110 ON THE ANATOMY OF THE FLY. 



The capsule exhibits well marked rings of chitine and numerous nuclei. 

 It is easily ruptured by pressure. The elastic tube connecting the capsule 

 with the oviduct has a very thick wall, of a light yellow tint, marked 

 with transverse wrinkles. The calibre of the tube is greatest in the 

 middle, where its diameter does not exceed l-400th of an inch. It tapers 

 gradually to a very fine opening at either extremity. Numerous small 

 cells may be observed adhering to the duct, which give it a beaded 

 appearance. They are probably concerned in the development of the 

 muscular coat which surrounds both the capsule and its duct, but which is 

 not well developed until the ova are mature. 



A little below the openings of the albumen glands and 

 seminal receptacles, about l-30th of an inch from the outlet of 

 the common oviduct, its membranous coat forms a pouch in 

 its ventral wall. This pouch is called the bursa copulatrix (Plate 

 X., figs. 1, 2, and 6). It is about l-80th of an inch in diameter. 

 The bursa has a narrow neck, which opens backwards into 

 the oviduct. It exhibits two curious lateral folds, one on 

 each side of the neck, which project into its interior, as if the 

 wall had been pushed inwards, and a third fold in the mesial 

 line, which forms a partial septum, dividing the pouch into 

 two lateral halves. The bursa is very elastic, resuming its 

 shape after dilatation or compression, and refracts light 

 powerfully. The neck of the bursa is studded with minute 

 corpuscular bodies, with a bright transparent centre. These 

 are not more than l-5000th of an inch in diameter, and may 

 be either papillse, connected with nerves, or merely centres 

 of chitinous deposit. I am decidedly inclined to the latter 

 view. 



The arrangement of the muscular fibres of the outer coat of the oviduct 

 below the entrance of the ducts of the albumen glands and seminal recepta- 

 cles, needs special notice. The muscular coat is very highly developed (Plate 

 X , fig. 2), and its outer layers form broad bands of muscle, chiefly having an 

 oblique direction round the oviduct. A well marked broad band surrounds 

 both the bursa and oviduct in a transverse direction, and conceals other layers 

 which have an oblique direction ; and others again, which surround only the 

 bursa or oviduct separately. A pair of large muscles, which arise from 

 the dorsal part of the second segment of the ovipositor the seventh ab- 



