368 TELEOSTEI 



ovarial part in connection with the ovary itself ; and a posterior part, 

 passing back behind to the pore. In the Anguilliformes the genital 

 ridge remains as a simple band, with ova on its outer side. In 

 many Teleosts, such as ItJiodeus, Gobio, Cobitis, Esox, Clupea, and the 

 Cyprinidae. this genital fold bends upwards and outwards, thus 

 fusing with the coelomic wall (Fig. 55, F), so as to form an ovarian 

 sac with a lateral ' parovarial ' canal, blind in front. Or there may 

 appear on the outer surface of the genital ridge itself a groove, 

 which folds round so as to form when closed up a central or 

 'entovarial' canal. The genital surface of the ovary so en- 

 closed may become much folded (Perca, Acerina, etc.). That the 

 parovarial and the entovarial ducts are not fundamentally distinct 

 seems clear ; moreover,~in Salmo the ovary is folded to form a par- 

 ovarial canal in front and a short open entovarial canal behind, 

 which is not produced backwards (Felix [136]). 



The posterior duct is formed by a backward growth of the wall 

 of the ovisac and of its lumen. There is no sharp distinction 

 between the two, but a gradual passage from the fertile wall of the 

 ovary to the sterile wall of the duct. In some fish, as Zoarces and 

 Cyclopterus, the ovary reaches to quite near the pore. 



As to the first question, whether the free ovary is primitive or 

 not in the Teleostei, Balfour inclined to the view that it is secondary, 

 since already in Lepidosteus there is a closed ovisac [30]. Brock, on 

 the other hand, holds it to be primary [60]. The sporadic occur- 

 rence of this character among Teleosts of different families is very 

 strong evidence in favour of Balfour's view that it is a return to 

 the primitive condition. Much more difficult is it to determine 

 the homology of the oviduct. Waldeyer and Semper held that it 

 represents the Miillerian duct of other Gnathostomes, the whole 

 ovary having been enclosed by the tube, in forms with a closed sac. 

 Rathke and others have held that the oviduct is entirely derived 

 from the ovary, the posterior portion being a backward prolongation. 

 Jungersen adopts Balfour's suggestion that the closed sac is formed 

 by a junction of an ovarian canal with the open mouth of a short 

 Miillerian duct. The free condition in Teleosts would be brought 

 about by the failure of these two structures to fuse. 



The oviducts and sperm-ducts are so similar in the Teleostei, 

 that they are generally considered to be homologous with each 

 other and not with the Miillerian duct. In Polypterus and Lepido- 

 steus the anterior region of the oviduct develops as a parovarial 

 canal, into which open, in early stages only, the mesonephric funnels 

 (Fig. 55). The comparison with the longitudinal duct of the male 

 is obvious (Budgett [68]). But the homology will not apply in the 

 case of the Chondrostei (Fig. 356, A), where (Miillerian ]) ducts with 

 open funnels exist in both sexes, and the male has a longitudinal 

 testicular canal as well (Hyrtl [233a], Semon [398]). 



