THE FOKMATION OF THE ORGANS THE ALIMENTARY CANAL. 205 



stage, and the albuminiferous cells seem to be pressed more to 

 the left (Fig. 78). 



The complexes of nutritive cells arc said to be dorsal in position in 

 the land Pulmonates also, and the direct rise of the liver from them 

 has been described (JouKDAiN, No. 49). It appears, however, from 

 the figures of Pulmonates, especially of the land-form before ns, that 

 the large-celled mass extends well to the ventral side of the stomach. 

 so that there is here perhaps after all a near approach to the con- 



Fr<.. ( .t:;. .1-'', sagittal sections of tin- embryos of Fusus at various stages (after 

 Bobretzky). d, yolk; /, toot; kb, cephalic vesicle; /, liver; m, mouth: mil, 

 entemu ; mg, stomach ; s, shell ; sd, shell-gland ; vd, stomodaeum. 



ditions described above. The fact that the intestine, the stomach 

 and the liver are not clearly marked, makes it difficult to ascertain 

 the exact relation of these parts which is further complicated by 

 a frequent displacement of these organs. In Bythinia, the intestine 

 arises from the posterior part of the conical enteron, while the larger 

 part gives rise to the liver and stomach (P. Sarasin, v. Erlanger). 

 The liver appears in the form of a very wide anterior and a smaller 



