CONTENTS 



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 Dige.stive Gland 



(Liver) . . . . . . . . 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 



