Figure of Rotifer. 239 



Figure 5. 



Figure of Rotifer {Hydaiina Senta), Female, fi-om Pritchard's Infusoria. 

 Natural size. ^ to ^ of an inch. 



The body is divided into nine zonular segments by eight annular 

 muscles ; its anterior extremity, which is much the larger of the 

 two, carries the ciliated apparatus, from the appearance produced 

 by the action of which the name of the class is taken, and its 

 posterior end is a pincer-like foot. 



a. Emargination of ciliated border of anterior extremity of body, 

 leading into digestive tract. 



h. Mouth, o]3ening directly into a muscular pharynx or ''mastax^ 

 c, armed with chitinous teeth, which leads, by a short and 

 narrow canal d, into 



e. The stomach, a large sacculated and ciliated organ, with the 

 upper end of which two large glandular organs are in rela- 

 tion, one only of which, that of the right side, is here 

 figured. 



f. Cloaca, into which open, not only the rectum and the oviduct, 



but also 



g. The contractile vesicle, which receives the lateral terminations 



of the two water-vascular tubes. 



h. Ovary. 



i. Water-vascular tubes, convoluted at intervals, and giving oif 

 also certain pedunculate infundibula, which are richly 

 ciliated, and open into the perigastric cavity, as do the 

 segmental organs of the Annelids. There are never less 

 than five of these ciliated infundibula in Rotifers, 



h. Nerve ganglion, on the side of the body away from which the 

 mouth opens. 



I. Tentacular organ, consisting of a setigcrous pit, situated on 

 the dorsal surface of the body, and receiving filaments from 

 the nerve ganglion. There are no eyes in the genus Hy- 

 datina. The surface upon which the tentacular organ is 

 developed, and which corresponds in genera provided with a 

 lorica, to its convex portion, is kept upwards by the animal 

 in moving. 



