646 The American Naturalist. [July, 
Table Showing Relation of Color to Sez. 
(Based on 646 birds scattered over entire area.) 
GRAY. RED. 
ditiis |, Tuni Male. | fd: 
183 | 18 93 | 297 
quently include the figures from those localities where the red 
and gray respectively are the only forms known. Now it will 
be seen that the red birds are much more numerous than the 
grays—the total number being 390 as against 256 of the gray, - 
and if the influence of the exclusive red and gray regions on 
this average be considered, the proportion for the mixed areas 
will be somewhat increased. As a consequence, in that region 
shown on map 2, where red and gray birds are intermingled, 
with red in the majority, the reason is at once apparent why 
red and gray birds, or two red birds, are so often found mated, 
and so seldom a pair of grays. 
Granting now that the red birds are most numerous, does it 
not follow that the fewer the grays in any given region, and 
therefore the farther removed each generation of red birds 
from the parent stock, in just such ratio will the tendency to revert 
to ancestral characters decrease? It has been shown by Darwin? 
that in the struggle for existence, only those forms survive 
that are best fitted for the existing conditions of life to which 
they may be exposed, and, as a result, forms unfitted leave few 
progeny, and eventually become extinct. It will be shown 
farther on why the gray form is not fitted for those regions in 
which the red is now so greatly in the majority; accordingly, 
. it becomes evident that where the red males and females 
. already so greatly outnumber the gray, it requires but an 
indefinite lapse of time for the existence of the latter form to 
be forever terminated in certain sections. 
.. 5Origin of Species, 69. 
