HERMIT CRAB AND PELTOGASTER. 603 



per cent, are infested with a species of Peltogaster (P. curva- 

 tus, Kossmann). The same parasite is also found on E. 

 prideauxi, associated with E. meticulosus on the same 

 "•round and in almost equal numbers, but infected specimens 

 are very rare^ and in nearly a thousand crabs of this species 

 examined I could only find three with Peltogaster. 



Some hundreds of infected crabs of the former species were 

 examined with respect to the internal and external sexual 

 charactei's. It is quite easy to keep the animal in captivity, 

 and to observe that this differs from other cases of parasitic 

 influence in Crustacea in that the parasite does not completely 

 chock the general growth of the host after the moult, at which 

 it becomes external, and that under aquarium conditions 

 moults are fairly frequent. No exact comparison of the fre- 

 quency of moulting in infected and uninfected crabs are made, 

 but experience seemed to show that normal crabs did not 

 moult so frequently in captivity as infected. That castration 

 increases the rate of growth of animals is by no means a new 

 idea, and is put into practice in the rearing of stock and 

 poultry, and since E. meticulosus, at Naples, reproduces 

 the whole year round, it Avould appear most likely that a 

 relief from the reproductive functions would increase the 

 somatic growth. 



It is also interesting with regard to the general effect of 

 the parasitism to notice that infected crabs seem fully as 

 active and healthy as normal specimens. Though the internal 

 organs (for instance, the heart in its abdominal extension) 

 may be entirely enveloped by the enormous root system of 

 the Peltogaster, yet, with the exception of the gonads, they 

 do not appear to be affected by the parasitism. But even in 

 the period of the internus stage one finds the gonad reduced 

 in size, and the brown mature ova of the female giving place 

 to white ova with little yolk. In the male, however, sperm 

 production still occurs at this stage, and even for a time after 

 the commencement of the externus stage. The reduction in 



meticulosus. Probably then E. angulatus is only a variety of the last 

 named species. 



