98 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



that of Aiubljstoma. Furthermore, the caudad migration of the posterior 

 evaginatioii and the method of carrying the opening of the Mlilleriau 

 duct forward again along a trough of columnar cells by a progressive 

 fusion of the edges of the trough, is exactly similar to what was seen in 

 Amblystoma. On the other hand, the fusion of nephrostomes allies the 

 development with that of Rana. As in Kana the fusion of all three 

 nephrostomes caused either a suppression or a combination of the Mlil- 

 leriau evaginations into one, so in Ilyla the fusion of two nephrostomes 

 reduces the number of evaginations to two. 



D. COMPAKISON WITH THE RESULTS OF OTHER AUTHORS. 



Perhaps the most satisfactory way to give an idea of the various 

 views which have been held in regard to the development of the 

 Miillerian duct in Amphibia is to give a brief resume of those accounts 

 which are most important, either from their completeness or the recent- 

 ness of their appearance. 



Urodela. 



Fiirbringer ('78) states that during the early stages in the degen- 

 eration of the pronephros of Salamandra maculosa — at the time when 

 the gills are disappearing — its glomerular cavity becomes more exten- 

 sively separated from the body cavity. Along the lateral margin of the 

 glomerular cavity the peritoneal epithelium becomes thickened. This 

 thickening spreads out laterally and " distally " (that is, caudad) from tlie 

 pronephros and forms a part of the fundament of the Miillerian duct. 

 At the same time, from the ventral side of that portion of the Wolffian 

 duct which is immediately posterior to the pronephros, a solid cord of 

 cells is cut off, which then gains a lumen and is transformed into a duct. 

 The hollowing-out process begins proximally (cephalad) and progresses 

 caudad. Its cephalic end then fuses with the thickening above de- 

 scribed, and through it opens into the body cavity to form the ostium 

 abdominale. Caudad the duct continues to be cut off from the Wolffian 

 duct and to become hollowed out. Its caudal end dwindles to a cord 

 and is lost in the ventral or lateral wall of the Wolffian duct. It may, 

 however, end free, with a blunt point, this condition being observed 

 but once. 



If the development in Salamandra is like that in Amblystoma, it would 

 seem that in the earlier stages Fiirbringer mistook for the Miillerian 

 duct the degenerating duct which i)asses backward from the first evagi- 

 nation. If he observed that the duct from the first evagiuatiou ended 



