BEHAVIOR OF UNICELLULAR ORGANISMS. 95 



and simplify the phenomena exhibited by the many-celled crea- 

 tures. For one desirous only of getting at the real laws under- 

 lying the phenomena, the conflict on such points between high 

 authorities 1 is very confusing, and the only recourse is to a 

 first-hand study of the facts. 



In the hope of getting light on the problems proposed and 

 others of similar character, I shall set forth and discuss obser- 

 vations and experiments made upon a number of free-swimming 

 unicellular organisms. In the investigation it was found. well 

 to begin with some single species and work out its activities, 

 and the laws governing the same, completely enough to reveal 

 their essential nature, then to make a comparative study of the 

 activities of other organisms in the light of the knowledge so 

 gained. The same method will be advantageous for the pres- 

 entation of results. 



I give first, therefore, some of the results of a preliminary 

 study of the activities of Paramecium caudatum. This is one 

 of the commonest of the ciliate Infusoria, living by thousands 

 in vegetable matter decaying in water. It is a somewhat cigar- 

 shaped creature, having a broad groove passing obliquely from 

 one end (the anterior) to the mouth, which lies at about the 

 middle of the length of the body. The side on which the 

 mouth and groove lie may be called the oral side ; the opposite 

 one the aboral side. The entire surface of the animal is covered 

 with cilia, by means of which Paramecium moves. 



In beginning a study of the activities of such an organism, 

 we are at once confronted with the question of its psychic 

 powers. If these unicellular organisms do, as a matter of fact, 

 possess so complicated and highly developed a psychic life as 

 Binet, in his book on the Psychic Life of Micro-Organisms, has 

 attempted to show obtains among them, then indeed there is 

 little prospect of gaining light on simple migrations of proto- 

 plasmic masses during development, through a study of their 

 behavior. A study of the chick or the dog would perhaps be 

 as promising. The activities which Paramecium shows are at 



1 See, for example, Verworn, " General Physiology," and Loeb, " Einige 

 Bemerkungen iiber den Begriff, die Geschichte und Literatur der allgemeinen 

 Physiologic," Pfliiger's Archiv, Bd. Ixix, p. '249. 



