AMEBOID MOVEMENT 



61 



by a line for convenience of reference, were in the position in- 

 dicated at i when the forward end of the ameba occupied the 

 position indicated by outline I. As the ameba moved forward 



Figure 27. A part of an Amoeba proteus illustrating what is perhaps 

 the most characteristic quality of the surface layer of amebas, its fluid 

 nature. Three particles, a, b, c, were moving forward along an actively 

 growing pseudopod. In stage 2, particles b and c had arrived nearly at the 

 tip of the pseudopod. A pseudopod was then thrown out on the right, 

 which resulted in the movement of a in the same direction, while b and c 

 remained nearly stationary. Later on this pseudopod was retracted, b 

 and c were drawn back toward the main body of the ameba while c re- 

 mained behind, moving only very slowly. Thus the relative positions of 

 these particles was completely changed. 



the particle c gained slightly on a and b for no ascertainable 

 reason, unless it was on account of the projection of the large 

 pseudopod on the opposite side. At stage 2 a new pseudopod was 

 started on the right, which at stage 3 had grown to large size 



