MIND IN EVOLUTION 529 



hemisphere; they fly under water; they walk along the bed of 

 the torrent ; they are continually immersed without getting 

 wet. Doubtless the habit was gradually perfected, but it 

 is difficult to escape the view that the dippers showed more 

 than physiological endeavour in utilising their variations in 

 reference to the extraordinary change of life which they 

 illustrate. To some extent they probably selected the " va- 

 cant place" in Nature which they have won. For here " we 

 have a bird, which, in its whole structure, shows a close af- 

 finity to the smaller typical perching birds, but which has 

 departed from all its allies in its habits and mode of life, 

 and has secured for itself a place in nature where it has 

 few competitors and few enemies ' (Darwinism, 1889, p. 

 117). 



There is another prom isef ul line of inquiry, to study 

 among animals with complex brains any unusual devices 

 which are not part of the ordinary routine of the creatures' 

 life nor absolutely necessary for the survival of the race. 

 It is desirable to exclude, in the first instance, all devices 

 which fall into these two categories, lest we be misled by 

 extraordinary instinctive capacities, which, at any rate, are 

 not so clever as they look. The cases we are thinking of 

 may be illustrated by the way rooks and gulls lift exposed 

 cockles and mussels in their bills and allow them to fall from 

 a height on the hard shingle so that the shells are broken 

 and the flesh made available. It is very unlikely that the 

 device was thought out; but it is probable that the birds in- 

 telligently took advantage of a hint which a chance fall 

 afforded. 



A third line of evidence may perhaps be found in persist- 

 ent endeavour towards a distant goal. There is a kind of 

 vital inertia that admits of physiological explanation. A 



