ORIGIN OF THE SPECIFIC TYPE 311 



to the usual resting-place of the particular species to wliich it belongs ? 

 And yet it is on « priori grounds highly probable that this is the 

 case. But even this would by no means dispose of the whole problem, 

 for each of these protective colour schemes is composed of several, 

 often many, tints ; it must be so if they are to fulfil their end at all, 

 for a uniformly coloured wing would contrast with the bark of every 

 tree and with every wooden fence. Tlie wing-surface must therefore 

 bear on a lighter background a number of lines and streaks varying 

 from brown to black, and usually running zigzag across the wing ; 

 beside these are spots of lighter colour, which complete the deceptive 

 picture. This ' marking ' of the wing is similar in all twelve species, 

 and yet in each it is different in detail. It is constant in each, and 

 thus is a specific character. . But who would venture to undertake the 

 task of proving that each of these streaks, spots, zigzag lines, &c., is 

 or is not adaptive — that the details are necessarj' adaptations to the 

 resting-place which had become habitual to the species, or, on the 

 other hand, simply expressions of the variational tendencies of the 

 elements of marking, depending upon germinal selection 1 This would 

 be an impossible task, and 3-et we are here dealing with a character 

 which, as a whole, is undoubtedly adaptive ; in many of the differences 

 between other species even that is not certain. 



It seems to me, therefore, hardly reasonable to talk of the ' insufE- 

 ciency of natural selection ' because we are not able to demonstrate 

 that the minutiae of specific characters are adaptational results. 

 Personal selection intervenes whenever the variations produced by 

 germinal selection attain to selection-value ; and whether we can 

 determine the exact point at wliich this takes place in individual 

 cases is, as I have said before, theoretically quite indifferent. 



Moreover, there are cases in which we can prove that specific 

 differences are of an adaptive nature. When, of two nearly related 

 species of frog, the spermatozoon of one possesses a thick head and that 

 of the other a thin head, and when at the same time the micropyle 

 through which alone the spermatozoon can make its way into the 

 ovum is wide in the first species and narrow in the second, we have 

 before us a specific character which is obviouslj' adaptive. 



In order to gain clearness as to the significance of natural 

 selection in the restricted sense, that is of personal selection, it seems 

 to me much more important to study the different groups of animals 

 and plants with special reference to what they undoubtedly exhibit 

 in the way of adaptation. For that reason I discussed different 

 groups of adaptations in detail in some of the preceding lectures, 

 although, or rather because, they all teach us that every part of every 



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