DEVELOPMENT OF THE OVAUIES m THE BLOWFLY. 427 



In mature insects ready to lay eggs the 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 o£ the egg-string 

 between successive ova. The egg-string between the second and 

 third chambers (tp^) 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^) 

 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 Stublmann. 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 diff'ers 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 /i in its longest diameter, and 

 has a nucleus of 80 m 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 



