development: of the ovaeies in the blowfly. 427 
In mature insects ready to lay eggs tlie ovaries occupy the 
greater part of the cavity of the abdomen. There are about one 
hundred egg-tubes (80 to 100) in each ovary, each having four, 
five, or even six egg-chambers in different stages of develop- 
ment (fig. 8). 
A mature egg occupies the most posterior chamber (fig. 8, a ), a 
partially formed egg is seen in the second chamber, whilst the 
third, fourth, and terminal chambers contain very rudimentary 
ova. The whole terminates in a small empty, hollow, end- 
thread (tf). 
The cuticular tunica propria closely surrounds the egg and 
egg-strings, whilst the thin greatly distended egg-follicle passes 
from one egg to the other, leaving a considerable space between 
the eggs ; it does not follow the outline of the egg-string 
between successive ova. The egg-string between the second and 
third chambers ( tp l ) is exactly similar to the egg-stalk of the 
first chamber in the early stages of its development. 
The two or three anterior chambers are filled with small round 
cells like those of the terminal chamber or the whole egg-follicle 
at an earlier period. The unripe egg in the second chamber (ec 2 ) 
consists of large yelk-cells enclosed in an epithelial chorion. 
The lowest cell in such eggs is, however, always much larger, 
usually twice as large as the others, but its nucleus is also nearly 
twice as large, and stains just as deeply. It also contains the same 
kind of granules as the others. In these statements I agree in 
no way with Brandt and Stu'nlmann. Brandt states that the 
nucleus of the lowest cell is large and clear, Stuhlmann that it is 
very much smaller than the other nuclei, and that it is clear and 
flattened against the chorion. According to my observations it 
is neither one nor the other, and only differs from the nuclei of 
the other cells in being larger. 
The yelk-cells ultimately attain a giant size ; the largest cell, 
when full-grown, measures 200 /.t in its longest diameter, and 
has a nucleus of 80 p. in diameter. When the egg is enlarged 
to about two thirds of its maximum size the granules in the 
largest nucleus appear to stream out, the nucleus itself shrivels 
and is ultmately lost, whilst the whole protoplasm of the cell 
assumes a granular yelk-like appearance, in which the nuclear 
granules can no longer be distinguished. The remaining cells 
LINN. JOUEN. — ZOOLOGY, VOL. XX. 32 
