PREFACE 



In writing my husband's life I have tried, so far as 

 it was possible, to let him, especially in matters 

 scientific, speak for himself. 



For the purpose of his biographer it is unfortunate 

 that my husband lived in almost daily intercourse 

 for parts of many years with more than one of his 

 most intimate friends. Hence there are no letters 

 to several people with whom he was in the habit 

 of discussing scientific, philosophic, and theological 

 questions. 



The letters relating to his work will, I hope, 

 interest any one who cares for biological science. 

 Whatever may be the exact place which shall be 

 assigned to him, by those who come after, in the 

 great army of workers for Science, this much may 

 be said : that no one ever served in the cause of 

 Science with more passionate and whole-hearted 

 devotion, more entire disinterestedness — 



All for Love, and nothing for Beward. 



I have to acknowledge the kindness of many who 

 have put letters at my disposal. I cannot sufficiently 



