INTRODUCTION 9 



has ordained. The failure to realize this is painfully 

 obvious in the utterances of many who speak in the name 

 of the newly-founded " Eugenics " society, which seeks 

 the means to ensure the well-being of the race by 

 the spread of a more intimate knowledge of this all- 

 important subject. The existence of what Mr. Heape 

 has recently called a " sex-antagonism " is beyond 

 dispute, for the instincts of the male and female are 

 fundamentally different. The male is dominated by the 

 desire to gratify the sexual appetite ; in the female this 

 is counteracted by the stimulation of other instincts 

 concerned with the cares of offspring. 



Amorousness, then, is the dominant feature of the males 

 among all animals : and this sex presents yet another 

 characteristic which is to be borne in mind. In all that 

 concerns the evolution of ornamental characters the male 

 leads. In him we can trace the trend which evolution 

 is taking ; the female and young afford us the measure 

 of the advance along the new line which has been taken. 

 Why this should be is inexplicable. But sooner or later 

 the females assume, or will assume, all the features 

 originally possessed by their lords ; and finally the young 

 also follow suit. That is to say, the females and young 

 tend to retain the ancestral characters. In the course of 

 time the ability to develop new features by the male 

 loses its impetus, and not till then, apparently, do the 

 females, and still later, the young, begin to share his 

 glory. These remarkable features are strikingly illustrated 

 among the birds, as these pages will show. 



Nature is nothing, if not perverse. And hence it 

 happens that there are many exceptions to every rule 

 which one formulates. Among the birds, for example, 

 there are species wherein the rule that the female 



