. Éléments de zoologie, ou, histoire naturelle des animaux / éd. par D.M. Reese. Zoologie. echinida-l'ordre echinus. 493 Il a vu sur la bordure interne du mois ; et leurs points peuvent même être en saillie au-delà de la bouche, de manière à se saisir de proies portés à leur attention par les pieds tubulaires. Par l'action des dents, la nourriture est la masse avant qu'elle passe dans le tube intestinal, qui est ici d'une longueur considérable, et prend un couple de tours autour de la shell avant sa résiliation. La deuxième ronde de l'orifice de la coquille sont éliminés l'ovaria, qui sont très largement distendu par les oeufs à certains se

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. Elements of zoology, or, Natural history of animals / ed. by D.M. Reese. Zoology. order echinida—the echinus. 493 he seen on the inner margin of the month; and their points can even be protruded beyond the mouth, so as to lay hold of prey brought to them by the long tubular feet. By the action of the teeth, the food is ground down before it passes into the intestinal tube, which is here of considerable length, and takes a couple of turns round the shell before its termination. Round the second orifice of the shell are disposed the ovaria, which are very largely distended with eggs at some seasons, and are eaten under the name of the roe of the sea-egg. 861. It is the exterior organization of these animals, how- ever, that presents us with the greatest sources of interest. On looking at the Echinida in their living state, we see that most of them are covered with spines of considerable size, instead of with such small prickles as the Asterias bears. Moreover, these spines are seen to be movable at their bases, and this power of motion is due to their peculiar connection with the shell. Each spine is spread, at its root, into a cup-like form, and the hollow of this cup fits upon a little knob or tubercle projecting from the surface of the shell, so that a complete ball- and-socket joint is formed. The spines are connected to each other, and held on the shell, by the skin which covers the latter, and which is attached around their roots; and it is by the con- tractions of this skin that they are moved. In the Cidaris, which may perhaps be regarded as the highest form of the Echinida, the spines are generally few in number, but of large size ; their tubercles are very prominent; and they are united by an elastic ligament which is imbedded in the top of each knob, and the hollow of each cup, like the round liga- ment of the hip-joint in man. Thus, they are firmly held together, and great freedom of motion is allowed. 862. On looking at the exterior of the shell of an

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