XI] THE REPRODUCTIVE SYSTEM 219 



For further details of the almost endless variety of structure 

 of the external genitalia, the reader should consult Selys [151], 

 Thompson [161] and BackhofE [4]. The Gomphinae in particular 

 shew the most extraordinary formations, especially in the penis. 



THE FEMALE. 

 1. Internal Organs (figs. 97, 98). 



These consist of a pair of ovaries with their oviducts, a bursa or 

 spermatheca, and a pair of accessory sacs [128]. 



The ovaries (fig. 97, ovy) are very large, extending from the 

 base of the abdomen down to the seventh segment, dorsally on 

 either side of the alimentary canal. Anteriorly they are united 

 by a median dorsal ligament, formed by fusion of the anterior 

 ends of the egg-strings, and attached to the posterior wall of the 

 thorax. Each ovary is enclosed in a thick sheath formed by the 

 fat-body. Numerous tracheae given off from the ventral trunk pass 

 to the lower ventral surface of the ovary, and ramify over its walls. 



The ovary is formed of numerous separate egg-strings, arranged 

 longitudinally, and held in place by the genital tracheae and 

 the envelope of fat. Each egg-string is moniliform, and consists 

 originally of three areas, the end-filament, the germinal area, 

 and the maturation area. These areas are best examined in the 

 well-grown larva, since at metamorphosis the whole ovary is fairly 

 well advanced. The end-filament is the narrower anterior portion 

 in which the germ-cells are first formed. It is formed of a single 

 row of cells in a long thread. Most of these primitive germ-cells 

 develop later into oogonia, but a few form follicle cells. Posterior 

 to the filament is an area in which the egg-string is seen to be 

 enlarged, owing to the fact that the germ-cells here become 

 crowded together and are increasing in size. This is the germinal 

 area, in which the large rounded oogonia are formed, each with 

 a double nucleus, and in which also the formation of the yolk 

 is first noticeable. In the third portion, or maturation area, 

 forming the whole of the posterior part of the egg-string, the 

 moniliform appearance becomes most marked, because the deve- 

 loping ova have become fairly large, and are separated out from 

 the germinal mass as a single string of eggs. They lie with their 



