66 THE BEHAVIOR OF PROTOZOA 
pseudopods are protruded. The details of the movements 
vary considerably in different species. In Ameba verru- 
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 Amceba progresses, like an object on 
the surface of a rolling cylinder. The anterior edge of the 
Ameceba 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. 
Ameba limazx has a similar method of locomotion but has 
few pseudopods. Dellinger who has studied the locomotion 
of Ameba proteus 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 Ameceba 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 
Ameceba 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 isno rolling; particles on the 
