INTERNAL ANATOMY OF INSECTS. 155 



single membrane, and are joined to the oviduct by mem- 

 branous rugose cloacce a : in the Phalangia, however, 

 there are two tunics; the outer one of a cellular substance, 

 and the inner one consisting of spiral fibres like trachea; 

 a kind of structure which renders them capable of great 

 extension 1 *. Rifferschweils considers the ovaries as formed 

 upon two primary types. First, flagelliform ovaries, 

 consisting of conical tubes equal in length, and inserted 

 at the same place at the end of the primary branches as 

 in the Lepidoptera, the Bee, &c. Secondly, racemose 

 ovaries, consisting of short conical tubes, so proceeding 

 from the primary branches as to render the ovary race- 

 mose or pinnated, as in certain Neuroptera, Coleoptcra, 

 and Diptera c : but perhaps their structure will be better 

 understood if they are divided into agglomerate ovaries 

 and branching ovaries 4 in the^rs^ the egg-tubes form 

 two bundles, in which the branches are not discernible, 

 as in the Ephemera, the chamoeleon-fly, and spiders : 

 and in the second the branches are distinct, as in the 

 Lcpidoptera and the majority of insects. 



The number of branches varies in different genera and 

 species. In Echinomyia grosser, a large fly, there are 

 only the two primary branches e ; in the common dung- 

 beetle (Geotrupes stercorarius) these appear divided at 

 their apex into fingers f : in Scolia, a Hymenopterous 

 genus, and the butterfly of the nettle, there are three 

 secondary branches on each side s : in many other Le- 



a Rifferschw. DC Genital. Ins. 11. 



b Marcel cle Serres in Mem. du Mus. 1819. 109. PLATE XXX. 

 FIG. 12. a. c Rifferschw. ubi siqir. 23 . Swamm. Bibt. 



Nat. t. xlii./. 8. ,/, g, h. d Ibid. i. 104. t. xv. /. 3. ii. 62. 



t. xii./. 8. Treviran. Arachnid, t. iv./. 32. c Renum. iv, 391. 



f Posselt Anal, dcr Ins. t. If. 28, 29. G N. Did. 



Nat. xxx. 38/. Swamm. ubi supr. ii. 23. i. xxxv./. 3. 



