THE BEHAVIOR OF AMCEBA 



19 



Sometimes the taking of food is in Amoeba verrucosa a much more 

 complicated process than that just described. Rhumbler (1898) has 

 given a very interesting account of the way in which this species feeds 

 upon filaments of algae 

 many times its own 

 length (Fig. 22). The 

 animal settles upon 

 the middle of an 

 Oscillaria filament, en- 

 velopes it, and length- 

 ens out along it (a). 

 Then one end bends 

 over (b), so that a loop 

 is formed in the fila- 

 ment (c). The Amceba 

 then stretches out on 

 the filament again, 

 bends it over anew, 

 and the process is 

 repeated until the fila- 

 ment forms a close coil within the Amceba (c to g, Fig. 22). Leidy 

 (1879, P- 86) has given a similar account of the method of feeding on 

 filaments of algae in Dinamceba. 



Filaments that have been partly coiled up are often ejected when 

 light is thrown upon the animal (Rhumbler, 1898). 



Fig. 22. — Amceba verrucosa coiling up and ingesting a fila- 

 ment of Oscillaria. After Rhumbler (1898). The letters a to g 

 show successive stages in the process. 



Features of General Significance in the Behavior 



of Amceba 



We find that the simple naked mass of protoplasm reacts to all 

 classes of stimuli to which higher animals react (if we consider auditory 

 stimulation merely a special case of mechanical stimulation). Mechan- 

 ical stimuli, chemical stimuli, temperature differences, light, and elec- 

 tricity control the direction of movement, as they do in higher animals. 

 In other words, Amceba has some method of responding to all the chief 

 classes of life conditions which it meets. 



The cause of a reaction — that is, of a change of movement — is in 

 most cases some change in the environment, due either to an actual 

 alteration of the conditions, or to the movement of the animal into new 

 conditions. This is notably true of the reactions to mechanical, chemi- 

 cal, and thermal stimuli. In the reactions to light and the electric cur- 



