14 



ZOOLOGY 



bers on the surface of the sea, and is large enough to be 

 seen with the naked eye. 



The true Infusoria are covered with cilia, or hair-like 

 processes, by which they glide about over submerged leaves, 

 etc. One of the largest and commonest Infusorians is Pa- 

 ramecium. 



Fig. 10 represents Paramecium caudatum. This animal- 

 cule is a mass of protoplasm, representing a single cell. 

 In the body-mass are excavated a mouth and a throat lead- 

 ing to a so-called stomach or digestive cavity. Two hollows 

 in the body form the contractile vesicles, and another cavity 

 constitutes the nucleus (n). 



The trumpet-animalcule (Stentor) is largo enough to be 



Fig. 11.— Process of fission in Stentor polymorphus. h, a new Stentor budding 

 out; e, ready to separate from the original one;/, the two in a contracted 

 state. 



detected with the unaided eye. This Infusorian attaches 

 itself at one end by a stalk, and builds up a slight tube, into 

 which it contracts when disturbed. The Stentor may be 

 sometimes observed multiplying by self-division. 



In Stentor golymorphus the process of self-di vision takes 

 place in two hours. Fig. 11, /, represents the final stage 

 when the two individuals swim away separately, each as- 

 suming the original adult form, a. 



The bell-animalcules, Vorticella and Epistylis (Fig. 12), 

 form patches like white mould on aquatic plants. Their 

 motions as they suddenly contract and shoot out their bells 

 is exceedingly interesting. 



Many Infusorians, besides self-di viding, produce ciliated 



