HABITS AND FACULTIES. 189 



clAvelllngs, and has in some places become the pest of 

 the horticulturist. 



Whether this difference of habitat arises from original 

 constitution, or is the consequence of the long continued 

 operation of external causes, is a curious subject of in- 

 quiry. The preference for the forest over the open 

 country exhibited by the native species, even m situa- 

 tions where both have been for a long time equally 

 accessible to them, seems to indicate that the former 

 supposition is correct ; and this opinion is strengthened 

 by the disappearance of nearly every species with the 

 progress of agriculture. If their habits were not in- 

 superable, they might be expected to have been some- 

 what modified ere now, and to have become adapted to 

 the new physical conditions to which they are subjected. 

 That they have not been, suggests the thought, that like 

 the aboriginal race of men, and some of the larger 

 quadrupeds, they are destined to give way before the 

 advance of civilization, and to have their places filled by 

 foreign species. On the other hand, there are some 

 facts which tend to show that accidental causes may 

 have produced a slow and gradual revolution in the 

 habits of the European species, corresponding with the 

 changes which, within the historical period, have taken 

 place over the surface of the greater part of Europe ; 

 and that in process of time, the same influences will pro- 

 duce similar results on the habits of the North Amer- 

 ican species. All those parts of Europe which are now 

 the most populous were covered with forests, at no very 



