296 THE WHENCE AND THE WHITHER OF MAN 



what warrant have we for believing that the special 

 acquired characteristic can be transmitted ? Weis- 

 mann answers, None at all. The soniatoplasm can 

 only in the most general way affect the self-perpetu- 

 ating, close corporation of the germ-plasm.* 



There is thus, according to Weisinann, nothing to 

 direct variation to certain organs, or to guide and 

 combine the variations of these organs along certain 

 lines, except natural selection. To a certain extent 

 variation may be limited by the very structure of the 

 animal. But within these limits there are wide ranges 

 where one variation is apparently just as likely to 

 occur as another. 



Within these wide limits variation appears to be 

 fortuitous. Natural selection must wait until the 

 individuals appear in which these variations occur al- 

 ready correlated, and then seize upon these individ- 

 uals. It is apparently the only guiding, directing 

 force. Linear variation, that is, a variation advancing 

 continuously along one or very few straight lines, 

 would appear to be impossible. 



In Nageli's theory initial tendency is overwhelm- 

 ingly dominant ; in Weismann's, natural selection is 

 almighty. 



Weismann's followers have received the name of 

 Neo - Darwinians. The so - called Neo - Lamarckian 

 school believes in the transmissibility of acquired 

 characteristics, and of at least particular effects of use 

 and disuse. The one theory is neither more nor less 

 Darwinian than the other. For while Darwin empha- 

 sized natural selection, he accepted to a certain extent 

 the transmission of special effects of use and disuse. 



* Weismann, Essays, p. 286. 



