VORTICELLA 153 



Study the structure of the body. It consists of a single cell, as 

 does Paramecium, and is composed of two protoplasmic layers : 

 the ectosarc, which is the firm external layer, and the entosarc, 

 the more fluid protoplasm of which the inner portion of the 

 animal is composed. Covering its outer surface is the cuticula, 

 which, with the ectosarc, gives the animal its permanent shape. 

 The stalk is a continuation of the ectosarc and of the cuticula. 

 Its inner portion alone, that is, the axis, is contractile; its 

 cuticula simply accommodates itself by assuming a spiral shape. 

 Note the longitudinal striations in the ectosarc at the base of 

 the bell. 



Observe the granular nature of the entosarc and the spherical 

 food vacuoles within it ; note the circulation of the latter in the 

 granular protoplasm. Each food vacuole is composed of particles 

 of organic matter in a minute globule of water, which collect in 

 the oral groove and are then driven into the mouth. Watch the 

 formation of them ; this is done easily by placing grains of indigo 

 or carmine in the water. 



Vorticella has a single pulsating vacuole, which is in the upper 

 part of the body. It is the organ of excretion of the animal and 

 consists of a globule of clear liquid which collects near the surface 

 of the body and is then discharged through the ectosarc into the 

 water. As in Paramecium, the water which is ingested as a part 

 of the food vacuoles is discharged through the pulsating vacuole 

 together with renal products. Time the formation of the pulsat- 

 ing vacuoles ; how many form a minute ? 



Observe the macronucleus ; it is a narrow, elongated structure 

 and is easily seen ; near it is the small, spherical micronucleus. 



Exercise 2, Make a large semidiagrammatic drawing of a Vorticella 

 showing these details, and label all. 



Vorticella has no special vegetative organs except the pulsating 

 vacuole. The food particles which are ingested into the entosarc 

 are there digested, and waste matters are egested through a tem- 

 porary anus in the upper portion of the body. Respiration is 

 carried on through the external surface of the body. Organs of 

 locomotion are present in the cilia, by which the animal can swim 



