STRUCTURE AND DEVELOPMENTAL RATE 



237 



lowing closely behind the stomach, the canal buds off its most 

 striking secondary growth. This begins as an evagination follow- 

 ing rapid cell multiplication, the excessive growth becomes too 

 great to be longer retained by the wall and the liver pushes out, 

 always maintaining the original connection through the bile-duct, 

 its old stalk. This large liver bud generally contains some cells 



Fig. 32 A series of outlines indicating the primary linear, or cephalad, growth 

 of the foregut, and the subsequent lateral branches or outgrowths from it. A, 

 outlines the simple forward growths of entoderm to form the foregut. B, lateral 

 outgrowths have begun from the forward end to form the mandibular pouch. C, 

 a series of lateral branches, following the mandibular, now grow out to form the 

 hyoid and branchial pouches. 

 >l> 



not exactly of its own kind, and these later begin to increase and 

 again bud away from the wall of the bile-duct as the ventral pan- 

 creas. Other cells of a similar kind are left in the wall of the tube, 

 and these now grow^ out as the dorsal pancreas. This is the 

 behavior of the pancreas in higher forms, while in lower animals it 

 may arise from more than two separate buds or may fail entirely 

 to grow away from the tube, and remain as scattered masses of 



