REACTIONS OF AMCEBA PROTEUS TO FOOD. 42! 



podium. Hence the possibility of escape of the prey again 

 becomes the conditioning factor in the reaction, which is met in 

 the manner described on page 416. 



In the Amoeba which presented the reaction shown in Fig. 7 

 we again see that it is not the part stimulated that primarily 

 reacts nor is the response for a given stimulus a fixed one. The 

 stimulus in this case was made at the point d and at first the 

 tip of the pseudopodium a grew along the far side of the prey 

 while a smaller pseudopodium arose at b. Later this first re- 

 action was greatly modified to better meet the involved condi- 

 tions. This modification was accomplished through a negative 

 response at b and a positive response at c. This reaction, so 

 modified, was a better one in so far that it made the escape of 

 the Chilomonas less probable. Thus we have an example of 

 the Amceba proteus attaining its end through trial and error 

 since the reaction to a given stimulus was modified with reference 

 to more readily realizing the object of the reaction. 



CONCLUSIONS. 



1. The reactions of Amceba proteus are highly variable in 

 reference to : (a) power of accepting or rejecting food ; (6) method 

 of ingesting food. 



2. In all this variability of reaction there appears no hap- 

 hazardness. The reactions are not automatic responses. Each 

 reaction is a response made to suit the peculiar conditions pre- 

 sented at the moment of accepting or rejecting the food; and if 

 not well suited to meet these conditions, it is modified with 

 reference to better meeting them. Thus in each reaction there 

 is evidence of purposiveness. 



LITERATURE CITED.* 

 Calkins, G. N. 



'01 The Protozoa. Macmillan Co., New York. 

 '09 Protozoology. Lea and Febiger, Philad. 

 Bellinger, Oris P. 



'06 Locomotion of Amoeba and Allied Forms. Journ. of Exp. Zool., Vol. III., 



No. 3- 



1 The same day that the page proof of this article came to the authors Prof. F. 

 J. Wright sent us a reprint of " Daily Life of Amceba Proteus" by David Gibbs, 

 Clark University. No reference has been made to this important paper in our 

 paper. Authors. 



