ADAPTATION FOR THE INDIVIDUAL T15 
pictures. They are so conspicuous that we recognize 
them at once. More common in my region than the 
jay or the cardinal is the red-eyed vireo. This crea- 
ture moves industriously in and out among the leaves 
of our trees. It is persistently in motion, is nearly 
constant in song, and is a bird of fair size, being 
larger than our English sparrow, though smaller than 
a robin. Many a nature lover will recognize twenty- 
five or thirty birds at sight without any difficulty, and 
not know the vireo. Yet the vireo is more common 
than two-thirds of the birds he knows. There can be 
but one reason for this; the bird is inconspicuous. 
The olive-green of its back, with its light under parts, 
serves to hide it completely amid the foliage. Even 
the bird-lover learns to find it first by its jerky song, 
and then by watching for its movements among the 
leaves. 
One aspect of protective coloration has been 
brought to our attention by the artist, Mr. Abbott N. 
Thayer. He first clearly explained why it is that ani- 
mals are usually so much lighter on the under side than 
they are upon the upper. Mr. Thayer proves his posi- 
tion by taking some ordinary cobblestones and paint- 
ing one of them a uniform color and placing it upon 
a board painted the same color. One would think the 
stone would be inconspicuous; as a matter of fact, is 
quite easily seen. The underside of the stone, turned 
