CHAPTER IV 
THE BEHAVIOR OF PROTOZOA 
“One of the first lessons which the study of animal behaviour, in 
its organic aspect, should impress upon our minds is, that living cells 
may react to stimuli in a manner which we perceive to be subservi- 
ent to a biological end, and yet react without conscious purpose— 
that is automatically.”—C. Ltoyp Morcan, Animal Behaviour. 
The student of the evolution of mind naturally looks with 
interest to the behavior of those organisms which lie nearest 
to the root of the tree of life. What mental powers are 
evinced by the lowest animals, or whether, indeed, the lowest 
animals exhibit any mental powers at all are questions of 
fundamental importance to comparative psychology. Never- 
theless with all the theoretic interest and importance attach- 
ing to the study of the powers and performances of these 
low forms it is somewhat surprising that until quite recently 
the subject attracted few serious investigators. 
Binet in his book on the Psychic Life of Micro-organisms 
makes one of the first thorough-going attempts to estimate 
the extent of the protozoan mind. Among the psychic 
operations which he claims are manifested are: 
1. “Perception of the external object; 
2. “The choice made between a number of objects; 
3. ‘“The perception of their position in space; 
4. ‘Movements calculated, either to approach the body 
and seize it, or to flee from it.” 
Choice is manifested according to Binet in the selection of 
food. Many species live on a few kinds of food and refuse 
others. This choice cannot be explained as due to physical 
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