374 
duals, the anterior end of the body, instead of being abruptly truncated 
(figs. 9—13, 21), at its anterior end, tapers gradually, being drawn out, 
as it were, along with the flagellum (figs. 25, 26, 28); one can hardly 
call this, however, a rudimentary membrane. In the longer individuals, 
the tendency is to a more herpetomonad condition; the kinetonucleus is 
always well in front of the trophonucleus and may sometimes be near 
the anterior end (figs. 16,17, 29—31), the trophonucleus remaining, how- 
ever, near the middle of the body. The anterior end usually thins out 
along the flagellum and in this respect differs from the blunt extremity 
characteristic of a typical Herpetomonas. These forms recall, I may note, 
certain cultural phases of an Avian Trypanosome which I have described’, 
though I do not wish to lay any stress upon the point. Although I 
haye not found these elongated forms in all the preparations made of 
infected parasites, I think there can be no doubt that they belong in the 
same life-cycle as the short “crithidial” forms. A regular series of 
transitional phases between the two can be readily found (cf. figs. 14, 
27—29). | 
Many of the fixed and stained parasites shew a cytological pecu- 
liarity which probably stands in some relation to the rapid development 
of the free flagellum. In individuals caught in the resting phase, which 
have no free flagellum, there is usually a conspicuous pink-staining area 
or patch at the anterior end of the body (figs. 1—3); this does not ap- 
pear to me to be a vacuole. The attached, or body-portion of the flagel- 
lum, which is always well-defined in resting (non-encysted) forms, runs 
from the neighbourhood of the kinetonucleus to this area, in which it 
seems to merge. The same pink-staining substance is frequently present 
also in individuals which have a short, spike-like flagellum, but its area 
is much less (cf. figs. 5, 18). In the forms with fully developed flagellum 
there is rarely any sign of it. Apparently, this area represents the sub- 
stance of the retracted, free portion of the flagellum. 
In the preparations made in the autumn, many of the parasites, 
both short and elongated forms, contain numerous large, deeply staining 
granules, situated chiefly in the posterior region of the cytoplasm. These 
probably represent reserve food-material. 
I will mention here that in one of the preparations made of the four 
infected digestive tracts in the autumn, a few cysts have been found 
after much searching, but these will be more suitably described after 
considering the infection in the mosquitoes in the subsequent spring, 
when the cysts were first observed. 
With a view to seeing whether the Flagellates would persist alive 
5 Vide Quart. J. Micr. Sci. vol. 55. 1910. pl. 30, figs. 140, 141. 
