BELL AND SLIPPER ANIMALCULES 17 



means of a great number of fine, contractile threads 

 or cilia. The cilia by their rapid vibration either 

 aid in propelling the organism forwards, or else 

 create water-currents in which the minute animal 

 or vegetable organisms destined as food for the 

 Protozoon become wafted to their destination the 

 cell mouth of the organism for, unlike most of 

 the Protozoa, the 

 Ciliates are pro- 

 vided with a 

 special opening, 

 or cell mouth, by 

 which food is 

 taken. 



The Ciliata ex- 

 hibit the highest 

 morphological 

 differentiation 

 among the Proto- 

 zoa. Many have 

 two nuclei, one 

 of which only is 

 concerned in re- 

 production, while 

 the other controls 

 nutrition. Among the Ciliates are some of the most 

 beautiful of our fresh-water organisms, the slipper 

 animalcule (Paramcecium) with its rapid movements, 

 and the graceful, delicate bell animalcule, Vorticella 

 (Fig- 3)5 being two good examples. 



Having thus briefly outlined some of the char- 

 acters of the main groups, the life-histories of some 



FIG. 3 VORTICELLA, AN EXAMPLE OF A 



ClLIATE, ATTACHED TO A PlECE OF 

 WOOD 



