322 



THE POPULAR SCIENCE MONTHLY. 



which we will presently speak. The mouth is in the centre of the 

 under side, and beneath each ray there are a large number of locomotive 

 suckers. An eye is situated at the end of each ray ; and on the back, 

 near the junction of two arms, is a sort of water-filter called the madre- 

 poric body. 



As in all similar cases, the dried specimens give us only a partial 

 idea of the real starfishes, and those who have studied these animals in 

 museums only have little idea of the readiness with which they make 

 their way along the vertical and overhanging surfaces of rocks, and 

 into holes and narrow fissures. 



Starfishes are very voracious, and feed mainly on mollusks. They 

 are exceedingly destructive to oysters in many places, and thus come 

 in direct competition with man for the possession of this delicious 

 bivalve. Instead of swallowing their food as other animals do, they 

 turn the stomach out of the mouth and over the animal which they 

 wish to devour ! 



Starfishes have a wonderful power of reproducing lost parts. If 

 an arm is bitten oflf by a hungry fish, another grows in its place ; and 

 cases are known where all the arms but one have been detached, and 

 the remaining arm and central portion of the body have lived on and 

 reproduced all the destroyed parts. Examples of this may be seen 

 wherever starfishes are abundant. 



Starfishes are quite numerous in species, and vary greatly in form 

 and size. The ordinary kinds are only three or four inches across, others 

 a foot. 



In the same localities where we find true starfishes, we may confi- 

 dently expect to find the " serpent-stars " or serpent-tailed starfishes, 



so called because their arms taper 

 like a snake's tail. They are also 

 called "brittle-stars," because they 

 break so easily. 



Many visitors to the sea-shore 

 come away without seeing a single 

 living brittle-star, because the curi- 

 ous echinoderms which bear this 

 name hide under the sea-weeds, 

 and in the dark holes and crevices 

 among the rocks, and are, therefore, 

 found only by those who search 



carefully for them. 

 Fig. 23.— Serpent -Star (Oi)Ai<>pAoii«6e«4S, •^, .i j. • 



Lyman). The long, gently-tapering arms, 



starting out abruptly from a well- 

 defined disk, make the form of serpent-stars very distinct from that 

 of the Asteroidce or genuine sea-stars, already noticed. And, unlike 

 the true starfishes, they have no interambulacral plates, but a series 

 of large plates envelops the whole of each ray or arm, meeting in a 



