STUDIES ON AVIAN H^MOPEOTOZOA. 687 



those of figs. 112 to 114, are probably simply the smaller 

 daughter-individuals which have retained the pyriform shape, 

 instead of taking on the fusiform, more active one. On tlie 

 other hand, most of the ovoid or rounded forms, especially 

 where they are of medium to large size, would seem to 

 ai'ise from the accentuated trypanomonad type of dauo-hter- 

 individual. Transitional phases can be found, showing 

 different degrees in the retraction of the drawn-out flagellar 

 end and the concurrent reduction or disappearance of the 

 undulating membrane. Thus, both the large and the small 

 ovoid individual (figs. 115 and 118) have still a delicate but 

 distinct continuation of the body along the proximal part of 

 the flagellum, which doubtless corresponds, for the most part, 

 to undulating membrane. And in others of these rounded 

 forms, indications of the original membrane are still afforded 

 by the attachment of the flagellum to the side of the body for 

 some distance, the flagellum curving with it — at times partly 

 curling round it, as it were — before becoming free (fig. 119). 

 In general these rounded forms of the parasite do not, 

 apparently, undergo division. In most instances where I 

 have observed these forms, they are, as I have mentioned, of 

 small or only medium size, and these never show indications of 

 division. One of my culture-series, however, for some reason 

 or other for which I was unable to account, but which was 

 probably due to some variation in the condition of the culture 

 medium, behaved differently from the usual manner. In this 

 culture a pronounced tendency in the development of the 

 parasites was the production of large, massive forms, which 

 are sometimes ovoid or rounded in shape. Examples are seen 

 in figs. 120-123. The parasites in my preparations of this 

 series (taken when the culture was seven days old) are 

 certainly not degenerate or abnormal ; this is clearly shown 

 by a comparison of their structure with that of distinctly 

 atypical or degenerate forms (c f . below, p. 693). There is 

 none of the irregular multiplication of organellae, nor of the 

 alteration in the cytoplasmic constituents which is apparent 

 in the latter. I consider that the unusually large proportion 



