iv WEISMANN'S CRITICISMS 223 



to be heard upon the question of the transformation 

 of species." These are rather big words, and Professor 

 Weismann has perhaps written somewhat hastily. It 

 may be answered that all evolutionists, and more 

 especially " Natural Selectionists," to whom Professor 

 Weismann belongs, assume the production of " useful 

 changes " with or without change of external condi- 

 tions, since those only survive in the struggle for life 

 who offer beneficial modifications or adaptations. 

 And of course the production of such " useful 

 changes " is of much higher importance when the en- 

 vironment changes than when it remains unmodified. 

 Professor Weismann denies the importance and trans- 

 missibility of variations due to external modifica- 

 tions. But then how does he explain the fact now 

 repeatedly ascertained in all bacteriological labora- 

 tories that all micro-organisms, bacilli, bacteria, etc., 

 undergo under cultivation in different external condi- 

 tionswhether of light, heat, or food, it matters little 

 such important modifications that they may be made 

 to lose their essential characters, and that these charac- 

 ters are lost as long as the external modification per- 

 sists ? Take Bacillus anthracis, for instance. Com- 

 pared with many other bacilli, it differs very slightly 

 in external characters ; the principal and all-important 

 difference is that it determines in many animals a 

 disease of a very precise character which can be mis- 



