RESEARCH ON THE DIGESTIVE SYSTEM OF THE SCHIZOPODA 33 



brane beginning at the stomach and extending a certain distance in the 

 thoracic part. 



The vvalls of the intestine are very contractile; in the Hving animal 

 the peristaltic movements are easily seen. 



Its walls are transparent, and in the région of the pleon where as \ve 

 hâve already observed, the intestine runs close to the dorsal integument, 

 the fecal matters are visible to the naked eye. 



At the terminal portion not far from the anus, the intestine increases 

 in width, fig. 22; at the same time, its epithelial cells become elongated, 

 FiG. 22, 23. 



At its greatest diameter, the columnar epithelium ceases and gives 

 place to a loose epithelium formed of a mass of small cells which continue 

 as far as the anus, fig. 22. 



In transverse section the lumen of the tube close to the anus is no 

 longer cylindrical but of an irregular disposition formed by two large ridges 

 on the dorsal and ventral surfaces and a pair of latéral folds, fig. 24. 



The. surface of this loose tissue is protected by a very thin chitinous 

 cuticle. 



The terminal portion of the intestine possesses numerous circular 

 muscle bands running in an oblique direction round the tube, fig. 22, m. c. 

 It is connected with the external integument by numerous bands of striated 

 muscle, fig. 22 and 24, ;n. 



The folds therefore in this région hâve a valvular function, the power- 

 ful muscles enabling the animal to open or to close the end of the intestine 

 at will. 



The anus is in the form of a slit, fig. 25. 



A tongue shapcd fold is secn attached to its dorsal surface between two 

 latéral folds. 



According to Van Beneden, the vvideterminal portion of the intestine 

 dra-ws in water from the exterior and seems to be of the same disposition 

 as that of the cray-fish. 



In some Crustacea the anus is known to contract and expand alter- 

 natively, but in the Mysis we hâve no reason whatever for supposing that 

 this contraction and expansion has a respiratory function. 



