28 THE SURVIVAL OF THE UNLIKE, [l. 



condition of life," he repeats, "even extremely slight 

 changes, often suffice to cause variability. Excess of 

 nutriment is perhaps the most efficient single exciting 

 cause." (See Essay XIV.) Cope, in his discussion of 

 the "Causes of variation," starts out with the propo- 

 sition "to cite examples of the direct modifying effect 

 of external influences on the characters of individual 

 animals and plants;" and he closes with this paragraph: 

 ' ' I trust that I have adduced evidence to show that the 

 stimuli of chemical and physical forces, and also molar 

 motion or use and its absence, are abundantly sufficient 

 to produce variations of all kinds in organic beings. 

 The variations may be in color, proportions, or details of 

 structure, according to the conditions which are present." 

 This is, in great part, the thesis to which Darwin ex- 

 tended the proofs of a most laborious collection of data 

 from gardeners and stock-breeders and from feral nature. 

 It has been the great misfortune of the interpretation of 

 Darwin's writings that his hypothesis of natural selec- 

 tion has so completely overtopped everything else in the 

 reader's mind that other important matters have been 

 overlooked. 



Whilst the one central truth in the plant creation is 

 the fact that differences arise as the result of variations 

 in environment, there are, nevertheless, many exceptions 

 to it. There are various types of differences, which are 

 merely incidental or secondary to the main stem of 

 adaptive ascent. Some of these are such as arise from 

 the cessation of the constructive agencies, and others are 

 mere correlatives or accompaniments of type differences. 

 As an example of the former, we may cite the behavior 

 of the potato. By high cultivation and careful breeding, 

 the plant has been developed to produce enormous crops 



