A Frozen World 211 



in its iionniil position. It browses at times on the 

 siihnierifed weeds in the pond ; Init it lias to come 

 to tlie smi'ace at fiei-jneiu intervals to breathe ; 

 thou^^h, in conniion with most aquatic air-breathers, 

 it can ^o a lon^ time without a new store of oxy- 

 gen, like a man when he dives, or a duck or swan 

 when it feeds on the bottom — of course to a mucii 

 j^reater degree, because the snail is cold-blooded ; 

 that is to say, in other words, needs much less 

 aeration. On a still evening in summer you will 

 often iind the surface of the pond covered by 

 dozens of these pretty shells, each with its slimy 

 animal protruded, and each drinking in air at the 

 top by its open-mouthed lung-sac. 



In winter, however, as you see in No. 1, our 

 pond-snail retires to the mud at the bottom, and 

 there quietly sleeps away the cold season. Being 

 a cold-blooded gentleman, lie hibernates easily, 

 and his snug nest in the ooze, where he buries 

 himself tw(^ or three inches deep, leaves him re- 

 latively little exposed to the attacks of enemies. 

 Indeed, since the whole pond is then sleeping and 

 hibernating together, there is small risk of assault 

 till spring comes round again. 



Now, it may sound odd at hrst hearing when I 

 tell you that what the animals thus do, the plants 

 do also. ** What ? " you will say. " A plant move 

 bodily from the surface of the water and bury 

 itself in the mud I It secmis almost incredible." 

 But the accompanying illustrations of one such 

 plant, the curled pond-weed, will show you that 

 the aquatic weeds take just as good care of 



