304 Biology in Amerid 



and the animal moves toward the cathode or negative pole. 

 The behavior of Amoeba moreover is not stereotyped, but can 

 be adapted to suit varying conditions. If a bright light be 

 thrown upon it, it contracts into a small inactive mass, but 

 after a time the pseudopodia are again thrust out and activity 

 resumed. When starved, Amoeba becomes more active than 

 usual, while after a heavy meal it becomes sluggish. 



' * All these responses are purposive in that they are adapted 

 to the preservation of the organism. Simple as Amoeba ap- 

 parently is it manages to cope very effectively with the condi- 

 tions of its existence. One might conceivably construct a 

 machine which would run itself, gather the food needed to 

 supply the energy used in its workings, avoid automatically 

 contact with obstacles which would impair its running, move 

 away from regions too hot or too cold for its efficient opera- 

 tion, protect itself by producing coverings in unfavorable 

 situations, and guide itself into the most favorable regions 

 for its maintenance; but what a wonderfully complicated 

 mechanism it would have to be! Yet a simple, apparently 

 almost structureless mass of jelly does all this and more. 

 And if our mechanism had the property of repairing its own 

 injuries and producing other pieces of mechanism like itself, 

 its structural arrangements would be almost if not quite 

 beyond our power to conceive. One cannot, therefore, but 

 look with a feeling of admiration and wonder at so com- 

 paratively simple a creature as Amoeba, which is capable 

 of performing so much. . . . 



"The behavior of Amoeba is essentially like that of higher 

 animals : it avoids things which are injurious ; it seeks things 

 which are beneficial and it adapts its behavior to new condi- 

 tions. Life is very much the same sort of thing whether in 

 an Amoeba or a man." 2 



One must not however be too sure as to the simplicity of 

 an Amoeba. While to the eye of the microscopist it appears 

 as an "almost structureless mass of jelly," nevertheless the 

 complexity of the molecules composing this jelly is such as 

 to defy analysis by the most skillful chemist. And even were 

 it possible to obtain an exact analysis of the Amoeba molecules, 

 the number of atoms composing the latter is so great as 

 to render possible several million combinations of these 

 atoms, each in a different way and each possibly respon- 

 sible for every new response which it makes to its sur- 

 roundings. 



While the behavior of Amoeba is generally such as to benefit, 

 rather than harm it, this is not invariably true of all organ- 



2 Holmes, "The Evolution of Animal Intelligence," pp. 70-71. By 

 permission of Henry Holt and Company. 



