VORTICELLA, OXYTRICHA 



29 



simultaneously with the contraction of the stalk. What pur- 

 pose does the contraction of the stalk serve? 



Vorticella is distinguished from its allied genera by its 

 simple unbranched stalk and also by the spiral form as- 

 sumed by the contracted stalk. In which order of the Ciliata 

 does the ciliation 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.) 



9. Study, by means of finely powdered carmine, the vor- 

 tex 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 food vacuoles. Is there 

 a definite circulation in the endoplasm? 



10. Endeavor to find several stages of reproduction by 

 division. 



Large fresh-water species of Vorticella are preferable for 

 study, but marine species may be substituted when neces- 

 sary. If time and material permit, study Lichnophora, a 

 marine peritrichous form parasitic on Crepidula. (See Cal- 

 kins' 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 following study. These forms belong to the order Hypo- 

 trichida. 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 is not exceeded 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 

 contractile vacuole, etc., as in other forms studied. Compare 



