THE MOVEMENTS AND REACTIONS OF AMCEBA. 193 



movements cease, while in red light they begin again ; lights of other 

 colors have various intermediate effects. 



It seems to the writer that further experimentation is desirable on the 

 results of a perpendicular illumination of one-half the animal. The 

 difference between the results thus far obtained from such illumination 

 and those from Davenport's experiments where light is admitted from 

 one side is very remarkable. If this difference is constant, it is of much 

 significance for the theory of light reactions. Possibly the lack of re- 

 action when but one-half the animal is illuminated may be accounted 

 for as follows : When one end of an Amoeba is illuminated from below, 

 as in Verworn's experiments, it is difficult or impossible to keep this 

 difference of illumination constant for any considerable period. If the 

 Amoeba does not react at once it passes completely into the lighted area, 

 where there is no cause for changing the direction of movement. On 

 the other hand, in the case of light falling obliquely from one side, the 

 different action of the light on the two sides is constant, so that in time 

 a reaction is produced. The slowness of Amoeba in reacting is such 

 as to make this possibility worth considering. For further work from 

 this point of view a source of powerful artificial light is needed. This 

 I have not had at command during the present investigation. 



It is evident that the reaction of Amoeba to light falling from one side 

 is exactly that which would be produced were the Amoeba strongly 

 stimulated on the side on which the light impinges. 



For an account of the reactions of Amoeba to general (not localized) 

 stimuli, see Verworn, 1888, and the Allgemeine Physiologic of the 

 same author. 



SOME COMPLEX ACTIVITIES. 



Under this heading I propose to describe certain striking phenomena 

 in the behavior of Amoeba, the stimuli to which are complex or not 

 sharply definable. These concern the reactions of Amoeba to food and 

 to injuries, and the relations of one Amoeba to another. 



ACTIVITIES CONNECTED WITH FOOD-TAKING. 



The behavior of Amoeba in taking food or in attempting to take food 

 shows many features of great interest for one attempting to understand 

 the behavior of these organisms. I have observed the process of food- 

 taking many times, and will describe it, together with a number of 

 related activities. 



Let us take a concrete case. A specimen ofAmce&a proteus was creep- 

 ing about on a slide which contained many spherical cysts of Euglena 

 viridis. One of these, which was not attached to the bottom (as most 

 of them are), was lying in the path of the Amoeba. The latter in its 

 forward movement came against the cyst and pushed it forward a short 

 distance. There was no evidence of a tendency of the cyst to adhere to 



