84 E. H. STRICKLAND 
5, r.f.). Inno cases of parasitised larvae was this stage of matur- 
ation observed, and it is probably seldom, or never, reached. 
In comparing sections of healthy and parasitised larvae, it is 
seen that in the latter the quantity of fat-body stored up for 
the formation of adult tissues is greatly reduced, and is probably 
entirely inadequate for the requirements of a full-sized fly. It 
is also evident that, owing to the large quantity of parasitic mater- 
ial, which is of a somewhat firm consistency, a large rent in the 
skin of the host would be necessary, in order to liberate it, and 
this would certainly cause the death of the host. Such was ob- 
served to be the case in larvae which died in this way when in 
captivity. On the other hand, should the parasite pass over 
into the adult, it is inconceivable how the fly, already weakened 
by the diminution of its fat body, could ever get out of the water 
when handicapped with a solid mass of spores which would 
swell its abdomen to quite three times its normal size. Taking 
into account all these facts, which in brief are the absence of 
mature larvae containing parasites, the absence of parasites in 
the pupae, the suppression of the reproductive organs, and often 
of the histoblasts, the voluminous proportions of the parasite 
and the resulting restriction of fat-body, I feel justified in stating + 
that in almost if not all instances, the presence of Glugeid par- 
asites prevents the maturation of their larval host. 
A GREGARINE PARASITE OF SIMULIUM LARVAE: (Plate 5) 
During early October and later it was found that, in two of 
the streams inhabited by Simulium bracteatum, a number of 
the larvae were somewhat enlarged: and had generally a lighter 
color than the average individuals. Closer inspection showed that 
they were heavily parasitised by innumerable small cysts meas- 
uring up to 0.25 mm. (pl. 5, fig. 1). A numben of these larvae 
were collected, killed and sectioned, when it was seen that these 
cysts affected various tissues of the body. The greater number 
of them were already free, floating in the blood plasma, but those 
which were still retained at the point where they began growth, 
were situated in the epithelial cells of the integument (pl. 5, fig. 
2), in the cells of the fat body (fig. 3) and in the pigment cells 
