■H)i 



COMPARATIVE AIs^ATOMY. 



§ 236. 



The male generative organs of Insects very often repeat in 

 tlieir development the forms of tlie female organs, so that even 

 the separate divisions of both sets of glands not unfrequently 

 correspond. The testes, which are always paired, and seldom fused 

 into one organ, are composed of c^cal tubes, just like the ovaries ; 

 they also vary in number and size, and are connected with one 

 another in all kinds of ways (Figs. 161, 162, t). The testes of either 

 side are often united in the Lepidoptera. The Diptera and Strep- 

 siptera, as well as many Neuroptera, have two simple, long, and 

 always separate testicular tubes. In many Coleoptera, also, each 

 testis is a long, closely-coiled caecal tube, surrounded by a special 

 membrane. The testes of most insects are made up of a number 

 of tubes. Thus each testis, in most of the Hemiptera, consists 



Fig. 161. Testes and efferent cincts 



of Acheta campestris. t Testes. 



V Vas deferens, g Seminal vesicle. 



Fig. 162. Male generative organs of Melo- 



lontha vulgaris, t Testes, vd Yas defe- 



rens. vs Its widened portion, gl Coiled 



appended gland. 



either of several tubes connected together to form a fan-like 

 organ, or of a large number of separate tubes; this form of testis 

 is also found in a large number of the Coleoptera. The testes 

 of most Orthoptera consist of closely-applied tubes, which thus 

 form a single mass, or of rounded vesicles grouped in a racemose 

 fashion ; similar structures are also found in the Tlymenoptera. 



The efferent ducts of the separate testicular tubes are united 

 into seminal ducts, and these, on each side, into a vas deferens 

 (Fig. 161, t;; Fig. 162, vd), which, when the tubes are closely 

 united, passes directly from them. The two seminal ducts are, as 

 a rule, not very long, but in some cases they are considerably 

 elongated, and the widened portions of the coiled canals then function 

 as seminal reservoirs (Fig. 162, vs). A common efferent duct 

 (ductus ejaculatorius) is given off from their point of union ; this, 

 too, varies greatly in length, and also serves in part as a reservoir 

 for the sperm. 



The accessory glandular organs are as a rule paired, and like those 

 of the female apparatus are either long coiled canals (Fig. 162, rjJ), 



