AMEBA 



45 



FIG. 13 continued. D and E show the extension and attachment of a long 

 thin pseudopod. (From Bellinger in Journ. Exp. ZooL) 



same time the posterior end is contracting and the substance 

 thus pushed and pulled forward goes to form the new anterior 

 end. This continues as long as the Ameba advances (Fig. 13, 

 A, B, C). Often the anterior end is pushed along the substratum, 

 but no attachments form except at definite points. 



" In other cases the anterior end is lifted free and then curves 

 down to the substratum and attaches, forming a long loop. The 

 posterior end is then released, and the substance flows over to 

 the anterior end. At the same time another anterior end is ex- 

 tended " (34, p. 351, Fig. 13, D, E). When creeping on the ceil- 

 ing the movements are the same as when creeping on the floor. 

 When beginning to move, pseudopodia are extended in all direc- 

 tions until one becomes attached, when the animal advances in 

 the direction of the point of attachment. That a contractile 

 substance is present in Ameba and accounts for its movements 

 seems to be proven by Bellinger's observations. 



Many attempts have been made to imitate the movements o] 



