The class of the Annelides, or annulated worms--to which also our common earth-worm and the leech belong--peoples the seas with by far the greater number of its genera and species. All of them are distinguished by an elongated, and generally worm-like form of body, susceptible of great extension and contraction. The body consists of a series of rings, or segments, joined by a common elastic skin; and each ring, with the exception of the first or foremost, which forms the head, and the last which constitutes the tail, exactly resembles the others, only that the rings in the middle part of the body are larger than those at the extremities. The head is frequently provided with eyes, and more or less perfect feelers; the mouth is armed in many species with strong jaws, or incisive teeth. The blood is red, and circulates in a system of arteries and veins. [Illustration: Nervous Axis of an Annelidan.] With the idea of a worm we generally connect that of incompleteness; we are apt to consider them as beings equally uninteresting and ugly, and disdain to enquire into the wonders of their organisation. But a cursory examination of the _Eunice sanguinea_, a worm about two and a half feet long, and frequently occurring on our coasts, would alone suffice to give us a very different opinion of these despised, but far from despicable creatures. The whole body is divided into segments scarce a line and a half long, and ten or twelve lines broad, and thus consists of about three hundred rings. A brain and three hundred ganglions, from which about three thousand nervous branches proceed, regulate the movements, sensations, and vegetative functions of an Eunice. Two hundred and eighty stomachs digest its food, five hundred and fifty branchiæ refresh its blood, six hundred hearts distribute this vital fluid throughout the whole body, and thirty thousand muscles obey the will of the worm, and execute its snake-like movements. What an astonishing profusion of organs! Surely there is here but little occasion to commiserate want, or to scoff at poverty! And if we look to outward appearance, we shall find that many of the marine annelides may well be reckoned among the handsomest of creatures. They display the rainbow tints of the humming-birds, and the velvet, metallic brilliancy of the most lustrous beetles. The vagrant species that glide, serpent-like, through the crevices of the submarine rocks, or half creeping, half swimming conceal themselves in the sand or mud, are pre-eminently beautiful. The delighted naturalists have consequently given them the most flattering and charming names of Greek mythology,--Nereis, Euphrosyne, Eunice, Alciopa. [Illustration: Nereis.]