viii THE LAWS OF HEREDITY 



authentic evidence available, or that facts newly asserted are 

 of greater value than truths long familiar and disputed by no one, 

 or that it is beneath the dignity or not within the mission of 

 science to furnish proof, or that knowledge derived from a simple 

 enumeration of instances is superior to knowledge which is 

 founded on a discovery of causes, or that we should found 

 hypotheses on the exception rather than the rule, or that it is 

 right to uphold contradictories, if in short he has individual and 

 original views as to what constitutes proof and what science, then 

 I hope he will endeavour to formulate his reasons clearly. Unless 

 he does so, his opinions, no matter how correct they may be, are 

 apt to bear the appearance of prejudices. 



Professor H. H. Turner has contributed an Appendix in which 

 some of the main arguments of the text are thrown into diagram- 

 matic form. No part of the work is likely to prove so interesting 

 and convincing as this Appendix. I have, besides, to record my 

 great indebtedness to him for much very valuable advice. 



It is impossible to express adequately my deep sense of obliga- 

 tion to Dr H. B. Donkin. Not only has he been a sort of reference 

 library, but he has read and re-read the whole of the rough and 

 the more finished manuscript, and the former has grown into the 

 latter largely under his guidance. 



Other helpers, whom I take this opportunity of thanking most 

 heartily, are Miss J. Ritter, Mr A. D. Darbishire, Mr. P. C. Glubb, 

 and Mr D. Waudby. 



While writing the volume, I have received great kindness and 

 encouragement from Dr Alfred Russel Wallace, Sir William 

 Thiselton-Dyer, and Sir E. Ray Lankester. 



SOUTHSEA, April 1910 



