The organization of the Echinodermata is the most perfect of all the zoophytes, serving as a transition between them and animals of more complicated frame. They have a digestive and vascular system, and a muscular system is almost always present; in short, they have internal or external respiratory organs, and a rudimentary nervous system has been detected in many of the species. The nutritive system is very simple, presenting in most of the family a single orifice in the centre of the lower surface of the body, destitute of teeth, performing the functions both of mouth and anus. De Blainville says that "the liver is apparent and rather considerable in the star-fishes, forming bunches occupying the whole circumference of the stomach, and extending to the cavities of the appendages where these exist." The mouth and gullet is admirably adapted for securing the testaceous mollusks and other substances on which they feed. Reproduction in the Echinodermata appears to be monoecious. Ovaries are, as far as is known, the only organs of generation. They vary in number in different species. The sexes are usually separate: the young are produced by eggs, the embryo of which undergo important metamorphoses. Immediately after birth, the young asteriæ have a depressed and rounded body, with four club-shaped appendages or arms at their anterior extremity. When they are a little more developed, papillæ may be observed on the upper surface, in fine radiating rows: after twelve days the fine rays begin to increase, and after eight days more two rows of feet, or tentacula, are developed under each ray, which assist in the locomotion of the animal by alternate elongation and contraction, performing also the office of suckers. Like most other zoophytes, they have the power of reproducing parts of their bodies which may have been accidentally destroyed. ASTERIAS, OR STAR-FISHES. As to the animal which commonly and sometimes scientifically bears the name of Star-fish, in walking on the sea-shore at low tide, your eyes have often seen this strange creature half buried in the sand. It is so regular and geometrical in its form that it has more the appearance of being the production of man's hand than of a creation which breathes and moves. The Divine Geometrician who created it never realised a creature more regularly finished in shape, or more perfectly harmonious in symmetry.