154 THE BEHAVIOR OF LOWER ORGANISMS. 



The pseudopodium lengthened, carrying the particle with it, the latter 

 maintaining its distance from the tip nearly or quite constant, but being 

 carried far from the body (Fig. 47, b}. The pseudopodium finally became 

 very long and slender (c), the particle remaining attached near the tip. 



2. Amoeba -proteus : A particle clinging to the surface of one side, 

 near the anterior end. A pseudopodium was formed at exactly this 

 point, extending freely into the water, so that the particle was borne 

 on the tip of the pseudopodium. It maintained this position while the 

 pseudopodium was extending, and was still found at the tip after the 

 pseudopodium had become long and slender (Fig. 48). 



The third example which I give is one of much interest, because it 

 shows the movements of a given point on the surface in both the retrac- 

 tion and extension of pseudopodia, as well as in transference from the 

 posterior to the anterior region of the body. 



3. Amceba proteus : When first observed the animal was rather 



slender, creeping in a certain direc- 

 tion, and with two long pseudo- 

 podia at the posterior end, extend- 

 ing, one on each side, at right 

 angles to the axis of progression 

 (Fig. 49, a}. The left pseudo- 

 podium was the longer, and bore 

 at about one-fourth its length from 

 its base a small particle (x) at- 

 p IG . * tached to its surface by a very 



short stalk in such a way that it 



was seen in profile (Fig. 49, a). The pseudopodium was not in 

 contact with the bottom, and was slowly retracting, its internal con- 

 tents flowing into the body, while the pseudopodium itself shortened. 

 As this occurred the particle approached the body and finally passed 

 on to its surface ( b, c) while the pseudopodium was yet of considerable 

 length. It was evident that the shortening of the pseudopodium took 

 place chieflv at its base, since the part between the base and the particle 

 x had become incorporated with the body when the portion between x 

 and the tip had changed only a little in length (6, c) . This distal 

 portion apparently did become somewhat shorter at the same time, 

 while its surface became slightly wrinkled. By the time the tip of the 

 pseudopodium had united with the body (d) the particle x had moved 

 a considerable distance forward on the latter. The posterior portion 

 of the body was here thick, and the particle was still seen in profile, 

 though it was some distance above the substratum. It now moved 



* FIG. 48. Movement of a particle attached to surface of an Amceba at point 

 where a free pseudopodium is pushed forth. The particle remains at the tip. 



