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1

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AN t:XAMINAT10N

OF

WEISMANNISM

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AN ILXAMINATION

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OF

WEISMANNISM

BY

(JKOKdK JOHN KOMANKS, M.A., I.I.D.. K.R.S.

IIONOKAKV FELLOW or (iONVII.LK AND CAIIIS ( o| l.h'liR,
CAMIIKIIM.K

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PUBLISHERS NOTE.

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Several parts of this book, especially the article in rh,„*

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CONTENTS

CHAP.

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I. STATKNfKNT OF WkIsMANN's SysTFM r

Year issr. .

PACE

P TO THE

II. LATr ADDITIONS TO WeisMANN's Sv.sTEM UP To , „,
YEAR l8y2 .

28

W.I'TION

III. Weismann's Theory of IlEREniTY (1S9,) . . . s

IV. KXAMINATION OF WeISMANNS TllEOkV OF !■ V.

('890

• • • .

V. WeISMANNISM irp TO nATE(lSy.3) .

Appendix I._On Germ-pi.asm

* • • •

.. II.— On Tei.egony .

86
117

191

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PRHl^\Cli

As alrPHfly stated in the Preface to the second
edition of Darwin and after Darwin. Part I, seven
and protracted illness has hitherto prevented me from
proceeding to the puuh'cation of Part 11. It is now
more than year since I had to suspend work of
every kind, and therefore, althoiijrh at that time
Part II was almost ready for press, I have not yet been
able to write its concluding chai)tcrs. Shortly before
and during this interval Professor Weisniann has
produced his essays on Amthiviixis and The Gervi-
plasm. These works present extensive additions to,
and considerable modifications of, his previous theories
as collected together in the English translation, under
the title Essays on Heredity, VoL I. Consequently,
it has become necessary for me either to re-write the
examination of his system which I had prepared for
Part II of my own treatise, or else to leave that
examination as it stood, and to add a further chapter
dealing with those later devcloi)ments of his system
to which I have just alluded. After due reflection

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VI

Preface.

I have decided ipon the latter course, because in this
way we arc most likely to obtain a clear view of the
growth of Wcismann's elaborate structure of theories
— a view which it is almost necessary, for the purposes
of criticism, that we should obtain.

Having decided upon this point, it occurred to me
that certain advantai^cs would be gained by removing
the whole criticism from the position which it was
originally intended to occupy as a section of my
forthcoming volume on the Post-Darwinian period.
For, in con.-equcncc of the criticism having been
written at successive intervals during the last six or
eight years as Professor VVeismann's works succes-
sively appeared, it has now swelled to a bulk which
would unduly encumber the volume just mentioned,
i^gain, the growth of Professor Wcismann's system
has of late become so rapid, that if the criticism
is to keep pace with it in future, the best plan
will doubtless be the one which it is now my
intention to adopt — viz., to publish the criticism in
a separate form, and in comparatively small editions,
so that further chapters may be added with as much
celerity as Professor Wcismann may hereafter pro-
duce his successive works. Lastly, where so much
elaborate speculation and so many changes of doctrine
are concerned, it is inevitable that some misunder-
standings on the part of a critic are likely to have
arisen ; and therefore, should Professor Wcismann
deem ic worth his while to correct any such failings
on my part, tlu; pi in of publication just alluded to

Pnface.

Vll

because in this
lear view of the
ture of theories
for the purposes

occurred to me
cd by removing
1 which it was
section of my
rwinian period,
n having been
the last six or
works succcs-
o a bulk which
just mentioned.
Imann's system
f the criticism
the best plan
t is now my
le criticism in
mall editions,
with as much
lercaftcr pro-
icre so much
es of doctrine
mc misundcr-
kcly to ha\e
)r Wcismann
such failings
t alluded to

will furnish mc with the best opportunity of dealing
with whatever he may have to sa)-.

It must be understood, however, that under the
term '' W'eismannism '' I d() not inclutle any re'.creiice
to the important question with which the name of
Wcismann has been mainly associated — i.e., the

of

.d ch

ritance or non-uihcntance ot acquncd characters.

This is a question of fact, which stands to be an-
swered by the inductive methods of observation and
experiment: not by the deductive methods of general
reasoning. Of course Professor Wcismann is fully
entitled to assume a negative answer as a basis
whereon to construct his theory of the continuity of
germ-plasm ; but no amount of speculation as to what
the mechanism of heredity is likely to be if once this
assumption is granted, can even so much as tend to
prove that the assumption itself is true. Therefore,
in this "examination of Weismannism"' I intend to
restrict our attention to the elaborate system of
theories which Wcismann has reared upon his funda-
mental postulate of the non-inheritance of acquired
characters, reserving for my next volume our con-
sideration of this postulate itself

Lest, however, it should be felt that "an examina-
tion of Weismannism " m which the question of the
transmission of accpiired characters is omitted must
indeed i)rove a case of Hamlet without the Prince of
Denmark, I may be allowed to make two observations.
In the fust place, this great (juestion of fact is clearly
quite distinct from that of any theories which may be

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Prejace.

framed upon cither side of it. And, in the second
place, the question was not raised by Weismann. It
appears, indeed, from what he says, that he never
caught a glimpse of it till about ten years ago, and
that he then did so as a result of his own indei)endent
thought. Moreover, it is perfectly true that to him
belongs the great merit of having been the first to
call general attention to the subject, and so to arouse
a world-wide interest with reference to it. But to
suppose that the question was first propounded by
Weismann is merely to display a want of acquaint-
ance with the course of Darwinian thought in this
country. As far back as 1874 I had long conversa-
tions with Darwin himself upon the matter, and under
his guidance performed what I suppose are the only
systematic experiments which have ever been under-
taken with regard to it. These occupied more than
five years of almost exclusive devotion ; but, as
they all proved failures, they were never published.
Therefore I here mention them merely for the pur-
pose of showing that the idea of what is now called
a " coiitinuity of germ-plasm " was present to Dar-
win's mind as a logically possible alternative to the
one which he adopted in his theory of pangenesis — an
alternative, therefore, which he was anxious to ex-
clude by way of experimental disproof. If it be said
that no one could have been aware of this in the absence
of publication, I reply that I think it may be perceived
by any one who reads attentively his chapter on
Pangenesis. Moreover, early in the seventies his

Preface.

IX

n the second
cismann. It
hat he never
cars ago, and
I independent

that to him
I the first to

so to arouse
• it. But to
)pounded by

of acquaint-
)ught in this
ng conversa-
er, and under
are the only

been under-
d more than
on ; but, as
er published.

for the pur-
s now called
5ent to Dar-
lative to the
ngenesis — an
siious to ex-

If it be said
1 the absence

be perceived

chapter on
seventies his

cousin, Mr. Francis Galton, published a " Theory of
Heredity," which, as we shall see in the course of
the following pages, presented as distinctly as could
possibly be presented the question of the transmission
of acquired characters, and answered it in almost
exactly the same manner as Weismann did about ten
years later. Lastly, as Weismann has himself been
careful to point out, he was likewise anticipated in thi.s
matter by Jiiger (1S78), and Nussbaum and Raubcr
(1880).

For these reasons, then, I exclude this question
from the following examination of what I think we
ought to understand as distinctively '• Wcismannism."

G. J. R.

Christ Church, Oxford,
July, '89.'^

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■■■■1

1

1

AN

] EXAMINATION OF WEISMANNISM.

CHAPTER I.

Statkment of VVfcismann's System
UP TO THE Year i8(S6i.

Seeing that Professor Weismann's theory of
heredity, besides being somewhat elaborate in itself, is
presented in a series of disconnected essays, originally
published at different times, it is a matter of no small
difficulty to gather from the present collection of
them a complete view of the system as a whole.
Therefore I propose to give a brief sketch of his
several cognate theories, arranged in a manner
calculated to show their logical connexion one with
another. And, in order also to show the relation in
which his resulting theory of hcredi.y stands to what
has hitherto been the more usual way of regarding
the facts, I will begin by furnishing a similarly con-
densed accoii. of Mr. Darwin's theory upon the
subject. It will be observed that these two theories
constitute the logical extremes of explanatory thought •
and therefore it may be said, in a general way, that

' Considerable portions of this chapter have already appeared as an
article .„ th. Confe„,j,orary /Review for May. iSyo. Mv tlanks are due
to the editor for kindly allowing n>e to reproduce them L

TT

^

, t

I <: * f

a /In Exauiination of IVcisiiianmsin.

all other modern theories of heredity — such as those of
Spencer, H.ickel, Elsberg, Galton, Niigeli, His, Brooks,
Hertvvig. and De Vries — occupy positions more or less
intermediate between these two extremes. Therefore,
also, we need not wait to consider these intermediate
theories ^

When closely analyzed, Mr. Darwin's theory — or
the " provisional hypothesis of Pangenesis " — will
be found to embody aUogethcr seven assumptions,
namely : —

1. That all the component cells of a multicellular
organism throw off inconceivably minute germs, or
" gemmules," which are then dispersed throughout the
whole system.

2. That these gemmules, when so dispersed and
supplied with proper nutriment, multiply by self-
dnnsipn, and, under suitable conditions, are capable of
developing into physiological cells like those from
which they were originally and severally derived.

3. That, while still in this gemmular condition,
these cell-seeds have for one another a mutual affinity,
which leads to their being collected from all parts of
the system by the reproductive glands of the organ-
isHT; and that, when so collected, they go to con-
stitute the essential material of the sexual elemenfs —

* Til as far ns these sundry tbcorics of heredity are not more or less
intermediate between those of I arwin and Weismann, the differences
have reference cither to points of comparative detail, or else to the
introduction of ideas derived from chemistry and physics — whereby it
is sought to show that the jirinciples of chemical combination and. of
rhythmic vibration may have a more or less considerable share, in the
matter. For my own j)art I do not see that the introduction of such
ideas has been of any avail in lielpinp — even hypothetically — to explain
the phenomena of heredity; and therefore I do not deem it worth our
.vhilc to consider them.

m

msm.

Statement of Weismanns System (1886). 3

:h as those of
His, Brooks,
more or less
. Therefore,
intermediate

> theory — or
;nesis " — will
assumptions,

multicellular
te germs, or
roughout the

ispersed and
ply by self-
ire capable of
those from
derived,
ir condition,
utual affinity,
all parts of
the organ -
go to con-
elemenfs —

lot more or less
the differences
, or else to the
sics — whereby it
ibination and. of
ble share, in the
duction of such
ally — to explain
em it worth our

■1
•I

"!

ova and spermatozoa being thus aggregated packets
of gemmules, which have emanated from all the cells
of all the tissues of the organisrn.

4. That the development of a new organism, out of
the fusion of two such packets of gemmules, is due to
a summation of all the developments of some of the
gemmules which these two packets contain.

5. That ajarge proportional number of the gem-
mules in each packet, however, fail to deyclop, and
are then transmitted in a dormant state to future
generations, in any of which they may be developed
subsequently — thus giving rise to the phenomena of
reversion or atavism.

6. That in all cases the development of gemmules
into the form of their parent cells depends on their
suitable union with other partially developed gem-
mules, which precede them in the regular course of
growth.

7. That gemmules are thrown off by all physio-
logical cells, not only during the adult state of the
organism, but during all stages of its development.
Or, in other words, that the production of these cell-
seeds depends upon the adult condition of parent cells :
not upon that of the multicellular organism as a
whole.

At first sight it may well appear that we have
here a very formidable array of assumptions. But
Darwin ably argues in favour of each of them by
pointing to well-known analogies, drawn from the
vital processes of living cells both in the protozoa
and metazoa. For example, it is already a well-
recognized doctrine of physiology that each cell of
a metazoon, or multicellular organism, thowgh to

B 2

f1

rf^Tf-

''1

, )

4 An Examination of Weis?nannism.

a lar^Tc extent dependent on others, is likewise to
a certain extent independent or autonomous, and has
the power of multiplying by self-division. Therefore,
as it is certain that the sexual elements (and also buds
of all descriptions) include formative material of some
kind, the first assumption — or that which supposes such
formative matter to be particulate — is certainly not
a gratuitous assumption.

Again, the second assumption — viz., that this par-
ticulate and formative material is dispersed throughout
all the tissues of the organism — is sustained by the fact
that, both in certain plants and in certain invertebratcd
animals, a severed portion of the organism will develop
into an entire organism similar to that from which it
was derived, as, for example, is the case with a leaf of
Begonia, and with portions cut from certain inver-
tebratcd arimals, such as sea-anemones, jelly-fish, &c.
This well-known fact in itself seems enough to prove
that the formative material in question must certainly
admit, at all events in many cases, of being distributed
throughout all the tissues of living organisms.

The third assumption — or that which supposes
the formative material to be especially aggregated in
the sexual elements — is not so much an assumption
as a statement of obvious fact ; while the fourth, fifth,
sixth, .nd seventh assumptions all folloAv deductively
from their predecessors. In other words, if the first
and second assumptions be granted, and if the theory
is to comprise all the facts of heredity, then the
remaining five assumptions are bound to follow.

To the probable objection that the supposed gem-
mules must be of a size impossibly minute — seeing
that thousands of millions of them would have to

Statevjcnt of Weismanns System (1886). 5

\ by the fact
nvertebratcd
will develop
rom which it
vith a leaf of
ertain inver-
iclly-fish, &c.
Ligh to prove
lUst certainly
distributed
sms.

;h supposes

ggregated in

assumption

fourth, fifth,

deductively

;, if the first

f the theory

y, then the

ollow.

)poscd gem-
mte — seeing
uld have to

be packed into a single ovum or spermatozoon —
Darwin opposes a calculation that a cube_of_glass or
water, having only one ten-thousandth of an incb_tQ
a side, contaTiis" somewhere between sixteen and a
hundred" and thirty-one billions of molccuJcs. Again,
as touching the supposed power of multiplication on
the part of his gemmulcs, he alludes to the fact
that infectious material of all kinds exhibits a ratio
of increase quite as great as any that his theory
requires to attribute to gemrnulcs. Furthermore, with
respect to the elective affinity of gcmmules, he
remarks that " in all ordinary cases of sexual repro-
duction, the male and female elements certainly have
an elective affinity for each other " : of the ten
thousand species of Coviposifac, for example, " there
can be no doubt that if the pollen of all these
species could be simultaneously placed on the stigma
ofany one species, this one would elect, with unerring
certainty, its own pollen."
"^uch, in brief outline, is Mr. Darwin's theory of
Pangenesis.

Professor Weismann's theory of Germ-plasm is
fundamentally based upon the great distinction,
in respect of their transmissibility, between char-
acters that are congenital and characters that are
acquired. By a congenital character is meant any
individual peculiarity," whether structural or mental,
with wHicK' the individual is born. By an acquired
cHai-acter is meant any peculiarity which the individual
may subsequently develop in consequence of its own
individual experience. For example, a man may be
born with sonie malformation of one of his fingers ; or
he may subsequently acquire such a malformation as

-rwrr

f -1

■Hi:

6 An Examination of Weismannism.

the result of accident or disease. Now, in the former
case — i.e., in that where the malformation is con-
genital—it is extremely probable that the peculiarity
will be transmitted to his children ; while in the latter
case — i.e., where the malformation is subsequently
acquired — it is virtually certain that it will not be
transmitted to his children. And this great difiference
between the transmissibility of characters that are
congenital and characters that are acquired extends
universally as a general Ir.w throughout the vegetable
as well as the animal kingdom, and in the province of
mental as in that of bodily organization. Of course
this gengrgl hiw has always been well known, and
more or less fully recognized by all modern physi-
ologists and medical men- I^ut before the subject
was taken up by Professor Weismann, it was generally
supposed that the difference in question was one of
degree, not one of kind. In other words, it was
assumed that acquired characters, although not so
fully — and therefore not so certainly — inherited as
congenital characters, nevertheless were inherited in
some lesser degree ; so that if the same character
continued to be developed successively in a number
of sequent generations, what was at first only a slight
tendency to be inherited would become by summation
a more and more pronounced tendency, till eventually
the acquired character might be as strongly inherited
as any other character which was ab initio congeixital.
Now it is the validity of this assumption that is
challenged by Professor Weismann. He says there is
no evidence of any acquired characters being in any
degree inherited ; and, therefore, that in this important
respect they may be held to differ from congenital

Statement of Weismanns System (1886). 7

characters in kind. On the supposition that they do
thus difi'er in kind, he furnishes a very attractive
theory of heredity, which serves at once to explain
the difference, and to represent it as a matter of
physiolofjical impossibility that any acquired char-
acter can, under any circumstances whatsoever, be
transmitted to progeny.

But, in order fully to comprehend this theory, it is
desirable first of all to explain Professor VV'eismann's
views upon certain other topics which are intimately
connected with — and, indeed, logically sequent upon —
the use to which he puts the distinction just men-
tioned.

Starting from the fact that unicellular organisms ,
multiply by fission and gemmation, he argues that,^,^^/^».j/^
aboriginally and potentially, life is immortal. For 0

when a protozoon divides itself into two more or less
equal parts by fission, and each of the two halves
thereupon grows into another protozoon, it does not
appear that there has been any death on the part of
the living material involved ; and inasmuch as this
process of fission goes on continuously from generation
to generation, there is seemingly never any death
on the part of such protoplasmic material, although
there is a continuous addition to it as the numbers
of individuals increase. Similarly, in the case of
gemmation, when a protozoon parts with a small
portion of its living material in the form of a bud,
this portion does not die, but devclo[)s into a new
individual ; and, therefore, the process is exactly
analogous to that of fission, save that a small
instead of a large part of the parent substance is
involved. Now, if life be thus immortal in the

■fm*

i II'

i i

8 y/;/ Examination of irdsnianuism.

case of unicellular organisms, why should it have
ceased to be so in the case of multicellular? Weis-
mann's answer is, that all the multicellular orj^anisnis
propagate themselves, not exclusively by fission or
gemmation, but by sexual fertilization, where the
condition to a new organism arising is that minute
and specialized portions of two parent organisius
should fuse together. Now, it is evident that with
this change in the method of propagation, serious
disadvantage would accrue to any species if its sexual
individuals were to continue to be immortal ; for in
that case every species which multiplies by sexual
methods would in time become composed of indi-
viduals broken down and decrepit through the results
of accident and disease — always operating and ever
accumulating throughout the course of their immortal
lives. Consequently, as soon as i^cxual methods of
propagation superseded the more primitive a-sexual
methods, it became desirable in the interests of the
sexually-propagating species that their constituent
individuals should cease to be immortal, so that the
species should always be recuperated by fresh, young,
and well-formed representatives. Consequently, also,
natural selection would speedily see to it that all
sexually-propagating species should become deprived
of the aboriginal endowment of immorality, with the
result that death is now universal among all the
individuals of such species — that is to say, among
all the metazoa and metaphyta. Nevertheless, it is
to be remembered that this destiny extends only to
the parts of the individual other than the contents
of those specialized cells which constitute the repro-
ductive elements. For although in each individual

Ill sin.

Statement of IWisnuinns System (1886). 9

lid it liave
lar? Wcis-
r organisms
y fission or
where the
tliat minute
t organisms
It that with
Lion, serious
if its sexual
irtal ; for in
s by sexual
scd of indi-
h the results
ng and ever
eir immortal
methods of
ive a-scxual
rests of the
constituent
so that the
resh, younf:^,
uently, also,
it that all
me deprived
ty, with the
long all the
say, among
thcless, it is
nds only to
he contents
e the repro-
h individual

metazoon or metaphyton an innumerable number of
these specialized cells arc destined to perish during
the life, or with the death, of the organism to which
they belong, this is only due to the accident, so to
speak, of their contents not h.iving met with their
complements in the opposite sex : it (^K^^-f, not belong
to their essential nature that they shoultl pirish, seeing
that those which do happen to meet with their com-
plements in the opposite sex help to form a new living
individual, and so on through successive generations
ad infinitum. Therefore the reproductive elements
of the meta/.oa and nutaphyta are in this respect
precisely analogous to the protozqa : potentially, or in
their own nature, they arc immortal ; andMJke^thc
protozoa, if they die. their death is an accident duc_to
unfavourable circumstar. "es. But the case Js cpjite
different with a^' the other parts of a multicellular
organism. Mere, no matter how favourable the cir-
cumstances may be, every cell contains within itself,
or in its very nature, the eventual doom of death.
Thus, of the mctazoa and metaphyta it is the
" germ-plasms " alone that retain their primitive
endowment of everlasting life, passed on continuously
through generation after generation of successively
perishing organisms.

So far, it is contended, we are dealing with matters
of fact. It must be taker, as true that the protoplasm
of the unicellular organisms, and the germ-plasm of the
multicellular organisms, has been continuous through
the time since life first appeared upon this earth ; and
although large quantities of each are perpetually dying
through being exposed to conditions unfa\ourable to
life, this, as Weismann presents the matter, is quite

7T

"ir^

' ■ • ■ ^

lo An Examination of Weismannism.

a dififerent case from that of all the othe/ constituent
parts of multicellular organisms, which contain within
themselves the doom of death. Furthermore, it appears
extremely probable that this doom of death has been
brought about by natural selection for the reasons
assigned by Weismann— namely, because it is for the
benefit of all species which perpetuate themselves by
sexual methods, that their constituent individuals
should not live longer than is necessary for the sake
of orginating the next generation, and fairly starting
it in its own struggle for existence. For Weismann
has shown, by a somewhat laborious though still
largely imperfect research, that there is throughout
all the metazoa a general correlation between the
natural lifetime of individuals composing any given
species and the age at which they reach maturity,
or first become capable of procreation. This general
correlation, however, is somewhat modified by the
time during which progeny are dependent upon their
parents for support and protection. Nevertheless,
it is evident that this fact tends rather to confirm
the view that expcctvation of life on the part of
individuals has in all cases been determined with
strict reference to the requirements of propagation,
if under propagation we include the rearing as well
as the production of offspring. I may observe in
passing that I do not think this general law can
be found to apply to plants in nearly so close
a manner as Weismann has shown it to apply to
animals ; but, leaving this consideration aside, I think
that Weismann has made out a good case in favour
of such a general law with regard to animals*.

* Sue Appendix.

j^i

^r/'

Statement of Wcisinanns System (1886). 11

constituent
itain within
e, it appears
th has been
the reasons
it is for the
jmselves by
individuals
or the sake
iriy starting
* Weismann
though still
throughout
jetvveen the
I any given
:h maturity,
rhis general
fied by the
t upon their
evertheless,
to confirm
he part of
mined with
propagation,
ing as well
observe in
al law can
y so close
o apply to
5ide, I think
e in favour
mals ^.

We have come, th^n, to these results. Proto-
plasm v;as originally immortal, barring accidents ;
and it still continues to be immortal in the case of
unicellular organisms which propagate a-sexually.
But in the case of all multicellular organisms, which
propagate sexually, natural selection has reduced
the term of life within the smallest limits that in
each given case are compatible with the performance
of the sexual act and the subsequent rearing of ])ro-
geny — reserving, however, the original endownsent
of immortality for the germinal elements, whereby
a contimmm of life has been secured from the earliest
appearance of life until the present day.

Now, in view of these results the question arises, —
Why should the sexual methods of propagation have
become so general, if their effect has been that of
determining the necessary death of all individuals
presenting them ? Why, in the course of organic
evolution, should these newer methods have been
imposed on all the higher organisms, when the conse-
quence is that all these higher organisms must pay
for the innovation with tlieir lives? Weismann's
answer to this question is as inteiesting and ingenious
as all that has gone before. Seeing that sexual pro-
pagation is so general as to be practically universal
among multicellular organisms, it is obvious that in
some way or another it must have had a most important
part to play in the general scheme of organic evolution.
What, then, is the part that it does play? What is
its raison d'etre ? Briefly, according to Weismann, its
function is j^iat of furmshiiig congenital variations to
the jever;^atchful agency of natural selection,^ in order
that natural selection may always prcseive the most

J

^r

> < ill
i ill

12 An Examination of Weismannism,

favourable, and pass them on to the next generation
by heredity. That sexual propagation is well calcu-
lated to furnish congenital variations may easily be
rendered apparent. We have only to remember that
at each union there is a mixture of two sets of
germinal elements ; that each of these was in turn
the product of two other sets in the preceding
generation, and so backwards ad infinitum in an
ever doubling ratio. Remembering this, it follows
that the germinal elements of no one member, of
a s£ecies can ever be the same as those of any. other
member born of different parents ; on the contrary,
while both are enormously complex products, each
has had a different ancestral history, such that
while one presents the congenital admixtures of
thousands of individuals in one line of descent, the
other presents similar admixtures of thousands of
other individuals in a different line of descent. Con-
sequently, when in any sexual union two of these
enormously complex germinal elements fuse together,
and constitute a new individual out of their joint
endowments, it is perfectly certain that that individual
cannot be exactly like any other individual of the
same species which has been born of different parents.
The chances must be infinity to one aga'nst any single
mass of germ-plasm being exactly like any other mass
of germ-plasm ; while any amount of latitude as to
difference is allowed, up to the point at which the
difference becomes too pronounced to satisfy the
conditions of fertilization — in which case, of course,
no new individual is born. Hence, theoretically, we
have here a sufficient cause for all individual variations
of a congenital kind that can possibly occur within

msm.

Slat' men t of Weistnaitns Sys/e f u (iSS6). 13

t generation

( well caicu-

y easily be

nember that

two sets of

was in turn

e precedinij

i/?itn in an

3, it follows

member, of

)f any. other

le contrary,

iducts, each

such that

mixtures of

descent, the

liousands of

cent. Con-

vo of these

ise together,

their joint

it individual

dual of the

ent parents.

t any single

other mass

titude as to

which the

satisfy the

, of course,

etically, we

il variations

>ccur within

the limits of fertility, and, therefore, that can ever
become actual in living organisms. In point of fact,
Wcismann believes — or, at any rate, provisionally
maintains — that this is the sole .and only causQ of
variations that are congenital, and therefore (according
to his views) transmissible by heredity. Now, whether
or not he is right as regards these latter points, I
think there can be n^3_^uestion that sexual propagation
is, at all events, one of the rnain causes of congenital
variation ; and seeing of what enormous importance
congenital variation m.ust always nave been in
supplying material for the operation of natural se-
lection, we appear to have found a most satisfactory
answer to our question, — Why has sexual propagation
become so universal among all the higher plants and
animals? IthcUL-bxiCQnie so because it is thus shown • ^^^
to have been the condition to producing congenital/^ / ///>
variations, which in turn constitute one of the primary ^ 1 ^^
conditions to the working of natural selection.

Having got thus far, I should like to make two or
three subsidiary remarks. In the first place, it ought
to be observed that this theory touching the causes of
congenital variations was not originally propounded
bj^Professor Weismann, but occurs in the writings of
several previous authors, and is expressly alluded to
by Darwin ^ Nevertheless, it occupies so prominent
a place in Weismann's system of theories, and has by
him been wrought up so much more elaborately than
by any of his predecessors, that we are entitled to
regard it as, par excellence, the Weismannian theory of
variation. In^the next place, it ought to be observed
that Weismann is careful t- guard against^tlic
• E.g., Variation, &c., vol. i. pp. 197, 398; vol. ii. pp. 237, 252.

t4U^ tv^ Cf

I' r (■

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• • •

ft • *

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III

14 An Examination of Weismannism.

seductive fallacy of attributing the origin of sexual
propagation to the agency of natural selection. Great
as the benefit of this newer mode of propagation must
have been to the species presenting it, the benefit
cannot have been conferred by natural selection,
seeing that the benefit arose from the fact of the
new method furnishing material to the operation
of natural selection, and therefore constituting the
condition to the agency of natural selection having
been called into exiGiance at all. Or, in other
words, we cannot attribute to natural selection
the origin of sexual reproduction without involv-
ing ourselves in the absurdity of supposing natural
selection to have originated the conditions of its
own activity '. What the causes may have been

' Since this chapter was written and sent as a contribution to the
Contemporary Revic^v, Professor Weismann has published in Nature
(Feb. 6, 1890) an elaborate answer to a criticism of his theory by
Professor Vines (Oct. 24, 1889). In the course of this answer Professor
NVeismann saysthat he </<mj attribute the origin of sexual reproduction
to natural selection. This directly contradicts what he says in his
Essays ; aiu!, for the reasons given in the text, appears to me an illogical
departure from his previously logical attitude. I herewith appenil
quotations, in order to reveal the contradiction.

" But when I maintain that the meaning of sexual reproduction is to
render possible tiie transformation of the higher organisms by means of
natural selection, such a statement is not equivalent to the assertion that
sexual reproduction originally came into existence in order to achieve
this end. The effects which are now protiuced by sexual reproduction
did not constitute the causes which led to its first appearance. Sexual
reproduction came into existence before it could lead to hereditary
individual variability [i.e., to the possibility of natural selection]. Its
first appearance must, therefore, have had some other cause [than
natural selection] ; but the nature of this cause can hardly be determined
with any degree of certainty or precision from the facts with which we
are at present acciuainted." — Essay on the Signijicance of Sexual Re-
production in the Theory of Natural Selection. English Translation,
pp. 2S1 282.

" I am still of opinion that the origin of sexual reproduction depends

i

I

■9

ism.

Statement of Weismami s System (1886). 15

I of sexual
ion. Great
gation must
the benefit
1 selection,
fact of the
I operation
tituting the
:tion having
r, in other
al selection
lout involv-
sing natural
tions of its
have been

itribution to the
ihecl in Nature
f his theory by
insvver Professor
xsX reproduction
he says in his
me an illo{;ical
lerewith append

production is to
sms by means of
le assertion that
jrder to achieve
ual reproduction

arance. Sexual
,d to hereditary

selection]. Its
her cause [than
ly be determined

s with which we
<:e of Sexual Ke-

isli Translation,

duction depends

which originally led to sexual reproduction is at
present a matter that awaits suggestion by way of
hypothesis; and, therefore, it now only remains to add
that the general structure of Professor Weismann's
system of hypotheses leads to this curious result —
namely, that the otherwise ubiquitous and (as he
supposes) exclusive dominion of natural selection
stops short at the protozoa, over which it cannot
exercise any inHucnce at all. For if natural selection
depends for its activity on the occurrence of congenital
vanationSj and if congenital variations depend for
their occurrence on sexual modes of reproduction, it
follows that no organisms which propagate by any
other modes can present congenital variations, or thus
become subject to the sway of natural selection.
And inasmuch as Weismann believes that such is the
case with all the protozoa, as well as with all
parthenogenctic organisms he does not hesitate to
accept the necessary conclusion that in these cases
natural selection is without any jurisdiction. How,
then, does he account for individual variations in
the protozoa ? And, still more, how does he ac-
count for the origin of their innumerable species ?
He accounts for both these things by the direct
action of external conditions of life. In other words,
so far as the unicellular organisms are concerned,
Weismann IF rigidly and" unconditionally an advocate

on the advantage which it afTdrds to the operation of natural selection.
.... Sexual rej)roduction lias arisen by and for natural selcctinti as the
sole means by which individual variations can be united and combined
in every possible proportion." — Nature, vol. xli. p. 322.

How such contradictory statements can be reconciled I do not
perceive; but they furnish a ^ood example of the extreme laxity witii
vvliich the term '• natural selection " is Uicd by ultra-Darwinians.

^iiTir

f

i

• • t f

1 •

i

■!f!

m

'Mi

III! I

;.'ii

1 6 An Examination of Weismannism.

of the theory of Lamarck — just as much as in the case
of all the multicellular organisir, i he is ric^idly and un-
conditionally an opponent of that theory. Nevertheless,
there is here no inconsistency : on the contrary, it is
consistency with the logical requirements of his theory
that leads to this sharp partitioning of the unicellular
from the multicellular organisms with respect to the
causes of their evolution. For, according to his view,
the conditions of propagation among the unicellular
organisms are such that parent and offspring are one
and the same thing ; " the child is a part, and usually
a half, of its parent." Therefore, if the parent has
been in any way modified by the action of external
conditions, it is inevitable that the child should, from
the moment of its birth (i.e., fissiparous separation),
be siniilarly modified ; and if the modifying influences
continue in the same lines for a sufficient length of
time, • the resulting change of type may become
sufficiently pronounced to constitute a new species,
genus, &c. But in the case of the multicellular or
sexual organisms, the child is not thus merely a
severed moiety of its parent ; it is the result of the
fusion of two highly specialized and extremely miinute
particles of each of two parents. Therefore, whatever
may be thought touching the validity of Weismann's
deduction that in no case can any modification induced
by external conditions on these parents be trans-
mitted to their progeny, at least we must recognize
the validity of the distinction which he draws between
the facility with which such transmission must take
place in the unicellular organisms, as compared with
the difficulty — or, as he believes, the impossibility —
of its doing so in the multicellular.

%

'A ■
I

-I

*

lit

nism.

IS in the case
^idlyand un-
Nevertheless,
:ontrary, it is
of his theory
le unicellular
espect to the
T to his view,
le unicellular
3ring are one
, and usually
e parent has
n of external
should, from
5 separation),
ing influences
ent length of
may become

new species,
ilticellular or

us merely a

result of the
emely minute
ore, whatever
f Weismann's
;ation induced
its be trans-
lust recognize

raws between
on must take
om pared with
npossibility —

Statement of IVeisuianti s System (1886). 17

We are now in a position fully to understand Pro-
fessor Weismann's theory of heredity in all its bearings.
Briefly stated, it is as follows. The whole organiza-
tion of any jnulticelkilar organisnL.js .CQOipiQ/^ed

of two entirely different kinds of cclJs — namely, the
germ-cells, or those which have to do with repro-
duction, and the somatic-cells, or those which go to
constitute all the other parts of the organism. Now,
the somatic-cells, in their aggregations as tissues and
organs, may be modified in numberless ways by the
direct action of the_enyirqnmcnt, as well as by special
habits Formed during the individual hfetime of the
organism. 15ut although the modifications thus in-
duced may be, and generally are, adaptive — such as
the increased musculanty;_caused by the use of muscles,
" practice making perfect " where neural adjustments
are concerned, and so on, — in no case can these so-
called acquired, or " somatogenetic," characters exer-
cise any influence upon the germ-cells, such that
they should reappear in the next generation as con-
genital, or •' blastogenetic."' characters. For, according
to the theory, the germ-cells as to their germinal
contents differ in kind from the somatic-cells^_and
have no other connexion or dependence upon them
than that of deriving from them their food and
lodging. So much for the somatic-cells.

Turning now to the Gfcrm-cells, these are the re-
ceptacles of what Weismann calls the germ-plasm ;
alid tjiis it is that he supposes to differ in kind
from all the other constituent elements of the
organism. For the germ-plasm he believes to have
had its origin in the unicellular organisms, and to
have been handed down from them in one continuous

C

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.11

• 11

;M';i

1 8 An Examination of Wcisniannistn.

stream through all successive generations of multi-
cellular organisms. Thus, for example, suppose that
we take a certain quanttun of germ-plasm as this
occurs in any individual organism of to-day. A
minute portion of this germ-plasm, when mixed
with a similarly minute portion from another in-
dividual, goes to form a new individual. But, in
doing so, only a portion of this minute portion is
consumed ; tKe' residue is stored up in the germinal
cells of the new individual, in order to secure that
continuity of the germ-plasm which Weismann
assumes as the necessary basis of his whole theory.
Furthermore, he assumes that this overplus portion of
germ-plasm, which is .so handed over to the custody
of the new individual, is there capable of growth or
multiplication at the expense of the nutrient materials
which are supplied to it by the new soma in which
it finds itself located ; while in thus growing, or
multiplying, it faithfully retains its highly complex
structure, so that in no one minute particular does
any part of a many thousand-fold increase differ, as
to its ancestral characters, from that inconceivably
smaTT overplus which was first of all entrusted to the
emBryo by its parents. Therefore one might re-
present the germ-plasm by the metaphor of a yeast-
plant, a single particle of which may be put into a vat
of nutrient fluid : there it lives and grows upon the
nutriment supplied, so that a new particle may next
be taken to impregnate another vat, and so on ad
infiniUim. Here the successive vats would represent
successive generations of progeny; but, to make the
metaphor complete, one would have to suppose that
in each case the yeast-cell was required to begin by

Statoncnt of lVci3})iadns System (icSSo). 19

makincf its own vat of nutrient material, and that it
was only the residual portion of tlie cell whieh was
afterwards able to grow and multiply. But althouijjh
the metaphor is thus necessarily a clumsy one, it
may serve to emphasize the all-important feature of
Weismann's theory — namely, the ahiiost absohite
independence of the germ-plasm. For. just as the
properties of the yeast-plant would be in no way
affected by anything that might happen to the vat,
short of its being broken up or having its malt
impaired, so, according to Weismann, the properties
of the germ- plasm cannot be affected by anything
that may happen to its containing soma, short of the
soma being destroyed or having its nutritive functions
disordered.

Such being the rc'ations that are supposed to
obtain between the soma and its germ-plasm, we have
next to observe what is supposed to happen when,
in the course of evolution, some modification of the
ancestral form of the soma is required in order to
adapt it to some change on the part of its environ-
ment. In other words, we have to consider Weis-
mann's views on the modus operandi of adaptive
development, with its result in the origination of new
species.

Seeing that, according to the theory, it is only con-
genital variations which can be inherited, all variations
subsequently acquired by the intercourse of individuals
with their environment, however beneficial such
variations may be to these indivaduals, are ruled out
as regards the species. Not falling within the
province of heredity, they are blocked off in the first
generation, and therefore present no significance at

c a '

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6VVt,*+V1^^4^<

20 y^« Examination of Wcismannism.

all in the process of organic evolution. No matter
how many generations of eagles, for instance, may have
used their wings for purposes of flight ; and no matter
how great an increase of muscularity, of endurance, and
of skill, may thus have been secured to each genera-
tion of eagles as the result of individual exercise ;
all these advantages are entirely lost to progeny, and
young eagles have ever to begin their lives with no
more benefit bequeathed by the activity of their
ancestors than if those ancestors had all been barn-
door fowls. The only material which is of any count
as regards the species, or with reference to the piOgess
of evolution, are fortuitous variations of the congenital
k[nd. Among all the numberless congenital varia-
tions, within narrow limits, which are perpetually
occurring in each generation of eagles, some will have
reference to the wings ; and although these will be
fortuitous, or occurring indiscriminately in all direc-
tions, a few of them will now and then be in the
direction of increased muscularity, others in the
direction of increased endurance, others in the direc-
tion of increased skill, and so on. Now each of these
fortuitous variations, which happens also to be a
beneficial variation, will be favoured by natural
selection ; and, because it likewise happens to be a
congenital variation, will be perpetuated by heredity.
InTthe course of time, other congenital variations will
happen to arise in the same directions ; these will be
added by natural selection to the advantage already
gained, and so on, till, after hundreds and thousands of
generations, the wings of eagles have become evolved
into the marvellous structures which they now present.
Such being the theory of natural selection when

State^ncnt of Wcismanns System (1886). 21

stripped of all remnants of so-called Lamarckiaii
principles, we have next to consider what the theory
means in its relation to germ-plasm. For, as before
explained, congenital variations are supposed by
VVeismann to be due to new combinations taking
place in the germ-plasm as a result of the union in
every act of fertilisation of two complex hereditary
histories. Well, if congenital variations are thus
nothing more than variations of germ-plasm "writ
large " in the organism which is developed out of the
plasm, it follows that natural selection is really
at work upon these variations of the plasm. For,
although it is proximately at work on the congenital
variations of organisms after birth, it is ultimately,
and through them, at work upon the variations of
germ-plasm out of which the organisms arise. In
other words, natural selection, in picking out of each
generation those individual organisms which are by
their congenital characters best suited to their sur-
rounding conditions of life, is thereby picking out
those peculiar combinations or variations of germ-
plasm, which, when expanded into a resulting organism,
give that organism the best chance in its struggle for
existence. And, inasmuch as a certain overplus of
this peculiar combination of germ-plasm is entrusted to
that organism for bequeathing to the next generation,
this to the next, and so on, it follows that natural
selection is all the while conserving that originally
peculiar combination of germ-plasm, until it happens
to meet with some other mass of germ-plasm by mixing
with which it may still further improve upon its original
peculiarity, when, other things equal, natural selection
will seize upon this improvement to perpetuate,

• r '.

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I '

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1 1

J'iil : i

22 -//;/ Exanii nation of Wcismannism.

as in the prcviou.s case. So that, on the whoio, we may
say that natural selection is ever waiting and watch-
in<T for such combinations of germ-plasm as will give
the resulting organisms the best possible chance in
their struggle for existence ; while, at the same time,
it is remorselessly destroying all those combinations
of germ-plasm which are handed over to the custody of
organisms not so well fitted to their conditions oflife.

It only remains to add that, according to VVeis-
mann's theory in its strictly logical form, combinations
of germ-plasm when once effected are so stable that
they would never alter except as a result of entering
into new combinations. In other words, no external
influences or internal processes can ever change
the hereditary nature of any particular mixture of
germ-plasm, save and except its admixture with
some other germ-plasm, which, being of a nature
equally stable, goes to unite with the fn-st in equal
proportions as regards hereditary ch. -acter. So that
really it would be more correct to say i> "- any given
mass of germ-plasm docs not change eveii "hen it
is mixed with some other mass — any more, lor in-
stance, than a handful of sand can be said to change
when it is mixed with a handful of clay.

Consequently, wc arrive at this •.uriou'j result.
No matter how many generations of organisms there
nay have been, and therefore no ni:itl\jr how many
combinations of germ-plasm may have taken place
to give rise to an existing population, each existing
unit of germ-plasni must have remaincd^of ihij—same
essential nature or constitution as _uhen_Jt was_first
started in its immortal career millions of years^go.
Or, reverting to our illustration of sand and clay, the

Statement of IW'isnianns System (1886). 2}^

particles of each must always remain the same, no

matter how many admixtures they may undcr<To

with particles of other materials, such as chalk, slate.

&c. Now, inasmuch as it is an essential — because

a lof^ically necessary — part of VVcismann's theory

to assume such absolute stability or unchancjcable-

ness on the part of germ-plasm, the question arises,

and has to be met. What was the origin of those

differences of character in the different rferm-plasms
, .^. . - p. r —

of multicellular organisms wliich^ first gave rise, and
still rnntinye \i:) give rise^ to congc^iital variations
by their mixture one with another ? This important
question Weismann answers by supposing that these
differences originally arose out of the dififcrcuces
in the unicellular organisms, which were the ancestors
of the primitive multicellular organisms. Now, as
before stated, different forms of unicellular organisms
are supposed to have originated as so many results of
differences in the direct action of the environment.
Consequently, according to the theory, all congenital
variations which now occur in multicellular organisms,
are really the distant results of variations that were
aboriginally induced in their unicellular ancestors by
the direct action of surrounding conditions of life.

1 think it will be well to conclude by briefly sum-
marising the main features of this elaborate theory.

Living material is essentially, or of its own nature,
imperishable; and it still continues to be so in the
case of unicellular organisms which propagate by
fission or gemmation. But as soon as these primitive
methods of propagation became, from whatever
cause, superseded by sexual it ceased to be for the
benefit of .species that their constituent individuals

f\

'i^ i

:hi:

...., -n; ,;|
• • • ■ il'

II

■i -11 1l

! I'liilj

!i4

24 ^/2 Exa7iiination of Weismannism.

should be immortal ; seeing that, if they continued
to L so, all speciesofsexually-rcproducinc^ organisms
would sooner or later have come to be composed of
broken-down and decrepit individuals. Consequently,
in all sexually-reproducing or multicellular organisms,
natural selection set to work to reduce the term ol
individual lifetimes within the narrowest liniits that
in the case of each species were compatible with thp
procreation and the rearing of progeny. Nevertheless,
in all these sexually-reproducing organisms the
primitive endowment of immortality has been re-
tained with respect to their germ-plasm, which has
thus been continuous, through numberless genera-
tions of perishing organisms, from the first origin of
sexual reproduction till the present time. Now, it
is the union of germ-plasms which is required to
reproduce new individuals of multicellular organisms
that determines congenital variations on the part of
such organisms, and thus furnishes natural selection
with the material for its work in the way of organic
evolution — work, therefore, which is impossible in
the case of unicellular organisms, where variation
can never be congenital, but always determined by
the direct action of surrounding conditions of life.
Again, as the germ-plasm of multicellular organisms
is continuous from generation to generation, and at
each impregnation gives rise to a more or less novel
set of congenital characters, natural selection, in
picking out of each generation the congenital char-
acters which are of most service to the organisms
presenting them, is really or fundamentally at work
upon those variations of the germ-plasm which in
turn give origin to these variations of organisms

Siatanent of Weis?nanns System {1886). 25

[hat we recognize as congenital. Thorefore, natural

^election has always to wait and to watch for such

variations of germ-plasm as will eventually prove

)cncficial to the individuals developed therefrom,

livho will then transmit this peculiar quality of gcrm-

)lasm to their progeny, and so on. Therefore also —

ind this is most important to remember — natural

selection as thus working becomes the one and only

:ause of organic evolution in all the multicellular

)rganisms, just as the direct action of the environ-

lent is the one and only cause of it in the case

)f all the unicellular organisms. But inasmuch as the

multicellular organisms were all in the first instance

lerived from the unicellular, and inasmuch as their

rerm-plasm is of so stable a nature that it can

icver be altered by any agencies internal or external

to the organisms presenting it, it follows that all

:ongcnital variations are the remote consequences

)f aboriginal differences on the part of unicellular

mcestors. And, lastly, it follows also that these

bongenital variations — although now so entirely in-

Idependent of external conditions of life, and even of

'activities internal to organisms themselves — were

loriginally and exclusively due to the direct action

lof such conditions on the lives of their unicellular

[ancestors ; while even at the present day no one con-

[gcnital variation can arise which is .lot ultimately

luuc to differences impressed upon the protoplasmic

[substance of the germinal elements, when the parts

of which these r re non^ composed constituted integral

[parts of the protozoc^, which were directly and differ-

[entially affected by their converse with their several

Icnvironments.

m

m^

..-iil!

c

• f t 1 1 ;i

• « t I '

• *

t • ( .

t ,

• :

I -. ■

c ■

'■ « 1 ■■■

' i ill

■i

26 ^« Examination of IVeismanuism.

Again, if for the sake of distinctness we neglect
all these far-reaching deductions from his theory ofj
heredity whereby Weismann constructs this elaborate!
theory of organic evolution, and fasten our attentionj
only upon the former, we may briefly summarize thel
fundamental difference between his theory of /ieredii)\
and Darwin's theory of heredity thus.

Darwin's theory of heredity is the theory of Pan\
genesis : it supposes that a/i parts of the organisrnj
generate anew in every individual the formative!
material which, when collected together in the germ-j
cells, constitutes the potentiality of a new organism]
and that this new organism, when developed, resembles!
its parents simply because all the formative material!
in each of the parents has been 'Caw^ generated hy^Tixm
collected from, all parts cf their respective bodies,
Weismann's theory of heredity, on the other hand, isj
the theory of the Continuity of Gervi-plasm: it supposes!
that no part of the parent organism generates atiy Ci\
the formative material which is to constitute the newj
organism ; but that, on the contrary, this material!
stands to all the rest of the body in much the samel
relation as a parasite to its host, showing a life indel
pendent of the body, save in so far as the body supplie?!
to it appropriate lodgement and nutrition ; that inj
each generation a small portion of this substance isj
told off to develop a new body to lodge and nourishj
the ever-growing and never-dying germ-plasm — this
new body, therefore, resembling its so-called parent!
body simply because it has been developed from one!
and the same mass of formative material ; and, lastly,
that this formative material, or germ-plasm, has beenj
continuous through all generations of successively

'anntsm.

ess we neglect!
I his theory of!
3 this elaboratej
1 our attention
summarize the!
sory of hen'dim

statement of Wcismanns System (i8S6). 27

[rishing bodies, which therefore stand to it \n much
same relation as annual shoots to a pcicnnial
?in : the shoots resemble one another simply
[cause they are all grown from one and the same

)ck.

m

theory of Pan-
f the organism!

the formative!
2r in the germ-
new organism;
3ped, resembles!
native material!
ncratcd by, and!
pective bodies,

other hand, isj
sm : it supposes!
merates any olj
ititute the nevj
, this material!
nuch the samel
ng a life indej
e body suppHesj
rition ; that inj
is substance ij
ge and nourish!
m-plasm — thisj
o-called parentl
Dped from one!
al ; and, lastly]
lasm, has bcenl
^f successively

H

1

■J.

.1;

i

f

c

i

1

I I

'i! ii

; •

CHAPTER II.

Later Additions to Wkismann's System
UP to the year 189a.

I HAVE now i 1 ' ed as complete a rhinn^ as |
seems desirable for i. . sent pur[)oses of Weismann'sj
theory of germ-plasm, considered both as a theory |
of heredity and as a sequent theory of organic
evolution. But before proceeding to examine this]
elaborate system as a whole, I must devote another]
chapter to a further statement of certain later
additions to — and also emendations of — the system
as it was originally propounded. These additions
and alterations have reference only to the theory of
heredity: they do not affect the theory of organic
evolution as originally deduced therefrom. More-
over they have all been due to our more recently
acquired knowledge touching the morphology and
physiology of cell-nuclei : it is for the purpose of
bringing his theory of germ-plasm into accord with
these results of later researches that Weismann has
thus modified the theory as it originally stood. For
my own part, I do not see that very much is gained
by these newer additions and modifications ; but, be
this as it may, they are certainly very complicated,
and on this account I have thought it best to devote a
separate chapter to their consideration. Furthermore,

Later Additions tip to the year 1892. 29

ertain later I

not only in the opinion of Weismann himself, but also
in that both of his friends and foes, the main qucsUon
with which_hjs_.iatcr cssays_are_conccrncd — viz.. as to
whether the nucleus of a cell is the only part of a cell
which is concerned in the phenomena of heredity — is
regarded as of fundamental importance to his entire
edifice. Hence, although I cannot myself perceive
that the indisputable importance of this question to
any speculations on the subject of heredity is of such
special or vital significance to Weismann's theory, it
becomes necessary for me to supply this further
chapter for the purpose of presenting the further
developments of his theory.

First of all, Weismann has of late years considerably
modified his original view touching the relation of
germ-cells to body-cells. For while he originally
supposed the fundamental distinction in kind to obtain
as between the whole contents of a germ-cell and the
whole contents of a somatic-cell, he now regards this
distinction as obtaining only between the nucleus of
a germ-cell and tne nucleus of a somatic-cell. In
other words, he regards the whole of a germ-cell, with
the exception of its nucleus, as resembling the whole
of any other cell, with the exception of its nucleus.
It is the nucleus of a germ-cell alone that contains
germ-plasm : all the rest of such a cell being "' nutritive,
but not formative."

This transference of the peculiar or hereditary
powers of a germ-cell from the cell as a whole to
the nucleus, necessitates certain emendations of the
original theory of germ-plasm. In particular, the
broad distinction between the whole contents of
a germ-cell as "germ-plasm,"' and the whole contents

30 An Exanmiaiion of Weisnianmsm.

.')

il

'I

: J

%•

of a somatic-cell as " somato-plasm," is now discarded;
and in its stead we have all nuclear matter (whether
of <,rcrm-cclls or somatic-cells) comprised under the one
denomination of " nucleo-plasm," in contradistinction
to all the other protoplasm of a cell, which is called
'* cytoplasm." Hence VVeismann now regards the
cytoplasm of a germ-cell as identical with the cytoplasm
of all other cells. Its function is merely that of
" nourishing- " the nucleus, while, on the other hand, it
is '• controlled " by the nucleus as to its own growth,
shape, size, and eventual division.

But it is evident that the nucleo-plasm of a germ-cell
must differ from the nucleo-plasm of a somatic-cell, in
that it not only " controls " the growth, &c. of its own
cell, but likewise presents all the additional characters
peculiar to a germ-cell. That is to say, the nucleo-
plasm of a germ-cell resembles the nucleo-plasm of
a somatic-cell in that it is nourished by, and exercises
control over, the cytoplasm of its own particular cell ;
but it differs from the nucleo-plasm of a somatic-cell
in admitting of fertilizaJou, in the capability of
reproducing an entire organism, in the endowing of
that organism with all its hereditary characters, and.
lastly, in providing for its own reproduction in the next
generation.

Thus it is evident, as Weismann puts it, that the
nucleo-plasm of a germ-cell must be of tivo kinds —
one being concerned with the formation and control of
the germ-cell only, while the other has to do with the
construction of an entire future organism, and the sub-
sequent reproduction thereof. But not only so; for at
each stage in the construction of this future organism,
all the somatic-cells, as successively constructed, must

Later Additions np to the year 1892. ;^i

likewise contain nucleo-plasm in two kinds — one havin^^
to do only with the formation and control of its own
individual cell, and t'lie other havini^ to do with the
formation of the future somatic-cells, which will have
to follow in the course of ontogeny. Therefore, in
order to desit^nate this second kind of nucleo-pkism
(whether in a germ-cell or a somatic-cell) VVeismann
borrows from Niigeli the term " idio-plasm \" or rather,
I should say, he uses the term " nucleo-plasm " when
he is speaking of 11 the contents of a nucleus indis-
criminately, while he uses~nTeTcFm " idio^jilasm " when
he has occasion to speak specially of the two kinds of
nucleo-plasm now before us.

H nee, the nuclear contents fnucleo-plasm) of every
cell, whether germinal or somatic, present two sub-
stances, which we may, in the absence of any better
terms supplied by Wcismann himself, respectively
designate "idio-plasm- A" and ''idio-plasm-B." Idio-
l)lasm-A is the substance which has to do only with
the formation and control of the individual cell in
which it resides, like a mollusc in its shell. Idio-
plasm-B is the substance out of which future cells
are to be formed and controlled, when in due course
either of ontogeny or phylogeny this idio-plasm-]^
becomes converted into idio-plasm-A, — i.e., into each
subsequently developing tissue or organism, as the case
may be. I say ontogeny or phylogeny, and tissue
or organism, because, where a gcrni-ccll is concerned,
idio-plasm-B is capable of reproducing entire organ-
isms of its own and of subsequent generations ; whereas,

' The mc.ininc; of this term, however, as ori^in.illy used by Nii^eli,
he so j,'rcatly chanties to suit tlic rcquiiciiicnls ot liis own theory, that
1 thinic it would have been better had he coined some new one.

i

w

u: I

32

An Exaunnatiou of Wcismannism.

',

in the case of all Sflmatic ccWs, idio-plasm-B is capable
only of reproducirif^, stai^e by stage, some greater or
less number of the cells which are to construct the
single organism of which they form a part. Or, other-
wise expressed, in the particular case of a germ-cell
idio-plasm-B is germ-plasm, and therefore is alone
capable of producing an entire organism of somatic-
cells, while it is likewise alone capable of reproducing;
successive organisms ; for it alone contains the
carriers of heredity ^

Thus, idio-plasm-B of an unscgmented germ-
nucleus is germ-plasm. Ikit as soon as the germ-
nucleus has undergone its first nuclear division, its
nucleo-plasm is no longer germ-plasm, inasmuch as
each of the half-portions is now no longer capable of
reproducing an entire organism — un! ss it be in the
case of identical twins. Similarly in the second nuclear
division, each of the four resulting idio-plasms-B is
still further removed from the pristine character of

' I think it is to be ro<;rctted that for this other kind of iclio-plasni
(i.e., idio-plasm l'>) Weismann has not coined some distinctive name,
or some distinct: c jirefix, such as that which he sometimes employs whtii
speaking of tlie other kind (i.e., idio-plasm- A' — viz., '•somatic-idio-
plasm." Also, the interchanyi-able manner in which he uses his term
"idio-plasm" with the term " nuclco-plasm," is somewhat confusing
(e.g., pp. 217, 219, 220, 250, 251, &c. . I may add that the word
"plasm" in all its combinations appears to me an unfortunate one,
since it seems to betoken a substance tliat can be seen, instead of merely
inferred. 13ut, be this as it may, the following table of terms employed
may be u?:eful for ready reference : —

Nucleo-plasm = the whole contents of the nucleus of any cell.
Cytoplasm = all tlie other contents of any cell.

Idio-plasra-A = that juntion ol nucleo-plasm whicli " controls" a single

cell.
Idio-plasm 1j = that portion of nucleo-plasm which is destined tu

CDiiitruct future cells.
Germ-plasm = undifferentiated idio-plasm-B.
Somato-plasm - idio-plasm A + cyt»)plasm.

V— --y-^^^^.yywityyB

imsin.

■B is capable
e greater or
:onstruct the
t. Or, othcr-
" a germ-cell
"ore is alone
of somatic-
reproducing
ontains the

tited germ-
> the germ-
division, its
n as much as
r capable of
it be in the
:ond nuclear
^lasms-B is
aracter of

of idio-plasm

•<tinctive nnnif,

employs whLii

somatic-idio-

uses his term

lat confusing;

lat tlie word

forlunatc one,

lead of merely

rms employed

cell.

:rols"asin;,'le

destined tu

Later Addiiions up to the year 1892.

1 ■>

i-plj

and

through all

lasm ; ana so on tnrougn an successive stages
of segmentation. Hence these successive nuclear
divisions must indicate a partitioning and re-par-
titioning of the original idio-plasm-B (germ-plasm)
into the idio-plasms-B severally distinctive of all the
various cells of the soma.

Now, it is evident that not all the idio-plasm-B of
a germ-cell which thu.; passes over into the nuclei of
somatic-cells can be represented by the itlio-plasm-li
of those cells. At every stage of successive cell-
formation a certain part of the original idio-plasm-B of
the germ-cell must become the idio-plasm-A of somatic-
cells distinctive of that stage. For, supposing that at its
differentiation stage 99 the original germ-plasm (now
somatic-idio-plasm-B of 99th stage) has reached a
phase of ontogeny where the formation of tissue ;// has
next to be followed by the formation of tissue «, then
there still remain the further differentiation stages 101,
102, 103, &c., to be provided for, vdiich,v/hen their time
arrives, will go to form the still later tissues^,/, q, &c.
Consequently the idio-plasm-B of stage 100 cannot be
rt// consumed in making the tissue n. There must be
a residual portion which will afterwards be called upon
to form successively the idio-plasm-A of o, p, q, &c.
Where, then, is this residual portion of idio-plasm
posited ? Clearly it must be posited in the nuclei
of n. Thus it is that, as we began by stating, all the
nuclei of any given tissue n really contain two kinds of
substance, — ( 1 ) their own idio-plasm-A, which was part
of idio-plasm-B of the preceding tissue, w; and (2) the
idio-plasm-B, which is destined to become idio-plasms-
A of succeeding tissues o,p^ q, &c. Thus it follows also
that the more the original idio-plasm-B is differentiated

D

if

!

i. II
,-- It

II

34 An Examination of Weismannism.

into these successive formations of idio-plasms-A the
less of it remains for further dificrentiation, till, at the
last stage of ontogeny, all the original idio-plasm-B
(germ-plasm) has been thus changed into idio-plasms-A
severally distinctive of all the somatic-tissues a, b, c
— x,y^ 5^,— save only the portion of it which has been
carried through all these ontogenetic stages in a
wholly «;/differentiated condition, for the purpose of
securing the /!'//;'A;^^;/i7/V production of the next gener-
ation. And this, of course, is secured by the portion of
undifferentiated gorm-plasm in question being de-
posited in the nuclei of germ-cells, at whatever stage of
the ontogeny these may be formed.

Finally, it is evident that, at each stage of the
differentiation of idio-plasm-B into idio-plasms-A,
the portion concerned must be capable of self-multi-
plication to an almost incalculable extent, — yet this
only as idio-plasm-B of the particular kind required for
constructing the idio-plasm-A which is appropriate to
the particular stage. Such is a necessary deduction
from the terms of Weismann's theory, inasmuch as we
know that at each of the ontogenetic stages there i.s
an incalculable multiplication of cells belonging to that
stage — cells, the " cytoplasm " of which necessarily
presupposes for its formation its own appropriate
idio-plasm in both kinds, and this in similarly increased
quantities.

From the above theory it follows that an explana-
tion can be given of the healing of wounds (as in
ourselves), of the regeneration of lost parts (as the
limb of a newt), or even of the reproduction of an
entire organism from a mere fragment of somatic-

Later Additions tip to the year 1892. 35

tissue ''as in the cases already alluded to at the com-
mencement of this chapter — viz. the leaf of Begonia,
portions of sea-anemones, jelly-fish, &c.). For in
all these cases of repair, regeneration, and what may
be called somatic reproduction, we have only to suppose
that not all the idio-plasm-B of any given ontogenetic
stage is consumed in the formation of that stage, and
therefore that the residue is passed on to the later
stages in a latent condition. It will then be avail-
able at any time to re-develop tissue corresponding
to that particular stage, should that particular tissue
happen to be lost by accident or disease. For example,
if some of the idio-plasm-B of the very first onto-
genetic stage, or true germ-plasm, should thus be
passed on in an undifferentiated condition through
the somatic-tissues subsequently formed at later onto-
genetic stages, then we can understand why an entire
organism is reproduced from a fragment of these
tissues — or of those among which particles of such
residual and undifferentiated germ-plasm happen to
be scattered. Similarly, if idio-plasm-B of the onto-
genetic stage at which a limb is formed be not all
consumed in constructing the limb, then the limb,
if afterwards lost, will be re-constructed, although an
entire organism will not be reproduced from a frag-
ment of somatic-tissue. And similarly also with the
mere repair of injuries, where the only overplus of
idio-plasm-B is that of idio-plasm-B belonging to the
very last stages of ontogeny.

But, it is almost needless to observe, this kind of
transmission of idio-plasm-B from one stage of on-
an unaltered condition tc

)geny

ibsequent stages

is not to be confused with the other kind of trans-

D 2

;

36 An Exiifni nation of Weismannisju.

inission previously referred to, whereby idio-plasm-I5
of one stajTc becomes successively transformed into
the idio- plasms -A of successive stages. In the
former case, at whatever sta^^e of ontogeny the
transnn'ssion may start from, the idio-plasm-B from
that stage lies dormant, and is never destined to
undergo further differentiation, unless the results of
accident or disease should call upon it to do so. In
the latter case, on the other hand, the idio-plasm-B
of any given stage is passed on to the next stage
for the ex[)ress purpose of trani^forming itself into
the idio -plasms -A of that and, in due order, of all
subsequent stages.

It will be observed that all this elaboration of the
original theory a germ-plasm — an elaboration which
is largely derived from the speculative writings of
Niigeli — serves no other purpose than that of indicating
what Professor Weismann now regards as the most
probable mode in which germ-plasm undergoes its
modification into the various kinds of somatic-cells.
For, inasmuch as the idio-plasms-B of all somatic-cells
are originally derived from that of the germ-cell, and
inasmuch as each expends its formative energies
exclusively in constructing and controlling the cells
which, as idio-plasms-A, they respectively inhabit, it
is still the germ-plasm of the original germ-cell that
is finally converted into the various tissues which
together constitute the soma — notwithstanding that,
in order thus to become transmuted into body-sub-
stance, or somato-piasm.i'c must pass through the sundry
intermediate stages of idio-plasm-B, idio-plasm-A, and
cytoplasm, of any given ontogenetic stage. Hence

Later Additions up to the year 1892. 37

I do not see that it makes any substantial difference to
Weismann's theory of heredity, whether we speak of
germ-pkism being converted into " somato-plasm,"
or into " idio-plasm " phis " soniatic-idio- plasm," phis
*' cytoplasm." But as Weismann himself thinks that
it does make some great difference whether we adhere
to his original generic term " somato-plasm," or adopt
his newer and more specific terms as just enumerated,
I append in extenso the most recent exposition of his
views upon this subject \

Before quitting this somewhat complicated addition
to the original theory of germ-plasm, I must briefly
allude to the descriptions and illustrations of karyo-
kinesis which were given in Part I of Darivin and after
Darwin^ for the prospective benefit of any general
re.' '?rswho might afterwards be sufficiently interested
i) Hsmann's speculations to desire a statement of
the main facts on which this further development of his
theory rests. It seemed undesirable to burden the
present volume with an account of recent investigations
so well known to naturalists, while, on the other hand,
it was clearly desirable that such an account should be
given somewhere, if the speculations in question were
to be rendered intelligible to anybody else. There-
fore I must here request those of my readers who are
not already acquainted with the matter to consult
pp. J2(S-i34 of Part I. It will there be seen how
enormously complex are the visible processes which
take place in the nucleus of a germ-cell (and likewise
of a somatic-cell), preparatory to its division ; and
therefore, supposing that the nucleus alone contains
the material concerned in the phenomcma of heredity,

' See close of Appendix.

i't

I 'i:

jjl'.

■ffi^^Jf 1

Bk ' '4 j

I : I

'1 1

'■ I

I I «

•4 i'li

38 An Examination of Weistnannism,

it appears that no small corroboration is lent to Weis-
maniis views by these histological observations. And,
more particularly, if we suppose with him that the
material in question is restricted to that portion ot
the segregating nuclear matter which is called the
" nuclear thread ^" in t.'ie formation of the " loops "
or " rods " of this substance we seem to have pre-
sented a visible expression of the marshalling of "the
carriers of heredity," and the successive passage of the
originally generalized "germ-plasm" of the germ-eel)
into the ever more and more specialized "nucleo-
plasms" of the somatic-cells. Indeed, the new theory
of heredity, when thus brought into relation with the
new results of histological observation, appears so well
to fit the latter, that one would be sorry to find
the coincidence unmeaning, or the theory false. I^ut.
without passing any criticism, it is sufficient to note
that the question whether or not the theory is true —
and therefore correctly interprets the phenon.cna of
karyokinesis, — must depend chiefly on whether it
be eventually proved that the ** nuclear thread " is
indeed the only part of a germ-cell, or even the
only part of a tissue-cell, which is concerned in con-
trolling the plicnomena of heredity on the one hand,
and of ontogeny on the other. Into this v^uestion,
however, I do not propose tc enter. It will be enough
to assume, for the sake of argument, that Weismann's
view of the matter will eventually prove to be true.
At the same time, w must remember that at present
this view as to the nuclear thread being the sole

* See Part I, figs. .^6, 37, and 38. The substance of this thread, in
the various phases of its segmentation, is the " chromatin," as there
depicted, and so called because it takes a stain better than oth-jr parts
of the nucleus — thus showing some distinctive character.

Later Additions up to the year 1892. 39

repository of the material of heredity i,j merely hypo-
thetical.

We now arrive at the last of those features in
Weismann's theory of heredity, the importance of
which necessitates mention in such a mere statement
of the theory as the present chapter is concerned
with.

According to Weismann's own view of his theory,
two objections have to be met. In the first place,
there is the objection that all individuals :v/ii:h are
born of the same parents are not exactly alike, as the
theory might have expected they would be, s»_cing that
the admixture of identical germ-plasms has been con-
cerneil in the formation of the whole progeny. In
the second place, and quite apart from this objection,
there Is the difficulty that, if every act of fertilization
essentially consists in a fusion of one mass of germ-
plasm belonging to a male gcrm-ccU with another mass
belonging to a female germ-cell, ot each generation
the mass of germ-plasm contained in on egg-cell
mubt be doubled — with the result that ova must
progressively increase in size during the course
of phylogcny. ikit ova do not tlius progressively
increase in size. Therefore, if the imperishable nature
of germ-plasm is to be theoretically sustained, it
is necessary to show some means whereby ova
and spermatozoa are able to get rid of at least
one half of their respective germ-plasms in each
generation — i. e., before each act of impregnation.
Weismann meets both these difficulties by an appeal
to the following facts.

It is well known that the ripe ovum extrudes two

40 An Examination of Weismannism.

Wi

minute particles of protoplasmic substance, which are
called polar bodies ^ These both proceed from the
nucleus of the ovum, but are not formed simul-
taneously. For the first polar body is really one
half of the original nucleus of the cell, and therefore
is formed by the first segmentation of this nucleus.
The second polar body, on the other hand, is one half
of the remaining nucleus, and is similarly formed
by the second segmentation. Hence, when both
polar bodies have been extruded from the ovum, only
one quarter of the original nuclear matter remains. So
far, of course, the facts prove too much for Weis-
mann's theory, because the theory wants to get rid of
only one half of the original nuclear matter before
impregnation, if all the nuclear matter be g'^rvi-plasm.
Therefore Weismann concludes that all the original
nuclear matter of the ripe ovum is not germ-plasm,
but that only one half of it is so, while the other half —
or that half which goes to constitute the first polar
body — is idio-plasm-A,, which, as we have already
seen, the egg-cell shares in common with all other
cells. It is merely " ovogenetic " : its function is that
of constructing the ovum, quA cell : it has nothing
whatever to do with the germ-plasm which the
parti«-./!arcell contains. Therefore, having discharged
its function of constructing this cell, it is itself dis-
charged from the cell as the first polar body.

The nucleus of the fully-formed ovum having thus
got rid of all its superfluous idio-nlasm-A by throwing
off the first polar body, is supposed henceforth to

' For an .iccount of the formation and expulsion of these bodies, see
Part I, pp. 125-6. Tiiere is now no longer any doubt touching the
statement there made as to the n)ale-ccll likewise parting with some of
its nuclear substance prior to fertilizing the female.

Later Additions up to the year 1892. 41

consist of pure germ-plasm (i. e., of idio-plasm-B
belonging to the first ontogenetic stage), and one half
of this is next got rid of by the second segmentation
in the form of the second polar body. Therefore,
according to the theory and so far as the problems
of heredity are concerned, we need not any further
trouble ourselves about the first polar body. But it
will at once be seen that by the interpretation which
Weismann puts upon the second polar body, and
also, of course, upon the extrusion of some of its
nuclear matter by the male cell, he meets both the
difficulties against his theory of germ-plasm which
we are now engaged in considering.

That he thus meets the second of those difficulties —
i. e., concerning the otherwise perpetual accumulation
of germ-plasm — is evident without explanation. That
he likewise meets the first — i. e., concerning the non-
resemblance of individuals born of the same parents —
is scarcely less evident. For it is hardly conceivable
that such a complex mass of germ-plasms as the
nucleus of a fertilized ovum must be could ever
present in any two eggs precisely the same propor-
tional representation of the " carriers of heredity,"
after one half of each set had been thus discharged
from each ^^g. Therefore, if the second polar body
removes from each egg one half of the ancestral germ-
plasms, " every f^gg will contain a somewhat different
combination of hereditary tendencies, ind thus the
offspring which arise from the different germ-cells of
the same mother can never be identical ^

Such, then, is Weismann's theory of the physio-

' In the case of identical twins, both are probably always produced
from the same ovum.

i: ■

if

t

I

I 'i

:i '!

;jfi

42 An Examination of Weismannism.

logical meaning of polar bodies. And as the bearing
of this particular theory on his more general theory
of heredity does not appear to me a vitally intimate
one, I think my subsequent examination of the main
theory will be simplified if I now proceed at once
to an examination of the subordinate one. For by
doing this I shall hope to show that the bearings just
mentioned are of much less importance than he repre-
sents them to be ; and, therefore, that we may hereafter
proceed to consider his theory of heredity without any
special reference to his theory of polar bodies.

To be,^in with, as regards the first polar body, one
would like to know more clearly why it is necessary
that this residuum of merely " ovogenetic idio-plasm"
(or idio-plasm-A of the egg-cell) has to be got rid
of before the germ plasm can proceed to discharge
its physiological functions. Seeing that both these
(hypothetically) very different materials occur in the
self-same nucleus, some very delicate mechanism must
be needed for their separation ; and it is not apparent
why such a mechanism should have been evolved,
rather than what would have been the simpler plan of
adapting the germ-plasm to hold its own against the
idio-plasm-A, even if one could sea that any inter-
ference between these very different substances is in
any way probable. Yox my own part, at all events,
T cannot see why this microscopical atom of " ovo-
genetic idio-plasm " should not simply be left to
be absorbed among the millions of cells that after-
wards go to form the foetus.

Again, as regards the second polar body, Weismann's
theory of it is framed to explain, {a) how the excess of
germ-plasm is got rid of in each ontogeny, and {b^ why

Later Additions up to the year 1892. 43

the offspring of the same parents do not all precisely
resemble one another. These, be it observed, are the
only two functions which Weismann's theory of polar
bodies subserves in relation to his theory of germ-plasm.
But, it appears to me, neither of these functions is
necessary, in so far as any requirements of the latter
theory are concerned. For surely, polar bodies or no
polar bodies, there is already a mechanism at work in
each ontogeny which is of itself sufficient to discharge
both these functions, and so to anticipate both the
supposed difficulties which the subsidiary theory is
adduced to meet. The very essence of ontogeny,
as a process, itself consists in a continuous succession
of nuclear divisions — and this not only as regards
sovnatic-cells, but also as regards germ-cells. Now, in
the great majority of organisms, there is an infinitely
greater number of germ cells (both male and female)
than can possibly be required either for the purpose
of getting rid of any excess of germ-plasms in the
nucleus ol each cell, or of preventing the germ-plasms
of any one germ-cell precisely resembling those of
any other. If every plant or animal produced only
a single female-cell or a single male-cell, then indeed
we might require from Professor Weismann a demon-
.stration of some special mechanism to secure the ex-
pulsion of half its ancestral germ-plasms ; since other-
wise the single female-cell or male-cell would have to
increase its dimensions in each successive generation.
But, as matters actually stand, nature seems to have
made much more than ample provision for prevent-
ing the undue accumulation of ancestral germ-plasms
in any individual germ-cell, by enormously multiply-
ing, through continuous division and subdivision, the

% !

! I'

44 An Examination of Weismannism.

number of germ-cells in each ontogeny. And simi-
larly, of course, as regards the different aggregations of
ancestral germ-plasms which are left for distribution
among these innumerable germ-cells. " If one group
of ancestral germ-plasms is expelled from one ^^^^
and a different group from another Q^'g, it follows
that no two eggs can be exactly alike as regards their
contained hereditary tendencies." Granted ; but this
consideration applies equally to the original segre-
gation of germ-plasms in the multiplying eggs of each
ontogeny — for it follows from the theory of germ-
plasm that the most primitive egg-cell in each ontogeny
must have contained all the ancestral germ-plasms
which are afterwards distributed among its innumer-
able progeny of egg-cells. And, as far as the facts of
" individual variation " are concerned, I do not see why
the differential partitioning of " ancestral idio-plasms"
should be any better secured by nuclear division ot
a mature germ-cell than by that of an immature.
Less so, indeed ; for the wonder is that during
the many -thousand -fold division of an immature
ovum so precise a distribution of these "ancestral
idio-plasms " is maintained, as is proved to be main-
tained (on the theory of germ-plasm) by the facts of
heredity.

However, Weismann takes a widely different view of
the matter. For while he allows that " such an early
reducing division would offer advantages in that
nothing would be lost, for both the daughter nuclei
would (? might) become eggs, instead of one of
them being lost as a polar body " — while he allows
this, he nevertheless rejects the possibility of " such an
early reducing division." But I do not see that the

, »»

Later Additions ttp to the year 1892. 45

reasons which he assigns for this rejection of it are
adequate.

First, he says that if this were the way in which the
superfluous germ -plasm of each generation were got
rid of, far too much provision has been made for the
purpose, — seeing that the practically indefinite number
of nuclear divisions which the immature germ-cells
undergo would cause a much " greater decrease of
the ancestral idio-plasms of each than could afterwards
be compensated by the increase due to fertilization."
But this rejoinder is of cogency only if it be supposed
that at each nuclear division of an immature ovum,
"the ancestral idio-plasms" (germ -plasm) are in-
capable of the power of self-multiplication which soon
afterwards becomes one of its most essential characters.
Why, then, should we suppose this substance to be
totally incapable of increase in the multiplying ova of
ontogeny, when at the same time we arc to suppose
the same substance capable of any amount of increase
in the multiplying ova of phylogcny ? To this obvious
question no answer is supplied: in fact the question
is not put.

Secondly, Wcismann says that in parthenogcnetic
ova onlyone polar body is extruded. This he regards as
equivalent to the first polar body of a fcrtilizable ovum
(i. e., as composed of ovogenetic nuclear substance) ;
and hence he argues that the second polar body
of a fcrtilizable ovum must be regarded as composed
ol germ-plasm. But even supposing that he is right
as to the fact that parthenogcnetic ova invarir.oly
extrude but one polar body, his argument fn .n this
fact would only be available after we had already
accepted his view touching the characi:er of the

^1:

46 An Examination of Weismannism.

second polar body. So long as this view is itself the
subject of debate, he cannot prove it by the fact in
question. In other words, unless we have already
agreed that the second polar body has the function
which Weismann assigns to it, we cannot accept the
fact which he adduces as furnishing any evidence of
his view touching the function of the second polar
body.

For these reasons I cannot see that the subordinate
theory of polar bodies is required in the interests of
the general theory of germ-plasm. The difificulties
which it is adduced to meet do not appear to me to
be any difficulties at all. Therefore, in now proceeding
to consider what in my opinion are the real difficulties
which lie agairTst the major theory of germ-plasm, I
shall not again allude to the minor — and, in this con-
nexion, superfluous — theory of polar bodies.

Such, then, is Professor Weismann's theory of
heredity in its original and strictly logical form. In
the course of our examination of it which is to
follow in Chapter III and IV, we sli.til find that in
almost every one of its essential features, as above
stated, the theory has had to undergo — or is demon-
strably destined to undergo— someradical modification.
But I have thought it best to begin by presenting
the whole theory in its completely connected state,
as it is in this way alone that we shall be able to
disconnect what I regard as the untenable parts from
the parts which still remain for investigation at the
hands of biological science. Such, indeed, is the only
object of my " Examination of Weismannism." For,
rightly or wrongly, it appears to me that the unques-
tionable value of his elaborate speculations is seriously

; -M

Later Additions up to the year 1892. 47

discounted by certain oversights with regard to
matters of fact, and not a few inconsistencies touching
matters of theory. In displaying both these defects,
I am not without hope that the result may be that
of inducing Professor Wcismann so to modify his
system of theories as to strengthen the whole by
removing its weaker parts.

?•!

•-i n

ji

i; ! jj

CHAPTER III.

Wkismann's theory of Heredity (1H91).

We now proceed to examine Wcismann's theory of
germ-plasm, and as this in its various developments
has now become a highly complex theory, we had
best begin by marking out the lines on which the
examination will be conducted.

As I have already pointed out, the Weismannian
system is not concerned only with the physiology
of reproduction : it is concerned also — and in an even
larger measure — with the doctrine of descent. The
theory of germ-plasm as a whole is very much more
than a theory of heredity; it is a new theory of
evolution. The latter, indeed, is deduced from the
former; but although the two are thus intimately
related, they are nevertheless not mutually dependent.
P^or the relationship is such that the new theory of evo-
lution stands upon the basis supplied by the new theory
of heredity, and although it follows from this that
if the latter were disproved the former would collapse,
it does not follow that if the former were to be found
untenable the latter must necessarily be negatived.
Hence, for the sake of clearness, and also for the
sake of doing justice to both theories, we had best
deal with them separately. The present chapter, then,

IVcisinauiis l/icory of Heredity (1891). 49

will be devoted to cxaniininj; VV'eismann's theory of
heredity, while the ensiiinj^ chapter will be concerned
with his sequent theory of evolution,

Ai^ain, Weisinann's theory of herctiity stands on
his fundamental postulate— the continuity of j,'erni-
plasm; and also on a fact well recoj^nized by all other
theories of heredity, which he calls the stabilit)' of
gerni-plasni. liut his sequent theory of evolution
stands not only on this fundamental p;istulate and an
this well-recoL^nized fact ; it requires for its loj.;ical
basis two further postulates — viz., that ij^erm-plasm
has been perpetually continuous '' since the first origin
of life," and imalterably stable "since the first ori<^in
of sexual propai^ation." That these things are so.
a very few words will be sufficient to prove.

Any theory of heredity which su[)[)()ses the material
of heredity to occupy a more or less separ;ite " sphere '
of its own, is not obliged further to suppose that this
material has always been thus isolated, or even that
it is now invariably so. There have been one or two
such theories [)rior to Weismann's, and they were
founded on the well-known fact of congenital characters
being at any rate miteJi more heritable than are
acquired characters. Hut it has not been needful for
these theories to assume that the "continuity" thus
postulated has hcQw perpetnnliy unbroken. Even if it
has been frequently to some extent interrupted, all
the facts of heredity could be ecjually well compri.sed
under such theories — and this even if it be supposed
that acquired characters are but rarely, or never,
transmitted to progeny. T'or, in as far as the con-
tinuity may have been interrupted, it does not follow
that the acquired characters (body-changes), which by

E

ill

i

11

1

50 An Exatninatiou of U\is)itannism.

hypothesis caused the intcrrir tioii, must be inherited
by progcry exactly as they occurred in the parents.
Or, in otner words and adopting VVeismann's ter-
niinoIt)gy, so far as the fads if heredity are eeneerned,
there is no reason wliy gerni-plai-'ni should not
frequent!)' have had its hereditary qualities modified
by some greater or less ilcgrec of commerce with
somatic-tissues, and yet never have reproduced in pro-
geny the identical acquired characters which caused
the modification of germ-plasm in the parents : some
other and totally different characters might with etpial
— or even more — likelihood have been the result, as we
shall see more clearly a few pages further on. Why,
then, does Weisinatm so insist ui)on this continuity of
germ-plasm as perpetual '• since the origin of iife " ? It
appears to me that his only reason for doing so is
to provide a basis, not for his theory of heredity, but
for his additional theory of evolution. It is of no
consequence to the former that germ-i)lasm should
be regarded as thus peri)ctual, while it is of high
importance to the latter that the fundamental postulate
of continuity should be supjjlemcnted by this further
postulate of the continuity as thus perpetual.

Similarly as rei^ards the postul:.te of the stability
of germ-plasm as absolute. Il is enough for all the
requirements of VVeismann's theory of heredity that
the material basis of heredity should present a merely
high degree of stability, such as the facts of atavism,
degeneration, &c. abundantly prove that it possesses.
For his sequent theory of evolution, however, it is
necessary to postulate this stability as absolute "since
the first origin of sexual reproduction."' Other-
wise there would be no loiindation for any of the

i<|, ^^^.^JS^^^-.-

IVi'isuianns theory oj Ilcndily (1S91). 51

distinctive doctrines which go to constitute this
theory.

It may not be immediately apparent that Weis-
mann's theory of liereih'ty is not per sc concerned
with eitlier of these two additional postulates of the
contimiity of ^erm-plasm as pcrpctuaL and the stahiHty
of i;enn-[)lasm as absolnlc\ while both are loL;ically
necessary to his further theory of evolution. On this
account, and als(j for the sake of clearness in all
that is to follow, we had best bi.L;in b)- cotn[)arinL^
his thco)} of heredity with those of his principal
[)redecessors — Darwin and Galton.

For the purposes of this comparison we may start by
again alluding to the fact, that even in the multicellular
organisms reproduction is not confined to the sexual
methods. Many kinds of invertebrated animals will
re prod u CO entire organisms from the fragments into
which a single organism has been choi)ped : plants
of various kintls can be i)ropagateJ indefinitely by
cuttings, grafts, and buds, or even by leaves, as we
have already observed in Chapter I. Now. when
the whole organism is thus »eproduced from a severed
portion o£ s()matic-tissue, it reproduces its se.Kual
elements. Whence, then, in such cases are these
elements derived ? Obviously they are not derived
immediately from the sexual organs — or even from
the sexual cells — of their parents: they are derived
from the somatic-cells of a single parent, if we choose
to retam this term ; and therefore, as Strasburger
pointed out soon after Weismann's theory was pub-
lished, it seems as if such facts arc in themselves
destructive of the theory. I low. then does Weismann

!«: 2

•i,
■ 1

If

X

IS

1'^

|;

52 An Exaniinatiou of Weisniannism.

meet them? As we have already seen in Chapter II,
he '.nects them in the only way they can be met on
the lines of his theory — viz., by those newer amend-
ments of his theory which suppose that in all these
cases the £]^crm-plasm is ;/<;/^n fined. to the specially
sexual cells, but occurs also in the nuclear substance
of those somatic-cells which thus prove themselves
capable of developincj into entire ortj^anisms. In
other words, the sexual ciemcnts which develop
dvirincj what I have previously called this "somatic
reproduction" of multicellular organism, are supposed
to be derived from the sexual cells of ancestors, not
indeed immediately (for this they plainly are not),
but mediately through the somatic-tissues of their
a-sexual parent. Now, in view of this extension, the
theory cf germ- plasm becomes somewhat closely
alTietrto that of pangenesis. For example, when the
fragment of a leaf of Bci^onia is laid upon moist soil,
there strikes root, and grows a new Begonia plant
capable of sexual reproduction Darwin supposes the
explanat.ioa..tq be that what he calls "formative
material" occurs in all cells of the leaf, while Weismann
supposes the explanation to be that what he calls
" germ-plasm " occurs in all — or at any rate in most —
of the cells of the leaf. So that, except as regards the
terms employed, the t.vo theories are identical in their
mode of viewing this particular class of phenomena.

Moreover by thus allowing, in his second essay on
Heredity, that germ-plasm need not be restricted to
the specially sexual cells, but in some cases, at any
rate ^, may occur distributed in full measure of repro-

' We have no ino.ins of esliniatiiii; exactly tlic proportional number
of cases in whicii tliis is pussihle, eitiier amon^ tlu; lower or the liigher

'■T'g ■«!■'■;««■ .■S'gT

Weismatms theory of Heredity (1891). 53

ductivc efficiency throughout the general tissues of
the organism, VVeismann cannot refrain from taking
the further step of supposing that the germ-plasm, 'li^i \^ %„w>«^.,
like the gemmules of Darwin, is capable of any /^ ^j^ L^iv,
amount of multiplication in tJic goicral cellular tissues
of plants — seeing that plants can be propagated by
cuttings, buds, &c., indefinitely. And this, as we have
seen, Professor VVeismann, in his second essay, does
not shrink from doing. Moreover, although I cannot
remember that he has anywliere expressly said so, it
is obvious that the allied phenomena of regeneration
and rejoair admit of explanation by his hypothesis
of " ontogenetic grades,'' after tlic manner already
stated in Chapter II. Indeed, it is evident that in
no other way can these phenomena be brought
within the range of his theory. But from this it
follows that not only in the case of organisms which
are capable of somatic reproduction is the formative
nucleo^^lasm (idio-plasm-B) diffused throughout the
somatic-tissues : on the contrary, it must be univer-
sally diffused throughout all the somatic-cells of all
living^ganisms ; and whether as it there occurs it is
capable of reproducing entire organisms, single organs,

plants; but it is ccriainly much {greater than Wcismaiiii supposes.
" llow is it that all j)lanls cannot he ninocUiccd in this way?'' he a-.ks,
and then ailds,— " No one has ever ^rown a Itie from the leaf of a lime
or an oak, or a llowerinj^ jilant In \\\ a leaf of tlie tulip or the
convolvulus." lUit I am told hy l)(Jt.uii.-.ts llial the oidy reason wiiy
the phenomenon thus ajipears to he a rare one, is heeause it is not
worth anyhody's while to ^'row plants in this way at a necessarily
unsuitahle season of the year. Thus, the Rev. (ieorge llenslow
writes me; — "'I'lie fact is that a)iy plant will reproduce itself hy its
leaves, provided tliat the cells lie 'embryonic,' ('i.e., the leaf not
tooTiear its complete development, and that it he not too thin,
so as to provide enough nulument lor the hud t(j lurni tdl il iiai
roots."

Ill

I

A-

54 An Examination of Weismannism.

single tissues, or a mere cicatrix, depends only on
the '• ontogenetic grade " of differentiation which
this diffused nucleo-plasin has (or has not) previously
undergone. Moreover, as we have already seen, at
whatever ontogenetic grade of differentiation it may
be present in a given somatic-tissue, it must there be
capable of indefinite self-multiplication. Therefore,
in all these resi)ects this "formative nucleo-plasm '' (or
idio-|ilasm-B) of Weismann precisely resembles the
'' formative material" (or gemmules) of Darwin.

Lastly, as De Vries has pointed out^, there rnust
beat least as many divisions and subdivisions in
the substance of germ-plasm, as there are differences
between the somatic organs, tissues, and even cells,
to which germ-plasm eventually gives rise — no matter
through how many ontogenetic grades of idio-plasm
it may first have to pass. Or, in other words, we must
accept, as the material basis of heredity, ultimate
particles - of germ-plasm, which are already differen-
tiated into as many diverse categories as there are
differences between all the constituent parts of the
resulting soma; for. as shown in the Appendix, no
change in the facts of the case has been shown by
simply changing the origin.Tl term "germ-plasm" into
" idio-plasm." wherever the phenomena of ontogeny
are concerned. It m.iy be convenient, for the .sake of
presenting newer additions to the theory, to restrict
the tcim "germ-plasm" to 'idio-plasm of the first
ontogenetic stage"; but as idio-plasms of all subse-

' Inti (ht'l/itlarc J'ani^citrsis, s. 5,5.

" I cmiiloy the term " ii.ailiclcs," instead of " molcciilis," licc.iuse
fillhi)Ut^li Weismann nmX liis followers stem to prefer tiie Inller term,
I can scnicely ini:i},nnc that tlicy intend to use it in its oriijinnl, or
cliemiial, sen^e.

I'

IVetsmanns thcoiy of Heredity (1891). 55

quent ontogenetic stages are supposed to be ultimately
derived from this idio-plasm of the first stage, it is
evident that the particulate differences in question
must already have been present in the so-called
" undifferentiated idio-plasm of the first ontogenetic
stage." Unless we are to have a mere juufirliner with
words, we cannot put into our successive idio-plasms
any particles o. cinds difTeriiig from those which are
contained in the original germ-plasm. Therefore I
say that, notwithstanding this change of terminology.
Weismann must continue to assume, as the material
basis of heredity, ultimate particles of germ-plasm
which are already differentiated into as many diverse
categories as there are difTerences between the parts
of the resulting soma — although, of course, these
ultimate particles need not be nearly so numerous in
each of tJu'ir categories as they afterwards become by
self-multiplication while forming each of the resulting
tissues.

But this is precisely what the theory of pangenesis
supposes ; so that I see no reason why these ultimate
particles of germ-plasm should not be regarded as
■'gemmules," so far as their size. niDnber. tV^.d function
are concerned. In point of fact, they differ from
gemmules only in respect to their origTn : they are
not particles derived from somatic-cells of the preceding
generation, but particles derived from germ-plasm of
the preceding generation. Or, to state the difference
in another form, if vve regard the sexual elements as
constituting the physiological centre of the organism,
then the tTieory of germ-plasm supposes these ultimate
carriers oFTieredity to originate at this centre, and
then to travel rtntrifugally ; wliilc the theor\' of pan-

h:

iiii

I

lifi

56 All Exaniinatim of Weismannis7n.

genesis supposes them to oriiijinate at the periphery,
and then to travel centripetal ly.

This point of difference, however, arises from the
deeper ones, which — havint^ now exhausted the points
of aL^rcement — we must next proceed to state.

If, as we have seen, -'formative material" and
"germ-plasm" ^'^rce in being particulate: in consti-
tuting the material basis of heredity; in being mainly
lodged in highly .specialized, or germinal, cells ; in
being nevertheless also distributed throughout Vie
general cellular tissues, where they are alike concerned
in all processes of regeneration, repair, and a-sexual
reproduction ; in having an enormously complex
■(vvwf* ^lll^Sl!:'''^'' ^° ^'^^^ every constituent part of the future

organism is already represented in them by corre-
sponding particles ; in being everywhere ca})ab]e of a
virtually unlimited multiplicaiion, without ever losijjg
their hereditary endowments ; in often carrying these
endowments in a dormant state through a number of
generations, until at last tl:cy re-appear again in what
we recognize as reversions to ancestral characters; —
if in all these most important respects the two sub-
stances are supposed to be alike, it may well appear
at first sight that there is not much room left for
any difference between them. And. in point of fact,
the onlydiffgxcnce that does obtain between them
admits of being stated in two words, — Continuity,
and Stability. Nevertheless, although thi.s so few in
number, these two points of difference are points of
great importance, as I wil' now proceed briefly to
show.

If the substance which constitutes the material
basis of heredity has been perpetually continuous, in

Weisinaniis theory of Heredity (1891). 57

the sense ofncver havini^ had any of its hereditary
endowments in any \va)' affected by_£h.C-iIcneral body-
tissues in which it^ resides, the followin^j important
consequences, it will be remembered, arise. The
process of organic evolution must have been exclusively
due to a natural selection of favourable variations
occurring within the limits of this substance itself;
and therefore the so-called Larnarckian factors can
never have played any part at au m the evolution of
any but the unicelhilar organisms. On the other hand,
if this substance has not been thiis perpetually con-
tinuous, but more ox less formed anew at each ontogeny
by the general body-tissues in which it resides, natural
selection has probably been in some corresponding
degree assisted in its work of organic evolution by the
Larnarckian factors, with the result that the experi-
ences of parents count for something in the congenital
endowments of their offspring. So much for the
first of the two differences between germ-plasm and
gemmules, or the difference which arises from the
perpetual continuity of germ-plasm.

Touching the second difference, or that which arises
from the absolute stability of germ-plasm, it will be
remembered how from this character there arises
another important chain of consequences. Namely,
individual variations of the congenital kind can only
be~"3ue"to admixtures of different masses of germ-
pTasm in every act of .sexual fertilization ; natural
.scTectTon is therefore dependent, for the possibility
of its working, upon the sexual methods of propa-
gation ; hence, natural selectidu is without any juris-
diction among the unicellular organisms, where the
Larnarckian factors hold exclusive swa\' : and hence,

il

!!!i

mw

1 :\

58 An Examination of Weisniannism.

also, the multicellular organisms are ultimately depen-
dent upon this absolute stability of their germ-plasm
for all the progress which they have made in the
past, as well as for any progress which they may be
destined to make in the future.

Thus we see that the two points of difference
between gfrm-plasm and gem mules are not merely
of great importance as regards the particular problem
^vhich is presented by the phenomena of heredity :
they are of still greater importance as regards
the general theor\' of evolution. For if these two
qualities of perpetual continuity and absolute sta-
bility can be proved to belong to the material basis
of heredity, the entire theory of evolution will have
to be reconstructed from its very foundation — and
this quite apart from the more special question as
to the transmission of acquired characters. There-
fore we shall presently have to consider these two
alleged qualities with the care that they demand, as
having been seriously suggested by so eminent a
naturalist as Professor Weismann. But, before pro-
ceeding to do so, I must briefly compare his theory
with that of Mr. Galton.

"Stirp" resembles both "germ-plasm" and "gem-
mules " in all the respects which have above been
named as common to the two latter. ]^ut it differs
fro:i genunules and further resembles germ-plasm
in all the following particulars. It is derived from
the stirp of proceeding generations, and constitutes
the sole basis of heredity. Only a part of it. however,
is consumed in each ontogeny— the residue being
handed over to "contribute to form the stirps of
the offspring." where it undergoes self-multiplication

\ i

n

Weis7?iajtns tJieoiy of Heredity (1891). 59

at the expense of the nutriment supplied to it from
the somatic system of the offspring, and so on through
successive generations Again, stirp is concerned in
all processes of regeneration and repair, in the same
centrifugal manner as germ-plasm is so concerned.
Furthermore, the influence of sexual proi)agation
in the blending of hereditary qualities of the stirp
is recognized, while the principle of panmixia, or the
cessation of selection, is entertained, and shown to
invalidate the evidence of pangenesis which Darwin
derived from the apparently transmitted effects of
use and disuse in our domesticated animals ^ Lastly,
it is clearly stated that on the basis supplied by
this "theory of heredity," it becomes logically pos-
sible to_ dispense with the Lamarckian principles
/// toto^ leaving- natural selection as the sole known
cause of^rganic evolution through a perpetual con-
tinuity of stirp, together with individual variations of
the same, whether b\' sexual admixture or otherwise.
So far, then, there is not merely resemblance, but
virtual identity, between the theories of stirp and
germ-plasm. Disregarding certain speculative details,
the coincidence is as complete as that between
a die and its impress. Rut although the two
theories are thus similar in logical coustniction, they
differ in their interpretati(Mis of biological fact. That
is to say. although Galton anticii)ated by some ten
years all the main features of Wcismann's theory of
heredity'-, and showed that, as a matter of form, it was

' Tliis principle will be considcidl at some leiii^'tli in my next
volume.

'•^ Calton fust publislu'fl his tlicory in 1S72 Proc. R. S.. No. 17,6),
but presented it in a nioio complete form three years later Coiilciiiporary
Review, Dec. 1^75, nnd /oiinil. Avtliropol. Ins/., 1S75I.

II

il'ii

I

60 An Examination of Weismannism.

logically intact, he refrained from concluding on this
account that it must be the true theory of heredity.
He argued, indeed, that in the main it was probably
the true theory ; but he guarded his presentation of
it by not undertaking to deny that there might
still be some degree of intercommunication between
the material basis of heredity in stirp, and the
somatic tissues of successive organisms. The con-
struction of a theory which, as a matter of theory,
could dispense with the Lamarckian principles i?i toto,
was seeri to be a very different thing from proving,
as a matter of fact, that these princii)les are non-
existent— and this, even though it was seen that
a recognition of the principle of panmixia must be
taken to have considerably attenuated the degree of
their operation as previously estimated by Darwin in
the theory of pangenesis. In short, after pointing out
that the doctrine of stirp might very well adopt
the position which about a decade later was adopted
by the doctrine of germ- plasm — namely, that of
altogether supplantiug the doctrine of gemmules, —
Galton allowed that this could be done only as
a matter of formal speculation ; and that, as a matter
of real interpretation of the facts of nature, it seemed
more judicious to stop at modifying the doctrine of
gemmules, by provisionally retaining the hypothesis
of gemmules, but assigning to their agency a greatly
subordinate rule. Or to quote his own words : —

The conclusion to be drawn from the foregoing arguments is,
that we might ahnost reserve our belief that the structural [i.e.,
"somatic"] cells can react on the sexual elements at all, and
we may be confident that at the most they do so in a very faint
degree ; in other words, that acquired modifications are barely,

w

IVeisiuamis t/icory of Heredity (1891). 61

if at .ill, inherited, in the correct sense of that word. If they
were not herital:)le, then tlie second t^roiip of cases |i.e., those of
acquired as distingiiislied from con;4enital characters] would
vanish, and we should he absolved from all further trouljle ;
if they exist, in however faint a degree, a complete theory of
heredity must account for them. I propose, as already stated,
to accept the supposition of their being faintly heritable, and to
account for them by a modification of I'cmgenesis '.

Seeing, then, that Galton did not undertake to
deny a possibly slight influence of somatic-tissues
on the hereditary qualities of stirp, it follows that
he did not have to proceed to those drastic modi-
fications of the general theory of descent which
Wcismann has attempted. Stirp, like germ-plasm,
is continuous ; but, unlike germ-plasm, it is not
necessarily or absolutely so. Again, stirp, like germ-
plasm, is stable; yet, unlike germ-plasm, it is not
perpetually or unalterably so. Hence we hear nothing
from Galton about our having to explain the un-
likcness of our children to ourselves by variations
in our protozoan ancestors ; nor do we meet with
any of those other immense reaches of deductive
speculation which, in my opinion, merely disfigure
the republication of stirp under the name of germ-
plasm.

Now, I allude to these, the only important points of
difference bi'tween stirp and germ-plasm, for the
sake of drawing prominent attention to the fact that it
makes a literally immeasurable difference whether we
suppose the material basis of heredity to be per-
petually continuous and unalterably stable, or whether
we suppose that it is but largely continuous and higJily

(

' Journ. Anthropol, Inst. 1S75, p. 7,46.

1

r

f'

62 An Exinniuatioti of Wcisniauui^ui.

stiiblc. In the former case, all the far-reaching
d'^duction.s which Weisniann draws with reference to
the general theory of descent — or apart from the
more special problem of heredity — follow by way
of logical consequence. In the latter case, there is
no justification for any such deductions. For, no
matter how faintly or how fitfully the hereditary
(jualitics of Lhe material in cjuestion may be modified
by the somatic-tissues in which it resides, or by
the external conditions of life to which it is exposed,
these disturbances of its absolute stability, and these
interru[)tions of its perpetual continuity, must cause
more or less frequent changes on the part of its
hereditary qualities — with the result that specific or
other modifications of organic types need not have
been solely due to the varying admixture of such
material in sexual unions on the f)ne hand, or to the
unassisted power of natural selection on the other.
Numberless additional causes of individual variation
are admitted, while the Lamarckian princii)les arc;
still allowed some degree of play. And although
this is a lower degree than Darwin supposed, their
influence in determining the course of organic evolu-
tion may still have been enormous ; seeing that their
action, in whatever measure it may be supposed
to obtain, must al\va}'s have been cuiimlativc on the
one hand, and dircciiiw of variations in adaptive
lines on the other. Or, as Galton himself observes,
in the passage already quoted, '• if they exist, in Junv-
evcr faint a degree, a complete theory of heredity
must account for them." He saw, indeed, that a most
inviting logic ai system could be framed by denying
that they can ever exist in any degree — or, in

Weisiiianjis ikcory of llcndi/y (1891). 63

other words, by supposing that stirp was cxiictly
the same as what was afterwards called gerni-i)lasni,
in that it always occupied a separate '"sphere"' of
its own, where its continuity has been uninterrupted
"since the first origin o life." liut Galton was not
seduced by the temptation to construct an ideally
logical system ; and he had what I regard as the
sound judgement to abstain from carrying his theory
of stirp into any such transcendental "si)hcre'" as that
which is occupied by Weismanns theory of germ-
plasm, in relation to the general doctrine of descent.

There is, then, a vast distinction between any
theory of heredity which postulates the material of
heredity as highly stable and largely continuous, and
VVeismann's theory, which postulates this material as
absolutely stable and perpetually continuous. But
we must next take notice that Weismann himself has
not kept this distinction in view with the constancy
which we should have expected from so forcible
a thinker. On the contrary, although in the con-
struction of his theory of evolution he never fails
to press the postulates of absoltitc stability and per-
petual continuity to their logical conclusions in the
various doctrines above enumerated (pp. .'>7-o<S), when
engaged on his more special theory of heredity he
every now and then appears to lose sight of the
distinction. Indeed, he occasionally makes such large
concessions with regard to both these postulates,
that, were they to be entertained, the occupation of
his critics would be gone : his theory of heredity
would become converted into Galton's, while his
theory of evolution would vanish altogether. It is

r ^

'f! i

'I

64 ^'Ifi Jixanii nation oj [Vcisniamitsni.

thcrcTnic necessary to quote some of these con-
cessions, if only to justify ourselves in subseijuently
if^norinfj them. I will i,nve one instance of each ;
but it is necessary to preface the illustrations with
a few words to mark emphatically three very
distinct cases of coiiijcnital variation — leavini,^ aside
for tlic present tlie question whether or not they all
occur in fact, as they are held to do by one or other
of the theories of heredity.

1. The case where impoverished nutrition of the
body has the effect of simply starving its germinal
material. This is not a case where either the continuity
or the stability of such material is affected. Its full
efficiency as " formative material " may indeed be
thus deteriorated to any extent, so that the proircny
may be to any extent puny or malformed ; but this
will not necessarily cause any such re-shufflint^ of its
"molecules" .ts will thereafter result in a permanent
phylocjenctic chan<^e. At most it will affect only the
immediate offsprinij of jjoorly nourished parents ; and
natural selection will always be ready to eliminate
such inefficient individuals. This case I will always
hereat ' r call the case of nutritive congenital chanties.

2. The case where germinal material is influenced
by causes which do effect a re-shuflling of its '• mole-
cules," so that a permanent phylogenetic change
docs result. Observe, in this case, it does not signify
whether the causes arise from external conditic^ns of
life, from any action of the soma on its own germinal
material, or from so-called " spontaneous " changes
on the part of such material itself But the one
cause which has not been concerned in producing an
hcreditaiy modification of this class is the mixture

Wcisnianns theory of Ihrcdity (1891). 65

Mfl

of "fjerm-plasfiis" in an act of sexual union. In
hereafter spcakini; of til is case I will follow Weismann's
terminology, and call coni^cnital cluui'^cs thus produced
specialized coiij.^eiiital chanj^cs.

3. Lastly, we have the case of the Lamarckian
factors. This precisely resembles case 3, save that
the congenital changes produced are still more
"specialized." For while in the preceding case
the re-shuflling before mentioned may have [)roduced
a congenital change of any kind, in the [Mescnt case
the congenital change produced must be of one
particular kind — viz., a reproduction by heredity of
the very same modification which occurred in the
parents. "The fathers have eaten sour grapes, and
the children's teeth are set on edge." This would be
an extreme example of " use-inheritance," and so of
case 3. But if the fathers had eaten sour grapes,
and the children, instead of having their teeth set
on edge, were to be born with a wryneck or a scjuint,
then wc should have a good example of case 2. In
order, then, to mark the important distinction between
these two cases, I will hereafter call ^he highly
specialized changes due to the Lamarckian factors —
supposing such chan^^cs to be possible — representative
congenital changes.

These several distinctions being understood, I will
proceed to furnish the two quotations from Wcismann,
which arc respective'/ illustrative of his concessions
touching his two fundamental postulates, as previously
explained.

We may fairly attribute to the adult organism influences
which determine the phyletic development of its descendants.
For the germ-cells arfe contained in the organism, and the

F

if .1

66 An Exaininaiion of Weismaiinisrn.

external influences which affect them are intimately connected
with the state of the organism in which they he hid. If it be
well nourished, the germ-cells will have abundant nutriment ;
and, conversely, if it be weak and sickly, the germ-cells will be
arrested in their growth. It is even possil-'le that the effc cts of
these influences may be more specialized ; that is to say, they
may act only upon certain parts of the germ cells. But this is
indeed very different from be'itjving that the changes of the
organism which result from extcrii.il stimuli can be transmitted
to the gcrm-ccils, anrl will re-devclop in the next generation at
the same time as that at v>'hich they arose in the parent, and in
the same part of the organism ^

It will be perceived that Weismanti himself here
very clearly draws all the distinctions between cases
I, 2, and 3, as above explained. Therefore it
beconvs the more remarkable that he should not
have perceived how radically inconsistent it is in him
thus to entertain as '"possible" cont^enital variations
belonging to the case 2. For, as we have now so
fully seen, the t^^icorv of germ-plasm (as distinguished
from that of stirp) cannot entertain the possibility of
an hereditary and specialized change of any kind as
thus produced by external conditions of life : should
such a possibility be entertained, there must obviously
be an end to the absolute stability of germ-plasm,
and a conseciuent co'l ipse of Weismann's theory of
evolution. ICither germ-plasm is absolutely stable,
or else it is but highly stable. If it is absolutely
stable, individual variations of an hereditary kind can
occur only as results of sexual admixtures of germ-
plasm, and Weismana's theory of evolution is
established. But if germ-plasm is not absolutely
stable (no matter in how high a degree it may be so)

' Esiays, 6tc., 2ud cd., p. 105.

Wcisinanns theory of Heredity (1891). 67

hereditary individual variations may be produced by
other causes, and Wcismaun's theory of cvokition
collapses. Therefore, if \vc arc to examine his
theory of evolution^ \vc can tlo so onl)' by iij^noring
such a passage as the one just (luotetl, which sur-
renders the postuhi' J of the absolitlc stability of germ-
plasm.

Again, if we arc to examine Weismann's theory of
heredity, we must similarly ignore such a passap,- as
the following, where he represents that he is similarly
prepared to surrender his still more fundamental
postulate of the pei-pctual continuity of germ-plasm.

After remarking that some of his own experiments
on the climatic varieties of certain butterflies raise
such difficulties against his whole theory of heredity
that even now he '• cannot explain the facts otherwise
than by supposing the passive acquisition of characters
produced by the direct influence of climate," he goes
on to remark more generally — ' We cannot exclude
the possibility of such a transmission occasionally
occurring, for, even if the greater part of the effects
must be attributed to natural selection, there might
be a smaller part in certiin cases which depends
on this exceptional factor ^ " — i.e., the Lamarckian
factor !

Now, it must be particularly noted that in this
passage Weismann is speaking, not as in the previous
passage, of scpcialized congenital characters, but of
representative congenital characters. In other words,
he here entertains the possibility which in the passage
previously quoted he very properly rejects — namely,
"that changes of the organism which result from

' Essays, ike, ami l\1., p. loo.
F 2

ii

i

6S An Examination of Weismannism.

external stimuli can be trahsmitted to the germ-cells,
and will rc-dcvclop in the next generation at the same
time as that at ivltich they arose in the parent, and in
the same part of the organism." But it is evident that
if the theory of germ-plasm is undermined by the
concession made in the passage thus previously
quoted, in the passage last quoted a match is put
to the fuse. It does not signify v/hether the particular
case of the butterflies in question will ever admit of
any other explanation more in accordance with the
tlieory of germ-plasm : the point is that in no case
can this theory entertain the possibility of causes
other than admixtures of germ-plasm in sexual
unions producing hereditary changes, (A) of any
kind, (B) still less of a specialized kind, and (C) least
of all of a representative kind. For the distinguishing
essence of this theory is, that germ-plasm must always
have moved, so to speak, in a closed orbit of its own :
its " sphere " must have been perpetually distinct
from those of whatever other " plasms " there may
be in the constellations of living things. So that, in
such passages as those just quoted, Weismann is not
only destroying the very foundations of his general
theory of evolution, but at the same time he is
identifying his more special theory of heredity with
those which had been already published by his
predecessors, and more particularly by Galton.
Now, it is not Galton's theory that we are con-
sidering ; and therefore we must hereafter ignore
those fundamental admissions, whereby Weismann
every now and p^ain appears ready to relincjuish all
that is most distinctive of, or original in, his own
elaborate system of tlieories.

4 S,a>flEfr-

Weismanns theory of Heredity (1891). 69

It is, indeed, impossible not to admire the candour
of these admissions, or to avoid recognizing the truly
scientific spirit which they betoken. But, at the same
time, one is led to doubt whether in making them
Professor Weismann has sufficiently considered their
full import. He appears to deem it of compnrativcly
little importance whether or not acquired characters
can sometimes and in some degrees influence the
hereditary qualities of germ-plasm, provided he can
show that much tJic .arger part of the phenomena of
heredity must be ascribed to the continuity of germ-
plasm. In o^her words, he seems to think that it
matters but little whether in the course of organic
evolu^^^ion the Lamarckian factors have played but
a very ^^v'bordinate part, or whether they have not
played Dny- part at all. Moreover, I have heard one
or two prominent followers of Weismann give public
expression to the same opinion. Therefore I must
re[)eat that it makes a literally immeasurable difference
whether we suppose, with Galton, that the Lamarckian
factors .may sometimes and in some degrees assert
themselves, or whether we suppose;, with the great
bulk of Weismann's writings and in accordance with
the logical requirements of his theory, that they can
never possibly occur in any degree. The distinctive
postulate of his theory of heredity, and one of the
two fundamental doctrines on which he founds his
further theory of evolution, is, that the physiology of
sexual reproduction cannot admit of any inversion of
the relations between '"germ-plasm " and '"somatic idio-
plasm ^" This is a perfectly intelligible postulate, but
it is not one with which we may play fast and loose.

' Set- lor L'xampl ■, Essays, \>. 2:.(j.

li

I

I

1

70 An Examination of Wcisniannism.

luthcr there is such a physiological mechanism as it
announces, in which case the relations in question can
never be inverted "occasionally," any more than ra£;;s
may "occasionally" help to construct the mill which
is to form them into paper ; — or else there is no such
mechanism, in wiiich case we may have to do with
c^emmules, physiological units, stirp, micellae, pangenes,
plastidules, or any of the other hypothetical " carriers
of heredity " to which our predilections may happen
to incline ; but the one substance with which we
certainly have not to do is germ-plasm ^

After these tedious but necessary preambles, we
may now proceed to examine Professor Weismanns
postulate as to the perpetual continuity of germ-plasm,
with its superstructure in his theory of heredity —
reserving for the next chapter our examination of his
further postulate touching the absolute stability of
germ-plasm, with its superstructure in his theory of
evolution.

The evidence which Weismann has presented in
favour of his fundamental postulate of the perpetual
continuity of germ-plasm may be conveniently dealt

' On previous nccnsions, when inconsistencies have been brought to
the notice' of I'roitv^SDr Weismann by his critics, he has complained that
sufficient allowance was not made for the fact of his having published
his sundry essays at different times. This, of course, is a satisfactory
answer in cases where criticism refers to a growing theory, the later
additions to which supersede certain parts of the earlier construction.
But clearly the answer is not avnilaltle in cases where one set of
statements, touching fundamental iirincijiles of tlie theory, are directly
opjiosed to otliers. A logical contradiction is not affected by dates
of jndilication, and where the contradictory statements have reference
to the vital essence of a theory, it is njunily impossiMe for the theory
to ci)nipiise tiiem whether they be presented simultanei)usly or suc-
cessively.

!1

IJS*-

Weisuumns theory of H end if y (1891). 71

with under two heads — namely, indirect evidence as
derived from general reasoning, and direct evidence
derived from particular facts.

The general reasoning is directed to show, (1) that
there is no evidence of the transmission of acquired
characters ; (2) that the theory of pangenesis is
"inconceivable": and. (3) that the alternative theory
of germ-plasm is amply conceivable. Now, to the
best of my judgement, not one of these propositions is
borne out by the general reasoning in question. Ikit
as the latter is almost entirely of an a prion character,
and also of a somewhat abstruse construction, I think
the patience of any ordinary reader will be saved by
relegating this part of our subject to an Appendix.
Therefore, remarking only that any one who cares to
look at Appendix I ought, in my ojjinion, to perceive
that there is no real evidence against the iransmission
of acquired characters to be derived from Weismann's
cjeneral reasonini:^ in this connexion, I will at once
proceed to consider the evidence which he has
adduced in the way of particular facts.

In the first place, as one result of his brilliant
researches on the llydrouicdiisac, he has found that
the generative cells occur only in certain locali/.ed
situations, which, however, vary greatly in different
species, though they are always constant for the same
species. lie has also found that the varying situations
in different species of the localized or generative areas
correspond, place for place, with successive stages in
a process of gradual transposition which has occurred
in the phylogenx' of the Ilydroineditsac. Lastly, he
has found that in each ontogeny these successive

■|f. m^

W'

72 An Exammation of Weisrnarinhm.

stages of transposition are repeated, with the result
that during the individual lifetime of one of these
animals the germ-celh' migrate through the body, from
what used to be their ancestral situation to what 's
now the normal situation for that particular speciei..
Such being the facts, Weismann argues from them
that the germ-cells of the llydrovieditsae are thus
proved to present properties of a peculiar kind, which
cannot be supplied by any of the other cells of the
organism ; for, if they could, whence the necessity for
this migration of these particular cells? Of course
it follows that these peculiar properties must depend
on the presence of some peculiar substance, and that
this is none other than the " germ-plasm," which here
exhibits a demonstrable "continuity" throughout the
entire phylogeny of these unquestionably very ancient
Metazoa.

The second line of direct evidence in favour of the
continuity of germ-plasm which Weismann has ad-
duced is, that in the case of some invertcbrated animals
t!>e sexual apparatus is demonstrably separated as
reproductive cells (or cells which afterwards give rise
to the reproductive glands) at a very early period of
ontogeny — so early indeed, in certain cases, that this
separation constitutes actually the first stage in the
process of ontogeny. Therefore, it is argued, we may
regard it as antecedently improbable that the after-life
of the individual can in any way affect the congenital
endowments of its ova, seeing that the ova have been
thus from the first anatomically isolated from all the
other tissues of the organism.

The third and only cither line of direct evidence is,
that organisms which ha\e been produced partheno-

Weis7nanns theory of Heredity (189 1). 73

genetically, or without admixture of germ-plasms in
any previous act of sexual fertilization, do not exhibit
conejenital variations.

Taking, then, these three lines of verification separ-
ately, none of them need detain us long. For although
the fact of the migration of germ-cells becomes one ot
great interest in relation to Wcismann's theory after
the tJieory has been accepted^ the fact in itself docs not
furnish any evidence in support of the theory. In
the first place, it tends equally well to support Galton's
theory of stirp ; and therefore does not lend any
special countenance to the theory of germ-plasm — or
the theory that there cannot now be, and never can
have been, any communication at all between the
plasm of the germ and that of the soma. In the
second place, the fact of such migration is not incom-
patible even with the theory of pangenesis, or the
theory which supposes such a communication to be
extremely intimate. There may be many other
reasons for this migration of germ-cells besides the
one which Weisrnann's theory supposes. For example,
the principle of physiological economy may very
well have determined that it is better to continue for
reproductive purposes the use of cells which have
already been specialized t nd set apart for the execu-
tion of those purposes, tban to discard these cells
and transform others into a kind fitted to replace
them. Even the theory of pangenesis requires to
assume a very high tlcgree of specialization on the
part of germ -cells ; and as it is the fact of such
specialization alone which is proved by VVeismann's
observations. I do not see that it constitutes any
criterion between his theory of heredity and that of

74 -^^^ Exa7nination of Weisinannism.

Darwin — still less, of course, between his theory and
that of Galton. Lastly, in this connexion we ought
to remember that the Ilydyomcditsae are organ-
isms in which the specialization in question happens
to be least, as is shown by the fact that entire indi-
viduals admit of being reproduced from fragments ot
somatic-tissues ; so that these are organisms where
we would least ex[)cct to meet with the migration
of germ-cells, were the purpose of such migration
that which Weismann suggests. This line of evidence
therefore seems valueless.

Nor does it appear to me that the second line of
evidence is of any more value. In the first place,
there is no shadow of a reason for supposing that an
apparently anatomical isolation of germ-cells neces-
sarily entails a physiological isolati.Qn as regards
their special function— all "physiological analogy,"
indeed, being opposed to such a view, as is shown
in Appendix I. In the second place, there^js no
proof of any anatomical isolation, as we may like-
wise see in that Appendix. In the tlijrd place, the
fact relied upon to indicate such an isolation — viz.,
the early formation of germ-cells — is not a fact of any
general occurrence. On the contrar}', it obtains only
in a comparatively small number of animals, while it
does not obtain in any plants. In the Vertebrates,
for example, the reproductive cells are not dif-
ferentiated from the somatic cells till after the em-
bryo has been fully formed; while in plants their
development constitutes the very last stage of onto-
geny. In the fourth place, the argument, even for
what it is worth, is purely deductive ; and deductive
reasoning in such a case as this — where the phonemena

m

•i

IVcisnianiis theory of Heredity (1891). 75

are enormously complex and our I'f^norancc unusually
profound — is always precarious. Lastly, in the fifth
place, Weismann has now himself abandoned this
argument. For in one of his later essays he says : —

Those instances of early separation of sexual from somatic
ce'ls, upon which I have often insisted as indicatint^ the con-
tinuity of the gerni-[)lasm, do not now appear to be of such
conckisive importance as at the time when we were not sure
about the locaUzation of the plasm in the nuclei. In the great
majority of cases the germ-cells are not separated at the
beginning of embryonic development, but only in some of the
..iter stages. ... It therefore follows that cases of early separa-
tion of the germ-cells afford no proof of a direct jjersistence of
the parent germ-cells in those of the offspring.

The last line of direct evidence, or that derived
from the alleged non-variabilily of parthenogenetic
organisms, is, as Professor Vines has shown, opposed
to fact. Therefore, in liis later writings, Weismann
has abandoned this line of evidence also.

Upon the whole, then, we must conclude with regard
to the fundamental postulate of perpetual continuity,
that there is actually no evidence of a direct kind in
its favour. And, as Weismann's arguments of an
indirect kind are dealt with in Appendix I, it remains
only to state such evidence per contra as, to the best
of my judgement, appears valid.

The fundamental proposition which we have been
considering, and to the further consideration of which
we have now to proceed, is, in effect, that germ-plasm
differs from stirp in having hcQU pcrpet/ia/iy restricted
to a " sphere " of its own. " si/icc tJic first origin of
life." Criticism, therefore, must be directed to show
that the "sphere"' in ciuestion has not been proved

il :

3 i

76 An Examination of Weismannism.

so entirely inclci)cnclent as this fundamental proposition
sets forth ; but that, on the contrary, there appears
to be a certain aiTiDunt of reciprocal action between
this sphere and that of the somatic-iissucs — even
though we may ai^ree (as I myself agree) with Galton
in holdinc^ that the degree of such reciprocal
action is neither so intimate nor so constant as it
was held to be by Darwin. This, indeed, is the
direction which the course of our criticism has taken
already. For it has just been shown that Weismann
has failed to adduce any facts (preceding text) or
considerations (Appendix I) in support of his fun-
damental proposition as above stated, save such as
proceed on a prior acceptance of the proposition
itself. The facts and considerations which he has
adduced are therefore useless as evidence in support
of this proposition, although they would admit of
being explained by it supposing it to have been
already substantiated by any facts or c )nsiderations of
an independent kind. Which is merely another way of
saying, as already said, that there is no evidence in
favour of the proposition.

But I am now about to argue that there is evidence
against the proposition. For I am about to argue,
not only as heretofore that for anything Weismann has
shown to the contrary there may be a certain amount
of reciprocal action between the sphere of germinal-
substance and the sphere of body-substance ; but that,
as a matter of fact, there is a certain amount of such
reciprocal action.

Without laying undue stress on the intimate
" correlation " that subsists between the reproductive
organs and all other parts of the organism, I never-

Weismanns theory of Heredity (1891). 77

thcK'ss think that the fact ou^ht here to be noted.
For the chani^cs which occur at puberty and after the
reproductive functions have ceased, as well as those
wliicir~fYiiiy" be artifTcially produced by castration.
&c., prove at any rate some extremely important
association between the soma as a whole and its
reproductive apj^aratus as a whole. No doubt it may
projjerly enouL^h be answered that this proof does not
extend to the vital point of showing the association
to be between the soma as a whole, and that i)articular
part of tile reproductive apparatus in which the
"carriers of heredity" reside — niunely, the ova and
spermatozoa ; and, therefore, that the facts in question
may be due only to some chanj^^ed conditions of
nutrition on the part of the somatic-tissues which
these alterations on the part of the reproductive Ljlands
entail. On this account we must fully allow that the
facts in question are not in themselves of any con-
clusive weight ; but I think they are worth mentioning,
because they certainly seem to countenance the theory
which sup[)ose3 some reciprocal influence as exercised
by the germinal elements on the somatic-tissucs_and
vice versa, rather than they do the theory which sup-
poses the germinal elements and the somatic-tissues
to have always occupied totally different " spheres."

Here, however, is a stronger class of facts. It has
not unfrequently been observed, at any rate in mam-
mals, that when a female has borne progeny to
a maleof one variety, and subsequently bears progeny
to a male of another variety, the younger progeny
presents a more or less unmistakable resemblance to
the father of the older one. Now. this is a fact to
which Weismann has nowhere alluded ; and therefore

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78 An F.XiVtiination of IVcisniaiinism.

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I do not know how he would meet it. Hut, as far as
I can sec, it can l)e explained only in one or other of
two ways. Either there must be some action of_the
spermatic element on the hitherto unripe_ovum^oj;j;lse
this element must e.xercisc some influence on the so-
matic-tissues of the female, which in their turn act uiwn
the ovum \ Now, I do not deny that the first of these
possibilities micjlit be reconcilable with the hypothesis
of an absolute continuity of ^crm-plasm ; for it is
conceivable that the life of L^ermplasm is not co-
terminous with that of the spermato/oa which convey
it. and hence that, if the carriers of heredity, after the
disintei^ration of their containing si)ermato/.oa, should
ever penetrate an unri[)e ovum, the L'erm-j)lasm thus
introduced mi_L!;ht remain dormant in the ovum until the
latter becomes mature, and is then fertilized by another
sire. In this way it is conceivable that the hitherto
dormant germ-plasm of the previous uire might exercise
some inlluence on the progeny of a subse(]uent one.
lUit it seems clear that the second of the two possi-
bilities above named could not be thus brought within
the hypothesis of an absolute continuity of germ-
l)lasm. Therefore it seems that the school of VVeis-
mann muse adopt the first, to the exclusion of the
second. Unfortunately for them, however, there is
another (and clearly analogous) fact, which goes to
exclude the first po.ssibility, and most definitely to
substantiate the second. For, in the case of plants,
where there can be no second [)ro-^eny borne by the

su

* The possil)ility of any s]iciniati>zoa of the first iinprcQiiatioii
rviviiij; to lake part in the sfcoml is cxchidcd by tlie fact tiiat the
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or tlucc Inters.

U'cismaiin s theory of Heredity (1891). 79

same " ovary," but where \vc happen to be able to see
that a. marked effect is sometimes produced on the
somatic-tissues of the rnother by the pollen of the
father, there can be no question as to the male element
being able to exercise a ilircct influence on the soma
of the female. Consequently, whatever we may think
with regard to the case of animals, the facts with reL,Nucl
to plants are in themselves enough to sustain the only
position with which we are concerned viz., that the
male element is capable of directly modifying the
female soma.

The facts with regard to plants are these. When
one variety fcrtili/cs the ovules of another, not
unfrequcntly the influence extends bejond the ovules
to the ovarium, and even to the calyx and flower-
stalk, of the mother plant. This influence, which
may affect the shape, size, colour, and texture of the
somatic-tissues of the mother, has been observed in a
large number of plants belonging to many different
orders. The details of the matter have ahead)' been
dealt with by Darwin, in the eleventh chai)ter of his
work on \ 'ariadon, &c. ; and this is what he says.
The italics are mine.

^h

The proofs of the action of forcifrn po'len on the mother -plant
have been given in considenible iletail, l)cc;uise this aciiun is of
the hij^^hest theoretical iinporlance, and Ijecaiise it is in itself
a remarkable and ai)|)arently anomalous circumstance. Thai it
if remarkable undir a |)hysiological point of \ iew is clear, for
the male element not only affects, in accordance with its proper
function, the },'erm, but at the same time various i)arts of the
mother-plant, in the siuiie maiincr as il itjj\cls ilic saiiic piirts in
tlie seminal offspriiii:; from tlie siivie lico parents. We thu!r
learn that an ovule is not indispensable for the reception of tha
intluence ol the male element.

8o An Examination of Weisniannism,

Darwin then proceeds to show that this direct action
of the male clement on the somatic tissues of another
organism is not so rare or anomalous as i^^ at first
sight appears ; for in the case of not a few Howers it
comes into ;)lay as a needful preliminary to fertiliza-
tion. Thus, for instance : —

Cjirtner j^'radually increased the number of pollen grains
until In; succeeded in fertilizing a Malva. and has proved that
many grains arc first expended in the development, or, as he
expresses it, in the satiation, of the pistil and ovarium. Again,
when one plant is fertilized by a widely distinct species, it often
happens that the ovarium is fully and quickly developed
without any seeds lieing formeil ; or the coats of the seeds are
formed without any embryo being developed therein.

So mucli, then, in proof of the direct action of
the male element on the somatic-tissues of another
organism. It remains to show that a similar action
may be exercised by this element on the somatic-
tissues of its own organism. This has been proved by
llildebrand, who found "that in the normal fertiliza-
tion of several Orchideae, the action of the plants
own pollen is necessary for the development of the
ovarium ; and that this development takes place not
only long before the pollen tubes have reached the
ovules, but even before the placentae and ovules have
been formed " ; so that with these orchids the pollen
acts directly on their own ovaria, as a prelim inary~to
the formation of the ovules which are subsequently
to be fertilized.

It is to be regretted that Professor Weismann
has not given us his opinion upon this whole class
of facts, for assuredly they api)ear directly to con-
tradict his theory. The theory is, '• that the germ-

IVci's/fiaini's theory of Ilcrcdiiy (1891). 81

plasm and the somato-plasin liavc always occupied
different spheres": thejact_is, that the j^erin-phisni
may directly act upon the somato-plasm, both within
and beyond the lin^its of the same ur;.;anism.

Hitherto we have been considcrini; certain very
definite facts, which seem to prove that the Ljerminal
elements are able directly to affect the somatic-tissues.
VVe have next to consider such facts as seem to prove
the opposite side of a reciprocal relationship — viz.,
that the somatic-tissues are able_directly to idfect
the germinal elements.

And here there are two distinct lines of evidence
to be distinguished.

Firstly, in certain cases — exceptional it is true, but
this does not signify— somatic-tissues have been found
capable of modifying the hereditary endowments of
germinal elements by means of simple grafting. This
Hne of evidence has also been disregarded both by
Weismann and his followers ; but it is nevertheless an
important one to consider. For, if it be the case
that the somatic-tissues of an organism A, by being
merely grafted on those of organism B. can so affect
the germinal elements of B as to cause their offspring
to i'escmble A — or, contrariwise, if the somatic-tissues
of A can thus act on B -then, although it may not
be properly said that any "acquired cnaracters" have
been transmitted from A to the progeii)- of B, (or
vice versa,) such an a-sexual transmission of alien
characters, in its relation to the theory of germ-i)hism,
is scarcely less awkward than are certain facts which
they appear to prove.

Secondly, that acquired characters may be trans-

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82 An Exauiination of W^cisnianmsm.

mittcd to prc\cjcny by the more ordinary methods of
sexual propa<4'ation(Laniarckian factors). This second
line of evidence will be fully and independently dealt
with in future chapters, specially devoted to the
subject. Therefore we have here to consider only the
first.

Now, the force of this first line of evidence will
become apparent, if wc rcfiect that the only way
in which the facts can be met by W'eismann's theory,
would be by supi)()sin^f that the somatic germ-plasms
which are respectively diffused throu;j[h the cellular
tissues of the scion and the L^raft become mixed in
some such way as they mii^ht have been, had the
hybrid been due to seminal propagation instead of to
simple grafting. But against this, the only interpre-
tation of the facts wliich is open to the theory, there
lies the follcnving objection, which to me appears
insuperable.

Where sexual cells are concerned there is alwa)'s
a definite arrangement to secure penetration of the
one by the other, and we can see the necessity for
such an arrangement in order to effect an admixture of
their nuclear contents, where alone germ-plasm is
supposed by Weismann's theory to reside. Ikit in
tissue-cells which have not been, thus s[)eciali/,ed, it
would be difficult to believe that nuclear contents can
admit of being intimately fiised by a mere apposition
of cell-walls. For not only are the nuclear contents of
any two such cells thus separatetl from one another
by two cell-walls and two masses of " cytoplasm " ;
but it is not enough to supi)Ose that in order to
produce a graft-h\brid only two of these .somatic-cells
need mix their nuclear contents as we know is all

ays

the

for

of

is

in

it

an

lion

of

to

:lls
ill

Wcisnuinns theory of lie natty (1891). 83

that is required in order to ])roduce a seminal hybrid
by means of sexual cells. On the contrary, in the
former case most, if not all, the .somatic-cells which
arc brought in'.o apposition by the i^rat't must be
supposed thus to mi.\ thtir nuclear contents at the
plane of the i^raft ; for otherwise the hybi'id would not
afterwards present equally the characters of stock and
scion. Now, there may be hundreds of thousands of
such cells, and therefore it seems impossible that the
facts of t^raft-hybridization can be reconciled with the
theory of L;erm-plasms '.

The third line of evidence ac^ainst this theory —
i.e., the evidence in favour of the transmission of
acquired characters — is to constitute the subject-
matter of future chapters. Therefore it will here be
sufficient tt) adduce only one fact t)f this kind. And
I select it because it is one that has b<,'en dealt with by
VVeismann himself. In one of his more recent state-
ments he sa)s : —

The distinguished botanist De Vrics has proved that certain
constituents of the cell body e.;,;., llie chroniatuphores ot
.•\l;-jac pass directly from the maternal ovum to the dauj^hter
organism, while the male ^erm-cells {generally lontain no
chromatophores. Here it appears possible tlial a transmission
of somatu'jenelic variation has occurred '".

Now althouLjh. as W'cismanii i^ncs on to observe,

' Possibly the sclujol of Wcisiiiaiiii may siiii|il\' r( fuse to accept tlie
f.icts, which arc conrL'ssi<l]y raic. aiul, iii many ot llic cases allci^eii,
(iul)ious. In ullier easts, however, tlie e\i(le!ice is sufficient to have
salislied tlie caiilious jiulj;cmeiit of |)ar\\in, who ha-. <iiscus.-<e(i it in
detail. Tlierefore, even if the Meo-Darwiniaiis reimdiue llii> evidence,
ac least they iiiii;lit to state lli.it sucli is liie \ ositioa wlaoh ihey
adojil.

^ Aatwc, Feb. Otii, iSyo.

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84 An Hxaniinatioii of Wcismaiuiism.

'* in tlicsc lower plants, the scj)arati()n between somatic
and reproductive cells is sli^dit,"' in the facts to which
he alludes we appear to have ^ood evidence of an
influence excrcisetl by somatic cells upon the germinal
contents of reproductive cells. And if such an influence
is capable of bcin;^ exercised in the case of " these
lower plants," it follows that there is no such absolute
separation between somatic tissues and ^erm-plasm as
VVeismann's theory recpiires. Moreover it follows
that, if the essential distinction between ^erm-plasm
and somato-plasm (or " somatic idioplasm ") is thus
violated at the very foundation of the multicellular
orr][anisms. there ceases to be any a priori reason for
drawing arbitrary limits, cither as to the level of organ-
ization at which such " transmi.ssion of somatogenetic
variation has occurred." or as to the degree of detail
into which it may extend. ]?oth these matters then
.stand to be tested by observation ; and the burden of
proof lies with the school of Weismann to show at
what level of organization, and at what degree of
representation, somatogenctic changes cease to repro-
duce themselves by heredity.

Passing on, then, to higher levels of organization,
and therefore to higher degrees of representation,
I shall endeavour to show that this burden of proof
cannot be discharged. For I shall endeavour to
show, not merely, as just shown, that there ceases
to be any a priori reason for drawing arbitrary
limits with respect either to levels of organization
or to tlegrces of representation, but that, as a matter
of fact, there are no such limits as the passage above
quoted assigns. On the contrar\'. I believe there
is as good evidence to prove the not unfrequent

Wcismanns theory of Heredity (1891). 85

transmission of acquired (" somatofrcnctic ") characters
amonjT the higher plants -and even among the higher
animals — as there is of the occurrence of this phe-
nomenon in the case of the Alga just mentioned. But
in order to do this evidence justice, I shall have to
take a new point of de[)arture and consider as a
separate question the transmissibility of accjuired char-
acters. Meanwhile, and as far as W^eismann's theory
of heredity is concerned, it is jnough to have shown, —
if I have been successful in doing so, — that not only
is there no evidence to sustain his fundamental postu-
late touching the material of heredity having always
occupied a separate "sphere" of its own "since the
first origin of life"; but that there is good evidence
to prove the contrary. For whether or not the re-
ciprocal action of "somato-i)lasm " and "germ-plasm"
can ever proceed to the extent of causing acquired
characters to be inherited (so as to produce '' repre-
sentative congenital changes "), all that is distinctive
in this theory must be regarded as barren speculation,
unless it can be shown that the foregoing facts have
failed to prove such a reciprocal action as ever
occurring in any lower degree (so as to produce
"specialized congenital changes ").

':!

I I

CHAITICR IV.

KXAMINATIOX OV Wf.ISMANN's TiIKORY
OK lOVOLKTION ( I -Si; I ).

IIavixc. now considered cfcrm-plasm as perpetually
continuous. \vc have next to regard it as unalter-
abl\' stable.

First, let it be noted that these two fundamental
and distinctive postulates of the whole Weismannian
system are so intimate!}' connected as to be in lari^^e
measure mutually dependent. I"\-)r. on the one
hand, if u^erm-plasm has not been pcri)etually con-
tinuous since the Hrst ori^rin of life, it cannot have
been absolutely stable "since the Hrst orit:jin of sexual
propat^ation " : every time that its hereditary characters
are mollified by its containincj soma (whether or
not represeniatively so), its stability has been so
tar upset. On the other hand, if L^erm-plasm has
not been ab.solntcly stable, it cannot have been per-
petually continuous ''since the first origin of life."
As oftjen as its stability has been upset, it.s " mo-
lecular structure'' has been modified by gauscS-_<T^^
extra, as distinc^uished from mixtures of f^ermjj^)l;L?ms
in sexual unions. Therefore, it can no longer have
been continuous in the sense of having borne an
ineffaceable record of all congenital variations, due to
sexual unions^ throughout the entire phylogeny of

IVcistnanns theory of livolution (1S91). 87

the Mctaphyt.i and Mcta/oa. At most it can have
been continuous only in the attenuated sense, that
however much and however often its herechtary
characters may have been modified by somatic
changes on the one hand or by changes in tiie
external conditions of hfe on tlie other, they can
never have been thus modit'ied rc[^rcscntatively, as
supposed by tiie thet)ry of paiiLjenesis.

l"*rom which it follows that, while examininij in
our last chapter Wei.smann's doctrine ol the i)er-
pctual continuity of i^erm-plasm, we have been
ii.tlirectly examinini,' also his companion doctrine of
the unalterable stability of germ-plasm. Neverthe-
less, for the sake of doing justice to both these
doctrines. I have thought it desirable to examine
each on lis own merits, without prejudice arising
from our criticism of the other. To such a .separate
and independent examination of the doctrine of
unalterable stability wc will, therefore, now proceed.

As we have already and repeatedly seen, this
doctrine of the unalterable or absolute stability of
germ-plasm "since the first origin of sexual propaga-
tion" is a logically es.sential part of VVeismann's
theory of evolution, or of his system of hypotheses
consideretl as a whole. It is so because upon this
doctrine de[)cnds his reference of individual variations
in the Meta/.oa to an ultimate origin in the Protozoa,
the significance of sexual reproduction in the theory
of natural selection. &c., &c. Therefore this doctrine
of the absolute stability of gcrm-[)lasm is enunciated
by Weismann, not merely for the purpose of meeting
any one class of facts, such as tho.se of atavism

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88 ylfi Jixiwiiuation of U'eisfinviuism.

pcrslstincc of rudinicntary orfjans, &c. Tlie doctrine
is enunciated for the purpose of constituting one of
the foundation-stones of liis ;^fcneral tlieory of evolu-
tion. We have now to consider how far the (juality
of this stone renders it trustworthy as a basis to build
upon.

In the first place, wc can .scarcely fail to perceive
that this doctrine of the absolute stability of ^^erni-
|)lasm is not only gratuitous, but intrinsically imi)ro-
bable. That the most complex material in nature
.should likewi.se be the most .stable is oppo.sed
to all the ana!(^^ies of nature, and theref(jrc to
all the probabilities of the case.

Again, the ^a-rm-plasm, as it oriujinaliy occurred
(and .still exists) in unicellular or^janisms. is sujjposed
to be exactly the same kind of material as now
occurs in the ^crm-cells of multicellular (.rjjanism.s.
Yet the ver>' same theory wiiich suppo.ses so
absolute a stability on the [)art of gerni-plasm
when located in y;erm-cells (or diffused throu<^h
somatic-cells), likeui.se supposes so hi<;h a de^jree of
variability on the part of ^^erm-plasm when not thus
located, as to represent that all individual variations
which have ever taken place in the unicellular
ort,Mnisms — and all the innumerable species of such
orL^anisms which have arisen therefrom — have been
due to the direct action of external cond ijt ion sof_ life ;
or. in other words, to the instability of germ-plasin.
The very same substance which at one time and in one
place is supposed to be .st) absolutely unchaufj^eable,
at another time and in another place is supposed to
be hiL^hly susceptible of chan^jc.

Lastly — and this is. perhaps, the most curious part

ll'cismanns theory of Evolution (1891). S9

of the whole matter — the place where ^erm-plasm is
supposed to be unchangeable is not the place where
it is most likely to be so, but the place where it is
least likely. For ^'crin-plasm as it occurs in the ^crm-
cells of multicellular orijanisnis must have a constitu-
tion greatly more complex even than that which it has
in unicellular ori^anisms— seeing that in the former
case, and by hypothesis, it bears a living; record of the
whole phylo{^'eny of the Melaphyl.i and Meta/oa in
all their innumerable branchin^rs. And not only so,
but when germ-plasm occurs in germ-cells it becomes
exposed to much greater vicissitudes : its environment
has become vastly more complex, aj>j\vell as greatb
rnore liable to change with the changing conditions of
life of the many^ m..Lii!jle species in which it resides,
and on the ir ''vidual somas of which it now depends
for its nourishment. So that, altogether, we have here
on merely a priori grounds about as strong a case
against this doctrine of absolute stability as it is well
conceivable that on merely a priori grounds a case
can be.

Turning next to arguments a posteriori, let us begin
by considering those which \\ eismann has adduced in
support of the doctrine.

First, he alleges that there is a total absence of
variability on the part of all organisms which have
been produced parthcnogcnctically. t)r from unfer-
tilized ova. We may look in vain, he says, for any
individual differences on the part of any multi-
cellular organisms, which have been brought into ex-
istence independently of the blending of germ-plasms
in a previous act of sexual union. Now, u.ique.s-
tionably, if this statement could be corroborated by

ilj

■i,i±

n

J

1.1)

90 yin Exavii nation of Weisinannis7n.

sufficiently extensive observation, the fact would
become one of immense si[^nificancc — so much so,
indeed, that of itself it would ^o far to neutralize all
antecedent objections, and to verify his theory as to
sexual propaL;jation being the sole cause of coni^enital
variation. Ikit seeing that the alleged fact stands so
entirely out of analogy with the phenomena of bud-
variation (which will be alluded to later on), it is
highly improbable, even on antecedent grounds; while
Professor Vines has refuted the statement on grounds
of actual fact. Thus, speaking of the Basidiomycetes^
he says —

These Fiinj;i are not .)nly entirely a-scxual, but it would appear
that they have been evolved in a purely a-scxual manner from
a-sexual ascomycetous or ;ucidiomycetous ancestors. The
Uasidiomycetcs, in fact, affonl an example of a vast family of
plants, of the most varied form and habit, including hundreds
of genera and species, in which, so far as minute and long-
continued investigation has shown, there is not, and probably
never has been, any trace of a sexual process '.

Here, then, we have actual proof of "hereditary
individual variations" among a-sexually propagating
organisms, sufficient in amount to have given origin,
not merely to ''individual differences." but to in-
numerable speci3s, and even genera. Consequently
Weismann allows that the criticism abolishes this line
of evidence in favour of the absolute stability of germ-
plasm '-. Consquently. also, wc must now add, in
whatever measure the alleged fact would have corro-
borated the theory had it been proved to be a fact,
in that measure is the theory discredited by proof that

* Nature, vol, xl. p. 626.
' Ibiii., vol. xH. p. 33a.

IVeisfuann's theory of Evolution (1891). 91

it is not a fact. For, if tlie theory were sound, this
particular fact would certainly have admitted of de-
monstration : therefore the proof that it is not a fact
— but the reverse of a fact — amounts at the same time
to a disproof of the theory ^.

The only other line of evidence to be adduced in
favour of the absolute stability of <:(crm-plasni is that
which is furnished by the hiL;"h antitjuity of some specific
ty[)es, by the facts of atavism, and by the persistency
of vcstit;ial orij^ans. But this line of evidence is as
futile as the other. Nobody has ever questioned
that hereditary characters are persistently stable as
lontf as they arc persistently maintained by natural
selection ; and this. accordiuLj to Weismann himself,
must have been th" case with all lon<^-endurini^
species : these, therefore, fail to furnish any evidence
of the inJicrcni stability of germ-[)lasm, which is the
only point in question.

Ai^ain, as ret^ards the facts of atavism, nobody is
disputing these facts. What we are disputing is
whether the degree of inherent stability which they
uncjuestionably prove can be rationally regarded as

' In his Essays (vol. i. p. 2^2^ Wiismann snys: — " If it could he shown
that a purely imrtheiiogenctic si)cci(.s hnd hccome transformed into a
new one, such an observation would i^rove the existence «)f some m w
force of transformation otlier than seleetivc processes, for the new species
could not have been produced by these latter." lUit now it has been
shown that a ]nnely ]iartlKiiot;enetic specii s can bi' transformed into
a new one, and tiierefore it seems desiralilc to note tliat the observation
does not so much as tend to prove the existence of some iicw force
of transformation other than selective prc::esscs. Fortius most singular
statement can only stand on a prior aci:eptance of \\ eismaim's f)wn
assum|)tion, as to ajiij^hij^ony lieini^ the only possible cause of indivi(hial
hereditary variation. Only if we have already, and wilii aljsolute
certainty, embraced the whole Weismamii;\n creed, could we consent to
aftirm that " natural selection is an impossiLiility in a species propagated
by a-sexual repioiluclion."

H^X

92 An Examination of Weismamiism.

such that it may endure, not merely for such a com-
paratively small number of generations as these facts
imply, but actually for any number of generations,
or through the practically infinite series of generations
that now intervene between the higher metazoa and
their primeval parentage in the protozoa. Clearly,
the ratio between these two things is such that no
argument derived from the facts of at ivism can be
of any avail Tfor the purposes of this VVeismannian
doctrine.

Lastly, as regards vestigial organs, the consideration
that, surprisingly persistent as they unquestionably are,
nevertheless they do eventually disappear, seems to
prove that the power of heredity does in time become
exhausted, even in cases most favourable to its con-
tinuance. That it should thus become finally ex-
hausted is no more than Darwin's theory of perishable
gemmules, or Galton's theory of a not absolutely
stable stirp, would expect. But the fact is irre-
concilable with Wcismann's theory of an absolutely
stable germ-plasm.

Hence, we can only conclude that there is no
evidence in favour of the hypothesis that germ-plasm
has been unalterably stable "since the first origin
of sexual propagation"; while the suggestion that
it may have been so is on antecedent grounds im-
probable, and on inductive grounds untenable. It
only remains to add that the dc^'ee of stability
has been proved in not a few cases to be less than
even the theory of gemmules might anticipate. Many
facts in proof of this statement might be given, but it
will here suffice to quote one, which I select because
it has been dealt with by Professor Weismann himself.

lelf.

Weismanns theory of Evolution (1891). 93

Professor Hoffmann has published an abstract of
a research, which consisted in subjecting; plants with
normal flowers to changed conditions of life through
a series of generations. In course of time, certain well-
marked variations appeared. Now, in some cases such
directly-produced variations were transmitted by seed
from the affected plants ; and therefore Weismann
acknowledges,—" I have no doubt that the results are,
at any rate in part, due to the operation of heredity."
Hence, whether these results be due to the trans-
mission of somatogenetic characters (" representative
changes"), or to the direct action of changed conditions
of life on the germ-plasm itself (" specialized changes"),
it is equally certain that the hereditary characters
of the plants were congenitally modified to a large
extent, within (at most) a few generations. In other
words, it is certain that, if there be such a material as
germ-plasm, it has been proved in this case to have
been highly unstable. Therefore, in dealing with
these and other similar facts, Weismann himself can
only save his postulate of continuity by surrendering
for the time being his postulate of stability ^.

If to this it be replied that Hoffmann's facts are
exceptional— that Gartner, Niigeli, De Candolle, Peter,

' What he says is : — " It was only after a preritcr or less number
of {jenerations ha<l elajiscd ihat a vaiinhle ] rojiortion of douljle flowers
appeared, sometimes accompanied liy ciianL,'es in ifie leaves and in the
colours of the flowers. 'I'liis fact adniils of oily one ititcypyctation : —
the changed conditicms at first produceii slii^lit and in(.tTeciual changes
in the idio-plasm of the individual, which was transmitted to the following

generation Now, the idio-plasm of the fust iintugtnclic giaoe

(VIZ., germ-plasm alone passes from one generation to another, and
hence it is clear that the germ-plasm itself must have been gradually
changed by the conditions of life, until the alteration became sufficient to
produce changes in the soma, whicli appeared as visible characters in
either floiver or leafy — l\ssays, pp. 42O-7 j italics nuue.

I

»■

M

\i

i

1

!i

94 An Examination of Weismannism.

Jordan, and others, did not find individual variations
produced in plants by chan<;cd conditions of life to
be inherited, — the reply would be irrelevant. It does
not require to be proved that all variations produced
by chanijed conditions of life are inherited. If only
some — even thou^^h it be but an extremely small
pcrcentac,^e — of such variations are proved to be
inherited, the many millions of years that separate
the i^erm-plasm of to-day from its supposed origin
in the protozoa, must have furnished opportunities
enoucfh for the occurrence of such variations to have
obliterated, and re-obliterated numberless times, any
aborii^inal differences in the j^crm-plasms of in-
cipiently sexual organisms. Moreover, it is probable
that when further experiments shall have been made
in this direction, Hoffmann's results will be found
not so exceptional as they at present appear.
Mr. Mivart, for example, has mentioned several
instances ' ; while there are not a few facts of
gener^v' knowledge — such as the modifications under-
gone by certain Crustacea as a direct result of
increased salinity of the water in which they live —
that will probably soon be proved to be facts of the
same order. lUit here attention must be directed
to another large body of facts, which are of high
importance in the present connexion.

The phenomena of what is called bud-variation in
plants are phenomena of not infrequent occurrence,
and they consist in the sudden ap[)earance of a
peculiarity on the part of a shoot which develops
from a single bud. When such a peculiarity arises,
it admits of being propagated, not only by cuttings
' Nature, Nov. 14, i88y, p. 41.

Wei s maun s theory of Evolution (1891). 95

a

and by other buds from that shoot, but sometimes
also by seeds which the flowers of the shoot sub-
sequently produce — in wliich case all the laws

)f inhei

thj

ritance tnat apply to conLjenitai vanatums
are found to apply also to bud-variation. Or, as
Darwin puts it, '' there is not any particular in which
new characters arising by bud-variati(jn can be dis-
tinguished from those due to seminal variation " ;
and, therefore, any theory which deals with the latter
is bound also to take cognizance of the former. Now,
as far as I can fuid, there is only one paragrai)h in
which Weismann alludes to bud-variation, and what
he there says I do nut find very easy to understand.
Therefore I will quote the whole paragraph verbatim.

I have not hitherto consiilcred budding in relation to my
theories, but it is obvious tliat it is to l)e explained, from my
point of view, by sujjposinj,' tliat the t;enn-pkisin which passes
on into a butldini; indiviilual consists not only of tiie un-
changed germ-pl.ism of the first ontogenetic stage, but of this
substance altered, so far as tt) correspond with the altered
structure of the indivitlual which arises from it -viz., the root-
less shoot which sjjrings from the stem or branches. Th:;
alteration must be very slight, and perhaps c|uite insignificant,
for it is possii)le that the differences between die secondary
shoots and the primary plant may cepend chiefly o. the changed
conditions of development, which takes place lieneath the
earth in the latter case, and in the tissues of the plant in the
former. Thus we may ''^lagine that the idio-plasm |.' of that
particular budj, when itdc.elops into a (lowering shoot, produces
at the same time the germ-celis which are found in the latter.
We thus approach an understanding of Fritz Miiller's obser-
vation ; for if the whole shoot which produces the tlower arises
from the same idio-plasm which also forms its germ-cell^, we can
readily understand why the latter should cont.iin the same
hereditary tendencies which were previously expressed in the
tiower which produced them. The fact that variations may

' M

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i If

it'

■i!

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iii ■

96 An lixainination of Weismannism.

occur in ;i single shoot depends on the changes explained above,
which occur in the idio-plasni durin},' the course of its growth,
as a result of the varying proportions ir (which the ancestral
idio-plasms may be contained in it '.

The meaniiiL^ here appc;ir.s to be twofold. For
there are only two ways of explaining the phenomena
of biid-vaiiation. Either they are due to the influ-
ence of external conditions actini^ on the particukir
bud in question, or else they are due to so-called
"spontaneous" chan<jes taking place within the bud
itself. Possibly it may be both, but at least it must
be either. Well, in the above passage, Weismann
appears to assume that it is both. For at the begin-
ning of the passage he speaks of the " germ- plasm of
the first ontogenetic stage " becoming " altered so
far as to correspond with the altered structure of the
individual which arises therefrom," and he goes on
to say that the alteration " may depend chiefly on
the changed conditions of development " — that is, as
I understand, the influence of external conditions.
But at the end of the paragraph he says that " the
changes which occur in the idio-plasm during the
course of its growth " in the sporting bud, are due to
" the varying proportions in which the ancestral idio-
plasms may be contained in it." Thus, I take it,
Weismann here entertains both explanations of the
phenomena in question : he appears to regard these
phenomema as partly due to peculiar adm'xtures of
ancestral idio-plasms in the bud itself (or ''spon-
taneous " variation), but partly also to an alteration
of the germ-plasm by its changed condition of develop-
ment (or variation caused by external conditions;),

* Essays, ind Ed., pp. 331-3.

above,
rowth,
ccslral

For

)mcna
influ-
ticukir
-called
\e bud
t must
ismann
bcgin-
iasm of
red HO
2 of the
roes on
cfly on
is, as
itions.
; '-the
the
due to
al idio-
take it,
of the
d these
:ures of
" spon-
:eration
levelop-

ng

Weismaiius theory of Evolution (1891). 97

However, it is but of little consequence whether or
not this is the meaning which Weismann intends to
convey. For the point we are coming to is, that,
whatever he intends to convey, ** from the point of
view " of the theory of germ-plasm, there is only otic
interpretation possible. It is not open to Weismann
(as it was to Darwin, or even to Galton,) to entertain
both the explanations, whether separately or in con-
junction. For germ-plasm (unlike gemmules, or even
stirp) must be held always and everywhere unalterably
stable : else the whole superstructure of Weismann's
theory of evolution falls to the ground. We cannot
consent to his retaining this theory on the one hand,
and, on the other, explaining bud-variation by "germ-
plasm of the first ontogenetic stage " becoming
altered "chiefly by changed conditions of develop-
ment." Even if it were true that " the alteration
must be very slight, if not quite insignificant," there
would here be a rift in the lute, which must finally
stop any further harping on the subject of Evolution.

From the point of view of this theory, then, there
is only one interpretation open, — viz., that a bud-
variation is ultimately due to a peculiar admixture
of germ-plasms in the seed from which the bud was
ultimately derived. But the objections to entertaining
this as even a logically possible explanation of the
phenomena in all cases, is insuperable.

In the first place, such a variation, when it does
arise, is usually a variation of an extremely pronounced
character ; therefore it is very far from supporting
Weismann's view, that the " alteration " of germ-plasm
which is needed to produce it '* must be very slight,
and perhaps quite insignificant." In most cases where

U

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i1

H,

tt.

h

i

Hi.

98 An Bxamina/jon of Wetsmannisnt.

it occurs bud- variation presents so extreme a departure
from the normal type, that no other kind of variation
can be fitly compared with it in this respect. In
particular, the degree of variation is usually very
much greater than that which customarily obtains in
congenital vai iations of the ordinary kind ; and. there-
fore, if there be supposed due to particular admixtures
of germ-plasm in sexual propagation, much more
must those admixtures which give rise to sporting
buds be characterized by peculiarities of no "insigni-
ficant " order. And much more, therefore, ought
they to assert themselves in sister-buds developed
from the same individual seed (ovule), than we find
to be the case with any sister-organisms which are
developed from different individual seeds. Yet, in the
second place, so far is this from being the case, that
the most remarkahie feature connected with bud-
variation — next to the suddenness and extreme amount
of the variation itself — is the usually isolated nature
of its occurrence. There mav be thousands of other
buds on the same plant, and yet it is one bud alone
that deviates so suddenly and so widely from its
ancestral characters. Nay, more, a single bud-varia-
tion may — and usually does — occur in plants which
are habitually propagated by cuttings and graftings ;
so that there may not only be thousands, but millions
of buds all derived from one original seed, and all for
many years remaining perfectly true to their parent
type, with the single exception of the sporting bud,
which, while it departs so widely from that t}'pe, is
usually capable of transmitting its extraordinary char-
acters indefinitely by a-sexual, and not infrequently
also by sexual, methods. So that, altogether, it seems

« r » • '

•ture

ition
In

very

ins in

;here-

ctures

more

orting

isigni-

ought

eloped

/c find

ich are

, in the

se, that

h bud-
mount
nature
f other
d alone

[rom its
varia- .
which
laftings ;
millions
all for
parent
ing bud,
I type, is
[ry char-
jqucntly
lit seems

Weisnmuns theory of Evolution {1891). 99

impossible to suppose that in millions and millions of
sister-buds, which through years and years exhibit no
variation, a highly peculiar admixture of germ-plasm
(which was originally present in the parent-seed)
should have been latent ; that it should then suddenly
become so patent in a single bud, after which it never
occurs in any other bud, save in the progeny of the
sporting one.

On the whole, then, while it thus seems impossible
to attribute all cases of bud-variation to mixtures of
germ-plasms in sexual propagation, the theory of
germ-plasm is unable to entertain any other explana-
tion, on pain of surrendering its postulate touching
the unalterable stability of germ-plasm, on which the
Wcismannian theory of evolution is founded.

So much for Weismann's evidence touching the
extreme, or virtually everlasting, stability of germ-
plasm. We have seen that this evidence is not merely
of a very poor character per st\ or on antecedent
grounds ; but that it is directly negatived as evidence
by the a-sexual origin of species in the plants alluded
to by Professor Vines ; by certain facts which prove so
high a degree of instability on the part of this hypo-
thetical substance, that in some cases it admits of
being very considerably modified in the course of
only two or three generations by exposure to changed
conditions of life ; while in other cases it may "' sport,"
so as to produce " hereditary individual variations,"
which are much more pronounced than any of those
that ordinarily result from a blending of hereditary
qualities in an act of sexual union.

It will be well to conclude our examination of

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lOo -<4« Examination of Weisniannism.

Wcismann's system by statinj^ exactly the effect
produced on his theory of evolution by the foregoing
disproof of its fundamental postulate — the absolute
stability of germ-plasm.

Clearly, in the first place, if germ-plasm has not
been absolutely stable "since the first origin of sexual
propagation," the hereditary characters of germ-plasm
may have been modified any number of times, and
in always accumulating degrees. It matters not
whether the modifications have been due mainly to
external or to internal causes. It is enough to have
shown that modifications occur. For, it will be re-
membered, the doctrine of the absolute stability of
germ-plasm is, that inasmuch as the "molecular"
structure of germ-plasm cannot be affected either
from without or from within, the only source of
"hereditary individual variations" is to be found in
admixtures of germ-plasms taking place in sexual
fertilization. Slight " molecular " differences having
been originally impressed ui)on different masses of
germ-plasm when these were severally derived from
their unicellular sources, so unalterable has been the
stability of germ-plasm ever since, that these slight
'•molecular" differences have never been in any
degree effaced ; and although in sexual unions they
have for untold ages been obliged to mix in ever-
varying proportions, they still continue — and ever
must continue — to assert themselves in each ontogeny.
Therefore, as Weismann himself formulates this
astonishing doctrine, — " The origin of hereditary in-
dividual variations cannot indeed be found in the
higher organisms, the Metazoa and Metaphyta ; but
is to be sought for in the lowest — the unicellular

WcisjJianns theory of Evolution (1891). 10 1

orcranisms.

»»

Or aj^ain, — ** The formation of new
species, which amoni^ the lower Protozoa could be
achieved without amphigony, could only be attained
by means of this process in the Metazoa and Mcta-
phyta. It was only in this way that hereditary
individual differences could arise and persist ^"

Now this doctrine is the most distinctive, as it is
the most original feature in Weismann's system of
theories. That it is of interest as an example of
boldly carrying the premises of a theory to their
logical termination, no one will deny. But as little
can it be denied that the very stringency of this logical
process brings the theory itself into collision with such
facts as those which have now been stated, and which,
as far as I can see, are destructive of the theory — or.
at any rate, of all that side of the theory which
depends on the doctrine of absolute stability.

Take, for instance, the sequent doctrine that natural
.selection is inoperative among the unicellular or-
ganisms. Here, indeed, we have another of those
doctrines which are so improbable on merely ante-
cedent grounds, that their presence might well be
deemed a source of irremediable weakness to the
whole theory of evolution of which they form integral,
or logically essential, parts. For seeing that the
rate of increase in most of the unicellular organisms
is quite as high as — and in most cases very much
higher than— the rate that obtains in any of
the multicellular, it becomes on merely antecedent
grounds incredible that the struggle for existence
should here 7iot lead to any survival of the fittest.
When, for instance, we learn from Maupas that

' Essays, p. 296.

tl

r^^

III fi
\\

! 'I

'I

it

I

I02 An Exa)fn'ualion of IVcismannism.

a sincjlc Stj'lonichia is potentially cajvible of yield-
ing a billion descendants vvitliin a week, we should
need some extraordinarily good evidence to make
us believe that as regards this organism natural
selection is inoperative. Hut the point at present is
that, quite apart from all general and a p-iori con-
siderations of this kind, VVeismann's doctrine that
unicellular organisms cannot be influenced by natural
selection must be abandoned. I^'or this doctrine
followed deductivcl}' from the premiss that in the
multicellular organisms congenital variations can only
be due to admixtures of germ-plasms in acts of
sexual fertilization ; so that, in the absence of such
admixtures, there could be no material for natural
selection to work upon. But now we have found that
this premiss must be given up ; and, therefore, the
deduction with resi)ect to the unicellular organisms
falls to the ground. Although it is true that the
unicellular organisms propagate by fission, and
although we grant, for the sake of argument, that
they never propagate by way of sexual unions — even
so this can no longer be taken to argue that none of
their innumerable species owe their origin to natural
selection. And, although it is probably true that the
sexual methods of propagation constitute one source
of hereditary individual variation among the multi-
cellular organisms, there is no vestige of any indepen-
dent reason for supposing that this is the only source
of such variation ; while the sundry facts which have
now been given amount to nothing short of a demon-
stration to the contrary ^

' In this connexion it oui.',hl to be observed that Darwin believed
the causes of variation to be internal as well as external — or arising

Summary,

103

Lastly, and as rejijards the multicellular organisms,
it is evident that VV'eismann s essay On the Sii^iiijkatice
of Sexual Reproduction in the Theory of Natural
Seleetion must be cancelled. For, apart from the
contradictory manner in which this matter has been
stated (pp. 70, 93, notes), and apart also from the con-
sideration that other and quite as probable reasons
have been suj^Ljcstcd for the oriffin of sexual repro-
duction, there is the fact that W'cismann's theory is
no longer tenable after the above destruction of its
logical postulate in the absolute stability of germ-
plasm. For, in the absence (jf this postulate, there is
no basis for the theory that admixtures of germ-
plasms in sexual reproduction furnish the sole means
whereby heritable variations can be supplied for the
working of natural selection.

Summary.

The theory of ^erm-plasm is not only a theory of
heredity : it is also, and more distinctively, a theory
of evolution. As a theory of heredity it is grounded
on its author's fundamental postulate — the continuity
of germ-plasm ; and, further, on a fact well recog-
nized by all other theories of heredity, which he
expresses by the term stability of germ-plasm. But
as a theory of evolution it requires two additional
postulates for its support — viz., thai germ-plasm has

from "the nature of the organism" no less — or cveti more — than from
"changed conditions ot lile." But altliuugh he appears to have enter-
tained the a(hnixture of hereditary endowments in sexual unions as one
of the causes of variation belonging to the former category, he expressly
says that he did not ri-gardit as the only, or even the main, cause. (Sec
Variation, &c., vol. i, pp. 197, 39S ; vol. ii, pp. 337, 35a.)

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104 An Examination of Weismannism.

been perpetually continuous " since the first origin of
life," and absolutely stable " since the first origin of
sexual reproduction." It is clear that these two
additional postulates are not needed for his theory of
heredity, but only for his additional theory of evolu-
tion. There have been other theories of heredity,
prior to this one, which, like it, have been founded on
the postulate of" continuity " (in Weismann's sense) of
the substance of heredity; but it has not been needful
for any of these theories to postulate further that this
substance has been alivays thus isolated, or even that
it is now invariably so. For even though the isolation
be frequently invaded by influences of body-changes
on the congenital characters of this substance, it does
not follow that the body-changes must be transmitted
to offspring exactly as they occurred in parents. They
may produce in offspring what we have agreed to call
" specialized " hereditary changes, even if they never
produce ''representative" hereditary changes, — i.e.,
the transmission of acquired characters. But it is
essential to Weismann's theory of evolniion that body-
changes should not exercise a modifying influence
ot any kind on the ancestral endowments of this
substance ; hence, for the purposes of this further
theory he has to assume that germ-plasm presents,
not only eontinuity^ but continuity unbroken since the
first origin of life.

Similarly as regards his postulate of the stability of
germ-plasm as absolute. It is enough for all the
requirements of his theory of heredity, that the sub-
stance in question should present the high degree of
stability which the facts of atavism, persistence of
vestigial organs, &c., prove it to possess. But for his

SMmmary,

105

further theory of e^'olutnn it is necessary to make
this further postulate of the stability of germ-plasm
as undisturbed since the first origin of sexual propaga-
tion : otherwi. there would be no logical foundation
for any of the distinctive doctrines which go to
constitute that theory.

Thus much understood, we proceeded to examine
the theory of germ-plasm in each of its departments
separately — i.e., first as a theory of heredity, and
next as a theory of evolution. And we begun by
comparing it as a theory of heredity with the prj-
ceding theories of Darwin and Galton. In the result
we found that germ-plasm resembles gemniulcs in all
the following respects. It is particulate ; constitutes the
material basis of heredity; is mainly lodged in highly
specialized cells ; is nevertheless also distributed
throughout the general cellular tissues, where it is
concerned in all processes of regeneration, repair, and
a-sexual reproduction ; presents an enormously com-
plex structure, in that every constituent part of
a potentially future organism is represented in a fer-
tilized ovum by corresponding particles ; is every-
where capable of virtually unlimited multiplication,
without ever losing its hereditary endowments ; is
often capable of carrying these endowments in a dor-
mant state through a long series of generations, until
at last they re-appear again in what we recognize as
reversions. Such being the points of resemblance, the
only points of difference may be summed up in the
two words — continuity, and stability. For, as regards
continuity, while Darwin's theory supposes the sub-
stance of heredity to be more or less formed anew in
each generation by the body-tissues of that generation,

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1 06 An Examination of IVcismannism.

Wcismann's theory rec^ards tliis substance as owing
nothing to the body-tissues, further than lodgement
and nutrition. Therefore, while the theory of gem-
mules can freely entertain the doctrines of Lamarck,
the theory of ^"-erm-plasm excludes them as physio-
logically impossible, in all cases where sexual repro-
duction is concerned. Again, as rcgarJs stability,
while Darwin's theory simply accepts the fact of such
a degree of stability appertaining to the substance of
heredity as the phenomena of atavism. &c. prove,
Wcismann's theory postulates the stability of this
substance as absolute. But, as we have now so often
seen, he does so in order to provide a hypothetical
basis for his further theory of evolution. In as far as
his theory of heredity is concerned, there is no reason
why it should differ from Darwin's in this respect.

Again, comparing Wcismann's theory of heredity
with that of Galton. we found that germ-plasm
resembles stirp in all the points wherein we have just
seen that it resembles germ-plasm. Or, otherwise
.stated, all three theories are thus far coincident. But
germ-plasm resembles stirp much more closel}^ than
it docs gemmules, seeing that the theory of st.rp is
founded on the postulate of "continuity" in exactly
the same manner as is the theory of germ-plasm. In
point of fact, the only difference between these wo
theories consists in the two further postulates presented
by the latter — viz., that the "continuity" in question
has been unbroken since the origin of life, while the
" .stability " in question has been uninterrupted since
the origin of sexual prcpagation. But seeing that
both these additional postulates have reference to
Wcismann's theory of evolution, we may say that his

Summary.

107

tlicoiy of heredity is. as regards all essential points,
indistinguishable from that of Galton.

The truly scientific attitude of mind with regard to
the problem of heredity is to say, as Galton says.
" that wc might almost reserve our belief that the
structural [i.e., somatic] cells can react on the
sexual elements at all, and we may be confident that
at most they do so in a very faint degree ; in other
words, that acquired modifications are barely, if at
all, inJicritcd. in the correct sense of that word." But
for Weismanns further theory of evolution, it is
necessary to postulate the two additional doctrines
in question ; and it makes a literally immeasurable
difference to the theory of evolution whether or not
we entertain these two additional postulates. For no
matter how faintly or how fitfully the substance of
heredity may be modi led by somatic tissues, by
external conditions ol life, or even by so-called
spontaneous changes on the part of this substance
itself, numberless causes of congenital variation are
thus admitted, while even the Lamarckian principles
are hypothetically allowed some degree of play. And
although this is a lower degree than Darwin sui)i)osed,
their influence in determining the course of organic
evolution may still have been enormous ; seeing that
their action in any degree must always have been
directive on the one hand, and cuuiulative on the
other.

Having thus pointed out the great distinction
between the theories of stir[) and of germ-plasm,
it became needful to note that Wcismann himself
is not consistent m observing i.. On the con-
trary, in some passages he apparently expresses

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1 08 An Examination of Weismannism,

himself as willinf^ to resign both his distinctive postu-
lates— continuity ixs perpetual ^ and stability as absolute.
But it is evident that such passages must be ignored
by his critics, because, although as far as his theory
of heredity is concerned they betoken an approach to
the less speculative views of Galton, any such approach
is proportionally destructive of his theory of evolution.
It must not be supposed that I am taking an
ungenerous advantage of these ocasionally funda-
mental concessions. On the coalrary, one cannot but
admire the candour which they display. But, as
I have said, it is necessary for us to ignore them, if
only in order to examine the VVeismannian theory of
germ-plasm as a distinctive theory at all. And more
than this. Seeing that his theory of heredity differs
from Galton's chiefly in being further an elaborate
theory of evolution (founded on the two additional
postulates in question), my main object has been to
show the enfeeblement of the former which Wcis-
mann has caused by his addition of the latter. If he
were to express his willingness to abandon his theory
of evolution for the sake of strengthening his theory of
heredity by identifying its main features with those of
Galton's, personally I should have no criticism to pass.
Indeed, I was myself one of the first evolutionists who
called in question the Lamarckian factors ; and ever
since the publication of Galton's theory of heredity at
about the same time, I have felt that in regard to its
main principles — or those in which it agrees with
Weismann's — it is probably the true one. But I can
nowhere find that Weismann is thus prepared to
surrender his theory of evolution. Occasionally he
plays fast and loose with the two additional postulates

Stuiimary.

109

on which this theory is founded ; but he docs so
without appearing to perceive the speculative im-
possibility of any longer sustaining his temple of
evolution if he w^rc to remove its pillars of germ-
plasm.

Ignoring, then, these iiiconsistencies, we proceeded
to examine separately, and on their own respective
merits, the two distinctive postulates of the theory
of germ-plasm — perpetual continuity since the first
origin of life, and absolute stability since the first
origin of sexual propagation.

It does not appear to me that very much has to
be said, either for or against the former postulate,
on merely antecedent grounds, or grounds of general
reasoning. Therefore I relegated to an Appendix
my examination of what Weismann has argued on
these grounds, while in the text I considered only
what he has advanced as evidence a posteriori. Here,
as we saw, he has developed three distinct lines of
verification — viz. (A) the migration of germ-cells in
some of the Ilydroviedusae, (1^) the early separation
of germ-cells in the ontogeny of certain Invertebrata,
and (C) the alleged invariability of organisms which
are produced parthcnogcnetically. But we have seen,
with respect to (A), that the specialized character
of germinal cells is a fact which every theory of
heredity must more or less recognize ; and, therefore,
that the migration of these cells, wherever it may be
found to occur, does not lend any peculiar countenance
to Weismann's theory. There may be many reasons
for such migratioji other than the one which this
theory assigns ; while the reason which it does assign
is rendered improbable by the consideration that in

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no An Examination of Weismannism.

the Hydromcdusae the material of heredity is already
and richly diffused throughout the geneal tissues.
(B) and (C) arc both contrary to fact ; and, therefore,
in whatever measure they would have corroborated
the theory had they proved to be true, in that
measure must they be held to discountenance the
theory now that they have been shown to be false.

It appears, then, that there is no evidence in support
of the postulate of the perpetual continuity of germ-
plasm. There is nothing to show the necessary
non-inheritance of acquired characters. The only
evidence which one can recognize as good, is that which
makes equally in favour of the theoiy of stirp — or
rather, of the well-known fact that congenital charac-
ters are at any rate much viovc heritable than are
acquired : which, 't is needless to repeat, is a widely
different thing from proving — or even rendering prob-
able— the absolute restriction of germ -plasm to
a separate " sphere " of its own " since the origin of
life."

But now, although there is no evidence in support
of this postulate, there is no small amount of evidence
against it. For this evidence goes to indicate that
no small amount of reciprocal action habitually takes
place between body-tissues and germinal elements :
indeed it seems almost to prove that the orbits of
germ -plasm and somato- plasm are not mutually
exclusive, but touch and cut each other to a con-
siderable extent. The evidence in question, it will be
remembered, is derived from the effects of puberty,
enility, castration, &c. ; the occasional effect of poUen-
'zation on the somatic tissues of plants ; the influence
which a stock occasionally exercises upon a scion,

Situiniary.

1 II

or vice versa, which proves the possibility of a trans-
mission of hereditary characters by a mere grafting
together of somatic tissues ; the direct evidence given
by De Vries that in certain Algae constituents of
cellular tissue pass immediately from the maternal
ovum to the daughter organism ; and the evidence,
both direct and indirect, which remains to be given
on a larger scale in my subsequent volume, where we
shall have to challenge the validity of Weismann's
fundamental postulate touching the non- occurrence
of Lamarckian factors in any of the multicellular

organisms.

It iDust here again be noticed that in those passages
where ho concedes the possibly 'occasional" trans-
mission of acquired characters Wcismann is anni-
hilating his own theory, root and branch. Thus, for
example, in allusion to De Vrics' observation just
mentioned, he says that we cannot exclude the
possibility of " changes being induced by external
conditions in the organism as a whole, and then com-
municated to the germ-cells after the manner in-
dicated in Darwin's hypothesis of pangenesis." But
it is obvious that the theory of germ-plasm must
"exclude the possibility of such a transmission occa-
sionally occurring '' ; for the very essence of that
theory consists in its postulatiiig a difference between
germ-plasm and the general body-substance in kind,
such that there never can be anv '•communication"
from the one to the other •' after the manner indicated
by Darwin's hypothesis of pangenesis." Any pre-
varication over this point amounts simply to aban-
doning the theory of germ-plasm altogether, and
opening up a totally distinct issue — namely, the

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112 An Examination of Weismannisjn.

relative importance of natural selection and the
Lamarckian factors in the process of organic evolution.
It may be perfectly true — and I myself believe it
is perfectly true — that Darwin attributed too large
a measure of importance to the Lamarckian factors ;
but whether or not he did so is quite a different
question from that which obtains between his theory
of pangenesis and VVcismann's theory of germ-plasm.
The former question is whether we are to " modify "
the theory of pangenesis, so as to constitute it the
theory of stirp ; the latter question is whether we are
to " abolish " the theory of pangenesis, in favour of its
logical antithesis, the theory of germ-plasm. And
this question remains to be dealt with in my next
volume.

Coming then, lastly, to the companion postulate
of germ -plasm as absolutely stable since the first
origin of sexual propagation, we had to observe
that, unlike the one we have just been considering,
there is an immensely strong presumption against it
on merely antecedent grounds. That the most com-
plex substance in nature should likewise be the most
stable substance with regard to complexity of " mole-
cular structure " ; that the greater its complexity
becomes the greater becomes its stability, so that
while in the comparatively simple unicellular organ-
isms it is eminently susceptible of modification by
external conditions, it entirely ceases to be thus
susceptible when it becomes evolved into the incom-
parably more complex and immensely more varied
structures which form the bases of heredity in the
multicellular organisms — where, also, it must come

Siunmary.

113

into ever more and more intricate as well as more and
more diverse relations with the external world ; — all
this is, I repeat, well niijjh incredible. At any rate,
speaking for myself, I should require some enormous
weight of evidence to balance so enormous an ante-
cedent improbability, or before I could reL;ard such
a doctrine as meriting any serious attention.

What, then, is the evidence that has been adduced ?
We have found that this evidence is ;///. On the
other hand, we have found that the evidence against
the doctrine is abundantly sufficient to annihilate the
doctrine — and this cjuitc apart from all the antecedent
considerations just alluded to. Vox not only have we
the sundry facts of bud-variation, a-sexual origin of
species, &c., which contradict the doctrine ; but we
have also the results of direct experiment, which
prove that the all(;gcd stability of germ-plasm may be
conspicuously upset by slight changes in the external
conditions of life. So that both from within and from
without the stability which is alleged in theory admits
of being overturned by facts.

And here, in order to avoid all possible confusion,
I must ask it once more to be noted that there is not,
and never has been, any question touching the hii^h
degree of stability which is exhibited by whatever
substance it is that constitutes the material basis of
heredity. Ikit this is a widely different thing from
supposing the stability absolute, so that it can never
have been affected in any degree since the first origin
of multicellular organisms, or in any of the millions of
species into which these organisms have ramified.
And the fact that in some cases we are actually
able to observe a change of congenital characters as

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114 An Exam ituit ion of Wcismannisni.

resulting from some " spontaneous " chaiv^x' in the
hereditary material itself (as in bud-variation), or from
some chani^^e in the external conditions of life (as in
Hoffmann's experiments) — this fact is more than is
required in order finally to overthrow the intrinsically
untenable doctrine which is in question.

Now, with the collapse of this doctrine there
collai)ses also the important chain of deductions
therefrom, which together constitute Weismann's new
theory of evolution. In particular, that natural selec-
tion is the exclusive means of modification among all
the Metazoa and Metaphyta, while it is as exclusively
ruled out with respect to all the Protozoa and Pro-
tophyta ; that individual variations among the former
can only be determined by sexual unions, while among
the latter they can only be determined by the direct
action of the environment ; that the origin of con-
genital variability in all the Metazoa and Metaphyta
is to be sought, and can only be found, in variations
which occurred millions of years ago in the Protozoa
and Protophyta ; that the " significance of sexual
propagation " is to be found in the view, that by this
means alone can congenital variations have been ever
since produced ; &c., &c.

Upon the whole then, it appears to me that both
the fundamental postulates of the theory of germ-
plasm are unsound. That the substance of heredity
is largely continuous and highly stable I see many
and coeent reasons for believing. But that this sub-
stance has been uninterruptedly continuous since the
origin of life, and absolutely stable since the origin
of sexual propagation, I see even more and better

Shin ma I

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reasons for cHsl)clicvi^L,^ And inasmuch as these two
latter, or distinctive, postulates are not nceiled for
Weisniaiuis theory of hercdit)', while they are both
essential to his theory of evolulinii, I cannot but
rcifret that he sh(nild thus have crii)i)lcd the former
by burdeninf:^ it with the latter. Hence my object
throuL^hout has been to (lisj)lay, as shar[)l\' as possible,
the contrast that is presented bctuern the brass
and the clay in the colossal fiLjure which Weismann
has constructed. Hence, also, my emphatic dissent
from his theory of evolution does not prevent me
from sincerely a[)preciatin<; the L;reat value which
attaches to his theory of heredity. And althoui;h I have
not hesitated to say that this theory is, in my opinion,
incomplete; that it presents not a few manifest
inconsistencies, and even logical contradictions; that
the facts on which it is foiuided have always been facts
of general knowledi;e ; that in all its main features it
was present to the mind of Darwin, and distinctly
formulated by Galton ; that in so far as it has been
constituted the basis of a more general the ry of
organic evolution, it has clearly proved a failure : —
such considerations in no wise diminish my cordial
recognition of the services which its distinguished
author has rendered to science by his speculations
upon these topics. For not onl)' has he been suc-
cessful in drawing renewed and much more general
attention to the important questions touching the
transmissibility of ac(iuired characters, the causes of
variation, and so on ; but e\ en those parts of his
system which have proved untenable are not without
such value as tem[)orary scatloldings present in re-
lation to permanent buildings. Therefore, if I have

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I 16 Aji /examination of IVcismannism.

appeared to play the rdlc of a hostile critic, this has
only been an exjjression of my desire to separate
what seems to me the ^nain of ^ood science from the
chaff of bad speculation. And the candour which
Professor VVeismann has always displaj-ed towards
criticism of this character enables nie to hope with
assurance, that I have said nt thinij which he him-
self will re<;ard as inconsistent with high admiration
of his work as a naturalist, or of his orij^inality as
a philosopher.

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Whismannis.m ui' to datk (1H93).

Hitherto wc have been consldciintr rrofossor
Wcisniann's system as it stood prior to the publica-
tion of his most recent works on Ai)ipJiiuiixis and TItc
Germ-plasm, in i (S(^. 1 and 1 (Sy^ resi)ectively. These
later and hii^hly elaborate essays present considerable
modifications of the system, as it stood when the
forej;f)ing criticism was written. lint, for reasons
already stated in the Preface, it ajjpears to me
desirable to leave that criticism as it was -"risj^inally
constructed, and to su[)ply this further chapter for
the purpose of dcalini^ with the large alterations of,
and important additions to, the theory of germ-plasm,
which the maturer thought of its gifted author has led
him to announce.

A few general remarks may be most conveniently
made at the outset.

In the first place, these recent publications present
the advantage over their predecessors of being sys-
tematic treatises, instead of more or less independent
papers. On this account they present a logical
sequence of thought, which renders the task of ex-
amination much less difficult than it was in the case
of the first volume of the Essays.

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ii8 A7t Examinatio7i of Wcisviannism.

In the second place, as a result of hts more matured
reflection, Professor Wcismann lias himself perceived
a considerable number of the difficulties and objections
which I have set forth in the precedinc^ chapters.
And not only has he thus anticipated many of my
criticisms ; but. as a result of doing so, he has changed
not a few of the most important parts of his previous
system, with the result of greatly improving it.

But, in the third place, notwith.standing that his
remarkable power of .speculative thinking is every-
where united with adequate knowledge in the sundry
branches of biological science with which it deals,
I confess to a serious doubt whether it has not been
permitted to enjoy an undue amount of liberty. If
only they can be laced together by a thread of logical
connexion, hypotheses are added to hypotheses in
such profusion as we are acquainted with in the works
of metaphysicians, but w'hich has rarely been ap-
proached in those of naturalists. The whole mechanism
of heredity has been now planned out in such minute-
ness of detail and assurance of accuracy, that in reading
the account one is reminded of that which is ijiven
by Dante of the topography of Inferno. For not
only is the " sphere " of germ-plasm now composed
of nine circles (molecules, biophores, determinants, ids,
idants, idio-plasm, somatic-idioplasm, morpho-plasm,
apical-plasm), but in most of these regions our guide
is able to show us such strange and interesting phe-
nomena, that we return to the fields of science with
a sense of hav'ng been indeed in some other world.
Or, to change the metaphor, if it be the case that
'"a true scientific judgement consi.sts in giving a free
rein to speculation with one hand, while holding

IVeisiuaiinisvi up to date (1893). 119

ready the break of verification with the other," I think
it must be admitted that, in as far as he has erred.
Professor Wcismann has done so by driving a chariot
which is unprovided with any break at all.

Hence, fourthly, it is needless to follow, even in
epitome, the innumerable windings of these never-
ending speculations. For, on the one hand, it would
be impossible to do so without adding an unduly
extended chapter to our already tediously prolonged
consideration of Wcismann's views ; while, on the
other hand, we should have to deal merely with matters
of comparative detail. The additions which have
been made to his theory by his most recent publica-
tions are chiefly concerned with the matter just
alluded to — viz., a minute (elaboration of the hypo-
thetical mechanism of heredity, in accordance with
the general theory of germ- plasm. Without question
this elaboration is everywhere thoughtful, and often
highly ingenious ; but until the general theory in
question shall have been satisfactorily grounded, it
seems premature to supply so immense a design of
purely deductive construction, l^eautiful though it
may be in its imposing elevation, this drawit'^g of 'the
architecture of germ-plasm " must be regarded as
a work of artistic imagination rather than as one of
scientific generalization. Frcm the latter ponit of
view it is at most a temple /// fosse, and even if it is
ever to be realized /// esse, we cannot allow the actual
building to begin until we are much more sure than
anybody is at present entitled to be touching the
foundations < ., hich it is pro^iosed to rear so great
an edifice.

Again, and fifthly, even if Weismann should ever be

1^

III

1 20 An Examination of Weismannism.

able to satisfy us upon this matter, or fully to demon-
strate his basal proposition touching the perpetual
continuity of i]jerm-plasm, there would still be a far cry
between accepting this sufficiently simple proposition
and supposing that there is any adequate reason for
entertaining so comi)lcx a scheme of the structure of
germ-plasm. No doubt Weismann himself would be
quite ready to admit, that from his basal proposition
of the continuity of germ-plasm it is logically possible
to construct many other designs of the architecture of
germ-plasm, besides the one which he has so beautifully
drawn. And although most of such alternative designs
would doubtless embody some one or other of the
features which are presented by his own, no one could
say which features common to any two of the designs
represent the facts. For in the case of all alike
there would be a necessary absence of verification :
the architects would all and etiually have to ac-
knowledge that their imposing pictures of "the palace
of truth " were but imai;inary. S^h, in my opinion,
has been the case with all theories of the ultimate
mechanism of heredity hitherto published ; but the
difference between them and Weismann's theory in
this respect is, that while most of the others have not
f;one into speculative details further than was necessary
as a means of substantiating their basal postulates,
Weismann's, as now developed in TJic Gcrvi-plasvi, is
mainly concerned with .such .speculative details as aa
end, or object per se.

l^ut, it may be replied, by thus constructing an
ideal mechanism of heredity Weismann is greatly
strengthening his fundamental postulate of the con-
tinuity of germ-plasm, becau.se he shows how all the

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Wcisnmttiiism up to date (1S93). 121

main facts of heredity, and allied phenomena, admit
of being explained if once the postulate be accepted.
If this were urged, however, I should have two remarks
to offer. The first is that VVeismann, in constructing
his ideal mechanism, has gone very much further in
the way of elaboration than can possibly be required
for this purpose. So much further, indeed, that his
purpose has evidently been the constructing of his
ideal mechanism, as I have just said, for its own sake,
and not for the sake of substantiating its basal pro-
position by showing how well the latter can be made
to wot'; in explaining the phenomena of heredity, &c.
Mor;.:;; * — and this is my second remark — however
wc.'i ihe basal proposition may be made to work in
this respect, we must not be deceived into supposing
that such a fact is equivalent to a substantiation of
the proposition. This proposition — the continuity of
germ-plasm — is the inverse of that which constitutes
the basis of the theory of pangenesis. Voy while the
latter assumes that in the last resort it is always
somatic tissues which produce the substance of
heredity, the forn^cr simply inverts the terms of this
assunrption, ar J liolds that it is always the substance
of heredity w;,j:h ^roduces the somatic tissues. Now,
in all cases ,vV *%; me theory consists in thus simply
inverting the t^i ^'s uf another, it will be found that
the facts which ihey both seek to ex[)lain lend
themselves equally to explanation by either, up to
some certain and usually distant point, where a crucial
test becomes possible. Take, as an example, the
geocentric ind heliocentric theories of the solar
system. I -c the question was whether the earth
moved rou- -A ^ .sun, or vice versa \ and so many of

m

•^

i: I

lis

122 ^« Examination of Weismannis^n.

the facts of observation lent themselves equally well
to either interpretation, that it was very many centuries
before the crucial tests were forthcoming. So, in the
present instance, the question is as to whether the
carriers of heredity move from body-cells to germ-
cells, or vice versa ; and it is because the theory
which sustains the latter view has merely to invert
the terms of the one which takes the former, that so
many of the facts of observation lend themselves
equally well to both — a'- ve have seen in chapter III

(pp. 56-59)-

Lastly, yet another rea.s ♦or not considering in

any detail Professor Wcismanns intricate speculations

on the ultimate mechanism of heredity is, that by so

doing I should have found it impossible to avoid

obscuring the main issues. For even Professor Weis-

mann himself, by the extreme care which he has

taken in fully presenting his scheme of this ultimate

mechanism, has not found it practicable to keep

distinctly before our view the relative insignificance

of such details, as conii)ared with the fundamental

importance of his original postulates. Hence, I have

deemed it best in the present chapter to restrict our

attention to the changes which he has recently made

in these the foundations of his entire system.

For these reasons, then, I will mention only those

main features in the '• architecture of germ-plasm "

which it is necessary to understand for the purposes of

the following criticism touching the general theory of

germ-plasm in the most recent phase of its evolution.

To begin with, Wcismann has now seen the desira-
bility of ceasing to designate the ultimate ''carriers of

"

m

Weis7fiaitn7sni itp to date (1893). 123

heredity" by the term "molecules." Indeed, in these
later volumes he has fully anticipated my remarks
touching the use of this term in his previous " Ussays ^"
The result of his more mature reflection may be
presented in epitome thus.

A number of " molecules," in the proper or chemical
sense of the word, go to form a " biophore,'' which is
the ultimate unit of living substance.

A number of " biophores " go to form a "deter-
minant," which is a special element in the germ-plasm,
capable of directing the ontogeny of such and such
a group of cells as is independently variable from the
germ onwards.

A number of "determinants " go to form an "id,"
which is the same hypothetical body as Weismann
has hitherto designated by the term " ancestral germ-
plasm." That is to say, it is a group of determinants
indissolubly united in phylogeny, and therefore
transmitted by heredity as one complex whole. Ids
are, perhaps, microscopically visible ; and, if so, they
probably correspond to the small granules (micro-
somata), which are familiar to the histologist in the
structure of chromosomes.

A number of " ids " go to form an " idant," which
is a chromosome, or chromatin fibre-.

In my opinion the most important advance which
Weismann has made in his theory by means of this
scheme has reference to the third of these divisions —
the determinant. It is a matter of observation that
every cell of a multicelluar organism does not vary

* See aliovo, p. -.j^, note,

* Sec /><iru'iii (iii.i (t//er Ihinvin, Pnrt T, p. 129.

' tf ff

m

m l\\

1 24 Afi Examination of Wcisviannism,

independently : it appears to be always the case that
in the phenomena of variation a smaller or a larger
group of cells is concerned. Now there must be
something that determines the similar and simul-
taneous variation of such a whole group of cells;
and, in all cases where such a variation is congenital,
it is certain that this something must be contained
in the substance of heredity. So far, I think, we
must all agree, whether or not we regard this sub-
stance as "germ-plasm," In other words, whether
we regard the carriers of heredity as proceeding
ccntrifugally (germ-plasm) or centripetal ly (gemmules),
it seems to me that we ought to accept Weismann's
doctrine of determinants. Indeed, pathologists have
already furnished a foreshadowing of such a doctrine
in regard to the phenomena presented by certain
diseases, such as cancer ; but it is an important step
to have extended the idea from pathology to biology
in general — and, at the same time, to have given it
a more definite shape than it has hitherto presented.
In Weismann's hands it serves to render more con-
ceivable— if not also more intelligible — that process
of marshalling cell-formations, which, be our theories
what they may, is assuredly the most distinctive and
remarkable fact of ontogenetic organization.

Again, as regards the id, I do not sec how any one
can attentively read Professor Weismann's discussion
without acknowledging that, if we once accept his
doctrine of determinants, his sequent doctrine of ids
becomes a logical necessity.

On the other hand, however, I do not see that
such is the case with respect to idants , and still less
do I see any reason for identifying the latter with

IVeismannism tip to date (1893). 125

chromosomes — even assumincj that chromosomes arc
the visible repositories of the carriers of heredity ^

Referring the reader to Weismann's own exposition
for a full account of these and many othert additions
to his general theory of germ-plasm, I will at once
proceed to consider the alterations or emendations of
that theory which have been published in his last two
volumes, and which, as we shall find, have in large
measure anticipated some of the most important points
in the foicijoing criticism. Therefore in the foUowincr
criticism I will consi^'er seriatim what he has now said
touching all these points, and conclude by offering
some general remarks on the resulting position of his
general system of theories up to the present date.

Pursuing the same method of criticism as that
adopted in the preceding chapters, we will first con-
sider the further modifications of Weismann's theory
of heredity, and next those of his theory of organic
evolution.

WcisDiann's theory of Heredity ( 1 Hy^^).

First of all, Weismann has now profoundly modified
his theory of polar bodies. For, owing to certain
more recent researches of Professor O. Ilertwig. he
very candidly allows : — "• My previous interpretation
of the first polar body as the removal of ovogenetic
nucleo-plasm from the egg must fall to the ground :
about this there is no possible duubt -."

* It must always l)e renieml)crcil tliat the view ndoiited by Wcismmin
touchiii_^' the mieleus i,niul more especiall) the chroiiHisomes) of a i;erin-
cell beiny; tlie sole seat ui heieilily, is still tar Imin havinj; hecii estal>
lished.

'•* Essays, vol. ii. p. 122.

"W

i :

ill

I

i<

'

i; :

126 An Exauiiiiation of Wcisinannisiu.

He now rej^^ards both pol.ir bodies as concerned in
the same function of removinij supcrnuous germ-plasm.
Tiiereforeone-half of his previous theory is abandoned :
" the ovoL;enetic idio-plasm " is now supposed to be
simply absorbed in the couise of ontot^eny, as I had
suLj^t^ested in one of the precedin<^ chapters (pp. 42-46).
Tile consequence is that he has now nothini^ to oppose
to the view which is likewise there sui;-gested (pp. 43-
44)— viz., that his whole theory of polar bodies is
rendered needless and improbable by the fact that the
very mode in which ova are produced renders ample
provision for the removal of any amount of superfluous
i:jerm-plasm which the theory of germ-plasm may
require.

It is needless to say. after what ' as already been
said in the pages just referred to, that in my opinion
Professor Weismann has improved his main system
of theories by dropping this part of his subordinate
and, for the most part, separate theory of polar bodies.
I only wi h he could have seen his way to dropping
the whole.

Again, he has now fully considered the phenomena
of repair. regeneraticMi, reproduction from somatic
tissues, budding, and graft-hybridi/.ation.

Touching the four former he takes the view which
I have supposed that he would (p. 53). As regards the
latter, he fully accepts the fact of an occasional trans-
mission of characters from one species or variety of
plant to another by mere grafting ^ But. although the
explanation which he gives of this fact may pass
muster so far as the only case which he deals with in

' The iio/n Jltisiit, p. 342.

ri

IVeisJUiHiiiisni up to date (1893). 127

detail is concerned. I do not see how it can tlo so
to many others. l*\)r tlie case which he considers is
that of Cystisus adaDii, where a bud of one species
of Laburnum having been inserted in the wood of
another produced a shoot which prcsiMited inter-
mediate characters ; and these have ever since been
propai;ated by cuttint^s. Weismann's interpretation of
the facts here is, " that they were due to an abnormal
kind of amphimixis, so that the idants of both si)ecies
were combined in the apical cell of the first shoot '."
Now, although this explanation may well apply to
a case of graft-hybridization by means of buds, it
obviously cannot do so to any case where hybridization
is produced by the grafting of woody tissues. For
here there is no " apical cell " in the question ; and
therefore the difficulties which I have adduced on
page 82 remain. Possibly Wcismann may dispute
the fact of hybridization in any of these cases ; but,
as he has not expressly done so, I will not go into
the question of evidence ^.

One important addition to this side of Weis-
mann's system has been made in order to meet
the class of difficulties which are presented by the
apparent inheritance of certain climatic variations, as
already mentioned on pp. 67-(S. For example, his
own butterflies seemed to render definite proof of
somatogenetic variations c:iused by changed con-
ditions of life being transmitted to progeny. There-
fore, it will be remembered. Wcismann candidly
admitted, " even now I cannot explain the facts
otherwise than by supposing a passive accjuisition of

' TJu GcriH-plasm, p. 342. ^ Sec, however, j). 83, note.

11' -itT^

P !

i i

128 An Examination of Weismannism.

characters produced by the direct influence of
ch'mate" — i.e., an exactly representative copyin<T in
progeny of characters acquired by parents. I have
already quoted these words in order to show their
logical inadmissibility as used by Weismann. He
cannot be allowed thus to entertain the Lamarckian
factors and at the same time to maintain his theory
of germ-plasm, which excludes them as physiologically
impossible. Doubtless he was himself aware of this,
for he immediately added that " new experiments will
be necessary to afford the true explanation ^"

The explanation, however, which he now gives is
not based on any new experiments, but on a new
suggestion to the effect that all such seemingly
conclusive instances of the inheritance of acquired
characters are, in truth, illusory. This suggestion is
that " Many climatic variations may be due wholly
or in part to the simultaneous variation of corre-
sponding determinants in some parts of the soma, and
in the germ-plasm of the reproductive cells,-" For
example, if, as Weismann now supposes, determinants
of the same kinds occur in the somatic tissues as well
as in the germ-cells, when a particular spot occurs on
a butterfly's wing, it has been due to a particular kind
of determinant which in the course of ontogeny was
transmitted from the germ-cell for the express purpose
of controlling the size and colour of the spot. But
a residue of precisely similar determinants was re-
served in the germ-cell (germ-plasm), for the purpose
of determining a precisely similar spot in the next
generation. Hence, if a rise of temperattjre, or any
other external change, is capable of so acting on the

' Essays, vol. i p. 101. Italics mine. * 'J'kc Germ-plasm, p. 406.

Weis))iaiinis)ii np to date (1893). 129

:nce of
►ying in
I have
ow their
nn. He
narckian
is theory
.logically
e of this,
-lents will

^ gives is
Dn a new
seemingly
■ acquired
fTcstion is
|ue wholly
of corre-
soma, and
s.-" For
;erminants
les as well
occurs on
cular kind
Dgcny was
ss purpose
pot. But
was re-
le purpose
the next
re, or any
ng on the

asm, 1'. 406'

determinant in the soma as to cause it to impart an
abnormal colour to the spot when formed, a similar
change is likely to be simultaneously effected in the
corresponding determinants which arc lying dormant
in the germ-plasm. Therefore, when the latter become
active in the ontogeny of the next generation, they
will produce spots presenting the same variations as
those of the i)rcccding generation. Obviously, how-
ever, there would not be here any transmission of
acquiretl characters. The change would be " special-
ized," but not '• representative."

No doubt we have here a sufficiently ingenious
method of circumventing an awkward class of facts.
But I should like to make two observations with
regard to it.

In the first place, the suggestion is highly specu-
lative, and has been advanced solelv for the sake of
saving the theory of germ-plasm. There are no facts
adduced in its favour, and it could scarcely be enter-
tained as in the least degree probable by any one
who has not already accepted the theory in question.
Hence, unless we are to embark on a course of
circular reasoning, we must refuse to accept the
explanation of hereditary climatic variation now
offered, until it shall have been fully corroborated by
the experimental enquiry to which Weismann says he
is now submitting it.

My second observation is. that the suggestion is
not new ; but appears to have been derived from
Professor Weismann's recent study of Mr. Galton's
Theory of Heredity. At all events, the suggestion is
there presented with sufficient lucidity, thus: —
It is said that the structure uf an animal changes when he is

K

..J* • I'jl

J i

\i U

i^^o An Examination of Weisniannism.

placed under changed conditions ; that his <ifTspring inherit some
of his change ; and that tliey vary still luriher on their own ac-
count, in the same direction, and so on through successive genera-
tions, until a notable change in the congenital characteristics of the
race has heen efiected. Hence, it is concluded that a change
in the personal structure has reacted .m the sexual elements.
For my part, 1 object to so general a conclusion, for the fol-
lowing reason3. It is universally ailmitted that the primary
agents in the processes (S growth, nutrition, and reproduction
are the same, and that a true theory of heredity must so regard
them. In other words, the)- are all due to the development
of some germinal maticr, variously located. Conseciuently, when
similar gcri-n.inal matter is everywhere affected by the same
condilif/ns, we should expect that it would be everywhere
affected in the same way. The particular knid of germ whence
the hair sprang, that* was induced to throw out a new variety
in the cells nearest to the surface of the body under certain
changed conditions of climate and food, might be expected to
throw out a similar variety in the sexual elements at the same
time. The changes in the germs would everywhere be collateral,
although the moments when any of the changed germs hap-
pened to receive their development might be different',,

This allusion to Mr. Galton's TJicory of Heredity
leads me to consider what Professor Weisrnann has
said with regard to it in this latest publication,
where, for the first time, he has dealt with it.
In my opinion he has done but scant justice to the
views of his predecessor, and therefore I will occupy
some considerable space in seeking to justify this
opinion.

As already stated, from the time that Mr. Galton
published his theory I have felt that in its main con-
tention it presents a probably true solution of the main
problem of heredity — viz., to account for the contrast

' Galiou, loc. cit., pp. 343-34-1.

IVcisnuinnisnt up to date {1893).

.">

it some

3\vn ac-

gencra-

csofthc
chani^c

Icmcnts.
the fol-
primary

oduction

0 rc},^1rcl
elopmcnt
tly, when
;he same
'erywhcre
n whence
w variety
cr certain
pectcd to
the same

1 collateral,
rms hap-

Heredity
lann has
3lication,

with it.

e to the
occupy

itifv thi>^

Galton
lain con-
the main

contrast

between concijenital and acquired cliaracters in respect
of transmissibility. And this sokition, as likewise
ah-eady stated, was substaiiti dly identical with tliat
which Professor VWismann published in the next
decade. Indeeil, the only important difference be-
tween these two theories of heredity is, tliat while
Wcismann's excludes on deductive grounds the
physioloL^ical i)ossibility of the inheritance of acquired
characters, Galton's more judiciously leaves to be
determined, by subsccjuent encpiiry of the inductive
kind, the question whether acquired ciiaracters are
ever transmitted in faint decrees, or whether they arc
never transmitted at all. In addition to this important
difference, however, there are certain others which
seem to me of very little conseciuence. inasmuch as
they have reference to speculations on the ultimate
mechanism of heredity, or the intimate morpholoi^y
and physiolof^y of the carriers of heredity — specula-
lations which it wotdd be absurd to suppose can be
other than purely conjectural. Therefore in my
previous criticism I did not allude to these subordinate
points of difference, but stated merely, in general
terms, that Galton's view of the ultimate mechanism
in question was such as to leave room for the possi-
bility of the occasional transmission of acquired
characters. And in this respect, it still seems to me,
his theory has an advantage over that of Weismann.
No doubt the latter is a much more elaborate and
highly finished piece of work ; but beauty of ideal
construction is no guarantee of scientific truth — as we
shall presently find exemplified in a striking manner
with regard to Weismann's theory of evolution. And
if his theory of heredity, in its final shape, is a mucli

K 2

«

T

It •■

i

•ill

11'

132 An Exanmiation of Weisinannistn,

more precise, detailed, and logically coherent structure
than any which has ever been fraraed in this depart-
ment of biological thought, there is all the more reason
to scan critically the fundamental postulate on which
it rests. Hence I cannot help feeling that it will be
time enough to consider minor differences between
the two theories when the physiological possibility of
the occasional transmission of ac([uired characters, as
entertained by Galton's theory, shall have been ruled
out as demonstrably opposed to fact.

Seeing, however, that Professor Weismann thinks
otherwise, and ap[)ears to attach as much importance
to differences concerning tleducti^-e miuutiac as he
does to those concerning fundamental principles,
I will here contrast the two theories somewhat more
in detail than heretofore, and with special refer-
ence to what he has now himself said touching their
relationship.

It will be remembered that the primary or funda-
mental difference just alluded to is, that while the
theory of germ-plasm p')stulates an absolute continuity,
the theory of stirp postulates but a partial con-
tinuity, of the substance of heredity. Hence, ac-
cording to We'smann's view, we must go back to
the unice'lular organisms for the origin of this sub-
stance in the multicellular ; and we must regard use-
inheritance as physiologically impossible. On the
other hand, according to Galton's view, there is no
necessity for us to do 'Mther of these things. The
origin of stirp is to be found in the somatic tissues of
the multicellular organisms themselves. Nevertheless,
this theory differs greatly from i)angenesis, in that the
former supposes the origin of hereditary substance to

IVezsmannism up to date (189:). 133

be mainly given in the phylogcny of any group ol
multicellular organisms, while the latter sui^poscs it to
be given mainly in each ontogeny. Galton's theory is,
that in each ontogeny only a small part of the stirp
derived from parents is consumed in making the
new organism — the larger part being handed over in
trust for passing on to the next generation, in the
same way as Weismann supposes to be the case with
germ-plasm. Darwin's theory, on the other hand,
does not entertain any such notion of "continuity"
in the substance of heredity from gnrm-cell to germ-
cell of parent and offspring ; it supposes that in
each successive generation the gerni-cells are ivliolly
supplied with their germinal material from somatic-
cells of each indi^•idual organism. Or, adopting our
previous terminology, the three theories may be
ranked thus.

The particulate elements of heredity all proceed
centripetally from somatic-cells to germ-cells (gem-
mules) : the inheritance of acquired characters is
therefore habitual.

These particulate elements proceed for the most
part, though not exclusively, from germ-cells to
somatic-C(;l!3 (stirp) : the inheritance of acquired
characters is therefore but occasional.

The elements in question proceed exclusively in
the centrifugal direction last mentioned (germ-plasm;
the inheritance of acquired characters is thercf !o
impossible '.

0

' I'rofessnr Wcismnnn still jn:;irit;iins tlint thee is a further irnportint
flistiiictioii httwccii tiic thcniius oJ imii^ciicsis mid Ljeriii-plasni, in thai
the OIK' is ijrf.-formative whilL- the oilier is e|>it;Liutic. Jiiit I aiii still
iinnble to jurceive that such is the c.ise. He ari^ucs, indeed, tiiat his
new doctii;-," of determinants emphasizes this distinction : the ar{^ament,

134 ^^ Exaniination of Weisuiannism.

\\m

1 !

.

1

Such bcinj:^ the fundamental points of difference
between these three theories of heredity, we have now
to consider more particularly those which obtain
between Galtons and Weismann's.

The jTcncral doctrine of f^em mules (i. e. somatic-
cell-[^ernis) is accepted by Galton : but instead of
supposing, as Darwin supposed, that these minute
bodies freely circulate through all the body tissues,
so that some of them arc absorbed from all the
somatic-cells by the q^erm-cells, and there constitute
the entire mass of hereditary material out of which
the offspring will afterwards be formed, Galton sup-
poses that gemmules circulate with comparative diffi-
culty, and that only comparatively few of them gain
access to the germ-cells in each generation. Hence,
characters acquired in the individual lifetime are
much less heritable than those which are called con-
genital. For congenital characters arc due to the
"continuity" of stirp through numberless genera-
tions in the phylogeny of the organism ; hence such
characters are represented by a vastly greater number
of equivalent hereditary elements. Weismann, on the
other hand, rejects the doctrine of gemmules /// toto.

Again, according to Galton 's view, " individual

however, appenrs to me radically un'oiind. For instance, he says, " The
hereditary conliiuiati)!! in each pan is pic-ckterniincd in each jiail
from the i;erm onwards. The rii^lit and left cars could not possibly
reseml)lc each other, if the relative strcni^th of the hereditary tendencies
on both sides were not ]ire-dcterniiiicd for all jiarts of the child by the
nature of the patiriial and material idanls." Very well. ]5uf. if so, the
theory of dcierniinants is jii.-t as much jire-formative as is that of
gemmules. Or, convi isely, the latter i« quite as epi,<,"netic as the former.
Koth are alike dctenniiiatirc. while neither supposes tliat the determina-
tion is due to a ]iie-fornu'd miuiaturo of tlir Intuie child in the feriili/ed
epp of its mother; but to a particulate representation in the latter of
every heritable part of the former.

Wcisvianvisin up to date (1893). 135

[congenital] variation depends upon two factors ;
the one is the variability of the i^erm ' and of its
progeny : the other is that of all kinds of external
circumstances, in determining which out of many
competing germs, of nearly equal suitability, shall be
the one that becomes developed. The variability
of germs under changed conditions, and that of their
progeny, may be small, but it is indubitable ; absolute
uniformity being scarcely conceivable in the condition
and growth, and, therefore, in the reproduction of any
organism. The law of heredity goes no further than
to say, that like tends to produce like ; the tendency
may be very strong, but jt cannot be absolute-."

Here, of course, there is a wide difference between
stirp and germ-plasm. For while Galton does not
entertain amphimixis among the " factors" of con-
genital variation, Weismann, as we are now well
aware, has hitherto regarded it as the sole cause
of such variation. Nevertheless, as we shall presently
find, Weismann has now greatly modified his views
upon this point, and does entertain, in The Germ lasvi.
both the " factors " mentioned by Galton. Hence, the
difference between the two theories in question with
regard to this matter is not nearly so wide as it was
prior to the publication of Weismann's last work.

The next most imi)ortant point of difference
between the theories of stirp and germ-plasm has
reference to the mechanism of ontogeny. Acc-^rding
to Galton, this is simply a struggle between all the

• lU' "^erm" Cinlton means a carrier of hciedity, which is capable
of sclf-muiU|ilicatiiiii. In thi.>c fn.Mdamcntal lespects. ihcicforc, it is
equivalent to a " j^riinmilo " on the one hand and a "determinant" on
the other. The tiir; c II mis are so far synonymous.

■^ Loc. iit., p. 33S,

WWflW-Uiill if^iPF"Vl,PT/«^r^». lufPJUUijii^'^PUu<ii>^'lii^ii«iniiMi^ivii»l

S fl!

a i|

l!!|il

136 An Examination of IVeismanntsm.

carriers of heredity composing the stirp of a fertilized
ovum. It is not, however, a struggle for existence,
but what may be called a struggle for development.
In the fertilized ovum all the carriers of heredity are,
to begin with, in a " latent " condition ; but of this
enormous multitude of '• germs " or " gemmules," only
a very small proportional number are destined to
become " patent " — i. e., developed into the tissue-cells
composing the new organism. The vast majority
of the gemmules, or those which fail to be thus de-
veloped, go to constitute the stirp of the new organism
when this has been formed by the development of the
comparatively few successful gemmules. Thus much
understood, the following quotation will be fully
intelligible.

My argument is this : Of the two groups of germs, the
one consisting of those that succeed in becoming developed
and in forming the bodily structure, and the other consisting of
those that remain continually latent, the latent vastly prepon-
derates in number. We should expect the latent germs to
exercise a corresponding predominance in matters of heredity,
unless it can be shown that, on the whole, the germ tl -^.t is
developed into a cell becomes thereby more fertile than if it had
remained latent. But the evidence points the other way. It
appears both that the period of feitility is shorter, and the
fecundity even during that period is less in the germ that
becomes developed into a cell, th.m they are in the gerai that
remains latent. Much less then would the entire bodily
structure, which consists of a relatively small number of these
comparatively sterile units, successfully compete in matters of
heredity with the 'otal eftect of the much more numerous and
more prolitic units which are in a latent form'.

Thus, Galtons theory of the mechanism of onto-

' /.oc. (it., p. .'',,■',9.

Ul

•1 '■

'^.t IS

Weis7ttannis7n up to date (1893), 137

geny is a theory of struggle ; and this constitutes
a point of difference on which Weismann lays much
stress in his latest work. For, as wc know, Weismann
regards the mechanism of ontogeny as charac'.erized
by a peaceful succession of " stages," which are " pre-
determined from the germ onwards "; and in his latest
work this idea of orderly sequence has been further
elaborated in his doctrine of "determinants." In
short, to adopt their own metaphors, while Galton
tells us that the mechanism of ontogeny is like that
of a political election, where rival candidates compete
to " represent " the nation (stirp) in Parliament (indi-
vidual organism) ; Weismann likens it to the mechan-
ism of a well-drilled army, where ultimate carriers
of heredity (privates) are banded together in com-
panies, regiments, battalions, &c., under the command
of corresponding officers (determinants).

Lastly, there is yet one further point of difference
between stirp and germ-plasm, which is thus stated
by We'smann : —

Galton's idea is only conceivable on the presupposition of the
occurrence of sexual reproduction, while the theory of the
continuity of the germ-plasm is entirely independent of any
assumption as to whether each primary constituent is present in
the germ singly or in numbers. According to my idea, the
active and the rcservj , '.Tin -plasm contain precisely similar
primary constituents, gemmules, or dcttrminants ; and on this
the resemblance of a child to its parent depends. The theory
of the continuity of the germ-plasm, as I undorstand it, is not
based on the fact that each "gemmule" necessary for the con-
struction of tile soma is [)resent many times only, so that a resiikie
remains from which the germ-cells of the next generation maybe
formed : it is founded on the view of the existence of a special
adaptation, which is inevitable in the case of multicellular organ-
isms, and which consists in the germ-plasm of the fertilized

m

III

^I

iPli" il»^ H) VVJ

if<m'f ' t"i I ■ iiivmifirwf^rww^W

1 ■ il

:i!;i

138 An Exammation of Wcismannism.

cgg-ccll becoming doubled priniarily,one of the resulting portions
being reserved for the lormation of gcnn-cells '.

These being the main points of difference between
the theories of stirp and of germ-plasm to which
Professor Weismann has alluded, I will now proceed to
consider them separately, in reverse order to that in
which the\' have been here stated.

The point of difference last mentioned need not
detain us long, because it seems to me one of very
little importance. '• Whether each primary constituent
is present in the germ singly or in numbers" cannot
greatly signify, so long as both theories agree that,
sooner or latter, they must be present plurally.
Galton supposes them to be thus present from the
first (i. e. in the unfertilized ovum), while Weismann
supposes them to be so only as a result of their self-
multiplication at a somewhat later stage (i. e. in
the segmenting ovum, and onwards throughout the
procreativc life of the individual). Doubtless Weis-
mann does not suppose that they ever become so
numerous as Galton imagines ; but the whole question
is so highly speculative that I do not see how any
useful purpose can be served by debating it. Nor do
I see why Weismann should conclude that " Galton's
idea is only conceivable on the presupposition of the
occurrence of sexual reproduction." It is true that
Galton has discussed exclusively the case of sexual
reproduction ; but I cannot perceive that any of his
ideas are inapplicable to a-.sexual.

Touching the question whether the phenomena of
ontogeny had best be ascribed to a competition
among a vast number of " germs," or to a strictly

' The (Jcnn-plasm, pp. 199, 220.

eismann

Weis)naniiis))i up to date (1893). ^39

•

ordered evolution of a comparatively small number
of "determinants," a considerable array of arguments
might be adduced in support of either view. Thus,
Galton might well maintain that his interpictation
of the observable facts is most in accordance with the
general analogies sup[)lied by organic nature as a
whole. The ancient aphorism of Heraclitus, '' Struggle
is the father, king, and lord of all tilings," has been in
large measure justified by Darwin and his followers,
at any rate within the range of biology. Not only
have we the " strucfcfle for existence" where "the
origin of si^ecics " is concerned ; but Roux has well
argued, in his remarkable work on Dcr KcDiipf dcr
Tlicilcivi Orj^a?iis?Nus, that the principle of "struggle"
is concerned to an equally im[)oitant extent as
between all the constituent parts of the same indi-
vidual. J^ut if this is so — if every tissue-cell of the
organism owes its maintenance to success in a general
contest for nutriment, &c., — do we not find at least
a probability that it owes its origin as a visible
cell to a similar success in a similarly general contest
among the invisible elements Irom which tissue-cells
arc de/elo[:)ed? Nay, does it not seem well nigh
incredible that when this selection-principle is seen to
be the governing cause of evoluticMi everywhere else,
it should cease to play any part at all just at the
place where we are unable to see what is going on ?
As we are agreed that this '' father of all thinfrs "
is of prime importance in phylogeny — to say nothing
of physiology, psychology, and sociology. - must we
not deem it absurd to suppose th.it it ' . supplanted
in ontogeny by the opposite principle of absolute
peace ?

R

I

■^ I ip^ wwi^ il^lnilHIIIil

,1 i

140 An Examination of Weis^nannism.

On the other hand, Weismann adduces many
forcible considerations per contra ; so that, in the
result, I deem it best to dispose of the question with
two general remarks. The first is, that the rival views
are not necessarily incompatible. Each may present
one aspect of the truth. Weismann's doctrine of
determinants may be— and, to the best of my judge-
ment, must be — sound ; but this does not hinder that
Gallon's doctrine of struggling " germs " may be so
likewise. For, as we have already seen, these germs
present the same compound character which belong
to determinants ; in fact I do not suppose that Galton
would object to identifying them with determinants.
On the other hand, I do not see why Weismann
should object to supposing that similar determinants
compete among themselves for ontogenetic develop-
ment. Indeed, he has already argued, in his
suggestive theory of "germ-tracts," that it is usually
only one among a number of similar determinants
which does succeed in achi( ving such development —
or, as he expresses it, whi '^ " becomes active."' But
what is it that causes this activity? Surely it must be
some superiority on the part of the active determinant
over its passive companions. And, if so, it is the
selection-principle that is here at work. In fact, he
has himself laid no small stress on what he calls "the
struggle of the determinants of the two parents in
ontogeny," and has even supplied a long section op
'' the Struggle of the Ids in Ontogeny." Therefore
I do not see why he should so emphatically dissent
from Galton's view upon this matter as he does
in his work on The Gcnu-phisin'^.

Weismaiinisni up to date (1893). 141

My second remark is a brief one — viz., that the
\vln)le (juestioii is of so very speculative a character,
that I cannot sec the smallest use in debatini; it.

The only remainintj point of difference between
strip and germ-plasm is the one referring to stability.
Needless to sa>', Galton is at one with Weismann in
recognizing a high degree of stability on the part of
the substance of heredity ; but the agreement extends
only so far as is necessitated by the facts of atavism,
&c. Indeed, he does not even mention— although he
l)erhaps implies what Weismann has called ami)hi-
mixis as among the factors of individual congenital
variation. W'eismaiui, on the other hand, has hitherto
regarded am[)himixis as the sole cause of all such
variations. But. as we shall presently find, in his
recent work on y/ic Gcnn-plasin he has now greatly
modified his views upon this subject, and, in fully
recognizing the ''factors'' of variability to which
Galton alludes, has corresi)ondingIy lessened the
ilifference between germ-plasm and stirp. But this is
a point which can be better dealt with when we come
to consider the important modifications which in this
respect the theory of germ-plasm has undergone.

The only other matter which has to be mentioned
in connexion with Weismann's theory of heredity is,
that in The Gcj-m-plasmhn has for the first time given
us his views upon the influence of a previous sire on
the progeny of a subsequent one by the same dam.
The phenomena in question, which I have already
detailed in pp. 77-9, 110. he designates by the term
"telegony." The analogous phenomena in plants he
calls, followuig Focke, " xenia."

Ill

it

^w-fW<nrm<W'^

i t

142 An Ex'.iuiitiation of IVcisniaiinism.

With regard to tclcgony, he adopts, almost pre-
cisely, the position which I surmised that he would.
That is to say, he first disputes the alleged facts, and
then argues that, even if they be facts, they admit of
being explained on the theory of germ-plasm by
supposing that some of the germ-plasm from the
first sire penetrates the unripe ova which are after-
wards fertilized by the second '. The only difference
between his views and my own upon this matter is,
therefore, as follows.

Supposing that the phenomena alleged ever occur
in fact, I have said that the only way of explaining
them would seem to be, '• that the life of ' germ-plasm '
is not conterminous with that of the spermatozoa which
convey it, and hence that, if the carriers of heredity,
after the disintegration of their contninnig sperma-
tozoa, should ever penetrate an unripe ovum, the
germ-plasm thus introduced might remain dormant
in the ovum until the latter becomes mature, and is
then fertilized by another sire. In this way it is con-
ceivable that the hitherto dormant germ-plasm of the
previous sire might exercise some influence on the
ontogeny of the embryo -."

Now, this is substantially the position which Weis-
mann takes up ; only instead of supposing that it is
the " carriers of heredity " of the first sire which gain
access to the unripe ovum " after the disintegration
of their containing spermatozoa," he supposes that it
is one of the spermatozoa which does so before its
disintegration has commenced. Of course there is
here no difference in principle, but only a question
touching the mode in which the access is presumably

' The Germ-plasm, pp. 383-386. 2 Quoted troin above, p. 78.

Wcisfiiaiinisifi up to date (1S9;). 14;^

effected. But, as rec^ards this question, I retain my
original opinion. For, while I can see no theoretical
difficulty in supposing that ''the carriers of heredity,''
when set free by the disintegration of their containing
spermatozoa, may reacli the unripe ova while still
embedded in the depths of the ovary, I do see a
difficulty, amounting almost to a physiological im-
possibility, in supposing that a whole spermatozoon
can perform such a feat. From all that we know
about the powers and functions of spermatozoa in the
vertcbrata, it appears simply absurd to imagine that
these bodies are able to penetrate the dense coating of
an ovary, and then delve their way through the stroma.
There is, indeed, a remarkable investigation which
was published a year or two ago by Mr. Whitman ^
which appears to prove that in certain leeches the male
injects his seminal fluid into any part of the body of
the female, and that the spermatozoa then reach the
ova by wandering about her general tissues until some
of them happen to hit upon her ovary. But in this
case the spermatozoa are specially adai)ted to perform
such acts of penetration — being spear-like bodies
provided with a sharp point. Hence, if Weismann
should quote this instance, it would not tend to
support his view, seeing that the spermatozoa of
mammals do not exhibit any such specializations of
structure ; and therefore, before any one of them can
effect fertilization, must wait for the ovum to mature,
reach the surface of the ovary, and rupture its follicle.
But, as already observed, it docs not signify, so
far as we are here concerned with the matter, in what
precise manner the telegonous influence may be

' Alorph. Journal, vol. ii.

144 "'^^^ Exaniinatioti of Wcis))ianni$m.

sui)po.scd to be exercised — provided tliat it may be
so directly, and not necessarily tiirouj^h first having
to influence the whole material organism. Therefore
I quite a;^n-ce with VVeisniann that the facts — sup-
posinfj them to be facts — are quite as explicable by
the theory of |jjerm-i)lasm as by that of panj;enesis ^
A<^ain, with resi)ect to xenia. VVeismann writes : —

As such I'liiincnt botanists ;is Kockc, unci inure recently
I)e Vries, have expressed nuich doubt with rei;ard to these obse*--
vations— or rather interpretations we nuist wait until these
cases have been critically re-investi,^'ated before atteinptin^^ to
account for them theoretically. The chief difriculty we should
meet with in any such explmation would be due to the fact that
weare here concerni'd with ilie innuence of the^'t77;/-/Arv/// of the
sperm-cell on a tissue of another plant which only constitutes
a pixrt of this plant. It wt)uld thus be necessary to assume that
all the determinants of this j^erm-plasm are not activCj and that
only those take erferl which determine the nature of the fruit.

Now, it docs not a[)pcar that I)c Vries has looked
into the matter on his own account, as he merely
refers to what Focke has said. And this amounts
merely to showini; the dubious character of some
half-dozen cases which Focke o;ives as those which
alone have fallen within his coLjnizance. Why he
does not mention an)' of the numerous cases which
are quoted by Darwin, I do not understand. Nor
can I understand why he does not consider what seem
to be the particularly conclusive facts given on
p. 80, — i.e., where xenia api)cars to constitute "a
needful preliminary to fertilization." But the whole
matter is one for botanists to deal with, and if any
doubt attaches to it, at least the grounds of such
doubt should be fully stated. Still more, in my

' See Appendix II.

IVcisiiiautiisin up to date (iiSq;,). 145

opinion, should the matter be freed from any such
doubt. The ([uestion — if there be a question — is one
of ^rcat interest from a merely physiological i)oint
of view, while in relation to the fundamental
problems of heredity its importance is immense.
Surely, then, any competent botatu'st who disi)utcs
'^he facts ought to test them by way of experiment.

Ikit, be this as it may, I must call prominent
attention to the following very remarkaljle words
wherewith Weismann concludes the passage above
quoted. For he there says, that even supposing there
were no doubt as to the facts or their interpretation,
''the chief difficulty" which they would oppose to
the theory of germ-plasm would be, " that we are
here concerned with the influence of the s^cnn-p/asm
of the sperm-cell on a tissue of another plant which
only constitutes a part of this plant." In other words,
Weismann now freely entertains the possibility of a
direct action of germ plasm on the somatic tissues,
even though these belong to another individual !
Thus he now concedes the only point for the
establishment of which I adduced the phenomena
of xenia, in Chapter III : the whole of one side
of that " reciprocal action between the sphere of
germinal-substance and the si)hcre of body-sub-
stance," which I contended for on pp. 76-S;'5, is now
conceded ; and although it is the less important
side, its surrender goes far to weaken the doctrine
of a per[)etual isolation of germinal-substance to
a "sphere" of its own. If we suppose that the
germinal substance of one organism may thus
directly act upon the somatic tissues of another,
and that changed conditions of life are able to

L

146 An Bxainination of IVeisinaunism.

produce simultaneously an acquired character in
the soma and a precisely identical character as
congenital in the germ (pp. 129-30), we are plainly
inviting ourselves to abandon the complex explana-
tion of living material in '• twd kinds," where one is
capable in .ill sorts of way? of communicating with
the other, while the possibility of any reciprocal action
is excluded. For the simpler hypothesis of living
material as all of one kind encounters no such
antinomies. So long as one kind of this material
was supposed to be as distinct from the other as a
parasite is distinct from its host, there was not so
much to choose between the theory of germ-plasm
and that of gem mules in this respect of simplicity.
But the more that the former theory has had to be
adjusted to facts, the greater has its complexity
become, until now its own author is obli 'jjed to make
SO many additional assumptions for the purpose
of maintaining it, that we begin to wonder how long
it can continue to support the weight of its accuma-
lating difficulties.

So ruich for the m'lln modifications which have
this year been made in Weismann's postulate of the
periietual contitiuity of germ-[)lasm. We must next
consider the changes which he has effected in his
companion postulate of the absolute stability of
germ-plasm.

•w»™^^rTV»W*'"'ivi! 11 |i,l!*W ■

fP

Weismanmsm up to date (1893). ^47

Weisvimuis Theory of livoliition (1H93).

Of far more importance than any of the alterations
whicli Professor Weismann has rccenti)' made in his
theory of heredity, are those whereby he has modi-
fied his sequent theory of evolution. For while,
as we have just seen, his work on TJic Gaiii-plasui
leaves the former theory substantially unaltered --
althoui^h largely added to '\\\ matters of detail. — it
so profoundly modifies the latter tluit careful readers
will find no small difficulty in ascertaining how much
of it has been allowed to remain. I will consider
only the main modifications, and these I will take
separately.

1

i

,

I ; >{

It will be rememberetl that one distinctive feature;
in Weismanns theory of evolution has hitherto been,
that the unicellular organisms differ from the multi-
cellular in the following important i)articu]ars.

1. lliere being no division in unicellular organisms
between germ-cells and somatic-cells, there is n<^
possibility in them of the occurrence of amphimixis.

2. Consequently, there is no possibility in them of
congenital variations, in the sense that these occur
in multicellular organisms.

3. Hence the only causes of individual variation
and of the origin of species in the unicellular organ-
isms are the Lamarckian factors, just as in the multi-
cellular the only cause ol these things is natural
selection.

4. Hence, also, the unicellular orgp.nisms arc poten-

Via

^

148 All Exaviination of Wcisviannism.

tially immortal, while the multicellular have acquired
mortality for certain adaptive reasons.

But now, with the exception of No. 4, all these
positions have been abandoned. For, chiefly on
account of the beautiful researches of Maupas, Weis-
mann has come to perceive that no real distinction
can be drawn between an act of sexual union in
the multicellular organisms, and an act of conjuga-
tion in the unicellular. Amphimixis, therefore, is
now held by him to occur equally in both these
divisions of organic nature, with the consequence
that the Protozoa and Protophyta owe their indi-
vidual variations, and therefore the origin of their
innumerable species, as exclusively to the action
of natural selection as is the case with the Metazoa
and Metaphyta. In fact, the term "amphimixis " has
been coined in express relation to these very points.

It will be seen, however, that this important change
of view merely postpones the question as to the
origin of amphimixis, if the object of this process be
that which Weismann supposes — viz., the providing of
material in the w^ay of congenital variations on which
natural selection can act. Therefore he is obliged
to assume that there now are, or once have been,
organisms of a less organized character than even the
lowest of the unicellular forms — organsims, that is
to say, which possess no nucleus, but are wholly
composed of undifferentiated bioplasm. These most
primitive organisms it must have been that were not
subject to any process of natural selection, but, in virtue
of an exclusive action of the Lamarckian factors upon
their protoplasmic substance, gave rise to individual
variations which subsequently gave rise to a unicellular

Wcismannism tip to date (1893). 149

:ss be

inij of

which

)bH'j:cd

progeny— when the process of natural selection was
immediately inaugurated, and thereafter entirely
superseded the Lamarckian factors. Or, to state the
matter in VVeismann's own words : —

IVIy earlier views f)n unicellular organisms as the source of
individual dilTerenrcs, in the sense that each chani^e called forth
in them by external intliiences, or by use and disuse, Vviis
sup[)osecl ' ■ be hereditary, must therefore be dismissed to some
sta;4e less distant frt)m the orii^in of life. I now l)elieve that
oUch reactions under external influences can only obtain in the
lowest organisms which are without any distinctii'n between
nucleus and cell-body. All variations which have arisen in
them, by the ojieration of any causes whatever, must be in-
herited, and their htreditaiy individual varial)ility is due to the

direct influence of the external world If I am correct in

my view of the meaning of conjugation as a method of amphi-
mixis, wc must believe that all unicellular organisms possess it,
and that it wiJ be found in numerous low organisms, in which
it has not yet been observed '.

It is not very clear, at first sight, how Professor
Wcismann, after having thus abandoned the pro-
positions 1 . 2, and 3, as above stated, manages to retain
his former view as given in No. 4. Nevertheless he
does so, by representing that a unicellular organism,
even though it present such a considerable degree of
organization as we meet with in the hicfher Protozoa,
still resembles a germ-cell of a multicellular organism,
in that it consists of all the essential constituents of
a germ-cell, inchiding germ-plasm in its nucleus. And
inasmuch as a germ-cell is potentially immortal, so it
must be with a unicelluUar organism ; in the one
case, as in the other, the design of the structure is
that its contained germ-plasm shall ftise with the germ-
plasm contained in the nucleus of another individual
' Essays on Heredity, vol. ii. pp. 193-4.

150 An Exahiinatioii of Weismannism.

J;!»i

«' '

cell, when the life of both will be preserved. For
my own part, however, I cannot see that in either
case the ccl^ hs distinguished from its contained ^^r;«-
plasni, is thus shown to be potentially immortal. On
the contrary, it appears to me a mere accident of
the case that in a unicellular organism the immortal
substanc (germ-plasm) is contained in a single cell,
which is at the same time 2, free cell, and, as such, is
denominated an ''organism." We might just as well
call a LTcrm-cell an "orcranism." whether a'^ an ovum
it happens to be embedded in a mass of somatic-cells,
or as a locomotive spermatozoon it happens to be
free. In fact Wcismann himself appears to recognize
this. P)Ut, if .so, it is surely a distinction without
a difference to say that unicellular organisms are
immortal, while m\ilticcllular are mortal. h'or in
neither case is the organism immortal, while in both
cases it is the germ-plasm (i.e., the substance of heredity)
that is .so. Where the cell containini? the ecrm-plasm
happens to be a irce cell, it is called an " organism " ;
but whether it be a germ-cell or a protozoan, it alike
ceases to be a cell when it has Qiven oricfin to a
multitude of other cells, whether the.se happen to be
other germ-cells {plus somatic-cells) or other proto-
zoan cells. In short, qua cell, all cells arc mortal :
it is only the .substance of heredity which some ceils
contain that can be said, in any sense of the term, to
be immortal. Vox the immortality in question does
not belong to unicellular organisms as such, but to the
germ-plasm whicii they contain. And from this it
follows that, as the immortality of germ-plasm is
one and the .same thing as the continuity of germ-
plasm, by alleging an immortality as belonging to

Weisma7iiiisin up to date (1893). 151

the unicellular ori^anisms, Wcismann is merely re-
stating his fundamental postulate. Hence, also, he
is^ but dcnyin^^, in a somewhat round-about way, the
occurrence of spontaneous generation.

I conclude, therefore, that his sole remaining
distinction between the unicellular and the multi-
cellular organisms is but illusory, or unreal. And,
with recrard to the great change which he has thus
effected in his system b}' xpressly abolishing all the
other distinctions, I have only to say that in my
opinion he has thereby greatly iniprovctl his system.
For he has thus relieved it of all the formidable
difficulties which he had needlessly created for him-
self, and which I have alrcadv enumerated in the
foregoing pages (88-M9). In his ever-shifting drama
of evolution the unicellular organisms have left the
stage en masse, and, so far as they are concerned,
we arc all as wc were before the curtain rose.

But of even more importance than this funda-
mental change of view with regard to the unicellular
organisms, is a further and no less fundamental
change with regard to the multicellular. That such
is the case will immediately become apparent by
a simple statement of the fact, that Weismann has
now expressly surrendered his postulate of the abso-
lute stability of germ-plasm !

We have already seen that, even in the first volume
of his Essays, there were some passages which gave
an uncertain sound with regard to this matter. But
as they seemed attributable to mere carelessness on
the })art of their author, after quoting a sample
of them, I showed it was necessary to ignore such

BJ

5

152 An Examination of Weismannism.

inconsistent utterances — necessary, that is, for the
purpose of examining the theory of germ-plasm as
even so much as a logically coherent system of ideas ^.
For \vc have seen that if any doubt were to be
entertained touching the absolute stability of germ-
plr.sm "since the first origin of sexual propagation,"
a, corresponding measure of doubt would be cast on
Wcismann's theory of congenital variation as solely
due to amphimixis, with the result that his whole
theory of evolution would be similarly rendered
dubious. Since then, however, he has gone very
much further in this direction. First, in reply to
Professor Vines he says (1 ^90) : —

i am at present inclined to believe that Professor Vines is
correct in questioning whether sexual reproduction is the only
factor which maintains Metazoa and Metaphyta in a state of
variability. I could have pointed out in the English edition
of my "Essays" that my views on this point had altered since
their publication ; my friend Professor da Bary, too early lost to
science, had already called my attention tD those parthenogenetic
Fungi which I'rofessor Vines justly citef, agairst my views; but
I desired, on grounds already mentioned, to undertake no altera-
tion in the essays ".

Next, in his essay on AinpJdmixis (1892), there are
several passages to somewhat the same eiTect ; while,
lastly, in his Germ-plasm (1^)93), the fun("imental
postulate in question is, as I have said, expressly
surrendered. For example, we have in the following
words the final conclusions of his recent arguments.
Speaking of amphimixis, he says : —

// is not the primary cause of hereditary variation. P>y its
means those specilic variations which already exist in a species

' See above, pp. 6,v^>7-

Wit lire, vol. xli. p. 322.

IVcismannisDi up to date (1893). 153

may continually be blended in a fresh manner, but it is incap-
able of giving rise to new variations, even though it often
appears to do so. . , . 'J'hc otitsc of hereditary xniriation must lie
deeper than this. It must be due to the direct effects of external
influences on the biophores and determinanis\

These quotations are cnoiicjh to show that Wcis-
mann has now abandoned his original theory of
congenital variations being exclusively due to amphi-
mixis, and adopts in its stead the precisely opposite
view — viz., that the origin of all such variations must
be ascribed to the direct influence of causes acting (mi
germ-plasm from without. Up to the present year
the very essence of the whole Weismannian theory
of evolution has been that, owing to the stability
of germ-plasm since the first origin of sexual pro-
pagation, "the origin of hereditary individual varia-
tions cannot indeed be found in the higher organisms,
the Metazoa and Metaphyta ; but is to be sought
for in the lowest — the unicellular organisms," because
" the formation of new species, which among the
lower Protozoa cotdd be achieved without amphigony,
could only be attained by means of this process in
the Metazoa and Metaphyta. It was only in this
way that hereditary individual differences could arise
and persist V

But about the beginning of the present year we
have this fundamental doctrine directly contradicted
in such words as : —

The origin of a variation is equally independent of selection
and amphimixis, and is due to llie constant occurrence of slight
inequalities of nutrition in the germ-plasm '.

* The Germ-plnsm, pp. 414-415. IlnliLS Wci^mmin's.
- Essays, vol. i. p. 2S4. The (Jenii-/>liisin, p. 431,

I

154 ^^ Examination of Weismannism.

li

m

' l':\

This complete reversal of his previous doctrine
brings Weismann into line with Darwin, who long
ago gave very good reasons for the following con-
clusion : —

Those authors who, like Pallas, attribute all variability to the
crnssin>i cither of distinct races, or to distinct individuals belong-
ing to the same race but somewhat different from each other,
are in error; as are those authors who attribute all variabi'ty
to the mere act of sexual union \iii}iphiviixis\ *.

And again : —

These several considerations alone render it probable that
variability of every kind is directly or indirectly caused by
changed conditions of life. O;, to put it under another point
of view, if it were possible to expose all the individuals of a
species during many generations to absolutely uniform con-
ditions of life, there would be no variability'''.

Hence, Darwin was disposed to find the main,
if not the only, causes of congenital variations in
circumstances depending for their efficacy on the
iustability of what Weismann calls gcrm-plasm. And
the noteworthy fact is, that Weismann has now
adopted this view, to the destruction of his originally
fundamental postulate touching the stability of germ-
plasm since the first origin of sexual propagation.

By such a right-about-face manoeuvre. Weismann
has placed his critics in a somewhat difficult position.
For, in the first place, it is only towards the close
of T/ie Gcrni-plasin that the manoeuvre is executed,
and then only in a few sentences such as 1 have just
quoted— italici/.ed, it is true, but otherwise so slightly

I

* Vai iation &.c., vol. i. p. .vjH.

/I'll/., vol. ii. p. 242.

Weisinannisju tip to date (1893). 155

emphasized that, as Professor Hartof]^ has observed,
no one of his reviewers has noticed it '. In the
second place, he nowhere expressly recoi^nizcs the
effects upon his theory of evolution, which necessarily
follow from the change. And, lastly, the manner in
which he endeavours to underpin that theory after
having thus removed its logical foundation in his
former postulate of the absolute stability of germ-
plasm, is so peculiar that it is hard to epitomize his
reasoning with due regard to brevity.

Speaking for myself, I can only say that my first
impulse, after reading the sentences above cjuoted,
was to cancel the whole of Chapter IV, as well as all
those parts of Chapters I and III where the Weis-
mannian theory of evolution is alluded to ; and then
to start anew with a bare statement that this theory
had now been wholly discarded by its author. lUit
after due consideration it seemed desirable to leave
the criticism as it was originally written, not only on
account of the reasons already stated in the Preface,
but still more because I found it would be impractic-
able to start a new criticism of the greatly modified
theory of evolution without introducing many and

' Nature, May ii, pp. 28 -29. — In 1S91-2 I'rofessor Ilaitog furnished
a criticism of Wci^niann's theory of Ilercilily (A'a/nre, vol. 44. p. 613,
and ContcuiponD-y A't't'/cTt', July, 1S92K Although disputed at the time
by some of W'eismann's followers in luiyland, this criticism was one of
im(|uestionat)le cogency, anil has now been recognized as such hy
Weismann himself ^'Ihe O'enn-plasiii, pp. 4,^4:;). 'i'he main point of
the criticism had been missed by previous critics of \\ eisiuann, and
consisted in revealing an imi)ortant "difficulty" inherent in the structure
of the theory itself. How far this criticism had the effi ct of causing
Professor Weismann to abandon his theory of variation being ex-
clusively due to anii)liimixis, as Trofessor Ilartog appears to think
{Aalurr, May 11, li^93, p. 2S), is immaterial. But it must be obseived
that as lar back as February, 1S90, Professor Weismann in his answer to
Professor Vines' criticism wrote the passage already quoted on page 152.

I

:' M

"'•^wplf^'^^pf^lp'

156 An Examination of Wcisniannisni.

Icn^^thy jiarts of the old one, for the purpose of
shovvinj^ how the most recent theory liad been arrived
at. Mence, seeing that my previous criticism was
far from havinj^ been rendered obsolete by the larcje
clianj^es which liad taken place in Weismann's system
of theories, I concluded that it was best to retain
what I had written, and add the present paraf^n-ajihs
for the i)urpose of dealing exclusively with the
changes in question.

In now proceeding to do this, I think it is needless
to occupy space by giving the reasons which have
caused Weismann thus to abandon his doctrine of the
universal stability of germ-plasm since the first origin
of sexual propagation, and to substitute the precisely
opposite doctrine of its universal instability. It is
enough to say that these reasons all arise by way
of logical necessity from the further working out in
TJic Germ-plasm of his theory of heredity — or, more
correctly, from the additions which he has there made
to his previous views on the mechanism of heredity.
Thus he has reversed his former doctrine touching
the absolute stability of germ-plasm, not so much
on account of any of the general considerations or
particular facts which I have adduced against it in
Chapter IV, as because it would not tally with the
recent additions which he has made to other parts
of his system. Any one who cares to follow this
matter will find the reasons in question fully and
lucidly stated in Chapter XIV of The Germ-plasm ^

' It is almost iiccillcss to say that no fault is to be found with
Weismann for havini; thus reversed his opinion touciiinij one of his
fundamental postulates Consistency is no merit in a m;in of science;
and least of all where matters of sucii hii,di speculation arc concerned.
I think, however, that it is open to question w hether an author of any

IVeisinaiinisni tip to date (I^>93). 157

It is of more inii)()rtancc to consider the means
whereby Weisinann seeks to save his theory of cvo-
kition after he has thus removed its foundation in his

for

mer postulate of the absolute stabih'ty of j^erm-
phism. A far as 1 can understand, he seeks to do so
as follows.

In the first place, it must be noted that after
his changes of view with regard to polar bodies,
unicellular organisms, and the significance 01 sexual
reproduction, nothing remains of his original theory
of evolution save what he can manage to retain of his
original theory of variation as due to atiii)himi,\is.
But, as we have just seen, he has surrendered this
latter theory also. Therefore, at first sigiit it appears
that no i)art of the former can possibly remain.
Beginning at the apex, he has removed, stone by
stone, his doctrine of descent, and, on arriving at
its fundamental postulate — the absolute stabi''ty of
germ-plasm — simply turns it upside down. Surely,
therefore, it may be thought, there is here as complete
a destruction as well could be of all this side of
Weismann's system. Such, however, he enileavours
to show is not the case. He regards it as still possible
to retain so much of his theory of descent as is
presented by what he can save of his theory of vari-
ation, thus : —

Although he now represents that the instability of

kind should suffer an cLiljoratc system of thcoiiL-s to he [)ul)lislicd and
translated, at the very time when lie is himselt engaged in producini;
another woriv siiouinj; the untenable cliaraeter of tiicir basal premises.
At any rate, it would have saved his Knj;li h readers no small trouble
and confusion, if W'eismann iiad added notes to the translations of his
essays on Polar l^odics, on The Sv^nificiDicc of Sexual Reproduction,
and on AnrphiiiiLxis, to tlie effect that lie had aixindoned some of
their most distinctive fealuies before the translations liad gone to press.

J:.t

I5<S y/;/ Exiwii nation of ll\isniatinisni.

I^cnn-plasin is such that in no case can ami)himixis
have had aiiythini,^ to do with the orii!;in of congenital
variations, he continues to rci^ard the stability of
^erni-i)lasni sufficiently j;rcat to necessitate, in all
cases, the occurrence of amphimixis in order to
promote the (tcvclopntcut of conijenital variations. In
other words, nolwithstandinj^ that he now thinks all
congenital variations must be het^un by external
conditions actinij directly on an unstable i^erm-plasm,
he also thinks that the amount of variation thus
[jHuiuced is likely to be cxceeilin<^ly minute, and
must therefore be increased by subsic[uent amphi-
mixis in order to fall within the ransjc of natural
selection. So that, alth()UL,di powerless to initiate
coni^enital variation, amphimixis must still play an
indisi)ensal)le part in the process of evolution, as in
all cases a necessary condition to the occurrence of
natural selection. External conditions first cause
slii^ht chani^es in the determinants of a species ; but
these are so sliL;ht that they have to be augmented by
amphimixis before they constitute material on which
natural selection can act, and hence before they can
become of any significance either in ontogeny or
[)hylogeny.

Such, I take it, is what Professor Weismann would
now have us to understand ; for otherwise I should
have expected from him as frank a surrender of his
theory of evolution (or the remnant thereof in his
theory of variation) as he has made of its funda-
mental postulate. But, if such is his meaning, I may
mention the reasons which appear to me to render
it nugatory.

In the first place, it is evident that in thus

'sin.

Wi'ismannisin up to dale (KS93). 159

ii[)himixis
:on^cnital
ability of
tc, in all
order to
:ions. In
thinks all

cxtcrn.il
'm-plasni,
tion thus
nutc, and
it amphi-
f natural
) initiate
. play an
ion, as in
rrcnce of
"St cause

ies ; but
ented by
)n which

hey can

geny or

n would
should

r of his
in his
funda-

j, I may

) render

in thus

niinimi/ini; the possible range of congenital variation
due to the action of external conditions on a non-
absolutely stable substance of hendity, Weistnann
is making a wiiolly gratuitous a.ssum[)ti{)n, for the
sole purpose of saving what remains of his theory
of evolution— i. e., the doctrine of the immense im-
portance of am[)himixis.

We have already seen in the foregoing chajiter,
that his original assumption of the ahsolutc stabih't)'
of germ-plasm was a gratuitous one, made for the
pur[)ose of suppl\'ing a foundation for constructing
his theory of evolution. lUil still more gratuitous
is the assumption which he has now substituted, for
the purjxise of saving as much of this theory as
is left— the assum[)tion, namely, that germ-plasm,
although universally unstable, nevertheless everywhere
presents only a certain low degree of instabilit)-,
which serves to accommodate his modifieil theory
of heredity on the one hand, and all that is jjossible
of his previous theory of evolution on the other. His
original assum[)tion, ujitenable though it was, fur-
nished at least a logical basis for the necessary con-
elusion that am[)himixis v- -.s the only iKXssible cause
of congenital variations, liut there is not so much as
any logical sequence in the now substituted assuni[)tion,
that (A) all congenital variations are ultimately due
to the universal instability of germ-plasm, and (H) that
nevertheless they are all more proximately due to such
a liigJi degree of stability o( germ-plasm as necessitates
am[)himixis as the only means whereby variations can
be made " perceptible." These statements are as
independent of one another as any two statements
can well be ; and, therelore, if the second of them is to

i6o An Exaudfiation of Weismannism.

\i

:3

Pi! i

]'P! i

ill)

be substantiated, it can only be so by some totally
distinct line of reasoning The first statement does not
even tend to suggest the second ; ni fact it tends to
suggest the precise contrary. For, obviously, there is
nothing in the logic of the matter to show why, if
all congenital variations depend for their origin on
the instability of germ-plasm, such instability must
nevertheless be always so slight that the variations
due to it must afterwards depend on amphimixis for
their devchjpment to the point where they become
"perceptible." As above indicated, it is surely little
short of absurd thus to assume that a universally
unstable germ-plasm universally presents only that
particular degree of instability which will serve to
accommodate Professor Weismann's newer theory of
heredity, and at the same time to save thus much
of hiS previous theory of evolution.

But now, in the second place, not only is this
assumption wholly gratuitous, but there are many
considerations which render it in the highest degree
improbable, while there ai^ not wanting facts which
appear to demonstrate that it is false. For. unquestion-
ably, most of the considerations which have already
been advanced in the preceding chapter against the
assumption of an absolute stability of germ-plasm, are
here equally available against the assumption of an
imperceptibly small amount of instability ^ Similarly,
all the facts thcie given with regard to the a-sexual
origin of species — and even genera — of partheno-

' See especially pp 86-89. All thnt is there said about the unicellular

organisms is not, 'n the jiresmt connexion, affecteil by Weismann's

;hange of view with ic^ard tu thcin. \\'e have only to substitute

'primonliril" or "protoplasmic'' lor "unicellular," and ncaily all the

points ol the ciilicisni remain.

m.

ic totally
; does not

tends to
T^ there is
V why, if
oriLrin on
lity must
i^ariations
imixis for
7 become
rely little
nivcrsally
only that

serve to
theory of
us much

/ is this

re many

t degree

s which

uestion-

al ready

linst the

ism, are

)n of an

milarly,

a-sexual

arthcno-

unicellular
Vcisnmnn's

substitute
uly all the

Weisniannisfu itp to date (1893). i6t

genetic organisms, bud-variation ^, &c., amply de-
monstrate that congenital variations due to the
instability of germ -plasm alone, or apart from amphi-
mixis, are somc'imcs enormous. Hence, we cannot
accept the gratuitous suggestion that in all other
cases they arc 100 insignificant to count for anything
till they have been augmented by amphimixis, even
although we may be prepared to agree tha: amphi-
mixis is probably one important factor in Uie pro-
duction of congenital variations. What degree of
importance it presents in this connexion, however,
we have not at present any means of determining ;
all we can conclude with certainty is, that in some
cases it is demonstrably ve/y much less than Weis-
mann supposes, while it is extremely improbable that
it is ever in any case the sole and necessary antecedent
to the operation of natural selection.

This extreme improbability is shown, not only by
what I have already .said in the previous chapter, and
need not here repeat ; but likewise by the *' sever-\l
considerations " which Darwin has adduced with
regard to this very point, aivl which, as he says,
"alone render it probabJe that variability of every
kind is directly or indirectly caused by changed
conditions of lite," with the con.sequence that "tho.se
authors who attribute all variability to the mere act
of sexual union are in error." I have already quoted
tliL ic words further back in the [jresent chapter, in
order to show that by now attributing the origin

' Professor Weismaiin has now considered more fully than heretofore
the phenomena of bud-variation ' 7'/u Ucrm-plasin, i)p. 439-442) ; but
as he continues (though witli diffidcncL') to lake substantially the same
\iew of tiiem as that which I have already ([Uuted on pp. y^ -y6, it is
needless fur nic to rc-discuss (he m.attcr hii'j.

M

1 62 Ah Examination of Wcismanmsin.

I|

of all conc^cnital variations to the direct action of
external conditions. Weismann has brought himself
into line with Darwin so far as this fundamental
point of doctrine is concerned. But I here re-quote
the words in order to show that by further attributing
the development of congenital variations •' to the mere
act of sexual union," Weismann is again falling out
of line with Darwin. So to speak, he first performs
a right-about-fiiCe movement as regards his original
position towards the '• stability of germ-plasm," and
immediately afterwards makes a half-turn back again.
Now, it is this half-turn to which I object as un-
warranted in logic and opposed to fact.

In a previous chapter (pp. 66-j) I presented to him
the dilemma, that germ-[)lasm must be either ab-
.soUitely stable or else but highly stable, and that in
the former case his theory of amphimixis as the sole
cause of congenital variations would be valid, while
in the latter case the theory would collapse. But it
did not then occur to me that Weismann might seek
a narrow seat between the horns of this dilemma, by
representing that germ-plasm is universally unstable
up to a certain very low degree of instability — viz.,
exactly that degree which is required for starting
a congenital variation by means of external causes,
without its being possible for the variation to become
perceptible unless afterwards incn.^sed by means of
amphimixis. And now that this extremely sophis-
tical position has been adopted, I cannot see any
imaginable reason for adopting it other than a la.-it
endeav ir to .save as much as possible of his former
theory of evolution. There can be nothing in the
nature of things thus to limit, within the narrowest

iVPI

:tion of
himself
amcntal
•e-quote
ributing
he mere
ling out
)erforms
original
m,"' and
;k again.
: as Lin-

Weisffiannism tip to date (1893). 1^3

possible range, the instability of a universally unstable
germ-plasm — distributed, as this most complex of
known substances is. throughout all species of plants
and animals, and exposed to inconceivably varied
conditions of life in all quarters of the globe. And
these considerations are surely of themselves enough
to dispose of the assumi)tion as absurd, without again
rehearsirg the facts of congenital variation which
definitely prove ii to be false.

1 to him

;her ab-

i that in

the sole

d, while

But it

ht seek

nma, by

unstable

;y— viz.,

starting

causes,

become

leans of

sophis-

ice any

a la^t

former

in the

rrowest

Conchisioii.

For reasons stated at the commencement of this
chapter, I have restricted its subject-matter almost
exclusively to a consideration of the more fundamental
changes which Professor Weismann has wrought in
his general system of theories by the publication of
his most recent works. In other words, I have pur-
posely avoided considering those inmiensely elaborate
additions to his theory of heredity which constitute
by far the largest portion of his essays on AmpJiiuiixii
and The Gcnn-plasin, and which have {or their object
an ideal construction of " the architecture of germ-
plasm."

The fundamental changes to which allusion has
just been made are as follows.

Professor Weismann has to a large extent abandoned
his theory of polar bodies, and in my opinion would

M 2

; ■ • ' 1

t -Tw

164 All Examinatio7i of Weismannism.

have done well had he taken a further step and
surrendered the theory in toto.

Similarly, he has withdrawn his previous distinctions
between the unicellular and multicellular organisms.
The Protozoa and Protophyta are now included by
him in the same category as the Meta/.oa and Meta-
[)hyta, as regards all matters of individual variation,
reproduction, subjection to the law of natural selection,
and so forth. The only difference which he continues
to allege is the somewhat metai)hysical one touching
mortality and imiuortality. Ikit I have given what
appears to me sufficiently good reasons for ignoring
this distinction ; and therefore, as it seems to me,
everyone of Weisniann's previous doctrines respecting
unicellular organisms have vanished — very much to
the benefit of his system as a whole.

By far the greatest change, however, which he has
made in this general s}stem is that which he has
effected by surrendering the postulate of the absolute
stability of germ-plasm. The rift in his lute which
has been noticed with regard to this matter lias
now been widened to an extent which docs prevent
any further harping on the theme of evolution. It
is true that Weismann endeavours to retain as far as
possible the general character of his former postulate
of the universal stability of germ-plasm, with the
consecjuent '' significance of sexual reproduction " as
the sole cause of congenital variation. For although
he now reverses both these doctrines by saying that
germ-i)lasm is universally unstable, and that sexual
reproduction is in no case the sole cause of congenital
variation, he seeks at the same time to minimize tht
logical consequences of such reversal by making ar

MiT

Weismannis7u up to date (1893). 165

what

that
lexLial
Icnital

ie tht

ingenious assumption, the possilDiHty of which I had
not foreseen when writing the previous chapters.
The assumption is, that altliough germ-plasm is
universally unstable, the degree of its instability is
everywhere restricted within the narrowest possible
limits ; so that sexual propagr^ 'on is still necessary
for the purpose of developing congenital variations to
the point where they can fall within the range of
natural selection, notwithstanding that they must all
have been originated by external causes acting
directly on a germ-plasm universally unstable within
the narrow limits assumed. But clearly this as-
sumption is arbitrary to the last degree, and, no less
clearly, it is made by Weismann for the sole purpose
of saving as much as he can of his previ(^us theory of
variation. His more recent speculations touching
the mechanism of heredity arc incompatible with his
former view of amphimixis as the sole cause of con-
genital variations, and therefore he makes this arbitrary
assumption for the purpose of representing that am-
phimixis may nevertheless still be regarded as
a necessary con-cause. I need not here repeat what
has .so recently been said touching the sophistry of this
assumption in theory, or the demonstrable falsity of it
in fact, it is enough to remark, in conclusion, that
the game is not worth the candle. It was originally
well worth Weismann's while to sustain his funda-
mental postulate of the absolute stability of gcrm-
nlasm, because he was al)le to re;

>P

theory of evolution. lUit tlie only part of this theory
which he has now left standing, or which he can now
save by his newer postulate of a germ-])lasm both stable
and unstable at the same time, is his doctrine o^

#

W'

1 66 An Examination of Weisniannism.

variation. So to speak, it is his desire to reserve as
much as is speculatively possible from the general
ruin of his theory of descent, that causes him to go so
far to attempt so little. For I cannot si jpose that he
himself will expect any of his readers to entertain
so arbitrary, fanciful, and demonstrably false an
assumption as the one in question. Surely it would
have been better to have surrendered in toto this
*' Weismannian theory of variation,"' rather than to
have attempted its rescue by means so plainly
nugatory. It might still have been held that ami)hi-
niixis plays a large and important part as one of the
causes of variation, and therefore also as one of the
factors of organic evolution. After having reversed
his postulate of amphimixis being the sole cause of
variability, and therefore having agreed with Darwin
that " those writers are in error who attribute all
variability to the mere act of sexual union," he might
well have questioned Darwin's further statement as to
its being " probable that variability of every kind is
directly or indirectly caused by changed conditions
of life." But by now assuming that variations due to
any causes other than amphimixis must be '• imper-
ceptible " until they have been augmented by amphi-
mixis, Weismann is shutting out, with a futile hypo-
thesi.s, the important question as to whether, or how
far, amphimixis really is a cause of variation. Observe,
the case is not as it might have been were there no
reasons assignable for the occurrence of sexual pro-
pagation, other than that of assisting in the production
of congenital variaticnis. The theory of " rejuve-
nescence," for example, i^ prima faci • a more probable
one than that which ascribes to sexual propagation

H :l'i

m.

eserve as
: general
to go so
e that he
entertain
false an
it would
toto this
than to

plainly
t amphi-
ne of the
)e of the
reversed
cause of
I Darwin
ibute all
le might
ent as to
r kind is
auditions
IS due to

impcr-
r am phi -
c hypo-

or how
Observe,
there no
ual pro-
xluction

rejuve-
)robable
,)agation

Wcismannism itp to date (1893). 167

the function of causing variability ' ; while Galton's
hypothesis, which supposes the object of this form of
propagation to be that of conserving the " germs "
( = " determinants ") of the phyla, has a good deal
to say for itself-. Of course such alternative hypo-

' " l^eiuvenescence '

means the rencwnl of vital enerijies which is
supposed to result from a fusion of tlic contents of two cilis. For an
excellent discussion of this and the other theories on the object of sexual
propagation, see a brief article by Professor Marcus Hartog, in the
Contemporary Rcvieiv for July, i S92. vSince then Weismann has pul>lished
The Germ-plasm, and here his main argument against this theory is that
tens, or even hundreds of generations of unicellular organisms have l)ec'n
observed to succeed one anotlier before any act of conjugation takes
jilace. Hut I cannot see that it signifies how many generations may in
different species be jiroved capaMe of resulting from a single act of con-
jugation. Weismann himself now accepts the analogy between cell-
proliferation as resulting from conjugation in unicellular organisms, and
from fertilization in multicellular. But even three hundred generations
of the former can scarcely be regarded as equal to all the " ontogenetic
stages " of the latter.

'* This view of the function of sexual propagation is now universally
ascribed to Strasburger, and it is quite true that he has indeiKiidently
adduced it. Ikit as this was not done until about ti n years afiti it iiad been
published byGalton, I have designedly associated the idea with Galton's
name. The following are the words in which it was announced
by him : —

"The necessity of a system of double parentage in complex organisa-
tions is the immediate consequence of a tlieory of organic units niid
gcims, as we shall see if ue lix oUI attention u|>on any one definite series
of unisexual descents, and follow out its historj'. Suppose we select,
cut off, and plant the second bud. then after it has grow n to niatmity we
similarly take the secom' of its buds, and so on consecutively. At each
successive stage tiicre is aluajs a chance of some one or more of the
various species of germs ii^ the slirp dying out, or being omitted; and of
course when they are gunrlhtyare lost for ever, and arc irreplaceable
jjy others. From time to time this chance must fall unfavcniraljlj . an<l
will cause a deficiency in some of the structural elements, and a consc
quenl deterioration of the race. If the loss be vital, this particular line
of descent will of course be extinguished at once ; but on tiie more
favourable supposition, the race will linger on, submitting to successive
decrements in its constituent elements, until the accumulation of small
'osses becomes latal." — loc. cit.. \>. 3.^.',.

(jalton also p(jints out a further advantage that is secured by

1 68 An Examination of Weismannisvi.

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theses touching "the significance of sexual repro-
duction " are not necessarily exclusive of one another :
the process may subserve two or more adaptive
purposes ^ But he would be a bold man who, in the
present state of our knowledge, could accept unre-
servedly the particular view of this process which
Darwin so emphatically rejected ; and I think he
must be a biased man who could entertain for
an instant the modification of this view which Wcis-
mann has now substituted.

Thus, the Wejsmannian theory of evolution has
entirely fallen to pieces with the removal of its
fundamental postulate — the absolute stability of
germ-plasm. It only remains to mention once more
the effects of this removal upon the other side of his
system — viz., the companion postulate of the uninter-
rupted continuity of germ-plasm, with its superstructure
in his theory of heredity.

Briefly, these effects are as follows : —

I. Germ-plasm ceases to be continuous in the
sense of having borne a perpetual record of con-

" amphimixis," and one which shows the non-necessity of what remains
of Wfismann's theory of polar bodies, thus —

" Tiiere is yet another advaiitaj^e in double parentnc^c, namely, that as
the stirp whence the child sijrang can only be half the size of the
combined stirps of his two parents, it follows that one half of his possible
heritage must have been suppressed. Tiiis implies a sharp struijgle for
place among the competing germs, and the success, as we may infer,
of the fitter half of their numerous varieties." — loc. cit., p. 334.

' In fact, it seems to me that this is the sole supposition whereby it
can be held that sexual propagation has bten developed both " /rj' " and
'^for'" natural selection, in order to supply variations as material for the
action of this priiiciple. Natural selection cannot thus supply tlie
conditions to its own activity, if, as Weismann supposes, there is but
one purpose for it to subserve (see above, pp. 13-15). liut, if it
is acting for more than one purpose, the " by " and the " for" argument
may hold.

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Weismaitnism np to date (189;^). 169

genital variations from the first origin of sexual
propagation.

2. On the contrary, as all such variations have
been originated by the direct action of external
conditions, the continuity of germ-plasm in this sense
has been interrupted at the commencement of every
inherited change during the phylogcny of all plants
and animals, unicellular as well as multicellular.

3. But germ-plasm remains continuous in the
restricted, though still highly important sense, of
being the sole repository of hereditary characters of
each .successive generation, so that accpu'red characters
can never have been transmitted to progeny " repre-
sentatively," even although they have frequently
caused those " specialized " changes in the structure
of germ-plasm which, as we have .seen, must certainly
have been of considerable importance in the history
of organic evolution.

4. By surrendering his doctrine of the absolute ^
stability of germ-plasm on the one hand, and of its
perpetual^ continuity on the other, Weismann has
greatly improved his theory of heredity. For, what-
ever may be thought of his recent additions to this
theory in the way of elaborate speculation touching

* I find that a passage cxjdainiiif,^ il;j sense in wliicli 1 use these leims
has been accidentally omitteil from Chajiter III, wliere tliey are first
introduced ; and, as the sheets of that chapter have been already printed
off, I here supply the omission. The terms in italics are not Weismaim's,
and I have employed them merely for tiie purjiose ot gi\iiii^ i)recision to
his views. By " absohtte stability of j,'erm-plasm " I mean to indicate
that degree of stability which he has hillierto postulated as the necessary
basis for his doctrine of heritable variations beinj^^ solel}- due to admix
tures of germ-plasm in sexual uiuons. 15y "■perpetual continuity of
germ-plasm" I intend to denote that amount of continuity wiiich he still
postulates as the neccssar) basis for his correlative doctrine touching the
non-inheritance of acquired characters.

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1 70 An Examination of IVcisnianiiism.

the ultimate mechanism of heredity, it is a great
gain to have freed his fundamental postulate of the
continuity of germ-plasm from the two further
postulates which have just been mentioned, and the
sole purpose of which was to provide a basis for his
untenable theory of evolution.

5. In my opinion it only remains for him to
withdraw the last remnant of his theory of evolution
by cancelling his modified and even less tenable
views on amphimixis, in order to give us a theory of
heredity which is at once logically intact and bio-
logically probable.

6. The theory of germ-plasm would then resemble
that of stirp in all points of fundamental importance,
save that while the latter leaves the question open as
to whether acquired characters are ever inherited in
any degree, the former would dogmatically close it,
chiefly on the grounds which I have considered in
Appendix II. It seems to me that in the present
state of our knowledge it is more prudent to follow
Galton in suspending our judgement with regard to
this (juestion, until time shall have been allowed for
answering it by the inductive methods of observation
and exi)erimeiit.

7. Hence, in conclusion, we have for the present
only to repeat what VVeismann himself has said in
one of the wisest of his utterances,—" The question
as to the inheritance of acquired characters remains,
whether the theory of germ-plasm be accepted or
rejected." ' "

It is now close upon twenty years that I accepted
the substance of this theory under the name of stirp ;
and since that time the question as to the inheritance

IVetsmanmsm np to date (189;,). 171

of acquired characters remains exactly where it was.
No new facts, and no new considerations of much
importance, have been fortlicominj; to assist us in
answering it. Therefore, as already stated in the
Preface, I intend to deal with this question hereafter
as a question per sc. or one which is not specially
associated with the labours of Professor VVeismann.

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APPENDIX I :

ON GliKM-l'LASM.

As alnaily slated in the text (p. 71), Wcisinann's j^iiicral
reasoning in suppoil of liis own theory of germ-plasm, as
against Darwin's theory of genmiules in any lonn, aihnits
of being reduced to arguments in iavour of three proi)osi-
tions — viz., first, tiiat there is no evidence of liie transmission
of somatogenetic cliaractcrs ; secondly, dial the theory of i)an-
gcnesis, which seeks to explain tlu'ir sujtposed transmission,
is "inconceivable"; and, thirdly, that its logical antithesis —
the theory of germ-plasm — is so nuu h less beset with
difliculiies, that by comparison it is simple, self-coherent,
and otVers a real, as liistinguished Irom a " formal," ex-
planation of the facts of hereility.

I'he first of these propositions will be discussed at con-
siderable length in my next volume. The second and ihirtl
propositions, however, may be ilealt with here.

The following paragiaph, whii h I sh.dl (juote sentence
by sentence, sets forth the grounds on which W'eismaiin bases
the sccon(' proposition, namely, that any theory belonging
to the order of pangenesis — i.e., which sujiposes the carriers
of heredity ever to travel centripelally — i.'-., from its very
nature, inconceivable.

At first sight this hypothesis seems to be quite reasonable.
It is not only coneeivable thai jjarticles mighl proceed bom the
iouiatic to the reproductive cells, but the very nutrition v{ the

174 ^^^^ Examination of Wcisnianmsm,

latter at the expense of the former is a demonstration t^ it such
a passajje actually takes place. IJut a closer examination reveals
immense difficuKfCS. In the first place, the molecules of the
body devoured are never simi)ly added to those of the fcedinj,'
ind' idual without. underj^oin^ any chanj,";, but, as far as we
k.iow, they are really assimilated, that is, converted into the
molecules of the latter. We cannot therefore gain much by
assuming' that a number of molecules can pass from the },Towing
somatic cells into the growing reproductive cells, and can be
deposited unchanged in the latter, so that, at their next division,
the molecules are separated to become the somatic cells of the
following generation '.

The obvious answer to this is. that no one has ever
supposed "gemmulcs" to be merely "■molecules" in the
chemical sense of this word ; nor has any one ever imagined
that they are ^'devoured" by the germ-cells into which they
pass. Of course, if this were the case — i.e., if genimules serve
merely as/ood to the germ-cells — they wouhl become disin-
tegrated down even to their chemically molecular structure,
and there would be an end of them as organized " carriers
of heredity."

In the second place, it is askul : —

I low can such a process \\.e. the passage of geinmules into
growing germ-cells | be conceivable, when the colony becomes
more complex, when the number of somatic cells becomes so
large that they surround the reproductive cells with many
layers, and when at the same time, by an increasing division
of labour, a great number of different tissues and cells are
produced, all ot which must originate de novo from a single
reproductive cell ?

Hero, again, the obvious answer is, lliat no one has ever
propounded such a staienieiil. Far froin supposing that
" all the iliflferent cells and tissues of a complex organism

' /Assays, pp. 76-77, from which the following tiuotations are likewise
taken seriaiim.

Appendix I.

175

must orii^inate de novo from a siv.gle reproiluctive cell," the
theory of pangenesis sui),)Oses the very contrary — viz., thai
somatic clumges in the past history of the phyla have not
thus originated in any reproductive cell. The idea of
somatic changes originating in reproductive cells belongs
to the theory of gcrjn-plas?n ; but even this theory does
not suppose all the great number of different cells and
tissues which compose a complex organism to have ever
originatetl de novo from a single reproductive cell.

The difficulty touching germ-cells becoming isolated, or
buried, by the phylogcuetic increase of somatic cells, is
enforced in the immediately succeeding sentences, thus: —

Each of these various elements [somatic cells] must, ex
hypothesis give up certain molecules to the reproductive cells;
hence those which are in immediate contact with the latter
would obviously possess an ailvantage over those which are
more remote. If, then, any somatic cell must send the same
number of molecules to each reproductive cell ', we are compelled
to suspend all known pliysical and physiological conceptions,
and must make the entirely gratuit"us assumption of an affinity
on the part of the molecules for tlie reproductive cells. Even if
we admit the existence of this aflinity, its origin and means of
control remain perfectly unintelligil)le if we suppose that it has
arisen trom differentiation of the complete colony. An unknown
controlling force must be added to this mysterious anungement,
in order to marshal the molecules which enter the rejjp auctive
cell in such a manner that their arningement corresponds with
the order in which they must emerge as cells at a later period.

Now I do not see much force in the s'jggestion that
those somatic cells which happen to be in immeiliate con-
tact with germ-cells, " must obviously possess an advantage

' " Or, more precisely, they must give up as many molecules as would
correspond to the lunnlK-r of the kind of cell in (|uesiion found in the
mature ortjanism." Of course Ijy "molecules" Wcismaim means what
Darwin does by "gcmmules."

1 76 An Examination of Weismannism.

ovcT those which are more remote." On the contniry, I
do not see that mere proximity of one species of cell to
another species witliin ihe same organism need have any-
thing to do with the matter— still less that " we must
suspend all physical and physiological conceptions," if we
demur to the statement that it " obviously must." As for
''physical conceptions," how many thousands of cases might
not be pointed to among chemical and mechanical pro-
cesses where contact or proximity are conilitions of com-
paratively little importance? And as for "physiological
conceptions, ' do we find that any part of the organism is
affected by its distance, say, from the liver and kidneys,
for getting rid of its effete protlucts? Is it not rather the
case that every gland in the body is wholly unaffected by
its distance from any part of the body, in regard to its
function of draining off the particular substances with which
it is concerned? Why then should the reproductive gland
constitute a conspicuous exception? Or how do we sus-
l)cnd all physiological conceptions, if we suppose that this
gland resembles every other gland in being specialized to
secrete a particular kind of '• molecule," which, because thus
sjjecially sdecicd, may l)e said to have for that gland a
special "affniity"? If there are such things as gemmules,
1 do not see any violation t)f physic>logical analogies — still
less an " entirely gratuitous assumption " — in supposing
that they can be filtjretl out from all parts of the body by
the sexual glands, and there aggregateil as a special product
to be discharged in the form of sexual elements'.

' If tlicre arc such lliiiif^s as yciimiules, it appears to me to follow
that the only physiological (li»tinctioii between the leproiluctive inlands
and ylanils in general is, that the former discharge their products in the
form of living cells. Even here, however, there appears to be one
analogous case in those salivary glands which di^charge the so-called
salivary corpuscles — i.e., nucleated cells, undergoing amoeboid changes
of form, and exhibiting the movements of living protoplasm in their
interior.

Appendix /.

177

But, it is further represented, "even if wc admit the
existence of this aflinity, an unknown controlling force
must be added to this mysterious arnmgemcnt, in order
to marshal the molecules wliieh enter the [growing] repro-
ductive cell in such a manner that their arrangement
corresponds with the order in which they emerge as cells
at a later period." Surely, however, for Weismann of all
naturalists it ought not to be diiricult to find tiiis " unknown
controlling force." For of all naturalists he is perhaps the
most ready to invoke the agency of natural selection as
sufficient to explain every case — actual or imaginable — of
adaptation. Now, here is a case where natural selection,
one would think, is positively bound to act — supposing
that there be such things as gemmules. For. if " the
carriers of heredity" are gemmules, it is evident that their
n^utual " affinities " must be adaptivcly " marshalletl " at
each step of phylogenetic evolution, before any further
advance of such evolution can be possible. And 1 do
not see anything more "inconceivable" in sup| osing the
establishment of such mutual affinities step l)y stej) tiirougli
natural selection, than in supposing any other course of
adaptive develoi)ment by similar means. For, as Darwin
has well shown, while anticipating this particular objection
to his theory, — " The assumed elective affinity of each
gemmule for that particular cell which precedes it in due
order of development is supported by many analogies."
The analogies which he then gives are so numerous that
I must here refer to his own discussion of the sul)ject' —
a discussion which is entirely ignored by Weismann.

Lastly, the principal ground, as far as 1 can see,
which Weismann has for regarding Darwin's theory in
any shape '' inconceivable," is his own supi)Osiiion that
there is as complete an ainitomical separation between the

ik|

Variation, ike, ind ed., vol. ii. pp. 374-6.
N

iyS An Jixivnination of Wcisiuannism.

som.i and its ^erni-cells as there is, for example, between
the inumnKilian soma and these same cells when afterwards
detaclicd from the ovary and developing as foetuses in
utero. In other words, the only connexion is supposed
to i)e that of ieriving nourishment by way of imbibition.
Hut, as regards the germ-cell while still forming in the
ovary or testicle, there is for this supi)Osition no basis in
fact. There is nothing in the histology of spermatogenesis
that lends countenance to the su{)position, while in the case
of the ovum such histological evidence as wc posse^^s makes
altogether against it. As Professor Vines has remarked : —

It cannot be seriously maintained that the whole body of the
embryo is developed solely from the germ-plasm of the ovum.
On the contniry, since the embryo is developed from the whole
of the nucleus and more or less of the cytoplasm of the ovum,
it must be jdniittcd that the non-gcrm-plasm of the ovum
provides a large part of the material in embryogcny. It is an
obvious inference that, under these circumstances, hereditary
characters may be transmitted from the parent to the offspring,
not only by the germ-plasm, but also by the somato-plasm, of the
ovum '.

Again, and apart from this consideration, it is now
known that a very intimate network of protoplasmic fibres
connects the cell-contents of cellular tissues, both in plants
and animals. So that here we have another very possible
means of communication between the gcrm-cclls and the
somatic-cells which together constitute a multicellular
organism.

Therefore, in so far as histology can be trusted to
constitute a basis for generalizations of this kind at all, it
does not sustain the supposition that there can be no
medium of communication between the general cellular

' Nature, vol. xl. p. 624. Wc|.smann's answer to this and other parts
of Professor Vines' criticism where the term "somatoplasm" occurs, will
be considered later on.

Appendix I.

179

lissues of ail ori^.inism and ils spct iully rc|iiodib live
clcuK-iits. On the contrary, the microscope is able to
demonstrate possible roails of connexion — and this even
upon Weismann's own view as to a specialized germinal
substance which is restricted to the nucleus of an ovum.
In short, the supposition as to an absolute anatomical
separation between germ-plasm and somato-j 'asm is a de-
duction from Weismann's theory itself: it is not supported
— it is discredited — by histological observation. Hence,
it cannot be accepted as valid evidence in favour of the
theory from which alone it is derived, or as a valid
objection to the rival theory of pangenesis.

Once more, even if it were true that histology proves
an absolute anatomical isolation on the part of germ-cells,
it would still have remained unquestionable that there is no
absolute physiological isolation. For, at least, the germ-
plasm derives ils nourishment from the soma in which ii
resides ; and who shall say that the process of mere imbibi-
tion is not amply sufficient to admit of the passage of
"gemmules"? Call them what we choose, the "carriers
of heredity " must be so unimaginably small, that in relation
to histological cells they must be as gnats to camels. Yet
we know that even camels in the form of "migrating cells"
of various kinds are able to pass through living membranes ;
and we also know that the microbes of syphilis can
penetrate both ova and spermatozoa. Why then should it
be deemed inconceivable that, where all such things can
pass, gemmules can do so likewise?

Lastly, I have recently spoken of the detached condition
of a ripe ovum in utero. Now it seems to me more " in-
conceivable " that such an ovum should be capable of
announcing, as it were, to the walls of the uterus v/helher or
not it is in a fertilized condition, than it is thf"/, before quit-
ling the ovary, it should have had some kind of physiological
converse with its environing soma. Yet it is certain that,

N 2

f^'l

I

i8o An Examination of IVcismannism.

Nvilhoiit any visible mcilium of communication, the impreg-
nated ovum is able to inform the uterus that it is impreg-
nated; and thereupon the uterus behaves towards that
ovum in an altogether astonishing manner, such as it never
• lisplays towards an unimpregnated ovum. Of course various
hypotheses may now be formed to account for this fact,
seeing that no one can question it as a fact. But sup-
posing that the fact could be questioned, with how much
greater effect might it be argued that any communication
between the ovum and its soma is even more antecedently
incredible when the ovum is entirely free than when it is
still contained within its ovary.

Now these, as far as 1 can find, are the only grounds
for VVeismann's repeated assertion that the theory of pan-
genesis in any form is " inconceivable." I have therefore
endeavoured to show that this is too strong a statement.
.\11 the facts and considerations whereby he seeks to support
it were present to the mind of Darwin ; and, quite apart from
any quesli(jn of relative authority, I cannot avoid agreeing
with Darwin that, whether or not the theory is true, at all
events the " difljcullies" attaching to it on these merely
a priori grounds are not insuperable, or such as to render
his "pet child" an unconceived monstrosity in logic, or
a proved absurdity in science.

Be it understood, howevei, that I am not here defending
the theory of pangenesis. I am investigating the theory
of germ-plasm ; and it is because VVeismann seeks to
sustain the latter by excluding the former as preposterous,
that I have been obliged thus to consider the validity of
his criticism. For the point to which I am leading is,
that Weismann gains nothing in the way of support to
his own theory by this disparagement of Darwin's, unless
he can show thai the former supplies some more " conceivable "
explanation touching the mechanism of heredity. Now 1 am
unable to see that he has shown this. What I do see

Appendix /.

i8i

is that his a priori argument from "inconceivability"
cuts both ways, and that it niakt-s at least as much against
germ-plasm as it does against gcmmulcs. Therefore,
having now considered what Wcismann has said against
the conceivability of gemmules on grounds of general
reasoning, I shall proceed to show that (juite as much —
or even more — may l)c said in the way of a lu qiioque.
In other words, we have now fniished with the second of
the three propositions which we are examining (see p. 71),
and proceed to our consideration of the third.

First of all, I do not see any greater difluulty in
supposing that the " carriers of heredity" proceed cenlri-
petally from somatic-cells to germ-cells, than in supposing that
they proceed centrifiii;ally . am the germ-cells to the somatic-
cells which they are engaged in constructing. Nor do I
see any more diflicull)i in imagining these " carriers of
heredity" to be capable of constructing a new organism
if they have first proceeded centripetally, and are thus
severally representative of all parts of the parent organism
after its construction Juis Imn cciuplttcd, than I do if they
have proceeded centrilugiiiy, and are thus similarly repre-
sentative of all parts of that organism he/ore its construction
has been commenced^.

' Wcismann speaks disparaginpjly of Darwin's throry as a "theory
of fyeformation " (p. 31(1). " \Vc must assume," )ie adds hy way of
explanation, "that eacli single ])art of the body at each developmental
stage is, from tlie first, represented in the j;erni-cell as distinct particles
of matter, whicli will reproduce each part of the body at its appropriate
stage as their turn for development arrives," lliil must we not likewise
"assume" exactly the same tliinj,' in the case of Weismann's own
theory? To me, at any rate, it apj'cars tliat the desciiption is quite as
api)ropriate to germ-jda^m as it i* to gemmules. Nor can I see any
distinction, even where he seeks to draw it more expressly, as for
instance — "Every detail in the wliole ori;anism must be represented in
the germ-idasrn by its own special and peculiar arrani,'ement of the
groups of molecules, . . . not imlei. d as tlie preformed germsof structure (the
gemmules of panj^enesis), i)ut as variations in its molecular constitution."
\_Essays, p. 194.] Again, on page 325 he gives a foot-note explaining

■ .|

1 82 An Examination of IVeisnuinnism,

Similarly, it seems to me, whatever cop;cncy there may be
in Weismann's objcdion to Darwin's theory on the score
that it must assume " an unknown controlling force in order
to marshal the molecules," is ecjually great as regards his
own. True, Weismann has a lot to say about the control
which nuclco-plasm can exercise on cell-formal ion, and
germ-plasm on marshalling successive stages of ontogeny ;
hut all that this amounts to is a rc-statcment of the facts.
Such a controlling force must he i-qually assumed by both
theories; but in each alike there is an ab ence of any ghost
of an explanation.

Again, whatever difficulty there may be in conceiving
the transition of somatic substance, mulalis ?nii/<int//s there
must be an equal difficulty in conceiving the transition of
germinal substance into somatic substance. Indeed, as far
as I can sec, the difficulty is even greater in the latter case
than it is in the former. For the very essence of Weismann's
view is that germ-jjlasm diders from all or any other
"plasm" in origin or kind: germ-plasm, and germ-plasm
alone, has been immortal, perpetually continuous, capable
of indefinite self-mulliplication, and so of difTerentiating
itself into an endless number and variety of somatic tissues.
But, according to Darwin's view, there is not, and never
has been, any such fundamental difTerence between the
essential nature of somatic elements, and the essential
nature of sexual elements. On the contrary, it is supposed
that both formative and formed material are one in kind

the distinction by alluding; to the controversy between the preformation-
ists ami cpij^eiiesists, I!ut the theory of pant^Liiosis does not supi)oscthe
future oiganism to exist in tlie egg-cdl as a viiuiaturc: it supposes
merely that every part of the future organism is represented in the egg-
ccll by corresponding material particles. And this, as far as I can
understand, is exactly what the theory of germ-jdasm supposes ; only
it calls the particles "molecules," and seemingly attaches more im-
portance to themattcr of variations in their arrangement or "constitution,"
whatever these vague expressions may be intended to signify.

Appendix /,

183

lind

— that all the ccllul.ir li-Mics of a multicoUnlar organism,
like the sin<j;Ie cell of a unicclliilir or<j;;uiism, are per st
endowed wiih the vital proi)erty of self-muliij^lication ; and
that whether this proptMty finds its expivssion in normal
growth, in abnormd increments of j^rowth (such as tumours),
in processes of repair, in the various forms of a-sexual
reproduct on, or in the more specialized form of sexual
fertilization, there is everywhere an exhibition of one and
the same capacity. Now, without f^oing further tiian this
contrast between the fundamental principles of the two
theories, does it not become evident that the difficulty of
conceivinj; a transition of A into A' is at any rale no
greater than that of conceiving a transition of A into B,
where A is in both cases the formau.c substance, A' this
same substance in another sta- of evolution (i.e., elaboratid
for the performance of some special function, but never
so as to lose its original function A), while li is a substance
which differs from A almost as much as a woven texture
differs from the hands that weave it?

Once more, in all his arguments which are directed to
prove the continuity of germ-plasm, VVeismann nowhere
seems to perceive the necessity of arguing the correlative
hypothesis — viz., that of the discontinuity of som.Uo-plasm.
Yet, as Professor Vines has remarked, it is as incuml)ent
on him to disprove any possible continuity on the part of
somato-plasm, as it is to prove a perpetual continuity on
the part of germ-plasm. And here I am disposed to go
further than Professor Vines has gone; for it apjtears to me
even more incumbent on Weismann to argue a discontinuity
on the part of somato-plasm, than it is on him to argue
a continuity on the part of germ-plasm.

This must be immediately apparent if we remember that,
unless the discontinuity of somato-plasm be assumed, the
theory of the continuity of germ-plasm in telluric time (as
distinguished from eternity) becomes identical in form with

Ml

III

I?

184 An Examination of U^isiuamiisni.

all those theories of heredity to the Ainiily of which pan-
genesis belongs. All these theories go upon the assumption
that living material has been continuous in telluric time —
i.e., always derived from pre-existing material of the same
kind ; but they embody the further assumption that all living
material is material of the same kind — i.e., everywhere
presents the same fundamental properties. Weismann's
theory on the other hand, while adopting the first assump-
tion, rejects ihe second ; and assumes in its stead that living
material exists in " two kinds," only one of which has been
continuous, while the other is discontinuous — being, in fact,
formed anew at each ontogeny. Therefore, to my mind, it
seems more needful to aigue the point wherein his theory
dilTers from these other theories of heredity, than it is to
argue the point wherein it agrees with them. We look to
him for a proof of the discontinuity of somato-plasin much
more than we do for a proof of the continuity of germ-plasm.
Now the only proof that he has to give of the discontinuity
of somato-plasm— or, in other words, that the self-multiplica-
tion of somatic cells cannot take i)lace unless the nucleus of
each contains a self-multiplying idio-plasm derived from the
nucleus of a germ-cell — is the non-transmissibility of somato-
gcnetic characters. Here, however, there is an obvious
equivoque. For his only test of characters as somatogenetic
and blastogenetic consists in observing whether or not they
are inherited : if they are inherited, he says they are blasto-
genetic : if they are not inherited, he says they are somato-
genetic. But this is manifestly circular reasoning, so long
as the question in debate is as to the truth of his theory.
What we require in proof of the distinguishing feature of that
theory -i.e., the discontinuity of the hypothetical somato-
plasm— is not merely the obvious fact that some characters
are inherited while others are not, but independent proof
that inherited and non-inherited characters correspond to
a continuity of germ-plasm on the one hand, and a dis-

Appefidjx I,

185

conlimiity of somato-plasm on llie otlier. He shows us,
indeed, what was well known before, that characters developed
during the lifetime of the individual are seldom (if ever)
inherited, while characters developed during the lifetime of
the species are always inherited. Obviously, however, this
fact is no proof of the assumed correlation just mentioned,
because, as Darwin has clearly pointed out, it may very well
be due to the much shorter time which has been allowed for
what may be termed the impress of heredity. Therefore,
supposing (with Darwin and others) that living material is all
of one kind, and continuous, the fact on which Weismann
relies admits of being explained without resorting to his more
complex supposition of living material in two kinds, the one
perpetually continuous, and the other interrupted at each
ontogeny.

For these reasons it appears to me that, so far as the
argument from "inconceivability" is concerned, it makes at
least as much against the theory of qerm-plasm as it does
against the theory of pangenesis ; and, therefore, that no
argumentative advantage is gained from its use by Weismann.
The truth probably is that, whaiivcr the mechanism of
heredity may actually be, it is at once so minute and
so complex that its action is '• inconceivable," or, more
correctly, unimaginable. Be it again understood, therefore,
that I am not arguing in favour of i)angenesis. I am merely
criticising what apjiears to me an unsound argument in
favour of germ-plasm. All this general or merely a priori
reasoning with regard to inconceivability is, as I have
attempted to show, as available on the one side as on the other,
and so fails to yield any observable advantage to either.

In conclusion it must be noticed, that Weismann now
appears to have himself perceived the grave ditliculties whit h
lie against his aniithesis between a hypothetical "germ-
plasm " and a hypothetical "somato-plasm," notwithstanding

1 86 An Examination of Weismannism.

that the former becomes converted into the latter at each
ontogeny. At any rate, he allows that Vines' criticism upon
this head is sound. But he is strongly of the opinion that,
by means of a later emendation of his theory as originally
published, he has succeeded in obviating these difficulties
in toio. For my own part, as already several times observed
in the text, I cannot in the least perceive that such is the
case ; and theicfore I will quote in exiemo what he has said
in answer to Professor Vines. It will be seen that his newer
emendation of the theory consists in substituting for his
original " somato-plasm " two substances, which are called
respectively " somatic idio-plasm '' and " cytoplasm.** And
it is by means of this substitution that he thinks he has, in
some way or another, overcome the contradiction involved in
the doctrine (and, as it still seems to me, the essential
doctrine of his whole theory of heredity) that " germ-plasm **
becomes converted into " somato-plasm " during the course
of every ontogeny. The following, at any rate, is his latest
utterance upon the subject : —

I believe that the objections which Professor Vines makes to
my theory of the continuity of germ-plasma rest solely on an
unintentional confusion of my ideas, as he compares the opinions
expressed in the second essay with those of the later ones,
with which they do not tally. I will endeavour to make this
clear. In this second essay (1883) I contrasted the body (soma)
with the germ-cells, and explained heredity by the hypothesis
of a " Vererbungs-substanz " in the germ-cells (in fact the germ-
plasma), which is transmitted without breach of continuity from
one generation to the next. I was not then aware that this lay
only in the nucleus of the ovum, and could therefore contrast
the entire substance of the ovum with the substance of the
body-cells, and term the latter "somato-plasm." In Essay IV
(1885) 1 had arrived, like Strasburger and O. Hertwig, at the
conviction that the nuclear substance, the chromatin of the
nuclear loops, was the carrier of heredity, and that the body of
the cell was nutritive but not formative. Like the investigators

Appendix I.

187

just named, I transferred the conception of idio-plasm, which
Nageli had enunciated in essentially dififcrcnt terms, to the
" Vererbungs-substanz " of the ovum-nucleus, and laid down
that the nuclear chromatin was the idio-plasm not only of the
ovum but of every cell, that it was the dominant cell-element
which impressed its specific character upon the originally
indifferent cell-mass. From then onwards, I no longer desig-
nated the cells of the body simply as " somato-plasm," but
distinguished, on the one hand, the idio-plasm or " Anlagcn-
plasma" of the nucleus from the cell-body or " Cytoplasma,'*
and, on the other, the idio-plasm of the ovum-nucleus from that
of the somatic cell-nucleus ; I also for the future applied " germ-
plasm " to the nuclear idio-plasm of ovum and spermatozoon,
and "somatic idio-plasm" to that of the body cells (e.g, p. it'4).
The embryogenesis rests, according to my idea, on alterations
in the nuclear idio-plasm of the ovum, or "germ-plasm"; on
p. 1S6, et seq., is pictured the way in which the nuclear idio-
plasm is halved in the first ccll-divicion, undergoing regular
alterations of its substance in such a way that neither half
contains all the hereditary tendencies, but the one daughter-
nucleus has those of the ectoblast, the other those of the cnto-
blast ; the whole remaining embryogenesis rests on a con-
tinuation of this process of regular alterations of the idio-plasm.
Each fresh cell-division sorts out tendencies which were mixed
in the nucleus of the mother-cell, until the complete mass of
embryonic cells is formed, each with a nuclear idio-plasm which
stamps its specific histological character on the cell.

I really do not understand how Professor Vines can find such
remarkable difficulties in this idea. The appearance of the
sexual cells generally occurs late in the embryogcny ; in order,
then, to preserve the continuity of germ-i)l,ism from one
generation to the next, I propound the hypothesis that in
segmentation it is not all the germ-plasm (i.e. idio-plasm of the
first ontogenetic grade) which is transformed into the second
grade, but that a minute portion remains unaltered in one of
the daughter-cells, mingled with its nuclear idio-plasm, but in
an inactive state ; and that it traverses in this manner a longer
or shorter series of cells, till, reaching those cells on which it
stamps the character of germinal cells, it at last assumes the

1 88 An Examination of Weismanmsm.

active state. This hypothesis is not purely gratuitous, but is
supported by observations, notably by the remarkable wander-
ings of the germinal cells of Hydroids from their original
positions.

But let us neglect the proba'^ility of my hypothesis, and
consider nurcly its logical accuracy. I'rofcssor Vines says: —
" The fate of the germ-plasm of the fertilized ovum is, according
to Professor Weismann, to be converted in part into the somato-
plasm (!) of the embryo, and in part to be stored up in the
germ-cells of the cmbrj'o. This being so, how are we to conceive
that the germ-plasm of the ovum can impress upon the somato-
plasm (!) of the developing embryo the hereditary character of
which it (the germ-plasm) is the bearer.'' This function cannot
be discharged by that portion of th germ-plasm of the ovum
which has become converted into the somato-plasm (1) of the
embryo, for the simple reason that it has ceased to be germ-plasm^
and must therefore have lost the properties characteristic of that
substance. Neither can it be discharged by that portion of the
germ-plasm of the ovum which is aggregated in the germ-cells
of the embryo, for under these circumstances it is withdrawn
from all dirert relation with the developing somatic-cells. The
question remains without an answer." I believe myself to have
answered this above. I do not recognize the somato-plasm of
Professor Vines ; my germ-plasm, or idio-plasm of the first
ontogenetic grade, is not modified into the somato-plasm of
Professor Vines, but into idio-plasm of the second, third, fourth,
hundredth, &c. grade, and every one impresses its character on
the cell containing it.

:1 ;i

It may be dullness, but I confess that this does not
appear to me an " answer " to Professor Vines' criticism.
Even though " idio-plasm of the first ontogenetic grade "
has to become " idio-plasm of the second, third, fourth,
hundredth, &c. grade," before in each of the grades con-
cerned it can give origin to the somatic-cells which are
distinctive of that grade, I cannot see that it makes any
difference (in relation to Vines' criticism) whether we speak
of those cells as containing "somato-plasm," or as con-

Appendix I,

1S9

taininp; "somatic idio-plasm " of such and such a grade,
//wj '• cytoplasm." For whether we thus follow Weismann's
earlier terminology or his later, we are so far speaking
about exactly the same thing, namely, the transformation of
" germ-plasm " into all the constituent cells of the " soma."
The difficulty is, in Vines' words above cited, " to con-
ceive that the germ-plasm of the ovum can impress upon
the somato-plasm of the developing embryo the hereditary
characters of which it (the germ-plasm) is the bearer " ;
and Weismann says that this difliculty, which he acknow-
ledges, can now be answered by substituting for his
original statement that "germ-plasm" becomes changed
into " somato-plasm," the statement that it is " idio-plusm "
derived from " germ-plasm " which thus " impresses its
character on the cell containing it." But, '' as a matter
of logical accuracy," there is surely here a distinction
without a difTerence. For what is the difTerence between
saying that germ-plasm "impresses" its character on the
contents of all somatic cells considered collectively under
the term "somato-plasm," and saying that every "onto-
genetic grade " of germ-plasm " impresses " its character
on each successive group ot somadc cells considered sever-
ally under the term " idio-plasm " oi such and such a
grade? At best this newer terminology has reference
merely to a superadded hypothesis touching the mode —
or rather the history — of the nsition in question : it
does not affect the original and essential doctrine of the
transition itself.

APPENDIX II:

ON TELEGONY.

A WIDELY different view, however, is taken by Mr. Herbert
Spencer with regard to the theoretical interpretation of tele-
gony. This, indeed, is precisely the opposite view to the
one which is given in the text. For while I agree with
Professor Weismann in holding that the facts of telcgony
(supposing them to be facts) are as compatible with the
theory of germ-plasm as with that of gemmulcs, " physio-
logical units," or any other theory which postulates a centri-
petal flow of the carriers of heredity from somatic-cells to
germ-cells, Mr. Spencer is of the opinion that these facts are
destructive of any theory which postulates a continuity in the
substance of heredity — i. e., a centrifugal flow of the carriers
of heredity. And, imquestionably, Mr. Spencer's view is the
prevalent one. Therefore, seeing that his opinion is not
only of weight />fr se, but is shared by the scientific world in
general, I will here transcribe a somewhat lengthy discussion
which I have recently held with him upon the subject.

In the Contemporary Review for March, Mr. Spencer wrote
as follows: —

We pass now to evidence not much known in the world at
large, but widely known in the biological world, though known
in so incomplete a manner as to be undervalued in it. Indeed,
when I name it probably many will vent a mcital pooh-pooh.
The fact to which I refer is one of which record is preserved

It

192 An Exaviination of IVeisniannism.

in the museum of the College of Surgeons, in the shape oi
paintings of a foal borne by a mare not quite thoroughbred,
to a sire wliich was thoroughbred— a foal which bears the
markings of the quagga. The history of this remarkable foal
is given by the Karl of Morton, F.K.S., in a letter to the Presi-
dent of the Royal Society (read November 23, 1820). In it he
states that wishing to domesticate the quagga, and having
obtained a male, but not a female, he made an experiment.

I tried to breed from the male quag[,'a and a youn^j chotnut mare of
seven-eighths Aratiian Moud, and whicl) had never been bred from ; the
result was the production of a female hybrid, now Ove years old, and
bearing, both in her form and in her colour, very decided indications of
her mixed origin. I subseciuently parted with tlie seven-eighths Arabian
mare to Sir Gore Ouseley. who has bred from her by a very fine black
Arabian horse. I yesterday morning examined the produce, namely,
a two-year-old filly and a year-old colt. They have the character of the
Arabian breed as decidedly as can be expected, where fifteen-sixttenths
of the blood are Arabian; and they arc fine specimens of that breed;
but both in their colour and in the hair of their manes they have
a striking resemblance to the quagga. Their colour is bay, marked
more or less like the quagga in a darker tint. I5olh are distinguished
by the dark line along the ridge of tiie back, the dark stripes across the
fore-hand, and the dark bars across the back part of the legs '.

Lord Morton then names sundry further correspondences.
Dr. Wollaston, at that time President of the Royal Society,
who had seen the animals, testified to the correctness of his
description, and, as shown by his remarks, entertained no
doubt about the alleged fact."^ But good reason for doubt
may be assigned. There naturally arises the question — How
does it hajjpen that parallel results are not observed in other
cases? If in any progeny certain traits not belonging to the
sire, but belonging to a sire of preceding progeny, are re-
produced, how is it that such anomalously-inherited traits are
not observed in domestic animals, and indeed in mankind ?
How is it that the children of a widow by a second husband do
not bear traceable resemblances of the first husband ? To these
questions nothing like satisfactory replies seem forthcoming ;

* • rnildsophical Transactions of the Royal Society for the Year 1831,'
Part I. pp, 20-24.

Appendix II.

193

and, in the absence of replies, scepticism, if not disbclitf,
may be held reasonable.

There is an explanation, however. Forty years ago I made
acquaintance with a fact which impressed me by its sij^nificant
implications; and has, for this reason 1 suppose, remained in my
memory. It is set forth in \\\Kt Joiinuil of the Royal Ay^ricttl-
iural Society, vol. xiv. (1X53), pp. 214 et seq., and concerns
certain results of crossin<j English and French breeds of sheep.
The writer of the translated paper, M. Malingie-Nouel, Director
of the Agricultural School of Fa Cliarmoise, slates that when
the French breeds of sheep (in which were inckided "the
;//<7;/^;'^/ Merinos") were crossed with an lOnglish breed, "the
lambs present the following results. Most of them resemble the
mother more than the father ; some show no trace of the father."'
Joining the admission respecting the mongrels with the facts
subsequently stated, it is tolerably clear that the cases in which
the lambs bore no traces of the father were cases in which the
mother was of pure breed. Speaking of the results of these
crossings in the second generation " having seventy-five per cent,
of English blood," M. Nouel says: — "The lambs thrive, wear
a beautiful appearance, and complete the joy of the breeder. . . .
No sooner are the lambs weaned than their strength, their
vigour, and their beauty begin to decay. ... At last the con-
stitution gives way . . . he remains stunted for life": the
constitution being thus proved unstable or unadaptcd to the
requirements. How, then, did M. Nouel succeed in obtaining
a desirable combination of a fme English breed with the rela-
tively poor French breeds ?

He took ail animal from " flocks originally sprung from a nii\iurc of
the two distinct races tliat are established in these two provinces
[Herry and La Sologne]," and these he "united with animals of another
mixed breed . . . whicii blended tiie Touiangelle and native Merino
blood of" La IJeauce and Touraine, and obtained a mixture of all four
races" without decided character, without fixity, . . . but possessing the
advantage of being used to our climate and management."

Putting one of these "mixed-blood ewes to a pure New- Kent ram
. . . one obtains a lamb containing fifty-hundred ths of the purest and
most ancient English blood, with twelve and a-half hundredths of four
:lifferent French races, which are individually lost in the preponderance
af English blood, and disappear almost entirely, leaving the improving

k^"

r94 ^n Examinatioti of Wcisffiamii'sm.

tyjie in the ascendant. . . . All tlic lainhs produced strikingly resembled
vach other, and even Englishmen took tliem for animals of their own
country."

M. Noucl jjoes on to remark that when this derived breed was
bred with itself, the marks of the Krei>ch breeds were lost.
" Some sli^'ht traces could be detected by experts, but these
soon disappeared."

Thus we get proof that relatively pure constitutions pre-
dominate in proj^eny over much mixed constitutions. The
leason is not difficult to see. Every organism tends to become
adapted to its conditions of life ; and all the structures of
a species, accustomed through multitudinous generations to the
climate, food, and various influences of its locality, are moulded
into harmonious co-operation favourable to life in that locality :
the result being that in the development of each young indi-
vidual, the tendencies conspire to produce the fit organization.
It is otherwise when the species is removed to a habitat of
different character, or when it is of mixed breed. In the one
case its organs, partially out of harmony with the requirements
of its new life, become partially out of harmony with one another ;
since, while one influence, say of climate, is but little changed,
another influence, say of food, is much changed ; and, con-
secjuently, the perturbed relations of the organs interfere with
their original stable equilibrium. Still more in the other case is
there a disturbance of equilibrium. In a mongrel the constitu-
tion derived from each source repeats itself as far as possible.
Hence a conflict of tendencies to evolve two structures more or
less unlike. The tendencies do not harmoniously conspire ;
but produce partially incongruous sets of organs. And evidently
where the breed is one in which there are united the traits of
various lines of ancestry, there results an organization so full of
small incongruities of structure and action, that it has a much-
diminished power of maintaining its balance ; and while it
cannot withstand so well adverse influences, it cannot so well
hold its own in the offspring. Concerning parents of pure and
mixed breeds respectively, severally tending to reproduce their
own structures in progeny, we may therefore say, figuratively,
that the house divided against itself cannot withstand the house
of which the members are in concord.

1

!

Appendix II.

195

Now if this is shown to be the case with breeds the purest of
which have been adapted to their habitats and nioilcs of life
durinjj some few hundred years only, what shall we say when the
question is of a breed which has had a constant mode of life in
the same locality for ten thousand years or more, like the (pia^Ha ?
In this the stability of constitution must be such as no domestic
animal can approach. Relatively stable as may have been the
constitutions of Lord Morton's horses, as compared with the
constitutions of ordinary horses, yet, since Arab horses, even in
their native country, have probably in the course of successive
conquests and migrations of tribes become more or less mixed,
and since they have been subject to the conditions of domestic
life, differing much from the conditions of their original wild life,
and since the English breed has undergone the perturbing
effects of change from the climate and food of the East to the
climate and food of the West, the organizations of the horse and
mare in question could have had nothing like that perfect balance
produced in the quagga by a hundred centuries of harmonious
co-operation. Hence the result. And hence at the same time
the interpretation of the fact that analogous phenomena are not
perceived among domestic animals, or among ourselves ; since
both have relatively mixed, and generally extremely mixed, con-
stitutions, which, as we see in ourselves, have been made
generation after generation, not by the formation of a mean
between two parents, but by the jumbling of traits of the one
with traits of the other, until there exist no such conspiring
tendencies among the parts as cause repetition of combined
details of structure in posterity.

Expectation that scepticism might be felt respecting this
alleged anomaly presented by the quagga-marked foal, had led
me to think over the matter ; and I had reached this inter-
pretation before sending to the College of Surgeons Museum
(being unable to go myself) to obtain the particulars and refer to
the records. When there was brought to me a copy of the
account as set forth in the " Philosophical Transactions," it was
joined with the information that there existed an appended
account of pigs, in which a parallel fact had been observed.
To my immediate inquiry — " Was the male a wild pig.-"' — there
came the reply : " I did not observe." Of course I forthwith

O 2

196 An Iixiiniinaliou of ]l\isiiiiinnisin.

obtained the vohiinc, and there found what 1 expected. It
was contained in a |)a|)(r ( ommiinicited by Dr. W'ollaston from
Daniel (iiles, I'lsc|., concerniiiy liis " sow anil her produce," which
said tiiat

she was uiic 111 a well-known lilark and wliitc hurd ol Mr. NVeslcrn,
the Member lor l^s^ex. Alxait ten ye.nrs since I |>iil hir lo a f)o.nr of the
wild liriiMJ. and of a <leep clustniit eidoiir, wliicli 1 had jiisl receisxil
liom llaltielij House, and which was soon aricrw.ods drowned by
accident. Thi- pij;s produced (which were her lirst litter) paitook in
nppearnncc of both boar and sow. but in some the che<<tnut colour of the
boar stron^jly iirevailed.

The sow w.as afterwards put to a boar of Mr. Western's breed (the
wild boar havin;; been lonj,' dead). The produce was a litter of jti^s
some of which, we observed with much ^urpiise, to be stained an<l
clearly marked with the chestnut cole ur which had prevailed in the
I'lrnier litter.

IMr. (iiles adds that in a second litter of [)i,L;s, the fatherof which
was of Mr. Western's breed, he and his bailiff believe there was
a recurrence, in some, of the chestnut colour, but admits that
their "recollection is much less peifect than 1 wish it to be."
He also adds that, in the course of many years' experience, he
had never known the least appearance of the chestnut colour in
Mr. Western's breed.

What are tlie probabilities that these two anomalous results
should have arisen, under these exceptional conditions, as
a matter of chance? Evidently the probabilities against such
a coincidence are enormous. The testimony is in both cases
so good that, even apart from the coincidence, it would be
unreasonable to reject it ; but the coincidence makes accept-
ance of it imperative. There is mutual verification, at the
same time that there is a joint interpretation yielded of the
strange phenomenon, and of its non-occurrence under ordinary
circumstances.

And now, in the presence of these facts, what are we to say?
Simply that they are fatal to Weismann's hypothesis. They
show that there is none of the alleged independence of the
reproductive cells ; but that the two sets of cells arc in close
communion. They prove that while the reproductive cells
multiply and arrange themselves during the evolution of the

Appendix 11.

197

embryo, some of their ffcnn-plasin |)ii!>sfs into the mass of
soinatic-cclls constituting' the parental Ixuly, and becomes
a permanent component of it. Further, tliey necessitate the
inference that this introduced ^erm-plasm, everywhere ilifTused,
is some of it inchided in the reproductive cells, suhsetjuently
formed. .And if we thus jjet a dciiKinstration that tin; some-
what different units of a forei^^n Ki''''""Pl''^'i^ permeating the
organism, permeate also the sul)sei|uently-lnrnied reproductive
cells, and affect the structures of the individuals arising from
them, the implication is that the like happens with thc^e native
units which have been made somewhat dilfctiu by modilied
functions : there must be a tendency to inheritance of acquired
characters.

M reply to this appeared in llie April i.ss'ie of the Conlem-
poratj Review^ as follows : —

Injlucnce on Ptns^eny of a Previous Sire.

This is the last of the an^uments which Mr. Spencer .advances
against the posilicm of I'rofcssor Weismann. Alluding t<» the
case of Lord Morton's mare, he represents that the phenomenon
which it serves so well to illustrate viz., the influence of
a previous sire on the pro^tiiy of another by the same dam is
hopelessly at variance with the theory of germ-plasm. I cannot
quite gather the explanation which he would give of this
phenomenon, further than that in some way or another it
betokens an immediate influence of the hereditary material of
the male on the body-tissues (" somatic cells ') of the female.
And this is the view which is taken of the phenomenon by th'j
Lamarckians in gener.il. Yet, if we consider all that such an
explanation involves, we shall lind that it is a highly complex
explanation, for it involves the following chain of hypotheses: —
The first impregnation affects many, if not all, the somatic
tissues of the mother by the germinal matter of the father;
these tissues, in their turn, re-act on the maturing ova; this
action and reaction is such that when one of the ova is after-
wards fertilized by a different sire, the resulting offspring more

198 Afi Examination of Weismannism.

p.

Vr

^'^

j^i

or less resemble the preceding sire. Unfortunately, neither
Wcisuiann himself nor any of his followers, as far as I know,
has hitherto published an opinion on the subject ; bui I imagine
that his answer would be three-fold. First, he may question
the fact. Secondly, even admitting the fact, he may say it
is much more easy to ex[)!iiin it by supposing that the germ-
plasm of the first sire has in some way or another become
partly commingled with that of the immature ova, as well as
with that of the mature one which it actually fertilizes; and, if
so, it would naturally assert its influence on the progeny of
a subseciucni sire. Millions of spermatozoa must have been
playing around the ovaries after the first copulation, and only
one of them was needed to fertilize the mature ovum. It is not
necessary to suppose that some of the others succeeded in
penetrating any of the immature ova, whilo these were still
embedded in the substance of their ovaries. It may be that the
life of "ids" is not commensurate with that of their containing
spermatozoa. After the latter have perished and disintegrated,
their ids may escape in thousands of millions, bathing in
a dormant state the whole surfaces of both ovaries. And, if so,
it is conceivable that when subsequent ova mature- i.e, come
to the surface of their ovaries and rupture their follicles — these
dormant ids adhere to their porous walls, through which they
may pass. This may not seem a very probable explanation;
but, at any rate, it is a less improbable one than that on which
the Neo-Lamarckians would found an argument against the
continuity of germ-plasm. F"or,—

Thirdly, is it not literally inconceivable that this Nco-
Lamarckian explanation can be the true one .'' Can it be
seriously contemplated that there is any such mechanism as the
explanation must needs assume .'' If it is difficult to accept such
a machinery as is supposed by the theory of pangenesis, whereby
every cell in the body casts off "gemmules," which are the
carriers of heredity from their respective tissues to the germinal
elements, what arc we to say of such a machinery as the
following : — A machinery which distributes through the body of
a female gemmules from the disintegrated spermatozoa of her
mate ; which distributes them schxtivcly, so that they shall
all eventually lodge in those tissue-cells of the female which

V\ •*.

"., " ■"' --r.tijfv

Appendix II.

199

correspond, part for part, with the tissiic-cclls of the male from
which they were originr / derived; whic'.i then insures that
when a genimule has thus reached its apjiropriatc cell in the
female body, it will thereupon modify the pre-existing gemmulcs
in that cell, so that when they arc shed and go to form tl>c
germinal contents of future ova, they cnclow the latter with the
hereditary qualities of the male in c|ucstion ?

Such, it seems to me, is a fair statement of the whole case up
to date. But I think it may be apposite now to publish the
main results of an inquiry on which I have been engaged for the
last three years.

First as to the facts. The investigations have been pursued
on three different lines: (i) 1 raised discussions on the subject
in the principal breeders' and fanciers' journals of this country,
and also of America. (2) I entered into private correspondence
with contributors of the largest experience, and also with pro-
fessional and amateur breeders, fanciers, ike, who addressed me
directly on the subject. (3) .' started experiments with the
varieties which these inquiries indicated as most likely to
yield positive results. At present nothing need be said with
regard to these experiments, because they are aoL sufficiently
matured. But it is desirable to state the general upshot of
the correspondence.

The principal result is to show that the p!\cnomenon is of
much less frequent occurrence than is ger-jrally supposed.
Indeed, it is so rare that I doubt whether it takes place in more
than one or two per cent, of cases. 1 must aild, however, that
nearly all my professional correspondents would deem this an
absurdly low estimate. Most of them are quite persuaded that
it is of frequent occurrence, many of them regard it as a general
rule, while some of them go so far as to make a point of always
putting a mare, a bitch, &c. to a good jiedigret^ male in her first
season, so that her subsei|uent i)rogeni:;s may be benefited by
his influence, even though they l)e engendered by inferior sires.
But I am certain that these estimates must be largely discounted
in view of merely accidental resemblances, and still more on
account of the prevalent belief upon the subje( t, which, where
unquestioningly entertained, prevents anything like a critical
estimate beinji formed.

ii

i«!

200 An Examination of Weisniannism.

But that the phenomenon docs occur in some small percentage
of cases there can be no reasonable doubt— as a result, I mean,
of analysing the hundreds of cases which have now been sub-
mitted to me, especially with regard to dogs. One thoroughly
well observed case occurring among pedigree animals is worth
any number of slipshod statements, when precedent belief, in-
efficient isolation, exaggeration of memory, and so forth, have to
be allowed for. On the present occasion space does not admit
of giving such special instances, so I must ask it to be taken
for granted that my evidence is enough to prove the fact of a
previous sire asserting his influence on a subsequent progeny,
although this fact is one of comparatively rare occurrence. It
may be added that 1 have failed to find any good evidence of
its ever occurring at all in the case of man. For although I have
met with an alleged instance of a white woman, who, after having
borne children to a negro husband, had a second family to a
white one, in which some negro characteristics appeared, I have
not been able to meet with any corroboration of this instance.
I have made inquiries among medical men in the Southern
States of America, where in the days of slavery it was frequently
the custom that young negresses should bear their first children
to their masters, and their subsequent children to negro hus-
bands ; but it never seems to have been observed, according to
my correspondents, that these subsequent children were other
than pure negroes. Such, however, was not the same case as the
one above mentioned, but a reciprocal case ; and this may have
made a difference. If any reader should liapi)cn to know of
another instance where a negro was the first husband, I hope he
will inform me as to the result.

It has hitherto puzzled me why the phenomcncm in question,
since it does certainly occur in some cases, should occur so rarely
as the above inciuiiies prove. But 1 think that Mr. Spencer's
suggestion on this point is a valuable one, as it seems to
present an excellent promise of solving the puzzle.

This suggestion, it will be remembered, is that when the first
sire is of a relatively stable and also of a markedly different
ancestral stock from the dam — e.g., of a different species, as in
the case of Lord Morton's mare — there will be most likelihood of
his inq)rcssing his ancestral characters on the progeny of the

Appendix II.

20 1

second sire '. And, as he remarks, it would indtxd be an
extraordinary coincidence if both the well-authenticated cases
given in the College of Surgeons Catalogue should have con-
formed to his explanation by mere accident. To which I may
add that the supposition of such an accidental coincidence would
seem to be virtually excluded by the recent occurrence of yet
a third case of exactly the same kind. This took place in the
Zoological Gardens, where a wild ass of one species was the
previous sire to a foal born of another species : the subsequent
sire was of the same species as the mother, and his foal, lorn
a few months ago, presented an unmistakable resemblance to
the other species. A brief account of the particulars is given
by Mr. Tegetmcier in the Field iox December 14, 1892.

So much, then, for the facts. As regards their interpretation,
it certainly seems to me that the one which I have supposed to
be given by VVeismann is less difficult of acceptance than the
one which is given by the Lamarckians, as we have seen above.
But it also seems to me that the latter e.\i)lanation is not the on. y
one available under the Lamarckian hypothesis. For, even
under this hypothesis, there is no need to assume that the in-
lluence of the first sire is exerted on all the somatic tissues
of the mother, and that these again rellcct this influence on
the ovum which is afterwards fertilized by the second sire.
A mechanism that could effect all this may well be deemed im-
possible. l!ut a much simpler explanation can be furnished
by the Neo-Lamarckians, on lines similar to those upon which
I have supposed that Weismann's explanation woidd run. For,
on their common supposition that the substance of heredity is
particulate, it matters not in the ptosent connexion whether we
suppose the particles to be ids or gemnuiles. Indeed, it is more
in accordance with the hypothetical endowments of the latter
than of the former, that they should be capable of penetrating
the coats of an ovum, if they can survive tie disintegration of
their containing spermatozoon. Nevertheless, thus tar it does
not seem to me that any theory belonging to the ...mily of pan-
genesis can gain any advantage over the theory of germ-plasm,

• Readers who may ha|ipen to he ai(|uaiiile<l wilii De Vrie'.' impoitmt
essay on hticdity will jurceive how well this suggestion (its iu wiih his
modification of Pangenesis.

!t t

202 An Exaviination of Weismannism.

by appealing to the fact of a previous sire sometimes affecting
the progeny of a subsequent one. The case, however, is widely
different if we turn from animals to plants, thus.

The .idvantage which any theory of gemmules seeks to gain
over the theory of germ-plasm by an appeal to the fact in ques-
tion, consists in supposing that the influence of the previous sire
is exercised in the first instance on the somatic cells of the female.
For this would prove that the germinal elements of ^he male arc
capable of communicating their hereditary q'lal'iies, not only
by mixing with the germinal elements of the female (as in
ordinary fertilization) but also by direc, contact with the general
tissues of the female. And this agair. would prove that the
funchunentai postulate of the theory of germ-plasm is erroneous

i.e., the postulate of the continuity of germ-plasm, or of its
perpetual restriction to a " sphere " of its own. This, as all who
are acquainted with the literature of the subject will at once
perceive, would be a serious blow to the whole Weismannian
system. Jiut, as we have seen, the current Lamarckian inter-
pretation of the fact in question involves the supposition of
a physiological machinery so inconceivably complex that instead
of serving to corroborate the theory of gemmules (or of physio-
logical units) it would go to render that theory incredible '.

' As already indicated, I cannot gather fiom his remarks on the suliject
which, if any, of the allornative interpretations of the phenomena that
we are considering Mr. Spencer adojits. From the following sentences
it would appear that he assi^-ns yet a third interi)retation, and this as the
only possible one. For lie says of these phenomena: "They prove
that while the reprnductivc cells multiply and arrange themselves
duiing the e\()lutif)n of the emhryo, some of tlieir germ-plasm passes
into the mass of somatic cells constituting the parental hody, and
hecomes a permanent component of it. Further, they necessitate the
inference tli;it this introduced j,'erm-plasm. everywhere diffused, is some
of it included in the reproductive celli suhsecjuently formed" [iontcm-
porary Review, March, p. 4-;2^. This apiiears to mean that the
influence of a previous siie can only he explained t)y supposing that Che
developing embryo inoculates the somatic tissues of its mother with
hereditary material derived from its fatlitr, and that the maternal tissue
afterwards lellect some of this material (or its inlhunce) to the still
unri]ie ovarian ova. If this be the hyjiothesis intended, it seems to me
more complex than any of the thiee which I have sugj^ested. Hut, be
this as it m.ay, we ceitainly cannot agiee that such an hypothesis

Appendix II.

203

If, however, we turn lO plants, we find a considerable niimlier
of facts which unqucstionablv demonstrate the only point which
this interpretation has been adduced to suggest. For these
facts show that, in not a few cases, the germinal matter of
pollen-grains is capable of asserting its influence beyond the
ovules to the somatic tissues of the ovary, and even to the flower-
stalk of the mother plant. Here, then, we have simple and con-
clusive evidence of the material of heredity exercising a direct
influence on somatic tissues. How this well-known fact is to be
met by the theory of germ-plasm is a question which does not
seem to have thus far engaged the attention of Professor Weis-
mann, or of any of his followers. For particulars touching this
phenomenon, so highly important in its relation to the theory
of germ-plasm, 1 cannot do better than refer to the eleventh
chapter of Darwin's work on the *• Variation of Animals and
Plants under Domestication."

Again, in the Contemporary Rivieiv for May, Mr. Spencer
wrote : —

In the essay to which this is a p(u,t.'fript, conclusions were
drawn from the remarkable lase of the horse and quagga there
narrated, along with an analogous case observed among pigs.
These conclusions have since been confirmed. I am much
indel)ted to a distinguished corresjiondent who has drawn my
attention to verifying facts furnished by the offspring of whites
and negroes in the United States. Referring to information
given him many years ago, he says : — " It was to the effect that
the children of white women by a white father had been re-
peatedly observed to show traces of black blood, in cases when
the woman had previous connexion with [i.e., a child by| a negro."
At the time I received this information, an American was
visiting me ; and, on being appealed to, answered that in the
United States there was an established belief to this effect.
Not wishing, however, to depend upon hearsay, I at once wrt-te
to America to make int|uiries. Professor Cope of Philadeiphia
has written to friends in the South, but has not yet sent me the

is "proved " by the fatts, or tlint the latter "ncctssilate " the inference
as to its being some of the embryos germinal matter which enters the
unripe ova.

204 An Examination of Weismanmsm.

results. Professor Marsh, the distinguished paleontologist, of
Yalo, New Haven, who is also collecting evidence, sends
a preliminaiy letter in which he says : "I do not myself know
of such a case, but have heard many statements that make their
existence prol}able. One instance, in Connecticut, is vouched
for so strongly by an acquaintance of mine, that I have good
reason to believe it to be authentic."

That cases of the kind should not be frequently seen in the
North, especially nowadays, is of course to be expected. The
first of the above quotations refers to facts observed in the South
during slavery days; and, even then, the implied conditions
were naturally very infrequent. Dr. W. J. Youmans of New York
has, on my behalf, interviewed several medical professors, who,
though they have not themselves met with instances, say that
the alleged result, described above, " is generally accepted as
a fact." 13ut he gives me what I think must be regarded as
authoritative testimony. It is a quotation from the standard
work of Professor Austin Flint, and runs as follows : —

A neculiar and, it seems to me, an iiicxi)licable fact is, that previous
pregnancies have an influence upon oflsiiring. Tliis is well known to
brctilers of animals. Jf pure-blooded mares or bitches have been once
covered by an inferior male, in sulisequent fecundations the young are
likely to partake of the character of the first male, even if they be after-
wards bred with males of unimpeachable pedigree. What the mechanism
of the influence of the (irst conception is, it is impossible to say; l)Ut the
fact is incontestable. The same influence is observed in the human
subject. A woman may iiave, l)y a second husband, children who
resemble a former hus])an'l, and this is particulaily well marked in
certain instances by the colour of the hair and eyes A white woman
who has had children by a negro may subsequently bear children to
a while man, these children presenting some of the unmistakable peculi
arities of the negro race '.

Dr. Youmans railed on Professor Flint, who remembered
"investigating the subject at the time his larger work was
written |' alxive is from an abridgment], and said that he
had nevei i -^d the statement questioned."

Some day ^ before I received this Utter and its contained

1 "A Text Book of Human l'h\ siology." By Austin Hint, M.D., LL. D.
Fouith edition. New York: D. Apjili-ton & Co. i8SS. I'age 797.

Appendix II.

205

quotatinn, the rem niljiancc of a rcm;iik I litard many years
ago concerning clogs, led to the incjuiry wluther they furnished
analogous evidence. It occurred to me that a friend who is
frequently appointed judge of animals at agricultural shows,
Mr. Fookes, of Fairfield, I'ewsey, \\ iltshire, might know some-
thing about the matter. A letter to him brougiit various
oonfirmatory statements. From one " who had bred dogs for
many years'' he learnt that -

It is a well-known and aihnitlcd fact that if a hitch has two littcis
by two dilTcient dogs, the cliaracter ol the liiit fallier i? sure to be
perpetuated in any litters slie may aftei wards have, no matter how
piuc-breil a dog may be the begetter.

After citing this testimony, Mr. Fookes goes on to give illustra-
tions known to himself.

A friend of mine near tliis had a very valual>le Dachshund bitch,
which most unfortunately had a litter by a stray sheep-dog The next
yenr her owner sent her on a vi it to a ])ure Daclishuiid dog. but the
[iroduce look ((uite as nuich of the llr^t lather as the -ecoiul. and the
next year he sent her to another Duchshuml with the same result.
Anoliicr case: — .\ friend of mine in Devizes had a litter of pujipies,
unsought for, by a setter from a favourite ])f)inter bitch, and after this
she never bred any true pointers, no matter of what the paternity was.

These further evidences, to which Mr. Fookes has since
added others, render the general conclusion incontestable.
Coming from remote places, from those who have no theory to
support, and who are some of them astonished by the unexpected
phenomena, the agreement dissipates all doubt. In four kinds
of mammals, widely divergent in their natures man, horse, dog,
and pig — we have this same seemingly anomalous kind of
heredity made visible under analogt)us conditions. We must
take it as a demonstrated fact that, during gestation, traits
of constitution inherited from the father produce effects upon
the constitution of the mother ; and tliat these communicated
effects are transmitted by her to subsequent oftspring. We are
supplied with an absolute disproof of I'rolessor Weismann's
doctrine that the reproductive cells arc independent of, and
uninfluenced by, the somatic cells ; and tbeie disapjiears abso-
lutely the alleged obstacle to the transmission of actiuired
characters. . . .

2o6 An Examination of Weismannism.

%m

■1 :.;:■<

Biil

m

There is one other passage in Dr. Romanes' criticism — that
conccrninj; the influence of a previous sire on progeny — which
calls for comment. He sets down what he supposes Weismann
will say in response to my argument. " First, he may question
the fact." Well, after the additional evidence given above,
I think he is not 'ikely to do that ; unless, indeed, it be that
along with readiness to base conclusions on things "it is easy
to imagine " there goes reluctance to accept testimony which it
is difficult to doubt. Second, he is supposed to reply that " the
germ-plasm of t^e first sire has in some way or another become
partly commingled with that of the immature ova"; and
Dr. Romanes goes on to describe how there may be millions
of spermatozoa and "thousands of millions " of their contained
" ids " around the ovaries, to which these secondary effects are
due. But, on the one hand, he docs not explain why in such
case each subsequent ovum, as it becomes matured, is not
fertilized by the sperm-cells present, or their contained germ-
plasm, rendering all subsequent fecundations needless ; and, on
the other hand, he does not explain why, if this does not happen,
the potency of this remaining germ-plasm is nevertheless such
as to affi'ct not only the next succeeding offspring, but all
subsequent offspring. The irreconcilability of these two impli-
cations would, I think, sufificiently dispose of the supposition,
even had we not daily multitudinous proof that the surface of a
mammalian ovarium is not a sperm-atheca. The third difficulty
Dr. Romanes urges is the inconceivability of the process by
which the germ-plasm of a preceding male parent affects the
constitution of the female and her subsequent offspring. In
response, I have to ask why he piles up a mountain of
difficulties based on the assumption that Mr. Darwin's
explanation of heredity by "Pangenesis" is the only available
explanation preceding that of Weismann? and why he presents
these difficulties to me more especially, deliberately ignoring
my own hypothesis of physiological units.? It cannot be that
he is ignorant of this hypothesis, since the work in which it is
variously set forth (" Principles of Biology," §§ 66-97) is one
with which he is well acquainted : witness his " Scientific
Evidences of Organic Evolution " ; and he has had recent
reminders of it in Weismann's "Germ-plasm," where it is

\%A\

'~n

Appendix II.

207

repeatedly rcfeneil to. Why, then, docs he assume that
I abandon my own hypothesis and adopt that of Darwin, there-
by entangling myself in difficulties which my own hypothesis
avoids ? If, as I have argued, the germ-plasm consists of
substantially similar units (having only tiiose minute differences
expressive of individual and ancestral differences of structure),
none of the complicated requirements which I)r, Romanes
empii ises exists, and the alleged inconceivability disappears.

To this I responded, in the Coniemporary Raiiw for
June :—

With regard to the influence of a previous sire, I ventured
in my article to show that, even supposing it to be a fact,
the phenomena concerned would not constitute any valid
evidence against Weismann's theory of germ-p'asm, and, of
course, still less would " they prove that while the reproductive
cells multiply and arrange themselves during the evolution
cf the embryo, some of their germ-plasm passes into the mass
of somatic cells constituting the parental body, and becomes
a permanent component of it," with the result that the phe-
nomena in question " are simply fatal to Weismann's hypothesis."
For a much simpler and more probable explanation is to be
found in supposing that the unused germ-plasm of the first sire
may survive the disintegration of its containing spermatozoa in
the Fallopian tubes of the female, and thus gain access to the
hitherto unripe ova directly^ instead of first having to affect the
whole maternal organism, and then being rcjlt-rted from it to
them. I showed, at some length, how immensely complex the
mechanism of any such process would necessarily have to be ;
and for the purposes of exposition I employed the terminology
of Darwin's theory of Pangenesis. Mr. Spencer now says:
" In respcmse, I have to ask why he [I] piles up a mountain
of difficulties based on the assumption that Mr. Darwin's
explanation of heredity by 'Pangenesis' is the only available
explanation preceding that of Weismann ? and why he presents
these difficulties to me more expecially, deliberately ignoring
my own hypothesis of physiological units.'" Now my answer
to this is very simple. I do not hold a brief for W'eismann.
On the contrary, I am in large measure an opponent of his

u I

r.

i , i ir
ilil

III

r*

208 ^« Iixaininafion of Weisniaiinism,

views ; and my only object in pul)lislii}ii:j my previous article
was to save the theory of usc-inlicritance from what seemed to
me the weaker parts of Mr. Spencer's ad\ocacy, while thus all
the more eniphasizin.sf my acceptance of its stronger parts.
Therefore, the impression which he seems to have gained from
my attempts at imi)artiality is entirely erroneous. Far from
"deliberately i;4noring" any of his arguments or hypotheses
whirh seemed to meat all available on the side of use-inherit-
ance, I everywhere endeavoured tf) make the most of them.
And, as re.q^ards this particular instance, I expressly used the
term *' gemnuiles," instead of " johysiological units," simply
because I could not see that, as far as my "mountain of dif-
ficulties'* was concerned, it could make one atom of difference
which term I emi)loyed. It now appears, however, that,, in
Mr. Spencer's opinion, there is some very great difference.
For, while he allows that the "mountain of difficulties" which
I have "piled up" against his interpretation of the alleged
phenomena would be valid on the supposition that the ultimate
carriers of heredity arc "gemmules," he denies that such is the
case if we suppose these ultimate carriers to be " physiological
units." For this statement, however, he gives no justification ;
and, as I am unable to conceive wherein the difference lies,
I sincerely hope that in any subsequent editions of his pamphlet
Mr. Spencer will furnish the requisite explanation. Cdadly
substituting the words "physiological units" wherever I have
used the word "gemmules," I am genuinely anxious to ascertain
how he would overcome the "mountain of difficulties" in
question. For I do not regard the subject as one of mere
di;ilectics. It is a subject of no small importance to the general
issue, Weismann versus Lamarck ; and, therefore, if Mr. Spencer
could show that the phenomena in question make exclusively in
favour of the latter, as he alleges, he might profitably inform us
in what way he supposes them to do so.

In conclusion, I would like to take this opportunity of ex-
plaining that my former article was written in Madeira, where
I did not receive a copy of Weismann's most recent work,
entitled The Germ-plasm, until the Contemporary Re7new for
April was being printed off. Thus, I was not then aware that in
this work Professor Weismann had fully anticipated several

Appendix II.

209

of Mr. Spencer's criticisms— including this matter of the
influence of a previous sire. Here he adopts exactly the position
which in my article I surmised that he would ; so that, to all
who have read The Germ-plasm, it must have appeared that
I was prophesying after the event. Hence the need of this
explanation.

Lastly, in the same issue of the Contemporary Rein'eiv,
Mi. Spencer explained: —

Mr. Darwin's hypothesis of Pangenesis implies not only that
the reproductive cell must contain numerous kinds of gemmules
derived from different organs, but that the numbers of these
gemmules must bear to one another something like the pro-
portions which the originating organs bear to one another in
size. The conception involves many different /diiiis, whose
numbers are in many different proportions, and I supposed the
difficulty alleged was, that for the influence of a previous sire to
be communicated from the growing fcetus to the mother would
imply not only the transfer of the various kinds of gemmules
derived from him, but also maintenance of their numerical
proportions, and that again these gemmules, diffused throughout
the maternal system, would have to be transferred in these pro-
portions to the subsequently formed ova. No such difficulties
arise if the units conveying hereditary characters are of one
kind only.

From this it is apparent that Mr. Spencer has misunder-
stood " the difilculty alleged," and that the desired explanation
is not yet forthcoming. I did not say anything about " kinds "
or " proportions " of the carriers of heredity ; my difTiculty
is to conceive of any mechanism whereby these carriers can
first directly influence the somatic-cells of the mother, and
then indirectly reflect this influence upon her germ-cells.
Also, I cannot see any obvious necessity for the intervention
of the " embryo " in the process.

It , ..'

"It

. lit *

GLOSSARY.

-*♦-

Acquh'ed character.._.S« Somato^cnctic characters.
Amphigony iHackel).-SexuaI reproduction

AmphimixiscWeismann).-Tl,emin,Min,M.fthcla.reditary«„bs^^^^^^^
or two individuals in an act of sexual union

Ancestral Kerm-plosm.— iVt' ji 123

,crm els contanunfj the potentiality of the a.iult or,^,nism, tnU

gi 'Wtls, &c. which develop into the j.arent form. There are
many forms of asexual reproduction.
Atavi«m._The al>r.ormal occurrence in existing, species of character,

rt//t^; Uarwin, 2nd ed., Part I, p. 94.

Biophore.— 5'tv p. 123.

Blastogenetio characters.-.9.. IMasmo,r,nefic characters.

Calyx._The outermost eoverin^^ of the (lower, which protects it l.efore
opening. Its position and precise function vary

Cell nucleus A spherical or ovoid body embe,lde<l in the cell proto-
plasm, whtch has,mpor.ant functions in cell division ..nd in re o-
duction. t consists of chromatin and acluomatin. There are n

w a ::t:;:t:r^"' ^^'^'^^ -'"-^''^ '--■---^--

Cessation of Selection (Romanes\-.S-.. I'anmixii
Chromatin threads.-Immediately before a cell diiides the nucleus is
r^olved into chromatin hbres or threads and an achromatin ma i
Ihese chrcHnatin fibres are then marshalled into either rods or 1 ^ ;
&c a. the division of the cell proceeds ;see Danvin and after
^anon^, fjgs 36, 37, and 38^. Sul.sec,uent cban.H. in the thn .^ s
conclude the division for a description of which ctnsult the ac;;:.!:

Chromosomes.— 5^^ Chromatin thieads.

Pa

.'212

Glossary,

Compositae. — Plants in which the inflorescence consists of numerous
small flowers brought together into a dense head, the base of which
is enclosed by a common envelope (e.g. the Daisy, Dandelion, &c.).

Congenital characters. — See Plasmogenetic characters.

Conjugation. — This term is applied to a process observed in the
Protozoa (q. v.", which seems to correspond to the sexual reproduction
of the Metazoa (q. v.). The majority of the I'rotozoa cannot long
continue to reproduce themselves ascxually without becoming
degenerate, or rather without becoming altogether extinct. Two
individuals (as a rule) consequently unite either temporarily or
permanently. In the former case, an exch.mge of material is eflectcd ;
and in the Intter, complete fusion takes place.

Correlation. — The normal coiiiciiicnce of one phenomenon, character,
&c., with another.

Cytoplasm. — See pp. 30 and 33.

Determinant. — Sce\*. 123.

Ectoblast. — Syn. of cj)ibiast and ectoderm. The general result of the
division of a fertilized ovi;m is a two layered ball of cells (a gastrula).
The outer l.iyer is called the eotobl isl and the inner layer the cnto-
blast. (See J)a>i.vin and after Dariuin, p. 137 et seq.).

Embryology. — [fence embryogenesis, &c. The study of the develop-
ment or the early growth of thf individual.

Entoblaat. — Syn. of hypobl.ast and endoderm. See Ectoblast.

Epigenesis (Harvey). — The theory that organisms are formed by the
development of the egg itself, and not by tiie ex[)ansion of a miniature
within the egg (prelormation).

Fallopian Tubes. — The tubes through which the spermatozoa pass to
effect iertilizalion, and through which the ova pass from the ovary to
the uterus.

Fission. — .Syn. of fissiparous separation. Tiie breaking into two
(without karyokinesis— q. v.^ of a cell, wliich Ii.is, by overgrowth,
disturbed its physiological etjuilibrium. This process is almost
meclianical.

Formative material. — See p. f/).

Gemmation. — That form of asexual reproduction known as budding.

Gemmules (Darwin). — Minute granites, formed liy the division of the
general body-cells, which are supposed to I)e dispersed tin oughout the
entire system. These themselves multiply by division, and are
collected from all parts of the body to constitute the sexual
elements.

Germ-plasm. — See p. 32.

Hydroids. Belong to a division (Hydrozoa) of the stinging-animals
or Coelenlcrata. They occur both in tiie sea and in fresh water, and
are solely polypoid (i.e. tubulai and tentacled).

Glossary.

213

Hydromedusae. — Also Ilydrozoans. Ilydroid colonies with special
sexually reproductive persons, which are often liljeraled as floating
bells or discs.
Idio-plasm ,A and B). — See pp. 31 and 32.
Ids. — See p. 123.

Invertebrata. — Animals with a dorsal lieart and without a backbone.
Karyokinesis.— The chan_t,'es wiiich are oljserved in the nucleus both

immediately before and after cell division. See Chromatin tlireads.
Lamarckian factors. See Somatogenetic characters. Also Neo-

Lamarckians.
Metaphyta. — Multicellular plants (q. v.).
Metazoa. — Multicellular animals (q. v.).

Micellae (Niigeli). — See Molecules, with which they are identical.
Microsomata. — The protoplasm of certain vej^etable cells is in places
characterized by the pr;sence of minute corpuscles, wluch may be
rei^ardcd as part of the proto])lasm, and are certainly of a j)rotoplasmic
nature. These are termed Microsomata.
Molecules (Weismann). — .S"^^ p. 122.

Multicellular orgauisms. — Ori^anisms composed of many cells, as
distinguished from the Unicellular org.inisms, where each individual
is constituted of only one cell.
Natural Selection. — Survival of the Fittest in the struggle for
existence. For a full account of the process see Danvin and after
Darivin, p. 251 el seq.
Neo-Darwiuiana. — Those who believe that Natural Selection has
been the only modilying intliience in the evolution of species, and
that the material for its action has been only piasmogenetic
characters (q. v.).
Neo-Lamarckians. — Those who hold that organic evolution has Ijeen
effected solely by means of the occurrence and preservation (inheritance)
of somatogenetic characters ((|. v. .
Nuclear Thread or Loops.- .SVc- Chromatin threads.
Nucieo-plasm. — See pp. 30 and 32.
Nucleus. — See Cell nuc' us.
Nutritive congenital charactci's. — See p. 64.
Ontogenetic grades.- See ■ • i.
Ontogeny. — The life history or tlie individunl, as distinguished from the

ancestral history (*f the race ( I'hylogeny i.
Ova. — i-ggs — the product of the lemale leproductivc gland (ovary or

ovarium).
Ovule. — The seed in its earliest condition.

Pangenesis iDarwin . The th< ory of Heredity by gemmules ((|. v.).
Panmixia < 'Weismann'). — The cf)ndition ol fne intercrossing, i.e
where Natural Selection \,q. v.) cannot act.

214

Glossary.

PI

Parthenogenesis. — A degenerate form of sexual reproduction, in which
the egg develops without having been fertilized by the male
element.

Phylogen: . — The ancestral history of the race, as distinguished from
the life history of the individual (Ontogeny).

Physiological Units (Spencer). — Special units which it is inferred
a plant or animal of any species is made up of, and in all of which
dwells the intrinsic aptitude to aggregate into the form of tiiat
sjiecies.

Plasma. — The constituent material of cells, e. g. gerniplasma (of sexual-
cells), somatoplnsma (of body-cells).

Plasmogenetic characters. — Variations due to admixtures of germ-
nlasm in acts of sexual fertilization (and therefore present at birth),
as d'.stiiiguished from somatogenetic characters — variations which
have been acquired independently of germ-plasm. See Somato-
genetic characters.

Polar bodies. — Hefore an egg is fertilized the nucleus moves tovards
the jieriphery and divides twice. The two cells that are thus
formed are the polar bodies. The extrusion of polar bodies is
probably universnl among animals, but only one polar body is
extrui'ed from |iarthenogcnetic ova. See Darivin and after Darwin,
pp. 125 and I 26.

Preformation. — The old conjecture (1672 — M:dpiglii) that the de-
velopment of nn embryo was merely tin- expansion or unfolding of
a miniature of the adult within the egg.

Protophyta. — Unicellular plants (q. v.).

Protoplasm. — Living matter.

Protozoa. — Unici llular animals q. v.).

Representative Congenital characters. — See p. 65.

Reversion. — See Atavism.

Rudimentary Organs. — Usually considered a synonym of the term
"vestigial characters," and is the name under wiiich are included all
those organs which, either from having become us less or from other
causes, have been much reduced in size, e.g. the muscles o<" the
external ear in man (see Darvun and after l\inuin, p. 76), &c.
Latterly the former expression has been used to describe organs in
process of development (e.g. the electric organ of the skate — loc.cit.y
p. 365 et setj. , whilst the latter is made to embrace all those organs
in process of elimination.

Soma. — A general term desciiptive of the whole mass of the body-cells
of an organism.

Somatic-idio-plasra. — See p. 3a.

Somatogenetic characters. — Ch .acters acquired by the soma (i.e.
variations acquired alter birth by the action of the environnunt), as

1*

I*

Glossary.

215

distinguished from characters /m///,.-,/ and potentially present from
the first by a union of two masses of gcrm-plaMn-plasmuLrenetic
characters (q. v.\

Soraato-plasm. — See p. 32.

Specialized congenital characters.— 5^^ p. 65.

Spermathecae.-Ori,rans for the storing of the seminal fluid received in
copulation.

Spermatogenesis.— The precise development of spermatozoa
Spermatozoa.-'l'he essential elements in the male seminal fluid, and

secreted bv the testis— the male reproductive gland.
Stirp (Qalioi;. -See p. 58.
Telegcn.v. 0 141.

Unicellu) O, . ...asms.-Organisms composed of a sin-le cell only

as distu!gu'.,ied Irom those consisting of aggiegations of cell.-'

Multicellu'iar organisms.
Vertebrj,ta.— Animals with a backbone and a ventral lieait.
Vestigial Orgars. -Ac Rudimentary organs.
Xeuia. — See p. 141.

: m_

!/n

'lii

INDEX.

Acquired characters, definition of,
p. 5 ; inheritance of, 6, 15. 49, 57,
f>o, 67,69, 71, 81, 83-84, 93-
9f». 104, 107, iio-iii, 127,
173. ^^ ^eq. ; Gallon on inheri-
tance of, 62, 106.

Adaptive development, Weismann
on, 19.

Algae, De Vries on the chromato-
phores of, 83. in.

Amphipony, the cause of indi-
vidual liereditary variation, 91,

lOO-IOI.

Amphimixis, see Sexual propaga-
tion.
Ancestral germ-j>lasm, 123.
Atavism, 3, 91, lo;;.

B.

Bary, De, on Weismann 's theory,

152-
Basidiomycctes, 90.
l^egonia, rtgeneratiun in, 4, 52.
liiophorcs, 123.
Body-cells, and gcrm-cells, 29.
Brooks, theory of heredity, 2.
Bud- variation, 90, 94, 96,'9S-99 ;

Weismann on, 95, 97, ,6, ;

Pntz Miillcr on, 95.
Butterflies, climr.'ic' varieties of

and Weismann's theory, 67

68, 137-128. '

Candolle, De, on inheritance of
acquired characters in jdants, (,3.

"Carriers of Heredity," 32, j,8,
70, 78, 122.

Cessation of Selection, see Pan-
mixia.
Chromntophores, of Algae,S3, 1 1 1.
Compositae, pollen of, 5.
Congenital variations, ' definition
of, 5; inheritance of, 6, no;
sexual propagation the cause
of, n ; Darwin on, 13; oris^in
°f' 23, 2,ii, 100, 102; nutritive
congenital changes, 64; exam-
ples of, 64; specialized con-
genital changes. 65 ; representa-
tive congenital changes, 65 ;
(ialton on, 134.
Continuity of germ-plasm, see

Germ plasm.
Crustacea, and the inheritance of

acquired characters, 94.
Cuitmgs, and bud-variation, 98.
Cylisus cuiami, grafting of, 127.

D.

Darwin, Charles, and Pangenesis,
2, 2O; arguments in favour of
pangenesis, 3, 59; on the cause
of congenital v^iriations, i^;
comparison of his theory "of
heredity with that of Weis-
mann, 52, 55, 73, 92, 105-

'°''» 115- '.^3. 173 et seq.; on
germ and somatic-cells, 76 ; on
tile influence of pollen upon
somatic tissues, 79-.S0; on graft-
hyt.ridization, S3 ; on t,u(l-
variation, 95 ; on the causes of
. yaiiation, 102, 161 ; on the
iniierilance of acquired charac-
ters, 107, ni-n2; on .\enia,
I.J4; oii sexual union, 154.

2l8

Index,

Death, Wcismann on the origin of,

S, lo ; in plints, lo.
Determinants, 1 23.
Direct action of environment, on

unicellular organisms, 15, 23.

E.

Elsberg, theory of heredity, 2.
Environment, direct aciion of o'

Protozoa, 15.
Evolution, see Organic evolution.

F,

Flint, Prof. Austiu.on Telegony,
204.

Pocke, on Xenia, 141, 144.

" Formative material," and germ-
plasm, 56.

Fungi, Prof. Vines on Basidiomy-
cetes, yo.

Galton, Francis, theory of here-
dity (stirp), 2 ; and VVeismann's,
51) 5^-.=^9. 69, 73, 92, 105-106,
108, 115, 129, 130 et sei],\ on
gemmules, 60 ; on inheritance
of acquired characters, <'>2, Txj,
107; nnd stability of the ma-
tei i f'.isis of heredity, 63 ; on
origin of sexual reproduction,
103, 167.

Giirtner, on Malva, 80 ; on in-
heritance of acquired characters
in plants, 93.

Gemmules, 2 ; Darwin on the
si/e of, 4 ; and gerni-plasm, 52,
55, 58, 92, 105; and stirp, 58;
Galton on, 60.

Generative cells of the Ilydro-
medusae,\Veismnnn on, 71. 109 ;
example of continuity of germ-
plasm, 72-73.

Germ-cells, and body-cells, 29,
7.'i~77 ; nucleo-plasm of, 30;
number of 43, 45.

Germ-plasm, Weismann's theory
of, 5, 103, 173 ct sct].\ immor-
tality of, 9, 24 ; continuity of, 9,
18, 49, 5^-67, 69-77, 72, 75,

7S, 86 87, 104-105, 109-110,
114, 120, 16S ; difterenees in,
12; origin of, 17; indepen-
dence of, 19 ; and natural selec-
tion, 21 ; stnbility of, 22, 49,
57,66, 86-S9, 91-93, 99-100,
104-105, 109, 112-114, 151
et scq. ; lodged in nuckus, 29 ;
and ?omato-plasm, 29, 81, no;
the modification of, 36 ; exami-
nation of Weismann's theory of,
48 ; Weismann's theory of and
Pangenesis, 52 ; and gemmules,
.S2. 55, 58, 105-106, 121;
multii)lication of in the general
cellular tissues of plants, 53;
DeVrieson, 54; Differentiation
of, 55 ; and " formative ma-
terial," 56 ; and stirp, 5S-59,
61, 75, 106 ; and somatic-idio-
plasm, 6(j ; as a basis of heredity,
70 ; ancestral germ-plasm, 1 23.
Grafting, and the effect of the
somatic-tissues on the germinal
elements, 81 -8 2 ; Darwin on,
83; and bud-variation, 98;
Weismann on, 126.

H.

Hackel, theory of heredity, 2.

Hartog, Prof. M., on \\ ei^mnna
155 ; on sexual propagation,
166-167.

Healing of wounds, 34.

Henslow, Rev. G., on regenera-
tion in plants, 53.

Heredity, various theories of 2,
49, 70; statement of Weismann's
theory of, 17; modification of
Weismann's theory of, 2"^, 46,
52, 65, 68, 75, 163 et sci]. ; the
nucleus and, 29; "carriers of,"
32, 38, 70, 78, 122; theory of
and histology, 38 ; examination
of Weismann's theory of, 48,
105, 117; compaiison of Weis-
mann's, Darwin's, and Gallon's
theories of, 51, 105-106; criti-
cism of Weismann'stheoiy of by
.Strasburger, 51; the material
basis of, 61, 63.

Index.

219

Hertwig, O., theory of heredity, 2 ;

on polar bodies, 46, 1 1^,
Hildebrand, or effect of pollen

upon somatic tissues (Xenia),

80 ; on Orchideae, 80.
His, theory of heredity, 2.
Hoffmann, on the inheritance

of acquired characters, 93-4,

114.
Hydromedusaj, VVeisniann on

generative cells o 71, 109;

illustrate continuity of germ-
plasm, 72-73.

I.

Identicnl twins, 41.

Idi plasm, Nii^eli's term, 31 ; A
and Ij, 31-32 ; sell-multiplica-
tion of, 34 ; amount of idio-
plasm A in the nucleus, 40.

Ids, 123.

Individual differences, VVeismann,
39. 4^ 43-

Influence of a previous sire upon
the progeny of the same dam,
set Telegony.

Influence of external conditions,
see Acquired characters.

Influence of pollen upon somatic
tissues, see Xenia.

Inheritance of acquired characters,
see Acquired characters.

luveitebrates, Weismann on sexual
apjiaratus of, 72, 74, 109.

Jelly-fish, regeneration in, 4.
Jordan, on mliei iuiiice of ac(juired
characters ni plants, 03.

K.

Karyokinesis, 37.

L.

Ijamarck, Wei-.mnnn and, 16, 21.

Lamarekian fiiclors, importance
o'. .S7, .S9> 62, 65, O7, 69, 82,
106 loH, 111-112, I2,S, 147.

Lile, duration of, 7, 10.

M.

Malingi6 Nouel, on Telegony,
193 et seq.

Malva. (Jdrtner on, 80.

Maupas, on the Protozoa, 101,
148.

Metazoa and Metaphyta, cause of
mortality ol, 7, 24, 148; rela-
tion of progeny to paienl> in,
16; transmission of acijuiied
characters in, i6 ; propagaliin
in, 51-

Mivart, on inheritance of acquired
characters, 94.

Molecules, 54, 123.

Morton, Earl of, on Telegony,
192.

Miiller, Fritz, on bud variation,
95-.

Multicellular organisms, see Me-
tazoa and Metaphyla.

N.

Nageli, theory of heredity, 2 ; and
idio-plasm, 31, 187 ; and germ-
plasm, 36; on inheritance of
acquired characters in plants,
93-

Natural selection, the cau.se of
death, 8 ; action of, 20 ; the
material for the operation of,
I3> 57 ; uot the cause of sexual
propagation, 13-14; and the
i'rotozoa, 15, loi 102 ; and
germ-plasm, 21 ; sole cause of
organic evolution, 25, 59, m,
114.

Nouel, Malingi^-, on Telegony,
1 9,', ct seq,

Nucleo plasm, of germ and soma-
tic cells, 30.

Nucleus, alone contains germ-
plasm, 29 ; contains two
suiistances, 33 ; and heredity,
37; and polar bodies, 40;
amount of idio j)lasm A in, 40.
Nutritive congenital changes, 64.

o.

Orchideae, Ilildeband on, 80.
Organic evolution, the cause of.

220

Index.

:i

25 ; Weismnnn's theory of, 26,
4^, 50. 5^. '^>^. fiS, '"^r. 100, 104,
I06-I0S, 1 14-1 15, 147.
Ova, Weismann on the size of, 39.

Pallas, on variability, 154.

Pangenesis, Darwin's theory of, 3,
iU ; and Weismann's theory of,
52, 55. 71. 73. 12' ; and i'an-
mixia, 59-60 ; Gallon on, 60.

Panmixia, and Pangenesis, 59-60.

Parthcnogenetic organisms, and
natural selection, 15; no con-
genital variations in, 7-', 75.

Parthenogenetic ova, Weismann
on, 45, 89, 91, 109.

Phylogenesis, 34.

Physiological isolation, of germ-
oells, 74.

Plants, reproductive cells of, 74 ;
intluence of polhn upon so-
matic tissues of (^Xenia, 7S So;
bud-variation in, 91, 94 99 ;
Hoffmnnn's inveslii;ations on
the inheritance of accjuired char-
acters in, 93.

Polar bodies, Weismann on, 40
46, 125; examination of Wtis-
manii's explanation of, \i\
O. Ilertwig on, 46, 125.

Protophyta, natural selection and,
114.

Protozoa, immortality of, 7 ; and
natural selection, 15, 114;
origin of species of, 15, 102;
action of environment on, 15;
Maupas on, loi.

R.

Regeneration, in sea-anemones and
jelly-fish, 4, 35; of an entire
organism, 34 ; Weismann on,
51 et seq. ; in Hegonia, 32;
Rev. (J. Ilenslow on, 53 ; and
stirp, 59.

Rejuvenescence, 166.

Representative congenital changes,
65.

Reproduction, essential meaning

of sexual, 8, 11 ; in the Pro-
tozoa, 16; somatic. 35.

Reproductive elements, potential
immortality of, 9 ; of Vertebrates
and Plants, 74.

Reversion, 3, 91, 105.

Roux, on the principle of "strug-
Klt:." 139-

s.

Sea-anemones, regeneration in, 4.

Sexual apparatus of Invertebrates.
Weismann on, 72, 74.

Sexual-cells and somatic-cells, 75 -
77,81,84.

Sexual propagation, essential
meaning of, 8, 11, 87; sole
cause of congenital variations,
12, S9-90, 102, 135, 141, I^3,
15S; di<l not arise tiuough he
agency of natural seliction, 13-
14; in multicellular organisms,
51 ; Gnlton on the origin of,
103; in CytisHS adami, 127.

Signil'icance of sexual re|iroduction,
sec Sexual Reproduction.

3omatic-cells, nucleo-plasm of, 30;
and sexual cells, 75-77, 81, S^.

Somatic-idio jilasm, 32-33; and
germ-plasm, 69.

Somatic reproduction, 35, 52.

Somato-plasm and germ-plasm.

Specialized congenital changes, 65.
Species, Weismann on the origin of

new, 100-101.
Spencer, Herbert, theory of

heredity, 2 ; on Telegony, 191

et scij.
Stability of germ-plasm, j^^ Germ -

plasm.
Stirp, and gemmules, 5S-59, 61 ;

andsonialic tissues, 60; and the

germinal cells of llydromedusae,

73; and germ-])Iasm, 75, 92,

106, 133.
Strasburger, on Weismann's

theory of here<lity, 51 ; on the

origin of sexual propagation,

167.
Stylotitchia, Maupas on, loi.
Summary, 103.

Index.

221

I'ro-

T.

Telegony, 77-79, no, 141 et scq.,
igi et scij.

Tiansinissi',)ii of .ic<iuiie(l char-
acters, see Ac(juirf(l characters.

Twins, identical, 41.

U.

Unicellular or<;anisins, reproduc-
tion of, 16; action ot environ-
ment on, 23, 147 ct scq. ; poten-
tially immortal, 23 ; natural
selection and the, 24,57, 114 5
and the origin of hereditary in-
dividual variations, 100.

V.

Variation, see Congenital varia-
tions, Acquired characters, A:c.;
Darwin on the causes of, 102;
Weismann on the origin of,

Veitebrates, reproductive cells of,

74-
Vestigial organs, persistence of,

Vines, Prof. S,, criticism on
Weismann, 14, 75, 90, 99, 152,
178 ; on tile Hasidioiiiycetes, ijo.

Vries, De, theory of heredity, 2 ;
on germ-plasm, 54 ; on the
chromatophorcs of Algae, 83,
111; on Xenia, 1 44.

W.

Weismann, Prof. August.,
theory of germ-plasm, 5, 17,
173 et scq. ; on tlie duration of
life, 7, io;onllieessenti:d nil aning
of sexual propagation, 11, 103,
135, 141 ; on natural selection
as the origin of sexual repro-
duction, 14; on I'lof. \ iiies'
criticism, 14, 90, i>9, 17S et seq. ;
on the Protozoa and natural se-
lection, 15, 102 ; on Lamarck,
If) ; on adaptive devclojiment,
ii>; and natural selection, 21;
summary of tlieory of germ-
plasm, 23 ; theory of organic

evolution, 26, 48, 50, 58,66, 68,
87, 100, 104, 106-108, 114 115,
147 ; modilications of theory of
heredity, 2S, 46, 52, 65, 68, 75,
163 ct seq.; and of self-mul-
tiplical'on of idio-jjlasm, 34;
on "ontogenetic grades," 35,
53 ; on the modification of germ-
plasm, 36; on chromatin, 38;
on iniii vidua! differences, 39,
41, 43 ; on the size of ova,
39 ; on polar bodies, 40, 42, 46,
125; on the number of germ-
cells, 44-4,s ; on jjarthenogenetic
ova, 45, 89, 91 ; examination
of his theory of germ-))lasm or
heredity, 48, 8,; ; on the staliility
and Continuity of germ-plasm,
49. 63, 66, 86-89, 91-93, 99-
100, 103-105, 107, 109-110,
I12-114, 120, 151, 158; com-
parison of his theory with those
of Darwin and Galton, ,-1, 58;
on Strasburger's critici-m of his
theory, 52 ; on the multiplication
of g:riii-plasin in the general
cellular tissues of plants, 53;
on regeneration in plants, 53 ;
anticii)ated by Galton, 59, 68;
and Galton, 63, 130 et seq.\
on transmi.ssion of acquired
ciiaracters, 67, 83, yfi, n i,
127 ; and his critics, 70; on the
llydromediisae, 71, 109; on the
sexual apparatus ot Invertebrates,
72 ; and the inlluence of germ-
cells upon sf)nialic tissues , 'lele-
gony and Xenia), 8081, i<j6
et seq. ; and the signilicance
of grafting, 8i 82, 126; and
votigial ciiaracters, i)z; on
IKillmann's invesligatiims, 93;
on bud-variation, 95, 97, if>i;
on the origin of henditary
individual variations, loo-ioi ;
on tlie origin of new species, 101.
\\ ounds, healing of, 34.

X.

-Xenia, 78-^1, uo, 141, ij^^ctseq.

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