PREFACE vii 



Chiefly of course I am indebted to Prof. Bateson's 

 recent work on Mendel's Principles of Heredity as 



the most complete and authoritative account of the 

 subject, from the acknowledged leader of the Meh- 

 delian school. For permission to reproduce several 

 figures from this book I tender my thanks. In 

 addition to information from many original papers, I 

 have also not hesitated to make use of Lock's Recent 

 Progress in the Study of Variation, Heredity and 

 Evolution, Thomson's Heredity, and some other 

 books dealing with the general aspects of the subject ; 

 to these authors, and to several friends who have 

 been kind enough to give me written information 

 on matters with which they are especially conversant, 

 I wish to record my indebtedness. I wish also 

 especially to thank Mrs A. C. Seward for drawing 

 the sections of Primula reproduced in fig. 10 

 (p. 81). 



L. DO^CASTER. 



Cambridge, 

 June 1910. 



