INHERITANCE OF SEX 261 



extend root-like throughout the body. The parasite 

 may kill the crab ; if it fails to do this, and the crab 

 recovers, the effects which it produces are sufficiently 

 profound. The internal root-like part attacks the 

 genital organs and destroys them. If the crab 

 recovers the genital organs are regenerated. What 

 is remarkable about the case is that the effect differs 

 according to the sex of the crab affected. If it is 

 a female that was affected very little effect beyond 

 such a slight diminution in the size of her filamentous 

 limbs as could be attributed to the shock of the 

 infection and strain of recovery is observed when 

 she has recovered. 



But if it was a male that was affected, the changes 

 brought about are very much more profound, and of a 

 very remarkable nature. They consist not only in 

 the assumption by the male of the external features, 

 already described, which distinguish the female, but 

 in the actual development by him, in the place of 

 the destroyed testis, of a genital organ which contains 

 eggs. The pincers of the male lose their robustness 

 and become reduced to the size characteristic of the 

 female. So do the copulatory appendages. This 

 change might, however, be ascribed to shock and 

 general debility consequent on it ; but the other two 

 changes which occur cannot be so interpreted. Not 

 only does the abdomen lose the pointed shape charac- 

 teristic of the male, but it actually develops the long 

 filamentous swimmerets characteristic of the female. 



In a word, this parasite is capable of making a 

 male crab undergo a series of changes which, in bad 



