HIGHWAY OF ANIMAL EVOLUTION 247 



respect to them. It may grow, for example, directly 

 away from the earth's centre of gravity, like the stem 

 of a plant; or towards it, like the roots; or, like many 

 animals, it may move in straight lines, up, or down, 

 the invisible lines of gravity; along a beam of light; 

 or along a radiating line, or trail of chemical emission, 

 or diffusion, etc., either toward, or away from its 

 source. Or it may be made to swerve from a balanced 

 attitude, or straight line action, one way or the other, 

 in gradient response to gradient changes in direction, 

 or relative intensity of the source, or sources, of in- 

 fluence. 



These measurable vital responses to measurable ex- 

 ternal agencies are very convincing, and from them it 

 would appear that behavior, or conduct, even in the 

 most highly organized animals, is the resultant of many 

 mingled external influences each acting in definite 

 ways, on definite organic structures. And that is 

 doubtless true. But we may not assume that conduct 

 is merely the algebraic sum of certain constituent acts. 

 We cannot measure conduct wholly in that way, any 

 more than we can measure the action, or quality, or 

 behavior, of water, as a world agent, by the acts of its 

 separate chemical constituents. 



There is a creative attribute in the cooperative op- 

 eration of organic acts, as there is in the cooperative 

 action of chemical elements. For that reason the ex- 

 perienced biologist, while he always welcomes the in- 

 formation which may come from the experimental dis- 

 section and analysis of animal behavior, does not cease 

 to look on the living animal, on the one hand, as an or- 

 ganic unit having a special value of its own in its unity, 



