30 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



all kinds of particles into the gullet which opens into the inte- 

 rior. Food particles surrounded by a film of water are taken 

 into the body through this opening and are digested just as 

 they are in the body of the Amoebae. The water drops are 

 ejected at a spot in the cell membrane just below the gullet. 

 If a little finely powdered carmine is added to the water 

 in which the Paramcecia are swim- 

 ming some of the grains will be taken 

 into the body where they will be seen 

 to follow a rather definite course from 

 one end of it to the other. Instead of 

 one contractile vacuole as in the 

 Amcebae there are two, and there are 

 also two nuclei, which can be seen in 

 specimens stained with carmine. The 

 large one, ovoid in shape, is called the 

 macronucleus, and the smaller oval 

 one close beside it is the micronucleus. 

 Between the bases of the cilia there 

 may be seen many minute oval sacs 

 lying side by side. These are called 

 the trichocysts, and from each a fine 

 stinging thread can be thrust out 

 which, it is believed, help to protect 

 the Paramcecium from other minute 

 animals. 



The Paramcecia reproduce by sim- 

 ple division as do the Amcebae. The 

 macro- and micro-nuclei divide and 

 the body becomes constricted in the 

 middle and the organism is finally 

 divided into two smaller animals which 

 soon grow to be like the original. 

 But after multiplication has gone on in this way for many 

 generations, often from one to two hundred or more, the Para- 

 mcecia seem to be unable to divide further until a new pro- 

 cess takes place. Two Paramcecia approach each other and 

 unite, usually with their buccal grooves together; then there 



FIG. 9. Paramcecium 

 sp. Buccal groove at 

 right. (Greatly magni- 

 fied; from life.) 



