THE BEHAVIOR OF PROTOZOA 65 



but it is plain that their interpretation presents difficulties. 

 It may be asked whether the Bodos combine designedly hi 

 groups of ten or twenty, understanding that they are more 

 powerful when united than when divided. But it is more 

 probable that voluntary combinations for purposes of attack 

 do not take place among these organisms; that would be to 

 grant them a high mental capacity. We may more readily 

 admit that the meeting of a number of Bodos happens by 

 chance; when one of them begins an attack upon a Colopod, 

 the other animalcula lurking in the vicinity dash into the 

 combat to profit by a favorable opportunity." 



More recent investigations have shown that the behavior 

 of protozoa gives no evidence of the high psychic develop- 

 ment assumed by Binet. There has been a strong tendency 

 on the part of certain investigators to explain the behavior 

 of these low forms as due hi large measure to comparatively 

 simple physical and chemical factors. Others contend that 

 the phenomena are much more complex and at present defy 

 analysis into physical and chemical processes, while a few 

 go further and maintain that we must assume some super- 

 physical agency, a vital principle, or entelechy of some 

 sort, to explain the results. 



Much attention has been bestowed upon the activities of 

 Amoeba, which is generally assumed to be one of the most 

 primitive of the protozoa. Amoeba is a jelly-like organism 

 with a clear, outer, relatively dense layer of protoplasm, the 

 ectosarc, surrounding a more fluid, granular substance, the 

 endosarc, which contains the nucleus. The Amoeba com- 

 monly moves by sending forth blunt processes or pseudopodia 

 from the side of the body; material flows into the pseudopod 

 which may increase greatly in size; then other pseudopods 

 are put forth on the same side, the posterior part of the body 

 being pulled, in the meantime, in the direction in which the 



