14 PROTOZOANS. 



that, while pseudopodia are pushed out in all directions, 

 they grow principally in one direction, and that the direc- 

 tion in which the amoeba is traveling. Observe that about 

 as fast as pseudopodia are formed in one direction, the body 

 follows them, all its granular content flowing into their 

 bases, swelling them, and uniting them. 



Watch also the withdrawal of pseudopodia, first a flow- 

 ing toward the center of the granular part, leaving an 

 emptied projection of ectosarc, which follows on in the rear. 



Such is amoeba's primitive method of locomotion. The 

 pseudopodia which are pushed out on one side hold their 

 ground ; and, when the semifluid body begins to follow, 

 they advance, and the whole mass is seen setting forward 

 in an exceedingly slow, flowing or gliding motion. 



If an active amoeba be watched a short time, it may be 

 seen to change its direction. To do this it does not need 

 to turn around: it simply puts out pseudopodia in the 

 new direction, and follows them. It has neither head nor 

 tail. All parts are alike, and one is as well adapted as 

 another to go first. It may be seen to avoid large objects 

 with which it comes in contact in its course. If it meet a 

 conveniently small object, it may sometimes be seen to 

 encircle it with pseudopodia, and ingulf it into its soft 

 body mass, swallow it, so to speak, after which the 

 object may be seen within the granular endosarc, where it 

 is lodged as food for digestion. If it prove indigestible, 

 it is gotten rid of in a correspondingly simple way. The 

 body mass flows away from it, and it is left behind. 



If the amoeba be irritated in any way, as by touching 

 the cover glass, it immediately draws in its pseudopodia, 

 and assumes a more or less spherical form. If not injured 

 in any way, it soon resumes activity. 



Make a series of half a dozen outlines of an amoeba, 

 drawn at intervals of a minute or two, or less if it be 

 moving actively, to show the changes in form. 



