204 DARWINISM TO-DAY. 



disuse weakens. His is the great merit of having clearly 

 explained the extraordinary importance (Tragwcite), in the 

 building of new forms and adaptive structures, of this ele- 

 mentary attribute of organisms. We have to thank him for 

 the best putting together of all those observations which 

 permit of but the one conclusion, that the functional stimuli 

 exercise a trophic activity, that is, that each organ by the 

 constant exercise of its function becomes stimulated to 

 stronger assimilation and increased multiplication of its 

 elementary parts, and that out of this there results a height- 

 ened functional capacity." However, as Plate points out r 

 The law of tms "^ aw f functional adaptation" does not 

 functional adap- app iy to a n organs and tissues; "the teeth of 



tation does not 



apply to all many mammals become impaired through con- 

 organs, stant use, and most of the sense-organs are 

 apparently not bettered through use in regard to their per- 

 ceiving elements but only in regard to their carrying ele- 

 ments. Every exercise is followed by a certain fatigue 

 which, in cases of exhaustion, is greater than the aimed at 

 (ergielte) increase of functional capacity. Also the trophic 

 stimulation can, in certain cases, lead to hypertrophy and 

 other unadaptive results." But as regards the actual "strug- 

 gle of the parts," and especially as regards the claim that- 

 such a struggle is to account for inner adaptations, Plate, as 

 a consistent natural selectionist, is wholly sceptical. He 

 offers five objections to any usurpation of the functions of 

 natural selection by this intra-selection theory. First, he 

 holds, with Wolff, that it is impossible to place the inner 

 adaptations in any sharp contrast with outer adaptations. 

 They are contrasted only in that the former stand in a more 

 indirect relation to the conditions of life. Indeed a single 

 organ, as a claw for example, can show an external adaptive- 

 ness in that it might be especially well arranged to scratch 

 hard dry ground, and at the same time be distinctly adap- 

 tively constructed as regards its fine inner structure. "If 



