Several other kinds are mentioned, in a previous page, in the list of animals placed by Mr. Gosse in his first experimental Aquarium.
The Pogge, Aspidophorus cataphractus, is a singularly formed fish that might be added by way of experiment. The plate-armour in which his body is clothed runs in regular longitudinal lines, showing eight sharp ridges, running from head to tail, that have a singular and unfish-like appearance. In confinement, however, he does not display himself to advantage, generally lying near the bottom of the Aquarium.
The beautiful crimson maculations of the Ancient Wrasse, Labrus maculatus, render him a very desirable tenant; but his size—small specimens being eight or nine inches long—causes him to be inconvenient; and, moreover, he is difficult to manage, and would probably require altogether a special treatment. One of the smaller Wrasses, however, Crenilabrus cornubicus, is a desirable guest; his minute size, and varying and often gay colours, rendering him very attractive. He is an active and eager searcher for food, but never takes any loosely floating object, only darting at and detaching such atoms as are attached to the different species of Algæ.
The Pipe-Fish, Syngnathus acus, is interesting in the tank, and also the two-spotted sucker, Lepidogaster bimaculatus, a prettily coloured and curious little fish, which has the faculty of attaching itself to the side of the tank, or any other hard flat surface, by means of two singularly-formed ventral fins, which act like the leather suckers by means of which boys enjoy the sport of lifting heavy stones at the end of a string. The spawn of this fish is like tiny amber beads, and is attached to shells and other substances.
Among the Crustacea fitted for an Aquarium, the common Prawn, Palæmon serratus, holds the first rank. In the first place, his cleansing properties, in devouring all decaying animal matter, are most important. But not less interesting are his graceful movements: Now, he steals stealthily over the pebbles or the fronds of the Algæ, with his long, slender, hair-like horns in gentle motion, with all the seeming wariness of a cat (the resemblance being increased by candle-light by the fiery glare of the eye); next, leaving his walking apparatus, or legs, inactive, he uses only the swimming members, which are larger and flatter, and bordered with a compact fringe; agitating these instruments with beautiful regularity, he rises in the water with graceful ease (see [Plate VI.]), his semi-transparent body, as he rises, giving to his appearance a strange and somewhat apparition-like aspect, which has caused him to be compared to a marine spectre.
The Prawn takes its food with its second feet, two-fingered hands or claws, and carries it to its mouth. The hands of the first pair of legs are only rudimental in appearance, but are precisely fitted to their special purpose. They are his cleansing apparatus; and it is most interesting to watch the operations of his toilet when he uses these fringes as brushes, with which he cleanses his whole person most thoroughly, being almost unmerciful in the amount of severe scrubbing to which he subjects himself.
An allied species, P. squilla, is scarcely distinguishable from P. serratus; but the handsome scarlet-striped Prawn, Pardulus annuticornis, about the size of a Shrimp, is quite distinct, and would make a valuable addition to the collection. The Lobster Prawn, also, Athanas nilescens, has likewise been tried.
Some kinds of Crabs may be admitted, but not many; for several are extremely voracious, and would soon clear off all the naked Zoöphytes and most of the Molluscs.
The Climbing Crab, Eurynome aspera, is interesting in a tank from his habits. His climbing is as graceful and skilful as that of a monkey, and when he has succeeded in perching himself upon the highest object in the tank, he forms a picturesque object.
Crabs, like Prawns, are sea-scavengers, and the kinds that do not attack living creatures as well as dead are consequently useful in a tank. The great Fiddler Crab, Portunus puber, is remarkably handsome. He is clothed, in part, with a velvety brown fur, and the bare places of his shell are of a shining black. His eyes are marked with scarlet, and there are a few touches of bright blue about the head. If introduced, his proceedings should be carefully watched.