51 1 ANATOMY OF VERTEBRATES. 



Blenny (Zoarces), the Anableps, the Pceeilia, and Embiotoca 1 

 are examples of ovo-viviparous Osseous Fishes, and at the same 

 time manifest naturally, what occurs as a rare adnormality in 

 higher Vertebrates, viz. ovarian gestation. In the Plaice and 

 other Pleuronectidic the parallelism between the male and female 

 organs is so close that the ovaria also escape from the abdomen, 

 and become lodged in greater or less proportion in subcutaneous 

 scrotal cavities above the basis of the anal fin. 2 



In the Lamprey the short and narrow lateral infundibuliform 

 passages behind the rectum, into which the ureters open, and 

 which terminate in the peritoneal outlets, fig. 381, e, I, have been 

 compared to short oviducts. In the Sturgeon actual oviducts 

 are continued from the ureters forward, which open by wide 

 infundibular apertures, comparable to the ' morsus diaboli ' of 

 antliropotomy, into the general peritoneal cavity, and receive the 

 ripe ova as they burst from the ovarium. The urine is prevented 

 from regurgitation into the serous cavity through the same 

 passage by a valve which only allows the passage of the ova 

 backward into the common urogenital duct. 



The hio'her grade of the sexual organisation of the female 

 Plagiostome, as compared with the cartilaginous Ganoid fish, is 

 manifested chiefly by modification of the oviducts : they are 

 always two in number, fig. 384, q, r, and distinct from one end 

 to the other, but they are brought into close proximity, or 

 coalesce at both ends : they are always distinct from the ureters, 

 which terminate on the prominent urethral clitoris, ib. t, between 

 the oviducal outlets, ib. s, s. Different parts of the oviducts are 

 modified, moreover, for special functions, superadded to that of 

 effecting the safe transit of the generative product. The ovaria 

 of Plagiostomes, fig. 384, n, are relatively much smaller than in 

 other Fishes, of a more compact form, and confined to the fore 

 part of the abdominal cavity : they are sometimes blended into a 

 single body. The stroma is not spread over the walls of a cavity, 

 but is collected into a loose cellular mass, circumscribed by a 

 fibrous membrane, and suspended by a duplicature of peritoneum 

 to the dorsal parietes of the abdomen, at the sides of the 

 oesophagus. The ova are much fewer in number than in the 

 i roe ' of Osseous Fishes, and are seen in different stages of 

 growth, being developed more consecutively. The approximate 

 or confluent abdominal apertures of the oviduct, ib. q, are anterior 

 to the ovarium, between the liver and the pericardial septum ; 

 they form together a heart-shaped opening, with entire margins, 



1 CCCXXXV - XLIII. V. pi. 4, fig. 1. 



