46 CONTROLLED NATURAL SELECTION 



The Relation of Species to Species. The 

 environment of one species may form that 

 of another beneath forest trees, tree-ferns 

 thrive ; on the stems of tree-ferns, filmy ferns 

 find suitable homes. The cat feeds on the 

 mouse, whose enemy the cat is. Thus, one 

 species can, through its environment, affect 

 that of another ; but a species, per se, cannot 

 affect another species because action implies 

 something acted upon, and anything upon 

 which a species acts is its environment. 

 Species may occupy a common environment, 

 but, as will be shown, in so doing, neither 

 each other nor their specific environments 

 are affected. 



fc. The Species and its Environment. Their 

 Relations. So far, the following conceptions 

 have been arrived at. Structure equals en- 

 vironment. The boundaries of the specific 

 environment of a species are defined. Each 

 species has its own specific environment. A 

 species completely fills its specific environ- 

 ment. A species can only be acted upon 

 by physical and biological forces, through its 

 environment. 



Further consideration must now be made 

 of the selecting agent, the Environment. It 

 has been shown not to be homogeneous, but 



