XVI 



CONTENTS 



The Perception of Space — contd. page 



3. Uniocular and Binocular Vision ....... 697 



Spatial Judgments . . . . . . . . .700 



Fishes, 701 ; Amphibians and Reptiles, 702 ; Birds, 702 ; 

 Manmials, 704 

 V. The Perception of Movement . . . . . . . .705 



Part IV. Evolutionary By-ways 



Chapter XIX 

 Median Eyes 



1. Pineal and Parietal Organs . . . . . . . .. 711 



Cyclostomes, 713 ; Fishes, 713 ; Amphibians, 714 ; Reptiles, 715 



(a) The Median Eye of the Lamprey . . . . . .716 



(6) The Median Eyes of Lizards and /S^/ienorfon . . . . .716 



2. The Function of the Pineal and Parietal Organs . . . . .718 



Chapter XX 



Rudimentary Eyes 



Habit and Regression . . . . . . . . . .721 



1. The Sedentary Habit 722 



Molluscs, 722 ; Crustaceans, 722 



2. The Abyssal Habit 722 



Molluscs, 723 ; Crustaceans, 723 ; Fishes, 723 



3. The Cavernicolous or Limicoline Habit . . . . . .724 



Invertebrates, 724 ; Cave-fishes, 725 ; Amphibians, 726 



4. The Fossorial or Burrowing Habit . . . . . . .728 



Invertebrates, 728 ; Amphibians, 730 ; Reptiles, 731 ; Mammals, 733 



5. The Parasitic Habit 733 



Invertebrates, 733 ; Cyclostomes, 734 ; Fishes, 734 



Chapter XXI 

 Luminous Organs 

 Bioluminescence ..... 



1. The Occurrence of Bioluminescence . 



The Biological Purpose of Bioluminescence 



2. The Biological Mechanism of Bioluminescence 



Extracellular Bioluminescence 

 Intracellular Production of Bioluminescence 



3. The Chemical Mechanism of Bioluminescence 



736 

 737 

 741 



744 

 745 

 746 



747 



Chapter XXII 

 Electric Organs 

 The Electric Organs of Fishes : Astroscopus 



EPILOGUE 



APPENDIX. Pala^ontological Table . 

 Zoological Glossary .... 

 Index ...... 



751 



753 



754 

 756 

 779 



