136 



GENERAL ZOOLOGY 



grains or other worthless particles, but persistently follows 

 moving animals or plants which may serve for food. Such 

 behavior shows that the amoeba has a simple " chemical 

 sense/' or what corresponds to taste and smell in higher 

 animals. 



After food has been absorbed, it flows about in the endo- 

 plasm so that all parts are supplied with nourishment. 



FIG. 62. Protozoa. A-D, Class Sarcodinia; E-G, Class Mastigophora; 

 H-K, Class Infusoria. A, Amoeba; B, Arcella; C, Diffiugia; D, Actinosphoerium; 

 E, Mastigamoeba; F, Euglena, G, Volvox; H, Paramcecium; I, Vorticella; J, 

 Stentor; K, Stylonychia. 



The amceba is less than a thousandth of an inch in length 

 and therefore does not need special adaptations for respira- 

 tion. Waste gases are shed into the surrounding water and 

 oxygen is readily absorbed. Waste products resulting 

 from metabolism are dissolved in the water fluids within 

 the body and flow into a little reservoir, the contractile 



