280 INSECTA. 



body ; but, in the engraving, those of one side only are delineated. 

 Every testis consists of a vesicular organ, hollow internally, which, 

 being immersed in the juices of the insect, separates therefrom 

 the seminal fluid. Six ducts (5, b, b) may be called Vasa 

 deferentia, and convey the spermatic liquor into a common 

 canal (c, c), of considerable length and much convoluted. 

 Although slender at its commencement, this tube ultimately 

 expands into a wider portion (d), wherein, no doubt, the semen 

 accumulates, and which has been called by authors the vesica 

 seminalis. 



The canal (d) terminates by joining the corresponding duct 

 from the opposite side (d?) to form a common tube (g), but just 

 at the point of junction they are joined by two long auxiliary 

 vessels (y, f) that have been named sperm-vessels, gluten-vessels, 

 and gum-vessels, by different authors, but which appear to be 

 appropriated to the production of some fluid, perhaps analogous to 

 the prostatic fluid of mammalia, whereby the bulk of the seminal 

 liquor is increased in order to facilitate its expulsion. Each of 

 these auxiliary vessels consists of two parts, a long and much con- 

 voluted portion (e, e, e), forming the secreting organ ; and a dila- 

 tation (f), that must be looked upon as a reservoir for the fluid 

 elaborated. The common canal (g) receives all these secretions ; 

 it is at first enclosed in a kind of sheath (A), but, soon becom- 

 ing muscular, it dilates into a strong contractile canal (g, z), called 

 the ductus ejaculatorius, which is continued to the extremity of 

 the penis. 



The intromittent organ itself is composed of two parts ; a pro- 

 trusible corneous tube (/, /), and an external horny sheath (n, n), 

 in which the former is usually concealed and protected. 



(325.) Great variety, of course, exists in the number, form, and 

 general arrangement of all the parts alluded to in the above descrip- 

 tion, when examined in different insects.* In the hive-bee, for 

 example, the testes (Jig. 125, a) are only two in number, and 

 are simple oval vesicles ; the vasa defer entia (b, b) are short ; and 

 the seminal receptacles (c) form membranous sacculi. The aux- 

 iliary secreting organs (d), although placed in the same position 

 as in Melolontha, are represented by capacious cseca ; while the 

 common excretory duct (e) swells into a strong and muscular bag 



* For more ample details relative to the various forms of the testis in insects, the 

 reader is referred to the Cyclop, of Anat. and Phys. ; art. GENERATION, ORGANS 



