8 
ANNALS NEW YORK ACADEMY OF SCIENCES 
D 
INSTINCTS 
The “mental” operation of lower orders of animals, termed instinctive 
reactions, are well exemplified by the nest-building habits of birds and 
insects. The materials employed and the character of the nests display the 
adaptive nature of the instinctive adjustments to different environmental 
conditions. The behavior of crustaceans like the Spider-Crab illustrates 
another peculiar instinctive habit. 
Illustrations 
1. Nests of various species of birds. 
2. Nests of various social insects. 
3. A Spider-Crab allowed to decorate itself with various natural 
objects, so as to be inconspicuous through its resemblance to 
its surroundings. 
4. The death-feigning instinct in Bluebirds. 
E 
NATURAL SELECTION AND COLORATION 
Some striking results of the survival of the fittest are found in the adaptive 
coloration of several kinds of animals. Many organisms harmonize in 
color and form with their environment, others mimic natural objects of 
various kinds, gaining similar protection by such resemblances. 
Illustrations 
1. The Leaf-Butterflies and other insects, illustrating various kinds 
of protective resemblances and coloration. 
2. Protective resemblance and color-adaptation in the Sargassum- 
Fish and other lower vertebrates. 
3. The uses of color in various species of birds. 
4. A group showing the seasonal changes in the coloration of the 
Ptarmigan. 
F 
HYBRIDISM 
When differing but related forms of animals or plants are crossed, the 
hybrid offspring may resemble one parent in some features, and the other 
