ASPECTS OF KINETIC EVOLUTION 233 



ficial sense ; the first step toward a better solution of the riddle 

 is to reorganize the vocabulary of variations so that it can be 

 used to express something more than erroneous deductions from 

 natural selection. Many words and distinctions of use in pre- 

 senting the idea that natural selection is a true, actuating cause 

 of evolution, may be spared, but there are others whose utility 

 is not destroyed by this change of view. 



VARIATIONS AND INTRASPECIFIC DIFFERENCES. 



Before entering upon a discussion of a general scheme of 

 variations it is necessary to notice a fundamental error commonly 

 attached to the word variation itself. Most of the exponents of 

 selective theories of evolution have made, either tacitly or 

 avowedly, the assumption that all the individuals of a species 

 are normally alike and tend to remain uniform, and that the 

 differences found among them are of external origin and of the 

 same nature as the differences between species, and hence of 

 evolutionary significance. It has been assumed, in other words, 

 that all the differences to be found among the members of a 

 species are variations in the evolutionary sense, and hence that 

 a cause of difference among the members of a species is neces- 

 sarily a cause of the evolution of species. It is not too much to 

 say that this assumption of normal specific stability and uni- 

 formity, either absolute or within constant limits, begs in advance 

 the whole question of the nature and causes of evolutionary 

 change. Notwithstanding the popularity it has enjoyed, this 

 static idea of species is worthy of no more respect than any other 

 unsupported hypothesis. 



For the former purposes it appeared desirable to divide 

 the variations, that is, the differences to be found among the 

 individuals of a species, into two classes — (i) those with which 

 they are endowed at birth, and (2) those which they acquired 

 later from the external conditions of their existence. Variations 

 were classified, in other words, as either congenital or acquired. 

 The distinction is not illogical, but it has proved worse than 

 useless for evolutionary purposes, because the static theory by 

 which it was suggested was an erroneous assumption. 



Many objections to natural selection, or to evolution as based 



