1917] McCuUoch: Crithidia euryophthalmi 79 



the crop into which projects the cardiac valve. This portion of the 

 crop is of smaller calibre than that posterior to it and usually appears 

 to be invaginated into the main cavity of the crop. 



The Mid-gut. — The mid-gut of Euryophthahnus convivus is rela- 

 tively much more complex than that of Leptocoris trivittatus or of 

 the Heteroptera in general. One of the early investigators (Dufour, 

 1833, pi. 2, fig. 13) figures in Coreus niarginatus a digestive tract 

 with similar parts but the nomenclature for these parts has not been 

 definiteh' established. The digestive tract of Lygaeus militaris (Pat- 

 ton, 1908) is somewhat like that of Euryophthalmus convivus. His 

 use of the term uiid-intestine is questionable; hence we have preferred 

 to use the word intestine (fig. 1, int.), believing that the anterior three 

 parts of the mid-gut are all parts of the stomach proper. Accordingly 

 these three parts have been designated respectively, as the crop, the 

 mid-stomach and the pyloric expansion. 



The crop is the first division of the mid-gut and is characteristically 

 of a light yellow color. This portion of the gut presents an ellipsoidal 

 shape, more or less irregularly lobed, and capable of great dilation. 

 During the fasting period this region is filled wath gas. 



Immediately posterior to the crop is another enlargement of the 

 mid-gut which we have designated as the mid-stomach (fig. 1, 7nid- 

 stom.). This enlargement occurs regularly, and is of a yellowish 

 brown color which is due almost entirely to the contents. The size 

 of this portion varies from one-half to one-third of that of the crop. 

 The mid-stomach and the next enlargement, the pyloric expansion, 

 may contain equal amounts of the contents, or either one may be 

 greatly distended at the expense of the other, depending upon the 

 stage of digestion. 



A narrow tube connects the mid-stomach with the pyloric (fig. 1, 

 pyl. ex.). This pyloric division is a symmetrical bulb-like enlarge- 

 ment filled with a dark brown liquid giving to this part of the tract 

 a blackish appearance. 



The last division of the mid-gut is a unique structure which we 

 have called the intestine (fig. 1, int.) with a continuously attached 

 intestinal gland (fig. 1, int. gl.). The canal or intestine passes through 

 the center of the rufifle-like band of white, almost transparent, gland- 

 ular tissue (fig. 1, int. gl.). The intestine and gland of the intestine 

 are approximately equal in length to the anterior three portions of 

 the mid-gut just described. A similar structure was described by 

 Dufour (1833, pi. 2, fig. 13) in the hemipteran bug, Coreus mar- 

 ginatus. 



