154 TH E URINOGENITAL ORGANS OF VERTEBRATES. 



have generally, though not always, an opening or openings inde- 

 pendent of the ureter close behind the rectum, but no abdominal 

 pores are present. It seems, therefore, that in Osseous fish the 

 generative ducts are complementary to abdominal pores, which 

 might lead to the view that the generative ducts were formed 

 by a coalescence of the investment of the generative glands with 

 the short duct of abdominal pore. 



Against this view there are, however, the following facts : 



(1) In the cases of the salmon and the eel it is perfectly 

 true that the abdominal pore exactly corresponds with the 

 opening of the genital duct in other Osseous fishes, but the 

 absence of genital ducts in these cases must rather be viewed, 

 as Vogt and Pappenheim (loc. cit.) have already insisted, as a 

 case of degeneration than of a primitive condition. The pre- 

 sence of genital ducts in the near allies of the Salmonidae, and 

 even in the male salmon, are conclusive proofs of this. If we 

 admit that the presence of an abdominal pore in Salmonidae is 

 merely a result of degeneration, it obviously cannot be used as 

 an argument for the complementary nature of abdominal pores 

 and generative ducts. 



(2) Hyrtl (Denkschriften der k. Akad. Wien, Vol I.) states 

 that in Mormyrus oxyrynchus there is a pair of abdominal 

 pores in addition to true generative ducts. If his statements 

 are correct, we have a strong argument against the generative 

 ducts of Osseous fishes being related to abdominal pores. For 

 though this is the solitary instance of the presence of both a 

 genital opening and abdominal pores known to me in Osseous 

 fishes, yet we have no right to assume that the abdominal pores 

 of Mormyrus are not equivalent to those of Ganoids and Se- 

 lachians. It must be admitted, with Gegenbaur, that embry- 

 ology alone can elucidate the meaning of the genital ducts of 

 Osseous fishes. 



In Lepidosteus, as was before mentioned, the generative 

 ducts, though continuous with the investment of the genera- 

 tive bodies, unite with the ureters, and in this differ from the 

 generative ducts of Osseous fishes. The relation, indeed, of the 



which the seminal tubules open. I could find at the posterior end of the testis no 

 central cavity which could be distinguished from the cavity of this duct. 



