viii CONTEXTS 



SECTION V 



PHYLUM PLATYHELMINTHES 129 



I. The Trematoda 129 



II. The Turhellaria 137 



III. The Cestoda 138 



IV. The Nemertinea 145 



SECTION VI 



NEMATHELMINTHES 149 



SECTION VII 



PHYLUM ECHINODERMATA 157 



I. The Asteroidea 157 



II. The Ophiuroidea 169 



III. The Echinoidea 170 



IV. The Holothuroidea 173 



V. The Crinoidea 1 74 



SECTION VIII 



ROTIFERA, POLYZOA AND BRACHIOPODA 178 



I. The Eotifera 178 



II. The Polyzoa 181 



III. The Brachiopoda 184 



SECTION IX 



PHYLUM ANNULATA 188 



I. The Chaetopoda . . i8g 



II. The Hirudinea 203 



