322 A. A. SCHAEFFER. 



pseudopod. The final effect of the peptone in this case was to 

 produce negative behavior, nevertheless the attractive qualities 

 were quite strong. 



In the path of another granular ameba was placed a new tube 

 containing a dilute solution of peptone 358. A number of 

 very small flagellates gathered near the open end of the tube. 

 The ameba moved forward toward the tube until it came within 

 thirty microns of it when a pseudopod was thrown out on the 

 right 360 which appeared destined to become the main pseudo- 

 pod, but the tendency toward positive reaction gained the upper 

 hand again and a food cup was formed over the open end of the 

 tube together with the flagellates, by a reactivation of the 

 previous main pseudopod 362. Ten minutes after the forma- 

 tion of the food cup the ameba began to make efforts to move 

 away. The protoplasmic current was reversed several times, 

 but finally the ameba moved on, after having been in contact 

 with the tube for eighteen minutes. It is impossible to tell 

 whether the flagellates had any influence on the reactions in this 

 experiment or not. 



In the majority of cases peptone in dilute solution diffusing 

 from a small capillary tube attracts amebas. In one ameba four 

 food cups were induced, one being completely formed at 100 

 microns from the open end of the tube. There can be no doubt, 

 then, that a solution of a chemical, such as peptone, even when 

 entirely free from the presence of a solid, is an adequate stimulus 

 to set off the feeding reaction. It is, nevertheless, interesting 

 to note that in the other three cases of food cup formation the 

 solid source, that is, the tube opening, was sought and enclosed 

 as if the chemical in solution acted only as a guide to the solid 

 object from which the chemical was diffusing. 



Egg Albumin. Capillary tubes were filled with a solution 

 made from Eimer and Amend's crystallized egg albumin and 

 filtered culture fluid. This solution diffuses much more slowly 

 than peptone. The solutions were very dilute: one part of 

 albumin to 200 parts water. 



A tube of egg albumin was placed in the path of a granular 

 ameba 369. The ameba moved forward into contact with the 

 tube, though apparently without being attracted toward it. 



