CH. II.] 



PROTOPLASMIC MOVEMENT. 



from the main body and retracted ; a second mass is then pro- 

 truded in another direction, and gradually the whole protoplasmic 

 substance is, as it were, drawn into it. The Amoeba thus comes 

 to occupy a new position, and when this is repeated several times 

 we have locomotion in a definite direction, together with a 

 continual change of form. These movements, when observed in 

 other cells, such as the colour- 

 less blood-corpuscles of higher 

 animals (fig. 13), in the branched 

 corneal cells of the frog and else- 

 where, are hence termed amoe- 

 fjoid. The projections which are 

 alternately protruded and re- 

 tracted are called pseudopodia. p . 12 _ Amoe 



A streaming movement is not 

 infrequently seen in certain of the protozoa, in which the mass 

 of protoplasm extends long and fine processes, themselves very 



Fig. 13. Human colourless blood-corpuscle, showing its successive changes of outline 

 within ten minutes when kept moist on a warm stage. (Schofleld.) 



little moveable, but upon the surface of which freely-moving or 

 streaming granules are seen. A gliding movement has also been 



\r 



Fig. 14. (A.) Young vegetable cells, showing cell-cavity entirely filled with granular 



protoplasm enclosing a large oval nucleus, with one or more nucieoli. 

 (B.) Older cells from same plant, showing distinct cellulose- wall and vacuola- 

 tion of protoplasm. 



noticed in certain animal cells ; the motile part of the cell is 

 composed of protoplasm bounding a central and more compact 

 mass ; by means of the free movement of this layer, the cell 

 may be observed to move along. 



In vegetable cells the protoplasmic movement can be well seen 



