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of an agent gives us a process. Thus an organism, a plant society, or 

 an animal community is a very complex unit or agent, which largely 

 through chemical energy, under conditions of a normal environment, 

 responds in an orderly sequence or changes. The environment changes, 

 the internal conditions of the animal change, and so do the correspond- 

 ing responses on the part of the animal. When all of these changes 

 are studied as orderly processes we are able to see the advantage of 

 this method of study. It is desirable to investigate all phases of animal 

 responses in this manner, such as growth, development, heredity, etc., 

 in order to determine the causes and conditions of this orderly se- 

 quence. As a rule our recognition of the orderly sequence or laws of 

 action or succession precedes our knowledge of the causes and condi- 

 tions of the sequence. This order of sequence is thus of fundamental 

 importance and must be recognized before it can be investigated or 

 explained. This method of studying the activity of agents, the char- 

 acter of their processes, constitutes the dynamic standpoint. 



When the dynamic relations of an agent have been investigated, the 

 orderly sequence of its responses established, and the causes and con- 

 ditions of its activity determined, it is then possible to explain fully the 

 origin or genesis of its activities. The genetic method is the study of 

 origins in terms of the processes involved, and therefore the classifica- 

 tion of facts genetically implies a knowledge of the processes involved 

 in their origin. There are thus many degrees or stages in the develop- 

 ment of a genetic classification, the first step of which is to determine 

 the orderly sequence of changes. In a certain sense, in its broadest 

 application, the process method is universal and includes the genetic, 

 but until their mutual relations become clearly recognized and are gen- 

 erally understood both should be emphasized. 



Particular attention should be called to the fact that the activity of 

 an agent results in a process, and processes give us the laivs of change. 

 Many processes are reversible ; that is a process may go forward in 

 one direction and then become reversed and proceed in the opposite 

 direction. Other processes are non-reversible, and operate in only one 

 direction, being in a sense orthogenetic, as in the later stages of the 

 ontogenetic process. 



Let us summarize the main characteristics and principles involved 

 in the dynamic and genetic method. They have been well expressed 

 by Keyes ('98), and for my purpose are arranged as follows : 



"A truly genetic scheme for the classification of natund phenomena 

 thus always has prominently presented its underlying principle of 

 cause and effect. ... To begin with, an adeciuate scheme should be 

 based directly upon . . . agencies. ... All products must find accu- 

 rate expression in terms of the agencies. . . . The primary groupmgs 



