STARFISHES. 239 



These tubes are seen in Figure 468, which shows the 

 upper part of the Starfish, three of the rays being 

 sHghtly turned backward. The mouth is on the under 

 side in the center, and there is an eye, or eye-spot, 

 at the end of each ray. By means of the ambu- 

 lacral tubes Starfishes move slowly but surely over 

 the rocks and all kinds of surfaces, and they can cling 

 to the rocks so firmly that they are often removed with 

 difficulty, and will sometimes even allow their ambu- 

 lacra to be pulled off rather than let go their hold- 

 Their covering is not solid as in the Sea Urchins, but 

 is composed of movable plates, so that these animals 

 are able to bend themselves in every direction, and 

 thus work their way into holes and fissures in rocks 

 where we should hardly expect to find them. Star- 

 fishes feed upon moUusks and other marine animals, 

 and when they feed they turn the stomach out of the 

 mouth and over the food to be devoured. A curious 

 spot is seen on the back near the junction of two of 

 the arms. This is the madreporic body described in 

 speaking of the Sea Urchins. It is a sort of minute 

 sieve, and forms an entrance to a series of internal 

 water-tubes, some of them connecting with the loco- 

 motive suckers and supplying them with water. Water 

 is also admitted into the body through minute pores 

 which cover the whole surface of the animal. Star- 

 fishes often lose one or more of their arms, or rays, 

 by being dashed against the rocks by the waves, 

 or the arm is bitten off by a fish. In all such 

 cases a new one sprouts out in the place of the old 

 one, and specimens may be found showing such new 

 rays in all stages, from those that are just sprouting to 

 those that have nearly reached their full growth. 



