214 



THE REPRODUCTIVE SYSTEM 



[CH. 



forwards. In the Libellulidae, the tail is much shorter and less 

 slender. 



The vas defer ens (vd) is a rather narrow tube, which runs 

 along the middle of the inner side of the testis, being enclosed 

 within that organ by the overgrowth of its lobes around it. It 

 leaves the bent-up end of the testis in the eighth segment, and 

 passes backwards to the ninth. There it makes a small bend or 

 loop, turning forwards, inwards and downwards to enter a short 

 common duct just above the genital pore. In the mature male, 

 this common duct is dilated dorsally into a conspicuous sperm- 

 sac (sr), lying above the points of entry of the two vasa deferentia. 



Pig. 94. Mature spermatozoon 

 of Calopteryx splendens Harris 

 ( x 250). h head ; m middle- 

 piece ; nu nucleus ; t tail. After 

 Butschli. 



Fig. 95. Sperm-capsule of Aeschna brevi- 

 styla Ramb. ( x 330). Original. 



If the vas deferens of a mature male be opened 1 , it is found to 

 contain, not separate sperms, but a large number of little round 

 balls, or sperm-capsules (fig. 95). Each of these is about 0-15 mm. 

 in diameter, and appears to contain the whole mass of sperms 

 derived from a single testis-lobule. The sperms are all radially 

 arranged, their inner ends (apparently the heads) forming a 

 slight spiral (about a turn and a half) around the centre. 

 Externally, the capsule is enclosed by a thick coat, apparently 

 formed of minute gelatinous globules, one affixed to each sperm. 

 1 The observation was made with Aeschna brevistyla. 



