614 F. A. POTTS. 



Effect of the Parasite on the Cellular Chaeactee op 

 THE Gonad. 



A large namber of testes of infected males have been ex 

 amined by sections, showing a very curious cytological change 

 of a widespread nature. This is the appearance of small but 

 distinct ova-like cells in the glandular part of the testes 

 (pi. 34, figs. 4, 5, ovi, oug). They may be followed in their 

 development from spermatocytes by the enlargement of the 

 nucleus, the appearance of a single large and distinct nucle- 

 olus, and the loosening of the chromatic network, together 

 with the aggregation of cytoplasm round the nucleus. This 

 phenomenon may occur while sperm production, though in 

 diminished activity, is still proceeding in other parts of the 

 testes (pi. 34, fig. 5). A very large number of infected males 

 with external Peltogasters exhibit it, and it seems likely that 

 all of them, when a certain period of infection was reached, 

 would be capable of producing ova in their testes. As to the 

 period of appearance it is impossible to be sure ; but in the 

 only male I found, with an internal stage of Peltogaster, 

 spermatogenesis was but slightly checked, and there was no 

 sign of the appearance of female cells. But though in the 

 majority of infected crabs with small just external Pelto- 

 gasters the testis was of normal character, in one or two I 

 found signs of incipient change on sectioning. Probably 

 there is much individual variation in this particular, though 

 the variability of the organism is much more clearly demon- 

 strated in the reaction of the secondary sexual characters to 

 the parasitic stimulus. 



It must not be forgotten that the occurrence of ova is a 

 phenomenon of normal occurrence in the testes of various 

 animals, such as, for instance, Orchestia and Homarus among 

 Crustacea, in Phalangids, and in the toad. A number of 

 normal testes of Eupagurus were examined, but without 

 finding that it could be added to the above list. 



With the object of ascertaining whether this apparently 



