Pond Life 
poles, or pollywogs. These pollywogs 
wriggling about in swarms in the shallow 
dirty water of a horse-pond may seem to 
you only common, uninteresting things, 
not worth troubling your head about. 
But that a tadpole, living in the water 
and breathing like a fish by means of 
gills, can change in a few days to a land 
reptile breathing air in its lungs, the 
same as you do, is in reality one of the 
most astonishing things in nature, and 
much more than merely an interesting 
curiosity. It is an example, and a very 
striking one, of the power of change 
possessed by living things. It is rather 
difficult to find a suitable and simple 
word to express this power. We may call 
it elasticity if you like, this power which 
things have of adapting themselves to 
their life, when conditions alter, or when 
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