16 PROTOZOA. 



manner in which the peristome folds over simultaneously with 

 the contraction of the stalk. What purpose does the contrac- 

 tion of the stalk serve? 



Vorticella is distinguished from its allied genera by its sim- 

 ple unbranched stalk and also by the spiral form assumed by the 

 contracted stalk. In which order of the Ciliata does the cilia- 

 tion of Vorticella place it? Compare with Zoothamnium. 



Make a drawing of an expanded individual and a sketch to 

 show the condition when contracted. (Minchin, p. 434; Doflein, 

 p. 1144.) 



9. Study, by means of finely powdered carmine, the vortex 

 currents set up by the cilia. Note how the particles are collected 

 in the gullet, and at intervals are forced in rounded masses into 

 the endoplasm to form gastric vacuoles. Is there a definite 

 circulation in the endoplasm? 



10. Endeavor to find several stages of reproduction by divi- 

 sion. 



Large fresh-water species of Vorticella are preferable for 

 study, but marine species may be substituted when necessary. 

 If time and material permit, study Lichnophora, a marine peri- 

 trichous form parasitic on Crepidida. (See Calkins' Protozoa, 

 p. 203.) 



Schroder: Beitrage zur Kenntnis von V. monilata. Arch. f. Protistenk., 7, 

 1906. 



OXYTRICHA. 



Infusoria belonging to the genus Oxytricha, or the genera 

 Stylonychia, Pleurotricha, Euplotes, etc., may be used for the fol- 

 lowing study. These forms belong to the order Hypotrichida. 

 Hypotrichous forms are among the most highly organized of 

 the class Infusoria, as well as of the entire phylum of Protozoa, 

 and present a complexity of structure and function which 

 probably if not exceeded within the limits of a single cell else- 

 where in the animal series. 



1. In an animal which is becoming quiet, note the mode of 

 locomotion, the shape of the body, the buccal groove, the con- 

 tractile vacuole, etc., as in other forms studied. Compare the 



