Keferate. 161 



exhibiting the phenomenon of "cross-over", presumably for the reason that 

 there is no homologous chromosome into which the character in question 

 may be transferred, while in the corresponding female in which the sex- 

 chromosomes are paired, such "cross overs" or separations of the coupled char- 

 acters do occasionally occur. 



Various problems and hypotheses relating to fertility and sterility are 

 discussed in chapter VII, and the last chapter takes up certain special cases 

 of sex-inheritance, considering in particular, various modifications of the 

 sex-ratios. The author holds that disturbances in the sex-ratios give no 

 proper basis for the formulation of far-reaching conclusions in regard to 

 sex-determination itself. In the final section sex -inheritance in man is 

 considered and it is shown that both cytological and genetic evidence 

 point to the probability that in man the female is homozygous and the male 

 heterozygous. 



In public lectures it is impossible to give a large number of refer- 

 ences to the literature, but the author has made up this necessary defect 

 by presenting a bibliography including 475 titles which will be valuable 

 to those who wish to go more deeply into any particular phase of the 

 subject. When bibliographies become so extensive it is not fair to expect 

 that they shall be complete. One important omission noted in the present 

 case is the work of von Winiwarter 1 ) whose studies on human cytology 

 are prominently presented in the text, but not included in the bibliography. 



G. H. Shull. 



*) H. von Winiwarter, Etudes sur la spermatogenese humaine. Arch, de 

 Biol. 27, 1912. 



