narrower than are Corixæ, which do not swim on their backs, are smaller, broader, and live much more under water than the water-boatman. It is generally advisable to avoid water-beetles, as most of them are more likely to do harm than good, such a number of our water-beetles being carnivorous. They will probably not harm adult fish, but they will destroy ova and fry. I have known a Dytiscus marginalis kill a trout of nearly a quarter of a pound in weight.

In order to make sure of not introducing carnivorous water-beetles into a water, I think it best as a rule not to introduce beetles at all. Corixæ are, however, so like beetles, that many people call them beetles, and therefore I will give a few points which will make them easily distinguishable from each other. In beetles, the wing-cases (elytra) meet exactly in the middle line, in Corixæ and other water-bugs, the anterior wings, which resemble the elytra of beetles, overlap, which causes the line on the back to curve away to one side at the lower end. In beetles the wings which lie under the wing-cases are folded up on themselves, and when spread out are much larger than the wing-cases. The wings are transparent and very delicate. In Corixæ the posterior wings, which lie under the hard and horny anterior wings, are a little shorter than the anterior wings; they are not folded up on themselves and are not so delicate and transparent as the wings of the beetle.

Such small creatures as Daphnia pulex, Cyclops quadricornis and Rotifera should be introduced into ponds.

Snails (Gasteropoda) may be roughly divided into three classes, according to the shape of their shells: (1) Flat-shaped coils (type Planorbis corneus); (2) Oblong-shaped, somewhat like a trumpet (type Limnæa stagnalis); and (3) Ear-shaped (type Limnæa auricularia). Limnæa auricularia is particularly suitable for deep waters, and L. pereger, whose shell is of type 2, is a most valuable addition to the food supply in any fish pond. It is one of the commonest of our fresh-water snails.

Mussels (Conchifera) are another valuable article of food. There are a great many different kinds, and the larger ones should, as a rule, be avoided. Sphæriidæ and Pisidia are probably the best.

In many cases it is advisable to attempt the introduction of some flies which are not present. There are several cases in which the May-fly has been successfully introduced, and also the Grannom. Small Ephemeridæ seem to me preferable to any other flies.

With regard to suitable plants for comparatively deep water in ponds or lakes, lakewort and stonewort grow on the bottom, and do not, as a rule, attain any considerable height. White and yellow water-lilies also grow in fairly deep water; the water-lobelia is also an excellent plant for ponds.

In streams some of the best plants are water-crowfoot, water-starwort, and the great water moss. Anacharis should not be introduced into any water, either pond or stream, unless it can be kept down easily. It will otherwise become an unmitigated nuisance.

Marginal plants are a very important consideration, and plenty of them should be grown. Water-celery and water-cress are perhaps the best food-producing marginal plants that can be grown. Bullrushes and brooklime are also good, but the bullrushes must be planted judiciously.

CHAPTER III

SUITABLE FISH AND SUITABLE WATERS

Having stocked his water with suitable vegetation and food, the next matter which should engage the attention of the amateur, is what fish he had better introduce. He should, where there is a fair chance of success, introduce a trout of some sort, as they give better sport than coarse fish.

The introduction of salmon into a river is not likely to be attempted by the amateur, but the head of salmon frequenting a river is undoubtedly affected in the most marvellous manner by artificial means. In Canada and the United States this is particularly remarkable, but the operations are conducted on a gigantic scale.

In the case of a stream or river where brown trout already exist, or have recently existed, in fair numbers, re-stock with these fish, for they can hardly be bettered in our waters. There are, however, some sluggish rivers where brown trout do not thrive when they are introduced. In such rivers and in many ponds in the South of England I believe that no better fish exists than the rainbow trout. I say particularly in the south, because I do not think that the rainbow trout will ever really thrive and breed in cold waters. I have at other times given numerous examples which go to show that the rainbow will only thrive in warm waters.[1] I will therefore only quote the case of New Zealand. The rainbow trout was introduced into both islands, but while it thrived amazingly in the warm waters of the North Island, it has proved a comparative failure in the cold waters of the South Island.

While the common or brown trout (Salmo fario) and the rainbow trout (Salmo irideus) are, in my opinion, to be strongly encouraged in the waters suitable to their respective qualities, the American brook trout (Salvelinus fontinalis) does not seem to have met with the approval of most of the authorities on pisciculture in this country. My experience of this fish is not sufficient for my holding any very strong views with regard to its suitability to British waters. In one case I know that it was a great success for two seasons, but I have not had any opportunity of following it up in this particular instance. In another case it was a decided failure. I am sure that it should not be introduced into streams where brown trout thrive, and I am doubtful of its ever succeeding in waters which are suitable to the rainbow trout.

Of all the trout, the rainbow is the hardiest, and the one with which the amateur pisciculturist is most likely to be successful. It is also the fish most likely to supply a want felt by very many fishermen, a good sporting fish in waters where the common trout will not thrive.

In large and deep ponds with a good stream, or in lakes, char may be tried with a prospect of success. They require cold waters, and I have never heard of their being successfully introduced in the South of England. They are a more difficult fish to rear than trout.

Grayling have many violent opponents, but I am inclined to think that they do but little if any harm in a trout stream, and they supply excellent fishing during part of the close season for trout. They seem to thrive best in chalk streams, but there are no doubt many waters which would carry a good head of grayling which at present contain only trout. They probably do much less harm than most of the coarse fish constantly found in trout streams. The great crime attributed to them is that they eat the spawn of the trout, but I am inclined to think that the harm they do in this way is much over estimated. They spawn at