PHYSIOLOGICAL STATES AS DETERMINING FACTORS. 113 



of decreasing intensity. Such a case is that described in my previous 

 paper, when water mixed with carmine particles is allowed to reach 

 the disk of Stentor. 



The first physiological condition is again No. i that of the undis- 

 turbed extended Stentor. In this condition the organism does not 

 respond to the stimulus at all. After the stimulus has continued 

 for some time, the organism does respond by turning into a new 

 position. We have, therefore, a new physiological condition. The 

 reaction in this case is the same as that given in condition No. 3, 

 described above. Whether the condition now existing is the same as 

 in the former case we do not know ; as we have no positive evidence 

 to the contrary, we will number it 3 also. 



Next, after several repetitions of this reaction, the organism responds 

 in a still different manner, by momentarily reversing the ciliary current. 

 Since the stimulus and other external conditions remain the same, the 

 organism itself must have changed. We may call its physiological 

 condition at the present time No. 4. 



Next, the animal contracts strongly and repeatedly. This is clearly 

 the result of a still different physiological condition which we may call 

 No. 5. 



After thus contracting repeatedly we find that the organism remains 

 contracted much longer than it did at first. It is thus now in a new 

 physiological condition, which we may designate as Xo. 6. 



Finally, it breaks its attachment to the bottom of the tube and swims 

 away through the water. Probably, therefore, we should distinguish 

 a seventh physiological state, corresponding to this reaction. It is 

 possible, however, that the breaking of the attachment is due to the 

 strong contractions which characterize condition No. 6, so that the 

 evidence for a seventh physiological condition is not unmistakable, and 

 it may be omitted from consideration. 



We are able to distinguish clearly, therefore, in the study of these 

 two sets of reactions, at least six different physiological states. In each 

 of these states Stentor is a different organism, so far as its reactions to 

 stimuli are concerned. Clearly, then, the external stimuli and the 

 permanent anatomical configuration of the body are by no means the 

 deciding factors in the behavior. These factors, in the reaction series 

 last described, permit at least five different methods of behavior. 

 Which of these methods is actually realized depends not on the quality 

 or intensity of the stimulus, nor on the anatomical structure of the 

 organism, but on its physiological condition. 



I do not wish to imply that I hold that the six different physiological 

 states above distinguished are sharply defined, separate things. On 

 the contrary, it is much more probable that the different physiological 



