102 BULLETIN: MUSEUM OF COMrARATIVE ZOOLOGY. 



pletely functional and before its glomus has become enclosed in a glo- 

 merular cavity. At this stage the fundament appears as a thickening of 

 the peritoneal epithelium lateral (morphologically ventral) to the second 

 nephrostome. This thickening is reinforced by connective tissue, so 

 that there is formed a pad which becomes a groove, probably by an 

 evagination of the epithelium. The floor of the groove is continued as 

 a solid cord extending caudad a short distance between the Wolffian duct 

 and the peritoneum and imJependent of both. In sliglitly older larvae 

 the peritoneal thickening also stretches caudad as a narrow welt (the 

 oviducal welt) which indicates the path along which the MUllerian duct 

 develops, but which does not contribute cells to the groicimj duct. The 

 Mlillerian duct develops from the cord described above. Tlie groove is 

 the fundament of the ostium. Immediately anterior to the mesonephros 

 the cord fuses indistinguishably with the Wolfhan duct, and in its fur- 

 ther growth the posterior end is always represented by a thickening of 

 the ventral side of that duct. As this growth proceeds, the proximal por- 

 tion separates from the "Wolffian duct, and receives a connective sheath 

 of its own. The lumen of the duct appears as a prolongation of the 

 lumen of the groove and progresses regularly caudad. Gemmill be- 

 lieves that the growth of the duct is brought about by a multiplication 

 of its own cells with the addition of cells from the W^olffian duct. The 

 ostium he considers as absolutely independent of the pronephric nephro- 

 stomes, and holds that the Mlillerian duct cannot therefore be considered 

 as representing in any way a duct of the pronephros. Aside from the 

 lack of an}'' mention of an anterior evagination and a cephalic displace- 

 ment of the ostium, Genimill's description is in close agreement with my 

 own. The fact that I had not seen his paper until after my description 

 of the oviducal development in Amblystoma, Rana, and Hyla was com- 

 pleted makes this agreement the more satisfactory to me. 



Gymnophiona. 



The fundament of the Mlillerian duct is, according to Semon ('92), 

 very simple in Ichthyophis, and entirely different from that of the 

 higher Amphibia. It arises entirely independent of pronephros or its 

 duct, from a thickening of the peritoneum. This thickening extends 

 two or three segments anterior to the pronephros, and from it the 

 ostium is formed — sometimes on a level with the pronephros, gener- 

 ally somewhat anterior to it — by the fusion of the edges of a groove 

 which exists in the thickening. The lumen of the ostium is continued 

 back for a short distance in the form of a tube which loses itself in the 



