thinned out, or, better still, put into larger pond."

I should advise the amateur who is dealing with only a few thousand fish to work on a smaller scale in these proportions, and to make these changes gradually, and yet more gradually as the season advances. That is to say, work with a third of the number of fry in ponds half the size and move some fish several times before the end of July. As October approaches, make changes of smaller numbers of fish more frequently.

Late in the autumn is, in my opinion, the best time to put the young fish into the water they are to inhabit permanently. It must be a mistake to rear them artificially longer than is necessary, and by the end of November they should be fairly capable of looking after themselves.

Trout, which are artificially reared on chopped meat and other soft foods, suffer from a lack of development in the stomach walls, and also, probably, in the rest of their digestive apparatus. The first case I saw of the stomach of an artificially reared trout was a two-year-old trout, upon which Dr. C. S. Patterson performed an autopsy. The stomach walls were as thin as a sheet of tissue paper. At the time I believed, and, if I remember rightly, he also thought that this was due to atrophy, but I am inclined to think that this idea was only partially correct. The stomach walls of the autumn yearling trout, which is artificially reared on soft food, do not show any marked abnormality in the way of thinness; but as the trout's age increases, so does the thickness of the stomach wall decrease in proportion to its size. This leads me to believe that the development of the stomach wall, at any rate, and probably also of the glands secreting the gastric juice and the digestive apparatus generally, gradually ceases when at about the age of eight or nine months if the trout is fed upon soft food. Probably, also, a certain amount of atrophy and dilatation of the stomach wall is produced. If my observations are correct, so also is the conclusion that a trout which cannot digest hard food, of which a great part of his natural food consists, will not have a really fair chance when turned out. Therefore, I say, turn out your trout in November, unless you can feed them on such food as shrimps, snails, bivalves and Corixæ; and if you stock with "ready made" fish, stock with yearlings in the late autumn.

The turning out of his fish in November will also allow the amateur plenty of time to prepare his ponds and apparatus for next year's operations. If the ponds are made on a stream, probably the very best place that can be chosen is where there is a fairly sharp bend in the stream just below a fall. An artificial fall can often be made where the banks are high by damming up the stream several feet. Care must be taken, however, to avoid any risk of the ponds being flooded.

CHAPTER V

TROUT. REARING PONDS, BOXES, AND HATCHING TRAYS

Having decided upon a suitable spot, the amateur must now proceed to make his ponds. Whether he derive his water supply from a spring or from a stream, the amateur had better bring it into his ponds through a pipe. A three-inch pipe will be large enough for a pond thirty feet long, three feet wide, and two feet deep at the deepest part. It is a good thing for the water to fall, some inches at any rate, through the air before it reaches the pond, and in a series of ponds with only one supply, the water should flow through an open trough with stones and other impediments in it, between the ponds. The ponds may be lined entirely with brickwork faced with cement, and in this case the sides should be made perpendicular. The cement should, however, be exposed freely to the action of the running water for a couple of months at least before any ova or fry are introduced.

Another plan, and a simpler and less expensive one, is to face only the ends of the ponds with brick and cement work, carrying the brickwork into the earth on each side, as shown in Fig. 1. In this case the sides of the ponds should be slightly sloped as shown in Figs. 2 and 3. It is advisable if possible to make the outlet at the level of the bottom of the pond, if the pond is lined with cement, but if the pond is only cemented at the ends, it is better to have one in mid-water or even near the surface. As I have said before however, an outlet should be made at the level lowest part of the bottom, so as to facilitate the emptying of the pond. The pond should however be made shallower at the lower end. Fig. 2 shows a section of the upper end, and Fig. 3 of the lower end of such a pond.

The open trough between ponds in a series should be at least three yards in length, but it is better if not straight. Stones and gravel should be put in these troughs in order to make the water as rough as possible, and if some fresh-water shrimps can be introduced so much the better.

If the water is taken from a stream, a leaf screen must be placed at some distance in front of the inlet. This may be made of a hurdle fastened to strong stakes sunk into the bed of the stream. The opening of the inlet should be at least double the size of the sectional area of the pipe through which the water is carried to the ponds, and should be some distance, a couple of feet if possible, below the surface of the water. It is a good thing to put a wire cage over the inlet, and under this a perforated zinc screen is necessary. The inlet from the stream should be so placed that it is easy to get at and clean. The best form of covering for the inlet into the pond I have seen, is a zinc cylinder, the base of which fits over the end of the inlet pipe. The part of this cylinder, which projects 18 inches beyond the pipe, is perforated, as is also the flat end. This can easily be taken off and cleaned, and breaks up the water, making it fall into the pond like a shower bath, causing considerable aeration.

The inlet from the stream should have a trap with which the water may be shut off, as also should the outlet from the pond. When the cylinder on the inlet into the pond is taken off for a minute or so to be cleaned out, both these traps must be closed. This lessens the chance of any creatures likely to do harm getting in during the cleaning. The perforated zinc screen at the inlet from the stream will probably stop any such creatures, but too great care cannot be exercised, and it is always best to be on the safe side.

Movable covers of netting over the ponds are most certainly advisable, particularly if the rearing ponds are in an unfrequented spot near a stream. On one occasion I caught four kingfishers during a period of three weeks, all of which had in some way got under some herring net, which was pegged out carefully over a rearing pond containing trout fry. I never found out how they got in, but once in they were unable to escape.

Ponds such as I have described are of course for the fry when they have reached a certain size, and have already begun to feed well. Other appliances are necessary for hatching out the ova and for the young fish when first hatched. A very good apparatus may be made from a champagne case. This should have large square holes sawn through each end, leaving enough wood to ensure strength and solidity to the box. The box should then have two coats of asphalt varnish, and the square apertures covered with fine perforated zinc. A still better box