10 



Elementary Zoology. 



The vorticella is, like the amceba, an unicellular animal.i 

 So far it does not present us with an advance of structure upon 

 the last described organism, which is one of the simplest of 

 organized creatures. But the vorticella is a useful example of 

 a single cell, which is highly specialized in many and different 

 directions ; it is still a unit of structure, but illustrates the very 

 great amount of differentiationVhich can occur in a cell. 



MTH 



PERISTOME 



VESTE 



CONT. VACUOLE 

 .FOOD VACUOLE 



Fig. 4. — Vorticella, Infill* in ij'iified. (After Biitschli). 



MTH, mouth : VEST", funnel-shaped vestibule: MAC. Nuc, macronucleus ; 



MIC. NUC, micronucleus. ; 



The body of the vorticella is somewhat wineglass shaped ; 

 it has a thick rim above, which is, when the animal is fully 

 extended, slightly everted. This rim is fringed with vibratile 

 cilia. Just inside this rim, on one side of the body, is a funnel- 

 shaped depression leading some way into the interior of the 

 animal ; this is the aperture through which food particles are 

 taken in. The body itself has a delicate, slightly hardened, 

 outer layer, the cuticula ; beneath this is a firm layer, the 

 ' This anticipates what is dealt with on p. 14. 



