Chap. XV.] COLOR AND NIDIFICATION". 160 



the other hand, the differences in color between the sexes, 

 whether great or small, may to a large extent be ex- 

 plained on the principle of the successive variations, 

 acquired by the males through sexual selection, having 

 been from the first more or less limited in their transmis- 

 sion to the females. That the degree of limitation should 

 differ in different species of the same group will not sur- 

 prise any one who has studied the laws of inheritance, for 

 they are so complex that they appear to us in our igno- 

 rance to be capricious in their action." 



As far as I can discover, there are very few groups 

 of birds, containing a considerable number of species, in 

 which all have both sexes brilliantly colored and alike ; 

 but this appears to be the case, as I hear from Mr. Sclater, 

 with the Musophagae ' or plantain-eaters. Nor do I be- 

 lieve that any large group exists in which the sexes of all 

 the species are widely dissimilar in color : Mr. Wallace 

 informs me that the chatterers of South America ( Cotin- 

 gidce) offer one of the best instances ; but with some of 

 the species, in which the male has a splendid red breast, 

 the female exhibits some red on her breast ; and the fe- 

 males of other species show traces of the green and other 

 colors of the males* Nevertheless, we have a near ap- 

 proach to close sexual similarity or dissimilarity tli rough- 

 out several groups : and this, from what has just been 

 said of the fluctuating nature of inheritance, is a some- 

 what surprising circumstance. But that the same laws 

 should largely prevail with allied animals is not surpris- 

 ing. The domestic fowl has produced a great number of 

 breeds and sub-breeds, and in these the sexes generally 

 differ in plumage ; so that it has been noticed as a re- 

 markable circumstance when in certain sub-breeds they 

 resemble each other. On the other hand, the domestic 



27 See remarks to this effect in my work on ' Variation under Domes- 

 tication,' vol ii. chap. xii. 



27 



