CONTENTS xi 



PAGE 



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



2. ORIGIN OF THE CROSSING OF THE PLEUROVISCERAL CON- 



NECTIVE (CHIASTOXEURY) . . . . V 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 



XA~II. THE CIRCULATORY SYSTEM ...... 198 



A. GENERAL . 198 



