152 University of California Publications in Zoology [VOL. 19 



from the blepharoplast and the cytoplasmic sheath surrounding it. 

 The entire flagellum stains as a single heavy line, almost chromatoidal 

 in appearance. It does not stain so deeply as does the nucleus, but 

 much deeper than the cytoplasm of the body and of the undulating 

 membrane. As the flagellum forms and lengthens, there is an accom- 

 panying elongation of the protoplasm which forms the undulating 

 membrane (und. m.). Both endoplasm and ectoplasm enter into the 

 formation of this organelle. Usually there is a thin, narrow band of 

 clear ectoplasm lying parallel to the flagellum (fig. A, 5). The length 

 of the membrane, and consequently of the intracellular part of the 

 flagellum, is greater among the crithidias of the stomach phase than of 

 the rectal phase owing to the shifting of the cytoplasm of the body 

 in the transition. This is usually true also of the crithidias as com^ 

 pared with the crithidial stages of the trypanosomes (fig. A, 1, 2, 3, 4). 

 As previously noted, the length of the free flagellum (fig. A, 3) has 

 no significance from the viewpoint of comparative morphology, since 

 there is a wide variation in the length of this organelle for each species 

 of Crithidia and of Trypanosoma. 



THE LIFE CYCLE OF CRITHIDIA EURYOPHTHALMI 



The life cycle of C. euryophthalmi in Euryophthalmus convivus 

 begins, so far as known, with the casual ingestion with food of 

 spores from the fecal matter of infected insects. E. convivus com- 

 monly feeds upon the sap from the growing tips of the lupine, which 

 show many indications of excreta. In these same regions of the lupine 

 galls and other abnormal growths occur in great abundance. The pos- 

 sibility that these insects were getting their infection of C. euryo- 

 phthalmi from the sap of the lupine was suggested by the work of 

 Franga (1914). Examinations of the sap of the lupine were accord- 

 ingly made. Nematodes, numerous yeast-like spores, and bacteria 

 were found. No organisms were discovered, however, of any descrip- 

 tion which could be linked to the known stages of C. euryophthalmi 

 in the digestive tract of the host. 



The large number of parasites in the life cycle of C. euryophthalmi 

 can be grouped readily into two series : the developmental, or infective, 

 and the degenerative, which are comparable to the developmental and 

 degenerative series of T. lewisi in the flea, as described by Minchin 

 and Thomson. That the correlation between these two life cycles is 

 marked will become clear in following the discussion of the life cycle 



