28 MAN AN ADAPTIVE MECHANISM 



to counter the attacks of enemies and to procreate. 

 Where there is a negative defense, such as a shell or 

 quills, there is little need and no evidence of intelli- 

 gence ; where a rank odor, no need and no presence of 

 claws or carapace ; where sting or venom, no need 

 and no possession of odor, claws, shell, extraordinary 

 strength or sagacity. 



Where the struggle is most bitter, there exist the most 

 complex and most numerous contrivances for living. 

 Where food is easy of access, as, for instance, among 

 some sea animals which feed upon the microorganisms 

 in the water, there is little need of more than the 

 siphon-like appendages which are waved about in 

 the medium containing food while the animal like a 

 plant clings to a rock or shell. 



Form and Color Obliteration 



Obliteration of color and form is one of the most 

 effectual methods by which certain animals survive. 

 So useful has been this device of color obliteration 

 that in practically every part of the world many liv- 

 ing things are in color similar to the immobile things 

 among which they live. Thus green is a common 

 color for animals in the evergreen forests of the 

 tropics; white is the prevailing color in the arctic 

 regions and a yellowish hue is common in desert 

 places. Some birds, like the ptarmigan, an inhabitant 

 of the Canadian Rockies, alter their color according 

 to the season of the year to match colors in the en- 

 vironment, their coats being white in the winter, green 

 or gray in the summer and mottled in the spring and 

 fall. (Fig. 1.) The ermine fox of the north has the 



