56 INFUSORIA. 



If one of these vase-like bodies (b) be carefully 

 examined, its edge is seen to be surrounded by a 

 projecting rim or border, wbich has received the 

 name of ^ peristome ' (tt). Within the latter is 

 placed the ' disk/ the outer edge of which is 

 provided with one or more circlets of cilia (^). 

 The peristome itself is not fm-nished with these 

 appendages. The mouth is placed in a small 

 opening situated near the edge of the disk, 

 between it and the peristome. The disk, which is 

 separated from the peristome by an intervening 

 furrow, forms the upper surface of a peculiar pro- 

 cess termed the ' rotatory organ,' which the 

 animal has the power of retracting deeply into the 

 interior of the body, over which latter a covering 

 is then formed by the contraction of the peri- 

 stome. The cilia with which the outer edge of the 

 disk is furnished are arranged in a spiral line. 

 This spiral commences a little to the right of the 

 oral orifice, above which it proceeds towards 

 the left, and, after performing one or more revolu- 

 tions round the edge of the disk, descends into the 

 ' vestibulum ' or commencement of the digestive 

 apparatus. In addition to the oral orifice, the 

 vestibulum is provided with a lateral aperture 

 which would appear to discharge the fimction of 

 an anus. Between the anus and the mouth 

 springs a stiff bent ' bristle ' (/S), which usually 

 projects beyond the edge of the peristome. From 

 the vestibulum a short tube called the * oesophar- 

 gus ' leads to a wider portion of the digestive 

 canal which has been termed the 'pharynx.' 

 The latter is fusiform in shape, being truncated at 

 its lower extremity, which hangs down into the in- 

 terior of the body, forming an abrupt termination 



