Birds and Nature, Vol. 12 No. 1 [June 1902] / Illustrated by Color Photography

by Various

No one could tell, should they try:

For a chestnut heifer is Cherry,

And a country milkmaid, I.

—Elizabeth Walling.

STARFISHES.
FROM COL. CHI. ACAD. SCIENCES.

First row: Asterias ochracea (California.) Asterias vulgaris (Massachusetts.) Second row: Asterias forbesii (Rhode Island.) Asterias forbesii (Massachusetts.) Third row: Nidorella armata (Panama.) Asterina miniata (California.)

STARFISHES.

One of the most unique and interesting branches of the animal kingdom is that division called by scientists Echinodermata, comprising animals familiarly known as starfishes, sea urchins, sand dollars and sea cucumbers. So far as is known no member of this group of animals has ever ventured on land or into fresh water. All are inhabitants of the ocean and are found from the tide-washed shore to the abysses of the sea.

The present article deals with the true starfishes (Asteroidea) and a good idea of the general structure may be gained by a careful examination of a specimen of the common five-finger (Asterias vulgaris) so common on the New England coast. It is made up of a central disk or body, from which extend five rays or arms, whence the name starfish. The animal is protected by a hard framework or skeleton, composed of many limestone plates, attached by a tough membrane and covered with a skin. Between these plates there are many small openings through which the water enters the body cavity. The plates are armed with numerous spines, attached by a ball and socket joint. Some of these spines bear little pincer-like organs called pedicellariæ, which are capable of considerable movement. Many of these little organs are arranged in groups about the spines, which swell at the point of attachment to the surface of the starfish, thus forming a shelf or base, around which these organs arrange themselves in the form of a wreath, the spine projecting high above the center. The exact function of these little organs is not known, although they have been seen to catch small animals, such as crustacea, and this is probably one of their duties.