120 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



coalescence of the folded edges. This tube, the MuUerian duct, soon 

 ends blindly in close proximity to the peritoneum. The latter does not, 

 however, contribute cells to the growing duct. The ostium seems thus 

 to be formed entirely from one Miillerian evagination, but from both the 

 description and figures of Brauer (compare especially Fig. 145, Taf. 9) 

 there is no doubt in my mind that several other evagiuations in a degen- 

 erate condition are present posterior to the chief one. Such an interpre- 

 tation of the structures in question occurred to Brauer himself, for he 

 says in describing them (page 140) : " Weiter caudalwarts" (referring 

 to the permanent ostial evagination) " erkennt man zwar noch erhotes 

 Epithel, auch, wenn auch unregelmiissig, scheinbare Anfange von einer 

 Faltenbildung, so dass der Anschein erweckt wird, als ob das Pei'itoneal- 

 epithel in aluilicher Weise wie zur Bildung der Tube sich rimienformig 

 einsenl<e." One other similarity to the development of the duct in 

 Amblystoma consists in a caudad transference of the ostium from its 

 original position on the anterior half of the pronephros to one at tlie 

 anterior end of the mesonephros. In Amblystoma the caudad migration 

 is not so great and is seen in the ^Miillerian evagination, not in tlic adult 

 ostium. 



June, 1902. 



