VI INTRODUCTION. 



It is my pleasant duty to express my hearty 

 thanks to many kind friends who have helped in 

 the production of this little work. Mr. Francis 

 Darwin has kindly permitted the use of many of 

 Darwin's letters, which have not as yet been published, 

 and he has given me valuable information and 

 criticism on many points. I have also gained much 

 by discussion and correspondence with my friends 

 Dr. A. R Wallace, Professor E. Ray Lankester, and 

 Professor Meldola. The latter has freely given me 

 the use of his valuable series of letters; and I owe 

 to my friend, Mr. Rowland H. Wedgwood, the oppor- 

 tunity of publishing a single letter of very great 

 interest. 



The greater part of the volume formed the subject 

 of two short courses of lectures delivered in the Hope 

 Department of the Oxford University Museum in 

 Michaelmas Term 1894 and Lent Term 1895. 



Edward B. Poulton. 



Oxford, October, 1896. 



