64 INTERNAL SECRETIONS 



by changes in the quantitative relations between the two 

 substances. 



A third explanation of the sexual inversion of the male 

 Inachus was attempted by Biedl (1913, p. 225). According 

 to him the Sacculina parasitic on the crab is always female, 

 and he thinks that there is in reality an influence exerted by the 

 female sexual gland of the parasite on its host. There is, 

 according to Biedl, not only parasitic castration, but also a 

 kind of transplantation of a heterosexual gland, a feminization 

 in the sense of Steinach. But Biedl' s suggestion is not justified 

 since Sacculina is hermaphrodite {Smith, 1906, pp. 19-33). 



In the first edition of this book I intimated that parasitic 

 castration in crabs involved something wholly different from 

 what has been observed in experimental castration in Arthro- 

 poda. I thought that the persistence of the sexual characters in 

 the moth after castration was an exception even in the group of 

 Arthropoda, and that no general conclusions could be drawn 

 from these experiments in regard to the relation between the 

 sexual characters and the gonads. But I see now that this con- 

 clusion is not justified, and I am inclined to accept in principle 

 the explanation of Smith. We have already mentioned that 

 only in 70 per cent, of the male and female Inachus in which the 

 external sexual characters changed, were the sexual glands 

 affected. Evidently the destruction of the sexual gland is not a 

 conditio sine qua non for the changes in the sexual characters. 

 Similar observations have been made by Potts on male shore 

 crabs infected by Sacculina; here certain female characters 

 appeared even when the castration was not a complete one. 

 The question has been recently studied also by Coiirrier (1921). 

 He examined 66 male Carcinus maenas infected by Sacculina. 

 In 46 cases the abdomen was female in appearance, but only 

 in four were the testicles absent. In most of the animals the 

 testicles were in full activity, athough they were a little 

 smaller than in normal crabs. It would be a mistake to think 

 that the changes in the sexual characters could be changed 

 by the testicular mass being diminished ; we know that minute 

 particles of a sexual gland can quantitatively replace the 

 normal testicular mass. 



On the other hand one might object to Smith's explanation 

 on the ground that female characters, as already mentioned, 

 often appear in the infected male without an ovary or an 



