DEVELOPMENT OF LIVER AND PANCREAS 219 



Posterior to the anlage of the heart a sagittal section shows 

 a ventrally and somewhat caudally directed projection of the 

 gut-lumen, (fig. 1) which extends backward near the dorsal side of 

 the yolk-mass. The anterior wall of the ventrally directed exten- 

 sion of the gut-lumen is lined by yolk-laden columnar cells and 

 its posterior wall is formed by the cells of the large yolk-mass. 

 This cavity is quite wide transversely and is connected to the 

 gut-lumen above by a wide cleft. 



Fig. 1 Sagittal section of an Amblystoma embryo 4.5 mm. long taken at 

 about the median plane. X 30. F.g., foregut; He, heart; Li, liver; Y, yolk mass. 



Fig. 2 Sagittal section of an Amblystoma embryo 5 mm. long, taken to the 

 right of the median line. X 30. F.g., foregut; G, caudal extension of gut; He, 

 heart; Li, liver; Y, yolk mass. 



Weysse ('95) has described this cavity in frog as a cleft in the 

 ventral mass of yolk-cells, and Hammar ('97) has termed it 

 the 'Leberbucht.' From the study of a slightly more advanced 

 stage Weysse concluded that the caudal and ventral end of this 

 cleft finally formed a caudal hepatic duct. He correlated this 

 with the caudal hepatic duct described in the chick. That the 

 caudal projection does not form a caudal hepatic duct in amphibia 

 seems clear from a study of the later development. The reason 

 for this error was probably, as Hammar has pointed out, that 



