312 A. A. SCHAEFFER. 



reaction. In no case was ingestion attempted. The solubility 

 of graphite was not tested by me. 



Silicic Acid. Merck's Pure, by Wet Process. A small grain 

 of silicic acid was laid in the path of a granular ameba 309. 

 The ameba moved forward a short distance within about forty 

 microns of the silicic acid then swelled up at the anterior end 

 and finally sent out a pseudopod on the left through which the 

 ameba moved off. A new grain of silicic acid was then encoun- 

 tered 314. The ameba moved directly into contact with it 

 at the side. The ameba then moved off through a pseudopod 

 sent out posterior to the test object 319-321. A new grain of 

 silicic acid was then laid in the ameba's path 322. After mov- 

 ing toward it a short distance until within about thirty-five 

 microns of the acids 323, 324 the ameba moved away through 

 a pseudopod thrown out on the left. Another new grain of silicic 

 acid was then laid in front of the ameba 328. The ameba 

 moved forward to within sixty-five microns of the acid, then 

 moved off through a pseudopod thrown out on the left. 



Silicic acid is sensed at a distance like carbon, glass and 

 graphite, but with the ameba used in the experiments recorded 

 above, the behavior was nearly always negative. Owing to 

 incomplete knowledge concerning the purity of this substance, 

 it is not clear what the meaning is of the preponderance of nega- 

 tive behavior in the reactions of this ameba. The negative 

 tendency cannot have been due to lack of hunger however for 

 a grain of globulin was readily eaten a few minutes later. 



Hematin. Merck's, according to Nencki. This compound 

 results from the decomposition of haemoglobin, and is very rich 

 in iron. The black "melanin" produced by the malarial organ- 

 ism is supposed to be hematin, and is said to have a toxic effect 

 on the human body. The following experiment is typical of 

 the behavior of ameba toward hematin. A grain of hematin 

 was placed in the path of a granular ameba 28. As the ameba 

 passed it on the right at a distance of about forty microns, several 

 small pseudopods were sent out but none of .them came into 

 contact with the hematin. 



Hematin seems to call forth about the same behavior as glass 

 or carbon ; perhaps the positive reactions are not quite so decided. 



