THE INADEQUACY 
OF THE 
Cell-Theory of development 
BY 
C. O. WHITMAN 
Reprinted from Journal of Morphology, Vol. VIII., No. 3 
BOSTON 
GINN & COMPANY 
1893 THE INADEQUACY 
OF THE 
Cell-Theory of Development 
BY 
C. O. WHITMAN 
Reprinted from Journal of Morphology, VoI. VIII., No. 3 
BOSTON 
GINN & COMPANY 
1893 THE INADEQUACY OF THE CELL-THEORY OF 
DEVELOPMENT.1 
C. O. WHITMAN. 
The doctrine of Schleiden and Schwann that in 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” (Muller’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 own development alone; and another inci- 
dental, in so far as it has become an integral part of a plant." 
“The entire plant appears to live only for and through the 
elementary organ ” (cell). 
Schwann, in his classical Researches of 1839, extends the 
same view to the entire organic world. 
“Each cell," he affirms, “is, within certain limits, an individ- 
ual, an independent whole. The vital phenomena of one are 
repeated, entirely or in part, in all the rest. These individuals, 
however, are not ranged side by side as a mere aggregate, but 
so operate together, in a manner unknown to us, as to produce 
an harmonious whole." (Introduction, p. 2.) 
“ The whole organism subsists only by means of the recipro- 
cal action of the single elementary parts." (Theory of cells, 
p. 191.) 
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 the World’s Columbian Exposition. 640 
WHITMAN. 
[Vol. VIII. 
elementary parts, not differing from the others, are capable of 
separating themselves from 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 own, an inde- 
pendent life, by means of which it would be enabled to develop 
independently, if 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.” 
(/. c. 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 gleiche Elementarorganis- 
mus ist es, der Thiere und Pflanzen zusammensetzt.” (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 have 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 maxim, “ omnis cellida e cellula ”/ 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 fundamentally the same in both 
pla7its and animals, — all these capital steps forward have 
tended to magnify the importance of the cell as a universal 
unit of structure. No. 3.] THE INADEQUACY OF THE CELL-THEORY. 
641 
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 definitely 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 intra-cellular and inter-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 within 
the cell and among 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 642 
WHITMAN. 
[Vol. VIII. 
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 mouth — of 
such an animal and the corresponding structure of a cellular 
organism, would be quickly relegated to the limbus fatuorum. 
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 coelo, 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 point of view; and 
more recently Wilson has expressed similar views, but with 
reservations that still uphold 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 No. 3.] 
THE INADEQUACY OF THE CELL-THEORY. 
643 
theory. * A certain grade of organization 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, even 
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 precociously 
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 egg 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 egg does 
not lie in its mode of cleavage, but in subtile formative pro- 
cesses. We find the most unlike forms of cleavage issuing 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 644 
WHITMAN. 
[Vol. VIII. 
results ; for example, in the egg of the polyclad as compared 
with that of the mollusc or the annelid, where “ cells having 
precisely the same origin in the cleavage, occupying the same 
position in the embryo, and placed under the same mechanical 
conditions, may nevertheless 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 egg 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 
egg. Watch the expansion of the blastoderm in the pelagic 
teleost egg, the formation of the germ-ring, and especially 
the axial concentration of material, 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 
ation, no more disproves the existence of definite organization 
in the case of the egg than in the case of hydra. 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 the first two or four blastomeres, when 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 blastomere continues for a while to form cells 
as if it were a half-unit or a quarter-unit, and only later mani- 
fests the whole unit-power of the organism, I see no reason to 
conclude that the case is fundamentally different. In either 
case the part has the power of reorganizing itself into the 
whole, and it makes no essential difference whether the reor- No. 3.] 
THE INADEQUACY OF THE CELL-THEORY. 
645 
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 egg 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 zVz/ra-cellular ; if of many cells, then it is inter-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 intra- 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. The nephrostome is a nephrostome all the 
same whether it consist of one cell, two cells, or many cells. Its 
form and function are both independent of the number of com- 
ponent cells. Cells multiply, but the organ remains the same 
throughout. So far as homology is concerned, the existence of 
cells may be ignored. 
May we 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 organization would 
be the essential thing, while division into cell-territories might WHITMAN. 
[Vol. VIII. 
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 does 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 primary elements in com- 
parison with which the cells appear as complex organisms. 
Since Ernst Briicke 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. Engelmann, the “pan- 
gens” of de Vries, the “plasomes” of Wiesner, the “idioblasts” 
of Oscar Hertwig, and the “biophores” of Weismann. 
After the discovery of cell-division 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 Briicke, who, seeing that 
the phenomena of life could not be referred to a structureless 
substance, declared for the organization 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 they 
contain, still another, and otherwise complicated, structure ; and this 
it is that we designate by the name organization.” 
Further, in his own words : “ Wir miissen in der Zelle immer emen 
kleinen Thierleib sehen, und diirfen die Analogicn, welche zwischen ihr 
und den kleinsten Thierforme?i existire?i, niemals aus den Augen lassen.” 
(Elementarorganismen, p. 387.) No. 3.] THE INADEQUACY OF THE CELL-THEORY. 
647 
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 significance; 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.) 
Brticke’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. Development, no less than 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 view is well expressed in his classical work, the 
“ Theorie der 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 egg differs from the frog’s 
egg just as widely as the hen from the frog.” 
While all will admit that the organization of the egg is such 
as to predetermine the organism, few will be prepared to admit 
that the adult organization is identical in its individuality 648 
WHITMAN. 
[Vol. VIII. 
with that of the egg. The organism is regarded rather as a 
community of such individualities, 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 
organisms, 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. P'rom a simple 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 Spencer1 has recently stated it, “an 
exchange 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 mutual dependence.” 
We habitually apply this anthropomorphic conception to 
every grade of organization; The higher organism is regarded 
as a colony of cells ; the cell as a colony 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 
1 The Contemporary Review, February, March, and May, 1893. No. 3.] 
THE INADEQUACY OF THE CELL-THEORY. 
649 
“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, inter- 
dependence 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 
economy nor social instinct that binds the two halves of an egg 
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- 650 
WHITMAN. 
[Vol. VIII. 
eration 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 
Fig. i. — Regeneration of a Stentor cut into three parts, A, B, C. vc = pulsating 
vacuole. S — regenerating frontal field. 
end regenerated posterior end, and vice versa. The middle 
piece regenerated both ends — the complicated frontal field 
with its mouth, pharynx, long cilia, pulsating vesicle, etc., as 
well as the simpler posterior region. 
Treat a Hydra in the same way and 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 651 
No. 3.] 
THE INADEQUACY OF THE CELL-THEORY. 
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 four blasto- 
meres. 
Gruber’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 (Cyclas 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 ridge1 
(Leiste), and a basal lamella which is continued into a termi- 
nal fibre. All these fibres are connected by the basal fibril, 
through which the movements of the membranellae are evi- 
dently regulated. 
Now this highly differentiated organ, the membranella, is 
reproduced with most remarkable exactness in the “ corner- 
cell ” of Cyclas. But here the organ represents an individual 
1 This seam consists of a series of microsomes, as Dr. Watase has discovered. 652 
WHITMAN. 
[Vol. VIII. 
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 “ however great the difference between an infusorium and a 
highly organized animal, it cannot be a qualitative one. We 
can assume that the same vital elements serve in both as the 
foundation, only in ever new combinations. This kinship 
declares itself very clearly in the correspondence of many organs 
of the infusoria with those of the higher organisms ” (l.c. p. 16). 
Fig. 3. — A, “ Corner cell ” of Cyclas cornea. B, Section of three cells. Other 
letters as in Fig. 2. 
“ 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 Natur" 
(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 happens, in parasitic 
degradation, cell-formation has been dispensed with. The entoderm remains 
throughout life as a single cell, and the whole process of reproduction, for both 
kinds of embryos, is carried on in the body of this cell without any cellular organs 
whatever. 
In one respect this unicellular organ, which was undoubtedly once multicellular, No. 3.] 
THE 1DADEQUACY OF THE CELL-THEORY. 
653 
What is the 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. Even 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 egg. If we 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 
same 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 present I must limit myself 
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 become the receptacle of nuclei belonging originally 
to other cells; in other words, it becomes multinucleate, not by the 7nultiplication 
of its 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, and each undergoes the 
differentiations characteristic of the trtie 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 Boveri’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. 654 
WHITMAN. 
[VOL. VIII. 
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 
migrating 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 Kupffer’s vesicle in the 
teleost. 
There is no longer any doubt in my mind — and here 
I am 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 living 
as well as the dead egg, I cannot help thinking 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 should trace 
step by step its mode of origin in the pelagic fish-egg. Here 
one may see this remnant of an archenteric cavity arise, not No. 3.] 
THE INADEQUACY OF THE CELL-THEORY. 
655 
inside the embryonic tissues as in the eggs of fresh-water 
fishes, but actually outside the tissues on the inner face of the 
embryo, near its posterior end. Its whole ventral and lateral 
boundary 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 
unit, 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 who 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- 656 
WHITMAN. 
[Vol. VIII. 
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 cell-formation. 
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 
regional 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 directive influence 
on the formative processes. The cleavage runs on from begin- 
ning to end, regularly or irregularly, without modifying in 
any essential way the form of the blastodisc. All at once, 
when this segmentation has been carried to a certain point, 
the transformation sets in and goes rapidly on, without inter- 
rupting cell-formation, but to all appearance quite indepen- 
dently of it. 
In the axial concentration of the very 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 part of the germ-ring which 
represents, historically at least, this end can be brought into 
place, we have another decisive test of formative power assert- 
ing itself, not only independently of cell-division, but also 
against all the obstructions interposed by the yolk. This pre- 
potency of the “plastic power” (Schwann) is seen to great No. 3.] 
THE INADEQUACY OF THE CELL-THEORY. 
657 
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 put 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 difficult 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 idiosomes 
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 long insisted, 
the continuity of these elements is not broken by cell-walls. 
The organization of the egg 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,1 and the interesting pressure 
experiments of Driesch by which a new distribution of nuclei 
is forced upon the egg, without any sensible modification of the 
1 As will be shown later. 658 
WHITMAN. 
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] are no more the producers of the vital 
phenomena than the shells scattered along the sea-beach are 
the instruments by which 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 
1 British and Foreign Medico-chirurgical Review, Vol. XII, p. 314. Oct., 1853.