144 



THE BEHAVIOR OF LOWER ORGANISMS. 



creeping on the slide and bearing on its upper surface a small granule, 

 which was moving forward in the usual way. The Amoeba stopped 

 and raised its anterior edge, which came in contact with the cover 

 glass ; it then loosened itself entirely from the slide, while its upper 

 surface became attached to the cover. It now began to move forward 

 on the cover glass. The granule on the upper surface now remained 

 quiet, until it was reached by the posterior end, when it passed down- 

 ward to the lower free surface, there moving forward in the usual way. 

 Upper and lower surfaces had completely exchanged roles. In a sim- 

 ilar way I have seen the thin lateral edge of a specimen become the 

 middle of the upper moving surface. 



Objects of the most varied sort cling to the surface of Amceba verru- 

 cosa and its relatives. I have seen the following attached to the surface 

 and showing the typical movements : Particles and masses of soot, 

 granules of India ink, motionless bacteria, diatom shells, dead flagel- 

 lates, masses of debris, 

 -^ cysts of Euglena, a small 



Amceba proteus (the lat- 

 ter was inclosed after it 

 had passed to the under 

 surface). Usually only 

 one or two small objects 

 are seen attached to any 

 given specimen, but to 

 this extent the phenomenon is very common, so that it seems rather 

 surprising that the movements of such particles should not have been 

 described before. 



A number of other points must be set forth before we can form a 

 clear conception of the movements of these Amoebae. The species 

 under consideration are much flattened and have usually an oval form 

 as they move forward, the anterior-posterior axis being the longer, 

 while the posterior end is the more pointed (Fig. 38). Not the whole 

 lower surface is in contact with the substratum, but only a band at the 

 anterior and lateral margins. In an Amoeba that was creeping on the 



Fig. 42.* 



* Fig. 42. — Movement of bodies attached to the surface in Amoeba verrucosa, 

 when the direction of locomotion is changed, a, A small granule ; b, a Euglena 

 cyst. In A the Amoeba is progressing to the right, as shown by the large arrow ; 

 the two bodies attached to the surface moved in the same direction, traversing 

 the stretch x-y, as shown by the small arrows. At this point a solution of 

 methyl green (»«) was allowed to diffuse against the surface; the Amoeba there- 

 upon changed its course, as indicated by the large arrow of ^. At the same 

 time the bodies a and b changed their course, traversing the stretch y-z. The 

 stretch x-y-z in B shows thus the path of the attached bodies before and after 

 the reaction. 



