SECT, i PHYLUM PROTOZOA 15 



Amoeba is not one of these. It is to be recognised as a 

 glassy-looking, irregularly shaped particle with a definite out- 

 line. From a particle of some crystalline mineral substance, 

 to which such a description would equally well apply, 

 Amoeba would soon be distinguishable owing to the cir- 

 cumstance that it is constantly changing its shape. 



This change is effected by the pushing out of projections 

 or processes, called pseudopods or pseudopodia (psd), which 



FIG. i. Amoeba proteus , a living specimen, c. vac, contractile vacuole, 

 nu, nucleus; psd, pseudopods. (From Parker's Biology, after Gruber.) 



undergo various alterations of size and shape, and may be- 

 come withdrawn, other similar processes being developed 

 in their place. At the same time careful watching shows 

 that the Amoeba is also, with extreme slowness, changing its 

 position. This it effects by a kind of streaming motion. A 

 projection forms itself on one side, and the entire substance 

 of the Amoeba gradually streams into it ; a fresh projec- 

 tion appears towards the same side, the streaming move- 

 ment is repeated, and, by a constant succession of such 

 movements, an extremely gradual locomotion, which it often 

 takes very close watching to detect, is brought about. In 

 these movements, it is to be noticed, the Amoeba is influenced 



