290 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Sex of Mice.* — S. M. Copeman and F. G. Parsons publish a record 

 of fifteen months' experimental work, undertaken with a view to deter- 

 mining the extent, if any, to which the relative proportion of the sexes 

 is capable of being influenced by varying conditions of age, nutrition, 

 interbreeding, etc. The work is still in progress, but the results for 

 this period arc published with a view to inviting criticism on method 

 and suggestions for the future, and also to indicate to other breeders 

 clues which may appear worth following up. Some interesting conclu- 

 sions are that there is a hereditary tendency in certain males to beget 

 a markedly large proportion of males, and in others of females. The 

 evidence for a similar tendency in does is not so conclusive. Inbreed- 

 ing between a male and his offspring is borne for five generations, 

 without loss of fertility or any apparent bodily degeneracy. In large 

 litters the proportion of females is greater tban in small ones ; more 

 males are produced by does over six months than by does under that age. 



Heredity of Pigmentation in Mice.j — L. Cuenot concludes as the 

 result of crossing grey, black, yellow, albino, and other mice, that 

 Mendel's law holds both as regards dominance and disjunction in 

 gametes. In the germ-plasma there must be four sorts of non-corre- 

 lative determinants completely independent, because they can be inherited 

 separately. 



Fertilisation and Hybridisation 4— Hugo De Vries gives a lucid 

 account of his views as to the material basis of inheritance. He accepts 

 Boveri's conclusions as to the individuality of the chromosomes and 

 Hacker's hypothesis of the " Doppelkern." It is characteristic of his 

 position that he regards the mingling of parental contributions as of 

 subordinate importance as regards the children, but of fundamental 

 importance as regards the grandchildren. The actual mingling takes 

 place immediately before the formation of the sex-cells of the individual 

 in question. 



Maturation of Germ-Cells and Mendel's Law.§ — E. B. Wilson 

 reports that in his laboratory two independent investigations, one 

 botanical (by Cannon), and another zoological (on spermatogenesis in 

 Brachystola, by Sutton), led to the same general conclusion, that in the 

 maturation of the germ-cells there is a segregate transference of paternal 

 and maternal contributions to different cells, which would make Mendel's 

 law more intelligible. To this, Cook objects,)! on the ground that the 

 small number of chromosomes in the above cases implies that there is 

 not a separation of individual hereditary qualities, but of whole groups 

 of qualities. 



Interstitial Testicular Gland and Secondary Sex Characters.^ — 

 P. Ancel and P. Bouin infer from a study of a unilateral cryptorchid 

 pig, in which the testis remained embryonic, while the interstitial gland 



* Proc. Roy. Soc, lxxiii. (1904) pp. 32-48. 



f Arch, de Zool. Exp., ii. (1904) Notes et Revue, pp. xlv-lv. 



% See Zool. Centralbl., xi. (1904) p. 161. 



§ Science, xvi. (1903) pp. 991-3. 



|| Popular Science Monthly, 1903, p. 88. See Zool. Centralbl., xi. (1904) p. 16& 



II Comptes Rendus, cxxxviii. (1904) pp. 168-70. 



