94 THE VALUE OF COLOUE 



that all pigmentary colours were originally inci- 

 dental ; but now and for immense periods of 

 time the visible tints of animals have been modi- 

 fied and arranged so as to assist in the struggle 

 with other organisms or in courtship. The domi- 

 nant colouring of plants, on the other hand, is an 

 essential element in the paramount physiological 

 activity of chlorophyll. In exceptional instances, 

 however, the shapes and visible colours of plants 

 may be modified in order to promote conceal- 

 ment.^ 



TELEOLOGY AND ADAPTATION 



In the department of Biology, which forms the 

 subject of this essay, the adaptation of means to an 

 end is probably more evident than in any other ; 

 and it is therefore of interest to compare, in 

 a brief introductory section, the older with the 

 newer teleological views. 



The distinctive feature of Natural Selection as 

 contrasted with other attempts to explain the 

 process of evolution is the part played by the 

 struggle for existence. All naturalists in all ages 

 must have known something of the operations of 

 ' Nature red in tooth and claw ' ; but it was left 

 for this great theory to suggest that vast exter- 

 mination is a necessary condition of progress, 

 and even of maintaining the ground already 

 gained. 



Kealizing that fitness is the outcome of this 



• See pp. 96-8, 102, 103. 



