. When considering in detail the structure and mode of reproduction
of the Acalephs, I shall have occasion fully and conclusively to show that the
parts generally considered as generative organs in the Hydroids are truly indi-
vidual animals, in every way homologous to true Meduse, and themselves provided
with the sexual organs that are wanting in the Hydroids. For the present I must
limit myself to the assertion that it is so.

As to the homology between Polyps and Acalephs, it must be apparent, from
what precedes, that the comparisons which have been instituted between them are
not accurate. If the central opening between the tentacles of the Polyps is not
homologous to the so-called mouth of the Acalephs, but simply an aperture arising
from such an inversion of the body-wall that the opening at the bottom of the
digestive cavity is in reality the external opening of the body, it is plain that
the name iouth has been applied to very different parts in these animals. It
must further appear, that, from the position of this opening and its relation to the
whole structure of the animal, the name mouth can hardly be applied to it. Indeed,
the more we study the lower animals, the more are we impressed with the imper-
fection of the nomenclature used to designate their parts. To me it now seems
quite Inappropriate to designate the opening through which the food is introduced
into the body by the same name in all animals. Since the study of homologies
has become a safe guide in the appreciation of the true nature of the parts of
an animal, I can no longer see why we should use the name moulh to designate
a simple opening in the centre of a radiated structure, when that name was

originally applied to a cavity circumscribed by a bony frame, with a muscular

Cuap. IT. THE CLASSES OF RADIATA. 69

apparatus provided with nerves and blood-vessels, and the seat of a special organ
of sense. In fact, the Vertebrates alone have a real mouth; and the opening leading
to the digestive cavity in other animals is in no way homologous to their mouth,
and ought to be called by another name, and by a different name in each type,
according to the general homologies of its structure. The so-called mouth of the
Articulates is as different from that of the Vertebrates, as it is from that of the
Mollusks and that of the Radiates. And if the name mouth is to be retained for
all, it must be with the distinct understanding that the mouth is essentially differ-
ent, both in its relations and in its structure, in Radiates, in Mollusks, in Articu-
lates, and in Vertebrates. I do not consider innovations in the nomenclature as
favorable to the progress of science, as long as it is possible to convey clear and
distinct ideas by the use of ordinary language; but I believe, nevertheless, that
a new name, applied to an object long known under another appellation, impresses
more forcibly the difference it is intended to express, than a mere qualification
of a generally received name. I would, therefore, propose to designate henceforth
the mouth of the Radiates by the name of Actinostome, that of the Articulates by
the name of Arthrostome, and that of the Mollusks by the name of Malacostome,
in allusion to the typical structure of these animals. I shall introduce similar
changes in the nomenclature of other parts as often as, in the progress of my
exposition, I may have an opportunity of showing, not only the necessity of the
change, but also, by a fuller illustration of the homologies of these parts, the
propriety of adopting the new name _ proposed.

The class of Echinoderms is characterized by as different a mode of execution
of the plan of structure, involved in the idea of radiation, as the Acalephs and
Polyps are; but the plan itself is the same in all. The peculiarity les in the
construction only. The body-wall in Echinoderms forms a radiating cavity, in which
are suspended different systems of organs, distinct from the walls themselves, but
in various ways connected with them. The ambulacral system, which is homol-
ogous to the radiating tubes of the Acalephs and to the radiatmg chambers of
the Polyps, stands in the closest relation to the walls of the body. It traverses
them in the form of tubes, radiating from one pole of the body to the other, and
emitting, in most of them, external suckers, arranged in rows upon the surface.
The alimentary canal, connected with the walls of the body only at the central
opening, and, in some, also at the opposite end, extends as a distinct tube or sac,
free in the main cavity, and is not circumscribed by the perisome or spherosome'

itself, as in Acalephs. The reproductive apparatus consists also of distinct organs,

1 T call spherosome the body-wall of a radiated of perisome because that of perisome has already

animal. I prefer the name of spherosome to that been applied with different meanings.

70 ACALEPHS IN GENERAL. IP qeraill

arranged radiatingly between the ambulacral rows, with which they alternate. This
arrangement is strictly homologous to that of the sexual organs of the Polyps and
Acalephs; for in Polyps the ovaries and spermaries hang from the edges of the
radiating partitions, and in Acalephs they are placed upon the sides of the radi-
ating tubes, or, what amounts to the same, they alternate with the radiating cham-
bers in Polyps and with the radiatmg tubes in Acalephs, as they alternate with
the ambulacral system in Kchinoderms. That in Echinoderms the ambulacral
system is more or less complicated, assuming now the appearance of gill-like ten-
tacles around the oral aperture in Holothuriz and Echini, and now that of simple
tubes with external suckers, as in most members of this class, does in no way
alter the primary organic relations of these parts. The homological identity of the
ambulacra of the Echinoderms with the radiating tubes of the Acalephs is most
easily ascertained by comparing that system in those Holothurie which have no
external ambulacral appendages with the disposition of the radiating tubes in the
Ctenophore. In Synapta, for instance, and in allied genera, the ambulacral system
consists of tubes as simple as the radiating tubes of the naked-eyed Meduse ;
while in some Beroid Meduse, such as Bolina, Alcinoé, and Mnemia, the radiating
tubes are really more complicated than the ambulacral tubes of Synapta. This
apparatus is so strictly homologous in both families, that the Ctenophorze may
fairly be said to possess an ambulacral system identical im its general disposition
with that of the lower Holothuriw. Even the form of some of the Ctenophore,
such as Beroe proper, Idyia, ete. recalls that of the Holothurie.

At the peripheric ends of the ambulacral system of a large number of Kcehi-
noderms there are ocelli, which deserve a special notice in this connection. Above
each of these ocelli there is frequently an odd ambulacral tube, particularly promi-
nent im some Star-fishes. This odd ambulacral tube bears the same relation to
its ocellus as the hollow tentacle of a Sarsia bears to the ocellus at its base;
and both have an homologous connection with their respective aquiferous systems.
In Sarsia, each hollow tentacle with its ocellus communicates in the same manner
with the corresponding radiating tube, as the odd ambulacral tube of a Star-fish
with the whole ambulacral system of its ray. When I represent the ambulacral
system of the Echinoderms as homologous to the radiating tubes of the Acalephs
and to the radiating chambers of the Polyps, I do not overlook the difference
there is between them in structure and in functions. But these differences consist
in a more or less complicated structure and more or less specialized functions,
as we frequently observe even between members of one and the same class and
not in a typical modification. Similar differences exist among Echinoderms taken
as a class, and even among different families of the same order of that class. In

some Star-fishes the digestive cavity is a blind sac, while in others it is open at

Cuap. II. THE CLASSES OF RADIATA. vial

both ends. So also, in the class of Acalephs, the digestive cavity in most Medusze
is simply hollowed out of the central part of their spherosome, while in Ctenophorse
that cavity has its walls, not only distinct from the spherosome, but in its upper
part these walls recede from the mass of the body, and leave an open space
between the two, into which the products of digestion are poured. There is,
besides, in these animals, a double opening in the upper part of the spherosome,
through which the fecal matters are discharged. Nothing of the kind exists in
any other Acaleph. Notwithstandmg this, the Ctenophore are strictly homologous
in all their parts to the other Acalephs. On the other hand, this peculiarity of
the digestive cavity of the Ctenophore recalls the disposition already noticed in
some Star-fishes, and establishes a sort of transition between the extreme modi-
fications in the latter; for, while the digestive sac of some Star-fishes is a closed
sac rising into the main cavity of the body without an open communication with
it, in other Star-fishes it rises to the upper wall of the body, through which § it
passes, to open externally, and in Ctenophore it opens into the cavity of the body,
the walls of which are in their turn pierced with two distinct openings, to afford
a passage for the fieces. These two openings cannot be considered as anal openings,
since they do not directly communicate with the digestive cavity; nor is the aboral
end of the digestive sac to be compared to an anus, for it discharges its contents
directly into the main cavity of the body. We have here, throughout, combi-
nations which are entirely foreign to the plan of structure of the other branches
of the animal kingdom, and which fully justify what I have already said above
respecting the impropriety of calling the parts of these animals by the same names
as those of other types. But while the Radiates are thus shown to differ in every
respect from the Mollusks, Articulates, and Vertebrates, they at the same time
become more and more intimately linked together, in proportion as we are better
acquainted with the typical features of their organization.

As to the so-called external skeleton of Echinoderms, it in no way constitutes
a peculiarity of this class, in contradistinction to the Acalephs and Polyps; for in
Holothurie the amount of calcareous deposits is comparatively small and does not
affect the flexibility of the spherosome, while the rigidity of the Echini is not
greater than that of the Corals compared to Actiniw. In both it is only a con-
solidation of the spherosome, resulting from the accumulation of limestone in its
tissue; but the actinostome, as well as the diverticles of the aquiferous system,
the tentacles and ambulacral suckers, remains soft and movable. To judge correctly
of these relations, it is indispensable to observe these animals alive, with all their
soft parts fully expanded. In that condition Star-fishes and Sea-urchins have a very
different aspect from that which they exhibit when dried up or preserved in alcohol.

By comparisons made in this way we are enabled to establish the closest homology

WD ACALEPHS IN GENERAL. Parr I.

between all Radiates, from the Echinoderms down to the Polyps, without losing the
connection between their organic systems; nay, even the form and special disposition
of certain organs in the two most remote classes of Radiates are intimately linked
together by peculiarities characteristic of some of the Acalephs. For instance, the
system of radiating tubes in the lower part of the dise of the genuine Meduse,
and still more strikingly in the Rhizostomes and Cassiopeiw, presents the most
striking resemblance to the distribution of the ambulacral tubes in the lower wall
of the spherosome in Clypeaster, Scutella, and Echinarachnius; so much so that
the difference between the two types is reduced to the difference there is between
a soft wall and a solid wall, and that of an ambulacral system with and without

external suckers. But since there are Holothuris

the Synapta and allied genera
—in which these external suckers are wanting, the whole difference amounts only
to a different degree of complication in one and the same system, similar to the
various degrees of complication observed throughout the animal kingdom in the
differentiation of the organs. The comparisons I have been able to make between
Cassiopeia and Kehinarachnius and Clypeaster are conclusive upon this point, as
will be shown in the sequel.

After tracing so close a correspondence and so many connecting links in the
structure of the Echinoderms, Acalephs, and Polyps, I may be permitted to ask
what there is left to support the idea of a typical difference between the Echi-
nodermata and Coelenterata, now so generally and so strongly insisted upon by
German naturalists. The truth is that the Coelenterata do not constitute a primary
division in the animal kingdom, but must be united with the Echinoderms as
members of one and the same type, including three, and only three, natural classes,
equally distinct one from the other, — the Potyps, AcALepns, and Ecutnoprrms.!

I need hardly remind anatomists of the importance, for their own special studies,

attaching to every improvement in the classification of animals; for it is only when
their natural affinities are satisfactorily known, that it is possible to give a compre-

hensive account of their structure.

1 Tf this be so, then the name of Calenterata dusina as including the naked-eyed Meduse with
as designating a distinct type, as well as that of their polypoid congeners, must be dropped from
Anthozoa as designating the Polyps in contra- the system of Zodlogy, and the older names Radi-

distinction to the Hydroidea, and that of Hydrome- ata, Polypi, Acalepha, and Echinodermata, restored.

Cuap. IT. MORPHOLOGY AND NOMENCLATURE. 73

SH Cee LON, IY.
MORPHOLOGY AND NOMENCLATURE.

Thus far, my aim has been to present an outline of the views entertained by
different naturalists upon the various relations among the animals referred to the
type of Radiata, taking that group in the widest sense in which it has ever been
considered. I have accompanied this survey with incidental critical remarks, and
with a few considerations upon the mode of ascertaining the natural limits of a
class, and have arrived at the conclusion, that the type of Radiates embraces only
three natural classes. This conclusion is founded upon the evidence adduced, that
the animals heretofore referred to Radiates, and not belonging to the one or the
other of these three classes, are not genuine Radiates, and must therefore be ex-
cluded from that type.

I have attempted to show, farther, that the proposed division of Radiates into
Coelenterata and Echinodermata, as distinct primary types, is a mistake arising
from an incorrect appreciation of what constitutes respectively a type or branch,
and a class, in the animal kingdom. If the views I hold on this subject are true,
the Echinoderms, being built upon the same plan as the Polyps and <Acalephs,
belong to the same type as the so-called Coelenterata, and constitute only one
class of that type. The peculiarities insisted upon as a ground for considering
Echinoderms as a distinct type are not differences in the plan of structure, but
merely differences in the mode of execution of one and the same plan.

I hold, farther, that the Coelenterata, as circumscribed by Leuckart, embrace
two distinct classes, the essential characters of which are of the same kind as those
that separate the Echinoderms from either of them; so that, considering classes to
be founded on different ways of carrying out the same structural plan, the type
of Radiata should’ be divided into three classes,—the Polyps, the Acalephs, and the
Echinoderms. It is true ‘that the range of structural differences in these classes,
within their respective limits, is not always exactly parallel; but it is a fact, too
much overlooked by naturalists, that there are very few groups in nature of the
same essential value, presenting identical degrees of difference, or even approximating
each other in their number of genera and_ species.

In the regular sequence of my exposition I should now present a sketch of
the natural features of the class of Acalephs; but before I make the attempt, a
few words upon their morphology and nomenclature are indispensable. This is
important, in order that I may be able to present the characteristics of the class

VOL. Ill. 10

74 ACALEPHS IN GENERAL. Parr I.

with more confidence, and with a clear understanding respecting the true value of
the differences noticed between the animals now referred to it, and also that I
may point out the various names under which the different parts of these animals
have been designated by different authors in their descriptions.

It is much to be regretted that no uniform nomenclature has yet been adopted
in describing these animals. Indeed, there are scarcely two authors, among those
who have contributed most to build up our knowledge of the Acalephs, who describe
their parts under the same name, and this ever-recurring discrepancy is a serious
obstacle to an easy perusal of their works. This difficulty has arisen from two
causes. First, from a difference of opinion among investigators respecting the real
nature of the parts described, and secondly, from a laudable desire to avoid ex-
pressing premature opinions upon these structures. Thus, special names were given
to any parts m the body of Acalephs that seemed to present characteristic differ-
ences, even though these parts might be homological. This conflicting nomenclature
has not only made it very difficult to understand the full meaning of the descrip-
tions of Acalephs published by different writers, but has also led to the impression,
that the differences among the different families of this class are far greater than
is really the case. Such Acalephs, for instance, as have a certain external resem-
blance to Polyps, as the Hydroids, have been described with the terminology
generally applied to Polyps; while the Medusx proper have been designated by
a nomenclature of their own; and the Siphonophore in another way still: the
latter, indeed, being described in one way by those naturalists who consider them as
single animals, and in another way by those who look upon them as communities
of combined individuals.

To avoid this complication of nomenclature hereafter, I deem it indispensable to
consider not only their relations among themselves, but also their relations to the
members of the other classes of the same type. Now, surely, if Acalephs are
Radiates, they should bear such a structural relation to the Polyps and Echi-
noderms, assuming that they belong to the same type, as the Acephala, Gasteropoda,
and Cephalopoda, considered as Mollusks, bear to each other; or the Worms,
Crustaceans, and Insects considered as Articulates; or the Fishes, Reptiles, Birds, and
Mammals considered as Vertebrates. This is so well understood in our days with
reference to the Vertebrates and Articulates, and in a measure also with reference
to the Mollusks, that no naturalist could consider it as a progress in his science
were a new name introduced to designate the webbed hand of a bat or the
flapper of a Cetacean, or the rudimentary extremity of the Lizards with imperfect
feet, or any other such serial gradation in the development of their different. sys-
tems of organs. On the contrary, modern naturalists constantly endeavor to

simplify the nomenclature of Zotlogy by tracing the homologies of the most

o

Cuar. II. MORPHOLOGY AND NOMENCLATURE. 75

diversified parts of the same system. Surely, the head of a fish is not to be called
by another name than that of Birds or Mammals, because it is not separated from
the chest by a long neck; nor are we to have as many different names as there
are different combinations of structure in the parts of the face. The olfactory
organ, or the nose, must be called nose or olfactory organ, whether it be as promi-
nent as the proboscis of the elephant, or as blunt as the snout of a fish. The
ear must be called ear, be it ever so prolonged externally, or entirely concealed
below the surface of the head. All this can be readily done among Vertebrates
and among Articulates, because the structure of all these animals is sufficiently
well known to force a uniform nomenclature upon the attention of any one who
studies them.

The correspondence of the rings of an Articulate, be it a Worm or a Crus-
tacean or an Insect, is evident, whether it be altogether deprived of locomotive
appendages, or provided with legs only, or with wings as well as legs; and it
will be at once understood, by any one who extends these comparisons sufficiently,
that the parts now generally called legs and wings among Insects, though bearing
the same names for the present, are not homologous with legs and wings in
Vertebrates. The parts of the mouth of a sucking or a chewing Insect, on the
contrary, will with the same readiness be recognized as homologous with their
so-called legs. Unfortunately, this is not the case with the Radiates. We find
almost as many different opinions respecting the parts of Echinoderms, Acalephs,
and Polyps, as there are writers on the subject. Even with reference to Echi-
noderms alone, there are authors who have denied the homology of the solid parts
of the Sea-urchins with those of the Star-fishes, and described the solid frame of
the one as external, and that of the other as internal.

It is not my intention here to consider the general homologies of the Radi-
ates in detail, as I shall take up the subject again at the end of this monograph.
But for the purpose of introducing a more uniform nomenclature among these
animals, or, at least, paving the way to it, I will attempt such a general com-
parison between them as may facilitate a reference of the parts of one class to
the parts of another.

The plan upon which the Radiates are built is so peculiar, and so distinct from
that of the Mollusks, Articulates, and Vertebrates, that the essential elements of
their structure are entirely different. A common Star-fish or a common Sea-urchin
is as readily divided into five segments, as a common Medusa into four, or an
individual animal of a Gorgonia into eight, or that of an Actinoid Polyp into a
larger number, according to different families. Such segments bear to the body
as a whole, a relation similar to that observed in the ring of an Insect as one

of the essential elements of its structure, or a vertebra with its muscular band

76 ACALEPHS IN GENERAL. Parr I.

and corresponding pair of nerves and vessels in either Fish, Reptile, Bird, or
Mammal, as a segment of the body of a Vertebrate.

Now, it requires no formidable stretch of the imagination to reduce any single
Polyp, or any Acaleph or any Echinoderm, to a spheroidal form. Indeed, the
sphere is the essential form of all Radiates,—not the mathematical sphere, but the
organic sphere, loaded in different directions, according to the peculiarities of the
subordinate groups of this type. It has its nearest approach to the sphere in the
Echinus; it becomes a cylinder in the Holothuria; it is stellate in the Star-fish ;
it is bell shaped in the Acaleph; it is trumpet shaped in the Polyp; and in all
it has an oral opening in the centre of structure, which may not be the centre
of figure.

Keeping in mind this starting point, if we consider the natural position of the
animal in its element, we find in Polyps the so-called mouth tured upward in
the centre of the broadest expansion of one side of that organic and flexible sphere,
while the opposite end, more or less tapering, becomes a base of attachment.
Hydroids retain the same attitude, and bear the same general relation to the
surrounding medium. Not so with the Meduse, in which the sphere is freed from
ul attachment and the oral aperture turned downward, the whole body being
more or less hemispheric or bell shaped. In Echinoderms we have not only the
Crinoids, recalling, in their relations to the surrounding mediums, the Polyps and
Hydroids, but also the Sea-urchins and Star-fishes, in which the mouth is turned
downward as in Meduse, and the Holothurians, in which it is directed forward.
In order, therefore, to have a normal position for all Radiates, we must compare
them with one another, not in their natural attitudes, but in such a position as
would exhibit, in all, the centre of their structure in the same relation to the
surrounding mediun.

The necessity of thus distinguishing the natural attitude and the normal position
of animals is particularly obvious in the study of Radiates. But the distinction
is quite as important in other branches of the animal kingdom. Everywhere the
possibility of acquirmg an insight into the typical structure of any natural group
depends primarily upon the position in which its representatives are compared.
Had not Rathke taken these relations into consideration, we should not know the
antagonism which prevails between the Articulates and Mollusks in their embry-
onic development. Without keeping them in mind, we shall never be able to
homologize the Bryozoa and Tunicata with the other Acephala. Without knowing
that an animal may move in a position entirely at variance with the normal position
of the other representatives of its class, a description of its characteristic features
may appear in direct contradiction to its habits, or mislead us with reference to

its natural relation to the surrounding medium. In proportion as we are better

Cuap. II. MORPHOLOGY AND NOMENCLATURE. beng

acquainted with an animal, the difficulties arising from this discrepancy between
natural attitudes and normal positions grow less and less. No one could be misled
by a description of a Turbot or a Flounder, representing their structure according
to their normal position, even though, in their natural attitude, they le upon one
side; nor would any philosophical observer describe the back of these fishes as
lateral on account of their natural attitude. And yet it seems hardly to have
occurred to some naturalists, that they make frequently a similar mistake when they
describe the lower animals, in almost every group, in a different way; taking every-
where the natural attitude, and not the normal position, as their guide.

It is fitting, that, after alluding to the different attitudes in which the Radiates
are found in their natural element, we should attempt to determine what is their
normal position. Considering the plan of their structure, we have already seen
that there exists in all of them an axis and centre of radiation, around which
all their parts are symmetrically arranged in a radiating and concentric order, even
though that axis or centre of structure be not the centre of figure or form. At
one end of this axis we invariably find the so-called mouth or actinostome, while
the opposite end of the alimentary canal may have an excentric position. We
find, moreover, that in their natural attitude, the actinostome is in all of them
turned either upward or downward, with the sole exception of the Holothurie,
in which it is directed forward. This exception is, moreover, of little importance,
since the structural relations of the Holothurix to the other Echinoderms leave no
doubt as to what is their normal position; and whatever rule we recognize as
binding for the other Echinoderms must be followed for the Holothurie also.

Once agreed upon this point, there can be no farther doubt, that, in the Radiates,
the normal position of the main axis of the body is the vertical, since all, with
the single exception of the Holothurie, stand in their natural element with that
axis in a vertical position. We shall, therefore, not hesitate hereafter to describe
the Holothurie as if they also were in the habit of standing upright.

It is not quite so easy to determine what should be considered as the upper,
and what as the lower, end of the axis. If we look to the Polyps as a guide,
we should certainly take the region of the actinostome as the upper end; but
if we allow the relations of the higher Radiates to influence us, we should natu-
rally consider the same region as the lower end of the body. It would be incorrect,
unquestionably, to assume that the natural ‘attitude of the Holothurix is to decide
the question, and to describe all the radiated animals with the actinostome forward,
as it is evident that the similarity in the natural attitude of the Holothuriw and
Worms is only an analogy, and not a leading feature applicable to the whole type
of Radiates. The main axis of the body of these animals is truly vertical; and

in this essential relation of their whole structure to the surrounding medium, we

78 ACALEPHS IN GENERAL. Part I.

have an additional characteristic of this branch, distinguishing it from the three
other branches of the animal kingdom. The significance of this upright position
of the lowest type of animals with a radiating structure is most striking in view
of the upright position of man, at the head of the animal creation.

The same reasons which induce me to discard the indications of the Holothurize
in determining the normal position of the Radiates, apply to the Meduse, Star-
fishes, and Sea-urchins, when considering which end of the vertical axis should be
regarded as the upper and which as the lower. The centre of radiation, as
developed in the actinostome, is evidently the prominent feature of the whole
organization of this type; it is the climax of the concentration of their structure ;
upon that side the most sensitive parts of the body are combined; around it the
nervous ring with its ganglions is placed, in those representatives of the type in
which the differentiation of the tissues goes so far as to lead to the development
of a nervous system. It seems natural, therefore, to consider the oral end of the
vertical axis as its upper end. But why that end should be turned upwards in
the lower Radiates only, I am unable to say: I can only surmise that this position
is connected with the immovability of the Polyps, the Hydroids, and the peduncu-
lated Crinoids, and that the advantage they have in that respect over the Medusa,
the Star-fishes, and the Sea-urchins, is a compensation for their inability to move
about freely.

Supposing, however, that the actinostome should be considered as the upper end
of the vertical axis, it would not be advisable to use the expressions of upper
and dower end or side of the body, in describing the one or the other end of
the vertical axis of the Radiates; for, evidently, there would be something unnatural
in constantly contrasting the normal position and the natural attitude of the differ-
ent representatives of this type. I would therefore prefer to apply the name of
actinal to the side or pole at which the so-called mouth or actinostome is placed,
and that of abactinal to the opposite side or pole. In this way the description
of a Sea-urchm, compared to that of an Actinia, will not involve a seeming con-
tradiction with the attitudes in which these animals are constantly observed in
their natural element.

This once fully understood, and assuming that the body of a Radiate, whatever
be its real figure and its natural attitudes, may be reduced to a spheroidal form
by homological transformations, it is Selfevident that the essential segments com-
posing this living sphere will bear to one another identical relations, and as parts
of a sphere be homologous to one another, as far as they retain symmetrical
relations to the main axis. For these homological segments of the body of Radi-
ates I would propose the name of Spheromeres, and, in allusion to the well-known

structure of these animals, describe the body of a Holothuria, for instance, or that

Cuap. II. MORPHOLOGY AND NOMENCLATURE. 79

of an Echinus and a common Star-fish, as consisting of five converging spheromeres,
as the body of a Caterpillar or a Butterfly consists of thirteen rings movable
upon a longitudinal axis. In most Crinoids we have also five spheromeres, but
occasionally four or six, and im some Asterioids even a larger number. In Aca-
lephs the body is generally built of four or eight or twelve spheromeres; but here
and there the numbers vary, as we find also that the number of rings varies in
the lower Worms. In the Haleyonoid Polyps the number of spheromeres is
constantly eight, they beige the highest Polyps. In the Actinoids we find, in the
lowest families, a large and varying number of spheromeres, sometimes increasing
regularly with age; whilst in the highest Actinoids—the Madrepores proper — the
individual Polyps are made up of twelve spheromeres, six of which are more
prominently developed than the six others. A similar difference between alternating
spheromeres is observable among the higher Acalephs. Here unequal spheromeres
may combine in such a manner as to produce the appearance of bilateral symmetry ;
and though this feature is not only common among Radiates, but even prominent
in some of the higher representatives in each class of this type, it is yet subordi-
nate to the plan of their structure: for, upon close analysis, it is found, that, even
in those Radiates in which bilateral symmetry is most marked, it is in reality
the result of a symmetrical arrangement of radiating elements around a vertical
axis, and not of elements symmetrically placed upon the two sides of a longi-
tudinal axis.

Thus it appears that the body of all Radiates, be they Polyps, Acalephs, or
Kehinoderms, is composed of identical elements, which may be called spheromeres ;
and that these parts are arranged symmetrically around a vertical axis, in the
same manner as the wedge-shaped segments of an orange are arranged within its
bark. There is no propriety, therefore, in considering the body of Acalephs as
something peculiar, and different from that of a Polyp or an Echinoderm, and it
is unnecessary to give it a distinct name, as Huxley does, who calls it Hydrosoma,
else this name must be extended to all Radiates; for the body of the Actinia is
as much a Hydrosoma as that of any Acaleph, and so also is that of Pluteus and
allied forms (young Ophiurioids and Echinoids), that of Bipinnaria and Brachiolaria
(young Asterioids), and that of Auricularia (young Holothuria). We need, however,
distinct names to designate the different stages of development of these animals;
which, once sanctioned by use, may become as significant as the names applied
to the larval conditions of the Insects.

I should not object to the name of Hydrosoma for the young Acalephs, had we
not already, for every stage of their growth, names which are very generally adopted,
and which render new ones superfluous. For the earliest state of the embryo
Hydroids we have the name of Planula, for the Meduse buds of the Hydroids that

80 ACALEPHS IN GENERAL. Parr?

of Pyrulum, and for the young free Medusxe of the Campanularians that of Tintinna-
bulum, all proposed by Dalyell; for the young of the Discophora we may choose
between the name of Hydra, also proposed by Dalyell, and that of Seyphistoma,'
used by Sars; and for the next stage of their development we have the name
of Strobila, introduced by Sars and generally adopted. The young free Medusa
may best be called Ephyra, as that name was first apphed to it when it was
considered as a distinct genus. If we retain the name Hydra for the sterile animals
of the Hydroid type, and that of Seyphostoma for the young Medusa, the name
of Medusa would be most appropriate for all the adult Medusoids. Our termi-
nology would then be fixed in the following manner: Paula would designate the
embryonic state of the young Acaleph just hatched from the egg, and moving
about by the aid of vibratile cilia; such planule are born not only from the eggs
of Hydroids, but also from those of Discophore, and the young Polyps exhibit
the same appearance. The name Scyphostoma would apply to the young, from the
time it is attached and the tentacles begin to make their appearance. In the
Hydroids and Polyps this condition becomes permanent, as the worm-like state of
the larve of the higher Articulates becomes permanent in the Worms; it is there-
fore appropriate to retain the name Hydra to designate the adult Seyphostoma,
which undergoes no further development, and that same name may equally well
be used to designate the single individuals in a Hydroid community, as we apply
the name Polyps to designate either single Polyps, or single dividuals in a Polyp
community. The name Sérodila is so generally used to designate the stage of
Scyphostoma in which the vertical axis becomes divided by transverse constrictions,
and that of Ephyra las so long been applied to the young Meduse freed from
this axis before they assume their final form, that no further argument is needed
to sanction their further use. Let it only be remembered, that, as there are Insects
with imperfect metamorphosis in which no pupa state is observed, so are there
Acalephs in which the larva, overleaping the Strobila segmentation, passes directly
from the Scyphostoma to the Ephyra state. This is the case in Pelagia (Pl. XIL
Figs. 4-11). For the adult Acalephs there can be no more appropriate name than
that of IMedusw, under which they have always been known. The name of Pyrulum
for the Meduse buds of the Hydroids, and that of Zntinnabulum for their free
Meduse, are entirely superfluous. .

Were all Acalephs simple animals, this nomenclature would be quite sufficient
to describe them accurately. But in this class, as among Polyps, there are a great
many species in which the individuals combine to form more or less extensive

communities; and the Acalephs present this additional peculiarity, that the indi-

1 This name should be written Scyphostoma, in accordance with its etymology.

ov

Cuar. II. MORPHOLOGY AND NOMENCLATURE. g1

viduals of one and the same community are by no means so uniform among them-
selves as in the class of Polyps. The Acalephian communities are, indeed, generally
polymorphous, and cases of great uniformity among their individuals are rare. For
these communities we need comprehensive names, as much as for the Polyp
communities. Now, just as the name Polyparivm has been framed to designate a
Polyp community, we may apply the name of Hydrarium to a conmumity of combined
Hydre. Jn this sense, a bunch of Coryne or of Tubulariz united by their stems
and stolons, a patch of Hydractiniew rismg from their common basis, a branching
Campanularia or a Laomedea communicating with others by stolons, or even a
single stem with its lateral buds, constitutes MWydraria. And so also are Sertularie
and Plumularie genuine Hydraria. The same name must also apply to the Siphono-
phore as far as they are communities. But here a distinction is at once suggested,
in accordance with the special character of the individuals forming these communities.
As long as the combined individuals are all Hydra, the name Hydrarium correctly
apples; but among Siphonophorse, as among Corynoids and Tubularioids, there
arise Meduse buds from the Hydra, and these buds are either single, or form by
themselves communities of individuals in no way to be distinguished from genuine
Medusx, to which the name of Hydraria cannot be applied, but for which that
of Medusarium seems very appropriate. I would therefore call Medusarium every
bunch of Meduse buds arising from a Hydra, in contradistinction to the single
Medusze buds produced by other kinds of Hydra. For instance, the Hydre of
a Coryne Hydrarium never produce Medusaria, but always single Medusze buds,
while the Hydre of a Tubularia Hydrarium always produce Medusaria. The
structural combinations in these animals are so complicated, that, unless we make
these distinctions, it will become necessary to resort to long circumlocutions correctly
to describe them, and duly to discriminate the true nature of the different kinds of
individuals united in one and the same community. It is evident, that a Tubularia
community, so long as it produces no Meduse buds, is simply a Hydrarium; but
presently it brings forth Medusze buds in large clusters, hanging from the single
Hydrx in the form of Medusaria, and each Hydra produces several such Medusaria,
which are as much parts of the enlarged community as the single Hydre them-
selves. By this time the community is no longer a mere Hydrarium, but a Hydrarium
bearmg Medusaria. It is now a community of heterogeneous communities, which
may well be called a Hydro-Medusarium.

The use of such names for these different communities and their combinations
will greatly simplify our descriptions, and add much precision to our characteristics
of the different families and genera of the Hydroids. For instance, the Tubularioids
as a family may be described as Hydro-Medusaria arising from single Hydre which
by budding and by stolons become Hydraria; each adult Hydra producing in time

VOL. III. 11

82 ACALEPHS IN GENERAL. Panals

several pendent Medusaria. The different genera of the family may then be
characterized by the peculiarities of their Hydra and of their Meduse. The Cai
panularians as a family may be described as Hydraria with two kinds of LHydre:
some being sterile and more numerous, while others are fertile and produce Meduse
from their proboscis. The different genera may easily be distinguished by the
peculiarities of the two kinds of Hydra, as well as by their Medusa. Similar
differences exist among the Siphonophore. The Veledide are simply Hydraria avising
from a single Hydra which grows larger and larger until it produces other /ydra
of a different form, and from these single Medusz buds sprme forth and finally
free themselves. The Physalide, on the contrary, are LMydro-Medusaria, arising, like
the Velellide, from a single Lydra, which also grows larger and larger, and even
acquires an enormous size, forming in the end the large swimming-bag, from which
single additional Hydra at first arise, and afterward a larger and larger number,
forming several distinct Zydraria suspended from the original enlarged Hydra. These
Hydraria themselves consist of heterogeneous Hydra, though of Hydra only. Others
produce Medusaria, and thus become LHydro-Meduswia; so that a Physalia community
is really made up of many heterogeneous communities attached to a gigantic
Hydra. The Diphyide are also LHydro-Medusaria, but of a very different kind from
those of the Physalide. Here the community begins with a medusoid individual,
from which arises another Medusa, thus forming Meduse twins. This twin community
produces a string of medusoid Hydroids, from each of which arises another kind of
Medusw, in close connection with thew Hydroids, thus forming secondary twin com-
munities, each of which consists of a medusoid Hydra and a genuine Medusa. In
the LPhysophoride, the combinations are still different. The community constitutes
also a Lydro-Medusarium ; ut it arises from a single Z/ydra, from the upper part
of which bud sterile MWeduse, while other Hydrw arise from its lower part, between
which, finally, a number of Medusaria make their appearance.

As soon as it is conceded that the so-called sexual organs of the Siphonophoree
are themselves individual animals provided with ovaries and spermaries, there is no
possibility of avoiding the conclusions presented in the preceding paragraphs
respecting the structural constitution of the Acalephs, and the close affinity of the
Siphonophore and Hydroids proper becomes very striking. For, notwithstanding
the extraordinary diversity of the form of these aninals, there are, properly speaking,
only two kinds of individuals among them: the sterile ones, for which the name
Hydra is ost appropriate; and the fertile ones, which we may best call Meduse.
IT must, however, qualify this statement somewhat, in order to avoid every possible
misapprehension. There are fertile Hydra, if the production of buds constitutes
fertility, for most Hydra produce Meduse buds; but Hydre are themselves desti-

tute of sexual organs, there being neither males nor females among them; and

MORPHOLOGY AND NOMENCLATURE. 83

Cuap. II.

yet, some of these Hydra — Hydractinia, for instance — produce only male Meduse
buds, and others only female Medusee buds, and in this genus the individuals
producing either male or female Medusa buds form distinct communities. Again,
not all Medusx are fertile; for instance, the so-called swimming-bells of the Diph-
yide and Siphonophorsx, though evidently medusoid in their structure, have neither
male nor female organs.

After this digression, which was indispensable as an introduction to a_ critical
survey of the prevalent nomenclature of the Acalephs, let us now consider the
different names under which the different elements forming the communities of the
Siphonophorz have been described, that we may hereafter more readily compare
them with the other members of the class; for the chief difficulty im harmonizing
the nomenclature of the Acalephs arises from the complication of the names applied
to the Siphonophore. In these communities we have at first to distinguish the
medusoid and the hydroid individuals, in the same manner as among the Hydroids
proper; and, to do this with accuracy, we must recall the comparison already made
(p. 50) between Siphonophorx and Hydroids as compound communities, and remember
the prevalence of polymorphism in most of these animals.

The extensive investigations of Leuckart, Voet, Koélliker, Gegenbauer, and Huxley
upon Siphonophore, and the many species now known in all their stages of growth,

The
young Velella, as described and figured by Huxley (Oceanic Hydrozoa, Pl. XI. Wigs.

furnish the most welcome materials upon which to base further comparisons.

9 and 14), is unquestionably a simple genuine Hydra, provided at first with only
few tentacles, and in that condition comparable to any single head of a common
Hydroid freed from its stem. An adult Velella, on the contrary, is a Hydrarium,
that is, a community of secondary Hydre grown up between the actinostome and

the tentacles of the primary Hydra, and from which in due time genuine Medusx

buds arise. The presence of a shield with a crest in the disc or bell of the
primary Hydra is only a structural peculi- Fig. 48.
arity of that animal, but not any more ‘
him

altering its true nature and affinities, than

the presence of a shell in the mantle of a

Gasteropod. The enlarged primary Hydra

of the Velella community, when it has

VELELLA MuTICA, Bosc.

m So-called mouth. —aa So-called
tentacles.
tentacles and the mouth arise

become a complicated floating apparatus (F%y.

Between the sterile

the secondary Hydre, or so-
called fertile tentacles. the gono-
blastidial Polypites of Huxley.

47) from which hang numerous fertile Hy-
dra, the so-called fertile tentacles, —“ eono-

iS
b}

blastidial Polypites” of Huxley, “individus

reproducteurs” of Vogt, “peripherische Polypen” of Leuckart,

“kleme Polypen” of Kolliker (Fig. 48),—is still as much a Hydra

Single so-called fertile ten-
tacle of
VELELLA MUTICA, Bose,
Bearing Meduse buds d d.—a
Ba: eof attachment.— > Blunt
end of the tentacle, as it
appears when the mouth is

closed,

84 ACALEPHS IN GENERAL. Pagal

as Helix with its shell is an animal of the same order as a Limax with a rudi-
mentary shell, or a Tebennophorus without any shell. Similar differences occur
amone the Hydroids proper in the genera Coryne, Tubularia, Campanularia, and
Sertularia. In Porpita, we observe the same relations between the primary enlarged
Hydra with its tentacles and the secondary fertile Hydra, as in Velella. The poly-
morphism in these two genera extends only to a marked difference between the
primary Hydra and the secondary Hydra, analogous to the difference there is
between the sterile and fertile Hydra in Campanularia. (Compare Fy. 15, p. 46.)
Both Velella and Porpita acquire their full size before Meduse buds appear upon
their fertile Hydre.

In Physalia, the community is also formed upon an enlarged primary Hydra.
The young of this genus has been described and figured by Huxley in two
different stages of growth (Oceanic Hydrozoa, Pl. X. vgs. 1 and 2). In the earliest
stage it is a simple Hydra with a single tentacle (#¥g. 1); and while that primary
Fig. 49. Hydra is enlarging and assuming its permanent character-
istics, other secondary Hydra, somewhat different from the
first, bud forth from it, and form with it a Mydrarium (2%.
2), gradually enlargme by the addition of others. But
there is this difference between such a Physalia Hydrarium
and a Velella Hydrarium, that im the former the successive

secondary Hydra differ among themselves greatly, — some

a
(a

acquiring a considerable size and having a large tentacle,

K while others remain small and have a small tentacle, and

4 the proboscis of some having an open mouth, while in others

| it remains closed. But, as I shall show hereafter, similar
i differences are also observed among the Hydroids proper ;
; so that the peculiarities noticed in the different Hydre
{ amount only to a more extensive polymorphism in_ this
} genus than in Velella and Porpita, akin to what we have
i already seen in’ Hydractinia. As I myself have seen a
t great many small Physalix in the Gulf of Mexico, I may
j add that these communities acquire a considerable size

PrysaviA Areruusa, Til. ey 5
a Blunt end of the air sae, supporting Defore any other but Hydra buds are developed from their
the whole community, at which the
youngest Medusie buds may be found,
—hb Open end of the air sac, the mouth
of the primary Hydra.—e Crest of

pendent bunches. But when about one fourth the size
(Fig. 49) of the largest I have ever seen, the Meduse

the air sac.—2 Bunches of single ; ~ : A 3 _
individuals; and among them te DUGS begin to make their appearance and increase in num-
oungest Meduse buds. — 7 Contracted . . ae : am: <
pastes ek a ai ber, until they form distinet Medusaria combined with

tentacle. —7¢¢ Tentacles of the largest
kind extended.

Hydraria; and the whole community is then a most com-

plicated Hydro-Medusarium. The androphores and gynophores of such a community

Cuap. II. MORPHOLOGY AND NOMENCLATURE. 85

are respectively the male and female Meduse; and buds of both sexes arise from
one and the same Hydra, the so-called gonoblastidium.

In Physophoride also, the community begins with a single Hydra. Leuckart
(Zoologische Untersuchungen, I. Pl. 2, Fig. 23), Koélliker (Schwimmpolypen von
Messina, Pl. I. Ay. 11), Vogt (Siphonophores de la mer de Nice, Pl. VI. Mig. 24;
Pl. X. Figs. 32 and 35; and Pl. XI.), Gegenbauer (Beitriige, etc, in Zeitsch. f. wiss.
Zool. vol. 5, Pl. XVII. Mgs. 7, 8, 9, and 11), and Huxley (Oceanic Hydrozoa, PI.
VI. Fig. 12, and Pl. VIL Wg. 2), have described and figured many such young

Physophoridx, exhibiting the primary Hydre of different genera

Fig. 50.

more or less free from the secondary productions budding from
their sides. In the youngest of them the Hydra character is
quite plain, and their resemblance to the young Physalia most
striking (Fig. 50). But their resemblance to the Hydroid of
Nemopsis Gibbesit MeCrady is still more important, since it
shows, beyond the possibility of a doubt, the close affinity of

the naked-eyed Medusx and the Siphonophore. Thus far, all

the Medusee known as originating from Hydroids had been Sqayouie Medea
observed to bud from Hydroids attached by their basis; but, — (ied from Gegenbauer)
e Buds of so-called swimming-bells.
in a recent paper (Gymnophthalmata of Charleston harbor, Se aieeee?
published in the Proceedings of the Elliott Society of Nat. ine. — Ai ter te
Hist. for 1858), Mr. McCrady has described a species of Ne- Hand onary Hyde; the
mopsis, which originates from a floating, locomotive Hydroid, See
so similar to a young Physophora with incipient buds of swimming-bells, that, had
he not traced the connection of the free Medusa to its Hydroid, or had the Hydroid
alone, with its young Medusxe buds, been observed, it would unquestionably have
been considered as a distinct genus belonging to the Siphonophore. A more direct
proof that the so-called swimming-bells (Nectocalyces) of the Physophoride are genu-
ine Medusee buds remaining connected with the elongated axis of the primary
Hydra (the Coenosare) from which they grow, cannot be desired. And the only
marked generic difference between Nemopsis and Physophora consists in the presence
of tentacles and sexual organs in the Medusx of the former which become free,
while those of the latter are sterile and remain attached. But such differences are
not essential among animals in which polymorphism occurs so extensively as in
the lower Acalephs.

Very early the single Hydre, from which arise the communities of Physo-
phorida, bring forth two kinds of buds, —Meduse buds on their abactinal pole,
and Hydre buds on their actinal pole. Thus the community at once becomes
a Hydro-Medusarium, consisting of one kind of Medusze which remain sterile and

never free themselves, and of two kinds of Hydre; namely, the primary Hydra,

ACALEPHS IN GENERAL. Parr T;

ioe)
o>

eed and elongated and from which hang all the other

c

which is gradually enlar
secondary buds, and the secondary Hydra, which are more or less similar to one
another and remain small through life.

The next step in the complication of these communities consists in the appear-
ance of other kinds of Medusze and other kinds of Hydroids, variously combined
in different genera: the additional Medusie being genuine sexual Meduse, and the
additional Hydroids partaking also, more or less, of the character of Meduse. A
comparison of these sexual Medusx buds of Siphonophor with the Meduse buds of
ordinary Hydroids must satisfy any one, equally familiar with the mode of develop-
ment of the two types, that there is no essential difference between them. The
illustrations published by Kélliker in the “Schwimmpolypen” (Pl. VU. igs. 4 and
5) afford the best example on record for a comparison with #gs. 13, 14, 15,
and 16 of Pl XVIII. of this work. /%y. 4 of Kolliker represents what he calls
the testis of Vogtia pentacantha; it is the exact counterpart of my /%ys. 13 and 14,
which represent a male Medusa of Coryne mirabilis. Kolliker’s #%y. 5 represents
what he calls the ovary of the Vogtia; it corresponds exactly to my gs. 15
and 16, which represent the female Medusa of Coryne. Now this so-called testis
and this so-called ovary consist of a genuine Medusa bell, with four radiating
chymiferous tubes and a circular tube, identical in their structure and arrangement
with the chymiferous tubes of all the naked-eyed Meduse. The resemblance extends
even further: Kolliker’s /%g. 4 shows distinctly the proboscis of this supposed testis ;
it is marked e in his figure and described as sperm sac, and its vibratile cavity
is marked d. The proboscis of the supposed ovary is not less distinct in Fy. 5;
it is marked ¢, and described as an ege sac. But had Kolliker examined more
fully these prominent sacs arising from the centre of their Medusx bells, he would
have satisfied himself that the sperm cells and the eggs are not contained in the
cavity of the sacs, but arise, as the eges and sperm cells of the Coryne, in the
outer wall of the sacs; that is, upon the proboscis of the Medusew, as im Coryne
and a large number of other genera of naked-eyed Meduse.

The second kind of secondary Hydra, upon the actinal prolongation of the axis
of the primary Hydra of many Physophoridx, differs from those already described
in having a so-called covering scale (Deckblatt, Hydrophyllium) by the side of their
pendent proboscis. As I have already shown (pp. 54 to 56), this is a kind of open
bell, intermediate in its character between the calyx of an ordimary Hydroid and
the bell of an ordimary Medusa, more medusoid than the calyx of a Hydroid but
less so than a Medusa proper, having no radiating chymiferous tubes, and differme
from both in being one sided and more or less flattened. But as one-sided calyces
occur also among Hydroids, this does not constitute an important difference, nor

a distinguishing feature for Siphonophore.

Cuap. II. MORPHOLOGY AND NOMENCLATURE. QT

Tt has already been stated, that the communities of Diphyide’ begin with a

Medusa (Fig. 51), judging from the investigations of Gegenbauer detailed above

Fig. 51. Fig. 52. Fig. 53.

GALEOLARIA FILIFORMIS, Leuck.
Embryo of Diphyes quadrivalvis, Gegenb.

2 : Two twin individuals of the pen-
Dienyes Siesoupi, Koll. ( Copied from Gegenbauer.)

dent string of the community of

ab Anterior and posterior swimming- Dieuyes SrEBotpr, Kéll
S SIEB , Koll.

bells. —c String of twin individuals.

—d Feelers with lasso cells. — e Ceecal

termination or base of the connecting

bryonal body. tube or axis of the community. sule.—c External feeler, with lasso
cells. —d Feeler contracted.

( Copied from Gegenbauer.)

aa The so-called scales.—4 6 The so-called
Polyps. — m The so-called sexual cap-

e Remnant of the embryonal body. —a
Swimming-bell developed from the em-

(pp. 53 and 54), and that from the first twin community, formed of two sterile Me-
duse (Fg. 52 ab), arise a string of similar twin communities (/%. 52 ¢), consisting
of a medusoid Hydra (Fg. 53 aa) and a fertile sexual Medusa (Fig. 53 m), the
so-called Gonocalyx, dropping off together and living for a time as independent
beings, several of which have been described as distinct genera.

If the views I have here presented of the nature of the Siphonophore are
correct, there is no need of a special nomenclature to describe the different indi-
viduals of their communities; and we shall hereafter deal with them as with differ-
ent kinds of Hydre and of Medusx, describing successively their polymorphous
individuals as we would describe different genera and species of Hydroids and of
free Acalephs belonging to other families of the class, and introduce only one new
element in these descriptions, on account of the different modes of association of the
many individuals united together in one and the same community, as it becomes

necessary here to allude to their various combinations.

1 Since the preceding pages were printed I have Eudoxiernbrut, Jena, 4to. fig; and Neue Beitriige
received two interesting papers upon Diphyide and zur niihern Kenntniss der Siphonophoren ; separately
Physophorid from their distinguished author, Dr. printed from the Act. Noy. Acad. Natur. Curios.

C. Gegenbauer: Ueber Abyla trigona und deren for the current year.

(oe)
(oa)

ACALEPHS IN GENERAL. Part I.

SbOTLON «Ve

INDIVIDUALITY AND SPECIFIC DIFFERENCES AMONG ACALEPHS.

The morphological phenomena discussed in the preceding section naturally lead
to a consideration of individuality, and of the extent and importance of specific
differences among the Acalephs. A few years ago the prevailing opinion among
naturalists was, that, while genera, families, orders, classes, and any other more or
less comprehensive division among animals, were artificial devices of science to
facilitate our studies, species alone had a real existence in nature. Whether the
views I have presented in the first volume of this work (p. 163), where I showed
that species do not exist in any different sense from genera, families, ete., ete.
had any thing to do with the change which seems to have been brought about
upon this point among scientific men, is not for me to say. But, whatever be
the cause, it is certainly true, that, at the present day, the number of naturalists
who deny the real existence of species is greatly increased.

Darwin, in his recent work on the “Origin of Species”?! has also done much
to shake the belief in the real existence of species; but the views he advocates are
entirely at variance with those I have attempted to establish. For many years
past I have lost no opportunity to urge the idea, that while species have no
material existence, they yet exist as categories of thought, in the same way as
genera, families, orders, classes, and branches of the animal kingdom. Darwin’s
fundamental idea, on the contrary, is, that species, genera, families, orders, classes,
and any other kind of more or Jess comprehensive divisions among animals, do
not exist at all, and are altogether artificial, differing from one another only in
degree, all having originated from a successive differentiation of a primordial
organic form, undergoing successively such changes as would at first produce a

o

variety of species; then genera, as the difference became more extensive and
deeper; then families, as the gap widened still farther between the groups; until,
in the end, all that diversity was produced which has existed or which now exists.
Far from agreeing with these views, I have, on the contrary, taken the ground
that all the natural divisions in the animal kingdom are primarily distinct, founded
upon different categories of characters, and that all exist in the same way, that
is, as categories of thought embodied in individual living forms. I have attempted

(=)

? Darwin (Cuarzes), On the Origin of Spe- vation of favored Races in the Struggle for Life,

cies by means of Natural Selection, or the Preser- London, 1860, 1 vol. 8vo.

Cuap. IL. INDIVIDUALITY AMONG ACALEPHS. 89

to show that branches in the animal kingdom are founded upon different plans
of structure, and for that very reason have embraced from the beginning repre-
sentatives between which there could be no community of origin; that classes are
founded upon different modes of execution of these plans, and therefore they also
embrace representatives which could have no community of origin; that orders
represent the different degrees of complication in the mode of execution of each
class, and therefore embrace representatives that could not have a community of
origin any more than the members of different classes or branches; that families
are founded upon different patterns of form, and embrace representatives equally
independent in their origin; that genera are founded upon ultimate peculiarities
of structure, embracing representatives, which, from the very nature of their
peculiarities, could have no community of origin; and that, finally, species are
based upon relations and proportions that exclude, as much as all the preceding
distinctions, the idea of a common descent.

As the community of characters among the beings belonging to these different
categories arises from the intellectual connection which shows them to be categories
of thought, they cannot be the result of a gradual material differentiation of the
objects themselves. The argument on which these views are founded may be
summed up in the following few words: species, genera, families, ete., exist as
thoughts; individuals, as facts. It is presented at full length in the first volume
of this work (pp. 137-168), where I have shown that individuals alone have a
definite material existence, and that they are for the time being the bearers, not
only of specific characteristics, but of all the natural features in which animal life
is displayed in all its diversity; individuality being, in fact, the great mystery of
organic life.

Since the arguments presented by Darwin in favor of a universal derivation,
from one primary form, of all the peculiarities existing now among living beings,
have not made the slightest impression on my mind, or modified in any way the
views I have already propounded, I may fairly refer the reader to the paragraphs
alluded to above as containing sufficient evidence of their correctness; and I will
here only add a single argument, which seems to leave the question where I
have placed it. Had Darwin or his followers furnished a single fact to show
that individuals change, in the course of time, in such a manner as to produce,
at last, species different from those known before, the state of the case might be

different.'. But it stands recorded now as before, that the animals known to the

1 Tt seems to me that there is much confusion not exist at all, as the supporters of the trans-
of ideas in the general statement, of the variability mutation theory maintain, how can they vary? And
of species, so often repeated of late. If species do if individuals alone exist, how can the differences

VOL. III. 12

90 ACALEPHS

IN GENERAL.

Part IL.

ancients are still in existence, exhibiting to this day the characters they exhibited

of old.

The geological record, even with all its imperfections exaggerated to

distortion, tells now, what it has told from the beginning, that the supposed

intermediate forms between the species of different geological periods are imaginary

beings, called up merely in support of a fanciful theory.

The origin of all the

diversity among living bemgs remains a mystery, as totally unexplained as if the

book of Darwin had never been written; for no theory, unsupported by fact,

however plausible it may appear, can be admitted in science.

which may be observed among them prove the
variability of species? The fact seems to me to be,
that, while species are based upon definite relations
among individuals, which differ in various ways
among themselves, each individual, as a distinct
being, has a definite course to run from the time
of its first formation to the end of its existence,
during which it never loses its identity nor changes
its individuality, nor its relations to other individuals
belonging to the same species, but preserves all the
categories of relationship which constitute specific
or generic or family affinity, or any other kind or
degree of affinity. Zo prove that species vary, tt
should be proved that individuals, born from common
ancestors, change the different categories of relation-
ship which they bore primitively to one another ;
while all that has thus far been shown is, that
there exists a considerable difference among indi-
viduals of one and the same species. This may be
new to those who have looked upon every indi-
vidual picked up at random, as affording the means
of describing satisfactorily any species ; but no natu-
ralist who has studied carefully any of the species
now best known, can have failed to perceive that
it requires extensive series of specimens accurately
to describe a species, and that the more complete
such series are, the more precise appear the limits
which separate species. Surely the aim of science
cannot be to furnish amateur zoblogists or collectors
a recipe for a ready identification of any chance
And the

difficulties with which we may meet in attempting

t=)

specimen that may fall into their hands.

to characterize species do not afford the first indi-
cation that species do not exist at all, as long as

most of them can be distinguished, as such, almost

at first sight. I foresee that some convert to the
transmutation creed will at once object, that the
facility with which species may be distinguished is
no evidence that they were not derived from other
species. It may be so. But, as long as no fact is
adduced to show that any one well-known species
among the many thousands that are buried in the
whole series of fossiliferous rocks is actually the
parent of any one of the species now living, such
arguments can have no weight; and thus far the
supporters of the transmutation theory have failed
to produce any such facts. Instead of facts, we
are treated with marvellous bear, cuckoo, and other
Credat Judwus Apella!

1 Tt seems generally admitted, that the work of

stories.

Darwin is particularly remarkable for the fairness
with which he presents the facts adverse to his views.
It may be so; but I confess that it has made a
very different impression upon me. I have been
more forcibly struck with his inability to perceive
when the facts are fatal to his argument, than with
any thing else in the whole work. Tis chapter on
the Geological Record, in particular, appears to me
to be, from beginning to end, a series of illogical de-
ductions and misrepresentations of the modern results
of Geology and Palwontology. I do not intend to
argue here, one by one, the questions he has dis-
cussed. Such arguments end too often in special
pleading ; and any one familiar with the subject may
readily perceive where the truth lies, by confronting
his assertions with the geological record itself. But,
since the question at issue is chiefly to be settled
by paleontological evidence, and I have devoted the
greater part of my life to the special study of the

fossils, I wish to record my protest against his mode

Cuaap. II.

INDIVIDUALITY AMONG ACALEPHS. 91

It would be out of place to discuss here in detail the arguments by which

Darwin attempts to explain the diversity among animals.

of treating this part of the subject. Not only does
Darwin never perceive when the facts are fatal to
his views, but, when he has succeeded by an ingenious
circumlocution in overleaping the facts, he would
have us believe that he has lessened their impor-
tance, or changed their meaning. He would thus
have us believe that there have been periods during
which all that had taken place during other periods
was destroyed; and this solely to explain the absence
of intermediate forms between the fossils found in
successive deposits, for the origin of which he looks
to those missing links, whilst every recent progress
in Geology shows more and more fully how gradual
and successive all the deposits have been which
form the crust of our earth. — He would have us
believe that entire fauna have disappeared before
those were preserved, the remains of which are
found in the lowest fossiliferous strata; when we
find everywhere non-fossiliferous strata below those
that contain the oldest fossils now known. It is
true, he explains their absence by the supposition
that they were too delicate to be preserved; but
any animals from which Crinoids, Brachiopods,
Cephalopods, and Trilobites could arise, must have
been similar enough to them to have left, at
least, traces of their presence in the lowest non-
fossiliferous rocks, had they ever existed at all.—
He would have us believe that the oldest organisms
that existed were simple cells, or something like the
lowest living beings now in existence; when such
highly organized animals as Trilobites and Ortho-
ceratites are among the oldest known.— He would
have us believe that these lowest first born became
extinet, in consequence of the gradual advantage
some of their more favored descendants gained over
the majority of their predecessors ; when there exist
now, and have existed at all periods in past times,
as large a proportion of more simply organized
beings, as of more favored types; and when such
types as Lingula were among the lowest Silurian
fossils, and are alive at the present day. — He

would haye us believe that each new species

Suffice it to say

originated in consequence of some slight change in
those that preceded; when every geological formation
teems with types that did not exist before. — He
would have us believe that animals and _ plants
became gradually more and more numerous; when
most species appear in myriads of individuals, in
the first bed in which they are found.— He would
have us believe that animals disappear gradually ;
when they are as common in the uppermost bed
in which they occur, as in the lowest, or any
intermediate bed. Species appear suddenly and
That is
the fact proclaimed by Palxontology; they neither

disappear suddenly in successive strata.

increase successively in number, nor do they grad-
ually dwindle down; none of the fossil remains
thus far observed show signs of a gradual improye-
ment or of a slow decay.— He would have us
believe that geological deposits took place during
periods of subsidence; when it can be proved that
the whole continent of North America is formed
of beds which were deposited during a series of
successive upheavals. I quote North America in
preference to any other part of the world, because
the evidence is so complete here that it can be over-
looked only by those who may mistake subsidence
for the general shrinking of the earth’s surface, in
In this

part of the globe, fossils are as common along the

consequence of the cooling of its mass.

successive shores of the rising deposits of the Silu-
rian system, as anywhere along our beaches; and
each of these successive shores extends from the
Atlantic States to the foot of the Rocky Mountains.
The evidence goes even further; each of these suc-
cessive sets of beds of the Silurian system contains
peculiar fossils, neither found in the beds above nor
in the beds below, and between them there are no
intermediate forms. And yet Darwin affirms that
“the littoral and sub-littoral deposits are continually
worn away, as soon as they are brought up by the
slow and gradual rising of the land within the
grinding action of the coast waves.” Origin of

Species, p. 290.—He would also have us believe

92 ACALEPHS

IN GENERAL.

Part I.

that he has lost sight of the most striking of the features, and the one which

yervades the whole, namely, that there
9: oF hee,

runs throughout nature unmistakable

evidence of thought, corresponding to the mental operations of our own mind,

and therefore intelligible to us as thinking beings, and unaccountable on any other

basis than that they owe their existence to the working of intelligence ; and no

theory that overlooks this element can be true to nature.

that the most perfect organs of the body of animals
are the product of gradual improvement; when
eyes as perfect as those of the Trilobites are pre-
served with the remains of these oldest animals. —
He would have us believe that it required millions
of years to effect any one of these changes; when
far more extraordinary transformations are daily
going on, under our eyes, in the shortest periods of
time, during the growth of animals.— He would
have us believe that animals acquire their instincts
gradually ; when even those that never see their
parents, perform at birth the same acts, in the same
way, as their progenitors. — He would have us be-
lieve that the geographical distribution of animals
is the result of accidental transfers; when most spe-
cies are so narrowly confined within the limits of
their natural range, that even slight changes in
their external relations may cause their death.
And all these, and many other calls upon our cre-
dulity, are coolly made in the face of an amount of
precise information, readily accessible, which would
overwhelm any one who does not place his opinions
aboye the records of an age eminently characterized
for its industry; and during whieh, that information
was laboriously accumulated by crowds of faithful
laborers.

1 There are naturalists who seem to look upon
the idea of creation — that is, a manifestation of an
intellectual power by material means—as a kind of
bigotry ; forgetting, no doubt, that whenever they
carry out a thought of their own, they do something
akin to creating; unless they look upon their own
elucubrations as something in which their individu-
ality is not concerned, but arising without an inter-
vention of their mind, in consequence of the working
of some “bundles of forees,’ about which they

know nothing themselves. And yet such men are

It is true, Darwin

ready to admit that matter is omnipotent, and con-
sider a disbelief in the omnipotence of matter
tantamout to imbecility; for, what is the assumed
power of matter to produce all finite beings, but
omnipotence ? And what the outery raised against
those who cannot admit it, but an insinuation that
they are non compos? The book of Mr, Darwin is
free of all such uncharitable sentiments towards
his fellow-laborers in the field of science; never-
theless, his mistake lies in a similar assumption that
the most complicated system of combined thoughts
can be the result of accidental causes: for he ought
to know, as every physicist will concede, that all
the influences to which he would ascribe the origin
of species are accidental in their very nature; and
he must know, as every naturalist familiar with the
modern progress of science does know, that the
organized beings which live now, and have lived in
former geological periods, constitute an organic
whole, intelligibly and methodically combined in all
its parts. As a zodlogist he must know, in par-
ticular, that the animal kingdom is built upon four
different plans of structure ; and that the reproduc-
tion and growth of animals take place according to
four different modes of development; and that, unless
it is shown that these four plans of structure and
these four modes of development are transmutable
one into the other, no transmutation theory can
account for the origin of species. The fallacy
of Darwin’s theory of the origin of species by
means of natural selection may be traced in the
first few pages of his book, where he oyerlooks the
difference between the voluntary and deliberate
acts ef selection applied methodically by man to
the breeding of domesticated animals and the grow-
ing of cultivated plants, and the chance influences

which may affect animals and plants in a state of

* nature.

Cuap. II. INDIVIDUALITY AMONG ACALEPHS. 93

states that the close affinity existing among animals can only be explained by a
community of descent, and he goes so far as to represent these affinities as evidence
of such a genealogical relationship; but I apprehend that the meaning of the
words he uses has misled him into the belief that he had found the clue to
phenomena which he does not even seem correctly to understand. There is nothing
parallel between the relations of animals belonging to the same genus or the same
family, and the relations between the progeny of common ancestors. In the one
ease we have the result of a physiological law regulating reproduction, and in
the other, affinities which no observation has thus far shown to be in any way
connected with reproduction. The most closely allied species of the same genus
or the different species of closely allied genera, or the different genera of one
and the same natural family, embrace representatives, which, at some period or |
other of their growth, resemble one another more closely than the nearest blood
relations; and yet we know that they are only stages of development of different
species distinct from one another at every period of their life. The embryo of
our common fresh-water turtle (Chrysemis picta) and the embryo of our snapping
turtle (Chelydra serpentina) resemble one another far more than the different species
of Chrysemis in their adult state; and yet not a single fact can be adduced to
show that any one egg of an animal has ever produced an individual of any
species but its own. A young snake resembles a young turtle or a young bird
much more than any two species of snakes resemble one another; and yet they
go on reproducing their kinds, and nothing but their kinds. So that no degree

of affinity, however close, can, in the present state of our science, be urged as

To call these influences “natural selection,” afford a clue to determine their relative degree of
(3)

is a misnomer which will not alter the conditions affinity by a comparison with the pedigrees of well-

under which they may produce the desired results. known domesticated races. Again, if there were

Selection implies design; the powers to which any such parallelism, the distinctive characteristics

Darwin refers the origin of species can design
nothing. Selection is no doubt the essential princi-
ple on which the raising of breeds is founded; and
the subject of breeds is presented in its true light
by Darwin: but this process of raising breeds
by the selection of favorable subjects is in no way
similar to that which regulates specific differences.
Nothing is more remote from the truth than the
attempted parallelism between the breeds of domes-
ticated animals and the species of wild ones. Did
there exist such a parallelism as Darwin maintains,
the differences among the domesticated breeds should

be akin to the differences among wild species; and

of different breeds should be akin to the differences
which exist between fossil species of earlier periods,
Now,

let any one familiar with the fossil species of the

and those of the same genera now living.

the genera Bos and Canis compare them with the
races of our dogs and of our cattle, and he will
find no correspondence whateyer between them; for
the simple reason, that they do not owe their exist-
ence to the same causes. It must therefore be
distinctly stated, that Darwin has failed to estab-
lish a connection between the mode of raising
domesticated breeds and the cause or causes to

which wild animals owe their specific differences.

94 ACALEPHS IN GENERAL. Parr I.

exhibiting any evidence of community of descent; while the power that imparted
all their peculiarities to the primitive eggs of all the species now living side by
side, could also impart similar peculiarities with similar relations, and all degrees
Until,
therefore, it can be shown that any one species has the ability to delegate such

of relationship, to any number of other species that have existed previously.

specified peculiarities and relations to any other species or set of species, it is not
logical to assume that such a power is inherent in any animal, or that it con-
stitutes part of its nature’ We must look to the original power that imparted
life to the first being for the origin of all other beings, however mysterious and

inaccessible the modes by which all this diversity has been produced, may remain

for us.

whole ground?

1 The difficulty of ascertaining the natural limits
of some species, and the mistakes made by natu-
ralists when describing individual peculiarities as
specific, have nothing to do with the question of the
origin of species; and yet, Darwin places great
weight, in support of his theory, upon the differ-
ences which exist among naturalists in their views
of species. Some of the metals are difficult to
distinguish, and have frequently been mistaken, and
the specific differences of some may be questioned ;
but what could that have to do with the question
of the origin of metals, in the minds of those who
Noth-

ing more than the blunders of some naturalists, in

may doubt the original difference of metals?

identifying species, with the origin of species of ani-
mals and plants. The great mischief in our science
now lies in the self-complacent confidence with which
certain zodlogists look upon a few insignificant lines,
called diagnoses, which they have the presumption
to offer as characteristics of species, or, what is still
worse, as checks upon others to secure to themselves
a nominal priority. Such a treatment of scientific
subjects is unworthy of our age.

2 All the attempts to explain the origin of species
may be brought under two categories: some natu-
ralists admitting that all organized beings are cre-
ated (that is to say, endowed from the beginning
of their existence with all their characteristics), while
others assume that they arise spontaneously. This

classification of the different theories of the origin

A plausible explanation is no explanation at all, if it does not cover the

of species may appear objectionable to the sup-
porters of the transmutation theory ; but I can
perceive no essential difference between their views
and the old idea that animals may have arisen
spontaneously. They differ only in the modes by
which the spontaneous appearance is assumed to be
effected. Some believe that physical agents may
so influence organized beings as to modify them;
this is the view of DeMaillet, and the Vestiges of
Creation: others believe that the organized beings
themselves change in consequence of their own
acts, by changing their mode of life, ete.; this is
the view of Lamarck: others still assume that ani-
mals and plants tend necessarily to improve, in
consequence of the struggle for life, in which the
favored races are supposed to survive; this is the
view lately propounded by Darwin. I believe these
theories will, in the end, all share the fate of the
theory of spontaneous generations, so called, as the
facts of nature shall be confronted more closely with
The theories of De-

Maillet, Oken, and Lamarck, are already abandoned

the theoretical assumptions.

by all those who have adopted the transmutation
theory of Darwin; and unless Darwin and his
followers succeed in showing that the struggle for
life tends to something beyond favoring the exist-
ence of certain individuals over that of other indi-
viduals, they will soon find that they are following
a shadow. The assertion of Darwin, which has

crept into the title of his work, is, that favored

Cuap. II. INDIVIDUALITY AMONG ACALEPHS. 95

Whatever views are correct concerning the origin of species, one thing is certain,
that as long as they exist they continue to produce, generation after generation,
individuals which differ from one another only in such peculiarities as relate to their
individuality. The great defect in Darwin’s treatment of the subject of species lies
in the total absence of any statement respecting the features that constitute indi-
viduality. Surely, if individuals may vary within the limits assumed by Darwin, he
was bound first to show that individuality does not consist of a sum of hereditary
characteristics, combined with variable elements, not necessarily transmitted in their
integrity, but only of variable elements. That the latter is not the case, stands
recorded in every accurate monograph of all the types of the animal kingdom upon
which minute embryological investigations have been made. It is known that every
individual eg undergoes a series of definite changes before it reaches its mature
condition; that every germ formed in the ege passes through a series of meta-
morphoses before it assumes the structural features of the adult; that in this
development the differences of sex may very early become distinct; and that all

this is accomplished in a comparatively very short time,— extremely short, indeed,

in comparison to the immeasurable periods required by Darwin’s theory to produce
any change among species; and yet all this takes place without any deviation from
the original type of the species, though under circumstances which would seem most
unfavorable to the maintenance of the type. Whatever minor differences may exist
between the products of this succession of generations are all individual peculiarities,
in no way connected with the essential features of the species, and therefore as

races are preserved; while all his facts go only to
substantiate the assertion that favored individuals
have a better chance in the struggle for life than
others. But who has ever overlooked the fact that
myriads of individuals of every species constantly
die before coming to maturity? What ought to be
shown, if the transmutation theory is to stand, is,
that these favored individuals diverge from their
specific type; and neither Darwin nor anybody else
has furnished a single fact to show that they go on
diverging. The criterion of a true theory consists
in the facility with which it accounts for facts
accumulated in the course of long-continued investi-
gations, and for which the existing theories afforded
no explanation. It cannot, certainly, be said that
Darwin’s theory will stand by that test. It would
be easy to invent other theories that might account

for the diversity of species quite as well, if not

better, than Darwin’s preservation of favored races.
The difficulty would only be to prove that they
agree with the facts of nature. It might be as-
sumed, for instance, that any one primary being
contained the possibilities of all those that have
followed, in the same manner as the egg of any
animal possesses all the elements of the full-grown
individual; but this would only remove the diffi-
culty one step further back. It would tell us
nothing about the nature of the operation by which
the change is introduced. Since the knowledge we
now have, that similar metamorphoses go on in the
eggs of all living beings, has not yet put us on the
track of the forces by which the changes they
undergo are brought about, it is not likely that by
mere guesses we shall arrive at any satisfactory
explanation of the very origin of these beings

themselves.

96 ACALEPHS IN GENERAL. Parr I,

transient as the individuals; while the specific characters are for ever fixed. A
single example will prove this. All the robins of North America now living have
been for a short time in existence; not one of them was alive a century ago,
when Linnzus for the first time made known that species, under the name of
Turdus migratorius, and not one of the specimens observed by Linneeus and_ his
contemporaries was alive when the pilgrims of the Mayflower first set foot upon the

rock of Plymouth. Where was the species at these different periods, and where

is it now? Certainly nowhere but in the individuals alive for the time being ;
but not in any single one of them, for that one must be either a male or a
female, and not the species; not in a pair of them, for the species exhibits its
peculiarities in its mode of breeding, in its nest, in its eggs, In its young, as
much as in the appearance of the adult; not in all the individuals of any par-
ticular district, for the geographical distribution of a species over its whole area
forms also part of its specific characters." A species is only known when its
whole history has been ascertained, and that history is recorded in the life of
individuals through successive generations. The same kind of argument might be
adduced from every existing species, and with still greater force, by a reference
to those species already known to the ancients.

Let it not be objected, that the individuals of successive generations have pre-
sented marked differences among themselves; for these differences, with all the
monstrosities that may have occurred during these countless generations, have
passed away with the individuals as individual peculiarities, and the specifie char-
acteristics alone. have been preserved, together with all that distmguishes the genus,
the family, the order, the class, and the branch to which the individual belonged.

And all

amounting in each individual to the whole range of transformations through which

this has been maintained through a succession of repeated changes,

an individual passes, from the time it is individualized as an ege to the time it
is itself capable of reproducing its kind, and, perhaps, with all the intervening
phases of an unequal production of males and females, of sterile individuals, of
dwarfs, of giants, ete. ete, during which there were millions of chances for a
deviation from the type. Does this not prove, that, while individuals are perish-
able, they transmit, generation after generation, all that is specifie or generic, or,
in one word, /ypical in them, to the exclusion of every individual peculiarity, which

1 We are so much accustomed to see animals

this regular succession. And upon this law the

reproducing themselves generation after generation,
that the fact no longer attracts our attention, and
the mystery involved in it no longer excites our
admiration. But there is certainly no more mar-

vellous law in all nature than that which regulates

maintenance of species depends; for observation
teaches us that all that is not individual peculi-
arity is unceasingly and integrally reproduced, while
all that constitutes individuality, as such, constantly

disappears.

Cuap. II. INDIVIDUALITY AMONG ACALEPHS. 97

passes away with them; and that, therefore, while individuals alone have a material
existence, species, genera, families, orders, classes, and branches of the animal king-
dom, exist only as categories of thought in the Supreme Intelligence, and, as such,
have as truly an independent existence, and are as unvarying, as thought itself
after it has once been expressed.

Returning, after this digression, to the question of individuality among Acalephs,
we meet here phenomena far more complicated than among higher animals. Indi-
viduality, as far as it depends upon material isolation, is complete and absolute in
all the higher animals, and there maintained by genetic transmission, generation
after generation. Individuality, in that sense, exists only in comparatively few of
the Radiates. Among Acalephs it is ascertained only for the Ctenophore and
some Discophore. In others, the individuals born from eggs end by dividing into
a number of distinct individuals. In others still, the successive individuals derived
from a primary one remain connected to form compound communities. We must,
therefore, distinguish different kinds and different degrees of individuality, and may
eall hereditary indinduality that kind of independent existence manifested in the
successive evolutions of a single egg, producing a single individual, as is observed
in all the higher animals. We may call derivative or consecutive individuality that
kind of independence resulting from an individualization of parts of the product
of a single egg. We have such derivative individuals among the Nudibranchiate
Mollusks, whose eggs produce singly, by a process of complete segmentation, several
independent individuals. We observe a similar phenomenon among those Acalephs,
the young of which (Seyphostoma) ends in producing, by transverse division (Stro-
bila), a number of independent free Meduse (Ephyre). We have it also among
the Hydroids which produce free Meduse. Next, we must distinguish secondary
wndidualty, which is inherent in those individuals arising as buds from other indi-
viduals, and remaining connected with them. This condition prevails in all the
immovable Polyparia and Hydraria, and I say intentionally in the immovable ones ;
for, in the movable communities,—such as Renilla, Pennatula, ete., among Polyps,
and all the Siphonophoree among Acalephs,—we must still further distinguish another
kind of individuality, which I know not how to designate properly, unless the name
of complex individuality may he applied to it. In complex individuality a new element
is introduced, which is not noticeable in the former case. The individuals of the

community are not only connected together, but, under

given circumstances, they
act together as if they were one individual, while at the same time each individual
may perform acts of its own.

As to the specific differences observed among <Acalephs, there is as great a
diversity between them as between their individuals. In some types of this class
the species are very uniform,—all the individuals belonging to one and the same

VOL. III. 13

98 ACALEPHS IN GENERAL. Part I.

species resembling one another very closely, and exhibiting hardly any differences
among themselves, excepting such as arise from age. This identity of the individuals
of one and the same species is particularly striking among the Ctenophore. In
this order, there are not even sexual differences among the individuals, as they are
all hermaphrodites. In the Discophoree proper, a somewhat greater diversity pre-
vails. In the first place, we notice male and female individuals; and the difference
between the sexes is quite striking in some genera, as, for instance, in Aurelia.
Next, there occur frequent deviations among them in the normal number of. their
parts, — their body consisting frequently of one or two spheromeres more than
usual, sometimes even of double the normal number, or of a few less. And
yet year after year the same Discophore reappear upon our shores, with the same
range of differences among their individuals. Among Hydroids, polymorphism pre-
vails to a greater or less extent, besides the differences arising from sex. Few
species have only one kind of individuals. Mostly the cycle of individual differ-
ences embraces two distinct types of individuals, one recalling the peculiarities of
common Hydrx, the other those of Medusxe; but even the Hydra type of one and
the same species may exhibit more or less diversity, there being frequently two
kinds of Hydra united in one and the same community, and sometimes even a
larger number of heterogeneous Hydre. And this is equally true, though to a
less extent, of the Medusa type. Yet, among Siphonophora, there are generally
at least two kinds of Meduse in one and the same community. But, notwith-
standing this polymorphism among the individuals of one and the same community
genetically connected together, each successive generation reproduces the same kinds
of heterogeneous individuals, and nothing but individuals, linked together in the
same way. Surely, we have here a much greater diversity of individuals, born
one from the other, than is exhibited by the most diversified breeds of our domesti-
cated animals; and yet all these heterogeneous individuals remain true to their
species, In one case as in the other, and do not afford the slightest evidence of a
transmutation of species.

Would the supporters of the fanciful theories lately propounded, only extend
their studies a little beyond the range of domesticated animals,—would they investi-
gate the alternate generations of the Acalephs, the extraordinary modes of develop-
ment of the Helminths, the reproduction of the Salpe, ete., ete.,

they would soon
learn that there are in the world far more astonishing phenomena, strictly cireum-
scribed between the natural limits of unvarying species, than the slight differences
produced by the intervention of men, among domesticated animals; and, perhaps,
cease to be so confident, as they seem to be, that these differences are trustworthy
indications of the variability of species. For my own part, I must emphatically

declare that I do not know a single fact tending to show that species do vary

Cuap. II. LIMITS OF THE CLASS. : 99

in any way, while it is true that the individuals of one and the same species
are more or less polymorphous. The circumstance that naturalists may find it
difficult to trace the natural limits of any one particular species, or the mistakes
they may make in their attempts to distinguish them, has nothing whatsoever to
do with the question of their origin.

There is another feature of the species of Acalephs, which deserves particularly
to be noticed. All these animals are periodical in their appearance, and last for
a short period in their perfect state of development. In our latitude, most Me-
duse make their appearance as Ephyre early in the spring, and rapidly enlarge
to their full size. In September and October, they lay their eggs and disappear;
while the young hatched from the eggs move about as Planule for a short time, and
then become attached as Scyphostomes, and pass the winter in undergoing their
Strobila metamorphosis. The Ctenophore appear also very early, and lay their
eggs in the autumn, passing the winter as young, and growing to their full size
towards the beginning of the summer. Among the Hydroids there is more
diversity in their periodicity. Hydraria are found all the year round; but the
Meduse buds, the free Medusx, and the Medusaria make their appearance in
different seasons, in different species. Some bring forth Meduse buds and free
Medusze or Medusaria during winter; others, and in our latitude this is the case
with by far the largest number of the Hydroids, produce their Meduse brood in
the spring; while a few breed later, in the summer or in the autumn: so_ that,
notwithstanding the regularity of their periodical return, Acalephs may be studied,
in some condition or other, during the whole year.

SECTION Vi.
NATURAL LIMITS OF THE CLASS OF ACALEPHS.

The principles upon which the natural limits of this class may be determined
have already been discussed (Sect. I. p. 36). They are based upon our knowledge
of the structure and embryonic growth of these animals. Upon both points our
information is both satisfactory and sufficient. The anatomical researches of the
writers quoted from p. 18 to p. 28, and the additional facts I have traced in
the preparation of this monograph, cover the ground sufficiently to open a fair
view, not only into the general structure of the whole class, but also into the
correspondence of the structural features of the different groups of the class, as
compared with one another. The same may be said of the embryology of these

100 ACALEPHS IN GENERAL. Part I.

animals. Besides the data furnished by the investigations already referred to from
p- 28 to p. 35, I had most desirable facilities for tracing the embryonic changes
of a considerable number of Acalephs. Indeed, I have been able to investigate
the embryonic growth of all the types of the class, with the sole exception of the
Diphyide and Physophoride. But Leuckart, Kolliker, Vogt, Gegenbaur, and Hux-
ley have published such full accounts and exhausting researches upon these very
families, that little is now wanting to complete the anatomical and embryological
history of the whole class. At all events, our comparisons may now extend to
every type belonging to this class) And the anatomy and embryology of the

other classes of Radiates—the Polyps and Echinoderms

are also sufficiently well
known to enable us to institute comparisons between them and the Acalephs, and
to trace the differences which bear upon the limitation of their respective classes
and subordinate groups. In attempting these comparisons, it is, however, indis-
pensable to bear in mind the difference there is between general and special
homologies.

General homologies lead to the knowledge of the identity of such systems
of organs as present special structural combinations, and are perhaps adapted to
different functions. The extremities of Vertebrates afford a good example of this
kind of homologies; the pectoral fins with the thoracic arch of a fish, the wing
of a Bird or that of a Bat, and the arms of Man, are identical organs, however
different they may appear, between all of which general homologies may be traced.
Special homologies, on the contrary, indicate the correspondence of identical parts,
differing only in their relative proportions and special adaptations. The different
systems of teeth, characteristic of the different genera and families of Mammalia,
afford good examples of special homologies; and may be studied from the extensive
investigations of Professor Owen upon that subject. Now, the more animals are
compared in all thei structural details, as well as im their various kinds and
different degrees of relationship, the more distinctly does it appear that general
homologies are co-extensive with the branches of the animal kingdom, while special
homologies are circumscribed within the limits of the classes; or, in other words,
that all the classes of one and the same branch have identical systems of organs,
however different the organs themselves may be, while the representatives of one
and the same class only exhibit identical adaptations in the structure of their
organs. Such a distinction, as far as it may be carried out, affords, therefore,
a valuable additional test in the delimitation of the classes of animals.

What the types are, which should be referred to the class of Acalephs, will
already appear from what has been stated in Section IL, p. 41, where I have
compared the different types of Radiates with one another. It remains, however,

for me to prove that the assertions there made are founded in nature; or, in other

Cuap. IL. LIMITS OF THE CLASS. 101

words, that the structural features of the animals represented as belonging to the
class of Acalephs are not only homologous to one another, in a general way, for
this would only prove that they belong to the same branch of the animal kingdom,
but that they are homologous in the strictest sense, which will prove them to be
members of the same class, if special homologies are really a criterion of class
affinities.

The animals which I have considered above as belonging to the class of Aca-
lephs are the Ctenophorx, the Discophore, the Hydroids proper, and the Sipho-
nophore, within the limits ascribed to these groups by most authors. I have no
hesitation in referring all these to the Acalephs; nor do I think there can be
any doubt left that Hydra and the Tabulata, still referred to the class of Polyps
by Milne-Edwards, also belong to that of Acalephs. To these I would further add
the Rugosa, a type of Corals first recognized as distinct by Milne-Edwards, and
referred by him to the class of Polyps. Respecting these last, some uncertainty
still remains, since they are all fossil, and their affinities can only be inferred from
the structure of their solid parts. As to all the other groups, the evidence that
they belong to the class of Acalephs seems to me satisfactory, though it is not
throughout of the same kind, For instance, the evidence that the Ctenophore are
Acalephs is altogether anatomical, and chiefly based upon the special homologies
of their parts: it receives no additional confirmation from Embryology, as the
young at birth are already very similar to the parent, and do not exhibit those
complex relations which we observe in other Acalephs. The affinities of the Dis-
cophore, Siphonophore, and Hydroids, on the contrary, are established upon embry-
ological as well as anatomical evidence.

Beginning with the Ctenophore, we have first to sift the arguments brought
forward to support their connection with the Mollusks. The idea that the Cteno-
phore are allied to the Tunicata, and especially to the Salpx, was first suggested
by Quoy in the Zovlogy of the Astrolabe (vol. 4, p. 36), and afterwards more
fully developed by Vogt im his Zoblogical Letters (vol. 1, p. 254), where he repre-
sents them as a distinct class, intermediate between the Bryozoa and the Tunicata,
which are themselves also considered as distinct classes. The ground upon which
they are brought to the branch of Mollusks is chiefly their bilateral appearance ;
and it is there stated, that, with the exception of their glassy transparency, they
have not one trait of their organization in common with the Acalephs. Such an
assertion, from a naturalist to whom science owes important contributions to our
present knowledge of an extensive and most intricate group of Acalephs (the
Siphonophore ), cannot be passed unnoticed. That Bryozoa and Tunicata are bilateral
animals and truly belong to the type of Mollusks, is unquestionable ; and that the
Ctenophorze share the peculiar consistency of their body as fully with the Salpze

102 ACALEPHS IN GENERAL. Parr I.

as with the common <Acalephs, might appear true were it not known that the
Ascidians, to which Salpx belong, have a mantle consisting of Cellulose,’ while of
all Acalephs the Ctenophor are the most perishable, and dissolve entirely in
water, — their body, however, consisting of cells of the same kind as those of the
other Acalephs.

Fig. 54.

BouinA ALATA, Ag.

(Seen from the broad side.)
aand f/ Long rows of locomotive fringes. —
gandh Short rows of locomotive fringes.
—o Central black speck (eye-speck ?). —
7 to m Triangular digestive cavity. —7 to o
Funnel-like prolongation of the main cay-
ity.—v Chymiferous tube of the tenta-
cular apparatus.—m Tentacular appa-
ratus on the side of the mouth. —rr Ear-
like lobe, or auricles, in the prolongation
of the short rows of locomotive fringes.
—tt Prolongation of the vertical chymife-
rous tubes. —nn The same tubes turning
upwards.— xx Bend of the same tubes,
—zz Extremity of the same tubes meet-
ing with those of the opposite side. —w
Recurrent tube anastomozing with those
of the auricles.

As to the assertion that
far correct that the body is

BoLinaA ALATA, Ag.
(Seen from the narrow side.)

ab Long rows of locomotive fringes. —c h
Short rows of locomotive fringes. — 0 Cen-
tral black speck (eye speck?).—z Upper
end of the digestive cavity. —i too Fun-
nel-like prolongation of the main cavity of
the body. —m toi Digestive cayity.—7r
Auricles.— mm Mouth.—t ¢ Prolong-
ation of the vertical chymiferous tubes.
—nn The same turning upwards. —2z x
Bend of the same tubes. —z Anastomosis
of the two longitudinal tubes tt. — ww
Recurrent tube, anastomozing with those
of the auricles. — A comparison of this fig-
ure with Fig. 4 gives a distinct idea of the
relative position of the digestive cavity 2
to7, and the chymiferous tubes of the ten-
tacular apparatus v.

Bovina ALATA, Ag.
(Seen from above.)

o Central black speck (eye speck ?).—abef
Long rows of locomotive fringes. —cdgh
Short rows of locomotive fringes. — rr
Auricles.— ss Cireumscribed area of the
upper end of the body.

Fig. 57.

BouinA ALATA, Ag.
(Seen from below.)
m Mouth. —rr Auricles.— tttt Prolonga-
tion of the vertical chymiferous tubes. —
zz Anastomosis of these tubes.

the Ctenophorx are bilateral animals, it is only in so

more or less compressed, as the adjoiming wood-cuts

show (gs. 54, 55, 56, and 57), which represent a Bolina most common along
the northern Atlantic coast of America. But the arrangement of all the parts of
these animals is truly radiate. Their bilateral appearance is only the result of
the inequality of their spheromeres, as is the case with the Spatangoids also, and,
in a less degree, with all Echinoderms. But in all these animals the structure
is typically radiate, and the bilaterality subordinate to the plan of radiation, in the
same manner as in Cephalopods and in Bryozoa the radiated arrangement of the
arms and tentacles is subordinate to their bilateral type. The closest comparison
of the structure of the Ctenophors with that of the Bryozoa and Tunicata on

one side and the common Meduse on the other, will show, that, while all their

1 See the memorable paper of KO LLIKER and enveloppes des Tuniciers. Ann. Se. Nat. de sér.

Lowia: De la composition et de la structure des vol. 5, p. 193.

Cuap. II. LIMITS OF THE CLASS. 103

parts are strictly homologous to those of the Acalephs, they bear no resemblance
to those of Mollusks. I have purposely selected, for this comparison, one of
the Ctenophor in which the bilateral symmetry is most prominent, that the
bilateral appearance may not seem intentionally lessened. In our Bolina alata
seen from above (Fig. 49), there appear eight rays, diverging from the centre:
these are formed by the eight rows of locomotive flappers which extend, like
meridians, upon the sides of the body. Under these flappers extend eight chym-
iferous tubes, which are symmetrically radiate in their arrangement, like the ambu-
lacral rows upon the sides of a Sea-urchin. But this is not all. These tubes are
also homologous to the radiating chymiferous tubes of the ordinary Medusa, and
to the. ambulacral system of the Echinoderms; and while they bear only a general
homology to the latter, they have the most special homology to the radiating tubes
of the Meduse. In both they arise from the main cavity of the body; in both
they diverge from that centre towards the periphery; in both they connect through
anastomoses at the periphery; in both they carry the nutritive fluids to all parts
of the body; in both they are accompanied by the sexual organs; while neither
Bryozoa nor Tunicata, nor any other Mollusks, have such radiating tubes. In the
Ctenophore, as in the other Acalephs, the digestive cavity is hollowed out of the
mass of the body, with the single difference that the abactinal end of that cavity
is freed from the spherosome in Ctenophore, while it is not so in the other
Acalephs. The Bryozoa and Tunicata, on the contrary, have a distinct alimentary
canal entirely free from the walls of the body, and provided with two openings;
besides which Tunicata have a heart and a gill, and muscular bundles arranged
symmetrically upon the two sides of the body. Fuller evidence of the bilateral
structure of the Bryozoa and Tunicata, and of their typical difference from the
Ctenophore, could hardly be desired.

Assuming, then, that the Ctenophorse are genuine Radiates, it remains to be
seen whether they form a class by themselves, as not only Vogt, but also Leuckart
and Gegenbaur, will have it, or whether they are only members of the class of
Acalephs: for I hold that naturalists have no more right to please themselves in
the limitation of the classes, than in the limitation of genera and species, or any
part of a systematic exposition of the relations of animals; and that their task
should simply consist in ascertaining, upon clearly defined principles, what nature
teaches us respecting these affinities. They may, no doubt, disagree in the appli-
cation of these principles; but a purely arbitrary classification is no longer ad-
missible. The validity of every group proposed hereafter by an investigator must
be discussed before it is admitted or rejected; and the principles upon which the
discussions are conducted will themselves become more precise, and be settled more

firmly by these discussions.

104 ACALEPHS IN GENERAL. Part I.

If, then, classes are characterized by the mode of exeeution of a given plan,
the Ctenophore being radiated animals, we have only one point more to ascertain
respecting them. Does their structure exhibit only a general homology to that
of the Acalephs, or are the Ctenophorx linked to the ordinary Acalephs by special
homologies? What has already been said when considering their typical relations
seems to me conclusive in that respect. Ctenophore differ only in degree, and
not in kind, from the animals thus far generally considered as true Meduse; they
must, therefore, be considered as belonging to the class of Acalephs, in which, as
we shall see in the next section, they constitute a natural order.

As the Diseophore have always been considered as the typical group of the
class of Acalephs, and as the Acalephian character of all the other groups that
have successively been associated with them, or removed from them, has uniformly
been measured by the degree of their affinity to the Discophore, as soon as it
is ascertained that these animals exhibit a special mode of execution of the plan
of radiation, the independence of the Acalephs, as a class, is also proved. And
this has already been done in a preceding section (p. 65). In the next, we shall
consider the position of the Discophore in their class, amidst all the other repre-
sentatives of that class.

The evidence that the Hydroids should be associated in one and the same
class with the Discophore and Ctenophore is of two kinds. In the first place,
Hydroids produce Meduse; next, they are not themselves Polyps, as was long
admitted. The first of these facts furnishes a direct argument for the necessity
of uniting that kind of Hydroids with the other Acalephs; and the circumstance
that the Hydroids from which free Meduse arise are not identical in their structure
with Polyps, but themselves resemble Meduse® more than Polyps, in connection
with what is already known of the reproduction of the latter, shows that Polyps
never produce free Meduse, but that the Polyp-like animals, from which free Me-
dusx arise, are themselves Acalephs.

It is hardly necessary, nowadays, to demonstrate that such animals as Sarsia,
Lizzia, Zanclea, Cladonema, Hippocrene, Nemopsis, Hybocodon, Tiaropsis, Thaumantias,
ete, are genuine Medusa. Their close affinity to the highest representatives of
this order of Acalephs has been recognized by all the investigators of this class
of animals. Péron and LeSueur, Eschscholtz, deBlainville, Milne-Edwards, Lesson,
Sars, Forbes, Dujardin, Leuckart, Gegenbaur, and others have expressed their con-
viction that they are such, not only by direct declarations, but also in various
other ways, when alluding to them. To the arguments adduced by other investi-
gators, new facts have been more recently added: their mode of reproduction has
been made known; their sexual organs have been studied; the development of

their eggs has been traced through every stage of growth; the formation of their

a?

Cuap. II. LIMITS OF THE CLASS. 105

spermatic particles in the sperm cells has been observed; their special homologies
with the highest Discophorse have been made out; and nothing is wanting to prove
that the naked-eyed Medus, in their adult condition, are genuine Acalephs, closely
allied to the covered-eyed Discophore. The naturalists who, haying identified them
with the so-called sexual bunches of the Siphonophore, would consider them as
free sexual organs because these bunches appear to them to be sexual organs,
and not clusters of sterile Meduse, are bound to show that spermaries and ovaries
may have the structure of perfect Medusx, that is, a gelatinous bell, radiating and
circular chymiferous tubes, and a proboscis; not simply by affirming that certain low
sessile Medusee are sexual organs, but by adducing the evidence of a similar structure
of the sexual organs in other Acalephs. The burden of furnishing that proof rests
with them, because other naturalists have already shown that these supposed free
sexual organs, including the gonocalyx of the Diphyide and the androphores and
gynophores of the Physophorid, not only exhibit all the characteristic structural
features of genuine Acalephs, but are themselves either male or female individuals
provided with ovaries and spermaries.

As the divergence of opinions upon this point has arisen from the peculiar
phenomena known as alternate generations, it is proper that we should now turn
our attention to this subject for a moment, and examine critically the dis-
tinctive features of the various facts now generally considered as constituting one
peculiar mode of reproduction; since, from the beginning, heterogeneous phenomena
have been confounded under that name. Without stepping beyond the limits of
the class of Acalephs, we have, in the first place, the case of the higher Discophore,
in which, as for instance in Aurelia and Cyanea, the young born from eges (PL
X. Figs. 1 and 2, and Pl X*. Figs. 16-24) as independent, locomotive, single indi-
viduals (Pl. X. Figs. 3 to 10, and Pl. X*. Figs. 25 to 36), become attached (PI. X.
Figs. 11, 12, 13, and 14), and then tentacles appear gradually (Pl. X. Figs. 13 and
14), the young thus assuming the form of Hydra, with an increasing number of
tentacles (Pl. X. Migs. 16 to 37, and Pl. X*. Figs. 11 to 15). The body is next
furrowed.by transverse grooves, and assumes an annulate appearance, and the rings
thus formed (Pl. XL Fig. 19) become gradually more distinct and more numerous,
until the Hydra is changed into a Strobila, which is only a Hydra undergoing a
process of transverse segmentation. As the process of isolation resulting from a
deeper and deeper contraction of the ambulacral segments becomes more complete,
the whole resembles a pile of scalloped saucers, with a fringe of tentacles; next, the
uppermost segment drops off; then the next disk, then the next, and so on until
in the end, each disk has separated successively from that below (Pl. XI. F%y. 29),
and the base of the original Hydra, having reproduced tentacles, remains alone,
perhaps with a few disks attached to it (Pl. XI. Figs. 1, 4, and 17), or with a

VOL. III. 14

106 ACALEPHS IN GENERAL. Pasi

single disk, as in F¥y. 13. These free disks are genuine Medusx, and have long
been known as Ephyrx (PI. XI").— Figs. 58, 59, and 60, below, represent a summary
history of this mode of reproduction. —The Ephyre are, in course of time, trans-
formed into common Meduse: those of our Aurelia flavidula, Pér. and LeS., Fig. 60,
assume the characters of that genus, consisting in innumerable small tentacles all
along the margin of the disk, with four long, pendent so-called arms around the
mouth, ete. (comp. Plates VI, VIL, and VUIL); while those of Cyanea arctica, which
at first hardly differ from those of Aurelia, are transformed into the largest Jelly-

fish of our coast, and end in having the appearance of Pl. TIL, HL‘, IV., and V.

Fig. 59.

Seyphostoma of Strobila of
AURELIA FLAVIDULA, Pér. & LeS. AURELIA FLAVIDULA, Pér. & LeS. Ephyra of
In this stage of growth, Aurelia is a Scyphostoma reproduced at the base AURELIA FLAVIDULA, Pér. & LeS.
simply a Hydroid. of a Strobila ) >, all the disks of which ¢ Mouth.—ee Eyes.—oo Ovaries. —

Dave Arab ned Ola but ie last: ww Tentacular spaces.

We have thus a complete metamorphosis of an Ephyrowt animal into a perfect Medusa
entirely different from it both im form and complication of structure, and this
metamorphosis is the sequel of another series of genetic phenomena, during which
one single being avising from an egg of Aurelia or Cyanea, at first free and after-
wards attached, ends in dividing into a dozen and more, may be twenty and more, distinct
free Ephyre, without ceasmg to live, for the Strobila reproduces tentacles below
the last Ephyra (/%. 59) before this drops off} and resumes its Scyphostoma or
Hydra form. Now, this part of the process is neither a metamorphosis proper nor
an alternate generation comparable to that of the ordinary Hydroids, for here the
body of the Hydra is partially lost in the formation of the Ephyre. The crown,
or row of tentacles, at its actinal end, after separating, dies and decomposes; while
the central portion of the Hydra, intermediate between the tentacles and_ its
abactinal end, divides into numerous free, active Ephyre, which continue to live
until they have completed their metamorphosis, and laid an immense number of
eggs. The base of the Hydra, with its new tentacles, also survives, and may live
for years. Its further history, to which I shall allude again hereafter, still presents,
however, some mystery.

In the Hydroids proper, which also produce free Meduse, the origin of the
free brood is entirely different, and truly leads to a succession of alternate gener-

ations. Arising from the eggs of their free Meduse, these Hydroids, when mature,

oo

Cuap. IT. LIMITS OF THE CLASS. 107

bring forth buds from different parts of their axis, in different families, and even
in different genera of the same family. These buds start either from the stem
or from the upper part of the body, or even from the proboscis of the Hydra:
they gradually enlarge, and assume the appearance of Meduse, even while still
connected with the Hydra, and free themselves finally, and become independent
animals, undergoing but slight changes comparatively after their separation, except
that they grow larger, develop their sexual organs, and finally lay eggs, out of
which arise new Hydre. The Hydre themselves undergo no changes whatever
in consequence of this production of free Meduse: they neither lose their tentacles

nor any part of their body, and continue to live for an indefinite period of time,

and may produce other crops of free Medusx,—although I have not traced directly
such a repetition of their reproduction.

Here, as im the case of Aurelia and Cyanea, the connection of the free
Medusee and the Hydre is unquestionable, and hardly less direct in the one
than in the other; for, though the Ephyre are parts of the body of Hydra,
the free Medusz of the common Hydroids are buds from Hydra, some of which
differ but slightly from the Hydre of Aurelia and Cyanea. If, therefore, the
Hydre from which Ephyre arise, belong to the class of Acalephs as young of
the highest type of Discophors, surely the Hydra born from the eggs of naked-
eyed Meduse, though reproducing again the same kind of Medusz only through
buds, must equally belong to that class; and this the more since these Hydra
themselves have already been shown to be strictly homologous to Acalephs, and
not to Polyps (p. 44). The doubts entertained by some naturalists respecting the
systematic position of the Hydroids have arisen from a belief that Hydroids were
Polyps, in connection with the fact, disclosed during the last twenty years, that
they produce free Meduse, when the following alternative seemed inevitable: either
must Polyps and Acalephs be united as a class, or, if considered distinct, it must
be acknowledged that Polyps produce Meduse. But neither is true. Hydroids
are not genuine Polyps, and the true Polyps may be considered as a distinct
class, without forcing upon us the conclusion that they produce Medus; since
the Polyp-like Radiates from which free Medus# arise are themselves a low type
of Acalephs, remarkable for the polymorphism of its representatives. And yet,
however great the diversity of the individuals of one and the same kind of these
Acalephs may be, it is easily reduced to two forms, one of which belongs to the
Hydra type, the other to the Medusa type.

The genetic connection of certain Hydroids and certain free Meduse once
established, it remains only to be settled what are the kinds of Acalephs which
should be considered as belonging to their type, among those Hydroids not known

to produce free Meduswe and among those Meduse not known to originate from

108 ACALEPHS IN GENERAL. Part I.

Hydroids; and also under what common name they should be designated. The
answer to these two questions is not difficult.

Since the free Meduse known to originate from Hydroids all belong to the
type of the Discophore Cryptocarpa of Eschscholtz, the Gymnophthalmata of Forbes, or
Craspedota of Gegenbaur, there is presumptive evidence that the final investigation
of the true affinities of these Meduse will lead to a natural association of all those
which are really and closely related to one another, to the exclusion of the possible
foreign admixtures now left in this group, and that such a natural group will in
the end embrace all the Meduse originating from Hydroids. It is also possible,
however, that such a natural group of Meduse may embrace genera undergoing
a direct metamorphosis from the ege to the perfect Medusa without intervening
Hydra stock, as we already know that there are higher Discophore, such as
Pelagia, which reproduce themselves without passing through the Strobila state.
But this would not alter the case of the affinity of such Meduse: it would only
show that the natural group to which they belong exhibits a wider range in its
modes of development. The systematie position of any Medusa must be determined
by an investigation of its special structure, and if there are any Medusex, not
arising from Hydroids, but growing up directly from eges to their permanent form,
and presenting the same special structure as those that arise from Hydroids, there
is no reason why they should be separated. Upon this view we shall hereafter
consider the affinities of the A%quoride, the mode of development of which is not
yet fully ascertained, and those of the ASginide, some of which are known to
undergo a direct metamorphosis. As to the Polyp-like Acalephs already known

to produce free Meduse, they have all been united by Johnston into one natural

Fig. 61. division, which he has called //y- Fig. 62
AW) droidea. But among these Hydroi-

dea there are those which produce
no free Meduse, and yet as Hy-
droids in no way differ from those
that produce them. There © is,
therefore, no reason why they

should be separated: the less since,
HypRACTINIA POLYCLINA, Ag.

aes eee instead of free Medusze, they pro-
individual, producing male Me- (luce sessile Medusx buds identical HypracTinia POLYCLINA, Ag.

See poe % a a 1 ] s D a Sterile individual. —? Fertile individual pro-
pemeeretele a re ie in their structure with the free ducing female Medusze. — de Female Meduse,
lena ofthe see atts Medusa originating from the other — {rantscat’tiate aia
ee ; ‘ o Peduncle of the mouth with short elobular

simple knobs o. Hydroids. ( mn account of its re- tentacles. —¢c Individual, with globular ten-
4 oe : ‘i oe . n tacles, upon which no Medusz haye as yet
semblance to Siphonophora, Hydractinia (Figs. 61 and appeared, or from which they have already

dropped.

62) affords an excellent example of this type.

— os

Cuap. II.

PELAGIA CYANELLA, Pér. and LeS.

aa Umbrella. —m m Mouth tentacles or arms ;
the prolongation of the angles of the mouth.
—tt Marginal tentacles,

Medusa bud of
HyBocopoNn PROLIFER, Ag.

a Base of attachment to the Hydra stock.
—o Proboscis.—e Circular chymife-
rous tube. — Radiating chymiferous
tube.— dt Proliferous Medusa with
its single tentacle. —¢ Single tentacle
of the primary Medusa. — Nearec An-
other small proliferous Medusa-bud.

CoRYNE MIRABILIS, Ag.

Hydra with a Medusa bud. This
bud when freed becomes a Sarsia,
Fig. 70.

a Stem of the Hydra.—wv Its elub-
shaped body. —o Its mouth.—tt Ten-
tacles scattered over the body —d
Medusa bud.

LIMITS

OF THE CLASS.

It appears thus, that, wheth-
er originating from Hydroids
or not, all genuine Gymnoph-
thalmata, the Discophorz: Cryp-
tocarpx of Eschscholtz, must
be united into one great natu-
ral division with all the genu-
ine Hydroids, whether these
produce free Medus or not.
But, while I acknowledge that
the free Meduse born from
Hydroids show their Acalephian

Free Medusa of
HyBocopon PROLIFER, Ag.
The longest vertical tube being
seen in profile.
v Proboscis. —7 o Radiating tubes. — $

Circular tube.—t Tentacle. —m Buds
of Medusz, proliferous from its base.

Medusa bud of
CoryNE MIRABILIS, Ag.

The bud represented here sepa-
rately, with its base of attachment
a cut through, is younger than that
represented in its natural connection
in Fig. 68d. The free Medusa is
represented Fig. 70, and described
as Sarsia mirabilis in the Contribu-
tions to the Nat. Hist. of the Acalephs.
a Base of attachment to the Hydra

stock.—o Proboscis. —b Radiating

chymiferous tubes. —?t Tentacles. —

All the intermediate forms, from the

youngest buds to the adult Medusa,

will be described in the next yolume.

109

HyBocopon PROLIFER, Ag.

a Stem of a single Hydra.—o Its mouth sur-
rounded with tentacles.—z¢¢ Its marginal
tentacles. —ddd The most advanced of its
Meduse buds.

Free Medusa of
HyBocopon PROLIFER, Ag.
Facing the longest chymiferous
tube.

a Point of attachment before its separa-
tion.—c Radiating or vertical chy-
miferous tubes, ¢ pointing to the circu-
lar tube.—¢ Tentacle.—f Bunch of
proliferous Medusze buds. —e Rows of
epithelial cells forming distinct bands
at the surface. —o Proboscis.

The free Medusa, SarsiA, of
CoRYNE MIRABILIS, Ag.
o Proboscis.— 4 Vertical chymiferous
tube. —c Circular tube. —ee Dia-
phragm. —¢¢ Tentacles.

110 ACALEPHS IN GENERAL. Parr i

nature in the resemblance they bear to the common Meduse of the type of
Aurelia, Cyanea, and Pelagia (/¥. 65), 1 do not believe that their affinity to the
latter is sufficiently close to justify their association with them im one and the
same order. (Compare /%gs. 65, 66, and 67, which are the Meduse buds and the
free Medusa of the Hydroid of Fy. 64; and Figs. 69 and 70, which are the Me-
dusee buds and free Medusa of the Hydroid of Fiy. 68, with genuine Discophore
as represented in F¥g. 63.) I take here, therefore, the group of Discophors Crypto-
carpe (Figs. 66, 67, and 70) as entirely distinct from that of Discophora Phane-
rocarpe (/%y. 63), for which alone, I shall retain the name of Discophora. For
the present, I desired only to trace the natural limits of the class of Acalephs, to
give examples of their various types, and to prove that the Hydroids cannot be
separated from the naked-eyed Meduse any more than from the Siphonophorz.
We shall see presently that this natural division differs essentially, as an order, from

the Discophore proper, the Steganophthalmata of Forbes, or Aecraspeda of Gegenbaur.

VELELLA MuUTICA, Bose.

Free Medusa of m So-called mouth. —aa So-called
VELELLA MUTICA, Bose tentacles. Between the sterile
oF h A, sc.

Bunch of Meduse of

o Proboseis. — Radiating echy-
miferous tubes. — c Circular
tube.

tentacles and the mouth arise
the secondary Hydra, or so-
called fertile tentacles, the gono-
blastidial Polypites of Huxley.

For the united Gymnophthalmata and

Hydroidea, there is only one name accept-

able, according to the law of priority:

they must be called Hyprows. But

PuysaviA ARETHUSA, Til.

In various stages of develop-
ment.

a Common hollow base of attach-
ment of the whole bunch, com-
municating with the chymiferous
cavity of the air sac. —b So-called
Polyp, or sucker. —d ddd The
Medusze buds arising from the
simplest kind of Hydre existing
in the whole community.

Bunch of single Hydre and
clusters of Meduse of Puy-
SALIA ARETHUSA, Til.
6b The Hydre, with their tenta-

cles cc.—dd The bunches of

Medusz,

this order must further include the Siphonophore, since they likewise exhibit two
structural types, some individuals of their communities beme Hydra and others
Medusw, variously combined, and the Medusw either becoming free (Fig. 71, derived
from Fig. 72) or remaining sessile (#%gs. 73 and 74), as among the majority of
the Hydroids proper.

As soon as the different families of this order are brought together side by
side, and their structure and modes of development are compared, it is impossible
to overlook the typical conformity which exists among them, and unites them
all into one natural group. Had the peculiar modes of reproduction of the Aca-
lephs been known as early as their adult condition, this affinity would have

been much sooner recognized. The idea of pedunculated Acalephs, attached to the

Cuap. II. LIMITS OF THE OLASS: W

ground, must have appeared unnatural to those who were familiar with the large
free Medusee so common everywhere; and it is hardly a matter of surprise that
even now, there should be naturalists who oppose the views I have here pre-
sented. Let it be remembered, however, that it is not so very long since the
pedunculated Crinoids were arranged among the Polyps, and that it has only
required a direct comparison between them and the free Crinoids to show their
close affinity with the other members of the class of Echinoderms. Now, the
pedunculated Hydroids bear the same relation to the swimming Hydroids (the
Siphonophorx) as the pedunculated Crinoids bear to the free Crinoids; and, the
close affinity of the Siphonophoree and Hydroids proper once admitted, their mode
of reproduction renders their separation from the higher Acalephs forever impossible,
while it forbids, at the same time, their association with the Polyps.

That Lucernaria (Figs. 75 and 76) and Mtge 00: Ti geties
Millepora (Figs. 77, 78, and 79) belong to
the Hydroids proper has already been shown
(pp. 59 and 61).
Millepora is with Hydractinia (compare Fygs.

The nearest affinity of

PO\. te mn os p 1
61 and 62); but its mode of reproduction ee oe

LuCERNARIA,
Seen in profile.

has thus far remained unknown. Seen froin above.

a Peduncle.—} 6 Tentacular m Mouth.—c c Ovaries.

bunches. bb Tentacular bunches.

Fig. 79.

MILLEPORA ALCICORNIS, Lmk.

A branch of the Coral of that
name, natural size. The little pro-

MILLEPORA ALCICORNIS, Lmk.

MILLEPORA ALCICORNIS, Lmk. A
Transverse section of a branch of

jections along the edge are meant
for the extended Polyps. They are
extremely shy and delicate, and
never show themselves again after
a branch has once been taken out
of the water.

Magnified view of the extended
Polyps or Hydroids of the same
Coral stock.
aa Smaller Hydroids.—> Larger Hy-

droid, 7 its mouth, ¢ its tentacles.

the Coral stock, magnified.

aa Pits of the Hydroids, with their suc-
cessive floors. It is very difficult to
obtain sections of the pits occupied
by the smaller Hydroids.

The structural features of all these various representatives of the class of Aca-
lephs will, of course, be more fully illustrated in the following chapters. My
object here was mainly to show, upon the most general evidence, what are the
types of Radiates that constitute the class of Acalephs, and incidentally to call
attention to their special affinities. If the views I entertain upon this subject are
correct, this class embraces three orders,—the Crexopnorm, the DiscopHor® proper,
to the exclusion of the naked-eyed Meduse, and the Hyprow, including the

112 ACALEPHS IN GENERAL. Parr I.

naked-eyed Medusx, the Hydroids proper, the Siphonophore, the Milleporide with
all the Tabulata of Milne-Edwards, and perhaps the Rugosa also, if their true
affinity is actually indicated by the peculiarities of their solid parts and their
resemblance to those of the Tabulata.

When considering Individuality and Specific Differences as manifested in the
class of Acalephs, | have taken an opportunity of showing, upon general grounds,
how futile the arguments are upon which the theory of transmutation of species
is founded. Having now shown that that class is cireumseribed within definite
limits, I may be permitted to add here a few more objections to that theory,
based chiefly upon special grounds, connected with the characteristics of classes.
If there is any thing striking in the features which distinguish classes, it is the
definiteness of their structural peculiarities ; and this definiteness goes on increasing,
with new and additional qualifications, as we pass from the class characters to those
which mark the orders, the families, the genera, and the species. Granting, for
the sake of argument, that organized beings, living at a later period, may have
originated by a gradual change of those of earlier periods, one of the most
characteristic features of all organized beings remains totally unexplained by the
various theories brought forward to explain that change,—the definiteness of their
respective groups, be these ever so comprehensive or ever so limited, combined
with the greatest inequality in their numeric relations. There exist a few thousand
Mammalia and Reptiles, and at least three times their number of Birds and Fishes.
There may be about twenty thousand Mollusks; but there are over one hundred
thousand Insects, and only a few thousand Radiates. And yet the limits of the class
of Insects are as well defined as those of any other class, with the sole exception
of the class of Birds, which is unquestionably the most definite im its natural
boundaries. | Now, the supporters of the transmutation theory may shape their
views in whatever way they please, to suit the requirements of the theory, instead
of building the theory upon the facts of nature, and they can never make it appear
that the definiteness of the characters of the class of Birds is the result of a
common descent of all Birds; for the first Bird must have been brother or cousin
to some other animal that was not a Bird, since there are other animals besides
Birds in the world, to no one of which does any Bird bear so close a relation as it
bears to its own class. The same argument applies to every other class. And as
to the facts, they are fatal to such an assumption; for Geology teaches us that
among the oldest inhabitants of our globe known, there are representatives of
nine distinct classes of animals, which by no possibility can be descendants of
one another, since they are contemporaries.

The same line of argument and the same class of facts forbid the assumption

that either the representatives of one and the same order, or those of one and

Cuar. II. GRADATION AMONG ACALEPHS. Iie

the same family, or those of one and the same genus, should be considered as
lineal descendants of a common stock; for orders, families, and genera are based
upon different categories of characters, and not upon more or less extensive char-
acters of the same kind, as I have shown years ago (vol. 1, p. 150-163), and
numbers of different kinds of representatives of these various groups make their
appearance simultaneously in all the successive geological periods. There appear
together Corals and Echinoderms of different families and of different genera in
the earliest geological formation, and this is equally true of Bryozoa, Brachio-
pods, and Lamellibranchiates, of Trilobites and the other Crustacea, in fact of the
representatives of all the classes of the animal kingdom, making due allowance
for the period of the first appearance of each; and at all times and in all classes,
the representatives of these different kinds of groups are found to present the
same definiteness in their characteristics and limitation. Were the transmutation
theory true, the geological record should exhibit an uninterrupted succession of
types, blending gradually into one another. The fact is, that throughout all
geological times, each period is characterized by definite, specific types, belonging
to definite genera, and these to definite families, referable to definite orders, con-
stituting definite classes, and definite branches built upon definite plans. Until the
facts of nature are shown to have been mistaken by those who have made them
known, and that they have a different meaning from that now generally assigned
to them, I shall, therefore, consider the transmutation theory as a scientific mistake,

untrue in its facts, unscientific in its method, and mischievous in its tendency.

SHC TION ‘V.It.
GRADATION AMONG ACALEPHS.

Confident that I have correctly ascertained the limits of the class of Acalephs,
and that the method I have followed in that investigation is the only one that
may furnish the means of avoiding arbitrary decisions with reference to the natural
affinities of animals, I now proceed to an inquiry into the gradation or relative
standing of the different members of this class. Keeping in view the principles
laid down in the first volume of this work (p. 150), this inquiry should lead us
to a knowledge of the Orders among Acalephs, if orders, as natural divisions, are
based upon the different degrees of complication of the structure of the members
of one and the same class; and that this is the true view to take of orders,
I have at present not the least doubt. It is certainly so in all the classes, of

VOL. Ill. 15

114 ACALEPHS IN GENERAL. Parr ik

which the natural orders have been most fully investigated. It is so among Polyps,
if the Actinoids and Halcyonoids constitute natural orders in that class; for the
Haleyonoids, with their eight spheromeres, and lobed tentacles, stand higher than
the Actinoids. It is so among Echinoderms, the orders of which truly correspond
to different degrees of complication of their structure, and most naturally mark
the relative rank of these animals. It is so among Crustacea, taking the Rotifera,
the Entomostraca, the Isopods, the Amphipods, the Stomatopods, and the Decapods
as their natural orders. It is so among Acephala, if the Bryozoa, the Brachiopods,'
the Tunicata, and Lamellibranchiata constitute natural orders. This gradation, in
accordance with the complication of structure, is equally apparent among the
Batrachians and the true Reptiles; and if it is not traceable at present with the
same certainty in all the classes of the animal kingdom, I am inclined to believe
that it is not because this principle is incorrect, but because we have not yet
obtained a satisfactory standard, by which to determine the relative importance
of their structural differences. At all events, a majority of the classes, and those
best known to me, coincide with the view I have expressed respecting the meaning
of orders. It would be surprisme should there be some classes in which no such
gradation exists, when it is so apparent in others. Let us now see what are the
different degrees of complication of structure observed among Acalephs.

After tracing the special homologies of the Ctenophorae, and ascertaining their
close relationship to the ordinary Medusx, it is evident that they belong to the
class of Acalephs; but in this class they constitute a natural and distinct order.
Their chief difference from the Discophore consists in the mode of ramification
of the chymiferous tubes, originating in two main trunks, in opposite directions,
each of which is divided into two horizontal branches, and each branch into two
horizontal forks; so that the number of horizontal chymiferous tubes is always
eight. But, unlike other Acalephs, these tubes do not terminate at the periphery,
but open into eight vertical branches, converging in opposite directions towards
the actinal and the abactinal ends of the body, and giving out minor branches
into the spherosome. The main trunks of these vertical branches are parallel to
the surface of the spherosome, and follow the same course as the rows of locomotive
flappers, which extend, like eight ribs, upon the surface of the body. Towards the

actinal and towards the abactinal poles of the spherosome, the vertical branches of

1 The position I have assigned to the Brachio- irresistible that Bryozoa and Brachiopods are more
pods, near the Bryozoa, has been confirmed by a closely related to one another than any other groups
paper just published, in which a Brachiopod is of Acephala. See Beschreibung einer Brachiopoden-
described, resembling so closely a young Bryozoan larve von Fritz Miriier in Desterro (Brasilien),

just hatched from the egg, that the conclusion is in Archiv fiir Anat. Phys. und wiss. Med. 1860, p. 72.

Cuap. II. GRADATION AMONG ACALEPHS. 115

the chymiferous tubes terminate in different ways m different genera; anastomozing
in a more or less direct manner with one another around the actinostome. Besides
the vertical chymiferous tubes which follow the course of the rows of flappers,
there are two other vertical chymiferous tubes, presenting various degrees of com-
plication in different genera. These two tubes are placed opposite to one another,
in the same direction as the main branches of the whole system. All Ctenophore
have a decided tendency to a bilateral symmetry, their body being more or less
compressed. In some the outline is spheroidal, in others more cylindrical, while
in others still, the spherosome expands on the actinal side of the body into wing-
like appendages.

The most prominent peculiarities of the Ctenophore as an order consist, there-
fore, in the complication of their system of chymiferous tubes, in the presence of
locomotive flappers on the surface, and in a tendency to a bilateral symmetry,
resulting from the inequality of their spheromeres.

All these peculiarities show distinctly that the Ctenophore are superior to the
Discophore ; for in the latter the chymiferous tubes simply radiate from the main
cavity towards the periphery, and, when branching, divide in one and the same
plane. Moreover, Discophore have no rows of locomotive flappers, and move only
by the contraction of their spherosome, which assumes the form of a hemispheric
disk, spreading uniformly in every direction, without exhibiting the slightest tendency
to bilateral symmetry. It is true that in Discophore the actinostome is apparently
more complicated than in Ctenophore, because it is surrounded by long appendages
hanging below the main cavity; but, notwithstanding this seeming superiority of
development, it will be shown hereafter that the actinostome of the Ctenophore
is in reality more highly organized than that of the Discophore, although the
bulk of its appendages in the latter gives it a greater prominence. It is true
also that in a large number of Discophoree the margin of the disk is provided
with numerous tentacles, but these tentacles are only peripheric diverticles of the
chymiferous tubes, and in no way constitute a higher complication of that system
than the vertical branches of the chymiferous tubes of the Ctenophore with their
locomotive flappers. It is true also that the Discophore have distinct sexes, their
ovaries and spermaries forming large bunches, in separate cavities, while the Cte-
nophore are hermaphrodites ; but the special arrangement of the ovaries and
spermaries in the latter, placed as they are on opposite sides of the vertical
branches of the chymiferous tubes, contributes to render the complication of the
structure of each individual more apparent in Ctenophore than in Discophore.
It is true also that the Discophore have eight, and sometimes twelve or even
more distinct eyes at the end of their radiating chymiferous tubes, while in Cte-
nophore there is a single eye at the abactinal pole; but then that single eye

116 ACALEPHS IN GENERAL. Parr I.

stands in direct communication with a special stem of the chymiferous system,
occupying a central position in the axis of the body, while in Discophore there
is one eye to each simple radiating tube.

Thus, whatever be the special combination of the organs in the Discophore
proper, and however high they may appear to stand on account of the extra-
ordinary development of some of their parts, the sum total of the structural
complication in the Ctenophorz is unquestionably greater than that of the Dis-
cophore. This will appear more distinctly, when we consider the similarity in
general appearance of the Discophore to the naked-eyed Medusee born from
Hydroids. In this connection it must also be remembered, that, while the majority
of Discophore enjoy only a consecutive individuality (see p. 97), since several
Meduse arise from the division of one single larva, in Ctenophore the reproduction
takes place by a direct metamorphosis, each ege producing a single individual.

If multiplication of identical parts is everywhere an indication of inferiority, and
definite numbers with definite relations a mark of superiority, Ctenophora will
undoubtedly take the lead in that respect also over the Discophora, in which
repetition of identical parts prevails, without a perceptible difference in their
relations ; while in Ctenophorz the number of spherosomes never varies, and there
exist between them such definite relations as simulate bilateral symmetry.

The Hydroids, as a whole, and considered within the limits assigned to that
order in the preceding section, unquestionably occupy the lowest place in the class.
For, in addition to the permanent character of indefinite repetition of identical
parts, we observe among them, almost universally, a more or less characteristic
polymorphism, sometimes to such an extent that it becomes difficult to distinguish
secondary individuals from actual organs. Individuality is almost lost in the
dependence in which the members of a community stand toward each other.
Even when individuality becomes most prominent, it is so in individuals which
are short-lived, in comparison to the duration of the combined individuals to which
they owe their existence.

That the Discophore proper constitute a distinct order by themselves, appears
plainly from the higher complication of their structure when compared to that of
the naked-eyed Medusx. In the latter, the radiating chymiferous tubes are all
alike, equally distant one from another, simple, and either few or very numerous,
and meet with a simple circular tube, instead of forming a complicated network
of anastomoses along the margin of the disk, as in the Discophorze proper, whose
radiating tubes are alternately more or less complicated in their course, some
extending as straight tubes to the margin of the disk and communicating with
the base of the eyes, while others branch in various ways, and end in a net-

work of anastomoses at the margin. In Discophorz proper, there exist always

Cuar. IL. GRADATION AMONG ACALEPHS. 7

highly organized eyes, in definite number, and these eyes are always placed at
the marginal end of some specially organized radiating tube, alternating with other
tubes of a different character; thus exhibiting a higher complication of these parts,
not only in their structure, but also in the definiteness of their relations to one
another, in their alternation with one another, and in their numeric limitation.
Some Discophors have no other marginal organs besides eyes; but there are those
that are provided with variously combined tentacles also: in none, however, are
the eye-specks connected with tentacles, though the eyes are themselves modified
tentacles.

In the naked-eyed Medusx, the ovaries and spermaries follow the track of the
radiating chymiferous tubes, and are variously circumscribed in their extent: in
some, they are limited to the walls of the proboscis, in others they extend all
along the chymiferous tubes proper, and in others they occupy only a part of the
course of these tubes; but they are never circumscribed within distinct pouches,
as in the Discophore proper. In these, the ovaries and spermaries bear identical
homological relations to the chymiferous tubes, as far as their position is concerned ;
but, owing to their higher development and to their isolation, they form distinct
bunches, hanging in distinct pouches on the lower side of the disk, and stand in
definite relations to the parts surrounding the actinostome, through which the eggs
are laid, while in the naked-eyed Meduse the eggs simply drop from the ovary
into the water without ever passing through the actinostome. Imperfect and
injured specimens may leave a different impression respecting the mode of escape
of the eggs from the ovaries; but I shall show hereafter that these egg pouches
are really closed, and do not naturally open outward, as Ehrenberg represents them,
but communicate only with the main cavity of the body, and through it with the
actinostome, through which the eggs or the young finally make their escape into
the water, after having remained for a longer or shorter time suspended in the
peripheric folds of the actinostome.

In Discophoree proper, the actinostome is far more complicated than in the
naked-eyed Medusee. In the latter, it is only a projecting fold of the lower wall
of the spherosome, either extending simply as a circular rim beyond the main
cavity, with or without fringes, or forming a more or less elongated proboscis.
In Discophorse proper, the actinostome is as it were suspended between distinct
pillars hanging from the spherosome, which expand into more or less complicated
leafy folds, the edges of which are either free, as in Aurelia, Pelagia, Cyanea, etc.,
or partially soldered together, as in Rhizostoma, Polyclonia, ete. thus forming either
open or partially closed channels leading from their peripheric termination to the
main cavity, which is itself wide and capacious, and supported laterally by the
pillars of the actinostome. The cavities formed by the leafy folds of the acti-

118 ACALEPHS IN GENERAL. Parr I.

nostome are so far distinct from the main cavity, that they only communicate with it
through the channels extending along the centre of these folds; while in the naked-
eyed Medusx the actinostome opens broadly into the main cavity. The chymiferous
tubes arise from the upper part of the sides of the maim cavity.

It thus appears that the Discophore proper have a far more complicated struct-
ure than the naked-eyed Medusx, and that, in a natural classification, they cannot
therefore be united into one and the same order, as has thus far been done by
most naturalists. Moreover, the Discophorse resemble one another very much in
their general appearance and in their motions, which are effected by a slow alternate
expansion and contraction of the dise.

The Hydroids, as the lowest order of the class of Acalephs, are far more
In the
first place we find among them simple Hydroids, in the next place more or less

diversified among themselves than either the Ctenophore or Discophors.!

medusoid Hydroids, then communities of variously combined individuals with more

or less medusoid or hydroid characters; and among these communities there are

1 Jt is a striking fact, conflicting with all pre-
conceived ideas, that throughout the animal king-
dom, the lower types, in every class, are far more
diversified than their higher representatives. It is
so among Polyps, if the Actinoids are inferior to
the Haleyonoids ; it is so again among the Actinoids,
if the Madrepores are the highest among them. It
is so among the Acalephs, if the Ctenophore are
the highest and the Hydroids the lowest. It is
so among Echinoderms, if the Holothurians stand
highest and the Crinoids lowest. It is so among
Acephala, if the Bryozoa belong to that class. It
is so among Gasteropods, if the Pulmonates are
superior to the Branchiates. It is so among Cepha-
lopods, if the Dibranchiates deserve to be placed
above the Tetrabranchiates. It is so among Worms,
if the Helminths belong to the same class with
the Amnelids. It is so among Crustacea, if Rotifera
and Entomostraca are their lowest representatives.
It is so among Insects, if the Myriapods and Arach-
nids are united into one class with the Insects
proper; and it would still be so if the winged
Insects were considered as a class by themselves,
for the madibulate Insects are more numerous and
more diversified than the sucking Insects, and those

which undergo the most complete metamorphoses

fewer and less diversified than those whose meta-
morphoses are less complete. It is so among
Fishes, if the bony Fishes are inferior to the Se-
lachians. It is so among Amphibians, if the caudate
Amphibians are inferior to the Frogs and Toads.
It is so among Reptiles proper, if the Chelonians
deserve the highest, and the Ophidians the lowest,
place in that class. It is so among Birds, if the
It is

so among Mammalia, if we contrast the Marsupials

Palmipeds are their lowest representatives.

with the higher Mammalia; or if, among the latter,
we compare the Rodents with the Human family.
Of course, this greater diversity does not involve
respectively greater differences among the lower
representatives of any class when compared to one
another, than among the highest; since their very
inferiority, combined with great diversity, renders
the possible amount of difference among the many
lower ones less than among the fewer more highly
organized ones. This very extraordinary diversity
among the lowest types of all the classes of the
animal kingdom stands in flagrant contradiction
with Darwin’s theory of the origin of species,
according to which the lowest types should grad-
ually give way to higher and higher types, in

consequence of the struggle for life.

Cuap. II. GRADATION AMONG ACALEPHS. 119

those which produce free Meduse, and others which do not; some which consist
entirely of Hydra, and others of combined Hydra and Meduse; some start from
Hydre, others from Medusxe,—the communities themselves consisting either of a
larger number of Hydroids, or of a larger number of Medusew, when the two types
are combined. These various combinations lead naturally to the formation of
subordinate groups among Hydroids. Considering the mode of reproduction of the
Acalephs in general, the highest Hydroids would, of course, be those in which the
medusoid elements prevail, and the lowest, those in which the hydroid elements are
most prominent. We have, therefore, to inquire first whether there are any genuine
naked-eyed Medusze which do not originate from Hydra, in order to answer a
question already raised respecting the true limits of the order of Hydroids, and the
true position of the Aquoride and Adginide.

There are Aiginide, unquestionably, which undergo a direct metamorphosis, and
it is probable that this is the case with all of them. But are the Mginide
genuime naked-eyed Meduse, or a low type of the Discophore allied to the
Charybdeide ? My knowledge of this family is too limited to enable me to speak
confidently upon that point; but I am inclined to consider them as belonging rather
to the Discophore proper than to the Hydroids. In the first place the Aginide
have no radiating chymiferous tubes, as all true naked-eyed Medusze have; but
instead of them there arise broad, flat pouches from the main cavity, extending
toward the margin of the disk, as in Ephyra, the young of Aurelia and Cyanea,
and as in the adult of the latter and of many other genera of Discophors proper.
The ginide have no circular chymiferous tube, as all true naked-eyed Meduse
have. Again, the tentacles of the Alginide are not strictly marginal, and, in the
absence of a circular tube, cannot be closely connected with it as is the case in
all true naked-eyed Meduse, but are in direct communication with the radiating
pouches of the main cavity, as in Pelagia and Cyanea. If, then, for these reasons,
the Aiginide should be associated with the higher Discophors, instead of oceupying
a place among the naked-eyed Meduse, the importance attached by Gegenbaur
to the marginal seam of the umbrella, as a distinctive character of the lower
Discophore, would be greatly lessened; and I rather think rightly so, for many
of the higher Discophore, and among them our common Aurelia, have the margin
of their umbrella not only very thin, but twmed inward and downward as in all
Craspedota, and their tentacles arise between indentations of the disc (Pl. VIL.
Figs. 2, 3, and 4; Pl. VILL. Mg. 5, and Pl. IX. Mig. 4), at some distance from its
margin, as is the case in the Aginide.

As to the Aquoride, I have no doubt that they are genuine Hydroids, though
I have not been able to trace with certainty the origin of the quorea of
our coast to any true Hydroid. But the structure of Aquorea, in its adult

120 ACALEPHS IN GENERAL. Part I.

Medusa state, is so strictly homologous to that of all other naked-eyed Meduse,
that, even if it were ascertained that it undergoes a direct metamorphosis from
the egg to the perfect Medusa, I would not hesitate to consider it as a member
of the order of Hydroids, since it has simple radiating chymiferous tubes, a circular
tube, and marginal tentacles closely connected with it, and provided with mere
pigment specks upon their base.

It will require a more extensive knowledge than we now possess of the
development of all Hydroids, before the relative standing of their various types
can definitely be ascertained. As far as our information goes, the rank of Hydroids
among themselves does not seem to be determined primarily by the production of
free Medusx, since Campanulariz produce free Meduse ; while among Tubularie we
have those which bring forth free Meduse, and others which do not. The distinet-
ness of the medusoid and hydroid elements, without reference to the liberation of
the Medusx, seems more significant; for, unquestionably, a Physalia with its extra-
ordinary polymorphism has an organization inferior to that of a Sarsia born from a
Coryne. In the first case we have a very complicated community, it is true, but
it consists chiefly of low, heterogeneous elements variously combined, and the Medusz
buds themselves are of the simplest kind, and without tentacles; while in the
second case the hydroid and medusoid elements are quite distinct, and the Meduse
arising from the simple Hydrarium are as perfect as any other naked-eyed Meduse.
The same may be said of Lizzia, Hippocrene, and Hybocodon, all of which have
a limited and definite number of radiating chymiferous tubes, a limited and definite
number of tentacles or bunches of tentacles, all characters which seem to assign
to them a marked superiority over Tiaropsis and Thaumantias with their numerous
marginal tentacles which arise from Campanulariw, that is, from Hydroids exhibiting
already signs of polymorphism, while the Hydraria from which Sarsia, Lizzia, ete.,
arise, consist only of one kind of Hydre.

It would thus appear that the distinctness of the hydroid and medusoid elements
in this order is inverse to the polymorphism of their communities. The Medusze
buds of most Siphonophore play a rather indifferent part in their economy; and
yet their prominence coincides with the degree of complication of the hydroid and
medusoid elements of their communities. Velella, the community of which consists
only of two kinds of Hydra, produces distinct free Medusxe; while the Diphyidz and
the Physophoridx, in which the hydroid and medusoid elements are most completely
mixed, are also those which are most remote from the true type of Discophora,
and resemble most, in their mode of living, the free locomotive Polyp communities.
But even as compound communities consisting of heterogeneous elements, it is
remarkable that those in which the medusoid elements prevail are also the most

active, while those in which the hydroid elements are predominant, are more

Cuap. IL. GRADATION AMONG ACALEPHS. 121

floating than active. A comparison between Porpita, Velella, and Physalia on one
side, and the Diphyidwe and Physophoride on the other side, cannot fail to convince
any one who has seen any of these animals alive of the truth of this general
statement. When describing, in the sequel, the North American Hydroids in detail,
I shall have an opportunity of showing that the subdivisions founded upon the
differences here noticed among these animals are genuine sub-orders, and neither
orders nor families.

Though I have not the remotest doubt that the Tabulata (Migs. 81 and 82) are

genuine Hydroids, I am not quite so confident that the Rugosa (71. 80) also belong

SS
GONIOPHYLLUM PYRAMIDALE,
(Copied from M.-Edwards §: Haime.)
Upper figure, view from above;
lower figure, profile. Fossil of the

Silurian period. Comp. Lucernaria,
p- 111, Figs. 75 and 76.

MILLEPORA ALCICORNIS, Link.

Transverse section of a branch of
the Coral stock, magnified.
aa Pits of the Hydroids, with their suc-
cessive floors. It is very difficult to
obtain sections of the pits occupied
by the smaller Hydroids.

BEAUMONTIA EGERTONI,
(Copied from M.-Edwards § Haime.)
Fossil of the Carboniferous period.
It resembles so closely the living Po-
cillopores, that it certainly belongs to
the same sub-order.

to this class. I have not had sufficient opportunity of studying the Rugosa anew,
since I have known the acalephian affinities of the Tabulata, to feel justified in
expressing a decided opinion upon that point. I will therefore simply present my
reasons for believing that the Rugosa belong to the same class as the Tabulata.
The cavity occupied by the animal is divided by horizontal floors, evidently built
successively as in course of its growth the animal rose higher and higher, and
these floors are continuous from wall to wall across the whole width of the
cavity of the Coral; and wherever there exist radiating partitions, they rise only
from the surface of these floors, without extending through them to any other
floor above or below. No Coral known to be the solid frame of a Polyp has
On the contrary, in Polyparia the radiating partitions of the
individual cavities occupied by distinct animals extend uninterruptedly from top to
bottom of their cavities, and if there exist horizontal floors, these stretch only

across the intervals between two radiating partitions, and never across the whole

such a structure.

cavity occupied by the Polyp. The radiating partitions of the Rugosa, beside

being limited to successive floors, present another striking peculiarity, never observed

among the Polyps,— they are arranged in fours, or multiples of four.
VOL. IIL 16

This quadri-

122 ACALEPHS IN GENERAL. Part I.

partite structure of the Rugosa is an acalephian feature, nowhere observed among
true Polyps, but characteristic of Lucernaria, which is a genuine Hydroid Acaleph.
I may also allude to a more remote argument for referrmg the Rugosa to the
Acalephs. There are simple ones among them, and others forming rather loose
communities, composed of comparatively few individuals; but, whether simple or
combined, each individual of this type, with its successive floors, presents a striking
resemblance to a Strobila. Rugosa, indeed, may be considered as a prototype of
the Acalephs, combining the most characteristic embryonic features of the class
with the simplicity and peculiarity of structure of its lowest type.

When considering the different orders of Acalephs singly, I shall show that their
families are founded upon different patterns of form, their genera upon ultimate
structural details, and their species upon the proportions of their parts, and the
relations of individuals to one another and to the surrounding mediums. To
introduce these topics here, would involve me in an amount of details, which are
best referred to the special parts of this monograph.

Although an order in Zodlogy especially signifies the relative rank of the
members of a class, as exhibited in the complication of their structure, it is not
in the orders alone that we recognize different degrees and different kinds of
superiority or inferiority. As I have already stated elsewhere (vol. 1, p. 152),
groups of a more or less comprehensive value may exhibit a relative superiority
or inferiority; nor is an order a natural group that has no other meaning but
that which it derives from its higher or lower position. The primary branches
of the animal kingdom do not all stand on a level: Radiates, as such, are un-
questionably inferior to Mollusks or Articulates or Vertebrates, even though some
Radiates may have a more highly complicated organization than some of the lowest
Fishes. We assign to the Radiates a lower position than that of the other branches,
because the elements of their plan of structure are of an inferior stamp; and we
place the Vertebrates highest, because the plan of their structure is in itself the
most complicated: but it would be difficult to weigh the different organic tendencies
combined in either the Mollusks or Articulates so nicely as to prove that either
of them is superior to the other, though, unquestionably, as primary divisions of
the animal kingdom, they are superior to the Radiates and inferior to the Verte-
brates. The idea of placing either the Mollusks or the Articulates immediately
above the Radiates, so as to establish a gradual transition between them and the
Vertebrates, seems entirely out of the question, since the most distinguished natu-
ralists who have attempted to arrange the first primary divisions of the animal
kingdom in a series have failed to produce convincing arguments in favor of the
superiority of the Mollusks over the Articulates, or of the latter over the former.

The fact is, there is quite as high authority for one as for the other position

2 il

Cuap. II. GRADATION AMONG ACALEPHS. 128

of these two branches. The most natural view seems to me to be that which
assigns to them an equal standing, and recognizes their difference in the different
tendencies of their plan; so that, taking the sum of their characteristics, the four
primary branches of the animal kingdom should not be placed in one series.

Their true relations seem to be best expressed by a diagram like this :—

VERTEBRATES,
MOLLUSKS, ARTICULATES,
RADIATES.

Again, the different classes of each branch show a relative superiority one above
the other. Polyps as a class are certainly inferior to Acalephs as a class, and
these, again, inferior to Echinoderms. Acephala as a class are unquestionably
inferior to Gasteropoda, and these, again, inferior to Cephalopoda. Worms as a
class are certainly inferior to Crustacea, and these in their turn inferior to Insects,
etc. And yet there are Worms, such as the higher Annelids, in which the structural
complication much exceeds that of the lowest Crustacea, such as the Rotifera.
Some Lamellibranchiates are much more highly organized than some of the Phle-
benterate Gasteropods. Some of the Fishes may be considered superior to some
Batrachian Reptiles; but no Reptile seems to rise to a level with Birds. Here
again we see, therefore, that difference of rank is only a secondary feature for
classes. The same may be said of families and of genera, as well as of species, and
it is much to be lamented that our language has not a greater variety of words
to express the many shades of relative standing; so that we are limited to the
almost exclusive use of the words superior and inferior, which are inadequate to
render the comparative relations of beings in themselves so exquisitely organized
as are the representatives of every class in the animal kingdom. In the groups
called orders, however, the idea of superiority and inferiority seems to be the
prevalent feature. Yet orders themselves exhibit also another kind of relations,
to which I have already incidentally alluded in an article on the Categories of
Analogy, added to the London edition of my Essay on Classification! It is curious
to observe how the views entertained by Oken? respecting certain affinities among
animals, resulting, in his opinion, from the repetition of the same principle in
groups of different value, loom up again in the relations of the orders of certain
classes to other groups, to which they themselves do not belong.

If it be true that Hydroids, Discophore, and Ctenophore are three distinct

orders among <Acalephs, it cannot be overlooked, that, by their general appearance,

1 Essay on Classification, by L. Agassiz, London, * Compare vol. 1, p. 211. See also OKEN’s
1849, 8vo., pp. 271-284. Physio-philosophy, London, 1847, 1 vol. 8yvo.

124 ACALEPHS IN GENERAL. Pann 1

the Hydroids resemble the Polyps, with which, indeed, they have been united as
members of the same class; while the Discophor proper constitute the character-
istic group of Acalephs, the group which has always been considered the typical
group of this class. The Ctenophore bear the same relation to Echimoderms as
the Hydroids bear to the Polyps; and this resemblance of the Ctenophore and Echi-
noderms is especially recognizable in the peculiarity of their vertical chymiferous
tubes with their locomotive flappers, and the homology there is between them and
the ambulacral system of the Echinoderms. But neither the resemblance of Hy-
droids to Polyps nor that of Ctenophors to Echinoderms is a real indication of
affinity: it is only an analogy, arising from a similarity of form in parts which
have only a general homology, and no special homology with one another. But
this analogy, once recognized, has its significance. It confirms the views presented
above respecting the relative standing of the three orders of Acalephs. | Hydroids,
as the lower order of Acalephs, are analogous to the Polyps, the lowest class of
Radiates ; Discophors, the most characteristic type of Acalephs, occupy a middle
position between them and the Polyps, as the Acalephs, considered as a_ class,
occupy an intermediate position between the Polyps and Echinoderms; and the
Ctenophore, as the highest order in the class of Acalephs, correspond to the Echi-
noderms, and especially to the Holothurioids, the highest order of the highest class
among Radiates.

Such analogies may be traced in other classes of the animal kingdom. — As-
suming that the Articulates embrace only three classes,—the Worms, Crustacea,
and Insects; and that the Insects themselves form only three orders, — Myriapods,
Arachnids, and Insects proper, no one can fail to perceive the analogy between
the Myriapods as the lowest order of Insects, and the Worms as the lowest class
of Articulates, or between the Arachnids as the second order of Insects, and the
Crustacea as the second class of Articulates; and the highest order among Insects
consists of those best representing the character of the class of Insects, which
stands highest among Articulates. Perhaps objections may be raised against this
primary division of the Insects into three orders, and perhaps also against the
division of Articulates into three classes; but to my mind these analogies would
have great weight in establishing this classification as correct. Whatever may be
said of the analogies alluded to between the orders of Acalephs and the classes
of Radiates, I have no hesitation in affirming that there are only three orders in
the class of Acalephs, and that these orders stand to one another in the position
I have assigned to them,—the Hydroids being the lowest, the Discophor next,
and the Ctenophore highest.

Cuap. II. SUCCESSION OF ACALEPHS. 125

SE CON ver iT.

SUCCESSION OF ACALEPHS.

Thirty-three years ago, while examining the Museum of the Grand Duke of
Baden, in Carlsruhe, my attention was attracted by two slabs of limestone slate
from Solenhofen, the counterparts of one another, upon which a perfect impression
of a Discophorous Acaleph was distinctly visible. The impression made upon my
mind by the preservation, through countless ages, of an animal so soft as a jelly-fish,
was so vivid, that, though I have never seen those fossils since, I well remember
their general appearance. I regret the more, however, that I did not at the time
make a sketch of them, since to this day they have remained undescribed ; and,
so far as I know, no allusion to genuine fossil Acalephs is to be found anywhere
except in the first volume of this work (p. 24), where I mention the occurrence
of Meduss in the limestone of Solenhofen as indicative of the earliest period of
the existence of that class upon earth. At the time I saw these fossils, our
knowledge of the Acalephs was very scanty; few good illustrations existed; and
the works of Eschscholtz and his followers had not yet been published: so that, had
I even been conversant with every thing then known about this class of animals,
I could not have determined to what family they belonged. I earnestly hope
that some of the German naturalists, who of late have so largely contributed to
the advancement of our knowledge of that class, may be induced by this notice
to hunt up those fossils, and publish an accurate description of them with good
illustrations, that their close affinity to the numerous families now distinguished
among Acalephs may be ascertained. It is now a matter of great importance,
for it may afford indications of the connection between the living types of Aca-
lephs and their oldest representatives on earth; since it has been ascertained that
certain Coral stocks, a large number of which occur in the Paleozoic rocks, called
Tabulata by Milne-Edwards, and thus far referred to the class of Polyps, are
genuine Hydroid Acalephs, while a comparison of another type of Corals, called
Rugosa by Milne-Edwards, with the Tabulata, makes it highly probable that they
also are Acalephs, rather than Polyps.

As shown before, the Tabulata, unquestionably, are Hydroids. Direct evidence
to that effect has been obtaimed by an examination of the animal of Millepora ;
and as all the other Tabulata, both living and fossil, have the same structure of
their solid Polyparium as Millepora, it is evident that the whole group must be
considered as essentially acalephian. As far as the Polyparium of the Rugosa is

126 ACALEPHS IN GENERAL. Parr E

concerned, the evidence of their acalephian nature is hardly less strong than that
adduced for the acalephian affinities of the fossil Tabulata. The only difference
in the evidence is, that for the Tabulata we have the confirmation of these affinities
in the structure of the animal of one of their living members, while that evidence
is wanting for the Rugosa. But, as I have already stated, the Coral stock of
the Rugosa coincides so far with that of the Tabulata, that it is built up with
successive floors, extending uninterruptedly across the bottom of the whole cavity,
which was evidently occupied by the animal; while the Coral stock of all genuine
Polyps presents radiating partitions extending uninterruptedly from top to bottom
of the cavity occupied by the animal, and the horizontal floors that may exist,
stretch only from one of these radiating partitions to the other.

Now, if both Rugosa and Tabulata are Acalephian Corals, it is very desirable
that correct views of their affinities with the other Acalephs should be obtained,
in order to arrive at correct conclusions respecting the order of succession of the
Acalephs in past geological times, and of their connection, through the only known
fossil Discophorous Medusa, with the living representatives of the class.

Seanty as is our information of the fossil Acalephs beyond the knowledge of
the order of the succession of the Rugosa and the Tabulata, it is already highly
interesting, even with these imperfect ‘data, to institute comparisons between all
the members of the class respecting their order of succession. We have seen that
the Ctenophore are the highest order of Acalephs, and that the Discophors proper
are next to these in standing; while the Hydroids, including the naked-eyed Me-
dus and the Siphonophors, constitute the lowest order of the class. We have
seen, further, that among the Hydroids themselves, those in which the medusoid
elements prevail over the hydroid elements should be considered as the superior
ones. Taking, now, the only indication we have in Millepora as our guide to an
appreciation of the standing of the Tabulata among the Hydroids, it is plain, from
the circumstance that these Hydra communities form large, permanent Coral stocks,
living probably for centuries, that they have a character of inferiority as con-
trasted with the short-lived Hydro-Medusaria, and especially with those which
produce free Medusx in alternate generations. But if the Tabulata stand low in
the lowest order of Acalephs, we have in this fact a striking coincidence with
the character of the representatives of other classes in earlier periods. Since Crinoids
prevail in Paleozoic times, while free Star-fishes and Echinoids make their appear-
ance later ;—since Bryozoa and Brachiopods prevail during the same old_ periods,
while Lamellibranchiates become prominent in later geological epochs ;— since
Trilobites are the earliest Crustaceans, followed by gigantic Entomostraca, and

higher Crustacea appear only in the middle geological ages, ete, ete, we should

(=)

expect that Acalephs also should make their appearance with the representatives

Cuap. II. SUCCESSION OF ACALEPHS. 127

of their lowest order; and we have just seen that the Tabulata occupy an inferior
position in that lowest order.

Assuming that Rugosa are Hydroids also, the question of their standing in their
order is not difficult to determine, if we take into consideration the general char-
acter of the class, and its relations both to the class of Polyps and to that of
Echinoderms. I have already alluded to the analogy between the Hydroids and
the Polyps, and to that between the Ctenophore and Echinoderms. Starting from
this fact, let us see what are the elements of superiority and inferiority among
the Radiates, at the two ends of the type. In Polyps we distinguish two orders,
the Actinoids and the Haleyonoids. Taking their whole structure into consideration,
the Actinoids with their simple tentacles and the indefinite repetition of similar
parts in most of them, are, unquestionably, inferior to the Haleyonoids with their
eight-lobed tentacles and invariable eight spheromeres. Now, among Halcyonoids
there are no simple individuals: all the types of this order consist of compound
communities, while among the Actinoids we have both simple individuals and
compound communities. But here again it is among the compound communities that
we find the higher organic combinations: for certainly the Madrepores, with their
twelve tentacles, alternately larger and smaller, are superior to the Astraeoids, and
these again superior to the Actinioids; and that these latter are the lowest will
hardly be doubted, if we consider the absence of solid deposits in them, and the
equally characteristic absence of horizontal floors between their radiating partitions.
It will be conceded also that the Fungide stand next above them, since they
have a large number of tentacles, like the Actiniw, and only transverse beams
extending from one radiating partition to the other, instead of continuous floors
as in the Astraoids, which stand above them on that account, as well as on account
of their limited number of tentacles. The Madrepores, unquestionably, are the
highest among the Actinoids, since they not only present a limited number of
tentacles, but a number which is always constant, and, in addition to this, another
higher combination of structural features, arising from an alternation of larger and
smaller tentacles and a marked one-sidedness of their calycles.

It is thus plain that the gradation among Actinoids,— that is, the higher and
higher rank they occupy when compared with one another,— stands in direct ratio
to their complication and to their combination into communities, and in an inverse
ratio to their individual independence. The simple Polyps, such as Actinie, are the
lowest; the Fungide, among which there are simple types, such as the genus
Fungia proper, are next in rank; the Astraoids and allied families, which form
always compound communities, with a reduced but more definite number of tenta-
cles, come next; and the Madrepores, forming among the Actinoids the most compli-
cated communities, stand highest,

128 ACALEPHS IN GENERAL. Parr I.

There is still another feature among Polyps, which ought to be considered in
this connection. Not only do the Haleyonoids, the higher order among Polyps,
form compound communities in all their representatives, but we find that these
compound communities tend to acquire a marked individual imdependence, which
is fully reached in those types of this order which, like Veretilluwm, Renilla, and
Pennatula, move about freely, and these are the highest among the Haleyonoids.
A similar tendency to individualization of communities is also observed in the
highest Actinoids; for some Madrepores not only form complicated communities,
but exhibit, at the top of their branches, an individual which, though forming
part of the community, is larger than all the lateral individuals, and gives, as it
were, individuality to each branch.

With these facts before us, it will not be difficult to determine the relative
standing of the Rugosa and Tabulata. The Rugosa differ from the Tabulata in
having a considerable number of representatives which are simple individuals; or,
when they form communities, these are a loose aggregation of a few individuals
maintaining a certain degree of independence: we never find among them communities
formed of innumerable closely combined individuals, such as occur among Tabulata,
in many of which there exists a direct communication between adjoining individuals
through pores in their walls. I am, therefore, inclined to consider the Rugosa as
inferior to the Tabulata; and their prevalence in the oldest rocks and their early
extinction in geological times, while Tabulata are continued to this day, confirm
this view. The Rugosa seem to me to stand in the same relation to the Lucer-
narioids among Hydroids, as the Actinie stand to the Fungide among genuine
Polyps. And here, again, we have a remarkable analogy between the two types,
in the circumstance that Fungide are the oldest genuine Corals known, as the
Rugosa are the oldest type among Hydroids.

All this is in perfect accordance with the character of the higher Acalephs.
As we have seen before, the Ctenophorz are analogous to Echinoderms ; but
Echinoderms have reached a degree in organie complication in which individuality,
as such, becomes a character of superiority. In conformity with this analogy, we
find that all Ctenophorse are free idividuals, and so are the Discophore also ;
while the free naked-eyed Meduse arising from Hydroids occupy, in that respect,
an intermediate position between the higher Acalephs and the lower Hydroids,
which form large and highly complicated communities, and bear, in their perfect
state, sessile Medusx buds only. I do not see that any objection can be made
to the rank here assigned to the Acalephs in general. It seems to me to be
determined by their whole structure, as well as by their mode of development,
and must be considered as the true expression of their natural affinities, if the

lowest Hydroids are those in which the hydroid elements prevail over the me-

Cuap. I. CLASSIFICATIONS OF ACALEPHS. 129

dusoid elements, and if free Meduse born from Hydroids are inferior to the Dis
cophore proper, and these, again, inferior to the Ctenophore. It is certainly a
most striking circumstance, that the only fossil free Acalephs known should be a
Discophorous Medusa, for it is the type we should naturally expect to follow
Hydroids in course of time, when it has once been ascertained that the earliest
representatives of all classes are either the lowest of their type, or embryonic in
their character or synthetic in the complication of their structure, as I have shown
in the first volume of this work (pp. 107-122).

Some general remarks upon the geographical distribution of the Acalephs should
naturally find a place here; but it is so indispensable to a true appreciation of
the mode of distribution of animals, that their types should be correctly referred
to their respective natural divisions, that, before considering the classification of
the Acalephs in its details down to the genera and species, no accurate picture
of their geographical range and mutual relations in space can fairly be presented.
I must, therefore, postpone the consideration of this subject to another part of this
monograph, when, in addition to the information already collected, I shall be able
to avail myself of the investigations made by my son upon the Acalephs of the
Pacific coast of North America. It is a matter of great interest to me thus to
have the means of comparing critically the Acalephs of the temperate zone, not
only of the two sides of the Atlantic, but also of the Pacific, and to be able to
complete, in a measure, the statements of Brandt relating to the Discophorous
Medusx collected by Mertens, most of which were described, after his death, from

the drawings made by the naturalists of the Seniavin.

SS KiCeT LL OmNoe TX.
CLASSIFICATIONS OF ACALEPHS.

The improvements in the classification of the Acalephs have been the consequence
of a gradual and successive expansion of the boundaries of that class, resulting
from the recognition of Acalephian characters in animals at first not suspected to
be at all related to them. The class, as such, has not been at once recognized
as a natural group, im consequence of the want of such a striking similarity of its
members, as is observed, for imstance, among Birds or Insects; but it has grown
by successive additions, forced, as it were, by internal evidence upon the notice of
naturalists, and slowly acquired, at long intervals, by laborious, successive steps.
However, the very character of this gradual progress renders the study of the

v

VOL. III. 17

130 ACALEPHS IN GENERAL. Parr I.

classifications of Acalephs the more interesting to the philosophical student; and a
comparison of these different arrangements may teach us how to proceed in our
attempts to improve the classification of animals generally.

Though, from the beginning of his brilliant career, Cuvier had tured his
attention to the study of the Acalephs, and published his anatomy of Rhizostoma
long before the * Régne animal” appeared, his “Tableau ¢lémentaire,” published in
1798, contains nothing of importance upon these animals. It was Lamarck who

took the lead in their systematic arrangement.

CLASSIFICATION OF LAMARCK, 1801 and 1816.

In his “Systeme des Animaux sans Vertibres,” published in 1801, Lamarck unites the Acalephs
and Echinoderms in one and the same class under the name of Raprarmres, separating them, however,
as two distinct orders of that class, as Radiatres Echinodermes and Radiaires Mollasses. The second order,
which corresponds to the Acalephs, embraces the following genera: Medusa, Rhizostoma, Beroe, Lucer-
naria, Porpita, Velella, Physalia, Thalis, and Physophora. The Hydroids proper are referred to the
class of Polyps. In proposing this arrangement, Lamarck made the first step towards recognizing the
natural limits of the class of Acalephs.

In the “Tlistoire naturelle des Animaux sans Verttbres,” published from 1815 to 1822, he adopts the

same general classification of these animals; but subdivides the Acalephs in the following manner :—

Ist Section, Raprarres ANoMALES:—1° Stephanomia. 2° Cestum, Callianira, Beroe, Noctiluca,
Lucernaria. 5° Physophora, Rhizophysa, Physalia, Velella, and Porpita.

2d Section. Raprarres Mépusarres :—1° Eudora, Phoreynia, Carybdea, /Equorea, Callirhoe, Dianea.
2° Ephyra, Obelia, Cassiopea, Aurelia, Cephea, Cyanea.

The classification of Lamarck is evidently based upon a mere general appreciation
of the relationship of the animals considered by him in detail. Comparative anatomy
was not yet sufficiently advanced to furnish definite characteristics of the different
groups adopted by the systematic writers of that period. The reunion of the
Acalephs and Echinoderms as one class, for instance, is undoubtedly a great exag-
geration of their affinity; but it marks, nevertheless, an important progress in
the natural history of the lower animals, since such a combination could only be
proposed by one who had already freed himself, at least partially, from the impression
that the presence or absence of a solid frame was an essential character of these
animals, and who began to perceive that the plan of structure, or at least the
degrees of complication of that structure, was of higher importance, in a natural
classification, than such secondary features. In this connection, it is important to
remember that Lamarck was one of the naturalists who knew the Echinoderms
best, and that he never could have united the Meduse with them, had he not
perceived the structural relation which forever will unite into one and the same

great division such animals as Aurelia and Scutella.

Cuar. II. CLASSIFICATIONS OF ACALEPHS. 131

The naturalists who have known the Acalephs best during the first quarter of
this century are unquestionably Péron and LeSueur, and their publications are, to
this day, among the most important upon all the members of this class, with the
sole exception of the Hydroids.

CLASSIFICATION OF THE MEDUSA PROPER BY PERON AND LESUEUR, 1809.

Though Péron and LeSueur have contributed, more extensively than any other naturalists of the
beginning of this century, to the advancement of our knowledge of the Acalephs, their systematic efforts
were limited to the classification of the Meduse proper, of which they have published the following
diagram in the 14th vol. of the Annales du Muséum, 1809, 4to. :—

Premiére division. Méduses agastriques.
a. Non pédoneulées.
+ Non tentaculées. Eudora.
++ Tentaculées. Berenix.
b. Pédonculées.
+ Non tentaculées. Orythia, Favonia.
++ Tentaculées. Lymnorea, Geryonia.
Seconde division. Meéduses gastriques.
Premitre section. Gastriques monostomes.
a. Non pédonculées.
+ Non _ brachidées.
@ Non tentaculées. Carybdea, Phoreynia, Eulimenes.
® ® Tentaculées. Ee quorea, Foveolia, Pegasia.
++ Brachidées.
@ Non tentaculées. Callirhoe.
b. Pédonculées.
+ Non brachidées. Non représentées.
++ Brachidées.
@® Non tentaculées. Melitea, Evagora.
@® ® Tentaculées. Oceania, Pelagia, Aglaura, Melicerta.
Seconde section. Gastriques Polystomes.
a. Non pédonculées.
+ Non brachidées.
@® Non tentaculées. Euryale, Ephyra.
® ® Tentaculées. Obelia.
++ Brachidées.
@® Non tentaculées. Ocyroe, Cassiopea.
@® @® Tentaculées. Aurelia.
b. Pédonculées.
+ Non brachidées.
++ Brachidées. Non représentées.
@® Non tentaculées. Cephea, Rhizostoma.
® ® Tentaculées. Cyanea, Chrysaora.

132 ACALEPHS IN GENERAL. Parr I.

The peculiar form of the diagram of Péron and LeSueur recalls the character
of the classifications generally adopted in France at the time of its publication,
consisting in dichotomic divisions and subdivisions, providing even for the position
of unknown representatives of the methodical framework, and exhibiting more
ingenuity than insight into the nature of true classifications. The chief object
naturalists had in view in devising such arrangements was rather to facilitate the
identification of genera and species, than to ascertain their natural relations. At
that time Cuvier had not published his views upon classification; so that the idea
of the subordmation of characters, so fruitful in important results, did not yet
pervade the systematic works of the beginning of this century.

It is much to be regretted, that the very extensive investigations of Péron and
LeSueur, and the many admirable drawings of Acalephs made from nature by the
latter durmg his travels in every part of the world, should have been but partially

published, and should have remained unknown to most naturalists outside of France.

CLASSIFICATION OF THE SIPHONOPHORA BY LESUEUR.

Lesson, in his “ Histoire naturelle des Zoophytes, Acalephes,” has published a classification of the
Siphonophore by LeSueur, the original of which I have been unable to obtain. LeSueur calls these
animals Radiaires mollasses composcés, and divides them in the following manner :—

Ist Group. Jsolated: 1° Porpita and Velella. 2° Rhizophysa and Physalia.
United: 1° Physophora and Stephanomia. 2° Protomedea and Amphiroa.

From the place this paper occupies in Lesson’s account, I am induced to believe that it must have
been drawn up about the time of the publication of the classification of the Meduse proper by Péron

and LeSueur.

Cuvier’s influence upon the progress of the natural history of the Acalephs is
not to be measured by the amount of special information he has contributed to
the stock of our knowledge of these animals, but rather by the spirit he has
infused into the study of Natural History. His recognition of the four primary
groups of aninals, based upon four different plans of structure, not only justified
the separation of the Acalephs as a class, but established at the same time their
true relation to the Kchimoderms and Polyps in one great natural division: and
though Cuvier made the mistake of uniting with them the Helminths and Infusoria,
on account of the simplicity of their structure, he nevertheless disclosed the princi-
ple upon which their classification is finally to be settled; and the mistake he made
on that oceasion was only the result of his own departure from that very principle,
when he allowed the consideration of the simplicity of the structure of the Intestinal

Worms and of the Infusoria to overrule that of the plan of their structure.

Cuar. IL. CLASSIFICATIONS OF ACALEPHS. 133

CLASSIFICATION OF CUVIER, 1817 and 1830.

It was Cuvier who first separated the Acalephs as a distinct class, in the first edition of the

“Regne animal,” published in 1817. There he divides these animals into three orders, as follows :—

Ist Order. Fixep Acaterus:— Actinia, Zoanthus, Lucernaria.

2d Order. Free AcALterpHs:— Meduse: Medusa, A®quorea, Phoreynia, Foveolia, Pelagia; Cyanea,
Rhizostoma, Cassiopea; Geryonia, Lymnorea, Favonia, Orythia, Berenice, Eudora; Caryb-
dea; Beroe, Callianira, Cestum ;— Diphyes ;— Porpita, Velella.

3d Order. Hyprostatic AcALEPHS : — Physalia, Physophora, Rhizophysa, Stephanomia.

The HUydroids are referred to the class of Polyps; and some genuine Polyps, Actinia, and Zoanthus
are ranked among the Acalephs.

In the second edition of that work, published in 1830, Cuvier, excluding now the Actiniw from this
class, but still leaving the Hydroids out of consideration, admits the following arrangement for the genuine
Acalephs : —

Ist Order. Siete AcaLerus:— Medusa, /®quorea, Pelagia, Cyanea, Rhizostoma, Cephea, Cassiopea.
— Astomes: Lymnorea, Favyonia, Geryonia, Orythia, Berenice, Eudora. — Carybdea. —
Beroe, Idya, Doliolum, Callianira, Janira, Alcinoe, Ocyroe, Cestum.— Porpita, Velella.

2d Order. Hyprostaric AcAaLerns:— Physalia, Physophora, Hippopus, Capulites, Racemides, Rhi-

zophysa, Stephanomia.— Diphyes, Calpe, Abyla, Cuboides, Navicule.

A glance at the works of Schweigger is sufficient to satisfy any one that his
investigations are to be valued chiefly for their minuteness and accuracy, and that
his systematic arrangement of the lower animals is not the result of matured
principles, or deep insight into their affinities.

CLASSIFICATION OF SCHWEIGGER, 1820.

Schweigger was one of the naturalists who knew the soft-bodied Invertebrates best, during the first
quarter of this century. In his extensive journeys on the coast of the Mediterranean, he had collected
vast stores of materials to illustrate their natural history, and his “ Handbuch der Naturgeschichte der
skelettlosen ungegliederten Thiere, Leipzig, 1820, 1 vol. 8vo.” is chiefly based upon original investigations ;
wherefore I allude to it here, even though he has done nothing to improve the classification of the
Acalephs: but he gives the best summary of their structure for that period. The animals now
included in the type of Radiata are referred by him to three classes, —the Zoophytes, the Acalephs, and
the Radiata; and under the last name the Echinoderms are combined with Actinia, Zoanthus, and Lucer-
naria. To the Zoophytes he refers the Hydroids and Polyps, with which he also associates Infusoria ;
but he judiciously removes from them the Ascidians, which he considers as Mollusks. The Crinoids he
rightly regards as Echinoderms allied to Comatula, and the Corallinw as Algw.

The Acalephs are arranged nearly as in the system of Lamarck.

I. Stephanomia — Physophora — Physalia, Velella, Porpita— Cestum, Callianira, Diphyes, Beroe,
Noctiluca.

Il. Medusa, Lin., and subdivided as in Péron and LeSueur.

154 ACALEPHS IN GENERAL. Parr I.

Goldfuss was one of the most eminent zovlogists of the German school of
Physio-philosophers. | Adopting the general view of Oken, that the animal kingdom
is an organic whole, representing as it were the individualized parts of the highest
living beings, he considers the classes and their subdivisions as determined by the
nature of the organs through which animal life is maintained. In the special
parts of his Text-book he displays an extensive acquaintance with the whole animal
kingdom, and suggests many important improvements over the classifications of his
predecessors. His arrangement of the Acalephs especially, discloses a better ap-

preciation of their affinities than any previous system.

CLASSIFICATION OF GOLDFUSS, 1820.

In his “Handbuch der Zoologie,” published in 1820, Goldfuss unites into one class, under the name
of Protozoa, the following groups of animals, which he considers as orders of that class: 1° Infusoria,
°

2° Phytozoa, 3° Lithozoa, 4° Medusinw. This fourth order embraces the Acalephs proper, which are

divided into the following families : —

Ist Family. 2Qquorem: Eudora, Ephyra, /E2quorea, Orythia, Oceania, Cephea, Pelagia, Cassiopea,
Callirhoe.

2d Family. Berors: Idia, Beroe, Cestum, Callianira.

3d Family. Puysornora: Rhizophysa, Physophora, Stephanomia, Arethusa.

4th Family. Porprre: Porpita, Velella.

The Hydroids are divided among the orders Infusoria and Phytozoa, and the Coralline and Crinoids
among the Lithozoa. The separation of the Beroes and Porpite from the Medusw proper is a marked

improvement over the classification of Cuvier.

As naturalist of the expedition of the Rurick around the world, Chamisso had
excellent opportunities for studying the Acalephs, and his special investigations of
many new forms are truly valuable. His paper upon Salpa, also the result of
this voyage, is the most important contribution of the poet-naturalist to the advance-
ment of science. In working up his materials relating to the Acalephs, he was

assisted by his friend Eysenhardt, himself the author of an excellent paper upon

the anatomy of Rhizostoma.

CLASSIFICATION OF CHAMISSO AND EYSENHARDT, 1821.

Mepus®. Vesiculares: Physalia, Physophora, Rhizophysa.
Medusx proper: Rhizostoma, Cephea, Pelagia, Cyanea, Aurelia, A%quorea.
Vibrantes: Beroe, Callianira, Cestum, Appendicularia.
Chondrophore: Velella, Porpita.

Anomale: Diphyes, Stephanomia.

This classification is a mere reproduction of that of Goldfuss, with a change of names and an

injudicious separation of Stephanomia and Diphyes from the other Siphonophore.

Cuap. II. CLASSIFICATIONS OF ACALEPHS. 135

Were not Latreille the first entomologist of all ages, and had he not shown himself
a master in describing species, characterizing genera, defining natural families, and
improving generally the classification of Insects, it would hardly be worth our
while to consider his attempt at classifying the Acalephs. But this attempt of
his may serve as a warning against the temptation, too frequently indulged by
eminent men, to express opinions upon matters with which they are not familiar,
or to cover their ignorance by an easy display of high-sounding but empty words.
On looking at the diagram of Latreille’s classification of the Acalephs, it might
seem, at first sight, that he presents in it a new and original arrangement of
these animals. The names Poecilomorpha and Cyclomorpha, with which he designates
the two orders into which the class is divided, are certainly new to science, but
they are utterly useless and superfluous, inasmuch as they neither represent a new
view nor a new combination in the classification of these animals, and are in no
way better than those which had already been proposed by Lamarck and Cuvier
for the very same division. The limitation of the families is, if possible, worse,
and the names applied to them are liable to the same objections as those of

the orders.
CLASSIFICATION OF LATREILLE, 1825.

The views of Latreille upon the affinities of the Acalephs were published in his “ Familles natu-
relles du Régne animal,” Paris, 1825, 1 vol. 8vo. Adopting the class of Acalephs as circumscribed by

Cuvier, he divides them into two orders and six families.

Ist Order. Porcttomorrma, corresponding to the Radiaires Mollasses Anomales of Lamarck, exclusive
of Lucernaria.
Ist Family. Ciliata: Beroe, Callianira, Cestum, Diphyes.
2d Family. Papyracea: Porpita, Velella, Noctiluca.
3d Family. UHydrostatica: Physalia, Physophora, Rhizophysa, Stephanomia.
2d Order. CycLromorra, corresponding to the Radiaires Mollasses Médusaires of Lamarck.
Ist Family. Monocotyla: Medusa, Aquorea, Foveolia, Phorcynia.
2d Family. Polycotyla: Cyanea; Rhizostoma.
3d Family. Acotyla: Lymnorea, Favonia, Geryonia; Berenice, Eudora, Carybdea.

The families of the Cyclomorpha are entirely artificial, and in no way express the natural affinities
of the animals; and the families of the Poecilomorpha are borrowed from other writers, —the name of
Beroes, proposed by Goldfuss, being changed to Ciliata, that of Porpite to Papyracea, and the name
Hydrostatica retained from Cuvier. The Hydroids are referred partly to the class of Polyps, in the tribe

Vaginiformia, and partly to his class Helianthoidea, which embraces Actinia, Zoanthus, and Lucernaria.

The animals belonging to the class of Acalephs are so peculiarly delicate, so
difficult to handle, and so perishable, that the circumstances under which they may

be studied, form almost as important an element in their investigation, as the aptitude

136 ACALEPHS IN GENERAL. Parr I.

of the observer to trace their history. But when the naturalist who devotes
years to their study is not only an eminent physician, but at the same time a
minute, accurate, and philosophical observer, pursuing his task under the most
favorable circumstances, great results may be expected. This was the case of
Eschscholtz, who, during two voyages around the world, applied himself chiefly to
the investigation of these animals, and had better opportunities for studying their
various types in their natural element than any other man had enjoyed before,
not even excepting Péron and LeSueur. Aside from the large amount of infor-
mation it contains, the “System der Acalephen” of Eschscholtz is a model work
for the manner in which the subject is treated. Full, minute, explicit, decided,
where he speaks from personal observation; unpretending, candid, and fair, where
he alludes to the investigations of other distinguished authors; cautious and reserved
where he has reasons to question the correctness of the statements of others, —he
secured the admiration of his contemporaries and the gratitude of his followers,

and those who have known him lament his early loss.

CLASSIFICATION OF ESCHSCHOLTZ, 1829.

The limits of the class of Acalephs, as circumscribed by Eschscholtz in 1829, coincide with those
assigned to it by Cuvier from the beginning, with the only exception that the Actiniw are excluded.
The Hydroids are entirely ignored by Eschscholtz, as if they had no relations to the Acalephs. He
divides, for the first time, this class into three natural orders, and distinguishes a number of natural
families. All later classifications of the Acalephs are mere modifications or improvements of that of

Hschscholtz.

Ist Order. Crrnornore.
Ist Family. Callianiridw, with three genera: Cestum, Cydippe, Callianira.
2d Family. Mnemiidw: Eucharis, Mnemia, Calymma, Axiotima.
53d Family. Beroidw: Beroe, Medea, Pandora.
2d Order. Discopnor”.
First Division. Discophore phanerocarpe.
Ist Family. Rhizostomidw: Cassiopea, Rhizostoma, Cephea.
2d Family. Medusidw: Sthenonia, Medusa, Cyanea, Pelagia, Chrysaora, Ephyva.
Second Division. Discophore eryptocarpe.
Ist Family. Geryonidw: Geryonia, Dianwa, Linuche, Saphenia, Eirene, Lymnorea, Favonia.
2d Family. Oceanidw: Oceania, Callirhoe, Taumantias, Tima, Cyteis, Melicertum, Phor-
eynia.
3d Family. A quoridw: /quorea, Mesonema, gina, Cunina, Eurybia, Polyxena.
4th Family. Berenicidw: Eudora, Berenice.
5d Order. SrpHonopuor®.
Ist Family. Diphyide: Eudoxia, Erswa, Aglaisma, Abyla, Diphyes, Cymba.
2d Family. Physophoridw: Apolemia, Physophora, Hippopodius, Rhizophysa, Epibulia,
Agalma, Athorybia, Stephanomia, Discolabe, Physalia.

3d Family. Velellidw: Rataria, Velella, Porpita.
J }

Crap. I. CLASSIFICATIONS OF ACALEPHS. 137

CLASSIFICATION OF DeBLAINVILLE, 1830-1854.

DeBlainville has introduced great modifications in the classification of the Acalephs, part of which
he removed to the Mollusks. The following diagram gives a general idea of his views respecting the

classification of the lower animals :—

Zooruytes. 1. False Zoophytes, to be referred to the Mollusks: Physogrades and Diphyes, or
perhaps to the Holothurians: Ciliobranches.
& se se a to the Articulates. Entozoa.
« « forming a heterogeneous assemblage of very small animals. Infusoria.
2. Genuine Zoophytes. Actinozoaria, containing 5 Classes: Cirrhodermaria, Arachno-
dermaria, Zoantharia, Polypiaria, and Zoophytaria.
Amophozoaria: Spongix.
3. False Zoophytes, to be referred to the vegetable kingdom: Corallinw, Nematozoa, Psy-
chodiaria.

S us neither animals nor plants. Zodsperms and Nullipores.

It appears from this sketch of DeBlainville’s system, that he considers the Siphonophore of Esch-
scholtz as Mollusks, and the Ctenophore either as Mollusks or Echinoderms. The other Acalephs he

calls ARACHNODERMARIA, and divides them in the following manner :—

Ist Order. PuLmoGrapa. :

Ist Section. Simple Pulmogrades: Eudora, Ephyra, Phoreynia, Eulimenes, Carybdea, Euryale.

2d Section. Zentaculate Pulmogrades: Berenice, Aiquorea, Mesonema, Polyxena, /Mgina,
Cunina, Faveolia, Eurybia, Pegasia, Obelia.

3d Section. Subproboscidate Pulmogrades: Oceania, Aglaura, Melicerta, Cytais, Thaumantias,
Tima, Campanella.

4th Section. Proboseidate Pulmogrades: Orythia, Geryonia, Saphenia, Dianea, Linuche, Favonia,
Lymnorea, Sthenonia.

5th Section. Brachiate and pedunculate Pulmogrades: Ocyroe, Cassiopea, Aurelia, Melitea,
Evagora, Cephea, Rhizostoma, Chrysaora, Pelagia.

2d Order. Cirruograpa. Velella, Rataria, Porpita.

The Hydroids are referred to the class of Polypiaria. An earlier diagram of these animals was
published by DeBlainville in 1822, in his work “De V’Organisation des Animaux.” See vol. 1 of this
work, p. 198.

DeBlainville did not enjoy the same favorable opportunities for the study of
the Acalephs as Eschscholtz; and yet he is the author of an original classification
of these animals, which differs entirely from those of his predecessors. Eminent
as a closet student, and deeply imbued with the conviction that Zoblogy required
great reforms, and that methods may supply the deficiency of actual knowledge,
he never hesitated in introducing great changes in the classification of the animal
kingdom whenever a suggestion was presented to his mind, and without awaiting

the opportunity for making the necessary investigations to test its accuracy and
VOL, Il. 18

138 ACALEPHS IN GENERAL. Parr) E

correctness. His views respecting some of the animals referred to the class of
Acalephs, which he would remove from it, exemplify this disposition of his; and
the many unnecessary changes which he made in the nomenclature of the lower
animals are another evidence of that unhappy propensity. There are few examples
of a more appropriate name for a new class in the animal kingdom, than that of
Acalephex, selected by Cuvier to designate, in general, all the animals allied to
those known by the ancients under that name. It was at once adopted by all
naturalists. The most important work ever published upon this class, as a whole,
bears that name upon its very title; and yet DeBlainville does not hesitate to
substitute for it a new, ill-sounding name, Arachnodermaria, the meaning of which,
if it suggests any thing, recalls affinities with another type of animals, with which
the Acalephs have no affinity.

CLASSIFICATION OF OKEN, 1835.

The views held by Oken upon classification and the affinities of animals have already been presented
in my first volume (p. 212). It remains only to give a special account of his arrangement of the animals
belonging to the type of Radiata. Oken does not unite the Echinoderms with the other radiated animals;
but, founding upon the manner in which the parts of their solid envelope are movably united, and also
upon the worm-like form of the Holothuriw, unites them with the Articulates, in one and the same class
with the Worms, as a distinct order of that class. The Acalephs are united, with the Polyps and
Tnfusoria, into another primary division, the Jntestinal animals, divided into three classes: the Infusoria,
as Stomach-animals; the Polyps, as Intestine-animals; and the Acalephs, as Lacteal-animals. The class

of Acalephs is itself subdivided into three orders :—

Ist Order. The IJnfusorial Acalephs, or Siphonophore.
1st Tribe. Diphyes, Calpe, Abyla, Cymba, Aglaisma, Eudoxia.
2d Tribe. Rhizophysa, Stephanomia, — Physophora, — Physalia.
3d Tribe. Porpita, Lithactinia, Rataria, Velella.

2d Order. The Polypotd Acalephs, or Ctenophore.
Ist Tribe. Eucharis, Cydippe,— Idya, — Medea, Pandora.
2d Tribe. Mnemia, Callianira, Cestum.
3d Tribe. Axiotima, Calymma, Alcinoe, Ocyrhoe.

3d Order. The Acalephs proper, or Discophore.
Ist Tribe. Eudora, Berenice, — Geryonia, — Rhizostoma, Cassiopea, Cephea.
2d Tribe. Phoreynia, Melicertum, Thaumantias, Oceania, Callirhoe — AXquorea, — /Egina,

Cunina, Polyxenia.
3d Tribe. © Ephyra, — Aurelia, — Pelagia, Chrysaora, Cyanea.
This classification may be considered as a remodelling of Eschscholtz’s, adapted to the views of the

author respecting the manner in which the structure of the higher animals is represented by independent

beings, — recalling, as it were, the different systems of their organs.

Cuap. II. CLASSIFICATIONS OF ACALEPHS. 139

The history of the Acalephs has received very important accessions from the
investigations of Mertens, who was naturalist in the Russian exploring expedition
of the Seniavin. Unfortunately he died before having published his labors; and
the only paper he left so far finished as to have appeared under his name is
his “Beobachtungen und Untersuchungen iiber die Beroeartigen Akalephen,” in 2d
vol. 6° sér., Mém. Acad. Scien. Pétersbourg. Brandt, who had superintended the
publication of this paper, afterwards worked up the materials left by Mertens
relating to the other families of the Acalephs, and gave a full account of them
in the “Ausfiihrliche Beschreibung der von C. H. Mertens, auf seer Weltumse-
gelung beobachteten Schirmquallen,” 4° vol. Mém. Acad. Se. Pétersbourg. The value
of Mertens’s contributions to the natural history of these animals may be inferred
from the simple fact, that Brandt, without having seen the Acalephs he describes,
could make elaborate descriptions of them merely from the drawings and scanty
notes found among Mertens’s papers. The fact is, the drawings of Mertens, and
those of his travelling companion, Professor Postels, are among the most accurate
and beautiful representations of Acalephs thus far published, and constitute by
themselves an ample atlas of the whole order of Discophore.

CLASSIFICATION OF BRANDT, 1833.

Brandt, in his “ Prodromus Descriptionis animalium ab H. Mertensio observatorum,” published in the
Memoirs of the Imperial Academy of Sciences of St. Petersburg, in 1835, has the following classification
yi 8 g

of the Acalephs, exclusive of the Beroids :—

DISCOPHORZ. Mepusip#.
Monostome.
Oceanidw: Circe, Conis.
ZEquoridx : Equorea, Stomobrachiota, Mesonema, Zygodactyla, /Eginopsis, Polyxenia.
Medusidw: Phacellophora; Cyanea and Cyaneopsis; Aurelia: Monocraspedon, Diplocraspedon ;
Pelagia, Chrysaora.
Polystome.
Geryonidex: Geryonia, Proboscidactyla, Hippocrene.
Rhizostomide : Cassiopea.
Iucerte sedis.
Berenicide: Staurophora.
SIPHONOPHORE.
Diphyidx: Diphyes.
Physophoridx: Physophora.
Rhizophysidw: Epibulia: Macrosoma, Brachysoma.
Agalmide: Agalma.
Anthophysidw: Athorybia, Anthophysa, Apolemiopsis.
Physalide: Physalia: Salacia, Alophota.

Velellidew: Veleline: Velella, Aristerodexia; Porpitine: Porpita.

140 ACALEPHS IN GENERAL. Parr I.

Lesson is one of the naturalists who had the best opportunities for observing
the Acalephs. Embarked with Garnot on board the Coquille, he made the voyage
around the world with Captain Duperrey, and prepared many beautiful illustrations
of Acalephs for the zoological atlas of that expedition. On his return he made
the most extensive collection of drawings of these animals ever brought together,
with the intention of publishing a complete Iconography of this class; but the
magnitude of the undertaking prevented its execution, and nothing was published
but a “Prodrome dune Monographie des Méduses,” with a short notice of two
hundred and thirty-seven species, arranged in seventy genera. Some of the plates
were afterwards introduced in the “Centurie Zoologique,” and the text appeared,
in 1845, among the “Suites a Buffon,’ under the title of “Histoire naturelle des
Zoophytes, Acaléphes.” To this day, this is the chief work of reference for the study
of the Acalephs; but it is much to be regretted that it is neither methodical in
its plan nor critical in its details. It is rather a compilation than an original work ;
and yet it contains much that cannot be found elsewhere. Edw. Forbes has the
following just but severe criticism of this extraordmary production: “This work is
one of the most useful, and yet one of the most provoking, in its department of
Natural History: useful, because it brings together, verbatim, every thing that has
been written upon the Meduse in France ; provoking, because every attempt in it
at an arrangement or digest of the matter so collected serves only to make the
obscure more obscure and the crude more crude. It is executed without any
judgment, though with considerable industry. Of what has been done outside of

France it is a most imperfect account.” !

CLASSIFICATION OF LESSON, 1843.

Like his predecessors, Lesson does not allude to the Hydroids in connection with the Acalephs.

Ist Family. 3JEROIDER.

Ist Division. Crlobranches or Iripteres.
Ist Tribe. Cestoidew: Cestum, Lemniscus.
2d Tribe. Callianirw: Callianira, Chiaia, Polyptera, Mnemia, Bucephalon, Bolina.
3d Tribe. Leucothoew: Leucothoea.
4th Tribe. Calymmew: Calymma, Eucharis, Alcinoe, LeSueuria, Axiotima.
5th Tribe. Neisidw: Neis.
6th Tribe. Ocyroew: Ocyroe.
7th Tribe. Cydippxw: Mertensia, Anais, Eschscholtzia, Janira, Cydippe.
8th Tribe. Berow: Beroe, Idya, Medea, Cydalisia, Pandora.

2d Division. <Acils.

False Beroids: Galeolaria, Doliolum, Rosacea, Suleuleolaria, Praia, Noctiluca, Appendicularia.

1 Epw. Forres. A monograph of the British Naked-eyed Meduswe, London, 1818, p. 98.

Cnap. I. CLASSIFICATIONS OF ACALEPHS. 141

2d Family. Mepusm.
Ist Group. Meduse without proboscis.
Ist Tribe. Eudore: Discus, Eudora, Eulimenes, Phorcynia, Pileola, Epomis, Ephyra.
2d Tribe. Carybdew: Carybdea, Obelia.
3d Tribe. Marsupiale: Marsupialis, Bursarius, Mitra, Eurybia, Cyteis, Campanella, Seyphis.
4th Tribe. Nucleifere: Turris, Circe, Conis, Tiara, Tholus, Pandea, Bougainvillia, Pro-
boseidactyla, Melicertum, Aglaura, Laodicea, Microstoma.
oth Tribe. Berenicidw: Berenix, Staurophora.
2d Group. Oceanides, or genuine Meduse with a round mouth but no proboscis.
Ist Tribe. Thalassanthe: Pegasia, Faveolia, Cunina, gina, /Eginopsis.
2d Tribe. Ei quoride: quorea, Polyxenia.
3d Tribe. Oceanide: Stomobrachiota, Mesonema, Oceania, Patera.
3d Group. Agaricine Meduse, or Meduse with proboscis: Melicerta, Saphenia, Dianea, Orythia,
Geryonia, Liriope, Xanthea, Sarsia, Tima, Thaumantias, Linuche, Usous, Lym-
norea, Favonia.
4th Group. Rhizostomee, or Meduse with a central peduncle.
Ist Tribes Medusidxw, or Meduse monostomee.
Ist Section. Without tentacles around the disc: Biblis, Melitea, Evagora, Salamis, Pha-
cellophora.
2d Section. With tentacles around the dise: Callirhoe, Sthenonia, Aurelia, Claustra,
Cyanea, Cyaneopsis, Pelagia, Chrysaora.
2d Tribe. Rhizostomide, or Medusw Polystomee: Ocyroe, Cassiopea, Cephea, Rhi-
zostoma.
3d Family. Dipayip x.
Ist Tribe. Polygastricw: Diphyes, Heterodiphyes; Calpe, Abyla.
2d Tribe. Monogastriew: Microdiphyes, Cymba, Enneagonum, Cuboides, Cucubalus, Cu-
cullus, Eudoxia, Amphiroa, Ersea, Aglaisma.
4th Family. PoLtyromm®, or PLEeTHOSOM”.
Ist Tribe. Plethosomw: Plethosoma, Polytomus, Hippopodius, Elephantopes, Racemis.
2d Tribe. Stephanomiw: Stephanomia, Sarcoconus, Strobila.
Sth Family. PuysopnHorm.
Ist Tribe. Rhizophysx: Rhizophysa, Brachysoma.
2d Tribe. Discolabw: Discolabe, Diphysa.
dd Tribe. Angele: Angela.
4th Tribe. Athorybiw: Athorybia, Anthophysa.
oth Tribe. Physophorw: Physophora.
6th Tribe. Agalmaw: Agalma.
7th Tribe. Apolemiw: Apolemia, Apolemiopsis.
6th Family. PHysaLtte: Physalia.
7th Family. VeLeLtia: Velella, Rataria.
8th Family. Porpirx: Porpita, Ratis, Acies.

A sketch of this classification was already published in 1835 (Proceed. Zool. Soc. London, 1835, Part
Ill. p. 2), and a special paper upon the Beroids, in Ann. Se. Nat. 2de sér. 1837, vol. 5. The above

diagram gives the classification of Lesson, as it appears in his last work, in the Suites & Buffon.

142 ACALEPHS IN GENERAL. Payee

There is hardly a branch of Natural History to which Edw. Forbes has not
made some valuable contribution. His investigations upon the distribution of marine
animals, as bearing upon the geological changes which have affected their area,
have left a permanent impression upon the progress of modern Geology. Among
his special zoological studies, the natural history of the Acalephs formed always
a favorite topic, to which he constantly returned with renewed interest. His
monograph of the British naked-eyed Meduse contains a summary of what he had
done in that direction up to the year 1848. In the preface to this work he pays
a just tribute of gratitude to his friend Mr. McAndrew, to whom he was mainly
indebted for the facilities he enjoyed in collecting these materials, and whose
name will forever remain associated with that of Edw. Forbes in the memory of

naturalists.

CLASSIFICATION OF EDW. FORBES, 1848.

Forbes’s classification, published in his “ Monograph of the British Naked-eyed Medusw,” relates only
to the Discophore, which he divides into two natural groups, corresponding to the Discophorw phane-
rocarpe and eryptocarpe of Eschscholtz, but based upon different characters, not before taken into con-
sideration in the arrangement of the Acalephs. They are as follows :—

I. GymNorntTHaLMAra.

Ist Family. Willsiadew: Wilsia.

2d Family. Oceanidw: Turris, Saphenia, Oceania.

3d Family. i quoreadw: Stomobrachium, Polyxenia.

4th Family. Circeadx: Circe.

5th Family. Geryoniadw: Geryonia, Tima, Geryonopsis, Thaumantias, Slabberia.

6th Family. Sarsiadw: Sarsia, Bougainvillea, Lizzia, Modeeria, Euphysa, Steenstruppia.

II. Srecanorurnarmata. Aurelia, Pelagia, Chrysaora, Rhizostoma, Cassiopea, Cyanza.

MY OWN VIEWS OF THE CLASSIFICATION OF ACALEPHS.

In a series of lectures, delivered before the Lowell Institute in the winter of
1848-1849, a phonographic report of which appeared first in the “Traveller” and
afterwards in the form of a separate pamphlet, I have presented my views of the
natural affinities of the Radiates in general, and there began to trace the homologies
of these animals with the other Radiates, and introduced some changes in their
classification, which an uninterrupted study for more than ten years longer, along
the whole Atlantic coast of North America, from Canada to Texas, has only con-
firmed and enlarged by furnishing additional means of comparisons.

There I circumscribed the type of Radiata in the same manner in which I now
think it should be circumscribed, admitting in it three classes only, — the Polyps,

the Acalephs, and the Echinoderms. There I showed also that the Hydroids are

Cuap. II. CLASSIFICATIONS OF ACALEPHS. 143

genuine Acalephs, and should be united, not only with the naked-eyed Medusse, but
also with the Siphonophore. There also I traced the special homologies of the Cte-
nophore and other Acalephs, and the general homologies of all Radiata, including
the Echinoderms. There I advocated the. compound character of the Siphonophor,
and carried that view even further than it is carried by some naturalists, showing,
what I believe to be true, that certain parts of their communities, which are still
considered by some anatomists as organs, are in reality distinct individuals.

I do not make this somewhat extended reference to my “Lectures,” in order
to substantiate special claims of priority, but solely to prevent any imputation of
having borrowed from others the views I have derived from my own investigations,
and upon which I may have to dwell more fully in the course of this work.
This appears to me the more necessary, since the reports of my lectures have
had only a very limited circulation in Europe.

We are indebted to Liitken for valuable contributions to the natural history
of the Acalephs of Greenland and Scandinavia, in connection with which he has
published a new systematic arrangement of the naked-eyed Meduse. As I know
this paper only from the abstracts given by Leuckart in the Archiv fiir Natur-
geschichte for 1854, 2d vol. p. 424, I abstain from further remarks about it.

LUTKEN’S CLASSIFICATION OF THE NAKED-EYED MEDUS, 1850.

Ist Group. Ist Family. AS ginew: Carybdea, Eurybia, Cunina, gina, A®ginopsis, Polyxenia.
2d Group. Ist Family. i quoreadw: /quorea, Mesonema, Stomobrachium, Thaumantias.
2d Family. Oceanidw: Oceania, Saphenia, Turris, Modeeria.
3d Family. Bougainvillew: Bougainvillea, Lizzia, Rathkia.
4th Family. Geryonide: Geryonia, Tima, Geryonopsis, Dianwa, Circe.
5th Family. Sarsiadwe: Sarsia, Slabberia, Steenstruppia, Euphysa.

35d Group. Ist Family. Willsiadaw: Willsia, Proboscidactyla, Berenice.

Milne-Edwards never attempted systematically to present his views of the
affinities of the Acalephs in the form of a special classification, though we owe
to him important contributions to the history of this class. Von Siebold, in’ his
text-book of comparative anatomy, has adopted the classification of Eschscholtz,
which, to this day, is followed by most naturalists.

Since, judging from my observations upon Millepora, a large number of Corals
must be considered as belonging to the type of Hydroids, it is necessary to intro-
duce here the classification of Corals by Milne-Edwards, in order more directly to
show what changes are likely to be rendered necessary in the systematic arrange-
ment of the Corals, in consequence of my discovery of the acalephian affinities
of the genus Millepora.

144 ACALEPHS IN GENERAL. Part I.

When the two highest authorities in the natural history of Corals, Milne-
Edwards and Dana, agree in considermg the genus Millepora as a member of the
class of Polyps, I would not venture to suggest a different view of its affinities,
had I not been able leisurely to examine the animal of that kind of Coral, which
had never been observed before, and satisfied myself that it has none of the typical
characteristics of the Polyps, neither radiating partitions, nor digestive sac hanging
in the main cavity, while it agrees so closely with the true Hydroids, and especially
with the genus Hydractinia, that there can be no doubt left in what direction its
natural affinities pomt. (Compare Pl XV. /igs. 3-15 with Pl. XVI, respecting which
more will be found in the sequel.) With these facts before us, Millepora must un-
questionably be removed from the class of Polyps and referred to that of the
Acalephs, as soon as it is conceded that the Hydroids are Acalephs, and not Polyps.

RELATIONS ASSIGNED BY MILNE-EDWARDS TO THE TABULATA AND RUGOSA, AND TO
SOME OF THE HYDROIDS IN THE CLASS OF POLYPI, 1850-1852.

Ist Sub-class) CoraLLarra.
Ist Order. Zoantharia.
Ist Group. Malacodermata. Families: Actinide; Actinine, Thalassianthine, Phyllactine,
Zoanthine ; Cerianthide ; Minyadide.
2d Group. Aporosa. Families: Turbinolide; Cyathinine, Turbinolinw ; Pseudotur binolide ;
Oculinide ; Pseudoculinide ; Astreide ; Eusmiline, Astreine ; Pseudastreide ; Fungide ;
Fungine, Lophoserine.
dd Group. Perforata. Families: Madreporide, Euspammide, Madreporine, Turbinarie ;
Poritide ; Poritine, Alveoporine.
4th Group. Tabulata. Families: Milleporide; Favositide : Favositinw, Chetitine, Taly-
sitine, Pocilloporinas: Seriatoporide ; Theside.
5th Group. Tubulosa. Family: Auloporide.
6th Group. Rugosa. Families: Stauride ; Cyathaxonide ; Cyathophyllide : Zaphrentine,
Cyathophyllide, Axophylline.
2d Order. Aleyonaria. Families: Alcyonide; Cornularine, Telesthine, Alcyonine, Tubiporine ;
Gorgonide ; Gorgoninew, Isidinw, Coralliinew ; Pennatulide.
3d Order. Podactinaria. Family: Lucernaride.
2d Sub-class. Uyprarra. Family: Hydride.
Of these groups I hold that the Zoantharia, Malacodermata, Aporosa and Perforata, and the Aley-

onaria alone, are genuine Polyps; and that the Tabulata, Tubulosa, Rugosa, Podactinaria, and Hydraria

are Acalephs.

Since, from this time forward, the influence of Embryology upon the classifi-
cations of Acalephs is more or less distinctly felt, I deem it necessary to introduce
here some comparisons between the earlier attempts at a systematic arrangement
of these animals and the later systems, in order to render more evident the

progress made thus far.

Cuap. I. CLASSIFICATIONS OF ACALEPHS. 145

The classification of Lamarck, and the names he gave to the primary sub-
divisions of the Acalephs, truly express the condition of our science at that period.
The natural limits of the class had not yet been found,—nay, the Acalephs were
not yet separated from the Echinoderms, as a class, but Medusee had been observed,
a considerable number of them were superficially known, and, next to them, many
animals had been noticed, bearing evidently some relation or other to the Medusve ;
but what these relations were, was not understood; and so all these species were
united into one group by the side of the regular Meduse, under the name of
Anomalous Radiates.

Péron and LeSueur next investigated these groups singly,—LeSueur devoting
his attention chiefly to the compound ones, which he at this early period already
separated from the compound Tunicata, while, together with Péron, he illustrated
the Discophore generally.

Cuvier’s merits consist mainly in the separation of the Acalephs as a class; but
the limits he assigned to it were not altogether true to nature. Schweigger only
copied Lamarck and Cuvier as far as classification is concerned.

To Goldfuss, science is indebted for the first discriminating subdivision of the
Acalephs. For the first time the Ctenophoree were brought together by him and
separated from the Siphonophore, and these again divided into two families, while
all Discophore remained together. Chamisso and Eysenhardt copied Goldfuss, while,
still later, Latreille fell back upon the first outlines of Lamarck.

Eschscholtz, next to Cuvier, may be considered as the founder of the classi-
fication of Acalephs, for while Cuvier distinguished the class, Eschscholtz first divided
it into three natural orders, one of which he very properly subdivided into two
divisions, already pointing in the direction of future progress; for hereafter the
Discophore cryptocarpx will appear more clearly allied to the Siphonophore than
they are to the Discophorse phanerocarpe. His subdivision of the orders into
natural families was a still greater improvement. DeBlainville did not mark a
progress in the study of this class: his suggestions were mere guesses, mostly far
out of the right course. Oken simply copied Eschscholtz. Brandt added a few
families among the Siphonophore, the number of which was still further increased,
often without much discrimination or criticism, by Lesson. Forbes, and Liitken also,
described some new families; but Forbes made an important addition to the classi-
fication of Eschscholtz, by pointing out further differences between the two divisions
of the Discophore, which he called Steganophthalmata and Gymnophthalmata.

With Sars and Steenstrup a new epoch begins for the history of the Acalephs,
though neither of them has attempted to classify these animals; but it is to their
investigations that science is indebted for the first facts bearing upon the affini-
ties. of the Hydroids to the Discophore cryptocarpe, or the Gymnophthalmata of

VOL. ITT. 19

146 ACALEPHS IN GENERAL. Parr I.

Forbes. These affinities I have recognized in uniting the Hydroids and Gym-
nophthalmata with the Siphonophorze in one order, to which I have lately added
the Tabulata and Rugosa of Milne-Edwards. This step seems to me to have at
last circumscribed the class within its natural limits, and fixed its boundaries on
the side of the Polyps, where the dividing line had remained more vague than
in any other direction.

I have already presented my objections to some points of the classification of
Vogt relating to the Acalephs in general. I have only to give here an outline
of the minor divisions which he admits among these animals. But while I cannot
agree with his classification, it is but justice to him to say that his paper upon the
Siphonophore of Nizza is one of the most valuable contributions of modern times
to the natural history of these animals, forming, in connection with similar papers
by Leuckart, Koélliker, Gegenbaur, and Huxley, a very full description of all the

representatives of this type.

CLASSIFICATION OF VOGT, 1851.

Referring the Ctenophore to the Mollusks, Vogt, in his “ Zoologische Briefe,’ published in 1851, has
adopted the following classification for the Acalephs, after dividing the Radiata into four classes: Polyps,

including Lucernaria but not the other Hydroids, Hydromeduse, Siphonophore, and Echinoderms.

The class of Hypromepusa (Quallenpolypen) is divided into two orders :—

Ist Order. Hydroids, with three families: Hydrida, Tubularida, Campanularida.
2d Order. Meduse@, with six families: Medusida, Oceanida, ®quorida, Berenicida, Rhizostomida,

Geryonida.

The class of StpnonorHor® (Rohrenquallen) is divided into three families: Physalida, Velellida,
and Diphyida, to which Stephanomia is appended.

The class of Crrnorpnora (Rippenquallen) is divided into two families: Beroida and Callianirida.
ppeng

In his paper upon the Siphonophorw of Nizza, published in 1854, Vogt has appended the follow-
ing classification of the order of his Hydromedusw, which embraces them :—

‘

Order I. Potypr NECHALET.
Ist Division. With active natatory organs. Polyps provided with fishing threads. Swimming belly
hollow.

Ist Family. Agalnides: Apolemia, Agalma, Physophora. —The genera Rhizophysa, Brachysoma,
Stephanomia, Epibulia, Sarcoconus, and Discolabe, are considered as founded
upon mutilated animals.

2d Family. Hippopodides: Tippopodius, Vogtia. — Elephantopes and Racemis are questionable.

3d Family. Diphyides: Praya, Galeolaria, Diphyes. All the other genera referred to this
family are rejected.

4th Family. Athorybides: Athorybia.—The genus Anthophysa is questioned.

2d Division. With passive natatory organs.

(st Family. Physalides: Physalia.— The sub-genera Salacias, Cystisoma, and Alophotes, are

considered as useless; and Angela as probably near Physalia.

2d Family. Velellides: Velella and Porpita.— Rataria is young Velella.

Cuap. I. CLASSIFICATIONS OF ACALEPHS. 147

The contributions of Killiker to the natural history of the Acalephs are as
varied as they are important, though sometimes consisting simply of short notices.
A report of the investigations made by him in Messina, in connection with
Gegenbaur and H. Miiller, and published in the “Zeitschrift fur wissenschaftliche
Zoologie,” vol. 4, p. 299, contains a vast amount of information upon the Acalephs
of the Mediterranean. In his larger work on Siphonophore, “Die Schwimmpolypen
yon Messina,” however, he has not only given a very full account of the species
he observed in Messina, including new genera and the characteristics of new families,
but he has also published a diagram of his views respecting the affinities of the
lower animals generally, as follows :—

CLASSIFICATION OF KOLLIKER, 1853.

The members of the class of Acalephs are so combined with the Polyps and Bryozoa by Kélliker,
that his views respecting their affinities can only be appreciated by a comparative study of his whole
diagram of the Radiates with other classifications of the Invertebrates generally. He divides the Radiata

in the following manner :—

I. RADIATA MOLLUSCOIDEA.

Ist Group. Hypromesa. <A. Hydroidea sessilia: Hydra.
B. Hydroidea nechalea: Physophora, Diphyes, Athorybia, ete.

2d Group. Hypromepusipa: Coryne, Sertularia, Tubularia, Velella, and Gymnopthalmata: Oceania,
Bougainvillea, ete.

3d Group. DiscopHora: Steganophthalmata: Medusa, Rhizostoma, Cephwa.

4th Group. CrenopHoRa.

5th Group. ANTHOZOA.

6th Group. Bryozoa.

Il. RADIATA ECHINODERMATA.
Ist Group. Hototruurma.—2d Group. Ecuripa.— 3d Group. Astertpa.— 4th Group. CRrINoIDEA.

Kélliker thus coincides with Leuckart in separating the Echinoderms from the Polyps and Acalephs
as a primary group of the animal kingdom, and uniting the minor sections of the two latter classes into
another great division. Disregarding, however, all the categories of the system of Zoélogy by which animals
may be divided into classes and orders, he divides the Hydroidea nechalea, which he calls also Poryrt
NECHALEI, into five families :—

Ist Family. Physophoride: Forskalia, Agalmopsis, Apolemia, — Physophora,

2d Family. Hippopodiide: Hippopodius, Vogtia.

Athorybia.

3d Family. Prayide: Praya.
4th Family. Diphyide: Diphyes, Abyla.
5th Family. Velellidw: Velella, Porpita.

Though Leuckart has not published a general classification of the Acalephs, he
has done so much for the advancement of the natural history of that class of

148 ACALEPHS IN GENERAL. Parr I.

animals, and for a more correct appreciation of the affinities of the lower animals
generally, that he deserves a prominent place in a history of their classification.
(Compare vol. 1, pp. 179 and 209.) His special contributions to the systematic
arrangement of the Acalephs relate chiefly to the Siphonophora, and are expressed

in the followmg diagram :—
LEUCKART’S CLASSIFICATION OF THE SIPHONOPHORA, 1854.

Ist Family. Calycophorida.
Ist Sub-family. Diphyide: Abyla, Diphyes, Galeolaria, — Praya.
2d Sub-family. Hippopoditde : Hippopodius.

2d Family. Physophoride.
Ist Sub-family. Stephanomide: Apolemia, Agalma, Forskalia.
2d Sub-family. Physophoride proper: Physophora.

dd Family. Rhizophysidw: Rhizophysa.

4th Family. Physalidw: Physalia.

5th Family. Velellidw: Velella, Porpita.

In the additions to the German edition of Van der Hoeven’s Handbook of
Zoology, Leuckart has divided the Ctenophore into two orders, the Lurystomata and
Stenostomata, —an arrangement already hinted at by Eschscholtz and Van der Hoeven.

Since Eschscholtz, no naturalist has made more extensive and more valuable
contributions to the natural history and anatomy of the Acalephs in general, than
Gegenbaur, who has extended his researches to all the orders of the class, imclud-
ing the study of their development, in his comprehensive investigations. His classi-
fications of the different groups of the class contain much also that is new and
important, though I think he is mistaken in the rank he assigns to some of
them. The different works in which he has published his researches are enumerated
above (p. 27, note 15, and p. 87, note 1.) The chief importance of Gegenbaur’s
contributions to the classification of the Acalephs consists in the discrimination of
several new families among the naked-eyed Meduse, and more especially in’ the
introduction of a new consideration by which to distinguish the Discophorz proper
from the naked-eyed Medusx. It has been seen above, that Eschscholtz admitted
two divisions among the Discophore, one of which he called Discophorze phanero-
carpe, and the other Discophore cryptocarpxe, founding this distinction upon the
presence or absence of special pouches for the reception of the sexual apparatus.
Forbes admitted also two divisions, calling one Steganophthalmata, because the eye-
specks are enclosed in a scalloped fold of the margm of the disk, and the other
Gymnophthalmata, because the eyespecks are exposed alone the margin, in close
connection with the tentacles and the circular tubes. Gegenbaur founded a similar
subdivision upon the presence or absence of an inverted rim alone that same

margin.

Cuapr. I. CLASSIFICATIONS OF ACALEPHS. 149

CLASSIFICATION OF GEGENBAUR, 1856-1859.

Gegenbaur is the last author to whose systematic views I have to allude, as far as they relate to
the Acalephs in general: later authors have only considered parts of the subject. He, like most recent
German writers, adopts the primary division of the Radiata into Coelenterata and Echinodermata, proposed
by Leuckart, and in his Textbook of Comparative Anatomy subdivides the Coelenterata into three classes :
Potyrr, Hypromepusipa, and CrenopHora. Here the Hydroids are all referred to the class of the
Hydromedusida, with the sole exception of Lucernaria, which is left among the Polyps. The Hydro-

medusida themselves are divided in the following manner : —

Ist Order. Hyprorpra: Coryne, Syncoryne, Hydractinia, Sertularia, Pennaria ;—Campanularia, Eu-
dendrium, Tubularia.

2d Order. Mepvusma: 1° Craspedota: Oceania, Sarsia, Lizzia ;— Geryonia ; — AZquorea ;— Mgineta,
Cunina. 2° Acraspeda: Pelagia, Aurelia, Chrysaora ;— Rhizostoma, Cas-
siopeia.

3d Order. SrteHonopnora: Velella, Porpita;— Diphyes, Abyla;— Agalma, Physophora, Physalia.

and

To the class Ctenophora the genera Cestum, Cydippe;— Mnemia, LeSueuria ; — Eucharis ;
P g 3

Beroe, are referred. But Gegenbaur had already published a more special account of his view of the
Ctenophora in 1856, in the “ Archiy fiir Naturgeschichte,” p. 163, in which he adopts the following
I f=) ? i 5

families : —

Callianiride: Callianira.

Calymnidw: Calymna, Mnemia, Axiotima, Bolina, Eucharis, Leucothoe, Aleinoe, Chiaja, LeSueuria, and
Euramphiea.

Cestidw: Cestum.

Cydippide: Neis, Ocyroe, Mertensia Zess., Anais, Eschscholtzia, Mertensia Gegend., Janira, Cydippe,
Pleurobrachia, Beroe Jert., Owenia.

Beroidw: Beroe (Idya, Cydalisa, Medea). — Sicyosoma.

In 1857, Gegenbaur published a special paper upon the Discophore in the Zeitschrift fiir wissen-
schaftliche Zodlogie, in which he admits two great divisions, corresponding to the Phanerocarpe and

Cryptocarpe of Eschscholtz, and to the Steganophthalmata and Gymnophthalmata of Forbes, as follows :—

ACRASPEDA, with four families : —

Rhizostomidx: Rhizostoma, Cephea, and Cassiopeia.

Medusidew: Aurelia, Sthenonia, and Cyanea.

Pelagidw: Chrysaora, Pelagia, and. Nausithoe (Octogonia).

Charybdeidx: Charybdea.

Crasrepota, with seven families : —

Oceanidw: Oceania, Saphenia, Turris, Sarsia, Modeeria, Bougainvillea, Lizzia, Cytwis, Zanclea,
Steenstruppia, Euphysa, Cladonema, Willsia, Chrysomitra; with five sub-families, Oceanid@ proper,
Sarsiade, Bougainvillide, Willsiade, and Cladonemide.

Thaumantidew: Thaumantias, Staurophora, Tiaropsis, and Tima.

ZEquoridx: /®quorea, Mesonema, Stomobrachium.

Eucopidw: Eucope, Sminthea, Eurybiopsis, Aglaura.

Trachynemide: Trachynema, Rhopalonema.

Geryonidw: Geryonia, Liriope.

ZEginide: Cunina, A®gineta, “gina, Avginopsis, Polyxenia.

150 ACALEPHS IN GENERAL. Parr

The paper of J. McCrady upon the Gymnophthalmata of Charleston harbor,
published in the Proceedings of the Elliott Society of Natural History in 1858,
contains much interesting, and some highly important and novel, information upon
the naked-eyed Meduse of South Carolina, to which I shall have frequent oppor-
tunities of referring hereafter. For the present, I shall only allude to the classi-
fication he has proposed of the lowest order of the Acalephs. He is the first
naturalist who has adopted the order of Hydroids with the limits I have assigned

to it; but he has introduced a new arrangement of the minor groups.

CLASSIFICATION OF THE HYDROIDS BY J. McCRADY, 1858.

Ist Sub-order. Enpostomara.
Ist Family. Corynide. Oceanidw: Oceania, Turritopsis, Turris, Modeeria, Saphenia.
Sarsiadw: Sarsia, Corynitis, Dipurena, Slabberia.
Clavide: Clava.
2d Family. Velelide. —-Velella, Porpita, Chrysomitra, Rataria.
3d Family. Tubularide.
Pennaridxw: Cladonema, Zanclea, Pennaria, Willsia.
Tubularidew : Steenstruppia, Euphysa, Tubularia, Corymorpha.
ILippocrenidw : Nemopsis, Lizzia, Bougainvillea, Hippocrene, Cytzis,
Eudendrium, Hydractinia.
4th Family. Siphonophore.
Physophoridew: Forskalia, Agalma, Agalmopsis, Physophora, ete.
Iippopodidw : Hippopodius, Vogtia.
Diphyide: Prayia, Diphyes, Eudoxia, ete.
Physalidw: Physalia.
2d Sub-order. Exosromata.
Ist Family. Campanularide.
Thaumantiadxw: Thaumantias, Staurophora, Tiaropsis.
Eucopidw: Geryonopsis, Tima, Eucope, Eucheilota, Epenthesis, Cam-
panularia.
2d Family. Sertwlaride. Sertularia, Halecium, Thuiaria, Plumularia, Aglaophenia, Antennularia.
Circeade. Circe, Persa, Aglaura.
Trachynemide. 'Trachynema, Rhopalonema.
3d Family. ~ Stomobrachide. Stomobrachium, Mesonema.
Greryonide. Geryonia, Liriope.
| -Hquoriade. Equorea, Rhacostoma.

4th Family. @ginide. Cunina, Aegina, Agineta, ‘Eginopsis, Polyxenia.

Besides extensive and valuable contributions upon the structure and _ affinities
of the Acalephs in general, published in the Transactions of the Royal Society of
London, and of the Siphonophore in particular, published in Miiller’s Archiv, Huxley

has lately proposed a new classification of the latter, which he calls Hydrozoa.

Cuap. II. CLASSIFICATIONS OF ACALEPHS. 151

HUXLEY’S CLASSIFICATION OF THE SIPHONOPHORA, 1859.

HYDROZOA.

I. Carycornorip2.

Ist Family. Diphyde: Diphyes, Galeolaria, Abyla.

2d Family. Spheronectide: Spheronectes.

3d Family. Prayide: Praya.

4th Family. Hippopodiide: Hippopodius, Vogtia.
II. Puysornoripx.

Ist Family. Apolemiade: Apolemia.

2d Family. Stephanomiade: Halistemma, Forskalia, Stephanomia, Agalma.

dd Family. Physophoriade: Physophora.

4th Family. Athorybiadw: Athorybia.

oth Family. Rhizophysiadw: Rhizophysa.

6th Family. Physalidw: Physalia.

7th Family. Velellidw: Velella, Porpita.

From the circumstance that his last work embraces all the animals then referred
to the class, Lesson truly marks the close of a period in the history of the progress
of the classification of Acalephs. From his days forward, the improvements bear
chiefly upon the arrangement of the Hydroids, first brought imto the sphere of
attraction of the Meduse about that time. Affinities, unsuspected before, lead to new
combinations; and a more intimate acquaintance with the structure of all these ani-

mals, by the very novelty of the disclosures, suggests comparisons with the remotest

types, and mere analogies are exalted into real affinities. But step by step, the test
of homological relationship being applied to these aberrations, and embryological
study adding its controlling influence, the Acalephs are finally circumscribed within
limits which would now seem natural, and subdivided into groups which are not

likely to undergo other than changes of secondary importance.

In concluding this rapid sketch of the classifications of the Acalephs I may
be permitted to remark, that a retrospective glance over the many attempts thus
far made to express the various degrees and different kinds of affinities of these
animals, in the shape of diagrams, should satisfy any one how readily different
authors, approaching the study of these animals with a very different preparation,
have in the end agreed upon the natural limits of a larger and larger number
of their subordinate groups, in proportion as the information concerning these groups
has become more and more precise. The disagreement among authors has been
most persistent upon the classification of those animals only, respecting the structure

of which our knowledge has also remained deficient for a longer period; and it is

152 ACALEPHS IN GENERAL. Parr

cheering to see how, with increasing knowledge, the most extreme views have been
gradually converging in the same direction. This condition of things excites a
strong hope, that, ultimately, all differences among naturalists respecting classi-
fication may be settled; when the conformity of views will itself become an
_ additional evidence that the system exists In nature, and not in the minds of
those who have contributed to decipher it.

Pere Il.

CTENOPHORE.

VOL. III. » 20

-_—

Coe OoP TH OO R A,

CHAPTER FIRS ©,

CTENOPHORZ IN GENERAL.

SCE TONe I.
STRUCTURAL FEATURES OF THE CTENOPHORE IN GENERAL.

I neED not repeat here what I have stated in the first part of this volume

respecting the affinities of the Ctenophore. They are unquestionably Radiates

belonging to the class of Acalephs, in which they form a natural order. This

being admitted, it remains now for me to present a sketch of their structural

peculiarities, in conformity with their general and special homologies, and an outline

of their mode of life founded upon a knowledge of their special structure,
g I

1 We are indebted to Gegenbaur for the latest
and most comprehensive summary of what is now
known about Ctenophore. It is therefore proper,
that whatever critical remarks I may haye to
present upon the views entertained by other natu-
ralists, respecting this group of animals, should be
made with special reference to his paper, “Studien
iiber Organisation und Systematik der Ctenophoren,”
in “Archiv ftir Naturgeschichte, 1856,” 1 vol. p.
163. Gegenbaur, with Leuckart, considers them
as constituting one harmonious primary group with

the Meduse, Hydroids, and Anthozoa, called Co-

lenterata by the latter. I have already presented
my objections to the separation of the Coelenterata
and Echinodermata as two distinct primary divisions
of the animal kingdom, upon the broad ground
that these divisions do not differ in the plan of
their structure, but simply in the mode of execution
of that plan (pp. 64-72); and it only remains for
me to show that the structure of all these animals is
strictly homological, and to remind those naturalists
who may feel inclined to regard the distinction
between a plan of structure and its mode of exe-

cution as of secondary importance, or as an inno-

156 CTENOPHORA.

Part II.

The Ctenophorse are free Acalephs moving in various ways, their main axis

being generally turned in the direction of their onward motion, but at times also

vation of mine, that K. E. von Baer long ago
already insisted upon the necessity of the distinction,
in view of an accurate appreciation of the true re-
lations of

animals, though his warning has not

been heeded. (Comp. vol. 1, p. 221.) The reason
why Baer’s suggestion to distinguish between the
degree of perfection in the structure of animals and
the type of organization lias not been followed
out, lies perhaps in the vagueness of the ex-

pressions he uses: but whosoever has compre-
hended that distinction for himself cannot fail to

perceive that what I have alluded to when dis-

cussing the value and significance of the plans of
t=} t=)

structure of the animal kingdom with reference to

classification, is the same thing as what Baer calls

the type of organization; and that what he calls
the degree of perfection in the structure of animals
corresponds to the two features of their structure
which I have distinguished as modes of execution
and degrees of complication, after I had perceived
that Baer eccnfounds under one expression two
distinct categories of structure,—one relating, indeed,

to the relative degrees of perfection in the animal

structure upon which orders are founded, but
not necessarily including another, broader con-

sideration, the ways and means of the execution
of the plan, upon which alone classes are based.
(Comp. vol. 1, p. 137-176). To some extent I
have already pointed out the general homologies
which unite the Echinoderms and the Ccelenterata
(pp. 64-87, and pp. 99-113); but it is so difficult
to trace these general comparisons through the
obstructions of a confused nomenclature, and in the
face of the still greater obstacles arising from the
remoteness of the whole type of Radiates from
that to which we ourselves belong, that a thorough
appreciation of the general as well as the special
homologies of these animals can only be the result
of a prolonged comparative study of all their types,
and an equal familiarity with all of them. I
venture to say, that if Leuckart and Gegenbaur

had devoted their special attention to the Echi-

noderms as extensively as to the Acalephs, they
would feel less confident that there is a typical
difference between them. As for myself, I must
declare, in the words of K. E. von Baer, that I
can perceive only “different degrees of perfection
in their structure,” and no difference “in the type
of their organization;” or, in the words of my
Essay on Classification, Polyps, Acalephs, and Echi-
noderms are built upon “one and the same plan
of structure,” and therefore belong to the same
branch of the animal kingdom, while as classes
they differ in the “modes of execution of that
plan.” As classes of one branch, they are held
together by general homologies, while special homolo-
gies may be traced respectively in all the repre-
sentatives of these classes. The most striking of
these general homologies, because thus far least
noticed, unquestionably, is that of the aquiferous
system of the Echinoderms, and the radiating
chambers of the Polyps, linked together by the
chymiferous tubes of the Acalephs. It is not my
intention here to trace all these homologies, to
which I shall devote a special chapter in the
sequel; but, since the appreciation of the true
relations of the Echinoderms to the other Radiates
must depend upon the views entertained of their
homologies, I would urge upon the naturalists who
consider the Echinoderms as a distinct type, the
importance of closely comparing on one side the
simpler ambulacral system of the lower Holothurians
with the radiating chymiferous tubes of the naked-
eyed Meduse, and on the other side the peculiar
mode of branching of the chymiferous tubes in the
genus Aurelia with the ramifications of the aquiferous
system in Scutella and Echinarachnius; or the
radiating pouches of Cyanea, and their numerous
tentacles opening freely into these cavities, with the
ambulacral suckers of any Star-fish; or the circular
aquiferous tube of Echinarachnius with the circular
chymiferous tubé@sof the naked-eyed Medusx,— and
I doubt not that the result of such comparisons will

be a growing conviction, that the spherosome of the

Cuap. I. STRUCTURAL FEATURES. Lor

standing at various angles with the direction of their movements, and, what is
still more perplexing, the actinal and abactinal poles of the axis are now turned
one way and now the opposite way. This variability of the motions of the
Acalephs renders it exceedingly difficult to deseribe their natural attitudes in a
manner which shall not conflict with their organic structure. When at rest,
Ctenophorze assume three different attitudes, peculiar to three different types of
the order: Bolina and allied genera stand in a vertical position, with the actinal
pole of their main axis downward; Pleurobrachia and allied genera stand also in
a vertical position, but the actinal pole of their main axis is turned upward ;
Idya and allied genera, on the contrary, assume a nearly horizontal position, their
main axis slightly slanting, the actinal pole being lower in the water than the
abactinal pole. When moving onward, in whatever direction the motion may take
place, whether it be straight forward, or upward or downward, or in a circuitous
course, these different types of Ctenophore retain the same general relation of
their main axis to the surrounding medium, that is, the actinal and the abactinal
poles are in the direction of the motion, the abactinal pole moving forward in
Bolina, while in Pleurobrachia the actinal pole is turned forward and in Idyia
obliquely backward. Besides moving in these ways by the more energetic action
of the whole spherosome, the Ctenophors may change their position by the activity
of the locomotive flappers, when the main axis may assume any direction, according
to the greater or less energy, or the total inactivity, of some of the rows of these
locomotive flappers, or of parts of one and the same row. In this way a slow
rotatory motion may also be produced, during which the main axis may, or may
not, change its direction.

It is plain from these statements, that unless a nomenclature entirely irre-
spective of the various positions of these animals be adopted to describe their

structure and their movements, the strongest conflicts between the structural relations

Echinoderms differs only from that of the Acalephs
by its hardness, that the chymiferous tubes of the
Acalephs are homologous to the aquiferous system
of the Echinoderms, the marginal tentacles of the
Acalephs homologous to the ambulacral suckers of
the Echinoderms, ete.; and once upon that track
it will be easy to embrace in these comparisons
all the organic systems of all Radiates, from the
simplest Polyp to the most highly organized Echi-
noderm. As to. the Ctenophora® in particular, I
have already shown (pp. 99-124) that they do not

form a class by themselves, but belong to the class

of Acalephs, and that they constitute one order,
standing highest in that class. I cannot agree with
Leuckart and Gegenbaur, who consider them as
a distinct class; nor does Gegenbaur’s expression
appear to me correct, when he describes the di-
gestive cavity of the Ctenophore as extending in
the longitudinal axis of the body, if what I have
stated of the morphology of Acalephs in general
is true: for I hold that the main axis of all the
Radiates ought to be considered as the vertical
axis, around which the spheromeres are symmetri-

eally and radiatingly arranged.
fo} >

158 CTENOPHORA. Part II.

of their parts, and their attitudes, will be unavoidable, and the same motion in
two different types of this order might be designated by contrary expressions.
The only way of avoiding these difficulties is to adopt a nomenclature in accordance
with the general homologies of these animals, and to keep in view the fact that
the normal attitude of all the Radiates is that in which their main axis is placed
in a vertical position. With this understanding we may then say, that, when at
rest, Bolina and allied genera stand upright, with the actmostome turned down-
ward; that Pleurobrachia also stands upright, but with the actimostome turned
upward; that Idyia lies nearly horizontally, with the actimostome slanting slightly
downward; and that Bolina and Idyia move with the abactinal pole forward, while
Pleurobrachia moves with the actinal pole forward.

Next, we have to distinguish two other diameters, at right angles with one
another and with the main vertical axis. In order correctly to appreciate the
peculiar symmetry of the Ctenophore, it must be remembered, in the first place,
that their body is made up of eight spheromeres, arranged in pairs on opposite
sides of an imaginary plane dividmg the whole structure into equal halves, and
passing through the longer diameter of the circumscribed area of the abactinal
pole, as well as through the longer diameter of the actinostome and of the digestive
cavity; and, in the second place, that there are two or more distinct radiating tubes,
opposite one another, and respectively intermediate between two rows of locomotive
flappers, trending in the direction of another imaginary plane dividing also the whole
structure into equal halves, but at right angles with the first. Thus the body
of the Ctenophore may he divided into equal halves in two opposite directions ; but
the greatest diameter of these two sets of halves is not equal: that which passes,
at right angles with the main axis, through the longer diameter of the actinostome
and of the circumscribed area, is either greater or smaller than that which passes
through the two intermediate radiating tubes, and the preponderance of the one
over the other seems to be typical in different groups of Ctenophore. In Idyia,
the transverse diameter passing through the intermediate radiating tubes is much
shorter than that which coincides with the longer diameter of the actinostome ;
while in Pleurobrachia the relations are reversed, the transverse diameter passing
through the intermediate radiating tubes being longer than the other, except that

fo)

in this type the difference between the length of these two diameters is not so
marked. Bolina, again, coincides with Idyia as to the respective length of its
transverse diameters, and exhibits the same disproportion between the two.

We have thus, unmistakably, two different kinds of transverse diameters, though
in different representatives of the order one or the other of the two kinds may
be respectively the longer or the shorter. This distinction once recognized, the

question arises how far one of these diameters may be considered as lateral, and

Cuap. I. STRUCTURAL FEATURES. 159

the other longitudinal or antero-posterior. This question can only be answered
in connection with those features in the structure of certaim Radiates which exhibit
more distinct traces of bilateral symmetry than the Ctenophore, and in which right
and left become unmistakable in consequence of the presence of an odd spherosome.
Such combinations exist among the Echmoderms, in which, in addition to two or
more pairs of spheromeres, there is an odd one, in the direction of a plane passing
through the opposite ends of the alimentary canal. And now, when it is con-
sidered that the tendency of the digestive tube to open in an excentric position
coincides with the elongation of the body of Echinoderms, and that the anus is
farthest removed from the mouth in those Spatangoids in which bilateral symmetry
is most strikingly blended with radiation; when it is further considered, that in
these animals the odd ambulacral zone coincides with the diameter along which
the mouth and anus are placed, at opposite ends of the body, and that the sym-
metrical pairs of ambulacral zones are placed on opposite sides of that longitudinal
diameter, — the conclusion seems irresistible, that the flattening of the digestive
cavity of the Ctenophore in the direction of the longer diameter of the actinostome
is the first indication among Acalephs of a tendency to form an alimentary canal
in the direction of the longitudinal diameter of their body, and that the additional
radiating tubes must be lateral.

Another consideration seems to militate in favor of that view. Admitting the
general homology of the radiating chymiferous tubes with the ambulacral system
of the Echinoderms, and that there are as many spheromeres in the body of
Radiates as there are main branches of these systems, it must be apparent, that
while the majority of Echinoderms have five spheromeres, the Ctenophorz have
eight; that in Echinoderms there are two pairs and an odd one, and in Cte-
nophore four pairs; and that, therefore, the zones alternating with the ambulacra
in Echinoderms form also two pairs, with an odd interambulacral zone opposite the
odd ambulacral zone, while in Ctenophors there are four pairs of zones homologous
to the ambulacra, and four pairs homologous to the interambulacral zones. — If,
therefore, the diameter passing through the intermediate chymiferous tubes were
considered as the antero-posterior diameter, there would be identical zones, that. is,
interambulacral zones, at both ends of that diameter; while in Echinoderms, the
zone at one end of the longitudinal diameter differs from that at the other end,
one being ambulacral and the other interambulacral. Now it is true, as there is
no odd zone im Ctenophore, it may seem indifferent to consider either of their
interambulacral zones in the direction of the transverse diameters as the anterior
and posterior or the lateral ones; but if there is no odd zone, there is at least
a substantial reason for considering the diameter which coincides with the longer

diameter of the actinostome as the antero-posterior diameter, namely, the fact that

160 CTENOPHORA. Part II.

in the Actinoids, in which the digestive cavity is compressed in the same manner
as in the Ctenophore, one end of the actinostome differs in form and structure
and functions from the other end, which amounts to a difference between the
two ends of the compressed digestive cavity, analogous to the difference existing
between the odd ambulacral and the odd = interambulacral zone at the two ends
of the antero-posterior diameter of the Echinoderms. I do not, therefore, hesitate
in considering that transverse diameter of the Ctenophorx which comeides with
the longer diameter of the actinostome and of the circumscribed area as the
longitudinal diameter of these animals, and that which traverses the body im the
direction of the intermediate chymiferous tubes as the lateral diameter, and these
tubes therefore as an interambulacral structure homologous to the imterambulacral
vesicles or tubes of the aquiferous system of the Echinoderms, and not homologous
to the radiating chymiferous tubes nor to the ambulacral tubes proper. As soon
as these comparisons are admitted as correct, it must be also acknowledged, further,
that one of the leading peculiarities of the Radiates consists in the position of
the mouth, which, instead of appearing at the anterior end of the longitudinal or
antero-posterior diameter, is placed at the actinal end of the vertical diameter, or,
in other words, in the centre of radiation of the whole structure.

The special structure of the Ctenophore readily accounts for their peculiar
symmetry. Built up of eight homologous segments, their spheroidal body would
approach much nearer to a sphere, the primary form of all Radiates, were these
segments or spheromeres not unequal among themselves in certain directions, and
again perfectly identical in every respect in other directions. Had the similarity
of the structure of the Acalephs and Echinoderms been sooner traced in its details,
—had, especially, the repetition of homologous segments around the vertical axis
of the Acalephs, and the homology of these segments and the ambulacral zones
of the Echinoderms, been perceived,—it would have been easy to recognize the
foundation of their resemblance as well as that of their difference. The typical
architecture of the Echinoderms depends upon the presence of five homologous
zones, occasionally reduced to four, and sometimes increased to a larger number ;
while that of the Ctenophore is based upon eight homologous segments. These
parts are distinguished by special homologies in their respective classes, but present
an unmistakable general homology when compared to one another. When tracing
these general homologies, it must, however, be remembered, that the distinction of
ambulacral and interambulacral zones, introduced in the characteristics of the Echi-
noderms, should be discarded to the extent to which they merely express a speciali-
zation of parts peculiar to that class, since, in the Holothurians, the interambulacral
zones are not more distinct than in the Ctenophore.

Reealling now to our mind the statement made before, that the body of the

Cuar. I. STRUCTURAL FEATURES. 161

Ctenophore has a vertical main axis, which is usually the greatest diameter of
the spherosome, and two distinct transverse diameters, one of which is to be con-
sidered as the antero-posterior or longitudinal, and the other as the transverse,
diameter proper, it will appear that the eight spheromeres are arranged in _ pairs
upon the sides of the longitudinal diameter, in such a manner that there are two
pairs upon the sides, one pair in front, and one pair behind,—one spheromere of
each pair being on one side, and the other on the other side, of the longitudinal
diameter. Now, in all Ctenophore, the spheromeres, which as pairs correspond to
one another, are always equally developed and of exactly the same structure, the
same size, and the same form, balancing one another completely upon the two
sides of the body, so that the spherosome exhibits no trace of one-sidedness or
unequal bulging, as exists in some of the Acephala. But while this is so, so long
as we compare the spheromeres of one and the same pair with one another, the
symmetry of the spherosome assumes a very different aspect when we -extend the
comparison from one pair to another pair; for while the anterior and the posterior
pairs are again identical in structure, size, and form, they balance one another in
opposite directions, and differ still more widely from the two lateral pairs, which
also balance one another in opposite directions. These differences may be carried
so far that the anterior and the posterior pair balancing one another symmetrically
may be much more developed than the lateral pairs, and have a greatly modified
though homological structure. The natural consequence of this peculiar symmetry
is, that the anterior and posterior surfaces of the spherosome are exactly alike; and
that therefore, notwithstanding the existence of a distinct antero-posterior diameter,
it is impossible to determine which is its anterior and which its posterior end.
For the same reason it is impossible to determine which is the right and which
is the left side, even though it cannot be doubted that there are two symmetrical
pairs of lateral spheromeres. We are, on that account, unable to distinguish the
regions of the body of the Ctenophore with all the desirable precision, and shall
be obliged to designate four of the spheromeres as the lateral spheromeres, and
the four others as the anterior or posterior spheromeres; remembering, however,
that one pair of the latter stands opposed to the other, while two single sphero-
meres belonging to different pairs are opposed to one another upon the sides.
The intermediate or interambulacral chymiferous tubes are always placed between
two lateral spheromeres. This is a truly remarkable feature of the Ctenophore,
unique among Acalephs, since all the other types of the class have all their
spheromeres evenly balanced. We shall see presently, that this peculiarity stands
in direct relation to the general mode of branching of the chymiferous tubes. I
may, however, at once call attention to the bearing which this fact has upon the

whole symmetry of the Acalephs. In giving prominence to the sides, it renders the
VOL. II. 21

162 CTENOPHORA. Parr II.

bilateral symmetry of the Ctenophorz even more conspicuous, and certainly more
perfect, than in most Echinoderms, notwithstanding the presence of an odd zone
in these; for as soon as the anterior extremity of the body assumes prominence
by its specialization, the sides recede, as it were, to a lower relation. But in
Echinoderms there is no such specialization of the anterior extremity: the structural
progress of this class over the Acalephs consists only in the introduction of an
odd zone. This zone is mostly identical in structure with the lateral zones, and
scarcely ever so far differentiated as to give preponderance to the sides in the
general configuration of the body. In Ctenophorze, on the contrary, the absence
of an odd spheromere, combined with the identity of development of the anterior
and of the posterior pairs, and the differentiation of the two lateral pairs, including
an additional, interambulacral chymiferous tube, throws the whole weight of the
extreme structural differences of the spheromeres upon the sides, in such perfect
balance with reference to the antero-posterior diameter, that the reciprocal action
of the most important function in the life of these animals is to be traced in
the alternate contractions of the two sides of the body. Again, the opposite poles
of the main axis are strikingly contrasted: at one end we find the mouth or
actinostome, and at the other end the circumscribed area, and in an asymetrical
relation to it, the two discharging openings of the chymiferous system. The
curves of the sides contribute also to render the contrast between the actinal and
abactinal poles more prominent. Thus, in Ctenophor the opposite ends of their
three diameters are evenly balanced, presenting identical parts in antitropic relations
on the anterior and posterior sides and on the lateral sides of the body, and
heterogeneous parts in similar relations on opposite poles.

As in all Radiates, the body of the Ctenophore is a spherosome; that is to
say, it is essentially radiated in its structure, and as in all Acalephs it consists
of cells, and of cells only, variously combined and of a variety of forms. There
are no specialized tissues in it. The distinction of a muscular system, as described
in my former papers upon Acalephs, was a mistake, as will be shown hereafter,
arising from the peculiar constitution of the motory cells; nor is there a distinct
nervous system. The whole bulk of the body is made up of large contractile cells,
and is covered with epithelial cells, which also line the digestive cavity and the
system of chymiferous tubes arising from its abactinal prolongation. The thickness
and form of the spherosome yary in different families; the size and form of the
digestive cavity, and the mode of ramification of the system of chymiferous tubes,
also exhibit striking differences: but all Ctenophore agree in this, that the sphero-
some has a uniform structure, being made up of a continuous mass of large motory
cells, combined into distinct systems, bearing definite relations to the various and

complicated motions of the different parts of the body. The assumption of Mertens,

Cuar. I. STRUCTURAL FEATURES. 163

that some Ctenophoree have a mantle, which is wanting in others, is incorrect.
As we shall see in the sequel, the lobe-like appendages of the anterior and pos-
terior spheromeres of some representatives of this order are direct prolongations
of the spherosome, over which the rows of locomotive flappers are extended, and
to which they bear the same relations as in the more spheroidal or more cylindrical
forms. The chymiferous tubes also extend uninterruptedly into these lobes, in the
same manner as they extend into the peripheric parts of the plainest species. So
that, whatever be the general form of the spherosome, it is one and the same
body in all Ctenophore. Again, whatever be its form and size, the Ctenophore
have all a compressed digestive cavity, trending in the same plane as the cireum-
scribed area of the abactinal pole, and at right angles with the intermediate
chymiferous tubes; and in all, that cavity is broadest towards the mouth and tapers
in the opposite direction, its lateral walls being flattened against one another when
it is empty. The narrow abactinal opening of the digestive cavity opens directly
into the centre of the chymiferous system, which in all Ctenophors has a very
peculiar mode of ramification, the general outline of which agrees in all, though
marked peculiarities may be noticed in its details in different families. The most
striking and characteristic features of this chymiferous system, when contrasted with
that of the other Acalephs, consist in its bilateral symmetry, the axial funnellike
prolongation of its central portion, into which the digestive cavity opens directly,
and the presence of two asymetrical openings at the abactinal pole, through which
it discharges its contents.

Immediately beyond the abactinal opening of the digestive cavity there arise
two main trunks of the chymiferous system, in opposite directions one from the
other and at right angles with the plane of the digestive cavity; so that the
main stems extend right and left, and almost horizontally, into the spherosome.
Before dividing, each trunk sends off a vertical branch along the adjoining sides
of the digestive cavity, and then divides into two nearly horizontal branches, which
soon divide again; so that each trunk has four nearly horizontal or slightly inclined
forks extending to the periphery, where they open into as many vertical branches,
which converge in opposite directions toward the actinal and the abactinal poles.
The further course of these vertical peripheric branches varies with different families ;
but, as far as I can ascertain, all Ctenophore have a chymiferous tube upon each
flat side of the digestive cavity; in all, the two main trunks divide into four forks:
and these eight forks open in all into eight vertical peripheric chymiferous tubes;
and in addition to these, there are, in some families, other vertical and lateral
chymiferous tubes arising between the lateral horizontal forks of the main trunk,
which again vary in their ultimate relations in different families, lateral tentacles
existing in some, and being absent in others. All these tubes, whatever be their

164 CTENOPHORE. Parr IT.

final course, circulate the chymiferous fluid with which they are filled into all parts
of the spherosome; and there is this remarkable peculiarity in the general current
of this chyme circulation, that the fluid contained in one half of the body, reversing
regularly its course, is alternately poured into the opposite half and back again.
Thus the chief peculiarity of the chymiferous system of the Ctenophorz does not
only consist in its bilateral symmetry, but also in the antagonism of the cur-
rents of its two lateral halves.

Next, we have to notice the vertical prolongation of the chymiferous system
in the shape of a funnel, extending to the abactinal pole of the body, in the
prolongation of the main axis, and there, dividing into two forks, running to some
distance in opposite directions, between the anterior and posterior pairs of locomotive
flappers. The fork of this funnel forms a sort of cloaca, in which the refuse of
the chymiferous fluid accumulates, to be at intervals discharged through two distinct
openings, placed obliquely on opposite sides of the circumscribed area of the
abactinal pole. The physiological significance of the circumscribed area has not
yet been ascertained. It is an elongated field, circumscribed by a more or less
prominent wall of vibratile fringes, interrupted in the middle by a promment organ,
considered to be an organ of hearing by some anatomists, and described by others
as an eye-speck, towards which converge the abactinal prolongations of the rows
of locomotive flappers.

One of the most apparent peculiarities of the Ctenophore, and to which this
order of Acalephs owes its name, consists of eight rows of locomotive flappers,
extending along the eight vertical and peripheric chymiferous tubes, with which
they are closely connected. As far as I can ascertain, all Ctenophorz have eight
such rows, though some of them are represented with only four and others with
twelve. But their close connection with the ambulacral tubes, and the constancy of
the number of these tubes in all the Ctenophoree which I ever had an opportunity
of examining, lead me to take it for granted that the typical number of the
vertical rows of locomotive flappers must be eight. I am inclined to ascribe the
conflicting statements upon this point to the marked imequality observed among these
rows in different families) The fact is that while they are, all eight, of equal
length and equal prominence in certain representatives of this order, in others
there are four larger, longer, and more prominent ones, and four shorter and
smaller ones, differimg more or less in their course. I hold, therefore, that the
smaller rows may have been overlooked in those genera which are described as
having only four rows of locomotive flappers; and that, in those which are repre-
sented as having twelve rows, the vibratile cilia of the epithelial cells lining the
digestive cavity may have been mistaken for additional rows of locomotive flappers.
Gegenbaur gives the same explanation of the singular figure of the Alcinoe

Cuap. I. STRUCTURAL FEATURES. 165

papillosa of Delle Chiaje. The close connection which exists between the rows of
locomotive flappers and the chymiferous tubes is so similar to the general organi-
zation of the ambulacral system of the Echinoderms, that I do not hesitate to
consider these structures as homologous.

The sexual organs of the Ctenophore are closely connected with the chymiferous
tubes, as in all Acalephs, and, indeed, in all Radiates; for they bear the same
homological relations to the radiating chambers of the Polyps, as they do to the
ambulacral system of the Echinoderms. In Ctenophorz the ovaries and spermaries
occupy small pouches upon the sides of the ambulacral chymiferous tubes: sperm-
aries and ovaries existing in all individuals, and alternating with one another in
such a manner, that, while each chymiferous tube has spermaries on one side and
ovaries on the other, the proximate sides of adjoining tubes have the same kind
of sexual organs, that is, either spermaries or ovaries, and, alternate intervals between
adjoining tubes, different kinds of organs. The mode of reproduction of the Cte-
nophore has been traced recently by Semper and McCrady ; and fragments relating
to the same subject have also been contributed by Vogt, Kolliker, J. Miiller, and
Gegenbaur. Since the publication of my paper upon Beroid Meduse, I have had
an opportunity myself of studying the entire development of Pleurobrachia, an
account of which will be given in the sequel. They undergo a direct transfor-
mation, and the young very early acquire the characters of the adults.

From this general sketch of the Ctenophore, it may already be inferred that
they constitute a very natural group among Acalephs, entirely distinct from the
Discophore and from the Hydroids, and unquestionably occupying, as an order,
the highest position in the class, if the degrees of complication of strictly homo-
logical structures are at all characteristic of orders and may determine their relative
standing. Since Goldfuss first recognized the natural limits of this group of
Acalephs, and Eschscholtz, with his usual precision and accuracy, characterized it
as a distinct order, all naturalists have acknowledged the propriety of combining
these animals into one and the same division; though some have considered them
simply as a natural family, while others have raised them to the rank of a class.
As I have already stated, I believe them to be an order of the class of Acalephs,
and shall hold them to be nothing more and nothing less than an order, so long

as there is a possibility of distinguishing families, orders, and classes upon definite

1 Of course, in following up this homology it Asterioids ; for it is very simple in the Synaptoids
must be remembered that the ambulacral system among the Holothurians, even more so than in some
of the Echinoderms is not so complicated in all Ctenophorw, as, for instance, in Bolina. But of
of them, as it is, for instance, in the Spatangoids this, and of the special homologies of the chy-

and Clypeastroids, or even in the Echinoids and miferous tubes, more presently.

166 CTENOPHORA. Part II.

principles. DeBlainville and Lesson are the only zodlogists who have associated
heterogeneous types with the Ctenophore.

In now closing this sketch of the anatomical characters of the Ctenophore, I
have only to add a few remarks upon some controverted points of their structure,
with a view of eliciting further investigations, and preventing some mistakes from
being more widely circulated. I have already stated that there exists no distinct
muscular system in the Ctenophore. The appearance of fibres resembling muscles
arises from the peculiar form of the large cells (Pl U% Fig. 24) forming the
spherosome, about which more may be found in a subsequent chapter, where
I shall also consider the true nature of the parts which, from their position and
appearance, have been mistaken for nerves.

The Ctenophore move in two different ways; and the two kinds of motion
are produced by different parts. The more energetic movements, which propel
the body forward, are produced by the contraction of the various systems of
motory cells hereafter to be described, and take place by jerks when they are
most powerful, though during a slow, onward progress they produce a more sliding
motion; besides, these animals are kept hovering in the water by the unceasing
and rapid motion of their locomotive flappers. Of course, durmg a slow progress,
the movements of these rows of flappers combine with the action of the motory cell
systems, while in a more rapid progression they can contribute but little, if any thing,
toward a change of place. As the mode of locomotion of the Discophors differs
in different families according to their different form and the part their various
appendages take in their movements, we must postpone a more detailed account
of these differences to another chapter. Suffice it here to say, that the long
tentacles of Pleurobrachia and the broad lobes of Bolina become important auxili-
aries in regulating the motions of these types. That the powerful contractions
of the spherosome greatly modify the form of the Ctenophore is now generally
understood; but I would warn the student against a belief that the form of these
animals is on that account less characteristic than in other animals. <A bird flying
has certainly a very different appearance from what it presents when at rest; but,
whatever position it may assume, its form is always characteristically its own. So
is it with the Acalephs in general, and, more especially, with those Ctenophore
which are capable of performing the most diversified movements. As soon as the
mode of execution of these movements is fully understood, the form preserves all
its characteristics.

The chymiferous system of all Ctenophore requires more careful study than
has generally been devoted to it. The mode of ramification of its main trunks, the
form of the funnel, the course of its branches and their anastomoses, are very
characteristic of the different families. That these details should have been neg-

Cuar. L STRUCTURAL FEATURES. 167

lected by earlier observers is not surprising; but that Gegenbaur should have
published a figure and description of a new Cydippe, without noticing the
course of these tubes and the connection of the tentacles with this system, is
unpardonable, the more so since he positively affirms that that species, Cydippe
hormiphora, has not only a hollow tentacle, but that the peculiar cirrhi attached
to it are also hollow, and communicate with the cavity of the tentacle. If these
tentacles were truly hollow, it would be of the highest interest to know in what
way the interambulacral tubes penetrate into their cavity, and what are the
relations of the currents extending into these tubes to the general circulation of
the chymiferous fluid through the whole system; since in Pleurobrachia the inter-
ambulacral tubes do not extend beyond the base of the tentacular apparatus, and
the tentacles are not hollow. It may be that there are two types in the structure
of these interambulacral or tentacular tubes, as there are two types of tentacles
among the naked-eyed Medusx, some being hollow, as in Sarsia, and others plain,
as in Bougainvillea; but, until the connection of the tentacular cavity of Cydippe
hormiphora with the interambulacral tubes, and the connection of these with the
central cavity of the chymiferous system, be more fully ascertained, the statement
of Gegenbaur remains unsatisfactory. That a current through the tentacles is not
a necessary condition of their extraordinary power of extension and rapid con-
traction, is plainly seen by the fact, that the tentacles of Sarsia, which are hollow,
are neither more active, nor, comparatively to their size, more extensively movable,
than those of Bougainyillea, which are full. Milne-Edwards has mistaken the
bulb of the tentacular apparatus of LeSueuria for a secretory organ, and erroneously
considered it as discharging its contents outward. It is certainly closed, and
no more open than the interambulacral dilatations of the radiating tubes of
Aurelia, which Ehrenberg also erroneously described as opening outward, and per-
forming the functions of multiple anal apertures. I have carefully examined these
swellmgs im Bolina, LeSueuria, and Aurelia, and am certain, that, unless they are

© medium.

accidentally injured, they in no way communicate with the surrounding

That these tentacular tubes are interambulacral, and not ambulacral, is at once
settled by their position, smce they are intermediate between the radiating tubes
extending to and communicating with the vertical, peripheric, ambulacral tubes ;
but they are homologous to the simple radiating tubes arising in Aurelia from
the angles of the sexual cavity, and enlarging in the margin into the little pouches
mistaken by Ehrenberg for cloacas, and supposed by him to open outward through
as many anal apertures as there are such interambulacral radiating tubes. The
tentacles connected with these tubes are therefore also interambulacral, and on
that account cannot be considered as homologous to the simple ambulacral tenta-

cles of Sarsia, or to the bunches of tentacles of Bougainvillea. We shall see

168 CTENOPHORA. Part II.

presently, that the lasso cells of the tentacles of the Ctenophorz differ also greatly
from those of the Discophors. I shall take occasion to consider more minutely the
direction of the sac containing these interambulacral tentacles, when describing the
Cydippide in detail. The homologies of the whole chymiferous system of the
Ctenophore and Discophore being thus fully established, it would be idle to
animadvert further upon the comparisons which haye been made between the
Ctenophore and Tunicata: their resemblance is merely analogical. There is, how-
ever, one point in the structure of the Ctenophore, which, in this connection,
deserves further consideration.

I have already alluded to the homology of the whole chymiferous system of
the Acalephs, and the ambulacral system of the Echinoderms. <A careful study of
this homology may throw some additional light upon the true nature of the black
speck in the centre of the circumscribed area of the Ctenophore, and upon the
significance of the area itself. Remembering that the eye-specks, or whatever the
organs at the peripheric end of the ambulacral zones of the Echinoderms may be,
are placed at the tip of the rays im the Star-fishes, and in the Sea-urchins on
the abactinal side of the spherosome, alternating with the ovarial plates ; remember-
ing, further, that similar sensitive specks are placed at the tip of the ambulacral
chymiferous tubes in the Discophore, while there is but one such speck in the
centre of the axial prolongation of the funnel in the Ctenophors,—the conclusion
seems unavoidable, that the broad expansion of the abactinal surface of the Dis-
cophore corresponds to the broad field occupied by the dorsal surface of the Star-
fishes, and that therefore the eye-specks of the Discophore are not only homologous
to the eye-specks of the Star-fishes, but also occupy a homological position in
the periphery of the spherosome, while in Ctenophore the single eye-speck has
a homological position with the five eye-specks of the Sea-urchins at the abactinal
pole of the spherosome, with this additional peculiarity, that im Ctenophore there
is but one single eye-speck, and that there are five in the Sea-urchins. Such a
Cyclops-like fusion of the eyes occurs in other types of the animal kingdom, and
is not unfrequent in the Crustacea; it cannot be an objection, therefore, to such
a homology. Moreover, the single eye-speck of the Ctenophorz is closely connected
with the chymiferous system, as the many eye-specks are in the Discophore and
Echinoderms; and that connection, in accordance with the central position of. the
eye-speck, takes place in the axial prolongation of the system.

Whether these sensitive specks are to be considered as eye-specks, or as auditory
organs, is another question, which also requires our consideration. Strictly speaking,
they are not homologous to either eyes or ears, if the mode of development of
these organs of the senses in Vertebrates is considered ; nor can they be com-

pared to the eyes or ears of the Articulates, since in the former the higher organs

Cuap. I. STRUCTURAL FEATURES. 169

of the senses are prolongations of the lateral evolutions of the brain, combining
with involutions from the surface, while in the latter they are modifications of
the lateral appendages of the annular elements of the body of these animals.
Whatever be the real functions of these controverted organs in the Radiates, one
thing is certain,—they are all modifications of the ambulacral tubes connected
with the ambulacral tentacles. This homology is readily ascertamed by a careful
comparison of the so-called eye-specks of the Discophora, especially those of Aurelia
(Pl IX. Figs. 3 and 4); and if the homology I have attempted to trace between
them and the eye-specks of the Echinoderms and the single speck of the Cte-
nophorx, in the centre of the circumscribed area, is correct, then all these organs,—
whether eye-specks or auditory bags, whether simple pigment cells upon the surface
of the tentacles, or vesicular cavities, including various concretions and apparently
independent of the system of tentacles, —are homologous modifications of one and
the same apparatus throughout the whole type of the Radiates, and constitute
organs with more or less specified functions, possibly analogous to the functions of
seeing and hearing in the other branches of the animal kingdom, but certainly
built upon a different plan, congruent with the idea of radiation, which pervades
them all. Gegenbaur states that he has looked in vain for the eye-speck in
Euramphea. Is it possible that this genus should present such a departure from
the universal structure of its type? It does not appear probable to me.

Having thus far traced the special homologies of the sensitive organs connected
with the chymiferous system, I would suggest, that, if the comparisons I have
made are correct, it becomes probable that the circumscribed area of the abactinal
pole of the Ctenophore corresponds to the line encircling the dorsal surface of
the Star-fishes, or the narrow field included between the abactinal termination of
the ambulacral zones in the Sea-urchins. Whether the fringes of the edge of the
circumscribed area of Beroe correspond in any way to the marginal tentacles of
the Discophore, as McCrady suggests, or not, I am not prepared to say. If the
homology I assign to the area itself is correct, it would scarcely be possible to
homologize its marginal fringes with the marginal tentacles of the Discophore,
since these are themselves homologous to the ambulacral suckers.

Gegenbaur has correctly homologized the lateral auricles of the Mnemiide, in
comparing them to the anterior and posterior lobes of that type, only he should
have added that there is, however, this structural difference between them, that
while two spheromeres, with their ambulacral tubes and rows of locomotive flappers,
combine on the anterior and on the posterior side of the spherosome, to form one
anterior and one posterior lobe, each lateral spheromere has its independent auricle,
so situated that while those of one side are the mates of those on the other side,

those of the same side stand also in antitropic relation to one another. Their

VOL. Ul. 22

170 CTENOPHORE. Part IL.

structure does not justify the supposition that the auricles are strictly homologous
to the marginal tentacles of the Discophore; but, at the same time, it should
not be overlooked that they are a prolongation of the ambulacral tubes of their
sphoromeres, and to that extent they bear homological relations to the marginal
tentacles of the Discophore.

Remote as the comparison may seem, it cannot be doubted, upon reflection, that
the simple radiating tubes of the naked-eyed Meduse and those of the medusoid
individuals of the Siphonophore are strictly homologous to the ambulacral tubes
of the Ctenophore, as they are also to those of the Discophoree proper. Their
number generally coincides in the Ctenophore and higher Discophore, though there
are only four in the Siphonophorze and most Hydroids proper. Sometimes they
are, however, very numerous in the latter, as we frequently find an indefinite
repetition of identical parts in the lowest representatives of almost every type.

We have already seen that the peripheric branches of the chymiferous system
do not open outward, as Ehrenberg and Milne-Edwards supposed; but there are,
unquestionably, openings in its axial prolongation, in Ctenophore, which have gen-
erally been considered as anal apertures. Milne-Edwards has accurately described
them in LeSueuria, and they have been observed by all later investigators. Les-
son alone has mistaken accidental openings in the circumscribed area for structural
features. There can be no doubt of his mistake, since he describes those holes in
the Beroids proper as surrounded by fringes, while the position of the natural
openings of the abactinal pole of the Ctenophore is outside of the area, as well as
outside of the fringes which encirele it. In all the Ctenophora which I have exam-
ined, I have invariably found two such openings, in an excentric position, one on
one side and the other on the other side of the antero-posterior diameter, and
obliquely opposite to one another. Gegenbaur states that there is only one such
opening in the species which he has examined with reference to this pomt. It is
much to be regretted that he should not have mentioned its position; for if the
opening which he saw was excentric, as I have always found these openings to be,
I should infer, that while he saw one gaping and shutting, the opposite one may
have remained closed, as it sometimes does for a considerable length of time.
Gegenbaur further affirms that water may be admitted into the system through
that opening. I have only seen the openings gaping to discharge parts of the
contents of the funnel, and never observed an inward current of the surrounding
medium. But whether these holes are simply discharging openings, or at the same
time afferent apertures also, it is equally important to consider their relations to
the whole system more fully than has generally been done. }

The Ctenophore are very greedy, and do not spare their own kindred; but,

generally, they feed on different kinds of Acalephs and a variety of small marine

Cuap. I. STRUCTURAL FEATURES. aval

animals, which they digest very rapidly. I have seen an Idyia swallow a Bolina
nearly as large as itself and consume it in half an hour, rejecting the more con-
sistent parts, such as the locomotive flappers, ete. During the process of digestion
the funnel is greatly distended, and the chymiferous tubes swell enormously, so
that their diameter much exceeds the width of the rows of locomotive flappers,
and an active circulation may be traced through the whole system, when even
the most minute branches appear gorged with fluid. Undoubtedly this fluid is
subservient to the purpose of alimentation; and the whole body enlarges, and, when
full-grown, derives its maintenance, through what it assimilates out of it. But
when considering its relations to the whole organism of the Ctenophore and the
part it plays in their general economy, it should not be overlooked that it is
neither blood, nor in any way comparable to the fluid circulating in the vascular
system of either the Vertebrates, the Articulates, or the Mollusks, but simply a
fluid elaborated in the digestive cavity by a disintegration of the food, with which
a large quantity of water is mixed, and then, after the coarser parts have been
rejected through the mouth, directly poured into another cavity, the funnel, whence
it passes into the radiating tubes, parts of it being from time to time discharged
through the two openings near the abactinal pole.

In consequence of these very peculiar combinations, it is not easy to ascertain
what these openings are. Some anatomists unhesitatingly call them anal apertures ;
but the anus, throughout the animal kingdom, is the posterior opening of the
alimentary canal, while here we have two openings in the central part of a system
which is distinct from the digestive cavity, and through which nutritive fluid is
circulated. These openings cannot, therefore, be identified with anal apertures, even
though the nutritive mass be only chyme, and neither chyle nor blood; but ought
to be considered as a special structural combination peculiar to this type of the
animal kingdom. It cannot be strictly homologous to any structure among the
higher types of animals; and the nearest resemblance which it has to the structural
complications of the Vertebrates is.a mere analogy, and may be thus expressed :
Supposing the alimentary canal and the lymphatic vessels arising from its wall to
be in direct and open communication with the veins which carry the products of
digestion to the heart, and through this with the arteries providing the materials
that are discharged by perspiration at the surface of the body, and that the fluids
moving through this succession of distinct structural systems should be throughout
the same fluid, and the channels through which it is discharged at the surface,
not only unobstructed by intervening capillary networks, but uniform from one end
to the other, and we should have homological structures. The difference between
the one and the other case shows the remoteness of their analogy ; and, instead of

calling these openings anal apertures, 1 would prefer the name of celiac apertures.

172 CTENOPHORZ. Part II.

The motions of the chymiferous system are of two kinds. The tubes them-
selves are distended by the influx of the fluid elaborated in the digestive cavity,
and their diameter is reduced by the contractions of the cells forming the sphero-
some. The alternate currents from one half of the body to the other and vice
versa are also the result of the alternate contraction of the opposite halves of
the spherosome; but the slower flow of the fluid through the chymiferous tubes,
and especially its undulating motions, now in one direction and then in the oppo-
site direction, within comparatively short tracks of the tubes, are unquestionably
determined by the vibratile cilia which line their inner surface.

For the same reasons, | am not inclined to consider the colored cells lining in
vertical rows the walls of the abactinal portion of the digestive cavity as homolo-
vous to liver cells. No doubt they are analogous to a liver; but, to be homolo-

g
gous with such a complicated glandular organ, they should derive the fluid they
contain from bloodvessels, and not from chymiferous tubes. As pigment cells do
not occur at the surface of all Ctenophore, but only in some of their representa-
tives, I shall describe them in their proper place.

In our temperate latitudes the Ctenophore are annual animals, laying their
eggs in the autumn and then dying, and the young brood making its appearance
in the spring. I have watched the species of the coast of Massachusetts during
twelve successive years, and invariably found that in the earlier part of the sum-
mer the majority of specimens observed were small and destitute of sexual organs,
or, at least, not yet filled with eges and spermatic cells, as they are later in the
season. The largest specimens are always seen during the last summer months,
and all disappear after the autumnal gales. The sexual organs of the Ctenophore
are described by some anatomists as sexual glands, and called ovaries and_ testes,
according to the sexes. While I retain the name of ovaries for the female, and
propose that of spermaries for the male organs, I must record my objection to
the use of the word gland to designate these organs. A glandular sexual organ
can only exist in animals which have a distinct vascular system, through which
blood is cireulated; and this is not the case in the Acalephs. Here again the
reproductive organs are only analogous, and not homologous, with the organs per-
forming the same functions in the higher animals. In Ctenophoree they are simple
pouches or lateral sacs of the chymiferous tubes, and have no special walls dis-
tinct from those of the tubes with which they communicate. The actinal disposi-
tion of the sexual organs is another peculiarity of the Radiates, which distinguishes
them strikingly from similar organs in other types of the animal kingdom. — It
should also be remembered, that hermaphroditism is not very uncommon among

these animals, in which case the male alternate with the female organs in their

radiated arrangement. Among Polyps, we have such a combination in Cerianthus :

fo)

Cuar. I. STRUCTURAL FEATURES. 173

among Acalephs, in the Ctenophore generally. I have never observed hermaphro-
dites among Echinoderms.

McCrady has described facts which he considers indicative of a fissiparous mul-
tiplication of the Ctenophors. What I have seen of the persistence of parts of
the body of Ctenophorz has rather appeared to me as indications of the protracted
vitality of disconnected parts of these animals. When injecting Ctenophore, I often
had occasion to make incisions into their spherosome, and I have always been
struck with the power with which these wounds were closed up, by the contraction
of the surrounding cells, but never observed a healing process. I have often cut
Ctenophore and other Acalephs into halves, or into smaller segments, without ma-
terially interfering, for some time at least, with the manifestations of their vitality.
Idyias cut into halves in any direction continued to live in my jars as long as
uninjured specimens. I even once saw half of an Idyia close over a small Bolina
and digest it, its cut edges overlapping its prey. It seemed to me, sometimes, as if
mutilated individuals fared even better in confinement than entire ones. I am certain
that this is the case with larger Discophore. I never succeeded in preserving
large specimens of Cyanea entire in my tanks for more than two days; but, after
cutting off all their long tentacles and their oral appendages and dividing the disk
into halves or quarters, I have often preserved such segments for weeks, swimming
about as if uninjured, when entire specimens caught at the same time would die
and decompose in one or two days. But I never saw the slightest trace of
reproduction of lost parts.

In order to avoid the difficulties which, in describing species, might arise from
a strict adherence to a nomenclature based upon homologies, it would seem advisable
not to use the expression vertical axis or vertical diameter to designate the main
axis of the Radiates in general; for the very obvious reason, that that axis is
oblique im a very large number of Echinoderms, as, for instance, in the Spatangoids.
I would, therefore, prefer the use of the word actinal avis or actinal diameter, as
expressing the axis which unites the actinal and the abactinal poles. The diameter
which passes through the longer diameter of the actinostome and corresponds to
the longitudinal diameter of the Spatangoids had better be called celiac diameter,
because it is not, obviously, the longest diameter; though in all Radiates, in Polyps
as well as in Acalephs and Echinoderms, it trends in the direction of the digestive
cavity, or of the maim cavity of the body. The name celiac, moreover, does not
imply the necessity of distinguishing the anterior and posterior ends of a longi-
tudinal diameter, which in Acalephs do not differ, as they do in some Echinoderms.
For the diameter which, homologically speaking, I have designated as the ¢ransverse
diameter, 1 would prefer the name of diaceliac diameter, as it stands in rectangular

relation to the celac diameter.

174 CTENOPHORA. Part II.

SE COm VON «ak
SUBDIVISIONS OF CTENOPHORE, FORMING SUB-ORDERS.

A comparison of the various attempts to subdivide the Ctenophore is very
instructive with reference to the principles upon which classifications may be based.
Eschscholtz, as early as the year 1829, divided them into three families: CaLur
ANIRIDA, with the genera Cestum, Cydippe, and Callianira ; Myemip, with the genera
Eucharis, Mnemia, Calymma, and Axiotima; and Berom®, with the genera Beroe,
Cestums, Callianiras, Beroes,

Medea, and Pandora. Mertens admits four families:

and Idyas. Lesson, who considers the whole order as a family under the name
of Brrowex, subdivides them into eight tribes: Cesfoidew, with the genera Cestum
and Lemniseus; Callanire, with the genera Callianira, Chiaia, Polyptera, Mnemia,
Bucephalon, and Bolina; Leucothoew, with the single genus Leucothoea; Calymmec,
with the genera Calymma, Eucharis, Aleinoe, LeSueuria, and Axiotima; Neiside,
with the genus Neis; Ocyroee, with the genus Ocyroe; Cydippe, with the genera
Mertensia, Anais, Eschscholtzia, Janira, and Cydippe; and the Lerow proper, with

the genera Beroe, Idya, Medea, Cydalisia, and Pandora: to which, strange to say, a

number of Diphyidx, Tunicata, Noctiluca, and Bipimnaria, are added.

Leuckart, who

considers them as a distinct class, subdivides them primarily into two orders, the

Eurystomata and Stenostomata.

under three heads:

Gegenbaur admits five families, which he groups

1°, those the body of which is extended into lobes, with or

30

without tentacles, the Cadlauride and Calymnide; 2°, those which have no lobes,

1 When considering the works of a master in
any department of Natural History, I am in the
habit, first, of identifying myself with his views as
completely as I possibly can, and ascertaining how
far, in the course of the progress of our science,
additional evidence may have been accumulated in
support of his opinions, even if the new facts should
tend at the same time to modify them; for it
is generally the case, that those who have been
long engaged upon a difficult subject instinctively
perceive relations which become more apparent
only with the lapse of time. Next, I proceed to
a critical revision of the bearing of each faet, in

order to avoid one-sided appreciations and useless

discussions. And, finally, I present the result of
my own investigations, combined with the information
thus obtained from the labors of my predecessors.
This method I have found particularly useful in
the study of the Acalephs, most of which are de-
scribed in so many different ways by different
authors and at different periods, with such unequal
knowledge of their structure, that, unless we supply
the deficiencies of older writers by the light cast
upon these animals from modern investigations, a
large number of the most interesting types of the
class would have to be entirely left out of con-
sideration in our renewed attempts at tracing their

natural aflinities.

Crap. I. SUB-ORDERS OF CTENOPHOR. 175

but always tentacles, the Cestide and Cydippide; and 3°, those without lobes and
without tentacles, the erode.

Here, as everywhere in our science, the total absence of a principle in assigning
a rank to the divisions adopted by different authors is painfully felt. While
Eschscholtz considers the Beroids as an order, to which he first applied the name
of Crrxopnor®, Lesson considers the whole group simply as a family, with which
he unites most heterogeneous animals, belonging to several distinct classes; and
Leuckart, whom Gegenbaur has followed in that respect, regards them as a distinct
class. The three families distinguished by Eschscholtz coincide very closely with
the three more comprehensive groups into which Gegenbaur arranges the five
families which he admits. Mertens, again, separates Cestum from Cydippe, as a
distinct family, unfortunately retaining the name Beroe for the family of the latter
genus, and applying that of Idyia to the family called Beroidee by Eschscholtz
and that of Callianira to the family called Mnemidx by Eschscholtz, who had
already used the name Callianiridee for the family to which he refers the genera
Cestum, Cydippe, and Callianira. It is in view of this confusion, probably, that
Gegenbaur has again changed the family name of Mnemiidx Lsch. to Calymnide
Gegenb.; but in so doing he has only made the matter worse, since his family
Calymnid again differs from the tribe called Calymmex by Lesson. This affords
another evidence of the absolute necessity of strictly adhering to the law of priority.
The family names first proposed by Eschscholtz cannot be discarded so long as
there remains a natural group of Ctenophore to which they can be applied. We
shall see presently what is the value of the eight tribes distinguished by Lesson.
The first question that should now engage our attention is, whether the families
adopted by Eschscholtz and Gegenbaur bear family characters or not; since I have
already shown that the Ctenophore, as a natural group, are neither a class, as
Leuckart and Gegenbaur admit, nor a family, as Lesson would have it, but a
natural order of the class of Acalephs.

Eschscholtz assigns the following characters to his three families of Ctenophore :
Callianiride, with small digestive cavity and tentacles; Mnemiide, with small digestive
cavity, but without tentacles; Beroide, with large cavity of the body acting as
digestive cavity. Gegenbaur characterizes his families as follows: Callianiride, with
lateral, wing-like appendages supporting the locomotive flappers; Calymnide, with
two lobe-like appendages upon the sides of the mouth; Cestidw, body riband-like,
expanding transversely ; Cydippide, body oval or rounded; Peroide, body ovally
elongated. The characters assigned by Eschscholtz to his families are entirely
derived from their structure, without reference to form: Gegenbaur, on the con-
trary, distinguishes some of his families by anatomical characters, others by their
form. Which of these two methods is correct? for I mean, at present, only

176 CTENOPHORA. Parr II.

to consider the method, and not the value, of the characters assigned to the groups
themselves. Inasmuch as Gegenbaur has introduced the element of form in the
characteristics of his families, instead of alluding solely to the features of their
structural complication, as Eschscholtz had done, he has made a decided advance
over the classification of the latter. This is the more apparent when it is re-
membered that these structural complications are not at all overlooked by him;
but, on the contrary, are made use of in grouping the families under three more
comprehensive heads, to which, however, he has assigned no names, but which
correspond very closely to the groups called families by Eschscholtz. It is proper,
therefore, that we should inquire into the meaning of these groups, and at the
same time remember also that Leuckart likewise admits divisions among the Cte-
nophore superior to the families, which he calls orders, and of which he admits
two,— the Kurysromara and Srenosromara, the former corresponding to Exschscholtz’s
family Beroide, the latter to Eschscholtz’s united families Callianiridee and Mne-
mide; admitting, further, that the Ctenophorz are a class and not an order. We
have thus, as subdivisions of Ctenophore, fice families distinguished by Eschscholtz,
corresponding to three higher divisions, including jive families admitted by Gegenbaur,
and ¢wo orders admitted by Leuckart.

With these facts before us it cannot be difficult to untie the knot of these
conflicting views, only leaving, for the present, the question of the natural limits
of all these groups out of consideration.’ Leuckart and Gegenbaur have evidently
both felt that the natural families of the Ctenophore are linked together by features
of a more comprehensive value than family characters; but, placing only a sub-
ordinate importance in questions of classification, one of them has given no names
to the groups based upon those features, while the other has called them orders.
If, as 1 have urged again and again, families are based upon peculiar patterns
of form, and orders, natural groups founded upon the degree of complication
of the structure, the characters assigned by Gegenbaur and Leuckart to these
divisions are truly of the kind upon which orders are founded; but, the char-
acters of orders resting upon the sum of structural complications which determine
their relative standing in the class, it is plain that special points in that compli-
cation which do not extend to all the members of the order can only lead to
the recognition of secondary natural groups sharing the characteristics of orders,

but not themselves orders, and for which I have proposed the name of. sub-orders.

1 In all discussions like the present, a perfect there is an end to every critical inquiry into the

familiarity with the objeets themselves is a neces- importance and relative value of the characters

sary requirement; for if the natural features of these assigned to the divisions adopted by different authors,
objects are first to be ascertained during the dis- and the meaning and rank of the divisions them-

cussion and by the study of a given classification, selves.

Cuap. I. SUB-ORDERS OF CTENOPHORA. Ndr

This once settled, it remains to be seen how many such sub-orders there are among
Ctenophore, and what is the range of their structural peculiarities, and next to
ascertain in the same way the number and natural limits of the families in each
of these natural groups.

As Gegenbaur has already noticed, Leuckart has based his primary subdivisions

of the Ctenophorse upon a character of comparatively little value,—the dimensions
of the digestive cavity. It is nevertheless true, that the group thus separated
from the other types under the name Eurystomata is a very natural one, already
distinguished by Eschscholtz, to whose family of Beroide it exactly corresponds,
as well as to Gegenbaur’s third group of Ctenophore, without lobes and without
tentacles. There is therefore no discrepancy among naturalists as to the existence
of a natural division among Ctenophors, including the species most closely allied
to the genus Beroe of Brown. Eschscholtz recognizes it as a family under the
name of Beroide; Mertens as a family under the name of Idya; Lesson as a
tribe under the name of Berow; Leuckart as an order under the name of Eu-
rystomata; and Gegenbaur as one primary division of the Ctenophora including
the only family of Beroide. But while all agree upon the limits of that group
of Acalephs, there is the widest discrepancy among them as to its rank and
standing in the class.

In attempting to decide between these conflicting opinions, it must be borne
in mind, that, in analyzing the characteristic features of these Beroids, we have to
consider different categories of characters. In the first place, the Beroe proper
have all those structural peculiarities in common with the other Ctenophors, which,
from their complication, place them highest in the class of Acalephs as a distinct
order. But, though agreeing with the Ctenophore generally in the complication
of their structure, they differ from all other Ctenophore in one striking anatomical
character, entirely independent of their peculiar form,— they have no interambulacral
chynuferous tube, which exists in all others. The existence of two parallel chy-
miferous tubes in the transverse plane of some Ctenophore, on both sides of the
digestive cavity, was first pointed out by Milne-Edwards in his admirable description
of LeSueuria vitrea (Ann. Sc. Nat. 2° sér. vol. 16, p. 203, Pl. 3, Fig. 1 A and 7).
Will has described them in Eucharis multicornis (Hore tergestine, p. 31, PL I.
Fig. 3, 6 and c). I myself have traced them in Bolina (Mem. Am. Ac. IV. Pl. 7,
Figs. 4, 7, and 8). Gegenbaur, however, mentions and figures only one of them.
As they are easily confounded, on account of their parallel course, I have no doubt
that he must have confounded them. One is deeply seated, close to the digestive
cavity, and communicates with the tube encircling the mouth; the other is more
superficial, and quite at the surface, near the mouth. They are best seen facing
the anterior or the posterior surface of the animal, as their divergence is thus

VOL. III. 23

178 CTENOPHORE. Part II.

brought imto view. In the attitude in which Gegenbaur has represented his
Euramphexa vexilligera, they cover one another, as they then lie in the same plane.
In order readily to designate these two tubes, which are eminently characteristic
of the Mnemiide or Calymnidx, I shall hereafter designate that which follows
closely the outline of the digestive cavity as the stomachal or caliae chymiferous tube,
and call that which lies outside, the ierambulacral or tentacular chymiferous tube. Now,
the structural peculiarity of the Beroids proper consists in having a very large
stomachal or coeliac chymiferous tube opening into an equally wide oral tube
(Pl. UL. Fig. 10), whilst the interambulacral or tentacular tube is entirely wanting. The
centre of the whole chymiferous system, its main trunks and the axial funnel, is
remarkably small in comparison to the wide ambulacral, coeliac, and oral tubes.

There are other secondary anatomical peculiarities, equally characteristic of this
group, Which may now be mentioned also. The eight ambulacral chymiferous tubes
are equally developed; there is no difference in the extent or size or structure
of those running along the sides, or along the anterior and posterior surfaces ;
they all give out numerous, rather conspicuous, and highly ramified branches, while
the coeliac tube is entirely destitute of ramifications. The ovaries and spermaries
(PL Ul. 2g. 4, and Pl. L), the special arrangement of which has already been
described above, are large and very conspicuous at the spawning season. The
circumscribed area (Pl. I. Ag. 3, and PL UW. #%y. 9) is encircled by a prominent
wall of elegantly branched fringes.

The structural character bearmg more directly upon the form of this group of
Ctenophorze consists chiefly in the even thickness of the spheromere (Pl. I. Figs.
3 and 4), which renders it movable in every direction; so that the changes of
outlines of the Beroids proper are far more extensive than those of any other
members of the whole order. This ability to change their form is further enhanced
in these animals by the circumstance, that the digestive cavity extends so far
towards the abactinal pole as to reduce the bulk of the spherosome in that
direction to the average thickness which it has upon the sides. A comparison of the
different figures of Pl. I. may give some idea of these changes of form; and /%g. 10,
especially, which represents a specimen of the same size as vgs. 7 and 8 gorged
with «a Bolina nearly of its own size, will show to what extent they may be
distended. #%g. 5 represents a specimen with the actinostome turned inside the
digestive cavity. Notwithstanding this remarkable movability, all these animals
preserve a very regular and symmetrical form in a state of rest, the sides appearing
uniformly compressed.

Thus we have here two different categories of characters: first, anatomical
peculiarities of the same kind as those upon which the order of Ctenophore is

founded, only relating to certain limited points of their structure; and, secondly,

Cuap. I. SUB-ORDERS OF CTENOPHORZ. 179

a distinct pattern of form determined by the even thickness of the spherosome,
or, more accurately, by the even arrangement of the motory cells of the sphero-
meres. I hold, therefore, that the Beroids proper constitute a distinct sub-order,
and not merely a family nor a distinct order, since their distinguishing characters,
though of the kind of those upon which orders may be founded, do not extend to
their whole organization. We shall see presently whether these Acalephs constitute
only one single family, or not.

It would be tedious, were I to analyze at the same length the value of all
the characters wpon which are founded the other subdivisions of the Ctenophore
proposed by different naturalists. Suffice it for me to say, the division proposed
by Leuckart under the name of Stenostomata is neither an order, as he takes it,
nor a natural sub-order,—not simply because the characters which he assigns to
these Ctenophore are not of the kind upon which orders may be distinguished,
but because it is in itself a heterogeneous assemblage of different types. The
groups designated by Eschscholtz as two distinct families, and the corresponding
groups proposed by Gegenbaur, under which he unites respectively the families of
the Callianiride and Calymnide, and the Cestide and Cydippide, approach much
nearer to the idea of sub-orders. At all events, they include the representatives
of two distinct sub-orders; but, from want of personal acquaintance with the Calli-
aniridee and Cestide, I am unable to state with certainty how closely these may be
allied to the types of the two sub-orders which I have investigated. It may also
be noticed, that Eschscholtz and Gegenbaur disagree as to the affinities of Cestum
and Callianira, — Eschscholtz uniting both with Cydippe, while Gegenbaur separates
them as types of distinct families. So, leaving for the present the question of the
closer affinities of the genera Cestum and Callianira out of consideration, IT am
prepared to show that Eschscholtz’s Mnemiidx and his Callianirade do not constitute
two natural families, but two distinct sub-orders equivalent to that of the Beroids
proper. On account of the questionable affinities of the genera Callianira and
Cestum, I am, however, compelled for the present to designate one of these sub-
orders by a different name from that applied to it by Eschscholtz, and shall adopt
for it that of Cydippide, instead of Callianiridee.

The anatomical peculiarities of the Cydippide, which show them to be a sub-
order, and not merely a family, correspond exactly to those which distinguish the
Beroide. The eight ambulacral tubes are equal or nearly so, as in Beroide, but
they terminate, on both sides of the main axis, at a considerable distance from
the poles of the spherosome, and do not open into an oral tube; for there is no
such cireular chymiferous tube around the actinostome in this group of Ctenophore.
The coeliac tubes are very large, and terminate as blind sacks upon the sides of

the actinostome. Neither the ambulacral nor the coeliac tubes give out conspicuous

180 CTENOPHOR®. Parr II.

ramifications. But while the peripheric part of the chymiferous system is thus
limited, its central part is more fully developed than in any other Ctenophore ;
the main trunks and their eight forks are very large, and the axial funnel is
equally wide. The most conspicuous structural feature of the Cydippide consists
in the presence of to extensive tentacular organs, one on each side, attached at the
bottom of a deep sack, along the proximal surface of which extend two large parallel
chynuferous tubes, homologous to the one simple interambulacral tube of Bolina,
already mentioned above. The chief differences in the distribution of the chy-
miferous system of the Beroidw and Cydippide consist, therefore, not only in the
limitation of its peripheric branches, the absence of an oral tube, and the broad
development of its centre, but also in the presence of a double interambulacral
or tentacular tube on each side. The ovaries and spermaries are very small in
comparison to those of the Beroids, and the circumscribed area of the abactinal
pole, covered with vibratile cilia, is simply limited by a narrow ridge. The deep
and wide sac containing the tentacular apparatus, and the bilateral disposition of the
main trunks of the chymiferous tubes, combined with their ample dimensions, have
a powerful influence in controlling the form of these animals. But we shall
consider this point more fully when discussing the characters of the different
families of Cydippide.

The sub-order of the Mnemiide is at once distinguished by the waequal de-
velopment of the ambulacral tubes and of the locomotive flappers, and by the presence of
lwo more or less extensiwe lobes, formed by a peculiar expansion of the spherosome.
Of the eight ambulacral tubes there are four, the two lateral pairs, which are
antitropically symmetrical to one another and identical in form and extent with
one another, but differ greatly from the four others, the anterior and the posterior
pairs, though these are also symmetrical and identical among themselves. When
contrasted with one another, these two sets of tubes present very peculiar combi-
nations. In the first place, the anterior pair, which faces the posterior pair, or
vice versa, is separated from the latter by two pairs of lateral tubes, so arranged,
however, that one tube of each pair is on one side, and the other tube of each
par on the other side, of the coeliac diameter or plane, which may divide the
anterior as well as the posterior pair of tubes into equal halves; and not so
placed that one pair would be on one side and the other pair on the other side,
though at first sight it would seem as if four pairs of tubes were placed crosswise
to one another. A correct appreciation of the peculiar symmetry of the Cte-
nophore is so difficult, that, even at the risk of being tedious, I must try to
make clear the arrangement of these tubes by another explanation. Calling one
side the right, the other the left side, and one of the connecting surfaces the anterior

and the other the posterior, we find that one of the tubes of the anterior pair

ea
‘

Cuar. I. SUB-ORDERS OF CTENOPHOR®. 181

is on the right side, and the other on the left side; next to these we have on
each side one of the tubes of the first lateral pair, which may be called the
anterior lateral pair; next, on each side, one of the tubes of the second lateral
pair, the posterior lateral pair; and, finally, opposite to the anterior pair, on each
side, one of the tubes of the posterior pair: so that the two lateral tubes of the
same side do not form together one pair, but are each the counterpart of those on

the opposite side.

Amer, Ac. may readily render this intelligible.

Bourna ALATA, Ag.
(Seen from the broad side.)

aand f Long rows of locomotive fringes. —
gandA Short rows of locomotive fringes.
—o Central black speck (eye-speck ?).—
7 to m Triangular digestive cavity. —7? to o
Funnel-like prolongation of the main cay-
ity.—v Chymiferous tube of the tenta-
cular apparatus.— mm Tentacular appa-
ratus on the side of the mouth. —rr Ear-
like lobe, or auricles, in the prolongation
of the short rows of locomotive fringes.
—tt Prolongation of the vertical chymife-
rous tubes. —nn The same tubes turning
upwards.—xx Bend of the same tubes.
—zz Extremity of the same tubes meet-
ing with those of the opposite side. —w
Recurrent tube anastomozing with those
of the auricles.

Fig. 84.

zm

BoLinA ALATA, Ag.
(Seen from the narrow side.)

ab Long rows of locomotive fringes. —c hk
Short rows of locomotive fringes. —o Cen-
tral black speck (eye speck?).—z? Upper
end of the digestive cavity. —7 too Fun-
nel-like prolongation of the main cavity of
the body.— 2 toz Digestive cavity. —rr
Auriiles.— 2 Mouth.—?t ¢ Prolong-
ation of the vertical chymiferous tubes.
—nn The same turning upwards. — xx
Bend of the same tubes. —z Anastomosis
of the two longitudinal tubes tt. —ww
Recurrent tube, anastomozing with those
of the auricles. — A comparison of this fig-
Me, 83 gives a distinct idea of the
relative position of the digestive cavity mm
to 7, and the chymiferous tubes of the ten-
tacular apparatus v.

(A comparison with Pl. VU. of my paper in the Mem. of the
See also the adjoming /gs. 83, 84, 85,

BoLina ALATA, Ag.
(Seen from above.)

o Central black speck (eye speck ?).—abef

Long rows of locomotive fringes. —cdgh
Short rows of locomotive fringes. — rr
Auricles. — ss Circumscribed area of the
upper end of the body.

BoutnA ALATA, Ag.
(Seen from below.)
m Mouth. —rr Auricles. — tttt Prolonga-
tion of the vertical chymiferous tubes. —
= Anastomosis of these tubes.

and 86.")

All other Ctenophor have their ambulacral chymiferous tubes arranged

in the same way as in the Mnemude, only that their combinations are not so readily

1 Fig. 89, which represents our Bolina from the
abactinal pole, will best explain these relations.
The line ss indicating the longitudinal or ccliae
diameter, the ambulacral rows a, h, g, and f of
one side are the counterparts of those marked 3,
e, d, and e of the other side; @ and 6 being the
anterior pair, and f and e the posterior pair;
and e the anterior lateral pair, and g and d the
posterior lateral pair. 7g. 86, representing the
actinal pole in the same position, shows the con-

tinuation of the same rows, or their tubes, on this

pole. Jy. 83 represents one side of the animal
in profile, but in the same position as Fig. 85, so
that the rows a, hf, g, and f alone are visible,
which correspond to the rows a, hf, g, and f on
one side of the celiac diameter in Fig. 85. Fig.
84, finally, represents the anterior surface of the
same specimen, so that here the anterior pair of
rows a and 64, and the anterior lateral pair ¢ and
h, are alone visible; that is to say, the rows on
one side of the diaccliac diameter, corresponding

to the rows a and 6 and e and / of Fig. 85.

182 CTENOPHORA. Part II.

perceived, on account of the great uniformity of the tubes themselves. Even in
Pleurobrachia, in which the chymiferous tubes seem absolutely identical in size,
and evenly radiating in eight directions, the same arrangement may be recognized,
upon careful examination.

In the second place, these four pairs of chymiferous tubes, so combined, are
unequal in their development,—the lateral pairs being short, and terminating each
in a small free lobe or auricle, while the anterior as well as the posterior pair,
meandering through the thickness of Jlobe-like prolongation of the spherosome,
anastomoze with one another, and form a curious lattice-work of chymiferous tubes
upon the inner surface of the base.

The most striking peculiarity of all the ambulacral chymiferous tubes of the
Mnemiide consists, however, in the great inequality of the diameter cf the tubes
in different parts of their course. Upon the sides of the spherosome, and as far
as the locomotive flappers extend along with them, they are wide and_ highly
contractile ; but beyond these limits they are more like capillary vessels of an equal
diameter, especially in their prolongation upon the imner surface of the great lobes
of the spherosome, where those of the two sides of the anterior and of the posterior
pair anastomose with one another, as well as with branches from the lateral pairs
and from the oral tube. The centre of the whole chymiferous system is neither
so fully developed as in the Cydippidee nor so reduced as in the Beroidx ; but the
main trunks and the axial funnel are of moderate dimensions. The coeliac and
the interambulacral tubes, of which there is but one on each side, run parallel to
one another, and present nearly the same development. The tentacular appa-
ratus is connected with the extremity of the interambulacral tube, but not enclosed
in a deep sac. The circumscribed area of the abactinal pole is not more distinct
than in the Cydippide, nor are the ovaries and spermaries prominent. The
digestive cavity is comparatively small, as in Cydippide; but there is this re-
markable difference between the Mnemiide and Cydippide in the relations of the
actinostome, that while in Cydippide the mouth is prominent on the actinal
pole, in Mnemiide the broad lobes formed by an actinal prolongation of the two

anterior and the two posterior spheromeres extend far beyond the mouth, and may

1 Whether this network of chymiferous tubes,
thus far only noticed in Bolina, Alcinoe, Chiaja, and
Leucothoe by Mertens, Will, and myself, exists in
all Mnemiidw, or not, I am unable to say. I am,
however, inclined to believe that it will be found in
all. Its anastomosis with the recurrent tube of the
auricles seems a typical indication of its natural

connections; and as the recurrent tube has been

observed in LeSueuria and Euramphwa, I infer
that the rectangular, anastomotic ramifications of
the chymiferous tubes upon the lower surface of
the lobe-like prolongation of the spherosome is
likely to exist in all the representatives of this
sub-order. The appearance of this network of
tubes is very similar to the mode of ramification

of the branchial vessels of the Naiades.

Cuap. I. SUB-ORDERS OF CTENOPHORA. 183

cover it entirely, when brought together by an antitropic movement, in the direction
of the antero-posterior diameter. The relative size of these lobes, as well as of
the auricles, at the actinal end of the lateral chymiferous tubes, varies greatly in
different representatives of this sub-order, but the lobes and auricles exist in all;
in all there are four auricles, one to each lateral chymiferous tube; and in all
there are only two lobes of the spherosome, each formed by the combination of
two spheromeres. The locomotive flappers are limited to the compact part of the
spherosome, the lateral ones being generally much shorter than the anterior and
posterior ones. In no Ctenophore is the bilateral symmetry more prominently
marked than in the Mnemiide; and when the lobes of the spherosome are fully
extended, the coeliac diameter greatly exceeds the diacceliac diameter.

To these three sub-orders I would refer all the Ctenophore I know; and unless
Cestum proves to have marked structural peculiarities not described by the natural-
ists who had an opportunity of examining that~ genus, it must be referred to the
Cydippidx, with which Eschscholtz has already associated it. I believe, however,
that Cestum is likely to prove the type of a distinct sub-order, if the account
given by Eschscholtz and Mertens of its chymiferous tubes is at all correct. But
the circumstance that both have overlooked the cceliac tube, which exists in all
Ctenophore, lessens my confidence in their description. The figure of Vogt is
still more defective, as it also omits the interambulacral tube which Eschscholtz
represents. The most striking difference between Cestum and the true Cydippide,
to which Eschscholtz refers this genus, consists, according to the figures I have
examined, in the trend of the tentacular sac, which in Cestum is in the direct
prolongation of the interambulacral tube, and opens on the actinal side of the
spherosome, while in Pleurobrachia it is bent in the opposite direction and opens
on the abactinal side. There can be no question on that point. LeSueur,— who
has published the first figure of Cestum,— Eschscholtz, Mertens, and Vogt, all repre-
sent it in the same position, in illustrations which are not copied one from the
other, and even represent different species. All the authors who have described
Pleurobrachia represent that apparatus in this genus as I have myself seen it,
trending in the opposite direction, with the sole exception of Grant, who erroneously
represents it im a reverse position, in a paper specially intended to illustrate a
neryous system which is wanting. This mistake may show the importance of
studying minutely the symmetry of these animals.

Another peculiarity of Cestum, mentioned by some naturalists who have observed
this genus, is the presence of only four rows of locomotive flappers along the
abactinal side of the elongated spherosome: this is the statement of Eschscholtz.
Vogt represents such flappers on both sides of the animal, and says expressly

(Zool. Briefe, p. 257) that they exist upon all the margins of the body.

184 CTENOPHORA. Part II.

As to the dimensions of Cestum, Vogt calls width what is truly the height
of the animal; LeSueur, Cuvier, Blainville, Mertens, and Gegenbaur apply the
same designation of width to the surface which has the longest diameter, and
which Vogt correctly calls length; the transverse diameter, or that which measures
the thickness of the tape-like body, being the shortest diameter. A comparison
with Pleurobrachia or Bolina, taking the relative positions of the actinal and
abactinal poles and of the interambulacral tubes into consideration, will at once
set this matter right. But it is obvious that this genus requires reéxamination
with reference to the general course of its chymiferous tubes and the number of
rows of its locomotive flappers. I have no doubt that the chymiferous tubes which
follow the rows of locomotive flappers on both sides of the elongated abactinal
pole are the two anterior and the two posterior ambulacral tubes, and those which
Eschscholtz has described as median tubes, the four lateral ambulacral tubes; but it
remains to be ascertained whether these tubes are entirely destitute of locomotive
flappers or not. From the figure of Eschscholtz, I suspect that each row of loco-
motive flappers may correspond to a double row, as in young Cydippide. If this
should be the case, Cestum would truly form a fourth sub-order, characterized, in
addition to these structural peculiarities, by the trend of its tentacular sac, and the
extraordinary development of its anterior and posterior pairs of spheromeres. The
natatory flappers of the actinal margins described and figured by Vogt are likely
to be homologous to the auricular fringes of the Mnemude.

As to Callianira, judging from the descriptions and figures thus far published,
it would seem to be but slightly different from Pleurobrachia, and therefore to
belong to the sub-order of Cydippide; but as no recent imyestigator had an
opportunity of examining any species of that genus since the structure of the
Ctenophore has begun to be better known, it is impossible to form a decided
opinion upon its affinities. [ merely infer its Cydippian relationship from the
position of the tentacles in Callianira triploptera. The most striking character
assigned to it consists in the wing-like projection of the rows of locomotive flappers,
of which there are three pairs, according to the descriptions, though the figures
show that there must be four pairs.

Thus far, I have designated the different sub-orders of the Ctenophorx by the
name of the best-known family belonging to each; but as these names will have
to be retained for the families themselves, it is necessary now to select some others
for the sub-orders. For the Beroide the name Lurystonie, or Lurystomata, applied
to them by Leuckart, may be retained; for the Cydippide I would propose that
of Saccate, on account of the deep pouch in which the tentacular apparatus is
received ; and with Exschscholtz (Isis, 1825, p. 741), that of Zobate for the Mne-

miidew, on account of the lobe-like prolongation of the spherosome. Should Cestum

Cuap. I. SUB-ORDERS OF CTENOPHOR. 185

prove the type of a distinct sub-order, these Ctenophore may be called Teniate.
A few Acalephs referred to the order of Ctenophore do not belong to it at all;
such are the Beroe Gargantua Less., which is a genuine Discophore, and the Acils
Less., which are mostly Siphonophore. Berosoma Less. may be a Pyrosoma; but
since it was described and figured from memory, it hardly deserves further notice
till it has been observed satisfactorily.

It may now be asked how far these sub-orders may be superior or inferior
to one another. This is a question which I am not fully prepared to answer.
Indeed, it seems as if natural sub-orders exhibit fewer indications of superiority
or inferiority among themselves than any other kind of natural divisions in the
animal kingdom, the characteristic features of sub-orders resting chiefly upon the
prominence of one or the other subordmate elements of the structural complication
which distinguishes the order itself. We find, for instance, that while the inter-
ambulacral chymiferous tube is wanting in the Eurystome, they have a large oral
tube, which is wanting in the Saccate; but these have a complicated tentacular
apparatus with a double interambulacral tube, all of which is wanting in the Eu-
rystome: and again, the Lobate have four auricles and two lobes of the sphero-
some, which do not exist in either the Saccate or the Eurystome, but in the
Lobate the oral tube is small and the tentacular apparatus very imperfect in
comparison to that of the Saccate. So that, unless comparative embryology
some day furnishes the means of determining the relative importance of these
structural differences, it is not likely that these sub-orders can be linked together in
a gradual series, without falling back upon arbitrary considerations for their sys-
tematic arrangement.

McCrady, who has admitted as sub-orders the same divisions which Leuckart
calls orders, does not hesitate to consider the Beroids proper as superior to the
tentaculated Ctenophore. It seems to me that his argument is untenable. The
reduction in the number of identical parts is truly a character of superiority, and
the absence of tentacles in the Ctenophora Eurystome might be an indication of
their superiority, if the tentacles of Ctenophore were homologous with the tentacles
of Discophore; but I have proved that they are not, their position showing
distinctly that they are an interambulacral, and not an ambulacral, apparatus.
Their limited number in some Ctenophore, and their total absence in others, are
therefore not to the point. I am rather inclined to assign to the Beroids proper
the lowest position, on account of that very absence of tentacular apparatus, the
presence of which in Saccate and Lobate I view as an additional structural
complication; and, judging from Mr. McCrady’s own statements respecting the
embryology of Bolina, which I have not myself traced, I would assign the highest
position to the Lobate, on account of their resemblance to the Saccate during

VOL. IIL. 24

186 CTENOPHOR. Part II.

the earlier stages of their growth, and the later development of those peculiarities
which distinguish the Lobatse as a sub-order. Indeed, the facts already ascertained
respecting the embryonic growth of the Ctenophora seem to justify the inference,
that while the Eurystome are the lowest, the Lobate are the highest, and the
other sub-orders occupy an intermediate position between them; for the promi-
nence of the anterior and posterior spheromeres over the lateral pairs and their
lobe-like prolongation in the Lobatz are characters not observed in the earliest
stages of their development, and marking therefore a progress which, not being
reached by the other sub-orders, assigns the highest position to the Lobate. Again,
the amplitude of the coeliac cavity and of the chymiferous tubes in the very young
Lobatee coincides with the essential character of the Eurystome. So that, if the
development of Cestum should not interfere, it would be natural to arrange the
Ctenophore in the following order: Eurystome, Saccate, Taeniate, and Lobatee.

CHAPTER SECOND.

THE NATURAL FAMILIES OF THE CTENOPHOR&.

SHC TLON. 1.
FAMILY CHARACTERS IN GENERAL AMONG CTENOPHORZ.

Since it is probable that hereafter the natural families of animals may be
characterized by a distinct category of structural features, and with greater pre-
cision than before, in accordance with suggestions I have already made in the
first volume of this work (p. 155), I will only add here a few remarks upon the
manner in which I conceive that this should be done in the class of Acalephs.
The characteristics of the families require a thorough revision throughout the
animal kingdom; for, of late, it has been customary among naturalists simply to
select some prominent genus among those which appeared closely related, and, giving
its name a patronymic termination, to call family almost any kind of combination
of genera associated under such a head, sometimes even without assigning to such
would-be families any characters at all. There are many hundred families now
recorded in descriptive works of Zodlogy which have no better foundation than
this, and a great many more to which characters are assigned in no way bearing
upon the features upon which natural families may be founded. This state of
things should no longer be tolerated; or, at least, if such loose proceedings cannot
be prevented in our science, they should no longer be received as contributions
to its advancement. It is one thing to give a family name to an arbitrary associ-
ation of animals, and quite another thing to investigate the structural features
upon which a family may be founded. If the essential character of a family
consists in the typical form of its representatives, it becomes a scientific problem
in Zodlogy to ascertain what are the structural features which determine their
peculiar pattern; and I hold, that, to characterize a natural family correctly, it is

188 CTENOPHORZ. Parr II.

not sufficient to describe the mere outlmes or the figure of its representatives, but
it is indispensable to point out the structural elements which determine the par-
ticular form, characteristic of the family under consideration. I may add, from
the attempts I have made to characterize the natural families of different classes
of animals, that this is one of the most difficult tasks a zodlogist can undertake ;
but I am at the same time satisfied, from the results at which I have already
arrived, that it is one of the most profitable sources of new and interesting
discoveries.

It may perhaps be objected, that the limitation of families depends, in a great
measure, upon preconceived views; and that naturalists disagree entirely in their
estimate of the natural range of most of them. This is undoubtedly the case
at present; but let those who think that they may divide animals as they please,
conscientiously try to distinguish the different categories of characters of those
classes of animals with which they are particularly familiar, and they will soon
perceive how much this method will improve their studies, and how easily order
will replace the chaotic accumulation of characters which are generally given
as diagnoses of the groups they consider, whether they apply themselves to the
description of species or genera or families or orders or classes or branches. And
as to families in particular, they will soon find out how fully the term form,
understood as the pattern of a definite figure, expresses the general character of
families; and they will also be made to feel how difficult it is correctly to investi-
gate the essential elements of these family forms, and what extensive anatomical
investigations are required before a single one can be satisfactorily described.
An acquaintance with the changes which animals undergo during their embryonic
erowth is particularly useful in this kind of investigations. In Ctenophore, the
family characters rest chiefly in the various combinations of the different sys-
tems of motory cells which make up the bulk of the spherosome.

Another objection may perhaps be raised upon the ground, that if every modi-
fication in the form of animals is to be considered as the basis of a distinct family,
the number of families will be increased beyond measure. Supposing, for a moment,
it were so; if the imvestigation of the structural elements determining the form
should reveal to us, in the course of time, an unexpected number of structural
patterns unknown at present, this would be a decided gai for science, and not
an objection to our method. But I may say that nothing of the kind is to be
apprehended, if I may judge from those classes to which I have thus far paid the
most special attention. The analytical method I propose has in most cases only
helped me to define with greater precision, families already pointed out or partially
characterized, and in a few instances only rendered necessary the further subdivision

of certain families and the reunion of others. In this connection, it is of the

Cua. IL. FAMILY CHARACTERS. 189

highest importance to remember that the independence of any natural group in
the animal kingdom can in no way be determined by the number of its repre-
sentatives. The Squirrels and Mice are very: numerous in comparison to the
different families of Edentata or of Pachyderms; the Warblers or Herons are very
numerous in comparison to the Ostriches or Pelicans; the Snakes and Lizards are
very numerous in comparison to the Turtles or Toads; the Perches, the Mackerels,
and the Suckers are very numerous in comparison to the Sharks and Skates, ete.
But all the natural groups founded upon a knowledge of many of them are no
more natural than if their existence had been ascertained from a careful exami-
nation of a single representative of each. The history of our science affords ample
evidence to substantiate this assertion. The genus Lsor, as limited by Linneus,
contains nine species, every one of which is now referred to a distinct genus:
Esox Lucius has become the type of the genus Esor proper; Esor Belone, the type
of the genus Belone; LEsox brasiliensis, the type of the genus Hemirhamphus : Esox
Vulpes belongs to the genus Butirinus ; Esoxr Synodus, to the genus Saurus ; Esox
Hepsetus, to the genus Engraulis'; Esox gymnocephalus, to the genus Erythrinus: Esox
Sphyrena has become the type of the genus Sphyrena; and Esor osseus, the type
of the genus Lepidosteus. These nine genera are referred by some ichthyologists
to four different families, and by others to eight distinct families. Now, if either
Linneus or Artedi had carefully studied the species in their time referred to the
genus LHsor, they might have recognized the different genera to which they were
afterwards referred, quite as well as Lacépéde or Cuvier, or any other ichthy-
ologist; and they might even have perceived the necessity of separating some of
them more widely than they were in the days of Cuvier, since, as I have shown,
Lepidosteus differs greatly from all the other living fishes.

But, to come to the point I am aiming at. The genera Belone, Hemirhamphus,
Saurus, Engraulis, Butirinus, Erythrinus, Sphyrena, and Lepidosteus, could as truly
have been separated from sox by Linnzeus with the aid of that one species he
knew of each, as they can be characterized now that we know many species of
all of them; and, upon a discriminating discussion of their differences, they might
have been characterized, not only in the same way as they are now in most works,
but even with greater precision. What is needed for such systematic work is
accurate knowledge of the animals before us, and not a large number of species;
though it is true that we derive additional aid, and our task is made comparatively
easy, when we become acquainted with many closely allied species, leading, by
their near affinity, to a readier perception of their generic relations.

1 I do not mean to enter here into a critical Esox, which have also led to extensive discussions
controversy as to the true affinities of this species, among ichthyologists: for my purpose, one view

nor of two other Linnean species of the genus of the case is as acceptable as another.

190 CTENOPHORA. Part IT.

If genera and families exist at all in nature, the genera above mentioned, and
the families to which they have been referred, or some other divisions more or less
nearly approaching them, really exist; and the discrepancies between the statements
of Linneus, Cuvier, and Miiller, respecting their affinities, will have nothing to do
with the existence of the groups to which they belong, when their natural limits
shall be ascertained beyond controversy. The differences now so generally pre-
vailing among naturalists respecting the circumscription of the groups they adopt
do not arise, in my opinion, from inherent difficulties in the subject, but from
the circumstance, that, in defining groups of any kind, zodlogists are too ready to
snatch at the first feature which strikes their eye and seems to afford a ground
for distinction, without making themselves thoroughly acquainted with the whole
range of peculiarities of the animals they study, and then sifting the different
categories of their characteristic features to lay the foundation for a durable edifice.
As soon as genera and families and the higher divisions of animals begin to be
studied with the view of ascertaining the nature of their difference, and no longer
simply as means of classifymg species, we shall hear no more of the unmeaning
complaints about making too many genera, or about useless genera, and the non-
existence of genera and families and the real existence of species, and the like;

but shall enter upon an era of truly scientific studies in systematic zodlogy.

SECTION If.

THE NATURAL FAMILIES OF THE CTENOPHORH EURYSTOME.

There is a much greater uniformity among the representatives of the Cte-
nophore Eurystome than among either the Saccate or Lobate; and it is not easy
to ascertain whether they all belong to one family or not, for the simple reason
that very few of them have been examined with the minuteness now required
in the investigation of Acalephs. There is, in fact, a single figure among the
many thus far published, and representing Beroids proper, which gives an accurate
idea of the structure and form of one of these Acalephs, and that is nearly twenty
years old; it accompanies Milne-Edwards’s highly instructive paper on Acalephs, in
the Annales des Sciences naturelles for 1841. What the other illustrations are
intended for may be guessed at; but it is impossible with certainty to refer
them to their respective species, or to ascertain the peculiarity of the species by
a comparison of the figures, and the descriptions are generally neither better nor

more instructive than the plates. This state of things is the more to be lamented,

Cnap. II. CTENOPHORE EURYSTOMS. 191

since these Acalephs are among the most delicate known, and so frail that it is
utterly impossible to preserve them for any length of time, in alcohol or any other
fluid. Direct comparisons of species inhabiting distant regions are therefore out of
the question; and all that can be done in attempting to arrange them systemati-
cally is to infer their true characteristics and affinities from the scanty information
furnished by various authors. Milne-Edwards justly remarks, that, in the present
state of our knowledge, it would be difficult to point out any real differences
between the Beroe of the Mediterranean and those observed in the Antilles, in
the northern Atlantic, about the Cape of Good Hope, and in the South Seas. As
I have had frequent opportunities of examining two very different American species
of this type, I feel in a measure prepared to call attention to the characteristic
features of these animals.

As Milne-Edwards has already shown, the Beroids proper are not broadly open
at both ends; and there is only one free communication with their main cavity, at
the actinal pole. The opening mentioned by Cuvier, Delle Chiaje, and Lesson as
existing at the opposite pole, is either an illusion resulting from the inversion of
the abactinal end of the spherosome, or the result of an accidental perforation of
that region. The form of the body varies greatly in different states of contraction ;
but under all its changing aspects, it is easy to perceive that the characteristic
form is that of a compressed egg, truncated at one end, at which the mouth is
situated. The chief differences among extreme forms consist in the greater or less
extension of the actinal axis, in the more or less tapering of the abactinal or of
the actinal pole, the blunter or the narrower end of the body being at opposite
poles in different species, and in the compression of the lateral spheromeres. The
prominence of the abactinal ends of the lateral spheromeres, while the anterior and
posterior spheromeres may be depressed in the direction of the circumscribed area,
constitutes another element of the differences noticed in the form of these animals.
In all the representatives of this sub-order the oral opening is truncate, with the
sole exception of Lesson’s Idya dentata, from the western coast of Africa, which
is represented from a sketch by Rang (Acal. Pl. IL Fi. 3) as deeply indented
between the rows of locomotive flappers, and having a tentacle projecting from
the angle of each indentation. If this is really so, and not the result of laceration,
this species should be considered as the type of a distinct genus, forming a distinct
family. The circumstance that Lesson was indebted to Rang for the drawing he
published, strongly favors the supposition that we have here the first indication
of a distinct genus, forming by itself a family of the Ctenophore Eurystome, distinct
from the Beroids proper. For this genus I would propose the name of Rangia,
in memory of the distinguished author of important contributions to the natural
history of the Ctenophore, and call the family Rayeup».

192 CTENOPHOR. Part IL.

Notwithstanding Lesson’s assertion to the contrary, I see no reason why the
genus Neis Less. should be removed from the immediate vicinity of the Beroids
proper and brought into close relationship with Mnemia. Every word in the
description of that beautiful Acaleph bearmg upon its structure, coincides with the
impression made by the figure published in the Zoologie de la Coquille, Pl. XVI.
Fig. 2, in strengthening the conviction that Neis belongs to the Ctenophore
Eurystome. It has the wide mouth and truncated oral margin, and the vascular
reticulation throughout the spherosome; and if the anterior and posterior sphero-
meres seem to project like the lobes of the Ctenophore Lobate, a careful analysis
of the description, compared with the figure, will show at once that the inter-
ambulacral space between these spheromeres alone differs from the rest of the
surface of the body in being more brightly colored, but that they do not form
a lobe-like expansion, nor are there tentacular tubes or auricles, which exist in
all the Mnemiide. While I am convinced, therefore, that Neis belongs to the
Eurystome, I am not quite so sure that it should not be considered as the type
of a distinct family, the Nets Less.; for Lesson expressly states that the abactinal
pole is not only much more compressed than the actinal, but also deeply emarginate,
and thus giving the whole body a wedge-shaped and heart-shaped form, which can
scarcely be the result of the same arrangement of the motory cells as exists im
the Beroids proper, the body of which is thinner at the actinal pole. According
to his figure and description there is also a marked difference in the disposition
of the rows of locomotive flappers, which are nearly equal in the true Beroids ;
while in Neis the anterior and posterior pairs are much longer than the lateral
pairs, and converge towards the circumscribed area, the lateral ones converging
towards one another. If these traits are not in themselves family characters, they
seem at least to indicate family differences. Gegenbaur erroneously refers Neis to
the family of the Cydippide.

The Beroids proper as a family would then embrace the species thus far referred
to the genera Beroe, Idya, Cydalisia, Medea, and Pandora, subject to a critical
revision of their closer affinities. The names Berow and Beroide, it is true, were
first introduced by Goldfuss and Rang to designate the whole order of Ctenophore,
and then limited by Exchscholtz and Lesson to the Ctenophore Eurystome ; but
if Neis and Idya dentata Jess. constitute distinct families, the family of Berow»
will in the end only embrace those Ctenophore Eurystomez whose body is evenly
compressed laterally and provided with nearly equal rows of locomotive flappers,’

the regular forms of which arise from the even distribution of the radiating and

1 Tn all regular rounded or slightly compressed flappers is only nominal. A searching comparison

Ctenophore, the equality of the rows of locomotive discloses in all these Acalephs, even in the most

Cuap. II. CTENOPHORAH SACCATA. 193

concentric systems of motory cells in all the eight spheromeres. It is impossi-
ble to read the true family characters of the Rangiide and Neiside in Lesson’s
indifferent descriptions, and but for the familiarity I have acquired with the different
types of Acalephs, I should not have ventured to point them out at all; but I
hope, in this way, to call the attention of naturalists more directly to these curious
species. However, while I indulge in this piece of presumption, I feel compelled
to repeat a remark already made elsewhere, that the difference between character-
izing a family by its peculiar structural form and simply pointing out its existence
and probable differences should never be lost sight of. When considering the North
American species of this type, we shall also examine how far Gegenbaur is correct
in referring all the true Beroide to a single genus, Beroe Brown. Meanwhile, I
would only call attention to the fact, that Lesson has referred to this genus many
species which belong to the family of Cydippide, and were mistaken by him for
genuine Beroidw, because the specimens he noticed had lost their tentacles: such
are most, if not all, his Béroés Mélonides.

We have thus three families of Ctenophore Kurystome: the Berromx® proper,

the Netsip#, and the Rancupm, one of which only —the Beroidse —is satisfactorily

known.

Se CLR OPN: aL Ind:
THE NATURAL FAMILIES OF THE CTENOPHOR® SACCATA.

As was shown in a preceding section, the Ctenophore Saccatew constitute a
natural sub-order, corresponding to the genera Callianira and Cydippe of Péron and
Eschscholtz, to the families Callianiride and Cydippide of Gegenbaur, and to the
tribe Cydippx, and part of the tribe Callianire, of Lesson. We have now to
consider the natural limits of the families of this group.

The genus Callianira of Péron, from which Eschscholtz derived the name of his
family Callianividee,— in which, besides Callianira, he includes Cydippe and Cestum.
—has not been observed for more than half a century. Our knowledge of these
Acalephs is therefore limited to the few and rather indifferent statements included
in the characteristics of the genus as described by Péron, and some other remarks,

uniformly arched, an unquestionable difference be- difference in the curve of corresponding rows of the
tween the anterior and the posterior rows on one same pair among the anterior and posterior ones,
side and the lateral rows on the other side; and as well as among the proximate lateral rows of
a practised eye cannot fail to perceive a marked the same side.

VOL. III. 20

194 CTENOPHORA. Part IT.

equally meagre, by Slabber and Modeer. The figure published by Péron is rather
indistinct; and it is impossible to determine with certamty whether the Acaleph
he had before him when he named that genus belongs to the same type as the
two species afterwards referred to it by Eschscholtz. That Péron himself did not
appreciate correctly its structural peculiarities is plain, from the fact that he referred
the genus Callianira to the Pteropods and not to the Acalephs. Eschscholtz never
had an opportunity of examining a species of this genus, though it was he who
referred to it the other two nominal species now associated with the Callianira
of Péron, Judging from the figures adduced under the names of Callianira_ trip-
loptera and C. hexagona, there can be no doubt that the genus Callianira belongs
to the Ctenophora Saccatex, since they exhibit two long lateral tentacles, occupying
the same position as those of Pleurobrachia; and were not the descriptions unani-
mous in representing the rows of locomotive flappers as extending along prominent
ribs upon the sides of the spherosome, I should not hesitate to refer the genus
Callianira to the same family as the genus Pleurobrachia: but since the surface
of Pleurobrachia is nearly even, and the locomotive flappers are never raised into
wing-like appendages, I am inclined to believe that when Callianira is observed
again it will be found to constitute the type of a distinct family closely allied
to Pleurobrachia, but chiefly distinguished by the prominent development of the
rows of motory cells which underlie the vertical chymiferous tubes. That no
Callianira can have only six or four rows of locomotive flappers,' as might be
inferred from their descriptions, is already plain from an inspection of the figures
of Slabber copied by Brugiére in the Encyclopédie Méthodique. The descriptions
seem to have been made without remembering that the middle rows visible in
the figure must have been repeated on the opposite side. Should the structure
of these species, when examined again in the light of our modern knowledge of
the Acalephs, prove to constitute a family by themselves, the name of Catuta-
NikIDE must be restricted to them. Should it on the contrary appear that they
cannot be separated from Pleurobrachia, which with its allied genera now consti-
tutes the family of Cydippide, then this name must be suppressed, and the united
Cydippidee and Callianiride retain the name of Callianiride.

Gegenbaur, perceiving the imappropriateness of uniting the genera Cestum, Cy-

dippe, and Calhanira into one family, has called the species included in the genus

* The distinctive differences noticed by Esch- difference among them, already acknowledged by
scholtz in the diagnoses of the species of Callianira Eschscholtz, who, in the Isis for 1825, p. 742,
seem rather to indicate an inequality in the develop- adopts the genus Sophia Pér. for the Callianira
ment of the spheromeres, than a difference in their diploptera, by the side of the genus Callianira

nunber, and, therefore, probably mark a generic Lamk. for the C. triploptera.

Crap. IL. CTENOPHORE SACCAT. 195

Cydippe of Eschscholtz Cypippmx, and at-the same time pointed out two groups
among these Acalephs, which seem to me to constitute in reality two distinct
families. To one of these groups he refers the compressed species, of which the
to the other, he refers the more
But, in

enumerating the species which he would associate with the latter, he mentions

Eschscholtzia cordata of K6lliker is the type ;
rounded species, of which the Cydippe Pileus of Eschscholtz is the type.

those which are quite as remarkable for their compressed form as the Eschscholtzia
cordata. We have therefore to make a preliminary survey of the whole group
before we can proceed any further in characterizing this family. It is obvious
that when Eschscholtz characterized the genus Cydippe he had chiefly round or
Tt is}

further, unquestionable that his genus Cydippe is synonymous with Pleurobrachia

oval species in view, the cnly ones belonging to this type he ever saw.

of Fleming, and that, since Pleurobrachia is the older name, it must be retained.
The plea entered by Eschscholtz for discarding it, rests on a mistake: Fleming
did not call his genus Pleurobranchea, but Pleurobrachia, on account of its lateral
arms, and it can never be confounded with Pleurobranchwa, so named on account

ceneric

The name Cydippe must therefore be dropped as a g

of its lateral gills.
name, though there is no objection to retaining it as a famify name. The genus
Mertensia Less. which Gegenbaur would suppress, is a good genus, as remarkable
for its lateral compression as Eschscholtzia cordata, and therefore not belonging
The

It was therefore a mistake on the part of Kolliker to refer

strictly to the type of Cydippe. genus Eschscholtzia ess. was established
for round species.
his Eschscholtzia cordata to it. We shall see hereafter, that the genus Janira
Oken also contains oval species belonging to the Cydippide proper, and that several
other species, referred either to Eschscholtzia or Cydippe, constitute also distinct
genera of that family.

What I have already said is sufficient to show that Gegenbaur was on the

1 Lesson has made a singular mistake in naming
this genus, which he intended to dedicate to the
oldest observer of the species he regards as its
type. Now, the oldest observer of this arctic
Acaleph is not H. Mertens, the naturalist of the
Russian exploring expedition in the Seniavin, but
Friderich Martens, of Hamburg, the precursor of
Scoresby in the exploration of the seas of Green-
land and Spitzbergen, whose work was printed in
1675, and whom Lesson quotes again and again
as Mertens. I shall therefore make good the mistake
-of Lesson, and compensate for his error, by calling

another genus of the same family Martensia, the

type of which was first observed by H. Mertens,
and deseribed by the latter under the name of
Beroe octoptera. It is much to be regretted that
Gegenbaur should have overlooked the claims of
Mertensia Zess. to a distinction as genus, and on
that account proposed to transfer the name Mer-
tensia to another type. But this cannot be done,
not only because the genus Mertensia Less. must
stand, but also because the transfer of one generic
name to another genus, even when that name has
become vacant, leads to confusion, instead of simpli-
fying our scientific nomenclature. The rule I insist

upon here is of long standing.

196 CTENOPHOR. Part II.

right track when he began to subdivide the Cydippide into two distinct groups,
and he was only prevented from carrying out his suggestion to its legitimate limits
by insufficient materials Taking the rounded forms of Cydippide as the repre-
sentatives of the limited family of that name, and the compressed ones as the
representatives of another family, for which I would propose the name of Mer-
tenside, we may now proceed to a comparative survey of the distinguishing
characters of the two.

The Cypirrip® proper are remarkable for the striking similarity of their eight
There is so little difference between them, that though I have been
familiar with one representative of this group for a great many years, and though I

spheromeres.

have kept hundreds alive annually for weeks in succession, it was not until recently
that I perceived how, under this seemingly perfect radiation, the same antitropy
of the spheromeres may be recognized which characterizes the most compressed
types of Ctenophore, in which bilateral symmetry is most prominent. Here, then,
as in all Ctenophore, there are an anterior and a posterior pair of spheromeres
and two lateral pairs, and the direction of the circumscribed area and of the
actinostome marks the direction of a plane which may divide the body into equal
lateral halves; and Here, as in all the Ctenophore, the cceliaec and the tentacular
chymiferous tubes trend in another plane, at right angles with the preceding. Their
apparent equality, however, and their symmetrical radiation, combined with the
presence of two lateral tentacles protruding in the direction of the abactinal pole,
constitute the most striking character of the family, to which the following genera
belong: Pleurobrachia Flem. (Cydippe £sch.), Janira Oken, Eschscholtzia Less, and
Mertensia Gegenb., for which I would substitute the name Dryodora, since Lesson’s
genus Mertensia must be retained. To these I would add the genus Hormiphora
for Gegenbaur’s Cydippe hormiphora. Lesson’s genus Anais’ must be suppressed.
Gegenbaur erroneously refers the genus Ocyroe Rang to the family of the Cydippi-
de: it belongs to the Ctenophore Lobate.

Mentexsipe. A very ostensible character of this family consists in the flatness
of the sides of its representatives. But this is a more apparent than real pecu-
liarity ; for in animals, whose spherosome is extensively movable in every direction,
a slight lateral compression vanishes from sight whenever the body is greatly
Yet the that
flatness is not only a permanent. but also a very striking, characteristic, readily

expanded or contracted. structural combination which determines

1 Trt is with deep regret that I feel compelled to
lay the unsparing hand of criticism upon a monu-
ment of parental affection erected by Lesson to a
beloved child; but the genus Anais cannot stand

in our science. It is founded upon a young Aca-

leph, described by Sars as Cydippe quadricostata,
and probably the immature state of his Mnemia
norvegica, as MeCrady suggested. after tracing the
embryonie growth of his Bolina littoralis. He also
regards Will's Cydippe brevicostata as immature.

Se

|

Cua. II. CTENOPHORZH SACCATE. 197

distinguishing the Mertenside from the Cydippide proper. As we have seen, the
spheromeres of the Cydippide are so uniform in their size, structure, and radiated
arrangement, that their conformity to the type of the Ctenophore, in their bilateral
disposition, is barely perceptible: in the Mertenside, on the contrary, the anterior
and posterior spheromeres are very different in their form and size, and even in
their structure, from the lateral ones, so that the bilateral symmetry of these Cte-
nophore is one of their most characteristic family distinctions. But this symmetry
is so peculiar, that, far from exhibiting a transition to the Cestidee and Calymnide
or Mnemiide, as Gegenbaur believes, it presents the most striking contrast with
them. In the Cestidw, as well as in the Calymnide and Beroids proper, the com-
pression is lateral; that is to say, the lateral spheromeres are reduced in comparison
to the great development of the anterior and posterior pairs, or, in other words,
the coeliac diameter is the longest, and the diacceliac the shortest, of the two
transverse diameters: while in the Mertenside the compression is diametrically
opposite, the lateral spheromeres being greatly developed, while the anterior and
posterior pairs are much reduced, so that here the coeliac diameter is much shorter
than the diacceliac. Mertens, in his description of Beroe compressa, has already
alluded to this difference between the two types, and also noticed another structural

peculiarity coinciding with the antero-posterior compression in the form of the

circumscribed area, which is short and petaloid, while in the Cydippide it is long,
with parallel sides. In conformity with this inequality of the spheromeres and
the prominence of the anterior and posterior pairs, the abactinal side of the larger
spheromeres projects more or less, thus giving a heart-shaped outline to the abactinal
pole, on which the circumscribed area is seen in a depression of the short coeliac
diameter. A corresponding inequality is observed in the development of the vertical
chymiferous tubes and their rows of locomotive flappers. In the Cydippide proper,
there is hardly a perceptible difference between them: in the Mertensidew, on the
contrary, the lateral pairs are much longer than the anterior and the posterior
pair. This again might easily be mistaken for a resemblance between the Mer-
tensidse and the Mnemiide or Calymnide, were not the most developed chymiferous
tubes and rows of locomotive flappers in the latter those of the anterior and
posterior spheromeres, while in the Mertenside the most extensive chymiferous
tubes and rows of locomotive flappers are those of the lateral spheromeres. The
extraordinary development of the parts arranged in the direction of the diacceliac
diameter constitutes, in fact, the most striking family character of the Mertensidex,
and determines its peculiar form. In accordance with this preponderance of the
sides, it is worthy of remark that the whole tentacular apparatus of the repre-
sentatives of this family is larger and more complicated than that of any other
group of Ctenophore, in comparison to the absolute size of these animals. Mertens

198 CTENOPHORE. Parr II.

has mistaken the base of the tentacles for ovaries. To this family belong the
genera Mertensia Less. (Beroe compressa JVert.), Owenia All, Gegenbauria Ag.
(Eschscholtzia cordata A@/.), and Martensia Ay. (Beroe octoptera Mert.).

We have thus three families of the Ctenophorae Saccate: the CaLiranirip®,
the Cypiprip® proper, and the Merrensw, the first of which is still very im-
perfectly known.

Cestipe. Whether the genus Cestum constitutes a sub-order by itself or not,
it is unquestionably the type of a distinct family, for which the names Cestoidese
and Cestidse have been proposed by Lesson and by Gegenbaur. These names are
objectionable so far as they resemble too much that of the Helminths called
Cestoidea, and a mere grammatical difference in the termination of a systematic
name hardly constitutes a satisfactory distinction. Eschscholtz united Cestum with
Cydippe and Callianira; but, leaving the peculiar arrangement of the rows of loco-
motive flappers out of consideration, the tendency of the Cydippide, and especially
of the Mertenside, to elongate in the direction of the transverse or diacceliac
diameter, while in the Cestide the prominent diameter is the longitudinal or cceliac
diameter, seems to indicate different affinities and a closer relation to the Cte-
nophore Lobate. This relation seems further supported by the position and
termination of the tentacular apparatus, which trends in the direction of the coeliac
cavity, and protrudes on the sides of the actimostome, and not in the direction of
the abactinal pole, as in the Cydippides and Mertenside. It is true, MeCrady has
noticed that a change in the direction of the tentacular tubes takes place with
the growth of Bolina; but this does not militate agaist the importance of the
course of the tentacular apparatus in adult Ctenophore, since in all the Lobate
known it protrudes from the sides of the actinostome im their adult state, and in all
the Saccate examined with reference to this point its opening is turned towards
the abactinal pole. Among the less known species, Cydippe dimidiata £sch., and
Beroe glandiformis JJert., are the only ones in which it is represented as trending
in the opposite direction. But Grant also represents that of Beroe Pileus as
trending in the direction of the mouth, when its real position is certainly the
reverse. We may, therefore, well consider the direction of the tentacles as char-
acteristic of the sub-order of the Ctenophorz Saceatee and Lobate; and, making
due allowance for the possibility of mistakes with reference to a structural feature
thus far not sufficiently noticed among the characters of these animals, allow it its
due weight in the estimation of the affinities of Cestum.

If I am not greatly mistaken, the singular animal described by Gegenbaur as
a distinct genus, under the name of Sicyosoma, is a young Cestum; for what he
takes to be the ovaries reminds me rather of the remnants of the yolk of an egg.

When it is remembered that Cestum is the largest of all the Ctenophorz, and

Cuar. II. CTENOPHORH LOBATS. 199

that therefore its young may be widely different from the adult, and is not
likely to resemble the young of other genera, considering the typical peculiarities
of Cestum; when it is further remembered that the tentacular apparatus of Sicy-
osoma trends in the direction of the mouth, as in Cestum,—this supposition will
appear more probable than that of Gegenbaur, who regards it as an adult form
of a very low organization.

SwCLEON LY.
THE NATURAL FAMILIES OF THE CTENOPHORE LOBAT®.

Eschscholtz was the first to perceive the affinities which unite these Acalephs
ito one natural group, to which he gave the name of Beroide Lobatw in the
account of his investigations published in the Isis for 1825. Four years later, he
changed that name to Mnemiidex, in his “System der Acalephen ;” but, as we have
already seen, the Ctenophors Lobatse constitute a natural sub-order, and not simply
a family. Lesson, on the other hand, regarding the whole type of Ctenophore
as one family, subdivided it into eight tribes, three of which, the Leucothoex, the
Seuroee, and the Calymmex, belong to the Ctenophore Lobate, while his Calli-
anire embrace Cydippide as well as genuine Lobate. Gegenbaur unites all these
Acalephs into one family, called by him Calymnide. It is not difficult, however,
to trace different patterns among them. In the first place, I would call attention
to the very peculiar form of the genus described by Gegenbaur under the name
of Euramphea. It differs from all other Ctenophore by the remarkable promi-
nence of the actimal diameter, which gives this type a very elongated appearance,
strikingly contrasting with the prominence of the cceliac diameter in others. Again,
the compression of the sides, combined with the sudden dilatation of the anterior
and posterior spheromeres into broad lobes projecting from the actinal part of the
narrow sides of the body, and the equally prominent projection of the abactinal
part of the broad sides of the body, extending sideways much beyond the abactinal
pole, give this Acaleph a very unusual appearance, and show it to be the type of
a distinct family, for which I propose the name of Eurampraipm. Besides the genus
Euramphxa, I am inclined to refer to it another Acaleph, thus far very imperfectly
known, because it was described and figured from a mutilated specimen by Cha-
misso, and has not been observed since; but the parts preserved agree so fully
with Gegenbaur’s Euramphea, that the close affinity of the two can hardly be
doubted. I allude to Chamisso’s Callianira heteroptera (Noy. Act. Acad. Nat.

200 CTENOPHORE. Part IT:

Curios. X. Pl. 51, Fi. 5), the type of Eschscholtz’s genus Hapalia, afterwards called
Polyptera by Lesson.! Fully to appreciate the peculiarity of the form of the
Euramphide, it must be borne in mind that the lobe-like prolongations of their
most prominent spheromeres trend in the direction of the cceliac diameter on the
actinal side of the body, as in the Mnemiidz proper, while the appendages on the
abactinal side rise as keels from the broad side of the animal and project in the
direction of the diacceliaec diameter, like the most prominent spheromeres of the
Mertensid, except that in the family of Eurampheide they are still more promi-
nent and assume the shape of elongated horns. In consequence of this arrangement,
the appendages of the actinal and those of the abactinal side of the spherosome
stand crosswise.

The Bou constitute a second family among the Ctenophore Lobati, including
part of Eschscholtz’s Mnemiide and of Gegenbaur’s Calymnid, part of Lesson’s
tribe of Callianire, his Leucothoex, and part of his Calymmex. Lesson’s attempt
to subdivide the Ctenophorx into minor groups was a failure, the tribes he adopted
being entirely artificial The characters he assigns to the Callianire exist only
in a few of them; for neither Mnemia nor Bolina has prominent ribs, the rows
of locomotive flappers being nearly on a level with the surface of the spherosome:
while Leucothea, which he separates, as a tribe, from Bolina, is closely allied to
it; and Chiaja, which he refers to the Callianire, is identical with Eucharis multi-
cornis,—and yet Lesson places Eucharis in another tribe. Under such circumstances,
the first step we have to take in order to ascertain the general relations of all
these Acalephs is to compare them more minutely with one another. I shall, of
course, take as my standard the representative of the whole type which I know
best,— the Bolina alata of the American coast of the Northern Atlantic. The
characteristic form of this Acaleph is determined by the prominence of the anterior
and posterior spheromeres over the lateral pairs, and the equable convergence of the
eight spheromeres towards the abactinal pole, which gives a rounded form to that
side of the spherosome, while the anterior and posterior spheromeres extend beyond
the actinal pole, and the shape of two lobes, more or less expanded in different
genera, but always closely connected with the actinal region. Upon the sides arise
two auricles in the prolongation of the lateral rows of locomotive flappers.

Mnemia norvegica Sars and Bolina septentrionalis J/ert. have exactly the same
form, and agree so fully in the details of their structure with Bolina alata, that I

1 Lesson’s name cannot be retained, not only tem der Acalephen,’ Eschscholtz does not mention
because it is preoccupied, but also because it is of this genus, not even as synonym, but refers the
later date than that proposed by Eschscholtz (Isis, species upon which it was founded to the genus

1825, p. 742) for the same Acaleph. In his “Sys- Mnemia as M. Chamissonis.

CTENOPHORZ LOBATA. 201

Cuap. II.

have no doubt respecting the generic identity of these three species, to which
Bolina hibernica Pafters. must be added, probably as synonyme of Sars’s Mnemia nor-
vegica. The form of Bolina elegans Mert. does not differ at all from that of
Bolina alata, but there are generic differences between them, the course of the
chymiferous tubes in the lobes of the tropical Bolina elegans being different from
that of the northern Bolina alata and allied species, and the surface papillate, as in
Leucothea, Chiaja, and Eucharis. But whether Leucothea’ formosa Mert., Alcinoe
papillosa Delle Chiaje, and Eucharis multicornis Esch, belong to this or the next
family, I am unable to determine, as the connection of the lobes with the sphero-
some is not accurately described. Again, Leucothea differs in having a complicated
tentacular apparatus, which is simple in Eucharis multicornis. I believe Gegenbaur
to be correct in assuming that Eucharis Tiedemanni &sch. differs generically from
Eucharis multicornis; and that the latter is identical with Alcinoe papillosa, for
which Lesson has proposed the generic name of Chiaja, so that Alcinoe papillosa
should be called Chiaja multicornis, and the name Eucharis retained for Eucharis
Tiedemanni.

Gegenbaur has questioned the validity of the genus Bolina, and believes it to

coincide with Mnemia. Mnemia has

I believe he is mistaken in that respect.
not the form of Bolina, but coimcides with Alcinoe ang in the structure of its
lobes, which are not simple prolongations of the actinal side of their spheromeres,
but rise as lateral folds above the actinal pole of the spherosome, and overlap
the lateral spheromeres. On that account, I do not hesitate to consider the genera
Alcinoe and Mnemia as belonging to a distinct family, for which the name of Myeg-
Mup& must be retained, and to which the genera LeSueuria and Eucharis proper
may also belong. Beroe costata Reyn. probably forms another genus of this family.
The prolongation of the external row of flappers of the auricles, in the direction
of the abactinal pole, along the furrows which separate the lobes of the spherosome
from the lateral spheromeres, seems characteristic of this family. I have observed
nothing of the kind in Bolinide.

I shall retain the name of Catymipx, applied by Gegenbaur’ to the whole sub-

1 Most writers erroneously call this genus Leuco-
thoe. Mertens gave. it the name Leucothea.

2 As this page came up from the printing-office,
I noticed that I had not alluded to a very inter-
esting paper by Mirne-Epwarps, Note sur I’appareil
gastro-vasculaire de quelques Acalephes Cténophores,
published in the Annales des Sciences naturelles,
4e série, vol. 7, p. 285. Owing to the irregularity
with which this important periodical has been re-

VOL. ID. 26

ceived at our university library, I did not know of
Milne-Edwards’s earlier investigations upon the same
subject when I published my paper on the Beroid
Meduse in 1850, and had almost missed an oppor-
tunity of referring to this later communication, which
I shall have to quote frequently hereafter.

® Gegenbaur writes Calymnide; but, the name
being derived from Calymma, should be spelled

Calymmide.

202 CTENOPHORS. Part II.

order of the Ctenophore Lobate, for a small family, of which the genus Calymma
Esch. is the type. This family does not correspond to Lesson’s tribe Calymmez,
for under that head Lesson unites some Bolinidzee and some true Mnemiide with
the genus Calymma. As limited here, the family of Calymmide represents a
morphological step beyond the Mnemidx. We have seen that in the family of
Bolinidw the lobes formed by the actinal prolongation of the anterior and posterior
spheromeres are not separated from the spherosome along the lateral spheromeres,
but are simply an extension of the actinal portion of their respective spheromeres.
In the Mnemiuide, the separation of the lobes from the spherosome extends in the
shape of a furrow along the lateral spheromeres, which the lobes overlap. In the
Calymmidxe, judging from the figures of Mertens, the actinal region and the sides
of the spherosome are rendered still more independent by the course of the lateral
rows of locomotive flappers and the preponderance of the coeliac diameter. Con-
trary to the disposition of the Bolinide, the anterior and posterior rows of loco-
motive flappers are the shorter ones, and the lateral pairs, instead of trending
in the direction of the actinal diameter, run forward and backward and form
arches in an antitropic direction at the point where the auricles arise, thus leaving
on each side a broad lateral area uncovered, the centre of which is occupied by
the coeliac cavity. Besides Calymma, I think that Lesson’s genus Bucephalon
belongs to this family. Owing to the imperfect illustrations of the genus Axiotima,
IT am unable to decide whether it also belongs here or with the Bolinide.

The family of Ocyrompm, Lesson’s tribe of Ocyroex, constitutes, morphologically
considered, the counterpart of the Calymmide, as far as I can judge from Rang’s
illustrations. The actinal region of the spherosome seems entirely free from the
anterior and posterior lobes, which, instead of arising from an actinal prolongation
of their respective spheromeres, as in the Bolimide, are formed by an abactinal
development of the anterior and of the posterior spheromeres. Moreover, each
lobe is bilobed, mdicating clearly that it is formed of two spheromeres, corresponding
to the lateral spheromeres and their respective auricles. The lateral rows of loco-
motive flappers trend in the direction of the cceliac diameter, as in the Calymmide,
but are very short, in conformity with the actinal projection of the central part
of the spherosome, and give rise to auricles, the base of which is nearer the
abactinal poles than in any other family. Owing to their bilobed form, the anterior
and posterior lobes resemble strikingly the auricles. They are, in fact, the morpho-
logical equivalents of the auricles, only much larger, soldered together, and sup-
porting long rows of locomotive flappers; while the auricles of the four lateral
spheromeres are free and short. The view which Rang has published of Ocyroe
maculata as seen from the abactinal pole is one of the most instructive illustrations
extant for the study of the morphology of the Ctenophore.

; C HeAgr rE Rel Hel RD"

NORTH AMERICAN CTENOPHORE.

SHOCTLON. §.
THE GENUS PLEUROBRACHIA AND ITS SPECIES.

Au. our knowledge of the animal kingdom being derived from a study of
individuals, and our insight into their various relations growing out of the fullest
comparisons between them, it is natural, that, in describing animals, we should at
times dwell more extensively upon the results of such comparisons, and at other
times turn our attention more especially to the conditions under which they live.
Investigations neglecting either the one or the other side of the subject must,
from the nature of things, remain imperfect. It is only when the study of the
structure and functions of an animal draws to a close, and we have made ourselves
perfectly familiar with its mode of life, that we may begin a systematic survey
of its various connections, and ascertain its position in the system, as determined
by its anatomical peculiarities, its embryonic growth, the period of its appearance
upon our globe, and its geographical distribution upon its surface. But science
cannot take for granted mere results, presented in a dogmatic form: it requires
the fullest evidence of every statement and the fullest demonstration of every
inference. Special descriptions must therefore be full and minute: they must,
moreover, be comparative, and even embrace the widest range of comparisons, that
no doubts may remain in the mind of the reader respecting the correctness of
the information offered him. I have on that account thought it desirable to
reproduce here such parts of the descriptions of the North American Ctenophore
published in the Memoirs of the American Academy for 1849 as may throw
additional light upon the subjects discussed in the preceding chapters. I begin
with our Pleurobrachia, a small, rounded, transparent body with two long threads

204 CTENOPHORA. Part If.

on opposite sides, which may be observed, durmg the whole summer, along the
shores of Massachusetts and Maine, and, further north, to the shores of Greenland.

The Ctenophore differ essentially from the Discophors. Both their form and
organs of locomotion give them a different appearance. The Discophori, setting
aside the various modifications arising from marked peculiarities of their outline,
move like an umbrella, which, by alternately opening and shutting, would make its
way under water by means of such movements. It is by the contraction of the
body alone, or rather by the agency of the motory cells which form that mass,
that motion is produced in these animals. Not so in the Beroid Medusx, where,
besides the action of the motory cells, the whole body, more or less spherical or
ovate, compact or split at one end, is kept swimming by the flapping of imnumer-
able small paddles arranged in vertical rows, like the ribs of an orange, upon the
outer surface. These rows are generally eight in number, extending from one
pole of their spheroid body to the opposite, like the meridians of an artificial globe.
But, owing to the imequalities in the motions of their vertical flappers, and their
radiated arrangement upon the more or less spherical body, these animals have
a somewhat rotatory motion, unless the paddles move on all sides with perfect
steadiness and uniformity.

There can be searcely any thing more beautiful to behold than such a living
transparent sphere sailing through the water, coursmg one way or another, now
slowly revolving upon itself, then assuming a straight course, or retrograding,
advancing, or moving sideways, in all directions with equal precision and rapidity ;
then stopping to pause, and remaiming for a time almost immovable, a shght waving
of some of its vibrating organs easily counterbalancing the difference of its specific
eravity and that of the water in which it lives. So Pleurobrachia may appear at
times, and so does it also appear when moving in a state of contraction. But
generally, when active, it hangs out a pair of most remarkable appendages, the
structure and length and contractility of which are equally surprising, and exceed
in wonderful adaptation all I have ever known among animal structures. Two
apparently simple, irregular, and unequal threads hang out from opposite sides of the
sphere. Presently these appendages may elongate, and equal in length the diameter
of the sphere, or surpass it, and increase to two, three, five, ten, and twenty times
the diameter of the body, and more and more; so much so that it would seem
as if these threads had the power of endless extension and development. But
as they lengthen they appear more complicated: from one of their sides other
delicate threads shoot out like fringes, formimg a row of beards like those of the
most elegant ostrich feather, and each of these threads itself elongates till it equals
in length the diameter of the whole body, and bends in the most graceful curves,

These two lone streamers, stretching out in straight or undulating lines, sometimes

Cuar. IIT. GENUS PLEUROBRACHIA. 205

parallel, then diverging or variously curving, follow the motions of the main sphere,
being carried on with it in all its movements, which are no doubt influenced by
them to a considerable extent. Upon considering this wonderful being, one is at
a loss which most to admire, the elegance and complication of that structure, or
the delicacy of the colors and hues, which, with the freshness of the morning dew
upon the rose, shine from its whole surface. Like a planet round its sun, or, more
exactly, like the comet with its magic tail, our little animal moves in its element
as those larger bodies revolve in space, but unlike them and to our admiration,
it moves freely in all directions; and nothing can be more attractive than to
watch such a little living comet as it carts with its tail in undetermined ways
and revolves upon itself, unfolding and bending its appendages with equal ease
and elegance, at times allowing them to float for their whole length, at times
shortening them in quick contractions and causing them to disappear suddenly,
then dropping them as it were from its surface so that they seem to fall entirely
away, till, lengthened to the utmost, they again follow in the direction of the body
to which they are attached, and with which the connection that regulates their
movements seems as mysterious as the changes are extraordmary and unexpected.
For hours and hours I have sat before them and watched their movements, and
have never been tired of admiring their graceful undulations. And though I have
found contractile fibres in these thin threads, showing that these movements are
of a muscular nature, it is still a unique fact in the organization of animal bodies,
that parts may be elongated and contracted to such extraordinary and extensive
limits by means of muscular action. And what is so surprising, is not so much the
sudden and powerful contraction which brings within the compact limits of a pin’s
head the whole mass of these tentacles that a moment before were floating so ele-
gantly through such a great extent in the water, as the relaxation, which takes
place in an absolutely passive manner; for when watching them we are suddenly
struck with astonishment on finding that the tentacle which we expected to see
drop to the bottom of the jar is still in organic connection with the body from
which it hangs. Plate I. of my paper in the Memoirs of the American Academy
represents some few of the attitudes of our Pleurobrachia in its various movements,
one of which is reproduced in this work (Pl. I. Fv. 25); but I cannot find words
to describe all the beautiful changes which the parts thus in motion assume in
different attitudes. At one moment the threads, when contracted, seem nodose ;
next, when more elongated, these knots are stretched into the appearance of a
spiral; next, the spiral, elongating, assumes the appearance of a straight or waving
line. But it is especially im the successive appearances of the lateral fringes
arising from the main thread that the most extraordinary diversity is displayed.

Not only are they stretched under all possible angles from the main stem, at times

206 CTENOPHORA. Parr II.

seeming perpendicular to it, or bent more or less in the same direction, and again
as if combed into one mass; but a moment afterwards every thread seems to be
curled or waving, the main thread being straight or undulating; then the shorter
threads will be stretched straight for some distance and then suddenly bent at
various angles upon themselves, and perhaps repeat such zigzags several times, or
they may be stretched in one direction and bent at various angles in the plane
of another direction; then they may be coiled up from the tip and remain
hanging like pearls suspended by a delicate thread to the main stem, or like a
broken whip be bent in an acute angle upon themselves with as stiff an appearance
as if the whole were made up of wires; and, to complete the wonder, a part
of the length of the main thread will assume one appearance and another part
another, and pass from one into the other in the quickest possible succession: so
that I can truly say, I have not known in the animal kingdom an organism
exhibiting more sudden changes and presenting more diversified and beautiful
images, the action meanwhile being produced in such a way as hardly to be
understood. For, when expanded, these threads resemble rather a delicate fabric
spun with the finest spiders thread, at times brought close together, combed in
one direction without entangling, next stretched apart, and preserving in this evo-
lution the most perfect paralleism among themselves, and at no time and under
no circumstances confusing the frmges of the two threads: they may cross each
other, they may be apparently entangled throughout their length, but let the animal
suddenly contract, and all these innumerable interwoven fringes unfold, contract,
and disappear, reduced as it were to one little drop of most elastic india-rubber.
Week after week I have preserved these animals alive, and have never been tired
of comparing again and again their changes in these thousand-fold developments
of their appendages. I have called together those who felt the slightest curiosity
for such objects to witness these phenomena, and have found them all interested
to the utmost; and if I have any thing to regret, it is not the time lost in this
contemplation, —for the more I became familiar with the sight, the more was I
impressed with its beauty, as I could contrast with the new forms presenting them-
selves before my eyes those different states with which I had been familiar before,
—hbut the circumstance that the time was too short to trace such a connection
between all the microscopic details of their structure and their functions, as would
fully explain the latter; although I am aware that I have noticed many particulars
which had not been observed before.

The chief difficulty in the comparative study of the different genera of this family
arises from the circumstance, that they move permanently in different directions,
some haying the mouth naturally turned upward and others downward; and_ that,

from not haying perceived this difference, the parts placed in opposite positions

Cuap. II. GENUS PLEUROBRACHIA. 207

have been identified with each other by different writers in different genera, and
therefore require a complete revision.

The type under consideration, for which I retain the name of Pleurobrachia
as the most ancient applied to species of this particular conformation, is one of
those which are deprived of peripheric lobes, that is to say, in which the gelatinous
body is undivided, and the mouth constantly turned upward or forward when in
motion; while the genus Bolina, to which I shall next call attention, is one of
those in which one extremity of the sphere is split into two lobes, between which
the mouth is situated, and in which this opening is almost constantly turned
downward when the animal is moving, though sometimes, when the animal is at
rest, it turns in the opposite direction, opening widely its two lobes. It will be
obvious how great mistakes may arise from comparing two animals constructed
upon the same plan, but kept in a reversed position when contrasted. Unhappily,
all these animals have been figured without reference to the normal position in
which they should be compared, and, no allusion to these prominent differences
being made, it is hardly possible to reconcile the descriptions of one author with
those of another.

The genus Pleurobrachia is limited to those species of Cydippide in which the
body is nearly spherical or slightly elongated, and slightly compressed laterally ;
the locomotive flappers extending from near the margin of the mouth all round
the sphere, in eight vertical rows, towards the opposite centre, where they approach
much closer to each other than on the side of the mouth. The tentacular sacs are
wide and arched sideways, their bottom rising toward the actinal pole, while the
aperture is turned towards the abactinal side of the spherosome, and opens in the
interambulacral space between the lateral pairs of spheromeres. Pleurobrachia differs
from Exschscholtzia chiefly in the development of the rows of locomotive flappers,
which, in the latter genus, do not extend beyond half or two thirds of the whole
height. This is also the case with Dryodora (Gegenbaur’s Mertensia, and Mertens’s
Beroe glandiformis); but Dryodora has simple tentacles, while they bear lateral
threads of a uniform structure in Eschscholtzia and Pleurobrachia, and two kinds
of appendages in Hormiphora (Cydippe hormiphora, Gegenb.). Janira is chiefly
characterized by the prominence of the actinal diameter.

I know at present only three species of this genus sufficiently well to char-

5

acterize them as distinct species:*+ one is the common Pleurobrachia of the shores
1 After defining the natural limits of the genus relating to them. All I am able to do is to point

Pleurobrachia in accordance with its structural pe- out those I believe to belong here. About Pleuro-

culiarities, it would be desirable to enter into a brachia Pileus Flem. there can be no doubt: it

critical comparison of its species ; but this is impossi- is the common species of the German Ocean, with

ble, owing to the imperfection of the illustrations which Cydippe Pileus Esch. is identical. Judging

208 CTENOPHORA.

Part II.

of Europe; the second, which I have named Pleurobrachia rhododactyla, occurs on the

eastern shores of the northern United States; and the third was recently observed

on the north-west coast of America by my son, Alexander Agassiz.

s
Though, at first sight, our Pleurobrachia appears spherical, it is slightly com-

pressed in a direction at right angles with the base of the tentacles; so that the

coeliac diameter is really shorter than the diacceliac.

from the range of differences observed among indi-
viduals of different ages of the species I have
described as PI. rhododactyla, I hold that the two
species described by Forbes and Patterson are one
and the same with Pl. Pileus, the rows of loco-
motive flappers being comparatively broader, and
the number of flappers less, in young than in old
specimens, and the tentacles, having generally not
yet sustained any injuries, are longer and more
active. I therefore consider Cydippe Flemingii
Forb., Cydippe pomiformis atters., Beroe ovatus
Flem., and even Cydippe Infundibulum £sch. (Beroe
Miilleri Zess.), as synonymes of Pleurobrachia or Cy-
dippe Pileus. Whether the Mediterranean repre-
sentative of this genus, described as Cydippe densa
Esch., to which Beroe Pileus Risso and Beroe
albens Forsk. also belong, is identical with the
northern Pl. Pileus, or not, I have no means of
ascertaining ; the red tentacles seem to indicate a
specific difference, and the circumstance that this
species has thus far only been noticed in the
Lusitanie fauna, while Pl. Pileus belongs to the
Celtic fauna, would justify this inference. The
3eroe Pileus of Fabricius (which must not be con-
founded with Cydippe Cucullus, as was done by Esch-
scholtz) is very likely the North American PI. rho-
dodactyla. This Beroe Cucullus, erroneously called
Cydippe Cucumis by Lesson, is a Mertensia, identical
with the Beroe Pileus of Scoresby (Mertensia Scores-
by ZLess.), and also identical with Beroe ovam Fubr.
(Cydippe ovum Zsch.). Lesson has made another
mistake in referring Cydippe bicolor Sars to his
Cydippe Cucumis. Sars’s species is a genuine
Pleurobrachia, distinct from Pl. Pileus, but closely
allied to our PI. rhododactyla. It is, in fact, the
European representative of the Pl. rhododactyla,

and, like this, belongs to the boreal fauna; while

As it is of great importance

Mertensia Secoresbyi, which should be called M.
Cucullus, is an aretie species. Pl. Bachei, dis-
covered by my son on the shores of Washington
Territory, is another species with red tentacles, but
differs from Pl. rhododactyla in having a longer
funnel, a shorter coeliac cavity, and the actinal part
of the tentacular sac also shorter. Pl. bicolor,
judging from Sars’s deseription, has white lateral
threads, the tentacle itself being alone red. To these
species must be added Beroe Basteri Zess. from
the coast of Peru, Beroe rosens Q. and G. from
the straits of Timor, and Beroe Santonum Less.,
which is probably identical with Pl. Pileus. Les-
son refers these three species to the true Beroids,
but they unquestionably belong to the genus Pleuro-
brachia: the tentacles must have been overlooked.
No true Beroid ever has the form of these Aca-
lephs. The genus Janira, which comes nearest to
Pleurobrachia, embraces, as far as I know, only
the following three species: Cydippe elliptica Lsch.,
Beroe Cucumis J/ert., and Beroe elongatus @Q. and
G. Janira hexagona is a Callianira, and Janira
octoptera a Martensia, well to distinguish from
Mertensia, though both belong to the family Mer-
tenside. To Eschscholtzia I refer only Cydippe
dimidiata Hsch.; Eschscholtzia glandiformis Zess. is
the type of the genus Dryodora (Mertensia Gegenb.) ;
while Eschscholtzia cordata is the type of the genus
Gegenbauria Ag., and belongs to the family of
Mertensidw. © Cydippe hormiphora is also the type
of a distinct genus, for which I would propose the
name Hormiphora: it is closely allied to Esch-
scholtzia and Pleurobrachia, and belongs with them
to the family of Cydippide proper. Cydippe brevi-
costata Will, and Cydippe quadricostata Sars are
very likely young Ctenophorwe Lobate, according

to the observations of MeCrady.

Cuap. III. GENUS PLEUROBRACHIA. 209

to the full understanding of the internal structure of this animal and the correct
appreciation of all its organs to form a correct idea of their respective position,
I feel compelled to enter into some tedious details respecting this slight variation
from the spherical form; for, though scarcely appreciable, it has a direct bearing
upon the connection of all the organs, which, upon close examination, are found to
preserve, throughout the order of Ctenophore, a constant relation to this apparently
insignificant difference between the three diameters of the body,—so much so that
these globular animals are as truly bilateral in the arrangement of all their parts,
as any other species of the whole group.

The mouth opens transversely; and there is upon the opposite pole of the
sphere an oblong, narrow, circumscribed area, placed also in the same direction,
transversely to the greater diameter. The two tentacles with their fusiform sockets
are placed at right angles with the transverse split of the mouth and the opposite
oblong area, the tentacles being in the diacceliac diameter, the mouth and the area
in the coeliac diameter, and the main axis of the digestive cavity trending vertically
between them. The rows of locomotive flappers alternate, two and two, with these
four radiating directions. So that there are four rows on one side of the plane
passing through the tentacles, and four on the other; and also four on one side
of the plane passing through the mouth and the opposite area, and four on the
other,— no one being placed either in the prolongation of the mouth or in that
of the bases of the tentacles (PI. II Figs. 20, 21, 22, and 23).

Owing to the compression of the body, and the difference in the curvature of
its actinal and abactinal sides, the eight rows of locomotive flappers have their upper
and lower halves bending in a somewhat different manner. Again, two pairs, per-
fectly equal, inclosing the base of the tentacles, stand in antitropic relation to one
another along the prominent side; while two other pairs, inclosing the prolongation
of the angles of the mouth and the circumscribed area at the opposite pole, extend
in a similar manner along the flattened side. The consequence of this arrangement
is, that each side of the body has two equal rows of locomotive fringes placed
in a symmetrical manner opposite each other from side to side and crosswise,
those of opposite sides being identical, but differimg from those which stand at right
angles with them.

Having thus ascertained that the body of this animal is neither vertically nor
transversely circular, and that there is a medial axis with reference to which the
arrangement of all the parts is regulated, the question at once arises how we
should consider these diameters: whether the mouth should be placed upward
or downward, or whether it should be considered as the anterior extremity, and
what are the relations of the sides. As with the other Medusxe, whatever view
we take of the subject, when we compare these animals with either Polypi or

VOL. Ill. 27

210 CTENOPHOR®. Part II.

Kehmoderms to ascertain their homologies, we must, as a matter of necessity, bring
them all into the same respective position, and contrast the arrangement of their
parts in their mutual correspondence. There is, however, no difficulty about their
identification, inasmuch as the mouth is made in every case the central point of
comparison. It has been already ascertained, that Polypi, though truly radiated
animals, have, in most of their types, if not in all, a rudimentary indication of a
longitudinal axis in the oblong form of their mouth, which is the first indication
of a bilateral symmetry in the animal kingdom, occurring even among the lowest
Radiata ; while in Echinoderms it rises higher and higher, and becomes so promi-
nent in the Spatangoids as to influence not only the general form, but even the
number and arrangement of the internal parts, and the length and special develop-
ment of the external appendages and of the ambulacral rows.

The class of Acalephe, which is intermediate between those of Polypi and
Kehinoderms, holds in these respects also an intermediate position. In Ctenophore,
we have a slightly compressed body and an oblong mouth. But the mouth may
open in a direction transverse to the elongation of the body. The question there-
fore is, Does the mouth, with the plane which passes through it and the opposite
area, in this case indicate the length of the axis of the body, and divide it into a
right and a left half; and are therefore the tentacles lateral appendages, one on the
right side and the other on the left side, as we should consider them if we were
to place the axis of the mouth in the same direction as the axis of the mouth
in Polypi? or have we to consider the tentacles as arranged along the longitudinal
axis, one on the anterior, and the other on the posterior, extremity? And in that
ease, are the folds of the mouth rather the first indications of an upper and a lower
lip,—as we should consider them were we to compare the transverse position of
the mouth with the position this opening assumes in the oblong symmetrical Echi-
noderms, in which the bilateral symmetry has been made prominent,—or have we
to view also the indication of bilateral symmetry among Polypi as a tendency to
such an arrangement of the two lips? I think I can be positive in the case of
Polypi; for in Actinia, as well as in Astrangia and many other Actinoid Polyps,
the oblong fold of the mouth has unequal angles; and it would be to suppose the
right and left angles of the mouth to be assymetrical, and the upper and the lower
lip to be identical, if we should not consider this split as running in the longitudinal
axis. And that it indicates really a longitudinal axis is shown by the circumstance,
that fecal matters are discharged along the rounded angle of the oblong mouth,
opposite to which there is, in many Polypi, a tentacle of a peculiar form, and some-
times differme im color from the others.

This being the case, are there reasons to view Pleurobrachia in a different

light? Are the Ctenophors more nearly related to Echinoderms in their arrange-

Cane glia GENUS PLEUROBRACHIA. o11

ment than to Polypi? I hardly believe it; for, as the mouth is transverse in many
Echini, so also do their anterior and posterior extremities differ more and more,
in the same proportion that the bilateral symmetry is increased and made more
prominent. It seems to me, therefore, more natural to compare Pleurobrachia with
the other Radiata in a position in which the split of the mouth will indicate the
antero-posterior diameter, even though the diameter considered as the transverse be
thus greater than the longitudinal. This, however, is not the only instance of
such a disposition in the animal kingdom. In many Mollusca of the class of
Acephala, in the family of Cardiacea, we have numbers of genera and species in
which the longitudinal axis is shorter than the transverse. Though the vertical
chymiferous tubes with their rows of locomotive fringes are homologous with the
ambulacra of Echinoderms, I hold that the position I assign to the Ctenophorse
is in perfect accordance with the general progress of symmetry among Radiata ;
for the anterior position of the mouth in the Spatangoids does not interfere with
its being the centre of radiation, as in all other Kchinoderms. The first tendency,
beyond a perfectly radiated arrangement, which is introduced among the Radiates,
is to a symmetrical disposition and parity between right and left, when the
anterior and posterior extremities may be marked by this lateral symmetry only, and
not made to differ from each other. Next, the two ends of the antero-posterior
diameter are made to differ; and this we see introduced among the higher Kcehi-
noderms only. For, though bilateral symmetry can be recognized among Star-fishes
and Echini proper, their anterior row does not yet differ from the others; and the
first appearance of such a difference is introduced in the Clypeastoids, and more
developed in the Spatangoids. If, therefore, the Echinoderms, which as a whole rank
above Meduse, still retain so completely the radiated type, and the bilateral sym-
metry is developed in them, among so many of their types, solely in their perfect
symmetry of right and left, without a difference between forward and backward,
why should we expect this in the class of Acalephew, especially when we are able so
easily to refer this type to that of Polypi? I assume therefore decidedly, that the
diameter which corresponds to the split of the mouth indicates the longitudinal axis,
and shall, in the following pages, describe all parts with reference to this view. I
thus consider the halves of the body which would be divided by a plane passing
through the split of the mouth and through the opposite oblong area as the right
and left halves of this animal, and therefore the tentacles as being placed right
and left. But I must for the present leave it doubtful which is right and which
is left; for the sides are so completely identical, the two angles of the mouth
so absolutely equal, and the prominent projections of the opposite area so uniform,
as to afford no indication upon this pomt. This is a very remarkable circumstance

to occur in a class intermediate between two others, in which, notwithstanding their

212 CTENOPHORA. Part II,

But

there may be a compensation for this identity of the anterior and posterior sides

radiated arrangement, the anterior and posterior sides can be fully ascertained.

in the prominence of the lateral parts of the body.

The parts already mentioned in a general way are not the only ones which
have reference to the bilateral arrangement. The tentacles also arise on opposite
sides, in two sacs extending inward in an obliquely vertical direction, and reaching
a point about as far from the actinal pole as the point from which the tentacles
issue is from the abactinal pole. These sacs stand in the interambulacral space
between the lateral rows of flappers, with their proximal surface near the fork of
the main trunks of the chymiferous tubes," which also branch in opposite directions
in the transverse diameter of the body. The disposition of this complicated system
is, therefore, also bilateral: two main trunks penetrating symmetrically right and
left from the funnel, and branching in such a manner as to reach on each side, with
four arms, the four vertical rows of locomotive flappers, and giving on each side
also two branches to the base of the tentacles” The chymiferous cavity is full
of fluid, which is in constant movement by the agency of vibratory cilia, and also
under the influence of a regular pulsation of the whole system in the two halves
of the body, so alternating im their contraction and dilatation, that at one time
the fluid moves to a considerable extent from one side to the other, and next
returns by the contraction of the opposite side through the same tubes in the

opposite direction, presenting something similar to what exists in Salpa under differ-

ent combinations.

1 To facilitate comparisons with the paper of
Milne-Edwards on the gastro-vascular apparatus of
the Ctenophore, I would remark, that he calls ven-
tricule chylifére the axial chymiferous cavity, which
I have called funnel; trones périgastriques supé-
rieurs, What I have called main trunks and forks of
the chymiferous system; vatsseaux costaur, what I
have called ambulacral tubes; vaisseau périgas-
trique inférieur superficiel, what I have called ¢nter-
ambulacral or tentacular tube; vaisseau périgas-
trique inférieur profond, what I have called stom-
achal or celiac tube. I would also take this oppor-
tunity to state, that the description of the chy-
miferous system of Cestum, published by Milne-
Edwards, has convinced me that this genus really
constitutes a distinct sub-order, as I suspected; for
the course of the lateral ambulacral tubes is quite

peculiar, and they are destitute of locomotive flappers.

There is really a regular circulation through the large axial

Milne-Edwards is explicit upon that point. I am,
however, still inclined to question the absence of
celiac tubes, which exist in all the Ctenophore I
have examined, and I have seen as many as seven
species of this order: the figures of Milne-Edwards
are drawn in a position in which the cceliae tubes
would be covered by the interambulacral tubes, and
might therefore be overlooked. Neither Eschscholtz
nor Mertens represents coeliac tubes in the species
of Cestum which he has described.

* There are certainly two parallel interambu-
lacral tubes to each tentacular apparatus, as I have
represented them in the Memoirs of the American
Academy, Pl. I. Fig. 8; and Milne-Edwards must
be mistaken in representing only one. In a view
like that published by him only one tube is visible ;
but, facing the trend of the tentacular sockets, both

tubes are brought into sight.

Cuap. II. GENUS PLEUROBRACHIA. 213

cavity; for the main trunks of the chymiferous tubes, with their forks branching
in a very symmetrical way in the right and left parts of the body, undergo a
rhythmic movement of contraction and dilatation, alternating between the two sides.
In those Ctenophore which have an oral chymiferous tube communicating with the
recurrent branches of the ambulacral tubes, the bilateral circulation is not so promi-
nent. The axial cavity, which I have called funnel, is not to be mistaken for
the digestive cavity, though it extends in the same axis with it, in the direction
of the abactinal pole; nor is the digestive cavity entirely surrounded by the
chymiferous system, as I had supposed when I published my paper in the Memoirs
of the American Academy, but only flanked on each side by so wide a cceliae
tube as readily to appear like a sac surrounding the whole digestive cavity.’ The
funnel has two apertures, by which it communicates with the surrounding water,
and through which it discharges the refuse chyme. These apertures are placed
in a symmetrical position on the two sides of the oblong area, opposite the mouth
and near its centre, obliquely opposite each other; so that one is in the anterior
half upon one side of the body, the other in the posterior half upon the other
side. These openings are generally shut; but they open at intervals to discharge
the fecal matters, and are afterwards instantaneously shut again. It is very diffi-
cult to catch these movements; and even after I had seen them open and _ shut,
I have frequently watched for days without observing a repetition of the oper-
ation, which I have, however, seen so many times now, that I entertain no doubt
respecting the position of these openings and their natural function. Moreover,
balls of fecal matters may almost constantly be seen floating with a rotating motion
below these apertures.

This sketch gives as yet but a slight, very incomplete, and superficial idea of
the remarkable complication of structure which may be observed in these animals;
but such a preliminary illustration was necessary before undertaking a minute
description of all parts and their natural relations. And, before alluding to these
details, I would request the reader to bear the following poits in mind: that
Pleurobrachia is not strictly spherical, nor even strictly circular, in any direction ;
that there is a longitudinal axis, which passes through the mouth and the area
opposite; that the tentacles are in the transverse axis, at right angles with the
fissure of the mouth; that the digestive cavity trends in the vertical and in the
longitudinal axis; that the chymiferous system branches symmetrically in the right

and left halves of the body, eight branches reaching the eight vertical rows of

1 Milne-Edwards has made the same mistake in Sc. Nat. 4e sér. vol. 7, Pl. XVI. Fig. 2. The ceeliac
representing the chymiferous cavity as surrounding tubes occupy only the more deeply colored part of

the sae into which the mouth leads. Comp. Ann. his drawing, on the sides of the digestive cavity.

214 CTENOPHORA. Parr IL.

locomotive flappers, two other branches the sacs from which the tentacles issue,
and two others following the walls of the digestive cavity,—the four latter arising
from the main lateral trunks in the trend of the transverse diameter, while the
forks which supply the locomotive flappers trend at first in the direction of the
longitudinal diameter, and emit each another fork parallel to the transverse diame-
ter, so that all parts have a precise geometrical relation to each other; and,
finally, that the right half of this system alternates in its contractions with the
left half.

In the special investigation of the minute structure of the different systems of
organs developed in these animals, it will be better to proceed in the order which
will assist us in the understanding of all the other systems, rather than to follow
a physiological principle.

Though the form is apparently well determined and regular, even superficial
investigation will satisfy the observer that it is constantly changing within more
extensive limits than might be at first suspected. In the first place, the apparently
spherical form is not only frequently altered into an ovate by the vertical elongation
of the mass, but it even assumes at times a form rather cylindrical than ovate,
especially on the side of the mouth, by the extensive dilatation of this opening.
The changes which the mouth assumes in its outlines are very extensive and
frequent. When completely shut, it disappears almost entirely; and its position
is scarcely marked by any thing more than an indistinct outline, towards which
the actinal ends of the rows of locomotive flappers converge. When halfway open
or while opening, it assumes an oval form, like a fissure, across the body, which
becomes gradually more and more elongated, then widens, and finally expands into
an ample, cireular, funnel-shaped depression. These movements are rather slow, and
may be compared to the undulations of a slug or snail adapting its mouth to the
form of its food. The changes in Pleurobrachia, however, do not seem to be
called forth by the approach of food, but are rather the result of a natural dispo-
sition in this animal to be im an attitude ready to seize upon its prey. Various
aspects of the mouth are represented in my former paper.

The whole bulk of the body of Pleurobrachia, excepting the spaces occupied by
the digestive and the chymiferous system and the tentacular sockets, is a solid mass
of closely packed cells, most of which are of enormous size (Pl. I. Fig. 24). Such
is the extreme transparency of these cells, that it is very difficult to follow their
contour except in profile, and on this account the thickness of their walls has been
mistaken for long and slender muscular fibres; and this illusion is oftentimes
heightened when the wall wrinkles (2%. 24, 6, ¢) during contraction, and appears
like shrunken fibres. But there is no muscular system apart from the constituent

cells of the body, and therefore no contractile fibres of any kind so grouped as

(=

Cuap. II. GENUS PLEUROBRACHIA. 915

to appear to be specially fitted for the movement of any particular organ. Yet
the cellular system is not a confused mass, as perhaps might be inferred from the
foregoing remarks, but these gigantie vesicles, reminding one of the fusiform pulp-
sacs of the orange both by their shape and disposition, have a most beautiful
and extraordinary arrangement, which is thus far only known among Ctenophore.

In order that there may be no misapprehension in regard to the nature of
‘this extensive motory system, it is advisable to render its cellular character as
distinct as possible in the mind of the reader, and therefore, before proceeding
further, we will describe the cells in detail. We have already remarked on their
extreme transparency: this, combined with their great length and the prominence
of their walls, in profile, conspires to obscure their true character, and suggests the
idea, even to the observer well acquaimted with them, that they are a network
of widely separated fibres; and as such they have been described in a_ previous
memoir, though their vesicular character was already observed to some extent.
They are in reality elongate, irregularly spindle-shaped vesicles (/%g. 24), either
with blunt ends (a) or with all degrees of acuteness to quite slender, pointed
terminations (e). When seen from either the actinal or the abactinal pole of the
body, they generally display a broader outline than from any other point; and, as
the eye passes along the sides towards the middle region of the body, they present
successively narrower and narrower boundaries, until, at a right angle with the first
point of view, they show a minimum of breadth. Viewed transversely, they are
irregularly polygonal, and on that account each cell appears to have three, four,
or five narrow ribs, trending parallelwise to its longer axis, and corresponding to
its angles. When in a state of contraction, the walls are wrinkled transversely
to the longer axis (Fy. 24 6 ¢); but, owing to their transparency, the angles alone
are readily seen, and they appear like thin, tortuous fibres, or oftentimes, strange
to say, as if they were spiral springs, adapted to keep the body in a state of
tension. This false appearance is not easily dispelled if it impresses the mind at
the first view of these cells, especially as it is very difficult to trace the true
relations of their sides and angles, without having some sort of hint as to their
true nature. The total absence of the usual cell constituents — mesoblast and more
or less granular contents— contributes also to keep up the illusion; for every thing
within is as clear and homogeneous to the eye as blank space itself Indeed,
any one, after remarking the glass-like transparency of these animals, would be apt
to doubt whether any structure could be detected in them. Such is the almost

ethereal nature of the motive power which governs the actions of Pleurobrachia.

1 Contributions to the Natural History of the American Academy of Arts and Sciences, Boston,
Acalephe of North America, by L. Agassiz, Mem. Mass., vol. 4, part 2, 1850, p. 530.

216 CTENOPHORA. Part II.

The adaptation of means to an end is nowhere in the animal kingdom more
beautifully and plainly displayed than in the mode of disposition of the simple
material which constitutes, at the same time, the mass and the moving power of
this animal: a specialization by arrangement, without a segregation, as a distinct
system apart from the other organs. If the greater part of the body of certain
Mollusea is subservient to muscular action, how much more extensively does this
obtain in the Ctenophore.

Viewing the body of Pleurobrachia from the actinal pole (fy. 21 a), the whole
mass appears, at first sight, to be composed of an aggregation of cells (m m’*),
which radiate in every direction from the centre to the periphery, as if an ex-
emplification of the radiate type to which this animal belongs. It is true, these
cells are arranged as we have here described; they do not, however, occupy the
whole of the space through which they project, but are intimately interwoven with
the cells of another system (p p”), diverging from the tentacular sockets (j) to
the periphery. The radiating system, however, is the most extensive, and pervades
almost every region of the body: in fact, the only portions which it does not
occupy are a small space lying in a direct course between the tentacular sockets
and the periphery, and also a thin layer of the periphery, which is exclusively
devoted to the system of cells (x x') which traverse the spaces between and under
the locomotive flappers. In all these systems the longer axes of the component
cells trend in the lines of radiation of each system to which they belong: in fact,
it is their longitudinal outline which gives the characteristic fibre-like appearance to
the mass of the body. This will suffice to give an idea of the general disposition
of these cells, and of their relation to each other; but each system needs a much
fuller treatment by itself; in order to elucidate its share of influence upon the
movements of the body.

For the sake of convenience, we will describe the peripheric system first. It
will be seen by the figures drawn from the actinal and abactinal poles (Figs. 20 and
21), that the outline of the body is waved or slightly lobed, the lobes corresponding
to the spaces between the rows of locomotive flappers (/' 7’), so that there may be
said to be eight broad ribs alternating with as many narrow and_ shallow furrows,
extending like meridians from the actinal to the abactinal areas. The proportionate
breadth of the ribs may be ascertained by inspecting the figures, and they are
deseribed more fully in another place. Now, the peripheric cellulo-motory system
is divided into two sets of layers, the one corresponding to the broad ribs and
the other to the shallow furrows. The first system (z x') is by far the most
extensive, both in breadth and depth. The surface of each broad rib is at the
same time the outer convex surface (J%. 21 7) of a broad band of transversely

trending cells; and the inner face (n*) of each band has the same degree of cur-

Cuap. UI. GENUS PLEUROBRACHIA. 917

vature as the outer surface. Thus every layer of the dterambulacral system is doubly
convex, and therefore thickest along the median line of the lobe, and thins out nearly
to an edge, on each side, where it meets the ambulacral layer. It also thins out
at the actinal and abactinal ends, and finally terminates (/%y. 25 7? 7°?) on a line
with the ends of the rows of locomotive flappers. The longer axes of the cells of
this system trend more or less parallel with the surface of each band (fy. 21
n n) to which they severally belong, and directly across from one ambulacral row
to another (Fig. 23 n° x). Therefore, when they contract longitudinally they tend
to draw the rows of locomotive flappers closer to each other, and consequently
decrease the peripheric extent of the spherosome. This, we shall see hereafter, has
an important bearing upon the peristaltic movements of the body.

A band of similar cells (7%. 21 m')—the oral system— encircles the mouth, the
longer cells trending parallel to the edge of the lips, so that, when the mouth is
open and rounded, they are parallel also to the longer axes of those which con-
stitute the interambulacral system. In fact, the boundaries of the two systems —
the oral and the interambulacral— merge one into the other, at least at the cor-
ners of the mouth, but more faintly at right angles to these points.

The ambulacral system consists of bands of cells (#7. 26 2’ 2? x), which are identi-
cal in their nature with those of the interambulacral layers, and are eight in number,
one of each underlying a row of flappers (w). The thickness of a band is equal
to the distance between the ambulacral tube (v7) and the surface of the body, and
its lateral expanse corresponds to the breadth of the row of flappers which it
underlies; although it cannot be said whether this system belongs exclusively to
the locomotive apparatus, or takes part in the peristaltic movements of the body
in common with the interambulacral system into which it so gradually passes.
The latter agency most unquestionably obtains in the area about the mouth and
on the opposite pole, where the different peripheric systems merge into each other,
and where neither the ambulacral tubes nor the flappers are present: but im the
ambulacral region, the specialization of these cells, for the purpose of locomotion,
no doubt, is predominant; and, perhaps, as we shall presently see, some of them
are exclusively devoted to the flappers. This assertion will appear to be true upon
inspecting J/g. 26, in the region (w') from which the flappers (w) arise. The ridge
(w) upon which each flapper is based is a simple projection from the surface of
the body; but its cellular constituents (w') are arranged in a peculiar manner, which
indicates, as we think, the particular and exclusive use to which they are appointed.
The longer axes of these cells each and all trend outwardly in the direction of
the base of the flapper; and, unless we misinterpret appearances, they may be
recognized in the flapper itself, where their outlines appear as longitudinal strie.
In plain terms, we would say that it is our conviction that these cells are arranged

VOL, IIL. 28

918 CTENOPHORZ. Part II.

parallelly in the flapper, and that their outer free ends constitute the marginal
fringe of this organ, and furthermore that each cell is as it were a single tooth
in the comb-like flapper, reaching in one stretch from the base to the margin.
Thus the locomotive flappers would be formed by the simple projection of these
cellulo-rmotory vesicles beyond the surface of the body,’ and by their arrangement
in a single row, combined with lateral coalescence. As these cells are simple pro-
longations from the midst of other similar cells, we should take it for granted that
they have similar motive powers; for no action of special muscles — supposing that
they were present, which is not true—could be so transmitted from the base
along the flapper as to give it that peculiar curve which it frequently assumes
when in a stationary condition: but any one may understand how the cells them-
selves can assume such a curve, and that each combined row of cells moves by
the inherent power of its components, for, as we have frequently observed, when
the flappers are minutely split up from edge to base, each cell vibrates isolatedly,
and either in consonance with the others or at random.

It has oftentimes been noticed by observers, that whilst Pleurobrachia is in a
dying state and even falling to pieces, and the epithelial cells peel off from the
body, and, as we have observed, from the flappers too, m the form of a filmy
mucus, the flappers themselves remain to the last moment flapping convulsively,
wherever there is a bit of the body to which they may adhere, thus showing their
intimate connection with the deeper seated cells. The ganglion-like bodies described
in my former paper on Beroid Medusx are nothing but the points of convergence
of several such cells: they are very irregular in shape, and not always to be seen.

The remarkable iridescence of the flappers, we think, can be easily explained by
reference to what we now know of their intricate structure. Each cell bemg
excessively flattened, the walls are approximated like superposed laminw, and_ these,
with the surfaces of the epithelial cells, form all that is required to produce the
same kind of action upon light as a pile of thin plates of mica or glass.

The tentacular sockets (/%y. 15 j j') are embraced by a wall whose cellular
constituents closely resemble those of the interambulacral system; and, in fact, as
will be shown hereafter in detail, these sockets are nothing more nor less than
deep depressions in the latter system: the cells trend in the same general direction,
that is, their longer axes trend transversely to the length of the sockets, and, for
nearly one half of their distal extent, from the base of the tentacles (vy) to the
aperture (j"), completely encircle them, like a constrictor muscle. At the basal

half of the sockets, these cells form only a semicircle (7%. 15 7 7%, Fig. 21 u°) on

1 This being true, the locomotive fringes are in posed before I knew fully their structure, and as

no way comparable to vibratile cilia, as 1 had sup- Will also admitted.

a ve

Cuar. II. GENUS PLEUROBRACHIA. 219

the peripheric side; but the wall is continuous with the outer wall (page 255, Fry.
87 p’ 8") of the tentacular apparatus, and thus the circle is completed.

The next system that demands our consideration is the largest of all; and we
may call it the radial system, from the fact that it radiates equally on all sides,
from the digestive cavity and the axial funnel to the peripheric systems. When
seen from the actinal (#%. 21) or abactinal pole, the cells seem to radiate im direct
lines from an imaginary centre; but in a profile view (My. 23), the true course
of these bodies (m ¢ 7) is discovered to be in two oblique directions, one of which,
radiating from the digestive cavity (6 ¢), recedes from the actinal toward the oppo-
site pole, and the other, radiating from the axial funnel (/), is inflected toward the
digestive cavity as it passes on to the periphery. Besides the general direction
of these two courses, there is another peculiarity which is quite remarkable: the
axis of each cell, instead of being a straight line, is curved (Fig. 24); so that the
main trend of these bodies does not recede in a direct course from the two polar
ends of the body, but in long arches. The degree of flexure in these two courses
varies in different parts of the body, and may be most appropriately described
in connection with the details of this system, to which we now proceed. The
shortest span which the radial system makes, lies between the corners of the mouth
(Fig. 21 a') and digestive cavity, and those bands of the interambulacral system
which are in the plane of the latter organ, and therefore at right angles to the
plane which passes through the tentacular sockets (7) and the two chymiferous
tubes (7 7) on each side of the digestive cavity. In this region the cells pass
to the periphery in a course which recedes but little from the mouth, and which
curves very slightly toward the centre of the body. In the same plane, at the
opposite pole, the span is longer, on account of the smaller dimensions of the axial
funnel (Fi. 23 f), but the trend of the cells is about the same: in fact, they have
the same trend and curve as at right angles to this plane (f¥y. 23 ¢ 7') and at
all intermediate angles.

But, to return to the actinal pole, we would remark that we find the trend
of the radial system (F%gy. 21 m im”) very much modified as we trace it through
ninety degrees from the plane of the digestive cavity; for the recession becomes
gradually more noticeable, until it reaches its maximum in the region where (My. 23
m*) the cells pass to the tentacular sockets (j) with a trend of forty-five degrees
to the axis of the body. The span, which is so short opposite the corners of
the mouth and digestive cavity, gradually increases in length, until it attains to
the longest reach in passing to the chymiferous tubes (/' 7° and /* 7°) which embrace
the tentacular sockets (7); and then the latter, by obstructing the way, suddenly
shorten it by more than one half.

This will be more fully comprehended as we now proceed to describe the several

99) CTENOPHORS. Part IT.

points of attachment throughout the system. The cells which radiate from the
corners (/¥g. 21 a’) of the digestive cavity and thereabouts occupy at their outer
ends the whole breadth of the nearest interambulacral band (A, E) of the peripheric
system; while those which arise from the sides of the digestive cavity, midway
between its corners (a') and the vertical tubes (7 7) which embrace it, terminate
against the four chymiferous tubes (/? /* and 7° 7°) which lie nearest to the oral
plane. In this as well as im the instance of the other four chymiferous tubes,
nothing but their thin wall separates the motory cells from the circulating fluid,
and therefore this system must have an immediate and direct influence upon the
diameter of these channels. The four peripheric bands (B, D, F, H) which lie
intermediate to those im ‘the oral and tentacular planes receive the outward
prolongation of all those cells which arise at the median third of the digestive
cavity and close upon the vertical chymiferous tubes (7 7). The four peripheric
chymiferous tubes (/' 7° and /* 7°) which trend nearest to the tentacular plane
receive the ends of those cells which arise from the vertical tubes (7 7) on the
sides which face toward the corners of the digestive cavity. The two peripheric
bands (C, G) which le in the tentacular plane have no connection whatever with
the radial system, excepting a very small part of their terminations, which extend
beyond the opening (j") of the tentacular sockets and toward the abactinal area ;
but all those cells (Avy. 21, and 25 im’) which radiate from the vertical tubes (7 7) in
proximity to the tentacular plane terminate against the proximal side of the ten-
tacular apparatus (4' 2°), and occupy the whole breadth of the same. The length
of the span of this part of the radial system varies very much, according to the
degree of expansion or contraction of the body; but it usually decreases in the
direction of the main chymiferous tubes (ee). In the oral region this system
merges into the lateral system along the tentacular plane, the cells of the former
(fig. 25 nm?) having the same general trend as the latter (m*), which radiate from
the base (j*) of the tentacular sockets to the oral area.

It is a difficult matter to distinguish the two systems from one another, when
they are seen in profile. But, by a study of the boundaries of the lateral system
from another point of view (fig. 21), we find that all those cells which radiate
from the tentacular sockets to the oral area, even close up to the terminations
of the vertical tubes (7 7), belong to this system; whereas only those cells
which radiate from the aforesaid vertical tubes belong to the radial system in this
plane. In regard to that portion of this system which radiates from the axial
funnel (/), we have only to add a word or two, to point out, partly in reiteration
of what has already been stated, the fact that the cells (¢7') trend altogether from
one axial line toward the periphery, and are only interrupted at two opposite points
by the tentacular sockets (/).

Cuar. IT. GENUS PLEUROBRACHIA. 99]

Next to the radial system, the lateral system (Fig. 21 p p', and Fig. 23 p*) is
the largest, and, of the two, the most curiously arranged. The tentacular appa-
ratus (2 12) may be said to be the basis of this system; at least, from these two
points all its cells radiate to the periphery. In a view from the oral end of
the body (F%g. 21), each half (p p') of the system presents an outline which reminds
one of the wings of a butterfly, the tentacular apparatus simulating the body of
the insect: nowhere do we find the cells trending in straight lines, but always
in gentle curves, whéther it be toward the oral plane or in the tentacular plane,
or to all intermediate points of the periphery; or whether, as a profile view shows
(Fig. 23), toward the oral area, or in the opposite direction toward the orifice of
the tentacular sockets, or to all intermediate points. In order to simplify the
description as much as possible, we will speak of the curved rows of cells as of
the cells themselves, which is the more appropriate since the long curves are made
by adding one curved cell to the end of another. In the first place we would
mention the important fact, that the tentacular sockets (j) alone form the basis of
this system, and that the tentacular apparatus proper (/' 4°) has no connection
whatever with it. As we see it from the oral end (F¥y. 21), the immer and proxi-
mal face (p?) of each of the four wings of this system forms the hypothenuse
of a right-angled triangle, of which the oral and tentacular planes constitute the
other two sides. Properly speaking, this face is the hypothenuse of a spherical
triangle, since it makes one continuous curve from the edge of the tentacular
socket (j) to the median line of that peripheric band (A, E) which is bisected by
the oral plane, and meets its corresponding hypothenuse from the opposite side, at
a very acute angle, all along this line, to the end (x) of the band, and then the
edge of this face diverges from the oral plane and follows the outlines of the oral
system (m') to the tentacular plane. It will be readily inferred, that the greatest
span of this face is on a level with the equatorial plane of the body, and that
it gradually shortens toward the oral region, and also in the opposite direction.
If we follow it along its attachment to the tentacular socket toward the oral area,
we find that it meets the face of the wing on the other side at a short distance
from the bottom of the socket; so that the two faces form one continuous surface,
which arches, as it were, over that portion (fig. 25 m°) of the radial system that
lies in the tentacular plane. The bottom (j*) of the tentacular socket projects
considerably beyond the base of the tentacular apparatus (2! 7’), and is free from
it; and it is where the wall of this part of the socket joins the terminal edge of

the tentacular base that the margins of the above-mentioned faces come together.

If, now, in looking at this face in profile (#%g. 21 p*),— as we may do by viewing
it from the oral end of the body,—we follow it with the eye from the equatorial

region toward the oral area, its component cells gradually change their trend, in

929 CTENOPHORSE. Parr IL

order to point in a general way perpendicularly to the curvature of the periphery
of the body, and become by degrees foreshortened, until they point directly at
the eye from the bottom of the socket. In a profile view of the sockets (fi.
23), the cells at the last-mentioned place (mm) trend in lines at right angles to
the line of vision, and therefore directly toward the oral area; whilst, now, the
cells in the equatorial plane point directly at the eye.

The merging of this into the radial system at this point, we have already
indicated; but the precise line of juncture of the two may be better and more
clearly described now that the boundaries of the former have been distinctly traced.
Where the oral plane strikes the inner face (2%. 21 A, x) of the opposite peri-
pheric band, the cells of the two systems in question trend so nearly in the same
direction as to make it very difficult to distmguish them apart; and, in truth, it
is only when seen from the horizontal end that the oral curve (p*) of the cells of
the lateral system furnishes the means of elimimating them from those of the radial
system. This apparent confusion of the peripheric borders of the two systems
obtains all along the median line of the peripheric band just mentioned to its
termination, and then along the borders of the oral system (m’). The cells (p*)
cross each other at wider and wider angles, until, halfway between the oral and
tentacular planes, they mutually traverse one another at right angles, and then
again their trend grows more and more nearly parallel, till they run in the same
direction side by side at the tentacular plane. At the latter point the parallelism
is more perfect, and extends deeper into the body than along the median line of
the peripherie band; and, in a profile view of the sockets (/), that part of the
radial system (m) which passes from the tentacular apparatus to the vertical chy-
miferous tubes (7 7), seems to be one and the same with the lateral system (m’),
which radiates from the base of these sockets. In passing to the several bands (A,
B, C, D, E, F, G, H,) of the peripheric system, and to the chymiferous tubes (/* to 7°),
the cells of the lateral system preserve the same curve, both horizontally and
vertically, as along the hypothenusal face. As we have already remarked, these
cells trend very nearly parallel with those of the radial system, where they meet
along the median line of the peripheric bands which are in the oral plane, and,
as we pass around the periphery toward the tentacular plane, we here also find
the two, abutting against the several bands (A to H) with a like trend; but it
is only at the periphery that this parallelism obtains, whilst towards the axis of
the body the cells cross at all angles between the most acute and a right angle,
according to their position: thus those cells which radiate to the peripheric inter-
ambulacral band (A and E) in the oral plane, cross the radial cells which proceed
from about the corners (F%y. 21 a’), from the outer third, and from the median

third of the digestive cavity, severally at a very acute angle, at an angle of

Cuap. III. “GENUS PLEUROBRACHIA. 223

about forty-five degrees, and at a right angle; and after the same manner all the
cells of the lateral system, receding from their peripheric terminations toward their
bases, cross those of the radial system. It must be borne in mind, however, that
these various angles of traverse are not as if formed by lines coursing on a plane,
but as if on the surface of a sphere; that is, they are spherical angles.

This, in general terms, may be said to be the relation of those cells of the
radial and lateral systems which le between the equatorial plane and such a
plane as would divide the body by traversing it on a level with the basal ends
(Fig. 25 7°) of the tentacular apparatus; but beyond this zone and towards the
mouth, the relations of these cells change very rapidly: within the zone the cells
of the lateral system diverge from the tentacular socket about at right angles to
its axis, but beyond this they diverge at a gradually lessening angle, till at the
tip of the socket (j*) they trend, as it were in direct continuation of its axis, to
the nearest pomt in the periphery, somewhat in the same manner as the hairs
project from the tail of a squirrel along the sides and at the end. As the cells
of the radial system do not penetrate the spaces which intervene between the
tentacular sockets and the interambulacral bands, which the plane of the former
bisects, the cells of the lateral system are here left free to act by themselves.

The motory system of the tentacles is so intimately interwoven with their whole
structure, that it is most convenient to describe it when presenting the anatomy
of these organs in detail; but we will make one or two remarks in this connection
in regard to the relations which their different walls bear to those of the body.
Although the outer wall (7%. 15 8 6’ 8%, and p. 255 Fig. 87 8” 6”) of the tenta-
cular base is composed of much smaller and differently shaped cells from those of
the sockets (j' y’ y*), yet we must believe that the walls of the two are essentially
one continuous layer; and, referring to what we have previously ventured to sug-
gest, that these sockets are depressions in the interambulacral layer, and also that
the whole tentacular apparatus is a prolongation of two opposite points of the
peripheric system, endowed with the faculty of more extensive motion than the basis
from which it arises. Any one familiar with the very simple tentacular apparatus
of Bolina, Chiaja, LeSueuria, and Euramphea, will readily comprehend that whilst in
them the tentacular sockets are shallow depressions from which the peripheric
prolongations arise, in Pleurobrachia these sockets differ only in degree by being
more deeply plunged into the mass of the body. The inner wall (f¥%y. 15 g? and
Fig. 87 7 7’) of the tentacle (/) and its base (y 7), although very thick at the
latter point, is, to all appearance, identical in cellular structure and continuous
with the thin wall (fig. 87 7” 7” e) of the chymiferous tubes, which we have
next to describe. Throughout the whole extent of the digestive cavity and chy-
miferous system, the wall is composed of extremely elongated cells, which, trending

224 CTENOPHOR®. Parr IL

lengthwise with the tubes, give them a finely striated appearance, as if they were
composed of filaments laid parallel to each other. In the wall of the bulbous
forks (Fig. 14 f* f*) of the axial funnel, these cells trend lengthwise, like meridians
of longitude, converging at the two obliquely opposite apertures, the anterior and
the posterior coeliac openings (f ¢). The only place where this wall varies from
one uniform very thin layer is where it constitutes at the same time the inner
wall (#iy. 87 y 7") of the tentacular base; and there it is of variable thickness,
as has already been described.

The vertical rows of locomotive flappers are entirely superficial. Each row
consists of a great number of isolated, transverse, comb-like bodies, placed one
above the other, and movable, either isolatedly or in regular succession or simul-
taneously. Each comb consists of a large number of ribband-like bristles, slightly
arched upward and downward, of which the middle ones are the longest, tapering
gradually sideways; so that the combs are, properly speaking, crescent-shaped, with
a straight base, the teeth or frmges of which are movable in quick vibrations up
and down, independently in each comb, and even independently to some degree
in each portion of the same comb, as the middle fringes may be seen to move
when the lateral are motionless, and the reverse. But, generally, all the fringes
of one comb act simultaneously; but the motion in all the many combs of one
row is successive, so that, when the combs are very active, they seem like waves
moving up and down in rapid succession along each vertical row, or like the
waving spikes in a corn-field agitated by the wind. Again, the undulations of the
different rows are independent, — sometimes all the rows playing at the same time,
at other times parts of the rows, or parts of each row, or parts of some rows,
playing independently. Pleurobrachia moving with the mouth forward, the pre-
vailing direction of the locomotive flappers is toward the abactinal pole, while in
Bolina and Idyia it is toward the actinal pole.

The number of teeth or fringes in one of the larger combs may be about
fifty; but they are not equally numerous through all the combs in one _ vertical
row. The combs in the upper parts and in the lower parts of each row nearer
the mouth and the area opposite are gradually shorter and shorter, and contain
fewer and shorter fringes, the largest bemg about the middle of the vertical height.
They terminate more abruptly and at a greater distance from the centre on the
actinal than on the abactinal side, where they are naturally prolonged toward the
central eye-speck.

The movements of these flappers seem at first to be identical with those of
vibratile cilia; and one might be tempted to suppose that they are formed by a
row of compressed vibratile cells, arranged in such a manner as to bring their

cilia in one row, and the cells themselves in such superposition above each other

Cuap. HI. GENUS PLEUROBRACHIA. 925

as to form vertical series. But the cilia or fringes are far larger than any
vibratile cilia ever described, and their motion shows distinctly that they are under
the voluntary control of the animal; for their movements are neither incessant nor
constantly equal. They are at times accelerated or retarded, or entirely stopped, and
resumed at shorter or longer intervals; so that the evidence of their voluntary
movement is as full as can be, and, indeed, the structure which determines the
movements is the same as in all cases of voluntary motion.

Fully to understand the character of the vertical rows of locomotive flappers, it
should be borne in mind that they are connected for their whole length with
vascular tubes following the same course, and which arise from the central
chymiferous cavity. This intimate connection leads naturally to the supposition,
that, besides their functions as locomotive organs, the vertical rows of flappers are
in some way connected with respiratory functions, and that there is between these
two systems the same natural physiological connection which exists in Echinoderms
between the inner branchiz and the ambulacral tubes, or in Worms between the
respiratory vesicles and the locomotive bristles.

The circulation of fluids, and the respiratory movements connected with this
circulation, are, almost throughout the animal kingdom, in direct relation to loco-
motion, even in the higher animals. Among Polypi, the dilatations and con-
tractions of the body renew constantly the water which fills their cavity, and
provide them with a fresh supply of aerated water. The same is the case among
Meduse. For, even where there is no distinct, individualized system of respiratory
organs, it is obvious that a constant renewal of the surrounding medium, by means
of which oxygenation takes place, is an essential condition for the maintenance of
life; and where there are no special organs adapted to this purpose, the main
movements of the body supply the deficiency. The water-pores in Echinoderms,
through which their main cavity is constantly filled with fresh sea-water, undoubtedly
perform a similar office. Again, among Mollusca, respiration and locomotion are
still more intimately connected; but in a manner which differs decidedly from what
we observe in higher animals. For here, by the dilatation and contraction of the
respiratory cavities, and the circulation of the blood through the respiratory organs,
the body is amply supplied. But, unless Acephala open their valves, unless they
expand and contract alternately the whole body, the supply of fresh aerated water
must be much less; and I doubt whether oysters and clams could be kept alive if
their valves were shut constantly by pressure, and muscular motion, the contraction
and expansion of the large bundles which preside chiefly over locomotion, were
prevented from coming into play in aid of the vibratory cilia of the mantle and
gills. The manner in which the respiratory cavity is shut in so many Gasteropods,
unless the fleshy parts are fully expanded, shows plainly that here again there

VOL. III. 29

226 CTENOPHORA. Parr II.

is an intimate connection between respiratory movements and locomotion. In
Cephalopoda this is still plainer; for, from the form of the respiratory cavities, and
from the disposition of the sacs in which the gills are placed, we can easily
infer that the contractions and dilatations of these sacs, by which the water
is renewed, must afford a material mechanical assistance in the progress of loco-
motion. Again, throughout the type of Articulata this connection is most intimate,
the respiratory organs being directly connected with the locomotive appendages, and
forming, indeed, part of the various kinds of oars, fins, legs, and chewing appendages,
by which the principal motions of the body are sustained. Not a joint can be
moved here, without influencing respiration; and, again, the expansion and con-
traction of the respiratory cavities, the filling of the respiratory vesicles or the
large circulatory sacs connected with the gills or fins, and the introduction of
air into the tracheal tubes, must, in their turn, influence locomotion. It is a
subject worthy of the attention of physiologists, to trace more minutely this
double connection throughout the animal kingdom. Perhaps the type of Articu-
lata is best adapted to make a beginning in these investigations. For among
them, in the Crustacea for instance, the chewing of the food itself is directly
connected with the process of respiration. The motion of the jaws aids in forming
and maintaining a regular current of water along the gills through the respiratory
cavities; and, even when not otherwise employed, the jaws are kept im motion in
some degree to assist respiration. And it can hardly be doubted, that the process
of respiration also materially aids the Insects in their flight, and that the degree
of expansion or contraction of the respiratory cavities is very different in the state
of repose or during flight. While watching grasshoppers I have often been struck
with the wide expansion of their abdomen at the moment of starting, and with
the collapsed condition of the whole body soon after they have alighted, which
is even so great as to prevent their rising again immediately when chased.
Again, among Vertebrata we find in Fishes that the respiratory movements —
the lifting and shutting of the operculum, the filling and emptying of the branchial
cavity —aid the fish in slowly progressing; so much so, that, when resting upon
the bottom of a glass jar, apparently immovable, these animals are at times sud-
denly propelled forward under the action of a powerful occasional contraction of
the branchial cavity, even though the ordinary locomotive organs—the tail and fins
—remain absolutely quiet. How close a connection exists between locomotion and
respiration in the Ichthyoid Batrachians, I have often had occasion to witness in
a Proteus kept in confinement, in which the gills grew gradually paler and paler
when the animal was absolutely motionless, but would instantly be filled with a large
quantity of blood and appear intensely red after some violent motion. It might
be objected, that this is a mere influence of locomotion upon circulation; but if

Cuap. TL. GENUS PLEUROBRACHIA. 997

there were not this natural disposition in all locomotion to influence the process
of respiration more than any other system, why should not the blood, when such
powerful motions take place, be accumulated in any other part of the body, —
for instance, in the tail, which is the very cause of the motion,—rather than in
the gills? In Birds, the extensive development of the lungs, and the prolongation
of air sacs into the abdominal cavity, the wings, and the sternum, in those most
remarkable for their power of flight, plaily indicate again the most strict con-
nection between locomotion and respiration, though the nature of this connection
is perhaps different from that observed in the lower classes. Nevertheless, it exists
even in these, and can be traced to a very remarkable extent. We cannot fail
to trace similar relations among Mammalia also, though here the influence between
the two functions is not so direct. However, it must be acknowledged that it
is important enough, when we consider how the aquatic types have to accommo-
date all their movements to the wants of the system for atmospheric air, and
remain constantly within reach of the surface, in order to be able to return to
it in a short time. How much the breathing is affected by violent movements
is so well known to every one, that the existence of accessory muscles of respi-
ration in Mammalia, the antagonism between the pectoral and abdominal muscles
and the diaphragm, and the use of belts by athletes in running, leaping, or wrest-
ling, need only to be mentioned as evidence of this mutual relation. Of course,
in animals in which all the functions have reached a great degree of independence,
they are no longer subservient to each other to such a degree as they are in
the lower types; but even the unpleasant influence which excessive exercise of
the locomotive powers has upon respiration in the higher animals, shows the inti-
mate relation which prevails in the plan of organization.

It has already been mentioned, that there is a wide chymiferous cavity in the
centre of the body of this animal, trending in the vertical direction of the digestive
cavity; but the natural relations of these parts are so difficult to appreciate, the
ramifications of the chymiferous tubes so complicated and nevertheless so regular,
and again so movable in their constant contractions and dilatations, that, with all the
assistance of numerous drawings as given in my paper in the Memoirs of the
American Academy, I hardly expect to be able to give a correct idea of this
apparatus, unless the reader is willing to consider attentively every point of the
following description by itself, and to keep at the same time constantly in mind
the relative connection of all parts, and their bearing upon the general appearance
of the body.

In the first place, let it be remembered that the central chymiferous cavity
and its main trunks undergo constant changes as to their size and outlines, ac-

cording to their temporary state of contraction and dilatation, and that both halves

298 CTENOPHORA. Parr II.

of the system of tubes which arise from the main cavity and branch into the
right and left halves of the body alternate constantly in their contractions, — so
much so that the one may be in the state of fullest expansion when the other
is in the most complete state of contraction; and after a while the reverse will
take place, when the last will be fully expanded and the first fully contracted.
But in these alternate movements there is a moment when both halves are in
a state of apparent equilibrium, though one be in the process of emptying and
the other in the process of filling; while at the moment an equal amount of liquid
has been pressed from that half which is contracting into that half which is filling,
the symmetry is most complete. These alternate contractions are nearly as regular
as the movements of diastole and systole of the heart, and take place by a constant
balancing of the fluid one way and the other. The difficulty of watching this
singular circulation arises chiefly from the necessity of keepimg the living animal in
one and the same position, as the slightest obliquity will interfere with the perspective,
so as to make it altogether impossible to follow the natural movements; and unless
the parts are placed in a strictly identical position, those which are in pairs will
create confusion, as they may come into various positions, presenting apparently a
close connection with parts to which they are not at all related. Again, the peripheric
tubes extending in vertical arches over the surface, cover so easily the origin of
the different trunks arising from the main cavity, that it is indeed very perplexing
to trace them all in their true connection. Add to these difficulties the cireum-
stance, that the arrangement of parts, owing to the bilateral symmetry of the body,
appears entirely different when viewed in profile, from the side, or in front, and
it will be plain, that, unless the observer keep in mind several distinct images of
the various connections of all these stems and their ramifications, in a front view
and in a lateral view, combining them in thought with the rapidity with which
such an animal may revolve upon itself, it will be impossible for him to trace
for a moment its structure while alive; and he will only have constantly before
his eyes the tantalizing image of a piece of machinery, apparently very compli-
cated, the structure of which he has to decipher while it is moving, but moving
almost too fast to allow him to seize the connection of the different parts as they
pass along, and which is not only deranged, but destroyed, the moment it is stopped.
It was under such circumstances that I undertook to study the circulation of these
animals; and though I succeeded in injecting indigo into their main cavity, and
in having it circulate for hours at a time within the body of the same animal
before it died, and though I was satisfied that not a particle of the colored liquid
had passed into any part of the body into which the liquid before it was colored
had not naturally free access, and though it was thus plain to me, that, even after
being colored, the circulating fluid continued its normal course, I must say that

Cuar. TIL. GENUS PLEUROBRACHIA. 999

I never investigated a more difficult subject, never had to devote so much time
to the same point, and never taxed my patience to such an extent as during
these investigations. I insist upon these details, and state them at full length,
because I know that I have now cleared up this subject, and may perhaps induce
some other student to go through the long description I am about to give of it,
since he may expect to have the matter settled for him. Let us proceed in this
description as we should with a minute description of the ramifications of the
bloodvessels of some highly organized animal. The difference which exists between
the digestive cavity and the main cavity of the chymiferous system will first engage
our attention.

In a front view (Pl I. 2%. 23), when the two tentacles appear right and
left, and the plane which passes through the longitudinal fissure of the mouth
divides the body into halves, we have before us, on our right, one of those halves
of the body, which alternates in its contractions with the other half on the left.
It is according to this diameter that the antagonism between the two sides is
introduced. Seen in this view, the digestive cavity appears throughout like a nar-
row fissure (bc); but as it is much wider in another direction, its outline, as seen
in Fig. 22, is very broad. The fact is, this cavity is a flattened sac, flat as
long as it is not full of food, and the two surfaces of the flattened bag are pressed
upon each other: so that when seen in profile, that is to say, facing the diacceliac
diameter of the body, as in Fig. 23, it appears like a mere double skin, or a slit
lined with a membrane; but when seen from its broadside, that is to say, facing
the right or left side of the body, as, in /%g. 22, it appears like a wide sae.
During the process of digestion, when filled with food, it is swollen into a more
rounded sac or cylinder. The abactinal extremity of this sac opens into the main
cavity of the chymiferous system, terminating there in an oblong fissure, which, at the
will of the animal, can be shut or opened; so that, like the stomach of Actinia,
the digestive cavity of Pleurobrachia communicates with the chymiferous cavity, or
may be shut by itself. The difference between the two types, however, consists
in the limitation of the cavity of the body, which is circumscribed within the centre
of the animal in Pleurobrachia, and sends off large trunks and tubes, branching
diversely into its mass and along its surface; while in Actinia the whole body is
hollow, and the stomach empties into that one large cavity.

The central chymiferous cavity has two main stems, one extending into the
right, and the other into the left, half of the animal (/¥%y. 25 ee). It would seem,
from Fig. 23, as if the digestive sac (6 ¢) were hanging loosely into the chymiferous
cavity: this is, however, not the case, for the spaces (77) which communicate with
the main chymiferous cavity right and left of the digestive sac do not form a
continuous cavity encircling the whole digestive sac, but are only two simple but

250 CTENOPHORA. Part II.

rather wide tubes arising from the main trunks of the central chymiferous cavity,
and following the middle of the lateral surface of the compressed digestive sac in
a vertical course up to the margin of the mouth, as Fy. 21 rr shows. Toward
the abactinal pole, however, the main cavity extends in the form of a funnel, and
terminates with two holes near the centre of the circumscribed area. This funnel
lies vertically in the centre of the animal, and extends therefore in its central axis.
Tt assumes nearly the same appearance in whatever position it is seen, excepting
only its abactinal termination, which is furcate when seen from the side, as in
Fig. 22 f* f’, and simple when seen in front, as in Fig. 23 f'. This part of the
cavity with its main lateral trunks being, as it were, the centre of the circulation,
we may view it as a hollow axis branching right and left, and extending along the
centre in two parallel forks, one on each side of the digestive cavity, as far as the
mouth; so that, when examined from the side, only one of the two actinal forks is
visible behind the tentacular socket, while the short abactinal forks, which are at
right angles with the former, are both distinctly seen, and vice versd. The main
lateral stems and their ramifications present their broad side in the last position,
and appear foreshortened in the other.

The two main lateral trunks (/’%. 25 ee) branch off at right angles from the
central cavity, and extend sideways and for some distance horizontally, with a slight
inclination towards the actinal pole, changing however their position to some extent,
according to the state of contraction or distension of the digestive cavity. Six
branches, or rather three, if we take their closer connection into account, arise on
each side from these main trunks, besides those which are close to the digestive
cavity. The fact is, that after giving off the coeliac tubes and before branching
again, the two main trunks form, at their extremity, sideways, a sort of dilatation,
from which arise two lateral branches extending horizontally backward and forward,
and two others close together which extend in a vertical direction. The branches
extending horizontally forward and backward give out, not far from their origin,
two other branches, which also extend horizontally, but bend sideways, nearly at
right angles with the former. All these branches origimate so near the point where
they communicate with the primitive main trunks, that they might, with almost
equal propriety, be considered as arising directly from it. The termination of the
main trunk may, indeed, contract or dilate in such a manner as to appear alternately
divided into three, four, five, or six branches. In its most contracted state, for
instance, when seen from the actinal pole, as in /%y. 21, there are distinctly six
branches visible, arising from the main horizontal trunk, the two vertical ones
appearing like very short tubes, because their whole length is foreshortened upon
their origin, though they are actually as long as the others, while the four horizontal

branches are seen for their whole extent,—two and two however, united by their

Cuap. II. GENUS PLEUROBRACHIA. 931

base; so that it may with equal propriety be said, that, on the whole, there are only
four tubes, the two horizontal ones branching soon again into two. In the dilated
state of the main trunk, but when the branches arising from it are in a state of
contraction, these all seem to originate from one common cavity, and the four
horizontal tubes appear independent of each other, while the two vertical ones are
brought so close together as to look like one,—making altogether five branches.
In another state of contraction, the two vertical tubes may seem united, and the
two pairs of horizontal ones also, when there appear to be only three branches
to the main trunk. Unless the dilatations and contractions of these curious rami-
fications of the stems have been watched for a long time, these differences may
remain unnoticed; but when fully understood, there is no contradiction im the
apparently conflicting statements, that there seem at times to be three, at times
four, at times five, and at times six branches, to the main trunk. I should add,
that when seen from the actinal or from the abactinal pole, unless the body is
somewhat inclined, the vertical tubes altogether escape attention, and that the best
position to ascertain their relative connection is an external side view, as in Mg.
15. In Fig. 22, which represents the whole system in the same position as My. 15,
the view of the horizontal main trunk and its branches is somewhat confused, from
the circumstance that it is projected upon the vertical central cavity and the actinal
prolongation of that cavity upward and downward; but in My. 15 we have only
the peripheric branches arising from the main trunk, that is to say, the portion
seen to the left in Mg. 23, while in Fig. 22 we have, besides that half, the

central axis also, as likewise in FY. 25.

I have described these peripheric branches as horizontal,—and so they appear
when seen from above or from below; but in a vertical position they are seen
to be somewhat deviating from a horizontal plane, the anterior and _ posterior
branches reaching the periphery at a greater distance from the abactinal pole than
the lateral branches, and the vertical branches inclining slightly outward. These
different branches have by no means the same functions, and are not connected
with the same apparatus; the vertical branches, which I have called interambulacral
or tentacular tubes, extending to the disk from which the tentacles are protruded,
while the horizontal branches communicate with vertical tubes,—the ambulacral
tubes, — which follow the inner surface of the vertical rows of locomotive flappers
for their whole extent.

As there are on each side four such horizontal branches and four vertical rows
of locomotive flappers, there are also, in the whole, eight vertical superficial chy-
miferous tubes, widest in the middle, and tapering upward and downward, which
are in direct communication with the central chymiferous cavity through the four
horizontal tubes and the two main trunks, from which they themselves arise. The

939 CTENOPHORA. Parr II.

actinal ends of the superficial vertical tubes, which I may call the ambulacral tubes,
terminate as blind canals; at least, I have been unable to trace a direct com-
munication between any of them and the vertical tubes which follow the sides of
the digestive cavity, though such a communication is seen in the genus Bolina,
as I shall mention hereafter. The fluid circulated upward through these tubes can
be distinctly seen to retrace its way downward; so that, in the ascending branch
of the ambulacral tubes, the fluid injected through its horizontal branch is moved
up and down alternately. This is also the case with the lower branch of the
same vertical tubes, and, though the abactinal end tapers more gradually, it
terminates also in blind canals; and I was mistaken in formerly supposing them
to open again into the main cavity. The movement in reality takes place im
the following manner. Each of the eight horizontal tubes fills its vertical ambu-
lacral branches, the fluid flowing, at the junction of the vertical tube with the
horizontal stem, in opposite directions, upward and downward; then, flowing back
through the same channels durmg the contraction of the mass of one side of the
body, it is pressed into the horizontal tube, and returns to the centre of the move-
ment to pass into the opposite side of the body. There can be no doubt, that
the liquid moves decidedly to and fro in the ambulacral tubes and returns to the
central cavity through the horizontal tubes, and that the dilatation of the four tubes
of one side alternates with the dilatation of the four tubes of the opposite side ;
but in each vertical ambulacral tube the motion of the fluid is an undulatory one,
owing to the alternate dilatation and contraction of the tube itself.

The movement of the fluid in these tubes can be traced very satisfactorily
when following the course of the minute granules of colored matter suspended in
the water after injection; but even in fresh uninjected specimens, the circulation
can be tolerably well traced by watching the small particles of undigested food
suspended in the mixture of water and chyme which is circulated throughout this
system. As in Polypi, the whole mass of digested food, comminuted and reduced
to a very uniform state, but in which the parts capable of being assimilated are
still mixed with parts of the refuse matter, is emptied bodily into the chymiferous
cavity, and, with a certain quantity of water introduced in the same way into
this cavity through the mouth, kept in a constant, regular, undulatory circulation
throughout life. But as there is a double outlet through which this system ean
discharge its contents on the side of the circumscribed area, the circulation is more
or less active, all the tubes more or less turgescent, and the whole cavity more
or less dilated, as the quantity of fluid in circulation is greater or less; which, to
some degree, changes the relative position of the tubes and of the central cavity.
When very full, the wider central space is considerably raised; while in a state

of relaxation it sinks lower down, nearer the abactinal extremity of the body. As

Cuapr. III. GENUS PLEUROBRACHIA.

bo
ao)
oo

long as the circulatory system is relaxed, the ambulacral tubes are very much
contracted, and their diameter is much less than under other circumstances, and
by no means equals the width of the vertical rows of locomotive flappers; but
when turgescent and full, they swell beyond their width. The foree which acts
in propelling the liquid through the system is not the same throughout. The
alternate contractions of the two sides result from the regularly alternating muscular
contractions of the two sides of the body; but the main cavity in its central part
is entirely lined with vibratory cilia, so that even when the body is perfectly at
rest, the fluid is maintained in a constant rotatory motion through their agency.
I have repeatedly and distinctly seen these cilia playing round the abactinal opening
of the digestive cavity, and upon the walls of the central chymiferous cavity, as
well as upon the walls of its main horizontal stems, upon the walls of the coeliac
tubes, and upon the walls of the two forks of the funnel. I have been unable,
however, to discover similar cilia within the secondary horizontal tubes and the
vertical ambulacral tubes; though recently I have noticed them in the vertical
tubes of the tentacular apparatus, where I had failed to discover them before.
However, the contractions of the spherosome are so powerful that the vibratory
cilia can do but little, of themselves, to keep the fluid in motion in some of
these tubes. I should also add, that even the walls of the central chymiferous
cavity, where they are most distinctly lined with vibratory cilia, are nevertheless
distinctly contractile; and that the capacity of the cavity is not only increased and
reduced in a passive manner by the accumulation of fluid or its expulsion, but
also actively by the contraction and dilatation of the walls themselves. How the
contents of this circular system are diffused into the substance of the body for
nourishment is not very plain, as there are no capillaries, but everywhere broad
tubes. From the cellular structure of the whole mass, however, we may infer
that assimilation takes place by a process of endosmosis and exosmosis. If this
view is correct, we should consider the two coeliac tubes upon the middle of the
main walls of the digestive cavity as the nourishing vessels of the stomach; the two
horizontal trunks as two respiratory vessels, branching into eight branchial vessels,
which are the main trunks of the eight ambulacral vessels; and the vertical funnel
as a vascular cloaca, discharging its contents through two distinct apertures, the
coeliac apertures, on the sides of the circumscribed area near the abactinal centre.

The vertical tubes of the tentacular apparatus seem to have a peculiar function,
and to be directly connected with the movements of the tentacles, and these move-
ments again to be connected with the alternate contraction of the two halves of
the body, as there are no parts which undergo so extensive changes in their size,
and in their state of contraction and dilatation, as these sacs. But their structure

is so complicated as to require a minute description. The two tentacles with their
VOL. Il, 30

254 CTENOPHORZ. Part II.

elongated cavity, and the vertical tubes extending along the base of the tentacular
apparatus, constitute, Indeed, most complicated pieces of machinery, in which hydro-
static power, elastic levers, and the contractions of the motory cells, give rise to
highly complicated combinations and most. diversified phenomena.

In the first place, the cavity itself from which each of the two tentacles issues
(Pl. I". Fig. 1579", Figs. 22 and 237) is a wide, elongated, fusiform sac, the rounded
extremity of which is turned towards the actinal pole and bent obliquely sideways,
so that its flat base is turned towards the vertical axis, and its open extremity
towards the abactinal pole and sideways. In this cavity, to which the surrounding
water has free access through the opening j', the tentacle with its complicated
base is attached by a broad surface to the inner side of the sac. And though
the central chymiferous cavity communicates freely, through the interambulacral
tubes, with the base of the tentacular apparatus, there is no free passage from
one of the cavities into the other. The fluid which is injected into the tentacular
tubes runs back through the same channels into the main trunk, and the water
which fills the cavity of the tentacular apparatus empties through the same opening
by which it is introduced. In a state of dilatation, water penetrates from without
into the tentacular sac, and diluted chyme is injected from within into the tentacular
tubes; and in a state of contraction, the chymiferous tubes are emptied at the
same time that the water is pressed out. During these alternate contractions and
dilatations, the tentacle itself may be coiled up in the cavity or drawn out at
full length, though in the most dilated state the threads generally hang out. There
seems to be also an antagonism, in a middle state of dilatation, between the filling
of the tentacular chymiferous tubes and the protrusion of the tentacles themselves.
But I was mistaken formerly, when supposing that the chymiferous tubes penetrate

into the basal dilatation of the tentacles :1

they only extend along their basal disk.
The fillmg of these tubes may, however, cause the whole tentacular apparatus to
protrude into the sac to which it is attached.

Nearly two thirds of the length and breadth of the proximate side of the
actinal or closed end (fvy. 87 7° to 7°) of the tentacular socket is occupied by an
oblong disk (Pl. Il® Fig. 15 and Fy. 87 Bp’ BY B'S 77/7" 7”), from the mid-length
of which the tentacle (g 7’) arises. The distal side (/¥%. 15 3) of the disk, or
that which faces toward the periphery of the body, is convex, with a shallow
furrow (Ag. 15 7), extending from the base (g) of the tentacle to the actinal end (7”)

of the disk; and the proximate side (F¥y. 87 7”), or that which faces toward the axis

of the body, is a plane, immediately beneath whose surface and next to the edge

1 When comparing the plates of my paper in should be made for this mistake, which is especially

the Memoirs of the American Academy, allowance noticeable in J%gs. 1 and 2 of PI. IV.

Cuap. III. GENUS PLEUROBRACHIA. 235

(Fig. 15 8’), two chymiferous tubes (a @ a” «@”) run parallel; leaving between them,
Fig. 87.

along the median line, a thick: ridge (Fig. 15 7), which is
nearly as broad as the diameter of the tubes. The relations
of these parts, as seen in profile, may be better understood
by referring to the annexed wood-cut (Fig..87) and : the ac-
companying explanation, at the same time comparing it with
The thick-
ness, of the disk as a whole is equal’ to about two thirds

Pl. Il". 4%. 15, which is lettered correspondingly.

of the breadth, but it thins out at the actinal end (y”) in
just about the same proportion that it. narrows; whereas at

a1
d

the other extremity ($”), where it is slightly narrowed, it is
thickest, and also terminates. abruptly: directly - opposite — the
junction of the main chymiferous trunk (7) with the two par-
allel tubes (@ @ @’) just mentioned. It seems appropriate
to compare the shape and proportions of this. disk ‘to a
flat-soled, broad shoe-last. The structural details of this organ

appear very simple, when once fully - understood ; but, owing

to the fact that it is situated at the bottom of a deep socket

Longitudinal section of the
tentacular apparatus of PLEURO-

Only imagine the socket »nacnia rnopopacryna, 4g.

(jj 7°) and as if plunged into the midst of other organs,
it seems to be quite complicated.
to be removed or reverted, as oftentimes does happen in a great measure, and
the whole apparatus will. appear like a peripheric ridge, which, at one point, is
drawn. out into a slender thread, the tentacle. The base (Fig. 15 gg'g") of the
tentacle has the form of a high, narrow ridge or keel (4. 15 9' 9? and Fig. 87 7’),
more or less plicated or distorted, according to whether the apparatus is extended or
retracted; but we have never seen it projecting beyond the aperture (j') of the
socket. At the basal end (y) of the keel it is as broad as the disk from which it

arises, but it suddenly narrows to a uniform thickness, which it retains to the other

1 Fig. 87 represents a longitudinal section of
Fig. 15, Pl. II*, one of the chymiferous tubes (a «’)
being in the distance; +e wall of the main horizontal
chymiferous trunk; e! opposite side to e where it
passes into the inner wall (7") of the disc; g the
base of the tentacle; 7 tentacular socket; 7? aper-
ture of 7; j? apex of 7 near to where it passes
into the outer wall (6”) of the disc; j* the inner
or proximal side of 7 where its wall passes into
the outer layer (3’”) of the dise; & the tentacle ;

q point of junction of e and «@ «@; the dotted lines

represent the outlines of the channel which diverges,
at right angles, from e (see g! Mig. 15, Pl. Ta) ;
a the apex of the chymiferous tube; «’ entrance
to a; a” base of «; B” outer wall of the disk;
6” same as 6” at the thickest part of the disk;

y the inner layer of the disk; y’ inner layer of

‘

g3 7" the thin proximal wall of @ where it passes

ut wie

into 7; 7” same as 7” further along; 7” the

thickest part of the inner layer of the disk. De-
signed from nature by H. J. Clark, to correct the
Magnified.

9

mistake alluded to p. 254, note.

bo
wo
oo

CTENOPHORE. Part II.

end, where it merges into the cylindrical part of the tentacle. As the tentacular
fringes (Fig. 15%") are not to be found upon this ridge, but just at its distal termi-
nation, and onward, —and, if we mistake not, the lasso-cells are absent,—it may be
proper to consider it as essentially a part of the disk, simply subservient to the
movements of the prehensile organ, which is prolonged from it.

There are two distinct walls or layers, which constitute the body of the disk,
and which are continued, in the same relation, into the tentacle; but the greater
proportion of this apparatus is composed of the inner layer (Fig. 87 y 7 7” 7”), the
outer one (#¥g. 15 and Fig. 87 p’ 8” 8”) bemg comparatively a very thin stratum.
The thinnest part of the inner layer may be found about the proximate side (7’”)
of the two parallel chymiferous tubes (@ to @””), which penetrate to the apex (7”)
of the disk, where it occupies one half of their circumference, as a mere film
(7) of long, slender cells, identical with those which we have already pointed out
(pp. 225, 224) as forming the walls of the whole chymiferous system. On the solid
side (Hy. 87 7) of these tubes and between them (/%y. 157), this layer more or
less suddenly becomes very thick; at the distal side of the apex (7”) of the tubes
the transition is comparatively gradual, as one might very naturally infer from the
form of the disk; but at all other points the passage, from the filmy wall to the
highly imerassated core of the disk, is very abrupt, especially at the abactinal end
(7), where it projects like a hook or nose. In the tentacles (/) again it loses
its bulky proportions, whilst the outer layer gains the ascendency (within the
main stem of this organ the decrease is not so great as in the fringes); in the
former the inner layer forms a solid axis, occupying about two thirds of the
diameter of the tentacle, whereas in the latter (4%. 13 d, Fig. 18 d) it forms
but one third of the whole thickness. Along the median line of this layer, in
the fringes, there is a slender string (J/g. 15 e, Fiy. 18 e) of matter which is
much more transparent than the rest, and has the appearance of a canal; but no
distinct cavity could be detected. The course of the longer axes of the cells
constituting this layer is very simple. Within the disk it is lengthwise (7%. 15 «),
and in a general way parallel to the surface of this body; and so, too, in’ the
tentacle and its fringes (My. 15 d). At the origin of the fringes (/%. 15 2*)
the cells of the main body (/) of the tentacle bend nearly at right angles upon
themselves, and enter at once into the former without any break; they are as
directly continuous from the one to the other as from the disk into the tentacle.
When the tentacle is contracted it is transversely wrinkled, and in this condition
the cells which diverge at right angles into the fringes appear to traverse the
whole diameter of the main layer as if they were distinct bands, originating inde-
pendently of the cells of the latter; and this deceptive appearance is all the more

heightened if a portion of the tentacle be cut away and laid out on a slip of

Cuap. UI. GENUS PLEUROBRACHIA. 937

glass, when the chances are frequent that the fringes will become folded directly
across the main stem.

The outer wall (4%. 15 6’ 6” 6’, p. 218) of the disk and the transversely striate
wall of the socket (jy y’ y*) are directly continuous the one with the other, and
together constitute the lining of the cavity which they embrace. The cells (f £’)
of the disk wall are as broad as they are long, simulating irregularly polygonal
prisms, and the inner ends are flattened against the subjacent layer, whilst the
outer free ends are rounded. In size they are very large, being on the average
from one fifth to one fourth as long as the largest cells (7%. 24) of the cellulo-
motor system. At the base (vy) of the narrow ridge (gy g'g’) they decrease in
size very rapidly, and continue to do so until we come to the base of the tentacle
proper, at which point we find them diminished in diameter by nearly two thirds ;
but from this place to the end of the stem and its fringes, the diminution is very
gradual, until at the tips (#%y. 15 ¢) of the latter they measure not more than
one fourth the diameter of those in the disk. The contents of these cells are
perfectly homogeneous, nor have we been able to see any mesoblast. During the
contraction of the frmges the surface is ribbed lengthwise, owing to the fact that
the outer wall folds upon itself (#%y. 18 ¢ c'), and the inner one (d d') projects
more or less into the duplicatures. By taking advantage of the doubling of a
frmge upon itself, we may get a very satisfactory sectional view (f%y. 18) of these
walls when in this plicated condition.

The outermost, or epithelial layer (7%. 15 a6 and Fig. 18 0), of the tentacular
apparatus, is described below, and therefore need only be: referred to in this con-
nection. Although the wall of the socket (jj? y*) is a very distinct layer, yet
it does not hang loosely, apart from the mass of cells which surround it, but
it is more like a ling to a cavity which has been excavated in the cellulo-
motor system. The transition from the comparatively thick outer wall of the disk
(Fig. 15 3) to the thin wall which constitutes the cellulo-motor system of the
sockets is very abrupt; but yet there is not so sudden a change in the nature
of the cellular constituents as would appear at first sight. The only appreciable
difference is in the shape of the two kinds of cells, the form of the discal cells
being adapted to a different purpose from those of the sockets.

All the extensible parts of the tentacles, as well as their lateral fringes, are
covered by a layer of thick epithelial cells, every one of which is a dasso-cell}
When the tentacle is fully prolonged, these cells scarcely touch each other, and

then they display a perfectly rounded contour, excepting a very narrow portion,

1 The following investigation of the lasso-cells and colleague, Professor H. J. Clark, who discovered
t=} to) tae ’

of Pleurobrachia is entirely the work of my friend their peculiar structure last year.

238 CTENOPHORE.

‘Part IT.

which is flattened at the base of attachment In this condition it is easy to
observe that each cell is covered exteriorly by a single layer of exceedingly minute
granular bodies (Pl. Il* Figs. 7, 9, and 12 /).

cells become mutually compressed; at first but slightly (Fys.. 16 and:17), but

As the tentacle contracts, the lasso-

finally so as to be sharply polygonal (/%y. 15 a). The granular coating is so dense
that the coiled thread within is not so conspicuous as in the lasso-cells of the
Discophore. Even with a magnifying power of five hundred diameters, it is very
difficult to detect the thread whilst the cell remains attached to the tentacle,
and then it is seen foreshortened; for a profile view is out of the question, except
when the tentacle is stretched to the utmost, and then, owing to its activity, only
a mere glimpse can be obtained. The only convenient method of observing them
is by cutting off one of the fringes, when with unusual readiness the lasso-cells
drop away from their attachment. If now they are placed upon a glass slide
they may be rolled about in every direction, and thus exposed in any desired
position. No satisfactory elucidation of the nature of these cells can be obtained

by using objectives of ordinary definitions, for the granular coating is confounded

3

with every thing else ;

1 Tt is not possible to see these cells in this
condition unless the objective of the microscope is
plunged without ceremony into the water of the
deep jar in which these animals must be kept.
By gradually cooling the water until it becomes
icy cold, a small quantity will serve to keep Me-
dus in the full vigor of life, and then they may be
observed without mutilation. | Unless the brass-work
be varnished, the chemical reaction of the sea-
water invariably disturbs the animal, and causes it
to contract very closely. With a little care, a power
of from three hundred and fifty to five hundred
diameters may be used.

* Gegenbaur, who was the first to publish any
thing about these cells (Wiegmann’s Archiv, March,
1856, p. 179, Taf. VIII. Fig. 12 ¢ «’), gives a very
meagre account of them, and shows that he does
not know their typical difference from the lasso-
cells of the discoid Meduse and all Polypi. His
brief notice of the lasso-cells of what he considers
a new species of Cydippe—but which is probably
a new genus—reads thus: “ Both the cirrhi and
the margin of the appendage are covered by round

nettling cells, 0,005’” in diameter (by mistake for

but, in order to plunge into the midst of the contents

0,005”, no doubt), which inclose a smooth, spiral
thread. If the thread extrudes, it shows the pe-
culiarity of not straightening out at once, as do
all other lasso-threads observed by me, but remains
for some time in a long drawn out spiral. The
end remaining, during protrusion, within the vesicle,
stands in connection with a number of round gran-
ules, which are grouped in a blackberry-like form.”
Later in the same year, Dr. T. Strethell Wright
(Edinburgh New Phil. Mag. October, 1856) also
published a brief notice of these cells, which repeats
the errors of Gegenbaur, and adds nothing new
whatever. The animal which he examined was
a genuine Pleurobrachia, if it was the same as the
one he refers to in the July number of the Journal
of the same year. He says: ‘“ These cells were
spherical, and opaque from the presence of mole-
cular matter in their interior, When ruptured by
pressure, they were found to contain a simple short
thread, more or less closely coiled in a spiral form.
The application of distilled water burst the cell
walls and uncoiled the threads.” From the above
it is evident, that neither Gegenbaur nor Dr.

Wright had studied the lasso-thread whilst coiled

Cuap. III. GENUS PLEUROBRACHIA. 239

and see them by themselves, a very flat field is required. With such an objective
the field acts like a section upon the walls and contents of the vesicle, and the
granular coating can be brought into strict profile (Figs. 2 and 7 f) and displayed
as a single layer upon the outside of the wall of the cell, whilst the interior
surface of the same wall is proved to be lined by the spirally coiled lasso-thread
(Fig. 2 bed). The surface of attachment must be very small, or else the granular
covering prevails as much on that side as elsewhere: at any rate, we always find
the whole cell, when loosened, covered by these granules.

The first feature that strikes the eye when investigating the interior of these
lasso-cells is the total absence of the axial, rod-like body, so commonly observed
in all other lasso-cells (see Pl. XIX. Fig. 5 4b’): the whole middle portion appears
totally void, and such is the true state of things, for the coil always presses
closely against the inner surface of the wall, as long as it is in a quiescent state.
The wall has one uniform thickness throughout, excepting at one point, corresponding
to one of the ends of the coiled thread, and there it thickens and forms a broad,
conical basis, with which the lasso is continuous, the one gradually passing into
the other (#7. 2 ¢). Although the thread arises from the wall very obliquely,
it is not attached by one side, but at the extreme tip, and suddenly bends upon
itself to follow its spiral course. When partially uncoiled (/%y. 8), this sharp bend
(c) may be more plainly seen; but when it is straightened out (Figs. 3, 4, 5, 10 ¢)
the bend disappears, and the thread meets the wall at right angles. In this state
the broadened base is a marked feature. Returning to the uncoiled lasso again
(Fig. 2), we will observe that the coils (4) are set very far apart, but at equal
distances, and do not make more than seven or eight turns before the thread
terminates very abruptly, at a point (d) directly opposite to the basis of attach-
ment (¢); but the end is perfectly free from the wall against which it presses.
Another noticeable feature in the thread is, that it is as easily seen at one part
as at any other; and this is owing to the fact, that it has one uniform thickness
from the base to the tip. This, when compared to the gracefully tapering lassos
of Discophore (Pl. XV. and XIX. Fy. 5*), appears very clumsy, and looks as if it
might be rather inefficient; yet nowhere do we find lassos so tenacious of their
hold as among the Ctenophore: and this is all the more remarkable because, in
addition to the shortness of the thread, which is only eight or nime times longer
than the diameter of the cell, it is perfectly smooth, and also blunt at the tip.

With this amount of knowledge of the lasso-cell, one might very naturally suppose
that the lasso makes its exit from the cell as all other lassos among Discophore

up within the cell, and knew nothing of the pe- the vesicle; and both mistook the granular bodies

culiar mode of connection between the thread and to be within the cells, instead of without.

240 CTENOPHORE. Parr II.

and Polypi have been known to do; that is, by turning inside out, and at the
same time sliding through its own base, like the inversion or eversion of the
finger of a glove, or the feelers of a snail: but nothing of the kind occurs. In
the first place ¢he thread is solid, and therefore demands a mode of extension cor-
relative with this peculiarity, and a mode, too, which is typically different from the
method by eyersion. We must confess to having been completely taken by surprise
when we discovered that part of the cell opposite to the base of attachment gaping
wide open (Figs. 8, and 11e), as if a segment of a sphere had been cut off, and
the thread, more or less uncoiled, thrust out, directly from its point of attachment,
freely into open space. Sometimes the thread was partially extended; but the
aperture of the cell was closed around it (Fiys. 6, 7, 9, 12), and, as in the first
ease, it was the free end of the lasso which projected. It might be supposed that
the extension was effected by the contraction of the cell wall, or by pressure from
surrounding parts, or from behind, were it not that the cell is seen to open widely,
drawing back as if by means of retractor muscles, in order to let the lasso spring
out, through the broad-spread aperture. No amount of compression can straighten
out, or even partially extend, the thread; but this is evidently done by its own
inherent power, the mouth of the cell simply gaping to let it pass. This must of
necessity be the case, or how otherwise could the thread coil itself up and retreat
into the cell, as we have seen hundreds, and we might say thousands of them do?
At one time the tentacle was as if covered by short, curly hairs, and the next
moment the little curls had disappeared, like magic. After the thread is out, the
cell closes or remains wide open (figs. 5, 4, 8), and contracts more or less upon
itself, the wall thickening according to the amount of contraction.

After the foregoing description, it hardly need be remarked that the base by
which these cells (Fig. 154) are attached to the subjacent outer wall (¢) of the
tentacle is the same side on which the lasso-thread has its connection (Figs. 1 to
12 ¢); and therefore the latter can never be wholly extruded, unless the vesicle
turns inside out. The thickness of the lasso is not only uniform from base to
tip, but it does not change either by extension or by contraction. There is much
difference between the degree of consistency of the wall of the cell and the
lasso-thread, as may be demonstrated by allowing decomposition to set in, when
the wall will disappear altogether, before the thread shows the least sign of decay
(Fig. 5). As to the manner of proceeding when these coils have arrested any
foreign body, we have made no positive observations: we only know, that, as far as
their tenacity of hold is concerned, they cling as pertinaciously to a smooth glass
rod or a well-polished needle as to any other body; not by coiling the tentacle
around them, but by simple adhesion of the thread itself; and this is the more
remarkable, since the latter is not only short, but perfectly smooth, possessing none

Crap. II. GENUS PLEUROBRACHIA. 24]

of those salient points, which, in more or less spiral lines, beset the lassos of the
majority of Discophore.

In order to form a correct idea of the ever-changing state of the tentacular appa-
ratus, it is necessary to keep in mind, not only the form and structure of all its
parts, but also their relative position in different points of view, as represented in
my paper in the Memoirs of the American Academy, Pls. III. and IV. The base of
this apparatus being attached by its flat side to the inner wall of the cavity, appears
in profile, in a front view of the animal, so that the flat disk is represented by
a narrow margin, and its whole height is apparent. Seen from the sides of the
animal its width becomes distinct, and the edges, encircling its margin and rising
from the abactinal summit of the disk along its middle line to form the pro-
jecting base of the tentacle, are seen in front. Seen in half profile or in a three-
quarter view, both margins and the tentacular base become distinct, and the ten-
tacle which arises from the disk can be traced from its origin along the basal
part of its course. In such views the whole height of the apparatus is equally
apparent; but when seen from above or from below, the cavity of the tentacles
and the tentacular apparatus itself are shortened, and the two chymiferous tubes
along the inner wall of the disk appear like two holes. Correctly to appreciate
the relations of the tentacle proper with the flat disk from which it arises, it is
necessary further to keep distinctly in view the arrangement of the margin en-
circling the disk. Along the vertical chymiferous tubes which extend to near the
actinal end of the tentacular cavity, there are, on each side, linear edges slightly
swollen in their middle, and curved over the middle of the disk from the actinal
side, where they unite (PI. Il*% Fig. 15); then extending again toward the abactinal
side, they are detached from the outer surface of the disk, to meet on their abacti-
nal margin a similar fold rising from that side, and then hang downward into the
bottle-shaped cavity free, as an independent thread, surrounded as soon as it is free
from the disk by numerous small elastic and contractile tentacles. The main
thread, however, forms the stem of the tentacle, which is capable of extraordinary
development, and can also be contracted into a coiled bundle; so that, in the state
of utmost contraction, it forms a sort of irregular ball of tuberculated appearance
hanging from the hook, the tubercles of the surface being the lateral fringes: but
when elongated it is changed into a fine thread, and the fringes appear at intervals
either in a contracted or elongated form, assuming in the former state the ap-
pearance of little tubercles, which in their elongated condition are themselves like
so many little threads. Their arrangement near the base of the tentacle is not
easily ascertained; but when expanded, or regularly contracted within moderate
limits, it is evident that they all arise from one side of the main thread, and
are throughout unilateral; and where one is occasionally seen in a different position,

VOL. III. 31

249 CTENOPHOR®. Parr II.

it is easily ascertained to be out of place, owing to some accidental pressure.
The variations which they undergo in their various degrees of contraction and
expansion having already been described when speaking of the movements of these
animals, I need not refer to the subject again. I have only to add, that they
appear frequently coiled up like a corkscrew, in a regular and more or less elon-
gated spiral. But, strange to say, in this position, though placed upon the two
sides of the body in a symmetrical position, the spiral is not antitropic, but coiled
in the same direction on both sides of the body, though their bases and hooks,
and, indeed, the whole upper part of their structure, shows a regular antitropic
arrangement, like all symmetrical parts throughout the animal kingdom. Here,
however, I have constantly found the spirals of the thread, when coiled up, curved
in the same direction, both of them turning to the left in an ascending direction
or to the right in the opposite direction. This is the more surprising, as in
animals in which there are parts twisted upon the two sides of the body, those
of the right side are ewled in one direction, and those of the left side in the
opposite direction, in order to establish perfect symmetry. Thus, the horns of
cattle, sheep, and goats are twisted, the right to the left, and the left to the
right; while in antelopes the direction is reversed, the right horn being twisted
to the right and the left horn to the left. The same antitropy is also ob-
served in the bend of the tusks in elephants and wild boars, or of the horns
in deer, ete. Such an antagonism seems, therefore, not yet to prevail among
Radiata, im which the anterior and posterior extremities have not become promi-
nent.

The lateral frmges have the same structure as the main thread, consisting, in
the middle, of a bundle of elongated cells surrounded by epithelial cells. When
contracted, the longitudinal cells, extending into the main thread, appear like
transverse fibres. There are, however, no transverse fibres proper in the main
thread, any more than in the lateral fringes; as in every instance those trans-
verse fibres of the main thread can be traced into the centre of the lateral
ones. The extension of the threads must therefore be of a more passive char-
acter, owing to the relaxation of the fibres, and cannot be produced by the con-
traction of annular fibres; though the longitudinal cells of the lateral fringes may
perhaps contribute by their contraction to the elongation of the main thread. This
disposition explains very fully the slow elongation of the tentacles, in comparison
with their quick and almost instantaneous contractions, and also the peculiar
phenomenon attending this elongation, when, by starts, the main thread seems
rather to be dropping from point to point to its fullest elongation in a passive
way by the relaxation of the fibres. I am, however, at a loss to explain by

their structure the elongation of the lateral threads at right angles with the main

Cuap. UI. GENUS PLEUROBRACHIA. 943

thread when this is fully expanded, and their various other dispositions, their
frequent straight and apparently stiff elongation, and, still more, their sudden
bending even in acute angles. These motions are so diversified, and sometimes
so sudden, as to astonish even those familiar with the movements of these animals.

Having described above the position and changes of form of the digestive cavity,
I have now only to add, that its inner surface has not throughout the same
appearance, and is not uniformly flat. Near the aperture of the mouth, indeed,
it is smooth; and, when the mouth is fully expanded, a broad funnel is opened,
leading directly into the digestive cavity, assuming, however, in its contractions,
very diversified forms, being at times perfectly circular, and at other times oblong,
oval, or even angular. The anterior and posterior angles of the mouth form fre-
quently a fold, or it assumes a linear shape, or a stellate form. The more the
mouth is open and spread out, the more easy is it to follow to a considerable
depth the tubes which extend vertically along the walls of the stomach or cceliac
cavity. The walls of this cavity present four folds, two of which are in the
direction of the fissure of the mouth, along the anterior and posterior walls of the
stomach, and two others at right angles with them along the middle of its broader
wall, in the plane of the transverse axis of the body. These four folds are lined
with brown cells, suggesting the idea of a rudimentary liver, or, at least, that of
secreting cells aiding in the process of digestion. Towards the abactinal extremity
of the digestive sac, between those prominent folds, the walls of the digestive cavity
are lined with a vibrating epithelium, which is particularly active round the abacti-
nal opening of the sac, when this is fully open. This vibrating epithelium is con-
tinued upon the inner surface of the central chymiferous cavity, into which the
stomach pours its contents.

If we now view this animal from the abactinal side, we find a variety of organs,
the structure and connections of which are not easily understood. Considering them
at first chiefly in their relations to one another, it will be seen that there is in
that region an elongated area, well circumscribed in its outlies, extending in a
longitudinal direction, in the same plane as the mouth, with a black speck in its
centre (Pl. II. Fig. 20). Towards the centre of this area eight narrow bands are
seen converging, and, in an oblique position to its axis, near the black speck, two
slight projections may be observed near the margin of the area. The black speck
in the centre rests upon a tubercle within, which is itself encircled by a fork of
the funnel. This organ, which is considered as an eye-speck by some anatomists,
and as an auditive sac by others, is a globular or broad pyriform mass (0) of large,
highly refractile cells or vesicular bodies, altogether enclosed in a large, exceedingly
transparent, dome-like capsule (0”). The pyriform mass (0) is attached to the bot-
tom of its capsule (0’) by its narrower end, and is constantly nodding or vibrating,

244 CTENOPHORS. Parr ID.

whether by its own power or by the action of the vibratile cilia which line the
capsule it is not possible to say, as we have never seen the cilia in a quiescent
state. The narrow longitudinal area is a shallow furrow with a well-cireumscribed
and somewhat prominent margin. The irregular transverse bulbs at the base of
its anterior and posterior halves, near the black speck, are the swollen extremities
of two branches of the medial vertical funnel. Starting from these facts, we may
perhaps throw some light upon the structure and functions of the whole structure.
Let us, for this purpose, consider anew the funnel itself’ We have seen that it
is simply a central, vertical prolongation of the digestive cavity, tapermg gradually
into a narrow neck; but before it reaches the abactinal surface it enlarges again
very suddenly, branching into two forks, which are themselves swollen into two
irregular bulbs projecting towards the surface, one in front, and the other behind
the central black speck, but both close to it and partly encircling the tubercle
upon which the black speck rests. These two bulbs are therefore simple dilatations
of the forked abactinal extremity of the funnel, and we constantly see undigested
matters crowded in them and revolving in their cavity, with a tendency to accumu-
late laterally in an obliquely opposite direction in each of them. And at long
intervals these prominent oblique angles will open outward, when the foecal matter
within the bulbs is discharged, the aperture remaining for a longer or shorter time
extended, and the vibrating cilia lining the inner surface playmg very actively ;
but after a little while these openings shut again.

These apertures might therefore be considered as a double anus; but I think it
would be a very injudicious comparison to homologize them with the anus of higher
animals, for in this type the process of digestion and assimilation and the cireu-
lation of the nutritive digested food are carried on by means of organs widely
different from those of either Mollusca, Articulata, or Vertebrata. We have seen
above, that the food is introduced into the digestive sac which occupies the centre
of the spherosome; that this sac opens freely into the central chymiferous cavity,
and discharges into it its contents, mixed with a large quantity of water; that
this peculiar apparatus is subject to regular contractions, and circulates the fluid,
with the nutritive parts suspended in it, into the various tubes branching through
the whole system; and that gradually the refuse matters accumulate on the abactinal
prolongation of the central vertical funnel, to be discharged through the openings
of the two hollow bulbs branching from its extremity. We have here, therefore,
rather openings in the circulatory system than anal apertures; or, rather, we have
here an apparatus entirely different in its adaptation from either the alimentary
canal or the circulatory system of higher animals, but constructed upon the same
plan as similar organs in the class of Polypi and in other Acalephs, with only

this difference, — that in Polypi the digestive central sac empties its contents into

Cuap. IIT. GENUS PLEUROBRACHIA. 945

a large cavity subdivided only by partitions, without definite circulatory tubes, but
along which the fluids are nevertheless circulated up and down and into the
tentacles, and discharged either in a retrograde current through the stomach and
mouth, or through the tentacles and lateral pores, when such exist. In Discoid
Meduse a similar circulation takes place, but without openings either in the peri-
phery or opposite the mouth; here, the fluid accumulated in the digestive cavity
is circulated through tubes into the periphery and around it, and the refuse matters,
retracing their course, are emptied through the mouth. No Meduse have peripheric
openings of their chymiferous system through which the refuse matters may be
discharged, as Ehrenberg maintains; but in all of them, as well as in Polypi, the
whole digestive apparatus is in direct broad communication with the circulatory
apparatus. The fluid circulated is simply chyme mixed with water, and carried to
all parts through the chymiferous tubes. In Medusx proper this fluid retraces its
course, and may be discharged through the mouth. In some Polyps it is also
discharged through the mouth only, while in others it may also find an outlet
through the tip of the tentacles and through the lateral pores of the spherosome ;
but in Ctenophore it is discharged through the openings of the funnel. These
animals never have a continuous alimentary canal with a simple anterior and pos-
terior opening, nor a distinct circulatory system deriving its fluid through lym-
phatics from the alimentary cavity; but all have two closely connected systems
broadly communicating with one another, through which alimentation takes place,
one of which presides chiefly over the function of digestion, while the other circu-
lates the whole mass of digested food—that is, chyme mixed with water— throughout
the system. It is therefore proper, in describing these organs, to avoid any names
which may suggest an identity with those of other animals with which they are
only analogous. For this reason I have adopted the name of coeliac cavity for
the digestive sac, and called funnel the central chymiferous cavity; and its branching
tubes, chymiferous tubes or chymiferous vessels. The circulation which takes place
in this system of tubes is not to be homologized with a blood circulation: it is
only a chyme circulation, the fluid moving to and fro in opposite halves of the
body by their alternate contractions.

If we next consider the oblong area, I must first correct a mistake I made
in my paper upon Beroid Meduse, in which I stated that the space circumscribed
by its outline is a hollow space, extending forward and backward from the two
cloacal bulbs, in a direct prolongation of the cavity of the bulbs. I must have
been misled by an oblique view of the funnel, producing the appearance of a
circulation in the area itself The ridge which circumscribes this area is very
definite, and, though smooth, slightly prominent upon the surface, so that the circum-

scribed area is really a broad, shallow depression, covered with superficial vibratile

Fg
246 CTENOPHORE. Part II.
cilia. But in some Ctenophora, such as the true Beroids, this ridge is fringed;
and the marked outline of the area in our Pleurobrachia is a rudimentary develop-
ment of such fringes.
The narrow bands, alluded to in my first paper as tubes converging toward
the centre of the circumscribed area, can be traced from the abactinal extremity

of the vertical rows of locomotive flappers to the very base of the black speck
in the centre of the abactinal pole of the body. These bands are not tubes, but
a double or triple row of coarse, immovable cilia, or, more properly speaking, short, .
acute ridges, which trend in one direction in the same band. They are direct
prolongations of the rows of locomotive flappers, tapering gradually toward the
abactinal pole of the animal, and so reduced in their diameter as to appear like
very slender threads conyerging from the abactinal termination of the locomotive
flappers to the centre of the abactinal surface of the animal. They terminate under
the eye capsule (7%. 14 and 190), and at the very base of the pyriform eye
(0). These bands are eight in number, like the ambulacral rows of which they |
are the continuation, and they converge two and two, being more closely brought |

together in pairs toward the eye-speck. In their respective position they differ
somewhat: four of them, rising from the four lateral ambulacra, preserve a rather }
straight course from the summit of the rows of flappers to the centre of the area ; |
the four others, the anterior and posterior ones, however, bend toward the elongated
part of the area and follow obliquely the course of its margin, thus contrasting |
jn some degree with the lateral ones.

I am somewhat at a loss to account for the precise connection between all the
parts which may be seen around the central black speck (Pl. U*. Figs. 14 and 19)
and in the fork of the funnel. Even the nature of the central organ is in a
measure problematical. In its appearance it resembles the marginal colored specks
observed in Discoid Meduse, and on that account has been viewed by some as
an eye-speck ; while by those who consider the so-called eye-specks of Meduse as
rudimentary auditory organs, it has been regarded as a rudimentary ear. But,
notwithstanding the difference of opinion respecting its functions, all naturalists
who have examined Ctenophore have thus far identified the black speck, which
occurs in a central position upon the abactinal pole of these animals, with similar
specks occurring about the periphery of Discoid Meduse. The opinion I formerly
entertained of the nature of this organ has been disproved by embryological
researches. Since I have become acquainted with the development of the Cte-
nophorx, I am myself satisfied that it cannot be considered as the remnant of
a point of attachment to a Hydroid stock; for the Ctenophore undergo a direct
metamorphosis. Nor do I now doubt its identity with the marginal specks of the

higher Discophore ; and I have already stated, that I am inclined to regard it as

Cuap. II. GENUS PLEUROBRACHIA. 247

a Cyclopean formation, resulting from a central combination of the specks, which,
in Discophore, occupy a peripheric position.

The nature of the tubercle, or ganglion-like mass, placed between the eye-capsule
and the fork of the funnel, is still more problematical. This body is of larger size
than the black speck and its capsule, under which converge the eight narrow pro-
longations of the ambulacral rows, and on the anterior and the posterior side of which
are seen four smaller tubercles or swellings, between which arise two ridges rapidly
diverging forward and backward. I can offer only suggestions respecting these
parts. I am, however, inclined to believe that the two ridges between the four
small swellings extending forward and backward are only outlines of the folds which
form the circumscribed area; that the four small swellings themselves are clusters
of cells connected with the narrow termination of the ambulacral rows; and_ that
the wall-like outlines of the tubercle are determined by the fork of the funnel.
As for nerves, which are said to arise from the ganglion connected with the black
speck, I have been unable to make them out. I have traced the motory cells
which surround the abactinal extremity of the chymiferous funnel; I have seen
these cells diverging from the actinal side of the so-called ganglion, but have
never been able to trace any one of them beyond the usual length of these cells;
I have repeatedly seen these cells in a state of contraction or relaxation, pre-
senting so little resemblance to nerves that I think it rather assuming to ascribe
a nervous system to the Ctenophore. I am even satisfied, from the descriptions
published, that the eight converging narrow prolongations of the ambulacral rows,
of which I find no mention in former authors, must have been mistaken for ner-
vous threads by some; and when Professor Grant states that Beroe has eight main
nerves arising from eight ganglions, I suppose he alludes to some contracted cells
of the spherosome, or to the eight narrow abactinal bands, the connection of
which with the rows of locomotive flappers is so easily traced. I do not, however,
deny that this centre is a point where we have to look for at least one part of
the nervous system, and the movable margin of the mouth for the other part,
if there really be a distinct nervous system in Ctenophore. But, as for myself,
I have failed in tracing it out; though, I may add, I am sufficiently acquainted
with the structure of the region where it is said to have been observed, to doubt
the accuracy of the statements which have been made about it. And I express
these doubts, notwithstanding the doubts I myself entertain respecting the real
nature of some organs around the central black speck, for the very reason, that,
after finding there more than has been seen and described, and various things
which may answer the vague descriptions given, I do not in reality find what
has been said to exist in that part of the animal.

When I first described our Pleurobrachia I did not know its mode of develop-

248 CTENOPHORA. Parr II.

ment; but, during the latter part of the summer of 1858, I had ample opportunities
of tracing it through all its stages, and am now engaged upon a comparative study
of its embryology with that of Bolina and Idyia, which have appeared in unusual
abundance this summer. I will therefore postpone the publication of my earlier
observations until the more recent ones are completed, and, in order not longer to
delay the printing of this volume, pass them over here, and simply state, that
before the young has reached one twenty-fifth of an inch in diameter, it has
already assumed the appearance of the adult, while in its earlier stages it presents
the greatest uniformity in the three types which came under my observation. The
sexual organs have the same typical structure as in the other Ctenophora, but they
are only distinctly visible when the spawning season approaches, late in the summer.

Having recently seen myriads of these animals, it may not be superfluous to
add, that all the various attitudes in which I have formerly seen them in confine-
ment may be observed at one glance, when coming suddenly upon a bank of
them slowly drifting with the tide. Under these circumstances, however, they
are not altogether at the mercy of the current; and it is curious to see how
they resist its action by stretching their tentacles in a straight line in opposite
directions and at right angles with the vertical axis of the body. I have also
satisfied myself that they are aware of the approach of danger; for day after
day I have seen thousands of them, which were quietly moving near the sur-
face with the mouth wide open in search of food, suddenly turn upon them-
selves and with a quick jerk dive into the deep as my boat drew nearer and
nearer. In fact, all Acalephs dive away from the surface when approached, and
make accelerated motions to escape the net or glass dipped into the water to
catch them. It seems as if they were endowed with the power of seeing, for
noise has no effect upon them.

In conclusion, I would mention the most prominent specific characters of our
Pleurobrachia. It is the smallest of the genus; of remarkable transparency and
throughout hyaline, with a flesh-colored lining of the coeliac cavity, turning to brown
at its abactinal end and shining through the body; the tentacles are through-
out rose colored, the main thread as well as the lateral threads; the rows of loco-
motive flappers rather milk-white and iridescent. Inhabits the coasts of New Eng-
land and Canada, where it is seen through the whole summer. Spawns in August

and September.

Cuap. III. GENUS BOLINA. 249

5.4, C AO Noa i:
THE GENUS BOLINA AND ITS SPECIES; WITH REMARKS ON ALLIED GENERA.

The genus Bolina was first described by Mertens, from two species observed in
the Pacific and in Behring Strait! It is considered as differmg from other genera
of Ctenophore by the great development of the mantle lobes, and by the cireum-
stance of its eight rows of locomotive flappers not extending beyond the body
itself; and though this characteristic is not strictly correct in as far as I shall
be able to show that the ambulacral rows are not. strictly circumscribed within
their apparent limits, the genus itself is a very natural group, which ought to be
generally acknowledged. I have already stated (page 201), that the genus Bolina
differs so far from Mnemia as to constitute a distinct family, the lobes of the
spherosome being only actinal prolongations of the anterior and_ posterior sphero-
meres, while in Mnemia and Alcinoe they arise as lateral folds between the lateral
and the anterior and posterior spheromeres. I have also pointed out generic differ-
ences between Bolina elegans Mert. and Bolina septentrionalis Mert., which will require
their separation; but I would retain the name of Bolina for the type to which
B. septentrionalis Mert. our B. alata, and Sars’s Mnemia norvegica belong. — It is
difficult to give a correct idea of the form of these animals, as they assume most
diversified aspects in their various moyements, and in the different attitudes in
which they have to be considered. Having had ample opportunities repeatedly and
for a longer time to examine a new species of this genus which I have kept
alive, at intervals, for months, I shall attempt to give a more complete idea of its
remarkable structure, which may throw some new light upon the organization of the
whole family, and also upon the natural relations which exist between its different
genera. I saw this new animal for the first time with Mrs. Arnold, of New Bed-
ford, who had preserved it alive for my examination, in December, 1848. I myself
afterwards found large numbers of specimens during the months of March and
April, and even as late as June, in various parts of Boston Bay. I now know
that it may be found through the whole summer, not only along the coast of
Massachusetts and Maine, but even as far north as Labrador. Dr. A. A. Gould,

however, had already noticed this species as an inhabitant of the shores of Massa-

1 This genus is characterized in a remarkable ences, in St. Petersburg, in the second volume of
paper by Mertens on Beroid Meduse, published in the sixth series, 1833. The species described are
the Transactions of the Imperial Academy of Sci- chiefly from the Pacific.

VOL. Ill. 32

250 CTENOPHORAE. Part II.

chusetts, in his Report on the Invertebrated Animals of that State, where he
considers it, however, as identical with the Aleinoe vermicularis of the coast of Bra-
zil. But a close examination has satisfied me, that it is neither identical with that
species, nor even belongs to the genus Alcinoe, but constitutes the first Atlantic
representative of the genus Bolina.’

There is a marked difference between this species and Bolina septentrionalis
Mert, in the less limited development of its longitudinal diameter, in the greater
approximation of the two auricles of each side, and in the greater width of the

Like all

Bolina norvegica, Sars’s Mnemia

large lobes; for which reason I have called our species Bolina alata.

true Boline, it is of a transparent bluish white.

norvegica, is at once distinguished from the species found along the north-west and

the north-eastern coast of America, by the sudden projection of its lobes. A fourth
species, which I call Bolina vitrea, occurs on the southern coast of Florida. It dif

fers from the preceding ones by its greater height, the narrowness of its locomotive
flappers, and its extraordinary transparency. I am unable to state with certainty,
whether Bolina hybernica Patt. differs from the species described by Sars or not.

Bolina alata is a most delicate, transparent, and diffluent animal; so soft that
it readily decomposes under the least unfavorable circumstances. The admixture
of a small proportion of fresh water in the bowls in which I used to preserve
them caused not only their immediate death, but also their instantaneous decompo-
sition. All my efforts at preserving specimens in Goadby’s liquor have entirely
failed; and when, under identical circumstances, I succeeded in keeping for a long
time specimens of Pleurobrachia rhododactyla, I failed in preserving specimens of
Bolina alata longer than twenty-four hours. Again, this species being by no means
so common as the Pleurobrachia, with which it is always found associated, I had
to contend with great difficulties in my investigations of its structure. I succeeded
several times, nevertheless, in injecting it with indigo; and, though the injection soon
caused the death of the animal and its decomposition, I have been able to trace

1Tt is a remarkable circumstance, that the rhododactyla, another species of the genus, de-

Atlantic shores of America should furnish, in lower seribed as Mnemia norvegica by Sars, accompanies

latitudes, a species of the genus Bolina very similar the Pleurobrachia bicolor of the boreal fauna of

to that which occurs in Behring Strait; but this
is only one of the many instances showing that
species on the opposite shores of this continent are
adapted to the differences which exist in the cli-
matic conditions, and the different course of the
isothermal lines on the eastern and western. sides
of the Old and New Worlds.

to notice, that while Bolina alata is, everywhere

It is also interesting

on our coast, found associated with Pleurobrachia

Europe; and that the Bolina septentrionalis of Mer-
tens belongs to the same fauna with the Pleurobra-
chia Bachei discovered by my son in the Gulf of
Georgia, where it occurs together with Bolina sep-
tentrionalis. | Moreover, a distinet species of Idyia
is also found in each of these three faunie, one of
which is described by Sars in his “ Beskrivelser,”
and the other two in the following section of this

chapter.

Cuar. TL. GENUS BOLINA. 951

the circulation for a sufficient time to follow the entire course of the chymiferous
fluids within the body, throughout all its parts. Besides, being already minutely
acquainted with the arrangement of the chymiferous tubes in Pleurobrachia, I was
fully prepared to institute a minute comparison between the two genera, to ascer-
tain their differences, and to recognize the homology of their structure. I was even
able to trace the connection of all the parts of the chymiferous system so fully
in Bolina that I could ascertain the natural connections between all its peripheric
tubes and the central chymiferous cavity, as well as the peripheric anastomoses of
the tubes themselves. Such anastomoses are entirely wanting in Pleurobrachia, in
which the ambulacral tubes end in blind sacs, on the actinal as well as the abactinal
side of the body. Milne-EKdwards presses too far the typical identity of the chymife-
rous system in Ctenophore. Had he perceived that these Acalephs, instead of form-
ing one natural family, constitute four sub-orders with many distinct families, he
would, no doubt, have given more weight to the differences which he himself has
observed in their chymiferous system, and of which he makes too light.

In order fully to understand the structure of Bolina alata,’ and the relations
of its various parts, it is necessary first to have a precise idea of its external
form, which it is by no means easy to acquire, even after repeated investigations.
Like Pleurobrachia, the body of Bolina is more or less ovate, but in an inverse
direction; for its greater diameter follows the plane of the corresponding organs
in such a connection as to show that the antero-posterior diameter is the longer,
while it is the shorter in Pleurobrachia, and ace versé that the transverse diameter
is the shorter, while it is the greater in Pleurobrachia. This inverse agreement
between the natural relations of the organs and the external form is most. satis-
factorily ascertained, upon comparing the position and direction of the circumscribed
area and of the tentacles; and we shall hereafter see that the proportions of the
body with reference to their longitudinal and transverse development are in every
respect reversed in the two genera. Before this contrast had been established, I
was unable to trace the homology of parts between the two genera. Indeed, taking
the general form as a guide, I began by comparing the two animals in a_ position
in which I undertook to place their prominent diameters in the same relation,
and thus arrived at the conclusion, that the tentacles of Bolina, which are far less
developed and issue from the margin of the mouth itself, were organs entirely dif
ferent from the tentacles of Pleurobrachia. The latter I} considered as a system pe-
culiar to this type of Ctenophore, because they are protruded from the sides of the
body ; while the tentacles of the type of Bolina appeared to me as a sort of fringes

1 As I have published numerous views of this Academy, I would refer to them for further com-

animal, in different attitudes, in my paper on Beroid parisons, having only reproduced a few of them in

Medusx, printed in the Memoirs of the American the wood-cuts of the following pages.

bo
Or
bo

CTENOPHORA. Part II.

of the mouth. But the moment I placed the diameters of the two bodies in a_po-
sition inverse to their length, all parts being placed in the same natural relation
as far as they correspond by structure, their perfect homology, throughout the sys-
tem, was at once established. And not only the correspondence and antagonism
between the abactinal area and the tentacles, but also the minor details im the rami-
fications of the chymiferous system, agreed in every respect. The difficulty under
which I had labored was precisely that of an artist attempting in a family picture
to bring out the resemblance between two kindred faces, while contemplating one
individual in profile and the other in a front view, but believing their position to
be the same. With this inverse relation between the homologous parts, considered
in their reference to form in the two genera Bolina and Pleurobrachia, there is a
corresponding opposition between the natural positions of the two animals in the
surrounding medium. Pleurobrachia, as I have stated, swims naturally with the
mouth upward or forward, and the circumscribed area downward or backward; Bo-
lina moves with the mouth downward and the abactinal area upward.

The position of the tentacles, their natural relations to the body when in motion,
and the direction of the aperture through which they issue, were the chief sources
of error which led me at first to consider them as different organs; for m Pleuro-
brachia (Pl. I". Figs. 22, 23, and 25) they are turned toward the coeliac apertures,
while in Bolina (/%gs. 88 and 89m) they are turned toward the oral aperture, But
now we may ascertain the homo-
logical identity of these appen-
dages, by placing these two ani-
mals in their normal position, in-
stead of viewing them in their
natural attitudes. And it will

be easy to understand how, in

accordance with the form and

BoLina ALATA, Ag.

BouinA ALATA, Ag.
(Seen from the broad side.)

aand f Long rows of locomotive fringes. —
gandh Short rows of locomotive fringes.
—o Central black speck (eye-speck).—
i to m Triangular digestive cavity. —1 to 0
Funnel-like prolongation of the main cay-
ity. —v Chymiferous tube of the tenta-
cular apparatus. — 7m Tentacular appa-
ratus on the side of the mouth. —7r7 Ear-
like lobes, or auricles, in the prolongation
of the short rows of locomotive fringes.
—tt Prolongation of the vertical chymife-
rous tubes. —2 The same tubes turning
upwards.—xx Bend of the same tubes.
—zz Extremity of the same tubes meet-
ing with those of the opposite side. — w
Recurrent tube anastomozing with those
of the auricles.

movements of the various mem-
bers of the whole family, the
tentacles may issue from differ-
ent heights of the vertical di-
ameter upon the sides of the
body, and, according to the di-
rection of its movements, be bent
either toward the mouth or
toward the coeliac apertures.

Judging from Pleurobrachia and

(Seen from the narrow side.)

ab Long rows of locomotive fringes. —c hk

Short rows of locomotive fringes. — 0 Cen-
tral black speck (eye-speck).—« Upper
end of the digestive cavity. —7 too Fun-
nel-like prolongation of the main cavity of
the body.—m to7z Digestive cavity. —7r7r
Auricles.— 2m Mouth.—t ¢t Prolong-
ation of the vertical chymiferous tubes.
—nn The same turning upwards. — xx
Bend of the same tubes. —~ Anastomosis
of the two longitudinal tubes t¢.—ww
Recurrent tube, anastomozing with those
of the auricles. — A comparison of this fig-
ure with Fig. 88 gives a distinct idea of the
relative position of the digestive cavity, 7
to 7, and the chymiferous tubes of the ten-
tacular apparatus v.

Mertensia when contrasted with Bolina and Euramphea, we might infer that the

Crap. IIT. GENUS BOLINA. 253

tentacles are more and more developed in proportion as they are further removed
from the mouth. But Leucothea shows that oral tentacles may be as extensively
developed as those which issue from the sides of the body. That the tentacles
of the Ctenophore cannot be homologized with either the tentacles around the
mouth, or those around the disk, of Discoid Meduse, has already been shown.
After this digression, if we return to a more direct consideration of the form
of Bolina, we find that it differs from Pleurobrachia in the extraordinary develop-
ment of two lobes in the actinal prolongation of the anterior and posterior sphero-
meres (/vgs. 88, and 89 z2¢n x), inclosing, when shut, the mouth and its appendages,
each lobe extending transversely to the antero-posterior diameter, one forward and
the other backward; so that they contribute, when expanded, to increase the already
prominent length of the longitudinal diameter, leaving a deep, transverse chasm
between them, at the bottom and centre of which the mouth (/%y. 88 i) is situated.
The body thus shuts up by the alternate approximation and separation of two valve-
like lobes, hanging downward, and placed, one in front and the other behind the
spherosome, in a position precisely inverse to that of the valves of Acephala, which
rest upon the sides of the body, and move laterally. In addition to these two
large, broad lobes, there are on each side two smaller lobes (77), the auricles,
which arise from the body at about the same height as the anterior and posterior
lobes. They are simple, short, narrow appendages, converging or diverging alter-
nately, and thus shutting from the side and above the great transverse fissure of
the animal. With the power which these animals enjoy of opening widely or
shutting closely the anterior and posterior lobes by contraction and dilatation, and
thus bringing them alternately close together or stretching them far forward and
backward, their general appearance is constantly so completely changing that it
requires a long acquaintance with them fully to appreciate the connection of all
their parts in their different attitudes, and the influence of the movements of certain
parts upon the position of others and upon their functions. The activity of the
circulation through the chymiferous tubes, and the position the main branches of
the central cavity assume during these changes, are constantly modified, as are also
the width of the body and the power of its contractions. And, in the same pro-
portion that the extent of the longitudinal diameter is modified by the expansion
and contraction of the anterior and posterior lobes, the height of the animal, com-
pared to its width and length, is also constantly changing. If we add to this
the diversity of images which are brought before us when we watch these animals
in their various movements from different sides, facing alternately the longer or
the shorter diameter, the sides or the actinal and the abactinal areas, I venture
to say, that it is impossible to make correct descriptions and to give true rep-

resentations of such animals, unless they have been watched for a long time in

254 CTENOPHORA. Part IL.

a living state; for it is out of the question to examine their forms out of the
water, as all parts then collapse, fall together, break to pieces, or dissolve into a
shapeless mass. And, although I acknowledge the great interest of the descriptions
published by travelling naturalists, making us acquainted with the extensive
diversity of types of these remarkable animals all over the world, satisfactory illus-
trations cannot be expected from any quarters, save those where able observers
have resided for a longer time. The accounts of the generic and specific characters
of most Medusxe must therefore be considered as provisional, so long as they are
not revised under favorable circumstances.

Viewed from the abactinal side, with the lobes con-
tracted, Bolina appears very much like Pleurobrachia, as-
suming then the form of a slightly compressed sphere (/%.
90); and were it not for the fact that the circumscribed

area runs in the longer diameter, while it is transverse
BoLina ALATA, Ag.

to it in Pleurobrachia (Pl. I" 7%. 20), the identity would (Secagtumanctas
be almost perfect. Seen from the actinal side, however ° Central Diack speck (eye-speck).—a>es
Long rows of locomotive flappers. —cdgh
(2%g. 91), even when the lobes are contracted, the differ- Sbort tows of locomotive fappers. — 77
y Auricles, —ss Cireumscribed area of the
ence from Pleurobrachia (Pl. II*. fig. 21) is already marked, —*srtins end of the boay.
owing to the circumstance that the vertical rows of loco-
motive flappers do not extend uniformly from one extremity
of the animal to the other, the two ambulacra of the

anterior and posterior lobes being much longer than those

of the sides, which terminate at about half the height

BoLinaA ALATA, Ag.

(Seen from below.) of the body.
an Sage Bune eee Viewed from the abactinal side with slightly opened
tion of the long vertical chymiferous co) ”

tubes. —22 Anastomosis of these tubes. Jobes, the difference between the longitudinal and the
transverse diameter is already more marked; but the four lateral lobes, or auri-
cles, appear as appendages to the anterior and posterior lobes. However, as the
larger lobes expand more and more, the small lateral lobes appear detached from
them, and their real connection with the sides of the main body begins to be
noticeable ; and the greater length of the anterior and posterior ambulacra and the
shortness of the lateral ones are quite apparent. In proportion as the anterior and
posterior lobes are more and more stretched forward and backward, their edges as-
sume a more pointed form, similar to the horns of a crescent, or rather to the blade
of a tomahawk, and the whole body may be compared to two tomahawks in minia-
ture, placed head to head in opposite symmetrical directions, the four short lateral
appendages looking like two small sticks projecting like short handles through the
eyes of the two heads for an equal length on both sides. Seen from the actinal

side in the same development of all parts, the general outlines do not differ

=

Cuap. III. GENUS BOLINA. 955

‘

materially from the view just described, excepting that the mouth is in sight in
the centre, extending forward and backward in the same plane as the circum-
scribed area opposite, and the ambulacra appear only indistinctly through the mass.
The body is sometimes stretched to so great a degree in the direction of the
longitudinal diameter, as to give its outline an irregular, square, oblong form. How-
ever, this attitude is only assumed when the animal swims at the surface of the
water, with the mouth turned upward.

Viewed in profile, the body presents also two very distinct aspects: when seen
by the broad face or by the narrow face, or when examined from its anterior or
posterior or from its lateral sides. Facing the anterior or posterior end, the sym-
metry of the outline (F%. 89) arises from the parity and symmetry of the right
and left halves of the body, the two sides of the anterior and posterior lobes
being perfectly symmetrical. But here again the outlines may differ greatly, in
consequence of the expansion or contraction of the lobes, which may hang down
and look almost straight with the main mass of the body above, or spread laterally
and assume a rounded form, like a broad apron suspended from the chest with
projecting auricles or appendages about its point of insertion. In this position the
anterior or posterior pairs of ambulacra are seen im their fullest development,
extending from the summit along the middle of the lobe to its lower margin,
tapering gradually as the lobes grow thinner. Seen from the sides (Vy. 88), the
symmetry of the outline arises from the perfect symmetry and equality between
the anterior and the posterior extremity of the body; but the outlines may vary as
the two lobes are pressed nearer together, or stretched apart to a greater or less
extent. The modifications in this respect are almost endless, as also are the ways
in which the margins of the lobes fold over; for their lower margin may hang
loosely down, or it may bend inward, curving itself in rounded or square outlines,
and reaching also over the sides or stretching more flatly. In these various states
of dilatation or contraction, the lobes may diverge from each other im all possible
degrees: one may even overlap the other alternately, and thus reduce to the utmost
the difference between the longitudinal and the transverse axis. The small lateral
lobes, two in number on each side, may, in these various changes of form, assume
also the most diversified positions, — at times stretching straight downward, at times
arching upward, at times hanging down and converging toward, and even crossing
each other; so that there is no end to the diversity of these aspects. I should
say, however, that the motions of these lobes, especially those of the two large an-
terior and posterior lobes, are comparatively very slow and graceful; while those
of the small lateral lobes are somewhat more brisk.

Seen from the sides, the two lateral ambulacra converge from the abactinal area

toward the base of the lateral lobes, and the anterior and posterior ambulacra of

bo
OK
[=P)

CTENOPHORA. Part IL

the same side appear in profile near the anterior and posterior margin, encircling
in parallel curves the lateral ambulacra, but extending and gradually tapering all
the way down to the margin of the lobes.

Our Bolina progresses rather slowly, its movements being tremulous, like dancing
in slow steps through the water, and now and then revolving upon itself. It
never performs those quick, darting motions which characterize Pleurobrachia, nor
does it exhibit any thing

Oo

r like the graceful curves of the tentacles following like
a comet’s tail in the wake of Pleurobrachia; for in Bolina the tentacles do not
extend beyond the margin of the lobes. And the lobes themselves, though the
principal organs of locomotion, are an impediment to quick and graceful movements,
the anterior and posterior ones being disproportionate in comparison to the size of
the body. There is, however, one attitude in which the movements of this animal
are exceedingly graceful: it is when the lateral lobes are fully expanded, and even
recurved forward and backward, and so elongated as to appear like the petals of a
flower spreading in opposite directions and curving outward. In this development
the animal generally reverses its position, the mouth being turned upward, and the
lateral lobes, also curved outward, present their vibrating fringes in the utmost
degree of activity,—the whole animal resembling an open white flower, with two
large and four small petals, revolving slowly upon its peduncle, or changing its
place in various directions.

The ambulacra are so closely connected with the general appearance and the
movements of our Bolina, that it is appropriate to consider them in this relation
first. As in all Ctenophora, they consist of vertical rows of locomotive flappers,
in every respect identical in their structure with those of Pleurobrachia, the differ-
ence consisting mainly in their extent. The pairs which run along the anterior
and the posterior sides of the body and extend upon the two large lobes, are by
far the longest, and also somewhat wider, their flapping combs tapering gradually
toward the abactinal area, so that the ambulacral rows terminate in points at
some distance from the central black speck. This is equally the case with the two
lateral pairs of locomotive flappers, which, however, extend somewhat farther towards
the centre of the abactinal area. The tips of these eight rows of flappers encircle
the circumscribed area, which, however, extends far beyond, forward and backward,
between the rows of combs of the anterior and posterior pairs of ambulacra.
Another distinctive peculiarity of Bolina consists in the form of this side of the
body, which is not uniformly rounded, as in Pleurobrachia, but somewhat depressed
along the longitudmal axis; so much so that the two sides bulge sensibly above
the level of the central speck, while the anterior and posterior spheromeres are
on a level with it. The consequence of this prominence of the sides is that the

abactinal extremities of the anterior and posterior rows of locomotive flappers run

Cuap. IIT. GENUS BOLINA. O57

almost straight to their termination, while those of the lateral ambulacra are arched
over the two rounded parallel ridges which inclose the circumscribed area. It is
easily ascertained, that eight narrow bands, similar to those observed in Pleuro-
brachia, extend beyond the extremity of the ambulacra toward the central black
speck, or rather toward the bulb under it, and that they are the prolongation of
the vertical rows of locomotive flappers. Along the sides of the body the rows
of locomotive flappers also gradually taper toward their actinal extremity, and, as
soon as they reach the height of the dilatation of the lobes, the locomotive combs
disappear, and the chymiferous tubes which accompany them can alone be traced
farther. In the lateral ambulacra, however, the rows of locomotive flappers taper
much sooner, and terminate at the base of the small lateral lobes, near their inner
margin, for a considerable length above the actinal extremity of the ambulacra of
the large lobes. In the small lobes we trace also a narrow prolongation of the
chymiferous tubes of the lateral ambulacra, which extend beyond the locomotive
fringes. The course of these narrow tubes in the lobes is very difficult to follow,
and their connection with each other and with the central chymiferous cavity has
been entirely overlooked by former observers, with the exception of Milne-Edwards ;*
though in the figures of Bolina elegans published by Mertens, there are already
indications that he noticed the outline of their convolutions. I shall first trace
the course of these tubes upon the larger lobes. As long as the tubes follow a
straight course in the prolongation of the anterior and posterior ambulacra (fv.
92 ¢), they remain at the surface of the lobes, covered only by the epidermis,
beyond the ambulacral rows themselves. But as soon as
they converge towards the lower margin, where they bend
to take an inward course, they penetrate deeper into the
substance, across the whole thickness of the lobe itself, till
they reappear upon its inner surface, where they are nearest
to each other; they then rise again, diverging toward the

sides and following almost exactly the outline of the lateral

margins of the lobes, along which they ascend (n) toward

BoLinA ALATA, Ag.
their bases, rising even higher than the lower termination (Seen from the narrow side.)

of the ambulacral combs, indeed nearly as high as the bases of the auricles; they
then converge again, bend downward, and in a sinuous, winding course (7)
descend a second time toward the middle of the lobe, to rise and converge again,
and then descend for the third time, in a parallel course, to nearly the same
level with their first bend, and, converging once more from the two sides, unite

(z) in the medial line of the lobe: so that there is a direct communication

1 Mitne-Epwarps, Recherches, ete. Ann. Sc. Nat. 2de sér., vol. 16, p. 203, Pl. 3.

VOL. II. 33

258 CTENOPHORA. Parr Il.

between the right and the left ambulacral tube of the anterior and posterior pairs,
passing in their course from the margin of the outer surface to the middle of
the inner surface, first descending, then rising, then descending again m undulating
lines, then rising and descending again, until they meet to form an anastomose
in the lower central part of the lobe. Such a connection between any of the
tubes on the oral side of the body does not exist in Pleurobrachia. — Besides the
meandering tubes of the long ambulacra, there may be seen, all over the inner
surface of the large lobes, a curious network of angular meshes, resembling small
vessels and connected with one another in a way which recalls somewhat the
branchial vessels of the Naiades, though their arrangement is less regular and not so
strictly rectilinear and parallel. When I first noticed these meshes I mistook them
for real vessels, and have so described them in my paper on Beroid Medusxe; but
I have recently ascertained that they are simply the outlines of the gigantic po-
lygonal cells which form the inner layer of the large lobes. The ends of these cells
are flattened against the inner surface of the lobes and covered by small epithelial
cells, crowded in rows in the intervals or upon the outline of the large cells. A
similar network exists also in Leucothea formosa, Alcinoe rosea, and Bolina septentri-
onalis, judging from the drawings of Mertens. . Will has described the same thing
in Chiaja;' but Milne-Edwards makes no allusion to it. Like Leuckart, Forbes, and
Milne-Edwards, I have seen nothing in Ctenophor answering to the so-called blood-
vessels described and figured by Will.

The ambulacra of the sides are reduced to simple chymiferous tubes as soon
as they reach the base of the small lobes, whence the tubes continue in a very
complicated course through these lobes, and then toward the mouth, sending also
a branch to the large lobes. Each tube first follows the inner margin of its small
lobe, then turns round the obtuse point of the lobe and retraces its course along
the outer margin of the same lobe to its very base; here it branches in such
a way as to unite simultaneously with a tube extending along the margin of the
mouth, and with the marginal tube of the inner surface of the large lobes: or, it
may rather be said, an anastomosis is established at the base of the small lobes,
on their external margin, with a recurrent tube (f7gs. 88 and 89 w) trending along
the outer margin of the large lobes, as well as with another tube rising from the
margin of the mouth. vy. 5 of Pl VIL of my paper in the Memoirs of the
American Academy, in which the imner surface of the large lobes is turned out-

ward for the whole extent of their margin, shows these connections most distinctly?

1 Witt, Hore Tergestinew, p. 55, Pl. TL. Fig. * The letter-press mentions also distinctly these
14, considers these meshes as forming part of the anastomoses, (p. 398). Iam therefore surprised that
skin, and describes them as similar in structure to Milne-Edwards should state that I have failed to

the tentacular threads. notice the connection of the “canaux costaux laté-

Cua. III. GENUS BOLINA. 259

The anastomosis with the large lobe is established through a tube which arises
from the lower sinuosities of the inner convolutions of the long ambulacral tube.
The communication with the oral tube is more direct, and may be considered as
a branch from the tube of the short ambulacra: indeed, both may be considered
so, the anastomosis with the large lobe, as well as that with the mouth. But, in
the first case, the communication with the tube of the long ambulacra is more
indirect ; while the connection with the oral system is direct, through a tube which
only bends at right angles upon itself.

The large lobes and the auricles are not identical in their structure, though
homologous with one another. Each large lobe is formed of the actinal prolon-
gation of two united spheromeres, while each of the small lobes or auricles is an
actinal prolongation of a distinct spheromere. Moreover, the large lobes are bulky
and thick, consisting of a large mass of the same kind of large cells of which the
whole body is built; while the small lobes are simply membraneous, or rather
diverticula arising from a folding of the surface of the body at the lower extremity
of the short ambulacra, in the shape of flat sacs with hollow margins. They are,
indeed, a mere fold in the direct prolongation of the short ambulacra, along the
margin of which the ambulacral tubes and the locomotive flappers are continued
all round the lobe; when the fringes disappear and the tube alone is continued,
branching into the adjoiming large lobe, as well as towards the margin of the mouth.
We may therefore view the small lobes simply as modifications of the lateral
ambulacra, rising above the general surface of the body and bent inward in_ pro-
portion as the great transverse chasm which separates the two large lobes rises
higher along the sides of the mouth, thus leading to the formation of a loop in
the lateral ambulacra, instead of a straight course, as on the sides. The vibrating
fringes of the small lobes are in direct continuation of the locomotive gombs of
the ambulacra proper, which would appear as long on this side of the body, and
even longer, than upon the anterior and _ posterior spheromeres, if they were
stretched in the same manner; but, being here folded over in the shape of promi-
nent auricles, they act more energetically as lateral oars. There is, however, one
marked difference between the ambulacral rows of locomotive fringes and_ their
continuation along the margin of the auricles. As far as the locomotive flappers
follow a straight course along the vertical ambulacra, their combs are transverse
to the chymiferous tubes; but as soon as the tubes aiverge sideways to follow

the margin of the auricles, the locomotive flappers assume a longitudinal arrange-

raux” (the ambulacral tubes of the large lobes) nection between the ambulacral tubes of Pleuro-
with the “yaisseaux périgastriques inférieurs” (the brachia and its coeliac tubes (p. 357), which really

coeliac tubes). What I did not observe was a con- does not exist.

260 CTENOPHORA. Parr II.

ment, that is to say, they form a crest projecting outward along the tube. If
this view of the small lobes is correct, we may consider the vertical branch or
fork of the chymiferous tube, which extends beyond the auricles toward the corners
of the mouth, as the direct prolongation of the ambulacral tube proper, and the
fork which diverges into the large lobes as the anastomotic fork connecting the
ambulacral tubes all round the body. The horizontal branches along the sides of
the mouth should then be considered as the anastomotic branches between the
two lateral ambulacral tubes of each side, and thus the circle would be made
pertect.

With these facts respecting the structure of our Bolima before us, we are pre-
pared to take another and not less instructive view of its peculiar symmetry, which
may lead to a fuller insight into the characteristic features of Radiata. Not only
are the two anterior and the two posterior spheromeres different m their develop-
ment from the two lateral pairs, but they stand also in peculiar antitropic relations
to one another. In the first place, the large lobes, each considered as a whole,
are antitropic to one another, that is to say, they bend in opposite directions
toward the vertical axis; and every point of the symmetry presented in a lateral
view of the animal arises from this even balance of the anterior and_ posterior
parts of the body, as seen in Fi. 88. But each lobe again consists of antitropic
halves; or, in other words, the two spheromeres which form one lobe are as truly
antitropic to one another as the two lobes themselves, for the outlines of the lobes
as well as the course of their chymiferous tubes are evenly balanced, as Pg. 89
shows. The same is true of the lateral spheromeres: for here those of the same
side, as seen in Fig. 88, are antitropic to one another, not only in their general
outline, but more especially in the relative position and antagonistic movements
of the auricles; and yet these adjoining spheromeres do not form a pair together,
but stand again in antitropic relation to the lateral spheromeres of the opposite
side, as Mg. 90 may show. Such a symmetry exists nowhere among bilateral
animals, and appears to me one of the most striking peculiarities of the Radiates.
Again, the opposite poles of the vertical axis exhibit the most striking contrasts,
both in their differences and their antitropy, for the spheromeres converge as well
toward the actinal as toward the abactinal area, though the two are occupied
by different organs, or by identical parts unequally developed. A comparison of
Figs. 90 and 91 may show at a glance the correspondence and the difference.

There is a great interest connected with a further investigation of the vibrating
cilia of the small lobes, in comparison with the locomotive combs of the ambulacra.
The former being very similar to common vibratile cilia, and the latter forming
a more complicated system of locomotive organs, while both are morphologically

fully homologous, it follows, that, in a series of structural complications, the loco-

Cuap. III. GENUS BOLINA. 261

motive flappers of the Ctenophore, in which each fringe is a whole cell, do not
necessarily appear as a specific type of structure, but may constitute a natural link
between more complicated organs with distinct muscles and the simplest fringes
of structural cells. I entertain now so little doubt respecting such transitions, that
I have not hesitated, throughout this description, to consider the rows of vertical
locomotive fringes as true ambulacra; though there is as great a difference between
them and the ambulacra of Echinoderms, as there is between them and simple
vibratory cilia. We are, in fact, led to recognize, through the whole type of
Radiata, a natural gradation in the structure of the organs through which currents
of water are produced around the body, from the simplest combinations in Polypi
to the most complicated apparatus in Echinoderms. In Polypi we have only vibra-
tile cilia arismg from structural cells over extensive surfaces of the whole body,
while in Beroid Medusx there are, in addition to such cilia, peculiar rows of fringes,
made up of special cells, which move by their own contraction, and im Echinoderms
each fringe, in the shape of an independent ambulacral tube, assumes as great a
structural complication as the whole system in Acalephe. The ambulacral tubes
in Echinoderms generally, indeed, seem to me to bear the same relation to the
aquiferous system with its vesicles in Star-fishes, and to the true ambulacral gills
in Echini, as the fringes of the locomotive combs with their contractile base bear
to the ambulacral chymiferous tubes in Ctenophoree.

If, from this review of the superficial ramifications of the chymiferous tubes,
we proceed to an investigation of their connection with the internal stems and the
central cavity of the whole system, we find a very close resemblance in_ their
arrangement to what has already been noticed in the genus Pleurobrachia, — the
chief difference between the two genera consisting in the peculiar termination and
connections of these tubes in the lobes of Bolina. The centre of the chymiferous
system constitutes in Bolina, as in Pleurobrachia, a vertical hollow axis, extending
from the centre of the abactinal area to the abactinal opening of the digestive
cavity, upon the sides of which it gives off two coeliac tubes extending as far as
the mouth. These tubes, however, are not so wide as in Pleurobrachia, while the
digestive cavity itself is larger, extending nearer the central black speck; so that
the funnel, which branches toward the circumscribed area, as in Pleurobrachia, is
shorter, the main cavity from which the maim trunks to the ambulacra arise much
narrower, and the tubes extending toward the margin of the mouth along the
lateral walls of the digestive cavity in the same proportion longer. But the general
arrangement is identical. The differences exist only in the proportional development
of the different parts of the whole system, as also in the curve of the main trunks
of the ambulacral branches, which are more strongly bent upward, instead of

stretching horizontally across the body. Owing to the lesser development of the

262 CTENOPHORS. Part II.

central cavity of this system, and the difficulty of preserving these animals alive
after injecting colored liquid into the chymiferous sac, I have not succeeded in
discovering a regular alternation between the contractions of the right and left
sides of the system. It may be also, that, the transverse diameter being so much
shorter in this genus than in Pleurobrachia and the means of establishing a retro-
grade current from the periphery very extensive, the circulation takes place through
alternate dilatations and contractions of the whole body, causing an injection of
the fluid in all directions, rather than by an alternate passage from one side to
another; and, for various reasons based upon analogy, I incline to this view. In the
Discoid Meduse we have an absolutely radiating circulation, and a movement
simply to and fro from the centre to the periphery and back throughout the
whole system. In Pleurobrachia there is an alternation between right and left,
with a prominent circulation to and fro. In Bolina there is also a bilateral sym-
metry, but the radiating circulation seems to be recurring in itself through a com-
plete circle in the lobes and around the mouth, which arrangement would already
approximate the Beroid Medusxe of the genus Bolina to the type of Echinoderms,
though in a lower condition of the circulatory system.

Whatever may be the value of these suggestions, so much is plain, that the
digestive cavity constitutes a capacious sac with a longitudinal mouth, the fissure
of which opens in the same plane with the circumscribed area precisely as in
Pleurobrachia, in an oblong disk, extending with its longer diameter flat between
the anterior and posterior lobes (/%. 91). This disk is entirely surrounded by the
large lobes when they are shut, but it forms the lower outline of the body when
the lobes are entirely open and fully spread. In this attitude the mouth is shut,
but the lobes are wide open, to inclose any food that may come within reach;
and whilst dropping fragments of oysters upon them, as they are generally turned
mouth upward, in this extreme state of dilatation, I have sometimes seen the lobes
close upon such morsels to secure them, and afterward the mouth expand and
open within to swallow the food, the tentacles being alternately drawn out and
retracted.

The visible outline of the digestive cavity changes most remarkably in these
various operations. When the mouth is shut and the digestive cavity is empty,
the digestive sac is completely flattened and compressed in the direction of the
longer diameter, rising like a tapering funnel toward the central chymiferous cavity ;
that is to say, the folds of the digestive sae which are stretched between the
anterior and the posterior angles of the mouth converge towards the abactinal
extremity of the body, and the flattened walls are pressed upon each other. In
this position the celiac chymiferous tubes run in a straight course toward the

actinal pole along the middle of the outer surface of the digestive cavity, and reach,

Crap. II. GENUS BOLINA. 263

near the lateral margin of the mouth, the sac of the tentacles. But after food
has been swallowed, the mouth is contracted into a more sphincter-like shape, and
the digestive sac itself is so much narrowed immediately above its external opening,
that the digestive cavity appears like a loose bag suspended in a mass of trans-
parent jelly, widest about half its height, with prominent angles in advance and
backward, and also swollen laterally, but tapermg above and below. In such a
state the coeliac chymiferous tubes have a more curved, and even sinuous course,
upon the sides of the digestive cavity, in accordance with the position of the
morsels of food within, whilst the upper end of the digestive sac opens freely into
the central chymiferous cavity. Along the abactinal end of the digestive sac there
are, as in Pleurobrachia, marked vertical folds, of a brownish color, much darker
than the transparent walls of the other parts of the sac; but I have failed to
see distinctly the vibratory cilia of its abactinal opening, which play so conspicu-
ously about this region in Pleurobrachia, though there is also in Bolina a constant
movement of the minute particles of digested food about the aperture leading from
the digestive cavity into the chymiferous cavity.

As mentioned above, the central chymiferous cavity and its funnel are not only
shorter, but also narrower, in the genus Bolina, than in Pleurobrachia, and the
fibrous appearance of the cell walls of that region is very distinct. The actinal
part of this cavity has also a somewhat different form from that of Pleurobrachia,
though it exhibits the same general disposition, —its sides bulging simply outward,
instead of forming two distinct trunks for the branches to the ambulacral tubes,
as in Pleurobrachia. The four main branches, from which the eight ambulacral
tubes are derived, arise in pairs, almost directly from the main cavity, and, bending
slightly sideways, run almost parallel with one another in opposite directions, that
is, forward and backward. The ambulacral tubes themselves present a remarkable
arrangement: those of the lateral spheromeres bemg much further apart from one
another than the anterior or the corresponding posterior ones, and diverging side-
ways, while those of the anterior and posterior spheromeres follow a more direct
course forward and backward, owing, no doubt, to the lateral compression of the
body. And from the wide space between the two main branches of one side arise
the vertical tubes which descend along the digestive cavity toward the base of
the tentacles, as well as the tentacular tubes themselves, the coeliac tubes occu-
pying the proximal, and the tentacular tubes the distal side of the lateral inter-
ambulacra.

Again, the four main branches of ambulacral tubes, instead of stretching hori-
zontally toward the ambulacra, as in Pleurobrachia, are bent toward the abactinal
area, and then divide each into two branches, to provide the eight ambulacra with

as many vertical ambulacral tubes. The consequence of this arrangement is, that

264 CTENOPHORA. Part Il.

the impulse of the liquid pressed into the ambulacral tubes is chiefly in one
direction, the branches from the main cavity meeting the ambulacra near their
upper termination, and not at about half their height, as im Pleurobrachia. So
that the chief, and, I may say, almost the only constant current, is from the
abactinal side of the body toward the actinal region, along the sides, following
the ambulacra and all the sinuosities of their tubes in their lower course through
the great lobes, as well as through the lateral auricles; and a comparatively small
portion of fluid flows through the comparatively short abactinal end of the ambu-
lacral lobes toward the circumscribed area. The ambulacral tubes therefore are
not the direct prolongation of the eight forks of the main branches of this system,
any more than in Pleurobrachia, but form an angle with these forks; and there
is an abactinal prolongation of the ambulacral tubes, as well as a main actinal
branch, above and below the insertion of the fork from the main trunks. I there-
fore question the accuracy of those illustrations of the ambulacral tubes which
represent them as the direct prolongation of the forks arising from the main trunks.’
The antagonism between the main currents is thus between the upper and the
lower side of the body, and by no means between the right and the left side, as in
Pleurobrachia. Whether, however, the retrograde current runs exclusively backward
through the same tubes in which it has moved onward, or whether the winding
course of the narrow tubes in the lobes constitutes a kind of capillary system,
through which the liquid may pass from one side of the ambulacral tubes imto
the other, I am unable to decide. But I cannot help thinking that this long,
winding course of the ambulacral tubes upon the inner surface of the large lobes
and along the margins of the auricles and of the mouth contributes to a more
extensive aeration of the chyme in circulation, than the straighter course in’ the
wider vessels of the whole system in Pleurobrachia. Perhaps the more active
alternate contractions in Pleurobrachia compensate, by their quicker movements, for
the absence of ramifications of the tubes which are so extensive in Bolina.

The tentacular tubes, which run parallel with and upon the sides of the coeliac
tubes, enlarge near the middle of the lateral margins of the mouth into a small,
bulb-like dilatation, from which a bunch of tentacles may be projected or retracted.
But this bulb is by no means so complicated as the tentacular sac of Pleuro-
brachia. There is no flat disk at the base of the tentacles, no deep socket into

' Comp. Mitne-Epwarps, Ann. Se. Nat. 2de papers differ from those of the genera I have ex-
sér. vol. 16, Pl. III. and 4e sér. vol. 7, Pl. XIV.; amined, in such a way as the figures suggest, this
Wirt, Hore tergestinw, Pl. I.; and GrGennavr, would constitute a remarkable, and to me unexpected,
Archiv fur Naturg. vol. 22, Pl. VII. Should the difference between them; but the letter-press gives

ambulacral tubes of the genera described in these no details upon this point.

Crap, III. GENUS BOLINA. 265

which the tentacles may be withdrawn, but simply two narrow tubes arising close
together from the main chymiferous cavity, a little outside of the tubes of the
digestive cavity, and following the course of the latter to the tentacular bulb. As,
on account of the lateral compression of the body, the tubes of the digestive cavity
and those of the tentacular bulb are brought into close proximity, they appear, at
first sight, to constitute a single cord on each side; but in reality that cord consists
of three tubes running in the same direction, which, being close together, are very
easily mistaken one for the other, and whose natural connections are still more
difficult to ascertain, as the bulb of the tentacle exactly covers the termination of
the tube resting immediately upon the digestive cavity and extending to the margin
of the mouth. But whenever, by an oblique movement of the margins of the mouth,
or by the dilatation of the digestive sac one way or the other, the coeliac tube
is moved out of its vertical course, the relative position of the bulb of the ten-
tacular tube with reference to the coeliac tube is changed, it may he seen how
the tube following the walls of the digestive cavity divides into two horizontal
branches, extending in opposite directions along the lateral margins of the mouth,
forward and backward, at right angles with the tube from which they arise. As
these branches meet the actinal prolongations of the lateral ambulacra, a direct
communication is established between the peripheric course of the ambulacral tubes
and the main chymiferous cavity, and this anastomosis very likely gives passage
to so much of the circulating fluid as does not return through the same tubes
through which it is propelled from the main trunks of the chymiferous system.
As for the two small tubes which extend to the bulb of the tentacles, they arise
from the same lateral bulging of the main chymiferous cavity from which the lateral
tube of the stomach originates, but they arise more vertically.

The greater simplicity of the tentacular bulb of Bolina, when compared to the
large socket and complicated tentacular apparatus of Pleurobrachia, has reference,
no doubt, to the shortness of the tentacles, and to the circumstance that they are
not protruded to any length beyond the margin of the mouth, but simply extend
in a winding course forward and backward along that margin, forming, when con-
tracted, a compact bunch, and appearing, when expanded, like a disorderly brush
of irregularly curled threads tied together on one side.

The best attitude in which to study the ramifications of the coeliac tubes on
the side of the digestive cavity, or rather along the outer margin of the mouth,
and to ascertain their position with reference to the tentacular bulb, which lies
farther outward, is when the animal is turned mouth upward with its large lobes
fully expanded. The mouth then appears like a narrow rim in the centre of the
prominent gelatinous mass, encircled by large lobes, which constitutes a sort of
compressed isthmus trending backward and forward on the actinal side of the body,

VOL. Il. 34

°66 CTENOPHORA. Parr It.

and along the margin of which the horizontal tubes from the stomachal tube are
seen to extend as far as the outer margin of the lateral auricles, without entering
into direct communication with the tubes of the tentacular bulb. (See Plate VU.
Fig. 6 of my paper in the Memoirs of the American Academy.)

Parts of the walls of the cells surrounding the central chymiferous cavity, and
the main trunks which arise from it, are readily distinguished as fibres, which may
be seen to shorten or elongate, and enlarge or contract their cavity. The funnel
enlarges on the abactinal side of the body into two distinct branches, forming two
bulbs, as in Pleurobrachia, with oblique openings forward and backward, on the
sides of the circumscribed area, and with the black speck in the centre. This
black speck is covered by a transparent cap, like that of Pleurobrachia. What I
have formerly described as a ring, extending in the form of narrow tubes along
the margin of the circumscribed area, is nothing but the optical effect of the
thickening of the rising edge which encircles the abactinal area. As to the eight
narrow bands converging from the summit of the ambulacral combs and supposed
to be tubes emptying into this ring, I have ascertained that they are not hollow,
but, like similar bands in Pleurobrachia, the direct prolongation of the locomotive
flappers fading away as they converge toward the abactinal pole. Their relative
position, when converging toward the abactinal pole, differs considerably in the
different pairs, the two anterior and the two posterior ones being very near
together, almost in the longitudinal axis of the body, while the two lateral pairs
are at least as far apart from each other as they are from the anterior and
the posterior pairs. The ambulacral tubes are not continuous under these eight
bands, and do not communicate here with the central chymiferous cavity; but they
communicate with it on the actinal side of the body through the tube encircling
the mouth, which directly anastomoses with the lateral ambulacral tubes and indi-
rectly with the anterior and the posterior ambulacral tubes, through the marginal
recurrent tube of the large lobes. The currents arising from the main chymiferous
cavity run therefore chiefly through the ambulacral tubes, from the abactinal toward
the actinal side of the spherosome, with a small eddy toward the circumscribed
area. In the prolongations of the anterior and posterior ambulacral tubes the currents
may run to and fro from the tube of one of the spheromeres to that of the
other, or directly back to the central cavity, or pass through the recurrent marginal
tubes of the lobes into the lateral tubes. In the prolongation of the lateral ambu-
lacral tubes the current may pass into the oral tube through the oral anastomoses,
or into the large lobes through their marginal tubes; but the current of the coeliac
tubes may also run from the main cavity to the sides of the mouth, and thence
through the oral anastomoses into the ambulacral tubes. In the tentacular tubes

Cuar. III. GENUS BOLINA. 267

the current is always to and fro, from the main cavity to the tentacular bulb
and back. These tubes do not anastomose with the tentacular tubes.

I have not succeeded in making out a distinct nervous system connected in
any way with the central tubercle, though numerous fibres diverging in all directions
may be seen in connection with the abactinal part of the funnel. But it has
always seemed to me that they were contractile fibres, or rather the fibre-like
angles of the motory cells, and not nervous threads, for they change their length,
and are by no means so symmetrically arranged as might be expected in the
nervous system of radiated animals, the disposition of which is known im some
of their types. This point, however, and the periphery of the mouth, are the
regions to which to look for it; but, notwithstanding all my efforts, I confess I
have failed in the search, and only noticed the walls of motory cells. I have
already expressed my opinion respecting the nature of the central black speck of
Pleurobrachia. This organ presents precisely the same appearance in Bolina, and
the same general relations with the surrounding parts.

The extraordinary transparency of the gelatinous mass, and the impossibility of
preserving the animal after death in a contracted state, forbid the prospect of ever
knowing fully the arrangement of the contractile fibres throughout the body, unless
we obtain great improvements in the construction of the microscope, enabling us
to examine bulky animals alive, and to bury the focus to any depth of the sub-
stance of their body without removing the superficial parts. As far as I have
been able to trace the structure of the spherosome of Bolina, the general arrange-
ment of its cells is to a great extent similar to that of Pleurobrachia. — The radi-
ating system of motory cells is unquestionably the most extensive, though the
interambulacral system is the most conspicuous. Parts of the walls of its cells are
easily seen as bunches of fibres converging toward the intervals of the successive
combs of locomotive flappers, and extending brush-like across the interambulacral
spaces, though diverging in each bundle. These fibres seem more powerful, and,
at all events, far more distinct, than the vertical fibres, which I have never been
able to trace in continuous rows.

Though I first obtained specimens of this species at short intervals through six
successive months, from December to June, I never succeeded in discovering the
sexual system, not even in the most rudimentary state, until I had an opportunity
of watching them uninterruptedly in the latter part of the summer and during
the autumn, when I found the ovaries and spermaries following the course of the
ambulacral tubes, as first noticed by Will, in Eucharis, and alternating with one another
in the eight interambulacra. The circumstance of my failing to trace the repro-
ductive system for so long a time, may show how great difficulties these investigations
are attended with, and how much remains to be done before the whole history

268 OTENOPHORG. Parr IL.

of these animals is satisfactorily made out. I shall describe their embryonic devel-
opment hereafter, in connection with that of Pleurobrachia and Idyia.

The extraordinary metamorphoses of certain Echinoderms, which the late J. Miiller
first observed, ought not to be neglected in connection with the study of the
Ctenophore ; for the remarkable resemblance between the singular transparent frame
which protects the growing embryo of some Star-fishes and Sea-urchins and the
body of Ctenophors Lobatse cannot be overlooked by an attentive observer, while
the fact that the parts of that external frame present numeric combinations which
are unusual among Echinoderms, but correspond to those of the Beroid Medusz,
will be an inducement to institute, at some future day, a close comparison between
their structure. The ciliated appendages which hang downward in those larval
Echinoderms closely resemble the vertical rows of locomotive flappers with their
chymiferous tubes, as observed in Beroid Meduse. And it is interesting to find,
that in Echinoderms there is a metamorphosis gomg on in the embryo, recalling
the structure of the class of Acalephs in a manner very similar to the analogy
which exists between the embryos of the Acalephs and the Polyps. For whether
we compare the Strobila in its earliest conditions, or the young buds of Hydroids
from which Meduse arise, the analogy of these earliest states of development of
the Acalephs with Polyps is unmistakable; and I have no doubt that the external
frame of the young Echinoderms, which Miiller has so beautifully illustrated, will
be found to bear the closest resemblance to the structure of the Ctenophors, as
soon as an actual comparison can be instituted with reference to the homology of
their structure. But it is hardly possible to make such comparisons from descriptions
and figures, however accurate these may be; and Miiller’s attention seems not to
have been attracted by this remarkable resemblance, otherwise he could not have
failed to allude to their typical identity while describing those embryos. So much,
however, may already be stated, that the general arrangement of the ciliated lobes
of the Pluteus corresponds to the ambulacral rows of the Ctenophore, and that
the tubes which accompany them compare closely with the chymiferous tubes of
the Acalephs; but notwithstanding my constant efforts im studying the embryology
of a number of Echinoderms, I have, up to this time, been able to observe the
growth of such species only as follow the peculiar mode of development first
described by Sars.

Bowtva vitrea Ay. is a second species, of which I have seen only a few specimens,
at Key West, in Florida. It is easily distinguished from Bolina alata by its more
elongated vertical diameter and the narrowness of the locomotive flappers. Its
substance is so transparent that it is difficult to follow its movements, even in the
clearest glass jars with the purest water; for its ambulacra are scarcely visible as

grayish bands upon the sides of the spherosome, and, though iridescent, the play

Cuap. II. GENUS BOLINA. 269

of colors is so faint as scarcely to be noticed. I have not been able to make
a thorough study of this species, and therefore limit myself to calling the attention
of naturalists to its occurrence on Rigi 92.

ig the shores of the coral reef of Flor-
ida. Fig. 93 gives an outlme view

of this species; and a comparison with
Fig. 94, which represents the northern
\he Bolina alata in the same _ position,
oe may show their specific difference.

nv ; Myemopsis Garpent dg. While

BoLinA ALATA, Ag.
(Seen from the broad side.)

Ve : BOLINA VITREA, Ag.
residing upon Sullivan’s Island, near e @ tong ambutacra.—n & short

ambulacra. —f funnel, — d diges-

a and f Long rows of locomotive flappers.— Qharleston, South Carolina, I occasion- tive cavity.—¢ tentacular tube.

gandh Short rows of locomotive flappers. —y1 x8 auricles. ee anton

=a Central black speck (eye-speck)— ally caught, during the winter, about and posterior tobes. — At tenta-

i to m Triangular digestive cavity.—7 too se

Funnel-like prolongation of the maineay- the breakwater near the Fort, speci-
ity.—v Chymiferous tube of the tenta-

_ cular apparatus.—mm ‘Tentacular appa- meng of a species of Acaleph somewhat resembling Bolina,

ratus on the side of the mouth. —rr Ear-

like lobes, or auricles, in the prolongation yt evidently constituting a distinct genus, which I pro-

of the short rows of locomotive flappers.

— tt Prolongation of the vertical chymife- ose to call Mwemiopsis, on account of its still greater

rous tubes. —2 2 The same tubes turning

upwards. —zz Bend of the same tubes. resemblance to Mnemia. It is at once distinguished by

—zz Extremity of the same tubes meet-

Fe aoe: eo tatnth toe the deep furrow separating the anterior and posterior
Sad baer, lobes from the lateral spheromeres, a character by which
the Bolinide are readily separated from the Mnemiide proper. The generic pecu-
liarity of Mnemiopsis consists in the great development of the auricles, and in the
prolongation of the locomotive flappers to the actinal margin of the large lobes, so
that the rows of locomotive combs are visible from the actinal side, as well as
from the abactinal side, of the body.
Figs. 95 and 96 represent, in the size of
life, the only species I know of this
genus. I have called it MvNemtopsis

GarpeNt in memory of Dr. Garden, a

distinguished naturalist of Charleston, con-

temporary of Linnzus and friend and

Mnemiorsis GARDENI, Ag. MNemtopsis GARDENI, Ag.

correspondent of the great Swedish natu-

ET long ambulacra.—21 18 short o mouth, — Al h2 tentacles. —/1 18,
i lateral ambulacra. — 7° y!,

ambulacra.—f funnel, —a folds 1 gC] is ]
AN ries Sst ea ralist, to whom science is indebted for 4s 1 sutictes.—11 anterior and

of the digestive cayity.—d di- ior lob 1278, [7 1G i
gestive cavity.— ¢ tentacular tube. fr ce aoa Ah oa
the knowledge of the large number of ina posterior ambulnera.

—Id tentacle.— y1 78 auricles. —

2 anterior and: posterfonjobes, the North American animals enumerated

in the “Systema Nature.’ This species is very transparent, hyaline, of a milkish
white tint, with grayish ambulacra, faintly iridescent. Whether it is identical with
the species mentioned by McCrady as Bolina littoral’s or not, I have at present no

means of ascertaining.

bo
=]
roma)

CTENOPHORZE. Part IL

SHOT ay rr.

THE GENUS IDYIA AND OTHER TRUE BEROIDS.

I find it very difficult to trace the natural limits of the genera belonging to
the family of the Beroid proper. With the exception of Milne-Edwards’s illus-
trations of Beroe Forskali, all the descriptions and figures of these animals are so
imperfect that they afford very indifferent means of comparison; and the circumstance
that it is absolutely impossible to preserve specimens of these Acalephs for pro-
longed examination after their death, necessarily limits all comparative investigations
within very narrow bounds. There is another obstacle to a thorough revision of
the family, arising from the fact that most species known have only been observed
for a short time, and therefore only in one condition of their natural development.
Availing myself of the opportunities I have had of studying for the last three
years one species of this family in every stage of growth, I am able to state
positively that the genus Medea is founded on the peculiarities of the young before
they have reached half their size. Several naturalists have already suspected that
the genus Medea could not be retained, and that it was based upon the exami-
nation of immature specimens. I am able to state with confidence that this is
really the case. The genus Medea is characterized by the shortness of its rows
of locomotive flappers, which do not extend more than half way from the abactinal
side toward the mouth, while in the genus Beroe the ambulacral rows are said to
extend all the way to near the margin of the mouth. Now it may be seen (PI. I),
that, in the smaller specimens of the Idyia of our shore (/¥%y. 6), the rows of loco-
motive flappers approach less closely to the margin of the mouth in proportion as
the specimens are younger; and that, while in the largest (fs. 1 and 2) they
extend comparatively much nearer to the edge of the mouth, in the smallest they
are so limited as already to answer to the generic character of Medea. I may add,
that, in still younger specimens, the difference is even greater. Indeed, in very
young specimens, almost too small to be detected by the naked eye, the locomotive
flappers are so little developed as to occupy, on the abactinal side of the body, only
one third of its height. There can be no doubt, therefore, that the extent of the
rows of locomotive flappers does not constitute a generic character among the Beroids
proper, without the special qualification that their extent is increasing with age.
Eschscholtz mentions the great length of the cilia as another generic character of
Medea; but this also is only a peculiarity of the earlier periods of growth, all Cte-
nophore when very young having their rows of locomotive flappers much further

Cap. IIL. GENUS IDYIA. 271

apart, in comparison to their size, than the adults, and the cilia themselves much
longer, and fewer in number, so that the motions of the young are much more
energetic, and quicker, than those of the adults. This will appear very natural,
when it is considered that the smaller individuals have the longer oars to move
with, and the older and bulkier individuals the shorter locomotive apparatus, ac-
cordmg to their size.

But though there are true Beroids in which the locomotive flappers are ever
enlarging with age in the direction of the mouth, there are others which, even
in their adult condition, have their rows of locomotive flappers limited to as short
a range as the young of the former, and, on account of some other peculiarities,
may be considered as a distinct genus. I shall take an opportunity hereafter to
describe the species of this type which I have observed. The genus Pandora Esch.
has such limited rows of locomotive flappers; but it differs further in having the
abactinal part of the spherosome broader and more rounded, the vertical axis
shorter than any of the other true Beroids, and the interambulacra so much devel-
oped, as, in their contraction, to overlap the locomotive flappers. As for the genus
described by Lesson under the name of Cydalisia, I agree with Gegenbaur that it
is founded upon characters which have no generic value, and yet I am not inclined
to go as far as he does, in uniting all true Beroids in one single genus; for on
comparing the descriptions and figures published by Milne-Edwards of Beroe Forskili,
I find that the species of our coast never assumes that sugar-loaf form which Milne-
Edwards represents, but exhibits always rounded outlines on its abactinal side.
There must, therefore, be some marked structural difference in the abactinal area
of our species and that of the Mediterranean. Accordingly, instead of uniting into
one genus all the Beroids which in their adult state have rows of locomotive flap-
pers extending to near the margin of the mouth, I would retain the distinction
hitherto made between Beroe proper and Idyia, and+refer to the genus Beroe those
species which resemble the Beroe Forskali, and to the genus Idyia those which
resemble the Beroe Cucumis of Sars and the species of our coast.

Thus circumscribed, the genus Idyia may be characterized by the inequality of
its anterior and posterior spheromeres, compared to the lateral ones; and though
this mequality is but slight, it is no doubt sufficient to prevent the abactinal side
of the body from being raised into a projecting cone. The structure is this. On
their abactinal side the lateral spheromeres are bulging while they converge towards
the central eye-speck, whereas the anterior and the posterior spheromeres curve
evenly towards the same point. The consequence of this inequality is, that, how-
ever much the centre itself may be projected, the anterior and the posterior
spheromeres act as bridles upon the lateral ones to prevent the centre from rising
into the shape of a cone; while in a state of comparative rest, the abactinal area

279, CTENOPHORE. Parr II,

is depressed in the direction of the circumscribed area, and the lateral spheromeres
slightly project upon its sides. I infer that the possibility of protruding uniformly
the abactinal end of the body, in Beroe Forskali, may depend upon an even
development of the eight spheromeres on their abactinal side. If this be so, the
generic separation of these two animals and their allied species is fully justified.
There is another peculiarity which coincides with this difference in form. In Idyia
the circumscribed area is very much elongated, and its margin adorned with a row
of fringes, diverging forward and backward, and rounded off at its anterior and
posterior extremities; while in Beroe proper the fringes encircling the circumscribed
area give it a lanceolate form. Had these characters been observed only in two
species, they might be considered as specific differences; but all the conical Beroids
thus far figured by Mertens and Lesson agree in every respect with that so beauti-
fully illustrated by Milne-Edwards, as closely as those with the dome-shaped outline,
figured by Péron, Chamisso, and Sars, resemble that which I have examined. And
though the repetition of the same character in several species is not in itself a
generic distinction, it is generally a good indication, that such species, having closer
affinities, may also present true generic peculiarities not yet observed. As I never
had an opportunity of examining a conical species of Beroid, it is impossible for
me to give a more direct account of the generic differences of the members of
this family. I will therefore only say in conclusion, that, taking Beroe Forskali
as the type of Beroe proper, I would refer to it also Beroe mitreformis of Lesson,
the type of his genus Cydalisia, and Mertens’s Beroe penicillata; and, takimg the
species of our coast as the type of the genus Idyia, I would refer to it the oldest
species for which it was instituted, and Beroe cucumis of Sars, Beroe macrostomus
of Péron, Beroe capensis of Chamisso, and a new species discovered by my son
Alexander Agassiz in the Gulf of Georgia.

For our species I propose the name of Ipyia Roszova. This is the species
alluded to in my paper on Beroid Meduse in the Memoirs of the American Academy,
which, at the time of its publication, I knew too imperfectly to describe. In the
year 1858 it appeared in such quantities upon our coast during the whole summer,
that at times it would tinge with its delicate rosy hue extensive patches of the
surface of the sea during the warmest hours of the day. It made its first
appearance early in July, when all the specimens were of a small size, rarely
exceeding an inch or an inch and a half But it grew rapidly larger and larger,
and towards the end of August most of them had reached the size of from three to
four inches in vertical height, and about half that size in width, while many had
twice these dimensions. At this period they were brightest and deepest in their
coloration, the darker colored ovaries, and especially the deep pink colored spermaries,

adding to the intensity of their hues. But as the spawning season advanced, and

Crap. III. GENUS IDYIA. 273

the contents of these organs were emptied, they grew again paler and paler, and, after
the eggs and spermatic particles had been entirely discharged, the spherosome itself
faded and assumed a livid, pale, grayish color, only a slight tinge of pink remaining.
The first September storms broke them all to pieces, and nothing could be found
afterwards but floating fragments. This year I have found them again in great
abundance, and, as before, they made their first appearance early in July. Several
years ago, in 1852, I had also an opportunity of seeing large numbers of them
in the harbor of Provincetown on Cape Cod, in the month of August. They had
reached about half the size of those seen later, and had probably made their
appearance not long before. Afterwards I traced them as far north as the Bay
of Fundy, always larger in proportion as the season advanced. But I have never
seen them during the winter or in early spring. <A careful search, however, made
this year by my son, from the beginning of August to the first week of September,
led him to the discovery of a large number of young, barely visible to the naked
eye. They grew gradually larger; but after the first September gale the young
disappeared with the adult, which, as I have already stated, break into fragments
in our heavy September storms. The young, of course, must survive; and the ques-
tion arises, what becomes of them during their temporary disappearance, on the
approach of the winter, until the followmg summer? I can find only one explanation
for this phenomenon, suggested by the habits of the adult.

I have already stated, that in the summer months our pretty Idyia appears in
great quantities at the surface of the water during the hottest hours of the day.
In the morning and evening they are not visible, but as the sun rises above the
horizon they may be seen deep below the surface, betrayed by the iridescent
colors of their locomotive flappers, and slowly ascending until about ten o’clock,
when they are fully in sight near the surface, where they appear in all their
beauty. It is thus evident, that these animals may, under different circumstances,
voluntarily rise to the surface of the water or dive into the deep; and the nature
of the circumstances so influencing them is plainly indicated, not only by the fact
that the warmest hours of the day bring them to the surface, but also by the
fact, ascertained with equal certainty, that the slightest ripple upon the surface,
hardly producing perceptible agitation of the water, is sufficient to cause their instan-
taneous disappearance, and that they remain out of sight for days in succession when
the sky is overcast or the weather chilly. What can be more natural therefore
than to assume, that the adult Idyias, having performed their part in life, break
up under the influence of the waning summer; while, during the whole winter, the
young do what their parents have been doing at intervals during the summer, that
is, subside into deep waters, to reappear only with the more genial season, when
they complete their growth, reproduce their kind, and die in their turn.

VOL. IIL. 35

274 CTENOPHORZ. Part II.

Though our Idyia is slow in its locomotion, its movements are particularly
eraceful. Its most common attitude is horizontal; that is to say, the main or
vertical axis is generally maintained in a horizontal position, or rather slightly
inclined, so that the actinal pole, which moves forward, stands higher than the
abactinal, which is turned backward. In this respect Idyia coincides with Pleuro-
brachia, which also moves with the actinal pole forward; but, in its most common
attitude, Pleurobrachia stands with its vertical diameter upright. Again: Idyia, while
moving horizontally, keeps almost uniformly upon its broad side, and may readily
‘aise its actinal end, with the mouth gaping and ready to seize its prey, as in
Pl. I. Fig. 8, the flatness of the body facilitating the changes of its attitude. Occa-
sionally it turns, with one or the other side rising; but I have never seen Idyia
revolving upon itself around its vertical axis, as Pleurobrachia constantly does, and
only now and then does it make somersaults, turning upon its vertical axis in the
direction of the broader plane. It should further be remarked, that the older the
specimens grow, and the larger they are, the more sluggish become their movements.
The young are far more active, and the smallest of them are comparatively quick ;
but the motion is always a gliding one, long continued in the same direction, with
the body stretched to its full length. Only now and then a powerful contraction
may be noticed, durmg which the animal reduces its greatest diameter by at least
one third, and, as the spherosome is extremely flexible, it then assumes very varied
forms, according to the condition of the digestive cavity. When this is empty, the
actinal end may even be turned inside durmg such contractions (J%gs. 5 and 5*) ;
the vertical diameter is then reduced by about one half, and the outline becomes
almost circular (/%. 5"). When the contraction is one-sided, the body curves in
various directions. The mouth also may spread or contract, so as to assume the
most different outlines: at times gaping widely (/%g. 1), at other times contracting
in the centre with the opposite ends wide open (/%¥%y. 9), or bending sideways (/%g. 2°),
or closmg up in a straight line (F¥y. 4), or even shutting by the inversion of its
edges (Fig. 14). When the digestive cavity is gorged with food (/%. 10), the body
may be distended in any direction and assume the most irregular shapes.

Our Idyia is very voracious, and feeds chiefly on other Ctenophore. Whenever
I have kept Bolinas and Pleurobrachias in the same vessel with it, they rapidly
disappeared, being generally swallowed entire. In the attempt to seize upon its
prey, Idyia readily changes the direction of its motion, but always keeps the mouth
forward toward its prey, gaping widely as in F%y. 1, and when close upon it turning
the edges of the mouth still further outward. A small Pleurobrachia or a small
Bolina would frequently pass into its wide digestive sac without any other effort
on the part of the Idyia than that of shutting its mouth. But when its prey
is larger, perhaps nearly of its own size, our Idyia may be seen distending its

Cuap. III. GENUS IDYIA. 275

mouth to the utmost, and working its prey down into the digestive cavity by
repeated contractions, slowly overlapping with the edge of the mouth more and
more of the large morsel it is attempting to swallow, until it is finally engulfed.
Fig. 10 represents an Idyia immediately after it had swallowed a Bolina nearly as large
ast itself, the outlines of which may be seen in its distended cavity, in a position
transverse to the vertical diameter of its own body. If the animal seized upon
is too large to be swallowed entire, after forcing into its digestive cavity what is suf
ficient to fill it, our Idyia will, by powerful contractions of the margins of the mouth,
cut off the parts which cannot be swallowed. I have once seen an Idyia, of about
the size of that of Mg. 7, seize upon a Bolina nearly double its own size, and,
after working the abactinal part of the Bolina into its digestive cavity, cut off in
that way about two thirds of the actinal side of the Bolina and let it drop. This
operation lasted for about an hour; and while portions of the swallowed body showed
signs of life in the contraction of the locomotive flappers during three quarters of
an hour, the process of digestion was nevertheless going on so fast, that, after an
hour and a half, fragments of the indigestible parts, such as the locomotive flappers,
began to be discharged through the mouth. In four hours, the whole portion
introduced into the digestive cavity had disappeared from it, the more fibrous cell
walls and the locomotive flappers bemg thrown out through the mouth and the
more fluid portions passing into the chymiferous system, so that the main chy-
miferous cavity and all the chymiferous tubes were distended to the utmost, and
the fluid contained in them was moving rapidly up and down through the ambu-
lacral tubes into the oral tube and back through the coeliac tubes. Shortly
afterward the two coeliac apertures opened successively and discharged some more
of the indigestible matter, and the animal seemed as empty as before, with this
difference only, that the interambulacral zones, which, when the animal has been
fasting, are depressed, and the digestive cavity itself very much flattened, were now
distended and presented a rounded outline, as in Fy. 3. On another occasion I
noticed a large Idyia swallowing a whole Bolina of sufficient size to fill its cavity ;
and yet, after five hours, no trace of the prey could be observed within it.
From the preceding remarks it may be inferred how difficult it is accurately
to describe these animals without prolonged study, under the different circumstances
which may modify their appearance. But after collecting many hundreds and
keeping them together for weeks at different periods of their growth, in a large
tank well supplied with food, I may well say, that the different illustrations pub-
lished of allied animals observed in other parts of the world, though showing the
existence of the genus Idyia in all seas, do not yet furnish us with the means
of distinguishing the species inhabiting different zoological provinces with sufficient
precision. For not only do the young differ from the adult in the manner already

276 CTENOPHORZ. Part I.

mentioned, the rows of locomotive flappers extending only over a limited part of
their surface (/¥y. 6 and magnified F%g. 6"), but they are also more rounded, the
sides not being so flattened as in the adults. Moreover, the flappers in each row
are fewer, and, comparatively to the size of the body, much longer, than in the
adults, and the rows themselves much further apart. The chymiferous tubes, which
penetrate like a network through the whole thickness of the spherosome, are also
much fewer and much less branching in the young than in the adult. Again, before
the spawning season approaches, the color over the whole surface is more uniform
and paler, as in Figs. 7 and 8, the ovaries and spermaries being not yet visible ;
while in the adult (gs. 1, 2, and 3), they appear as bright rows of branching
sacs on the sides of the ambulacral tubes. The arrangement of these organs is
so peculiar that it increases the differences resulting already from the inequality
of the spheromeres, the ovaries forming broader sacs, of a paler color than the
spermaries, which are accompanied by more intensely tinged pigment cells. And
then, owing to the fact that alternate interambulacral zones are occupied by ovaries
and spermaries, each ambulacrum has ovaries on one and spermaries on the other
side of its ambulacral tube, so that, though each ambulacrum is more brightly colored
than the intervening space, it is paler on one side than on the other, the pale
sides, occupied by the ovaries, being always turned toward each other, as are the
bright sides also, which are occupied by the spermaries (/7gs. 1, 2, and 3). But
none of these differences are visible in early life. Again, when well fed the outlines
are rounded (Fig. 3); but after fasting the imterambulacral zones subside and the
ambulacral zones become prominent (/7%gs. 1 and 2).

In the plates representing Idyia roseola I have attempted to reproduce the
appearance of all the parts of the animal as nearly as possible like life, and have
been assisted in this attempt beyond my expectation by the skill of Mr. Sonrel.
But so delicate is the substance of this animal, and so slight are the outlines of
its different parts when seen through the thickness of the spherosome, that they
could only be faintly represented, in order not to exaggerate their natural appear-
ance. Upon careful examination of the figures of Plates I. and II. it may, however,
be found, that, faint as they are, the outlines of all the organs are correctly rendered.
Yet, to obviate the difficulty that may arise in comparmg the descriptions with
these plates, I have had wood-cuts made of the most characteristic details of the
structure, corresponding to the colored plates and explanatory of them. F%y. 10
of Pl. Il. is the only one in which the structural details are reproduced with a
dark tint which they never had in nature. As already stated when characterizing
the family of the Beroids proper, our Idyia has the spherosome of a very uniform
thickness, though the spheromeres are not perfectly equal in their size. The anterior
and the posterior pairs are somewhat nearer to one another, and their lateral

Cuae. II. GENUS IDYIA. 277

interambulacral expansion is somewhat wider, in consequence of which the outline
of the animal appears oval, the sides being more or less flattened.

The cellular structure of the spherosome is easily seen, and, by following the
fibre-like outlines of their angles, the arrangement of the cells may be traced without
much difficulty. It is much more simple and uniform than in either Pleuro-
brachia or Bolina, and, owing to the total absence of tentacles and tentacular tubes,
no trace of the complicated arrangement of motory cells, which in Pleurobrachia
constitute the lateral system, is visible. The radiating system is most prominent,
and, in fact, forms the chief bulk of the body. Its general arrangement is that
described in Pleurobrachia, with this difference however, that, owing to the much
greater elongation of the vertical diameter of the body, the cells of which it is
composed form long rows parallel to one another, converging only toward the
abactinal pole, but remaining straight on the actinal side. The interambulacral
system is the least developed, and, far from forming the doubly convex vertical bands
of transverse cells which we have seen in Pleurobrachia, it consists only of a few
cells extending between the ambulacra. Hence the marked difference from Pleuro-
brachia in the outline of the body when seen from either the actinal or abactinal
side, the surface of the interambulacra appearing concave (F%y. 99, p. 283), unless
the body be fully distended, while the ambulacra are raised above the general level
of the surface. In Pleurobrachia the reverse is the case, in consequence of the great
development of the interambulacral system. But this contrast between the inter-
ambulacra and the ambulacra is only striking along the sides, for toward the
abactinal pole, and especially beyond the extent of the rows of locomotive flappers,
the peripheric system is interwoven with the radiating system, very much as in
Pleurobrachia, and the surface of that region of the body is more even. The
lateral interambulacra, however, are here somewhat prominent, bulging above the
level of the ambulacra about as much as in Pleurobrachia. On the actinal side and
beyond the extent of the rows of locomotive flappers, the peripheric system is again
interwoven with the radiating system and powerfully developed; and, as the sphero-
meres do not converge and are not arched on the actinal pole, but extend in
a straight course to the edge of the mouth, this part of the body is capable of
the most varied and extensive motions. Notwithstanding the prominence of the
ambulacra, the ambulacral system of motory cells is not more developed than in
Pleurobrachia.

These structural details may explain the characteristic movements of Idyia. The
weakness of the interambulacral system forbids a close approximation of the ambu-
lacra, so that the vertical diameter is not reduced by its contractions, but by the
contractions of the radiating system, which may go so far as to bend the actinal
side of the body inward and reduce the length of the animal in a most remarkable

278 CTENOPHORE. . Parr IT.

way, as already mentioned. Again, the great strength of the oral system determines
the very extensive and powerful contractions of the mouth, and, no doubt, is most
active when these animals divide too large a prey.

The slight difference already noticed in the development of the spheromeres is
also observable in the extent of the rows of locomotive flappers, and though all
terminate at a considerable distance from the abactinal pole, the lateral pairs
approach it a little more than the anterior and the posterior pairs; so that the
figure circumscribed by their abactinal termination coincides with the outline of the
body as seen from that side (J%. 5), and overlaps but little the outlmes of the
digestive cavity as it appears in the same view. On the actinal side the eight
rows terminate at the same height, taperimg and narrowing gradually as they
approach the mouth, and extending nearer to it in proportion as the animal is
older. In the largest, the space on the actinal side not occupied by the loco-
motive flappers is about one sixth of the vertical diameter, and, in young specimens,
about one half. In the smallest specimens that may be seen with the naked eye
the locomotive flappers do not occupy one third of the height. As the animal
crows larger, the rows of locomotive flappers not only extend farther and farther
toward the mouth, but the ambulacral zones become also more prominent and more
distinct, not only owing to the growth of the ovaries and spermaries, but also in
consequence of the appearance of a larger and larger number of pigment cells in
the epidermal layer. At first these are few, far apart, and rounded in form; but
eradually they become more numerous, acquire the stellate or branching, and
sometimes highly ramified, appearance (Pl. UL. Fy. 17) characteristic of ordinary
pigment cells, varying in color as well as in form. In younger specimens these
cells are of a pale yellowish tint, but become more rosy afterward, and those of
the adult assume gradually a deeper pink. Now such cells are clustered in larger
number upon the spermaries, where they have the deepest color, and, as they
extend beyond the locomotive flappers (Pl. Il. /y. 17), seem to reach the very
margin of the mouth (Pl. Il. Figs. 1, 2, 4, and 9).

As in all Ctenophore, the locomotive flappers consist of combs arranged in rows
along the ambulacral tubes; but what is peculiar in the genus Idyia is, that the
combs taper very suddenly toward the abactinal pole (Pl. Il. Figs. 14 and 18),
while on the actinal side they narrow very gradually, and disappear so insensibly
as to be lost like a thread among the pigment cells (Pl. Hl. fv. 17). Owing to
the steady and slow motion of this animal, it affords the best opportunity to watch
the play of the flappers. It may be seen, in Figs. 1, 2, and 5 of Pl. I, that the
locomotive flappers project beyond the general surface of the spherosome, and also
that the waves formed by the flappers along one and the same row when they
move successively may be quite distinct (4%. 1), while at other times they seem

Cuar. III. GENUS IDYIA. 979

to move all together (Jy. 2). The appearance of the flappers themselves when
in different states of expansion and contraction also varies greatly, and hence the
different aspects of Figs. 1 and 2 in Pl. I. and Pl. IL, though they represent identical
attitudes, Fig. 1 of Pl. I. corresponding to My. 2 of Pl. IL, and Fig. 1 of Pl. IL
to Fig. 2 of Pl. I. Magnified figures (Pl. Il. Figs. 4, 5, 11, 12, 18, 14, 15, 16, 17,
and 18) illustrate these differences still more clearly. In a state of rest, or during
slow progression, the combs have their cilia nearly straight (/%. 11), and bent
toward the actinal side of the body. When raised into action they curve, gently
if the motion is moderate (/¥%gs. 13 and 15), and more strongly if the action is
more energetic (Figs. 12 and 16).

The relations of the locomotive flappers to the ambulacral tubes and to the
ovaries and spermaries are more easily traced in our Idyia than in any other
Ctenophore I have seen. Facing the surface (Pl I. Fig. 5 and Pl. II. Fy. 4),
nothing can be more evident than that the pouches on the two sides of the ambu-
lacra are not identical, and also that identical pouches are never on the same side
of adjoiming ambulacral tubes; for pale pouches face another in Fig. 4, and both are
ovarian sacs, while those on the other side of the ambulacral tube, the spermatic
pouches, are almost entirely concealed by the crowded deep pink pigment cells.
Now the same parts seen in profile (Pl. I. Ag. 15) show the undeveloped sexual
pouches to be diverticula of the ambulacral tubes, which retain the same relations
to the chymiferous tubes and the locomotive flappers after they have completed their
growth and are full either of spermatic particles (f%. 11) or of eggs (My. 16).
This close connection of the sexual organs with the ambulacral tubes and the loco-
motive flappers is one of the most interesting features of the structure of the
Ctenophore, because, in my opinion, it shows the close homology which this appa-
ratus presents with the ambulacral system of Echinoderms, and especially with that
of the Crinoids with their ege-bearing pinnulz upon the sides of the ambulacral rows.

There is hardly any thing among Acalephs equal in beauty to the iridescence
of the locomotive flappers of our Idyia, playing with all the colors of the rainbow
between the rosy edges of its ambulacral zones. Beyond the rows of locomotive
flappers on the abactinal side, eight narrow bands (/¥y. 3) may also be seen
extending to the base of the central eye-speck. These bands consist of slight,
immovable projections accompanied by pigment cells. Those extending from the
anterior and posterior pairs converge toward the sides of the circumscribed area,
which they follow to the eye-speck, while the lateral ones extend straight to the
same point. The course of these bands to the very base of the central eye-speck
is well shown in our Idyia (Pl. IL Figs. 3, 8, 9, and 18), and more easily traced
than in Pleurobrachia and Bolina.

The circumscribed area forms a prominent feature of the abactinal pole, bemg

280 CTENOPHORA. Part IT.

circumscribed by upright branching fringes dotted with many pigment cells (PL L
Fig. 3; Pl. Il. Figs. 3, 7, 8, 9, and 18). In Fig. 3 of Pl. I. they are represented from
above, so that the form of the space they circumscribe is best seen in such a view.
The circumscribed area consists, properly speaking, of two oblong, pear-shaped spaces,
tapering toward the central eye-speck, and widening forward and backward where
their outlines are rounded off In Fig. 3 of Pl. IL. their termination near the eye-
speck is represented in a magnified view in the same position as in My. 3 of
Pl. I. Fig. 9 of Pl. II. represents one of these spaces in an oblique side view,
while Figs. 8 and 18 represent them in perfect profile from the side, so that their
height above the spherosome is plainly visible, the two halves being separated by
the eye-speck and its transparent cap. On the side of each of these spaces, about
mid-length but somewhat nearer to the eye-speck than to their rounded extremities,
may be seen on opposite sides the coeliac openings (Pl. I. Fy. 3; Pl. IL Hy. 9).
Fig. 7 represents in an oblique view the bulging of the bulb through which these
apertures open. Nowhere among Ctenophore are these coeliac openings more easily
seen than in Idyia, and nowhere is the circumscribed area more distinct and more
prominent. I cannot, therefore, conceive how these animals can have been described
by earlier observers as perforated in the centre, unless they were satisfied with
the most superficial inspection of very much injured specimens.

Of all Ctenophore the Beroids proper have the largest digestive cavity, and
in the genus Idyia it seems to have the widest dimensions, judging from the illus-
trations of the Beroe punctata and Forskali published by Eschscholtz and Milne-
Edwards. That cavity begins with a wide mouth occupying the whole length of
the actinal side, where the walls of the spherosome are thinnest, and extends very
nearly to the abactinal pole. Its outline, as seen from the broad side of the body,
may faintly be traced, especially on the actinal side, through the transparent sphero-
some, in Pl. I. Migs. 2 and 7, and more distinctly in Fig. 10, Pl. IL, in which the
cavity is laid open; while in F%gs. 1 and 8 of Pl. I. the anterior or posterior ambu-
lacra are so projected upon it as to hide its outlines. In Js. 5 and 4 its outlmes
are faintly visible from the actinal and the abactinal side. In these specimens the
digestive cavity is gorged with chyme, so that the general outline of the body
is ovate, and the interambulacra are as turgescent as possible; but the figure is
not deformed by the presence of irregular pieces of food as in Fig. 10. In such
a condition it may be seen how uniform the thickness of the spherosome is in
every part of the body. In F%y. 10 the outline ‘of the digestive cavity may also
be seen distinctly on the actinal side of that specimen, where it is contracted above
the mouth, and beyond which it closes over the larger Bolina which fills it. It
thus appears, that while the digestive cavity is always wider in the direction of its
longitudinal diameter in consequence of its structure, its transverse diameter may

Cnap. III. GENUS IDYIA. 281

greatly vary when it is more or less distended (Figs. 5 and 4), but when it is
entirely empty and the interambulacra have subsided, its walls are pressed against
each other from the side. The whole surface of the digestive cavity is lined with
a very peculiar epithelium (PI. Il. Fy. 19), resembling somewhat a vibratile epi-
thelium, the cilia, however, being much stouter and blunter than those of ordmary
vibratile cells, and resembling somewhat the baculi of the retina. Between them
there are rows of branching pigment. cells.

The structure of the mouth still requires further vestigation. All my efforts
to make out the microscopic structure of its edge have thus far been unavailing.
From figures drawn in a natural size (Pl. I. Figs. 2° and 4, and Pl. II. Fig. 10), it
may be seen that the stout vibratile fringes lining the digestive’ cavity, and the
pigment cells intervening between them, are arranged near the edge of the mouth
in vertical rows, giving it a striate appearance (PI. I. Fug. 2°, and Pl. Il. Fig. 19
magnified). When the mouth gapes, the abrupt termination of these parts gives
it a well-defined outline, which may be waving as in Pl. I. Fy. 2%, or double §
shaped as in /¥%y. 9, or straight hy the apposition of the two sides when the mouth
is closed, as in My. 4. Outside of this well-marked edge and between it and the
circular oral tube (Js. 4 and 2") is a pale circle, the most movable and most
powerfully contractile part of the whole body. iy. 19 of Pl. UL. represents that
band magnified, in connection with the rows of vibratile cilia and pigment cells of
the digestive cavity on the right of the figure, and the superficial stellate pigment
cells scattered between the epithelial cells of the outer surface, on the left of the
figure. The band without pigment cells, to the left of number 19, corresponds to
the pale circle surrounding the mouth. It is evident, from the glimpses I could
obtain of this part under the microscope, that cells arranged concentrically form
the edge of the mouth, and that its striated appearance is
owing to the fibre-like aspect of the angles of these cells, over
which a thick epithelium without pigment cells reaches from the
outside to about as near the edge itself as the pigment cells
extend on the inner surface. It is with this sharp edge that

Idyia cuts its prey. While swimming in pursuit of it with

the: mouth gaping, the anterior and posterior interambulacra — Funnel, or central chymiferous
& cavity of

are so contracted as to appear more or less deeply emarginate, IpyIA ROSEOLA Ay.
v ' * a@ capsule of tk -speck. —) eye-
and the sides assume the form of two broad lips (Figs. 1 and 8). “Sih > tubercle of the eye-
speck. —f funnel. —71 ceeliac tube
upon the distended digestive cay-
oe ity. —7 ceeliac tube, supposing the
of this digestive cavity empty. —/1/* lat-

The chymiferous cavity (My. 97) is very short, though
wide ; indeed, much shorter than in any other type

eral chymiferous tubes. —/? 23 an-
terior chymiferous tubes. — d coe-
liac aperture.

order, and the digestive cavity opens into it through a long
fissure, which may gape and contract so as to render it very
difficult to trace its outlines, unless the whole chymiferous system be fully distended

VOL. IIL. 36

289 CTENOPHORA. Parr IL.

and the digestive cavity itself empty. Under such conditions and in a side view of
the animal (PL IL 7. 18 and Ly. 98), the origin of the two lateral ambulacral tubes
of one side and the anterior and posterior ambu-
lacral tubes of the same side may be distinctly
seen arismg from an ample common cavity, from
which arise also, between the lateral ambulacral
tubes, the still broader coeliac tube of that side, the

lumen of which, g, is projected like a round hole

Funnel and chymiferous tubes of upon the centre of the cavity. Above it, right and
IpyIA ROSEOLA Ag.

, left, are the two large forks of the funnel, rismg to
capsule of the eye-speck.— eye-speck.—ce cireum- ? 5 5

scribed area. —d coeliac aperture. —e tubercle of the the surface on the two sides of the eent ral eye-

eye-speck. —f f forks of the funnel. —g opening of the

creliae tube. —r cceliae tube itself. — 4h narrow pro- snecl and forming, when projecting outward, the

longations of the rows of locomotive flappers. —/7 2 an- o?

terior and posterior ambulacral tubes with the flappersof — Jypogylap pao -epres y J iy WA This g
&.—I82 lateral ambulacral tubes with their flappers. irregular bag repr esented mm Ly. ‘. Ss same

¢

“Pt internal ramifications of the amibdlocral tobes. annaratuiswmay also.) be, .S6en IM) Ags... and ae at
Pl I. In Fy. 3, the outline of the whole system may distinctly be traced in faint
outlines, from the abactinal pole, the eight chymiferous tubes nearly following the
outlines of the narrow bands in the prolongation of the rows of locomotive flappers,
and the coeliac tubes running between the lateral ambulacra and projecting beyond
the outlines of the digestive cavity.

All these tubes follow the course of the ambulacra, from the central chymiferous
cavity to the margin of the mouth, where they open into a wide, circular tube
encircling the mouth. The tubes are very wide, and their diameter uniform for
their whole length. They may best be seen, and their connection with the oral
tube is most distinct, in younger specimens (/%y. 6° magnified and ‘yg. 7), in which
the rows of locomotive flappers do not cover them. They are also distinctly seen
in views from the actinal side (Figs. 4, 9, and 2°), in which the oral tube encircling
the mouth is seen to anastomose with all the ambulacral tubes, or rather the
ambulacral tubes empty into the oral tube. The coeliac tube may be perceived
for its whole length through the thickness of the spherosome between the lateral
ambulacra in Jy. 2, and to communicate also with the oral tube. This anastomosis
is particularly distinct in a view from the actinal side (fiz. 4). The course of the
fluid contained in this system is somewhat peculiar. The great width of the tubes
has reference, no doubt, to the very great size of the digestive cavity; but as they

>

are capable of great extension and contraction, they readily adapt themselves to
the quantity of fluid poured into the chymiferous system from the digestive cavity.
There is in this family another structural adaptation, which makes it possible for
the larger digestive cavity to discharge the nutritive fluid accumulated im it more
promptly into the chymiferous system than this takes place in Pleurobrachia. The

chymiferous tubes, instead of following a simple course as in the other Ctenophore,

eS

Cuap. III. GENUS IDYIA. 983
send off along their whole course innumerable branches, ramifying in the thickness
of the spherosome (PL. II. Fig. 10).

the transparent spherosome, give it a very peculiar appearance, as if made up of

These ramified tubes,’ everywhere visible through

Nothing of the kind is seen in any other type of Ctenophore.
thie

origin and ramification of the minor tubes pervading the spherosome present some

irregular meshes.

The coeliac tubes alone are simple, and do not give off or receive any branches.

striking peculiarities. Those of the anterior and lateral interambulacra (Jigs. 1 and 2),
running nearer to the surface and consisting of thinner branches, arise from the
ovarian side of the ambulacral tubes, and, in fact, are direct prolongations of the
ovisacs; while those occupying the anterior and the posterior pairs of interambulacra
have a deeper origin, from the inner side of the

; 5 Fig. 99.

ambulacral tubes, and, bending over the spermatic sacs,
ramify nearer the inner surface of the spherosome, and
are, on the whole, wider than the others (PI. IL F%g. 10).
Fig. 99, which gives a transverse section across the
middle of the body, shows the origin and distribution

of these different branches, and makes it evident that

none arise, either from the side of the spermatic sacs

IpDYIA ROSEOLA, Ag.

or from the cceliac tubes.

Transverse section across the middle of the
Fig. 10, Pl. IL, representing a vertical section of ody.
a i rr eceliac tubes. — 2371, 14475 lateral tubes,—/? /3,
the whole animal nearly to the abactinal pole where w= anterior and posterior tubes.—o 0 ovaries.
° e — Ss, 58 spermaries.—¢¢ internal ramifications
the spherosome is cut transversely, gives the best of the anterior and posterior tubes.— ¢1 internal
5 ss s. e ramifications of the lateral tubes.
idea of the ramifications of the chymiferous tubes on
the inner surface of the spherosome, and shows how
much they differ on that side from those on the ex-
ternal surface (Pl. I. Fig. 1).

of the abactinal part of 7%. 10, Pl. HW. Along its mar-

Fig. 100 is a reproduction

gins are seen one of the anterior and one of the

posterior ambulacral tubes for their whole length, the

IpYIA ROSEOLA, Ag.

corresponding tubes J‘ 7? (Fig. 100) of the opposite side

rr. cceliac tubes, 7 is cut near its origin. —2 71 lat-
eral ambulacral tubes cut near their origin. —/7 2
anterior and posterior ambulacral tubes, cut near
their origin ; all the cut ambulacral tubes are on

being cut through. In the centre is the large cceliac

the same side of the body; on the opposite side
the following organs are visible from their internal
face: —16 13 anterior and posterior ambulacral
tubes. —/5/+ lateral ambulacral tubes. —a aaa
represents the section of the spherosome.

#7}, are cut through.

1 Among some Echinoderms there is something

quite similar to these ramifications of the ambu-

tube of one side, and its corresponding tube of the
opposite side 7 is cut through. The two lateral ambu-
lacral tubes of one side are also seen for their whole

length, and the corresponding tubes of the opposite side,

Between the abactinal end of these branches the short but

lacral tubes; for I do not doubt that the tube

extending throughout the thickness of the shell of

984. CTENOPHORZ. Part I.

wide central chymiferous cavity may be seen. On the actinal side, half the oral
tube is exposed, and on the margins its sections through the anterior and the
posterior interambulacra are visible as black specks.

The course of the fluid in all these tubes is very easily traced. Starting from
the central chymiferous cavity, the main currents flow toward the actinal side of
the body through the ambulacral tubes and empty into the circular oral tube, but,
owing to the frequent contraction and great activity of the actinal region, the
progress of the fluid is constantly interrupted; it then flows back and moves to
and fro in the ambulacral tubes, filling and distending to the utmost their rami-
fications in the spherosome, and thus distending it in the manner in which erectile
tissues are distended by capillary vessels. But when the obstacle arising from the
contraction of the actinal region is overcome, the fluid rushes into the circular
tube, from which arise also branches ramifying into the spherosome, and then runs
back through the cceliae tubes into the central chymiferous cavity. The total
absence of ramifications from the coeliac tubes into the spherosome or upon the
walls of the digestive cavity shows, that, in this type at least, the essential function
of the cceliac tubes is not to provide the digestive apparatus with nutritive fluid.
In very young specimens these ramifications do not exist at all, and the chymiferous
tubes are as simple as in Pleurobrachia; but as they increase in size there arise
a few lateral branches, at first simple, then dividing (PL I. Fig. 6* and 6* magni-
fied), and then becoming more and more numerous and branching more extensively
so long as they continue to grow.

The ovaries and spermaries stand in such close connection with the ambulacral
tubes and their ramifications, that they are best considered in this connection. In
very young specimens the ambulacral tubes are straight, simple canals; but as they
advance in age, shallow pouches grow out of them upon the sides, increasing
gradually in size and expanding into irregular sacs, sometimes with a broad base
tapering gradually, at other times with a narrow base and expanding into irregular
vesicular sacs, usually, but not always, continued into slender ramifications pene-
trating into the spherosome. In these sacs the ovarian and spermatic cells are
developed; but, as already remarked, each ambulacral tube produces eggs in the
sacs of one of its sides and spermatic cells in the other: and while pigment cells
of a pale color line these sacs, superficial pigment cells of a deep pink color are

the Clypeastroidw, and forming a regular circular 1 Milne-Edwards represents the coeliac tubes as
tube along the margin in the Scutellide, are ho- ramified in Beroe Forskali, Ann. Se. Nat. 2d. sér.
mologous to the lateral tubes of the Beroids branch- vol. 16, Pl. VI. Fig. 14,6. It certainly gives off
ing from the ambulacral tubes in the spherosome. no branches at all in our Idyia, nor have I seen
Tn Echinoderms, however, the tubes send off suckers any such ramifications of the celiac tubes in the
similar to though smaller than the ambulacral tubes. other true Beroids which I have observed.

Cuap. III. GENUS IDYIA. 985

crowded upon the surface of the spermatic sacs, so that all the ambulacral rows
appear one-sided, on account of the prominence imparted to them by the pigment
cells crowded over the spermatic sacs. Moreover, the ovarian and the spermatic
sacs are developed on opposite sides in adjoining ambulacra, so that proximate sides
of different ambulacra have the same kind of sexual organs, while alternate inter-
ambulacra have different kinds, the total arrangement being such that ovaries occupy
the anterior and the posterior interambulacra, as well as the lateral imterambulacra
in which trend the cceliac tubes, while the four imtervening interambulacra are occu-
pied by spermaries. The sexual sacs begin to appear early in August or in the
latter part of July. They are filled with eggs and spermatic cells in the latter
part of August; and at that time, in the larger specimens, these may be seen
circulating in the ramified tubes arising from the ambulacral tubes, which soon fill
so completely with eggs (Pl. Il. Fg. 6) as to appear like blood dises in a_blood-
vessel. Owing to the ramifications of the ambulacral tubes and the extension of
the ovisac in the shape of similar branches extending into the spherosome, while
the spermatic sacs communicate only with the main tubes of the ambulacra, it
follows that the contents of the spermaries are emptied into the ambulacral tubes,
and through them circulated into the ovarian sacs as soon as the eggs begin to pass
into the ramifications of their pouches, and, finally, eggs and spermatic particles are
lodged together in the ramifications of the chymiferous system, which penetrate the
spherosome, where the eggs remain enclosed until the spherosome itself is broken
up and decomposes, when the eges and the young, in various stages of development,
are set free. This constitutes a marked difference from Pleurobrachia and Bolina,
in which the eggs are only moved to and fro through the main chymiferous tubes.

The central eye-speck (Pl. II. Figs. 5, 8, 9, and 18) has the same structure
as in Pleurobrachia and Bolina, and may be so easily observed, that, were there
distinct nerves connected with its bulb, I could hardly have failed to see them.
That the eight narrow branches converging under the base of its bulb (Pl. IL Fy.
3) are not nerves, but a direct prolongation of the rows of locomotive fringes,
presenting in their abactinal extension (Pl. H. Figs. 8 and 9) the same character
as on their actinal prolongation (Fig. 17), is easily ascertained; and the circumstance,
that while they are plainly visible at the two extremities of the rows of loco-
motive flappers nothing of the kind can be seen under them, not even when
the ambulacra are examined from their inner surface as in F%y. 10, shows distinctly
that they form a part of the system of locomotive flappers. But why they should
reach the base of the eye and terminate there is not so easily understood; unless it
is to establish a connection of some kind between sight and locomotion, in the same
way as the eye-specks of the Echinoderms are placed in the prolongation of the
ambulacra. This connection seems to me an additional evidence that the eye-speck

286 CTENOPHORE. Parr I.

of the Ctenophor is a Cyclopean structure, resulting from the central combination
of the several eye-specks occupying in other types of the class a peripheric position
at the end of the ambulacral zones. The whole structure of Radiates, however, is
so remote from that of the other branches of the animal kingdom, that any attempt
to homologize their functions beyond the respective limits of the primary types is
more likely to lead to errors than to explain their peculiarities.

Having thus described our Idyia, the question now arises, What are its specific
characters? for, if the views I have advocated in the first part of this work are at
all well founded, it must be obvious that I have embraced in this description many
features which are in no way specific. The fundamental structure of our Idyia,
as composed of eight spheromeres, is not a specific character, since it is common
to all the Ctenophore; nor are the equable development of the spheromeres and
the ramifications of the ambulacral tubes specific characters, since all the true Beroids
agree in this respect; nor is the absence of tentacular tubes and of tentacles a
specific character, since no member of this sub-order has them; nor is the great
width of the digestive cavity, nor the limited extent of the main chymiferous cavity,
specific, since all the Beroids agree in the development of these parts; nor is the
structure of the ovaries and spermaries, nor that of the circumscribed area. But,
instead of enumerating anew all the structural details mentioned in this section,
I may as well at once express my conviction, that no structural peculiarity can
ever be considered as a specific character, since the essence of species does not
lie in the plan of structure, nor in its mode of execution, nor in its complication,
nor in the combinations which determine the form, nor even in the details of
the structure. These categories of structure determine respectively the branches, the
classes, the orders, the families, and the genera of the animal kingdom; while the
species are characterized by their size, the relative proportions of their parts, their
ornamentation, their geographical range, their relation to the elements in which they
live, their mode of existence, the duration of their life, their association with one
another, the period of their reproduction, the changes they undergo during their
life, and their association with other beings. Considering, now, our Idyia in this
light, I may say that its most striking specifie peculiarities are its great size; the
prominence of its vertical diameter; its equable and gradual widening from the
abactinal pole toward its middle height, and its still more gradual tapering toward
the mouth; its light rosy color, intensified with age, and particularly bright about
the sexual organs, and deep pink upon the spermaries during the season of spawning,
the color growing deeper in consequence of the accumulation of pigment cells.
This species lives along the coasts of New England, and northward: it is found
near the shores, and, though sometimes appearing in immense numbers, it cannot

be said to lead a gregarious life and to form shoals, as they do not move together,

Cuar. II. GENUS IDYIA. 28

|

like herrings or mackerels. They feed upon other Ctenophore, and are very voracious,
their digestion being very rapid. They are short-lived, and appear periodically
in the early part of the summer, when their dimensions are one sixth of their
full size: they are at first pale, but grow deeper and deeper in color as they
enlarge, and are brightest toward the end of the summer during the spawning
season; after the ovaries and spermaries have been emptied, they grow paler and
paler; and, finally, they are broken up into fragments by the autumnal gales. The
young, hatched about this time, probably pass the winter, like most shore animals,
in deeper water; and they differ from the adults chiefly in having their rows of
locomotive flappers much shorter than afterwards. They are usually found associ-
ated with Pleurobrachia, Bolina, and Thaumantias near the surface of the water
during the hottest hours of the day; but whenever the sea is rippled or the sky
overcast, they sink out of sight below the surface.

A comparison of Idyia roseola with another species, Idyia cyathina A. Ag., dis-
covered by my son in the Gulf of Georgia, has satisfied me that such are truly
the specific characters of our Idyia; for I find that there is not the slightest
structural difference between the two, and yet there can be no doubt that they
differ specifically. In Idyia cyathina the spherosome widens rapidly from the
abactinal pole, and is widest at two thirds of the distance from the mouth, when it
again tapers suddenly, and then more gradually, in the same direction; the actinal
side of the spherosome being narrower and thinner than the actinal, and therefore
much more flexible, and the anterior and posterior interambulacra on that account
capable of more extensive contractions, in consequence of which the angles of the
mouth may be drawn into very deep curves, and the lips thus formed assume
the shape of more distinct lobes than is ever the case with Idyia roseola. It may
be said, that though both have the same pattern, Idyia roseola has rather the
form of a shuttle, and Idyia cyathina resembles more an Etruscan vase. The habits
of Idyia cyathina have not been sufficiently studied to carry farther the comparison
of the two species; but, as mentioned above (p. 250, note), so much is already
known, that it is also found associated with a Pleurobrachia and a Bolina.

Many years ago I noticed in the harbor of Charleston, South Carolina, and in
Florida, two Acalephs belonging to the family of the true Beroids, respecting which
my memoranda are very scanty, and quite insufficient to describe them as they
should be. And yet I am unwilling to omit them entirely, as they seem to
indicate the presence, along our southern coast, of a genus intermediate between
Pandora and Idyia, and thus far unknown. Their most striking peculiarity is the
shortness of the vertical axis, which barely exceeds the longitudinal diameter. In
this respect they resemble the genus Pandora Lsch.; but they differ from it in

having their ambulacra very prominent and the interambulacra concave, while in

988s CTENOPHORA. Part I.

Pandora the rows of locomotive flappers lie in a furrow, the margins of which
may close over them. They differ further from Pandora in the more extensive
development of the rows of flappers, which reach near to the oral tube, and in
this respect they resemble more Idyia, with which they agree also in being much
compressed laterally. The circumscribed area is bounded by a fringe of deeply
lobed processes arranged in two prolonged circles, with the eye-speck between them,
in the centre. The eye-speck is not raised on a peduncle. The branching tubes
penetrating into the spherosome, which Eschscholtz does not mention in Pandora,
are even more distinct than in Idyia; and those arising from the circular oral
tube are quite numerous. The main chymiferous cavity, from which arise the
chymiferous tubes, is a globular hollow, situated in the abactinal part of the sphero-
some and communicating with the wide digestive cavity through a narrow fissure.
The compression of the body is quite striking, and, upon contrasting a lateral and
a front view, these species appear rather flat. For this genus I would propose
the name of Ipyopsis.

Ipyorsis Crarxu dy. (Fy. 101). I inscribe this species to my friend Prof. H.
J. Clark, to whom I am indebted
for a sketch of its outlines, certain
that, when he has an opportunity
for examining it leisurely, he will

give us a most minute account of

its structure. From notes made

Ipyorstis CLARKII, Ag.

years ago, it appears that the rows _ Seen from the abactinal side.

——

°

ene Ct oe { . circumscribed area. —/1 /8, [4 15
pyorsts OLarku, Ag. of locomotive flappers have on iateral ambulacra.—2 0, 67
Seen from the broad side. anterior and posterior ambu-

/ funnel. —V@ anterior and posterior ambulacra. each side a band of yellow and lacra.

ce pouth cunmuintat by the nal wake, brown stellate dots, and that the edge of the mouth,
geo ee as well as the fringes around the circumscribed area,
were dotted in the same manner. The digestive cavity is occasionally constricted
about half way up its height, and may remain so for a long time, while the mouth
is broadly opened, and the constriction gliding toward the abactinal end of the
digestive cavity may reach the fissure leading into the main chymiferous cavity, and
disappear when the latter opens. Seen in profile from its broad side, this species
is nearly globular. Found in the harbor of Charleston.

Ipyorsis arrinis Ay. differs from the preceding in being more flattened in front
and behind, and less rounded in its outlines when seen from the broad side, the
actinal side being broader. Found along the reef of Florida, at Key West, and
about the Tortugas.

Cuap. IIL. TABULAR VIEW. 289

Sy CEO ING TEA.

TABULAR VIEW OF THE CTENOPHORZ KNOWN AT PRESENT.

In order not to occupy too much room with the following table, I introduce only
the names and authority of the species and their principal synonymes, as the refer-
ences may be found in Eschscholtz or Lesson, and only add such critical remarks
as are indispensable to settle questionable statements. I have also carefully revised
the indications of all authors respecting the localities in which the species occur.

Order of CTENOPHOR L£sch.: Beroes Goldf. 1820.— Vibrantes Cham. and Eysenh.
1821.— Beroide Esch. 1825.—Ciliata Latr, 1825.—Ctenophoree Lsch. 1829.
—Iriptéres Rang 1829.—Ciliobranches and Ciliogrades DeBlainw. 1830.

Ist Sub-order. LOBATA Esch. 1825.— Mnemiide Lsch. 1829.
Ist Family. Evrampraipx Ag. 1860, p. 199.
Euramphea Gegenb. 1856.— Mnemia Sars 1857.

E. vexilligera Gegenb.— Mnemia elegans Surs. — Mediterranean :

Messina (Gegenbaur and Sars).
Hapalia sch. 1825: Callianira Cham. 1821.—Mnemia Esch. 1829.
— Eucharis DeBlainv. 1850.— Polyptera Less. 1843.
The validity of this genus is questionable, since it is
founded upon an imperfect specimen.

H. heteroptera “sch. — Callianira heteroptera Cham.— Mnemia Cha-
missonis Lsch. — Eucharis heteroptera DePlaiw.— Polyptera
Chamissonis Less. — Cape of Good Hope, Table Bay (Chamisso).

2d Family. Boinx Ag. 1860, p. 200.
Bolina Mert. 1835.—Mnemia Sars 1855.— Alcinoe Less. 1843. —
Anais Less. 1845.

B. septentrionalis Mert.— Of Matthai Island, Behring Strait (Mer-
tens); Gulf of Georgia (A. Agassiz).

B. norvegica Agy.—Mnemia norvegica Sars. — Alcinoe norvegica
Less. — Bolina hibernica Pa/t.— Alcinoe rotunda Fors. and
Goods. — Beroe bilobata Dalyell.—Cydippe quadricostata Sars,
the young? (Anais quadricostata Less.) — Coast of Bergen, Nor-
way (Sars); eastern and southern coast of Ireland (Patterson).

B. alata Ag.— Coast of New England and northward to the Bay of
Fundy (Agassiz).

B. vitrea Agy.— Reef of Florida (Agassiz).

VOL. III. 37

290 CTENOPHORE. Parr IL.

Bolinopsis Ay. 1860, p. 201.—Bolina Mert, 1833.

This genus differs from Bolina in having its anterior and
posterior rows of locomotive flappers extending to the bend of
the chymiferous tubes, and the abactinal direction of the medial
anastomosis of the latter, which trend in the opposite direction
in Bolina. The spherosome is papillate, while that of Bolina
is smooth. The large lobes are deeply indented.

B. elegans Ag.— Bolina elegans Mert.— South Sea (Mertens).
od Family. Myemipm Lsch. (restricted).

There are two groups of genera included in this family:
Mnemia (Aleinoe), LeSueuria, and Mnemiopsis the body of
which is smooth, and Eucharis, Chiaja, and Leucothea with
a papillate surface; but, until the structure of these papillae
is better known, the value of this difference in regard to
classification must remain doubtful.

Mnemia Lsch, 1825.
M. Schweiggert Lsch.— Rio Janeiro, Brazil (Eschscholtz).
M. Kuhhi Lsch. — Pacijfie Ocean, near the Equator, Long. 180° of Greenwich.

Judging from the figure and description of Eschscholtz,
this species must be generically distinct from M. Schweiggeri
on account of its abactinal appendages.

Alcinoe Rang 1829.
A. vermiculata Raig.— Coast of Brazil; abundant in the Bay of Rio
Janeiro (Rang).
A. rosea Mert. — Of the Falkland Islands (Mertens).

Although this genus is generally adopted, I am_ strongly
inclined to believe that it is founded upon the same species
as the genus Mnemia of Eschscholtz. There is nothing in
the description of Mnemia Schweiggeri Lsch. to preclude the
possibility of its identity with Alcimoe vermiculata Rang, and
both were observed in the same locality.

Alcinoe norvegica Less. is a true Bolina, B. norvegica.

Tam unable to ascertain what Alcinoe Smithi Forbes may
be. It is said to be found near Ailsa Craig and on the
Trish coast.

LeSueuria Milne-Edw. 1841.
L. vitrea Jf-Kdw.— Mediterranean: Bay of Nizza (Milne-Edwards).
Mnemiopsis Agass. 1860, p. 269.

M. Gardeni Ay. See p. 269.— Charleston, S. Carolina (Agassiz).

Cuap. II. TABULAR VIEW. 291

Eucharis Lech. 1825.

E. Tiedemanni Lsch. — Northern Pacific, East of Japan (Eschscholtz).

The genus Eucharis should be limited to the species first
described in the Isis m 1825.

Eucharis multicornis /sch., founded upon Beroe multicornis
Q. and G., is a genuine Chiaja, as far as the mutilated condition
of the species allows an identification. At least, there is no
other Mediterranean genus to which it may be referred.

Judging from Reynaud’s figure, Eucharis novemcostata Less.,
founded upon Beroe costata Reyn., from the Indian Ocean, off
Ceylon, is the type of a distinct genus, which may be called
Evcwarina, and the species E. costata.

Chiaja Less. 1843.

Ch. papillosa J-Edw.— Alcinoe papillosa Delle Chiaje. — Chiaja
neapolitana. Less.— Bay of Naples (Delle Chiaje).

Ch. multicornis M/-Ldw.— Eucharis multicornis W7/.— Beroe multi-
cornis Q. and @.?— Adriatic: Trieste (Will); Mediterranean (Quoy
and Gaimard).

Ch. palermitana J/-Edw.— Palermo (Milne-Edwards).

Considering the extensive geographical range of most Aca-
lephs, it seems hardly probable that there should exist three
species of Chiaja in the Mediterranean. I cannot agree with
Milne-Edwards, when he considers the genus Chiaja as identical
with Leucothea Mert. The tentacular apparatus is very differ-
ent in the two: at least, if is so described and figured by
Mertens, Will, and Milne-Edwards as to lead to the impression
that there exists a generic difference in the structure of the
tentacles of Leucothea and Chiaja.

Leucothea Mert. 1855.— Leucothoex Less.— Leucothoea Less.
L. formosa Mert. — Azores (Mertens).
4th Family. Caryionpx Gegend.’ (restricted). — Mnemidx Lsch, — Calym-
mee Less.
Calymma Fisch. 1825.
C. Trevirani Esch. — Pacifie Ocean, nea the Equator (Eschscholtz).
Atlantic Ocean, off
the coast of Africa, near the Equator (Mertens).— The separation

C. Mertensii Less. —Calymma Trevirani Mert.

of this species is founded upon its occurrence in the Atlantic.

1 Gegenbaur writes it CaLymnip£; but it should be Catymmip.

292 CTENOPHORZE. Barre Oe

Bucephalon Less. 1845.
B. Reynaudi Less. — Callianira Bucephalon Reyn.— OFF Ceylon
(Reynaud),
Axiotima Lsch. 1829.— Axia Esch. 18265.
A. Geedei Esch. — Pacifie Ocean, near the Equator (Eschscholtz).

Whether this genus belongs to this family, or not, is a

matter of doubt. Eschscholtz’s description and figure are eyi-
dently drawn from an imperfect specimen.
5th Family. Ocyrore Less. 1843.
Ocyroe Rang 1829.

(30)
L

O. crystallina Rang.— Atlantic Ocean, under the Equator, Long.
W. of Greenvich (Rang).
O. fusca Rang.— Atlantic Ocean, off Cape Verd Islands (Rang).
O. maculata Rang.— Among the Antilles (Rang).
2d Sub-order, TAENIATA Ay. 1860.— Cestoidex Less. — Cestide Gegenb.
Ist Family. Cursrompm Less. 1845. — Cestidas Gegenb. 1856.
These family names are objectionable on account of their
tautonomy with the Cestoid Worms.
Cestum LeSuew 1815.—Sicyosoma Cegenb. 1856?
C. breve Grdffe. — C. Meyeri

Griffe.—Sicyosoma rutilum Gegenb. (young?) — Mediterranean :

C. Veneris LeS.—C. Rissoanum Less.

WNizza (LeSueur and Risso); Naples (Delle Chiaje); Messina
(Kolliker and Gegenbaur).

C. Najadis sch. — Pacifie Ocean, near the Equator (Eschscholtz).

C. Amphitrites Mert.— Pacifie Ocean, under and near the Equator,
Long. 127° and 280° W. of Greenwich (Mertens).

C. Mertensii Ay.— Mentioned without name by Mertens. — Atlantic
(Mertens).

Lemniscus @Q. and @. 1822.

L. marginatus Q@. and G.— Of Timor (Quoy and Gaimard); of

New Guinea (Lesson).

The genus Lemniscus was characterized from fragments
unquestionably belonging to the family of Cestoidex ; but its
generic difference from Cestum remains doubtful. It should
be remembered, however, that Eschscholtz has already poited
out differences between C. Najadis and C. Veneris which seem
rather generic than specific, and that therefore Lemniscus also
may be a distinct genus, even though the facts observed may

SS

not, for the present, justify its adoption. But whether the

Cuap, HI. VAVB UsTPAC RS Valen Wee 293

genus Lemniscus be distinct from Cestum or not, the species
upon which it is founded certainly differs from the species
of Cestum thus far described; so that this family already
numbers five species, including that alluded to, but not de-
scribed, by Mertens.
3d Sub-order. SACCATA Ag.— Callianiride Esch.
Ist Family. Merrensipm Ay. 1860, p. 196.—Cydippide Lsch.
Mertensia Less. 1843 (not Gegenb.).
M. Cucullus Ay. — Beroe Cucullus Mod.— Cydippe Cucullus Esch. —
Mertensia Scoresbyi Less. —Beroe Pileus Scor. nec Fubr. nec
Mill. —Cydippe Cucumis Less. (The synonymes of Lesson
are all wrong).— Beroe Ovum Fudbr. (Cydippe Ovum Lsch.). —
Aretie Ocean (Martens and Scoresby). — Baffin’s Bay (Fabricius).
M. compressa Less. — Beroe compressa Mert.— Bay of the Holy
Cross, mouth of the Anadyr (Mertens).
Martensia Agass. 1860, p. 198.
M. octoptera Ay.— Beroe octoptera Mert.—Janira octoptera Less.
— Coast of Chili: Bay of Conception and of Valparaiso (Mertens) ;
Behring Strait, near the Bay of St. Lawrence (Mertens).
Gegenbauria Agass. 1860, p. 198.
G. cordata Ay.— Eschscholtzia cordata A67/.— Callianira diploptera
Delle Ch.— Mediterranean: Bay of Naples (Delle Chiaje); Mes-

sia (Kolker and Gegenbaur).

Owenia Al. 1853.— Mertensia Gegenb. 1856.
O. rubra Aoi. — O. filigera AGI. — Mediterranean: Messina (Killiker).
2d Family. Cypirrinm Gegenb. (restricted). — Callianiridee Esch. (partly).
Pleurobrachia Flem. 1828.—Cydippe Esch. 1829.
Pl. Pileus #7.—Beroe Pileus Mil/.—Cydippe Pileus Esch. — Cy-
dippe Flemingii Forb.— Beroe ovatus Link.—Cydippe ovatus
Less. — Cydippe pomiformis Patt.— Beroe infundibulum Miil.—
Cydippe infundibulum Zsch.—Beroe Miilleri Less. — Cydippe
lagena Forbes. — Beroe hexagona Mod.— Callianira hexagona
Esch. — Janira hexagona Oken.— Beroe Santonum Less. — Eu-
rope: Holland (Slabber) ; German Ocean (Miiller) ; Scotland (Flem-

1 Although the paper of Mertens gives the coast to Beroe (Martensia) octoptera with those relating
of Chili and Behring Strait as the home of this to Beroe (Mertensia) compressa, which is truly an
species, I suspect, that, in the arrangement of his arctic species; for it is hardly credible that the same
manuscript, which was printed after his death, the species should occur in the waters of Behring

editor may have confounded the memoranda relating Strait and on the coast of Chili.

294 ' CTENOPHORA. SPany Ue

ing); Sf Andrews (Forbes); Mouth of the Thames (Dr. Grant) ;
Coast of Ireland (Patterson); Atlantic coast of France (Lesson).

Pl. densa Ay.— Beroe densa Forsk.— Cydippe densa Lsch.— Beroe
Pileus £isso.— Beroe albens Forsk.— Mediterranean (Forskal
and Risso).

Pl. rhododactyla Ay. — Beroe Pileus Fubr,.— New England (Agassiz) ;
Greenland (Fabricius).

Pl. bicolor Ag.—Cydippe bicolor Sars. — Norway: Florden (Sars).

Pl. Bachei A. Ay.— Washington Territory, West coast of North America
(A. Agassiz).

Pl. Basteri Ay.— Beroe Basteri Less. — Coast of Peru, not far from
Callao (Lesson). :

Pl. rosea Ay.— Beroe roseus @. and G.— Slraits of Timor (Quoy
and Gaimard).

Janira Oken 1815.—Cydippe Esch. 1829.

J. elliptica Less. —Cydippe elliptica Lsch.— Pacific Ocean, near the
Equator (Eschscholtz).

J. Cucumis Less.— Beroe Cucumis Mert.— Between Sitka and Una-
laschka, and under the 36° N. Lat. and 211° W. Long. (Mertens).

J. elongata Ay.— Beroe elongatus Q. and G.—Janira Quoyil Less.
— Atlantic Ocean, off the coast of Africa in 8° N. Lat. (Quoy
and Gaimard).

Eschscholtzia Less. 1845.— Cydippe Esch. 1829.
As the only species left in this genus was described from
a drawing, the genus rests upon a very slender basis.

E. dimidiata Less. — Cydippe dimidiata sch. — South Sea, between
New Zealand and New South Wales (Banks and Solander, ac-
cording to Exschscholtz).

Dryodora Agass. 1860, p. 196.— Exschscholtzia Less. 1843.— Mertensia
Gegenb. 1856 (not Less.).
This and the next genus are founded upon theoretical
grounds, and require confirmation.

D. glandiformis Ay.—Beroe glandiformis Mert.— Eschscholtzia glandi-
formis Less. —Mertensia glandiformis Gegenb. — Behring Strait :
Bay of St Lawrence (Mertens).

Hormiphora Agass. 1860, p. 196.—Cydippe Gegenb. 1856.

H. plumosa Ay.—Cydippe hormiphora Gegenb.— Cydippe plumosa

Suis. — Mediterranean: Messina (Gegenbaur and Sars).

Cuar. IIL. TABULAR VIEW. 295

3d Family. Caruana Esch. 1829, and Gegenb. 1856 (restricted).
Callianira Pér. 181014
C. triploptera Limk.— Beroe hexagonus Brag. — Indian Ocean, in the
wcinily of Madagascar (Bruguiére).
Sophia Pér. auctore Lamarck, Anim. s. Vertebr., and Eschscholtz,
Isis, 1825.
8. diploptera Pér.— Callianira diploptera Link.— Indian Ocean, off
Australia (Péron).
4th Sub-order. EURYSTOMA Leuch, 1856.— Beroide Cave Esch. 1825.
Ist Family. Brromm Esch. 1829.

The true characteristics of the species of this family are
not yet discovered. Were the synonymy of some authors
taken for granted, it would follow that there are species
ranging all the world over, which cannot be admitted without
the most careful comparison. On the other hand the charac-
ters ascribed to the species observed in different localities
hardly justify their admission as true species. It is there-
fore necessary to await further information before considering
either the geographical distribution of these Acalephs, or their
specific limitation, as satisfactorily traced.

Beroe Brown 1756.—Medea Esch. 1825.—Cydalisia Less. 1843.
B. Forskaliit Midne-Edw.— Medusa Beroe Linn. — Beroe. rufescens
Forsk.— Beroe ovatus Lam. and Delle Chiaje.— Beroe elongatus
Tiss. —Idyia Forskalii Less.— Beroe Chiaji Less. — Mediter-
rancan (Forskal, Delle Chiaje, Risso, and Milne-Edwards).
B. punctata Cham. and L£ys.—Cydalisia punctata Less. — Atlantic :
North of the Azores (Eschscholtz).
B. Mertensii Br.—Idyia Mertensii Br.— Southern Atlantic, 35° 50!
S. Lat. and 223° #. Long. of Green. (Mertens).
B. mitreformis Less.—Cydalisia mitraformis Less. —Idyia peni-
cillata Mert.— Pacific: Coast of Peru, 6° S.. of the Equator
(Lesson and Mertens).
Idyia Frem. 1809.— Medea Esch. 1825.
I. ovata Less. — Beroe Brown.— Medusa Beroe Linn. — Beroe ovata
Esch. — Tropical Atlantic: Jamaica (Patrick Brown).

17 find it impossible to ascertain positively synonymes in 1829, and for which Lamarck, An.
whether the genera Callianira and Sophia, which s. Vert., seems to have the priority, really consti-

Eschscholtz represents as distinct in 1825, and as tute two genera or not.

96

CTENOPHORE. Part II.

I. gilva Less. —Beroe gilva Esch.— Coast of Brazil (Eschscholtz).

I. macrostoma Less. —Beroe macrostomus Pér. and LeS.— Idyia
Péronii Less. — Medea constricta Esch. (Beroe constricta Cham.
and Eys.), and Medea rufescens Lsch., are probably the young
of this species. — Pacific Ocean (Péron and LeSueur).

I. Cucumis Less. —Beroe Cucumis Fabr.— Medea fulgens Less,
(Beroe fulgens Mc Cart.) is probably the young of this species;
I would also refer to it Beroe ovata Dalyell and Beroe punc-
tata Dalyell. — Baffi’s Bay (Fabricius); Norway (Sars); Coast
of Scotland and England, from the Zetland Isles to the Isle of
Wight (Forbes).

I. borealis Less. —Beroe fallax Less.— Beroe Scoresbyi Less. —
Medea arctica Zess.—and Medea dubia Less.—all founded upon
the figures of Scoresby, are probably one and the same species.
— Seas of Greenland, 75° Lat. N. and from 5° to 8° Long. W.
of Greenwich (Scoresby).

I. roseola Agass.— Coast of New England, and northward to the Bay
of Fundy (Agassiz).

I. cyathina A. Agass.— North-west coast of N. America (A. Agassiz).

I. capensis Less. — Beroe capensis Cham. and Eysenh.— South Atlantic,
near Cape of Good Hope (Chamisso).

Idyiopsis Agass. 1860, p. 288.
I. Clarkii Ag.— Adlantic coast of North America: S. Carolina (Agassiz).
I. affiinis Ag.— Gulf of Mexico, Tortugas, and Florida (Agassiz).
Pandora Esch. 1829.
P. Flemingii Lsch.— Northern Pacific, East of Japan (Exschscholtz).
2d Family. Nuts Less, 1843.
Neis Less. 1826.
N. cordigera Less. — Port Jackson, Australia (Lesson).
3d Family. Ranewx Agass. 1860, p. 191.
Rangia Ag.—Idyia Less. 1843.
R. dentata Ag.— Idyia dentata Less. — Western coast of Africa (Rang).

Cuap. III. GEOGRAPHICAL DISTRIBUTION. 297

Sil Col TO Nee.
GEOGRAPHICAL DISTRIBUTION OF THE CTENOPHOR.

The preceding enumeration may furnish the means of tracing, to some extent,
the geographical range of the Ctenophore, though it must be apparent, from a
survey of the localities where Acalephs of this order have thus far been observed,
that much remains to be done before the laws which regulate their distribution can
be ascertained. One fact, however, is already plain, that there exist Ctenophore im
all the oceans, and that they are as common in the arctic as in the temperate and
tropical seas; though the range of the different genera and species does not seem to
be more extensive or more limited than that of most marine animals. Peculiar genera
and species are known to be limited to certain parts of the ocean, while other genera
have a wider range and seem everywhere to have special representatives. The
Beroids proper are unquestionably the most widely distributed, species of this family
having been noticed under all latitudes and in every ocean. Next to them the
Saceatz have the most extensive range; but among these there is already a marked
difference between different families, the Mertenside having a more northern range
than the Cydippide proper. Indeed, the genus Mertensia is entirely arctic, while
the genera Martensia, Gegenbauria, and Owenia belong to the temperate zone.
Pleurobrachia and Janira seem to be cosmopolite, Eschscholtzia and Hormiphora are
the representatives of the same family in the temperate zone, while Dryodora is
arctic. The Callianirids proper belong to the warm regions. The Tzniate are
entirely foreign to the cold climates, and seem to be more numerous in the tropical
regions than even in the temperate parts of the globe where they were first observed.
As to the Lobatx, we find the family of Bolinidz in the cold and temperate zones,
extending to the limits of the tropics; while the Eurampheide, the Mnemiide, the
Calymmide, and the Ocyroidx are almost exclusively tropical, and have only a few
representatives in the warmer temperate zones.

If it were certain that the Beroide proper are the lowest Ctenophore and the
Lobate the highest, it would follow, that, on the whole, the lower representatives
of this order are the most widely distributed, and that the highest are more ex-
tensively found in the tropical regions, while those occupying an intermediate position
are either cosmopolites, or denizens of the temperate zone, or more tropical. — It
seems at least to follow from the facts thus far ascertained, that the most elegant
and largest representatives of the Lobate, such as Chiaja and Leucothea, belong

to the warmer temperate and to the tropical zones, and that the most aberrant
8

eo

VOL. III.

298 CTENOPHORS. Part IL.

forms of the whole order, such as Ocyroe and Calymma, are exclusively tropical,
Ocyroe being peculiar to the equatorial zone of the Atlantic, while Calymma. is
found in the Pacific as well as in the Atlantic.

For want of materials, it would be premature, at this time, to attempt tracing
with precision the natural boundaries of the Acalephian faunz. But, im connection
with data obtained from other classes, much may already be done towards a better
understanding of what zoological provinces truly are. In studying the geographical
distribution of animals and plants, naturalists have followed different methods, leading
to different results, and bearing in different ways upon the question before us.
While investigating the relations under which animals and plants are placed, in
different parts of the world, in reference to the physical influences to which they
are exposed, we no doubt ascertain much that is of great importance for the limi-
tation of the faunxz; but such studies do not lead, after all, to the knowledge of
natural zoological provinces, but only to a fuller insight into the mutual dependence
of the organized beings, and the limiting or fostering conditions under which they
may live. This study, as I understand it, may end in giving us a more extensive
physical history of the organic world, but cannot, by itself, furnish even the foundation
for an organic geography, that is to say, for a knowledge of the natural mode
of association of animals and plants of the same family or of the same class, which,
properly speaking, constitutes natural faunz or zoological provinces. Nay, this natu-
ral mode of association of a variety of animals, belonging either to one and the same
class or to different classes and different kingdoms, might be obtained without a
deeper knowledge of the physical influences which limit the geographical range of
the species considered singly.

Again, much confusion seems to prevail among zovlogists and paleontologists in
the use which they make of the word fawi. Some designate by it a definite area,
within which a variety of animals appears to be naturally associated; and I believe
it is in this sense that the term should hereafter be exclusively used. It is
self-evident, that if the term /fwuna is applied to such circumscribed areas, and is
at the same time used to designate entire zones, over which many distinct zoo-
logical provinces may be distributed, as is frequently done when zodlogists speak
of the tropical fauna, the temperate fauna, ete, two very different ideas are thus
confounded, and no accurate views can be introduced in our science, since in the
first case a geographical area is intended, characterized by a peculiar association of
various animals, and in the second case a special combination of physical features
limiting the range of organized beings. It is far better here to use the expression
of gone, consecrated in physical geography, and to speak of the tropical zone, the
northern and the southern temperate zones, ete.; or, if the two ideas are to be

combined, to speak of the faunz of the tropical zone, in contradistinction to the

Cnap. II. GEOGRAPHICAL DISTRIBUTION.” ~ 299

faunee of the temperate and arctic zones: for enough is already known of the
geographical distribution of animals to make it certain, that the inhabitants of
tropical America, of tropical Africa, of tropical Asia, and of tropical Australia, belong
to different faune, as well as those of the temperate zones of these continents,
and of the oceans bathing their shores.

Again, when paleontologists speak of a Silurian fauna, a Devonian fauna, a
Carboniferous fauna, a Jurassic fauna, ete. they either prejudge questions which are
far from being settled, or, if aware of the difficulties involved in their nomenclature,
allow themselves to use this term still more vaguely than zovlogists do. In the
first place, neither the Silurian nor the Jurassic era, nor any other of the long
eras generally designated by geologists as geological formations, was inhabited from
its beginning to its end by the same kinds of animals. Taking, for instance, the
Silurian series, within the narrow limits of the State of New York, or the Oolitic
series within the limits of the Jura, or the Cretaceous series within the limits of
central Europe, we find in each of these series a succession of different species,
combined in such a manner as to form a suecession of faune, the natural geo-
graphical boundaries of which may be left out of consideration in view of our
present object, but constituting as truly distinct faunse as the animals living along
the Atlantic shores of the southern United States constitute a different fauna from
those of the Mediterranean. Here, then, we have, in course of time and within
the same boundaries, a succession of faune, bearing to one another relations similar
to those existing between faunx of the present period within different boundaries ;
showing the impropriety of applymg the name of faune to the organic remains
found in these different series, and of using it at the same time for the zoological
provinces, as defined by zodlogists, for the animals now living. The matter is not
improved by limiting the term faunz to shorter geological periods. No doubt the
fossils found together by Barrande in the lowest fossiliferous beds of Bohemia repre-

’

sent the first fauna of that region. But the “faune premiére,” if it means any
thing, must mean the oldest fauna extending over an area, not yet fully defined
perhaps, including the first organisms only that lived upon earth in the geographical
area now called Bohemia. It cannot at the same time mean any other combi-
nation of more or less closely allied species, living at the same period, in other
parts of the world; unless it be at the same time shown, that, in these earlier
ages of the world’s history, there were no faunal differences among animals.
Enough, however, is already known of these primeval inhabitants of our globe to
leave no doubt, that, though the differences in their geographical range may not
everywhere be so striking as they are now, they nevertheless differed in different
parts of its surface; so that, to extend the expression of “faune premiere” to all

the inhabitants of the globe belonging to the geological age of the lower Silurian

300 CTENOPHOR. Parr IT.

deposits of Bohemia, is to introduce the element of time in the definition of fauna,
which is foreign to it If the expression of “first fauna” could be made to mean
all the animals of that epoch, then we should in the same way be justified in
speaking of the present fauna as including all the animals now living upon earth ;
while it is well known that there are numerous frune at present ranging over our
globe, as there no doubt have been at all times. We may speak of the “ first era” or
“first period” in the development of animal life upon earth, but certainly not of the
“first fauna;” though we may say that the “Bohemian fauna” of the first geological
era has been described in a masterly manner by Barrande. In so doing we shall
avoid confounding geological periods with geographical areas. In the same way will
it be necessary to distinguish between the French, the German, and the English faune
of the different geological horizons of the Jurassic and of the Cretaceous series. We
shall have a German and an English fauna of the Lias period, a Swiss and a
French fauna of the Neocomian period, ete. ete. as soon as the natural boundaries
of all these faunx, for all the successive geological epochs, have been satisfactorily
traced. And the surest method to advance the solution of this problem is, un-
questionably, to distinguish carefully the different elements of the question before us,
and not to confound time and_ space.

These distinctions being admitted, we may now proceed to consider the Aca-
lephian faune of the present period, as characterized by the Ctenophore. I have
already alluded to the relations noticed between the representatives of the different
families of this order, and the physical conditions under which they live. It remains
to examine their combinations in different zoological provinces.

The aretie regions having been scantily explored, as far as the Acalephs are
concerned, it can hardly be expected that much should be known of the faune of
this zone; and yet it already appears, from the observations of Martens, Scoresby, and
Mertens, that the northernmost parts of the globe are inhabited by Acalephs which
differ from those of the boreal zone. Mertensia Cucullus and M. depressa are the
two most northern Ctenophora known; and if these two species prove to be really
distinct, it would follow, that the Atlantic side of the Arctic Ocean, on which Idyia
borealis is found with Mertensia Cucullus, forms a distinct fauna from that of the
Pacific side, where Dryodora glandiformis accompanies Mertensia compressa.

In the boreal zone we may already distinguish three faume: 1°, a Scandinavian
fauna; 2°, an Acadian fauna; and, 3°, a Columbian fauna. The Scandinavian fauna is

characterized sby Bolina norvegica, Pleurobrachia bicolor, and Idyia Cucumis; the Aca-

1 Barrande has already shown that “the range in the direction from Sweden to Bohemia, than
of distribution of the Trilobites, during the period is the case with the living Crustacea.” Parallele

of three successive silurian fauna, was more limited entre les dépots siluriens, etc., p. 67.

Cuap. III. GEOGRAPHICAL DISTRIBUTION. 301

dian fauna by Bolina alata, Pleurobrachia rhododactyla, and Idyia roseola; and the
Columbian fauna by Bolina septentrionalis, Pleurobrachia Bachei, Janira Cucumis, and
Idyia cyathina.

The Celtic fauna with its Pleurobrachia Pileus, and the Lusitanie fauna with
its rich array of Chiajas, its Euramphea, its LeSueuria, its Cestum, its Gegenbauria,
its Owenia, its Pleurobrachia, its Hormiphora, and its Beroe Forskali, are barely
represented, in the Carolinian fauna, by its Mnemiopsis and Idyopsis. The Cha-
rybean fauna thus far only numbers four species, Bolina vitrea, Ocyroe maculata,
Idyia ovata, and Idyopsis affinis; while the Brazilian fauna has two, Mnemia or
Alcinoe, and Idyia gilva and the Azorian fauna three, Leucothea formosa, Cestum
Mertensii, and Beroe punctata. Off the coast of Africa, further south, the following
species have been noticed: Calymma Mertensii, Ocyroe crystallina and fusca, Rangia
dentata, and Janira elongata. The South African and the Patagonian faune are
scarcely known. Off the Cape of Good Hope, Hapalia heteroptera, Beroe Mertensii,
and Idyia capensis have been noticed, and Alcinoe rosea off the Falkland Islands.

In the Indian Ocean we may already distinguish the fauna of Madagascar, and
in the Pacific that of the low Islands, as distinct from that of Western Australia
and of the Sunda Islands. Off Madagascar, Callianira triploptera is mentioned. About
Australia, Sophia diploptera, Eschscholtzia dimidiata, and Neis cordata have been
found; about Timor and New Guinea, Lemniscus marginatus and Pleurobrachia rosea ;
off Ceylon, Eucharina costata and Bucephalon Reynaudi. On the coast of Japan,
Eucharis Tiedemanni, Janira Cucumis, and Pandora Flemingii seem to indicate a
special fauna; on the coast of Chili and Peru, Martensia octoptera, Pleurobrachia
Basteri, and Beroe mitraeformis point to another; while Bolinopsis elegans, Mnemia
Kubhli, Calymma Trevirani, Axiotima Gedei, Cestum Najadis and C. Amphitrites and
Idyia macrostoma have been indicated, without special localities, as found in the
Pacific, though it is not to be taken for granted, on that account, that these species
have necessarily a wide range of distribution. But how much remains to be done
here before the boundaries of most of these faune can be defined, may easily be
inferred from the fact, that a dozen species only are known from the whole expanse
of the Pacific, exclusive of the coasts of Asia and America.

ee ae

a re
s

EXPLANATION OF THE PLATES.

In order not to spoil the appearance of any of the most delicate and of the smallest figures drawn upon the following plates, which

require a large number of signs to explain their details, I have only added special references to the largest of them, or to

those which would not be injured by crowded marks of every kind; but, to supply this deficiency, I have had wood-cuts made

corresponding to the figures requiring the most minute explanations, and trust that the others will explain themselves by comparison.

PLATES I. and I.

Ipyra ROSEOLA Ag.

[All the figures of these Plates were drawn from nature by A. Sonrel.]

Prater I. requires but little explanation. It represents Idyia
roseola in different stages of growth and in different
attitudes, in the size of life, and with its natural
colors.

Figs. 1-3 represent adult specimens; figs. 4 to 10 are not
full grown; fig. 6 is a young, magnified in fig. 6a.

Fig. 1 is a view from the narrow side of the body,
showing the two anterior or posterior ambulacra and
two of the lateral ambulacra, one on each side of the
figure. The circumscribed area is visible, but fore-
shortened, as it trends at right angles with the surface
represented.

Fig. 1a shows how the lips may close up.

Fig. 2 represents the same animal from the broad side
of the body, showing the two lateral ambulacra of one
side in the centre of the figure, and two of the an-
terior and posterior pairs, one on each side of the
figure. On the abactinal side the lateral interambu-
lacrum rises above the level of the circumscribed area,
which trends in the plane of the figure.

Fig. 2a represents the mouth turned sideways, showing
the linear arrangement of the epithelium lining the

interior of the digestive cavity.

Fig. 3 represents the abactinal side of the body as it
appears when fully distended by the filling of the chy-
miferous system. In the centre appear the circum-
scribed area and the eye-speck, towards which trend
the eight narrow bands extending from the summit of
the ambulacral rows of locomotive flappers to the eye-
speck. On the sides of the circumscribed area, nearly
midway of its two halves, the ecceliaec apertures may
be seen. Nearly concentrically with the abactinal
termination of the locomotive flappers, the outline of
the digestive or cceliae cavity may faintly be seen
through the thickness of the spherosome, as well as
the eight ambulacral tubes which trend in the direction
of the locomotive flappers and the ecelac tubes which
run between the lateral ambulacra, and are seen pro-
jected beyond the outlines of the digestive cavity. The
deep pink rows on the sides of the locomotive flappers
are formed by the accumulation of pigment cells over
the spermaries, while the paler rows on the opposite
sides of the ambulacra indicate the ovaries.

Fig. 4 is a view from the actinal side with the mouth
shut in a straight line. The outlines of the digestive
cavity and the chymiferous tubes are visible through
the thickness of the spherosome. The ecliac and the
oral tubes are particularly distinct.

Fig. 5 represents a half-crown specimen from the broad
side, with the actinal end of the body turned inside
into the digestive cavity, in consequence of which the

(1)

ee — a

a

(2) EXPLANATION OF THE PLATES.

general form appears more rounded than under ordinary
circumstances, as may be seen upon comparing fig. 5%,
which represents the same animal in the same con-
dition from the actinal side with fig. 4, in which the
mouth is visible.

Fig. 6 is a view of a young specimen, as they appear
early in July, magnified in fig. 6%, to show more dis-
tinctly that the short rows of locomotive flappers leave
the ambulacral tubes uncovered for half the height of
the body, and that the ramifications of these tubes are
much fewer and much more simple than in older
individuals.

Figs. 7 and 8 represent one and the same specimen, about |
half grown, from the side in fig. 7, and from the anterior |
or posterior surface in fig. 8. The locomotive flappers
extend already much nearer the mouth than in fig.
6, and the ramifications of the ambulacral tubes are
more numerous; but the whole body is still much paler
than that of adult specimens.

Fig. 9 is a view of the mouth, contracted in the centre
and gaping forward and backward.

Fig. 10 represents a specimen gorged with a Bolina nearly
as large as itself, distorting its form to so great an extent
as barely to resemble another view of the same, given
in fig. 7.

Prarte II. represents structural details of Idyia roseola.

Figs. 1 and 2 show the difference there is in the appear-
ance of the abactinal end of the body when seen from
its broad or narrow side. Fig. 1 shows the broad or
lateral side, with the lateral spheromere and especially
the lateral interambulacrum bulging above the anterior
and posterior pairs, and concealing partly the circum-
scribed area, which however shines through, with the
eye-speck in the centre. Fig. 2 shows the narrow
anterior or posterior side, with the eye-speck and the
foreshortened circumscribed area visible in the trough
formed by the depression in the abactinal termination
of the anterior and posterior spheromeres.

Fig. 3 is a magnified view of the abactinal pole, repre-
senting the position of the eye-speck in the centre of the
abactinal area, between the anterior and the posterior
halves of the circumscribed area, and with the central
termination of the eight narrow bands extending from
the summit of the locomotive flappers to the eye-speck.
The gray bands forming a zigzag around the eye are
the outlines of the funnel.

Fig. 4 represents a magnified band across one ambulacrum
and part of another. Right and left of the row of

locomotive flappers are the ovaries and the spermaries ;

the first covered with deep pink-colored pigment cells,

and the latter only lined with paler pigment. Another
row of ovaries belonging to the adjoining ambulacrum
is seen in the same interambulacrum, and the inter-
vening part of the spherosome is traversed by numer-
ous branches of the ambulacral tube, arising partly
from the ovarian pouches and partly from the tube
itself. Along the spermaries there are no ramifications
of the chymiferous tubes.

‘ig. 5. The abactinal end of the ambulacrum of a
younger specimen, in which the ovaries and spermaries
are not yet developed, more highly magnified, in
order to show the trend of the cells of the radiating
system.

Fig. 6. Ramifications of the chymiferous tubes of an adult
specimen more highly magnified, to show to what extent
the eggs may be crowded in these tubes, after they
have lett the ovaries.

Fig. 7 gives an oblique view of the celiac bulb, rising

upon the side of the circumscribed area. The lower

part of the figure represents a part of the surface of
the area itself, with its marginal fringes, to show that
the cceliae bulb is outside the area, as is again shown
in fig. 9, where the eceliac aperture is represented gaping,
in the shape of a circular hole.

Fig. 8. Profile view of the eye-speck with its transparent
cap, magnified and seen from the broad side of the
body, so that only four of the narrow bands are visible
below it, and part of the circumscribed area in profile.
This figure corresponds exactly to fig. 3, which repre-
sents the same parts, and in the same size, from
above.

Fig. 9. Circumscribed area on one side of the eye; seen
obliquely, in order to show at the same time its entire
outline, the surface encircled by its fringes, the celiac
aperture on its side, and the narrow band of one of
the anterior ambulacra following its outline.

Fig. 10. Vertical section of the whole body, in the di-
rection of the longest or axial diameter, with the exception
of the abactinal side, through which passes a transverse
section reaching the digestive cavity. The adjoining
wood-cut (fig. A), which represents only the abactinal
part of fig. 10, Pl. IL, may best explain the parts so
brought into view. The actinal part of fig. 10 shows
the prolongation of the parts cut through in fig. A,
one half of the mouth and one half of the oral tube
being cut through in the anterior and in the posterior
interambulacra, and the lumen of the oral tube ap-
pearing in the thickness of the spherosome. The epi-
theliel lining of the digestive cavity appears as vertical

striae above the margin of the mouth.

EXPLANATION

rr\ celiac tubes, r is cut near its origin. — 7° 1 lateral ambulacral tubes, cut
near their origin. —Z P anterior and posterior ambulacral tubes, cut near
their origin; all the cut ambulacral tubes are on the same side of the
body; on the opposite side the following organs are visible from their
internal face: —/5 3 anterior and posterior ambulacral tubes. —/5 /# lat-
eral ambulacral tubes. —aaqaa represents the section of the spherosome.

with three
a band of

as pouches

Fig. 11. Profile view of an ambulacral tube,
rows of extended locomotive flappers and
pigment cells upon the spermaries projecting

from that side of the tube.

Fig. 12. Oblique view of seven rows of locomotive flappers,
greatly curved.
Fig. 13. Magnified view of an ambulacral tube, with four

rows of slightly arched locomotive flappers, and the
incipient pouches of the spermaries partly covered by
pigment cells.

Fig. 14.
how rapidly the rows of locomotive flappers taper on

Abactinal termination of an ambulacrum, to show

that side, in comparison with their actinal termination,
as represented in fig. 17.

Fig. 15.
rows of slightly arched locomotive flappers.

Profile view of an ambulacral tube, with five

The ad-
joining interambulacrum is so raised that the row of
pigment cells covering the spermaries is seen in profile,
while in fig. 13 it is depressed and the whole diameter
of the tube is visible.

Fig. 16.

specimen, slightly magnified, with the adjoining inter-

Profile view of the ambulacral tube of an aduli;

ambulacrum depressed so that the ovarian pouches are

fully seen. As these organs and the spermaries are
on opposite sides of the ambulacral tubes, the loco-
motive flappers appear curved in a different direction
in fig. 16 and in fig. 13, as they are seen in opposite
directions.

Fig. 17.
flappers, tapering to a mere thread and surrounded by

Actinal prolongation of the row of locomotive
branching pigment cells. Here the underlying ambu-
lJacral tube, from which arise two small branches on
the same side, is much broader than the row of flap-
pers. It is interesting to notice, that even in the
prolongation of the tube beyond the ovaries and the
spermaries, the pigment cells are much more crowded
on the spermatic side of the tube than on the oppo-
site side, and that the branches extending into the

spherosome arise only on its ovarian side.

VOL. III. 39

OF THE PLATES.

(3)

Fig. 18. This figure is reproduced in the adjoining wood-
cut, fig. B.

Idyia in profile and sufficiently magnified to show the

It represents the abactinal pole of our

relations of the central chymiferous cavity to the ambu-
lacral and celiac chymiferous tubes, to the forks of
the funnel, and to the celiac aperture.

a capsule of the eye-speck.—Jb eye-speck.—cc circumscribed area. —d
coeliac aperture. — e tubercle of the eye-speck.— ff forks of the funnel.
—g opening of the celiac tube. —7 cceliac tube itself. —h h narrow pro-
longations of the rows of locomotive flappers. —Z /2 anterior and posterior
ambulacral tubes with the flappers of 2.—/8/) lateral ambulacral tubes
with their flappers. — 1 internal ramifications of the ambulacral tubes.

Fig. 19 is fully explained on page 281 of the text.

PLATE Ia.
PLEUROBRACHIA RHODODACTYLA.
[Figs. 1 to 19, and 21, 23, 24, and 26, drawn from nature by H.
J. Clark, the others by A. Sonrel.]

A, B, C, D, E, F, G, H, the eight broad interambulacra
trending from the actinal to the abactinal poles: in figs.
20, 21,
A and E in the plane of the digestive cavity, and

These letters also

mark the position of the eight interambulacral bands

oD
“hy

and 23, they are placed correspondingly,
C and G in the tentacular plane.

of the peripheric cellulo-motor system, which are shown
in a transverse section at the equatorial region.

a, the mouth. It assumes the most diversified outlines when
shut, or expanded in various ways.

a', the corners of the mouth, or the edge of the digestive

cavity, seen in the distance.

b, the actinal part of the digestive cavity.

c, the abactinal part of the digestive cavity upon the
walls of which exist the brown hepatic cells, through
which the substances which have been digested are
emptied into the maii chymiferous cavity d. There
is, at its bottom, an opening c’.

d, central chymiferous cavity. This cavity with its vertical

prolongation f corresponds truly to the main cavity of

Polypi, with this difference, that in Polypi there are

partitions dividing it off around the periphery, while

in Meduse the mass of cells forming the body occupies,

to a great extent, the inner space of the animal, and

(4) EXPLANATION

leaves only tubes for the peripheric circulation of the
fluid contained in it. The vertical prolongation f of this
main cavity extends in the direction of the circumscribed
area, and branches into two forks /', f°, at its termi-
nation. The other tubes arising from it are the two main
chymiferous horizontal tubes e, e, with their branches q,
q, and their eight ambulacral tubes 7 to *, which open
The tubes 7, 7, which

follow the walls of the digestive cavity, arise also from

into the vertical tubes [ to P.

it near the main horizontal trunks; and from these latter
arise the tubes of the tentacular apparatus a, a.

e, e, the main horizontal trunks of the chymiferous tubes,
from which arise the eight radiating branches opening
into the ambulacral tubes.

F, the vertical or axial funnel-like prolongation of the main
cavity of the body. (f', f° the two forks of that fun-
nel. It should be remarked, that the direction of that
fork is in the plane of the longest diameter of the cir-
cumscribed area, which is also the direction of the
longitudinal diameter of the mouth.

g, the roots of the tentacle; g'’ the edge of the ridge
of the tentacular base; g° the side of the ridge.

h, Wt, 1?.—h designates the whole tentacular apparatus
with all its complicated parts, 4’ being the tentacular
apparatus of one side, and 4? the tentacular apparatus
of the other side. These numbers are appropriated to

the same apparatus in every figure, whatever may be

It will

be noticed, that these tentacles are placed at right

the position in which the animal is observed.

angles with the plane of the mouth and of the circum-
scribed area.

i, the eight horizontal tubes of the chymiferous apparatus
which reach the vertical tubes, following the vertical rows
of locomotive flappers. In all the figures the horizon-

tal tubes are numbered in the same way, beginning

with No. 1 and ending with No. 8. No. 1 is assigned
to that tube which extends to the vertical row in
sight on the left hand when the mouth is turned up-
ward and the tentacular apparatus appears symmetri-

cally on the right and on the left; so that 7, %, 3,

z# are the four horizontal tubes of one half of the

body, and ®, ®, 7, & are the four horizontal tubes of

the opposite half. And if the view I have taken of
the diameters of these animals is correct, that the longi-
tudinal diameter of the mouth divides the body into
symmetrical halves, one to the right and the other to
the left, the tubes * to # are the tubes of the an-
terior half, and the tubes * to ® are the tubes of the
posterior half, and the tubes @, i', ®, 7 are the tubes

of the left side, and the tubes 7, @, ®, ? are those of

OF THE PLATES.

the right side, or vice vers, as we can only establish

these general relations between the different diameters

without determining strictly which is the anterior and

which is the posterior edge of the mouth. It is prob-
able, however, that no distinction is intended in the
structure of these animals, as they are capable of as-
suming inverse positions, mouth upward and mouth
downward, in which case the edges of the mouth
appear in an inverse position.

j, the tentacular socket or cavity in which the tentacular
apparatus is suspended, and to the inner wall of which
it is attached. This cavity opens at j’, and through
this opening the tentacle may be extended; but it is
also capable of such contraction as to be entirely with-
drawn within the cavity /.

j', opening of the tentacular cavity, through which the

tentacle is protruded.

k, the main stem of the tentacle from which the fringes
arise.

k’, fringes of the tentacles which arise uniformly upon

the same side, the outside, of the tentacle, so that

they are stretched in opposite directions from the two
sides. But this direction is constantly modified in
the various attitudes and the various degrees of elon-
gation of the tentacles, as these are capable of being
twisted upon themselves; so that the fringes may
appear as forming a spiral upon the main stem, or
may be stretched in all possible directions, in their
more or less extensive elongations. However, at the
base they arise strictly in opposite directions.
1,1, the vertical rows of locomotive flappers, of which there

These

vertical rows are numbered in the same manner as the

are eight of uniform length in Pleurobrachia.

horizontal tubes which open into the vertical chymiferous
tubes accompanying the flappers, and these numbers
correspond in the different figures, in the same man-
ner as in the tubes; /' to /* being the rows of one
extremity, and 7 to those of the other extremity,
and 7, [, &, & being the rows of one side, and P, U*,
&, 8 the rows of the other side.

m, the radial cellulo-motor system around the corners of
the mouth.

m', the oral motor system.

m, the radial system in the tentacular plane.

m’, the lateral system where it passes from the actinal

end of the tentacular sockets to the periphery of the

body.

the interambulacral motor bands in the plane of the

ty

digestive cavity.

nt, the same as v, but in the tentacular plane.

EXPLANATION

n', the abactinal end of the interambulacral motor bands.

n‘, the inner face of x.

n’, the actinal end of the interambulacral motor bands.

n°, the tentacular motor system.

p to p’, the lateral cellulo-motor system ; p where the wings
from two opposite sides meet; p' those cells which pass
from the tentacular sockets to 7, /°, lt, 3, and C and
G; p* the profile of the inner face of the wings;
p* the superficial termination of this system, along the
borders of m!. This system is shown only on one half
of the figure, in order to avoid confusion.

q,@; the four main trunks from which the eight radiating

It should be noticed, that these

tubes are not strictly in the same horizontal plane, since

chymiferous tubes arise.

their respective position varies more or less in the differ-
ent contractions of the body, and those on one side
are successively higher than those of the opposite side
in the alternate contractions of the opposite halves of
the body, which regulate the general circulation of the
nutritive fluid.

r, r', the celiac tubes following the digestive cavity.
They arise from the main horizontal tube, and extend
to the margin of the mouth, following the middle of
the fiat surface of the digestive cavity.

7’, entrance to r, 7.

s, the eight epidermic narrow bands of fixed ciliate bodies
which pass from the abactinal ends of the rows of loco-
motive flappers to the base of the cap over the peduncu-
lated globular eye 6.

t, (, the radial cellulo-motor system around the axial funnel.

u, rows of locomotive flappers.

v, vertical chymiferous tubes, which accompany, on the
inner surface, the rows of locomotive combs.

v', the same as v in a contracted state.

w, basal line of the locomotive flappers.

wi, the sub-ambulacral motor cells, probably continuous with
those which constitute the flappers.

z, ganglions? These swellings are more or less eva-
nescent, and appear rather to be small bodies caught
in the symmetrically arranged folds of the chymiferous
tubes.

x x*, cells of the interambulacral system on the borders
of the sub-ambulacral system <*.

y, ganglion-like bodies, arising probably from the aceumu-
lation of granules in the contracted state of the ver-
tical chymiferous tubes when the circulation has ceased.

a, chymiferous tubes of the tentacular apparatus.

a!, the opening through which the vertical chymiferous tubes
of the tentacle open into the main horizontal chymife-
rous tubes between their main forks.

OF THE PLATES.

a' a/!!, the same as a, one on each side of the tentacular
base.

B, elongated disk from which the tentacles arise.

8’, margin or outer wall of /.

g', outer wall in profile at the margin of y.

6!'', outer wall at the thickest part of the disk.

y, the longitudinal furrow of the disk (in fig. 15), or the
keellike prolongation of the inner layer of the disk
between the tentacular tubes, to which it is a wall.

y', the inner layer of the tentacular base.

yl, the apex of the disk.

6, eye-speck in the centre of the circumscribed area.

6’, globular cavity containing the eye-speck 6.

e, the shallow, oblong furrow of the circumscribed area lined
with vibratile cilia.

é, raised line following the inner outline of ©, probably the
analogue of that row of fringes so conspicuous around
the circumscribed area in some other genera of Beroid
Meduse, and particularly distinct in the genus Idyia.

e*, another line, parallel to the former and within it, the
special nature of which I have failed to ascertain.

¢, the openings, cceliae apertures, of the two bulbs of the
vertical funnel, through which the focal matters are
from time to time discharged.

6, the tubercle upon which the eye-speck 6 rests.

4, k; concentric swellings connected with the ganglion of
the eye-speck, stretching in the direction of the Jongi-
tudinal diameter of the circumscribed area.

4, four ganglionic swellings within the inner of the swollen
margins near the ganglion of the eye-speck, the nature
of which I have also failed to determine.

Figs. 1-12. Lasso-cells from the fringes of the tentacles.

Fig. 1 is magnified 500 diameters, the others 200 di-

ameters, by means of Spencer’s one fourth inch ob-

In all

these figures a is the wall of the cell, b the lasso, ¢

jective and Tolles’s solid ocular, number E.

the base or point of attachment of 5, d the free
end of 6, e the mouth of the cell, f the granular
covering of a.

ig. 1. A closed Jasso-cell as seen with 500 diameters.

coer
a” dR

ig. 2. The same as fig. 1, magnified as above, with the

granular coating in profile.

Fig. 3. An open cell, partially contracted, and-the lasso
out.

Fig. 4. Still more contracted than fig. 3.

Fig. 5. The wall almost entirely decomposed.

Fig. 6. The lasso forcing its way through the closed
mouth.

Fig. 7. Foreshortened view of fig. 6, the granular coating

in profile.

(6)

Fig. 8. Profile view of a cell, like fig. 3.
Fig. 9. The lasso partially thrust out, and the rest of
the thread distant from the wall, showing that no cell

contraction forces it out, but that it is protruded by its

own act. The granular coating covers the whole cell.

Fig. 10. Similar to fig. 5, in profile.

Fig. 11. Profile view; the thread extruded, but not
uncoiled.

Fig. 12. Showing the same as fig. 9, but more of the
thread is out.

Fig. 13. The tip of one of the tentacular fringes. a the

lasso-cells; the same as a, in profile; ¢ outer wall;
d inner wall; e transparent axis. 350 diameters.

Fig. 14.
circumscribed area covered by vibratile cilia; the bulb

Portions of the elongate shallow furrows of the

and cap of the eye-speck, the two bulbs of the axial
funnel, and the eight epidermic bands of ciliate bodies
prolonged from the rows of natatory flappers. 25
diameters.

Fig. 15.

phery, to show the mode of the attachment of the

The tentacular apparatus as seen from the peri-

tentacle to the disk, and the relation of the latter to
the double chymiferous tubes; taken from a halfcrown

individual. 80 diameters. The better to understand

the relations of these parts, a profile view (Fig. C)

Fig. C.

a a’’ chymiferous tube.

a’ entrance to q.

é wall of the main horizontal
chymiferous trunk.

e/ wall of the opposite side of e.

g The base of the tentacle.

j tentacular socket.

ji aperture of 7.

j? apex of j.

j® proximal side of 7.

Ak the tentacle,

q point of junction of e and a/.

pir outer wall of the disk.

Bee same as 3/7.

y_ the inner layer of the disk.

y inner layer of the disk at the
base of the tentacle.

it the thin proximal wall of a.

//7 the same as er

7y/// the thickest part of the

same layer.

A full account of the structure

of this apparatus may be found
on page 235.

of the same apparatus is here introduced, with the
same lettering as fig. 15 of Pl. I".

EXPLANATION OF THE PLATES.

Fig. 16. A few lasso-cells from fig. 17. 500 diameters.
Fig. 17. One of the tentacular fringes, showing the lasso-
cells to be arranged side by side in an uninterrupted

layer ab; here and there the threads are out. 350
diameters.

Fig. 18.
tacular fringe.
outer wall; dd! the immer wall; e the transparent
axis. 350 diam.

Fig. 19. The eye and its cap; the bulb underlying the
eye; the eight rows of immovable cilia; and the

Transversely sectional view of a contracted ten-
b the layer of lasso-cells; ¢ ct the

oblong shallow furrow, more highly magnified than in
fig. 14.
Figs. 20, 21, 22, and 23 represent the same animal in

50 diameters.

four different views, so that, after a careful study, its
form might be carved from them.

Fig. 20.
tinal end, to show the organs in their relative position ;

A full-grown individual, seen from the abac-

the eye and the shallow oblong furrow of the cireum-
scribed area are nearest the observer; the tentacular
apparatus comes next, and the two great main chymife-
rous trunks are about the middle of the body. 4
diameters.

Fig. 21.

to show principally the relation of the cellulo-motor

Same as fig. 20; seen from the actinal end,

systems to the organs; the mouth is nearest the eye,
then come the tentacular sockets, and lastly the two
great chymiferous trunks.

Fig. 22.
next the observer, the digestive cavity ()) presents
its broad side to the eye, and the bulbs (jf? /*) of
the axial funnel stand right and _ left.

Fig. 23.
stand right and left, as do also the two chymiferous

Profile view, in which one of the tentacles is

View at right angles to fig. 22. The tentacles
tubes (r 7) which embrace the digestive cavity; the
latter (>) presenting its edge to the eye.

Fig. 24.
tems.
b same as a, but contracted and wrinkled; ¢ the wavy

The enormous cells of the cellulo-motor sys-
These are from the radial system. a the wall;
face of b; d transparent cavity of the cell; e the
slender points of the cells. 500 diameters.
Fig. 25.

tentacles trailing behind, and the fringes curved, waved,

An individual, natural size, swimming with its

bent at various sharp angles, and stretched to the
utmost or closely retracted. For other views, see my
paper in Mem. Amer. Acad. Vol. IV. Pl. I.

Fig. 26. One of the natatory paddles and the subjacent
cells of the cellulo-motor systems, to show the relation
of the cells of the paddles to those of the motor sys-

tem. 50 diameters.

: EXPLANATION OF THE PLATES. (7)

PLATES Ii, IV., V., and V2.

Cyanrea arctica, Per. and LeS.

[All the figures of these plates were drawn from nature by A. Sonrel.]

Prate III. represents Cyanea arctica in one of its natural

attitudes, quietly floating near the surface of the water
with all its appendages hanging loosely down, most of
the tentacles being fully extended, and a few only
contracted.
appreciate the position of the different parts, in their

The attitude chosen makes it possible to
natural relations, as seen in profile. One of the pillars
of the digestive cavity being in the centre of the figure,
two of the ovarian pouches are visible to the right
and left of it, behind the curtain formed by the four
bunches of tentacles of the same side. The crescent-
shaped line of insertion of the tentacles is well dis-
played by the two bunches on the right and left of
the pillar of the main cavity; it is foreshortened in
the two bunches occupying the margins of the figure.
Three eyes are visible, one in the centre of the margin
of the disc and one on each side, a lobe without eye-
The festoon-like
ramifications of the chymiferous tubes in the lobes of

speck intervening between them.

the margin of the disk are plainly visible, the disk being
slightly contracted, in which case the margin is bent
The dark ridges in the centre of the

figure, terminating in sharp points, mark the outlines

downwards.

of the lower surface of the gelatinous disk, which is
of a rich reddish brown color, and forms the roof of
the main cavity of the body, exhibiting deep radiating
furrows arising from an even central flat disk. Be-
tween the margin of the disk and the pillars of the
digestive cavity appear the circular and the radiating
folds of the lower floor of the main cavity of the body,
and below the ovarian pouches and behind the ten-
tacles hang the folds of the prolongation of the oral
tentacles, which are more extensive in the genus Cya-

nea than in any other Medusa.

The specimen represented was an adult of ordinary size,

four times larger than the figure, which may give some
idea of the magnificence of such a Medusa when in
full activity, with all its tentacles stretching in every
direction. Specimens measuring three feet across the
disk are not rare in the Bay of Boston, in September,
and their tentacles may be seen trailing to a distance
In our
figure the lower ends of a large number of tentacles
are cut off. When perfectly undisturbed the tentacles
may be extended to an extraordinary length.

of ten feet in every direction from the disk.

Prate IV. represents our Cyanea from the lower surface,

with different parts removed, and reproduced by them-
selves.

Fig. 1 may give a general idea of the relations of all

the parts visible from the lower side, some of them
being removed to allow the others to be seen in their
Of the four lobes

extending from the four corners of the mouth, two

natural connection with the whole.

are entirely removed, and one (s) is retained entire, its
two halves d! and d!! being spread wide open to show the
medial furrow leading into the digestive cavity; of the
fourth (s’) only one half d is preserved with the medial
furrow, and the other half is cut off along the furrow.
One half d of the lobe s’ and one half d! of the lobe
s are seen as they unite near the mouth, to show
how the four lobes are separated from one another,
The four

ovarian pouches alternate with these four lobes; but

and how their margins are folded all round.

only two are preserved in this figure, one of which
is almost entirely covered by the oral lobes of that
side, while the other is entirely uncovered, the two oral
lobes which hang to the right and left of it having
been removed. It is thus seen that the sexual pouches
hang down between the pillars of the corners of the
mouth, and lie in the centre of a ray terminating with
an eye o!, each being flanked by two bunches of tenta-
cles lying in the direction of two lobes a!! and al’,
in the centre of which there are no eyes. The cavities
of the sexual pouches open freely into the main cavity
of the body; one of the cavities is laid open in the
direction of the eye o!!’, the walls of the pouches
being cut through near the pillars of the digestive
cavity. On the opposite side, the lower floor of the
main cavity is entirely removed in the direction of
the lobe a’, while in the direction of the lobe a the
sexual pouch is alone cut off. The four oral lobes
alternating with the four sexual pouches are thus
seen to occupy the centre of eight rays, each of
which terminates with an eye, 0 0 0 o! o!! oll’, two
These

eight rays are the centres of the eight spheromeres

eyes being covered by the oral lobes s and s!.
of which a Cyanea consists. Homologically speaking,
they are the eight ambulacral zones of the Cyanea.
With them alternate eight interambulacral zones, a a!
a! a!'', the centres of the four others being covered
by a bunch of tentacles on the left side of the figure
and by the oral lobes at d!! d! and d. In the cen-
tres of these eight interambulacral zones there are eight
bunches of tentacles, three of which are covered by the
oral lobes preserved in this figure, and one of which

(8) EXPLANATION OF THE PLATES.

is entirely removed in the zone a’; another is cut to
the base of the tentacles in the zone a; two others, in
the zones a!’ and a!!', are cut very short; and one,

between o!! and ol!!!

8 preserved to a greater extent.
The circular folds of the lower floor are entirely pre-
served between the zones o!! and o!!! and in the zone
a, and partially so in the zone a’! and o. The radi-
ating folds are best seen in the zones o! o!! o!!!, and
partially in the zone a.

Fig. 2 represents a part of the outer surface of the lower
floor in connection with the oral appendages, a a being
the smooth membrane in the direction of the centre
of the ambulacra, as seen in fig. 1, in the zones o!
o!” and o!!'; bb the radiating folds in the same zones;
ee the radiating folds in the interambulacral zones ;
d d' and e the circular or concentric folds, e being
in the ambulacral and d and qd! in the interambu-
lacral zones; 1 and 1 are the two pillars of one corner
of the mouth, to the right and left of which projects
a sexual pouch: at 2 these pillars unite with the hori-
zontal and circular thickenings (3 and 4) of the oral
circle, and at 5 arise the folds of the oral lobes.

Fig. 3 represents the marginal folds of the disk surrounding
the eye abc; a being the ambulacral tube of the
eye, narrowed in 0}, before reaching the eye proper e.
The whole magnified twenty-five diameters.

Fig. 4. A fold of the margin of the oral lobes magnified
twelve diameters, to show the clusters of lasso-cells scat-
tered upon their inner surface; one of these clusters
is magnified 250 diameters in fig. 4a.

Fig. 5. A lobe of the margin of the disk to show the
ramifications of the chymiferous tubes.

Fig. 6. The margin of the disk folded downward over
the furrow in which the eye lies, to show the thick-
ness of the gelatinous upper layer of the umbrella.

Fig. 7. A portion of the lower floor of the disk, seen
from its upper or inner surface, to show how the cavity
of the tentacles opens into the main cavity of the
body.

PLare V. Besides many structural details relating chiefly
to the tentacles, this plate represents our Cyanea as
seen from above, with the margin fully expanded.

Fig. 1 gives a general view from above, the animal resting
upon a dark ground. All the figures visible in this
drawing are the optical expression of the unequal trans-
parency of the gelatinous mass of the disk, through
which shines the reddish-brown lining of the lower side
of its upper layer. In the centre appears a tessel-
lated, circular disk, which in adult specimens readily

separates from the peripherie part. The straight rays

mark the deep furrows of the lower surface, radiating
from the central disk to the base of the eyes and to
the middle of the interambulacral zones; the eight
longer rays being the ambulacral furrows, the eight
shorter ones the interambulacral furrows. The thicker
bands, converging and diverging again about half-way
their length, correspond to the thickenings of the gelati-
nous mass to which the lower floor of the disk is
attached; so that by this connection of the two floors
the main cavity of the body is divided into an open
circular central space and sixteen radiating flat cham-
bers, the eight narrower of which, trending in the
direction of the eyes, are the ambulacral chambers, and
the cight wider ones alternating with them the inter-
ambulacral chambers. Upon comparing this figure with
fig. 1 of PI. TV. it will be seen that the eight bunches
of tentacles communicate with the eight interambulacral
chambers; and that the four sexual pouches and the
four angles of the mouth face alternate ambulacral
chambers.

Fig. 2 corresponds to fig. 6 of Pl. IV., but represents the
same segment of the margin of the disk from the upper
side. This shows the eyes to be above the margin
of the disk, as the tentacles also are.

Fig. 3 represents a band of the inner surface of the oral
lobes magnified, from the margin upwards; showing
that along the margin the epitheliel cells are smallest
and consist chietly of lasso-cells, fig. 3d, while higher
up the lassos are in clusters, and the intervening epi-
theliel cells are gradually larger and larger. On the
outer surface the lasso cells are few and far apart.

Fig. 4. Section of a tentacle, covered with clusters of
lasso-cells, showing its inner channel and the trans-
parent gelatinous wall. Magnified 12 diameters.

Fig. 5. Clusters of lasso-cells from the surface of a tenta-
cle. Magnified 250 diameters.

Fig. 6. Other clusters of similar cells. Magnified 250 diams.

Figs. 7, 8, 9, and 10. Segments of tentacles, magnified
60 diameters, showing different combinations of epi-
thelial cells and clusters of lassos. @ indicates the
central cavity of the tentacles, and } the band of
longitudinal cells by the contraction of which the tenta-
cles are shortened.

Figs. 11 and 12. Cells lining the cavity of the tentacles.
Magnified 250 diameters.

Pirate V®. Structural details of Cyanea arctica.

Fig. 1. Transverse section of the peripheric part of one
side of an ambulacrum, across the furrow for the eye.
o furrow for the eye; a® a’ sections of the chymife-

rous tubes.

Eee

EXPLANATION OF THE PLATES.

Fig. 2.
farther from the margin of the disk, across the peri-

Transverse section of the same ambulacrum,

pheric end of the radiating folds of the lower floor.
o lower floor; ot ambulacral chamber; 0) radiating
folds of the lower floor; a’ section of the chymiferous
tubes.
Fig, 3.
the middle of the radiating folds of the lower floor

Transverse section of the same ambulacrum, across

and extending to the centre of the adjoining inter-

ambulacrum. o' ambulacral chamber; 0 radiating folds
of the ambulacrum; c¢ radiating folds of the adjoining
interambulacrum; f tentacles of the adjoining inter-
ambulacrum ; a’ interambulacral chamber; a* chymife-
rous tubes of the adjoining interambulacrum; g thick-
ness of the upper floor; o lower floor.

Fig. 4.

the region where the concentric folds of the lower

Transverse section of the same ambulacrum, across
floor occur. o' ambulacral chamber; a! interambulacral
chamber of the adjoining interambulacrum; e lower
floor of the ambulacrum with concentric folds; e' lower
floor of the interambulacrum with concentric folds;
g thickness of the upper floor. The isthmus between
the two corresponds to the broad radiating bands of
feds Pl Vv.
Fig. 5. Transverse section of an interambulacrum, in the
g upper
floor; a lower floor of the interambulacrum; 0 lower

region where the concentric folds occur.

floor of the adjoining ambulacrum; a! interambulacral
chamber ; 0! ambulacral chamber of the adjoining
ambulacrum; e and e! folds of the lower floor of the
ambulacrum and of the interambulacrum.

Fig. 6.

across the tentacles.

Transverse section of the same interambulacrum,

a interambulacral chamber; 0}
radiating folds of the adjoining ambulacrum; c radi-
ating folds of the interambulacrum; e¢* lower floor of
the interambulacrum; jf! openings of the cavities of
the tentacles; f tentacles; g g upper floor.

Fig. 7.

ot ambulacral chamber; e concentric folds of the lower

Longitudinal section of an ambulacrum. o eye;

floor; g upper floor.

Fig. 8. Longitudinal section of the ocular chymiferous
tube. o eye; o' peripheric prolongation of the ambu-
lacral chamber or chymiferous tube of the eye.

Fig. 9. Transverse section of part of the upper floor, at

disk. 0
ambulacral furrow leading into an ambulacral chamber ;

a little distance from the central circular

a interambulacral furrow leading into an interambu-
lacral chamber.
Fig. 10.

near the central circular disk.

Transverse section of part of the upper floor,

o beginning of the

—
(Jeo)
os

ambulacral furrow; a a beginning of two adjoining
interambulacral furrows.

Fig. 11. Transverse section of a marginal lobe of the

disk, corresponding to the left part of fig. 1. g g

upper floor; 0 o lower floor; a*® a® chymiferous
tubes.
Fig. 12.

surface.

Part of the lower floor, seen from the outer
d' d‘ concentric folds in that part of the
lower floor which is detached from the upper floor ;
e concentric folds in that part of the lower floor which
is united with the upper floor along the line k; ¢'
radiating folds intersecting the circular or concentric
folds; ¢ radiating folds of an interambulacral zone :
b radiating folds of the adjoining ambulacral zone.

Fig. 13.
the direction of e in fig. 12.

12s

Longitudinal section of an interambulacrum, in
d' concentric folds
e' concentrie folds

corresponding to d' in fig.
to] fo)

corresponding to e! in fig. 12; f! openings of the
D> c—) 2 P fo)

cavities of the tentacles in the prolongation of the
same zone; f the tentacles.
Fig. 14. Transverse section across the middle of a Cya-
nea, to show the general relations of the upper and
lower floors of the disk. The section passes through
two interambulacral, and through two sexual pouches,
and divides the mouth so as to leave two oral lobes
99
floor; f! f! and e e lower floor; /' f! being the

entire. This figure is much reduced. upper
openings of the tentacles leading into the ambulacral
chamber, and e e the concentric folds of the lower
floor; ff tentacles; os, os, sexual pouches; 3 3 thick-
ened ring of the mouth; dd the oral lobes; d* d*
the marginal folds of the oral lobes.

Fig. 15 is intended to show the connection of the oral
lobes with the lower floor, e e' and d' being the part
of the lower floor with concentric folds. 1 is one

of the pillars arising with two roots from the margin

of d! to form one of the corners of the mouth, while,
at the same time, supporting the lateral walls of the
main cavity, 5 marking the point where the pillar
divides again to form the two halves of each oral
lobe, as seen in Pl. 4, fig. 1 s, 2 being one of the
branches; 3 is the thickened ring of the mouth con-

necting the four pillars; under its thickest part, 4,

the oral lobes bend inward to shut the mouth; os
folds of a sexual pouch, o 0 being the sexual organs ;
dd oral lobes; d* d* folds of the oral lobes.

Fig. 16. Internal view of the mouth, the four pillars

supporting its four corners and their prolongations into

the oral lobes being cut through in different ways, so

as to exhibit in different sections the varying thick-

(10)

yi Cy
the four pillars; s s ss the furrows along the middle
of the lower surface of the oral lobes; d d d the oral
lobes, meeting from below in the centre of the figure

ness of the pillars and of their prolongation.

to shut the mouth; os, os, os, the cut edges of the
sexual pouches.

Fig. 17 explains more fully the relations of the parts
represented in fig. 16. 3 oral ring; 4 thickening of
the oral lobe d bending over the mouth; os fold of
the sexual pouch.

Fig. 18 shows how the sexual organs of are supported
in the folds of the sexual pouch os.

Fig. 19 shows the connection of an oral pouch with the
concentric folds ¢' of the lower floor, and, with the
tentacles ¢ ¢, connected with the sexual organs of.

Fig. 20.
ries; of folds formed by the ovaries; ¢ their tentacles.

Lobes of a sexual pouch stretched out. 0 ova-

Fig. 21. Lobes of the sexual pouch of a young female.
o undeveloped ovary; of folds of the ovary; ¢ their
tentacles.

Fig. 22.

out.

Lobes of a sexual pouch of a male stretched

os folds of the pouch passing into the concentric
folds of the lower floor; s spermatie cells; sf folds
of the spermatic sacs; ¢ their tentacles.

Fig. 23. Part of the lower floor, embracing one entire
ambulacrum o and one entire interambulacrum a, with
one half of the adjoining ambulacrum and interambu-
lacrum, to show the inequality of the width of the
ambulacral, e, and of the interambulacral, e’, chambers,
kk being the gelatinous bands along which the upper
and lower floors are united; 7 the tentacles, and d' the
point where the folded part of the lower floor passes
into the folds of the sexual pouches and into the pillars

. of the digestive cavity.

Fig. 24. Ramifications of the chymiferous channels along
the margin of the disk. ¢ tube of the eye; 0 lobe

of the eye; @ interambulacral incision; a @ inter-

The

in white of

ambulacral lobes; o0' and o ambulacral lobes.

parts in black correspond to the parts
fig. 23, the channels being kept light in fig. 24 and dark

in fig. 23, having been drawn upon different grounds.

PLATES VI., VIl., VI., and IX.
AURELIA FLAVIpDULa, Per. and LeS.

[All the figures of these plates were drawn from nature by A. Sonrel.]

Pirate VI. represents our Aurelia from below, with sundry
details.

EXPLANATION OF THE PLATES.

Fig. 1. When the disk is fully expanded, and the ap-
pendages of the lower side are in their natural position,
several features appear in this species, which seem not
to have been noticed in other allied Acalephs. The
mouth is closed by folds of the oral lobes, and one
of these folds forms a transverse ridge across the oral
aperture. The oral lobes, or so-called arms, are not
stretched out at the same angles with one another,
but stand nearer each other on opposite sides in one
direction than in the other. In the ramifications of
the chymiferous system it should also be noticed, that,
of the sixteen simple radiating tubes, eight reach the
base of an ocular apparatus, and eight others, alter-
nating with them, anastomose with the marginal circular
tube without branching.

Fig. 2.
downward. ‘This figure shows that during the con-
tractions of the disk rr, the oral lobes are not pro-
jected beyond its margin, but are bent along the furrow
formed by the curve, and the tentacles, >, thrown out.
oo eyes; dd chymiferous tubes; a @ folds of the

Segment of the same, the margin being arched

oral lobes or arms; e their stem; 7 opening leading
into a blind sac below the sexual pouch (this opening
is generally but falsely represented as leading into
the sexual cavity and communicating with the main
cavity).

Fig. 3. Oral opening laid open by the reversion of the
oral lobes a a? a’, a remaining in place.
of the centre of the disk projecting into the oral

o pyramid

aperture, which exhibits eight emarginations, four, ¢ 7,
in the angles corresponding to the base of the stems
of the oral lobes, and four, e e, in the direction of
the sexual pouches.

Fig. 4.
where this is curved down.
of the margin of the disk; e e, 7 7 chymiferous tubes

Eye, as seen facing the margin of the disk
o eye: cc ocular lobes

of the ocular apparatus.

Fig. 5. ‘Transverse section of the oral arm of a male
individual, showing how much thinner its stem is than
that of the female, fig. 6. @ stem of the oral lobes;
b and ¢ its two halves spreading to form the folds
or lobes, e e, of the arms.

Fig. 6. ‘Transverse section of the oral arm of a female
individual. a@ stem; } ¢ its halves; e e the folds
or lobes in the pouches of which the eggs are received
and remain until the young is freed to swim about.

Prare VII. General view of Aurelia flavidula from above,
with structural details.

Fig. 1. View of our Aurelia from above, in which the
ovaries appear plainly through the transparent disk,

a Ua

and the oral arms are faintly visible below. This
figure shows distinctly, that in four directions the chy-
miferous tubes arise directly from the main cavity, and
in four other directions, alternating with the former,
they arise from the peripheric side of the sexual
pouches.

Fig. 2. Magnified view of the margin of the disk, seen
from below, to show the origin of the tentacles a a,
between the lobules of the margin b b 6, the veil
ce extending along the under side. d represents a
chymiferous tube.

Fig. 3. View of the same from above, more highly mag-
nified, showing the clusters of lasso-cells scattered over
the upper surface. a a tentacles; b b lobules of the
margin; ¢ circular marginal chymiferous tube; d d
radiating chymiferous tubes.

Fig. 4. Longitudinal section of the margin of the disk,
the better to show the relations of the tentacles a a a,
and the marginal lobules b D.

Fig. 5. View of the centre of the disk from below, the
oral appendages being removed. 0 pyramidal pro-
jection of the centre of the disk; adc radiating chy-
miferous tubes arising directly from the main cavity
of the body; ddd radiating chymiferous tubes arising
from the peripheric side of the sexual pouches, one
of which, ¢, is laid open by the removal of its lower
floor, while in the others the floor is preserved; 7 in-
dicates the arch over the opening leading into the
blind sac which extends below the sexual pouches.
This opening is generally represented as leading into
the sexual pouches, but this is not the case; the arch
~ supports a thin vein which separates the sexual
pouches from the blind sacs below.

Fig. 6. Top of a tentacle, magnified. e its cavity; a
epithelial layer covering its surface.

Fig. 7. Termination of one of the oral appendages or
arms with its marginal fringes b, 6; the channel a
extends along its middle from the tip of the mar-
ginal lobes to the main cavity of the body.

Pirate VII. Profile view of our Aurelia with structural
details.

Fig. 1. Profile view, in a state of contraction of the
disk, when the oral appendages appear inclosed in the
cavity thus formed, and the sexual pouches are seen
in profile, exhibiting distinctly the wreath formed by
the sexual organs, as well as the origin of the chy-
miferous tubes arising from the margin of the sexual
pouches.

Fig. 2. Transverse section of the margin of the disk, to
show the difference of thickness of the upper and lower

VOL. III. 40

EXPLANATION OF THE PLATES. (a1)

floors a and c, with the chymiferous tubes b b!, formed
by the union of the two.

Fig. 3. Similar section, magnified. a@ upper floor; ¢

Fig

Fig

lower floor; % line of separation between the upper
and lower floors; ! chymiferous tube formed by the
recession of the upper and lower floors; d lower sur-
face of the lower floor.

. 4. Upper surface of the upper floor magnified, to
show the clusters of lasso-cells scattered over it.

. 5. Transverse section of the margin of the disk,
which, in connection with fig. 4 of Pl. VIL, may fully
explain the relations of all the parts there combined.
a opening of the marginal circular chymiferous tube ;
e the tube itself; 6 section of the veil extending along
the lower surface; ¢ part of the veil itself; d d ten-
tacles; d! cavity of one of the tentacles; f radiating
chymiferous tube, opening into the circular tube of
the margin; /* another radiating tube cut through in
the section, in which h marks the upper floor, and

g the lower surface of the lower floor.

Fig. 6. Magnified tentacles to show their connection with

the circular marginal tube. d tentacle; d' d' cavity
of the tentacles; e e marginal tube into which the

tentacles open.

Fig. 7. Lobes of the ovary with their tentacles. a folds

of the sexual pouch; b b ovarian lobes; ¢ ¢ tentacles

of the ovarian folds.

Fig. 8. An ovarian lobe, stretched out to show that the

folds of the sexual pouches surround the sexual organ
on both sides. aa folds of the pouch; b b ovarian

lobes stretched; c ¢ tentacles of the ovarian folds.

Fig. 9. Margin of the oral lobes, in the depressions of

cs

which the eggs and planule are received, magnified.
aaa clusters of eggs and planule in different stages
of development, gathered in the sac-like depressions
of the margin of the oral lobes, where they remain
until they are capable of living independently of their
parent; & b the fringes or tentacles of the margin of

the oral lobes, adapted to seize upon the prey.

Puare IX. Structural details of our Aurelia.

Fig. 1. Spermarian lobes stretched out, magnified sixty

diams. 6 b spermaries; ¢ ¢ tentacles of the spermaries.

Fig. 2... Several spermarian lobes, less extended, magni-

fied 12 diams. 0 b spermaries; c¢ c tentacles of the

spermarian folds.

Fig. 3. Eye, with its chymiferous tubes and the tenta-

cles on its sides. 0 eye; e e marginal circular tube,
from which arise the tentacle-like tubes 7, 7, ce; fff
radiating chymiferous tubes; d! d! tentacles opening into

the marginal tube.

(12)

Fig. 4.

eye; ee¢e marginal circular tube; c c outer tubes;

Eye, with a larger part of its surroundings. 0

i i marginal folds inclosing the ocular apparatus; f/f

radiating chymiferous tubes; d d d_ tentacles.
To understand correctly the sections represented in figs.
5, 6, 7, 8, and 9, the direction in which they are cut
should be first ascertained by a comparison with figs.
1 Pls VL and Vals
tween two ovarian pouches, to the margin of the
disk. If it were prolonged across the whole ani-
mal, it would divide fig. 1 of Pl. VI. and VII. into

and the

Section 5 runs from the centre, be-

halves ; part represented corresponds — to
the right side of the upper half, the tube running
between the bisected arm 0 and the ovary 7, along
the lower surface of the disk, being one of the chy-
miferous tubes which arise from the main cavity of
the body. Figs. 7, 8, and 9 also pass through the
centre of the disk, but extend through the centres of
two opposite ovarian pouches, that is, they run at
an angle of 45° with the section fig. 5, or obliquely
across fig. 1 of Pls. VI. and VII.

tral pyramid of the disk is removed to show more

In fig. 7, the cen-

plainly the mode of communication of the ovarian
pouch x p, with the central cavity of the body s;
and, to bring these relations more plainly into view,
the left ovarian pouch is also removed, and in the
right ovarian pouch the veil which separates the
pouch from the blind sae below is removed with the
ovaries themselves, while in figs. 8 and 9 they are
left in place. Fig. 9 corresponds to fig. 8, except
that fig. 8 passes through the centre of the pouch
and shows the cavity from one side and fig. 9 from
the opposite side, the section passing somewhat ob-
liquely through the pouch. Fig. 6 is a transverse
section across an ovarian pouch from side to side of
the
the

pouch, and not, like all the others, radiating from
centre to the periphery.

Fig. 5. Section across the disk, including the centre and
one side.

the

o pyramid of the centre; p veil forming

lower floor of the sexual pouch; g channel lead-

ing from the central cavity into the sexual pouch;

r sexual organ; n sexual pouch; s central cavity;

aa oral lobe; } its stem cut through; ¢ ¢ its mar-
ginal folds; mm m upper floor or gelatinous mass of
the disk.

Fig. 6.

munication with the central cavity.

Sexual pouch, seen from the side opposite its com-
d d lower floor
of the disk; p arch of the veil p', which separates
the sexual cavity , in which the sexual organs rr

are inclosed, from the blind sac jf, which is below and

EXPLANATION OF THE PLATES.

communicates through the hole f with the surrounding
medium.
Fig. 7.

across two opposite ovarian pouches, leaving one, in

Another section through the centre of the disk,
the centre of the figure, entire in the distance. s cen-
tral cavity; a@ a oral appendages or arms; b b stems
of the oral appendages cut through; ¢ ¢ marginal folds
of the arms; d and e the thickened pillars in the lower
floor surrounding the hole /, below the sexual cavity ;
r r sexual organs; p veil forming the lower floor of
the sexual pouches; n sexual cavity; mm upper floor.
Fig. 8.

o pyramid of the centre of the disk; s central cavity

Another section passing through a sexual pouch.
of the body; a@ oral appendage or arm, cut through
at 6; cc its marginal fringes; d and e lower floor
thickened and inclosing the blind sac f; q channel
leading from the main cavity into the sexual pouch
nm; 7 sexual organ; p' veil separating the sexual
pouch from the blind sac below; m m upper floor.
Fig. 9.

a sexual pouch.

Another section, passing somewhat obliquely through
a arm, cut through at 6; d and e
thickened lower floor, surrounding the blind sae 7; 0
pyramid of the centre of the disk; s main cavity ;
q channel leading into the ovarian pouch; p veil sepa-
rating the ovarian pouch from the blind sae below;
p section of the veil; r 7 sexual organ; nn sexual

pouch; m m upper floor of the disk.

PLATE X.

ScypHostoMA OF CYANEA ARCTICA AND AURELIA

FLAVIDULA.

[Figs. 18, 22, 31, 32, and 36, Aurelia flavidula, were drawn by

A. Sonrel; the others, Cyanea arctica, by H. J. Clark.]

Figs. 1 and 2. Eges from the ovary of Cyanea arctica,
Sept. 28, 1857, magnified 500 diameters. —v vitelline
sac; y y' yolk; p Purkinjean vesicle; w Wagnerian
vesicle.

In all the remaining figures, 3 to 38, the following letters
refer to the same parts. a the outer wall of the body;

a' the outer wall of the tentacle; J the inner wall of the

body; ¢ the mouth or proboscis; c! the basal or pos-

terior end; d the digestive cavity; e e' the tentacles ;

f the base of the horn-like sheath or tube.

Fig. 3. A globular embryo, just eseaped from the pouches.
Magnified 500 diameters.
Fig. 4. Profile view of an ovate embryo just from the

pouches. 500 diameters.

1s.

EXPLANATION

Fig. 4%. View of the broad end of fig. 4.
Fig. 5. Profile of a cylindrical embryo. 200 diams.
Fig. 5a. End view of fig. 5.

Fig. 6. One of the smaller forms of cylindrical embryos.
200 diameters.

Profile of an embryo, swimming with the clear

space (d) behind. 200 diameters.

Fig. 72. End view of the darker end of fig. 7.

Fig. 8. In this embryo the clear space ((/) is very large.
200 diameters.
Fig. 8% The same as fig. 8, contracted, and the clear

space obliterated.

Fig. 9. View of the flat side of an oval, concave, disci-
form embryo. 200 diameters.
Fig. 92. Edge view of fig. 9, showing the double con-

cave sides.

Fig. 10. View of the flat side of an ovate, compressed
embryo. 200 diameters.
Fig. 108 Edge view of fig. 10.

Fig. 10.

ig Broader end of fig. 10.
Fig. 10°,

Narrower end of fig. 10; the cilia are reversed
by the embryo.

Fig. 104. The mouth of fig. 10; the cilia are quiet, and

look like bristles. 500 diameters.

Fig. 11. An irregularly ovate, cylindrical embryo, recently

attached to a sea-weed, the tentacles (¢) just beginning

to bud. The vibratile cilia do not move any more,

and have begun to decompose. 200 diameters.

Fig. 12. A scyphostoma with an incipient horn-like sheath.
The cilia are quiet and decomposing. 200 diameters.

Fig. 122.

fig. 13.

View of the actinal end of fig. 12.

A scyphostoma with two incipient tentacles;
the cilia are still persistent but immovable.

Fig. 138,

Fig. 14.

200 diams.

Actinal end of fig. 13.

A scyphostoma with four young tentacles and

a narrow base, but no horn-like sheath. 200 diams.

Fig. 14a. The same as fig. 14, with the mouth very
wide open.

Fig. 14b. View of actinal end of fig. 14, showing the
asymmetrical development of the tentacles (e).

Fig. 14. The same as fig. 14, with the mouth (c) enor-

mously distended, and the tentacles so completely re-

tracted as to be undiscernible.

Fig. 15. An abnormally developed scyphostoma. 100

diameters.

Fig. 16. | Another form of abnormal development. 100
diameters.

Fig. 16. <Actinal end of fig. 16.

Fig. 17. Actinal end of an individual with three ten-
tacles. 100 diameters.

OF THE PLATES. (#3)

Fig. 18. Similar to fig. 17, but a little older.
Fig. 19.

100 diams.

A profile view of a scyphostoma with four ten-

tacles, which are only half extended, and the pro-

boseis retracted. 200 diameters.

Fig. 20. Similar to fig. 19, but the tentacles and base

more extended. 100 diameters.

Fig. 21. Similar to figs. 19 and 20. One of the ten-
tacles has seized upon a wandering embryo, and is
drawing it toward its mouth. 100 diameters.

Fig. 22. Actinal end of an individual similar to figs. 19,
20, and 21.

Fig. 23.
proboscis as in fig. 16, but foreshortened.

Fig. 24.

100 diameters.

Actinal end, with two double tentacles; the
100 diams.
Actinal end, with four unequally developed ten-
tacles. 100 diameters.
Fig. 25.

of the second group; the quadrangular mouth is dis-

Actinal end, with three incipient tentacles (¢)

torted. 100 diameters.
Fig. 26.

quinary development of tentacles, and a very large

Three quarters view of a scyphostoma, with a

proboscis. 100 diameters.

Fig. 27. Actinal end, with one tentacle, of the second

group, unduly developed. 100 diameters.

Fig. 28. Actinal end, with three double tentacles. 100
diameters.

Fig. 29. Actinal end, with a three-cornered mouth. 100
diameters.

Fig. 30.

g Actinal end, showing a captured embryo re-

volving in the digestive cavity. 100 diameters.
Fig. 31. Profile view of an individual similar to fig. 30,
with the tentacles and base fully extended. 100 diams.
Fig. 32. Actinal end, the mouth rounded and one ten-
tacle forked.
Fig. 33.

100 diameters.
Profile, with eight tentacles, a slender base, and

the corners of the lips prominent. 100 diameters.

Fig. 34. Three quarters view, with eight well developed
tentacles. The outer and inner walls are made prom-

inent. 100 diameters.

Fig. 34%. Actinal end of fig. 34, with the tentacles re-

tracted to mere papillae, and the mouth shaped into

an eight-sided figure. 100 diameters.

Fig. 34h. Actinal end of fig. 34, with tentacles retracted
and curled inwardly.

Fig. 35. Profile view, with eight tentacles, one of which
is drawing the excrementitious matter from the open
proboscis.

Fig. 36. Actinal end, similar to fig. 34, but the mouth

contracted to a small oval aperture and the tentacles

partly retracted and curled inwardly. 100 diameters.

Fig. 37. Profile of a double-headed scyphostoma, with

(14)

eight tentacles on one head and only four on the

other. 100 diameters.
Fig. 37a. The same as fig. 37, with the tentacles retracted.
Fig. 38. A forked tentacle. 100 diameters.

PLATE Xa.

ScypHostoMA OF CYANEA ARCTICA AND AURELIA

FLAVIDULA, ETC.

[Figs. 1, 2, 3, 4, 4a, 5, 6,7, 8, 10, 11, 12, 12a, 14, and 15 are drawn
by H. J. Clark; figs. 4b, 9, 18, 15a, 16 to 41, by A. Sonrel.]

All the figures by H. J. Clark, and fig. 9, are Cyanea are-
tica; and all those by A. Sonrel, excepting fig. 9, are
Aurelia flavidula. Unless when stated otherwise, the
following letters refer to the same parts: a outer
wall of the body; a' outer wall of the tentacle; a
lasso-cells; a® end of the tentacle; % inner wall of
the body; 2' inner wall of the tentacle; & radiating
partition in the body; 0° transverse wall of the cells
in the axis of the tentacle; ¢ mouth; c® proboscis;
cl base of the body; d digestive cavity; e ¢' tenta-
cles; jf horn-like sheath; p, Purkinjean vesicle; w,
Wagnerian vesicle; y, yolk.

Fig. 1.
scyphostoma.

Fig. 2.
phostoma.

Fig. 3.
500 diameters.

Fig. 4.
contracted tentacles, the mouth wide open, and the

The mouth and one tentacle of an eight-armed
500 diameters.

Partially retracted tentacle of a four-armed scy-
500 diameters.

Contracted tentacle of an eight-armed seyphostoma.
An eight-armed seyphostoma, showing the strongly

horn-like sheath. 200 diameters.
Fig. 42.

like sheath.

Base of fig. 4, to show the details of the horn-

500 diameters.

Fig. 4>. Similar to fig. 4, but the tentacles only partly
retracted. 200 diameters.
Fig. 5. Actinal end of an eight-armed seyphostoma to

show the details of the mouth, radiating partitions, ete.

200 diams. The arrangement of the cells around the

mouth and along the tentacles shows an unmistak-
able resemblance to the plates forming the borders
of the corresponding parts in Echinoderms, and espee-
ially in Star-fishes.

Fig. 6.

cellular structure of the walls.

Basal portion of fig. 20, Pl. X., to show the

a’ outer surface of the
outer wall (a); 0" outer surface of inner wall (?).
500 diameters.

Fig. 7. Tentacle of fig. 14, Pl. X., to show the lasso-

cells. 500 diameters.

EXPLANATION OF THE PLATES.

Fig. 8. Cells from the inner surface of the inner wall
of fig. 14¢, Pl. X.

Fig. 9.
the wall of the cell; 6 the coil.

Fig. 10. Lasso-cells from the tentacle of Fig. 14, Pl. X.
500 diameters.

Fig. 11.
two of the first set forked.

Fig. 12.

500 diameters.
A to G lasso-cells of a full-grown Cyanea. a

500 diameters.

The second set of tentacles half developed, and
100 diameters.
Shows one hydra fixed temporarily in the

mouth of another. 100 diameters.

Fig. 12% Actinal end of A, fig. 12.
Fig. 13. The third set of tentacles partially developed.

b° intervals between the radiating partitions (2°). 100
diameters.

Fig. 14.
developed in fives, and the mouth five-sided.

Fig. 15.

Actinal end of a scyphostoma with ten tentacles,
100 diams.
Actinal end of a scyphostoma with fourteen
tentacles, in various stages of growth; the numbers
refer to their relative ages. 100 diameters.
Fig. 15a,
Figs. 16 to 24.

from the ovary of a full-grown Aurelia.

Similar to fig. 15, but very much contracted.
The serial development of the egg; taken
200 diams.
Figs. 25 to 36. The progressive development of the free

seyphostoma planula of Aurelia. Figs. 26, 27, 28,
30, 31, and 32 from the ovary; figs. 25, 29, 33, 34,
35, and 36 from the pouches. 200 diameters.

Fig. 37. The proboscis and sexual organs (¢) of fig. 22,
Pl. Na.
the proboscis; d aperture of the mouth.

Figs. 39, 40, and 41.

with the same letters.

a lips; a@ incipient fringes of the edge of
? I to) Po)
20 diams.

Details of the proboscis of fig. 37,

PLATE XI.

STROBILA OF AURELIA FLAVIDULA.

[Drawn by A. Sonrel.]

Unless otherwise stated, all the figures are magnified 15
In all the figures of Plates XI., XIs., XTb.,

and XIc., the following letters refer to the same parts,

diameters.

unless otherwise stated.

For the scyphostoma, ¢ is the mouth or proboscis; ct
base of body; c? c® ct offshoots from the body; d
digestive cavity ; e el tentacles; g g' g° g° gg? constric-
tions preparatory to the formation of the saucer-shaped
disks.

For the ephyra, a is the proboscis; a‘ the mouth or lip;
a? the cavity of a; b the digestive cavity ; )' limit of ); ¢

chymiferous canal leading to the eyes; c’ c* branch of

e; c entrance to c; ct end of c; c® chymiferous canal
in the peduncle of the eye; d ridge of c; d? fork
of d; d? floor of c; e chymiferous canal to the ten-
tacles; ¢! lateral branch of e; e inner wall; ¢ en-
trance to e; f ridge of e; g sexual appendages; g!
common opening of g; g? second row of appendages ;
g

+ outer wall of h; A? inner wall of 2; 23 base of

* common opening of g?; g* exterior pouch; h eye;
h; i facets of eyes; h° base of h above; h° base of
facet 14; h’ centre of h; h® lateral base of h; ia

2

veil; © marginal lobules; # tentacle, or tentacular
lobe; i* inner wall above; #® inner wall below; @
outer wall above; # outer wall below; @® lower side
of the veil; @ edge of the disk; j oculiferous lobe ;
J’ lappets of 7; j? ridge of j'; j* ridge in transverse
section; j* back of the lappet; j® edge of j above;
j® outer wall above; j7 inner wall above; j* inner
wall below; j® outer wall below; & partitions between

canals; i

partially isolated partition; 2? an insular
partition; 7 the disk; 7 axis of the strobila; [ axis
of the disk; m muscular ring, inner edge; m!' outer
edge of m; me marginal canal; aj edge of lobe /,
below; %/ commsisure of lappets j*; cj depression at
the base of bj; dj fold of the lappet below.

Fig. 1. The lowest ephyre of a strobila which has already
lost the upper ones, ready to drop; they are drawn
here whilst in the systole of one of their convulsive
contractions, by which they break loose, and the
remains of the scyphostoma has its fully developed ten-
tacles extended to the utmost.

Fig. 2. The remains of a scyphostoma, showing the off-
shoots.

Fig. 3. Another old seyphostoma, with a few distorted
ephyre.

Fig. 4. An old scyphostoma, with distorted tentacles, and
a few nearly mature ephyre.

Fig. 5. The base of a column of ephyre, and a scy-
phostoma with eye spots, h, at the base of the ten-
tacles.

Fig. 6. A scyphostoma, with its second row of tentacles,
bearing a column of thirteen ephyre in various stages
of development.

Fig. 7. A scyphostoma with twenty tentacles, probably
belonging to the second group formed after the fall
of the ephyre. '

Fig. 74. Proboscis of fig. 7. 20 diameters.

Fig. 8. Interior view of the edge of the ephyra of fig.
14. 30 diameters.

Fig. 9. The plicated lip of the proboscis of fig. 13 1.
30 diameters.

EXPLANATION OF THE PLATES. (15)

Fig. 10. A young strobila, still incomplete ; the terminal
ephyra has the deciduous false tentacles.

Fig. 11. A strobila casting its last ephyra.

Fig. 12. The base of a double strobila, formed by trans-
verse division of the discs B and C.

Fig. 13. The last ephyra just ready to drop.

Fig. 14. The last and youngest of a pile of ephyra,
bearing sixteen deciduous, false tentacles.

Fig. 15. An incipient pile of ephyra, the terminal one
bearing sixteen deciduous tentacles.

Fig. 16. An old strobila, the terminal ephyra bearing
sixteen deciduous tentacles, and the seyphostoma having
two rows of tentacles.

Fig. 17. The three oldest ephyre are nearly mature,
whilst the fourth is far behind in age.

Fig. 18. An old seyphostoma with three rows of ten-
tacles.

Fig. 19. The terminal ephyra shows the homologies be-
tween the tentacles of the seyphostoma and the ocu-
liferous lobes and eye-peduncles of the ephyra.

Fig. 20. One of the ephyre of fig. 10.

Fig. 21. Scyphostoma-like ephyre, similar to figs. 18
and 19.

Fig. 22. A form combining the features of fig. 15 and
fig. 21.

Fig. 23. A double oculiferous lobe from an ephyra of
fiz. 29. 30 diameters.

Fig. 24. A portion of the disk of one of the ephyre
of fig. 29. 20 diameters.

Fig. 25. A mass of monstrosities both of the ephyre
and seyphostoma.

Fig. 26. Proboscis and sexual appendages of fig. 11, 1.

There is no fig. 27. It was omitted in numbering the
plate.

Fig. 28. A terminal ephyra with branching deciduous
tentacles.

Fig. 29. Shows an ephyra just escaping from its axial

attachment, which passes into the proboscis of the next

lower individual.

PLATE Xia.

ScyrpHosTOMA AND EPHYRA OF AURELIA FLAVIDULA.

[All the figures drawn from nature by A. Sonrel.]

Unless when otherwise stated, the figures are magnified
15 diameters. For the lettering, see Pl. XI.
Fig. 1. An old seyphostoma attached by a lateral pro-

cess of its base.

Fig. 2. A seyphostoma-like process (c?) budding from
the base of an old scyphostoma. 20 diameters.
Two seyphostomas arising from a common. basis.

20 diameters.

Fig. 4. An old scyphostoma, with large offshoots.

Fig. 5. Similar to fig. 4, with one rigid-looking off-hoot.

Fig. 6. A scyphostoma bearing an offshoot with a glob-
ular tip.

Fig. 7. A longitudinally ridged scyphostoma with a

distorted offshoot.
Fig. 8. Here the offshoot is forked (c? c’).
Fig. 9. The offshoots are remarkably long and_ ten-
tacular.
Fig. 10. A strobila just making its first constriction.
Fig. 11. A strobila with two constrictions.

Fig. 12. A deformed strobila.

Fig. 13. Two of the disks are well formed, but not
mature.
Figs. 14 and 15. <A foreshortened and a three-quarters

view of the proboscis of fig. 19. d aperture of the

mouth; e the sexual appendages. 20 diameters.
Figs. 16 and 17. Various attitudes
fig. 26. a the cruciate aperture; a’
the proboscis; e sexual organs.
Fig. 18.

fig. 19.

20 diameters.

the proboscis, in the distance; ¢ inner surface of the
folds of the aperture d; e sexual appendages. 60
diameters.

Fig. 19.

it became

Lower side of an ephyra, a short time after

free. The broad radiating canals d and

e occupy as much space as the intervals. 10 diams.

Fig. 20. Upper side of fig. 19 when it is in a con-
tracted state.

Fig. 21. Same as figs. 19 and 20 when the umbrella
is reverted.

Fig. 22. Profile view of an ephyra, which has the corners

(a') of the lips and the veil (7) very prominently

developed ; @ the tentacular lobe. 10 diameters.

Fig. 23. Same as fig. 20 in profile. 5 diameters.

Fig. 24. Another reverted form of fig. 19.

Fig. 25.
than fig. 22.
the

Fig. 26.

Upper surface of an ephyra a little younger
The branching lines are dorsal folds in
canals. 10 diameters.

Upper side of an ephyra, which is a_ little
younger than fig. 25. About 15 diameters.
Fig. 27. A three-quarters dorsal view of fig. 19 in a
reverted or diastolic state. 5 diameters.
Fig. 28. Profile of fig. 19 in the diastole.

Fig. 29. Portion of the edge of an ephyra, bearing

EXPLANATION OF THE PLATES.

of the proboscis of

lip; d cavity of

More highly magnified view of the proboscis of

a cruciate fold of the lips a'; } outline of

several tentacles and having an incipient lacunar
branching of the canals.

Fig. 30. Same as fig. 25, in a contracted state.

Fig. 31. Oculiferous lobe of fig. 19, lower side. 20
diameters.

Fig. 82. Dorsal view of fig. 22 in a contracted state.

Fig. 33. Foreshortened view of fig. 31.

Fig. 34. Eye peduncle of fig. 31. 60 diameters.

Fig. 35. Cells from the upper surface of the lappet of

the oculiferous lobe of fig. 25. 1 lasso-cells. 470 diams.

PLATE XIb.

EpuyraA OF AURELIA FLAVIDULA.

[Drawn from nature by H. J. Clark.]

Figs. 1 and 2, from an ephyra a little younger than that
of fig. 19, Pl. XIa.
Fig. 1. The incipient sexual organ, seen from below,
with two rows of digitate appendages, the longer ones
(7) seen beyond the shorter. 100 diameters.
Fig. 2. The edge of the disc, seen from below, between
two oculiferous lobes, bearing a single budding tentacle
(*) and a tongue-shaped veil. 100 diameters.
Fig. 3.

fig. 4.

Similar to fig. 2 but older, and belonging to
The principal feature is the incipient folding
of the tentacular lobules @ 100

Fig. 4.

diameters.

Inferior view, from centre to margin, including
one of the oculiferous lobes and the two veils on each
side, of an ephyra in which the radiating canals have
begun to branch; a single tentacle has developed, and
the veil is half as long as the oculiferous lobes. 40
diameters.

Profile of an ephyra with thirty-two tentacles
at every interval. The disk is contracted; the same
See Pl. XIc. fig. 5.

Shows the vibratile cilia on the inner surface

as fig. 20. Natural size.
Fig. 6.
of the proboscis of fig. 5. 500 diameters.

Fig. 7. The eye and eye peduncle of fig. 4, seen from

below, to show the relation of the layer of the len-
ticular bodies of the eye to the walls. 500 diameters.
Fig. 8. Longitudinal sectional view of the eye of fig.
7, showing that the lenses are in the inner wall.
Fig. 9. Longitudinal section of fig. 3, to show the re-
lations of the walls of the upper and lower floors.
100

Fig. 10.

diameters.
The sexual organ, with several rows of digitate
appendages, from figs. 17 and 18. View from below.

100 diameters.

EXPLANATION OF THE PLATES.

Fig. 11.

from the flat or inner end, showing its polyhedral out-

One of the crystalline lenses of fig. 7, seen
line and the branching cavity. @ the wall of the cell
which belongs to the outer wall of the peduncle and
overlies the cell which contains the lens; it is seen

in the distance (see @ fig. 16); 4 the flat side of the

prism foreshortened, and as the outer end is broader
than the inner, the outline of the latter is concentric
to that of the former; @ the solid part of the lens,
to compare with @ in fig. 16; ¢ to compare with ¢ in
fiz. 16; @ the diverticuli from the cavity », in the
centre. 2,000 diameters.
Fig. 12. One of the lappets of an oculiferous lobe of
fiz. 4, curved downwards, so as to give a sectional
view of its thickness, and to show the keel. 100
diameters.
Fig. 13. Transverse section of the simple radiating canal
(e e fig. 17), and the two canals on each side which
come from the forked canal (ec, fig. 17); @, 8, groups
of long-drawn-out cells, remnants of the attachment of
the superposed walls. 100 diameters.

Fig. 14. End view of the so-called eye-speck 4, fig. 7.
500 diameters.

Fig. 15.
diameters.

Fig. 16.

Profile and sectional view of fig. 7. 300

Shows the position of the crystalline lenses in
the cells of the inner wall of the ocular peduncle.
a a superposed cell of the outer wall (see fig. 11 @);
2 the wall of @ where it rests on the outer end, 6,
of the underlying cell; y the clear, homogeneous con-
tents of a; 0d the outer end of the lens-bearing cell;
e the cavity of 7 in front of the lens; ¢ the inner
end or bottom of 7; 6 the side of the prism receding
from the eye; ¢ the side of the prism nearest the
eye; « the rounded anterior surface of the lens; 4
the cylindrical axial cavity of the lens; « the canals
radiating from 2 and following close to the flat pos-
terior face of the lens; » posterior opening of 4.
2,000 diameters.

Fig. 162, A lasso-cell from fig. 7. a the cell wall; >

the aperture of the cell and base of the thread; c

the end of the thread; d point of junction between

the straight axial portion and the coils of the thread;

e the first coil of the spiral; f the transversely spiral

coils. 2,000 diameters.
Fig. 17. <A quarter part of the disk of fig. 18, seen
from below. There are fourteen tentacles. The

branching radiating canals are nearly or altogether
six pronged, and the edge of the disk occupies two
Next the

thirds of the circumference. 40 diameters.

(17)

oculiferous lobe on the right, the veil and the tenta-

cles are curved downwards and inwards.

Fig. 18. An ephyra, seen from below. Natural size.
Fig. 19. One of the marginal fringes of fig. 6, Pl. Xe.

a the end, where the wall is thickened and contains
numerous lasso-cells; % group of lasso-cells; ¢ the
same as } in profile. 200 diameters.
Fig. 20. Profile of an ephyra, with the disk expanded,

the same as fig. 5. (See Pl. XTe. fig. 5.)
Fig. 21. One of the digitate bodies of fig. 18 e, PI.

Xia.

the inner wall of the lower floor from which @ arises ;

Natural size.
a the single wall studded with lasso-cells;

y the entrance to @ 300 diameters.

PLATE Xie.
AURELIA FLAVIDULA (EPHYRA) AND CORYNE
MIRABILIS.
[Drawn from nature by H. J. Clark.]

For the general lettering, see description of Pl. XI.
Fig. 1.

9. aaa the outer wall, seen in a sectional view

A tentacle from the edge of the disk of fig.

(a) near the end of the tentacle, in a surface view
(a’), and again in section where it is very thick (a’)
and contains a group of lasso-cells, and finally where
it is stretched so as to be very thin (a°); } the inner
wall near the end of the tentacle; 0! seen through
a', in a sectional view (0*) underneath a group of
lasso-cells, and extremely extended (4°) like a’; ¢ the
end of the tentacle in section, crowded with lasso-
cells; ct a group of lasso-cells in section; d d_ the
channel extending from base to tip directly from the
circular canal; e groups of lasso-cells. 500 diameters.
Fic. 2.

ately surrounding parts of the disk, from an ephyra

View from above of the eye and the immedi-

an inch and a half in diameter and having fifty ten-
tacles; principally to show the prolongation of the
chymiferous tube into the lappets of the oculiferous
lobe, and the mode of formation and broadening of the
radiating canals. 40 diameters.

View from above of a portion of the tentaculate
from fig. 18, Pl. XI>. Beside
we have a the outer and / the
of a
wall (e) of @; 6 the inner wall
the

Fig. 3.
margin and the veil,
the general lettering

inner wall of @; y

the outer wall where it
passes into the outer
of @ where it passes into the inner wall of 7; ©
outer wall of @; ¢ the inner wall of @ seen in the

distance; 7 the inner wall of ” nearer to the eye

(18) EXPLANATION

than ¢; @ the same as 7, but still nearer to the eye;
« where 7 and @ merge into one outline; « the cavity

between the outer and inner walls of 7; 2 hollow

of the tentacle; @ entrance to 4; © superior margin

;3

of the socket from which ® arises. 200 diameters.

Fig. 4. The same as fig. 3, but seen from below, with the
following additional letters: v the same as A, but fore-

shortened by the curvature of the tentacle; § the in-
ferior margin of the socket from which the tentacle
arises; 7 the broad line of attachment of the veil (7).
200 diameters.

Fig. 5.

XI>., principally to show the branching of the radi-

Inferior side of a quarter of figs. 5 and 20 of PI.

ating canals, the extent of the veil, and the fringes

(cz) of the proboscis. 24 diameters.

Fig. 6. The fringes (@) of the proboscis of fig. 5 in
profile.
Fig. 7. Cells (e) and lasso-cells (a b) from the upper

surface of the disk of fig. 9. 500 diameters.

Fig. 8. The same as d' fig. 2, more enlarged. a entrance ;
@ dorsal side toward the outer veil; y profile of the
wall at the dorsal side of the bend; 4 profile of the

lower side of the curve. 100 diameters.

Fig. 9. View similar to fig. 4, from the same ephyra as
fig. 2. The letters as in fig. 4 excepting e, which

is the outer wall of a very young lobule developing be-
tween the larger ones; p cavity of the young lobule
(€); ¢ groups of lasso-cells. 100 diameters.
Fig. 10, Cellular tissue from the proboscis of an adult
Aurelia, treated with alcohol. 500 diameters.
Fig. 11.

from the outer end.

The eye and the immediate organs, seen obliquely
In addition to the general letter-
ing, there is a the entrance to d'; 3 the dorsal side
of the external half of d'; y profile of the wall at
the bend of d'; © ¢ the wall of d'. 200 diameters.

Fig. 1

7)

2. The same as fig. 10, but in a natural state.
500 diameters.
Fig. 13.

1

Similar to fig. 8, but from fig. 5. The figures

»)

2a 3 refer to the tentacles, from the oldest to

the youngest. Lettering as in fig. 2, with this differ-

ence, that ¢ is seen through the tentacles; 7 where
the outer wall of the tentacles passes into that of its
neighbor. 100 diameters.

Fig. 14.

t=}

Profile sectional view of the walls of the hydra

stem of Coryne mirabilis. a the horn-like sheath;
cells of the outer wall; ' mesoblast of b; ¢ the same
as }, seen in the distance; d cells of the inner wall;
dd brown cells; e the same as d, in the distance.
500 diameters.

Fig. 15. from

A. lasso-cell the outer wall of fig. 14.

OF THE PLATES:

a the cell wall; 0 the straight part of the thread;
e de the first, second, and third coils; f aperture of
the cell and base of 6. 2,000 diameters.

PLATE XII.
PELAGIA CYANELLA, Per. and LeS.

{Drawn from nature by J. Burckbardt.]

lis

9:

Profile view, natural size.

View from below, the mouth appendages being

removed. q@ arms; 0 ovaries; ¢ mouth; d tentacles ;
e eyes.

Fig. 3.
c digestive cavity; d tentacles.

Figs. 4 to 16.

View from above. a eyes; } chymiferous tubes ;

Planule and ephyra of the same.

Fig. 4. Young planula, seen in profile.

Fig. 5. Older planula, seen in profile.

Figs. 6 and 7. Older planula, seen from above, and in
profile.

Figs. 8 and 9. Passage of the planula into the ephyra,
in profile fig. 8, and from below fig. 9.

Figs. 10 and 11.
below.

Fig. 1

Young ephyra, in profile and from

2

2. Older ephyra, from below. ¢ mouth; b eye-
specks; a@ position of the tentacles at a more advanced
period.

Fig. 13. Magnified spheromere in connection with the

mouth. a chymiferous lobes; % eye; ¢ mouth.
Figs. 14 and 15. Magnified eyes. a eye proper; >

chymiterous tube of the eye.

Fig. 16. Magnified mouth, still simple and without arms.

PLATES NUT and NII

PoLycLonia FRONDOSA, Ag.

(Drawn from nature by J. Burckhardt.]

Prate XIII. Profile view and various structural details
of Polyclonia frondosa.
Fig. 1.

dosa of Pallas), with the oral appendages drawn up

Profile view of our Polyclonia (the Medusa fron-

under the disk.
The same, seen from below, different parts being
removed in different segments and shown in a differ-
ent condition in each. 0 o eyes, twelve in number.
2

In segments 1 and 2 may be seen the two branches

of one arm with their marginal lobes entire, and

EXPLANATION OF THE PLATES.

covered with lasso-bearing papille at the base. In
segments 4 and 5 another arm is visible with its marginal
lobes and papilla removed, in order to show that the
arms have the same structure in the Discophore Rhi-
zostomex as in the Semxostomez, only that their margin
is soldered in the Rhizostomee, having only narrow
openings for the admission of the food, instead of
forming open channels. In segments 7 and 8 the base
of the arm, with its papillae m, is alone preserved.
In segments 10 and 11, and parts of 9 and 12, the
base of the oral appendages is removed to show the
main cavity of the body ¢ c. In segments 6' and 7
the ramifications of the chymiferous tubes are repre-
sented as they appear through the lower floor when
injected. In segments 8, 9, 10, 11, and 12 different
aspects of the lower surface of the lower floor are
represented ; in segments 11 and 12 from a specimen
in which it was almost smooth; in segments 9 and
10, with various folds, concentric near the margin,
convolute further inward, and pennate between the
principal chymiferous tubes. In segment § the same

arrangement prevails, but differently combined.

Fig. 3. Young specimen of Polyclonia frondosa seen
from below. o eyes; ¢ arms or oral appendages.
Fig. 4. Internal view of the main cavity with the four

sexual pouches 0 0s oa. 0 sexual organ suspended
between the folds os of the sexual pouches; oa openings
of the sexual pouches, alternating with the arms ¢ ¢,
i ¢, @ #, & 0; s openings of the channels of the four
arms into the main cavity.

Fig. 5.
chymiferous tubes radiating from one of its corners.

Figs. 6

t=}

Central cavity seen from below, with a few

and 7. Openings of the channels leading into
the main cavity.

Figs. 8, 9, 10, 11, 12, 13, and 14.
bearing papille, /, from the base of the arms.

Figs. 15 and 16.

Various kinds of lasso-

Lobes of the margin of the arms with
their fringes ¢, to show the openings s, leading into
the main channel of the oral appendages.

Fig. 17. — Lasso-cells.

Pirate XIII*.
various structural details.

Fig. 1.

what raised in front to show the opening of a sexual

Side view of Polyclonia frondosa, with

Profile view of Polyclonia, with the disk some-

pouch between two arms.
Fig. 2.

Fig. 3.

oD

Transverse section of the disk.
Portion of the same, magnified. g upper floor;
a layer of the chymiferous tubes; 0 lower floor.
Fig. 4.

the marginal lobes and fringes extended.

il 4l

Portion of an arm, seen from its outer side, with

VOL.

(19)

Fig. 5.

leading into the main cavity; d marginal lobes and

The same, from the inner side. s channels

fringes; d' papille of the base of the arm.

Fig. 6. View of the disk from above.

Fig. 7. Segment of the same, in which the colored ring
is not divided into several zones as in fig. 6.

Fig. 8. Portion of the margin, with two eyes, o° 0’, in

the same spheromere.
Fig. 9.
anastomoses of the chymiferous tubes a’.
Figs. 10, 11, and 12.

the edge is thinned out into a sort of veil, beyond

Magnified portion of the margin, showing the
Margin of the disk, to show how

the marginal lobules, between which the eyes, o (figs.
11 and 12), are situated.
Figs. 13, 14, and 15,
Figs. 16, 17, 18, 19, 20, 21, and 22.

Eyes.
Eges in various
stages of development.

Spermatic particles.

PLATE XIV.

SromoLorHus MeLraanis, Ag.
[Drawn from nature by A. Sonrel and J. Burekhardt.]
Profile
Profile

two rows of

Fig. 1.

Fig. 2.

view of Stomolophus Meleagris.

view of the oral appendages, presenting

prominent crests, the upper of which is
concealed under the disk in their natural position.

Fig. 3.
oral appendages, just below the main cavity.

Fig. 4.

letters and figures in figs. 2,

Transverse section across the upper part of the

The
3, and 4 correspond to

View of the oral appendages from below.

one another.

Fig. 5. One of the crests of the upper row seen side-
ways.

Fig. 6. The same, its two halves being separated.

Vig. 7. One of the crests of the lowey row seen side-

Fis. 8. The end of the same seen from above.

PLATE XV.

PeNNARIA GiBpposa Ag., MILLEPORA ALCICORNIS Linn,
PocILLOPORA DAMICORNIS Link., SERIATOPORA SU-
BULATA Lmk.

[Figs. 1, la, 2, 9, 10, 11, 12, 13, 14, 14a, 15, and 15a drawn from
nature by A. Sonrel; figs. 4, 5, 5a, 5b, 5c, 6, 7, and 8 by H.
J. Clark, from sketches by L. Agassiz and the help of alco-
holic specimens; fig. 3 by J. Burckhardt. ]

Millepora, Pocillopora, and Seriatopora were thus far re-

ferred to the Polyps.

(20)

EXPLANATION

Figs. 1, 1a, and 2.
Fig. 1.
the stem; the large terminal hydrx of the branches

Pennaria gibbosa.
A broadside view of a stem, natural size. @

(ce); d the large terminal hydra of the stem.

Fig. la. View at right angles to fig. 1, to show the
curve of the stem and branches.
Fig. 2. A portion of the stem, bearing a branch. A

the main stem; A’ rings of A; B_ the large terminal
hydra of the branch; C the youngest hydra, a mere
bud as yet; D E F G hydra, lettered according to
their ages; @ basal rings of the branch; a’ rings along
the branch; a? terminal rings of the branch; a® pe-
dicel of C; at end of the pedicel of D; 6 pedicel
of the large medusa (d*) of G; d the medusa of D;
d' medusa of E; @ @ meduse of F; d* d* meduse
of G; e é the sexual organs of the medusa (d*) ;
e circular canal of a; f the proboscis of d; g the
tentacles of @; h the radiating canals of d°; m mouth
of the hydra; p proboscis of the hydra; p! the bulging
side of p; p*? the proboscis of F, stretched out; ¢ &
the crown of tapering tentacles; ¢ & the globe-tipped
tentacles of the proboscis. 15 diameters.

Figs. 8 to 13. Millepora alcicornis.

Fig. 3. A branch, natural size, covered by the extruded
hydree.
Fig. 4. A portion of fig. 3, magnified. @ the outer wall

in profile; & the surface of the branch; ¢ g h the
larger forms of hydra, with only four to six tenta-
cles; ¢ k 1 m n the smaller hydra, with numerous
tentacles; d the mouth of c, shown by the bending
of the head to one side; e the aperture of the cell
of c; f aperture of the cell of g; p aperture of the
cell of a small hydra. 25 diameters.

Fig. 5. One of the smaller hydre of fig. 4, @ the
outer and } the inner wall; ¢ c! digestive cavity;
d mouth; e f g h ik lm the short, globe-tipped
tentacles; n the groups of brown cells (fig. 5¢) in
the inner wall. 100 diameters.

Fig. 58 A lasso-cell from the tentacles. @ the empty
cell; 4 the base of the thread (d e f); ¢ the thickened
portion. 500 diameters.

Fig. 5. =A B CDE F other forms of lasso-cells. a

the cell; } the base of the thread (in A the barbs); ¢

the thread.

Fig. 5% abe brown cells from the inner wall. 500
diameters.

Fig. 6. One of the larger hydre of fig. 4, with four
tentacles. Letters as in fig. 5 excepting h, the stem
of the tentacle. 100 diameters.

Fig. 7. Sectional view of fig. 6, to show the form of

OF THE PLATES.

the cells of the inner wall. Letters as in fig. 5. 100
diameters.

Fig. 8. A portion of the surface of a branch, to show
the form of the cells. @ aperture of a cell of a large
hydra; } cell of a small hydra; ¢ the soft walls of
the hydro-medusarium through which the calcareous,
spongiform coral shines; d the spongiform body of the
coral denuded; e f views into the cells of the large
hydre; g g' cells of small hydre; h ij & irregular

radiating partitions of the cells of small hydre; J m
radiating partitions of a large cell (e). 100 diame-
ters.

Fig. 9. Longitudinal section of the cell of a large hydra

with three transverse partitions, taken at a point one
half of an inch below the tip of the branch. a@ the
mouth of the cell; @ the bottom of the cell; ¢ trans-
yerse partitions; d irregular projections from the bot-
tom of the cell; e apertures in the side of the cell,
leading off into the spongiform mass; f branching
cavities in the coral; g h sections of cavities like e.
100 diameters.
Fig. 10. large hydra,
taken at a point half an inch below the tip of a
young branch. a@ mouth of the cell; > bottom of the
cell; c¢ sides of the cell; de f radiating partitions;

Longitudinal section of a young,

g section of an aperture like h; ij branching cavi-

ties in the coral; & solid part of the coral. 100
diameters.
Fig. 11. Transverse section of a branch one inch be-

low its top. a@ highly spongiform axis; & mouth and
e bottom of the cell; d@ ¢ & transverse partitions;
e fg hi cells more or less exposed; / surface of the
branch. 40 diameters.
Fig. 12.

low the top of a branch.

Transverse section one eighth of an inch be-
a the spongiform axis;
bd e f cells in various stages of development; ¢ g
bottom of the cells.
Fig. 13.
stem half an inch

40 diameters.

Longitudinal section of a large cell, from a
in diameter. a@ mouth and 6
bottom of the cell; c the numerous transverse par-
titions; d@ the upper part of the cell only partially
laid open. 40 diameters.

Fig. 14, 14%, 14>. Pocillopora damicornis.
Fig. 14.

est, and b e de f g successively older

a the young-
cells. 40

The tip of a young branch.

diameters.

Fig. 14%. Transverse section of two young cells, a b,
from fig. 14; d and e the bottom of the cells; ¢ c
ridges between the cells.

Fig. 14%. Longitudinal section of an old branch. a

EXPLANATION

ce dehik cells laid open, and exposing their
numerous transverse partitions; fg mouths of cells
not opened by the section; j transverse partition of
k; l common bottom of i and k; m bottom of h
and c, and perhaps of others. 5 diameters.
Fig. 15,. 154.
Fig. 15.

Jf and ¢ the quadruple aperture of the cell; & the pro-

Seriatopora subulata.
Tip of a branche abcde fghi the cells;
jection of the central column, from which four par-
titions radiate to the walls of the cell. 40 diameters.
Fig. 152.

inch from the top of the branch.

Longitudinal section of a cell of fig. 15, one
a@ mouth and b
bottom of the cell; ¢ axial column; d e the four
cavities around the column; / g transverse partition;
hi solid part of the coral; j bottom of the upper-

most cell. 40 diameters.

TABLE XVI.
TlypRACTINIA POLYCLINA Ag.

[Figs. 1, 1a, 1b, le, 1d, le, 2, 2a, 2b, 2c, 2e, 4a, 4b, are drawn from

nature by A. Sonrel; the others by H. J. Clark.]

Fig. 1. A female hydromedusarium. A B C F fertile
individuals; D E G TI sterile individuals; K basal
or stolonie layer; ¢ medusa; 4 head of fertile individ-
uals; p proboscis; s spiny, horn-like processes from
the base. 25 diameters.

Figs. 1%, 1b, 1¢, 14, 1e, different attitudes of the proboscis
and tentacles which the sterile heads assume. m the

mouth or actinostome; ¢ the tentacles. 100 diameters.

Fig. 1¢.

g Profile of a sterile female strongly contracted.

m mouth; ¢ tentacles. 60 diameters.

Fig. 18.
tentacles.

Fig. 2. A male hydromedusarium. A B C K the fer-
tile individuals; D E F G HI sterile individuals;
letters as in fig. i. 25 diameters.

Fig. 22.

and the mouth (m) wide open.

A fertile female hydra without any meduse. t

100 diameters.

A fertile male with the proboscis expanded
¢ the globular ten-
tacles. 100 diameters.
Fig. 2b.
Fig. 2¢.

tops of the tentacles are globular, and in two rows

(t ¢).

The same as fig. 24 with the mouth (m) shut.

A sterile male strongly contracted, so that the

100 diameters.

Fig. 24. The tentacles more strongly contracted than
in fig. 2¢; the proboscis reverted and the mouth

wide open. 125 diameters.
Fig. 2c. The same as fig. 2, but the proboscis (p)

more enlarged.

OF THE PLATES. (21)

Fig. 2f.

and % inner wall; d prolongation of the digestive

A globular tentacle of a fertile male. a outer

cavity. 500 diameters.

Fig. 2. A sterile male strongly contracted. p probos-

cis; ¢ tentacles. 60 diameters.

Fig. 2h, The proboscis of a sterile male. @ outer and

b inner wall; d digestive cavity; m mouth. 300
diameters.
Fig. 3. A fertile female crowded with meduse. a

outer and 6 inner wall; a! outer and %' inner wall
of the medusa; c peduncle of the medusa; d diges-
tive cavity; d' digestive cavity of the proboscis of
the medusa; e eggs; p proboscis of the medusa; ¢
tentacles; A a medusa foreshortened. 300 diameters.
Fig. 3%.
fig. 3.

yolk; p Purkinjean vesicle;

View from the actinal end of a medusa of

«@ outer and b' inner wall; v yolk sac; y
w Wagnerian vesicle ;
vl Valentinian vesicle; A one of the eggs in a
superficial view. 500 diameters.
Fig. 4. A fertile

are discharging their spermatic particles.

male crowded with meduse, which

a_ partially
empty and 0 entirely empty meduse; % the head.
125 diameters.

Fig. 4°.

different stages of development of the meduse; m

Actinal end of a fertile male hydra. a@ toi

the open mouth. 100 diameters.
Fig. 4b.

Fig. 5.

h the head.

A young sterile male and a portion of the

Similar to fig. 42, but younger.
retiform stolon. a@ outer wall of the stolon; a outer
wall of the hydra; network formed by the interior
wall; c digestive cavity; d@ inner wall; e and f
horn-like’ spines; p proboscis; ¢ tentacles. 300 diams.
Fig. 5°.

show a budding of a new channel (/); ¢ outer

A portion of the edge of a stolonie base to

wall; a b line of the section from which fig. 5¢ was

taken; d cells of the outer wall; e chymiferous canal;

f young canal budding; g granular contents of e.
400 diameters.

Fig. 5».

base.

A yery young male hydra budding from the
a outer and 6} inner wall of the stolon; a’
outer and #' inner wall of the hydra; ¢ digestive
400 diameters.

A section through a @, fig. 5% a@ a’ outer

cavity.
Fig. 5¢.
wall; } cells in a@ a; ¢ chymiferous canal of the inner
wall (d).
Fig. 6. One of the horn-lke spines of fig. 5, to show
that it is covered by the retiform stolon. a inter-
stices of the net-work: } 2' the canals; ¢ the spinules
of the spine; d outer wall. 300 diameters.

Fig. 7. A very young male medusa bud. a outer

(22)

and } inner wall of the hydra; d digestive cavity ;
400 diameters.
A two-thirds grown medusa.

1 lasso-cells.
Fig. 8.
fiz, 7; 0 inner wall of the medusa; /* point of

abdtlasin

transition of 2' into the wall of the proboscis c;
e cavity of the disk, containing the spermatic mass.
+400 diameters.

Fig. 9.

peduncle; 7? as in fig. 8; ¢ proboscis; d digestive

A ripe medusa. a@ outer } inner wall of the

cavity; e the spermatic mass.

Fig. 92.
fied 500 diameters; B an exaggerated figure to show
the form of A; h the so-called head; ¢ the fila-
ment.

Spermatic particles from fig. 9; A is magni-

Fig. 10. Lasso-cells from the meduse of fig. 4. 500
diameters.
Fig. 11. Lasso-cells from fig. 2% a@ a closed cell; b a

cell with the thread (c) out; 0! the base of ce.
diameters.

800

Pirates XVIL, XVII, and XIX. represent the structure
and growth of one of the most common Hydroids of
the Bay of Boston, and the mode of growth and
structure of its medusa, which I have already described
in my first paper on the Acalephs of North America,
under the name of Sarsia mirabilis.

PLATE XVII.
CoRYNE MIRABILIS Ag.

[Figs. 1, la, 3, 4, 5, 6, 7, 8, 9,10, and 1a drawn by A. Sonrel; the

others by H. J. Clark.]

Unless when stated otherwise, the following letters refer
to the same parts in all the figures. a@ inner wall
of the hydra; % outer wall; c horn-like sheath; cn
top of the stem; d d! digestive cavity of the stem
and head of the hydra; de disk of the medusa; m
mouth of the hydra; md medusa buds; x proboscis;
p peduncle of the medusa; pr transverse veil of the
medusa; 7 tentacles of the medusa; s stem of the
hydra; ¢ tentacles of the hydra.

Fig. 1.
being the beginning of the breeding season (January

A group of hydre attached to a sea-weed. It

31, 1855), the young medusa buds are not conspicu-

ous. Natural size.
Fig. 14. A portion of fig. 1 magnified about 20 diame-
ters. @ a very young hydra bud.

EXPLANATION OF THE PLATES.

Fig. 2. A single individual, showing that the meduse
are sometimes developed among the tentacles (see md).
m other meduse below the tentacles. 40 diameters.

Figs. 3 to 8. Show the various ages and attitudes of
the hydra. a a' medusie buds in different stages of
growth. 40 diameters.

Fig. 9. A head of a hydra, contracted, showing the
horn-like sheath (c) separated from the neck. 100
diameters.

Fig. 10. A group of hydro-meduse late in the breeding
season (April 25, 1855), when the heads are resorbing
and the meduse are prominent. (See figs. 11, 12,
13, 14, and 15.) Natural _ size.

Fig. 11.

sistent, and developing the spermatic mass around the

A male hydra from fig. 10, the medusa per-

proboscis (7) to an enormous extent. 60 diameters.
Fig. 11% View of fig. 11 from the actinal end.
Fig. 12.

fect medusa is persistent and withering, having dis-

A male hydra from fig. 10; the almost per-

charged its spermatic contents. d peduncle of the
medusa. 40 diameters.

Fig. 13. Similar to fig. 12, but the tentacles of the
hydra have begun to be resorbed. The medusa is
proportionately larger, and has no tentacles. 40
diameters.

Fig. 14. The head of the hydra is nearly all resorbed,
and the medusa, without tentacles, is withering, having
discharged its spermatic particles. 40 diameters.

Fig. 15. The head of the hydra, a female, is altogether
resorbed, and the medusa terminates the stem, like a
head.
five.

Fig. 16.

proboscis enormously distended and crowded with eggs.

a’ the radiating canals, of which there are
60 diameters.
A female medusa attached to a hydra, and the

40 diameters.

PLATE XVII.

CoRYNE MIRABILIS Ag.

[All the figures are drawn from nature by H. J. Clark.]

Figs. 1 to 12 are magnified 400 diameters.

Fig. 1.
b outer wall of hydra; c inner and 0 outer wall of
the bud.

Fig. 2.
and } inner wall of the hydra; ¢ inner and d outer
wall of the medusa; e ¢ chymiferous cavity leading
into the medusa.

A medusa just beginning to bud. @ inner and

The medusa bud already semi-globular. @ outer

EXPLANATION OF THE PLATES.

Fig. 3. Little older than fig. 2, and stretched longitudi-
nally. Letters the same as in the last.
Fig. 4. The radiating tubes beginning to develop.

Fig. D represents fig. 4 in outline. a@ inner and } outer wall of the hydra.
—ceclc?¢3 the four radiating tubes. —ch channel of c.—d outer wall
of the medusa. //1 f2 edge of the inner wall in which ¢ c3 are hollowed.

Fig. 5. A little further advanced than fig. 4.

Fig. E represents fig. 5 in outline.
—c outer and ¢ inner sides of the radiating canal.—/ff1l edge of
the inner wall. —d outer wall.

Fig. 6. A little older than fig. 5.

Fig. F.

Fig. F represents fig. 6 in outline. @ inner and + outer wall of the hydra.
—c abroad radiating tube seen from its outer face.—cl inner and c2
outer face of the radiating tubes, in profile. —d outer wall. —g g! base
of the radiating tubes.

Fig. 7. Sectional view of fig. 6, to show the projection

(d*) of the outer wall into the cup-like hollow of the
| inner wall (c). a@ inner and 2} outer wall of the
hydra. As this figure was drawn for the purpose
only of showing how the outer wall projects into the
hollow of the inner wall, no special references are
needed to the other parts, which, by comparison with

fiz. 6, explain themselves.

Fig. 8.

Fig. G represents fig. 8 in outline.

Fig. 82.

a@ inner and > outer wall of the hydra.

Fig. Il represents fig. 8a in outline.

Fi

(28)

Considerably older than figs. 6 and 7, showing
the prolongation of the horn-like sheath over the disc,

and the broad radiating tubes.

Fig. G
Vi
L£

Cc. tv
Us

gI— We

J-
bee

In the plate the proboscis (/) is omitted.
@ inner and > outer wall of the hydra.—e outer and cl inner face of
the radiating tubes, in profile. —c? a broad tube next the eye. —d
outer wall of the dise.—g base of the radiating tubes and the proboscis
(A) in profile. — g1 g2 outlines of the wall where the proboscis and the
tubes meet. —7 horn-like sheath.

View of the actinal end of fig. 8.

Fig. H.

c the radiating tubes.—d the outer
wall. —& edges of c.—m inner and m! outer surface of the innermost
wall. —A the proboscis.

ic. 9. <A little older than fig. 8, showing the lateral
projection of the radiating tubes preparatory to the
formation of the circular tube. aa’ inner wall of the
radiating tube; 0 2? outer wall of the disk; 0' outer
wall of radiating tube near the edge of the disk; ¢ the
same as b', but near the abactinal end; 7 the lateral

projections from the radiating tubes; x the proboscis.

Fig. I represents a sectional view of fig. 9 at a point between the radiating
canals, —a@ the middle wall. —a* edge of a. —» outer wall, continuous
at 62 with the innermost wall (b1).—d digestive cavity.—2 outer wall
of the proboscis, continuous with 41. — x! inner wall of the proboscis con-
tinuous with a.

(24)

Fig. 10. The radiating tubes about uniting laterally to
form the cireular tube. The horn-like sheath is very
conspicuous.

Fig. K represents fig. 10 in outline. @ a? middle wall of the disk, in which

~ the radiating tubes are hollowed. — outer wall. — 8! outer wall inverted.

—® ale of the inversion 8, — 4 bottom of the hollow formed by the

inversion of 51, — ¢ innermost wall, thrown into profile by the projection

of the radiating tubes. —/ horn-like sheath.—/ diverticuli from the
radisting tubes to form the circular tube.

Fig. 11.

junction of the radiating

The circular tube is just formed by the lateral
tubes. The tentacles begin

to be prominent.

Fig. L represents fig. 11 in outline. @ a? the middle wall, in which the
radisting tubes are hollowed. — a! in profile in the plane of the axis. —
6 outer wall of the disk. — © outer wall at the point of involution. —¢
et innermost wall. —/ circular canal. — 7 junction of the radisting and
circular canals. —n the proboscis. —o the incipient tentacles.

Fig. 12. The circular tube is complete, the transverse
veil is distinctly three walled, and the proboscis is
quite large. but it oceupies still a comparatively larger
part of the eavity of the body than afterwards, and

is globular.

EXPLANATION OF THE PLATES.

a2

Fig. M represents fig. 12 in outline. This figure is a combination of a pro-
file and a surface view, the radiating tubes being nearest to the eye. @
outer wall of the disk or pedicel. —@! outer wall of the tentacles. — a?
continuation of @ and al slong the edge of the disk. — a’ where al and
a2? meet.—a? corresponds to a2, in profile. —a@> outer wall of the veil,
here seen in profile, in the distance. — A the point of the innermost
wall, in profile, which corresponds to &.—} the middle wall of the disk, or
inner wall of the pedicel. — 6! the same as 4 but nearer the eye, and hol-
lowed out by the radiating canal. 8° inner wall of the proboscis contin-
uous at ot with 8.— 5 the middle wall of the veil, continuous with d.—
& origin of the radiating canals 81. — 5 circular canal. —¢ the outer and
inner outlines of the innermost wall. — cc? the outer wall of the proboscis
at continuous with c. — ct the innermost wall of the veil in profile. —
eS the same as ct but nearer the eye. — cf the circular tube cut across in 5.
—A the horn-like sheath, which completely incloses the medusa.

Fig. 18. Shows the tentacles (@) before they are curled
into the cavity of the disk.
Fig. 14. The tentacles highly developed, and curled
inwardly, forcing the transverse veil into the cavity
of the disk.

Fig. N.

Fig. N represents fig. 14 in outline. Although the tentacles are curled in-
wanily, they sre shut off from the cavity of the disk by the veil (< ct).
a the outer wall. —5 the inner wall of the pedicel. or middle wall of the
disk, and containing the radiating canals. — the bulbous cavity of the
tentacles. —& inner wall of the proboscis, continuous with 5.—c¢ the
innermost wall. —¢? outer wall of the proboscis, continuous with ¢.—
periphery of the veil (ct). — 3 point of union of ¢ and cl. —ct the veil.
—d the tentaculsr bulb. — + the evespeck. —/ the tentacles. —g the
future digestive cavity. —& the horn-like shesth.

EXPLANATION

Fig. 15. A medusa just dropped from the hydra. Feb.
14, 1855.
Fig. 15a.
ters.

Natural size.
The same as fig. 15, magnified about 40 diame-
a remains of the chymiferous channel of the pe-
duncular attachment; / outer wall of the proboscis; ¢
radiating tubes; c’ circular tube; d fold of the inner-
most wall; d* transverse fold of the inner wall; ¢ aper-
ture of the proboscis.
Fig. 16.
pressed and folded longitudinally.

A young free medusa, in a dying state, com-
Seen from the

abactinal end. a innermost wall receding from the

disk (0); © radiating tubes; d digestive cavity. 100
diameters.
Fig. 17. View from the abactinal end of a medusa a little

older than fig. 15% a the veil; b circular tube; c

1

proboscis; d digestive cavity; e¢ innermost wall; ¢

point of attachment of e to the disk. 100 diams.

Fig. 18. About the same age as fig. 17, but very much
contracted. a longitudinal folds; 4 ¢ corrugated lines

on the outer surface of the disk. 125 diameters.

Figs. 19, 20, 21, 22, 23, and 24 are all lettered alike.
v the vitelline sae; y yolk; p Purkinjean vesicle;
w Wagnerian vesicle; v/ Valentinian vesicle.

Figs. 19, 20, 22, 23, and 24.
ment of the eggs of a full-erown free medusa.
17, 1855. 500 diameters.

Fig. 21. An egg from fig. 15, Pl. XVII. 500 diameters.

Fig. 21a. A layer of eggs from fig. 15, Pl. XVII.

and } inner wall of the proboscis.

Various stages of develop-
May

a@ outer

400 diameters.

Figs. 25 and 25a,
medusa. Fig.
the better to

Spermatic particle of a full-grown free
25, 500 diameters; fig. 254 exaggerated,

show the form.

PLATE XIX.
CoryNE MIRABILIS Aq.

[All the figures are drawn from nature by H. J. Clark.]

Fig. 1.

showing the furrows g g' in

A portion of the body and a tentacle of a hydra,
the wall b D.

500 diameters.

outer
f globular mass of lasso-cells.
Fig. 2.

partially extended tentacle.

Portion of the body and a sectional view of a
a outer wall of the body
in profile; a! the same as a, in a full view; @ a? a?
cells of the inner wall of the tentacle; 4 outer wall
of the body; 6! outer wall of the tentacle; ¢ horn-
like sheath; d outline of the digestive cavity; e space

between the outer and inner walls of the tentacle ;

OF THE PLATES.

(25)

JS layer of lasso-cells at the tip of the tentacle; g
processes around the mesoblast of the cells of the tenta-
cle. 400 diameters.

Fig. 3. Surface view of a tentacle. ab cells of the

ig.
inner wall; ¢ outer wall; d e g profile of cell walls
of ab; f globular mass of tentacles. 300 diameters.
Fig. 4.

cles.

Sectional view of the body just below the tenta-
a inner wall; b outer wall; ¢ horn-like sheath ;
d digestive cavity. 500 diameters.

Tig. 5. Lasso-cell of a hydra. a wall of the cell; b
& axial column, which corresponds to the base of
the lasso-thread; ¢ the anchors; d coil of the lasso;
f aperture. 1100 diameters.
Fig. 52.

cell; & thicker part of the base of the lasso-thread ;

The same as fig. 5 uncoiled. a the empty
t' where the thread begins to taper; ¢ c' the anchors
or barbs, c' is seen through 6; d the thread; d' end
of the basal portion; ¢ cavity of a; f aperture of
the cell.

Fig. 6.
medusa.
of the cell.

Fig. 6a,

Lasso-cell from the proboscis of a full-grown free
a profile of the spiral coil d; f aperture
1100 diameters.

The same as fig. 6, but the basal portion of the

thread everted. a the inverted thread passing through
the basal part back to the coiled part d.

Fig. 7. Edge of the disk and a tentacle of fig. 13, PI.
XVIIL, principally to show the cellular structure of the
outer wall (a') of the tentacle, and disk (a); 6 wall
of the radiating tube; 6‘ inner wall of the tentacle,
continuous with 4; ¢ circular canal; d cavity at the
base of the tentacle; d' channel of the tentacle; e@
innermost wall of the disk. 400 diameters.

Fig. 74. The outer wall of the disk of fig. 7 in profile,

and more highly magnified. @ outer ends; & inner

ends. 500 diameters.

Fig. 7». Superficial or end view of fig. 7a.

Fig. 8. Eye-speck of fig. 154, Pl. XVUI. wu outer wall,
and v inner wall, of the exterior base of the tenta-
cle; w a lasso-cell. 1100 diameters.

Fig. 8%. A few oily globules from the dark mass of fig. 8.
Fig. 9. The edge of the disk and the base of a tenta-

cle of the medusa of fig. 12, PL XVIL a outer wall
of the tentacle; 6 circular tube; d entrance of b into
the radiating tube (¢); e innermost wall of the disk.
200 diameters.

Fig. 10.

ating tube of a medusa about ready to drop from the

Profile section of a part of the disk and radi-

a wall of the tube; 4 innermost wall, and
500

hydra.
middle wall, of the disk; ¢ outermost wall.

diameters.

(26) EXPLANATION OF THE PLATES.

Fig. 11. About the same age as fig. 10, showing the
radiating tube a a’ a* to be distinct from either the
outer (c) or the innermost wall (); d_ striae of 0.
500 diameters.

Fig. 12. Part of the disk of a medusa only a day or
two old; after being in alcohol; a dotted strive of the
innermost wall; a the same as a in profile; 0 blister-
like projections of the cells of the same wall; J! the same
as b, in profile; ¢ outer surface of the disc. 500 diams.

Fig. 13. Inner face of the disk and radiating tube of a
medusa just set free. a cells of the innermost wall;
b the same as ce, covering the tube (c). 500 diams.

Fig. 14. From a medusa ready to drop from the
hydra; the edge of the disk was involuted so as to
bring its thickness into sharp profile; @ outer wall;

' cells of a; b middle wall, continuous with the

w
inner wall of the hydra, and the same as the inner
wall of the very young medusa; /' thickening of D
where it embraces the radiating canal d', which is
hollowed out in it; ¢ innermost wall; c! the papil-
late cells in profile; c? the same as c in the distance;
d radiating canal passing into the distance; d‘ the same
as d in transverse section; e the horn-like sheath. 400
diameters.

Fig. 14a. Cells from the outer wall of a medusa of the
same age as fig. 14. a@ the cell wall or ectoblast ;
b the mesoblast; ¢ the entoblast. 500 diameters.

Fig. 14>. Cells of the innermost wall of the same
medusa as those of fig. 14a. 500 diameters.

Fig. 15. The proboscis of a medusa two or three days
old. Superficial and profile views combined in one
figure, as one may see it merely by changing the
focus; ¢ radiating tubes nearest the eye; ce’ the same as
e where they open into the digestive cavity; g outer
wall of the proboscis, which at g! becomes the inner-
most wall of the disk; h% the large wedge-shaped cells
of the inner wall, in profile; 4! the same as h in a
superficial view; 2? the same as h and h' where it be-
comes the middle wall of the disk; and 2? where it
becomes the wall of the radiating tube (ce); 2 the
remains of the same wall when it has formed the inner
wall of the peduncle; 2° where h diverges to form a
broad space for the digestive cavity of the disk ; 7
cavity of the proboscis; & lasso-cells; mm to mm longitu-
dinal furrows upon the outer wall of the proboscis ;
n the outer wall of the disk dragged inward by the
retraction of the adherent inner or middle wall (A‘) ;
o o' parietes of the outermost wall of the disk around
the depression formed by the inflection of mn. 500

diameters.

Fig. 16. Base of the proboscis and the neighboring
centre of the disk of a medusa a little younger than
fiz. 15, and with the same lettering; beside which
is the wall of e; 7 digestive cavity of the disk. 400
diameters.

Fig. 17. Edge of the disk and the base of a tentacle
of a medusa about as old as fig. 16. @ parietes of
the disk; a? a? outer wall of the tentacle; 6 the thick
irregular wall of the radiating tube; 0! the circular
tube ; 0? the junction of b and , or the bulb cavity ;
v® inner wall of the tentacle continuous with b 0"; ¢
cl innermost wall of the disk; d the eye-speck. 400
diameters.

Fig. 18. Exterior face view of the base of a tentacle
and its bulb cavity; from a medusa three days old.
a eye-speck; 6 inner wall of the bulb, or point of
junction of the radiating (¢) and circular (7) canals ;
e outer wall of the butb; f projection of the disk
over the base of the tentacle; g outer wall of the
tentacle; inner wall of the tentacle; ¢@ cavity of
the tentacle; % lasso-cells; 1 bulb cavity. 400 diams.

Fig. 19. The same as fig. 18, seen from above, with the
same letters; showing the truncate cone (a) of the
eye-speck. 500 diameters.

Fig. 20. View from above of the digestive cavity of
the disk of a medusa three days old. a the diges-
tive cavity; 6 radiating tubes; ec wall of 6; c! where
the wall of 6 passes into the inner wall of the pro-
boseis (d); c? mnermost wall of the disk; c® the thick
inner wall at the base of the proboscis, continuous
with c, but seen in the distance. 500 diameters.

Fig. 21. Cells from the outer surface of the disk and
veil of a medusa probably two or three days old;
they are slightly swollen by fresh water. 500 diams.

Fig. 22. The same as fig. 21, in a natural state. a
the mesoblast; 6 the entoblast. 500 diameters.

Fig. 23. The same as fig
nermost wall of the veil seen from the outside and
through the concentric striw of the middle wall.
They are a little changed by alcohol. 500 diameters.

Fig. 24. Cells of the innermost wall of the disc, through
which are seen the horizontal striz of the middle
wall. a the mesoblast. 500 diameters.

Fig. 25. Lasso-cells upon the tentacular bulb of a full-
grown free medusa. 500 diameters.

Fie. 26. The same as fig. 25. The cells of the outer
wall of the tentacular bulb. 500 diameters.

Fig. 27. The same as figs. 25 and 26. Cells of the
radiating canal brought out by fresh water. a face

view; in profile. 300 diameters.

s. 21 and 22. Cells of the in-.

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