REPRODUCTION IN DROSOPHILA. 



Picric acid ( i p.c. sol. in abs. ale.) 6 c.c. 



Chloroform i c.c. 



40 per cent, formalin i c.c. 



Glacial acetic acid 0.5 c.c. 



This fluid kills instantly and penetrates very well ; but the 

 preservation obtained is poor for cytological purposes yet good 

 enough for histological study. The abdomens of the flies were 

 cut off from the rest of the body while in the fixative, then trans- 

 ferred to 95 per cent, alcohol and cleared with cedar oil, after 

 dehydration with absolute alcohol. Sagittal sections were used 

 almost exclusively and were stained with Delafield's hematoxylin 

 and eosin. 



2. THE MORPHOLOGY OF THE INTERNAL GENERATIVE ORGANS. 



The internal generative organs of Drosophila are much like 

 those in other flies. In the female they show certain character- 

 istics absent or feebly developed in other diptera. 2 



Male. 



The testes (Fig. i, t~) are two tightly convoluted tubes of 

 orange or yellow color, which communicate with the vas deferens 

 (d) by means of rather short, paired ducts, the vasa efferentia- 

 (v}. The latter are swollen in their initial portion and probably 

 store the ripe spermatozoa before they are discharged into the 

 vas deferens. The vas deferens is a long duct, much swollen ia 

 its anterior section, tapering gradually towards its termination 

 at the side of the ejaculatory sac (s}. Its walls are highly con- 

 tractile. 



The ejaculatory sac is a curious structure which deserves spe- 

 cial mention since it plays an important role in the ejaculation of 

 the sperm. It acts as a pump and drives the sperm through a 

 narrow ejaculatory duct (e} which has stiff walls lined internally 

 with a tough cuticle. The sac can be regarded as an outpocketing 

 of the ejaculatory duct, since it is also lined internally with a 

 cuticle, but its cavity has been cut off from the lumen of the duct 

 which is in communication with the vas deferens through an en- 



- So far as is known to the writer, the occurrence of a ventral seminal 

 receptacle has never been mentioned in any of the Diptera. Cf. Berlese, ig9- 



