164 ANIMALS AND PLANTS. [LECT. 



a structure is of common occurrence among the lowest 

 plants and animals, and is known as a contractile 

 vacuole. 



The little creature thus described sometimes pro- 

 pelled itself with great activity, with a curious rolling 

 motion, by the lashing of the front cilium, while the 

 second cilium trailed behind ; sometimes it anchored 

 itself by the hinder cilium and was spun round by the 

 working of the other, its motions resembling those of 

 an anchor buoy in a heavy sea. Sometimes, when two 

 were in full career towards one another, each would 

 appear dexterously to get out of the other's way ; 

 sometimes a crowd would assemble and jostle one 

 another, with as much semblance of individual effort 

 as a spectator on the Grands Mulets might observe 

 with a telescope among the specks representing men 

 in the valley of Chamounix. 



The spectacle, though always surprising, was not 

 new to me. So my reply to the question put to me 

 was, that these organisms were what biologists call 

 Monads, and though they might be animals, it was 

 also possible that they might, like the Bacteria, be 

 plants. My friend received my verdict with an 

 expression which showed a sad want of respect for 

 authority. He would as soon believe that a sheep was 

 a plant. Naturally piqued by this want of faith, I 

 have thought a good deal over the matter ; and as I 

 still rest in the lame conclusion I originally expressed, 

 and must even now confess that I cannot certainly say 

 whether this creature is an animal or a plant, I think 

 it may be well to state the grounds of my hesitation 



