LIST OF ILLUSTRATIONS xxi 



FIG. PAGE 



82. Sycon gelatinosuni, pore-membrane .... . . 109 



83. ,, apopyle 109 



84. External form of various Sponges 115 



85. Ascetta primordialis 116 



86. Diagrams of canal-system of various Sponges . . . . ' . 117 



87. Vertical Section of Spongilla 118 



88. Cells of ectoderm of Sponge 119 



89. Development of tri-radiate spicule 120 



90. Skeleton of various Sponges 121 



91. Various forms of Sponge spicules ... 122 



92. Pheronema Carpenteri 123 



93. Larva of Clathrina blanca 124 



94. Development of Sycon raphanus . . . . . . 125 



95. Obelia 1 ... . .- . .130 



96. ,, Vertical section of polype ........ . . 132 



97. Nematocysts of Hydra . . ...... . . . 133 



98. Tentacle of Eucopella 134 



99. Obelia, medusa 135 



100. Diagram of medusa . . 136 



101. Derivation of medusa from polype 137 



102. Projections of polype and medusa 138 



103. Development of zoophyte ... . . . . . . . 140 



104. Bougainvillea ramosa . ... ; . . . . . . 144 



105. Various forms of Leptolinre . . . . . . . . . 145 



106. Ceratella . , . . . . . . . . . 146 



107. Hydra . . , . . ... . . .147 



108. Protohydra leuckartii ...... ... . . . 148 



109. Various forms of leptoline Medusse . . . . . . .150 



110. Diagram illustrating formation of sporosac by degeneration of 



medusa . . . . . . .151 



111. Early development of Eucope . . . . ... . . . 152 



112. Two Trachymeduste 154 



113. Two Narcomedusse 154 



114. JEginura, tentaculocyst . '. . . 155 



115. Larva of ^Eginopsis . . . . , . 156 



116. Millepora alcicornis, skeleton . . . . . . 157 



117. Millepora, diagram of structure 158 



118. Stylaster sanguineus, skeleton . . . 159 



119. Halistemma tergestinum . .160 



120. Diagram of a Siphonophore . . 162 



121. Development of Halistemma 163 



122. Physalia 164 



123. Diphyes campanula^ . ..;... . . . . 165 



124. Porpita pacifica . . .,'.... 166 



125. Graptolites . . . 167 



126. Aurelia aurita, dorsal and ventral views 169 



127. ,, ,, side view and vertical section 171 



128. ,, ,, portion of umbrella with tentaculocyst . . .172 



