INFUSORIAL ANIMALCULES. 17 



It may be remarked here, that naturalists have been 

 greatly divided in opinion with respect to the functions 

 performed by the cilia, more especially those belonging to 

 the Rotatoria. It has been contended by some, that these 

 organs form the chief instrument for respiration ; nor is it 

 at all improbable that such is the case, as we find that 

 similar ones are placed round the gills or beard of the 

 oyster, muscle, &c., to produce currents in the water, and 

 bring a fresh supply to the creatures. The disposition of 

 the bundles or clusters of cilia in the Rotatoria, and their 

 appearance when in motion, may be considered as one of 

 the most interesting and curious spectacles in the animal 

 creation. Their strong resemblance to toothed- wheels, 

 and their continual revolution, have been most fertile 

 subjects for the exercise of the imagination ; indeed, there 

 are few, if any other, which can excite more astonishment 

 in the beholder. Let the reader turn to the various plates 

 representing the Rotatoria, and mark the great variety of 

 design, and exquisite beauty of execution, there displayed 

 in the forms and dispositions of these wheel-like organs, 

 and his mind can hardly be restrained from reverting, in 

 the profoundest admiration, to that Divine Intelligence by 

 which such wonders could alone have been called into 

 existence. 



Seta, or bristles, are a kind of rigid hairs or cilia, used 

 as organs for the support of the body, and for climbing, 

 but without having the power of vibrating like real cilia. 

 These organs are sometimes devoid of the thickened base 

 or articulation, as with the genus Actinophrys (jig. 266) ; 

 whilst others possess a true articulation, as exemplified in 

 the posterior three of the Stylonchia mytillus. Some are 



