8o GENERAL BIOLOGY 



a) The complete differentiation of the body into bell- 

 shaped "head" and contractile stalk. What is the 

 distribution of ectosarc and endosarc in each ? 



b) The great development of the peristome, and the 

 restriction of the cilia thereto. Note the size of the 

 cilia, and the contractility of the ridges that bear 

 them. 



c) The band of contractile substance, a highly de- 

 veloped myoneme, extending in an open spiral down 

 the stalk. Observe its position in extended and in 

 contracted specimens. 



4. In the body of the cell, observe the usual internal 

 structures : 



a) A curved, often horse-shoe-shaped meganucleus 

 near the middle of the body, and a micronucleus 

 lying close beside it. If the latter be not visible in 

 the living specimen it may be demonstrated later 

 with iodine, as in Paramoecium. 



b) A clear contractile vacuole, near the nucleus, appear- 

 ing and disappearing. 



c) Food-balls, moved about within the endosarc. 

 The taking of food and the formation of these 

 balls at the end of the rudimentary esophagus, 

 may be demonstrated by feeding with carmine, 

 as in Paramoecium. 



5. By surveying a large cluster of vorticellas, a number 

 are likely to be seen in process of division. In such observe 

 the plane of division, and its relation to nucleus, peristome 

 and stalk. 



The record of the study of Vorticella may well consist in : 



1. A drawing in outline of a little group in various 

 positions. 



2. The details of structure of a single cell much 

 enlarged. 



