16 



PROTOZOA 



[OH. 



necessitate the use of a microscope for their examination. When 

 magnified an Amoeba appears like a small, almost transparent lump 

 of jelly, in which we can distinguish a thin outer rind and inner 

 substance. The first, called the ectoplasm, is almost absolutely 

 transparent, the second, called the en do plasm, has usually a 

 grayish tinge, due to the presence of minute solid particles or 

 granules, and is therefore described as granular. Often indeed, 

 good sized objects of various shapes and generally of a green or 

 yellow colour, can be seen in the endoplasm ; these are the 

 undigested remains of the microscopic plants which the animal has 



FIG. 1. Amoeba proteus x 330. From Gruber. 



1. Nucleus. 2. Contractile vacuole. 3. Pseudopodia, the dotted line 



points to the clear ectoplasm. 4. Food vacuoles. 5. Grains of sand. 



eaten and are surrounded by bubbles of water, termed food- 

 vacuoles. Amoeba frequently engulfs particles of sand, though for 

 what purpose is unknown ; possibly in order to render itself less 

 palatable to animals which might eat it. If the Amoeba is healthy 

 we shall see it move. The transparent ectoplasm slowly sends out 

 a projection, and then the granular endoplasm flows into it. As of 

 course the size of the animal does not alter, when a process is 

 thrust out in front, the rest of the animal must follow it by 

 shrinking away behind. 



These projections are called by the awkward name of pseudo- 

 podia (Gr. i/feu&fs, false, Tro'Sioi/, a little foot); the adjective 



