424 Hawkins, Sexual Selection and Bird Song. [oct. 



do with us." If superabundant vigor can account for the songs 

 and ornaments of birds " then no other mode of selection is needed 

 to account for the presence of such ornament." 



Brooks attacks the theory of Wallace that the duller colors of 

 the female are acquired by natural selection. Thus there is found 

 a difference in the colors of lizards where the female does not 

 incubate and does not require the duller colors for the purpose of 

 protection. In domestic fowl where danger from natural enemies 

 is almost nothing the same difference in the color between the male 

 and female continues. Thus the explanation is more fundamental 

 than the one proposed by either Darwin or Wallace. Brooks bases 

 his explanation upon a theory of heredity which supposes that the 

 body gives off gemmules and that " the male reproductive cell has 

 gradually acquired, as its special and distinctive function, a peculiar 

 power to gather and store up these gemmules." The male cell, 

 therefore, has acquired the power to transmit variation while the 

 female cell keeps up the constancy of the species. "We thus look 

 to the cells of the male body for the origin of most of the variations 

 through which the species has attained its present organization." 

 Darwin said that the plumage and song of the male bird were trans- 

 mitted by the selection on the part of the female of the gayest bird 

 and the best singer. Brooks goes deeper and finds the cause for 

 these secondary sexual characteristics in the power of the male cell 

 to transmit the variations. He does not deny that the female may 

 choose the best singer but affirms that the male must lead in varia- 

 tions from his very nature. 



Geddes and Thompson carry forward still further the criticism 

 of Wallace and Brooks. Wallace accounts, on the theory of 

 natural selection, for the dull colors of the female and for the more 

 brilliant colors and song of the male. Darwin on the other hand 

 rivets his attention upon the gorgeous colors, the plumes, combs 

 and wattles of the male, accounting for them by the theory of 

 sexual selection but fails to tell us why the same process does not 

 brighten up the coat of the female. The mere statement of the 

 position must make it clear that there is some deeper cause than 

 that discovered by either Darwin or Wallace, some internal factor 

 much more powerful in its operation than any external cause. 

 Geddes and Thompson finds this in the essential difference be- 



