Every part of the body—eyes, antennæ, and especially the sub-abdominal fins, to certain portions of which the ova are attached in groups, and the lobes of the tail—are submitted to a severe rubbing and brushing process. The appearance of the prawn at this period is really most interesting, and, I may also add, amusing. Sometimes the tail is compressed inwards, beneath the body for a few seconds, and then suddenly elevated and forced out with donkey-like extravagance of gesture, the animal the while standing upon its first pair of forcep-like feet.
At the appointed time the shell opens at the back part of the head, and the prawn becomes gradually freed from its old covering. The marvellous process completed, like all its crustaceous brethren, the creature becomes to a certain extent helpless, and if such convenience be afforded, retires for protection beneath some shell or fragment of rock, from whence it soon re-appears, and repeats its gymnastic exercises, which cease, however, for a few days, as soon as the new coat is sufficiently hardened.
The prawn is an extremely interesting occupant of an aquarium, from the fact of its being constantly on the move, and also on account of the pretty blue and orange markings of its many-jointed legs, and the singular transparent appearance of its body. This latter feature is made still more notable when the animal happens to have the ova attached, as the latter are opaque, and of a deep brown colour approaching to black. By the prawn the act of exuviation seems to be considered an event of no slight importance, and, although occurring so frequently, is fraught with danger. Specimens oftener die at the moulting time than at any other. In fact, unless I am very much mistaken, they are then subject to some peculiar disease, which is apt to prove fatal. At all events, several of my little captives, after having performed their gymnastic movements (before alluded to) for several days, turned sickly, and died. The commencement of their illness was always denoted by a small, white, opaque dot that mysteriously appeared in the centre of the body. This object speedily increased in size, until it eventually spread over the entire animal. Then, no longer diaphanous, the flesh of the prawn seemed composed of a solid substance not unlike lime or pounded chalk.
The Shrimp is so common, and so well known, that a lengthened description of it is unnecessary. I shall, therefore, merely record an ingenious plan by which specimens of the Crangon vulgaris may be procured by visitors at the sea-side, who do not care to wade in the water with a large net.
It is one generally pursued by Scotch boys as a mere amusement, for neither shrimps nor prawns are eaten to any great extent by the inhabitants of Scotland generally.
On arriving at a pool, a person will soon know whether shrimps are contained therein, from the number of sand clouds that are raised by these little crusty fellows at any intrusion upon their privacy. Many persons employ a hand net, and pass it rapidly through the water, thinking thereby to startle and entrap the animals in question. Sometimes the plan succeeds, but more often it turns out a failure.
Instead of using the net, let the young zoologist stoop down, place the palms of his hands suddenly upon the surface of the sand, then slowly draw them near each other, at same time cautiously close the fingers, and he will in all probability feel the objects of his search wriggling to escape from his unwelcome and unfriendly grasp.
To satisfy curiosity, take one of the captured specimens and drop it in the sand that surrounds the cavity in which your skill as a shrimper has been exercised, and I will venture to assert that, in an instant, the little creature will have disappeared as if by magic—such is the wonderful rapidity with which the shrimp burrows itself. Even when lying upon the surface a practised eye is required to detect the presence of a shrimp, in consequence of its colour being of the exact shade of the sand in which it hides. In clear pools its body is of a light drab colour, which becomes changed to a dark tint when the animal is located in a pool, the base of which is of a sombre hue.
The prawn, or shrimp, is somewhat of a gourmand, and requires to be fed occasionally. The most simple food to give either, when in an aquarium, is an open mussel or cockle. A marine worm, such for instance as the Terrebella, however (as on one occasion I vexatiously discovered), is a dainty more highly prized than the flesh of a bivalve, but one which cannot often be indulged in from its comparative rarity.