xiv COMPARATIVE ANATOMY 



PAGE 



(/) THE WATER PORES . . 377 



6. BLASTOIDEA ... ... 379 



(a) THE AMBULACRAL SKELETON .... 379 



(6) THE STEM . 384 



7. CYSTIDEA ....... 384 



D. THE SPINES AND THEIR DERIVATIVES THE SPH^RIDIA AND 



THE PEDICELLARI.E . . ... 387 



E. THE MASTICATORY APPARATUS OF THE ECHINOIDEA. (Aris- 



totle's Lantern) ....... 400 



F. THE CALCAREOUS RING OF THE HOLOTHURIOIDEA . . 403 



G. FURTHER DEPOSITS OF CALCAREOUS MATTER . . . 405 

 H. CONCLUDING REMARKS ON THE SKELETON . . . 405 



III. THE OUTER MORPHOLOGY OF THE HOLOTHURIOIDEA . . 406 



IV. THE POSITION AND ARRANGEMENT OF THE MOST IMPORTANT 



ORGANS IN THE RADII ...... 409 



V. THE INTEGUMENT . ..... 414 



VI. THE WATER VASCULAR SYSTEM . . 416 



A. THE MADREPORITE AND STONE CANAL . . . .417 



B. THE WATER VASCULAR RING ..... 423 



C. THE RADIAL CANALS, THE CANALS OF THE TENTACLES AND 



TUBE-FEET, ETC. ....... 426 



D. THE AMBULACRAL APPENDAGES . ... 431 



VII. THE CCELOM . 436 



A. THE BODY CAVITY . . . . 437 



B. THE BRACHIAL CAVITIES ...... 440 



C. THE PERKESOPHAGEAL SINUS ..... 441 



D. THE PERIANAL SINUS ...... 444 



E. THE AXIAL SINUS . .... 444 



F. THE AXIAL ORGAN . . .445 



G. THE CHAMBERED SINUS . . 446 



VIII. THE PSEUDOH^MAL SYSTEM . . 447 



IX. THE EPINEURAL SYSTEM . . 448 



X. THE BLOOD VASCULAR OR LACUNAR SYSTEM . . 449 



XI. THE NERVOUS SYSTEM . . . . 453 



A. THE SUPERFICIAL ORAL SYSTEM . . . 454 



B. THE DEEPER ORAL NERVOUS SYSTEM . . . 458 



C. THE APICAL OR ABORAL NERVOUS SYSTEM 459 



D. THE THIRD NERVOUS SYSTEM OF THE CRINOIDEA . . 461 



