LIFE-HISTOKY OF LEPTOMONAS MUSC.E DOMESTICS. 647 



anterior end truncated, and the elongated one with anterior 

 extremity drawn out into a membrane attached to the 

 flagellum, are found (PI. 31, figs. 3, 4, and 11). A form 

 resembling that in fig. 11 was found by Chatton and 

 Alilaire (2) in Drosophila confusa, and described under 

 the name Trypanosoma d r o s o p h i 1 a^, although the authors 

 recognised the possibility of its being a stage in the life- 

 history of a Leptomonas found by them in the same fly. Werner 

 (24) also described the same form from "Stubenfliegen," 

 and named it Crithidia muscas domesticae to distinguish 

 it f rom the biflagellate Herpetomonas muscas domestics 

 of Prowazek. Miss Mackinnon (14) also, whose paper ap- 

 peared while this work was in progress^ in describing what she 

 regards as a Herpetomonas from Homalomyia corvina(7) 

 pointed out the similarity between some of the forms found 

 by her and the Crithidia of Werner, which would not be 

 surprising if both are stages in the life-history of organisms 

 belonging to the same genus, possibly to the same species. 

 The forms shown in PI. 31, figs. 12, 13, and 14 possess, 

 undoubtedly, an undulating membrane, though the flagellum 

 is not produced beyond it, and these resemble in a striking 

 manner some stages of Trypanosoma cazalboui in cul- 

 tures, described by Eoubaud (22, pi. viii, figs. 2 and 6), thus 

 indicating a close relationship between the parasite of a non- 

 blood-sucking fly like Homalomyia and the trypanosomes of 

 vertebrates. Patton (18, and 17, p. 142, note), in objecting 

 to Prowazek's account of Herpetomonas (which, however, 

 has been supported by other observers, Lingard and Jen- 

 nings [12], Roubaud [22]) decided that all uni-flagellate 

 parasites of insects with the kinetonucleus anterior to the 

 trophonucleus and without undulating membrane are to be 

 called Herpetomonas, and that those having the kinetonucleus 

 posterior to the trophonucleus, and possessing an undulating 

 membrane, should receive the generic name of Crithidia. 

 Liihe (13) and Hartmann and JoUos (5) have pointed out that 

 Patton's failure to see the characters observed by Prowazek 

 and others does not prove their non-existence ; and as to his 



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