916 
resting condition and swarmed out actively from any part of the 
ruptured intestine or rectum just as before, on the liquid reaching 
them, I did not expect to find any encysted forms. It was naturally to 
be expected that, if the Flagellates were going to encyst, the great 
majority would be encysted after that lapse of time, especially in the 
hinder part of the digestive tract. As a matter of fact, however, in study- 
ing the permanent preparations made in the spring, of these infected 
digestive tracts, with a view to making drawings for this paper, I have 
recently come across a few encysted forms from one gut, as well as a 
certain number of parasites commencing to encyst. Nevertheless, in 
view of the enormous number of individuals actually present, the encyst- 
ment is taking place to a surprisingly small extent, and it is no wonder 
that the few cysts were not observed in life. Moreover, in two other 
cases, preparations have been thoroughly searched with out a single cyst 
being found. On the other hand, in one of the 4 infected digestive tracts 
preserved in the autumn, renewed search has shewn the presence also 
of a few cysts. The important point therefore, is that both at the end 
of the period of hibernation, as at the commencement, the vast majority 
of the parasites are unencysted. 
The cysts of “Crithidia” fasciculata, which are described here for 
the first time, so far as I am aware, are very similar to those of other 
Flagellates occurring in Insects, which are already known. They are 
oval or slightly pear-shaped (figs. 37, 39), in the latter case, the hinder 
end of the body forms the broader end of the pear. They vary somewhat 
in size, being usually rather larger than the small truncated, “crithi- 
dial” parasites, and are apparently formed by intermediate-sized indi- 
viduals (cf. figs. 4, 15), or by semi-herpetomonad forms (fig. 30). The 
cyst-wall is fairly thick, especially at the posterior end, where it is often 
much thicker than at other parts. It stains deeply with Giemsa and its 
external contour is at times rather irregular (fig. 40); it is most probably 
formed of the same kind of semi-granular, semi-viscid secretion which 
constitutes the wall of the “Schleimeysten” of Prowazek. In some 
cases, the wall stains so intensely that the cyst appears very dark and 
opaque (fig. 41). The body of an encysted parasite is often very granu- 
lar, now and again rendering it difficult to distinguish the limit of the 
trophonuclear area (fig. 40). The kinetonucleus, which is always quite 
definite, is situated close to the trophonucleus. Sometimes the basal 
part of the attached flagellum (rhizoplast?) can be made out in the 
completed cyst (figs. 38, 41), but in other cases, it is no longer distinguish- 
able (figs. 39, 40). Stages in cyst-formation are seen in figs. 34—37. 
The outline of the body becomes less sharply defined, with fine granules 
adhering to it, which perhaps represent the commencing secretion 
