OMNIPRESENCE OF LIFE 1291 



Observe how transparent it is, and with what 

 easy, undulating grace it swims about; yet this 

 swimmer has no arms, no legs, no tail, no backbone 

 to serve as a fulcrum to moving muscles nay, it has 

 no muscles to move with. 'Tis a creature of the 

 most absolute abnegations sans eyes, sans teeth, 

 sans everything; no, not sans everything, for, as 

 we look attentively, we see certain currents pro- 

 duced in the liquid, and, on applying a higher mag- 

 nifying power, we detect how these currents are 

 produced. All over the surface of the Opalina there 

 are delicate hairs in incessant vibration; these are 

 the cilia* They lash the water, and the animal is 

 propelled by their strokes, as a galley by its hundred 

 oars. This is your first sight of that ciliary action 

 of which you have so often read, and which you will 

 henceforth find performing some important service 

 in almost every animal you examine. Sometimes the 

 cilia act as instruments of locomotion; sometimes as 

 instruments of respiration, by continually renewing 

 the current of water; sometimes as the means of 

 drawing in food, for which purpose they surround 

 the mouth, and by their incessant action produce a 

 small whirlpool into which the food is sucked. An 

 example of this is seen in the Vorticella. 



Having studied the action of these cilia in micro- 

 scopic animals, you will be prepared to understand 

 their ofHce in your own organism. 



It is an interesting fact, that while the direction 

 in which the cilia propel fluids and particles is gen- 



* From cilium, a hair. 



