Polype of Alcyonidium elegans 120 125. Spicula of Alcyonium digitatum 121 126. Red coral branch 126 127. Red coral greatly magnified 127 128. Tubipora musica 130 129. Actinian polype 131 130. Lobophylla angulosa 135 131. Nervous system of Leech 151 132. Foot of Naïs 152 133. Terebella conchilega 154 134. Pushing poles of Serpula 155 135. Foot of a Polynoë 160 136. Brachionus pala 163 137. Common Rotifer 167 138. Section of shell of Echinus 177 139. Sucker-plate of Sea-Egg 179 140. Section of a sucker-plate 179 141. Spine of Echinus miliaris 181 142. Pluteus of the Echinus 181 143. Larvæ of Echinus in various stages of development 182 144. Skeleton of Synapta 185 145. Wheel-like plates of Chirodota violacea 186 146. Ear of Crab 191 147. Section of a Crab 193 148. Young of Carcinus mœnas in various stages of development 195 149. Lucifer, a stomapod crustacean 200 150. Female Cyclops 205 151. Cypris 207 152. Section of Daphnia pulex 208 153. Balanus culcatus 213 154. Tentacles or feet of the Balanus 214 155. Section of Lepas anatifera 215 156. Development of Balanus balanoïdes 216 157. Lepas 217 158. Cells of Lepraliæ 219 159. Cellularia ciliata and Bugula avicularia 220 160. Magnified group of Perophora 222 161. Highly magnified Perophora 223 162. Ascidia virginea 225 163. Salpa maxima 227 164. Young of Salpa zonaria 227 165.