VJ^

BIOLOGICAL LECTURES

DELIVERED AT

THE MARINE BIOLOGICAL LABORATORY
OF WOOD'S HOLL

In the Summer Session of 1893

BOSTON, U.S.A.
PUBLISHED BY GINN & COMPANY

1894

Copyright, 1894,
By GINN & COMPANY.

ALL RIGHTS RESERVED.

PREFACE.

In offering the second volume of these lectures,^ it may be
well to remind the reader who may not be acquainted with the
Laboratory, that only 07ie side of our work is here represented.
Such a series of lectures on special problems in biology is
offered every summer; but the main body of our lectures
is of quite a different type, having direct reference to the
instruction going on in the laboratories. As a rule, these
special lectures are given by investigators, who undertake not
only to reviciv the field, but also to set forth the results of their
own ivork. While these lectures may show the general drift
of the authors' investigations, they cannot, of course, be ex-
pected to give a complete account of the facts on which the
conclusions are based. In lectures of this kind due allowance
must be made for the authors' limitations in time, as the sub-
ject is often one which would require a dozen or more lectures
for its complete elaboration. Somewhat greater freedom in the
expression of opinion than might be expected in strictly scientific
communications, must also be permitted. In fact, it is one of
the leading objects of this course of lectures to bring forward the
misettled problems of the day, and to discuss them freely. It is
to be expected, of course, that now and then opposed stand-
points will be developed, as has happened this time; but these
differences exist, and will continue to exist, as long as anything
remains for investigation, and the scientific reader will not be
surprised to find them here. It may be hardly necessary to
add that the authors are severally responsible for the method
and form of their lectures. A brief account of the work and
aims of the Laboratory will be found in the appendix.

C. O. Whitman.

1 The first volume appeared in 1890.

CONTENTS.

LECTURE PAGE

I. The Mosaic Theory of Development. E.B.Wilson. i

II. TJie Fertilization of the Oviivi. E. G. Coxklix . 15

III. On Some Faets and Prineiples of Physiological

Morphology. J. Loeb -^J

IV. Dynamics in Evolution. J. A. Ryder .... 61

V. On the Xature of Cell Organization. S. Watase . "^l

VI. The Inadequacy of the Cell- Theory of Development.

C. O. Whitmax 105

VII. Bdellostoma Dombeyi, Lac. Howard Avers . . 125

VIII. The Influence of External Conditions on Plant

Life. W. P. Wilson 163

IX. Irrito-Contractility in Plants. J. Muirhead Mac-

farlane 185

X. The Marine Biological Stations of Europe. Bash-
ford Deax 211

Appendix — The Work and the Aims of the Ma-

ritie Biological Laboratory. C. O. Whitman. 235

FIRST LECTURE.

THE MOSAIC THEORY OF DEVELOPMENT.

EDMUND B. WILSON.

A REMARKABLE awakening of interest and change of opinion
has of late taken place among working embryologists in regard
to the cleavage of the ovum. So long as the study of embry-
ology was dominated by the so-called biogenetic law, so long
as the main motive of investigation was the search for phyletic
relationships and the construction of systems of classification,
the earlier stages of development were little heeded. The
two-layered gastrula was for the most part taken as the real
starting-point for research, and the segmentation stages were
briefly dismissed as having little purport for the more serious
problems involved in the investigation of later stages. The
cleavage is equal or unequal, total or partial, regular or irregular;
the diblastic condition attained by delamination, migration or
invagination ; the gastrulation embolic or epibolic : — such
were the general conclusions announced regarding the pras-
gastrular stages in a large proportion of the embryological
papers published down to the time of Balfour and even later.
The last decade has, however, witnessed so extraordinary a
change of front on this subject that it will not be out of place
to review briefly the three leading causes by which it has been
brought to pass.

First, it has become more and more clear that the germ-layer
theory is, to a certain extent, inadequate and misleading, and
that even the primary layers of the "gastrula" cannot be
regarded as strictly homologous throughout the animal kingdom.
To assume that they are so involves us in inextricable difficul-
ties — such as those for instance encountered in the comparison
of the annelid gastrula with that of the chordates, or the com-

2 BIOLOGICAL LECTURES.

parison of the sexual and asexual modes of development in
tunicates, bryozoa, worms and coelenterates. This considera-
tion led some morphologists to insist on the need of a more
precise investigation of the prae-gastrular stages, and the desi-
rability of taking as a starting-point not the two-layered gastrula
but the undivided ovum. "The 'gastrula' cannot be taken as
a starting-point for the investigation of comparative organo-
geny unless we are certain that the two layers are everywhere
homologous. Simply to assume this homology is simply to
beg the question. The relationsJiip of the inner and outer
layers in the vai'ioiis forms of gastriilas must be investigated
not only by detei'mining their relationship to the adult body, but
also by traeing out the cell-lineage or eytogeny of the individual
blastovieres from the begiiining of development y

The second of the causes referred to was the discovery of the
so-called pro-morphological relations of the segmenting ovum.
It is now just ten years since Roux and Pfluger independently
announced the discovery that the first plane of cleavage in the
frog's tgg coincides with the median plane of the adult body
(a fact announced many years earlier by Newport, whose obser-
vation fell, however, into oblivion). The same result was soon
afterwards reached in the case of the cephalopod (Watase) and
tunicate (Van Benden and Julin), and for a time it seemed not
improbable that a general law had been determined. Later
researches disappointed this expectation ; for it was demon-
strated that the first cleavage plane may be transverse to the
body (annelids, gasteropods, urodeles), or even in some cases
show a purely variable and inconstant relation (teleosts).
The fact remained, however, that in the greater number of
known cases definite relations 6f symmetry can be made out
between the early cleavage stages and the adult body ; and
this fact invested these stages with a new and captivating
interest.

The third and most important cause lay in the new and
startling results attained by the application of experimental
methods to embryological study, and especially to the investi-
gation of cleavage. The initial impulse in this direction was
given in 1883 by the investigations of Pfluger upon the influ-

THE MOSAIC THEORY OF DEVELOPMENT. 3

ence of gravity and mechanical pressure upon the segmenting
ova of the frog. These pioneer studies formed the starting-
point for a series of remarkable researches by Roux, Driesch,
Born and others, that have absorbed a large share of interest
on the part of morphologists and physiologists alike ; and it
is perhaps not too much to say that at the present day the
questions raised by these experimental researches on cleavage
stand foremost in the arena of biological discussion, and have
for the time being thrown into the background many problems
which were but yesterday generally regarded as the burning
questions of the time. It is the purpose of this lecture to
consider, briefly, the most central and fundamental subject of
the current controversy.

It is an interesting illustration of how even scientific history
repeats itself that the leading issue of to-day has many points
of similarity to that raised two hundred years ago between the
prae-formationists and the epigenesists. Many leading biolo-
gical thinkers now find themselves compelled to accept a view
that has somewhat in common with the theory of prae-forma-
tion, though differing radically from its early form as held by
Bonnet and other evolutionists of the eighteenth century. No
one would now maintain the archaic view that the embryo
prae-exists as such in the ovum. Every one of its hereditary
characters is, however, believed to be represented by definite
structural units in the idioplasm of the germ-cell, which is
therefore conceived as a kind of microcosm, not similar to,
but a perfect symbol of, the macrocosm to which it gives rise
(Hertwig). In its modern form this doctrine was first clearly
set forth by Darwin in the theory of Pangenesis ('68). Twenty
years later ('89) it was remodeled and given new life by Hugo
de Vries, in a profoundly interesting treatise entitled Intra-
cellnlar Pangenesis and in its new form was accepted by
Oscar Hertwig, and pushed to its uttermost logical limit by
Weismann. Kindred theories have been maintained by many
other leading naturalists.

The considerations which have led to the rehabilitation of
the theory of pangenesis are based upon the facts of what

4 BIOLOGICAL LECTURES.

Galton has called particulate inheritance. The phenomena of
atavism, the characters of hybrids, the facts of spontaneous
variation, all show that even the most minute characteristics
may independently appear or disappear, may independently
vary, and may independently be inherited from either parent
without in any way disturbing the equilibrium of the organ-
ism, or showing any correlation with other variations. These
facts, it is argued, compel the belief that hereditary character-
istics are represented in the idioplasm by distinct and definite
germs ("pangens," " idioblasts," "biophores," etc), which
may vary, appear or disappear, become active or latent, without
affecting the general architecture of the substance of which
they form a part. Under any other theory we must suppose
variations to be caused by changes in the molecular composi-
tion of the idioplasm as a whole, and no writer has shown,
even in the most approximate manner, how particulate inheri-
tance can thus be conceived.

Based upon this conception two radically different theories
of development have recently been propounded. The first of

these the so-called mosaic theory of Roux and Weismann,

which forms the subject of this lecture — is based upon the
assumption that the cause of differentiation lies in the nature
of cell-division. Karyokinesis is conceived as qualitative in
character in such wise that the idioplasmic germs are sifted
apart, and cells of different prospective values receive their
appropriate specific germs at the moment of their forma-
tion. The idioplasm therefore becomes progressively simpler
as the ontogeny goes forward, except in the case of the germ-
cells ; these retain a store of the original mixture ("germ-
plasm" of Weismann). Every cell must therefore possess an
independent power of self-determination inherent in the specific
structure of its idioplasm, and the entire ontogeny is aptly
compared by Roux to a mosaic-work ; it is essentially a whole
arising from a number of independent self-determining parts,
though Roux qualifies this conception by the admission that
the self-determining power of the cell is capable in some
measure, of modification, through interaction with its fellows
( <' correlative differentiation " ).

THE MOSAIC THEORY OF DEVELOPMENT. 5

In the hands of Weismann this theory attains truly colossal
proportions. The primary germs or units (which he calls
" biophores " ) are aggregated to form "determinants," the
determinants to form "ids," and the ids to form " idants,"
which are identified with the chromosomes of the ordinary
karyokinetic figure. Upon this basis is reared a stately group
of theories relating to reproduction, variation, inheritance and
regeneration, which are boldly pushed to their utmost logical
limit. These theories await the judgment of the future.
Brilliantly elaborated and persuasively presented as they are,
they do not at present, I believe, carry conviction to the minds
of most naturalists, but arouse a feeling of scepticism and
uncertainty; for the fine-spun thread of theory leads us little
by little into an unknown region, so remote from the terra fi mm
of observed fact that verification and disproof are alike impos-
sible.

In its original form the mosaic theory has, I believe, received
its death-blow from the facts of experimental embryology,
though both Roux and Weismann still endeavor to maintain
their position. It is rather curious that the very line of
research struck out by Roux, by which he was led to the
mosaic theory, should in later years have ended in a view dia-
metrically opposed to his own. In 1888 Roux succeeded in
killing (by puncture with a heated needle) one of the first two
blastomeres of the segmenting frog's ^^^. The uninjured
blastomere continued its development as if still forming a part
of an entire embryo, giving rise successively to a half-blastula,
half-gastrula, and half-tadpole embryo, with a single medullary
fold. Analogous results were reached by operation upon four-
celled stages. It was this result that led Roux to compare the
development to a mosaic-work, asserting that " the development
of the frog-gastrula, and of the embryo immediately derived
from it is, from the second cleavage onward, a mosaic-work,
consisting of at least four vertical independently developing
pieces." Roux himself, however, showed that in later stages
the missing half (or fourth) is perfectly restored by a process
of "post-generation," which begins about the time of the
formation of the medullary folds — a result which, in itself,

6 BIOLOGICAL LECTURES.

really contradicts the mosaic hypothesis ; for the course of
events in the uninjured blastomere, or its products, is radically
altered by changes on the other side of the embryo.

A more decisive result was reached in 1891 by Driesch, who
succeeded, in the case of Echinus, in effecting a complete sepa-
ration of the blastomeres by shaking them apart. A blastomere
of the 2-celled stage, thus isolated, gave rise to a perfect but
half-sized blastula, gastrula, and Pluteus larva ; an isolated
blastomere of the 4-celled stage produced a perfect dwarf gas-
trula one-fourth the normal size. Even in this case, however,
the earliest stages of development (cleavage) showed traces of
the normal development, the isolated blastomere segmenting,
as if it were a half-embryo, and only becoming a perfect whole
in the blastula stage. In the following year, however, the
writer repeated Driesch's experiments in the case of Amphi-
oxiis (the egg of which is extremely favorable for experiment),
and found that in this case there is, as a rule, no preliminary
half-development whatever. The isolated blastomere behaves
from the beginning like an entire ovum of one-half or one-
fourth the normal size.

It is quite clear that in AmpJiioxiis the first two divisions of
the ovum are not qualitative, as the mosaic theory assumes,
but purely quantitative ; for the fact that each of the two or
four blastomeres may give rise to a perfect gastrula proves that
all contain the same materials. Nevertheless, in the normal
development, these cells give rise to different structures — /. c,
they have a different prospective value — from which it follows
that, in this case at least, differentiation is not caused by quali-
tative cell-division, but by the conditions under which the cell

develops.

These facts are obviously a serious blow to the mosaic
theory, and the efforts of Roux and Weismann to sustain their
hypothesis in the face of such evidence only serve to emphasize
the weakness of their case. In order to explain the facts of
post-generation — i.e., the capability of isolated blastomeres
to produce complete embryos — both Roux and Weismann are
compelled to set up a subsidiary hypothesis, assuming that
during cell-division each cell may receive, in addition to its

THE MOSAIC THEORY OF DEVELOPMEXT. 7

specific form of idioplasm, a portion of unmodified idioplasm
afforded by purely quantitative division. This unmodified
idioplasm ("accessory idioplasm" of Weismann, or in some
cases "germ-plasm"; "post-generation or regeneration idio-
plasm " of Roux) remains latent in normal development which
is controlled by the active specific idioplasm. Injury to the
ovum — c. g., mechanical separation of the blastomeres — acts
as a stimulus to the latent idioplasm, which thereupon becomes
active, and causes a repetition of the original development.
By assuming a variable latent period following the stimulus,
Roux is able to explain the fact that regeneration takes place
at different periods in different animals.

Considered as a purely formal explanation this subsidiary
hypothesis is perfectly logical and complete. A little reflection
will show, however, that it really abandons the entire mosaic
position, by rendering the assumption of qualitative division
superfluous; and, aside from this, its forced and artificial char-
acter, places a strain upon the mosaic theory under which it
breaks down. Both of the two fundamental postulates of the
modified theory — vi::., qualitative nuclear division, and accessory
latent idioplasm — are purely imaginary. They are complicated
assumptions in regard to phenomena of which we are really
quite ignorant, and they lie at present beyond the reach of
investigation. The "explanation" is, therefore, unreal; it
carries no conviction, and no real explanation will be possible
until we possess more certain knowledge regarding the seat of
the idioplasm (which is entirely an open question), and its
internal composition and mode of action (which is wholly
unknown). In the meantime we certainly are not bound to
accept an artificial explanation like that of Roux, however
logical and complete, unless it can be shown that the phenomena
are not conceivable in any other way.

We turn now to a brief consideration of opposing views,
among which I ask attention especially to those of Driesch and
Hertwig. In common with Kolliker and many other eminent
authorities, these authors insist that cell -division is not quali-
tative but quantitative only, and hence is not, per sc, a cause

8 BIOLOGICAL LECTURES.

of differentiation, for there is no sifting apart of the idioplasmic
units, but an equal distribution of them to all the cells of the
body. In other words, the cleavage of the ovum does not effect
an analysis of the idioplasm into its constituent elements, but
only breaks it up into a large number of similar masses. Dif-
ferentiation follows upon cell-division, is caused by the inter-
action of the parts of the embryo, and the character of the
individual cell is determined by its environment — /. e., by its
relation to the whole of which it forms a part. "The ^gg,''
says Hertwig, " is an organism, which multiplies by division
to form numerous organisms equivalent to itself, and it is
through the interactions of all these elementary organisms, at
every stage of the development, that the embryo, as a whole,
undergoes progressive differentiation. The development of a
living creature is therefore in no wise a mosaic work, but, on
the contrary, all the individual parts develop in constant rela-
tion one to another, and the development of the part is always
dependent on the development of the whole." There is there-
fore no necessary relation between the individual blastomeres
of the segmenting ovum and the parts of the adult body to
which they give rise ; this relation is purely fortuitous. The
most extreme statement of this view appears in the writings of
Pfliiger and Driesch. " I would accordingly conceive," says
Pflu"er, '• that the fertilized <i^ig has no more essential relation
to the later organization of the animal than the snowflake has
to the size and form of the avalanche which, under appropriate
conditions, may develop out of it." Driesch, writing ten years
later ('89), is no less explicit. He regards the blastomeres of
the lichiiuis embryo, as "composed of an indifferent material,
so that they may be thrown about at will, like balls in a pile,
without the least impairment of their power of development."
The ultimate fate of any particular blastomere is determined
by its relative position in the mass ; that is (to quote his own
striking aphorism), "their prospective value {Bcdcutung) is a
function of their location " (cf. His).

We shall presently return to these more extreme views, but
1 will here point out one all-important point which is definitely
established by the work of Driesch and other experimentalists,

THE MOSAIC THEORY OF DEVELOPMENT. 9

and which is accepted by all opponents of the mosaic theory,
namely, that the cell cannot be regarded as an isolated and
independent unit. The only real unity is that of the entire
organism, and as long as its ce;lls remain in continuity they
are to be regarded, not as morphological individuals, but as
specialized centres of action into which the living body resolves
itself, and by means of which the physiological division of
labor is effected. This view, at which a number of embryolo-
gists have independently arrived, has been most ably urged by
Whitman, in one of the lectures of this volume, though in
connection with a general conception of development peculiarly
his own.

It is important not to lose sight of the fact that Hertwig,
no less than Roux and Weismann, conceives the idioplasm
(which he would locate in the cell-nucleus) as an aggregate of
units ( " idioblasts " ) which severally correspond to the heredi-
tary qualities of the organism ; and since cell-division is not
qualitative, every cell must contain the sum total of the heredi-
tary character of the species. Differentiation is conceived by
Hertwig (following de Vries) as the result of physiological
changes in the idioblasts, some of which remain latent, while
others become active, and thus determine the specific character
of the cell, according to the nature of the active idioblasts. In
regeneration such of the latent idioblasts are called into action
as are necessary to carry out the regenerative process.

We have found good reason for the conclusion that the
mosaic theory cannot, in its extreme form, be maintained. It
remains to inquire whether the extreme anti-mosaic conception
rests upon a more secure foundation, and whether the mosaic
hypothesis may not contain certain elements of truth. I have
elsewhere more than once pointed out that the views of Hert-
wig and Driesch have received a strong bias, from the circum-
stance that the discussion has hitherto been confined mainly
to the echinoderm ^%^, which shows no visible differentiation
in the cells until a relatively late period (i6-celled stage).

The whole question assumes a somewhat different aspect
when we regard such highly differentiated types of cleavage as

lO BIOLOGICAL LECTURES.

we find, for example, among the annelids ; and I would ask
attention for a moment to the case of Nereis, which is, at
present, the best known form. Differentiation here begins at
the very first cleavage (which is conspicuously unequal), and
it becomes more pronounced with every succeeding division.
The median plane is marked out at the second cleavage ; at
the third the entire ectoblast of the trochal and prae-trochal
reo-ions is formed ; at the fourth the material for the entire
"ventral plate" (including the ventral nerve-cord and the seta-
sacs) is segregated in a single cell, that for the stomodaeum in
three cells ; the iifth cleavage completes the ectoblast, and by
the 38-celled stage the germ-layers are completely segregated
(the mesoblast in a single cell) and the architecture of the
embryo is fully outlined in the arrangement of the parent
blastomeres, or protoblasts.

We do not know whether, in this case, the first two blasto-
meres are qualitatively different, though there may be some
ground for holding that they are, from the fact that the larger
of the two contains a relatively larger proportion of protoplasm
than the smaller.^ But in any case their difference in size
renders it impossible that they should play interchangeable
parts in the cleavage. The entire later development is, how-
ever, moulded upon the 2-celled stage, every blastomere having
a definite relation to it and a definite morphological value. The
development is a visible mosaic-work, not one ideally conceived
by a mental projection of the adult characteristics back upon
the cleavage stages. The principle of " organbildende Keim-
bezirke " has here a real meaning and value, and this would
remain true even if it should hereafter be shown that both of
the first two blastomeres of Nereis, if isolated, could produce a
l)erfect embryo.

It is clear, from such a case, that the more extreme views
of Driesch and Hertwig cannot be accepted without consider-
able modification. It seems to me, however, that they may be
modified in such a way as, without sacrificing the principle of
epigenesis for which they contend, to recognize certain ele-

1 All my attempts to separate these blastomeres by shaking have thus far been
unsuccessful.

THE MOSAIC THEORY OF DEVELOPMENT \\

ments of truth in the mosaic hypothesis ; and I will attempt
to indicate this modification by a comparison between Amphi-
oxns and Nereis. In the case of AmpJiioxus we have the clear-
est evidence that differentiation is, in a measure, dependent
upon the relation of the cell to the whole of which it forms a
part. The first visible differentiation in this case is at the
third cleavage, which consists in an unequal division of each
of the four blastomeres, so as to give rise to four micromeres
and four macromeres, the former giving rise to ectoblast only,
while the latter give rise to entoblast
and mesoblast as well {Diagram I).
If, however, the blastomeres of the
4-celled stage be separated (shaken
apart) the course of events is entirely
changed ; for in this case each divides
equally, not unequally, and ultimately
gives rise to a complete quarter-sized Uiagrvm I

dwarf, instead of one-quarter of a

normal embryo, as it would have done under ordinary cir-
cumstances. The character of the fourth cleavage is here
directly or indirectly determined in each cell by the relation
of the cell to its fellows ; and if this is true of any one
stage of the ontogeny, a very strong presumption is created
that it is true of all — that, in the process of progressive
differentiation occurring in the course of every animal on-
togeny, the character of each step is determined by the
condition of the entire organism. The ontogeny is, in other
words, a connected series of interactions between the
various parts of the embryo, in which each step estab-
lishes new relations, through which the following step is
determined. The character of the series, as a whole, depends
upon the first step, and this in turn upon the constitution of the
original ovum. In AinpJiioxtis differentiation proceeds slowly,
the earlier blastomeres show no appreciable divergence, and the
first stages show no trace of a mosaic work. In Nereis, on the
other hand, a mosaic-like character appears from the begin-
ning, because of the inequality of the first cleavage, which
conditions the entire subsequent development through the

12

BIOLOGICAL LECTURES.

peculiar relations established by it. The cause of the inequa-
lity must lie in the undivided ovum, and a study of the first
cleavage-spindle shows that the inequality is unmistakably
foreshadowed before the least outward sign of division appears ;
for the asters at the spindle-poles are conspicuously unequal
in size, the larger aster corresponding with the future larger
cell (Diagram II). This difference is not connected with any

determinable mechanical
conditions ; for the centro-
somes lie nearly equidistant
from the membrane (the
egg is spherical), and the
deutoplasm shows no per-
ceptible inequality in hori-
zontal distribution. The
conclusion seems unavoid-
able that the differentiation
in size is caused by a specific
form of activity in the
cytoplasm (or archoplasm),
occurring prior to cell-division. But if a differentiation in
size may have such an origin, we may fairly argue that other
differentiations may likewise precede cell-division, and that
in such cases the division may be, in a sense, qualitative.

It seems to me, that in these considerations we may find, in
some measure, a reconciliation between the extremes of both
the rival theories under discussion — that we may consistently
hold with Driesch that the prospective value of a cell may be
a function of its location, and at the same time hold with Roux
that the cell has, in some measure, an independent power of
self-determination due to its inherent specific structure. Such
a view is only possible, however, if we regard the specific struc-
ture of the cell to have arisen not through the segregation and
isolation within its boundaries of special idioblasts or germ-
substances, that have been sifted out by qualitative division,
but through a physiological specialization (as de Vries oxA
Hertwig insist) that may have taken place before, during, or
after cell-division, according to circumstances. If differentia-

DlAGKAM II.

THE MOSAIC THEORY OF DEVELOPMENT. 13

tion precedes or accompanies division, the latter process may
be in a sense qualitative. If it follows, division will be purely
quantitative, and in such a case we may rightly speak of differ-
entiation as a result of cellular interaction. The segmentation
of the ^%^ presents more or less of a mosaic-like character,
according to the period at which differentiation appears, and
the rate at which it proceeds, as expressed in limitations of
the power of development in the individual blastomeres, and
their differences in size and structure.

The general interpretation of development which I have thus
endeavored to sketch will be found to differ widely in some
respects from that set forth in one of the subsequent lectures
of this volume, from which, through Professor Whitman's
courtesy, I am enabled to quote. Whitman argues that
"cell-orientation may enable us to infer organization, but to
regard it as a measure of organization is a serious error."
"The question as to the presence of organization," he says,
" is not settled by the form of cleavage. Eggs that admit of
complete orientation at the first or second cleavage, or even
before cleavage begins, are commonly supposed to reflect
precociously the later organization, while eggs in which such
early orientation is impossible are supposed to be more or less
completely isotropic and destitute of organization. When the
region of apical growth is represented by conspicuous telo-
blasts, the fate of which is seen to be definitely fixed from
the moment of their appearance, we find it impossible to doubt
the evidence of organization, or ' precocious differentiation ' as
it is conventionally called. When the same region is composed
of more numerous cells, among which we are unable to distin-
guish special proliferating cells, we lapse into the irrational
conviction that the absence of definitely orientable cells means
just so much less organization."

It would be manifestly out of place to enter here upon any
of the interesting discussions suggested by the passage just
quoted, and I will therefore only add that Professor Whitman's
position seems to me to rest upon a special and peculiar use
of the word "organization," and that his view leads to a denial
of the principle of epigenesis. No one would maintain that

14 BIOLOGICAL LECTURES.

the living Q:g^ is "destitute of organization," but neither can
any one maintain that the egg-organization is identical with
that of the adult. Development is essentially a transformation
of one form of organization into another along the path of
cell-division and cell-differentiation ; and it is undeniable that
the adult form of organization is thus expressed earlier in some
cases than in others — for example, in the segregation of the
germ-layers in the polyclade, as compared with the annelid or
gasteropod. We are still profoundly ignorant of the nature
and causes of differentiation, and of its precise relation to
cell-formation ; and the question is probably not yet ripe for
discussion. It is, however, impossible to maintain that differ-
entiation in the Metazoa is entirely independent of cell-forma-
tion, when we recall the multitude of cases in which the lines
of differentiation coincide with cell-boundaries.

SECOND LECTURE.

THE FERTILIZATION OF THE OVUM.

E. G. CONKLIN.

In the history of the biological sciences perhaps no problem
has received more attention than the fertilization of the ovum.
The first important advance in our knowledge of this phe-
nomenon within recent years was made by O. Hertwig^ about
twenty years ago. He showed that after a period of prepara-
tion in which the egg cell extrudes two small corpuscles, the
polar bodies, the nuclei of the male and female cells fuse to
form the first or segmentation nucleus of the new organism.
He therefore held that the process of fertilization consisted
essentially in the fusion of two nuclei coming from different
individuals.

This idea has dominated biology for the past decade, and it
is the generally accepted view to-day. In his recent work, Die
Zelle imd die Gewebe, Hertwig says (p. 220), "The nuclear sub-
stances which are derived in equal quantities from two different
individuals, are the only essential substances upon whose union
the act of fertilization depends ; they are the real fertilization
materials. All other substances, such as protoplasm, yolk,
nuclear sap, etc., have nothing to do with fertilization as such."
It is well known that Weismann in his various essays and
works upon heredity has expressed himself as fully satisfied
that the essence of fertilization consists in the fusion of the
nuclei of the ovum and spermatozoon. In fact his whole
theory is to a very large extent founded upon this fundamental
assumption that fertilization is essentially a nuclear process.
And quite recently Boveri,^ after a full discussion of the ques-

1 O. Hertwig, Beitrage zur Kenntniss der Bildung, Befruchtung und 'rheilung
des thierischen Eies. Morphol. Jahrbilcher, 1875, 1877, 1878.

2 Boveri, Befruchtung. Ergebiiisse der Aiiatoviie 71. Entwick., 1892.

1 6 BIOLOGICAL LECTURES.

tion, concludes with these words :^ "Their union [that of the
Q%% and sperm nucleus] is not the condition but the goal of
fertilization, and in this sense the statement is true to-day in
which O. Hertwig summed up the results of his first funda-
mental investigations, that ' the essential thing iji fertilization is
the union of egg and spcnii nucleus' "

It is only within the most recent times that a different view
has arisen, and for the sake of clearness I will sketch briefly
the rise of the idea that fertilization is not a purely nuclear
phenomenon, that it does not consist simply in a union of
nuclei coming from different individuals, but rather, as it seems
to me, in a union of all the essential parts of the reproductive
cells, cytoplasm as well as nuclei.

In 1873 Hermann FoP described in the eggs of a jelly-fish
two star-shaped figures or asters at the two poles of the
nucleus, and one year later E. Van Beneden ^ described a
polar corpjtscle as present in the cytoplasm during the karyoki-
netic division of the nucleus in some small parasitic organisms,
the Dicyemidae ; but it was certainly not until a much later
date that anything satisfactory was known of these bodies.

In 1887, only six years ago. Van Beneden'* in his work on
the fertilization of the ^^g of Ascaris, a thread-worm inhabit-
ing the intestine of the horse, gave a very minute account
of two granular bodies, the sphtres attractives which he
believed to be present at all times in the cytoplasm of the cell.
He described each sphere as consisting of a central refractive
body, the cejitral corpuscle, around which was a clear space, the
tnedullary zone, which in turn was surrounded by a deeply
staining granular area, the cortical zone, Fig. i, A and C.
Although he regarded these spheres as permanent organs of
the cell, he did not know how they originated in the Q.%g under-
going fertilization, but he thought that tlie two spheres appeared
simultaneously in the egg as newly formed structures, and he

1 Loc. cit., p. 433.

2 Hermann Fol, Die erste Ijitwicklung ties (leryonideneies. Jenaische Ziit-
schrift, 1873.

3 E. Van lieneden, Recherches sur les Dicyemides. Ihill. Acad. roy. Bcti^., 1S74.
* Van licneden et Xeyt, Nouvelles Recherches sur la Fecondation et la Division

mitosique chez I'Ascaride megalocephale.

THE FERTILIZATION OF THE OVUM. I 7

believed that they were derived " from the division of the q.^%
nucleus after it had given rise to the second polar body" (p. 60).
As described by Van Beneden, the position of the attraction
spheres at their earliest appearance, is shown in Fig. i A.
They appear together in close proximity to the female pro-
nucleus and at a considerable distance from the male pro-
nucleus. Van Beneden therefore suppbsed that the male
pronucleus had nothing to do with their formation. In later
stages, Fig. i, B and C, the two spheres begin to separate,
the spindle fibres appearing between their central corpuscles
and at the same time the two pronuclei approach each other
and the first cleavage spindle is formed, in large part at least,
from the two attraction spheres.

One year later, 1888, Boveri ^ described these bodies in
the same Qgg, that of Ascaris ; the central corpuscle of Van
Beneden he called the ccntrosouic, and the dark granular sub-
stance surrounding this, which probably corresponds to the
cortical zone of Van Beneden, he named the archoplasDi. The
relation of these parts to each other, and to the pronuclei, is
shown in Fig. i, D, E and F, which are taken from Boveri.
When first seen in the ovum, the male pronucleus lies in the
midst of a mass of granular material, the archoplasm. Later
it moves out of this, and in the place where it first lay a single
highly refractive body, the centrosome, appears. The centro-
some is at first single but later it divides, as shown in E, and
then around each of the centrosomes the archoplasm aggregates
to form two granular spheres. Meanwhile the two pronuclei
enlarge greatly and approach each other while the spindle
fibres are formed from the two spheres of archoplasm. With
regard to the oriirin of the constituents of the archoplasmic
system, Boveri believed that the centrosome was derived from
the spermatozoon, since it first appears in the archoplasm at
the very place previously occupied by the male pronucleus,
while the archoplasm itself, he supposed, came entirely or at
least in large part from the egg cell.^

1 Boveri, Zellen-Studien, Heft 2, Die Defruchtung und Theilung des Eies von
Ascaris megalocephala, 188S.
- Loc. cit., p. 167.

1 8 BIOLOGICAL LECTURES.

Two years ago Hermann Fol ^ published a preliminary account
of the fertilization of the egg of a sea-urchin, in which he com-
municated the new and remarkable fact that each of the sexual
cells, ovum as well as spermatozoon, contains a kinetic center
or centrosome, which he called respectively the ovoccntcr and
the spcrmoccntcr. When the spermatozoon enters the ovum
the spermocenter precedes the nucleus of tlie male cell,
Fig. I G, and finally reaches a point on the surface of the
female pronucleus opposite the ovocenter ; then the male pro-
nucleus comes to lie closely against the surface of the female
pronucleus, though it does not intimately fuse with it. The
two centers then divide. Fig. i H, and the half-centers push-
ing apart move in opposite directions around the cleavage
nucleus until one half of the ovocenter meets half of the
spermocenter at a point about 90° from that originally occu-
pied by the centers, Fig. i I. By the fusion of these half-
centres, one derived from the ovocenter the other from the
spermocenter, the astroccntcrs are formed. Around each of
these astroccntcrs there is formed a clear space, the asirococl,
which probably corresponds to the medullary zone of Van
Beneden, as the astrocenter corresponds to the central cor-
puscle, while the astrocoel is surrounded by a zone of astral
radiations, which is probably the cortical zone of \^an Beneden
and the archoplasm of Boveri. From these facts regarding
the formation of the astrocenters, Fol concluded that " fertiliza-
tion consists not only in the adding together of two pronuclei
derived from individuals of different sexes, but also in the
fusion of four half-centers derived from the father and the
mother into two new bodies, the astrocenters." -

In November of the same year, 1891, (iuignard''^ published
a most admirable account of the process of fertilization in some
of the flowering plants. He showed that the male pronucleus,
which is brought into close proximity to the female pronucleus
by the growth of the pollen tube, is always i)receded by two

1 Hermann l-Ol, Die C"entren(jii;ulrille eine neiie ICpisode aus der ISofruchtungs-
geschichte. Aiiat. Anzeiger, May, 1S91.

2 Loc. cit., p. 274.

8 Guignard, Nouvelles Etudes siir la I'"t'condation. Aniiaiis i/c's sciences iiatur.
Tom. 14, Po/iJiii(/i(c, 1S91.

THE. FERTILIZATION OF THE OVUM.

19

Fig. 1. — Diagrams showing the process of fertilization according to different
authors. The first row (A, B and C), for Ascaris, according to Van Beneden ;
the second row, the same form, according to Boveri ; the third row for an Echmid,
according to Fol ; the fourth for Lilium, according to Guignard.

20 n/OLOGICAL LECTURES.

bodies, the spJicrcs directrices, which are the equivalents of
Van Beneden's spJiars attractivcs and Fol's asters ; two of
these spheres are also found in contact with the female pro-
nucleus, Fig. I K. The two spheres which precede the male
pronucleus join those which surmount the female pronucleus
in such a way as to form two couples, each of which is com-
posed of one element derived from the male cell, the other
from the female cell. When the pronuclei come in contact,
the two couples diverge until they come to lie at opposite poles
of the nuclei. Fig. i L. Then the elements of each couple
fuse together into a single sphere with a single central cor-
puscle, Fig. I M, and from these spheres the first cleavage
spindle is formed. Guignard concludes, therefore, that fertili-
zation is not a purely nuclear phenomenon. ." It consists not
only in the union of two nuclei of different sexual origin, but
also in the fusion of two protoplasmic bodies whose essential
elements are the spheres directrices of the male cell and of the
female cell. Even if the nuclei are of great importance in the
transmission of hereditary properties, the permanent presence
of spheres directrices in the sexual and somatic cells, and above
all their fusion at the moment of fecundation, oblige us to
assign to the protoplasm the primordial role in the accom-
plishment of this phenomenon. This fusion appertains to
the very essence of fertilization ; it is necessary for the
formation and subsequent evolution of the egg." ^

More than a year ago (July, 1892), I found that the eggs of
one of our marine Gasteropods, Crepiditla pUxiia, offered excep-
tional advantages for the study of the phenomena of fertiliza-
tion. In this egg, and that of other species of the same genus,
I had been able to trace the cell-lineage to more than one hun-
dred cells, and last summer, with more favorable material and
better methods, I was able to follow in surface preparations, as
well as in sections, the movements of the male and female pro-
nuclei, and what is much more important, the whole history of
the asters'^ from the time the first polar body is formed and the

' Loc. cit., p. 276.

2 Kor these permanent organs of the cell, known l)y various authors as the
"sp/iires attractives" '^ sp/ih-es i/iriitrhes,'"' " archoplasmic bodies," "periplasts,"

THE FEKTILIZATIOX OF THE OVUM.

21

spermatozoon enters the egg until a late stage in the cleavage
of the fertilized ovaim. In the main, my observations on the
fertilization confirm those of Fol, concerning which a good
deal of doubt has been expressed by some authorities, though
in some respects they differ from these and resemble more
closely the results obtained by Guignard.

Since the aster plays so important a part in the process of
fertilization, it will be well to begin with a description of this
structure. Every aster undergoes periodical changes in form
and size as well as constitution. When it has reached its
largest size, which is just before it divides, it is a spherical or
ellipsoidal body, almost as large as the nucleus. Fig. 2. It
has a very definite out-

line from which radiating
rows of granules or micro-
somes can be traced to all
parts of the cell. The
sphere itself consists of
an outer, d,a,rkly granular
zone and of a central clear
area. The granules of
the outer zone can in no
way be distinguished from
the microsomes scattered „ <_• • ^ r , ^ r

ric. 2. — Section of one of the first four
throughout the cell ; their micromeres of C. plana showing the structure
general appearance is very of the aster and its relations to other parts of
similar and they stain in ^ ^ '^'^ •

the same way. Moreover, at certain stages in the history
of the aster it loses its definite outline, astral radiations
proceed from it in every direction, and the granules of
which it is composed become confluent with the microsomes

"para-nuclei," etc., I have decided to employ the name "aster," first used by
Fol, I belie\'e. This name has the advantage of brevity, simplicity and accuracy,
which cannot be said of the others. Some of these names are not only unwieldy,
but absolutely misleading. For e.xample, the spli'eres attraclives have tlie function
of repulsion as well as attraction ; the spheres dircclriccs do not, in all cases at least,
direct the nuclear division, and the same may be said of the archoplasm or "con-
trolling" plasm. The exact connotation of the words "periplast" and "para-
nucleus" is so doubtful that they cannot safely be used.

22 BIOLOGICAL LECTURES.

of the cell ; at the same time the central clear area disappears.
This occurs in the formation of every nuclear spindle ; in the
later stages of the nuclear division, when the central portion
of the spindle begins to disappear, the granules which were
distributed along the radiating fibres are gathered together
in such a way that one or more rows of them are pressed
closely together to form the definite boundary of the aster,
while within this boundary the granules are less compactly
arranged. This granular .zone, with its radiations, corres-
ponds, I believe, to the cortical zone of Van Beneden and
the archoplasm of Boveri.

The central clear area probably corresponds to the medullary
zone of Van Beneden and the astrocoel of Fol, and in speaking
of it hereafter I shall employ the latter name. The astrocoel
always contains a large number of irregularly scattered granules,
which are considerably larger than those of the outer zone but
are not peculiar in any other respect. They show the same
micro-chemical reactions as the microsomes, and at an early
stage in the history of each aster they are closely connected
with the granules of the outer zone. After the nuclear spindle
has been formed these granules disaj^pear, and in their
place is found, at each pole of the spindle, a darkly staining
body much larger than any one of the central granules.
This is doubtless the central corpuscle of Van Beneden or
centrosome of Boveri, and I cannot doubt that the numerous
central granules represent a fragmented or scattered coitro-
somc.

The structure of the outer granular zone of the aster, its
micro-chemical reactions, and particularly its method of growth,
seem to me to indicate plainly that this portion of the aster
is merely a part of the general cytoplasm temporarily modified
or differentiated for a particular function. Regarding the
astrocoel and centrosomes there is more doubt, but I believe
that the evidence is clearly in fa\'or of the view recently
expressed by Watasc,^ that these structures are also a part
of the cytoplasm. Whatever the ultimate origin of the
centrosomes may be, there is no doubt that in Crepidula they

1 Watase. Homology of the f'entrosome. Jour. Morpli.. Vol. 8, No. 2.

THE FERTILIZATION OF THE Ori'M.

23

do not go back into the nucleus after every division, as
Brauer ^ asserts is the case in Ascaris. It therefore seems
highly probable that the entire aster is a cytoplasmic struc-
ture, temporarily modified or differentiated for the purpose
of contraction and expansion, whose chief function in the
reproductive cells is to bring the pro-nuclei together, accom-
plish nuclear division, and move the nuclei from place to place
in the resulting cells.

To return to the process of fertilization : the spermatozoon
usually, though not invariably, enters the ovum near the vege-
tal pole. I have not observed it in the actual process of enter-
ing, though I have seen it immediately afterward. In such
cases it consists of a small conical or sometimes fusiform
nucleus, surrounded by a clear non-granular area, Fig. 3. At
this stage the sperm nucleus
consists entirely of chromatin
closely packed together; there
is no nuclear sap and no aster
is visible, though, perhaps, the
clear area surrounding the
nucleus may be taken as an
indication of the presence of
such a body. In Fig. 3 the
^gg nucleus is shown in the
process of division preparatory
to the formation of the first -r^,,, , .^ ., r .• r .,

\ ic. 3. — L. pUDia ■ formation of the
polar body. There are two first polar body ; at the left the spemui-
CentrOSOmeS at the upper pole tozoon has just entered the ovum.

of the spindle, though but one is to be seen at the lower pole.
The centrosome at the upper pole has divided thus early,
preparatory to the division of the chromatin of the first
polar body. This division occurs soon after the polar body
is formed. The surface of the Qgg is indented over the
upper pole of the spindle, thus indicating, as it seems to me,
that the astral fibres are here attached to the surface and are
drawing it in by their contraction.

1 Brauer, Zur Kenntniss der llerkunft des Centrosomes. Biol. Centralblatt,
Bd. 13, Nos. 9 and 10.

24 BIOLOGICAL LECTURES.

The spermatozoon usually enters the ovum at about the same
time that the first polar body is being formed, though in a con-
siderable number of eggs it does not enter until after both
polar bodies have been extruded. Soon after its entrance, the
sperm nucleus begins to move toward the ^^^ nucleus. This
motion is quite slow, several hours (four to eight) being neces-
sary to bring the two nuclei together ; it i.s, therefore, possible
to find almost every stage in this process in eggs which have
been fixed and stained. During the whole of this journey
toward the egg nucleus, the sperm nucleus continually increases
in size ; but before this nucleus shows any appreciable enlarge-
ment, and when it is removed from the egg nucleus by almost
the whole diameter of the ovum, the sperm aster appears as a
granular sphere, considerably larger than the sperm nucleus,
and lying immediately in advance of it. Fig. 4. Throughout
the approach of the two })ronuclei, the sperm aster precedes
the sperm nucleus, and, as I believe, actually leads it to the
egg nucleus.

As already explained, Boveri believes that the centrosome
of the new organism is derived exclusively from the sperma-
tozoon. In his latest work (already referred to) he says that,
in the case of Ascaris, there is neither centrosome nor aster
present in the formation of the two polar bodies, although
they were present at an earlier stage in the oogenesis ; he
therefore concludes that in this case the centrosomes of the
segmentation spindle, which forms later, must be derived
exclusively from the sperm centro.some. Vejdovsky^ has
reached the same conclusion with regard to one of the anne-
lids, Rhinchelmis. He says, regarding l^\)rs communication
relative to the ovocenter, that no one has hitherto seen such
a body in connection with the female pronucleus, and that he
conceives it to be the scarcely functional remnant of the
Eikcnipcriplasic, or egg aster. " It is therefore," he says,
"questionable to assume the presence of an ovocenter in
order to make a general law that in fertilization not only the
pronuclei, but also the halves of the ovocenter and spermo-

1 Vejdovsky. l^emerkungen zur Mitteihing II. Fol's "Contribution a I'liistoire
de la fecondation." Auat. Anzciger, Bd. 6, No. 13.

THE FERTILIZATION OF THE OVUM.

25

center unite. The facts observed in the case of Rhinchehnis
speak against Fol's theory."

In the face of the conclusions of these well-known investi-
gators, it is interesting to find, in the case of the Crepidula
egg, a well marked centrosome and surrounding parts of the
aster present at each pole of the spindle in the formation of
each of the polar bodies ; and immediately after the second
polar body has been extruded, and while the sperm nucleus
and aster are still far removed from the egg nucleus, a large
and distinct aster can be seen in contact with this nucleus.
This egg aster lies below the egg nucleus, and usually slightly
to one side of the chief axis of the ovum, as shown in Fig. 4.

Fig. 4. — Ovum of C. plana, side view; FiG. 5. — Ovum of C. plana seen from
the asters are sliown in dotted outline, upper pole ; in tliis and the following
the clear spheres with dark centers, at figures the male aster and nucleus lie to
the upper pole, are the two polar bodies, the left, the female to the right. First

contact of the two asters.

It is at first much larger than the sperm aster, and in fact
remains larger until it enters upon "/cr MarcJic dc la Quadrille T
The sperm nucleus always approaches the ^g^ nucleus from
below and in such a way that the sperm aster is directed
toward the egg aster. Fig. 4. The force which draws the two
pronuclei together seems to exist between the two asters rather
than between the pronuclei. Accordingly, in the progress of
the sperm nucleus toward the Q^g nucleus, the asters first
come in contact. Fig. 5. In all movements of the nucleus, the
latter appears to be passive while the asters are active. This

26

BIOLOGICAL LECTURES.

principle is illustrated throughout the whole history of the
cleavage ; whenever the nucleus is moved from one position to
another in the cell it is preceded by its aster. The method by
which the asters draw the two pronuclei together is, I believe,
by the formation, attachment and contraction of the astral or
archoplasmic fibrils. In this connection it is interesting to
contrast the methods by which the male and female cells
approach each other before and after the spermatozoon has
reached the ovum. In the case of Crepidula, as in most
other forms, the spermatozoon moves toward the ovum by the
lashing from side to side of a long thread-like flagellum. As
soon, however, as the sperm enters the ovum this flagellum is

Fic. 6. — Ovum of C. plana from FiG. 7. — Separation of the two

upper pole; first contact of the two asters; the polar bodies lie immediately
pronuclei. over the female pronucleus.

lost in most cases, and the rest of the progress toward the egg
nucleus and aster must be accomplished in some other way.
This, as just said, seems to be done by the formation and con-
traction of astral fibers. This movement of the sperm cell
within the ovum is the result of protoplasmic contractility
no less than is the movement of the spermatozoon outside of
of the nucleus, operating, however, in a slightly different way.
After the two asters have come in contact, they move slightly
to one side, remaining however connected, though individually
distinct, and the two pronuclei then come together. Fig. 6.
Even at this time, the sperm aster and nucleus are usually a

THE FERTILIZATION OF THE OVUM.

27

little smaller than those of the egg cell, and they frequently
remain slightly smaller as long as they can be distinguished.
In cases where there is no appreciable difference in size
between the two pronuclei, the one may be distinguished from
the other, as long as they remain distinct, by the position of
the polar bodies which lie directly over the female pronucleus.
After the two pronuclei have met, the two asters begin to
move apart. They continue to separate, moving around the
appressed nuclei, until they lie at opposite poles, P"ig. 7. The
sperm aster now lies on the outer side of the sperm nucleus,
and the ^gg aster on the outer side of the Q.^g nucleus ; it is
thus seen that the position which the asters occup)' relative to

Fig. 8. — The halves of the male and FiG. 9. — The halves of the female
female asters about to unite at the aster at the poles of the pronuclei ; the
poles of the pronuclei. male aster still undivided.

the pronuclei, is just the reverse of that which obtained previ-
ous to the meeting of the two pronuclei. It must also be
allowed, I think, that the function now exercised by the asters
must be the reverse of that which prevailed before the pro-
nuclei met. Then, by active contraction, they drew the two
pronuclei together; now, by active expansion, they diverge, move
to opposite poles, and press the pronuclei together. This func-
tional alternation of contraction and expansion, or perhaps
better, attraction and repulsion, is manifest not only during
fertilization, but throughout the entire process of cleavage.
The contraction can be seen in the way in which the asters

28

BIOLOGICAL LECTURES.

draw the nuclei from one place to another in the cell, as well
as in the pulling asunder of the chromatic elements of the
nucleus, the expansion in the division of the asters and the
subsequent divergence of the resulting daughter asters, as well
as in the formation of the karyokinetic spindle and the pushing
together of the chromatic elements into the equatorial plate.

After the asters have reached the outer sides of the two pro-
nuclei, each divides into two half-asters, which diverge from
each other until they come to lie at opposite poles of the
nuclei and in the plane of contact between the two. At this
stage, therefore, there is found at each pole of the two pro-
nuclei one-half of the sperm aster and one-half of the Q.^g aster,
Fig. 8. Each of these couples soon fuses into a single aster,
and the two asters thus formed lie at opposite poles of the
first cleavage-spindle, Fig. lo, and from them all the other
asters of the developing ovum are derived.

As an interesting variation of this more usual behavior of
the asters, it should be mentioned that in cases where the
sperm nucleus and aster meet the corresponding parts of the

0.%% cell, while there is yet
considerable disparity in size
between the two, the Q:g^^
aster after having reached its
full size divides, and the two
half-asters pass to the two
poles of the nuclei, while the
sperm aster, during all this
time, remains undivided until
it has reached its full size,
when it divides, and its halves
move around to meet the
waiting liaK'es of the egg
aster. Fig. 9.

With tlie fusion of the half-
asters, one jwrt of the fecunda-
tion, and that a very important one, is completed, although the
two pronuclei may still be recognized as such. In fact, the
boundary line between the egg and the sperm nucleus can be

Fig. 10. — Formation of the first
cleavage-spindle. The half-asters have
fused, but a trace of the nuclear mem
brane remains between the two pro-
nuclei.

THE FERTILIZATION OF THE OVUM. 29

distinguished even after the first cleavage spindle begins to
form, and their chromatin masses remain distinct, Fig. 10,
until the equatorial plate stage.

After the chromatin of the two pronuclei has assumed the
shape of distinct rods, the chromosomes, and before these rods
have been pressed together into the equatorial plate, it is
possible to determine that each pronucleus contains twelve of
these elements. Since these elements are doubled at every
division of the nucleus, it follows that each of the first two
nuclei contains twenty-four chromosomes, twelve derived from
the sperm nucleus and twelve from the ^gg nucleus, and this
number is probably constant for all the nuclei of this species.

It is difficult to define exactly the time at which the two
pronuclei have sufficiently united to be considered a single
element, but perhaps this can be most conveniently located at
the time when the boundary wall between the two vesicular
nuclei disappears, although, as just said, the two masses of
chromatin remain distinct until a somewhat later period. Cer-
tain it is that a fusion of the pronuclei to form a resting scg-
vientation nucleus, as described by Hertwig, does not take
place.

With the union of the pronuclei, the entire process of
fecundation may be considered as ended. So far from being
a purely nuclear phenomenon, it must be evident to any one
who follows the history of the asters that they take an
extremely important part in this process. If we are amazed
at the precision with which the chromatic elements of the
nucleus are divided and distributed, we can be no less astonished
at the wonderful directive influence exercised by the asters
upon the nuclei ; and if it is justifiable to conclude that the
chromosomes have an extremely important function in the
building of the new organism because of the way in which
they are distributed, how is it possible to avoid the same con-
clusion with regard to the asters, which, as we have seen, are
equally divided in a manner not clearly understood into half-
asters, which then fuse in such a way that one-half of each
aster of the new organism comes from the paternal and one-
half from the maternal organism .-*

30

BIOLOGICAL LECTURES.

Hertwig, Boveri and Weismann, as well as a number of other
well-known investigators, assert that the hereditary substance,
by means of which heritable qualities are transmitted from one
generation to another, is contained wholly within the nucleus,
and, speaking more strictly still, within that part of the nucleus
called the chromatin. Since, however, many of the characters
of the cytoplasm are heritable, and in fact are generally the
only characters which are known by observation to be herit-
able, these authorities are compelled to assume that the control
of the cell, if not the actual genesis of all its constituents, is
located wholly within the chromatin. As a matter of fact, it
must be acknowledged that this assumption that the chromatin
makes the cell-body just what it is in point of structure, func-
tion, shape, position and size, does not rest upon observation
but upon supposed theoretical necessities. All these necessi-
ties find their source in the assumption that the nucleus, and
especially the chromatin, is the only bearer of heredity, an
assumption which was wholly justified so long as it was sup-
posed that fertilization consisted merely in the fusion of the
two pronuclei ; but now since it is known that the cytoplasm,
and especially the male and female asters, take a very import-
ant part in the process of fertilization, it seems to me that
such an assumption is wholly unwarrantable.

The spermatozoon does not cease to be a cell the moment it
has entered the ovum. Both its cytoplasm (in the form of an
aster) and its nucleus are represented, and they grow just as a
cleavage or tissue cell does by the assimilation of food material,
which in this case is contained within the egg cell. Although
within the ovum the spermatozoon must be considered a dis-
tinct cell, preserving all its fundamental peculiarities, until that
time when its various constituents lose their identity by fusion
with corresponding parts of the egg cell. While it is known
in several cases that the spermatozoon introduces a nucleus
and an aster, which then fuse with similar parts of the ovum,
it is not known, with one or two exceptions, that any portion
of the general cytoplasm of the male cell is carried into the
ovum. In the case of Ascaris, both Van Beneden and Boveri
agree that a certain part of the cytoplasm of the spermatozoon

THE FERTILIZATION OF THE OVUM.

31

is carried into the eg-g, and is there absorbed, used as food, by
the cytoplasm of the ovum. On the ground of direct observa-
tion, the fusion of the general cytoplasm of the sperm with
that of the ovum can neither be affirmed nor denied in most
cases ; but it is a matter of observation that there is a union
of those portions of the cytoplasm which can be followed, viz.,
the asters, and in view of what we know of conjugation among
the simplest animals and plants, where there is a fusion of
the cell-bodies as well as of the nuclei, I question whether
the cytoplasm which the sperm carries into the ovum, in the
case of Ascaris, merely degenerates and serves as food for the
egg cytoplasm. It seems to me more probable that this sperm
cytoplasm does not act as so much dead matter, but that it also
takes part in this union of the essential constituents of the two
cells.

On a priori ground, I think we ought to expect that in fer-
tilization all the essential parts of one cell would unite with
corresponding parts of another cell. In fact, the form of
fertilization characteristic of the higher animals and plants
is generally supposed to have been derived from a condition
similar to that which at present obtains among the lower
animals and plants in which there is a fusion of two entire
cells. Most persons would probably agree that fertilization
consists in the union of the essential parts of two cells ; the
question is, "What are essential parts.'" It is known that if
some of the Infusoria are cut to pieces so that some of the
pieces contain portions of the nucleus, while others do not, the
nucleated portions will regenerate all the lost parts, while those
pieces which contain no part of the nucleus do not regenerate
but sooner or later perish. It is, therefore, certain that the
cytoplasm cannot perform the normal funtions of growth and
regeneration apart from the nucleus. It seems equally certain,
although much more difficult of demonstration, that the nucleus
cannot perform all its normal functions apart from the cyto-
plasm. Both nucleus and cytoplasm are essential constituents
of the cell, and one cannot be said to be more important than
the other. In spite of the assumption of smaller structural
units within the cell (such as the biopJiors of Weismann, the

32 BIOLOGICAL LECTURES.

pangcncs of De Vries, the plasonics of Wiesner, which assump-
tion, in one form or another, seejns to me a necessity), the
independent unit of structure is still the entire cell, not cyto-
plasm alone, nor nucleus alone, but the two together. So far
as we know, the cytoplasm of every cell comes from the cyto-
plasm of some parental cell, just as certainly as the nucleus
comes from a preceding nucleus. Until, therefore, it can be
shown that the nucleus can exist independently of the cyto-
plasm, it is unsound to assert that the cytoplasm is not an
essential constituent of the cell. And until some one has
shown that cytoplasm is not derived from pre-existing cyto-
plasm, but is the product of the nucleus,^ it is too soon
to assert that the control of the entire cell lies in the
nucleus, and hence that the nucleus is the sole bearer of
heredity.

In seeking to show that the nucleus is not the sole bearer
of heredity, we are not confined entirely to the a priori argu-
ment ; aside from the important evidence already adduced in
the presence and function of the asters observations are not
altogether wanting to show that the cytoplasm, in many
respects at least, is not controlled b}' the nucleus. In the
early cleavage stages of Crepidnla plana, it can be shown beyond
question that the direction of the cleavage, the size of the cells
formed, and the shape of those cells is the result of cytoplasmic
activity rather than of nuclear.'-^ It is generally believed that

^ This is, I know, what Weismann asserts (The Germ I'lasm, p. 50), and he
urges in proof the observations of Riickert on the alteration in size of the
chromosomes of the nucleus during the growth of the ovum ot the dogfish.
These chromosomes first enlarge greatly, and afterward diminish in size until
they are not much larger than at first. Riickert, therefore, believes that the
chromosomes give off a large amount of substance to the cytoplasm, and this
conclusion is probably correct. It does not follow, however, that this material
controls the cytoplasm, as Weismann assumes, any more than the fact that the
cyto|)lasm supj^lies the nucleus with a large amount of nuclear sap in its j^re-
division stages, argues that the cytoplasm controls the nucleus. It is probable
that each supplies substances to the other, and it is interesting to note that at
the very stage described by Riickert (the pre-division stage), in which the chro-
mosomes are giving off substances to the cytoplasm, the nucleus, in many
forms at least, is receiving a large amount of material in the form of nuclear
sap from the cytoplasm.

2 Since this lecture was given, I have found that Boveri, in his recent work on

THE FERTILIZATION OF THE OVUM. 33

the nuclear spindle predetermines the direction of the cleavage,
yet, in this case, the spindle may be formed in any possible
direction, and yet the cleavage invariably takes place in the
same direction. It is frequently asserted that the division-wall
between the daughter-cells appears at right angles to the
spindle, and yet, in this case, it may form at a greater or a
smaller angle than 90°. The direction of the cleavage is pre-
determined not only before the nucleus divides, but long before
the asters divide. Certain oscillatory movements of the cyto-
plasm, which begin -with the first division of the ovum and can
be observed throughout a large part of the cleavage, determine
with absolute certainty the direction of the cleavage before any
indication of division can be found within the cell. Since the
direction of the cleavage is not determined by the nucleus, it
follows that the rotation of the cells and the position which
they take, with reference to each other, are not determined by
the nucleus ; and since it can be shown that the shape of the
cleavage cells is very largely the result of intercellular rela-
tions, it follows that in this case, at least, the shape of the
cell is not determined by the nucleus.

Still farther, the size of the cell seems to be determined by
the cytoplasm rather than by the nucleus. The indirect or
karyokenetic division of the nucleus results in an equal division
of the chromatic substance. After the division has taken
place, the two-daughter nuclei are for a considerable period
equal in size, though the cell-bodies in which they lie may be
very unequal. Likewise, the division of the asters is always
an equal division, and in the early stages of karyokinesis the
two asters are always equal in size. Yet in these very stages
in which the nuclei and the asters are equal in size, the lobing
of the cytoplasm may show beyond doubt that the division of
the cell-body is to be very unequal. I believe, therefore, that
neither the nuclei nor the asters determine the initial size of

fertilization (" ISefruchtung," p. 469), mentions the fact that he fertilized ova of
one genus of sea-urchin with the sperm of another, from which cross a larval
form developed which was intermediate in character l)etween the two genera.
The cleavage, however, was purely maternal, thus indicating that it was not
influenced by the sperm nucleus. He, therefore, concludes that the process of
cleavage, to all appearances at least, is not directed l)y the nucleus.

34 BIOLOGICAL LECTURES.

the cells which are formed by division ; it is determined rather
by the general cytoplasm. In the later stages of karyokinesis,
after the lobing of the cytoplasm has indicated the size of the
daughter cells, but sometime before the division-wall is formed,
the asters become unequal in size if the division is to be an
unequal one, and by the time that the division-wall is formed
the asters are proportional in size to the daughter cells in
which they lie. At a considerably later period the nuclei
become proportional in size to the cells in which they are
found.

In Crepidula, therefore, I believe it is certain that the direc-
tion of the cleavage, as also the position, the shape and the
size of the resulting cells are not directly governed by the
nucleus. These definite forms of cleavage which are so
excellently exemplified in Crepidula are inherited as certainly
as any definite adult structures are, and if they are not
under nuclear control, these hereditary tendencies must be
transmitted through the cytoplasm.

Of course, it may be urged that there is some unknown and
invisible influence emanating from the nucleus which controls
all the processes of cell life. In the nature of the case such
an assertion cannot be affirmed nor denied on the ground of
observation, and it seems to me sufficient to urge in reply that
we should believe things are what they seem unless we are
compelled to believe differently. Many of the processes of
cell life seem to be controlled by the cytoplasm more inti-
mately than by the nucleus ; so far as we can observe, all
cytoplasm comes from pre-existing cytoplasm, just as all
nuclei come from previous nuclei. We know that the cyto-
plasm from both the father and mother are represented in
every stage of fertilization, and it is unnecessary and therefore
unscientific to assume that the nucleus controls all the
processes of cell life, and that the heritable characters of the
cytoplasm are transmitted only through the nucleus.

If, in stating my objections to the view held by the vast
majority of the biologists of the present day, I may seem to
have denied the importance of the nucleus while emphasizing
the importance of the cytoplasm, I would wish to say, in con-

THE FERTILIZATION OF THE OVUM. 35

elusion, what has been said several times already, that I con-
sider both cytoplasm and nucleus essential constituents of the
cell, and therefore one cannot be said to be more important
than the other. In all the phenomena of cell life, — growth,
regeneration, fertilization, division, the building of the organ-
ism, the transmission of heritable characters, — both nucleus
and cytoplasm take part, though probably not always an equal
part. The entire cell is still the ultimate independent unit of
organic structure and function.

THIRD LECTURE.

ON SOME FACTS AND PRINCIPLES OF PHYSIO-
LOGICAL MORPHOLOGY.

JACQUES LOEB.

In this address I shall give a short account of a series of
experiments which were undertaken in order to
determine the causes of animal forms. Some of
the results of these investigations have already
been published. ^ Among others, which are new,
are experiments upon the artificial production of
double and multiple monstrosities from one ovum
in the sea-urchin.

^>^

I. Heteromorphosis.

If we look at an animal we perceive that its
various organs are arranged in a definite way.
From our shoulders originate arms, and from our
hips legs, but we never see that legs grow out
from the shoulders or arms from the hips. In
the lower animals there exists the same definite
arrangement of parts.

Fio-. I is a diagram of a hydroid Antennularia,
which is pretty common at Naples. From a
bundle of roots or stolons a perfectly straight
stem arises to a height of six inches or more.
From this main stem originate, in regular suc-
cession, very short and slender branches, which
carry polyps on their upper sides.

In this case we never find that a root originates
at the apex, or in the place of a branch, or that
polyps originate at the lower side of a branch.

1 Untersuchungen ziir physiologischen Morphologie der Thieve. I, Heteromor-
phosis, Wiirzburg, 1S91. II, Organbildung und Wachsthum, Wiirzburg, 1S92.

r.

3^

BIOLOGICAL LECTURES.

physiologist the question arises: What are the circumstances
which determine that only one kind of organs originate at
certain places in the body ? I conceived that the answer to
this question might be obtained by finding out
whether or not it was possible to make any
desired organ of an animal grow at any desired
place. In case of success, the question to be
decided was whether the same circumstances by
which we can change the arrangement of organs
experimentally determine also the arrangement
of organs in the natural development.

If we cut out a piece (Fig. 2) of an Antennu-
laria, and hang it up vertically in the water, the
apical end b above and the root end a below, we
find that after a few days the root end a forms
little roots, r, which grow downward,
and the apical end, b, forms a new
apex, c.

If we cut out a similar piece and
hang it upside down (Fig. 3), the
root end a, which now is above,
forms a new apex, ac, and the apical
end b, which is below, forms roots.
In such an apex the arrangement
of organs is just the same as in the normal
animal, namely, branches growing obliquely
upward bearing polyps on their upper sides. We
are, therefore, able to substitute a root for an
apex and an apex for a root. I have called this
substitution of one organ for another hetero-
morphosis. If we place the cut-out piece of
Antennularia horizontally instead of vertically,
something still more remarkable happens, namely,
the branches on the lower side suddenly begin to
grow vertically downward, and the outgrowing
parts are no longer branches but roots, ;-/', Fig. 4. This we can
prove by their physiological reactions, for the roots fix them-
selves to the surface of solid bodies, for instance, the glass of

r

Fig. 2.

Fk;. 3.

OA^ PHYSIOLOGICAL MORPHOLOGY.

39

the aquarium, while the stems never show any reaction of this
kind. These new parts growing out from the branches of
the under side of the stem attach themselves to solid bodies,
if we bring them in
contact with the same.
Moreover, they are pos-
itively geotropic (that
is, they grow toward
the centre of the earth),
while the branches
never show any pos-
itive geotropism. The
branches on the upper
side are not trans-
formed into roots.
They either perish or give rise to very long, slender, perfectly
straight stems {b, Fig. 4), which grow vertically upward.
These stems, as a rule, are too slender to bear branches,
but at parts of the upper surface of the main stem there
originate new stems (r. Fig. 4) which grow vertically upward
and produce the typical little branches with polyps.

If we bring the stem into an oblique position (Fig 5), with
the apex b upward, from every element of the main stem new

Fig. 4.

Fig. 5.

Fig. 6.

Stems and roots may originate, but with this difference, stems
always originate from the upper side of an element and roots
from its lower side. But if we place the stem in an oblique

40

BIOLOGICAL LECTURES.

position (Fig. 6), with the root end above, the branches on the
under side grow out as roots and at the upper end, a stem
arises as usual.

What circumstances have all these experiments in common?
These two : stems always originate from the upper end or side
of an element, and roots always originate from the lower side
or end of the same element. These facts can be explained
only through the assumption that gravitation, in this case,
determines the place of origin of organs.

Now we may ask whether the
action of this force, gravitation,
produces the natural arrangements
of parts, /. i\, roots growing only at
the base of the stem and never at
the apex or in the place of a branch.
I think that it does. By reason of
its negative geotropism, the stem
grows vertically upwards. Gravita-
tion does not permit roots to arise
at an)- place except the under side
of the organs, and that, in the
normal position, is the base of the
stem. The same force determines
that polyps can originate only at
the upper side of branches, and so
the main arrangement of organs is
brought about by gravitation. But
how does gravitation determine that
roots grow at the upper and stems
This is a question to which I shall return

Fic. 7.

at the under side 1
later.

Fig. 7 is a drawing of a case of heteromorphosis in Margeliss,
a hydroid common at Woods Holl.

If we cut off a stem, or a small piece of a stem, and place it
in a dish containing sea water, and protect it carefully from
every motion, a curious change takes place in the organism.
Almost all, and in some cases all of the stems which touch
the glass begin to give rise to roots that spread out and very

ON PHYSIOLOGICAL MORPHOLOGY. 4 1

soon cover a large area of the glass. In this way the apical
end of a stem may continue to grow as a totally different
organ, namely, as a root. Every organ not in contact with
some solid body gives rise to polyps. Even the main root, if
not in contact with a solid body, no longer grows as a root, but
gives rise to a great number of small polyps which appear at
the end of long stems. Fig. 7, which Mr. Tower was kind
enough to draw for me, shows a branch which formed roots
at its apex and polyps at its roots in this way. The stem
touched the bottom of the dish with the apical ends, a, b, c and d.
All these ends gave rise to roots. From the upper side of the
original root, r, which was not in contact with the glass, later
on small polyps, //>, grew out. Every place which was in con-
tact with solid bodies gave rise to roots, and every place which
was in contact with sea water gave rise to polyps.

This is not the only species of hydroid found at Woods Holl
in which such forms of Heteromorphosis can be produced.
Another form, Pennaria, is just as favorable. In Pennaria I
succeeded repeatedly in producing roots at both ends of a
small stem that bore no polyps. ^

What circumstances are common in these experiments on
Margelis and Pennaria.? Organs brought into contact with
solid bodies continue to grow as roots, if they grow at all.
Organs surrounded on all sides by water continue to grow in
the form of polyps, if they grow at all. In Margelis, contact

1 In a Tubularian I was able to produce the opposite case, namely, to get an
animal that ended at botli ends in a polyp and had no root. Weismann seems
to assume, in his " Germ Plasm," that the latter result is to be explained by the
principle of natural selection, inasmuch as an animal without polyps could not
continue to live, and hence it would be impossible to produce roots at both ends.
In Pennaria this supposed impossibility was realized. One may say that these
roots in Pennaria may give rise later on to polyps. Tn the special case that I
observed they did not, although as a rule they do. But the same is the case in
Tubularia, in which polyps also ari.se from the roots. It might be said, perhaps,
that the formation of roots in Pennaria is, for some reason, absolutely necessary.
But it is just as easy to produce polyps at both ends. Even if it were possible to
reconcile these facts with the principles of natural selection, causal or phys'o-
logical morphology would not gain thereby, as the circumstances that determine
the forms of animals and plants are only the different forms of energy in the
sense in which this word is used by the physicist, and have nothing to do with
natural selection.

42 BIOLOGICAL LECTURES.

with a solid body plays the same role as did gravitation in the
case of Antennularia. In what way the contact may have an
influence shall be mentioned later. We may add, however,
one more point. In Antennularia, gravitation not only deter-
mines the place of origin of the various organs, but also the
direction of their growth ; the stem, growing upward, is nega-
tively geotropic, the root, growing downward, is positively
geotropic. In Pennaria, the nature of the contact not only
determines the place of origin of the various organs, but also
the direction of their growth. If we bring an outgrowing
polyp of Pennaria into contact with a solid body, the polyp
begins to grow away from the body, and the new stem is very
soon nearly perpendicular to the part of the surface with which
it came into contact.

I have called this form of irritability Stereotropism. We
may speak of positive Stereotropism in the case of the root,
and of negative Stereotropism in the case of the polyp.

Here, too, it may be asked whether contact with foreign
bodies, which in these experiments determined the arrange-
ment of the various organs, may not have the same effect in
the natural development of the organism. I believe that such
is the case. Negative Stereotropism forces the polyps to grow
away from the ground into the water, and so parts surroundetl
by water form i)olyps only. Positive Stereotropism forces roots
in contact with the ground to grow toward it, so parts in con-
tact with the ground give rise to roots onl)'. Thus it happens
that, under ordinary circumstances, in the animal we find roots
only at the base where it touches the ground. In other hydroids
the place of origin of the different organs is determined by
light, and in others we find more complicated relations.

It may appear from the foregoing

that such cases of heteromorphosis are

confined to hydroids, but such is not

the case. We find similar cases in

TiDiicatcs. Ciomi iiitcstinalis (I'ig. 8),

a solitary ascidian, has eye-spots around tlie two openings

into the pharyngeal cavity, a and b. If we make an incision

at c, eye-spots are formed on both sides of the incision.

ox PHYSIOLOGICAL MORPHOLOGY.

43

Fig. 9.

C d

Fig. 10.

II. Polarization.

While the foregoing experiments were in progress, I
observed that in many animals I was unable to produce
any kind of heteromorphism. These animals showed, in

regard to the formation of organs, a
phenomenon with which we are familiar in
a mao-net. If we break a magnet into
pieces, every piece has its north pole on
that side which in the unbroken magnet
was directed toward the north. Likewise,
there are animals every piece
of which produces, at either \\\\\l///// ^
end, that organ toward which ^ ' ^

it was directed in the normal
condition. We may speak in
such cases of polarization.
The clearest example of this
I found in an actinian, Ceri-
antJius uicmbranaceits.
If we cut a rectangular piece, abed, out of the body-wall
of Cerianthus (Fig. 9), very soon new tentacles begin to grow
out of this piece, but only from the side
ab (Fig. 10), which was directed toward
the oral end of the animal. Nothing of
the sort occurs in the side, c d, or ac,
or bd. The production of tentacles
takes place before any other regeneration
begins. The same polarization is shown
in the following variation of the preceding
experiment : If we make an incision,
abc (Fig. 11), into the body-wall of the J^
actinian, only the lower lip, b c, produces
tentacles, while the upper lip, a c, pro-
duces none. The two ends heal together
in such a way that one-half of a mouth,
^'^- "• with its surrounding tentacles, a (Fig. 12),
is formed. It is curious to see how these tentacles behave if

c^'

Fig. 12.

44

BIOLOGICAL LECTi'RES.

we offer them bits of meat. They endeavor to force it into
the new oral disc, where the mouth ought to be, but where no
mouth exists, and only after a struggle of some minutes give up
the hopeless attempt. I tried in every possible way to produce
tentacles in the aboral end of a piece which had been cut out,
but without success.

Hydra behaves, as regards polarization, a little differently
from Cerianthus. If we make an incision in the stem, a
whole new oral pole grows out, but otherwise it, too, shows
polarization.

A good many animals, so far as is yet known, reproduce
only the lost organ, but never show any heteromorphism. We
see, therefore, that while in some animals we are able to pro-
duce heteromorphosis, in others the most definite polarization
exists, and we are able to produce regeneration of lost parts
only in the arrangement which exists in the normal animal.
In this case we must assume that unknown intcfnal conditions
determine the arrangement of limbs.

In addition to examples of heteromorphosis or polarization
occurring separately, we find cases in which both phenomena
are exhibited by the same animal. If we cut out a sufficiently
large piece of the stem of Tubularia mesembryanthemuni, and
place it in the bottom of a dish of water, carefully protected
from jarring, the anterior end of the piece gives rise to a new
polyp, the posterior end to a root ; but if we hang up the stem
in such a way that the posterior end does not touch the surface
of the glass, and is sufficiently provided with oxygen, this end,
too, produces a polyp, and we have a true case of heteromor-
phosis. In all cases the polyp at the oral end is formed first,
and a relatively long time (one or more weeks) elapses before
the aboral polyp is formed. But under one condition I could
cause the stem to form a polyj) at the aboral as quickly as at
the oral end, namelv, by inhibiting or retarding the formation
of the oral polyp. This could be done readily bv diminishing
the supply of oxygen at the oral end. In such cases the
aboral pohps were produced nearly as quickly as the oral
polyps.

OA' PHYSIOLOGICAL MORPHOLOGY. 45

III. Thk Mechanics of Growth i\ Animals.

In order to get an explanation of the phenomena of organiza-
tion we must ask, What are the physical forces that determine
the formation of a new organ } We know that the ultimate
sources of energy for all the functions of living bodies are
chemical processes. The question is, How can these chemical
forces be brought into relation with the visible changes which
take place in the formation of a new organ .'' The answer to
this question is to be obtained by a knowledge of the mechanics
of growth. It is very remarkable that the mechanics of growth
forms almost an empty page in the history of animal morphol-
ogy and physiology. I can refer here only to the few experi-
ments that I have made on this subject ; but fortunately the
subject has been worked out very carefully in plants, and as
my experiments show that the conditions for growth in animals
are, to a certain extent at least, the same as the conditions for
growth in plants, we have the beginning of a basis for work.

A brief outline of the manner of growth in plants is as fol-
lows : Before the cell grows it forms substances which attract
water from the surroundings, or, as the physicist expresses it,
it forms substances which determine a higher osmotic pressure
within the cell than did the substances from which they origi-
nate. The walls of the cell, or rather the protoplasmic layer
that lines the cell wall, possesses peculiar osmotic properties,
in consequence of which it allows molecules of water to pass
through freely while remaining resistant to the passing through
of the molecules of many salts dissolved in the water. The
result is that when substances of higher osmotic pressure are
formed inside the cell, water from the outside passes in
until the pressure within again equals the pressure without.
The cell-wall becomes stretched and, according to Traube,
new material is precipitated in the enlarged interstices,
thus rendering growth permanent. This method of growth is
most conspicuous, perhaps, in the germinating seed. The rising
temperature in spring produces in the seed substances of higher
osmotic pressure (with greater attraction for water) than the
substances from which they originate. The result is that

46

BIOL OGICA L LECTL 'RES.

water enters the seed ; by the pressure of the water within the
cells their walls are stretched out and the seed grows. The
chemical and osmotic changes are the sources for the energy
which is needed to overcome the resistance to growth.

To see whether I could determine what are the mechanical
causes of growth in animals, I began at Naples some experi-
ments on Tubularia mesembryanthemum. I chose long stems
belonging to the same colony and distributed them in a series
of dishes containing sea-water of different concentrations. In
some of the dishes the concentration had been raised by adding
sodium chloride, and in others it had been lowered by adding
distilled water. According to the laws of osmosis the amount
of water contained in the cells of these tubularians differed
with the concentration of the sea-water, the amount being
greatest in the most diluted solution and least in the most
concentrated solution. If now in reality the mechanics of

/ 2 d

OIL i/T£0 SfA • tyAT£P

If 6- (,

CO/rCEAr/?ATED S^4-yV/fr£7i
Fig. t3.

growth are the same for animals as for plants, it must result
that the more diluted the sea-water the more rapid would be
the <rrovvth in the tubularian stem. Of course, at last, a limit
is reached where the water begins to have a poisonous effect.
It was found, indeed, that within certain limits of concentra-
tion the increase in the length of the stems during the same
period was greatest in the most diluted and least in the most
concentrated sea-water. It is remarkable that the ma.ximum of
growth took place not in sea-water of normal concentration,
but in more diluted sea-water, though that of course may not
be the case in all animals. The following curve (Fig. 13) will
give an idea of the dependence of growth upon the concentra-
ticm of the sea-water in Tubularia. The values for the amount

av PHYSIOLOGICAL MORI'IIOLOGY.

47

of sodium chloride, in loo cubic centimetres of sea-vv^ter, are
represented on the axis of the abscissa, the values for the
increase in growth on the ordinate axis.

These and similar experiments, which on account of lack of
time I cannot mention here, show that growth in animals is de-
termined bv the same mechanical forces that determine growth
in plants. An ol^stacle to such a conclusion seems to lie in
the fact that many plant cells have solid walls, while such is
not the case in most animal cells. But the solid cell-wall does
not determine the peculiar character of growth. This charac-
ter is determined first, by chemical processes within the cell,
which result in a higher osmotic pressure, and, secondly, by
the osmotic qualities of the outer layer of protoplasm, which
allows water to pass through freely, but does not allow all salts
dissolved in it to do the same. Both these qualities are inde-
pendent of the solid cell-wall, and I see no reason why the
animal cell should not agree in these two salient features with
the plant cell.

In order that the foregoing explanation of the mechanism of
growth in the animal cell might be based only upon known
processes, it was necessary to find out whether, indeed, in case
of growth, chemical processes of such a character take place
that there are formed substances of higher osmotic pressure
than those from which they originate. Every one knows that
by practice our muscles increase in size. No satisfactory
explanation of this fact has been given. If my interpretation
of the method of growth was correct, I must expect that during
activity there are formed in the muscle substances which deter-
mine a higher osmotic pressure than those from which they
originate. This is exactly the case. Ranke had already shown
that the blood of a tetanized frog loses water and that this
water is taken up by the muscles. In experiments which were
carried on by Miss E. Cooke in my laboratory, we were able to
show directly that during activity the osmotic pressure inside
the cell-wall is raised. We determined the concentration of a
solution of Na CI, or rather of a so-called Ringers mixture, in
which the gastroconemius of a frog neither lost nor took up
water. We found that while this concentration for the restinsr

48 BIOLOGICAL LECTURES.

gastroconemius was about 0.75 per cent, to 0.85 per cent., for
the gastroconemius that had been tetanized from 20 to 40
minutes it varied from 1.2 per cent, to 1.5 per cent.

This increase of osmotic pressure inside the muscle cell
leads, during normal activity, to a taking up of water from the
blood and lymph, and the consequence is an increase in volume.
The same muscle, as soon as it ceases to be exercised, begins
to decrease in size. Activity, therefore, plays the same role
in the growth of a muscle that the heat of spring plays in the
growth of the seed.

Upon endeavoring to determine whether the function of seg-
mentation, like other functions of growth, is influenced by
the amount of water contained in the cell, I found that by
decreasing the amount of water in the ovum of the sea-urchin
segmentation is retarded, and that by using a sufficiently high
concentration of sea-water it may be stopped entirely. There-
fore the amount of water contained in the cell plays still
another role in the process of organization and influences the
process of cell division.

IV. The Artificial Production of Double and Multiple
Monstrosities in Sea-Urchins.

The idea that the formation of the vertebrate embryo is a
function of growth has been made the basis of the embryo-
logical investigations of His. In a masterly way. His has
shown how inequality of growth determines the differentiation
of organs. In the blastoderm of a chick, for example, the first
step in the formation of the embryo is a process of folding.
There originates a head fold, a tail fold, a medullary groove
and the system of amniotic folds. According to His, all these
processes of folding arc due simply to inequalities of growth,
the centre of the blastoderm growing more rapidly than the
periphery. It can be shown, ver)- simply, that such a process
of unequal growth must, indeed, lead to the formation of exactly
such a system of folds as we find in the blastoderm of a chick.
If we take a thin, flat plate of elastic rubber, such as is used
for medical purposes, and lay it on a drawing-board, we can

ox PHYSIOLOGICAL MORPHOLOGY. 49

imitate the stronger growth in the centre by sticking two tacks
into the micklle of the rubber, a short distance apart, and
then pulling them in opposite directions. In this way we
imitate unequal growth, the centre growing faster than the
periphery. If we, then, fix the tacks in the drawing-board,
so that the rubber in the middle remains stretched, we
get the same system of folds shown by the embryo of a
chick. I mention this way of demonstrating the effects of
unequal growth as the ideas of His are still doubted by some
morphologists.

His raised the question, Why is growth different in different
parts of the blastoderm .■* But instead of trying to answer it
from the physiological standpoint he answered it from the
anatomical standpoint. According to His, the different regions
of the unsegmented ovum correspond already to the different
regions of the differentiated embryo. But this so-called theory
of preformed germ-regions gives no answer to the question,
Why do some parts of the embryo grow faster than others }
Nevertheless, it is not necessarily in opposition to the theory
of growth that I offered in the preceding chapter. Starting
with the idea of His, we may well imagine that the different
regions of the ovum are somewhat different chemically, and
that these chemical differences of the different germ-regions
determine the differences of growth in the blastoderm. Thus
the phenomena of heteromorphosis would show that, in some
animals at least, the arrangement of preformed germ-regions
may be changed by gravitation, light, adhesion, etc.

But, from the standpoint of causal morphology, it must be
asked what determines the arrangement of the different germ-
regions in the ovum. If we answer "heredity," causal mor-
phology can make no use of such an explanation. Our blood
has the temperature of about T)'j°, but although our parents had
the same temperature its heat is not inherited, but is the result
of certain chemical processes in our tissues. Still it may be
possible that the molecular forces of the chemically different
substances of the ovum determine a separation of these
substances and at the same time the chief directions of the
future embryo.

50

n/OLOGICAL LECTL RES.

Driesch has shown ^ that bv shakintr a sea-urchin's csrg in the
four-celled stage the four cells may be separated, and each one
be capable of giving rise to a complete embryo, which is only
different in size from the normal embryo. If the theory of
preformed germ-regions with its later modifications were true,
we ought to expect that every one of the isolated cells would
give rise to one-fourth of an embryo, l^ut it has been said
that the artificial isolation of one cleavage cell causes a process
of post generation or regeneration. Driesch, moreover, changed
the mode of the first cleavage by submitting the ovum to one-
sided pressure. In this way the nuclei were brought into
somewhat different places from those they wmild have held in
the case of normal segmentation. Still, normal embryos
resulted. One might object again that the i)reformation of
the germ-regions existed in the protoplasm, and not in the
nucleus. I have made a series of experiments to the results
of which these objections cannot be made. I shall describe
these experiments somewhat fully, as they have not yet
been published, though I cannot enter into details at this
place.

I brought eggs of a sea-urchin, within ten to twenty minutes
after impregnation, into sea-water that had been diluted by

the addition of about lOO per
cent, distilled water. In this
solution the eggs took up so
much water that the mem-
brane (///, Fig. 14) burst and
part of the protoplasm escaped
in the form of a drop (b, Fig.
14), which often, however, re-
mained in connection with the protoplasm inside the membrane
after the eggs were brought back into normal sea-water.
These eggs gave rise to adherent twins, the ejected part of the
protoplasm, b, as well as the j)art remaining inside the mem-
brane, developing into a normal and perfectly comj^lete embryo.
The part of the protoplasm which at first had connected
the two drops, formed the part where the twins remained

"^ Zeituhrift f. wissensch. Zoologie, Vol. l.III and I \'.

Fig. 14.

OA PH YSIOL OGICA L MORFHOL OG J \

51

grown together. Of course, it often happened that, by
accident or rapid movement, the twins were separated, and
they then developed into perfectly normal single embryos.
Since we cannot assume that in every case the same part
of the protoplasm escapes, we must conclude that every
part of the protoplasm may give
rise to fully developed embryos
without regard to preformed
germ-regions. In many eggs a

Fig. 15.

repeated outflow of the proto-
plasm takes place (Fig. 15). In
such cases each of the drops
of the protoplasm may give rise
to an embryo, and I obtained not only double embryos,
but triplets and quadruplets all grown together.

In order to understand these experiments more fully, let us
follow out the history of development in these double and
multiple monstrosities. The ova were put into the diluted
sea-water before any segmentation had taken place and while
they had still but one nucleus. When parts of the protoplasm
flowed out, the nucleus either remained in the protoplasm,
inside of the membrane, or passed out with the part that was
ejected. Therefore, at first, only one part of the protoplasm
contained a nucleus. The other part obtained its nucleus by
the cleavage which took place, as follows : In case the nucleus
had remained inside the membrane (Fig. 16), the first cleavage

took place inside the membrane, the
cleavage plane being always at right
andes to the common diameter of
the two protoplasmic drops (Fig. 16).
(Only when the nuclear-spindle had
already formed, at the time of the
F"^" 1 6- bursting of the membrane, were

there exceptions to this rule.) A peculiarity of the first
cleavage was that the protoplasm was always divided into a
larger sphere (I, Fig. 16), and a smaller sphere (II) which was
connected with the extra-ovate.

52

BIOLOGICAL LECTURES.

The next stage was a normal division of I (Fig. 17), and
then II, divided (Fig. 18), the cleavage plane, as a rule, lying

Fig. 17.

Fig. 18.

in the extra-ovate. In this way the extra-ovate obtained its
nucleus, receiving in this case but one-fourth of the whole.
It very often happens that the extra-ovate receives its nucleus
later, obtaining in that case a still smaller fragment, but, never-
theless, the outcome is a perfectly normal embryo. Later on

Fig. 19.

Fig. 20.

the division takes its regular course. Fig. 19 shows the morula
stage, and one recognizes already the double monster. Figs.
20, 21 and 22 show double, triple and quadruple gastrulae.

Fig. 21.

Fig

OA' PH ] 'SIOL OGICA L MORFHOL OG V.

53

Figs. 23 and 24 represent double Plutei and Fig. 25 a triple
Pluteus.

It is remarkable that the development of these monstrosities
goes on nearly at the same rate as that of the normal embryo,
provided they are equally well
supplied with oxygen and
equally protected from mi-
crobes and infusoria. If pre-
formed germ-regions deter-
mined the arrangements of
organs in the embryo, we
ought to expect that these
ruptured ova would give rise
to single embryos, with a
modified arrangement of
limbs, and not to several
embryos with normally ar-
ranged limbs. Nevertheless,
it remains true that the de-
velopment in most eggs takes
place in such a regular and
typical manner that it seems as if there were a pre-arrangement
of some kind. But it is perfectly well possible that this pre-
arrangement consists in a separation of different liquid sub-
stances in the ovum by the molecular qualities of these
liquids. Such a separation, of course, might be called a
preformation of germ-regions, but it would be something
totally different from what is now understood by that term.

Fig. 23.

V. Theoretical Rem.\rks.

I. All life phenomena are determined by chemical processes.
This is equally the case whether we have to do with the
contraction of a muscle, with the process of secretion or with
the formation of an embryo or a single organ. One of the
steps that physiological morphology has to take is to show in
every case the connecting link between the chemical processes
and the formation of organs. I have tried to show that in a

54

/>'/( U. OC/CAL LECTURES.

few cases at least this connecting link was to be sought in the
changes of osmotic pressure determined by the chemical changes
which take place in the growing organ.

But this fact alone does not explain why it is that we get
differences in the forms of organs. In order to understand
this we must bear in mind that the processes of growth must
necessarily be different for different organs, as for example in
the formation of a root, and the formation of a stem. As

Fig.

growth is a process in which energy is used up in overcoming
the resistance to growth, differences of growth can onl}- be
determined either by differences in the amount of energy set
free in the growing organ or by differences in resistance. Dif-
ferences in the energy must be the outcome of differences in the
chemical processes which determine growth. Therefore we
are led to the idea that differences in the forms of different
organs must be determined by differences in llicir chemical

a^' PIIVSIOLOGICAL MORPHOLOuY

55

constitution, or, if the chemical constitutions be similar, by
differences in resistance to growth. That organs which differ
in shape very often are chemically different is a well known
fact. The formation of urea in the liver and the synthesis of
hippuric acid by the kidneys are the consequences of chemical

differences.

In this way we are led through the mechanics of growth to
a conclusion which forms the nucleus of Sachs' theory of

Fig. 25.

organization, namely, "that differences in the form of organs
are accompanied by differences in their chemical constitution,
and that according to the principles of science we have to
derive the former from the latter." According to Sachs there
are as many " spezifische Bildungsstoffe " in a plant as there
are different organs.^

1 J. Sachs, staff tind Form der Pffanzenorgane, Gesammelte Abhandlungen, Vol.
II, 1893.

56 BIOLOGICAL LECrrRES.

2. In adopting the theory of Sachs and applying it to
animal morphology, we must avoid a mistake very often made
even in the case of good theories, namely, the endeavor to
explain special cases which are complicated by unknown
conditions. Huyghens explained by his theory of light the
phenomena of refraction, but he could not and did not attempt
to explain the sensations of color. For these phenomena
the wave theory of light remains true, but color sensations
depend not only on the wave motion of the ether, but also
on the peculiar chemical and physical structure of the retina.
I think it perfectly safe to say that every animal has specific
eerm substances, and that the germ substances of different
animals differ chemically. Its chemical qualities determine
that from a chick's egg only a chick can arise. But it would
be a mistake and a falling back into the German Natur-
philosophie to attempt at present an explanation of how the
unknown chemical nature of the germ determines all the
different organs and characters that belong to the species.
For instance, the yolk sac of the Fundulus embryo has a tiger-
like coloration. We might say that these markings may be
due to a certain arrangement of molecules or complexes of
molecules (determinants), which later on give rise to the colored
places of the yolk sac, but I found that this coloration
originates in a manner much more simple. The pigment cells
are formed irregularly on the surface of the yolk. The pigment
is chemically closely related to haemoglobin, and so its forma-
tion may from the first be connected with the formation of the
blood corpuscles. But the arrangement of the pigment cells
during the first days of development is not such as to produce
any definite markings. They lie upon the walls of the blood
vessels as well as in the spaces between the capillaries. Later
on, however, all of the pigment cells have crept upon the
surface of the neighboring blood vessels. I succeeded experi-
mentally in showing it to be probable that some of the
substances contained in the blood determine this reaction.
These substances, if they diffuse from the blood vessel and
touch the chromatophore, make, according to the laws of
surface tension, the protoplasm of the chromatophore flow

OA' PHYSIOLOGICAL MORrHOLOGY. 57

towards and at last over the blood vessel and form a sheath
around it, while the gaps between the blood vessels become
empty of chromatophores. In this way the chromatophores
are arranged in stripes, and changes in the surface tension, and
not a preformed arrangement of the germ, determine the
marking. We do not know what processes determine the
coloration of animals which owe their markings to interference
colors, but the task of deriving such a coloration in the adult
from a similar arrangement of molecules in the germ plasm
would prove too much even for a genius like Huyghens, and
without the possibility of such a derivation the theory is of
no use.

3. The reasons why roots grow on the under side of the
stem of Antennularia and stems on the upper side, can only be
given when the special physical and chemical conditions inside
the stem of Antennularia have been worked out. At present
we can only think of possibilities. It is possible that the
hypothetical root substances of Sachs may have a greater
specific gravity than the substances which form stems, and
therefore take the lowest position in the cell. Since outgrowth
can take place only at the free surface of a stem or branch,
roots could grow only at the under side and stems only at the
upper side of an element. But there are still other possibilities
which we must omit here. In the case of Margelis and other
hydroids, it might happen that contact with solid bodies
produced an increase of surface in the touched elements in
case they contained specific root substances, while the opposite
took place in the case of elements containing polyp substances.
The consequence would be an increase in the surface of the
roots if they came into contact with solid bodies, while polyps
only would grow out in the opposite direction. I found, indeed,
in some forms at Naples that roots of hydroids which grew free
in the water began to grow much faster and to branch off more
abundantly when brought into contact with solid bodies. But
in these cases we must wait with our attempts at explanation
until the physical and chemical conditions for the form are
worked out. For the same reasons I will not go into a discus-
sion of the question of what determines the polarization of

58 BIOLOGICAL LECTURES.

animals like Cerianthus. It may suffice to suggest the possi-
bility tliat in polarized animals the tissues or cells may
have such a peculiar structure as to allow the specific
formative substances to migrate or arrange themselves only
in one direction, while in cases of heteromorphosis migra-
tion or arrangement in every or in several directions is
possible.

4. The ovum of a sea-urchin under normal conditions gives
rise to but one embryo. This circumstance is due simply to
the geometrical shape of the protoplasm, which, under normal
conditions, is that of a sphere. When we make the eggs
burst, the protoplasm outside the (tgg membrane and that
which remains within it assume spherical forms, by reason of
the surface tension of the protoplasm. When this ha^Dpens,
as a rule, we get twins, if two separate segmentation cavities
are formed, and only one embryo, if both cavities communi-
cate with one another. Whether the first or the second case
will happen depends upon the molecular condition of the part
of the protoplasm connecting the two drops. Therefore, the
number of embryos which come from one ovum is not deter-
mined by the preformation of germ regions in the protoplasm,
or nucleus, but by the geometrical shape of the ovum and
the molecular condition of the protoplasm, in so far as these
circumstances determine the number of blastulae. In my
experiments, I got double or triple embryos when the ovum
formed a double or triple sphere, as every sphere determines
a blastula. In Driesch's experiments, one single cell of the
four-cell stage necessarily formed a whole embryo after it had
been isolated, as it assumed the shape of a single sphere or
ellipsoid. Of course, there must be a limit to the number of
embryos that can arise from one egg; but the limit is not due
to any i)reformati()n, but to other circumstances, the chief
one being that with too small an amount of protoplasm the
formation of a blastula — from merely geometrical reasons,
as tiiere must be a minimum size for the cleavage cells, —
becomes impossible. Without the formation of the blastula,
of course it is not possible to get the later stages which
are determined by the blastula.

ox PHYSIOLOGICAL MORPHOLOl: V.

59

5. The formation of the embryo begins with the formation
of the gastrula. The hollow sphere (the blastula, Fig. 26)
begins to fold at one place {a, c, b, Fig. 26), and an invagina-
tion takes place (Fig. 27). The formation of the fold {a, c, b,
FTg. 27) is due, undoubtedly, to unequal growth. The fact
that invagination, and not evagination (Fig. 28), takes place

Fig.

Fir,. 28.

depends upon other conditions. So far as the first phenom-
enon is concerned, there are different possibilities by which
unequal growth may lead to a process of invagination. It is
possible, for instance, that the part c (Fig. 26), between a and
/;, may begin to grow more rapidly than the rest. But such
an unequal growth can only be the outcome of a chemical
difference between the parts a, c, b, and the rest. Such a
distribution of chemically different material e.xists in the
blastula which originates from the extra ovate, as well as in
the one which develops within the membrane. In the normal
ovum this distribution of material finds, perhaps, its first mor-
phological expression in the formation of micromeres. But
Driesch has shown that all possible variations in the formation
of micromeres may occur without affecting the formation of
the embryo. A necessary condition for the formation of the
embryo is the chemical differentiation which leads to unequal
growth; but whether this differentiation exists from the first,
or whether it takes place in the eight or the sixteen or the
sixty-four-cell stage is of minor importance. In order to
demonstrate this I made eggs burst in the two, four, sixteen,
and sixty-cell stages. In all cases except the sixty-cell stage
I produced the doublets, triplets, etc. The only condition

6o BIOLOGICAL LECTURES.

necessary was that one part of the protoplasm should flow out.
The chief facts for causal morphology are the chemical differ-
ences and the local distribution of the chemically different
material by molecular forces.

In regard to the question why under normal conditions
the entoderm is pushed inside the segmentation -cavity
I wish to direct attention to a point that, as far as I
know, has not yet been considered. The sea-urchin's egg,
during the first stages of development, has a higher specific
gravity than the sea-water. In the blastula stage, however,
its specific gravity decreases and the egg begins to float and
comes at last to the surface of the water. This is possible
only through the eggs taking up substances which have a
lower specific gravity than the sea-water, and the only sub-
stance that could, in this case, be taken up is water. As the
cells themselves do not become larger, we must assume that
by a process of secretion the segmentation-cavity is filled with
a liquid of lower specific gravity than sea-water. In this way
the cells of the blastula come to have their peripheral surfaces
in contact with sea-water while their central surfaces are in
contact with a fluid containing less salts. This might result
in such differences of tension, between the inner and outer
walls of the blastula as to determine invagination. I found,
last year, that when I raised the eggs in diluted sea-water,
evagination (Fig. 28), instead of invagination, took place.
Herbst got the same result by using solutions of lithium salts. ^
It is possible, too, that in these cases the hydrostatic pressure
within the segmentation-cavity is increased, and this increase
of pressure may have a direct or an indirect effect upon
growth.

It is for further investigation, and not for speculation, to
settle all these questions in detail. I only wish to point out
where, and how far, there exists a relation between substance
and form in the early stages of the development of the sea-
urchin.

I have chosen the name Physiological Morphology for these
investigations, inasmuch as their object has been to derive the

1 Ilerbst, Zeitsclir. f. loisscusch. ZooL, Ikl. 55.

^^

ox PHYSIOLOGICAL MORPHOLOGY. 6 1

laws of organization from the common source of all life phe-
nomena, i.e., the chemical activity of the cell. In what way
this is to be done is indicated in the chapter on the mechanics
of growth.

But the aim of Physiological Morphology is not alone an
analytical one. It has another and higher aim, which is
synthetical or constructive, that is, to form new combina-
tions from the elements of living nature, just as the physicist
and chemist form new combinations from the elements of
non-living nature.

FOURTH LECTURE.

DYNAMICS IN EVOLUTION.

JOHN A. RYDER.

The statement that energy, in its kinetic and static forms,
has been a factor in the production of the shapes of organisms,
does not admit of question at the present time. In order that
the data in support of this statement may be presented in their
simplest forms, it is necessary to begin with the consideration of
the physical causes of the configuration of some of the simplest
unicellular organisms. In this way it will eventually be pos-
sible to pass from the consideration of the unicellular to that
of the multicellular type, viewed from the same standpoint.
It requires but little familiarity with the principles of physical
science to discover that similar laws hold with respect to the
behavior of fluid and semi-fluid bodies, notwithstanding the
fact that we may have before us, in one case, a so-called
" dead " fluid body, and in the other, a fluid or fluent " living "
chemical compound or mixture of compounds. Though the one
presents the phenomena of 'dead,' and the other of living,
matter, both exhibit the similar and common properties of
fluids, namely, those of surface-tension, viscosity and adhesion
to the surfaces of other bodies, with which they are brought
into contact. Under certain conditions, also, the semi-fluid
cells of living bodies undergo reciprocal deformation or altera-
tion in configuration, as a result of the interaction of the
inherent forces above specified, in ways so precisely similar to
those seen when a number of semi-fluid, or fluid dead masses,
are juxtaposed or brought into contact, that the resemblances
are seen to be due to the cooperation of closely similar, if not
identical, forces and properties.

64 BIOLOGICAL LECTURES.

This remarkable resemblance of the physical behavior of
semi-fluid living protoplasm to that of semi-fluid dead matter
of certain kinds, such as the oils, has led me to apply the term
cytophysics to the study of the physical properties of the
substance of the cell. The convenient terms cytostatics and
cytokinctics very naturally follow from a consideration of
the contrasted states of rest and activity presented by the
"living" cellular unit of organization. The cytostatic state
will be one in which no visible physical activity, other than
its secular metabolism, will characterize the cell, during which
time, also, the parts of its substance will be in a condition of
statical equilibrium in respect to each other, and the cell will,
so long as this equilibrium lasts, maintain a constant configu-
ration. The cytokinetic state, on the other hand, is one in
which the visible or invisible parts of the cell are undergoing
a displacement in respect to each other, as a consequence of
which the cell as a whole will manifest changes of configuration.
Free and interfacial surface-tension is probably the most
important factor in determining the shapes of cells, since
there is associated with it, in multicellular organisms, a com-
plicated series of definite and constant space relations and
reciprocal interactions, as respects the cells of definite tissue-
tracts, that grow out of the very conditions of combination of
those tracts. Still more important, perhaps, are the incessant
unequal disturbances of surface-tension, due to metabolic
changes, at different points on the surfaces of cellular masses
of plasma — a fact beautifully illustrated by the proteus ani-
malcule, Amccba proteus. Differences of surface-tension are
thus developed at different points and times coexistently and
consecutively which lead to the assumption of the most diverse
and inconstant shapes by the bodies of these lowly organisms.
Such differences of surface-tension are, however, themselves
caused by chemical and molecular transformations at definite,
but previously unspecifiable, points at or near the surface of
the mass of plasma. These processes are, therefore, ultimately
to be associated with molecular or chemical transformations,
the production of heat, the disintegration and integration of

living matter.

DYNAMICS IN EVOLUTION. 65

But, it will be asked, what is surface-tension ? If a drop of
water falls through a vacuum, as long as it is falling in space
it will present very nearly the form of a sphere. This is due
to the fact that the very outermost layers of molecules which
lie at insensible distances apart, attract each other with a force
that is apparently very much greater than that developed by
the action of gravitation. It results from this that the remain-
ing molecules contained within this outer molecular film are
held as within an elastic bag, the walls of which are of exactly
the same strength at every point. This exactly equal strength
and elasticity of the outer molecular film at every point on the
surface also causes it to fall into a condition of spherical,
statical equilibrium. This is true because the molecules at
every point on the surface of the drop are of exactly the same
size, therefore every one attracts its fellows that are in contact
with it, with exactly the same force at every point on that
surface. Now, let any change in the dimensions of these
molecules occur at any point on the surface of such a fluid
sphere, such as may be accomplished by chemical transforma-
tions and recombinations, such as oxidation or decomposition,
and it must follow that the surface-tension or reciprocal pull
of the molecules upon each other, adjacent to the point of
such disturbance, must be increased or diminished. The
inevitable result of this will be that the form of the drop must
instantly change in order that a new condition of statical
equilibrium may be attained. The surface of the drop is
finite and returns in every direction upon itself since it is
approximately spherical. Any deformation of the drop due to
surface-tensional disturbances will therefore affect the shape and
curvature of some or all of the surface of the drop so that its
shape may become very irregular, provided its surface-tension
be disturbed at a number of irregularly distributed points
simultaneously ; but, since the drop is a finite mass made up
of solid particles moving freely among themselves, no matter
how much the drop may be deformed or how irregular it may
become, its most superficial layer of molecules will always form
a closed surface. This fact is important, since, no matter how
irregular in shape an Aniceba may become, its outermost stratum

66 BIOLOGICAL LECTURES.

of molecules always form a closed surface and a molecular
envelope for the organism.

Since the molecules within a semi-fluid mass also move freely
over one another there is friction developed between them.
This friction is known as viscosity, and differs in fluids of
differing densities and chemical compositions, just as, in fact,
the surface-tension of a unit- surface, formed of different fluids,
differs, owing to the differing dimensions and properties of the
superficial layer of molecules of each fluid. The specific
viscosities and surface-tensions manifested by any given fluid
are therefore correlated, so that we may infer that these two
properties of fluent living matter are also correlated. Since,
again, living matter, as found in the cell, is not a homogeneous
body or compound, it will be plain that the correlative disturb-
ances in viscosity and surface-tension, due to the processes of
metabolism and the associated interplay of osmotic changes,
are so complex, when considered together with still other facts,
that it will be difficult, if not impossible, in the present state
of our knowledge, to trace all the steps of their interrelations
and interdependences in any given case.

The recent progress in the study of the process of fertiliza-
tion or conjugation shows that dynamical considerations must
here also be taken into account. As is well known, the nucleus
and archoplasm undergo alternate expansion and contraction
in linear dimensions. The male and female pronuclei increase
greatly in size during the phases just before conjugation. In the
Qgg of Ascaris, for example, I have noticed that the pronuclei
soon assume a globular form and rapidly grow into large
spherical bodies by absorbing substance from the surrounding
cytoplasm. This rapid growth and spherical form show that
surface-tension is being disturbed uniformly over the whole
surface of the nucleus, otherwise i/s fon)i could not rcviain
spherical. The remarkable growth of the rays of the asters
has the same meaning and must also be interpreted, in part, as
a physical process involving radial interdiffusion of heteroge-
neous molecules to and from the centrosomes into the nucleus
and cytoplasm, consequent osmotic disturbances, metabolism
and changes of surface-tension. The comparison of the astral

DYNAMICS IX EVOLUTION. 67

figures, with their rays extending in every direction from the
archoplasm, with the rays developed on the surface of a fluid
when another fluid of definite properties is dropped ui)on the
former, leading instantly to the production of a "cohesion
figure" with rays extending out in every direction, is no mere
analogy. In the case of the archoplasm, the rays with their
lines of microsomes are probably the effects of diffusion of
one kind of plasma, the archoplasm, through another, the
cytoplasm, and is therefore not necessarily a phenomenon of
contractility, but simply an interdiffusion of the unlike sub-
stances produced by the metabolism of growth, which tends to
reestablish statical equilibrium among the parts of the molecular
system represented by the cell. This diffusion or osmotic
redistribution is conditioned at every step by surface-tension in
precisely the same way that the rays of many Heliozoa and
Radiolarians are conditioned in water by states of unequal
surface-tension at very close but nearly equal intervals over a
spherical surface, so that a summation of these uniformly
distributed and seemingly conflicting surface tensional forces
does not interfere with the maintenance of the spherical figure
by the body of the organism. The alternate inflation and col-
lapse of the nucleus during fertilization, and growth during
indirect cell-division, is a rhythmical process, and we may char-
acterize it as the diastole and systole of the nucleus. The alter-
nate extension and retraction of the rays of the archoplasm, as
I have observed in the egg of Asearis, is similarly an osmotic or
metabolic diastole and systole of the radial figures formed by it,
which is intimately associated with and absolutely conditioned
by metabolism and osmosis, as the direct experimental researches
of Prof. Jacques Loeb have rendered exceedingly probable.
Unless the processes of karyokinesis are traced with the
utmost caution in the light of dynamical and physiological
considerations, there is great danger of our misinterpreting the
facts and of assuming that certain of the phenomena guide
and control others. It may indeed be possible that embryolo-
gists have been until nov/ steadily confounding ontogenetic
effects due to the physical processes of growth, as visualized
in karyokinesis, with their causes. I anticipate that this

68 BIOLOGICAL LECTURES.

remark will meet with a decided denial from most morpholo-
gists ; nevertheless it seems opportune to warn them that the
problems they have before them can never be settled by purely
morphological methods. If my contention that all ontogenetic
problems must be approached by a most intimate combination
of the methods of physical, physiological and morphological
research is true, we are still far from having anywhere an
ideal biological investigator. If it is true that "we have been
mistaking ontogenetic effects for ontogenetic causes, what a
mass of speculation must probably be set aside. All that will
remain, in fact, will be the many most valuable and beautiful
results of observation made by our foremost morphologists.

It is not intended to thus minimize in any way the great
and increasing value of morphological research ; what is really
meant is, that there is danger of overrating the importance of
morphology to the injury or exclusion of other disciplines of
paramount importance. If, as we must suppose, there is such
a perpetual flux and interflux of particles and molecules going
on throughout the plasma of an egg, owing to the metabolism
due to respiration and the consequent surface-tensional and
osmotic disturbances during the earliest steps of development,
it becomes inconceivable that any such morphologically con-
ceived and entirely hypothetical bodies as "ids," "idants,"
"determinates," etc., can have a stable existence. The exist-
ence of such bodies as fixed entities of finite complexity is
absolutely disproved by experiments of the most varied charac-
ter in separating the first two or four blastomeres of the ^g^,
since it is then found that, in each of these blastomeres, there
still inheres the power to produce a perfect embryo. I'he
hypothetical ids, determinants, biopJiores, genunules, etc., must,
therefore, be supposed to be capable of being halved and then
quartered without destroying their potentialities. These and
numerous other difficulties that cannot be discussed here,
render it exceedingly probable that we must look in altogether
another direction for an explanation of the processes of
ontogeny, viz., to a study of the modes and conditions of the
manifestations of the energies that constitute the "life" of
the simplest organized forms.

DYXAMICS IX EVOLUTION. 69

In the very simplest unicellular organisms we have also
unicellular molecular mechanisms of a most peculiar kind.
The fearfully complex molecular structure of these mechan-
isms conditions their actions, their forms and powers, no less
than does the nature of the watery media, in which these first-
lings of life, as w.^11 as the germs of higher organisms, must
in common develop. In the belief that the study of the
"living" mechanism of some of the lowest types of organized
existence, in relation to and as affected by their not-living sur-
roundings, might throw some light upon the origin of their
forms, the writer has here, in the main, taken up the problems
thus raised as physical ones. In the belief, also, that these
studies have not been entirely fruitless, the following evidence
is offered.

An Aniccba protcus may be compared to a smoke- or vortex-
ring of particles that has been greatly modified, owing to the
very complex interaction of disturbances of the surface-tension
of its outer enveloping film of molecules, the viscosity of its
own plasma, its gravity and power of adhesion to other bodies.
If we conceive a smoke-ring to have become a viscous semi-
fluid body with an outer film of molecules, and that this ring
has contracted until the central opening in it has completely
closed, we shall have a mechanism which may be compared in
detail with an Amoeba in motion, provided only that we modify
it still further and in such ways as we are obliged to suppose
that the combination of the four forces above specified cooper-
ate in order to produce and maintain the form of an amoeboid
organism. Verworn ^ has already referred to the flux of the
particles of the Amoeba through itself, in discussing the
general subject of contraction, but as he has not understood
the complexity of the process, we need not here concern
ourselves further than to say that he has failed to correctly
interpret this vortical flux of amoeboid organisms. There
is, however, such a central flux of particles through the centre
of the body of an amoeboid, as any one can soon convince
himself by carefully observing the behavior of a large living
proteus animalcule. The chemical transformations that go on

1 Bewegung der lebendigen Suljstanz. Jena, 1S92.

70 BIOLOGICAL LECTURES.

within the body of an amoeboid, amongst its molecules, are
responsible for disturbances of the surface-tension at one or
more points over its surface. It is certain that the chemo-
tropism, or affinity for oxygen of its surface molecules, as Ver-
worn holds, is essential to this; but we must remember that in
order to call forth local disturbances of surface-tension in this
way, there must also be a locally exaggerated chemotropism, or
affinity for oxygen, at some one point on the surface of the
organism. This point has apparently not been made clear by
Verworn, but it is essential to a clear understanding of the
processes presently to be described. How the positions of
such local disturbances of the chemical complexity of the sur-
face-layer of molecules of an amoeboid are determined, we do
not know. That they are definitely determined, according to
some definite law, we may be certain.

As every one knows who has ever watched a proteus animal-
cule under the microscope, the "anterior" pole of the creature,
for the time being, is tensely filled with its own substance, so
as to present a rounded, full "anterior" extremity while in
motion. "Posteriorly," on the other hand, the creature is
found to present a wrinkled, partially collapsed appearance.
A study of the motions of the organism discloses the fact that
its substance is flowing through itself. The central jxirt of
this current is moving most rapidly along the middle of the
body, while toward the sides it is observed to become progress-
ively slower until the outer layers of its substance, along the
sides of the creature, are seen to come to rest. It thus results
that the outer layers of molecules, along the sides, form a sort
of shell or tunnel through which the central current flows.
This flux, however, means that there must be a continual or
fitful rui)ture of the "anterior" end of the organism in order
to let some of itself escape out of itself in front, in order to let
some of itself flow into itself behind, in order that some of
itself may thus continuously flow through itself in order to
make the progressive forward motion of itself possible. In
this way the substance of the "posterior" jxirt of the organism
can be picked up and carried through the tunnel-like physical
shell, formed of the outer layers of molecules of the organism.

DYNAMICS IX El^OLUTION. 7 I

and thus be transported forwards and poured out "anteriorly."
It will readily be seen that, in order to do this, work must be
performed, energy dissipated. This energy is dissipated in
reestablishing a dynamical balance between the parts of the dy-
namical system represented by the molecular aggregate that we
behold in the body of the Amoeba. We have here before us a
finite molecular mechanism, or dynamical system, every part of
the surface of which returns upon itself. Any disturbance of
the equilibrium of the molecules at the surface of that system
will provoke a deformation of the whole. If the disturbance
is great enough at any one point, there will inevitably be
developed a vortex-ring motion of the particles amongst them-
selves, due to the friction of the constituent molecules. If
this vortical motion of the particles of an amoeboid mass of
"living" matter be due to a preponderating superficial dis-
turbance of the equilibrium of the system at one point on the
surface, that alone will suffice to determine the direction of
the motion of the whole. For this reason the proteus animal-
cule has no fixed "head" or "tail" end. "Head" and "tail"
seems to be entirely a matter of the combination of inner and
outer conditions that determine the point on the surface of the
organism, at which the maximum chemical and physical dis-
turbance of surface-tension will occur. These are absolutely
determined by the physical processes of the readjustment of
the equilibrium of its molecules, in respect to outer conditions,
during every consecutive moment of its motions. It is pos-
sible, in fact, to show that every change of the shape of this
interesting organism is the result of energies inter-acting in a
very complex way.

If an Amoeba is allowed to fall through the water, its
surface-tensions are apparently disturbed with great uniformity
over its whole surface, and at nearly equal distances apart.
It results from this that short, blunt pseudopodia are pushed
out in every direction, as in Fig. i and it becomes nearly
globular in outline. The moment, however, that the organ-
ism touches a plane surface, as in Fig. 2, it flattens out
into the form of a biscuit-shaped mass. It now behaves
like a mass of dough, and falls into a new condition of

72

BIOLOGICAL LECTURES.

equilibrium, due to its own gravity, its viscosity, and the
force with which the particles on its under side tend to adhere
to the fixed solid surface upon which it rests. The upper part
of the mass now falls into an equilibrium determined by the
surface-tension of its superficial molecules and the viscosity or
reciprocal friction of the latter upon each other. Gravity,
viscosity, surface-tension, and adhesion are the four cooper-
ating agents that now determine its figure. So long as it was
floating or suspended in the water, the influence of gravity
and adhesion operating in relation to a fixed surface were
excluded. We thus see how completely this organism is
the creature or subject of energy-conditions in this state.

In the next phase of its motions this is still further
illustrated. In Figs, i and 2, short, blunt pseudopodia are
being protruded in all directions; but in Fig. 3, the sequence
of events changes, and the organism begins to take up its
march by means of a vortical flux of its substance across the
surface upon which it rests, and in the direction of the arrow.
Surfacc-tensional disturbances of greater magnitude have evi-
dently affected the right side of the mass, and one or more of
the small original blunt pseudopodia at this point have been
merged into a strong, single "anterior," pseudopodal current,
in which a maximum flux of molecules is taking place in the

DYNAMICS fX El'OLC'T/OX. 'j T^

direction of the motion of tlic wliole organism. This maxhinim
vortical flux of the material particles of the amoeboid in this
new direction will result in elongating the organism in th
direction of the motion thus set up. The elongation of the
organism is, therefore, due to the flow of its own particles
amongst and through themselves. We are thus made aware
of the fact that this simplest organism is elongated in the
direction of its own motions, as a consequence of the continuous
readjustment of the internal equilibrium of its parts in respect
to influences affecting it from without. The shape of this
organism, at every instant of its motions, is, therefore,
mechanically caused.

We may pursue our analyses still further. If we now look
down upon such an amoeboid organism from above, when
moving upon a plane surface, as in Fig. 4, we find that it is
not only elongated in the direction of its motion, but that its
anterior end is tensely filled with substance; its outer layer of
molecules at the "anterior" end is tensely stretched. At the
tail end the organism is wrinkled or papillated; this wrinkled
or papillated appearance of the posterior end of the organism
is due to physical causes, as the following observation proves:
In Fig. 4 there are two anterior pseudopodia, — b and c, —
through which there are fluxes of particles in progress at
about the same rate. The vortical current is seen to divide
and to flow into both these pseudopodia, thus keeping the
outer molecular film over both tense and rounded. Let,
however, a disturbance of the surface-tension occur at the
end of b, while at the end of c' this disturbance subsides, as
in Fig. 5 and there will be a flux of particles out of c' — in
the direction of the arrow — into b, and c' will lose its tense,
full outline, and its surface will become wrinkled or papillated,
just as appears at the "tail" end of the organism at a. In
every detail of the morphology of this organism, we therefore
discover that physical or "physiological" agencies are
operative in determining its figure. We are, therefore, in a
position to aflirm, with positive certainty, that the morphology
of this organism has little significance until its actions and
their physical causes have been studied. This is only one of

7^ BIOLOGICAL LECTURES.

many reasons why the present speaker holds that all purely
morphological work is one-sided, and incapable of dealing with
the deeper problems of biology. In the same way, physiology
alone is equally incapable of dealing with the great general
problems in biology. Neither of the two disciplines alojic can
ever, by any stretch of imagination, command the power to
produce a theory of life. Such an expectation is simi)ly

fatuous.

The many other dynamical phenomena, especially the singular
manner in which the nucleus of an Aniceba protens is caused
to oscillate back and forth within its body within certain limits,
all take place in accord with the views above developed. For
example, the curious lateral flow of the plasma of Ainceba proteiis
when in a fully extended condition, along the sides of the
body on either side of its posterior and middle thirds, may be
explained by the physical tendency of this part of the organism
to adhere to the substratum upon which it is moving. This
lateral spreading does not take place at its " anterior " end
because here the influx of molecules from behind is taking
place so rapidly that this spreading due to adhesion has not
yet had time to take place. This spreading due to adhesion
causes the central current to be narrowed and elevated so that
the discoidal nucleus is lifted and rolled along on its edge in
this narrow elevated part of the body of the organism as if
passing through a tunnel with its sides wider than its floor.
Rolled along in this way through this narrow passage by the
vortical current of plasma, the nucleus is finally arrested by
contact of its edge with the molecular boundary wall of the
organism, and is thus automatically kept from being bodily
rolled to the outside of the plasma of the organism. Reaching
a certain point at the "anterior" end of the mass of plasma,
it also falls over on its side, wedged between the roof and floor
of the mass of plasma of which it forms a part. It is thus
prevented from passing out of the organism with the vortical
current that must now flow jiast it aiid on forward to continually
form anew the "anterior" end of this singular being that is
thus continually turning itself inside outward in front and
outside inward behind.

DVXAMICS IX EVOLUTION. 75

The manner in which the successive rents in the outer
molecular skin of the organism are produced is such that a
sudden rupture occurs through which a fresh outpour of
substance happens over which a new molecular skin is instantly
formed continuous with the ruptured edge of the old. These
rents do not take place in relatively the same place in succession.
For example, rents may occur in the outer film one after the
other at points a little off of the extreme central point of the
" anterior " end, and alternately a little to the right and left side
of the latter. The vortical flux is thus throw^n slightly aside
alternately to the right and then to the left, then to the right,
then to the left again, and so on, indefinitely. It thus results,
however, that the summation of these alternating outbursts of
substance become the components of the aggregate motion of
the whole organism in one general direction.

If a rent occurs at one side of the organism, due to a
disturbance of surface-tension at an anterior lateral point, a
lateral flux of particles may thus be set up, as a result of
which the entire contents of the organism may be sucked up
"anteriorly" and "posteriorly" to the point where the new
outflow has taken place. In other words, the "head" and
" tail " ends of the organism may be thus caused to flow in
opposite directions into the lateral outburst and the whole
organism take a new direction of motion with all its parts
oriented in respect thereto. Ainceba protciis, therefore, cannot
move except by developing a vortical flux of particles, and
it therefore is a "living" vortex-ring of particles. These
outbursts, in large individuals, occur successively at short
intervals of time, so that the motion of the creature is
fitful. In young proteus animalcules the bursting out or
pouring forth of the plasma at the "anterior" end maybe
continuous, so that the motion is uniform and an ideally perfect
type of the "living" vortex-ring of particles is realized.

Every pseudopodium is, however, so long as it is being
protruded, a vortex-current in which the motion of the particles
is swiftest at its center and at its tip, while at the sides the
particles are quiescent and form a shell through which the
central ones are moving. The pseudopodia, therefore, divide

76 BIOLOGICAL LECTURES.

the vortex-current of particles into diverging currents, the
summation of the motions of which may, when the organism
is moving on a plane surface, become resolved mechanically
into a single motion of translation in one direction.

When the organism is freely suspended in water it protrudes
pseudopodia equally in every direction and assumes a globular
figure, somewhat like a Heliozoan or Radiolarian, because
its surface-tension is now being disturbed at nearly equallv
separated points over its whole surface. It therefore falls into
a condition of spherical equilibrium, since the components of
all the surface-tensions are resolved at the centre of the
organism. The moment it touches a fixed surface, distortion of
the formerly globular organism takes place under the influence
of gravity and adhesion, and the vortical flux of particles that
is now set up is different in nature from that which took place
in every direction when it w^as in the suspended globular con-
dition. There is at once a maximum flux of particles in the
direction of the point at which the most active disturbance of
surface-tension occurred, and the resulting current becomes very
massive so that the whole contents of the organism, except the
nucleus and water vacuole, flow forward as a massive pseudopod,
that is somewhat flattened or depressed by the action of gravity
and adhesion, but which is much larger than any of those
produced while in the spherical condition. How little \'erworn
has appreciated and understood these complex jirocesses may
be judged by any one who has read his work on the motion of
livimr substance. He has affirmed what does not exist in
regard to small Amceba protcnx, where the flux is continuous
and where no retreat of particles to the nucleus, such as he
postulates, can take place for hours together. In short,
Verworn has totally failed to understand the real significance
of these complex phenomena. Greef, also, has made assump-
tions with regard to amoeboid motion, especiall}' the existence
of muscular fibrils, which by no stretch of the imagination can
be conceived to hold of the proteus animalcule.

Verworn has also failed to understand the physical reasons
why small blebs or pseudopodial warts Avere produced along the
sides of a retracting pseudopod. He speaks of " stimulation "

DYNAMICS I\ EVOLUTION. 77

{Rciz), a word which to me has a very indefinite meaning.
The production of these blebs or incipient pseudopodia, which
I have often observed, and in a great variety of forms, may be
equally well explained by surface-tensional disturbance, the
viscosity of the plasma, etc., and not necessarily as caused by
a retreat of the substance toward the nucleus, as claimed
by Verworn, in order to receive a reinforcement or accession
of new nuclear molecules.

The differentiation of the substance of an amoeboid, such as
A. protciis, into an outer hyaline layer and a central or medul-
lary part, — the so-called " endosarc " and "ectosarc," — is
again a purely physical phenomenon. The surface-tensional
forces must be exerted, for physical reasons, between molecules
of approximately the same dimensions, otherwise there could
be no tolerably coherent and stable outer stratum formed.
In other words, the molecules of the outer layers are recipro-
cally attracted to each other with a greater force at insensible
distances apart, than the larger and coarser particles are
attracted by the small uniform molecules at the same intervals
apart. The materials of an amoeboid are thus dynamically
sorted into two kinds, in virtue of their differences of attrac-
tion for one another. It thus comes about that "endosarc"
and "ectosarc" are merely names for the results of a
dynamical process that, so to speak, sorts the particles of
a living amoeboid into two kinds. The small surface-particles
or molecules necessarily attract each other under such condi-
tions of dynamical advantage over and above their attraction
for the larger particles, that the latter are constantly driven
inward and kept there for this reason. ^ In this case, again, a
morphological fact is only understood when subjected to
dynamical analysis.

In this way one might go on and subject every detail of the
organization of an amoeboid to physical scrutiny, and show
that complex energy-combinations determined every detail of
its structure. Not a single amoeboid form that I have
yet encountered has failed to disclose this mechanical
and dynamical complex of agencies as factors competent to

1 A geometrical diagram would be needed to make tliis statement perfectly clear.

yS BIOLOGICAL LECTURES.

determine its figure at every instant of its existence. There
may be those, however, who will find fault with my identifi-
cation of the motions of an amoeboid with that of a whirl- or
vortex-ring of particles. It may be well, also, to explain here
that this notion has nothing to do with the physical con-
ception of Lord Kelvin respecting the existence of vortex
atoms. The identification of amoeboid motion with a vortex-
ring of particles is perfect, provided certain reservations are
made that grow out of the very nature of the conditions and
nature of amoeboid motion. In a typical smoke- or vortex-
ring the impulse of rotation that impels all its particles is
imparted from without; in the living vortex-ring secular
changes in the nature of its constituent particles condition
its motions and provoke them. And, while it is true that the
energy that drives the living vortex-ring is primarily derived
from without, it is not set free until the constituent particles
have changed their dimensions, affinities, and reciprocal attrac-
tions within the ring, due to causes acting antecedently from
without. The living vortex-ring is a constantly changing,
closed, and regenerative dynamical system; the other is a
dynamical system that derives all its energy from without in
the form of a single impulse, and comes to rest after a time,
owing to the friction of its superficial particles with their
surroundings.

It may be objected, also, that there is only a remote resem-
blance of a smoke-ring to that of the flux of living particles
through an amoeboid organism. This objection may be met
by the statement, that not only do I suppose the li\-ing vortex-
ring to be flattened by its gravity, but I also suppose it to
have no central opening, and that the median longitudinal
stream of particles represents the ])oint where the opening
would be in a smoke-ring — now a line in Amoeba — along
which the central "living" vortex current is flowing. I
moreover suppose that the ring is greatly elongated, owing
to the viscosity of its substance and the adhesion of the
surface of the living amoeboid to the substratum upon which
it moves. I would not have any one suppose that I imagined
that amoeboids ever existed that had a central opening in them

V\\\AM/CS IN EVOLUriON. 79

like a smoke-ring. I have only used this comparison because
of the obvious identity of the living and dead vortices, when
proper allowance is made for the physical conditions under
which both subsist on account of the different nature of their
constituent substances. The outer molecular shell, for example,
of a living vortex-ring is fixed to its substratum, and is only
involuted " posteriorlV," and evoluted "anteriorly" as it moves
over a fixed surface. These ideas once clearly grasped, will
enable any one to see that, underlying the apparent unlikeness
of the smoke-ring to a living amoeboid vortex, there is in reality
a fundamental similarity. The kind of " contractility" which is
exhibited by an amceboid is thus also seen to be fundamentally
different in nature from that presented by a muscle, in which
contraction is conditioned by a vastly more complex structure.
When an Amoeba passes into the resting stage its plasma is
very apt to assume an almost perfectly globular form. Its
pseudopodia are retracted ; its surface becomes smooth, and
the whole organism passes into the almost homogeneous,
quiescent or lethargic condition of a ball of protoplasm that no
longer manifests its characteristic types of motion and irrita-
bility, at least externally. Unequal surface-tensional disturb-
ances no longer affect it ; it is now under the domination of
the same phvsical influences that determine the globular form
of a sphere of oil in a mixture of alcohol and water of the same
specific gravity as itself. Its cytoplasmic substance is nearly
or quite homogeneous, and the excessively slow and torpid meta-
bolic processes, within the protoplasmic mass of the Amoeba,
now secrete or pour out a cuticle or envelope over its surface
and in which the organism is said to be -encysted." All of
these processes are purely dynamical, just as were all of those
associated with the motion of the organism. Not only are all
of these processes dynamical, but all are also directly "adap-
tive," in virtue of the fact that the equilibria successively
attained are merely a quantitative dynamical response from
within a " living " molecular mechanism to a change in external
energy-conditions. All "adaptation" is to be so interpreted,
so that "natural selection" may be at last resolved into pure
energy-factors, and thus brought into codrdination with the

8o BIOLOGICAL LECTURES.

rest of the forces of the cosmical universe. The mischievous
metaphor, "natural selection," has blinded many naturalists to
the real meaning of this expression.

In the same way we may discuss the characters of other
amoeboids. Each is found to have its own kind of plasma,
that behaves differently in each species. Some move more
rapidly than others, some have blunt, others long, slender or
attenuated pseudopodia ; some may have bent pseudopodia, or
have the axes of their straight pseudopodia normal to the sur-
face of the spherical body of the organism ; others obey a
different rule in this respect. In some the plasma is clear,
in others more opaque ; in some the nucleus is globular, in
others flattened. Thus one might go on and show that the
different proportions and behaviors of the same parts, in dif-
ferent species, was evidence that totally different molecular
mechanisms were simply making their necessarih' different
responses to the same environment, because of differences
in the physical and chemical properties of their constituent
plasma. Herein, probably, also lies the whole secret of the dif-
ference of power presented by the germs of different creatures.
They develop as they do in the case of each species, because
of their specific chemical constitutions, and not because there
are a lot of "biophores," "gemmules," etc., "superintending"
the business of development in a particular way during the
evolution of the egg of each form. The preposterous assump-
tion that enough energy can be squeezed intt) an Qg'-^ poten-
tially to carry the materials into place that are assimilated during
development in order to build an elephant, for example, is
worthy of mediaeval philosophers, but not of those of the close
of the nineteenth century. Every form of energy, including
that of "life," is correlated, and is amenable to the same laws.
V\A\ knowledge of the mode of operation of the material
energy-complexes that we call "living," will disclose the true
theory of morphology and the true meaning of life as well.

These, here incompletely reported, observations make it toler-
ably clear that amoeboid motion is worth studying, in order to
get clear notions of how living motions and energies are oper-
ative in one of the simplest organisms known to the zoologist.

DYNAMICS IX EVOLUTION. 8 1

They also make it very evident that observers have hitherto
allowed purely morphological considerations to becloud their
vision. In order to discover the meaning of the morphology
of the simplest organisms, their actions must be subjected to
the most searching analysis. These observations have proved
that the functions of an organism are also functions of its form.
It has been pretty clearly established, by what has been said
above, that every action of the Amoeba was followed by a mor-
phological change. In the belief that this same thing holds
good throughout the whole animal and vegetable world under
most complexly interacting energy-conditions, I will predict
what I believe will yet be possible, viz., the discovery of the
true causes, in detail, of the forms of all organized existences.
In order, however, to accomplish this end, the following will
first have to happen, namely, an abandonment of all hitherto
accepted hypotheses of inheritance, a new conception of the
nature of life, new views of the nature of the process of natural
selection, and, above all, the abandonment of all such concep-
tions as gemmules, biophores, pangenes, plastidules, plassomes,
etc, and\he admission that the phenomena of life are ulti-
mately physical in their nature and are to be treated in detail
as phvsical problems.

It is now my firm conviction, also, that experimental investi-
gation in embryology will make no solid pr'ogress until the
foregoing prepossessions are abandoned, or until the mischiev-
ous Influence of such speculations and their kindred, as those
recrarding a -germ-plasm," etc., have been entirely eradicated
from the minds of the present generation. In conclusion,
let me remark that five sciences are indissolubly connected
too-ether in the study of the fundamental problems of life;
these are ■ phvsics, chemistry, physiology, morphology, and
psychology. When each of these sciences shall have been
o-iven its due weight and place in the conduct of the study of
Hfe-forms, we shall begin to know what the latter really mean,
but not until then.

FIFTH LECTURE.

ON THE NATURE OF CELL-ORGANIZATION.i

S. WATASE.

L

If the true nature of a higher organism cannot be
understood without considering the structure and the function
of its component organs, it is equally certain that the nature
of an individual cell cannot be made intelligible without a
comprehensive study of the different organs of which it is
composed.

At the present time, when morphologists are explaining
the origin and development of the different structures in an
organism in terms of cell-growth and of cell-metamorphosis,
and when physiologists are referring the activities of the whole
organism back to the functions of its component cells, it is
natural that considerable attention should now be directed
toward the solution of more elementary problems concerning
the nature of the cell-organism. The cell-theory, while it
explains the structure and functions of a tissue on a cellular
basis, leaves the real nature of the cell itself unexplained.

The vital properties of a nucleated cell manifest themselves
in various ways, but they may be broadly classified under two
categories, •z'/.c., (i), those tending to the preservation of the
individual cell, and (2), those tending to the maintenance of
the species. Under the first are included the general phe-
nomena of cell-metabolism and different forms of irritability,
and under the second those of cell-division and cell-fusion.

Diverse as are these special cell-phenomena which tend
directly or indirectly to the preservation of the cell, it must

1 Lecture given before the Biological Club of the University of Chicago,
February 7, 1893, ^•'"^ afterward written out in the present form.

84 BIOLOGICAL LECTURES.

be admitted that their real significance can only be under-
stood when each is taken in connection with the others,
the tout ensemble of which form the life of the nucleated
cell. If any explanation of special phenomena be attempted,
it should be in the light of what we know of the whole.

We do not gain much, however, by so saying, as long as
this knowledge of the whole is merely a name for the sum
total of incoherent observations on diverse cell-phenomena.
Beneath and beyond all vital manifestations of a cell, there
must exist a primary physiological condition, on which the
details of secondary cell-phenomena depend. Just what con-
stitutes the primary physiological phenomenon of the cell,
is the point that I wish to discuss in the present paper,
believing, as I do, that such a problem as that of cell-organ-
ization, can be approached from the functional side with
better effect than has thus far been attained from the side of
pure morphology.

Before we proceed further, it may not be out of place here
to introduce a general schematic description of a nucleated

cell.i

Excluding the centrosome and chromatophore for the present,
an animal cell may be described as composed of two sharply
distinct organs : the cell-body {eytosonie), and the nucleus
{caryosonie).

The nucleus, in its "resting stage," has a definite membrane
around it, called the nuclear membrane or caryotlieea. The
cell-body consists of a net-work of cytoplasm. This net-work
contains within its own substance small bodies of varying
sizes, which are known as the microsomes or, more strictly,
the cytomicrosomes. Surrounding the cytosome, there is a
membrane known as the cell-membrane or cytotJteea. It may
exist as a thickened border of the cytosome or as a distinct
membrane separated from the cytosome.

1 The descriptive cytological terms adopted here have merely an anatomical
significance, and do not refer to the chemical or functional properties of the struc-
ture. Several terms recently used by Hscckel (Aiit/iropos^oiif, 4th edition, Leipzig,
1891), have therefore been found most convenient. ( )nly the more salient features
of the cell will be emphasized in this place, that being sufficient for our present
purpose.

OA' THE NATURE OE CELL-ORGAMZATIOX. 85

The meshes of the cytoplasm are filled with a Hukl sub-
stance, commonly called the cytoplasmic fluid, or to use
Haeckel's term, the cytolyuiph.

The cytoplasm is, however, the only living portion of the
cell-body, and hence properly belongs to the category of
protoplasm in the more strict technical sense of the term. The
cytolymph is the inert, passive, non-living portion of the
cell-body. Besides the cytolymph, there usually exist a number
of non-living bodies in the cell-body, as yolk-granules, oil drops,
debris of food, zymogen granules, etc., according to the nature
of different cells. These non-living substances altogether
belong to the group known as victaplasni or paraplasm, in
contradistinction to the substance which is the real living
element of the cell — the protoplasm.

The contents of the nucleus (caryosojiic) may be arranged
also into two similar groups of living and non-living elements.
The chromosome is distinctly protoplasmic in character, and so
is the fine net-work of the "achromatic" thread-like substance
which is often found traversing the nuclear cavity. In several
cases, if not in all, these filaments are the actual continuation
of the cytoplasmic net-work existing around the nuclear
membrane.

The fluid substance which bathes these semi-solid living
constituents of the nucleus is known as nuclear fluid or caryo-
lyinph. In the caryolymph there exists a body known as the
iiiiclcolus. In certain cases, the filaments of the chromosome
have been found passing through the substance of the nucleolus
or directly ending in it. Sometimes only one nucleolus exists
in each nucleus, while in other cases over one hundred nucleoli
may be found in one nucleus. The number of nucleoli is quite
variable in different cells, but fairly constant in a given species
of cell. The nucleolus is not a permanent body in the nucleus.
It may exist at one stage of the cell, and may disappear at the
next. The micro-chemical reaction of the nucleolus is entirely
different from that of the chromosome. It appears probable
that three or more different bodies are included under the
same name of nucleolus. Indeed, one sees no reason why the
inside of the nuclear membrane may not be used as a deposi-

86 BIOLOGICAL LECTURES.

tory for some solid products of cell-metabolism, under certain
circumstances, just as the spaces in the cell-body are used for
such a purpose. And thus sonic of the bodies included under
the generic name of nucleolus, may belong to the group of
metaplasm. It is, however, difficult to pass any definite
opinion on the nature of the nucleolus at the present stage
of our knowledge on the subject.

To recapitulate briefly, then, the chromosome and cyptoplasm
are the two active, living constituents of the cell. The rest of
the bulk of a cell consists of non-living substances, which have
yet to be converted into vital elements, or are the products of
metabolism which have now lost the distinctive characteristic
of a living substance.

The behavior of the cytoplasmic thread or network suggests
that it is formed of a group of small, living particles, each
with the power to assimilate, to grow and multiply by division.
The chromosome, in the same way, is itself a colony of
minute organisms of another kind, each endowed with similar
attributes of vitality. The media, in which they live, — the
cytolymph and caryolymph — are the media in which they
breathe, from which they derive their nourishment, or within
which they deposit the products of their metabolism. The
reason why the cell as a whole assimilates, grows and divides,
is ultimately due to the fact that the minute particles which
compose the cytoplasm and chromosome are endowed with
these functions.

Keeping in mind then such a simple nucleated cell like
an amoeba or an animal ovum, as a type, let us ask ourselves
the following questions : What is the relation of nucleus^ to
cytoplasm, and of cytoplasm to nucleus in a cell .' What is
the significance of this duplex morphological organization .-*
Through what process may such an organization as the
nucleated cell be considered to have come into existence.-*

The biogenetic law as applied to the stud)' of metazoan
organisms, has been an important instrument of research in the
field of comparative anatomy and cmbrvologv. but it is hard to

^ In the following, the word " nucleus " is used, unless otherwise stated,
synonymous with its essential constituent, the " chromosome."

ox thb: nature of CELL-ORGANIZATIOX. 87

use it as a working theory in the explanation of cellular
phenomena such as I have already indicated. For it is possible
that the law followed by the ccll-aggrcgatc in the course of its
development, may not have been followed in the formation of
the individual cell.

It is perfectly conceivable that the process by which the cell
was first formed may have been due to causes of special
character, while the conversion of the cell thus formed, into an
organism of higher complexity, may have been due to causes
entirely different from those that operated in the production of
the nucleated cell.

There is no necessary reason to conclude, as has been done
by several naturalists, that because the complex organism
develops by a process of differentiation of the homogeneous
germ, the duplex structure of the cellular units which compose
the organism, must have also had a parallel course of develop-
ment from its antecedent germ.

It is this point that I wish to discuss more in detail in the

following.

II.

The parts of a living organism commonly termed its organs
may be studied from three points of view : —

1. How far are these parts adapted, by their form and
structure, to perform their physiological work } This mode of
studying the organs belongs to physiology.

2. Where and how do they arise in a given organism t This
field of study is a branch of morphology.

3. If the morphological study of the organ be extended
through organisms of different grades of complexity, it may
enable us to infer the probable steps through which the given
organ may have passed in the course of its phylogenetic history.

When these three modes of study as pursued by naturalists
at the present day, are applied to the study of organs of an
individual cell, it resolves itself into three problems : —

I. How far are nucleus and cytoplasm adapted by their form
and structure, to perform their physiological work in a given
cell?

88 BIOLOGIC.!/, LECTURES.

2. In what manner do they originate in a given cell ? This
ultimately resolves itself into the problem of cell-division
{Cytouicry) on the one hand and cell-fusion on the other.

3. What are the probable steps in the ancestral history, by
which these structures came into existence ? This belonsrs to
the broad question of Cytogcny as understood in its phylogenetic
sense.

In following out these ciuestions more in detail, it is
important to bear in mind at the outset, some vital distinctions
in\-olved in the use of the term organ, whether we understand
it in a ^wxo^y pJiysiological, or in a morphological •><ix\'~,<t. P^^om
the purely physiological standpoint, any structure or member
which, by its activity, contributes to the general welfare of the
whole organism is an organ, whether that structure may have
originated primarily in the organism, or may have been derived
secandarily from an external source. Thus, the chromatophores ^
in the leaves of a plant are the organs of assimilation in that
plant ; the " gonidia " in the thallus of a lichen are the organs
of a lichen, in a physiological sense as the heart or lung is the
organ in the body of a higher organism.

But from the morphological side of the case it is different.
According to the morphological view, every diffcroitiatcd
organism, every organism composed of organs, can only Jiave
originated from a //omogeneons sfage by the differentiation of
its parts. To state this in another wa\', "however complicated
one ot the higher animals and j^lants may be, it begins its
separate existence under the form of a nucleated cell. This,
bv division, becomes converted into an aggregate of nucleated
cells : the ])arts of this aggregate, following different laws of
growth and multiplication, give rise to the ludiments of the
organs ; and the parts of these rudiments again take those
modes of growth and multiplication and metamorphosis which
are needful to con\ert the rudiment into the perfect structure." ^

' TliL' term chromatophorc (Schmitz) is here usud in a broad sense, including
leiicoplasts and the various coloring substances in the llower and the fruit, as well
as the chrophyll granules in the leaves of a green plant. The term is synonymous
with .\rthur Meyer's tro/>/io/>/ast a.x\d. Schimper's/A/.f/'/V.

- T. II. Huxley : Article /y/otoxy, Encyclopaedia I'.ritannica, 9th edition. \'()1. Ill,
p. 6S2, 1S7S.

OA' THE XATLRE OF CELL-ORGAXIZATJUX. 89

Now, this morphological criterion of an organ, which
necessarily relates to the history and mode of its origin within
tJic on^wtisiii, by the dijfiTcntiatioji of its parts, does not apply
to the chromatophore in a green plant, nor to the "gonidia"
in a lichen thallus, although there can be no doubt whatever
that these structures serve as organs in the physiological sense,
in the respective organisms. The chromatophores are not
the products of differentiation of an homogeneous germ of
the plant. They can only originate b}' the division of i)re-
existing chromatophores, if we follow such botanists as Schmitz,
Schimpcr and Meyer. ^ The colorless protoplasm of the i)lant
and the chromatophores are the coexistent but independent
structures, with no genetic connection between them.

In the organization of a lichen, the case is clearer and more
to the point of our inquiry. As is well known, the "gonidia"
and their supporting meshwork are derived from two different
groups of plants, I'i.z., AlgcE and Finigi, respectively, although
their physiological adaptation to each other is so perfect, so
much so, in fact, that in several lichens the hyphas of the
fungus cannot live when separated from the algal portion, the
"gonidia." Here, again, it is needless to say that these two
organs are not the products of differentiation from some homo-
geneous anlagc as different organs are in one of the complex
animals.^ On the other hand, the "gonidia" of one individual
lichen are genetically related to the "gonidia" of another, and
not at all to the hyphae of the thallus. In a similar way the
hyphae of one individual lichen are genetically related to the
hyphae of another lichen of the same species, and iiot to

1 Schmitz : Dk Ctiromatophorcii dcr Ali^en, Bonn, 1882. Schimper : Ueher die
EnttoickcliiHg der C/ilcrophylliydnicr mid Farhiyorpcr, Bot. Zeit., 1S83, 41. Jahrg.
Meyer : Ueber Krystalloide der Tropltoplaslcii mid iibcr die CJirimioplastcii dcr
Atigtospertnen, Bot. Zeit., 1S83, 41. Jahrg.

- Before the discovery of the true nature of lichens, it was thought that both
" gonidia " and supporting fungal hypha; were the products of development of a
single germinating spore. "Gonidia," which are the symbiotic algal cells, were
supposed to be, as the term indicates, ase.xual organs of reproduction produced
from the hyphre and capable of development into a new and perfect lichen-thallus.
The view that hyphae might also be produced from the "gonidia" was often
expressed. De Bary, Historical Ahitice of tJic LicJiens. Comp. Morphology and
Biology of Fungi, etc., p. 416.

2

go BIOLOGICAL LECTURES.

the " <;-()nidia,"' with which they live in ch)se symbiotic rela-
tions.^

Thus the morphological and physiological consideration of
an organ, such as we have just given, leads us to conclude that
when we find two structures in an individual organism most
intimately associated in their physiological relationship, it does
not necessarily follow that they are organs in the morphological
sense also. The history of the lichen clearly shows that cm
iiidcpcndcut organism, composed of orgcuis, coin be created by tJie
union of two dissimilar organisms by the establishment of an
intimate physiological relationship between them. In fact, a
certain number of species of lichens have been actually pro
duced by bringing fungi and algae together in a synthetic way
The fungus and alga, by the interchange of their metabolic
products, supply the nutritive wants of each, and thus produce
the autonomous whole which can exist in places where neither
the alija nor the fungus would be able to e.xist separately.

In dealing with the structures in an organism commonly
called organs, I repeat, we must clearly bear in mind wdiether
tl-ie structure in question is an organ in the physiological and
morphological senses, or whether it is an organ simply in the
physiological sense. If the structure is an organ in the mor-
phological sense, the study of the development of the whole
or<^anism will show that it is a part of the products of differ-
entiation of some preexisting germ from which the entire
organism was derived ; if it be an organ in a purely physio-
logical sense alone, there will be no genetic connection between
the different structures, although each is indispensable to the
existence of the other. In short, the perfection to which the
physiological adaptation of different organs is carried out in a
given organism, is, in itself, no procf that they were derived
by the differentiation cf some common germ : but, on the con-
trary, t7U0 dissimilar organisms may, by mutual adaptation,

1 In u.sing the term "symbiotic," to express the relation between the alga and
fungus in the organism of a lichen, I simply follow such botanists as JJe Bary
{Die Ersckeinung der Sytnbiose, Strassburg, 1879, P- '5- *^t seq.), Frank {Symbiose,
Lehrbuch der Botanik, Bd. I, 1892. T,eipzig), and others.

- See, for example, the recent work by Bonnier, l\ccln-rihes sttr la syiitJiisc dcs
lichens. Ann. des sc. nat., 7'"^ serie, IX, Botanique, 18S9.

ON THE XATURE OF CELL-ORGANIZATIOX. 91

give rise to a third organisui in ivhich each of them serves as
an orgaji to the zvhoie.

It is needless to say that almost all structures in higher
organisms ^ are derived by the differentiation of some pre-
existing germ, but at the same time it is important to bear in
mind that this is not always the case, particularly in the lower
forms. It is this consideration which interests us particularly,
as it may be the key to the interpretation of the organization
represented by the single nucleated cell.

III.

The permanent organs of the cell are, following the recent
exposition of Strasburger,- considered to be (i) Cytoplasm,
(2) Nucleus, (3) Centrosome, (4) Chromatophore.

The last named structure occurs normally in the cells of
green plants, and sometimes in those of animals.^ Following

1 If Riickert's observation [Ubcr physiologischc Poly sperm ic bci incrohlastischen
Wirbeltiereiern, Anat. Anzeiger, Bd. VII, 1892) that in a certain vertebrate the
merocyte-nuclei come from the nuclei of the supernumerary sperm-cells which
enter the ovum, be confirmed, it would seem that a part of one important
embryonic organ, in an organism like Torpedo, is bodily derived from the outside
source.

■■^ E. Strasburger : Das Protoplasnia lutd die Reizbarkeit, 1S91, Jena.

^ See in this connection, Lankester's article Animal Chlorophyll (Xature, vol. 44,
1891) which is the review of G. Haberlandt's paper Ueber den Ban und die Beden-
tung der Chlorophyllzellen von Convoliita Roscoffensis, in von Graff's Die Organi-
sation der Tnrbellaria aeada, 1S91, Leipzig. I have not been able to see
Haberlandt's original paper. Haberlandt suggests, to quote Prof. Lankester,
"that while phylogenetically they [chlorophyll-cells in Convolnfa] must be regarded
as Algee (that is to say, have descended from Algae) yet at the present time they
have by profound adaptation to life in and with the Convolnta, altogether lost
their character as algal organisms, and have become an integral histological
element of the worm, and in fact constitute its assimilation tissue. . . . Haber-
landt is inclined to place his theory as to the green cells of Convoliita alongside
the suggestion of Schimper as to the origin of the chlorophyll corpuscles of higher
plant — namely, that these are due to the union in the remote past of a green
colored with a colorless organism."

Schimper has shown that the chromatophores (Schimper's plastids) are formed
by the division of the preexisting chromatophores, and not by the differentiation
of the cell-protoplasm. .Schimper's view referred to above on the origin of the
chlorophyll bodies in the plant cells may be gathered from the following quota-
tions : " Sollte es sich definitiv bestatigen," says Schimper, " dass die Plastiden in
den luzellen nicht neu gebildet werden, so wurde ihre Beziehung zu dem sie
enthaltenden Organismus einigermassen an eine Symbiose erinnern. Moglicher-

g2 BIOLOGICAL LECTURES.

the views held by Schmitz, Schimper and others, we have
already regarded this structure as an organ totally independent
of the colorless protoplasm of the green plant. In regard to
the centrosome, aside from its apparent function during the
division of the nucleus, we know very little to justify our
discussion in the present connection. Personally, I cannot
ao-ree with those who place the centrosome in the same category
of the permanent cell-organs as the nucleus. On the other
hand, I believe that the centrosome is a special form of the
cytomicrosome, which exists almost in every part of the cell.
Yox the reason of this homology of the centrosome, I may
refer the reader to my former paper. ^

weise verdanken die griinen Pflanzen wirklich einer Vereinigung eines farblosen
Urganismus niit eiiiem von Chlorophyll gleichmassig thigirten ihren Ursprung."
(Schimper : Ueber die Eittwickcliiii^^ dcr C/ilorop/iyll/conwr mid Farbkorper, Bot.
Zeit., 41. Jahrg., 1883, pp. 111-112.) Schimper supports this statement by quoting
Reinke (Allg. IJotanik, p. 62), who states that the chlorophyll bodies in the
decomposing cells of a cucumber attacked by a certain fungus, still continued to
grow and multiply.

In view of the fact that there e.xists a close analogy between the nucleus
and the chromatophore (see Schmitz, Die CliroDiatophorcn dcr Ali^cn, ISonn, 1SS2,
p. 167), the observations by Metschnikoff and Soudakewitch {La phagocytose
iHiisciilairc : coiitribiitio)! <) l^iiidc de F i)iJIammalioH paroichyniatcnse. Annales de
rinstitut I'asteur, 6»ie Annce, No. i, Janvier, 1S92, pp. 1-20, Pis. I-III), on the
repeated division of the vtusele iiuelei in the debris of degenerating viusele fibres
whieh originally constituted a part of their cytoplasm, in the course of muscle
degeneration, may be interpreted in the same way as Schimi>er did of Reinke's
observation on the behavior of the chlorophyll bodies in the clecomijosing vegetable
tissue referred to above.

For the view that considers the animal chlorophylls as the veritable AlgK, see
the well-known ])apers by C'fesa-p:ntz and K. IJrandt. Keli.x le Dantec, in his
recent paper, Recherclies sur la sy»ibiose des algues et des protozoaires ( Annales de
rinstitut Pasteur, t. VI, No. 3, 1S92), has brought further experimental evidence
in support of the view that the chlorophyll corpuscles in an animal organism as
Parama-cium, are the symbiotic Alg?e. I mention these simply Xo call attention
once more to the fact that certain parts of an organism, which were originally
considered to be integral elements of the organism, derived by the differentiation
of the germ, have been shown to be due, in reality, to a secondary association of
two or more different organisms, originally separate and independent, and what
we call organs from the physiological side, in such an organism, are in reality
organisms by tliemselves.

is. Watase : Jfomology of the Centrosome, Jdi-rnai. ok MoKriiiU.ocv, Vol. VI 1 1,
Pt. 2, 1893. ^- l^rauer {Zur Kenntniss der Jlerkunft des Ceulrosomas, liiol. Central-
blatt, Bd. XIIi. Nr. 9 u. 10, May, 1893), has recently come to the conclusion that
in the spermatocyte of Ascaris megaloeephala, variety uniTalens, the centrosome

OiV THE NATURE OF CELL-ORGANIZATION. 93

If, therefore, I omit from consideration the chromatophore
and the centrosome in the following, it is because the former
has been fully treated by able botanists, and the latter is
not sufficiently known, to my knowledge, to admit of useful
discussion in connection with our subject. If, however, the
centrosome be shown to be an organ of the cell, contrary to
my former conclusion above alluded to, with a morphological
significance comparable to that of the nucleus or the cyto-
plasm, the inference I advance in regard to the nature of the
latter organs will apply equally well to the former.

Confining our remarks, then, to the nucleus and the cyto-
plasm, we may first ask whether the nucleus is to be regarded
as an organ in a morphological sense, or only in a physiological
one. Are nucleus and cytoplasm products of differentiation
from some homogeneous aiilagc in the sense that all morpho-
logical organs are, or may not their constant occurrence in
the cell rather be regarded as the result of a union formed in
the remote past, between two organisms originally independent
and dissimilar — a union of such a kind that ages of mutual
adaptations have rendered their independent existence no longer
possible 1 Is it not possible to regard the cell as a symbiotic
community, in which the cytoplasm represents one group of

originates in the inside of the nuclear membrane. Brauer's view, however, does
not militate against my statement that the centrosome is the cyto-microsome of a
gigantic size, and that wherever cytoplasmic net-work exists there is a possibility
of developing a microsome. When the centrosome originates inside of the
nuclear membrane, it may be said, for a descriptive purpose, that it is derived
from the nucleus; when it originates outside of the nuclear membrane, such
a centrosome may be said to be cytoplasmic in its origin. Such a distinction is
purely a nominal one, however, from my standpoint, and I believe the general
statement that all centrosomes are cytoplasmic in their origin is fundamentally a
correct one. Confusion only arises when we do not keep in mind the fact that
the cytoplasmic net-work, in the substance of -which the microsome and centrosome
arise, exists on both sides of the nuclear metnbrane, and the strnctin-e known as
nucleus, contains a great deal of cytoplasmic substance in it.

As is beautifully shown in Brauer's more recent paper (Zjtr Kcuutniss dcr Sper-
matogenese von Ascaris tnegalocephala. Arch. f. mikr. Anat., Bd. 42, 1893, August,
p. 185), the fact that in one variety of Ascaris inegalocephala, namely, univalens,
the centrosome lies inside, and in another variety, bivalens, outside of the nuclear
membrane, is enough, to my mind, to show that it is the substance which gives
rise to the centrosome, and not the position where the centrosome makes its first
appearance, which we must consider in the determination of its homology.

94

BIOLOGICAL LECTURES.

extremely minute organisms, each with a power of growing,
assimilating, and dividing ; and the nucleus, or, more strictly,
the chromosomes, a colony of still different forms, each with
the same powers, — the whole making an organization compar-
able to that of the lichen, which is composed of two totally
dissimilar organisms ?

If this be so, then, there are two possible ways of explaining
the nature of a nucleated cell ; viz., the Theory of Diffcreii-
tiation, such as was held by Hasckel, Auerbach, and several
others, and more recently by Verworn ^ and Wiesner,^ and the
Theory of Symbiosis, as I have briefly suggested.

Let us examine the fundamental phenomena of the nucle-
ated cell from the standpoint of the symbiotic theory, and,
incidentally, point out the inadequacy of the differentiation
hypothesis as an explanation of the cell phenomena in general.

IV.

Two important activities in the developmental phases of
protoplasmic lifc^zxo. cell-division, e.g., caryokinesis, and cell-
fusion, e.g., fecundation. In both cases, the identity of the
nucleus and of the cytoplasm is never once lost during the
whole series of remarkable changes. There is a continuity of
nuclear matter from one phase to another, just as there is a
continuity of the cytoplasm through the successive periods in
the history of the cell. In other words, the nucleus always
originates from a preceding nucleus, and the cytoplasm from a
preceding cytoplasm. There is no evidence proving that the
nucleus is formed by the process of differentiation from the
cytoplasm, nor that the cytoplasm is formed by the differen-

1 Max Verworn: Die physiologische Bedciitiing dcs Zcll-kcnis, Bonn, 1S91,

p. 115.

2 J. Wiesner: Die Elemcntarstnutur und das Wachsthttm der iel>e)ideii Substanz,

Wien, 1892, p. 266.

3 Following the suggestion brought out by Professor Burdon Sanderson in his
discourse on the elementary problems in physiology (Xatiire, Vol. XI, Sept. 26,
18S9), it is convenient to divide the protoplasmic activities into two main groups

the developmental and the iion-developme>ttal. The former refers to those

phenomena of the cell which are more especially connected with the development
or unfolding of latent character of the germ, and the latter to such functions as
respiration, secretion, excretion, etc.

O.V THE XATURE OF CELL-ORGANIZATIOX. 95

tiation of nuclear substance. The developmental history of
these two substances naturally leads us to regard them as
independent structures, although each is necessary to the
physiological existence of the other. They are not, therefore,
morphological organs of the cell in the sense of the term as
we have explained it. Furthermore, the phenomena of division
in the nucleus and cytoplasm remind us forcibly of the mode
of origin of the soredia in the lichen ; nor is this remarkable, if
a nucleated cell is, like the lichen, a symbiotic community of
two dissimilar organisms. The single soredium is a miniature
lichen, consisting of one or more algal cells with a weft of
fungal tissue around them. The algal and fungal elements in
a single soredium are derived from the corresponding elements
in the mother lichen-thallus, just as the daughter cell derives
its nucleus and cytoplasm from the corresponding elements in
the mother cell.

The most convincing argument proving the symbiotic
character of a lichen consists in the synthetic production of
certain species of lichens, by bringing algal and fungal
elements together. If, therefore, the morphological rela-
tionship between nucleus and cytoplasm in a ceil is that of
a symbiotic community, the fact analogous to the artificial
synthesis of lichens must be found in the cell. I venture to
suggest that such a synthesis of a living cell has been accom-
plished. I refer to Verworn's ^ experiment on the Radiolarian,
TJialassicolla. Verworn took three vessels of equal size, and
in the first he put a number of normal TJialassicolla ; in the
second, he put one which had its central capsule with its
nucleus removed ; in the third, he placed an individual whose
central capsule had been removed and replaced by the trans-
plantation of the central capsule of another individual of the
same species. The Radiolarian in the third vessel was,
therefore, a synthetic one, the extra capsular protoplasm lying
outside of the central capsule, being derived from one indi-
vidual, and the central capsule itself, with its nucleus, being
derived from another. In the course of time, the TJialassi-
colla which had lost its nucleus by the removal of its central

1 Verworn, loc. cit., p. 42.

g6 BIOLOGICAL LECTURES.

capsule died, while the other Radiolarian which had lost its
nucleus and then regained it, by the acquisition of a central
capsule of another individual, throve well, and could not be
distinguished from the normal ThalassicoIIa in the first vessel,
upon which no operation had been performed.

This is, in my judgment, a genuine case of synthesis of a
living nucleated cell, by bringing, from two dissimilar sources,
the cytoplasmic and nuclear elements together. If Stahl's and
Bonnier's results, on the synthesis of lichens are the conclusive
evidence of their symbiotic character, may not the Verworn's
experiments on ThalassicoIIa be interpreted as equally conclu-
sive evidence of the symbiotic origin of the nucleated cell .''
In fact, the process of fecundation is nothing more than a
synthetic production of one nucleated cell from two nucleated
cells that are derived from independent sources. And, further,
there is good ground, as the phenomena of heredity show, for
believing that each germ substance retains the individual
qualities characteristic of its origin, throughout all stages of
later development of the organism.

It is true that, in the case of a lichen, the algal and the
fungal elements may exist independently, while in case of the
nucleated cell, all investigation leads to the conclusion that
when the nucleus is separated permanently from the cytoplasm
or the cytoplasm separated from the nucleus, they invariably
die, sooner or later.^

This is, however, no objection to the idea of the symbiotic
origin of the nucleated cell, as a moment's reflection will
show, for the more perfect the symbiotic adaptation of two
organisms, the greater is their inability to live independently,
until at last the symbiotic existence between the two organisms
becomes imperative, if they are to continue to exist. Remove

1 For recent contributions and a general summary of our knowledge on the
relation between nucleus and cytoplasm, see O. Ilertwig : Die Zdk und dU
Gi-iuche, Jena, 1893 ; E. G. Balbiani : A'ouvcUes recherches exphimcntalcs sur la
tnerotomie c/cs iitfusoires cities. Annales de micrographie, Nos. 8, 9 and 10, t. IV,
1892, Paris; Verworn : Die fhysiologische Bedeutuiig des Zell kerns, Bonn, 1891 ;
Korschelt : Beitrdge zur Morphologic itnd Physiologic des Zellkernes, Jena, 1S89 ;
Whitman : The Seat of Formative and Regenerative Energy, Journal or Mor-
phology Vol. II, 1888, Boston.

ox THE NATURE OE CELL-ORGAN/Z AT/ON. 97

that opportunity, by one means or another, of their combining
thus and death is the result, somewhat in the same way as in
the case of an obhgatory parasite, which though descended
from a free-living ancestor, dies if deprived of its appropriate
host.

The minute organisms which we assume to make up the
cytoplasm on the one hand and nucleus on the other, probably
once were free and lived independently, but if so, it is plain
they have since lost their power by the acquisition of sym-
biotic habits. By adopting symbiotic habits, however, they
acquired the ability to adapt themselves to surroundings so
different from the normal habitat of each that neither symbiont
alone could have lived in them, and thus possibilities each was
incapable of accomplishing alone, are performed successfully
by the composite organism. ^ We can reasonably suppose,
therefore, that those cell- forming organisms, which entered into
the symbiotic relation in the past, zvith others, have survived in
a modified form, in the body of the nucleated cell, zvhile those
oro-anisms zvhicJi did not, have perished ozving to their iiiability
to adapt themselves to the vicissitudes of circumstances. The
nucleated cell, then, is a colony of heterogeneous organisms,
which maintains a complete autonomy and behaves as if it were
an independent organic being, subject to the law of growth and
development peculiar to itself.

It is perhaps needless to point out, after we have dwelt so
much on the subject, that the fundamental assumption of our
theory is that at least some of the earliest living beings that
■ever existed ivere not in the form of a cell, but a great deal
simpler, somezvhat like those individual physiological units
zuhich constitute the cytoplasm and the nucleus of the cell. The
cell itself was formed later out of these still smaller organisms
which already existed. It is not our purpose, in this place, to
enter into an extensive examination of the different views that
have been brought forward to explain what these cell-forming
units are. All that is essential for our present purpose is the
existence, as all writers unanimously agree, of such units in

1 See important remarks on the result of commensalism between two organisms.
Sachs : Physiology of Plants, pp. 391-394.

gS BIOLOGICAL LECTURES.

¥

the cell, each with the power of assimilating, of growing and
of multiplying by division.^

Perhaps the easiest way of arriving at the conception of
the existence of such ultra-microscopic organisms in the cell is
attained by separating the cytoplasm from the nucleus in a
given cell, say an Amoeba, and dividing each of them into
smaller and smaller pieces, as far as our imagination can carry
us. "Just as in division of the chemical mass we come to the
chemical molecule, the further division of which changes the
properties of the substance, so in the continual division of the
Amoeba we should come to a stage in which farther division
interfered with the physiological action ; we should come to a
physiological unit, corresponding to, but greatly more complex
than the chemical molecule." ^ Such a physiological unit,
Foster suggests, might be called a Soviacidc. This physiologi-
cal unit is what Weismann calls the "bearer of vitality," or
Biopho?-, because it is the smallest unit which exhibits the
primary vital forces., viz, assimilation and metabolism, growth,
and multiplication by fission''' This unit is not the chemical
molecule, hence it has all the essential characteristics of living
organisms, such as assimilation and division, and mere
molecules can neither assimilate nor multiply. It is, in fact,
the organism itself, with all fundamental attributes of the
higher organism; indeed, the reason why a higher organism
exhibits these fundamental properties, is, as has already been
mentioned, because its component units are endowed with such
properties.

Although it is difficult to define the exact nature and morpho-
logical character of the physiological units individually, we can
study them collectively in the phenomena of their gronpitigs.

1 The following are the examples of names recently proposed for the cell-form-
ing units, by clitlerent writers: Bioblasts (.\ltmann, 1SS7): r.iiii^ciu's (Hugo de
Vries, 1889); Somaculcs (M. Foster, 188S); Ptasoincs (J. Wiesner, 1892); Biophors
(Weismann, 1893); IdioMasts (i). Hertwig, 1893). Darwin's 6Vww«^-j, Nageli's
MicdliC, .Spencer's Pliysioloi^ical units, IClsberg-IIaeckel's Plastidiiles, Bechamp-
Estor's Microzyvuis are already well known. It is important, however, to bear in
mind that these names are not always synonymous.

2 M. Foster; .\ Text-lSook of I'hysiology, 5th edition, pp 5-6.
8 A. Weismann; The C'.erm-plasma, pp. 39-40.

OA' THE NATURE OF CELL-ORGANIZATION. 99

Take chromosomes of the nucleus, for example. In some cells
the physiological units of the chromosome arrange themselves
in a series of short rods — chromatomeres — at a certain period
of their existence, while in others they arrange themselves in
a series of elongated filaments at the corresponding period.
What, therefore, we see in the grouping of micro-organisms
such as bacteria, exactly applies to those uifits which form the
chromosomes. As De Bary 1 says of bacteria, so we may say
here, that it is precisely in the phenomena of grouping that
specific peculiarities of conformation of such physiological
units best display themselves, being collected together, as it
were, in large quantity. These groupings are forms of vegeta-
tive development, grozvth-forms of the minute organism which
constitutes the physiological unit of the chromosome.

The growth-forms of the physiological unit forming the
cytoplasm of the cell are equally characteristic, as is plainly
shown in the reticular, striated, or fibrillar arrangements of
the cytoplasm in different kinds of cells.

V.

To re-state the problem, then, we may say that there
exist two easily recognizable elements in every cell, viz,,
(a) the nucleus, or more strictly the chromosome, and (d)
the cytoplasm.

It has been conclusively settled by a number of investigators
that the presence of both is essential for the continued
manifestation of life activity in a given cell. A piece of
cytoplasm or nucleus may continue to maintain a certain activity
after it has been detached from the cell, but it perishes, sooner
or later, if left alone by itself.

So much is certain, but how and why each is essential to the
other are quite other questions, and have received different
answers from different investigators. Some claim that the
nucleus influences the cytoplasm by some dynamical action ;
others hold that some invisible living particles of the nuclear
matter diffuse through the nuclear membrane, and become
converted into the substance of the cytoplasm ; while still

1 De T5ary : Lectures on Bacteria, Oxford. 1S87.

lOO BIOLOGICAL LECTURES.

others believe ,that the influence of the nucleus upon the
cytoplasm is that of a fermentative action. To a fourth group
of investigators, {e.g., Verworn), again, the action of nucleus
and of cytoplasm is a reciprocal one, the nucleus influencing
the cytoplasm, and the cytoplasm influencing the nucleus in
return, by the interchange of the metabolic products. This
last view is adopted in the present paper. The results of
operations performed on the nucleated cell seem best to
support this view.

All of these explanations are finally reduceable to two funda-
mentally different views one may take in regard to the nature
of chromosome and cytoplasm in each cell. Some hold {a) that
the nucleus and cytoplasm are essentially one and the same
substance, and that they only differ from each other, in so
far as their stages of development are concerned. Hence the
difference between the nucleus and the cytoplasm is merely
that of degree. Others, on the other hand, maintain (/;) that
the difference between the nucleus and the cytoplasm is not
that of a degree of development of one and the same substance,
but of the kind of material of which each is composed.

So far as we can judge from the micro-chemical reactions
of nucleus and cytoplasm, they must be regarded as belonging
to two substances entirely different from each other. There
is no evidence to show that one is actually produced from the
other, but the cytoplasm always originates from the preced-
ing cytoplasm, and the nucleus always from the preceding
nucleus.

There are, then, four well ascertained facts, in regard to
the nature of nucleus and cytoplasm ; viz.,

1. The two elements in each cell — the chromosome and
the cytoplasm — have the capacity for assimilation, growth and
multiplication by division.

2. Each is essential to the physiological existence of the
other.

3. The chromosome always originates from the preceding
chromosome, and the cytoplasm from the preceding cytoplasm.

4. Each has a definite micro-chemical reaction, different
from the other, and is composed of different chemical substance.

OA' THE XATURE OF CELL-ORGANIZATION. loi

Any theory that explains the nature of a nucleated cell
must explain all of these, and hold them under one common
point of view. Such a theory luiist, in short, recognize not only
the profoiDid physiological interdependence betzveen nucleus and
cytoplasm, but it must also recognize their natural motphological
independoice.

The doctrine of symbiosis, first propounded b)- De Bary,^
just fulfils these requirements, inasmuch as it means now, in a
more restricted sense, the normal felloivship or the cojisortiai
union of tivo or more organisms of dissimilar origin, each of
li'Jiich acts as the physiological compliment to the other in the
struggle for existence.

Under the assumption of such a principle as that of
mutualistic symbiosis, the fact of natural anatomical difference
between the chromosome and the cytoplasm can only be har-
monized with the fact of their complimentary physiological
adaptation. Only on the assumption that the chromosome and
cytoplasm had dissimilar origin, can we understand their
constant difference in optical, microchemical and anatomical
characters, through all phases of their activity.

To summarize for the sake of clearness, then, the general
consequence of the symbiotic existence to its participants, we
may say, that, (i) inasmuch as one organic being comes in
connection with another in order to be nourished and nourish
the other in return, they obtain a freedom in the choice of
dwelling place, which is not enjoyed by them otherwise; (2)
symbiosis of two dissimilar organisms induces certain modifi-
cation in each symbiont, by the suppression of certain
characters originally present in each, or by the acquisition of
others, which were formerly absent; (3) when the adaptation
of one symbiont to the other becomes perfect, the whole
community behaves like a new organism, subject to new laws
of growth and of development, and is no longer subjected to
those relating to each symbiont separately, and thus, (4) a
power of adaptation to the external world which each symbiont
did not possess individually, in the struggle for existence, may
be acquired indirectly, by the combined efforts of the two. (5)

^ De ]-5ary : Die Erscheinwig dcr Symbiose. Strassburg, 1S79.

I02 BIOLOGICAL LECTURES.

In proportion as the symbiotic adaptation of two or more
organisms becomes more and more perfect, each symbiont
loses the power of living independently which it originally
possessed.

The view that ascribes a symbiotic significance to the
association of these two different kinds of cell-forming
organisms in each cell, explains the following points, viz., (I)
the constant difference in anatomical, optical and micro-chemi-
cal characteristics between the chromosome and the cytoplasm;
(II) the maintenance of their specific identity through all
phases of developmental changes, as caryokinesis and fecunda-
tion; (III) the participation of both nucleus and cytoplasm in
the manifestation of non-developmental phenomena of cell-
life, such as secretion, excretion, etc. ; (IV) the interchange of
metabolic products between nucleus and cytoplasm as the
necessary outcome of a symbiotic mode of existence; (V) the
reason why the cytoplasm separated from the nucleus, or the
nucleus isolated from the cytoplasm invariably perishes; and,
therefore, (VI) why the nucleus and cytoplasm are the j^hysio-
logical organs of a cell, and yet they are not organs from a
morphological or developmental standpoint.

The nuclear substance must not be considered, in any sense,
as inactive, which becomes only active when it migrates into
the cytoplasm as Hugo de Vries^ maintains in his well-known
work. The nuclear substance of a cell is just as much active
as the cytoplasm, according to the present view, but in an
entllf-ely different manner, somewhat in the same way as the
chlorophyll-bearing algal cells and the colorless fungal elements
in a lichen are active at the same time, but each in its own way.

The vital properties of a cell do not reside in the nucleus
alone, nor in the cytoplasm which surrounds it, but in the two
together. The cell maybe destitute of a cell-wall — cytotlieca
— or each may be enclosed within its own cell-membrane, or a
cell may exist side by side without any visible boundary
between them — the syncytium. The division of an organism
into distinct cell -entities in a multicellular organism is a
phenomenon widely distributed, it is true, but still of secondary

1 Hugo de \'ries: hitraidlulare Pangenesis, Jena, 1SS9.

ON THE NATURE OE CELL-ORGANIZATION. 103

significance,! aue to physiological causes, I believe, emanating
from the fundamental difference existing between the chromo-
some and the cytoplasm. —the difference between the two
beino- of such a character that makes their mutual association
necessary for the existence of each. The chromosome
cannot grow beyond a certain bulk, nor is the cytoplasm
capable of unlimited growth, without each meeting with
restraining influence from the other, if one may express it in
a metaphorical way. The formation of a nucleated cell is,
in other words, a secondary adaptation to keep the nuclear and
cytoplasmic material within the reach of reciprocal physiologi-
cal influence of each. The division of the cell, when such exists,
is the result incidental to the increase in the number of two
kinds of cell-forming organisms existing in each nucleated cell.
The sphere within which the symbiotic reciprocal influence of
these two cell-forming organisms is felt, corresponds to what
Sachs 2 calls the cnergid. The term cncrgid as a substitute for
the modern idea of the nncleated cell, aptly expresses one
aspect of the cell-organism, namely, its physiological side.
From the genetic standpoint, as given in the present paper,
this single energid is already a complex of at least two kinds
of organisms, different in their anatomical character, in their
function, and in their origin.

Stated in this way, the view is not a new one, but agrees, in
its broadest feature, with the idea of a cell expressed by
Darwin in his theory of Pangenesis,^ and in its special aspect
which considers mutualistic symbiosis as the basis of cellular
organization, may perhaps add a more concrete meaning to his
well-known passage, without necessarily adopting his further
inference from it, when he said that "an organic being is a
microcosm — a little universe, formed of a host of self-propa-
o-ating organisms inconceivably minute and numerous as the
Stars in the heavens."

1 Sachs: Lectures on the Physiology of Plants, p. 73.

2 Julius V. Sachs: Physiologische Notizen IL Beitrdge zur Zellentheone. Flora:
Jahrg. 75, T892. Reprinted in his Gesammelte Abhandlungen, II. , 1893, pp. 1 1 5°-

"sDarwin: Provuumal Hypothesis of Pangenesis {Animals and Plants under
Domestication, vol. ii.); The Descent of Man, Appleton, p. 22S.

SIXTH LECTURE.

THE INADEQUACY OE THE CEEL-THEORV OE

DEVELOPMENT.^

C. O. WHITMAN.

The doctrine of Schleiden and Schwann that hi cell -formation
lies the whole secret of organic development, has held the place
of a central axiom in biological work and speculation for over
half a century. All this time the cell has been, as it were, the
alpha and omega of both morphological and physiological
research. Regarded as a primary element of structure, it has
come to signify in the organic world what the atom and mole-
cule signify in the physical world.

The traditional cell-standpoint has been most exactly defined
by Schleiden and Schwann. In his celebrated " Beitrage zur
Phytogenesis " (Miiller's Archiv, 1838), Schleiden sets forth
the cell-doctrine, which he limited to plants, in the following
words : ''Each cell leads a double life ; an independent one,
pertaining to its oiun developnient alone ; and another inci-
dental, in so far as it has become an integral part of a plants

Schwann, in his classical Researches of 1839, extends the
same view to the entire organic world.

''Each cell,'' he affirms, "is, zuithin certain limits, an individ-
ual, an independent zuhole. The vital phenomena of one are
repeated, entirely or in part, in all the rest. These ijidividuals,
however, are not ranged side by side as a mere aggregate, but
so operate together, in a manner unknoxvn to us, as to produce
an Jiarmoniojis zvhole.'' (Introduction, p. 2.)

" The zuhole organism subsists only by means of the recipro-
cal action of the single elementary parts."

The method of reasoning is precisely the same as we have
seen in some of the latest experimental studies on cleavage.
Witness the following : " If we find that some of these

1 Read Aug. 31, at the Zoological Congress of tiie World's Columbian E.xpositiou.

I06 BIOLOGICAL LECTURES.

elementary parts, not differing from the others, arc capable of
separating themselves frovi the organism, and pursuing" an
independent growth, we may thence conclude that each of the
other elementary parts, each cell, is already possessed of power
to take up fresh molecules and grow ; and that, therefore,
every elementary part possesses a power of its oivii, an inde-
pendent life, by means of ivhich it zvould be cjiabled to develop
independently, \v the relations which it bore to external

PARTS were but SIMILAR TO THOSE IN WHICH IT STANDS IN

THE ORGANISM. The ova of animals afford us examples of
such independent cells, growing apart from the organism."
{I.e. p. 192).

In these words of Schleiden and Schwann we see no vague
anticipation, but a clear statement, of the cell-standpoint of
to-day. The organism consists, morphologically, of cells, and
subsists, physiologically, by means of the "reciprocal action"
of the cells. Organization means cellular structure, and
ontogeny means cell-formation. " Der gleichc Elementarorgatiis-
mus ist es, der TJiiere und Pflanzen ziisammensetzt.'" (Schwann.)

In this "double life," this "harmonious whole," this "recip-
rocal action" of "elementary organisms," this "operating
together in an unknown manner," we see the "cell-state"
theory, the "unknown principle of correlation," the "correlative
differentiation," the "cellular interaction " of current literature.

Much as we have enlarged our knowledge of the cell, we
are still looking at the problems of life from the point of
view occupied by the founder of the cell-doctrine. The most
notable advances in cytology ha\e but tended to define and
emphasize the cell-standpoint. The discovery that all cells
arise by division of preexisting cells, neatly embodied in Vir-
chow's ma.xim, '' ouinis cclhila e cellnla'\- the extension and
verification of this maxim furnished by Gegenbaur in 1861,
in demonstrating the vertebrate egg to be a single cell ; and the
proof obtained during the last twenty years that the internal
processes of cell-division are fnndanientally the same in both
plajits and animals, — all these capital steps forward have
tended to magnify the importance of the cell as a universal
unit of structure.

THE IXADEQUACY OF THE CELL-THEORY. lOJ

All higher organization is supposed to begin with cell-forma-
tion, and to reach its fullest expression in the mutuality of the
constituent cells. Whether the cytoplasm be regarded as
isotropic or as definitel}' organized, whether the hereditary
substance be identified with the egg as a whole, or with the
nuclear chromosomes alone, the cell-dogma is still supreme.

Our microscopes resolve the organism into cells, and onto-
geny shows that the many cells arise from one cell ; hence,
the organism seems to be the product of cell-formation, and
the cleavage of the germ seems to be a building process.
The cell-theory points us to very definite units, as the ele-
ments of organization, and thus offers what has for a long time
appeared to be a rational basis for the investigation of life-
phenomena. All the search-lights of the biological sciences
have been turned upon the cell ; it has been hunted up and
down through every grade of organization ; it has been
searched inside and out, experimented upon, and studied in its
manifold relations as a unit of form and function. It has been
taken as the key to ontogeny and phylogeny, and on it theories
of heredity and variation have been built. For a long time it
has been regarded as a decisive test of homology in germ-
layers, tissues, and organs. Fundamental distinctions have
been made between z^/rrt-cellular and ////^/--cellular organiza-
tion, between unicellular and multicellular organisms and
organs, between cellular and acellular growth and develop-
ment, between the processes of fission and regeneration in the
protozoan and the metazoan, between differentiation zuitJiin
the cell and ajuoiig cells, between the formative forces which
shape the infusorian and those which act in a many-celled
organism.

An organism of many cells is supposed to differ from one of
one cell, somewhat as a complex molecule differs from a simple
one. The complex unit bears not only the structure of its in-
dividual parts, but also a totally new structure formed by the
union of these parts. In like manner the organism is fancied
to carry at least two distinct organizations, the organization of
the separate cells and that of the cells united. The higher
organization thus differs, qualitatively, from the lower, so that

I08 BIOLOGICAL LECTURES.

we may have analogies, but no homology of organs between
unicellular and multicellular organisms.

How sharply the line is drawn in this regard is shown in
the scrupulous care with which authors avoid the suggestion
of anything comparable to muscle or nerve in the infusorian.
The Ehrenberg view of infusorian organization demanded
altogether too much, and we have swung to the opposite
extreme of thinking that the very idea of such comparison is
forbidden by the cell-doctrine. Any suggestion of a possible
community of origin between an organ — say the vionth — of
such an animal and the corresponding structure of a cellular
organism, would be quickly relegated to the lijnbus fatuoruDi.
Who dares question the proposition that there can be no
morphological identity between an organ formed without cells
and one formed with cells } No matter how complete the
physiological correspondence, the two things must be assumed
to differ toto coclo, as measured by the cell-rule. That is the
cell-standpoint.

While the cell-doctrine has been carried steadily forward,
confidence in its all-sufficiency has been somewhat shaken from
time to time, and a few cautious protests have been ventured
against the complete ascendancy of the cell as a unit of organ-
ization. Botanists, among whom in this particular the name
of Sachs stands foremost, have led the way to another stand-
point, which, in contradistinction to the prevailing one. may
be called the organism-standpoint. Among zoologists, Rauber
has most boldly and ably defended this pt)int of view; and
more recently Wilson has expressed similar views, but with
reservations that still ui)hold the cell-standpoint. Driesch,
too, obtains experimental proof that "the mode of cleavage is
something unessential to the future animal," but still he feels
compelled to explain the organism from the cell-standpoint, —
that is, he supposes that the organism is determined by
correlative differentiation of homodynamous ("omnipotent")
cells or nuclei. The position is altogether similar to that of
Oscar Hertwig and Wilson. Wilson, however, holds that the
cleavage may secondarily acquire a "mosaic" significance, and
herein makes a decided advance towards a pre-organization

THE IXADEQUACY OF THE CEEL- THEORY. 1 09

theon'. A certain grade of organirjatioi as the result of
heredity rather than of cleavage is conceded for annelid
development, and for all forms, in so far as future characters
are foreshadowed in cleavage stages. This is a limited appli-
cation of the view which I believe holds true of all eggs, eve/i
before cleavage begins. It will be easy to show that the very
facts generally relied upon to disprove the existence of organi-
zation in the egg furnish very strong evidence in support of it.

The question as to the presence of organization is not set-
tled by the form of cleavage. Eggs that admit of complete
orientation at the first or second cleavage, or even before cleav-
age begins, are commonly supposed to reflect precocioaslv
the later organization, while eggs, in which such early orien-
tation is impossible, are supposed to be more or less completely
isotropic and destitute of organization. When the region of
apical growth is represented by conspicuous teloblasts, the
fate of which is seen to be definitely fixed from the moment of
their appearance, we find it impossible to doubt the evidence
of organization, or "precocious differentiation," as it is con-
ventionally called. When the same region is composed of
more numerous cells, among which we are unable to distin-
guish special proliferating cells, we lapse into the irrational
conviction that the absence of definitely orientable cells means
just so much less organization.

Cell-orientation may enable us to infer organization, but to
regard it as a measure of organization is a serious error. The
organization of a vertebrate embryo cannot be said to be
less advanced than that of an annelid embryo, because it
lacks the unicellular teloblasts which the latter may possess.
The regular holoblastic cleavage of the mammalian Qg^ is
evidently no index to its grade of organization. The more
carefully we compare the cleavage in different eggs, the more
clear it becomes that the test of organization in the Q:gg does
not lie in its mode of cleavage, but in subtile formative pro-
cesses. We find the most unlike forms of cleavage issuins: in
the same remarkable form-phases ; for example, the primitive
streak of mammalian and avian eggs ; and conversely, we find
identical forms of cleavage leading to fundamentally different

no BIOLOGICAL LECTURES.

results ; for example, in the egg of tlje polyclad as compared
with that of the mollusc or the annelid, where "■ cells Jiaviiig
precisely the same origin in the cleavage, occupying the same
position in the evibryo, and placed under the saute mechanical
conditions, may nevertJieless differ fundamentally in morpho-
logical significance. '' (Wilson.)

The most remarkable feature of avian development is the
primitive streak. The presence of this feature in typical form,
in such an Qg^ as that of the mammal, is certainly one of the
most significant facts in embryology. The conclusion is here
forced upon us — - and I see no escape from it — that the forma-
tion of the embryo is not controlled by the form of cleavage.
The plastic forces heed no cell-boundaries, but mould the
germ-mass regardless of the way it is cut up into cells. That
the forms assumed by the embryo in successive stages are not
dependent on cell-division, may be demonstrated in almost any
Q^%. Watch the expansion of the blastoderm in tlie pelagic
teleost egg, the formation of the germ-ring, and especially
the axial concentration of nuitcj-ial, which is so beautifully
illustrated in these eggs. Such developmental processes
are, if I mistake not, clearly indicative of some sort of organ-
ization.

The formation of the whole from a part, regarded by some
as conclusive evidence of isotropy and correlative rr //-differenti-
ation, no more disproves the existence of definite organization
in the case of the egg than in tlie case of h\-dra. A fragment
of a hydra may reproduce the whole organism ; and in so doing
act as a unit, not as a fraction of a unit. In the same way,
one of tlie first two or four blastomeres, wlien severed from
vital connection with its fellow or fellows, may develop as a
unit, not as a half-unit, precisely as Wilson insists is the case
in Amphioxus.

If the isolated blastomcre continues for a while to form cells
as if it were a half-unit or a quarter-unit, and only later mani-
fests the w^hole unit-power of the organism, 1 see no reason to
conclude that the case is fundamentally different. In either
case the part has the ])ower of reorganizing itself into the
whole, and it makes no essential difference whether the reor-

THE ly ADEQUACY OE THE CELL-THEuRY. I I I

ganization be accomplished at once, before cells are formed, or
gradually, while cell-formation is going on.

If we no longer hesitate to accept Briicke's view that the
functions of the cell are proof of organization, although our
best microscopes fail to give us any idea of what it consists in,
it certainly ought not to be difficult to regard the o.^^ as .a
young organism, and the developmental phenomena as proof of
organization. Such organization is, in fact, conceded when we
speak of the egg as the rudiment of an organism ("Anlage
eines Organismus," O. Hertwig), but, nevertheless, we go on
insisting that cellular structure is the essence of a higher
organization.

We are so captured with the personality of the cell that we
habitually draw a boundary-line around it, and question the
testimony of our microscopes when we fail to find such an
indication of isolation. We have so long insisted on these
boundary-lines as limiting homologies that we find it extremely
difficult to ignore them. How difficult it is, for example to
regard a multicellular nephridial funnel as the exact homologue
of the unicellular funnel. If the organ consist of one cell, the
tube is ////rcr-cellular ; if of many cells, then it is ////cr-cellular.
But we have the "tube" and the "flame" just as perfect with
one cell as with many, as Vejdovsky's studies make very
certain. How idle, then, to deny homology between two
such organs merely because one is infra- and the other inter-
cellular. And yet that is precisely what we have been accus-
tomed to do.

Now this one case illustrates, as I believe, a general truth of
no little importance. TJic nephrostonic is a ncpJirostoiiic all the
same whether it consist of one cell, txvo cells, or n/any cells. Its-
form and function are hot It independent of the nnmber of com-
ponent cells. Cells mnltiply, hnt the organ remains the same
throiigliont. So far as homology is concerned, the existence of
cells may be ignored.

May \\Q not go further, and say that an organism is an organ-
ism from the egg onward, quite independently of the number
of cells present .^ In that case continuity of organisation would
be the essential thing, while division into cell-territories might

ri2 BIOLOGICAL LECTURES.

be a matter of quite secondary importance. As the nephro-
stome is not the result of cell-formation, but exists as such
before division into cells, so the organism exists before cleavage
sets in, and persists throughout every stage of cell-multipli-
cation. Continuity of organization docs not of course mean
preformed organs, it means only that a definite structural
foundation must be taken as the starting-point of each organ-
ism, and that the organism is not multiplied by cell-division,
but rather continued as an individuality through all stages of
transformation and sub-division into cells.

We have long been aware that the cell could not be taken as
the ultimate unit of life, and every notable effort to account for
heredity has led to the postulation of primar)' elements in com-
parison with which the cells appear as complex organisms.
Since Ernst Brlicke first contended for the organization of the
cell in 1861, and the existence of "smallest parts" as the basis
of this organization, we have seen similar ideas reappear in the
"physiological units" of Herbert Spencer, the "gemmules" of
Darwin, the "micellae " of Nageli, the " plastidules " of Elsberg
and Haeckel, the " inotagmata " of Th. Engelmaiin. the " pan-
gens " of de Vries, the "plasomes" of Wiesner, tlu' " idioblasts"
of Oscar Hertwig, and the " biophores " of Weismann.

After the discover}' of cell-di\'isi()n as the law of cell-forma-
tion, and after the scheme of the cell set up by Schleiden and
Schwann had been revised and reduced to essentialities by
Leydig, Max Schultze, and others, the next great step forward
in the cell-doctrine must be credited to Hriicke, who, seeing that
the phenomena of life could not be referred to a strnctunlcss
substance, declared for the orga7iizatio)i of the cell in words
that were scarcely less than revolutionary.

"We must therefore," says Briicke, ascribe to living cells, in addi-
tion to the molecular structure of the organic compounds which thev
contain, still another, and otherwise complicated, structure ; and this
it is tliat we designate by the name organization."

Further, in Ills own words : " ]\'ir miisseu in il,r Zcllr iiiuiur liiicn
kh'inen Thirrlcih St'/ie/i, i/iid itiirfcn i/ir .Inalogicu, welihc zwischcii i/ir
iind (ten kiciustcn Thicrformcn cxistirrii. iiirmah aiis Jen .li/i:^cn Idssc/i."'
fElementarorganismen, p. 387.)

THE IX ADEQUACY OE THE CELL-THEORY. II3

On the botanical side, Sachs has maintained since 1865 (" Experi-
mental-Physiologie ") that protoplasm is an '■'■organized body" (cf.
Lectures on Physiology, 1887, p. 206-7). While Briicke contended
for organization within the cell, and remained true to the cell-theory
of all higher organization, Sachs, Goebel and some other botanists
early challenged the doctrine of cell-hegemony. Sachs briefly indi-
cates his standpoint in the following words :

" To many, the cell is always an independent living being, which
sometimes exists for itself alone, and sometimes ' becomes joined with '
others — millions of its like, in order to form a cell-colony, or, as
Haeckel has named it for the plant particularly, a cell-republic. To
others again, to whom the author of this book also belongs, cell-
formation is a phenomenon very general, it is true, in organic life, but
still only of secondary sigtiijicancc ; at all events, it is merely one of
the numerous expressions of the formative forces which reside in all
matter, in the highest degree, however, in organic substance." (Lect-
ures, etc., p. 73.)

Briicke's great merit consists in this, that he taught us the
necessity of assuming structure as the basis of vital phenomena,
in spite of the negative testimony of our imperfect microscopes.
That function presupposes structure is now an accepted axiom,
and we need only extend Briicke's method of reasoning, from
the tissue-cell to the egg-cell, in order to see that there is no
escape from the conclusion that the whole course of develop-
mental phenomena must be referred to organization of some
sort. Dcvclopniciit, no less titan other vital phenomena, is a
function of organization.

Nageli followed the same method of reasoning when he con-
cluded that the organism was, in a certain sense, " vorgebildet "
in the germ-cell (Beitrage zur wiss. Botanik, Heft II. i860).
This point of \-iew is well expressed in his classical work, the
" Theorie dcr Abstammungslehre," where he says: " Organisms
differ from one another as egg-cells no less than in the adult
state. The species is contained in the egg of the hen as com-
pletely as in the hen, and the hen's lig^^ differs from the frog's
Gigg just as widely as the hen from the frog."

While all will admit that the organization of the ^gg is such
as to predetermine the organism, few will be prepared to admit
that tJie adult onrani.zation is identical in its individuality

114 BIOLOGICAL LECTURES.

with that of the egg. The organism is regarded rather as a
community of such individuahties, bound together by inter-
action and mutual dependence. According to this view, de-
velopment does not consist in carrying forward continuous
changes in the same individual organization, but in multiplying
individualities, the complex of which represents, at every
stage, not the organism, but one of an ascending series of
orgfanisms, which is to terminate in the adult form.

In the egg-cell we are supposed to have an elementary organ-
ism ; in the two-cell stage, two elementary organisms, forming-
together an organism of a totally different order, based on
a new scheme of organization. In the four-cell stage we
have another organism, in the eight-cell stage another, and
so on.

" Physiological division of labor," as Milne-Edwards first
phrased it, is unquestionably a principle of wide application.
Given the cells as morphological units and this physiological
principle, the evolution of a cellular organism, may be con-
ceived of as a most simple affair. From a simi)le colony of
like cells, we pass to a commonwealth of differentiated and
mutually dependent cells. A multitude of independent cell-
organisms, adopting mutual service as the best economy, find
themselves in the end incapable of independent life, and so
firmly bound together in interdependence, that they constitute
a complex individual. The usual conception of this division
of labor is, as Herbert Spencer^ has recently stated it. "an
cxehange of services, — an arrangement under which, while one
part devotes itself to one kind of action, and yields benefits to
all the rest, all the rest, jointly and severally performing their
special actions, yield benefits to it in exchange. Otherwise
described, it is a system of ////////c?/ dependence."

We habitually aj)!)]}- this anthr()i)()moii)hic conception to
every grade of organization. The higher organism is regardetl
as a colony of cells ; the cell as a colon_\- of simpler units,
nucleus, centrosome, and so on ; the nucleus as a colony of
chromosomes ; the chromosome, according to Weismann's ter-
minology, as a colony of "ids"; the "id" as a colony of

' The CoiUeniporaiy Ucvicw, February, March, and May, 1S93.

THE IXADEQUACY OF THE CELL-THEORY. II5

"determinants"; the "determinant" as a colony of " bio-
phores," and the " biophore " as a colony of molecules.

In proportion as division of labor is carried out, i)itcr-
dependcnce is increased, and the units become more and more
intimately associated. The struggle for existence is supposed
to extend to the cells, and even to the biophores. Symbiotic
relations are fought out, refined, and confirmed by natural
selection, and eventually reduced to a system of mutual adap-
tations which are fancied to be the basis of organic unity.

Whether organization is wholly a matter of acquisition, and
whether it became possible only as a result of symbiotic ad-
vantages accidentally discovered in the struggle for existence,
need not here be discussed. It is enough for present purposes
to know that organization exists, and that organic unity
depends on intrinsic properties no less than does molecular
unity.

It is not division of labor and mutual dependence that
control the union of the blastomeres. It is neither functional
econoviy nor social instinct that binds the two halves of an &g^
together, but the constitutional bond of individual organiza-
tion. It is not simple adhesion of independent cells, but
integral structural cohesion.

That organization precedes cell-formation and regulates it,
rather than the reverse, is a conclusion that forces itself upon
us from many sides. In the infusoria we see most complex
organizations worked out within the limits of a single cell.
We often see the formative forces at work and structural
features established before fission is accomplished. Cell-
division is here plainly the result, not the cause, of structural
duplication. The multicellular Microstoma behaves essentially
in the same way as the unicellular Stentor, or the multinucleate
Opalinopsis of Sepia. The Microstoma organization duplicates
itself, and fission follows. The chain of buds thus formed
bears a most striking resemblance to that of Opalinopsis, and
the resemblance must lie deeper in the organization than cell-
boundaries.

Compare the results obtained by artificial division in two
such forms as Stentor and Hydra. The two courses of regen-

ii6

BIOLOGICAL LECTURES.

cration are so exactly parallel that one cannot fail to see at
once that the formative forces operate in essentially the same
manner with the one-celled as with the many-celled organism.
Gruber's experiment, as described in his recent article, "■Micro-
scopic Vivisection'' (Berichte der Naturforschenden Gesellschaft
zu Freiburg, Vol. VII, Part i, 1893), illustrates well this point.
A Stentor was cut into three pieces, A, B, C, each of which
regenerated the missing parts within 24 hours. The anterior

yi

fc

Fu;. I. — Regeneration «f a Stentor cut into iliree parts. ./, />", C. rr = pulsating

vacuole. 6"= regenerating frontal lieUl.

end regenerated posterior end, and 7>icc versa. The middle
jiiece regenerated both ends — the comj^licated frontal field
with its mouth, ])har\nx, long cilia, ]-)u1sating vesicle, etc., as
well as the sini])lei' posterior region.

Treat a ll\clra in the same wa\' \\\u\ similar results will follow.
In both cases the orientation of the parts will remain the same
as that of the whole. Gruber repeated the division of Stentor
four times in succession, getting perfect regeneration each

THE IXADEQi'ACY OF THE CELL-TH I-IORV.

I I

time, but smaller individuals, as no growth was possible.
The experiment reminds one of the half- or quarter-sized
embryos obtained by separating the first two or ionr blasto-
meres.

Grubcr's highly interesting paper calls attention to the iden-
tity in form and structural detail of the "membranellae " of
Stentor with the so-called "corner-cells" (Eckzellen) of mol-
luscs {Cj'c/as cornea). The comparison is a most instructive
one, illustrating in the most conclusive manner that differenti-
ation of the parts of the soma depends, not on the interaction
of cells, but upon the elementary structure of the protoplasm.

Fig. 2. — A, three membranellae of Stentor, B, membranella in section.
C, Section at the base of the two plates. Bl, Basal lamella. Ef, Terminal fibre.
Bf, Basal fibril. K, Nucleus.

The membranellae of the frontal field of Stentor consist of two
thin, adherent plates, each of which represents a number of
coalesced cilia. The structure has a basal seam or ridge ^
(Leiste), and a basal lamella which is continued into a termi-
nal fibre. All these fibres are connected by the basal fibril,
throuo-h which the movements of the membranellae are evi-
dently regulated.

Now this highlv differentiated organ, the membranella, is
reproduced with most remarkable exactness in the " corner-
cell " of Cyclas. But here the organ represents an individual

^ This seam consists of a series of microsomes, as Dr. Watase has discovered.

ii8

BIOLOGIC A L LECTi'RES.

cell, while in Stentor a whole crown of such organs is formed
without any division into cells. Could one ask for a clearer
demonstration ? Are we not forced to conclude with Gruber
that " /unvvvcr g-irnt the dijfcrciicc bctivccn an iiifusoritiui aud a
highly organized auinial, it eaiinot be a qualiiati^'e one. Wc
can assnnie that the same vital elements serve in both as the
fonndation, only in ever new combinations. This kinship
declares itself very clearly in the correspondence of many organs
of the infusoria ivith those of the higher organisms'' (I.e. p. 1 6).

C(^^^

Fig. 3.

./, ■•Corner cell" of Cyclas cornea. B, Section of three cells
letters as in V\^. 2.

Other

" So finden wir," says Gruber, " in einem Thiere, das
schon hoch auf der Stufenleiter der vielzelligen Organismen
steht, dieselben Grundelemente wieder wie in dem einzelligen
Infusionsthierchen. . . .

" Wieder und wieder der Beweis von dem gottlich einfachen
aber auch gottlich gewaltigen Gesetze der Einheit der Xatnr''
(p. 18).

The entoderm of Dicyema illustrates one or two points of interest in this
connection. We have here an organ in which, as often iiappens, in parasitic
degradation, cell-formation has been dispensed with. I'lie entoderm remains
throughout life as a single cell, and the whole process of reproduction, for both
kinds of embryos, is carried on /// t/ie hoJy of titis cell without any cellular organs

whatever.

In one respect this unicellular organ, which was undoulnedly (juce multicellular.

THE IDADEQUACY OE THE CELL-TJ/EO/n: IIQ

What is tlic difference between an organization embracing
one cell and one embracing two or many cells ? Certainly the
essential difference cannot lie in the number of cells. We must
look entirely behind the cellular structure for the basis of
organization. Kven a highly differentiated organism may
reach a relatively late stage of development just as well without
cell-boundaries as with them, as we see so well illustrated in
the insect Q.g^. If wc fall back on the number of nuclei as the
essential thing, then we shall have to reckon with multinucleate
infusoria. In these forms do we not see that it is always the
savic organism before us, as we follow its history through the
whole cycle of nuclear phases .''

The essence of organization can no more lie in the number
of nuclei than in the number of cells. The structure which we
see in a cell-mosaic is something superadded to organization,
not itself the foundation of organization. Comparative embry-
ology reminds us at every turn that the organism dominates
cell-formation, using for the same purpose one, several, or many
cells, massing its material and directing its movements, and
shaping its organs, as if cells did not exist, or as if they existed
only in complete subordination to its will, if I may so speak.

In the phenomena of regeneration and embryogenesis we
find abundant evidence. For the j^iresent I must limit mvself
to a few features of development.

Perhaps the peculiar formation of the embryo Toad-fish
(Batrachus) is as instructive a case as I am acquainted with.

is quite unique, for it may iiecome the receptacle of nuclei belonging originally
to other cells; in other words, it becomes viulliiincleatc, not by tlic initltiplicatioii
of tts own nucleus, but by the acquisition of exotic nuclei.

The acquired nuclei are what I have called elsewhere the "residual " nuclei,
which are left over when the formation of "infusoriform embryos" ceases. Each
of these nuclei enters into vital relations with the cell, a}td each undergoes the
differottiations characteristic of the true entoderm nucleus, so that in the end they
can only be distinguished by their positions. This seems to show that the differ-
entiation of nuclei may be controlled by the cell to which they are transplanted.

One of lioveri's observations* shows that the same may be said of the chromo-
somes. One or more of the chromosomes, normally eliminated in the polar
globules, are sometimes carried into the cleavage-nucleus. The supernumerary
chromosomes here undergo the regular transformations, quite unlike those which
they show when carried out in the polar globule.

* Zellen-Studien. Heft 2, pp. 171 - 175.

I20 BIOLOGICAL LECTURES.

If one will take the trouble to compare this formation with the
ordinary type of teleostean development, he will not fail to see
that the organizing forces, whatever they may be, operate to
form an embryo under peculiar difficulties. It will be seen
towards the end of embryogenesis that the material of the
germ-ring, owing to the enormous size of the egg, has to travel
over quite a long distance, in order to reach the embryo. A
very thin bridge of cells connects the hind end of the embryo
with the closing germ-ring, and this bridge is formed by the
mio-ratinc: cells of the germ-ring. What determines this
wholly exceptional movement of the cell-material required to
form the embryo.? Is it possible that the cells move as so
many independent individualities.? But they do move, and
no doubt in obedience to directing influences, acting, not in
the cells as individuals, but in and through the entire forma-
tive material, irrespective of cells.

Whoever doubts this would do well to study more faithfully
the living embryo during its formation. If the cell-ghost
should still haunt his vision, I would suggest still another field
for study. I would suggest first of all that he try to get as
clear a notion as possible of the formation of the archenteron
in Amphioxus, Petromzyon, and the Frog. The case of the
reptile might then be studied with profit. Next the "chorda-
canal " of mammals, and finally Kuj^ffer's vesicle in the

teleost.

There is no longer any doubt in my mind — and here
lam in accord with most authorities on this subject — that
this little vesicle is a reminiscence of the archenteron. The
development of Gecco, as traced by Ludwig Will, removes, as
I think, the last doubt on this point.

If the development of Kupffer's vesicle be studied in the
light of its phylogenetic significance, and studied in the livuig
as well as the dead egg, I cannot help lliinking that candid
reflection on the facts will be sufficient to force conviction to
the standpoint here taken.

Having learned the meaning of the vesicle, one sliould trace
step by step its mode of origin in the pelagic fish-egg. Mere
one mav see this remnant of an archenteric cavity arise, not

THE I.VADEQi'ACV OF THE CEIJ.-THEORY. 121

inside the embrvonic tissues as in the ejjo-s of fresh-water
fishes, but actually outside the tissues on the inner face of the
embryt), near its posterior end. Its whole ventral and lateral
boundar}' is formed, not by archenteric cells, but by a periblastic
layer often as thin as the wall of a soap-bubble, and completely
free from all nuclei. It does not even arise as a single cavity,
but as numerous minute cavities that look like a cluster of
granules. These expand, flow together gradually, and finally
form one bubble-like vesicle projecting almost wholly into the
transparent yolk. Having attained a maximum size, its slightly
concave roof becomes more and more deeply hollowed out, and
thus it comes to inclose more and more the cavity, while the
latter gradually shrinks in size, and finally vanishes as the true
cell-walls close up. Such is briefly the history of this floor-less
form-reminiscence of what is a more substantial rudiment in
many other embryos.

This remarkable reproduction of a form-phase that is to last
only for a few hours and then pass away without leaving a
visible trace of its existence, cannot be explained as due to cell-
formation nor as the result of individual action or interaction
on the part of the cells. The embryonic mass acts rather as a
;/////, tending always to assume the form peculiar to the state of
development reached by its " essential architectonic elements "
(Briicke) — elements that are no less real because, like the atom
and molecule, they are too minute to be seen by the aid of our
present microscopes.

That cells as such do not participate in this formative act, is
shown by the mode of development of the vesicle and by the
absence of cells in its ventral and lateral walls. This fact, the
absence of cells, has actually been urged recently against the
identity of the structure with Kupffer's vesicle, — -an error
which one is likely to fall into only while under the delusion
that acellular walls cannot be homologous with cellular walls.

The evidence furnished by Kupffer's vesicle will doubtless
lose much of its force with those w^ho have not had an oppor-
tunity to study the subject sufficiently to form an independent
opinion about it. To some who are better acquainted with the
structure, its meaning may still appear to be somewhat prob-

122 BIOLOGICAL LECTURES.

lematical, and the evidence drawn from it as therefore unsatis-
factory. It would be useless in such a case to urge the point,
and also wholly needless, as examples abound that are not open
to such objections.

The form-changes by which the fish blastodisc passes into
the germ-ring stage are examples of this kind. It is well
known that the transformation of the blastodisc just before
the appearance of the germ-ring is quite rapid, at least in the
pelagic fish-egg, and also quite independent of eell-fonnation.
The discoidal germ-mass suddenly thins out, but not uniformly
in all parts. The half of the disc in which the embryo is to
be formed remains thick, anticipating as it were the axial con-
centration which is to follow, while the half lying in front of
this is rapidly reduced to a thin epithelial membrane. This
;r^/V;;m/ differentiation of the outer layer and the concomitant
formation of the germ-ring, including the forward movement
of the embryonic plate ("head process"), which advances in
an axial direction to the very centre of the disc, are indubi-
tably accomplished, not by the aid of cell-formation, but by
formative processes of an unknown nature, but nevertheless
real and all-controlling. Cell-formation, to be sure, goes on,
but it seems to me certain that it has no direetive influence
on the formative processes. The cleavage runs on from begin-
ning to end, regularly or irregularly, without modifying in
anv essential wav the form of the blastodisc. All at once,
when this segmentation has been carried to a certain i)oint,
the transformation sets in and goes rapidly on, without inter-
rupting cell-formation, but to all aj^pearance quite indepen-
dently of il.

In the axial concentration ol the \-er\' broad embryonic plate
we see a formative process that can have nothing whatever to
do with cell-division. Again, in the establishment of the caudal
end of the embryo, long before that i)art of the germ-ring wliich
represent.s, historically at least, this end can be brought into
])lace, we have another decisive test of formative' power assert-
ing itself, not only independently of cell-di\-ision, but also
against all the obstructions interposed by the yolk. This pre-
potency of the "plastic power" (Schwann) is seen to great

THE INADEQUACY OF THE CELL-THEORY. 123

advantage in the pelagic fish-egg, but still better in the Toad-
fish-egg. It is needless to cite further examples of this sort,
for the embryology of every animal is full of them, and no one
can fail to find who looks for them.

If the formative processes cannot be referred to cell-division,
to what can they be referred ? To cellular interaction ? That
would only be offering a misleading name for what we cannot
explain ; and such an answer is not simply worthless, but posi-
tively mischievous, if it jnit us on the wrong track. Loeb's
experiments in heterogenesis furnish a refutation of the inter-
action theory. The answer to our question may be difificult to
find, but we may be quite certain that when found it will recog-
nize the regenerative and formative power as one and the same
thing throughout the organic world. It will find, as Wiesner
has so well insisted, a common basis for every grade of organi-
zation, and it will abolish those fictitious distinctions we are
accustomed to make between the formative processes of the
unicellular and multicellular organisms. It will find the secret
of organization, growth, development, not in cell-formation, but
in those ultimate elements of living matter, for which idiosouics
seems to me an appropriate name.

What these idiosomes are, and how they determine organi-
zation, form, and differentiation, is the problem of problems
on which we must wait for more light. All growth, assimi-
lation, reproduction, and regeneration may be supposed to have
their seat in these fundamental elements. They make up all
living matter, are the bearers of heredity, and the real builders
of the organism. Their action and control are not limited by
cell-boundaries. As Heitzmann and others have loni>- insisted,
the continuity of these elements is not broken by cell-walls.
The organization of the O:^^ is carried forward to the adult as
an unbroken physiological unity, or individuality, through all
modifications and transformations. The remarkable inversions
of embryonic material in many eggs, all of which are orderly
arranged in advance of cleavage,^ and the interesting pressure
experiments of Driesch by which a new distribution of nuclei
is forced upon the Q%2,, without any sensible modification of the

1 A.S will be shown later.

124 BIOLOGICAL LECTURES.

embryo, furnish, as I believe, decisive proof of a definite
organization in the egg, prior to any cell-formation. The opinion
expressed by Huxley in his review of "The Cell-Theory," in
1853, forms a fitting conclusion to this introductory sketch.

"They [the cells] arc no more the producers of the vital
phenomena than the shells scattered along the sea-beach are
the instruments bv wliich the gravitative force of the moon
acts upon the ocean. Like these, the cells mark only where
the vital tides have been, and how they have acted. "^

1 British and Foreign Medico-chirurgical Review, Vol. XIT, p. 314. Oct.. 1853.

SEVENTH LECTURE.

BDELLOSTOMA DOMBEYI, LAC.

A STUDY FROM THE HOPKINS MARINE LABORATORY.

Problems in Biology are inexhaustible, they renew them-
selves continually. They appear with kaleidoscopic changes
to successive generations of men, who receive them to study
in new light and from new standpoints. The results of these
studies are not all as stable as the problems themselves.
These results present themselves to us as facts, and as theories
based on facts. Although one well-established fact is worth
much speculation about its significance, yet, without the aid
of well-considered theories concerning the causes which lie
back of the facts and the meaning of the facts in themselves,
progress were well-nigh impossible.

These are trite sayings, but they have very appropriate
applications to the problems of the nature and functions of
the ear at the present time. The general problems of the
morphology and physiology of the vertebrate ear are much
the same as they were when first taken up, for the two ques-
tions, "How is the vertebrate ear constructed.'" and "How
does it operate.'" still express the aims of our researches in
this field as well as they did when man first began to study
into his auditory anatomy. But our conception of the manner
in which these problems are to be solved at the present day is
no longer what it was fifty years ago, or, indeed, ten years ago.
We now appreciate the full force of the requirements which the
present condition of morphological and physiological science
demands in the investigation of these problems. To know
the structure and function of our own ear, we find it not only
necessary to study the adult anatomy and function of the ear
in man, but also in every other vertebrate form as far as pos-

126 . BIOLOGICAL LECTURES.

sible. Nor can we stop here. We must trace out the ontogeny
of this organ in all those forms whose adult anatomy we
study, and in so doing apply the known laws of physics and of
chemistry to the development of their forms and contents. We
must trace out the phylogenetic development of the ear by the
comparative study of what we have gained from the above out-
lined investigations, combined with knowledge from two sources
yet untouched, viz., the morphology and physiology of those
sense-organs, genetically related to the ear sense-organs, and
the scanty store of facts pertaining to our problems which
palaeontology can give us. Investigations undertaken on a
basis less broad than this, or which do not fall within some
one of the categories above mentioned, are sure to fall far
short of the solution in the first case, and, in the second case,
to be of little or no service in the general progress toward the
final solution of these problems.

It is thus made apparent, I think, that although the physio-
logical problem is not as extensive as the morphological, it is
not for that reason less difiicult or more likely of an early solu-
tion, for its final solution depends quite as much ujion our
advances in a knowledge of the anatomy and physiology of
the central nervous system as upon experiments upon the ear
itself. With this prospect of long-postponed final solution,
facts which have direct bearing upon any of the fundamental
topics of ear physiology, are all the more valuable. One such
fact I wish to announce, viz., that there is at least one verte-
brate which does not depend upon its internal ears for the
equilibration of its body. I had previously concluded that the
semi-circular canals were not organs of equilibration, and inci-
dentally during my anatomical work I was able to determine
that the ear of this vertebrate is in wo way more concerned in
maintaining the i:)()sition of its body in space than are the other
sense organs.

In the lectures for 1891, I brought to your attention certain
facts and arguments to illustrate the gradations of structure
of the ear found among vertebrate animals, which have led up
to the production of the human ear. And I showed the man-
ner in which the ear of Marsipobranch fishes presents us with

BDELLOSTOMA DOMBEVL LAC. I 27

the simplest form of this organ now in existence. In continu-
ance of my investigations of this important organ, it became
necessary for me to study in the living condition some repre-
sentative of this group of fishes, of which we have only two
species in American waters, viz., the Myxine, or Hag-fish, of
our Atlantic coast, which is found from Greenland to Cape
Cod, and the Bdellostoma of the Pacific coast, which has been
found along nearly the whole Pacific coast-line of both North
and South America. In reply to a letter of inquiry addressed
to President Jordan, of Leland Stanford Jr. University, who is,
as you know, preeminent for his knowledge of American Ich-
thyology, I learned that Bdellostoma occurs in great abundance
in the Bay of Monterey and that it could be obtained there with
comparative ease. These two factors determined the direction
of my journey, and I accepted the kind invitation extended me
by Profs. C. H. Gilbert and O. S. Jenkins of Stanford Univer-
sity, placing the facilities of the Hopkins Seaside Laboratory at
my disposal. This marine station is an adjunct of Stanford
University and has just passed through its second season.

It is a great pleasure for me to be able to tell you of the
true scientific spirit in which the affairs of this rapidly growing
laboratory are conducted, and to acknowledge the generous
assistance accorded me by the directors, Drs. Gilbert and
Jenkins. In the interest of biology in America, it should be
made widely known that Mr. Timothy Hopkins of San Fran-
cisco, in whose honor the laboratory has been named, has alone
rendered it possible to found the institution, and he has pro-
vided it with the means of growth. With an insight into both
the great scientific and practical importance of the biological
researches rendered possible by such a station, an insight as
rare in a man of affairs as it is admirable, Mr. Hopkins has
supplied the indispensible funds for the undertaking, and has
assured the directors of his desire to have the station grow,
not by words alone, but by meeting the expenses of the
additions to the station buildings and equipment. In doing
this Mr. Hopkins has not been unmindful of the library which
is a fundamental need of all research work, for he proposes to
make and keep it the most complete collection of biological

128 BIOLOGICAL LECTURES.

literature in connection with any biological laboratory in this

country. From this time on the station is to be kept in readi-

*
ness for the use of investigators at all seasons of the year.

Thus you see the needs of biological research at the sea-
shore are appreciated and provided for on the Pacific coast in
a manner worthy of emulation by men of means on this side
of the continent. How long must we wait for the needed
financial support of our permanent station here } Our need:?
are urgent, and they should be met at once. Here is a great
opportunity which will hardly recur in this generation.

The Hopkins Seaside Laboratory stands near the beach on
a rocky point forming part of the peninsula which constitutes
the southern boundary of the granite basin known as the Bay
of Monterey. It is in the town of Pacific Grove, two miles
distant, west from Monterey, anel 128 miles south of San
Francisco. The station consists, at present, of a plain frame-
building, very similar to the original building of the Wood's
Holl Laboratory, though additions to it are to be made this
year. A pump and tank house is added to the east end of the
building for supplying the station with sea-water, which is
pumped up more than twenty-five feet above the sea level to
the supjily tank, from which it flows through the various
aquaria in the building, and thence into the large, out-ot-door
ground aquarium, in which large animals and class supplies of
the hardier small animals are kej^t. The faima and flora of
the Bay of Monterey are very rich ; but, until they are more
thoroughly studied, we cannot accuratel)' estimate the cer-
tainly very large number of forms, both rare and common, or
the abundance of the indi\iduals of the species most valuable
for the work of the station.

In general, we may sa\- that the fauna and flora is sub-
tropical, and it is rendeied so b)- a very constant, almost
unvarying temperature, which axerages 65'/- the year through,
and also by its nearness to the northern boimds of the tropical
seas of Central and South America.

One of the features of the station is its nearness to a
Chinese fishing village, from which much of the material for
work is obtained. I'ish ai'c caught almost entircK' In' means

BDELLOSTOMA DOMBllVl, LAC. I 29

of trawl lines ; and, while nets of several kinds are used from
boats, no pound nets, such as we find in the shallow waters
about here, are used, because of the depth of water and the
rocky character of the coast.

On arriving at the station, it became at once apparent that
I should have to depend upon the Chinese fishermen for the
collection of my material. Bdellostoma is so abundant as to
be pestiferous to the fishermen by clogging the lines with
their peculiar tenacious slii/ic.

Bdellostoma, as you know, belongs to the so-called Myxinoid
fishes, this name having been applied to them on account of
their unusually slimy bodies. The first of these fishes to be
discovered was the European Hagfish, which is identical with
our Atlantic coast species, and it has been classed with the
Worms, Mollusks, Amphibia, and finally with the Fishes,
where it properly belongs. The great Linnreus called it a
worm, even though his attention was called to its affinity with
the fishes. Bdellostoma lives on the bottom of the ocean, out
to the depth of one hundred fathoms and more, but seems
occasionally to ascend fresh-water streams for short distances.
It is supposed to be in its habits more or less parasitic on the
Halibut, agreeing in this respect with Myxine, which is para-
sitic on the Codfish. I have seen large skins of the Halibut
beautifully deprived of all contents save the skeleton, and with
but a single opening in the region of the gills to show where
the devastator had entered the body. Bdellostoma is about
twenty inches in length (an average size), but varies from
about fifteen inches to twenty-five inches in length. The
relative projiortions of the body in the two sexes, as well as
in youth and age, are much the same. The body is cylin-
drical in shape, but flattened from side to side in the tail
region. In color it varies from light pink to a dark-purple
brown. The color has a pinkish tinge during life, owing to
the shining: throus-h of the red blood in the vessels of the
white skin below the surface coloration spoken of above. The
median ventral line remains uncolored from the region of
the yolk duct or umbilicus to the cloaca, and in old individuals
the snout and a broad stripe on the ventral surface of the body

130 BIOLOGICAL LECTURES.

is white. In other words, as age increases, those parts of the
body which come into frequent contact with objects other
than water lose their purple color. The color grows gradually
darker from the ventral surface to the dorsum. The .skin is
attached to the surface of the body of the animal by a thin
median dorsal ligament and by a broad median ventral area of
trabeculous processes. The gill holes show a narrow, whitish
border, which is especially well marked about the ductus
oesophago-cutaneus, or the tube wdiich permits the water to
escape from the oesophagus without going through the gills
(Fig. 9, D). The cloacal opening is edged with white. Over
the region of the eyes the skin is pigmentless and transparent,
so that light penetrates freely to the eye below ; but this
corneal membrane is not in any wa}- invaginated or fixed to
the surface of the eye, and, since the skin in this region is
very movable, the transparent area is very much enlarged
when compared with the size of the eyes (Figs, i and 5). The
latter are small and devoid of pigment in the retina, as far as
can be discerned from the exterior, and the whole bulb is
imbedded in a fat pad between the two diverging cutaneous
branches of the V nerve where they issue from the sides of the
head. The fish are very sensitive to light, and seek for cov-
ering until the head is shaded, when they come to rest, it may
be, with most of the body exposed.

Bdellostoma is not provided with appendages, i.e., pectoral
or pelvic fins, and dciiends for locomotion upon movements of
its body, eel-fashion. It is a graceful and rapid swimmer. In
the acjuaria it remains most of the time quiet upon the bottom,
resting upon its ventral edge or side. In order to maintain an
upright position, i.e., back uj^pcrmost, it is necessary for it to
curve the body more or less, in order to provide a base of
support. Oftentimes the curve is slight, as is always the case
when the animal is in poor health. The normal j^osition is
that of a right or left-handed coil ; and they coil both ways,
apparently to rest the muscles occasionally (Fig. 3, a to Ji).
Sometimes the whole body is taken up in the formation of
the coil ; again, often only the posterior part is used, thus the
head-end being reserved free, and held straight or bent into an

BDELLOSTOMA DOM BEY L LAC. I3I

S-shapcd figure. A slight disturbance or an internal irritation
will cause them to uncoil slightly, when, like a delicate watch-
spring, they recoil and vibrate for an instant before coming
back to rest (Fig. 3, a and /;). This motion is one of the most
beautiful illustrations of muscular elasticity which I have ever
seen. As shown in the Fig. 3, Bdellostoma can curve its body
into very complicated figures, the most complex being the
double and triple knots into which the fish can quickly tie
itself for the purpose of removing anything attached to the
surface of its body. This it accomplishes by keeping its body
in motion through the knot, and tying up as fast as it comes
untied. When in a position of complete rest, the fish rests
equally well with only a slight bend in the head or the tail
region, though it is the tail that is normally used as a support
for the body to lean upon. When irritated the fish discharges
from a series of minute holes in the skin, running along either

o, o, 0.0.0.0.0.0.0.0.0

Xanque muscles ^""^^^^^S^^R^gl^

Fig. I.— The Cephalo-Branchial region of Bdellostoma dombeyi seen from
the left side to show the truncated anterior end of the body and its complement
of feelers. The position of the eye-spot and the mutual relations of the external
branchial pores and the thread gland pores is also given, X natural size.

side of the body, which project like minute nipples above the
surface of the skin, a milky-white fluid, which almost instantly
disappears from sight when the fish is in the water. These
holes arc the openings into the so-called mucous sacs or, as
I shall designate them hereafter, the thread cell pockets or
nidamental organs. These sacs are imbedded in the muscles
of the body, and not in the subcutaneous tissue, as Jackson
affirms in his recent edition of Rollcston. The discharge is in
the form of minute jets, and is caused for the most part by
the muscular contraction of the skin about the body. The
fluid is composed of minute bodies about the size and having
something of the appearance of starch grains. Each grain is
a thread cell, and was originally a columnar cell, derived from

I->2 BIOLOGICAL LLCrULiES.

J

the skin lining the pocket, and which has been transformed
into one continuous thread in such a manner that when
brought into contact with water it unrolls itself in layers,
much like a spool of knitting-silk, when it comes to pieces in
layers, and straightens out in the water in an incredibly short
space of time. After such a discharge, if one attempt to take
the fish out of the water, one will notice that the fish is
pushed away from before the hand, and that it is impossible
to touch it ; and, further, that there is an invisible something
between one's hand and the fish. By pouring off the water,
or raising the fish above the surface, you find the creature
inclosed in a transparent, gelatinous mass of about the con-
sistency of thick egg albumen, which is extremely slippery,
and yet adhesive and, at the same time, not readily broken
into pieces, notwithstanding its apparent gelatinous nature.

A sino-le fish will quickly fill a
..^;(•Hx•;V/P"V•?^^j;•:.::.;^/...■... bucket with this so-called slime ;

';:i:r::. i.e., convert the water mto such

; a thick iellv. But the amount of

^•^•.■•'V/..;:.v:X''•^>>•'.'^■•<?^V•^•••^..■:'.h,-:■ "' ■'

"•'"^"'"■''j";;'-'^il^'V'--^'''r' •••'•••"••• solid substance, i.e., the mass of

the exploded thread cells required
— ...•,v..';':--.<.:-..\------ |-() h^)i(i ti-^e water together in this

Fig. 2. — To illustrate the way in way, is not equal to a piece of tis-

which Bdellostoma surrounds itself ^^^^ paper the size of the bottom
with a mass of tangled threads, in
the meshes of which a great quan- ^^ t'"*^ bUCkCt.

tity of water is held. The consist- You SCC from this short aCCOUnt

ency of the mass is that of egg ^j^.-^^ BdcUostoma is provided with
^'^""''^"- a simple but effective means of

protection from its enemies, and at the same time with a good
nest-building apparatus, for it can at a moment's notice secrete
a dwelling-place exactly fitted to its body without stirring out of
its place, no matter what position it may be in. Oftentimes these
nest-.shaped masses are brought ujiwith the tlsh from the bottom.
Bdellostoma is not so much of a parasite as it is commonly
reputed to be. It lives on or close to the bottom ot the sea^
and like its relative, Myxine, it seems to prefer mud-covered
surfaces in which it may partly conceal itself. It feeds upon
fishes of the Teleost group. It is not known that they ever

BDELLO STOMA DOM BEY I, LAC. 133

disturb Elasmobranchs. They devour their own eggs, and I

have frequently taken the remains of small squids from the

stomachs of these animals. It is certain that they do penetrate

the bodies of such iish as the Halibut, the Flounder, the Rock

Cod and Codfish, though there is not the slightest evidence

that they do so while the fish is in the living condition. They

might readily do so, however, and the fishermen all believe that

they do attack living fishes and bore their way into them. This

much is certain ; very frequently fish are taken in the trawl

nets from which one may see the Bdellostoma issuing in haste

to o:et into the water again. These fish hulks are found to be,

usually, thoroughly despoiled of all their soft parts. They

retain the fish form by means of the skeleton within an intact

sl^in — intact with the exception of the small hole in the region

of the "'ills throuu'h which the squirming fish was seen to come.

Since Bdellostoma bites the sardine-baited, trawl-line hooks of

the fishermen with extreme avidity,^ and is able to swallow

pieces of fish or other food nearly as large as its own ordinary

diameter, it does not seem to be entirely correct to designate it

a strictly parasitic animal. And if it is not parasitic, its sense

organs can hardly be said to have been degraded by parasitism.

If they are not degraded, they must represent primitive

conditions, and so far as the structure of the nose, eye and

ear are known to us, they contain absolutely no anatomical

characters which would justify the conclusion that they are

degraded from a more perfect ancestral condition. The eye

lies beneath the skin, it is true, but this is doubtless a stage in

the phylogenetic development of the eye, just as the existing

and very primitive condition of the nose is, without question,

a stage in the genesis of the nose of higher forms.

The head end of Bdellostoma is obliquely cut off from above,
downwards and backwards, in such a fashion as to bring the
anterior end of the long tubular nose at the extreme front
end of the body ; and since this anterior nasal aperture is

1 The trawl-lines are often brought up with as many Bdellostomas as other fishes,
and my Chinaman assured me that sometimes nearly all of the hooks were taken
by this Ilagfish; or, as he expressed it, " Evely hook — one Sliklostome," i.e.
Cyclostome — he having learned the scientific name of the creature from the
students of the Hopkins Laboratory.

134

BIOLOGICAL LECTURES.

surrounded by four elongate conical feelers, and is further under
the control of a set of muscles which effect its movements in
all directions about the long axis of the body, we see that
Bdellostoma is provided with a very sensitive and effective
organ of touch, and as such it makes continual use of it.
Each of the feelers is erectile ; that is to say, it may be laid
back against the side of the head or thrust out in any given
direction at the will of the creature (Fig. 4). Each feeler is
richly supplied with nerves and blood vessels, and has a slender
and flexible, though very tough filament running through it
to give it strength and to help in keeping its form. These

Fig. 3. — Ten representations of the positions tatcen by lidellostoma at rest
(a, b, c, d, e, /,) and in motion (g, h, t, j). a and b, right- and left-handed coils.
(-, with bent tail to act as support for l)ody. i and /, single and double bow-knots,
into which Bdellostoma ties itself in order to draw its body through the knot for
the purpose of removing the thread cells or other foreign substances from the
surface of the body.

sensitive feelers about the nostril give warning of the presence
of solid particles in the water which is being respired, for a
constant stream of water is drawn into the nose to pass into
the mouth through the hole in the roof of the palate and
thence onward to the gills. The genuine nasal nerve end-organ
is the simplest in structure of any presented to us by the
vertebrate series, and consist (l^^ig. 7) of seven scmi-oval plates
of mucous membrane which hang from the roof of the nasal
cavity down into the stream of water as it turns downward
to pass into the mouth. These plates are bilaterally disposed
in sets of three, on either side of the median plate, which is

BDELLOSTOMA DOMBEYL LAC. 135

the largest of the seven. The others decrease in size fi'oni
within outwards. The median plate is charaeterized by its
larger size, and the possession of a terminal knob at its
anterior end. This knob is continued forward for some distance
along the roof of the nasal tube as a continually decreasing
ridse. So far as my investigations have gone, the olfactorv
nerves end in Bdellostoma, as they do in Petromyzon, on
either side of this median raphe, so that we now know that all
Craniate vertebrates possess bilaterally symmetrical special
sense organs since neither group of the Cyclostome forms an
exception to the rule.

The eyes in Bdellostoma have been considered greatly
degenerated, and this view is still generally accepted on the
strength of Johannes Muller's view of their condition. I feel
assured, from a preliminary examination of the eyes, — and
my examination is more extended than the one upon w^hich
Miiller based his conclusion,^ — that the Bdellostoma eye really
represents a phylogenetic stage in the differentiation of the
vertebrate eye. Two striking features of this eye are the lack
of visible pigment in the retina when viewed from the outside,
and the absence of a genuine cornea. From a study of the
adult condition, it is highly probable that the skin of the body
is never drawn into the formation of the eye as we meet with
it in the fishes ; conseciuently, neither crystalline lens nor
cornea are present. The original optic cup budded out from
the arowino: brain wall forms all there is of this creature's
eyeball, and hence it stands as an important and extremely
interesting intermediate stage between the Branchiostoma
condition and that obtaining among the rest of the sub-kingdom.
The large transparent oval spot over each eye serves as a
cornea, permitting the light to enter the eye no matter how
much the skin may be moved out of its ordinary position.
The eyes, along with the rest of the body beneath the skin,
are constantly bathed in the lymph which occupies the space
between the skin and the muscles.

1 Kohl (Zoolog. Beitrage) has given us an account of the histology of the eye in
Myxine glutinosa and he adheres still to the old view of the degeneracy of this
organ.

1^6

BIOL OGICA L LECTi l^ES.

The ear of Bdellostoma lies imbedded in the cartilage of the
base of the skull and below a thick layer of muscle. The
membranous portion is essentially like the ear of ]\Iyxine,
and the reader is referred to the previous volume of lectures
where I have described the Hagfish's ear in considerable detail.

Bdellostoma lacks all traces of the
system of lateral line organs so far
as is yet known, and it has no rep-
resentatives of the other specialized
sense organs of the skin, common
to most fishes.

Isolated sensory cells are the only
special sensory structures yet found
in this animal's skin. The absence
of these surface sense organs, to-
gether with the entire lack of
appendages, renders Bdellostoma an
Fig. 4. — A full front view of extremciv valuable animal with
theface of Bdellostoma. //.nasal ^^,|^i^|-^ ^^ perform ear-function ex-
aperture. I, 2, 3 and 4, the tenta- . ..... ^ ^

, . , 1 ^u • -^ permients; this is cue m great part,

cles or feelers, i and 0, the mside ^ ' t> r '

and outside rows of teeth, w, the of coursc, to the very simple condi-
mouth. T, the tongue, which is tion of the ear itself.

here thrust forwards out of the tx ,.• ,1 i ti i^

, , Upon cuttmg through the scale-

mouth and nearly conceals the ^ <=> ^

opening. The tongue stands here Icss and relatively thin skin along
at right angles, in two direction.s, the ventral line, the body muscles
to its usual position inside of the ^^^^^ ^^ ^,j^^^, Qf ^^yn^^, there are

hgQQ n3.t S1Z6

two ]3rincipal layers covering the
whole body. When they arc cut through along the ventral
line, from the mmith to the cloaca, most of the viscera are
exposed. In the branchial region, as shown in b'ig. 9, we find
the heart with its large ventral aorta running forwards, giving
off gill-arteries as it goes, in such a manner that either side
receives as many branches as there are gills on that side. The
gills themselves are compressed sacks, circular in outline, which
assume a sub-globular shape when they fill with water. The
current of water which we have traced from the nose into the
mouth, passes back through the oesophagus, and then out into
the gills by as many short tubes leading from the oesophagus

BDELLOSTOM-l IHlMBEVI, LAC. I 37

as there are gills. After entering these sacks the water is
forced out through the sides of the body through other short
tubes which connect the gill-sacks with the surface of the skin.
Here they form the circular gill-holes to be seen on the side of
the head region of the animal. Two features in the arrange-
ment of the gills deserve attention. First, the large tongue-
muscle seen in Figs. 5, 9 extends backwards among the gills, in
this individual separating the anterior five pairs, effectually pre-
venting any contact between the gill-sacks of the opposite
sides and also bringing about a compression of the sacks in this

Fig. r_ \ side view of the cephalo-branchial region of Bdellostoma. Some

of the mternal organs are drawn into the figure, the body walls being thought
transparent. The arrow shows the direction of the respiratory current of water
toward the nose, r i, 2, 3, and 4, the tentacles. Th, the teeth, which here are
erected and thrown outwards by the unfolding of the tongue. X, olfactory organ.
E, the ear. /, the eye. J/, the club-shaped tongue-muscle. E, the external
branchial pores. Tr, the thread gland pores. S. C, the spinal cord. A', the
kidneys. /A the intestine. Z, liver. H, heart, Below and behind each gill
opening is seen the opening of a thread gland, u, above the figure, the single,
median, pharyngeal tooth.

region whenever the tongue-muscle is in action ; second, the
apparent relation of the point of bifurcation of the branchial
aorta to the posterior end of this tongue-muscle. The number
of gills varies to an astonishing degree, and the significance of
this variation has not heretofore been the subject of any serious
inquiry so far as I am aware. There are two series of facts
concerning this flexibility of the branchial system which
deserve separate consideration. First, the number of gills of
individuals from different localities varies from 6 on either
side to 14 on either side, with the observed intermediate
stages as follows:

138

BIOLOGICAL LECTURES.

Six gills on both sides, 6 on one, 7 on the other side, and
7 gills on both sides. This series is from the Cape of Good
Hope, /. c, practically Indian Ocean, and was discovered by

Johannes Miiller in 1834. Aluller originally
gave a separate specific name to each of these
varieties but later concluded that they formed
only a single species. No representatives of
the series with more than 7 gills on both sides
and less than 10 on both sides, have as yet
been recorded, or so far as I knov/, observed.
This leaves a gap of 2 gills. But from 10
gills on both sides, up to 14 gills on both
sides the series is complete and is as follows:

10 gills on both sides, 1 1 gills on both sides,

1 1 gills on one side, 12 on the other, 12 gills
on both sides, 1 2 on one side, 1 3 on the other,
13 gills on both sides and 14 gills on both
sides. It is interesting to note the fact
as first made out by Willey that during
its larval development, the number of
primary gills laid down in Branchiostoma ^
varies from about 8 to 16, with an average
number of 14. This may be a mere coin-
cidence, but I am disposed to look upon

partly exploded and un- ^|^jg ^^ ^ f,^^,}- ,)f fundamental importance.

ravelled thread-cell. </, -^ , , r ^ ^ i- i ^.i. „ ^\ ^c

c •, , • 1 Kowalewsky first studied the growth of

a portion of a coil which -' ^

has slipped off the cell, the gills in Branchiostoma, and Willey has
A the unravelled thread, gi-eatly increased our knowledge of the
much magnified. proccsscs of differentiation met with in

these organs. Unlike other members of the vertebrate stock
this animal has the gills on one side laid ilown before those of
the opposite side make their appearance, but this is a mere
retardation and not an essential difference. The second gill-
slit is the first to appear and is soon followed by the first, after
which increase in number takes place, only from before back-

1 It is advisable on account of priority to use the term Branchiostoma in place
of the more familiar term Amphio.\us. as Prof. K. A. .\ndre\vs has recently pointed
out in his paper on An Undcscribcd Acraniatc. .Studies Hiol. I.ab. Johns Hopkins
Univ., V, no. 4, 1893-

Fig. 6.— Two thread-
cells. I, une.xplotled,
showing two crossing
layers of the threads. 2,

BDELLOSTOMA DOMBEVI, LAC. I 39

wards. These simple primitive slits increase in number until
about 14 of them are laid down, when a stage is reached during
which no more slits are formed in the antero-posterior series.
This stage has been designated the critical stage by Willey.
When the activities of growth again manifest themselves in
these organs it is an entirely new fashion and results in the
splitting of each primitive gill-slit into two by the downward
growth of a uicdian gill-bar which thus separates an anterior
from a posterior portion of the original aperture. After this
process has begun, increase in the number of gills from before
backwards again takes place ; but is now evidently related to
the acquired habits of the animal, as I have already pointed
out in another place. ^ In the matter of gills, we see that
Bdellostoma approaches very close to Branchiostoma, and in
this sense the Myxinoid retains very primitive relations of its
gill-apparatus. To return to the question of the variability of
the gills in Bdellostoma, what can be its significance } Have
we to do with an increase or decrease in the number of gills of
this animal, seeing that by far the largest number of individuals
now existing have either 10 or 12 gills on both sides of the
body .^ I think there can be no doubt as to the answer. We
are here dealing with a reduction in the number of gills and in
no case with an increase. This conclusion is supported by the
fact that the more highly differentiated Marsipobranchs have a
smaller number of gills, and this is true not only of Myxine,
which belongs to the same group as Bdellostoma, but in a
greater degree of the Petromyzonts. In view of these facts it
is extremely probable that the ancestors of Bdellostoma were
provided with about 13 to 14 gills, and this number may be
taken as representing the numerical relations of the branchial
apparatus of the primitive forms of the vertebrate stock
generally. The relation of the base of the tongue-muscle to
the gills is of interest, and here again we find great variability.
Muller found it to lie entirely in front of the gills in the 6 and
7-gilled forms from the Cape of Good Hope, and this condition
obtains in Myxine so far as known. In Bdellostoma with 10
or 1 1 gills the base of this muscle may lie between the 6th and

^ Concerning Vertebrate Cephalogenesis. — Jour)ial of Morpholof^y, IV, 1890.

140

BIOLOGICAL LECTURES.

8th pairs of gills, according to Putnam. In the 12 and 13-gilled
forms I have found it between the 5th, or at most, the 6th pairs
of gill-sacks.

In the material which I was able to collect at Monterey the
following proportions of the several variations prevailed :

[oi individuals liad ii gills on both sides.

26 " "II " " one side

and 12 " " the other side.

208 " had \i " " both sides.

II " " 12 " " one side

and 13 " " the other side.

8 " had I ^ " " both sides.

354 total number of individuals counted.

Fig. 7. — The olfactory organ
seen from its ventral surface. ^A',
nasal tube. /-, the nasal plates,
of which there are three on either
side of the median raphe. K.
X 2 diameters.

Fig. S. — A transverse section of the
olfactory organ of Bdellostoma, showing
the nasal plates cut across G, and also
partly in surface view, S. R, the raphe,
and Z, the lateral wall of the nasal cap-
sule. X 4 diameters.

Of the eight II -1 2 variation, where the position of the gills
was noted, four had 1 1 gills on the right side and 1 2 on the
left, while the other four were just the reverse, with 12 gills
on the right side and i i on the left. The same alternate vari-
ation holds true of the 12-13 variation. This fact of alternate
variation proves conclusively that the variability in number of
gills between the two sides is in no way connected with the
formation of the ductus oisophago-cutaneus. which is always
upon the left side.

The vascular svstem of Iklellostoma is being studied in
Prof. Gilbert's laboratory at Stanford University, and I need
not enter into the interesting relations which this system ot
organs sustains to the general variability of this animal,

BDELLOSTOMA DOMBEYI, LAC.

141

especially with respect to the branchial
is shown in the cut. It is through the
that the blood is carried to the walls
of the gill sacks, by means of the
individual branches a, one of which
leaves the main trunk, so long as it
remains unpaired, for each gill.

Owing to the possibility of its play-
ing an important part in the develop-
ment of the variability of the gills, it
is desirable to examine the nature of
the so-called tongue and its muscles a
little more in detail than we have yet
done. In Figs. 9 and 5 these structures
are shown as they appear upon slitting
open the body muscles. The tongue
forms a somewhat heart-shaped plate,
when spread out flat as in Fig. 4, and
is composed of two .symmetrical lateral
pieces. These halves each bear two
rows of teeth, and during life, while
in the mouth, they are inclined at an
angle to each other, thus forming a
trough, whose shape is maintained by
the sides of the mouth. When, during
life, the tongue is thrust out of the
body, it is flattened out upon the
anterior edge of the solid floor of the
mouth cavity, as shown in Fig. 5,
when it is in the best possible position
for the use to which it is put, vie, the
rasping away of the flesh of the fish to
which Bdellostoma has fastened itself;
or, if it is a small bait, the rapid and
certain forcing of the bait into the
mouth cavity. The mechanism which
effects this end is quite complicated,
and I need not enter into a complete

arteries, whose position
large median vessel A,

^\-^

to

© 15

Fig. 9. — A ventral view
of a dissection of the gills
of a Bdellostoma dombeyi,
with 12-13 gills, to show their
relations to each other, to
their blood supply, and to
tlie surface of the body. J/,
the club-shaped tongue mus-
cle. L, its tendon, g. s.,
l:)ranchial sack, /-/j, the ex-
ternal branchial pores or gill
holes. T>:, the pores of the
thread glands. A, the ven-
tral aorta. <?, the branchial
arteries. I), the ductus oeso-
phago-cutaneus. /»: A, the
internal branchial tube. //,
the heart.

142

BIOLOGICAL LECTURES.

description of it here. It will suffice if I confine my remarks
to the large club-shaped muscle which lies between the
anterior pairs of gills. In cross section the muscle is seen to
be composed of an outer thin ring — the section of the thin
cylindrical muscle, and an inner solid muscular disc — the sec-
tion of the solid, club-shaped muscle, which is made up of two
equal lateral halves. Johannes Miiller has called the outer one
of these the hollow tongue muscle, and it certainly does at
first sight seem to deserve the name.

The long tendon into which the tongue muscles taper, runs
forward in a groove in the top of the cartilaginous floor of the
mouth until it reaches the posterior border of the tongue, when
it splits up into two unequal bundles of tendinous fibrillae,
which run forward and insert into the upper surface of the
tono-ue bodv. These slender tendinous slips are so arranged
that, when the tongue is drawn out of the mouth, the carti-
laginous bars carrying the teeth are turned, so as to throw
the teeth outwards and forwards in such a manner that their
points are erected, and catch readily the instant the club-
shaped muscle begins to draw it back into the mouth. The
teeth are corneous structures,^ borne upon the soft teeth
'papilhe, and the teeth of any one row are more or less fused
tojrether at their bases, so that w^hen separated from their
papillae, they hang together in a row or plate. (Figs. 4 and 5.)
Oftentimes, the inner tooth, which is also the larger, separates
from the others, and the outermost tooth of the row is not
always united with its fellow. Each tooth is an exceedingly
sharp-pointed, conical body, flattened from above downwards,
and curved from without inwards.

1 I have made a special examination of the teeth of Bdellostoma dombeyi and
Myxine glutinosa, and although I was desirous of finding the enamel cap described
by Beard I was unable to do so. There is not the slightest trace oiboitc in any of
the teeth of these two forms, and what I'-eard has taken to be such is doubtless
much hardened horn, produced by the methods used by this author in preparing
sections of teeth for microscopic examination. I have cut a large number of the
teeth of Bdellostoma and of Myxine and have found no difficulty in sectioning
them in situ when imbedded in celloidin. The Myxinoid teeth are cornefied
sheaths of the epidermal elevations on the tongue plate, and in adult life show no
trace of dentine or enamel.

BDELLOSTOMA D0MniC]7. LAC. 1 43

The number of teeth in Bdellostoma varies as much, if not
more, than the number of gills, so that the only two "constant"
characters which Miiller could find upon which to base a classi-
fication are both of them extremely variable. The limits
of the variability of the teeth, so far as known, are as

follows : —

Bdellostoma from the Cape of Good Hope, ^-y gills, -^1^

8'

11 Hi 12 112

lllll' ll|l2'

Bdellostoma from coast of Chili, 10 gills, U | H (Lacepede),
11 1 11 la 1 13

lllll' 12|l2-

Bdellostoma from coast of California, 1 1-13 gills, |||, \\ \ \\.

The California series which I have counted is the only one
extensive enough to give opportunity for the observation of
the variations, although Miiller evidently had nearly extreme
forms in the three individuals whose dental formulae he re-
corded.

In 22 individuals with 1 1 gills I found the dental formulae to

Kf- n« fnllnw^ • 110 19 1 1 0 I JL 4 J Jl I 1-0- 1 1-1 110 1 10 I 10

DC as lOilOWS . i-g-|^, J-yolio' ^ 9 I 9' 9 |lO' ^ 10|lO'

1 10 111 1 10 111 1 10 111 R 11 1 10 1 11110 5 11 11
^ 10 19' ^ 9 r9"' -•- lollO' ^ 10 I 10' ^ 11 I 10' "^ 10 I 10'

111111 1 I_2 1 1 1 '^12 112
■^ 1110' ^ 9'r9' "^ lllll-

In 6 1 individuals with 12 gills the following dental formulae

1 isiin iqi8 Qolio 1 9110 1 9|l0 9lo|o

occurred: — ! f ||{|, 1 i\%, » I]-'/' ^ io| 9 ' -"- io|to' -^-g"! ¥'

1 10 19 1 10 19 10 10 110 4 1 0 I i_o (^ 10. 1 10 7 j_o. 1 1 0

-*■ l¥ I 9' ^ 10 I TO' ^^ "919' ^ 10 19' " 10 I 10' ' 9 I 10'

110 111 110 111 1 1 1 I 1 0 1 11 1 i_o_ 10 11 1 1-0 3 11 1 11

^ '9"r9"' -•- ToItO' -^ '9 i'g' ^ lOl 9' ^^ 10 I 10' "^ 10 I 10'

1 ll|l|, 1 yflTf. These counts were made on consecutive
animals as they came from the trawl line, and must represent
fairly the dental conditions of Bdellostoma in the Bay of
Monterey. Two things are apparent. First, there is not the
least relation between the number of gills and the number of
teeth ; and, second, the teeth are subject to much greater
variation than the gills, notwithstanding they belong to the
so-called hard parts. Size and age do not affect the dental
formula.

On combining the dental formulae of the ii-gilled and 12-
gilled variations, we find the following numbers to obtain for
the %6 individuals whose dental formulae I have carefully
counted on both sides of the dentiferous plate.

144

BIOLOGICAL LECTURES.

No. of
indivi-
duals.

1

8
1
1
3

1

2

14

8
4
<

1
2

1

2

1

1
13
1
8
1
1
1
3

Predomi-
Dental nant Num-
Formula. ber of

Teeth

9

1J>
'9-

IJ)
'9

10
10

9.
9

9
9

_9_
10

IJl
9

iO
10

9

10 UO

-'-" I

J

his type specimen of 14 gills yfiyo,
Putnam found If I If or If I If

From this table we learn that more than
seven-tenths of the entire number of indi-
viduals belong to three groups, and over
half of these belong to the group in which
10 teeth occur in both rows oftener than
any other number. We have to do with a
reduction in the primitive number of teeth.
So much for the California specimens.

The Chilian specimens seem to average a
larger number of teeth, for Girard counted in

^2^ while
or ^^ I ^^ m the ma-
terial he studied from Talcahuano Bay,
brought to this country by the Hassler expe-
dition, which is reported as- having 10 gills.
Lockington gives the formula as ^^ I '^-^,
which harmonizes with what I find to be the
most abundant formula. Lacepede's example
from Chili had a dental formula of V-l U,
which is quite unusual, and indicates what
we may expect from a careful study of a
large series from the South American coast.
I fear that the dental formulae published in
the systematic accounts of Rdellostoma are
based for the most part on counts of the
teeth of one side of the tongue only, and in
this way only can I account for the bilateral
symmetry which characterizes them.
The reproductive organs of Bdellostoma are extremely simple
in their structure, and are composed in both male and female
of a simple, double-layered plate of the j^eritoneum which
hangs down as a fold from the dorsal wall of the body cavity
on the right side of the median line (I^'ig. 12). The ovary
occupies nearly the whole extent of the body ca\-it\' in the
female. The testis occupies only the posterior jiart of this
long fold, and in the female no eggs are developed in this
region. In hermaphrodites the two divisions of this organ are

9
9

9

_9_
10

„9_
0

9

10
10

u

"9

1J_
'9

1J_
"9

11
10

IJt
9'

IJL
"9

lii
10

10 I

11
10

10

r

lO'^

12
10

U
"9"

11
1 1

11

BDELLOSTOMA DOMBEYL LAC.

145

separated by a notch in the lower edge of the fold. The left
organ seems never to be developed in any of the Myxinoids.
In all cases, so far as my observation goes, each individual is
potentially bisexual, but Bdellostoma is not much like the
Myxine in changing its sex with increase of age ; certainly this
condition does not seem to be so clearly expressed in Bdellos-
toma as in Myxine. For whereas in Mixine only the young
animals seem to be males, in Bdellostoma large and presumably
old animals are found to be males as well as females, and both

Fig. 10. — A view
similar to that shown
in Fig. 9, but drawn
from a ■]-■] gilled
Bdellostoma. Let-
tering the same.

formed by
one side.

Fig. II. — The branchial
apparatus of My.xine, seen
from the ventral face, to
show what the changes are
which have made Myxine's
respiratory tract so differ-
ent from Bdellostoma's. It
is at once apparent that the
only structures in any way
changed are the external
branchial tubes, which, by
all uniting together, have
only to pierce the skin at
one place, ce., oesophagus,
1-6 and g. s., the branchial
sacks. /';-. A, the external
branchial tubes of the first
gill. D, the short duct
the union of all the gill tubes of

sexes are found among the smallest individuals taken. The
large anterior region of the peritoneal fold is always ovary, while
the much smaller posterior region of the fold is the testicular
region. The ovary is readily distinguished by the numerous
eggs in many stages of development, while the testicular part,
which is separated from the ovarian part by a notch or deep
scallop cut in the border of the fold, is to be distinguished by
its clear vesicles, grouped together like a bunch of grapes.
Of course a crucial test of the character of the small vesicles
is the presence of spermatozoa in the testicular part. Tested
in this way many individuals were found to be ripe, while
among the females very few were found to contain eggs in

146

BIOLOGICAL LECTURES.

the last stages of ripening. The explanation for this scarcity
of ripe females which has been applied to the case of Myxine,
viz., that the pregnant females, when the egg-laying time
comes on, cease to eat, and consequently are not to be
taken either in baited pots or on trawl lines, must suffice
for Bdellostoma until we have a better one. Other causes
may be operative here, but nothing is known with certainty
of the conditions of life which surround the q^^ laying and
embryology of Bdellostoma.

Fig. 12. — A side view of the sexual gland of an hermaphroditic Bdellostoma
dombeyi. a and /», cross-sections of the gland at the points indicated by the
arrows, v, the dorsal blood vessel, below which the gland is suspended as a
double fold of the peritoneum. /. o7\ ovary. A-, testis. /•". nearly ripe eggs.
e, very young ova. f, testicular follicles.

Some individuals of Bdellostoma arc truly hermaphroditic,
having at the same time a genuine testis with ripe sperm and
an ovary with eggs nearly or cpiite ripe. These individuals are
rare, so far as my experience goes, but others with the two
organs in a more unequal state of development are more
numerous. However, by far. the largest number of individuals
are genuinely male or female. Males are much more numerous
than the females, but this statement applies only to the catches
which I had the opportunity of examining. It may be merely
a coincidence, or on the other hand it may faithfully represent
the true conditions of things in the Bay of Monterey. All
things considered, I believe a preponderance of males represents
the ordinary condition.

The sex of 209 out of 354 individuals was noted, and they

BDELLOSTOMA DOMBEVI, LAC. 147

are distributed between the males, females and hermaphrodites
in the manner indicated by the following table :

Of loi individuals having 1 1

gills on both sides, . 61 were males, 37 were females, and 3 hermaphrodites.
Of 26 individuals having 1 1

gills on one, 12 on the

other side, . . . 14 " " 12 " " " o "

Of 163 individuals having 12

gills on both sides, . 94 " " 66 " " " 3 "

Of II individuals having 12

gills on one side and 13

on the other, . . 8 " " 3 " " " o

Of S individuals having 13

gills on both sides, • 5 " " 3 " '' " o

Totals, 182 121 6

The sexuality of the Bdellostoma does not appear to depend
upon size or age, for of 10 small individuals (under 15 inches)
there were 7 males with gills, \%, 2 females with gills, l|, and
I female with gills, \\.

Of 1 5 large individuals (over 20 inches) there were 8 males
with gills, i|, I female with gills, 1|, 5 males with gills, \\,
and I male with gills, l|.

In 1875, Anton Dohrn, the founder and talented director
of the Zoological Station of Naples, first clearly defined the
hypothesis of degeneration, and fully illustrated its application
to the vertebrata in his famous paper, " Origin of Vertebrates."
Dohrn corrected the then prevalent ideas, according to which
all the simpler forms of animals, anatomically considered, were
to be looked upon as more primitive and as representing
ancestral stages in the development of the groups to which
they belonged. He was not fortunate in his selections of
cases of degeneracy among vertebrates, as I hope to make
clear to you. As a typical case of true degeneracy we have
the well-known case of the Tunicate, which during its devel-
opment passes through a stage which, according to the
'' biogenetisches Grnndgesetz'' must be considered to be strictly
vertebrate in its morphological characters. These vertebrate
characters are not retained by the Tunicate, however, but are
absolutely destroyed during the growth of the larval body, so
that in the adult condition there is nothing left to ever remind

148

BIOL OGICA L L E C TURES.

one of the vertebrate type of organization, and the body ever
after remains in this inferior condition of structure, though it
produces germs which in their development attain the higher
level of vertebrate organization, only to sink back to the lower
level of Tunicate structure.

Fig. 13. — A view of three ripe eggs of Bdellostoma dombeyi, showing their
natural size, the variations in shape, the manner in which they hold together by
means of their anchor hooks, and the position of the suture which allows of the
ready separation of the cap from the body of the egg membrane, a, an end view
of an egg cap. The anchor filaments have all been radially spread to show the
spiral arrangement of the filaments upon the cap surface, x, the anchor head.
/, the filament, b, a side view of another cap. st, the cap membrane. /', the
row of enlargements forming the bases of the filament.s, f. .r, the anchor heads.
The central dot in a shows the position of the micropylar funnel which leads into
the micropylar canal. The egg membrane is composed of a thin genuine vitelline
memljrane and a thick corneous follicular (granulosa) membrane, and the anchor
threads are hollow evaginations from the end parts of tlie latter. Natural size,
a and b 'X 2 diameters. •

1 .\fter a study of the development and the adult condition of the egg mem-
branes in Bdellostoma dombeyi I am certain that Cunningham is in error in calling
the egg membrane of the Myxinoids a vitelline meml)rane. Tlie corneous part of
the egg .shell is cellular in nature and the cell remnants are to be seen in the ripe
egg .shell. The anchor hooks are formed by the evaginations of this granulosa
layer in late stages of egg life, due to the outgrowth of solid rods of the vitelline
membrane. These rods appear to be resorbed before the ripening of the egg and
thus the anchor filaments are left hollow. The My.xinoid egg is thus very much
like other fi.sh eggs as regards its envelopes. .\n illustrated account of these
facts, among others is ready for the press.

BDELLOSTOMA DOMBEYI, LAC. 1 49

Thus it is that the evidence in favor of progressive simplifi-
cation of structure (which is all that is meant by the term
degeneracy) depend upon two factors :

(a) The comparison of the anatomy of the fully developed
degenerate animal with that of its supposed congeners. In
this way we can often be sure that the less complex animal
does not represent ^ny of the ancestral stages common to its
nearest relatives. This is the anatomical method, and {b) by
the study of the embryological development of the forms under
consideration. This is the embryological method, and it is very
generally admitted to be conclusive whenever it can be shown
that either the embryonic or larval stages of the animal
under consideration possess a higher degree of morphological
differentiation than is possessed by the adult form. c. g.
barnacles (Cirrhipedes), Tunicates. In many instances the
embryological history may be, and is, so shortened as to give no
trace of a higher stage of existence having ever been enjoyed.
e.g. many Tunicates. Even from this very short review of
the degeneration hypothesis, it is evident that we must
conclude that a priori there is much reason to suppose that
any given animal form may have developed from a more highly
organized ancestor by a process of simplification as to assume
that it has developed from a relatively simpler form by an
unbroken process of complication, and that our only means
outside of morphological research is to be derived solely from
the life habits of the animal, i.e. whether they are such as to
favor degeneracy or not. In saying that there is much reason,
on a priori grounds, to assume that an animal has degenerated
or developed downward to its present condition as that it has
developed upward, I certainly cannot acquiese in the view
expressed by Dohrn and adopted by Lankester that there is as
much probability in favor of the one process as of the other,
for it is evident that cases of degeneracy must be much less
common than cases of progression, otherwise the Law of
Agassiz, fully established by Darwin, would not be so easy
of observation in embryology and palaeontology. The law of
progressive differentiation is so universal in its application that
we are on safe ground in always considering any existing form

I50

BIOLOGICAL LECTi'RES.

as the result of a series of progressive changes, or viewing
any fossil form as the highest of its kind up to the time of its
existence, unless in cither case there is positive proof to the
contrary ; for the biogenetic law lays the burden of proof
upon the degenerationist. Life habits, favoring simplification
or obliteration of structure, are parasitism, sessile or fixed
life, burrowing and hiding in crevices and holes, and indiscrim-
inate and diffuse food habits, while free and unrestricted motion
within the aqueous and aerial oceans upon and over their
bottoms, involving the pursuit of fleeing prey and the struggle
with other forms for its possession and for life itself, are highly
favorable to increasing complication of structure. It is at
once evident that we cannot take existing vertebrates and
group them either in an arbor-like or ladder-like geneological
arrangement, and at the same time express the true relation-
ships of the many modifications of structure which have been
produced. This brings us to the consideration of the question
of the classification of Bdellostoma, and to this I shall return
after throwing what light I can upon the conditions under
which Bdellostoma exists and the probable relations which this
fish bears to these conditions of its environments.

What evidence can we bring forward to show that " the small
and degenerate group Cyclostouiata " as Lankester - calls them,
arc not deo-cncmic Wrtcbratcs ? In previous publications I have
pointed out some of the facts, and I am sorry to say they have
not been accorded that consideration which they merit as
anatomical facts. In 1889- I showed that ''the higher sense
oigans of the Cvelostoiiiatn are all paired, since the nose {i.e., the
nasal or olfaetive epitheliinii) exists in the embryo as ivell as the
adult in the form of tieo eirenmscribed areas lying on either side
of the median lim\ each of 7ehieh reeeives the entire nerve supply
afforded by the olfactory nerve of its side. I then ventured to
predict that the Myxinoids would show the bilaterally sym-
metrical or ]Kiired nasal areas as distinctly as Petromyzon does.
I can now state that my conclusion was well founded, for in
Bdellostoma we have the nose divided into right and left halves

1 Reprint Aiticlc, Vertebrates, A;/<v. /hit. ed. 1887. London, 1S90.
- Concerning Vertelirate Cephalogenesis, Jottrual J/cr/Z/cA',;,';!', IV, 1890.

BDELLOSTOMA DOMBEYI, LAC. 151

by a median plate which is the homologue of the median raphe
of Petromyzon. In Figs. 7, 8 is shown this important feature
as seen from the ventral surface (inner face) of the nasal organ.
As concerns Bdello.stoma's eye, we know very little of its adult
structure and nothing of its development, and the conclusion
that it is a degenerate organ in lacking a lens, choroid, etc.,
and being entirely below the surface of the body and under the
skin, is purely hypothetical, for it can just as well represent
a stage in the phylogenetic development of vertebrates. I
believe such to be the truth. The undegenerate nature of
the ear I have already established in another publication.^ On
the basis of our knowledge of the higher sense organs we may
well ask: Why are the Myxinoids primitive fisJics ? instead of
" Why are they degenerate vertebrates } " The following con-
siderations enable us to understand why they are primitive and
not degenerate:

1. Their unusually great geographical distribution indicates
that they are descendants of a very ancient stock.

2. They are in a morphologically undifferentiated condition,
as compared with all other groups of craniate vertebrates and
their several organs show no certain traces of degradation
of structure. In this regard I have examined the following
organs : skin (here the absence of surface sense organs, scales,
except the teeth, and a lateral line is noteworthy and entirely
unexplained ; they are not degraded but have entirely vanished
from adult life), muscular system, skeleton, vascular system,
alimentary system, urino-genital system and the higher sense
organs, eye, ear and nose. Of these latter the two last are
normal stages in the development of the vertebrate stock,
and so far as I have examined the structure of the eyeball,
its lack of lens and eye muscles and its small optic nerve,
I have found no conditions which are not harmonious with the
view that this eye has simply never been highly developed.

The degeneration hypothesis fails completely to account for
Myxinoid anatomy, and the habits of the animal give no
grounds for this assumption. Certainly the natural conditions
surrounding the life of the animal as far as we know them, are

1 Contributions to the MoFphotogy of the Y.z.x, Jourji. Morp'kol. VII, 1S92.

152

BIOL OGICA L L ECTURES.

not such as to cause the extensive retro^n-essive development
which they are supposed to have undergone and which it is
assumed has affected nearly all of the organs of the body.

It seems to have become a settled belief among the large
majority of zoologists of both morphological and systematic
proclivities that the number of gills found among vertebrates
never rises above eight pairs in existing forms. The few who
have recognized the true state of the case have had little to do
with the education of the younger men, and so the error has
continued to be taught. Lankester ^ wrote in 1 890 — regarding
the gills of vertebrates, "The pharyngeal slits follow closely
upon the mouth, and in existing Craniata never number more
than eight pairs." Wiedersheim ^ gives seven pairs of gills as
the largest number occurring among craniate vertebrates, while
Claus, Huxley, Jackson-Rolleston, Hertwig and others give the
number varying from 5 to 8, but never greater than 8. They
evidently confine themselves to Miiller's statement concerning
the number of gills {^-J) in Myxinoids and to the known facts
concerning Petromyzoa (7) and the Notidanidae {6-7). In
1854 Charles Girard described a fish from the coast of Chili
which he called Bdellostoma polytrema, and which lie found to
have 14 pairs of gills. In 1873 Putnam found that the
Bdellostomas of the Hassler expedition, collected off the coast
of Chili, had 10 pairs of gills. Later on Lockington (1878)
described a similar fish from San Francisco which had 1 1 pairs
of gills. These are the only original observations, wdth which I
am acquainted, which give the number of Myxinoid gills greater
than the accepted numbers (6-7). Yet these facts have been
many times confirmed by such men as Gunther, 1873, Gill.
1880, and Jordan and Gilbert, 1882, who gave the number of
gills of the Pacific Bdellostomid as 1 1-14. Notwithstanding all
these published accounts, morphologists have completely over-
looked these facts, and while speculating on the ancestral
number of gills of vertebrates, have depended for the most pari
upon the embryological stages of Elasmobranch and Teleost
fishes.

1 I-incy. Brit. Article on vertebrates.
* Grundriss d. vergl. Anat. Jena, 1S93.

BDELLOSTOMA DOMBEYI, LAC. 153

I have already referred to this matter in connection with the
brief description of Bdellostoma's gills, but it is sufficiently
important to call for a more detailed account, in which I shall
try to bring the branchial apparatus of Bdellostoma into
harmony with the primitive condition of the same organs in
Branschiostoma.

Having shown that there is a great degree of variability in
some of the organs of Bdellostoma, it will be in jjlace to seek
for the conditions which keep up this variability, — for the
conditions must be present conditions and in no sense past
ones. Three conditions suggest themselves as probably con-
cerned in keeping up this variability among the Bdellostomas
as a group of animals of common descent and as families of
individuals living under common conditions in circumscribed
areas. These are Geographical Distribution, Panmixia and
Hermaproditism.

The geographical distribution of Bdellostoma cannot be
satisfactorily accounted for by assuming several separate crea-
tions of these animals, for though so widely distributed on the
floor of the Indo-Pacific oceanic depression, all its morphologi-
cal characters and its life habits point to its origin from a single
ancestor at some place in the South Pacific ocean. Admitting
the common descent of the varieties of Bdellostoma, the
phenomena connected with the geographical distribution of
animals in general lead us to conclude that Bdellostoma has
existed for a very long period of time and that it has been but
little modified during this long period. We do not know that
it has always been as variable as it is at present ; but if it has
been, it is a most remarkable case, since ordinary animals
zvoiild have become zvell diffei'entiated ijito distinct species during
the process of dispersion over sncJi a great territory and the
consequent operating of more or less changed conditions in
different ways upon different parts of the variable organism
during the great period of time necessary to accomplish this
dispersion. Bdellostoma has been widely distributed, and
while the conditions in different parts of the territory which it
inhabits can hardly be held to be identical, still the sea bottom
is far more stable in its temperature and other features produc-

154

BIOLOGICAL LECTURES.

tive of variation than the shallower waters of inland basins or
the surface of the land itself. Hence so far as the effects of
g-coirraphical distribution are concerned, they may be said to have
had very little or almost no effect upon the anatomical structure
of the animal. This conclusion is fully sustained by the fact
that in each locality Bdellostoma shows similar variability in
the same organs, while individuals from widely separated
localities show variations which are frequently numerically
identical. The variability is of the same kind and comparable in
deeree in individuals from all the localities yet studied. This
is by no means a satisfactory presentation of the effect of
geographical distribution, but it must suffice for the present,
and until our knowledge of the distribution of the animal has
been more fully elucidated.

What effect should these facts have upon our ideas of the
classification of Bdellostoma.' Most authorities are inclined to
look upon the difference in the number of gills as a sufficient
ground for the establishment of distinct genera. That this
character has not a generic value it is needless to state, for
reasons already sufficiently repeated. But it would be conven-
ient to recognize these several varieties by some name, if
possible, and, according to the present system of nomenclature,
there are tv*^o opportunities, — one for a specific, the other
for a variety name. Is the gill variation a sufficient specific
character .!" I think not, for the reason that we have all
p-rades of the variations, and the further reason that the\- all
belong to one colony of freely intercrossing individuals. It
appears to me by far the best plan to recognize one genus
of Bdellostomids, with one species composed of the several
varieties, and I propose that we return to the first satisfactory
name that was applied to our animal. The first account of
this animal which we find in the literature is that of Lacepede,
who described it from a dried skin sent from the Chilian coast.
He named it le Gastrobranche dojnbey} Later, in 1815. Home
described the gills of a Ileptatrema which he obtained from

1 Gastrobranchus is the old name applied to My.xine, and these forms were kept
with Myxine till Dumeril put them in the genus Heptatrema, which of course
gives this name priority over Mulkr's Iklellostoma.

BDELLOSTOMA DOM BE \ I, E.IC. I 55

Banks' South Sea collection. Johannes Miiller published his
well-known monograph on these forms in 1834, and applied
the name Bdellostoma to the forms from the South Sea,
Cape of Good Hope, and Chilian coast, making species on
the basis of the number of gills. He called the Chilian form
B. dombeyi, and made five species in all. In 1854, C. Girard
described a fish from the Chilian coast with fourteen gills, and
called it Bdellostoma polytrema.

In 1878, Lockington described the form found in San
Francisco l^ay as V>. stouti, and Gill changed the name in
1880 to Polistotrema stouti, which has again been changed to
Polistotrema dombeyi. Retaining the name polytrema for the
Chilian form, he changed it over to his genus Polistotrema,
which he says is characterized by 1 1 to 14 gills. These
accounts all refer to the varieties of what I shall call Bdello-
stoma dombeyi, adopting MUller's genus, on account of the
inapplicability of Lacepede's Gastrobranchus, and of the inap-
propriateness of Cuvier's Heptatremes, which could only be
used for the seven-gilled form or variety. Bdellostoma, the
generic name proposed by Miiller, is satisfactory in every way,
and we may well use it.

The specific name dombeyi, applied by Lacepede in 1798, is
satisfactory in that it avoids all difficulties of a morphological
kind, and perpetuates the name of the discoverer of this
remarkable animal. Bdellostoma dombeyi is the name under
which are gathered all the variations we know of in the
branchial and dental systems and the correlated organs. P"or
the purpose of distinguishing these varieties, we may use
either Latin variety names or a simpler numerical termination.
If we choose the Latin names, we meet with difficulty in sup-
plying all of the Jietcrotrcnics with sufficiently exact names, for
some are 6-^ , others 11-12, and still others 12-13-gilled, and
no one knows when or where more of these Jieterotretnes may
be found.

Gastrobranchus dombeyi (Lacepede), 1798.
Heptatrernes dombeyi (Cuvier), 1829.
Bdellostoma " (Miiller), 1834.

" " (Gray), 1851,

1^6 BIOLOGICAL LECTURES.

Edellostoma polytrema (Girard), 1854.

" " (Giinther), 1870.

" " (Putnam), 1S74.

" Stoutii (Lockington), 1S78.

I'olistotrema dombeyi ((iill), 1S81.

" " (Jordan, Gilbert), 1882.

Iklellostoma forsteri. /

" cirrhatus. )

" hexatrema.

" heterotrema.

" lieptatrema.

I shall, for my own convenience, hereafter use the numerical
method of designating the varieties ; and, unless sufficient
reasons be brought against this style of name, I would urge
its adoption on the ground of convenience, to go no further.

Iklellostoma dombeyi, 6 gills.

'• '■ 6-7. ( Indicating the sides of the body upon

" " 7-6. S which the respecti\e numbers occur.

" " ID.

" " II.

" " II-I2.

" " 1 2-1 I. "

'* u j2.

(( t< J '>_j -•^

" " 13-1--

13.
14.

Physiological.

From previous experience it seemed to me very desirable
that physiological experiments should be tried upon the car
of some vertebrate with the simplest existing ty])e, and, if
possible, upon an animal which lacked fins, — /. r., paired
appendages, which in all fishes are specially used in main-
taining the equilibriimi of the body. I felt that by seciu-ing
these conditions, we shoidd be able to get much cleanei"
responses or, in any case, safer results from operations on
-the ear, for the presence of the paired fins — especially the
pectoral fins — complicates the reaction to ear operations by
introducing into observable jihenomena mechanical factors
whose influences have not been carefully enough studied and

BDELLOSTOMA DOM BE VI, LAC. I 57

allowed for. The desired vertebrate was found in Bdeliostoma,
which thus presented me with material for both morphological
and physiological investigations. Physiological operations on
the ear of Cyclostomes have been tried on Petromyzon only, so
far as I know, and then they were abandoned without obtain-
ing results, on account of the difficulty of the operations. The
first operations I performed were on anaesthetized animals ; but
I soon abandoned the use of anaDsthetics for several very
sufficient reasons.

My method of operation was the following : In order to
hold the extremely slimy and slippery animal, I used large
sheets of blotting-paper, such as botanists require for drying
plants. Bdeliostoma was taken from the aquarium, and at
once rolled up in the sheet in such a fashion as to hold it
extended during the operation. One sheet makes a roll suffi-
ciently stiff to retain the fish perfectly. A stout needle was
thrust through the skin at the side of the mouth, and another
throufrh the skin and muscles of the tail, and both forced into
the table at such a distance apart as to prevent the fish from
squirming or crawling out of the paper cylinder. The blotting-
paper was removed over the region of the ear, and an incision
made through skin and muscle, exposing the cartilaginous
ear capsule. The top of this was shaved off with a sharp
scalpel of suitable shape and size, and the auditory nerves
cut inside the ear capsule, either with a scalpel or scissors.
The columella was then cut, and the ear lifted out with
forceps or with a small bent needle. An _ examination was
made with a lens to see if any part of the ear or auditory
nerve had been left in the capsule, and any such fragments
were removed before the cut in the skin was sewed up. This
done the animal was unrolled into the aquarium, and its
motions watched. The whole operation does not require more
than two minutes, and the fish does not appear to suffer in the
least from suspended respiration, so far as I could make out.

A fish thus operated upon, with both ears removed, will
swim from the moment it is placed in the aquarium like a
normal fish. In some cases the creature will tie itself into
a knot, with the evident purpose of removing the irritation

LS8

BIOLOGICAL LECTURES.

from the skin of the head, but it soon leaves off such attempts,
and settles down on the bottom of the aquarium, coiling up in
the normal fashion, or else it will continue to swim about the
tank for a time. In case only one ear is taken out, the animal
may (it does not always do so) swim with the injured side
lower than the other, or may even roll as it swims — especially
if it is excited to sioi)/i rapidly ; but like others, it will settle
to the bottom, and rest normally in its coil, coiling either away
from or toward the injured side. I thought I could notice in
some cases a tendency to coil away from the injured side ; i.e.,
the normal side did the work of coiling ; but the case is by no
means clear that this coil is done oftener than the other.

mu..

Fig. 14. — The right internal ear of the Hagfish
(.Mvx/>:e gliitinosa), seen from the inside or cerebral
face. Figure after G. Retzius. The figure represents
the ear somewhat enlarged, and does not show the
"r shape or e.xact positions of the contained sense-
organs.

ah

a Anterior ampulla.

a/' Posterior ampulla.

c Anterior and posterior canals.

^'^ ! .\nipullar ends of the same.
cp S ^

d Ductus endolymphaticus.

iini Macula utriculi et sacculi.

;/ Xerve branchlets.

// Utriculo-sacculus.

s Sacculus endolymphaticus.

Now, on the hypothesis that the ear is llie specific organ of
the cquilibrative sense, it might be argued that the removal
of one ear does not necessarily so jiowerfully affect the equi-
librium of the body as to destroy even the control of the
injured side ; for the imiii)iu"e(l side is able to take upon itself
the functions of the injured oi-gan in part at least. If that
were the case, when both ears were removed we should cer-
tainly expect to see the animal lose contiol ot its body ; but,
as I have alreadv said, the animal is even better off ivith both
ears reinored tliaii with one ear removed, Jor all traces of eqiii-
librativc disturbance disappear at once on the removal of the
second ear.

How can the semi-circular canal with its two ampullae be
the special organ of dynamical equilibrium and the utriculo-
sacculus with its sense organs the special organ of statical

BDELLOSTOMA DOMBEYI, LAC. 1 59

equilibrium when the animal maintains its perfect equipoise
without them? If in hii;her forms each canal appreciates
movements in its own plane and by definite functional combi-
nations of two or more canals is able to mediate all possible
rotational movements, what function has the single canal in
Myxime, or the two canals in Petromyzon ? Both of these
creatures are subject to the same mechanical conditions in their
progress through the water that the higher vertebrates are.
The fact that thev do not have the canals proves that vertebrates
can swim as admirably without this apparatus as with it, and
such being the case, what was the physiological incentive
which lead to the production of the other canals ? I have
elsewhere given a sufficient mechanical explanation of the
genesis of the canals, but I have yet to learn of a sufficient
physiological one. Who will add to our knowledge in this
particular .''

It is said that the semi-circular canals in man, for example,
are delicate organs whose special function is to take cognizance
of all the motions of the body in their respective planes, and
that they thus control either singly or by various combinations
with the other canals of the opposite side of the body, all
possible movements of the body.

One mav readil}' disprove this assumption by a very simple
experiment. Have some person with normal ears and normally
developed muscles swim for a distance on his back with closed
eyes — first with his hands and arms alone, keeping his legs
straight, and second with his feet alone, folding his arms on his
breast. The average man is stronger on the right side of his
body than on the left, and consequently when he pulls himself
through the water with his arms alone — eyes closed — he
unconsciously pulls himself to the right and swims in a circle
— {Rcitbaliu bcivcgiingcii of Gcnnan physiologists !) When he
swims with his feet alone he pushes himself through the water
and consequently ])ushes himself over to the left side and
swims in a circle in an opposite direction to what he did before
{circus i/ioi'ciiiait to the left!) and he is, so long as his eyes
remain closed, unconscious of the fact that he is moving to
one side i.e., diverging from a straight line — but he becomes

l6o BIOLOGICAL LECTURES.

conscious of this fact the moment liis eyes I'est upon some-
thing which enables liim to orient himself, and yet tliis normal
individual has six organs in his head which are there for
the special jnu-pose of controlling of his mox'ements in s}xice,
so say the physiologists. His two eyes are of more service to
him than are his six canals.^

It may be objected that the canals are not intended to take
cognizance of such minute changes in position in space as are
involved in swimming around in a circle; but if they cannot
perceive such changes of position when swimming, how can
they perceive them when on a rotating table {e.g., Crum.
Brown's experiment). It would be a great service to determine
the minimum amount of angular motion of which the canals
can take cognizance, in order that we may know liow much to
expect of our ear canals in this wa)'.

It may be objected that the man in tlie water on his back is
in an unusual position and consequently his canals do not work
with sufficient delicacy on account of the unaccustomed
pressure, etc. But it is a necessary consequence of the
assumption that the canals are special organs of equilibrium,
that they should work in any position; otherwise wliat were
the use of them } Otiier organs of specific function work in
all positions of the body. The eyes see, tlie nose smells, tlie
ears hear, the brain thinks, the heart beats, and so on ad
infijiituDi, all except the ear canals, whose special work is to
cognize just such unusual si)atial conditions, and according to
the hypothesis, the only organs iu the bod\' having this
function, — they fail of their function when most needed. In
the experiment with the rotating table the canals are subject
to even a severer test of \ery small angular motion and are
supposed to be able to operate very precisely, in some cases.

' Kxperimental rides on the great Ferris wheel at Chicago during the Columbian
Exposition proved that a perception of the direction of the motion of one's body
in space was impossil)le unless one made use of the eyes. I found that the
upward motion could not be detected by the ears alone. Without the evidence
of one's eyes one seemed to be standing still upon a trembling platform, and the
while was really making a great circle through the air in a geotropically oriented
position. It is notorious that balloonists have difficulty in determining whether
they are moving upward or in any other direction when sight is hindered, and
that it is impossible to detect motion in the midst of a cloud.

BDELLOSTOMA DOMBEYI, LAC. l6l

I think this swimming experiment gives very satisfactory
evidence to the effect that the semi-circular canals in man do
not function as organs of dynamical equilibration. At the
opposite end of the scale — Bdellostoma is certainly not
dependent upon its ear for the equilibrium of its body. I may
say in conclusion that I think Professor Ewald has made a
great discovery in showing how intimately the auditory nerve
is related to the musculature of the body and in proving that
some of the complicated phenomena which follow section of
this nerve and of its branches are fully accounted for by the
fact o^ the lessened muscular tonicity of the injured side and
not on the ground that these phenomena indicate the special
functions of the several parts of the ear.

EIGHTH LECTURE.

THE INFLUENCE OF EXTERNAL CONDITIONS

ON PLANT LIFE.

\V. r. WILSON.

If you open your eyes and look carefully about, as you are ,
traveling from place to place, you will easily see that there
are very many differences between the plants of one region
and those of another. In the high mountains you will find
many thick-leaved plants, such as the Rhododendrons and
Sedums, and quite a number of peculiar forms not seen lower
down. Many of these may have a stunted, gnarly or dwarfed
look, quite strange to the vegetation at the sea level. In still
another region the plants may have lost much of their natural
grace and beauty of form. They may look rigid and stiff, with
small thickened leaves or none, with short thickened stems, or
round and consolidated forms such as we find in the Cacti or
Euphorbias. These are the tenants of desert regions.

Again, if you happen to go south into the tropics, sheltered
and shaded by immense thin-leaved trees, with the waving
green of the palm and the vine, you will find dense masses
and banks of dark green foliage belonging to Ferns and Sella-
ginellas, with climbing plants of various kinds intermingled.

About your own door may be quite as interesting forms as
in more remote districts, only you are accustomed to them and
do not see their peculiarities. You may look out on pines and
oaks, on a great diversity of small plants, with the Indian pipe,
a partial parasite, and a few ferns which can bear more wind
and cold than most of their relatives, plenty of mosses and
lichens, and, in fact, representatives of all the great plant
families. .

164 BIOLOGICAL LECTURES.

The ancients looked upon the whole animate world as having
been directly created by some higher power, and believed that
each species indicated a distinct and individual creation. They
also observed these differences between the plants of different
regions, and, in fact, between those of the same region. They
thought that all living organisms were created to fit the
special location and conditions under which they existed.
They believed that water animals and water plants, for
example, had always been and would always remain such ;
that the desert region had always been a desert region, and
that the Cactus had been created to fit it. We are not
obliged to go very far back in the history of our own times
to find eminent naturalists who have strongly advocated this
view. No less a man than Louis Agassiz was one of the
most strenuous defenders of this theory. He believed that
species of both plants and animals were invariable, living
and dying in form and color and habit just as they were
created. And there were many other naturalists the world
over who held to this doctrine of special creation. It must
not be forgotten, however, that though their views attained
no prominence, such men as Lamarck had at different times
indicated a strong belief in the variability of forms.

During the last twenty years there has been a great revision
of thought in regard to these subjects. At present all
naturalists believe not only in the possibility of a continual
change in both plants and animals, to fit them for varying
conditions, but also in the gradual growth and development of
very diverse changes in climates, rendering equal modifications
in both fauna and flora absolutely essential to their continued
existence. Since great changes have always been slowly taking
place in the earth's surface and climate, and since present
vegetation has always been subject to these gradually varying
conditions, it must have adapted itself, with a slowness commen-
surate with the earth's changes, to the ever-appearing new
conditions. In this way, we think, can be solved the problem
of the infinite variety of vegetation.

By experiment we may determine the two factors underlying
plant variation. On the one hand the laws of inheritance are

EXTERNAL CONDITIO AS ON PLANT LIFE. 165

ever holding the plant invariable, while the external torees
are ever pushing it toward variation. In this lecture we
will disregard entirely the interesting phenomena which relate
to that internal force the manifestations of which we call
inheritance, and try to discover how much the plant world is
moulded and shaped by what is exterior to it.

If you are inclined to think about all these differences in
the vegetation of the many regions through which you have
travelled you will soon see that where there is great change
in the appearance of the plants, in passing from one place to
another, there is also an equally marked difference in the
surroundings or soil or climate. You will soon find yourself
always looking for the one when you have found an expression
of the other, i.r., if the plants give you a new flora, you seek
at once to find the cause in external conditions ; or, if you
have great external difference in surroundings and climate, you
expect this to be at once reflected in the varying vegetation

about you.

Let us study a few plants a little more closely, and see
if we are able to determine on what this variation depends
and how rapidly it may take place. I shall assume at the
outset two sets of causes, both of which may be active in
bringing about variations in plants, the one wholly external,
such as light, heat, moisture and the like, and the other
internal, and concerned with the laws of inheritance, about
which we know so very little.

Let us for our present purpose consider only the external
influencing conditions, for I believe that they are much more
potent and determinative than the laws of inheritance. They
may be enumerated as follows :

I. The Water Supply. — This is more important than any of
the following points, as it is intimately connected with the
very vital process of organizing materials for growth and
their transport throughout the plant.

If the water supply is cramped and too little, we have
immediately before our minds the desert plants.

If the water supply is too great, equally important changes
take place.

1 66 BIOLOGICAL LECTURES.

2. The Lio-Jit Supply — Here again we may have too much

or too little, either condition leaving its strong impress
on the plant.

3. Altitude is a third factor in the growth of plants, which

strongly influences the light, the moisture and the tempera-
ture, as we shall see in a later discussion.

4. Temperature. — Temperature and light, together, govern

largely the transpiration of water from the plant.
The character and position of the leaves are often wholly
adapted to both the conservation and the loss of water by
transpiration.

5. Tlie Food Supply produces the most fundamental changes

in the life of the plant, strongly influencing not only the
production and character of the flower and the fruit, but
in all probability determining the sex itself.

6. The Influence of the Sea upon Plant Forms. — It will be

seen that quite as remarkable changes come to the sea as
to the desert plants, and in truth based upon similar

reasons.

(I) Let us first consider the water supply. You will readily
bring before the mind's eye the picture of desert plants, which
represent in their modifications a lack of water. But you will
not so easily call to remembrance plants whicli have undergone
changes from an oversupply of water. Yet there are many of
them even in your own neighborhood.

The Bald Cypress {Taxodium distichum) grew in the present
Arctic region before the Glacial Epoch, in company with oaks,
maples, willows, the Redwoods {Sequoia giga>itea, S. sempcr-
vircns), the Gingko tree {Salisburia adiantifolia), Torreya, and
Glyptostrobus. During later changes in climate these trees
were driven from their home and travelled down widely different
lines into the South. For reasons which we are unable to
understand, the Sequoia, or Redwood, descended along the
California coast, the Glyptostrobus and the Salisburia or Gingko
tree, down the coasts of China and Japan, the Torreya and
Taxodium, or Cypress, to the eastern and southern parts
of North America. At present the Bald Cypress, to which I
wish especially to call attention, grows only along the water-

EXTERNAL C0A7J/T/0XS O.V PLAXT LIEE. 167

courses and in the swamps of the south-eastern part of the
United States. It seeds itself naturally nowhere outside of
areas which are for several months during the year under water.
This tree belongs to the Pine family, but has some very marked
peculiarities which make it differ strongly from any of its
relatives.

The tree shown in Plate No. i stands normally surrounded
by water. Many root-like projections are seen underneath and
around the tree, which are popularly known as cypress knees.
These are all connected with the root system below the water.
They have extended their growth upwards until they are sure
to remain in the air at the ordinary level of the water during
most of the year. They are in such numbers that wagon-loads
of them could be taken away from one tree. From many
careful experiments. made on the growing seedlings, it has been
determined without doubt that these knees are organs of
respiration. All dry-land trees secure free oxygen from the soil
to carry on the oxidations needed in root growth. This tree
growing in water, which holds much less oxygen than the soil,
is unable to draw its full supply from the medium surrounding
the roots. To fill this want, these knees are pushed up out of
the water into the air as aerating organs. Although the plant
does not now grow normally on dry land, yet when planted
there it thrives as it once did in previous geologic ages in the
Arctic regions. Plant two sets of seedlings, the one in dry
soil, the other in soil flooded with water ; the first will show no
signs of the root-aerating organs, while the second will develop
them in abundance, as small vertical roots pushed above the
surface of the water.

In the water growth, the branches of the Cypress are
spreading and the top flattened, a marked departure from the
most striking characteristic of the Pine family, to which it
belongs. When grown, however, in dry soil, in our parks
and public grounds, it reverts to the normal type. The
branches are short and make a sharp angle with the main
stem, and its cone-like form is as pointed as in any of
the tall conifers. This will be seen in Plate No. 2, photo-
graphed from a tree planted in Fairmount Park, Philadelphia.

1 68 BIOLOGICAL LECTURES.

It will be observed, too, that there are no signs of knees
underneath.

Plate No. I represents a water form from the James River.
The base, in this form, is always very much enlarged. This
enlargement is a part of the aerating system needed to secure
the necessary oxygen, and is, of course, entirely absent from
the land form.

The departure from the sharp, cone-like form natural to the
conifers, is due to the difificulty in obtaining both air and food
from the water. This lack of nourishment shows itself in the
dwindling, depauperate and dying branches of the upper part,
since that part is most remote from the food supply.

In some of the lakes of Southern Florida it now and then
happens that a cypress tree has obtained a foothold in much
deeper water than is its normal habit. Here all of these water
peculiarities are greatly exaggerated. The trunk of the tree
produces an immense cone, the top of which points up to the
surface of the water and ends with a few flat sprayey branches.
The base of the cone may be forty or fifty times the diameter
of the top, from which come the few straggling branches which
project above the surface of the water. There are at its base
innumerable knees. In a tree having the height of twenty-
five or thirty feet, the cone below the water will represent a
little over one-half, and the branches above the other half of its
altitude. Plate No. 3 represents such a tree in South Florida
after the waters of the lake had been drained away. The
knees, being of no further use, quickly rotted and disappeared
and are not shown in the photograph. Originally the water
was high enough to touch the lower branches, and the tree
eked out a miserable existence, struggling hard in the deep
water for both air and food. The difficulties under which
it labored developed it into a great monstrosity. It is an
extreme expression of excessive water supply. Conij^are its
short, cone-like trunk, entirely immersed in water, with what
may be called the normal development now found only in
our parks (Plate No. 2). In this form the trunk is tall and
slender, with branches towering to a very sharp point. The
water form has acquired its knees and greatly enlarged

No. 1 . -- TAXODIUM DISTICHUfv"; RICH.— JAMES RlVER, VA.

(vIO. 2. — TAXODIUr.l DlSTlCHUM RICH, — FAiKMur.Ni t.■^K^,

p

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D

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O
H

EXTERNAL CONDITIONS ON PLANT LIFE. 1 69

base for purposes of respiration. Its flattened cone is the
result of the bad nutrition. The land form, dropping into its
native dry earth habitat, does not develop the knees and
enlargement, because its oxygen supply is ample. Its nourish-
ment, too, is sufficient, so that it will have as a result of these
normal, favorable conditions, the tall, sharp, cone-like form
natural to the pine family. Doubtless the cypress has been
millions of years adapting itself from its dry land conditions
to its watery surroundings, and the most interesting fact in this
connection is its readiness to fall back into its old habit of
growth, and even in the first generation on land to lose every
trace of these wonderful acquisitions.

There are many other plants which have acquired equally
remarkable organs in the same way. Some of the mangroves
of the Florida coast such as Aviccwiia nitida and Lagnnciilaiia
raccmosa, growing in the ooze between tide-waters, have developed
vertical roots which project out of the mud by hundreds under
each tree and are exposed to the air at every low tide. These
organs aerate the plant as the knees aerated the cypress.
They are much more highly organized, being covered on the
parts above the mud with great numbers of large, open
lenticels.

It is not necessary for us to go so far from home to find
numbers of plants which have adapted themselves, through
special aerating organs, to a change from dry land to water
growth. One of the most common is Dccodon vcrticillatits,
which develops over the surface of all its roots an extremely
thickened, corky, air-holding layer. A similar development
covers the branches when they happen to drop into the water.

Let us now see how plants are modified when they lack
water. If the supply is inadequate, the plant makes an
attempt to conserve the little that it has. As the surface of
ordinary plants allows large quantities of water to escape by
transpiration, and as this loss is largely proportioned to the
amount of surface exposed, such plants usually lessen this
surface by making the leaves smaller and thicker, or by losing
them entirely, by shortening the branches and by consolida-
tion generally. As the light and the heat of the sun increase

I70

r.lOLOGlCAL LECn RES.

transpiration, the surface of the plant may become for protec-
tive purposes hairy; the cuticular and epidermal layers may
be thickened; the interior air passages in the leaf which
communicate with the surface may become obliterated through
consolidation of the cellular structure; and, in certain cases,
the leaf may have added to it definite kinds of tissue for
storins: water to be used in time of need.

(2) That light readily causes various reactions in many of
our ordinary plants, every one knows. Watch the folding of the

Pl.ATI, \n. 4. I'l.ATE No. 5.

Clover leaves as daylight decreases, and you will see them go
into their sleeping position, while in the morning they open
their faces and present them to the sky. Look at the Wistaria
vine by the aid of a lamp, late at night, and you will see that
the little leaflets liave dropped down and closed together. It
the morning is bright and warm, they will rise early and by
nine o'clock every young tender leaflet will point its tip directly
at the sun, in a direction parallel with both the light and heat
rays. As the heat of the sun increases toward noon and during

EXTERNAL COXPITIOXS OX PLAXT LIFE.

I 71

the hotter part of the day, you will find these leaflets constantly
rotating, maintaining their parallelism to the sun's rays. If the
day is cloudy and the heat of the sun obscured, these same
movable sensitive leaflets may remain in a stationary position
so as to receive the most direct light possible during the whole
day. If you choose to wander in your nearest woods, many
similarly-acting plants cannot fail to escape your notice, such

Plate No. 6.

Plate No. 7.

as the Dcsmodiiini, the Lcspcdcza, the Mclilotns, and, among
the tree-like forms, AmorpJia, and Robinia, or the Locust.

Plate No. 4 shows the Melilotus, or Sweet Clover, on a cool,
moist, somewhat cloudy morning, when the leaves are spread
out fully, striving to receive all the light and warmth possible.
The direction of the light is generally at right angles to the
surface of the foliage.

Plate No. 5 represents another plant on an extremely hot,
dry morning in midsummer, photographed at nine o'clock.

172

BIOL OGICA L LECTi/RES.

The photograph was taken from the south. It will be seen
that the three leaflets, elevated on their sensitive petioles, are
all i)ointing directly at the sun in the south-east. The leaflets
being parallel to the heat and light rays, escape much of the
consequent transpiration of water which would occur were they
thrown down to the sun's rays as in Plate Xo. 4.

Another plant, Plate No. 6, photographed under similar
conditions of dryness and hot sun at twelve o'clock in the

morning, shows the leaves
pointing directly to the
zenith, thus again parallel
to the sun's ra}'S and for
similar reasons.

Plate No. 7 shows still
another plant taken on the
same hot and dry day,
with the leaves pointing
directly toward the sun.
7^his photograph was taken
at 2 p. M. in the afternoon
from a position 15''^ north
of west, at right angles to
a profile view of the leaves.
It will be seen from
tliese illustrations that
when the conditions are
ripe for rapid loss of moist-
ure, that these sensitive
leaves continually keep
themselves parallel with the sun's rays during the day. As
the leaves in the morning are first influenced by heat and
light, they elevate themselves and point toward the eastern
sun. They continue to rotate during the day, so that at noon
they are erect, .slightly inclined to the south, and at night are
directed to the west.

Plate No. 8 shows a cluster of tliese plants photographed
from the north at si.x o'clock in the afternoon after a compara-
tively warm, dry day. The leaves are mainly pointing to the

Plate No. S.

EXTERNAL CONDITIOXS OX PLAXT LIEE.

^11

right toward the western sun which is still quite high. At
sundown, after the influence of the falling dew has been slightly
felt, the leaves will begin to assume the position seen in
Plate No. 4.

If we continue to watch this plant as darkness comes on,
we shall find all these leaflets dropping down slightly, each
turnino- itself one-fourth around on its petiole until the three
present their edges up-
permost. The two outer
leaflets, having their faces
toward each other, move
slightly toward the cen-
tral one until they touch
it. It will be seen that
the three little leaflets
have thus placed them-
selves together in such a
way as to reduce their
surface to nearly one-
third of the original area.
This protects them from
radiation and the loss of
much heat during the
night. Plate No. 9 shows
a plant while sleeping,
the photograph having
been taken at twelve
o'clock midnight.

But there are other
effects of light more
marked than these re-
actionary movements. In ordinary plant assimilation, which
takes place only under the influence of light, the leaves are
generally the active organs. It sometimes happens that w^hen
the light becomes insufficient for assimilative purposes, certain
parts of the organ itself — the leaf — become quickly atrophied
or disappear entirely. Thus the form of the elm leaf has
gradually become oblique on account of the shading of one

Plate No. 9.

174

BIOLOGICAL LECTURES.

of its sides. This is true, too, of the house begonia and many
others of our common plants.

At high altitudes, where the differences of light and shade
are much more intense, these changes are correspondingly
more quickly brought about. With these external changes of
form there are microscopic differences which are even more
striking. In Plate No. lo are shown two cross-sections of
leaves taken from the Mountain Balsam (Abies frascri), a from
a sunny exposure and b from the more densely shaded part of
the tree. In Fig. a we have on the upper part of the leaf the
palisade cells above, and the more loosely arranged tissues,

Fic;. a.

Fig. b.

Plate No. ro.

for assimilation, below. About the middle of the leaf is a
laro-e resin duct. Fig. b is the cross-section of a similar
leaf from the same tree, carefully selected from a point
underneath the heavy branches which the direct sunlight never
reached. Above the resin duct, on the upper side of the leaf,
are the palisade cells, much as in a ; but the loosely arranged
assimilating tissue beneath the resin duct is seen to be absent '
in /;. In other words, the light was not strong enough in the
lower shaded parts of this tree for assimilative purposes, and
in consequence these tissues have been dispensed with.

(3) And here let me speak of the influence of altitude, which
affects not only the light but also the temperature and the air

EXTERNAL CONDITIOXS OX PLANT LIFE. I 75

supply. It will be readily understood that at any very high alti-
tude the amount of dust in the air is at a minimum; also, that
the greater the altitude the less dense the atmosphere, which
will, consequently, contain less moisture. But as the illumina-
tion of general space depends wholly upon the refraction of
light from the dust and particles of moisture in the air, it will
be seen that refraction at high altitudes must be at a minimum,
and that air spaces outside of the direct line of the rays of
lio-ht will be much darker than at lower altitudes. The light
given to shaded leaves, then, at these high altitudes through
refraction, often proves too little for the purposes of assimi-
lation, and the assimilating tissue consequently disappears.

This shows the relation of altitude to light and assimilation.
But altitude is many-sided in its influences. Because we have
here less dust and less moisture in the air, the sun's rays, not
being refracted out of their course, are much more direct. In
the shade, at an elevation of seven thousand feet, you are too
cool, but step into the sunlight and your upturned face will be
quickly burned by its strong, direct rays. These same rays
burn the moisture rapidly out of mountain leaves. To avoid
this as much as possible, they become thickened in many ways,
often decrease in size, and travel along the same lines
generally for water retention as have the desert plants. High
altitudes, then, will produce desert-like plants, as seen in the
Live-for-evers, or Scdnins. Not only are the leaves found
decreasing in size and becoming thickened, but in all sensitive
plants the movements are much more rapid.

Many plants which do not have daily movements of leaves
to accommodate themselves to the light, still put their young
leaves, when thoroughly exposed to the sun, parallel to its rays
in the hottest part of the day. Later in the season, when the
epidermal tissues are more thoroughly developed and the cuticle
has been fully thickened, the leaves, thus becoming better able
to resist the heat rays, drop down to a position more or less at
right angles to the approaching light. Select another plant of
the same species, which is thoroughly shaded during the whole
day — it may not be twenty feet from the first — and we shall
find that the young leaves, as they develop themselves, at once

176

BIOLOGICAL LECTURES,

drop down to a position in which the approaching hght will be
at right angles to their surfaces. Plate No. 1 1 is a photograph
of RJLododendro7i maxuniini taken at an altitude of over 4000
feet. It developed itself entirely in the sunshine. It shows
the upper, or young leaves, erected vertically upward until
they are nearly parallel with the sun's rays during the hotter
portion of the day. The leaves below, which are more or less
horizontal, are more than one year old. At the end of the

Plate No. ii.

first year, the upper leaves, having become tough and coria-
ceous, will assume a position parallel to the older ones below\

In Plate No. 12 is shown a photograph of RJiododcndron
cataivbicnse at the same altitude, but standing in a thoroughly
shaded spot. Although a different species, the action of the
leaves is the same. It will be seen that the vounsr and urowins:
leaves above \)\\\ themselves quickl)- in a ]iosition jiarallel with
the leaves below during development.

The differences between the microscopic structures of the
leaves exposed to direct sunlight and of those wholly shaded

EXTERA'AL CONDITIONS ON PLANT LITE,

177

are even more marked than the corresponding differences in
position. Plate No. 13 shows two sections of leaves from
RJiododcndron tnaxiuuiDi, the one from the sunlight, the other
from the shade. Section a, from the sun, shows four super-
imposed rows of palisade cells, extremely long and narrow,
arranged with their long diameters pointing to the surface of
the leaf in a way to afford the best protection from the heat
rays. Section b, from the shade, has no very well marked
palisade system, for no such protection is needed. The section

i'LATE No. 12.

from the sun is much thicker than that from the shade, but
while the loosely arranged mesophyll in the under part of the
leaf, where assimilation is most active, occupies in the sun
section only one-half of the space of the whole leaf, yet in the
shade section it includes more than two-thirds. The explana-
tion is simple. The exposed leaf requires less space for the
work of assimilation on account of the strong light. The shaded
leaf, on the contrary, as much less light reaches it, must have a
greater number of cells in which to do a given amount of work.
(4) The food supply of the plant may exert a very strong
influence upon its development and life. It is a well-known

I 78

BIOL OGICA L LEC Tl/RES.

fact among gardeners that over-fed plants will often produce no
fruit. When pear-trees refuse to bear fruit, they can often be
made prolific by cutting away the central root, thus lessening
the supply of nourishment. As a rule, when plants are poorly
fed, they put forth blossoms and ripen their fruit earlier,
although it may be smaller and of poorer quality.

(5) The influence of the sea upon plants is quite remark-
able. We have seen that in desert regions, and to some extent
in high altitudes, plants have greater or less tendencies to take
on consolidated forms. This is also true of seashore plants.

aonQO

^qqotd;

c^

5Sr

n

u.

Section a.

Plate No. 13.

Section i>.

The cause in both desert and mountain regions was a lack of
moisture. On the seashore, at the water's edge, and even
with many plants standing in the water, we find these thick-
ened leaves and leafless forms. Hence we must look for
another cause for this than lack of water.

Ordinary land plants secure the water which they need
mostly through their roots. Although the soil may be appar-
ently dry, yet the plant has no difficulty in supplying its
necessities, for every particle of the soil is surrounded by a

EXTERNAL CONDITIONS ON PLANT LIFE. i 79

film of water, which is forcibly taken from it by the osmotic
action of the root hairs. Each hair is an elongation of a
single epidermal cell. Its external wall is composed of porous
cellulose. Besides the ordinary cell contents, such as nucleus,
masses of living protoplasm, vacuoles, microsomata, and the
like, there is a thin semi-fluid layer of protoplasm, closely
appressed to the whole interior of this porous cellulose wall.
This forms, with its cellulose support, an osmometer, and
when the root hair is tightly crowded in its growth against
the surrounding particles of earth, thus coming in contact
with the water film, there is at once set up, with great force,
a current from the thin fluid surrounding the particles
through the walls to the more or less thickened one within.
Under a pressure often of nearly an atmosphere, this water
is forced from the exterior cells of the root to the interior
conducting fibro- vascular bundles, through which it .finds its
way to every part of the plant. It will be seen that the
condition of this forcible absorption is the interposition of
a protoplasmic membrane between two fluids of different
densities, the more dense, toward which the current always
tends, being within the cell. It is only necessary to state
that in sea-water we have a fluid of even greater density
than is usually found within the cells of plants, and that
this would tend at once to make it either very difficult or
utterly impossible for the plant to secure its water. Plants
which have adapted themselves to the influence of sea- water
have done it in a number of ways — sometimes by taking large
quantities of salt into the cells, which balances much of the
salt without. In this way the density of the fluid within is
made greater than that of the water without, and absorption
takes place to a limited extent. But since it is still very
difficult for the plant to secure a large amount of water,
although it may stand in it, — " Water, water everywhere, and
not a drop to drink," like Coleridge's shipwrecked mariner, —
all the other methods of retaining its scanty supply, usually
found in desert plants, are here also exemplified. Thus, the
leaves may become smaller or thickened or disappear alto-
gether, in order to lessen the transpiring surface. If the

i8o

BIOLOGICAL LECTURES.

plant can get but little moisture, it also retains that little, or
lets it go with great difficulty. Hence, we have on the sea-
shore a vegetation corresponding in some respects to that in
high altitudes, or to that in desert regions, although the
apparent conditions are radically different from either.

Hydrocotylc uuibellata is a plant common in moist or watery
places from Maine to Florida. In the semi-tropical fresh-water
marshes of Florida, it places its slightly thickened, rounded
leaves at right angles to the sun's rays, parallel to the surface
of the water in which it grows. When it happens to encroach
uj^tju the salt-water marshes of this same region the difficulty
of water supply is so heightened that the slender petioles
all make a right-angled turn at their upper end and put

Fig. b.

I'l.AlE No. 14.

the now thickened leaves in a vertical position, in order to
avoid the direct rays of tlie sun, thus lessening the loss of
water.

Plate No. 14. fig. a, shows a sketch of this little jjlant, taken
from a fresh-water stream in South Florida. T^ig. b on the
same plate shows another plant taken from a salt marsh near
by. All of its leaves are rendered vertical b}- this turn in their
petioles. The microscopic differences are much greater than
this relative difference in position. The leaves of the one in
the salt marsh have become much thicker, the epidermal tissues
much heavier, the number of the palisade cells has increased,
the intercellular spaces have nearly di.sappeared, and the

EXTERXAL COXDITIOXS OE PL A XT IJEE. l8l

openings into the stomata have been transformed, tlirough
tliickening of the cuticle, into narrower, deeper channels.
These differences are common to many other plants which
inhabit indifferently fresh and salt water locations.

The plants which grow many miles from the sea-shore are
also more or less influenced by the salt in the spray which
is mechanically lifted by the winds and carried long distances
inland. Lighting on the leaves, it has a tendency to draw out
the moisture from within and in this way very materially
increases the normal transpiration. To guard against this
many plants near the sea-shore thicken up both the cuticular
and epidermal layers. Where the wind blows somewhat
constantly from the sea over the land, these effects may be
seen in plants extending from the shore sometimes as far
as twenty miles.

Many strand plants exhibit the same peculiarities as those
of the Rhododendrons of the mountains, i. e., they erect their
leaves parallel with the rays of the mid-day sun to avoid loss of
moisture. This is especially marked in the Mangroves of our
Southern coast, which, for a greater part of the day, stand
directly in the water. The plants on our New Jersey shore
illustrate many of these facts and are quite as interesting for
study as those of South Florida. A half-dozen plants of one
of our pigweeds {Atriplex littoralis) taken from a salt marsh,
potted, and carried to a greenhouse in the city, exhibited the
following interesting characteristics: On the salt marshes from
which they were taken, all the leaves were rigidly erect, making
no shadow with the mid-day sun. But after being watered with
fresh water for five or six days in the greenhouse, all of the
leaves dropped down to a normal position, presenting their
faces to the direct rays of the sun. Upon watering them for
several days following with a strong salt solution, the leaves
again erected themselves, assuming the precise position in
which they had grown on the salt marshes.

It has long been known, through physiological experimen-
tation, that almost any salt or alkaline solution decreases
transpiration, because it at once lessens the water supply. The
converse is true of acid solutions. This law may be taken as

1 82 BIOLOGICAL LECTURES.

a partial explanation of the conduct of the little New Jersey
Pigweed.

Perhaps enough has been already said to convince anyone
that the almost infinite variety of plant forms may have some
fairly direct connection with their environment. The cypress
tree produces its needful aerating organs when grown in the
water, but no sign of them in dry soil. It may be a matter
of wonderment, however, why these characteristic organs are
so quickly and readily lost. They are an acquired character to
fill a definite want — when this want no longer exists, they dis-
appear. Perhaps this character, which we know was acquired
since the Eocene period, has endured for too short a time
for permanent inheritance. Many other plant characteristics
acquired on physiological grounds, but regarding the duration
of which we have no record, although we have reason to
believe that they have been serving their purpose for an
immense period of time, are perfectly permanent, and inherited
by their offspring long after the developing cause has disap-
peared. We have in Australia a large number of trees which
have adapted themselves to a hot and dry climate by various
manipulations of the leaves. In some Acacias, for example,
the leaf-blade has entirely disappeared, and the wing growth
on the upper and under sides of the petiole is an apparently
vertical leaf. Other members of the same family make
the true leaf vertical by a twist of the petiole. Although
accomplished in two very different ways, the object in each
case is plainly to lessen the tranpiration. Apparently, this is
a much more trivial change than the acquirement of knees by
the Cypress. Both fulfil a physiological necessity ; but while
the knees of the Cypress are lost in succeeding generations
if the developing cause is removed, the Acacias ma}' be
cultivated for generation after generation, entirely removed
from the climatic conditions which produced the changes, yet
they will be as permanently inherited as in their own native
land.

Avicemiia nitida, the so-called l^lack Mangrove of our
Florida and West Indies coast, of which I have already spoken,
belongs to the W'rbena family. Normally a dry land form, it

EXTERXAL COXDITIOXS OF PLAXT LIFE. 1 8

J

has adapted itself to a growth between tide waters. In so
doing it not only produces the remarkable, vertical, negatively
geotropic roots, which grow up out of the salt mud, so that
at low tide they remain each day several hours in the air for
oxygen absorption, without which it could not live, but it has
also remarkably thickened its leaves and appressed them
vertically against the stems in order to protect itself from loss
of water, for reasons which have been already stated.

From the history and general relation of this mangroove
to the Verbena family, we judge that this adaptation is of
comparatively recent date. When removed to dry cultivation
it loses all these characteristics in the first offspring. In the
case of the Cypress we have not merely theoretical reasoning
from family relationship, but also definite data from fossil
remains, which prove that it was a dry land form in a very
recent geologic age, and that its aquatic habits are modern.
It is certainly curious, and you may interpret it as you please,
that both these plants, when subjected to opposite conditions,
immediately lose their acquired characters. In the Australian
plants, on the contrary, similarly acquired characteristics under
opposite conditions are perfectly permanent. That they have
been in this condition for an immensely longer period of time,
and that in consequence this development is so stamped upon
their parent stock that it reappears generation after generation,
even when withdrawn from their causal surroundings, is,
perhaps, the key to this riddle.

Let me, then, remind you once more of the almost infinite
variety and diversity of plant forms, and that, as seen in
nature, we can generally trace the relationship between the
peculiarities of the plant and its surroundings ; also, that in
general, these peculiarities, no matter what they may be,
reproduce themselves in the offspring. Let me state once
more that any plant which we may select as an example, no
matter how peculiar in form or habit of growth, gives us an
expression in this peculiar form and special habit of the forces
which have surrounded it and touched it all the way down its
long line of descent, from its earliest more simple and primary
condition to its present more complete expression of plant life.

NINTH LECTURE.

IRRITO-CONTRACTILITY IN PLANTS.

Prof. J. MLIRHEAD MACFAKLANE, D. Sc.

Ix a paper published by me about nine months ago, I
showed that the generally accepted view that the leaf of
Dioiicea contracted after one stimulus of the irritable hairs was
incorrect, and that two stimuli were necessary to cause contrac-
tion. The other phenomena connected with leaf-closure, and
described in the paper, were so remarkable as to cause me to
inquire whether these phenomena were unique in the vegetable
kinc^dom or whether conditions could be traced that connected
Dioiicea with other sensitive plants.

The behavior of the leaf of Dioncea to mechanical stimuli
given at varying intervals of time was such as to suggest a
very definite and exact contraction of the protoplasm of certain
cells. The outcome of the inquiries which are epitomized in
the present lecture, and which I hope in time to bring forward
in extended form, proves that in the vegetable as in the
animal kingdom, we have to do with a true contractile
tissue. Further, among those higher plants that we are now
to study, this tissue is made up of cells, each consisting of an
irrito-contractile protoplasmic sac enclosing a quantity of sap,
and each cell is joined to neighboring cells by protoplasmic
processes that pass through minute pores in the common
cellulose membranes.

In order to make clear the relation that is shown by many
sensitive leaves to environmental stimuli, it may not be inap-
propriate to indicate first the possible movements that such
leaves can perform, as generally stated in memoirs and text-
books on the subject. A plant of the common yellow sorrel

1 86 BIOLOGICAL LECTURES.

{Oxalis stricta), if examined on a quiet and moderately cool
day when the temperature is 25° C, will show the trifoliate leaf
fully expanded, and the three leaflets so placed on their stalks
that their surfaces lie at right angles to the sun's rays ; i.c .,
they are not only heliotropic in that they grow toward the
light, but they are diaheliotropic in that they can, if need be,
so place their surfaces to the light as to receive the rays
at right angles. But if the temperature rise to 29°- 30°
C. in the shade, the leaflets will begin to fall down ; and if
a steady increase in temperature goes on, they will continue
to fall till at 33° C. they will incline downwards back to back.
This day-movement has long been known to occur in many
plants, and was regarded as a means by which the leaves
were screened from intense illumination ; but my colleague,
Prof. W. P. Wilson, considers it to be a heat-movement, or an
attempt on the part of the plant to screen itself from
intense solar thermal action. As connected with the varying
results of stimulation on different species afterward to be
described, it may here be noted that Oxa/is stricta shows
distinct heat-movement at 29° C. ; Oxalis Dcppci at 31° C;
Oxalis dendroides at 33°-34° C. ; while the common sensitive
plant {Mimosa piidica) that has thin and apparently delicate
leaflets only becomes affected when the shade temperature
rises to 37° C. This movement, described by Darwin as a
paraheliotropic one, I propose to term ' parathermotropic'

But as the sun's rays become tempered in the afternoon, or
as plants formerly exposed to the full heat of the rays get
sheltered by foliage, the flat, expanded condition is resumed.
Toward the approach of evening the leaflets again begin to
fall, and by 8.15 or 8.30 during midsummer have taken up the
same position that they had during the heat of the day. This
night-sleep, or nyctitropism, has, with every show of reason,
been viewed by Darwin and others as a protection against too
rapid radiation of heat and reduction of temperature in the
tissues. We would emphasize it, then, that alike during the
parathermotropic and nyctitropic states the leaflets of Oxalis
stricta are similarly placed. The nyctitropic position is
retained till the following morning, and in some plants, at

IRRITO-COXTRACTILITY IX PLANTS. 187

least, we have evidence for believing that the effects of it are
not fully overcome till 7 or 7.30 a.m., in June or July,

The movements now described are characteristic of a large
series of plants belonging to many natural orders, but the
group OxalidccB of the order GeraniacecB, and the order
Leg2iininos(Z probably include between them about three-
fourths of the entire number.

You are doubtless all aware, however, that leaves or leaf-
parts may exhibit movements which serve a different purpose
in the economy of the plants that bear them. The leaves of
Diojicea and Droscra, as well as tendriliform leaves and leailets,
are examples in point ; and the question naturally presents itself,
— How are these movements effected .-' Before attempting an
answer, we propose to lay before you the results of observa-
tions and experiments which may aid in the solution of
the question.

Naturally, in the vegetable as in the animal world, irrito-
contractility can only be started by stimuli of a mechanical,
chemical, thermal, luminous, or electrical nature. For several
reasons, I can only treat briefly here the effect of the first three
forms of energy, and I will select plants for illustration in the
order that seems most suited for elucidating the subject.
First, we may recapitulate regarding Dioncsa. As my published
researches show,^ a summation of two mechanical stimuli is
ordinarily necessary to start contraction. Further, these must
be applied with a time interval between of at least i second ;
for if two stimuli are given in rapid succession, both are propa-
gated through the protoplasm as one wave, so far, at least, as
motion of contraction is the visible outcome. But though one
stimulus or two rapidly applied stimuli are insufficient to start
contraction of the leaf-halves, we know that active molecular
changes are in process, for the leaf-halves exhibit delicate but
visible wave impulses passing along them from base to apex,
while Burdon Sanderson has demonstrated that active elec-
trical chano;es are oroing on. After a second mechanical
stimulus, or three, if two are rapidly applied, the leaf closes
partially, — /. r., the marginal bristles loosely interlock. If

1 Bot. Cont. Univ. Penn., Vol. I, No. i, 1892.

I 88 BIOLOGICAL LECTURES.

the leaf be not further irritated by some instrument, or by a
caught animal, it slowly relaxes after 12-15 hours; but if
additional stimuli are given, the leaf gradually and firmly
tightens up till its margins become recurved. Prolonged
stimuli, either of a mechanical, chemical, or electrical nature,
start eventually (after 8-10 hours usually) the flow of an acid
secretion from glands that cover both halves of the leaf. It is
clear, therefore, that complete contraction of Dionaa leaf can
only be effected by a summation of stimuli ; and such stimuli
may either be partially or entirely mechanical, chemical, or
electrical. I have further shown, contrary to prevailing
ophiions, that not merely the three hairs of each leaf-half, but
the entire surface is irrito-contractile. Thus, a minute bit of
ice or a drop of hot water placed on any part of the leaf away
from the hairs, also a forceps' pinch, a mechanical shock, and
many chemical agents, excite to closure.

We have already said that the time-interval between two
shocks may be too short to start contraction, but it is equally
true that too great a time interval is attended with no visible
change ; in other words, the piling on of the second stimulus
to the first, if too long delaved, is insufficient to effect closure.
With an interval between of 50-60 seconds, at a temperature
of i4"-2i° C, contraction takes place after a second excitation;
and I stated that if the interval were increased to 90-120
seconds, the strength of the two was almost entirely cancelled.
Through tlic kindness, however, of my friend Mr. Aldrich
Pennock, I have studied ]ilants in his hot-houses at high tem-
peratures (35--40°C.), and find that the effects of previous
stimuli can be retained for 4 minutes at least. l^ut a
second stimulus applied 4 minutes after the first causes no
visible movement of closure ; a third, 4 minutes after the
second is similar; and not till the sixth stimulus does an
almost inappreciable contraction of the halves take place.
Summation of successive stimuli from the eighth to the
twelfth gives added force — sufficient to bring the halves
together. Here, then, is an irritable tissue that steadily
contracts, or prepares for contraction, through a period of
from 30-45 minutes.

IRRITO-COXTRACTILITY IX PLAXTS. 1 89

The conditions thus revealed by DioiicEa were so arresting
as to cause me to inquire whether similar phenomena might
not be demonstrated in other sensitive plants. Botanists
have long been acquainted with certain species which from
their contractile movements were aptly designated " sensitive
plants." These included species of Oxalis, Avcrr/ioa, Jlliniosa,
Cassia, ScJirankia, etc., some of which were considered to be
highly irritable, others less so, and others, again, scarcely
deserving the name. The best account hitherto given of the
action of some of these when affected by mechanical stimuli
is to be found in Pfeffer's PJlanzoipJiysiologic (pp. 224-254),
where Mimosa pndica and Oxalis acctosclla are chiefly dealt
with.

Now I hope not only to show you that various transition
types exist between such roughly classified groups as are
expressed in the descriptions "very sensitive," "slightly sensi-
tive," "scarcely sensitive," but that under giv^en environmental
conditions all exhibit a definite irrito-contractility, characterized
by varying degrees of latent period, of contraction period, of
expansion period, and of summation effects, or, to put it in a
broader sense, that tJie same pJienomcjia of irrito-contractility
are encoiintered i)i the vegetable as in the animal kingdom.
The optimum temperature for most of the plants now to be
mentioned is an average of 26° C, exposure for a short time or
for a prolonged period to low temperatures (8°-i5° C) causing
an extension of the latent period, slower rate of contraction,
and a reduced power of conducting stimuli.

As being both a common plant and a central type in its
physiological behavior, we may now take the field and wayside
weed Oxalis stricta, the yellow sorrel. When plants are grown
in a rather shady situation and exposed to a temperature of
i8°-24° C, the leaves have a rich green color, and the three
leaflets tos-ether form a triradiate rosette. We need not now
refer to structural details further than to say that at the base
of each leaflet is a little cushion composed chiefly of small,
densely aggregated, and vacuolated cells forming a typical
sensitive pulvinus. After a sharp but delicate mechanical
stimulus applied with a pencil or other instrument to a terminal

igO BIOLOGICAL LECTURES.

leaflet, a latent period of 3^^ seconds elapses, followed by a
period of slow but gradually accelerating contraction during
the next 4 seconds. From the seventh to the twentieth
second the motion is rapid, but thereafter slows down gradually
to the thirtieth second, and then becomes increasingly slow till
the forty-fifth second when the contraction ceases. After
15-18 minutes expansion begins, and a very slow rise can be
traced till the leaf regains its expanded state in 45-50 minutes.
The angle through which such a leaf falls is on the average
37°, but varies with the daily periodicity of cell tension, as well
as the temperature and moisture of the air and soil.

It should be stated that young, active — not necessarily
growing — leaves are to be preferred for experiment, but even
the oldest and fully matured leaves are sensitive to a definite
degree, though less so than those younger. Some interesting
statistics will be adduced later in this connection.

When the three leaflets of a leaf are simultaneously excited,
all contract, and the movement shown is as follows: The
terminal leaflet simply drops and folds its halves together
more or less toward their upper faces, ])ut the two side leaflets
move forward and downward so that each describes a segment of
an ellipse. If care be taken, however, to stimulate the terminal
one of the three, it alone will contract, or, at most, the side
leaflets will move to a small extent. This, among other things,
proves that the capability of conducting a stimulus through its
tissues is comparatively feeble in this species.

In no case have I found that a single shock is sufficient to
produce a contraction approaching in amount to the nyctitropic
or the most pronounced parathermotropic states. The angle
fallen through varies from 25° to 48°. A summation of
stimuli, however, produces very different results. If an excited
leaflet be left till the downward movement has ceased, and
a second stimulus be applied, it will fall still further, but
through a less angle than before, and its motion will cease
sooner ; if a third stimulus be then applied there will be an
additional fall less in extent than the second, and greatly
less than the first, the time of motion being correspondingly
shortened. A fourth stimulus will give a slight but appreciable

IRRITO-COXTRACTILITY IN PLANTS. 191

additional contraction. I may best illustrate by a concrete
example selected at random from many others. A leaflet
stimulated fell through 42^ in 45 seconds, a second stimulus
increased the angle to 69° within 38 seconds after rest, a third
stimulus increased it to 81° after 33 seconds, and a fourth to
84° after 27 seconds.

Thus, by four successive stimuli applied during a period of
143 seconds, the leaf described an angular movement of 84°.
But, as I have already stated, the period of ma.ximal movement
after first excitation occurs between the seventh and twentieth
seconds. Taking advantage of this fact, by shortening the time
interval between the stimuli, the same amount of contraction
can be got in a much shorter time. A leaf was irritated and
allowed to contract for 22 seconds, when it had fallen through
38° ; it was again irritated, and allowed to contract for 20
seconds when it had fallen through 61°. Again irritated it
fell through an additional 15°, and after the fourth stimulus
had fallen through 81°.

The above time-intervals remain wonderfully constant in all
active leaves when the environmental conditions remain
constant, but a distinct shortening of the latent period by |
to \ second was noted on a moist, close and warm morning in
early July after a thunder-storm of the previous evening. It
should also be stated that when the plants are continuously
exposed to such high shade temperatures as 35°- 40° C, they
become smaller in size and irregular in action.

We now turn to thermal stimuli, and I may at once state
that ice particles produce a very marked effect on this and all
other sensitive plants. When a piece weighing \-\ grain is
placed at the junction of three leaflets a longer latent period
than for mechanical stimuli ensues, but when once started
contraction steadily proceeds till the ice has melted and the
resulting water has attained a temperature that fails to excite
the protoplasm. If by aid of a pipette or blotting paper the
water is sipped off and a fresh bit of ice is placed, contraction
will go on till the nyctitropic position has been reached. But
as in the case of mechanical stimuli more localized action can
be started, for if ice be placed not on the pulvini but near

192 BIOLOGICAL LECTURES.

the base of the termhial leaflet, the latter will move through
a large angle, while the side leaflets will not at all or only
slightly participate. A bit laid similarly on one of the side
leaflets will make it move independently of the others. By
conducting control experiments with weights equal to the
particles of ice used, it can be proved that cold stimulus and
not weight of the particles is the determining factor.

As with DioiicBa, so here a drop of hot water and the appli-
cation of a heated wire excite to contraction, but instead
of touching analytically on these I should prefer to dwell
on the question of parathermotropism. All my observations
go to show that this is largely due to heat stimulation
of the irrito-contractile cells, acting steadily for some minutes
on these, and that the movements can be hastened or arrested
by a rise or fall of a few degrees of temperature. Moreover,
it seems undoubted that the soil temperature has much to do
with the amount of contraction that each leaf undergoes. It
is not difficult to understand why this should be. Given a soil
on which Oxalis is growing that is covered by a pretty close
herbage, above which the plant rears its tuft of leaves ; the
soil protected from the sun's rays, and retaining its moisture
by reason of the roots that spread through it, will furnish
currents of cool water that will constantly rise into tlie leaves
of the plant. ICvaporation of the surplus moisture thus passed
into the leaves will further lessen the temperature of the
tissues. I may be allowed to quote only one set of statistics
in support. On a close, dull, but rather warm day, with
the temperature at 25° C. in the shade, several plants were
studied that grew under the shade of trees, and amid an
abundant herbage. The ground temperature was 23° C. All
the leaflets were either fully expanded or inclined slightly
upwards from their point of union. Another set grew on a
rather moist bank and were slightly overshadowed by a tree.
The thermometer placed alongside the plants, and like them
exposed to a 'slightly higher tlian the true shade heat, registered
27° C, while the surface of the soil below registered 25.5° C.
The leaflets were flat or faintly inclined downwards. Alongside
a third set, about two yards from the last, the thermometer

IRKrrO-COXTRACTILITY IX PLANTS.

193

registered 29.5° C. when exposed, and 27.5'^ C. on the ground.
Some plants that were exposed to the sun's heat grew on a
rather dry soil with scant herbage, and their leaflets were
deflected through an angle of 52° to 65°. Lastly, on a bit of
hard, dry, whitish soil, the exposed temperature alongside the
plants was 31° C, and on the soil 33° C. The leaflets of
the plants were as strongly deflected as during night-sleep.

The amount of moisture, therefore, that is drawn from a
cool shaded soil or from a hot, dry soil may largely determine,
by its temperature, the stimulus given to the protoplasm and
the position that the leaflets are to assume accordingly. A
cooperating factor in the parathermotropic movement may be
a lack of sufficient moisture, which, in all sensitive plants
studied, causes flaccidity and a want of tone in the tissues.

We shall have occasion in treating of other plants to speak
of the action of such chemicals as ammonia, carbonate of
ammonia, chloroform, ether, alcohol, etc., which all act as
excitants.

Oxalis Dcppci is a large succulent species, commonly grown
now as an edging plant in herbaceous borders. Each leaf is
quadrifid, and examination of the base of the leaflets reveals
large reddish swellings or pulvini. Mechanical stimulus is
followed by a latent period of 3| seconds ; then slow but
accelerating contraction is observed for the next 4 seconds,
when rapid contraction follows for 22-23 seconds, and a very
gradual slowing down goes on till contraction ceases 80-90
seconds after stimulation. The striking and main difference
between this species and Oxalis stricta consists in the con-
traction period being about twice as prolonged. As with
Oxalis stricta, summation series can be obtained that vary
with the. time-intervals between stimuli and the environmental
surroundings.

Observation of the contraction and expansion movements of
this and other sensitive plants shows that each is made up of
numerous minor contraction and expansion waves that cause
the leaf to move by minute jerks, each minor contraction phase
during the great period of contraction being much greater in
amount than the succeeding expansion phase. In all prob-

194

BIOLOGICAL LECTURES.

ability this is due to the gradual passage of sap through the
contractile protoplasmic layer of each cell and the elastic recoil
of it and of the wall as additional liquid is extruded or absorbed.

I now pass to Oxalis dendroides, a plant eminently suited for
investigations like the present, and which has yielded results
as interesting as they were unexpected. For a suppl)' of fine
specimens I am indebted to the kindness of Mr. G. Oliver of
the Washington Botanic Garden. It is an abundant weed in
Brazil and is often confounded with Oxalis scusitiva, that is
native from Persia to China. It is one of a series of nearly
related forms, some of which like the present have a simple
unbranched upright habit, while others incline to a proliferous
mode of growth. Though seldom seen outside botanic gardens,
it grows with the utmost readiness, fruits freely, and scatters its
seeds widely. Four noteworthy points can be readily demon-
strated on this species, though witnessed less perfectly in
others. These are: First, that the latent period varies accord-
ing to the age of the leaf; second, that a gradual propagation
of stimulus from base to apex or vice versa can be shown to
exist; third, that the rate of propagation of the contraction-
stimulus can be exactly measured ; and fourth, that the rate of
contraction and expansion of leaflets is quickest in young and
slowest in old leaves.

If the tip of the blade of a terminal leaflet be stimulated
by a forceps snip, in an atmosphere whose temperature
is 28°- 32° C., it and the companion leaflet will fall
down through an angle of 40°-45° in about 20 seconds.
That irritation of a leaflet should excite to a rapid movement
not merely of one but of neighboring leaflets, suggests the idea
that at hast some of the cells of every leaflet can conduct a
stiviiiliis. This idea is entirely confirmed by many other
experimental results. If the leaflet that has been irritated be
part of an old leaf, the succeeding pairs of leaflets will close in
regular succession from apex to base with a time interval
between each pair of 2\ seconds. By this we mean the time
required for propagation of the shock from one pair of pulvini
to another pair below, and succeeding contraction of the living
protoplasm of the different cells in the path of the stimulus.

IRRirO-COXTRACTILITY IX PLANTS. I 95

But as I shall point out later, it would be a mistake to suppose
that the actual rate of propagation of stimulus from apex to
base of the leaf is so slow as this. If the leaf operated on was
the fifteenth from the growing apex of the stem and the tenth
leaf be now chosen and similarly operated on, the time interval
between contraction of succeeding pairs of leaflets will be
i|-2 seconds; with the seventh leaf from the apex the interval
will be i^-if seconds; and finally a delicate light-green leaf,
such as the second or third from the apex, shows closure of
successive pairs with an interval between of i-i^ seconds.
The latent period shown after general stimulus in such a set
of leaves is equally variable, and under optimum surroundings
is only %—% of a second in young leaves such as the third from
the apex, |-i second in the seventh or eighth, i-ij in the
tenth or eleventh, and 1^-14 in the fifteenth.

As mentioned above, the angle through which the leaflets
fall on excitation, is from 40° -45°. If a general shock
be given to the entire leaf, the leaflets fall simultaneously
through an angle of equal amplitude. But summation action
can now be brought to bear, for on second stimulus the leaflets
will fall through an angle of 24°-28° and in a correspondingly
short time. On third stimulus the leaflets will fall through
I2°-I4° in a still shorter interval, while a fourth stimulus will
cause a fall through 4°- 5° in a shorter interval than the last.
By this time the leaflets will be folded downward back to back
as in night-sleep, or a fifth stimulus effecting a slight additional
movement may be needed to complete the process.

A small bit of ice weighing |- of a grain, if delicately placed
on the tip of a terminal leaflet so as not to touch or directly
stimulate the pulvinus cells, starts motion in the one opposite
within 7 seconds. A steady impulse is then propagated down
the leaf-stalk from pair to pair, the time interval, as in
mechanically stimulated leaves, depending on the age of the
leaf. If, as has repeatedly been noticed, a pair of leaflets is
encountered which is somewhat benumbed from the effect of
previously applied chemical or other agents, these will remain
motionless, or nearly so, but the same interval of time will elapse
before the next pair beneath will contract as would have been

ig6 BIOLOGICAL LECTURES.

needed to start movement in the benumbed ones as well as in
these. On several occasions, a behavior has been noted, both in
Oralis dendroidcs and the common sensitive plant, that is worth
recording, whether the suggested explanation of the behavior
is the correct one or not. A bit of ice laid directly on the
pulvini of two opposite leaflets failed to excite them to motion
and even a pair beneath would only partially contract, while
those still further down would move in normal fashion. I
satisfied myself that the position and weight of the ice particle
offered no obstacle, and learned also that if within 20-30
seconds the ice be removed, the leaflets after an added interval
of 7-15 seconds fall backwards as if recently stimulated. We
believe a probable explanation here to be that during the latent
})eriod of excitation, the ice had so lowered the temperature of
the subjacent cells as to benumb the protoplasm, which only
regained its contractile properties with returning irritability
after removal of the ice.

We may next inquire whether a peripheral or centripetal
stimulus is propagated to the leaf base or to the stem more
rapidly than a centrifugal stimulus initiated at the basal leaflets.
The only plant that has hitherto been experimented on is
the common sensitive plant, but Dutrochet and Bert expressed
different views. Oxalis is much more convenient for the deter-
mination of this question. Each leaf carries 15-24 pairs of
leaflets. A particle of ice placed on the pulvini of the
middle pair, i.e., the tenth if there are 19 pairs, will excite all
the pairs above it within 15-17 seconds, but 21-23 seconds will
elapse before the lowest pair in such a leaf as the tenth from
the apex-bud closes. With the ice in varying positions and
on leaves of different age I have invariably found that a cen-
trifugal is more rapid than a centripetal impulse, and I have
studied many examples. But the records are less satisfactory
as regards simultaneous basal and apical initiation of excitation,
though the balance of experimental proof is in favor of centri-
fugal stimulus.

As with sensitive plants in general, carbonate of ammonia is
a powerful stimulant, and its rapidity is proportioned to the
strength of the solution. When a small drop of a 20 ^

IRRITO-COXTRACriLITV IX PLAXTS. 197

solution is laid on the tip of a terminal leaflet, striking changes
occur. Both of the terminal leaflets close within 7 seconds, and
the succeeding pairs below begin to close at the rate already
given. But before 5 or 6 pairs out of, it may be, 19-22 have
closed, a leaflet near the base may be noticed to twitch, or, as
often happens, leaflets on distinct leaves, that are placed
however, on the same side of the plant as the excited one, may
twitch or even fold together in succession, or move irregularly.
When this was first observed, it seemed likely that the volatile
fumes were the cause, but though they do act as slow excitants,
I was soon convinced that twitches and other movements give
us a hint as to the true rate of propagation of stimuli through
the special conducting tissue, and that the rate of conduc-
tivity is greatly more rapid than that more specialized or
detailed exhibition of it which ends in the falling back of the
leaflets.

Before passing from this species I may observe that the
leaves as a whole seem to be very feebly responsive to shocks,
but they, as well as the flower stalks, perform periodic move-
ments of great regularity. There seems to be an equally
marked periodic movement in the carpels at time of dehiscence,
for they always open in the morning while still green, and
after scattering of the seeds in the forenoon they close again
permanently.

The above species, I believe, will prove to be the most
valuable plant that can be chosen for laboratory purposes, not
alone to the botanist, but as well to the animal physiologist.

Mimosa pudica deserves well its common appellation, "■the
sensitive plant,'' for whether we take account of its short latent
period, rapid contraction, relatively rapid expansion, delicacy of
sensitiveness and rapidity of propagation of an impulse, it
deservedly earns its popular name. It has engaged the
attention of such earnest workers as Lindsay, Dutrochet,
Brlicke, Sachs, Batalin, Bert, Millardet, Pfeffer, and during
the past year or two of Cunningham and Gaston Bonnier.
But much yet remains to be done.

While tracing out and comparing the contraction and expan-
sion periods in plants six weeks old, ten weeks old, and fifteen

198 BIOLOGICAL LECTURES.

weeks old respectively, it was found that expansion in a leaf of
one of the first took place within 4^-5^ minutes, in one of the
second (selecting the fifth or sixth leaf from the cotyledons)
the expansion period was 8Jy-ioV minutes, in one of the third
(selecting the eleventh or twelfth leaf) the expansion period was
13-16 minutes. To fully verify the observations, I compared
plants of known age in several establishments, and found the
results in all cases to agree, the longest period occupied in
expansion — 23 minutes — having been witnessed in a plant
kindly placed at my disposal by Dr. Schively and which was
four or five years old, but had formed fresh shoots for the
season.

The relative rapidity of contraction and expansion shown by
leaves at different levels on the stem is to a large extent retained
during the life of each, though with age the movements
become more sluggish.

As regards rate of propagation of stimuli Dutrochet calculated
it to be 2-3 m. m. per second in the stem, and 8-15 m. m. in
the petiole. Bert in comparing his own results with those of
Dutrochet considered that this estimate was much too high and
gave 2-5 m. m. per second as the rate. But undoubtedly the
estimates of both observers are greatly below the true rate for
certain parts of the leaf, as the following will prove. With
forceps I delicately pinched the tip of a terminal leaflet borne
on a primary leaflet that had 17 pairs of secondary ones. The
end leaflets closed within a second, the next lower pair after 5
seconds, and all had closed within 9| seconds. Now, even if we
grant that the wave of excitation started immediately on applica-
tion of the excitatory stimulus, the entire distance having been
65 m. m. an average rate of 7 m. m. per second would be the
outcome. But many experiments which cannot here be detailed
convinced me not only that excitations can be started over any
part of the leaflets, but that there is a rapid propagation along
the leaf stalk. The starting of cold stimuli by ice clearly
verified this. Whether delicately held in the leaf axil against
the pulvinus, or placed alongside the pulvinus or against its
lower surface that is specially irritable, a bit of ice made the
leaf fall within i^ — ij] seconds. Now the length of each

IRRITO-COXTRACTILITY IX I'LAXTS. 199

primary petiole is 48-55 m. m. If a bit of ice or a drop or two
of ice-water be applied to its distal end, the petiole will fall in
as short a time as already stated. This shows that in the
primary petiole at least, the rate of propagation is not less than
25 m. m. per second, a rate quite equal to that met with in the
contractile tissues of various animals.

Confirmatory evidence is got by the use of various chemicals.
When a minute drop of carbonate of ammonia is delicately
placed on the tip of a young leaflet, one notices \.\\?Ci for the first
4-4^ seconds a change in color or density gradually creeps doivn
the leaf substance, but b}' the time that this has spread over half
the leailet contraction ensues, and thereafter the other leaflets
close at the time rate already given for them. But even by the
time that the second or third pair has contracted, twitching and
partial closure of pairs near the leaf base prove that the stimu-
lus has already travelled down the secondary mid-rib greatly
faster than is indicated by the movement of the leaflets.

Ether is a very serviceable stimulant, though I will not now
enter into disputed questions as to the action of its vapor. A
small drop of 20/0 ether was placed on one of two end
leaflets. The others closed in succession within 8 seconds, the
leaf fell at 14 seconds, within 18 seconds the leaf next above
fell, and within 3 1 seconds the leaf still higher. From the
leaflet tip to the pulvinus of the last mentioned leaf, the distance
was 160 m. m., so that the average rate of propagation necessary
for movement of parts was, at least, 5 m. m. a second. Guided
by Elfving's experiments on various of the lower plants, where
he found that 2 to 5 /o chloroform and 1 5 '/o ether might not
prove permanently injurious to some organisms, experiments
were made with 6 fo ether. When a drop was applied to the
tip of a leaflet very slight movement followed in most instances;
in three cases there was a half-closing of the terminal leaflets,
and in one only did they close, to re-open again in 4I- minutes.
In two of them the second and third pairs of leaflets were
visibly affected and slightly moved upward and forward. No
injurious effect followed the application.

Hot water and heated wire applied to any part of the petiole
or of the leaflets stimulate rapidly.

200 BIOLOGICAL LECTURES.

Sachs, Pfeffer and others have noticed that Mimosa plants
when left unwatered for a few days lose their power of con-
tractility. This is true of all irritable plants that I have
examined, and is capable of ready explanation.

My plan till now has been to lead }'ou up from one or
two well-known plants that exhibit a rather sluggish irrito-
contractility to the true sensitive plant that is unique in its
physiology. I propose now to pass down the scale again and
briefly pass in review some common field weeds, that may, like
Oxalis stricta, be found around us here. Had time permitted
I should have pointed out how the sensitive plant is related
to its near ally. Mimosa lupnliiia, and this again to Miviosa
scnsitiva, both of which I have had the opportunity of studying
from the Washington Botanic Garden, through the kindness of
Mr. Oliver. But from the last an ea.sy transition is established
with our Eastern American weed. Cassia Jiictitans, while C.
cJiamaecrista unites it again with C. i/iaryiandica, that shows
a very feeble though measurable response to mechanical,
chemical, and other stimuli.

Cassia nictitans, the wild sensitive plant, is generally stated
in botanical manuals to be " somewhat sensitive." When a
delicate mechanical shock is given to the leaf, close observation
will show that the leaflets almost instantaneously change
position slightly, but succeeding to this is what I can only at
present, for w^ant of better knowledge, designate as a latent
period of 5^ seconds. Thereafter the leaf stalk falls through
an angle of 15-23° and the leaflets simultaneously move
forward and rotate inward so that their outer etlges become
uppermost as in the sensitive plant. This is accomplished in
85-86 seconds on the average, and by the end of that time the
leaflets are half-closed. But if a second shock be given after
the effects of the first have ceased, the leaf will now fall through
an angle of 8-9° and the leaflets will come together till they
nearly lie face to face as in Mimosa piidica. A third stimulus
may even give slightly ackled results.

An interesting feature in this species is the propagation of
stimuli along thv.' leaf though to a feebler degree than in
Mimosa. As many of you must have ()bser\-ed, a brownish-

IRRITO-COXTRACTILITY IX PLAXfS. 20I

red knob-like gland is situated on the upper surface of the
petiole, about 3 m. ni. below the insertion of the lowest
leaflets. If a minute drop of carbonate of ammonia be
cautiously placed on it, contraction of all the leaflets ensues,
proof this that a continuity of irritable tissue exists between
it and the leaflets that arc inserted above. The structural
relations of this gland with the pulvini of the leaflets is inter-
esting, but cannot be dealt with now. Ice and cold water,
hot water and dry heat stimuli are all irritants to it, as are
chloroform and ether of 15/0 strength and upwards. These
can all act so continuous!}- that they cause the leaf to fall
and the leaflets to rise to the extent that is seen in the
nyctitropic state.

The hog pea-nut {AmpJiicarpaa nionoica), as delicate and
graceful as it is abundant, is convenient for study alike in the
field and laboratory, but we can expeditiously treat it along
with its companions of our woods and thickets, the tick trefoils
or Desmodiums. My attention has been mainly confined to
three species of the genus, viz., Dcsj/iodim/i cajiesccns, Dcsdio-
diuni pcDiiciilatujn, and Dcsuiodiiiin rotundifolinui. They show
a degree of sensitivity in the order that I have given them.
The latent period in ADiphicarpcra and DcsniodiiiDi cancsccns
under ordinary conditions is 3^-34 seconds, but when plants
are grown in a green-house it is shortened to 2\-2\ seconds.
In Desniodiiini pajiicnlatiun the motion is so slow that I ha\'e
failed as yet to determine it exactly.

The period of contraction is considerably longer than in any
yet described and is for Auiphicarpcea i 50- 160 seconds on clear
dry days, and 180-200 on close moist days; for Dcsuiodiiini
cancscens and Dcsi/iodiuin panicnlatiiDi from 120— 140 seconds.
The amplitude of movement in AmpJncaip(Ea is greater, however,
for equal stimuli than in the two last, thus while AvipJiicarpcea
after one stimulus falls in the forenoon of a drv dav throuirh as
much as 65-70°, the others seldom fall through more than
48-50°. But a result got with some plants of AmpJiicarpcBa
on a close, warm, but dull day, is worth recording. Like most
leguminous species it raises its leaflets during the parathermo-
tropic period so as to point the tips at the sun. At 12.30 a

202 BIOLOGICAL LECTURES.

leaf was mechanically stimulated and fell through 58° in 155
seconds, again stimulated it fell through ^j ° in 114 seconds,
again stimulated it fell through 16° in 85 seconds, and on
fourth stimuKis it fell through 9° in 69 seconds. It thus swept
through an arc of \20° in little more than 7 minutes, but as I
have since proved, by shortening the time intervals between
stimuli, the same movement can be got in less than half
the period. The average rate of expansion is from 12-15
minutes in the first three species now under consideration, but
under certain conditions may be only 7-9. Ice and ice-water,
hot water and dry-heat stimuli, alcohol, ether, etc., are all
irritants. 6 ^Jo ether when placed not merely at the base of a
leaflet but even in the middle of it, excites to movement.

I have already referred to the fact that Cassia nictitans,
thou'1-h closely resembling Mimosa pndica in its leaf move-
ments, shows a greatly reduced capacity for propagation of
stimuli from one leaflet or pair of leaflets to another. The
four species now under consideration are still less sensitive in
this respect, for it is possible to make a terminal or lateral
leaflet fall through 38°-67° without participation of the other
two leaflets in the change.

Dcsiiiodiiiiii rotundifolinm is the least sensitive of the genus,
for in its sluggish action and limited amplitude of movement
(amounting to io°-2 5°) it more nearly resembles some of the
Lespedezas. Now AuipJiicarpica, Dcsniodiuui cancscois, and
Dcsniodiitui paiiiciilatuvi are all ujiright growers, and are
therefore exposed in their leaflets to the full effects of night
cold and heat radiation from the tissues, and I believe that
this may largely explain why in evolutionary development they
have become much sui)crIor to Dcsmodinm ivtnndifoliujn, whose
Ion"- sucker-like shoots run along the ground, and give off
leaflets that nestle amongst surrounding herbage.
' Aniphicarpcea, Dcsiiiodiiiin and Lcspcdcza all seem to resemble
the species of Oxalis, and to differ from such as Mimosa
pudica or Cassia nictitans in that the primary stalk of the leaf
does not appear to move, or only moves so slightly that it
has hitherto escaped my observation. But this difference is
secondary and not fundamental, I believe, for in two such

IRRirO-COXTRACTILITY IN PLANTS. 203

closely related species as Mimosa pudica and Mmiosa lupu/uia,
the former has the most rapid motion in its leaf stalk at present
known, the latter seems to be quite stationary.

It may now be asked, How do the seed leaves of sensitive
plants behave ? De Candolle first noticed that the cotyledons
of Mimosa are irritable to touch, while Bert, Pfeffer and
Darwin have confirmed his observations. To the last writer,
also, we owe a list of additional plants with sensitive cotyledons,
for he pointed out that several species of Oxalis, Mimosa,
Trifolium, Cassia and Lotus all show sleep movements, and
further that eight species of Cassia, a species of Smithia,
Mimosa pudica and Mimosa sciisitiva, also Oxalis scnsitiva,
are irritable to contact. I have not only been able to add
several to Darwin's list, but have learned much as to their
extreme sensitiveness. Various of them are not merely irritable
to a single impact, but undergo a definite amount of contraction
that varies, as in the vegetative leaves, with age and environ-
ment. They contract to their fullest extent with a summation
of stimuli, they are highly irritable to heat and cold stimuli,
also to chemical agents that excite contractile tissue.

Those of the sensitive plant are most active during the
period that their activity is of greatest benefit, viz., in the
very young state (seedlings 2-10 days old), since their great
function is to protect the first leaves and growing bud. When
the latter have pushed out above the cotyledonary tips, the pro-
tective function has ceased, and their irritable movements are
greatly lost. This, of course, is owing to the protoplasm
becoming senile, for as their irritability becomes less their
green color is transformed into yellow, and they then shrivel
and soon after drop off. This may have misled Darwin into
supposing that the seed leaves of Mimosa pudica were feebly
sensitive, for he speaks of their rising after irritation by
rubbing, or by tapping for from 30 seconds to 3 minutes,
but I cannot understand why he considered so much effort
necessary, unless it be that he happened to choose rather
old seedlings or experimented at low temperatures.

The irritable movements of the cotyledons as compared with
the foliage leaves of Oxalis dendroides are of great importance.

204

BIOLOGIC A L LECTURES.

Some botanists have attempted to distinguish between plants
that show a heat-sleep with the leaflets directed upwards, and
a night-sleep in which they fall down, as compared with others
that have the same position alike in heat and sleep. But here
is a plant which folds upwards its seed leaves, and downwards
its folia2:e leaves under all kinds of stimuli.

In such a condensed statement as I now give, it would be
impossible to dwell on the anatomical details of the species
already named. Suffice it that they all exhibit beautiful
intercellular protoplasmic unions from cell to cell, as was first
demonstrated for the sensitive plant by Gardiner.

We may now attempt shortly to answer the question, How
are the irrito-contractile movements originated and propagated,
and what are the cell changes which accompany them .^ Until
within the last decade, botanists were compelled to view living
vegetable cells as organic units that were sharply demarcated
from each other by cellulose walls, and whose life phenomena
were due to protoplasmic activity of each cell. J>ut no matter
how complex and intricate the chemical changes that were
effected, they still viewed the protoplasm as a rather watery
substance of no great consistency, tenacity, or structural
complexity. The study of nuclear changes during new cell
formation, of the existence of sensitive movements in different
plants, but especially the demonstration of intercellular proto-
plasmic threads that link together the cell protoplasms into
one harmonized body, compel us to accept the conclusion that
the protoplasm of a vacuolated cell is a very complex and
resistant substance that is extremely responsive to environ-
mental stimuli. Still, with few exceptions — and chief among
these we reckon Gardiner of Cambridge — botanists clung,
and even now cling, to the idea that irrito-contractile move-
ments are simjily, or at least chiefly, due to migration of cell
sap from a living cell or cells into intercellular spaces, owing
to contraction of the cellulose walls. Sachs, Bert, Niigeli and
Schwendener, Pfeffer and DeVries have propounded the view
that contraction of the walls is the important factor.

The untenableness of this position is being gradually recog-
nized, and one can see that a change is coming. The

/AVxVTO-CO.yTA\l C'/7/./ '/']■ /X PL.I.VTS. 205

aofo-recration process which Darwin first observed in the cells
of Droscra tentacle has been carefully studied, and is now
known to be due to expulsion of cell sap through the
protoplasmic sac of certain cells, and that this escapes into
intercellular spaces in at least some instances, {e.g. iMiiiiosa
pndica), is practically demonstrated by Pfeffer's experiments.
The opinion is now being gradually accepted that irritation of
the lower region of the pulvinus causes a sudden exudation of
the cell sap through special pores in the protoplasmic sac, and
that this sap then escapes into the intercellular spaces, or to
the exterior if an incision be made. As the cells of the
upper pulvinus region are now more turgid, fall of the leaf
follows.^

But from Wortmann's studies on PJiycoviyccs and other
plants, it is demonstrated that irritation of any part of a cell
causes the protoplasmic sac to retreat from the wall at the
irritated region, owing to extrusion of a quantity of the sap
that is enclosed within the sac. The process of expansion
then would consist in the gradual resorption of sap into the
contracted cell. Many results point to this conclusion, and
the fact that sensitive plants if starved in their water supply
cease to be irritable, is in its favor.

I previously showed, however, for DioiKFa, — and have now
proved for several other plants, — that summation stimuli can
be given with definite results ; also, that under heat and cold
stimuli, chemical stimuli, and electrical stimuli, plant tissues
behave exactly as do the contractile tissues of animals, while
the rate of propagation of the stimulus is greater than that in
various animal tissues. It may be affirmed, then, of many
plants that their protoplasm is irritated by, and responds to,

1 Since writing the above the author has observed a striking change to occur in
the leaflet pulvini of Jl/imosa fiidica, M. hipidina Schraiikia,aiigustata, and most
beautifully in Mwiosa setisitiva. After stimulation of a leaflet, and toward the
close of the latent period a sudden flush travels centrifugally across the surface
of the pulvinus. Immediately thereafter the leaflet contracts, and the pulvinus
previously of a whitish hue assumes a dull greenish aspect. The author has
grounds for believing that this is due to migration of liquid into the upper region
of the pulvinus, and corresponds to a similar change in a girdle of tissue above
the swollen leaf pulvinus, which is possibly the area referred to by Lindsay nearly
seventy years ago.

206 BIOLOGICAL LECTURES.

mechanical, thermal, luminous, chemical and electrical stimuli,
and that the degree of contraction is ]:)r()i)()rtione(l to the rela-
tive molecular activity of the protoplasm and the strength or
continuity of the stimulus.

Accepting this position, I venture to think that we can
harmonize many movements that appeared superfluous or dis-
tinct from each other. It may be asked, — and indeed has
been asked by Darwin, — Why are plants that are nyctitropic
and parathermotropic often very sensitive to impact, though
apparently deriving no benefit from impact sensitivity .' We
reply that, being sensitive to, or irritated by, light, heat, or
cold, they must of necessity be also sensitive to impact,
even though deriving no benefit therefrom, since contraction-
sensitivity involves response to all forms of energy. Hut let
us be cautious in assuming that no benefit is got from a
certain movement unless such benefit is patent to us. Sachs
says about the sensitive plant, " So far as I am aware, no one
has attempted an explanation of the use of the irritabilit\- of
the leaves of Mimosa ; but I believe that I am able to afford
one ; for I have often had opportunities of obser\-ing that after
a severe hail-storm, when plants of the mcxst various kinds —
and even robust plants, close to my mimosas, before the
window or in the open — have been dashed and broken by
the hail-stones, the mimosas, m spite of their delicate
structure, have come out quite uninjured ; a few minutes after
the rough weather they expanded their leaves again, entirely
unhurt." He might have added that not mereh' from hail,
but froni beating winds and rain, the leaves are the better
protected ; as I have proved for Mimosa, Oxalis, Disi/io-
t/i/nn, Amphicarpcea, etc. As with animal contractile tissues,
then, every irritable plant is to a greater or less degree
irritable to all forms of stimuli. We derive now from this a
likely explanation of nyctitropic and parathermotrojiic move-
ments in plants. It is universally recognized that every
species has an optiinujii as well as a minimum and maximum
temperature relation. To return to Oxalis stricta again, the
optimum during the day is 24°-26° C, but when it is exposed
to a steady heat-stimulus from the sun's ravs of 30°-32° C,

IRRITO-COXTRACTJIJTY IN PLANTS. 207

the protoplasm will almost certainly contract, and the leaflets
will fall. But as evening advances, lowering of the air temper-
ature, radiation from the leaflets, — and still more importantly,
I believe, — the cutting off of the light stimuli along with
reduced temperature of the soil, will all act steadily, and the
leaflets, newly recovered from the parathermotropic state, will
pass soon after into the nyctitropic state.

To distinguish the relation to altered environmental surround-
ings, we speak of night-sleep or nyctitropism, and heat-sleep or
parathermotropism, but fundamentally both are due, we believe,
to one and the same fundamental peculiarity of the protoplasm,
though we cannot stop here to discuss Brucke's assertion of a
difference owing to difference of tension.

A distinct exception to this principle, however, seemed to be
involved in Pfeffer's statement first made in \)\9^ Pflanzcn physi-
ologic, and afterwards extended into a paper published in his
Laboratory Jon nun I. He there asserted that sensitive plants like
Mimosa, Oxalis, Diojlcea, etc. differed fundamentally from such
stem or leaf parts as tendrils and from the hairs of Droscra,
in that the former were sensitive to impact, the latter only to
contact. So many cases of summation of stimuli being needed
to effect movement had been met with by me, that I deter-
mined to ascertain experimentally, whether coiling of a tendril
was not due to a summation of distinct impacts combined, of
course, with circumnutation of the organ. Fortunately, I had
fine plants of those he experimented on growing in my garden
or within easy reach. Pfeffer states that the long, graceful
tendril of Sicyos — the bur cucumber — only coils into a helix
if subjected to contact rubbing. I first selected a primary
tendril of EcJiiiiocystis lobata, that was 5^ inches long and
faintly incurved at its tip, as is usual. Thirty delicate
mechanical shocks were given in series of five at intervals of
10 seconds, and spread over i^- inches of the tip. Soon
after delivery of the second five — i.e., within 25 seconds —
there was a distinct curving of the irritated region. In 6
minutes the tendril had curved sharply through f of a circle,
and in 23 minutes through i^ of a circle. It was first
irritated at 7.21 p.m., and when examined i^ hours later

2o8 BIOLOGICAL LECTURES.

by lamplight, it was still incurved. Next morning it had
again straightened out. I have often, and admiringly,
repeated the experiment on primary and secondary tendrils,
have varied the time-interval between the shocks, and have
varied the number of shocks given, but they have never failed
to respond. Though in a few instances Sicyos tendrils did
not sensibly respond when given 20 to 30 stimuli, the majoritv
behaved like those of Echinocystis.

Thereafter, a large and vigorous plant of Ciicin)iis niaxinux,
was experimented with. Series of 5 stimuli at intervals of one
second were given every \ minute, and in 6 minutes, i.e. after
60 stimuli, two had incur\-ed very distinctly. After 14 minutes
one had curved through |^ of a circle, the other throuo;h '?.
Three of different length and age were then chosen v\'ith
essentially similar outcome. The whole subject of tendril
movement, as viewed in the above light, opens up a wide held
for comparative and critical in\'estigation. Why not mcreh-
elonofation of cells but growth in thickness of tissue should
then follow on the side away from that irritated, is not difficult
to understand, in view of De Vries' and Wortmann's studies of
protoplasmic movement.'

Equally must I take exception to Pfeffer's assertion that
Droscra tentacle does not inflect after contact stimulus.
Darwin stated that inflexion usually took place after three or
more touches, thougli this is denied by Pfeffer. I find that if
the leaves of D. rotiiiidifolia, D. intcnncdia oi" D. dichotoma
are health)' and secreting their \iscous juice freely, two stimuli
with a time-intei-val between of at least 25 seconds, causes
powerful incurx'ing, but onl}' after a latent period of 55-70
seconds. Vcw things in the range of plant life have seemed
so impressive as watching Droscra tentacle after second stim-
ulus. To know that, as tlie seconds pass with apparentl}-
no chantre in the tentacle, active though invisible molecular
movement is progressing which culminates after about 60
seconds in a steady, sweeping incur\'ation of the tentacle for

' McDougall's experiniL-iUs (A'c/. Cuizctti, \'ol. .\\'III, iSc)3) on the- stiimilation
and movements of tLiidrils, sinisjcsl l)ioad lint-s of invcstiijation tliat may yield
good results.

IRRITO-COXTRACTILITY IX PLANTS. 209

65-70 seconds, is a revelation to us of the complexity of proto-
plasmic machinery. Droscra, then, like Dioncca, moves only
after a summation of at least two stimuli.

I cannot sit clown without acknowledging here my great
indebtedness to Air. Oliver, of the Washington Botanic Garden,
for fine specimens of the rarer species experimented with, and
to my friend and former student, Mr. Aldrich Pennock, who
not only threw open his hot-houses for my use, but aided me
practically in many ways.

TENTH LECTURE.

THE MARINE BIOLOGICAL STATIONS OF EUROPE.

P.ASIIFORI) DEAN,

Columbia CuLLiicu, New Yokk.

Among European nations the Marine Laboratory has long
been- recognized as an important aid to the advancement of
biological studies. Groups of universities, centralizing their
marine work in convenient localities, have caused the entire
coast line of Europe to become dotted with stations, well
equipped and well maintained. Societies, individuals and not
infrequently governments contribute to their support.

Marine stations have become distributing centers, important

equally in every grade of biological work or training. A

student, for example, should he visit a small university in the

interior of France, would receive his first lessons aided

by material sent regularly from Roscoff or Banyuls : — he

would examine living sponges, pennatulids, heroes, hydroids,

Loxosoma, Comatula, Amphioxus. Or, at Munich, remote

from the coast, as in the laboratory of Prof. Richard Hertwig,

he is enabled by means of material from Naples to demonstrate

the larval characters of ascidians, or the fertilization processes

of the sea-urchin. During his winter studies the marine

station would thus provide him with the best material —

sometimes preserved and well fixed, sometimes living, to be

prepared according to his wants. In summer it affords him

the best opportunities to see and collect his study types, without

physical discomforts and with the greatest economy of time.

To the investigator the station has become, in the broadest

sense, a university. He may there meet the representative

students of far and wide, fellow-workers perhaps in the very

212 BIOLOGICAL LECTURES.

line of his own research, and must himself unknowingly teach
and learn. He finds out gradually of recent work, of technical
methods which often happen most pertinent to his needs.
He carries on his work quietly and thoroughly ; his works of
reference are at hand ; he has the most necessary comforts in
working, and is untroubled by the rigid hours of demonstrations
or lectures. The station, becomes, in short, a literal emporium,
cosmopolitan, bringing together side by side the best workers
of many universities, tending, moreover, to make their observa-
tions upon the best material sharper by criticism, most fruitful
in results. It has often been remarked how large a proportion
of recently published researches was dependent, directly or
indirectly, upon marine laboratories.

A brief account of the more important of these stations
should not prove lacking in suggestions ; especially as in
America the work of the marine laboratory is often imperfectly
understood. Its aims have been associated popularly with
those of practical fish culture ; and even among the trustees
of universities a disposition has often been to regard an annual
subscription for a work place in a summer school as among the
little needed expenditures of a biological department. So little
important has a marine station seemed that the greatest
difficulties have ever been encountered to ensure the support
of an American table at Naples, — although it was well known
how large a number of our investigators were each }ear
indebted to foreign courtesy for the privileges of this station.

General interest in the advancement of pure science has in
Europe become a prominent feature of the jxast decade, and
there can be no doubt of the importance that has come to be
attached to studies bearing upon the problems of life, evolution,
heredity. Nor, at the same time, does it appear that matters
relating to practical fisheries have in any way lost their interest
or support. To these, on the contrary, the rise of pure biology
has often given important aids. What has aj^jpeared abstract
theory to-day has often been converted into practice to-morrow.
And even so ardent a partisan of pure biology as Prof,
de Lacaze-Duthiers does not hesitate to urge this, as sufficiently
important in general argument, to vindicate the governmental

J/AAVA'E BIOLOGICAL STATIOXS OF EUROPE. 21 3

support of the laboratories of Roscoff and Banyuls. " Facts
have been found at every step of science which were valueless
at their discovery, but which, little by little, fell into line and
led to applications of the highest importance — how the obser-
vation of the tarnishing of silver or the twitching leg of the
frog was the origin of photography or telegraphy — how
the purely abstract problem of spontaneous generation gave
rise to the antiseptics of surgery."

As a preface to the present discussion the general number
and location of the European marine stations might conven-
iently be indicated in the accompanving outline map.

I.

Fk.AN'CE.

The extended sea-coast has ever been of the greatest aid to
the French student — along the entire northern coast the
channel is not unlike our Bay of Fundy in the way it sweeps
the waters out at the lunar tides. The rocks on the coast of
Britany, massive bowlders, swept and rounded by the rushing

2 14 BIOLOGICAL LECTURES.

waters, will at these times become exposed to a depth as great
as forty feet. This is the harvest-time of the collector; he is
enabled to secure the animals of the deep with his own hanti,
to take them carefully from the rocky crevices where they would
ever have avoided the collecting tlredge. From earliest times
this region has not unreasonably been the field of the naturalist.
It was here that Cuvier, during the Reign of Terror, made
his studies on marine invertebrates which were to precede
his Rtgnc Animal. The extreme westernmost promontories of
Brittany have, for the last half-century, *been the summer
homes of de Quatrefages, Coste, Audouin, Milne-Edwards and
de Lacaze-Duthiers. Coste created a laboratory at Concarneau,
but this has come to be devoted to practical fish culture, and
is, at the present day, of little scientific interest. It is owing
to the exertions of Professor de Lacaze-Duthiers of the
Sorbonne, that the two governmental stations of biology ha\-e
since been founded. The first was established at Roscoff, in
one of the most attractive and favorable collecting regions in
Brittany, and has continued to grow in importance for the last
twenty years. As this station, however, could be serviceable
during summer onl}', it gave rise to a smaller dependency of
the Sorbonne in the southernmost part of France, on the
Mediterranean, at Ban>uls, which had the additional advantage
of a Mediterranean fauna.

To these French stations should be added that of Professor
Giard, at W'imereux near Boulogne, in the ricli collecting
funnel of the Straits of Dover; that of i^rofessor Sabatier at
Cette, not far from Banyuls, a dependency of the University of
Montpelier; that of Marseilles, and the Russian station at \'ille-
Franche, near the Italian frontier. An interesting station in
addition, is that at Arcachon near Bordeaux, founded by a local
scientific society. Smaller stations are not wanting, as at the
Sables d'Olonne.

At Roscoff the laboratory building looks directly out upon
the channel. In its main room on the ground floor, work
places are partitioned off for a dozen investigators; this on the
one hand leads to a large glass-walled aquarium room, seen in
the accompanying figure, while on the other opens directly to

.]fAR/A'I-: BIOLOGICAL ST.JT/OA'.W OF L.T/CO/Wi.

15

adjoininji; buildings which include lodging quarters, a well-
furnished library and a lab()r;itory for elementary students.
Surrounding the building" is an attractive garden which gives
one anything but a just idea of the barrenness of the soil of
Brittany. From the sea wall of the laboratory one looks out
over the rocks that are becoming exposed by tlie receding tide.
A strong enclosure of masonry serves as a viviej^ to be used for

Marine Station at Roscoff, Brittany.
(From photograph, July, 1S91.)

experiments as well as to retain water for supplying the
laboratory. The students are, in the main, those of the Sor-
bonne, and under the direction of Dr. Prouho, their viaitrc dc
conferences. They are given every opportunity to take part in
the collecting excursions, frequently made in the laboratory's
small sailing vessels, among the rocky islands of the neighbor-
ing coast. Strangers, too, are not infrequent, and ' are
generously granted every privilege of the French student.

2l6

BIOLOGICAL LECTURES.

Liberality is one of the characteristic features of Roscoff. The
stranger who writes to Professor de Lacaze-Duthiers is accorded
a work place which entitles him gratuitously to every privilege
of the laboratory — his microsco]:)e, his reagents, even his
lodging-room should a place be vacant. It seems, in fact, to
be a point of pride with Professor Lacaze that the stranger
shall be welcomed to Roscoff, and upon entering the laboratory

ROSCOFP'. INIKRIoK ok AilUARH'M RooM.

(July, iS<;i.)

for the first time, feel entirely at home. He finds his table in
order, his microscope awaiting him, and the material for which
he had written displayed in stately array in the glass jars and
dishes of his work place. So, too, he may have been assigned
one of the large aquaria in the glass acpiarium room — massive
stone-base stands, aerated by a constant jet of sea water.

He finds a surprising wealth of material at Roscoff, and his
wants are promptly supplied.

MAR/.YE BIOLOGICAL STATIONS OF EUROPE

17

At Banyuls, the sccontl station of tlic Sorbonnc, the build-
ings are less imposing than those of Roscoff. It is a plain,
three-story building facing the north, at the edge of the i:)roni-
ontory which shelters the harbor at Banyuls. The vivicr is in
front of the station, behind is a reservoir cut in the solid rock
— receiving the waters of the Mediterranean and distributing
it throughout the building. On the first floor is a large
aquarium room lighted by electricity, well-supplied with tanks

^J

"fft I M ^ • i

French Marine Station at Eanyuls-Sur-Mer.
(October, 1891.)

and decorated not a little with statuary donated by the
Administration of the Beaux-Arts. The bust of Arago
occupies an important place, as the laboratory has been named
in his honor. A suit of a diver sugests the different tactics in
collecting made necessary by the slightly falling tides of the
Mediterranean. The wealth of living forms in the aquaria

2lS

BI O LOGIC. I L L I-:C'l Y RES.

shows at once by variety of bright colors the richness of
southern fauna. Sea lilies are in profusion, and are gathered
at the very steps of the laboratory. The work-rooms of the
students are on the second fioor, equipped in a manner similar
to those of Roscoff. The director of this station is Dr. Frederic
Guitel. It is usual during" the holidays at fall or winter, for the
entire classes of the Sorbonne to spend several days in
collecting-trips in the neighborhood. The region, with its

Banyuls-.Sur-Mer. Inierior oi- .\(juarhm Room.
(October, 1891.)

little port, is famous for its fisheries, and one in especial is that
of the Angler, Lof^hiiis. a fish that would not be regarded as
especiall)' dainty on our side of the Atlantic.

The station on the .Straits of Dover, at Wimereux, has
earned a luiropcan reputation in the work of I'rofessor Giard.
Tt is but a small frame building, scarcely large enough to
include the advanced students selected from the Sorbonne.

MAN /Ml biological STA IIOA'S OF EUROTE. 219

The laboratory is, in a way, a rival of Roscoff, and it is
noteworthy that its workers seem to make a point of studying
the laboratory methods of the German universities.

The marine laboratory of Arcachon, cmic of the oldest of
France, was built in 1867 by the local scientific society, and
was carried on independently until the time of the losses of the
Franco-Prussian War. Its management was then fused with
that of the faculty of medicine of Bordeaux, with whose assist-
ance, aided by that of a small .subsidy from the government,
the work of the institution is carried on. Arcachon, near
Bordeau.x, is in itself a mo.st interesting locality. It has become
a summering place, noted for its pine lands and the broad, sandy
plage, picturesque in summer with swarms of quaintly-dressed
children, the local head-dress of the peasant mingling with the
latest toilets from Paris. Here and there is to be seen that
accompaniment of every p-rench watering place, the goat boy
in smock and berret, fluting to his dozen charges who walk
in a stately way before him. The Bay of Arcachon is a
small, tranquil, inland sea, long known for its rich fauna. In
large part it is laid out in oyster parks, which constitute to no
small degree the .source of wealth of the- entire region. Shal-
low and warm waters seem to give the marine life the best
conditions for growth and development. The laboratory is
placed just at the margin of the water. It includes a dozen or
more work places for investigators, well supplied with aquaria,
a library on the second floor, a smaU museum containing col-
lections of local fauna, including numerous relics of Cetaceans
that have found their way into this inland sea. A small
aquarium room, opened to the public, is well provided with
local forms of fishes, and like that of Naples, is eagerly visited.
Those who are entitled freely to the use of the work places are
instructors in French colleges, members of the Society, and all
the advanced students from the colleges of the State. For
other students, work place is given upon the payment of a fee
whose amount is regulated each year by the trustees. As at
Roscoff, material is plentifully supplied.

The Zoological Station at Cette is a direct annex of the
University of Montpelier, and it will be gladly learned that

2 20 BIOLOGICAL LECTURES.

its temporary building is being replaced by one of stone,
which will enable Professor Sabatier to add in no little way to
the working facilities of his students. The region, in every
essential regard, is similar to that of Banyuls.

The station at Marseilles is devoted in great part to ques-
tions relating to the Mediterranean fisheries, and owes, in a
measure, its financial support to this practical work.

The station at Ville-Franche is essentially Russian. An
account of this with figures has recently been published
(Russian text) in Cracow. The station itself is well known
through the work of Dr. Bolles Lee, and it is here that
Professor Carl Vo2:t has been a constant visitor.

'&'

II. — England.

The laboratory at Pl)niouth is quite a recent one, its
foundation due in the first instance to the efforts of Professor
Rav Lankester. Its building, first opened in 1888, is. in many
regards, hardly second to Najiles. This locality was found
well-suited for the needs of an extensive marine station.
Opposite Brittany it takes advantage of the same extremes of
tide, and the rockv Devonshire coast affords one of the richest
collecting grounds. The situation of the building is a remark-
able one; it stands at one end (^f the ancient Hoe of Plymouth
— a broad, k-x-el jiark whose high situation looks far c^ff over
the channel. At the rear (^f the building are the old fortifica-
tions of the town. As shown in the adjoining figure, tlie
building is, at the ends, three-storied. On the ground fioor is
the general aquarium room, well-suiijilied wilh local marine
fauna, and open to the jiublic. The laboratory proper is u]ion
the second fioor, di\-ided into eleven compartments, the work
places of the students. A series of small tanks i)asses tlown
the middle of the room. In the western end are the library,
the museum, the chemical, photogra]-)hic. ami physiological
rooms : in the eastern are tlie living c|uartei"s of the director.
The water supi)ly of the laboratory is contained in two small
reservoirs directly between tlie buililing and the fortifications,
and is carried throughout the building by gas engines. Tidal

MARLVE BIOLOGICAL STATIOXS OF KUROPE.

2 2 1

aquaria are in constant use for developmental studies. The
collecting" for the laboratory is aided by a 38-foot steam launch.

The present support of the station is not, unfortunatel}', as
gfenerous a one as might be desired. The station is obliged to
consider in the work of its director matters relating to public
fisheries, and is only enabled by this means to secure govern-
mental assistance. The building itself was constructed by the
efforts of the Marine Biological Association of the United

British Marine Laboratory, Plymouth.

(August, 1S92.)

Kingdom, under whose auspices the present work is being
carried on. The investigators' tables are occupied by any
founder of the Association, or his representative, by the natu-
ralist or institutions who have rented them. The subscription
price per year of an investigator's place is ^^40, but tables may
be leased for as short a time as a month. The laboratory pro-

222 BIOLOGICAL LECTURES.

vides material for investigation and the ordinary apparatus of
tiie marine laboratory, excluding microscopes and accessories.
The use of the larger tanks of the main aquarium is also per-
mitted to the working student. The work of the laboratory
includes investigation of fishery matters, the preservation of
animals to supply the classes of zoology in the universities
and the formation of type collections of the British marine
fauna. The naturalist of this station has been, for a number
of years, Mr. J. T. Cunningham, whose experiments upon the
hatching of the Sole have here been carried on.

Other British marine stations are those of Liverpool and St.
Andrews, northeast, and Dunbar, southeast, of Edinburgh.
The work of these stations is only in part purely biological ;
the practical matters of fisheries must be considered to insure
financial support. In addition to these is to be mentioned a
station, recently equipped, on the Isle of Man. Still another,
most favorable in its locality, has been established in the
Channel Isands.

At St. Andrews, Professor Macintosh has studied the ques-
tions relating to the hatching and development of the North
Sea fishes. Its situation upon the promontory leading into
the Firth of Forth seems to have been especially favorable
for the study of the North Sea fauna — the locality, moreover,
is far enoutrh northward to include a numer of boreal forms.
The importance of St. Andrews is at length better recognized,
and a substantial grant from the government will enable a
large and permanent marine station to be here constructed.
The facilities for work have, up to the present time, been
somewhat primitive, — a simple wooden building, single-storied,
has been partitioned off into small rooms, a general laboratory,
with work places for half a dozen investigators, a director's
room, aquarium, and a small out-lying engine house witli
storage tanks. To the laboratory belongs a small sail-boat to
assist in the work of collecting.

.VAR/XE BIOLOGICAL SlAriOXS ()/■' IJKOI'i:. 22X

III. — Holland.

Holland, in the summer of i S90. opened its zoological
station in the Helder, a locality which, for this purpose, had
long been looked upon with the greatest favor. There is here
an old town at the mouth of the Zuyder Zee, the naval strong-
hold of Holland, a station favorable for biological work on
account of the rapid-running current renewing the waters of

ffV-^'" " iiidii'ift

Dutch Zoological Station at thk. llF.i.nER.
(Fig. from Tijdschr. d. Ned. Dierk. Veieen. 5 Juli, 1890.)

the Zee. The station was founded by the support of the
Zoological Society of the Netherlands, whose valuable work
by the contributions of Hubrecht, Hoek, and Horst, has long
been known in connection with the development of the oyster
industry of Holland. The work of the Society had formerly
been carried on by means of a portable zoological station

224

BIOLOGICAL LECTURES.

which the investigators caused to be transplanted to different
points along the East Schelde, favorable on account of their
nearness to the supplies of spawning oysters. The present
station at the Helder is situated directly adjoining the great
Dyke, a small stone buiding, two stories, surrounded by a
small park, as seen in the adjacent figure. In itself the labo-
ratory is a model one, — the rooms are carefully finished, and
every arrangement has been made to secure working conven-
iences. A large vestibule leads directly into two laboratory
rooms, and, by a hallway, communicates with the large, well-
lighted library and the rooms of the director. The aquarium
room has, for convenience, been placed in a small adjacent
building. The director of this station is Professor Hoek, and
the President of the Society is Professor Hubrecht.

IV. — Naples.

The Stazione Zoologica at Naples during the past twenty
years has earned its reputation as the center of marine bio-
loeical work. Its success has been aided h\ the richness of
the fauna of the Gulf, but is due in no small degree to
careful and energetic administration. The director of the
station. Professor Dohrn, deserves no little gratitude from
every worker in science for his untiring efforts in securing its
foundation and systematic management. Partly by liis ])rivate
generosity and partly by the financial supjxjrt he obtained, the
ori"-inal or eastern buildintr was constructed. Its annual main-
tenance was next assured by the aid he obtained throughout
(mainly) Germany and Austria. By the leasing of work tables
to be used by the representatives of universities, a sufficient
income was maintained to carry on the work ot tlie station
most efficiently. A gift by the German government of
a small steam launcli added not a little to the collecting
facilities.

Attractiveness is one of the striking features of the Naples
station. It has n(^thing of the dusty, uncomfortable, gloomy
air of the average universitv laboratory. Its situation is one
of the brightest ; it has the gulf directly in front, about it the

MARINE BIOLOGICAL STATIONS OF EUROPE. 225

city gardens, rich in palm trees and holm oaks. The building
itself rises out of beds of century plant and cactus like a white
palace ; the fashionable drive-way alone separates it from the
water's edge. In full view is the Island of Capri, to the east-
ward is Vesuvius, — a bright and restful picture to one who
leaves his work for a five minutes' stroll on the long, covered
balcony which looks out over the sea.

The Stazione Zoologica at Naples.
(May, 1892.)

The student, in fact, knows the Naples station before he
visits it, although he can hardly anticipate the busy and
profitable stay that there awaits him. He has received the
circular from the Secretary of the laboratory while perhaps in
Germany, when he secured the privilege of a table. He is
told of the best method of reaching Naples, the precautions he
must take to secure the safe arrival of his boxes and instru-

2 26 BIOLOGICAL LECTURES.

ments. He is told to send directions as to the material he
desires for study ; he is notified of the supplies which will he
allowed him, and of the matters of hotels, lodging, and bank-
ing, necessary even to a biologist. At the first sight of the
building he is impressed most favorably, and it is not long
before he comes to look upon his work-place as his particular
home, open to him day, night, and holiday. He likes the gen-
eral air of quietness — in no little way significant of system in
every branch of the station's organization ; his neighbors are
friendly, and he feels that even the attendants are willing,
often anxicms to give him help.

At present the station at Naples consists of two buildings ;
the first, shown in the foreground in the accompanying figure,
is the older, the main building ; behind it is the newly built
physiological laboratory. In the basement of the main
building is the aquarium, well managed, open to the public, and
eagerly visited. Passing into the aquarium room from the
main entrance, one descends into a long, dark, concreted room,
lighted only through wall-tanks brilliant on every side with the
varied forms of life. There are in all about two dozen large
aquaria embedded in the walls of the sides and of the main
partition of the room. The water is clear and V:)lue. The
background in each aquaria, built of rock work, catches the
li'-'ht from above and throws in clear relief the living inmates.
The first tank will perhaps be full of star fish and sea urchins,
bright in color, often clustered on the glass eacli with a dim
halo of pale, thread-like feet. In the background may be a
living clump of crinoids, flowering out like a garden of briglit-
colored lilies. In a neighboring tank, rich with dark-colored
seaweeds, will be a group of flying gurnards, reddish and
brilliantly spotted, feeling cautiously along the bottom with the
finger-like rays of their wing-shaped fins. Here, too, may be
squids, delicate and fish-like, swimming timidly u]) and down ;
perhaps a series of huge triton snails below amid clustered
eo-trs of cuttle fish. In another tank would be a bank of sea
anemones with all the large and brilliant forms common to
southern waters. Here maybe corals in the background and a
forest of sea fans in orange, red and yellow, with a precious

MARIXE BIOLOGICAL STATIOXS OF KLROPE. 227

fringe of pink coral, flowering out in yellow star-like polyps.
There may again be a host of ascidians, delicate, transparent,
solitary forms, the lanky Ciona, the brilliantly crimson Cynthia
and huge masses of varied, compound forms. Swimming in
the water may be chains of Salpa and occasionally a number
of Amphioxus, the latter, as they from time to time emerge
from the sandy bottom, flurry about as if with sudden fright,
quickly to disappear. Variety is one of the striking characters
of neighboring tanks. In one, brilliant forms will outvie the
colors of their neighbors ; in another, the least obtrusive
mimicry will be exemplified. The stranger has often to examine
carefully before, in the seemingly empty tank, he can determine
on every side the living forms whose color characters screen
them effectively. Thus he will see sand-colored rays and
flounders, the upturned eyes of the curious star-gazer almost
buried in the sand, a series of mottled crustaceans wedged in
a rocky background, an occasional crab wandering cautiously
about, carrying a protective garden of seaweeds on his broad
back ; odd sea horses posing motionless mimicing the rough
stems of the seaweeds. In the larger tank sea turtles float
sluggishly about ; and coiled amid broken earthern jars are
the sharp-jawed murr^'s, suggestive of Roman dinners and of
the cultural experiments of Pollio. Aeration in the aquaria
is secured effectively by streams of air which are forced in at
the water surface and subdivide into bright clouds of minute
silvery bubbles. The tanks are cared for from the rear passage-
ways ; attendants are never seen by visitors, and constant
attention has given the aquaria a well earned reputation. Well
illustrated catalogues in French, German, English and Italian
enable the stranger to better appreciate the aquarium.

To the remainder of the building strangers are not admitted.
A marble stairway leads from the door of the aquarium to a
loggia which opens into the territory of the students. A long
pathway of grating extends across the open center of the
building,— whose skylight top admits the light to the aquarium
below. On the one hand is the main laboratory room, on
the other the library and separate rooms intended for more
fortunate investigators. One enters the main laboratory, passes

228

BIOLOGICAL LECTURES.

a wall of student aquaria and sees a series of alcoves formed
i)V low partitions, each work-place with its occupant, his
apparatus, his books, his jars — altogether often a picture not
of the utmost tidiness. A small iron staircase leads to a
gallery which gives a second tier of work places and doubles

The T,ii;karv of thk Xapt.f.s Station.
(June, 1892.)

the working capacity of the room. Here, side by side, will be
representative workers from universities of every country of
Kur()i)c.

The library room adds not a little to the attractiveness of
the Naples station. It is a Ion-; room, and, as shown in the

J/.IAVA'K lUOI.OGICAI. STAT/OXS OF I'lrROPE. 229

figure, is adorned with frescoes in a truly Italian style. It
looks out into a long loggia with view of the sea and Capri,
where the student is wont to retire in after luncheon hour
with easy-chair and book. The working library is of the
best and is sure to contain the results of the most recent
researches. The desk shown in the figure is one on which
each day is to be found the latest publications. In the
upper pigeon-holes are the cards prepared for each investigator
on his advent to Naples ; with these he replaces the volumes
which he has taken to his work place. Every division of the
laboratory is carefully organized and is under the charge of a
special assistant. Prof. Hugo Eisig, the assistant director, has
taken the welfare of each student under his personal charge,
and it is not until the end of his stay that the visitor recognizes
how much has been done for him.

There is no more interesting department of the station
than that of receiving and distributing the material. Its
headquarters is in the basement of the physiological laboratory,
and here Cav. Lo Bianco is to be found busy with his aids
and attendants amid a confusion of pans, dishes and tables,
encountering the Neapolitan fishermen who have learned to
bring all of their rarities to the station. The specimens are
quickly assorted by the attendants ; such as may not be needed
for the immediate use of the investigators are retained and
prepared for shipment to the universities throughout Europe.
The methods of killing and preserving marine forms have been
made a most careful study by Lo Bianco, and his preparations
have gained him a world-wide reputation. Delicate jelly-fish
are to be preserved distended, and the frail forms of almost
every group have been successfully fixed. The methods of the
Naples station were kept secret only until it was possible to
verify and improve them, as it was not deemed desirable to
have them given out in a scattered way by a number of
investigators.

Lo Bianco has made the best use of the rich material passing
daily through his department, and has been enabled to prepare
the most valuable records as to spawning seasons and as to
larval conditions. He knows the exact station of the rarest

230 BIOLOGICAL LECTURES.

species, and it seems to the stranger a difficult matter to ask
for a form which cannot be directly or indirectly procured. It
adds no little to the time saving of the student to lind each
morning at his work place the fresh material which he has
ordered the day before, and there is usually an embarrassment
rather than a dearth of riches.

A collecting trip often occurs as a pleasant change from the
indoor work of the investigator. An excursion to Capri may
be planned ; the launch will be brought to the quay near the
station and the party will embark. The collecting tubs are
soon scattered over the deck and filled with the dredge
contents. Some of the passengers are quickly at work sorting
out their material, one seizing brachiopods, another compound
ascidians, another sponges. Others will wait until the surface
nets have been brought in and the contents turned into jars.
All will depend upon Lo Bianco as an appellate judge in
matters of identification.

Many Americans have availed themselves of the privileges
of Naples and the former lack of support of an American
table needs little comment. Of those who have hitherto
visited Naples more than three-quarters have been indebted
to the courtesies of German universities. At jM-esent of the
two American tables one is supported b)' the Smithsonian
Institution, the other by gift of Mr. Agassiz.

The entire Italian coast is so rich in its fauna that it is due,
perhaps only to the greatness of Naples, that so few stations
have been founded. Messina has its interesting laboratory well
known in the work of its director. Professor Kleinenberg. The
Adriatic, especially favorable for collecting, has at Istria a
small station on the Dalmatian coast, and at Trieste is the
Austrian station.

V. — Trieste.

Trieste possesses one of ^the oldest and most honored of
Marine Observatories, although its station is but small in
comparison with that of Naples, Plymouth or Roscoff. Its
work has in no small way been limited by scanty income; it
has offered the investigator fewer advantages and has there-

MAR/XK BIOLOGICAL STATIOXS OF FJl^OI'Il.

231

fore become outrivalled. Durini;" a greater part of the }'ear it
is but little more than the supply station of the University of
Vienna, providing fresh material for the students of Professor
Claus. Its percentage of foreign investigators appears small ;
its visitors are usually from Vienna and of its university.

Trieste is in itself a small but busy city, growing in active
commerce. Its quays are massive and bristle with odd-shaped
shipping of the Eastern Mediterranean. Its deep and basin-

The Statu )\ at Trieste.

like harbor affords a collecting ground as rich as the Gulf of
Naples.

The station has been located at a quiet corner of the harbor,
just beyond the edge of the lighthouse. Its building is some-
what chalet-like, situated on a small, well-wooded knoll, as seen
in the adjacent figure. About it are trellis-covered grounds
enclosed by high walls, and separated from the harbor only by
the main roadwav of the quays. One enters the laboratory

2^2 BIOLOGICAL LECTURES.

garden through a large gateway and passes into a court-yard
whose outhouses disclose the pails and nets of the marine
laboratory. Perhaps an attendant will here be sorting out the
i:)lunder which a bronze-legged fisherman has just brought in.

A library and the rooms of the director, Dr. Graeffe, are
close by the entrance of the building. In the basement is the
aquarium room, — somewhat dark and cellar-like ; its tanks
small and shallow, their inmates representing especially stages
of Adriatic hydroids and anthozoans. On the second story are
the investigators' rooms, — large, well-lighted, looking out over
garden and sea. Near by is a museum of local fauna, rich in
crustaceans and in the larval stages of Adriatic fishes.

VI-IX. — Germany, Norway, Sweden, Russia.

The German universities have contributed to such a degree
to the building up of the station at Naples that they have
hitherto been little able to avail themselves of the more con-
venient but less favorable region of German coasts. The
collect insf resources of the North Sea and of the Baltic have
perhaps been not sufficiently rich to warrant the establish-
ment of a central station. On the side of the Baltic, the
University of Kiel, directly on the coast, may itself be regarded
as a marine station. At present the interest in founding local
marine laboratories has, however, become stronger. The newly
acquired Heligoland has become the seat of a well-equipped
Governmental station. The island has been long known as
most favorable in collecting regions, and its position in the
midst of the North Sea fisheries gives it especial importance.

Its present building is three-storied, of stone, situated near
the water on tlie Jutland side of the island. Work places are
provided for four investigators. Its director is Dr. V. Heinke ;
his assistants, Drs. Hartlaub, IChrenbaum, and Kuckuck. The
Istrian laboratory at Rovigno, a favorable collecting point on
the Adriatic, is to be included among the German stations It
was destined bv Dr. Ilermes, its founder, as the supply depot
of the Berlin ac|uaiium. 0\ its work ])]aces, two have been
rented by the Prussian government, and a third is to be
obtained by application to Dr. Hermes.

MARIXE BIOLOGICAL STATIOXS OF ECROl'i:. 233

Norway like Germany is strengthening its interest in local
marine laboratories. Two permanent stations have quite
recently been established, one at Bergen, — the other at
Drobak, a dozen miles south of Christiana. The former is
the larger, a dependency of the Museum of Bergen. It is
under the charge of Dr. Brunchorst, — to whom its founda-
tion is due, — and Drs. Appellof and Hansen. Its two-
storied villa-like building provides work places for eight
investigators : a well maintained aquarium on the first floor
is open to the public. The second and smaller station is
devoted almost exclusively to research in morphology. It
is a dependency of the University of Christiana and is under
the directorship of one of its professors. Dr. Johan Hjort.
With the richest collecting resources these new stations may
naturally be expected to yield most important results.

The Swedish station has long been associated with the work
of its late director, Professor Loven. It is situated on the west
coast near the city of Gothenburg. Its three original buildings,
a laboratory and two dwelling-houses, were constructed about
fifteen years ago by a gift of Dr. Regnell of Stockholm. The
laboratory is a wooden building well furnished with aquaria,
provided in its second story with separate work places for
investigators. It is at present maintained by governmental
subsidy ; its recently appointed director is Dr. Hjalmar Theel
of the State Museum at Stockholm. Its students are mainly
from the University of Upsala ; up to the present time
foreigners have not been admitted.

Russians have ever been most enthusiatic in marine research,
and their investigators are to be found in nearly every marine
station of Europe. The French laboratory on the Mediterranean
at Ville-Franche is essentially supported by Russians. At
Naples they are often next in numbers to the Germans and
Austrians. The learned societies of Moscow and St. Petersburg
have contributed in no little way to marine research. The
station at Sebastopol, on the Black Sea, has become permanent,
possessing an assured income. That near the Convent Solovet-
sky, on the White Sea, though small, is of marked importance.
It is already in its thirteenth year. Professor Wagner, of

2 34 BIOLOGICAL LECTURES.

St. Petersburg, has been its must earnest promoter as well as
constant visitor. He in fact caused the Superior of the Convent
to become interested in its work and secured a permanent
building by the Convent's grant ; he was then enabled by an
appropriation from the government to provide an equipment.
Its annual maintenance is due to the Society of Naturalists of
"St. Petersburg. The matter of the appointment of a perma-
nent director for the summer months is now being agitated by
him. The station Solovetskaia is said to possess the richest
collecting region of the Russian coasts. It is certainly the
only laboratory which has at its command a truly Arctic
fauna.

APPENDIX,

THE WORK AND THE AIMS OF THE MARINE
BIOLOGICAL LABORATORY.

C. O. WHITMAN.

The Marine Biological laboratory of Wood's Holl combines the
functions of a research laboratory with those of a school. While it
differs thus from the marine laboratories of Europe, it may also
be said to take a somewhat exceptional position among American
sea-side laboratories, both in its organization and its scope of work.
It supplements the work of the biological departments of the schools
and colleges, and at the same time serves as a scientific centre for
investigation. It provides not only for general courses of study
in zoology and botany, but also — what is of quite exceptional
importance — for technical training preparatory to investigation and
special instruction and guidance for beginners in investigation. It is
this advanced instruction that makes the school tributary to the side
of original investigation, in which the work and the aims of the
laboratory centre. Research is the dominating function of the
laboratory ; instruction is merely a means to this end.

Although the laboratory is wholly free from government control, it
is truly national in organization and aims. It is governed by a board
of trustees, on which the leading colleges and universities of the
country are represented. Its officers of instruction and investigation
have been drawn from no less than fifteen educational institutions,
and its membership has extended to one hundred and thirty-one
colleges, universities, seminaries, academies, schools and laboratories.

From the beginning of this undertaking it has been clearly seen
that the realization of its aims depended largely on securing the general
support of the colleges, and the active cooperation of all who were
interested in the foundation of a national marine station. To secure
these ends the clearly defined aims of the laboratory were made

236 A mix nix.

known as widely as possible, and the invitation for united action was
extended to institutions and investigators throughout the countrv.
Tiie result is that during the last session the following eighteen
institutions subscribed for rooms and tables :

Bowdoin College, Missouri Botanical (harden,

Brown University, Mt. Holyoke College,

Bryn Mawr College, Xortlnvestern Universitv.

Chicago University, I'rincLton College,

Cincinnati University. Rochester University,

Columbia College. .Smith College,

Hamilton College, V'assar College,
Massachusetts Institute of Technology, Wellesley College,

Miami University. Williams College.

To this list may be added the American Association for the
Advancement of Science, as its subscription for next year has been
announced.

During the same session forty-one investigators were at work at
the laboratory, thirty-three of whom occupied private rooms, while
the rest had tables in the general laboratories for beginners in
investigation. The whole number of students and investigators
was one hundred and eleven, representing seventy-two colleges,
universities and schools, and no less than seventeen states.

■]"() those who by word and example have encouraged cooperation,
this record will certainly be gratifying ; and perhaps it will be
accepted by all as an assurance that good-will and united effort have
not been fruitless. For six years the Marine l^iologic d Laboratorv
has stood for the first and the only cooperative organizition in the
interest of Marine Biology in America. Gradually it has come to
be understood tliat the creation of such an organization was a step
in the right direction. .\n important need was felt and there was
but one way to meet it. That way was coop Malive ailion. It was
clearly seen that the (icnernment could not be expected to undertake
the work. \\\ independent foundation was needed and one removed
from all danger of sectional domination. The effort to reach such
a foundation through a cooperative organization was no menace to
any existing laboratory. Time has shown that the laborator\- was
not an imneeded creation. it is no longer necessary to search "the
by-ways and hedges " for investigators, but our buildings ha\e to
be extended every year or two in order to provide room for them.
Each summer now sees a congress of biologists assembled at the

APPENDIX. 237

laboratory, and every new comer learns the value of scientific
fellowship.

Had the Marine Biological Laboratory done nothing beyond the
creation of a sound cooperative organization, it would at least have
fulfilled one all-essential part of its mission. That it has done, and
so effectively that it is not likely to be undone.

The record of the laboratory as a scientific station is shown in the
following list of works :

PAPERS PUBLISHED.

H. Avers.

A Contribution to the Morphology of the \'ertebrate Head. Zool.

A?tz., 1890.
On the Origin of the Internal Ear and the Functions of the Semi^

circular Canals and Cochlea. Milwaukee, 1890.
Concerning Vertebrate Cephalogenesis. Journ.of Morph., IV, 1890.
The Ear of Man ; its Past, its Present, and its Future. Biol.

Lectures, I, Boston, 1890.
Die Membrana tectoria, was sie ist, und die Membrana basilaris, was

sie verrichtet. Anat. Anz., VI, 1891.
A Contribution to the Morphology of the Vertebrate Ear, with a

Reconsideration of its Functions. Journ. of Morph., VI, Nos.

I and 2, 1892.
The Macula Neglecta again. Anat. Ans., VIII, 1893.
ijeber das peripherische Verhalten der Gehornerven und den

Werth der Haarzellen des Gehororgans. Anat. Ans., VIII,

1893.
The Auditory or Hair-cells of the Ear and their Relations to the

Auditory Nerve. Journ. of Morph., VIII, 1893.
Bdellostoma dombey. Biol. Lectures, II, 1893.

H. C. BuMPUS.

The Embryology of the American Lobster. Journ. of Morph.,

V, 1891.
A New Method in the Use of Celloidin. A/ner. Nat., 1892.
A Laboratory Course in Invertebrate Zoology. Providence, 1892.

Cornelia M. Clapp.

Some Points in the Development of the Toad-fish (Batrachus Tau).
Journ. of Morph., V, 1891.

E. G. CONKUN.

The Cleavage of the Ovum in Crepidula fornicata. Zool. Anz.,

No. 391.
The Fertilization of the Ovum. Biol. Lectures, II, 1893.

23S APPENDIX.

Bradley M. Davis.

Development of the Frond of Champia parvula, Harv., from the
Carpospore. Annals of Botany^ Vol. VI, Ao. 24, Dec,
1892.

E. (j. Gardiner.

Weismann and Maupas on the Origin of Death. Biol. Lectures

I, 1890.

J. E. Humphrey.

Notes on Technique. Botanical Gazette, XV, 7, 1890.

E. O. Jordan.

The Habits and Development of the Newt. Jouj-n. of Morpli.,
Vol. VII, No. 2, 1893.

J. S. Kingslev.

The Ontogeny of Limulus. Preliminary. Zool. Ans.,- No. 345,

1890, and Afner. Nat., 1890.
The Embryology of Limulus. Joiirn. of Morph., Vol. VII, No. i,

and Vol. VIII, No. 2.
The Marine Biological Laboratory. Popular Science Monthly,

Sept., 1892.

Frederic S. Lee.

Ueber den Gleichgewichtssinn. Centralblatt fiir Physiologie, 1892.

Wm. Libbev, Jr.

The Study of Ocean Temperatures and Currents. Biol. Lectures y
I, 1890.

F. R. LiLLIE.

Preliminary Account of the Embryology of Unio complanata.
fourn. of Morph., VIII, No. 3, 1893.

Wm. a. Locy.

The Formation of the Medullary Groove, and Some Other Features

of Embryonic Development in the Elasmobranchs. fourn. of

Morph., Vol. VIII, No. 2.
The Optic Vesicles in Elasmobranchs and their Serial Relation to

Other Structures on the Cephalic Plate, fourn. of Morph.,

Vol. IX, No. I, 1893.

Jacques Loeh.

Ueber kiinstliche Umwandlung positiv heliotropischer Thiere in

negativ heliotropische und umgekehrt. Pfliigers Archiv fiir

Physiologic, Bd. LIV.
A Contribution to the Physiology of Coloration in Animals, fourn.

of Morph., Vol. VI 11, 1893.
Investigations in Physiological Morphologv. 3. fourn. of Morph.,

\'ol. \'1I.

APPENDIX. 239

Ueber die Entwicklung von Fischembryonen ohne Kreislauf.

Pfliiger's Archiv, Bd. LV.
On some Facts and Principles of Pliysiological Morphology. Biol.

Lectures, II, 1893.

J. MUIRHEAD MaCFARLANE.

Irrito-Contractility in Plants. Biol. Lectures,- II, 1893.

E. L. Mark.

Polychoerus caudatus, nov. gen. et nov. spec. Festschrift zuiii
siebensigsten Geburtstage Rudolf Leuckarts, Leipzig, 1892.

T. H. Morgan.

The Relationships of the Sea Spiders. Biol. Lectures, I, 1892.

A Contribution to the Ontogeny and Phylogeny of the Pycnogonids.

fohns Hopkins Studies, Vol. V, No. i, 1891.
The Test-cells of the Ascidians. Journ. of Mar ph., V, 1891.
The Growth and Metamorphosis of Tornaria. fount, of Morph.,

Vol. V, No. 2, 1892.
Spiral Modilication of Metamerism, fourn. of Morph., Vol. VII,

No. 2, 1892.
Balanoglossus and Tornaria of New England. Zool. Anz., No.

407, 1892.
Experimental Studies on Teleost Eggs. Anat. Anz., Vol. VIII,

No. 2, 1893.

J. P. MCMURRICH.

Contributions on the Morphology of the Actinozoa. (2) The
Embryology of the Hexactiniae. fotirn. of Morph., Vol. IV,
1890.

Contributions on the Morphology of the Actinozoa. (3) The Phylo-
geny of the Actinozoa. fourn. of Morph., \'o\. V, 1891.

The Development of Cyanea arctica. Atner. Nat., XXV.

The Gastraea Theory and its Successors. Biol. Lectures, I, 1890.

The Formation of the Germ-layers in the Isopod Crustacea. Zool.
» Aftz., No. 397, 1892.

Julia B. Platt.

Contribution to the Morphology of the Vertebrate Head, fourn. of

Morph., Yo\. V, 1891.
The Anterior Head-cavities of Acanthias. Zool. Anz., No. 344,

May, 1890.
Further Contributions to the Morphology of the Vertebrate Head.

Anat. Anz., Vol. VI, pp. 251.

H. F. OSBORX.

Evolution and Heredity. Biol. Lectures, \,\%(^o.

John A. Ryder.

Dynamics in Evolution. Biol. Lectures, II, 1893.

240

APPENDIX.

W. A. Setchell.

Preliminary Notes on the Five Species of Doassansia Cornu. P7-oc.

Amer. Acad., XXVI, 1891.
An Examination of the Species of the Genus Doassansia Cornu.

Aftftals of Botany, VI, 1892.

Louise B. Wallace.

The Structure and Development of the Axillary Gland of Batrachus.
Jourti. of Morph., Vol. VIII, No. 3, 1893.

S. Watase.

On Caryokinesis. Biol. Lectures, I, 1890.

The Origin of the Sertoli's Cell (abstract). Amer. A'at., May,

1892.
On the Significance of Spermatogenesis (abstract). Amer. Nat.,

July, 1892.
On the Phenomena of Sex- Differentiation. Journ. of Morph.,

Vol. VI, No. 3, 1892.
Homology of the Centrosome. Journ. of Morph., \o\. VIII, No.

2, 1893.

Herbert J. Webber.

On the Antheridia of Lomentaria. Annals of Botany, \'ol. V,
April, 1 89 1.

Wm. M. Wheeler.

A Contribution to Insect Embryology. Journ. of Morph.. \'ol.
VIII, No. 1, 1893.

W. P. Wilson.

The Influence of External Conditions on Plant Life. Biol. Lectures _^
II, 1893.

E. B. Wilson.

Some Problems of Annelid Morphology. Biol. Lectures, I, 1890.
Origin of the Mesoblast-Bands in Annelids. Journ. of Morph.,

Vol. IV, No. 2, 1890.
The Cell-lineage of Nereis. A Contribution to the Cytogeny of

the Annelid Body. Journ. of Morph., Vol. VI, 1892.
The Mosaic Theory of Development. Biol. Lectures, II, 1893.

C. O. Whitman.

Specialization and Organization. Biol. Lectures, I, 1890.

The Naturalist's Occupation. Biol. Lectures, I, 1890.

The Inadequacy of the Cell-theory of Development. Journ. of

Morph., Vol. VIII, No. 3, and Biol. Lectures. 11, 1893.-
A Marine Observatory. Popular Science Monthly, Feb., 1893.
A Marine Observatory the Prime Need of American Biology.

Atlantic Monthly, June, 1893.

APPENDIX. 241

The Work and Aims of the Marine Biological Laboratory. Biol.

Lectures, II, 1893.
The Echinoderm Egg and the Theory of Isotropism. Journ. of

Morph., Vol. IX, 1893.
The Metamerism of Clepsine. Festschrift ziim siebenzigsten

Gebtirtstage Rudolf Lenckarts., Leipzig, 1892.
A Sketch of the Structure and Development of the Eye of

Clepsine. SpengeVs Zool. fahrb., VI, 1893.

PAPERS IN PRESS.

H. Ayers.

The Relations of the Peripheral Territory of the Auditory Nerve

as shown by Methylen-blue.
Certain Facts and Theories in Modern Neurology.

E. G. CONKLIX.

The Embryology of Crepidula. Part I. History of the Cleavage.
The Dynamics of Fertilization and Cleavage.

Elizabeth E. Bickford.

Experiments on Regeneration and Heteromorphosis in Tubularian
Hydroids.

Martha Bunting.

The Origin of the Sex-cells in Hydractinia and Podocoryne and the
Development of Hydractinia. Journ. of Morph., Vol. IX, 1894,

Elizabeth Cooke.

On the Osmotic Qualities of the Muscles of Marine Animals.

E. G. Gardiner.

Early Development of Polychoerus caudatus.

Ida H. Hyde.

The Nervous Mechanism of Respiratory Movements in Limulus.

F. S. Lee.

A Study of the Sense of Equilibrium in Fishes. I. Journ. of
Physiology.

D. J. LiNGLE.

On the Reversal of the Direction of the Contraction of the Heart
in Ascidians.

Jacques Loeb.

Ueber das Sauerstoffbediirfniss des Embryo in verschiedenen

Entwicklungsstadien.
Ueber die Herstellung zusammengewachsener Doppelt- und Mehr-

fachembryonen by Seeigeln.
Ueber die Bedeutung von Gehirn und Auge fvir die Reactionen

niederer Thiere auf Licht.

242 APPENDIX.

A. D. Morrill.

Pectoral Appendages and their Innervation in Prionotus.

Julia B. Platt.

The Ontogenetic Differentiation of the Ectoderm in Necturus.
(Preliminary Notice.)

Marv Schivelv.

Ueber den Einfluss der Concentration des Seewassers auf die
Herzthatigheit einiger Seethiere. PJiiiger-s Archiv fiir
Physiologic.

S. Wat AS E.

On the Nature of Cell-Organization. Biol. Lectures, Vol. II, 1894.

Wm. M. Wheeler.

Syncoelidium pellucidum, a New Marine Triclad. Journ. of Morph.
Planocera inguilina, a Polyclad Inhabiting the Branchial Chamber

of Sycotj'pus Canaliculatus Gill. Joiirn. of Morph., Vol. IX,

1894.

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