OF SENSATION AND THE SENSES. 485 



I made expressly for the purpose in Dyticus inarginalis and Calosoma 

 sycophanta, HydropMlus piceus, and Scarabceus vernalis that it must 

 have shown itself if it had been present at the spot mentioned. In 

 freshly opened insects I could discover really nothing of the kind, and 

 in those which had been long immersed in spirits I saw the space in 

 front and between the clypetis and the most approximate organs filled 

 with nothing but coagulated blood. I cannot therefore determine in 

 favour of Kirby and Spence's opinion, but prefer the earlier hypothesis, 

 that the internal surfaces of insects receive smell, and supply the place 

 of an organ especially devoted to that sense. 



The majority of modern physiologists and entomologists agree in 

 explaining the antennae as organs of hearing, as we have already 

 remarked. Kirby and Spence's representation, whose names were 

 inadvertently omitted to be mentioned there as the authorities for our 

 opinion, conveys so much conviction that we may almost consider it as 

 settled., although we must at the same time admit that all the difficulties 

 are not yet solved : we have already indicated above that the real percep- 

 tion of sound may possibly depend upon the trembling produced by the 

 vibration of the air in organs so easily moved as are the antennae, and 

 we here repeat this opinion as the explanation of the mode by which 

 insects hear. According to Kirby and Spence, Wollaston suggested 

 this opinion, and even supposed that insects could perceive much more 

 delicate tones than our ears are capable of distinguishing, from their 

 very much greater irritability. This irritability, however, in conse- 

 quence of the much harder integument in which insects are enveloped, 

 can be possessed only by the antennae, which are so easily moveable, 

 and which, indeed, in many insects are in a constant state of motion; 

 even the slightest vibration of the atmosphere must be sufficient to put 

 into motion an organ of the structure of the antennae of a gnat, and 

 thereby apprise its possessor of the approximation of some occurring 

 change ; this is equally the case with the delicate and easily moveable 

 antennae of the Grylll, and indeed of all insects furnished with long 

 antennae ; the same with the short fan-shaped flaps, as well as with the 

 delicately haired joints forming a knob in the antennas of other insects ; 

 the very structure of all betrays the possibility of very delicate percep- 

 tion. Organs of touch they cannot be, for their surface is too hard 

 and horny, and besides, all insects have for this purpose organs fur- 

 nished \vith a very delicate touching surface. Hence the mode whereby 

 insects hear will necessarily differ from the hearing of the superior 



