Unicellular, Microscopic Animals 353 



the food vacuoles because of the contained digestive enzymes secreted 

 by the cytoplasm. Foods are absorbed and assimilated into living proto- 

 plasm. 



Circulation. — There is no special circulatory equipment, but the foods, 

 wastes, etc., are circulated by the natural streaming of the cytoplasm 

 and is known as cyclosis. 



Fig. 167. — Neuromotor mechanism (in part), trichocysts, and cilia of Parame- 

 cium sp. A, Section showing trichocysts attached to the ridges of the hexagonal 

 depressions of the pellicle ; B, surface and side view, showing the coordinating 

 fibers which connect the basal granules which control the actions of the cilia. 1, 

 Cilium; 2, basal granule of cilium; 3, interciliary fibril to connect basal granules; 

 4, trichocyst pore; 5, trichocyst; 6, discharged trichocyst; 7, hexagonal area of 

 pellicle. (From various sources, from data discovered by Lund.) 



Fig. 168. — Galvanotropism (reaction to electricity) shown by Paramecia. A, 

 General appearance of the apparatus and Paramecia reacting to electric current. 

 The current is passed through a cell with porous walls by means of unpolarizable 

 brush electrodes. Paramecia have moved toward the negative pole or cathode. 

 B, Magnified view showing movement toward the cathode. (From Jennings: 

 Behavior of the Lower Organisms, published by Columbia University Press.) 



