LIST OF ILLUSTRATION. xiii 



FIG. PAGE 



76. Diagrams of types of Alcyonaria (Hickson) . . . 161 



77. Diagram of a gymnoblastic Hydromedusa (Allman) . . 162 



78. Graptolites . . . . . . . . .163 



79. Graptolites . . . . . . . . .164 



80. A medusoid with hints of Ctenophore structure . . . 165 



81. Commensalism of sea-anemones and hermit-crab . . 167 



82. Diagrammatic figure of a simple Turbellarian . . . 172 



83. Diagrammatic figure of part of the structure of a simple 



Turbellarian . . . . . . . .172 



84. Structure of liver fluke (Sommer) . . . . .174 



85. Reproductive organs of liver fluke (Sommer) . . . 175 



86. Life history of liver fluke (Thomas) ..... 177 



87. Diagram of reproductive organs in Cestode joint (Leuckart) 181 



88. Life history of T^nia sol i inn (Leuckart) . . . .182 



89. Diagrammatic longitudinal section of a Nemertean (Atnfhi- 



porus lactifloreus} (M'Intosh) . . . . .185 



90. Transverse section of the Nemertean Drepanopkorus lafiis 



(Burger) 186 



91. Transverse section of a simple Xemertean (Canne/la) 



(Burger) 187 



92. Illustrating the structure of a Xematode (O.\yitris) (Galeb) . 191 



93. Trichina in muscle, about to be encapsuled (Leuckart) . 194 



94. Trichinae in muscle, encapsuled (Leuckart) . . .194 



95. Earthworm- . . . . . . . . .198 



96. Anterior region of earthworm (Hering) .... 200 



97. Transverse section of earthworm (Claparede) . . . 203 



98. Reproductive organs of earthworm (Hering) . . . 205 



99. Stages in the development of earthworm (Wilson) . . 207 



100. Arcnicola marina . . . . . . . .211 



101. Anterior part of nervous system in Arenicola (Vogt and Yung) 212 



102. Dissection of lob-worm from dorsal surface . . . .213 



103. Cross-section of Arcnicola (Cosmovici) . . . .214 



104. Development of /' \\,ordins (Fraipont) .... 217 



105. Parapodium of " Heteronereis " of Nereis pelagica (Ehlers). 219 



1 06. Free-living Polychaete (Nereis ciilfrifera) . . . .221 



107. Transverse section of leech (Bourne) ..... 226 



108. Alimentary system of leech (Mojoin-Tandon) . . 227 



109. Dissection of leech (Bourne) ...... 228 



no. A nephridium of leech (Bourne) ..... 229 



111. Development of Sagitta (Hertwig) ..... 233 



112. Actinotrocha or larva of Phoronis (Masterman) . . . 236 



113. Interior of Brachiopod shell, showing calcareous support 



for the "arms'" (Davidson) ..... 237 



114. Pluteus larva of Ophiuroid, with rudiment of adult (Johannes 



Miiller) ......... 240 



115. Star-fish .......... 243 



1 1 6. Alimentary system of star-fish (Miiller and Troschel) . . 244 



117. Diagrammatic cross-section of star-fish arm (Ludwig) . . 246 



1 1 8. Ventral surface of disc of an Ophiuroid (Ophiothrix fragilis] 



(Gegenbaur) ........ 248 



