Vol. XIV 
eae Fourteenth Congress of the A. O. U. 85 
Some bird-drawings, the work of Mr. Ernest FE. Thompson, 
were shown by Mr. Frank M. Chapman. 
A vote of thanks was given Mr. Dutcher for the admirable 
manner in which his accounts with the Union had been kept 
during his long service as Treasurer. 
The feature of the afternoon session was the open-air talk by 
Mr. Abbott H. Thayer, demonstrating his theory of the principles 
of protective coloration. Mr. Thayer placed three sweet potatoes, 
or objects of corresponding shape and size, horizontally on a wire 
a few inches above the ground. They were covered with some 
sticky material, and dry earth from the road on which they stood 
was sprinkled over them so that they would be the same color as 
the background. The two end ones were then painted white on 
the under side, and the white color was shaded up and gradually 
mixed with the brown of the sides. When viewed from a little 
distance these two end ones, which were white below, disappeared 
from sight, while the middle one stood out in strong relief and 
appeared much darker than it really was. Mr. Thayer explained 
that terrestrial birds and mammals which are protectively colored 
have the under parts white or very light in color, and that the 
color of the under parts usually shades gradually into that of the 
upper parts. This is essential in order to counteract the effect 
of the shadow, which otherwise, as shown by the middle potato, 
makes the object abnormally conspicuous and causes it to appear 
much darker than it really is. In the case of Mr. Thayer’s 
experiment some of the witnesses could hardly believe that the 
striking difference in the visibility of the three potatoes was 
entirely due to the coloring of the under side, and Mr. Thayer 
was asked to color the middle one like the two others in order 
that the effect might be observed. Mr. Thayer complied with 
the request, painting the under side of the middle potato white, 
and shading the white up into the sides as in the case of the 
others. The effect was almost magical. The middle potato at 
once disappeared from view. A similar experiment was tried on 
the lawn. Two potatoes were painted green to resemble the 
green of the grass above which they were suspended. One was 
painted white on the under side and at once became invisible 
when viewed from a little distance, while the other showed plainly 
and seemed very dark, the shadow, superadded to the green of 
