38 PBOTOZOA CH. 



some Indian ink under the cover-glass we shall have a demonstra- 

 tion of how this is managed. The black particles are caught in 

 the whirlpool made by the cilia, they course round and round and 

 finally accumulate in a pit which opens into the ciliated groove 

 and from the bottom of this they pass one by one into the internal 

 protoplasm of the body. This pit which obviously passes through 

 both the cuticle and the cortical layer is the pharynx and its 

 opening the mouth. The particles of Indian ink which have passed 

 into the body are surrounded by little drops of fluid which are 

 partly swallowed with it and partly secreted by the protoplasm, in 

 order to effect the solution of the particle, that is, its digestion. 

 Such a drop is called a food-vacuole in order to distinguish it from 

 the contractile vacuole, which, as we have seen (page 17), has 

 probably an excretory office to perform. As there is nothing nutri- 

 tious in Indian ink, the Vorticella soon gets tired of trying to digest 

 it, and the particles after having travelled through the body in a 

 more or less definite tract, are thrust out into the ciliated groove. 

 Since this takes place at only one spot, there must be a permanent 

 hole in the cuticle here though we cannot discern it, and this opening 

 may be called the anus. Therefore in contradistinction to Amoeba, 

 where food can be taken in and undigested remnants cast out at 

 any spot on the surface, in Vorticella it is only at one particular 

 spot that either action can take place. 



The reproduction of Vorticella is a most interesting process. It 

 takes place by longitudinal splitting, or, as it is technically called, 

 fission. The disc splits into two, and the cleft soon reaches right 

 down to the beginning of the stalk, so that for a time we have two 

 bodies attached to the same stalk. One of these acquires a new row 

 of cilia round its base ; soon after the original circle of cilia and 

 the peristomial groove disappear; the animal then breaks loose 

 from the stalk and swimming by means of its new circle of cilia 

 seeks a new place of rest. The other body remains on the original 

 stalk and resumes its ordinary life. 



Like Amoeba, Vorticella encysts and it appears still more 

 frequently than Amoeba in infusions. The Vorticellae which are 

 found under these circumstances are usually small and transparent 

 and more favourable for observation than those occurring in ditches. 

 The genus occurs both in fresh and salt water. 



The class Ciliata is a large one and we may now describe 

 another member of it which is frequently found in infusions of 

 decaying animal and vegetable matter. This animal is termed 



