56 A. A. SCHAEFFER 



Globulin was used in this work as the 'standard' food sub- 

 stance. This accounts for the frequent use of it in many of the 

 experiments. The strength of the stimulus proceeding from 

 any other substance may thus be compared directly with that 

 of globulin. The degree of hunger or satiety may also be de- 

 termined within certain limits in this way. That globulin is a 

 real food substance undergoing solution (digestion?) inside the 

 body of the ameba is shown in figures 532 and 534. The ame- 

 bas were fed in filtered culture solution and occasionally in tap 

 water. 



Granular amehas 



An ameba ate a piece of grain gluten (326-336,) then moved 

 past another piece of grain gluten, then moved past this piece of 

 grain gluten a second time. A piece of globulin was then laid 

 in its path (366). The ameba flowed directly into contact 

 with the globulin, formed a food cup over it and ingested it. 

 A second piece of globuUn was partly surrounded as if ingestion 

 was about to follow, but the ameba presently withdrew (377). 

 Three and one-half minutes later, when the same grain of glob- 

 uhn was presented, it was promptly eaten (383). In this ex- 

 periment globulin seems to have been somewhat more attrac- 

 tive than grain gluten. 



A grain of globuHn was placed near another ameba that had 

 come to rest. It was moving only very slightly (387). At once 

 two pseudopods were sent out toward the globulin, but they 

 were withdrawn before they came into contact with it, the 

 protoplasmic stream then turning to the left. The ameba con- 

 tinued flowing in this direction until the posterior part was 

 being dragged past the globulin (399). The protoplasmic cur- 

 rent was then reversed, and also a side pseudopod was thrown 

 out on the right (now the left), which turned strongly toward 

 the globulin until it came into contact with it. The side pseudo- 

 pod was then withdrawn, and a little later another was formed 

 on the left and anterior to the globuUn. It also started to turn 

 toward the globulin, but was at this stage retracted, whereupon 

 the ameba moved past the globulin without further reaction. 



