16 E. J. LUND 



during the work. In these it was found that when normal, 

 active animals were fed vitellin under what seemed to be the 

 best experimental conditions, five to seven or even nine grains 

 were retained, and digestion of the whole mass continued to com- 

 pletion, leaving no residues. 



In the experiments, to determine the average rate of digestion 

 of vitellin the maximum number of grains fed was six, and it 

 was found that with this number as the maximum extrusion 

 very rarely took place. 



Rise in temperature accelerates the digestive process, but the 

 variations due to temperature were eliminated, since all the sets 

 of individuals were side by side in an oven kept at 25 to 26°C., 

 and the fluctuations in temperature due to taking the moist 

 chambers from the oven while the records were taken, were the 

 same for each set of individuals. 



The organisms used in each experiment were from the same 

 healthy culture. They were starved in tap water twenty-four 

 hours previous to the beginning of the experiments, so that a 

 clear cell was obtained. 



When the animals were to be fed, a large number were removed 

 from the 500 cc. dish of tap water in which they had been starved, 

 to an 8 cc. dish containing tap water. Some of the vitellin 

 suspension prepared as described above (p. 3), was added to the 

 tap water in the dish containing the animals. The quantity of 

 vitellin suspension added varied according to whether it was de- 

 sired to feed a small or large number of grains to each individual. 

 If a large number of individuals were to be fed only one grain, a 

 very weak suspension was added; the result was that the rate of 

 feeding was slow, and hence gave sufficient time to remove the 

 individuals as soon as one grain had been swallowed. As feed- 

 ing went on, the individuals that had eaten the desired number of 

 grains were picked out with a pipette and placed in separate 

 dishes containing tap water. In this way, under favorable con- 

 ditions, it was possible to obtain several sets of individuals 

 simultaneously, each individual of each set having eaten a defi- 

 nite number of protein grains. After feeding, the animals were 



