rows of perforated plates of the shell. The mechanism of their protrusion depends on the presence of a special system of vessels, known as the 'ambulacral' vessels, which carry water to the little feet, for the purpose of their inflation and distension.

Thus on the upper surface of the shell we find a single large plate perforated with holes like the lid of a pepper-box. This plate opens into a long tube called the 'sand-canal'—a name which is decidedly a misnomer, since the function of the plate resembling the pepper-box lid is to allow water to enter this tube, but at the same time to exclude particles of sand and like matters. The sand-canal terminates in a circular vessel, which, like the nerve-cord, surrounds the gullet; and from this central ring a great vessel, like a main water-pipe, runs up each of the five rows of perforated plates in company with the nerve-cord. At the base of each little tube-foot is a little muscular sac or bag, and into these sacs the water admitted by the sand-canal ultimately passes. When therefore the sea-egg wishes to distend its feet for the purpose of protruding them through the shell-pores, and of thus walking by applying their sucker-like tips to fixed objects, the water in the little sacs is forced into the feet, which are thus distended. Whilst conversely, when the feet are to be withdrawn, the water is forced back, by the contraction of the feet into the sacs, or may be allowed to escape from the perforated tips of the feet, so as to admit of a fresh supply being brought in from the interior.

The development of the sea-egg may be briefly glanced at by way of conclusion, along with a few points in its economic history. The animal, solid as it appears in its adult state, is developed from a small egg, which gives origin to a little body, usually named the 'larva,' but which, from its resemblance in form to a painter's easel, has received the name of Pluteus. This little body does not in the least resemble the sea-egg; possesses a mouth and digestive system of its own, and swims freely through the sea. Sooner or later, however, a second body begins to be formed within and at the expense of this Pluteus-larva; whilst as development proceeds and ends, the sea-egg appears as the result of this secondary development, and the now useless remainder of the first-formed being is cast off and simply perishes. Thus the development of the sea-egg is by no means the least curious part of the animal's history, and presents a singular resemblance to the production of the Star-fishes and their neighbours.

The mere mention of the economic or rather gastronomic relations of the sea-eggs may appropriately form a concluding remark to our gossiping remarks concerning these animals. With our British prejudices in favour of eating only what our forefathers were accustomed to consider wholesome, it is not likely that the sea-eggs will appeal with success to be included as culinary dainties. Yet on the continent these animals are much esteemed as articles of dietary and even of luxury. The Corsicans and Algerians eat one species, whilst the Neapolitans relish another kind; and in classic times, when variety rather than quantity or quality was the chief feature of high-class entertainments, the Echini were esteemed morsels at the tables of the Greeks and Romans. Here then is an opportunity for another Soyer to tempt the modern cultivated appetite with a new and wholesome dish. Considering that crabs and lobsters are so highly esteemed, the sea-eggs but wait a suitable introduction to become, it may be, the favourite tit-bits of future generations.

A wise philosopher—the great Newton himself—remarked concerning the limitation of our knowledge, that we were but as children, picking up at most a few stray grains of sand on the sea-shore, whilst around us lies the great region of the unknown. Our present study may not inaptly be related to Newton's comparison, since it serves to shew that even the brief and imperfect history of a stray shell picked up on the sea-beach may teem with features so curious and with problems so deep, that the furthest science may be unequal to the explanation of the one or the elucidation of the other. Whilst the subject no less powerfully pleads for the wider extension of the knowledge of this world and its living tenants—knowledge which in every aspect reveals things which are not only wondrously grand, but also 'fair to see.'