JUNE 4, 1914] 
—— 
instability in which, among other contributing 
factors, cross-breeding may perhaps play a part— 
arouses little misgiving. 
The definitions of genera, of which there are 
140, and of species, of which there are 406, are 
polished, and can be read without fatigue, and 
conspicuous attributes and suggestive relations 
are effectively summarised. The text-figures illus- 
trating genera are for the most part very clear and 
good. 
(6) The construction of this monumental work 
goes steadily on, to the infinite honour of its 
author. 
This thirteenth volume, of more than 600 pages, 
represents two subfamilies, and part of a third, of 
the great group Noctuide. The species included 
are of Catocaline 379, bringing up the total 
number for the subfamily to 1022, of Momine 74, 
and of Phytometrime 226. 
The key to the Catocaline is reprinted from 
vol. xii., for convenience. This key, with its clear 
dichotomies for no fewer than 10g genera, as well 
as similar keys to the species of the larger genera, 
embracing some 26, some 40, and one even Io1 
species, enables the casual critic to form some idea 
of the prodigious amount of attentive labour em- 
bodied—one might almost say enshrined, when one 
considers that this is an ordered part of a monu- 
ment dere perennius, pyramidum altius—in this 
volume. 
The illustrations are on a generous scale; in 
addition to 455 beautiful coloured figures, in 
eighteen plates separately bound, there are 130 
figures in the text, so that every genus is repre- 
sented at least once. 
SIX ESSAYS ON SEX. 
(1) Ursprung der Geschlechtsunterschiede. By 
Dr. Paul Kammerer, in Fortschritte der Natur- 
wissenschaftlichen Forschung. Herausgegeben 
von Prog (Emil Abderhalden. hd. V-, pp. 1— 
240. (Berlin and Vienna, Urban and Schwarzen- 
berg, 1912.) Price 15 marks. 
(2) Die biologischen Grundlagen der sekundéren 
Geschlechtscharaktere. By Dr. J. Tandler and 
Dr. S. Grosz. Pp. 169. (Berlin: Julius Springer, 
1913.) Price 8 marks. 
(3) Sex Antagonism. By Walter Heape. Pp. 217. 
(London: Constable and Co., Ltd., 1913.) 
Price 75. 6d.° net. 
(4) The Nature and Origin of Secondary Sex 
Characters. By F. W. Ash. ‘Trans. North 
Staffordshire Field Club. xlvii. (1913), pp. 
SEB 
(5) Les Problémes de la Sexualité. By Prof. 
Maurice Caullery.. Pp. 332. (Paris: Ernest 
Flammarion, 1913.) Price 3.50 francs. 
NO. 2327, VOL. 93| 
a 
NATURE 345 
) 
(6) Heredity and Sex. By Prof. T. H. Morgan. 
Pp. ix+282. (New York: Columbia University 
Press ; London: Oxford University Press, 1913.) 
Price 7s. 6d. net. 
(r) Ian KAMMERER has made all students 
of the biology of sex his debtors by 
taking a scholarly and critical survey of most of 
the recent contributions to the subject, and of the 
experimental work in particular. His treatise is 
a model of fairness and thoroughness, and must 
have involved a prodigious industry. He deals 
with the determination of sex, the theories of sex 
dimorphism, the results of experiments in castra- 
tion, regeneration, transplantation, breeding, and 
environmental influence, and at very considerable 
length with the recent work on the internal secre- 
tions of the reproductive organs. The bibliography 
occupies twenty-three pages of small type! An 
attempt may be made to indicate Kammerer’s 
general conclusions. The first important step in 
the evolution of sexual reproduction was_ the 
specialising of germ-cells as distinguished from 
body-cells. The second was the differentiation of 
macrogametes and microgametes, which are con- 
trasted in their assimilation capacities, amount of 
cytoplasm, size, and activity. The factors that 
condition maleness (‘‘mikrogametismus’’) or 
femaleness (“makrogametismus”’) are ultimately 
assimilation differences—the thesis, it may be re- 
called, of “The Evolution of Sex’’ (1889), to 
which no reference is made in text or bibliography. 
The differentiation of sex doubtless occurred very 
early in phylogeny, and the determination of sex 
occurs correspondingly early in ontogeny. During 
maturation the gametes are probably in varying 
degrees susceptible to environmental influence, so 
that their predisposition to one sex or the other 
may be changed, but the higher the animal the less 
is its susceptibility. Only in plants and in the 
lower animals can we now succeed in experiment- 
ally changing the progamic predisposition, activa- 
ting the tendency which should otherwise remain 
latent. 
Removal of the essential gonads changes the 
metabolism of the body, and is usually followed 
by a degeneration of the subsidiary sex characters. 
But it is practically impossible to draw a definite 
line between sex characters and body characters. 
It seems as though the body were ‘“‘ sexed ” through 
and through. The castration, however early, 
never prevents the appearance of the embryonic 
primordium of any character; it merely exerts a 
quantitative influence on the development. When 
the essential gonadial substances are introduced by 
transplantation or injection into a_ castrated 
animal, the effects of castration are alleviated or 
reversed, and what can be done with ovarian sub- 
