Protozoa. 



295 



Examination with a higher power shows more of the 

 structure of the body. The bell-shaped body is not hol- 

 low, but is made up of protoplasm. Across the mouth of 

 the bell is a disk, which is slightly narrower than the 

 mouth of the bell. Between the disk and the rim of the 

 bell is a circular groove. At one point the groove dips 

 down into the body of the bell, forming a mouth and a 

 gullet. The borders of 'the disk and the bell are fringed 



Vestibule 

 Cilia 



Gullet 



Contractile vacuole 



Endoderm ' 

 Ectoderm 



Disk 



Groove 



Macronucleus 



Micronucleus 



Stalk ... 



Contractile axis 



FIG. 172. VORTICELLA, THE BELL ANIMALCULE. 



with cilia, which by their vibrations create water currents 

 and thus accumulate food material in the inner end of 

 the gullet. The food material consists largely of minute 

 plants and animals or fragments of larger forms. As in 

 the paramecium, the collection of food particles becomes 

 pushed farther into the body, becoming a food ball, or food 

 vacuole, which, with others preceding and following, rotate 

 around the body in regular order. At the outer end of 

 the gullet is a space called the vestibule. Into this any 

 undigested residue is passed, and thus swept out by the 



