Emery[34] likewise sees only the alternative of a {84} "definitely directed variation" from internal causes and of a summation of "accidental" variations. He says: "A summation of entirely accidental variations in a given direction is extremely difficult," because "natural selection thus always awaits its fortune at the hands of accident whereby it is possible that the little good thereby produced will be swept away by other accidents (disadvantages of position) or obliterated in the following generations by unfortunate crossings." We can, therefore, continues Emery, well conceive "how many scientists look upon the whole theory of selection as a fable, or else throw themselves into the arms of Lamarckism." Unquestionably Emery has here singled out the insufficient points in the assumption of a selection of "accidental" variations; he has recognised the necessity of operating, not with single variations, but with "directions of variation." He has not, however, attempted the derivation of directed tendencies of variation from known factors; he apparently thinks of them as of something which has sprung from unknown constitutional factors and consequently ascribes to them the capacity of shooting beyond their mark, so to speak, that is, of acting beyond and ahead of utility, and so of producing modifications which may lead to the destruction of the species. * * * * * {85} INDEX. Accidental variations, 3, 83. Acquired variations, 33. Acracids, 19. Acraea, 52. Active selection, 38. Adaptations, 3, 10, 22, 61, 82. Adaptiveness, 66 footnote, 67, 74 et seq. Ageronia, 19. Anaea, 22. _Anlagen_, 35, 47, 53. Arthropoda, 32, 62. Articulata, 30. Artificial selection, 33. Askenasy, 24, 60, 82. Atoms, 57, 58. Baer, K. E. von, 73. Bateson, 18, 73, 80. "Better" individuals, 76. Biology, character of research in, 7. Biophores, 40, 47, 58. Boltzmann, 4, 5. Bonnet, 53. Bourne, footnote, 54. Bruecke, 40. Butterflies, 14 et seq., 18 et seq., 81. Catonephele, 50. Chance, 61. Chemical selection, 71. Chitons, 28. Coadaptation, 30. Colorings, protective, 14 et seq. Constancy of species, 46. Constructs, 8. Cormi, 66 footnote. Correlation, 21. Danaids, 19. Darwin, 11, 25, 29, 36, 38, 66, 81, 83. Definite variation, 3, 4, 60, 76-79, 82. Degeneration, 30 et seq., 39 et seq. 55, 63, 64, 79. Delage, Yves, 40, 69. Determinants, 6 et seq., 10, 36 et seq. 42, 54, 58. Developmental mechanics, 8, 9. De Vries, 40. Dimorphism, 58. Directions of variations, 83. Directive forces, 23, 24. Dixey, 51 footnote. Dohrn, 81. Driesch, Hans, 12. Dyer, Thiselton, 78-79. Eimer, 16, 70. Emery, 71, 83-84. Empedocles, 75. Epigenesis, 53 footnote, 58, 59. Euploids, 19. Europeans, exempt from malarial fevers, 82. Eurypheme, 22. Evolution, 53 footnote, 59.