24 AMEBOID MOVEMENT 



extended at their anterior ends continually, and unless the direc- 

 tion of locomotion is changed, the ridges may retain their iden- 

 tity while the ameba moves several scores of times the length 

 of its body. Along the sides, however, new ridges are continually 

 replacing older ones. When the direction of locomotion is 

 changed, the old ridges usually all disappear into a jumble of 

 ridges and crinkles running in every conceivable direction, and 

 with the reestablishment of locomotion along a more or less 

 straight path, a new set of ridges appears. In sphaeronucleosus 

 and its congeners, the ridges are also not wrinkles, but ridges 

 that are formed later than the surface contiguous to them. 



It is interesting to recall also that the ectoplasm in sphaero- 

 nucleosus, vcrrucosa and the rest of this group, is much firmer 

 than in most other amebas. 



