THE ROTIFERA. 53 



cle. The rotatory organs are rows of cilia, placed on 

 circular or semi-circular eminences on the upper part of 

 the body. In some species, the cilia are in a single 

 series; in others, in several rows of different forms: 

 and in one genus, (Stephanoceros), they assume the 

 character of ciliated tentacula, rather than that of 

 simple vibrating processes. There are distinct muscles 

 for the internal and external movements. In some 

 species, the pedicle has a sucker at its extremity, which 

 serves to fix the body during the rapid motions of the 

 rotators ; and, without this power of attachment, the 

 upper part of the body would be drawn in by the ac- 

 tion of these organs. The digestive canal is a tube more 

 or less straight, which in many genera is provided with 

 jaws and teeth : these, like the masticatory organs in 

 birds, are situated low down, are very distinct, and pre- 

 sent considerable diversity of form and arrangement. 



MASTICATORY ORGANS OF THE ROTIFERA. The 

 reader, from what has already been submitted to his 

 notice, is familiar with the marvellous powers of the 

 microscope, or he would probably receive with some 

 degree of scepticism the following account of the jaws 

 and teeth of animalcules, none of which exceed two- 

 thirds of a line in length, and are, therefore, but just 

 perceptible to our unassisted vision. 



