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, 
