352 OILMAN A. DEEW. 



animal lias reached sexual maturity. At first the intestine 

 passes through the middle of the heart (fig. 67). The sides 

 of the heart seem later to be forced dorsally by the growth 

 of the kidneys, and the intestine becomes applied to the 

 ventral wall of the heart. By the continued growth of the 

 kidneys the ventral portion of the ventricle is drawn out into 

 a trough, in which the intestine lies (fig. 68) . The growth is 

 continued until the trough is considerably deeper than the 

 width of the intestine. By gradually closing in dorsal to 

 the intestine at the anterior and posterior ends the trough is 

 shortened, and the intestine fiually becomes free from the 

 heart and lies ventral to it (fig. 69). 



In the adult animal (fig. 48) the oesophagus is a rather 

 broad and long, nearly cylindrical tube, that opens between 

 the palps just posterior to the anterior adductor muscle. I 

 find no indication of anything that can be interpreted as 

 salivary glands at any stage in the development (13). 

 Throughout its length it is evenly ciliated and quite devoid 

 of ridges. The corners of the mouth are continuous with 

 the groove between the two labial palps. The stomach is 

 large, somewhat spindle-shaped, and extends from near the 

 dorsal margin of the shell to the level of the pedal ganglia. 

 Near its middle there is a nearly complete ridge of elougated 

 epithelial cells, aud frequently a more or less well-marked 

 external groove that divides it into a dorsal and a ventral 

 portion. The posterior and part of the lateral walls of the 

 dorsal portion of the stomach are formed by long and slender 

 epithelial cells that stain but slightly. They secrete a 

 mucus-like material that stains deeply, and probably corre- 

 sponds to the crystalline style. In adults this secretion 

 seldom takes the form of a rod, but in embryos a rod is 

 commonly present (figs. 26, 28, 30, aud 64). The remaining 

 cells in the dorsal portion of the stomach are short, stain 

 deeply, aud are evenl}^ ciliated. The ducts from the liver 

 open in the dorsal end of this portion of the stomach. The 

 epithelial cells of the ventral portion of the stomach are 

 short, stain deeply, and carry a quantity of short cilia. 



