GENERATIVE ORGANS. 



541 



lid 



fluence of the secretion of an accessory gland. Beneath the recepta- 



culum seminis, a large pouch-like diverticulum, the bursa copulatrix, 



which assumes the function of the vagina, is sometimes separated 



from the vagina. In the butterflies (fig. 448) a narrow duct serves 



to convey the sperm from this bursa, which 



opens separately, to the receptaculum. 



The male generative organs consist of 



paired testes and their vasa deferentia, of 



a common ductus ejaculatorius and of the 



external copulatory organ (fig. 450). The 



testes are long blind tubes, which are present 



either singly or in number on either side, 



and are often coiled together so as to form a 



seemingly compact brightly-coloured body. 



They may also be united to form an unpaired 



organ in the middle line. The testicular 



tubes are prolonged on either side into a 



usually coiled efferent duct or vas deferens, 



the lower end of which dilates considerably, 



and may even swell out to the form of a 



vesicle (vesicula seminalis). At the point 



where the two vasa deferentia join to form the muscular ductus 



ejaculatorius, one or more glandular tubes often pour their coagulable 



secretion into the latter ; the secretion serving to form a case 



round the balls of spermatozoa. The transference of the sperrnato- 



phores into the body of the female 

 is effected by a horny tube or 

 groove which surrounds the end 

 of the ductus ejaculatorius. This 

 tube, when not in use, usually lies 

 retracted in the abdomen, and 

 when protruded is surrounded by 

 external organs for attachment 

 (valves or pincers), as by a sheath. 

 In exceptional cases (Libellula) the 

 copulatory apparatus which serves 

 to transfer the sperm is remote 

 from the generative opening, as in 

 the male spiders, being placed on 



the ventral side of the enlarged second abdominal segment. 



Almost all insects are oviparous, and only a few, as the Tachincv, 



FIG. 449. Terminal region of 

 the female generative organs 

 of 3IiiKca domestica (after 

 Stein). Od, Oviduct, Re, the 

 three receptacula seminis ; 

 Dr, glandular appendages 

 of the vagina ; Bl. blind 

 sac-like appendage. 



FIG. 450. Male generative organs of the 



Cockchafer ; (after Gegenbaur). T, Tes- 

 tes; Vd, dilated portion of the seminal 

 duct; Dr coiled accessory gland. 



