THEORY OF SEX-DIMORPHISM 97 



the view that the sex-characters behave in 

 inheritance as Mendelian characters. The 

 hypothesis concerns the origin, not the 

 development, or the evolution, or the mode 

 of inheritance. 



One of the arguments that may be used 

 in support of our hypothesis is that used in 

 a slightly different connection in The Evolution 

 of Sex. It is this. There are numerous 

 distinctively masculine characters which have 

 some measure of " family resemblance," 

 which look as if they had something in 

 common, which are congruent with the 

 intenser metabolism of the male sex. To a 

 thorough -going Lamarckian this is readily 

 intelligible, for he regards the colour-display, 

 the exuberance of integumentary outgrowth, 

 the erection of parts of the body such as 

 crests and tail-feathers, the growth of weapons 

 on the one hand and embracing organs on the 

 other, as natural developments of the in- 

 tensely living, lusty male, as natural individual 

 developments, whose results have gradually 

 been incorporated in the heredity-bundle. 

 But is not this too simple a view of the matter ? 

 It has not been proved that Nature works in 

 this direct way. The suggestion above made is 

 that such measure of congruence as there is in, 

 say, masculine sex-characters (e.g. brighter 

 colouring, exuberant decoration, smaller size) 

 may be hypothetically interpreted as due to 

 their having arisen as germinal variations 

 or mutations in germ-cells predetermined to 

 develop into males. 



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