3 i2 THE POPULAR SCIENCE MONTHLY. 



We are considering the functions of the body when we are in- 

 quiring into such actions of the various structures internal and exter- 

 nal as involve internal processes, simple or complex. But, when we 

 begin to consider combinations of actions externally manifested, we 

 are dealing with conduct except only in the case of such actions as 

 are independent of control. 



But at the outset of the evolution of conduct even this distinction 

 is scarcely to be recognized. Every external combination of actions 

 is in the lower types of animal life a part of conduct at least of such 

 conduct as is possible in the lowest orders of creatures. Evolution of 

 conduct begins with the gradual development of purpose where at first 

 actions were random and aimless. The Amoeba wanders from place 

 to place, not by the action of limbs, but by a process which may be 

 called diffluence. In so doing it may come into the neighborhood of 

 objects fit to form its food ; these it in wraps, and absorbing what is 

 digestible rejects the rest. Or its wanderings may lead it into the 

 way of some creature by which it is itself absorbed and digested. 

 There may be some higher law than chance guiding the movements 

 of such creatures ; but so far as can be judged this is not the case. 

 In other words there is but the suspicion of something like conduct in 

 the actions of the Amoeba. Among other creatures belonging to the 

 same kingdom, but higher in type, we find actions so much better 

 adjusted, that, though even yet we can not recognize such evidence of 

 purpose as enables us to describe their actions as conduct, we yet see 

 in their adjustment to certain ends the development of something akin 

 to conduct. The actions seem guided by what mimics purpose if it is 

 not purpose itself. 



Now, we note that with the improved adjustment of actions comes 

 an increase in the average duration of life, or rather in the proportion 

 of this average to the length of life possible among these several 

 creatures. 



So when we pass to higher and higher orders of animals, we find 

 in every case among the lower types irregular and seemingly purpose- 

 less actions, while among the higher we find actions better adjusted 

 to the surroundings. And, again, we note that, where the combination 

 of actions, or what we may now call the conduct, is not adjusted to 

 the environment, the creatures' chances of life are small, great num- 

 bers dying for each whose life approaches the average duration. An 

 improved adjustment of conduct to environment increases the chances 

 of survival, many attaining and some passing the average of longevity 

 in their particular type or order. 



Now, structural development is guided by the fitness or unfitness 

 of particular proportions in such and such structures for the great life- 

 struggle in which all animal life is constantly engaged ; and functional 

 development is guided by the corresponding fitness or unfitness of such 

 and such functional activities. Just as certainly the development of 



