APRIL 2, 1914] 
NATURE 
107 
lished theory. As the author puts it, the localised 
distribution of substances in the egg, upon which 
this hypothesis is based, is to be regarded rather 
as a process or result of development than as a 
primary determining factor of the course of 
development. A good account is given of the 
idiochromosome and its relation to sex, and the 
book ends with a chapter on blastula, gastrula, 
and germ-layers. 
The book is excellently written, and clearly 
illustrated; it fills an obvious gap in the teaching 
literature of zoology, and it deserves to have a 
wide circulation amongst students of that 
science. 
(2) The two biological volumes here under dis- 
cussion fully maintain the high standard of the 
great series of volumes entitled “Die Kultur der 
Gegenwart.” The botanical volume is composed 
of an excellent section on plant histology from 
the pen of the late Prof. Strasburger, followed by 
one on plant morphology and development by 
Benecke. 
The zoological volume forms an interesting 
text-book which will be of use to the senior 
student as a help towards getting a grip of 
the current views regarding some of the more 
important problems of morphology. The volume 
opens with a charming essay by Richard Hert- 
wig upon unicellular organisms, which gives an 
excellent sketch of present-day ideas, together 
with valuable indications regarding future work. 
Hertwig’s essay is followed by a useful sketch of 
modern histology by Poll, and this in turn by an 
admirable chapter by Oscar Hertwig on general 
and experimental morphology and embryology. 
This commences with a masterly account of the 
main features of gametogeny and fertilisation— 
one of the most interesting sections being that in 
which is given an account of recent experiments 
in which gametes or zygotes have been subjected 
to the influence of such substances as radium and 
mesothorium. An excellent chapter is devoted to 
parthenogenesis, and the suggestion is brushed 
aside with scant ceremony that the production of 
parthenogenesis: by artificial means — whether 
chemical or mechanical—gives any clue whatever 
to the ultimate nature of the fertilisation process. 
A witty paragraph is quoted from Bolzmann as 
to Loeb’s work and the exaggerated claims based 
upon it. How important was the discovery that 
a process believed to be so essentially vital in its 
nature was merely chemical! What important 
consequences the discovery might have when 
future developments rendered possible its applica- 
tion to the human race—the emancipation of 
woman to a degree undreamt of by the greatest 
enthusiast for women’s rights ! 
WO. 24707, VOLY.93 | 
The mere man ! 
becomes. superfluous; he is replaced by a 
flask of chemical solution; sex-determination by 
chemical means follows, and males, now mere 
useless curiosities, are produced only as occa- 
sional specimens for zoological gardens ! 
A general description is given of the processes 
of segmentation and gastrulation, and the chapter 
concludes with a short sketch of the chief results 
of experimental embryology. 
About 150 pages are occupied by a really admir- 
able account by Heider of the morphology of the 
invertebrate metazoa. It is most clearly and in- 
terestingly written, and is illustrated by excellent 
figures. Naturally, views are occasionally ex- 
pressed to which some may take exception, but, 
on the whole, we know of no better general 
account of the morphology of invertebrates. The 
subject-matter of the chapter is rightly termed 
morphology rather than comparative anatomy, 
confining itself as it does to really important 
features and ignoring those masses of unimpor- 
tant detail that so usually make a modern text- 
book of zoology an effective stifler of all interest 
in the subject. We notice very few slips. The 
familiar German misuse of the word splanchno- 
pleure when splanchnic mesoderm is meant 
catches the eye of the English reader. The fre- 
quent reference made to the trochosphere type of 
larva as an evidence of phylogenetic affinity will 
not altogether appeal to those who suspect the 
various larve of this type of being simply conver- 
gent adaptations to a pelagic existence, while 
some morphologists of the Cambridge school will 
look askance at the not unfamiliar attitude 
towards the primitive and ancestral nature of the 
iower platyhelminths. But the general opinion 
will be that Heider has produced a very admirable 
sketch of his subject. 
The remaining two chapters—on vertebrate 
embryology by Keibel and on vertebrate morph- 
ology by Gaupp—are less satisfactory. It seems 
an error in planning the book to have two such 
separate chapters, as there can be no morphology 
worth the name without embryology, and no em- 
bryology worth the name without morphology. 
We are glad to see that Keibel is not overawed 
by the sanctity of that—in some respects—most 
highly specialised vertebrate Amphioxus, and that 
he takes the common-sensible position in regard 
to the greatly degenerate character of its head 
region, though we fail to follow him in his some- 
what derogatory remarks regarding its gastrula- 
tion processes. It seems, by the way, regrettable 
that Keibel, like many others who are specially 
interested in the embryology of the higher verte- 
brates, uses the word gastrulation in a sense 
which does not seem to be justified. Strictly 
