The Scope of Natural Selection. 



By J. Lionel Tayler. 



A reconsideration of a few of the chief objections which have from 

 time to time been urged against the theory of natural selection may, 

 in view of the more recent development of its principles, be not 

 without some value at a time when test cases to decide the question 

 of use -inheritance and the power of natural selection are being 

 continually brought forward. 



In this paper I shall throughout follow Lloyd Morgan, Mark 

 Baldwin, and others in the precise usage of the terms, variation, 

 modification, adaptation, and accommodation. 



Variation will apply to changes which are of germinal origin. 

 Modification will apply to changes which are impressed on the 



" body " or soma in the course of individual life. 

 Adaptation will apply to those changes which have been produced 



by the selection of favourable variations. 

 Accommodation will apply to those alterations which have been 



produced by the reaction of the soma to environmental 



conditions. 



"We may seek to interpret the facts of organic evolution by 

 resting wholly or in part upon one, or a combination of more than 

 one, of the following assumptions : — 



1. That organisms have evolved along definite lines, wholly or 

 chiefly dependent upon the nature of each organism, developing either 

 completely or partially irrespective of the peculiarities of the environ- 

 ment. On this view the more or less unsuitable organisms are simply 

 eliminated, but this elimination is of little or no importance in 

 development, the assumption being that every organism that is not 

 exterminated evolves at its own rate, and that its development is 

 neither retarded nor accelerated by the presence or absence of other 

 organisms. 



2. That organisms are modifiable by environment and that 

 modifications so produced are inherited, the hereditary relation being 

 subservient to the action of the environment. This assumption has 

 to be considered under two heads. 



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