262 
THE OCEAN WORLD. 
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 singl 0 
orifice in the centre of the lower surface of the body, destitute of 
teeth, performing the functions both of mouth and anus. Be Blain- 
ville says that “ the liver is apparent and rather considerable in the 
star-fishes, forming bunches occupying the whole circumference of th 0 
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 h 0 ' 
portant metamorphoses. Immediately after birth, the young astern 0 
have a depressed and rounded body, with four club-shaped appendages 
or arms at their anterior extremity. When they are a little moi' e 
developed, papilla; may be observed on the upper surface, in fi 0fi 
radiating rows : after twelve days the fine rays begin to increase, and 
after eight days more two rows of feet, or tentacula, are develop e 
under each ray, which assist in the locomotion of the animal by 
alternate elongation and contraction, performing also the office 0 
suckers. Like most other zoophytes, they have the power of rep 00 ' 
ducing parts of their bodies which may have been accidentally 
destroved. 
Astebias, ob Stab-fishes. 
As to the animal which commonly and sometimes scientifically beaf s 
the name of Star-fish, in walking on the sea-shore at low tide, y ° 111 
eyes have often seen this strange creature half buried in the sand. B lS 
so regular and geometrical in its form that it has more the appearand 
of being the production of man’s hand than of a creation which breath eS 
and moves. The divine geometrician who created it never realised 9 
creature more regularly finished in shape, or more perfectly harmoi 00 ’ 1, 
in symmetry. 
