_ OOGENESIS IN PHILOSAMIA 3 
In the study of the early stages of oogenesis, both caterpillars 
and pupae were used. The ovaries in the early pupal stage 
lie enveloped in the fat bodies just beneath the dorsal wall of 
the abdomen in the fifth segment. Upon removing the wall, 
the ovaries were located and transferred immediately to the 
fixing fluid. Flemming’s, Bouin’s and Carnoy’s fluids were 
used, the latter being the only one good for all stages. The 
stains employed were safranin and iron hematoxylin. 
MATURATION DIVISIONS 
1. OBSERVATIONS 
a. Chromosomes in the embryo 
The number of chromosomes in the spermatogonia is 26 (Ded- 
erer ’07), all rounded bodies, approximately equal in size. For 
determining the somatic number, sections were made of eggs 
several hours after fertilization. Ten counts from three differ- 
ent lots of eggs showed clearly 26 chromosomes. In polar view 
of metaphase (fig. 1) they appear as slightly elongated, often 
bipartite, bodies of comparatively slight difference in size. Owing 
to their similarity it is impossible to attempt any arrangement 
of the chromosomes in pairs, as has been done in some animals. 
b. First maturation division 
The mature eggs are oval bodies about 1.5 mm. long, each 
invested in a tough white chorion, which is flatter and broader 
at the animal pole. The flattened area appears to be due to the 
contact of the nurse cells in this region, while in the egg tubes. 
Figure 32 is from a longitudinal section through the animal 
pole of an egg, showing a spindle with chromosomes in ana- 
phase, within a dense granular mass, whose long protoplasmic 
processes reach out into the more reticular portion of the cyto- 
plasm. This latter region is free from yolk, and is cone-shaped 
in form, the apex pointing inward, and extending as a sort of 
narrow vacuolated core, into the center of theegg. The remainder 
of the egg is filled with large yolk spheres. At the periphery 
of the egg appears a thin layer of dark granular protoplasm. 
