30 
as crithidial or leptomonad. It is entirely a question of degree; for such 
a condition is transitional between a typical Crithidia and a typical 
Leptomonas, and may be quite as readily connected with the one type 
as with the other — if anything, indeed, more readily with the former. 
On the other hand, so far as I have been able to ascertain from a 
comparison of the different species described, no “Crithidia” shews a 
true leptomonad phase, that is to say, of course, in the elongated, 
monadine condition. I think this is a most important point, and one to 
be borne in mind when we try to distinguish a generic type, Crithidia. 
While one would not go so far as to say that all Crithidiae entirely 
lack such a phase, (remembering that the crithidial type is derived from 
a leptomonad one), still, its absence appear to be a very general feature. 
As already indicated, I have no reason to suppose that the few Lepto- 
monad individuals which I found represent a form distinct from the 
other phases; everything points to their belonging to the life-cycle of 
one and the same parasite. It seems best, therefore, to regard this 
parasite from Culex pipiens for the time being as a Leptomonas, its 
name becoming L. fasciculata (= Crithidia f. N. McN., and T., nec 
Léger). This implies, of course, that it does not really possess any 
undulating membrane2. I find that Patton, in the two papers already 
referred to (3 and 4), has also expressed the same opinion with regana 
to the form studied by the American workers. 
Before leaving the subject of the flagellate parasites of Culex, a 
few observations may be noted with regard to certain other forms which 
have been described. As mentioned above, Novy, McNeal and 
Torrey gave at the same time an account of another parasite from C. 
pipiens and other sp. which they called Trypanosoma (Herpetomonas) 
culicis, n. sp. As Patton has also pointed out, a typical Crithidia as 
now understood (with well-developed membrane) is concerned here; in 
this case the authors’ description and figures leave no doubt upon the 
matter. This form is certainly not a Herpetomonas (Leptomonas) at all. 
Of course, in the phase described, it is not a true Trypanosome, because 
the kinetonucleus and the origin of the flagellum are not near the 
aflagellar end of the body. But for all that, it is quite likely that this 
2 This certainly renders it less likely that this parasite is connected with a 
Trypanosome; but does not, of course, affect the question of “Orzthidia” fasciculata. 
3 I may add, however, that I had come to the conclusion indicated quite inde- 
pendently, as a result of my own work, and before reading Patton’s earlier remarks 
on this parasite. As will be apparent from what has been written above, one had 
not sufficient evidence, from a consideration of Novy, McNeal and Torrey’s 
account alone, to regard this form as a Leptomonad rather than a Crithidia, any 
more than one has to say that the small forms of Léger’s “CO.” fasciculata do not 
belong to the same parasite as the larger (monadine) individuals. 
