Referate. 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-deterraination 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') whose studies on human cytology 

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



G. H. Shull. 



Y. Taiiaka. A study of 3Iciuleliaii factors in the Silkworm, Boinbyx 

 Mori. Journ. Coll. Agric, Tohoku Imp. University, Sapporo, Japan 

 Vol. V. Pt. IV. 1913. p. 91—113. — Gametic Coupling and Repulsion 

 in Silkworms. Ibid. Vol. V. Pt. V. 1913. p. 115-148. 



In the first of these papers the author analyses the Mendelian factor 

 for the larval and cocoon-colours of silkworms. In larval markings he finds 

 factors for striping, zebra- pattern, "moricaud", and normal pattern; the absence 

 of all of these gives plain. The first three are epistatic over normal pattern. 

 The factors tor cocooncolours are yellow, the absence of which gives recessive 

 white, and an inhibiting factor which gives dominant white. In the second 

 pa])er he gives examples of gametic coupling and repulsion, e. g. if normal 

 white is paired with plain yellow, the gametes produced by the F, individual 

 are of two sorts only, all bearing Ny or iiY. He similarly finds 'repulsion 

 between striping and yellowness, and between striping and normal colour, 

 when introduced from different parents. In a case in which a striped yellow 

 was crossed with a normal white, there appeared to be partial coupling (in 

 about the ratio of 7 : 1) between striping and yellowness, but it is noticed 

 that partial repulsion between normal and yellow would bring about the 

 same result; when however the heterozygous striped yellows (SsYy) were 

 mated among themselves, the result indicated 7 : 1 coupling between S and 

 Y. In another case in the same stock complete coupling between S and Y 

 was observed; an individual of constitution SsYy was mated with ssyy, 

 and the offspring were 215 striped yellow, (SsYy) 188 normal white (ssyy). 

 In one experiment there were indications of coupling in the ratio of about 

 7 : 1 between the "moricaud" factor and yellow. L. Doncaster. 



') H. von Winiwarter. Etudes sur la spermatogi'iiese luiinaine. Arch, ile 

 Biol. 27, 1912. 



