212 E. A. BAUMGARTNER 



almost unknown. Although the formation of the anlagen of 

 the liver and pancreas has been investigated in almost ever}' 

 group of vertebrates, the later histor^^ of duct systems of these 

 structures has been quite neglected. The two exceptions to 

 this statement are furnished by the work of Corner ('13) who 

 investigated the development of the pancreatic ducts of the 

 pig by means of injection methods and Scammon's study of the 

 biliary system of selachians.^ 



The following study is an attempt to follow in detail the de- 

 velopment of these duct-systems in the tailed amphibia, and 

 to point out the embryologic significance of the principal varia- 

 tions which are encountered in the adult and the mechanical 

 influences which are, in part at least, responsible for them. 

 Although we are not as yet in possession of sufficient data to 

 formulate a statement of the typical vertebrate plan of biliary 

 and pancreatic duct-systems, it is hoped that this description 

 of these structures in a representative amphibian may add to 

 the material upon which such a schema must eventually be based. 



The material used for this work consisted of embryos of Am- 

 blystoma punctatum froin 4 nmi. to 20 cm. in length. These 

 were sectioned serially in transverse and sagittal planes. Graphic 

 and wax reconstructions were made of the hepatic ducts, gall- 

 bladder, liver and pancreas of different embryos and adults. 



It is a pleasure to express my thanks to Dr. Richard E. Scam- 

 mon for his constant interest and helpful criticisms throughout 

 this study. 



A correlation of the embryos employed in this study with 

 those described in the Normal Plates of Necturus maculosus 

 by Eycleshymer and Wilson may be desirable. This correla- 

 tion is based on a comparison of the digestive system including 

 liver and pancreas, as well as partially on the external form. 

 Probably the greatest difference in the de\'elopment of the 

 digestive tract between these two forms is in the time of union 

 of the dorsal and ventral pancreatic anlagen which had taken 



' The terms used by Scaininou ("lo) in (Icsciiiiing the ihicls of Ehismobraiichs 

 have been used in tliis i)a|)er. 



