THE MOVEMENTS AND REACTIONS OF AMCEBA. 1 79 



of the pseudopodia in many cases to the vibrations of flagella. Similar 

 movements of pseudopodia have, of course, been described by other 

 authors, incUiding Biitschli (1S7S, p. 372; iSSo, p. 123). The strik- 

 ing resemblance of the movements of the pseudopodia in some cases to 

 those of flagella (see especially the account of Podostoma, Claparede & 

 Lachmann, 1S5S, p. 441) seems to indicate that the motion in these 

 two classes of structures must be essentially similar in character, and 

 that no theory of amoeboid movement is likely to be correct that is 

 inconsistent with the movements of flagella. Certain suggestions as to 

 the possibility of bringing the two in relation are given in the theoretical 

 portion of the present paper (p. 218). 



The whole body is sometimes moved rapidly by such movements of 

 the pseudopodia. This happens especially when the body is suspended 

 in the water and bears many long pseudopodia, one of which comes 

 in contact with the substratum. This pseudopodium spreads out and 

 extends along the surface for a distance, the part along the surface 

 forming nearly a right angle with the free portion. Suddenly the 

 pseudopodium straightens; since the distal end is attached, the body 

 is thrown almost violently against the substratum. 



Somewhat similar movements take place frequently in Atnoeba ver- 

 rucosa and its relatives, without the formation of pseudopodia. The 

 course of events is usually as follows: A specimen is creeping in a 

 certain direction in the usual manner with the anterior border attached, 

 while the posterior end is raised a slight distance from the substratum. 

 As a reaction to stimulus, or for some other reason, the anterior end 

 releases itself from the bottom. The posterior end thereupon sinks 

 down and becomes attached. Then its ectosarc contracts slightly, in 

 such a way as to lift the anterior end suddenly. The animal thus stands 

 upon what was its posterior end. Now, by varied contractions of the 

 parts of the ectosarc in contact with the substratum, the animal may 

 jerk from side to side rapidly and repeatedly, reminding one of the 

 movements of certain caterpillars which jerk their anterior ends about 

 in a similar manner. These movements are very striking and are much 

 more rapid than any that occur in other species of Amoeba, so far as 

 I have observed. 



The animal may even move from place to place in this manner. 

 Standing on one end, it jerks its body suddenly over to one side, so that 

 the previously upper end comes close to the substratum. This end now 

 becomes attached, while the other is released. Next a new sudden con- 

 traction brings the released end upward, so that the animal now occupies 

 a new location, one body's length from that previously occupied. I have 

 never seen the movement go any farther than what I have just described, 

 so that there is no evidence that this method is employed for bringing 

 about orderly locomotion. 



