618 \)V, GREGG WILSON ON 



Mullerian duct, while the other ends close to the anterior attachment of the liver. It 

 is noteworthy that the ventral extension of the anterior plate passes posteriorly across 

 the secondary bridge, connecting the alimentary tract and the lateral body-wall, and 

 comes to project freely into the coelom from near the base of the lung. 



The Mullerian Ducts of Chelone. 



As 1 mentioned above, the development of the Mullerian ducts of Chelone has been 

 investigated by Professor Wiedersheim. He describes, in a 13 mm. embryo, a well- 

 marked proliferation of the peritoneal epithelium on the side of the anterior region of 

 the mesonephros. This extends to the parietal peritoneum. The formerly smooth 

 surface has become rough and uneven, a.nd in numerous places involution of the epi- 

 thelium is visible, and proliferation inwards. In an embryo of 21 mm. the inequalities 

 have, for the most part, disappeared, and in their place there is a rapidly increasing fold 

 hanging into the body-cavity. This fold, according to Wiedersheim, hangs down the 

 side of the mesonephros, is applied to it, and fuses with it ; and so the ostium ah- 

 dominale is formed. Three sections further towards the posterior the duct stops, and 

 is followed by a solid pointed rod, such as occurs at the growing tip of the foundation 

 in the crocodile. As in the case of the crocodile, this solid rod lies in the immediate 

 neighbourhood of the mesonephric duct and of the Tubenfalte. In the rod, a few 

 sections posterior to the ostium, a slight lumen appears. 



As to backward growth, Wiedersheim asserts that there is not merely appositional 

 growth, such as is generally described for Amniota. He figures two sections, showing 

 proliferation inwards of the thickened epithelium of the Tubenfalte ; and he believes that 

 the ectilomic epithelium thus contributes directly to the backward growth of the foundation. 



By the kindness of Professor Wiedersheim, in whose laboratory much of the work 

 recorded in this paper was done, I have had an opportunity of examining a number of series 

 of sections of embryos of Chelone ; and I shall now state the facts that I have observed. 



In an embryo (A) of 13 mm. in length, there is a lateral thickening of the coelomic 

 epithelium lining the anterior diverticulum, and extending on to the excretory organ ; 

 along which it passes, as described by Wiedersheim. 



A specimen (B), 21 mm. long, shows the lateral thickening to be undermined 

 anteriorly (fig. 12). Further back, the plate is divided, as in the case of the crocodile 

 by the breaking down of the partition between the two diverticula (fig. 13). One 

 remnant of the thickening projects into the ccelom from the ventral body-wall ; another 

 is intimately connected with the mesonephros (fig. 14). In the posterior extension of 

 the plate that passes along the mesonephros there is a funnel-like pit (fig. 15). This 

 conical funnel is the ostium ahdominale tubal. It is quite distinct from the meso- 

 nephric duct, and its inner pointed end, which extends a very short distance towards the 

 posterior, is quite independent of the epithelial thickening that continues back external 

 to the mesonephric duct. 



