12 
Psyche 
March 
the time that small fat droplets begin to appear in the 
center of the oocyte, the peripheral droplets and protein- 
aceous globules have greatly enlarged (3 to 7 microns in 
diameter) and are present in about equal numbers. The 
diminishing central layer of cytoplasm around the nucleus 
is connected by the fine network between the yolk globules 
to a thin peripheral cytoplasmic layer, the periplasm. By 
the time the perinuclear cytoplasm has become very thin, 
the fat droplets appear to have coalesced, for the visible 
proteinaceous yolk globules, some of which are now as large 
as 11 microns in diameter, stand out in fixed preparations 
against a clear background. 
The oocyte has been growing only slightly meanwhile, 
and is still very narrow in proportion to its length. Before 
oviposition the maximum length of the egg increases by 
about two and one-half times, and its maximum width 
increases about eighteen times. Growth is accomplished 
chiefly by an increase in the proteinaceous yolk. Just before 
oviposition the egg contains relatively little fatty yolk. 
At the start of the growth period the nucleus moves to 
the periphery. The nuclear network condenses at the peri- 
phery of the nucleus and the chromatin becomes distinctly 
visible with the Feulgen technique. Evidence of tetrads is 
seen. The interior of the large nucleus now appears homo- 
geneous and has little affinity for the stains used. Before 
oviposition there occur both a marked decrease in nuclear 
volume and further condensation of the chromatin into 
small compact chromosomes. 
The follicle cells start to secrete the endochorion at the 
time when yolk accumulation first begins. The process is 
best studied in preparations stained with phosphotungstic 
hematoxylin. Just before secretion of the endochorion 
starts, the brown-staining connective tissue sheath sur- 
rounding the ovariole becomes greatly thickened. It ap- 
pears that the follicle cells withdraw material from the 
sheath and secrete it to form the endochorion. Comparison 
with the accompanying process of yolk accumulation indi- 
cates that the sheath is reduced to its former size within 
a relatively short time. The secretion of the exochorion, 
which occurs much later, is mentioned below. 
