2O2 Inheritance of Acquired Characters 



change in their former manner of life, and in whom 

 consequently the whole organism will be modified through 

 functional adaptation. In this way may be explained 

 the transformation of only one group of the individuals 

 constituting a species into a new species, while the others 

 remain unchanged. 



These few examples, even though so briefly outlined, 

 are nevertheless quite enough to show us that the 

 Lamarckian theory is capable of explaining at the same 

 time both the evolution and the fixity of a species. But 

 how can Weismann account for the inalterability and 

 constancy of a given species? It goes without saying 

 that he has no hesitation in attributing it, like variation 

 itself, to natural selection again. But even if one were 

 willing to suppose the environment immutable, is it 

 possible that any species could ever come to such a 

 degree of perfection in relation to its environment that 

 every new variation in any direction whatever must make 

 the conditions of this species worse and make its mem- 

 bers less likely to be victorious in the struggle for 

 existence? Is it not much more probable that however 

 high a degree of adaptation to its environment a species 

 may have attained, it can always become even better 

 equipped for the struggle for existence through further 

 transformations in certain directions, and consequently 

 offer still greater opportunities for natural selection 

 which is everywhere and always upon the qui vive? 



We must nevertheless be careful, in relation to this 

 question of the fixity of species, not to attribute to the 

 arguments which we have just set forth any greater value 

 than they actually possess, especially because we know 

 nothing, or only a very little, concerning the immediate 

 circumstances that have actually existed in the develop- 



