DEVELOPMENT OF LIVER AND PANCREAS 241 



somewhat dorsally, the gall-bladder being distinctly to the right 

 of the midline. In figure 19 the larger of these two embryos the 

 cystic duct is not quite at the anterior end, but the cranio- 

 caudal length of the gall-bladder is distinctly greater. The 

 general direction of the cystic duct is the same. The gall- 

 bladder is relatively as far caudally here as the one shown in 

 figure 18. From the connection of the cystic duct to the gall- 

 bladder, it appears that there has been a marked growth 

 cranialward. 



In an embryo 14 mm. (fig. 39) long the gall-bladder has 

 decidedly increased in its cranio-caudal diameter. In trans- 

 verse section it is almost circular. The cystic duct is of very 

 small diameter as compared with its earlier size. It projects 

 now somewhat upward but almost directly to the left, due to 

 the increased lateral shifting of the liver and the gall-bladder. 

 In this embryo the cystic duct is attached to the extreme ante- 

 rior dorsal end of the gall-bladder. 



Figure 41 is of a model of a 13.5 mm. embryo. In this the 

 general shape of the gall-bladder is the same as of the one just 

 described, except that there is a slight increase in the vertical 

 diameter (fig. 9). The cystic duct, however, is not attached 

 at the extreme anterior end but to the left upper side. It ex- 

 tends towards the left as before but is now almost horizontal. 



In a 15 mm. embryo the attachment of cystic duct to the 

 gall-bladder is further caudalward than the previous one (fig. 

 42). This seems to mark the limit in its caudal attachment for 

 all sizes examined. It would be difficult to say whether this 

 shifting in attachment of the duct to the gall-bladder were due 

 to a difference in the antero-posterior growth of the gall-bladder 

 or to the rapidity of differentiation and growth of hepatic ducts. 

 The cystic duct in this embryo extends toward the left, but 

 now slightly ventrally, which can be taken as evidence of con- 

 tinued rotation to the right and dorsalward of the entire biliary 

 apparatus (fig. 10). 



Marshall ('93) has described the gall-bladder of amphibians 

 developing as a lateral outgrowth from the bile ducts. From 



