360 COMPARATIVE ANATOMY 



other Vertebrates, they are originally paired. There is usually a 

 want of symmetry observable between the organ of the right and 

 left sides. 



The testes and ovaries of Teleostei closely correspond \yith one 

 another as regards position and the arrangement of their ducts. 

 Dorsal and ventral folds of the peritoneum are developed in con- 

 nection with the elongated ovary, and these in most cases meet 

 along its outer side, so as to enclose a portion of the coelome and 

 thus convert the ovary into a hollow sac, blind anteriorly, 

 on the inner folded walls of which the ova arise ; this sac is 

 continued backwards to form the oviduct (compare Fig. 286). The 

 latter, which is generally short, as a rule fuses with its fellow to 

 form an unpaired canal; this opens either by a genital pore 

 (p. 298) between the rectum and the urinary aperture on a level 

 with the integument, or on a papilla, which may become elongated 

 to form a tube or " ovipositor " ; or the ducts may communicate 

 with a urinogenital sinus. 



The testis of Teleosts is elongated, and often lobulated in form. 

 Its duct has similar relations to those seen in the female. 



Thus the ducts, both of the ovary and testis, correspond to folds 

 of the peritoneum enclosing a coelomic cavity continuous with that 

 of the gonads, and originate quite independently of the nephridial 

 system. The oviducts must therefore be distinguished from true 

 Mlillerian ducts. 



In some Teleosts the ovary is solid, and the ova are shed into 

 the body-cavity. In the Smelt (Osmerus) and in Mallotus the 

 oviducts (" peritoneal funnels ") have open coelomic apertures close 

 to the ovaries into which the ova pass (compare Fig. 286, B) ; whUe 

 in other Salmonidse and in the MurEenidffi and Cobitis, for 

 instance, these peritoneal funnels are shorter, and may even be 

 absent, the ova then being shed into the urinogenital sinus 

 through a paired or single genital pore. It is uncertain whether 

 the latter is the primitive arrangement amongst Teleostei, or 

 whether the peritoneal funnels represent reduced oviducts. 



Most Teleostei are oviparous, but viviparous forms occur (p. .336). The 

 male Stickeback builds a nest for the protection of the young formed of a 

 hardened secretion (mucm) of the kidney, which undergoes a change of 

 function at the breeding-season ; in Syngnathus and Hippocampus the young 

 are protected within a pouch on the abdomen of the male, and in the female 

 Solenostoma on a pouch between the ventral fins. Amongst Siluroids they 

 are carried within the pharynx in the male Arius, and the eggs are attached 

 to the .soft ventral integument in the female Aspredo. 



Amongst G-anoidei the female organs of Lepidosteus are formed 

 on the same type as those of the Teleostei. In Amia (Fig. 

 286, b) and Acipenser each oviduct opens by a funnel into the 

 coelome, but in all Ganoids the oviduct is probably comparable to 

 that of Teleosts, and not to a Mlillerian duct. In the male 

 Lepidosteus a series of vasa efferentia pass out from the testis and 



