10 CONTENTS 



CHAPTER VIII PAGE 



Metazoan Organization __________----- 103 



General Characteristics, 103; Cellular Differentiation, 104; Cellular 

 Organization, 105; Development of Sexual Reproduction, 111; Meta- 

 zoan and Ontogeny, 113. 



CHAPTER IX 

 Phylum Porifera _____-___-------- 119 



Sponges, 119; Classification, 120; Fresh-Water Sponges, 121; The 

 Simple Sponge, 122; Habitat and Behavior, 122; External Anatomy, 

 123; Internal Anatomy, 124; Metabolism, 127; Reproduction and 

 Life History, 127; Economic Relations, 129; Phylogenetic Advances 

 of Sponges When Compared With Protozoa, 129. 



CHAPTER X 

 Phylum Coelenterata ______---------- 130 



Classification of the Phylum, 131 ; Hydra, 144 ; Habitat and Behavior, 

 144; External Anatomy, 146; Internal Anatomy, 148; Metabolism, 

 151; The Nervous System and Nervous Conduction, 153; Reproduc- 

 tion and Life Cycle, 153; Regeneration, 156; Economic Relations of 

 the Phylum, 156 ; Phylogenetic Advances of Coelenterates, 156. 



CHAPTER XI 



Phylum Ctenophora ______---------- 157 



Habitat and Behavior, 157; Anatomy, 157. 



CHAPTER XII 



Phylum Platyhelminthes ____---------- 160 



Classification, 160; Planaria, 163; Habitat and Behavior, 163; Ex- 

 ternal Anatomy, 165; Internal Anatomy, 165; Metabolism, 170; Re- 

 production and Life History, 170; Regeneration, 173; Economic Rela- 

 tions of the Phylum, 174; Phylogenetic Advances of Platyhelminthes, 



174. 



CHAPTER XIII 



Phylum Nemathelminthes _____---------175 



Classification, 175; Asearis, A Representative Roundworm, 179; Habi- 

 tat and Behavior, 179; External Anatomy, 179; Internal Anatomy, 

 181; Reproduction and the Life Cycle, 183; Relations to Man, 183. 



CHAPTER XIV 



Molluscoida, Trochelminthes, and Chaetoonatha ___---_ 184 

 Molluscoida, 184; Bugula, 184; Trochelminthes, 188. 



CHAPTER XV 



Phylum Annelida (By J. Teague Self) ___-__----- 194 

 Earthworm, 199; Internal Anatomy, 201; Reproductive Organs, 202; 

 Digestive System, 203; Circulatory System, 205; Respiratory System, 



