[ 





- PRONEPHRIC 



DUCT GIVES 



ORIGIN TO 



MESONEPHRIC 



DUCT 



MULLERIAN 

 DUCT ARISES BY 

 LONGITUDINAL 

 SPLITTINGOF 

 PRONEPHRIC 

 DUCT 



MULLERIAN DUCT ARISES 

 FROM THREE COELOMIC 

 INVAGINATIONS NEAR 

 PRONEPHRIC FUNNELS; 

 CAUDAL END GROWS 

 BACKWARD TO CLOACA 



VASA 



EFFERENTIA 



(MESONEPHRIC 



TUBULES) 



RENAL 



PORTION OF 



OPISTHONEPHRIC 



KIDNEY 



SPERM SAC 



POSSIBLY SOME 

 CONTRIBUTIONS FROM 

 WOLFFIAN DUCT TO 

 MULLERIAN DUCT IN 



URODELES 



* PRONEPHRIC 



(MESONEPHRIC) 



DUCT 



DUCT OF LEYDIG = 



SPERM DUCT PLUS 



MFSONFPHHir / URINARY DUCT. IT 



TUBULES FORM THEREFORE REPRESENTS 



TESTIS- MESONEPh"r,c a specialized 



DuIt CoSnIcVioS I .^.^-"-E. . QF_ WOLFFI 



B-2 



NDIFFERENT 

 CONDITION 



Fig. 351. Development of the reproductive and urinary ducts in vertebrates. (A-1 

 to A-4) Development of the reproductive ducts in Squalus acanthias. In A-2 the origin 

 of the ostial funnel or coelomic opening of the oviduct is presented as a derivative of 

 the opening of one or more pronephric tubules into the coelomic cavity. In fig. A-3, 

 the urinary or opisthonephric duct is independent of the mesonephric (pronephric) duct 

 which now is the vas deferens. The opisthonephric duct appears to take its origin as an 

 evagination from the caudal end of the original pronephric duct. (B-1 to B-4) Devel- 

 opment of the reproductive ducts in the frog. B-1 is adapted from data given by Hall, 

 1904, Bull. Mus. Comp. Zool. at Harvard College, vol. 45. (C-1 to C-7) Development 

 of the reproductive and urinary ducts in mammals. The Miillerian duct arises as an 

 invagination of the coelomic epithelium at the anterior end of the mesonephric kidney. 

 (See fig. 35 ID.) Once its formation is initiated, it grows caudalward along the pronephric 



{Continued on facing page.) 



798 



