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METAMOEPHOSES

OP

MM MD THE LOWEK ANIMALS.

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METAMORPHOSES OE

AND THE

LOWEE ANIMALS.

A. DE QUATREFAGES,

MEMBKE DE L'lJfSTITUT (aCADEMIE DES SCIENCES), PKOFESSBUK AU MUSEUM
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TEANSLATOR'S PREFACE.

JT may be said that the aim of all science is the
discovery of grand natural laws, which control
everything that holds a place within the universe.
This is its final object ; but in order to attain it_, three
very distinct processes must be brought into opera-
tion. Firstly_, it is necessary to observe closely the
various phenomena which Nature presents in all her
works : by this means facts are established. Secondly,
the information thus obtained, and which "is unavoid-
ably of a very heterogeneous character, must be
submitted to a mental examination ; those portions
which are alike being associated with each other, and
with relation to the phenomena they refer to : in this
way, kindred ideas become grouped together. Thirdly,
the mind is required to investigate the relationship
between the ideas thus called into existence and the
things which may be said to have, indirectly, deve-
loped them ; and the result of this comparison is the
framing of certain generalizations, which are then

h

vi

teanslator's peeface.

termed laws. By the operation of tliese^ or some
SLicli processes^ liave men been enabled to form all
those general conclusions, whicli constitute the founda-'
tion of each branch of the natural sciences. It is,
however, unhappily the case, that biology stands, in
this aspect, lowest in the scale ; for not only has the
difficulty in carrying out experimentation been an
obstacle of a very formidable character, but it has
been customary among its devotees to arrive at fixed
conclusions from very uncertain premisses. Hence the
laws which control life in its widest limits have ever
been imperfectly defined ; and although Nature^s
statute-book has a certain existence, those of its
leaves which have fallen into human hands have been
so fragmentary, that at present we may safely aver, in
the language of a celebrated anatomist, that '''the
known is very small compared with the knowable.^-'

Such being the state of things, our deepest gra-
titude is due to the man who, uniting the results of
his own inquiries to those acquired by the investiga-
tions of others, and lending a clear mind to the
analysis of the whole, sketches for us even the rude
and imperfect outlines of that plan upon which force
is permitted to labour in the production of hving
beings. Professor De Quatrefages is the person to
whom we owe our thanks ; for, in the present volume.

TEANSLATOE^S PEEPACE.

vii

lie has brought together all the facts bearing upon
the subject of generation^ and by a cautious and
impartial comparison of them_, has succeeded in
detecting that hitherto,, to us^ obscure scheme which
governs the production of animal forms.

The immortal Harvey gave rise to the aphorism
that everything living proceeds from an ovum; but
though in his time, as in the present day, his dictum
could not be disproved, there was a period in the
annals of natural science when it appeared to be little
better than a pure assumption. The reader is doubt-
less aware that, among the higher animals, the forma-
tion of new individuals takes place invariably in one
and the same manner ; — by the contact of sperm and
germ, an ovum is developed, which, in its turn, gives
rise to a being similar to those from which it pro-
ceeded. The discoveries of naturalists, however,
demonstrated apparently that the production of indi-
viduals does not depend upon this combination of two
dissimilar factors. This circumstance inaugurated an
entirely new era in the history of natural science. It
was found that certain insects {AjpJddes), entirely devoid
of both germ- and sperm-producing organs, possess
the power of bringing into the world new beings like
themselves ; males and females being absent, and the
animals which originate the offspring being essen-

h 2

viii translator's preface.

tially neuter^ there seemed to be no other explana-
tion of the phenomenon^ than that reproduction by
ova was as much an accessory as a fundamental
process. The beautiful researches of Kiichenmeis-
ter and Yan Beneden showed that the tapeworm
which infests the human and other intestines, pro-
duces_, as its immediate progeny, creatures exceedingly
Tinlike itself, and destined to live within the body of
an animal of a very different character from that in-
habited by their parent. Chamisso proved that there
are moUusks {Salpce) which by ova produce others
devoid of reproductive organs, but which, in the
absence of these structures, give rise to the sexual
individuals by a kind of gemmation. Saars' obser-
vations led him to believe that the Folyi^s present
similar phenomena. How, then, were all these excep-
tional facts to be explained? In what light was
sexual generation to be regarded? Were animals
to be considered as being produced indiscriminately
by two distinct processes — gemmation and ova-
development ?

In the following pages the author has grouped all
the phenomena, in accordance with their real affinities,
and, as the result of this subjective mode of inquiry,
he has reduced all the varieties of generation to one
common law, which he has termed Genea-genesis.

TEANSLATOE^S PEEFACE.

ix

The expression itself, simply meaning the develop-
ment of generations,, does not involve a theory,
although it is associated with one. It simply implies
a fact patent to all zoologists. The theory, which is
actually the embodiment of the law sought for, ex-
presses itself in the following words : — TJie formation
of neiu individuals may take idace, in some instances ^
hy gemmation fromy or division of the parent-heing ; hut
this process is an exhaitstive one, and cannot he carried
on indefinitely ; when, therefore, it is necessary to
insure the continuance of the species, the sexes must
present themselves, and germ and, sperm must he
alloiued to come in contact vjith each other.

There is another philosophic generalization framed
by the author, and which it appears to us should
follow, rather than precede the first. It relates to
the manner in which the animal proceeds from what
it has been as an ovum, to what it is in its adult con-
dition. If we watch the development of any mammal,
we shall see that during its entire progress from
simple to complex, from an embryonic to a mature
state, it has been confined not only within the uterus
of the mother, but also within those membranous
folds which really constitute its egg-shell. But, on
the other hand, if we turn our attention from the
mammal to the insect, we shall find that the product

X

TEAKSLATOE^S PREFACE.

of the ovum is very differently circumstanced. In its
case_, tlie nutriment wliicL. is necessary to the con-
struction of its organism, cannot be supplied either
directly by the yolk or indirectly by a draught upon
the mother's supplies; the egg is too small to admit
of the former_, and the possibility of the latter is
equally precluded by the transient existence of the
parent. The materials of growth must therefore be
derived from external sources ; the embryo cannot be
passive in the undertaking ; and hence it is thrown
upon the world to provide for its own development.
What the membranous uterus and appended blood-
vessels supply to the mammal, surrounding objects
and the active exercise of its faculties furnish to the
insect larva. Every animal, in journeying through
the successive phases of development, assumes an
immense variety of forms, in fact undergoes meta-
m orthoses ; in Mammalia, these are concealed from
the view of the ordinary observer; in Insecta they
are present to the gaze of the entire world. It is
true, then, that all animal forms undergo metamor-
phoses, and it only remains to be shown why in some
these alterations take place in hidden depths, and in
others are exposed to common observation. This
brings us to the next great law, which we may thus
lay down : — Those creatures whose ova — owing to an

TRANSLATOR'S PREFACE.

XI

insufficient siiio^ly of nutritious contents, and an inca-
facity on the ]3aTt of the mother to iirovide for their
comjplete development ivithin her ovm substance — are
rapidly hatched, give hirth to imperfect offspring, ujhich,
in proceeding to their definitive characters, undergo
several alterations in structure and form, hnoivn as
metamorphoses.

Tlie above are tlie most important results of tlie
inductive reasoning whicli the autlior employs^ and
we have given an idea of their nature^, because they
are not only the most striking, but are also those
upon which our opinions are in exact coincidence.
When, however. Professor de Quatrefages intimately
associates metamorphosis and geneagenesis, we can-
not agree with his conclusions ; and when he assumes
that vital operations are not to be explained by a
reference to the known laY\^s of force as it exerts
itself through matter, and are only explicable on the
supposition of a vital power,'' we must decidedly
express our dissent. We merely mention these cir-
cumstances in order to guard the reader against the
impression, that the translator of a treatise upon
science implies, by his silence, an assent to the
doctrines therein enunciated.

In introducing this volume to the English Natural
History world, we believe that we are filling a gap

xii TEANSLATOE^S PEEFACE.

in the scientific literature of tlie country^ and are
removing a want wMcli long existed. Wlio lias not
felt tlie desire to possess some essay upon general
embryology? And who has not found considerable
difficulty in embracing a knowledge of the various
modes of development presented by the members of
the animal world ? It is a book addressed not only
to the working naturalist^ but the amateur also_, and
whilst it will be found to possess the most copious
references to the works of scientific writers on the
subject of embryo-life^ it is written in a style so
unmarked by technicality as to render the reading of
it a matter of comparative ease. Whether we have
succeeded in rendering it as intelligible in its Anglo-
Saxon as in its Gallic garb^ remains to be seen ; but
that our efforts have at all events received both
the sanction and assistance of the distinguished
author,, the following letter will be adequate testi-
mony : —

Paeis, 30 Mai, 1864.

MON CHEE MONSIEUE^

Je viens de recevoir et de lire vos dernieres
epreuves. Mille remerciments pour la peine qu^a du
vous donner cette traduction. Elle est aussi exacte
que je pouvais le desirer^ et en tant que ma con-
naissance^ malheureusement imparfaite; de la langue

TRANSLATOE^S PEEFACE.

Xlll

anglaise me permet d^eii juger_, elle est aussi elegante
que fidele. II ne me reste plus qu^a faire des vceux
pour que vos compatriotes jugent moii petit livre
aussi favorablement que vous Favez fait vous-meme.

Recevez_, cher Monsieur^ avec mes remerciments
reiteres_, ^expression de mes sentiments les plus dis-
tingues.

A. DE QUATEEFAGES.

Monsieur le Dr. H. Lawson.

To say that tlie author possesses the highest quali-
fications for the task of interpreting developmental
phenomena^ would be to argue ignorance on the part
of the reader and a want of modesty on our own side .
We shall therefore leave him to discharge the duty
he has taken upon himself.

We have said our say ; but ere we conclude^ we
would express our sincere thanks to the Author^
Professor Huxley^ Dr. Divers^ and Messrs. Henry J.
Slack and J. Daly, for their kindness in assisting
us to examine and correct the proofs, as the following
pages travelled through the press.

H. L.

Jiine 20th, 1864.

AUTHOE'S PEEFACE.

Tl OR some time past I liave liad an idea of writing
a treatise on General Emhryogeny ; and in 1855
and 1856 I publislied a series of articles on this
subject in tlie Revue des Deux Mondes/^ with the
double object of determining the results of my own
researches^ and calling the attention of an intelligent
but unscientific public to the wondrous phenomena
accompanying the development of hving beings.

These articles are here reprinted^ together with
an account of the progress made since their first
appearance. The doctrines and plan remain the
same; but^ independently of several additions and
modifications of detail^ I have almost entirely
rewritten the chapter on Infusoria^ and have added
that on Parthenogenesis^ the study of which began
just at the period of my first publication.

Its origin will explain the character of the book.
In the original articles I avoided being very technical.

xvi

AUTHOR^S PEEFACE.

merely giving accurate views^ supported by tlie most
striking illustrations. In the present volume I am
forced to preserve this feature^ unless I were to
produce a completely new work.

Sucli as it is_, I trust that this treatise may be
accessible to all who are accustomed to serious read-
ing. At the same time_, it will present to naturalists
the principal facts with which they are acquainted^
arranged in a manner peculiarly my own^ and with
references to several works scattered here and there.
Perhaps in these diflPerent aspects it may prove of
service. Such^ at all events, is the object with
which I publish it.

March im, 1862.

CONTENTS.

CHAPTER I.
The Vital Vortex Page 1

CHAPTEE II.
Metamorphosis Generally — Definitions 6

CHAPTER III.
Transformations of the Egjy ... 15

'CHAPTER IV.

Transformations which the Mammal undergoes within

the Egg— Cell Theory 26

CHAPTER V.

Transformations which Mammals undergo after they have

left the Egg , 42

XVIU CONTENTS.

CHAPTEE VI.
General Processes of Transformation — Conclusion

CHAPTER VII.

Metamorphosis properly so called — Metamorphoses of
Butterflies

CHAPTER VIII.

Metamorphoses of Insects generally

CHAPTER IX.
Metamorphoses of Batrachia and Lampreys

CHAPTER X.
Metamorphoses of Myriapods, Crustacea, and Annelids...

CHAPTER XI.
Metamorphoses of Castropodous and Acephalous Mollusks

CHAPTER XII.

Nature, Causes, and Processes of Metamorphoses. — Con-
clusion ... ... ... ...

CONTENTS.

CHAPTER XIII. Page

Geneagenesis. — First Phenomena of Geneagenesis dis-
covered in Animals. — Agamic Generation (Aphides).
— Reproduction by Fissuration and by Gemmation
(Polyps, Hydrai, Compoimd Ascidians) 124

CHAPTER XIV.
Discovery of Alternate Generation (Salpas and Medusae) 145

CHAPTER XV.
New Explanation of Facts long loiown ... ... 157

CHAPTER XVI.
Geneagenetic Phenomena in Annulosa and Mollusca ... 166

CHAPTER XVII.
Geneagenetic Phenomena of Radiata ... ... ... 172

CHAPTER XVIII.

Geneagenesis in the Helminthes or intestinal Worms. —

Spontaneous Generation ... 201

CHAPTER XIX.
Theory of Geneagenesis 219

XX CONTENTS.

CHAPTER XX. Fag&

Partlienogenesis, or Virginal Reproduction — Fundamental

Facts 243

CHAPTER XXI.
Theory of Parthenogenesis 249

CHAPTER XXII.

Geneagenesis in Plants — Relation of the Animal to the

Vegetable Kmgdoni ... ... 261

CHAPTER XXIII.
General Considerations — Conclusion 276

METAMOEPHOSES

OF

MAN AND THE LOWEE ANIMALS.

CHAPTER 1.

THE VITAL VOETEX.

Ovid said_, our bodies undergo transformations ; ive
shall he to-morrovj, neither what we are to-day, nor
ivhat we were yesterday.'^ Tlie poet-author of ^Hhe
Metamorplioses proclaimed tlierein a far more im-
portant truth than doubtless he imagined ; and
modern science, after three centuries of experiment
and observation, has fully confirmed the words of the
Augustan bard.

Unlike inorganic bodies, which are continually in a
state of absolute rest, living beings are during their
existence the seat of constant changes. Place an
animal or plant in the scale-pan of a balance and
endeavour to ascertain its weight with the exactitude
of our most perfect instruments ; you will have much
difficulty in establishing equilibrium, and as soon as
it is produced it will be disturbed, almost as it were
by some inherent influence. The pan containing
the animal will invariably be elevated, and that in

" Corpora vertimtur ; nec quod fuimusve, sumusye,
Cras erimus "

B

0

2

METAMOEPHOSES OP MAN

wiiicli tlie corresponding weights were placed will be
depressed. From this result we are forced to con-
clude that^ in every moment of their lives_, plants^
animals, and even man himself, lose a portion of their
substance. In order to preserve life, these constant
losses must be incessantly repaired; and hence it
results that the beings included in the two kingdoms
must be supplied with food. Animals and plants,
then, borrow from the external world certain materials,
which, when properly elaborated, fill up the gap that
is being constantly made. During the early life of
all organized beings, and during the entire life of a
certain number of them, the quantity of matter fixed
by the organism exceeds to some extent that which
is rejected, and from this the growth of the individual
results. In the adult these quantities are usually
exactly equal : hence his stationary condition. In
the aged, finally, the force of decomposition gains the
upper hand. But whether the loss and gain balance
each other, or whether the one or the other is in
excess, the double movement of arrival and departure
never ceases.

Here a very important problem presents itself,
which it is difiicult enough to solve. Does the vital
stream (to employ the appropriate expression) hold
the entire organism under its control, or are there
certain portions beyond its sphere of government ?

This latter hypothesis has been, and is still, perhaps
that of some physiologists who have urged to its
greatest lengths, the comparison between living bodies
and the apparatus used in our laboratories, and for in-
dustrial purposes. According to them, even the human
body is something like a locomotive. The solid parts

AND THE LOWER ANIMALS.

3

of our organs represent collectively tlie wlieels_, tubes,
pistons, &c. The macMne receives but tlie coal and
the water ; it carries its grate with it, and prepares,
without the direct assistance of the artisan, the steam
required to set the apparatus in motion ; similarly, say
the mechanical physiologists, our body receives every
day its supply of solids and liquids ; it burns a por-
tion of these substances to maintain the animal heat,
and with the rest it builds up the organs which require
it, and supplies the liquids necessary to put the whole
in working order. In us, moreover, as in the loco-
motive, the solid matter once fixed, undergoes no
change, or at the most is eventually worn out. The
materials expended, and which must be re-supplied
— the coal and water, the food and drink — are con-
verted in the machine into smoke and steam, in man
into steam (vapour) also, and into various secretions.

This theory we see, leaps over the difficulties which
are presented by the history of development; it is
framed for an organism fully formed and performing
all its functions. But then, does it stand the test of
application, and does it account for the facts with
which the maintenance and decay of organisms supply
us ? Certainly not, at least in the animal kingdom.

In the adult and in the aged, numerous normal and
pathological phenomena demonstrate the constant
change of the solid, as well as of the liquid consti-
tuents. The now antiquated experiments of Duhamel,
so ingeniously begun and carried out by M. Flour ens,
and the works of M. Chossat, leave no room for doubt
on this point. The latter, among others, fed poultry
and pigeons upon food from which he had removed
the calcareous salts only. Thus he supplied these

B 2

4

METAMORPHOSES OF MAN

birds witli tlie materials necessary for tlie nutrition of
their tissues^ minus tlie inorganic substances, wMcli,
arranged in a living woof, give solidity to tlie bones.
At the end of a certain period, fowls and pigeons
became languid and died. Then the skeleton was
found altered, and the bones attenuated or even
perforated. The rest of the organism had been
nourished ; the bony tissue alone had not repaired its
losses, and these were betrayed by serious injuries.*
Thus the bones themselves, organs perhaps the least
vital of all, and which the physiologists whose opinions
we oppose have almost compared with brute matter,
are, like the most delicate structures in the body,
although to a less extent, under the control of the
vital vortex. t

The development of the iDones and the molecular movements
which take place in them, have been the subject of several works
and very animated discussions. In a treatise like the present, I
can only refer to a small number of these essays. Those of
M. Flourens were first published in the " Archives du Museum "
for 1842, afterwards with numerous additions, in his work called
" Theorie experimentale de la Formation des Os," Paris, 1847. The
experiment of M. Chossat which I described, was communicated to
the Academy from his great work "Eecherches experimentales sur
rinanition," which obtained the physiological prize in 1841.

t The results arrived at by the physiologists just cited, com-
pared with those made known by MM. Serres and Doyere, Brulle
and Hugueny, and with those deducible from a very remarkable
analytical memoir read before the Academy by M. Fremy, lead us
to the conclusion already clearly expressed by M. Flourens, that in
the bones the vital force is occasionally subject to an arrest which
is sometimes very prolonged. It is probable that the other tissues
exhibit more or less analogous phenomena. But as regards the
fact of the renewal of matter, it is sufficient to remove all doubt on
this point, to read a few lines devoted to this question by Miiller
in his " Manuel de Physiologic," translated by Jourdan, 2nd edition,
Paris, 1851, vol. i. p. 325.

AND THE LOWER ANIMALS.

5

We see that in the most hidden depths of hving
beings two contrary currents flow; one^ molecule by
molecule^ constantly removing something from the
organism ; the other as rapidly repairing the breaches
which^ too much widened^ would bring on death. At
the end of a given period the total, or almost total
renewal of the substance of the body_, must follow
from this double action.

This is a fact of the greatest importance. In the
presence of this instability of the organic components_,
the decided persistency of form and proportion among
living beings can hardly be understood, and the mind
is enabled without difficulty to admit the possibility
of the most extensive alterations. Truly, we are
ignorant of the cause which brings these changes
about, determines the order of their succession and
includes them within impassable limits; but at all
events, we may glance at one of the chief processes
which Nature sets at work to create, develop, main-
tain, and destroy, under the influence of life.

6

METAMOEPHOSES OF MAN

CHAPTER 11.

METAMOEPHOSIS GENEEALLY DEFINITIONS .

All vegetable and animal germs^ seeds_, buds^
bulbSj and eggs_, have tlieir origin in a few granules^
scarcely visible under tlie higliest magnifying powers^
or even in a single vesicle^ smaller than the point
of the finest needle. Thus commence alike the
elephant and the oak^ the moss and the earthworm ;
and such is really the first appearance of what at a
later period will become a man. We may conceive of
the intermediate stages which exist between these
points of departure and arrival^ and of the immense
field which here presents itself to the observer.
Apparently exactly similar at the outset^ all kinds of
animals and plants must become distinct,, and assume
their special characters. Each of them^ then^ will
present peculiar facts for research.

It is to the conquest of this land of wonders that
modern Science marched, at first a little hazardously,
and as it were groping its way ; then with a firmer
and firmer step, till at last it has discovered the
general tendencies, if not the absolute laius of develop-
ment. To glance retrospectively at this series of
facts and ideas, even limiting ourselves to Zoology,
would be to step far beyond the bounds that we have
fixed j but ani'ong the subjects which recent researches
have elucidated, there is one — that of metamorphosis —

AND THE LOWEE ANIMALS.

7

which is familiar_, at least by name^ to most cultivated
minds. To tell the truths it comprises most of the
others. This is why I have attempted to treat of it
in its entirety ; hoping thus to afford to all serious
readers a general notion of the wonderful phenomena
presented by the development of living beings.

The word metamorphosis has been for a long while
employed in a restrained and an inaccurate sense.
By it have been designated the very important
changes undergone by certain animals_, insects in
particular, after proceeding from the egg. There was
thus made of these alterations a group of phenomena_,
quite separate and distinct from those presented in
the formation of the embryos of ordinary ovipara.
With far more reason, we should regard them as
having at most a very remote analogy with those
processes observed in the development of vivipara.
The term metamorphosis has been almost exclusively
applied to modifications either of external form or
of some extensive apparatus influencing directly the
mode of life of the animal.

These were serious errors. The nature of a phe-
nomenon does not alter with the locality in which it
takes place_, nor with its greater or lesser extent. As
regards the passage from an egg-shell, or from the
uterus of the mother, as regards the modelling of a
single organ, or the formation of an entire body,
changes of form and function lose none of their
essential qualities. All are primarily caused by the
force which animates matter, which incessantly de-
stroys and rebuilds, through the assistance of the vital
power, those wonderful structures which we call living
beings.

8

METAMOEPHOSES OP MAN

We have shown elsewhere,, why we must translate
the celebrated aphorism^ " Omne vivum ex ovo/^ *
— Every living being, [and consequently every animal,]
starts from a gGr7n. With the organization of this
germ begins a series of transformations, general or
partial, rapid or tedious, which only terminate with
life itself. Thus Harvey^s expression leads us, as a
matter of course, to this one, — every living being
undergoes metamorphoses. For the most part, these
latter are due to the same cause working through the
same processes. To regard these as distinct orders of
facts, because they are not readily identified, would
be neither scientific nor correct.

It is this opinion which modern naturalists, and
especially Duges, Isidore Geoffrey Saint-Hilaire,
Carus, and Burdach, have formed and expressed more
or less distinctly ; but M. Duvernoy was the first who
thoroughly appreciated the idea, and systematized it
in his lectures and writings. f In 1841 this naturalist

" Revue des deiix Mondes," March 15, 1850, and " Souvenirs
d'un Naturalist," 1854. [The latter work has been translated into
English.— Ed.]

-j- M. Duvernoy, a fellow-countryman and colleague of Cuvier,
had even while very young attached his name jointly with
M. Dumeril to one of the great scientific undertakings of the
age, — " L' Anatomic comparee." He was then nominated pro-
fessor in Sorbonne, but soon gave in his resignation. After a
very long interruption, caused by family affairs, he re-entered the
field of science and began teaching, as professor of zoology in the
faculty of Strasburg. Afterwards called successively to the ColMge
de France and the Museum, he filled the two principal chairs of
his illustrious master. He maintained the position which he held
most worthily. Few men have given such numerous proofs of a
sincere and energetic devotion to science. One may say of
M. Duvernoy that he died on the field of glory ; for almost on the
day of his death, and in spite of the advice of his physicians, he

AND THE LOWER ANIMALS.

9

selected the metamorplioses as the text of his dis-
course to the College of France. Dividing the entire
life of every animal into five distinct periods, he
examined the species themselves, and the groups
containing them, in these five periods, under the triple
point of view of external form, internal organization,
and performance of function. Four years hardly
sufficed to complete this huge scheme, doubtless the
best one calculated to give a complete notion of the
animal kingdom. It would certainly be required now-
adays. Since that time Science has enrolled many
new facts, and the doctrines of twenty years ago have
been very much modified. But I desire to recall here
the part taken in this scientific movement by him who
was my first master in Zoology, and my constant friend.

The germs or first rudiments of organized beings
may be referred to three principal and distinct types,
which are found in both kingdoms.* Animals espe-
cially multiply by eggs, or by free or attached buds.
Further on we shall see more of these two modes of
reproduction. Let us state here, that the first form
alone is fundamental, and that the distinction between
oviparous and viviparous animals, although still al-
lowed in scientific parlance, is in reality only an appa-
rent one. Baer, in discovering the mammalian egg, and
M. Coste in discovering that it possessed the same
features as the egg of birds, have established this

revised the proofs of a most important work upon the group of
man-like apes, and especially upon the Gorilla. M. Duvernoy died
in 1855.

* I have discussed this question of germs at some length in the
" Souvenirs d'un Naturaliste," in the chapter headed " Saint-
Sebastian."

10

METAMOEPHOSES OE MAN

fact^ which is placed beyond doubt by the further and
more searching investigations of these two naturalists^
and the splendid works of the English and German
physiologists^ Barry^ Bernhardt^ Bischoff, Wharton
Jones_, Yalentin_, Wagner^ &c. &c. It is at present
satisfactorily proved that mammals^ and even man
himself, as well as birds and reptiles,, proceed from
actual eggs.

From one end to the other of the animal kingdom,
the structure of these latter is probably identical in
every essential particular. In mammalia, as in the
Kadiata or the Worms; in man, as in Hermella or
Synapta, three spheres lying one within the other, and
inclosed by a transparent membrane, constitute the
germ. To these three spheres may be added various
envelopes and accessory layers for their protection, or
to aid in supporting the new creature ; but, within the
vitelline membrane may invariably be found the
vitellus or yolk, embracing the germinal vesicle of
Purkinje, which itself incloses the germinal spot of
Wagner.

The exact function performed by each of these
spheres is far from being known; but it is certain
that the vitellus consists of organizable and nutritious
matter. In some ovipara, this supply of food is ex-
tensive ; a small portion is sufficient for the construc-
tion of the new being, which is nourished and grows
at the expense of the remainder. The fish, for ex-
ample, springs from the egg completely formed. How-
ever, it still carries attached to its belly a large bag,
containing the greater part of the yolk-substance ; and
this being slowly absorbed, provides it with nourish-
ment for more than a month after it has been hatched.

AND THE LOWEE ANIMALS.

11

In all vivipara_, on tlie contrary^ the vitellus is very
small. It would not suffice for the nutrition of the
embryo_, which is obliged to draw from external
sources the materials requisite for its further de-
velopment.

On account of this difference alone, it follows that
certain germs can separate themselves completely from
the parent, and others are forced to remain for some
time in the interior of the latter. The egg of ovipara
with a large vitellus is laid, that is to say expelled
from the body, and often abandoned to every external
influence without any protection save a delicate mem-
brane or a thin shell of a mineral character. The egg
of vivipara, left in a condition of complete activity, en-
grafts itself upon the maternal womb like a parasitic
plant, absorbs from it the nutritious juices which it
gives to the embryo, and grows ]?ari ^assu with the
latter. The phenomena which it exhibits, called into
action by the necessity which exists for the nutrition
of the young animal, alter its nature in no way, and at
the final moment its special features make their ap-
pearance. In coming into the world, the mammal
and man burst through thin envelopes, just in the
same manner as a bird breaks through its shell.
Birth is actually a process of hatching.

Now, in certain species the embryo, once fully formed
and arrived at the foetal condition, resembles its
parents. At the moment of em.ergence from the
shell, it presents almost the general form that it will
maintain during life. The mode of performance of the
principal functions is definitively fixed, and though a few
organs may still be imperfectly developed, yet all are
present, and none disappear. The alterations which

12

METAMOEPHOSES OP MAN

occur in the creature after emergence from the egg are
very trivial, and relate chiefly to a few variations as to
size and proportion. Such is the state of things
among all vivipara_, * and among a considerable
number of ovipara also. Nature seems in these to
have pursued a straight course. Every change im-
pressed upon the germ has brought the new being
nearer its final plan.

On the contrary, in all other oviparous species, the
creature which springs from the egg differs in nearly
every respect from its parents. It has neither their
form nor their mode of life. Frequently it inhabits a
different medium. We find in it complete apparatus
undiscoverable in its parents ; on the other hand, these
latter possess other organs which are absent in their
oSspring. In returning to the original type, the de-
scendant must undergo important changes. Here
Nature seems pleased to prolong the route, and to
arrive at the end of her journey only after many turn-
ings ; but, at all events, this route is a definite one,
clearly marked out, and without a single cross-way.

In the two preceding cases, each germ gave rise to
but a single individual, thus preserving its unity whole
from birth to death. The three lower sub-kingdoms
— Annulosa, MoUusca, and Coelenterata — supply us
with far stranger facts, whose real meaning is one of
the latest discoveries of science. In certain species,
always oviparous, each egg produces a creature bear-

* The marsupials (Kangaroo, &c.) may be enumerated as excep-
tions ; but these vivipara, although having a double gestation, being
hatched in the uterus of the mother, and carried for a while in the
marsupial pouch, present in the main the same phenomena as
ordinary mammals.

AND THE LOWER ANIMALS.

13

ing no apparent resemblance to that from whicli it
sprung. Then this animal begets_, of itself alone, and
from all parts, a great number of other creatures,
which most frequently are unlike itself. Here several
individuals and several generations start from one and
the same germ. Moreover the differences are seen
not only in a single specimen examined at various
periods of its life, but among all the generations which
succeed it ; these invariably differing from one another
up to the last, which alone reproduces the primary
type. True to our metaphor, we may say that the
course pursued by Nature is at first single, and almost
direct, but that it soon divides and subdivides into
more or less tortuous paths, which lead invariably to
the same terminus.

Although these facts are referrible to the same
cause, and to common fundamental principles ;
although they are in reality but a continuation of the
embryogenical phenomena, they are sufficiently dif-
ferent to admit of our distinguishing them by appro-
priate expressions. We shall see, moreover, that the
simpler forms are involved in the more complex
ones ; and unless we would add to the difficulties of
the subject, we must designate them by special
names.

Consequently I shall term transformation, the series
of changes which every germ undergoes in reaching
the embryonic condition ; those which we observe in
every creature still within the egg; those, finally,
which the species born in an imperfectly developed
state, present in the course of their external life.

I shall retain the term metamorjplwsis for the alter-
ations undergone after exclusion from the egg, and

14

METAMORPHOSES OF MAN

wliicli alter extensively tlie general form and mode of
life of the individual.

Finally, I shall designate by the term geneagenesis *
tlie clianges wMcli relate to generations themselves.
It is upon this latter order of phenomena that I shall
dwell more especially, as being the least known, t

* From yevea and ysvemg, literally the reproduction of genera-
tions. Other expressions have been coined to designate the phe-
nomena referred to here* Further on we shall examine this ques-
tion in detail and make the facts known.

t M. Ed. Claparide published (" Bibliotheque universelle de
Geneve," 1854) a work on one of the principal phenomena of genea-
genesis (" La Metagenese, ou Generation alternante "), but it is im-
possible to approach this subject without touching upon other
modes of development ; and, in consequence we have sometimes
treated of the same questions. Now I have remarked that this
naturalist admits also three modes of development among the
lower animals ; viz., " 1st. Development by metamorphoses, of
which we see examples in Batrachia, Insecta, Crustacea, Arachnida,
MoUusca, and a portion of the Annelida. 2nd. Development by
metagenesis, either alternate generation, or through two degrees ; of
which we find examples among the Aphides, the Salpae, the Hel-
minthes, the Medusse, and the Infusoria properly so caUed. 3rd.
Mixed development, in which metagenesis and metamorphosis
coexist, one beside the other, or rather blended together. This is
the case in the Echinoderms." This extract shows that there are
certain harmonies and also great difierences between our opinions.

AND THE LOWER ANIMALS.

15

CHAPTER III.

TRANSFORMATIONS OF THE EGG.

From the almost exact resemblance presented by all
tlie ova whicli have been already examined^ we may
conclude that the earlier phenomena of transformation
are the same. Such appears to me to be the general
result of the already numerous researches of hosts of
naturalists. It is true^ that with regard to the higher
animals the harmony is far from being complete ; but
in very many of the instances the differences may be
explained on the supposition that each observer per-
ceived only certain phases of a complex phenomenon^
which he was ignorant of in its entirety. To under-
stand this entirety^ we must have recourse to the
lower animals ; and even here we must select special
groups. An untransparent shell, the opacity of the
yolk_, the length of time required for the alterations of
form and texture, are very frequently insurmountable
difficulties. It is because I found among annehds
and moUusks, animals having rapid transformations
and transparent eggs, that I have been able to dis-
tinguish the phenomena resulting from the vitality of
the germ itself from those induced by impregnation,
to determine the entire period of incubation, and to
prove the extraordinary fact of an egg-shell becoming
the skin of the future animal. Perhaps some of my
readers may recollect what takes place in Hermella

16

METAMOEPHOSES OP MAN

and Teredo.* Apart from an autlior^s egotism^ and
because the earlier stages of tlieir development are
more familiar to me personally tlian to any one else,
I liave selected tliese two species for the purpose of
illustration. In addition to what we shall learn from
an examination of these, I shall describe the chief
features of mammalian development, but I shall not
allude to the ordinary ovipara, whose embryogeny,
seen from our point of view, would be of little
interest.

As soon as the egg of Hermella and Teredo is laid,
whether it be impregnated or not, it becomes the seat
of internal changes, which do not alter its general
form, and which we notice, as affecting its trans-
parency. A mysterious power operates upon the yolk,
accumulating its particles, sometimes at one point,
sometimes at another, affecting the outer surface, and
exhibiting in the mass shadowy figures which alter
in form every moment. If we assume that similar
changes take place in the mammalian egg, we can
then understand how Messrs. Barry and Bischoff,

My researches on these two creatures, the first belonging to
the Annulosa, the second to Mollusca, were published in the
"Annales des Sciences naturelles" for the years 1848 and 1849.
In the articles on embryogeny, I laid especial stress on the changes
dependent on the vitality of the egg itself, and particularly upon
the phenomenon of segmentation which takes place even in unim-
pregnated ova. In 1849 I observed the same thing in TJnio —
(Comptes rendus.) Among the naturalists who have made similar
statements I may mention one, M. Vogt, whose authority in a
matter of this sort is very great, and who has seen segmentation take
place in the unfecundated eggs of Firola (referred to by Siebold in
his work on true parthenogenesis).

[The latter work has been translated into English by Mr. W. S.
Dallas.— Ed.]

AND THE LOWER ANIMALS. 17

notwithstanding all the knowledge and skill ex-
hibited in their researches^ have not always agreed;
and how the latter has occasionally observed ova
of an exceptional character. The slowness of the
changes which the yolk undergoes^ and the ntter
impossibility of continuous observation^ account
easily for these apparent contradictions. Most pro-
bably the phenomena are in reality identical.* In
Hermella and Teredo^ the structure of the egg,
whether impregnated or not, is modified by this
agitation of the yolk. The germinal vesicle and the
germinal spot both disappear. Their contents become
mingled or blended, as it were, with the substance of
the yolk. Here the analogy we are demonstrating is
complete. In Mammalia, as in Mollusca, and Worms,
the distinction between the three vesicles is lost,
whether impregnation has taken place or not. In
the highest, as in the lowest member of the animal
scale, the egg thus exhibits its peculiar activity.

If the egg of Hermella or Teredo has not been
impregnated, the movements of the yolk-mass increase
in rapidity, and become more and more irregular.
The egg at first becomes discoloured, and eventually
decomposes. In like manner, doubtless, the un-

* Some of Messrs. Barry's and Bisclioff's drawings have forcibly
reminded me of the transitional appearances which I observed in
the eggs of Hermella. Thanks to the rapidity of the phenomena
in the latter, I have been able to see these appearances obliterated
and replaced by others. — (Annales des Sciences naturelles, 1848.)
I did not then attach any importance to this general fact. Deprived
of this advantage, my fellow-workers have been unable to examine
the matter as I have done. Moreover, since the publication of my
memoir on the development of Hermella, everything that I have
stated on the subject has been confirmed.

C

18

METAMOEPHOSES OF MAN

fecundated eggs of mammalia also disappear. Not
only in tlie Mgliest,, but in tlie lowest member of the
animal series,, the object of the male element is to
bestow^ or rather to reveal, a vitality which already
exists within the egg, and which exhibits itself by
appreciable phenomena. Its function is but to regulate
the employment of this vital force, so as to ensure
its duration. Let us bear this important fact in
mind now, and hereafter we shall be able to form
an estimate of its value.

After the changes of which we have spoken, and
whether the egg be impregnated or not,* there is
formed on the surface of the modified yolk, in Hermella
and Teredo, a kind of papilla, from which, as though
they had been forced from the interior, one or two
transparent globules make their escape. What is the
real office of these globules ? We know not. Already
they have been observed in the egg of the rabbit, by
Barry, Bischoflf, and Pouchet; in that of the bitch, by
Bischofi"; and in that of the triton, by Wharton Jones ;
and they will be found in all probability in the other
Mammalia, Reptiles, and Fishes. Vertebrata, Annu-
losa, and Mollusca resemble each other in this parti-
cular also.f

When the egg has been impregnated, the ex-

* M. Lacaze du Thiers has observed the expulsion of the trans-
parent globule from the unirnpregnated egg of Acephala. — (Histoire
du Dentale, Paris, 1858.) This fact is of importance, in the pre-
sence of theories deduced from the penetration of the spermatozoids
into the egg.

t According to the researches recently communicated to the
Academy by M. Ch. Eobin, the globules referred to, are absent in
certain diptera, the earlier stages of whose development present
many other phenomena equally exceptional and strange.

'AND THE LOWER ANIMALS.

19

pulsion of the globules is followed in tlie mammal_, as
in Hermella and Teredo^ by a sbort period of repose.
The germ recovers its spherical form which had been
momentarily lost^and exhibits an entirely homogeneous
structure ; then the motion of the granules recom-
mences, this time affecting both the internal and
external portions. A ring-like constriction takes
place about the middle of the vital sphere and deepens
rapidly.* A second constriction then crosses the first
at right angles ; and this is followed by several others.
As the grooves increase in number, the entire mass
appears composed of hundreds of adherent vesicles,
which give it rather the aspect of a raspberry; but
the progressive multiplication of these vesicles gra-
dually renders the surface smooth, and brings it
almost to the original condition. The germ becomes
transparent, and its outer layers begin to present the
features of young tissue. These strange phenomena
are also common to all animals. f Discovered in the
frog by Messrs. Prevost and Dumas, they were soon
observed in a great number of invertebrata ; then in
fish, by Rusconi ; in mammals, by Bischoff ; and
finally in birds and scaly reptiles, by M. Coste.J At

■"' According to M. Ch. Robin, the first groove makes its appear-
ance at the point from which the transparent globule has escaped,
and on this account he terms the latter the polar globule. But
this generalization is, to say the least, premature.

t M. Ch. Robin states that the diptera of which we have
spoken are an exception to this rule. M. Lacaze du Thiers has
informed me of a similar state of things which he has seen in other
groups, but he wishes to confirm his observations by further inves-
tigations before giving them publicity.

X M. Coste has shown that, in birds, scaly reptiles, and cartila-
ginous fishes, the segmentation in the neighbourhood of the little

c 2

20

METAMOEPHOSES OF MAN

this point some slight differences are occasionally
exhibited. In certain eggs with a large vitellus^ a
portion of the yolk escapes segmentation ; but in all
animals the result of this change is the formation of a
primitive organized layer which embraces the yolk^
and has been termed the hlastoderm.^

These first traces of organization have hardly ap-
peared when all resemblance between the various
germs ceases. The germ becomes an embryo^ and at
the very outset exhibits the fundamental characters of
the group to which the new being will belong. Up to
this period both Vertebrates and Invertebrates have
travelled together along the developmental road ; but
now they part^ never to meet again. Henceforth the
two great divisions of the animal kingdom^ the two
sub-kingdoms will remain entirely separate.

In Yertebrata^ the organic elements — cells and gra-
nules— accumulate and arrange themselves^ at one
point in the blastoderm in the form of a minute spot,
which is circular at first. This spot is the germinal

scar is obscure. This cicatricule is according to him the real egg ;
the remainder, or yolk, being merely an accessory body which
masks and obscures the phenomena of the earlier stages of existence.

The phenomena observed by M. C. Siebold in the planaria
(Manuel d' Anatomic comparee), and by Messrs. Koren and Daniel-
sen in the pectinibranchiate niollusks, form two remarkable excep-
tions to the general rule (Ann. des Sciences naturelles, 1852). But
Dr. Carpenter has already shown that in the case of Purpura
lapillus, these naturalists have been in error. The peculiarity of
development in these niollusks is, doubtless, still exceptional ; but,
as regards the general processes of segmentation, and the expulsion
of the globules (directive vesicles, Carus and Carpenter), they come
under the general law. — (" On the Development of the Embryo of
Purpura lapillus." — Transactions of the Microscopical Society of
London.)

AND THE LOWER ANIMALS.

21

area. It is the place where the creative forces exert
their greatest power^ or rather it is the embryo itself.
The area increases very rapidly^ and becomes oval.
A transparent line appears in the direction of its
greater axis. This is the primitive streah which
already indicates the position of the future brain and
spinal cord — the two great nervous centres that con-
trol the entire organism. Next^ a series of obscure
points placed symmetrically along this line shows us
that the vertebral column is being formed.

The sub-kingdom being thus fixed on^ the class to
which the animal will belong is afterwards deter-
mined.

In Mammalia,, as in the others^ the proper coat —
vitelline membrane — undergoes change also. Al-
though at first thick and uncovered^ it is soon sur-
rounded by a layer of albumen, which is blended
and grows with it. The egg is still free and un-
attached ; but it soon throws out a number of delicate
folds, [the first rudiments of the series of rootlets
which at a later period it will dip into the substance
of the mother's womb,] for the purpose of absorbings
the juices intended for the nutrition of both the-
embryo and itself.

In Hermella and Teredo, as soon as the blastoderm
is formed, the vitelline membrane, hitherto inactive,
commences its labours. Its irregular folds disappear,,
it increases in thickness, and, like a sort of flexible
egg-shell, it is fitted exactly to the incomplete embryo,
as though it were an actual epidermis or skin. A few
cilia are seen on its surface. At first they are as
motionless as crystal filaments, but afterwards they
commence jerking violently. Their number rapidly

22

METAMORPHOSES OP MAX

increases^ and tlieir quicker and more constant vibra-
tions disturb tlie body wliicli carries them. Tliis little
beings wbicli is no longer an egg and is not yet an
animal^ seems almost to poise itself upon the plate of
glass placed in the field of the microscope. At last it
undergoes its transformation. Suddenly the young
larva escapes^ as if urged by some mechanical force^
and swims round and round^ in the liquid_, looking*
just like a little hedgehog covered with sharp
spines.

Hermella and Teredo are animals which undergo
two metamorphoses. We shall leave for a while these
eccentric larv8e_, but to study them at a later period_,
and will return to the mammalian egg.

We have seen that within the already large vitelline
membrane^ the germ lay^ surrounded by the blastoderm_,
and that the germinal area was formed upon a portion
of this membrane. The germinal membrane almost
in its earliest stages is composed of two layers^ which
may be exposed by a little dehcate manipulation.
Yery soon a third one is developed between the other
two_, and grows with them. All the organs^ and also
the various membranes which constitute the envelopes
of the germ_, are developed from these three layers.
A special stratum formed from the external layer
becomes the amnion, which like a veil of gauze sur-
rounds the embryo, and secretes a large quantity of
liquid in which the young mammal is plunged up to
the moment of its birth. Another detaching itself
gradually from the same point, doubles within the
vitelline membrane, and helps to form the cJiorion,
which is a kind of egg-shell. From the two other
aminge there is formed, at the posterior end of the

AND THE LOWER ANIMALS.

23

embryO;, a sort of poucli — the allantois — wMcb. grows
rapidly^ and elongating itself like a long-necked bal-
loon^ is applied against tlie inner surface of tbe chorion.
This allantois carries with it veins and arteries com-
municating with those of the embryo. Moreover, at
the point of contact the vital activity of the mem-
brane is increased. The villi of the chorion grow
rapidly and become more numerous. Finally, the egg
grafts itself upon the uterus of the mother, being
retained there till the time of its birth ; and from this
period it receives nutrition at the expense of the
parent.

While the transformations that I have been
alluding to are going on, the germ itself is not
inactive.

We have seen, that at the period to which I have
referred, this germ is composed of modified yolk
embraced by the blastodermic membrane, upon a
limited portion of whose surface the germinal area
and rudiments of the embryo are borne. In pro-
portion as the latter assumes its special characters,
and as the walls of its great cavities close in, it
gradually withdraws from the surface of the sphere
which contains it, and remains attached only by a
sort of canal. At the end of a certain period the
embryo and blastodermic vesicle are only united by a
kind of hollow cord and a few blood-vessels, some-
what (if I may be excused the comparison) like the
bowl and handle of a cup and ball. From this time
the blastodermic vesicle is styled the umbilical vesicle.
The latter in some cases becomes atrophied, and dis-
appears, as in man and the ruminants ; in others, on
the contrary, as in carnivora and rodentia, it increases

24

METAMOEPHOSES OF MAN

in size, and fills those portions of tlie chorion which
are not occupied by the allantois.

Thus, in Hermella and Teredo, the entire egg,
including the envelope, is converted directly into a
real animal. In mammalia, on the other hand, an
embryo, consisting of a few elements, whose final
condition will alone reveal their real nature, shows
itself upon an almost imperceptible portion of the
germ, and becomes more and more isolated. The
germ itself contributes directly to the development
of the new being only in the earlier stages of its
formation. After the egg becomes attached to the
uterus, and possibly before that period, it draws all
its nutritive supplies from external sources, and the
envelopes are the parts which play this important
function intermediate between the mother and her
offspring.

Indeed, there are not always such very considerable
difierences between vertebrata and invertebrata. In
frogs, for example, not only is the egg separated
from the mother, and consequently charged with the
nutrition of the embryo, but even the germ itself
encroached on rapidly by the skin, organizes, so to
speak, layer after layer, and at the moment of its
final transformations seems as though it had been
directly formed; so much so, that some naturalists
appear to think that it really is thus formed. On
the other hand, Weber and Grube, two German
naturalists, have described, in the leech and clepsine,
phenomena recalling in many ways those which take
place in mammalia.

However, it does not appear that in Annulosa,
Melius ca, or Coelenterata, there is a true germinal

AND THE LOWEE ANIMALS.

25

area, and in no case can anything resembling a
primitive streak be observed. This first indication
of a controlling apparatus — absent in all inverte-
brates_, — is never perceived, even in a transitional
form, in the course of their transformations.

26

METAMOEPHOSES OF MAN

CHAPTER IV.

TEANSPOEMATIONS WHICH THE MAMMAL UNDEEGOES
WITHIN THE EGG CELL THEOEY.

structures is connected with animal life^ the other
with that series of phenomena common to animals and
plants_, and hence termed vegetal ; whilst both derive
their support from a nutritious fluid — the blood — which
is borne to every tissue in the body by special canals^
termed arteries and veins. Here_, then_, we have three
distinct systems and organs ; what do they arise from ?
From the three folds or leaflets of the germinal area_,
which we have described elsewhere.

The external or upper leaflet develops the organs
of thought^ sensibihty_, and motion; or^ in other
wordSj the brain^ spinal cord_, nerves_, bones_, and
muscles^ whose operations are controlled by the will.
The internal or lower fold produces those organs^
such as the digestive canal and its appendages,, whose
functions^ though of the greatest import^ are per-
formed without our being conscious of them. Finally,
the heart, veins, and arteries, are developed from

AND THE LOWER ANIMALS.

27

the intermediate leaflet or lamella. These groups
of organs do not commence their development at
the same period^ nor do they at first present their
characteristic features. Before assuming the latter^
all undergo transformations. Now_, unless we were
to begin a special treatise on embryogeny^ it would
be impossible to give more than a general and
abridged account of these phenomena here; and^
moreover^ we must be cautious in selecting our
examples. We shall^ therefore_, limit ourselves to
such facts as will enable us to form a general con-
clusion applicable to the entire animal kingdom.

Those who have observed the successive appearance
of the various organs during the development of the
embryo^ state that the first structures apparent in
mammalia are those most characteristic not only of
the animal kingdom generally but of the sub -kingdom
Yertebrata ; viz.^ the vertebral column^ cranium^ and
the great nervous masses which they contain. The
question arises^ are these the earliest structures in all
animals ? In answering this query if we were to
depend on the results of direct observation alone_, we
should at once reply in the negative. It is unquestion-
able that other portions of the animal apparatus^ such
as the skin and locomotive organs_, are the first seen ;
but then the nervous system_, which is usually con-
sidered to afiect the vitality of the others^ is only
observed when in a very advanced condition. Possibly
it is the first to be developed^ but owing to its extreme
transparency^ we are unable to detect it with the aid
of our present optical apparatus.

In mammalia_, the heart accompanied by the blood-
vessels makes its appearance at an early date^ and

28

METAMORPHOSES OF MAN

shortly after tlie nervous system. The digestive tube
is seen at a later period.

This order of succession seems necessary when we
consider that the embryo receives its nutritive supply
from external sources,, through the intervention of the
blood-vessels. When this necessity does not exists
the order of phenomena is in all probability altered;
in fact^ we see this alteration take place in most of the
invertebrates whose development we are acquainted
with. The digestive system is formed before the cir-
culatory organs^ and occasionally the latter are com-
pletely absent^ even after the young animal has been
hatched^ and has begun life on its own account.

We should be almost inclined to associate this law
with the imperfect development of the circulatory
organs of certain adult invertebrates^ were it not that
the same thing has been shown to occur in animals
whose circulation is complete and closed. If^ then^ we
would understand why this system is so slowly deve-
loped^ we must examine another phenomenon^ which
though confusing to some^ will be easily appreciated
by those who can form a proper estimate of the function
of the general cavity of the body and the office of its
contained liquid.* In those animals which have a
free general cavity, the various organs of the body are

Elsewhere I have described at some length, the function of
this general cavity (Souvenirs d'un Naturaliste) ; my remarks may
thus he briefly summed up : — " Invertebrates have as a general
rule, neither lymphatic nor chyliferous vessels. Moreover,
they have no connective tissue in the literal sense of the word.
Consequently we find the various organs separated from each other
by spaces or lacunae, filled with a peculiar liquid which represents
both lymph and chyle. Besides, when the circulation is incom-
plete, the blood is poured from the vessels into these lacunae and

AND THE LOWER ANIMALS.

29

as it were plunged in a nourishing hath, and conse-
quently a heart and blood-vessels ; in fact^ a system of
irrigation, is not at all required. Their presence or
absence is merely indicative of a higher or lower
organization. Hence it follows that the young and
adults of many species do not possess a vascular
system.

All the systems of organs whose order of succession
we have been considering are connected with the
preservation of the individual. Those connected
with procreation_, and which ensure the perpetuation
of the species, appear at a much later date than any
of the others. We must bear this general law in
mind, for not only is it applicable to all animals
which undergo transformations, but in those subject
to metamorphoses and geneacjenesis it is even still more
marked.

The various apparatus we have mentioned are all
complex enough, being each composed of several
organs, and these again being built up of different
tissues. Hence we naturally inquire how three folds
of such a simple character as those of the germinal
area, have been able to give rise to such a complicated
machinery, and under what form the material which
the vital force has thus transformed, appears in the
beginning. Before going further, then, we must con-
sider a few fundamental laws, and analyze a theory
whose name at least is familiar to all anatomists.

All naturalists who have investigated this subject
agree in stating that every organ consists in its ear-
there mixing with the products of secretion and digestion, consti-
tutes a fluid to which the term ' nourishing hath,'' employed in the
text, seems hardly inappropriate."

30

METAMORPHOSES OP MAN

liest stage of a mass of homogeneous,, transparent^ gela-
tinous matter^ wMcli lias little or no distinct structure.
M. Dujardin has judiciously named this elementary
substance sarcode, a term which signifies^ as it were,
the road or highway upon which the tissues set out on
their journey to their adult condition. From this mass
of living matter all the anatomical elements are pro-
duced, and then, by the union of these latter, the
various organs of the body are formed also. All
physiologists who have devoted their attention to the
development of mammalia, and of the lower inver-
tebrata, agree upon this point ; and even when they do
not draw the conclusion in set terms, it follows from
their researches.

But then, is the sarcode directly transformed into
tissue, or is there a series of intermediate changes ?
In answering this question, we come to a doctrine
which has been almost universally believed in, in
Germany, for the last twenty years, and which many
distinguished naturalists of other countries have put
their trust in also. We allude to that hypothesis
which Schwann, a pupil of the famous Miiller, bor-
rowed in part from botanical science, and applied to
zoology, under the title of the Cell theory.

Botanists admit the existence in plants of a primary
anatomical element, which may be converted by a
series of modifications into the several vegetable
tissues and organs. * This element they term a
cell ; it is a small vesicle formed of a single or double

* For some years the theory to which I allude was regarded as
having no exceptions ; but the progress of knowledge shows us
that it only applies within certain limits even to the branch of
natural science which at one time appeared to bear it out fully.

AND THE LOWBE ANIMALS. ' SI

membrane_, and containing in its interior a slightly
viscid fluids and an exceedingly minute corpuscle^
called a nucleuSy wMch again contains within itself
another^ wMcli is called nucleolus. These cells —
spherical when isolated^ or polygonal because of the
pressure_, when packed closely together — constitute
cellular tissue^ of which we have familiar examples in
the pith and cork of vegetables. When these are
elongated in the form of spindles, and filled with
ligneous matter, they constitute the fibres of bark
and wood ; and still more developed, excavated,
and fused end to end, they form the vessels by which
the circulating fluid is transmitted. Now as these
three tissues — cellular, woody, and vascular — form by
their union, the roots, stem, branches, leaves, and
flowers, — in fact every organ of a plant, it follows as a
natural consequence, that every vegetable commences
its existence as a cell; moreover, this organogenical
law is fully borne out by comparative anatomy, some
of the lower forms of plants being entirely composed
of a single cell.

The foregoing remarks show us why botanists
deem it of importance to be acquainted with the
phenomena of cell multiplication and development.
But even upon this question there has not been much
harmony among them. Schleiden, who is one of the
most distinguished botanists in Germany, put forward
a theory on the subject of cell-formation, which has
been adopted by his fellow-countrymen, and has
found many disciples among the botanists of other
nations also. According to him, cellular tissue is at
first quite liquid, and gradually assumes a jelly-like
appearance, without, however, the faintest trace of

32

METAMOEPHOSES OP MAN

organization.* Next a number of little corpuscles or
nucleoli make tlieir appearance in the mass, and tliese
becoming surrounded by tlie gelatinous material_, con-
stitute as many nuclei. From each of these a delicate
membrane is produced, whicli after a while completely
incloses the nucleus, and thus converts it into a
perfect cell. Each cell, as soon as it is fully formed,
is capable of developing others by a series of pro-
cesses, admitted by botanists generally. These pro-
cesses are three in number. 1st. By budding from
its outer walls. 2nd. By division, which may take
place either by constriction of the entire cell, or by
the formation of partitions in its interior. 3rd. By
the development of free cells within it, which are
eventually set free by the bursting of the parent
one.

Schwann sought for the same state of things in the
animal as in the vegetable kingdom. He fancied that
he had discovered the similarity, and endeavoured to
apply botanical theories to the development of the
animal. Closely following Schleiden^s view, he gave
to the primary material, which we have styled sarcode,
the name of Cystoblastema.f According to him, this
amorphous substance was transformed successively
into the nucleolus, the nucleus, and finally the cell
itself. From the latter sprung every tissue, and
consequently every organ in the animal body. Even

* M. de Mirbel, our distinguished physiological botanist, de-
scribes a similar substance, which he calls cambium ; but according
to him, the corpuscles or nucleoli of which Schleiden speaks, are
only minute cavities gradually enlarging and forcing back the sur-
rounding matrix, which when more organized forms the cell-walls.

t KvoTtf a vesicle, and (iXdcrrrji-ia, a bud, or, figuratively, pro-
duction.

AND THE LOWER ANIMALS.

33

the egg itself was a cell in whicli the germinal spot w^as
the nucleolus^ the germinal vesicle the nucleus_, and
the vitelline membrane and yolk the cell-wall and its
contents. Finally according to the German anato-
mist^ the segmentation of the yolk_, the raspberry-like
appearance which we mentioned in another chapter^
was but the production of a new series of cells within
what he would term^ par excellmce, the parent cell.

Schwann^s work was very highly thought of, and
was supported^ almost on its publication^ by several
distinguished men of science. That this success was
deserved will be apparent to those who^ on looking
back^ can recollect the condition of histology twenty
years ago.* This doctrine was a very beautiful and
captivating one ; it established a decided fundamental
relationship between the two grand sections of the
organic world; it showed that all forms of organized
matter^ whether plants or animals, started from the same
developmental point; and it simplified several com-
plex and laborious researches; finally, it was confirmed
in numerous instances, by the results of actual obser-
vation, and though, at the outset, a few exceptional
cases presented themselves, it was quite fair to
imagine that, after a while, even these would be
overcome, and the theory would become a certain law.
Gradually, however, these exceptions became more
numerous, and even his most ardent followers were
obliged to reject some of the author^s opinions.
Nowadays the comparison between the ovum and a
single cell would hardly receive much support. More-

* " Mikroscopische Untersucliiingen iiber die Uebereinstim-
mung in der Structur und dem Wachsthum der Tliiere imd Pflan-
zen." BerUn, 1832.

D

34

METAMOEPHOSES OP MAN

over^ the segmentation of tlie yolk_, and formation of
the raspberry mass^ cannot be due to tlie development
of a series of cells^ as Schwann asserted ; for we find
that^ among certain moUusks and worms, tlie most
complete lobes of tlie vitelline structure occasionally
coalesce; thus showing that they are not provided
with any distinct covering.*

Many serious mistakes, arising from the study of
the higher animals exclusively, have been corrected
by an anatomical investigation of marine invert ebrata,
and we find that such an investigation is fatal to the
cell theory. It is quite true that this theory and the
facts to which it is applied, agree in many instances.
The majority of the mollusks, the Nemertes, Planarise,
Synhydrse, and almost all the creatures which I have
described elsewhere,t have skins of a more or less
decidedly cellular character ; and, moreover, all these
external tissues are primarily formed from cells. We
know this to be the case in membranes lining the
inner and outer surfaces of the various organs, but
we cannot say the same of the organs themselves.
We have never seen either muscular or nervous fibre
begin its development in the cellular condition, nor

* I saw this for the first time in the eggs of Hermella. — (Ann. des
Sciences naturelles, 1848.) It has since been observed by others.

f See the " Souvenirs d'un Naturaliste," 1842. Some of my
readers may think that I allude to this work oftener than is con-
sistent with modesty, but I know of no other in which this subject
is treated of in so popular a style. I cannot refer my present
readers to the " Annales des Sciences naturelles," nor to the
similar publications in England and Germany I trust there-
fore that I may be pardoned for alluding to a work in which the
general reader will find much matter for which there is no space
in a volume like the present.

AND THE LOWER ANIMALS.

35

have we ever found the shghtest trace of a celkilar
formation in either of these structures.*

There cannot be the slightest doubt in regard to
the non-cellular character of the muscular tissue.
We have seen entire apparatus^ fully formed^ and
quite perceptible^ yet composed of sarcode alone. In
certain mollusks_, the digestive tube may be detected
soon after it has separated from the general blastema ;
in this case the stomach_, gullet_, and intestine^ have
assumed their proper form and position^ but there is
no distinct cavity^ and consequently no adult mucous
or muscular layers. Among Annelids the development
of the feet demonstrates the same fact. Furthermore,
we have observed decided contractions take place in
exclusively sarcodic masses_, in which no reagent
could show the fibres^, although these are present at a
later period.

Thus, we see that in certain instances not only the
external features, but the intrinsic properties, pre-
exist in the tissues, and that the latter originate
directly in the sarcode, either by a sort of progression,
or by condensation, or by an aggregation of mate-
rials drawn from the general nutritive supply of the
being.

There are already many facts in opposition to
Schwann^ s doctrine, and it is most probable that, as
the subject is more considered, they will increase

I may state here, that, in a most interesting memoir on the
anatomy of Meclnsidse, M. Agassiz, a naturalist of great repute in
Europe, but who nevertheless abandoned the Old World for the
United States, describes one of these radiates, whose nervous and
muscular systems are entirely cellular ; but even this exception
from its exaggerated character is quite beyond the range of
Schwann's theory.

D 2

36

METAMOEPHOSES OP MAN

in number. Several works wliicli liave been since
published, even in Germany present a decided re-
action. Possibly injustice may follow infatuation.
For our part, we should regret it exceedingly. We
could never see in this theory those characters of truth
and universal application which Schwann and some
of his followers attributed to it, but we have not, on
that account, denied the great benefits which it has
effected for science. Like all general speculations
which embrace a large number of isolated facts, it has
enlarged the field of science, given more scope for
research, and elucidated much of what had been before
obscure. More fortunate than many of its predeces-
sors, it is still to some extent correct, and even at the
present time we might almost give it our support.

We may say of Schwann^ s theory, that, with a few
exceptions, and save some questionable points which
v/e cannot treat of here, it applies fairly to all the
more lowly organized tissues of the body, and also —
where the strata are sufficiently distinct — to the
membranes which invest the various organs. There
is, so to speak, a sort of histological relationship
between the two great kingdoms. On the other
hand, the more highly organized tissues, those which
especially characterize the animal, are formed in the
midst or at the expense of the sarcode. Up to this
we have been speaking of the higher animals only,
for as we approach the inferior extremes of the three
.invertebrate sub-types, we observe animals whose
tissues are very indistinct, and of a half-sarcode nature;
and in these instances the cell theory would be more
in error than ever.

All organs spring from a hlastemaj which is pri-

AND THE LOWEE ANIMALS.

37

marily composed of sarcode, and gradually assume
their special features afterwards ; but wlien first
perceived they differ only in size from the adult
forms. The embryo_, in point of fact_, is a miniature
of the perfect being. In the course of develop-
ment every animal exhibits very strange phenomena^
both as to its entire economy^ and in regard to
special organs ; and this is particularly the case
with reference to mammalia. Daily ay^ even hourly^
the scene is changed^ and this unsettled con-
dition applies not only to essential, but also to
merely accessory organs. One might fancy that
ISTature was feeling her way to a conclusion. Here
may be seen cavities being gradually partitioned
off*, divided, as it were, into distinct chambers, or
drawn out in the form of canals, which, in their
turn, are often refilled with solid matter and con-
verted into ligaments ; in another locality we ob-
serve previously solid masses transformed into cavi-
ties, membranous folds being rolled out into tubes,
isolated portions of tissue drawn together to form a
continuous organ, or even a mass hitherto entire,
being gradually cut up into several new structures.
Not only the form and proportions, but the relations
also of the various mechanisms are being momentarily
altered. Parts which at first had been closely related
separate from each other and become distinct, and
organs which had heretofore been distant from each
other, form ties of close alliance. Those apparatus
whose office is a temporary one rapidly increase in
size, acquire an enormous volume, and eventually
disappear altogether. Others are arrested in their
growth at a certain period, and though all the organs

38

METAMOEPHOSES OF MAN

in their neiglibourliood continue tlieir development,
yet they remain in their primitive condition_, and
may be detected in the adult_, where they testify to a
former state of things very different from the existing
one. Thus we perceive that the history of embryonic
development may be summed up as consisting in
incessant transformations and constant activity.*

This condition of change is nowhere so strongly
marked as in the circulatory system. Having for its
office to supply the organs of the body with nutritious
materials, it shares all their alterations. The various
branches and ramifications of the vessels increase with
the organs they supply with blood, and when the
latter disappear, the blood-vessels undergo a propor-
tionate diminution. Besides, this apparatus has its own
peculiar changes, which affect not only the central
portions and ultimate branches, but even the heart
itself. The latter makes its first appearance as a
transparent, solid, straight or slightly curved cylinder,
which is converted into a tube by resorption of the

* In treating of the embryogenical changes of mammals, it is
impossible to rise above vague generalizations. I cannot even
mention the names of the authors to whom we are indebted for
many of these interesting facts. There are very many of them,
and besides, the memoirs and general works on this subject are
rapidly increasing in number. However, I may mention among
others, those of Messrs. Baer, Barry, Bischoff, Burdach, Coste,
Dumas, Duvernoy, Flourens, Hausmann, Henle, Buschke, Kolliker,
Lebert, Martin Saint-Ange, Meckel, Miiller, Oken, Owen, Pur-
kinge, Eathke, Keichert, Eemak, Schultze, Serres, Schwann, Thom-
son, Valentin, Wagner, Weber, &c. M. Bischoff published a most
interesting and vahiable work, combining his own researches and
those of other embryologists, which has since been translated into
French under the title of " Traite du Developpement de I'Homme
et des Mammiferes." Paris, 1843.

AND THE LOWER ANIMALS.

39

central matter. Next^ it becomes S-sliaped_, twists
upon itself^ is constricted at one point_, and widened
at another^ acquires dense and muscular walls_, and is
eventually converted into the large apparatus with,
four separate chambers_, which occupies nearly the
entire central portion of the chest.

In the embryo as in the adult^ the heart is placed
between the organs for the purification of the blood
on the one hand^ and those to which the pure blood is
supplied on the other. In the fully-formed mammal^
which leads an independent existence and breathes
the surrounding air_, the purifying organs are the
lungs; but in the embryo^ plunged in liquid and
dependent on the mother for its nutrition^ the func-
tion of respiration^ or rather its equivalent^ is per-
formed by the envelopes of the egg. It is on this
account that the circulatory apparatus is so different
in the two stages.

In the adult each half of the heart is composed of
two separate chambers_, and comes in contact with one
kind of blood (venous or arterial) only. The ricjlit
auricle receives the venous hloocl which has flowed from
all parts of the body and requires purification, and
forces it into the right ventricle, which then propels it
through a large artery to the lungs. Having been
purified in the latter, the blood (now arterial) flows
into the left auricle, and" then from this into the left
ventricle, from which a large vessel called aortci arises,
whose numerous ramifications convey the vital fluid to
the several organs of the body.

In the embryo the lungs are inactive, and the blood-
vessels which supply them are quite rudimentary.
To compensate for this absence of true respiration, a

40

METAMOEPHOSES OP MAJf

special set of vessels intervenes_, between the young
animal and tlie coverings of tlie egg. The blood
highly charged with nutritious matter flows from these
envelopes toward the right side of the heart. As soon
as it arrives there^ it is permitted to flow into the aorta
without passing into the lungs^ by the aid of two
contrivances for the purpose — the foramen ovaloy an
aperture through which the blood can flow from one
auricle into the other; and the ductus arteriosus ^ or
artery of communication between the great pulmonary
vessel and the aorta.*

These anatomical peculiarities being only required
during the embryonic condition, are not found in the
adult. When the young mammal has been discharged
from the mother^s uterus, the atmospheric air rushes
into the chest, and, dilating the lungs, causes the blood
to flow toward these organs. Then the partition
between the two auricles is gradually completed, the
foramen ovale is stopped up, and the ductus arteriosus is
obliterated, and not unfrequently disappears altogether.
From this time forward the blood, in passing from one
side of the heart to the other, must flow through the
lungs, whose vessels have been permanently enlarged.
At the same period the blood-vessels, which, having
played the part of rootlets, had provided for the early
nutrition of the foetus, having been torn during birth,
become atrophied and are lost. The young animal
begins to feed itself, and the alimentary materials
are prepared and transmitted to the digestive organs,
by a mechanism which till now had been inactive.

For a detailed account of these special apparatus, the reader
will do well to consult the supplement to Miiller's " Elements of
Physiology," translated by Baly. — Ed.

AND THE LOWER ANIMALS.

41

The brancMal respiration and its consequent peculiar
circulation are followed by pulmonary respiration^ and
the true and permanent circulation of the blood. In-
stead of living on the juices of the mother^ the animal
now digests its own food. Thus in a few days takes
place the last important transformation which a mam-
mal undergoes ; and since this converts the being from
a parasite into an independent animal^ we may fairly
term it a metamorjpliosis.

The phenomena we have been describing, no
matter what be their complexities or rapidity, succeed
each other in regular order in each species of mammal,
when the development is systematic; but they are
occasionally interrupted by various disturbing causes,
some of which we suspect, others we are entirely un-
acquainted with. Organs may have their transforma-
tions interrupted withou.t the vital force being arrested,
or the growth of the new creature checked; but then
these organs depart from the natural type or plan. It
is thus that monstrosities are produced. We see,
therefore, that these departures from the normal plan
take place at a very remote period of embryonic life,
and that, cceteris parihuSj the earlier the date of the
disturbing cause, the more extensive will these depar-
tures be. Hence M. I. Geoffroy had good reasons for
asserting that all mammalian monstrosities are con-
genital, or, in other words, that they take place prior
to the birth of the animal. We may say, then, that all
monstrosities are produced by an accidental, but deci-
dedly embryogenical phenomenon. Having stated this
general law, whose importance will be explained by
the study of animals which undergo metamorphoses,
we shall return to mammalia.

42

METAMOEPHOSES OP MAN

CHAPTER y.

TEANSFOEMATIONS WHICH MAMMALS UNDEEGO AFTEE THEY
HAVE LEFT THE EGG.

The development of mammals is_, as we liave seen^
exceedingly energetic in the commencement; tlien
gradually the organs appear in their proper order^
assume their distinctive forms and proportions_, and
take up their right positions. The embryo_, in fact_,
has become a foetus_, and has now strength enough to
make its own way in the world. Finally^ it is born ;
its lungs perform their function_, its digestive apparatus
discharges its duties^ and its circulation is complete.
Does this last step leave the organism, which has
already undergone so many changes,, in a state of rest ?
We saw in the first chapter how the balance answered
this question, and here again we must employ accurate
instruments in extending our observations to the
animal kingdom. Is the infant in the same condition
as the youth, or the adult as the aged ? Is it not pro-
bable that at every period of life the form and propor-
tion of an animal undergo alterations ? And, unless
we admit that our organs are the seat of perpetual
changes and modifications, how shall we explain these
alterations ?

Of all the periods mapped out by the successive
external features of an animal, there are none which
are more remarkable, viewed from our stand-point,

ANL> THE LOWER ANIMALS.

43

than tliat at wliicli tlie capability of procreation ex-
hibits itself. This period is indicated in most animals
by well-marked phenomena. Mammals,, Birds^ Eeptiles,
and Fishes throw off, as it were^ the garb of youth^ and
assume the costume of adult age. Not only are super-
ficial characters affected^ and a few special organs
completed, but new functions present themselves, and
control all those which heretofore held the entire or-
ganism beneath their sway. In fact, the whole animal
is altered in regard to those functions which most
directly affect its general life. Here, again, man
affords us a striking illustration.

Respiration is, as we know, a sort of combustion,
and at every expiration we give off a certain quantity
of carbonic acid. We can estimate the activity of this
function by knowing' the quantity of the latter gas
formed by the combination of the oxygen of the air
with the carbon derived from the decay of the tissues.
Now, the researches of Messrs. Andral and Gravarret
prove that respiration is a little more energetic in
youth of both sexes than in adults.* Grirls and boys
of eight years old consume from five to six grammes
of carbon per hour. This amount increases slowly, in
proportion to each, up to the period of puberty. Till
this period they are neither males nor females, but
neuters. But as soon as the sexes are marked, respira-
tion becomes twice as energetic in the man, although
it remains the same as before in the woman. At about
the age of thirty the former consumes from eleven to
twelve grammes of carbon per hour, whilst the female

" Kecherches sur la quantite d'acide carboniqiie exhale par le
poumon dans I'espece liuniaine." — Annales des Sciences naturelles,
1843.

44

METAMOEPHOSES OE MAN

consumes during tlie same period not more than six
or seven.* Then as old age and the changes which
accompany it efface the more marked distinctions
between the sexes_, the respiration of the female
becomes more active^ and although it never reaches
the height of man^s_, it makes some approach to it.
These strange results afford an argument to those un-
courteous physiologists who see in woman but a man
whose development has been arrested, and who_, con-
sequently, place her a degree lower in the animal
scale.

We are far from supposing that the above opinion
is correct, but the facts from which it is formed are
not the less remarkable on that account. Here we
see that, even when the organism is most complete,
an important function is partially arrested and becomes
stationary. Therefore this onward movement is not
invariably a progressive one. This conclusion is fully
borne out by an investigation of Mammalia generally,
and of their mental faculties especially. Almost any
wild animal may be tamed whilst young ; for memory
and intelligence are still present, and admit of its being
educated to a certain extent. But when fully formed,
instinct has the superiority, and the quasi-domesticated
animal becomes a savage beast. f Yery frequently

The above apparent anomaly disappears when we recollect
that at this period a new function is established in the female,
which in all probability compensates for the deficient respiratory
activity. This view is further borne out by the author's statement
that the respiratory energy is increased in after-life. Why ? Be-
cause then this peculiar function is not discharged. — Ed.

t Thanks to the researches of Frederic Cuvier, we know now
that almost every animal possesses both instinct and intelligence ;
that is to say, its actions are partly the result of reason and partly

AND THE LOWER ANIMALS.

45

tMs change of character is exhibited in the external
features of the being. The head of the young orang-
outang_, on the whole_, resembles that of man; the
skull is smooth and rounds the forehead high_, and the
face hardly more projecting than that of certain human
races. In the adult one_, on the contrary^ the cranium
is covered with bony processes^ the brow depressed^
the face is prolonged in the form of a snout, and alto-
gether the creature bears, in the highest degree, the
stamp of everything that is purely animal. What we
have said of the orang is equally true of all those apes
which, from their resemblance to the human species,
have been termed anthropomorphic or man-like.^
The transformation which they undergo after a certain
date, instead of elevating them, places them a grade
lower in the scale, and therefore we may regard them
as instances of that mode of evolution which M.
Edwards has very appropriately styled recurrent
development.

due to a blind instinct. Most of the writings on this subject are
contained in an abridged form in M. Flourens' work, " Del'Instinct
et de rintelhgence des Animaux." See also M. Fee's work, " Etudes
philosophiques sur I'lnstinct et I'lntelligence des Animaux."

''• On this point the reader should consult Professor Huxley's
valuable work " Man's Place in Nature.*' — Ed.

46

METAMORPHOSES OF MAN

CHAPTER YI.

GENEEAL PEOCESSES OF TEANSPOEMATION CONCLUSION.

Having sketclied the more compreliensive features of
embryonic development in general^ and of that of
mammals in particular, we shall now examine the various
methods by which these phenomena are brought
about. We saw, at the outset, that Nature does her
work in a far more complete manner than some
philosophers imagine, and that she accomplishes her
purpose by a series of different processes, rather than
by a single one.

Of these processes we may mention two by name —
Epigenesis and Evolution; terms which have been for
ages the standards of rival schools, and the subjects
of many a noisy controversy.

According to the doctrine of Epigenesis, neither
tissues nor organs exist in the embryo prior to their
appearance ; they are all formed upon the spot, suc-
cessively, and, as it were, spontaneously also. The
innate nature of each animal determines their form
and structure. The Evolution theory, on the other
hand, asserts that all the organs of the future being
exist in the germ ; that the latter has the power of
growth alone, and is unable to give the being a hair,
a feather, or a scale, in addition to what it already
possesses, if it be an animal ; or a leaflet, if it be a
plant.

A'NB THE LOWER ANIMALS.

47

Epigenesis is really the starting-point of every organ
in the body. We have shown this elsewhere^* and
the details we have already given prove it to be
unquestionable. Science armed with the optical in-
struments of the present day_, asserts most positively
that the blastoderm does not exist until formed from
the elements of the germ. Thus_, we see that even the
first trace of the future being is a purely epigenetic
formation^ and we can say the same of all the
organs in the body. All multiplication^, according
to Schwann^s doctrine^ is nothing but epigenesis ;
and this mode of formation is still more evident in
those cases for which the cell theory makes no pro-
vision. An organ first appears in the blastema^ and
is developed at the expense of the latter^ just as the
primary membrane itself is organized at the expense
of the altered yolk.

The germinal area is the first seat of these epi-
genetic formations^ as each of its leaflets gives rise
to a special series of apparatus^ which are at first
very simple^ and made up of elementary materials.
These,, however^ are afterwards completed^ and
develop adjacent and accessory organs. The ali-
mentary canal^ for example, has, when first formed,
none of the glands attached to it, whose juices will
afterwards be required in digestion. Soon, however,
a little cul-de-sac, developing a blastema, makes its
appearance at a certain point, and quickly exhibits
a cavity with indistinct walls, which, though simple
at first, gradually divide into branches. We perceive

The general questions relative to tlie doctrines of Evolution,
Epigenesis, and Accolement, are discussed at length in the " Sou-
venirs d'un Naturaliste."

48

METAMOEPHOSES OF MAN

here an excreting canal^ and the earliest traces of a
secreting organ or gland. Tliese primitive lobules
increase in number, and divide and subdivide, until
at last that huge bile- secreting organ, the liver, is
completely formed. All the other glands, the lungs,
&c., are formed in an exactly similar manner. Hence
it is very clear that none of these organs exist prior
to their appearance.

Thus we see the developmental force first exhibiting
itself within a special centre, — the germinal area ; then
in three secondary centres, — the three layers; and
finally, in several different centres, as it helps to
complete the various structures which at first were of
a simple character. But epigenesis exhibits itself
especially in laying the foundation of the embryo
itself and of all its structures.

Each organ being at first roughly formed as it
were, and exceedingly small, must eventually increase
in size. Then, the purely epigenetic phenomena are
followed by those of evolution, which present them-
selves under two principal forms.

An organ may grow without having its form or
structure changed in any particular. The envelopes
of the egg, the amnion of the embryo, and almost all
the apparatus of the child, afford us numerous proofs
of this. But in some cases organs must change their
form, proportions, and size, ere they undergo this the
most simple process of evolution. Now, in order to
concentrate our attention, we shall here confine our-
selves to two facts borrowed from human embryogeny.
In man, the arms, when they first appear, are like a pair
of little rounded paddles placed near the centre of the
body, and the tail, which is now quite as long as in other

AND THE LOVv^EE ANIMALS.

49

mammals^ extends beyond the legs_, v/McIl as yet are
quite like tlie arms. At this period the human embryo
is not by any means a bad representation of a certain
species of seal. In order to be converted into the
foetal limbs and arms_, these organs must undergo
considerable modifications^ and be increased in size.

In the construction of a new being there is some-
thing more than the creation and successive fashioning
of organs which will eventually assume their adult
characters. In the higher animals Nature always
supplies those wants which the progress of develop-
ment brings with it, and as these requirements are
not unfrequently temporary, the organs which cor-
respond to them are often transitional. Hence we
often find her simultaneously building up one set of
structures and destroying another.

A careful study of the circulatory apparatus would
supply us with several curious examples, but we
undoubtedly meet with the most remarkable instances
in the organs of secretion. Among the manifold por-
tions of the frame we find certain structures, vv^hicli
have been called after the great anatomist who first
examined them carefully, the Wolffian bodies. These
bodies remind us forcibly of the kidneys, at least as
to structure, and appear to have a similar ofiice to
fulfil. They are seen at a very early period of em-
bryonic life, and soon extend from one end of the
body to the other, lying on either side of the intestinal
canal. As soon as the true kidneys present them-
selves, these WoMan organs disappear, so much so,
that in a few adult mammals we can find but very
questionable traces of them, and the detection even
of these is a matter of some difficulty.

E

50

METAMOEPHOSES OF MAN

Tlie organs whose functions are discliarged during
embryonic life do not all sliare tlie same fate. Some^
as tlie thymus, whicli is situate in tlie chesty and tlie
supra-renal capsules, are only arrested in their develop-
ment, and are found in the adult, although seemingly
without having any function to discharge : others
are still employed and engaged in some new occu-
pation. It is in this way that the vessels which are
connected with the nutrition of the foetal lungs are
enlarged to such an extent after birth, that all the
blood forced from the heart during a single con-
traction, can flow through them to the respiratory
organ.

The important phenomena which are exhibited in
the mammal from the first appearance of the germ,
till death takes place, may be stated as follows :
first, epigenesis ; then evolution of the simple or
complex type, formation, modification, progressive
development, arrest of development, atrophy, and
destruction, or appropriation of organs. All these
phenomena, therefore, imply that, continual mole-
cular currents are established in every portion of
the frame.

If to this unavoidable conclusion we add the
general law applicable to all vertebrates, that there
exist in the embryo at the time of its most rapid
growth, as well as in the adult, important organs
which carry out of the body the worn-out materials,
the term vital current will then appear in the sense
we have employed it. It alone allows the performance
of the various actions we have detailed already.
Assuredly it is this which carries with it the materials
of which the new being will be built, which lays

AND THE LOWEE ANIMALS .

51

them down and distributes tliem_, one moment ac-
cumulating tliem in one locality^ anon drawing
them away to anotlier_, and producing those manifold
transformations which we have been endeavouring to
describe.

E 2

52

METAMORPHOSES OP MAN

CHAPTER YIL

METAMORPHOSIS PROPERLY SO CALLED METAMORPHOSES

OP BUTTERPLIES.

We liave seen elsewliere tliat tlie germ of viviparous
animals prior to rupturing its envelopes and leaving
tlie motlier^s womb, is converted into an animal ca-
pable of leading an independent existence. All ovi-
parous animals present, in the main, a similar state of
tilings. ■ The observations which have been published
up to this, lead us to believe that a blastoderm, formed
on the surface of the yolk, is the starting-point of the
organism ; and that the latter, assum^ing several trans-
itory forms, and becoming more and more complex,
undergoes, in the course of its egg-development, a
series of successive alterations affecting the entire or-
ganism, as well as the structures which it comprises.

But, from the period of hatching, the newly-born
animals constitute two distinct groups. The first have
all the parental features ; the second do not resemble
their parents in any way. In producing the primary
type, the first have only to increase in size, and
undergo the modifications that we saw in the case
of mammalia and man; the second, on the contrary,
have to be completely altered. The latter, having
undergone their transformations in the egg, must
undergo their metamorphoses after they have left it.

For the sake of clearness, and for the purpose of

AND THE LOWER ANTiMALS.

53

comp.arison^ let us see in what this phenomenon con-
sists_, as we find it among insects where it has been
longest known and most fully investigated. We shall
select the Lepidoptera^ commonly called butterflies^ as
an example,, and study the life-history of one of the
commonest species — the cabbage-butterfly {Fieris
Brassicce), which we can do almost with certainty
by bringing together the facts observed by different
naturalists.

All our readers must have seen these butterflies in
theh" gardens^ or in the country ; they have black
bodies^ y/hite ringed antennae^ and wings which are
white on the upper side^ but yellowish below^ and
covered with black spots^ whose number and position
mark the sexes. They are frequently seen in the
months of August and September flying in pairs^
sometimes in pursuit of each other^ and occasionally
rushing round and round^ as though engaged in some
severe contest. It seems as if a real struggle was
going on. It is absolutely nothing of the sort ; it is
the prelude of sexual union^ and has been investigated^
described^ and figured in all its stages by Reaumur^
whose talent for observation seems almost to have
amounted to genius.* The male urges his suit^ and
the female rejects it in true coquettish spirit. Finally,
she settles down, but her wings are closely applied to
each other, in this way covering the entire body. The
male moves round and round her for a few moments,
and then, as if he had taken his final departure, flies

" Memoires pour servir a I'Histoire des Insectes," torn. i. 1734.
This work, in six large volumes 4to, is accompanied by a great
number of plates, and even at the present day is unequalled of its
kind.

54

METAMORPHOSES OF MAN

almost out of sight ; but this is evidently a ruse. As
soon as the female unfolds her wings and exhibits her
entire form, he returns quickly enough_, but to no pur-
pose; for she folds her wings together on his approach_,
and then the flirtations, pursuits, refusals, and pre-
tended departures commence again.

These performances sometimes last for more than
half an hour, no inconsiderable portion of a butterfly^ s
lifetime. When they have ended, the female deposits
its eggs, several hundred in number, upon some por-
tion of a cabbage-leaf. The eggs are like little pyra-
mids, three or four times as high as wide, and grooved
by deep channels, which separate the rounded, undu-
lating sides from each other. The Pieris arranges
its eggs in a most artistic manner, side by side, and,
having glued them firmly to the leaf, leaves them
entirely to their fate. By far the greater number of
them perish, but still some are hatched, and thus
insure the perpetuation of the species.

Every one knows that there springs from each of
these eggs a worm-like animal called a caterpillar,
which must pass into the intermediate condition of
chrysalis before it will become a perfect butterfly.
We shall now pursue this series of modifications,
beginning with the external ones.

The egg which our Pieris lays is much smaller than
a millet-seed, and the caterpillar which emerges from
it, is proportionally diminutive. When fully formed,
however, it measures four centimetres in length, and
about five millimetres in width, and four in depth.
We see what a great diflerence there is in size be-
tween the animal when it emerges from the egg, and
when it is fully formed, and how rapidly the increase

AND THE LOWER ANI3IALS.

DO

tp.kes place. Moreover,, tliis growth is not gTadual^,
as in most other animals. We may describe it as
occurring suddenly^ and by a series of forniative leaps
taken at eacb. of those periods ordinarily called riwulf-
ings. In fact^ as soon as it leaves the egg the young
caterpillar eats with a voracity too familiar to our gar-
deners^ but^ nevertheless^ does not increase in size.

After some days this enormous appetite is lost;
the caterpillar becomes quite languid^ and its skin
loses its colom* and appears to wither. It then cravvds
away to some sheltered locality. If we foUow it to
its retreat; we shall see it attach itself firmly to the
ground; alternately contracting and inflating its body
and twisting it about in every way ; then resting for
a while; as if completely exhausted; and finally com-
mencing anew. Sometimes whole hours are spent
before we can see the object of all these tiresome
operations. Eventually the skin bursts at the third or
fourth ring; and splits in a straight line from one end
of the body to the other. The caterpillar now pushes
out first its head and afterwards its entire body; and
appears in a new skin as flexible and as brilliantly-
coloured as ever. It has also increased in size; so
that it would be quite impossible to inclose it in the
case which before enveloped it. Its organs have in-
creased in volume; but having been pent up and com-
pressed by the old skiu; when suddenly liberated they
attained their proper sizO; as it were, through their
natural elasticity.

There are several moultings gone through before the
caterpillar arrives at its adult size and acquires its final
characters. At this period vfe can distinguish but
two anatomical regions in our insect — the head and

56

METAMOEPHOSES OF MAN

the trunk. The head is small^ of a blue colour picked
with black_, covered with a hard skin^ and pro\dded
with six simple eyes^ which are quite separate from
each other. The mouth_, as in other caterpillar s_, is
formed for dividing and chewing the tough leaves of
cabbage and other cruciferous plants. It is provided
laterally with a pair of solid horny mandibles^ and a
pair of less powerful jaws^ which are partly concealed by
an upper lip and a wide lower one. In the middle of the
latter may be seen a small tubular elongated organ^
pierced by a microscopic aperture ; this is the spin-
ning apparatus^ by which is made the soft wool-like
material which the animal will soon require.

The body of the caterpillar is of cylindrical form^
and is composed of twelve almost similar rings. It
is of a greenish or yellowish grey colour^ marked by
three yellow bands which pass from end to end, and is
covered with black spots. These spots are little tuber-
cles, each of which carries a white hair, easily seen
with a pocket lens. There are eight pairs of feet for
the purpose of locomotion, and, as in all caterpillars,
these are of two kinds. The three first of each side
are conical, jointed, and terminated by booklets or
little claws : these are the horny or truG feet. The
others are termed membranous or false feet. The
latter are like large tubercles, whose ends are trun-
cated and furnished with a circle of booklets. The
most remarkable feature in connection v/ith these is,
that the caterpillar can move them in every direction,
can push them out, or draw them into the body so
completely that there is hardly a trace left of the posi-
tions they occupied. To conclude this description of
our caterpillar, we may mention that there is on each

AND THE LOWEE ANIMALS.

57

side of its body and extending over ten segments, a
series of little orifices, eacli of v/hich is surrounded
by a brown circle; these are the stigmata, or aper-
tures tlirougli wliich. the air is admitted to the
respiratory organs, of which we shall say more fur-
ther on.

The caterpillar of the cabbage butterfly completes its
growth about the month of October or November. It
now prepares for its first metamorphosis by ceasing
to eat, and thus completely emptying its digestive
tube j then it seeks the hollow of some tree, or hole
in some neighbouring wall, and having found a suitable
spot, it begins its preparations.

Unhke the silkworm, this caterpillar spins no cocoon
for its concealment and protection, but undergoes its
metamorphosis in the open air. It now commences
covering the spot it has chosen with filaments which
cross each other in every direction; and this silken
couch, delicate in texture, but withal of considerable
strength, serves as a solid and firm support for the
hinder limbs. Then bending its trunk and head pos-
teriorly almost to the middle of the back — like an
acrobat who makes a hoop of his body — it fixes a
thread first on one side and then upon the other, and
continues the operation till it has formed a kind of
girth, composed of about fifty filaments. This done, it
straightens its body, and undergoes its last moulting ;
the animal however which emerges from the cast-oS*
skin is no longer a caterpillar, but a chrysalis, which is
sustained horizontally by the booklets of its tail and
the girth we have described, just like the reptiles and
fishes which are too large for the cases in our natural
history museums.

58

METAMORPHOSES OP MAN

The Pieris in the new condition which it will main-
tain during the winter_, bears hardly any resemblance
to the caterpillar. The skin^ which is dense and horny,
is covered with a sort of varnish, thrown out at the
moment of the metamorphosis, and rapidly dried.
It has now assumed an ashy hue, picked out with
black and yellow. The body has become thicker, but,
as it were to compensate for this increase, has been
shortened by about one-third. Instead of being made
up of rings from end to end, it now exhibits two prin-
cipal segments. The hinder one alone, which is short
and conical, presents the annulose condition, although
there is a keel-like elevation upon the dorsal portion
of the anterior segment, and a kind of crest upon its
under surface. The head and feet seem at first sight
to have disappeared altogether. On closer examina-
tion, however, we can detect a series of rounded eleva-
tions and projections, arranged S3mimetrically. Know-
ing what this inert mass will eventually become, we can
almost fancy that we see the various organs beneath
the skin, or rather beneath the cement which invests
it ; the proboscis, antenna, and wings being indicated
in the same manner as the form and proportions of
a mummy are rudely mapped out by the bandages
which enshroud it. To all intents and purposes the
chrysahs is a mummy.

About the middle of spring, or beginning of sum-
mer, the Pieris undergoes its second metamorphosis.
Its envelope splits along the dorsal portion, and the
organs which had been inclosed by the crests and
elevations come out, as if from a case ; then the entire
animal disengages itself, and from the chrysalis coffin
there emerges a perfect butterfly. At first its feet are

AND THE LOWER ANIMALS.

59

of too pliant a character to support tlie body ; the
wings are heavy thrown into microscopic zigzag folds^
and unfit for flight; and the proboscis_, with its com-
ponent halves often separate^ is extended in a right
line. But after a while the surrounding- liquids are
eyaporatedj the limbs are strengthened^ the pro-
boscis is adjusted and coiled up^ the wings are un-
folded^ and the insect^ which in its early days was
Sb creeping thing/^ and afterwards a motionless
one_, flies to the nearest flower and makes its first
repast.

We shall now describe in a few words the being
produced from the little worm which sprung from the
Pieris^ egg.

The body^ which is entirely clothed with hairs per-
ceptible to the naked eye, consists of three segments,
which are separated from each other by well-marked
constrictions ; these three are : the head, the chest or
thorax, and the belly or abdomen. The head is small,
and has attached to it in front two long*, horny,
jointed, club-shaped feelers or antennce, which had no
existence in the caterpillar. The little simple eyes are
still present ; but in addition, a large round mass with
a treUised surface may be seen on each side. These
masses are the compound eyes, each facette of which is
a true organ of vision ; and since, according to the cal-
culations of several naturahsts, there are no less than
thirty thousand of these facettes, it follows that the
animal has this enormous number of distinct eyes.
The mouth, which now, instead of being used for divi-
sion and mastication, is only employed for suction, is
admirably adapted to its new office. We can hardly
find a trace of the upper and lower lips or of the man-

60

METAMOEPHOSES OF MAN

dibles. The jaws liave been immensely elongated;
their horny tissne has disappeared^ and flexor and
extensor mnscles have been developed in its place.
Bach jaw is penetrated by nerves and trache;^^ and is
grooved deeply on its inner surface. These orga^ns,
when placed side by side and soldered to each other^
constitute a sort of tube twice as long as the whole body,
and continuous with the mouth. From having been
organs of mastication, they are now converted by this
process of fusion into a proboscis, which the insect
rolls or unrolls at will, and which can penetrate the
deepest calyx and allow it to suck up the juices of the
flower as perfectly as if a siphon had been employed.

The chest or thorax bears the legs and wings. The
first correspond to the horny feet of the caterpillar,
but are very unlike them in appearance. The limbs
of the caterpillar were short and massive, those of the
butterfly are long and slender. Besides, then* struc-
ture is entirely difierent. In the butterfly^s limb there
are five distinct parts, and the last or tarsus is itself
composed of five joints and a pair of booklets. The four
wings are attached in pairs to each side of the back.
Each one is united to the solid structures through the
intervention of a chain of horny pieces, connected
together by sti^ong ligaments and supplied with power-
ful muscles, and to these are due the suppleness
and force which are exhibited in the movements of
flight. Erom this basal portion spring four main
nervures, which diverge from each other, and by
their ramifications support the wing-membranes, which
are thus stretched upon a horny frame. Notwith-
standing then' solid appearance, these nervures are
really hollow in their interior, and are pierced by tra-

AND THE LOWER ANIMALS.

61

cliece, or air-tubes_, which extend almost to their extre-
mities. Moreover they are covered by two exquisitely
dehcate transparent membranes^ which_, firmly united
together^, clothe the upper and under surfaces. It is
to these that the little scales are attached which give
the peculiar colours to this and other butterflies_, being
implanted in the membrane somewhat in the same
manner as a bhd's feathers are implanted in its skin.
The caterpillar did not present the slightest trace of
these wings or their appendages.

The abdomen^ which corresponds to the hinder
portion of the caterpHlar^s body^ has lost all its false
feet^ but with that exception has undergone very little
alteration. The general form has been slightly modi-
fied^ the colour is no longer the same^, but the abdo-
men is invariably divided into seven rather distinct
rings.

Before proceeding any further, we must state,, what
it is of some importance to bear in mind : viz., that
these moultings, metamorphoses, and alterations,
although apparently occurring spasmodically, do not
do so in reahty. Beneath the veil of skin, which will
be thrown off in course of time, even within those
parts which will eventually disappear or be transformed
into others, the new integument is being gradually
formed ; the general plan of the future animal is being-
drawn out, and the various organs which will after-
wards be required are being organized. The old gar-
ment alone is cast off, both at the period of moulting
and of metamorphosis. If we cautiously detach the
old but still vital skin, a few days before the moulting
takes place, we may see its successor lying beneath
it. By doing the same with the caterpillar, a few

62

METAMOEPHOSES OF MAN

days before it passes into tlie clirysalis condition, we
shall discover tlie rudimentary wings and antennae.
If at this period we cut ofF tlie little scaly feet, we
shall find that when the butterfly emerges from the
case, its legs will be imperfect.

Hereafter we shall recur to these facts : sufiice it
to say here, that the metamorphosis of the Pieris is
gradual, not sudden ; and that in this, as in every
other instance, nature does nothing j;er saltum. We
shall see presently that this conclusion, which is suffi-
ciently demonstrated by an external examination, is
further borne out by dissection.

Laying aside the internal changes which we have
already alluded to, we shall consider neither the sub-
cutaneous muscles nor those which are connected mtli
the chewing apparatus, false feet, &c., and which dis-
appear with them. We shall also avoid those associated
with the existing Hmbs and the movement of the
wings. We shall not refer to the hundreds of nervous
trunks and filaments, to the numerous branches and
ramifications of the tracheae, which spring into exist-
ence and disappear with the organs they are distri-
buted to. We shall confine ourselves to the study of
Herold^s beautiful researches on the metamorphoses of
some of the large apparatus, and more especially of
the digestive tube and nervous centres.*

The digestive apparatus which this caterpillar presents
when it first springs from the egg, and even when it com-
mences its transformation, is very simple in character.

■'^ " Entwickelungsgeschichte der Schiiietterlmge," 1815, In this
splendid work, which even at the present day may be considered
a model, the author takes the pieris we have been examinmg as an
ilhistration.

AND THE LOWEE ANIMALS.

63

The alimentary canal begins as a very short and wide
oesoj)hagus, and ends in an intestine,, somewhat of the
same kind^ but which can hardly be said to consist of
two regions. Between these organs we find a stomach
disproportionately large^ which fills almost the entire
cavity of the body. In addition to these^ two salivary
glands^ composed of long tortuous tubes^ are attached
to them in fronts and six well-formed biliary canals^
which represent the liver^ are connected with them
behind. Opening into the mouth and the spinning-
apparatus which we alluded to before^ may be seen
two peculiar organs^ which extend in a tortuous man-
ner along the entire length of the stomachy and whose
ofiice is the secretion of the fluid from which the silk
is formed. Every portion of this digestive apparatus
is calculated to extract the nutritious materials from
the crude masses of unsubstantial food which has been
imperfectly prepared by the action of the jaws.

Even on the second day after the caterpillar has
been converted into the* chrysalis^ very considerable
alterations may be observed. The oesophagus is
narrowed and elongated ; the intestine^ similarly modi-
fied, is now divided into two well-marked regions ;
the stomach has been diminished by about one-half
of its breadth and a quarter of its length ; the sahvary
and biliary glands have been shortened, and the
organs which secrete the silk have become smaller.
On the eighth day, the entire digestive tube is exactly
like a spindle one half of which is covered with thread,
and which is loaded with lead in order to balance it.
The oesophagus represents the upper portion of the
spindle ; the stomach corresponds to the middle, which
is covered with thread ; the small intestine to the thin

64

METAMORPHOSES OF MAX

portion^ and the large intestine to tlie loaded part.
At the same period the salivary glands and bihary
coeca are reduced by about two-thirds_, and the silk-
secreting organs appear as two very slender threads.

During the entire winter — that is to say^ for five or
six months of the year — these operations are sus-
pended; but they are recommenced in fine weather^
and continued till the insect is fully formed. In a
short time the silk-forming canals have entirely dis-
appeared ; hardly a trace of the salivary glands is to
be found; and the stomachy though preserving its
former shape^, has decreased in size ; but to compen-
sate for this, it has developed a new cavity called a
crop, which is destined to assist in sucking* up the
juices of the flowers and retaining them till required
by the insect. Moreover, the two intestinal regions
have become more distinct, and the large intestine
has developed an accessory pouch, not a trace of
which existed hitherto.

We come now to the nervous system. In Annulosa
generally, and hence in insects in every condition,
this system is composed of two distinct portions. The
hrain is placed in the head just above the oesophagus.
The other nervous masses, or fjanglia, are situate
below the digestive tube, where they constitute a
ganglionic chain. The brain is united to the first
ganglion, this to the second, and so on, by a series of
nervous filaments, technically termed commissures. In
each ring of the caterpillar^s body there is a distinct
ganglion; consequently there are in all twelve of
these structures, equally distant from each other, with
the exception of the two first, which are more closely
approximated than the rest. The brain itself is very

f

AXD THE LOWER AXIMALS.

65

small and is composed of two smooth lobes whicli are
obliquely united_, and give off a few slender nervous
filaments.

Two days after tlie caterpillar lias been converted
into tlie chrysalis^ tlie ganglionic chain has been
shortened one-fourth^ and various changes of alteration
and concentration have begun. Some gangha are
approximated_, others^ on the contrary, are separated.
At about the eighth day the chain has been shortened
one-half. On the fourteenth the brain and first gan-
glion have come so close together that their commis-
sures smTound the oesophagus; the fom*th and fifth
ganglia have been fused together ; and the sixth and
seventh are hardly perceptible. Now there is a period
of rest, brought about by the approach of winter.
Then, after the latter season, the operations are re-
commenced, and when they are again arrested, after
the last apparent transformation, there are only eight
ganglia to be seen. The second, third, fourth, and
fifth have given rise, by their fusion, to two large
masses, which are placed in the chest quite close to
each other; the sixth and seventh have completely
disappeared, and their former position is alone marked
by the origin of a few nervous filaments ; the five
posterior ones have undergone little or no change.
Finally, the brain itself has become twice as large,
its lobes have assumed a transverse position, and each
of them gives origin to a large optic nerve which
travels to one of the compound eyes.^

* This short sketch of the changes imdergoiie by the nervous
system has been taken in great part from the researches of Herold,
because his investigations refer to the same insect (Pieris Brassicae)
which Reaumur studied. On vhich account we have been enabled

F

66

METAMORPHOSES OF MAN

The changes which the organs of circulation and
respiration undergo are not by any means as well
known as those we have been describing, and this
ignorance is due, most Hkely, to the great simphcity
of the first, and the equally complex character of the
second. In this caterpillar, as in every other one,
the circulation is almost entirely lacunar. In it, as in
the butterfly, there is a distinct heart, or rather its
representation, in the form of a long many-chambered
canal, stretching from end to end of the body. "V^Hien
the latter is shortened, this dorsal vessel, as it is called,
is also diminished in length, and becomes more and
more tortuous, in proportion as the regions of the
body are mapped out and separated from each other.

This degradation of the circulatory organ is com-
pensated for by the formation and distribution of a
series of respiratory organs, or tracheaa. These open
externally at the stigmata to which we have alluded
already. They consist, in Pieris, as in all other cater-
to form a complete history of this butterfly. Those, however, who
desire to pursue the study of the nervous system in insects, should
consult the memoirs devoted to this subject by the English naturaUst
Newi3ort, who was prematurely called from the field of science.
His w^ork upon the nervous system of the privet-moth (Sphinx
Ligustri) is characterized throughout by clear powers of observation,
accurate demonstration, and really scientific deductions. Daily,
nay hourly, he followed the modifications which the nervous sys-
tem undergoes, not only in the species on which his work is written,
but also in the case of the nettle-butterfly. He proved that oven
in the course of a single hour the brain undergoes very appreciable
changes in both its form and the disposition of its optic nerves. —
(" On the Nervous System of the Sphinx Ligustri," Philosophical
Transactions, 1832.) The metamorphoses (general and special) of a
butterfly are also described in the splendid work of M. Cornalia
on the Silkworm, " Monografia del Bombice del Gelso."

AND THE LOWER ANIMALS.

67

pillars,, of two great lateral trunks^ reaching from end
to end of tLe body^ and giving off hundreds of branches
and ramifications^ which travel over the whole frame^
penetrate the smallest cavities^ and supply the most
delicate organs. In all insects with the power of
flighty and consequently in the Pieris^ this apparatus
develops a pair of pouches destined to contain air^
and thus, of course^ diminishes the specific gra\dty of
the body. According to Newport^* it is only in the
chrysalis that these organs are formed w4th rapidity.
In Pieris^ they first appear some time in autumn^ and
are half-formed before the winter; they remain at a
standstill during this season^ and assume their perfect
form a short time after the last metamorphosis.

The function of all the organs we have already
described is that of preserA^ng or maintaining the
life of the individual. They are all^ moreover^ in the
full exercise of their duties from the moment that the
creature emerges from the egg. Those organs con-
nected with the perpetuation of the species are very
differently situate. These are so slightly developed^
and so imperceptible whilst the insect is in the cater-
pillar stage^ that the penetrating researches of Herold
could not demonstrate their existence. These organs
are quite rudimentary^ even at a period of five months
after the conversion of the caterpillar into a chrysalis.
It is only at the last moment^ and just as the butterfly
is about to make its escape^ that they are to be seen in
process of completion^ whilst they undergo their entire
development only in the perfect insect.

* " On the Eespiration of Insects." — Philosophical Transactions.
1836.

F 2

68

3IETAM0EPH0SES OF MAX

Thus we see tliat this apparatus, though it marks
out but an epoch in the Kves of mammals and birds^
is here characteristic of an entire change in the mor-
phology of the animal. Its physiological significa-
tion is therefore, from this circumstance alone, of far
greater value, and, as we shall see further on, this
value is sometimes enhanced.

Here we must notice a very significant fact, and
one which bears forcibly on the present subject. The
female Pieris dies soon after depositing her eggs,
and the male ceases to exist at a still earlier period.
Matrimony is as fatal to them as it is to all insects,
and their existence terminates when the preservation
of the species has been insured. There is, however,
an occasional circumstance which, by preventing the
discharge of the functions essential to this final object,
prolongs the usually short life of these insects to an
extent beyond that which is intended. Some but-
terflies do not emerge from the chrysalis case till late
in autumn, and then the cold temperature of the sur-
rounding atmosphere retards their development, and
winter comes on ere they have begun their amours.

In consequence of this, they retire to some sheltered
spot, remain there during the whole season, and
reappear in spring. Thanks to this condition of
celibacy, the result rather of circumstances than of
desire, their lives, instead of being limited to a fevv'
weeks, extend over several months.

AND THE LOWER ANIMALS.

69

CHAPTER YIIL

IIETAMOEPHOSES OF INSECTS GENERALLY.

We liave studied tlie complete life-liistory of an insect.
By examining several species of each, group from tlie
same point of view^ we are enabled to form a notion
of tlie ideal plan upon wliicli this class is constructed.

The typical insect would be an annulose animal^
breathing by trachese,, with a body composed of three
distinct segments^ of which the middle bears three pairs
of legs and two pairs of wings_, and which arrives at its
perfect condition after undergoing two metamorphoses.
ITence^ independently of the time spent in the egg,
its lifetime is divided into three separate periods^ the
first of which is characterized by both an external and
internal activity^ whose only object is the growth of
the individual; the second by an internal activity alone,
whose object is the modification of the individual; and
the third by an internal and external activity, the sole
object of which is the perpetuation of the species.
Some insects are constructed exactly upon this ideal
plan, and we need not go beyond the Lepidoptera to
find an example. From the egg of the wood-eating
cossus (Cossus ligniperda), a caterpillar is produced
which spends two years or rather more in this stage,
and then becomes converted into a chrysalis ; the latter
is transformed into a moth, which never eats any--
thing, has no proboscis, and spends the few days of its;

70

METAMORPHOSES OP MAN

lifetime in tlie performance of those acts necessary to
tlie production of offspring.

Tlie greater number of insects differ more or less
from this general type. Most of them, even on attain-
ing their final condition, have still to maintain or com-
plete their organization, and hence must provide for
the nutrition of their bodies. Yery many assume the
perfect condition on leaving the egg, and, like mam-
malia, have only to increase in size. Others are
entirely devoid of wings. These variations, however,
are limited, and certain characters present themselves
so constantly that there can be no question as to their
being fundamental.

Every perfect insect is composed of a head, thorax,
and abdomen ; breathes by tracheas, and has three
pairs of legs. Looking at the insect class from our
point of view, we can group together all these differ-
ences and affinities by regarding them as the results
of a series of modifications of one and the same phe-
nomenon. In common with all entomologists, we
grant that metamorphoses may be either complete or
incomplete.* The former term applies to those

* There may be also a sort of exaggerated metamorphosis, as J\I.
Fabre has shown in his interesting researches upon the develop-
ment of the meloes. The larva of this insect, before being con-
verted into the chrysalis, passes through four distinct stages, which
the author has termed /irs^ or jirimitive larva, second larva, j^-'^cudo-
chriisalis, awl thlnl larva. But these changes, which are simply a
series of moultings, are dependent upon the diifereut conditions by
which the animal is surrounded, on account of its frequent migra-
tions, and have no reference to the internal organization of the
creature. Hence they are included in the expression compldc meta-
morphoses. This has been fully understood by the author of the
remarkable papere upon " rHypermetamorphose et les Moeurs des
Meloides," Annalcs des Sciences naturelles, 1857-58. Siebold, in his

AND THE LOWER ANIMALS.

71

insects in whicli there are three distinct stages of
existence^ corresponding to tlie larva, nymph ov pupa,
and perfect form or imago. But if we compare it with
our ideal type_, we shall see that an insect^ although
passing through these three stages^ may yet want one
of the essential characters already referred to. Thus,
its last transformation may be as it were arrested at a
certain point, and consequently the metamorphosis
may be in reality incomplete. There is a sort of tran-
sition to those species whose changes are consecutive,
slightly marked, or even absent.

With such exceptions we may look upon the follow-
ing groups as insects which undergo complete meta-
morphoses— the Neuroptera (dragon-flies, day-flies,
and white ants) ; the Hymenoptera (bees and wasps) ;
the Coleoptera (beetles, lady-birds, &c.) ; and, finally,
the Lepidoptera or butterflies. Having done vath the
latter, we shall now give a brief sketch of the other
orders, a.nd in doing so contrast the more remark-
able points in their life-history with the facts already
detailed.-''

memoir on the metamorphoses of strepsiptera (Wiegmann's Archiv,
1843), and M. Joly, in his " Eecherches zoologiqnes, anatoiniques
et physiologiques sur les (Estrides," 1846, have pointed out similar
facts. The latter proved, moreover, that the anatomical changes and
alterations of external form are simultaneous. He very correctly
ascribes these phenomena to the conditions of life which the para-
sitic habits of the insect bring with them. — " Note sur THypermeta-
morphose des Strepsipteres et des QEstrides," Comptes rendus, 1848.

* These metamorphoses do not always take place in the same
manner in different orders. We may find a sub-order present-
ing peculiarities of its own, and even the individuals v/hich
it comprises may differ from each other as to the way in which
these changes occur. Although limited as to the selection of
species, I have chosen those which follow the general plan as closely

72

METAMOPtPHOSES OF MAN

We shall now consider the Coleoptera^ selecting the
common cockchafer as an example. About the end of
April_, and some time after sunset_, the female of this
insect may be seen preparing for the hatching of her
eggs. Having selected a light_, well-cultivated^ and
manured soil^ such as that of a kitchen garden^ she
dig-s a hole of about fifteen to eighteen centimetres
deep, and deposits in it her eggs, which are thirty in
number. This act accomplished, she ceases to exist.
In a month after, a little whitish larva springs from
each egg ; it is half- twisted upon itself ; its head is of
a reddish hue and of a horny structure, and is provided
with powerful chewing organs, and its body, which is
soft, is composed of twelve rings, possessing six scaly
feet and eighteen very well-marked stigmata.

The young larvas lead a gregarious life at first. At
this period the whole family is dependent for sub-
sistence on the rootlets of the neighbouring plants,
and the refuse vegetable matter scattered through
the soil. Even on the approach of cold weather they
still remain together; but they burrow deeper, and
construct a large chamber completely removed from
the influence of cold, where they pass the winter
in common. When spring appears, these larvce have
become larger and more ravenous, and they can no
longer enjoy each other^s society, from the simple fact
that no one locality could furnish them with enough
of food ; they now part company, each working- its
way up to the region of rootlets, through a little gal-
lery or tunnel of its own. It is now that, under their

as possible, or which present facts whose aiDplication will be after-
wards explained. The transformations about to be described are
not quite typical.

AND THE LOWEE ANIMALS.

73

too familiar name of ivhite ivorms, they do so mucli mis-
chief to our garden vegetables^ nurseries^ and natural
and artificial plantations ; sometimes destroying even
huge trees by devouring their rootlets. On the ap-
proach of the cold season they again retire^ oi^ly^
however^, to reappear in the following year. This sub-
terranean life lasts for three years_, or even more in
occasional instances.

However^ when fully grown^ each larva makes a
larger tunnel than ever^ and constructs an ovoid
chamber of a sort of mortar composed of clay and a
gelatinous fluid which it secretes,, and in this rough
cocoon it is transformed into the nymph or puija. In
this condition it is very like a chrysalis ; but the wings^
legs^ and antenn^^ instead of being covered by the
varnish before mentioned^ are inclosed in special cases^
and are applied to the surface of the body.

The cockchafer in its new condition remains torpid
for five or six months. It wakes up toward the end
of February and emerges from its case ; but its body
is still quite soft and uncoloured^ and hence it is un-
fitted to brave the dangers of its future world. It
remains in the ground^ therefore^ till its skin has become
hard and strongs and finally leaves its subterranean
abode about the end of April. It now files to some
adjacent tree^ and though in its perfect insect condition^
commences to devour the leafiets just as it destroyed
the rootlets when it was in the white- worm stage.

In most classifications^ the ISTeuroptera come after
the Coleoptera ; but in order to study^ step by step^
the phenomena we are now considering, we must
invert the zoological order of succession, and pass on
in the next place to the Hymenoptera.

74

METAMORPHOSES OF MAN

To this group the IclineumonidaB belong, — those
insects which_, by destroying other species in thou-
sands_, effect so much for our gardens, fields, and
plantations, — benefits which we fancy very few are
aware of. We shall study one of these insects,
whose history can hardly be separated from that of
the cabbage butterfly, and which has engaged the
attention of Goedaert, Swammerdam, Yallisnieri, and
Keaumur. It is called the glomerate microgaster
[Microfjaster glomeratus) .

This insect is like a small fly, and has four wings
supported on nervures whose interspaces are large, a
black body, yellow legs, and antennae which are kept
in constant motion. The female carries within the
posterior portion of the abdomen, a lancet, or hollow
sting {ovipositor), composed of three distinct pieces,
whose function we shall now explain.

When she is about to deposit her eggs, she looks
out for the caterpillar of the Pieris; as soon as she
has found it, she settles down upon it, and grasping it
tightly by the back, she pierces its skin with a single
stab of this instrument, whose three component parts
constitute a sort of hollow tube. She next drives it
more deeply into the substance of the body, and at
the same moment an egg escapes from the ovary, and,
gliding down this canal, is deposited in the tissues of
the caterpillar. The Microgaster then draws back its
ovipositor, advances a little, and recommences this
performance. In vain does the poor caterpillar writhe
at every successive puncture ; its enemy continues the
operation in the calmest manner possible, and never
gives over till it has eftected its purpose, and deposited
from forty to fifty eggs in places of safety. This

AND THE LOWER ANIMALS.

75

done^ it flies away and speedily perishes. Once it lias
gone^ the caterpillar no longer exhibits any symptom
of suffering. Its wounds are healed_, and it prepares
to undergo its first metamorphosis^ just as if nothing
had occurred; but it undergoes no further develop-
mentj and instead of a butterfly there spring from the
chrysalis as many little maggots as there had been eggs.

In fact each of these eggs has produced a larva^
with a smooth white body entirely devoid of limbs^
and whose head_, concealed in part by a sort of hood,
is provided with a chewing apparatus well calculated
to divide the caterpillar^s tissues. These larvae begin
gnawing around them, at first carefully avoiding
the more essential organs, and attacking only
the fatty structures which surround and connect
them. Afterwards having become more voracious,
and just as their involuntary nurse has completed its
growth and transformation, they devour everything
remaining, and then piercing the skin which they
have emptied of its contents, they come out and spin
their pretty little yellow cocoons. In these they pass
the winter without undergoing any alteration in form ;
but by the time spring arrives they have become
jpiipce, and a few days subsequently they appear as
perfect winged insects.

Twenty or twenty-five — in other words about half of
this brood — are perfect females, who very soon sacrifice
as many caterpillars to the production of their off*-
spring. We now see how the Pierides are destroyed
by the Microgaster. "jReaumur calculated that at
least nine-tenths of all the ova are lost in this way,
and of two hundred pupae collected by M. Blanchard,
only three gave rise to butterflies ; the remaining

76

METAMORPHOSES OF MAX

liiindred and ninety- seven having been devoured by
tliese ravenous icbneumons.^' Assui-edly tlie Paris
gardeners ouglit to reverence this insect as liiglily
as its mammalian namesake was respected by the
Egyptians.

We shall now return to the Neuroptera and take for
illustration a group, the short life of whose different
species has received the attention of philosophers,
naturahsts, and even literary men, from the earliest
ages.f Following the account given by Reaumur, we
shall give a brief sketch of the life-history of the
white-winged day-fly [Eplicrnera allripcnnis) .

If, following the example of our distinguished guide,
we were to take boat and sail up the Seine or the
Marne, we should find that the banks below water-

" Dictionnaire universel d'Histoire iiatureUe," article " Icbneu-
moniens."

t Aristotle was the first who treated of the ephemeridce, in a
X)assage where truth is curiously blended with the erroneous ideas
of his age, and which may possibly interest the reader. '* Near the
river Hypanis, which flows into the. Bosphorus," says the author of
the treatise upon animals, " and about midsummer, may be seen
several vesicles about the size of a grape-stone, Avhich in bursting
give rise to an animal with four legs and as many wing-s. These
creatures live and fly about until evening ; they become exhausted
as the sun sinks in the west, and die when it sets : their life has
lasted but a day ; on which account they have been called ephe-
mera (which means, lasting for a day)." Pliny and ^Ehan liave
but repeated Aristotle's statements. In the middle ages, Scahger
made known tlie fact that ej)hemerida3 were found in France on
the banks of the Garonne, and that from their abundance at certain
seasons they had been called Jislies' manna. Clusius afterwards
discovered them in Holland, and described their larvie. At a
later period, Swammerdam, Reaumur, &c., and in our time Kirby,
Siebold, Leon Dufour, Burmcister, Pictet, &c., have studied them
carefully ; so that at the present day we may consider that the
history of these insects is one of the best-known.

AND THE LOWER ANIMALS.

77

level were pierced by numerous little round holes
from three to four millimetres wide_, and usually
grouped in pairs. These are the entrances of as
many arciform galleries extending for about six to
eight centimetres into the earthy and inhabited by
ephemera larvse. Each larva is about two centi-
metres long ; its head bears two very large compound
eyes^ a pair of mandibles which are used in burrowing-^
and jaws adapted to grind the slimy mud upon which
the creature seems to subsist. The thorax is quite
distinct^ and has six legs already attached to it ; the
abdomen ends in three long hairy filament s_, and is
covered with large fringed laminse^ which the creature
moves with great rapidity. These laminse are actual
gills^ that is to say^ they are organs of aquatic
respiration. Large tracheal trunks ramify through
them^ and extract from the surrounding water the air
which is necessary to the preservation of life.

The ephemeron remains in this larval condition for
about two years^ gradually acquires its proper size_,
and then becomes a pupa. But this^ quite the reverse
of all the insects we have been describing^, does not
alter its larval mode of life. It lives in the same
gallery^ is just as active as before^ and only differs in
the possession of rudimentary wings attached to the
upper part of the thorax. We see then^ that this first
metamorphosis is in certain particulars an incomplete
one. It is not so with the second; this takes place
every year at the same period^ and occurs daily nay
hourly, without being influenced to any decided
extent by variations of temperature. The nymphs or
pupae may be seen quitting the water for dry land,
between eight and half-past eight every evening, from

78

METAMORPHOSES OF MAN

tlie 8tli to the IStli of August. The skiu of the
animal bursts very soon after and the perfect insect
throws oflF its envelope as easily as we would throw
off a coat. It now flies away^ leaving its gills^ which
have been replaced by stigmata^ and its chewing-
apparatus, which it no longer requires, attached to
the cast-off skin. Gradually the number of winged
ephemera increases ; about nine o'clock they fill the
whole air; from this till about half-past nine they
form perfect clouds, enshrouding the observer, and,
falling upon him, and the ground, and water, like a
heavy snow-shower, constitute heaps which are some-
times many inches thick. At ten o'clock there are
only a few isolated specimens to be seen. In the
space of a single hour these insects, which lived for
two years under water, have been metamorphosed
into air-breathing animals, with finely reticulated
wings j have exercised their amatory passions in the
atmosphere ; have deposited masses of from seven to
eight hundred eggs ; and finally have ceased to exist, —
deserving the epithet ephemeral in its modern sense,
far more justly than their Hypanian brethren.

In the group we have just been examining, the
metamorphoses are rather indistinctly marked. The
organization of the ephemeron does not differ very
widely from that of its larva. Moreover, the pupa is
almost a fac-simile of the larva, leads quite as active a
life, and, like the latter, inhabits the water also. The
white ants and di-agon-flies are pretty similar in these
respects; in all, however, but especially among the
ephemera, we find that the perfect insect corresponds
to the ideal type. We shall see that this is sometimes
unrepresented, and that in occasional instances the

AND THE LOWER AXIMALS.

79

cliaracters of the insect at different periods resemble
each other so strongly^ that the transformations are
almost nndistinguishable. We come now to insects
with incomiolete metamorphoses.

The Diptera^ or true flies^ constitute a sort of con-
necting link between the above and the groups we
have already considered. In these the three stages
are very well marked_, and certain metamorphoses are
rendered more complex by the appearance of a new
set of phenomena ; but in the perfect insect we find
that the posterior pair of T^-ings is absent_, being only
represented by a couple of rudimentary organs called
halancers, which, regulate the flight of the insect. We see
then that the Diptera are departures from our ideal plan.

Let us examine one of these flies_, — the chameleon
stratiomys (Stratiomys cliameleon), which is common
enough in the woods about Paris^ and whose history
has been clearly made out by Eeaumur and Swammer-
dam. It is a large insect^ a little longer and much
wider than a bee. From its head spring two fusiform
antennge^ its two compound eyes are separated by a
hairy interval, and its large proboscis_, which serves to
abstract the saccharine juices from the nectaries of
flowers, remains concealed, when at rest, within a
special cavity. Its back, which is of a reddish hue,
carries, independently of its pair of wing's and
balancers, two horny curved booklets, which are
directed backwards. Its belly is coloured brown, and
is covered with white semilunar spots. Such is the
perfect insect. Let us now see what the larva is like.

This is a sort of flat worm, inflated about the middle,
terminating at both ends of its body in a snout-like
point ; it is about six or seven centimetres long-, com-

80

METAMORPHOSES OF JIAN

posed of about twelve rings, is provided witli a very
imperfect buccal apparatus_, is witliout a vestige of
limbs, and its dense tuberculated body is like a piece
of saturated parcbment. It may be found in almost
all our ponds, where it swims about somewhat in tlie
manner of a leech. It can only breathe by air, and it
does so in a very peculiar way. In the last segment
of the body, which is much elongated, two very large
tracheal canals, which pass from end to end of the
larva, terminate in a single orij&ce ; this orifice is sur-
rounded by a bunch of branching filaments ; and by
the approximation of these latter it is kept constantly
closed. As soon as the creature wants fresh air, it
ascends to the surface, expands this filamentous or-
gan, which thus constitutes a sort of float, and then,
head downw^ards, it allows the atmospheric air to enter
through the orifice, pass along the trachea, and so fill
the entire body.

Reaumur has not told us how long the stratiomys
lives in the larval condition. Invariably about the
beginning of summer we find some of them twisted
in a zigzag manner, and quite motionless and stiff";
and if one of them be carefully opened, the fully-
formed pupa may be seen in its interior. At the
moment of its metamorphosis the stratiomys detaches
itself as completely from the larval skin as occurs in
the case of other insects ; but instead of emero-ino-
from it and throwing it away, it still remains mthin it,
thus saving itself the trouble of preparing a chamber
in the earth or spinning a cocoon. In fact this skin
forms a kind of house for the pupa, which in its
present condition it is unable to fill completely. In
assuming its nymph form, its body is so much con-

AND THE LOWER ANIATALS.

81

tracted tliat it hardly extends over five of tlie larval
rings. But, as it were to compensate for tliis^ the
eyes_, proboscis^ antennge_, feet_, and wings^ have been
added to the outer surface_, and important anatomical
changes have also taken place within. The larval skin_,
which thus forms a sort of shell for the pupa^ being in
great part empty, floats upon the surface of the water.
After five or six days the nymph begins to move about
in this case, which incloses it ; and finally the latter
bursts above, and the stratiomys, disengaging its limbs
of their envelopes one by one, springs from its floating
cradle. More fortunate than most aquatic species, it
is incapable of being submerged, and consequently has
little dread of shipwreck ; and it is whilst treading as
securely upon water as on land that it casts off the last
garments in which it had been enswathed.

Leaving the Diptera, we find only insects which
have incomplete metamorphoses, or none at all. It
is usual to state this fact alone, but the generally
accepted notion that we ourselves are developed in
obedience to the same general principles as those
which control the formation of insects, allows us to go
a step further, and to regard all these modifications,
and even the entire absence of the phenomenon, as the
result of two immediately distinct causes, or at least
as the products of two very different processes. The
incompleteness of the metamorphoses may be due either
to a premature development of the insect while within
the egg, or to an arrest of development after it has been
hatched. The entire absence of metamorphoses is
owing to the influence of these two causes combined.

The Orthoptera, including the grasshoppers and
crickets, and the Ilemiptera, embracing the bugs,

o

82

METAMORPHOSES OF MAN

cuckoo-spits, and lantern-flies, undergo ver}^ indistinct
metamorplioses, for tlie simple reason ttiat in spring-
ing from the egg', they possess almost all the charac-
teristic features of the perfect insect. Hence, they do
not exhibit those varied modes of life which we find
among other species. The larva of the grasshopper,
for example, leaps about, and browses upon the young
herbs just as its parents did ; the organs of locomotion
and digestion havino^ had their adult forms, and rela-
tions to each other, from the very commencement of its
existence. It is true that its generative apparatus is
still to some extent imperfect ; but even at this period
the future female carries at the end of her abdomen a
sort of doubles word, which is nothing less than the
ovipo.ntor by which the eg'gs will eventually be placed
in some sheltered portion of the soil. It wants but
wings and an increase of size in order to be a perfect
insect in outer appearance. It grows at each period
of moulting, and the organs of flight soon appear in
the form of stunted projections. At this period the
njrmph stage begins. Without changing its mode of
life, it continues its development, and after the last
moult, the wings acquire their full size; the grass-
hopper has arrived at the perfect condition, rather by
a series of transformations than by metamorpJioses.

Insects with incomplete metamorphoses due to pre-
mature development, usually resemble the ideal type
when they reach their perfect condition ; those, on the
other hand, whose metamorphoses are incomplete,
because of an arrest of development, are always more
or less departures from the common plan. This brings
us to the Flea tribe.

The eggs of the female flea are scarcely as large as

AND THE LOWER ANIMALS.

83

the head of the smallest pin_, and the mother when lay-
ing them spreads over them little particles of dried-up
blood. From each of these eggs springs a diminutive
whitish larva^ which soon assumes a brownish tint^ and
carries a small tuft of filamentous hairs upon each
segment of its body. Although devoid both of legs
and eyes_, this larva is not the less active on that
account , and is very well able to supply itself with
nutritious food. In the course of twelve or fifteen days
it has undergone its complete development. It then
spins a cocoon_, composed of threads of very fine silk
closely interwoven_, but which_, being extremely transpa-
rentj allows us to watch the progress of the transforma-
tions which are going on within. As in the insects
before mentioned^ the nymph is perfectly motionless,
and with the exception of the wings, exhibits all the
structures of the perfect creature, folded up_, and, as it
were, shortened also. The adult flea can leap famously,
but he cannot fly. In this instance the metamorphosis
is incomplete, because of the non- development of the
organs of flight.

Sometimes the arrest of development affects the
internal organs alone, leaving the outer essential
structures to be fully formed. In these cases, how-
ever, the metamorphosis is just as incomplete.

It is in this way that naturalists account for the
peculiar characters of certain individuals which con-
stitute by far the greater portion of every insect
colony, and which, from the fact that they are neither
males nor females, have been called neuters. The
latter are really females, which have been modified by
the combined influence of an innutritions diet and
close confinement. As far as bees are concerned, this

G 2

84

METAMORPHOSES OF MAX

fact has been incontestably proved by tlie observa-
tions of Eeaumur^ Scliiracli, and Huber. The cell
whicli contains the larva of the queen hee, or, in other
words, that of the egg-laying insect, is much larger
and better constructed than any of the others. More-
over the future monarch is supplied with a peculiar
form of food. When the bees wish to produce a
queen, they break down several intercellular parti-
tions, and enlarge and strengthen some of the cells ;
next, they supply the larvee they contain with that
peculiar food which is reserved for royal mouths
alone; and under the stimulating influence of this
new system of diet and hygiene, those larviB which
would, under other circumstances, have proved neuters,
are converted into fertile females, capable of laying
from thirty to forty thousand eggs. Furthermore,
should any of this prolific jidice fall into the neigh-
bouring cells and be eaten by the larvae which have
been placed under ordinary conditions, even these are
raised a degree in the animal scale, and become semi-
fertile females.*

In bees, white ants, and emmets, in fact among all
monarchical or republican insects which live in colonies,
the neuters are abortive females. Beino- from this

o

circumstance removed from the preoccupation and
duties which require the whole life of the perfect
insect, they strike out a new path for themselves. It
is these alone which, under the name of u-orl'crs, do
all the labour, tunnel out the subterranean chambers,
or erect the habitations, and nurse the eggs and young
of the colony; it is these which, at the risk of tlieii'

Hereafter we shall describe the reproduction of bees in detail.
(See the chapters on Parthenogenesis.)

AND THE LOWER ANIMALS.

85

own lives^ protect and defend those of the whole com-
munity. Looking at it from a mode-of-life point of
view^ we may say that incom,plete metamoT]3]iosis pro-
duces a series of new beings.

Normal metamorphosis may be as it were dimi-
nished either by the premature acceleration of certain
parts^ or from an arrest in their development^ or from
their entire absence. Each of these causes ac ting-
separately alters the phenomenon differently; when
united, they suppress it completely. An insect which
undergoes no metamorphosis_, departs so widely from
the ideal type, that it may be considered as external
to the class to which it belongs, if we view it in a
physiological aspect; and its exceptional nature is
represented by negative characters. It never pos-
sesses wings, and consequently is never, properly
speaking, a complete insect; for organs of flight
belong as exclusively to insects among invertebrata
as they do to birds among vertebrata, and they are
quite as characteristic of one group as of the other.

Besides, as we have already seen, the existence of
wings and their fimctional development are closely
associated with metamorphosis. They never exist in
the larva, nor are they to be found even in the
nymph ; they only make their appearance at the very
last stage of the animaFs existence.

All insects of powerful flight, and which can remain
on the wing for a considerable time, have to undergo
metamorphoses ; no insect whose metamorphoses are
incomplete, not even excepting the celebrated voyager
grasshopper,* is possessed of these advantages. On

* The voyager grasshopper (Acridium migratorium) is that species
of the family Gryllidce whose heavy columns often ravage entire

86 METAMOEPHOSES OF MAN

the contrary, tliere are many of tliom wliicli never
possess any organ of fligM at all. Insects wliicli
undergo no metamorplioses can never have ^^-ings.
This is what occurs in all those insects, such as the
lice, spring- tails, and lepismae, which leave the egg
fully formed, and only increase in size afterwards.
These are purely oviparous animals, and their develop-
ment is effected by a series of simple transformations;
they never reach the condition of the perfect insect,
and as regards external characters, they remain larvce
to the end of their lives.

continents, and engender plague or typhus by the putrefaction of
their bodies, after they have produced famine by their voracity.
Although these large orthoptera measure nearly ten centimetres
om wing to wing, single individuals cannot undertake long jour-
neys. The flight of an isolated insect is hea^-y, and moreover is
never sustained for any length of time. It is in great part the wind
which drives these living clouds to such immense distances, occa-
sionally carrying them out to sea.

AND THE LOWER ANIMALS.

87

CHAPTER IX.

METAMOEPHOSES OF BATRACHIA AXD LAMPREYS.

In treating of insects^ we entered^ as was necessary^
into some detail. Their metamorphoses form^ as it
were^ a key to the study of these phenomena gene-
rally. Besides^ the terms cat erpillar_,clirysalis_, butterfly^
worm_, beetle,, and grasshopper^ recall to our readers^
minds certain familiar objects. Whilst following us
through this land of wonders^ readers have been meet-
ing old acquaintances; and thanks to these^ it is
hoped that they have grasped the anatomical facts and
physiological generalizations^ which are more foreign
to their usual occupations than the other portion of
our remarks. We must now retrace our steps^ and
from the same point of view explore the whole animal
kingdom. Consequently we must enter regions much
less known to the general reader. In order that we
may be easily understood^ we shall be brief, and shall
henceforth confine ourselves to pointing out those
important facts from which general conclusions may
be drawn.

In the very outset we come upon a group with
which every one is acquainted^ and which deserves
special attention^ from the fact that for a long while
it had been considered as the only vertebrate class
exhibiting metamorphoses. We allude to Batrachia^
including frogs^ land and water newts^ and the

88

METxUrOEPHOSES OF :MAX

kindred genera. In this group we meet witli botli
complete and incomplete metamorplioses ; but here
we find them marked by quite different features from
those we saw among insects. The changes do not
tippear to take place suddenly, nor is there anything
like the apparently torpid condition of the pupa. All
the transformations take place gradually, and as far
as the external organs are concerned, the development
may be closely watched by the observer.

The development of frogs presents another curious
phenomenon quite different from what we have already
seen. It is this : the young animal, after it has left
the egg, and before it has become a larva, is still
in a semi- embryonic condition. At this ]3eriod the
digestive tube and its appendages are exceedingly
rudimentary. The greater portion of the body is
filled by a large mass of yolk or vitellus, inclosed by
the skin, which has been formed for some time ; and
it is at the expense of this alimentary matter that the
development proceeds.

The external characters are in keeping with the
imperfect condition of the animal at this period. The
head is large, and appears to be divided in two on
the under surface, each half being prolonged as a
sort of process by which the animal attaches itself
to surrounding objects; as yet there are no traces
of either eyes, nostrils, respiratory or auditory organs ;
and the belly, of an oblong form, is continued pos-
teriorly as a short tail bordered with a riband-like
membrane. This primitive condition, however, does
not last long. About the fourth day after birth, the
head, which is now as long as the body, has somewhat
the appearance of a thimble; the mouth is provided

1

AXD THE LOWER AXIjIALS.

89

with, a pair of soft lips j the nostrils^ eyes^ and auditoiy
apparatus haA^e made their appearance; the head is
separated by a deep groove from the belly^ which has
assumed a spherical form^ and from Avhich spring a
pair of opercula^ clothed with little branching gills ;
and the tail has grown so much that it is now quite as
large as the body. The mouth, is very soon armed with
a horny beak^ capable of dividing the vegetable food ;
the intestine^ which is now very long^ becomes more
fully formed^ and assumes a spiral arrangement ; the
tail is elongated and widenedj and the little creature
is then called a tadpole.

At this period^ one of those alterations occurs which
are so intimately associated with the ideas we are
endeavouring to convey^ that we must not pass them
by in silence. Our larva first breathed by its skin
alone^ and afterwards by a pair of little branching
gills attached to the opercula. About the seventh
or eighth day^ however^ the opercula are gradually
soldered to the abdomen^ and the gills fade away and
disappear. At the same time a set of neAv and more
complex branchia are developed^ in chambers situate
on either side of the neck. The new chills are arrano-ed
in tufts attached to a solid framework of four carti-
laginous arches^ and are about a hundred and tAvelve
in number for each side of the body. Here we see
a rapid substitution of one organ for another^ though
both discharge their functions in the same nianner_,
inasmuch as the respiration is just as aquatic in
character after the alteration as it vv'as before it.

But the modifications of the respiratory apparatus
do not cease here. Before the tadpole can become a
frog, it must do away with these second gills and

90

METAMORPHOSES OF MAN

replace tlieni by lungs; and at tlie necessaiy time,
a set of clianges takes place analogous to tliose Ave
liave already described. The vascular tufts are
atrophied, and the lungs, wliicli till now were solid
and rudimentary^, open up and increase in size. The
circulatory organs are correspondingly modified. The
calibre of the large branchial vessels is diminished,
and the pulmonary trunks increase in number and
diameter. Later on, the solid parts of the branchial
apparatus disappear also, the bones and cartilages
being gradually reabsorbed. Eventually the alteration
is fully accomplished, and there remains not the
slightest trace of the former branchial apparatus. In
this instance, not only has there been transformation
and substitution, but an actual metamorphosis has
occurred ; for the respiration, which was aquatic before,
has become atmospheric, and, strictly speaking, the
animal from having been a fish has been converted
into a batrachian.

If we examine any particular apparatus, we shall find
it also presenting many curious phenomena in the
course of its development. We shall find that as the
herbivorous habits give place to carnivorous ones, the
digestive apparatus undergoes a change adapting it
to the new form of diet. The mouth increases in size
and gape ; the little beak-organs, or more correctly,
the horny lips, are replaced by teeth, which are
attached to the palatine arch, and not to the jaw;
the intestine, which before was long and almost
cylindrical, becomes shorter, and is inflated in certain
portions of its length; and the abdomen, which had
been almost spherical, becomes thin and slender.
The metamorphosis may now be seen in its entire

AND THE LOWER ANIMALS.

91

extent^ and more distinctly as regards tlie loco-
motive system tlian any other. We wish we could
give the reader the details of this subject just as
they have been given by A. Duges^ but the cha-
racter of this work forbids our going beyond gene-
ralizations.*

The tadpole at first exhibits no trace of either
internal or external limbs. It swims about like a
fish by the action of its tail_,t which is an extensive
organ_, longer and wider than the body^ supported by
a prolongation of the vertebral column^ moved by
powerful muscles_, and supplied with large blood-
vessels and numerous nervous branches. Beneath
the skin and muscles of the anterior and posterior
regions of the body two little projections appear at a
certain period. These are the limbs^ and are at first
attached to the adjacent structures by the nerves and
blood-vessels which are supplied to them. These pro-
jections increase in size, their appendages appear in
due course, and eventually the hip and shoulder bones
are developed. As soon as these locomotive organs
enter upon the discharge of their functions, the tail
begins to disappear. Its skin, muscles, nerves, bones,
and blood-vessels atrophy, and vanish from our sight.

* " Keclierclies sur I'Osteologie et la Myologie des Batrachieiis a
leurs differentes ages," 1834. This work, which is from the pen of one
who was prematurely removed from among us, obtained the phy-
siological prize awarded by the Academie des Sciences.

t Fishes' fins seem rather to guide them when swimming than
to aid directly in producing motion. At most they are employed
in the latter capacity when the movements are very slow, and are
also of use in stopping progression. It is the tail alone which urges
forward the fish with rapidity. We may easily be convinced of the
truth of this statement by watching the movements of gold-fish in
an aquarium.

92

METAMORPHOSES OF MAX

Tliey liave not faded away^ tliey liavo not simply
fallen off, they liave not been cast off by a species of
moulting, as in tlie case of insect larviB. They have
been got rid by none of these methods ; their sub-
stance has been re-absorbed, atom by atom ; and
hence, although it has ceased to exist, it is not the less
alive on that account.

We see then that frogs undergo complete meta-
morphoses, not only in regard to their entire organism,
but as to each set of aj^i^aratus, with the exception
of the nervous system. The salamanders are not
similarly situated. These maintain their external
gills throughout the entire larval period, and never
acquire internal branchige. When reaching the air-
breathing condition, they skip, as it were, one of
the transformations which frogs undergo. The sala-
manders have also four legs in the perfect state;
but then, in addition to these, they preserve the tail.

The metamorphoses become simpler and simpler as
we approach the lower grades of this peculiar class.
The Proteus, which is found only in the subterranean
lakes of Carniola, and the Axolotl, which inhabits the
lakes in the interior of ]\Iexico, retain the gills all
through life, and as they possess lungs also, they can
breathe by air or water indifferently, — they are really
amphibious animals. Finally the Lepidosiren, that
type of transitional beings, presents even in the adnlt
state, and in regard to its circulatory and other
apparatus, such a combination of the essential cha-
racters of reptiles and fishes, that the most skilled of
living anatomists are divided as to its true position,
and are unable to say to which of the two classes this
really paradoxical creature belongs.

AND THE LOV/ER ANIMALS.

93

Until the year 1856 it was thouglit by all naturalists
tliat batracliia vfere tlie only vertebrate beings wbicli
underwent metamorplioses. It was M. Auguste
Miiller wIlo first proved tliat phenomena exceedingly
like tliose we liave described may also take place in
fiskes. This naturalist kas proved beyond all doubt
tkat tke Ammocetidas are notking less tkan tke larv^
of tke lampreys. However^ in reacking tkeir perfect
statO;, tkey kave a muck skorter distance to travel tkan
tke tadpoles. In tkeir case^ botk larva and adult
breatke by branckial organs; tke ammocetis is in
reality as muck a fisk as tke lamprey. Tke only
apparatus wkick undergo a decided modification are^
tke moutk^ wkick is converted into a sucking- and
ckewing organ^ tke anterior portions of tke digestive
tube^ wkick are connected witk tke orifice of tke
moutk^ and tke series of bones and muscles associated
witk tke respiratory function.* If tkese ckanges
took place in tke egg, instead of in tke animal leading
an independent existence^ we skould simply term
tkem transformations ; but as tkey are accomplisked
after tke animal kas left tke egg, tkey belong to tkat
series of pkenomena collectively styled metamor-
pkoses.

" Ueber die Entwickeking der Neunaugen." — Miiller s Archives,
1856. The ammocetis had been considered almost the lowest form
of fish, until this great discovery of M. Augiiste Miiller. The
amphioxns, which is a still more aberrant fish, and which approaches
in some respects certain annelides (Dorsibranchiata), was, and is
still, regarded as the lowest member of the class Pisces. But we
are now justified in asking whether such an exceptional creature as
the amphioxns is a perfect animal. There are many features in its
organization which remind one of the common river ammocetes.
May it not be the larva of Petromyzon marinus, or of some other
species ?

94

METAMOKPHOSES OF MAX

CHAPTER X.

METAMOEPHOSES OF MYRIAPODS^ CRUSTACEA_, xVXD
ANNELIDS.

We sliall now return to tlie invertebrata. Tlie sub-
kingdom Annulosa contains^ besides the insects^ tlie
Myriapoda or Centipedes (Scolopendra Iiilus, &c.),
Araclinida (spiders and scorpions) and Crustacea
(crabs_, crayfisli^ wood-lice^ &c.). Of these three
classes,, the second undergoes no metamorphosis; but
the first and third exhibit this phenomenon^ and
though not as generally as insects^ yet occasionally
with characters that we have not met with among the
latter.

The lulidee have been the most fully investigated of
all the Myriapoda which undergo metamorphoses ; and
among those who have devoted attention to them we
may mention De Geer, Savi^ Waga^ and Gervais.
When in the adult condition, these animals are com-
posed of a series of segments placed end to end like
the beads in a chaplet, of which nearly every segment
is provided with two pairs of limbs. These hmbs
vary in number from 140 to 200, according to the
species. When the lulus first leaves the egg, its body
is quite smooth and devoid of leg's. After a short
time it becomes divided into a number of separate
segments, and three pairs of legs are, as it were,
pushed out. As the animal grows older and goes

AND THE LOWER ANIMALS.

95

tlirough its successive moultiiigs_, tlie number of seg-
ments and legs increases^ without tlie other characters
being at all altered. When first hatched^ our little
iulus is blind_, but the eyes make their appearance
shortly after the locomotive organs^ and increase in
number with the growth of the animal. We see that
in this instance there is no real metamorphosis^ the
organism being completed_, first by the addition of new
structures, and then by the repetition of existing ones.

The Crustacea furnish us with similar phenomena.
In the little fresh- water prawn and in Garidina Des-
marestu M. Joly observed that certain thoracic and
abdominal feet, and even the branchiae of the stoma-
chal pieces, do not exhibit themselves till after the
animal leaves the egg.* Moreover, of the organs which
already exist, some are modified, whilst others, such as
the appendages of certain feet, are atrophied. We
see that even here there is an approach to metamor-
phosis in the ordinary acceptation of the term; but
on leaving this great section Macrura,-f and passing
on to the Bmchy ura, J we shall find the phenomenon
even better marked.

Is there any one of our readers who has spent a

"Etudes surles Moeurs,le Developpement et les Metamorphoses
d'une petite Salicoque, d'eau douce." — Aniiales des Sciences uatu-
relles, 1843.

t Literally, long-tailed. To this division of Crustacea belong the
lobsters, crayfish, shrimps, &c. ; in fact, all Crustacea whose abdomen,
commonly called the tail, is large, well-developed, and is employed
in swimming.

X Literally, short-tailed. This group includes all crabs and
Crustacea whose abdomens are slightly developed, curved forwards,
and applied against the thorax, which is usually regarded as the
body of these animals.

96

METAMORPHOSES OF MAN

few hours on tlie sea-shore durini2: low-water ? If so
lie must have observed the little Fortumis moenas,
le crabe enrage/^ as our sailors call it_, which of all
its tribe leaves its native element the most willingly,
and being little sought after, on account of the insipid
character of its flesh, brino-s forth its vouno- in the
very neighbourhood of the fishermen^s cottages. In
its earlier days, and before it assumed this amphibious
sort of life, it swam about in the open sea under the
form of a Zoe.* Its head was then indistinct from
the thorax, both being covered by a sort of globular
carapace, from which long processes projected ante-
riorly, posteriorly, and laterally; its long abdomen
terminated in a wide deeply bifurcated extremity; its
mouth was of the simplest form ; its limbs, which in
the adult are complex, and are partly employed in
mastication, were represented by four long double
oar-like filaments, and its true feet were entirel}^
rudimentary. In fact there was not a single feature
to remind one of the flattened greenish crab, which
is so regardless of the observer that it hardly troubles
itself to run away from him, and which seems in its
jerking sidelong gait to imitate the little impish boys
of the streets of Paris.

* The rarvjie of certain Crustacea had been named and classified as
distmct species, until Thompson, and afterwards Captain Ducasse,
described the strange metamorphoses which these animals undergo.
— (" Zoological Researches and Illustrations," 1831 ; "On the double
Metamorphosis in the decapodous Crustacea," 1835. — Philosophical
Transactions.) In the Zoii group were ranged the larvae of Bracliyura
and of some others, which the discoveries of the English naturalists
have done away with. Facts of this sort are abundant enough now-
adays ; and it has been recently sho^vii by Messrs. Coste and Gerbe,
that the Phyllosomida^ are only the larva} of the lobster.

AXD THE LOWER AXIMALS,

97

Among tlie otlier crustacean orders^ and especially
among Entomostraca, ^\Q find an immense number of
species wliicli undergo more or less complete meta-
morphoses. Tliere is still mucli work to be done in
tlie great field opened by Ducasse and Thompson ;
but even now we may confidently assert tliat tlie
species of Crustacea wliicli assume tbe perfect form
on emerging' from tlie egg are probably in the
minority. It would be idle and indeed impossible to
enter into further details without the assistance of
numerous engravings. Besides^ we should really be
travelling on ground we have already gone over; we
should only find what we have already observed ; viz.
the creation of new structures^ and the destruction^
modification^ and increase of others. AYe find almost
invariably^ that the final result of metamorphosis is
the progressive completion and elevation of the
organism.

We see quite an opposite state of things in two
very curious secondary groups of this class Crustacea.
Here^ to jndge from appearances^ metamorphosis
degrades the creature instead of elevating it^ and
modifies the organism in such an unusual manner
that one is puzzled to know whether the animal is not
an abnormal one. Ciivier died in the belief that the
Baleenidge and Anatifera were moUusks^ and that the
Lerneas were intestinal worms.

It was Messrs. Thompson and Xordmann who first
corrected this double error. The former discovered
the true nature of the Cirrhipedia^'*' the latter that of

* " Zoological Researches and Illustrations ; or, Natmal History
of Xondescript or imperfectly-known Animals," 1831.

H

98

METAMORPHOSES OF MAN

the Siplionostomidsc.* In both cases the truth was
arrived at by examining the animals as they emerged
from the eg-g^ by contrasting them with larva3 known
to belong with certainty to other Crustacea^ and by
watching closely their various transformations. A^Tien
the results of these researches were first published,
they were received with some scepticism, but ha\'ing
been confirmed by numerous observers, they are now
unquestionable, and no one can deny these naturalists
the honour of having been the first to reveal that
cm-ious mode of evolution, which we have termed
Temirvent development.^

Uniting the observations of Darwin and his rivals,
we shall endeavour to describe the metamorphoses of
one of these Bal^enidae, whose pointed, jagged shells
cover the rocks most exposed to the waves with a sort
of crust.

From the egg laid by the mother there springs an
almost microscopic larva, whose narrow body is divided

* " Micrographische Beitrage zur Naturgeschichte der wirbelloseii
Thiere," 1832.

t Among those who have added to the history of the devek^p-
meiit of Cirrhipedia, I may mention the names of Bate, Burmeister,
and Goodsir, and especially that of Mr. Darwin, who has written
a most valuable work upon the entire group, — " A Monograph of
the Sub-class Cirrhipedia," — Publications of the Eay Society, 1854.
Three French naturalists also devoted themselves to this subject —
M. Souleyet who died when engaged in his researches ; M. Bou-
chard-Chantereaux, kno-\\Tii by his works on molkisks ; and Hesse,
Commissaire de la marine. Of works on the Siphonostomida^, I
may refer to tlie vahiable memoir of M. Van Beneden, in which he
brings together the researches of his predecessors and the results
of his own numerous and persevering investigations (" Annales des
Sciences naturelles," 1831), and the several connnunications which
he has since made to the " M6noires " and " Bulletins " of the
Academy of Brussels.

AND THE LOWER ANIMALS.

99

into a few long segments^ and carries anteriorly two
free antennas,, and laterally two other appendages
of a similar nature inclosed in horny cases. Three
pairs of feet clothed with long stout hairs answer the
purpose of oars. A carapace, composed of a single
piece, covers the back, and laps over the body ante-
riorly and laterally, disclosing a single solitary eye in
front. The little balaenus being thus provided with
sense-organs and locomotive apparatus, swims rapidly
through the water, reminding us forcibly of the larva
of a Cyclops.*

A change is now undergone, and the creature re-
sembles a cypris or an adult limnadia.f Its body is
entirely concealed by a pair of valves like those of
acephalous mollusks j J the number of feet increases ;
and by the aid of two anterior appendages, which
spring from the shell, it is enabled to attach itself
to seaweeds and other submarine bodies. It is by
grasping the rock with these peculiar organs that the
little crustacean fixes itself in some position where the
waves beat most violently; it then loses its bivalve
shell, and replaces it by several distinct pieces, which,
like so many plates, cover the back and sides of the
animal. This, however, is essentially a transitory
condition. A sort of calcareous wall is very soon
raised aroimd this species of nymph, and assumes the
form of an irregular hollow pyramid, with a wide and

* The Cyclops is a small crustacean of an inferior order, which is
common enough in certain fresh- water ponds, &c., and which also
undergoes metamorphoses that have been known for a long while.

t The Cypris and Limnadia are small fresh-water Crustacea also.

% The oysters, scallops, mussels, &c. ; in fact all mollusks whose
shell is composed of two valves nnited by a hinge, belong to this
group, of which we shall say more hereafter.

H 2

100

METAMORPHOSES OF MAN

jagged orifice. It is in tliis prison tliat tlie young
balosnus, hitherto free and unrestrained, is confined
for the rest of its days. It is folded in two; and its
feet_, henceforth useless as fins, are transformed into
recurved and beautifully ciliated cirrhi. It is these
latter which, when moved by powerful muscles, hence-
forth provide our little monk with food. They form
a sort of double plume above the head, projecting
beyond the opening of the valves, and when rapidly
moved backwards and forwards, they draw to its
mouth the food which the balgenus cannot now go in
pursuit of.

The modifications which metamorphosis brings
about, extend beyond mere form and structure.
Very important functional changes are also effected
by it. It is only when the balasnus is thus impri-
soned and deformed, when it is blind and can no
longer move from place to place, that its reproductive
organs are developed. Here is an instance of an
animal which when in its nymph and larval state is,
as regards the possession of the essential characters
of an animal^ a higher being than when it assumes
the adult form ; but in neither of the former condi-
tions can it be a parent. The progress of develop-
ment has degraded it in the animal scale ; but whilst
this progress has made all the functions but one sub-
ordinate to that of nutrition, it has been the means
of producing the apparatus which insures the con-
tinuance of the species.

The result of recurrent development seems in many
cases to be the sacrifice of all other functions to that
of reproduction. This final object is even still more
apparent in the lower crustacea, and especially among

AND THE LOWEE ANIMALS.

101

tlie Lernege^, ov fiali-lice, as they are termed^ than in the
Cirrhipedia. Among the Lerne^e the degradation of
the being extends much further than we should
imagine possible.

The young lernea is a genuine crustacean when it
emerges from the egg. At first it is like a cyclops
larva ; it has eyes^ and swims freely about by the aid
of two feet^ each of which ends in a large bunch of
filaments. During the second period of its existence^
it has three pairs of feet in front_, and as these are
provided with hooked claws, they are equally well
adapted to assist in locomotion or to grasp the smooth
skin and gills of fishes. At this period^, moreover, it
acquires four posterior swimming feet, and a tail or
abdomen like that of other Crustacea. Up to this,
metamorphosis was elevating the being more and
more ; it now begins to destroy what it has con-
structed.

In assuming the adult condition, the female grows
to an immense size ; two of her anterior appendages
become more developed, curved in a semicircular
manner, and united by their extremities, which ter-
minate in a sort of projection, are plunged into the
tissues of the animal upon which she is parasitic, and
then fastened there permanently ; two others, reduced
to mere booklets, attach in a similar manner the
mouth, which is converted into a sucking organ ; the
remaining appendages disappear, and the body, in-
flated and deformed, is now but an irregularly-shaped
pouch, containing a stomach and a quantity of ova.
At the same time the male, disfigured to a lesser
extent, but still two or three hundred times smaller
than the female, attaches himself to the body of his

102

METAMORPHOSES OF MAN

spouse^ and seems to live upon her juices just as slie
does upon those of the fish. In both, the locomotive
and sense organs have disappeared ; and as the two
lead a purely vegetative existence_, they may fairly
be regarded as mere reproductive machines.

We shall now leave the Articulata and pass on to the
Annuloida or worms, which with the former consti-
tute the sub-kingdom Annulosa. The first are purely
oviparous animals ; the second present in a well-
marked manner the phenomena of geneagenesis, which
we shall examine in another chapter. In reality, the
class Annelida is the only one which presents pheno-
mena of the kind we are now alluding to. In a work
to which perhaps I have already alluded too often,* I
described, at length, the metamorphoses of Terebella
according to the investigations of M. Edwards, and
those of Hermella according to my own researches.
Here, I shall limit myself to stating that in these crea-
tures also the organism is considerably altered in pro-
portion as the mode of life differs from what it has
been heretofore. These animals, which are at first of
an erratic character, afterwards become sedentary,
and are inclosed in tubes which they never leave. In
one respect this is a step backwards ; for locomotion
is one of the most characteristic attributes of the
animal, which, when deprived of it, is injured to a certain
extent. But although, from this point of ^dew, Her-
mella and Terebella are degraded by the progress of
development, they are elevated in other respects, and
on the whole gain rather than lose by the alteration.
In this instance metamorphosis exhibits itself in an

* " Souvenirs (Xww Natiiraliste.'

AND THE LOWEE ANIMALS.

103

entirely new ligM., inasmucli as it tends at tlie same
time to elevate and degrade an animal in tlie zoological
series. Hereafter we sliall find several examples of
tliis double action j consequently^ we sliall see tlie
animal in its perfect condition^ placed sometimes above^
and at others below its larval state^ according as one
or other of these opposite tendencies has the upper
hand.

104

METAMORPHOSES OF MAN

CHAPTEE XI.

METAMOEPHOSES OP GASTROPODOUS AND ACEPHALOUS
MOLLUSKS.

The discovery of metamorplioscs among mollusks is
quite a modern one^ and there are doubtless very many
more discoveries to be made in this branch of science.
In the year 1832, the celebrated German anatomist
Carus described for the first time the larvae of Ana-
donta, a sort of fresh-water mussel, which is abundant
in all the canals and ponds throughout Europe.* But
as always occurs in such cases, the facts, being quite
unexpected, were at first denied. It was asserted
that the larva3 were only parasites, which existed in
great numbers in the gills of mollusks. They were
given a distinct name, and this erroneous interpre-
tation having had the authority of Carus^s opponents
Rathke and Jacobson, became generally accepted.

At this period, whilst modestly pursuing the practice
of medicine, and having, if anything, too much time
upon my hands, I devoted myself to natural histor}^
when waiting for patients. In ignorance of the labours
of my distinguished contemporaries, I pursued the
same subject. I watched the development of the
anadonta^s eggs daily, during at least five months,
from the time they were deposited, until aii accident

Carus's incmoir appearcMl in the " Nova Acta Natunu Curio-
soruni."

AXD THE LOWEE AXIXALS. 105

occurred wMcli destroyed the whole brood. I had
seen enough^ however ; and I beheve I may say^ that
from the publication of my researches and of M. de
Blainyille^s report,, the metamorphosis of mollusks be-
came an established fact.* Other inrestigations have
since been made. From an examination of all these
works^ vfe are justified in concluding that metamorpho-
sis occurs^ in the entire group as well as in the classes
it comprises^ and that it is in some instances complete,
in others incomplete, and occasionally entirely absent.

Of all classes of mollusks, the most fully investigated
from a development point of view is that of gastro-
pods, including such animals as the snail and slug*. Both
these are air-breathing mollusks, and simply o^'iparous ;
and those which inhabit fresh water bring forth their
young in a somewhat similar manner. f Marine species,
on the other hand, undergo true metamorphoses. Let
us see, for example, what takes place in one of those
l^ldehenterate mollusks which have subjected me to so
many severe controversial attacks. J These animals

This report was read before the French Academy in 1835, and
had been j^repared by a commission, consisting of Messrs. Geoffroy
Saint-Hilaire, F. Cuvier, and De BLainville. Perhaps the reader
may imagine that I allude too frequently to my o^w\ researches, but
I trust he will appreciate and excuse the feeling by which I am
actuated in thus referring to my earliest contribution to science.

t Neritina fluviatilis is an exception ; the larvse of this mollusk
are exceedingly like those described and figured in M. Ed. Cla-
parede's beautiful work " Anatomie und Entwickelungsgescliichte
der fluviatilis Neritina." — Miiller's Archives, 1857.

J When first I published my researches on phlebenterate mol-
lusks, and asserted that these animals have no distinct vruis, I was
opposed by nearly every naturalist who had paid attention to the
subject. I think I may safely say that at present it is just the
reverse.

106 METAMORPHOSES OP MAN

have no shelly even in the adult condition ; tlieir liead
is provided witli four long stout liorns or tentacles, at
whose base a sing-le pair of eyes may be seen ; and
tlieir back is covered with, little projections^, wliicli for
a long while had been considered simple branchise-
They crawl along the bottom of the sea, by means of
a thick fleshy disk, which is called a foot. These
pretty little creatures are most brilliantly coloured,
and look as if they were composed of enamel and
crystal. So much for their external characters. In
the interior we find, besides other organs, a stomach,
which terminates in an exceedingly short intestine,
and gives off from its opposite side a series of more or
less numerous canals, which ramify, and send pro-
longations almost to the extremities of the dorsal
appendages. The liver, which is usually so extensive
in mollusks, is here represented by delicate glandular
layers which surround the terminal coeca of the gastro-
vascular apparatus. Let us see what these exceptional
mollusks are like in their earliest stages. On emerging
from the egg, each larva is provided with a shell, and
its foot, rudimentary as yet, has a sort of horny plate
attached to it, which it raises or lowers like a draw-
bridge when it wishes to close or open its shell.
Being unable to creep along, it is furnished with a
locomotive organ, in the form of a large double collar
placed above the mouth. The edges of this structm^e
are clothed with long vibratile cilia, which make it a
very powerful swimming organ, that the animal folds
or unfolds at Avill, when retreating into its shell. The
animal, surrounded by the latter, and fixed to it by a
set of strong muscles, possesses a digestive apparatus
and liver like those of other mollusks. After a certain

AND THE LOWER ANi:^IALS.

107

length of time^ however^ tlie adhereiit muscles become
detaclied_, and tlie animal leaves tlie dwelling wMcli it
inhabited since its birth; its body is elongated; the
foot having cast off its operciilum_, which is now useless_,
begins to discharge its real function^ and on the other
hand^ the rotatory apparatus becomes atrophied; the
stomach is prolonged backwards as a cul-de-sac^ which
rapidly increases in size^ and sends off ramifications ; a
pair of appendages is seen upon the dorsal surface :
these are soon followed by others_, and eventually the
larva^ which at first resembled that of an ordinary
moUusk^ becomes a tvue j^^ilehenterate.

The embryogeny of gastropods has been the -subject
of several works ; and among those who have helped
to clear up that branch which we are considering^ we
find the names of some of our most distinguished con-
temporaries ; * but it is not the same with the Acephala
or bivalve mollusks. The only researches upon this
subject^ in addition to those already mentioned^ are^ so
far as I am aware, Loeven-'s great work_, some essays

* The first researches upon the development of gastropods are
those of M. Stiebel, a German naturalist, and are dated 1815.
Among those who have since devoted themselves to the subject, I
may mention the names of AUman, W. B. Carpenter, Cams,
Danielsen, Dumortier, Frey, Grant, Jacquemin, Koren, Klark,
Lacaze du Thiers, Laurent, Leydig, F. Miiller, Loeven, Nordmaim,
Pouchet, Prevost, Eathke, Eeid, Saars, Von Siebold, Yan Beneden,
Vogt, Windischmann, &c. The earlier writings of these naturalists
were devoted to the terrestrial and fresh-water species, and conse-
quently the metamorphoses of the marine classes remained for a
long while unknown. In 1827, the English naturalist Grant dis-
covered the rotatory apparatus and poiated out its fimction ;
but it was not until the year 1837 that M. Saars, a clergyman of
Berghem, made known the important fact that the larvae of naked
mollusks are provided with a distinct shell.

108

METAilOEPHOSES OF MAN

on the development of oysters,* my own memoir on
the embryogeny of teredo, and tlie beautiful researclies
of M. Lacaze du Thiers upon that of dcntalium.f It
is in the latter that the most complex metamorphoses
are observed; these phenomena are of a far simpler
nature in the oyster, are still more so in the
anodon, and are entirely absent in other small
bivalve mollusks, which inhabit fresh-water ponds
and lakes. The larvaB of all the marine members
of this group present at first the ciliated form, and
are naked ; but shortly afterwards they are fui^nished
with a shell, and with a rotatory apparatus, like that
of gastropods. This organ may be drawn within or
extended beyond the shell, at the desire of the animal,
which is in addition provided with a foot, which is
occasionally very long, and movable. By the assist-
ance of the latter, the creature can either crawl along
the sea-bottom or swim through the water, although
at a later date it may be soldered to a rock, like the
oyster, or fixed immovably to the chamber it has
constructed, like the teredo.

* Written by M. Davaine, and called " Eeelierclies sur la Eepro-
duction des Huitres." These memoirs obtained the Academy's
prize for experimental physiology in 1855, and some of their results
have since been corrected by M. Lacaze du Thiers.

t M. Lacaze du Thiers published a monograph on this peculiar
animal, and it is unquestionably the most complete work which has
ever been written upon a single mollusk (" Histoire de TOrganisa-
tion, du Developpement, des Moeurs et des Eapports zoologiques du
Dentale "). I am sorry that I cannot give some of the details of
this creature's liistory ; but on account of its very exceptional
character, it does not come within the limits of my present scheme.
I may, however, state that, at a certain period of its life the larva
of dentalium is so like that of an annelid that it may be mistaken for
one, and that its shell, although symmetrical at first, is always univalve.

AND THE LOWER ANIMALS.

109

The young anodon has none of these organs; but
to compensate for their absence, it possesses a very
pecuHar apparatus for closing its shell and preventing*
the entrance of parasitic infusoria. Each valve, which
is then of a triangular form, has attached to its upper
portion a long flexible structure, and this latter is
covered with strong teeth, which are arranged in
squares of five each — four forming the sides, and one
in the centre. By means of muscles for the purpose,
these two structures can be drawn inwards, somewhat
in the way in which a knife turns in its handle ; and
the teeth being thus firmly clenched, the shell is as
securely closed as if it were done by machinery.

The larvae of oysters, teredos, and anodons are
retained, either in the gills or mouth of the parent,
from the time they leave the egg till the moment of
their metamorphosis ; they then lose their temporary
organs and assume the adult features, being sometimes
elevated a few degrees in the animal scale, at others
descending to a lower grade than they occupied as
larvee. The former takes place in the case of the
anodons, which acquire a foot, and can at all events
crawl along the mud ; the latter among oysters ; and,
still more so, among teredos. The latter, which were
the most highly organized of the three groups when
in the larval state, are by far the most degraded in
the adult condition.

Thus we see, that even among Acephala, the two
forms of metamorphoses are presented, and that in
some instances the development elevates the being, as
in the case of insects ; in others, it is as recurrent, as
in the Cirrhipedia and Lernete.

110

METAMORPHOSES OF MAN

CHAPTER XIL

NATUEE_, CAUSES^ AND PROCESSES OF METAMORPHOSES.

CONCLUSION.

The general conceptions as to tlie nature of metanior-
pliosis have always varied witli tlie ruling pliilosopliic
doctrines of tlie time. Some of tlie facts we have
already pointed out were at one period brought for-
ward to support the theory of spontaneous generation,
of which we shall see more hereafter. And when, by
a natural reaction, the hypothesis of evolution was
announced, and, owing to the superiority of those who
supported it, was almost universally accepted, these
same facts and many others were employed in its
defence.

For example, according to Reaumur, there is no
such thing as real production ; development is the only
phenomenon he recognized. Plants and animals which
to us appear to be newly formed, have always existed,
but only appear when circumstances admit of their
growing sufficiently large to be recognized by our
senses. What is true of the whole is true of its parts ;
consequently the metamorphoses of an insect are only
apparent. According to this doctrine, the butterfly,
which flies from flower to flower, has lived since
the creation of the world, and has possessed all its
organs, wings, proboscis, feet, scales, etc. The
chrysalis and cater2)illar inclose it, and are, as

AXD THE LOWEE AXIXALS.

Ill

Harvey stated^ genuine ova_, included one witMn tlie
other. Curious ova^ certainly^ possessing limbs^ a
moutli^ and digestive apparatus^ wMcli are destined
for the locomotion^ defence^ and nutrition of the real
animal : eggs^ which chew^ grind^ and digest food as
the mother does that which supplies the foetus. Thus
protected^ and nourished by the animal apparatus
which surrounds it_, the butterfly exhibits no outward
traces of infancy; when the proper time arrives_, it
throws oflP this organized garh, which is no longer
required_, and would_, in fact^ inconvenience it^ and^
devoid of all disguise^ it now exhibits itself in its real
character^ being only altered as to its size^ which is
greater than before.* These are some of the inex-
tricable difficulties into which the supjoorters of the
evolution theory were led_, despite their high character
for intelligence.

Notwithstanding the eiTors which these precon-
ceived ideas gave rise to_, Eeaumur perceived and
appreciated a very important fact. He looked upon
the butterfly in the caterpillar state as an infant. He
should have said an embryo. The infant in being*
converted into an adult is only increased in size and
developed; but the caterpillar has quite a different
part to play in assuming the butterfly form. In the
metamorphoses it undergoes in approaching its perfect
state_, we are reminded of the embryogenic pheno-
mena we spoke of in an earlier chapter. We see
them during the entire larval stage^ for the caterpillar
possesses many of these temporary organs_, whose

"Memoires pour semr a I'Histoire des Insecte^." These
views are very distinctly stated in the eighth memoir of vol. i. ; I
have almost transcribed the author's own remarks.

112

METAMORPHOSES OF MAN

existence shows us tliat the animal is on the road to a
final perfect condition; we. see them with increased
vital activity before the first transformation, and for
some time after it. It is indeed a critical period, not
only for insects in general, but for butterflies in par-
ticular, in which the animal is, so to speak, re-cast
and constructed upon a very different plan from that
which was adopted before. It would be idle to dwell
upon this fact ; let the reader turn, instead, to the
earlier pages of this work ; or, better still, to HerokVs
and Ne^^^ort^s beautiful illustrations. In glancing
even at the changes undergone by the nervous system,
and in watching the re-alteration and development of
the gangha from hour to hour, we are reminded of that
period in the transformations of the mammalian em-
bryo when the most intense and energetic action was
taking ]3lace.

The insect whilst in the larval condition has only
to increase in size, like the infant to which Ecaumur
compared it. But even from this point of view it
exhibits a decidedly embryogenic character, viz., the
rapidity of this growth. In fact, it is the common rule
among all viviparous animals that the increase in weight
and volume, which at first takes jolace with rapidity,
becomes less marked as the organism approaches its
perfect form. The human embryo, which is quite
distinct about the third week after impregnation,
measures at this time 6*75 millimetres in length, and
weighs about 12 centigrammes. About the eighth
week, or, in other words, thirty-five days after the
above-mentioned period, it is 20 millimetres long,
and wcio'hs 216 centio-rammes. About the fourth
month, when it may abnost be called a fcx?tus, it

AND THE LOWER ANIMALS.

113

measures 20 centimetres in lengtli_, and lias attained
a weight of 224 grammes. In the course of four
months^ tlien^ it has become thirty times as long and
eighteen hundred times as heavy as it was when we
first examined it. From this time forward it groAvs
about an inch^ or nearly three centimetres^ every
fifteen days ; till^ at the time of its birth^ it has
attained a length of nearly half a metre^ and a weight
of about three and a half kilogrammes.* Thus we
see that in less than nine months the human embryo
has become^ in round numbers^ seventy times longer
and twenty-nine times heavier than it was when three
weeks old.

Amonof insects we find an analoo'ous state of thino-s.
According to Redi^ the larva of a meat-fly [Miisra
carnaria) becomes^ in the short space of twenty-four
hours^ from a hundred and forty to two hundred times
heavier than it was before. f Lyonnet has shown_, by
direct observation^ and by calculation^ that the cater-
pillar we spoke of before {Cossns Ugiiiperda) is
seventy-tivo thousand times heavier in the chrysalis
condition than when it emerged from the egg.

Insects do not generally increase in size as they
reach the perfect condition^ but^ on the contrary^ are
very much smaller than when in the larval state. This
decrease in size is particularly well marked in the
Stratiotnydce, whose history we have given in another
chapter ; but these insects may be regarded as excep-

* In giving these dimensions of the embryo at different periods
of its existence, I have quoted the figures of Olivier and Ghaussier,
whose results were arrived at by an examination of fifteen thousand
specimens. — Dictionnaire de Medecine.

t " Introduction a I'Entomologie," by Tli, Lacordaire.

I

114 IIETMIORPHOSES OF MAN

tions to tlie general rule. Animals wMcli undergo meta-
morplioses^ almost always grow after birtli_, just as in
the case of man. Many of them are like certain ovi-
para^ and grow during tlie wliole of their lives. Hence
it is not surprising that the differences of weight and
volume between young and old individuals should be
greater than it is among vivipara. At the age of
twenty^ man is rarely four times as long as the new-
born infant ; and his average weight is hardly thirty
times greater. The Teredo larva_, which is about to
undergo a change of form_, is four thousand times
larger than when it sprung from the egg, and is still
many million times smaller than its mother.*

There is another fact of a more decisive nature
which shows the embryonic character of the larva.
We saw in an earlier chapter that every monstrosity
is congenital^ and is referable to a period when the
embryonic development is going on. We have fre-
quently seen monster insects. Instances of herma-
phrodite insects are common enough in entomological,
collections^ for amateurs carefully preserve these in-
teresting specimens instead of delivering them to the
anatomist's scalpel. Sometimes^ however^ we meet
with persons actuated by a more truly scientific spirit :
it was in this way that Rudolphi was enabled to dis-

* Indefinite growth during tlie entire life of the individual is
met mth only among the lower species of the superior animals.
Thus, among vertebrates this peculiarity is presented only by cer-
tain fishes and reptiles. In these even, the growth slackens con-
siderably as life is prolonged : we may observe this occasionally
in the carp. I once saw one of these fish which was said to have
been transmitted in a fisherman's fiimily, from father to son, for
more than a hundred years. It was hardly longer than an ordinary
carp, but was nuicli thicker.

AND THE LOWEE AJyIMALS.

115

sect a specimen whicL. had tlie external marks of both
sexes^ and to proye that its internal characters were
equally monstrous ; thus showing* that a moth ex-
hibited one of those anomahes rarest among verte-
brate d animals.

Among insects as among* vertebrates we meet with
monstrous limbs. Several observers have described
the double and triple legs of beetles^, just as Meckel
saw similar organs in the di'ake_, and M. G-eofii^oy in
the sheep.

It is questionable whether the foregoing monstro-
sities are really referable to that period of the animars
life immediately after its emergence from the egg. In
fact^ there is nothing to oppose the view that they
have occurred whilst development was going on iritliin
the ovum ; but we cannot say the same of the following
ones. The larva does not possess antenn^e^ and yet
we have seen beetles with more than the usual num-
ber of these organs. Stannius described a neuter bee_,
which_, like certain forms of the human foetus^ fiilly
realized the fable of the Cyclops : its two compound
eyes were fused together_, constituting a single ocular
mass^ which was situated almost on the top of the
creature^ s head. In these two cases we can point to
the period when the labour of natm^al development
was interrupted. It was about the period of the last
month^ when the larva was preparing to assume the
n^Tuph form_, that the disturbing cause affected the
course of normal organization.

It is to this period also in the history of develop-
ment that we must refer a series of monsters whose
very forms are the best solution of the problem we
are trying to solve. We allude to those insects which

I 2

116

METAMOEPHOSES OF MAN

present certain larval cliaracters in tlieir perfect
state — sucli^ for example,, as the mulberry bombj^s
{Bomhijx mori), mentioned by Majoli^ whose thorax and
abdomen were those of the silkworm; and especially
the insect described by J. F. Miiller, w^hose entire
body was that of a butterfly^ wdth the addition of a
caterpillar^s head. In this instance the arrest of
development occurred evidently as the animal was
passing from the larval to the higher condition.*

We see^ therefore^ that the larva^ nymph, and per-
fect insect are but one animal, in the same way as the
embryo, foetus, and young mammal are but so many
stashes of the one individual. Reaumur imao^ined that
the larva and the insect w'ere two distinct beings,
and that the first inclosed and supported the second,
somewhat in the same manner as the mother carries
and supports the foetus in iitero. This distinguished
observer brought forward the results of both Swam-
merdam-'s and his own researches in support of this
theor}^ If,^^ said he, you open a caterpillar's
skin two or three days before it is converted into a
chrysalis, you will perceive the wings, antennte, and
proboscis of the butterfly ; and if you cut off one of
this caterpillar's scaly feet, the butterfly will be lame.'''

These facts are, as we said before, quite correct;
but where Reaumur has seen evidence in support of
the evolution theory, we have found proof of that
doctrine of epigenesis which w^ e have seen fully con-
firmed by the development of mammalia. Reaumur,

* The above exaiuplos of insect inonstrosities may be found in
citlier Isidore Geotfroy Saint-Hilaire's " L'Histoire des Anomalies
de rOrganisation," or M. Lacordaire's " L'Introduction a rEntonio-
logie."

AND THE LOWER ANIMALS.

117

when obliged to confess that he could not see the
characteristic organs of the butterfly in less-advanced
caterpillars^, attributed their apparent absence to the
feebleness of his powers of vision_, and the imperfect
state of his instruments. Thanks to the means of
investigation we possess nowadays^ we can assert
most positively that the young caterpillar has neither
wings^ nor antennas^ nor even a proboscis. But at all
events we have been shown by our predecessors^ ob-
servations that none of these organs appear suddenly^
that the most abrupt changes have been in progress
for a long while, and that in insects, as in all other
animals which undergo metamorphoses, their pheno-
mena are gradual and progressive. There is this
distinction, however : that which in Mollusks, Worms,
Crustacea, and Batrachia takes place openly, is con-
cealed in insects by a veil, which is only removed
when everything has been completed. Moreover, in
this latter class, the Hemiptera and Orthoptera manifest
the same continuity in their metamorphoses which we
observed in other instances.

The phenomena associated with the inmost nature
of living beings are too far beyond the grasp of
human knowledge to admit of our framing even an
hypothesis as to the primary cause of metamorphoses ;
but, without outstepping the limits of a fair reserve,
we can at least in certain cases conjecture what is
the inmnediate cause.

In the earlier pages of this work we contrasted the
voluminous vitellus of ovipara with the very small one
of vivipara ; and we saw how the former was sufficient
for the formation and afterwards for the growth of the
embryo, whilst the latter could only discharge one of

118

METAMOEPHOSES OF MAN

these functions. We stated, also, tliat as a conse-
quence of this provision, birds and lizards are completely
organized within the isolated egg, whilst, on the con-
trary, mammals are forced, in order to reach the same
condition of development, to remain within the
mother^ s uterus, where they are nourished through
the medium of truly temporary organs. Now, as (for
a reason which doubtless we shall never be acquainted
vdth) an egg with a small vitellus may be destined to
be expelled, there is, nevertheless, a necessity for a
mode of existence during the state intermediate be-
tween the embryonic and fully-formed animal ; and
this necessity must be provided for.

This is one of those problems which Nature sets for
herself, as it were, for the mere pleasure of solving
them — the solution in this instance being found in
the phenomenon of metamorphoses. We invariably
find, even among species which undergo recurrent
metamorphoses, that the embryo which springs from
the egg presents a relatively more simple organiza-
tion than the adult ; hence its wants are fewer, and it
can satisfy them. Gradually it becomes fully formed,
its sphere of activity is enlarged, and finally it assumes
its adult characters when it has received the requisite
materials from the external world.

The larva, then, is but an embryo leading an inde-
pendent life, which feeds itself instead of being
nourished by the mother, and which undergoes,
externally, beneath our very eyes, changes — trans-
formations— which take place, among vivipara, in the
depth of the mother's uterus.* In assigning the

* I f2;ivc, word for word, the substance of an article which may
"be considered as the first edition of this chapter (1855). M. Cla-

AND THE LOWER ANIMALS.

119

insufficiency of tlie organizable materials of tlie
vitellus as an approximate canse of tlie phenomena
we have under consideration^ we can explain, or
rather co-ordinate, facts which, apart from this view,
we could not associate together. The greater this
insufficiency is, the more imperfect will the embryo
be which is formed at the expense of the vitellus,
the more removed will it be from its final characters,
and the greater must be the supply with which it is
furnished in approaching to and attaining them.
Observation bears out this conclusion. Insects^ ©g'gs
are enormous when compared with those of certain
mollusks. The egg of Cossus ligniperda is about
thirty thousand times larger than that of the Teredo.
Moreover, the little caterpillar which springs from
it is already a very complex animal, or, in other words,
a very advanced embryo. The Teredo, on the other
hand, is in the first instance as simple as possible.
Its body is, so to speak, but a homogeneous pulp,
in which a digestive tube is vaguely discernible. The
caterpillar will, doubtless, have to form some organs,
but more especially to develop and modify those
which it has got already : the Teredo will have to
acquire all its parts.

We have pointed out the nature, and at least one,
of the chief causes of metamorphosis, and of its
modifications.* Is it necessary to dwell upon the

parede has expressed the same idea, in summing up the views pro-
pounded by Leuckart. These are his words : — " What does meta-
morphosis consist in ? ... It is the passage of an animal deprived
of its egg-envelope through phases whose object is to bring it to
its own or its parent's type, and which among other creatures takes
place within the egg itself."

* In 1855 I said reservedly, " It is not my intention to lay down

120

METAMOEPHOSES OF MAN

processes ? Wlio does not see tliat these phenomena^
wMcli are so curious even in tlie commencement^ and
whicli in a general aspect are identical witli those of
vivipara^ and are performed by an entirely similar
apparatus^ are after all but transformations ? Firsts
epigenesis, and tlien simple or complex evolution.
These are the processes we see taking place in every
organ which is added to those of the larva^ in con-
verting it into an insect^ a crustacean_, or a perfect
reptile. Formation is evident ; and modification and
^progressive development occur beneath our eyes_, when
we see the external gills and the internal which
succeed them and precede the lung in the frog^ the
dorsal projections which appear in the phlebenterate
mollusk, the wings which are pushed out from the
thorax of the insect^ and the segments which are
added to those already existing in the myriapod.

an absokite law, nor to associate the greater or lesser complication
of the metamorphoses, 07ily with the greater or lesser volume of
vitellus. I merely wish to point out one cause which has not
been taken sufficiently into account, but which is doubtless only
one of a series. The period of incubation, for example, may also
be regarded as an important element in the inquiry, and as exerting
a decided influence. The egg of Hermella and of Teredo is in twelve
hours entirely transformed into an animal endowed with the power
of voluntary movement. This is, doubtless, another of the prin-
cipal causes of the extreme simplicity of the larva." I have siAce
become aware — through M. Claparecle's work — that Leuckart had
attributed metamorphoses to the insufficiency of the plastic ele-
ments of the yolk, even before I had done so. I am glad to meet
on this point with a naturalist who has given us so many splendid
memoirs since that period. But, so far as I can see, I cannot
admit with him that it is the sole cause of metamor23hoses. M.
Claparede has already maintained that this conclusion is too abso-
lute, and has, it seems to me, gone too far in the opposite direction.
— Bibliotheque Universelle de Geneve, I. c.

AND THE LOWER ANIMALS.

121

Look at tlie g-radual disappearance of tlie gills and
tail of a tadpole_, and of the rotary apparatus of
tlie Teredo^ and although, you be not a naturalist^
you will say_, " These are organs which have htrojMed.''
Compare the young crab^s tail with that of the adult ;
the reproductive organs of a neuter with those of a
queen bee ; and you will yourself employ the expres-
sion— arrest of development.

Observe the feet of the Lernea_, at first employed as
oars^ and afterwards_, when converted into a sort of
anchor^ serving to attach the animal to its hving
residence^ and you will be struck with the manner in
which Nature adapts an already existing organ to an
entirely new function. You will then perceive that
metamorphosis J properly so called^ is above all things
characterized by transformations.

In order that these phenomena shall take place_, it
is necessary that the same stream of matter shall
flow to and from the parts as that which exists in
Mammalia. In the great majority of cases the altera-
tions do not occur suddenly^ and they take place_,
moreover_, in the very depth of the tissues. The
branchiae of the tadpole do not fall off directly to give
place to the lung ; nor does the tail become detached
when the limbs are formed. No; in proportion as
the one is developed^ with its bones, muscles, nerves,
and vessels, the other decreases in every portion of
its structure and in all its parts simultaneously. The
latter is actually resorbed molecule by molecule, just
as the former is being built up atom by atom.

It is true that in Insects and Crustacea there is
appareiitly a different state of things. At each period
of moulting, and during every metamorphosis, the old

122

METAMOEPHOSES OF MAN

skin^ or carapace^ as tlie case may be_, is cast aside
as a useless covering; but this is because of its
inflexible nature^ owing to the liorny and inorganic
matter it contains preventing tlie growth of the
animal. Look into the interior of these beings.
With Swammerdam^ Reaumur_, Herold_, and Newport
as your guides^ follow the series of important changes
which the central organs undergo_, and you will see
that the phenomenon of molecular absorption is present
in these creatures also.

Here is a striking example,, in addition to those we
have already cited. The larva^ prior to becoming a
chrysalis^ stores up^ so to speak, the materials requisite
for its transformations. Its organs are almost em-
bedded in a peculiar fatty tissue. If, however, you
examine the perfect insect, you will not find a trace of
this substance. It has been nearly all employed in
repairing the organs ; and as matter cannot be acted
on by the vital force without the production of a
certain amount of waste, the intestine (which was
empty at the commencement of metamorphosis) is
found, when the crisis is over, charged with a quantity
of excrementitious matter which was then formed.*

We see, then, that the study of metamorphosis,
like that of transformation, carries us forcibly to the
point from which we started. We can understand
neither one nor the other, unless we admit the exist-
ence of a force inherent in all hving organisms, ever

In certain lepidoptera this matter is of a reddish colour.
The insect discharges it as it leaves the cocoon, and the spots which
are thus left upon Avails, stones, branches, etc., in the neighbour-
hood, are often sufficiently numerous to give rise to the supposition
that there has been a shower of blood.

AND THE LOWEE ANIMALS.

123

present and ever active_, . controlling tlie materials
borrowed from the external world_, arranging tliem in
accordance with a preconceived iplsm, and rejecting
them when they are not longer fit for use. Life, then
— the vital vortex — we must regard as the first cause_,
and as the general process of all the phenomena which
we have been describing.

124

METAMORPHOSES OF MAN

CHAPTER XIIL

GENEAGENESTS. FIEST PHENOMENA OF GENEAGENESIS

DISCOVERED IN ANIMALS. AGAMIC* GENERATION (aPHI-

DES). REPRODUCTION BY FISSURATION AND BY GEM-
MATION (polyps^ HYDRtE^ COMPOUND ASCIDIANS).

In tlie two earlier portions of tMs work we saw tliat
tlie lower animals_, and even man Mmself, spring from
germs wliicli are invariably similar at firsts and wliich
moreover are genuine ova. I pointed out^ also^ liow,
under the influence of vital action_, this resemblance
disappeared, and tliere resulted an infinite variety of
forms. At tbe same time I showed that no single
species exhibited at the outset its definitive or adult
features, — that the embryo is never the miniature of
the perfect being. From this the reader has been
led to conclude that every animal undergoes metamor-
phoses. Nevertheless, this phenomenon, although in
all important particulars the same, assumes different
features in different groups. In man, and in almost
all vertebrates, the transformations take place chiefly
within the egg, and on that account are familiar
only to scientific men. In insects, on the contrary,
the true metamoiyhoses occurring external to the
egg, and modifying the form of an animal as ex-
tensively as if a fish were converted into a bird,

'"■ Without intercourse of the sexes.

AND THE LOWER ANIMALS.

125

liave attracted the attention of even ordinary ob-
servers.

In a developmental point of view^ tlie histories of
man and of the butterfly^ although presenting very
marked contrasts^ yet have some important features
in common. In both we find a male and female
parent^ and offspring which are directly derived from
this couple_, and which must pass^ in reaching their
final statCj through the same phases as those which
characterized their parents. In the verteb rated as in
the annulose animal we perceive that the progeny^
male and female^ resemble the parents^ allowing of
course for individual differences. In all the groups
which have engaged our attention up to the present_,
the individuality of each being is manifest from the
first appearance of the germ_, and in the first rudi-
ments of the egg, and remains entirely distinct until
the being itself ceases to exist. These facts are well
known even to vulgar experience^ and till lately
scientific and unscientific persons agreed in regarding
them as the expression of absolute laws.

We must now proceed to consider a set of phe-
nomena as novel as they are remarkable. Here we
meet with animals which^ strictly speaking-^ have
neither father nor mother^ but simply a single loavcnt,
which produces them directly from its own body.
We shall meet with sons which never resembled their
father^ and which produce offspring quite unlike
themselves. We shall see a single germ give rise^
more or less directly, not to a single individual, but to
multitudes of individuals, and even occasionally to
distinct generations, which are not related either as
to form or structure, or mode of life. We shall thus

126

METAMOEPHOSES OP MAN

perceive that tlie primitive individuality of tlie germ
is lost, and is replaced by a series of new indi-
vidualities ere the products of this germ reach their
final condition.

We are now entering upon a world where the most
fundamental laws of the animal kingdom appear as it
were reversed. The reader, however, will, I trust, be
enabled to conclude that there are no real contradic-
tions, and that even in cases so apparently exceptional,
creative nature displays a wonderful regularity.

In approaching this portion of my task, I feel how
great the difiiculties are which encompass both my
readers and myself. Even without having taken out
a course of lectures on anatomy, every one has a vague
notion of the position of the heart, lungs, stomach, and
liver of mammalia : the external characters of these
animals are at all events familiar to all. To speak of
their transformations is to lead even an enlightened
man to a class of ideas and facts with which he is
doubtless little familiar, but where he meets at least
some points with which he is acquainted. In regard
to metamorphoses, properly so called, the Lepidoptera
afibrded us a sort of type to which we could refer not
only the history of other insects, but even in most
cases that of Annulosa in general, of Mollusca and
Batrachia. In their different groups, too, the various
species to which it was necessary to allude are more
or less known to every person.

Now, on the contrary, I am about to treat of beings
whose form and organization have been studied by
naturalists only. The names of the animals will be
new, and many of them will seem rude and barbarous.
I shall now be obliged to demonstrate everything, for

AND THE LOWEE ANIMALS.

127

the precise reason that the phenomena we considered
before^ become here more strange and complex than
ever. I shall_, however^ attempt the task^ which
without the assistance of illustrative figures is by no
means an easy one.

In the first place_, we shall mention the simplest
facts bearing upon the subject_, and those also which
were first observed.

In all the animals previously spoken of^ a new
generation can be produced only through the inter-
course of two individuals of opposite sexes. This
fact is so well known that it has been always regarded
by the mass as one of the great laws of Nature. The
exceptional facts observed in the case of man himself,
and perhaps also the fables of the ancients^ prepared
naturalists for the discovery of certain animals in
which the attributes of both sexes were united in a
single individual. The idea of hermaphroditism_,
which they had readily accepted^ was at last proved
correct^ and exempHfied among some of the inferior
animals by which we are smTOunded, — the earth-
worms and slugs for example.

These discoveries^ extended at a later period by
Adanson^s beautiful researches upon moUusks^* gave
a new interest to the veiy dijB&cult problem — Can
any animal be a male and female parent in the entire
acceptation of the word_, without having intercourse
with another individual ?

A great many naturalists^ led by reason only^ re-
plied in the afcmative j but the direct observation of
animals placed apparently under the most favourable

" Histoire Natnrelle clii Senegal," 1759.

128

METAMOEPHOSES OF MAN

anatomical conditions,, was in opposition to this con-
clusion. It was known tliat in tlie earthworm and
tlie slug tlie intercourse of two individuals was as
necessary to tlie ends of procreation as in mammalia
and birds. Reaumur also^ who was then universally
recognized as arbiter in all matters relating to Natural
History^ was about to decide in the negative^ when he
was suddenly left in a state of doubt by some facts
which he had observed when studying the plant-bugs
(Aphides) .

Most of our readers are acquainted with these
insects in the larval stage. They are the creatures
which appear in thousands upon the branches of fruit-
trees^ and the stems of flowers and of peas.* They are

The plant-bugs (AjDhides) are insects belonging to the order
Heniiptera, that is to say to the group which inchides the Cicadid?e,
Cimicid^e (bugs), &c. They form a very extensive genus, whose
species are even yet far from being all known. These insects are
genuine parasites, living upon vegetables, and in these temperate
climates there is hardly a single plant but what supports its own
species of aphis either upon its stems, or its leaves, or about its roots.
Many species of Aphis may be classed among the noxious insects.
Reaumur discovered that the punctures made by them, when in
sufficient quantity, not only exhausted the plants, but gave rise to
nodular swellings, and to alteration of the tissues. The laniger
plant-bug {Lachnus laniger), which attacks apple-trees especially,
has on many occasions destroyed the plantations of Normandy.
This species, which is one of the disastrous results of commercial
intercommunication with other countries, was found in England,
according to M. Tougard, in 1787. In 1812, it had reached the
French departments of C6tes-du-Nord, Manche, and Calvados. In
1818, it made its appearance in Paris in the garden of the " Ecole
de Pharmacie ; " it was seen in the departments of the Seine-Infe-
rieure, the Somme, and the Aisne in 1822. Finally, it was dis-
covered in Belgium in 1827. This formidable little insect has for
some years held its sway in the southern departments, no means of
destroying it having been discovered.

A-KJ) THE LOWER ANIMALS.

129

almost invariably motionless^ and having- their long-
proboscis deeply buried in the epidermis of the plants
they appear capable of only one movement^ — that of
raising from time to time the great round abdomen
which is terminated by tvfo small tubes in the form
of moveable horns. Each time they move^ a drop of
sugary liquid escapes from these openings^ and in the
neighbourhood may usually be seen a few ants^ ready
to suck up the honeyed secretion, which according to
Hubert, — the distinguished observer of these insects,
— is probably their sole nourishment. These larvae,
when completely developed, become pretty insects,
with four transparent wings almost twice as long and
as wide as the entire body, and which are supported
by a few thin nervures. So far there is very little
extraordinary in the history of these hemiptera.

The larvse alone were at first examined by Leu-
wenhoek. La Hire, and Eeaumur. The latter, whose
attention was absorbed by other researches, after-
wards engaged Ch. Bonnet to investigate the subject,
and the Swiss naturalist fully justified the confidence
reposed in him by his illustrious master.

It was already known that the plant-bugs produced
two generations, and it was suspected that each
individual possessed the two sexual attributes. To
ascertain the truth of this suspicion. Bonnet isolated
one of these insects almost immediately after its
birth, and reared it in captivity, taking' the greatest
precautions to prevent any intercourse with other indi-
viduals. This nurseling was treated by our observer
with an amount of care which he has naively described
in his work.^ He watched it with a lens, from

-•• "Trait^' tVInsectologie," 1745.
K

130

METAMOEPHOSES OP MAN

morning till niglit_, noting its every action and gesture,
anxiously following its slightest movement^ trembling
almost at tlie clianges wMcli seemed to result from
excessive liealtli, shuddering at the notion of an
attack which might prove fatal ; but all these anxieties
were quickly forgotten when he saw the little being
four times change its skin_, and attain its normal
specific characters. Bonnet was enabled to prove that
a complete removal from all other members of its
species did not affect its fecundity. On the eleventh
day his virgin aphis — for so he thought fit to term it
— gave birth to a young one_, which was perfectly
healthy; and a second soon followed the first. The
same occurred during the succeeding days. Every
twenty-four hom'S the family was increased by an
addition of from three or four to ten new members.
At the end of twenty-one days the mother, whose
virginity was unquestionable, had given birth to
ninety -five new beings.

This experiment, which was first made upon the
aphis of the spindle-tree, and was repeated afterwards
on a great many sj^ecies by different observers, was
decisive. The lucina sim co'itu of the ancients was
proved incontestably in the plant-bugs; but these
insects reserved for Bonnet a discovery which was
quite unexpected.

Stimulated by some remarks of a rival, of whom we
shall soon have more to say. Bonnet commenced a
new series of experiments to ascertain how far the
reproductive powers of the mother would extend to
the offspring and grand-offspring-. The aphis of the
elder-tree was isolated immediately after its birth,
and, as in the case of the former one, produced a

AND THE LOWER ANIMALS.

131

number of young. One of tliese latter was tlien
iniprisoned_, and it gave birtli to a third generation.
A young specimen of this generation was placed
under exactly similar conditions^ and gave rise to a
fourth^ and so on. Five genera^tions of virgin aphides
were produced in BonneVs first experiment. He after-
wards obtained as many as ten_, in the case or the
spindle-tree aphis; and this number hasbeenexceeded.*

It seemed fair to conclude from all these experi-
ments_, that^ among aphides^ a single isolated indivi-
dual is capable of perpetuating the si^ecies. But in
Zoology^ of all sciences^ it is especially necessary to
guard against hasty generalizations_, and Bonnet very
soon proved the truth of this statement.

About the end of the 'year which afforded him so
many interesting results^ and whilst he was investi-
gating the aphides of the oak^ Bonnet distinctly
observed the males and females of this species ; he
witnessed performances exactly like those which take
place among other insects ; in fact^ he saw the female
aphides produce genuine ova^ instead of the virgin
larv93 which he had before observed. This species
exhibited, moreover, the phenomena of solitary vivi-
parous reproduction which he had seen before in
other instances.

These results show with what rapidity reproduction is effected
among the plant-bugs. Supposing a single aphis to produce only
fifty young ones — which is certainly below the average — it foUov/s
that one of these insects beginning to breed in spring would give
rise in the course of a summer to no less than 4,000,000,000,000,000
of larvae, which would cover a space of at least forty thousand
square metres. The entire surface of the globe would be covered
with aphides, were it not for the number and voracity of the
animals which prey upon them.

132

METAMOEPHOSES OF MAN

Bonnet was enabled by a new series of obseryations,
to associate and explain in the most satisfactory
manner these apparently contradictory facts. He
discovered that the aphides produce larvae without
sexual intercourse^ during the summer months only^
and that when the external temperature diminishes_,
these insects return to the ordinary process^ and
propagate by ova_, which can only be produced through
the intercommunication of the two sexes. These ova
remain attached to the branches of trees during the
winter, occupying the position which the colony — ■
now destroyed by cold — formerly held. They are
hatched in spring, and viviparous individuals alone
are produced; but in the autumn males and females
again appear, and with them the oviparous repro-
duction presents itself.*

The facts to which we have just called attention

De Geer, who may be caUed the Swedish Eeaumur, Lyonnet,
the distinguished anatomist of the willow caterpillar, and several
others, have confirmed this conclusion. One of them, Kyber, has
demonstrated incontestably the influence of temperature upon
these phenomena. He placed a twig of carnation covered with
aphides, in a chamber, which was maintained at a constant tem-
perature all the year round, and observed, that these insects pro-
pagated viviparously, and in this manner only, for four successive
years. — {Germar's Magazin der Entomologie, 1815.) These strange
phenomena have often puzzled naturalists, and among those whose
attention they have engaged, we may mention: Duveau Nouvelles
Eecherches suT Ics Fucerons,'' — Memoires du Museum, 1825); Morren
(" Memoire sur I'Eniigration du Puceron du Pecher et sur les Carac-
teres et I'Anatomie de cette Espece," — Annales des Sciences natu-
relles, 1836) ; Siebold " Ueber die inneren Geschlecteswerkzeuge
der viviparen und oviparen Blattlause ; " Froriep's " Neue Noti-
zen," 1839 ; and V. Carus " Zur nahern Kenntniss des Generation-
wechsels," 1849.

AND THE LOWER ANIMALS. loo

were of too peculiar a na;ture_, and too inconsistent
with accepted views^ not to have given rise to many
hypotheses. If the aphides always produced their larvae
v/ithout sexual intercourse^ then the theory of Andro-
gynism would have afforded a sufficient explanation.
It would have been easy to suppose the existence in
these insects of a double reproductive organ (mpJe and
female) in each individual^ which could originate new
beings in the same manner as those of opposite sexes
vfhen distinct. But the alternation of these two modes
of generation set this hypothesis aside.

Bonnet_, who was an acknowledged supporter of the
'^^ pre-existing germ^^ doctrine^ saw no difficulty in
the viviparous production of larv83 without previous
sexual connection. According to hini^ the larvte were
only germs which were well supplied with nutritious
materials by the mother during the summer months^
and which on that account were fully developed before
leaving the parent. The ova, on the other hand, were
germs which had been imperfectly nourished. The
action of the male aphis was regarded as an additional
means of supplying the ova with nutriment, in order
that they might survive the winter and be hatched in
spring.

Reaumur, who v,^as more observant and less meta-
physical than his disciple, was much more puzzled.
He put forward several hypotheses without committing
himself seriously to any of them. One of these was
at all events ingenious. It tended to show that ovi-
parous reproduction and its results were in some
measure dependent on the arrival of the insect at a
state of puberty. He supposed that the adult con-
dition was not reached after the individual had lived

134

METAMORPHOSES OF MAX

for a certain period^ but that it could only be attained
in proportion to tlie number of generations wliicli liad
preceded tlie birth of tlie insect. This explanation
did not hold its ground any more than those which
had preceded it^ and took no position in science^ for
it deserved none^ seeing that it never touched on the
real difficulty — the fecundity of the virgin aphis.

According to another author^ the aphides invariabty
produce ova in the same manner as other insects^ but
the fecundation instead of affecting merely one gene-
ration^ extends its influence to several successive ones ;
hencOj, a second impregnation is unnecessary till the
entire of this transmitted influence has been exhausted.
According to this hypothesis^ the ova are developed
in a fecundated condition^ and are hatched in the
mother^ s uterus_, just as they are among the ovo-
vivipara.* The phenomena observed in the aphides,
when seen from this point of view, resembled those
already known, and although somewhat exceptional,
still they came almost within the limits of the general
law. The very vagueness of this explanation was a
recommendation to some zoologists, and caused it to
be accepted generally ; and until of late years it re-
mained almost unquestioned.

Shortly after Bonnet made his curious discoveries,
naturalists observed another series of phenomena far

* Animals are termed ovoviviparoiis, which produce ova like
true ovipara but which retain them in tlie uterus until the period
of hatching ; the young being then expelled without however
possessing any of those connections with the mother's organism
which are seen among mammalia. There are instances of ovo-vivi-
parity among reptiles (the viper\ fishes (the blenny), moUusca, and
a,nnulosa.

AND THE LOWER AXI3IALS.

135

less reconcilable to what were tlien regarded as tlie
fundamental laws of science.

Until about tlie first tMrd of tlie last century^ the
real nature of various bodies was unknown or misun-
derstood. One distinguished botanist^ Tournefort^
relying upon some observations which he had made
in the cave of Antiparos^ and as Fontenelle said^
transformant tout en ce qu'il aimait h ^niimix^' beheved
in the vegetative growth of stones. Notwithstanding
the very clear views which had been enounced more
than a century before by an Italian named Imperato^*
he and most naturalists with him beheved that cal-
careous polyparies were nothing more than vegetative
stones. Others_, seeing a sort of relation between them
and the horny polyparies^ regarded both as plants.
Indeed this opinion seemed demonstrated by Marsigli^t
who described the animals of the corals and other
allied forms_, as being' nothing more nor less than
flowers. But whilst the Italian naturalist published a
discovery which was probably due to the fishermen
of Marseilles^ a French naval physician observed
similar appearances_, and grasped more fully their
importance and signification. Peysonnel declared
(in a memoir addressed to the French Academy in
1 727) that he had ascertained by repeated observations^
that the so-called flowers of corals^ madrepores^ and
lithophytes, were genuine animals like the actineae^
zoophytes known since the time of Aristotle as sea-
nettles (Acalephse).

There was a very powerful reason for the rejection

•"' " Historia natnralis," 1599.

t " Histoire 23liy,siqne de la Mer," 1725.

136

METAMORPHOSES OF MAN

of PeysoiinePs views. Reaumur^ wlio was imbued with
tlie existing opinions^ announced the discovery to the
Academy^ but opposed it also^ and gave the entire
weight of his authority in support of a shghtly modified
version of Marsigh^s doctrine. Being desirous^ hoAv-
ever_, of sparing one whom he esteemed^ the annoyance
of such a sudden rejection_, he refrained from mention-
ing PeysonnePs name.* The latter^ certain of the
accuracy of his observations^ appealed to men of science
in other countries^ and pubUshed his researches in the
'^Philosophical Transactions ''^t of "the Eoyal Society
of London. Some years afterwards^ Trembley^ the
fellow-countryman of Bonnet, re-discovered, in Hol-
land, the hydra, — which had already been met by
Leuwenhoek — examined this fresh-water polyp, and
announced those discoveries which have immortalized
him; Bernard de Jussieu and Guettard having been
sent by the Academy to investigate the sea-shore
animals, and having carefully studied this portion of
the marine world, confirmed all PeysonneFs state-
ments. Reaumur bowed to the evidence of these wit-
nesses, and with a greatness of mind and generosity
which cannot be too highly praised, he himself pro-
claimed his past error, and the immense importance
of the discovery made by him whom he had opposed^
thirteen years before. J

One of those accidents which often happen for those

■"' This essay of Eeaiimiir's was reprinted in the " Menioires de
rAcademie des Sciences," 1727.

f " Philosophical Transactions," vol. xlvii. This work Avas partly
reprinted in London, in 1756, when the accuracy of his views had
been demonstrated.

J " Menioires pour servir a I'Histoire des Insectes," prefece to
the sixth volume, 1742.

AND TKE LOWER ANIMALS.

137

who seek them, placed Trembley upon a new patli of
study. He placed in a glass vessel a quantity of
ditch water^ whose surface was covered with those
little isolated plants which consist of two spread-
ing green leaves and some fine rootlets^ and which
are commonly known as " duck-weed.''^ After a while
he perceived a number of small bodies of a beautiful
green hue attached to the transparent walls of the
bowl^ and vfhich gradually changed their form and
proportions^ sometimes remaining perfectly motion-
less^ and at others travelling slowly along the glass.
When completely elougated_, their bodies were like
hollow cylinders^ five or six lines long-, whose free
extremity exhibited a central orifice, and was sur-
rounded by a variable number of retractile tentacles,
moveable in every direction. On touching them,
these tentacles were rapidly drawn in, seeming to dis-
appear altogether, and the cylinder was reduced to
the form of a conical projection, hardly one line in
length.

Trembley was for a long while ignorant of the real
nature of these curious bodies. Were they animals ?
or were they plants endowed with the power of sensa-
tion ? The form and colour were those of a plant ;
but on the other hand these bodies moved along some-
times indeed very slowly, but at others by making a
series of bounds, by no means unlike those of a
mountebank. To solve this problem, he cat one of
these enigmatical beings in two, and in forty-eight
hours after, each half had become a perfect organism
like the original. When it was divided into twenty,
thirty, and even fifty portions, there were as many
perfect individuals produced. At the same time

138

METAMORPHOSES OP MAN

Trembloy discovered Tipon these living cylinders a
number of small elevations^ wliicli gradually increased
in length, developed tentacles at their free extremities,
and ended by becoming detached, when they were
found to resemble in every particular the body from
which they had sprung.

Here, Trembley observed two important phenomena
which till then had been regarded as belonging to
plants exclusively — multiplication by fissuration and
by huds. He also saw these pseudo-plants feeding
like beasts of prey, seizing with their tentacles the
aquatic insects as they swam along, swallowing them
— sometimes as large as themselves — wholesale, digest-
ing them, and rejecting the effete matters by the same
orifice through which the food was admitted. These
facts seemed to him to decide the question. The
beings which he had been studying so long were
actually and certainly animals. Reaumur, who was
consulted as to this conclusion, adopted it as soon as
he had seen the creatures themselves, and thereupon
gave them the name of polyps, which has since been
applied to the entire class. With the assistance of
Bernard de Jussieu he found a species akin to that of
Holland in the outskirts of Paris, and other animals
also v^^hich he thought, but incorrectly, were related
to it.^'

Trembley^s discoveries so fully confirming those of
Peysonnel, produced quite a sensation ; in fact, to use
the language of the period, ^' court and town were

* The " polyi^es a panache " (Polyzoa), of Reaumur and his con-
temporaries, have only a faint external resemblance to the true
polyps. The latter belong to the sub-kingdom Radiata ; the former
have been properly ranked among mollusca.

AND THE LOVfER ANIMALS.

139

full of it. The first polyps sent from Holland were
solemnly presented to tlie Academy by Reaumur him-
self^ who at the same time pointed out other animals
capable of exhibiting similar phenomena. The subject
was then taken up on every side. On the coasts of
Bretagne and Anjou^ there was almost a species of
rivalry exhibited by Bernard de Jussieu and Guettard
in the manner in which they cut up the Actinias and
Asteriadas. The reproduction of lost parts was shown
to take place in both these groups. They not only
determined the animal character of a great number of
polypSj but they went even farther in grouping among
the latter several calcareous plants which have been
very gradually restored to their proper places. Then,
again, Reaumur and his colleagues investigated the
fresh waters ; and the Bryozoa of our ponds, the Pla-
nariae and Nai'des of our streams, and even the earth-
worms, exhibited in various degrees an insensibility to
mutilation, the prominent result of which was their
individual multiplication. A grand physiological truth
was deduced from all these experiments ; viz., that
certain animals may, like plants, be reproduced both
by slips (fissuration) and by buds (gemmation) .

It was evident that in these instances there could
be no question of ovo-viviparism ; hence it became
necessary to go in search of some new explanation,
and the metaphysicians, whether naturalists or not,
took part in the inquiry. At this period the doctrine
of 'pre-existing germs reigned supreme. How then
were the newly discovered facts to be reconciled with
this theory ? Bonnet, in his endeavour to solve the
problem, devoted a considerable deal of thought to
the subject, and concluded by developing an en-

140

METAMORPHOSES OP MAN

tirely new speculation — a peculiar theory termed tliat
of pansjjermy/' which supposed the constant exist-
ence and universal diffusion of germs that were always
ready to be developed. On the other side_, Descartes^
followers took the matter up, and asked those who
believed in the existence of a soul among the lower
animals, Avhat became of the soul of a polyp which
had been divided into fifty portions, each one of which
assumed the character of an individual ? Was the
soul divided into as many portions as the body, or did
it remain in some favoured segment ? Did the fiftieth
part of the soul, in the first instance, become even-
tually developed ? How, in the second case, could
the portions first deprived of a soul perform their
functions as well as those in which it was left intact ?
Or, were there indeed not only hodily germs but
spiritual ones also ? These questions, as well as many
others, were discussed at the time with considerable
spirit, but the excitement gradually calmed down.
Unsolved problems were laid aside ; and, thanks to
the ventilation, and even to the number of the facts,
it was considered as easy to conceive of an animal
reproducing itself after the manner of plants, as to
suppose that an insect could be oviparous and vivi-
parous alternately, and that a single act of fecundation
influenced not only the generation immediately suc-
ceeding it, but future generations also.

For more than three-quarters of a century, natural-
ists continued to explore the paths which had been
thrown open to them by the discoveries of Bonnet,
Peysonnel, and Tremble}^. Facts were rapidly accu-
mulated, but no new phenomena were observed.
There are among the works of this period some

AND THE LOWEE ANIMALS.

141

wMcli deserve attention^ and whose importance was
not appreciated till they were examined from a point
of view which was for a great length of time un-
recognized.

As the result of the discoveries we have alluded to^
several organisms were ranked among the relatives of
the hydra^ which were really in no way akin to it.
Such were the corallines^ which are undoubted vege-
table structures_,and thei^^ns^rce, Escliarce, Si>ndBotryUi,
which belong to the compound or aggregated mollushs.
Their true nature was demonstrated in 1816 by Sa-
vigny^ the companion of Geofiroy and Cuvier^ he who
suffered thirty years^ martyrdom for his endeavours to
advance science. The multiplication of individuals
occurs in all these species in the same manner as in
the polyp with which they were confounded.^ The
several modes of reproduction discovered by Reaumur^s
contemporaries were thus presented by different ani-
mals^ among some of which^ the various individuals
were connected together organically ; thus converting
them into animal colonies capable of growth and of
extension. Reproduction by fission and gemmation
only explained the multiplication of the individuals
of the colony in one locality, but left unsolved the
question of the distribution of the colonies them-
selves.

" Memoires sur les Animaux sans vertebres." On Savigny'j>
return from his Egyptian expedition, and v/liilst in the pursuit of
his studies, he was attacked by a very extraordinary and calamitous'
disease of the eyes, which deprived him of his vision for thirty
years. Cuvier remarked, in a report to the Institute upon one of
the first memoirs of this naturaUst, " Siivigny does not merely dis-
cover, he reveals ;" so unexpected but withal so clearly deirLOi -
st rated were the results enunciated.

142

METAMOEPHOSES OF MAN

This problem remained unexplained till about tlie '
first third of the present century.

It is quite true that Bernard de Jussieu had dis-
covered the hydra^s eggs ; that Cavolini_, then residing
at the sea-side^ had observed the eggs^ or the u-h lrUiuj
rjerias, as he termed them^ of the polyps^, and had seen
them attach themselves to some solid body and give
rise to a new polypidom and that many other facts
had been recorded. Nevertheless^ the problem was
left in nearly as much obscurity as ever, until Messrs.
Audouin and Milne Edwards declared that the com-
poimd ascidians deposited true ova_, from which sprung
larvae, at first restlessly active, but which eventually
became fixed, and developed a new colony. f This
important discovery, which was at first denied, but
afterwards confirmed by several naturalists, was the
start-point of a series of most valuable researches made
by Milne Edwards ; and we shall now proceed to give
a brief resume of them. J

The ascidians are marine mollusks without shells,
and may be divided into three distinct groups. In
some the individuals are free and isolated, and are
hence called simple ascidians ; in the second division
the members are loosely connected by trailing root-
like prolongations, and are termed social ascidians;
whilst the individuals of the third section are fused as

* " Meniorie per servire alia Storia dei Polypi marini," 1789.

t " Observations sur les Asciclies composees des cotes de la
Manche en 1834 et 1839." Since that date Van Beneden has
observed the same forms of reproduction among the sim^de ascidians.
— " Kecherches sur I'Embryogenie, I'Anatomie, et la Physiologie
Ascidies simples," 1846.

J " Resume dcs Kecherches sur les Animaux sans vertebres,
fiiites aux iles Chausey," 1828.

AND THE LOWER ANIMALS.

143

it were into a common mass_, and_, having tlie closest
possible organic relation to each otlier^ are therefore
styled compound ascicUaiis. The first appear as ir-
regularly globular masses attached to sub-marine
bodies ; the second are usually found suspended from
the roof of some rocky cavern^ and have the appear-
ance of beautiful crystal ornaments ; the third are
seen covering whole rocks^ stones^ and sea-weeds.
The mass is usually of a gelatinous character_, semi-
transparent, and tinted with red_, green, or brown;
and upon the surface of each colony a number of
irregular festoon-like markings may be observed,
figures which are by no means unlike those traced by
a mathematician's compass. Moreover, the organiza-
tion of all ascidians is in the main identical. They
have all a very simple nervous system, a very imper-
fect circulatory apparatus, a more or less contorted
digestive canal, and in many of them, owing to the
extreme transparency of the integument, the whole
anatomy may be studied with the aid of a simple lens,
without having any recourse to the dissecting-knife.

The egg of the compound ascidian is very rapidly
developed, and exhibits the same phenomena as those
described in the earlier chapters of this volume. It
is entirely converted into a larva like that of Hermella
and Teredo. This little creature is of an oval form,
and is furnished with a long tail which gives it some
resemblance to a tadpole. As yet there are no distinct
internal organs, but in their place is found a central
homogeneous yellow mass, from which they will be
formed, and which is surrounded by the thick, color-
less, and transparent envelope. A prolongation of
this mass extends into the tail, and three others act

144

METAMOEPHOSES OP MAN

as suckers_, by whidi the animal acllieres to submerged
bodies.

At first tlie young ascidian swims about very nimbly,
but its energy is soon exhausted, and after a few
hours it becomes permanently fixed. The prolonga-
tions of the yellow mass are drawn toward the centre
of the body, the tail becomes atrophied and is detached,
here and there may be seen traces of organization,
the heart and digestive apparatus gradually appear,
and at the end of the third day, all the organs have
begun to perform their functions. Simultaneously
with these changes the integument is thickened and
enlarged. It is this which vv^ill form the common matrix
for all the inhabitants of the future colony. Numbers
of buds now appear upon the body of this solitary
animal ; these force their way through the matrix and
reach the external surface in a certain definite order,
constant for each species, and then, instead of a single
isolated ascidian, there is a cluster of compound
mollusks, each of which will produce eggs at the
proper time.

We see then, that in the ascidians, as in the aphides,
an animal which has sprung from an egg develops,
without previous sexual intercourse, a number of new
beings, and finally, coming under the ordinary law,
deposits true ova.

AND THE LOWER ANIMALS.

145

CHAPTEE XIV.

discovery of alternate generation (salp^ and
medus.e) .

By combining tlie precise observations of Milne
Edwards with those of his predecessors and followers^
we are enabled to draw the following* general con-
clusion : — The distribution of fixed animals is appa-
rently always due to the development of eggs pro-
duced by the female^ and which are hatched at a
distance, giving rise, in most instances, to free and
active larvas. Here we observe both metamorphoses
properly so called, and the recurrent form to which we
referred elsewhere ; * besides, multiplication by buds
occurs in those individuals belonging to the social
group.

This twofold method of propagation is evidently
necessary, and might suffice to ensure the existence
of polyps and other animals which live in colonies.
But organic nature, which is not limited to a single
or to the most simple path, had other surprises in
store for naturalists. In 1819, a Germanized French-
man— who must be admired by those who have
read M. Ampere^s essay f — recorded a discovery,
which in novelty, and from the fact that it was un-
expected, was in no way inferior to those which pre-

Vide Chapter V.
t "Eevue des deux Mondes," May 15, 1840.
L

146

METAMORPHOSES OF MAN

ceded it. Gliamisso detected tlie mode of reproduction
of the bip]ior99^ and coined the expression alternation
of generations/^

The Salpae are marine mollusks of a very pecu-
liar form^ to give a general description of which
is exceedingly difficult. However^ we may describe
them as being like an irregular cylinder of perfectly
transparent crystal^ in the centre of which a pro-
poiidonally small mass of opaque^ brilliantly coloured
matter^ called the nucleus, is suspended. This nucleus
is composed of the principal viscera grouped together.
The cylinder represents the mantle and shell of other
mollusks^ and is perforated at both extremities. The
water which is required for respiration is introduced
through one of these orifices_, and by the contractions
of the mantle is as quickly expelled from the other ;
this action taking place with rapidity, the animal is
caused, as it were, to rebound; and thus by these
respiratory contractions the biphora is propelled
through the Y\rater.

For a long period the attention of travelling-
naturalists had been attracted by these animals, whose
phosphorescence was distinctly marked even in the
luminous waters of the intertropical ocean. They had
been seen sometimes in the isolated condition, and
at others in the form of long ribands composed of
exactly similar individuals. There were, moreover,
very considerable and well-marked differences between
the chained and isolated Salp83. The existence of
these two conditions seemed a sufficient reason for
the division of this singular group into two distinct
sections ; consequently, it was supposed by our cele-
brated traveller, Prron, that the Salp83, which were

AND THE LOWER ANIMALS.

147

connected in the young stage_, were afterwards isolated^
and caused to assume other characters in obedience
to the laws of development. He thus admiited the
existence of true metamorphoses^, for the distinction
between the two forms — solitary and aggregated —
extends not only to the external character, but also to
the form and disposition of the viscera.

Chamisso discovered that this phenomenon is far
more complex than was supposed.* He perceived that
the Salpas are both androgipious and viviparous, and
that they preserve their infant characters all through
life ; but, strange to say, a solitary mother produces
07ily individuals united into colonies, and vice versa.
Hence it follows, that a Salpa resembles neither its
parents nor its offspring, but is exactly like its grand-
parent and grand-offspring. The external and internal
characters of the alternate generations are, moreover,
in every respect identical.

In this case, metamorphosis does not affect indi-
viduals merely, but operates on entire generations.
The same result is produced as if the caterpillar,
instead of undergoing its transformation, were to
produce a fully-formed butterfly, which in its turn
would bring forth caterpillars. It is a true alterna-
tion of generations, and this lavv^ holds good for all
biphor^e.f Consequently, the species of these mollusks

=^ " De Animalibus quibusclam e classe Vermimn linneana. Fasc.
prim., de Salpis." 1819.

The follov/ing passages from Cliamisso's memoir will show that
I have almost employed the very Vv^ords of this naturalist, " Qua
reposita (Salpa bicorni), alternationem generatiomim legem esse, ut
posuimus genericum, omnibus comumnem speciebus, observationi-

bus innititur Talis speciei metamorphosis generationibus in

salpis duobus successivis perficitur, forma per generationes (nequa-

148

METAMOEPHOSES OF MAN

cpamot be determined by reference to the characters
presented by one individual^ even during its entire
hfe ; it will be necessary to examine the individuals of
two successive generations^ and to describe two forms
instead of one.

Chamisso's discoveries seemed as incredible as the
" Adventures of Peter Schlemihl." They were
denied in the first instance ; but then^ as they were
gradually confirmed by new observations, an effort
was made to unravel their mysteries; this, however,
could not be done satisfactorily so long as the facts
remained isolated. Besides, even the then existing
observations left a considerable gap in the history of
biphorge, which v/as only filled up at a much later
period by the works of Krohn,-!^ Huxley, f Leuckart,J
and Yogt,§ to which we shall allude presently.

quam in prole sen individuo) mutata. Verum eninivero qua lege
2)roles sivlparum, ut animal ab ove, imago a larva inter se differunt,
parmn elucet." — (De Salpis.) " Es ist als gebaere die Eaiipe den
Schmetterling, iind der Schmetterling hinwiederum die Eaupe." —
(Reise urn die Erde.) Professor Huxley, who I believe was the first
to do ample justice to Chamisso, has quoted, among others, the
above passages.

Observations sur la Genc^ration et le Peveloppement des
BijDhores." — Annales des Sciences naturelles, 1846.

t " Observations upon the Anatomy and Physiology of Salpa
and Pyrosoma." — Philosophical Transactions, 1851.

% "Zoologischc Untersuchungen," zweites Heft, 1854.

§ " Eecherches sur les Animaux inferieurs de la Mediterranee,"
second memoir, 1859. Although Vogt's v/ork stands last in the
order of publication, it is but fair to state that his observations
date from the year 1847, and were carried on with great care from
1850 to 1852, when they were communicated to the assembly of
Swiss naturalists. The very abundance of the materials collected
by this distinguished and industrious zoologist retarded the publi-
cation of the memoir referred to.

AND THE LOWEK ANIMALS.

149

Cliamisso^ less fortunate than Peysonnel_, died, not
only before his opinions had received recognition^ but
even without having himself understood the immense
importance of his discoveries.

Chamisso''s observations^ at first certainly incom-
prehensible_, and those_, still more obscure^ announced
by CaruS; in 1818^ as the result of his researches, on the
HelmiiitlieSy or intestinal worms, marked an entirely new
era in the history of development. By these pioneers
a path v^-'as thrown open^ along which we travel every
successive day with more and more security^ but in
which it is also possible to lose the right track_, and
thus commit serious errors. The entire history of
these explorations, made to determine the proper
route, is pregnant with interest, but it would occupy
far too much space, and is of too difficult a nature,
for us to pursue it. We must, therefore, confine
ourselves to setting dovvn the landmarks, as it were,
of the paths traced by those who first visited this
'^''unknown land;^^* and in doing so, we shall occa-
sion alty be obliged to invert the chronological order of
the discoveries, in order to present the reader at first
with the typical results. Under the latter category
the works of Saars and Charles von Siebold, on the
reproduction of Medusse, occupy unquestionably the
first rank.

We shall now detail certain facts which, though
well known to all naturalists, are unfamiliar to most
of our readers.

For almost half a centm-y, the classes Acaleplice
and Fohjps have held a place among the other

* An expression employed by Siebold, to designate especially
the history of the reproduction of the Helminthes.

150

METAMORPHOSES OF MAN

divisions of tlie sub-kingdom Radiata^ and tlie dis-
tinction between tlie two seemed a very justifiable
one. Indeed^ it liad been sbown^ tbat difierences
exist between tliem of a more decided character tban
those which separate reptiles from birds ; there is an
entire dissimilarity both as to internal organization and
external conformation.

All acalephs are free and floating, and most of
them are solitary. The movements of polyps (which
are confined to a few) are^ on the contrary^ of a
creeping nature. Almost all these animals are per-
manently fixed^ and the great majority of them live in
colonies. Trembley^s Hydra is a type of the latter^
while the Medusa belong to the former_, and may be
readily known by their peculiar iimhrella, shaped
like a bell or a mushroom, — in some instances colour-
less and transparent ; in others, beautifully opaline,
and having an appearance not unlike that of tinted
enamel. This umbrella is at once the body and loco-
motive organ of the animal ; the digestive cavities and
circulating canals are buried in its substance, and
by its rhythmic contractions the animal is propelled
through the water. In the centre of the concave
surface — in fact, in the same position as the stalk of
the mushroom and the tongue of the bell — is placed
the mouth, which is almost always surrounded by
various appendages. The border of the umbrella is
frequently furnished with cirrhi, which are occasionally
both long and contractile, and serve as arms or fish-
ing-lines, by which the prey is seized, destroyed, and
carried to the animal^s mouth.

The observations on the reproduction of Medus89
had been few and isolated when Saars and Siebold

AND THE LOYfEE ANIMALS.

151

publislied their beautiful researclies. The former^ who
was a native of Bergen and a clergyman^ devoted his
leisure hours to the study of the rich marine fauna of
the Norwegian coasts. In 1820 he described two
polyps akin to Hydra as new species_, giving them
the names of ScypMstoma and Strohila ; but he after-
wards (1833) discovered that the second of these
creatures was only a transformation of the first. In
1835 he stated that the strobila produces genuine
acalephee^ by a process which till then had been
unobserved.* On his side^ Siebold^ who was one of
the first of German naturalists to perceive the import
of marine creations^ clearly distinguished the sexual
organs of the Medusae, watched the r^rst transforma-
tions of the larvae which proceeded from the ova, and
saw them converted into true polyps, t Finally, Saars,
in a memoir, J which was soon translated into every
European language, co-ordinated and completed this
history, which till then had been in but a fragmentary
condition. "We shall now give a short sketch of the
results which have been arrived at.

The red Aurelia [Medusa aurita), which Ehrenberg^s
writings have made almost as celebrated, as those of
Lyonnet the willow-moth, § is a pretty creature, with

" Beskrivelser og Jattagelser over iiogle moerkehge eller iije
i Havet ved den Bergenske kyst levende Dyr." A portion of this
work was translated by M. Gervais in the " Annales dAnatomie
et de Physiologie " for 1838.

t " Beitrage zur Naturgescliiclite der wirbellosen Tliiere."

J " Memoire sur le Developpement de la Medusa aurita, et de la
Cyanea capillata," in the "Annales des Sciences naturelles" for 1841.

§ The organization of mediis?e had been considered very simple
till this work appeared in 1839, in the Memoirs of the Berlin
Academy. It was thought that the cavities and canals which

152

METAMOEPHOSES OF MAN

an almost hemispherical umbrella, of from ten to
twelve centimetres wide, of a pale red colom^ which
is due to the vascular ramifications, and provided at
its margin with numerous short reddish tentacles.

The Aurelia deposits ova, w^hich are characterized
by the presence of the three concentric spheres to
which we alluded in the third chapter of this volume,
and these eggs are converted into larv«, which are at
first not unlike those of Hermella and Teredo. Their
oval body, which is apparently quite homogeneous,
is covered with vibratile cilia, and presents a little
depression anteriorly. For some time they swim
about very actively, just like Infusoria, which they
resemble so strongly, that any one confining his
observations to this portion of their existence, would
certainly be deceived as to their real character.

This first phase in the life of Medusae extends over
a period of about forty-eight hours. The movements
then become more feeble, and the young larva seems
exhausted, and attaches itself to some solid body, by
means of -the little depression already mentioned.
The animal, which had hitherto been nomadic, hence-
forth is fixed and stationary, and a thick mucus, which

Dnmeril discovered, about the end of the last century, were mere
excavations in a homogeneous matter, devoid of the characters
of a tissue. Oken and his disciples founded part of their doctrines
on this statement, which they accepted without examining. Ehren-
berg demonstrated that there are tissues, organs, and even complex
systems present in the Aurelia. He did in our dsijs, for this group,
what Lyonnet did in his for the insect class, and by depriving the
" Philosophic de la Nature " of one of its chief foundations, he
conferred a signal benefit on Natural Science. Besides, other
naturalists, and especially Agassiz, Edwards, Huxley, and Will,
have confirmed the general results of the Berlin savant's researches,
and I myself have on many occasions perceived their accuracy.

AND THE LOAYEE ANIIvIALS.

153

it secretes_, spreads out in the form of a wide disk_,
f<.rid connects it firmly to its future liome.^

The young* Aureha changes its form and mode of
hfe simultaneously. It becomes elongated rapidly ;
its foot-stalk is narrowed^ and its free extremity
assumes a club -like form. An opening soon presents
itself in the centre of this extremity and exhibits an
internal cavity ; four small projections or papilla
appear upon its border_, and in process of growth are
converted into as many tentacles ; and gradually
others appear also_, and are completed in their turn.
In fact^ the infusorian is transformed into a polyp ; and
it is this which Saars first described under the name
of Scyphistoma.

In its polypoid condition the Medusa exhibits all
the characters and properties of the real polyps. It
is propagated both by buds and stolons.-f Occasionally
the buds produced upon a portion of the body soon
reproduce individuals like the parent ; in other in-
stances they give rise to a slender stem^ which trails
along the ground for a certa^in distance and develops
little tubercles_, which in their turn will become scy-
phistomse^ all resembling as many shorty wide-mouthed
trumpets^ whose borders are furnished with from
twenty to thirty slender moveable filaments. Each of

* I have merely given Saars's opinion ; but it is more probable
that this quasi-mucus is a true sarcodic expansion, analogous to
those observed in the development of many other inferior animals,
even of sponges.

t Stolons or shoots are terms applied to those slender branches
of a plant, which starting from the bottom of the stem, grow out
latereJly to some distance and then taking root produce a new
individual. The strawberry plant affords a very familiar instance
of this mode of multiphcation.

154

METAMOEPHOSES OF MAN

the beings thus produced performs the same functions
as its parent_, and gives rise to other generations ;
thus rapidly increasing the size of the whole colony.
The process is just that which we see in a strawberry
plants throwing out its slender runners in every
direction, which_, becoming contiguous^ eventually
produce an entire border of new plants.

The Medusa lives for some time in this condition^
but^ in course of time^ one of the trumpet-shaped
bodies becomes three or four times as long as its
fellows_, and assumes a cylindrical form. A single
circular depression is then seen, immediately below
the crown of tentacles ; this is quickly followed by
others_, till at length the entire stem is marked at
intervals almost to the very foot- disk, which, how-
ever, remains intact. The body of the polyp con-
sists now of a series of rings, from ten to fourteen in
number.

These rings are smooth at first, but after a while
their inferior borders are festooned; these festoons
then become more marked; and, finally, the angles
are drawn out, and they are converted into eight
little leash-like organs, bifurcated at their extremities.
At the same time, the intermediate grooves have gone
on deepening, till they have extended almost to the
central axis of the polyp. The latter at this period
resembles a pile of little plates, whose edges are
deeply cut and very flat, and which are attached to
each other by their centres. The scyphistoma has,
so to speak, cut itself up into slices. It is to this
stage in the life of the Medusa, that Saars gave the
name of strobila, and we see that the Norwegian
naturalist^ s mistake was a very pardonable one.

AND THE LOWER ANIMALS.

155

Althougli still iinperfect_, yet wlien tliey reach tMs
condition of development^ the divisions of the strobila
show unequivocal signs of individualization. Each
of them moves its own fringed border separately^
and if a single one be touched^ it alone will contract.
In order that all these divisions of the former animal
may become as many distinct individuals^ it is neces-
sary that they separate ; and this they speedily do.
The topmost one^ that which bears the tentacles
of the scyphistoma_, is first detached^ and those which
succeed it are similarly removed_, and swim away
through the water after the manner of acalephs.
They are now medusoids, but not yet aurelias^ and
Saars very fairly compared them to the species of
another genus — the eight-rayed ephyra [Eijhyra
octoradiata) .

Neither the form nor the oro*anization is what it
will be eventually, but the larvge are soon fully de-
veloped. At first flat, as above described^ they now
become more and more convex on one side and
concave on the other ; the gastro -vascular canals
make their appearance ; the mouth is opened and
surrounded by its tentacles ; the marginal cirrhi
present themselves, at first few in number, but after-
ward more numerous, and the reproductive organs,
male and female, are formed in separate individuals,
and soon commence the performance of their functions.
Finally, instead of a solitary infusorian, or of a more
or less branched scyphistoma, or of a strobila more
or less segmented, or^ even of a swarm of Epl Lyras,
we perceive numbers of red aurelias, exactly like that
which laid the primitive ovum, but was unable to
reproduce itself directly.

156

METAMOEPHOSES OF MAN

What would our readers think were we to express
ourselves thus : — A butterfly deposits an egg, from
which springs an earthworm that is soon converted
into a caterpillar; from this caterpillar a series of
buds are produced which become so many individuals
like the first one ; then each of these^ although pre-
serving the cater]3illar head^ assumes the body of the
chrysalis ; this body is constricted at intervals, and
gradually becomes converted into a cluster of
butterflies, piled up one upon the other; the cater-
pillar head then falls off, and the butterflies fly away
one by one. At first they resemble moths ; but by
degrees they assume their true characters, and become
beautiful diurnal Lepidoptera. Who would put any
trust in a history which described a series of trans-
formations as fantastic as those seen in a dream?
Yet change a few of the expressions, employ the
terms Acalephae and Medusa for those of insects and
butterflies, and that which but a moment before had
been mere fiction becomes simple truth.

AND THE LOWER ANIMALS.

157

CHAPTER XY.

liEW EXPLANATION OF EACTS LONG KNOVrN.

It is necessaiy^ before proceeding furtlierj to designate
the different phases of the successive mnltiplication
we have been describings by general terms_, analogous
to those of larva, nympli, and perfect insect , employed
in the description of true metamorphoses. These
principal phases are three in number. In the first
instance_, the egg gave rise to a simple being-^ an
individual having neutral characters ; that is to say^
being neither male nor female ; at a later period we
observed a compound being, quite as neutral as the
first, and each part of which was capable of carrying-
on an independent existence ; finally, we saw these
parts detached, and assuming the organs characteristic
of the sexes. M. van Beneden, a Belgian naturalist,
to whom we shall have to allude frequently, was the
first to distinguish these three stages, and to apply
separate names to them.* We shall gladly adopt his
nomenclature.

Thus, vre shall apply the term scoJex to the ani-
malcule which springs from the egg of the Medusa,
or of any other species which is reproduced by
analogous processes. Giving a more extended sig-
nification to the word strohila than that employed by

" Eecherches snr les Vers cestoid.es," 1850. "La Generation
alteniante et la Digenese," 1854.

158

METAMORPHOSES OF MAN

Saars^ we shall designate by it all tlie compound
beings wliicli proceed from tlie scolex^ and are
destined to give rise to isolated individuals. Finally,
borrowing Dujardin^s expression_, jproglottis, wiiicli
lias been used by him in almost a similar sense_, we
sliall apply it to tlie individual wMcli proceeds from
the strohila, and which_, acquiring true reproductive
organs, thus completes the circle.

We saw that from the Aurelia there was produced
a scolex, which at first exactly resembled an infusorian,
and afterwa.rds assumed the polyp form; and that
whilst in this condition it gave rise by gemmation
to other polyps like itself. Hence, we find that there
are several generations intercalated as it were between
the primitive scolex and the strobilse, which are
produced by it ; and, moreover, that these generations
are not always similar. It sometimes happens that
an individual which results from gemmation difiers
in many respects from its parent, or is even quite
unlike it; just as might occur if a hairy caterpillar
were budded from a smooth- skinned one. In this
case, the first form is tevmedi jprotoscolex,'^ the second
deutoscoleXjf and so on; Greek compounds being
employed to designate the numerical order of the
generation. J

* Signifying yirsi scolex.
t Signifying second scolex.

J Van Beneden, retaining the term scolex for the generation
which produces the strohila, applies in certain cases the term
proscolex to the race which precedes it. Hence there occasionally
arises some slight confusion in the description of the phenomena.
The simple rule which I suggest the adoption of, is merely a slight
modification of the Belgian naturalist's views, and does away with
the difficulty. M. ISIoulinie, in his splendid work on the Eiido-

AND THE LOWER ANIMALS.

159

We may regard tlie reproduction of the Aurelia
as typical of the group^ although in regard to the
number of the phenomena which it exhibits^ it holds
a median rank. There are far more complex and
far more simple forms^ but characters of plus or
minus do not alter the real nature of the process of
development.

Without inquiring into their precise signification^ we
may now indicate two important facts which bear upon
those which precede them : firstly^ each egg of the
Medusa_, instead of producing a single fertile animal,
as is the case with that of the butterfly^ gives rise to
several individuals; and secondly, this production
takes place 'mediately ; for between every two genera-
tions of Aurelia many races of dissimilar beings are
produced by gemmation.

To speak in a more general manner, v^e have
here the production of several generations, through the
medium of a single germ. This is, to my mind, the
fundamental fact which rules all the secondary pheno-
mena. It is this which I have endeavoured to convey
in the term gcneagenesis, which is applicable to all forms
of reproduction that possess this essential character.

If with the foregoing history of the Aurelia we

'parasitic Trematodes, rejects Van Beneden's nomenclature, and
employs the words embryo, nurse, and larva. In this particular he
agrees with the editor of the " Bibliotheque de Geneve," who
deprecates the change I have made in Steenstrup's nomenclature.
We shall see further on, that as this nomenclature conveyed ideas
which I considered inexact, and was out of keeping with the view
I took of the entire phenomenon, it was necessary to alter it.
Moreover, in adopting the expressions proposed by Van Beneden,
I think I have once more shown how little anxious I am to intro-
duce new terms into science.

IGO

METAMORPHOSES OF MAN

associate those of tlie Hydra, the plant-bugs_, and the
biphor^, and if we add the results of recent dis-
coveries to those of older ones, we shall see that the
phenomena of mnltiplication, which at first seemed
exceedingly unlike each other, assume a sort of rela-
tionship, and form a somewhat natural group. This
relationship was first made known by a Danish
naturalist in a work which has been justly celebrated.
By the publication of his treatise on " The Alternation of
Generations,^^* Steenstrup did good service for natural
science ; and although we do not share all his opinions,
and even occasionally take quite an opposite view to
those he has put forward, nevertheless we accord him
full praise for all that is valuable in his researches.

We have already seen that Bernard de Jussieu was
the first who discovered the Hydra^s eggs. His suc-
cessors, looking on this form of reproduction as useless
to an animal which was propagated both by buds
and by fission, regarded these ova as pimples which
resulted from some disease ; in fact held that the Hydra
possessed no organ comparable with an ovary. These
germs were secreted, so to speak, by the very walls
of the body. Upon some portion of the body, and
usually when buds have appeared, the skin is pushed
out in the form of a cupel : in this spot the elements
of the egg are gradually accumulated, and become
surrounded by a sort of shell or covering furnished
with bifid spines. The skin next bursts, and the
ovum thus expelled attaches itself to the nearest body.

* "Ueber den Generationswechsel, oder Fortpflan/Aing und
Entwickeluiig durcli abwecliselende Generationen," 1842. This
work, to which we shall allude in the next chapter, was translated
into English for the Ray Society hj Mr. George Busk, F.R.S.

AND THE LOWER ANIMALS. 161

This mode of reproduction was first pointed out by
Ehrenberg, the distinguished Berlin niicrographer^^
who afterwards discovered the zoosperms also of these
animals. The Hydra^ then^ is hermaphrodite^ and pro-
pagates both by ova and buds. But — and this is a
fact of the utmost importance — the buds are always
produced firsts and the Hydra perishes as soon as it
has produced ova. Thus^ there springs from the
Hydra^s egg a simple individual — a scolex — capable
of producing many others like itself^ and which can
also push out buds_, but which ends as the parent does^
by assuming the sexual attributes.

It is the same as if a butterfly^s egg gave rise to
an animal having all the external characters of the
perfect insect^ but devoid of reproductive organs,
having the power of producing by gemmation other
beings resembling itself, which, like it, would be
capable of acquiring at a later period the male and
female generative bodies.

Here we observe geneagenesis in its simplest form,
deprived of all accessory circumstances, and of all the
complications which result from change of form. The
several generations of scolex are exactly similar, and
each scolex is directly transformed into a lyrorjlottis, the
strohila stage being entirely absent. The very sim-
plicity of the process shows what is really its most
fundamental part — viz., the production of several
generations from a single germ.^

The compound ascidians show us something ad-
ditional.

In these the ovum develops a scolex, which becomes
fixed, acquires well-marked reproductive organs, and

* " Die fossilen Infusorien," 1S37.
M

162 METAMORPHOSES OF

gives rise by gemination to a series of new and
equally perfect individuals. In this instance tlie
scolex is directly converted into tlie proglottis^ wliicli
in its turn produces on all its sides an entii^ely new-
generation of individuals wliich. resemble itself. There
are^ liowever_, well-marked distinctions between these
two phases of development.

Employing the same comparison adopted before^
we should say in this case^ that the butterfly^ s egg
produced^ first^ a caterpillar, which reached the final
condition ; then, from the butterfly which was thus
formed, others like the first were originated by bud-
ding, and the former was neither the father nor the
mother of the latter, but simply the parent.

A somewhat more complex state of things takes
place among the aphides.

The ovum which is deposited in autumn gives rise
to a scolex having nymphal characters; and this
nymph produces no eggs during the summer, but
develops, instead, a number of genuine buds, which are
matured and organized in the interior of the body,
and not upon the external surface, as in the Hydra or
Aurelia. As soon, however, as the temperature of the
air becomes lower, the generative organs appear in
separate individuals, and we then find males and
females, or in other words true proglottides.^

According to M. Heiden's published observations, an apliis
after having produced, agamically, and during the whole summer,
individuals like itself, can in the end of the season assume the
sexual characters. In other words, a scolex may be transformed
into a proglottis. The conclusions draA\Ti from this fact regarded
as entirely new, are exaggerated. This transformation does not at
all alter the character of the phenomenon, especially when it is
viewed from our stand-point. Leydig, in a very valuable essay in

AND THE LOWER ANIMALS.

163

TMs is^ as it were^ tlie liistoiy of a butterfly^s egg,
from whicli sprung a chrysalis capable of producing,
by internal gemmation, first several generations of
beings like itself, and then a certain number of butter-
flies. Here, then, are several generations of scolex;
the strobila stage, as in the preceding cases, is
wanting, and the proglottis is sometimes, even during
its whole lifetime, like the scolex,* but at others
differs from it in certain particulars already re-
ferred to.

This analogy between the external forms of the
scolex and proglottis in the same species, renders
it occasionally difficult to distinguish between the
various phases of geneagenesis, and, as it were, masks
the phenomenon. The process is more clearly seen
among the biphorge, where the physiological laws are
in some measure indicated by the existence of per-
ceptible characters.

This subject has been investigated by many natural-

the " Zeitschrift fiir wissenschaftliche Zoologie," 1850, on the earlier
phenomena of development, was led to confound, so to speak,
reproduction by ova with reproduction by fully-formed individuals.
His view was opposed more or less clearly by Siebold, Owen,
V. Carus, and Dr. Burnet, and in a more direct manner by Lub-
bock " On the Double Method of Reproduction in Daphnia " — Philo-
sophical Transactions, 1857, — and Leuckart, " Zur Kenntniss des
Generationwechsels und der Parthenogenesis bei den Insecten ; "
Moleschott's " Untersuchungen," 1858. Professor Huxley's admir-
able memoir " On the Agamic Reproduction and Morphology of
Aphis — Transactions of the Linnean Society, 1858, — in which he
has not only summed up, but completed all the preceding researches,
leaves this subject settled beyond doubt. We shall discuss aU
these questions further on.

Bonnet has observed wingless individuals which performed
the same functions as those with wings, and gave unequivocal
proofs of sexuality.

M 2

164

METAMOEPEOSES OF MAT^

ists since Cliamisso^s time, and among otiiers by
Escliriclit of Copenhagen, wlio has given ns a remark-
able anatomical work, in wliicL. the very important
fact is establislied, that the chained salpse are united
in colonies from the earliest period of their embryonic
life.* Unfortunately, Eschricht^s observations were
confined to specimens preserved in spirit, and the
credit of clearing up this history, which was for
a long while considered fabulous, is due to two
naturalists, the one an Englishman, the other a
German. Thanks to the researches of Krohnf and
Huxley, J we can now assert that among the biphorse
there is an alternation not only of form and of mode
of life, but also of mode of reproduction. As the result
of their united observations, it may be stated that the
compound or aggregated biphora3 are hermaphrodite,
find deposit eggs only, from which spring isolated
biphorse. These latter are neuters, and produce, by
internal gemmation only, a series of aggregated
biphorge. Here we have, strictly speaking, no strobila,
and there is but a single generation of scolices which
produce directly a series of proglottides that remain
united for the rest of their existence. §

* " Anatomisk-Physiologiske Undersoegelser over Salperne,"
1841. I am acquainted witli this work only through various
extracts from it, given by other writers.

t "Memoire sur la Generation et le Developpement des Bipliores.'
— Annales des Sciences naturelles, 1846.

X " Observations upon the Anatomy and Physiology of Salpa
and Pyrosoma." — Philosophical Transactions, 1851.

§ It was shown by Eschricht, that the chain salpcB are developed
upon a sort of stolon situate in the interior of the isolated forms.
This might fairly be regarded as a kind of strobila produced by
internal gemmation, and concealed witliin the scolex.

AND THE LOWEE AJJIMALS.

165

Among tlie bipliorae^ tlieii_, we have the same state
of tilings as if a butterfly's egg gave birtli to a cater-
pillar_, from which sprung a string of butterflies
soldered to each other_, and flying about without being
able to separate.

We may here repeat^ that Peysonnel_, Trembley,
Bonnet^ and Chamisso were ignorant of the entire
importance of their discoveries. Their observations
were made on animals too far removed from each
other to admit of even a suspicion as to their mutual
relations. Besides_, they were too isolated_, and were
not sufiiciently numerous for comparison^ so that it
became impossible to distinguish the essential phe-
nomenon from others which^ although more apparent_,
were not the less accessory.

The problem could alone be solved b}^ modern
science^ and now the reader is in a position to per-
ceive that these various forms of reproduction^ although
apparently so very dissimilar_, have yet very much in
common. As we stated before^ we alwa^ys find that a
single germ enclosed in a soHtary ovum may give rise
to several individuals_, even to several generations. It
is only of late years that the discoveries were made
which established the generality of this law. They
embrace the various groups of the lov^er animals^ and
mark a new epoch in the history of the subject which
should be separp.tely considered.

166

METAMOEPHOSES OF MAN

CHAPTER XVI.

GENEAGENETIC PHENOMENA IN ANNULOSA AND
MOLLUSCA.

HiTHEETO I have been endeayouring to show how the
knowledge of geneagenetic phenomena was gradually
arrived at. It now remains for me to explain^ or
rather to describe^ how these apparently exceptional
phenomena are referable to the most general laws in
the scientific scheme. Bnt_, before touching on the
theoretical portion of my subject^ it is necessary to
bring forward a certain number of examples^ in order
to justify conclusions which are occasionally different
from those that some of my distinguished colleagues
have drawn from the same premises. These examples
are especially interesting. We find in them the defi-
nitive solution of perhaps the most debated question
which has ever engaged the attention of philosophers
and naturalists.

It has been already seen that geneagenesis becomes
more and more complex as we pass from the Hydra to
the Aurelia^ and since facts of a similar character
are multiplying and presenting peculiarities which
are every day assuming more varied features^ it
becomes necessary for the purposes of study to
arrange them in certain groups. This is what has
been done by Van Boneden^ who proposes to dis-
tribute them among five sections. We shall adopt

AND THE LOWEE ANIMALS.

167

Ms plan_, just making a few trivial alterations^^ and
shall regard eacL. one of the foregoing examples as
characterizing^ by the nature and succession of its
developmental phases^ one of these five groups. In
the first section we shall place the Hydra, and all
animals, no matter what their position in the zoologic
scale, which propagate in a similar manner; in the
second we shall rank the compound Ascidians ; in the
third the Aphides ; in the fourth the Biphorse ; and
in the fifth the Aureha.

It is necessary, too, that in each of these sections,
the process of geneagenesis shall alv/ays take place
identically. In proportion as we obtain an accurate
knowledge of these strange phenomena, we observe
that each phase of development is in almost every species
accompanied by different and occasionally quite un-
expected peculiarities. Since it would be impossible
here to describe all the facts in connection with this
subject, we shall limit ourselves to a resume of the
more curious ones which are presented to us by the
principal groups of the animal kingdom ; and we shall
follow the zoological scheme, without confining our-
selves closely to Van Beneden^s classification. In
taking this course we shall only be acting consistently
with the plan pursued in other portions of this volume.
Besides, we shall by this means expose a result of
much importance ; we shall show how the phenomena
become progressively more complex in proportion as

111 the work in which he proposes these divisions, " La Ge'ne-
ration alternante et la Digenese," Yan Beneden places under the
third section animals which in my opinion belong to the second.
He places the aphides last, although their geneagenesis is far more
.simple than that of either the Medusae or the intestinal worms.

IGS

METAMORPHOSES OP MAN

we descend in the scale of beings^ as tliougli ISTature
were compelled hy the very simplicity of tlie organisms
to multiply the means necessary to ensure repro-
duction.

In tlie outset we may state that no vertebrate
animal is reproduced by geneagenesis^ and that this
form of reproduction is very rare among highly
organized invertebrates. In the insect class_, where
the species number a hundred thousand^ very few
examples beyond those of aphides are known.*
About the most remarkable^ is that of one of the
hymenopterous family Pteromalidge {Opliionurus),\
which was discovered by Dr. Philippi. This insect^
like many of its kindred^ deposits its ova in the egg*

* I agree with Owen, Steensimp, Van Beneden, Carus, &c.,
in considering the agamic reproduction of aphis to be due to a
process of internal budding. It has been proved by the researches
of these naturalists that the reproductive bodies which are developed
during summer in the wingless aphides are simple deciduous buds.
Leydig, a German naturalist well known through his important
writings, believed he had satisfied himself that these bodies are
genuine eggs which are hatched within the mother's oviduct. If
this view were correct, the aphides would be ovo-viviparous, and it
would be no longer a question of geneagenesis but rather of par-
thenogenesis, which we shall treat of hereafter. But this opinion,,
which seemed to support Heiden's observations, to which we
alluded some few pages back, was refuted by the new and very
accurate researches of Leuckart, Lubbock, and esjMcially of Huxley,
which will be discussed further on.

t " Annales des Sciences naturelles," 1851. The order Hymen-
optera includes all insects akin to the bee and which are provided
with four membranous wings, and the Pteromalidce constitute one
family of this order. Philippi's observations were at first con-
tested, but he afterwards confirmed them by a series of new re-
searches, in his " Troisieme Memoire sur I'llistoire genesique des
Trematodes." — Memoires de I'Academie des Sciences de Turin^
1857.

AND THE LOWER ANIMALS.

169

of a small coleopteron* {Rliyncliitcs hetuleti), whiclidoes
considerable damage to the vine plants by gnawing
the buds, and rolling up the leaves, in order to
deposit its eggs in them. From the egg of
Ophionurus there is developed an infusoria-like
animal, which is transparent, has an almost homo-
geneous structure, presents posteriorly a few bristly
segments, and is possessed of a long tail, which it
whisks about with rapidity. In the interior of this
false larva there is slowly developed a sort of double-
jawed worm, which eventually entirely occupies the
place of the first animal, and then bursts from the
species of case formed by the skin of its parent, and
changes into a nymph, which will soon become a
perfect insect. This is an instance of the simplest
kind. The proglottis is directly ^Droduced by the
scolex, but it reaches the perfect condition only
through a metamorphosis.

Associatino; this fact with what occurs amono; butter-
flies, we may say : From the egg there sprung a naked
caterpillar, which produced a hairy one, by a process
of internal budding, and this was then transformed
into a chrysalis and afterwards into a butterfly.

Of the four classes included in the articulate division
of the Annulose sub-kingdom, only two — insects and
Crustacea — are reproduced by geneagenesis ; and even
among the latter the only example known is that of

The Coleoptera, commonly called beetles, have a single j^air
of membranous wings, which are covered when at rest by the
horny elytra.

[Philippi has since altered his opinions, and now regards the
peculiar development of Pteromalus as an instance of hypermeta-
morphosis rather than of development by nurses, as Steenstrup
believed. — Tr.]

170

METAMORPHOSES OF MAN

Daplmia.* Notliing of the kind has been yet observed
in the Myriapoda_, Arachnida^ or Cirrhipedia.

On the other hand^ this phenomenon has been
observed in many worms — that is to say, among the
inferior annulosa. Apart from the helminthes, whose
history deserves to be treated of separately, we find
it among the anneHds, nemertes, and the naides —
small aquatic beings related to the earth-worms.

Greneagenesis assumes peculiar features in each of
the groups which I have enumerated. It was known
for a long while under the name Jis sip arous generation,
or fissiparity . In this process, the animal divides
itself into two portions. In certain . planarige and
naides, this division takes place without any apparent
preparation, and each isolated portion produces either
a head or tail, as the case may be, by gemmation. The
animals thus produced are for several generations
neutral like the parent ; but eventually, through the
operation of conditions of which we are as yet
ignorant, the sexes are developed, and the being is
propagated by ova. Almost the same thing occm^s
in a little nemertes which I have often found in
the outskirts of Paris ; but in it the young being
always acquired its head before quitting' the parent.

It is similar with Myrianis and Syllis. In these
annelids, the creature which has been thus spon-
taneously created, grows from between the final and

* The origin and development of Daphnia's reproductive bodies
have been well described and with considerable detail by Mr. John
Lubbock in his excellent " Account of the two methods of repro-
duction in Daphnia, and of the structure of the Ephippium" —
Philosophical Transactions, 1857. I shall examine his conclusions
in another chapter.

AND THE LOWEE ANIMALS.

171

penultimate rings of the parentis bod}^ In the first
there may occasionally be seen as many as six indi-
viduals placed end to end, forming a sort of chaplet_,
the string of which is represented by the intestinal
canal which travels from one to the other. ^ In Syllis_,
I have never found more than one solitary individual ;
but to compensate for this_, it has very important
functions to perform ; it alone is either male or female,
whilst the parent is simply a neuter. f

Returning to the simile we have so often employed,
we should say here of the butterfly, that its egg pro-
duced a single caterpillar, which gave rise by spon-
taneous division to new individuals ; but that these
were in some instances a series of caterpillars like the
first one, and of which a certain number sooner or
later became perfect insects, and in other cases were
fully-formed butterflies, that remained for some time
attached to the parent, and kept flapping their wings
in order to effect their escape, which they did sub-
sequently.

In regard to the Molluscan sub -kingdom, there is
little to be said. 'No true mollusk presents any of
the phenomena we are now considering. In MoUus-
coida, on the contrary, geneagenesis appears to be
the rule. As all these animals are more or less akin
to the Ascidiae and Salpse, we might expect that
their mode of reproduction would be analogous ; and
such a supposition is fully borne out by what is
known of their generative processes.

" Memoire sur rEmbryogenie des Annelides," by M. Edwards,
in the " Annales des Sciences naturelles " for 1845.

t "Memoire sur la Generation alternante cbez les SyUis." — ■
Annales des Sciences naturelles, 1844 — " Eambles of a Naturalist."

172

METAMORPHOSES OP MAN

CHAPTEE XVIL

GENEAGENETIC PHENOMENA OF EADIATA.

The three classes — Ediinodermata (sea-urcliins^ &c.)_,
Acaleplige ( jelly-fisli), and Polyps — whicli collectively
constitute the sub-kingdom Eadiata, require to be
very fully treated, in order to give a detailed account
of the varied and complex phenomena presented in
their reproduction. Genea genesis is seen here in all
its phases ; and as in many other instances_, so in this
one, the study of embryogeny, by disclosing unex-
pected results, put the history of these beings in an
entirely new light, and modified received opinions in
many particulars. We have spoken of the Hydra and
Aurelia already, and we shall now mention some
additional facts in support of this assertion. As an
example, we shall select from the arborescent^
plant-like polyps which cover our rocks and sea-
weeds, the pretty Cam])anular{a geniculatcij w^hose
strange development has been so patiently watched
by Lowen ; * but we shall now and then explain the
results arrived at by the Swedish naturalist,t through
the assistance of Steenstrup^s writings and those of
his followers.

" Observations siir le Developpement et les Metamorphoses des
genres Campanulaire et Syncorne." This work, which was first
published in Swedish, was afterwards translated into French and
German. — Annales des Sciences naturelles, 1841.
t " Uber den Generationwechsel."

AND THE LOWER ANIMALS.

17S

From the egg of this Campanularia there springs a
cihated larva^ which attaches itself to a sohd body,
becomes flattened, and then resembles a little cake,
which has a cavity hollowed in its substance. In the
centre of this, granulations make their appearance,
and gradually increase in size, elongate, and are con-
verted into a straight hollow stem, which is soon
covered by a transparent horny sheath. The current
which traverses the internal canal of the stem accu-
mulates the granules at the extremity of this latter,
and develops a true bud, which becomes organized,
and assumes the form of an inverted bell, closed at
its orifice by a horny membrane. The organized
material is soon detached from the inner surface of
this structure, and converted into a sort of conical
button, from which tentacles are pushed out. Finally,
in the centre of this mass there appears an orifice,
which eventually constitutes a mouth like that of
Hydra. The first polyp is then complete, and, bursting
through the membrane, it grows out like a flower
which has unfolded its floral envelopes.

This primary polyp is invariably both a nurse and
neuter, and its office is to provide food for itself and
the future members of the community. These soon
present themselves, at first in the bud-form, but after-
wards, undergoing the same changes as the first, they
constitute an entire colony, which is by no means
unlike a little zigzag plant, to whose angles are
attached short stalks bearing these food - seeking
polyps.

In the axils of the branches there now appears a
new series of buds. These buds are at first like the
former, but they are attached to a much shorter foot-

174

METAMOEPHOSES OF MAN

stalk, and they grow to a far greater size. Tlie
vesicle vfliich results from the development of one of
tliese_, is five or six times as large as those above
described, and is traversed from end to end by the
living tube which enters into all the ramifications of
the polypidom. In the covered species it is upon this
axis that the reproductive ijolyps are produced, which
ensure the perpetuation of the species.

Each of the new productions presents within it,
even on its first appearance, one or two well-marked
ova; these grow jjciri ijctssii with the original, and
become converted into as many ciliated larvae. As
soon as they have reached a certain development, the
polyps burst the capsular membrane and appear ex-
ternally. They then resemble medusa, minus the
digestive apparatus, which they do not require, as
they remain in communication with the vital portions
of the polypidom, and thus derive nutriment from
the materials drawn in by their long-tentacled
brethren; besides, their lives are extremely short.
The larvae soon found new colonies at a distance ;
and now that their functions have been performed,
the polyp mothers fade away, and are gradually
resorbed.

Although there appears little analogy between the
phenomena presented in the development of Cam-
panularia and Aurelia, yet there are very close rela-
tionships between them.

In both cases a ciHated larva or scolex is produced
by the ovum. It happens, however, in Campanularia,
that the first polyp is the result, not of a process of
metamorphosis, but of one of budding, which produces
a being very difierent from that which preceded it.

AND THE LOWER ANIMALS.

175

Here^ then, there is a second generation of scolex — a
deuto-scolex — which multiphes under its new form of
campanularia. The resulting polypidom is in some
measure a compound deuto-scolex, which develops a
strobila_, represented by the capsule containing the
reproductive bodies. Finally^ the latter^ plus the ova
in their interior, are the proglottides_, and correspond
to the small medusoids which are transformed into
Am'eli^_, or even to Aurelise themselves. There
is this distinction_, however, between the two : the
reproductive bodies of Campanularia are fixed to the
polypidom, whilst those of Aurelia are free and
floating, and lead an independent existence.

The analogies we have attempted to establish may
appear questionable to those who are unacquainted
with the whole of the facts ; but a perusal of the
vf orks of Ehrenberg, * Krohn, Kolliker^ Dalyell^
Dujardin_,t and Derbes_, will leave hardly any room
for doubt. By studying Yan Beneden^s splendid
memoirs on Campanularia and Tubularia J — not-
withstanding the errors in determination which the
author has since corrected — it will be seen that
facts which are apparently devoid of analogy are
associated undeniably by a host of intermediate
ones.

It is very necessary, in a study of this sort^ to
point out^ in the commencement, the circum-

" Corallentliiere des rotheii Meeres," 1834.

■f " Memoire siu? le Deveioppemeiit des Meduses et des Polypes
Hydraixes."- — Annales des Sciences naturelles, 1845. The chief
results of this admirable memoir have been detailed in my
" Kambles of a Naturalist."

;|: " Memoires de T Academic de Bruxelles," 1843 and 1844.

178

METAMOEPHOSES OF MA^^

stance of extreme variety in the plienomena ex-
hibited.

In the case of the lower forms of animal life, Kature
seems, as it were, to despise that uniformity in
embryogenic laws which is so characteristic of the
development of the higher groups. We find the
most decided differences between the developmental
processes of even species of the same genus. Thus,
according to Lowen, the medusoid proglottis of one
campanularia remains attached to the polyp which
gave it birth ; whilst it is stated, on the authority of
M. Desors, that in another species — the gelatinous
Campanularia — it bursts the reproductive capsule ou
arriving at the same condition, and swims about
freely, undergoing its metamorphosis in the sur-
rounding water.* It was also observed by the same
naturalist, that some of the polypary^s branches pro-
duced only male, and others only female, repro-
ductive bodies. In fact, the greater the advance made
in the field of discovery, the larger the field appeared
to be, and the greater the number of new points
of view which it presented. We shall now endea-

* " Lettre sur la Generation Medusipare des Polypes hydraires."
— Annales des Sciences naturelles, 1849. I am sorry that I cannot
quote some of the passages from this memoir, especially those
regarding the difference between the author's observations and
those of Saars on the development of Aurelia. Desors saw the
proglottis (the fully-formed Medusa) produced by gemmation from
the interior of Scyphistoma (the Medusa in the hydroid state), and
lifted up in piled form, from the mouth of the polyp, which
remained, after entire separation of the proglottides. As the
matter is one dependent on plain observation, it seems to me that
both naturalists may be right, and that these differences may be
adequately explained by supposing a difierence of species.

AND THE LOWER AXIMALS.

177

TOur to place our readers in a position to observe
some of them.

From the preceding remarks we may concKide that
the relation of polyps to acalephs is far more intimate
than it was thought to be fifteen or twenty years ago.
The most recent researches tend still more to break
down the formerly established distinction between the
two classes. For example : —

Among the strange creatures which inhabit the
ocean may be mentioned the name of Stephanomia.
This is actually a living garland of animals; it has
flowers like the most lovely enamel, and filaments like
crystal, which are attached to a transparent stem,
surmounting a vesicle filled with air, that plays the
part of Si float. This strange being may be regarded
as the type of Cuvier^s group of H]/drostatic acalepliSy
a group which was afterwards styled SiphonojyJwra by
the German naturalist Escholtz. Zoologists were for
a long while in a state of doubt regarding the nature
of these being's. Yooft* and Leuckart.t who were led
back by a careful investigation to the views of the dis-
tinguished naturalist traveller Lesueur, put forward the
view that they were compound polyps ; and this idea
has been fully confirmed by the writings of Huxley, J

* " Ocean und Midlmeer," 1848.

t " Meinoire sur la Structure des Physalies et des Siplionopliores
en (general," 1851, also in the "Annales des Sciences naturelles,"
1852. This — Lenckart's first memoir — related to animals which
had been preserved in spirit. He has since completed and extended
his researches in a new memoir, which forms part of his " Zoolc-
gische Untersuchnngen," 1853.

^ " On the Structure of the Acalepha?." — Philosophical Trans-
actions, 1851.

N

178

METAMORPHOSES OF MAN

KoUikei^* Gegeiibaur_,t ^i^^ Yogi ;X ^'^^"^^ ^7 o^i* own
researches also.§

Hence we sliould expect to find tlie different forms
of reproduction^, before described^ occurring among tlie
Siphonopliora ; and sucli in fact is sliow^n to be the
case_, by the series of investigations we have just
referred to. There we observe geneagenesis in its
most complete and varied forms. Yet its final term
is almost always a medusiform animal^ sometimes
long-lived^ sometimes shorty with an organization
frequently of a very simple character_, but occasionally
more complex; in some instances free and floating,
as in the Aurelia^ in others fixed, as in the case of
Lowen^s Campanularia, and which alone assumes the
sexual attributes, male and female, and reproduces
itself by ova. We conceive it to be useless to intro-
duce the analogy we have so often employed, and to
contrast that which occurs among the Siphonophora
with the simple metamorphoses of the Lepidoptera.

Looking at this multiplicity of phenomena, all
coming- within the same scheme, one might feel
inclined to believe that geneagenesis, in spite of all
the complications to which it is liable, is a general
law for all the groups we have named ; that all polyps
spring from a medusa, and all medusas originate in
polyps which have reached their final condition of
development. But — and we cannot repeat it too

* " Die Schwimpolypen oder Siphonophoren von Messina,"
1853.

f " Beitriige zur niihren Kenntniss der Schwimpolypen," 1854.
" Eeclierches sur les Animaux inferieurs de la Mediterranee,"
first memoir, on the Siphonophora of the Sea of Nice, 1854.

§ Memoire sur I'Organisation des Physalies." — Annales des
Sciences naturellcs, 1854.

AIS'U THE LOWER ANIMALS.

179

frequently — it is necessary to institute many investi-
gations before generalizing, in regard to tlie lower
forms of animal life. It lias been shewn b}^ Krolin
and Lacaze du Thiers, that certain medusas and
polyps are reproduced directly, and by a simple
metamorphosis. The first proved that the larva of
Pelagia nodiluca becomes an acaleph without assum-
ing the polyp form and it was demonstrated by the
second, that neither the sea-anemones, nor corals and
their kindred, give rise to medusae. f When science
is concerned, well-proven exceptions are as valuable
as the discovery of a new series of geneagenetic
phenomena.

Leaving the Medusae and Polyps, we come to a
group of beings whose real nature is still somewhat
involved in obscurity — the Infusoria and Sponges,
united under the name of Protozoa. Here again we
meet with geneagenesis. Unfortunately, the obser-
vations which it is necessary to make in following
an animal through the progressively complex phases
of its existence, present in this instance many
difficulties, which, in consequence of the extreme
minuteness of the creatures to be investigated, are too
frequently insurmountable. Nevertheless, we shall

* " On the earliest stages in the Development of Pelagia
noctiluca." — Annals of Natural History, 1856.

t " Comptes Rendus de rAcademie des Sciences," 1859 and
1861. In the sea-anemones there is but a metamorplwsis proijevhj
so called. The ciliated larva} are transformed into perfect animals,
and each of them proceeds from a single egg and produces but one
individual. In the coral, the ciliated larva gives birth to an
entire colony. In this case then, there is geneagmesis, but the
phenomenon is reduced to its simplest condition, since the colony
produces directly both eggs and larvae.

180

METAMORPHOSES OF MAK

endeavour to separate tlie general and best-ascertained
results, from the cliaos of numberless contradictions
presented by the writings of those most distinguished
in this branch of study.*

The sponges are truly compound animals, although it
would be very difficult if not impossible to distinguish
a single individual. These beings, whose position is
still regarded by some naturalists as problematical,
possess a framework which is either horny or cal-
careous, and is frequently represented by a network
of simple spines or spicules. There is spread over
this form of skeleton, a sort of organized varnish or
coating'^ which extends to the very smallest rami-
fications. This varnish is really the living matter which
constitutes the animal ; and each species, although
having the elements common to all, is as variable in
form and proportions as a polyp colony.

Like the latter, the sponges can be reproduced
both by gemmation and fissuration. Grant^sf obser-

Notwithstanding the many improvements which the micro-
scope has undergone for the last thirty years, it is still far from
supplying the wants of Histologists. In order to become accurately
acquainted with many details, it would be necessary to have a
magnifying pow§r of from ten to twelve hundred diameters, with
the same clearness and definition as one of three or four hundred
diameters. My opinions on this matter are as decided as they were
twenty years ago, when I was engaged in the study of this group.
Of all my researches on this subject, I only published a short note
which was addressed as a letter to M. Dujardin, and which he
inserted in his article on Infusoria in D'Orbigny's dictionary (1846),
although it was in opposition to his fundamental views. This note
seems to have l)een unnoticed by most naturalists who have since
written upon this subject, among others by MM. Claparede and
Lachmann.

t Grant's writings date from 1826, and appeared in the "Edin-
burgh New Philosophical Journal."

AND THE LOWER ANIMALS. 181

vations^ which were confirmed by those of Audouin
and Milne Edwards^ and the researches of other
naturahsts^ prove that ciKated larv^^ like those of
infusoria^ make their escape from within. In Spongilla_,
which is a fresh-water genns^ very common in the
neighbourhood of Paris, and which was for a long
while looked on as a plant, this form of reproduction
was observed by M. Laurent to occur during the
entire summer. But, in the autumn, the SpongilWs
tissue becomes filled with small roundish bodies of a
yellowish- white colour, enclosed in a very resisting
envelope : these have been regarded as grains, and
have been termed by Laurent hdernal gcrvis. They
survive the destruction of the surrounding parenchyma,
and give rise in spring to as many spongilla3, which
in their turn produce others by the processes above
describecL The nature of the germs to which we
have alluded was for a long period as undecided as
their origin was imperfectly kno^vn. The problem,
however, was eventually solved, and still more impor-
tant truths revealed, by M. Lieberkiihn, in a memoir
which received the French Academy^s prize.* This

* The subject given by the Academy in 1854 for a prize essav
was that of " The Reproduction and Metamorphoses of Infusoria
and the prize was divided between M. Lieberkiihn s work and that
which was presented jointly by MM. Claparede and Lachmann.
The latter memoir has been published, and forms the second volume
of the " Etudes sur Ics Infusoires et les Rhisopodes." It is much
to be desired that M. Lieberktihn's work may be also published.
M. Lachmann died since that period, at a very early age, and
M. Claparede has briefly noticed the event, at the same time
expressing the sorrow of a friend who has lost the companion of
his studies, and the regret of a savant who sees the field of science
deprived of a man of genius, whose great talents promised far
more than his brief lifetime permitted him to accomplish.

182

METAMOEPHOSES OP MAN

naturalist detected in Spongilla tlie distinction and
fiindamental characters of tlie two sexes — tlie male
and female elements. The ova wHicli lie described
were clearly characterized by the existence of the
three concentric spheres_, and were^ according to him_,
transformed at first into non-ciliated embrj^os. These
are the grains of the older writers^ and the internal
germs of Laurent^ who saw them^ give rise directly to
spongillas. But a certain number_, if not all of them^
undergo new modifications,, become covered with ciliaj
and thus by travelling to a distance from their birth-
place^ distribute the parent species. Each of these
ova^ therefore^ is capable of producing^ not only one
but very many individuals^ which proceed indirectly^
frgm it^ but directly one from the other. Consequently^
we may class Spongilla^ and doubtless all sponges^
among the animals which are reproduced by genea-
genesis.

We may say the same^ and with far greater reason^
of the Infusoria.

The existence of the sexes in the Infusoria, the pro-
duction of ova in these microscopic organisms, and
especialty the presence of the male element, have been
actively debated on many occasions. Ehrenb erg, whom
we may call the re- discoverer of the world of micro-
scopic animals, admitted these three facts as the
results of his observations. On the other hand, our
skilful micrographer, F. Dujardin, who devoted himself
specially to the Infusoria, and who regards them as
composed exclusively of scircode, rejects the whole
three.

Naturalists waver between these two extremes ; it
is quite true, as Messrs. Claparede and Lachmann have

AND THE LOWER AXIMALS.

183

pointed out in their splendid treatise^ tliat strange
blunders and mistakes have been made hj some of
those whose viev/s more or less resembled those of
Ehrenberg. However^ my owm personal observations
have ahvays compelled me to admit the existence
of reproductive bodies^ which plaj the part of eggs^
and vv^hose minuteness alone prevented my perceiving-
very distinctly the three constituent parts. ^ At
present there is no room for doubt either on this jDoint
or on the others. In those beino-s, which, as re,o*ards
size^ approach the lowest bounds of organic develop-
ment^ modern science has^ after much hesitation_, de-
finitively proved the existence of all the essential
phenomena of normal reproduction. The Infusoria^
like Ma.mm.alia^ Birds^ MoUusks^ and all other animals_,
deposit ova which are characterized by the presence
of three concentric spheres. As in all other species^
these ova cannot be fertile till they have been
influenced by the male element^ but^ when this has
operated^ the germinal vesicle and spot disappear^
prior to the conversion of the yelk into a new being.

These facts were at once the most important
in a scientific aspect^ and the most cliflLicult to
prove. Perhaps one of the greatest benefits which
has been conferred on general physiology, is that
which has been rendered by a young French naturalist,
M. Balbiani, w^ho has placed these facts beyond
all discussion, and caused them to be accepted by
those who appeared least likely to admit the existence
of normal reproduction among infusoria, f

Eevue des Deux Moudes," 1856.
t Before M. Balbiani's publication, there had been but one or
Uvo very incomplete treatises on this difficult subject. One was

184

METAMOEPHOSES OF MAN

The Infusoria are not reproduced by ova alone;
indeed_, this is apparently their rarest form of propa-
gation^ for it appears only after the other modes, and
these were known long before it. As early as the
year 1765_, Charles de Saussure observed that they
multiplied usually, by a peculiar process of spontaneous
division, by which two individuals were produced,
which exactly resembled the single one from which

that of the illustrious Jean Miiller (1856), referred to in the works
of Lieberkiihn, and Claparede and Lachmann. The two latter
made similar observations some short time after (1859). Both dis-
covered in the bodies of certain Paramccia, fdaments which were
decidedly analogous with those in the fecundating element of all
animals. But neither of them determined the organ from which
they proceeded, and neither of them detected the peculiar move-
ments of these corpuscles. Nevertheless both admitted the possi-
bility of the union of the sexes in Infusoria, and this conclusion
was accepted by the Academy (" Eaj)port sur le grand Prix des
Sciences physiques pour I'annee 1857," by M. de Quatrefages),
M. Balbiani showed that the sexes were united in the Infusoria,
and that the enigmatical bodies which Siebold termed nucleus and
nucleolus, were really generative organs, distinguished by the pro-
ducts to which they gave rise. He described the modifications
which each undergoes when it enters upon its function, and he also
demonstrated the changes which take place in the ovum after
impregnation. Part of M. Balbiani's statements has been verified
by myself and the remainder has been accepted in its entirety by
M. Claparede, who, in the notes added in 1860 to his "Etudes sur
les Infusoires," renders ample justice to the valuable results arrived
at by M. Balbiani. The latter naturalist's writings have appeared
in the "Comptes Rendus," 1858 — 1860, and in the " Journal de la
Physiologic de I'llomme et des Anhnaux : " most of them have been
collectively published under the title of " Recherches sur les Phe-
nomenes sexuels des Infusoires," 1861. On his part. Stein, who
has published many beautiful memoirs upon the history of Infu-
soria, appears to have arrived at results in accordance with those
of M. Balbiani (Claparede) ; but I regret to say I am unacquainted
with the work which he has just published.

AND THE LOWEE ANIMALS.

185

they were formed.* Modern researches liave only
substantiated these ideas ; for e'xample, it has been
demonstrated by Siebold and Stein^ that the nucleus
and nucleolus [the reproductive organs according to
Balbiani] are^ like the other portions of the body,
divided between the two offspring, each of which is
actually half of its parent.

The Infusoria are reproduced by external gemmation
also, after the fashion of the Hydra ; t ^^i^d in addition,
we find the internal hudcUng which is characteristic of
the Aphides. In the Infusoria, as in the insects alluded
to, it is upon the egg-producing organ (nucleus), and
frequently at its expense, that the embryo is formed.
Siebold was the first who pointed this out, J but its
entire value was not understood, and indeed the obser-
vations were themselves forgotten, when Focke, Cohn,
and Stein published theirs ^ which, on the contrary, were
received with interest. § From the immense number
of memoirs published by the last-named authors, we
are enabled to conclude that this form of reproduction
is as general among Infusoria as that of fission.

Saussure was the first who regarded fissuration as a usual
method of reproduction (Dujardin "Histoire des Infusoires ").
Trembley made accurate observations on the Vorticella and StejitoTj
twelve years before (" Etudes sur les Infusoires "). In Messrs.
(Jlaparede and Lachmann's work, the details of the physical
characters of this mode of reproduction are very precisely stated.

t This has been long known. The phenomenon was investigated
by Spallanzani in 1776, and since his time by a great many observers ;
among others by Ehrenberg and Stein. New facts have been added by
Claparede and Laclmiann, to those discovered by their predecessors.

X " Helminthologische Beitraege." — Wiegmann's Archives, 1835.

§ For the entire history of this matter, I can hardly do better
than refer the reader to Messrs. Claparede ajid Lachmann's
volume, from Avhich I have borrowed most of the above details.

186

METAMORrHOSES OF MAN

JSTevertlieless^ it is well to be on our guard against
various sources of error. Occasionally^ certain organs^
or even the entire bodies of Infusoria^ are attacked by
parasites_, whicli^ as tliej pass away, are sometimes
regarded as the offspring of tlie animal wbicli they
are really victimizing.* It seems to me that M.
Balbiani^s discoveries will necessitate a careful revision
of the facts attributed to internal gemmation. It
may be' that in certain cases, the fragments of the
nucleus which have been hitherto looked on as destined
to the 'direct formation of the embryo, pass in reality
through the condition of ova, which are afterwards
hatched within the substance of the mother, as among
all viviparous animals.

But whether the embryo proceeds directly from
the ovary, or results from the transformation of an
ovum produced by it, it is quite unlike its parent
when it first starts in life, and has to undergo a
series of metamorphoses. In what do these con-
sist ? Here, unfortunately, we are placed among
uncertainties and contradictions, and even what
was believed as incontrovertible a few years since,
is now either questionable or proved to be erro-
neous.

Some of these instances of parasitism have been made knoA\ai
by Claparede and Lachmann. Balbiani has also drawn attention
to this matter, by a note in which he shows that the Acineta para-
sites which become introduced into the bodies of various Infusoria,
And especially into those of Paramecia, have been mistaken for
embryos formed by internal gemmation. This fact furnished the
French naturalist with a new argument against Stein's theory, the
rej)roduction of Infusoria by acinda-forms — which has been justly
opposed by Claparede and Lachmann in the " Comjotes Eendus''
for 1860.

AXD THE LOTVER AXIMALS.

187

Comparing the writings of Pineau^* Poucliet_,t and
Stein^J and admitting tliat the Tacts npon which these
observers agree are trne^ we are led to regard the
changes of form as exceedingly nnmerons. If we
associate some of these with the facts announced by
Jules Haime^§ we shall see that these alterations are
still more numerous^ and the Infusoria may be then
considered the group in which the metamorphoses
which a single species may undergo are carried to
their greatest length. Such in fact was the opinion
I myself put forward when first engaged in the study
of these complex questions ; but later chscoveries^ and
especially those of ClaparedCj Lachmann^ and Balbiani^
induced me to modify it.

Have not the two first writers whom I have men-
tioned gone into the other extreme ? According to
them_, the metamorphoses of ciliated infusoria in
general are most probably of a very simple character.
The embryo_, which is not very unlike the parent_, has
to undergo but slight modifications in acquiring its
definitive form.|| This conclusion is at all events a
premature one. It is based exclusively upon a very

" Annales des Sciences naturelles," 1845 — 1848.
t " L'Institnt," 1849.

X Stein's first writings date from 184.9 ; they appeared in various
German magazines, and were in part reproduced in the Annales
des Sciences naturelles."

§ " Observations sur les Metamorphoses et 1' Organisation de la
Trichodalynceus{Aspicliscalynceus, Ehrenb.)." — Annales des Sciences
naturelles, 1853.

II The transformations of the Acincta embryos have been all
observed by Cienkowski, Claparede, Lachmann, and D'Udekem ;
but none of these writers have extended the same form of researches
to the other gToups (" ]Etudes sur les Infasoires").

188

METAMORPHOSES OP MA:^

small number of facts, observed by four naturalists,,
in a single and very limited group of this extensive
class. Are generalizations framed in a similar manner
in all cases ? It would form a very marked exception
to wbat we have seen elsewhere. From all that we
know of Insects, MoUusks, and Radiata, or even of so
limited a group as that of Batrachia, we are justified
in believing that, in the Infusoria likewise, the meta-
morphoses present various and complex phenomena
which remain to be discovered.

This view is further borne out by Jules Haime's
observations upon Asioidisca lynceus. I am aware that
M. Claparede declares them to be erroneous from
beginning to end ; but then, he has not repeated
them himself, and notwithstanding the decided tone
of his condemnation, we cannot accept his opinions
till he has brought forward some proofs in support of
them.*

* In speaking of Jules Haime, M. Claparede thus expresses him-
self, in a note of four lines appended to the splendid work I have
so often alluded to. " There has evidently been a series of con-
fusions, the result of which has been the co-ordination of organisms
which have actually no relationship to each other." This is exactly
Avha t was said of Kiichenmeister's and Van Beneden's first researches
on the intestinal worms. It is well known what happened to this
hasty condemnation. I camiot think that Jules Haime's work is as
unworthy as M. Claparede imagines. The conscientious manner in
which this young naturalist laboured is well knoAvn, and I am
personally aware that the memoir in question occupied a very con-
siderable portion of his time, and that he took the greatest precau-
tions to isolate the objects under observation, and to avoid all pos-
sibility of mistake. Do such care and pains usually terminate in
but a series of confusions ? Certainly the thing is possible in such
instances. The history of science generally, and of microscopic
science in particular, shows us too frequently that it may be so.
But it would be only simple justice to begin by endeavouring ta

AND THE LOWER ANIMALS.

189

According to Jules Haime_, the infiisorian described
under the name of Oxytriclia gihha is but a transition
form ; and even in reacliing" this condition^ it has to
undergo other transformations.* Be that as it may,
Haime saw the Oxytricha reproduced by fission, and
he observed that at a given moment the individuals
thus produced became more and more inactive, became
contracted, and even encysted in a sort of flexible
shell secreted by the integument. At this period
the Oxytricha is but a small mass of living matter,
without a trace of organization, and enclosed within a
sphere which is about three-hundredths of a millimetre
in diameter. In the interior of this mass movements
take place, which, though imperceptible to the eye,
make themselves apparent by their results.

By degrees, numbers of irregular granulations grow
from this species of ball ; a small cavity is developed
in the interior, and vibratile cilia begin to make their
appearance; new changes take place; the internal

satisfy one's self, and this is exactly what M. Claparede does not
appear to have done ; for he alhides nowhere to contradictory
observations, and assuredly he could not fail to be acquainted with
them, did they exist.

Jules Haime is no longer here to defend himself. He, too, was
taken from among us at an early age, leaving upon the minds of
all who were acquainted with him, or who had only studied his
numerous writings upon various branches of natural history, the
stern conviction that science sustained a serious loss by his removal
from the field of labour. I have merely discharged a duty, in
defending a work which cost him much time, and upon which he
bestowed great care. No one could more fully appreciate this
than Lachmann's former friend.

* According to M. Pineau, the Oxytrichre are the result of the
metamorphosis of certain Vorticellaj ; but this statement certainly
requires to be proved anew.

190

METAMORPHOSES OP MAN

portion of tlie mass divides into two parts^ one alone of
wliicli possesses life ; and soon the new beings aban-
doning the lifeless part^ leaves its temporary prison_,
in the form of an ovoid infusorian^ about one-third
as long as the Oxytricha. In this condition it belongs to
the genus Loxodes of special zoologists. After having
lived for some time in this condition^ it again assumes
the ball-form; an abundant secretion is poured out
over all parts of its body^ and the mouth appears as a
small oblique slit ; a proportionally very long and
thick filament is pushed out from its side^ and four or
five others show themselves posteriorly; the body_,
convex above and almost flat below^ is covered with
large wrinkles^ and the infusorian moves about with
great rapidity sometimes swimming by the aid of the
cilia^ and at others walking with the help of the
filaments^ which play the part of feet. Under this
form, which is certainly very difierent from those
which it before presented_, it was known to the older
writers as Trichoda lynceus.

In concluding his memoir, Haime asks whether the
condition of Aspidisca (Trichoda) is the final one
assumed by the Oxytriclia, which was the starting-
point ? We are justified with him in doubting that
it is so. The reproductiue bodies which are at present
regarded even by M. Claparede as the true ova, were
never found in TrlcJwda by this accurate observer.
Therefore, from what we have already seen, and from
what we shall see more forcibly hereafter, it results that
an animal which undergoes metamorphoses should not
be considered adult till it has clearly presented the
sexual attributes. It seems to me that this rule
should be accepted as an absolute one. It should be

XND THE LOWER ANIMALS.

191

applied to the Infusoria as well as to otlier animals.
Consequently the Trichodge^ like otlier species^ can
only be definitively regarded as perfect animals wlien
the existence of tliese attributes lias been proved
in them.*

Notwithstanding that uncertainty which time and
study will eventually do away with^ science is in pos-
session of facts enough to prove that true metamor-
phoses, stages of transformation, and the various
phenomena of geneagenesis occur among the Infusoria.
The first are exceedingly simple. Let us, for example^
borrow from Messrs. Claparede and Lachmann^s
work, the history of those presented by the Vorticellco
tubcrosa of Miiller {Podojjhrya ([iiadripartita of Clapa-
rede and Lachmann), one of the most beautiful species
of the Acinetinean group.

This Yorticella or Podophrya is a stationary being*.
Its body is like a quadrangular pyramid, with very
rounded edges. The summit is prolonged into a.
cartilaginous stalk, twice as long as the body, and
is attached to some adjacent body. At each of the
basal angles of this pja^amid is a sort of papilla, from
which spring several filaments, which apparently
terminate in small button-like processes. These fila-
ments are really at the same time mouths and arms^
and are always extended in a radiate manner. Some-
times if a far larger and more powerful Infusorian
passes in the neighbourhood of this creature, it is
instantly seized, entangled in the filaments, which
then appear to become solid, and the terminal biitton-

* I am quite aware that, in thus exj^ressing myself, I am asking
for a revision of almost the entire class. But in these times
erfpocially, science should not recoil from such an undertaking.

102

METAMORPHOSES OF MAN

like org-ans^, wMcIl are real suckers^ are attached to
various portions of its body ; if tlien the prey is
sufficiently weak to admit of being devoured upon the
spot^ we can, with the aid of the microscope, see
the granules passing from its body into that of the
Podophrya.*

This infusorian sometimes produces a great number
of small embryos, but at others it gives rise to a
single one, much larger than itself, f The latter, at
the period of birth, is a little ovoid transparent body,
constricted at the middle, and carrying at this
point a sort of girdle, which consists of several rows
of vibratile cilia. By means of this apparatus it swims
about in the liquid, rapidly enough at first; but
after a few minutes this wandering propensity
is lost. The larva arrests its movements now and
then, as though desirous of rest, and eventually
becomes permanently fixed. Its cilia, henceforth
useless, disappear, the suckers begin to present
themselves, and the footstalk exhibits itself, and is
rapidly prolonged. In the course of four hours the
Fodoi^lirija has acquired its' definitive form, and has
now only to increase in size — to grow.

If the animal which we have followed from its birth
were now complete, it would be a case of simple
metamorphosis. But the Podophrya which has been
thus formed, gives rise to new individuals by sponta-

* I have given iinhesitatingly, but in an abridged form, the
details supplied by Messrs. Claparede and Lachmann, for, without
having gone as far as they, I observed a quite analogous state of
things.

t The fii-st appears to me to l)e one of those fects which (subject
to consideration) might be associated with true ovo-viviparitij.

AND THE LOWEE ANIMALS.

193

neous division and by gemmation;^' lience we liere
see geneagenesis with all its peculiar features.

The PodophryEe are simple animals ; but in the
Infusoria^ as in the Zoophytes_, there are many species
which live in colonies^ and cover with a miniature
arborescence submerged aquatic plants^ and the
shells of fresh and salt-water mollusks_, vv^hich thus
travel about laden with this living moss. Let us
see how these things occur in the case of the Epistijlis
2ylicatil{s. This is one of the commonest and best
known species^ and has been specially noticed by
the two skilled micrographers from whom we have
quoted so extensively.

From the body of one of these animals there
springs an embryo^ a larva, of an elongate almost
cylindrical form^ and supplied with a girdle of Aabratile
cilia. Placed in a fe^v drops of v\^ater_, which to
it, and to the eye^ assisted by the microscope^ are
almost an ocean^ what becomes of it ? Direct ob-
servation tells us nothing in this instance ; but with
Claparcde and Lachmann we may say^ it is more than
'prohahlG that it acts like the larva of Podophryse —
that it attaches itself at some suitable point, and
is at first metamorphosed into a simple Epistylis.

At this period the larva assumes a more or less
elonga^ted conical form ; its extremity_, which is
slightly expanded_, is provided with a circular hood^
sloping toward the mouth; a band of vibratile cilia
crowns the internal border of this hood_, and by its
movements produces a series of currents which carry
the nutritive corpuscles to the animaPs mouth. The

* Claparede and Laclimann first demonstrated this latter nioda
of reproduction in the species referred to.

O

194

METAMOEPHOSES OF MAN

body is borne upon a straiglit cylindrical stem^ ex-
panded at its base^ and wliicli seems a little tube
of tbe purest crystal.

Our Epistylis does not remain long in an isolated
condition ; nor does it give rise to the new members
of the future colony by budding merely^ as is the case
among the Campanularise^ but by fission also. The
single individual resulting from the metamorphosis
of the larva divides itself completely into two parts ;
each of these halves remains attached to the parent
stem^ undergoes its completion in that position^ and
develops posteriorly a smaller stem^ which gradually
elongates. We may say it is a sort of fork_, each
prong of which is terminated by a living being.
After a while_, each of these secondary branches
divides in its turn in a similar manner^ and so on,
until from the first Epistylis there is produced a
crystal tree, whose divisions are perfectly regular,
and all of whose branches attain exactly the same
height.*

The individuals thus formed by division are not
all destined to be constantly motionless. We oc-
casionally find that certain of them exhibit a con-
striction of the posterior portion of the body; a
circular groove is gradually formed, and its borders
are furnished with long vibratile cilia; the division
becomes deeper and deeper, and finally the Epistylis
drops from its stem like a wall-fruit. But it is not
destined to remain at the root of the tree from which
it falls. Thanks to the locomotive apparatus which is
placed posteriorly, it swims about with as much facility

The cluster of Epistylis has often been compared to flowers
which present a corymbose inflorescence.

AND THE LOWEE ANi:\IALS.

195

as the ciliated larva did. However^, it very soon
abandons tMs wandering existence^ attaclies itself
once more_, loses its vibratile cilia^ employs its buccal
apparatus_, which till then had been carefully folded
up_, and soon elevated upon a new steni_, which has
been developed from behind it, becomes the starting-
point of a new colony.*

If we were writing a history of the Infusoria, we
should have much to say on the subjects of encystmentf
and conjugation. 1^ These two phenomena are doubt-

* In treating of the formation ■ of the stems of Epistylis, most
authors iTse expressions Avhich seem to imply that these stems have
no share in the vitality of the mdividuals. I believe, on the con-
trary, that the stems are living organisms. In support of this
view, I may mention that they are the seat of phenomena which
cannot be explained by the adoption of any other opinion. Such
are : the increase in diameter as well as in length, the widening of
the base, the appearance of the central canal, described by Clapa-
rede and Lachmann, and which I myself have observed, &c.

t We apply the term Encystment to that act by which an
Infusorian surrounds itself with a solid shell secreted by itself, and
which places it beyond the control of external influences. Any
cause which brings about a result disagreeable to the animal, and
especially the evaporation of the drop of water in which it was
placed for examination, determines Encystment. Certain species
also appear to encyst themselves, in preparing to undergo spon-
taneous division. Stein especially investigated the phenomenon
from this point of view ; and finally it has been shov/n by Claparede
and Lachmann that certam species encyst themselves in order to
digest their captured prey more easily. Such is the case with
Amphileptus meleagris, which is nourished at the expense of Epis-
tylis, and whose curious mode of capturmg its prey has been
described by the writers just alluded to.

X Conjugation or Zygosis, discovered by KoUiker, and since in-
vestigated by most micrographers who have devoted themselves to
the study of Infusoria, is a phenomenon by Avhich two, or a greater
number of individuals of the same species, appear to became fused,
so to speak, into one. M. Balbiani thinks that it is only an illusion

196

METAMORPHOSES OF MAN

less associated^ at least in certain cases^ Avitli tlie
class of plienomena under discussion ; but occasionally
they have only very distant or accidental relations
with reproduction_, and we shall, therefore, confine
ourselves to pointing them out.

We reserved our comments on the history of JEcli/i-
noderms for the last, although this class, which com-
prises the Holothurice, the Sea-iirclilns, and Star-fishj
should be properly ranked at the head of the true
Radiata.* We have not done so without a reason.
Some naturalists deny that there is any fundamental
analogy between the phenomena presented by these
animals and those whose history we have just been
sketching. Others have expressed doubts on the
same subject. Whoever has thoroughly understood
what we have endeavoured to convey by the term
geneagenesis, — whoever will admit, with us, that the
fundamental character of this mode of generation is
the production of several distinct individuals by the
aid of a single primitive germ, will not have a
mementos hesitation; but he will at the same time
understand that the exceptional nature of the de-
velopment of Echinoderms is due to the combination
of the phenomena of geneagenesis with those of
simple metamorphosis.

The curious phenomena we have indicated have
'been seen by several observers only of late years.
In 1844 Saars — whom we always find at the head

resulting from the imperfection of our instruments, and caused by
the intimate approximation which takes place at the moment of
the reciprocal fecundations of adult individuals.

* The zoologist will perceive what an artificial arrangement the
ahove would be : the star-fish and hydra are as little akin as man
and the oyster. — Tr.

AND THE LOWER ANIMALS.

197

of the list of modern naturalists when we refer to
marine animals — described the development of two
Asterias [Asterias sanguinolenta and Aster acanthion
Millleri). He saw these Echinoderms^ contrary to the
rule among animals so low in the scale^ absolutely^
in some measure^ hatch their own ova. He proved
that the larva springing from the latter_, at first
resembled an infusorian_, and afterwards presented
the appearance of an animal composed of two lateral
symmetrical halves_, which at a later period became
converted into a radiated creature.* Shortly after^
the celebrated embryologist Baer tried the effect
of artificial fecundation on the sea-urchins^ but was
only able to observe the earlier stages of develop-
ment, f Almost at the same period two inhabitants of
Marseilles^ Messrs. DufosseJ and Derbes^§ observed
nearly similar phenomena in the sea-urchins ; but the
figures of the second are very difi'erent from those
of Saars. Two Norwegian naturalists^ Keren and
Danielssen_, discovered at this period that the Bijpin-
naria asterigera was a developmental phase of the
true Asterias.\\ Finally, in 1845, J. Miiller, the cele-
brated Berlin physiologist, investigated the marine
animals of the Korth Sea at Heligoland; described

* " Memoire sur le Developpement des Asteries," translated in
the " Annales des Sciences natiirelles," 1844.
+ " L'Institut," 1845.

:j: " Observations sur le Developpement des Oursins," in the
" Annales des Sciences natureUes," 1847.

§ " Observations sur les Phenomenes qui accompagnent la For-
mation de I'Embryon chez I'Oursin comestible," 1848. — Annales
des Sciences natureUes.

II " Obsen^ations sur la Bipinnaria asterigera," printed in Swe-
dish in 1847, and translated into French in the &ame year.

198

METAMOEPHOSES OF MAN

Phdeus paradoxus ; followed up his researclies in the
Mediterranean and Adriatic; and in 1848 commenced
a series of publications^ which added another chajoter
to the history of the development of animals.*

Like all his predecessors^ Miiller saw that the
Echinoderms deposited ova from which ciliated larvse
were produced. f These larvae are spherical at first;
then they become elongated^ acquire a calcareous
framework^ formed of long and slender branches^ and
assume the strangest forms_, being sometimes like a
painter^s easel;, and at others like a double ladder with-
out rungs. The arms are in some instances covered with
vibratile cilia^ but in others the latter are arranged in
tuftSj and are of service in the locomotion of these
peculiar beings^ which swim about with considerable
rapidity. All these have a complete digestive
apparatus^ with a large and distended stomach. It
is upon the very walls of the latter organ^ and upon
one of its sides_, that the future echinoderm begins to
show itself. In the sea-urchins and the Ophiuridse
it appears as a circular flattened disk^ which seems
to mould itself^ as it were_, upon the stomach_, and

* "Ueber die Larven unci Metamorphose der Echinodermen."
Six fasciculi appeared at different intervals ; tliey \Yere very care-
fully analyzed by M. Dareste in the " A.nnales des Sciences natu-
relles," for 1852 and 1853.

t This mode of reproduction, however, is jiot general among
Echinoderms. Certain species of the Ojihiuridce, animals closely
related to the star-fish, are ovo-viviparous. This I ascertained in
1842. — (Comptes Rendus Hebdomadaires de I'Academie des
Sciences.) I took from the abdomen of a single mother, six per-
fectly formed young, which, when placed in vessels of sea-water,
lived as though they had been born naturally. More importance
is, I believe, given to this observation in the works of my confreres
who have met with very different phenomena in other species.

AND THE LOWEE ANIMALS.

199

soon completely envelops it. As it grows,, this disk
assumes a radiate form; gradually the amhulacra and
spines present themselves; then the mou.th opens
externally^ always on the lateral surface of the larva.
The latter is partly resorbed^ and partly laid aside^
when the new animal is fuUy formed. In most
Asteriss these things occur in a similar manner^ but in
others the h^rva {tornaria) is completely absorbed by
the Echinoderm developed within. In the Holothuriee
the tentacular crown is developed upon the larva^s
stomachy but most of the organs immediately employed
are completed and acquire their final characters by a
simple transformation.

We cannot dvfell here upon all the remarkable
features of this mode of development. We shall^
therefore^ confine ourselves to those matters directly
related to the subject.* From the sea-urchin^s egg
there is produced a sort of infusorian^ which is meta-
morphosed into a iilutens. In the interior of the
latter there is developed an animal of quite another
nature. Here we have two very distinct generations
produced by different processes^ yet both owing their
existence to a single primitive germ. This^ then^ is a
case of geneagenesis.

But what here characterizes this phenomenon are
the loans^ so to speak^ which the second generation
gives to the first. In all the species which we have
hitherto examined^ the bud merely borrows the

* We desire, however, to call attention to the exceptional fact
of an animal which is destined to become radiated, beginning its
career with a bilateral symmetry like that of the Annulosa. It is
the only exception to the embryogenical rule which we have alvrays
maintaineJ. — Souvenirs d'un Naturaliste.

200

METAMOEPHOSES OP MAN

materials necessary for its growtli_, from the parent ; it
abstracts its nourisliment^ bnt it tends more and more
to become an isolated being. Yfiiether the operation
takes place externally as in Polyps^ or internally
as in SalpsG;, the phenomenon is essentially the same.
In the Echinoderms_, on the contrary^ the bnd in
the course of growth^ surrounds the existing organs
and appropriates them. Viewed as a whole^ the
process of gemmation is one of geneagenesis j but
the stomach in Sea-urchins and Ophiuridge^ and the
entire digestive apparatus_, and some other organs in
Holothurias^ are submitted to a simple metamorphosis
only.

The development of Echinoderms forms a sort of
connecting link between these two classes of phe-
nomena, and prevents one of those leaps to which
Nature ever seems to be so averse.*

M, ifidouard Claparede has come to a similar conclusion on
tMs subject, although we have investigated the matter from very
diiferent points of view.

A^^D THE LOWER AiTIMALS.

201

CHAPTER XYIII.

GENBAGENESIS IN THE HELSIIXTHES OR INTESTINAL
WORMS. ^ SPONTANEOUS GENERATION.

The animals we liave been treating of, up to the present,,
are of interest to tlie ordinary reader as well as
to tlie naturalist. The living blossoms of apolypidom^
and the garland of a Stephanomia^ are admired alike by
the child and the philosopher. We come now to speak
of very different beings^, whose name even creates an

* The French Academy at its sitting on the 22nd of March,
1852, offered the great prize of the physical sciences for the decision
in 1853, of the following question : — " To demonstrate hy observa-
tions and exiKriment the mode of development of intestinal ivorms,
and of their imssage from one animal to ariother, and to apply the
anatomical and physiological facts thus proved, to the determination
of their natural affinities'' The great difficulties which the ques-
tion presented, and the short period allowed for its solution left
some doubt as to the presence of competitors ; but two naturalists,
prepared for a long while, replied to the Academy's appeal. Van
Beneden, professor of zoology in the University of Louvain, and
Klichenmeister, a physician of Zittau, sent in essays ; that of the
first was a genuine work, where the history of Helminthes was
treated of in all its relations, and Avas accompanied by an atlas
containing nearly a thousand original figures ; that of the second
was a very important memoir, and was likemse accompanied by
plates. Upon a very extensive report which I made in the name
of a commission appointed to decide the merits, the Academy
awarded the prize to M. Van Beneden, and an honourable mention
to M. Klichenmeister. It decided also that Van Beneden's work
should be printed at its expense. It appeared under the title of
" Memoire sur les Vers intestinaux," 1858.

202

METAMOEPHOSES OF MAN

instinctive feeling of disgust. If tlie reader desires to
follow us_, we sliall spare him the teclinical details in
endeavouring to convey some portions of a history^
wMcIl touclies on tlie most important questions in
general and pMlosopliic physiology.

Until of late years tlie term Helmintlies liad
been exclusively applied to those worms which
remain concealed within the bodies of other ani-
mals. At present this limitation does not exist.
It is knovfn now that these internal parasites have
very close relations among external beings. The
Nemertes and Planarise are nearly akin to the Trema-
todaj of which we shall speak presently. These
affinities which have been but recently observed_, have
caused the Helminthes to be no longer ranged among
the Radiata where Cuvier placed them_, but along with
the Annelida. Consequently^ had we been faithful to
our scheme^ we should have considered these peculiar
beings before now ; but it seemed preferable to devote
a special chapter to them. The exceptional mode of
life of most of them, the very complex phenomena
of their development, and the unexpected light which
the study of Helminthes has thrown upon some of the
most obscure problems in science, amply justify the
departure from the order pursued in other portions of
this volume.

From our point of view, the Helminthes which lead
an external and independent life, are not of any
peculiar interest ; the parasitic species alone merit
our attention. The latter have been divided into a
certain number of groups, from which we shall select
the Trematodaj Gestmda, and the Cystic worms.

The first are usually animals of small size, flat and

AND THE LOWEE ANIMALS.

203

generally provided with one or more suckers_, by
means of wMcli tiiey attacli themselves after the
fashion of a leech. The liver-fluke, so common among
sheep^ may serve as an example of this group. The
second^ of which the Tcenice (improperly called sohtary
worms) may be taken as the type_, occasionally attain
a length of several metres. In these worms the so-
called body is composed of flattened joints,, very small
and slightly marked in fronts but becoming gradually
wider and more distinct. A rounded button-like
expansion, sometimes provided vfith suckers, and at
others with hooklets, terminates the slender extremity
of this festooned ribbon. It is this expansion which
is termed the head. Finally, the Cystic worms are
like little vesicles, from some portions of whose
surface are borne the heads of tseniee attached to a
short footstalk. The Cestoids inhabit the digestive
tube only ; the Trematodes are found in almost all the
viscera. The Cystic worms seem to prefer the tissues,
and we find them in the midst of muscles, in the
centre of the brain, &c.

All these worms are nourished, and what is more,
respire, only through the intermediation of the animal
which encloses them. From this fact, we can even
now draw a very important conclusion, the application
of which we shall find further on.

Every species of animal having its own proper form
of nutriment, its special temperature and its peculiar
liquids, it follows that each of them presents a series
of conditions different from the others, and conse-
quently constitutes a special world for the Helminthes.
Therefore, these parasites must distribute themselves
each according to its own requirements, and cannot

204

METAMORPHOSES OF MAN

inliabit all forms of animals indifferently. These
theoretical inductions are fully borne out by ex-
perience. Every animal supports^ so to speak, its own
particular Helminthes. If we were to enumerate all
these parasites, we should review the entire creation,
and should pry into the inmost bodily recesses of all
other animals.

But whence come these strange beings, which
attack the tissues and viscera in myriads, which
penetrate the cavity of the skull, and even that of the
eyes ! Destined to lead an exceptional and, so to
speak, second-hand existence, is it possible that they
are produced and propagated like other animals, in
fact like the very beings to which in truth they may be
regarded as parasitic appendages ? To reply to these
questions, is to touch on another which is far more
general, and which science has always handed down
from age to age, to our times in which alone its
solution could be attempted.

Is the creative power which has given rise to living
beings extinct, or is it still exerted on this globe ? In
other words, is the phenomenon styled equivocal or
spontaneous generation a reality ?

We know the reply of the ancients. They supposed
that all bodies in a state of putrefaction developed
new organisms, and Aristaeus' fable was only a special
application of a general doctrine. These ideas uni-
versally adopted spread almost to our own days. It
required the experiments and observations of Redi
and Yallisnieri to convince the savans of the seven-
teenth and eighteenth centuries, that insect larvse
were not a product of decomposition.

From that period, more correct ideas concerning

AND THE LOWER ANIMALS.

205

the origin of beings began to be formed_, and the
advocates of spontaneous generation lost ground.
They did not^ however^ maintain the fight^ but limited
the area of application of these doctrines. ISFow^ in
proportion as science progressed^ this area became
narrower and narrower. Then the partisans divided.
Some of them, among whom we may mention
Lamarck_, Burdach, and Duges, continued to regard
the physical forces — light, heat, and electricity — as
♦ sufficient to organize and animate matter, so as to
transform it into living beings ; the others, among
whom were Redi himself, Rudolphi, Morren, Oken,
and Nordmann, supposed that the plastic forces in
organized and living beings might suffer a sort of
deviation, from which new beings, different from the
first, would result. For example, according to them,
portions of the vitellus of a mollusk, isolated during
segmentation, would produce directly a species of
infusorian; food digested under the influence of the
vital force would be converted into Tcenice, and certain
juices destined to repair the muscular fibres would
organize a series of GysUcerd, &c.*

* M. Pouchet and the few other naturalists who, even nowadays,
constitute themselves, in The name of progress, defenders of these
antiquated views, hold a sort of median course. M. Pouchet does
not admit the spontaneous formation of an animal. He believes
that the aplastic force co-operating with the physico-chemical forces,
organizes at first proligerous 2ycUicle, ivJiich, in the case of sjpontaneous
generation, exactly, represents the ovary in normal generation. It is
in this pellicle and at its expense that the spontaneous ovule is
developed. — (Heterogenic ; ou Traite de la Generation spontanee,
1859.) This modification of the doctrine is certainly more apparent
than real. The spontaneous o7'gani?:ation of an ovary, or of an ovule,
is in a physiological point of view a phenomenon of exactly the
same order as the organization of an entire animal. The secor.d

206

METAMORPHOSES OF MAN

Tlie first of these two views is based especially
upon facts^ (?) borrov/ed from tlie history of the Infu-
soria; the second^ upon the existence of intestinal
worms. On some other occasion^ perhaps^ we shall
treat this great question of spontaneous generation
in detail J and show how the experiments of Schwann
and Henle demonstrated that germs * were carried
into infusions^ which were not protected by the im-
proved apparatus of modern science ; how Pasteur^s
experiments^ by fully confirming those of his prede- *
cessors and revealing new truths^ have overcome the
final cavillings of the Heterogenists ; and how the
discovery of male and female elements in the Infusoria
crowned this mass of evidence. We shall at present
limit ourselves to proving^ that the germs distributed
through the air develop only the animalcules^ or
microscopic vegetables,, that Spallanzani and so many
others supposed to be produced spontaneously; that
these germs have been re-collected and described by
various observers ; that M. Pasteur has collected and

would not seem strange to me, nor would it be more difficult for
the plastic and physico-chemical forces than the first. M, Pouchet
rejects absolutely, limits, or declares very doubtful all facts opposed
to his theory. For example, he no more believes in the migrations
and transformations of the intestinal worms, than he admits the
accuracy of the precise and conclusive experiments of M. Pasteur.
In acting thus, he is in opposition to almost all naturalists, and to all
the physicians and chemists whose opinions I am conversant with.

* It is unnecessary to state that the word germ is not used in
the sense employed by the partisans of evolution and the pansper-
mists of Bonnet's school. This general expression is adopted here
to designate reproductive bodies, whatever their nature, which give
rise to the appearance of animals or vegetables in the liquid experi-
mented on (spores and cellules of vegetables, ova, Infusorian
cysts, desiccated animals which revive when placed in water, &c.).

AND THE LOWEE A^^IMALS.

207

sown them^ as one would corn^ and tliat half tlie
arguments evoked in support of tlie doctrine of spon-
taneous generation are therefore annihilated.

There remain the arguments^ borrowed from the
history of the Helminthes^ especially from the cir-
cumstance of the isolation of certain species^ from the
absence in them of a reproductive apparatus^ and
from their existence in the closed cp.vities and interior
of the tissues. But are these argum.ents better based
than the others ? Are certain Helminthes_, if not all
• — by an exception henceforth to be regarded as
special — developed spontaneously in those localities
in v/hich the scalpel encounters them ?

It is to embryogeny alone that we can look for a
reply to this question^ and efforts have been made for
several years past to solve this latter difficulty.

Numerous and important^, though isolated dis-
coveries have been made^ in France by F. Dujardin^ and
in Grermany by Bojanus, Baer, Kolliker_, Nordmann^
Siebold^ Wagner_, and others. No intestinal worm had
been observed in the early stages of its evolution.
One constantly came in contact with agamic species ;
and it was so hard to explain their existence,, that^
for twenty years^ even the least cautious naturalists
admitted that here there must be a series of meta-
morphoses resembling that of insects.* Such was
the state of science in 1840. We knew absolutely
nothing of the embryogeny of either Cestoid or Cystic
worms.

Concerning the Trematodes^ it was said th&t in the

* Siebokl's observations on Monostomum mutahih were made in
1835. They prepared tlie way for a series of discoveries, now
very considerabk and constantly increasing.

208

METAMOEPHOSES Or MAX

yiscera of fresli-water mollusks there were developed
— liow_, it was unknovm — beings called SporocystSj
species of living envelopes^ provided witli a v/ell-
marked digestive tube^ but always devoid of repro-
ductive organs. Tliese sporocysts gave rise simul-
taneously to new bodies like tkemselves, and to
germs^ wbicli became developed into Gercarice, crea-
tures in the form of tadpoles^ able to inhabit water,
but of quite as neuter a ckaracter as tke others.
These Cercariss were the necessary ]jarasites of the
vSporo cysts. After undergoing their development in
the interior of the latter, the Cercarigs burst their
walls and became encysted, somewhat like the di-
pterous insects we spoke of in a preceding chapter,
and terminated their short lives in the prison in
which they were enclosed.

We see that, according to this method of explaining
observed facts, a sexless animal, of unknown origin,
produces simultaneously, by gemmation, creatures like
itself, and others of an entirely different character,
which could never be directly produced. It would
be idle to touch on the vague and evidently incom-
plete nature of such ideas.

Steenstrup, by his theory of alternate generation,
threw a light upon these dark clouds, which seemed
almost to lower in proportion as men laboured to
dispel them. Supported by his own and his prede-
cessors^ researches, he boldly classed the Bistomidm
(Helminthes of the trematode group) side by side
with the Corynid£e and Medusidae, in regard to their
mode of reproduction. It was shov^n by the Danish
savant, that the peculiar bodies then termed Sporocysts
were the true nurses of the Trematodes, and that the

AND THE LOWEE ANIMALS.

209

Cercarise were the larvae of the latter. From this
period the history of the group became clearer. In
1850^ Van Beneden^s very important memoir ap-
peared_, in which, on the support of direct observa-
tions, he asserted that the cystic worms were
nothing less than the scolices of the cestoids.* And
shortly after, this novel but important fact having
been demonstrated experimentally by Klichenmeister,
was pubhshed as one of the results of his first ex-
periments. In 1853, these two writers, in competing
for the Academy^s prize, completed their former
researches, each regarding the subject from his own
stand-point, and confirming the other in many im-
portant particulars. Yan Beneden, moreover, treated
of the Trematodes and other groups. Since that date
new facts have been announced. G-astaldi,t rilippi,t
Siebold,§ Moulinie,|| and others, have added to our
knowledge of the Distomidge ; and Lewald, Siebold,
Wagoner,^ Van Beneden, Leuckart, La Yallette, and
others, have repeated and extended Kiichenmeister^s

* " Les Vers cestoides ou Acotyles, consideres sous le Kapport
de leur Classification, de leur Anatomie et de leur Developpement."

t " Cenni sopra alcuni nouvi Elminti della Rana esculenta." 1854.

J "Memoire pour servir a I'Histoire genetique des Trematodes,"
in the " Memoires de I'Academie de Turin," 1854. This memoir is
reproduced in the "Annales des Sciences naturelles," fourth series,
Tol. ii. Second memoir on the same subject, 1855 ; third memoir,
1857.

§ " Memoire sur le Leucochloridium," 1854 ; " Memoire sur la
Reproduction des Hehninthes en general," 1854, translated in the
" Annales des Sciences naturelles," 1855.

II "Dela Reproduction chez les Trematodes endo-parasites," in
the " Memoires de I'lnstitut Genevois," 1856.

*1T "Die Entwickelung der Cestoden nach einigen UntcKuch-
ungen." 1854.

P

210

METAMOEPHOSES OF MAN

experiments; so tliat iiow_, thanks to tlie number of
their works^ we can trace^ if not tlie special history
of each species_, at all events^ the general history of
these beings^ which in former days were looked on
as such mysteries.

In the first place^ let us treat of the Trematodes.
We shall select^ as an example^ one of the species
akin to the Monostomum midahile, or the Distomum
militare/^ which have been investigated by both
Siebold and Van Beneden.

The general description of trematodes already given
will suffice to convey an idea of these animals. They
may be described as little leeches, inhabiting the bodies
of fresh-water mollusks. In the bodies of these hel-
minthes hundreds of ova may be found, whose vitelli
have already undergone their first transformations, and
have become ciliated larv£e. These latter leave their
envelopes, and, thus set free, make their way into the
bodies of mollusks hj some means or other. There
they remain, and appear to undergo destruction, whilst
in their places are left a number of very small ovoid
bodies, which have been developed within them.

Each of these bodies, which were regarded as
necessary parasites by the German authors, and as
enigmatical organs by P. Dujardin, increases in size,
elongates, and acquires two lateral appendages pos-
teriorly. This is the s]jorocyst of Baer, the " redie
of Filippi.f Judging by its movements, and its well-

* The Distoiiiiini and Monostomum are genera belonging to tlie
Trematode group.

f It lias been very reasonably proposed by Filippi to distinguish
the transitional beings by giving them different names, according
as they present a more or less complex organization, or rather

AND THE LOWEE ANIMALS.

211

marked digestive apparatus provided with a muscular
oesopliagus and bifid intestine^ it is impossible to deny
its animality. This peculiar creature has no repro-
ductive organ, hut, to compensate for its absence_, the
whole internal surface of the body is endowed with
the power of producing germs. The latter^ buried in
the general internal cavity from which they were pro-
duced_, are developed sometimes into sporocysts like
the firstj sometimes into Cercarise.

The Cercari£e_, which for a long while were considered
to be Infusoria_, are like small tadpoles with an oval
body^ which is provided with a long tail^ that serves as a
swimming organ. Their organization is complex^ and
is in process of completion. In addition to a digestive
tube^ which abeady reminds one of that of the future
Distoma_, there are secretory organs^ hooklets^ &c._, but
as yet there is no trace of a reproductive organ.

When their growth is completed,, the Cercari£6
burst the walls of the parent sporocyst^ and swim
about in the water^ where for a certain period they
live^ like infusorians. Then comes the time for their
metamorphoses. They then attach themselves to some
mollusk^ penetrate the interior of its body^ lose their
tails and become encysted^ almost in the same manner
as the StratiomySj of v/hich we spoke when treating
of the metamorphoses of insects. Their organism is
now the seat of a process of remodelling^ in every way
comparable with that which we alluded to as occur-

becaiise they are merely liying saccules. For the first he proposes
the term Bedies ; for the second, Sporocysts. Moulinie has adopted
this distinction, showing at the same time that it is associated vvdth
different modes of formation. — " De la Eeproduction des Trema-
tudes endo-parasites." 1856.

p 2

212

METAMOEPHOSES OF MAN

ring among the Diptera^ and tlie most important result
of wMch is tlie appearance of a double reproductive
apparatus. The Distomum gradually acquires its per-
fect form^ and all that remains for it to do is to burst
its shelly and adopt the peculiar mode of life for which
it is destined.*

Here we perceive all the characters of typical genea-
genesis^ complicated^ however^ by phenomena which
are related to metamorphosis properly so called.

From each ovum there is produced a ciliated larva^
which gives rise by internal gemmation to a Spo-
rocyst. The latter_, by the same process^ produces
simultaneously new Sporocysts and Cercariae, that is
to say_, generations which are sometimes less^ some-
times more advanced in point of development. More-
over^ each Cercaria passes through stages which may
be compared to those which mark the evolution of an
insect. It is at first free^ and endowed with powers
of motion like the larva of the Stratiomys. It becomes
encysted like the latter_, and by a very analogous
process ; and it becomes motionless^ and passes, so to
speak_, into the chrysalis condition. Then it under-
goes an organic remodelling, resembling in every
respect that by which the nymph is metamorphosed
into the perfect insect. Finally, in both cases the
termination of these changes is marked out by the
development of the apparatus which ensures repro-
duction by ova.

If we apply to the Trematoda the same nomen-
clature which we employed in the case of the other
groups of which we have treated, we shall say that

* According to Steenstrap, the Cercaritie, prior to assuming their
definitive features, remain encysted for nine or ten months.

AXD THE LOWER ANIMALS.

213

the ciliated larva of the distomum is the scolex, and
its sporocyst is the strohila. Each Cercaria is a pro-
glottis ; but in this instance the proglottis, before
reaching the state of perfect distomum, undergoes a
series of true metamorphoses, quite like those of
insects in general, and of the Diptera especially.

These complex phenomena are further complicated
by a very curious circumstance.

We met with insects living at first, when in the
larval state, in water, and then in air, when the
successive metamorphoses carried them to the con-
dition of perfect insects. According to the periods
of life which they have reached, these insects then
inhabit different media, distinct worlds.

Now, Trematodes present a similar state of things,
only in their case the media, or worlds, through
which they pass in order to possess the conditions
necessary to the progress of their development, are
so many distinct species of animals. They must travel
from one to another, and these migrations are most
frequently accomplished by a process as simple as it
is unexpected. The parasite is subject to the same
fortune as the individual that carries it. When the
latter is devoured by some other animal, the Hel-
minth is also eaten, and travels along \\^th the
aliment, of which, indeed, it is a part. According as
its new habitation is or is not suited to its require-
ments, it dies and is digested, or resists the solvent
action of the surrounding liquids, and begins a new
phase of its development.

For example, a Distomum^s egg falls upon the leaf of
some aquatic plant and is swallowed by a Lymn^ea or
Paludina ; it is hatched in the interior of the mollusk.

214

METAMORPHOSES OP MAN

and gives rise to a scolex (ciliated larva) ^ wMcli then
produces its strobila (sporocyst). From the latter
spring several proglottides (cercarise)^ which at first
swim for some time around the animal by which they
have been hatched. When the period of their meta-
morphoses arrives^ those which attach themselves to
stones,, leaves^ and such-like^ soon perish ; but some
of them invariably discover the larva of an insect or
mollusk adapted to their wants^ and pierce its integu-
ment. There they remain^ till their temporary host is
in his turn devoured by some frog or water-bird^ and
it is in the latter alone that the young Distomum
completes its organization^ and acquires its definitive
characters.

These strange migrations^ which are accomplished
by a process which seems very v/ell calculated to
destroy the vitality of the Helminthes, occur also
among the cestoid and cystic worms. For there it
has been proved by direct experiment ; and the result
of these experiments has been to show that these two
groups^ which hitherto had been almost universally
regarded as distinct^ are really but a single one. The
quasi- cystic worms are only a developmental phase of
the cestoid Helminthes. The credit of having formed
this conclusions from a series of observations and
perseveringly followed researches^ is due to M. Van
Beneden ; that of having demonstrated it by precise
experiments belongs to M. Kiichenmeister.* Thanks
to the labours of these two naturalists^ and to those

* "Kapport sur le grand Prix des Sciences physiques pour
1853," by A. De Quatreftiges ; " Comptes Eendus del'Academie des
Sciences," 1853; and "Annales des Sciences natureUes," quatrieme
s^rie, t. l'^'".

AND THE LOWER ANIMALS.

215

of their followers^ we are now in possession of a
general history of the development and migrations
of all these beings^ which^ though accepted hesi-
tatingly at first_, mnst be more and more regarded
as truthful_, in proportion as new facts are accumu-
lated.

According to the Belgian naturalist_, the Taenia^ s
egg produces a proto-scolex^ which is a little animal
with an almost homogeneous body^ in which it is only
possible to distinguish six booklets, or rather six very
sharp spicules_, arranged in three groups.* The two
middle ones form a sort of lancet^ and perforate the
tissues placed in front of them; the two lateral pair
pressing against the aperture thus formed, and working
backwards, send the embryo forwards, somewhat like
the manner in which a man employs his arms in hoist-
ing himself through a trap-door. The young cestoids
are urged forwards by an instinctive impulse. Many of
them perish on their journey, but some reach an organ
suited to their wants, and then they are transformed
into a vesicle, upon which are produced by genea-
genesis the heads of the Tsenise which are now so
many deidoscoUces.-f When the animal in which these
first phenomena have occurred, is devoured by some
other, the vesicle disappears, the tgenia-heads are
isolated, and each of them develops from its posterior

* Note on the Tcenia clisjpar and the mode in which the cestoid
embryos penetrate the tissues. — "Bulletin de I'Academie royale
de Belgique," 1854.

t In this sketch of the development of cestoids, which for the
most part is deduced unquestionably from Van Beneden's writings,
we have combined the results of his researches with those of
Kiichenmeister's. It was the latter who saw the vesicles which
are simple at first, give rise to the tsenia-heads by genmiation.

216

METAMOEPHOSES OF MAN

extremities a true cestoid worm. Tlie latter is smooth
at first_, but after awliile it becomes segmented^ each
segment being really an animal^ a distinct and bisexual
individual. As soon as this segment is sufficiently
developed^ and its reproductive apparatus is charged
with fecundated ova, it is detached and expelled from
the intestine, and soon dies. The thousands of eggs
which it contained are swept away by the winds
and mingled with the dust ; thus becoming scattered
in every direction. Most of them perish. A few are
swallowed by some animal whose organization is
adapted to their development, and each of these
becomes the starting-point of a new series of trans-
formations and migrations.

We say then, that the T83nige, which up to this
period were regarded by most Helminthologists as
simple beings, are really not only compound animals,
but are true strohilcc, and each of their apparent joints
is a proglottis.

These views of the Louvain savant have been fully
borne out by experiment.

Let us select, for example, the Goenuriis ccrebralis.
This worm, which has been known for a long while,
was thought to develop itself by some unknown pro-
cess in the midst of the brain- sub stance of the sheep.
It is the presence of this very unwelcome guest
which produces that disease, known to cattle-dealers
as staggers. The Coenurus is like a semi-transparent
sac filled with liquid, and sometimes as large as an
egg. Numbers of heads, like those of the T^nia, are
found upon its surface, and in continuity with the
tissue of its envelopes. The Coenurus is therefore a
cystic worm. Like the other species of this order, it

AND THE LOWER AXIMALS.

217

lias no trace of reproductive organ. How^ then^ is it
reproduced ?

This problem has been solved by Kiichenmeister.
Led by his former experiments, he fed a dog with the
Coenuri, and he soon found in its intestines the
Tasnise which till then had been regarded as peculiar
to the wolf.* Next, Avhen this worm was fully
developed, he fed sheep with those segments whose
eggs already exhibited embryos with six hooklets,
and in a few days these sheep were attacked with

* The determination of the species thus obtained presents some
difficulties, not 3'et quite got rid of ; this fact has been dwelt on
with some force by Valenciennes, and was first noticed by myself,
" Comptes Rendus," 1854. But these are difficulties of detail, and
do not affect the general results that I have been endeavouring to
convey an idea of ; the transformations and migrations of cestoids
are facts so clearly demonstrated now, that they are universally
accepted. Among the works which have contributed to decide the
question, I may mention the persevering researches of the two
writers to whom I have already alluded, Siebold's various works,
and especially two memoirs translated into French in the " Annales
des Sciences naturelles," for 1851 and 1852 ; Wagener's important
memoir, " Die Entwickelung der Cestoden," published in the
" Memoires de I'Academie de Breslau," 1854 ; that of Baillet,
entitled " Experiences sur le Cysticercus tenuicollis, et sur le
Tenia qui en resulte," 1861 ; and M. Koeberle's work, "Des Gysti-
cerques du Tenia chez 1' Homme," 1861, &c.

It nmst be reniembered that the experiments were not confined
to the lower animals, but were made even on man himself. Leuckart
experimented on his patients (" Die Blasenbandwiirmer und ihre
Entwickelung," 1856) ; Kiichenmeister operated on criminals
(" Gazette Hebdomadaire de Medecine et de Chirurgie," 1860). Dr.
Humbert of Geneva experimented upon himself, and voluntarily
produced tapevv orms within himself (Bertolus, " Dissertation sur
les Metamorphoses des Cestoides," 1856, alluded to by Koeberle).
The results of all these experiments were the same as those in the
cases of the lower animals.

218

METAMOEPHOSES OF MAN

staggers. On killing tlieni and opening tlie crania^
Coenuri in various stages of development were found
in tlie brains. In point of fact_, Kiicliennieister sowed
the Tsenige in the dog by feeding him on the Coenuri ;
and the C(snuri in the sheep by feeding them on the
matured segments of the Teenige.

The advocates of spontaneous generation ask :
How^ without our doctrine,, do you explain the ex-
istence of so many intestinal worms^ devoid of repro-
ductive organs^ and appearing in the very heart of
the tissues^ the muscles (cysticercus) and the brain
[coenurus) ? Thanks to the writings of the distin-
guished naturalists whose researches we have briefly
sketched^ we can now reply : — These apparently aga-
mic species are various developmental phases of truly
sexual animals. In some instances^ all the changes which
these beings undergo^ in passing from the larval to the
perfect condition^ have been observed^ and analogy^
which becomes more forcible every day^ justifies us in
believing that the same phenomena occur in the other
species also.

This^ therefore^ is a result of much importance.
The final argument of the supporters of spontaneous
generation falls^ to rise no more^ and we may now^
with every certainty, repeat ITarvey^s dictum, " Omne
vivum ex ovo.^^ Geneagenetic phenomena may mask,
but they never, in the main, alter this grand law.
We trust to be able to demonstrate this clearly in the
later chapters of this volume.

AXD THE LOWEE ANIMALS.

219

CHAPTER XIX.

THEORY OF GENEAGENESIS.

The investigation of tlie attempts at a scientific ex-
planation^ which were brought about by the existence
of geneagenetic phenomena^, leads us to the first
object of these researches^ — the discovery of a common
law governing the various general processes at work
in the formation of animals_, and the indefinite pre-
servation of species.

Our attention has been successively drawn to these
three processes — transformation, metamoiyhosis, and
geneagenesis. With the assistance of a few examples^
I have been able, without much difiiculty, to mark out
the application of this law in the phenomena which
characterize the two first. When we came to animals
in which geneagenesis presented itself, I was enabled
to go more fully into details. Here I had to intro-
duce the reader to a class of ideas little known
generally; and, in order to show their peculiarities
and exceptions, it was necessary to enter into a de-
scription of their variety and complication. I have
now to point out the results of theory, after having
spoken of those of observation ; and, in order to help
the reader to appreciate the difi'erent schemes of which
geneagenesis is the starting-point, I must in a few
words recapitulate the leading features of this phe-
nomenon.

220

METAMORPHOSES OF MAX

In animals wliose deyelopment is of tlie geneagene-
tic type^ the ovum, like tliat of animals wliicli under-
go transformations and metamorphoses^ shows itself
in the very outset, and gives rise to a simple being.
The latter is devoid of true reproductive organs, and
multiplies exclusively by fission, and by external or
internal gemmas. From these modes of reproduction,
different forms of animals may result. In most
instances, but by no means in all, the animal
resembles neither its parents nor its offspring. After
a certain number of generations the primary type is
reproduced, and with it appear the sexual attributes
and power of reproduction by ova. All intermediate
generations developed between the extreme terms of
the series are agamic, that is to say, they are devoid
of true reproductive organs, and multiply by internal
or external buds, and by fission, exclusively.

These are the facts : it now remains to be shown how
they have been explained at different periods.

In the commencement, the only attempt made was
to associate them with what was already known.
Those who discovered the process of multiplication,
by budding and fission in animals, — as soon as their
temporary surprise had subsided, — satisfied themselves
by a simple comparison with the known phenomena
of the vegetable world. It was a more difficult task
to reconcile the reproduction of Aphides to the gene-
rally accepted laws. Till comparatively recently, it
gave rise to the most opposite explanations. Anatomy
proved that hermaphroditism, although momentarily
admitted by Reaumur, had really no existence here ;
and, in order to support the hypothesis, most naturalists
limited themselves to an endeavour to prove the fact.

AND THE LOWER ANIMALS.

221

Of those wlio went still farther the greater number^
and^ among' others,, two distinguished English ento-
mologists^ Messrs. Kirby and Spence^* asserted that a
single intercommunication of the sexes was adequate
to the fecundation during several generations of all
the families which resulted from this union. Some^
and among them Leon Dufour^ the distinguished anato-
mist of Saint- Sever, boldly had recourse to spontaneous
generation, in order to explain this remarkably ex-
ceptional fact.f Others again, as M. Morren, admitting
that this oj)inion was not in unison with modern
science, supposed that generation occurred through
the individiialization of a previously organized tissue.'l
The first of these hypotheses either explained nothing,
or assumed the existence of a complete organic ap-
paratus, which was not present. As to the theories
which in a greater or lesser degree were based on the
spontaneous generation doctrine, we know that at
the present day they are inadmissible. Besides, all
these doctrines apphed to a special case, which till
then had been regarded as without an analogue, and
for that reason, must fall before the multiplicity and
exceeding complexity of the phenomena now known.

In discovering the alternation of form and condition
presented by each species of Salpa, Chamisso — and
to say so is but to do him a justice that has not been

* " Introduction to Entomology."

t " Eeclierches sur les Hemipteres," 1853. — Annales des Sciences
naturelles. Leon Diifour, who passed his life in the little town of
Landes, published Avorks on the anatomy of insects, which very
soon attained great repute.

X "Memoire sur I'i^migration du Puceron du Pecher {Ajjhis
persicce) et sur les Caracteres et 1' Anatomic de cette Espece," 183G.
— Annales des Sciences naturelles.

222

METAMORPHOSES OF MAN

sufficiently rendered — foresaw all tlie results of tMs
fact considered apart^ but he could go no farther.
The external differences between this mode of gene-
ration and that of the Aphides were too great to admit
even of a supposition of any analogy between the two
phenomena.

The splendid works of Saars, Siebold^ Loewen^Dalyell^
and finally of Steenstrup_, by filling up the gap and
forming a connecting link_, alone permitted the latter
to grasp relations^ which till then had been imper-
ceptible. Still_, he must have had a gifted and
synthetical mind to arrive at the result. Whatever
may be said of the other doctrines of the Danish
naturalist, this work will always be regarded as of the
greatest value, and as marking an entirely new era in
the history of the development of animals.

The very title of this work shows that the author
considered the subject from the same point of view as
Chamisso, and that he had been struck especially with
the alternation of forms presented by the various
generations produced in geneagenesis. This is incon-
testably proved by the very first passages in the book ;
but Steenstrup did not stop there. He pointed out
clearly the physiological fact which characterizes the
commencement and termination of the series of gene-
rations. This fact is, the reappearance not only of
the primary form, but of all the anatomical and
physiological characters also, especially of the repro-
duction by ova in the usual manner. This conclusion,
which was at first drawn from a very small series of
facts, has been confirmed by all subsequent researches.
It is one of the most important truths Steenstrup has
established, and one of his greatest triumphs.

AND THE LOWEE ANIilALS.

223

In fact_, from tMs generalization^ reasonably put
forward by tlie Danish naturalist_, as the result of direct
observation^ two consequences follow,, which are of
much importance to general physiology^ and which
seem to have escaped those men of science who have
considered this question.

Till our time^ it had been usual to regard all forms
of reproduction, no matter how different, as being
independent of each other, and hence as possessing
an equal hiologiccd importance. Whether it was an
ovum, a bulb, or a bud, it was looked on as a primi-
tive germ. Gemmiparous reproduction was equivalent
to reproduction by ova, because in both cases the
perpetuation of the species was insured.

This was clearly a deceptive view. Buds and bulbs,
no matter what appearance they may assume, are only
the less or more indirect products of a pre-existing
ovum. The latter alone includes the essential germ,
the primary germ of all the generations which proceed
from it ; consequently, buds are but secondary germs,
and are raediately associated with the primary ovum. <
Moreover, it results from all that is at present known
upon this subject, that gemmiparous reproduction does
not insure the perpetuation of the species, and that
after a certain period reproduction by ova becomes
necessary. The latter, therefore, is the only funda-
mentpol office — it is the function of the first order.
Reproduction by buds is merely accessory, and may
hence be styled a subordinate f unction.

Further on, we shall see how much light these very
simple doctrines shed on the nature of geneagenetic
phenomena. We must say that Steenstrup exagge-
rates the truth of his vievv^, in looking to the pheno-

224

METAMOEPHOSES OP MAN

menon itself for an explanation. His doctrines on
tliis subject appear to us exceedingly hypotlietical.
The phases of multiplication^ or rather the generations
to which we have given the terms scolcx, stvohila, &c.j
he styles grandnurses, nurses, and so forth. Nor does
he employ these expressions in a figurative sense^ but
in their special and absolute acceptations. Accord-
ing to him^ the Medusa in its hydroid form_, which pro-
duces polyps^ is not a motlier on that account ; it is not
a j)arent in the etymological sense of the word. It
cannot be a mother_, nor can it give birth to anything ;
and if it appears to produce buds and germs which
are converted into beings like itself, it is merely because
these beings have been entrusted to its care ; that it
in process of growth brings them with it. The germ
pre-exists in the organs in which it is deposited^ in
the body in which it presents itself^ and like it^ pro-
ceeds from the individual primitive mother. The nurse
has 710 'proper offsprmg ; her office is to bring up an
alien offspring which she has inherited * from her
own mother.

* These views are very clearly expressed in Steeiistrup's funda-
mental work, and also in his " Objections," published in reply to
Van Beneden's " Observations." They are if anything more
explicit in the latter, the very words of which I have almost quoted.
This circumstance, in conjunction with the passage in the opposite
page, which is reproduced verbatim, will serve as a reply to the
censure I received from one of the editors of the " Bibliotheque
Universelle," who fancied that I was not familiar with the exact
expressions of the Danish naturalist. I have not altered the text
since its first appearance ; I have confined myself to the removal of
passages relating to some very spirited controversies which took
place at the time when these articles first appeared, and which it
gives me much pleasure to eilace.

AND THE LOWER ANIMALS.

225

This is clearly the doctrine of compound concentric
germs. In the Aphides there intervene between the two
sexual generations^ ten or twelve agamic ones^ and^ as
we have also seen^ an insect which is produced from a
single egg gives rise to thousands of millions of indi-
viduals. Steenstrup^s theory would force us to admit
that the ovum contained this enormous number of
germs enclosed one within the other. Such a conclusion
is hardly more admissible than Bennetts Fansperniy.

Steenstrup endeavoured to render his views clearer
by a comparison, or even by an assimilation, which, to
my mind, does not appear more exact than the views
themselves. He supposes that the nurses, or, in other
words, the scolices of the Aphis, Medusa, and Salpa,
represent the neuters in a colony of bees, wasps,
or white ants, only they are placed lower in the scale
of development. ^' A female wasp,^^ he says, " having
survived the winter, and being isolated, at first con-
structs a few cells, and deposits therein her eggs, from
which workers exclusively are developed. As soon as
these are hatched, they set themselves to work,
widening the comb and increasing the number of
cells. The mother now deposits a new series of ova,
and from this second batch neuters are produced, and
are nursed by the workers which are already there.
This goes on till the workers are insufficient numbers.
Then, and then only, there spring from a few eggs,
both male and female insects, and these are attended to
by the neuters with the utmost care. These processes
are repeated, each batch of sexual insects being pre-
ceded by one of agamic individuals destined to take
charge of it, to watch the eggs, to collect the common
aliment, and to feed the larvae, &c. These neuters,

Q

226 METAMOEPHOSES OF MAN

therefore,, fulfil the office of nurses^ and may be com-
pared to tlie Medusa in tlie hydroid state^ ■vvhicli carries
and nourishes within itself the germ of the true
Medusa. There is^ however^ this distinction : what the
insect does voluntarily^ through the operation of in-
stinct betraying itself in acts^ the Scyphistoma does
through organic activity alone, and unconsciously.
In both cases JSTa^ture attains the same end ; viz., the
completion of the final product, by the assistance,
not of intermediate generations, but of several broods
belonging to the same generation.

The errors of the Danish savant's mode of reasoning
are apparent. In one instance, he asserts exactly
what he wants to prove; and in another, he draws
a comparison based upon results, although on his own
admission the processes which produce these results
are totally difierent.

Notwithstanding these faults, we repeat that Steen-
strup^s work conferred a decided benefit on science,
and this service was appreciated. What seldom
occurs, scientific men accepted at the very outset all
the truthful views of an author, who associated
together several phenomena, which till then had been
regarded as isolated or anomalous : they opposed his
purely theoretical views alone. Many attempts were
made to re-establish them, and the controversies were
occasionally of a very exciting character. We cannot
enter into the details of these discussions. We shall
limit ourselves to a resume of the chief opinions put
forward by the most competent authorities.

In the highest rank, in every respect,, we must
place the work of Professor Owen. This naturalist,
who, from the extent of his labours, should be called

AND THE LOWER ANIMALS.

227

tiie Englisli Cuvier^, just as we might style Laplace
the French Newton^ published upon this subject a
treatise,, entitled^ On Virginal Generation.* This
title is in itself the enunciation of a theory^ which we
regret exceedingly we cannot adopt.

In fact^ the idea of virginity is inseparably asso-
ciated with the possibility of the cessation of this
condition. The latter supposes the existence of the
apparatus which are the distinctive characters of the
sexes. When these organs are absent^ either from
normal or accidental causes^ the animal can no longer
be called a virgin. This term is not applied to a
eunuch^ or to a deformed animal. With far greater
reason it is inapplicable to a creature which has
never been either male or female. Now, the results
of observation and experiment go to prove that such
is unquestionably the case in all the animals of which
we have spoken, so long as they are in the state of
scolex or strobila, so long as they multiply by buds,
offshoots, or by spontaneous division. The most deli-
cate scalpel, the most powerful microscope fails to
show us, in either the Sporocyst or Scyphistoma, any-
thing conveying an idea of sexuality.

Nevertheless, according to Professor Owen, all
these beings are females. Although recognizing the
difficulty found in expressing certain parental rela-
tions, he conceives that the term mother may be
applied to them. This mode of view, adopted by the
English savant, is based upon a very singular excep-
tion. The individuals belonging to the intermediate

" On Parthenogenesis." 1849. In the course of this work the
author proposes another term, that of Metagenesis, which may be
translated by the words changeable generation.

Q 2

228

METAMOEPHOSES OP MAN

generations of apMdes possess female reproductive
organs — imperfect ones^ it is true^ but still quite
perceptible. In these organs^ tbe essential part_, tbe
ovary, appears to be constructed upon tlie same plan
as that of tbe viviparous individuals or scolices, and
tliat of the oviparous ones, which are the true females.
But in the latter we find genuine ova, with all their
characteristic parts ; whilst in the former we observe
only small granular masses, in which we can dis-
tinguish neither a true vitellus, nor a real germinal
vesicle, nor anything deserving the name of a germinal
spot.*

In supposing that all animals reproduced by genea-
genesis are placed under the same conditions as those
which are presented by the Aphides, Professor Owen
has certainly gone beyond the results of direct obser-
vation ; even were it otherwise, we could not accept
his theory.

In fact. Professor Owen, in explaining the pheno-
mena, refers to the origin of the simplest organisms,
and supports his views by Schwann^s cell theory, a
doctrine whose errors, in many particulars, we have
already demonstrated. Certain beings, says the
English savant — for example, the monads, regarded
as the lowest infusoria, and the gregarinidte, which
are parasitic infusorians, living in the interior of other
animals — are constituted, really, of a single cell,
with its nucleus. Propagation is effected in them by
division of the nucleus, which produces that of the
entire animal. f Now, the ovum is formed essentially

* When on the subject of true imrthenogenesis, we shall deal
with these peculiarities.

f From the circumstances that the nature of the micUus of

AND THE LOWER ANIMALS.

229

of a nucleated cell — tlie germinal vesicle, wMcli encloses
the germmal spot. The yelk_, properly so called, or
Vitellus, is but an accessory mass of matter for
alimentary purposes. The fundamental ovum is re-
produced, just as the monad, by fission; but this
phenomenon is alone determined by the intercom-
munication of the sexes. This act is necessary in
order to infuse a certain jjoiver, a peculiar prolific
forced into the germinal spot. In consequence of this
impregnation, the germinal vesicle disappears, the
germinal spot becomes contracted, and the first ger-
minal cell soon exhibits itself. At first, the latter
divides into two, then into four, and so on, the vitellus
itself undergoing, pari passu, the same multiplication.
It is in this way that Professor Owen explains the
segmentation of the yelk, and its transformation into
a mass of germinal cells, invariably endowed with the
prolific power which gave them birth, and which is
stored up within them.

According to Professor Owen, it is invariably this
mass of germinal cells which, endowed with a special
force, constitutes the starting-point in the trans-
formation of a new being. In Mammalia, all ver-
tebrates, and in a great number of invertebrates, this

Infusoria is now known, and that this organ, which plays so import-
ant an office, is really an ovary, it is evident that many of the
theories based upon Schleiden's views must be revised, and that
it will be necessary to verify many of the facts which perhaps have
been accepted only in so far as they were founded on those views.

* A spermatic force, a spermatic power. The arguments ad-
duced by Dr. Carpenter and Professor Huxley in opposition to the
views of their distinguished fellow-countryman, bear particularly on
the supposed existence of this special force. — Medico-Cliirurgical
Review, 1848 : " On the Agamic Reproduction and Morphology
of Aphis." Transactions of the Linna-an Society, 1858.

230

METAMOEPHOSES OF MAN

formation is sufficient to exhaust tlie provision of the
cells,, and of the prolific force kept in reserve. In the
Aphides^ Medusae^ Distoma^ &c., it is otherwise. A
portion of the mass^ composed of germinal cellsj passes
uncha7iged into the embryo^s body^ and the prolific
power being still in play^ the cells continue to mul-
tiply in their new abode. As soon as a sufficient
quantity is formed^ a new being is organized^ which
carries with it its own proportion of the cells and
reproductive force. But^ in consequence of the repe-
tition of this process, the prolific power becomes
eventually exhausted, and then only the inter-
vention of the two sexes is necessary, in order to
renew it.

All animal reproduction is the result of a single act
of fecundation, brought about by the connection of the
male and female, the first giving to the fundamental
element, which is supplied by the second, the power
of reproducing itself, during a period which varies
according to the species. In reproduction by ova this
force is exhausted during a single intercommunication,
and must be renewed at each generation. In par-
thenogenesis, this force is transmitted through several
generations, together with the material elements, pro-
ceeding from the first germinal cell. In both cases
the latter is the starting-point. In it is accumulated,
even at first, that prolific force which sets agoing the
more or less permanent but always identical phe-
nomena. Consequently, p art heno genetic reproduction
differs only in point of accessory circumstances from
ovarian reproduction. Fundamentally, they are one
and the same phenomenon.

This is a brief sketch of Professor Owen^s theory.

AND THE LOWER ANIMALS.

231

We may state that^ in tlie first place^ it justifies the
expression jparthenogenesis. According to tMs mode
of view_, bnds^ bulbs^ &c., are regarded as a sort of
offspring from the primitive ovum^ as composed in
part of the substance of tliis ovum_, and as being at
all events of tlie same nature. They are^ so to speak_,
genuine ova which have been fecundated in advance.
Now^ the female alone produces the ova. In the main^
therefore^ the scolices are of this sex, and may be
looked on as having some claim to virginity. Professor
Owen, by reducing all modes of reproduction to a single
fundamental law, simplifies all other questions, em-
braces and co-ordinates a great mass of scattered
facts, and elucidates relations till then unperceived.

Despite all these merits, and notwithstanding the
great and just authority of the author'' s name, Pro-
fessor Owen^s doctrine met with few supporters.
Without alluding to what is borrowed from Schwann^s
cell theory, of which, in certain points, it is but a new
application, we may say that this doctrine is ex-
clusively based upon certain hypotheses which have
not been borne out by facts. The disappearance of
the germinal vesicle, prior to fecundation, has been
demonstrated by a host of observers, not only in
Mammalia, but also in Hermella and Teredo.*
Now this fact is in direct opposition to Professor
Owen^s views ; it strikes the theory at its very founda-
tion. Moreover, since the publication of Schwann^s
work, many naturalists haA^e demonstrated that the
so-called segments of the yelk are by no means cells.
The observations which I published at the period

* Vide the earlier portions of this volume.

232

METAMOEPHOSES OP MAN

when tlie doctrine of ]oarf hem genesis first appeared^
and wMcli liave since been confirmed_, demonstrate
that segmentation is a manifestation of the special
vitahty of the ovmn_, and is not due to the influence of
the male element^ which only regulates the process.
Hence it is difficult to admit Professor Owen^s special
force^ at least in his acceptation of it. We may add_,
that the accumulation of this force^ its deterioration
and exhaustion^ are just so many hypotheses^ which
are doubtless exceedingly ingenious^ but which are
supported neither by direct observation nor by ex-
periment.* On the contrary^ the fact that among
Aphides_, agamic reproduction may be almost inde-
finitely prolonged by the employment of artificial
heat^ is decidedly in opposition to the English
naturalist^ s opinions. f

* In support of his view, Professor Owen brings forward the fact
that the crab's feet are not reproduced indiscriminately at all the
joints, but only at those where a peculiar cellular tissue is found,
which tissue he regards as a remnant of the germinal cellular mass
still endowed with the prolific power. Without dwelling upon the
resemblance of this explanation to that for which Bonnet was
reproached, I may observe that it is deciding one question by an
appeal to another, and that it is necessary, in the first instance, to
prove that the character of this tissue is that which the author
presumes it to be. Professor Owen asserts also that the hydra's
buds are developed only at certain fixed points ; but Laurent, who
devoted himself for many years to the study of this animal, proved
that it has the power of budding from every portion of its body,
somewhat like a plant whose adventitious buds appear in all parts
of the bark, and for the same reason.

f Every doctrine put forward by so distinguished a man as
Professor Owen carries with it, for that reason alone, a certain
amount of influence. This is why I have reproduced in detail
the statements which, on the first appearance of these essays, I
thought necessary to make in opposition to his views. As I have

AND THE LOWER ANIMALS.

233

Leuckart^ without seeking^ like Owen and Steen-
strup_, to discover the minute nature of the phenomena,
compared geneagenesis to metamorphosis.* Accord-
ing to his ideaS;, every scolex is a species of larva. The
Scyphistoma is^ so to speak^ a medusan caterpillar.
We do not think this view has any foundation_, and
in this we fully coincide with Steenstrup^ who^ before-
hand, refuted most of Leuckart^s arguments. The
nurse condition/^ said the Danish naturalist, differs
entirely from that of larva. The caterpillar is itself
converted into a butterfly. The Scyphistoma never
becomes an Aurelia.''^

The force of this reasoning is the more apparent,
as we often find the two phenomena, metamorphosis
and geneagenesis, in the same animal. For example,
in the Medusa, after the ovum has been transformed
into a ciliated larva, the latter is converted by meta-
morphosis into a Scyphistoma; then geneagenesis ap-
pears and produces the strobila, whose proglottis —
which is isolated, at first, under the form of Ephyra
— is aftervv^ards metamorphosed into an Aurelia. In
this case the ciliated larva is really the larva of the

already said, in these times, the expression proposed by the ilhis-
trious English zoologist would hold ground by being applied to
phenomena of an entirely different order, to which the serious atten-
tion of physiologists is being drawn. The result has proved the accu-
racy of these preconceptions, and farther on I shall have to treat of
tme parthenogenesis, our earliest notions of which are due to Pro-
fessor Owen.

* " Ueber Metamorphose ungeschlectliche Vermehrung Genera-
tionswechsel," 1851. — Zeitschrift fiir Wissenschafthche Zoologie.
My knowledge of this work is confined to Claparede's analysis in the
" Bibliotheque universelle de Geneve." But the interpreter's name
guarantees the accuracy of tlie interpretation.

234

METAMOEPHOSES OF MAN

Scypliistoma_, as the Ephyra is the larva of the
Aurelia.

Among the Distomidas the phenomena are still
more complicated^ for we find at the same time three
modes of development, and three processes of meta-
morphosis properly so called. The ovnm gives rise,
hy transformation, to a ciliated larva, which, by
geneagenesis, produces a Sporocyst, that in its turn
attains its final form by metamorphosis. The multi-
plication by buds, of the Sporocysts themselves, and
of the Cercarise, must be referred to geneagenesis. The
Cercariae are the true larvse of the future Distomae ; and
when they lose their tails and become encysted and
motionless, is it not in order to pass into the nymph
condition, after the fashion of the Stratiomys ? And
when, finally, they rise from this torpid state, under
the form of DistomaB, is it not by a true metamorphosis
comparable in every respect with that from which the
perfect insect results ?

So far from geneagenesis being a modification of
metamorphosis, the facts established by the first
tend rather to modify the most generally accepted
ideas which have been confirmed by the second.

Assuredly, if up to the present, there is any ad-
mission to be made, it is that the ofi'spring is the
direct product of the parent; that the individuality
of the germ is maintained from its birth till its death.
So far as reproduction by buds has been considered
as fundamental a process as reproduction by ova,
these views apply equally to both. Metamorphosis
does not afiect them in this particular. JSTo matter
how numerous and complete the changes are which
a butterfly undergoes, the animal is still one being ;

AND THE LOWER ANIMALS.

235

the individuality is preserved. Consequently^ in
passing through the caterpillar and chrysalis stages^
it is not the less the direct j^rodud of the germ con-
tained in the ovum^ nor is it the less the immediate
offspring of its parents — just like the infant, which
was first an embryo and then a foetus.

But when there occurs between the two forms of
reproduction such an essential relation as that the
first must always constitute the starting-point of the
second, this is no longer the case. The primitive
germ or ovum then acquires, as we have already
established, a very superior value to the secondary
germs which are derived from it. The parental
relations — those of father and mother to offspring —
can only exist among individuals which produce such
germs.

What takes place in the case of the Aurelia, for
example ?

From each ovum is developed a being which, at
first, is single, and devoid of reproductive organs, but
capable of producing spontaneously, and, as it were,
from its own special substance, a great number of
individuals. Each of these, in its turn, divides into a
certain number of others, which acquire reproductive
organs, and produce and fertilize ova. These latter
are the only true offspring of the first parent; but
they are very numerous, and all have sprung from a
single ovum containing a solitary germ.

Consequently, the unity and individuality of this
germ have been multiplied, that is to say, they have
been divided in the process of development. The
several aurelias proceeding from the single primitive
ovum are only the indirect idvodiict of the germ enclosed

236

METAMORPHOSES OE MAN

in tliat ovum ; they are but tlie mediate offspring of
their parents. This is the fundamental distinction
between geneagenesis and metamorphosis.

Van Beneden^s mode of view is more modest than
Steenstrup^s^ Owen^s^ or Leuckart^s. The Belgian
naturalist has not pretended to explain the essential
character of the phenomenon^ but he has been
especially impressed by the fact that certain species
of animals are reproduced by a single process, whilst
others are multiplied simultaneously by two different
means. Hence he divides the animal kingdom into
two classes, — monogenetic and digenetic. From this is
derived the term digenesis, applied to the entire series
of reproductive phenomena which occur without the
intervention of the sexes.

To those who fully coincide with the author^s
views, and desire to go no farther, this term seems
well conceived. It conveys a fact apart from all
hypotheses ; but, on the one hand, its only signifi-
cation is derived from its opposition to the term
monogenesis, which Yan Beneden applies to ordinary
reproduction ; and, on the other, it does not seem to
me to indicate sufficiently the prominent character-
istics of the order of phenomena to which it refers :
viz., the production of several types, and of an
indefinite number of individualities, from a single
primitive ovum.

This remark applies with equal intensity to the
other expressions to which I have referred. It is for
this reason that I propose to substitute the term
geneagenesis, which, to my mind, is sufficiently ex-
plicit, and wdiicli only convej^s a fact apart from all
theoretical considera^tions.

AND THE LOWER ANIMALS.

237

Does it follow from this that all these terms should
be erased from scientific terminology ? — ISTo. The
words multiplication by buds^ offshoots^ fission^ &c.^
and those of alternate generation_, metagenesis^ and
digenesis, really express correct ideas and distinct
facts. They will be often found useful in giving
precision to language^ and on that account they should
be preserved. But it follows^ from what has been
said^ that each of them must be employed to designate
onSj and one only^ of the special forms under which
geneagenesis in its most general condition may present
itself.

Although very well named, this phenomenon is not
explained. Moreover, we need not hope to discover
the primary cause, at least not for a long while. The
utmost we can do is to associate it with other facts
already understood, and thus elucidate its real nature.
Besides, the naturalists whose writings we have
alluded to, have all striven to refer agamic generation
to sexual generation, and reproduction by buds to
reproduction by ova and by fertilized ova. This
we believe to be the main cause of the diJBBculties they
encountered.

Dr. Carpenter has taken quite another point of view.*
According to this English savant, oviparity is an
entirely different process from gemmiparity. The
first requires the intercommunication of two systems
of special and distinct organs ; the second is simply
'^a multiplication of cells in the course of a con-
tinuous growth.-'^ There may be a few slight differ-

* " Medico-Chinirgical Review," 1848. I regret that I am only
acquainted with this essay through Professor Owen's comments
upon it in his " Parthenogenesis."

238

METAMOEPHOSES OF MAN

ences between Dr. Carpenter^s and my own opinion
as to tlie starting-point of tlie theory, and as to the
meclianism by whicli the phenomenon is accomphshed ;
but_, with these exceptions, his general ideas agree in
many particulars with my own. The following are
some of the considerations which led me to this mode
of view.

All forms of reproduction which we have as yet
touched on, except reproduction by ova, are in reality
so many processes of gemmation. This is quite
evident in the Hydra,, the Aurelia, and in all those
animals in which the process takes place externally.
Microscopic observation demonstrates that it is the
same with the Biphorse, the Helminthes, and the
Aphides. But in the last-named insects, the bud,
which is developed internally, is detached at a very
early period, and falls into the cavity of the body,
where it undergoes transformations, which bring it
toward its perfect form. Here, the germ, instead of
being simply a bud properly so called, is a bulb, that
is to say, a deciduous bud, destined to be developed
within the very animal from which it was produced.*

The very phenomenon of budding in its commence-
ment is simply one of local growth. When a bud,
whether internal, external, fixed, or deciduous, is
formed at any part, it results from the accumulation,
by the vital stream, of the plastic materials at one
point, instead of their distribution over the entire
body.

* Bulbs, properly so called, are like ordinary buds, but they
becorae spontaneously detached from the plant which produces
them, throw out roots, and give rise to a new plant, as though a
seed had been sown.

AND THE LOWER ANIMALS.

239

Thus,, all agamic reproduction is associated with
groiuthy properly so called.

Tids conclusion^ arrived at by a process of reason-
ing, is not unsupported by facts. Wlien we amputate
an eartb-worm^s bead, or a lizard^s tail, wbat first
appears on tbe circular wound resulting from tbe
operation ? A small tubercle, an actual bud, in which
we cannot at first detect either nerves, bones, muscles,
or blood- vessels. This bud increases in size, and,
after a while, the various organic elements reappear ;
the animal reproduces the parts which had been
destroyed. This is the first stage of reproduction by
bulbs. The hydra, each of whose parts, when it has
been divided, will reproduce a perfect animal, pos-
sesses this faculty in its highest degree. Each frag-
ment, in modifying the accidental form resulting from
the operation, has had to bud in every direction, that
is to say, it has had to grow.

That is what experience teaches us. Mere ordinary
observation leads us to the same result; it is even,
perhaps, more demonstrative. When treating of trans-
formation and metamorphosis properly so called, we
showed how the normal growth of animals took place.
We saw that this phenomenon was in some instances
manifested in the increase in volume, and in others, in
the midtiplication of the same parts of the body ; and
in the latter case it frequently happens that the super-
added part presents a series of organs, which almost
constitute it a separate individual. For example, in

I have made several experiments, especially upon the first of
tliese animals, but I postpone their publication tiU I have com-
pleted them. I may, perhaps, bring out this work at some future
period. ,

240

METAMORPHOSES OF MAN

tlie Annelids^ eacli segment tlirougliout almost tlie
entire body, lias its ov/n nervous centre,, its own loco-
motive apparatus, its vascular system, digestive cavity,
and reproductive organs, just like that which follows
and precedes it. It would require but one step farther
for each ring to carry on its own existence inde-
pendently ; indeed, it only wants a mouth and organs
of special sense in order to do so. In Syllis myrianis
and Nais, the mouth and organs of sense do really
present themselves, in a special segment, it is true,
but one which is formed just like the others.* All
the organs placed posteriorly to this abnormal head,
are placed under its control. A new individuality is
developed, and originates in a series of phenomena
differing in no particular from those of ordinary
growth, as observed throughout the whole class.

There is evidently no fundamental distinction
between the phenomena just referred to, and those of
gemmation in the Hydra in the Strobila, as observed
by Desors, and of segmentation of the same animal,
as described by Saars. The form alone of the animals,
and the laws which regulate their individual growth,
are quite sufficient to explain the apparent differences.
Thus, the phenomenon of mammalian growth, and that
of the most decided gemmation, pass, by insensible
gradations, the one into the other; and all observation
forces on us this one conclusion, that gemmation, and
consequently agamic reproduction, are fundamentally
hvit processes of (yroivih.

Vide M. Edwards' fine memoir on the embryology of the Au-
nulosa in the " Annales des Sciences natiirelles," 1845 ; and also
my own memoir, " Sur la Generation alternante des SyUis," in
the "Annales des Sciences naturelles " for 1854.

AND THE LOWEE ANIMALS.

241

From this point of view we can at once understand
liow it is tliat agamic reproduction cannot be indefi-
nite. Growth in every animal has its limits pre-
arranged. If J then, gemmation be a form of growth, it,
too, must have its limits ; therefore it cannot suffice
for the perpetuation of the species. Hence the inter-
vention of another mode of generation, by which the
continuance of the race becomes insured. As soon as
the process of gemmation ceases, the ovum exhibits
itself as the fundamental element; consequently,
even these animals most decidedly gemmiparous and
fissiparous — must, after a certain period, reproduce
themselves by ova.

Once formed, the bud proceeds with its develop-
ment in the same manner as any other germ, and in
obedience to the same laws by which the ova of a
bitch, a hen, and a teredo are converted respectively
into a mammal, a bird, and a mollusk. From this, we
should expect to find, in its case, all those phenomena
which we treated of in our earlier chapters. Whether
the bud remains fixed, as in the Hydra, till the time
comes when it will have only to increase in size, or
detaches itself in the condition of an almost unorga-
nized mass, and falls into some special cavity, where
it undergoes its subsequent changes, as in the Aphides,
or is borne away to a distance, as in Synhydra, it
nevertheless undergoes a series of tranrformations and
metamorphoses similar to those we have described,
and it is only under the influence of the vital force
that it assumes its definitive form and proportions.

These considerations lead us to believe that the
course which, in association with Dr. Carpenter, we
have struck out, is really the correct one. Without

R

242

METAMOEPHOSES OF MAN

framing any new li^^otliesis^ tliis mode of viewing
geneagenesis agrees with all tlie results of direct
observation and experiment ; it leads from the best
known and simplest facts presented by ordinary
growth^ to the most complex and most recently dis-
covered phenomena of the production of generations ;
it explains the neutrality of all the intermediate series
of the latter_, accounts for multiplication by agamic in-
dividuals_, and justifies the existence of cycles^ which
terminate in reproduction by ova; finally^ it distin-
guishes clearly between the phenomena in question
and those of metamorphoses_, whilst at the same time
it preserves the true relations which form a bond of
union between the two classes of facts_, and which
cannot be denied.

It appears to me now_, as it did on other occa-
sions_, that this doctrine is accurate in its entirety_, as
well as in its details.

AND THE LOWER ANIMALS.

243

CHAPTER XX.

PARTHENOGENESIS_, OR VIRGINAL REPRODUCTION

FUNDAMENTAL FACTS.

We have seen that, definitively, every animal springs
from an ovum, and that, mediately or immediately,
it has invariably not only a loarent, but even a true
mother.

Is the father^s existence as fully demonstrated ?
This is a question which the recent progress of
science puts to us so forcibly, that it cannot be over-
looked.*

When opposing Owen's views some six years since,
I said that the expression parthenogenesis would cling
to science, and be employed to designate a certain
number of exceptional phenomena, very imperfectly
known, but whose real existence seemed to me un-

In thelast century, an inspector-general of the silkworm-nurseries
of Sardinia, named Constant de Castellet, having seen in the silk-
Avorm analogous processes to those we are now considering, wrote to
Eeaumur, asking him to examine them. Eeaumur only replied, cx
nihilo nihil. Castellet could not beheve in the reality of his own
observations, and therefore fancied himself deceived. We leam
from this anecdote, which is borrowed from Dareste's excellent
article, written three years ago, in the " Eevue germanique," that
Eeaumur was unacquainted with Malpighi's observations, and that
he acted in this instance as he had done in Peysonnel's case.
Castellet was less persevering than our feUow-countryman, and
thus relinquished the glory of a discovery which was only confirmed
a century after his observations.

R 2

244 METAMOKPHOSES OP MAN

questionable, and wortliy of every naturalist's atten-
tion. At this very period Siebold supported my
assertions, and replied to my appeal by publishing bis
splendid work, which opened up an entirely new and
now actively explored field of research.*

From the isolated observations on nocturnal Lepi-
doptera collected by Bernouilli, Treviranus, Suckow,
and Burmeister, and on the silkworm by Malpighi,
Herold, Curtis, and Filippi, it follows that certain
females which have had no connection with the males
can deposit eggs, which become developed, and give
rise to caterpillars as active and healthy as those
which spring from fecundated ova. M. Carlier,
member of the Entomological Society of France,
obtained as many as three original generations of
Lijoaris disjyar.-f A belief in the virginal reproduction
of Psyche was popular for a long while among lepido-
pterists, and even at the present day there are many
species, the males of which are unknown. But we
may associate all these phenomena w^th those which
occur among the Aphides. Siebold being desirous
of explaining the matter, studied the anatomy of the
female Psyche, and unhesitatingly attributed the
opinions on this question to errors in observation. J

* " Walire Parthenogenesis bei Schmetterlingen und Bienen."
1856. This work was analyzed fully by Young in the " Annales
des Sciences naturelles," 1856 ; and it furnished the chief materials
for Dareste's article in the "Eevue germanique " for 1859. I have
borrowed from it nearly all the details respecting facts which have
been the start-point to all the actual researches.

t " Introduction a I'Histoire de I'Entomologie," by Th. Lacor-
daire. M. Carlier's last generation consisted of males alone, which,
as he observes, put an end to the experiment.

X " Ueber die Fortpflanzungen Psyche." — Zeitschrift fiir wissen-
schaftliche Zoologie, 1849.

AND THE LOWER ANIMALS.

245

He liad hardly made known his first opinion_, when
he himself observed similar phenomena to those
pointed out by his predecessors,, and these not only
in Psyche^ but in many kindred species.* At the
same time he learned that the problem of ova fertile
ivithout fertilization had been actively discussed for
four years previously by the numerous bee-culturists
of Germany.

In fact^ in 1845^ M. Zierzon^ a curate of Carlsmark^
in Silesia, an unscientific man^ but gifted with great
powers of observation, put forward certain propo-
sitions, which caused a division between the various
journals and societies then interested in the practical
study of bees. Zierzon asserted that the queen-bee
whilst preserving its virginity deposited ova, which,
however, gave rise to males only. He supposed, with
Huber, that this queen received only on one occasion
the fecundating fluid to be employed during the entire
period of her existence — that is to say, for several
years; he added, that the queen-bee could employ
this fluid as she wished, so as either to favour or
prevent its contact with the ovum about to be de-
posited. In the first, said Zierzon, the ovum is
fertilized, and produces a female ; in the second, the
same result follows as if the queen had remained
in her virgin state, and the ovum produces only a
male.f

Among the facts adduced by Zierzon and by
Berlepsch, who was the first to maintain and confirm

In Psyche helix and in Solenohia lichenclla and S. tri^uetrella.
+ Zierzon' s researches were published in two apicultural jour-
nals for which we might now seek in vain aU over Germany, but
they have been carefully analyzed in Siebold's work.

246

METAMORPHOSES OP MAN

the Carlsmark curate^s (ioctriiies_,* are a few of a
particularly interesting cliaracter_, wliicli we sliaU
briefly allude to.

Huberts observations^, and modern anatomical re-
searches^ have proved that the reproductive organs of
bees are so contrived, that the union of the sexes can
only occur during flight. Now, those females which,
through imperfect development, or accident, or the
scissors of an experimenter, have been deprived of
their wings, before unioUj nevertheless deposit fertile
ova, but the latter never give rise to any but male
individuals.

ISTay, more, if a matron queen be exposed to a cold
temperature, capable of altering the character of the
fertilizing liquid, or if through any organic lesion the
communication between the pouch containing this
liquid and the oviduct be cut off, she will henceforth
produce males alone,t although heretofore she may
have produced individuals of both sexes.

* M. Berlepsch, a skilful and well-known agriculturist, has a
magnificent establishment at Seebach, which is devoted to the
breeding of bees. On several occasions he has placed his apiary
at the disposal of both savants and interested practitioners. It was
with him that Siebold and Leuckart made those observations which
established the unexpected phenomena of which we have been
speaking. Siebold informs us, too, that Berlepsch had the honour
of preserving Zierzon's views when, on account of an unsuccessful
experiment, he was about to abandon them. His researches were
published in the journal of apiculture entitled " Erchstadter Bie-
nenzeitung" (Siebold).

t This was observed by M. Berlepsch. It is to this distinguished
amateur also that we owe the discovery of the influence of cold ;
and Leuckart having made a post-mortem examination of an indi-
vidual thus experimented on, found that the male element had
been destroyed.

AND THE LOWER ANIMALS.

247

Tlie phenomena resulting from cross-breeds sup-
port Zierzon^s views still more.

In Germany^ where bees are cultivated with as
much care as our farmyard fowls and beasts, it was
attempted to acclimatize foreign species remarkable
for different qualities, and to cross-breed them with
the local races, in order to improve them. One of the
finest among the former is the Ligiirian tee, which
has been described by Aristotle and sung of by Yirgil.
Now, the hybrids resulting from its connection with
the German races possessed the characters of both
parents ; but these traces of cross-breeding were con-
fined to the workers and female or queen bees. The
males always exhibited the parental characters in their
purity. The male parent, having nothing to do with
their formation, could not efiect any modification of
these characters.

Such are briefly the results of Zierzon^s and Ber-
lepscVs observations. Although nearly conclusive in
themselves, it was necessary that they should be
tested by scientific men; and to this task of con-
firmation Siebold and Leuckart addressed themselves.
They examined dead specimens of both virgin and
matron queens ; they investigated the reproductive
organs and the contained ova; and after a series of
careful researches, they both proclaimed the truth of
the facts put forward, and the accuracy of the propo-
sitions and opinions of the modest clergyman of
Carlsmark.

Neither of them confined himself to mere verifica-
tion. Siebold examined the silkworm from the same
point of view, and re-discovered the phenomena in-
dicated by Malpighi, Herold, and Filippi, and then.

248 METAMORPHOSES OP MAN

glancing at tlie invertebrata in their entirety^ lie
showed that parthenogenesis occurred in many other
groups of Insects_, in Crustacea, and in Mollusks.
Leuckart, on his part, investigated the virginal repro-
duction of worker-bees, and proved that this pheno-
menon, which is exceptional in our hives, occurs with
the same characters, but constantly, in colonies of
wasps, bumble-bees, and ants.* Then, extending his
researches, he found the same phenomena, if anything,
more fully characterized among the cochineal insects. f
We may add that similar occurrences have since been
recorded by other naturalists. For example, Messrs.
Barthelemy and Milliere have observed partheno-
genesis in four new species of Lepidoptera,J and
M. Hartig has discovered it in twenty-eight species of
Cynips. In regard to the latter, Lubbock observes,
that as yet we are only acquainted with the females,
though probably parthenogenesis is much the com-
monest form in them.

* " Zur Kenntniss des Generationswechsels und des Partheno-
genesis bei den Insecten." 1858. This work was briefly analyzed
in the " Bibhotheque universelle de Geneve," 1859.

t Ibid. 1861.

% By Milliere, for two species forming a new genus akin to the
Zeignes (Ann. de la Soc. Linn, de Lyon, 1857), and by M. Bar-
thelemy in Chelonia caja and Sphinx euphorbicB (Annales des
Sciences naturelles, 1859).

AND THE LOWER ANIilALS.

249

CHAPTER XXI.

THEORY OF PARTHENOGENESIS.

The plienomenon of geneageiiesis_, whicli may now be
regarded as established, develops new and numerous
problems for tbe minds of naturalists to solve. The
first of these which presents itself may be thus
stated. Although the reproductive bodies, which are
organized without the influence of a male parent,
resemble eggs, are they genuine ova ?

The reply to this query has been generally in the
affirmative, although we find, even in works written
to justify this opinion, that the contrary is proved, at
least in certain instances. Without entering into
details which do not concern our present inquiries,
we may consider the results arrived at by Huxley
and Lubbock, two savants who have thrown most light
upon this question.

The first, in his valuable memoir, On the Agamic
Reproduction and Morphology of Aphis,^^* followed

" Transactions of the Linncean Society," 1858. The author has
formed very different conclusions from those laid down by myself ;
for the tendency of his researches is to associate as much as possible
the true eggs (ova) and false ones (pseudova). Among other state-
ments, he observes, The rudiments of the true ovum cannot be
distinguished from those of the false one." The author's drawings
and descriptions have convinced me that the contrary is the case.
Doubtless, this difference of appreciation is due to the immense
number of ova which I have had an opportunity of observing in

250

METAMORPHOSES OF MAN

step by step the development of tlie germs in botli
viviparous and oviparous individuals. He tlius demon-
strated prominently tlie distinctions^ as to origin^
between tlie true and false ovum. The distinctions^
in some measure involuntarily^ drawn by tlie distin-
guished Professor in tbe " School of Mines are very
striking, especially to those who have observed the
embryogeny of some of those animals which, like the
Annelida and most marine Mollusca and Eadiata, are
best adapted to this class of investigations.

In the viviparous individuals there occur pheno-
mena resembling those which I have met with not
only in Hermella and Teredo, but in hundreds of other
animals belonging to the three sub-kingdoms. In
the three last chambers of the ovary of the oviparous
Aphis figured by Huxley, the ovum in its embryonic
state is represented by an isolated but well-marked
germinal vesicle, which already exhibits its germinal
spot. This vesicle increases in size as it passes
through the second chamber, but it is in the third
alone that it begins to be surrounded by the vitellus,
whilst the germinal spot remains still clear and
distinguishable .

The only difference that I can observe between
the ova of these insects and those of the marine
animals to which I have referred is, that we see the

my studies of marine animals. In such instances the phenomena
accompanying the earlier stages of development are presented even
to the uninquiring eye. The very opportunity which I have had of
forming a definite conclusion since the appearance of Professor
Huxley's memoir, is to my mind the most convincing proof of the
value of this work. In publishing it, the author has once more
shown that he deserves to be regarded as one of the most distin-
guished representatives of physiological zoology.

AND THE LOWEPw ANIMALS.

251

latter in all stages of development^ and^ in infinitely
greater number^ undergoing on the spot^ and in the
midst of the liquid of the general cavity^ those
changes which in the aphis take place in the various
chambers.* Here, then, we find that constancy of
fundamental phenomena on which I dwelt in the
earlier pages of this volume. This harmony is of
itself alone a proof of the accuracy of the investiga-
tions made and the structures figured by the two
observers, no matter what be then* method of inter-
preting them.

In the viviparous Aphides, Huxley describes and
figures a very different series of phenomena. Here
the ovarian chamber is filled with a pale homogeneous
substance, which encloses a dozen cells with opaque
nuclei. Portions of this material are separated from
the rest by a constriction of the walls of the chamber,
which becomes more and more decided. It is from it
that the new being will be entirely developed. In the
midst of this little mass there may indeed be seen a
small transparent sphere, which sometimes presents
within it a nucleus like those of the preceding- cells,
but of which occasionally there is no trace, and which
under other circumstances is replaced by a little mass
of rounded corpuscles. To experienced eyes there is
nothing here to recall either the true germinal vesicle
or the germinal spot, the fundamental elements of ova
properly so called.

I unhesitatingly express the same opinion, in regard
to the small transparent sphere, which Lubbock found

* Viewing the subject from this aspect, it is interesting to com-
pare the figures in my memoir with fig. 2, plate 40, of Huxley's
essay.

252

METAMOEPHOSES OP MAN

in tlie reproductive bodies or false ova of certain
cochineal insects of tlie orange-tree, and to wMcli lie
gave tlie name of germinal vesicle.* Far from being
tlie first structure visible, it does not exhibit itself
till the other parts are fully formed ; the period of its
appearance is irregular; and finally, to judge by the
author^ s drawings and descriptions, instead of enclos-
ing the true germinal spot, it always contains within
it a mass of infinitely minute corpuscles. In all its
features it far more closely resembles the transparent
cell of the aphis embryo than the germinal vesicle of
ova whose nature is established, and which should
always be selected for the purpose of comparison. f

The reproductive bodies of the cochineal or kermes
of the orange, J and those deposited by the kindred
species, are all developed without any intervention on
the part of the male. Nevertheless, they have been
regarded as true ova, because they are covered with
a shell, and are deposited like these latter. But in the
manner in which they are formed, and in primitive
composition, they are veritable internal buds, almost
exactly like those of the viviparous Aphides. Is their
nature altered because, from the circumstance of their
being destined to be developed outside the maternal
uterus, they have been provided with a more or less

■'^ " On the Ova and Pseudova of Insects." — Philosophical Trans-
actions, 1858.

t The reasons already given force nie also to deny the term ovum
to the reproductive bodies of Daphnia, which have been so weU
described in Lubbock's memoir, " An Account of the two Methods
of Eeproduction in Daphnia and of the Structure of the Ephippium."
— Philosophical Transactions, 1857.

J This and a certain number of kindred species form the present
genus Lccanium (Illiger).

AND THE LOWEK ANIMALS.

253

solid envelope according to the accidents they are
likely to incur^ and which is capable of preserving
them from external influences ?* Certainly not. Not
more so than an ovum becomes a bud, because it
never acquires a shell before it is transformed and
developed within the mother^s body.

But if these reproductive bodies are buds, and not
ova, it then follows that development without the
intervention of the male element occurs in the phe-
nomena just considered. This is not a case of _par-
thoiogenesis, but one oi geneagenesi^.

This conclusion appears to me to be clearly deducible
from these two series of researches, evidently carried
out with extreme care, and which have been more
strictly compared with each other than all the rest
which have been published on this subject. f Its

* The envelopes of these pretended ova evidently vary under the
conditions alluded to. They would be useless to the internal hud
of the aphis, which is developed within the organs of the mother.
Therefore they are not present. The internal buds of the peach-
tree kermes are as well protected as the true ova, although they
do not undergo their transformation till they have left the parent's
body. Between these two extremes we find the internal bud of
the orange-tree Kermes or Lecanium, which is almost entirely
developed within its parent's body, and has acquired its perfect
form a few hours after being deposited. Hence it is protected only
by a single envelope, which Lubbock compares to the vitelline
membrane (" On the Ova and Pseudova, &c."). Now that atten-
tion has been directed to this point, I am convinced that many
other instances will be found which may be serially arranged in
the group of phenomena referred to.

t Professor Huxley and Mr. Lubbock, between v/hom a friend-
ship exists, evidently commmnicated the results of their researches
to each other. It was on the invitation of the first that the inte-
resting investigations of the second were carried out ; and in his
turn, Huxley devoted his attention to the results obtained by

254

METAMOEPHOSES OF MAN

inevitable consequence is to throw doubt on all the
hitherto implicitly accepted facts regarding virginal
generation. Indeed_, the revision of most of these
facts appears to me to be quite necessary. Before
accepting the word ]iaTtlieno genesis, it is evidently
essential to be perfectly certain that the reproductive
body is an ovum and not a hud, enclosed in a more or
less solid envelope. In order to do this^ it is necessary
to refer to the origin of the formation in question.
To my mind_, every reproductive body which has not
the form of a germinal vesicle^ with its germinal spot,
belongs to the second category ; it should possess this
double and fundamental character in order to be
placed in t}i.G first one.

To judge from what we already know^ the result
of this revision will be to diminish considerably the
number of instances of true parthenogenesis. Will
it erase them all from the book of science ? I think
not. In this regard I have much pleasure in coin-
ciding with those confreres whose opinions I opposed
in the preceding pages. Without going so far as
Owen^ Huxley,, or Lubbock, I think that a series
of intermediate stages exists between the ovum and
the bud.* We have seen that such is the case with

Lubbock before they were publisbed, in order to ascertain the
accuracy of bis own views.

* It is evident that, according to my view, there is quite an
investigation to be made ; an investigation which is essential to
the progress of science. Hence it will be understood how much
pleased I was to see Mr. Lubbock engaged in this labour, in the
last writings of his which I have seen, and which tend to bear out
some of the views which I have already put forward Notes on
the Generative Organs and on the Formation of the Egg in the
Annulosa," — Philosophical Transactions, 1861).

AND THE LOWER ANIMALS.

255

respect to the anatomical facts ; it is the same
with those of the physiological kind. It is only
necessary to recall those animals which produce
either males or females_, according as the male
parent has had any share in the process or not
(bees), and especially those which deposit simulta-
neously ova capable of being developed, and others
which perish if they have not been previously fer-
tilized (silkworms).

There is at present nothing to warrant the suppo-
sition that in these animals the reproductive bodies
have a different primitive constitution ; and as some
are unquestionably ova, it ought to be the same with
the others.*

Notwithstanding my reservations, parthenogenesis
is still to my mind a constant phenomenon. With
my confreres, I believe that there exist true females
which deposit genuine ova that are developed with-
out any intervention on the part of the male. But I
believe that this phenomenon is far less frequent than
has been supposed.

Meanwhile it remains to be accounted for.

But is it possible? Is the cause of these phe-
nomena to be found in the fecundating action of the
older writers, in Owen^s spermatic force, or in herma-
phroditism of the ova as supposed by Barthelemy ?
These hypotheses are all gratuitous. They all lead us
far from direct observation. Let us therefore leave

'"^ To these purely theoretical reasons I may ackl that Lenckart's
figure of the ovary of Solenobia lichenella seems to prove that this
species, in which both he and Siebold demonstrated the existence
of parthenogenesis, produces true ova, vi^hich are marked in the
commencement by the presence of the germinal vesicle and spot.

256

METAMORPHOSES OP MAN

them aside, and, with Huxley, frankly admit that
physiology is as yet too young to solve every enigma
which the Sphinx of science proposes.

But although it is wise to abstain from explana-
tions which are evidently premature, still it is fair to
make some approach to an explanation, and that is
what I attempt to do.

In the earlier portions of these essays, we saw that
among animals in which we have at present no reason
to suppose the existence of anything hke partheno-
genesis, the unfecundated ovum demonstrates its own
special vitality by a series of movements quite analo-
gous to those which in the fecund ovum correspond to
the period of formation of the new being. We have seen
that in Hermella, Teredo, &c., this vitality is quickly
exhausted in proportion to its exertion. Now, conceive
of an ovum possessing a little more vital energy ; it
is evident that it will commence the process of organi-
zation. This is exactly what we find in by far the
greater number of eggs of the virgin female silk-
worm.* Let us in imagination increase this vital
power of the ovum, and we shall find it capable of
forming an embryo, which is quite perceptible, but
which will perish before it has been hatched.

* In the course of my investigations into the nature of the disease
which committed such ravages among our silkworms, I had occa-
sion to open several cocoons containing female insects which had
never been set free ; most of them had deposited eggs, yet assuredly
in these instances it would be impossible to suppose the interven-
tion of the male. In most cases the ova had changed colour, and
had assumed the characteristic tints indicative of the organization
of the superficial strata of their contents. In very many instances
it was impossible to distinguish these ova from normal ones of the
same age.

AND THE LOWER ANIMALS.

257

This is what Herold saw,* and what had been also
observed by Siebold. Let us suppose that — accident-
ally in some species_, normally in others — the vital
energy of the ovum is unusually intensified; then
this ovum will become capable of producing by itself
alone a complete animal, and we shall have partheno-
genesis in all its stages, such as it is in the silkworm
and the other species we have spoken of.

Seen from this point of view, parthenogenesis, it is
true, is not explained, but at all events it is associated
with other jphenomenay and that alone allows us to go
a step further.

Fundamentally, and from the period of the germinal
vesicle condition,t the corpuscle which will eventually
become the ovum is formed by the same process as
that which gives rise to the bud.

Both result from the accumulation at a given point
of a certain quantity of plastic material, abstracted
from a pre-existing individual. Both owe their first
origin to ^process of groiutJi.

Now, we have said already that the growth of a
living being cannot be indefinite. This is why re-
jyrocl'itrtion hi/ hiuls exhausts itself or is arrested.
Re] jvo chid ion by lui fee undated ova should also have
a limit.

Here the great importance of the male sex makes
itself apparent. But before the reader can grasp the

* "DisquisitionesdeAnimalium Yertebris carentiuni in ovo For-
matione." 1838.

t In my memoirs on the embryogeny of Herniella and Teredo, I
stated my reasons for believing that the germinal vesicle precedes
all the other elements of the egg. I believe that in the commence-
ment it is a homogeneous spherule devoid of an enveloping
membrane.

S

258

METAMORPHOSES OF MAN

nature of the function whicli I attribute to it in this
series of phenomena^ we must retrace our steps.

We saw that the imfecundatecl ova of Hermella and
Teredo^ when left to themselves, showed their special
vitality by a series of movements which recalled those
of the fecundated ova; but we also saw that these
movements were soon accelerated_,* became irregular_,
and brought about the destruction of the ova in which
they presented themselves.f Now if, by artificial fecun-
dation^ we caused the male element to come in contact
with these ova before the work of destruction was
complete, the movements would slacken and become
more regular, and a certain number of these ova,
which were in process of disintegration, would give
rise to as perfect larvee as though fecundation had
taken place in the commencement. J Here it is
evident that the result of the intervention of the
male would be the re -animation and regulation of the
egg^s vitality, which had begun to exhaust itself in
a series of inordinate actions.

Hence it seems to me that the intervention of the
male element, in the case of parthenogenetic phe-
nomena, exerts a very similar influence. The repro-

* This acceleration is so well marked in Hermella's ova, that the
changes of form can be almost as easily watched as those presented
in the movements of an amoeba.

t This destruction of the principle is certainly not due to either
physical or chemical forces. Putrefaction comes on at a relatively
much later period.

% In my memoir on the embryogeny of Hermella, I described at
some length an experiment which I made on this subject, and
which leaves no room for doubt. — Annales des Sciences naturelles,.
1848.

AND THE LOWEE ANIMALS.

259

duction by females only^ presents several irregu-
larities also; it tends to exhaust itself, by tlie very
exercise of its power. The male then steps in^ to
restore this almost extinct property, and by the
fundamental act of fecundation,, establishes the neces-
sary start-point of the production either of new
individuals or of new generations.

This mode of view is, I believe, justified by all that
we know at present concerning the phenomena of
geneagenesis. It is evident that, in bees, the inter-
vention of the male parent is necessary, at least once
for every two generations. Judging from Carlier^s
experiments, there may be three generations under
these conditions in Lijmris dispar. The range is pro-
bably still more extended in Psyche and analogous
genera.* But the intervention, at a given period, of
the male, as the element requisite for the perpetuation
of the species, is evidently one of the great laws of
nature.

We have in some measure a material proof of this,
in the external structure of the ova of the most
decidedl}^ parthenogenetic species. All of them pre-
sent special apertures, intended to permit the en-
trance of the fecundating fluid. This is, I beheve^
unanimously admitted by naturalists. This existence

* I do not refer to the Coccidce, as I know not how far true par-
thenogenesis may take place in them. Nor do I aUude to the vast
number of species regarded, I think, too hastily as being partheno-
genetic, simply because their males are as yet unknown. For the
same reason the Lernece were regarded as presenting the pheno-
menon in question. It seems to me that naturalists who draw con-
clusions so rapidly, would do well to read the sage reflections which
terminate Siebold's great work.

s 2

260

METAMORPHOSES OP MAN

of the mic7'opyle has satisfied all tliat it is of service
sooner or later_, and perhaps always.*

Definitively^ the male parent is as essential as the
female one to the constant duration of the species.
The start-point of generations forming any series is
not only an ovum, but a fecundated ovum.

Hence_, all that .we have said regarding buds_,
and of the generations proceeding from these germs^
applies to multiplication by unfecundated ova, and the
generations which they give rise to. They also are
intermediate beings_, of secondary value, interposed
between the true parents and the true ofispring. The
circle may enlarge or alter in form, it may undergo
central or circumferential changes, but it invariably
becomes closed.

We have already seen that reproduction hij huds
(whether internal or external), natural and artificial
reproduction by division, and alternate generation in
its varied forms, are really but so many manifestations
of one great phenomenon. We are led to say the
same of parthenogenesis — it is only a spjecial form of
geneagenesis.

* Leuckart, who began by separating parthenogenesis from alter-
nate generation, saw an essential difference between the two phe-
nomena ; viz., that in the first, fecundation may occur before every
reproductive act, but that in the second it must occur from time to
time in certain fixed acts of reproduction. — Bibliotheque Universelle
de Geneve, 1859.

AND THE LOWER ANIMALS.

261

CHAPTER XXII.

GENEAGENESIS IN PLANTS RELATION OF THE ANIMAL

TO THE VEGETABLE KINGDOM.

The various facts which have been summed up in
these essays lead to results of much importance to
general physiology. Certainly one of the most re-
markable has been the gradual establishment of a
relationship between the animal and vegetable king-
doms, and the removal of some of the greatest gaps
which existed, according to the ancients, between the
two great divisions of living beings. This conclusion
has been admitted by almost all naturalists devoted
to these curious researches, from PeysonneFs
time to that of Owen and Steenstrup. We our-
selves have on various occasions insisted on its ac-
curacy. In treating of Dujardin^s works, we pointed
out the decided resemblance which certain pheno-
mena, observed in Medusa, by the zoologist of Rennes,
presented to those observed by Dutrochet in the
Fungi.* We showed how, as regards mode of repro-
duction, there was an unexpected relation established
between the worms of our streams and the trees
of our forests, between the syllis we found at Brehat
and the date-trees cultivated by the inhabitant of the

* "Memoires pour servir a I'Histoire anatomique et physiolo-
gique cles Animaux et des Vegetaux." Paris, 1837.

262

METAMORPHOSES OF IVIAN

oases.* In proportion as researches multiplied_, these
relations became more numerous and general. At
present we may safely assert^, that wherever genea-
genesis occurs^ there is estabhshed between the two
kingdoms,, not only analogies requiring a certain
mental strain for their comprehension^ but an evident
resemblance^ and in some instances almost an
identity.

It is necessary, in order to avoid being charged
with exaggeration, to enter into some details, and to
describe the nature of a plant or tree ; but to do this,
it is first necessary to know what an indivichial is,
whether in the animal or vegetable kingdom.

Our ideas in this regard are sufficiently clear when
we speak of a man, a pigeon, or a frog. Each of
these words is associated in our minds with a certain
series of parts — definite in number and relations—-
which collectively constitute the individual. When
one of these parts is multiplied or transposed, we
attribute it to an anomaly. If one of them is absent,
we perceive that the individual is incomplete. This
appreciation is frequently expressed by special terms,
such as monstrous, blind, and maimed, which are
found in almost every language.

What we have said of man, and of animals familiar
to all our readers, is equally applicable to an infinite
number of other species. A naturalist can say, at a
first glance, whether an insect wants a leg or a wing, a
MoUusk a tentacle, a Star-fish one of its rays, or a
Medusa one of its filaments. He sees an incomplete
individual in every ivhole which has lost one of its

* " Souvenirs d'un Naturaliste."

AND THE LOWEE ANIMALS.

263

parts. If these same organs be more mimerous than
usual — albeit, their relations are but slightly changed
— the naturalist will see before him so many monstrous
individuals.

But if this same naturalist has placed before him a
portion of coral, or a piece of a compound ascidian
which has been slightly mutilated, he cannot now
decide as he had done before, unless, indeed, the
traces of its injuries indicate that some accident has
befallen the object he examines. No matter how
numerous the coraPs branches, or the geometric figures
of the ascidian may be, the most acute savant cannot
proclaim it to be a monstrosity. From this fact alone
we may conclude that neither the coral nor the
ascidian plate is an individual, notwithstanding the
general form which characterizes it, and which allows
of its various species being distinguizhed almost at a
glance.

Careful observation bears out this conclusion. In
both cases we perceive a great number of beings
whose aggregation constitutes an entirety. Now,
each of these beings presents a series of conditions
identical with those found in man himself. It is com-
posed of parts, whose number and relations are fixed.
Each of them is an animal, is a distinct individual.
The polypidom and the ascidian plate are only aggre-
gations. They are, so to speak, villages or towns,
in which the pol3rps represent the inhabitants, and the
cavities take the place of houses. Hence we can
understand that both houses and inhabitants may be
multiplied without altering the fundamental condition
of things. Paris and Constantinople hold the same
positions in the world, despite the influence of epidemics

264

METAMOEPHOSES OF MAX

or emigration,, and althougli tlie former is as constantly
enlarging its faubourgs as tlie latter is burning tliem
down from time to time. It is just the same with
the polypidoms and ascidian plates.

These views, though long since admitted into
zoological science, were embraced at a later period by
botany, although their truth is far more evident in
the latter.

No matter what may be the results of vegetation,
the oak and the lime are always trees; the myrtle
and the rose are always shrubs. Neither the savant
nor the ordinary observer can say that one or other
of these plants is monstrous or incomplete, whether
they be large or small, bushy or thickly- branched,
growing freely or closely clipped. The number of
their parts is not determinate, therefore they are not
individuals, they are only aggregations. A tree is a
species of vegetable i^ohjii, whose common parts are
the trunk, roots, and branches.

How can we distinguish and isolate the beings
which correspond to the polyps — the vegetable in-
dividuals ?

Botanists are not agreed on this point. Some, who
think that the leaf appears in a modified form in every
organ as the fundamental element, regard it as the
vegetahle indivicliial. Others, associating this same
leaf with the condition of an organ, suppose the
individuality to reside in the germ, that is to say, in
the seed and bud. They consider the branch pro-
duced by either to be an individual. Many facts,
and not unfrequently the same ones differently in-
terpreted, have been brought forward in support of
their views by the advocates of the two doctrines.

AND THE LOWEE ANIMALS.

265

We are not in a position to decide between tlieni ;
however^ the second^ which is chiefly based on em-
bryogeny and has analogy unquestionably to support
it, seems to us the more accurate of the two. Con-
sequently ive shall adopt it in the parallel we are about
to establish between plants and animals,, although
Professor Owen has chosen the first. Besides^ the
two theories tending equally to associate the facts
proved in both kingdoms^ the ideas we are about to
put forward will^ in the main, be those already pub-
lished by our illustrious confrere;, but the form will be
slightly different, and therefore we shall be led to
certain considerations overlooked by our predecessors.

We have seen that the tree resembles the polypi-
dom not only in form but in its complex natm-e.
Keither is a simple being. The individual vegetable
or animal is the fundamental element in each; both
form colonies — How do these colonies increase and
multiply ? Here the analogies we spoke of are seen
in the clearest manner. What do we first see when
a new branch is about to be added to the existing
ones ? — A bud. What announces the appearance of
a new polyp on the stalk of a Goryne? — A bud
also.

In both cases the colony^s new guest, the new
individual, is but a simple accumulation of organizable
matter, developed at some point in the common
system, constantly receiving additions from the vital
stream, and which is fashioned by the vital forces into
either an animal or vegetable.

In most cases the Coryne^s bud becomes an asexual
polyp, provided with long tentacles, and a capacious
digestive apparatus. Unfit for the purpose of repro-

266

METAMOEPHOSES OF MAN

duction, its office is to lie in wait for, seize and digest
every tiling in the sliape of prey wliicli conies within
reach of its arms. The nutritive juices thus prepared
flow through a system of canals to the main stem of
the polypidom, and then from it, to each of the indi-
viduals to which it gives attachment. The polyp to
which we have alluded is, then, solely employed in
nourishing the colony.

Exactly the same thing occurs in the case of the
rose-tree. Most frequently the bud becomes a branch
provided with leaves. The function of the latter is to
abstract from the atmosphere various gaseous fluids,
and especially carbonic acid ; to prepare from them a
hquid sap, which travels through the branches and
stem to the roots ; and to elaborate this compound,
and convert it into a nutritive juice, which, then
returning in the opposite direction, is employed in
nourishing the trunk itself and all its ramifications.
The leaves then are essentially the organs of absorp-
tion, exhalation, respiration, and elaboration, and the
branch to which they alone are attached has only a
function of nutrition to discharge.

On the rose, therefore, as on the coryne, we find
certain individuals ivliose sole office is that of nourisliing
the colony.

At a given period the corjme gives rise to buds,
which at first are like the preceding ones, but which
eventually become polyps of a very difi'erent character.
These new beings have neither arms nor mouth, and
their digestive apparatus is quite rudimentary. To
compensate for these they are provided with organs
which, from the nature of their products, are judged
to be sexual. If these polyps were isolated, they would

AND THE LOWER ANIMALS.

267

soon die from want of food ; but_, being nourislied by
their fellows,, they increase and become developed^
and serve to perpetuate the species. Their function
is limited to this end. They are^ in fact^ so many
reproductive individuctls.

It is just the same with the rose. A certain number
of buds, instead of being converted into branches, give
rise to flowers. The leaves, having been extensively
modified, and endowed with more important functions,
are changed into sepals and petals, to form the perianth,
and into stamens and pistils, to form the apparatus of
both sexes, which here, as in many animals, are com-
bined. The branch, thus metamorphosed, could not
support itself, but is dependent for nourishment on
the colony, whose propagation is ensured by it in
return. It has also become a reproductive individual.

In the rose-tree, as in the Coryne, things take place
in precisely the same manner.

The Coryne mother produces ova, the rose produces
seeds. Here again, if we except peculiarities of form
and of comphcation, or of specific simphcity, there is
no difference between the two kingdoms. We find in
both varieties of reproductive bodies, an essential part
(the germ in the ovum, the embryo in the seed) which
will eventually be converted into a living being. In
both we observe special accessory parts, intended for
the nutrition of the young animal and vegetable, and
which in the ovum are styled vitellus and albumen,
and in the seed perisperm and cotyledons. Both ovum
and seed, too, are enclosed in more or less numerous
protective envelopes, and may exist in hundreds, or
be completely isolated. If, therefore, combining their
general characters, we draw ideal figures of seed and

268

METAMOEPHOSES OF MAN

ovum^ it will be found impossible to distinguisli one
from the other.

In the animal as in the plant_, reproduction by
buds takes place spontaneously^ and at the imme-
diate expense of the parent; and in both kingdoms
reproduction by seed and ovum requires the inter-
communication of two elements produced by special
organs. Whether these organs are united in one
individual, or borne by two distinct beings, the pro-
cess is fundamentally the same. There is a father
and a mother, a stamen and pistil ; an element which
fecundates, and an element which is fecundated. The
ovum, when unfecundated, although almost invariably
presenting its three characteristic spheres, will never-
theless possess no true germ; so likewise, the un-
fecundated seed will present only a rudimentary body,
concealed at the base of the pistil, and devoid of an
embryo.

Thus, in both plants and animals, we find agamic
and sexual reproduction side by side. These two
processes are placed in both kingdoms under the
same conditions, and if we could enter here into tech-
nical details, we should see that they are accompanied
by almost identical phenomena.

In order to observe the extent of this resemblance
between the relations which unite these two modes
of reproduction in plants and animals, let us do, as
Professor Owen has done, — place an ovum and a seed
side by side. Both have been fecundated. From the
one springs a ciliated larva, from the other a primary
stem, carrying two thick fleshy cotyledonary leaves,
quite diflPerent from those which will succeed them.
The larva becomes fixed, and is transformed into a

AND THE LOWEE ANIMALS.

269

sort of cylindrical bud. The little stem of the rose
elongates^ and becomes terminated by a bud. Up to
this period the polypidom^ like the plants is developed
almost exclusively at the expense of the stored-up
materials ; by the vitellus,, in the case of the ovum ;
by the cotyledons, in that of the seed. But from
the animal bud is produced a polyp provided with
tentacles for the capture of prey_, and with a suitable
digestive apparatus ; whilst the vegetable bud becomes
a stem, provided with leaves. In both kingdoms the
individuals first produced have for their sole office to
supply and prepare the food of the colony. Thanks to
their labours, the colony is extended ; new buds appear
and become developed, but for a long while they give
rise to food-proclucincj individuals only. Evidently,
the most pressing necessity is that of founding and
extending the colony, and this is the only office with
which the first inhabitants of these animal and vege-
table cities are charged.

As soon as the special life of the polypidom and
shrub is established, it becomes necessary to provide
for the reproduction of these colonies. Then the
rejwodudive individuals appear, male and female
polyps, sometimes combined, and in the case of
the plant, fiowers bearing stamens or pistils, most
frequently both. The first produce and fecundate
ova ; the second produce and fecundate seeds. All is
ahke in both kingdoms. The polyp, with distinct
sexes, is an animal floivev ; the flower is a sexual
vegetable i^olyi).

The individuals successively produced in both shrub
and polypidom remain united by a common trunk ; but
it is very easy to understand that when a separation

270

METAMOEPHOSES OF MAN

takes place the relationsiiip is fundamentally the same.
Now this is precisely what occurs in certain other
caseSj — among the Aphides^ for example ; and a glance
at Professor Owen^s sketches will explain the matter
as fully as we can in words. Erom the egg laid in
autumn_, there is developed in the following spring
a neuter Aphis^ which by a process of gemmation pro-
duces others like itself, this process being continued
for several generations. If all these descendants of a
single germ were attached to one another_, we should
have a regular polypidom. In being isolated at birth_,
their relationship is not altered. This is what Steen-
strup suspected^ and what Professor Owen demon-
strated in a very lucid manner. The neuter Aphides
correspond to the food-seeking polyps of the Coryne,
and to the sterile branches of the rose-tree ; the male
and female Aphides represent the reproductive polyps
of the polypidom^, and the flowers of the rose-tree,
and from our point of view may also be styled
animal flowers.

Among the general facts bearing upon the class of
speculations we are now engaged in_, is one upon
which I have often dwelt heretofore,, and which I may
here recall.

There is but one mode of sexual reproduction,
whilst there are several forms of agamic generation
which are found equally in the two kingdoms. In
certain plants, we find, besides the true bud — the bulb
— a genuine bud, like that we have referred to, but
which becomes detached from the parent, and is
developed by itself, as though it had been a seed.
We ourselves have found this deciduous bud in Syn-
hydra, an animal closely akin to Coryne. The lower

AND THE LOWER ANIMALS. 271

Algae are propagated by spontaneous division_, and tlie
Infusoria are in no way behind them in this respect.
Trembley propagated the Hydra by artificia 1 cuttings_,
perhaps more extensively than any gardener ever
propagated a plant by the same means. Finally^
parthenogenesis shows itself in the vegetable king-
dom under conditions exactly like those we met with
among animals^ a fact which has been dwelt on^ with
much reason^ by both Lubbock and Dareste.

Spallanzanij whose name it is impossible to omit_,
when speaking of physiology,, pointed out this fact as
early as the last century. He found fertile seeds
in the female organs of hemp^ which had been care-
fully preserved from all external influences. But this
result was too much in opposition to accepted views
to be admitted then, and, on all sides, efforts were
made to prove that the skilful experimenter labom^ed
under a delusion. However, in 1820, M. H. Lecoq
reproduced and extended Spallanzani^s experiments,
and arrived at the same conclusions.^ Finally, M.
Naudin, assistant naturalist in The Museum, investi-
gated the matter, and his experiments, made under
Decaisne^s superintendence, established the fact in-
controvertibly. It is now unquestionable that certain
plants can produce fertile seeds, although the flower
has not been submitted to the action of pollen.

Indeed, a circumstance vv^hich occurred at this very
period, one may say, in all Europe, is the best proof
that can be adduced of the reality of vegetal jKcrthe-
nogenesis. In 1829, Dr. Cunningham brought from

* M. Henri Lecoq, Professor in the faculty of sciences at Cler-
mont, is now a corresponding member of the Institut.

272

METAMORPHOSES OF MAN

Moreton Bay (Australia) tliree specimens of an uni-
sexual euphorbium, whicli were placed in tlie Kew
Botanic gardens.* These tliree were females. Never-
theless they produced seeds^, which gave proofs of
fertility. From Kew the new plant spread to the
other European gardens_, and, in all_, produced only
female forms, which invariably gave rise to fertile
seeds.f

We see then that life in operating on brute matter
to the production of either plants or animals, employs
processes which are invariably the same ; from which
we are justified in concluding that in both plants and
animals, agamic reproduction in all its varieties is
simply a phenomenon of growth, whose result is the
progressive and more or less evident individualization
of a portion of the parent. This conclusion is further
borne out by direct observation. It is true that the
individuality of the bulb or deciduous bud detached
from its parent stem, cannot be denied, but that of
the fixed bud was observed at a later period ; and that
of any bud, whatever be its origin, can no more be
recognized in a plant than in the hydra.

As in both plants and animals growth has its limits,
so should agamic reproduction have its boundaries
also ; and here, as well as in the animal kingdom, it is
impossible to propagate a species indefinitely. Conse-

* Lubbock, " Account of the two Methods of Keproduction in
Daphnia."

t The Coelehogyne ilicifolia, which is here referred to, has been
investigated by our most skilful botanists, who have with the great-
est care sought in vain for a trace of male generative organs.
Hence we must regard it as an example of parthenogenetic repro-
duction, whose cycle embraces more than thirty generations.

AND THE LOWER ANIMALS.

273

quently, after a longer or shorter lapse of time^ repro-
duction by seeds becomes necessary; therefore^ in
plants as in animals^ this alone is a function of the
first class_, whilst agamic reproduction is but a sub-
ordinate office. It is almost idle to comment on the
harmony existing in this respect between facts and
our theoretical deductions_, at least in regard to plants
in a state of nature.*

We see then that these cycles of reprodAictlon which
Steenstrup first pointed out in animals,, appear in
plants also. In both kingdoms these cycles commence
by the development of an oviini or a fertile seed,

* The artificial propagation of vegetables by cutting, lajdng,
and grafting, constitutes a true process of multiplication by genea-
genesis. Is this process applicable indefinitely ? This question
which was put in the last century, has been answered in various
ways. Knight went so far as to say that the life of individuals
produced by difterent methods could not exceed in length that
of the parent from which the graft, slip, bud, &c., was taken. —
(Chevreul's report on Count Odart's work entitled " Ampelogra-
phie.") M. Puvis, while opposing Knight's evident exaggerations,
partly embraced his opinions, and applied to animals in general,
and to man himself, the views which Chevreul justly refuted. But
is not the exclusive employment of these various modes of rej)ro-
duction likely to result in the general deterioration or exhaustion
of the individuals thus obtained ? AU that we have learned in
these essays on geneagenesis, forces me to reply in the affirmative.
Moreover I have heard that M. Cosson maintains this opinion,
which he supports very ably on facts borrowed from the history of
cultivated plants. It is to the abuse of the geneagenetic method of
reproduction that this distinguished botanist attributes, at least
in part, those general diseases which commit such havoc among
our plants ; it is to the same cause also that he refers the gradual
disappearance of the weeping willow {Salix Bahylonica), formerly
so ver}'- common, but of which there are now in Europe only a few
female individuals, which it becomes more and more difficult to
reproduce by cuttings.

T

274

METAMORPHOSES OF MAN

embrace a certain number of generations^ and termi-
nate in tlie re-appearance of truly sexual individuals.
No matter how numerous the generations comprised
by a cycle may be_, all tlie individuals_, animal or
vegetable^ sexual or neutral^ which compose them^
are still the direct or indirect product of the same
ovum_, or the same seed. All are therefore the
mediate or immediate offspring of the male and female
parents which produced and fecundated this primary
germ.*

The analogies we have pointed out are maintained
to the end. We know that the Hydra and Aphis which
have acquired their sexual characters^ perish almost
immediately after having deposited their ova. The
Coryne mother becomes atrophied and resorbed as soon
as it has emitted its fecund germs. As soon as they
have started new series of cycles and insured the per-
petuation of the species, these reproductive individuals
have fulfilled their mission, and therefore disappear.
The hfe of the food-sucking individuals, on the contrary,
is prolonged, for they have to support the colony and
provide the materials for new buds. It is hardly
necessary to remind the reader, that here also we find
the analogy already observed between plants and
animals. The vegetal flower, more fleeting "than the
animal one, fades away as soon as the seed is formed,
and even before it has ripened. The floral branch, or
vegetal reproductive individual, is like the hydra and
the aphis mothers, and discharges its office but once
in its lifetime. On the other hand, the foliaceous por-

* The words male and female parent are here employed to
designate the male and female sexual apparatus, whether they are
distinct, or combined in the same individual.

AND THE LOWER ANIMALS.

275

tions of the food- sucking individuals remain^ in our
evergreens_, and in plants of tropical countries^ just as
the prey-seeking polyps of the Coryne do. And although
it happens otherwise in the case of most trees in our
climates, this apparent difference is explained by the
circumstance that the cold of winter suspends the
vital processes going on in the trunk.

Thus we perceive, that in regard to the multipli-
cation, to the propagation of the species, the parallel
between the most decided vegetables and animals
subject to geneagenesis, is maintained from the period
of birth to that of death.

T 2

276

MBTAIvIOEPHOSES OF MAN

CHAPTER XXIII.

GENERAL CONSIDEEATIONS . CONCLUSION.

We liave briefly analyzed tlie three great phenomena
presented by the animal kingdom in the development
of living beings. Resuming what we have already
stated in regard to each of them, we perceive that
transformation presents itself in all^ and that it alone
is concerned in the development of most of the higher
animals. Metamorphosis jDi'operly so called_, comes
next, but it is fundamentally a phenomenon of trans-
formation which occm^s beneath our eyes, instead of
taking place in the depths of the organism, or when
concealed by the envelopes of the ovum. Then genea-
genesis presents itself ; but from being essentially con-
nected with the processes of growth and progressive
individualization, it is for that reason associated with
the two other phenomena.

Thus we may with certainty repeat what we asserted
in the commencement of this work, that transformation,
metamorjpjiosisj and geneagenesis, are but three forms
of one and the same phenomenon, that they bring
about the same consequences, and terminate in the
same result.

The conversion of a rudimentary germ into a com-
plete individual is the final end and object of these
changes of form and proportions. Hence it follows
that general metamor]jliosis is essentially progressive.

AXD THE LOWER ANIMALS.

277

and that it tends incessantly to render structures more
perfect.

Doubtless^ in attaining tlie essential^ tlie accessory
is frequently sacrificed^ and the latter appears to be
the case to an almost excessive degree in the recurrent
development of certain animals. In these instances^
too^ more than in any others,, the truth of the general
law we have been laying down is apparent. For
example^ in the Lernea the entire body becomes
deformed and atrophied to the advantage of a single
apparatus ; but the function which this apparatus has
to perform is the perpetuation of the species. Hence
it is the most important one^ and as soon as its dis-
charge commences^ all the others are^ so to speak^
absorbed by it^ doubtless from the circumstance that
the animal is incapable of supporting all.

Apart from the apparent exceptions of the preced-
ing instance^ the character of the metamorphosis is
of a most striking nature. AYhen an animal^ which un-
dergoes simple transformations^ has its development
arrested at any stage^ a monstrosity is produced, as
the result of that circumstance alone. As to animals
with geneagenesis and metamorphosis properly so
called, then' larvae and scolices are always incomplete
beings ; they are true first sketches, which are ren-
dered more and more perfect at each developmental
phase and each new evolution, till the primitive type
makes its appearance.

Metamorphosis — simple transformation in the more
perfect animals — becomes more complex in proportion
as we approach the lower divisions of the animal
kingdom. Mdamorpliosis projjerly so called is quite
exceptional among the vertebrates. It is only

278 METAMOEPHOSES OF MAN

general among the members of the other sub-king-
dom^ and in these it is more complete the lower we
go. There is an immense difference between the
caterpillar (the butterfly^ s larva) and the little ciliated
creatm'e which is the larva of the Hermella. The
former is a very complex animal^ which performs
important functions; the latter is_, so to speak, only
a viteUus_, enclosed in its blastoderm, and clothed
with cilia. It is because the caterpillar belongs to a
superior, and the ciliated larva to an inferior member
of the same sub-kingdom.

Geneagenesis is controlled by the same law. Its
phases become more numerous and better defined, in
proportion as we descend in the scale of beings. It
is the exception among Articulata, but becomes the
rule among radiate animals.

Proportionally as metamorphosis becomes complex,
it renders the naturalist^s description of any species
less simple.

Among animals which undergo transformation this
description is simple enough. The important modifi-
cations take place out of sight, and we have only to
sum up the features resulting from changes of the
external characters of the young beings, and the dis-
tinctions which exist between the male and female.
In animals with metamorj^hoses properly so called^ the
difiiculty is increased. In insects, one must be ac-
quainted with the larva, nymph and perfect animal,
of the latter of which there are always male and
female. In the Teredo one must be familiar with a
series of forms, which are quite as well marked, but
far more variable. Finally, in animals with geneagene-
sisj we must embrace the characters of four or five

AND THE LOWER ANIMALS.

279

beings whose forms and modes of life are quite dis-
similar, if we desire to know the species. Had not
experience informed us, who could have suspected the
existence of the Distoma under its forms of ciliated
larva, Sporocyst, and of free and encysted Cercarise ?

Metamorphosis, under the form of fjeneagenesis, not
only complicates the idea which the mind conceives
of any particular species, but it even extensively
modifies our general and abstract notions of species.
Up to this, we have understood by this word a succes-
sion of beings proceeding- one from the other, and
whose individuality is maintained despite a number
of minor less apparent changes. At present, we must
add to this, that, in certain cases, the species is com-
posed of perfectly distinct beings, which proceed one
from another by a process of multiplication. To the
idea of continidti/ of individuals, which forms the
basis of all existing definitions, we must connect that
of succession of cycles. This is what was first under-
stood by Chamisso, and was fully demonstrated by
Steenstrup.

The general phenomenon which we are now con-
sidering seemed for a long while, under its forms
of true metamorplwsis and geneagenesis, to supply an
argument to the advocates of spontaneous generation.
Until the time of Redi and Yallisnieri, insect larvae
were thought to be formed by the action of the
physico-chemical forces on decomposing organic
matter. Even in a few modern works it is asserted
that the intestinal worms are the immediate products
of the animal in which they are found. We have
seen that the best-ascertained facts lead to a diame-
trically opposite conclusion. For a long period it has

280

METAMORPHOSES OF MAN

been known that the caterpillar proceeds from two
pre-existing butterflies ; and we mentioned how
recent investigations demonstrated the origin of the
Cercarige^, Cysticerci^ &c. We are now aware that all
those neuter individuals which reproduce without the
intervention of sexes_, and whose multiplication was
so long a mystery^ are tlie equivalents of simple buds.
We have shown that tlie bud and unfecundated ovum
can only produce individuals^ or at the utmost a few
generations ; and_, finally^ we have proved that to the
fecundated ovum alone belongs the task of perpetuating
the species.

Now_, in order to carry out this general law^ it is
necessary that there be a female to secrete th.e
ovum^ and a male to fecundate it. Hence every
animal proceeds^ mediately or immediately^ from a
father and mother ; * and what we here assert of
animals applies^, as we have seen^ with equal force to
vegetables. Consequently the discoveries_, relative to
geneagenesiSj strike at the very lowest foundations
of tlie spontaneous generation doctrine.

Every living being originates in a father and
mother^ that is to say_, in a male and female. The
existence of sexes^ of which there is not a trace in the
inorganic world_, is the distinctive character of orga-
nized nature, is, in fact, one of those primordial laws
instituted in the beginning of all things, and which
we must lay aside, at least for the moment, in order
to discover the reason of it. With a few exceptions,
which doubtless are more apparent than real, we may

* As we stated before, the terms father and mother apply respec-
tively to the individual generative apparatus when the two are
united in the same being.

AND THE LOWER ANIMALS.

281

say tliat tlie organic world has had a sort of double
creation ; that there are two worlds — male and female.
Yery close relations of co-existence may be found
between the two; but they may invariably be dis-
tinguished^ and it is truly remarkable^ that their
separation is an indication of high organization.
These two worlds appear indistinguishable only among
the very lowest members of both kingdoms. Her-
maphrodites are only found in the inferior groups
of the four sub-kingdoms. This character is not pre-
sented by any of the leading classes of these great
divisions ; and with the exception 'of certain fishes^
not a single vertebrate is hermaphroditic* Thus
the union of the two sexes in one individual^ so
far from being a sign of superiority^ is one of true
degradation^ and indicates in some measure a mon-
strosity.

Metamorphosis attains its greatest manifestation in
fjeneagenesis. The latter, which originates in a simple
process of growth, evidently commences by trans-
formation; but among the Medusae and intestinal
worms it is still further complicated by metamorphosis
proper, and thus comprises the general phenomenon
in all its phases.

From that circumstance alone we may conclude
that it is accomplished by the processes we have
already described. The proofs of this conclusion
are neither difficult of production nor will it take us

* M. Dufosse, a physician of Marseilles, called attention to facts
which had been well nigh forgotten, and demonstrated that in the
various species of the genus Serramis, a very well-marked herma-
phroditism is found. This is at present the only exception to the
rule amongst vertebrate animals.

282

METAMOEPHOSES OF MAN

very long to enunciate them. Is not the first forma-
tion of the bud essentially a process of ejngenesis, its
growth one of simple evohition, and are not its modi-
fications so many phenomena of complex evohition ?
Is not the imperfect condition of the organs of repro-
duction of the^neuter Aphis^the result of an actual arrest
of development ? Do not the histories of the Medusae^
Distomge^ and Tsenise supply us with a thousand
examples of the p^roduction, destrudiony and appro-
priation of organs ? Can we in this more than in any
other instance understand these results_, without
admitting the existence of the vital vortex ? Certainly
not. The latter reappears with the character of the
general process pointed out in the earlier pages of
this volume.

We have then^ as it were_, returned to our starting-
point. Let us for a moment dwell upon this fact, and
deduce certain conclusions from it.

We saw that the vital vortex presided over trans-
formation. It alone enabled us to comprehend meta-
morphosis; it alone explained the far more complex
phenomena of geneagenesis. It is impossible to avoid
seeing a fundamental law, and in some measure also
an immediate cause of the development and completion
of living beings, in the exercise of this twofold
movement of arrival and departure. Notwithstanding
the assertions of some naturalists, who desire to arrest
their inquiries at this stage, it is necessary to refer
this fact to some higher cause ; for matter, which
is of itself inert, can only be set in operation by the
impulse of some force or agent. Every material
operation is at first an effect before, in its turn, it
becomes a cause. What, then, is the agent which is

AND THE LOWER ANIMALS.

283

here at work in matter ? Shall we^ like some physi-
ologists_, invoke the six or eight forces admitted by
chemists and natural philosophers^ in explanation of
the phenomena occurring in inorganic matter?* Long
ago we gave the following' reply to this question if —
Yes ; in organized beings we find the phenomena
of heatj hght_, and electricity; chemical aflBinity and
capillary attraction are momentarily manifested^ and
possibly we may also find in them processes analogous
to those of catalysis and epipohsm. But these phe-
nomena are accomplished^, and these processes carried
on^ under the influence of a far higher power^ whose
existence it is in truth impossible to deny. Electricity,
heat_, and chemical affinity operate in living beings,
and are certainly engaged in the production of the
vital vortex. Nevertheless, they labom* only under
the control and regulation of a superior force — hfe,
which modifies all brute forces, and causes them to
produce muscle and blood instead of ammoniacal salts ;

* Chemists and natural phUosopliers accuse naturalists of endea-
vouring to cloak ignorance with a word, in supposing the existence
of a special force ia order to account for the series of phenomena
characteristic of Kving beings. It is true that astronomers explain
the motion of the heavenly bodies by the hypothesis of gravity
alone ; but in explaining the action of their instruments, or the
products of their laboratories, both chemists and physicists invoke
in their turn, hght, gravity, heat, electricity, and magnetism ; others
add, affinity, capillarity, endosmosis, catalysis, epipolisni, &c. ; all
these for mere inorganic matter ! After showing that they them-
selves are so little exacting, it is indeed dealuig generously with
naturalists, to deny them the right of supposing one solitary force
more, to preside over such characteristic, varied, and complex
phenomena as those of living beings !

t In my " Souvenirs d'un Naturaliste," and in many articles in
the " Kevue des deux Mondes."

284 METAMORPHOSES OF MAN^ ETC.

bones instead of phospliate of lime; and plants and
animals^ instead of mere inorganic lifeless masses.

All force is blind^ and mnst necessarily be directed.
In order to produce a certain determinate species and
not a kindred one^ in order to avoid being lost amid
the various paths of metamorphosis and geneagenesis^
it is requisite that even life itself should be placed
beneath the control of something still superior.

This something is the specific nature of each being_,
that which each plant and animal has received from
its ancestors, through the intermediation of the seed
or ovum from which it was produced_, and which it
will transmit to its descendants by the intermediation
of the germs which it gives rise to in its turn. If we
could go back for generations and ages, we should
still find the same questions presenting themselves,
and invariably similar facts would give rise to like
replies. In order to explain organic nature, it would
be necessary to refer to the very origin of all things.

But here, observation and experiment, those two
guides which human science ought never to lose sight of,
are absolutely unavailing. The true philosopher feels
compelled to pause, lest he should set his foot in a
land of hypotheses and conceptions, where it is so easy
to wander from the proper path, and where truth itself
— supposing it to be attainable — cannot be distin-
guished by any certain test.'

THE END.

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