xvi COMPARATIVE ANATOMY 



PAGE 



B. Ontogeny of the Holothubioidea . 510 



C. Ontogeny of the Echinoidea 519 



D. Ontogeny of the Astekoidea 524 



E. Ontogeny of the Ophiueoidea . 532 



F. Ontogeny of the Crinoidea 533 



XXII. Phylogeny . 545 



Review of the most Important Literature . 551 



CHAPTER IX 



ENTEROPNEUSTA 



I. Outer Organisation . 562 



II. The Body' Epithelium , 563 



III. The Nervous System 564 



IV. The Sensory Organs 565 

 V. The Alimentary Canal . . 565 



VI. The Ccelomic Sacs and the Body Musculature . 571 



VII. The "Heart Vesicle" . . . 578 



VIII. The Limiting JIembranes, the Probosoidal Skeleton, and the 



Branchial Skeleton . . , 579 



IX. The Blood Vascular System 581 



X. The Gonads . 585 



XI. Ontogeny' 58g 



XII. Phylogeny' 591 



Literature 595 



Appendage to the Enteropneusta 

 I. Cephalodisous 



II. Rhabdopleura 



Literature 



Index 



596 



600 



602 



603 



