216 E. A. BAUMGARTNER 



teron. The anterior wall of this depression is thrown into 

 folds, blood-vessels penetrate between these structures and 

 outgrowths from the hypoblast form the hepatic cylinders. 



Weysse ('95) found in the frog that the liver-anlage is a dorso- 

 ventral cleft extending into the yolk-mass from the gut lumen. 

 A caudal extension of this cleft forms the posterior hepatic 

 duct, while the cranial hepatic duct is formed by a folding of 

 the anterior wall of the hepatic anlage. The yolk-cells are 

 transformed into the true hepatic cells and can be early recog- 

 nized by the deposit of pigment within them. 



Hertwig ('96) and Kollman ('98) gave only short descriptions, 

 stating that in Amphibia the hepatic anlage is a single out- 

 pouching from the ventral wall of the duodenum. 



Hammar ('97) who worked on the development of the frog's 

 liver, has named the entodermal cell-mass posterior to the 

 heart the 'Leberprominenz.' Into this extends an early length- 

 ening cavity which is continuous with the lumen of the gut. 

 This he termed the 'Leberbucht.' By a cranio-caudal con- 

 striction this hepatic anlage is separated from the gut. The 

 cell-mass about the fundus of this anteriorly directed sac develops 

 into trabeculae of the adult organ and the posterior part forms 

 the ductus choledochus. The gall-bladder is developed very 

 early as a diverticulum of the ventral wall of the common bile 

 duct, and by further growth comes to be a pedunculated organ, 

 consisting of a cystic duct and gall-bladder proper. He re- 

 garded the origin of the trabeculae as perhaps due partially to 

 the developing capillary network tunnelling into the hepatic 

 cell mass as suggested by Shore. 



Choronshitzky ('00) showed the anlage of the liver in the sala- 

 mander in a figure of a sagittal section of a 9 mm. embryo, in 

 which there is a ventral fold in the wall of the foregut. This 

 fold is lined with yolk-laden cylindrical cells which posteriorly 

 pass gradually over into the polygonal yolk-cells which form 

 a mass projecting into the lumen of the gut. In the anterior 

 ventral wall of the gut is a second slight pouch which later 

 forms the gall-bladder. The two omphalo-mesenteric veins 

 crowd in on either side of the liver outpouching, thereby aid- 



