these and put it into the water so prepared, and gently squeeze the roe from it whilst the vent is immersed in the water. [7] Do this as quickly as possible, and return the fish into fresh water, and then pour off the water containing the impregnated roe, through a strainer, carefully preserving it for the remaining fish, and immediately return the roe into fresh spring or brook water.  Repeat the operation for every female Trout, and you will then have a quantity of impregnated roe, which if properly managed will hatch with great certainty.  Have ready as many boxes as you are able to stock with spawn (three feet long, two feet broad, and six inches deep).  Fill them to the depth of two inches of river sand, which ought to be previously so well washed that there is not a particle of mud left in it, and upon that put two inches of river gravel, also exceedingly well washed, the pebbles varying in size from a hazel nut to a pigeon or pullet’s egg.  These boxes must be so placed that the water from a spring will flow into the first, and from the surface of that into the second, and below the whole nest of boxes there ought to be a small reservoir made—­say three yards by two and eighteen inches deep, and well gravelled at the bottom.  All these matters having been previously arranged, and the water flowing nicely over the gravel, sprinkle the impregnated roe equally over the surface of the gravel, say a quarter of a pint to each box, and it will roll down into the interstices of the gravel and find a bed in which it will remain snugly until the spring, when, about March, if all has been properly managed, you will find, on a careful examination, that the young Trout are coming to life by hundreds.  I am very particular in recommending spring rather than brook water, for several reasons.  In the first place, brooks are liable to be flooded, and are sometimes so overcharged with sand and mud that the gravel in the spawning-boxes is completely choked with it and the spawn is lost, as I know to my great and frequent disappointments.  At other times all is washed away together.  In the second place, the gravel of brooks swarms with water-lice (shrimps) and the larvae of aquatic insects, as well as bull-heads and loaches, all of which prey upon the spawn of the Trout and Salmon.  In the third place, if you put your spawning-boxes in a brook, you will find it difficult to prevent the escape of the fry when hatched, and you are left in doubt as to the success of your experiment.  With spring water all these inconveniences are avoided.  But if your watercourse should contain water-lice or aquatic larvae, it is a very easy matter to destroy them before putting in your boxes, with a little salt or quicklime.  It is also desirable to cover your spawning-boxes with a wire grating, to exclude the light, and to protect them in severe weather from the chance of being frozen.