18 PROTOZOANS. 



another. But the movements of amoeba, simple as they 

 are, are yet more than the independent automatic contrac- 

 tions of protoplasm ; for they are controlled and coordi- 

 nated to certain ends, to reaction in response to stimuli 

 from without, to locomotion and to securing food in 

 response to impulses from within. 



IV. Sensation. These latter acts indicate spontaneous 

 activity, and show that the amoeba possesses in a low 

 degree sensibility, the dawning of faculties which are the 

 highest endowment of animal life. 



The Cell. The cell in biology is a minute mass of pro- 

 toplasm containing a nucleus with or without a cell wall. 

 The amoeba is a single cell that has developed about itself 

 a very delicate and pliant cell wall. 



The cell is the unit of all organic structure. Every 

 plant and every animal begins its existence as a single 

 cell. This cell grows and divides repeatedly; and the 

 cells thus formed remain together, and with their products 

 compose the bodies of the higher plants and animals. The 

 cellular character of the growing parts of all animals may 

 be easily recognized under the microscope. 



When the amoeba divides, its parts separate. It there- 

 fore retains this simple condition, never becoming more 

 than a single cell. 



THE SLIPPER ANIMALCULE. 



(Paramecium.) 



Study of Live Specimens. Examine a drop of water 

 containing slipper animalcules. They appear as minute 

 white specks rapidly moving to and fro through the water, 

 just large enough to be seen without a lens. 



Examine under the microscope a drop that has been 

 mounted on a slide in cotton fibers, or, better, in cherry- 



