102 ON THE ANATOMY OF THE FLY. 



the ducts of the testes into a common duct the vas deferens- 

 which terminates in an ejaculatory apparatus connected with 

 the intromittent organ by a very narrow ejaculatory duct. 



The testes are surrounded by a thick layer of folliculate 

 glands, and are largely supplied with a plexus of nerves of 

 organic life. Each testis consists of a sac of structureless 

 membrane, lined with a bright reddish brown pigment mem- 

 brane formed of coalesced pigment cells. In the earlier stages 

 it contains cells in which the spermatozoa are developed, 

 but is afterwards entirely filled with spermatozoa. The testis 

 often presents an hour-glass contraction almost dividing it into 

 two cavities. The length of the organ in its long diameter is 

 about l-30th of an inch. The duct of the testis is narrow, 

 about l-30th of an inch in length, and lined with conical 

 epithelium . 



The spermatozoa are very large, measuring l-100th of an 

 inch in length ; their large extremity is a flattened disc l-1000th 

 of an inch in diameter, but the filiform appendage is exceed- 

 ingly fine. 



The albumen glands are sacs l-15th of an inch in length; they 

 are lined with cylindrical epithelium which secretes a very 

 coagulable fluid ; when the gland is mature its interior assumes 

 a bright brown colour like that of the pigment coat of the 

 testis, probably from an accumulation of pigment on the surface 

 of its epithelial lining. The albumen glands open directly 

 into the vas deferens by narrow necks. 



The vas deferens is l-10thof an inch in length; it is widest 

 where it receives the ducts of the testes and albumen glands, 

 being nearly l-100th of an inch in diameter ; at its outlet, it has 

 only about half that calibre. It presents a very well defined 



