224 The Descent of Man. Tart H. 



that women would more frequently endeavour to conceal a 

 deformity of this kind than men. Again, Dr. L. Meyer asserts that 

 the ears of man are more variable in form than those of woman.-'' 

 Lastly the temperature is more variable in man than in woman.^' 



The cause of the greater general variability in the male sex, 

 than in the female is unknown, except in so far as secondary 

 sexual characters are extraordinarily variable, and are usually 

 confined to the males; and, as we shall presently see, this fact is, 

 to a certain extent, intelligible. Through the action of sexual 

 and natural selection male animals have been rendered in very 

 many instances widely different from their females; but in- 

 dependently of selection the two sexes, from differing constitu- 

 tionally, tend to vary in a somewhat different manner. The 

 female has to expend much organic matter in the formation of 

 her ova, whereas the male expends much force in fierce contests 

 with his rivals, in wandering about in search of the female, in 

 exerting his voice, pouring out odoriferous secretions, &c. : and 

 this expenditure is generally concentrated within a short period. 

 The great vigour of the male during the season of love seems 

 often to intensify his colours, independently of any marked dif- 

 ference from the female.^ In mankind, and even as low down 

 in the organic scale as in the Lepidoptera., the temperature of the 

 body is higher in the male than in the female, accompanied in the 

 case of man by a slower pulse.^" On the whole the expenditure 

 of matter and force by the two sexes is probably nearly equal, 

 though effected in very different ways and at different rates. 



From the causes just specified the two sexes can hardly fail to 

 differ somewhat in constitution, at least during the breeding 

 season; and, although they may be subjected to exactly the 

 same conditions, they will tend to vary in a different manner. 

 If such variations are of no service to either sex, they will not bo 

 accumulated and increased by sexual or natural selection. Never- 

 theless, they may become permanent if the exciting cause acts 



*' 'Archiv fiir Path. Anat. und and retention by them of the sperm- 



Phys.' 1871, p. 488. atic fluid; but this can hardly br 



™ The conclusions recently ar- the oase ; for mKny male birds, foi 



rived at by Dr. J. Stocl^ton Hough, instance young pheasants, become 



on the temperature of man, are brightly coloured in the autumn of 



given in the ' Pop. Science Review,' their first year. 



Jan. 1st, 1874, p. 97. =° For mankind, see Dr. J. Stocli- 



^^ Prof. Mantegazza is inclined ton Hough, whose conclusions are 



to believe (' Lettera a Carl o Darwin,' given in the ' Pop. Science Review,' 



' Archirio per 1' Anthr opologia,' 1874, p. 97. See Gl.-ard's observa- 



1871, p. 306) that tihe bright tions on the Lepidoptera, as gives 



colours, common in so many male in the ' Zoological Record,' 1869, p. 



animals, are due to the pi-eseuce 347. 



