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anything more liable to mislead others upon the already sufficiently 
confused and difficult subject of the nomenclature of these forms. 
I consider this parasite from C. fatigans is most probably a species 
distinct from Leptomonas fasciculata of C. pipiens. In the first place, 
the two hosts have a quite different distribution, and this is a factor 
which I have always maintained must be taken into account. Again, 
the elongated, monadine individuals of Patton’s parasite are consider- 
ably larger than any of fasciculata which I have found, or which are 
described and figured by the American authors. Moreover, although 
both parasites appear to be of the same general type, the monadine 
forms of the parasite from C. fatigans are more typically leptomonad 
than are, for the most part, those of fasciculata, as I have discussed 
above. On these grounds, therefore, the two are best regarded as sepa- 
rate species, and Patton’s form should bear the name L. culicis n. sp. 
Patton (nec Novy, McNeal and Torrey). 
It remains to add a few remarks upon the question of Crithidia 
as a generic type. We have, on the one hand, crithidiform (as well as 
herpetotrypaniform) phases occurring very generally in the life-cycle of 
Herpetomonas; on the other hand, crithidial (or, as they are conveniently 
termed, trypanomonad) forms occur as a developmental phase in the 
life-cycle of most — perhaps all — Trypanosomes. Is there, therefore, 
a separate and independent generic type, Crithidia, which can be 
distinguished and characterized? While it is evident from the above 
facts that there is much to be said in favour of the view that crithidial 
forms represent only a phase in a life-cycle of one or other of the above 
types, I think, nevertheless, that there is sufficient evidence to make it 
at any rate very convenient to continue to recognize a distinct type, 
Crithidia. Leaving aside the many instances of crithidial forms occur- 
ring in blood-sucking Insects and the question of the connection of 
such parasites with some Trypanosome — a question which, I may point 
out, still remains in statu quo — there are a few forms which, it seems 
to me, may be regarded as furnishing the nucleus of such a genus. We 
have, for example, C. campanulata, C. cleti and C. gerridis. All these 
forms are parasitic in non-bloodsucking hosts. They possess the typical 
crithidial characters (undulating membrane, proximity of the two nuclei, 
etc.); and in neither is anything like a leptomonad phase (i. e. of course, 
in the elongated, monadine forms) described. This last point seems to 
me to differentiate such a parasite from the crithidiform phase of a 
Herpetomonas. So far as I gather from the accounts of various species 
of H., when the crithidial forms are found, there is no difficulty in 
finding not only herpetotrypaniform individuals, but also the ordinary 
leptomonad forms; and Miss Robertson, for instance, in commenting 
