THE SEXES, AND CRITICISM OF SEXUAL SELECTION. 29 



or less cumbrous additional hypothesis of inheritance and so on 

 to explain them, are intelligible enough if we regard them as 

 illustrations of increasing katabolism throughout a series of species. 

 The third set may be supposed to be more male or katabolic 

 than the first, while the second set are midway ; although it 

 may be freely granted a knowledge of the habits, size, <S:c., of 

 the particular species, would be necessary to verify the legitimacy 

 of this interpretation in this particular case.* 



It is necessary once more to turn to the contrast between 

 the positions of Darwin and Wallace. According to Darwin, 

 sexual selection, for love's sake, has accelerated the males into 

 gay colouring ; according to Wallace, natural selection, for 

 safety's sake, has retarded the females (birds or butterflies) and 

 kept them inconspicuously plain. It is no longer difficult to 

 establish a compromise. The true view seems to be, that both 

 sexes have differentiated towards their respective goals, but the 

 males faster, because so katal)olic; the limits are constantly being 

 fixed by natural selection in Wallace's cases, and as constantly 

 increased by sexual selection in Darwin's. There is, in fact, no 

 reason why both should not be admitted as minor factors ; but 

 the greater part of the explanation is to be found in the view 

 above stated, viz., in the physiological constitution of males and 

 females themselves. In short, the present position allows some 

 truth in both these conclusions, but regards gay colouring as 

 the expression of the ])redominantly katabolic or male sex, and 

 quiet plainness as equally natural to the predominantly anabolic 

 females. On this view, too, we are able to restate part of the 

 position emphasised by Brooks. The greater variability of the 

 males is indeed natural, if they be the more katabolic sex. In 

 preponderant katabolism, the coml)inations and permutations 

 of molecules which constitute variation, are necessarily more 

 probable than in the quiescent, passive, or anabolic females. 

 No special theory of heredity is required, — the males transmit 

 the majority of variations, because they have most to transmit. 



At a later stage something more will be said of natural 

 selection, and its limits as an explanation of facts. But it 



* For a discussion of the progressive development of colouring and 

 markings, whether in butterflies or mammals, the reader may be referred 

 to the works of Professor Eimer, and especially to his forthcoming work 

 on Lejiidoptera. Reference should also be made to Weismann's " Studies 

 in the Theory of Descent," for a discussion of the markings of caterpillars 

 and butterflies. 



