surface of the water, as these animals require a resting-place above water. Small floats may be prepared for them by smearing a cork with marine glue and sprinkling it with sand. When the glue has dried, place the float in water and allow it to remain there for some time before putting it into the aquarium. These animals have also a disposition to rove, which must be checked by covering the aquarium. The cover should be of glass and flat, with a large opening in the centre. The cover is also advantageous to keep out dust. Molluscous animals, as the horny coil-shell (Planorhis corneus) and the pond mud-shell (Limnea stagnalis), may be added. They are both to be found among the grasses that grow in ponds and on the margin of brooks. Such insects as the common water-spider (Argyroneta aquatica), the large harmless beetle (Hydroüs piceus) and the little whirligig (Gyrinus natator), can be introduced to advantage. Pugnacious individuals, as the perch and the stickleback, though interesting, are not desirable objects for a general aquarium. The best food for the animals described is a little biscuit-powder kneaded into pills about the size of a pin-head and fine shreds of raw beef cut with scissors. The first should be fed once a day, the biscuit and meat being thrown in bit by bit alternately.
Fig. 5.
Marine Aquarium (Side View).
The marine aquarium must be supplied with sea-water taken not less than a mile from shore, or from the middle of a large river. When any is lost from the tank by evaporation, add fresh rain-water to supply the deficiency; losses otherwise occasioned must be made good by the addition of sea-water. Among the most curious and interesting animals are the shrimp or prawn; the smooth anemone (Actinia mesembryanthemum), one of the hardiest and most curious animals that can be found; the limpet (Patella vulgaris), with its shelly parasite the barnacle (Balanus); the hermit-cra (Pagurus Bernhardus); the stone-crab (Cancer pagurus); the smaller star-fish; and the tube-worm (Surpulæ). In introducing fish, care should be taken to select the most amicable; a small shark, for instance, was once introduced into the aquarium of the Emperor William, at his country-seat in Prussia. The effect was, that all the other fish forsook the tank, and fled in great confusion into a fresh-water one adjoining, nor could they be driven
