How to obtain it. 17 
has been taking place on the one hand decay has also been setting 
in on the other, and this decay has produced favourable conditions 
for vegetable growths peculiar to such situations. Trout fry 
turned into such ponds have developed into good fish, sometimes 
in an incredibly short space of time. The cause of this rapid 
development is to be found in the abundance of food produced 
by the surrounding conditions, but the submerged plants have at 
length decayed and disappeared, and with them, to a large extent, 
the parasitic forms for which they have provided a suitable nzdus. 
As a result the trout have ceased to grow—nay, have even fallen 
off in condition ; but aquatic vegetation having been introduced, 
in a few years the quality of the fish has improved. This needs 
little explanation, for the cause is obvious. Therefore, when 
ponds are constructed, a sufficient quantity of suitable vegetable 
life should be introduced. Some plants are peculiarly favourable 
for the development of fish food, some are positively hurtful, 
some are highly poisonous, and some actually devour fish. It will 
be apparent, therefore, that some knowledge of the subject is 
necessary before going to work, or the desired end may not be 
brought about. 
A great deal more depends upon keeping up the exact 
balance of suitable vegetable and animal life than the uninitiated 
imagine ; and I have seen considerable sums of money sunk to 
little purpose, in some cases thousands of pounds sterling, simply 
because the matter has not been understood, and consequently 
no attention has been paid to the most necessary details. It has, 
indeed, never occurred to many minds, that the utmost importance 
attaches to the presence or absence of various forms of vegetable 
and animal life in the water. 
Before any serious expenditure is incurred on any lake or 
pond, the water and its inhabitants should be accurately studied. 
The results of dredging and the use of the tow net in various 
waters, goes to show that in some there is an abundance of ‘trout 
food, whereas in others there is a great scarcity. Some contain 
many injurious pests to fish, whilst others are free from them. 
The study of fora and fauaa is of the most vital importance ; and 
the presence or absence of many microscopic as well as more 
conspicuous animals, too apt to be overlooked, will often render a 
