268 CLASS VIII. 
which were originally distinct, as at least in Butterflies is placed 
beyond all doubt by the history of development. In many Hymen- 
optera the two testes lie side by side in a common covering (scrotum 
Durour). Sometimes these organs, usually white, are distinguished 
by lively colours (deep red in Papilio brassicw, and in some Hemi- 
ptera, yellow or orange-coloured in some Coleoptera) which depend 
upon the investing membrane. Moreover the structure of the testes 
is very manifold, and, as in glands generally, nature has here solved 
the problem, in a small given space to increase as much as possible 
the secretory surface, in very different ways. The simplest form is 
that of a single blind canal, which is sometimes very tortuous!. In 
other cases this blind canal has more the form of a sac, ex. gr. in 
Scutellera, Edessa. Yet they are not always constructed in this 
simple way, when they have externally the form of a single blind 
sac and have also been so described by some writers; in Lebellula, 
for instance, this sac contains a number of small round vesicles?. In 
by far the greatest number of Insects each festis consists of a collec- 
tion of different, sometimes very numerous, vesicles, or cylindrical 
canals (capsules séminifiques L¥on Durour) terminating blindly, 
which are united in form of a fan, of a star, of an umbel, or in 
bunches, and from which canals arise that afterwards terminate in 
a single efferent canal*. This efferent canal forms sometimes at its 
commencement numerous tortuosities, to which the name of ep7- 
didymis has been given (as in many Carabici, in Melolontha‘, in 
Nepa, &c.). The lowest part has often an expansion® to which the 
name of vesicula seminalis has been fitly given. Far less propriety 
is there in giving this name to different blind canals which are met 
1 In Dytiscus marginalis the entire canal when unwound appears to surpass the 
length of the animal twenty times, HEGETSCHWEILER De Insector. genital. p. 19. 
3 Lion Durour, Mém. présentés, VI. p. 572. 
3 For a methodical review of all these forms an arrangement is requisite in which, 
at the same time, there are not too many divisions. Comp. Jon. MUELLER, De glan- 
dularum secernentium structura penitiori, 1830. fol. p. 103; BURMEISTER, Handb. der 
Entom. 1. 8. 217—219; WAGNER'S Lehrb. der vergl. Anat. 1834, 8. 329—332, and the 
figures chiefly borrowed from Lion Durour’s numerous investigations in MUELLER, 
1.1. Tab. xvi. figs. r—19, and in Wagner, Icones Physiol. 1839, Tab. XIX. figs. 1—26. 
4 Srravs, 1. 1. Tab. vr. fig. 1, c, c. 
5 For instance, in Hydrophilus, in Apis mellifica, in Gerris and Velia (L&oNn 
Durour, Rech. s. 1. Hémipt. Tab. x1. figs. 138, 139), in Cossus marginatus (Lion 
Dvrour, 7b. Tab. x. fig. 127). 
