SEXUAL SELECTION 593 



appears to be the case with the Musophagae or plantaiu 

 eaters. Nor do I believe 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 {^Gotingidce) offer one of the best instances; 

 but with some of the species, in which the male has a splen- 

 did red breast, the female exhibits some red on her breast; 

 and the females of other species show traces of the green 

 and other colors of the males. Nevertheless we have a near 

 approach to close sexual similarity or dissimilarity through- 

 out several groups; aud this, from what has just been said 

 of the fluctuating nature of inheritance, is a somewhat 

 surprising circumstance. But that the same laws should 

 largely prevail with allied animals is not surprising. The 

 domestic fowl has produced a great number of breeds and 

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

 mage; so that it has been noticed as an unusual circum- 

 stance when in certain sub-breeds they resemble each other. 

 On the other hand, the domestic pigeon has likewise pro- 

 duced a vast number of distinct breeds and sub-breeds, and 

 in these, wi-th rare exceptions, the two sexes are identically 

 alike. Therefore if other species of Gallus and Columba 

 were domesticated and varied, it would not be rash to pre- 

 dict that similar rules of sexual similarity and dissimilarity, 

 depending on the form of transmission, would hold good 

 in both cases. In like manner the same form of transmis- 

 sion has generally prevailed under nature throughout the 

 same groups, although marked exceptions to this rule oc- 

 cur. Thus within the same family, or even genus, the 

 sexes may be identically alike or very different in color. 

 Instances have already been given in the same genus, as 

 with sparrows, fly-catchers, thrushes, and grouse. • In the 

 family of pheasants the sexes of almost all the species 

 are wonderfully dissimilar, but are quite alike in the eared 

 pheasant or Grossoptilon auritum. In two species of Chloe- 

 phaga, a genus of geese, the male cannot be distinguished 

 from the females, except by size; while in two others, the 



