CONTENTS xi 



XVI. -BRANCH PORIFERA: THE SPONGES. 



EXAMPLE : THE FRESH-WATER SPONGE (SPONGILLA SP.) [Laboratory 

 exercise], 84. 



EXAMPLE: A CALCAREOUS OCEAN-SPONGE (GRANTIA SP.) [Laboratory 

 exercise], 85. 



EXAMPLE: A COMMERCIAL SPONGE [Laboratory exercise], 86. 



OTHER SPONGES. 



Form and size, 87. Skeleton, 88. Structure of body, 88. Feeding 

 habits, 88. Development and life-history, 89. The sponges of commerce, 

 90. Classification, 91. 



XVII. -BRANCH CCELENTERATA: THE POLYPS, SEA- 

 ANEMONES, CORALS, AND JELLYFISHES. 



POLYPS, SEA-ANEMONES, CORALS, AND JELLYFISHES. 



General form and organization of body, 93. Structure, 94. Skeleton, 

 95. Development and life-history, 95. Classification, 96. The polyps, 

 colonial jellyfishes, etc. (Hydrozoa), 97. The large jellyfishes, etc. 

 (Scyphozoa), 101. The sea-anemones and corals (Actinozoa), 102. The 

 Ctenophora, 107. 



XVIII. BRANCH ECHINODERMATA : THE STARFISHES, SEA- 

 URCHINS, SEA CUCUMBERS, ETC. 



EXAMPLE : STARFISH (ASTERIAS SP.) [Laboratory exercise]. External 

 structure. 108. Internal structure, no. Life-history and habits, 113. 



EXAMPLE : SEA-URCHIN (STRONGYLOCENTRUS SP.) [Laboratory exercise]. 

 External structure, 113. 



OTHER STARFISHES, SEA-URCHINS, SEA CUCUMBERS, ETC. 



Shape and organization of body, 116. Structure and organs, 117. De- 

 velopment and life-history. 119. Classification, 120. Starfishes (Asteroi- 

 dea), 121. Brittle stars (Ophiuroidea), 122. Sea-urchins (Echinoidea). 

 123. Sea-cucumbers (Holothuroidea), 124. Feather-stars (Crinoidea), 125. 



XIX. BRANCH VERMES: THE WORMS. 



EXAMPLE: THE EARTHWORM ILUMBRICUS SP.) [Laboratory exercise] 



External structure, 127. internal structure, 129. Life-history and habits, 



133 



OTHER WORMS. 



Classification, 135. Earthworms and leeches (Oligochaetae , 136. Flat 

 worms (Platyhelminlhes). 137. Round worms (Nemathelminthes), 140. 

 Wheel-animalcules (Rotifera), 142. 



