22 



PROTOZOA 



believed them to be the simplest form of animal. Von Siebold and 

 Kolliker (1849) proved that Protozoa are single cells and complete 

 organisms as well. Max Schultze (1865) gave the present idea. 



Natural History 



Class I. Sarcodina. Type of Group — Ameha proteus. Ex- 

 terna/ Anatomy. — Amebae resemble minute grayish animated par- 

 ticles of jelly. Some species of amebae, large enough to be seen 



Pseudopodium 



Cry:sfal 



4^ ii^fe^"'^^^'^ 



' •S:'a 



vacuole V . -fiT^ - ^^■■&-'-^^^^^=^- — -^^r—Food particle 





Fig. iA. Ameba proteus-dubia SchaefFer. (Drawn by H. N. Lammers, after E. F. 

 Botsford, Jour. Exp. Zool., vols. 45-46, 1927.) 



with the naked eye, have been selected and cultivated for laboratory 

 use. The diameter of the smaller ones is as little as five microns. 

 They constantly change their shape, sending out little projections 

 called pseudopodia, or "false feet" (Fig. 2, A and B). 



The outer covering of the ameba is called the ectosarc (ectoplasm) 

 and is lacking in color. The inner portion of the animal called the 

 endosarc (endoplasm) contains the nucleus, the synthetic and 

 hereditary center of life, and vacuoles of different types. The 



