29 
in house-flies, such a Leptomonas (a smaller form) has been described by various 
workers (e.g. Roubaud, Flu, Rosenbusch), which possesses in addition crithidial 
and trypanosome-like phases. This latter parasite is quite comparable in short to the 
various Leptomonads with leptotrypaniform phases (trypanoids), which have been 
described especially by Roubaud, Chatton and their co-workers from African 
flies (e. g. Drosophila sp.). Most of these authors have regarded the two forms as 
distinct parasites and have retained the generic name Herpetomonas for the large 
form and adopted that of Leptomonas for the other type. Dunkerly (5) has re- 
cently given a very good account of both forms from Birtish house-flies, and while 
not able to connect them definitely, has suggested the possibility of their being both 
different forms of one parasite. Lastly, Wenyon (6) has just published a paper 
on this subject in which he shews clearly that all the different forms actually belong 
to the life-cycle of one parasite. He proposes to retain the generic name Herpeto- 
monas for this parasite of house-flies, and to use that of Leptomonas for those Lep- 
tomonads (with a single flagellum, of course) which have not, so far as is known, any 
crithidial or trypanosome-like phase in their life-cycle. With this view I agree 
entirely. For, as he points out, although we do not yet know whether the type- 
species of this latter genus (L, bütschlii) possesses these additional phases, it is quite 
as likely that it lacks them, for several parasites are now known which certainly 
seem not to have them (e. g. the parasites described as Herpetomonas jaculum, lygaet, 
aspongop?, to name only a few). All these are best placed provisionally in the genus 
Leptomonas, as L. jaculum, and so on. On the other hand, all the forms of Roubaud, 
Chatton and others, which possess crithidiform phases and trypanoids (or “herpe- 
totrypaniform”’ phases), come in the genus Herpetomonas. Because, in addition to 
connecting the large Herpetomonas of the house-fly with the smaller (Leptomonas) 
form, Wenyoiu (l. c.) has come to the conclusion that the first-named is not to be 
regarded as really biflagellate, but as possessing a single flagellum which is fre- 
quently found precociously divided. Chatton himself, in one of his more recent 
papers (7) also expressed the same opinion and considered that H. muscae-domesticae 
and his L. drosophilae and other sp. were not so separate as had been formerly 
thought. Hence, it is best to write Herpetomonas drosophilae, mesnili and so on. 
To return to the discussion of the parasite from Culex pipiens, I 
have referred above to the reasons which particularly influenced me in 
continuing to regard it asa “Orzthidia”. I think now that I did not attach 
sufficient weight perhaps, to the occurrence, in the infections which I 
studied, of certain forms which can hardly be regarded as other than 
Leptomonads (ante Herpetomonads) (cf., for example, my fig. 31). It 
is true that these individuals are very scanty in number, most of the 
elongated forms being, as I pointed out in my previous note, not typical 
Leptomonads, but differing in having the anterior end of the body more 
or less tapering, the flagellum being consequently attached to the body 
for a greater or less distance, this depending also, of course, on the 
exact position of the kinetonucleus (cf. my figs. 16, 17, 29, 32, 33 and also 
the American workers’ fig. 4 pl. 8 of a rosette). Many of these forms 
resemble certain which develope in cultures of Avian Trypanosomes 
(e. g. T. fringillinarum), which I have distinguished in my first memoir 
on Avian Haemoprotozoa (8) as “pseudoherpetomonad” forms (I prefer 
to term them in future “semi-leptomonad” forms). It is just in such a 
case, of course, that it is difficult to decide whether to regard a parasite 
