A contribution to our knowledge of the Stylopidae. 955 
lose all appearance of being in separate masses or strands and form 
a single homogeneous mass. While in this form they seem gradually 
to lose their protoplasm as the embryos grow, until, in the stage 
shown in Fig. 13, they have become greatly shrivelled up. 
Maturation. 
The observations which I have been able to make upon this point 
are rather unsatisfactory owing to the poor preservation of the material 
in these stages. But as they throw some light upon the subject and 
suffice for a few conclusions they may as well be included. When 
the egg is fully formed and the nucleus is ready to give off the polar 
bodies, it moves from its central position towards the periphery to a 
point somewhere on the equator of the egg (Fig. 5). This point is 
equatorial with reference to the present oval shape of the egg, but 
perhaps not so with regard tho the future orientation of the embryo, 
although it is impossible to determine this point as there is no in- 
dication as to which is dorsal lateral or ventral at this time, and the 
orientation of the embryo at later stages bears no definite relation to 
the position of the egg in the body of the mother, as is the case in 
most insects. 
Maturation seems to be similar to the second type described by 
BRAUER (93) for the parthenogenetic eggs of Artemia. Two polar 
bodies are ‚produced and the female pronucleus retreats toward the 
center of the egg. It is closely followed by one of the polar bodies 
(Fig. 16), presumably the second; the chromatin in its nucleus assumes 
the reticulate form as does also that of the second polar body, which 
has a much smaller nucleus and protoplasmic body than the female 
pronucleus. When both have nearly reached the center of the egg 
(Fig. 17) they place themselves side by side and finally fuse, giving 
rise to the cleavage nucleus (Fig. 6). 
Cleavage and the Formation of the Blastoderm. 
- Immediately after the copulation of the pronuclei, or rather the 
fusion of the female pronucleus and the second polar body, the result- 
ing cleavage cell, which has now reached the center of the egg, grows 
through the addition of more protoplasm and its pseudopod-like pro- 
cesses become longer, almost reaching the periphery of the egg in 
some cases. 
Intermediate stages between this and the blastoderm stage show 
the typical accumulation of cleavage nuclei scattered through the yolk 
