No sooner have you paid your sixpence at the turnstile which admits you, than your eye is caught by what seems to be a large window in the wall, near the man who has taken your money. You look through the glass, and find yourself looking into a deep sea-pool, with low stone-grey rocks studded with sea-anemones in full bloom. There are twenty-one different species of sea-anemones in the Aquarium; but those to be seen in this particular pool are chosen from about seven of the largest kinds. The very biggest, a _Tealia crassicornis_, measures ten inches across when he spreads his pearly fingers to their full extent. "In my young days" we called him by the familiar name of Crassy; and found him so difficult to keep in domestic captivity, that it was delightful to see him blooming and thriving as he does in Tank No. 1 of the Great Aquarium. His squat build--low and broad--contrasts well with those tall white neighbours of his (_Dianthus plumosa_), whose faces are like a plume of snowy feathers. All the sea-anemones in this tank have settled themselves on the rocks according to their own fancy. They are of lovely shades of colour, rosy, salmon-coloured, and pearly-white. There are more than five thousand sea-anemones of various kinds in the Aquarium; and they have an attendant, whose sole occupation is to feed them, by means of a pair of long wooden forceps. Reluctantly breaking away from such old friends, we pass through a door into a long vault-like stone passage or hall, down one side of which there seem to be high large windows, about as far apart as windows of a long room commonly are. Behind each of these is a sea-pool like the first one. Take the first of the lot--Tank No. 2. It is stocked with _Serpulae_. Sea-anemones are well-known to most people, but tube-worms are not such familiar friends; so I will try to describe this particular kind of "sea-gentlemen." The tube-worms are so called because, though they are true worms (sea-worms), they do not trust their soft bodies to the sea, as our common earth-worms trust theirs in a garden-bed, but build themselves tubes inside which they live, popping their heads out at the top now and then like a chimney-sweep pushing his brush out at the top of a tall round chimney. Now if you can fancy one of our tall round manufactory chimneys to be white instead of black, and the round chimney-sweep's brush to have lovely gay-coloured feathers all round it instead of dirty bristles, or if you can fancy the sweep letting off a monster catherine-wheel at the chimney's mouth, you may have some idea what a tube-worm's head is like when he pokes it out of his tube.