Introduction 



XIX 



cover glass the movements of the paramecia may be 

 restricted so that they are more easily studied. 



THE VORTICELLA 



Vorticellae occur in nature in ponds and sluggish streams, 

 but are difficult to find in such situations in sufficient 

 quantity for class use. 

 They may be cultivated 

 in aquaria without diffi- 

 culty. They are likely 

 to develop in shallow 

 dishes containing 

 aquatic plants of any 

 kind, especially if the 

 dish be placed in a dark 

 situation. In the aqua- 

 rium in which such a 

 great quantity of para- 

 mecia were developed, 

 as described above, large 

 numbers of vorticellae 

 were also produced. 

 Several cultures of vor- 

 ticellae are desirable in 

 order to get the divid- 

 ing, the free-swimming, 

 and the encysted stages. 

 I have repeatedly ob- 

 tained cultures showing 

 each of these forms, the 

 seeing of which adds much to the value of the study by 

 the class. 



The VORTICELLA: A, stalked form; 5, free- 

 swimming form; C, encysted form. Mag- 

 nified. 



