THE METHOD 85 



The main point is, however, that all these causes and 

 effects are within the realm of natural law, and 

 the theory does not require the investigator to assume 

 any other. Evolution is a theory which scientists 

 have generally adopted, not entirely because of its 

 capability of conclusive demonstration, but because it 

 requires less assumption, than any other. It depends 

 upon the manifestations of phenomena only, for its 

 verification, and not upon assumptions of either cause, 

 or origin. 



PROTECTIVE FEATURES. When the insects on a black 

 space are black, and on a white space white, when 

 those, on green leaves, are green, and on the bark of 

 a tree, or shrub, or seaweed, grey; when the animals 

 of an arctic region are white, and those on heather 

 moor are reddish brown, it will be found that the 

 variations of color are not caused by the similar tints 

 of the environment, except in a very limited degree, 

 but that all natural colors of these organisms are born 

 with them in their different habitats. But those which 

 are black on a white ground, being conspicuous are 

 devoured by their enemies, and the white ones left, 

 because they are inconspicuous. This is natural selec- 

 tion. It is the same with the other colors, the con- 

 spicuous individuals are devoured, and those corre- 

 sponding to the color of their back ground are pre- 

 served. The exception to this law is that some species 

 of insects are distasteful to the insect eater, and these 

 are preserved in all the colors natural to them. These 

 distasteful ones are apt to have more or less imitators, 

 as is well known, for example, among certain butter- 

 flies. Certain individuals have the form and color of 

 the leaves, or twigs, on which they feed, and thus 

 escape destruction by being inconspicuous. These are 



