THE PROTOZOA 



193 



of the simplest form of life known, either plant or animal. Unlike 

 the plant and animal cells we have examined, the amoeba has no 

 fixed form. Viewed under the compound microscope, it has the 

 appearance of an irregular mass of granular protoplasm. Its form 

 is constantly changing as it moves about. This is due to the push- 

 ing out of tiny projections of the protoplasm of the cell, called 

 pseudopodia (false feet). The 

 outer layer of protoplasm is 

 not so granular as the inner 

 part; this outer layer is 

 called ectoplasm, the inside 



Amoeba, with pseudopodia (P.) ex- 

 tended ; EC., ectoplasm; END, 

 endoplasm ; the dark area (N.) 

 is the nucleus. From photo- 

 graph loaned by Professor G. N. 

 Calkins. 



Amoeba, showing the changes which take 

 place during division. The dark body 

 in each Figure is the nucleus ; the trans- 

 parent circle, the contractile vacuole ; 

 the outer, clear portion of the body the 

 ectoplasm ; the granular portion, the 

 endoplasm ; the granular masses, food 

 vacuoles. Much magnified. 



being called endoplasm. In the central part of the cell is the 

 nucleus. This important organ is difficult to see, except in cells 

 that have been stained. 



The locomotion is accomplished, according to Professor Jennings 

 of Johns Hopkins University, by a kind of rolling motion, " the 

 upper and lower surfaces constantly interchanging positions." 

 The pseudopodia are pushed forward in the direction which the 

 animal is to go, the rest of the body following. 



duckweed or other small water plants, or from green al^se growing in quiet localities. 

 No sure method of obtaining them can be given. 

 HUNT. ES. BIO. 13 



