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 .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 dilate Infusoria, in 

 contradistinction to Monads, which are often known as 

 flagellate Infusoria ; many kinds are common in putrefying 

 infusions, some occur in the intestines of the higher animals 



