268 CLASS virt. 



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 

 DUFOUR). Sometimes these organs, usually white, are distinguished 

 by lively colours (deep red in Papilio brassicce, 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 1 . 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 Libellula, 

 for instance, this sac contains a number of small round vesicles 2 . In 

 by far the greatest number of Insects each testis consists of a collec- 

 tion of different, sometimes very numerous, vesicles, or cylindrical 

 canals (capsules seminifiques LEON DUFOUR) 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 3 . This efferent canal forms sometimes at its 

 commencement numerous tortuosities, to which the name of epi- 

 didymis has been given (as in many Carabici, in Melolontha*, in 

 Nepa, &c.). The lowest part has often an expansion 5 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 LEON DDFOUR, Mem. presentes, vn. 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. JOH. MUELLER, De glan- 

 dularum secernentium sfructura penitiori, 1830. fol. p. 103 ; BURMEISTER, Handb. der 

 Entom. i. B. 217 219 ; WAGNER'S Lehrb. der vergl. Anat. 1834, s. 329 332, and the 

 figures chiefly borrowed from LEON DUFOUR'S numerous investigations in MUELLER, 

 1. 1. Tab. xvi. figs, i 19, and in WAGNER, Icones Physiol. 1839, Tab - XIX - % s - 126. 



4 STRAUS, 1. 1. Tab. vi. fig. i, c, c. 



5 For instance, in Hydrophilus, in Apis mellifica, in Gerris and Velio, (LoN 

 DOFOUR, Rech.s.l. Htmipt. Tab. XI. figs. 138, 139), in Oossus marginatus (LoN 

 DUFOUR, ?7>. Tab. x. fig. is-V 



