PREFACE ix 



the science of genetics of the more modest dimensions 

 which I had contemplated. I should wish, however, 

 particularly to recommend Dr. Lotsy's lectures to any 

 reader who wishes to go further into these matters. 



I am indebted to several friends for assistance during 

 the course of my work. Mr. R. P. Gregory kindly 

 read through the proof of the chapter on cytology ; and 

 I wish here to record my thanks to Mr. J. Stanley 

 Gardiner, to Mr. C. T. Regan, to Mr. W. S. Perrin, and 

 to Mr. R. C. Punnett for information on special points. 

 To the last-named I owe the photograph which appears 

 as Fig. 15. I am particularly grateful to Mr. R. H. 

 Biff en and to Mr. G. Udney Yule for access to work 

 which has not hitherto appeared in print. 



Adequately to acknowledge Mr. Bateson's influence 

 upon these pages is a more difficult matter, and not 

 the less so because I have deliberately refrained as 

 far as possible from consulting him whilst the book 

 was in course of preparation, in order that it might 

 retain if possible some traces of individuality. It is 

 therefore clear that he is in no way responsible for its 

 deficiencies. But, apart from the fact that I am 

 conscious of having quoted his ideas at more points 

 than could possibly be acknowledged seriatim, I owe 

 to Mr. Bateson both my first introduction to the science 

 of genetics, and a continual fund of encouragement in 

 the prosecution of studies connected with it. 



I have to thank Mr. Francis Darwin for, ,kind per- 

 mission to reproduce a portrait of his father ; Professor 



