154 Transactions of the Society. 



The third form of the Mendelian interpretation is supported by 

 a number of very striking facts, especially in regard to the common 

 magpie-moth (Abraxas grossulariata) and the canary. Let us re-state 

 it very briefly. Assuming that there are sex-determinants of male- 

 ness and femaleness, the experimenters suggest (1) that these behave 

 as Mendelian units, femaleness being always dominant over male- 

 ness ; (2) that female individuals are heterozygous as regards sex 

 (having maleness recessive) and that they give rise to equal con- 

 tingents of male-producing and female-producing ova ; (3) that male 

 individuals are homozygous as regards sex, and give rise only to 

 male-producing spermatozoa ; (4) when a male-producing sper- 

 matozoon fertilizes a male-producing ovum the result is of course a 

 male ; when a male-producing spermatozoon fertilizes a female-pro- 

 ducing ovum the result is a female, femaleness being by hypothesis 

 dominant over maleness. 



29. Doncaster refers to the confirmation which the Mendelian 

 theory of sex receives from the results of castration. In Vertebrates 

 the castration of the male may prevent the expression of masculine 

 features, but it does not induce the expression of feminine characters. 

 This may mean that the male is homozygous. I would, however, 

 point out that in many cases there is a lack of positiveness in the 

 feminine characters ; the masculine characters are usually positive 

 and distinctive. In other words, a good deal of latent femininity 

 might express itself in the castrated male without there being much 

 to show for it. It would be extremely interesting, if feasible, to 

 experiment with some case like the Red-necked Phalarope, where 

 the female bird is the more masculine of the two. 



When a Vertebrate female is castrated, or when the ovary 

 atrophies, there is often a development of masculine characters. 

 Let me quote a striking case from Guthrie. A spae'd pullet may 

 acquire not only the outward structural features of the opposite 

 sex — cock's comb, wattles, long hackle and tail feathers, rapidly 

 developing spurs, carriage, etc. — but the behaviour as well and the 

 pugnacious character. 



It may be pointed out that these facts, while fitting in well with 

 the Mendelian interpretation that the female is heterozygous, also 

 bear out the general idea that every germ-cell carries with it a 

 complete inheritance of masculine and feminine characters, and 

 that it is the particular kind of metabolic rhythm set up that de- 

 termines maleness and femaleness, and, through this, or more 

 directly, affords the liberating stimuli for the masculine or feminine 

 characters. 



In Crustaceans the course of events is curiously the reverse of 

 what is true of Vertebrates. A female whose ovary has been 

 destroyed by a Rhizocephalous parasite has its secondary sex 

 characters reduced, but a castrated male assumes more or less com- 

 pletely the characters of the female. Perhaps the female characters 



