Nos. 622-623] MIGRATION A FACTOR IN EVOLUTION 469 



ing gravitational energy upon other substances is in the 

 process of activity. Thus, running water, by the general 

 process of erosion, including the subsidiary processes of 

 weathering and transportation, wears down the land and 

 results in the formation of many features such as brooks, 

 creeks, plains, deltas, and a variety of other physio- 

 graphic products. An organism is also an agent which 

 expends physical and chemical energy, producing stress 

 and exerting pressure and expending energy on other 

 substances, exhibits its process of response or its process 

 of behavior. An animal, by the process of predation runs 

 down another animal and devours it, by its process of di- 

 gestion dissolves it, and by the process of assimilation 

 makes muscle, bone, feathers or fur out of it, and these 

 are all products of its activity. The process of response 

 is here strictly comparable to the process of erosion of 

 running water, and their products are similarly compar- 

 able. The general process is generic and includes many 

 species and varieties of subsidiary processes, ad infinitum. 

 As Keyes ('98) has well said, "Processes are merely 

 operative. If coupled with products at all . . . they must 

 be regarded as formative or constructive. The product's 

 destruction, its loss of identity, is wholly immaterial. 

 The action of agencies is merely to produce constant 

 change." It is, therefore, to the process of living, to the 

 process of evolution, rather than to its products such as 

 species, varieties, etc., which are of fundamental impor- 

 tance. For this reason the products must be subor- 

 dinated to the agencies and processes, because the laws 

 of change are in reality the object sought. 



The physiographer is not content to rest with the idea 

 that the agent, as, for example, running water, is the fin- 

 ished product of his analysis, for he also applies the same 

 methods of investigation to the agent itself, in order to 

 know its method of origin, the process by which it origi- 

 nates in the stream, whether indirectly from a spring, or 

 directly from the clouds. Thus the same methods which 

 the physiographer uses in studying the activity of the 

 agent, he again uses to explain the origin or derivation 



