220 TRANSITIONS OF ORGANIC BEINGS. [Chap. VI 



material for us, whether habits generally change first 

 and structure afterwards; or whether slight modifica- 

 tions of structure lead to changed habits; both probably 

 often occurring almost simultaneously. Of cases of 

 changed habits it will suffice merely to allude to that 

 of the many British insects which now feed on exotic 

 plants, or exclusively on artificial substances. Of diver- 

 sified habits innumerable instances could be given: I 

 have often watched a tyrant flycatcher (Saurophagus 

 sulphuratus) in South America, hovering over one spot 

 and then proceeding to another, like a kestrel, and at 

 other times standing stationary on the margin of water, 

 and then dashing into it like a kingfisher at a fish. In 

 our own country the larger titmouse (Parus major) may 

 be seen climbing branches, almost like a creeper; it 

 sometimes, like a shrike, kills small birds by blows on 

 the head; and I have many times seen and heard it 

 hammering the seeds of the yew on a branch, and thus 

 breaking them like a nuthatch. In North America the 

 black bear was seen by Heame swimming for hours with 

 widely open mouth, thus catching, almost like a whale, 

 insects in the water. 



As we sometimes see individuals following habits 

 different from those proper to their species and to the 

 other species of the same genus, we might expect that 

 such individuals would occasionally give rise to new 

 species, having anomalous habits, and with their struc- 

 ture either slightly or considerably modified from that 

 of their type. And such instances occur in nature. 

 Can a more striking instance of adaptation be given 

 than that of a woodpecker for climbing trees and seizing 

 insects in the chinks of the bark? Yet in North 

 America there are woodpeckers which feed largely on 



