INFUSORIA. 25 



they are propelled tlii'ougli the water by means of 

 vibratile cilia, which are sometimes distributed over 

 the entire surface of their bodies, while in others 

 these wonderful organs are restricted to certain parts, 

 more especially to the vicinity of the mouth. The 

 possession of a mouth, as the reader will at once per- 

 ceive, is in itself an important character, whereby they 

 are broadly separated from the mouthless Khizopods. 

 And when we add to this, that they are active in their 

 movements and definite in their shape, we have said 

 enough to insure their not being confounded with 

 any of the creatures we have as yet examined. The 

 movements of the ciliated infusoria are exceedingly 

 vivacious ; they swim about with great activity, avoid- 

 ing each other as they pass in their rapid dance, and 

 evidently directing their motions with precision and 

 accuracy. Their instruments of locomotion are of 

 various kinds : some are provided with stiff bristle- 

 like appendages which are moveable, and perform 

 in some measure the office of feet, and with little 

 booklets serving for attachment to foreign bodies. 

 But the most important locomotive agents are, as has 

 been already stated, the cilia with which they are 

 invariably furnished. Their movements never seem 

 to tire. At whatever period of the night they may be 

 examined, they are always found as actively at work 

 as in the day-time ; they never sleep. 



The cilia are intrusted with another function 

 equally important — viz., the procuration of food : for 

 those situated in the vicinity of the mouth, in which 

 position they are always most evident, produce by 

 their vibration, currents in the surroimding water, 

 Avhich bring to the mouth smaller animalcules, or 

 particles of vegetable matter that may be floating in 

 the neighbourhood, thus insuring an abundant supply 

 of nutriment which, without such assistance, it would 

 be impossible for these living atoms to obtain. The 

 food thus procured is at once svrallowed, and accu- 

 mulates in little pellets in the interior of the semifluid 

 substance of their bodies, giving rise to an appearance 



c 



