- An attempt to explain the foregoing laws of geographical distribution, on the theory of allied species having a common descent
- Improbability of finding fossil forms intermediate between existing species
CHAPTER VII
ON THE NATURE OF THE AFFINITIES AND CLASSIFICATION
OF ORGANIC BEINGS. [198]-[213]
- Gradual appearance and disappearance of groups
- What is the Natural System?
- On the kind of relation between distinct groups
- Classification of Races or Varieties
- Classification of Races and Species similar
- Origin of genera and families
CHAPTER VIII
UNITY OF TYPE IN THE GREAT CLASSES; AND MORPHOLOGICAL STRUCTURES.
- Unity of Type
- Morphology
- Embryology
- Attempt to explain the facts of embryology
- On the graduated complexity in each great class
- Modification by selection of the forms of immature animals
- Importance of embryology in classification
- Order in time in which the great classes have first appeared [214]-[230]
CHAPTER IX
ABORTIVE OR RUDIMENTARY ORGANS.
- The abortive organs of Naturalists
- The abortive organs of Physiologists
- Abortion from gradual disuse [231]-[238]
CHAPTER X
RECAPITULATION AND CONCLUSION.