LIST OF ILLUSTRATIONS xxi 



KIG. PAOE 



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 forma 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. ^ginura, tentaculocyst . ... 155 



116. Larva of ^Eginopsis .... 156 



117. Millepora alcicomis, skeleton . . . ... 157 



118. Millepora, diagram of structure . 158 



119. Stylaster sanguineus, skeleton . 159 



120. Halistemma tergestinum. . ...... 160 



121. Diagram of a Siphon ophore . ...... 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 



