Illustrations 



FIGURES 



PAGE 



1. Diagram of a Fish 6 



2. Pterichthys 8 



3. A Radiolarian Protozoan 14 



4. Porcupine-Fish 23 



5. Diagrammatic Cross-Section of Scales and Skin . . . 25 



6. Chromatophore, Greatly Magnified 33 



7. Primitive and Advanced Fishes 49 



8. Skeleton of the Yellow Perch 50 



9. Frogfish 52 



10. Body Muscles of the Fish 56 



11. The Fin-Fold Theory 64 



12. Eyes, Fish and Human 80 



13. Ears, Fish and Human 102 



14. Diagrammatic Representation of the Lateral-Line System 109 



15. Brains 1 1? 



16. Diagrammatic Representation of the Air-Bladder as a Sense 



Organ in the Carp 1 30 



17. Air and Food Systems of Early Fish and Modern Fish . 137 



18. Air and Food Systems of Man 138 



19. Internal Organs of the Striped Bass 142 



20. Lower Intestine of the Shark Cut Open to Show the Spiral 



Valve 144 



xi 



