kidney. 



ductuli efferentes 



.ovary 



^coelomic funnel 

 seen through 

 mesovorium 



-coelomic oviduct 



expanded (bladder) nephric duct 



n n 



_ovary turned away 

 from body wall 



. urinary bladder 

 _coelomic funnel 



-coelomic oviduct 



/ cross section shown in 



Figure 10-47 



A MALE B FEMALE 



POLYPTERUS 



C MALE 

 ACIPENSER 



D FEMALE 

 POLYODON 



Figure 10-45. Reproductive systems of Po/ypterus, A and B; mole of Acipenser, C, and female of 

 Po/yodon, D, as seen in ventral view. (A and B after van den Broek, 1938) 



is certain that the anterior part of the oviduct is a chamber 

 of the coelom closed off by a peritoneal fold between the 

 body wall and the genital fold. The peritoneal funnels of 

 the margin of the opisthonephros open into this space. The 

 posterior termination of this space lies in contact with the 

 nephric duct and at maturity opens into that duct (Figure 

 10-47). It has usually been assumed that this coelomic tube 

 grows posteriorly through the tissue underlying the nephric 

 duct and that this extension represents the Miillerian duct. 

 The position in which the oviduct opens into the nephric 

 duct does not suggest any such posterior growth; the entire 

 tube can be considered as coelomic in origin. 



Balfour and Parker (1882) have argued the pros and cons 

 of considering this tube a new structure or a modification, 

 at least in part, of the Miillerian duct. The greatest diffi- 

 culty is to account for the acquisition of an opening between 

 this coelomic funnel and the nephric duct. A possible solu- 



tion would be the enlargement of a peritoneal funnel within 

 this coelomic duct. Direct opening of such a funnel into the 

 nephric duct seems improbable. The problem becomes a 

 more general one in view of the evidence of the parovarial 

 and endovarial ducts opening through the body wall be- 

 tween the anus and the excretory pore. There is some sort 

 of developmental factor here which is not as yet understood. 

 It appears certain, however, that no actinopterygian has 

 any remnant of the Miillerian duct. 



The fact that Polypterus, Aapenser. and Amia share the 

 coelomic type of oviduct suggests that this type is more 

 primitive than the completely parovarial system of Lepisos- 

 teus. The endovarial and parovarial systems of teleosts, in 

 which peritoneal funnels are always lacking, would appear 

 to be modifications of the Lepisosleus system, achieved by a 

 gradual shift from the parovarial type to the endovarial. The 

 oviduct becomes a posterior outgrowth of the ovocoel, which 



332 



THE UROGENITAL SYSTEM 



