It is a pretty sight to watch the fishes glide under and around the marble arch, or throw themselves upon its highest point, there to enjoy the fresh air, and have a pleasant 'crack' together. This expression is literally correct, for the Blennies, when thus situated, usually make a kind of noise not inaptly expressed by snapping the nail of the thumb and finger together. The foregoing animals which constitute the entire stock of one tank, are, I am proud to state, all in a healthy condition, and if we may judge by appearances, all contented and happy. It will be from no fault of mine if they do not long continue thus, and exhibit no signs of yearning for their native haunts by the sea-shore. 'Those gay watery grots-- Small excavations on a rocky shore, That seem like fairy baths or mimic wells, Richly embossed with choicest weed and shells, As if her trinkets nature chose to hide Where nought invaded but the flowing tide.' In another tank I have introduced as a centre object a fine piece of white coral, the higher branches of which rise above the surface of the water. The roughness of the coral seems to be much approved of by many of the animals, who are not slow to avail themselves of the facility thus afforded them of climbing and otherwise exercising their peculiar propensities. When purchasing coral, care must be taken to procure a specimen that has not undergone any cleaning process, for although such may be more pleasing to the eye, it is not so suitable for a 'centre piece' as the cream-coloured, and less expensive coral. A third aquarium which I possess is fitted up in a somewhat novel style, which offers, for certain purposes, some slight advantages over others that I have seen employed. It can be adopted in almost any kind of tank; but the one under consideration is circular in form, and is, in fact, a bell-shaped inverted fern glass, the knob of which is sunk into a stand of wood supported on three legs. The plan alluded to, which was suggested to the writer by an ingenious friend,[22] consists of the introduction of a floating centre piece composed of gutta percha, which serves as a resting place for various small animals, such as Actiniæ, Mussels, Barnacles, Serpulæ, and even Pholades and Cockles. At the base of the vessel, which is quite uncovered, rest sundry members of the crustaceous family, whilst fishes of various kinds swim freely about over the entire vessel free from all annoyance. [22] Mr. Walter Hardie of Edinburgh, who has been my companion in many a delightful excursion among the rock-pools of the shores of the Frith of Forth, and to whom I feel myself greatly indebted for much valuable information relative to the subject of marine zoology.