REFLEXES IN BEHAVIOR 279 



that of other unicellular forms, so that it is difficult to make a positive 

 generalization on such a point as the present one. 



If we attempt to apply our definition of a reflex to the behavior of 

 the infusoria, — of Paramecium, for example, — we at once get into 

 difficulties. The "avoiding reaction" of Paramecium is sharply limited 

 in many ways, and always takes place in accordance with a definite type. 

 But it is far from being invariable. The reaction is composed of three 

 factors, which may vary more or less independently of each other, in 

 such a way that an absolutely unlimited number of combinations may 

 result, all fitting the generalized type. The possible variations may be 

 summed up as follows : If the animal be taken as a centre about which 

 a sphere is described, with a radius several times the length of the body, 

 then as a result of the avoiding reaction the animal may traverse the 

 peripheral surface of this sphere at any point, moving at the time either 

 backward or forward. In other words, the reaction may carry it in any 

 one of the unlimited number of directions leading from its position as a 

 centre. While the direction of turning is absolutely defined by the struc- 

 ture of the animal, yet the combination of this turning with the revolu- 

 tion on the long axis permits the animal to reach any conceivable position 

 with relation to the environment. In other words, Paramecium, in spite 

 of its curious limitations as to method of movement, is as free to vary its 

 relations to the environment in response to a stimulus as an organism 

 of its form and structure could conceivably be. Such behavior does not 

 fall within the concept of a reflex, if the latter is defined as a uniform 

 reaction. 



Still less does the behavior of Stentor yield itself to formulation as 

 purely reflex. To the same stimulus, under the same external conditions, 

 this animal may react, as we have seen, in several different ways; its 

 reaction depends upon its physiological condition. The same is true 

 for Hydra and other Ccelenterata, for the echinoderm, the flatworm, and 

 many other invertebrates, as we have set forth in detail in the descrip- 

 tion of the behavior of these organisms. In the sea anemone we have 

 examples of indecision, parts of the positive reaction being combined 

 with parts of the negative. In all these cases the behavior is far from 

 that sureness and fixity that characterizes the supposed reflex. 



Even in Amoeba it is difficult to apply the reflex concept to the be- 

 havior. So far are the reactions here from being uniform, that we can 

 almost say, on the contrary, that Amoeba never does the same thing 

 twice. The behavior is here formless, undefined, not held within nar- 

 row bounds by structural conditions, as in the infusoria and in most 

 higher animals; the essential criteria of reflex action seem lacking. It 

 would be very difficult to apply the reflex concept, for example, to the 



