on the Wing-Rmjs of Insects. 229 



Wood, a specimen of what I believe to he J rgijnnifi Pap/iia, m 

 wliich the membrane of the wing had been destroyed by some 

 extraneous and unknown agency ; the principal rays, however, 

 remained entire: the insect was on the ground and attacked by a 

 colony of ants, and the mutilation was so com})lcte that I had the 

 greatest difficulty in making out what the creature could be ; 

 yet, notwithstanding its injuries, it continued to move the denuded 

 rays up and down with great vigour and rapidity ; tlie erect and 

 horizontal position alternating as when an insect flies, and the 

 motion being, in all likelihood, a well-intentioned but abortive 

 effort to escape by flight from its assailants. Here, then, is posi- 

 tive proof that the motion of the rays is not communicated by 

 the membrane, and also strong presumptive proof that the con- 

 verse of this is the actual truth : viz. that the rays, under the 

 influence of the muscles and tendons, and these again under the 

 influence of the will, communicate motion to the wing, thus en- 

 tirely reversing that assumed sequence of facts, which would con- 

 stitute the wing a competent organ of progressive motion, and its 

 rays merely subservient to respiration, feeling or circulation. 



I therefore consider the rays of an insect's wing as performing 

 precisely the same functions as the bones of a bat's wing, and the 

 wing of a butterfly as the exact analogue of the wing of a bat. 

 And at this point I must beg leave to pause for a moment, in 

 order to express my uncpudified dissent from that superficial 

 mode of investigation, which seeks and supposes that it perceives, 

 in an exosteate, the homologues of organs familiar to us in 

 an endosteate animal. The distinction between analogues and 

 homologues is broad, well defined and perfectly intelligible : 

 analogues are organs essentially different, performing the same 

 functions ; homologues are organs essentially the same, yet, 

 under modified or altered forms, capable of performing widely 

 different functions : thus the ribs of Draco volins, the fingers of a 

 bat, and the rays of a butterfly, are only analogues, although the 

 function they perform is absolutely identical ; while the radius 

 and ulna of man, the lion and the whale, are strictly homologues, 

 although they perform three widely-different functions. 



Proceeding to consider the evidence afforded by structure, it 

 seems necessary to commence with the attachment of the rays to 

 the trunk of the insect. 



Libellula, a genus preeminently distinguished for its powers 

 of flight, the swallow, or perhaps the vulture, of the insect world, 

 has been selected by Chabrier for most of his explanatory dissec- 

 tions ; and in this insect the thoracic cavity is almo.st filled by 



