The Principles of Biology, Volume 2 (of 2)

I think that Prof. Morgan is right. Though at the close of the preface to volume I, I wrote:--“in all sections not marked as new, the essential ideas set forth are the same as they were in the original edition of 1864,” yet the reader who has not read this statement, or does not bear it in mind, will suppose that all or most of the enunciated conceptions are of recent date, whereas only a small part of them are. I have therefore decided to follow, in this second volume, a course somewhat like that suggested by Prof. Morgan--somewhat like, I say, because in sundry cases the amendments could not be satisfactorily made by appended notes.

But there has been a further reason for this change of method. An invalid who is nearly eighty cannot with prudence enter upon work which will take long to complete. Hence I have thought it better to make the needful alterations and additions in ways requiring relatively moderate time and labour.

The additions made to this volume are less numerous and less important than those made to the first volume. A new chapter ending Part V, on “The Integration of the Organic World,” serves to round off the general theory of Evolution in its application to living things. Beyond a new section (§ 289_a_) and the various foot-notes, serving chiefly the purpose of elucidation, there are notes of some significance appended to Chapters I, III, IV, and V, in Part IV, Chapters V and VIII, in Part V, and Chapters IX, X, and XII in Part VI. Moreover there are three further appendices, D^2, F, and G, which have, I think, considerable significance as serving to make clearer some of the views expressed in the body of the work.

Turning from the additions to the revisions, I have to say that the aid needed for bringing up to date the contents of this volume, has been given me by the gentlemen who gave me like aid in revising the first volume: omitting Prof. Perkin, within whose province none of the contents of this volume fall. Plant-Morphology and Plant-Physiology have been overseen by Mr. A. G. Tansley. Criticisms upon parts dealing with Animal Morphology I owe to Mr. J. T. Cunningham and Prof. E. W. MacBride. And the statements included under Animal Physiology have been checked by Mr. W. B. Hardy.

For reasons like those named in the preface to the first volume, I have not submitted the proofs of this revised second volume to these gentlemen: a fact which it is needful to name, since one or other of them might else be held responsible for some error which is not his but mine. It is the more requisite to say this because while, in respect of matters of fact, I have, save in one or two cases, accepted their corrections as not to be questioned, I have not always done this in respect of matters of inference, but in sundry places have adhered to my own interpretations.

Perhaps I may be excused for expressing some satisfaction that I have not been obliged to relinquish the views set forth in 1864–7. The hypothesis of physiological units--or, as I would now call them, constitutional units--has been adopted by several zoologists under modified forms. So far as I am aware, the alleged general law of organic symmetry has not called forth any manifestations of dissent. The suggested theory of vertebrate structure appears to have become current; and from the investigations of the late Prof. Cope, has received verification. The conclusions drawn in Part VI on “The Laws of Multiplication,” have not, I believe, been controverted. And though only some works on botany have given currency to the doctrine set forth in Appendix C, “On Circulation and the Formation of Wood in Plants,” yet I have met with no attempt to disprove it. The only views contested by certain of the gentlemen above named, are those concerning the origin of the two great phænogamic types of plants, and the origin of the annulose type of animals. I have not, however,--perhaps because of natural bias--found myself compelled to surrender these views. My reasons for adhering to them will be found in notes to the ends of Chapters III and IV in Part IV, and in Appendix D^2.

On now finally leaving biological studies, it remains only to say that I am glad I have survived long enough to give this work its finished form.

BRIGHTON, October, 1899.

PREFACE TO VOL. II.

The proof sheets of this volume, like those of the last volume, have been looked through by Dr. Hooker and Prof. Huxley; and I have, as before, to thank them for their valuable criticisms, and for the trouble they have taken in checking the numerous statements of fact on which the arguments proceed. The consciousness that their many duties render time extremely precious to them, makes me feel how heavy is my obligation.

Part IV., with which this volume commences, contains numerous figures. Nearly one half of them are repetitions, mostly altered in scale and simplified in execution, of figures, or parts of figures, contained in the works of various Botanists and Zoologists. Among the authors whom I have laid under contribution, I may name Berkeley, Carpenter, Cuvier, Green, Harvey, Hooker, Huxley, Milne-Edwards, Ralfs, Smith. The remaining figures, numbering 150, are from original sketches and diagrams.

The successive instalments which compose this volume, were issued to the Subscribers at the following dates:--No. 13 (pp. 1–80) in January, 1865; No. 14 (pp. 81–160) in June, 1865; No. 15 (pp. 161–240) in December, 1865; No. 16 (pp. 241–320) in June, 1866; No. 17 (pp. 321–400) in November, 1866; and No. 18 (pp. 401–566) in March, 1867.

LONDON, March 23rd, 1867.

CONTENTS OF VOL. II.

PART IV.--MORPHOLOGICAL DEVELOPMENT.