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larly in subsequent generations, would probably be regarded 

 as inherited, although in reality they are only independently 

 acquired by each individual. They would not be a part of 

 the inherited nature, but only the result of the ' nurture ' to 

 which each individual is subjected." 



Agency of Acquired Variations i^i Guidi^ig Natural 

 Selection 



" The essence of the theory of organic selection is, that 

 these acquired variations will keep the individuals in harmony 

 with their environment, and preserve them under new condi- 

 tions, until some congenital variation happens to appear of a 

 proper adaptive character. The significance of this conception 

 is perhaps not evident at a glance. It may be made clear by 

 considering, for illustration, the problem of development of 

 habits and organs adapted to each other. It is impossible to 

 believe that an organ develops before the habit of using it, for 

 if it did it would be useless. On the other hand, the habit of 

 using an organ could not arise before the organ makes its 

 appearance. We must thus believe that the organs and the 

 habit of their use appear together, a very difficult or impossible 

 conception for haphazard variation. Now organic selection 

 tries to show that the adoption of a new habit by an animal will 

 result in the development of structures adapted to the habit, 

 but by a principle that does not involve the inheritance of 

 acquired variations. Assuming that some changes in conditions 

 caused certain animals to adopt a new habit, Weismann's theory 

 would force us to believe that some structural changes would 

 follow, from variations in the germ plasm, which would be 

 parallel to the acquired variations developed by the new habit. 

 But when we conceive, as Weismann must, that congenital 

 variations are indefinite and in all directions, it becomes a 

 matter of infinite improbability to suppose that just the right 

 sort of variations will follow such a change in habit at just 

 the right moment. The Lamarckians, finding that habit and 

 structure follow each other so closely, have felt obliged to 



