FITNESS AND ADAPTATION 77 



ing profit, and a larger and longer life; the other leads 

 it away from those things that prevent cooperative ac- 

 tion, and that diminish life and power. All other re- 

 actions are neutral, or of secondary value. The per- 

 sistence of these reactions tends to open or uncover the 

 pathways of constructive living, and to hold the animal 

 to its dual course, a course which more and more surely 

 leads toward that which is good and away from that 

 which is evil. 



In other words, the fundamental tropism of plants 

 and animals to things that are good for them is positive, 

 and to the things that are bad for them is negative. 

 This dual reaction, or behavior, is cumulative in its 

 effects, and inevitably leads to the discovery of better 

 ways of doing things ; to more adaptive reactions to the 

 external world, and thereby to a longer and more cer- 

 tain tenure of life. The same principles apply to each 

 part and to each organ of any animal, or plant, and to 

 each member of any social aggregate. 



The local growth, for example, of fur, or feathers, 

 gills, or lungs, of valve, muscle, or nerve, which thereby 

 better aid and protect the animal ; and the increase in 

 numbers, and in power, of soldiers, laborers, bankers, 

 preachers, and scientists, which thereby better aid and 

 protect society, is in each case the resultant of this dual 

 response of individual parts to their environment, the 

 resultant of their successful avoidance of what is evil 

 to them and the attainment of what is good for them. 



Each part, or organ, of every cooperative system 

 thereby tends to grow indefinitely. But when it at- 

 tains the maximum of growth consistent with the wel- 

 fare of the whole, upon which it ultimately depends, 

 its growth is checked automatically. 



