274 THE OCEAN WORLD. 



cylindrical, and present a series of rays striated upon their articulated 

 faces. In Pentacrinus they are prismatic and pentagonal ; that is, they 

 present five projecting angles, and on their articulated face a star with 

 five branches, or, hetter still, a rose with five petals. At the base of 

 the stem of this animal-plant, in many of the Crinoidae, we find a sort 

 of spreading root, which is implanted in the rocks, and is capable of 

 growing by itself, of nourishing the stem, and of producing new ones. 



The root and stem of the fixed encrinites seem to indicate that the 

 animal can only live with the head erect. Their normal condition is 

 thus quite different from that of any other of the Echinoderms, 

 almost all of which keep their mouths invariably directed downwards. 



The Medusae heads are chiefly found on rocky beds, or in the midst 

 of banks of corals, at great depths. There, firmly fixed by their 

 roots, their long stems raise themselves vertically ; then, with expanded 

 calyx and long-spreading arms, they wait for the prey which passes 

 within their reach in order to seize it. 



The Pentacrinus caput Medusse have, as we have said, been fished 

 up from great depths in the Antilles. Its very small calyx is borne 

 upon a stem of from eighteen to twenty inches in height, terminating 

 in long movable arms, the internal surface of which bears its tentacles 

 in a groove. In the middle of the arms is a mouth, and at the side 

 the orifice for the expulsion of the digested residuum. 



In the Medusae head and European Pentacrine (P. Europasus, 

 Fig. 108), the presence of a digestive apparatus has been distinctly 

 traced. It is a sort of irregular sac, with a central mouth on the 

 upper surface, and another orifice situated at a little distance from the 

 mouth, and evidently intended as an outlet for the products of diges- 

 tion. The arms of these creatures, which are spreading or folded up 

 according to their wants, are provided with fleshy tentacula, which, 

 serving at once as organs of absorption and as vibratile cilia, are at the 

 same time organs of respiration. Such are these curious beings : they 

 occupy a sort of middle or transition state between animals permanently 

 fixed to some spot and those capable of motion, representing in our 

 own times the last -remains of extinct generations. Every type of the 

 Crinoidse furnished with arms presents incontestable evidence of their 

 mode of reproduction or redintegration that is, of the power of re- 

 storing those parts of the body broken or destroyed by accident ; but 

 as we have already drawn the attention of the reader to this strange 



