Preface xv 



Part of the History of Biological Science has been 

 taken, by kind permission of the Editors and of the 

 authorities of the Cambridge University Press, from 

 the " Cambridge History of English Literature." In 

 that portion of the chapter on Zoology which deals 

 with Charles Darwin considerable extracts have also 

 been made from the Presidential Address to the Zoo- 

 logical Section of the Winnipeg Meeting of the British 

 Association. 



Our thanks are due to the Council of the Royal 

 Society for permission to reproduce a number of por- 

 traits, and to the Editor of " Nature " for allowing 

 the reproduction of the excellent engraving of Clerk 

 Maxwell. The portraits which accompany the last five 

 chapters were prepared from photographs kindly taken 

 by the Rev. Alfred Rose, of Emanuel College, Cam- 

 bridge, from various well-known prints. The excellent 

 likeness of Joule, taken about 1875 by Lady Roscoe, 

 now appears for the first time. 



A. S. 

 A. E. S. 

 August 1917. 



