C. M. Wenyon 
323 
Though the gametes are equal in size, this is not the case with their 
nuclei, which are of two kinds. There are gametes with large nuclei 
and others with smaller nuclei. This difference in size of nuclei 
evidently has to do with a differentiation into male and female gametes. 
A similar difference in size of nuclei has been desci'ibed by Swarczewsky 
in Lankesteria sp. and Brasil has described an almost identical differen¬ 
tiation in the case of the gametes of Urospora lagidis. The difference 
in size of nuclei is best seen in the conjugating gametes, all stages of 
which can readily be followed in the sections (PI. XV, figs. 11, 13, 15). 
PI. XV, fig. 10, shows a gregarine cyst containing zygotes and several 
masses of residual protoplasm, in which are seen some of the incom¬ 
pletely divided nuclei. 
Development of sporocysts. The zygotes become elongated (PI. XV, 
fig. 20) and each becomes enclosed in a sporocyst which is flattened 
at the poles. Within the sporocyst the protoplasm divides into eight 
sporozoites after the nuclear divisions have taken place (PI. XV, figs, 21 
to 27). The nucleus of the zygote is a spherical body with the chromatin 
arranged irregularly over the surface of the membrane. The first 
division takes place regularly at right angles to the long axis of the 
sporocyst. The nucleus becomes elongated and the chromatin aggregated 
at the poles in the form of bands. After division the nuclei so formed 
migrate to the ends of the sporocyst, where they undergo a second 
division in a similar manner and in a line parallel to that of the first 
division. The final division takes place in the line of the long axis of 
the sporocyst and at right angles to the line of the first and second 
nuclear divisions. The eight nuclei then become arranged round the 
equator of the sporocyst. 
As a rule the whole process of development from the enc3^stment to 
the formation of the ripe sporocysts takes place during the pupal stage 
of the Stegomyia fasciata. In the newly hatched adult mosquito one 
finds the malpighian tubes containing gregarine cysts filled with ripe 
sporocysts. Very soon the cyst walls enclosing the sporocysts disappear 
and the sporocysts are found lying free in the cavity of the malpighian 
tubes. PI. XV, fig. 35, is from a longitudinal section of such a mal¬ 
pighian tube. The sporocysts make their way into the gut and are 
expelled, as Ross has described, with the faeces. Evidently these 
sporocysts escape into the water where the mosquito lays its eggs, 
and are taken up by the newly hatched larvae. I have not observed 
the escape of the sporozqites from the sporocyst in the gut of 
the larvae nor the infection of the epithelial cells in the earliest 
