274 STUDY OF NATURAL HISTORY. 



centipede, &c. Progression, however, among insects 

 is not confined to flying, running, or swimming ; 

 for although we lose sight of the leaping structure 

 after quitting quadrupeds, we see this form again 

 developed in the highest perfection both among the 

 apterous (Aptera L.) and winged classes (Ptilota) ; 

 of which the fleas in one, and the grasshoppers in 

 the other, are examples occurring to every one. We 

 cannot doubt, indeed, but that the saltatorial struc- 

 ture is one of the primary types or models of nature, 

 for she has produced it, under an infinite variety of 

 forms and modifications, in almost every group of 

 animals. Of this description is the hopping of some 

 birds, in opposition to those which walk ; the hop 

 being, in fact, but a short leap. Even among the 

 Lepidoptera, where we should not expect to find any 

 such analogous form, there are the Hesperidce, 

 which, from the sudden and peculiar quickness on 

 the wing, have acquired the common but expressive 

 name of Skippers. Not to mention the monilicorn 

 tribe of beetles (under which we place the Chryso- 

 melidce of Linnaeus), where we have hundreds of 

 little species, familiarly known to our farmers as 

 fleas ; meaning thereby, a little black beetle of the 

 same size, colour, and leaping in a similar manner 

 to real fleas. A knowledge of all these habits, and 

 of many others not alluded to, may be gained by 

 induction, with almost as mueh certainty as if they 

 were learned by experience. These inductions pro- 

 duce higher conclusions ; and if these are confirmed 

 by every thing we yet know, we arrive at a law of 

 nature. That the saltatorial structure is one of those 

 primary forms upon which all the variations of the 



