THE METHOD 77 



As numbers increase, there arises a struggle for ex- 

 istence. This struggle results in favor of those organ- 

 isms best fitted to spread out over more territory, and 

 adapt themselves to new sources of sustenance, and to 

 new conditions of life. If animal life continually in- 

 creased, and no deaths occurred, it would, in a com- 

 paratively short time, fill the whole earth, and devour 

 all means of subsistence. This would destroy all animal 

 life. But only the best fitted have survived; the less 

 fit have been overcome. 



When variations occur in the offspring which are of 

 benefit to them in obtaining food, or in increasing their 

 means of defense of life, such variation, if it become 

 heritable, is continued. That is, nature selects that for 

 continuance. That is natural selection. The result 

 has been a constant progress from the weak to the 

 strong, from the simple to the complex, from the com- 

 paratively homogeneous to the heterogeneous. The 

 principle cani be illustrated, by the gradations of 

 nerve structure in the organisms, from the nerveless 

 protozoa, to the brain of man. The latter is complex 

 in his mental, as well as in his physical structure, and 

 therefore has almost infinitely wider relationship with 

 his environment, than has the former. He therefore 

 'has the knowledge and power to sustain himself in a 

 much higher degree than any other animal. He is, 

 therefore, better fitted to survive, under any and all 

 conditions; while the trilobite, for instance, could sur- 

 vive only under one condition, and that a very lowly 

 environment, from the Cambrian to the last of the 

 Carboniferous periods. This holds good with all 

 grades of animal life in proportion to the complexity 

 of the nerve structure. 



Death is an important factor in the principle of 



