FIG. PAGE 1. Schematic Longitudinal Section of the Human Body 4 2. Human Skeleton 7 3. Skeleton of an Ox 9 4. Bending of the Arm by Contraction of the Biceps Muscle 10 5. Diagram to explain the Action of the Motor and Sensory Nerves 11 6. Diagram of the Course of the Circulation 13 7. Life History of the Small-winged Gall-fly (_Andricus terminalis_) 15 8. Diagram of a Fish’s Heart 18 9. Diagram of a Mammal’s Heart 20 10. Diagram of a Reptile’s Heart 20 11. Diagram of a Frog’s Heart 21 12. Vertical Section of a Human Grinding Tooth 22 13. Crown of an Ox’s Grinder 22 14. Skull of Domestic Cat 25 15. Pine Marten (_Mustela martes_) 27 16. Skull of Mole 30 17. Common Shrew (_Sorex vulgaris_) 31 18. Skeleton of Bat 34 19. Skull of Squirrel 35 20. Abnormal Tooth in Hare 37 21. Hamster (_Cricetus frumentarius_) 38 22. Long-tailed Field Mouse (_Mus sylvaticus_) 40 23. Upper Back Teeth of Brown Rat 41 24. Upper Back Teeth of Water Vole 41 25. Southern Field Vole (_Arvicola arvalis_) 43 26. Skull of Sheep 44 27. Development of Roebuck Antlers 45 28. Wing of Buzzard 50 29. Section through Bird’s Egg 51 30. Eagle Owl (_Otus maximus_) 52 31. Head and Foot of Falcon 53 32. Golden Eagle (_Aquila chrysaëtus_) 54 33. Barn Owl (_Strix flammea_) 55 34. Cuckoo (_Cuculus canorus_) 56 35. Goatsucker (_Caprimulgus europæus_) 58 36. Head of Rook (_Corvus frugilegus_) 60 37. Head of Bullfinch (_Pyrrhula vulgaris_) 62 38. Nightingale (_Daulias luscinia_) 65 39. Wood Pigeon (_Columba palumbus_) 66 40.