INDIVIDUAL AND SOCIAL SURPLUS 553 



negative reaction is useful in avoiding obstacles; the positive in secur- 

 ing contact with food. The food-taking reaction is the enveloping of 

 food by throwing pseudopodia about it. These three reactions together 

 with the ordinary crawling locomotion and the throwing out of pseudo- 

 podia in search of a solid on which to crawl, constitute the entire variety 

 of Amoeba's experiences as displayed in behavior. 



The structure of the Ciliata is much more complicated and in cer- 

 tain respects marks a distinct advance in equipment for the struggle 

 for existence. Paramecium may represent the type. In this animal 

 not only are the cilia modified locomotory structures, but there is a 

 definite region for food taking. A groove extends obliquely down one 

 side of the body, terminating at its lower end in a mouth. It is to the 

 cilia, chiefly, however, that Paramecium owes its superiority over 

 Amoeba. These are usually inclined backward and their stroke then 

 drives the animal forward. The most interesting characteristic of the 

 stroke is its obliqueness so that Paramecium always rotates on its long 

 axis, whether it moves forwards or backwards. In consequence of this 

 fact, according to Jennings, Paramecium solves the problem of how an 

 unsymmetrical organism, without eyes or other sense organs, may, never- 

 theless, maintain a definite course through trackless water. Not even 

 man succeeds in maintaining a straight course under similar but simpler 

 conditions. On the trackless snow-covered prairie the traveler without 

 compass, landmarks or other guide wanders in circles, though it is 

 possible to err only to right or left, not up and down as in the water. 



Paramecium, by rotation, compensates for any wandering by equal 

 wandering in the opposite direction. Nature anticipated the modern 

 rifle by several asons. With this equipment whenever a Paramecium 

 reacts negatively to some stimulus it is able to continue swimming in a 

 direction away from the stimulus until the stimulation ceases. Through 

 the additional power of slightly accentuating the rotation-swerve the 

 animal is enabled to swim in various directions and to remove itself 

 successively from many different environmental conditions, until it has 

 found what Jennings terms the "optimum." This behavior Jennings 

 characterizes briefly as a "selection from the environmental conditions 

 resulting from varied movements." It is in fact a "trial and error" 

 method with selection of the optimum — a method not unknown to man 

 himself. 



This characterization of it, however, may seem to imply too much. 

 Paramecium "tries" over and over again, but what is "tried" is 

 always the same thing — there seems to be no profiting by experience. 

 Whether the response of Paramecium to stimulation is conditioned in 

 any degree by subjective phenomena, or is even accompanied by them, is 

 a disputed point. Even if present there remains the further question 

 as to the extent such subjective phenomena may be considered similar 



VOL. LXXXI — 38. 



