CONTENTS xv 



B. RADIALLY SYMMETRICAL ANIMALS. 



V. FIVE-EAYED ANIMALS WITH CALCAREOUS DEPOSITS IN THE SKIN, 

 WHICH FREQUENTLY FORM PROJECTING SPINES ; WITH A WATER- 

 VASCULAR SYSTEM, AND WITH BODY CAVITY, INTESTINE, AND 

 BLOODVESSELS. 



PAGE 



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



(a) FREE, STAR-SHAPED, OR FIVE-CORNERED, THE ARMS USUALLY PASSING 



GRADUALLY INTO THE DlSC-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 BAYED ANIMALS WITH AN INTERNAL CAVITY 



WHICH REPRESENTS BODY CAVITY, INTESTINE, AND BLOODVESSELS. 



VI. Phylum : Ccelenterata ... ... ... ... ... ... 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 



C. 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 



