| FIG. | | Page |
| 1. | Hyoid Arch of the Conger. (Original.) | 58 |
| 2. | "Vertebra" of a Pleuronectid. (Geoffroy.) | 61 |
| 3. | Abdominal Segment of the Lobster. (Geoffroy.) | 63 |
| 4. | Ideal Typical Vertebra. (Owen.) | 102 |
| 5. | Natural Typical Vertebra. (Owen.) | 103 |
| 6. | The Archetype of the Vertebrate Skeleton. (Owen.) | 105 |
| 7. | Ideal Transverse Section of a Vertebrate Embryo. (Von Baer.) | 119 |
| 8. | Gill-slits of the Pig Embryo. (Rathke.) | 134 |
| 9. | Meckel's Cartilage and Ear-ossicles in Embryo of Pig. (Reichert.) | 145 |
| 10. | Cranial Vertebræ and Visceral Arches in Embryo of Pig. (Reichert.) | 148 |
| 11. | Embryonic Cranium of the Adder. (Rathke.) | 152 |
| 12. | Transverse Section of Chick Embryo. (Remak.) | 211 |
| 13. | Development of the Ascidian Larva (Kowalevsky.) | 272 |
| 14. | Transverse Section of the Worm Nais. (Semper.) | 280 |
| 15. | The Five Primary Stages of Ontogeny. (Haeckel.) | 292 |
