2O2 THE BEHAVIOR OF LOWER ORGANISMS. 



now contracted into a ball, its protoplasm clearly set off from the pro- 

 toplasm of its captor, and remained quiet for a time. Apparently the 

 drama was over. Amoeba c went on its way for about five minutes, 

 without any sign of life in b. In the movements of the Amoeba c the 

 ball b gradually became transferred to the posterior end of c, until 

 finally there was only a thin layer between b and the outer water. 

 Now b began to move again, sent out pseudopodia to the outside 

 through the thin wall, and then passed bodily out into the water (14). 

 This time Amoeba c did not return and recapture b. The two Amoeba 

 moved in different directions and remained completely separated. The 

 whole performance occupied, 1 should judge, about 12 to 15 minutes 

 (the time was not taken till several minutes after the beginning). 



After working with simple stimuli and getting always direct simple 

 responses, so that one begins to feel that he understands the behavior 

 of the animal, it is somewhat bewildering to become a spectator of so 

 striking and complicated a drama. If we attempt an analysis of the 

 observed behavior of the Amoeba c into stimuli and reactions, we ob- 

 tain some such a result as follows : At first the stimulus of contact with 

 ^, and perhaps a chemical stimulus from the same source, causes the 

 Amoeba c to react by flowing toward b, and at the same time to change 

 form, so as to hollow out the anterior end. Later, every change in the 

 direction of movement of a and b induces a corresponding change in 

 the direction of movement of c ; there is a finely co-ordinated adapta- 

 tion of the latter to the movements of the former. After the separation 

 of b from a, the movement of c (at 5-6) in a different direction may 

 have been due to some external stimulus. But what is the stimulus for 

 the change of direction of locomotion in the Amoeba c at 7 when b has 

 begun to escape ? And why does Amoeba c go in that direction only 

 long enough to get b firmly inclosed again, then reverse its course? 

 And, finally, why does Amoeba c reverse its course at 1 1-13, when b has 

 entirely escaped, and continue in this reversed direction till it reaches 

 and recaptures b? The action is remarkably like that of a higher 

 animal. Doubtless we must assume chemical and mechanical stimuli 

 as directives for each of the movements of c-, but the analysis so obtained 

 seems not very complete or satisfactory. 



REACTIONS TO INJURIES. 



Certain cases that belong under the heading of reactions to injuries 

 have already been described as evidences of the contractility of the 

 ectosarc ; for these page 180 should be consulted. The cases which 

 we take up here are of a different character. They concern Amoeba 

 angulata. 



Jensen (1896) has shown in the case of certain Foraminifera that 

 two pieces of protoplasm from the same individual will readily unite 



