PARASITES OF SIMULIUM LARVAE 59 
collar-like mass of protoplasm containing either two or four 
nuclei, while the apex projects into a large vacuole occupying 
almost half of the area of the spore. Both Mercier (’08) and Stemp- 
ell (09) find that in T. girardi Henn. and N. bombycis 
Nag. respectively there are two minute nuclei attached to the 
shell and one similarly minute nucleus attached to the polar cap- 
sule. 
By means of these spores the disease is disseminated among 
new hosts. Where the parasite infects the epithelial cells of 
the gut and other excretory organs the spores escape into the ali- 
mentary tract and are passed out of the body with the faeces. 
If other organs form the seat of attack the spores are liberated, 
either by forming a tumor through the bursting of which they 
escape, or they await the death and subsequent decay of their 
host. Pasteur (’70) showed, in the case of the pébrine of silk- 
worms that the spores can pass into the ovary and thus spread 
the disease by infecting the eggs. If the host is aquatic, as is 
most often the case, the spores fall to the bottom of the water, 
and there remain unchanged till taken into the alimentary tract 
of a new host, while in terrestrial hosts, as in the silk-worm, the 
spores are scattered in the faeces of infected larvae and thus con- 
taminate the food on which the healthy larvae are feeding. 
As soon as the spores reach the foregut of a new host, the 
digestive juices set up intrasporal pressure either by causing 
_ the shell to contract, or by passing through it by osmosis, which 
contracts the polar capsule and thus ejects the spirally coiled 
filament through the pore in the spore shell. Stempell (’09) 
points out that the filament, owing to the manner in which it is 
ejected, evidently consists of a hollow tube which is everted 
when it protrudes from the spore. The filament is often very 
long, that of the spore of [Nosema] Glugea simulii Lutz and 
Splendore (’08) and of Glugea fibrata sp. nov., which I have 
recently found in Simulium larvae, being thirty to forty times 
the length of its parent spore. The function of this filament 
has been the subject of much discussion. It was first discovered 
by Balbiani in 1863, when he attributed to it a function similar 
to that of the antherozoid of the Cryptogams. In 1882 Bitschli 
