Sti ieetataty re

0
‘) MONCH trletriclatete

iy ctecratnl fate
“FW hehe

ett

i anh

nid ee

Pat
sh aclbsip shai ba
‘a

Bees aii cat
ate
a peta
riteny oe rs agi

ayoraentteR

x
oi)
ey} sratapabsaid e paki bueah
by Pra

aret ti
" Cy (BASS: de thw hots Heth Aah st

‘aspen x i
soa Ht hp hue rate elisin ho

Ah As I See ual oats id
Ms eth vain ib tthe

RH tenat a MATA DCR
Sten aytaci
itp

nn why

oy et Wh iid i

gaia Nein bit ps tctytate! seater 4am) ne retsetsatig taken

MA We a

a 'P th annt Frkewn)
ih

scout ws
sibs ne » fray)

Hens hes wie
7 Hate
ine

itt
yon pe
4 Phebe My) " i ws " <i

ri ici! ia

i y ro ret Trempyabcate ining)
+i ini mp beef eit
she ‘

Peed pe

PA a a Netto peitet

a pedebe:
A

Ay
¥

wh
hap vens

Mise ala
PrP ree pha?
ii ee eh, 4, ini

at) ith ‘
( (siya
a

Ada bai)
fs cy Waal

ai fi i) dg i P isin

i
FUE SCH a
phew: iti
Vy

hy

ti
Dy aL Ma

ce
43

nt bal heats
aM
ata
etait rhet ty fv iy

S05 betas Magy
Nita had

ota
Hein ies ein pokes
a iabalel

rasarnte

died "
tee r
eke rie behets Ltt Mh

Poh a be
merce %
he un
DOAMog ts
dye

0 UST KE 2
woos

Hiv i) A teat vei
fi i

Terk
int iat We hale’

ae
lL nar

Hebi tt i
n

‘is

ahah do petty 8

cr)

ee ee ian
ary

5 eo Sy

ae? HP
datas: I: gehgal
HLA ‘Yel Bat te

ratiteateth
eg injenra aa hea
ue

'
4 us i hat fre ae W

vist we
i ih I
fog tet

Hack
vhagie
you, ab
i

i ew te

ay Mata
Pony piiiateti ani

ceneueneiy
eatin

inant ds

j
Here a Pi
coe iaebwo be

rma
a, 0 hich te A ibs ihaie le
TM Wir aM tt Mi }
vias ine i ‘4 ini bial ifn i i! (eH) Hy aa ivi aia Ay
i i Ht Weeasisie

s
postr s ee
eae
Sererces

=
$ret

oF

cEniateaiet

ieptetcieseie:
Pot.

oye eee ae vi

eeeee

sts

Tete

eatisecece: Sebiee:

CORNELL
UNIVERSITY
LIBRARY

Gift in memory of

MARY STEPHENS SHERMAN,
from
JOHN H. SHERMAN, ’11

13

Vv brary
QH
Euge ant

TTT

Cornell University

Library

The original of this book is in
the Cornell University Library.

There are no known copyright restrictions in
the United States on the use of the text.

http://www.archive.org/details/cu31924024561445

INHERITANCE OF ACQUIRED CHARACTERS

Eugenio Rignano

UPON THE

Inheritance of Acquired
Characters

A HYPOTHESIS OF HEREDITY, DEVELOPMENT,
AND ASSIMILATION

AUTHORIZED ENGLISH TRANSLATION
BY

BASIL C. H. HARVEY

ASSISTANT PROFESSOR OF ANATOMY, UNIVERSITY OF CHICAGO

WITH AN APPENDIX

UPON THE MNEMONIC ORIGIN AND NATURE
OF THE AFFECTIVE OR NATURAL TENDENCIES

CHICAGO
THE OPEN COURT PUBLISHING CO.
IgII

L:

Copyright, 1911,

by
The Open Court Pub. Company,
Chicago.

2014/08
ee

CONTENTS

INTRODUCTION a) 9g) oswia ened 2G Sangh eo este lua avy ee 5

CHAPTER I.

Ontogeny, as a Recapitulation of Phylogeny suggests the Idea
of a continuous Action exerted by the Germ Substance
upon the Soma throughout the whole of Development.... 11

CHAPTER II.

1. Phenomena which indicate a continuous formative Action
which is exerted by Parts of the Soma upon the other
Parts throughout the Whole of Development ............ 19

2. Hypothesis of the Nature of the formative Stimulus........ 29

CHAPTER III.
1. Phenomena which point to the Existence of a central Zone

Of Development assese nace ssceeedanenso44 Sameree eeesen4as 53

2. Hypothesis of the Structure of the germinal Substance..... 76
CHAPTER IV.

1. Phenomena which refute simple Epigenesis ............... 104

2. Phenomena which refute Preformation ................... 121

3. Inadmissibility of a homogeneous germ Substance.......... 144

4. Inadmissibility of preformistic Germs..................065 150
CHAPTER V.

The Question of the Inheritance of acquired Characters ....... 159

CHAPTER VI.

The most important of the existing biogenetic Theories in Rela-
tion to the Inheritance of acquired Characters ........... 224

CHAPTER VII.
The centroepigenetic Hypothesis and the Explanation of In-

heritance afforded by it ........ce cet eec cree cere ences 289
CHAPTER VIII.

The Phenomenon of Memory and the vital Phenomenon....... 316

COHGLUSION s.iicade-v'os 4 Saeieles veeee Ta Cte nt cna TE Se 356

Appendix 2... cece eee eect cere nee ene renee ttn e nner neees aan ee 359

[index .ccccccce ccc c cece teen e eres ees eeneeeee sees sereenneeeees 401

“Some deny flatly the possibility of ever arriving at
an understanding of the nature of life. But if we ask
ourselves in what this understanding of the nature of life
could consist, from the point of view of positive philos-
ophy, we have no difficulty in recognizing that such an
understanding must be reduced to comparing vital phe-
nomena with some physico-chemical model already known,
suitably modified by the particular special conditions im-
posed upon it so that just these special conditions shall
determine the differences which exist between this vital
phenomenon and that phenomenon of the inorganic world
most closely related to it. If this be so, it is then the duty
of science emphatically to refuse to give up the attempt to
understand the nature of living matter, for that would be
to belie the Spirit of all scientific endeavor. For whether
it be clearly recognized or not, it is just this search for the
nature of the vital principle which properly constitutes the
principal object and the final goal of all biologic study in
general.”—E. RiGNANO, in “Acquired Characters,’ p.

334-

TRANSLATOR’S PREFACE

Rignano is a student of Biology who has also the
training of an engineer and physicist. His attack on bio-
logical problems is from that side. In this book he offers
an explanation on a physical basis of assimilation, cell di-
vision, and the biogenetic law of recapitulation in ontog-
eny, and he suggests a mechanism whereby the inheritance
of acquired characters may be effected.

Such a study of the most fundamental and difficult of
biological problems can not fail to be of the greatest in-
terest to all students of science. It points out a way to
the understanding of the essential nature of living matter.
Therefore the translator has gladly consented to prepare
for publication this translation first made for his own sat-
isfaction. It has been revised by the author.

University of Chicago, 1911.

Basi, Harvey,

PREFACE TO THE ENGLISH EDITION

This work which appeared first in French in 1906 and
later in German and Italian now appears after some years
in English thanks to the interest shown by several Eng-
lish and American biologists and philosophers, who have
expressed a desire to have its circulation facilitated
among the savants of their countries. This new indica-
tion of the growing favor acquired in a short time by the
theories here advanced, notwithstanding the author’s fear
that their novelty would stand somewhat in the way of
their reception, is the best reward he could desire for the
great difficulty he has encountered in the study of these—
the most fundamental problems of biology. And he
wishes to pay here his sad and affectionate respect to the
revered memory of Professor C. O. Whitman, one of the
first to interest himself in this English edition, and at
the same time to express his gratitude to his friend Dr.
Basil Harvey for the great care which he has given to the
translation, as well as to Dr. Paul Carus and The Open
Court Publishing Co., who have been so good as to be-
come the publishers.

Milan, March, 1911. E.R.

INTRODUCTION

The question of the inheritance of acquired characters
is one which, by its generality, by its importance for the
theory of the origin of species, and by its close connec-
tion with still more difficult questions concerning the
essential nature of life lying in the border land between
physical chemistry and biology, passes beyond the con-
fines of pure biology, and enters the wider field of posi-
tive philosophy in the sense of August Comte, that is of
scientific philosophy, which concerns itself with the most
general results of the various sciences and with their
fundamental interrelations. Is it any wonder then that
this much discussed but unsolved question excites the
keenest interest in philosophers and even induces some of
them though they are not specialists, to attempt to study
it thoroughly utilizing the abundant and valuable mate-
rial which biologists and naturalists can now supply?

It is so with the author of the present study.

Formerly when he had not yet formed any fixed and
definite opinion upon this subject, he had been inclined in
a few philosophical and sociological studies to prefer
Weismann’s theory of the non-inheritance of acquired
characters to the contrary theory of Lamarck. The rea-
son for this inclination even though no logically tenable
opinion had been formed, lay in the demonstrated inabil-
ity of any of the biological theories which had then been

5

6 Introduction

devised to give any explanation whatever, even an un-
satisfactory one, of the mechanism of that inheritance.
Yet the author never lost sight of the fact that natural
selection in no way sufficed to explain phylogenetic evolu-
tion completely, and he was always convinced that
non-inheritance was irreconcilable with the fundamental
biogenetic law that ontogeny is only a recapitulation of
phylogeny. This law, whose remote and immediate
consequences constantly stimulated the reflection of the
author, has finally led him in a purely inductive way to
the new biogenetic hypothesis about to be presented.

It seerned to the author that he ought to devote a
special effort to the elaboration and exposition of this
hypothesis, for he saw from the outset that it promised
an explanation not only for the inheritance of acquired
characters but also, and quite independently, for a whole
series of fundamental biological phenomena, and how it
afforded an outlet from the blind alley into which onto-
genetic biology seems to have run: for while some facts
lead us to reject epigenesis as it is commonly understood,
others force us to reject preformation, and similarly
while a whole series of reasons force us to hold as
inadmissable a homogeneous germinal substance or a sub-
stance only chemically heterogeneous, another whole
series of reasons obliges us to hold no less inadmissable a
germinal substance constituted by the germs of the
preformists.

The author knows well that he must not entertain any
oversanguine expectations. In the position of biological
science today we can deal only with preliminary hypoth-
eses, of which each gives way to its successor and each,
taking in a greater number of phenomena than its pred-
ecessor prepares the way for a later hypothesis which

Introduction rs

is able in its turn to include a number greater still. So
soon as a hypothesis pushes a bit nearer to the beleaguered
fortress, so to speak, and indicates new lines for study,

observation and research, one must admit that it has ful-~

filled its purpose. And this applies to our view of the new
biogenetic hypothesis which we here submit to the judg-
ment of biologists and of positive philosophers in general.

We have believed it expedient to follow in the exposi-
tion of this theory the order in which it was conceived
and built up, and so the first chapter describes briefly the
inductive way in which the author, starting out from the
fundamental biogenetic law, was led to the conception of
his hypothesis. In the three following chapters are col-
lected and arranged as concisely as possible the principal,
different, biogenetic facts which, quite independently of
the ever controverted question of the inheritance of
acquired characters, serve best to set forth and define the
new hypothesis and which, since they find in it their most
complete explanation, confirm it again directly or in-
directly in a deductive way.

After having then undertaken in the fifth chapter a _
brief examination of the question of the inheritance or
the non-inheritance of acquired characters which until
then we had laid entirely aside, we pass in the sixth :
chapter to the critical exposition of the principal biogene-
tic theories which are current at present. And we do this
not only with the object of showing their inadequacy to
explain the mechanism of inheritance, but rather in
order that the perception of the reason of this inadequacy
may aid us in discovering the necessary and sufficient con-
ditions required in any theory which seeks to explain this
inheritance. After that we go on again in the seventh
chapter with the examination of our hypothesis whose

8 Introduction

conception and elaboration up till then was considered
quite independently of the question of the possibility or
impossibility of the inheritance of acquired characters,
but which supported by an elementary hypothetical
phenomenon, which in certain respects finds its counter-
part in the inorganic world, becomes recognizable at once
as a most complete explanation of this inheritance.

Finally in the last chapter we endeavor to show how
this elementary hypothetical phenomenon on which the
new biogenetic theory rests, explains also a fundamental,
psychic phenomenon, to wit, memory and indeed the most
characteristic properties of the vital phenomenon in gen-
eral. And so this elementary hypothetical phenomenon
seems to us capable of bringing together within it and
referring to one basis not only the whole group of genetic
phenomena, but all vital phenomena whatever in the very
widest sense of the word.

Since, for the reasons above stated, the inheritance of
acquired characters is a question affecting positive philos-
ophy in the Comtian sense or scientific philosophy, the
author ventures to hope that biologists and naturalists
may not regard him as an unbidden intruder into their
domain, but rather since he is the first to recognize the
many gaps and shortcomings of his work, he ventures to
hope that he may count upon especial consideration, be-
cause of the great difficulties with which he who is no
specialist has had to contend in studies of so difficult a
nature.

Milan, May, 1905. E.R.

ONTOGENY

CHAPTER ONE

ONTOGENY, AS A RECAPITULATION OF PHYLOGENY, SUG-
GESTS THE IDEA OF A CONTINUOUS ACTION EXERTED
BY THE GERM SUBSTANCE UPON THE SOMA THROUGH-
OUT THE WHOLE OF DEVELOPMENT.

Everyone knows the fundamental biogenetic law of
Haeckel: ontogeny is a recapitulation of phylogeny, that
is, the development of the individual is a rapid résumé of
the development of the species, a short reproduction of
the endless chain of its ancestors.

The most important facts establishing this law, now
perhaps irrefutably, are so well known that we hardly
need to mention them here; for example: solipedation
develops gradually in the horse and only in the last stages
of its development; many whales which later instead of
teeth have the so called whalebone have teeth in their jaws
while they are still in a fetal condition and cannot take
any nourishment; the serpent while it is in the embryonic
state possesses its two pair of limbs, and so on.

“The development of the organism,” writes Roux, “‘is
not merely a production of the complex from the simple
by the most direct route. The ways are devious; and
many a forward step must be retraced. We mention only
the well known examples of the gill clefts and gill arteries
and their ultimate concrescence, the notochord also, and
the pituitary and pineal glands, structures quite super-

II

12 Biogenetic Law of Recapitulation

fluous and functionless from the first.””! Development
of this sort, proceeding toward its goal not by the direct
line but by byways and often backwards, would be incom-
prehensible were it not for the fundamental biogenctic
law.

Also Delage draws attention to the fact that all those
structures which disappear during the progress of
development must nevertheless have their significance.?

Similarly Oscar Hertwig notes expressly that there
exist many embryonal organs “which never come into a
position to perform the function which they have once
performed during the course of phylogeny.” *

We must then regard this fundamental biogenetic law
as true. We can even suppose it to be a close approxima-
tion, that ontogeny represents phylogeny exactly.

It is true that during the first ontogenetic stages
phylogeny is only epitomized, but this becomes steadily
less true the farther development proceeds, and during the
later stages ontogeny can be regarded as an almost exact
repetition of all the corresponding phylogenetic stages.

The human embryo, on account of the more numerous
and careful researches of which it has been the object,
serves better than any cther to illustrate this almost exact
phylogenetic repetition in the later stages. Its develop-
ment demonstrates even to the smallest details how the
embryo passes through the whole series of forms of the
pithecanthropoids, its immediate ancestors. Thus for
example the articulations of the leg in man show during

*Wilhelm Roux: Der Kampf der Teile im Organismus. Leipzig,
Engelmann, 1881. P. 59.

*Delage: L’hérédité et les grands problémes de la biologie
générale. Paris, Schleicher, 1903. P. 176.

Oscar Hertwig: Die Zelle und die Gewebe. Zweites Buch.
Jena, Fischer, 1808. P. 232.

Significance of This Law 13

fetal life a much closer resemblance to those of anthro-
poids than during adult life. At a certain stage of
development the great toe instead of being parallel to the
others forms an angle with their direction as in the apes.
In the same way many of the bones of the foot of the
newborn infant, in their form, in their respective angles
of inclination, etc., resemble very closely those of the
climbing foot of the anthropoid apes, particularly of the
gorilla.

In the attempt to see what significance the funda-
mental biogenetic law can have for the biologist we can
come somewhat nearer to the question by supposing
ontogeny to be an exact repetition of phylogeny instead
of a rapid résumé of it. It is true that it will be necessary
later to make some important corrections in this first ap-
proximation and to study the significance or cause of the
abbreviation and suppression in ontogeny of many phylo-
genetic stages; and this more intimate study will allow us
to penetrate further into the innermost nature of the
phenomenon. But for the present we desire by this tenta-
tive supposition that ontogeny is an exact repetition of
phylogeny, to have the great advantage of defining the
phenomenon to be studied more simply and precisely, and
of making our comprehension of it correspondingly easier.
It is by this means, that is by successive degrees of
gradual approximation that mechanical, physical, and
chemical researches have usually proceeded.

This first degree of approximation of the fundamental
biogenetic law will permit us then to make the two fol-
lowing statements: Each stage of the ontogenetic devel-
opment of any organism represents exactly one species
among the ancestors of that organism. Two species hav-
ing a common ancestor have an identical ontogenetic

14 Biogenetic Law of Recapitulation

development up to the stage corresponding to that com-
mon ancestor; they do not commence to diverge until
they have passed that stage.

But since all the various theories of heredity admit
that two distinct species descending from a common re-
mote ancestor possess germinal substances different from
each other, the question at once presents itself: If these
germinal substances are different, how then is it possible
that throughout a long series of stages up to the stage
corresponding to the common ancestor they present like
ontogenetic forms, the very same as those through which
the ancestor passed? If the germinal substance of one
species is different from that of the other should they not
from the very beginning show a totally unlike series of
forms?

A germinal substance in process of development con-
stitutes to a certairi extent a dynamic system of forces in
continual transformation. But two systems commencing
to give rise to two series of successive transformations
which throughout a long time are quite alike must neces-
sarily be themselves alike. And if at a given moment one
series diverges from the other it is necessary to attribute
this divergence to one of two causes; either to some ex-
ternal circumstance acting at that moment, or to some
internal impulse becoming active just at that moment.

“The parallelism in the phenomena of ontogeny and
phylogeny,” says Delage, “shows that first something
develops which is similar to what was developed in the
ancestors, and that then something which remained till
then inactive is added and development proceeds
further.” 4

‘Delage: L’hérédité etc, P. 457.

Succession of Ontogenetic Stages I5

In other words the biogenetic law implies that up to .
each stage of development the productive cause of develop-'
ment remains the same as that which produced the
ancestral species corresponding to that stage.

We should next ascertain whether the new circum-
stance now added or the new force becoming active only
at this stage and causing the subsequent development is
to be sought for within or without the various parts of
the organism which are actually in process of formation.

If at the start we limit ourselves for the sake of
simplicity to the consideration of morphological trans-
formations only, each stage of development whether
ontogenetic or phylogenetic will appear to us only as a
special mode of distribution of the organic substance con-
stituting the organism. But this distribution is modified
during the life of the adult individual only by new func-
tional stimuli, that is to say, only by agents which are
external to the structure in progress of modification. In
other words the impulse by which the corresponding por-
tion of living organic substance is constrained to
distribute itself differently does not reside within this
portion but comes to it from without.

Until the contrary is proven we may accept the state-
ment that the properties of living organic substance dur-
ing development are not different essentially from those
which it presents when development is completed. Con-
sequently when any particular mode of distribution of
the organic substance becomes altered during the prog-
ress from one given ontogenetic stage to the succeeding
stage, we can admit as a provisional hypothesis that this
different distribution is effected by some provocation
external to the parts which change.

This provocation cannot be constituted merely by the

16 Biogenetic Law of Recapitulation

morphological and physiological state of the other part of
the organism at that moment; for in the corresponding
phylogenetic state the two portions were in perfect
equilibrium with each other. It is necessary then to sup-
pose that somewhere in the remaining parts of the or-
ganism, there enters into play just at that moment and
only at that moment, some factor which was not present
in the ancestral species.

Further, since the alteration in the organism during
ontogeny is not confined to a single part of the organism
but affects several parts at the same time, and since the
impulse which comes into play at the end of each stage of
development compelling the passage to the successive
stage must lie external to each of the parts undergoing
transformation, it cannot lie in any of these parts.

This will be possible, however, only on condition that
among all the different parts of the organism there is at
least one part which is not itself subject to any substantial
change, but in which there comes into activity a series of
specific energies one after another of which each provokes
the passage of all the other parts of the organism to the
next ontogenetic stage.

This special part may be called the central zone of
development. And one can give the name of centro-
epigenesis to this hypothesis by which ontogenetic
development is made to depend on an infinite number of
different influences which this zone gradually exerts upon
all the remainder of the organism by activating succes-
sively a regular series of specific energies, each remain-
ing in a potential state up to the time of its activation.

Now the part which actually does remain unaltered
from the first segmentation of the egg up to the giving off
of the reproductive cells by the new organism is the

Centroepigencsis vs. Preformation and Epigenesis 17

germinal substance, and one suspects at once that it may
be just this substance which constitutes the central zone.

If so it would follow that the central zone must be at
the same time the germinative zone, that is to say, the
place whence the sexual cells get the germinal substance
which makes them capable of reproduction. Let us
hasten to add now that the central zone must coincide
with the effective germinal zone, but may possibly be quite
separate and distinct from the apparent germinal zone.
The latter would be then only the place of formation of
the sexual cells, inasmuch as these constitute in a certain
sense the mere envelope in which later the germinal sub-
stance is assembled, which alone is able to give them
reproductive capacity.

The hypothesis of centroepigenesis includes then that
of a continuous action exercised by the germinal sub-
stance upon the soma throughout the whole duration of
its development. We shall endeavor in the second chapter
to learn what is the nature of this action and we shall
reserve for consideration in the third chapter the central
zone itself, as well as other facts and arguments which
make its existence seem probable and which serve to make
the hypothesis clearer.

We shall limit ourselves here to putting in special light
the fundamental characteristics which differentiate this
hypothesis as well from the preformistic as from the
epigenetic theories.

While Weismann and the preformists in general con-
sider that the germ plasm separates itself before the com-
mencement of development from the portion set apart to
form the new organism, and remains passively aside in a
detached part of the soma until it later steps in to form
the future sexual cells; consequently it would not control

\
1

18 Biogenetic Law of Recapitulation

development nor indeed have any part whatever in it;
that would fall entirely to the other portion alone, and it
would be just this passivity which would secure the in-
alterability of the germ plasm:

While on the other hand the epigenesists consider that
the idioplasm would participate in an important and con-
tinuous way in development, because it would be present
and active at every instant and in all cells; it would
remain, however, in spite of this participation permanently
unaltered, so that the cells of the soma would never be-
come differentiated by nuclear somatization from the
germ cells, but on the contrary retain the capacity of
reproduction to the same extent:

The centroepigenetic hypothesis postulates on the con-
trary that the germinal substance, although limited to a
single zone and separated and differentiated from the rest
of the soma, nevertheless exercises its epigenetic, forma-
tive action upon all the rest of the organism and during
the whole of development, without undergoing any altera-
tion whatever through this participation in development.

But this hypothesis thus sketched must now be made
more precise and clear by the consideration of other series
of phenomena, while at the same time the proof of the
facts is undertaken. And to this we propose to proceed
in the chapters which follow.

CHAPTER TWO

PHENOMENA WHICH INDICATE A CONTINUOUS FORMA-
TIVE ACTION WHICH IS EXERTED BY PARTS OF THE
SOMA UPON THE OTHER PARTS THROUGHOUT THE
WHOLE OF DEVELOPMENT—-HYPOTHESIS OF THE
NATURE OF THE FORMATIVE ACTION.

I. Phenomena Which Indicate a Continued Formative
Action

Among the phenomena which seem to indicate indis-
putably a continuous formative action exercised by a
more or less great part of the soma upon the other parts
throughout the whole of development, those of the re-
generation of amputated organs take a first place.

It is known that when the antennae of a snail, the
chelae of a crab, the feet of a salamander or the head of
a worm are amputated, these organs are reproduced even
when the amputation is performed during adult life.

Spallanzani has cut the feet and tail off the same sala-
mander six successive times, and Bonnett seven times,
and each time feet were reproduced of exactly the same
size as the former ones without any increase or decrease
in any part. These facts show that the formative agent
whatever it may be is always external to the part formed,
and that it exercises upon the whole development of that
part and throughout its entire duration a continuous ac-
tion, and further that it remains itself unaltered even

19

20 Indications of Continued Formative Influence

after the completion of its work and consequently is ca-
pable of renewing it at every favorable opportunity.

If on account of unusual conditions the regeneration
of the amputated part proceeds in an abnormal fashion,
the remaining part continues always in spite of that to be
capable of normal regeneration. For example: an axolotl
had a foot bitten off. The foot was reproduced but badly
formed. This foot was amputated and a third was
developed which was quite normal.®

We shall later at a proper place treat of the ill-starred
attempts of the preformists to bring their theory into
accord with similar phenomena, and of the arguments
and the special regenerative processes which the epigene-
sists have brought forward in support of their theory.
Here it may merely be noted that while epigenetic theories
furnish an immediate explanation for all phenomena of
regeneration, the preformation theory on the contrary
must have recourse to the addition of complicated sub-
sidiary hypotheses which are entirely opposed to the
principal one.

If the morphological capacity does not reside in the
somatic cells of the cut surface, which by their multiplica-
tion produce the regenerated organ, but is outside these,
it follows that the continuous action exercised upon all
cells at the end of the regenerated part as also upon all
cells which do not lie at the cut surface, by the remaining
part of the organism must be a mediate action exercised
from a distance, and therefore must traverse intermediate
cells.

A yet more striking demonstration of a continued,

5Darwin: The variation of animals and plants under domestica-
tion. Eighth impression of the second edition. London, Murray.

1899. P. 357, 358.

Mediate Formative Influence in Post-generation 21

formative action exercised mediately and at a distance by
one part of the organism upon another during the entire
development of this latter is furnished by the famous ex-
periments of Roux in the post-generation of his half
embryos.

The words in which he describes the process of this
post-generation which he has observed in half embryos
obtained from frogs’ eggs after he had killed one of the
first two blastomeres with a hot needle, deserve to be
reproduced here in full.

But we must remember at the outset that while the
uninjured blastomere develops into only a half embryo,
the injured blastomere lying beside its neighbor produces
often a late fragmentation of its protoplasmic mass con-
sisting only of undifferentiated cells. And this is effected
in one of the following two ways, either through only
partial killing of the nucleus concerned some individual
fragments of it continuing to live and multiply, or
through an emigration of naked nuclei from the part of
the egg remaining intact into the protoplasm of the in-
jured blastomere. Now we quote Roux.

“Postgeneration of germ layers of half organisms
proceeds always from the already differentiated germ
layers of the normally developed half of the egg. It
extends thence first to the yolk mass subsequently cel-
lulized, especially where such a germinal layer is in con-
tact with such a mass by a broken surface and conse-
quently by the lateral surfaces of its cells.”

“The formation commencing at this point proceeds
steadily and continuously through the yolk mass of the
undeveloped half of the egg. About the free margin of
the advancing germinal differentiation there are to be
found gradual transition stages between the undiffer-

22 Indications of Continued Formative Influence

entiated yolk cells and the cells of the already completely
differentiated germinal layer. With the elimination of
other possibilities this leads us to the conclusion that the
progressive differentiation is accomplished in material
already in position before differentiation commenced, and
remaining there throughout it, and therefore in passive
yolk material by direct transformation of the yolk cells
(accompanied in the case of the ectoderm and mesoderm
also by the division of these cells).”

“As to the location of the causes of these processes,”
continues Roux, ‘“‘we can draw a few further conclusions.”

“Since the yolk cell material later differentiated to form
the germ layers in the manner described above has been
quite disordered in its substance forming the bodies of the
cells, by the operation, and since also the nuclear material
of the cells which are later formed from it has never
yet taken its place by virtue of a typical division, but, being
derived partly from the nucleus of the half operated upon
and partly from the emigrated naked nuclei of the half
remaining intact, owes its disposition to the chance of
the moment, therefore the conception, possible in the
case of normal development that at typical places there
is always deposited typical material capable of quite
definite independent development, cannot be admitted in
this case.”

“We must conclude rather, that the cause of this typ-
ical formation of the germ layers of the first developed
half of the egg, extending into the half operated upon, lies
in forces which proceed from the germ layers of the first
half.”

“I conclude, then, that in our postgeneration the
progressive differentiation extends in space as the result
of a direct assimilating and differentiating action exercised

Continuous Formative Influence 23

by differentiated cells upon other less differentiated cells
which are immediately adjacent to them.”

“In the latter process very different degrees of action
are possible. There can, for example, emanate from the
differentiated cells an influence which simply sets free
the process of differentiation allowing the entire series
of necessary changes after this preliminary impulse to
proceed of itself. Or, each of these changes may not
merely receive from the differentiated cell a simple
initial impulse, but may on the contrary be determined
by that throughout. Between these two extremes one
can imagine a whole series of intermediate stages. On
account of the at first atypical disposition of the material
which at last becomes typically differentiated I am
inclined to think that the action of the differentiated cells
upon the nondifferentiated cells is not a mere liberating
one or a mere stimulating one.” ®

These facts of postgeneration indicate then above all
that the action of the half embryo already formed upon
the other half in process of formation is exercised in a
continuous manner throughout the whole development
of this latter.

One would be led also to this conclusion, that there
is a continuous action exercised throughout the whole of
development, by the fact that the postgeneration of the
undeveloped half goes on with greater rapidity, so that
it soon overtakes the other half and proceeds with it to
the same stage of development.

Wilhelm Roux: Uber die kiinstliche Hervorbringung ,,halber“
Embryonen durch Zerstorung einer der beiden ersten Furchungszellen,
sowie iiber die Nachentwicklung, Postgeneration der fehlenden
Kérperhalfte. Virchows Archiv, Bd. 114. October 1888, P. 279—28z.
Gesamm. Abhandl., Zw. Band. P. 507—509.

24 Indications of Continued Formative Influence

This continued action leads us to conclude also that as
a further consequence a remote action is exercised by
the half embryo already formed upon the parts of the
other half which are not in direct contact with the first.
This remote action can be transmitted only through all
the intermediate cell layers which lie between the surface
of contact of the two half embryos and the remote parts
in process of postgeneration.

It would seem necessary then to conclude that the first
half embryo exercises upon the far removed parts of the
second a remote, mediate and continuous action.

We shall now provisionally assume that postgenera-
tion does not differ in its essential nature from direct gen-
eration, and note some consequences which follow for
the hypothesis of the central zone of development which
during normal ontogenesis would exert an action similar
to that which the half of the embryo already formed
exerts upon the other half during postgeneration.

The nuclei obtained as the result of the first divisions
of the egg and destined to become somatic, even though
derived from those which according to this hypothesis
would later form the central zone, would then have to be
considered, in relation to the somatizing stimulus exerted
by that zone, as quite like the indifferent nuclei of the
embryonal half capable of post generation, which receive
now this now that stimulus without any preference from
the half already developed, and become somatized in
consequence now in one way now in another way
according as they may chance to be disposed.

The indifference in respect to somatizing stimuli of
these nuclei, which we should at least at the outset
suppose like those nuclei from which they are derived,
and which later according to this hypothesis give rise

Blastomeres Which Acquire Formative Control 25

to the effective germinal zone, leads us to a second
hypothesis, namely: that the especially germinative
energies of those nuclei destined to become somatic may
be once for all silenced, that is once for all put in a
potential state incapable of activation, on account of the
preponderance which the nuclei that go to form the
effective germinal zone or central zone acquire.

In fact we can suppose that the first blastomeric nuclei,
though exactly alike qualitatively, are different quanti-
tatively, that is to say are furnished with amounts of
energy which do not chance to be quite the same in all,
perhaps on account of special conditions of nutrition or,
perhaps, on account of special conditions of the proto-
plasm in which they are placed. Then, as soon as the
moment comes when because of the nature of the com-
mencing transformation, such as perhaps invagination or
some such thing, embryonal development can no longer
proceed after the same fashion in all cells, certain ones
will necessarily gain the upper hand, namely those which
possess more potential energy.

The other blastomeres whose nuclei would no longer
be able to activate their germinal energies will from now
on conduct themselves, in relation to the stimuli of the
nuclei of those blastomeres which constitute the central
zone of development, just like cells with indifferent
nuclei. And with the progressive somatization of these
latter the mass of their respective specific elements to
which is due the persistence, potentially at least, of their
germinal energies, will gradually diminish and finally
disappear.

There is only a single conceivable exception, namely
the case in which at the beginning of development or in
inferior forms, these blastomeres or cells just beginning

26 Indications of Continued Formative Influence

to be somatized accidentally remain isolated, in which
case the activation of their potential germinal energies
would be permitted, which might have been impossible
had they remained united with the other blastomeres or
cells.

The possiblity of such receptive indifference toward
somatizing stimuli in nuclei which if they were isolated
or in other conditions would on the contrary possess and
give practical demonstration of very definite specific
qualities, is indicated by those cases in which all the
nuclear material of the post generated half embryo is
furnished by the half already developed.

Indeed it often happens that on the side operated upon
the nutritive yolk alone is utilized; and into this latter
emigrate nuclei formed by normal division of the nuclei
of already somatized cells in the developed half of the
egg. And these emigrated nuclei then bring about the
division of the yolk mass of the part operated upon into
small indifferent cells only: ‘With the formation of a
right or left half embryo,’ Roux observes in a later
study, “the formative capacity of the uninjured half of
the egg is not yet exhausted. On the contrary certain
experimental results permit the conclusion that in many
cases there is an emigration from it of nuclei, and
perhaps indeed, of a little protoplasm also, going out
from those points which by the accident of position have
the most intimate contact with the side operated upon,
toward the contiguous half of the egg deprived of its
own capacity of development. These nuclei become
distributed throughout the whole of the large mass of
yolk and thereupon follows later a breaking up of the
half operated upon into cells, and this is not as in normal
division a division of the whole mass first into two nearly

Cells Partially Differentiated Can Be Altered 27

equal and consequently large cells, which divide again
later in their turn each into two correspondingly smaller
cells and so on; but on the contrary the breaking up is
from the first into small cells.”

It is upon these indifferent cells that the half of the
egg already developed exercises its formative action.
These nuclei which arise from cells of the half of the
embryo already developed must nevertheless possess very
definite specific properties; some come from ectodermic
cells, others from mesodermic and others from entodermic
cells. And if the medullary plate, the notochord, etc.,
have already been formed, the vagrant nuclei come also
from cells which are in an advanced stage of development.
And yet when they have once emigrated and have become
scattered through the yolk of the injured side, they
remain no less indifferent in relation to the formative
stimuli which come off later from the part already
formed, than in the cases where they arise entirely from
the injured half of the egg. From whatever cells of the
embryonal half already developed they may have been
produced, they are capable of any somatization whatever,
for this depends only on the place at which they happen
to stop or become arrested during their migration into
the yolk plasma of the injured half of the egg.

The same thing can take place in the blastomeric
nuclei also as soon as they once find themselves outside
the group, which, according to the hypothesis above
stated, would form the central zone of development: in
relation to the ontogenetic stimuli which from now on

TWilhelm Roux: Uber das entwicklungsmechanische Vermogen
jeder der beiden ersten Furchungszellen des Eies. Verhandlungen
der anat. Ges. Wien. June 1892. P. 34, 35. Gesamm. Abhandl.
Zw. Bd. P. 782, 783.

28 Indications of Continued Formative Influence

are sent out from this zone, they conduct themselves in
a quite indifferent way, though for a greater or less time
they preserve their germinative capacity potentially.

While the experiments of Roux carried on carefully
and with astonishing exactness of observation, dem-
onstrate directly the continued remote and mediate action
which the formative part exercises upon the part being
formed throughout the whole of development, the exist-
ence of this action is confirmed by other investigations,
in a way which though indirect is not any less certain
on that account.

They comprise all the cases in which the part removed
is regenerated by cells histologically different from those
of normal generation, for instance in which organs or
tissues of ectodermic, mesodermic, or entodermic origin
are reproduced in the regeneration by tissues having a
different blastodermic origin.

It will suffice for our object to recall the most typical
example which has stirred up the two hostile camps of
the epigenesists and the preformists; we refer to that
of the regeneration of the lens in the eye of the tritons,
which, after its extirpation, is reproduced from the cells
of the iris, that is to say, from a material quite different
in character from that of which it is formed in normal
generation.®

The double epithelial layer of the iris, from the
marginal proliferation of which the new lens springs,
must exercise upon the lens in process of formation a
continuous action persisting throughout the development

®See ve. g. Erik Miller: Uber die Regeneration der Augenlinse
nach Exstirpation derselben beim Triton. Archiv f. mikrosk. Anat.
und Entwicklungsgesch. Band, XLVII. erstes Heft. Bonn. Cohen,
1896. P. 23 ff., especially 29 and 30.

The Formative Stimulus the Determining Factor 29

of the lens. For the cells of the iris cannot preserve
within them potentially any trace of a formative capacity,
or of a germinal “anlage,” or of any “determinant” which
provokes the formation of the lens, seeing that in normal
development the latter takes its origin from another
tissue.

In these examples, both in the post generation of
Roux’s half embryos and in the regeneration of the lens
in the triton, the cells which serve as constructive
material appear then to be absolutely incapable of any
auto-transformation and ready on the contrary to differ-
entiate themselves and to dispose themselves indifferently
in any manner whatever, according to the formative
stimulus to which they happen to be exposed.

At this point the fundamental biological question pre-
sents itself: What is the nature of these formative
stimuli, of this continued action which the formative part
exercises upon the part being formed?

The attempt to build up a hypothesis relating to so
important a question is the object of the studies presented
in the second part of this chapter.

2. Hypothesis of the Nature of the Formative Stimulus

If, in our study of the nature of the formative stimulus
in the development of organisms, we start with the
primitive pluricellular form, consisting simply of aggre-
gations of cells that are all alike, we observe that during
some stages of their ontogeny the essential nature and
the behaviour of these cells is clearly determined by
phenomena of nervous nature in the widest sense of the
word. For example, phenomena of this nature exist
undoubtedly in the little mononuclear amoebae into which
the spores of the myxomycetes become changed, also in

30 Nature of the Formative Stimulus

the zoospores which move about by means of their
vibratile flagella and into which these mononuclear
amoebae become transformed. And it is certain that
phenomena likewise nervous in character must come into
play when the cells of Magosphera planula become
separated from one another and each one moves off
independently by means of its cilia.

One is justified then in suspecting that when these
cells are united in a colony they may then also be the
seat of phenomena of a nervous nature, and that the
other ontogenetic stages of these minute organisms ought
also to be attributed to such phenomena.

But then we should have to refer the development of
higher organisms also to phenomena of the same nature.

As a support of this hypothesis we recall the well
known fact that all cells of organisms, from these most
primitive pluricellular forms up, are united to one another
by a network of intercellular protoplasmic bridges.

We recall the example which the different species of
Volvox afford, a genus of lower algae consisting of a
vesicle formed of a single layer of cells, very much like
the blastula stage of the development of animals. All
the species of Volvox show a perfectly typical and
regular form of union between the different cells of the
body. In Volvox aureus for example, the superficial
cells of the trophic hemisphere of the vesicle lie in a thick
soft gelatinous mucus and each is not only provided with
two long flagellae, but also is connected with each of
the five or six adjoining cells by a long, thin protoplasmic
filament. In the germinal hemisphere the protoplasmic
filaments are more numerous so that each of the great
spores which arise there is connected with each one of
the large neighboring cells by bundles of from three to

Stimulus to Formation of Cell Membranes 31

six filaments. These protoplasmic connections persist
for some time even when the spores have been divided
into two, four, or more constituent parts.®

An experiment which has already become famous
appears to indicate that the intercellular bridges, as if
they were successors of the vibratile protoplasmic fila-
ments, substituted for them, are traversed incessantly by
nervous currents or discharges emanating from the
nucleus. For this experiment we are indebted to Pfeffer.

After having detached by plasmolysis the cell mem-
brane of the nucleated protoplasmic body of a plant cell,
and dividing the cell into halves, one containing a nucleus
and one without any, he observed that only the nucleated
half had surrounded itself with a new cell membrane.
If however, the part deprived of the nucleus remained
united to the nucleated fragment even by only a very
fine protoplasmic filament, it also was capable of secreting
its little cellulose membrane.

Pfeffer varied his experiment also in the following
manner. He prepared cells of a moss protonema in such
a way that an entirely isolated, anucleate mass of proto-
plasm remained united to the neighboring cell which con-
tained a nucleus by means of thin filaments piercing the
cell wall. In this case a membrane was formed round
the anucleate fragment. But the membrane was not
formed if the neighboring cell had been itself deprived
of its nucleus.

In the formation of this cellular membrane in
anucleated parts of the cytoplasm united by protoplasmic
filaments with other nucleated portions, the maximum
intervening distance observed by Pfeffer was 3.7 mm.

°Oscar Hertwig: Die Zelle und die Gewebe. Zw. Buch, P. 34,
35. Fig. 16, 17.

32 Nature of the Formative Stimulus

“But the nucleus can certainly exercise the membrane
forming stimulus at an even greater distance.” If the
nucleus remains united with a whole chain of anucleated
bits of cytoplasm “the production of the membrane appears
to advance centrifugally and so to commence a little later
in the more remote portions of cytoplasm, than in the
bits nearer the nucleus.” ?°

From these experiments one is inclined to think, this
author concludes, “that the production of a cellular
membrane required the continuous transmission and
cooperation of certain states of motion and vibration
which radiate out from cell nuclei or rather owe their
origin to the reciprocal action of nucleus and cytoplasm.”

Oscar Hertwig makes in this connection the following
remark: “This experiment proves that the stimulus
necessary for membrane formation can be transmitted
by thin connecting filaments which traverse the septum
interposed between two cells. Nothing hinders us then
from assuming that some similar transmission goes on
in other functional conditions.” 14

In these observations of Pfeffer the formation of the
membrane goes on independently of the situation and
remoteness of the nucleus and of the geometric form of
the line of communication which may be straight or
curved in any way, and consequently, (and we must keep
this especially in mind,) just as though this formation
were effected by a specifically stimulating current, passing

Pfeffer: Uber den Einflug des Zellkerns auf die Bildung der
Zellhaut. Berichte iiber die Verhandl. der kGnigl. sachs. Gesellsch.
d. Wissensch. zu Leipzig. 1897. P. 507.

“Oscar Hertwig: Die Zelle und die Gewebe. Zw. Buch, P.
40, 41.

Currents of Nervous Energy in Skin Cells 33

out from the nucleus and quite independent of the form
and extent of the conductor which carries it.

But it is very probable that this nervous current or
discharge which is conducted from the nucleated cell
along the protoplasmic filaments to the anucleated frag-
ment of the contiguous cell, also passes across into the
fragment even when it contains a nucleus and so also
when it is replaced by an entire cell. This leads us to
the conception that wherever intercellular protoplasmic
connections are present, the various nuclear currents or
discharges stream through these connections and so
permit a general nervous flux throughout the whole net-
work of these protoplasmic bridges, in the meshes of
which the nuclei themselves would constitute the nodal
points. In this way one would have a continuous
circulation or distribution of nervous energy throughout
the entire organism.

This supposition is supported by the experiments of
Siegfried Garten. On his own arm he cut out a little
disc of skin one centimeter in diameter so as to lay bare
the muscle fibers. Without suturing the wound he
covered it with an aseptic dressing and left it to the
process of granulation. After the wound was completely
covered with epithelium except only a small circle of
1.75 mm. radius he cut out the whole piece again and
enough around it to reach to the area in which the
skin was in quite normal condition.

Microscopic observation gave the following result:
Studying it from the center of the wound out, one met
first of all a greater or less number of wedge shaped
epithelial cells with the long axes radially disposed.
Surrounding this came next an annular zone, 0.45 mm.
broad, of fusiform epithelial cells whose long axes were

34 Nature of the Formative Stimulus

almost without exception tangentially disposed, that is
perpendicularly to the radius of the wound, and the
protoplasmic filaments within the cells ran parallel with
their axes. In correspondence with this interior cellular
arrangement, the intercellular bridges into which the
protoplasmic filaments were prolonged ran for the most
part from tip to tip of the fusiform cells and parallel to
their long axes.

Outside this annular zone, (from 2 to 2.5 mm. outside
the inner epithelial border,) were found large cells in
which the filaments and protoplasmic bridges were
remarkably well developed and there also were found
mitoses. It is therefore in this area that new cells are
formed. In this zone the intercellular spaces are larger
than elsewhere, from 3 to 6 » wide, whereas 1.8 to 3 2
represents the mean normal figure for the epidermis.
This considerable enlargement of the intercellular spaces
makes it possible for these cells to store up the larger
quantity of nutritive fluid which is necessary for their
more intense activity.”

If one admits for the moment that the intercellular
bridges are traversed by a continuous nervous flux this
result will find in this hypothesis its immediate
explanation.

In order to make our idea clearer let us consider the
concrete case of a.stream of flowing water, which at a
certain point divides up into several branches. Sooner
or later a dynamic equilibrium is established and the
quantity of water flowing during each unit of time into
each of the branches respectively will be constant. If

“Siegfried Garten: Die Interzellularbriicken der Epithelien und
ihre Funktion. Archiv fir Anatomie und Physiologie. Leipzig.
1895. P. 407—4009.

Action of Nervous Currents in Skin Wounds 35

we now effect artificially the obstruction of some of
these branches the entire volume of water must flow
through the others which remain open and their volume
of water will consequently be increased in proportion.

In the same way let us suppose that through the
intercellular bridges of the epidermis for example, there
go similar nervous currents, in which when once the
organism has attained its adult age dynamic equilibrium
is established. And let us remove a little disc of skin
as Siegfried Garten did, then the nervous flux which
heretofore had taken its way through the filaments and
protoplasmic bridges of the cells situated in the little disc
removed will now find these ways closed. Consequently
the entire flux must take a roundabout way through the
neighboring parts surrounding the little disc.

The augmentation of the nervous current in these
ways will have as its result an augmentation of the trophic
stimulus which it exercises; so that the cells situated
along these ways will grow and proliferate more rapidly,
thus producing a zone of reproduction characterized by
numerous mitoses. The augmentation of the vital
processes of these cells will in consequence of increased
osmotic attraction, attract a greater quantity of nutritive
fluid, exactly as the wick of a lamp which is stimulated
by a current of air draws up by capillarity a larger
quantity of combustible fluid. And this greater quantity
of nutritive fluid pressing in between one cell and another,
will distend the intercellular spaces so that in this zone
they undergo an enlargement. The further the new
formation of the skin proceeds, the shorter will be the
way through which the abnormally increased nervous
flux tends to pass, that is to say that the zone of the

36 Nature of the Formative Stimulus

most intense flux and the zone of reproduction thereby
determined will approach the center of the wound.

The tangential disposition of the cells of the circular
zone between the reproductive zone and the central
granular zone, would be due just to this nervous flux
which commences to flow through the new formed cells,
but is still always forced to flow around the wound in
some such way as the water of a river flows around
the circular pier of a bridge. The direction of the cell
axis would thus be determined by the direction of the
current.

According to Siegfried Garten’s views, on the con-
trary, there would exist all around the wound, in spite
of the aseptic dressing, an augmentation of the blood
circulation, which would have as its consequence an
increase of pressure and of the amount of nutritive
fluid in the tissue. And consequently there would arise
an augmentation of volume of the intercellular spaces
and an increased formation of new cells in the reproduc-
tive zone. As for the tangential disposition of the cells
of the surrounding zone, he believes that one can explain
that by the theory of sphincter action, that is through
the contraction of the intercellular bridges of these cells.
In consequence of this contraction the long axis of the
cells would turn into the direction of the tractile force
which is exercised upon the cells. At the same time the
consequent shortening of the respective circular zones of
these cells would cause the epithelium to press in toward
the center of the granulating surface, and thereby effect
the gradual contraction of the opening of the wound.%

But the increased blood supply and the shortening

Siegfried Garten: Ibid. P. 409—q11.

Efvects of Nervous Currents in Skin Wounds 37

of the intercellular bridges which this explanation pre-
supposes would require to be explained themselves. It
is to be remembered further that Roux in his studies
upon the struggle of the parts of the organism has
shown that the great affluence of necessary nutritive fluids
is always the consequence rather than the cause of the
growth of the organic substance.

This experiment of Siegfried Garten argues strongly
in favor then of the hypothesis that a continuous nervous
flux traverses the intercellular bridges. The nuclei, as
foci of nervous energy, would be precisely the sources
which feed it, and which in normal conditions preserve
it unaltered. At the same time, the nervous flux dis-
charged by the other nuclei in passing through any one
nucleus acts like a functional trophic stimulus, in so far
as it is favorable to the specific vital process of this
nucleus. Each increase or decrease of this current
passing through certain nuclei caused by conditions lying
without these nuclei, would have as a result an aug-
mentation or diminution first of their mass and later
of their number.

This augmentation of the nervous flux in given zones
following the ablation of neighboring parts would thus
‘be the general cause of the active proliferation of cells
by which all the phenomena of reproduction commence.

Later when there comes into play a disturbance of
the equilibrium, one can conceive that its reestablish-
ment can proceed and spread from any one whatever
of the numerous parts which surround the part cut off.
In other and more general terms one understands that
the reestablishment of the normal distribution of nervous
energy, necessary for the reformation of an organ, in
case it be prevented from following the ordinary way,

38 Nature of the Formative Stimulus

can reach the organ by any other way and indeed by a
way quite the opposite of the normal as happens for
example in any distribution of electric or hydrodynamic
energy, and that consequently it amounts to the same
thing whether the regeneration of the tissue or of the
organ ablated proceeds in the same way as in ontogeny
or by any other way.

And finally we must suppose that regeneration is
nothing else than a particular case of generation or
reproduction and that the nature of one is substantially
identical with that of the other: for, to use the words
of Delage “generation is only the regeneration of a
complete organism by a portion of greater or less size
attached to it or detached from it;”’ 44 so the causes of
the regeneration, for instance of a little disc of skin
which has been removed, must be essentially the same
as those which effect a complete reproduction.

Between the two phenomena the following difference
will however exist: The regeneration of a little disc
of skin will be due, according to what we have just stated,
to the fact that the continuous nervous flux which flows
through the whole organism and particularly through
those parts which were contiguous with the part removed,
would tend to reestablish its dynamic equilibrium, dis-
turbed by the operation. If we accept the fundamental
biogenetic law in its first degree of approximation,
complete generation, on the contrary, would be a whole
series of transitions of the nervous energy circulating or
distributed in the developing organism, from one dynamic
system to the other next in order, both meanwhile being
in a state of equilibrium since they were already formerly

14Delage: L’hérédité et les grands problémes de la biologie
générale. P. o8.

Protoplasmic Connections of Adjoining Cells 39

in equilibrium in both the corresponding phylogenetic
forms. To effect the transition it is necessary then that
in each ontogenetic stage there suddenly supervene at
some point of the system a change, which disturbs the
established equilibrium and provokes the passage of the
continuous nervous flux to a new dynamic equilibrium.

If the intercellular bridges have really the significance
which we have attributed to them, one can see how they
must be present in all organisms and in all stages of
development. It is superfluous to go more thoroughly
here into the fact that this is exactly what is fully
confirmed by histologic investigations which are being
ever more carefully prosecuted.

We recall for example the protoplasmic connection
observed by Hammar between the segmentation spheres
of the sea urchin egg: The cells of the blastula are
covered all over the outside of it by a protoplasmic layer
which adheres in each cell only to the part of its surface
which is directed toward the outside. This layer in a
few preparations not sufficiently protected against drying
separated itself a little from the blastula. There appeared
then thin filaments, variable in number and more or less
regular in disposition, which extended from the granular
protoplasm of the different blastomeres to the interior of
this layer and produced in this way a manifold connection
of the different cells with one another.’®

Sedgewick has observed the same thing in the develop-
ment of the eggs of Peripatus. The two cells which
come from the cleavage of the eggs are not completely

15Hammar: Ubereinen primaren Zusammenhang zwischen den
Furchungszellen des Seeigeleies. Archiv fiir mikrosk. Anat. und
Entwicklungsgesch. Bd. XLVII. Erstes Heft. Bonn, Cohen. 1896,

P. 14ff.

40 Nature of the Formative Stimulus

separated but remain connected by protoplasmic fila-
ments; the cells which arise from each of the first two
cells are associated in the same manner, and this con-
tinues indefinitely. So that during the whole of develop-
ment from the first segmentation of the egg up to the
adult stage all the cells of the organism remain in inter-
communication by means of these protoplasmic bridges.
“The connection of cell with cell is not a secondary
feature acquired late in development, but is primary
dating from the very beginning of development.” 16

It is quite unnecessary to recall the universality of
intercellular bridges not only between the cells of each
tissue but also between the cells of different tissues:
between the epithelial cells of gland ducts and contiguous
smooth muscle cells, between epithelial cells and con-
nective tissue cells, between connective tissue cells and
endothelial cells, between smooth muscle cells and con-
nective tissue cells, between connective tissue cells and
striated muscle fibers, between striated muscle fibers and
epithelial cells, and so on.’”

It is necessary to be remarked further that in animals
this circulation of nervous currents can and at least in
certain stages of development must certainly utilize
not only the protoplasmic network uniting the cells to

1®Adam Sedgwick: The Development of the Cape Species of
Peripatus. Quart. Journ. of microscopical Science. XXVI, 1886. P.
198—200, 206.

"See for instance: Heidenhain: Uber das Vorkommen von
Interzellularbriicken zwischen glatten Muskelzellen und Epithelzellen
des ausseren Keimblattes und deren theoretische Bedeutung. Anat.
Anzeiger, VIII, No. 12 and 13; May 13, 1893; P. 404—410; and
Schuberg: Uber den Zusammenhang verschiedener Gewebezellen im
tierischen Organismus. From the Sitzungsberichten der Phys.-Med.
Gesellschaft zu Wiirzburg. Sitzung vom Febr. 25, 1893; P. 1-8

The Whole Organism a Great Protoplasnvic Plexus 41

one another, but also the nervous system itself with all
its fibers and fibrils in so far as it is developed. This
leads to the conclusion that in the adult organism the
ordinary nervous currents passing along the various
nerves as a result of ordinary nervous discharges con-
stitute only momentary intensifications of permanent
nervous currents which pass continually through these
nerves.

The great frequency with which conductors of nuclear
stimuli in general and intercellular bridges in particular,
are found in both animal and vegetable kingdoms, is
as we have said, even by itself a very strong support for
the hypothesis proposed by us of a nervous circulation
or distribution throughout the whole organism.

In this hypothesis we approach, even though only in
certain respects, the most recent theories of some botan-
ists and physiologists who in consideration of this
striking general protoplasmic connection between the
different cells, regard the multicellular organism not as a
mere assembly or colony of cells, but rather as a single
voluminous protoplasmic body in which the nuclei are
inserted at different intervals as centers or foci of
energy, (synergids of Sachs), and in which the mem-
branes and other intermediate structures have produced
only incomplete divisions and serve merely as supports
of the organism. For example, according to Sedgewick
the body of the adult animal would be only an immense
syncytium whose nuclei or centers of force are dispersed
throughout a single protoplasmic network binding
together the whole organism.**

We approach especially the conception which Oscar

18Adam Sedgwick: The Development of the Cape Species of
Peripatus. P. 205—206.

42 Nature of the Formative Stimulus

Hertwig seems to have of protoplasmic connections, for
while it is true that he never discusses such a continuous
nervous flux and speaks only of the transmission of
nuclear stimuli, nevertheless this latter conception in our
mind implies the former. To sum up our conception of
these protoplasmic connections we could almost adopt
the very words of this investigator: “It is probable that
this transmission of nuclear stimuli by protoplasmic fila-
ments will be much less rapid and less intensive than
nerve conduction, but perhaps for this very reason will
be more continuous and by reason of its duration more
efficacious.” 19

It is quite unnecessary to draw especial attention to
the fact that the vegetable kingdom is not in any way an
obstacle to this conception of a continuous nervous flux
throughout the whole organism, for if nervous phe-
nomena are less apparent in it than in the animal kingdom,
they constitute nevertheless just as in the latter the essence
of the vital phenomenon.

From amoeboid movements, from the vibrations of
cilia and flagella up to the most complex psychic phe-
nomena, everywhere where life is, one finds also processes
of nervous nature. The reticular or fibrillar structure
which protoplasm in general exhibits, protoplasmic
currents, especially those in very long, fine filaments,
such as for example those in the pseudopodia of the
rhizipod Gromia oviformis, which by their peculiar
character make one suspect that they may be only the
consequence and sensible effect of currents provoked by
an energy of another kind, the striations consisting of
bundles of curved parallel lines without sharp angles in

“Oscar Hertwig: Die Zelle und die Gewebe, Zw. Buch. P. 40,

Protoplasmic Nervous Currents Universal 43

each little layer of the cell membranes of plants, the
formation of a membrane in an anuclear fragment of a
vegetable cell in consequence of a nuclear stimulus trans-
mitted from the nucleus of another cell along any proto-
plasmic conductor, all these facts speak together in favor
of the hypothesis that all living substance is traversed
by vital nervous energy in the form of currents.

Claude Bernard has already remarked that anaesthe-
tics act not only upon the nervous system but also upon
the cells of every animal or vegetable tissue, in that
they destroy or suspend the vital activity of every cell
in the same way, and from that he concludes that all
vital processes in general are substantially identical.2°

This substantial identity is demonstrated further by
the fact that phenomena of irrito-contractility present
themselves in the same way in both animal and vegetable
kingdoms and that there are all possible transition
stages between plants considered “especially sensitive’
and those considered not sensitive at all. The whole
group of “especially sensitive” plants present especially
well developed intercellular protoplasmic connections.?!

We recall further the microscopic movements of the
protoplasm within the membranes of plant cells, which
led Huxley to make the well known definition that a
plant is only ‘fan animal shut up in a wooden box.”

Everybody knows that in addition to these micro-
scopic movements there are now known in plants also
various movements visible to the naked eye, which cor-

?°Claude Bernard: Lecons sur les phénoménes de la vie communs
aux animaux et aux végétaux. Paris, Bailliére, 1878. P. 289—290.

*tMacfarlane: Irrito-contractility in plants. Biol. Lect. at the
Mar. Biol. Lab. of Wood’s Holl. Summer Session 1893. Boston,
U. S. A., Ginn. 1894. P. 189, 204.

44 Nature of the Formative Stimulus

respond fully with the reflex movements of animals; that
is, in which one can distinguish as in animals a region of
perception and another of motility, as well as the
transmission of a stimulus from the perceptive region to
the motor region.

Leaving aside the very well known example of
Mimosa it suffices to recall for example, that in certain
plants one can demonstrate that the sensibility of the
root to gravitation resides in its extreme tip while
the bending movements of that same root in order to
resume its vertical position after it has been disturbed
takes place in another part. In the same way the vertical
position of the stem is maintained. But a yet more
typical example is furnished by the grass, Setaria. “It
has a remarkable manner of germination; as soon as the
seed germinates it does not produce a simple cylindrical
stem but one terminating in a wedge shaped tip like a
lance head. When a group of Setaria is lighted from
one side it inclines strongly toward that side and all the
lance tips point toward the light. But these tips are not
curved at all, on the contrary the whole bending is
produced in the stem, although it is clearly these tips
which are sensitive to light and not the stems. It is easy
to prove this by covering the tops of some stems with
an opaque cap: the grass stalks so protected remain
vertical while others incline their stems toward the light.
The part that bends has not then any sensitiveness to
light and the part sensitive to light does not bend. The
little lance is the organ of perception, the stem the
motile region, and it is clear that a stimulus is transmitted
from the tip to the stem.” 22

a
*’Francis Darwin: Le mouvement chez les plantes. Revue
scientifique. March 1, 1902. P. 26s.

Specific Modes of Being of Nervous Currents 45

Consequently the view is not only justified but almost
required that in plant bodies also there is a nervous cir-
culation or distribution, which, though it manifests itself
only in its variations dependent on some change in the
external influences, is certainly none the less present
during the repose of the organism when it is in a state
of dynamic equilibrium. It is this constant circulation
or continuous distribution of nervous energy, which con-
stitutes in plants quite as well as in animals the “smali
yet mighty link” which unites the parts of the organism
into a “sympathetic whole,’ a function which Lewes
ascribes especially to the nervous system.?*

As to the properties of each of the respective excita-
tations or currents which constitute this general nervous
flux, it is sufficient for our purpose to suppose that these
latter appear in specifically differing modes of existence
which are capable now of combining now of disjoining;
we mean by this that two specific modes of being are
able for example to combine with each other and so to
give rise to a third specific mode of being, or indeed that
this latter can break up giving rise to the two preceding
specific modes of being or even to others different from
them.

While for the present we are not in a position to
discover what these different specific modes of being
really are, yet we can and indeed must necessarily regard
them as existing since in different tissues different specific
nuclear stimuli must certainly be present in the cells.
These different specific modes of being might consist in
something analogous with the intensity of the continuous
electric current, or perhaps in a rhythmic form correspond-

287 ewes: The physical basis of mind. New edition. London,
Kegan Paul, Trench, Tritbner & Co. 1893. P. 61.

46 Nature of the Formative Stimulus

ing somewhat for example with the alternating electric
current, or indeed might arise in another way of which
perhaps we can not in advance form any conception at all.
It is sufficient for our purpose, we repeat, to suppose that
these specific modes of being can combine and break up
according to laws which are definite even though so far
quite unknown. For the very fact of the existence of
these laws would imply also the existence of correspond-
ing laws on which the circulation or distribution of
nervous energy in definite networks would depend.

If one accepts such a hypothesis of the circulation
or the distribution of nervous energy in the organism,
one could find the immediate explanation of certain
phenomena of development whose cause has so far
remained a secret. These phenomena consist in the recip-
rocal influences which certain parts of the embryo, even
though widely separated, exert upon one another in spite
of the lack of any functional adaptation and by which the
development of these parts is wholly or partially
determined.

One can, indeed, attempt to give the beginning of
an explanation of these phenomena of correlation, by
supposing the different parts which exercise this reciprocal
influence to be situated, maybe upon the same partial
network of the general circulatory system, maybe upon
different partial networks which nevertheless come off
at one common given point from the same principal
branch, or maybe finally, in the case of contiguous parts,
upon different partial networks which are however
provided with direct communications between some of
their respective nuclei. The absence of any analogous
reciprocal action between other parts also contiguous
may be explained by the lack of any such direct con-

Correlative Differentiation and Growth 47

nection between the nuclei of the two partial networks
belonging to these parts, a fact which renders these net-
works in certain respects quite independent of one another
if at the same time they do not come from a common
principal branch.

It would be ‘fa very important matter,” writes Delage
“to know if secondary protoplasmic connections are
formed between neighboring cells which are not sisters
but which have been brought only secondarily into contact
with one another, for example after an invagination in
animals or through grafting in plants.” ?4 In the cases
in which this did not occur one could then have the
simultaneous and to a certain extent independent exist-
ence of partial circulatory systems even though they lie
close together or perhaps even enclose each other.

Roux designates by the term “correlative or dependent
differentiation” the complete or partial determination of
development by reciprocal influences of epigenetic nature
which become established, in a certain measure at least
as he admits himself, between the cells. We can then
designate these partial networks of the general cir-
culatory system by the name “networks of correlation.”
And we shall see that, conformably with our theoretical
conjectures very many processes seem actually to prove
that each of these networks is capable of existence by
itself, independent within certain limits of other partial
networks.

Among the phenomena of correlative differentiation
in development belong also those which are called com-
pensatory growths. The investigations of Ribbert (1889)
and his pupils upon the mammals have shown especially

“Delage: L’hérédité et les grands problémes de la biologie gén-
érale. P. 33.

48 Nature of the Formative Stimulus

well, that after the cutting off of organs not yet in
function, for example of the testicle or of an infantile
ovary or several infantile milk glands, the other similar
organs underwent in their respective parts a proportionate
growth as though they would thus compensate for absent
parts. It would appear from this that the networks of
correlation belonging to each of these parts of like organs
must come off from a common principal branch in such
a way that the whole current of this branch prevented
from the usual division by the absence of one part of
the network would now discharge itself entirely into
the remaining organ.

The hypothesis of the continuous circulation or the
continuous general distribution of nervous energy which
thus finds its support in certain special phenomena of
development, affords better than any other an explana-
tion for the fundamental process of every ontogeny,
which consists as Roux has very aptly said only in a
series of unequal localizations of growth.

“A given region grows,” writes Delage, “while the
neighboring parts by which it is surrounded, grow much
less or not at all. This part must necessarily then project
outward or become invaginated and form a cavity. But
at a given moment growth ceases in this place and goes
over to another place, and the same phenomenon is now
repeated at this new place.” 2°

The morphological means which ontogeny employs is
then always the same, always of the same identical nature
even when the tissues already partially differentiated
commence to differ from one another in their most
essential properties.

**Delage: L’hérédité et les grands problémes de la biologie
générale. P. 174.

Explanation of Ontogenetic Involutions 49

The hypothesis of a continuous trophic nervous flux
being admitted, these serial unequal localizations of
growth can be explained by changes in the distribution of
this flux at each new ontogenetic stage, from causes
which we shall examine in the next chapter. These
changes of distribution bring about now here, now there,
a great affluence of nervous energy and thereby induce
at the corresponding points proliferation of the cells from
which must necessarily arise later the invagination or
evagination in question.

But the ontogenetic phenomena which most clearly
call for the conception of such a distribution of nervous
energy which continually changes and shifts, streaming
now through one region now another of the developing
organism, are the phenomena of involution; that is to
say phenomena of reduction presented by the tissues of
an organ which after being formed in the course of
ontogeny tends at a later stage to disappear; for example
the involution of the tail of a tadpole during its meta-
morphosis into a frog.

The atrophy and degeneration of the skin, of the
notocord, of nerve and muscle fibers, by which this
involution is produced, have been described particularly
by Osborn. He as well as Metschnikoff has established
in this connection the great phagocytic activity of certain
cells and the formation of true and false giant cells.
Nevertheless he does not attribute to the phagocytes the
most important role in the elimination of material. The
whole of the process, in fact, results in the gathering
together of the cellular material in process of dis-
integration and conducting it into the lymph and blood
vessels for utilization later in the construction of other
organs and tissues peculiar to the adult animal.

50 Nature of the Formative Stimulus

This would indicate then that the greater phagocytic
activity would be not so much the cause as rather the
effect of the diminution of the vital resistance of the
organ. And this latter would seem necessarily to be
due exclusively to the fact that the organ itself would
be at this ontogenetic stage abandoned by the particular
energy which had formed it, and which up till now
had maintained it in full vital activity, and which now
has not indeed ceased to exist, but has turned to other
regions. This transference of cellular material in process
of disintegration to other organs and tissues in process
of formation would seem in fact to demonstrate that
simultaneously with the diminution or the cessation of
the trophic stimulus in one given region there appears
an increase of that stimulus in another region.

This utilization, as nutritive material, of the substance
of cells which are disintegrating is rendered necessary by
the fact that animals during their metamorphosis take
almost no nourishment. It follows that, if the nutritive
material which the abandoned parts give up to the parts
now more abundantly infused with trophic energy, should
be insufficient at the normal rapidity of disintegration,
the disappearance of the tissues must be accelerated. This
is indicated by Osborn’s researches upon the influence of
fasting upon metamorphosis, from which it appears that
it is appreciably accelerated by inanition, just because of
the more rapid reduction and absorption of the organs
about to disappear.?®

In the disappearance of the tail of the tadpole one has
not a senile but rather a premature involution of tissues,

26Qsborn: Alte und neue Probleme der Phylogenese. Ergebn.
d. Anat. u. Entwicklungsgesch., herausg. v. Merkel u, Bonnet. Bd.
III. 1893. Wiesbaden, Bergmann. 1894. P. 1098.

Distribution of Energy Explains Ontogeny 51

“in which nature destroys in a manner which may seem
to us cruel, cells which have just been produced.” The
hypothesis of the distribution of trophic nervous energy
seems to us the only one which can give a satisfactory ex-
planation of this phenomenon.

The struggle of the parts of the organism cannot in
fact be the exclusive cause of this involution of young
tissues. This struggle is not sufficient by itself to explain
the exactness of the epoch and of the stage of develop-
ment at which this physiological involution takes place.
Even if we were willing to admit that this struggle has
some effective participation in the production of this
phenomenon, we must nevertheless admit that in addition
an inciting ontogenetic stimulus, as Roux would say,
must at the appointed time exert its trophic action upon
the parts destined to victory, while it abandons others
previously favored, but which now are devoted to destruc-
tion. The distribution of trophic nervous energy with its
changes would thus always remain the only cause of the
phenomenon.

But if ontogenetic physiological involutions are due to
the fact that the distribution of trophic nervous energy
abandons one region to turn to another, similar changes
and shifting of this distribution must then be likewise
the cause of all invaginations and evaginations, of all
morphological phenomena in general and, with much
probability, consequently, of those ontogenetic phenomena
also which are not exclusively morphological in nature.

To produce each one of these serial ontogenetic mod-
ifications in the distribution of trophic nervous energy it
would suffice theoretically that at the required moment
there become active, were it only upon one certain point
of the circulatory system, a single new definite specific

52 Nature of the Formative Stimulus

current, different from the current previously present at
the same point. And this would be exactly the role, which
as we have already said the central zone of development
plays. This zone therefore will be the object of our study
in the next chapter.

CHAPTER THREE

PHENOMENA WHICH POINT TO THE EXISTENCE OF A
CENTRAL ZONE OF DEVELOPMENT—HYPOTHESIS OF
THE STRUCTURE OF THE GERMINAL SUBSTANCE,

i. Phenomena Which Point to the Existence of a
Central Zone of Development

The only group of organisms in which one can say
that the existence of a central zone of development is di-
rectly demonstrated is that of the unicellular organisms,
in which this zone is constituted by the nucleus. In
pluricellular organisms it is only indirectly that we are
able to arrive at the conclusion that the central zone
exists.

Experiment has shown that the necessary and suff-
cient condition for the ontogenetic development of the
Infusoria is the presence of a nucleus. This latter con-
stitutes therefore for them an effective central zone of
development and consequently ontogenesis consists in
them in a true and proper centroepigenesis.

If one divides an amoeba or a rhizopod or an infuso-
rian already completely developed, into many pieces, that
one of these fragments which remains provided with its
nucleus though it be the smallest of all, is yet capable of
reproducing by new formation all the missing organs and
of developing again into a normal individual; whereas the

53

54 Indications of a Central Zone of Development

other fragments, without nuclei, are incapable of it even
though they may be much larger.

Especially we recall the researches upon artificial di-
vision of the Infusoria made by Nussbaum and Gruber.
If, for example, one cuts a stentor into three pieces, of
which each contains one portion of its moniliform nucleus,
in the space of twenty-four hours each piece regenerates
the missing part. The anterior extremity regenerates the
posterior and vice versa; the middle piece reforms the two
extremities, that is to say, both the rather complex peri-
stomal region with its mouth, its pharynx, its long cilia,
etc., and also the simpler posterior part. If however the
fragment retains no part either of the paranucleus or of
the nucleus proper, even though it may be of much
greater size than those fragments retaining the nuclei, no
trace of regeneration is observed, a fact which does not
prevent the piece concerned from continuing to live for a
while, even for two or three days, nor from retaining com-
pletely the capacity of locomotion, of vibration of cilia,
of pulsation of the contractile vesicle, of defecation, of
capturing, engulfing and digesting its food.”

Gruber reports however the following experiment
which has caused a good deal of surprise, for according
to the view of some biologists it seems to be opposed to
the results of earlier researches.

He selected a Stentor coerelus which showed already
the first stages of spontaneous division, that is there had
already commenced in it the formation of a lateral, per-

*"See e. g. Balbiani: Recherches expérimentales sur la mérotomie
des infusoires ciliés. Recueil Zool. Suisse, t. V, no. 1, 1888. P. 48—
49, 54; und Verworn: Die physiologische Bedeutung des Zellkerns.
Archiv fiir die gesamte Physiologie, Band. 41. Bonn, Straup, 1892.
P. 13—14.

Objection of Anuclear Regeneration in Stentor 55

istomal, ciliated area, and he divided it in two halves.
Since in this stage the chief nucleus, ordinarily monili-
form, contracts into a round or bean shaped mass,
Gruber was able to remove it completely from both
halves. The division of the animal was effected in such
a way as to produce about the same two halves as would
later have been produced by spontaneous division. In the
fragment which contained the original peristome the
simple cicatrization of the wound was enough to repro-
duce a complete individual. In the other fragment which
contained the posterior extremity the wound closed in
the same way and the anterior extremity continued its
development until the peristomal area and the buccal
spiral were completely formed.?®

This result seemed to contradict the view that the
formative action of a nucleus, as a developmental center
for the unicellular organism, was exerted continuously
throughout the whole duration of development. But the
following considerations show that this premature con-
clusion is quite fallacious.

We should remember in this connection another ob-
servation of Gruber. He cut off from the anterior end
of a Stentor a fragment absolutely without a nucleus, but
containing a small portion of the peristomal band. The
cicatrization of the wound was followed by the ordinary
contraction of the fragment and thereby the small portion
of the peristomal band was given the appearance of a
complete Infusorian such as would be formed by regen-

28Gruber: Uber kiinstliche Teilung der Infusorien. Zweite
Mitteilung. Biol. Centralbl. Band, V, No. 5; May 1, 1885. P. 139—
140; und: Beitrage zur Kenntnis der Physiologie und Biologie der
Protozoen; Berichte der Naturforschenden Gesellsch. zu Freiburg
i. B., Freiburg i. B., Mohr, 1886, P. 13—14.

50 Indications of a Central Zone of Development

eration. But that this was not actually the case was
demonstrated by more careful observation by which it
was recognized that the completeness was only apparent,
for no part altogether lost was reproduced and no new
mouth was formed in the place of the old one which had
been removed.?9

From this one could almost infer that some analogous
phenomenon is the effective cause whereby the organs of
the peristomal field, as soon as they are all formed in their
essential parts, become arranged in the posterior anuclear
half in about the same way as they would be arranged
after the completion of spontaneous division.

Even if we admit a true and proper continuation of
development, we must yet bear in mind first that it is not
at all certain that this posterior half was completely de-
prived of macro- or micro-nuclear substance. For the
micro-nuclei sometimes attain the number of fifty-four or
sixty-six in Stentor coereleus, and it is always difficult to
see them, especially in individuals in process of sponta-
neous division.®°

Secondly we must above all things get a clear under-
standing of what the remaining alive for a while of
anuclear fragments of adult individuals can signify, keep-
ing in view at the same time the absolute generative inca-
pacity of these fragments. They signify nothing else than
a posthumous persistence for a while of the special action
or series of actions, partly simultaneous, partly succes-

29Gruber: Uber Kiinstliche Teilung der Infusorien. Zweite
Mitteilung. Biol. Centralbl., Bd., V. No. 5; May 1. P. 139—190.

°°H. P. Johnson: A Contribution to the Morphology and Biology
of the Stentors. Journal of Morphology, vol. VIII, no. 3. Boston,
U. S. A., Ginn, August 1893. P. 499.

Posthumous Action of the Nucleus 57

sive, which the nucleus was exerting at the moment of its
excision or shortly before.

We can suppose, as we shall see better later, that this
posthumous action of the nucleus (‘“‘Nachwirkung”) may
be explained in the following way: Each of the different
nervous currents which the nucleus can discharge simul-
taneously or successively into the protoplasm deposits in
it, of all the nuclear substances just that one which had
given origin to it, perhaps by reproducing it partially
while on its way. This substance once deposited in the
protoplasm, would act as a reserve which, while incapable
of growth by itself because it lies outside the nucleus,
would nevertheless preserve for a time, until its gradual
exhaustion, the capacity of producing the same current
again. It would produce in relation to the excision of the
nucleus, the same effect as would be produced by a very
slow propagation of the respective current through the
protoplasm.*4

Therefore one can easily understand how in Gruber’s
experiment, in which the adoral ciliated zone of the an-
imal was already in an advanced stage of formation, the
whole series of simultaneous or successive formative
stimuli had been already discharged shortly before the
excision of the nucleus, and that therefore it remained
only to await the slow unfolding of their effects, which
would bring to completion the development already far
advanced.

*1Compare the partly similar, partly different hypothesis of Ver-
worn on the posthumous action (“Nachwirkung”) of the nucleus,
which may be attributed to a reserve material built up gradually
by the nucleus and given off to the protoplasm, and persisting till
the protoplasm is used up, in the above mentioned article: Die phy-
siologische Bedeutung des Zellkerns, P. 90; also: Die Bewegung
der lebendigen Substanz. Jena, Fischer. 1892.

58 Indications of a Central Zone of Development

To one or other of these conclusions, either to the
presence of an undetected micronucleus or to the pos-
thumous action of the nucleus, one is necessarily driven,
as we said, by the fact that only the nucleated fragments
of an infusorian already completely developed, are capable
of regeneration. For this capacity of reorganization,
as one may call it, of the protoplasmic substance,
which gives to it again the form of the complete
individual but of correspondingly smaller size, cannot
possibly arise either from the properties of this sub-
stance itself or from its specific “physiological units” for
which the adult form of the individual would constitute
the only state of equilibrium. This is quite impossible
because a mass of protoplasm as large as the nucleated
part, but which contains no nucleus, does not manifest the
slightest tendency to regenerate, although it is capable of
surviving its ablation for several days. The impulse
tending to produce the specific form of the ordinary
equilibrium is present only when the nucleus is not
lacking.

Nevertheless the material which disposes itself in this
definite specific form of equilibrium is not the nuclear ma-
terial but the protoplasmic. The nuclear substance with-
out participating itself in the process of reorganization,
merely provokes it in the protoplasmic substance, which in
this respect remains totally indifferent. This is dem-
onstrated among other things by the observation of
Gruber that the four nucleated fragments into which one
individual was cut by a transverse and a longitudinal in-
cision required in all cases the same time to regain their
complete specific form including the adoral ciliated zone.
The anterior end which already contained a portion of it
and which one would suppose to be better adapted in its

Unicellular Organisms Like Pluricellular 59

protoplasm to this new formation requires just as long
as the posterior end remote from the adoral zone.??

This impulse to reorganization which enables proto-
plasmic substance already organized to take on any other
organization whatever speaks strongly in favor of the
hypothesis that it is due to a special formative energy
(‘“‘formgestaltenden Energie” as Nussbaum would call it)
emanating from the nucleus, which using the proto-
plasmic substance merely as a support or vehicle or as an
indifferent constructive material, would be in reality the
only quiddity which tends to dispose itself in that partic-
ular form, which constitutes for it the only possible
system in dynamic equilibrium. For the reasons above
stated we must think that this formative energy is prob-
ably nervous in nature.

This ontogenetic function of the nucleus which we see
in unicellular organisms permits of very important deduc-
tions in relation to all organisms whatever. For the com-
plicated unicellular organisms whose manifold organs
have different and mutually independent functions, such
as for example a Stentor coereleus or a Paramoecium
caudatum, are not essentially different from pluricellular
organisms, but on the contrary are comparable with them
in all essential respects.

“Between the internal differentiations of a complex
cell,” says Delage, “and so between the body of certain
Infusoria, and the organs of the pluricellular being there
exists I think only a casual difference, which depends not
so much on the requirements of the differentiation as on
the size of the organism.” #4

Gruber: Uber kiinstliche Teilung bei Infusorien. Zweite

Mitteilung. Biol. Centralbl., Bd. V. No. 5; May 1. P. 138.
Delage: L’hérédité et les grands problémes de la biologie gén-

érale. P. 97.

60 Indications of a Central Zone of Development

“Flowever great,’ says Whitman quoting Gruber “the
difference between an infusorian and a highly organized
animal it cannot be a qualitative one. We can assume
that the same vital elements serve in both as the founda-
tion, only in ever new combinations. This kinship
declares itself very clearly in the correspondence of many
organs of the Infusoria with those of the higher or-
ganisms. We mention only the membranellae of the
Infusoria which are quite similar to the corner cells of
the mollusk Cyclas cornea.” 34 :

But we have already seen that when one cuts the
infusorian into several nucleated fragments the membra-
nellae can be formed from any given part of the proto-
plasm of the original individual, and can be arranged in
definite relation to one another under the influence of the
nucleus as a center from which the formative activity of
the entire organism radiates. It is then probable that the
formation and manner of disposition of the corner cells
of the mollusk Cyclas cornea may be due also to a similar
process of centroepigenetic nature. But this justifies us
in suspecting that in all pluricellular organisms whatso-
ever, every formative process commencing with normal
ontogeny is of centroepigenetic nature.

This hypothesis is supported for example by the ex-
periments of King upon regeneration in Asteria vulgaris.
These have given among others the following results:
each of the arms cut off close to the body can remain liv-
ing by itself for two weeks but is incapable of regenerat-

34Whitman: The Inadequacy of the Cell-Theory of Development.
Biol. Lect. at the Mar. Biol. Lab. of Wood’s Holl, Summer Session
1893; Boston U. S. A., Ginn, 1894. P. 118; and Journal of Morphol-
ogy, Boston U. S. A. August 1893. Vol. VIII, No. 3, P. 651—
652; Fig. 2 and 3.

Regenerations Indicate Central Zone 61

ing the entire animal. If a fifth part of the body disc
remains regeneration can occur in exceptional cases. If
half of the disc is present the absent parts are always
reformed.

If one amputates all five arms of the same animal by
five transverse cuts, the first one very near the body, the
others at four different distances from it, then after a
certain time,—the same for all five arms,—the regen-
erated portion is largest for the first, and proportionately
smaller for the other four according as the site of amputa-
tion was farther from the central disc.

This regenerated part which has developed from the
amputated arm is much smaller in diameter than the
original arm which was cut off. That is an indication
that the regeneration is not produced by the cooperation
of all the parts immediately adjacent to the surface of
amputation.®®

These experiments thus seem to indicate a distinct
zone from which the process of regeneration proceeds
and to the activity of which it is due.

From another side the existence of this formative
central zone is almost required by the results of the
similar experiments of Roux, which we have mentioned
above, on the formation of half embryos of frogs.

These experiments show, in brief, that each half, right
or left, anterior or posterior, can develop independently.
If one admits also that this development is always en-
tirely epigenetic in nature, that is that it is due entirely to
correlative differentiations which the cells produce in one

*5Helen Dean King: Regeneration in Asteria vulgaris. Arch. f.
Entwicklungsmech, d, Org., Band, 7. Heft. 2. and 3. Leipzig, Engel-
mann. October 18, 1898. P. 351—361. Table VIII, especially
Fig. 11.

62 Indications of a Central Zone of Development

another, it follows that at least each quarter of the
embryo must have its own system of correlation networks
independent of the other quarter systems. But the four
quadrants have one zone which is common to all. Con-
sequently at least these four independent systems of cor-
relation networks for the four quadrants must come off
from this common zone.

This suffices to warrant the statement that this latter
must belong to a central zone of development, in the sense
which we have set forth above; and that from this zone
must branch off and diverge independently of one another
the different great correlation networks or principal
branches for the general distribution of nervous energy.
These latter divide further into progressively smaller
ramifications, one could almost say just as the great
arterial trunks coming off from the heart continually sub-
divide down to the terminal capillary vessels.

It is nevertheless advisable to study these phenomena
more closely. We must postulate that each of the two
blastomeric nuclei obtained in the frog’s egg after the first
segmentation, when it once becomes completely isolated,
is capable of giving rise to a complete embryo. But in
the experiments of Roux, the disposition of the nutritive
yoke or deutoplasm in the uninjured blastomere remains,
thanks to the retention of its place by the injured blasto-
mere, the same as the disposition which would have
existed in this same blastomere if development had pro-
ceeded normally. Therefore, of all the specific potential
energies which the uninjured blastomeric nucleus would
be capable of activating successively, there would com-
mence and continue to be activated only those which in
normal development would have flowed directly into the

Interpretation of Partial Formations 63

half of the egg affording such a definite deutoplasmic
disposition.

So it becomes clear that when once the development
of the uninjured half of the egg has commenced, the
central zone concerned, even though it may be exactly the
same as in the complete embryo, would activate only the
specific potential energies proper to the corresponding
half embryo and would produce only a half formation.

This half formation no matter how independent the
great correlation networks might be, could nevertheless
at each instant of its development, render the system of
nuclear actions and reactions an incomplete one, without
equilibrium, because at the plane of separation there
would not be opposed to its own nervous tensions any
equivalent system of tensions of the absent half. This
incomplete system of nuclear tensions, not of itself in
equilibrium, could nevertheless be prevented, even though
only transiently, from equilibrating itself normally, by
the special distribution of the nutritive yolk and by the
presence of the injured half of the egg, still placed op-
posite that which is developing. But as soon as the con-
tinual increase of energy in the nuclear system overcomes
these artificial barriers, equilibrium is once for all upset
and postgeneration will appear.

It is necessary nevertheless to note that some demi-
monsters which proceed almost to the completion of their
development would seem on the contrary to indicate for
this incomplete system of nuclear actions and reactions a
practical equilibrium existing from the commencement
and persisting through all the stages of development.
The typical example of these demimonsters is the famous
Hemitherium anterius which Roux so thoroughly
describes. It is constituted by the almost fully developed

64 Indications of a Central Zone of Development

foetus of a half-calf, in which all the posterior part of
the trunk was missing as if it had been removed by a
transverse cut.%®
- However that may be, one fact which speaks in favor
of the hypothesis that the nutritive yolk acts as a tem-
porary dam to a system of nuclear actions and reactions
not of itself of equilibrium, is that these half embryos can
be obtained only from those eggs in which, as in the
Amphibia and Ctenophera, the nutritive yolk is abundant.
Whereas in the case of animals whose eggs are poor in
nutritive yolk, and present cleavage cells that are almost
identical, as in the Echinodermata and Ascidiae, either a
complete organism develops at once from the isolated
blastomere or postgeneration appears very early.??

Another fact which speaks in favor of this hypothesis
is that toward the end of a spawning period when the
vitality of the egg, and consequently also of the blasto-
meric nuclei, is lower, the formation of pure half
embryos is much easier to effect.*8

While thus, after exclusion of preformation theories
one can say that the formation of half embryos is a direct
proof of the hypothesis of a centroepigenesis with its
ramifying, independent correlation networks, this hypoth-

*°Wilhelm Roux: Uber die kiinstliche Hervorbringung ,,halber“
Embryonen etc. Virchows Archiv, Bd. 114. Oct. 1868 P. 132.
Gesamm. Abhandl. Zw. Bd. P. 442.

*TWilhelm Roux: Uber das entwicklungsmechanische Vermégen
der beiden ersten Furchungszellen des Eies. Verhandlungen der
Anat. Gesellsch. Wien, 1892. P. 55—56. Gesamm. Abhandl. Zw.
Bd. P. 809—8r1o.

**Wilhelm Roux: Die Methoden zur Hervorbringung halber
Froschembryonen und zum Nachweis der Beziehung der ersten
Furchungsebenen des Froscheies zur Medianebene des Embryo.
Anatomischer Anzeiger, Bd. IX. February 1894. P. 257. Gesamm.
Abhandl. Zw. Bd. P. 954.

Development of Parts Not Due to Local Relations 65

esis becomes confirmed indirectly by a whole series of
other facts which Roux also has described and commented
upon with his customary carefulness.

Natural or artificial headless monsters for example,
and in general all monsters lacking entire parts but other-
wise normal, prove that no formative action or reaction
is exerted by the head or by these other parts upon the
rest of the organism.

They speak therefore in favor of a centroepigenesis
with independent networks of correlation in which it is
necessary to suppose that the formative action must
stream out entirely from a center toward the periphery.
In all these monsters of which some part is lacking, there
need be present only one part of the body namely the seat
of the central zone of development.

Roux in his researches upon the formation of half-
embryos once observed, as an example of the disturbance
of correlations of mass by the absence of one embryonal
half, a lateral dislocation of the notochord and a corre-
sponding retardation of development of the dorsal part of
the endoblast lying near the median line as marked by the
semi-medulla and by the ventral parts. “It is an interest-
ing fact,’ he remarks, “that the axial parts can be laid
down and developed with so considerable a shifting in
relation to one another. For this indicates further that
the development of many parts even of the main parts is
not included in the form as such; the embryo does not
live a formal life.” *® These facts would also confirm the
hypothesis of independent networks of correlation, the
displacement of whose material would not alter their

Wilhelm Roux: Uber die kiinstliche Hervorbringung halber
Embryonen etc Virchows Archiv. Bd. 114. October 1888. P. 132.
Gesamm. Abhandl. Zw. Bd. P. 442.

66 Indications of a Central Zone of Development

respective formative capacity, because it would leave un-
altered the reciprocal relations of the different parts in
each network.

Further, the deformations which the entire organism,
and consequently also each of its different networks,
undergo, would not seem to alter markedly the internal,
reciprocal relations of the different parts of each net-
work; thus from frog’s eggs which had been compressed
continuously during their development, the blastula and
gastrula having been forcibly flattened, folded, and bent,
there developed embryos whose internal and external
aspect was just the same as though they had been allowed
from the first to develop in a normal fashion and had
undergone the deformation only later.*°

“In the development of frog’s eggs it happens very
often,’ Roux writes further, “that the primitive mouth
of the gastrula is not yet closed when the medullary folds
appear, and this condition can persist in part up till the
time of the closure of the medullary tube and the forma-
tion of the branchial elevations and adhesion cups. The
formation of these latter can proceed in a manner which
appears quite normal in the anterior half of the body even
though the posterior half of the body may have quite an
abnormal form, the primitive mouth remaining persist-
ently wide open. Another instance, yet more surprising,
is that in which notwithstanding the entire absence of the
medullary ridges, the gastrula gradually exchanges its
round form for a pear shaped one, a thing which or-
dinarily occurs only after the formation and development

“Wilhelm Roux: Uber die ersten Teilungen des Froscheies und
ihre Beziehungen zu der Organbildung des Embryo. Anatomischer
Anzeiger, Band VIII. 1893. N. 18. P. 608—609. Gesamm. Abhandl.
Zw. Bd. P. 926.

Anachronisms Show Local Relations Inessential 67

of the medullary tube. These modes of behavior and
others like them indicate that the parts which continue to
develop normally require for their development neither
the absent parts, nor that the remaining parts should be
at the stage of development normally corresponding, and
thus that they can develop alone, independent to a cor-
responding extent of those absent or backward.” 4!

“Anachronisms of development,” continues Roux in
a later research, “appear also in the relative retardation
or acceleration of development of one of the germ layers
in relation to the others. For example several embryos
otherwise normal, in which the medullary fold is still
quite undifferentiated, show already in the mesoderm, in
the entoderm, and in the chorda dorsalis, formations
which appear normally only about the time of closure of
the medullary tube. In this case there is an evident re-
tardation of development of the ectoderm in relation to
the development of the other two layers. There occur
also inequalities of lesser degree in the rapidity of
development of the two lateral halves of the body, and
thus it is possible to observe two different stages of
development in the same object.” *

“Tf such large parts of the organism,” concludes our
author in a still later study, “can remain behind in their
development or indeed remain absent, without thereby
producing any disturbance in the development of the
others, it follows surely that the development of these

414Wilhelm Roux: Zur Orientierung iiber einige Probleme der
embryonalen Entwicklung. Zeitschrift fiir Biologie. Bd. XXI.
Miinchen, Jul 1885. P. 478—479. Gesamm. Abhandl. Zw. Bd. P.
203—204.

42Wilhelm Roux: Uber die ktinstliche Hervorbringung halber
Embryonen, usw. Virchows Archiv, P. 128—129. Gesamm, Abhandl.

Zw. Bd. P. 438.

68 Indications of a Central Zone of Development

latter is not at all bound up by reciprocal actions with the
absent parts, and also that it is not accomplished by the
reciprocal action of parts of the whole organism.” #%
These conditions are just those existing in a centro-
epigenesis with ramifying and independent networks of
correlation.

The formation of double monsters with double
symmetry in the disposition of their organs is particularly
in accord with centroepigenesis. Concerning this Roux
expresses himself in this way: “In these double forma-
tions the fragment which is lacking in a symmetrically
similar manner from each of the two individuals, can be
any selected piece limited by a plane surface; and in them
the organs are nearly all present and normal in form up
to the plane of union, as if from two embryos, fully
developed and ready to be born, one had cut off two
symmetrical pieces so as to leave plane surfaces, and the
twins had then been reunited by the cut surfaces.” “The
simultaneous development of two formations so exten-
sively united, into two distinct bodies, of which each is
centered in itself, indicates directly that there are not any
general reciprocal actions operating to combine them into
a single whole.” 44

According to the centroepigenetic hypothesis, the
formation of these monsters would be due to the fact that
the two blastomeres concerned, which are quite identical
with each other since they arise from the segmentation of
one and the same egg, have become, on account of ab-

‘“Wilhelm Roux: Uber Mosaikarbeit und neuere Entwicklungs-
hypothesen. Anat. Hefte, Edited by Merkel and Bonnet, Febru-
arheft 1893. P. 320. Gesamm. Abhandl. Zw. Bd. P. 859.

44Wilhelm Roux: Uber Mosaikarbeit etc. Anat. Hefte, P. 320.
Gesamm. Abhandl. Zw. Bd. P. 859—860.

Centroepigenesis Accords with General Phenomena 69

normal circumstances which have made them independent
of each other, two distinct nodal points,—two central
zones of development. The necessary consequences of
the independent action of these two centers of develop-
ment would be the centration of each individual by itself.
On the other hand, the similarity of the two first blasto-
meric nuclei, which through multiplication give rise to
both of the two central zones concerned, would bring
about a similarity of the formative actions given off from
these zones. Therefore those formative stimuli which
act upon all points of any one of the infinite number of
planes symmetrical in relation to these centers, would
offset and annul one another, because they would be
equal and opposite but only in so far as they do act
along these planes. In this way could be explained why
the parts lacking in both individuals must always be alike.

While thus all these different facts which have at-
tracted the careful attention of Roux and been made the
special object of his studies confirm, some directly others
indirectly, the hypothesis of centroepigenesis with ram-
ifying and independent networks of correlation, a further
support, indirect indeed, but nevertheless very real, will
be brought forward in the following chapter. For we
shall endeavor there to show that if a whole series of
facts compels us to throw over preformation, a series of
other facts forces us to throw over simple epigenesis also,
and this would give a high degree of probability to. any
other hypothesis with which both series of facts should
be in accord.

Finally, the symmetrical disposition which the greater
number of organisms present in relation to a point, to a
straight line, or to a plane, and also the advance of
growth along diverging ramifications, which indeed is a

70 Indications of a Central Zone of Development

general law of organic development, are phenomena
which indicate in their turn that this centroepigenesis
with ramifying, independent networks for the distribu-
tion of nervous energy, is also in harmony with the most
general biologic phenomena.

One could always bring forward the objection that it
is difficult to conceive how this series of energies acting
one after the other, all upon the same point of the de-
veloping organism, could give rise to a series of dynamic
systems of distributions as complex as we must neces-
sarily suppose those to be which constitute the successive
stages of ontogeny. To dissipate all doubts in this mat-
ter one may draw attention to the following simple
hydro-dynamic experiment.

Let us imagine a very large cylindrical glass container
almost filled with water, and having a hole at a selected
point in the bottom of it. By means of a suitable force
pump let us make more water enter the vessel through
this hole with a velocity varying from one moment to
another. To make the idea clear and the phenomenon
more intelligible let us suppose that the velocity varies
sharply each second, sometimes increasing, sometimes
diminishing very considerably. On account of the great
amount of water already contained in the vessel, the
series of successive systems of very complex: currents
which will be produced each moment by the incoming
water, whose newly added mass interpenetrates and dis-
places the other in a manner which we can make appar-
ent in part by previously coloring the water to be injected,
will depend on the entire series, and exclusively on the
series, of different velocities with which the water is
forced into the container.

A given series of dynamic actions, qualitatively alike

Centroepigencsis in Plants 71

but quantitatively different, starting successively always
from the same point could thus give rise to a succession
of dynamic systems of as complex a configuration as one
could imagine. Different series, that is to say those in
which quantitative variations of the same dynamic ac-
tion succeed one another in different ways, would natur-
ally give rise also to dynamic systems of different
configuration.

We can compare, though only roughly, this water
which enters the container always by the same opening
and with a velocity changing every instant, to the series
of nervous currents of different specificity which, accord-
ing to our hypothesis, would be discharged into the soma
in the course of development, or into the great mass of
yolk, by the activity of the germinal substance, always
from one and the same point of the organism, which
would thus constitute the central zone of development.

It would be proper at this point to touch upon the
probable location of this central zone. But important as
it is we do not need to stop long over it.

It is necessary at the outset to notice in a very general
way that in plants, and especially in the higher plants,
one must regard the leaf as the true individual and one
must attribute to it a centroepigenesis of its own. The
flower would then be merely the product of numerous
centroepigeneses not entirely independent of one another:
The corresponding simultaneous or rapidly successive
activations of multiple centers, and the reciprocal action
of these centers upon one another, would be indeed the
agents by which modifications of each of the centro-
epigeneses is effected, so as to produce for example here
a petal and there a pistil instead of an ordinary leaf.

It would also be possible for a center or a definite

72 Indications of a Central Zone of Development

group of these centers, perhaps on account of some
special situation, to become, in the course or at the end of
the particular centroepigenesis producing the different
parts of the flower, and in relation to all the other centers
and so to the whole flower, the director to a further de-
velopment; so that there would be present for the whole
development of the flower, or for a part of it-at least, a
centroepigenesis of the second degree.

By analogy one can conceive also of the possibility of
other centroepigeneses of still higher degrees (composite
flowers, etc.).

“Tt may appear,” writes Le Dantec, “that the sexual
individual belongs to a higher order than the asexual in-
dividual and may originate from the individualization of
an association of parts which are like asexual individuals,
It occurs perhaps in the Medusae; it is certain in Phane-
rogams. A flower corresponds morphologically to an
assemblage in a fixed form, of parts which are like the
asexual individuals of the plant. Goethe had already
noted this peculiarity. The asexual individual of a plant
is the internode with its leaf and auxillary bud: flowers
are much more complex.” *°

Centroepigeneses of a second or higher grade could
thus serve to explain the transformation of simple colonies
of individuals, (e. g., of the ancestors of the present
echinoderms), into complicated organisms, which tend
steadily toward an individualization of their own. One
could explain easily the transformation, for example, of
the original individuals of the colony, becoming more and
more differentiated from one another, into the organs of
this organism (siphonophores). With the growth of

“Le Dantec: Traité de Biologie. Paris, Alcan, 1903, P. 413.

Location and Structure of the Central Zone 73

centralization (annelids, arthropods), centroepigeneses of
the second or higher degrees would approximate grad-
ually more and more the simple centroepigeneses of the
first degree.

“The gastrula,’ adds Le Dantec further, “itself a
morphologic unit of higher order than the cell, can itself
bud off other gastrulas, just as the cell can produce other
cells by budding. This budding may take place always in
the same direction and so give rise to linear associations
of gastrulas, as in the worms, arthropods, etc.; or it may
take place in every direction and thus produce plant-
like associations, for example the fibroid polyps or coral
polyps; it may proceed radially and so give rise to the
echinoderms. Even the vertebrates themselves would be,
according to this, the result of an individualized assem-
blage of a linear series originally comparable with an
annelid worm. That is the theory of human polyzoism of
Durand de Gros and Edmond Perrier.” *°

After what has been said thus far the probable loca-
tion of the central zone of development of the various
types of organisms need not be especially treated of here.

The place in which we must suppose it to be, which
naturally lies in the plane of symmetry of the organism,
appears almost self evident from what we have said
above, and will become steadily clearer from what will be
said in continuation. It may here be remarked merely
that this zone cannot be imagined as any special tissue
asthe off distinctly from the surrounding somatic tis-
of some tissue whose special, “coma functions i in the
adult individual are such as predispose it best, in the

“Le Dantec: Traité de Biologie. P. 412.

74 Indications of a Central Zone of Development

descendant organism, to the definite function of develop-
ment, and which differentiates itself gradually from the
other parts of this tissue by quite inappreciable and
gradual transitions.

We have already said that the centroepigenetic
hypothesis makes it necessary to distinguish the effective
germinal zone, or true place of origin of the germinal
substance, from the apparent germinal zone, which would
be nothing else than the receiving station for the sub-
stance separated out or secreted by the effective germinal
zone, or the place where the sexual cells concerned are
built up out of this material. While we must regard only
the effective germinal zone as the central zone of develop-
ment, it is clear that the apparent germinal zone can be
located at any part whatever of the organism.

In the higher plants the apparent germinal zone of the
asexual budding cells, and that of the female, sexual cells,
would seem generally to coincide approximately with the
actual zone, that is, with the corresponding central zone
of the leaf and of the flower.

In this way can be explained the heretofore puzzling
phenomenon of the Xenia, in which as is known the
flower after a hybrid fecundation, often takes on the
form, size, color and tissue structure, characteristic of the
variety from which the pollen comes; that is, as Darwin
has already observed “in which the male element not
only influences the germ as is its proper function, but
at the same time influences various parts of the mother
plant, in the same manner as it influences the same parts
in the seminal offspring from the same two parents.” 47

47Darwin: The Var. of Animals and Plants under Domestication.
Eighth impression of the second edition. Vol, I. London, Murray,
1882. Chap. XI, P. 433.

Determination of Location of Central Zone 75

In the pluricellular animals we can start out with the
simple supposition that if a central zone of development
is present, it is probably that in which the blastomeres
multiply with unlike rapidity ; that is, it will be constituted
by these blastomeres which multiply most rapidly. For
this greater rapidity would in the majority of cases
indicate a greater vitality or energy, which may be
produced by a richer protoplasm or by any other special
condition favoring the nutrition. And this greater
energy would bring it about that the cells possessing it
would win the upper hand over the others.

“The zone,’ writes Oscar Hertwig, “where the
smallest embryonal cells lie, which are also those which
divide most rapidly, becomes the place of gastrular
invagination; it becomes something like a fixed center of
crystallization for the animal development.” ** But these
blastomeres are those which, in the vertebrates for
example, later constitute the medullary tube and
afterward the spinal cord.

As we shall see, everything seems to lead to the con-
clusion that in animals with specialized nervous systems

the central zone is constituted by the least differentiated |
part of the nervous system itself; in the vertebrates :

probably by the innermost periependymal part of the
spinal cord. This part after completion of its activity in
determining development would, on account of the so-
matic function pertaining to it, likewise constitute the
place where the infinitely manifold nervous activities of
all the rest of the nervous system or rather of the whole
organism are faintly re-echoed.

As we have already said, this location of the central

““8Oscar Hertwig: Zeit- und Streitfregen der Biologie. Heft. 2.
Mechanik und Biologie. Jena, Fischer, 1897. P. 180.

—

76 Hypothesis of Structure of Germ Substance

zone is almost self-evident from what has preceded, and
will be still more so from what is to follow. Here it may
only incidentally be remarked, (since we have treated of
the subject more thoroughly in another place), that this
hypothesis concerning the location of the central zone in
vertebrates, and in general in those animals which have
a specialized nervous system, finds a very strong support
also in the numerous researches and observations upon the
influence which the nervous system exercises upon de-
velopment and regeneration.*®

From this we can now pass on to the discussion, even
though very briefly, of the question of the probable com-
position and structure of the substance which constitutes
this zone, and which is consequently none other than the
germinal substance. This affords an opportunity of
speaking of the not essential but subordinate difference by
which the germinal nuclei are probably distinguished from
the somatic.

2. Hypothesis Upon the Structure of the Germinal
Substance

We have seen that according to the centroepigenetic
hypothesis, ontogeny can be attributed to a series of mod-

See e. g. Wolff: Die physiologischen Grundlagen der Lehre
von den Degenerationszeichen. Virchows Archiv, Bd. 164, 1902;—
Richard Rubin: Versuche tiber die Beziehung des Nervensystems zur
Regeneration bei Amphibien. Archiv f. Entw.-Mech. d. Org., Bd.
XVI, Heft 1; March 13, 1903;—Kurt Goldstein: Kritische und ex-
perimentelle Beitrage zur Frage nach dem Einflug des Zentralner-
vensystems auf die embryonale Entwicklung und die Regeneration.
Arch. fiir Entw.-Mech. d. Org., Bd. XVIII, Heft 1; February 26,
1904 ;—Eugenio Rignano: Die zentroepigenetische Hypothese und der
Einflug des Zentralnervensystems auf die embryonale Entwicklung
und die Regeneration, Arch. f. Entw.-Mech. d. Org., Bd. XXI, Heft.
4; September 11, 1906

Composed of Specific Potential Elements 977

ifications in the general distribution of nervous energy
of the organism. If we consider the law of Haeckel in
its first degree of approximation, we must suppose as we
have already said, that this distribution of nervous energy
constitutes by itself at each ontogenetic stage a system in
dynamic equilibrium, because the same distribution of
this energy was in equilibrium in the corresponding an-
cestors. To provoke the transition from one dynamic sys-
tem to the other, it is necessary that at each ontogenetic
stage there become active in the central zone a new spe-
cific energy, which disturbs the dynamic equilibrium
which has just been formed and effects the transition to
a new dynamic equilibrium.

This leads to the supposition that the germinal sub-
stance may be constituted by a number of material par-
ticles of which each would be able to activate only the
corresponding specific nervous energy. We can desig-
nate each of these particles by the term specific potential
element.

We must here provisionally postulate the possibility
that there may be substances capable of containing in the
respective potential condition, not only definite forms of
energy but also different specific modes of the same form
of energy. We shall take up the question again later in
order to make it clearer and to handle it more thoroughly.
It may be remarked here, however, that a chemical analy-\s
sis of the material particles of the nucleus, which actually”.
contain the hereditary mass, could hardly throw much - d
light upon the eventual differentiation of the different ma-
terials which compose the entire germinal substance. /
For, at least for the moment, it can give only the com-
position of the possibly homogeneous residue into which

78 Hypothesis of Structure of Germ Substance

all these different substances break up or decompose as
soon as life has gone out of them.

In conformity with the views of most biologists, we
can assume that the hereditary mass, and therefore all
the specific potential elements, are preserved and distrib-
uted during what is called the resting stage, in the gran-
ules of chromatin which are disposed like the beads of a
rosary upon the nuclear reticulum; but during mitosis, in
the chromosomes, and particularly in the little discs of
chromatin which the chromatic filaments into which the
nuclear reticulum and its granules contract, often present,
superimposed upon one another and separated by inter-
vening layers of linin.

We must nevertheless note that this mode of dispo-
sition of the different specific potential elements in the
nucleus is of importance to us only in relation to nuclear
division. For we must hold with the epigenesists, as we
shall see soon, that this division always proceeds in a
manner qualitatively the same.

But this disposition is of absolutely no importance to
us in relation to the effects which it will have upon the
serial activation of these elements. From this latter
point of view we can indeed suppose these elements to
be scattered through the germinal nucleus and mixed
with one another in any way whatever.

For, as we shall see better later, the activation of
every specific potential element in the proper ontogenetic
stage, depends in no way upon its position in relation to
the others, but rather on the condition that at this stage
only its activation requires the doing of only a moderate
amount of work—an amount which does not require more
energy than the total quantity inherent in each element.
Its activation in any other stage would require, on ac-

Nuclear Somatization and Equal Cell Division 79

count of the much greater modification which it would
then induce in the distribution of nervous energy already
existing, the doing of a large amount of work,—an
amount which would require more energy than the quan-
tity present in each element.

The centroepigenetic hypothesis of a single limited
zone containing the germinal substance, and the other
conception following upon it, that the germinal sub-
stance may consist of a number of different, material
particles, each representing one particular, specific, poten-
tial element brings up the question of nuclear somatiza-
tion.

We postulate the existence of a central germinal zone
distinct from the soma. We must not forget neverthe-
less that all nuclei arise by division from the first, that
of the egg. If we also admit with the epigenesists a
qualitatively equal nuclear division, then the nuclei des-
tined to become somatic must at first be equivalent with
those destined to become the central zone of development.
In what way then is the nuclear somatization brought
about in the cells which later must constitute all the dif-
ferent tissues of the body?

There presents itself at once the preliminary ques-
tion: Must we really admit this nuclear division to be
always qualitatively equal? Or shall we rather hold with
the preformists that in addition to equal nuclear divi-
sions there may be also unequal divisions? On this point
we believe we ought to agree unconditionally with the
epigenesists.

There does not exist any observation which gives even
the slightest ground for the conclusion that there is a
qualitatively unequal division. “By the most thorough
study of the longitudinal division of the chromosomes,”

80 Hypothesis of Structure of Germ Substance

writes Strassburger, “it is absolutely impossible to hunt
out anything but equal division. Unequal division is not
presented at all. There is not a single fact to support the
notion that it exists.” °°

We shall here limit ourselves to mentioning only two
orders of facts which speak directly against unequal divi-
sion:

First, it does not occur in any nucleus in the vast realm
of unicellular and of primitive pluricellular forms, con-
sisting of colonies of like cells; for in them the facts of
heredity show directly that nuclear division is always
equal.

But especially the oft repeated and keenly discussed
experiments upon the relative shifting and isolation of
blastomeres afford direct proof that nuclear division is
equal in the first segmentations of the egg. We recall for
éxample the experiments of Chabry upon the Ascidians,
those of Wilson upon Amphioxus, those of Herbst on the
separation of the blastomeres of the sea urchin merely by
adding chloride of potassium to ordinary sea water, of
Driesch on the Echinus microtuberculatus, of Oscar Hert-
wig upon frogs’ eggs, of Raffaello Zoja on the Medusae
and so on. These experiments in which one of the first
blastomeres, or one of the four, or eight, or sixteen, or
thirty-two first blastomeres, produce when isolated an
entire embryo, perfectly formed but proportionally
smaller, or in which the blastomeres, though shuffled
about in any way whatever, nevertheless developed in a
perfectly normal way, lead with the greatest certainty
that any one could desire to the conviction that in the

°StraBburger: Uber periodische Reduktion der Chromosomen-
zahl im Entwicklungsgang der Organismen. Biol. Centralbl., XIV.
No. 23-24. Leipzig, Dec. 1, and 15, 1894. P. 835.

Cell Division Hereditarily Equal 81

successive blastomeric divisions the nuclei always remain
like the first, that of the egg from which they sprung.

The contrary cases of the formation of half embryos,
or of incomplete embryos, after the separation or killing
of one of the two first, or of several of the first blasto-
meres, are found always and only in embryos rich in
deutoplasm, so that, as we have already seen, they cannot
afford any ground for the conclusion that the nucleus or
nuclei from which these incomplete embryos develop must
be different from the first nucleus, that of the egg.

We shall examine in the following chapter the very
complex and untenable subsidiary hypotheses, to which
the partisans of unequal division have been driven, in
order to bring their principal hypothesis into accord with
experiments upon the isolation and displacement of
blastomeres, and also with other equally irreconcilable
processes, such as post-generation and regeneration. Here
we shall only quote and adopt the conclusion which Oscar
Hertwig has drawn from these experiments, namely: “It
is self-evident that such an interchange of blastomeres
without injury to the product of development, is possible
only if one nucleus has the same characters as the others,
that is, only if all the nuclei are produced from the seg-
mentation nucleus by hereditarily equal division.” °*

In order that this hereditarily equal division may be
materially possible in a germinal nucleus constituted by
innumerable, different, infinitely small particles,—that is
in order to permit the division of each of these particles
or substances between the two daughter nuclei,—it would
be sufficient that they become disposed during mitosis in
little transverse layers one over another in the various

51Qscar Hertwig: Die Zelle und die Gewebe. Zw. Buch. P. 69.

82 Hypothesis of Structure of Germ Substance

little discs of chromatin of the chromatic filament, in
exactly the same disposition as that which these little
discs actually do present in the chromatic filament.

Admitting then that nuclear division is always quali-
tatively equal we must now ask: does this really mean
that the nuclei of all cells must remain alike throughout
the whole of development?

But before taking up this question we must first
answer a preliminary one: must we exclude nuclear som-
atization with the epigenesists or admit it with the pre-
formists ?

If it seemed to us impossible to disagree with the
epigenesists upon the first question of a qualitatively equal
nuclear division, it seems on the contrary impossible to
disagree with the preformists on this second of a nuclear
somatization. We shall certainly not repeat here all the
arguments by which these latter support their thesis.
They can be summed up in their essential parts in the
following words of Weismann.

“The chromatin is able to imprint upon the cell in
the nucleus of which it lies a specific character. Just as
the thousands of cells which make up the organism
possess very different characters and very different
functions, so the chromatin which controls them cannot
be every where alike, but must rather be different in
different kinds of cells.” 5?

The epigenesists, on the contrary, are well known
to be inclined to the view that all the somatic cells of
the organism have, without distinction, like nuclei con-
stituted by the same idioplasm. Oscar Hertwig indeed
ventures the assertion that each somatic cell if it were

“Weismann: Das Keimplasma, eine Theorie der Vererbung.
Jena, Fischer, 1892. P. 43 and 268.

Cells Become Differentiated and Somatized 83

possible to put it in conditions which would render it
capable of nourishing itself and preserving its life
independently separated from the rest of the organism,
could function as a germ cell.5?

And certain processes which appear in all the lower
organisms, with tissues that are not very highly
specialized, appear to justify this view.

If one places a piece of a Begonia phyllomaniaca in
some earth in moist air, after cutting through the leaf-
ribs in different places, one finds after some time, in the
neighborhood of each wound, one or more little new
plants. Any fragment whatever of a hydra or medusa
possesses the power of reforming an entire animal
without increasing its mass, but rather by a process of
differentiation and rearrangement of cells already existing.

A theory which admits equal nuclear division and also
a slow and gradual nuclear somatization, resulting from
the action of a determinate zone constituted only by the
germinal substance, would reconcile the different and
contradictory phenomena brought forward by the epi-
genesists on the one side, and by the preformists on the
other.

Oscar Hertwig who as we have just seen is a zealous
partisan of the idioplasmic equality of all nuclei, is com-
mitted in another place to the possibility of a certain
nuclear somatization. “The hypothesis of a hereditarily
equal nuclear division does not imply the view that the
‘anlage’ substance must therefore be an immutable
thing. . . . The idioplasms of certain groups of cells
of an organism which find themselves permanently in
unlike conditions in consequence of their different spatial
and functional disposition in the body as a whole, dif-

®Qscar Hertwig: Die Zelle und die Gewebe. Zw. Buch. P,
304—305.

84 Hypothesis of Structure of Germ Substance

ferentiated as it is through the division of labor, can
receive to a certain extent the stamp of local character.” °4

If we admit that each new specific current while
passing through a nucleus deposits there the substance
which was capable of producing it, and which would be
capable on occasion of reproducing this same specific
current,—a hypothesis of which we reserve a better
exposition till later—we can conceive of nuclear soma-
tization as a gradual and constant acquisition of new,
specific, potential, somatic elements.

The fact that each cell, as long as its differentiation
has not progressed too far, can upon occasion, provided
it be isolated from its neighbors, arise to the rank of a
germinal cell, appears to indicate that these new somatic
elements, thus gradually acquired, would from the start
be simply added to the germinal elements already existing,
without altering them at all, but merely relegating them
to the potential state, from which, under normal
conditions, they would not again emerge.

In other terms we must suppose that all the germinal
elements remain unaltered in the nuclei undergoing
somatization as long as the number or the mass of
acquired somatic elements does not progress beyond a
given limit.

But when this limit is once passed, then the require-
ments of nutrition or of space would cause the different
germinal elements to disappear gradually, and the nucleus
concerned would thus lose all generative capacity.

Further even those somatic elements, which each
nucleus acquired one after another at each successive
stage of development, will gradually disappear after

“Oscar Hertwig: Zeit- und Streitfragen der Biologie. Praforma-
tion oder Epigenese? Jena, Fischer, 1894. P. 142—143.

How Somatization Reduces Germinal Capacity 85

ontogeny is completed, for then the nuclei are always
exposed to one specific current or to a limited group of
specific currents peculiar to the adult state. There would
remain over only a small or very inconsiderable number
of those somatic elements which were acquired last and
which would thenceforth continually increase in mass.
The cell would thus lose by degrees its undifferentiated
embryonic aspect, and its exclusively somatic characters
would steadily increase.

While according to Weismann there would be a
fundamental distinction between the germinal nuclei set
apart for the preservation of the entire hereditary mass,
and the somatic nuclei which from the first would receive
only such particles of that hereditary mass as are indis-
pensable for their function, and the ontogenetic passage
from one to the other would take place suddenly and
directly at the very commencement of development;
according to the centroepigenetic hypothesis, on the
contrary, there would not exist any essential difference
‘between them, because they differ from each other only
in the number and the specificity of their respective
potential elements, and the passage from one to the
other would be effected gradually and slowly. And this
transition would be due we repeat only to the constant
acquisition by the nuclei destined to become somatic, of
new specific potential elements, which at first are simply
added to the germinal elements already present but finish
by causing the latter gradually to disappear on account
of the requirements of nutrition and space and by taking
their place themselves.

Without needing to have recourse to a reserve
idioplasm, or to any other equally involved subsidiary
hypothesis, one can explain in this way the phenomena,

86 Hypothesis of Structure of Germ Substance

common in plants, of the retention by some cells of the
germinal capacity even though they belong to somatic
tissues which have already advanced to a certain degree
of differentiation.

In the same way is easily explained how a given
piece of a hydra or medusa reorganizes itself so as to
reproduce the entire individual without any correspond-
ing increase of its mass.

For since histologic differentiation in the hydra is
not very pronounced one can surmise a priori that in
all or nearly all their cells, the whole of the specific
potential elements must coexist with the somatic elements
peculiar for each cell and acquired by it during develop-
ment. The separation of the fragment from all the rest
of the organism, which arrests the general circulation
of nervous energy, will therefore cause the somatic
elements which were active in the intact individual to
return to the exclusively potential state and thus enable
the germinal elements to become active again. That
cell or group of cells which surpasses the others in vigor
will have its germinal elements activated first and will
then form a central zone directing development of the
others; and the distribution of nervous energy, which
again passes through the wonted series of ontogenetic
stages, will now proceed in the fragment in the same
way as formerly in the entire individual.

There are often external circumstances which deter-
mine what cells of the fragment shall constitute the central
zone. Thus if one cuts off from the trunk of the hydra
both the tail end and the head end at the same time,
and then places the fragment with the lower cut surface
down, the head is reproduced at the same end as formerly,
whereas if one turns it over so that the former head end

More Vigorous Cell Groups Direct Development 87

of the polyp sticks into the sand of the aquarium, the
head is reproduced at the aboral pole.

Sometimes two distinct groups of cells seem to
struggle with each other to constitute the central zone
of development, and both may attain their object thus
‘producing double monsters. If from the trunk of a
hydra one cuts off at the same time both the tail and
the head end, and suspends the fragment horizontally
in the water it forms a head at both ends.

In an analogous way, Morgan in his experiment on
the regeneration of Planaria maculata once obtained
from a fragment which had been cut off by two trans-
verse sections, two heads one at the front end, the other
at the hind end.®®

This simultaneous activation of two centers of develop-
ment can go on also at the commencement of ontogeny
in the cells of the blastula itself. “From causes which
are yet beyond our knowledge, there are often produced
(in fish eggs) two gastrular invaginations instead of
one, at separate points of the blastula. And it depends
on the position of these two invaginations, which could
also be designated crystallization centres for the further
development of the embryos, how the embryonic cells
of the germinal disc are then drawn into the process of
development, given very definite positions in relation to
one another, and utilized for the formation of organs.” °°

The analogous phenomena of heteromorphosis in
general can likewise be explained, through the similar,

55Morgan: Experimental Studies on the Regeneration of Plan-
aria maculata. Arch. f. Entwicklungsmech. d. Org. Bd. VII. 2 and
Heft, 3. Leipzig, Engelman. Oct. 18, 1898. P. 381, 395.

5Oscar Hertwig: Zeit- und Streitfragen der Biologie. Prafor-

mation oder Epigenese? P. 60

88 Hypothesis of Structure of Germ Substance

abnormal activation of new centres of development after
amputations, incisions, or in any other abnormal condi-
tions whatever in the most different regions of the organ-
ism which otherwise would have continued to constitute
definite somatic parts of it.

In Planaria maculata for example these new develop-
mental centers of heteromorphous formations, of which
this animal affords perhaps the most typical cases, appear,
according to the results of recent researches, to be formed
always from one of the two ends of the piece of the
lateral nerve tract which is separated by the operation
from the other parts of this tract.5”

Indeed it appears to be indicated by these latest and
most careful researches that those pieces of the planarian
which contain no part of this nerve tract are not able
to regenerate themselves, any more than are those frag-
ments of infusoria which contain no part of the nucleus.®®

Therefore this animal forms perhaps the transition
from those pluricellular organisms in which all the somatic
cells preserve throughout their capacity of regeneration
undiminished, to those in which this capacity exists in
the adult in only a very definite and special zone.

The phenomenon which more than any other speaks
in favor of a nuclear somatization arising in the higher
multicellular organisms during development, is the cir-
cumstance that the capacity of regeneration diminishes
with age; for it is very much greater in embryos than
in fully developed animals. For example, if the feet of
an adult frog are cut off, they do not grow again, whereas

*"Charles Russell Bardeen: Factors in Heteromorphosis in Plan-
ariae. Arch. f. Entwicklungsmech. d. Org. Bd., XVII. 1. Heft. 13
March 1903. P. 1—20, esp. P. 6—8; Fig. 5, 6, 7.

**Charles Russell Bardeen: Ibid. P. 2, 3.

Transformations Show Epigenetic Somatization 89

Barfurth has demonstrated that during the first stages
of development this regeneration is complete. And Roux
has found that if one cuts quite young frog embryos
into longitudinal or antero-posterior halves the missing
parts are completely regenerated in a few hours.®®

On the other hand, if the regeneration of the optic
lens in the triton from a tissue other than that from
which it is developed in ontogeny, is of itself enough
to exclude preformation decisively, it is nevertheless not
in any way incompatible with the most complete nuclear
somatization. If one admits this latter, the histological
transformation of certain cells would indicate only the
possibility that in certain ways somatized nuclei may
become differently somatized, if unusual influences are
exerted upon them by neighboring nuclei, that is if
nervous energies other than the usual ones act upon
them; and they would undergo this new somatization
through the gradual acquisition of new specific, potential
somatic elements, different from the former ones. By
itself this transformation certainly does not prove that
all nuclei of the different cells consist of like idioplasm.

Further there is no firm support for this supposed
idioplasmic identity of the nuclei in the researches deal-
ing with vegetable and animal grafts.

In order to support such a hypothesis effectively,
these investigations would have to show a closer relation-
ship or “harmonicity” (as Véchting would say) between
different tissues of the same individual or of individuals
belonging to the same species, than between like tissues

®°Roux: Uber die verschiedene Entwicklung isolierter erster
Blastomeren. Arch. f. Entwicklungsmech. der Organismen, 1895,
Band, I. Heft 4. P. 614.

90 Hypothesis of Structure of Germ Substance

of different species. But this demonstration has not
been afforded in a single instance of animal grafting.

There are indeed examples of transfusion of blood
which do not succeed when they are made from one
animal to another of different species, whereas they do
succeed perfectly between animals of the same species.
There are the experiments of Bert upon the successful
transplantation of a fragment of the tail of a mouse
into the subcutaneous tissue at another part of the body
of the same individual or of another individual of the
game or a related species, as Mus decumanus and Mus
rattus, whereas such a transplantation is not successful
between species farther removed, such as Mus rattus
and Mus silvaticus. There are the experiments of Ollier
and Schmitt on the transplantation of fragments of
bony tissue, which were successful in transplantations
from one part to another of the same individual or to
another individual of the same species, but failed be-
tween individuals of different species.

But all these experiments indicate only that there is
more affinity between the parts of the same tissue or of
similar tissues when they belong to individuals of the
same species or of related species than when they are
taken from individuals, of different species. They do
not prove at all that there is more affinity between parts
of different tissues, which come from the same individual
or from individuals of the same species, than between
parts of the same tissue taken rrom different species.

On the other hand Joest’s experiments have demon-
strated the possibility of true heteroplastic grafts in the
annelids, in which it is easy to obtain transplantations

“Oscar Hertwig: Die Zelle und die Gewebe. II, P. 2aff.

Grafts Do Not Show Idioplasmic Identity gI

between different species. In contrast with the results
obtained by Ollier and Schmitt, the transplantation to
man of portions of bony tissue and of horny tissue which
were taken from carnivorous or rodent mammals, has
been entirely successful. It is known indeed that the
transplantation of a cock’s comb to a cow’s ear has been
successfully effected. Born, in his famous experiments,
has succeeded in transplanting definite parts of young
embryos of Rana esculenta to corresponding parts of
other embryos, not only of the same species but also
of different species (Rana fusca, arvalis and esculenta),
and indeed of different genera (Rana esculenta and
Bombinator igneus). °?

All these experiments show that the plasticity or
capacity of transformation of living organic substance
reaches much farther than between individuals of the
same species. Therefore it cannot be explained by the
idioplasmic identity of the nuclei, which in any case
could exist only between tissues of the same individual
and between individuals of the same species.

There are certain grafts in plants that appear to
justify the conclusion that there is a single nuclear
idioplasm, identical throughout the whole plant. For in
grafts between plants of the same species there has even
been obtained the union of parts which have nothing in
common with each other at all, as for example a root
with a leaf. Whereas if one attempts to transplant even
in quite normal relations, parts of plants belonging to

*1Compare e. g. Oscar Hertwig: Die Zelle und die Gewebe. II.
P 23; Delage: L’Hérédité etc. P. 114; G. Born: Uber Verwach-
sungsversuche mit Amphibienlarven. Leipzig, Engelmann. 1897. P.
146ff,

92 Hypothesis of Structure of Germ Substance

different species the result of the graft is not certain
and often unfavorable.

This can be explained by the fact that in numerous
species of plants, as we have seen, nearly all the cells
preserve the reproductive capacity. What one calls
“vegetative affinity’ is then perhaps nothing else than
a direct effect of the retention of the whole of the
specific germinal potential elements in addition to the
somatic elements peculiar to each of the different tissues,
in all or nearly all the different nuclei which do not
pass beyond a certain degree of differentiation.

In drawing a conclusion from all that has been said
so far, we are confronted with this apparent paradox:
on the one side, it seems that in conformity with the
epigenesists we must reject a nuclear division which
during one and the same development must be
sometimes qualitatively equal, sometimes unequal, as
inadmissable and refuted by the facts, and instead of
this admit only a nuclear division always qualitatively
equal. On the other hand it appears that in conformity
with the preformists, one must likewise exclude a nuclear
substance, identical in all the cells of the same organism,
and must accept on the contrary, the hypothesis of an
actual nuclear somatization. It follows that this nuclear
somatization can be effected only gradually and only by
a process of epigenetic nature.

But when one has once admitted equal nuclear divis-
ion and gradual nuclear somatization by a process of
epigenetic nature, there follows therefrom necessarily the
hypothesis of centroepigenesis. For if the nuclei of the
cells of the different tissues of the body finally become
completely somatized it is certain that some certain ones
of the nuclei constituting the organism do not become

Elasticity of Developing Organisms 93

somatized at all, namely those whose function it is to
supply the reproductive cells with germinal substance.
And if the first nuclei become somatized by a process of
epigenetic nature, this process even though it involve the
entire organism, must leave the other nuclei unaltered.
But this would be possible only when this process is
dependent on influences proceeding from the zone of
germinal nuclei, and being exerted by it in such a manner
that the germinal substance concerned does not become
altered at all.

The continuity of the germinal substance, the spec-
ificity of the nuclei, and the epigenetic nature of the
formative processes of organisms,—these three concep-
tions which individually are favored by a great number
of biologists—imply together the conception of centro-
epigenesis.

Another fact which has been considered perhaps less
than it deserves, supports the hypothesis that the process
of development is not only of epigenetic nature, but also
depends upon influences coming off incessantly and suc-
cessively from a point which is external to all the trans-
forming parts, but which remains itself unchangeable;
namely the elasticity by virtue of which developing organ-
isms, much more than those completely developed, are
able not only to undergo without injury enormous changes
of form but also to resume their original form as soon as
the disturbing influence ceases. And just to this greater
elasticity of the young organism is to be attributed the
fact that it is much less plastic than the adult organism.

In fact the centroepigenetic hypothesis would permit
one to deduce this a priori. For according to it the
young organism is so much more elastic, because in it
all the cells, being less specialized, are thus much more

94 Hypothesis of Structure of Germ Substance

easily able to assume any new somatic character what-
ever which may be imposed upon them. It makes no
difference in the case of the still unspecialized cell, or
even in that of the cell which is in the first stages of
specialization, whether the somatizing stimulus is onto-
genetic, proceeding by indirect ways from the central
zone, or functional, induced by the environment. For
the embryonic cell is in itself thoroughly plastic. Con-
sequently the young soma would also be plastic if
it were not continually influenced by the formative stimuli
proceeding from the central zone of development. This
influence though it is more feeble than the functional stim-
ulus proceeding from the environment and consequently
unable to resist it, has nevertheless the advantage of be-
ing continuously in action, and so of gaining the ground
lost, as soon as the action of the environment ceases.

The cells of the adult soma are on the contrary less
plastic, because they are already considerably specialized.
But every modification which their limited plasticity per-
mits in them remains, since the opposition of the central
zone of development has already ceased. The adult
organism is much less elastic. But in respect to the
permanence of results it is more plastic than the young
one.

And, as already said, this is entirely confirmed not
only by the most commonplace phenomena, but also by
the most careful embryologic researches. In fact con-
siderable changes of form, which would be destructive
to an adult organism are, on the contrary, very well
borne by the young. But attentive observation of these
processes shows us also, as stated, that the younger the
organism the greater is its elasticity, which tends, when
the disturbing action has ceased, to restore it to its

Roux's Self Regulating Mechanism 95

primitive state. Thus it is that a wound or a fracture
is never so detrimental to the child as to the adult; but
it is also true that with the same intensity and duration
of the educative influence directed toward the modifica-
tion of inborn tendencies the results are more permanent
the older the child is.

This elasticity of development is proved by Roux
with his customary care in the following way.

In one of his experiments on the effects of passive
deformations in the first stages of development he suc-
ceeded in bending a few frogs’ embryos within their
gelatin envelopes by squeezing them between needles. “If
the needles were removed immediately after the deforma-
tion, the embryo at once took on again its previous form;
if they remained however a few hours the deformation
tended to be a persistent one and disappeared again
only in the course of several hours; a proof that an inter-
nal adaptation to the new form had already commenced,
but which was in its turn caused to disappear in the
course of further development, perhaps by the action of
growth forces inhibited during the deformation but re-
sumed upon the restoration of the normal form.” °

Roux gives this dynamic elasticity of development
the name “mechanism of self regulation.” Let us note
again that the absence of this elasticity in adult organisms,
which remain plastic in relation to the somewhat persist-
ent, deforming influences of the environment, would de-
note that this mechanism is active only during embryonic
life. Now the continued action exercised by the central
zone of development constitutes precisely such a mechan-

*Wilhelm Roux: Zur Orientierung tiber einige Probleme der
embryonalen Entwicklung. Zeitschr. f. Biol. Bd. XXI. Miinchen,
July 1885. P. 515—516. Gesamm. Abhandl. Zw. Bd. P. 24s.

96 Hypothesis of Structure of Germ Substance

ism of self-regulation, active during the whole of onto-
geny but ceasing upon the completion of development.

Another example of the dynamic elasticity of devel-
opment, no less characteristic in certain respects than the
preceding, has been repeatedly observed by Roux in the
postgeneration of his half embryos. “In the postgenera-
tion of the mesoblast it can be observed that very young
yolk cells with nuclei not yet stainable, and also the re-
mains of substances not yet cellulized, hinder the differen-
tiation, and so divert the mesoblastic formation toward
the interior or divide the formation into two layers; but
after the circumvention of this obstacle the further dif-
ferentiation soon resumes its normal course; a procedure
in its essence extremely puzzling.” ®*

It may be merely noted here that this elasticity of de-
velopment helps to explain the interpolation of certain
newer ontogenetic formations or stages (placenta and
similar things) in the series of older ontogenetic stages,
without markedly altering the earlier or later members
or even the last member of this ancient series.

“We have reason to believe,” says Orr, “that the man-
ner of growth for some particular period of the develop-
ment may be secondarily changed without radically affect-
ing either the preceding or succeeding growth. As an ex-
ample of this may be mentioned the embryonic organs and
embryonic modifications which adapt the embryo to
undergo partial development in the body of the parent,
and allow it to receive nutriment from the parent, e. g.
the placenta.” %4

“Wilhelm Roux: Uber die kiinstliche Hervorbringung halber
Embryonen usw. Virchows Archiv. Bd. 114, October 1888. P. 276.
Gesamm. Abhandl. Zw. Bd. P. 504.

**Orr: A Theory of Development and Heredity. New York,
Macmillan, 1893. P. 210.

Temporarily Disturbing Action of Yolk Mass 97

These embryonal organs and modifications which in-
terpolate themselves in the series of ontogenetic stages,
leaving these latter unchanged, can then also serve as
proof that developing organisms are elastic but not plas-
tic, while contrariwise grown organisms remain piastic
but not elastic.

To these facts one can add that the large accumulation
of yolk in the egg cells exerts a great influence on the
first stages of development, but subsequently exerts abso-
lutely no influence on the other stages. “The organiza-
tion of the egg,” says Hertwig, “which depends on the
disposition of the deutoplasm, has fundamentally only a
subordinate influence, and that of a secondary and tran-
sient nature in the developmental process.” “Eggs of ani-
mals which belong to different races can present a very
similar type of cleavage and similar early embryonic
forms, while eggs from closely related divisions of one
and the same race divide in very different ways, and dif-
fer very extraordinarily in the nature of the blastula and
gastrula. The deposition of yolk material in the egg im-
prints a quite characteristic stamp upon the first embry-
onic stages,—the cleavage process, the blastula, gastrula
and so on,—but it has no influence on the essence of the
animal species itself, nor on the formation of any special
species of animal.’ ®

One has here then developments, which, altered in
the first stages by the influence exerted by the yolk mate-
rial, later resume their normal course, exactly as though
they had undergone no alteration. In other words the
yolk substance alters the normal development only tem-
porarily, only for so long as its action continues to make

*'Oscar Hertwig: Die Zelle und die Gewebe. II. P. 265—266.

98 Hypothesis of Structure of Germ Substance

itself felt. This process corresponds essentially to that
described in the above mentioned researches on the trans-
position of the blastomeres, in which the latter were com-
pressed for example between two plates and so all com-
pelled to lie in the same plane. But when the pressure
ceased they resumed at once their normal disposition.
Each of these two processes constitutes another proof
of the self-regulating capacity or elasticity of devel-
opment which finds in centroepigenesis its most simple
explanation.

Centroepigenesis implies further, as we have seen, that
the distribution of nervous energy in each stage of de-
velopment forms in itself a system in complete dynamic
equilibrium, which becomes disturbed and replaced by an-
other system in equilibrium, only through the activation
by the central zone of a new specific potential element.
This is the conception from which as a starting point we
have built up our hypothesis.

It follows that if the activation of the specific potential
elements successive to any given stage is prevented
through certain abnormal circumstances, development will
stop without thereby causing the organism thus remain-
ing behind in an earlier ontogenetic stage, to cease to
form a dynamic system in complete equilibrium.

Such transitory or permanent arrests of development
are extremely numerous, much more numerous than com-
monly believed. All the phenomena called atavistic rever-
sion belong in this category. Metamorphoses also, with
the exception of certain characteristic and remarkable
phenomena which have been added later, are only similar
arrests of development, which proceeds at once on its
course as soon as external conditions, and with them also

Atavism and Variation in Crosses 99

the conditions within the organism, become again favor-
able to further development.

As a typical example of these arrests of development
may be mentioned the well known case of the aquatic
salamanders, (newts). These tailed amphibians at a cer-
tain stage of their ontogeny take to the land, lose their
gills, and become accustomed to respiration by lungs. If
however they are prevented from doing that by impris-
onment in a closed aquarium, they retain their gills, and
the triton is halted for life at a low stage of development,
which its near relatives, the perennibranchs never pass.

The hypothesis of centroepigenesis, which has thus
been derived in its entirety from the fundamental bio-
genetic law taken in its first degree of approximation, that
is in the sense of an exact repetition of phylogeny by
ontogeny, implies also that in two species arising from a
common ancestor, the series of specific potential elements
remain the same up to the ontogenetic stage corre-
sponding to this common ancestor, and only after this
stage do the series of elements concerned in the two spe-
cies diverge from one another.

It follows that in crosses development can go on very
well so long as the two series of germinal elements are
identical, but it becomes hindered as soon as the elements
concerned, which strive to become active at the same time,
thwart one another by their difference. And through this
hindrance to development the organism will take on a
form similar to that of the common ancestor. Further a
few germinal elements too feeble heretofore in relation to
the others, and therefore unable to become active during
the development of organisms of the pure strain, are able,
if common to both races, to acquire by their union a pre-
ponderance over the others different in the two species,

100 Lfypothesis of Structure of Germ Substance

and so to secure the energy necessary to their activation,
and thus to bring out in the cross certain characters of
the ancestor which otherwise would not be found in the
existing species in any of its ontogenetic stages.

In this way then, by the arrest of development at the
ontogenetic stage at which the respective germinal ele-
ments of the two species begin to diverge from one an-
other, can be explained in the most direct possible manner
the above mentioned phenomena of atavistic reversion
which all hybrids present.

“The offspring of a cross of two such species,” writes
Orr, “might therefore continue its development so long
as the two inherited impulses were alike, but when the im-
pulses begin to impel growth in opposite ‘directions, de-
velopment must cease. This explains why the imper-
fectly developed offspring of a crossed species resembles
an ancestral form.” °

For example the distinct, colored, transverse stripes
on the foreleg and shoulder of the mule, which in the
horse and the ass are quite rare and usually very faint,
arise in this way and must be referred to the common an-
cestor of both species. From the crossing of certain races
of pigeons arise birds which have the slate colored plu-
mage of the wild dove, even though the races concerned
in the crossing possess quite a different color. But it has
been proven that these races branched off directly from
the wild races. In the same way the mixed breeds of do-
mestic ducks recall the wild ducks. And the hybrid of a
German and Japanese pig is quite similar to a wild boar.
The hybrids of Datura ferox and Datura laevis regularly
have blue flowers instead of the white of their parents;

Orr: A Theory of Development and Heredity. P. 230—231.

Activation of Last Element Ends Development 101

and Darwin proves that this is a reversion to a blue flow-
ering ancestor. The tendency to incubate, which domes-
tic hens so often lose, always appears again in their
hybrids. The hybrids of ducks show a tendency to mi-
grate, The mule is harder to break thoroughly than the
horse or the ass.®7

These examples afford, in our estimation, the most
certain proof that the ontogenetic stimuli of two species
arising from a common ancestor must remain alike dur-
ing a long series of earlier developmental stages, and only
in later stages begin to diverge from one another. And
this is just what the centroepigenetic hypothesis implies,
but what no other hypothesis has yet been able to explain.

Further the hypothesis of centroepigenesis teaches us
that the series of like germinal elements must be shorter
the farther removed the species are from the common
ancestor. Now Morgan as is well known has obtained
hybrids in which, for example, eggs from Asteria were
fecundated by sperm from Arbacia, which belongs to the
genus Echinus. The two parent forms belong here not
only to two different genera but also to two different
classes. But these hybrids have never got beyond the
larval form, the pluteus which represents only one of the
first stages of ontogeny.*®8

The hypothesis of centroepigenesis, finally, regards
development as completed at the moment when all the
germinal elements have achieved activation. We note
that the central zone is then no longer required to employ
its acquisitions of nutritive material for the growth of its

67Darwin: Animals and Plants under Domestication. II. P. 13—
21: Crossing as a direct Cause of Reversion; P. 254.

*®Morgan: Experimental Studies on Echinoderm Eggs. Anat.
Anzeiger, Bd. IX. No. 5 and 6; Dec. 23, 1893. P. 151—152.

102 Hypothesis of Structure of Germ Substance

entire mass or for the restoration of the masses of any of
its specific elements, as at the time when these latter were
being used up in proportion as they became activated.
And perhaps this explains also why the sex cells, which
according to our hypothesis form only the container for
the germinal substance given off by the central zone,
usually become “ripe” only at the end of development.

When the continuous activation of new specific po-
tential elements ceases, the disturbing influences exercised
by the central zone upon the dynamic equilibrium of each
ontogenetic stage will cease also. And thus the organism
arrives at the final equilibrium of the adult condition.
But now the functional stimulus in the widest sense of the
term can come into play, with the innumerable variations
possible for it, as new causes of perturbation.

So just as formerly the perturbing influence of the
central zone upset the just formed equilibrium, and there-
by provoked a transition to the next ontogenetic stage,
so now each persisting alteration of the functional stimu-
lus disturbs the dynamic equilibrium of the adult condi-
tion and thereby causes also a different distribution of the
general nervous energy. Through each cell of the entire
organism, or of definite portions of the organism, there
will consequently flow a nervous current specifically dif-
ferent from that present before, and also specifically dif-
ferent from one cell to another.

There is formed and deposited therefore in the nu-
cleus of each of these cells a particular specific potential
element, which will add itself to the element or elements
already present. But all the elements, the new as well as
the old, which are deposited in the somatic nuclei will be
lost with the death of the individual; and only those will
be preserved from annihilation, which have been depos-

How New Elements Are Deposited 103

ited in the nuclear substance of the central zone. The
permanent change of the functional stimulus will thus
have as its result, in so far as the species is concerned,
only the simple addition of a new specific potential ele-
ment to the germ substance.

We must therefore now study in what way this new
element behaves during the ontogenesis of the succeeding
organism. But this investigation will form the object of
one of the next chapters.

After we have thus brought to a conclusion this short
review of the most important processes, which according
to our view, if they do not exactly prove the centroepi-
genetic hypothesis, yet make it most probable, we now pass
to the following chapter, which will afford as stated still
another proof, even though a quite indirect one, for this
hypothesis. For in showing that while a whole series of
facts compels us to reject simple epigenesis, and a whole
series of other phenomena compels us to reject preforma-
tion, it will make it seem very probable that a hypothesis
which is able to bring both series of phenomena into
accord must come close to the truth.

CHAPTER FOUR

PHENOMENA WHICH REFUTE SIMPLE EPIGENESIS; AND
PHENOMENA WHICH REFUTE PREFORMATION. INAD-
MISSABILITY OF A HOMOGENEOUS GERM SUBSTANCE;
AND INADMISSABILITY OF PREFORMISTIC GERMS.

rt. Phenomena Which Refute Simple Epigenesis

Roux designates, with the expression “self-differenti-
ation” of a certain part of the organism, the process in
which, according to a certain hypothesis, “the cause of
whatever is specific in the differentiation of that part lies
within this latter.” And he calls “dependent or correla-
tive differentiation” the opposite process, in which, ac-
cording to other hypotheses, whatever is specific in the
alteration which goes on in a certain part of the organism
during development is determined by causes lying outside
this part.°°

If an ontogeny consisted only of self-differentiations,
we should designate the development as evolutionary. If
on the contrary, an ontogeny were produced only through
dependent differentiations, we should call that a process
of epigenetic nature.

Wilhelm Roux: Die Methoden zur Hervorbringung halber
Froschembryonen und zum Nachweis der Beziehung der ersten
Furchungsebene des Froscheies zur Medianebene des Embryo. Anat.
Anzeiger, Bd. IX. February 1894, P. 277—278. Gesamm. Abhandl,,
II, P. 978.

104

Evolution and Epigenesis 105

We note that theoretically a mixed or intermediate
hypothesis would be conceivable, according to which a
given part of the organism would be differentiated
through the cooperation of causes lying within and with-
out it. Incase however the causes lying at any moment of
ontogeny within the part concerned, do not arise through
any antecedent process of epigenetic nature, the develop-
ment at least up to this time must be considered as essen-
tially purely evolutionary. But if, on the contrary, the
internal causes do arise through an antecedent process of
epigenetic nature the whole development would then be
essentially of that nature.

Whitman states that the conception of modern evo-
lutionists differs essentially from that of the earlier ovists
and spermatists; for they excluded the formation of new
structural parts during development, a thing which is nat-
urally admitted by the evolutionists of to-day. Accord-
ing to Mivart’s definition which Whitman accepts com-
pletely, “the term evolution may be employed, as it has
been, to denote that the successive formation of parts pre-
viously not existent is due not to their imposition from
without but to their generation from within.” ‘°

According to this definition which is essentially iden-
tical with that of Roux above cited, evolution, it may
here be repeated, limits to a minimum the influence which
the various other parts of the organism exert upon the
development of each part, or considers it as absolutely
non-existent, since each part contains within itself, or in
any event in its immediate neighborhood, the causes of its
progressive development. According to the epigenetic

Whitman: Evolution and Epigenesis. Biol. Lect. at the Mar.
Biol. Lab. of Woods Holl, Summer Session 1894. Boston, U. S. A.,
Ginu, 1896. P. 224.

106 Phenomena Refuting Simple Epigenesis

hypothesis, this influence is, on the contrary, of the very
greatest importance and is considered to be the only
cause of each development.

We also can accept Mivart’s definition in this sense.
We note that it does not include in any way the con-
ception of preformistic germs; for it is possible that the
internal causes involved arise gradually in the course of
development and need not be already present in the germ
substance. In the first case, one has evolution without
preformistic germs; in the latter, evolution with pre-
formistic germs, which we would call preformation
proper. This preformation proper, for example Weis-
mann’s type, is also included in the definition of evolution
just given; it forms however only a special case of it,
which is limited and approximates more the conception of
preformation which the ovists and spermatists enter-
tained.

The processes of epigenetic nature can be regarded
likewise as belonging to two kinds, corresponding to the
above mentioned categories of evolution. For one can
conceive of processes of epigenetic nature both with pre-
formistic germs and without preformistic germs, and
both cases are actually met with.

In the first case the causes which bring about each
specificity of development would be already present in
the germinal substance. Only their liberation or acti-
vation in opportune time and place depends upon the
reciprocal action of the different parts of the organism
upon one another (for example DeVries, Oscar Hertwig,
etc.). In the second, on the contrary, the causes pro-
ducing the different specificities of development arise only
gradually in the course of ontogeny, and always in con-

Theoretically Conceivable Kinds of Epigenesis 107

sequence of the reciprocal action of the different parts
of the organism upon one another.

We will call the first of these processes epigenesis
with preformistic germs, the other, epigenesis without
preformistic germs, or epigenesis proper.

Further, each of these two processes can, theoretically,
be divided again into the two following categories.

One can conceive of the reciprocal action of the dif-
ferent parts of the organism upon one another, as such
that no part whatever should ever be considered different
in any way, in so far as its formative action on the other
parts is concerned, from these other parts, but rather all
are to be regarded as equally necessary and of equal
value in this respect. Or, on the other hand one can
suppose that among all the parts there is one whose action
upon the other parts differs through some peculiarity
from the corresponding action of all other parts, so that
it acquires in comparison with the latter much greater
importance.

We shall designate the first process with the name
“simple epigenesis,” or briefly “epigenesis,” which would
be equally possible either with or without preformistic
germs, and we shall call the second in which the form-
ative action would on the contrary become specially local-
ized in a definite zone of the organism, by the name of
“localized or centralized epigenesis,”’ or briefly ‘“centro-
epigenesis.”” Practically it would be conceivable only
without preformistic germs.

Finally, in all the different theories without pre-
formistic germs, one could conceive of the germinal sub-
stance as formed of a single homogeneous substance (or
a homogeneous mixture of different chemical substances),
or of a material which though not consisting of pre-

108 Phenomena Refuting Simple Epigenesis

formistic germs, would nevertheless be formed of a
greater or less number of specific parts different from
one another.

Of all these hypotheses which one can form concern-
ing the nature of the developmental process and the
structure of the germinal substance, we need discuss here
only the following chief ones, and consider these only
very briefly, mentioning the others only casually in
passing. We arrange them in the following way:

Concerning the nature of the developmental process:

1. Simple epigenesis with preformistic germs or
without such.

2. Evolution with preformistic germs, i. e., pre-
formation proper.

Concerning the structure of the germinal substance:

1. Germinal substance consisting of homogeneous
material.

2. Germinal substance consisting of heterogeneous
material. Here belongs the special case in which this
substance consists of preformistic germs.

We can now pass on without further comment to a
rapid review of the most important phenomena, on
account of which simple epigenesis with preformistic
germs or without such, cannot be admitted. This will
oblige us sometimes to return to the phenomena and
arguments with which we were occupied in the preceding
chapter.

With the chief facts which are opposed to simple
epigenesis we must now range the production, already
mentioned and discussed, of right and left, anterior and
posterior, half embryos of frogs, which resulted from
the killing by a hot needle of one of the two first

Partial Developments 109

blastomeres. As is well known it was these very half
embryos that caused Roux to construct his evolutionistic
theory, in which he compares development, at least in
so far as the four quarters of the embryo come into
consideration, with a mosaic work.

So long as the half formations arising from isolated
blastomeres are limited to the very first divisions, so
long for instance as one of the first two blastomeres,
when isolated, limits itself to giving half of the total
number of micromeres, or so long as the first cleavage
spheres arising from the isolated blastomeres succeed each
other and arrange themselves as if the two blastomeres
had remained united, so long there is still nothing to be seen
in these phenomena which would afford any proof against
simple epigenesis. For in general we can suppose that
the deutoplasm alone is the immediate cause of the num-
ber, and of the different relative sizes and disposition of
the first blastomeres. If then the relations to the yolk
of the blastomere and of the whole of the blastomeric
group, could not by themselves constitute any proof
change through the isolation of the blastomere, it is
clear that the first cleavages must proceed exactly as
though no isolation whatever had taken place.

So for example the isolated blastomeres of the two
or four cell stage of the egg of the gastropod, Ilyanassa
obsoleta, which divide in essentially the same manner as
they would if they were part of the complete blastomeric
group, could not by themselves constitute any proof
whatever for or against any given developmental theory,
so long as the separated blastomeric group does not take
on any really specific form. For in this Ilyanassa obsoleta
the yolk is distinguished by its great mass, thickness and

110 Phenomena Refuting Simple Epigenesis

density.7!_ And these peculiarities make it certain that
the relation of the isolated blastomere to the yolk plasm
is not different from that which would have existed had
it remained united to the other blastomere.

But the preponderance of the determinative action of
the yolk is limited usually to the early stages preceding
the gastrula. It has no influence whatever on the final
form of the embryo, no more than has for example, the
temporary compression of the blastomeres between two
plates or the shuffling of them. Therefore the early
cleavage stages have no specific morphological signi-
ficance, as is evident also from the above mentioned fact,
that different related species and even quite widely
separated species can present almost identical cleavage
systems.7?

It follows from this that as soon as development
commences to take on its really specific form, that indi-
cates that the action of the germ substance is preponder-
ating over the action of the yolkplasm no matter in what
way the latter may formerly have acted.

Consequently simple epigenesis certainly cannot have
recourse, in order to explain the half embryos of Roux,
to the fact that the deutoplasm remained unchanged in
the unsegmented blastomere. For these half embryos
arise at very advanced stages of development and
represent quite specific formations.

Nevertheless Driesch seems to want to explain the
half-formations in this way: “Each particle of the sur-

™H, E. Crampton, Jr.: Experimental Studies on Gasteropod De-
velopment. Arch. f. Entwicklungsmech. d. Organismen. Bd. 3;
Heft. 1. Leipzig, Engelmann, March 24, 1806.

"Cf. E. B. Wilson: The Cell-lineage of Nereis. Journ. of
Morph., Vol. VI, No. 3. Boston, U. S. A., Ginn, July 1892. P. 455.

Certain Regenerations rit

viving half preserves as is shown by Roux’s figures, the
position which it would have had in normal development.
Then after segmentation has taken place, the same form-
ative factors act on each particle and on each blastomere
respectively, which would have acted upon them in nor-
mal development, consequently also the same forms result ;
Ergo: half-embryo.” 78

From the epigenetic standpoint this explanation is
inadmissible. For when the half embryo begins to take
on the characteristic form of its species, and thereby
indicates as we have seen that the specific action of the
germ substance has from that time become preponderant
over that of the deutoplasm, one could not assert that
the same organ forming factors continue their action, for
that would be to deny that there is any formative action
at ali exerted by the idioplasmic nuclear substance of one
entire half, left or right, anterior or posterior, upon the
other, developing half. This would be exactly the op-
posite of what simple epigenesis postulates, for it
attributes the tendency of development to take on its
specific form of equilibrium to the reciprocal action of
all the innumerable little masses of one and the same
idioplasm, which are active at the same time in all the
nuclei of the entire organism.

Roux then can rightfully assert that the half embryos
constitute by themselves the most direct and decisive
refutation of the theory of epigenesis.

If we pass on now from half embryos to the regen-
eration of amputated organs, we know that this con-
stitutes one of the most important arguments that the
epigenesists ordinarily advance against preformation.

Driesch: Analytische Theorie der organischen Entwicklung.
Leipiz, Engelmann, 1894. P. 15—16.

112 Phenomena Refuting Simple Epigenesis

But the preformationists on their side cite certain partic-
ular cases of regeneration as unfavorable to epigenesis:
“Regeneration” remarks Roux, “takes place in tritons
when all four extremities are removed at one time, from
which it follows that for the formation of new extremities
in one antimere, the presence of the other extremities
is not in the least necessary, so that for this formation
it is not necessary that there be any formative correlating
influence extended from them.” ™4
The anachronisms of development in which, for
instance, certain parts remain behind other parts in their
formation, or in which the germ layers may even develop
with uneven speed, or one entire half of the body may
take a jump ahead of the other half so that one can
sometimes observe two different degrees of development
in the two halves of the same embryo, belong likewise
‘to the number of phenomena which simple epigenesis is
incapable of explaining: “How the (epigenetic) con-
ceptions of O. Hertwig,” Roux writes further,—and his
words, already quoted above, deserve to be repeated here,
—‘‘can be reconciled with these anachronisms in the
development of the germ layers which I have observed,
or indeed with the absence of the lower layer—the endo-
blast (Anentoblastia), while both of the other two layers
remain essentially normal in the disposition of their
parts, or finally with the formation of half embryos, may
well be left to the reader’s own judgment. For if such
large parts can remain behind in their development, or
indeed be lacking altogether, and the other parts be in
no wise disturbed thereby in their development, it surely
follows that the development of these latter is not con-

“Wilhelm Roux: Uber Mosaikarbeit etc. Anat. Hefte, Febr.
1893, P. 299. Gesamm. Abhand. II, P. 830.

Headless but Otherwise Normal Monsters 113

nected by reciprocal actions with the absent parts, and
therefore is not carried on by the reciprocal action of
all the parts of the whole, one upon another.” 7

It is the same with headless monsters as with all
monsters which lack entire parts of the organism but are
nevertheless normal in the other parts. Because they
show likewise that there does not exist any formative
action exercised by the head, or by other parts, upon
the rest of the organism.

While thus the head can be absent in development,
the presence of certain other parts seems on the con-
trary to be indispensable in headless omphalosite mon-
sters: “When one studies,’ writes Dareste, “headless,
omphalosite monsters comparatively, one notes that the
trunk is almost complete in some cases but in others
incomplete. And upon this fact is based Isadore Geoffroy
Saint Hilaire’s division of headless monsters into three
different types: the true acephali, in which the thoracic
region is as well developed as the abdominal region; the
paracephali, which have only the abdominal region; and
the mylacephali in which only the sacral region is pres-
ent. These three types arise through inequalities in the
development of the cerebro-spinal axis. But how is it
that the posterior part of this axis is always present,
while the anterior part is lacking to a greater or less
extent? Why does not the reverse appear in other cases?
This depends evidently on some as yet unknown fact
of embryogeny. For the present we must be content
with the mere question.” 7°

Wilhelm Roux: Uber Mosaikarbeit etc. Anat. Hefte, P. 320.

Gesamm. Abhandl. II. P. 859.
™Dareste: Recherches sur la production artificielle des mon-

struosités. Paris, Reinwald, 1801. P. 495.

114 Phenomena Refuting Simple Epigenesis

Nevertheless some other varieties of omphalosite
monsters seem to show that the presence of any part
whatever of the vertebral axis is sufficient to permit
at least partial development; for instance in the cephalic
monsters the embryo consists generally of the head
alone.*7 We note however that these monsters com-
monly contain the anterior extremity of the spinal cord
which can have been only slightly differentiated in the
embryonic stage at which the incomplete development is
arrested. In some of these cephalic omphalosite mon-
sters, a large part of this anterior extremity of the spinal
cord may even have undergone a process of reabsorption
after the previous arrest of the partial development.

As we shall see soon Born succeeded in producing
artificially a thing like these cephalic omaphalosite mon-
sters by grafting upon a complete tadpole a piece removed
from another tadpole, and consisting only of the head
and a small part of the elongated medulla.

Concerning the double monsters with double sym-
metry, it will be worth while to repeat once more in
extenso the following statement of Roux, even though
we have reported it already, for the most part, in the
preceding chapter:

“This additional fact speaks directly against the
achievement of development of the individual through
a general, reciprocal, formative cooperation of all parts
to form a whole; namely that in the chief class of double
monsters, and so in those double formations which cor-
respond to the law which I formulated of the double
symmetry of the anlagen of organs, the piece absent
in a symmetrically similar way from each of the two

™Dareste: Recherches sur la prod. artif. des monstr. P. 498.

Connected Partial Embryos of Roux 115

individuals may actually be any given piece whatever
that is limited by a plane surface; and that in them the
organs are nearly all present in their normal form up
to the plane of reunion, just as if two symmetrical pieces
had been cut away so as to leave two plane surfaces,
from two twins, after they were fully developed and
ready for birth, and the foetuses had then been united
by the cut surfaces. This normal formation of defective
organs up to any given plane of separation as, for
example, the 8-shaped double cornea or double lens of
the third eye common to both organisms, speaks likewise
strongly in favor of a capacity of self-differentiation
possessed even by parts of these organs, as the simul-
taneous development of two structures united so exten-
sively, to form bodies of which each is self centered,
indicates directly the absence of the action of general
reciprocal influences, connecting them into one whole.” 78

We remark nevertheless in our turn that the evolu-
tionistic theory does not in any way explain as Roux
asserts, how the two organisms are limited by a plane
surface which is perfectly symmetrical, rather than by
any kind of irregular surface whatever. This theory
merely shows that it is possible that the development of
organs which differentiate themselves automatically, may
be arrested at any given surface, without thereby dis-
turbing the normal form of any of the remaining portions,
not even in the neighborhood of the surface where
development is arrested. But it does not explain why
the surface of division must be a plane surface, and
perfectly symmetrical in the two individuals. One
should rather expect here a manifold reciprocal inter-

Wilhelm Roux: Uber Mosaikarbeit etc. Anat. Hefte, P. 320.
Gesamm., Abhandl. II. P. 859—860.

116 Phenomena Refuting Simple Epigenesis

locking of the two organisms which would give a most
asymmetrical and irregular dividing surface.

The continuation of development in the tail frag-
ment of the tadpole seems to speak likewise against both
epigenesis and preformation. For in his experiments
upon tadpoles, Born has proven the accuracy of Vulpian’s
statement that the amputated tails not only continue to
live for sometime (some even thirteen days), but con-
tinue to grow and to differentiate into their various
tissues. He has further observed the following processes
of new formation.

“A few days after the amputation, the margins of
the fin of the amputated tail commence to grow over the
cut surface of the axis; they unite in front of it to form
a high semicircular tail fin. The axis is not entirely
without participation in this process, for prolongations
of the notochord as well as of the spinal cord grow
into the newly formed fin, but the metameric muscu-
lature shows nothing like this and terminates sharply at
the original surface of amputation. But this prolonga-
tion of the notochord, like that of the spinal cord, even
in the most favorable instances, scarcely extends half as
far forward in front of the cut end of the original axis
as does the newly formed marginal fin. This latter is
formed of typical embryonic mucous connective tissue
with a few pigment cells scattered through it. I have
not been able to discover in it any rudiments of vessels.”

“This observation teaches then,” continues Born.
“that the provision of yolk in the tail end cut off from
a tadpole does not serve merely, as Vulpian has already
shown, for further growth, and further differentiation
of the tissues, and for the formation of a new structure
growing out from the cut surface, but it shows that

Growth of Amputated Parts and Grafts 117

besides the fin margin, the notochord and the spinal cord
take part in this new formation. It is interesting that
the tail of a tadpole is capable of such a regenerative
new formation not only in the caudal direction but also
in the opposite direction.” 7°

We say then that these phenomena, which the ampu-
tated tail of the tadpole presents, can be cited by the pre-
formationists against the epigenesists, as well as by the
latter against the former. For the former can object
that the progress of the histological differentiation in
the fragment of tail cut off from all the rest of the
organism would denote the absence of any action of
the organism upon the development of this part of the
body, and the epigenesists on their side could show that
the power of the tail to regenerate even in the direction
from the tail toward the head, could not be explained
by preformation, even with the aid of reserve idioplasm,
for that could effect regeneration only in the direction
from the head toward the tail.

It is the same with Born’s celebrated experiments on
the grafting of certain fragments of tadpoles upon one
another or upon complete tadpoles, which are opposed
to simple epigenesis and at the same time indicate a
process of epigenetic nature.

In the first place they are opposed to epigenesis. For
in all grafts of parts of tadpoles upon complete tadpoles,
the grafted parts have continued their development regu-
larly as if they had remained united to their own
organisms. Therefore the rest of this organism has not
under normal conditions any influence upon the
development of these portions.

Born: Uber Verwachsungsversuche mit Amphibienlarven.
Leipzig, Engelmann, 1897. P. 32—33.

118 Phenomena Refuting Simple Epigenesis

Thus for example a larva of Rana esculenta from
which there had been cut off the most anterior part of
the head including the eye anlagen, the anterior part
of the brain, the nasal groove, and the primitive mouth,
was so grafted upon the caudal half of the abdomen of
a complete larva, as to form an acute angle between the
back of the former and the abdomen of the latter, the
abdomen of the former being turned toward the head
of the latter. After allowing the double larva twelve
days of development, it was killed and it showed that
“all the organs of the partial larva up to the surface of
amputation and union had developed quite as com-
pletely as though there was no part of them lacking
and as though their normal environment and their or-
dinary relations were quite undisturbed.” ®°

The anterior portion of a larva so short that it
scarcely extended beyond the commencement of the elon-
gated spinal cord, was grafted upon the abdomen of a
complete larva, and continued to develop normally.
“All parts developed completely up to the surface of
amputation: the cartilaginous trabeculae, the quadrates
with the chewing muscles covering them, behind the
mouth cavity the cartilages of Meckel, the cartilages of
the lower jaw and behind these again the hyoids.” ®

Upon these and other similar examples, Born bases
the following conclusions: “Although up to the moment
of grafting there had been no trace (of primordial cra-
nium) present, and the mesoderm from which it develops
remained in a quite indifferent and almost primitive con-

*°Born: Uber Verwachsungsversuche mit Amphibienlarven.
P. 97.

“Born: Uber Verwachsungsversuche mit Amphibienlarven.
P. 108—109.

Nuclear Somatization 11g

dition, nevertheless the complicated and characteristic
parts of the head were developed up to the surface of
amputation completely and in their perfect form, and
not only entire structure but also parts of these structures.”

“Whatever development there is going on beyond
the stage at which amputation was performed depends
essentially on self-differentiation of the individual parts;
no correlative influence of the neighboring parts or of
the entire organism can ever be recognized, either nega-
tively or positively. Thus this development beyond the
stage at which amputation was performed, corresponds
entirely with Roux’s mosaic theory.” ®?

Nevertheless, we shall see soon that another whole
series of Born’s experiments, as also those just recorded
if one considers them from another point of view, are
no less opposed to evolutionary hypotheses in general
and to hypotheses of preformation properly so called in
particular.

In short, the observations and experiments which we
have thus far cited, from the half-embryos of Roux to
the tadpole fragments of Born, all show the possibility
that individual parts of the organism, provided they con-
tain any part whatever of the vertebral axis, can develop
independently of the remaining parts, and are sufficient
by themselves alone to prove the inadmissibility of simple
epigenesis.

But the preformists had yet another fundamental
objection to make to the epigenesists, who have sought
so far in vain for a reply to it: namely that epigenesis
requires the renunciation of nuclear somatization. For
these two hypotheses are absolutely irreconcilable. It

82Born: Uber Verwachsungsversuche mit Amphibienlarven.
P. 204—205.

120 Phenomena Refuting Simple Epigenesis

follows therefore that each fact or each argument which
speaks in favor of nuclear somatization, is at the same
time a proof against epigenesis. And we saw precisely
in the preceding chapter, that there is a whole series of
facts and arguments, which it would be useless to repeat
here, but which compel us to admit this nuclear
somatization as an incontrovertible fact.

The preformationists can finally object to epigenesis
and not unreasonably, that by its “attainment of equilib-
rium,” it does not explain the termination of ontogeny
as well as preformation does. For why should the
reciprocal actions of all parts, on which development
depended up to that time, suddenly cease to effect any
further change when once the adult stage is reached?
Because it is only then, reply the epigenesists, that the
dynamic equilibrium is attained. But if the successive
ontogenetic forms repeat the phylogenetic, how comes
it that the dynamic equilibrium which once existed in
each of these latter does not remain existent in any of
the former? And if the absence of equilibrium at all
these stages is due to some alteration of the formative
living substance, how then could this new substance pass
again during a long series of stages through the same
phylogenetic ancestral forms? The preformists, on the
contrary, have no trouble in explaining the arrest of
development since according to their theory it would
follow only at the moment when there would be present
in each cell only a single kind of preformistic or
determinant germs.

Having thus made a rapid review of the principal
objections which compel us to reject epigenesis, we can
pass on to an equally brief consideration of a number

Complexity of Preformistic Germ Plasm 121

of objections which stand in the way of admitting
preformation.

2. Facts Which Compel the Rejection of Preformation

If, limiting ourselves to the most typical theory of
preformation to which all the others can be finally
reduced, we consider that of Weismann, we encounter
at the outset a very simple argument which is yet so
formidable that it is in itself enough to discourage the
most firmly convinced partisan of that doctrine.

For the preformation theory of Weismann forces
him to suppose for the infinitely numerous particles
constituting the different determinants or groups of
determinants, an excessively complicated architecture or
excessively complicated arbitrary mode of disposition.
Now the elementary fact of reproduction demonstrates
that the constitution of the germ plasm, whatever it
may be, does not become at all altered when this latter
divides and distributes itself among the incalculable
number of germ cells which can be produced by eacii
organism and by all its succeeding generations. Weis-
mann must first then explain to us how the subdivision of
a given germ plasm into new parts in each of which this
very complicated structure is preserved uninjured or
is accurately reproduced again, is possible. That is
fundamentally the same difficulty which the old ovists
and spermatists encountered, and which they endeavored
to overcome by their idea of the encasement of the
germs.®?

Weismann has since endeavored to weaken the force

®3Among others compare e. g. Oscar Hertwig: Praformation
oder Epigenese? P. 11.

122 Facts Compelling Us to Reject Preformation

of this objection by taking into consideration, besides
the architecture of the germ plasm itself, also the uneven
rapidity of multiplication of the different determinants
and the reciprocal forces of attraction exercised by these
latter upon one another, as factors which determine the
orderly division of each plasm or each id.8* But, as
this author himself admits, the architecture of the germ
plasm remains necessarily the principal factor, and conse-
quently the objection of the incompatibility of this arbi-
trary architecture with constant complete division of the
plasm without alteration, remains in all its force.

Another argument which presents itself likewise
against preformation is, that with the exception of the
partial developments cited in the preceding section of
parts which each contained one very definite zone of the
organism, it has never been possible to obtain the devel-
opment or the continuation of development of somatic
parts, even though they are capable of living for some
time after they have been detached from the rest of the
organism.

One would certainly not regard as a continuation of
normal development the mere increase in mass which
takes place in parts cut off from the fetal organism,
when they are transplanted upon tissues which on account
of their great richness in blood vessels are especially
capable of affording abundant nourishment to their new
guests.

This simple increase in mass depends for the most
part on an actual multiplication of the respective cells,
which proceeds in directions determined either by nutri-
tion alone or by the path of least resistance in the environ-

**Weismann: Das Keimplasma. Eine Theorie der Vererbung.
Jena, Fischer, 1892. P. 86.

Transplanted Parts Soon Cease to Develop 123

ment, accompanied either by no morphologic alterations
or by quite aspecific ones, depending upon whether the
portion cut away consisted of a formless fragment of
tissue, or of an organ whose proper form was already
indicated. We may mention, for example, Zahn’s trans-
plantations of portions of cartilaginous or bony fetal
tissues to the lungs and kidneys of other individuals of
the same or different species,®® or Fischer’s transplanta-
tions of anterior and posterior extremities of chicken
embryos (especially of one incubated only eleven days)
to the comb or ruff of the cock.®®

It is true that both, and especially Fischer, have
observed that in these extremities of chicken embryos,
ossification, which at the time of amputation had not
commenced at all or had scarcely commenced, was
initiated or continued in the transplanted extremities.§”
But this process of ossification can be considered only
as the mere accumulation, and consequent intensification,
of the effects of the specific vital activity which was
already at work before the amputation, and which
persists unaltered after the transplantation.

Consequently we think that Roux is quite wrong
when, apropos of these experiments of Zahn, Fischer,
and others, he expresses himself as follows: “These
experiments have demonstrated that many isolated
embryonic parts can not only grow but even become

*Zahn: Uber das Schicksal der in den Organismus implantierten
Gewebe. Virchows Archiv, Bd. 95. Drittes Heft, 5. March 1884;
especially e. g. P. 374—375, 380, 381.

*eRischer: Uber Transplantationen von organischem Material.
Deutsche Zeitschrift der Chirurgie, Bd. 17. Erstes, Zw., Dr. u. Viertes
Heft, 1882; especially e. g. P. 362—363, 370—371.

°F, g. Zahn: Uber das Schicksal ete. P. 382ff.—Fischer: Uber
Transplantationen etc. P. 370, 374.

124 Facts Compelling Us to Reject Preformation

histologically differentiated in an approximately normal
way. It follows that the differentiation of these parts
is not a function of reciprocal actions between these
parts and other parts. Therefore there is thus already
proven a certain histologic and morphologic self-differ-
entiation of many parts of the developing egg.” *8

This is not correct. For these experiments show,
we repeat, only a mere increase in mass of these tissues,
which is morphologically without any specific character ;
and the continuation of the histologic differentiation
which had already commenced or was on the point of
commencing at the moment of amputation, is explicable
by the simple accumulation of the effects of the same
vital process which merely persists exactly as it was
before the amputation.

Another argument against preformation is the great
capacity of modification of the organism while it is
undergoing development, as well as when fully developed,
to which it owes its remarkable power of adapting itself
to quite abnormal conditions. For the preformation
theory with its determinants, which are bound up with
one another into a solid structure, and of which each
determines the formation even of the smallest particles
and their most minute variations, implies undeniably a
great morphological rigidity, which is not reconcilable
with the great mutability of the organism.

“Galls,’ says Oscar Hertwig, for example, “are
valuable witnesses against the germ theory of Weismann.
They teach us that cells of plant bodies can serve quite
other purposes than could have been foreseen during

Wilhelm Roux: Zur Orientierung iiber einige Probleme der
embryonalen Entwicklung. Zeitschrift fiir Biologie; Bd. XXI. July
1885. P. 480—482. Gesammelte Abhandlungen. II, P. 206—207.

Adaptability and Alterability of Structures 125

development, that they can adapt their form to new
conditions, and that their specific form is not determined
by special determinants in the nucleus but by external
stimuli.” 8°

The stomach of the tern, which ordinarily feeds
on fish, is lined by a soft mucous membrane. If
one feeds it with wheat for a few weeks its stomach
develops a superficial horny coat, its musculature is
strengthened and it takes on the character of a gizzard.°°
If these stomachs belonged to two varieties of the same
species, Weismann would have no hesitation in attribut-
ing the diversity to special, and thus different, determi-
nants which, as the facts show, do not really exist.

Loeb has demonstrated that the colored design of
the yolk sac of a fish embryo (Fundulus) is not in itself
predetermined, but depends upon the distribution of
blood vessels. The pigment cells are at first distributed
uniformly but when the circulation of the yolk sac is
established, they migrate toward the vessels, attracted
probably, as Loeb supposes, by a chemical substance in
the blood, and give rise thus to a definite design. Graf
has likewise recently demonstrated that the color designs
of the leech are not themselves inherited, but that they
depend upon the disposition of muscle fibers in which
the amoeboid pigment cells lie. It would be absurd,
concludes Wilson, to imagine in all of these cases a
special series of determinants for each individual color
design.

"Oscar Hertwig: Zeit- und Streitfragen der Biologie. I. Pra-
formation oder Epigenese? P. 48—a9.

Delage: L’hérédité etc. P. 604.

91E, B. Wilson: The embryological Criterion of Homology. Biol.

Lect. at the Mar. Biol. Lab. of Wood’s Holl; Summer Session 1894.
Boston, U. S. A., Ginn, 1896. P. 116.

126 Facts Compelling Us to Reject Preformation

Everybody knows the peculiar static structure of bone.
Substance becomes accumulated in bone at the points of
greatest pressure, and attains thus its best possible utiliza-
tion. Now it is known, as J. Wolff discovered and as
Kastor, Martiny and J. Rabe have confirmed, that similar
structures are formed also in quite new and abnormal
circumstances in connection with new static conditions,
for example, in bones broken and reset at an angle.
“From this it follows,” says Roux, “that these forma-
tions do not need to be fixed and inherited, but arise of
themselves whenever the conditions exist. As the static
structure of bones is developed in a clearly recognizable
form only after the first years of life, one can not say
anything of the necessarily hereditary transmission of
it, without special researches upon this point.” %

Teratogenesis in general, both natural and artificial,
is quite opposed to preformation. It denotes that the
organism, at any rate while it is still in process of devel-
opment, can adapt itself to exceptional conditions which
are quite different from the normal. And it accom-
plishes this by producing abnormal formations whose
development must consequently be due only to a process
of epigenetic nature, and cannot be of preformistic
nature.

Let us consider one of the simplest examples. In
the hemiteratic spina bifida, the spinal opening is ordi-
narily covered over by a layer consisting of fibrous
tissue like that of scars, which in some cases takes on
all the characters of the skin. Then the spinal opening
is not visible from the outside. But when the spinal
opening is in the lumbar region it is not rare for a

**Roux: Der Kampf der Teile im Organismus. P. 28.

Adaptability Irreconcilable with Preformation 127

considerably developed tuft of hair to appear on the
outside.°* Would Weismann also presuppose its own
determinants for this tuft? And if this tuft arises
without being represented in the germ plasm by its own
determinants, why cannot the same process occur in
normal development for other parts of the organism?
Normal and abnormal development do not differ essen-
tially from each other; and the causes which produce
them are of the same nature in both.

Weismann certainly recognized the great importance
of the capacity of alteration by functional adaptation,
possessed by both embryonic and adult organisms. “If
this principle did not exist,” he writes, “the organism
would be like a building, of which each stone is already
prepared before the situation and use of the building is
determined. Such a predetermined ontogenesis could
not produce any organism capable of living. The influ-
ences under which organisms exist during their develop-
ment are never exactly the same and to be able to
adapt themselves to them they must possess a certain
freedom.” %*

But we cannot repeat often enough, that this great
capacity of adaptation is absolutely irreconcilable with
his theory of determinants, or with any preformistic
composition of the germ substance. If functional adapta-
tion effects “the adjustment of the primary hereditary
anlagen, that is of the determinants, to new circum-
stances,” °° this signifies that these new circumstances

°2Dareste: Recherches sur la production artificielle des mon-
struosités. P. 327, 538.

‘Weismann: The Effect of External Influences upon Develop-
ment. The Romanes Lectures, 1894. P. 16—17.

*85Weismann: Ibid, P. 16.

128 Facts Compelling Us to Reject Preformation

external or internal to the individual exert upon these
determinants a certain formative action. But if one
assumes that a certain formative action becomes thus
exerted upon each of the determinants by abnormal cir-
cumstances in their development, one must then assume
that a similar formative action is exerted upon each of
these same determinants by the other parts of the organ-
ism when the development of these parts proceeds quite
normally. But what remains then of the preformistic
action of these determinants which should fashion the
organism like a piece of mosaic-work?

The experiments of Born also, which, as we have
seen above, are absolutely opposed to simple epigenesis
are just as little reconcilable with preformation, because
they denote in general the epigenetic nature of the process
of growth. We need recall here only the union of
portions of different tadpoles; for example, of the anterior
portion of one tadpole with the posterior portion of
another.

In this latter case, if the anterior portion were limited
by a section passing through the medulla oblongata, while
the posterior portion had been obtained by a section
passing through the medulla spinalis, it would follow
that the two surfaces of amputation of the medulla
which ought to match exactly would present on the con-
trary unlike forms and surfaces. In spite of this a
short time after the two ends of the medulla were united,
the two half tadpoles having meanwhile continued their
development, they showed a union in which no angle
or sharp fault persisted but gentle curves of transition
were present instead. The two medullary canals went
over into one another also gradually and without inter-
ruption, so that one could no longer recognize the exact

Secondary Coaptation in Grafts 129

point of their union. “This is an example of the phe-
nomenon observed also in all the other organs, that
after the growing together of two sections of unequal
size and form, the uneven character of the union, present
at first, disappears and gradually a smooth connection
of the surfaces is established.” °°

The union of the corresponding organs of the two
fragments is quite intimate: for example in the case
which we have just cited, longitudinal sections of the
two united medullas showed that the fibers of the white
substance of the medulla spinalis went over continuously
into those of the white substance of the elongated medulla
oblongata.°?

Among the experiments of Born, those upon the
artificial production of double monsters are especially
remarkable. They were obtained by joining two tadpoles
together in the most diverse ways. In the case which
we now report he cut away from each of two tadpoles
the upper part of the ventricles of the brain and joined
the two cut surfaces together so that both the tails and
the bellies of the two tadpoles constituting the double
monster were directed in opposite ways. Here also, there
took place, in so far as the two tadpoles developed, a
complete union so that after sometime there could not
be perceived any transition stage between the surfaces of
the corresponding organs which were united together.

“It is impossible to believe,” remarks Born in this
connection, “that in placing these two tadpoles one upon
the other, the small ventricular clefts and the external
walls of the two brains could be applied exactly one upon

°G Born: Uber Verwachsungsversuche mit Amphibienlarven.

P. 53—54.
°7G_ Born: Uber Verwachsungsversuche usw. P. 56.

130 Facts Compelling Us to Reject Preformation

another.” In such cases, which are repeated over and
over, there is no escape from the admission that with
the progress of growth there has taken place in the
blended organs a sort of smoothing out, “Ausglattung,”
of the external and internal walls, and perhaps even a
transitory modification of the normal form, caused simply
by the influence of the similar organs growing together.*®

In other cases there is more than a simple smoothing
out of the two surfaces which would not fit together
at first. Thus in the union of two parts of the intestine
of double monsters, thoracopagi, gastropagi, and ventro-
pagi, obtained by cutting off from each of two tadpoles
a thin layer of the abdomen, and superimposing the two
cut surfaces as usual, there results an exact conjunction
of the two thin-walled intestinal tubes in such a man-
ner as to constitute a single tube without any trace of
the junction which was made. So exact a coaptation
can certainly not be effected by the simple superposition
of the two tadpoles.%®

Sometimes the corresponding organs of the two
larvae seem as though seeking each other and reaching
out to each other. They both deviate from their ordinary
direction in order to be able to unite and extend one
into the other. This phenomenon appears character-
istically in the fusion of the two vascular systems as is
demonstrated in the clearest manner by certain experi-
ments in grafting definite portions of tadpoles upon
complete tadpoles: as for example, the grafting of the
posterior heartless portion of a tadpole upon the abdomen
of another complete tadpole: the fusion of the two vas-
cular systems is so complete that a single blood circulation

°8G. Born: Ibid. P. 141.
°°G. Born: Ibid. P. 69—86.

Form Not Dependent on Number of Divisions 131

is produced, the heart of the complete tadpole putting
in circulation the blood of the grafted portion also,!%

This phenomenon is presented also very strikingly
in the mutual prolongation one into another of the
pronephric and other secretory ducts. Thus in a double
monster obtained by uniting the anterior portions of two
tadpoles, the left pronephric ducts met and grew together
although at first their extremely fine cut ends certainly lay
some distance apart and their directions crossed almost at
right angles.104

All these phenomena are hard to reconcile with the
rigidity implied in Weismann’s determinants. They
speak on the contrary entirely in favor of a general
process of growth that is epigenetic in nature; for only
to a process of growth of this nature can be ascribed
all the phenomena of adaptation and of deviation from
the normal form which result in the complete and exact
conjunction of the various corresponding portions of
different individuals.

Against the rigid preformation of Weismann, which
attributes development exclusively to qualitative nuclear
divisions, Roux himself furnishes a most appropriate
argument which even the most pronounced anti-preform-
ists rarely cite.

“In the larger animals of the same species the cells
are not correspondingly larger than in individuals
which in consequence of lack of nourishment have re-
mained smaller. Thus the unequal size of the individuals
must be associated with an unequal number of cell
divisions, which by the method of qualitative differentia-
tion assumed by Weismann must lead to a very essential

1°°G. Born: Ibid. P. 87—88.
101G, Born: Ibid. P. 144.

132 Facts Compelling Us to Reject Preformation

disturbance. 1t follows that qualitative differentiation
can not have any close association with the number of
cell divisions, nor indeed with the process of cell division
itself, so that it is not possible for any definite qualitative
alteration to be so associated with each individual cell
division as to produce a definite character in each soma-
tic cell of the tenth, eleventh, twelfth, twentieth, and
fiftieth generation from the egg cell in consequence of
this number of generations.” 1°

To circumvent this objection to the preformation
theory, Roux has recourse to the hypothesis of a self
regulating mechanism of frankly epigenetic nature
which really amounts to reducing the part played by
preformative processes in ontogeny to a_ wholly
subordinate role.1°%

But the strongest objections against preformation
are on the one hand the above mentioned experiments
on isolation of blastomeres, and the production of
double monsters from a single egg and other similar ones,
and on the other hand the experiments upon regeneration.

The experiments upon the isolation of blastomeres
which showed that each one could produce an entire
individual are, as we have already explained in the pre-
ceding chapter, a convincing proof that at least the first
nuclear divisions are not qualitatively unequal. Having
recourse to a reserve idioplasm implies the renuncia-
tion of preformist theories. For in the first place, it
really admits that the whole of the idioplasm (active

“*°°Wilhelm Roux: Uber die Bestimmung der Hauptrichtungen
des Froschembryo im Ei und tiber die erste Teilung des Froscheies.
Sep.-Abdruck aus der Breslauer arztlichen Zeitschrift, 1885, P. 35.
Gesamm. Abhandl. II. P. 316—317.

103Wilhelm Roux: Ibid. P. 35, 317.

Double Formations 133
plus reserve idioplasm) remains after division just as
it was before; in the second place, the conception by
which one makes the activation or non-activation of
the reserve idioplasm depend upon the abnormal or nor-
mal relations of the different nuclei with one another is
very similar to that of epigenesis with preformistic germs,
such as would correspond somewhat with the hypothesis
of DeVries or that of Oscar Hertwig.

The formation of double monsters from a single
egg constitutes essentially an analogous case to that of
the formation of entire individuals from isolated blasto-
meres. We mention for example the experiments of
Wilson in which following the simple displacement in
relation to each other of the first two blastomeres of
the egg of Amphioxus, each of those blastomeres pro-
duced a gastrula united along a more or less extensive
surface with the gastrula produced by the other blasto-
mere in such a manner as to give rise to numerous and
very varied forms of double gastrulas in which the
axes and respective blastopores of the twin gastrulas
were oriented in the most diverse ways in relation to one
another.1°* The same thing occurred in the similar
double monsters obtained by Oscar Schultze from frogs’
eggs, which were produced by compressing the egg be-
tween two horizontal plates and turning them over
immediately after the first segmentation.*°°

If these double monsters,—and Roux has remarked

10% B. Wilson: Amphioxus and the Mosaic-Theory of Devel-
opment. Journ. of Morphology, vol. VIII, No. 3. Boston, U. S. A,
Ginn. August 1893; P. 591—595. Table XXXIV.

260, Schultze: Die kiinstliche Erzeugung von Doppelbildungen
bei Froschlarven mit Hilfe abnormer Gravitationswirkung. Arch. f.
Entwicklungsmech. d. Organismen Bd. I. Heft 2. Leipzig, Engel-
mann, 1894. P. 276—284. Tables XI and XII.

134 Facts Compelling Us to Reject Preformation

this himself, as we have seen in the case of those with
double symmetry,—are opposed on one side to simple
epigenesis because they show that between the two
organisms, even though they have so great a part of
the body in common there do not exist any general
reciprocal actions tending to make a single whole of the
two bodies, they are on the other side, also opposed to
preformation, in that they demonstrate in the same man-
ner as do the experiments upon isolation of blastomeres,
the equipotency or qualitative identity of the two first
segmentation nuclei.

And this equipotency is not limited only to the two
first but exists also in all the first blastomeric nuclei as is
demonstrated by the inverse phenomenon obtained by
Morgan of the formation of a single embryo from two
blastulas of Sphaerechinus which had grown together of
themselves.1°¢

Finally preformation as we have said, is quite irrecon-
cilable with all the manifold processes of regeneration
without exception.

Above all, Weismann interprets in fundamentally the
same sense as we, the experiments and observations of
Roux upon the peculiar regeneration constituted by the
postgeneration or completion of the half embryos which
we have so often mentioned. For they signify as he
himself admits, “that this completion took place by a kind
of cell infection, of such a nature that mere contiguity, for
example with ectoderm cells, caused the as yet undifferen-
tiated cells of the side operated upon to become developed
into ectodermal cells, while similar contiguity with me-

106K H. Morgan: The Formation of one Embryo from two
Blastulae. Arch. f. Entwicklungsmech. d. Org., 1895. Bd. II. Heft
1. P. 65—71.

Remodeling of Old Tissues in Regeneration 1 35

soblastic cells made them become mesoblastic cells.” And
Weismann finally calls into question the incontestability
of these facts, just because such a cell determination de-
pendent upon contiguity would upset at once his whole
theory of preformation.!°7

But there are also many cases of regeneration proper
in which one has a remodeling of old tissues into new
tissues that are quite different, and they constitute
phenomena which are analogous in this respect with post-
generation. As an example may be mentioned the
regeneration of Planaria maculata.

Fragments of this worm obtained by two transverse
sections regenerate the head and the tail by producing
new cells. But after their formation, this head and this
tail do not grow any further, but the entire subsequent
growth in length of the body takes place in the older more
pigmented parts, so that the normal relative proportions
of the planaria are restored simply by a remodeling of the
older tissues. “The fragment of the worm reacquires its
normal form but not through the addition of new tissue
at the anterior and posterior extremities, except to a very
small extent. The transformation is produced chiefly in
the old tissue after the head and tail are developed. Thus
we find here not only the capacity of regeneration but
also a subsequent self-regulation by means of which the
normal relations of the parts characteristic for the species
become re-established.” But that is not all. For in an-
imals regenerated from lateral fragments, the longitudinal
axis of the new worm is found often in the older tissue,
so that one portion of the old material which was in the
right side of the old animal becomes now part of the left

2°™Weismann: Das Keimplasma. P. 192.

136 Facts Compelling Us to Reject Preformation

side of the new animal or vice versa; and the development
of the new pharynx which is found in the exact lon-
gitudinal axis, indicates that it can be produced indiffer-
ently from any part whatever of the old tissue.1°

This remodeling of old tissues into new tissues differ-
ing from them indicates that the supposed determinants
of Weismann have not by themselves any value, for as
soon as the tissue finds itself in conditions different from
the normal ones it takes on forms and acquires properties
which would require determinants of quite another nature.
“The organism,” writes Whitman, “dominates cell forma-
tion using for the same purpose one, several, or many
cells, massing its material and directing its movements
and shaping its organs as if cells did not exist or as if
they existed only in complete subordination, if I may so
speak, to its will.” 7°? And one would not know how to
give any better proof of the correctness of this statement
than that which is constituted by these particular regener-
ations, which utilize the material already existing to
remodel it into the new.

And not only are these phenomena of peculiar regen-
eration irreconcilable with preformation but the very fact
of regeneration in general is irreconcilable with it.

“The germ tissue of the new organ,” writes Hertwig,
“does not contain any remnant of the amputated organ
itself from which it could be reproduced by simple
growth. The buds destined to reconstitute the eye-bear-

108 M. Morgan: Experimental Studies on the Regeneration of
Planaria maculata. Arch. f. Entwicklungsmech. d. Org. Bd. VII.
Heft 2. and 3. Leipzig, Engelmann. Oct. 18, 1808. P. 385, 380, 305
—306.

*°Whitman: The Inadequacy of the Cell-Theory of Develop-
ment. Biol. Lect. at the Mar. Biol. Lab. of Wood's Holl, Summer
Session 1893. Bostcn, U. S. A., Ginn 1804. P. 119.

Weismann’s Accessory Idioplasm 137

ing tentacles of the snail contain no trace whatever of
retinal cells nor of pigment cells, nor of any other sensory
cells whatever. Similarly the buds for the extremities do
not contain any trace of the material of the carpus and
phalanges nor of the muscles and tendons belonging to
them. It is a complete new formation.” 41°

The explanation which Weismann endeavors to give
of these complete new formations produced in every re-
generation is well known:

“If each cell of the completely developed bone con-
tains within it only that kind of idioplasm which con-
trols it and which is consequently the molecular expres-
sion of its own particular nature, it would be impossible
to understand how the regeneration could be effected of
a bone which had been, for instance, cut through lon-
gitudinally. Supposing that because of the wound there
would become exercised upon the cells of the stump a
stimulus which caused them to proliferate, a mass of bony
tissue would indeed be produced but never a bone of def-
inite size and shape. This can take place only in case the
cells undergoing proliferation possess, besides their ac-
tive determinants, an additional supply of determinants
which control the missing part about to be reformed. It
is then evident that, if we wish to transport the Nisus
formativus of Blumenbach into the cell and indeed into
its idioplasm, we must assume that each cell capable of
regeneration contains besides its principal idioplasm, also
an accessory idioplasm (‘Neben-Idioplasm’), consisting
of the determinants of the portion of the amputated organ
which can be regenerated by it. Thus, for instance, the
cells of the humerus must contain besides their own con-

119Qscar Hertwig: Die Zelle und die Gewebe. II. P. 180.

138 Facts Compelling Us to Reject Preformation

trolling determinants also all the determinants of the
forearm and of the hand as accessory idioplasm, for they
can cause the entire chain of these bones to be formed
anew; and the cells of the radius must contain as acces-
sory idioplasm all the determinants of the radial portion
of the wrist, hand and fingers.

“We can regard this theoretical requirement as quite
realizable also, since when the whole organ commences
to be formed, the necessary accessory idioplasm can very
well separate from the disintegrating embryonic idio-
plasm. We need only assume that this accessory idio-
plasm remains henceforth inactive in the nuclear sub-
stance of the cell until some cause for regeneration
arises,”’ 111

We note at once that, according to this hypothesis,
there is no reason at all why there should be held in re-
serve in each part of the bone only the accessory idio-
plasm capable of regenerating the bony parts distal to
that point, but never any other capable of regenerating a
larger or smaller part. Each particular reserve idioplasm,
when once it has separated itself in a given cell from the
principal idioplasm, and been segregated in the nucleus of
the cell itself in the latent state, will be able to preserve
itself unaltered through many generations of cells. Con-
sequently there must be present at any point at which a
bone may be broken several accessory idioplasms, each
capable of regenerating a more or less long portion of the
bone which was broken, and perhaps also of some other
bone. In the illustrative case cited by Weismann the sec-
ond phalanx should contain besides the reserve idioplasm
capable of regenerating the second and third phalanx,

111Weismann: Das Keimplasma. P. 136—138.

Regeneration and Generation 139

also that which is capable of regenerating all three pha-
langes; or the distal part of the second phalanx should
contain, besides the accessory idioplasm capable of regen-
erating the distal portions of the second phalanx and the
whole of the third phalanx, also that which is capable of
regenerating both the third phalanx and the entire second
phalanx itself. Why, then, should only that accessory
idioplasm become activated which is capable of regenerat-
ing just the particular part cut off?

Further, Weismann himself recognizes that when dif-
ferent tissues and organs are cut through, “it is only the
harmonious equipment of the cells of a definite cross sec-
tion with groups of determinants, different but mutually
adaptable, in accord among themselves and compliment-
ary, that could make regeneration of the higher type pos-
sible.” 112. But really it is not easy to conceive how this
harmonious equipment of reserve idioplasm could be
guaranteed in the great number of different cells of a
complex section.

Roux has seen so clearly this impossibility of explain-
ing the phenomena of regeneration by preformation
theories, that he asserts that in “direct” or “typical” gen-
eration self-differentiation may have the preponderance
over differentiation due to reciprocal actions among the
parts without nevertheless entirely excluding it; but in
regeneration, which he calls “indirect” or “atypical”
generation, he admits that differentiation of epigenetic
nature must necessarily prevail over preformation."®

Weismann has rightly been unwilling to fall into the
contradiction of imagining two different natures for two

112Weisann: Ibid. P. 297—208.
18Royx: Uber Mosaikarbeit usw. Anat. Hefte. P. 279—331.

Gesamm. Abhandl. II. P. 819—870.

140 Facts Compelling Us to Reject Preformation

processes which are essentially identical with each other,
but has been thereby driven to an attempt at explanation,
which is wholly artificial and indefensible.

In order to make the artificiality of his interpretation
of the most difficult cases clearer, let us consider further
the following examples.

It is known that regeneration is not usually an exact
repetition of the ontogenetic process.

“Until the last few years,” writes Delage, “it has been
regarded as a dogma that regeneration is a repetition of
ontogeny. That is that the regenerating organ or limb
goes through the successive stages of development
through which it went in its first formation. Yet the
question has not been thoroughly enough investigated to
permit the statement that it always does this, and in many
cases it is certain that it does not proceed in this way.
Thus a round tailed salamander regenerated a round tail
from the first and not the flattened finlike tail of the larva,
the crab regenerates an adult foot and not a foot like that
of its larva, Zoaea, The limb or organ regenerated after
a wound arrives at once at the stage which corresponds to
the age at which regeneration takes place.” 114

Further, regenerations of ectodermic tissues at the
expense of entodermal or mesodermal tissues are not
rare. We have already seen how the crystalline lens,
embryologically of ectodermic origin, regenerates in the
triton from the mesodermic iris. The anterior intestine
of Tubifex rivulorum, whose ontogenetic origin is
ectodermal, regenerates, with the exception of a small
portion at the end, from entodermal tissues.15

Delage: L’hérédité etc. P. 104—105.
45H. Haase: Uber Regenerationsvorginge bei Tubifex rivulorum
Lam. mit besonderer Beriicksichtigung des Darmkanals und Ner-

Regeneration Not Exact Repetition I4I

Finally, cases are not rare in which a regenerating
organ alters its form, as in the lizard in which the new
tail has a skeleton not formed of individual vertebrae at
all, but of a little continuous, cartilaginous cylinder.

Now the epigenetic theories explain very easily how
it comes that the part amputated can follow in its regen-
eration a shorter road than in its ontogeny (caenogenetic
regeneration), and how in many cases after completion of
the process, it may have a form quite different from that
of the original part. For the remaining part of the body,
on which the morphologic determination of the ampu-
tated part depends, is now in the adult state while for-
merly it was in the embryonic state.

The altered condition in which it now exerts its
formative action upon the part in process of regenera-
tion explains the diversity, not only of the earlier results
obtained, in which development and regeneration proceed
in different ways, but also of the final results, in which the
regenerated part is of abnormal conformation. For the
differences of conformation which are produced at the
commencement of the process of regeneration cannot
always be smoothed out and effaced when, at the end of
the regenerative process, the condition of the rest of the
organism from which the formative action is exerted
upon the part in process of regeneration becomes again
the same in relation to that latter as at the end of
normal ontogeny.

Weismann on the contrary, whose above quoted ex-
planation is clearly no more adapted to these cases, is
forced to take refuge in the following subsidiary

hypothesis :

vensystems. Zeitscher. f. wissensch. Zoologie. Bd., 65. Zw. Heft,
1898. P. 229-—235.

142 Facts Compelling Us To Reject Preformation

“In caenogenetic regeneration, (and a fortiori when
the regenerated part remains of abnormal conformation),
one cannot but admit that certain double or multiplied
determinants must be present beside one another in the
germ plasm, some of them being destined to embryonic
development, others to regeneration. These latter must
have their interior forces and particularly their growing
force so arranged in advance as to split off, either alone
or together with neighboring determinants of regenera-
tion, as reserve idioplasm, at the proper moment of
development.” 116

Epigenetic theories contain in themselves an imme-
diate explanation of the well known fact that when a
worm is cut in two, the anterior part regenerates the
posterior while the posterior regenerates the anterior.

Weismann on the contrary is forced to have recourse
to the following artificial hypothesis: “As the two halves
become always complete again, no matter at what place
the worm is cut, it therefore follows that the cells situated
in any particular transverse planes of the body are not
merely provided with reserve determinants for generating
in some planes the head, in others the tail, but every cell
must be able to act in either way, according to whether it
happens to lie anteriorly or posteriorly to this plane. In
order therefore to explain the twofold reaction of these
cells, and stick to our fundamental view,—which regards
the cells concerned in regeneration, as arranged and con-
trolled by forces lying within themselves, and not by any
external directing power,—it seems to me that we must
assume that each of them contains two different reserve
determinants, one for reconstruction of the head, the

*°Weismann: Das Keimplasma. P. 145—146, 147.

Weismann’s Explanation of Regeneration 143

other for that of the tail end, and that one or the other
becomes active according as the stimulus due to lying un-
covered, is applied to the anterior or posterior surface of
the cell concerned.” 117

Finally according to epigenetic theories the regenera-
tion of the hydra is a process which does not differ es-
sentially from any other process of regeneration, but ac-
cording to Weismann’s theory the following complicated
additional explanation becomes necessary.

“If one divides a hydra in a longitudinal plane the
two halves grow again into entire individuals, irrespective
of the plane of section. As a transverse section of the
animal at any point which may be selected is followed
likewise by the complete reconstruction of each of the
two halves it follows that every part of the body of the
hydra must be capable of regeneration in a threefold
direction, namely in the three directions of space. As the
body is differently constructed in these three directions
we are forced to the conclusion that each of its cells must
contain groups of determinants of three different kinds.
* * * And it cannot be the quality, but the direction
from which the stimulus of the wound comes to each
cell, which will decide for it which of the three groups of
determinants will become active.” 1*§

We believe that we do not pronounce too severe a
judgment, if we affirm that so artificial a hypothesis
demonstrates the absolute incompetency of preformation
theories to explain the phenomena of regeneration.

What is the conclusion which can be drawn from all
that we have said thus far in the present chapter?

117Weismann: Das Keimplasma. P. 169.
118Weismann: Das Keimplasma. P. 170.

144 A Homogeneous Germ Substance Inadmissable

The first part has shown us that simple epigenesis is
directly and decidedly controverted by a whole series of
indubitable facts and results which no one now opposes.
The second part, which refutes preformation, shows us
on the contrary that the nature of every process of
development is really epigenetic.

And thus a correspondingly greater probability is es-
tablished for those hypotheses which, concentrating the
power of sending forth the controlling influences of
development into a single well defined zone of the orga-
nism, thereby explain quite as well as epigenesis the facts
that are irreconcilable with preformation, and are at the
same time in accord also with all the facts which simple
epigenesis is incapable of explaining,

3. Inadmissibility of a Homogeneous Germinal
Substance

It will not be necessary to give this question more
than a very brief consideration, for it is sufficient to men-
tion the chief argument which all the partisans of pre-
formistic germs, the epigenesists as well as the preform-
ists proper, have repeated incessantly and still repeat.
The fact that in doing this each uses almost the same ex-
pressions as the others shows how conclusive this
argument is.

“The considerations,” remarks Wilson, “which have
led to the rehabilitation of the theory of pangenesis are
based upon the facts of what Galton has called particu-
late inheritance. The phenomena of atavism, the char-
acters of hybrids, the facts of spontaneous variation, all
show that even the most minute characteristics may ap-
pear or disappear independently, may be modified inde-

Particulate Inheritance 145

pendently, may be inherited independently from either
parent, without in any way disturbing the equilibrium of
the organism, or showing any correlation with other
variations. These facts, it is argued (by the partisans of
preformation), compel us to believe that hereditary char-
acters are represented in the idioplasm by distinct and
definite germs (pangens, idioblasts, biophores, etc.),
which may vary, appear or disappear, become active or
latent, without affecting the general architecture of the
substance of which they form a part. Under any other
theory we must suppose variations to be caused by
changes in the molecular composition of the idioplasm as
a whole, and no writer has shown even in the most ap-
proximate manner how particulate inheritance can thus
be conceived.” 119

It is well known that this is really the principal argu-
ment, one might say the only one, which Galton brings
up in defense of his germs, substituted by him for the
gemmules of Darwin: “The independent origin of the
several parts of the body can be argued from the separate
inheritance of their peculiarities. If a child has its
father’s eyes and its mother’s mouth these two features
must have had a separate origin. Now, it is observed that
peculiarities even of a microscopic kind are transmissible
by inheritance, therefore it may be concluded that the
most minute parts of the body have separate origins.” **°

The argument which DeVries brings up in favor of
his pangens, or material particles representative of the

119f B, Wilson: The Mosaic Theory of Development. Biol.
Lect. at the Mar. Biol. Lab. of Wood’s Holl: Summer Session 1893.
Boston, U. S. A., Ginn, 1804. P. 3—4.

12°F rancis Galton: A Theory of Heredity. Journ. of the Anthro-
pological Institute. January 1876. P. 331.

146 A Homogeneous Germ Substance Inadmissible

different characters of the organism, is quite similar to
that of Galton. It is summed up in the following passages
from his book: “Many species of plants,’ writes he,
“have the power of producing definite chemical com-
pounds: among the most important of these are the red
and blue coloring substances of flowers: also the various
tannic acids, the alkaloids, the etherial oils, and numer-
ous other products. A small number only of these com-
pounds are limited to a single species of plants: a large
number are present in two or more species, systematically
far removed from one another. There is no reason to
believe that there is a different mode of production of the
same compound in each particular case: on the contrary
one would naturally expect the same compound, in what-
ever place one meets it, to be produced always by the
same chemical mechanism.”

“Similarly we must admit the possibility of a break-
ing down of the morphologic signs of species. Morphol-
ogy is clearly not yet far enough advanced to permit of
such an analysis in each particular case. But the same
coarse or fine notching at the leaf margins are repeated
in numerous species and the customary terminology in-
forms us in advance that all forms of leaf patterns are
composed of a relatively small number of more simple
characters.”

“This shows that the character of each individual
species is made up of numerous hereditary peculiarities of
which the most part are present also in an almost infinite
number of other species. * * * According to this
view, we would regard each species as an extremely com-
plicated figure, and the organic world in its entirety as the
result of innumerable different permutations and com-
binations of a relatively small number of factors.”

Independence of Hereditary Peculiarities 147

“Experiments upon the production of varieties teaches
us further that nearly every peculiarity can vary inde-
pendently of the others. Many varieties in fact diverge
from their stock form by only a single character; for in-
stance the white blooming variety of a species with red
flowers. In the same way the villosity, the armanent of
spines or thorns, the green color of leaves, each of these
characters can vary by itself and can even disappear en-
tirely, and all the other hereditary properties remain
perfectly unaltered.”

It follows that: “The hereditary anlagen, of which
the hereditary peculiarities are the visible signs, are inde-
pendents units which may have had their origin at differ-
ent epochs, and which may also be lost independently.
They are miscible with one another in almost all propor-
tions, since each peculiarity can pass through all inter-
mediate degrees from its complete absence to its greatest
development.”

“Independence and miscibility, these are the essential
properties of the hereditary anlagen of all organisms.” 1+

Quite similar to this argument of DeVries is that of
Weismann in favor of his preformation or of preformistic
germs in general: “It is impossible for one part of the
body to vary independently of the others, and for these
variations to be hereditary, if it is not represented in the
germ plasm by a special particle, a variation of which in-
duces a corresponding variation of the part in question.
If this were represented, together with other parts of the
body, by a single particle of the germ plasm, then a
change of this latter would have as its consequence the
variation of all the parts which are determined by it. In

121De Vries: Intracellulare Pangenesis. Jena, Fischer, 1889. P.

89, 17, 32, 33. English Translation by C. Stuart Gager. Open
Court Publishing Co. 1910.

148 A Homogencous Germ Substance Inadmissible

those parts of the body which are independently and
hereditarily variable, we have thus an exact measure for
determining the number of the little vital particles which
must compose the germ plasm: they cannot be fewer.”

“We are then logically forced to assume that a special
element exists in the germ plasm for each of these pecul-
iarities, not because the inheritance of even the smallest
details is possible, but because each of these parts of the
body can have its variations inherited individually, each
by itself. If all men possessed a certain depression in
front of the ear, one could not conclude that because it
was hereditary, it must be represented in the germ plasm
by a special element * * * the fact which forces us
to accept this hypothesis is that all men do not possess this
depression, that we can imagine two people who resemble
each other in all other respects but of whom one pos-
sesses this depression and the other does not.” 1°?

This is then the great and only argument of all the
theories of preformistic germs.

One cannot fail to see that it really possesses a very
great value against such theories as that of Spencer, who
supposes the germ plasm to be constituted by a homogene-
ous substance. In the almost complete darkness in which
we still find ourselves in respect to the nature and causes
of ontogenetic phenomena, there are very few things
which we can venture to call impossible. Nevertheless
the supposition which is implied in the epigenetic theories
of the Spencer type, namely, that a homogeneous germ
substance a little different chemically from an other, is
able to give rise to an individual quite identical with that
which the other substance produces, except for one little

**°Weismann: Das Keimplasma. P. 72—74.

Theories of Chemical Development 149

peculiarity in a definite part of the organism, if it does not
seem quite impossible, certainly seems difficult to con-
ceive. It is true that these theories of the Spencer type
can always bring up the objection that to a visible varia-
tion of a certain group of cells there might possibly cor-
respond similar variations in all the other cells of the
organism, but always so small that they are not appre-
ciable. But such an explanation of the especially inherit-
able variations would be formal rather than actual.

This applies equally well, it may here be said paren-
thetically, to evolutionary theories without preformed
germs, such for example as the theories which are called
those of the chemical development of the egg. They start
out usually with a heterogeneous germ substance, con-
stituted by multiple and diverse chemical substances, from
chemical interactions of which new chemical compounds
are formed later, which give place in their turn,—in each
cell as in a separate crucible independent of the others,—
to new chemical reactions and consequently to new com-
pounds different in the different cells, and so on up to the
end of development. But one cannot conceive how each
one of these components of the germ substance, which
commences to exercise its chemical action upon the other
constituents from the very first moment of development,
even though it be the only point in which one germ differs
from another, can bring about an alteration of the or-
ganism limited to a single point rather than an alteration
extended over the entire organism.

The argument brought up by the partisans of pre-
formistic germs, both epigenesists and preformationists
properly so called, is then really weighty enough to force
us to hold as inadmissible every biogenetic hypothesis
which starts out from or is based upon a homogeneous

150 Inadmissibility of Preformistic Germs

germinal substance, even though it were as complex as
one could imagine; and a germ substance which is hetero-
geneous indeed but each of whose components would
nevertheless commence to be active from the very first
moment of development must be no less certainly
excluded.

On the other hand we ask: Is it in general possible to
conceive, much less accept, these preformistic germs, of
which each is set apart for some infinitesimal part of the
body,—any part provided that it can vary independently
of the others? Would the supposition of germs of this
nature constitute any explanation whatever of this par-
ticulate inheritance, or would this not rather be a pure
and simple repetition in other words of the phenomenon
which one pretends to explain?

That is what we propose to consider very briefly in
the following last section of this chapter.

4. Inadmissibility of Preformistic Germs

We note in advance that the independently variable
and inheritable peculiarities of the organism are not
limited merely to the form and structure of entire groups
of cells, but can include even the chemical characters of
each cell. One would arrive thus at the absurdity that
not only each cell, as Darwin’s pangenesis already admits,
but almost each molecule of the organism must have its
representative in the germ plasm.

Besides this material impossibility the idea of pre-
formistic germs encounters insurmountable difficulties
from the point of view of their conceivability.

Is it a conceivable thing that there is for instance a
preformistic germ of a certain nervous tic, or of a par-

Instincts and Particulate Inheritance 151

ticular instinct, that there is a pangen or a group of
pangens for the instinct of the hunting dog, that there is
a determinant or group of determinants of the instinct of
the new-born chick, which knows already how to peck at
the wheat and swallow it? How can we conceive of these
instincts which are the consequences of very complicated
combinations and interconnections of almost innumerable
centers and nerve tracts, as due to one separate germ,
which having come up at the opportune moment of on-
togeny, and at the exact point of the organism, produccs
them by itself, automatically, and we may say independ-
ently of all the rest of the organism already formed?

And yet these instincts actually constitute variable
and inheritable peculiarities of the organism, susceptible
of being present or absent independently of all the other
peculiarities of the organism. But if, in order to explain
this “particulate inheritance” one has recourse to germs
especially preformed just for this, would this constitute
anything else than a purely verbal explanation without
any real inherent significance?

“A man, for example,’’ Le Dantec very rightly says,
“Gs composed of about sixty trillions of cells, and he is
nevertheless reproduced by sexual elements of very small
size: this is the phenomenon to be explained. It has been
thought that the difficulty would be less, or at least would
not appear so distinctly, if one were to divide the problem
into sixty trillion parts, if one could replace the reproduc-
tion of the man by sixty trillions partial reproductions ;
and there have been consequently imagined infinitely
small particles which are to the cells as the whole germinal
substance is to the man.” 17%

1287 e Dantez: Traité de Biologie. P, 224—225.

152 Inadmissibility of Prefornustic Germs

The consequence of this has been that the problem has
become enormously complicated because it has given birth
to this other very great problem: How comes it that
these sixty trillions of autonomous and therefore inde-
pendent individual parts can constitute a complete and
harmonious whole?

It results from this that preformistic germs, which by
themselves are quite inadmissible, become yet more so
when they are separated from preformistic doctrines
properly so called. And Weismann endeavored to show
that they are inseparable.

“DeVries,” he says, ‘once mentions the zebra stripes.
How can such a character be transmissible if in the germ
the different pangens are free one beside another, without
being bound up into firm groups inheritable as such?
Zebra-pangens cannot give it, for the striping of the zebra
is no cell character. Perhaps there are pangens which for
brevity we can call “whites” or “blacks,” whose presence
would produce white or black color in the cell. But the
striping of the zebra does not consist in the development
of the black or of the white in the interior of the cell, but
rather in regular alternations of thousands of black
or white cells arranged so as to form stripes.”

“DeVries mentions also the long stemmed variety of
the alpine Primula acaulis occasionally produced by
atavistic return to a remote stem form. Here again the
character of the long stem cannot be due to ‘long stem
pangens,’ because the long stem is not an intracellular
property ; neither is the specific form of the leaves, etc. ; the
dentate border of a leaf cannot be due to the presence of
‘dentate pangens,’ but is due to a special arrangement of
the marginal cells. The same is true of nearly all the
characters which we designate as visible properties of the

Incapable of Explaining Particulate Inheritance 153

species, genus, or family etc., and so of the size, struc-
ture, and shape of a leaf, of the characteristic and often
constant spots upon the leaflets of flowers (orchids, and so
on). All these properties manifest themselves only by the
orderly cooperation of many cells. Or think of the prop-
erties of the human individual, of the form of the skull,
of the nose, and so on. All these very characteristic
properties cannot be due only to the presence in the germ
of pangens which must form the hundreds and thousands
of different cells which compose the property in question;
they must be due rather to a fixed grouping of the pan-
gens or of some other corresponding primary element of
the protoplasm, transmissible in its fixity from generation
to generation.” 124

But when under the pressure of logical necessity we
pass from simple preformistic germs, either free or in-
termingled in any way, to germs built up together into a
fixed structure, we fall at once into all the difficulties and
contradictions of pure Weismannian preformation, which
we have already discussed, beginning with the one which
we have seen to present itself first, namely that it is quite
inexplicable how this “fixed grouping of the pangens” can
divide in successive germ plasms and nevertheless remain
unaltered in its structure.

Preformed germs, materially impossible and theoreti-
cally inconceivable, are nothing else than empty, wordy
names, and appear besides to be quite incapable of ex-
plaining even the most important phenomena of particu-
late inheritance on account of which they were especially
devised, and which constitute the only excuse for their
existence, when once they are separated from the stronger

124Weismann: Das Keimplasma. P. 22—23.

154 Inadinissibility of Preformistic Germs

preformistic theories, the absolute inadmissibility of
which we have seen above.
ee

What conclusion can be drawn from the last two sec-
tions of the present chapter ?

The penultimate section has shown us that the actual
independence in variation and inheritance of the various
and particular characters of all the rest of the organism
can be explained neither by a homogeneous germ sub-
stance, nor by a heterogeneous germ substance of which
all the various constituents would become active from the
first moment of development. The last section has dem-
onstrated to us the inadmissibility of preformistic germs
although at first they appear to constitute the most im-
mediate explanation of the mutual independence of the
various particular characters.

It remains then for us to see if a heterogeneous germ
substance without preformistic germs, but whose con-
stituent parts instead of entering all into action from the
first moment of development, become active successively
from the commencement to the end of development, can
give the adequate explanation of particulate inheritance
which we are seeking.

Let us consider first the phenomena of particulate
inheritance which are shown by the presence in the child
of certain paternal characters simultaneously with other
maternal characters, intermingled but yet clearly distin-
guishable from one another. For the sake of clearness
we shall overlook for the moment all sexual peculiarities
and limit ourselves to considering only the clearly asexual
paternal and maternal characters. “The form of the
skull,’ remarks Weismann for instance, “can be paternal
and the face maternal; the form of the entire head and

Successively Activated Specific Elements 155

the face can be maternal and the eyes, in spite of that, be
entirely paternal in character; the dimple which the father
had on his chin may be found again in the child, although
in the form of its face and nose it may resemble the
mother rather than the father.’’ 12°

Let us note at the same time that the germ substance
of the fertilized egg must contain the anlagen of both the
paternal and maternal germ substance, and that the
former as well as the latter, since they correspond one to
another in pairs, tend to become active in pairs simulta-
neously or almost simultaneously, except in the cases
where they are of such nature as to be reciprocally
exclusive.

Now if we suppose that the process may be of epi-
genetic nature, and if we suppose also that the different
anlagen of the germ substance becoming successively ac-
tive, are all located in one definite zone of the organism
from which they send forth their formative action, then
it is clear that the different points of the soma must
experience the determinative influence of the paternal and
maternal germinal anlagen at the same time.

Consequently when the corresponding anlagen com-
posing each couple are quite identical, as will be the case
especially during the first stages of development and per-
haps also at subsequent stages more or less advanced,
then the two respective, determinative actions will be-
come fused into one, and there would result the exact
reproduction of the entirely similar characters which the
two parents possess in common.

When on the contrary the corresponding anlagen com-
posing each pair are different, provided that they are not,

125Weismann: Das Keimplasma. P. 377.

156 Explanation of Particulate Inheritance

we repeat, different to such a degree that the activation
of one prevents that of the other, the two formative
actions will be likewise different for all the points of the
soma upon which their action would be perferably or
exclusively directed, and they would be able thus either to
combine and thus unite into a single resultant formative
action, or, by developing their respective characters
separately, to bring about an intimate interlacing of
them, in such a way as to cause the appearance of a com-
mingled intermediate character, or finally the paternal
character developed by one of the formative actions can
at a given point prevail over the maternal to such an ex-
tent as to appear in all its purity, while perhaps the reverse
appears in a neighboring point of the soma, and the
maternal character comes alone to development.

A characteristic example of this interlacement of pa-
ternal and maternal characters remaining in part distinct
but in part fused, is shown us by the hybrid arising from
the spontaneous crossing of Vitis aestivalis and Vitis
labrusca, the epidermis of whose leaves is formed like a
mosaic, the cells of which belong either to the purely
paternal type or to the purely maternal type, or to an
intermediate form.'6

If now after considering the phenomena of particulate
inheritance due to sexual reproduction, we consider the
phenomena of this particulate inheritance in its broadest
extent and most general significance in order to be able to
answer the question; how can the simple fact be explained
that two individuals can be altogether alike except for a
single definite peculiarity at a single given point of the

*2¢Strasburger: Uber periodische Reduktion der Chromosomen-
zahl im Entwicklungsgang der Organismen. Biol. Centralbl., Bd.,
XIV. No. 23 and 24, Dec. 1. and 15, 1804. P. 850.

Explanation of Particulate Inheritance 157

organism? It will not be difficult to convince us that the
possibility of this phenomenon will be fully provided for
by the same hypothesis of the structure of the germ sub-
stance which has served to explain for us the same
phenomenon in so far as it is due to sexual reproduction.
Let us imagine, for example, two germinal substances
constituted by two series of specific anlagen, which are
qualitatively alike, but in one of which a certain entire
group of these anlagen is furnished with a little less
potential energy than in the other. We do not need to
suppose, even though we could, that this certain group of
specific anlagen is of such a nature that its activation in
the above mentioned common zone from which formative
stimuli are given out should determine preferably or exclu-
sively just that part of the organism which shows itself
capable of independent variation, such as for example the
dimple in front of the ear of which Weismann speaks.
Instead we could very well suppose that this group,
either by itself or in combination with others, brings
about definite ontogenetic modifications not only in this
one part but also in many other parts, perhaps even in
all the cells of the organism without exception. But
the epigenetic nature which we attribute to the process
of development implies the idea that the activation at
a given stage of ontogeny of a definite specific anlage
must exert very different influences not only qualitatively
but quantitatively upon the individual parts of the soma
that are already formed. It is thus conceivable that
a very small amount of potential energy in a given
group of specific germinal anlagen might exert inappre-
ciable effects or indeed no effect at all on a definite or
even great part of the organism, but yet exert quite an
appreciable or even considerable effect upon another very

158 Explanation of Particulate Inheritance

small part of it, and so much the more since the effects
produced by this particular group of germinal anlagen
must combine with those produced by all the others both
antecedent and subsequent.

It would amount to the same thing if this given group
of specific anlagen differed from the corresponding group
of the other germinal substance not only quantitatively
but also qualitatively to a certain extent.

We believe the final result to be that we can affirm
that the hypothesis of a heterogeneous germinal sub-
stance whose anlagen do not all enter into action from the
first moment of development, but rather become active
successively one by one, throughout the entire course of
development, explains the phenomena for which pre-
formistic germs were especially devised quite as satis-
factorily as they do, and at the same time is not open to
any of the formidable objections, which demonstate with
certainty the untenability of the hypothesis of pre-
formistic germs,

CHAPTER FIVE

THE QUESTION OF THE INHERITANCE OF ACQUIRED
CHARACTERS

The great service of Weismann, which is not yet
appreciated highly enough, is that he brought forward
this matter of the inheritance of acquired characters, and
questioned its existence, which previously had been not
only tacitly admitted by most biologists, but regarded as
not needing proof. And we must recognize the fact that
the great and justifiable desire to find for this inheritance
some proof which should be irrefutable and not open to
any objections has remained so far unfulfilled.

It is not proposed here to make a long list of all the
facts which have been brought forward as proofs of the
Lamarckian principle, but it will be worth while to
examine a few in order to show clearly that Weismann and
his school are not really far wrong in denying to most of
these facts any right to be considered conclusive proof.

We shall leave aside the question as to whether calves
have really been born without horns, as alleged, in con-
sequence of the breaking off before their conception of
the horns of one or other parent; or whether tailless
calves were produced by a bull whose tail had been
squeezed off at the root by the violent closing of the stable
door. It is clear that all these cases and many others like
them, which have been reported in dogs, cats, rats, and

159

160 Inheritance of Acquired Characters

so on, can not constitute any satisfactory proof in the
absence of reliable observation and confirmation of the
facts.

Darwin draws especial attention to the inheritance of
characters acquired by domestic animals. ‘The domes-
ticated duck,” he remarks, “flies less and walks more than
the wild duck and the bones of its anterior and posterior
limbs have become respectively diminished and increased
in comparison with those of the wild duck. A horse is
trained to certain paces and the colt inherits similar con-
sensual movements. The domesticated rabbit becomes
tame from close confinement ; the dog intelligent from as-
sociating with man; the retriever is taught to fetch and
carry; and these mental endowments and bodily powers
are all inherited.” 127

These examples, one must admit, deserve all considera-
tion, especially the first. But one encounters here the ob-
jection which can always be raised against such examples:
As functional adaptation has a great modifying influence
upon the organism, how can we be certain that the greater
size of the bones of the legs in the domestic duck really
springs from inheritance of acquired characters rather
than from the daily exercise of the individual itself?
Would not a wild duck if it were obliged to walk during
all its life from its coming out of the egg acquire a similar
hypertrophy of these bones? Unfortunately we have not
exact measurements on this point which alone could de-
cide the question whether hypertrophy acquired during
the life of an individual could attain the same degree as
that which has been observed in the domestic duck.

Several travellers have remarked that when men have

127Darwin: The Variation of Animals and Plants under Vol. IT.
P. 367.

Apparent Instances and Objections 161

disembarked for the first time upon uninhabited islands
the animals have not often any fear of them, but after a
very few generations the fear of man has become an
inborn instinct.

Weismann and his followers could object here also that
this fear of man is not even now an inborn character, but
rather is simply acquired after birth and due to the educa-
tion, in the largest sense, which the little animals con-
tinually receive from their parents and from all the other
adults merely by observation and imitation of their con-
duct on definite occasions.

“The co-ordination, arrangement, and connections of
the ganglion cells which innervate the muscles of speech,”
says Roux, “are already inborn in us to such an extent
that we learn to speak our mother language easiest, while
for example Europeans even when brought among the
Namas while still children never learn their language as
perfectly as the Namas themselves, or do so only with
the greatest difficulty.” 178

This does not prevent any one fundamentally opposed
to the inheritance of acquired characters from objecting
that the European language spoken by the parents and
ancestors of the child may not be the cause of these dis-
positions and inborn connections of the ganglion cells but
rather the effect; in other words, it is not the use of this
or that speech which develops such and such inheritable
connections; but rather the presence of certain connec-
tions due to natural selection has produced certain
peculiarities in the character of the language of a given
human race.

“When young hunting dogs,’

’ writes Exner, “which

228Roux: Der Kampf der Teile im Organismus. P. 38.

162 Inheritance of Acquired Characters

have never been out hunting, nor had occasion to become
otherwise acquainted with guns and their effects, hear one
in the fields for the first time they start up eagerly, just
like old hunting dogs, to retrieve the prey even when
they do not see any fall. This demonstrates that since the
invention of gunpowder the mnemonic image of a gun-
shot and its effects has passed hereditarily into the brain
of the dog, and so has been gathered up in the so called
instinct.’’ 7°

And here, we do not really know what objection the
Neo-Darwinians could bring forward; for it seems to us
that they would encounter difficulties in trying to attribute
the formation of this instinct in a brain which was abso-
lutely tabula rasa in so far as this instinct is concerned, to
the artificial selection of the breeders. We must never-
theless recognize that even this example does not fulfill,
and cannot from the nature of it fulfill all the requisite
conditions of exact observation, of measurement, of con-
trol, and particularly of comparison which alone could
give a single case the value of a decisive proof.

A very remarkable example is reported by LeDantec.
The shells of Hyatt’s oldest cephalopods have the form of
a cows horn nearly circular in transverse section. And
following the series of these fossils in the more recent
strata, one notes that these shells, at first almost straight,
are little by little rolled up upon themselves like an Arch-
imedes’ spiral. The presence of certain characters shows
clearly that the rolled up forms are descended from those
with the straight shell. Ina few types the rolling up is so
marked that the successive turns of the spiral press one

*°Exner: Physiologie der Grofhirnrinde, in Hermann: Hand-
buch der Physiologie. Zw. Bd., Zw. Teil. Leipzig, Vogel, 1879.
P, 282—283.

Apparent Instances and Objections 163

into another, giving rise to a dorsal groove the mechanical
production of which is evident since it undoubtedly re-
sults from the pressure of the preceding spiral upon the
succeeding. Now ina still more recent geological period
paleontological discoveries show that the descendants of
these cephalopods with a tightly rolled up shell have begun
to unroll, and have then the form of an Archimedes,
spiral with broader turns which no longer touch one
another. But the dorsal groove persists even in these half
rolled up shells, a proof that the younger cephalopods
have repeated hereditarily this character which was
acquired by their ancestors.'*°

This is certainly a most interesting example, but it
has not quite the force of complete proof. For besides
the objection, which we shall examine later, that the
groove is formed in the non-living substance of the shell,
it does not exclude the interpretation, though it be only
verbal and without any real foundation, that it was not
the rolling up of the spiral upon itself that produced the
inherited groove, but rather that both the tight rolling
up and the groove were selected and fixed independently
of one another by natural selection.

The influence of dry, hot climates upon the develop-
ment of the horns of cattle and sheep is well known. If
certain individuals of a certain breed of cattle are trans-
ported from a wet, cold climate to a hot dry climate, the
horns increase in length and circumference and the skin
thickens. The following fact seems to prove that this
acquired elongation of the horns is inheritable. A cow
was transported from Algau in Bavaria where the climate
is moist and cold, into the dryer and hotter steppes of

1297 6 Dantec: Traité de Biologie. P. 296—297.

164 Inheritance of Acquired Characters

Hungary. This cow whose horns were 19 cm. long gave
birth to a calf with horns 22 cm. long. The calf of this
calf born also in Hungary, (presumably from a father
of the same race as that of the mother?) had horns 23
cm. long and thicker than those of its mother and grand-
mother.13?

So of the three centimeters of elongation, due to the
action of the environment, which we can regard as
functional adaptation in the widest sense, one centimeter
would have become hereditary in a single generation. It
is however evident that experiments of this nature can-
not have any real significance unless they are made on
a large scale, so that an average can be established from
many instances. And this experiment of Wilckens has
been mentioned here just because the way in which it
was conducted comes close to possessing the requisite
and indispensable conditions of a fundamental proof.

Another instance which the partisans of the inherita-
bility of acquired characters adduce is brought forward
by Spencer: it is that of the Punjabi of India, who have
certain muscle imprints on the bones of the leg, and
certain facets in the articulations of the hip, knee and
foot, which are produced by their habit of squatting upon
the ground; and these peculiarities are hereditary, as is
demonstrated by the fact that they commence to show
themselves even in the foetus.

Weismann seeks to demonstrate that they are only
the continuation in man of certain peculiarities in the
articulations of anthropoid apes which natural selection
had already fixed in very ancient times becausé they

**tWilckens: Die Theorie erworbener Eigenschaften vom Stand-
punkte der landwirtschaftlichen Tierzucht in Bezug auf Weismanns
Theorie der Vererbung. Biol. Zentralbl., July 15, 1803. P. 426.

Apparent Instances and Objections 165

were useful then. But still, in our opinion, he has not
been able to explain correctly why these peculiarities are
retained only in the Punjabi, who are also the only ones
of all the tribes of the same family who are accustomed
to squat in this way.1%?

One could bring up also as examples the callosities
at the knees and sternum which are hereditary in the
domestic camels but are lacking in the wild camels. Thus
for example the camels of the tame stock of San Rossore
near Pisa (Italy) are covered with hair both over the
breast bone and on the knee at birth, but after a few
days they lose the hair in the breast bone region, which
is then permanently replaced by a horny plate. Every
camel up to three months old had these more or less
broad, hairless plates, though they still retained the hair
on the knee, but the thickened and hardened skin could
be felt under it. Of course these camels which were
only a few months old were not required to do any
work. On wild camels, on the contrary, no such swellings
are to be found either in the very young or the adult.'%?

Still more remarkable is the following fact reported
in 1888 by Prof. Fogliata. “A she ass from the Tuscan
Appenines, which long had borne the pack saddle, showed
on the back and on both sides over the ribs, a very
evident pad of soft fat, which in extent and shape was
like those which the pressure of an ordinary mountain
pack saddle produces. This she ass was put to an ordi-

182Weismann: Neue Gedanken zur Vererbungsfrage. Eine Ant-
wort an Herbert Spencer. Jena, Fischer, 1895. P. 54ff.

188Cattaneo: Le gobbe e le callosita dei cammelli in rapporto colla
questione della ereditarieta dei caratteri acquisiti. Estratto dai Ren-
diconti del R. Istituto Lombardo di sc. e lettere. Serie IJ, Bd. XXIX,
1896. P. 10-11; and: I fattori della Evoluzione Biologica. Genua,

Martini, 1897. P. 40—41.

166 Inheritance of Acquired Characters

nary male ass and bore a female colt which shows the
same peculiarity as the mother. Its fat pad which covers
the back and reaches almost half way down the ribs is
not less than 5 cm. thick, clearly defined, and has an
abrupt and perpendicular margin. It is to some extent
a distinct and separate fat mass,—a true lipoma,—cer-
tainly similar to those which according to Lombroso’s
description are produced by burden bearing. It has the
same character as the hump of the camel, is more or less
developed according to the condition of nutrition of the
animal, and appears exactly as though it had arisen by
the pressure exerted by a saddle on the back. Also the
hair is longer and thicker over the whole of the fat layer,
which agrees likewise with the observations of Lom-
broso on pack animals possessing such lipomas, and is
like the hump of camels also, which is covered with
thicker, longer wool. It is worthy of remark that this
young she ass has never borne a saddle and inherits its
peculiarity entirely from the mother, which proves be-
yond doubt, that this peculiarity, acquired by pressure
on the back, has been inherited.1*#

Even though this single fact cannot decide the ques-
tion finally we do not really see what objection Weismann
and his school could urge against it.

Finally we have the celebrated experiments of Brown
Sequard on guinea pigs, proving the transmissibility to
the young of effects produced in the parents by certain
accidental lesions.

Thus he has demonstrated that epilepsy, produced in
one of the parents by section of the sciatic nerve or of a
part of the spinal cord, is transmissible to the young.

***Cattaneo: Le gobbe e le callosita dei cammelli etc. P. g—10.

Instances Reported by Brown Sequard 167

After section of the sympathetic trunk in the neck
there was produced a particular change in the form of
the ear or a partial closing of the eyelids, and the same
modification of the ear, and the same closure of the
eyelid were reported in their respective descendants.

A lesion of the medulla oblongata produced exophthal-
mos in certain guinea pigs and the same exophthalmos
showed itself in the young.

Ecchymoses accompanied by dry gangrene and other
alterations of the nutrition of the ear have been reported
in the descendants of individuals in which this series of
phenomena had been produced by a lesion of the restiform
body.

Certain other guinea pigs in which section of the
sciatic nerve had rendered the hind foot insensible to
pain gradually destroyed their toes by gnawing them;
it is reported that in their descendants parts of the toes
or even whole toes were missing from one of the hind
feet.

Other individuals in which the sciatic nerve had been
cut had descendants which exhibited at first a diseased
condition of the same sciatic nerve, and later the phe-
nomena characteristic of the onset and decline of epilepsy,
particularly the development of an epileptogenous capac-
ity in a zone of skin of the head and neck, and a loss of
hair toward the decline of the affection.

Guinea pigs which had had an eye altered in conse-
quence of the transverse section of the restiform body
had descendants which all showed more or less imperfec-
tion in one or both of the two eyes.

In more than a score of guinea pigs representing
the total posterity of individuals in which muscular
atrophy had developed after section of the sciatic nerve

168 Inheritance of Acquired Characters

there appeared just such a muscular atrophy of the thigh
and of the leg.'*

The desperate endeavor which Weismann has made
to refute the results of these experiments, at least in
relation to the transmissibility of epilepsy, is well known,
objecting that this affection was due only to an infection
innoculated in the parents after operation and so trans-
mitted to the germ. Brown Sequard has signally over-
come this objection by showing that epilepsy is not
produced by all nerve sections but only by some, and
that further it can be provoked also by the simple crush-
ing of the sciatic nerve without any breaking of the skin,
and this would exclude the possibility of any infection
whatever.

Nevertheless it is necessary to recognize the fact that
these experiments, while they undoubtedly demonstrate
the inheritance of the effects of certain lesions, are not
enough to produce a firm and general conviction of the
inheritance of acquired characters among the numerous
naturalists and biologists who are in no wise blind fol-
lowers of Weismann’s theories; perhaps because what’
is inherited in these cases is always somewhat morbid
and abnormal. In short the determination of the ques-
tion requires certain proof of the inheritance of definite
normal peculiarities acquired by functional adaptation.

We see then, that whoever proposes systematically
to hunt out a weak point in every fact adduced in support
of the Lemarckian principle, by which its value as proof
can be shaken, can usually if not always find it. But

*5Brown Séquard: Faits nouveaux établissant l’extréme fré-
quence de la transmission, par hérédité, d’états organiques morbides,
produits accidentellement chez des ascendants. Comptes Rendus de
VAcad. der Sciences. T. XCIV, No. 11, March 13, 1882. P. 697—700.

The Non-inheritance of Amputations 169

this would justify the assertion that the inheritance of
acquired characters has not yet been directly proven, only
in the case that there were but a few facts or only a
single fact that could be brought forward in proof of
it. But when on the contrary there are a very large
number of facts favorable to a given principle, even
though each one of them by itself would not be an
absolutely incontestable proof, they would in spite of
that have, when taken as a whole, a very great value
as proof, and this value would be so much the greater
if the opponents of the principle, in seeking to deny the
incontestability of the individual facts, are forced to
resort to as many specially devised subtleties.

On the other hand the non-inheritance of certain
gross instantaneous modifications, such as amputations
and other similar things, of which Weismann and his
followers make so great a case, proves nothing against
the inheritance of functional adaptations which are of quite
different nature.

For let us consider the dynamic equilibrium existing
in the adult state in a given small portion of the soma,
and let us suppose also that this equilibrium was estab-
lished by a process of epigenetic nature dependent upon
all the rest of the organism. If this local equilibrium
is suddenly very much disturbed as is the case in
amputations, instead of gradually and slowly as in
functional adaptations, one can understand that it can
and must be promptly restored in the neighborhood
of the wound or in any case in the limited area of
the stump, before the disturbance has time to extend
much farther. Therefore if there is a definite place
in the organism to which non-transitory derangements
and the variations of equilibrium caused thereby must

170 Inheritance of Acquired Characters

penetrate if the corresponding morphological modification
is to be inheritable, it follows that amputations, unlike
functional adaptations, could not as a rule leave any
trace of themselves in the descendants.

But in still another very essential point amputations
are different from functional adaptation. The ampu-
tation of a limb, or of a piece of a tail, does not con-
stitute in any way the mode of reaction of the organism
to a definite external influence, but rather it is this
external influence itself. How then will its reproduction
in the new organism be possible? This would be the
same thing as expecting that an individual who had
been accustomed throughout his life to bear a burden
upon his shoulders as exercise, should transmit to his
son not only stronger bones and muscles but also the
burden itself which was the cause of this strengthening.

So that the most that could be transmitted to the
descendants of an animal which had undergone some
amputation, would be the mode of reaction of the organ-
ism to this gross external influence, that is all the phe-
nomena constituting the cicatrization, properly so called,
of the wound, as well as the establishment of a new local
equilibrium. We must however bear in mind in this
connection that the reproduction in the child of con-
siderably thicker and stronger bones and muscles will
not be hindered by the fact that it is not exposed to the
same external influence which acted upon the parent,
i. e. by the fact that it does not bear the same burden
as its father, but that if one does not also repeat the
amputation, the repetition of all the phenomena con-
stituting the cicatrization of the wound and the reestab-
lishment of a new equilibrium could not but be very
much hindered and usually quite prevented by the pres-

The Decisive Experiment 171

ence of the limb or other part of the body which was
destroyed in the parent.

In order to make this more apparent let us con-
sider some one of the numerous rats from which
Weismann cut off the tails, and which that author has
rightly brought forward as proving that the surgical
operation of amputation is not inherited. Let us sup-
pose that in the young rat when once his development
was completed and he had arrived at about the age at
which the old rat had undergone the amputation, really
showed at the spot at which the amputation took place
a tendency to reproduce the same phenomena of cicatri-
zation and reestablishment of the new local equilibrium
which had supervened in the parent. It is evident that
the absence of the tail is a necessary condition in order
to make the reproduction of these phenomena materially
possible. This tendency must then be hindered and per-
haps absolutely suppressed so long as the tail remains a
part of the organism.

It is interesting in this connection to note that Kohl-
wey has obtained in one and the same individual a com-
pletely negative result in respect to the inheritance of
mutilations, but a positive result in respect to the trans-
mission of habit: He cut off the posterior digit from
the feet of some pigeons which thereupon turned back
another digit in order to retain their perch; and in one
instance this habit was reproduced.'**

The decisive experiment upon the inheritance of ac-.
quired characters must leave amputations and similar
sudden variations out of consideration, since either their
effect is to bring about the reestablishment of an exclu-

18017 Kohlwey: Arten und Rassenbildung. Eine Einfithrung in
das Gebiet der Tierzucht. Leipzig, Engelmann, 1897, P. 6—7.

172 Inheritance of Acquired Characters

sively local equilibrium or the repetition in the
descendants of the phenomena by which the parent
organism reacted is hindered. This experiment must
rather be directed toward modifications of the functional
adaptation, wihch have a very extensive action and whose
repetition in the descendants is not hindered by anything.

In order that these experiments on the changes
dependent upon functional adaptation may constitute an
incontestable proof for or against the inheritance of
acquired characters,—which latter are to be understood
in Weismann’s sense as only somatic and not general
peculiarities of the entire organism,—they must be
planned in such a way as to make it certain that the
change effected by the transforming influence has affected
only the soma directly, and for still greater certainty it
ought to act upon only a definite part of the soma
and not upon the entire soma to the same extent. They
must also be undertaken on pluricellular organisms in
which the somatic germ cells are clearly differentiated,
and there ought to be employed as transforming influ-
ences only such as certainly exert no direct influence upon
the reproductive cells.197

All plants in which the difference between somatic
and germ cells is not a thorough going and definite one
will therefore be less suitable for these researches than
animals, and particularly higher animals, and all such
investigations both in animals and in plants which em-
ploy physical or chemical transforming agents exerting
a general action on the entire organism, on the somatic
cells as well as on the germ cells, as for example tem-

7Compare J. De Meyer: L’hérédité des caractéres acquis est-
elle expérimentalement vérifiable? Archives de Biologie. Tome XXI,
No. III and IV. Paris, Masson 1905, P. 625, 634—639.

The Decisive Experiment 173

perature, light or darkness, particular substances that are
nutritive, stimulating or poisonous, infections, immuniza-
tions, etc., could never afford such incontestable evidence
against Weismann’s theory, as those investigations which
employ agents having a very definitely localized action.
Thus for example Heschenhagen’s researches upon
the adaptability of the lower fungi to sodium chloride
have, for the reasons stated, little or no value for the
refutation of Weismann’s theory, even though they have
proved that the spores of the mycelium which had
adapted itself to a strongly concentrated saline solution
were capable of germinating in concentrations in which
the spores of a mycelium arising in normal conditions
were incapable of germinating. The same is true for
the similar researches carried on by Hunger-Errera,
DeMeyer, Pulst and Ray upon the inheritance of changes,
mostly physiological rather than morphological in nature,
which were brought about in the lower fungi by means
of concentrated salt solutions, for example by sodium
chloride or copper sulphate or concentrated sugar solu-
tions, although these results as well as Heschenhagen’s
are certainly very interesting from the point of view of
the adaptability of organisms to their environment.
Also Hoffman’s researches upon the inheritance of
variations produced by insufficient nourishment in
Papaver, Migella, and Argemone,—(a relatively large
number of atypical flowers) ,— and Schubeler’s researches
upon the inheritance of the more rapid development of
barley grains which had been transplanted from the south
part of Norway to the north part, prove incontrovertibly
the inheritance of the changes induced in organisms
through general conditions in their environment, but the
general influences very probably exerted in those cases also

174 Inheritance of Acquired Characters

by the selected transforming agent upon the whole organ-
ism, and our entire ignorance of the real nature of its
peculiar action, deprive these experiments of any value
as arguments against the theory of Weismann which
denies the inheritance of any peculiarly somatic char-
acters that have been acquired by means of local func-
tional adaptation to external influences that are very
definitely and clearly limited.

Just as little valuable as proof against Weismann’s
theories were the researches of Standfuss, Fischer, and
Bachmetjeff on the inheritance of changes in the color
design of butterflies’ wings, when the pupae concerned
were placed in an unusually high or low temperature,
so that Weismann, as we shall see further in the next
chapter, could acknowledge the otherwise unimpeachable
results of these researches without thereby being com-
pelled to retrench his own theory.

It would be best therefore to employ mechanical
means, and to produce changes whose mode and place
of working can be easily observed and definitely limited.
But amputations are to be excluded for the reasons
given, as are also sudden transformations, and so there
remains as the experiments best adapted for the final
decision of this disputed question, prolongation or fre-
quent repetition of the activity of certain organs or
definite parts of organs.

We might suggest for example the artificial and
therefore extraordinarily frequent extension or contrac-
tion of the muscles of the fore or hind legs of a certain
animal, such as could be effected in little amphibia or
little mammals with the help of an especially devised
clock work. Prolonged traction on the tail of the rat
leading to its elongation and growth should be substituted

The Decisive Experiment 175

for Weismann’s amputation which can prove nothing.
Similarly light hammering, continually repeated, which
a proper mechanism might automatically perform upon
certain parts of the skull of hornless animals, would be
better than cutting off or breaking the horns in horned
animals,

All these artificial stimuli would certainly produce in
each individual the hypertrophy of the organ upon which
they act. It could then be seen whether the repetition of
these stimuli throughout a series of generations would be
followed by the production of individuals in which these
organs would possess at birth even in a small proportion
the greater development that had been acquired in several
successive generations of its ancestors. The performance
of such experiments upon guinea pigs or rats would not
seem to present very great practical difficulties; never-
theless, so far as we know, it has never yet occurred to
any one to make them or to propose them.

But in all these experiments one must never forget
that it is just the littleness of the inheritable fraction of
an acquired quantitative variation, that constitutes the
great difficulty of verification of the Lamarckian principle.

Galton proposes as is known to select for experi-
ment rather the inheritance or non-inheritance of certain
acquired instincts. He advises for example to adopt the
method of the following experiment of Mobius upon the
pike; Mobius divided a large glass receptacle into two
compartments by means of a perfectly transparent glass
septum and placed the pike in one compartment and in
the other little gudgeons upon which the pike usually
feeds. It followed that whenever the pike precipitated
himself toward any of the little fishes he was stopped by
the glass against which he hit. After several weeks of

176 Inheritance of Acquired Characters

useless attempts the pike finally gave up any attempt
to catch this unseizable prey and he persisted in this atti-
tude even after the glass had been removed. Now Galton
advises repeating this same experiment on several genera-
tions of pikes, taking care that each generation should
always be brought up apart from the preceding to prevent
any possibility of the educative influence of imitation,
and seeing if one would finally obtain any descendant
in which the instinct to throw himself upon the gudgeons
would be replaced by the contrary instinct of indifference
toward them.1%8

We should remark in this connection that because
one is here concerned with establishing the transmission
of an acquired instinct that is opposed to the inborn
instinct, experiments of this nature are less advisable
than those which seek rather to verify the inheritance
of a simple quantitative increase acquired by already
existing organs or tendencies. In Galton’s experiment
the tendency of the descendants to produce the new in-
stinct even if it were present through a long series of
generations, might not possess sufficient potential energy
to enable it to manifest itself through activation because
it would have to overcome a pre-existing tendency which
in the beginning at any rate is certainly furnished with
a greater quantity of potential energy. Therefore it is
probable that it would be necessary to submit a very long
series of generations to this experiment of the glass par-
tition before the new tendency would be able to attain
a superiority over the former and to replace it. The
first pike upon which Mdébius made his experiment

138Galton: Feasible Experiments on the Possibility of transmit-
ting acquired Habits by Means of Inheritance. Paper read at the
British Association. Nature, October 17, 1889. P. 610.

Weismann’s Arguments Against Inheritance 1 77

furnishes us itself a proof of this. For from the first
impact against the glass partition the inclination con-
trary to its instinct must have commenced to arise;
nevertheless it effected the replacement of the latter
only after a large number of unavailing attempts.

From all that we have said thus far it follows that
it is much to be desired that new and absolutely incon-
testable experiments should once for all finally place the
inheritance of acquired characters beyond a doubt. But
it also follows, as we have said, that if no one of the
proofs which we possess already demonstrates this in-
heritance in an absolutely certain way, nevertheless all
together they supply a great weight of evidence for it.
As we shall see later this is true also of indirect proofs;
one cannot say of any one of them that it decides the
question in one way or the other, but all together
they constitute a strong presumption in favor of the
Lamarckian theory.

It will be convenient to examine next the chief argu-
ments which Weismann has adduced against this theory.
They can be reduced in substance to the following:

1. “In many animals,” he writes, “for instance in
many insects, instincts appear which are exercised only
once during life. It is sufficient to cite the laying of
eggs by ephemerids and many butterflies, the conjugation
of bees, the search for proper hiding places in which
caterpillars may change into chrysalids,—one species
suspends itself, another lying on the ground builds de-
fences, a third goes deep into the earth, a fourth spins
itself a case in a rolled up leaf, and so on, and so on.
Further there belong here the several species of cocoons
which some butterflies, especially the bombycids, spin
in a fashion so astonishingly complicated and so well

178 Inheritance of Acquired Characters

adapted to its purpose, a thing which each individual does
only once and from the most ancient times has done
only a single time in all its life.” °°

2. The second group of facts controverting the
inheritance of acquired characters is furnished, accord-
ing to Weismann, by the parts which have only a passive
function, “in so far as they show that they also become
rudimentary and finally disappear if they cease to be
used and are not necessary for the preservation of the
species. They show that the process of disappearance
which the Lamarckians attribute to the inheritance of
the direct effects of non-usage cannot be due to this
cause, since here the organ in question does not exert
any physiological function and so there are of course
no effects of such function in the individual life. To
this category belong for example the colors of animals,
which become unstable when they are no longer needed
for protection or as a means of recognition; here also
belongs the deterioration of the chitinous cuirass of
various crustaceans and insects which thrust one part
of their body into protective envelopes.” 1*°

3. The third argument against the inheritance of
acquired characters is that constituted by the neutral
individuals among bees, ants, and termites which, accord-
ing to Weismann, show that all the adaptations whether
positive or negative, isolated or co-ordinated, that are to
be observed in propagating individuals, appear also in
individuals which do not propagate at all and which
therefore do not transmit anything.1*4

*°Weismann: Neue Gedanken zur Vererbungsfrage. Eine Ant-
wort an Herbert Spencer. P. 61—62.

*°Weismann: Ibid. P. 62—63.

Weismann: Ibid. P. 66.

Consideration of Weismann’s Arguments 179

4. Finally the last argument of Weismann is that
it is incomprehensible how the inheritance of acquired
characters could be effected.1!2

In the endeavor to examine these four arguments
with the most scrupulous objectivity, we must first divide
them into two categories: The fourth is the only one
which attacks the principle of inheritance directly; the
first, the second, and the third, on the contrary, con-
trovert this theory only indirectly, in that they seek to
show that many formations are of such a nature or
arose under such circumstances that they can be explained
only by the theory of natural selection. The conclusion
which it is desired to have drawn from this is clear, and
is indeed admitted: If natural selection is capable of
explaining some formations it will be capable also of
explaining all the others; if all formations can be ex-
plained by natural selection alone, the inheritance of
acquired characters becomes useless for the purpose of
explaining the transformation of species; consequently
if it is useless it is very probable that it does not exist
at all.

The impartial reader will admit that this manner of
reasoning is deceptive. Even if it be proved that natural
selection must necessarily have been capable of producing
certain formations with the help of fortuitous individual
variations, it does not follow that it must also have been
capable of producing all other phylogenetic formations,
especially if they are different in nature from the former.
And even if the proof were forthcoming that it is capable
of explaining by itself all phylogenetic formations what-
ever, it is evident that even this would not constitute

142Weismann: Ibid. P. 61.

180 Inheritance of Acquired Characters

any argument against the inheritance of acquired char-
acters. The continuous electric current for example can
be produced by a battery as well as by a dynamo; and
the fact that one can always explain it as having been pro-
duced by a battery does not prevent it from being actually
produced by a dynamo in many cases.

This being so, let us now examine as succinctly and
objectively as we can each of the four arguments:

1. No value can be attributed to the fact of the
exercise of a function only a single time during life.
In the first place, it is possible that it may formerly have
been exercised repeatedly by the ancestors of individuals
now living. In the second place this singleness does
not exclude in any way its inheritance as a habit acquired
by exercise. For the fact of having performed a given
function even though only a single time, would certainly
leave in the parent organism a potential disposition to
perform it again and with greater facility in similar
physiological and external circumstances; therefore
the conception that this disposition and this greater
facility would be represented in descendent organisms

represents only an ordinary case of inheritance.

2. As for the second argument one cannot but
recognize that for certain formations the statement of
Weismann that they can be due only to natural selection
seems very probably true.

But it must be remarked that to support his assertion
Weismann attributes a merely passive function to many
parts in which it is very questionable.

Why for instance should we not regard the carapace
of the turtle as a true and functional adaptation due to
the stimulus of the environment to which the skin of
the animal had reacted by a secretion constantly richer

Consideration of Weismann’s Arguments 181

in hard substance, exactly as the skin of the sheep reacts
by the secretion of wool? There is nothing to prevent
such secretions, produced through functional adaptations,
serving later as protective shields and thus becoming
useful to the species in still another way.

On the other hand the envelopes into which the
crustaceans and insects cited by Weismann insert one
part of their body might preserve the external surface
of that part from the hardening action of external agents,
just as houses and clothes may have contributed to the
disappearance of the hair in man. For one should not
consider the passive function of the hair or of the chiti-
nous substance so much as the active function of the
tissues which secrete these substances; and this function
is essentially active for it is a specific reaction to external
influences.

In this respect the hermit crab constitutes one of the
most conclusive proofs of the Lamarckian theory. For
this crab which is accustomed to insert the hinder part
of his body into empty snail shells has completely adapted
itself to the conformation of its new habitation, and this
bodily adaptation acquired by it has become hereditary
so that it is present in advance before the animal inserts
itself into its house. According to Weismann’s view,
the animal must have first adopted the habit and natural
selection must have been able to exert its influence only
subsequently. Clearly both processes must go on at the
same time, the residence in the new habitation and the
adaptation to it; and the fact that these exist together
can be explained only through functional adaptation and
inheritance of its effects.***

1448G_ Cattaneo: I fattori della evoluzione biologica. P. 43—45;

182 Inheritance of Acquired Characters

Similarly, how can one escape attributing the colors
of butterflies’ scales to functional adaptaticn when one
sees the golden red butterfly Polyommatus phlaeas change
its color and take on a black tint merely from transporting
it to warmer climates?

Further, indubitable instances are known in which
the color of the environment stimulates the outer surface
of the animal directly or indirectly to take on the same
color. Thus some arctic animals and birds become per-
fectly white in winter, putting themselves thus in con-
formity with the general color of the environment.
Certain butterflies present phenomena of protective poly-
chromatism in the sense that they always take on the
color of their environment, and this should not appear
strange for there is nothing inadmissible in the sup-
position that a very sensitive skin can suffer much greater
discomfort when the light rays which strike it are of a
color different from its own than when they are of a
like color with it. This discomfort would correspond
to the disagreeable sense of heat or cold which makes
itself felt over the surface of the body when its tem-
perature difters from that of its environment.

Consequently if every functional adaptation of the
living substance to external agents consists in such a
modification of its own vital processes that these find in
the external agents no longer obstacles but rather co-
operative stimuli, one can understand the tendency of
every especially sensitive organ to make the color of
its surface conform with that of its environment. This
would not prevent the identity of colors from being of

and Cesare Lombroso: Ancora dei caratteri acquisiti; Paguri, Cam-
melli e Zebu. Rivista di Scienze Biologiche, Vol. II, No. 3. 1900.
P, 2—3.

Consideration of Weismann’s Arguments 183

service to the animals in a protective way also, but never-
theless the productive cause would remain always a
functional adaptation.

From the preceding instances in which the action of
the color of the environment upon the external surface
of the animal appears to be direct we pass on to those
in which this action is indirect. Thus many fishes,
amphibians, reptiles and cephalopods are capable of
changing their color in a very short time and thus of
putting themselves always in accord with the very vari-
able color of the environment. The color of the environ-
ment which determines that of the animal does not act
nevertheless, in this case, directly upon the elements of
the skin, the chromoblasts, which produce the color; but
by a complicated nervous apparatus connecting these
elements with the part which is first stimulated by the
color. This part is sometimes constituted merely by
the nerve ends of the skin, at other times by the retinal
nerve ends of the eye. In the latter case if the optic
lobes of the brain are artificially destroyed the capacity
of changing color disappears.’**

Further, according to LeDantec, many colorations of
the skin that are now fixed and correspond to the hence-
forth unchanging color of the environment are derived
from former colors that changed voluntarily with the
different colors of the environment, of which one certain
color has remained, persisting to the exclusion of all the
others.**°

One could perhaps also adopt the opposite view. Just

“4Weismann: The Effect of external Influences upon Develop-

ment. P. 26—27. ; :
457 @ Dantec: Lamarckiens et Darwiniens. Paris, Alcan, 1904,

Chap. XIV: Le mimétisme lamarckien. P. t29—149.

184 Inheritance of Acquired Characters

as the secretion of gastric juice was originally a func-
tional adaptation of the wall of the stomach to certain
foods but finally is poured out before the foods them-
selves are ingested but only tasted, in consequence of
psychic associations; so the assimilation to the color of
the environment, which originally was a functional
adaptation of the elements of the skin producing the
color, the chromatophores, may have gradually come to
be produced in anticipation and finally exclusively by
the perception through the eyes of the color of the
environment.

However that may be, all these facts show that far
from seeing in the protective colors of animals merely
the result of fortuitous variations which have become
fixed by natural selection just for their passive protective
function, we have legitimate reason for holding on the
contrary that usually they are the direct result of true
functional adaptation.

In this way would be explained the possibility that
as soon as the color of the environment alters, the pro-
tective color of the animal might also become unstable
or disappear entirely, and one would not be compelled
to resort for the explanation of the phenomenon, as
Weismann is, to panmyxia or to any other complicated
process of natural selection. For this tendency to give
up the color can in this case also be attributed to the
simple circumstance that when the color of the environ-
ment was altered the functional stimulus ceased, which
was the sole cause of the color of the animal.

It is true that Weismann points out certain cases
of more typical mimicry which seem to prove the cor-
rectness of his views very especially because they seem
to show that natural selection had undoubtedly been

Considcration of Weismann’s Arguments 185

alone sufficient to produce in some instances extraor-
dinarily complicated formations down to the most minute
peculiarities. The example of Kallima, a well known
leaf-like butterfly, will at once occur to every one. Never-
theless it is known that certain Lamarckians have had
the hardihood to wish to attribute these very perfect
resemblances to former, voluntary, chromoblastic, mime-
tic changes which do not now exist in the animal but
which can be demonstrated even now in certain other
animals, for instance in some fishes. The absence of
change in the object taken as a model which was imitated
only voluntarily at first, has resulted in the gradual with-
drawal of the imitative color mechanism from the con-
trol of the animal’s will4® Here it is sufficient to
remark that the last word has certainly not yet been said
upon this voluntary mimicry which rightly excites the
greatest interest. In any case such imitative formations
as that of Kallima cannot be disposed of by simply refer-
ring them to natural selection alone, seeing that their
protective utility can commence to be manifested only
after they have attained an advanced degree of perfection.

“A muscle,” insists Weismann, “can become greater
by use, but a claw, a bristle border, a dentition, a pro-
tuberance at an articulation, cannot become thicker,
longer or stronger by usage, it can only be used up.” 147
But does not the very use of these inactive parts or,
better, the transmission through the inert substance to
the living substance of the mechanical action constituted
by this repeated use, provoke the living tissue to secrete
in larger quantity the chitinous substance of the bristles
and of the claws?

1467 @ Dantec: Lamarckiens ct Darwiniens. P. 142—145.
“Weismann: Neue Gedanken zur Vererbungsfrage. P. 65.

186 Inheritance of Acquired Characters

“IT need not recall,” continues our author, “the host
of positive changes undergone by plants which cannot
be explained by the Lamarckian theory,—the appropri-
ately placed protective spines, bristles and hairs, the
poisons, the tannins, the etherial oils of all kinds, and
all the purposeful forms of leaves, of flowers and all
parts of plants in general. In the case of all these the
supposed inheritance of the effects of use and disuse
in general does not come into question; in them every-
thing proceeds without it,—an incontestable proof that
nature does not require this supposed factor for its trans-
formations.” 148 It is probable on the contrary that
many of these changes undergone in the past or in the
characters now existing are rather simply the result of
the reaction of the plant organs to a certain external
or internal stimulus which has not yet been remarked
nor indeed suspected. To this category belong very
probably, for instance, all the various secretions of
chemical substances. Further the very fact that secre-
tions that are entirely alike occur in plant species that
are quite unlike one another in everything else, speaks,
as we shall see at once, in favor of the hypothesis that
these same secretions are acquired and inherited char-
acters. Other characters which likewise were formerly
in all probability functional adaptations or are such now
can incidentally serve other purposes and can therefore
be useful to the species in other ways also, as we stated.

It is evident that Weismann, in order to support his
assertion that natural selection is quite capable of ex-
plaining by itself the transformation of species, has
allowed himself to be misled into denying arbitrarily

“®Weismann: Neue Gedanken zur Vererbungsfrage. P. 66.

Consideration of Weismann’s Arguments 187

to a large number of modifications, which do not differ
in their essence from the others, the character of func-
tional adaptations. We would not deny that there are
certain forms or structures, which, just because their
functional character has not been perceived, have not
heretofore received any explanation except through nat-
ural selection, even though it does not always furnish
an altogether satisfactory explanation. But the deeper
one goes into the essence of functional adaptation and
the wider its field of action is seen to be, the number of
these formations become less and less and with it
dwindles away also this seeming almightiness to explain
all physiologic transformations whatever, which Weis-
mann would like to attribute to natural selection without
producing proof for it.

3. The third argument based upon the neutral indi-
viduals of ants, bees and termites is well known as the
chief question about which turned the polemic between
Weismann and Spencer. The latter brought up as one
of the strongest arguments in favor of inheritance, the
co-adaptation, that is the co-ordinated modification of
different parts co-operating to produce a definite physio-
logical result. Weismann on the contrary sees in the
existence of neutral individuals among the ants, termites
and bees a refutation of Spencer’s theory, since these
individuals in the course of their phylogenetic develop-
ment have undergone harmonious modifications of di-
verse parts, without ever having been capable of repro-
duction. To this Spencer replied that all the harmonious
modifications of different parts, including the numerous
instincts which the neutrals present to-day, are only the
heritage of those which the ancestors of these now social
insects acquired in a state of isolation or in a society in

188 Inheritance of Acquired Characters

which there was equality and in which there were no
castes, the neutrals being nothing else than females
incompletely developed because of defective nutrition.

It would not be correct to state that the question
has been finally decided through this debate. While
Weismann has not been able to prove conclusively that
these harmonious modifications of the neutrals have been
at least partially acquired after the development of castes
and when the sterility of the neutrals had already
appeared, neither has Spencer been able to demonstrate
that all these harmonious modifications had been already
acquired by the presocial ancestors. Nevertheless the
conception of Spencer that the neutrals are produced by
an arrest of development of the females has in our
opinion won a decisive victory over that of his opponent,
and has in reality taken from the last rampart of the
Weismannists all the strength which it had derived from
the conception that the neutrals were special formations,
which had acquired special characters by fortuitous vari-
ations and natural selection only.

4. The fourth and last argument, that of the incon-
ceivability of the transmission of acquired characters, has
already been considered by Darwin in connection with
examples which he had himself communicated of the
inheritance of certain peculiarities, particularly of instincts
acquired by domestic animals. “Nothing in the whole
circuit of physiology,” he stated in this connection, “is
more wonderful. How can the use or disuse of a partic-
ular limb or of the brain affect a small aggregate of
reproductive cells seated in a distant part of the body,
in such a manner that the being developed from these
cells inherits the characters of either one or both parents?

Consideration of Weismann’s Arguments 189

Even an imperfect answer to this question would be
satisfactory.” 149

This argument which Weismann considered as the
strongest, without indeed saying so definitely but allow-
ing it to be seen, is in reality the feeblest of all. Even
admitting that the mechanism of transmission may be
at present quite inconceivable, that is no reason for believ-
ing that it does not exist, since the number of phenomena
and even of natural laws which we must regard as cer-
tainly established, even though we cannot so far explain
them in any way is, one can well say, infinite. It recalls
the former objection to Newton’s theory that it is incon-
ceivable how the heavenly bodies could mutually attract
one another at such a distance, and like this it is of no
logical value. Apart from this it can have only one
very important practical consequence, (and it has had
this effect and as a matter of fact is still producing it),
i. e. of bringing the reality of this inheritance into ques-
tion with very many investigators and stimulating them
therefore to a zealous search for a conclusive experiment
which should once for all establish or exclude it.

In any case it is interesting to note that Nussbaum
whose theory of the continuity of the germ cells sug-
gested to Weismann his fundamental conception of the
continuity of the germ plasm, is opposed to him in that
he does not exclude the possibility of the transmission
of acquired characters. For immediately after the expo-
sition of his theory he states “since seeds and eggs are
stored up in the parent organism, they are therefore
subjected to the action of conditions which bring about

149Warwin: The Variation of Animals and Plants under Domes-
tication. H. P. 367.

190 Inheritance of Acquired Characters

modifications of it, and so the transmission of acquired
characters is not excluded.” °°

After thus having brought forward and refuted the
four principal arguments adduced by Weismann against
the Lamarckian theory, we must now examine the value
of the corollaries and subsidiary theories which this
investigator devised to defend his doctrine from the mani-
fold objections which were brought forward from all
sides to show its inadmissability.

Panmixia presents itself as the first subsidiary
theory. It has entirely succumbed. It was devised by
Weismann to explain the progressive phyletic atrophy of
the organs which have become useless, and rests on the
supposition that as soon as the fortuitous variation of a
certain organ has become useless for the species, and is
therefore withdrawn from natural selection, the minus
variations which this organ would chance to present in
certain individuals would no longer cause the disappear-
ance of these latter in the struggle for existence. The
survival of organisms with such minus variations and
their sexual union with individuals which still preserve
the organ in its original state would lead gradually to
the degeneration, progressive atrophy and final disappear-
ance of the organ.

Spencer, nevertheless, rightly draws attention to the
fact that the appearance of plus variations is just as
probable as that of minus variations, and therefore pan-
mixia is not at all capable of explaining by itself this
progressive and continuous degeneration of useless
organs.

**°Nugbaum: Zur Differenzierung des Geschlechts im Tierreich.
Arch. f. mikr. Anat. Bd. 18. Erstes Heft. Bonn. Cohen. 1880.
P. 113.

Panmixia and the Principle of Economy 1g!

The addition suggested by Romanes that the tendency
to atavistic reversion favors minus variations at the
expense of plus variations, does not suffice! For in
the first place an atavistic reversion could appear at best
only in the phyletic characters acquired last, and in the
second place, after the first stages of atrophy had ap-
peared it would in any case tend from that time on to
insure the preponderance of plus over minus variations.

One could nevertheless assert that panmixia is not
necessary for Weismann’s theory. The principle of the
economy of the organism by which every useless and
unused organ is harmful because it withdraws nourish-
ment from other organs is by itself enough, if one
rejects the inheritance of acquired characters, to explain
the gradual phyletic disappearance of useless parts.

But this hypothesis is easily refuted by some calcula-
tions of Spencer, showing that it is impossible that the
advantage to the organism of a small inborn and fortu-
itous minus variation in the useless organ, particularly
when this is already very much degenerated as is for
instance the hind leg of the whale, can procure for the
individual an advantage over others and so provoke the
phylogenetic passage to a yet greater atrophy. And no
great value can be attributed to the counter observation,
which Weismann several times repeats, that we are still
quite unable to measure the selective efficacy of the
struggle for existence. One need think only of the
parasites and particularly of the endoparasites, which
have always an excess of nutrition and in which there-
fore the advantage of the degeneration of useless organs
would become reduced absolutely to zero. And it is

181Romanes: A Note on Panmixia. Contemporary Review. Octo-
ber 1893. P. 612.

192 Inheritance of Acquired Characters

nevertheless in these that this reduction reaches its
maximum.

However that may be, we might nevertheless admit
either that, as panmixia supposes, fortuitous minus
variations preponderate over plus variations, or that the
principle of the economy of the organism is alone enough
to secure the victory to those individuals whose useless
organs are most atrophied. But, even in that case how
could panmixia and the principle of economy in the
organism explain the fact that the atrophic state of
organs which have become useless, such as appears in
adult organisms, results in the course of ontogeny from
an involutive process of these organs which are better
developed in the early stages than in the later stages?
Although in so doing we anticipate a question which we
shall examine again later in all its generality, we may
note here that the most that panmixia and the principle
of economy could do would be to explain the fact that
the more recent a species with a given atrophied organ
is, the earlier should be the stage of development at
which the organ in question is arrested in ontogeny,
whereas in the ancestral species it attained a greater
development. But how can they explain how certain
tissues and organs develop during ontogeny up to a
certain and fairly advanced point and thereafter at a
certain moment undergo a physiologic involution result-
ing in their degeneration and often in their complete
disappearance ?

As we pass on now from continuous, gradual atrophy
of useless organs to the slowly progressive formation of
useful organs and so to phyletic evolution in general, we
must declare at the outset that of all the objections that
have been urged and which can yet be urged against the

All Sufficiency of Natural Selection 193

view that natural selection by itself is sufficient to account
for the transformation of species, we shall bring forward
only a very small number. For we believe it worth
while to limit ourselves to the most characteristic and
certain ones, which serve better than the others as an
indirect support for the Lamarckian theory. And so
much the more since in the case of many objections dis-
cussion is idle. For—and this may be said once for all
—if our adversary adopts the complete sufficiency of
natural selection both as his thesis and as the ground
for the defense of this thesis, naturally it will be very
difficult, indeed, often quite impossible for us to carry
on the contest from a purely logical standpoint.

Candidly one could wish that Weismann would prove
this omnipotence of natural selection by some facts. But
he has still to furnish this proof. For, as we have seen,
he has limited himself to showing that among the various
hypotheses which have been devised to give account for
certain special formations, natural selection is the one
which fulfills this purpose relatively best.

But when once our adversary sets up this almighti-
ness of natural selection as an axiom, to be employed
at need as thesis or as the support of the thesis, it will
then be very difficult, we repeat, in most cases to point
out any contradiction in his tenets, which is the only
means by which a logical refutation can proceed and
reach any result. In other words, if in order to demon-
strate the complete sufficiency of selection Weismann
starts off with the supposition that natural selection is
omnipotent, how can one by pure reasoning convict him
of error?

And in fact: One investigator offers the objection
that fortuitous variations even though they are useful

194 Inheritance of Acquired Characters

must nevertheless in many cases be so inconsiderable
in amount, that they could not possibly constitute such
an advantage as to give natural selection anything to act
on. But Weismann in order to extricate himself from
this embarassment needs only to repeat here again his
habitual, axiomatic, already mentioned reply that we
are unable to measure the degree of selective power of
the struggle for existence.

Others object that certain characters due to functional
adaptation are altogether useless to the species. One
can conceive how they might be inborn in individuals
if one admits the inheritance of acquired characters,
whereas they would be quite inexplicable if one sought
to ascribe them to natural selection alone. But Weis-
mann has always the answer at hand that one cannot
judge of their present or past usefulness. A _ typical
example of these discussions which logical processes are
powerless to decide is the question debated in the Spencer-
Weismann polemic upon the especially acute taste sense
of the tongue papillae. While Spencer attributes it to
the continual rubbing of the tongue against the teeth
and states that it is without utility for the organism;
Weismann on the contrary asserts that it may have been
of some use, at least in the past. We do not forget in
this connection that the question might also be raised
whether this fine sense of taste is really inborn or is
not rather acquired anew in each individual after birth.

Others regard natural selection as powerless to bring
about any transformation because the fortuitous vari-
ations or individual deviations, upon which it is able to
act, are constantly destroyed by amphimixis. Weismann
can always reply that the fortuitous variations or devi-
ations preserved in an individual by natural selection are

Amphimixis and Nutritive Irregularities in Germs 195

not prevented from passing to descendants by the con-
jugation of this individual with others which do not
possess any such variations, but are only diluted, so to
speak. Therefore all that is necessary is to suppose the
struggle for existence to be more severe or to have a
higher degree of selective capacity than that which would
have been sufficient if there had not been sexual repro-
duction.

It is well known further that Weismann, in order
to afford natural selection abundant and never failing
material upon which to act, has made for himself a
weapon of sexual reproduction, attributing to it a great
fruitfulness in the constant production of new variations.
But he seems to have been partly converted finally to the
opposite view of the Lamarckians already mentioned,
that sexual reproduction only contributes to securing the
unity and constancy of the species. For, in order to ex-
plain the production of a lot of fortuitous variations,
he finally sought refuge in the unavoidable irregularities
of nutrition in the germ plasm,)®? a thing which makes
his hypothesis upon the biologic function of amphimixis
quite superfluous. It may be merely noted here that when
once one sees in amphimixis a cause tending toward the
levelling of individual characters and consequently to-
ward the fixity of the species, and thereby reducing by
so much the probability that the selective capacity of the
struggle for existence is alone sufficient, one must then
feel so much the more strongly the necessity of discover-
ing some cause of variation capable of acting simul-
taneously and in the same way upon at least quite a
large part of the individuals of the species, and of

182Weismann: Das Keimplasma. P. 541—570.

196 Inheritance of Acquired Characters

acting also in this same direction throughout a decidedly
large number of successive generations.

“One must admit,” says Hartmann, very rightly,
“that minute and purely accidental variations even if
they are useful, are unable to preserve themselves from
disappearing again through crossing. Whatever is to
be preserved must, as Darwin also admits, appear in a
certain quantity, either all at once or successively, because
the number of similar variations must be sufficient to
overcome the suppression through crossing. But it is
not to be expected that similar variations will appear in
such frequence by chance, but only as a result of definite
external or internal causes which set a definitely directed
modification in the place of accidental ones.” 153

Of the causes of variation which possess this capac-
ity of simultaneous similar and constant action, we know
at present only functional adaptation aided by the inher-
itance of acquired characters.

The very fixity of many species has been rightly
urged against Weismann. Natural selection in fact,
because of the smallness of fortuitous individual vari-
ations, is forced, on the one side in order to explain by
itself the development of species, to fall back upon an
excessively great degree of selective capacity; but on
the other side if this great degree of selective capacity
is accorded, it encounters still greater difficulty in account-
ing for the contrary phenomenon presented by a host of
other species which have remained unaltered even dur-
ing a whole series of long geologic periods,

The Lamarckian theory does not find any special

*°Eduard von Hartmann: Die Abstammungslehre seit Darwin.

Annalen der Naturphilosophie, herausg. v. W. Ostwald. Zw. Bd.,
Heft. III. Leipzig, May 26, 1903. P. 280.

Transformations Due to Environmental Changes 197

difficulty in this. If tie true provocation to alteration
comes from the environment and not from natural
selection, the evolution of certain species and the con-
stancy of certain others may be explained simply by the
respective alteration or stability of their environment.

The alteration of the environment could be brought
about in the case of a given species not only through
natural telluric changes but also for instance by the
migration of this species toward other regions, or by the
immigration of other species into its territory, often
also by the overcrowding of its territory by the species
itself.

Emigration as a cause of variation of environment
does not need to be illustrated by examples.

The immigration of other species can immediately
induce a very considerable modification of the environ-
ment. The immigration of a bird of prey with rapid
flight will have as a result that the birds for instance of a
certain native species are compelled to fly more rapidly
in order to escape it. This repeated greater effort will
develop an increase of their swiftness, an increase which
would not have been attained, we must believe, by normal
daily exercise. For the normal exercise of a given
function after the respective organ has once been formed,
does not develop it any further but merely causes it to
preserve the degree of development already attained. In
this way one can readily see also that if the region
ravaged by the bird of prey is only one part of the
whole territory inhabited by this aboriginal species, one
portion only of that species will be forced to become
transformed into a swifter variety while the remaining
portion can and must remain unaltered.

The overcrowding of a given territory by a given

198 Inheritance of Acquired Characters

species can not only force this species to emigrate, or at
least to widen its range of habitation, thus placing
itself in contact with different telluric conditions and
with different fauna and flora, but also it can itself
induce directly very considerable modifications of the
environment.

Thus, to take an already famous example, it is pos-
sible that the long neck and forelegs of the giraffe are
to be ascribed to the overcrowding of the territory
inhabited by its ancestors. For if we suppose that these
ancestors at a definite time and in a definite region had
become altogether too numerous in proportion to the
trees present whose leaves served them for nourishment,
then all the leaves up to a certain height would naturally
have been eaten first, and there would finally remain only
those leaves situated very high, so that in order to reach
them the animal was forced to stretch out its neck with
a greater effort than formerly and to stand upon its
hind legs, falling later on the fore legs after plucking
off the leaf. And these efforts so very different from the
ordinary would have produced quite new morphological
adaptations. But it is not at all necessary to suppose
that all the individuals of this former species of giraffe
were forced indiscriminately to this transformation. For
many, perhaps becoming accustomed to another diet, could
remain unaltered or undergo transformations of little
importance.

In other cases, on the contrary, that part of the
species which was driven through overcrowding of the
territory to change its diet would be compelled to undergo
the most considerable transformations. This would be
the case, for example, when the overcrowding of a given
tract of meadow land by a species feeding exclusively

Consideration of Weismann’s Arguments 199

on grass and herbs would force some of these animals
to feed on tree leaves, others to become transformed into
rodents and insectivors or to undergo some transforma-
tion of still another kind.

In this connection it is to be especially noted that
just because a large number of the individuals of the
old species will thus have come to seek their nourish-
ment elsewhere, no change will appear in those remaining
behind in the former conditions of nourishment. In
other words the elimination caused by the change in
their habits of the overcrowding individuals from among
the company of the old species will leave the other
individuals of this species, whose number will now be
no longer too great, in the same conditions of environ-
ment as formerly, without any overcrowding and con-
sequently there will not be any further causes provoking
in these individuals also a transformation into another
species.

The change of nutrition will induce then a whole
series of changes in the functions of seeking food, hunt-
ing, fighting, seizing, chewing etc., but only for that
position of the species which has changed its mode of
living. Thus it is clear how, during a series of entire
geological periods, a certain number of the ancestors
of individual species that are now quite different from
them were able to preserve themselves unaltered and
so to reproduce their descendants unaltered to this day.

Man is distinguished from other animals perhaps in
this, that whereas the latter do not modify their environ-
ment or modify it only indirectly and intermittently by
emigration or by overcrowding and consequently make
no progress in their development so long as their environ-
ment undergoes no alteration from one of the causes

200 Inheritance of Acquired Characters

mentioned or from some other accidental cause, man
on the contrary modifies his environment directly and
continuously by the products of civilization. And this
unceasing modification of the environment results in the
unceasing evolution of the man.

It is thus for example with cerebral development.
Civilization itself and the continual progress of science
and arts make steadily increasing demands upon the
brain. And this mental exercise, steadily increasing from
generation to generation, contributes always to the
development of the brain. What wonder then, if the
cranial capacity of man has become markedly increased
even during the three last centuries, as is stated by the
anthropologists ?

Another cause whereby one portion of a given species
can remain unaltered while the remaining portion
becomes transformed, is found, when once the inherit-
ability of acquired characters is admitted, in the sudden
apparition of certain instincts. ‘Also in the domain of
biology,” writes Emery, “and very especially in that
domain, many characters of organisms seem to me to
permit of explanation only by sudden formation. This
is especially true of habits and instincts. How could
the first Velleius dilatatus arrive gradually at its para-
sitic life in the nest of the hornet? The first cuckoo
certainly commenced suddenly to deposit its eggs in the
nest of a strange bird.” 154

The first sudden appearing of a new instinct can be
compared to a happy thought. It is a definite association
of ideas which is formed for the first time. But when
it has once been formed, it is easily possible and indeed

***Emery: Gedanken zur Deszendenz- und Vererbungstheorie.
Biol., Centralbl., July 15, 1893. P. 416.

Appearance and Inheritance of Instincts 201

probable that it will be formed often again in the same
individual, and this repetition will produce a constantly
increasing, corresponding modification of the nervous
tissue in the individual concerned, which will be repro-
duced in his descendants. A new association of ideas
can arise and actually does arise independently, within
certain limits, of the nervous structure of the individual,
and therefore independently of the germ substance also
which has produced this latter, in so far as the fortu-
itous external circumstances which produce this new
association exert a strong and overmastering influence:
Among a thousand individuals, quite identical in regard
to the structure of their nervous mechanism, this new
association of ideas will be developed in only one, on
account of the special external circumstances in which
it happens to be placed.

But without the inheritance of acquired characters
this fortunate new association of ideas, and the repeated
employment of it by the individual later, would be com-
pletely lost for the species. To assure its transmission
from one generation to another there would remain only
imitation or education in the widest sense of the word.
But the fact is that nearly all the instincts are, on the
contrary, truly inborn, that is to say they are produced
without any psychic educative influence whatever.

It is clear also that not all the members of the older
species will be able to make use of a new, fortuitously
developed instinct through educative imitation and later
through heredity, but only the immediate descendants or
associates of the individual in whom it was developed.
All other members of the species would be excluded.
And so those will be the only ones, who, in consequence
of this newly adopted habit, will make a thorough

202 Inheritance of Acquired Characters

change in their former manner of life, and in whom
consequently the whole organism will be modified through
functional adaptation. In this way may be explained
the transformation of only one group of the individuals
constituting a species into a new species, while the others
remain unchanged.

These few examples, even though so briefly outlined,
are nevertheless quite enough to show us that the
Lamarckian theory is capable of explaining at the same
time both the evolution and the fixity of a species. But
how can Weismann account for the inalterability and
constancy of a given species? It goes without saying
that he has no hesitation in attributing it, like variation
itself, to natural selection again. But even if one were
willing to suppose the environment immutable, is it
possible that any species could ever come to such a
degree of perfection in relation to its environment that
every new variation in any direction whatever must make
the conditions of this species worse and make its mem-
bers less likely to be victorious in the struggle for
existence? Is it not much more probable that however
high a degree of adaptation to its environment a species
may have attained, it can always become even better
equipped for the struggle for existence through further
transformations in certain directions, and consequently
offer still greater opportunities for natural selection
which is everywhere and always upon the qui vive?

We must nevertheless be careful, in relation to this
question of the fixity of species, not to attribute to the
arguments which we have just set forth any greater value
than they actually possess, especially because we know
nothing, or only a very little, concerning the immediate
circumstances that have actually existed in the develop-

Adaptations in Tissue Structure 203

ment of even a single species, and still less, if that is
possible, concerning the true mode of procedure of this
natural selection which is so difficult to control. So that
we must content ourselves with putting forward the views
which we have just outlined merely as further con-
jectures speaking in favor of the Lamarckian theory,
without seeking to attribute to them the value of logical
proof.

Structural relations in general and the most remark-
able ones in particular, such as the static structure of
bone, of certain tendons, of certain membranes, the
dynamic structure of the smooth and striated muscle
tissues and other similar formations, which represent the
most perfect functional adaptation and the best utilization
of the material down to the minutest and most delicate
details, testify likewise in favor of the transmissibility
of acquired characters. “All these formations of con-
nective tissue, muscle and bone,” writes Roux, “could
never have been developed in such regularity and com-
pleteness by Darwinian selection from individual varia-
tions of form, since here there must necessarily have
been thousands of fibers and cellules already accidentally
arranged in this purposeful fashion in order to produce
even the smallest advantage appreciable in the economy
and capable of being acted upon by natural selection, and
so much the more since in the extremity of hunger these
would be exactly the parts, the heart excepted, which,
thanks to the small amount of metabolism in them,
would suffer last of all,—much later than other more
vitally important organs with more active metabolism.
These formations could not therefore arise from the
selection of individual variations in form, but are rather
derived only from those qualities of the respective tissues

204 Inheritance of Acquired Characters

to which is directly due the fashioning of the adaptation
even to the smallest details.” 1°

But Weismann could very lightly deny to these very
perfect structural formations any value as even indirect
proof of the principle of inheritance. From his point
of view he needs only to object that since they are useful
to the species they can then be very easily explained by
natural selection alone, and no refutation would be
possible.

Inborn characters have the tendency to become like
those which the ancestors acquired by functional adapta-
tion, and this coincidence speaks also in favor of the
hypothesis of the inheritance of acquired characters. But
against this also Weismann would have no lack of words
and apparent arguments.

Functional adaptation, he could reply, renders the
species more capable of resistance. The greater the
individual disposition to this adaptation the more
rapidly the adaptation will proceed. Consequently those
individuals upon which this disposition is especially
impressed will survive, and above all those individuals
in which this adaptation is already existent potentially

in their germ plasm. Thus the coincidence in question _

could be explained without requiring the adoption of
the inheritance of acquired characters.

In this way one would arrive at the conclusion that
all characters susceptible of being produced by the innu-
merable functional adaptations must for that very reason
be always useful to the species, so that they can be fixed
even when they happen to be actually produced by fortu-
itous inborn variation. We shall not consider this further

**°Roux: Der Kampf der Teile im Organismus. P. 3o.

Similarity of Adaptations in Different S pecies 205

for it would lead us back to the question which Spencer
has raised with his example of the more acute sense of
taste in the papillae of the tongue, and of which we have
spoken above. But apart from that, is it possible for
this argument, however unassailable it may be from a
purely logical point of view, really to weaken the strong
presumption in favor of transmissibility which is derived
from the fact that inborn structural relations always
follow—though slowly and tardily—those acquired in
life through functional adaptation, as the shadow follows
the body?

Another fact among those which speak most con-
vincingly in favor of the inheritance of acquired char-
acters is the similarity of certain structures in different
species which are subjected to the action of the same
mechanical conditions. Without needing to bring up
the most typical and most familiar case, viz., the trans-
formation of the extremities of the whale into fins, it
would be enough to recall as examples the like char-
acter of the leg joints in the two-hoofed animals
(Diplartha, Cope) and the rodents, which is attributed
to their rapid locomotion; the like structure of the
extremity of the radius in the edentates and the quadru-
mana which possess the power of supinating the hand;
the like reduction in number of the digits in many
orders of digitigrade mammals which run about on the
dry hard ground; the like modifications in the form and
development of crests on the skull following like employ-
ment of the canine teeth as fighting teeth in all orders
in which these teeth are strongly developed.***

156Cope: The mechanical Causes of the Development of the hard
Parts of the Mammalia. Journal of Morphology, vol. VIII, No. 2.
Boston, U. S. A., Ginn, Sept. 1899. P. 159—163, 164—165, 175—176,
182—183, 20I—203, 273.

206 Inheritance of Acquired Characters

For if these structures had all arisen through nat-
ural selection only, selecting the most fit from among all
the chance variations, one could not explain how, in
different species, even though they were subjected in
respect to that particular organ to like mechanical con-
ditions, it could lead to one and the same result. In
fact how could one affirm that the structure of any given
organ must be of one certain character only and no other,
in order to render the species most fit for the struggle
for existence? So mere chance must be invoked to
account for the fact that of the numerous structures
among which natural selection could choose, it has
selected in the most different species subjected to the
action of the same mechanical conditions in relation to
only one of their organs, just one single structure for
this organ, absolutely alike for all these different species.

A similar phenomenon, which leads one toward the
same view, is mentioned by DeVries, as already noted,
in support of his theory of pangens or preformistic
germs, representative of definite characters; namely, that
the most diverse species of plants have often the power
of producing a greater or less number of identical chem-
ical compounds. “Insectivorous plants, for example,
belong to the most different natural families, neverthe-
less they all possess the faculty of producing from their
leaves the necessary mixture of an enzyme and an acid
requisite for dissolving albuminous bodies.” 157 Darwin
himself has already remarked that this mixture is quite
similar to the gastric juice of the higher animals.

Now without wishing to touch anew upon the ques-
tion of preformistic germs which we have already dis-

*®71De Vries: Intracellulare Pangenesis. P. 8—10.

Similarity of Adaptations in Different Species 207

cussed, it may merely be remarked here that the existence
of these like properties, acquired in the most different
species, is easier to explain by the Lamarckian theory than
by natural selection. For just as substances exposed, for
example, to identical calorific influences finally all take
on the same degree of temperature, and yet all remain
quite different from one another in other characters,
so when quite different species are exposed, on account
of the environment, or nourishment, or peculiar condi-
tions of light, or of any other cause whatever, to func-
tional stimuli which incite them, for example, to secrete
tannic acids or alkaloids, and so on, these secretions,
acquired by means of functional adaptation and trans-
mitted later by heredity, must come to be present in
several species, even though all other characters can
remain different.

Here it seems to us, there remains for Weismann
nothing else than to affirm that these like characters
may have been fixed by natural selection in the most
different species because, from the likeness of the func-
tional stimuli to which, according to the hypothesis, these
species were exposed, the same characters must have
been the most useful for every one without exception.
But this must first be proved. And so much the more
since in this case it is more difficult than in other cases
to see the absolute necessity that all characters or pecu-
liarities whatever, which are due to the reaction of the
organism to the most different external influences and
often to insignificant ones, must always be useful to
the individual, and that therefore they must also possess
this utility even when they are produced rather by means
of inborn fortuitous variations.

If the soundness of this conception, required by the

208 Inheritance of Acquired Characters

theory of Weismann, of the selective utility of every
inborn character which happens to be a repetition of a
functional adaptation induced by reaction to any external
influence whatever, is very doubtful, and in any case far
from having yet been proved; yet the utility of one part
of these acquired characters is proven and indubitably
established. And indeed it is just from this utility that
one of the strongest arguments against the presumed
non-inheritance of acquired characters is derived.

Since in fact the usefulness of some functional
adaptations to the individual is great and sometimes
extremely great, it must immediately follow from that,
according to Weismann’s view, that the inheritance of
acquired characters is itself the result of natural selection.
For the species in which this inheritance began to mani-
fest itself even though to a slight extent would certainly
have had an advantage over the others, just because the
adaptation to the environment in their descendants could
go on with ever increasing rapidity.

“As modifications acquired by use during life,” writes
Cope, “‘are necessarily useful, it follows that if one accepts
the post-Darwinian or Weismannian theory the only mode
of acquisition of useful variations which we know is
excluded from the process of organic development.”

“Each generation should commence, in the matter
of useful characters acquired by use, at the same point
at which its ancestors had commenced, so that an accumu-
lation or development of these characters would hardly
be possible. The influence of the environment as well
as the energies of the living being would be incapable
of developing in a given generation more than only that
which this generation could acquire during its single life.
How could evolution, then, account for the law, which

Inheritance in Unicellular Forms 209

paleontology has demonstrated in so splendid a manner,
of the gradual modification of certain parts through long
geologic ages toward ideals of mechanical perfection,
for example, of the gradual perfecting of the skeletal
articulations? Not only does the post-Darwinian school
afford no explanation of this but with the acceptance of
its theories this progress is indeed impossible.” 15°

And Osborn’s view is similar. “Living matter,”
writes he, “is characterized by a capacity of adaptive or
purposeful reaction. If this capacity is inherited in the
Protozoa, thanks to the simplicity of their process of
propagation, it must be the same in the Metazoa. For
each newly developed metazoon which retains the advan-
tage of the inheritance of the adaptive reaction would
be preserved, while each individual which loses this would
degenerate. The mechanism of the inheritance of onto-
genic adaptation must then have been developed in
passing from the unicellular to the pluricellular forms
by means of natural selection.” °°

Weismann it seems to us could reply only by saying
that natural selection may not have established the inher-
itance of acquired characters in the pluricellular forms
also, because the production of the mechanism neces-
sary for that purpose had become materially impossible
by reason of the structure of the metazoic organism.
But this assertion, which would limit the capacities of
living organic substance, must appear a little too hazard-

158Cope: The mechanical Causes of the Development of the hard
Parts of the Mammalia. Journ. of Marph., vol. VIII, No. 2, Boston,
U. S. A. Ginn, Sept. 1889. P. 140—141.

282Ocshorn: Alte und neue Probleme der Phylogenese. Ergebnisse
der Anatomie und Entwicklungsgeschichte, herausgegeben von Mer-
kel und Bonnet. Band. III. 1893. Wiesbaden, Bergmann, 1894,

P. 607.

210 Inheritance of Acquired Characte~s

ous and quite unfounded, especially when one thinks that
apart from that there is no process or phenomenon in
the organic world which Weismann does not ascribe to
the almightiness of natural selection. Thus the power
of regeneration, sexual reproduction, the physiological
necessity of death in the pluricellular forms, all are based
upon natural selection. And is the almightiness of nat-
ural selection insufficient only for the inheritance of
acquired characters?

After bringing to a close this rapid review of the
objections which Weismann can always oppose to any
argument, thus enabling him to save himself from com-
plete defeat at least with the help of mere words and
with a semblance of logic, it remains for us, before
passing to the following chapter, to examine two other
objections to his views which seem to us particularly im-
portant, in that the arguments which he opposes to them
appear to involve his own theory in the most striking
contradictions. These are the inexplicability of co-
ordinated variations, and the repetition of phylogeny by
ontogeny, and with these we shall close the present
chapter.

The objection to the conception of the complete
sufficiency of natural selection which arises from co-
ordinated variations is well known. When the utility
of certain modifications of the organism depends upon
the correlative development of many quite different
parts natural selection cannot account for the inter-
dependent, phylogenetic modifications, since, for the
production of these latter, it can act at best only upon
special fortuitous variations which are independent of
others and. from that very fact totally useless.

Roux for example describes in a masterly way the

Coordinated Variations 211

contemporaneous formation of thousands and millions
of new characters each adapted to the others and all
combined to perform some function such as must be
necessary in the phylogenetic passage from an aquatic
to a terrestrial life. And he concludes in these words:
“One must necessarily conclude that functional adaptation,
such as is produced in alteration of the conditions of
life, can bring about purposeful co-ordinations simulta-
neously in all organs of the body concerned. And the
characteristic feature of this simultaneity of action in
millions of parts must be the fact that it is opposed to
the action of natural selection which can never develop
simultaneously more than a very limited number of
purposeful characters.” 1%

Weismann on whom the force of this objection aris-
ing from correlative development is not lost, has sought
to get around the difficulty by setting over against it,
as we have noted above, the neuter forms in bees, ants,
and termites. He does not deny the extraordinary diff-
culty of explaining co-ordinated variations by natural
selection, but expects to show that in spite of it there
exist undoubted examples in which this difficulty was
overcome by natural selection.

As to the polemic which raged between Weismann
and Spencer on the subject of these neuters, we have
already seen how in our view Spencer has succeeded in
driving his opponent from any tenable ground by
demonstrating convincingly that the neuters are really
nothing else than incompletely developed females. We
shall not return here to what has already been said.

But it is worth while to observe that Weismann thus

Roux: Der Kampf der Teile im Organismus. P. 39—44.

212 Inheritance of Acquired Characters

deprived of his last stronghold saw himself forced to
give an explanation for these co-ordinated variations
also, which should prove, at least from a theoretical
point of view, that they also might possibly be produced
through natural selection. But it is just in this attempted
explanation that he has fallen into the most evident
contradiction, a thing which was inevitable anyway seeing
that his thesis is untenable. It is worth while to spend
a little more time examining this contradiction.

He utilizes for this purpose a theory which, though
introduced only at the last to supplement or replace the
earlier, already discussed theories of panmyxia and the
economy of the organism, was originally intended to
give if possible some better explanation than the earlier
theories offered of the continuous regression of useless
organs even after any further regression is of no more
value for natural selection. According to this theory
when once the involutive process has begun in a given
organ from any external provocation whatever, it would
acquire in this very way an intrinsic tendency to bring
about more and more retrogression. And the tendency
acquired by this organ and now inherent in it toward
constant phylogenetic regression would be accounted for
by the following consideration.

Weismann affirms that when the tendency to degen-
erate once appears in an organ especially well developed,
let us suppose by natural selection, that proves that it
is represented from that time on in the germ plasm by
determinants “of smaller growing power.” ‘But since,”
he continues, “growth and assimilation are physiologic
functions, just as are contraction and secretion, so the
fundamental principle of intraselection is applicable to
them: the functional stimulus strengthens the function-

“Deterninants of Smaller Growing Power” 21 3

ing organ, and the part which performs its function
more energetically attracts to itself more nutrition and
repairs with interest its loss of matter more rapidly than
does the part performing its function less energetically.
So in the struggle of the parts for nutrition the more
feeble determinants will be at a disadvantage, they
become slowly but constantly feebler in the course of
generations until finally they degenerate completely.” 1%

So that according to the view of this investigator:
“It is not the functional change that is inherited; but
variations in the biologic value of a part, (for example,
of an organ which has become useless), give the im-
pulse to the regressive or progressive variations of the
germ plasm and these only would establish the heredi-
tary functional change of the somatic part.’’ 1%

Now it is just this conception of determinants “of
smaller growing power” which is quite inadmissible, and
which constitutes a contradiction in terms.

For what signifies in general “weaker” or “stronger”
determinants? The determinants of a small organ are
by their very definition not feebler than those of a larger
organ; they are only qualitatively different from them.
Also when the variation of an organ consists in a
diminution of its mass, this is not a diminution of grow-
ing power of the respective determinants but an alteration
of these latter, which is nothing else than their replace-
ment by other qualitatively different determinants.
Would Weismann himself say that the respective determi-
nants of the fore legs of the kangaroo are provided with
a smaller power of growth than those of the hind legs?
Or that the fingers of the human hand have determinants

161Weismann: Neue Gedanke nzur Vererbungsfrage. P. 14—15.
482Weismann: Ibid. P. 59.

214 Inheritance of Acquired Characters

whose power of growth stands in exact proportion with
their length? Would the shorter fingers therefore have
a phylogenetic tendency to become constantly still shorter,
and the longer fingers a tendency to become steadily
longer yet? If that were so it would lead directly into
this absurdity, that the formation in phylogeny of new
organs or of new structures in general could never have
any commencement, since originally their determinants,
just because of the very smallness of these formations,
must have been provided with only a very small power
of growth and therefore could never progress side by
side with determinants which must in any case be
stronger since they belong to organs or structures already
developed.

If on the contrary this is not the case and cannot be
the case because it contains an unavoidable contradiction,
then the determinants of any degenerated organ what-
ever, such for example as the hind leg of the immediate
ancestor of the whale, cannot be regarded as feebler, but
must rather be regarded as qualitatively different from
those of the complete organ. Consequently there cannot
exist for the degenerated organ any phylogenetic tendency
to become still more rudimentary.

Weismann would give, as we have said, a quite
similar explanation of co-ordinated variations:

If there were, for example an increase of the weight
of the head, as a direct result let us suppose of natural
selection, certain muscles of the body after having
received an initial impulse from natural selection itself,
would acquire a phylogenetic tendency to grow pari passu
with the weight of the head. For the first operation of
natural selection would be to eliminate individuals whose
muscles were too feeble. Then even if we suppose that

Weismann’s Explanation of Coordinated Variations 215

every fortuitous variation that is possible, both plus and
minus, actually develops, the net result after the elimi-
nation of the minus variations must be that the muscles
would be stronger. But this initial increase, this first
impulse toward strengthening, would be in turn the
cause of a phylogenetic tendency to a further strengthen-
ing, because it would indicate that these muscles were
represented in the germ plasm by determinants which
are endowed with a greater power of growth, and con-
sequently with greater power of assimilation. “The
affluence of nutritive fluids would become proportionally
augmented and would contribute likewise to giving the
plus variations a preponderance over minus variations.
There would thus be a phylogenetic tendency toward the
continual increase of these muscles and it would endure
just as long as the increase in the weight of the head,
and would stop when the latter stopped. For in this
case the plus variations of the determinants would be
eliminated by individual selection, as soon as_ they
attained selectable value.” ***

But this artificially constructed hypothesis, which did
not hold good at all in the case of rudimentary organs,
is still less adapted to the case of co-ordinated varia-
tions. For in these phenomena it appears still more
clearly that in phylogenetic changes there are concerned
not simply exclusively plus or minus variations, but
transformations which might be constituted by a com-
bination of increases in one direction and decreases in
another, or might not be susceptible of being decomposed
into merely quantitative variations. It should be noted
further that for certain correlative, histological varia-

168\Weismann: Neue Gedanken zur Vererbungsfrage. P. 22.

210 Inheritance of Acquired Characters

tions of physico-chemical nature, which are concerned
in any way in the fundamental specific characters of
vital processes, the expressions increase and decrease have
no significance at all.

Nevertheless it would not have been advisable not
to mention here these later explanations of the atrophy
of organs which have become useless and of co-ordinated
variations, because the fact that Weismann substituted
them for his earlier ones, shows that he himself regarded
the earlier explanations as insufficient, and because the
artificiality of these new explanations shows very clearly
the almost insurmountable difficulty encountered in the
attempt to explain these phylogenetic phenomena if the
inheritance of acquired characters is rejected.

But the phenomenon which more than any other
remains an enigma when the inheritance of acquired
characters is rejected, and which when this inheritance
is accepted becomes not only self explanatory, but sets
the whole mechanism of inheritance in the clearest light,
is that of the repetition of phylogeny by ontogeny, and
just because of this we reserved it for the last.

“Whenever a new species is formed,” writes Delage,
“it is accomplished by the addition of one or more new
characters, at the end of ontogeny, after all the old
specific characters have already appeared. And since this
goes on from the very commencement it is evident that
the characters must appear in ontogeny, in the same
sequence as in their phylogenetic formation.” 164

But if there is no inheritance of acquired characters
why should the new character be invariably just added
to those already present, and only after the development
of the latter is completed? Why should it not be possible

Delage: L’hérédité etc. P. 366.

New Characters in Phlogeny 217

for each variation of the germ substance to appear or
to become active, either from the beginning, or at any
time at all during the ontogeny?

“The phenomena of latency” says Osborn, “speak
absolutely against Weismann’s conception, according to
which phylogenetic development would take place in the
germ plasm by selection of advantageous elements, and
elimination of disadvantageous elements. These phe-
nomena of latency indicate that the phylogenetic process
does not consist in an elimination but in a shoving of
certain characters into the background (Zurickdrangung)
during the later stages of ontogeny.”

Osborn cites as example the well known experi-
ments of Cunningham on the color of the asymmetrical
flat fishes, pleuronectids, on whose lower colorless side
artificial illumination is followed by a reappearance of the
pigment disposed in the same designs and in the same
colors as on the upper side, and also Agassiz’s experi-
ments according to which the young of these same fishes
retain their original symmetry when they are kept at the
surface of the water for a longer time than under normal
conditions. “According to these experiments,’ Osborn
says very rightly, “progressive inheritance (and so phylo-
geny) appears to represent rather a process of substitu-
tion or of addition than one of true elimination in Weis-
mann’s sense.” 16° Thus these facts also speak in favor
of the conception that phylogeny rests upon an addition
of new characters and their superimposition upon the old.

We can see that to explain by the inheritance of ac-
quired characters this addition of a new character to the

%4Qcborn: Alte und neue Probleme der Phylogenese. Ergebn.
d. Anat. 1 Entwicklungsgesch., herausg. v. Merkel u. Bonnet. Bd.
III. 1893. Weisbaden, Bergmann, 1894. P. 610, 619.

218 Inheritance of Acquired Characters

old only after the completion of the development of these
latter, it is sufficient to suppose that the agent of trans-
mission of an acquired character becomes active in onto-
geny, only when the young organism finds itself in the
same conditions in which the parent organism was when
it acquired this character.

As soon as one admits this condition for the mech-
anism of inheritance the law of the repetition of phylo-
geny by ontogeny appears to be merely the immediate
consequence of the inheritance of acquired characters.

For so long as the embryo is developing in the egg or
in the maternal body and so long as it is nourished, sup-
ported and protected by its parents, it is withdrawn from
the changing influences of the environment. It is only
when the individual is left to himself that he finds him-
self driven perhaps to new functional adaptations. In
other words it is only in the adult state, after it has com-
pleted or almost completed its specific development, that
the organism in general can find itself in conditions neces-
sary for the acquisition of new characters.

But another fact also can explain why new phylo-
genetic characters are acquired only when all the old ones
are already quite developed. We have indeed already
seen that the organism undergoing development is much
more elastic but much less plastic than the adult, so that
the modifications which arise in it from the action of an
external force, even when it acts for a long time, have
the tendency to disappear without leaving any trace be-
hind so long as the organism has not yet completed its
development, whereas this tendency is no longer inherent
in the adult organism.

We have already mentioned the experiment of Roux,
in which he distorted a few frog embryos within their

Inheritance Explains Biogenetic Law 219

gelatinous envelope by compressing them between needles :
“If the needles were withdrawn again immediately after
the deformation, the embryo at once resumed its earlier
form. If on the contrary they were held in place for
several hours the deformation became from the first a
persistent one, and only after several hours would the
embryos resume their original form—a proof that an in-
ternal adaptation to the new form had already com-
menced, but that this adaptation is nevertheless caused to
disappear again in the course of further development, per-
haps by the action of those very forces of growth which
bring about the restoration of the normal form,
and which were inhibited during the time of the
deformation.” 166

We have thought it worth while to mention again this
very characteristic example of the elasticity of develop-
ment, because it, better than others which we have
already mentioned in the course of our investigation of
the cause of this elasticity, helps us to explain the rule
inviolably followed in the evolution of species, of the
addition of new phylogenetic characters to those already
present. For from this it is very evident that those
phylogenetic characters whose appearance is caused dur-
ing ontogeny to some extent by the action of external
influences, have the tendency to disappear again promptly
as soon as the cause which produced them has ceased to
act. So that, unless we have an extraordinary influence,
whose intensity and insistent action during ontogeny
through the course of successive generations give it an

466Roux: Zur Orientierung tiber einige Probleme der embryonalen
Entwicklung. Zeitschr. f. Biol.; Bd. XXI. Mlinchen. July 1885.
P, 515, 516. Gesamm. Abhandl. II. P. 245.

220 Inheritance of Acquired Characters

overmastering power, it will not leave behind any trace
in the individual and certainly none in the species.

Thus the inheritance of acquired characters, thanks
to these two facts that the embryo is usually withdrawn
from the influence of the environment, and that or-
ganisms undergoing development are elastic and not
plastic, shows itself to be completely capable of account-
ing for the fundamental biogenetic law. Whatever in it
could seem marvelous and enigmatic finds its natural so-
ultion and the law itself becomes an immediate and neces-
sary consequence of this inheritance.

What on the contrary is the explanation which Weis-
mann is able to give for this law? He thinks to explain
it merely by the following laconic words:

“The biogenetic law rests upon this, that phylogenetic
development is accomplished partly by the addition of
new ontogenetic stages at the end of ontogeny. In order
that this latter may be attained, the preceding terminal
stages must each time be run through again.” 1°

But in this Weismann leaves just the most important
part of the question out of consideration. Why can
phylogenetic development take place only by the addition
of new ontogenetic stages at the end of ontogeny?

According to Weismann’s theory, there is no reason
whatever why one should believe the determinants cor-
responding to the last ontogenetic stage to be the only
ones to undergo modifications, for one cannot forget that
according to this theory each cell of each ontogenetic
stage must have its own determinants.1® The same
causes of differences in the nutrition or any other thing,
which are capable of modifying the determinants cor-

**™Weismann: Das Keimplasma. P. 110.
***Weismann: Ibid. e. g. P. 97, 100, 232—233, 596.

Weismann’s Theory Cannot Explain Biogenetic Law 221

responding to the last ontogenetic stage, must be also
capable of transforming in the most different ways the
determinants of the other stages. According to that,
each phylogenetic stage would have its own ontogeny,
which would differ completely even in the first stages of
development from the ontogeneses of the preceding
phyletic stages.

And there is no more reason for the supposition that
the only way in which the determinants corresponding to
the last ontogenetic stage could undergo modification
must be by “obtaining a greater power of growth, aug-
menting consequently in number, differentiating each in
a new fashion, and adding thus at the end of the old
ontogeny one or more generations of cells.”1° For
these determinants could perhaps undergo any merely
qualitative variation whatever without first augmenting
in number, that is to say could become differentiated at
once in a new way so that the part determined by them
should at once take on a form different from the old one
without needing first to pass through its preceding
phylogenetic state.

We need just to recall again the example which we
have already cited above, furnished by one of the most
characteristic manifestations of the fundamental bio-
genetic law, namely ontogenetic involution, in order to
demonstrate in the clearest way the absolute inability of
Weismann’s theory, to account for that law. For accord-
ing to that theory one would understand for instance that
the tail of the ancestor of the tadpole, or that the limbs of
the ancestor of the existing serpent may have become con-
stantly shorter in the course of phylogeny by virtue of

26°Weismann: Ibid. P. 110.

222 Inheritance of Acquired Characters

natural selection, panmixia or something else, and that
consequently they have become arrested in successive
ontogeneses at successively earlier stages of development.
But the question cannot be repeated often enough; how
can this theory explain the growth of these organs up to
a certain stage of development and their retrogression
and disappearance in the later stages?

In short, it seems to us that one cannot imagine a
more complete overthrow even from a purely logical
point of view, where it is only a matter of avoiding con-
tradiction on one’s own premises, than thzt suffered by
Weismann in the attempt to find an explanation of the
repetition of phylogeny by ontogeny, and one can hardly
bring forward a more thorough failure of a theory built
up laboriously with the object of explaining all the differ-
ent phenomena of heredity, even the most peculiar and
secondary ones, than appears in the fact that this theory
is not even capable of giving the least explanation of the
most general biogenetic phenomenon—the one which
underlies all the others. And this contradiction and this
failure do not appear so much in the minute and partic-
ular parts of Weismann’s theory, in which it deals with
this or that peculiar detail, but much rather in the theory
itself in all its generality, which disputes the inheritance
of acquired characters. Weismann and his supporters
can, if the most evident facts are not enough for them,
deny this law of recapitulation. But that they admit it
and nevertheless dispute inheritance, this is a contradic-
tion from which the opponents of the Lamarckian
principle cannot escape now or ever—a destructive rock
upon which all their theories are wrecked.

If now we sum up succinctly the discussion in this

Summary of This Chapter 223

chapter, we are able to affirm that although no fact or
argument is capable by itself alone of affording an ir-
refutable and unconditional proof either direct or indirect,
of the inheritance of acquired characters, nevertheless the
sum total of the facts and the arguments which are fa-
vorable to it is so weighty that one is not only justified in
believing but is even compelled to believe that the
Lamarckian principle is in all probability correct.

But the difficulties of explaining the mechanism of
inheritance are so great, that many investigators may
have thought them to be insurmountable. It is conceiv-
able that many others, like Roux, have been led to dis-
pute its existence, just in order to free themselves in that
way froma veritable nightmare. But this position is no
longer possible.

The objective examination of the question leads to
the conviction that the inheritance of acquired characters
is to be considered as in all probability a reality, there-
fore we are in duty bound to seek an explanation of this
phenomenon by some hypothesis, even if it be only a
provisional one.

So in the following chapter we propose to examine
comparatively a few of the most recent and most im-
portant -hypotheses which have been devised for the
explanation of inheritance. After that in the penultimate
chapter we shall set forth more thoroughly the explana-
tion of the Lamarckian principle which the centro-
epigenetic hypothesis can give.

Further evidence that somatic changes induced in animals by
envircnmental influences may be repeated in their descendants as
a result of germinal influences is furnished by Sumner and by
Kammerer. See Archiv fiir Entwicklungs—Mechanik der Organ-
ismen, Leipzig, June and September, Ig10. (Translator. )

CHAPTER SIX

THE MOST IMPORTANT OF THE EXISTING BIOGENETIC
THEORIES IN RELATION TO THE INHERITANCE OF
ACQUIRED CHARACTERS,

We believe it is unnecessary to discuss here in an
exhaustive way the fact that the question of the admis-
sibility or inadmissibility of the Lamarckian principle re-
mains always distinct from, and entirely independent of
the question of the evolutionary or epigenetic nature of
development. Darwin in his evolutionary theory with
preformistic germs,—a true theory of preformation,—
accepts inheritance; Galton limits it to a few cases; Weis-
mann excludes it unconditionally. Hertwig accepts it in
his epigenetic theory, although he does not exclude some
sort of preformistic germs; DeVries excludes it. Roux
who was inclined at first to believe that this inheritance
might exist in combination with the chemical develop-
ment of the egg, a theory frankly evolutionary without
preformistic germs, has finally regarded the two theories
as irreconcilable. The only theories which appear es-
pecially inclined toward the complete acceptance of the
Lamarckian conception, are the epigenetic theories with-
out preformistic germs, for example that of Spencer.

We can now pass on to the rapid review of the
principal biogenetic theories current today, with especial
reference to their direct or indirect relation to the ques-

224

Spencer 225

tion of inheritance and to the conceptions of inheritance
which have been formed.

Spencer

This author’s idea of “physiological units,” inter-
mediate between the morphological units or cells and the
chemical units or molecules, and representing the last
irreducible vital elements, is well known.!7°

If one supposes that in each organism there exists
only a single variety of these units, Spencer believes the
explanation of the inheritance of acquired characters
would follow immediately from that.

“Just as the physiological units because of their
special polarities build themselves into an organism of a
special structure, so on the other hand, if the structure of
this organism is modified by modified function, it will
impress some corresponding modification upon the struc-
ture and polarities of its units. The units and the
aggregate must act and react on each other. If nothing
prevents, the units will mould the aggregate into a form
which will be in equilibrium with their pre-existing polar-
ities. If contrariwise the aggregate is made by incident
actions to take a new form, its forces must tend to mould
the units into harmony with this new form. And to say
that the physiological units are in any degree so moulded
as to bring their polar forces towards equilibrium with
the forces of the modified aggregate, is to say that when
separated in the shape of reproductive centers, these units
will tend to build themselves up into an aggregate mod-
ified in the same direction.” 171

Spencer: Principles of Biology, Sixth edition; London, Will-

jams and Norgate. 1898. Vol. I. Chap. IV, §66. P. 224—226.
1Spencer: Ibid. Vol. I. Chap. VIII: Heredity, § 84. P. 319.

226 Theories Treating of Inheritance

It seems to us quite superfluous to expose any further
here the pure verbality of such an explanation without
any real content. Neither shall we go more closely into
the objection, which is apparent on the very surface, that
physiological units identical throughout the whole or-
ganism cannot form muscles here, bones there, nerves
elsewhere, all of which represent special tissues with
totally different physical, chemical and vital properties.

We limit ourselves rather to noting that, according to
this, the inheritability of even quantitative and partial
modifications, for example the transmission of the merely
greater development of a tissue or an organ already ex-
isting, must be attributed to a uniform, qualitative change
of all the physiologic units of the organism. And not-
withstanding that, the properties of each group of these
units, not excepting the group constituting the tissue
which has undergone a simple increase in mass, must re-
main identically the same as they were before.

Let us consider the case which Spencer himself quotes
and regards as one of the examples of the inheritance of
acquired characters, namely, the increase in size or
greater development of the great toe as well as the
diminution or regression of the little toe, as a result of
the fact that our ape-like ancestors gave up life in the
trees for life on the surface of the ground.1”

Is it possible that so very local a morphologic change
has transformed qualitatively the physiological units of
the entire organism? And apart from the fact that the
change is limited to a certain very small part of the body,
it must yet be borne in mind that one has to do here with
no new quality nor with any new material introduced

*7?Spencer: A Rejoinder to Prof. Weismann. London, Williams
and Norgate. 1893. P. 3ff.

Spencer 227

into the organism by the new function, nor consequently
with any new physical or chemical or biological character
which the organism has now for the first time acquired;
but on the contrary there is involved only a different dis-
tribution of already existing qualities of matter. But
how can a change of quality in imaginary physiological
units, which would have proceeded uniformly in the
whole organism, accord with the fact that all the qualities
and properties of this organism remain unaltered, and
there is merely another distribution of these materials?
Let us consider as a further example the instinct of
ew born chickens. ‘In the first minutes of life,” writes
Jastrow, “chickens follow with their eyes the movements
of crawling insects, turning their heads with the precision
of an old fowl. In from two to fifteen minutes they
pecked at some speck or insect, showing not merely an
instinctive perception of distance but an original ability
to judge, to measure distance with something like in-
fallible accuracy. A chicken hooded as it emerged from
the shell was unhooded when three days old; six minutes
later it followed with its head and eyes the movements of
a fly twelve inches distant, and about ten minutes later
made a vigorous dart at the fly, seized and swallowed it
at the first stroke.” 174
Spencer would rightly attribute this instinct to the
long practice acquired by the ancestors of the chicken.
But if he wished to explain this inheritance through the
alteration of specific physiological units of the entire
organism, such an explanation would not be taken ser-
iously. How could the new physiologic units, capable
of effecting this local modification constituted by the

™3Tastrow: The Problems of Comparative Psychology. The
Popular Science Monthly. New-York. Nov. 1892. P. 36—37.

228 Theories Treating of Inheritance

formation of a few new nerve paths, at the same time
reproduce those parts of the organism which remained
entirely unaffected by this local change?

Finally, how can the hypothesis of Spencer account
for the law of repetition of phylogeny by ontogeny? If
the explanation of the inheritance of acquired characters
by means of physiological units were accepted, this law
would be futile. For the new physiologic units with
changed polarity must take on at once in the daughter
organism that form to which the parent organism had
last attained, without needing to pass first through the
preceding forms.

The physiologic units were devised in order to permit
the comparison of the formation of the organism with
that of a crystal. But a substance which because of a
slight qualitative alteration of its molecules changes its
form of crystallization, goes over from the very first
commencement of crystallization into a form different
from the preceding, and takes on at once the form which
it will have after the completion of crystallization, A
comparison between organisms and crystals is therefore
inadmissible; and this inability is especially evident when
it is attempted in this way to explain the laws and
phenomena of development, in which organisms and
crystals are totally different and are even antagonistic.

Haacke

The conception of Haacke is much like that of
Spencer.

“According to my view,”’ says he, ‘we have to do not
only with the genetic continuity of the germ cells of one
generation with those of the generation immediately pre-
ceding and following, but also with a material continuity

Haacke 229

of the germ cells with the other cells of the body. The
body represents a system in equilibrium; if this changes
the germ cells developing in it change also. But the
equilibrium of the system constituted by the body becomes
directly altered by the acquisition of new characters; con-
sequently the changes which it undergoes must be trans-
mitted also to the germ cells. But no matter whether the
germ cells become changed as a result of the acquisition
of new characters by the body which surrounds them, or
whether they remain unchanged, they always inherit the
same thing, namely, the capacity to form that body with
which they were in equilibrium.” 174

Like Spencer he supposes that this equilibrium is due
to the tendency possessed by an infinite number of par-
ticles, identical throughout the whole organism, to dis-
pose themselves in this way only. His rhomboidal
gemmes, grouped into composite units or gemmaria, are
fundamentally nothing else than the physiological units
of Spencer. The geometric form attributed to them,
which emphasizes the static character of this explanation,
does not make it in any way more acceptable.

Nevertheless there are to be noted and carefully con-
sidered, here perhaps, even more than in Spencer, the
close interaction and the reciprocal equilibrating influence,
which would always exist between the soma and the germ
substance,—that is to say, between the organism and that
small portion of its units contained in the reproductive
cells,—not only throughout the whole development of the
individual but also after the completion of development
when the organism becomes subject to the modifications
which external agents induce in it.

1%4TTaacke: Kritische Beitrage zur Theorie der Vererbung und
Formbildung. Biol. Centralbl., Bd. XV. 1895. P. 568.

230 Theories Treating of Inheritance

Sedgwick

This investigator deduces the possibility of the in-
heritance of acquired characters from his conception that
the pluricellular organism is simply a great syncytium.

“Tf the protoplasm of the body is essentially a syncy-
tium and the ovum until maturity a part of that
syncytium, the separation of the generative products does
not differ essentially from the internal gemmation of a
protozoan, and the inheritance by the offspring of pecul-
iarities first appearing in the parent, though not ex-
plained, is rendered less mysterious; for the protoplasm
of the whole body being continuous, we must naturally be
inclined to think that every change in the molecular con-
stitution of any parts of it would naturally be expected
to spread in time, through the whole mass.” 1%

This conception which recalls somewhat Naegeli’s
idea of an idioplasmic network, extending its meshes
throughout the whole body, though it gives a hint of the
possible mechanism of inheritance by means of this proto-
plasmic continuity, nevertheless does not give even the
most vague and remote notion of the nature of this
mechanism.

Bard

According to this author the cells participate in onto-
genetic development in two ways. The first way is by
their specific division or qualitative nuclear division, as
in Weismann’s theory of preformistic germs. The second
rests upon a special action of the germ cells upon the
somatic cells, acting indeed at a distance but nevertheless

Adam Sedgwick: The Development of the Cape Species of
Peripatus. Quart. Journ. of Microscopical Sc. Vol. XXVI. 1886:
P. 206.

Bard 231

not by any mediate path, like the influence exerted by
electric induction-currents in the production of induced
currents, and Bard has therefore given this process the
name of vital induction.

But this induction would be exercised not merely by
the germ cells upon the somatic, but also by the latter
upon the former. And the modified soma is capable of
bringing about the inheritance of the modifications it has
undergone, by means of an influence of exactly this na-
ture exerted upon the germ cells contained in it.17%

But the inheritance of these new characters by the
next succeeding organism by the means of the germ cells
which give rise to this latter can be accepted only upon
the supposition that it is effected by means of the same
vital induction which had already transmitted the char-
acters of the paternal soma into the germ, now acting in
the reverse way. And Bard himself seems to admit this.
But if this is true for the characters acquired last, it must
also be true for all the characters acquired phylogeneti-
cally. Consequently the role which specific cell division
or qualitative nuclear division in the Weismannian sense
would play in the histologic differentiation and in the
whole development would become reduced to nothing.

We shall limit ourselves then to drawing attention to
the inconceivability, made more evident by the considera-
tions just mentioned, of the idea that the germ cells could
participate in the development in two such extremely
different modes of action simultaneously, and the lack of
any experimental proof for this supposed vital induction.

“Bard: Influence spécifique 4 distance des éléments cellulaires
les uns sur les autres. Archives de Médecine expérimentale; 1. série,

t. II. Paris, Masson. May 1, 1890; and La spécificité cellulaire et ses
principales conséquences. La Semaine Médicale. Paris, March 10,

1894.

232 Theories Treating of Inheritance

Tormier

Tornier believes that the nervous system acts as in-
termediary, transmitting the acquired characters from the
soma to the germ cells and then fixing them in the latter.

“In the more highly organized individuals each adapt-
ation of the active end organs is accompanied by a
corresponding and equivalent adaptation in the central
nervous system. The central nervous system in its
turn transmits the acquired character to the sexual
organ forming with it a single functional and nutri-
tive unit, and especially to the sexual cells causing
them to undergo an equivalent transformation. When
the sexual cells become later generative cells, the property
acquired by the parent is by this means inherited by the
descendents.”’ 177

One does not see nevertheless how the modification
undergone by the sexual cells could be reversible; that is
to say how these cells could produce in the descendants
the new character which was acquired by the parent or-
ganism and to which their own modification was due.
To state it more exactly, one does not see at all how it
will have satisfied the condition to which we shall often
have occasion to return, and which appears indispensable
to this reversibility, namely that during ontogeny there
is produced at the right time and the right place an action,
which is of exactly the same nature as that by which this
part of the paternal soma had reacted to the modifying
action of external influences.

It is necessary nevertheless to note the important role
which is thus attributed to the nervous system as the in-

**Tornier: Uber Hyperdaktylie, Regeneration und Vererbung.

Arch. f. Entwicklungsmech. d. Org. Bd. III. Heft 4. and Bd. IV.
Heft 1. Leipzig, Engelmann. 1896. P. 192.

Hertwig 233

termediary through which must pass all the characters
newly acquired by the soma and thanks to which they
become transformed so that they can then be inherited by
following generations.

Oscar Hertwig

Oscar Hertwig gives in the following words the es-
sentials of his theory of biogenesis.

“The cells, necessarily equal specifically on account of
their origin in the segmentation of the egg, which are
combined to constitute an organic system of a higher
order, have their character determined by the relations in
which they become placed during the course of develop-
ment. Their state becomes modified when these relations
are modified. For the cell organism is an extremely ir-
ritable substance so that the slightest influences are suff-
cient to bring about modifications in it.”

“Contrary to the mosaic theory of Roux and the germ
plasm theory of Weismann, the theory of biogenesis is
based upon the principle, that from the commencement of
development, the cells arising from the segmentation of
the egg are constantly in the most intimate relation with
one another, and the character of the developmental pro-
cess is determined essentially by this fact. The cells do
not take their especial future character of their own initia-
tive, but their character becomes determined according to
laws which result from the co-operative action of all the
cells during the successive stages of development of the
entire organism.”

“The relations of the rapidly multiplying cells of the
substance capable of development are constantly chang-
ing in accordance with general laws, and the relations
between these internal factors and those which are with-

234 Theories Treating of Inheritance

out the organism are likewise undergoing continual
change, and because of these changes in relations new
conformations become produced at each stage of the
developmental process in a variety becoming ever more
complex.” 178

Nevertheless this does not hinder one, according to
that investigator, from considering the organism in its
entirety as a single physiological unit because of the idio-
plasmic identity of the nuclei of all its cells;—a thing
which he thinks, makes the inheritance of acquired
characters conceivable.179

For to explain the latter, Hertwig brings up the cases
of infection, immunization, and other similar examples,
in relation to which the organism can really be regarded
as a single entity. He quotes for instance the experi-
ments of Ehrlich who has succeeded by the administration
of extremely small doses of ricin in making rats immune
to this poison which is very powerful for them, and in
establishing the fact that this immunity was acquired not
only by the walls of the digestive canal with which the
poison comes into immediate contact, but also by all the
other tissues of the body, such as for example the sub-
cutaneous tissues and the ocular conjunctiva, and even
by the germ cells as was proved by the fact of the trans-
mission of this immunity to the young born of immunized
parents. 18°

Just as all the cells of the body are accessible to the
action of ricin and thanks to that fact all undergo a
material modification, which some of them, namely the:
germ cells, transmit later to the descendants as an im-

*8Oscar Hertwig: Die Zelle und die Gewcbe. II. P. 75, 144, 156.
Oscar Hertwig: Ibid. II. P. 241.
*°Oscar Hertwig: Ibid. I]. P. 24cff.

Hertwig 235

munity against ricin, just so according to Hertwig’s view
do all the cells behave toward acquired characters in gen-
eral. “In the same way as the cell is sensitive to the
action of ricin, which brings about an enduring material
modification of it, and this becomes inherited as im-
munity to ricin, so I think every cell is sensitive also to
the influence of the general condition of the body, which
brings about material modifications of its substance, that
is of its idioplasm or hereditary material, which is es-
pecially susceptible of such material modifications, and
these correspond to the cause as its effect both in the cells
of the soma and also in the sexual products.” 18?

We shall not consider here the fact demonstrated by
Ehrlich, that in the instance in which only one of the
parents was immunized, the immunity was transmitted
very well to the young of an immunized mother but on
the contrary was not transmitted to the young of an im-
munized father; a fact which seems to confirm the
hypothesis of Ehrlich that the immunity against ricin was
due to the formation of an anti-ricin, with which the
protoplasm of all the cells became impregnated, but with
which the spermatazoon could not become impregnated
because it is almost entirely devoid of protoplasm, show-
ing consequently that one has to do here not at all with a
permanent modification of the nuclear idioplasm. But
even apart from that and even admitting the hypothesis
that the immunity against ricin was due from the be-
ginning or at the time to the acquisition by the idioplasm
of a new and persistent character,’*® it is still evident
that this is not a just comparison.

For in the case of infections, immunizations, and so

181Oscar Hertwig: Ibid. II. P. 242.
182Qscar Hertwig: Ibid. P. 241.

230 Theories Treating of Inheritance

on, there would be a single identical influence exerted
upon the nuclei of all the cells without exception, which
makes it conceivable that thereby the special nuclei of the
different cells, and consequently of the germ cells also,
could all inherit the new reactive property, which would
be added to the other special characters already present in
each nucleus and different in the different cells.

But in the case, for instance, of a certain muscle,
which develops to a greater size because of a definite
modification in its local, trophic, functional stimulus, is it
possible to make the analogous statement that there is
thus obtained a new state of the body which brings about
a modification in the idioplasmic substance of all the cells
of the organism without exception—the same modifica-
tion in each of them? Certainly this modification induced
in the trophic functional stimulus of a muscle and the
greater development thereby provoked in it will exert an
influence on all or nearly all parts of the organism; but
the most probable supposition and that best corresponding
with the facts would be that the reaction is different in
each part. This case at least is quite different from that
in which one has to do with the transmission of a definite
infection or immunity, and cannot be compared with it
without further consideration.

In short Hertwig supposes that every local material
modification which appears at a given point of the idio-
plasm as a reaction to a new functional stimulus extends
at once throughout the whole idioplasm, so that the latter
becomes modified uniformly everywhere, like a true
physiologic unit:

“In the organism considered as a physiologic unit of
life the actions of all individual organs, tissues and cells
must be combined into a complex common action, the

Hertwig 237

nature of which will be conditional upon the general state
of the organism; this action will be felt by each individual
part and in so far as it amounts to a lasting modification
of the idioplasm it becomes a newly acquired character.”

At every fresh modification of the general state of the
organism, “‘the total heritage of the organism becomes
enriched by a new member, by a new anlage which mani-
fests itself again in the development of the succeeding
organism, in that now the newly developing individual
reproduces more or less ‘from the germ out’ or from
internal causes the character which its parents had ac-
quired during their lives from intercourse with the outer
world.” 183

Does Hertwig in this say that the reproductive sub-
stance is constituted by a heaping up of a whole series of
material modifications, which correspond to the successive
phylogenetic general states of the body, and constitute as
many potential tendencies?

That is hard to decide, because all that relates to his
conception of the idioplasm structure is obscure and often
contradictory. Thus in some places he seems to admit
that his idioplasm may be constituted by preformistic
germs, so that his theory would belong with that of De
Vries to the group of theories of epigenesis with pre-
formistic germs. In other places on the contrary where
he speaks of general states of the idioplasm, and other
similar things, every idea of preformistic germs seems to
be excluded, so that his theory appears to be very similar
to those of epigenesis without preformistic germs, like
that of Spencer. The same is true also of this heaping up
of different material modifications representing the suc-

188Qscar Hertwig: Ibid. II. P. 242, 243.

238 Theories Treating of Inheritance

cessive phylogenetic states; he appears sometimes to
exclude, sometimes to accept it.

If he accepts this heaping up, the explanation of the
inheritance of acquired characters which the hypothesis
of biogenesis could give would be reduced to this:

The uniform modification into which are summed up
during their extension throughout the whole body the
different transformations in the idioplasmic nuclear sub-
stance that are brought about in consequence of the
acquisition of new local characters is added to the
preceding phylogenetic modifications without altering
them, but merely reducing them to the potential state.
Then in the next following ontogeny, when the required
stage of development is attained, and this recently ac-
quired idioplasmic modification becomes active in its turn,
it induces the same general state of the body as was
induced in the parent as a result of the acquisition of new
local characters, and this general state, because of the
reversibility of the relation between action and reaction,
tends to bring about the formation of this character once
again.

But one must not be deceived even by this. Even
supposing this to be the explanation that the biogenetic
hypothesis could afford for the inheritance of acquired
characters, it would consist rather in mere words than in
ideas. For, as we have said above, this supposed summing
up of all these different, simultaneous, local variations
into a single idioplasmic modification, including them all
and uniform for the entire organism, lacks not only any
basis in fact but also any possibility of conception. And
the following questions remain unanswered: In what
do these different general states of the idioplasm consist ?
In what way do some come to be added to the others

Hertwig 230

during ontogeny one after another in the same order as
in phylogeny? How does each of the successive general
states of the idioplasm, identical for the entire organism,
exert upon each individual cell so many special actions,
which are not only quite different from one another but
also are the exact reverse of those which by their union
had produced this general state during phylogeny ?

But however that may be, it is not at all certain that
Hertwig accepts this heaping up. For, as we have said
above, if he seems in certain places inclined to accept it,
he appears in others to reject it absolutely.

He seems to accept it for example when he approves
and adopts the following passage from Nageli:

“The unfolding of the anlagen of the idioplasm fol-
lows faithfully the phylogenetic order. While the or-
ganism, developing in ontogeny, runs successively
through the stages through which its phylogenetic stem
has run, the idioplasmatic anlagen become developed in
just that order in which they came into existence.”

And this conception appears confirmed in the follow-
ing words of Hertwig: “On account of the progressive
multiplication of the cells, their combined action is con-
stantly producing new embryonic states in the same serial
order as that in which they appeared during phylogeny.
The individual cells are brought into new relations to one
another and to the external world, and through these
successive reciprocal relations the anlagen latent in the
cells become awakened.” 184

In other places on the contrary he seems to reject
completely this heaping up of a whole series of anlagen,
of which each should correspond to the phylogenetic state

184Qcscar Hertwig: Die Zelle und die Gewebe. II. P. 251, 253.

240 Theories Treating of Inheritance

in which it had arisen, and to suppose instead that when
once the idioplasm has been modified there remains in it
nothing more of the preceding states, not even in a latent
or potential condition. At least this would seem to be
indicated in the following passages.

“The theory of biogenesis makes it necessary for us
to introduce into Haeckel’s statement of the fundamental
biogenetic law, a few modifications and explanatory addi-
tions through which the contradiction (between this law
and this theory) may be avoided. We should drop the
expression: repetition of the forms of extinct ancestors,
and substitute for it: repetition of forms which obey the
laws of organic development and which progress from
the simple to the complex. We should lay the emphasis
upon this, that in embryonic forms, just as in the adult
forms of animals, are expressed general laws of develop-
ment of organized living substance.”

“The periodically repeated development of pluricellu-
lar individuals from unicellular representatives of the
species, or individual ontogeny, is brought about in general
accordance with the same rules as the preceding onto-
genies, but becomes each time a little modified correspond-
ing to the extent to which the characteristic cell of the
species was modified in phylogeny.”

“That certain conditions of form recur in the develop-
ment of animals with such great constancy, and in the
main in similar ways, is due chiefly to the fact that in all
circumstances they furnish the prerequisite conditions
under which the next later stages of ontogeny can be
produced.”

“The unicellular organism, on account of its very
nature, can be transformed into a pluricellular organism

‘

Hertwig 241

only by division. It follows that in all living beings onto-
geny must commence by the cleavage process.”

“An organism constituted by layers and groups of
cells disposed in a definite order can be formed from a
heap of cells only on condition that the cells while they
are multiplying, begin to be arranged in separate assem-
blages and so progress in accordance with certain rules
from the very simple initial forms to more complex ones.
Thus the gastrula implies as prerequisite the simpler
stage of the germinal vesicle. Thus the embryonic cells
must first be disposed in germinal layers, which constitute
the basis for further processes of differentiation in their
territory. The anlage of an eye in a vertebrate can be
formed only after a nerve tube has been separated from
the outer germinal layer, since in it is included also the
material for the formation of the optic vesicles.”

“Certain forms then become firmly fixed in the
developmental process, despite all the constantly acting,
modifying factors, because it is only by means of them
that the complicated final state can be reached in the most
simple way and in the most suitable manner.” 18°

Thus as we said, Hertwig seems in this really to sup-
pose, contrary to what he asserted above, that the idio-
plasm is not at all a heaping up of numerous anlagen
representing respectively the successive steps of the evolu-
tion of the species, but so transforms itself with each new
phyletic acquisition that it preserves no trace of preceding
phyletic states.

In this he is in complete accord with the hypothesis
of Spencer, from which in fact he quotes long passages
and makes them his own. And accordingly he supposes,

18Qscar Hertwig: Die Zelle und die Gewebe. II. P. 273, 274,
276.

242 Theories Treating of Inheritance

as appears from his own words here quoted, that if the
organism appears to pass again during ontogeny through
the preceding phyletic stages this depends merely upon
the fact that there is no other materially possible way for
the idioplasm to attain the phylogenetic equilibrium just
acquired.

But to accept this is to deny the law of repetition.

One notes that Hertwig was lead to reject this law, as
he himself admits, only because he wished to avoid the
objection which Weismann had already urged against
Nageli; namely that if one supposes that different phylo-
genetic forms may be due to respective idioplasms qual-
itatively different from one another it is not possible to
understand how the same forms when they succeed one
another in the ontogeny of a single species can then
depend only upon “different conditions of tension and
movement,” of one and the same idioplasm.

But it seems to us that Hertwig has attempted in vain
to circumvent this obstacle.

“A very general and very astonishing fact,” writes
Delage, “is that ontogeny almost never follows a direct
and simple course. The cells almost never dispose them-
selves from the beginning in the order which would bring
the embryo soonest to its final conformation. Ontogeny
approaches its goal gradually, but as though compelled to
tack against a contrary wind, and its long tacks carry it
sometimes far to the side. It shapes a number of rudi-
ments, permits purposeless members to arise, opens gill
clefts in a lung breathing animal only to close them again,
and so on.” 186

These tacks, these deviations hither and thither, cer-

*Delage: L’hérédité etc. P. 175—176.

Driesch 243

tainly do not denote any endeavor of the idioplasmic
substance to proceed by the shortest route to the condi-
tion of its equilibrium. They indicate that it is quite
impossible on the one hand to accept the passage of
ontogenetic through phylogenetic forms and on the other
hand to refuse to this process the significance of an actual
repetition of phylogeny by ontogeny. In other words
one must seek the cause of this repetition not merely in
biologic laws of maintenance of the equilibrium in an
existing homogeneous idioplasm, but chiefly in the entire
past of the species and just in the historic fact that it
passed during its development through such and such
phylogenetic forms.

And so the objection urged by Weismann against
Nageli can be urged in its full force and even more justly
against Hertwig. For though Nageli gave no explana-
tion of their causes and ways of action, he nevertheless
accepted the activation of a whole series of different
anlagen of the idioplasm in exactly the same serial order
as in their phylogenetic appearance. Hertwig on the con-
trary after he had first accepted this activation of succes-
sive anlagen of the idioplasm finally rejected it.

Driesch

This author’s conception of organic development
cannot in its very nature afford any explanation whatever
of the inheritance of acquired characters and conse-
quently, admitting that this inheritance exists, ought for
this very reason to be considered inadmissible. It can be
summed up in the following words of its author.

“Each cell concerned in the ontogenesis in so far as it
possesses a nucleus really carries within it the sum total
of all anlagen; in so far however as it possesses a specific

244 Theories Treating of Inheritance

protoplasmic body it is, just on account of this latter,
susceptible of being acted upon by only certain causes
(causes which effect the liberation of different individual
nuclear energies).”

“We believe that the capacity of reacting to stimuli
resides in the nucleus, but that the capacity of receiving
them resides in the protoplasm, which is chemically
specific in each elementary organ. The protoplasm is thus
the medium, (the zone of perception), between the
liberating causes and the nucleus, (the zone of action).”

“The appearance of elementary processes comes about
in each ontogeny through a liberation of potentialities.
* * * JT break the whole of ontogeny up into a series
of liberated effects.”

“Each liberating cause produces not only a chemical
specificity and thereby the new elementary process as such,
but it produces through this specificity at the same time
the limitation by which the new cell is capable of receiv-
ing later only certain further liberating causes.” 187

The especially striking thing in this conception is the
absence of any real, continuous, reciprocal dependence of
the different parts one upon another throughout the
whole course of development. Each cell will preserve in
its nucleus, it is true, the germinal substance uninjured;
but the successive liberation of special nuclear energies
which will impart to it its own especial character, depends
fundamentally only upon the specific properties which
its protoplasm had already acquired earlier, and not upon
the reciprocal actions which exist between all parts of the
body throughout the whole duration of ontogeny, as it
would according to Hertwig’s theory, for instance.

*"Driesch: Analytische Theorie der organischen Entwicklung.
P. 81, 49, 60, 82.

Driesch 245

For the specific protoplasm which a certain cell has
already acquired at a given moment of ontogeny by re-
ceiving only one certain stimulus corresponding to its
immediately preceding specificity, would really become
the special cause by which among all possible nuclear
energies only that one becomes liberated which should
become active at that instant. The activation of this new
nuclear energy would in its turn modify the specificity of
the protopiasm of this cell and of its immediate descend-
ants; and this protoplasm so altered would then become
the cause of the reception of a new specific stimulus and
of the consequent liberation of the next required nuclear
energy; and so on up to the completion of development.

Each cell of any given ontogenetic stage would thus
come to carry in itself all that is necessary to determine
its own future character and that of its most remote
descendants, with the exception of the various stimuli
which it is the duty of the protoplasm to select and to
receive.

One thing is not quite clear in this. Do these liberat-
ing causes of the different nuclear energies, that is these
stimuli, among which each protoplasm should select and
receive only those belonging to it, come only from the
world outside the organism, or also from the reciprocal
actions of the individual parts in the interior of the
organism? In the first case it would be necessary to place
Driesch among the out and out evolutionists; in the
second, his theory would be a mixed one, that is it would
rest upon phenomena of evolutionistic nature combined
with others of epigenetic nature.

We shall not set forth any further here what enor-
mous difficulties one would encounter in either case if one
sought to build up in accordance with this theory any

246 Theories Treating of Inheritance

conception of a mechanism for the inheritance of acquired
characters. Even if the hereditary substance should be
preserved in its entirety, and unaltered, in the nuclei of all
cells without exception throughout development, this
would be ascribable only to qualitatively equal nuclear
division. But one could not but ask why the modifica-
tions which supervene in the hereditary nuclear substance
of such and such somatic cells in consequence of a new
local functional adaptation in the adult stage should not
remain limited to these cells alone.

Very noteworthy, however, in Driesch’s theory is the
conception that ontogeny takes place by means of a series
of successive liberations of different energies remaining
up till then in the potential state, and also that one result
of the liberation of each of these energies and of the
effects which it produces is that the necessary and
sufficient conditions for the liberation of the next follow-
ing potential energy are brought about.

Herbst

The epigenetic conception of Herbst is still less
capable if possible, than that of Driesch of rendering con-
ceivable any mechanism whatever for the inheritance of
acquired characters.

He mentions at first several experiments upon the
way in which unicellular organisms and cells react to cer-
tain stimuli, and also a great number of facts serving to
show the great dependence of plant ontogenies especially
upon external influences. While it is evident that
external influences constitute most often only liberating
or releasing stimuli, they seem on the contrary to become
in certain formations real formative stimuli. In these
formations there is involved not only a true ontogenesis

Herbst 247

but an actual phyiogenesis which would repeat itself in
each generation cx novo, because of the repetition always
in the same way of the same external formative influence.

After having thus stored up a rich harvest of facts
upon the physiological actions exerted by the most differ-
ent stimuli upon organisms or upon given parts of
organisms,—actions which are properly nothing else than
functional adaptations in a broad sense of the word,—
Herbst believed he was able to build upon them his
epigenetic conception, by which he makes development
fundamentaly dependent upon a whole series of directive
stimuli.

“Just as freely moving organisms are influenced in
the direction of their movements by external agents, so
do independent tissue cells react to definite directive
stimuli, and thereby make possible the production of a
large number of ontogenetic formative processes.”

“Just as the germinal vesicles of Cuscuta, for ex-
ample, develop their stinging barbs at the points of
contact with the plant upon which they lodge, just as in
the leaf stalks of Helleborus niger the traction of a weight
causes the formation of new mechanical elements which
otherwise do not appear, or just as roots may be made to
grow on a grass stalk because of the secretion of a gall
fly, so, in the interior of an animal embryo in process of
development a given organ can cause new formative pro-
cesses to come into existence in another organ by means
of contact, pressure, traction, by a specific product of
metabolism or in some other way.”

And so, “just as in plants and sessile animals
morphological formations of the most different kinds are
produced through formative stimuli which either arise
from the external world or are exerted by one organ of

248 Theories Treating of Inheritance

the organism upon another; so also the morphological
changes in animal ontogeny arise in the same way
through manifold inductive stimuli ‘“Inductionsreize”
which are almost always of internal origin.” °°

This conception, especially if it is extended to the
whole process of development in general, would really
amount to a reduction of ontogeny, exactly as in the plant
formations above mentioned in which external agents act
as true formative stimuli, almost to a phylogeny, con-
stantly repeating itself anew in each generation. And
the fact that successively arising generations would in
spite of that remain always alike is to be attributed to the
repetition, proceeding always in the same way, of succes-
sive functional stimuli both without and within the
organism in process of development, which are produced
gradually one out of the other through the principle of
fructifying causality and give rise each time to these new
phylogeneses.

In this respect the conception of Herbst recalls the
purely mechanical explanation of development given by
His, who refers the appearance of the same ontogenetic
phenomena every time to the repetition of definite me-
chanical influences, proceeding always in the same way.
Since each influence, itself induced by the influences
preceding it, induces in its turn the influences following
it, then if only the first link of the chain is constantly
repeated in the same way in each generation, that would
be enough to cause the same thing to happen in the case
of all the others.

**8Herbst: Uber die Bedeutung der Reizphysiologie fiir die
kausale Auffassung von Vorgangen in der tierischen Ontogenese.
Biol. Centralbl. 1894. Bd. XIV. No, 18—22. P. 771; and Bd. XV,
N. 20—24. P. 852.

Herbst 249

One notes that these theories of Herbst and His and
other similar ones imply an extraordinary independence
and autonomy even during ontogeny not only in each part
of the organism but even in each cell. The development
of each particle, even the most minute, would thus depend
fundamentally upon the independence of its response to
the action of its immediate or close environment, even
though this response is given in a very definite manner
and is in no wise arbitrary. But this is hard to reconcile
with the mutual adaptedness which there must necessarily
be between the different parts constituting a single co-
ordinated whole. And it is still more irreconcilable with
the constancy and precision with which even the most
minute peculiarities of the organism are reproduced in
each development, even when the conditions of the en-
vironment in which it takes place do not always remain
alike in respect to nutrition, temperature or other factors.

And so much the more, since the principle of fructify-
ing causality, employed to explain this constancy and
rigorous precision with which the same series of onto-
genetic phenomena is always repeated, is a sword with
two edges. For, admitting that only a single one of the
numberless intermediate links of the chain should find
itself in a somewhat different condition in relation to its
environment, or should differ in any way even though
inconsiderably from the corresponding link of the preced-
ing generation, a thing which one might well assert occurs
in every ontogeny, then the remaining portions of the
chain would find themselves, because of the modifications
accumulating and multiplying like an avalanche, altered
throughout, and therefore in the last links also. The
mutual adaptedness of numberless different parts and
their co-ordination into a single harmonious whole, and

250 Theories Treating of Inheritance

the constant precision in the repetition even of the most
minute peculiarities, stipulate fundamentally an individual
ontogenetic factor, which is directive and at the same
time co-ordinative, acting at each moment of develop-
ment throughout the entire organism even to the smallest
single parts of it. But ontogenetic theories like those of
Herbst or His take a stand diametrically opposed to this.

It is also almost superfluous to remark that they cannot
give the least account of the repetition of phylogeny by
ontogeny, and still less of the inheritance of acquired
characters.

For the latter, as we can well assert without needing to
fear that we get too far from the truth, requires ab-
solutely the condition, certainly not sufficient, yet at least
necessary, that just this ontogenetic factor of individual
nature should act everywhere and incessantly and also
that it should not give up the control of development
even for a moment, so that it may thus be in a position
to experience in itself each variation even the smallest
appearing in the organism in consequence of any new
functional adaptation. But the theories of Herbst and
His, and all others like them, which have recourse only
to the principle of fructifying causality, rest upon the
conception that the successive influences would always
be left to themselves by their respective special causes,
as soon as they had once been produced and launched,
so to speak, into development, to produce in their turn
new influences.

Therefore these theories necessarily exclude any
inheritance of acquired characters. But if this latter
actually exists they become, as we have said, quite
untenable from this point of view also.

Orr 251

Orr

Orr takes as his starting point the conception that he
has formed concerning the way in which the pluricellular
organisms arise from the unicellular.

It is easy to understand that after the unicellular
organism in the course of generations had attained a
certain size, its external surface might have become
transformed in consequence of contact stimuli into a
denser protective layer, and thereby have lost its repro-
ductive capacity, which would have been preserved only
in the inner part of the organism.

“When such an organism as this would be divided
into a number of pieces by the natural process of repro-
duction those parts of the protoplasm which had not
undergone a grosser material differentiation would be
like the protoplasmic germs of all its ancestors, capable
of responding to the same stimuli, and therefore of devel-
oping in the same manner. The only difference between
these and the ancestral germs would be the increased
complexity of their nervous co-ordinations. But, on the
other hand, part of the organism which has been dif-
ferentiated into the denser outer layer would be in
structure so different from the germs of the species that
it would be incapable of responding to any of their accus-
tomed stimuli and therefore incapable of repeating the
development.”

“But at every step in the evolution a part of the
protoplasm retains its original qualities, only changing
its nervous condition to a condition of greater complexity
of co-ordinations. In this way the original protoplasm
gradually adds to itself the co-ordinations for developing

252 Theories Treating of Inheritance

in each generation, first cell walls, and then the differ-
entiated organs.” 189

From the whole work of Orr it seems to result with-
out any possible doubt, that according to his view this
non-differentiated part of the protoplasm is present in
all the cells of the organism, is everywhere quite similar,
and is continuous to the extent that stimulating influ-
ences can be transmitted from any given part whatever
to all parts of the animal, so that it constitutes a complete
physiological unit.1°°

But on the other hand it is never to be seen quite
clearly what this investigator understands by this greater
complexity of co-ordination. The fact that the nervous
system presides over all physiologic activities of the
organism makes him think rightly that development also
may be dependent on similar nervous phenomena. Only
in the nervous system of the organism is clearly to be
seen what is to be understood by a greater complexity
of nervous co-ordinations, because it is constituted by
numberless points, distinct from one another and con-
nected with one another in more or less complicated ways
by direct or indirect nerve tracts. In undifferentiated
protoplasm on the contrary, which remains always en-
tirely similar in the most different parts of the body,
and a fortiori in that infinitely small part contained in
the germ cells, one could not conceive in what these stup-
posed nervous co-ordinations and this ever greater com-
plexity of co-ordinations could consist, and what their
significance would be.

The following passages do not clear up any of the

*°Orr: A Theory of Development and Heredity. New York,
Macmillan, 1893. P. 127—128.
+90 g. Ibid. P. 124.

Orr Bea

obscurity: “When we consider the protoplasm’s respon-
siveness to stimuli and to the effects of repetition or prac-
tice, with the intricate co-ordinations that may thereby
be effected, also the impressions made by stimuli which
remain long fixed as “memory,” we are led directly to
suppose that the property which is the basis of bodily
development in organisms is the same property which
we recognize as the basis of psychic activity and psychic
development.”

“On the same principle that a thought in the mind
calls up an associated thought, or one tone of music
calls up another, or one action in an oft repeated series
of actions calls up the next subsequent action or actions,
so the initial stimulus being given to an incipient organ-
ism, its responsive activity each time tends to produce
by association the next activity in the oft repeated series
and so on through the successive steps of growth and
development.” 191

The points of contact between the mnemonic phenome-
non of the association or succession of ideas and the phe-
nomenon of ontogenetic development have already been
very rightly brought forward by others and we shall
return to them for closer examination in the last chapter.
It may be remarked here merely that the first can in no
way serve to explain the second. For in the first place
it belongs to a class of phenomena still more specialized
and more complex than the phenomenon to be explained,
in the second place the conditions of origin and of repeti-
tion are quite different in the two phenomena.

When a melody strikes the ear for the first time and
is later often repeated it leaves behind impressions on

21Orr: Ibid. P. 238—230, 142.

254 Theories Treating of Inheritance

several nerve centers and unites them by new nerve tracts
becoming always smoother. These new impressions and
tracts remain then unaltered in the same places in which
they were produced and it is just in their continuance
in the place of their origin that there must be sought the
reason of the always greater ease with which these
melodies are reawakened in our memory. When the
muscles of the hand become accustomed to producing a
musical exercise, the greater development of the muscles
and the greater complexity of the nervous co-ordinations
which connect them with the brain constitute well defined
material alterations which remain unaltered in the places
where they arise and make the exercise, at first difficult,
always easier.

In the development of the organism on the contrary
the causes of the repetition each time of always the same
ontogenetic stages must reside in a single cell, the germ
cell. But this cell is not in any way the place in which
are produced the material alterations which were acquired
by the parent organism and handed over to the descend-
ants, like the stronger development of certain muscles,
the greater complexity of certain nervous co-ordinations
and other similar variations. Of the stronger develop-
ment of muscles, of the greater complexity of the nervous
co-ordinations which are produced in the parent organ-
ism, there remains absolutely nothing, in so far as they
represent alterations of muscles and nerves, in the little
particle of matter which is destined to produce the
descendants.

Consequently the comparison of the two phenomena,
although certainly very suggestive, is not sufficient by
itself to afford in any way an explanation of ontogenetic
phenomena.

Orr 255

Orr continues in these words: “The co-ordination
of forces which determines development is not to be
considered a definite, localized mechanism, wound up,
and ready to go when touched. If such were the case
we ought to find one such mechanism allotted to a cer-
tain definite number of cells; but instead we find that
each piece (of a hydra), regardless of the number of
cells, or whether it be the half or the twentieth of the
hydra, is capable of producing only one new individual.”

“The quality upon which development depends seems
to reside in a small piece just as well as in a large piece
and moreover equally in all parts.”

“T think we can best compare the inheritance of the
plan and potentiality of development in the clump of
protoplasm to inherence of ideas and potentialities of
volition in the brain substance, not as though each idea
and potentiality were located there in its own minute
definite limited space, and attached to a definite mechan-
ism of matter; but rather we should think of development
and mental potentialities as dependent upon certain states
of living matter, which states are the result of the entire
past history of that living matter and which thus deter-
mine the method of response to external stimuli, and the
direction which shall be taken by the new energy con-
stantly entering from the outside.” 1%

This recalls again the above mentioned conception of
Nageli and Hertwig of idioplasm which is both general
and mnemonic, with all its short-comings which consist
in complete indefiniteness or worse yet in lack of content
masked by empty words.

Nevertheless it is worthy of notice that however

192Orr: Ibid. P. 172—173.

256 Theories Treating of Inheritance

indefinite the theory of Orr may be, it contains a clearly
expressed and very remarkable idea, namely: the con-
ception that nervous activity is the only general phe-
nomenon and basis of life. Orr attributes to it therefore
the great function of forming by itself the whole mechan-
ism of development as well as of the inheritance of
acquired characters, and seeks to explain through it the
striking analogy between this mechanism. and_ the
mnemonic phenomenon.

Cope

In order to explain the inheritance of acquired char-
acters Cope starts out with the following investigations
upon butterflies. By exposing larvee which were near
the stage of pupation to different colors, the correspond-
ing colors were produced in the chrysalids developed.
In another experiment larve, which were in the act of
weaving cocoons, on exposure to certain colors were
induced to weave cocoons of corresponding colors.

“Tn the first experiment,” explains Cope, “the dynamic
effect produced by the exposure was stored for the period
which elapsed between the exposure of the larva and
the full development of the pupa. The second experi-
ment demonstrates that a stimulus may be transmitted
to a gland so as to modify the character of its secretion
in a new direction. From both experiments we learn
the transmissibility of energy from the point of stimulus
to a remote region of the body, and its conversion into
growth energy (in this case by physiogenesis). This
prepares us to look upon heredity as an allied phe-
nomenon, i. e. the transmission of a special energy from
a point of stimulus to the germ cells, and its compo-

Cope 257

sion there with the emphytogenic (inherited) energy
into bathmism (or evolutionary energy).” 198

From this he at once diaws the conclusion that as
soon as a new character is acquired by the soma in con-
sequence of a definite stimulus, it appears at the same
time in the germ plasm also. This simultaneous double
acquisition of the same character by the soma and by
the germ represents his theory of “diplogenesis:” ‘“The
effects of use and disuse are twofold; viz.: the effect on
the soma and the effect on the germ plasm. Those who
sustain the view that acquired characters are inherited
must I believe understand it as thus stated. The char-
acter must be potentially acquired by the germ plasm
as well as actually by the soma. Those who insist that
acquired characters are not inherited forget that the
character acquired by the soma is identical with that
acquired by the germ plasm, so that the character acquired
by the former is inherited but not directly. It is
acquired contemporaneously by the germ plasm and in-
herited from it. There is then truth in the two appar-
ently opposed positions, and they appear ta me to be
harmonized by this theory of diplogenesis.” ***

It is almost unnecessary in this connection to remark
that, if one sticks to the letter, this supposed double
acquisition of the same character by the soma and by
the germ, lacks any foundation in fact and indeed appears
inconceivable. For in the first place the two experi-
ments quoted above concern phenomena too special, too
complex, and as yet too little analysed to permit of
their utilization as foundations for any theory. In the

183Cope: The primary Factors of organic Evolution. Chicago.
The Open Court publishing Company. 1896. P. 440.
1%4Cope: Ibid. P. 442, 443.

258 Theories Treating of Inheritance

second place if this character instead of consisting in a
general change existing in all the cells concerned, is
rather any given local morphological or physiological
modification whatever of definite organs or tissues, it
will evidently be impossible to represent this modification
as acquired at the same time also by the germ plasm,
since in the latter these organs and tissues do not exist.

It seems nevertheless that Cope’s meaning is that
each even local morphological or physiological modifi-
cation of the soma must always correspond at the same
time to a certain specific, dynamic state of the proto-
plasm in general, and that it is this new dynamic state
which would be acquired at the same time by the proto-
plasm of the soma and by that of the germ.

For to explain “the way in which the influences which
acted upon the general structure reach the germ cells,”
he builds up his “dynamic theory,” taken from the do-
main of molecular physics, and has recourse to that spe-
cial form of energy mentioned above, which he calls
“bathmism.” And this bathmism would consist acord-
ing to this author “in a mode of motion of the molecules
of living protoplasm by which the latter build tissue at
particular points, and do not do so at other points.”

“This action is most easily observed in the begin-
nings of growth, as in the segmentation of the oosperm,
the formation of the blastodermic layers, of the gastrula,
of the primitive groove, etc. In the meroblastic embryo
the energy is evidently in excess at one point of the
oosperm and in defect at another. This is a simple
example of the location of growth force or bathmism.
In all folding or invagination there is excess of growth
at the region which becomes the convex space of the
fold; i. e. a location or especial activity of bathmism at

Cope 259

that point. All modifications of form can thus be traced
to activity of this energy at particular points.”

“The building energy being thus understood to be a
mode of molecular motion, we are not at liberty to suppose
that its existence is dependent on the dimensions of the
organic body which exhibits it. It is as characteristic
of the organic unit or plastidule as the mode of motion
which builds the crystal is of the simplest molecular
aggregate from which the crystal arises. Bathmism has,
however, no other resemblance to crystalloid cohesion.
The latter is a simple energy which acts within geo-
metrically related spaces, without regard to anything
else than the present compulsion of superior weight-
energy. In bathmism we see the resultant of innumerable
antecedent influences, which builds an organism con-
structed for adaptation to the varied and irregularly
occuring contingencies which characterize the life of liv-
ing beings. As this resultant is distinctive for every
species, bathmism must be regarded as a generic term,
and the characteristic growth energy of each species as
distinct species of energy, which present also diversities
expressive of the peculiarities of individuals.” 1°

It would be superfluous to bring forward the extraor-
dinary indefiniteness and, we can almost say, pure
verbalism without any foundation in fact of this theory
of Cope’s which approximates closely Haeckel’s theory
of perigenesis with its undulatory plastidular movement.
We shall confine ourselves to remarking merely that each
given dynamic state of the protoplasm peculiar to a
given species, when it thus represents in itself the result-
ant of all dynamic states, which were peculiar to the

5Cope: Ibid. P. 447—449.

260 Theories Treating of Inheritance

protoplasm during the whole course of phylogeny, would
nevertheless not cease on that account to constitute still
a special dynamic state which is quite different from the
preceding ones, and which cannot possibly preserve
materially even the smallest trace of them. Therefore
this theory of Cope leaves the repetition of phylogeny
by ontogeny quite as incomprehensible as did that of
Haeckel. And on the other hand one cannot see how
the protoplasm could be in the same identical dynamic
state in all the most different parts of the soma and yet
give rise to specific biologic phenomena correspondingly
different in each of these parts.

It would have been on the contrary a much more
suggestive idea, had Cope sought to reduce all the dif-
ferent, contemporaneous, physiological and morphological
variations of the organism, not so much to a single
and everywhere uniform change of this given growth
energy, as rather to numerous specific variations of a
single generic form of energy, so that the latter would
thus represent to a certain extent the common denom-
inator of all these unlike morphological and physiological
variations. For this is in any case one of the means
which every theory must employ which essays to explain
the inheritance of acquired characters. For when once
all variations of the most manifold forms of energy,
acting simultaneously upon the most different points of
the organism, are attributed to as many specific varia-
tions of a single form of energy as the basis common
to all of them, then it would be easy to combine with
it the conception that for each complex state of the
organism there might appear in the germ a single, well
defined specific mode of being of this common form of
energy, as the resultant of all these specific different modes

Cope 261

which are active simultaneously, each in its own way in
the most different points of the soma. And just as the
resultant of several forces acting upon one point at the
same moment can be decomposed again into its former
component parts, all of which would still act simulta-
neously, so it is conceivable how this particular mode
of being of the common form of energy which arose
and was stored up in this way in the germ can become
decomposed again at the proper time at all the various
points of the new organism into the same modes of being
as formerly, which had already been its components in
the parent organism.

To mitigate the fault of indefiniteness in his theory
this investigator, just like Haeckel, Orr and many others,
also compares the ontogeny thus produced by bathmism
with the mnemonic phenomenon. And although he has
thereby certainly neither removed or even diminished
the general vagueness which characterizes his whole
theory he succeeds nevertheless in expressing here a
remarkable and suggestive idea.

“We may compare the building of the embryo to
the unfolding of a record or memory which is stored
in the central nervous system of the parent and impressed
in greater or less part on the germ plasm during its
construction, in the order in which it was stored. This
record may be supposed to be woven into the texture
of every organic cell and to be destroyed by specializa-
tion in modified cells in proportion as they are incapable
of reproducing anything but themselves.”

“In the case of the germ plasma no other specialization
exists so that the entire record may be repeated stage
after stage, thus producing the succession of type-
structures which embryology has made familiar to us.

262 Theories Treating of Inheritance

In the process of embryonic growth, one mode of motion
would generate its sucessor in obedience to the molecular
structural record first laid down in the ovum and sperma-
tozooid, and then combined and recomposed on the union
of the two in the odspore, or fertilized ovum.”

“Were all cells identical in characters, every one
would retain the structural record or memory of its past
physical history as do the unicellular organisms. Evolu-
tion has however so modified most of the structural
units of the organic body that none but the nervous
and reproductive cells retain this record in greater or
less perfection. The nervous cells have been specialized
as the recipients of new impressions, and the excitors of
definite corresponding movements in the cells of the re-
mainder of the organism. The somatic cells retain only
the record or memory of their special function. On
the other hand the reproductive cells which most nearly
resemble the independent unicellular organisms, retain
first the impression received during their primitive
unicellular ancestral condition; and second, those which
they have acquired through the organism of which they
have been and are only a part.” 19°

As we shall devote ourselves in the last chapter to
the comparison of the ontogenetic phenomenon with the
mnemonic, it will suffice here to bring forward, as a
contradiction to the same author’s assertion reported
above in respect to a single dynamic mode in the whole
organism, the complete mnemonic somatization of the
specialized somatic cells, or nuclear somatization, which
this investigator recognized, and also his suggestive sub-
stantial equalization of the nerve cells with the repro-

*°°Cope: Ibid. P. 451—453.

Delage 263

ductive cells as the only cells endowed with unsomatized
memory, and consequently as the only ones which would
be likewise capable of preserving more or less com-
pletely the memory of past generations. Nevertheless
he should in our opinion have limited this equalization
with the reproductive cells to those nerve cells which
are least differentiated.

Delage

According to Delage, “The egg is like a star thrown
out by an initial force into the midst of a system of
stars in movement. Its trajectory will be influenced and
determined by all the stars whose sphere of action it
traverses, but nevertheless, if anything had been altered
in its mass or in its initial movement, it would not have
been what it is. It is not dependent on the system alone
nor is it at any point independent of it. Every other
similar mass thrown out at the same point, with the
same force in the same direction will reproduce a tra-
jectory identical with its own; but every difference even
the most minute, in any one of these three factors will
be able to induce considerable differences in the form
of this curve.” 197

This comparison leaves the repetition of phylogeny
by ontogeny and the inheritance of acquired characters
out of consideration.

The inheritance of acquired characters is nevertheless
accepted in part at least hy Delage, who explains it thus:
“When a new chemical compound introduced into the
organism produces different effects at different points,
that is undoubtedly due to this, that it finds at each

1s7Delage: L’hérédité etc. P. 802—803.

264 Theories Treating of Inheritance

individual point a different cell substance as the pre-
dominant element. Then if the egg contains the sub-
stance characteristic of certain cells of the organism,
it must be affected at the same time as these cells and
by the same influences. According as these influences
exert an exciting or depressing influence and so provoke
the corresponding organ to further development or to
atrophy, there will be produced a similar action in the
egg, the corresponding substances will undergo a certain
growth or a certain regression and when the egg develops,
the cells whose task it is to localize these substances
within them, will experience the effects of this regression
or of this growth.” 798

In the first place it is to be noted here that the organs
whose modifications produce new phyletic stages do not
usually either develop or atrophy uniformly in all direc-
tions. Indeed, specific morphological alteration consists
rather in a growth or diminution always proportionally
unlike in different directions. The particular substance
which has increased in the egg can serve at most for
the explanation of a quantitative increase in mass of the
organ, but not for a morphological increase, different in
each different direction, like that which the parent organ-
ism has experienced.

In the second place this explanation cannot be satis-
factory since there may be growth in one organ, while
another organ consisting of the same tissue, such as
nervous, muscular, bony tissue, etc., may remain un-
changed or even regress. These organs consisting of
the same tissue ought all to grow or diminish alike with

*Delage: Ibid. P. 837.

Delage 265

each change which their particular substance experiences
in the egg.

In the third place, this would at all events suffice
only for the explanation of inheritance of those char-
acters which develop in the parent organism under the
influence of definite chemical actions, distributed through-
out the whole body, and acting only upon those particles
or cells of the body which have a certain chemical com-
position. But what explanation could that give of true
morphological inheritance and so of the inheritability
of the growth or of the atrophy of an organ resulting
from too much or too little use?—of the inheritability
of the spongy structure of bone, of the conformation of
the eye, and of all functional adaptations in general?

Yet Delage gives the following explanation of the
inheritance of the atrophy of unused organs.

“That only is determined in the egg, which is not
determined by functional excitation, but the amount
determined by the latter is enormous.” The absolute
uselessness of slight reductions of the atrophied femur
of the whale and the consequent inefficacy, in this respect,
of natural selection, and on the other hand, the impos-
sibility of understanding how the slight reduction in
volume which the femur undergoes during the life of
the individual can extend its influence to the egg, and
determine in that the modification necessary for the
reproduction, in the following generations, of this new
reduction in volume, ‘forces us to admit,” continues the
author, “that neither in consequence of a fortuitous
variation fixed by natural selection, nor in consequence
of an acquired and inherited modification does the egg
of the existing whale differ in so far as the femur is
concerned, from the eggs which produced the whales

266 Theories Treating of Inheritance

of centuries ago, whose femur was only a very little
greater than that of the whales of today.”

It still remains then to explain, without devising
some improbable hypothesis, how the same kind of egg
can produce two different forms. And that is not very
difficult when one keeps functional excitation in mind.”

“When an animal has a femur 20 cm. long, that
does not indicate that in its egg all the conditions were
present for the formation of a bone of this length. That
indicates only that the elements necessary for it are
there, which with the co-operation of the functional
stimulus can form a femur of such length. We cannot
know just what part this latter takes in the result, but
it must be considerable.”

“While the whale had still a femur, which though
not normal was yet only half atrophied, the femur pro-
ducing factors inherent in the egg were perhaps suffh-
cient to produce a bone of only the size of that present
in the whales of today, and the functional stimulus,
which as Roux has shown, begins to operate even in
embryonal life, did the rest. It is therefore not astonish-
ing that upon the cessation of the functional stimulus, the
femur became reduced to a very little rudiment.” 1°

But the embryonal functional stimulus in the whales
of many centuries ago whose femurs were only a very
little bigger than those of the whales of today, cannot have
been different from the embryonal functional stimulus
of the whales of today, no matter how much one may
limit direct morphological action of the egg, if one starts
out from the hypothesis that the eggs concerned are quite
identical. Why should the embryonal functional stimu-

Delage: Ibid. P. 854—857.

Delage 267

lus in respect to the useless femur, already so atrophied,
have been greater in the former than in the latter? The
progressive diminution of the femur remains thus entirely
unexplained.

Finally Delage accounts for the parallelism between
ontogeny and phylogeny in the following way:

“The functional stimulus appears, we agree with
Roux, even in embryonal life, but is at this time certainly
weaker than after birth. There results from that a note-
worthy consequence which escaped Roux. That is that
at least the relative atrophy of the organ becomes more
marked the older the animal becomes, and that, in respect
to the atrophied organ, the young, and above all the
embryo, must differ much less from the ancestral forms.
Thus there is explained at once the parallelism between
ontogeny and phylogeny in everything which is depend-
ent upon atrophy or hypertrophy induced by use or dis-
use, that is in very many cases.” 2°?

Is it inactivity that really causes in serpents the retro-
gression during embryonal life of the already partially
developed limbs? Or is it use that in the salamanders
causes to any extent the development, during embryonal
life, of the same limbs? Whence come these very unlike
embryonal processes of activity or inactivity? Why did
not this same inactivity, consequently this same atrophy,
show itself in the embryos of the remote ancestors of
the serpents of today? Why does the inactivity and
consequently the atrophy of these extremities depend,
in the egg of the present day serpents, upon conditions
within the embryonic organism itself, and manifest itself
at exactly that ontogenetic moment, which corresponds

20Delage: Ibid. P. 856—857.

268 Theories Treating of Inheritance

to the phylogenetic moment at which it was produced
in their ancestors, whereas in the latter this reaction
commenced only when the animal was exposed, after
leaving the egg, to the influences of the external world,
and was rendered necessary only in consequence of very
definite circumstances external to the organism? We
see thus that the question of the repetition of phylogeny
by ontogeny finds no answer at all. It seems to us
further that there remains only the erroneous view that
entire phylogenetic epochs could have gone by, without
leaving behind any trace in the egg, so that the progress
of each ontogeny would be nothing else than a phylogeny
which is almost entirely repeated each time.

In the second edition of his work Delage recognized
himself that the significance attributed by him to the
functional stimulus in ontogeny is exaggerated.2°! And
he admits that he was embarrassed in explaining by
it both the special fact of the formation of an organ so
complicated and so well adapted to its purpose as the
eye, for which during embryonal life there was never-
theless lacking any functional stimulus, and also the
phenomena of regeneration, or the general fact that
nearly all organs without exception show, from the first
stages of their development on, an adaptation to the func-
tions which they will perform only later.2°?

LeDantec

According to LeDantec’s theory, each individual,
living, elementary mass or plastid “contains a mixture
of different plastic substances, which are distributed in
such a way that assimilation represented by the equation:

201Delage: Ibid. P. 862. Remark.
*°*Delage: Ibid. P. 870,

Le Dantec 269

a+Q=nra+R (where a=mass of each single
specific assimilating substance; Q = mass of the nutritive
substances absorbed; » = coefficient > 1; and R = mass
of the substances of refuse), multiplies all these sub-
stances and preserves to them their original proportions.
Destruction however, or at least certain destructions, act
separately on each of these substances and alter the pro-
portions of the mixture and consequently the characters
of the plastid.” 2°%

From this it appears that LeDantec attributes all
variations which the plastids or organisms in general
can undergo, to total or partial destructions of the dif-
ferent, particular plastic substances (a) already present,
but never to the production of new plastic substances.
The numbers and characters of plastic substances, which
participate in the formation of the complex substance
of the plastid or rather of the organism in general, may
be different in different species. The difference between
different species and between different individuals of the
same species, would consist only in the proportions in
which the special plastic substances (a) peculiar to this
species, are united.

“We are inclined to regard the living substances of
the plastids as mixtures of different plastic substances,
the substances (a). The species of the plastids would
be determined by the nature or quality of these plastic
substances; their individual peculiarities, their person-
ality, would depend upon the proportions of the mixture of
these specific plastic substances. In the same way we must
regard the individual substances in the higher organisms
as characterized by a mixture in definite proportions of

#87 6 Dantec: Traité de Biologie. P. 93.

270 Theories Treating of Inheritance

the living substances characteristic of their species. We
are able in this way to present even a mathematical defini-
tion of the personality of a given individual of a species,
to a certain extent an arithmetical personal description
of this individual, namely the list of co-efficients of the
mixture of his specific substances.” 2°4

The proportions of this mixture persist unaltered in
all cells of the same organism. Upon this mixture
depends the quality of the chemical reactions, i. e. of the
molecular movements; upon these latter again depend
the molar movements or osmotic currents of nutritive and
excretive material; upon the molar movement finally
depends the form of each plastid as well as that of the
most complicated organism:

“Tt is absolutely useless to suppose, in the egg which
produces man, other characters present than for example
those of a simple hepatic or epithelial assimilative ele-
ment, determining by this assimilation the molar move-
ments around it. These molar movements associated
with the movements which result from assimilation in
neighboring elements, and also with the existence of the
skeleton such as is constituted in a thenceforth unchange-
able form from the moment of its first anlage, determine
the conditions of local equilibrium from which the local
form of the body results. Analogously as soon as a
human element (the fecundated egg) is capable of liv-
ing by itself alone, the molar movements, which assimila-
tion provokes first in this element alone and later in all
which are derived from it, determine the successive
forms of the growing mass arising from assimilation.
The phenomenon appears from the outside then to be

24 Le Dantec: Ibid. P. 267.

Le Dantec 271

quite otherwise than as though this element had assimi-
lated without being isolated, as though for example it
had belonged to a man in process of growth. It would
then have been the destiny of this element, thanks to
the combined “dynamisms” of the neighboring elements,
to build up a part of the man, but not a whole man.” 2°

Finally the transformations to which the living sub-
stance would be forced by the constraint of external
influences may be hereditary, i. e. can take place anew
in the descendant organism without any further need of
the action of the same constraint, because they would
alter the living substance itself in a corresponding way,
so that it adapts itself to the new conditions of
equilibrium :

“If assimilation were the only possible phenomenon
of living matter there would not take place any alteration
of the living substance through external influences; but
upon the truly vital phenomena of assimilation are super-
imposed as we have seen phenomena of destruction, and
the co-operation of these two phenomena can result in
changes in the nature of the substance, in the definite
proportions of the mixture forming it; thus education
can modify heredity.”

“Since the form is the result of the molar move-
ments of the metabolism of all cells of the body, a
variation imposed on the form reacts upon these molar
movements by which again the molecular movements in
the interior of the cell are determined. Then in con-
sequence of this form imposed on the body mass, there
will occur within the cells phenomena of destruction,
i. e., of variation. The variations may take any direction

2066 Te Dantec: Ibid. P. 257—258.

272 Theories Treating of Inheritance

whatever; but natural selection (which acts in each cell
of the organism among the different plastidular varia-
tions) intervenes and fixes only those which are adapted
to the new conditions of equilibrium.” ?°¢

We would just remark here, that the alteration
undergone by the molar movements within each cell will
be different in the different cells. For it would be incom-
prehensible how in the very complex structure of the
organism, a local change of form, imposed by external
agents, could induce quite identical alterations in the
molar movements of all the other cells of the body
indiscriminately. Consequently the alterations of the liv-
ing substance which internal natural selection preserves
as fittest will likewise be different in different cells. How
then can there be any question of the survival, in con-
sequence of this internal natural selection, of one single
plastidular variation identical at all points of the
organism?

LeDantec, like Hertwig, has recourse to the example
of immunization. But as we have already seen, this
case is quite different from the more or less local changes
of form, which individuals experience in consequence of
particular functional adaptations. In the case of immuni-
zation the transforming cause, i. e. antibacterion, is the
same for all cells. In the case of a morphological
alteration on the contrary the transforming cause, that
is, as we would concede it, the variation experienced by
the molar movement concerned, is different in each cell.

Even if one were willing to assume an identical
variation of the living substance at all points of the
organism indiscriminately, that would not explain the

2°67 e Dantec: Ibid. P. 270, 208.

Le Dantec 273

law of the repetition of phylogeny by ontogeny, as we
have already had occasion to remark in connection with
the similar hypotheses of Spencer, Hertwig and several
others. This requires, as we have seen, the conception
of the addition of a new substance to all those formerly
present.

All variations of the organism are ascribed by
LeDantec, as we have already seen, to total or partial
destruction of some of the different plastic substances
(a), which make up the living substance, whereby their
quantitative proportions become changed; but never to
the formation of new plastic substances. Likewise dif-
ferent species would differ from one another in the
number and quality of the plastic substances (a). From
this it follows: 1, that no further development can be
effected by any given living matter, if the number of
its substances has become very small, and thus an abso-
lute inalterability must be established as soon as this
number is reduced to one; 2, that the development of
the species can have been produced only by successive
total destructions of an always greater number of these
plastic substances; 3, that the further a species is devel-
oped, the smaller therefore must be the number of the
plastic substances which form its respective living matter.
One would thus arrive at the absurdity, that the simpler
the living substance is the more complex must be the
organisms formed from it.

Finally LeDantec, like Spencer, Hertwig and the
others is unable to explain histological differentiation by
this supposed similarity of living substance in all parts
of the organism:

“A muscular element differs entirely from a nervous
epithelial element, and these differences are manifested

274 Theories Treating of Inheritance

not only in the form of cells but also in their mode of
activity. Now what is the nature of these differences?
We do not know. Are they physical in character?
That would be hard to believe, because of the difference
of the chemical excreta of these elements. If the dif-
ferences are of chemical nature they must leave uninjured
the hereditary patrimony (the living substance similar
at all points of the organism). Now it is entirely impos-
sible that quantitative variations can be produced in the
elements, and leave untouched a quantitative character
already present. Perhaps there is properly speaking no
quantitative variation, but only a modification in the
nature of the non-living accessory substances which fill
out the aggregate at different points of the organism
according to the special conditions obtaining at these
points. To all these questions we have as yet no
answer.” 207

Before we leave this investigator we must bring up
one last point, namely: the logical necessity which forces
him to regard the living substance as similar at all points
of the organism. According to him, this conception is
a logical consequence of the inheritance of acquired
characters which he holds as a fact already proved
beyond a doubt. For, says he, let us consider any given
morphological variation acquired by the organisin and
transmissible to its descendant. And let us assume that
the hereditary patrimony, i. e. the living substance (@ ),
originally common to all elements of the individual by
descent from the egg, can, under the influence of the
morphological variation experienced by the latter, have
been replaced, here by a different substance ( @), there

*°7Le Dantec: Ibid. P. 461—462.

Le Dantec 275

by another substance ( 7) and so on, in such a way
that the whole of the “dynamism” existing in this hetero-
geneous mass, finds its expression in a form of equili-
brium F, which preserves accurately, without any need
of further constraint, those forms of equilibrium which
the individual had acquired in consequence of the com-
pulsion of external influences.

“Tf that were so,” continues LeDantec, “this form
could not be hereditary. For the substance @ produces
the form F only with the assistance of cells of the sub-
stances y and 6 , which are simultaneously present in
other elements of the altered individual, and no one of
these substances which does not belong to the sum total
of the elements is by itself a consequence of the total
form F. If then one detaches from this form a few
pieces capable of reproducing themselves, these pieces
endowed with different substances or heritages will give
rise to different individuals, namely to individuals or
groups of cells like those whose total constituted the
form F, but of which none had this form. There is thus
absolutely no reason existing why any one of these
individuals should take the form F. If then observation
teaches us that acquired characters can be inherited we
are thus obliged to suppose that in the case in which
they are hereditary they were acquired by the parent
organism in a homogeneous manner.” 2°*

Thus if it were possible to explain this inheritance
and at the same time to accept, nevertheless, the most
complete diversity of the substances constituting individ-
ual parts of the organism, LeDantec would be perhaps
the first to. renounce with joy his single individual sub-

208T e Dantec: Ibid. P. 294—205.

276 Theories Treating of Inheritance

stance, similar throughout the whole organism, which
as he himself states, makes histological differentiation at
least inexplicable.

THEORIES OF CHEMICAL DEVELOPMENT

In his fundamental work “The Struggle of the Parts
of the Organism,” and therefore at a time, before Roux
had yet reached the preformistic view of idioplasm or
germ plasm which he later very clearly adopted, and
which in many respects is like the conception of Weis-
mann; when also he still considered development to be
rather the complex result of a long series of purely
chemical phenomena, and nevertheless had not yet wel-
comed Weismann’s theory of the non-inheritance of
acquired characters as a deliverance from a nightmare,
at that time he sought to explain this inheritance in the
following way:

First he notes that the germ plasm although it be-
comes separated at the very commencement of develop-
ment from the organism in process of formation,
“remains nevertheless dependent upon and in relation
with this organism; for it must be fed and grow and
multiply and to that end it receives its nourishment from
its parent by chemical metabolism, and might still be
influenced in its own nature in this way.” ?°°

He supposes further that on the one hand each
structural formation may be conditioned by certain spe-
cial, chemical relations, and vice versa that each variation
of form which the adult organism undergoes through
functional adaptation produces in its turn a certain

*°°Roux: Der Kampf der Teile im Organismus. P. 60.

Theories of Chemical Development 297

special chemical change. This chemical change would
later become transmitted to the germ plasm by means
of the metabolism.??°

One can not rightly comprehend here, how a special
chemical modification, produced in the germ plasm by
a change of form in the adult organism, can later give
rise to such a development by that germ plasm as to
reproduce the same change of form at the proper time
in the new organism. If the chemical variation cor-
responding to a definite change of form were provoked
by the germ plasm in the new organism only at the
time when this latter reached the same age and conse-
quently a state of being which would be the same in its
entirety as that of the parent organism when this given
variation of form supervened in it, and were confined
to the same limited zone in which this chemical variation
was produced in that parent organism, then the concep-
tion of an actual reversibility of the phenomena would
not be in itself at all impossible, that is it would not be
impossible that the same chemical phenomenon might
provoke in the new organism the same variation of form
by which it had itself been produced in the parent orgar~
ism. But in our case on the contrary this chemical varia-
tion, no matter whether it transforms the whole chemical
composition of the germ plasm or only a part, will com-
mence to act upon the new organism immediately, at the
very commencement of its development, and will modify
therefore not merely a limited part of the cells of the
organism, but all the cells without exception. How then
could this same chemical change, which operates immedi-
ately at the commencement of development and conse-

21°Roux: Ibid. P. 61.

278 Theories Treating of Inheritance

quently upon all stages of development and upon all
cells of the organism, call forth the same result as
if it had come to act upon only a very definite point and
at a very definite time of the development of this organ-
ism? It seems to us that we ought much rather to
conclude that these results must be very different and
that with them there can be no question of any similarity
whatever.

This impossibility of explaining the inheritance of
acquired characters by Roux’s earlier theory is not limited
to it alone, but pertains to all theories of chemical develop-
ment in general. And the fault lies not only in the above
mentioned impossibility of the reversibility of the
phenomena of inheritance which we have just considered
but also in a still more generally characteristic circum-
stance, which is likewise common to all these theories of
chemical development, and which we have elsewhere
already stated for other theories. And it is mostly from
it that this impossibility of reversibility comes. It con-
sists in this, that according to all of these theories as soon
as the germinal substance has once given the initial
impulse to development it is unable to exercise even the
slightest influence upon the further course of this develop-
ment. If thus the reins by which development is directed
are let fall, and each bond severed which connects the
changes of the soma with those of the germ and vice
versa, then it is impossible to conceive how this union
could later be re-established, as soon as the need was felt
of transmitting to the germ and fixing in it the requisite
variation, corresponding to that which appeared in the
soma as the result of a new functional adaptation.

Hofmeister’s theory can be considered as an especially
typical example of this complete abandonment of develop-

Theories of Chemical Development 279

ment to itself, which constitutes the great defect of all
theories of chemical development.

This investigator believes that the chemical activity
of the cell is due in general to colloidal ferments which
are contained within them and of which each is destined
for a special chemical process. He admits thereby the
existence of numerous colloidal ferments in cells with
multiple chemical processes, and he sees in ontogeny the
result of a series of chemical reactions which follow one
another according to the principle of fructifying
causality :

“During the development of the embryo there takes
place a chemical differentiation parallel with the morpho-
logical differentiation. The formation of new chemical
anlagen indicates the appearance of different ferments at
definite stages of embryonal development.”—“One could
hardly form a better idea of the chemical transformations
going on during the early development of the embryo
than by supposing that at first only a very small number
of ferments become active, and that these transform
existing material into new substance, among which pro-
ferments or ferments of another kind appear, through
which the first then become annihilated, and which
become supplanted in their turn by a new generation of
ferments which they have themselves produced and so on
until the cycle of new chemical formations requisite for
the history of the race is run through. The epigenesis of
form would be then only the expression of the epigenesis
of chemical forces.” 2"

We shall pass over the fact that all these theories of
chemical development have yet to explain the connection

11F1ofmeister: La chimie de la cellule. Revue générale des
sciences; Aug. 15, 1902. P. 730—73I.

280 Theories Treating of Inheritance

between each chemical and the corresponding morpho-
logical stage of development; for this morphological
character of different chemical reactions has not so far
been observed in any phenomena of the inorganic world,
since it has absolutely no analogue in the process of
crystallization which is a property of the molecular struc-
ture of already formed, stable substances, that is of
substances in perfect statico-chemical equilibrium. But
we may mention the fact—and after all which has been
said above no further proof of it is required—that the
fundamental phenomena, such as the regeneration of
amputated organs, the occasional reappearance especially
in crosses of atavistic characters long since disappeared,
and especially the ontogenetic repetition of phylogeny
and the inheritance of acquired characters, not only find
no explanation in all these hypotheses of chemical
development but are on the contrary absolutely irrecon-
cilable with them.

Darwin, Galton, DeVries, Weismann

It would be useless for our purpose to tarry especially
over any one of these four theories, the underlying idea
of all being the same identical conception of preformistic
germs. The progressive elaboration of this idea which
has proceeded gradually from the first to the last of these
theories presents however the following noteworthy
phenomenon. Preformistic germs, which were devised
by Darwin, one could well say, chiefly for the purpose of
accounting for the inheritance of acquired characters,
were then deprived by Galton in great part but not com-
pletely of this property, and finally with DeVries, and
still more with Weismann became themselves the greatest
difficulty for accepting that inheritance.

Darwin. 281

Of Darwin’s pangenesis it is necessary here to men-
tion only the conception that the sexual or reproductive
organs in general were not so much the place of refuge to
which the germ plasm withdrew immediately after its
separation from the soma at the very commencement of
development, as rather the containers of the germinal
substance continually produced and secreted by other
parts of the organism lying without these organs, so that
they build up as it were the sexual or reproductive
cells out of this valuable material thus received and
accumulated.?12

In Darwin’s hypothesis this conception of the repro-
ductive organs as mere glands for the reception and
giving up again of the germinal substance was intimately
associated, although in its essence quite separate and
independent, with his further conception of the free
circulation of the gemmules throughout the organism;
and he supposes, as is known, that these gemmules were
produced and secreted continuously during the adult state
by all somatic cells indiscriminately—by those already
present as well as by those just appearing in consequence
of a new functional adaptation. Now if Galton by his
experiments on the transfusion of blood from a rabbit of
one species to the blood vessels of another belonging to a
related species, has provoked a thoroughly justifiable
doubt of this supposed circulation of gemmules, especially
in so far as it was carried on in the blood vessels, the
original idea remained nevertheless unshaken, that is that
the germinal substance is assembled in the sexual glands
after it has been formed in some real place of origin
external to them.

212Darwin: The Variation of Animals and Plants under Domesti-+
cation. II. P. 370, 379.

282 Theories Treating of Inheritance

Because of the fact that the theory of Darwin derives
the germinal substance from all parts of the soma. rather
than from one well defined region of it, its partisans
could certainly not object to these experiments that they
leave the conception still possible that the germinal sub-
stance might perhaps be transmitted from such a special
well defined region to the sexual organs only along certain
very definite special ways, which might be quite different
from the blood vessels. And on account of the nature and
properties attributed to the gemmules they would be still
less able to advance the conjecture that a substance might
possibly be reproduced at a distance, quite like another
substance, by the direct influence of the latter, by means
of some other means of connection of such nature that
it would not require any real and proper material trans-
mission. From this the conclusion may be drawn, that
all theories which do not exclude or perhaps even include
one or the other of these two hypotheses upon the manner
of transmission or upon the means of reproduction at a
distance of the germinal substance, are completely justi-
fied in accepting Darwin’s conception of the sexual
glands, acording to which the latter have nnly the func-
tion of receiving and accumulating a substance the real
origin of which is outside these organs.

In the case of Galton we shall recall only that he was
the first who introduced the theory that stirp,—i. e., the
germ plasm consisting of numerous germs or of gem-
mules which remain behind after the extrusion of the
particles concerned directly in the formation of the new
organism—separated itself entirely from the soma
immediately, at the commencement of development.
Through this separation of the stirp from the soma he
opened the way which later led necessarily to the uncon-

Galton; DeVries; Weismann 283

ditional rejection of the inheritance of acquired char-
acters. Nevertheless he did not immediately venture to
go so far but continued to admit as a sort of concession
that in the adult organism a gemmule might occasionally
escape from the somatic cell, which had produced it and
was also its customary abode, even though this cell had
been only shortly before acquired in consequence of a new
functional adaptation; then this gemmule might be taken
up by the reproductive organs and become likewise a part
of the stirp and the acquired character which had ap-
peared in the somatic cells might thus be inherited.?!3

In the case of DeVries we should remark that he
assumes that the germinal substance, that is the sum total
of the pangens, is present equally in all nuclei only be-
cause he, as we have also seen in the case of Driesch, took
it for granted that nuclear divisions are qualitatively
equal. If then a nucleus of a somatic cell acquired new
pangens, as a consequence of a new local functional
adaptation, then they would have to remain in the place
where they arose and could not enter the reproductive
cells also. And so much the more since he also asserts
that the substance which will later actually form the
sexual cells separate itself from the soma immediately, at
the commencement of development, and passes along cer-
tain “Keimbahnen,” which may be recognized, chiefly
because upon them the greater part of the pangens remain
inactive.?14

In respect to Weismann we remark once again that in
consequence of a more rigorous logical elaboration of the
doctrine of prefotmistic germs, which has convinced him

218Galton: A Theory of Heredity. Journ. of the Anthropo-

logical Institute. January 1876. P. 342—343.
214De Vries: Intracellulare Pangenesis. P. 188—180.

284 Theories Treating of Inheritance

of the necessity of regarding them as bound up with one
another into a rigid structure, he has been led, through
the conception of these preformistic germs which was
forced upon him by particulate inheritance, to deny most
energetically every possibility of the inheritance by the
germ of characters which the soma had acquired by
functional adaptation.

Weismann admits, it is true, that sometimes external
influences acting uniformly upon the whole organism, like
temperature and other such things, can alter the deter-
minants of the soma and the corresponding determinants
of the germ at the same time and in the same direction;
as occurs for example in the determinants of the wing
scales of the butterfly Polyommatus phlaeas, whose color
changes as we have seen when it is transported to a
warmer climate. But the cases which permit of this ex-
planation, which resembles in many respects the above
discussed diplogenesis of Cope,—the only cases which
Weismann admits,—are limited by this investigator to so
small a number, and are also of so peculiar a kind that it
would be wrong to assert that he held less determinedly
to his earlier stand as an opponent of the Lamarckian
theory.

We may point out however, the following contradic-
tions. He admits inheritance in unicellular organisms
while he denies it in the pluricellular and thinks he can
justify this by saying simply that as the unicellular divide
always into two equal halves they need only preserve
what they have acquired, in order to transmit it unaltered
to the new individuals. But this is not right. For new
functional adaptations acquired by the anterior end of the
infusorian Stentor, for instance the acquisition of “Mem-
branelles” by the peristome in consequence of the fusion

Weismann 285

of several cilia, would then become transmitted only to
that one of the two new individuals to which the anterior
part falls in the division, and could in no wise be trans-
mitted to the other individual in which this anterior part
is formed anew. If one assumes on the contrary, that
transmission goes on by means of the nuclei, and can
therefore proceed equally into both of the two newly
forming individuals, one could not then understand,
wherein the transmission of somatic modifications in the
unicellular animals, which is accomplished by means of a
part of the organism containing in itself no membranelles
and quite distinct from them, would differ from the trans-
mission of any modification experienced by any organ of
a pluricellular organism, which likewise goes on by means
of a fragment containing no part of the modified organ
and quite distinct from it. So much the more since the
substantial identity of the complex unicellular with the
pluricellular organisms, which we have already discussed
above, corresponds also with a substantial identity in their
development, as is shown by the fact that the funda-
mental biogenetic law of the repetition of phylogeny by
ontogeny is followed in the development of unicellular
animals also, as for example, in the formation of the new
frontal field in the division of Stentor coereleus.?’®

And in relation to all these theories with preformistic
germs from Darwin to Weismann we might mention
once more the insurmountable difficulties that would be
encountered if one were required to explain by them this
very fundamental law, either in unicellular or pluricellu-
lar organisms. This impossibility and the fact that in the

218Johnson: A contribution to the Morphology and Biology of
the Stentors. Journ. of Morphol.; vol. VIII, No. 3, Boston, U. S.A,
Ginn, August 1893. P. 519.

286 Theories Treating of Inheritance

end the acceptance of these germs has led necessarily to
systems which reject the inheritance of acquired char-
acters concur to prove, although more proof is certainly
no longer necessary after all the other considerations
which we have developed in an earlier chapter, that the
very idea of these preformistic germs is untenable, as is
thus every theory founded upon them.

However limited the number of theories or hypoth-
eses selected by us, and however rapid and brief the
critical exposition which we have made of them, it seems
to us nevertheless that it is unnecessary to proceed further
with our examination. For it has shown us that among
the principal theories, which up to the present have been
devised to explain the inheritance of acquired characters,
none has accomplished this difficult task, and it has
already served another purpose for which chiefly we
undertook it. This purpose consisted on the one hand in
bringing to light in other theories the most suggestive and
fruitful ideas put forward; on the other hand in deter-
mining the conditions which are necessary and sufficient
to render possible the inheritance of acquired characters,
and a critical examination of concrete theories already
developed has certainly helped to put these conditions in
evidence better than simple reflection upon them could
have done.

If we take a look over the road which we have thus far
traveled we see that among these conditions those which
have appeared to us as the essential and fundamental ones
are the three following:

1. All the manifold physical, chemical, morphologi-
cal, and physiologic variations, which can appear in the
most different parts of the organism, are to be ascribed

Conditions Necessary for Inheritance 287

to specific alterations of a single form of energy, so that
the latter appears, as it were, the common denominator
for these variations that are quite unlike in nature and
whose combination or separation is thus permitted as
often as required.

2. The determinative influence which the germ sub-
stance in its totality exerts upon the soma cannot be
limited to the first-moment of the first cleavage of the
egg but must persist throughout the whole of ontogeny
up to the adult condition, so that the germinal substance
never as it were loses touch with the soma, but rather
remains in a continual state of reciprocal action and
reaction with it.

3. The influence exerted by the soma in this way
must be reversible, that is the germ substance must be
influenced in such a way that it can call forth again at the
proper moment, at the numberless different points of the
soma of the new organism, all the same, respective,
special, somatic conditions by whose complex modes of
being the germ substance itself was already influenced in
the parent organism in so special a way.

This last condition which alone implies in itself the
whole question of inheritance falls again into two parts.
First the germ substance must be influenced always in
such a way that it is capable of giving back at the required
moment the same influence, qualitatively identical but in
the reverse direction, which it had already experienced
as the single resultant of all the elementary somatic in-
fluences to which this germinal substance was simulta-
neously subjected in the preceding organism. Second:
the germ substance which thus gives back again the
influence, by which it was influenced, qualitatively
identical but in reverse direction, must be localized at a

288 Theories Treating of Inheritance

single definite point of the organism, which is always the
same, both when the parent soma exerts its influence upon
the germ substance which it contains, and also when the
latter exerts upon the new organism its own determina-
tive ontogenetic influence.

It is therefore our task now to investigate in the
following chapter whether the centroepigenetic hypothesis
already set forth above really satisfies all these conditions
and is consequently capable of really affording the ade-
quate explanation for the inheritance of acquired
characters, which we seek,

CHAPTER SEVEN

THE CENTROEPIGENETIC HYPOTHESIS AND THE EXPLANA-
TION OF INHERITANCE AFFORDED BY IT.

As we said at the end of the third chapter, when the
end of development is reached, and there comes with it a
cessation of the steady activation by the central zone of
new specific potential elements, there is also a cessation of
the perturbing action which that zone had up till then
exercised upon the dynamic equilibrium of each onto-
genetic stage; so that the organism attains at that
moment the final equilibrium of the adult state. But we
should note that a new perturbing influence can now
come into play, namely, the functional stimulus in the
widest sense with all its innumerable variations.

In the same manner, we said, as the perturbing
action of the central zone had formerly upset the equili-
brium which was but just formed, and so provoked the
passage of the organism to a new ontogenetic state, so
now each lasting change of the functional stimulus by
disturbing the dynamic equilibrium of the adult state, will
induce another general distribution of nervous energy.
Consequently each cell of the entire organism or of cer-
tain portions of the organism will now be traversed by a
nervous flux which is specifically different from that be-
fore existing, and specifically different in different cells.

In each nucleus of these cells, we continued, a par-

289

290 Explanation of Inheritance

ticular specific potential element will consequently be
formed and deposited, which will be added to the element
or elements already present. All these elements, new as
well as old, deposited in the somatic nuclei, will, however,
be lost with the death of the individual; and those alone
will escape this destruction which are deposited in the
germinal substance of the central zone. The lasting
variation of the functional stimulus will thus have had
for its total effect, in so far as the species is concerned,
the simple addition of a new specific potential element to
the germinal substance.

Arrived at this point, we reserved for one of the
following chapters the examination of the manner in
which this new element would act in the ontogeny of the
next following organism. It is then with this examina-
tion that we must now occupy ourselves in the present
chapter.

We should first dwell a little more in detail upon this
hypothesis, which we mentioned only in passing in con-
nection with the posthumous action, or “Nachwirkung,”
of the nucleus in enucleated fragments of unicellular
forms. We mean the hypothesis that the substance
which constitutes each specific element, and which is cap-
able of giving as discharge a single well-determined
specific nerve-current, is also the same and only substance
which this specific nerve-current can in its turn form and
deposit.

This should not appear so very strange to us, since
the inorganic world itself presents a phenomenon similar
in certain respects. The substance which actually con-
stitutes the charge of ordinary electric accumulators is
capable of giving back inversely, during its discharge, the
same kind of energy which it had previously received,

Accumulators of Specific Nervous Energy 291

and by which it had itself been deposited, namely the
continuous electric current. The most important differ-
ence consists in this, that an electric accumulator is
capable of restoring always only one and the same kind
of energy, but not solely such or such intensity of current.
It constitutes, for that reason, only a generic potential
element; but such accumulators would attain the com-
pleteness of specific potential elements—receiving and
restoring instruments of the greatest delicacy—if one
could make it possible that each one of them should re-
ceive and restore only a single definite intensity of current.
The similarities and differences which nerve currents
present, in comparison with electric currents, quite war-
rant us in assuming in nerve currents some of the
properties of electric currents, and in attributing at the
same time to the first other properties which the electric
do not possess, provided these qualities are not incom-
patible with the others.

It is known that, if we designate by E the electro-
motor force of an accumulator or of any electro-chemical
generator, it can furnish currents of any intensity i
whatever, according to the resistance R of the circuit,
according to the equation i=E/R. Thus,—even though
the terms of motor force, of resistance, of intensity, or
more generally of specificity, transferred from electric to
nervous currents are very indefinite—we may very well
venture, nevertheless, as a preliminary trial hypothesis,
to attribute to nervous currents as among the properties
which they might have analogous to electric currents
precisely those contained in this equation.

As it involves nothing incompatible with the prop-
erties expressed by this equation, we may imagine a
nervous accumulator, constituted by a given substance

292 Explanation of Inheritance

capable of being produced and deposited solely by a
current of a definite intensity or specificity, and at the
same time capable of producing, by its decomposition,
this current only, of the same intensity or specificity i is
that of the charge. This accumulator, then, will discharge
itself and produce this current as often as its nervo-motive
force, which we may still call E, is sufficiently great to
overcome the respective resistance, according to the
equation: E=iR.

Finally, we can assume that the magnitude of this
nervo-motive force, is proportional to the quantity or
mass of the substance which has been gradually deposited
and accumulated, as if the successive infinitesimal deposits
of this substance were innumerable little Leyden jars ar-
ranged in serial order. Then the greater the mass of
the specific substance of this nervous accumulator the
greater in proportion will be the resistance which its dis-
charge will be able to overcome. At the same time, this
accumulator, capable of surmounting by its current of a
fixed intensity i a given resistance R, will be capable also
of surmounting every other resistance less great than R;
for to effect that, it will suffice that it be not the total
quantity of material at disposal that enters into action,
but only a portion more or less large, so as to furnish for
each resistance R’<R, the nervo-motor force E’<E,
given by the formula:

Ey =iR?

Suppose now that the discharge of this accumulator
on account of the ubication or the mode of its insertion,
is able to flow only upon a definite point of a given plexus
traversed along its meshes by as many currents of the
most diverse specificities capable of combining one with

Accumulators of Specific Nervous Energy 293

another and of decomposing again, and in dynamic
equilibrium among themselves. (It may be remarked
here that the expression “dynamic equilibrium” of a cir-
culatory system is always to be understood in the sense
of inalterability for the time in the conditions of move-
ment at each point of the system. Thus, for example,
the system of distribution of the drinking water of a city,
which is fed from a given constant number of reservoirs,
whose head of water is maintained always at the same
height, and in which a given constant number of water
taps are always open, will settle in a short time into a
dynamic equilibrium in our sense, and continue in it so
long as the accession of a new reservoir, for example, or
the opening of other water taps does not cause the transi-
tion to a new dynamic equilibrium. ).

As soon as the discharge of this nervous accumulator
occurs, which can produce thus only a single definite
specificity of current, and which can discharge itself upon
only a single fixed point, it will necessarily effect a single
very definite change in the dynamic equilibrium of this
given circulatory system. And in the cases in which this
change of the dynamic equilibrium requires the doing of
a certain amount of work, this required expenditure of
work or energy will be very definite for each discharge,
and can be provided only by the accumulator itself. Con-
sequently, in order that the discharge may take place, this
quantity will have to be less than, or at most equal to,
that which the accumulator can actually furnish.

But the quantity of work which each accumulator is
capable of furnishing will necessarily be proportional to
the mass of the substance which constitutes it. And
since, as we saw, the resistance R which each accumulator
with its current of definite specificity is able to surmount,

294 Explanation of Inheritance

is likewise proportional to the mass of the substance of
the accumulator, (because it is proportional to its nervo-
motive force, which also is in its turn proportional to this
mass, according to the preliminary hypothesis), then the
quantity of work required to effect the change under con-
sideration, must be regarded as equivalent to a resistance
R, which opposes the discharge.

If now we assume that in nearly all cases, which come
into consideration here, the quantity of work, requisite
for effecting a given change in the dynamic equilibrium
of the whole circulatory system, is proportionately
greater the more considerable (if we may be pardoned
for this much too indefinite expression) in quantity and
quality this change is, it becomes at once conceivable why
each specific potential element of the central zone can
becomes activated only when the embryo has reached
the ontogenetic stage, corresponding to the particular
phylogenetic stage at which this element was acquired by
the germinal substance. For then first will the change
which the dynamic system of the embryo undergoes, as
a result of the activation of this specific potential element,
be the very least possible, and therefore usually also the
only one whose resistance can be surmounted by the very
weak nervo-motor force of this specific potential element.

The following general rule can thus be established:

The smaller the mass and therefore the nervo-motor
force of a specific accumulator, so much the more
closely is its discharge dependent upon the condition
that the whole dynamic system, above all and very
especially in the immediate neighborhood of the ac-
cumulator, find itself again in exactly the same state in
which it was when the accumulator was formed. Con-
versely, the greater the mass of the accumulator, the

Conditions and Effects of Discharge 205

more easily are the conditions to be obtained which are
able to permit its discharge.

Let us suppose further that as a result of external in-
influences there are induced at the same moment at a few
points of the system a corresponding number of new
nerve currents, specifically different from the preceding,
so that the system is thereby caused to pass over to an-
other dynamic equilibrium. It is clear that there will
then be deposited in each point of the system,—and not
merely in those which external influences have directly
modified,—a new specific potential element, in mass more
or less large according to the time during which the new
state of dynamic equilibrium persists. At the same time,
however, all these same points of the system will preserve,
in a potential state—not in activation—,all the specific ele-
ments which were desposited during the preceding state
of dymanic equilibrium.

If, such being the state of things, it now happen that
even any single point whatever of the system is brought
back again, by any external influence, to the specificity
which it had already possessed in the preceding stage,
that will make it possible for the respective specific ele-
ments corresponding to that stage to come again into
activity, at first in the point nearest, and then from next
to next until in the most distant; for then each of these
elements will find its immediate environs in approximately
the same conditions as when its corresponding specific
current was in activity, by which it has been deposited. It
will suffice then that even a single point of a system re-
turn, through the action of external influences, to its
preceding state, in order that the whole system, through
the discharge of the different specific potential elements
corresponding to that former stage, should resume

296 Explanation of Inheritance

transitorily the whole dynamic condition of that stage.
We have here then a phenomenon of succession or of
association of nerve-currents which, as is easily conceiv-
able and becomes even clearer later, may serve as a basis
for the psychic law of succession or association of ideas.

In résumé, what we have designated hitherto by the
name of specific potential element, and what we may
henceforth designate by the name of elementary nervous
accumulator, is then nothing else, by hypothesis, than the
substance of a very small mass, deposited in the nucleus
by every specific nervous current which flows through it,
—a substance which adds itself to the others already
present without changing them, and which is able as soon
as it finds itself again in conditions of environment like
those present at the moment when it was deposited, to
restore the same specific current by which it was
produced.

This definition and the hypothesis involved answers at
once the question as to the mode of action which the new
specific potential element, acquired by the germinal sub-
stance of the central zone of an adult organism in
consequence of a new functional adaptation in this or-
ganism, will follow during the ontogeny of the next
following organism. For from all we have thus far said,
it results that this new specific potential element will first
be able to become active when the embryo shall have al-
ready attained the same state in which the parent
organism found itself immediately before it acquired this
same new specific potential element along with the new
character.

Let us consider now what happens as a result of its
activation: In the parent organism there was present at
first a certain circulatory system S, corresponding to the

Effects of Discharge or Activation 297

adult stage preceding the acquisition of the new character.
Then on account of an external influence acting at a given
point A of this system, the specificity of the respective
current was changed from i toi’. In consequence of that
the whole circulatory system S, in order to assume a new
state of dynamic equilibrium, transformed itself into a
different system S’, in such a way that at another given
point B, that of the central zone, the specificity of the re-
spective current underwent a very definite corresponding
variation from intensity i, to 141. If then there is now
present in the embryo of the young organism the same
circulatory system S of the parent organism, and if, on
account of the activation of the specific potential element
in question, there is produced at the same point B of this
system, the same variation of specificity from intensity
i, to i’1, it is evident—and we shall see later that a few
facts from the inorganic world prove experimentally the
general principle upon which our assertion rests—that
there must follow the same change as before of the
dynamic equilibrium of the general system from S to S’,
and that, consequently, there will now be produced at
the point A the same specific modification as before from
itoi’. In this way the inheritance of acquired characters
finds a most complete explanation.

Let us note parenthetically, that nuclear somatization
conceded, we must regard each of the substances forming
the different specific potential elements of any nucleus as
capable of gradually replacing the others by continual in-
crease of its mass, when the respective specific current, on
account of the incessant repetition always of only one and
the same stimulus, passes very frequently through the
nucleus. A nucleus thus somatized,—that is to say, one
composed wholly of a single specific substance,—would

298 Explanation of Inheritance

acquire in this way, on account of the considerable mass
of this substance, a potential energy capable of over-
coming a considerable resistance to its discharge, and
would then be able to respond always in that single way
only which corresponds to the single specific nervous cur-
rent which it is able to activate and which constitutes its
irritability, even if it be provoked to discharge by external
influences or accidental stimuli which are quite different
from those to which it is ordinarily exposed.

“A muscle cell,” says Oscar Hertwig, “replies to every
kind of stimulus by contraction, a gland cell by secretion;
an optic nerve can perceive only light, no matter whether
it be stimulated by light waves, by electricity or by press-
ure. Similarly plant cells also are endowed with their
own specific energies: the reaction to stimulation re-
ceives everywhere its specific stamp from the special struc-
ture of the irritable substance, or in other words,
irritability is a fundamental property of living protoplasm,
but under the action of the environment manifests itself
in specific reactions according to the specific structure of
that protoplasm.” 216

And Claude Bernard defined irritability as: “the
property of living elements of reacting each according to
its nature to an external provocation or stimulus.” 217

“One conceives of the irritable substance,” continues
Hertwig, “as a system of material particles in unstable
equilibrium, provided with forces at high tension. In
such a system, a very small shock of a single particle is
sufficient to put all the other particles in motion, each
transmitting its own motion to its neighbor. That ac-

°Oscar Hertwig: Die Zelle und die Gewebe. I, P. 76.
"Claude Bernard: Legons sur les phénoménes de la vie com-
muns aux animaux et aux végétaux. P. 248, 281,

The Only New Thing in the Hypothesis 299

counts for the fact that a small stimulus as cause may
often result in an extraordinarily great reaction, just as
a grain of gunpowder kindled by a small spark may
provoke the explosion of a great mass.” 218

We have opened this parenthesis on nuclear somatiza-
tion and cited these passages from the two investigators
in order to set in clear relief the fact that in the definition
given above of the specific potential elements, both the
conception of accumulators of nervous energy in tension,
and that of accumulators of a specific nervous energy con-
stituting their special irritability, are ordinary conceptions
very generally employed which are expressed here in
words at most only a little different from the ordinary.
The only new thing which the above definition includes
is the hypothesis that the substance which is thus capable
of giving as a discharge a given nervous current was pro-
duced and deposited only by a nervous current of the
same specificity, but in the inverse direction, and could
have been produced and deposited only by such a current.
But in this hypothesis, quite simple as it is, lies every-
thing; for it is just it which alone can explain completely
the fundamental law of the reversibility of the relation
between action and reaction, between stimulus and im-
pression, which governs all organic life. The inheritance
of acquired characters, the psycho-mnemonic phenomenon
proper, the process of specialization and somatization of
the cells in consequence of which they react in their
habitual manner to accidental stimuli unusual to them,
even the vital phenomenon itself in all its generality, all
of these, as we have seen and shall see, are only so many

218Oscar Hertwig: Die Zelle und die Gewebe I, P. 77.

300 Explanation of Inheritance

special cases of this reversibility, and all find their im-
mediate explanation in this very simple hypothesis.

In résumé: By this hypothesis of a nervous accumu-
lator formed and deposited by the same specific current
which it can afterward restore, the first of the two sub-
conditions, included in the third condition, necessary and
sufficient to account for the inheritance of acquired char-
acters, are fulfilled. On the other side the localization of
the germinal substance in the central zone, which con-
stitutes the point of departure and the foundation for the
hypothesis of centroepigenesis, has already satisfied com-
pletely the second of these sub-conditions. As to the two
other conditions, the first has already been satisfied by
considering the nervous current with its numerous differ-
ent specificities as the common denominator or as the
basis of vital phenomena of the most diverse kinds which
are in activity at each instant in the most varied points of
the soma; the second was satished by assuming a con-
tmuous action on the part of the germinal substance
throughout the whole of ontogeny, by means of the
steady activation of new specific potential elements pour-
ing their discharges into the general circulatory system.
It follows from this that centroepigenesis is able singly
and alone to explain the inheritance of acquired char-
acters, because it fulfills these conditions which we rightly
regarded not only as necessary, but also as sufficient.

For greater clearness, nevertheless, it will be worth
while to institute, as we have indicated above, a compar-
ison between this ontogenetic development, as it would be
constituted according to the hypothesis of centro-
epigenesis, and a very characteristic phenomenon, in some
respects analogous, which is presented by the inorganic
world. The reproduction of a sentence by a phonograph

Comparison with Phonograph and Telephone 301

is, in fact, if the expression be allowed, a true centro-
epigenesis. The needle placed at the center of the
membrane repasses through all the stages through which
it had passed when the sentence was spoken; and each of
these stages was only the total effect of the repercussion
upon this point of all the extremely complex vibrations
called forth in the membrane by external influences, in
this case the vibrations in the air. Since the needle,—one
single point of the dynamic system,—repeats thus the same
identical series of specific movements which were before
produced at this point by the concurrence and union of all
the complex movements of the system, these successive
specific movements of this one point are thereby again
decomposed into all the same successive complex modes
of the entire dynamic system, in this case constituted by
the extremely complex vibrations of the membrane.

Let us suppose, moreover, that it were possible to
interpose in an ordinary telephone wire transmitting a
series of variations of the electric current a complex ac-
cumulator capable of receiving the current and of return-
ing it after a certain time just as it was in its successive
variations. Then the whole series of complex dynamic
systems, which were formed by the successive complex
vibrations of the membrane receiving the spoken words
could be reproduced, just as at the receiving station, after
any interval whatever, exactly as with the phonograph.
Well, the role which centroepigenesis attributes to the
germinal substance is fundamentally nothing else than
that it forms a similar complex accumulator.

Finally it may appropriately be noted here, that this
comparison with the phonograph permits us to make still
more definite and clear all that we stated at the end of
the fourth chapter, namely that the centroepigenetic

302 Explanation of Inheritance

hypothesis is able to explain particulate inheritance com-
pletely, without requiring the help of any preformistic
germs whatever. Concretely: let us imagine two exactly
similar phonographs, and let us have the same singer
render the same melody in exactly the same way first
before one then before the other. Only let us suppose
that one hears at a certain moment during the second
song, for example, one of the audience cough, or a door
slam, or clapping of applause. Obviously both phono-
graphs now will reproduce the same melody in the same
way, with the single difference of the accessory noise,
which will not destroy in the slightest the otherwise com-
plete conformity of the two phonographic reproductions.
Thus we have here an actual and characteristic case of
particulate inheritance for the production of which it is
mechanically sufficient that the series of successive specific
vibrations of the middle point of the membrane differs
from the corresponding series of vibrations in the other
phonograph only through a single vibration or through
a very inconsiderable group of these specific vibrations.

From the explanation which centroepigenesis gives of
the inheritance of acquired characters there follows also
at once a very important consequence. If we mean by
functional stimulus not so much the external influence as
rather the immediate modification induced by it in the
vital process, then the functional stimulus according to
the centroepigenetic hypothesis is of quite the same
nature as the ontogenetic stimulus. And this appears to
be indicated also by the best demonstrated facts.

We regard it as absolutely necessary to understand
first clearly this distinction between external physical
actions and functional stimulus. For the former do not
themselves constitute the true and proper functional

Functional and Ontogenetic Stimuli 303

stimuli, but they do determine them. External influences
and functional stimuli are two special forms of energy,
the first of which can transform itself into the second,
but they are fundamentally different from each other.
The one is inorganic, the other biologic and vital in
nature. And the designation “functional stimulus”
properly applies to the external action, in so far as, and
at the moment when, it transforms itself into vital
energy. The possibility of a substantial identity between
the functional stimulus and the ontogenetic stimulus can
obviously exist only in case the former is understood in
this way.

That being disposed of, it becomes worth while to
recollect that Roux distinguishes embryonic life and adult
life as two things of totally different nature: ‘In the
life of all parts (of the organism) two periods must be
distinguished: an embryonic period in the widest sense
in which the parts develop, differentiate, and grow of
themselves, and an adult period in which growth, and in
many parts indeed, the complete replacement of material
used up, goes on only with the co-operation of stimuli.
These stimuli might thus give origin to something new
which, if it were produced in this manner throughout
several generations, would become hereditary, that is, be
formed without these stimuli in the descendant, and be-
come thus in our sense embryonal.” 71°

These two periods characterized respectively by
embryonic differentiations and by functional changes are
regarded by Roux, as we have said, as essentially differ-
ent: “Since the changes going on in adult men, are pro-
duced only by means of external transforming influences,

2°Roux: Der Kampf der Tcile im Organismus. P. 180—181.

304 Explanation of Inheritance

whereas embryonal differentiations, on the other hand,
take place without or almost without such differentiating
stimuli, there is reason to believe that these results are
produced in another way which, while undoubtedly con-
trolled by natural laws, is nevertheless for the time
incomprehensible by us. Consequently the essence of
embryonic differentiation and its immediate physico-
chemical causes are for the moment quite inaccessible to
us.” 220

Centroepigenesis, on the contrary, teaches us, as we
have seen, that embryonic and functional differentiation
are essentially the same. And in support of this view we
may recall among others the following principal orders
of facts:

“All the organs which fulfill their specific function
already in the embryo have there a life dependent upon
stimulus (Reizleben) in proportion to this function.” 2?!
This indicates that an organism in process of develop-
ment may be at one and the same moment in the
embryonic period in respect to some of its parts and in
the functional period in respect to other parts, without
ceasing for that reason to behave in all its manifestations
as a whole of a thoroughly individual nature.

A number of characters begin to develop embryon-
ically which later require the help of the functional
stimulus to complete their development: “In embryonic
development some parts are ontogenetically formed and
developed to a certain grade of functional capacity, which
have been formed phylogenetically entirely by functional
adaptation. Functional stimuli seem to be necessary only
for that remainder of development which belongs from its

"Roux: Ibid. P. 166.
*=Roux: Der Kampf der Teile im Organismus. P. 182.

Functional and Ontogenetic Stimuli Alike 305
essence to functional life proper.” 22? This would speak
for the gradual accomplishment of the transition from
the embryonal to the functional period without any sud-
den and precipitate change, and so speaks also for a
gradual, hardly noticeable replacement of the ontogenetic
stimulus by the functional so that one must suppose the
two stimuli to be active simultaneously ‘and in
combination.

So Hyrtle, having cut across the motor nerves of the
muscles of one side of the face of a new born rabbit,
stated that a year after there was not only atrophy of
the muscles but the bones of that side of the head had
undergone a surprising arrest of growth. He attributed
this arrest to the fact that ‘after muscular paralysis there
was lacking the traction and compression, which provoke
living parts of the bone to activity and cause the normal
growth of the bone.” 22%

Alesandrini and E. H. Weber similarly found in
monsters “that in the absence of the anlage of the spinal
cord there were lacking in the corresponding nerve ter-
ritory both the nerves and the muscles and that the bones
and joints belonging to these were abnormally formed,
the latter being in part rigid.” °?*

It may be remarked here that as some of these parts
had attained a certain development even without the
functional stimulus, and during the very period in which
normally they would have had the co-operation of the
functional stimulus, it is therefore clear that if there had

22Roux: Zur Orientierung iiber einige Probleme der embry-
onalen Entwicklung. Zeitschrift fiir Biologie. Bd. XXI; Munchen,
July 1885, P. 503. Gesammelte Abhandlungen, II, P. 231—232.

222Qscar Hertwig: Die Zelle und die Gewebe. II, P. 175.

224Roux: Der Kampf der Teile im Organismus. P. 51.

306 Explanation of Inheritance

not been this pathological absence of this latter, the
ontogenetic stimulus and the functional would have co-
operated at the same time in the same formation. There-
fore one cannot, as we have said, be oblivious of the
indication that this harmonious and parallel co-operation
of the two stimuli, in combination with the fact that in
no embryonic structure whatever is there to be demon-
strated any substantial difference in the manner of forma-
tion and development between the purely hereditary
portion due to the ontogenetic stimulus alone, and the
portion due to the functional stimulus, is strongly in
favor of the essentially identical nature of these two
stimuli.

Finally a number of organs which would attain their
complete development through the ontogenetic stimulus
alone, have their development hastened by the accidental
intervention before the proper time of the requisite
functional stimulus. Thus, for example, in prematurely
born children the visual sense develops earlier; that is to
say its development is accomplished in a total number of
days, counting’from the first instant of development, that
is smaller than the ordinary number such as would be
given by the time of ordinary gestation augmented by
the number of days necessary for the infant born at term
to acquire the same degree of development of sight.??°
And this demonstrates again, that the functional stimulus
can replace the ontogenetic stimulus, or better, that it can
co-operate with it and add itself to it, thus strengthening
its effect; a thing which would be difficult to conceive of
were the two stimuli of different nature.

To these facts of the most general character, we can

Roux: Der Kampf der Teile im Organismus. P. 182.

Functional and Ontogenetic Stimuli Alike 307

add further the following more special ones which are
quite similar in their nature to the preceding.

The tails of larval amphibians, cut off obliquely in
respect to their axes, become regenerated in such a way
that the axis of the regenerated fragment is always per-
pendicular to the plane of section and forms consequently
a certain angle with the axis of the stump. Nevertheless,
all these tails, because of regulative forces within the
organism, tend gradually to straighten themselves. Now
Barfurth has demonstrated that in frog larvae which are
prevented almost entirely from swimming by putting
them in shallow water divided into a number of small
compartments by water plants, this straightening goes on
in a much less complete manner and much more slowly
than in those which are placed in deep water and which
are thus able to swim freely. That is a proof that func-
tional adaptation of the tail to swimming co-operates with
the entire action of the internal regulative capacity, or in
a wider sense with the ontogenetic stimuli, and adds it-
self to them, intensifying and accelerating their action.??¢

An example of the ontogenetic stimulus having not
yet replaced the functional, or better, being not yet
endowed with a quantity of potential energy sufficient to
overcome by itself the resistance which opposes its acti-
vation, and which has therefore need of this functional
stimulus in order to commence to act, is furnished us
by the axolotls. These tailed batrachians can retain
their external gills indefinitely and live out their lives
and reproduce their kind with external gills, or be trans-
formed into amblystomae, according as they are or are

226Barfurth: Versuche zur funktionellen Anpassung. Arch. f.
mikrosk. Anatomie, Bd. XX XVII; Drittes Heft. Bonn, Cohen 1891;
especially P. 403—405.

308 Explanation of Inheritance

not prevented from passing at the proper moment of
their development to terrestrial life. ‘One could say
that this depends upon the amblystomal form being not
yet sufficiently fixed in the heredity of the species, since
the epigenesis resulting from this heredity does not yet
necessarily cause the appearance of the amblystomal form
so long as the conditions to which this form is adapted
are not realized.” 227

Finally the experiments of Cunningham on the colors
of flat fishes already quoted above, are well known. He
has shown that during their first metamorphoses, while
the pigment is still present on both sides, the action of
light artificially reflected upon the side of the fish which
is turned toward the bottom does not prevent the pigment
from disappearing even then from that side, so that in
this case the color passes rapidly through a retrograde
development. But a prolonged exposure to light pro-
vokes the reappearance of the pigment on the lower side,
and the pigment spots are in every respect like those
which are normally present on the upper side of the
fish.?28

In this experiment then one has a clear and direct
instance of a functional stimulus reinforcing the onto-
genetic stimulus. We say “reinforcing” because the fact
that the spots now appearing on the lower side are like
those above, demonstrates that they are not produced
de novo by the functional stimulus, but even now depend
upon the ontogenetic stimulus, which, with the help of

*°"Le Dantec: Traité de Biologie. P. 403-404.

228Qsborn: The hereditary Mechanism and the Search for the
unknown Factors of Evolution. Biol. Lect. at the Mar. Biol. Lab. of
Wood’s Holl, Summer Session 1894. Boston, U. S. A., Ginn, 1896.
P. or.

Conclusions 309

the functional stimulus acquires anew the power which
it once had possessed in the ancestors of the existing
species :—another proof that the functional and onto-
genetic stimuli can act at the same time, that their
actions can be added together, and that they must con-
sequently be of the same nature.

We can then draw the following conclusions:

1. The essential similarity of the two stimuli, onto-
genetic and functional, the reality of which the facts
which we have just cited and a thousand others like
them permit us to deduce, combined with the fact that
external influences, upon which alone the functional
stimulus depends, are generally lacking during the
embryonal period, is sufficient even by itself to justify
us in concluding that ontogenetic stimuli are nothing else
than the reactivation and restitution of the functional.
It constitutes thus at the same time a new argument in
favor of the inheritance of acquired characters.

2. This conception of development based upon the
essential identity of the functional stimulus and the onto-
genetic stimulus, and up till now at least only this con-
ception, makes it possible to explain the ontogenetic facts
without presupposing in any of the stages of development
any phenomenon which is not a normal physiological
phenomenon, of the very same nature as those mani-
fested by the organism in the adult state. And it thus
indicates that the whole of life, at every moment of it,
preserves an absolute unity in its nature.

3. Ontogeny finally appears to us in this way
simply as @ continual functional adaptation, by the
embryo, to the successive active modes of being of the
central gone of development.

Having thus set forth and explained the way in which

310 Explanation of Inheritance

centroepigenesis is able to account for the inheritance of
acquired characters in general, the particular case of this
inheritance, constituted by sexual dimorphism and by
polymorphism in general, which up till now we have
been compelled to leave aside, becomes explained at once.
The question of primary and secondary sexual char-
acters, writes Delage, is connected with one of the most
important questions of general biology: “When one
part develops in a certain way another part develops
correlatively in a certain way, and if the first had devel-
oped in another way, the development of the second
would also have been different; and this although no
direct connection exists between these two parts. The
question presents itself also in the following way: In
what way and under what form can this reciprocal
influence of the organs acting at a distance be effected
without any similarity between cause and effect?” 22°
The explanation which the centroepigenetic hypothesis
can afford for sexual dimorphism is the following: It is
due to the fact that in the whole series of germinal specific
potential elements there are found interpolated two dis-
tinct groups of these elements, such that the activation
by the central zone of one of these groups would pre-
clude the activation of the other and vice versa. Then as
soon as the two sexes have commenced to differ somat-
ically even a very little from each other, every later
sexual character, whether principal or secondary, acquired
by functional adaptation by the male or female, or better
the entire conformation of the whole organism resulting
therefrom, would become represented in the central zone
of that organism by a corresponding small group of

*°Delage: L’hérédité etc. P. 184—185.

Sexual Dimorphism and Polymorphism 311

specific potential elements. And these could become
activated in the next following organism only when the
general distribution of its nervous energy should find
itself in the same conditions as at the time when this
new sexual character was acquired: a thing which
requires above all that the organism be of the respective
sex.

In harmony with this the ordinary facts of embryonic
development teach us that as soon as the sexual organs
of one of the sexes become indicated, the accessory
organs just forming of the other sex cease to develop
and remain rudimentary, while the organs proper to
the sex which is already declared, both the essential and
the secondary, develop completely. There is thus an
arrest of growth in some organs from the fact of the
development of the others, which makes one suspect that
the conditions of environment created by this develop-
ment of some organs hinder the further activation of
energies which cause the production of organs of the
other sex.

Thus there always remains latent the possibility, that
the characters of the other sex may also appear in an
individual already developed in the opposite way, espe-
cially in advanced age, when with the cessation of their
respective functions all the sexual organs and characters
lose their vitality; a thing which often occurs in many
species and in man himself, and which occurred partic-
ularly in that famous old hen which Darwin has reported,
which after having ceased to lay eggs took on not only
the voice, but the plumage, the spurs, and the fighting
temperament of the cock.

One can say the same of polymorphism. In fact this
also can very well be regarded as dependent on an inter-

332 Explanation of Inheritance

polation, quite analogous to that of which we have
spoken above, of three or more groups of specific poten-
tial elements in the whole series of germinal elements,
with the result that the activation of one of these groups
prevents that of all the others. Thus each form of the
polymorphous kind would have its own characters which
arise entirely by the inheritance of characters acquired
through functional adaptation.

It is nevertheless to be remarked that a few forms
of certain polymorphous species are possibly to be
ascribed also to the circumstance that a few groups
among all the specific potential germinal elements of the
entire series are hindered in their activation, not so much
by properly ontogenetic conditions which depend upon
the development of other characters, as rather by quite
general conditions of temperature, nutrition, etc., so that
thus the form in which hese groups are not activated,
differs from the principal form only through the absence
of some single character. This might be the case, for
example, in the working bees and generally in the neuters
of many insects, the explanation of which would thus
be quite similar to that which Spencer gives in his polemic
with Weismann. But evidently these forms with incom-
plete development represent essentially only a special case
of the preceding supposition.

We can thus say also that the fundamental principle
to which centroepigenesis has recourse in order to explain
sexual dimorphism and polymorphism in general, that
is, to explain how it comes about that the development
of certain characters prevents that of certain others
which remain latent, is still the same principle which
has already served to explain the fact that ontogenetic

Instincts 413

characters present themselves exactly in the order of
their phylogenetic acquisition.

If the capacity which centroepigenesis possesses of
explaining the Lamarckian principle extends so far as to
account, without needing any subordinate hypothesis, for
the inheritance of those characters also’ which either sex
has acquired separately and at different times and each
on its own account, it shows itself still more especially
and completely adapted to explaining the inheritance of
those characters common to both sexes as well as those
belonging only to one sex which, in consequence of their
excessive complexity and of the circumstance that they
are located not simply in definite parts of the organism
but rather in numberless places at the same time, have
so far always constituted the greatest difficulty for every
theory which has attempted to explain the inheritance
of them. We refer to the instincts.

It is evident in fact that we can regard every instinct
as due to a special relative mode of being of the different
psychic centers and of the nervous network connecting
them. For it depends upon this relative mode of being
that to certain definite sensations which arrive at certain
perceptive centers there correspond necessarily certain
reflex movements induced by the motor centers which
are in definite communication with these perceptive
centers. Now, however, every deposition of new psychic
centers, perceptive or motor, mnemonic or volitional,
and every new connection of these by means of nervous
communications more or less direct or indirect, more
or less conductive or resistant, would be, according to
the centroepigenetic hypothesis, only the effect of as
many special modes of being of nervous circulation in
the limited territory of the nervous system alone. It

314 Explanation of Inheritance

is therefore easy to imagine, above all if we recollect
that the central zone would be just one part,—the least
differentiated part of this system, that for each one of
these complex modes of being of the nervous configura-
tion constituting a given instinct there must correspond
in the central zone itself its respective specific potential
element, and this latter becoming active later in the next
following ontogeny as soon as the general nervous con-
figuration again becomes like that which was present at
the moment immediately preceding that in which this
element was formed in the parent, must be capable of
so modifying this configuration as to make it acquire
the same instinct which the nervous configuration of
the parent had acquired by the action of external
influences.

If now we draw a conclusion from all that we have
said thus far, we can very well assert that the attempt
{o account by means of the centroepigenetic hypothesis,
for the Lamarckian principle in all its manifold and
comprehensive manifestations has not failed. One notes
also that this hypothesis can be assigned to the class of
mnemonic theories of heredity, but with this important
difference, that the theories of Haeckel, Hertwig, Orr,
Cope, and other similar ones, in order to explain the
phenomenon of the inheritance of acquired characters
appearing during development, have recourse to a phe-
nomenon still more special and more complex, the
mnemonic, and therefore do not and cannot constitute
any real explanation. Centroepigenesis on the contrary,
as we saw utilizes as subordinate hypothesis a very
general and very simple biological phenomenon, which
in many respects indeed is like certain phenomena of
the accumulation of energy in the inorganic world, and

Ontogenetic and Mnemonic Phenomena 315

which would be at the same time the basis of both the
phenomenon of heredity and the mnemonic phenomenon.
So that these latter instead of being explaine1 by each
other, would both be explained by this single phenome-
non, more simple and more general than either.

So it will be worth while for us, in the last chapter
which follows this, to subject the mnemonic phenomenon
to a rapid examination in order to see if it likewise
really finds an adequate explanation in this supposed
elementary biological phenomenon of a specific accumu-
lation of energy. And then we shall examine more
closely the question whether this same hypothetical ele-
mentary phenomenon cannot at the same time explain
at least partially the fundamental properties of the vital
phenomenon itself in all its generality.

CHAPTER VIII

THE PHENOMENON OF MEMORY AND THE VITAL
PHENOMENON

The comparison between the phenomena of develop-
ment and the phenomena of memory especially after the
discovery of the fundamental biogenetic law, that onto-
geny is a recapitulation of phylogeny, has presented
itself spontaneously to a large number of authors.
“The germ,” said Claude Bernard, “seems to preserve
the memory of the organism from which it came.’’?%°
Haeckel attributes development to the mnemonic quality
of his plastidules. We have seen in the sixth chapter
how Orr endeavored to explain the recapitulation of
phylogeny during ontogeny by the mnemonic law of
habit; how Cope held that ontogeny is called forth by
the unconscious memory of phylogeny; how Nageli and
in some places, Hertwig himself, attributes to the idio-
plasm the faculty of remembering, so to speak, the suc-
cessive stages through which it had gradually passed.

But by far the boldest contender for the acceptance
of the essential likeness of the ontogenetic and mnemonic
phenomena has been Hering: ‘What else is this re-
appearance in the developing daughter organism of
characters of the parent organism, than a reproduction,

7°Claude Bernard: Lecons sur les phénoménes de la vie com-
muns aux animaux et aux végétaux. P. 66.

316

Likeness of Ontogeny and Memory 317

on the part of organized matter, of processes in which
it already took part at another time, even if only as
a germ in the ovary, and which now at an opportune
moment it recalls exactly while reacting to the same or
similar stimuli in a way similar to that formerly followed
by that organism of which it was once a part, and
whose vicissitudes it then had shared? If the parent
organism by long custom or repeated action has changed
somewhat in nature in such a way that the germinal
cellule within it has also been affected however
feebly it may be, and if this latter commences a
new existence growing and developing into a new being
of which the different parts are yet only itself and flesh
of its flesh; and if in thus developing it reproduces that
experience which it had already shared at another time
as part of a great whole; this is indeed just as astonishing
as when the memory of his earliest childhood suddenly
comes back to the old man, but it is no more astonishing.
And whether it is still the same organized substance
which reproduces a process already once experienced,
or whether it is only a descendant, a portion of itself,
which in the interval has grown and become large, this
is manifestly a difference of degree only and not of
essence.” 231

We shall not repeat here the objections which have
been advanced against the similar affirmations of Orr

231Rwald Hering: Uber das Gedachtnis als eine allgemeine
Funktion der organisierten Materie. Wien, Gerold, 1876. P. 16—17.
Hering’s thesis has recently been taken up again by Richard Semon
and been treated more thoroughly and completely in his work: Die
Mneme als erhaltendes Prinzip im Wechsel des organischen Gesche-
hens. Leipzig, Engelmann, 1904. (See Eugenio Rignano: Une
nouvelle théorie mnémonique du développement. Revue Philoso-
phique. Paris, Alcan, November 1906. No. 11.)

318 The Mnemonic Phenomenon

and Cope. Only it may be noted once again that the
absence of any analysis, however conjectural, of the
nature of the phenomena of memory makes the explana-
tion of development which Hering tried to give in this
way, not only quite indefinite and nebulous, but alsa
gives it the appearance of a quite artificial comparison
between processes much too unlike.

The same is true ina yet greater degree of the general
theory of Hering of which development is a particular
case, and which considers memory a general function
of all living organized matter. Ribot accepts this theory
and modifies it in that he expresses the view that “mem-
ory is essentially a biological phenomenon and only
accidentally a psychological one.” ?%

This extension of the mnemonic faculty over every
vital phenomenon without exception, though it contains
much truth, cannot by itself constitute any explanation
of either one phenomenon or the other, but rather helps
to plunge both into greater obscurity; for while by this
comparison the obscure fundamental peculiarities com-
mon to both become in no wise clearer, one loses sight
of those most familiar and characteristic properties which
are different in the two phenomena, and which are the
ones which have served to give, up to the present day,
the most correct idea possible of both.

The mnemonic phenomenon can serve then neither
as an explanation of the phenomena of development nor
of vital phenomena in general, because it is as we said
a phenomenon even more special and more complex than
those which it has been summoned to explain. Never-
theless there may yet be the possibility that the resem-

*°Ribot: Les maladies de la mémoire. Paris, Alcan, root. P. 1.

Specific Mnemonic Elements 319

blance which appears to exist between some of the
essential properties of these three phenomena may be
explained by a still more general and more simple
phenomenon which would form the common basis of all
three categories of phenomena; the ontogenetic, the
mnemonic properly so called or psycho-mnemonic, and
the vital.

We have already shown that this common phe-
nomenon might perhaps be implied in the hypothesis
set forth above, in which we regarded the specific potential
elements as accumulators of specific nervous energy or
as specific elementary accumulators. In just this capacity
of restoring again the same specificity of nervous current
as that by which each element had been deposited one
would look for the cause of the mnemonic faculty in the
widest sense, which all living matter possesses. And
further the very essence of the mnemonic faculty would
consist entirely in this restitution.

It may be remarked here that the specific potential
elements which as we saw in the preceding chapter could
be called also specific elementary accumulators are thus
susceptible now of receiving a third name, namely that
of mnemonic elements.

According to this definition, ordinary electric accumu-
lators, which are as we saw merely generic accumulators,
represent, one may say, only very imperfect mnemonic
elements. On the contrary the more capable they were
of storing up each a single one of the innumerable minute
specific variations of such an energy and of reproducing
it identically at each discharge, the more perfect
mnemonic elements they would become.

As of all the vital phenomena the psycho-mnemonic
are those which present most distinctly the mnemonic

320 The Mnemonic Phenomenon

faculty possessed by all living substance, it is in them
that we shall be able best to verify the laws which be-
come impressed upon this mnemonic faculty through the
conception that it is based upon the specific accumula-
tion and reproduction suggested above. And the most
important of these laws have just been briefly outlined
in the preceding chapters.

Of the three elements of memory: the preservation
of certain states, their reproduction, and their localization
in the past, Ribot thinks that the first two alone are
necessary and characteristic.23? We can note, that the
hypothesis of mnemonic elements permits us to conceive
of this preservation of certain states as an accumulation
of specific energy and their reproduction as the discharge
of that specific energy.

“When we speak,” writes Maudsley, “of a trace, or
vestige or residuum all we mean to imply is that an
effect is left behind in the organic element, a something
retained by it which disposes it to a similar functional
act; a disposition has been acquired which differentiates
it henceforth, although we have no reason to think that
there was any original specific difference between one
nerve cell and another.” ?%* This something which
leaves an impression after it in the nerve cell and which
disposes it to other similar functional acts will be to our
mind, a true and real material residue of substance
capable of reproducing the same functional current as
that by which it had been deposited. And the differ-
entiation of nerve cells, as indeed of all other somatic
cells, consists in the acquisition by each of them of a

*8Ribot: Ibid. P. 2.
**4Maudsley: The Physiology of Mind. Third edition. Len-
don, Macmillan, 1876. P. 270.

Psycho-mnemonic Phenomena 321

greater or less number of specific or mnemonic potential
elements differing from one cell to another. But we
must bear in mind that this differentiation is not acquired
exclusively after birth, but appears already within cer-
tain limits, at least in relation to all the congenital
instincts, during ontogeny.

“We see,” writes Hering, “how an entire group of
sensations become reproduced with such vividness and
in such precise order of space and time that it can
deceive us as to its reality. This shows us in a most
striking way that even after the sensation and percep-
tion in question has long since disappeared, there remains
still in our nervous system a material trace, an alteration
of the molecular or atomic connections by which the
nervous substance is rendered capable of reproducing
these physical processes, with which the corresponding
psychic process of sensation and perception is also deter-
mined.”—“The representations do not last as representa-
tions but what does persist is that particular attunement
of the nervous substance, by virtue of which when it
is properly struck it sounds again today the same note
which it gave forth yesterday.” 2%

This conception of Hering of the disposition of the
nervous substance to sound again the tone of yesterday
is derived from the physical phenomenon of acoustic
resonators. The nervous substance which would be made
to vibrate in a given specific way at a given point by a
definite elementary sensation or representation would re-
main from that moment capable of vibrating always and
exclusively according to that specific mode. According
to the hypothesis of mnemonic elements on the contrary,

2%5Hering: Uber das Gediachtnis etc. P. 8, 9.

322 The Mnemonic Phenomenon

it is well to repeat again, each elementary sensation or
representation would consist not so much in a specific
vibration of the nervous substance at this or that point
as in the production by the action of external stimuli
of a given specific nervous current. In this way the
memory of an elementary sensation or representation
would consist only in the reproduction, by the action of
causes now internal, of the same specific nervous current.
In other words the way in which the hypothesis of
mnemonic elements or specific elementary accumulators
would conceive of the mnemonic phenomena is as
follows:

A series of sounds or of words, for example a certain
melody, or some phrase of a discourse, when once it has
entered by the ear, we can imagine, produces a series
of nervous currents in the auditory nerve specifically
different from one another, just as in a telephone the
successive electric currents are specifically different from
one another (in this particular case different in intensity)
which the same series of sounds produces in the receptive
apparatus and later transmits along the wire. If then
one or several nerve centers, after receiving these spe-
cifically different currents, are capable of storing up these
specific energies, each distinct from the other, and to
reproduce them unaltered later at the moment of dis-
charge, and if, further, the discharge of each immediately
preceding specific energy and it alone is capable of pro-
ducing the liberation of the specific energy immediately
following, (and we have seen above that this is one
consequence of the hypothesis of specific elementary
accumulators), it will be in this way possible for the
same succession of different ideas or impressions to be

Psycho-mnemonic Phenomena 323

repeated a great number of times and it is in just this
that the mnemonic phenomenon consists.

One could evidently say the same thing of the optic
phenomenon, that is to say, of any series of colors or
specific luminous vibrations which succeed one another
in space or time.

Ribot has rightly said that “There is not one memory,
but memories; that there is not one seat of memory,
but particular seats for each particular memory.” 236
And, according to our theory, each mnemonic element
would just constitute a particular seat for each elementary
sensation or each particular specific impression.

In this sense also, that is to say on the condition
that the expression “nervous elements” be not disjoined
from the conception of elementary specific accumulators
or mnemonic elements, we can accept the idea of memory
which this investigator (Ribot) has put forward: “If
we attempt,” writes he, “to conceive a good memory and
to express this in physiological terms, we must figure
to ourselves a great number of nervous elements, each
modified in a particular manner, each taking part in one
combination and probably capable of entering into sev-
eral. Memory has then static and dynamic bases. Its
strength is in relation to their number and stability.” 2°?

“Tt has been asked,” continues Ribot, “if each nerve
cell can preserve several different modifications or if
once modified it is forever polarized. The number of
cerebral cells being about 600,000,000 according to the
calculations of Meynert (and Sir Lionel Beale gives a
much higher figure) the hypothesis of a single impression

286Ribot: Les maladies de la mémoire. P. 11.
287Ribot: Ibid. P. 32.

324 The Mnemonic Phenomenon

is not inconceivable.” 78 It may be remarked here that
according to the hypothesis of mnenionic elements there
is room in each brain cell for a whole series of specific
deposits and not merely for one specific deposit. Indeed
we must suppose, as we have seen, that the germ sub-
stance contains a very great number of specific potential
or mnemonic elements, and we can also assume that the
same is true of the very complex mnemonic centers.

Provisionally it can be affirmed that the close depend-
ence of memory upon the nutritive processes,?*® indicates
strongly that the preservation of memories is to be
ascribed to accumulations of substance. Further, as was
very well remarked by Hensen, the fact that many mem-
ories may remain entirely dormant throughout several
years, and then can come again with great distinctness
into consciousness, notwithstanding that all the parts of
the organism have been renewed several times in the
interval,?*° indicates, (if one recollects that assimilation
consists in the incessant reproduction of new masses,
always of identically the same substance), that in order
to preserve these memories it is sufficient if for one given
substance there be substituted another identical one.

If it appears thus to be shown by facts, that the
preservation of memories is due to accumulation and
conservation of substance, a whole series of other facts
seems to demonstrate that the reawakening of these
memories consists in the restitution of the same currents
as had formerly constituted the actual sensation or
impression,

**8Ribot: Ibid. P. 17.

*°Ribot: Ibid. P. 155—163.

24°Hensen: Uber das Gedachtnis. Kiel, Universitats-Buchhand-
tung, 1877. P. 13.

Physiological Effects of Memories 325

We need not recall here all the innumerable examples
which show that the motor or secretory or in general
the physiological effects of the mnemonic reawakening
of a given sensation or impression are quite identical
with those of the real sensation or impression: for
example, the recollection of a certain dish produces the
same salivation as is provoked by the dish itself; the
memory of the beloved person can cause each time the
same reddening of the countenance, the same brightening
of the eyes, the same acceleration of the pulse as the
direct view of that person; every time that a mother
thinks of her nursing child there comes a flow of milk
into the breasts.241 These are some examples which show
the substantial identity of the functional and mnemonic
stimulus.

Here we should like to cite just the following experi-
ment of Wundt mentioned by Ribot: “If, after looking
for a long time at a picture with very vivid colors, we
keep the picture before our minds with the eyes closed
and after that suddenly open the eyes and fix them upon
a white surface, we see there the picture which we had
kept in our minds, but in the complementary colors. This
fact, remarks Wundt, proves that the nervous operation
is the same in the two cases, in the perception and in the
memory.” 242 According to our view this indicates that
the nerve current which corresponds to the color, let
us say red, of the picture, and reproduced, together with
all other currents corresponding to the other special
characters of this picture, by the mnemonic center
recalling it again, is equal but opposite in direction to
that current which the red rays coming from the white

2417 ewes: The physical basis of mind. P. 288.
242Ribot: Ibid. P. 11.

326 The Mnemonic Phenomenon

surface send toward the center: Consequently only the
currents sent by complementary rays from this white
surface can reach that center, and these combined with
the currents corresponding to the other characters of
the picture must give it the same aspect as before only
with a complementary color.

If the preservation of each memory is due to deposits
exactly equal in number to the specific elementary ner-
vous currents which the sensation or complex impression
had provoked in the nervous system, we are then in a
position to comprehend also the phenomenon known
under the name of abridgment. “Every memory,” says
Ribot, “however clear it may be, undergoes an enormous
abridgment. The farther the present recedes into the
past, the more do the states of consciousness diminish
and disappear. Reviewed at several days distance there
remains little or nothing of them; for the most part
they have darkened into a nothingness from which they
will never again emerge and have taken with them the
time duration inherent in them. Consequently a diminu-
tion of the states of consciousness is a diminution in
time.” 248

This disappearance of the elementary states of con-
sciousness producing the abbreviation of memory will
be due then, according to our view, to the disappearance
of the secondary mnemonic elements, that is to say those
provided with a minimum quantity of the respective
substance, (and of the potential energy which is the con-
sequence of it), from the series which constitutes the
entire memory. Possibly this disappearance can be
caused by the fact that the nutritive fluid has come

*“Ribot: Ibid. P. 44, 45.

Abridgment in Memory and Ontogeny a2

gradually to be entirely absorbed by the principal
mnemonic elements of the same series and by the new
elements which later supervene as a consequence of later
sensations also stored up in memory.

Let us note that this abridgment of every memory,
interpreted as above, becomes then completely capable
of explaining also the similar abridgment which phy-
logeny undergoes during ontogeny. In fact, of the
ancient mnemonic elements constituting the germinal
substance, the most pronounced, that is those which are
represented by the largest quantity of substance, will
alone persist. The less pronounced ancient mnemonic
elements, the total quantity of nourishment for all
mnemonic elements remaining the same or varying only
within definite limits, will have all their portion of
nourishment taken away by the more pronounced ancient
mnemonic elements, and by the new mnemonic elements
whose number will continually increase with each phy-
logenetic advancement. Not being able consequently to
regain their substance completely in each ontogeny they
will gradually disappear.

If we have always supposed so far, as the first degree
of approximation necessary to the comprehension of the
fundamental nature of the phenomenon, that ontogeny
reproduces phylogeny entirely, these abridgments of
memory permit us then to penetrate still farther into
the inner nature of this phenomenon and to recognize
that ontogeny instead of being an entire reproduction
of phylogeny can be only a succinct recapitulation.

In recalling a given memory the mnemonic cells do
not lose the “impression” as we call it which they
preserve of that memory; on the contrary the more a
memory is recalled the more the respective “impression”

328 The Mnemomc Phenomenon

is reinforced. This signifies that the activation of
mnemonic elements or the performance of their func-
tion merely causes their mass and their potential energy
to increase. This fact, that the active participation of
the mnemonic centers in the biological phenomena of
memory leaves them unaltered in the same state as
before, so that they are just as capable and even more
capable than formerly of reproducing many more times
the same phenomena, reveals them to us in this relation
also as entirely similar in nature to the germinal sub-
stance, which active participation in the biologic phe-
nomena of ontogeny leaves likewise in the same state
as before and even renders always more capable of again
producing the phenomenon of ontogeny.

According to the centroepigenetic hypothesis the
mnemonic elements of the germinal substance, with the
exception of the last belonging to the adult stage, can
become active only at each new ontogenesis; that is their
reawakening would take place only after long periods
of repose which might last even through several years.
Such reawakening of mnemonic centers at long inter-
vals of years constitutes a very ordinary phenomenon.
Cases are frequent, for example, of adults who are able
to repeat poetry which they had learned in their earliest
childhood, even after many years during which they have
never had occasion to repeat it at any time. Coleridge
speaks of a young girl who, in the delirium of fever,
repeated long pieces in the Hebrew tongue which she
did not understand, but which she had heard read aloud
a very long time before by a priest in whose service she
had been.24#4 A Lutheran preacher of German origin

*“4Maudsley: The physiology of mind. P. 25.

Persistence of Conditions Latent in Memory 320

living in America who had in his congregation a con-
siderable number of Germans and Swedes related to
Dr. Rush that nearly all a little before dying pray in
their mother tongue. “I have,” said he, “innumerable
examples of it and among them several in which I am
sure they had not spoken German or Swedish for fifty
or sixty years.” 245

The following two facts are still more typical:

A lady in the last stages of a chronic disease was
taken from London to the country. Her little daugh-
ter, who had not yet learned to talk, was sent to her
and after a short visit was sent back to the city. The
lady died several days later. The daughter grew up
to maturity without remembering her mother. She had
then occasion to see the room in which her mother died.
Although ignorant of that fact, upon entering the room
she started, and when asked the cause of her emotion,
she said “I have a distinct impression of having been
in this room before. There was in that corner a lady
in bed, apparently very ill, who leaned over me and
wept.” 246

Similarly, a man of very marked artistic tempera-
ment, as soon as he came in front of a castle in Sussex
had an extremely vivid impression of having already
seen it, and he recalled in his imagination the procession
of visitors in all its details. He learned from his mother
that he had actually been brought there on an excursion
at the age of sixteen months and that the recollection
which he had of the visit was very exact.?#7

These examples show then how remarkable can be

248Ribot: Les maladies de la mémoire. P. 146—147.
246Ribot: Ibid. P. 143—144.
“Ribot: Ibid. P. 144.

330 The Mnemonic Phenomenon

the persistence of conditions latent in memory. Let us
note further, that these last two cases present in a very
striking form one of those “revivifications of memory
through contiguity in space,” as Ribot would call them.
This reawakening of memory through contiguity in
space is only a particular case of the general law of the
association or succession of ideas. They indicate that
the mnemonic center becomes active only when the sight
of the same place induces in the environment of that
center almost the same state of distribution of nervous
energy as was present at the former time when it received
the impression. That is exactly, as we have seen in
the preceding chapter, the immediate result of the hypoth-
esis of specific elementary accumulators there advanced.
In the mnemonic phenomena properly so called, it
is the infinitely diverse and constantly changing condi-
tions of the outer world and the corresponding sensa-
tions following in the individual which call forth like
a phantasy such and such an association or succession
of ideas. But in the development of the embryo which
is removed from the action of every external perturbing
influence and above all, which is provoked by the acti-
vation of different specific germinal elements from one
and the same complex mnemonic center constituted by
the germinal substance, the succession of mnemonic states
of this latter called into activity one after the other and
of the corresponding stages of ontogeny must inevitably
proceed in an uninterrupted series, always the same for
all individual ontogenies of the same species. For to
reawaken each mnemonic element of this germinal sub-
stance there must again concur exactly and exclusively
those conditions of distribution of nervous energy in

Succession of Outogenetic Mnemonic States 331

the embryo which had been provoked by the reawaken-
ing of the mnemonic element immediately preceding.

It is then in development even more than in mnemonic
phenomena properly so called that there operates the law
of rigorous succession, in which, as Ribot says, each
member of a series “suggests” the following.?#8

In summing up all that we have said thus far we
can thus affirm that if the mnemonic phenomena, prop-
erly so called, cannot serve to explain ontogenetic phe-
nomena nor the latter to explain the former, their
resemblance which has nevertheless been noted by so
great a number of authors can be explained by a third
phenomenon more general and more simple than either.
And this phenomenon consists in the faculty possessed
by all living substance of accumulating and giving back
again individually the different particular specificities of
generic nervous energy, which constitutes the essence of
all vital phenomena whatever.
* DT * * * * *

This property of accumulating and giving back spe-
cific nervous energy, attributed by hypothesis to all living
organic substance, is thus shown to be capable of explain-
ing the most fundamental biological phenomena, from
histologic specialization of cells which respond always
in their customary specific manner no matter how unusual
may be the stimulus which excites them, to the inheritance
of acquired characters, from the evolution of species
and the repetition of phylogeny by ontogeny, direct con-
sequences of that inheritance, to mnemonic phenomena
properly so called.

It remains for us to demonstrate that this property,

248Ribot: Les maladies de la mémoire. P. 8

332 The Vital Phenomenon: Assimilation

as we have affirmed before, can help to explain in great
part the essential character of the vital phenomenon itself
in all its generality—that is assimilation.

The fact that strikes us first of all is, that the vital
phenomenon depends upon continual reproduction, for
assimilation constantly reproduces the substance which is
gradually consumed. It is to be expected therefore, that
if there are any fundamental properties of living organic
substance which explain the phenomena of development
or of reproduction in general, they must then be capable
of accounting for assimilation also, inasmuch as it is
itself a phenomenon of reproduction.

That being granted it will be worth while that we
next stop for an instant to take a look at and consider
briefly a few of the principal conceptions which biologists
have put forward on the nature of either the vital phe-
nomen or of assimilation, and which are of the greatest
interest from our point of view.

Roux, for example, rightly urges that the nature of
life must be dynamic. “Life is in its essence a process,
and cannot therefore have a static definition. It is
therefore only a processive and consequently functional
definition which can approximate the essence of organic
hte, #22

On the other side we have already seen the reasons
for concluding that the essence of the vital phenomenon
consists in an activation of nervous energy. We re-
call that according to Orr for example, the funda-
mental property of living substance is an “elemental
nervousness.” 75°

*°Roux: Uber die Bedeutung der Kernteilungsfiguren. Leipzig,
Engelmann, 1883. P. 18. Gesamm. Abhandl. Bd. II. P. 142.
*°Orr: A Theory of Development and Heredity P. 86.

Conceptions of Vital Energy Reviewed 333

We have already seen also that Claude Bernard, in
agreement with that, considers the sensibility of the ner-
vous substance as nothing else than a particular modality
of irritability, which would be a general property of
all living substance. ‘‘Sensibility,” writes he, ‘considered
as a property of the nervous system, is only a higher
degree of a simpler property which exists everywhere
in all living substance both animal and vegetable. It
has nothing essential or specifically distinct. It is the
special irritability of the nerve just as the property of
contraction is the special irritability of the muscle, and
as the property of secretion is the special irritability of
the glandular element. These phenomena are so many
different degrees of one and the same elementary phe-
nomenon.” 254

Bard also remarks that if the nature of the energy
constituting the basis of all vital phenomena must be
single, the infinitely varied modalities which the same
vital phenomena present must then be due to as many
corresponding modalities of this single energy.

“In spite of the complexity and multiplicity of physio-
logical functions,” he writes, “it is possible to refer them
fundamentally to a general function of the living cell,
namely the function of producing derived substances.
Cellular specificity can be explained and made compre-
hensible only as this single function is able to insure the
innumerable functions necessary for an entire organism.
The variety of derived substances is itself the effect and
the proof of the radically different vital properties of
the kinds of cells which create each of them.”

“It is necessary to establish an essential difference

231Claude Bernard: Lecons sur les phénoménes de la vie com-
muns aux animaux et aux végétaux. P. 289—z290.

334 The Vital Phenomenon: Assimilation

between the physico-chemical properties of the derived
substances created by the specific activity of each living
cell, and the properties of the cell nuclei which spring
directly from the special forces which constitute life.
The specific differences result from the very modality
of the cell life. Cell life is a special property of matter
which, like all its highest properties, undoubtedly con-
sists in a particular mode of movement. One can say
in some measure that the cell is a circuit of life. Further
vital force, like light or electricity, with which one can
compare it, not so much to show that it is very similar
to them as to facilitate the comprehension of it, presents
multiple varieties due to variations of wave lengths, of
their rythm, direction, or of any other element of this
movement which one could suppose or discover. These
variations are without doubt incomparably more numer-
ous than those of electricity, which are limited enough,
than those even of light, which are certainly infinitely
more numerous. And just as colors indicate the differ-
ences of the different kinds of light, so the different
physiological functions of species of cells indicate differ-
ent modalities of life.” 25?

It is worth while to stop a moment here, to show
in this connection how readily biologists are inclined to
fall into two opposite exaggerations.

Some deny flatly the possibility of ever arriving at
an understanding of the nature of life. But if we ask
ourselves in what this understanding of the nature of
life could consist, from the point of view of positive
philosophy, we have no difficulty in recognizing that

*"°Bard: La spécificité cellulaire et ses principales conséquences.
La semaine médicale. Paris, 10. March 1894. P. 116.

Understanding of the Nature of Life BK

such an understanding must be reduced to comparing
vital phenomena with some physico-chemical model al-
ready known, suitably modified by the particular special
conditions imposed upon it so that just these special con-
ditions shall determine the differences which exist be-
tween this vital phenomenon and the phenomenon of the
inorganic world most closely related to it. If this be
so, it is then the duty of science emphatically to reject
such a denial of scientific thought as the renunciation
of the quest of this understanding would constitute.
Whether one clearly recognizes it or not, it is just this
search for the nature of the vital principle which properly
constitutes the principal object and the final goal of all
biologic study in general.

Others again are not willing to accord to life even
the slightest property which should not be simply physico-
chemical in nature. Among all these it is enough to
cite the example of Verworn who not only relegates
assimilation to the category of purely chemical phe-
nomena, by means of his “Biogen” hypothesis, but who
would explain protoplasmic currents, the protusion of
pseudopodia, the movements of cilia, and in general all
movements of living beings by a double and alternative
chemotropism of protoplasmic substance rather than by
currents of nervous energy. Protoplasmic substance, in
fact, according as it remains unstimulated or is stimu-
lated, that is, partially decomposed by the stimulus which
would agitate it mechanically, would possess a chemical
affinity for the oxygen of the environment or for the
substances produced by the nucleus capable af rebuilding
the partially decomposed protoplasmic substance. And
to this alteration of different affinities, the opposite proto-

336 The Vital Phenomenon: Assimilation

plasmic movements of expansion and contraction would
correspond.?°*

Now it is evident that this endeavor not to attribute
to vital energy any specific nature of its own, and con-
sequently to explain even the most characteristic phe-
nomena of life by means of only those energies which
physics and chemistry afford us to-day, can have no
more success than as if one should attempt to explain
chemical phenomena by means of physical phenomena
only. For the conception that the form of energy on
which vital phenomena are based is different from all
forms of energy which have hitherto been observed in
non-living bodies, has absolutely nothing unscientific in
it, any more than the conception, for example, that electri-
city may also be a form of energy different from all
others.

Vital energy, nervous energy, we admit at once, will
certainly be a particular case of the more general physico-
chemical forms of energy already known or yet to be
known, and as such it must necessarily be subject to
the laws which control these latter; and also, a fortiori,
to the laws which control all energy in general. But even
as such, that is as a particular case of more general,
physico-chemical forms of energy, it will have besides
further special laws of its own which are only experi-
mentally to be determined and cannot be deduced from
the more general laws even though it must always be
subjected to them. And it is just these laws of its
own which, out of a physico-chemical energy, make it
vital energy. This conception has led us to attribute
to nervous energy, set forth as the basis of life, special

253Verworm: Die Biogenhypothese. Jena, Fischer, 1903; and
Die Bewegung der lebendigen Substanz, especially P. 100—103.

Conceptions of Assimilation Reviewed 337

properties, which electric energy, in certain respects
related to it, does not possess.

If, passing on now to assimilation, we examine the
conceptions which the biologists have formed of it, we
shall see that their opinions on that subject are quite re-
markably concordant.

Thus, for example, Lewes says: “The peculiarity
of vital processes consists in this, that living matter under-
goes molecular changes of composition and decomposition
which are simultaneous, and by this simultaneity it
preserves its integrity of structure.”?°4

“Life,” remarks in his turn Oscar Hertwig, “mani-
fests itself, expressed in the most general terms, in this
that the cell, by virtue of its own organization and
under the influences of the external world undergoes
continual changes and develops forces whereby its organic
substance, on the one hand continually destroyed with
determined manifestations of energy on the other hand
is regenerated.”—‘The life process depends then, on a
continual destruction and reformation of organic sub-
stance.” 255

But the clearest and most suggestive of all is Claude
Bernard in the following celebrated passage:

“The characteristics of life considered in their essence
and in their entirety can be classed in two groups.”

“7, The phenomena of consumption, of vital de-
struction, which correspond to the functional phenomena
of the organism.”

“2, Plastic phenomena or phenomena of vital crea-

2547 ewes: The Physical Basis of Mind. P. 5.
265Qscar Hertwig: Die Zelle und die Gewebe. Bad. I, P. 54, and
Bd. II, P. 190—191.

338 Assimilation

tion, which correspond to functional repose and to organic
regeneration.”

“Everything which goes on in the living being is in
relation to one or other of these types; and life is char-
acterized by the union and combination of these two
orders of phenomena.”

“Disorganization or dis-assimilation uses up living
material while the organs perform their functions. As-
similative synthesis regenerates the tissues. It reassem-
bles the reserve materials which the functioning organism
must use up. These two processes of destruction and
renovation, although inverse, are absolutely connected
and inseparable, in the sense at least that destruction
is the necessary condition of renovation. The phenomena
of functional destruction are themselves the precursors
and instigators of the renewal of material by the forma-
tive process which is accomplished silently in the interior
of the tissues.” 2°¢

Dastre remarks finally that “Claude Bernard devel-
oped from the analysis of substances excreted as the result
of physiological work, his conviction that every mani-
festation of functional phenomena is necessarily asso-
ciated with some organic destruction. For excretions
certainly bear witness of organic demolition.”

“But the underlying reason,” continues Dastre, “of
this interdependence between chemical destruction and
function is made recognizable by energetics. A part of
the organic material (reserve material, but also living
protoplasm) becomes decomposed, chemically simplified,
reduced to a lower degree of complexity, and abandons

*°°Claude Bernard: Lecons sur les phénoménes de la vie com-
muns aux animaux et aux végétaux. P. 125—127; 157; 347—348.

Conceptions of Assimilation Reviewed 339

in this descent the chemical energy which it enclosed
within it in the potential state.”

“Every act which gives out energy, which produces
heat, or movement, every manifestation whatever, which
can be regarded as a transformation of energy, neces-
sarily consumes energy, and this is borrowed from the
substances of the organism. The functioning muscle
produces heat and movement, the functioning of glands
produces heat, the functioning of nerve and brain pro-
duces a small quantity of electricity and heat. All these
manifestations of energy rest upon a destruction of
organic matter, a chemical simplification as the source
of the energy manifested. In this way material de-
struction not only coincides with functional activity but
is the measure and the expression of it.”

“The reconstructive synthesis of protoplasm is on
the contrary a phenomenon of evident synthesis, of a
certain chemical increase of complexity. Its formation at
the expense of simpler nutritive materials requires then
an appreciable quantity of energy.”

“The phenomena of living beings,” continues this
author, “may be divided into two categories. Some are
intermittent, alternative, and are produced or accentu-
ated at certain times but cannot be continuous. These
are functional processes. There are others in which
this property of sudden and intermittent expenditure of
energy does not appear at all. They are in general
nutritive processes. The muscle which contracts, func-
tions. It has an activity and a repose. During this ap-
parent repose one could not say that it is dead. It has
life and this is here obscure in comparison with the
manifest activity of the functional movement.”

“The phenomena of functional activity are those

340 Assimilation

which catch the eye and by which we are inclined to char-
acterize life. These are conditional on processes of
consumption, of chemical simplification, of organic de-
struction through which energy is set free. And it is
quite necessary that it should be so, since these functional
manifestations expend ‘energy. These phenomena in
which the vital activities are most apparent are the least
specific. They have only the character of general
phenomena.”

“The phenomena which accompany functional repose
correspond to the reconstruction of the reserve materials
destroyed in the preceding period, to organic synthesis.
This remains in the words of Claude Bernard, ‘internal,
silent, hidden in the expression of its nature, reassembling
silently the materials to be expended. We never see these
phenomena of organization directly. Only the histolo-
gist, the embryologist tracing the development of the
element or of the living being notes the changes, the
phases which discover to him this homely work, here a
deposition of material, there the formation of a mem-
brane or a nucleus, yonder a cleavage or a folding, or a
renovation.’ This category of phenomena is the only
one which has no direct analogues. It is peculiar to the
living being and limited to it. This developmental
synthesis is the true vital phenomenon. Life is a
creation.” 257

It is then this reconstructive synthesis of living matter
which goes on during the so called functional rest which
we must seek to explain through the properties which we
have postulated above for nervous energy taken as the
basis of the vital phenomenon.

**"Dastre: La Vie et la Mort. Paris, Flammarion, 1902. P.
103, 107, 208—209, 210—21T.

Explanation of Assimilation 341

For this purpose let us suppose in conformity with the
hypothesis set forth above that one could construct an
elementary electric accumulator capable of furnishing a
single given intensity or specificity of current and that its
electro-motive force or difference of potential between the
poles is proportional to the mass of substance constituting
its charge; as if each new increment however small of this
mass constituted an element by itself which would be
added in serial order to the others.

A A Let us consider two of these accumu-
lators, A and A’, inserted with their
? \\—- hp poles inverted in the same circuit. Sup-
7 NC pose they are quite identical, except
that the one, A’, is entirely without
charge, and the other, A, has its full
charge. Let us suppose now that the
current, c, generated by A which tends
to charge A’ can under certain circum-
stances cause an oscillatory discharge,
i. e., a continuous oscillation of the
current, now in the direction of c, now
in the contrary direction c’, and that certain external alternating
currents could induce in the oscillating circuit sinusoidal electro-
motive forces of the same frequence as this oscillating discharge
and thereby strengthen the sinusoidal electro-motor force of the
latter which at the beginning was determined by the original dif-
ference in charge of the two accumulators A and A’.

Then with each half oscillation the one accumulator
will become more strongly charged in proportion as the
other discharges, and there will be produced as a final
result of the series of oscillations a consequent continual
increase of the total mass of the two accumulators A and
A’, as long as the saline solution serving as their common
aliment is not insufficient.

If the amount of electro-motive force contributed by
the induction current at each oscillation is proportional

342 Assimilation

to the amount of electro-motive force which is directly
dependent upon the difference in charge between the two
accumulators existing at any moment, if for example, it
represents a definite fraction of the latter, and thereby
will gradually decrease in amount as this difference be-
tween the two charges becomes less with each oscillation,
then both the amount of this difference and that of the
induced electro-motive force will sink to nothing after a
certain period of time, theoretically infinitely long, prac-
tically more or less short, which we can call the period of
reconstitution or of replacement of material consumed.

As soon as the charges of the two accumulators have
become equal there will take place no more provocation
of oscillating currents and the total mass of the two ac-
cumulators whose increase had become always smaller
and smaller will now not increase any further at all.

But if at this instant either of the two accumulators,
suddenly becoming inserted, aside from its own oscillat-
ing circuit, into another circuit, discharges into the latter
wholly or partially, then the difference between the re-
spective charges of the two accumulators will again be
present and the former process of oscillation will begin
again. And this will result again in the increase of the
total mass of the two accumulators above the amount
which it had already reached before this last discharge.
We can compare this discharge of one of the two accumu-
lators outside the circuit of oscillation with the nervous
nuclear discharge outside the nucleus into its surrounding
protoplasm or its environment in general, that is with the
biological functional excitation which produces the same
trophic effect.

Further if at the moment when the two accumulators
have arrived at the condition of equality between their

Explanation of Assimilations: The Vital Element 343

respective charges and so of repose, one of them instead
of becoming discharged into another circuit, becomes re-
placed by a third accumulator whose charge 1s different
from the other two now equalized charges, the result will
be the same. And the impulse given to the process of
oscillation will be greater the greater the difference be-
tween the charge or electro-motive force of the new
accumulator and of the old one replaced. In other words,
to make use of biological expressions: the rejuvenescence
of the specific potential elements formed by the pair of
accumulators will be proportionally greater, the more
quantitatively unequal are the two half elements which
have become thus mutually fecundated.

If we substitute for the conception of electro-motive
force that of nervo-motive force, our hypothesis concern-
ing the nature of the vital process in each specific potential
element will consist simply in supposing that the latter is
comparable to this pair of accumulators inserted with in-
verted poles in the same elemental oscillating circuit,
which we would call intra-nuclear circuit, but in which
there enters into play instead of the alternating electric
induction current, general thermal energy in the same
way.

Assimilation, the new formation of living substance,
would then be dependent, according to the hypothesis,
upon a kind of oscillatory charging and discharging flux,
upon a kind of intra-nuclear oscillatory discharge which
becomes provoked by the extra-nuclear or functional
nervous discharge in consequence of the disturbance of
the equilibrium between the nervo-motive forces of the
two accumulators opposite each other. The vital element
would thus be conceived of as only a double specific

344 Assimilation

elemental accumulator of nervous energy in continual
charge and discharge.

As will be noted we have here a phenomenon in some
respects similar to the electric resonators of Hertz, in
which an electric discharge caused by the difference of
potential existing between the two armatures of a con-
denser, is transformed into an oscillatory discharge. It
will be appropriate here to indicate briefly in just what
this phenomenon consists.

A D B Let A and B be the armatures
of a charged condenser which are
suddenly connected with each

Zo other by an external conductor,

vu ArMLB, in such a way that the

latter makes a circuit open only at

the point D of the di-electric. In

L the accompanying figure r repre-

sents the total resistance of the

circuit, and L the inductance or co-

efficient of self induction of this

circuit. When the capacity c of

M the condenser and the inductance

L of the circuit are in a certain

relation to each other, and r is small, we can get an oscillatory dis-

charge which forms as it were a sinusoidal alternating current; that

is the electricity oscillates from A toward B and from B toward A,

with a frequency determined by the inductance L and the capacity

c. If we cause the resistance r of the circuit to become constantly

less by employing wires of constantly increasing thickness, we

approach the boundary at which this oscillation will be able of itself
to continue indefinitely.

If in this case, where r is very small, we excite in the
circuit by induction sinusoidal alternating electro-motive
forces of the same frequence as in the oscillatory dis-
charge, then there will arise in A and B differences of
very many volts even though the number of volts so
induced is small.

Upon this principle depends, as is well known, the

Electric Resonators 345

celebrated experiments of Hertz, which in turn have
formed the point of departure for wireless telegraphy.

It is known also that such an electric resonator has
been rightly compared to a vibrating dynamic system, to
a pendulum which has an oscillation time of its own, to a
sounding chord which the smallest impulses having the
same frequence as itself can set in vibration, even in
strong vibration. What happens in it is a continual
periodic transformation of energy. At the instant when
the sinusoidal alternating current reaches its maximum
intensity, one has the maximum of actual energy, while
the condenser, on the other hand, possesses then no
potential energy whatever. At the instant when the in-
tensity of the current drops to nothing, the condenser
shows the greatest deformation of the respective di-
electric, and possesses thus a potential energy fully equal
to the actual energy possessed by the discharge at the
moment of its greatest intensity, the process being thus
exactly the same as in a pendulum in which potential
energy is transformed continually into actual and vice
versa.

Tt will be sufficient here, for the purpose of a remote
comparison, to note the fact just indicated that a sinu-
soidal alternating electro-motive force induced in such an
electric resonator, which need amount only to a very few
volts, provided that it be of the same frequency as the
oscillating discharge, will be able to induce in A and B
differences of tension which may amount to many volts.
For if we assume in the current so oscillating the faculty
of depositing in each of the armatures of the condenser
infinitely small particles of substance in series one after
the other, so long as the total of their mass and the con-
sequent electro-motor force does not surpass the electro-

346 Assimilation

motor force in the opposite direction, which this current
possesses at this point and at this moment, then it will
not be difficult for us to conceive of the case in certain
respects analogous, which we have assumed for oscillat-
ing nervous discharges, in which the calorific oscillations,
which replace here the oscillations of the induction cur-
rent, continually increase the mass of living substance
which will in this way be “assimilated.”

Let us note that in the case of nervous currents we
must assume that their specificity is constant even during
the oscillation. Then the duration of each nervous dis-
charge, and hence of each oscillation also, in cases where
the specificity i of the nervous current is something
dynamically equivalent to the intensity of the electric
current, will likewise be definite and constant for every
given specificity.

For let us consider again an electric current. If its
intensity i persists for a time t, the total actual energy
furnished during the whole of this time by this current
will be Eit, where E represents the electro-motive force.
But this total energy will necessarily be proportional to
the mass M of the substance whose decomposition during
the time t has produced this current; one has thus
Eit=hm, where h is a coefficient of proportionality, de-
pendent solely upon the units of measure selected. But
if the supposition which we have accepted for nervous
currents in general holds good also for this electric cur-
rent, namely, that the electro-motive force is proportional
also to the mass of substance which tends by decomposi-
tion to produce the current, then also E=km, where k
again is a coefficient of proportionality dependent likewise
solely upon the units of measure which are adopted.

Source of Energy of Assimilation and Growth 347

Consequently the above equation would take on the
following form:

km. it=hm,
that is:

it=h/k=H,
where H again is another coefficient of proportionality
and dependent solely upon the units of measure already
fixed above, and so represents an arbitrary, constant
numerical value. It follows from this that it is constant.
And if i in its turn is likewise constant for each specific
current, t must also be constant; i. e., to each definite
specificity of current, i, will correspond a likewise deter-
minate and constant duration of discharge.

If then, no matter what conditions may induce the
different discharges of a current of the specificity i, all
these discharges can have invariably only the same dura-
tion t, and if this holds also for those which constitute the
oscillating discharge, then the oscillation itself, which
consists of a double discharge of which each one has a
direction contrary to that of the other, as we stated above,
will have necessarily a very definite and constant period
of its own which corresponds each time to the particular
specificity 1 of its respective current.

It follows that among all the infinite vibrations of the
different rays from any calorific source whatever, there
will be certainly present also those which have the same
oscillatory period as the mnemonic element in the way of
reconstituting itself, and those synchronous rays will
then be able to give to the oscillating discharge of the
latter an impulse which will be added to that received
through the difference in potential of the pair of accumu-
lators, and thus to have identically the same effect as that
which the sinusoidal-alternating, electric, induction cur-

348 Assimilation

rent has upon the electric resonator with an equal period
of vibration. And this becomes so much the more plaus-
ible since Maxwell’s theory, of which it is scarcely
necessary to remind any one, and which was wholly
confirmed by the Hertzian experiments, has demonstrated
the essential identity of these electric, induction oscilla-
tions across the di-electric formed by the air, with light
and heat vibrations in general. The only difference con-
sists in the period of vibration which in both the latter is
much more rapid than in the former.

So we can understand how thermal energy, whether
that which comes from the irradiation of the sun and
from the outer world in general, or that which is de-
veloped from chemical processes of decomposition. and
oxidation taking place in the interior of the organism,
can, in as far as it is composed of heat rays of the most
different periods of oscillation, constitute the general
external stimulus which activates indifferently all the
vital processes of synthesis:

Let us note that to each specific discharge, to the intra-
nuclear oscillating as well as to the extra-nuclear func-
tional there will correspond very definite substances of
dissimilation, for the different specificities of the nervous
currents can be due only to the decomposition of sub-
stances likewise different. And even if the diversity of
these extremely complex and unstable substances consists
only in the different number and different mode of
grouping of the same atoms of the principal elements
which constitute all organic substance, nevertheless the
respective substances of dissimilation to which each of
these complex substances will give rise, will necessarily
be different from one another. These substances of dis-
similation, definite and peculiar for each specific dis-

Physico-Chemical Character of Cytoplasm 349

charge, will in their turn afford, by their entire or partial
oxidation, products of excretion and secretion quite
definite and differing from one cell to another. These
products, in their turn, thanks to their peculiar physico-
chemical properties, will imprint upon the protoplasm or
cytoplasm a corresponding physico-chemical character
and a corresponding morphological structure. So it is
conceivable how the ensemble of the mnemonic elements
constituting a given nucleus can determine its own proto-
plasm or cytoplasm both from the purely physico-chemical
and from the properly morphological point of view.

We arrive thus at a constant double correlation be-
tween the cytoplasm, the species of nuclear excitation,
and the substance of the nucleus. For the nuclear sub-
stance will determine directly the specificity of the
corresponding nervous current and its rhythm of charge
and discharge; and this specificity of current thanks to
the substances of dissimilation to which it will give rise,
will determine the respective cytoplasm. Conversely, the
specificity of the current or its peculiar rhythm of charge
and discharge, once determined by the functional stim-
ulus, will determine the substance of synthetization or
nuclear substance, as also the substances of dissimilation
of which the cytoplasm is constituted.

Let us summarize what has been said. The specific
potential elements which have presented themselves in the
preceding chapter as specific elementary accumulators, .
and at the beginning of this chapter as mnemonic ele-
ments, appear now as specific vital elements, that is as
the smallest possible particles of organic substance cap-
able of life. At the same time the denominations
potential element, and vital element, which might at first
have appeared incompatible with each other, if the

350 The Vital Element: Its Three Modes

adjective potential had indicated a vital non-activity at
that time, become entirely compatible in consequence of
the hypothesis which we have just set forth. For accord-
ing to this hypothesis, the element would be potential in
so far as each of the two coupled accumulators would be
able to furnish at need its proper extra-nuclear functional
nervous discharge, and it would at the same time be con-
ceived as in a vital process by reason of the intra-nuclear
oscillating discharge, which continues incessantly between
the two accumulators. Vital energy could thus present
itself in three distinct modes: (1) In the potential,
properly so called, which expresses itself in the phenom-
ena of actual suspension of life or lethargy in its widest
sense; (2) In the oscillatory potential or the intra-
nuclear oscillating discharge, which constitutes the
essence of the period of so called “functional repose,”
“organic reconstitution” of materials afterwards to be
consumed, “assimilative synthesis,’ or “vital creation;”
(3) Finally in the actual proper, or the extra-nuclear
non-oscillating discharge, which constitutes the period of
“excitation,” “functional activity,” “wear and_ tear,”
“consumption of material stored up in the rest period,”
“disassimilation,” or ‘vital destruction.”

As conclusion of our exposition let us note very
briefly that also for three others of the most fundamental
phenomena associated with vital activity this hypothesis
_upon the nature of life presents at least the beginning of
an explanation. These are: rhythmicity, a characteristic
property of all life phenomena; the phenomena of fecun-
dation and rejuvenesence in general; and nuclear division
with its characteristic and remarkable details.

A whole series of facts forces us to the opinion, that

Rhythmicity and Periodicity 351

rhythmicity should be reckoned among the most general
characteristics of the modes of manifestation of vital
energy. Apart from the fact that nearly all, and perhaps
all external physical stimuli, from the thermal and
luminous to the acoustic, are characterized by vibrations;
and the other fact, a consequence of the first, of the
physiological action exercised by all the rhythmical or
periodical manifestations of the most diverse energies,
we see that a more or less manifest and more or less
regular periodicity is a fundamental character of all or
nearly all biological functions. One thinks at once, for
instance, of the synchronous rhythm of all the peristomal
cilia of an infusorian,—a rhythm which manifests itself
in the two parts of an animal which has been divided,
provided these parts remain connected by a bridge of
protoplasm; of the rhythmicity present in the protozoa in
general, present even within the cells, shown by the
pulsation of contractile vacuoles, which empty and refill
themselves continually at regular intervals; of the beat
of the heart, even independent of its connection with the
nervous system; of the similar pulsations of the whole
vascular system, the entire breathing apparatus, the
uterus, and of many other organs; and finally of the
periodicity of a whole series of physiological variations,
which animals and plants undergo as a result of corre-
sponding variations of the outer world, but which persist
unaltered for some time even when the outer world, or
the periodicity of its variations, may have changed.

Now it is not difficult to conceive of this rhythmicity
or periodicity which nearly all biological functions pre-
sent, as a consequence more or less direct or indirect of
the vital phenomenon in all its generality, when this

352 Fecundation

phenomenon, be it only in so far as a phenomenon of
assimilation, is itself essentially a rhythmic phenomenon.

In regard to fecundation we know that it was Spencer
who first recognized what has been more or less explicitly
accepted by others, that it consisted probably in a per-
turbation of an equilibrium which tended toward a
stability unfavorable to vital activity.2°°

Now we have already seen how our hypothesis set
forth above is able to make at once conceivable in what
this equilibrium unfavorable to vital activity may consist.
According to this hypothesis, it would consist in the
equalization toward which the masses, and the corres-
ponding potentials, of the coupled accumulators of each
mnemonic element would tend, and which they would
eventually attain, and this equilibrium would be disturbed
by the substitution for one of these accumulators of an-
other specifically equal to it but differing in mass and
potential. And it is precisely in this function of fecunda-
tion, of replacing in each couple one of the specific
accumulators by another differing quantitatively as
widely as possible, that we find an explanation of the fact
that the rejuvenation of the germ and the consequent
vitality of the progeny to which fecundation tends, are
proportionally greater when fecundation occurs not be-
tween individuals too closely related but rather between
individuals which belong indeed to the same species but
are somewhat dissimilar.

According to the same hypothesis, this equilibrium
could also be deranged by the extra-nuclear discharge of
one of the two coupled accumulators, and this is just what

*s*Spencer: Principles of Biology. I, P. 340—341, and II. P.
614—616.

Fecundation 353

is demonstrated by the universally known experiments
upon the rejuvenescence of the infusoria, by which it
appears that this rejuvenescence can be re-acquired even
without any need of the ordinary fecundating conjuga-
tion, simply by causing some change in the surrounding
conditions of life, and thereby provoking a strong renewal
of the functional activity of the animal.?5°

Let us note parenthetically that if oscillating dis-
charges take place between the corresponding separated
specific accumulators or half mnemonic elements of the
egg and spermatozoon respectively even when the egg
and the spermatozoon are still relatively distant from
each other, 1. e. before they could coalesce into a single
fecundated nucleus, we can then understand how the
space between each pair of these elements can and must
function just as the deformed di-electric between the two
armatures of the condenser of an electric resonator, and
thus be constrained to produce the attraction of each
spermatic half element to the corresponding half element
of the egg. And this would have as a final result an
energetic reciprocal attraction between the egg and the
spermatozoon.

The real cause of the sexual attraction of the two
germs, male and female, would then reside in their capac-
ity of vibrating in unison. Conversely the absence of all
attraction between ovum and spermatozoon belonging to
animal or vegetable species too different in kind would
be due to the fact that the one germ is constituted by
potential half elements of which too many are specifically

25°Compare e. g. Hartog: Problems of Reproduction: Conju-
gation, Fertilisation and Rejuvenescence. The Contemporary Re-
view, July 1892; esp. P. 94—95, 100—I02.

354 Karyokinesis

completely different from those of the other germ, and
consequently they are incapable of vibrating together
with the same rhythmicity.

Finally as to indirect or karyokinetic cell division, let
us admit that, when each of the two coupled accumu-
lators, in consequence of the continual increase of its
mass attains too high a potential, the two halves of each
of these accumulators will tend to repel each other, just as
would for example, the two halves of a conducting sphere
or disc, charged with too great a quantity of static
electiicity of the same sign.

It we admit at the same time, that the separation of
the two halves of each accumulator would break the cir-
cuit of oscillation, as would seem indicated by the rupture,
retraction, and disappearance of the meshes of the nuclear
reticulum during mitosis, and thus suspend abruptly the
oscillating discharge, then the actual energy of this dis-
charge still in activity at that moment will become trans-
formed into potential energy, and discharge itself upon
the first little bit of substance, or centrosome, most
capable of receiving it. Consequently, without pretending
thus to be able to penetrate into the smallest details of
this phenomenon, we understand nevertheless how the
vital phenomena of dynamic order, which are due to the
oscillating nervous discharge, must then necessarily be
followed by phenomena of static order, like those which
are characteristic of the karyokinetic cell division.

We limit ourselves here to recalling only:

1. Delage’s observation that in indirect division the
longitudinal splitting of the chromosomes or of the
nuclear filament begins before achromatic filaments are
present which are capable of exerting upon them any pull

Karyokinesis 355

whatever, which warrants the inference that it is repul-
sion which operates between the two halves.2°

2. Hanseman’s observation, that during karyo-
kinesis all the peculiarly vital functions of the cell,
as assimilation, secretion, etc., etc, are completely
suspended.?6!

3. Watase’s observation, according to which the
centrosome in reality is only a simple cytomicrosome but
of greater circumference and greater force of attraction,
and that the cytomicrosomes which always lie at the meet-
ing point of three or more cytoplasmic fibers likewise are
nothing else than small temporary clumps quite aspecific
which form anew in each cell division from the contract-
ing substance of the cytoplasmic fibers themselves.?®

4. Ziegler’s experiment, in which the poles of the
horseshoe magnet took the place of centrosomes and acted
upon iron dust strewn upon a thin horizontal wax plate
upon which previously pieces of iron wire of forms
similar to that of the chromosomes had been placed, and
in which figures were obtained which were similar to
those presented in nuclear division, which is a direct
proof of the conception already advanced by Roux, that
in the attraction exerted by the centrosomes upon the
chromosomes there are in play static energies of nature
similar to that of magnetic force or of static electricity.?°*

*6°Delage: L’hérédité etc. P. 149—I150.

2611 ansemann: Studien iiber die Spezifizitat, den Altruismus
und die Anaplasie der Zellen. P. 10.

282Watasé: On the nature of Cell-organisation. Biol. Lect. at
the Mar. Biol. Lab. of Wood’s Holl, Summer Session, 1893. Bos-
ton, U. S. A., Ginn, 1894. P. 92—93; und Origin of the Centrosomes,
Ibid. Summer Session 1894; Ginn, 1896. P. 282, 285.

2637iegler: Untersuchungen iiber die Zellteilung, Verhandl. der
Deutschen Zoolog. Gesellsch., Leipzig 1895. P. 78-83. — Roux:

350 Conclusion

Conclusion

As the reader who has followed us thus far has al-
ready noted, there are three new hypotheses or three new
fundamental conceptions which we submit to the judg-
ment of biologists and of positive philosophers in general.
Although they support one another mutually and all rest
upon the same general idea of the vital phenometion, they
are, nevertheless, independent of one another, especially
the first two are independent of the third.

The first is the hypothesis of centro-epigenesis to
which we, as was said in the preface and explained in the
first chapter, were led by the fundamental biogenetic law
of the repetition of phylogeny by ontogeny with all its
more or less mediate or immediate results.

The second hypothesis is that according to which each
specific nervous current deposits a very definite substance
which, in its turn, is capable of provoking again exclu-
sively the same specificity of current as that by which it
was itself deposited. This idea has enabled us on the one
hand with the aid of the centro-epigenetic hypothesis to
explain directly the inheritance of acquired characters;
and has on the other hand by itself alone afforded the
immediate explanation of all the mnemonic phenomena in
the widest sense of the word, from histologic specializa-
tion, in consequence of which the cells answer always
only in the same accustomed way to the most different
accidental stimuli, up to the psycho-mnemonic phenom-
ena or phenomena of memory properly so called.

Uber die Bedeutung der Kernteilungsfiguren, Leipzig, Engelmann,
1883, P. 18, Gesamm. Abhandl. Bd. II, P. 142. — Marcus Hartog:
The Dual Force of the Dividing Cell, Part I: The Achromatic Spin-
dle Figure illustrated by Magnetic Chains of Force, from the Pro-
ceedings of the Royal Society, B, Vol. 76, 1905, especially P. 555—559.

Conclusion 357

The third hypothesis attributes the vital phenomenon
essentially to an intra-nuclear oscillating nervous dis-
charge; and this idea has enabled us, with the help of the
above mentioned second hypothesis of specific accumu-
lators, to explain likewise the fundamental property of
the life phenomenon, which consists in assimilation.

It is hardly necessary to state that the first and second
hypotheses although, as we have said, all the three
hypotheses support each other mutually, are yet totally
independent of the third, and therefore can stand equally
well whether the latter is accepted or rejected.

We do not venture to offer this latter as a true and
proper hypothesis. The phenomenon of life is still too
little established for so bold a venture. We consider it
only as a provisional scheme of the vital process which
may serve as an initial concrete basis for further investi-
gation into the nature of life. For in affording
provisionally any firm foundation upon which the discus-
sion of a question still awaiting solution can be based, one
attains always the great advantage of determining exactly
the conditions of the question, of showing clearly the
untenability of certain views which was not possible
formerly while the question had yet too indefinite a form,
and of bringing us in this way slowly but certainly nearer
to a correct understanding of the phenomenon, in propor-
tion as after discarding the untenable propositions the
tenable stand out more clearly and convincingly and
thereby are given a more firm foundation.

It remains then only to await quietly the judgment of
the critic and to express in advance our thanks to all
those who are willing to accord us friendly support in
word and deed, and thereby make possible a somewhat
more thorough elaboration of the subject which we were

358 Conclusion

able here to handle only too cursorily. We should be
especially grateful to those who along with their crit-
icisms and objections would be good enough to send us
word of any new facts which can be adduced either in
support of any of our three hypotheses, or in opposition
io them.

APPENDIX

ON THE MNEMONIC ORIGIN AND NATURE OF
AFFECTIVE TENDENCIES.!

If we observe the behavior of the various organisms
from the unicellular up to man, we see that a large num-
ber of their processes, and especially the most important
ones, may be regarded as manifestations of a tendency
of the organism to maintain or to restore its “stationary”
physiological state (to use the term of Ostwald’s ener-
getics).

In other words, if we call “affective” that particular
class of organic tendencies which appear subjectively in
man as “desires” or “appetites” or “needs” and objec-
tively in both man and animals as “movements” com-
pleted or incipient (except those that have become
mechanical in character), then a large number of the
principal “affective tendencies” thus defined may be at
once reduced to the single fundamental tendency of each
organism to preserve its “physiological invariability.”

For instance, we see that hunger, the most fundamen-
tal of all affective tendencies, is in reality nothing but
the tendency to keep, or restore that qualitative and
quantitative condition of the nutritive system of the body
which will make possible a continuation of the stationary

1Translated for The Monist (July, 1911) by L. G. Robinson
from Rivista di Scienza Vol. XI, 3, 1909.

361

362 Appendix

metabolic state. This tendency of an organism toward
the invariability of its own metabolism has become, in
the course of its phyletic evolution, an inherent tendency
to pass through all the transient physiological states that
could re-establish this necessary condition within it, hence,
a tendency to perform all movements that have nour-
ishment for their object; yet in doing this it has never
relinquished its original character. This results directly
from the fact that all inclination to procure new food
ceases as soon as the internal nutritive system of the
animal has attained its normal state.

Accordingly, the hydra or sea anemone does not react
positively to food except when its metabolism is in a
state requiring more nutriment, “unless,” says Jennings,
“metabolism is in such a state as to require more ma-
terial”; for instance, when the large sea anemone
Stoichactis helianthus is not hungry, a bit of food
placed upon its oral disk occasions the same character-
istic “rejecting reaction” as if it were any other disturb-
ing object. And all other organisms, the higher as well
as the lower, behave in exactly the same fashion.?

Schiff’s experiments of injecting nutritive substances
into the veins of dogs are direct evidence, on the other
hand, that the fundamental condition of hunger is the ab-
sence of histogenetic substances in the blood, for these
injections resulted not only in nourishing the animal but
also in allaying its hunger.

Moreover the fact that hunger, especially as long
as it is only moderate, assumes in man the form of a
special and localized sensation originating in the wall of
the stomach and being the sole cause of the activities

2H. S. Jennings, Behavior of Lower Organisms, pp. 202, 205,
etc. New York, MacMillan, 1906.

Affective Tendencies 363

induced by real hunger, is—it is scarcely necessary to
state—a natural consequence and of but secondary im-
portance. It is only one of many forms in which we see
the substitution of the part for the whole, and this phe-
nomenon characteristic of all mnemonic physiological
processes appears also in the tendency to physiological
invariability, which is also essentially mnemonic as we
shall see more clearly later on. These peculiar sensa-
tions localized in the gastric mucous membrane and
produced by its swelling or by some other more or less
similar change caused by the empty condition of the
stomach, usually take place before or simultaneously
with the actual lack of histogenetic substance in the blood,
and so finally became representative or vicarious signs of
hunger.

The same is true of thirst and of its localization in
the upper part of the alimentary canal.

We might pass on from hunger and thirst to the
other more or less fundamental organic “appetites” or
“needs.”’ All would show us in their different manifes-
tations that they are directed simply and solely toward
the restoration of the stationary physiological state,
which has been lost or in some way disturbed.

Thus there exists for every animal species an opti-
mum of environment with reference to the degree of
saturation of the solution in which the animal lives, to
the temperature or to the intensity of light, etc., above
and below which the organism cannot maintain its nor-
mal physiological state and which the animal makes
every effort to maintain.

So for instance we see that the infusorian Paramac-
cium at 28° C. reacts negatively toward a rising but not
toward a falling temperature, whereas at 22° C. it

364 Appendix

reacts negatively toward a falling but not toward a rising
temperature. We see also that Euglena in a moderate
light reacts negatively toward a decrease but not toward
an increase in the intensity of light, whereas in a stronger
light the reaction is exactly reversed.*

The tendency of organisms to maintain their physio-
logical state unaltered consequently resolves itself into a
tendency to invariability in their external and internal
environments. Thus for instance, oysters and actinians
close when exposed to the air; that is, they behave so as
to keep the standard of moisture unaltered within them-
selves and in their immediate surroundings.*

To the tendency toward invariability of environment
is due also the position which the organism takes with
relation to the direction of the various forces to which
it is exposed, especially gravity. Hence the tendency to
preserve or restore its normal position. Thus, for in-
stance, the amceba draws in its pseudopodia when they
come in contact with solid non-edible bodies; but if it is
lifted off the bottom of the aquarium and is suspended
in the water it stretches out its pseudopodia in all direc-
tions. As soon as one of these touches a solid object,
the amceba takes hold of it, draws its body over to it, and
again resumes its original position. Likewise a starfish
when inverted tries to turn, over, that is, to return to
its normal environmental conditions with relation to
gravity.®

All “needs”to throw off substances which have been
produced by the general metabolism and which the or-

3Jennings, Behavior of Lower Organisms, pp. 294-205.

4H. Piéron, L’évolution de la mémoire, pp. 29, 74. Paris, Flam-
marion, I9Io.

5K. C. Schneider, Vorlesungen iiber Tierpsychologie, pp. 5, 57.
Leipsic, Engelmann, 1909.

Affective Tendencies 365

ganism can no longer use, are likewise no exceptions to
this general rule. For, although the need for eliminat-
ing them may be called forth by certain vicarious local
sensations capable of evoking the act of expulsion in ad-
vance, yet in reality, whether in the case of the smallest
and simplest infusorians or of the most highly developed
vertebrates, it is due only to the circumstance that the
accumulation of this waste material within the organism
would eventually disturb its normal physiological state.

To this class of eliminative affective tendencies ‘the
sextial hunger seems to belong. For we know that cer-
tain recent theories are inclined to regard the whole or-
ganism rather than any one definite part of the body as
the seat of sexual hunger just as in the case of hunger
proper, and at the same time to regard it as due to the
need of eliminating the germinal substance.®

It may be that just as infusoria after a certain num-
ber of divisions become subject to “senescence” (Maupas)
so also the germinal substance constantly produced in the
adult organism, especially after it has undergone the re-
ducing divisions, may be subject to a similar degenera-
tion if it has not also experienced the requisite caryo-
gamic rejuvenation. Therefore it seems quite plausible
that “sexual hunger” is originally nothing but the ten-
dency of the organism to free itself of this “senile cor-
ruption” which the germinal substance, being in its
nature a nuclear substance awaiting fertilization, pro-
duces by means of its hormonic secretions or substances
of disintegration and spreads throughout the entire or-
ganism.

6See, for instance, though only in certain respects, J. Roux,
L’instinct d’amour, ch, I, “Base organique de Tinstinct sexuel.”
Paris, Bailliére, 1904.

366 Appendix

The more or less brilliant or striking “wedding gar-
ment” which nearly all animals assume when in love,
arises from an abnormal condition of general hyper-
secretion occasioned again by the hormonic products of
the germinal substance. At any rate it shows how deep
is the physiological disturbance caused in all somatic
cells by the germinal substance. The effort to expel so
disturbing an element then becomes a tendency to copu-
lation as means of effecting this expulsion. Hence the
fundamentally selfish character (nature fonciérement
égoiste) of sexual love which Ribot rightly emphasizes:
“In the immense majority of animals, and frequently
in man, the sexual instinct is not accompanied by any
tender emotion. The act once accomplished, there is
separation and forgetting.” 7

It remains to be explained why copulation of the
sexes is the only means of eliminating the germinal
substance, whereas the single individual is sufficient for
the removal of all other more or less similar waste
matter.

It is easy to suppose that the reason lies in the
peculiar nature of the substance itself, and there are two
circumstances that may perhaps, if considered together,
contribute a little to the desired explanation: First, the
attraction by the ovum of the spermatozoon even at some
distance by means of secretions diffused in all direc-
tions; and second, the fact that hermaphroditism prob-
ably preceded sexual dimorphism in the phylogeny of
pluricellular organisms. Still we must recognize the fact
that the phylogenetic process, which by this elimina-

7Th. Ribot, La psychologie des sentiments, p. 258. Paris, Alcan,
1908 (English translation in Contemporary Science Series, London,
IQII, p. 253).—Essai sur les passions, pp. 67 ff. Paris, Alcan, 1907.

Affective Tendencies 367

tion has become so closely associated with copulation,
is still far from a satisfactory explanation.

But even in this incomplete form the hypothesis
which attributes to the sexual instinct no further signifi-
cance than a tendency to eliminate a disturbing element,
permits us to present this instinct in very different
light from that in which it has hitherto appeared.
For were this hypothesis to be accepted, the sexual in-
stinct would not have ‘originated and developed for the
“good” of the species, but of the individual. It would
therefore not represent the “will of the species” im-
posing itself upon the individual, as most people now
maintain with Schopenhauer, but much rather would it
mean here as always the “will” of the single individual;
that is, the usual tendency to keep its stationary physio-
logical condition unchanged. And instead of seeing in
it with Weismann and ‘all neo-Darwinists a new evidence
of the alleged omnipotence of natural selection, La-
marck’s principle of individual adaptation combined with
the inheritance of acquired characters would be sufficient
to account for this as well as for all other instincts.

Moreover, the “elimination”? hypothesis is sufficient
by itself to explain certain peculiarities of this impulse
which would be quite incomprehensible from the stand-
point of Schopenhauer and ‘the neo-Darwinians.

Ribot, for instance, is surprised that an instinct
which is so exceedingly important for the continuance
of the species is so often subjected to certain perversions
which seem to involve its complete negation.®

The fact that such perversions are common accords
poorly with the hypothesis that the only reason for the

8Ribot, La psych, des Sent., pp. 263, 265 (Engl. ed., pp. 257, 259).

368 Appendix

existence of stich an instinct is the need for the con-
tinuance of the race.

Finally, the fact that both animals and man now
desire copulation or even certain secondary sexual rela-
tions for their own sakes—hence independently of the
act of the elimination of the germinal substance, perhaps
even in default of any to eliminate,—this also, as we
shall better appreciate later on, is only the consequence
of the mnemonic law already mentioned of the substi-
tution of the part for the whole, and of its derivative,
the law of the transference of affective tendencies. Ac-
cording to this law all phenomena that constantly ac-
company the satisfaction of certain affectivities become
also in their turn objects of desire, and all habits ac-
quired for the satisfaction or in the satisfaction of cer-
tain affectivities likewise become affective tendencies.

If the sexual instinct also, on account of its origin,
can be referred to the class of tendencies which serve to
maintain the stationary physiological condition of the
organism, then the above law is open to no exception
as far as the fundamental organic tendencies are con-
cerned. Hence we can sum it up in the following
words:

Every organism is a physiological system in a sta-
tionary condition and tends to preserve this condition or
to restore it as soon as it is disturbed by any variation
occurring within or without the organism. This prop-
erty constitutes the foundation and essence of all
“needs,” of all “desires,” of all the most important
organic “appetites.” All movements of approach or
withdrawal, of attack of fight, of taking or rejecting,
which animals make are only so many direct or in-
direct consequences of this perfectly general tendency

Affective Tendencies 369

of every stationary physiological condition to remain
constant. We shall soon see that this tendency in its
turn is only the direct result of the mnemonic faculty
characteristic of all living matter.

This single physiological tendency of a general kind,
accordingly, is sufficient to give rise to a large number
of the most diversified particular affective tendencies.
Thus every cause of disturbance will produce a corres-
ponding tendency to repulsion with special characteris-
tics détermined by the kind of disturbance, by its
strength, and by the modes of reaction tending to circum-
vent the disturbing factor; and for every incidental means
of preserving or restoring the normal physiological con-
dition, there will be a quite definite corresponding ten-
dency such as “longing,” “desire,” “attraction” and so
forth.

Even the instinct of self-preservation—when under-
stood in the usual narrow sense of “preservation of
one’s own life”’—is only a particular derivative and
direct consequence of this very general tendency to pre-
serve physiological invariability. For every condition
which would eventually lead to death first presents itself
as a mere disturbance, and it is only as such that the
animal tries and learns to avoid it. Jenning’s amceba,
for instance, which had been completely swallowed by
another amceba, but had succeeded in getting away, did
not in all probability flee from a phenomenon that en-
dangered its life, but from a condition in its environ-
ment which even though a profound disturbance, was
nevertheless nothing but a disturbance.

It is well known that Quinton was the first to de-
velop a theory that organisms tend to maintain in their
internal intercellular environment the same chemical

370 Appendix

and physical conditions that obtained in the primordial
environment when life first appeared on earth.®

But it is easily seen that our theory is limited to a
consideration of the tendency to invariability only so far
as it manifests itself each moment in the behavior of
each individual. Therefore instead of serving as a
far too one-sided starting point for the explanation of
the evolution of species it forms the basis upon which
all the most important affective tendencies of the animal
world may be built up. .

As a factor of invariability for the individual, this
tendency to preserve its stationary physiological condi-
tion is indeed one of the most important factors in the
variation and progress of the species, but in quite a
different way from that pointed out by Quinton. For
from this tendency arose and developed the power of
motion which is the greatest difference between plants
and animals, and with which also has kept pace the
development and perfection of the whole motor ap-
paratus, including that of the nerves and senses, which
plays so important a part in determining the character-
istics which distinguish the different zoological species.

Finally as a factor of individual invariability it has
proved by its effect on man to be one of the most con-
spicuous factors in all social evolution, for we may
well say that technical inventions and industrial products
from the first cave dwellings, the first skins used for
clothing, the first discovery of fire to the most complex
attainments of to-day have tended constantly more or
less directly or indirectly towards one single goal,

®R. Quinton, L’eau de mer, milieu organique. Especially Book
II, “Loi générale de constance originelle,” pp. 429-456. Paris, Mas-
son, 1904.

Affective Tendencies 371

namely the artificial maintenance of the greatest possi-
ble constancy in the environment, which is the necessary
and sufficient condition for preserving physiological
invariability.

Il.

Closely connected with this inherent fundamental
tendency of every organism to strive to preserve its nor-
mal physiological condition or to restore it as soon as it
is disturbed, is still another attribute which in its turn
becomes the source of new affectivities.

For as soon as the previous stationary condition can-
not be restored by any means, that is by any movements
or change of location, the organism disposes itself in a
new stationary condition consistent with its new external
and internal environment. In this way there originate
a large number of new phenomena called “adaptations.”

Thus, for instance, Dallinger’s classical experiments
on the acclimatization of lower organisms—suggested by
the observation that many organisms usually living in
water of an ordinary temperature, ‘also live and flourish
in the hottest spring,—have proved that Infusoria may
gradually become accustomed to a constantly higher tem-
perature so that finally after years of continuous slow
increase in the degree of heat, they can stand a tempera-
ture so high that any other individual not acclimated
would certainly die if subjected to it. It is likewise
known that the same species of Protozoa are found in
both fresh and salt water, and that it is possible to ac-
custom fresh-water Amcebe and Infusoria to a salt
habitat which would have killed them at the start,—
and there are more instances of the same kind.’°

10See C. B.. Davenport and W. E. Castle, “On the Acclimatisa-

372 Appendix

One feature of special interest to us is the fact that
the new conditions of the environment to which the
animal gradually becomes accustomed tend in time to
become his optimum. “This individual adaptation
(e. g., to a different proportion of salt) is effected in
accordance with the rule that the conditions of density
under which an individual is living, tend to become in
time the optimum conditions for that individual.” 4

This may be observed even in plant organisms.
Plasmodia of the Myxomycetes die when plunged sud-
denly into 1 or 2% glucose solutions, and even draw
back from % or 4% solutions, and yet they may
gradually become accustomed to 2% solutions so that
they finally show by their behavior that they prefer their
new environment to the original one without glucose.!?

The diatom Navicula brevis ordinarily shuns even
the weakest light and tries to hide itself in the darkest
part of the drop of water in which it is being observed.
However, if a culture is placed in the bright light of a
window for two weeks, it exhibits exactly the opposite
tendency and makes for the brightest part of the drop
as soon as it is removed again to its former position in
a weak light.78

The common actinian (Actinia equina) often found
clinging to rocks in all possible positions with relation to
the force of gravity, sometimes with the axis of the

tion of Organisms to High Temperatures.”—Archives fiir. Entw.-
Mech. der Organismen, II, 2. Heft, July, 1895—C. B. Davenport
and R. V. Neal, “On the Acclimatisation of Organisms to Poisonous
Chemical Substances,” loc. cit., II, 4. Heft, Jan. 18096.

11Davenport and Castle, op. cit., p. 241.

12K. Stahl, “Zur Biologie der Myxomyceten,”’ Bot. Zeit., Mar.
7, 14 and 21, 1884, p. 166.

13Davenport and Castle, op cit., p. 246.

Affective Tendencies 373

body directed upward, sometimes downward and some-
times to one side, seems to become so accustomed to its
position that it tries to assume the same one when re-
moved to another spot. For instance, if several actin-
ians found in various positions are collected and placed
in an aquarium, “they show in attaching themselves a
distinct tendency to assume the same position they had
formerly adopted.” *4

We might bring forward innumerable other ex-
amples but are here chiefly concerned with pointing out
their significance. They show that the new physiologi-
cal state arising from adaptation to the new environ-
ment, when once it has supervened and has existed a
certain time within the organism, tends thereafter to
preserve or restore itself. This tendency of a past
physiological state to remanifest or reproduce itself is
nothing but the tendency inherent in every mnemonic
accumulation to “evoke” itself again. Hence it is a
tendency of a purely mnemonic nature.

From this then it follows directly that the tendency
to physiological invariability from which originate, as
we have seen, the most important organic affective ten-
dencies of all organisms must be equally mnemonic in
nature. For if according to the above mentioned ex-
amples an entirely new and recent physiological state
is nevertheless able to leave behind a mnemonic accumu-
lation producing a distinct tendency to its own restora-
tion, it is easy to understand that in proportion as the
normal physiological state persists longer it must possess
a correspondingly stronger mnemonic tendency toward
its restoration whenever it is disturbed.

This then implies that each of the innumerable

14Piéron, op cit., p. 144.

374 Appendix

different elementary physiological states, of which each
is effective at one definite point of the organism, and all
combined constitute the general physiological state,
possesses the faculty of depositing independently a “‘spe-
cific accumulation,” from all indications similar to that
deposited in the brain by each of the nervous currents
which make up the different sensations and leave behind
a mnemonic residue capable of being reactivated or
revived, By “specific accumulations” of the various ner-
vous currents we mean here only that every accumula-
tion is capable of giving as discharge only that par-
ticular specificity of the nervous current by which this
accumulation has itself been deposited.

The extension of this faculty of “specific accumula-
tion” to all physiological phenomena in general accords
with the hypothesis that nervous energy is the basis
for all the phenomena of life. If in the psycho-
mnemonic phenomena properly so called the action
of nervous energy produced by “discharge” or
by stimulation of the respective center appears in the
foreground, whereas the specific physico-chemical
phenomena accompanying the discharge remain in the
background so that until recently they were quite over-
looked, that would be—according to the fundamental
concept of Claude Bernard on the essential identity of
all the different forms of irritability of living matter—
a difference of degree only but not of essence, inasmuch
as true physiological phenomena accompanying the re-
spective stimulation (muscular contraction, glandular
secretion, etc.) appear with greater distinctness, where-
as the specific nervous phenomena which likewise accom-
pany this physiological activity are less perceptible. In
this way we have tried to explain the fundamental mne-

A fective Tendencies 375

monic property of all living substance which has re-
cently been especially emphasized by Hering, Semon
and Francis Darwin, and also to explain the most essen-
tial and significant biological phenomena proceeding
from it either directly or indirectly.!®

By this extension of the mnemonic faculty to all
elementary physiological phenomena we now obtain a
somatic or visceral theory of the fundamental affective
tendencies in the sense that the tendency toward physio-
logical invariability or toward the restoration of this or
that previous physiological state corresponding to this
or that previous environment, depends on innumerable
elementary specific accumulations, differing from point
to point of the body and whose combined potential
energy would form as it were a “force of gravitation”
toward that environment or those conditions which make
possible the preservation or restoration of the combined
physiological system represented by all these elementary
accumulations.

Naturally in organisms supplied with nervous sys-
tems there would arise and be gradually developed side
by side, in cooperation with, and often as a substitute
for, every one of these affective tendencies of purely
somatic origin and seat, the affective tendency repre-
sented by the corresponding mnemonic accumulations
which had been deposited in that particular zone of the
nervous system directly connected with the respective
points of the body. In man, for instance, this zone

15See above the chapter on “The Phenomena of Memory and
the Vital Phenomena.” See also “Die Zentroepigenese und die
nervose Natur der Lebenserscheinung,” Zeitschr. f. d. Ausbau d.
Entwicklungs-lehre, 11, 1909, Heft 8-o—“Das biologische Gedachtnis
in der Energetik,” Annalen der Naturphilosophie, VIII, and Scientia,
NI, 3, 1900.

376 Appendix

would be Flechsig’s K6érperfiihlsphare to which in cer-
tain cases may also be added the frontal zone.1®

Now after the cerebral mnemonic accumulations
had arisen phylogenetically under direct somatic action,
they would finally have become able to represent by
themselves, even if all connection with the body had
been severed, those former affective tendencies to which
they owed their origin. And indeed this is true be-
cause of the two fundamental mnemonic laws of (1)
the gradually increasing independence of the part with
reference to the whole and (2) the substitution of the
part for the whole, which arise directly from the fact
that every elementary specific accumulation when once
deposited is capable of an independent existence.
Therefore Sherrington’s “spinal” dog, for instance,
continued to experience the same repugnance to the
flesh of other dogs, to exhibit other similar affectivities
and even the same emotions as the normal dog, though
all of them are undoubtedly of phyletic somatic origia.’7

But this cooperation and this possibility of an even-
tual substitution of the affective tendency whose seat is
in the brain, for the corresponding affective tendency
of somatic origin, does not prevent the former from
being entirely in the control of the latter. Therefore
modern psychology generally admits that the affective
life “has its cause below in the variations of the cenes-

16P. Flechsig, Gehirn und Seele, pp. 19, 21-22, 92, 99-100.
Leipsic, Veit. 1896.

17See C. S. Sherrington, The Integrative Action of the Nerv-
ous System, pp. 260-165. London, Constable, 1906. Cf. the perti-
Nent discussion of these experiments by Lloyd Morgan, Animal Be-
haviour, 2d ed., p. 292, London, Arnold, 1908; and Revault d’Al-
lonnes, Les inclinations, pp. 101 ff., Paris, Alcan, 1908..

Affective Tendencies 377

thesia, which is itself a resultant, a combination of vital
operations.” 18

Nor does it in the least prevent affective tendencies
from keeping all the fundamental properties which
they owe to their mnemonic visceral origin, of which
the most important are first the possession of a “diffuse”
seat, and second that they are eminently “subjective.”

For every stationary physiological system in equilib-
rium with regard to its environment permeates the
whole organism and consequently also all that part of
the brain in which this organism is reflected. Accord-
ingly, in contrast to the mnemonic sense-accumulations
each of which to all appearances has a seat distinctly
localized at a single point or in a single center of the
cortex of the brain, we have every reason to conclude
that each affective tendency is made up of an infinitely
large number of different elementary mnemonic accumu-
lations, deposited respectively in every point of the body
and in every corresponding point in the brain.

To this mnemonic physiological origin of the affec-
tive tendencies is also due their eminently “subjective”
character; for the organism is equipped potentially with
this or that “idiosyncratic” affective tendency, with this
or that “appetite,” according to the various environ-
ments or conditions in which the species and the in-
dividual were placed for a longer or shorter time in
the past, in other words according to their individual
history.

Hence the subjectivity and infinite variety manifest
in the needs, the appetites and desires and consequently
in everything that furnishes an object of “affective

evaluation.”

18Ribot, Psych. des sent., p. 10.

378 Appendix

III.

The hypothesis here presented of the mnemonic
nature of the affective tendencies in general is further
confirmed by other examples of more special affec-
tivities which have also originated by way of “habit”
and yet bear special relations to the environment since
they affect only one part or another of the organism
and manifest an activity only periodically or intermit-
tently. They are especially in evidence in the higher
animals and in man most of all.

As a typical instance it will be sufficient to consider
maternal love.

Evidently the habit of having certain relations of
parasitism, or, in general, of symbiosis, with the progeny
throughout a long series of generations has become
gradually transformed in a mnemonic way into affective
tendencies towards these relations.

“Comparative ethology,” says Giard, “shows us most
clearly that the relations between the parent organism
and its progeny are in principle absolutely the same as
those existing between a parasite and the animal it lives
upon, and that after a period of unstable equilibrium in
which one or other of the two associated organisms
suffers to the advantage of its companion there is a
tendency to the establishment of a definite position of
mutual (mutualiste) equilibrium.” '°

This is true for instance of the relations of internal
incubation, which though first sought and effected by
the embryo itself in some phase of its development for
the purpose of nutrition or some other advantage, and

19A. Giard, “Les origines de l’amour maternel,’ Revue des
idées, April 15, 1905, p. 256.

Affective Tendencies 379

at first simply endured by one of the parents, either
father or mother, finally become actual “needs” to this
parent.

It is likewise true of the relations of external incuba-
tion (brooding) which arise at first as the result of some
particular circumstance and in this way become a habit.
For instance the attachment manifested by the female
spider Chiracanthium carnifex for her nest, whether it
be her own or one of which she has taken possession,
grows with time, that is with the length of her occu-
pation of it. Hence “mother love” seems in her case
to be really nothing but her attachment to a home to
which she has become accustomed.?°

It is just the same with the brooding of birds and
some reptiles, which owes its origin to the pleasant sen-
sation which the contact with the fresh eggs brings in
the feverish condition accompanying the egg-laying
process, but which by habit has become in itself an in-
stinctive inclination.*?

Finally as regards lactation the young have gradually
developed secretions in the lactiferous glands by sucking
the secretions of the perspiratory glands on the breast of
the mother brooding over them, and thus they have at
the same time so accustomed the mother to this process
that lactation finally becomes an actual need for her.
“With mammals we must look for the origin of the
mutually symbiotic relations which unite mother and
child in the phenomenon of lactation. The physiological
disorders of pregnancy and parturition lead, among other
very curious trophic effects, to an excessive secretion of

20A. Lécaillon, “Sur la biologie et la psychologie d’une araignée,”
Année psychologique, Année toe, pp. 63-83. Paris, Nasson, 1904
21Giard, op. cit., p. 266,

380 Appendix

the mammary glands which, as we know, are only locally
specialized sebaceous glands of the skin. The young
animal in taking its first nourishment thus alleviates the
discomfort of the female and becomes a means toward
the comfort of its mother.” 22

That the need for lactation is the origin of maternal
love is shown by the fact that the mother who is deprived
of her young tries to replace them by foster-nurslings.
“The necessity of getting rid of a troublesome secretion
is powerful enough sometimes to cause the female that
lost her young to steal the progeny of another, and these
robberies have been performed even by females that were
still suckling their own young, the satisfaction of a need
leading them, as is generally the case, to seek a still
greater satisfaction which might lead even to excess.” *3

In the cases observed by Lloyd Morgan, this need of
the mother takes the form of a mother love solicitous for
the nourishment of her young, and it is possible that it
may actually represent in them the beginning of an un-
selfish attachment. ‘Further, I have seen both bitches
and cats get up and again lie down so as to bring the
teats into closer proximity to the mouth of any young
which failed to find them. It has been noticed by a man
who is a remarkably good observer and has had much
to do with animals, and also by myself, that when a lamb
is weakly and fails to find the teat, the mother not in-
frequently uses its shoulders, head and neck as a lever
to place the lamb on its legs; and, having accomplished
this, straddles over the lamb, and brings the teats against

22Giard, op. cit., pp. 269-270.
238Giard, loc cit., p. 270,

Affective Tendencies 281

its lips; and these efforts are continued until the little
animal sucks.’ 24

This example is very significant for it shows clearly
how the necessity for the elimination of the milk must
end in arousing an attachment for the nursling as the
customary means for attaining this end, just as we have
seen that the need for the elimination of the germinal
substance must lead to an affectivity for the other sex,
here again as the customary means to effect this
elimination.

Just as “sexual attraction” ceases after the elimina-
tion of the germinal substance, so also does “mother
love” disappear as soon as the need for lactation is no
longer felt. ‘Maternal affection does not generally sur-
vive the causes which produced it and only vague traces
of it are noticeable after lactation has ceased.” 5

Finally, the fact that the mother’s affection is stronger
than that of the father, and that the parents’ love for
their children is stronger than that of the children for
their parents confirms the hypothesis that all these affec-
tivities have arisen exclusively by way of habit, for it
shows that affection for those with whom we have cer-
tain relations is the more intense the more numerous
and prolonged these relations are. “Among animals as
a whole,” remarks Ribot, “paternal love is rare and in-
constant and among the lower representatives of man-
kind it is a feeble sentiment and forms but a slight
bond.” 2 Paternal love exists only where the union of
the sexes is close, that is, where the communal life

241 loyd Morgan, Habit and Instinct, p. 115, New York, Arnold,
1896.
25Giard, op. cit., p. 273.
26Ribot, psych. des sent., 285.

382 Appendix

“creates a current of affection because of services ren-
dered.” 27

“Every one recognizes,” says Pillon in his turn, “that
the love of parents for their children exceeds in intensity
the children’s love for the parents, and that of the two
parents it is the mother whose love is stronger for her
child. . . . The reason is that in the mother’s case much
more than with the father the love for the child is nour-
ished and stimulated, because of her special functions,
that is, by the constant performance of the actions it
dictates.” 28

But mother-love and mutual love within the family in
general, owing its origin to certain relations grown into
habit, represents only one particular case of a universal
law. For every other relation to person or things (no
matter how special) which becomes in the slightest
degree a habit finally appears for this very reason as
something “desired.” In every environmental relation
whether general or particular is verified Lehmann’s law
of the “‘indispensability of the customary,” which this in-
vestigator established for every stimulus to which one
becomes accustomed and whose cessation arouses a need
for its presence.”

“T have a small clock in my room,” a friend once
wrote to G. E. Miller, “which will not run quite twenty-
four hours with one winding. It often happens therefore
that it stops. Whenever this occurs I notice it at once,
whereas of course I do not hear it at all when it is

27Ribot, Psych. des sent., p. 286.

28F, Pillon, “Sur la mémoire et l’imagination affective,’ Année
vhilosophique, XVII, 1903, pp. 69-70. Paris, Alcan, 1907.

#94. Lehmann, Die Hauptgesetze des menschlichen Gefiihlslebens,
pp. 194 ff. Leipsic, Reisland, 1892.

Affective Tendencies 383

running. The first time this occurred the sensation was
somewhat as follows: it happened that I was suddenly
aware of a very indefinite unrest, a lack of something
without being able to say just what the matter was. Not
until after some reflection did I discover the cause in
the stopping of my clock.” 3°

Moreover each of us has doubtless had opportunity
to observe how things which are disagreeable at first
finally become attractive from. custom, and how such
habits assumed in the course of man’s life become as per-
emptory “needs” as those which we call natural needs.
“Smokers, snuff-takers, and those who chew tobacco,
furnish familiar instances of the way in which long per-
sistence in a sensation not originally pleasurable, makes
it pleasurable—the sensation itself remaining unchanged.
The like happens with various foods and drinks, which,
at first distasteful, are afterwards greatly relished if fre-
quently taken.” 31

Thence arises the hankering after certain customary,
things which we suddenly miss: “In some animals there
is produced a condition resembling nostalgia, expressing
itself in a violent desire to return to former haunts, or
in a pining away resulting from the absence of accus-
tomed persons and things.” *

Mere habit, therefore, is enough, as we have seen in
the case of family love, to cause other similar affectivities
also to originate and take root. Such are gregariousness,
sociability, friendship, and the like: “The perception of

30G. E. Miiller, Zur Theorie der Sinnlichen Aufmerksamkeit,
p. 128, Leipsic, Edelmann.

31Herbert Spencer, The Principles of Psychology, 4th ed., I,
287. London, Williams and Norgate, 1899.

32Th. Ribot, Essay on the Creative Imagination, p. 95. Chi-
cago, The Open Court Publishing Company, 1906.

384 Appendix

kindred beings, perpetually seen, heard, and smelt, will
come to form a predominant part of consciousness—so
predominant a part that absence of it will inevitably
cause discomfort.” °8

Finally we are all well aware of the powerful influence
of the habits of life current in any family circle during
the earliest years of a child’s life—“nurture” in its broad
sense, as Galton would say—because from these habits
arise and grow the feelings and moral tendencies which
remain impressed upon the whole life as though they
were “innate.” 34

In short from these few instances adduced simply in
explanation of our position, we see how profound is the
truth contained in the saying that habit is a “second
nature.”

But if to a certain extent we can see the most diverse
tendencies originate by way of habit before our very eyes,
then we may also attribute a similar mnemonic origin to
all affective tendencies, since the nature of innate tenden-
cies differs in no wise from that of acquired tendencies.
Very similarly in the case of morphological evolution we
may consider that the Lamarckians are quite justified in
drawing from the few observable cases of adaptation ac-
quired during life, the conclusion that the entire structure
of the organism owes its existence to an infinite number
of similar functional adaptations.

Hence we may complete the saying quoted above with
the phrase that on the other hand “nature” is nothing
but a “former habit.”

33Spencer, op. cit., II, 626.
34Francis Galton, Jnquiries into Human Faculty and Its Devel-
opment, pp. 208-216. London, MacMillan, 1883.

Affective Tendencies 385

IV.

The hypothesis of the mnemonic origin and nature of
all affective tendencies finds still further support in a
property which is inherent in all of them, namely their
“transference” which likewise is itself essentially mmne-
monic and by which all other affectivities are derived
from those of direct mnemonic origin and thus come to
have an indirect mnemonic origin (Ribot’s “law of
transference’).

For in consequence of the “substitution of a part for
the whole,” a fundamental mnemonic principle frequently
mentioned above, it happens that merely parts or frag-
ments of certain environmental relations, striven for
originally in their totality, or that “analogous” environ-
mental relations, i. e., those that are only partly similar
to one desired, or that environmental relations constituting
“means” suited to the attainment of an “end” and there-
fore its necessary precursors, or, in fine, that environmen-
tal relations which constantly accompany this “end,”
evoke the same affectivity as the original “end’’ itself.
Hence this affectivity is “transferred” from the whole to
the part, and this attachment for the part then becomes
so much stronger that this partial relation which is first
sought as a substitute for the whole finally constitutes
in its turn an habitual environmental relation hencefor-
ward desired or sought for its own sake quite apart from
the real and original affective “transference.”

This is the case for instance, as has been mentioned
above, with regard to copulation, the customary means
for the elimination of germinal substance, and also with
regard to the secondary sexual relations as phenomena
usually accompanying copulation. The “conquest” of

386 : Appendix

the other sex though only a necessary means for the sat-
isfaction of sexual appetite finally becomes with certain
individuals an end in itself. The pleasure in seducing
for its own sake, the “sexual vanity” of both male and
female and the other similar affectivities are further
instances.

The case is the same with the tearing to pieces of prey
which was originally the customary means for satisfying
hunger but finally gave place to cruelty for cruelty’s sake.

“One half of the animal race live upon prey; and as
it is delightful to eat so it must be delightful to kill.
Pleasurable also must be all the signs of discomfiture,
the helpless struggles and agonized gestures of the
victim.” 3°

In man the love of victory for its own sake, ambi-
tion, thirst for power, desire for fame and glory, the
endeavor to surpass his fellows, are all derived as con-
sequences of further transference.

In these and all other similar cases of affective trans-
ferences to environmental relations constantly becoming
less material and more moral, besides the real proper
affective transference which transforms the part into a
new “end,” there is always involved in man and in the
higher animals the cooperation of their own intellectual
development.

For the intellect is constantly discovering new and
unsuspected similarities between the most diverse phe-
nomena, even between material and ethical phenomena,
extending the same affectivities to the one class that are
valid for the other; just as disgust for certain foods
characterized by taste or odor as unwholesome extends

35Alexander Bain, The Emotions of the Will, 4th ed., London,
Longmans Green, 1899, p. 65.

Affective Tendencies 387

to certain objects which can only be touched or seen
(viscous bodies), and then, carrying the analogy still
farther, even to simple “objects” or relations of an
ethical order.*°

At the same time inasmuch as the intellect foresees
with constantly increasing sharpness the external phe-
nomena to be expected as effects of given causes, it con-
tinues to devise new means more indirect and more
complex for attaining its end, and thereby to open a
broader sphere of efficiency for “affective transference.”
For instance the weapon which was invented by man as
means for self-preservation has rendered possible an
affective transference to itself which is characteristic of
the warrior and the hunter; and the earth which the
agriculturist has utilized to provide his own nourishment
has made possible that intense love for the soil frequent
among farmers.

Furthermore, since the intellect also foresees with in-
creasing certainty internal physical processes, it calls into
being a large number of new affectivities destined to pre-
vent possible future affective tendencies from remaining
unsatisfied. For instance the anticipation of future
hunger gives even the satiated man the inclination to lay
up food that is left from a meal, and to keep it in his
possession. ‘Thus arises in general the sepse of owner-
ship, and in the same way the anticipation of the in-
numerable other desires which civilized man cherishes
today excites in him an intense longing for wealth, covet-
ousness and similar passions.%7

Finally, the intellect renders possible that infinite vari-

36Ribot, Psych. des sent., p. 212.—Essai sur les passions, pp. 65 ff.
37Spencer, Princ. of Psychol., I, 488 f£—Ribot, Psychol. des sent.,

110, 269-270.

388 Appendix

ety of shades of which affective tendencies are capable in
man. For since it is able to observe from different
points of view, simultaneously or nearly so, all environ-
mental relations even when only slightly associated, it
can evoke diverse affectivities at the same time, and these,
as Bain would say, by association, combination, con-
fluence, interference or mutual partial inhibition, finally
produce an exceedingly complex affectivity which is
therefore capable of showing the finest imaginable grada-
tions from one case to another according to the number
and character of its component parts.

Thus, for instance, fear, anxiety and kindred feelings
had already developed in animals from the instinct of
self-preservation in its purely defensive form; but in man
this latter gave rise also to all the propitiatory affectivities
in innumerable varieties and shades, such as prostration,
humility, hypocrisy, flattery and the like. Even the re-
ligious sentiment in its lowest forms is a direct conse-
quence of this propitiatory affectivity, while the loftier
religious sentiment and the kindred feeling experienced
in the presence of the sublime are more highly developed
and more complete forms of the same thing.*8

Similarly from the instinct of self-preservation in its
double aspect, offensive and defensive at the same time,
had already developed in the higher animals the instinct
to attack and all the different varieties of counter-attack ;
but in man this instinct has assumed the most varied
forms and shades from deepest hatred to a scarcely per-
ceptible antipathy, from rapacity to the merest envy, and
from the most violent thirst for revenge to the slightest
resentment. The noble sentiment of justice is a very

38For instance, see Ribot, Psych. des sent, p. 100, and E. Rignano,
“IT fenomeno religioso,” Scientia, XIII, 1, 1910.

Affective Tendencies 389

remote and hardly distinguishable derivative of the
same instinct.®°

How high may be the degree of complexity which can
thus be attained is attested, for instance, by maternal love
which has grown from the purely bodily necessity for lac-
tation to the tenderest feelings of the noblest self-denial,
and especially also by conjugal affection which has been
transformed from coarse brutal sexual appetite to an
harmonious cooperation of the gentlest and most delicate
moral affectivities.*°

Yet it is easily comprehensible that it would be use-
less, and impossible to stop here to investigate all of the
affectivities and their slightest shades which have arisen
and in this way attained their development in the higher
animals and especially in man. Let these few indica-
tions stffice to render intelligible the fact that as soon
as the organism has acquired in the direct mnemonic
way a stock of affective tendencies and the intellect has
attained its proper development, the number of affec-
tivities which may be derived by “transference” and by
“combination,” that is to say, by indirect mnemonic
means, is infinite.

Vv.

But few words are needed to indicate the place of
affective tendencies among those fundamental physical
phenomena which are most closely connected with them,
such as the emotions, the will, and the states of pleasure
and pain.

Emotions are only sudden and violent modes of acti-

39See Bain, The Emotions and the Will, pp. 117 £—Ribot, Psych.
des sentiments, pp. 229 f., 271 £—Problémes de psychologie affective,
chap. III, “L’antipathie,” Paris, Alcan, 1910.

40Spencer, op cit., I, 487 f.

390 Appendix

vation of those very accumulations of energy of which the
affective tendencies consist.

Of course it is not always possible clearly to distin-
guish affective tendencies from emotions since the former
are perceptible neither objectively nor subjectively as long
as they remain in a potential state, but become so at their
activation which, when sudden and violent, represents
the corresponding emotion. But the importance and
necessity of distinguishing accurately between emotions
and affective tendencies—a distinction however which is
usually entirely neglected by most psychologists—lies in
the fact that one and the same affective tendency may ac-
cording to external circumstances give rise to the most
diverse emotions, to the most diverse degrees of their
intensity, or even to no emotion at all properly so called.
For instance if we see a vehicle approaching at a distance
we quietly step aside out of the way, but if it appears
suddenly before us at an abrupt turn in the street we
feel a strong emotional shock. And the same affective
tendency of the dog towards a piece of meat can give
rise to flight, anger, or the careful, coolly calculated search
for a safe hiding place, according to the circumstances
under which his dainty meal is endangered.

In short, every emotion, as Stout rightly emphasizes,
presupposes an affective tendency, but the reverse does
not follow; for an affective tendency even when in full
activation need not always imply any emotion.*4

Every affective tendency “impels” to action, that is, it
not only “‘starts” but really “impinges” upon the organs
of motion either directly as in the lower organisms or
by the aid of the nervous system as in the higher.

41See G. F. Stout, 4 Manual of Psychology, 2d. ed., p. 305,
London, 1907.

Affective Tendencies 391

Therefore from the first moment of its activation it has
the appearance of a “movement in the nascent state”
(Ribot).

If its activation is sudden and intense the resulting
activity of the motor muscles is accompanied by that of
all the viscera. This “visceral cooperation” which thus
takes place in connection with the emotions properly so
called, is not, as Sherrington believes, due solely to the
fact that the rapidity and intensity with which the muscles
are set in motion induces the immediate action of the
viscera which furnish the muscles wth the material for
their energy, but also and especially because there is an
overflow of nervous energy, which suddenly released in
great quantities acts like a flood, and pours forth in nu-
merous other tracks than those closely connected with the
locomotor apparatus.*

And this visceral commotion thus produced as a result
of the sudden intense impulse, according to the well-
known theory of James, Lange and Sergi, finds its cen-
tripetal echo in the brain in the form of an emotion.**

Hence it is the affective tendency which impels us and
not the emotion as Sherrington maintains in accordance
with the prevalent confusion between affective tendency
and emotion which cannot be too greatly deplored, and
the emotion is only the reaction of a too rapid and intense
manifestation of this tendency.

On the other hand if on account of external condi-
tions or the psychic disposition of the individual the acti-
vation of the affective tendency takes place neither too

42See Sherrington, The Integrative Action of the Nervous Sys-

tem, pp. 265 f. ;
43See the famous article of W. James, “What is an Emotion?”

Mind, April, 1884, pp. 188-205—Revault d’Allonnes, Les inclinations,
108 f.

392 Appendix

suddenly nor with too great intensity, then only are the
requisite muscles called into play without any emotion.
Thus the amount of useful work accomplished as a result
of the discharge of the affective tendency is greater in
inverse proportion to the amount lost in the coordinated
movements of a purely emotional significance. This is
the reason why we generally observe the greatest deter-
mination, the most tenacious persistence in transactions,
the most intense and feverish activity in “unemotional”
individuals.*#

As regards the will, an act of volition takes place
whenever an affective tendency directed towards a future
goal triumphs over an affective tendency whose aim is
for the present; in other words, whenever a far-sighted
affectivity is victorious over a short-sighted one. It is
not the man who sweating and panting after a long run
throws himself down to drink eagerly from a spring who
exercises an act of volition, but rather the one who for-
bears to slake his burning thirst for fear of a greater
future evil. Likewise no act of volition is exerted when
an exhausted wanderer throws himself down to sleep,
but rather when a mountain climber overcomes exhaus-
tion in order to reach the desired goal. And the act of
a man who on a momentary impulse falls upen his oppo-
nent at the slightest provocation with hard words and
fisticuffs does not demand any will power, as does the
conduct of the man who bridles his just anger in order
coolly to estimate to its remotest consequences the most
appropriate procedure to enter upon against the
offender.*®

44See Revault d’Allonnes, Les inclinations, pp. 207 f.
45Cf. E. Meumann, Intelligenz and Wille, pp. 181 f. (Leipsic,
Quelle und Meyer, 1908), although differing in many points.

Affective Tendencies 393

Essentially then the will is nothing else than a true
and proper affective tendency which checks other affective
tendencies because it is more far-sighted and which in its
turn impels to action like all affective tendencies. “There
is present in the action of will some desire of a good to
be obtained or of an evil to be shunned, which imparts
its driving force.’ 46

Two extreme instances deserve special mention, for
they include all other cases. The first of these may
again be divided into two.

Sometimes one of the affective tendencies is so strong
and persistent that it constantly outweighs all others; it
checks them if it is contrary to them and strengthens them
if itis in harmony with them. Such an “hypertrophied”
affective tendency is called “passion” (Ribot, Renda). If
it is directed towards some present aim we say that it
overthrows the will because it successfully withstands the
inhibitive effect of every other affective tendency directed
towards the future; if on the other hand its own aim is
in the future, an “ideal’’ whose attainment may require
the work of a lifetime, then we say that the individual
is persevering, stubborn, unyielding, endowed with an
iron will, because every other opposed affective tendency
directed toward an immediate end dashes in vain
against it.

On the other hand it sometimes happens that the two
conflicting affective tendencies are evenly balancd. At
one moment the far-sighted tendency gains greater force
and seems to triumph by turning the mind to new conse-
quences in the future, but the next instant the short-
sighted tendency discovers new or more clearly recog-

46Maudsley, The Physiology of Mind, p. 339. London, Mac-
Millan, 1876.

394 Appendix

nized aspects in the object desired for the time being,
and becomes more intense, threatening again to gain the
upper hand. The individual then falls in a state we call
“indecision.” When a philosopher discovers by intro-
spection that he is in this situation, he will easily realize
that both affectivities exist together within him, that they
are “flesh of his flesh,” and that the slightest and most
insignificant physical occurrence is enough to cause either
one to gain ascendency over the other. It is clear that
he can easily fall a prey to the illusion that nothing at
all, any chance breath of wind, is enough to give one the
preponderance over the other. This is the subjective
illusion of free will which for many centuries has con-
stituted the greatest and most difficult problem that philos-
ophy has been called upon to solve.

Finally to come to the consideration of “pleasure”
and “pain,” it is the merit of the modern psychological
school that it has shown the fallacy of Bain’s theory that
the fundamental fact of animal life is the pursuit of
“pleasure,” in other words, the search for everything
pleasant and the avoidance of everything unpleasant;
and on the other hand that it has clearly emphasized that
the conditions of pleasure and pain represent only the
superficial part of the affective life, “of which the deep
element consists in affective tendencies, positive or nega-
tive. . . . These are the elementary processes of
affective life, of which pleasure and pain represent only
the satisfaction or failure.” #7

Since an activation of nervous energy accompanies
every “satisfaction” of any affective tendency, and every
“disappointment” corresponds to an interruption or ces-
sation of this energy, pleasure really corresponds to every

47Ribot, Psychol. des sent., p. 2—Probl. de psych. aff., p. 16.

Affective Tendencies 395

state of discharge or activation of the nervous or vital
energy, and pain to every state of inhibition or suppression
of it.

In fact “painful” is every act inhibitive of certain
nervous activities; “unpleasant” every too perceptible
change of surrounding conditions which renders impos-
sible the continuance of the hitherto stationary physio-
logical state, “agonizing” every sudden and _ violent
change of environment which brings about the complete
stoppage or destruction of life in one or another part of
the organism, and “sad” is the individual when there is
a general diminution of vital functions within his
organism.

Inversely, it is “pleasant” to exercise one’s muscle in
play and sport; the cessation of a strained condition of
the soul is a ‘‘relief,” the return to an accustomed environ-
ment and the resumption of habits is “welcome,” and in
general full of “joy” and “pleasure” is every state in
which the organism experiences a greater activity of
nervous energy.*8

It is sufficient here to indicate that the theory of the
mnemonic origin of all affective tendencies which we have
endeavored to explain and substantiate in this essay,
offers a new argument in support of the modern psycho-
logical views with regard to the inmost nature of pleasure
and pain. For in assigning to these affective tendencies
the nature of mnemonic accumulations it implies that the
fundamental principle of affective life can be nothing
but the tendency to activation inherent in these accumu-

bf

48See Ribot, Psych. des sent., Part I, chapters I-III, especially
pp. 52 f. and 83 £—W. Ostwald, Vorlesungen iiber Naturphilosophie,
pp. 388 ff. Leipsic, Veit. 1905

396 Appendix

lations, such as exists also in every other accumulation
of potential energy, and that therefore pain and pleasure,
pleasant and painful states, can be nothing but the super-
ficial and subjective side of this activation or of its
inhibition.

VI.

Before terminating these few notes upon the nature
of affective tendencies, we shall add a few remarks,
which seem to us indispensable, on the fundamental
character of these tendencies, according to which they
constitute a force, so to speak, with a definite end to be
attained but with the path to be followed left unde-
termined.

Affective tendencies owe this property of gravitating
toward an end while the means remain undecided, to the
circumstance that they depend on the existence in a
potential state of a certain general or local physiological
system or state, which was determined in the past by the
outside world as a whole or by individual particular rela-
tions to this outside world, and which now like every
other potential energy simply endeavors to reactivate
itself as soon as it is released by the persistence or recur-
rence of even a small part of this environment or these
environmental relations. For the result of the existence
of this tendency is that the organism gravitates toward
this environment or these environmental relations ren-
dering possible the recurrence of this physiological state,
but it does not imply any “impulse” toward or “impinge-
ment” upon any one of the series of passing physiological
states or movements which, even if they were capable of
eventually bringing the organism back to the desired en-
vironment, nevertheless have nothing in common with

Affective Tendencies 3907

the definitive physiological state itself which corresponds
to this environment.

Only from the moment when one series of move-
ments happens to bring the organism back to the desired
environmental relations earlier than another one, will
it have acquired an advantage over the others, and this
result may be expressed by saying that the affective ten-
dency has exercised a “choice” (James, Baldwin and the
American school in general).

Hence it is only from that moment that the affective
tendency will by mnemonic association constitute a force
which “impels” these movements toward the end, just
as certain reflex movements “impinge” on one another
(Sherrington). And only from that moment will these
movements (so long as they have not become mechanical
in the form of reflexes) be determined exclusively under
the pressure of the corresponding affectivity or the equiv-
alent “act of the will.”

However, until this takes place the affectivity betrays
no tendency at all to discharge in one path rather than
in another, hence the great difference between the affec-
tive tendency or act or will on the one hand, and the
reflex movement on the other. This reflex movement, by
means of which the act so “chosen” when often re-
peated becomes by mnemonic accumulation gradually
mechanical and quite independent of the whole, repre-
sents a tendency to discharge along one single given path
which is determined in advance. It is a force whose point
of application and direction are known beforehand, and
might therefore be indicated graphically by the customary
arrow used to represent the forces of mechanics. On the
other hand the affective tendency constitutes a force of
which neither the point of application nor the direction

398 Appendix

are predetermined but only the point towards which it
tends. It is a “disposable” energy to be applied at will
to this or that act so long as it leads to the desired end.
Therefore it can be represented at the same time quite
indefinitely by any of the infinite number of arrows
which fill the entire volume of a cone and converge at
its apex.

The reflex movement admits therefore of but a single
solution. On the other hand the affective tendency
admits of an indefinitely large number of solutions so
long as none of the possible movements has been per-
formed by chance and given rise to a choice; or when
there are numerous equivalent paths to the goal.

This possibility of many solutions constitutes exactly
the “unforeseen,” the “antimechanical” behavior depend-
ent on the affectivity or will, in contrast to the predeter-
mined mechanical behavior of reflex movements or of
any such complex combinations of reflex movements as
certain instincts exhibit.

Finally it is this fundamental property of the affective
tendency of constituting in some degree a force grav-
itating toward that environment or those particular en-
vironmental relations which permit the reactivation of
certain mnemonic accumulations forming this very ten-
dency, which lends that environment or those environ-
mental relations the appearance of a wis a fronte or
“ultimate cause” differing very essentially from the ws
a tergo or “actual cause” which alone is operative in
inorganic nature.*®

The organism, writes Jennings, “seems to work to-
ward a definite purpose. In other words, the final result

49See W. James, Principles of Psychology, I. pp. 7 £. London,
Macmillan, 1gor.

Affective Tendencies 399

of its action seems to be present in some way at the be-
ginning, determining what the action shall be. In this
the action of living things appears to contrast with that
of inorganic things.” 5°

Now this “final result of its action” exists really from
the beginning in the form of mnemonic accumulation.
For that environment or those special environmental con-
ditions to which the animal is gravitating operate now as
vis a fronte in so far as they were formerly vis a tergo and
in so far as the physiological activities then determined
by them in the organism have left behind a mnemonic
accumulation which now itself constitutes the real and
true vis a tergo moving the living being.®!

Thus it is clear that one and the same explanation
applies to all the “finalism’” of life. For from the onto-
genetic development which creates organs that cannot per-
form their functions until the adult state, to the tendency
of all physiological states determined by certain environ-
mental conditions to remanifest themselves at the first ap-
pearance of phenomena usually preceding these conditions,
but in no wise constituting them; from the perfect way
in which the organism in its entirety is morphologically
adapted to its environment before the latter can exercise
its formative influence, to all the wonderful formations
and special structures so exactly adapted to all the most
probable conditions to which this organism might later be
exposed ; from the simplest reflex motions that are directed
so perfectly toward the preservation and welfare of the
individual to the most complex instincts by means of

50Jennings, Behavior of Lower Organisms, p. 338.
51, Mach, Die Analyse der Empfindungen, 5th ed., pp. 79, 78,
Jena, Fischer; English edition: Chicago, Open Court Publishing

Company, 1897.

400 Appendix

which animals prepare in advance for future conditions of
which they themselves are probably ignorant—all these
“finalistic”’ phenomena of life, identical in their nature, can
be explained as so many manifestations of a purely
mnemonic nature, as we have seen in our earlier writings
mentioned above.

And now in the present essay we see that affective
tendencies, which are even more conspicuously “‘finalistic”’
manifestations, are likewise based upon the mnemonic
property of living substance, and hence in the last analysis
upon the faculty of “specific accumulation,” a faculty be-
longing exclusively to the nervous energy which underlies
all life.

This mnemonic property, this faculty of “specific ac-
cumulation,” which by its absence leaves inorganic nature
exclusively in the power of forces a tergo and deprives
it of every finalistic aspect, is on the other hand every-
where present in organic nature and because of its pres-
ence makes the world of life a world apart, of which the
most characteristc elements cannot be explained by the
laws of physics and chemistry alone in the limited sense
assigned to them to-day.

EUGENIO RIGNANO.

Mian, ITALY,

INDEX

Abridgment of memory and
ontogeny, 326.

Accessory idioplasm, 137.

Acclimatization, 371.

Accumulation, mnemonic,
399; specific, 374, 400.

Accumulators, electric or nerv-
ous, 290 ff, 296 ff, 309, 310,
322, 341 ff; paired, 341, 353.

Actinia equina, 372.

Adaptation functional, 124, 127,
174, 180, 203.

Affective tendencies, 358; defined,
361; eliminative, 365; particu-
lar, 369; subjectivity of, 377;
originated by habit, 378; dis-
tinguished from emotions, 390;
hypertrophied, 393.

Affinity, vegetative, 92; of differ-
ent tissues, 90.

Agassiz, researches upon asym-
metrical flat fishes, 217.

Alessandrini, results of the ab-
sence of the spinal cord, 305.

Allonnes, d’, Les inclinations, 376;
391, 392.

Amblystoma, 307.

Amphimixis, 194, 195.

Amphioxus, 80, 133.

Amputations, non-inheritance cf
effects of, 160, 174.

Anachronisms of development,
66, 112.

Anesthetics, 43.

377;

Anentoblastia (absence of the
entoblast), 112.

Annelids, heteroplastic grafts in,
go.

Anthropoid apes, 12, 13.

Antibacterion, 272.

Arbacia, 101.

Arrests of development, 98.

Ascidians, 80.

Ass, pad of fat in the colt of the,
165.

Assimilation, 332, 336.

Association of ideas, 201, 330.

Asteria, 60, 101.

Atavism, 144.

Atavistic reversion, 98, 100, I9I,
280.

Axolotl, regeneration in, 20, 307.

Bachmetjeff; inheritance of al-
terations, 174.

Bain; pleasure in killing, 386;
simple affectivities into com-
plex, 388; sentiment of justice,
389; pursuit of pleasure, 304.

Balbiani (Note) fission in in-
fusoria, 54.

Baldwin; choice, 397.

Bard; vital induction, 231; cell

proliferation, 230; biogenetic
theory, 230; vital phenom-
enon, 333.

Bardeen, Charles Russell; note,
heteromorphosis, 88.

401

402

Barfurth; regeneration, 89;
straightening of the regener-
ated tail of tadpoles, 307.

Bathmism, 257, 258.

Beale, Sir Lionel;
the brain cells, 323.

Begonia phyllomaniaca, 83.

Bernard, Claude; anesthetics, 43;
irritability, 298, 374; memory
in the germ, 316; sensibility
of the nervous substance, 333;
characteristics of life, 337.

Bert; transplantation of parts
of the body, 90.

Biogenesis of Oscar Hertwig,
233.

Biogenetic Law of Haeckel, 6,
II, 77, 99, 221, 222, 240, 285,
316, 356; significance, 13.

Biogen hypothesis, 335.

Biophores, 145.

Blastomeres, shifting and isola-
tion of, 80, 132, 133.

Blood, transfusion of, 281.

Blumenbach, 137.

Bombinator igneus, 9I.

Bonnet; regeneration in the sal-
amander, Io.

Born; transplanting parts of the
body, 91, 114, 128; studies of
growth, 116, 118, 119, 128.

Brain, development of, 200.

Brooding, 379.

Brown-Séquard; inheritance of
the effects of injury in guinea
pigs, 166.

Butterflies, color of scales of,
174; Cope’s experiments upon,
256.

number of

Callosities of tame camels, 165.
Camels, callosities of, 165.

Index

Castle; acclimatization, 371 f.

Cattaneo G. note, 165. Note,
166. note, 181.

Central Zone of Development,
16, 25, 53, 61, 65, 77; structure
of, 73; location of, 71, 73, 75;
in plants, 71; formation of , 86.

Centroepigeneses of second or
higher degrees, 72.

Cephalic monsters, 65, I14.

Chabry; researches upon ascid-
ians, 80.

Chemical development, theories
of, 149, 276.

Chemotropism, 335.

Chicken, instinct in the, 227.

Chiracanthium carnifex, 379.

Choice, 397.

Chromatin, 78, 82.

Chromosomes, 78, 354, 355.

Clock, stopping of a, 382.

Co-adaptation, 178.

Coleridge; latent memories, 328.

Colloidal ferments, 279.

Compensatory growths, 47.

Completion of development, Io1,
120.

Composite flowers, 72.

Comte, August; Positivistic phi-
losophy, 5.

Conditions of inheritance, 286,
300.

Coordinated variations, 187, 210,
214.

Cope; likeness of certain struct-
ures in different races, 205;
useful variations, 209 ff; the-
ory of inheritance, 256 ff, 314.

Copulation, 366, 385.

Correlation networks, 46, 47, 62
ff.

Index

Crabs, regeneration of the feet
of, 140.

Crampton, H. E., 109. Note.

Crosses, good or defective de-
velopment in, 100.

Cruelty, 386.

Crystal-formation as compared
with formation of the organ-
ism, 228.

Cunningham; colors of asym-
metrical flat fishes, 217, 308.

Cuscuta, 247.

Cyclas cornea, 60.

Dallinger; experiments in ac-
climatization, 371.

Dareste; headless monsters, 113;
spina bifida, 127.

Darwin, Charles; 20. Note,
Xenia, 74; mixed races, 100;
gemmules, 145; pangenesis,
150, 281; inheritance in do-
mestic animals, 160, 224; gas-
tric juice, 206; theory of he-
redity, 280; hen with plumage
of a cock, 3IT.

Darwin, Francis; setaria grass,
44; mnemonic property of liv-
ing substance, 375.

Dastre; vital phenomenon, 338;
functional activity and rest,
340.

Datura ferox and levis, 100.

Davenport ; acclimatization, 371 f.

Decisive experiment on inherit-
ance, I7I.

De Gros, see Durand.

Delage; indirect ways of de-
velopment, 12; parallelism be-
tween ontogeny and phylog-
eny, 14; generation, 38; sec-
ondary protoplasmic connec-

403

tions, 47; localization of
growth, 48; unicellular and
pluricellular organisms alike,
59; regeneration, 140, 9I
Note, 125 Note; species forma-
tion, 216; indirect ways of
ontogeny, 12, 242; biogenetic
theory, 263; sexual characters,
310; indirect division of the
nucleus, 354.

DeMeyer, see Meyer.

Determinants, (Weismann’s),
122, 125, 127, 131, 136, 139, 142,
I5I, 213, 220, 221, 284; of
smaller growing power, 212.

De Vries; causes of the spe-
cificity of development, 106;
pangens, 145, 206, 283; Weis-
mann’s criticism of, 152;
chemical compounds in plants,
206; preformistic germs, 133;
qualitatively equal cell divi-
sion, 283.

Differentiation, histologic, 117,
124, 273; correlative, 47, 61,
104.

Dimorphism, 310 ff, 366.

Diplogenesis, 257, 284.

Disassimilation, 338, 348.

Dogs (hunting), instinct of, 166.

Double formations, 68, 87, 114,
129, 132, 133.

Driesch; Echinus microtubercu-
latus, 80; half embryos, 110;
theory of organic develop-
ment, 243.

Ducks, mixed races of, 100.

Durand de Gros; human poly-
zoism, 73.

Dynamic equilibrium, 120, 293.

404

Echinus microtuberculatus, 80.

Economy of the organism, 191.

Ehrlich; immunised mice, 234.

Elasticity of the organism, 93-
96, 98, 218.

Electric current, 180; compared
with nervous, 291; oscillating,
341 ff, 346, 372.

Electro-chemical generator, 291

Element; generic potential, 291;
mnemonic, 319, 326, 353; spe-
cific potential, 77, 79, 80, 92, 98,
IOI, 102, 290, 296, 299, 300,
+343, 349, deposition of so-
matic, 84; of germinal, 103;
vital, 343, 349.

Eliminative affective tendencies,
365.

Eliminative hypothesis, 367.

Emery, origin of instincts, 200.

Emotions, defined, 389.

Encasement of germs, 121.

Environmental invariability, 364.

Epigenesis, 6, 18, 104, 107.

Errera; inheritance of alter-
ations, 172.

Euglena reacting to light, 364.

Evolution (as opposed to pre-
formation), 104, 105, I19.

Exner, instinct of hunting dogs,
166.

Fasting; influence on metamor-
phosis, 50.

Fear, origin of, 388.

Ferments, 270.

Finalism, 399, 400.
Fischer; transplantations,
butterflies’ wings, 174.
Flat fishes, asymmetrical, 217,

308.
Flechsig, Kérperfiihlsphire, 376.

123;

Index

Flowers, centroepigeneses of two
grades, in, 72.

Fogliata; fat pads in asses’ colts,
165.

Formative stimulus, 20, 59.

Friendship caused by habit, 383.

Functional adaptation, 124, 127,
160, 169, 174, 180, 181, 182, 184,
194, 196, 202, 203, 207, 208, 211,
247, 208, 276, 2906, 304, 309-311.

Functional stimulus, 15, 94, 102,
184, 207, 236, 266-268, 289, 290,
302; cooperating with onto-
genetic, 305 ff; identical with
mnemonic, 325.

Fundulus, 125.

Galls, 124.

Gall flies, 247.

Galton, Francis; particulate in-
heritance, 145; inheritance, 175,
224; investigations of the in-
heritance of instincts, 175;
preformistic germs ‘and trans-
fusion of blood, 281; stirp, 282;
influence of habit, 384.

Garten, Siegfried; intercellular
bridges in epithelia, 33 ff.

Gemmaria (Haackes), 229.

Gemmes (Haackes), 2209.

Gemmules (Darwin), 145, 281.

Generator (see electrochemical
generator).

Generic element (see Element).

Germinal elements, 86, 92, 90,
100, 101, 311.

Germinal energies,

Germinal substance, 14, 17, 18,
76, 78, 93, 103, 106, 107, 108,
121, 144, 148, 154, 157, 201, 217,
220, 281, 287, 288, 290, 294, 296,
300, 301, 324, 328.

Index

Germinal tracks, “Keimbahnen,”
283.

Germinal zone, 74.

Germs, Galton’s, 145.

Germs, preformistic (see prefor-
mistic germs.)

Germ cells, 83, 84, 189, 228-231,
252, 254, 257, 258.

Giard; parasitic relation of off-
spring to parent, 378; brood-
ing, 379; lactation, 380; ma-
ternal affection, 381.

Giraffe, 198.

Goethe, nature of flowers, 72.

Goldstein, Kurt; influence of the
central nervous system on de-
velopment, 76.

Gorilla, 13.

Graf, leech, 125.

Grafts, 80, 90, 117.

Gregariousness caused by habit,
383.

Gromia oviformis, 42.

Gros (see Durand de Gros).

Gruber; division of infusoria,
54, 58; stentor coeruleus, 54,
55; unicellular and_ pluricel-
lular organisms, 60.

Guinea pig, inheritance of the
effects of injuries in, 166.

Haacke; theory of inheritance,
228.

Haase, H.; regeneration in Tubi-
fex rivulorum, 140.

Habit, origin of affective tenden-
cies, 378; influence of, 384.
Haeckel; perigenesis, 259; his
theory, 250, 314; mnemonic
character of plastidules, 316.
Haeckel’s biogenetic law (see

biogenetic law).

405

Hammar; communications be-
tween the cleavage cells of the
sea urchin egg, 39.

Hansemann; nuclear
355:

“Harmonicity” of Vochting, 89.

Hartmann, Eduard von; doctrine
of descent, 196.

Hartog, Marcus, 353.

Heidenhain; intercellular bridges
between cells of different tis-
sues, 40.

Helleborus niger, 247.

Hemitherium anterius, 63.

Hensen; memory, 324.

Herbst; sea urchin, 80; epigen-
etic theory, 246.

Hering; the phenomenon of
memory, 316 ff; the nervous
“substance as the preserver of
memories, 321, 375.

Heritage (all that is inherited),
77, 85, 237, 249, 274, 275.

Hermaphroditism, 366.

Hermit crabs, 181.

Hertwig, Oscar; embryonal
organs without function, 12;
transmission of the stimulus
for membrane formation, 32;
transmission of nuclear stim-
uli, 42; gastrular invagin-
ation, 75, 87; frogs’ eggs, 80;
shifting the blastomeres, 81;
hereditarily equal division, 81,
82; double gastrular invagina-
tion, 87; organization of the
egg, 97; causes of the specifi-
city of development, 106; galls,
124; new formations, 136; bi-
ogenetic theory, 233 ff; rejec-
tion of biogenetic law of
Haeckel, 242; specific action of

division,

406

the mnemonic
316; the vital

stimuli, 298;
phenomenon,
process, 337.

Hertz; researches, 344, 345, 348.

Heschenhagen ; capacity of
adaptation in the lower fungi,
173.

Heteromorphosis, 87.

Heteroplastic grafts, 9o.

His; conception of development,
248.

Hoffman; inheritance of alter-
ations, 172-3.

Hofmeister; chemical develop-
ment, 278.

Horns, development of, 163.

Hunger; inheritance of alter-
ations, 172, 361; leads to sense
of ownership, 387.

Huxley; definition of plants, 43.

Hyatt; shells of cephalopods,
162.

Hybrids, 99, 144.

Hydra, 83, 86, 143, 362.

Hypophysis, 11.

Hyrtle; defective growth, 305.

Idioblasts, 145.

Idioplasm, 18, 83, 80, 132, 145,
236, 230, 255, 316.

Ids, (Weismann’s), 122.

Ilyanassa obsoleta, 109.

Immunisation, 234, 272.

Independence of parts with ref-
erence to whole, 376.

Infusoria, regeneration in, 53.

Inheritance of acquired char-
acters, mechanism, 289.

Instincts, 151, 161, 175, 177, 200,
227, 313, 320.

Index

Intellect, an aid in transference
and source of new affectivities,

386 f.
Intercellular bridges, 30ff, 309,
40.

Interpolation of ontogenetic
stages, 96.

Invagination, 48, 49, 258; Gas-
trular double, 87.

Invariability, environmental, 364;
individual, 370; physiological,
361, 363, 368; physiological, a
factor in social evolution, 370 f;
tendency to physiological, mre-
monic, 373.

Involution, 49, 191, 212, 221.

Irritability, 298, 333.

Irrito-contractility, 43.

James; emotions, 391; choice,
397; actual and ultimate cause,
398.

Jastrow;
227.

Jennings; reactions to food, 362;
reactions to light and tempera-
ture, 364; ameba, 369; organism
works for an end, 398 f.

Johnson, H. P., 284, 285.

Jost; heteroplastic grafts, 90.

Justice, origin of, 388.

instinct in chickens,

Kallima, 185.

Karyokinesis, 354.

Kastor; structure of bone, 129.
King, Helen Dean, 60.
Kohlwey, 171.

Lactation, 379.

Lamarckian principle, 159, 175,
196, 202, 203, 207, 223, 224, 314,
367.

Index

Lange; emotions, 301.

Law, fundamental biogenetic
(see biogenetic law).

Lecaillon; mother-love of spider,
379.

Le Dantec; gastrula, 73; par-
ticulate inheritance, 151; re-
production, 151; shells of ce-
phalopods, 162; colors of the
skin, 183; biogenetic theory,
268 ff; amblystoma, 307.

Leech, 125.

Lehmann’s law, 382.

Lens of the eye of tritons, 28,
80.

Lewes; nervous system, 45;
physiological effects of mem-
ories, 325; vital phenomena,
337-

Lionel Beale; (see Beale.)

Lipomata, from burden bearing,
165.

Lizard, regeneration with alter-
ations, 141.

Localisation of growth, 48, 49,

258.
Loeb; fundulus, 125.
Lombroso, Cesare; lipomata

from burden bearing, 165.

Love, conjugal, 389; maternal,
378, 389; sexual, 365, 381, 3895
parental, 381.

Macfarlane, 43.

Mach; wis a tergo, 399.

Magosphaera planula, 30.

Martiny; structure of bone, 120.

Maudsley; impression upon a
mnemonic centre, 320, 328;
driving force of the will, 393.

Maupas; term “senescence,” 365.

Maxwell, 348.

407

Medusa, 80, 83.

Membranelles in Infusoria, 60,
284.

Memory, 251, 261, 262, 316 ff;
physiological effects, 324, 375;
latent, 328.

Metabolism, 362.

Metamorphoses, 98.

Metschnikoff ; phagocytes, 49.

Meumann; impulse and restraint,
392.

Meyer, J. de; inheritance of
alterations, 172, 173.

Meynert; brain cells, 323.

Mimicry, 184, 185.

Mimosa, 44.

Mivart; evolution, 105.

Mixed races, 100.

Mnemonic elements (see ele-
ments), |

Mnemonic laws. See “Substitu-
tion of part for whole,”

“Transference” and “Independ-
ence of part with reference to
whole.”

Mnemonic phenomena, 253, 256,
262, 2990, 316-8, 322, 330, 331,
356, 363.

Mobius; pike and gudgeons, 175.

Molar movements, 270-272.

Molecular movements, 271.

Monsters, 65, 113, 130, 132, 305.

Moral ends, transference to, 386.

Morgan; regeneration in Plana-
ria maculata, 87, 135; hybrids,
101; one embryo from two
blastulas, 134; experiments
with dogs, 376; origin of ma-
ternal love, 380 f.

Mosaic theory, 119.

Mosaic work, 109, 28.

408

Motion, difference between plants
and animals, 370.

Mule, transverse stripes in the,
100. ,

Miller, Erik; eye lens in the
tritons, 28.

Miller, G. E.;
clock, 382.

Mus decumanus, Mus rattus, Mus
sylvaticus, 90.

Myxomycetes, 29, 372.

stopping of a

Nageli; idioplasmic network,
230; unfolding of the anlagen
of the idioplasm, 239; Weis-

mann’s objection, 242, 243;
general and mnemonic idio-
plasm, 255; the mnemonic

phenomenon, 316.

Nature, former habit, 384.

Navicula brevis, reaction to light,
372.

Neal; acclimatization, 372.

Nerve cells, 262.

Nervous energy, 20, 33, 41, 43,
45, 46, 48, 49, 50, 70, 77, 79, 86,
98, 256, 289, 299, 319, 330-332,
336, 340, 344, 357. Specific, 62-
63.

Nervous coordinations, 45, 251,
252, 253.

Nervous current, nervous flux,
32, 35, 36, 37, 39, 41-43, 102,
295- 297, 290, 300, 319, 322, 325,
346, 347, 348, 356; compared
with electric, 289-292; specific,
16, 102, 290, 374; oscillating,
341 ff.

Nervous discharge, 41, 202 ff,
322, 342, 343, 346, 348, 352, 357.

Neuters among the insects, 178,
187, 312.

Index

Newts, arrests of development
of, 99; regeneration in, 19, 140.

Nisus formativus, 137.

Nostalgia, 383.

Nuclear division, 79, 83, 92, 132,
246, 283, 350, 354.

Nuclear somatisation, 18, 24-26,
27, 79, 83, 84, 89, 92, 119, 262,
297, 290.

Nuclei, somatic and germinal, 84,
85.

Nussbaum; division of Infuso-
ria, 54; form-determining en-
ergy, 50; continuity of the
germ cells, 189; inheritance of
acquired characters, 190.

Ollier; transplantation of bony
tissues, 90.

Omphalosite monsters, 113, 114.

Ontogenetic stimulus, 51, 59, 94,
IOI, 306, 309.

Optimum conditions,
towards, 372.

Orr; alteration of the nature of
growth, 96; crosses, 100; bio-
genetic theory, 251-256; com-
parison with the mnemonic
phenomenon, 316; vital phe-
nomenon, 332.

Osborn; phagocytes, 49; influ-
ence of fasting on transforma-
tions, 50; adaptive reactions,
209; latency, 217; colors in
pleuronectids, 217.

Osmotic currents, 270.

Ostwald; term “stationary,” 361;
pleasure, 395.

Overcrowding, effects of, 197.

Ownership, sense of, 387.

tendency

Pangenetic theory, 206.

Index

Pangens, 144, 145, 151, 153, 206,
283.

Panmixia, 184, 190-192.

Paramoecium caudatum, 59; re-
acting to temperature, 363.

Parasites, 191, 378.

Particulate inheritance, 144, 150,
I5I, 153, 154, 156, 302.

Passion, defined, 393.

Perigenesis, 259.

Periodicity of biologic functions,
350, 351.

Peripatus, 30.

Perrier, Edmond; polyzoism, 73.

Persistence, effect of, 383.

Pfeffer; formation of cell mem-
branes, 31.

Phagocytes, 49.

Phonograph, 300.

Physiologic unit; Spencer, 225,
227, 228; the organism a, 236,
252.

Physiological invariability, 361,
363, 368; a factor in social evo-
lution, 370 f; tendency to, mne-
monic, 373.

Piéron; oysters close when ex-
posed to air, 364.

Pigeons, crosses in, 100.

Pillon; parental love, 382.

Pineal gland, 11.

Placenta, 96.

Planaria maculata, 87, 88, 135.

Plasticity of the organism, 91,
94-96, 218.

Plastids, Ledantec’s, 268 ff.

Plastidules, Haeckel’s, 259, 316.

Pleasure and pain, 394.

Pleuronectids, 217.

Pluteus, IOT.

Polymorphism, 311 ff.

Polyommatus phlaeas, 182, 284.

409

Polyzoism, human, 73.

Post-generation, 21-27,
81, 96, 134.

Posthumous action of the nu-
cleus, 56, 290.

Fotential elements
ments).

Preformation, 6, 106, 119, 120,
153.

Preformistic germs, 106-108, 126,
133, 144, 147-152, 206, 224, 237,
280, 284, 300.

Primula acaulis, 152.

Propitiatory affectivities, 388.

Protective colors, 182 ff.

Protective polychromatism, 182.

Pulst; inheritance of alterations,
172.

29, 63,

(see ele-

Quinton; tendency to chemical
invariability, 369.

Rabe, J.; structure of bone, 126.

Rana arvalis, Rana _ esculenta,
Rana fusca, 91, 118.

Rapidity of division, 75.

Ray; inheritance of alterations,
172.

Recapitulation of phylogeny in
ontogeny, II, 12, 216, 218, 220,
228, 243, 250, 260, 263, 268, 273,
280, 285, 316, 327, 331, 356.

Reciprocal action of parts of the
organism, 106.

Regeneration, 19, 20, 28, 29, 54,
88, 112, 132, 135, 136, 280, 307;
cenogenetic, 139-143.

Rejuvenescence of Infusoria, 353;
of vital elements, 343.

Religious sentiment, origin of,
388.

Remodeling of tissties, 135.

410

Renda; passions, 393.

Reserve idioplasm, 85, 117, 132.

Resonator, 321, 344-346, 353.

Reversion, atavistic (see atavis-
tic reversion).

Rhomboidal gemmes, 229.

Rhythmicity of biological func-
tions, 350, 351.

Ribbert ; compensatory growth, 47.

Ribot; the mnemonic phenom-
enon, 318; elements of mem-
ory, 320; memories, 322; de-
pendence of memory on nu-
trition, 324; Wundt’s experi-
ment, 325; abridgment of
memories, 326; latent mem-
ories, 328, 329; rigorously
serial order in development,
331; selfishness of sexual love,
366; reproductive instinct sub-
ject to perversions, 376; af-
fective life dependent on brain,
376; paternal love in animals,
381; nostalgia, 383; law of
transference, 385; material and
ethical analogies, 387; religious
sentiment, 388; motion in nas-
cent state, 301; passions, 3933
pleasure and pain, 394, 305.

Rignano, Eugenio; influence of
the central nervous system on
development, 76; new mne-
monic theory, note, 317.

Ripening of sex cells, 102.

Romanes; minus-variations and
plus variations, IOI.

Roux; indirectness of develop-
ment, 11; trophic action, 37;
correlative differentiation, 47;
ontogenesis, 48; ontogenetic
stimulus, 51; half embryos,
61 ff, 134; mosaic theory, 68,

index

109, 119; regeneration of bi-
sected frog embryos, 89;
elasticity of development, 66,
95; anchronisms of devel-
opment, 66; half embryos,
96, 97; self differentiation
and corelative differentiation,
104, 124; half embryos, 108,
119; regeneration in tritons,
112; opposing O. Hertwig,
112; double formations, 68,
II4, 134; symmetrical planes,
115; on the researches of Zahn
and Fischer, 123; structure of
bone, 126; size of cells, 131;
self regulating mechanism, 95,
132; post generation, 21 ff, 96;
differentiation, 139; speech
muscles, 161; structural rela-
tions of the tissues, 203; tran-
sition from aquatic to terres-
trial life, 211; distorted frog
embryos, 66, 95, 219; correlated
development, 210; theory of in-
heritance, 224; functional stim-
ulus, 266-267; chemical devel-
opment, 276; embryonal and
adult life, 303; absence of the
spinal corn, 305 note; accel-
erated development, 306; the
vital phenomenon, 332; attrac-
tion of the chromosomes by
the centrosomes, 355; on sex-
ual hunger, 365.

Rubin, Richard; relation of the
nervous system to regenera-
tion, 76 note.

Rush; latent memories, 329.

Sachs; synergids, 41.
Saint-Hilaire, Isidore Geoffroy;
headless monsters, 113.

Index

Salamander, arrest of develop-
ment of, 99; regeneration in,
19, 140.

Schmitt; transplantation of bony
tissues, go.

Schneider; starfish, 364.

Schopenhauer; will of the spe-
cies, 367.

Schibeler; inheritance of more
rapid development of barley
seeds, 172.

Shuberg; connection of cells of
different tissues, 40 note.

Schultze, Oskar; double forma-

tions produced from frogs’
eggs, 133.

Sea urchin, 80; protoplasmic
connection of the cleavage
cells, 39.

Sedgwick; eggs of Peripatus,

390; the body as a syncytium,
39, 230.

Self differentiation, 104, 115, II9,
124, 130.

Self-preservation, 369, 388.

Self regulating mechanism, 95,
98, 132, 135, 307.

Semon, Richard; memory as un-
derlying principle, 317n, 375.
Séquard; (see Brown-Séquard).

Sergi; emotions, 391.

Setaria grass, 44.

Sexual, instinct, 365 ff, 381, 380;
vanity, 385.

Sherrington ;
muscular
emotions,
ments, 397.

Shifting of blastomeres, 80; of
parts of embryos, 65.

Social evolution, 370.

Somatic theory, 375.

spinal dog, 376;
accompaniment of
301; reflex move-

4II

Spallanzani; regeneration in the
salamanders, 19.

Species, morphologic indications
of, 146.

Specific accumulation, 374, 400.

Specific potential elements (see
elements).

Spencer, Herbert; germ plasm,
148; Punjabi, 164; polemic
with Weissman, 187, 211; plus
and minus variations, 190;
taste sense in the tongue papil-
lae, 194; physiological units,
225; Hertwig agrees with him,
241; fertilization, 352; effect of
persistence, 383; anticipation
cause of covetousness, 387; de-
velopment from brute instincts,
380.

Sphaerechnius, Morgan’s investi-
gation of, 134.

Spider, mother-love of, 379.

Spina bifida, 126.

Stahl; Myxomycetes, 372.

Standfuss; inheritance of altera-
tions, 174.

Stationary physiological condi-
tion, 361, 364, 368, 377.

Stentor, 54 ff, 284.

Stimuli, action of, 298; func-
tional—see Functional stimu-
lus, ontogenetic (see Ontoge-
netic, stimulus).

Stirp, Galton’s, 282.

Stoichactis helianthus, 362.

Stout; emotions, 390.

Strasburger; chromosomes divi-
sion of, 79; combination of
paternal and maternal charac-.
ters, 156.

Subjective illusion of free will,
394.

412

Subjectivity of affective tenden-
cies, 377.

Substitution of part for whole,
363, 368, 376, 385.

Succession of ontogenetic stages,
15, 246, 330.

Symmetrical planes, 69, 115.

Syncytium, 39, 230.

Synergids, Sach’s, 41.

Synthesis vital, 340.

Tadpole, disappearance of tail,
49; amputated tails of, 116,
307; grafts, 128.

Telephone, 301.

Teratogenesis, 126.

Terns, stomachs of, 125.

Thermal energy, 348.

Thirst, 363.

Tornier; theory of inheritance,
232.

Transference, 385 ff.

Transplantation of tissues, 90,
122.

Triton, regeneration of the lens
of the eye of, 28, 89, 140; ar-
rest of development of, 99.

Trophic stimulus, 37, 49.

Unicellular organisms like pluri-
cellular, 59.

Variations, coordinated, see Co-
ordinated variations; sponta-
neous, 144; plus and minus,
I9I.

Vegetative affinity, 92.

Velleius dilatatus, 200.

Verworn; physiologic — signifi-
cance of the cell nucleus, 54
note, 57 note; biogen-hypo-
thesis, 335.

index

Vis a fronte, 308 f.

Vis a tergo, 398 f. 400.

Vital energy, 336.

Vital induction, Bard, 231.

Vital phenomenon, geieral, 299,
315, 318, 319, 322 ff, 332, 343,
348, 350, 357.

Vital principle, search for the
nature of, 335.

Vital processes, identical, 43.

Vitis aestivalis, 156.

Vochting; “harmonicity,” 80.

Volvox, cell communications, 30.

Vulpian; continued life in am-
putated tails, 116.

Watasé; centrosomes, 355.

Weber, E. H.; effects of absence
of the spinal cord, 305.

Weismann; inactivity of the germ
plasm, 17; chromatin, 82; an-
tagonism between germinal and
somatic nuclei, 84, 85; pre-
formation proper, 106, 121; in-
admissibility of determinants
of, 125; principle of the ca-
pacity of alteration, 127; rigid-
ity of the determinants, 131;
post generation, 134; new
formations in regeneration,
137; regeneration, 139; ceno-
genetic regeneration, 142;
grouping of determinants, 143;
preformation, 147; pangens,
152; intermingling of paternal
and maternal characters, 154;
doubt of the inheritance of ac-
quired characters, 159; Punjabi,
164; opposed to Brown Sé-
quard, 168; non-inheritance of
the effects of amputations, 170;
arguments against the inherit-

Index 413

ance of acquired characters,
177 ff; action of external stim-
uli on development, 183 note;
panmixia, 184; alterations in
plants, 186; polemic with
Spencer, 187, 211; inconceiv-
ability of the inheritance of ac-
quired characters, 188; pan-
mixia, 190 ff; almightiness of
natural selection, 193, 210, 367;
taste sense in the tongue papil-
lae, 194; amphimixis, 1094 ff;
stability of many species, 196;
functional adaptation, 197, 204;
similar characters of different
species, 205; coordinated vari-
ations, 214; determinants of
lesser or greater power of
growth, 212, 221; biogenetic
law, 220; inability of his theory
to explain the biogenetic law,
222; opposing Nageli, 242, 243;
Polyommatus phlaeas, 284; in-
heritance in unicellular organ-
isms, 284.

Whitman, 2; the same vital ele-
ments in Infusoria and in
higher animals, 60; evolution,
105; cell formation, 136.
Wilckens; development of horns,
163.

Will, and impulse, 392; free, sub-
jective illusion of, 394; act of,
397.

Wilson, E. B.; Amphioxus, 80,
133; cell lineage in Nereis, 110
note; color designs in the ani-
mal body, 125; egg of Amphi-
oxus, 133; particulate inherit-
ance and the pangenetic theory,
144.

Wireless telegraphy, 345.

Wolff, G.; physiologic basis of
the theory of signs of degen-
eration, 76.

Wolff, J.; structure of bone, 126.

Wundt; the nervous process con-
cerned in perception and mem-
ory, 325.

Xenia, 74.

Zahn; transplantation of tissues,
123.

Zebra, stripes of the, 152.

Ziegler; researches upon cell di-
vision, 355.

Zoe, regeneration in, 140.

Zoja, Raffaelo; Medusa, 80.

Zoospores, phenomena of nervous
nature in, 30.

e
fee

eoneet
ena

Hoh
at

yy la iea

meen Heth a he
it :

I

fed Vets mses
ALAS Ay HH eh eh

donted

yr

a pony area
aaper meutaraceens

yr aunty
hah atte

it

Care ate: ctretrett At
Sabie seana a caeneted eos aereera jones

) ani
Ercetatealatetoes tate con heii
ce oishey oth

Hea Msg

Nata

5 etatstatatetstalalal CA ARGS D MMe

opened Reged Wr -§

o
ih

poe)
4 6 gay

read tamara
HAN EN

ee a

Neh een AM Neva | Potehein thee fel

ete

‘avifon
Sith

AWG oth vl
gel pe
Ail ghia

heh W
Aiet
4

eieasacauecast a

Wee tet Oe

4 8.)
Sete Ne talg dala tewcar yey vencwon Roecwdbehpeves
Habe Pos tppereh ry bran tibet rarely

Tatardtut ted estab et neat enesse

ry 4. sn of ee
eae ata ney Racy casen i

seeyipaseany

4

ty

slicalaty ctatntacatersey ane wetotsciear es
seers

Garcecheee eh ahs PA

F-sctet
itieaticetatnce ys

Fee 4-en-Pe

i,

ait 4

a7
anaes
nich fee ue hel
Hen tained td
argh stol

ri

Ne SHED HA 4)
iittala
i ie the

‘

Weertehohok Sabet= | -8 WN AeBed hHa N= Well: GoTo

cathe

Spa Ay

ope

Cy

pF

2a iyaieg
ais

coeeeven
ree

redbeatat. feet
fet hr

ibe

2 Bi 14.9:
ee ee ee ree ata)
tied ;

hing teareer near ee ert a Eh beraia
reoatalp Caen cit

ae

AEE «
9 he mt of aK el Nae
a sl

ecatgttly
ete ad Sani g oreo

paerirnt a rn ub relrnes

ie

Lh
Th
a oats

neh

Eee

ut
Hele eis
ie

Pre ee
=e

a

i

epee

C=
Webeaestt
taht cz

BT cele pM srt

ite,
neinap eh

menage 8

ada

ieeayewanae’h
Dae

if

unis
Beaters

eyo
obe toeteh ew
Ce ets
Citeeeteen ean

ee
rua
Se
ienyncuata®
rey

w) A
ay)
Lee

abs

RR HM

hice
a

fat eel iy
yh

ia

Ba
feta

i

ni anew
tt tre (re
Ne ina aey Y
Leh iat }
Teh page

aati
Way
Nanyfet

fate ote oe
thea
p

i
dh
ik

shabu &

uN "it
aM
AnD

uy

if
bie
Baht

wig
i ie

4
stich
aida
Bia
Beh degen,
‘atnaiot

tity

ity a
Ha
cL Le
i

ial

2 th Ait
ai

4

ataun
a yteall

al
Lit}
iat

HAA
Ficus
olatanate

Hy i aa
Haas
MEH ps

ing

Tin) i]

he alata
Hine feu tga

lg litityt

puri

nf

Lyla
Aw gt ne
et fn Lint i) i
erate ie na Hie
Poet viele aM
nie

sae

Perch alate ate A illo
ROE Baie Pea tate
ma
WEN Na pe
HIKE
pall

ci HM tit, een
Wat ‘ ty

Cv pee

oF
bt

Oyhu

ae

belie
i) alone
Salita

Us
Ho ged
Mind i)

“Hed i hehneee

egneres
Gare

ee
aS

=

4
z “tes y
=r

Hi)
oF

yp

“4
Pes
re
3

=

cs

rey ty
ae Zz
atta

moe

my