64 THE BEHAVIOR OF PROTOZOA 



causes; "it is one of the most incomprehensible of phe- 

 nomena; it is exceedingly difficult to explain it without resort 

 to anthropomorphism." Protozoa not only perceive ex- 

 ternal objects but "they also indicate, by their movements, 

 an exact knowledge of the position occupied by these bodies. 

 It might be said that they invariably possess a sense of 

 position in space. The possession of this sense is absolutely 

 indispensible to them, for it does not suffice them to know 

 of the presence of an exterior body in order to approach it 

 and seize it; they must furthermore know its position, so as 

 to direct their movements accordingly. 



"The simplest form of a sense of localization is met with in 

 the Amceba which, when it closes about a nutritive particle, 

 always emits its pseudopods at precisely that part of its body 

 where the foreign substance caused the irritation. The 

 most complicated instance of localization is met with in the 

 Didinium, which we have so often cited; the Didinium knows 

 exactly the position of the prey it follows, for it takes aim 

 at the object of its pursuit like a marksman, and trans- 

 pierces it with its nettle-like darts." 



Instinct, memory, fear and a certain degree of intelligence 

 are among the psychic endowments with which Binet credits 

 the protozoa. A good sample of his interpretation of 

 protozoan behavior is the following: "The Bodo caudatus 

 is a voracious Flagellate possessed of extraordinary audacity; 

 it combines in troops to attack animalcula one hundred 

 times as large as itself, as the Colpods for instance, which 

 are veritable giants when placed alongside of the Bodo. 

 Like a horse attacked by a pack of wolves, the Colpod is 

 soon rendered powerless; twenty, thirty, forty Bodos throw 

 themselves upon him, eviscerate and devour him completely 

 (Stein). 



"All these facts are of primary importance and interest, 



