THE PHENOMENA OF LIFE 



of protoplasm containing one or more nuclei, the protoplasm itself being 

 more or less granular and vacuolated. If watched for a minute or two, an 

 irregular projection is seen to be gradually thrust out from the main body; 

 other masses are then protruded until gradually the whole protoplasmic sub- 



l. 



2. 



FIG. 4. Changes of Form of a White Corpuscle, Sketched at Brief Intervals. The figures 

 show also the ingestion of two small granules. (Schafer.) 



stance is, as it were, drawn over to a new position, and when this is repeated 

 several times we have locomotion in a definite direction, together with a con- 

 tinual change of form. These movements, figures 3 and 4, are observed in 

 such cells as the colorless blood corpuscles of higher animals, in the branched 

 corneal cells of the frog and elsewhere, and are termed ameboid. 



FIG. 5. Cell of Tradescantia Drawn at Successive Intervals of Two Minutes. The 

 cell contents consist of a central mass connected by many irregular processes to a peripheral 

 film, the whole forming a vacuolated mass of protoplasm, which is continually changing 

 its shape. (Schofield.) 



The remarkable movement of pigment granules observed in the branched 

 pigment cells of the frog's skin by Lister are also probably due to ameboid 

 movement. These granules are seen at one time distributed uniformly 

 through the body and branched processes of the cell, while at another time 

 they collect in the central mass leaving the branches quite colorless. 



This movement within the pigment cells might also be considered an ex- 

 ample of the so-called streaming movement not infrequently seen in certain 

 of the protozoa, in which the mass of protoplasm extends long and fine proc- 



