x ILLUSTRATIONS IN THE TEXT 



FIGURE PACK 



20. THYSANOZOON BROCCHII, A MARINE PLANARIAN .... 72 



21. THYSANOZOON DIVIDED TRANSVERSELY 73 



22. THYSANOZOON WITH TRANSVERSE INCISION 75 



23. FRESH- WATER PLANARIAN (PLANARIA TORVA) .... 77 



24. TWO-HEADED PLANARIAN PRODUCED ARTIFICIALLY. (AFTER 



VAN DUYNE.) Si 



25. PLANARIAN WITH Two HEADS THAT ARE ATTEMPTING TO MOVE 



IN OPPOSITE DIRECTIONS, AND IN so DOING ARE TEARING 

 THE COMMON BODY. (AFTER VAN DUYNE.) .... 82 



26. THE BRAIN AND A SERIES OF SEGMENTAL GANGLIA OF AN AN- 



NELID (NEREIS) 83 



27. DORSAL VIEW OF THE CENTRAL NERVOUS SYSTEM OF AN EARTH- 



WORM 84 



28. SIDE VIEW OF THE CENTRAL NERVOUS SYSTEM OF THE EARTH- 



WORM 85 



29. A GROUP OF NEREIS WHOSE BRAINS HAVE BEEN REMOVED. THEY 



AT LAST COLLECT IN A CORNER OF THE AQUARIUM AND PERISH 

 IN THE VAIN ATTEMPT TO Go THROUGH THE GLASS. (AFTER 

 MAXWELL.) 93 



30. HEAD OF NEREIS. (AFTER QUATREFAGES.) 98 



31. LIMULUS POLYPHEMUS WITH THE CENTRAL NERVOUS SYSTEM 



EXPOSED 103 



32. LOBSTER WITH CENTRAL NERVOUS SYSTEM EXPOSED . . . 115 



33. DIAGRAMMATIC REPRESENTATION OF THE CENTRAL NERVOUS 



SYSTEM OF A SNAIL (PALUDINA VIVIPARA) .... 128 



34. BRAIN OF SEPIA 129 



35. THE FROG'S BRAIN 139 



36. POSITION OF THE APPENDAGES OF LIMULUS AFTER DESTRUCTION 



OF THE RIGHT HALF OF THE BRAIN 156 



37. ATTITUDE OF AN AMBLYSTOMA UNDER THE INFLUENCE OF A GAL- 



VANIC CURRENT PASSING FROM HEAD TO TAIL . . . 160 



38. ATTITUDE OF AN AMBLYSTOMA WHEN THE GALVANIC CURRENT 



PASSES FROM TAIL TO HEAD 160 



39. CEREBRAL HEMISPHERES OF A DOG 260 



