130 
Leptomonas Kent 
lewisi, and the newly discovered Trypanosoma brucei Pliminer and 
Bradford also was referred to it. Laveran and Mesnil showed that these 
two species really belong to the genus Trypanosoma, and accordingly 
Senn (1902) two years later returned to Butschli’s conception of the 
genus Herpetomonas. In the meantime yet another generic name, 
Herpetosoma Doflein (1901), had appeared, and this was included by 
Senn as one of the synonyms of Herpetomonas. 
The same year Leger (1902) formed a new genus Crithidia for 
the reception of a parasite of the intestinal tract of Anopheles macidi- 
pennis. Although Leger’s original description is very incomplete, yet 
the remark that its characters were intermediate between Herpetomonas 
and Trypanosoma, and the accompanying figures, show that he was 
describing a form very similar to the Crithidia subsequently described 
by Patton, Porter, Swingle and other writers, and Patton (1908) 
emended the original diagnosis of the genus. 
At first Leger was in some doubt about the parasite, for he writes— 
“ En raison du mode d’alimentation des Anopheles et de I’analogie que 
presentent les formes affilees de ce flagelle avec les Trypanosomes, on 
pent se demander si les Crithidia ne representeraient pas un certain 
stade evolutif de quelque hematozoaire flagelle des Vertebres” (Leger, 
1902 a, p. 356). 
In a subsequent paper, however, he (Leger, 1903) seemed convinced 
of the validity of the genus Crithidia and described two new species, 
minuta and campaniidata. The former of these species was later 
removed by Leger (1904) to the genus Herpetomonas, and the presence 
of a rudimentary undulating membrane was mentioned as occurring in 
the latter. The shape of the body was then considered as being the 
only distinct character of the genus Crithidia, for Leger remarks that 
the only two species are characterised by “ la forme massive, piriforme 
ou campanulee de leur corps” (1904, p. 616). 
Prowazek (1904) in describing the life history of Herpetomonas 
muscae-domesticae gave a very complicated account of both its structure 
and life cycle. In this paper the parasite was described as possessing 
two flagella united by a membrane and arising from an anteriorly 
situated diplosome. It is very difficult to accept all of Prowazek’s 
hypotheses regarding the structure of this parasite, and up to the 
present they have not been entirely confirmed {v. infra). 
However, it is certain, as Roubaud (1909) first pointed out, that if 
Herpetomonas mnscae-domesticae is biflagellate it differs in this character 
from many other species which have been referred to this genus. 
