Influence of Environment uijon the Organism. 4G7 



coast clear for the minority of fit variations, which throve 

 and bred better, and thus gradually established adapted 

 species. The merits of his theory are not at present under 

 discussion ; its relation to the general conception of environ- 

 mental influence must, however, be noted. While several 

 passages (especially of later date) fully recognise the 

 Buffonian position, Darwin may be fairly said to have laid 

 greatest stress on the destructive action of the animate and 

 inanimate environment, 



A few post -Darwinian positions may also be noticed. 

 Hgeckel, surpassing Darwin in the clear perspective in 

 which he placed the various factors, defines adaptation as 

 "the fact that the organism, in consequence of influences 

 from the surrounding external world, acquires certain new 

 peculiarities in life capacity (Lebensfahigkeit), constitution 

 and form, which were not inherited." This definition may not 

 be above criticism, but it is for our present purpose more 

 important to notice one of his eight laws of adaptation, that, 

 namely, in which he formulates the result of the persisting 

 influence of food, climate, medium, function, etc. 



Semper, again, distinguishes with perfect clearness those 

 modifications, which, as a Darwinian, he believes to be due 

 to the action of natural selection, from those which have 

 resulted from the direct hammering of the environment. 



Even IN'ageli, who more than any other has given precision 

 to the conception of independent internal or organismal varia- 

 tion, calls in the aid of external influences to act, on the one 

 hand, as a stimulus, and on the other, to form, as it were, 

 the mould to which the organismal variation adapts itself. 



It is important to note Weismann's positions. In his 

 " Studies in the Theory of Descent," he affirms that there can 

 be no progress apart from environmental changes ; he allows 

 the existence of a direct hammering action, though justly 

 cautious as to the extent to which it really exists. Its action 

 is limited internally by the constitution of the organism; 

 and important as this direct action may be, the indirect 

 action in the process of natural selection is a much more 

 vital factor in progress. In contrast to Nageli, he is quite 

 definite in regarding the environment, in its widest sense, as 



