324 A. A. SCHAEFFER. 



were formed near the tip of the main pseudopod, the right one 

 of which moved toward the tyrosin tube; but this pseudopod 

 was soon arrested and retracted while the main one enlarged 

 rapidly for a short time when it also was retracted. The pseudo- 

 pod on the left then became the main one through which the 

 ameba moved away after ingesting a flagellate 402-404. The 

 tube was then shifted, but the resulting behavior was indifferent. 

 Carmine. A capillary tube filled with a solution (not a sus- 

 pension) of carmine was placed in the path of a raptorial ameba 

 383. The ameba moved toward the tube a short distance 

 384 then reversed streaming and moved away. A new tube 

 of carmine solution was placed before another raptorial ameba 

 386. The ameba was disturbed in its movements but finally 

 sent out a pseudopod toward the carmine tube 388. But when 

 it came within about 100 microns of the tube it broke up into 

 several pseudopods 389 and finally the ameba moved away 

 to the left. The tube was then shifted 393. The ameba moved 

 toward the tube a short distance, then stopped and sent out a 

 pseudopod on either side 395. The one on the left enlarged 

 first, but when it came near the tube it was retracted and the 

 one on the right enlarged and carried the ameba away 396. 

 The tube was then laid before the advancing pseudopod 397. 

 This pseudopod was at once arrested and the pseudopod just 

 previously retracted became active and carried the ameba away. 



These experiments indicate that solid particles of carmine are 

 very much stronger in their stimulating power than solutions of 

 carmine. Carmine grains nearly always produce positive be- 

 havior which results in contact, while solutions induce only 

 negative reactions. It is at present impossible to tell why there 

 should be such a difference, for the chemical nature of the sub- 

 stance is presumably the same in both cases. Better technic 

 doubtless would do much to solve this difficulty. 



A number of experiments were also performed with sodium 

 chloride in small tubes, but the results were almost exactly like 

 those in which culture fluid was used for filling the tubes. Here 

 also better technic would probably give interesting results. 



