PREFACE 



A FEW years ago I published a short sketch of 

 Mendel's discovery in heredity, and of some of the 

 recent experiments which had arisen from it. Since 

 then progress in these studies has been rapid, and 

 the present account, though bearing the same title, 

 has been completely rewritten. A number of illustra- 

 tions have been added, and here I may acknowledge 

 my indebtedness to Miss Wheldale for the two 

 coloured plates of sweet peas, to the Hon. Walter 

 Rothschild for the butterflies figured on Plate VI., 

 to Professor Wood for photographs of sheep, and to 

 Dr. Drinkwater for the figures of human hands. To 

 my former publishers also, Messrs. Bowes and BoweSj 

 I wish to express my thanks for the courtesy with 

 which they acquiesced in my desire that the present 

 edition should be published elsewhere. 



As the book is intended to appeal to a wide 

 audience, I have not attempted to give more experi- 

 mental instances than were necessary to illustrate 

 the story, nor have I burdened it with bibliographical 

 reference. The reader who desires further informa- 

 tion may be referred to Mr. Bateson's indispensable 



