IIo How to obtain it. 
The sides of the raceways should be planted the whole 
length with suitable vegetation. Watercress (JVasturtium 
officinale) is excellent for the purpose, and also the marsh 
marigold (Caltha palustris). The pretty little golden saxifrage 
(Chrysosplenium oppositifolium) may also be used with advantage, 
and the brooklime ( Veronica beccabunga). There are many land 
plants that do very well in water for a time, and I have found that 
the decay of these plants is favourable to the growth of animal 
life (see page 88). No floods or freshets should be allowed to 
sweep through these nursery ponds. ‘This can easily be guarded 
against by a sluice, or what is more simple, allowing the water to 
enter them through a four-inch pipe. 
They should be made as tempting for the little fish as 
possible, by planting aquatic vegetation about them. It may 
sometimes be desirable to place a screen across the end of the 
lowest pond in the position of the dotted line at K, but should 
the fish be found to collect above this screen they must be fed or 
they will die, and in feeding them all pains should be taken to 
coax them away from the screen and get them up to the head of 
the pond. As soon as the bulk of the fish have settled in the 
ponds, remove the screen and let them have full scope to go 
where they like. These ponds may be made accessory to an 
artificial ova bed or a spawning race, or they may be stocked with 
fry that have been purchased or hatched elsewhere. 
The screen, if used, should be made loose, to slide in a 
grooved frame, or it may be simply fixed by embedding the frame 
in the sides and bottom of the pond. It will only be required for 
a short time after the fry are introduced, and may then be taken 
out and stowed away to use another season. It will be seen by 
the diagram (Fig. 3) that the ponds and raceways are arranged in 
the most compact form, instead of having them ranging over a 
long expanse of ground. This is an advantage, as they are readily 
inspected, and also can be more easily protected from the 
depredations of herons, kingfishers, etc. A few covers made of 
rough boards or basket-work may be advantageously used, and a 
few pieces of wire netting should at any rate be placed over the 
most exposed portions of the raceways. A little care of this kind 
will be well repaid. The covers not only serve as protection but 
