No. 9
The beasts all whitening roam the lifeless plain, And caves unfrequent scoop the couch for man.
Book I. Line 753.
The color of animals is acquired partly from the food they eat, thro successive generations, and partly from the objects with which they are usually surrounded. Dr. Darwin has a curious note on this subject, in which he remarks on the advantages that insects and other small animals derive from their color, as a means of rendering them invisible to their more powerful enemies; who thus find it difficult to distinguish them from other objects where they reside. Some animals which inhabit cold countries turn white in winter, when the earth is covered with snow; such as the snowbird of the Alps. Others in snowy regions are habitually white; such as the white bear of Russia.