154 An Examination of Weismannism. 



This complete reversal of his previous doctrine 

 brings Weismann into line with Darwin, who long 

 ago gave very good reasons for the following con- 

 clusion : — 



Those authors who. like Pallas, attribute all variability to the 

 crossing either of distinct races, or to distinct individuals belong- 

 ing to the same race but somewhat different from each other, 

 are in error ; as are those authors who attribute all variability 

 to the mere act of sexual union \aniphimixis\ \ 



And again : — 



These several considerations alone render it probable that 

 variability of every kind is directly or indirectly caused by 

 changed conditions of life. Or, to put it under another point 

 of view, if it were possible to expose all the individuals of a 

 species during many generations to absolutely uniform con- 

 ditions of life, there would be no variability 2 . 



Hence. Darwin was disposed to find the main, 

 if not the only, causes of congenital variations in 

 circumstances depending for their efficacy on the 

 instability of what Weismann calls germ-plasm. And 

 the noteworthy fact is, that Weismann has now 

 adopted this view, to the destruction of his originally 

 fundamental postulate touching the stability of germ- 

 plasm since the first origin of sexual propagation. 



By such a right-about-face manoeuvre. Weismann 

 has placed his critics in a somewhat difficult position. 

 For, in the first place, it is only towards the close 

 of The Germ-plasvi that the manoeuvre is executed, 

 and then only in a few sentences such as I have just 

 quoted — italicized, it is true, but otherwise so slightly 



1 Fa; iation &c, vol. i. p. 39S. 2 Ibid., vol. ii. p. 242. 



