CHAPTER III 



PARAMCECIUM : VORTICELLA AND ITS ALLIES COLONIAL 

 ORGANISMS 



WE have now to consider certain organisms in which 

 differentiation has gone much further than in the uni- 

 cellular forms already considered : which have, in fact, 

 acquired many of the characteristics of the higher 

 animals and plants while remaining unicellular (com- 

 pare 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 appear- 

 ance (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 innumerable 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 



