Consideration of Weismanris Arguments 199 



on grass and herbs would force some of these animals 

 to feed on tree leaves, others to become transformed into 

 rodents and insectivors or to undergo some transforma- 

 tion of still another kind. 



In this connection it is to be especially noted that 

 just because a large number of the individuals of the 

 old species will thus have come to seek their nourish- 

 ment elsewhere, no change will appear in those remaining 

 behind in the former conditions of nourishment. In 

 other words the elimination caused by the change in 

 their habits of the overcrowding individuals from among 

 the company of the old species will leave the other 

 individuals of this species, whose number will now be 

 no longer too great, in the same conditions of environ- 

 ment as formerly, without any overcrowding and con- 

 sequently there will not be any further causes provoking 

 in these individuals also a transformation into another 

 species. 



The change of nutrition will induce then a whole 

 series of changes in the functions of seeking food, hunt- 

 ing, fighting, seizing, chewing etc., but only for that 

 position of the species which has changed its mode of 

 living. Thus it is clear how, during a series of entire 

 geological periods, a certain number of the ancestors 

 of individual species that are now quite different from 

 them were able to preserve themselves unaltered and 

 so to reproduce their descendants unaltered to this day. 



Man is distinguished from other animals perhaps in 

 this, that whereas the latter do not modify their environ- 

 ment or modify it only indirectly and intermittently by 

 emigration or by overcrowding and consequently make 

 no progress in their development so long as their environ- 

 ment undergoes no alteration from one of the causes 



