Xll CONTENTS. 



CHAPTEK XV. 



SPONGES. 



Animal Nature of Sponges Their remarkable Structure Their Skeleton Spicula 

 Sensibility and Spontaneous Movements Their Mode of Propagation Their 

 Importance in the Household of the Seas . . v , . . PAGE 112 



CHAPTEK XVI. 



SEA-ANEMONES AND LITHOPHYTES. 



Submarine Gardens Internal Structure of the Sea-anemones Tentacles 

 Urticating Organs Their remarkable Tenacity of Life Their Modes of 

 Locomotion Lithophytes Social Eepublicans Coral Islands , .116 



CHAPTER XVII. 



ACALEPEUE OR JELLY-FISHES. 



Medusae and Ehizostomata Their Internal Structure Their Mode of Progression 

 Alternation of Generations Ciliograde Jelly-fishes Their Wonderful Fishing 

 Apparatus Diphyes Agalma Physalus Velella Importance of the Acale- 

 phae in the Economy of the Ocean $" . , . . 125 



CHAPTER XVIII. 



ECHINODERMATA. 



Primeval Sea-stars Feather-stars Snake-stars Star-fishes Their Suckers and 

 Mode of Locomotion Their Skeleton Their Victims and their Enemies Sea- 

 Urchins Structure of their Shell Their Dental Apparatus Pedicellarise, or 

 Sea-Cucumbers Metamorphoses of the Echinodermata . . .132 



CHAPTER XIX. 



MOLLUSCA. 



The Flustrse or Sea-Mats Aviculari a Metamorphoses of the Flustrse Salpae 

 and Ascidise Botrylli Pyrosomata Bivalve Shellfish Free and Sessile 

 The Byssus The File of the Pholades Respiration of the Bivalve Shellfish 

 Their Nourishment Snails Their Masticatory Apparatus Their Cautious 

 Habits Pteropods Conical Appendages of the Clio's Head Its wonderful 

 Dental Apparatus Cuttlefish Sucking-disks The Onychoteuthis Number 

 and Importance of the Molluscs . .141 



CHAPTER XX. 



WORMS. 



Are they in reality so helpless as is commonly supposed ? Beauty of the Free 

 Marine Annelides Their Mode of Life Tubicolar Worms Leeches Earth- 

 worms Nemerta Gigantea Rotifera Their Complex Organisation and their 



Habits 166 



