STAR-FISH. 7 1 3 



fitted pieces, so united as to be flexible, and around the mouth and in 

 strong frame-work. The star-fish has no teeth, but manages to dispose of a 

 vast quantity of matter, which if left alone would be injurious in decay. 



Thus Nature has provided a shore scavenger to devour what would be 

 harmful, just as the vulture on land eats the carrion. Besides this kind of 

 refuse food, the star-fish eats small crustaceans, and oysters fall victims to him. 

 By embracing the shell the star-fish manages to insert itself, and if it cannot 

 bring the oyster out to its mouth, it will quietly turn out its mouth into the 

 oyster-shell, and save the bivalve any trouble in the matter. Some writers 

 declare that the star-fish stupefies or poisons its victim, and then the shell 

 opens. These asteroidea can reproduce a ray that has been injured or cut 

 off, or they can break themselves to pieces if caught. 



The brittle stars and feather stars appertain to the order of the 

 Ophiuroida or " serpent-armed," because the rays are more flexible and thin 

 than the common star-fish. But they differ very much from the star-fish in 

 the arrangement, as well as in the shape of their arms. The former 

 possesses rays which form an appendage 

 of the stomach and enclose it. In the 

 brittle stars the rays are limbs, and could 

 be detached without taking the life of 

 the animal, except in so far as to de- 

 prive it of means to obtain its food. 

 The body is quite independent of the 

 rays, the mouth occupying the centre, 

 and is surrounded by minute suckers. 

 The stars are much more flexible than 

 the star-fishes, their rays are longer, 



and Serve either as feet, fins, tentacles, Fig. 8 3 9.-Spine of echinus (A, natural size; u, a section 



magnified). 



or arms. 



The crinoids also belong to the Echinodermata, and resemble plants 

 more than star-fish. They are fixed upon a stalk like a flower, growing 

 upright from the sea-bottom, and the body is called a calyx > which is com- 

 posed of a ventral and dorsal surface. The arms branch out from the calyx, 

 just as a small tree does, and if we can imagine one of the last planted trees 

 on the Thames embankment reduced to half a finger's length or less, we 

 have a sort of idea of the crinoid " in the rough." 



A polype supported on a stem branching out in feathery, grassy-looking 

 arms represents the Encrinites, the remains of which arc found as fossils. 

 The arms of the crinoids are subdivided, and quite a flowery crown may in 

 time result. The animal obtains its food by the motion of cilia. The stem 

 and the branches are jointed, as it were, and capable of flexible movement 

 in any direction. The crinoids remain stationary during their lives. 



The care taken by the star-fish of its young is remarkable. It carries 

 the eggs about in its suckers and with great caution. The young remain 

 attached to the mother until they are able to go about alone, and then the 



