HEST OF INSECTS. 401 



stomach, phenomena easily accounted for from the 

 want of a brain, and from each ganglion 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. f Dr Carus, of Dresden, is, indeed, 

 at present endeavouring to establish 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 (Phryganea, 

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

 the transparent thigh of the bird fly ( Ornithomyia, 

 avicularia) 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;|| 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 ;TT and M. Chabrier is of opinion 

 that insects possess the power of propelling a flujd 

 into the nervures of their wings, and withdrawing it 

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



* See page 139. 



t See Cuvie'r, Anat. Comp. vol. iv, p. 478, &c. And Mar- 

 cel de Serres, Mem. du Mus. pour 1819. 

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

 De Geer, vol. ii, p. 505; vol. vi, p. 287. 

 I! On the Microscope, vol. i, p. 130. TT Ibid. 



** Sur le Vol des Insectes. 

 VOL. vi, 34* 



