60 THE THEORIES OF EVOLUTION 



tect the author's prejudiced and consciously narrow 

 ideas. 



In his later works, Weismann, influenced by fre- 

 quent and searching 1 discussions, which cast doubt 

 upon many of the statements of the Neo-Darwinian 

 school, made a number of important concessions; he 

 added to his system some ideas which allowed the 



^ much-despised Lamarckian theory of environmental 

 influence to penetrate it gradually. But all these 

 new ideas, all these improvements of the original ed- 

 ifice, are in some way related to the theory of the life 

 struggle and the theory of selection. 



In the last published of Weismann's works 4 which 

 sums up all his scientific writings, we still find the 



\ one idea of natural selection applied to all biological 

 phenomena, especially to those on which its action is 

 considered as most doubtful: colouring of animals, 

 mimicry, development of instincts, etc. The direct 



\> action of environment, the Lamarckian theory of use 

 and disuse are still emphatically rejected. At the 

 same time, Weismann upholds the principle of the 

 usefulness of all existing characters, even when that 

 usefulness is not apparent. 



Natural selection appears to him not only the sole 

 factor but an unfailing factor. At the same time 

 the life-struggle and selection which in the "Or- 

 igin of Species" are simply an explanation of well 



* The Evolution Theory. 



