34 ON THE ANATOMY OF THE FLY. 



bable that their function is analogous that of the vibrissse, or 

 feelers of carnivorous animals. 



Section XI. The Generative Organs. 



The sexes are quite distinct in insects. The female fly is 

 distinguished from the male by the great eyes being more nearly 

 approximated and larger in the latter, as well as by the sexual 

 organs. These consist in the male of a pair of testes, a pair of 

 tubular glands, probably secreting an albuminous fluid, with 

 their ducts ; and of extremely complicated external organs, con- 

 sisting of the four last abdominal segments. 



The generative organs in the female consist of a pair of ovaries 

 with their ducts. Three curious chitinous sacs which receive 

 the male fluid, a remarkable receptacle containing two peculiar 

 gelatinous masses after impregnation, beside a pair of tubular 

 glands, which probably secrete the glutinous fluid with which the 

 ovum is surrounded when it is deposited. The ova are fecundated 

 at the time of deposition, and the larva is hatched twenty four hours 

 after fecundation ; but sometimes a single ovum is fecundated 

 and retained within the ovipositor until the larva is perfected, 

 and the insect is thus occasionally viviparous, or the egg is laid 

 only a tew seconds before hatching. There are three or four sets 

 of ova contained in the ovaries, which are matured in succession. 



The ovipositor consists of four joints, and is very long ; it is 

 introduced within the genital- fissure of the male, during copula- 

 tion, and it enables the insect to deposit its eggs in deep fissures, 

 or beneath decaying matter. It is furnished with a pair of 

 leaf-like appendages at its extremity, but has no hooks in the 

 blow-fly, although that of the house-fly is furnished with a set of 

 spines, pointed backwards around every ring. 



