dv COMPARATIVE ANATOMY 



PAGE 



{/) The Water Pores 377 



6. Blastoidea 379 

 (a) The Ambulacral Skeleton 379 

 (S) The Stem 384 



7. Cystidea 384 



D. The Spixes and their Derivatives — The SPHiERiDiA and 



the Pedioellarke . . 387 



E. The Masticatory Apparatus of the Eohinoidea. (Aris- 



totle's Lantern) . . 400 



F. The Calcareous Ring ob- the Holothurioidea 403 



G. Further Deposits op 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 Peeicesophageal 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 443 



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 . 46I 



