110 DOCTRINE OF EVOLUTION 



to obtain them. But we may expect to accomplish 

 our immediate object, which is to see that evolution 

 is natural. Our attention must be concentrated upon 

 the three biological subjects of adaptation, variation, 

 and inheritance, and we must learn why science describes 

 them as real organic phenomena and the results of 

 natural causes. 



At the very outset, when the general characteristics 

 of living things were considered, much was said on 

 the subject of adaptation as a universal phenomenon 

 of nature. It was not contended that perfection is 

 attained by any living mechanism, but it was held that 

 no place exists in nature for an organism that is in- 

 capable of adjusting itself to the manifold conditions 

 of life. A modus vivendi must be established and some 

 satisfactory degree of adaptation must be attained, 

 or else an animal or a species must perish. With 

 this fundamental point as a basis, we look to nature 

 for two kinds of natural processes or factors, first, 

 those which may originate variations as primary 

 factors, — the counterparts of human ingenuity and 

 invention in the case of locomotive evolution, — and 

 the secondary factors of a preservative nature which 

 will perpetuate the more adaptive organic changes 

 produced by the first influences; it is clear that the 

 latter are no less essential for evolution than the first 

 causes for the appearance of variations. 



The term ''variation" is employed for the natural 

 phenomenon of being or becoming different. It is an 

 obvious fact that no child is ever exactly like either 



