LIST OF ILLUSTRATIONS xxi 



FIG. PAGE 



85. External form of various Sponges . .116 



86. Ascetta primordialis 117 



87. Diagram of canal-system of various Sponges 118 



88. Vertical Section of Spongilla 119 



89. Cells of ectoderm of Sponge .120 



90. Development of tri -radiate spicule 120 



91. Skeleton of various Sponges 121 



92. Various forms of Sponge spicules 123 



93. Pheronema carpenteri 124 



94. Larva of Clathrina blanca 125 



95. Development of Sycon raphanus 126 



96. Obelia 131 



97. ,, Vertical section of polype 133 



98. Nematocysts of Hydra 134 



99. Tentacle of Eucopella 135 



100. Obelia medusa 136 



101. Diagram of medusa 137 



102. Derivation of medusa from polype 138 



103. Projections of polype and medusa 139 



104. Development of zoophyte 140 



105. Bougainvillea ramosa . . . 144 



106. Various forms of Leptolinse 145 



107. Ceratella 146 



108. Hydra 147 



109. Protohydra leuckartii 148 



110. Various forms of leptoline Medusae 150 



111. Diagram illustrating formation of sporosac by degradation of 



medusa 152 



112. Early development of Eucope 153 



113. Two Trachymedusse . ... 154 



114. Two Narcomedusse 155 



115. ^Eginura, tentaculocyst 155 



116. Larva of ^Eginopsis 156 



117. Millepora alcicornis, skeleton . . 157 



118. Millepora, diagram of structure 158 



119. Stylaster sanguineus, skeleton 159 



120. Halistemma tergestinum 160 



121. Diagram of a Siphonophore 161 



122. Development of Halistemma 162 



123. Physalia 163 



124. Diphyes campanulata 164 



125. Porpita pacifica 165 



126. Graptolites 166 



127. Aurelia aurita, dorsal and ventral views . . . . . .168 



128. side view and vertical section 170 



129. ,, ,, portion of umbrella with tentaculocyst . . . 171 



130. Aurelia aurita, development 173 



131. Tessera princeps , 177 



