OXYTRICHA. 13 



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 Crepidula. (See Calkins, p. 208.) 



OXYTRICHA. 



Infusoria belonging to the genus Oxytricha, or the genera 

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

 following study. These forms belong to the order Hypotrichida. 

 Hypotrichous forms are the most highly organized of the class 

 Infusoria, as well as of the entire phylum of Protozoa, and pre- 

 sent a complexity of structure and function which is not found 

 probably within the limits of a single cell elsewhere 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 

 dilation with that of other forms. Refer to Calkins, Fig. 98, 

 and understand the relation of cirri, membranelles, etc., to cilia. 



Draw, showing the structure in detail. 



2. Run some methyl-green under the cover-glass. What 

 is the shape of the macronucleus? The shape varies considera- 

 bly in the different genera. Is it possible to distinguish the 

 micronucleus? 



3. Prepare a fresh slide and observe in detail the character- 

 istic movements and manner of creeping over various objects. 

 As the animal turns sidewise, note the marked dorso-ventral 

 compression of the body. 



Represent this diagrammatically beside the previous drawing. 

 It is desirable to examine permanently stained preparations 

 for division stages, finer details of the nuclei, etc. 



