156 University of California Publications in Zoology [VOL. 19 



dance of the parasites in this preparation of the "crop" ample 

 material was at hand for an extensive study of the morphology of this 

 phase of the life cycle of Crithidia euryophthalmi. From time to 

 time more flagellates were observed, apparently multinucleated, but 

 little additional light was thrown upon their peculiar nuclear struc- 

 tures until a large flagellate, such as shown in figure 22, plate 1, was 

 observed. This crithidia was relatively large and contained approxi- 

 mately twelve ' * binucleated " spore-like forms. The structure of the 

 sporelike forms within the periplast of the large flagellate was similar 

 to that of the numerous small, oval spores in the immediately sur- 

 rounding field, which were, beyond doubt, stages of the life cycle of 

 C. euryophthalmi. Another large flagellate containing six nuclear 

 structures within the periplast (pi. 2, fig. 21) was also drawn. The 

 flagellum and parabasal body were clearly outlined, as in the former, 

 multinucleated flagellates. Some of the enclosed nuclear-like struc- 

 tures were deeply stained, owing to the thickness of the preparation, 

 but the majority presented the same appearance as did the nuclear- 

 like structures in figures 12 and 13. 



Investigation of the smear revealed more and more evidence of a 

 possible endogenous, or internal budding, in the life cycle of Crithidia 

 euryophthalmi. Past experience indicated that the preparations of 

 the ' ' crops ' ' of young nymphs furnished the best smears for the study 

 of the initial infections, of which the endogenous budding forms 

 were evidently a part. An effort was accordingly made during the 

 next breeding season of Euryophthalmus convivus to collect as many 

 young nymphs as possible in order to obtain additional prepara- 

 tions of the digestive tract, with reference to the * t crop ' ' in particular. 



Out of a large number of preparations of the "crops" prepared 

 during the following season, only two contained additional stages of 

 the process of endogenous budding. The percentage of infection of 

 the "crops" of young nymphs was found to be approximately twenty 

 per cent as compared with two per cent among adult insects. 



In the two preparations there were numerous small, "binucleated," 

 spore-like forms, grouped near discarded flagella, with or without ble- 

 pharoplasts, and with parabasal bodies still attached (pi. 2, fig. 23). 

 It was easy to conceive of the degeneration of the cytoplasm surround- 

 ing the spore-like forms, leaving a field covered with the internal 

 spores, or zooids, and the extranuclear organelles of the parent cell. 

 In the earlier stages of degeneration presumably the parabasal bodies 

 were still attached by the parabasal rhizoplasts to the blepharoplasts 



