THE LIFE OF THE SIMPLEST ANIMALS 



to press against it, and soon the plant or animal or organic 

 particle becomes sunken in the protoplasm of the formless 

 body and entirely inclosed in it (Fig. 3). The absorbed 

 particle soon wholly or partly disappears. This is the 

 manner in which the Amoeba eats. It has no mouth or 



FIG. 3. Amoeba eating a microscopic one-celled plant. After VEKWOBN. 



stomach. Any part of its body mass can take in and digest 

 food. The viscous, membraneless body simply flows about 

 the food and absorbs it. Such of the food particles as can 

 not be digested are thrust out of the body. 



The Amoeba breathes. Though we can not readily ob- 

 serve this act of respiration, it is true that the Amoeba takes 

 into its body through any part of its surface oxygen from 

 the air which is mixed with water, and it gives off from any 

 part of its body carbonic-acid gas. Although the Amoeba 

 has no lungs or gills or other special organs of respiration, 

 it breathes in oxygen and gives out carbonic-acid gas, which 

 is just what the horse does with its elaborately developed 

 organs of respiration. 



If the Amceba, in moving slowly about, comes into con- 

 tact with a sand grain or other foreign particle not suitable 

 for food, the soft body slowly recoils and flows for the 

 movement is really a flowing of the thickly fluid protoplasm 

 so as to leave the sand grain at one side. The Amoeba 

 feels. It shows the effects of stimulation. Its movements 

 can be changed, stopped, or induced by mechanical or 

 chemical stimuli or by changes in temperature. The 



