142 ANIMAL BIOLOGY 



ciliated body which has the general shape of a cigar with 

 a broad oblique groove on one side. At the end of the 

 oblique groove is a short gullet down which the food of 

 Paramcecium is swept by the action of cilia. At the end 

 of the gullet is a small enlargement, the crop, where the 

 food accumulates forming a sort of ball. When the crop 

 is filled with food it is pinched off by the contraction of 

 the surrounding substance, and the mass of food with a 

 small amount of water passes into the semi-fluid interior 

 of the body. The small vesicles with their contained food 

 are called food vacuoles. By a circular movement of 

 the inner substance, or endoplasm, the food is slowly 

 carried about the body, in the meantime undergoing a 



FIG. 116. Paramcecium. oil, cilia; cv, contractile vacuoles ; /, food vacu- 

 oles; g, gullet with crop at end; n, macronucleus; n f , micronucleus. 



process of digestion. The undigested residue is discharged 

 at the surface of the body at a spot a little behind the 

 mouth. Surplus water and products of excretion are 

 got rid of through the hollow vesicles called contractile 

 vacuoles, located near either end of the body. These 

 may be seen to slowly swell from the accumulation of 

 fluid and then suddenly contract, expelling the fluid to the 

 outside of the body. Paramcecia eliminate through these 

 organs several times their own bulk of water every 

 day. 



Paramcecium, like most other Infusoria, contains two 

 kinds of nuclei, a large one, the meganucleus, and a small 

 one, the micronucleus which usually lies close against the 



