PARAMECIUM ^y 



funnel-shaped gullet or vestibule, the opening from vestibule to 

 endoplasm being known as the mouth. The whole body is covered 

 with fine protoplasmic threads of the kind known as cilia (Fig. 21) 

 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 beat 



Fig. 21. — ^Electron photomicrographs of a ciUum (on the left) and tips of dis- 

 charged trichocysts of Paramecium. The cihum can be seen to consist of 1 1 

 separate threads. The measure in each photograph is i micron. — From. 

 Jakus and Hall. 



together to form an apparent undulating membrane which 

 hangs from the roof. The ciHa work regularly in waves, lashing 

 backwards and driving the blunt end of the animal forwards, 

 with a rotating movement hke that of a rifle bullet owing to its 

 spiral shape. The animal can encyst. 



ECTOPLASM AND ENDOPLASM 



Paramecium has a soft, granular endoplasm and an ectoplasm 

 which is firm and gives the body its shape, but elastic, so that the 

 an mal can bend and squeeze through narrow gaps. The outermost 

 layer of the ectoplasm is a tough pellicle. Below the pellicle comes 

 the cortex, a thicker, clear layer of ectoplasm in which are 



