INDEX. 



87 



Selection, natural, 10, 25 et seq., so, 



51, 67, 69-73, 81, 83. 

 Selective value of variations, 60. 

 Semper, 6g. 

 Siderone, 22. 

 Snails, 28. 



Spencer, 14, 28, 29, 40, 53, 56, 80. 

 Struggle for existence, 65. 

 Survival of tile fit, 52. 

 Symphaedra, 22. 



Tabula rasa, 1^, 24. 

 Tegetmeier, W. B., 34. 

 Teleological principles, 10, 16, 25. 

 Theories, nature of, 5 et seq. 

 Turbellaria, 28. 



Units,vital, biological, physiological, 

 etc., 8, 40, 41, S3, s6, 63, 80. 



Useful modifications, value of initial 

 stages of, 80-82. 



Utility, II, 18, 33, 45, 48, 62, 63, 83. 



Variations, necessary, their constant 

 presence, 26 et seq,, 31 et seq., 61; 

 generally, 3, 11-14, 61, 71 et seq. 



Waagen, 72. 



Wallace, 11, 23, 39, 51, 66, 81. 



Weldon, 36. 



Whale, hind leg of, 42, 56, 80. 



Whitman, C, O., 53. 



Wiesner, 40. 



Wigand, Albert, 11, 63. 



Wings of butterfiies, 14 et seq., 47-S2, 



56. 

 WolfiE, K. F., 53. 63, 63, 69. 

 "Worse" individuals, 76. 



Zero-point of variation, 36 et seq 

 45. 74. 79. 



