LIST OF ILLUSTRATIONS XI ii 



TIG. PAGE 



129. Helix pomatia, with the pulmonary chamber cut open . 288 



130. Longitudinal section of the head of Helix to show the radula 289 



131. Dissection of the Snail, Helix pomatia, to show the internal 



organs . . . . . ; . . 290 



132. View of the nervous system of Helix pomatia . . . 292 



133. Optical section through the auditory vesicle of Pterotrachea 



friederici . 293 



134. Nervous system of the Pond-snail, Limnaea . . . 293 



135. Nervous system, osphradium and gills of Haliotis . . 294 



136. The Pond-mussel, Anodonta mutabilis, with foot expanded 



and the empty shell of the same ..... 298 



137. Eight side of Anodonta mutabilis with mantle cut away and 



gills folded back . 300 



138. Diagrammatic transverse sections of Anodonta . . . 301 



139. Eight side of Anodonta mutabilis dissected to show the 



viscera . . . . . . . . . 303 



140. Dorsal view of Anodonta mutabilis, with the upper wall of 



the pericardium removed to show the heart . . . 306 



141. Solen vagina, the Eazor-shell 308 



142. Diagrams of a series of Mollusca to show the relations of the 



foot and visceral hump to each other and to the antero- 



posterior and dorso- ventral axes 31 1 



143. Posterior view of a male Cuttle-fish, Sepia officinalis, with 



the mantle- cavity opened . . .. . .313 



144. A diagram showing the relation of the kidneys to the peri- 



cardium in Sepia . . . ... . . 314 



145. View of heart and chief blood vessels of Sepia cultrata . 316 



146. Diagrammatic longitudinal section of Sepia to show the 



relation to one another of some of the principal viscera . 318 



147. Lateral view of the central nervous system of Sepia officinalis 319 



148. Ventral view of Sepia officinalis dissected so as to show the 



nervous system . . . . . . . . . 320 



149. Side view of the pearly Nautilus, Nautilus pompilius . 322 



150. Oral view of a Star-fish, Echinaster sentus .... 327 



151. Dissection of the common Star-fish, Asterias rubens, so as to 



show the motor, digestive and reproductive organs . . 329 



152. A Star-fish, Echinaster sentus, in the act of devouring a 



mussel . . . . . . . . . . 331 



153. Diagram of a transverse section of the arm of a Star-fish 332 



154. Pedicellariae from Asterias glacialis . . . . . 336 



155. Dorsal, upper or aboral view of a Brittle-star, Ophiocfh/pha 



bullata ... 339 



156. Section through an arm of an Ophiuroid . . . . 340 



157. A diagrammatic vertical section of an Ophiuroid . . 341 



158. Oral view of part of the disc and arms of Ophioglypha bullata 342 



