PARASITES OF SIMULiIUM LARVAE ia 
twice and in each case the nuclear matter had evidently assumed 
a ringlike form before division (fig. 12). It is very difficult to 
trace the developmental stages beyond this point until the sporo- 
blasts are in process of formation, since all the maturation stages 
are progressing simultaneously in such a small area that they are 
practically inseparable, and tracing the individual developmental 
stages is rendered almost impossible. In the next stage that I 
was able to distinguish with any certainty, there was evidently 
a third nuclear division for the much enlarged sporont contained 
eight distinct nuclei (fig. 13). 
Sporoblasts. The wall of the sporont now becomes much thick- 
ened and indented between the eight regularly spaced nuclei 
(pl. 3, fig. 14). This indentation progresses between the nuclei 
which thus become surrounded by a nearly globular mass of 
cytoplasm as shown in figure 16, which represents a section of 
one of these bodies. The walls gradually meet around each of 
these eight sporoblasts and the aggregate is then separated to 
form eight free spherical sporoblasts (fig. 17) which measure at 
first about 5.2u in diameter but later increase somewhat till they 
measure about 6.2u. 
Spores. The sporoblasts are transformed into spores by a 
process apparently similar to that described for G. bracteata, 
except that in this case the spores are entirely free throughout 
the whole of their development. The spore is oval in shape, 
measuring 5.8 to 6.6. x 3.5, and is surrounded by a very 
thick transparent shell. At the broader end there is a very 
large vacuole, plainly visible in the fresh spore, while at the 
smaller end is a much smaller vacuole which cannot be seen in 
untreated preparations. The nucleus does not differentiate so 
distinctly in the spore of this species as in G. bracteata, though I 
found indications of it as a minute body which was often dividing 
or already divided and situated just above the smaller vacuole 
(figs. 18 and 19). On one occasion each of the two nuclei formed 
by the division of this primary nucleus was again undergoing 
division (fig. 20). By staining deeply with haematoxylin the 
polar capsule is sometimes distinguishable, projecting through 
the dense protoplasm into the large vacuole (fig 21). The dia- 
