DEVELOPMENT OF BEHAVIOR 



321 



SO that in time an entire race may show the characteristics which first 

 arose as accidental variations along with many other useless ones. 



A great objection to this theory has been that it deals merely with 

 chance variations in all directions, so that progress along a definite line, 

 it is said, could never be brought about through it. The race progresses 

 just as the individuals do; what is first acquired by the individual is 

 later acquired by the race, as if the law of progress were the same in the 

 two cases. This, it is held, could not be brought about through the 

 selection of chance variations in all directions. 



In recent years a most successful attempt has been made by J. Mark 

 Baldwin (1902) and others to show that this objection is not a valid one ; 

 that the action of natural selection on characters playing a part in the 

 behavior would, in fact, be guided by laws similar to or identical with 

 those controlling the progress of the individual. To this guidance the 

 name organic selection has been given. Organic 'selection would then 

 account for the progress of the race in a continuous manner and in a 

 definite direction. We shall examine briefly, from this point of view, 

 the action of natural selection on behavior in the lower organisms. 



Observation and experiment show that there exist such variations 

 in the behavior of lower organisms as would under certain circumstances 

 give opportunity for the action of natural selection. If into an area 

 containing Paramecia a drop of a 10 per cent sugar solution is introduced, 

 most of the animals enter it and are killed, but a few react. negatively 

 on coming in contact with it, and escape. If such solutions were a con- 

 stant feature of the environment, it seems probable that in time there 

 would be produced through selection a race of Paramecia that would 

 always react negatively to them, and would, therefore, not be endan- 

 gered by their existence. Similar differences exist among different indi- 

 viduals as to sensitiveness to other chemicals, to heat, and to electricity, 

 as we have seen in previous pages. There is thus undoubtedly an oppor- 

 tunity for the action of natural selection to produce a race of organisms 

 more sensitive to weak stimuli than is the average at present, if the en- 

 vironment should require it. But if the environment does not require it, 

 the action of natural selection, Kke that of individual accommodation, 

 will not bring jt about. By either method only that is preserved which 

 is useful. 



There is likewise clearly an opportunity for natural selection to pro- 

 duce a race showing increased precision and adaptiveness in the move- 

 ments brought about by stimulation. As we have seen on page 305, the 

 reactions of Paramecium to heat are so much more effective than those 

 of Bursaria that if locally heated regions were part of the usual environ- 

 ment of the two organisms, the Bursariae would, for the greater part. 



