INFLUENCE OF NUCLEUS ON BEHAVIOR OF AMCEBA. 267 



locomotion for five trials, each continuing for one minute. The 

 figures in the left column show the rate of locomotion in the 

 nucleated parts; those figures immediately opposite, in the other 

 column, show the rate of locomotion in enucleated parts. For 

 instance, the nucleated segment of the individual first cut moved 

 in five trials at an average rate of 0.15 mm. per minute, and the 

 enucleated part cut from the same individual moved at an 

 average rate of 0.002 mm. per minute. From the table one 

 thing is strikingly evident: movement in nucleated parts is 

 always much more rapid than that in enucleated parts; in no 

 case does the rate of locomotion in parts without a nucleus equal 

 that in parts with a nucleus. 



POSSIBLE CAUSES OF DIFFERENCES IN BEHAVIOR. 



From the experiments cited above, it is evident that there 

 are differences in the behavior of parts of Amoeba with a nucleus 

 and parts without a nucleus; differences in the character of 

 movement, in orientation, and in the rate of locomotion. Now, 

 to what may these differences be attributed? The two parts 

 differed in size, in their position in the amceba cut to produce 

 them, in the possession of a contractile vacuole and a nucleus. 

 The difference observed in their behavior must be ascribed to 

 some of these differences in structure. 



Size. In this work nearly 125 amoebae were cut, each into two 

 parts, one of which contained a nucleus. In approximately one 

 half of these cases, the part without a nucleus was as large as or 

 larger than the part with a nucleus. Records of the two parts 

 of 13 of these amoebae, taken at random, may be found in Table I. 

 Both parts in all cases were kept under the same cover-glass and 

 were subjected to the same or similar conditions. All of the 

 nucleated parts behaved like normal specimens, but none of the 

 enucleated parts, regardless of the relative size of the two parts. 

 It appears, therefore, that differences in the size of parts do not 

 determine the differences in behavior. 



Contractile Vacuole. The contractile vacuole was present in 

 the nucleated parts of the 125 specimens experimented upon 

 about as often as it was in the enucleated parts. There was no 

 observable difference in behavior associated with the presence or 



