64 A., A. SCHAEFFER 



intensity of hunger determine, at least to some extent, whether 

 the globuhn 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. Intense hunger calls forth large food caps; 

 mild hunger, small food cups with little water; and very slight 

 hunger may prevent the formation of food cups altogether, the 

 protoplasm merely wrapping itself around the globulin. 



Globulin is an actual food substance. Grains of it undergo 

 gradual but marked diminution in size in the body of the ameba. 

 Globulin is disintegrat,ed somewhat more slowly than fragments 

 of aelosoma meat. On account of its food properties globulin 

 has been used in these experiments as the 'standard' test sub- 

 stance by which the attractiveness of other substances may be 

 compared and estimated. Of all the chemically prepared and 

 isolated substances used in this work, globuhn is the most at- 

 tractive, excepting perhaps carmine. AATienever globulin is eaten 

 and retained the inference is that the ameba is hungry. 



The experiments in which large pieces of globulin were used 

 show that if an ameba comes into full contact with a single 

 piece several times in succession, the globulin becomes less and 

 less attractive, just as carmine does if a piece is ingested repeat- 

 edly. Just what causes this change in behavior is not known. 

 These experiments also show that particles much too large to 

 be eaten call forth typical feeding reactions. 



The granular and the raptorial amebas differ strikingly in their 

 behavior toward globulin; the granular eat it with great readi- 

 ness while the raptorial amebas seldom eat it, and in many cases 

 after it is eaten egestion soon follows. This indicates a consid- 

 erable and definite difference between these forms, but whether 

 this difference is hereditary of acquired has not been determined. 



Several of the experiments show quite clearly that in raptorial 

 amebas disagreeable stimuli may proceed from globulin after it 

 is ingested. No definite explanation can be given at present of 

 these exceptional cases. 



