244 GRAND STRATEGY OF EVOLUTION 



of life's terrestrial environment, whence radiate from 

 countless individual centres, right and left, the inter- 

 mittent influences of light, sound, and chemical emis- 

 sions, to which life must for the moment adjust itself 

 in order to live with them in profitable relations. 



Owing to this gravitational orientation and to this 

 symmetrical structure and arrangement of right and 

 left receptors and affectors, balanced cooperative ac- 

 tion, or rectilinear locomotion inevitably follows, 

 other things being equal, so long as both right and left 

 sides are subject, from without, to the same influences. 

 But when that outward symmetry is disturbed, bodily 

 reorientation, or various degrees of rebalancing action 

 necessarily follow, such as swerving, or circus, move- 

 ments to right and left, toward or away from the mo- 

 mentarily dominant actor. 



A waltzing body, like a rifle bullet, might move 

 faster, it is true, or straighter, or have greater stabil- 

 ity, or greater power of penetration, but it could not 

 keep its "eye on the ball" or on its objective, nor could 

 the objective remain in that constant regulative touch 

 with the living body, which is so essential to directive 

 control. 



Exactly mated pairs of organs, acting either against 

 each other, or in unison, are in many other ways capa-, 

 ble of the highest degree of cooperative action, an es- 

 sential factor in their functioning being their right and 

 left symmetry. 



In many coelenterates, worms, and molluscs, where 

 directive locomotion, or even any locomotion at all, 

 is little in evidence, there may be an extraordinary 

 number of visual organs (two hundred, or more, in 

 some cases), either irregularly distributed over the 



