414 ON THE ORDERS 



expected. Nor do these wings differ more in appearance 

 from the feet of which they occupy the place, than the 

 fins of Fishes do from the organs of Mammalia which 

 they represent. Nay, there are certain Annulose animals 

 which afford us indubitable examples of this analogy be- 

 tween wings and feet. The Cyamus, for example, is a 

 Crustaceous animal with ten feet; yet, for the purposes 

 of locomotion, it has only three paii's, the remaining two 

 pairs being organs which M. Latreille has termed bran- 

 chial feet, and which indeed undoubtedly serve for pur- 

 poses of respiration. Again, when wings are deficient in 

 any great division of Hexapod insects, we always find 

 them replaced by the vestiges or semblance of wings, or, 

 finally, by other organs having even a greater appearance 

 of being tracheal feet, as, for instance, the halteres of the 

 Diptera occupying the place of the two under wings which 

 in this order are null. 



It is, however, sufficiently obvious that, so far fi-om this 

 theory being confirmed by incontrovertible proof, it is as 

 yet little more than enunciated : but as I know no fact di-^ 

 rectly in opposition to it, and many by which it is indirectly 

 favoured, no course of proceeding would in my opinion be 

 more Vjlameable than hastily to reject the hypothesis before 

 we have seen the result of M. Latreille's present labours. 

 Undoubtedly those persons who are unacquainted with the 

 conformity of Nature to certain general principles, will have 

 great difficulty to understand how the wing of an Hymen- 

 opterous insect can be one of its feet ; yet they are not so 

 dissimilar perhaps as the fore foot of a quadruped and the 

 wing of a bird, which often agree almost to the number 

 of digiti. 



My chief reason for entering on this subject so fully, 



