REPRODUCTION IN DROSOPHILA. 229 



which would readily mate, having been kept isolated in a vial for 

 three or four days, becomes discouraged after smelling the poste- 

 rior end of the female, where normally a white matter acting as a 

 cause of sexual excitement protrudes (Sturtevant, '15). Sterile 

 flies usually die after a few days, their abdomens attaining con- 

 siderable distension. In the only female dissected the paired ovi- 

 ducts lacked a lumen ; some four or five eggs had fallen into the 

 body cavity by rupture of the ovarian wall, and were entirely 

 degenerated, the cytoplasm appearing in irregular clumps. All 

 the seminal receptacles, which like the uterus were normal, did 

 not contain sperm. 



CONCLUSIONS. 



1. In the internal genitalia of Drosophila melanogaster there 

 are only two spermathecse and a ventral seminal receptacle in the 

 form of a long, convoluted tube which opens proximally into the 

 anterior portion of the uterus, ventral to the oviduct. 



2. The spermatozoa after ejaculation into the uterus during 

 copulation appear almost motionless, only a few showing faint 

 undulatory movements. The ejaculation of the sperm by the 

 male is greatly aided through the action of the ejaculatory sac, an 

 organ which acts as a pump, driving the sperm at a high pressure 

 through the narrow ejaculatory duct. 



3. After ejaculation of the sperm there is a pause which lasts 

 two or three minutes, during which the spermatozoa do not show 

 active movements. Then they begin to swim actively to enter 

 the seminal receptacles. There seems to be an activation of the 

 spermatozoa at this moment on the part of the parovaria, two 

 glandular structures connected with the anterior portion of the 

 uterus by means oi narrow ducts. 



4. The ventral receptacle is the first to receive the sperm, which 

 is also stored in the spermathecse. The spermatozoa form bun- 

 dles when in the receptacles. In the ventral receptacle all the 

 heads are directed toward the distal end of this organ. The 

 bundles are concentric in the spermathecse. 



5. The position of the egg within the uterus is constant; the 

 surface bearing a pair of divergent appendages is applied against 

 the dorsal wall of the uterus. The anterior end of the egg with 

 the micropyle is lodged in the anterior portion of the uterus, with 



