STAR-FISHES. 



35 



r, that encircles the mouth ; here it flows into tubes that 

 branch into each ray, then into numerous sacs, or am- 

 pullae, v v, that have long extensions provided with suck- 

 ers. By the contraction of the sacs, water fills the exten- 

 sions that penetrate the four rows of holes, and they ap- 

 pear as feet, suckers, or locomotive organs, //. 



Class I. CRINOIDS (Lily-form). 



Eight living genera of these forms are known. One 

 of the most beautiful, the Pentacrinus, is found in deep 

 water off the West In- 

 dia Islands. They may 

 be described as inverted 

 star-fishes growing on 

 stems. Some are always 

 fastened to the bottom 

 (Fig. 31), while others 

 break off when attaining 

 a mature growth and 

 lead a wandering life, 

 as the Antedon. In the 

 Pentacrinus the stem is 

 about a foot long, resem- 

 bling pentagonal but- 

 tons piled one upon 

 another, sending off at intervals short whorls of branches 

 that are jointed in a similar way. The stem is rooted in 

 the mud, while the animal is cup- shaped, presenting the 

 appearance of a bunch of rich, waving plumes. These 

 are the arms, arranged about the mouth, closing over it, 

 or spreading out at will. The Crinoid (Antedon) is found 

 in the Gulf of Maine. They multiply by eggs, that pass 

 through several complex changes before assuming the 

 parent form. 



FIG. 32. Sand-star. 



