22 LIVING AND LIFELESS MATTER 



plasm around the walls, but streams of flowing protoplasm 

 reach into and pass through the central cavity so that a more or 

 less perfect circulation occurs (Fig. 9 B). 



Amoeboid Movement. In flowing movement the fluid proto- 

 plasm moves more or less briskly according to the temperature, 

 but it is usually kept within bounds by the firm lifeless cell walls. 

 A free living organism without such walls might be expected to 

 move in any direction and without restraint. Such a form is 

 Amoeba proteus, a small animal found in stagnant pools and 

 consisting of one cell only. Here the protoplasmic granules are 

 almost always in motion, and, having no firm covering, the 



FIG. 10. Different forms assumed by Amoeba proteus. Photographs from 



preparations. 



periphery gives way and a line of flow is started in the direction 

 of the outbreak. This flow continues until the forces which 

 caused the rupture are expended, or until some point offering 

 less resistance gives way and a new line of flow is started. In 

 this way the bulk of the minute organism moves about in the 

 water, its form constantly changing the while (Fig. 10). 



This amoeboid motion is not uncommon in certain cells of 

 higher animals, especially in the white blood cells or leucocytes. 



Ciliary Movement. In both flowing and amoeboid movement 

 the source of energy probably lies in the chemical processes 



