MEMBRANES, OVARIES, AND OVIDUCTS OF SALMONOIDS. 20I 



tending toward the separation of the ureteric from the oviducal ducts, two terms of 

 which were presented by the ganoids, and the arrangement of the parts which obtain 

 in the ordinary Salmonidae a fourth term. Huxley stated as follows: 



Theabortionof the oviducts, commenced in Osmerus, is completed in Salmo, and all that remains 

 of the primitive arrangement is the fold described by Rathke and the so-culled abdominal pore, which, 

 it will be observed, is tlie homologue of half of the urogenital opening of the ganoids and has nothing to 

 do with the abdominal pores of these fish and of the selachians. 



He also says that, as is well known, Lepidosteus presents an example of a ganoid 

 with oviducts like those of the higher Teleostei; in Osmerus, on the other hand, we have 

 a teleostean with oviducts like those of the ordinary Ganoidei. It is tolerably obvious, 

 he continues, that, therefore, the characters of the female reproductive organs can lend 

 no support to any attempt to draw a sharp line of demarcation between the ganoids and 

 the teleosteans. 



Bridge (1904) distinguishes two types of genital ducts in fishes: (i) Those which 

 are obviously derived from some part of the kidney system; and (2) those which are 

 special ducts and appear to have no connection with kidney ducts. The elasmobranchs 

 offer a typical example of the first, and the Teleostei afford an equally typical example 

 of the other. Representatives of certain other orders, among which are Acipenser, 

 Polyodon, and Amia (Amiatus), are regarded as more or less transitional. 



Whatever may have been their embryological origin, it is quite clear that in the 

 adult teleost the ovaries and oviducts have no relation to organs other than that of 

 peritoneal attachment. These fishes, according to previously cited authorities, present 

 two types of ovaries, free and closed, and three oviducal adaptations, closed peritoneal 

 tubes, peritoneal funnels, and no oviducts at all except the ovipore. 



The closed ovary is said to develop in two ways from the genital ridge: (i) By the 

 upturning and attachment above of the lower edge of the genital ridge, thus infolding 

 the genital cells; and (2) by the formation of a groove on the surface of the ridge, the 

 genital cells becoming infolded by the conjunction of the two edges of the groove. 



The so-called free ovary, accordingly, was supposed to be formed by the genital 

 cells developing on the outer side of the ridge and the lower edge folding up only slightly 

 or not at all. 



In each instance of closed ovary the closed oviduct is formed by a backward exten- 

 sion of the ovarian peritoneal membrane, the process of its formation being somewhat 

 different, according to whether the ovary is of the upturning or groove development. 

 In either case an extension backward of the mesovarium is involved. In the case of the 

 free ovary, the oviduct, if any, is developed wholly from the backward extension of the 

 mesovarium. In the case of the closed ovary, according to Goodrich (1909), the oviduct 

 begins as a parovarial or endovarial channel blind in front. In the case of the free 

 ovary, if there fe any oviduct, it is said to begin as the wide mouth of a funnel near the 

 posterior end of the ovary or at some distance behind it. 



In the case of the ganoids previously mentioned, there is obviously a veritable 

 fimnel formed by the folding of the peritoneal membrane on itself, which is well exem- 

 plified by that of Amia (Amiatus), as shown by Huxley. 



According to the same authority, the smelt differs from the ganoids in having the 

 outer edge of the peritoneal fold attached to the abdominal wall, yet it is still called a 

 "funnel" and considered homologous with the oviducal funnels of ganoids. 



