HERMIT CRAB AND PBLTOG ASTER. 615 



hermaphrodite state of the gonad of the infected male is 

 merely transient^ or persists on the removal of the parasite 

 and the recovery of the host, from a large number of infected 

 crabs of both sexes, the external part of the Peltogaster was 

 removed, cut off with scissors as close to the crab's abdomen 

 as possible. As mentioned above, the operated animals, 

 which were fed regularly, soon became quite healthy and 

 moulted very frequently. They were kept for various periods, 

 varying from two to five months, but up till the time of 

 writing no crabs had so far recovered as to completely 

 regenerate the gonad. It is difficult in most cases to prove 

 that the gonads increase in size at all, but in one of the 

 crabs of problematical sex (in which the gonad, if present, is 

 of very small size), when two months had elapsed after re- 

 moval of its Peltogaster, a fairly large sized ovary with eggs 

 approaching maturity was found. From this fact and others 

 it appears certain that a slow regeneration of the gonad does 

 take place. How slow this regeneration is may be judged 

 from the evidence of a crab once infected, but which was 

 found naturally freed from its Peltogaster. Though, in the 

 few other crabs of the kind which were found, the experience 

 appeared to have been recently undergone, this one, a slightly 

 modified male, preserved no trace of the Peltogaster ex- 

 ternally, indicating that several moults must have occurred, 

 enabling it to lose the scar of the Peltogaster. On dissection, 

 the roots, though degenerate, were found, but the gonad of 

 the host, in spite of the presumably extended period since 

 the loss of the parasite, was still very small, though showing 

 some signs of regeneration. 



With regard to the question whether the egg cells, which 

 appear during the period of activity of the parasite, are 

 resorbed when the influence is removed, or whether, with 

 recovery of the gonad, they grow and become functional ova, 

 there is some little evidence to be cited from a histological 

 study of the testes of operated crabs. In nearly all those, 

 sectioned ova were still present, and in one case at least 

 seemed to have attained a greater size than had been ob- 



