Basis of Sex Determination 217 



Carcinus mcBnas by the form of the abdomen, but when 

 a male is attacked by the parasite its abdomen assumes 

 the female shape. Smith observed in another crab 

 that in such cases even the abdominal appendages of the 

 male may be transformed into those of a female. The 

 transformation is so complete that the older observers 

 had reached the conclusion that the parasite attacked 

 only the females, since they overlooked the fact that 

 the castration by the parasite transformed the sec- 

 ondary sexual characters of the male into those of a 

 female. 



Giard observed that in a dioecious plant, Lychnis 

 dioica, a parasitic fungus brings about the transfor- 

 mation of the host into a hermaphrodite. 



G. Smith has discovered a fact which shows that 

 chemical changes must underlie these morphological 

 transformations of primary or secondary sexual char- 

 acters. He noticed that in male crabs the presence of 

 the parasite Sacculina changes the contents of the 

 fatty constituents in the blood, making them equal 

 to that of the female. Vaney and Meignon had pre- 

 viously shown that during the chrysalid stage the female 

 silkworms have always more glycogen and less fat than 

 the males. The castration by parasites is paralleled 

 by what Caullery calls the castration by senility. ' 

 In certain birds and also in mammals at the time when 

 the sexual glands cease to function certain secondary 

 'Caullery, M,, Les Problemes de la Sexualite. Paris, 1913. 



