Variation and Natural Selection. 119 



the guise and sharing the bad reputation of the mimicked 

 forms. Such forms of convergence are in special adaptation 

 to a very special environment. 



We must remember that in all cases adaptation is a 

 matter of life and environment. And these, we may now 

 note, may be related in one or more of three ways. In 

 the first place, there is the adaptation of life to an un- 

 changing environment ; for example, the adaptation of all 

 forms of life to the fixed and unchanging properties of 

 inorganic matter. If we liken life to a statue and the 

 environment to a mould in which it is cast, we have in 

 this case a rigid mould and a plastic statue. Secondly, 

 the adaptation may be mutual, as, for example, when the 

 structures of insects and flowers are fitted each to the 

 other, or when the speed of hunters and hunted is steadily 

 increased through the elimination of the slow in either 

 group. Here the mould and statue are both somewhat 

 plastic, and yield to each other's influence. Thirdly, the 

 environment may be moulded to life. This, again, is only 

 relative, since life never wholly loses its plasticity. The 

 bird that builds a nest, the beaver that constructs a dam, 

 the insect that gives rise to a gall, these, so far, mould 

 the environment to the needs of their existence. Man in 

 especial has the power, through his developed intelligence, 

 of manufacturing his own environment. Here the statue 

 is relatively rigid, and the mould plastic. 



Progress may be defined as continuous adaptation. In 

 modern phrase, this is called evolution. The continuity 

 makes the difference between evolution and revolution. 

 Both are natural. Both occur in the organic, the social, 

 and the intellectual sphere. Evolution is the orderly 

 progress of the organism or group of organisms, by which 

 it becomes more and more in harmony with surrounding 

 conditions. If the conditions become more and more com- 

 plex, the organism will progress in complexity ; but if the 

 conditions be more and more simple, progress (if such it 

 may still be called) will be towards simplicity of structure, 

 unnecessary complexity being eliminated, or, in any case, 



