66 THE BEHAVIOR OF PROTOZOA 



pseudopods are protruded. The details of the movements 

 vary considerably in different species. In Amoeba verm- 

 cosa Jennings describes the locomotion as "in many 

 respects comparable to rolling, the upper surface continually 

 passing forward and rolling under the anterior end so as to 

 form the under side." This is shown by placing in the 

 water particles of soot some of which adhere to the surface 

 of the animal; if a single particle be watched it will be seen 

 to pass around, as the Amoeba progresses, like an object on 

 the surface of a rolling cylinder. The anterior edge of the 

 Amceba is thin and flat and adheres closely to the substance 

 while the thicker posterior edge is free. The movement is 

 like the rolling of a contractile sac with semifluid contents. 

 Amoeba Umax has a similar method of locomotion but has 

 few pseudopods. Bellinger who has studied the locomotion 

 of Amceba proteiis describes a method of locomotion quite 

 different from that found by Jennings. Dellinger hit upon 

 the device of observing Amceba from the side, by means 

 of a horizontal miscroscope. The Amceba sends out a 

 pseudopod free into the water, which is then bent down and 

 attached to the substrate; the posterior end is now raised 

 and pulled forward; then another pseudopod is pushed out 

 and attached like the first and the body pulled forward again. 

 During the progress the Amceba is attached only at a few 

 points on short improvised feet which are drawn in as the 

 Amoeba passes over them. 



In a small unidentified species of Amceba the method of 

 locomotion, as observed by the writer, differs from all the 

 foregoing ones. There are broad ectoplasmic pseudopods 

 put out at the clear anterior end, commonly first on one side 

 and then on the other; the endoplasm flows into them and 

 the hinder part of the body which contains the contractile 

 vacuole is drawn forward. There is no rolling ; particles on the 



