30 THOUGHTS ON ANIMALCULES. 



Infusoria given to this class of animals, in allusion 

 to their supposed origin. This name is still employ- 

 ed as a general designation, although it has long been 

 known that the presence of animalcules in infusions 

 has no necessary relation to the vegetable ingredients, 

 except so far as the decomposition of the latter may 

 tend to the production of a proper medium, for the de- 

 velopment of the invisible eggs, or germs, of these crea- 

 tures, which are everywhere present. The essential 

 characters of the Infusoria — in other words, those points 

 of their organisation in which they differ from all other 

 animals — consist in their bodies being destitute of any 

 true articulated or jointed limbs and locomotive mem- 

 bers or feet; their varied movements being perfonned 

 by means of peculiar processes, or filaments, which are 

 always in motion, and are termed Cilia*, from their sup- 

 posed resemblance to the eyelashes. The ciha, in many 

 species of Infusoria, are more or less generally distri- 

 buted over the surface of the body ; in others, they are 

 disposed in one or more circles around the mouth or 

 aperture of the digestive organs ; and, in some, are ar- 

 ranged in zones on one or more circular, or semicircular 

 projections, on the upper part of the body. In the last 

 modification, the successive action of the rows of cilia 



* Cilia, the plural of cilium, an eyelash. 



