1899] EVOLUTION AND CHANCE 363 



of laying hold of it that suits their own organisation. The con- 

 trivances for seizing food are many and various, and with none of them 

 does the environment find fault. For this purpose most mammals use 

 their teeth, the " snake-handed " elephant uses his trunk, the bird his 

 beak and supple neck. The boa constrictor's whole body is used for 

 grasping. The lobster has his claws, and for man there is his hand, 

 that almost perfect grasping implement. The environment is so 

 accommodating that almost any good piece of machinery works well 

 there. When we see a Kallima butterfly we are apt to think of the 

 environment as a procrustean mould into which it has had to fit itself : 

 the insect has had to become, we may imagine, like a decaying leaf, 

 or perish. This is true, no doubt, of the individual Kallima now. It 

 is not true of the species long ago before it had advanced any distance 

 along its line of development. At that distant date it might have 

 maintained itself by resemblance, not to decaying leaves, but to some- 

 thing else, by " mimicry " of some other species protected by its 

 nauseating flavour, by itself developing a nauseating flavour, by the 

 vigour of its flight, or by its great fertility. In this particular 

 butterfly we must imagine some slight accidental resemblance to a 

 dead leaf at the outset. The perfection of adaptation is due to its 

 proceeding along the line of development it has once adopted. In 

 each generation those were eliminated which were not in this par- 

 ticular point up to the standard of excellence. 



In many instances of adaptation there is much to wonder at. 

 There is, on the one hand, the marvellous variability of living organisms, 

 due to causes which we can only speculate upon, and on the other 

 there is the easy-going elasticity of the environment which can find 

 places for so many different types. The variations that an organism 

 may develop are determined by its own character, which character has 

 been built up in the long course of its phylogeny. When a species 

 has proceeded far along its particular line, then the environment may 

 seem to be an exacting tyrant, allowing of only two alternatives — 

 extreme specialisation in one direction, or extinction. 



It is not, however, the environment, but the species, which is to 

 blame. It has lost its plasticity. Its own phylogeny compels it to 

 follow a certain mode of life. The environment is as accommodating 

 as ever, but the organisms that make up the species claim to main- 

 tain themselves in one way and no other. And such a demand a 

 changing environment may sometimes refuse. 



Haileyf.ury College, 

 Hertford. 



