x PREFACE 



the American Book Co., for the use of figures 2, 52, 



97, and 109; to Messrs. G. P. Putnam's Sons, for 

 the use of figure 16; to Messrs. D. Appleton and 

 Co., for the use of figures 19, 58, 62, 67, 70, 90, 93, 

 95, 96, and 113; to Messrs. Longmans, Green, and 

 Co., for the use of figure 23 ; to Messrs. P. Blakis- 

 ton's Son and Co., for the use of figure 64 ; to Pro- 

 fessor C. B. Davenport and the Editors of the 

 Popular Science Monthly, for the use of figure 71 ; 

 to Professor Davenport and Messrs. John Wiley and 

 Sons, for the use of figure 73 ; to the Columbia 

 University Press, for the use of figure 110; to Pro- 

 fessor John Schaffner, for permission to copy figure 

 66; to Professor C. C. Curtis, for the use of figures 

 51 and 107 ; to the Editors of the American Review 

 of Reviews, for the use of figure 108 ; and to Sir E. 

 Ray Lankester, for permission to copy figure 112. 

 For photographs from which were made figures 85, 



98, and 99 I am indebted to the kindness of Profes- 

 sor S. M. Coulter. All the other illustrations, with 

 the exception of figures 6, 10, 24, 25, 37, 40, 42-44, 

 50, 54, 56, 57, 63, 74, 77; 88, 89, and 114, are from 



publications of The Macmillan Co. 



J. F. A. 



JANUARY, 1914. 



