ON THE RELATION BETWEEN, ETC. 375 



podia ; the Amoeba radiosa resembles a ball with numbers 

 of thorn-shaped pseudopodia ; the Amoeba liuiax consists, 

 as it were, of one long club-shaped pseudopod which flows 

 almost entirely in the direction of its longitudinal axis. It 

 is an interesting fact that one and the same Amoeba may 

 for a certain period be an Amoeba limax, then for another 

 period an Amoeba radiosa, i.e., it may assume two entirely 

 different outward forms accordino- to the condition of the 

 surrounding medium. 



A large number of small and very active Amoeba of the 

 Umax species {c.) were placed in a culture glass in neutral 

 water. When, by a small addition of potassium hydrate, I 

 rendered the water slightly alkaline, all the Amoeba, after 

 the lapse of a quarter of an hour, assumed the typical form 

 of the A. radiosa {e, /.) and retained this shape without 

 showing the least interruption of their vitality. 



Again, an Amoeba protetis having finger-shaped pseudo- 

 podia spreading in all directions, may be made to assume 

 the form of an A. limax. If a chemical which causes the 

 expansion of the pseudopodia be added so as to act only on 

 one side, or if it be attracted by oxygen or food in one 

 definite direction, the shape of the animal changes, i.e., it 

 assumes the form of one large pseudopodium extended 

 towards the point from which the new influence emanates. 

 The whole mass of the organism flows along this one pseu- 

 dopodium, creeping towards the oxygen or food in the 

 shape of a thick club, this shape being retained as long as 

 its metabolism is influenced from the side. In spite of this 

 rigidity of the form the whole substance of the body is in 

 active movement ; a current flows, as in a fountain, forwards 

 in the longitudinal axis and backwards at the circum- 

 ference. 



These observations show plainly that, in a protoplasmic 

 body which varies in shape, the form is determined by the 

 different conditions and changes of the metabolism, and 

 that every modification in the latter is associated with some 

 definite shape. If a certain condition of the metabolism 

 continues for a length of time, the form of body appertain- 

 ing to it will also continue, even though, as in the case of 



