34 THE ORGANIC GROWTH OF THE LIVING WORLD SEC. 



nised, as we shall see, the inheritance of characters acquired during 

 the individual life, particularly in emphasising the use and disuse of 

 organs as important in the modification of forms. Kollman certainly 

 goes too far when he supposes that by adaptation we have only to 

 understand the acquisition of definite characters during the individual 

 life under the pressure of external agents. 1 For each character which 

 seems adapted in an organism is not necessarily acquired during the 

 individual life. But the closer consideration of this question is con- 

 tained in my discussion of the whole theory of evolution. According 

 to the foregoing, we have in any case to distinguish, besides general 

 (cosmic) adaptation, a special adaptation in the usual sense of the 

 word, and in this again personal (individual) and race (or species) 

 adaptation. 



The characters above classed under (1), those called forth directly 

 by the influence of external conditions on the organism, without other 

 aid from the latter than physiological reaction, I have previously de- 

 scribed as arising by impression. Example : the production of a 

 darker skin by light and warmth. Light and warmth are here the 

 causce efficientes (0. Schmidt). Here belong a number of characters which 

 cannot be described as adaptations, which are rather unessential (indif- 

 ferent). Also, however, those which are due to the composition of the 

 organism which has been produced by the action of external conditions, 

 and which may be accidentally useful, but cannot have been increased 

 by selection. A host of characters which seem to have arisen through 

 selection will certainly come into this group of the accidentally useful. 

 If the brilliant mother-of-pearl of the internal surface of the mussel- 

 shell, which is completely hidden under the mantle, were visible on 

 the outer surface, it would certainly be indicated as useful. To the 

 same category belong the black back and bright silvery belly of fishes, 

 etc. Probably also many colours due simply to interference, such as 

 the splendid blue of the wings of the male Calopteryx virgo and others. 

 There can be nothing, indeed, more splendid in colour than the 

 iridescence of Labradorite, and is this useful to the stone? And 

 are colour and brightness useful to gold and countless other minerals ? 

 Are they useful to the soap-bubble ? 



Among the characters described under (2) I place those which have 

 been produced with the aid of the external action of the parts of the 

 organism concerned. Example : the formation of the hard skin of the 

 heel, of the hard skin of the sole of the foot in the barefooted African 



1 Compare Kollmann, loc. cit., and Weismann, loc. cit., E'wlog. C'entralblatt. 



