# The Book of the Aquarium/Part 3/Chapter 3

CHAPTER III.
THE STOCK.
I have already indicated some of the varieties best suited for the cabinet, but will here briefly enumerate those which form the leading features of attraction, leaving the development of the collection to the perseverance of the student. The great division of Coleoptera will furnish by far the largest number of showy species, all of them interesting and lively creatures, many of them possessed of great beauty. The ravenous Dytiscus marginalis and dimidiatus, with their strong hooked claws, and brightly bronzed elytra; and the pretty, docile, and harmless Colymbetes, with its shining silver breast-plate, and jet black limbs and elytra, must take the first place among the beetles for beauty of form and colour. The large, ​harmless Hydrous piceus, the lively Notanecta, Gyrinus, and Nepa, are essential to the collection.
Among the larva, those of the Caddis fly should be kept in abundance, on account of the amusement afforded by their strange habits and their remarkable metamorphosis. Larva of the Dytiscus, known as the Water Tiger, of the Dragon fly, the gnat, the May fly, and of the two-winged fly, Stratiomys Chamcæleon, the pretty blood-worm, which is the larva of the Chironomus plumosus, a very pretty gnat, with feathered antennæ; and the telescope-tailed grubs of Helophilus pendulus, which, in its larva form, is one of the most curious examples in the cabinet, and, in its imago, is frequently mistaken for the honey-bee.
The drag-net will also bring out many curious water-mites, than which there can be no more interesting subjects for the microscope, or prettier objects for ordinary observation. While writing this, I have before me several specimens of the beautiful mites, Hydrachna geographica and abstergens (Müller), in a jar of Nitella; they are ever in action, treading the water as if it were air, with a kind of motion that cannot be termed swimming, but rather a walking or dancing, maintained with the greatest ease at any level, or at the bottom of the vessel. Another, and much more showy one, is the bright carmine-coloured mite Limnochares holosericea (Latreille), of which I find an abundance in a neighbouring brook. Its pretty, spidery motions, and vivid colouring, render a jar, containing a dozen specimens, very attractive to the eye of a student of nature.
​The Diving Spiders are amusing, and should be kept in plenty in large jars, well stocked with healthy weed; and the curious Raft Spider may also be preserved in a
DIVING SPIDER AND NESTS.
shallow vessel, closely covered with gauze. Aquatic Spiders are most abundant in clear brooks and ditches ​near rivers; the small tributaries of the Lea, and the dykes that abound in the marshes at Tottenham, supply me with specimens whenever I seek them.
Among the water-worms most easily obtained, the hair-like Gordius aquaticus (Linnæus), and the curiously-formed Nais, may be recommended as curious and interesting. The latter requires a bottom of sand in which to burrow, and should be covered with only a few inches of water. When it takes to its new home, it plunges its body into the sand or mud, and extends its telescope-tail upwards to the surface for air, adapting its length to the depth of the water.
The generation and development of reptilia and mollusca may be better studied by the use of jars for the specimens, than by their immersion in the aquarium. Tadpoles, the larva of newts, and the spawn of mollusks, may be preserved in the cabinet for purposes of study, much better than in the tank; each species being separate in a bright and portable vessel, every minute change can be observed, and a lens applied at any time, or the specimens removed for close inspection without difficulty. I find it a good practice to remove any spawn, which may be deposited on the large vessels, to the small jars on my shelves. There the little Lymnea and Planorbis are developed in hundreds, without molestation; and if increase of Paludina vivipara be required, a jar is at once converted into a breeding tank by throwing a couple into it, with a bunch of Callitriche, and any vegetable waste from the tanks. In the aquarium, the young mollusks are devoured almost as soon as they are born; and the ​pleasing spectacle of their increase, coming forth from the gelatinous mass in hundreds, like minute beads of gold, is lost without the aid of the cabinet in which to rear them. The young of most species of univalve mollusks are vagrant in their habits, and the jars in which spawn is hatched should be closely covered with perforated card or gauze, fitting closely by means of India rubber rings.
Since it is unnecessary in this work to give a classified history of the several creatures that may be kept in water-cabinets, I shall devote the remainder of the space at my command to notices of a few of the most attractive and best known species, and to a few hints on the general management of the cabinet.