172 NATURAL HISTORY 



careful management three red eyes may be discerned ; 

 two of these are situated in front of the rotatory organs, 

 and one behind them^ near the bulbous oesophagus. The 

 different parts of the internal structure of this animalcule, 

 by a reference to the drawings of the senta, may be 

 readily distinguished, and therefore it is unnecessary to 

 describe them here : we may remark, however, with re- 

 spect to the insertion of the eight muscles which move the 

 body, that by their being more extended along the mid- 

 dle of the body than in the st';//«, tbis creature possesses 

 greater powers of contraction. Length, l-96th of an 

 inch. 



399. VoRTicELLA luvva, — This animalcule has not been 

 accurately examined. MUller is the only one who has 

 figured it: it probably belongs to the family Poli/trocha : 

 the cilia are arranged in the manner of the preceding, and 

 the aperture crescent-shaped. The alimentary canal is 

 large, and surrounded by the ovary, and the tail consists 

 of two short spines, diverging from each other ; this, and 

 the contraction of the different parts of the body, render 

 it easy to be distinguished. Its entire length is about 

 l-50th of an inch. These are often found with the senta, 

 but if kept together in a small vessel, the former soon 

 disappear : their eggs are more globular than those of 

 the latter; and they measure about 1 -480th of an inch 

 in diameter. 



400. VoRTicEi LA succolata resembles the f. felis, 

 except that the head is distinctly marked from the body 

 by an annular contraction. 



