Part 4

CEREBRAL DEVELOPMENT OF THE EARLIER VERTEBRATA.—ITS APPARENT PRINCIPLE 62

THE ASTEROLEPIS.—ITS STRUCTURE, BULK, AND ASPECT 94

FISHES OF THE SILURIAN ROCKS, UPPER AND LOWER.—THEIR RECENT HISTORY, ORDER, AND SIZE 130

HIGH STANDING OF THE PLACOIDS.—OBJECTIONS CONSIDERED 147

THE PLACOID BRAIN.—EMBRYONIC CHARACTERISTICS NOT NECESSARILY OF A LOW ORDER 160

THE PROGRESS OF DEGRADATION.—ITS HISTORY 181

EVIDENCE OF THE SILURIAN MOLLUSCS.—OF THE FOSSIL FLORA.—ANCIENT TREE 205

SUPERPOSITION NOT PARENTAL RELATION.—THE BEGINNINGS OF LIFE 230

LAMARCKIAN HYPOTHESIS OF THE ORIGIN OF PLANTS.—ITS CONSEQUENCES 243

THE TWO FLORAS, MARINE AND TERRESTRIAL.—BEARING OF THE EXPERIENCE ARGUMENT 262

THE DEVELOPMENT HYPOTHESIS IN ITS EMBRYONIC STATE.—OLDER THAN ITS ALLEGED FOUNDATIONS 277

FINAL CAUSES—THEIR BEARING ON GEOLOGIC HISTORY—CONCLUSION 303

LIST OF WOOD-CUTS

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1. Internal ridge of hyoid plate of Asterolepis 31

2. Shagreen of Raja clavata:—of Sphagodus 54

3. Scales of Acanthodes sulcatus:—shagreen of Scyllium stellare 55

4. Scales of Cheiracanthus microlepidotus:—shagreen of Spinax Acanthias 56

5. Section of shagreen of Scyllium stellare:—of scales of Cheiracanthus microlepidotus 56

6. Scales of Osteolepis microlepidotus:—of an undescribed species of Glyptolepis 57

7. Osseous points Of Placoid Cranium 65

8. Osseous centrum of Spinax Acanthias:—of Raja clavata 67

9. Portions of caudal fin of Cheiracanthus:—of Cheirolepis 69

10. Upper surface of cranium of Cod 72

11. Cranial buckler of Coccosteus 74

12. Cranial buckler of Osteolepis 75

13. Upper surface of head of Osteolepis 77

14. Under surface of head of Osteolepis 79