But you will want more than these anemones, both for your own amusement, and for the health of your tank. Microscopic animals will breed, and will also die; and you need for them some such scavenger as our poor friend Squinado, to whom you were introduced a few pages back. Turn, then, a few stones which lie piled on each other at extreme low-water mark, and five minutes’ search will give you the very animal you want,—a little crab, of a dingy russet above, and on the under side like smooth porcelain. His back is quite flat, and so are his large angular fringed claws, which, when he folds them up, lie in the same plane with his shell, and fit neatly into its edges. Compact little rogue that he is, made especially for sidling in and out of cracks and crannies, he carries with him such an apparatus of combs and brushes as Isidor or Floris never dreamed of; with which he sweeps out of the sea-water at every moment shoals of minute animalcules, and sucks them into his tiny mouth. Mr. Gosse will tell you more of this marvel, in his “Aquarium,” p. 48. Next, your sea-weeds, if they thrive as they ought to do, will sow their minute spores in millions around them; and these, as they vegetate, will form a green film on the inside of the glass, spoiling your prospect: you may rub it off for yourself, if you will, with a rag fastened to a stick; but if you wish at once to save yourself trouble, and to see how all emergencies in nature are provided for, you will set three or four live shells to do it for you, and to keep your sub-aqueous lawn close mown. That last word is no figure of speech. Look among the beds of sea-weed for a few of the bright yellow or green sea-snails (Nerita), or Conical Tops (Trochus), especially that beautiful pink one spotted with brown (Ziziphinus), which you are sure to find about shaded rock-ledges at dead low tide, and put them into your aquarium. For the present, they will only nibble the green ulvæ; but when the film of young weed begins to form, you will see it mown off every morning as fast as it grows, in little semicircular sweeps, just as if a fairy’s scythe had been at work during the night. [Picture: Plate 8: Littorina Littorea etc.] And a scythe has been at work; none other than the tongue of the little shell-fish; a description of its extraordinary mechanism (too long to quote here, but which is well worth reading) may be found in Gosse’s “Aquarium.” {201} A prawn or two, and a few minute star-fish, will make your aquarium complete; though you may add to it endlessly, as one glance at the salt-water tanks of the Zoological Gardens, and the strange and beautiful forms which they contain, will prove to you sufficiently.