110 INTERNAL ANATOMY OF INSECTS. 



some, screw-shaped a : in one larva, with hemispherical 

 elevations 5 : in the cockchafer, part of them are fringed 

 on each side with an infinity of short, blind, minute, 

 setiform tubes, while the rest are naked c ; they are 

 composed of a single, thin, transparent membrane, ac- 

 cording to Ramdohr d ; but Cuvier thinks their texture 

 is spongy e . They appear to contain a number of small, 

 irregular, dark granules, which float in a peculiar fluid, 

 with which, however, they are not always filled through- 

 out, nor are they constantly permeable from one end to 

 the other. Thus in the meal-worm beetle (Tenebrio 

 Molitor], the common trunk by which they are attached 

 to the intestinal canal is composed of gelatinous gra- 

 nules f . The place of their insertion is generally a little 

 below the pylorus, but in the common cockroach they 

 are inserted into the stomach just above that parts. 

 Usually each vessel opens singly into the intestinal ca- 

 nal, which the whole number surround at an equal di- 

 stance from each other 11 . Sometimes, however, they are 

 connected with it by a common tube in which they all 

 unite, as in the asparagus-beetle (Lema Asparagi i ), and 

 the mole-cricket (Gryllotalpa wlgaris k ); in the house- 

 fly (Musca domestica), and other Muscidce, each pair 

 unites so as to form a single branch on each side of the 

 canal previously to their insertion 1 ; in the field-cricket 

 (Gryttus campestris) they are all inserted in one spot" 1 ; 



Notonecta glauca, Ibid. t. xxiii./. 5. 

 Of Musca vomitoria, Ibid. t. xix./. 5. 



Ibid. t. viii./. 1. H. and G./. 2. d Ibid. 50. e Ibid. 



Ibid. g Ibid. 44. t. i./. 9. h Ibid. * Ibid, t. vi./. 5, H. 

 Kidd in Philos. Trans. 1825. t. xv./. 6. 

 Ibid. t. xix./. l.N t N, O,/. 2. P, P, O, 

 Ibid. t. I./, 1. kick. 



