ROTIFEEA. 



231 



cession the action of the adjoining one, that cilinm 

 which, by being completely folded up, formed the 

 lowest point between any two waves, in its turn, by 

 its complete extension forms the highest point of the 

 next wave, and thus, while the cilia are alternately 

 bending and unbending themselves, the ivaves appear 

 to travel onward, while the cilia never change their 

 position. 



The ciliary apparatus is evidently under the con- 

 trol of the animal. The whole fringe of ciha may 

 be instantly set in motion, and as instantly stopped, 

 or their action regulated to any degree of rapidity. 



A very slight examination of these minute crea- 

 tures with the microscope, will show that the ciliary 

 movement answers a double pm-pose. If the little 

 Rotifer attaches itself to some fixed object, by means 

 of its forcipated tail, as represented in the figure 

 (Fig. 177), the cilia, by producing currents in the 

 water, all converging towards the mouth, insure an 

 abundant supply of food, by hurrying down the 

 gaping throat whatever minute aliment may be 



1, 2, DracMonus. Fig. ItT.-EOTiFEr.A. 3, Stephanoccros. 



brought within range of the vortex thus caused ; or, 

 on the other hand, if the animal disengages itsell 

 from the substance to which it is held by its curious 

 anchor, the wheels acting upon tlie principle of 



