I909 ] CURRENT LITERATURE 155 



■ 



she generations; and by 'inheritance' we mean 'organic inheritance '—all that 

 the organism is or has to start with in virtue of its hereditary relation to parents 



and ancestors." 



In the chapter on the physical basis of inheritance the author discusses the 

 phenomena and experiments connected with chromosome reduction and fertiliza- 

 tion, and concludes from the evidence that the chromosomes are the bearers of 

 hereditary characters, but that "we should be chary in committing ourselves unre- 

 servedly to the conclusion that the heritable organization is exclusively resident 

 in the chromatin of the nuclei of the germ cells. " The chapter on heredity and 

 variation contains a clear exposition of the facts and theories of mutation and 

 continuous variation. The author believes that both are important evolutionary 

 factors; that mutation, so far as present evidence goes, may have been a much 

 more important factor in plants than with animals; and that the distinction be- 

 tween "large fluctuations" and "small mutations" is merely a verbal one. Re- 

 garding the causes of variation he considers it "useful to say that variation is the 

 expression of a qualitative asymmetry beginning in gametogenesis." "Variation 

 is a novel cell division." 



There is a lengthy treatment of the question of the transmission of acquired 

 characters or "somatic modifications;" with a critical analysis of the data usually 

 ated as evidence. The result may be stated in the author's own words (p. 242) : 

 "The question resolves itself into a matter of fact. Have we any concrete evidence 

 to warrant us believing that definite modifications are ever, as such or in any 

 representative degree, transmitted ? It appears to us that we have not. But to 

 ^•dogmatically that such transmission is impossible is unscientific." The 

 statistical studies of Galton, Pearson, and others are summarized, and under 

 the experimental study of inheritance an array of data from the work of Mendel, 

 Juries, Bateson, Correns, and many others of the recent school of genetics, 

 *hich has begun to illuminate some of the obscure problems of hybridity, is 

 r «ught together and discussed. These are largely the facts of Mendelism. In 



another 

 Presented. 



prepond 



Other chapters are devoted to theories of heredity, which are largely theories 



representative particles in some guise or other; and to theories of development, 



well £ thC aUth ° r cham Pions the determinants of Weismann and the latter's 



-known theory of germinal selection. Under the topic heredity and sex, 



rmination 



sexes ' and thC aUth ° r ' S theor y is P rcsented > namel y that the difference in thC . 



asmic 



much a ThiS View a PP ears t0 ° va g" e t0 be of an >' value in directing thC 

 -needed experiments on the subject. The author also apparently attaches 



too littl 



■ttle significance to the discovery that in many insects an extra chromosome 



companies the fp™u — : J 



the female sex. 



At tli 



a very * ° f the work there is a representative bibliography of 48 pages, 

 ' USCful Sub Ject-index to the bibliography, and a general index to the volume. 



