114 f-IRST LESSONS IN ZOOLOGY 



life whicli we are accustomed to see in the more familiar 

 world of larger animals. 



Amoeba. — The simplest and one of the smallest of all 

 known animals is Amceba. If in a drop of stagnant 

 water taken from the slime on a dead leaf or stick from 

 the bottom of the pool you discover a microscopic, nearly 

 transparent, granular, jelly-like speck which slowly but 

 constantly changes its form then you have an Ama-ba. 

 Its whole body is nothing but a tiny, formless, viscous 

 speck of protoplasm. It is an animal without legs or 

 feelers, skeleton or muscles, without mouth or stomach, 

 eyes or brain ; without heart or lungs, nerves or blood, 

 and yet is as trul\' an animal as a horse, and as capable 

 as the horse of performing, although in the simplest pos- 

 sible \\ay, all the processes necessar}' to life, such as 

 taking in and digesting food, taking up o.xygen and giv'- 

 ing off carbon dio.xidc, feeling and moving about. Its 

 whole body is composed of a single one of the units 

 called cells, thousands and millions of which are included 

 in the body of an}' one of the larger and more familiar 

 animals. 



Having found an Amreba note its irregular shape and 

 observe its mode of moving (fig. 79). How does it 

 move .■' The little processes which stick out in various 

 directions are called false feet or pseudopodia. They are 

 simply parts of the body protoj)Iasm. Has Amceba a 

 definite body-wall.' Do the false feet protrude from cer- 

 tain parts of the body only.'' Inside note a clear globular 

 spot which contracts and expands or pulsates more or 

 less regularly. This is tlie contractile vacuole. Note the 

 small granules which move about in the body. These 

 are food particles which have been taken in through the 

 body-wall. Note how the false feet flow about food parti- 

 cles (tiny one-celled i)lants or other bits of organic mat- 

 ter) in the water. When these are surrounded by the 



