236 The Science of Life. 



Prof. H. F. Osborn, who have independently suggested 

 an ingenious theory as to the possible evolutionary 

 interest of modifications. To this theory the unfor- 

 tunate title "organic selection" has been given. 



There are many facts which show that the body of an 

 organism may react adaptively to changes in function 

 and environment ; the skin may be hardened, a muscle 

 may be strengthened, even a bone may be modified. 

 These modifications are obviously of individual value, 

 but if they are not in any degree transmissible they are 

 not of direct racial value. It may happen, however, 

 that a congenital variation occurs in the same direction 

 as the adaptive modification, and if the modification be 

 of importance of value in deciding survival it may 

 act, so to speak, as a shield for the incipient congenital 

 variation until this has gained strength. The two 

 processes of modification and variation will thus help 

 one another. 



As Prof. Lloyd Morgan puts it: "Any congenital 

 variations similar in direction to these modifications will 

 tend to support them and to favour the organism in 

 which they occur. Thus will arise a congenital predis- 

 position to the modifications in question. The longer 

 this process continues, the more marked will be the 

 predisposition, and the greater the tendency of the 

 congenital variations to conform in all respects to the 

 persistent plastic modifications; while the plasticity 

 still continuing, the modifications become yet further 

 adaptive. Thus plastic modification leads, and germinal 

 variation follows: the one paves the way for the other." 



In short, it is suggested that "the modification as 

 such is not inherited, but is the condition under which 

 congenital variations are favoured and given time to 

 get a hold on the organism, and are thus enabled by 

 degrees to reach the fully adaptive level ". 



What can one say in conclusion, except this, that 



while the general conception of evolution stands more 



firmly than ever as a reasonable modal in- 



Conclusion. J . , . ,, , , 



terpretation of nature, there is great uncer- 

 tainty in regard to almost every question concerning 

 the factors in the evolution process. 



