524 The American Naturalist. [June, 
Again, Dr. W. Wood (Am. Nat., Vol. II, 1868, p. 371), men- 
tions two cases :—the one, a Mottled Owl, taken from the nest 
with one young, neither of which had a red mark on them; 
the other, a Red Owl, taken with four young, all red. His 
deductions are, that there are two adults, one red without a 
gray feather, the other gray without the slightest trace of red; 
also, that there are young of each before they are able to fly, 
one gray and white without a red feather, the other with a 
reddish tinge to all the feathers. These facts he is unable to 
reconcile, unless, as he says, “ It is admitted that the color of 
the plumage is either ‘ variable or uncertain, or else there are 
two distinct species as described by Wilson.” 
The whole is admirably summarized and described in 
Baird, Brewer and Ridgway (Vol. III, 1874, p. 51), in the fol- 
lowing words, “ That these two very different plumages are 
entirely independent of age, sex or season, and that they are 
purely individual there can be no doubt, since in one nest 
there may often be found both red and gray young ones, while 
their parents may be either both red or both gray, the male 
red and the female gray, or vice versa. Occasionally specimens 
are exactly intermediate between these two plumages, it being 
difficult to decide which predominates.” 
This difference in plumage has been termed Dichromatism, 
and while a hundred and twenty-five years have succeeded in 
establishing the fact that the red and gray screech owls are 
one and the same species, no satisfactory theory known to 
the writer has been advanced as to what dichromatism is due 
in this case or as to the possible causes governing it. 
Naturally enough, this is far from satisfactory, while the opin- 
ions of various authors just quoted, and which comprise the 
most of what has been written upon the subject, tend but to 
raise innumerable queries for which there appear to be no sat- 
isfactory answers. Why, for instance, is the gray form doml- 
nant in one part of the country and the red in another? Why 
are both forms equally common in a third? Why is the red 
phase peculiar to the eastern members of the genus, while 1n 
the western forms it is unknown? Above all, why, at the 
northern boundary of asio proper, is the red form entirely 
