PARASITES OF SIMULIUM LARVAE 57 
that given by Stempell (09) of Nosema bombycis Nag. Owing 
to their intercellular life the planonts are readily distinguished 
from the following stages which are intracellular. They measure 
(in N. bombycis) from 0.5 to 1.54 in length and are _ bullet- 
shaped, but have sufficient amoeboid movement to enable them 
to spread over the body. Under favorable conditions the nuclei 
can be seen. Division occurs in this stage, often quite actively 
so that masses of these minute organisms are seen. 
Stage III: the meront. The plaront enters a cell and at once 
loses its motility, becoming spherical or oval. In this stage 
division of the nucleus is rapid. In certain genera each division 
of the nucleus is accompanied by a division of the protoplasm 
so that numerous meronts ares formed. In other genera the 
nucleus divides independently of the protoplasm so that a multi- 
nucleate body is formed, which may attain considerable dimen- 
sions. This body is usually termed a ‘myxosporidium’ or ‘tro- 
phozoite.’ The typical myxosporidium consists of a very clear 
ectoplasm surrounding a granular entoplasm. The former may 
be capable of throwing out pseudopodium-like processes which 
are used only as locomotor organs. Most often the myxosporid- 
ium is sessile, and in some genera is capable of encystment. The 
entoplasm is coarsely granular and sometimes slightly yellowish. 
It contains numerous rapidly dividing nuclei and in addition 
may possess fat globules, pigments and one or more vacuoles. 
In the genus Nosema, where the meronts are numerous and uni- 
nucleate, each of them matures directly into a ‘spore,’ but in 
all the other genera there are intermediate stages between the 
meronts and spores. During the meront stage the parasite usu- 
ually breaks down the cell of the host in which it was formed 
from the planont, and lives for the remainder of its life as an 
intercellular parasite. 
Stage IV: sporont. A small clearly defined sphere of proto- 
plasm collects around each of the nuclei and its peripheral layer 
condenses to form a delicate envelope. The subsequent devel- 
opment of the sporont varies in different genera and _ species. 
Mercier (08) interpreted the subsequent developmental stages 
in Thélohania giardi Henn. as follows: The indefinite nucleus 
