CHAPTER XXI. 



PHILOSOPHICAL CONCLUSIONS REGARDING THE CAUSES 

 DETERMINING THE COURSE OF EVOLUTION. 



What is the Philosophy of Evolution ? — Statement of the Case. 



— In the foregoing chapters a few of the prominent facts re- 

 garding the history of organisms have been examined, 

 and the primary conclusion from their study is that 

 the method of acquirement of all that is characteristic of 

 organisms has been evolutional. Evolution is a matter of fact 

 in the description of the history of organisms; but there re- 

 main for consideration the questions, Why should organisms 

 express a law of evolution ? and, What are the immediate con- 

 ditions determining the particular steps of evolutional his- 

 tory ? and, finally. What is the rational philosophy of evolu- 

 tion ? 



The theory of natural selection may be so applied as to 

 lead to the philosophical belief that difference in the condi- 

 tions of environment is the primary cause of the differences 

 expressed in the form and functions of organisms; and sec- 

 ondly, the theory of the unchangeableness of matter and the 

 universal conservation of energy may be carried so far as to 

 lead to the belief that in the matter of organism, under the 

 names germ plasm, biophors, pangenes, gcmumlcs, physiological 

 units, or some other names resides the power and potency 

 of all that is evolved in the course of the total history of 

 organisms. 



Are these beliefs incident to the proposition that evolu- 

 tion is a fact in nature, or is there a philosophy of evolution 

 which more completely recognizes the whole body of facts in 

 the case? 



The Point of View. — If we were to discuss such a common 

 topic as the weather, we would find that, although every- 



371 



