xii List of Illustrations. 



FlO. PAGE 



129. Nervous system in different Chsetopods . 166 



130. Anterior end of an Annelid 166 



131. Diagrammatic section through the sMn of a Chaetopod 168 



132. Anterior end of a Chatopod 168 



133. Diagrammatic sections of different Cihaetopods . . 168 



134. Diagram of the reproductive apparatus of an Earthworm. 171 



135. Larva of Nereis . 171 



136. Myrianida fasciata . . 172 



137. Digestive tract, etc., of a Leech 175 



138. Genital apparatus of a Leech . 176 



139. Peripatus . . 177 



140. A, B, diagrammatic longitudinal sections of a Polyzoon ; C Avioularia . 179 



141. Plumatella polymorpha 180 



142. Fresh-water Polyzoon 181 



143. Diagrammatic longitudinal section of a Brachiopod . 182 

 144 and 145. Larvae of Brachiopods ... . 183 



146. Section through a seta and the adjacent skin of an Arthropod 185 



147. The last four joints of an Arthropod limb . . . 186 



148. Longitudinal section through a joint of an Arthropod 186 



149. STervous system of Gammarus . . 187 



150. Examples of typical Crustacean limbs 189 



151. Limbs of different Crustacea . . 190 



152. Vascular system of the Lobster 191 



153. Nauplius of Penseus 192 



154. Brcmchipus vemalis. 194 



155. Apus pro&uctus 194 



156. Sida crystallina . 195 



157. Limulus polyphemus . 196 



158. Young Limulus ....... 197 



159. A Limulus, B Belinurus, C Eurypterus, D Dalmanites 198 



160. Stages in the development of Sao hirsuta . 198 



161. Gypris . 199 



162. Nauplius of an Ostracode . 199 



163. Cyclops 200 



164. Various parasitic Copepoda 202 



165. A, B, Penella sagitta, C Rerpyllobius arcticus 202 



166. Lepas . . 203 



167. Balanus 203 



168. Diagrammatic figures showing the transition from Lepas to Balanus . 204 



169. SaccuUna on the ventral side of the abdomen of a Shore-crab 207 



170. The appendages of a Lobster . . 208 



171. Nelalia Geoffroyi . . 210 



172. Thysanopus tricuspidatus 211 



173. Boreomysis megalops . 212 



174. Mysis-nauplius . . 212 



175. Diastylis neapolitana . . 213 



176. 1 Arga, 2-3 Cymothoa ..... 214 



177. 1 Cepon elegans, 2-3 Portvmion KossmoMni . 215 



178. Apseudes Latreillei .... . • 216 



