RESULTS OF CASTRATION 67 



It seems after all unjustifiable to explain the changes caused 

 by the parasite by destruction of the sexual glands. The 

 inversion of the male towards the female type in the infected 

 Arthropoda must be caused directly by the parasite, and 

 does not necessarily bear any relation to the influence which 

 the parasite has on the sexual gland. 



This is further evidence of the fact that the sexual characters 

 are independent of the sexual glands in the Arthropoda. 



F. THE RESULTS OF CASTRATION IN OTHER 

 INVERTEBRATA. 



We may begin by referring to the parasitic castration of the 

 earthworm. This animal has normally an hermaphrodite gonad 

 and somatic sexual characters of both sexes. Now Sottas (1911) 

 observed in Lumhricus herctdeus a destruction of the male 

 part of the gonad caused by bacterial parasites; the pouches 

 in which the testicles are normally to be found are empty in 

 many infected animals, whereas the ovaries remain normal. 

 The clitellum disappears in such infected animals. The 

 €litellum is an organ consisting of thickened skin near the 

 sexual pores with glands secreting a sticky substance facili- 

 tating adherence during copulation; the clitellum increases 

 in size during the breeding season and decreases afterwards. 

 In animals in which the male part of the gonad was 

 destroyed the vesiculae seminales were sometimes found to 

 be smaller. In those animals in which the degeneration of the 

 vesiculae was most pronounced, alterations of the vas deferens 

 and of the genital bristles were also present. In some 

 places where infected w^orms were found, about half of the 

 individuals were without a chtellum. 



We see that in the earthworm many of the male sexual 

 characters are controlled by the male gonad. But the question 

 arises whether we have here a dependence of seasonal changes 

 only upon the gonad as in amphibians or also a dependence of 

 the sexual characters in general as in mammals and birds. 

 This question cannot yet be answered. 



Another peculiarity is of the greatest interest. The observa- 

 tions of Sollas show that the ovary which remains intact in the 



