■98 



ZOOLOGY. 



s, nervous cord to the eye at the end of the ray. It may be 

 discovered by pressing apart the ambulacral feet along the 

 median line of each arm. Fine nerves are sent off to each 

 sucker, passing through the opening between the calcareous 

 plates and extending to each ampulla, thus controlling the 

 movements of the ambulacral feet. 



Fig. ^. — ^Longitadina] section thmngh tlie body and one arm of Asierias vulgaHs. 

 «j, mouth; s, stomacli; I, lobe of Btomacli extending into the arm; a, anns ; nr, ner- 

 Tons ring ; n, radial nerve ; -ztt, water-vascolar ring, sending a ladial vessel (c) into the 

 arm ; mp, madreporic plate ; t , stone canal : A, haemal canal ; ov, oviduct ; o, ovary ; 

 ■OTn, ampnlls, the ambulacra! feet projecting below; d, cceca or liver. — Drawn by 

 A. F. Gray, under author's direction. 



The mouth (Fig. 62, m) is capacious, opening by a short 

 «sophagus into a capacious stomach (Fig. 0'^. s) with thin 

 distensible walls, and sending a long lobe or sac (Fig. 6-i, I) 

 into the base of each arm ; each sac is bound down by two 

 Tetractor muscles attached to the median ridge lying be- 

 tween the two rows of water-sacs (ampullse, see also Fig. 63). 



Fi^. 63.— Diagram of the cross-section of an arm. A, of Asierias rabens : B, of 

 Ophtura texturata ; n. ambulacral feet ; j/, ampullae ; t. dermal tentacles ; n, nen-otia 

 «ords ; w, ambulacra] plates ; m, muscles ; a, ambulacral vein ; 6, ventral plate ; c, lat- 

 ■eral plates; d, dorsal plate : h, calcified portion of the mtegnment.^After W. Lan<»e 

 from Gegenbaur. * 



The stomach ends in a short intestine, the limits between 

 the two not distinctly seen. The intestine suddenly con- 

 tracts and ends in a minute rectum situated in an angle 

 between two of five fleshy ridges radiating from the centra 



