22 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



monly forced partly out of tbe cell l)odies so tliat their outlines 

 are often difficult to determine. At its posterior end the stomach 

 of Carinella, Cakinoma (PI. 12, fig. 76; PI. 13, fig. 82), Cari- 

 NOMELLA (PI. 8, fig. 57), and certain heteronemerteans is con- 

 stricted and its lumen rendered very small by the massive develop- 

 ment of the inner circular muscle. 



Intestine. — The change from stomach to intestine is often very 

 gradual, the most anterior lateral pouches being very rudimentary 

 and increasing gradually in depth. This is well shown in Carinoma 

 (PI. 12, fig. 76). The epithelium characteristic of the stomach often 

 persists, especially in the central canal, behind the small anterior 

 pouches even after the latter have taken on the peculiar intestinal 

 character. The anterior portions of the intestine are characterized 

 by a wide central lumen and comparatively shallow pouches, while 

 its posterior portions have very deep pouches and a narrow axial 

 lumen. The sexual glands and dorso-ventral muscles alternate with 

 the intestinal pouches, while the blood vessels of the Herteronemertea 

 and the rhynchocoel appendages of Drepanophorus lie opposite 

 them. 



The most striking peculiarity of the epithelium of the intestine, or 

 mid gut, is that it is composed of a single layer of very tall columnar 

 cells, each of which reaches quite to the basement layer and is packed 

 full of globules and granules of various sorts. These cells are 

 actually provided each with a few very long cilia of such delicacy that 

 they are seldom distinguishable in prepared sections, although they 

 are readily demonstrated in life. They are not gland cells, as are 

 those of the more anterior portions of the alimentary canal, but are 

 rather of the nature of absorbing and assimilative cells. The sub- 

 stance composing the body of each cell is very different in appear- 

 ance from that of any of the cells in other parts of the digestive 

 tract, and its appearance varies greatly not only in different species 

 but in different individuals, and doubtless also at different times in 

 the same individual, according to the nature of the food and the state 

 of its digestion. 



In some instances when examined in -life after crushing, most of 

 the cells are packed full with clear vacuoles, others contain granules 

 of various sorts, some of which are opaque, others being of a certain 

 color, as black, brown, 3^ellow, or green. In Paranemertes cali- 

 fornica, for example, the cells contain vast numbers of fine granules 



