396 WM. A. KEPNER AND J. GRAHAM EDWARDS 



Starved Pelomyxas and those containing food show a con- 

 stancy in the rate of reaction towards the two types of food 

 motile and non-motile). We have not had it indicated that 

 " differences in the intensity of hunger determine, at least to 

 some extent, whether the globulin shall be eaten by means of 

 a food-cup or not, and whether the quantity of water taken in 

 with the globulin shall be large or small," Schaeffer ('17), page 

 64. 



In the majority of cases of encircling reactions to food, it 

 would appear that conditions would impose a gradual increase 

 in the intensity of stimulation ;• for as a Pelomyxa's encircling 

 pseudopods close about a paramaecium, the .disturbance of the 

 enclosed water by the cilia of the protozoan must be increased; 

 and, in addition, the concentration of carbon dioxide and other 

 excretions of the ciliate must become more (pronounced) there- 

 by causing a greatly intensified stimulation. This increase in 

 intensity of stimulation does not lead to an acceleration of the 

 rate of reaction. Yerworn ('13) says: "All phenomena can 

 change in their rapidity as well as in their nature. That is, 

 quantitatively and qualitatively. In this way the specific 

 vital process of an organism can be altered by the stimulus, 

 on the one hand, in its rapidity; on the other, in the manner 

 of its reaction. The majority of temporary responses to stimuli 

 consist in alterations of rapidity of the vital process, and from 

 either a quickening or retardation of its course," page 73. In 

 the majority of encircling movements, in which there is an in- 

 crease in the stimulation, we do not have a ' quickening' nor 

 a 'retardation' of the course of the reactions. Again, in ex- 

 amples in which objects of prey escape in a manner that by 

 irregular gradation reduces the amount of stimulation, the 

 reaction may not be accelerated, though sustained until the 

 completion of food-vacuoles (fig. 13, A) ; while in other instances 

 the removal of stimulation results in a reversal of the reaction 

 (fig. 13, B and fig. 12). The reaction of Pelomyxa to motile 

 objects of prey is, therefore, primarily a qualitative one. 



Because of the qualitative character of the reactions of Pelo- 

 myxa we cannot recognize in them factors that can be reduced 



