INFUSOIilAL AJJIMALCULES. 15 



or spread over the body generally, in which case they arc often dis- 

 posed in regular rows, as in Paramecmm, Opliryorjlena, and Urohptus, 

 {vide figs. 329-334). 



It may be remarked here, that naturalists have been greatly 

 di^dded in opinion with respect to the functions performed by the 

 cilia, more especially those belonging to the Rotatoria. It has been 

 contended hy 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 creatui-es. The disposition of the bimdles or clusters 

 of cilia in the Rotatoria, and theii- 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-Avheels, 

 and their seeming continual revolution, have been most fertile sub- 

 jects for the exercise of the imagination ; indeed, there are few, if 

 any other phenomena, 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 disposition of these 

 wheel-like organs, and his mind can hardly be restrained from revert- 

 ing, in the profoundest admiration, to that Divine Intelligence by 

 which such wonders could alone have been called into existence. 



Setcc, 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 in the genus 

 Actino^ihrys {fig. 266) ; whilst others possess a true articulation, as 

 exemplified in the posterior three of the Stylonychia mytilm. Some 

 are (awl-shaped) suhulate ; others have a knob at the extremity, and 

 hence termed capitate. 



Styles are tliick straight seta3, usually seated on the under side of 

 the body, projecting backwards like the tail feathers of birds. These 

 never vibrate ; neither have they a bulbous base, nor are their ex- 

 tremities bent or hooked. They are used for the support of the 

 body, and for climbing, and are capable of more extended motion 

 than setce. 



