_ 
DECEMBER 21, 1916] 
Mr. Russell displays a fine sense of the his- 
torian’s function in the way in which he has 
thought himself into the position of the various 
morphologists whose ideas he expounds. He 
shows a remarkably sympathetic imagination, and 
we suspect that he has understood some of the 
old masters—Lamarck, for instance—better than 
they understood themselves. We think his esti- 
mate of Haeckel is too severe, but his fair- 
mindedness is so conspicuous that we suspect our 
partiality may be at fault. The whole book shows 
fine workmanship, but we may perhaps refer to 
the outstanding excellence of the discussion of 
the controversy between Cuvier and Etienne Geof- 
froy Saint-Hilaire, of the Meckel-Serres law and 
its successor the recapitulation doctrine, of the 
work of von Baer, of the cell-theory, and of the 
import of the young subscience of experimental 
embryology which Roux founded. No previous 
English discussions of these subjects show in 
such high degree the qualities of scholarship, 
clearness, and grasp of essentials. 
This masterly book suggests many reflections, 
and we would try to state two of these. (a) Mr. 
Russell bids us choose between the position held 
by Cuvier, which insists on the priority of func- 
tion to structure, and the position of Geoffroy, 
which maintains the priority of structure to func- 
tion. But may we not recognise a partial truth 
in both positions? The organism is indeed a 
particular kind of activity, a unified reaction 
system, but it cannot get on without organisation, 
any more than a stream without a bed. It condi- 
tions its organisation as’ the stream makes its 
bed, but the organisation soon begins to condition 
it, as the bed the stream. We do not feel com- 
pelled to admit the rigid antithesis which Mr. 
Russell would force on us. (b) In his account of 
the embryological work of Roux the author says 
that “the introduction of a functional moment into 
- the concept of heredity was a methodological ad- 
vance of the first importance, for it linked up in an 
understandable way the problems of embryology, 
and indirectly of all morphology, with the problem 
of hereditary transmission, and gave form and 
substance to the conception of the organism as 
a historical being.” What Mr. Russell has said in 
this book and elsewhere concerning the conception 
of the organism as a historical being is very im- 
portant, but what we are not sure’ about is that 
Roux’s “linking-up”’ was “understandable.” As 
regards linking-up, did Roux do more than suggest 
the hypothesis that specific chemical substances 
produced in connection with functionally acquired 
form-changes might soak through from body to 
germ-cells and induce in them a predisposition to 
similar form-changes in the offspring? The hypo- 
thesis surely takes a good deal of understanding, 
and, speaking for ourselves, we are not enamoured 
with the prospect of interpreting the form of 
animals in terms of their activity if it cannot be 
attained without a belief in the transmission of 
functional modifications more firmly based in fact 
than that of Lamarck, Samuel Butler, or Semon. 
Is there not some other way in which an organism 
may be a historical being ? 
NO. 2460, VOL. 98] 
NATURE 
$97 
EXPERIMENTAL INVESTIGATIONS INTO 
THE DEVELOPMENT OF VERTEBRATA, 
Growth in Length: Embryological Essays. By 
Richard Assheton. Pp. xi+104. (Cambridge: 
oak the University Press, 1916.) Price 2s. 6d. 
foc zoologists will be grateful to Mrs. 
Assheton for the publication of these 
embryological essays found amongst the papers 
of her late husband. Whilst nominally dealing, 
as the title indicates, with ‘growth in length,” 
they are really a beautiful and clearly expressed 
summary of the early stages in development of 
the Vertebrate embryo, ranging through the whole 
series from the Elasmobranch to the Mammal. 
The facts are, of course, interpreted according to 
the late Dr. Assheton’s views, with most of which 
we should be inclined to agree. The only point 
of criticism that seems to us worth raising is . 
whether Dr. Assheton was justified in accepting 
on the evidence the statement that the “segmen- 
tation cavity” in the segmenting eggs of 
Amphibia becomes incorporated in the gut. 
Brachet’s work (which Dr. Assheton quoted) does 
not warrant such a conclusion; he found, indeed, 
that the wall dividing the gut from the segmenta- 
tion cavity was often torn during growth, but 
that the rent healed up again. This tem- 
porary communication between the two cavities 
is therefore only one of the dislocations produced 
by unequal growth, and has no _ further 
significance. 
Dr. Assheton arrived at the conclusion that the 
blastopore in all Vertebrata (including Balano- 
glossus) becomes the anus, and that the mouth 
is an entirely new formation—as appears to be 
the case also in Echinodermata. This is a view 
for which there is strong evidence. The only 
consideration which makes us hesitate in accepting 
the ontogenetic processes in these two groups as 
a full record of their evolutionary history is that 
the formation of a new mouth seems to us to in- 
volve a breach of functional continuity which we 
find it difficult to picture to ourselves as actually 
occurring in the history of the race. 
To the essays on “Growth in Length” is 
appended a reprint of Dr. Assheton’s paper on 
“The Geometrical Relation of the Nuclei in an 
Invaginating Gastrula (Amphioxus),” which was 
an endeavour to substitute for Driesch’s vague 
conception of the “entelechy” a force alter- 
nately monopolar and bipolar, radiating from 
the nuclei of the blastomeres as the efficient 
agent in bringing about invagination. This 
explanation of vital phenomena, like so many 
others, can be made to fit this particular 
case; but our doubts as to its validity are 
raised by its inability to fit other similar cases. 
How can the position of the nuclei in the cells 
explain the invagination in the gastrula of 
Echinus, when this invagination can be changed 
into an evagination by allowing the egg to de- 
velop in warmer water? Still, it is only by pro- 
pounding and testing theories of this kind that 
progress can be made, and Dr. Assheton’s clear 
