60 PEACTICAL ZOOLOGY. 



In swimming, is the same end always foremost? 

 Read " The Structure of Paramcecium " in Brooks' 

 " Handbook of Invertebrate Zoology." 



THE BELL-ANIMALCULE (VORTICELLA). 



Collect leaves and grasses that have fallen into water, 

 and the stems and leaves of water plants from ponds and 

 ditches ; place some of these leaves in a plate of water, 

 and examine them closely; with the naked eye there 

 may sometimes be seen on them little patches resembling 

 mould ; when observed more closely these appear to be in 

 the form of minute tufts , if these tufts shrink back when 

 touched, take a lens and examine carefully ; cut out a part 

 of a leaf bearing these clusters, put on a slide with a drop 

 of water, cover with a cover-glass, and examine with a 

 one-inch objective. 



Sometimes these tufts, which are colonies of Vorticellae, 

 may be attached to the sides of an aquarium, or jar, in 

 which clams have been kept. 



Some kinds of Vorticellse are not in colonies, but are 

 borne singly on independent stalks. 



When one is found, note, using a one-inch objective: — 



1. The bell-shaped body. 



2. The contractile stalk ; suddenly jar the table, or 

 stage of the microscope, by tapping with a hard 

 object ; what follows ? 



Put on a high power objective and make out the follow- 

 ing parts of the body : — 



