INTERNAL GENERATIVE ORGANS OF THE FEMALE. 671 



In most insects in which the egg-tubes are numerous, the 

 ovarian stroma and capsule present similar characters. 



In the Blow-fly the peritoneal tissue (Fig. 93) which forms 

 the stroma and capsule of the ovary consists of adenoid tissue 

 similar to that which invests the other organs, but denser and 

 permeated by muscle-fibres which diverge in a stellate manner 

 from large cells, the processes of which are clearly differentiated 

 into muscle-fibres. A similar condition is described by Graber 

 in the pericardial septum of the larva of Phryganea striata 

 [313, PI. IX., Fig. 13]. In the septa which separate the egg- 

 tubes numerous muscle-fibres extend from the concave to the 

 convex surface of the ovary. In the young ovary these septa 

 are seen to be the walls of distinct blood sinuses filled with 

 pseudo-yelk ; so that, if they are not to be regarded as peri- 

 toneal tissue, it would be better not to use the term for any of 

 the tissues of an Arthropod. 



The Oviducts commence by wide-open trumpets which are 

 attached to the capsule of the ovary and open freely into its 

 cavity. They are directed forwards, and unite beneath the 

 ovaries in the middle line to form the azygos oviduct. This 

 curves upon itself and opens into the utero-vaginal tube on the 

 dorsal aspect of the latter. The oviducts are very muscular, 

 exceedingly distensile tubes; in the empty condition their walls 

 are strongly plicated. There are two dilatations at the terminal 

 extremity of the azygos oviduct, immediately before it joins 

 the utero-vaginal tube. The anterior of these is similar in 

 structure to the oviduct itself. I term it the sinus of the 

 oviduct. The more posterior, unlike the oviduct proper, is 

 lined by a plicated cuticular layer. I term it the sacculus. 



The oviduct consists externally of a peritoneal layer con- 

 tinuous with the capsule of the ovary ; beneath this there is a 

 thick muscular coat, consisting of two layers of striated muscle- 

 fibres, an external longitudinal and an internal circular layer. 

 The tube is lined by large cubical epithelial cells, which in the 

 distended oviduct are flattened out into a pavement layer. 



In the contracted state the trumpet-shaped tubse measure 

 about 75 mm. in length, and have a diameter of '5 mm. in 



44 



