320 Our Surroundings 



electricity. This shows that it possesses some degree of sensa- 

 tion. 



Motion. That it has the power of motion is readily seen when 

 the animal is looked at under the microscope. Motion is effected 

 by the cilia, which are hair-like projections of protoplasm, ex- 

 ceedingly numerous on all parts of its outer surface. Using these 

 cilia like tiny oars, it changes its position with great rapidity. 



Respiration. Oxygen is taken in through the very delicate 

 thin covering of the organism and carbon dioxide, resulting from 

 oxidation of the protoplasm and the food, is thrown off by the 

 same process. 



Food-taking. Bacteria and other minute forms of plant and 

 animal life constitute the food of a paramecium. On one side of 

 the animal there is a funnel-shaped opening, called the gullet. 

 Its walls are lined with cilia, by the movement of which the food 

 is taken into the body. There the food is gathered into little 

 balls which appear to be enclosed in a rounded area known as a 

 vacuole. 



Digestion. The food is made soluble by digestive juices, or 

 enzymes, supposed to be similar to those which serve the same 

 purpose in other animals. 



Absorption and Circulation. The digested food is absorbed 

 as it is circulated within the cell by a movement called streaming 

 of the protoplasm. 



Assimilation. As in other animals, there is a constant using 

 up of protoplasm, which must be renewed. This is effected by 

 assimilating the nourishing part of the digested food. Since the 

 animal is constantly reproducing by division, the necessity of 

 assimilation of material to produce new protoplasm, not only to 

 sustain its own life but also the life of its offspring, is apparent. 



Excretion. Excretion of wastes is effected by means of con- 

 tracting vacuoles in which the wastes collect. These vacuoles 

 appear to burst and thus eliminate the wastes from the cell body. 



Reproduction. Reproduction is effected by cell-division, or 

 fission, and by cell-union. In the first method the animal sim- 

 ply divides into two parts, each part taking one-half of the 

 material essential to life. It has been observed that after a num- 



