THE BEHAVIOR OF AMCEBA 3 



is repeated as long as the particles cling to the surface. Single particles 

 have been seen to pass thus many times around the body of the animal. 

 Diagrams of the movements of the particles clinging to the surface are 

 shown in Figs. 4 and 5. 



It is not only the outermost layer of the ectosarc that thus moves 

 forward. On the contrary, the whole substance of the Amoeba, from the 



Fig. 5. — Diagram of the movements of a particle attached to the outer surface of Amceba 

 verrucosa, in side view. In position 1 the particle is at the posterior end; as the Amceba pro- 

 gresses, it moves forward, as shown at 2, and when the Amoeba has reached the position 3, the 

 particle is at its anterior edge, at x. Here it is rolled under and remains in position, so that 

 when the Amceba has reached the position 4, the particle is still at x, at the middle of its lower 

 surface. In position 5 the particle is still at the same place x, save that it is lifted upward 

 a little as the posterior end of the animal becomes free from the substratum. Now as the Amceba 

 passes forward, the particle is carried to the upper surface, as shown at 6. Thence it continues 

 forward, and again passes beneath the Amceba. 



outer surface to the interior of the endosarc, moves steadily forward 

 as a single stream, only the part in contact with the substratum being at 

 rest. At times small particles are at first attached to the outer surface, 

 then gradually sink through the ectosarc into the endosarc. Through- 

 out the entire process of sinking inward the movement is steadily for- 

 ward. 



It is clear, then, that Amceba rolls, the upper surface continually pass- 

 ing across the anterior end to form the lower surface. The anterior 

 edge is thin and flat and is attached to the substratum, while the posterior 



Fig. 6. — Diagram of the movements in a progressing Amceba in side view. A,. anterior 

 end; P, posterior end. The large arrow above shows the direction of locomotion: the other 

 arrows show the direction of the protoplasmic currents, the longer ones representing more rapid 

 currents. From a to x the surface is attached and at rest. From x to y the protoplasm is not 

 attached and is slowly contracting, on the lower surface as well as above, a, b, c, successive 

 positions occupied by the anterior edge. As the animal rolls forward, it comes later to occupy 

 the position shown by the broken outline. 



end is high and rounded, and is not attached to the substratum. A 

 very good idea of the character of the movements of Amceba may be 



