captain assured us, most favourable for the fishing. In fact, we saw that each diver returned to the surface with at least one animal, and sometimes two, in his hands. It appears that the higher the sun is above the horizon, the more easily is the creature distinguished at the bottom. The divers were so rapid in their movements that they scarcely touched the boat, into which they threw the animals before they dived again. When the boat was filled with them, it proceeded to the shore, and its place was supplied by an empty one.” The Holothuria taken there were five to six inches long. D’Urville tasted it when prepared, and says that it resembled lobster. His men, however, took more kindly to it than did he. [Illustration: SEA‐CUCUMBER (_Holothuria tubulosa_).] We must now examine a most important class of pulpy animals, the Mollusca, of which the bivalve molluscs are by far the most important to man. In consequence of their very softness and delicacy, Nature has provided them with a shell coat of calcareous mail. The sub‐class _Acephala_, are as their names indicate, _headless_ molluscs, and though sometimes _partially_ naked, are usually very well protected by shells. When it is known that there are over 4,000 species of bivalve molluscs, the impossibility of describing more than a few typical and prominent examples will be seen. The genus _Teredo_ consists of marine worm‐like animals having a special and irresistible inclination for boring wood, whatever its hardness. Ships have been thus silently and secretly undermined, till the planks have been either like sponges or have crumbled into dust under the very feet of their crews. The holes bored by these imperceptible miners riddle the entire interior of a piece of wood, without any external indication of their ravages. Piles and piers have been utterly ruined, and vessels have sometimes gone to the bottom through them. At the beginning of the last century half the coast of Holland was threatened with inundation and practical annihilation because the piles which support its dykes were attacked by the teredo, and hundreds of thousands of pounds damage was done by this wretched worm. It has been now discovered that the worm has a great antipathy to oxide of iron, and wood impregnated with it is secure from its ravages. Other animals of the same group are capable of boring even rock. Another important bivalve is the well known Solen or “razor‐fish,” varieties of which are common all over the globe. “These molluscs,” says Figuier, “live with their shells buried vertically in the sand, a short distance from the shore; the hole which they have hollowed, and which they never quit, sometimes attains as much as two yards in depth; by means of their foot, which is large, conical, swollen in the middle and pointed at its extremity, they raise themselves with great agility to the entrance of their burrow. They bury themselves rapidly, and disappear on the slightest approach of danger.