CONTENTS xv 



B. EADIALLY SYMMETRICAL ANIMALS. 



V. Five-rayed Animals with Calcareous Deposits in the Skin, 

 which frequently form projecting spines ; with a water- 

 vascular System, and with Body Cavity, Intestine, and 

 Bloodvessels. 



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V. Phylum : Echinodermata ... ... ... ... ... ... 459 



(a) Free, Star-shaped, or Five-cornered, the Arms usually passing 

 gradually into the Disc-shaped Body. 



Class I.: Star-Fishes ... ... ... ... ... ... ... 459 



(6) Free, Star-shaped, Arms in Most Cases definitely articulated 

 to the Disc-shaped Body. 



Class II. : Brittle Stars ... ... ... ... ... ... 463 



(c) Fixed by a Stalk either throughout Life or in the Young Stages. 

 Class III.: Feather Stars ... ... ... ... ... ... 463 



(d) Without Arms, Spherical, Heart-shaped or Disc-shaped. 



Class IV. : Sea-Urchins ... ... ... ... ... ... 464 



(e) Cylindrical in Shape. 



Class V. : Sea-Cucumbers ... ... ... ... ... ... 464 



VI. Four or Six Eayed Animals with an Internal Cavity 

 which represents Body Cavity, Intestine, and Bloodvessels. 



VI. Phylum : Coelenterata ... ... ... ... ... ... 465 



(a) Form either that of Jelly-Fish (Medusa) or Polyp, without 

 Gullet and without Partitions in the Body Cavity. 



Class I: : Jelly-Fishes and Hydroids ... ... ... ... ... 469 



Order I.: Lobed Jelly-Fishes ... ... ... ... ... 469 



„ II.: Velate Jelly-Fishes and Hydroid Polyps ... ... 471 



(6) With Gullet, and Partitions in the Body Cavity. 

 Class II.: Corals and Sea- Anemones ... ... ... ... ... 473 



0. ASYMMETRICAL ANIMALS. 



VII. Body asymmetrical, consisting of a Cellular Mass usually 

 containing spicules, and traversed by a system of canals and 

 Ciliated Chambers. 



VII. Phylum: Porifera 476 



