2° 
term Trypanosoma (Herpetomonas) culicis from Crithidia fasciculata, 
both on morphological grounds and by means of cultivation. Adopting 
this view, it would result that Léger’s fasciculata, the type-species!, 
was a small form, with only a rudimentary membrane, and lacked the 
elongated phase with wavy membrane shewn by many other crithidial 
parasites. 
On further consideration of the whole subject, however, and 
especially since, for the purpose of this note, I have been comparing 
the various phases of the different “Crithidiae” which have been de- 
scribed, I prefer another explanation, which is, I think, much more prob- 
able. In the first place, I can see no reason for concluding that Léger 
has indeed described more than one form in his account of “ Crithidia” 
fasciculata. This parasite is by no means the only form with an un- 
dulating membrane, i. e. a Crithidia, which possesses a short, oval or 
pear-shaped, so-called “gregariniform” phase, serving for attachment 
(I propose to call this the haptomonad phase). Thus both the “Cr1- 
thidia” minuta and “C.” subulata (which latter is not a Herpetomonas) 
subsequently described by Léger shew very similar stages in their life- 
history, certain individuals having just the same truncated appearance 
shewn by many of the small forms of fasciculata; and so has equally the 
“(.” sp. described by Patton (4) from Tabanus sp. In view of this I fail 
to understand why Patton should have thought it necessary to suppose 
that Léger’s small forms of “C.” fasciculata should belong to a Her- 
petomonad (rather a Leptomonad, see below) and not to the Crithadia, 
particularly when, as he has himself specially pointed out, it cannot be 
determined from the short, haptomonad phase alone whether a para- 
site is a Crithidia or a Leptomonad, since in both this phase is essen- 
tially of the same type, with the two nuclei usually close together and 
the rhizoplastic part of the flagellum drawn back. Contrary to the 
opinion both of the American authors and of Patton, I think it most 
likely that all the forms described by Léger under the name fasciculata 
do belong to that parasite, because they form a regular and connected 
series. This being so, it appears also most probable, in the second 
place, that the parasite from Culex pipiens which the American workers 
and myself have had under observation is not Léger’s actual form, 
“CO.” fasciculata, but is on the contrary preferably regarded, so far as 
can be judged from the phases at present known, as a Lepto- 
monad rather than a Crithidia. 
Before going further, however, a brief explanation is desirable as to why I use 
the term Leptomonad, and not Herpetomonad, in this connection. Hitherto, both 
1 The specific name fasciculata would have to be applied, of course, to the 
parasite first described, i. e. the small ‘‘crithidial” form. 
