REST OF INSECTS. 401 



stomach, — phenomena easily accounted for from the 

 want of a brain, and from each ganghon having its 

 own set of nerves. This may be better understood by 

 looking at the central chain of ganglia in the larva of 

 the day-fly before figured.* 



Insects again differ from man in having no heart 

 nor circulating blood, at least so far as has hitherto 

 been discovered.! Dr Cams, of Dresden, is, indeed, 

 at present endeavouring to estabhsh a claim to the dis- 

 covery of the circulation of the blood in insects; but 

 this circulation, which is most probably only partial, 

 has, we think, been observed by naturalists of a former 

 age. * De Geer,' say Kirby and Spence, ' whose 

 love of truth and accuracy no one will call in 

 question, saw the appearance of blood-vessels in 

 the leg of the larva of a caddis fly {Phnjganeaj 

 LiNX.), as Lyonnet did in those of a flea,J and in 

 the transparent thigh of the bird fly (OrniUioimjiaj 

 avicuhtria) he discovered a pulse like that of an 

 artery. § Baker, whose only object was to record 

 what he saw, speaks of the current of the blood 

 being remarkably visible in the legs of some small 

 bugs;i what he meant by that term is uncer- 

 tain, but they could not be spiders, which he had 

 just distinguished. This author has likewise seen 

 a green fluid passing through the vessels of the wings 

 of grasshoppers;ir and M. Chabrier is of opinion 

 that insects possess the power of propelling a fluid 

 into the nervures of their wings, and withdrawing it 

 at pleasure, as they are elevated or depressed;** but 



* See page 139. 



+ See Cuvier, Anat. Comp. vol. iv, p. 478, &c. And Mar- 

 cel de Seires, Mem. du Mus. pour 1S19. 

 i Lesser, vol. ii, p. 84, note. 

 § De Geer, vol. ii, p. .50.t; vol. vi, p. 287. 

 II On the IVFicroscope, vol. i, p. 130. T Ibid. 



** Sur le Vol des Insectes. 

 vol.. VI. .34* 



