LIST OF ILLUSTRATIONS XVll 



riG. PAGE 



127. Transverse section of the Nemertine Drepanophorus latus 



— after Biirger . . . • • .232 



128. Transverse section of a simple Nemertine {Carinella) — after 



Biirger ....... 233 



129. Cross-section through Ascaris ..... 237 



130. Diagram of the structure of a male Nematode . . . 238 



131. Trichinae in muscle, about to be encapsuled — after Leuckart 241 



132. Trichinae in muscle, encapsuled. There may be 12,000 in 



a gramme of pig's muscle. After Leuckart . . 241 



133. Earthworms ....... 246 



134. Anterior region of earthworm — after Hering . . . 247 



135. Transverse section of earthworm .... 251 



136. Reproductive organs of earthworm — after Hering . . 253 



137. Stages in the development of earthworm — after Wilson . 255 



138. Arenicola marina . . . . . • '2 57 



139. Anterior part of nervous system in Arenicola — after Vogt 



and Yung ....... 259 



140. Dissection of lob-worm from dorsal surface . . . 260 



141. Cross-section of Arenicola — after Cosmovici . . . 261 



142. Diagram showing structure of a Trochosphere of Eupomatus 



— after Shearer ...... 263 



143. Development of Polygordius — after Fraipont . . • 265 



144. Parapodium of " Heteronereis " of Nereis pelagica — after 



Ehlers ....... 267 



145. Free-living Polychaete {Nereis cuUrifera) . . . 268 



146. Sex dimorphism in Bonellia viridis . . . • .269 



147. Transverse section of leech — after Bourne . . • 274 



148. Alimentary system of leech — after Moquin-Tandon . . 275 



149. Dissection of leech — after Bourne .... 276 



150. A nephridium of leech — after Boiume .... 277 



151. Development of Sagitta — after O. Hertwig. Illustrating 



formation of a body cavity by pockets from the archen- 



teron ; also the early separation of reproductive cells . 281 



152. Diagram of a Rotifer {Hydatina) — after Plate . . 283 



153. Actinotrocha or larva of Phoronis — after Masterman . 285 



154. Phoronis . . . . .... . . 285 



155. Diagram of an Ectoproctous Polyzoon {Plumatella) . . 286 



156. Interior of Brachiopod shell, showing calcareous support for 



the " arms " — after Davidson .... 287 



157. Pluteus larva of Ophiuroid, with rudiment of adult — after 



Johannes Miiller ...... 290 



158. Starfish ........ 293 



