254 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 



the whole value of that organism which determined its survival. 

 This fact is continually disregarded by opponents of the neo-Darwinian 

 position, yet this selection of the organism as a whole is the 

 fundamental postulate from which the theory of selection starts. 

 Thus it is not uncom.mom to read criticisms bearing on the early 

 development of some organ, in which the inadequacy of selection is 

 supposed to be proved by the writer demonstrating, or believing he 

 has demonstrated, the fact that the particular variation in question 

 must have been too small to be by itself of selection value. In many 

 cases the particular variation would, no doubt, if taken alone be, as 

 the objector asserts, too unimportant to be selected, but as it is the 

 whole organism that is selected, it is not logical to make an artificial 

 separation and study the development of one organ or structure 

 irrespective of the other organs with which it is in nature associated. 

 Every organ in its evolution must he considered in relation to the whole 

 of the particular orga^iism in which that particular stage of development 

 of that organ is found. 



Starting, therefore, with this fact that the net value of adaptability 

 of the whole organism to its environment must be the basis which 

 determines selection or elimination, it will follow that certain lines of 

 development will result from the application of this criterion. In a 

 series of organisms placed under new conditions, elimination will 

 proceed along lines essential to bring about a proper adjustment to 

 the new conditions. If the offspring of these adjusted organisms 

 merely repeated in their generation the characters of the exterminated 

 as well as of the surviving organisms, that temporary adjustment 

 would be permanent as long as the conditions were unchanged. But 

 since the offspring are produced only by the surviving organisms, 

 selection is continually raised to higher and higher planes of adapta- 

 tion, and, therefore, as long as conditions remain constant, the 

 tendency of selection must be, as Darwin clearly saw, cumulative. 

 He did not, however, apparently see that from this cumulative 

 tendency definite variability must arise out of indefinite. 



Selection in direct relation to climatic conditions is, therefore, of 

 very minor importance, while selection among the members of a 

 species and all forms of inter-organismal selection is of infinitely more 

 importance, since it is this interaction, produced by the offspring in 

 different degrees inheriting the advantages of both parents (both of 

 whom have survived on account of certain advantages), that leads to 

 the cumulative development and never-ending struggle for survival. 



