50 MANUAL OF ANIMAL BIOLOGY 



This band encircles the body near where the stalk is normally 

 attached, and the stalkless animal is able to swim freely through 

 the water. This is a temporary condition, however, and when a 

 suitable environment is found a new stalk is developed, and the 

 locomotor cilia are lost. 



B. Life Processes of Vorticella 

 1. Nutrition 



The nutrition of Vorticella is holozoic and essentially the same 

 as that of Paramecium. The food particles, consisting largely of 

 Bacteria which are swept into the vestibule and through the 

 mouth, are collected at the base of the gullet in a gastric vacuole. 

 As in Paramecium, there is a definite cyclosis of the endoplasm, 

 as the result of which the gastric vacuoles are carried along in a 

 regular path through the endoplasm. The indigestible refuse is 

 egested through a definite anal spot which opens into the vestibule. 

 Carmine particles can be used with Vorticella just as with Parame- 

 cium to show various features of the process. 



2. Respiration and Excretion 



The intake of oxygen and the excretion of liquid and gaseous 

 wastes, resulting from the katabolic processes in the organism, are 

 also similar to Paramecium. There is a single large contractile 

 vacuole which expels the body wastes to the exterior through 

 an opening into the vestibule. Respiration also occurs over the 

 entire surface of the cell body. 



3. Reproduction 



In Vorticella, asexual reproduction by binary fission takes place 

 very frequently if conditions are favorable. Three or four divi- 

 sions a day are not uncommon, so that, from a single animal, six- 

 teen or even more typical individuals may be formed within 

 twenty-four hours. In dividing, the micronucleus is the fust to 

 act, then the macronucleus, and, finally, the cell body. The split- 

 ting of the cell body begins in the region of the peristome and pro- 

 ceeds toward the apex of the bell where the stalk is attached. For 

 a short time after the body has completely divided, two small but 

 complete individuals may be attached to a single stalk. Shortly 

 afterwards, however, one animal develops a temporary band of 



