be/ween Man and all other Animals. 135 



birds, but is particularly noticeable in the insect tribes; various 

 species of which, though solitary in their usual habit, have 

 been known to assemble at times in prodigious multitudes, 

 prompted by a general impulse, which, however, appears to be 

 less conferred with intent to extend the previous range of their 

 distribution, than to preserve the species within due bounds 

 in its native locality; for the numerous dangers with which 

 these wanderers are necessarily every where beset absolutely 

 appear to suffice, in most instances, to prevent their perma- 

 nently establishing themselves in other places ; a remarkable 

 fact, notorious to all who have attended to the subject. So 

 many causes are there in operation which combine to circum- 

 scribe the geographic range of species. 



A variety of important considerations here crowd upon the 

 mind ; foremost of which is the enquiry, that, as man, by re- 

 moving species from their appropriate haunts, superinduces 

 changes on their physical constitution and adaptations, to what 

 extent may not the same take place in wild nature, so that, in 

 a few generations, distinctive characters may be acquired, 

 such as are recognised as indicative of specific diversity ? It 

 is a positive fact, for example, that the nestling plumage of 

 larks, hatched in a red gravelly locality, is of a paler and 

 more rufous tint than in those bred upon a dark soil.* May 

 not, then, a large proportion of what are considered species 

 have descended from a common parentage ? 



I would briefly despatch this interrogatory, as abler writers 

 have often taken the subject in hand. It is, moreover, foreign 

 to the professed object of this paper. There are many phe- 

 nomena which tend, in no small degree, to favour the sup- 

 position, and none more so than what I have termed the 

 localising principle, which must occasion, to a great extent, 

 what is called " breeding in and in," and, therefore, the 

 transmission of individual peculiarities. We have seen, 

 however, the extreme difficulties which most species have 



* Such is, at least, the uniform result of my experience ; though I could 

 never discern a corresponding difference in the adults. This curious fact 

 was first intimated to me by a person who had a number of young larks 

 for sale, among which were two nests of very rufous birds, and three of 

 a much darker colour : the former, he assured me, were found in a gravelly 

 situation ; the others on a dark soil. Some cases I have since noticed 

 have verified the observation. On another occasion, I may probably bring 

 together a number of analogous facts, in the form of a paper ; but it 

 would occupy too much space to do so here. It may, however, be added, 

 that the agency of many species confers a reciprocity of adaptation ; thus, 

 the mode in which sheep graze has a decided tendency to reduce a country 

 to that bare and bleak state which suits best with their healthy condition. 

 Hence would accrue a necessary return of varieties to their normal 

 characters. 



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