THE MOVEMENTS AND REACTIONS OF AMCEBA. 175 



ELASTICITY OF FORM IN AMCEBA. 



For a real understanding of the phenomena shown by amoeboid 

 protoplasm it is important to realize that it has, besides some of the 

 chief characteristics of fluids, a number of properties that are usually 

 considered characteristic of solids. This came out clearly in certain 

 of my experiments. They show that Amoeba has elasticity of form to 

 a considerable degree. 



These experiments consisted in changing the shapes of Amoebse with 

 a fine capillary glass rod, under the microscope, in the open drop. 

 From numerous experiments of this character the following may be 

 selected as typical : 



An Amoeba had sent out one rather long, thick pseudopodium, as 

 shown in Fig. 59, a. With the capillary glass rod this pseudopodium, 

 0, was pulled loose from the bottom and bent over into the position 

 shown by the dotted outline b. On being released it rather quickly 



FIG. 59.* FIG. 6o.f 



sprang back into its original position, a. This experiment was repeated 

 on different Amoebae many times. 



An elongated Amoeba (a-a, Fig. 60) was bent with the rod at about 

 its middle, so that the anterior half was pushed far to one side of the 

 original median axis (to b}. This anterior half at once attached itself 

 to the bottom, whereupon the posterior half, which was not attached, 

 immediately swung round into line with it, so that the Amoeba occu- 

 pied the position b-c. Thus the original straight Amoeba on being 

 bent immediately straightens itself out again. On repeating this experi- 

 ment with many elongated individuals it was found that frequently the 

 straightening out was not quite complete, so that after it had occurred 

 there was still a slight bend in the middle. 



An Amoeba had a long pseudopodium curved over to one side, as in 

 Fig. 61, a. This pseudopodium was loosened from the bottom with 



*FiG. 59. A straight pseudopodium, a, is bent into the position b with a rod. 

 It at once returns to the position a. 



tFio. 60. A narrow Amoeba, a-a, is bent with the rod into the position a-b , 

 the end, 3, then becomes attached, and the animal at once straightens into the 

 position b-c. 



