STUDIES ON AVIAN H^AIOPROTOZOA. 701 



Summary and General Remarks on tlie Cultural 



Forms. 



From my observations on the cultural forms of T. fringil- 

 linarum a few interesting and important data have been 

 obtained, relative to the course of the development of the 

 parasites on passiug into the culture-medium. The earliest 

 type of form which I have found is a slender, trypaniform 

 phase. This is soon replaced by the characteristic trypano- 

 mouad phase, into which most of the trypanifoim individuals 

 pass. This trypanomonad phiise is the predominating 

 cultural form, and it is persistent, apparently, so long as the 

 condition of the medium remains healthy. During this period, 

 however, in a culture of six days' age, trypaniform individuals 

 have also been seen, though they were extremely few in 

 number. Further, rare instances of another form h^ve been 

 found, which is distinguished by its vermiform appearance, 

 and by the remarkable ladder-like character of its trophonu- 

 cleus. This phase is doubtless simply a further development 

 oF the ordinary trypaniform type. Whether these later try- 

 paniform individuals represent forms of this character which 

 have been persistent from the commencement of the infection, 

 or whether they indicate a second development of this phase 

 from the trypanomonad type, I ha.ve not sufficient evidence to 

 decide. I am rather inclined to think, however, that the 

 latter may be the case; for one or two individuals have been 

 found which might correspond to transition-forms in such a 

 passage (fig. 128). 



Since the above research was carried out, I have been 

 studying, in conjunction with Prof. Minchin, the paiasites of 

 Athene noctua, andl have observed the early developmental 

 phases of a trypanosome (most probably T. noctufB) from 

 this bird, in the stomach of the mosquito (Culex pipiens). 

 We hope to publish in due course a full account of this work, 

 but 1 wish to refer here to one or two general facts. In the 

 first place, to answer any possible criticisms, it may be stated 



