In this group, animals that are extremely unlike in appearance are associated together. Some like the Star-fish (Fig. 15, 23), have arms, radiating from a common centre; some like the Sea-urchin (Fig. 24), are globular and have no arms; and some there are which so resemble worms that they have even been classed as such.

All the animals of this Class are produced from ova or eggs, which, in some species at least, are objects of great maternal solicitude. This is evinced in a striking manner

by the Cribella, a Star-fish, which is found on our own shores. The mother, by bending the arms and the lower surface of her body, forms a receptacle, which in its uses may be compared to that of the pouch of the Opossum or Kangaroo. Here the ova are hatched; and for the space of eleven successive days during which this process is going on, the female Star-fish has been known to remain with the body bent up, as represented in the annexed figure (Fig. 20), and consequently without the power of taking nourishment during that period.

In Professor Edward Forbes' "History of British Starfishes," they are arranged in six families. The first of these divisions includes those animals which, in a fossil state, are known as stone-lilies." These beautiful animals were in former periods among the most numerous of the ocean's inhabitants; so numerous, that their skeletons

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constitute great tracts of the existing dry land (Fig. 22). Now they are of rare occurrence, and in European seas are represented by a species so small that it measures only about three quarters of an inch in length. In this state

Fig. 21.-POLYPE STATE OF THE
FEATHER-STAR (MAGNIFIED).

in fact a diminutive,

feathery looking star-
fish, mounted on a
stalk; and wonderful
are the changes it un-
dergoes. At a certain
period the little ani-
mal separates from
the stem, and swims
freely about. It gra-
dually increases in
size, is known as the
"Rosy Feather Star,"

and gives origin to a

race of descendants,

each of which, in its Fig. 22.-STONE LILY.

young state, looks like a plant or a coralline, and attains, when more mature, the free condition of the parent.

The second family consists of those Star-fishes which have a roundish central body, furnished with five long arms, not unlike the tails of serpents (Fig. 23). These are merely

Fig. 23.-STAR-FISII.

arms external to the body, and easily separated from it at the pleasure of the animal, from which circumstance the English name of "Brittle-stars" has been bestowed upon the tribe. Its members differ very much in size and appearance. Some of them measure as much as sixteen inches in diameter; others are so small, that a score or two of them might be displayed on an ordinary visiting-card. Professor Forbes, in speaking of a spine-covered species, remarks:— "Of all our native Brittle-stars, this is the most common and the most variable. It is also one of the handsomest, presenting every variety of variegation, and the most splendid displays of vivid hues arranged in beautiful patterns. It is

the most brittle of all Brittle-stars, separating itself into pieces with wonderful quickness and ease. Touch it, and

it flings away an arm; hold it, and in a moment not an arm remains attached to the body."

To the third family, the common Cross-fish or "Fivefingers" belongs. Each of its arms has deep grooves along its entire length, through which the animal can extend a multitude of little suckers, or tubular organs, which serve as feet to carry it along, and as arms to seize and master its prey. No one can rightly estimate the beauty and singularity of their mechanism, who has not seen them in action. Let any one, when opportunity offers, pick up from the beach one of these animals, which, as it lies upon the sand, left by the retiring waves, appears so incapable of movement, so utterly helpless and inanimate; let him place it in a large glass jar, filled with seawater. Slowly he perceives its arms expand to their full stretch, hundreds of feet are protruded, and each one, as if possessed of independent action, fixes itself to the vessel as the animal begins to march. The numerous suckers are soon all at work, some remaining fixed, while others change their position; and thus the Starfish, by an easy, equable, gliding motion, changes its place along the bottom, or climbs the smooth sides of the glass in which it is confined.

The members of the fourth family, that of the Sea-urchins, are furnished with spines; and, from the resemblance in this respect to the Hedgehog, the family takes its scientific

name (Echinidae) (Fig. 24). Here the arms have disappeared, and the form has become more or less rounded, according to the species. The spines do not grow from the shell," or, to use a more correct term, the integument, as thorns do on the branches of the common hawthorn. They

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are attached to little round projections or tubercles, and move upon them in the manner of so many ball-and-socket joints. The Sea-urchins are also furnished with suckers, similar to those described in the Star-fishes; and by the joint action of their spines and suckers, they can move in

*Fig. 24. The spines have been removed from the left side for the purpose of exhibiting the arrangement of the pieces composing the "shell" underneath.