GENERATION OP INSECTS. 401 



insects. The internal female sexual organs consist of the ovaries, the 

 oviducts, the uterus, the sperraatheca, the bursa copulatrix, the mucous 

 glands or coUeteria, the scent-glands, and the vagina ; but these are 

 not all present in all insects. The external organs are the vulva, 

 the sting, the holders, and ovipositor ; some of which are likewise 

 peculiar to particular species. 



The most constant and essential parts of generation of the fe- 

 male insect, viz., the ovaria, are subject to almost as many varieties 

 as the testes in the male ; their forms may be arranged into almost as 

 many genera and species, which are very often analogous to those of 

 the essential glands in the opposite sex. The ovaria in the Lepido- 

 ptera do not, however, coalesce into a single mass, like the testes in 

 the male ; they are either digitate or verticillate ; that is to say, they 

 consist either of a few egg-tubes suspended to the end of the oviduct, 

 becoming attenuated as they recede from it ; or they consist of nu- 

 merous very long egg-tubes, proceeding from a very short oviduct, 

 and terminating in filiform extremities, when they are usually disposed 

 in spiral coils bending at the two sides in opposite directions, as in the 

 Noctua Brassicce {Jig. 154, a, a). In the forest-fly each ovarium 

 consists of two egg-tubes ; in the flesh-fly it consists of a single tube, 

 which is of great length, and twisted spirally. In the mantis a single 

 series of short egg-tubes are attached to one side of a common duct. 

 In the gnats, crickets, and locusts, the numerous egg-tubes, which are 

 somewhat compressed, lie upon one another like scales, or the tiles 

 upon a roof. In the Ephemera and Stratiomys the ovaries have the 

 primitive form of simple elongated bags, in which the eggs are 

 contained linked together by delicate filaments. In almost all cases 

 the caecal terminations of the ovaries are attached by a delicate thread 

 to the thorax : the tubes themselves being connected together by a 

 complex tracheal network. 



Swammerdam* has given an accurate description, with excellent 

 figures of the female organs of the louse, the discovery of which 

 helped him to an excellent argument, requisite in his day, against the 

 spontaneous generation of that parasite from the filth of the abject 

 members of our species which it commonly infests. Five egg-tubes 

 converge and coalesce into a single short oviduct on each side ; the 

 two unite into a common tube, with which a pair of branched or 

 varicose accessory follicles communicate. The vulva is surrounded 

 by four mammillary eminences : the spermatheca and bursa copulatrix 

 are wanting. 



* CCXXXni. p. 37, pi. 2. 



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