BEHAVIOR OF AMEBA TOWARDS VARIOUS SUBSTANCES. 32! 



remained quiet for about six minutes, during which time the 

 water and the peptone solution disappeared from the food cup. 

 The ameba then started to move away. As the posterior end 

 passed the tube opening another food cup was started over the 

 tube but was not completed, and the ameba then soon moved 

 away 335. But when the tube was again laid in the ameba's 

 path 336 another food cup was formed over it. (A control 

 tube containing culture fluid was then placed in the path of the 

 ameba but only slight positive behavior resulted.) The peptone 

 tube was then shifted 337. The ameba formed a complete 

 food cup at a distance of about 100 microns from the end of the 

 tube 337, 338 showing conclusively that substances in solu- 

 tion are capable of causing the formation of a normal food cup. 

 The ameba then started to move away to the right 339 but 

 presently changed its course, returned to the tube 340 and 

 enclosed it again in a food cup 341. After remaining in this 

 position for a minute and a half, the ameba moved off. (The 

 control tube was then again laid before the ameba but no definite 

 change in behavior was observed.) 



A fresh tube containing dilute peptone solution was placed in 

 the path of another raptorial ameba 342. The general result 

 was negative behavior, due possibly to the commotion produced 

 by placing the tube in position. 



Another ameba in the same dish happened to come within 

 range of the tube 346. A pseudopod was thrown out which 

 moved directly toward the tube opening 347 but when it 

 came within about 100 microns of the tube it turned to the right 

 and moved on. The small pseudopod extended toward the 

 tube from the convex side of the ameba as it turned to the right 

 349 indicates a slight tendency to positive reaction. The 

 tube was then shifted 351. The ameba threw out a pseudopod 

 which moved toward the peptone tube for some distance, then 

 through a new pseudopod the ameba moved off to the right 

 352. While passing by the tube a side pseudopod was thrown 

 out toward it 354 but it was soon partially retracted. Very 

 soon it was again extended 356 and after it came within 

 twenty microns of the opening of the tube, it was retracted, and 

 the ameba moved directly away from the tube through a new 



