Many of the specimens of this division are placed on the top of the wall cases, being too large to be placed inside the cases. The Cartilaginous fishes here brought together include the varieties of the ray; torpedos; and sharks. At the western extremity of this room the visitor should terminate the onward course of his first visit, and, remembering that the table cases of the northern and eastern galleries through which he has passed, remain to be examined on his way back to the grand staircase, should begin to retrace his steps, confining his attention, as he returns, to the table cases placed in the central space of the rooms through which his way lies. He should now therefore face the east, and return, in the northern zoological gallery towards its eastern extremity. The table cases deposited in the room with the cartilaginous fish are covered with SPONGES of different kinds. It will be interesting to the visitor to know something of the natural history of the sponge. It has been ascertained, beyond a doubt, that the sponge is an animal that sucks in its food and excretes its superfluities; that certain of its pores imbibe, while others exude; and that according to the relative positions of the two distinct sets of pores, is the shape of the sponge determined. In a natural state, as it is found in the Mediterranean, the sponge is surrounded with a thick glutinous matter, which is its vital part; like coral, it is a zoophyte: it propagates in the same manner, and its life is indestructible till it is removed from its proper element, and the glutinous matter which makes its vitality has been boiled out of its pores, leaving the soft and beautiful skeletons, of which these cases contain many specimens. Here also are some old sponges preserved in flint. Having noticed these beautiful zoophytes, the visitor should proceed in an easterly direction into the room he recently quitted, to examine the table cases it contains. The first tables to which he should direct his attention here, are those in which a series of Crustacea or hard-coated animals are deposited. They are of Cuvier's order of animal life, known as the articulata, or animals whose bodies consist of a series of moveable joints. These are mostly inhabitants of the sea, and rank in the animal kingdom as the highest class of the Articulata, except the insects, who head the order. The tables upon which the Crustacea or SHELL FISH,