PEEFACE. 



IN this little book I have endeavoured to give a brief 

 account of the subject of " Variation/' so far as the 

 present state of our knowledge admits. Though I did 

 not in any degree aim at giving a complete representa- 

 tion of the subject, yet I hope that most of the more 

 important and more recent work has been included. I 

 have not treated Variation of Plants so fully as that of 

 Animals, and from lack of thorough acquaintance with 

 the literature, have probably made some omissions of 

 real importance to the adequate comprehension of the 

 subject in its bearing on living organisms taken as a 

 whole. For such I offer my apologies. I have pur- 

 posely avoided any higher mathematics in discussing 

 the facts of variation, as it seemed out of place in a book 

 of this character. 



An obvious criticism upon the contents of the book 

 will be that I have given greater prominence to my own 

 researches than their intrinsic importance warrants. 

 To this I frankly plead guilty, urging in extenuation 

 that I did not intend to write a text-book in the ordi- 

 nary sense of the term. Thus some of the hypotheses 

 and interpretations of facts which I have given are my 

 own personal opinions, and by no means current views 

 held in general acceptation. Also a few of the data 

 published in the latter part of Chapter VI., and those 

 on " identical twins " in Chapter IV., are here published 



iii 



