MALE OKGANS OF GENERATION. 217 



tween them lies the short tubular penis. A very similar structure is 

 observed in the predacious flies, particularly Laphria and Asilus, yet 

 the large cylinder is bound by membranes to the ventral side, in which 

 shape it forms an actual bivalved sheath, and the exterior superior 

 smaller appendage is wanting. The sexual organs are most striking in 

 the Empidodea and Dolickopodea. In the former we observe at the 

 last abdominal segment of the male two large orbicular sloping valves, 

 which are fringed at their margin ; between their lower edges there is 

 a long, fine, upward bending bristle, which frequently lies completely 

 concealed between the valves. This bristle, in which we detect above 

 a fine channel, I consider as the penis, and the valves as its case. In 

 the Dolichopodea the last segment of the abdomen, turned downwards 

 towards the venter, forms the case, which is exteriorly convex but inte- 

 riorly concave. The upper free space of this cavity is occupied by a 

 horny bristle, which is so united by membrane to the case that it can 

 open and shut its aperture. In the thus formed cavity of the capsule 

 the penis lies. In front, attached to the capsule, there are two bent, 

 thickly fringed lamellae, completely resembling those of Nematocera. 

 I am almost induced to consider them as the projecting inner valves, 

 but they evidently serve as retaining organs. The anal aperture 

 appears to lie at the base of these valves. 



In the true flies (Musca, for example,) the sexual organs are placed 

 at the ventral portion of the last abdominal segment, the ring of Avhich 

 is hook -shaped, and by this curve covers the organs in repose; con- 

 tiguous to the apex of the hook there are two moveable, differently 

 formed valves, the analogues of the exterior valves in Dolichopus, and 

 in front lies the anal aperture ; further towards the venter, about the 

 middle of the hook, we find the sexual organs, likewise two either 

 longer or shorter bent lobes, between which a simple, thicker, some- 

 times clavate process (the penis) is displayed. Occasionally we find, 

 contiguously to the larger ones, two small triangular valves, which may 

 be considered as the inner valves of the penis. 



Among the Hemiptera, we discover in Cercopis sanguinolenta, both 

 in the male and in the female, two valves at the apex of the abdomen, 

 of which those of the male are considerably the smallest ; when opened, 

 we find at the base, between the exterior valves (PI. XXVI. f. 18.), 

 two smaller internal ones (f. 19. a, a), which are attached by articula- 

 tion to two horny bones. Between these the penis rises, and is, like 

 the ovipositor, a long, thin, setiform organ, which is not however,, as in 



