52 



Contrast Paramecium with Vorticella, and state the Main 



Points of Difference. 

 (The main points of difference are printed in bold type.) 



Paramecium (Slipper Animalcule). 

 In shape a loitg oval. 



A cortex with an outer pellicle. 

 Free-swimming in water. 



Cilia not restricted, and covering 

 body uniformly (Holotricha). 

 Actively moving by means of cilia. 



Numerous trichocysts (stinging 

 hairs). 



A mouth within peristome and 

 an anal spot near. 



Food particles inwafted by cilia 

 into mouth via the peristome. 



Food vacuoles formed. 

 A large oval meganucleus and 

 one small micronucleus (or two) 

 alongside it. 



TWO Contractile Vaouoles. 

 Reproduction by 

 (a) Simple division (trans- 

 verse binary fission). 



(6) Temporary conjugation, 

 with exchange of mioro- 

 nuolei. 



Vorticella (Bell Animalcule). 



In shape like a bell with a long 

 handle. A disc on top of the belL 



A cortex with an outer pellicle. 



Fixed by a Stalk to water- weeds. 

 Stalk has an axial contractile 

 fibre or " myophan " thread. 



Cilia restricted to lip of bell, 

 disc, and peristome (Peritricha). 



Although fixed, contracts its 

 stalk freely; and bell may swim 

 free when detached from stalk. 



A mouth within peristome and' 

 an anal spot near. A ciliated 

 groove between disc and lip of bell. 



Cilia of disc and groove cause 

 vortex currents which inwaft food 

 particles into mouth via the 

 peristome. 



Food vacuoles formed. 

 ^ A large horse-shoe-shaped mega- 

 nucleus, and close to it one small 

 micronucleus. 



One Contractile Vaouole. 



Reproduction by 



(a) Simple division (longi- 



tudinal fission) one half 

 being separated off as 

 one or more microzooids 

 which swim free, and 



(b) completely conjugate with 



ordinary stalked indi- 

 viduals. 



