The Principles of Biology, Volume 2 (of 2)

HERBERT SPENCER
IN TWO VOLUMES VOL. II
REVISED AND ENLARGED EDITION 1899
NEW YORK D. APPLETON AND COMPANY 1900
Copyright, 1867, 1899, By D. APPLETON AND COMPANY.
To the statements made in the preface to the first volume of this revised edition, there must here be added a few having special reference to this second volume.
One of them is that the revision has not been carried out in quite the same way, but in a way somewhat less complete. When reviewing the first volume a friendly critic, Prof. Lloyd Morgan, said:—
“But though the intellectual weight has also been augmented, it is an open question whether it would not have been wiser to leave intact a treatise, &c... relegating corrections and additions to notes and appendices.”
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.
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.