CHAPTER 6 



N/ \/ ^/ V ex. c--. ^-- V 



^^•^••••t, \.**.V>**«M <i^*/|^***« »,,«4Sm^ •..-H-*^* ■•••^Slk-*-** *i^^fr"**« •mX.P**^ 



HE ciliates are relatively large and the 

 most complex in structure of the Protozoa, 

 The slipperlike animal Paramecium cauda- 

 tum is ordinarily used as a type since it is 

 easy to obtain for study and reaches the 

 comparatively great length of about 0.3 mm. 

 Many other species of ciliates may be found 

 in cultures made from pond weeds and de- 

 caying plant and animal infusions. 



The ciliates (class Cilia ta) are distin- 

 guished from other protozoans in possessing 

 cilia, which are sometimes modified into 

 cirri, during a part or all of their life cycle. 

 In most of them the nuclear material is 

 separated into a large macronucleus and one 

 or more smaller micronuclei. Most ciliates 

 are free-living in fresh or salt water. Some, 

 however, are important parasites of man and 

 other animals. 



Phylum Protozoa. 



Ciliates 



PARAMECIUM CAUDATUM- 

 A FRESH-WATER CILIATE 



Paramecia are common animals usually 

 found in pond water which contains con- 

 siderable decaying vegetation. This little ani- 

 mal was among the first living things seen 

 with the newly invented microscope in the 

 seventeenth century. The paramecium then 

 became of biological interest and has con- 

 tinued to be investigated down through the 

 years. Recently, it and related ciliates have 

 been used for studies of nutrition, respira- 

 tion, cancer, heredity, sex, behavior, and 

 ecology. 



The protozoans generally play a consider- 

 able role in aquatic food chains. Many spe- 

 cies use dissolved nutrients in the water and 

 serve as food for small many-celled animals, 

 which in turn are eaten by larger animals. 



54 



Morphology 



The 10 well-known species of paramecia 

 differ from one another in size, shape, and 

 structure. The following description applies 



