178 



THE BEHAVIOR OF LOWER ORGANISMS. 



4. An Amoeba was creeping on the surface film, with a very long, 

 slender pseudopodium trailing behind down into the water and bent to 

 one side. This pseudopodium suddenly swung far over to the other side. 



5. Amoeba with many pseudopodia extending in all directions freely 

 into the water. Just as withdrawal begins, a given pseudopodium 

 bends over to one side, becomes curved to form a half circle, or waves 

 back and forth from one side to the other. 



An indefinite number of such observations could be adduced, showing 

 that with its other movements Amoeba has the power of bending and 



straightening its pseudopodia and waving 

 them from side to side. Such movements 

 have, of course, been described by many 

 authors ; in the magnificent monograph of 

 the Rhizopoda by Penard (1902) many 

 still more striking cases than those I have 

 described are set forth. Some of them 

 should be quoted. In Amoeba radiosa the 

 pseudopodia " may be displaced as a whole 

 in the liquid, and I have seen them de- 

 scribe in this manner a quarter of a full 

 circle in a second, like the hands of a watch 

 which one pushes forward suddenly by fif- 

 teen minutes. On two or three occasions 

 also I have noticed in the very sharp point 

 of a pseudopodium a rapid movement of 

 wave-like vibration, so that one could com- 

 pare it withaflagellum" (/. c.,p.8S). Simi- 

 lar phenomena are described for Amoeba 

 Umax (p. 36), A. gorgonia (p. 79), and 

 especially for A. ambulacralis (pp. 91 , 92), 

 in which the pseudopodia act like tentacles. 

 In other rhizopods, relatives of Amoeba, 

 Penard describes similar phenomena. Thus 

 in Pamphagus mutabilis (p. 439) the pseudopodia are said to move 

 as a whole in the water "almost as quickly as flagella." Similar 

 facts are described for Difflugia pristis (p. 255), Cystodifflugia sac- 

 culus (p. 429), Pamphagus granulatus (p. 436), Nadinella tenella 

 (p. 462), and various other rhizopods. Penard compares the movements 



FIG. 62.* 



* FIG. 62. Movements of pseudopodia: a, a pseudopodium in the position I 

 bends quickly in the direction shown by the arrow, and unites with the body; 

 b, a curved pseudopodium, t, straightens into the position 2; c, the antenna-like 

 anterior pseudopodium of Amceba angulata; it vibrates from i to 2, thence back 

 through i to 3, etc. 



