178 
SEXUAL SELECTION: BIEDS. 
PAR ! 1 
great number of breeds and sub-breeds, and in 
tbes e 
~ MS 
tbe sexes generally differ in plumage; so that n . 
been noticed as a remarkable circumstance whe B ^ 
certain sub-breeds they resemble each other. On j 
other hand, the domestic pigeon has likewise prodn^ 
a vast number of distinct breeds and sub-breeds* ^ 
in these, with rare exceptions, the two sexes are id e ” j 
cally alike. Therefore if other species of Galln s a 
Columba were domesticated and varied, it would no 1 j 
rash to predict that the same general rules of seXl ^{ 
similarity and dissimilarity, depending on the for®® ,, 
transmission, would, in both cases, hold good. ^ 
similar maner the same form of transmission has g e 
rally prevailed throughout the same natural 
although marked exceptions to this rule occur, d 1 ^ 
the same family or even genus, the sexes naif 
identically alike or very different in colour. Inst^ 0 
have already been given relating to the same g eI 
as with sparrows, fly-catchers, thrushes and grouse- , 
the family of pheasants the males and females of 
all the species are wonderfully dissimilar, but are 
similar in the eared pheasant or Crossopiilon aui' 1 ^ 
In two species of Chloephaga, a genus of geese, 
males cannot be distinguished from the females, e> p 
by size; whilst in two others, the sexes are so ul y s*. 
that they might easily be mistaken for distinct s]> eCl< ^j ie , 
The laws of inheritance can alone account ^ 
following cases, in which the female by acquiri 11 ^^ 
a late period ol life certain characters proper to ^ 
male, ultimately comes to resemble him in a jjy 
less complete manner. Here protection can l^.'t 
have come into play. Mr. Blyth informs » ie 
the females of Oriolus melanoceplialus and of 
28 The ‘Ibis,’ vol. vi. 1S61, p. 122. 
