218 E. A. BAUMGARTNER 



He has described a bile-duct which lies free in the body-cavity 

 for a short distance and then enters the pancreas which lies 

 between the liver and the intestine. Here it is joined by two 

 hepatic ducts and just as this enters the intestine it is joined 

 by two other hepatic ducts. 



To summarize briefly, the early investigators described the 

 liver and pancreas as developing at the same time from the 

 ventral wall of the gut, and also considered that they were parts 

 or lobes of the same organ. Remak ('55) first noted that the 

 liver is separate and distinct from the pancreas. Goette first 

 gave a detailed account of the development of the liver in am- 

 phibia. Most of the investigators from that time have agreed 

 that the liver begins as a single ventral outpouching of the gut- 

 wall caudal to the heart. The question as to the origin of the 

 gall-bladder, whether from the caudal end of the ductus chole- 

 dochus or from the wall of the intestine in this region may be, 

 as Piper ('02) stated, one of interpretation rather than one of 

 observation. Whether the hepatic cylinders divide and the 

 blood-capillaries then grow between them, or whether the capil- 

 laries grow into the solid hepatic anlage so forming hepatic cyl- 

 inders seems not to have been definitely determined. Shore's 

 ('91) observations support the latter theory. According to 

 the observations of Weysse and others the yolk-cells are trans- 

 formed directly into hepatic cells. Very little has been written 

 about the development of the hepatic ducts. The common 

 bile-duct is described as the constricted attachment of the 

 hepatic anlage, or the posterior end of the hepatic outpouching. 



2. Early development of the liver 



The liver in Amblystoma first appears in embryos about 

 4.5 mm. in length, which corresponds roughly to no. 21 of Keibel's 

 Normal-plate series. The digestive tract at this stage is quite 

 simple. The pharyngeal cavity is large and extends anteriorly 

 to the oral cavity. Caudally it opens widely into the mesenteron 

 which is composed of a large mass of yolk-cells and extends 

 backward to the proctodaeum. The yolk-mass extends dorsally 

 to the notochord and bulges ventrally. 



