SEXUAL SELECTION 233 



brown females, and among these there occasionally occur females more 

 or less tinged with blue. These lead on to L. ineleager, which has two 

 forms of female, a common brown and a rarer blue; and thus we 

 reach L. tiresias, L. optUete, and L. argiolus, in which all the females 

 are blue, although less intensely and completely so than their mates. 

 The climax of this evolutionary series is reached by some species like 

 L. beatica, belonging to tropical or at least warm countries, in which 

 both sexes are of an equally intense blue. As we know that, in sj)ecies 

 with an excess of males, sexual characters always begin in the males, 

 there can be no doubt as to the direction of evolution— from brown to 

 blue — in this series. Furthermore, the entire absence of scent-scales 

 in most of the species with brown males indicates the great age of 

 these species, for, as far as I have been able to investigate, all the 

 males of the blue species possess them. 



Darwin resrarded this transferring of the male characters to the 

 females as due to inheritance, and it really seems as if it were simply 

 a case of transmission by inheritance to one sex of what has been 

 acquired by the other. Yet we have to ask whether we can continue 

 to regard the facts in this light. In any case this 'transmission' 

 is not an inevitable physiological process, necessarily resulting from 

 the intrinsic conditions of inheritance, for we see that it often does 

 not occur, even in many cases in which we can see no external reasons 

 why it should not do so, though in other cases the failure may be 

 presumably correlated with the external conditions of life. Thus, 

 for instance, the persistent retention of the brown colour in the 

 majority of our female Lyc^nidre has probably its reason in the 

 greater need of protection on the part of the much rarer females, 

 and this must be so also in the case of many birds in wdiich the 

 brilliant colours of the males have not been transferred to the females. 

 Wallace first pointed out that all birds whose females brood in exposed 

 nests are inconspicuously coloured in the female sex, even if the 

 males are brightly coloured, while those whose nests are concealed 

 in holes of trees or the like, or Avhich Ijuild domes over them, not 

 rarely exhibit brilliant colouring in both sexes. This is the case 

 in woodpeckers and parrots, while the gallinaceous birds, which 

 brood in the open, have usually inconspicuously coloured females, 

 for the most part very well adapted to their surroundings. 



If w-e grasp the fact that a transference of the characters 

 which have arisen through sexual selection can take place, we have 

 a valuable aid in the interpretation of many phenomena which would 

 otherwise remain quite inexplicable. What is the meaning of the gay 

 colours of the parrots, which occur in such incredibly diverse com- 



