FEMALE ORGANS OP GENERATION. 195 



dry specimens, to have precisely the same structure, only that in these, 

 as well as in the flies, each ring has its horny covering, which are con- 

 nected together by membranous parts. 



144. 



The VAGINA BIVALVTS is most closely related to the vagina tuln- 

 formis. It is found in the Orthoptera, some Neuroptera (Raphidia), 

 and the Tipularia. In its most complete development it is a sabre- 

 shaped tube, which curves upwards, into which the vagina opens, and 

 it is formed of two valves (Locusta, PI. XXIV. f. 10 14.) I consider 

 these two valves as the two lateral horny leaves mentioned above in the 

 description of the orifice of the vagina, and which here are prolonged 

 and now take the form of valves to that organ. The internal valves 

 corresponding with the last abdominal segment become also visible, and 

 here appear as the cover both above and below (f. 10. A, B,) at the base 

 of the vagina bivalvis itself. All Orthoptera, consequently, have nine 

 distinctly visible abdominal segments. In Locusta this vagina is long, 

 sometimes indeed (Locus, viridissimd) even longer than the body, each 

 valve is gently sloped, and has a channel upon it's exterior surface which 

 projects internally as an elevated ridge. At the base it is covered 

 beneath by the last deeply emarginate ventral segment, above it lies 

 the anus, and contiguous to it two short, simple, spinous processes. 

 Between the two larger valves there are two smaller ones (f. 12 and 14. 

 b, i,) which are connected by a delicate membrane with the internal 

 elevated ridge, and sometimes lse themselves in this or remain sepa- 

 rated from it. Frequently the apex of the exterior vagina is split at 

 the channel, when the exterior sheath appears, at least at its end, to 

 consist of four pieces *. In Gryllus, instead of this projecting vagina 

 we observe four short thick processes, the lower ones of which are 

 moveable, and form one articulation with the superior ones that are 

 closely attached to the abdominal cover. From the superior, stronger, 

 thicker ones thus intimately connected two processes are continued 

 within the abdomen, and to which are attached the muscles moving 

 the lower ones ; the orifice of the vagina lies between the lower ones, 

 and the anus above the superior ones. We may make the following 



* Kirby and Spencc, Introd. to Ent., vol. iv. p. 152., mention six pieces, but I have 

 never observed in our indigenous Locusts any but the structure described above, and never 

 six divided pieces. 



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