PKOTOZOA 9 



Amoebaea. This order, with the orders Foraminifera, 

 Heliozoa, and the Eadiolaria, constitutes the class Khizopoda 

 of the Protozoa. This is the method universally adopted by 

 systematists to arrange and classify the various kinds of 

 animals. 



Another large and important class is the Infusoria, which, 

 instead of having pseudopodia or long filamentous extensions 

 of the cytoplasm, are provided with numerous active, short, 

 hair-like processes which are termed cilia. These Protozoa we 

 may study with reference to two genera, Paramecium and 

 Vorticella. 



Paramecium, the slipper animalcule, is very common. It 

 may be procured from stagnant water, rain tubs, fresh waters 

 generally, and even from the sea. It is commonly found in 

 infusions of hay and other vegetable matter. 



The cell, which is the individual, consists of cytoplasm, 

 and there are two nuclei, a macronucleus and a micronucleus. 

 The cytoplasm is resolved into an internal endoplasm, granular 

 and circulating like that of Amoeba, and an ectoplasm which 

 is firm and forms a tough, elastic outer layer of characteristic 

 shape. A special funnel-like depression leads to a mouth 

 opening into the endoplasm. The whole surface, including 

 the depression, is clothed with numerous fine cilia. The cilia 

 by their combined action enable the animal to move about 

 rapidly and freely, rotating on its axis, and their action in the 

 neighbourhood of the vestibule and in the vestibule wafts 

 food into the interior. The food is treated as in Amoeba, and 

 the food and other vacuoles may be seen in the endoplasm. 

 The two nuclei occur close together near to the vestibule, and 

 there are two contractile vacuoles, one near each end. 



It will be observed that Paramecium is long, somewhat 

 blunt at one end and more pointed at the other. It moves 

 almost in a straight line, but the movement is really a spiral 

 one with the blunt end forwards and the mouth below. We 

 may therefore speak of an oral or ventral surface, an adoral 

 or dorsal surface, an anterior and a posterior end, and right and 

 left sides. Polarity is thus strongly developed and manifested 

 structurally. 



