528 THE EVOLUTION OF MIND 



There is little knowledge as yet in regard to variations 

 which arise in response to environmental stimuli, and as to 

 modifications which result from changed environmental in- 

 fluence we do not know that they are transmissible, so that 

 the importance of subjective selection may not be so direct as 

 Professor Ward supposes. But its importance may be great 

 if the organism picks out corners in which it can use its 

 individual peculiarities most effectively, where it can give 

 them a chance, where it can test them, where it can gain 

 elbow-room for having more. Needless to say in attributing 

 importance to the animal's selection of environment, we must 

 walk warily. Professor Ward says that " in subjective selec- 

 tion there is nothing metaphorical ", but we have to make 

 sure in each case that there is really selection, in which the 

 organism feels and wills and knows. In a green environ- 

 ment a spider-crab masks itself with green Algae, but it will 

 do this without guidance from its brain. If when covered 

 with borrowed livery of green it be transferred to an aqua- 

 rium half green, half red, it always goes to the green half. 

 If its livery be red seaweed, put on in a red environment, 

 it will go to the red half. But we must not say very much 

 about the choice being consciously related to the disguise, 

 for a crab that has lived for a while in a green environment 

 is always positively susceptible to green, and will always 

 go to the green side even with no disguise on. 



It is probable that personal agency has operated in cases 

 among big-brained animals where there has been a drastic 

 change of habit and habitat. Thus Alfred Russel Wallace 

 referred with reasonable admiration to the water-ouzels or 

 dippers. These well-known birds are relatives of wrens, 

 with very short wings and tail, and very dense plumage. 

 They frequent, exclusively, mountain streams in the northern 



