156 Transactions of the Society. 



sexes seems enough to show that the dieting of the parent is not of 

 great importance. Schenk's notorious theory (1898) that the sex 

 of children could be adjusted by dieting the mothers, rested on 

 entirely insufficient evidence — a very small number of cases. 



In a statistical enquiry in London, Prof. Punnett found that 

 the proportion of males is lowest (99 ■ 5) in the poorest quarter 

 and highest (100*7) in the wealthiest, but he concluded that the 

 differences are due to differential infantile mortality, birth-rate, 

 and probably marriage-rate. 



33. Careful experiments have been made, e.g. by Cuenot and 

 Schultze, on the possible influence of the nutrition of the mam- 

 malian parent (e.g. mouse) on the sex of the offspring ; but the 

 results are all against the reality of this supposed influence, in 

 which, however, some breeders strongly believe. Schultze extended 

 his experiments over three generations, but the high feeding of 

 grandparents as well as parents did not seem to have any influence 

 on the proportion of the sexes among the offspring. 



Against these results, however, we have to balance the very 

 important work of Heape, who has brought forward evidence for 

 mammals and birds that peculiarities in nutrition and in other 

 environmental influences may exert a selective influence on the 

 germ-cells, affecting the proportion of male-producing and female- 

 producing gametes. "Through the medium of nutrition supplied 

 to the ovary, either by the quantity or the quality of that nutrition, 

 either by its direct effect upon the ovarian ova or by its indirect 

 effect, a variation in the proportion of the sexes of the ova pro- 

 duced, and therefore of the young born, is effected in all animals 

 in which the ripening of the ovarian ova is subject to selective 

 action." " When no selective action occurs in the ovary, the pro- 

 portion of the sexes of ovarian ova produced is governed by the 

 laws of heredity." 



34. As it seems to us, Eusso's recent experiments in feeding 

 rabbits with lecithin lend considerable support to the view that 

 the germ-cells may be pre-disposed to one sex or the other by the 

 nutritive condition of the parent, and to the view that the differ- 

 ence between the sexes is primarily a question of the rhythm of 

 metabolism. Eusso attaches much less importance to the chromo- 

 somes and much more importance to the nature of the metabolism 

 than do most biologists of to-day. He says, in so many words, 

 that he believes the sex of the offspring to depend on the special 

 metabolism of the germ-cells ; and he thinks he has succeeded in 

 artificially altering the metabolism of the ovarian ova, and thus 

 altering the normal proportions of the sexes. In the normal ovary 

 there are well-nourished and ill-nourished ova, and the proportion 

 of the former can be increased by lecithin treatment. 



Female rabbits fed (in various ways) with lecithin developed 

 large ovaries, large Graafian follicles, ova rich in nutritive material, 



