Jennings, The Movements and Enactions of Amoeba. 93 



typically no backward current in a progressing Amoeba, though the 

 appearance of one is produced by the contrast between the rapidly 

 moving internal fluid and the lateral margins, in contact with the 

 substratum, which are at rest. A diagram of the movements of 

 Amoeba is shown in Fig. 2. 



The same method of study shows that in the pseudopodia the 

 movement of material is uniformity outward, both on the surface 

 and within. In a pseudopodium in contact with the substratum the 

 attached surface is at rest, while the remainder moves outward. 



Fig. 1. 



P 



a 



Fig. 2. 



P 



In a free pseudopodium all parts move outward, new portions of 

 the surface of the body continually passing to the surface of the 

 pseudopodium. 



That the movements of Amoeba are of a rolling character 

 was held by Lachmann in 1858, while Wallich in 1863 set 

 forth briefly but clearly and correctly the real nature of the 

 movements. Wallich's correct statement has been neglected in 

 recent years. Biitschli observed in 1892 that the currents of 

 water about Pelomyxa are forward, not backward, as would be 

 expected if the surface moves forward, while Blochmann in 1894 

 observed distinctly that the surface moves forward in Pelomyxa. 

 Both these authors held however that this forward movement was 

 confined to a thin surface film; experimental study shows that this 

 is not the case in Amoeba. 



In accordance with the foregoing account, the movements of 

 Amoeba lose their supposed resemblance to those of a fluid mass 

 moving a s a result of a local change in surface tension. In 



