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CHAPTER IV.

Characters as Hereditary and Acquired (Continued)

C. Experimental evidence in favour of the Inheritance of Acquired Characters103

CHAPTER V.

Characters as Hereditary and Acquired (Continued)

A. and B. Direct and Indirect Evidence in favour of the Non-inheritance of Acquired Characters133

C. Experimental Evidence as to the Non-inheritance of Acquired Characters142

CHAPTER VI.

Characters as Hereditary and Acquired (Conclusion)150

CHAPTER VII.

Characters as Adaptive and Specific159

CHAPTER VIII.

Characters as Adaptive and Specific (Continued)

I. Climate200

II. Food217

III. Sexual Selection219

IV. Isolation223

V. Laws of Growth226

CHAPTER IX.

Characters as Adaptive and Specific (Continued)228

CHAPTER X.

Characters as Adaptive and Specific (Concluded)251

Summary274

Appendix I. On Panmixia291

Appendix II. On Characters as Adaptive and Specific307

Note A to Page 57333

Note B to Page 89337

LIST OF ILLUSTRATIONS

Portrait of George John RomanesFrontispiece

Diagram of Prof. Weismann's Theories43

Fig. 1. Guinea pigs, showing gangrene of ears due to injury of restiform bodies118

Fig. 2. Old Irish Pig (after Richardson)188

Fig. 3. Skulls of Niata Ox and of Wild White Ox192

Fig. 4. Lower teeth of Orang (after Tomes)261

CHAPTER I.
Introductory: The Darwinism of Darwin, and of the Post-Darwinian Schools.

It is desirable to open this volume of the treatise on Darwin and after Darwin by taking a brief survey of the general theory of descent, first, as this was held by Darwin himself, and next, as it is now held by the several divergent schools of thought which have arisen since Darwin's death.

The most important of the questions in debate is one which I have already had occasion to mention, while dealing, in historical order, with the objections that were brought against the theory of natural selection during the life-time of Darwin[1]. Here, however, we must consider it somewhat more in detail, and justify by quotation what was previously said regarding the very definite nature of his utterances upon the matter. This question is whether natural selection has been the sole, or but the main, cause of organic evolution.

Must we regard survival of the fittest as the one and only principle which has been concerned in the progressive modification of living forms, or are we to suppose that this great and leading principle has been assisted by other and subordinate principles, without the co-operation of which the results, as presented in the animal and vegetable kingdoms, could not have been effected? Now Darwin's