604 F. A. POTTS. 



size of the gonad is first effected at the expense of the 

 glandular portion — the testis of an infected specimen con- 

 sists typically of a coiled duct with reproductive cells only 

 toward the termination, — and it is noticeable that the secretory 

 function of the duct is not checked, but even accelerated up 

 till an advanced stage of infection. The duct is at first filled 

 with irregular spermatophores, which may contain a reduced 

 number of spermatozoa, but at later stages, where the testis 

 is still clearly recognisable, the ducts present a swollen 

 appearance, and are filled with irregular and unequal masses 

 of chitin derived from the cells producing the dense cap- 

 part of the spermatophore (pi. 34, fig. 5, ch.). It was often 

 observable that the duct on the same side as the Peltogaster 

 presents this phenomenon in a greater degree. Perhaps the 

 excessive production of chitin in the male ducts and the 

 increased capacity for moulting may be closely related. 



With regard to the way in which the reduction of the gonad 

 is effected it should be said that though the Peltogaster roots 

 often completely enclose the gonads, in no stage of infection 

 was it shown by dissection or serial sections that they pene- 

 trated the bounding wall. That the parasite derives its 

 nourishment from the general body fluid rather than the 

 gonads, and hence that the effect on the latter is indirect and 

 effected through the general metabolism, seems conclusively 

 shown by the fact that though the parasite in the internal 

 stage proceeds to envelop first the gonad of the side where 

 it is destined to become external — and so must exercise a 

 more extended action on that gonad, — yet in the occasional 

 cases observed in which the aperture of one side had dis- 

 appeared, indicating entire and long-standing abortion of the 

 corresponding gland and duct, this had taken place on the 

 side opposite to the Peltogaster. This may be contrasted 

 with the case of Andrena parasitised by Stylops, worked out 

 by Perez and quoted by Giard, where the testis of the side on 

 which the parasite is situated, becomes non-functional, but 

 that of the other side continues to produce sperm. 



