i8o 



Index. 



Gui.iCK, Rev. J., on natural 

 selection as a mode of isolation, 

 9 ; on divergence, 1 1 ; on segre- 

 gate breeding. 19; on geogra- 

 phical distrihution, 27 ; on the 

 prevention of intercrossing, 127; 

 on Mr. Wallace's criticisms, 151. 



H. 



Herbert, on hybridization, 173 ; 



advance on his position, 174. 

 Herdman, Prof., on physiological 



isolation, 123. 

 Historical sketch of opinions on 



isolation, loi. 

 Homogamy, 5, 6 ; forms of, 7, 19, 



29. 

 Hybridization, Herbert on, 1 73 ; 



in plants, 175. 

 Hypothesis, additional, concerning 



physiological selection, 178. 



Independent variability, 12-29. 



Isolation, defined, 2 ; forms of. 

 3, 6 ; geographical, 3 ; discri- 

 minate and indiscriminate, 5 ; 

 physiological, 9, 41, 58; Us 

 importance, 39 ; sketch of 

 opinions on, 10 1 ; general con- 

 clusions, 144; Seebohm on, 1 73. 



J- 



Jordan, M., on cross sterile 

 varieties of plants, 86 ; his re- 

 searches summarized, 87. 



K. 



Kerner, Prof. A., on prepotency, 



176. 



L. 



Lankester, Prof. Ray, on di 



vergent evolution, 15. 

 Le Conte, Prof., on fossil snails 



of Steinheim, 95 ; on isolation, 



129. 

 Livingstone, Dr. David, quoted, 



123. 



M. 



Meldola, Prof., on difficulty 

 from intercrossing, 121. 



Misunderstandings of physio- 

 logical selection, 59. 



Monotypic evolution, see Evolu- 

 tion. 



Morgan, Prof. Lloyd, on steri- 

 lity, 56; on isolation, 128. 



Moulton, Mr. Fletcher, an 

 examination of Mr. Wallace's 

 calculations on physiological 

 selection, 157. 



MiJLLER, Fritz, on cross-infertility, 

 174. 



N. 



Nageli, on isolation, 76 ; on 

 synoicy, 78, 82. 



Natural selection, a form of dis- 

 criminate isolation, 9, 10, 23; 

 leads to monotypic evolution, 

 24-29; difficulties of, 41, 51. 



Panmixia, 12. 



Physiological selection, 9, 41 ; 

 summarized, 58; misunderstand- 

 ings of, 59 ; evidences of, 81- 

 IT9; and Weismannism, 169; 

 additional hypothesis, 178. 



Polytypic evolution, see Evolution. 



Prepotency, 89 ; importance of, 

 176. 



Schmidt, Prof. Oscar, on do- 

 mesticated cattle, 171. 



Seebohm on isolation, 173. 



Segregation, 28. 



Selection, physiological, see Physi- 

 ological selection. 



Self-fertilization and variability, 



177. 



Snails of Sandwich Islands, 16, 

 1 30 ; fossil of Steinheim, 95. 



Specific differentiation and cross- 

 infertility, 170. 



Stability and cross-infertility, 170. 



Synoicy, 78. 



