CONTENTS xi 



PAGE 



1. THE AREAS OF INNERVATION OF THE VARIOUS GANGLIA . 133 



2. ORIGIN OF THE CROSSING OF THE PLEUROVISCERAL CON- 



NECTIVE (CHIASTONEURY) . . . . .135 



3. SPECIAL REMARKS ON THE NERVOUS SYSTEM OF THE GAS- 



TROPODA ....... 137 



C. SCAPHOPODA . . . . . .142 



D. LAMELLIBRANCHIA ....... 143 



E. CEPHALOPODA ....... 145 



XIV. AN ATTEMPT TO EXPLAIN THE ASYMMETRY OF THE GASTROPODA 149 



XV. THE SENSORY ORGANS .... .162 



A. INTEGUMENTAL SENSORY ORGANS .... 162 



1. TACTILE ORGANS .... .162 



2. OLFACTORY ORGANS . . . . . .162 



3. THE "LATERAL ORGANS" OF THE DIOTOCARDIA . . 165 



4. GUSTATORY ORGANS .... 166 



5. SUBRADULAR SENSORY ORGAN OF CHITON . . 166 



6. THE SENSORY ORGANS ON THE SHELL OF CHITON . 166 



B. AUDITORY ORGANS ...... 167 



C. VISUAL ORGANS ....... 169 



1. OPTIC PITS ..... .169 



2. OPTIC VESICLES OR VESICULAR EYES . . .170 



3. THE EYE OF THE DIBRANCHIATE CEPHALOPODA . . 170 



4. THE DORSAL EYES OF ONCIDIUM AND THE EYES AT THE 



EDGE OF THE MANTLE IN PECTEN . .173 



5. THE EYES ON THE SHELL OF CHITON . . . 175 



6. THE COMPOUND EYES OF ARCA AND PECTUNCULUS . 175 



7. DEGENERATION OF THE CEPHALIC EYES . . 176 



XVI. THE ALIMENTARY CANAL . . . . . .176 



A. BUCCAL CAVITY, SNOUT, PROBOSCIS . . . .178 



B. THE PHARYNX AND JAWS, THE TONGUE AND SALIVARY 



GLANDS ...... 180 



FORMATION OF THE RADULA . ... 183 



C. THE (ESOPHAGUS ...... 187 



D. THE MID-GUT WITH THE STOMACH AND DIGESTIVE GLAND 



(LlVER) ........ 190 



1. AMPHINEURA ... ... 191 



2. GASTROPODA ... . .192 



3. SCAPHOPODA ... ... 193 



4. LAMELLIBRANCHIA ... 194 



5. CEPHALOPODA . . ... 194 



E. HIND-GUT (RECTUM) ..... 195 



XVII. THE CIRCULATORY SYSTEM . . 198 



A. GENERAL 198 



