CHAPTER IX 



PARAMECIUM AND VORTICELLA. PROTOZOA 



Paramecium caudatum, the Slipper Animalcule, is a 

 minute animal found in water in which dead 

 General ' 1 "" ! leaves or other remains of organisms are decay- 

 Features, ing. The decay is brought about by bacteria, 

 and upon these the slipper animalcules feed. A 

 rich culture of Paramecium may be obtained by steeping hay 

 in water, allowing it to decay, and adding to the infusion thus 

 made mud or weeds from a freshwater pond which contains 

 Paramecium. The animals may easily be seen with the 

 naked eye as minute, greyish white, oblong creatures, shoot- 

 ing swiftly about in the water. The body of Paramecium 

 is spindle-shaped, somewhat flattened on one side, and 

 with one end blunter than the other. The flat side is called 

 " ventral " and the blunt end is anterior. This end appears 

 as though it had been twisted, so that a groove which it 

 bears is spiral, starting in front on the left and curving 

 round to the ventral side, where it is continued back in 

 the middle line to within about a third of the length of 

 the body from its hinder end. The groove is known as 

 the vestibule or peristome : from its hinder end there passes 

 backwards into the body a funnel-shaped gullet, the open- 

 ing from vestibule to gullet being known as the mouth. 

 The whole body is covered with fine protoplasmic threads 

 of the kind known as cilia (see p. 88), by whose lashing the 

 animal swims and gathers its food. The cilia are set at 

 equal distances in rows, which run lengthwise in the hinder 

 part of the body, but follow the spiral twist in front : they 

 also line the gullet, where two or three rows of them are 

 fused to form an undulating membrane which hangs from 

 the roof. The cilia work regularly in waves, lashing back- 



