PARAMCECIUM, 89 



cyst. Under the protection of this cyst the encysted Amoeba 

 lies dormant. All the active vital processes are suspended 

 and are only resumed in more favourable surroundings. 

 Such a cyst is termed a hyp?iocyst. Encysted Amoebce are 

 doubtless transported from pond to pond by the wind or 

 other means. 



Such is the simple structure and life-history of this 

 little animal. It may be taken as a type of the Sub- 

 kingdom PROTOZOA, for it is a single cell and its 

 vital activities are conducted within the limits of this cell. 

 It is a type of the phylum GYMNOMYXA (naked jelly), 

 for its protoplasm is freely exposed to the surrounding water. 

 The whole surface of the bod»y performs the functions of 

 ingestion, egestion, sensation, and respiration. Lastly, it is 

 a type of the class Rhizopoda, for the protoplasm throws 

 out blunt pseudopodia. 



II.— PARAMCECIUM. 



Sub-Kingdom - . . . Protozoa. 



Phylum Corticata. 



Class Ciliata. 



Order Holotricha. 



Paramoecium caudatum is a minute freshwater 

 animal which can be easily distinguished with the naked 

 eye. Its body is flexible but has a definite shape. It is 

 elongated, cylindrical, and rounded at each end. The 

 protoplasm in the interior of the animal is of a semi-fluid 

 consistency, like that of Afnceba^ but the definite shape is 

 maintained by a hardened outer part of the protoplasm, 

 called the cortex. 'i'his cortex should be carefully dis- 

 tinguished from the ectoplasm of Amoeba^ which is but 

 slightly differentiated from the endoplasm, and is too 

 mobile to affect the shape of the body. 



The cortex secretes on its outer surface a thin hyaline 

 cuticle^ which is punctured by numerous minute holes. 

 Through these holes the cortical protoplasm protrudes in 

 the form of cilia, short vibratile hair-like processes which 

 contract forcibly in a definite direction. 



