138 Determinate Evolution 



papers under the term * accommodations,' — while not directly 

 inherited, are yet influential in determining the course of 

 evolution indirectly. For such modifications and accommo- 

 dations keep certain animals alive, in this way screen the 

 variations which they represent from the action of natural 

 selection, and so allow new variations in the same direc- 

 tions to arise in the next and following generations ; while 

 variations in other directions are not thus kept alive and 

 so are lost. The species will therefore make progress in 

 the same directions as those first marked out by the ac- 

 quired modifications, and will gradually ' pick up,' by con- 

 genital variation, the same characters which were at first 

 only individually acquired. The result will be the same 

 as to these characters, as if they had been directly inher- 

 ited, and the appearance of such heredity in these cases, 

 at least, will be fully explained ; while the long-continued 

 operation of the principle will account for 'determinate or 

 definite ' lines of change. 



This principle comes to mediate to a considerable degree 

 between the two rival theories, since it goes far to meet 

 the objections to both of them. In the first place, the 

 two great objections as stated above to the current natu- 

 ral selection theory are met by it. (i) The 'determinate ' 

 direction in evolution is secured by the indirect directive 

 influence of organic selection — at any rate, in cases in 

 which the direction which evolution takes is the same as 

 that which was taken by individual modifications in earlier 

 generations. For where the variations in the early 

 stages of the character in question were not of utility, 

 there we may suppose the individual accommodations to 

 have supplemented them and so kept them in existence. 

 An instance is seen in the fact that young chicks and 



