POND LIFE. 107 



However, I have occupied enough time in speaking of ponds 

 in general, and so will now proceed to the immediate subject — 

 the living creatures which are found in them ; and I will venture 

 for one moment to dwell on the question, what do we mean by 

 living creatures ? I do not intend to give a learned disquisition 

 on life, but there are certain points in which you can easily see 

 that a living thing differs from a not-living thing, and it is just as 

 well that these should be very briefly put before you, so that 

 you may have clear ideas regarding living animals, and their 

 relations to other things about them. In the first instance, most 

 of you know that living things move ; that is the ordinary test of 

 life. We instinctively poke the body of an animal we have found 

 to see whether it move or no, and if it do not, we say " It is 

 dead." Of course there are instances in which this test will fail. 

 You do not expect to see an egg or a seed move, yet an egg is 

 alive, and so is a seed. Again, there is another point in which all 

 living things agree, and in which they differ from not-living things; 

 they take in substances which are about them, and convert them 

 into a part of themselves^ or, in one word, they feed. Now, no 

 living thing can exist for more than a very limited time without 

 food, and every living thing feeds at some period of its life. So 

 that what we do when we eat our dinner is precisely analogous 

 to what the plant does when by its roots it sucks up nourishment 

 from the earth, or takes it in from the atmosphere by means of its 

 leaves. 



Then a third, and perhaps the most characteristic of all the 

 points of difference is that living things have somehow or other 

 the power to bring about a reproduction of themselves ; that is to 

 say that each plant produces seeds, or spores, or something of 

 that kind, which give rise to a new plant exactly resembling the 

 old one ; and each animal lays eggs, or something of that kind, 

 and has young which grow up exactly to resemble their parents. 

 So that each living being has the power by some means or other 

 of reproducing a being similar to itself. Living things therefore 

 inove^ feed, and reproduce themselves, and in these three points 

 they differ most clearly and most definitely from any not-living 

 thing. 



I shall come now to speak more especially about the plants 



