HEREDITY AXD SEX 129 



Cliampy has recorded the gradual traasformation of tlie external 

 sex characters of the male newt (Triton cristata) intcj female 

 ones as a result of abnormal nutritive conditions. The gonads 

 also changed. Crew has described a most interesting instance 

 of sex reversal in a frog which changed from a fully functional 

 female to a fully functional male. In the latter condition 

 the frog copulated with females and had 774 offspring, 

 and it is especially noteworthy that every one of these was a 

 female. This is believed to have been due to the frog, wliich 

 started as a female, having a female chromosome coastitution. 

 Julian Huxley, in referring to certain very unusual sex ratios 

 in the young of the millions fish (Girardinus jjcecil/jides), is 

 disposed to explain these as due to sex reversal on the part of one 

 of the parents in the same kind of way as occurred with the frog 

 observed by Crew. 



Intersex uality is very common among iiLsects and other 

 arthropods. It has been recorded by Sexton and Julian Huxley 

 in Gammarus, by Keilin and Xuttall in lice, and notably by 

 Goldschmidt in the gypsy moth. As further proof of the existence 

 in the same individual of the potentialities of both, sexes, the 

 phenomena of " parasitic castration " may be cited. Giard was 

 the first to observ^e that in certain male crabs {e.g. Steru/rhyrtchm) 

 affected by other Crustacea parasitic upon them, not only were 

 the gonads destroyed, but the host assumed some of the character- 

 istics of the female. It was afterwards found by Smith and 

 Potts that in alhed genera {Iruichus, Peltogaster) the "parasitised" 

 male crabs developed egg-bearing appendages on the abdomen 

 like those of the normal female and afterwards produced eggs. 

 The testis, therefore, changed into an ovary. " Parasitic castra- 

 tion," therefore, is really sex reversal. It is remarkable, however, 

 that in this case the metabolism changed first, fat and lutein 

 being formed as in the female, while the glycogenic function, 

 which is more characteristic of the male, was depressed. Smith 

 concluded that the parasite acted upon the male host as the 

 ovary does in the female and called forth fat production, whereby 

 the normal female individual is able to withstand the drain on 

 the system incurred by egg formation, and this condition having 

 been brought into existence, stimulated the sexually indifferent 

 germ cells to develop after the manner of the female. Courrier 

 has lately shown that when the male of the common shore crab 



