301 
which I am aware is a brief mention by Léger and Duboscq! of the 
presence of Crithidiae in a hibernating Anopheles. The earliest notice 
of Flagellates in Culex is the graphic description of Ronald Ross?, 
with which the general condition of the parasites and their behaviour 
under observation, in the present case, agree very well, leaving aside 
for the moment the question of the exact nature of the forms seen by 
Ross. The vast majority of the Flagellates were in the resting, attached 
phase; they formed a carpet along the surface of the wall of the intestine, 
with their flagellar ends in contact with this, and also constituted large 
“free” rosettes, blocking the lumen to a very considerable extent, and 
sometimes causing distension of the wall. In one or two mosquitoes, 
the digestive tracts of which were immediately looked at whole, without 
having been ruptured at all, a few free, actively moving Flagellates were 
seen, about the pyloric region of the stomach. Nearly all the resting 
forms had the typical appearance of a barley grain, as it was first charac- 
terized by Léger’. In most, a very short free flagellum was present, 
little more than a spike-like projection (figs. 4, 18), but some individuals 
had practically no free flagellum. In such, however, the attached, or 
body-portion of the flagellum was always present, and is clearly seen in 
the stained preparations (figs. 1—3). 
A remarkable feature of the parasites which was noticed by Ross 
but the significance of which has not been pointed out by more recent 
workers, is their behaviour when brought into contact with water. As 
soon as the infected part of the digestive tract was teased up, either in 
ordinary water or in salt-solution, and the liquid had access to the 
Flagellates, these became active; many of them broke away immediately 
from the cluster of which they formed part and swam about vigorously, 
others following suit after a short interval. This resumption of the 
active condition took place in nearly all the individuals which came into 
contact with the water, only a small proportion of those hemmed in, as 
it were, in the middle of a large clump remaining motionless. In the 
great majority, the flagellum must have developed almost at once to its 
full length. This process appeared to take place just as much in the 
parasites situated in the rectal part of the digestive tract as in those in 
other parts of the intestine, numbers of active individuals swimming out 
of the cut, anal end of the rectum, behind the glands. No encysted 
forms were observed in the living preparations studied (but cf. below). 
While most of the active parasites were fairly short, a few elon- 
| gated, more herpetomonad-like ones were seen. In neither form, however, 
1 C. R. Ass. franc. avanc. sci., 31. 1902. p. 703. 
2 Vide his resumé in J. Hyg. 6. 1906. p. 101. 
3 C. R. soc. biol. 54. 1902. p. 354. 
