THE FORMATION OF THE ORGANS — THE ALIMENTARY (ANAL. 207 



albuminous cells of other Gastropods described above. The yolk- 

 mass, which is still very large, limits directly the lumen of the 

 entoderm-vesicle (Figs. 92 and 93). This latter is already found to 

 be partly rilled with disintegrated yolk-substance (Fig. 62 B), this 

 being taken up by the large entoderm-cells, which, according to 

 Bobrktzkv, represent the rudiment of the liver (Figs. (52, 93 and 

 '.'!./). The large-celled "hepatic vesicle" may be said to form the 



Fig. 95.— A-D, longitudinal sections through embryos of JVassa mutabilis at different 

 ages (after Bobketzkv, from Balfour's Text-book). /-//, blastopore ; ep, ectoderm : 

 /. rudiment of foot; hy, entoderm; in, epithelium of the enterou ; m, mesoderm; 

 sg, shell-gland ; st, lumen of the enterou. 



dorsal and posterior part of the entoderm-sac, if the rudiment of the 

 intestine is left out of consideration (Figs. 93 and 94, md). It 

 occupies the left side of the body while the food-yolk is pressed more 

 to the right. From the sections given in Figs. 93 and 94 a good 

 idea of the relative positions of these parts and of the stomach may 

 be gained. The food-yolk still directly limits the lumen of the 

 intestine, but is gradually absorbed as development advances. 



