MOTOR RESPONSES 



335 



pH 7.1 and then joined this drop with other drops which were respec- 

 tively pH 6 and 8. He found that the amoebae at the border between 

 the drops formed pseudopods which protruded toward the drop added, 

 no matter whether it was alkahne or acid. This indicates that amoebae in 



Figure 120. The relation between rate of locomotion, gel/sol ratio, hydrogen-ion con- 

 centration, and sodium-ion concentration. Each of the curves represents a series of ex- 

 periments conducted at constant sodium-ion concentration. The four solid curves are 

 based on the measurement of the rate of locomotion of an average of 14.8 different 

 specimens for an average of 88.1 minutes in each hydrogen-ion concentration tested. 

 The two broken curves are based on the measurement of the gel/sol ratio in an average 

 of 19 different individuals in each hydrogen-ion concentration tested. (After Pitts and 

 Mast, 1934b.) 



a neutral solution tend to aggregate, either in acid or alkaline regions. 

 The observations made were, however, not extensive enough to war- 

 rant any definite conclusions. There is, then, nothing definite known 

 concerning the relation between differences in the chemical composition 

 of the medium and aggregation in any of the rhizopods, and but little 

 concerning the action of chemicals in relation to changes in direction of 



