CHAPTER III 



PARAMCECIUM, OPALINA, VORTICELLA AND ITS ALLIES — • 

 PARASITIC AND COLONIAL ORGANISMS — BIOGENESIS AND 

 ABIOGENESIS — CLASSIFICATION OF THE UNICELLULAR 

 - OE:GANISMS EXAMINED. 



We have now to consider certain organisms in which 

 differentiation has gone much further than in the unicellular 

 forms already considered : which have, in fact, acquired 

 many of the characteristics of the higher animals and plants 

 while remaining unicellular (compare p. 238). The study 

 of several of these more or less highly differentiated though 

 unicellular forms will occupy the present chapter. 



It was mentioned above that, in the earlier stages of the 

 putrefaction of an organic infusion, bacteria only were found, 

 and that later, monads made their appearance (p. 257). 

 Still later organisms much larger than monads are seen, 

 generally of an ovoidal form, moving about very quickly, 

 and seen by the use of a high power to be covered with in- 

 numerable fine cilia. These are called ciliate Infusoria, in 

 contradistinction to monads which are often known as 

 flagellate Infusoria : many kinds are common in putrefying 

 infusions, some occur in the intestine? of the higher animals 



