482 



The Embryology of Hylodes Martinicensis 



IV, folds are formed in the anterior or more strictly speaking dorsal wall 

 of the diverticulum, in that portion of the diverticulum which lies nearest 

 to the archenteron and immediately posterior to the heart. The liver 

 develops from the folds and the lumen of the more anterior part of the 

 diverticulum becomes obliterated. With the mesoderm covering the 

 folds, blood-vessels are carried into the substance of the liver, and be- 

 tween the two deepest folds runs a large vitelline vein, which leads directly 

 into the posterior end of the heart (see horizontal section of stage IV, Fig. 

 Gl, rl, vv) . The heart through several stages, abuts against the anterior 



pcv 



© 



hk 



vv 



hk 



a 



'^-~ 



pcy 



I u 



■S 



Fig. G. 1, horizontal section of stage IV; 3, cross section of stage V. ao, aorta; g, gut; 

 gl, glomus; hk, head-kidney; ne, nephrostome; rl, rudiment of liver; r'p, 1st rudiment of 

 pancreas ; vv, vitelline vein ; y, yolk-mass. 



end of the liver, and as the liver differentiates, the spaces filled with 

 blood between the trabecules, are in direct communication with the sinus 

 venosus (Fig. F, 1 and sv). 



As the liver develops, it is surrounded by the splanchnopleure and is 

 suspended from the dorsal wall of the body cavity; the portion of the 

 gut from which the stomach develops lies to the left of the mesentery 

 thus formed (Fig. 112, 3). The communication between the liver and 

 gut is gradually reduced to a small opening (stage VII), the definitive 

 bile-duct, which enters the gut close to its connection with the central 

 yolk-mass. As the gut is lengthened at the expense of the yolk-mass, the 



