78 Flow to obtain tt. 
piece of water fruitful or barren, as the case may be. The more 
intimately we become acquainted with these important matters the 
more likely are we to manage them properly. 
Many old ponds are so completely overgrown as to be 
choked with vegetation, and the only course that can be taken 
with most of these is to let off the water, clean them out 
thoroughly, allow them to remain dry for a period, and then deal 
with them as I shall direct presently. The advantage of having a 
properly constructed bottom outlet, as described in my last 
chapter, will now be apparent, and at a time like this it will be 
found very useful. At the same time it must be remembered 
that when the water is run off a large quantity of valuable fish 
food goes with it. This stock of food has to be replaced before 
the water can again support the usual number of trout which the 
pond has been accustomed to hold. When it is one of the lower 
ones of aseries this does not so much matter, as water can be let 
down from the pond above, which is charged with animal life, 
and from this source a stock is soon produced. 
In connection with the aqua-culture of the period, perhaps 
there is no subject of greater importance than the study of the 
various forms of life that are to be found in greater or lesser 
quantities in our waters. To work out the life histories of the 
creatures, and ascertain the peculiar conditions under which each 
one exists or ceases to exist, and also those conditions which are 
most favourable for reproduction, in the largest quantities, of 
each species, is a work of no ordinary kind. Passing over the 
more prominent and visible creatures, we come to a wonderful 
series of microscopic beings, which in some localities are found in 
enormous numbers, whilst in others they either do not occur at all, 
or if they do, it is simply a case of bare existence. I have 
examined some waters in which the so-called lower forms of life, 
both animal and vegetable, are conspicuous by their absence, and 
the fish in these waters are very naturally stunted in growth, and 
are never known to attain any size, save where an individual 
develops cannibal propensities, and soon outgrows his fellows. It 
will be seen, therefore, that the conditions under which fishes are 
wont to thrive are those to be first ascertained before stocking is 
resorted to. It ought to be needless to point out that it is not 
