THE MOVEMENTS AND REACTIONS OF AMCEBA. 



i6 S 



MOVEMENTS OF THE POSTERIOR PART OF THE BODY. 



In an Amoeba moving as a simple, elongated mass, the anterior por- 

 tion of the body is broadest and very thin, being flattened against the 

 substratum, while the posterior part is narrower and much thicker. In 

 many cases the posterior end rises to an actual hump, the body being 

 thickest at the posterior edge, or a little in front of this edge (Figs. 44, 

 58). This is true as well of the AmoebaB of nearly constant form (A. 

 verrucosa, etc., Fig. 44), as of 

 those related to A. proteus. From 

 this hump the upper surface slopes 

 forward to the thin anterior edge. 

 The margins in the posterior part of 

 the body are not thin, but rounded 

 like the surface of a cylinder. 



The anterior portion of the 

 Amoeba is attached to the substra- 

 tum. This attachment of the ante- 

 rior portion has been clearly demon- 

 strated by Rhumbler (1898), and I 

 can confirm his results throughout. f 

 The attachment is probably by a 

 mucus-like secretion ; at least such 

 a secretion exists, as Rhumbler and 



others have shown and I can confirm. I have sometimes been able to 

 pull an Amoeba about by using a glass rod to which a thread of this 

 mucus had become attached (Fig. 55). The animal then seems to 

 follow the rod at a distance, the thread of mucus not being visible. 

 In virtue of this attachment the Amoeba resists currents of water, 

 or the impinging of solid bodies against it. The posterior portion 

 of the body is not thus attached, but is entirely free from the bottom. 



In many cases the most posterior part of the body forms a more or 

 less distinctly marked off portion, the surface of which is wrinkled or 

 warty or villous, or otherwise irregular. This is variously known as 

 the tail, the villous patch, or appendage (Wallich, Leidy), houppe 

 (Penard), Schopf (Rhumbler), etc. The occurrence of this appendage 

 is variable. In some species it is usually present, in others less com- 

 mon. Its occurrence and degree of development vary, indeed, in the 

 same individual. 



FIG. 54.* 



*FiG. 54. Amoeba angulata in locomotion, showing the numerous points in 

 the anterior region, some attached to the substratum, others projecting freely into 

 the water, a is the "antenna-like" pseudopodium, described on p. 177. 



tit is rather curious that Biitschli (1892), in his discussion of the movements 

 of Amoeba, is inclined to deny that there is any attachment to the substratum. 



