BEHAVIOR OF AMEBA TOWARDS VARIOUS SUBSTANCES. 317 



distance but it soon came again within sensing range of the tyrosin 

 grain 59. The ameba became aware of the center of diffusion 

 of the tyrosin at a distance of about 125 microns. The ameba 

 moved toward the tyrosin grain, then over it, then formed a 

 food cup, and later withdrew, just as in the preceding trial. The 

 tyrosin had gone completely into solution however when the 

 ameba withdrew. Another tyrosin grain was then laid before 

 the ameba 64. The ameba moved forward into contact with 

 it and then repeated, substantially, the behavior observed in the 

 two preceding tests. 



After the ameba had withdrawn a short distance from the 

 tyrosin, and had become more or less quiet, another ameba 71 

 came from the opposite direction and proceeded at once to form 

 a typical food cup over the tyrosin grain. When the food cup 

 was nearly completed over the tyrosin, it was suddenly extended 

 to take in part of the original ameba 73. The tyrosin became 

 imbedded in the protoplasm while the new ameba attempted to 

 eat the other one 74. The attempt to capture the old ameba 

 was soon given up as this ameba became active and moved out 

 of reach of its would-be captor 75~77- 



A new grain of tyrosin was laid in the path of the ameba that 

 had been partially captured (the ameba shown in Fig. 70) 79. 

 The ameba turned to the left avoiding the tyrosin, but later 

 while passing by the tyrosin, a side pseudopod was sent out 

 toward it 84, 85. This pseudopod moved over the tyrosin, 

 swelled out and formed a food cup, and then withdrew from the 

 tyrosin, just as in the previous experiments. A second attempt 

 was made to move over the tyrosin 92, 93 but the pseudopod 

 was retracted before the tyrosin was entirely covered. Then 

 the vestige of the previous main pseudopod became active again 

 and the ameba moved off. The food cup that was formed was 

 completed. It remained undiminished in size for at least thirty 

 minutes. 



A grain of tyrosin was then laid to the right of the path of 

 another granular ameba 98. The ameba sent out a pseudopod 

 toward the tyrosin. After it came into contact with the tyrosin 

 the ameba formed a food cup and ingested it. At the time of 

 closing of the food cup the ameba loosened its hold on the sub- 



