SEA-FISHERIES LABORATORY. 291 



structure lying between, and anterior to the vitellaria, 

 and smaller than either of the latter glands. In none 

 of the specimens could I make out with certainty the 

 position and relations of a receptaculum seminis. 



The testes are two in number. They are rather 

 small, and not at all conspicuous in either living or 

 preserved specimens. The vasa deferentia cannot easily 

 be traced ; probably they are separate and unite quite 

 close to the seminal vesicle, or possibly enter the latter 

 independently. The cirrus and its accessory structures 

 lie all in front of the ventral sucker. The seminal 

 vesicle is small and oval in shape. From it the ductus 

 ejaculatorius passes straight forwards in the median line 

 as an apparently strongly muscular organ, terminating 

 in a prominent genital papilla which is situated imme- 

 diately behind the forking of the intestine. Throughout 

 all its length, between the seminal vesicle and the genital 

 papilla, the ductus ejaculatorius is surrounded by a very 

 voluminous prostate gland. 



In none of my specimens could the exact configura- 

 tions of the convolutions of the uterus be made out with 

 certainty. It is voluminous in most specimens and is 

 crowded with ova. These latter are thick-shelled and 

 slightly yellow or red in colour. The vagina and cirrus 

 both open into a common genital cloaca, situated at the 

 summit of the genital papilla. The opening of this 

 genital cloaca is in all my specimens A -shaped, or 

 crescentic, the apex of the V, or the convexity of the 

 crescent being directed forwards. 



Most of these characters would apply equally well 

 to Derogenes minor, Looss,* or to D. various (0. F. 

 Muller).t It is indeed rather difficult to make out 

 absolutely diagnostic differences between these two 

 species. D. minor was described by Looss from a 



