10 



ANIMAL LIFE 



which are fine processes of the dense protoplasm of the 

 surface. There is on one side an oblique shallow groove 

 that leads to a small, funnel-shaped depression in the body 

 which serves as a primitive sort of mouth 

 or opening for the ingress of food. 

 The Paramcecium swims about in the 

 water by vibrating the cilia which cov- 

 er the body, and brings food to the 

 mouth opening by producing tiny cur- 

 rents in the water by means of the 

 cilia in the oblique groove. The food, 

 which consists of other living Proto- 

 zoa, is taken into the body mass only 

 through the funnel-shaped opening, and 

 that part of it which is undigested is 

 thrust out always through a particular 

 part of the body surface. (The taking 

 in and ejecting of foreign particles can 

 be seen by putting a little powdered 

 carmine in the water.) Within the 

 body there are two nuclei and two so- 

 called pulsating vacuoles. These pul- 

 sating vacuoles (Amceba has one) seem 

 to aid in discharging waste products 

 from the body. When the Paramce- 

 cium touches some foreign substance or 

 is otherwise irritated it swims away, 

 and it shoots out from the surface of its body some fine 

 long threads which when at rest are probably coiled up in 

 little sacs on the surface of the body. When the Parar 

 mcecium has taken in enough food and grown so that it 

 has reached the limit of its size, it divides transversely into 

 halves as the Amoeba does. Both nuclei divide first, and 

 then the cytoplasm constricts and divides (Fig. 6). Thus 

 two new Paramwcia are formed. One of them has to de- 

 velop a new mouth opening and groove, so that there is in 



FIG. 5. Paramcecium au- 

 relia (after VEBWORN). 

 At each end there is a 

 contractile vacuole, and 

 in the center is one of 

 the nuclei. 



