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 SPHJERIDIA AND 



THE PEDICELLARI^G . ... 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 COSLOM ........ 436 



A. THE BODY CAVITY . .... 437 



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



C. THE PERICESOPHAGEAL 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^EMAL 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 



