14 



HANDBOOK OF INVERTEBRATE ZOOLOGY. 



h. The stem is thrown into a spiral, thus dragging the 

 body back towards the point of attachment. 



c. Watch the changes by which the colony gradually 

 expands after the disturbance ceases. 



1. The stems straighten. 



2. The rims of the bells are slowly everted. 



3. The cilia suddenly resume their active motion. 



d. Notice the marked contrast between the rapid con- 

 traction and the gradual expansion. 



V. Make a sketch of the community, showing as many 

 of these points as possible. 



VI. Study a portion of the community with a magnify- 

 ing power of 200 to 500 diameters, and notice : — 



a. The l^ody of a single animal : circular when seen 

 from above or below, and bell-shaped in side view, and 

 attached to a stem by its lower or narrow end. 



1. The upper edge of the bell is bent out to form a 



thickened margmal rim, 

 \he jieristome, Fig. 4, c. 



2. Notice the crown of 

 large cilia carried by the 

 peristome. 



a. 



Fro. 4. 



Fig. 4. — A single adult, fully 

 expanded individual of Vorti- 

 cella nebulifera (Ehrb.) magni- 

 fied about six hundred diameters. 

 {Slightly altered from Everts. 

 Untersuchungen an Vorticella 

 Nebulifera, von Dr. pJnl. Eduard 



Everts; Zeitf. Wlss. Zool. xxiii. 592: 1873. Taf. 



XXX. fig. 1). 



a. Cilia of ciliated disc. b. Ciliated disc. 



c. Peristome. d. Vestibule. e. (Esophagus. 



/. Contractile vesicle, g. Food vacuoles. /(. En- 



doplast. i. Endosarc. k. Ectosarc. I. Cuticle. 



m. Axis of stem. 



