286 PROTOZOA chap. 



Each of ihe organisms which we have studied in this 

 and the two previous chapters consists of a single cell — or 

 in the case of Carchesium and Epistylis of a colony of cells 

 to a large extent independent of one another. They are 

 therefore placed in the lowest primary division of the animal 

 kingdom — the phylum Protozoa (p. 220). This phylum is 

 subdivided into a number of f/asses, examples of certain of 

 which we have examined. Those in which, like the Amoeba, 

 the amceboid form is predominant constitute the class 

 Rhizopoda : those in which, like the Monads and EugJenaj 

 (Flagellata), the flagellate form is predominant are often 

 included with the ciliated forms (Ciliata) — such as Para- 

 moecium, Opalina and \'orticella — in a single class, the 

 Infusoria. 



The animals above the Protozoa are classed, as we have 

 seen, in a number of different phyla, but as they are all 

 multicellular they are often spoken of collectively as the 

 Metazoa, one of the simplest of which we must next 

 examine. 



I'R.\CTICAL 1JIK1-;CTI( ii\S. 



ParamCBCium. — Spread a liLllc coUon-wool on a slide over a drop 

 of water containing l-'aramrecia, in order to entangle them in its meshes, 

 and put on a cover-glass. Examine first \\ilh the low power and then 

 with the high power. Note — 



1. The elongated form of the 'animal ; its anterior (more rounded) 

 and posterior (more pointed) end ; its i^attened dorsal and ventral 

 surfaces ; and its buccal i^roove and ntoiith, on the ventral surface. 



2. The active nio\'ements, due to the (ilia covering the body. 



3. The marked distinction l>etween ("(';'/(U- and mcdttUa. 



4. The characters of the elastic lorl^x : — [a) the superficial ititi':lt\ 

 and deeper striated layer ; (^) the (ilia arising from the deeper layer, 

 and projecting through the cuticle ; (c) the triihocysh — smalt oval sacs, 

 imbedded in the deeper layer ; (</) the two spherical (I'litractik vadioles, 

 situated in the deeper layer on the dorsal side : note that canals radiate 



