102 HEREDITY AND SEX 



gregate, and successive males display, with the most 

 elaborate care, and show off in the best manner, their 

 gorgeous plumage ; they likewise perform strange 

 antics before the females, which, standing by as spec- 

 tators, at last choose the most attractive partner," 



Here we have two different pictures, each of which 

 attempts to give an account of how certain differences 

 between the sexes have arisen — differences that we 

 call '^ secondary sexual characters." 



On the one hand w^e deal with a contest between 

 the males ; on the other with choice by the female. 

 The modus operandi is also different. After battle 

 the successful male takes his pick of the females. If 

 the scheme is to work, he must choose one that will 

 leave the most offspring. 



On the other hand, we have the tourney of love. 

 The males ^^show off"; the females stand by spell- 

 bound and ''at last choose the most attractive partner." 



Now, concerning this display of the males, I beg 

 leave to quote a paragraph from Wallace's ''Natural 

 Selection and Tropical Nature" : 



''It is a well-known fact that when male birds possess 

 any unusual ornaments, they take such positions or 

 perform such evolutions as to exhibit them to the best 

 advantage while endeavoring to attract or charm 

 the females, or in rivalry with other males. It is 

 therefore probable that the wonderfully varied decora- 

 tions of humming-birds, whether burnished breast- 

 shields, resplendent tail, crested head, or glittering 

 back, are thus exhibited ; but almost the only actual ob- 

 servation of this kind is that of Mr. Belt, who describes 

 how two males of the Florisuga mellivora displayed 



