142 University of California Publications in Zoology [VOL. 19 



apparently that of a more primitive flagellate (pis. 2-6) found living 

 in the medium of the fluid contents of the alimentary . tract of a 

 plant-feeding insect. As such, C. euryophthalmi (fig. A, 2) lacks in 

 the stomach phase the trypaniform characteristics, namely, the ble- 

 pharoplast (bl.), the parabasal (pi).) (or kinetonucleus) located poste- 

 rior to the nucleus (n.), and the well developed undulating membrane. 

 In this connection it is interesting to note that, regardless of the con- 

 trast in the initial stages of the stomach phase in each life cycle, the 

 process of multiple fission characterizes the stomach phase for both 

 the haemoflagellate and the more primitive crithidial flagellate. In 

 the stomach phase of the crithidial parasite there are also found the 

 "rounding up" forms (pi. 3, figs. 24, 25), the spheres (pi. 3, figs. 

 26-32), and the final stages of multiple fission wherein the resulting 

 merozoites are about to escape from the epithelial cell of the host (pi. 3, 

 fig. 39) . In addition to this I found numerous stages of an endogenous 

 process of multiple fission (pi. 2, figs. 11-23). 



Correlation of the life histories of these forms (C. euryophthalmi 

 and T. lewisi) became more difficult in the stage following the process 

 of multiple fission, on account of the structure of the digestive tract 

 of the host, Euryophthalmus convivus. The digestive tract of the flea 

 (cf. Minchin and Thomson, 1915, text-fig. 1) shows the stomach as a 

 prominent enlargement of the tube, followed by a comparatively long, 

 slender intestine, at the posterior end of which is the rectal enlarge- 

 ment. The digestive tract of Euryophthalmus convivus, or lupine bug, 

 on the other hand, is quite unlike that of the flea (cf. McCulloch, 1917, 

 text-fig. 1 ) . The first enlargement of the mid-gut proper is followed by 

 a second and a third enlargement, a narrow constriction of the diges- 

 tive tract separating the three expansions. Posterior to these there is a 

 relatively long intestine which passes through the center of a ruffled, 

 ribbon-like gland. The intestine opens into the slight enlargement 

 near the entrance of the malpighian tubules, which in turn opens into 

 the rectum. Since the several parts of the digestive tract of the hem- 

 ipteran and other insects have not been satisfactorily homologized as 

 yet and the nomenclature used in describing the divisions is confused, 

 it is exceedingly difficult to ascertain the homology of these several 

 parts of the digestive tract. However, as indicated in my preliminary 

 paper (McCulloch, 1917), all three enlargements anterior to the intes- 

 tine were considered as parts of the stomach proper and were accord- 

 ingly designated as the "crop," mid-stomach, and pyloric expansion. 

 With this disposal of the three enlargements of the digestive tract, the 



