210 



INDEX 



Psilura monacha, PL 56. 



Psyche unicolor, PI. 56. 



Ptarmigan, seasonal color change, i2i,P/. 57. 



Pterodactylus spectabilis, PL 45. 



Pterogon proserpina, PL 70. 



Pterophryne histrio, 124, 126, PL 65. 



Public opinion, a part of man's environ- 

 ment, 172, 179. 



Pupa, color adaptation, 121, PI. 59; Logoa, 

 123, PI. 63; protective color, PL 56. 



Putorius ermineus, PI. 67. 



Quail, protective color, 118, PL 49. 



Rabbit, confusing coloration, 148; em- 

 bryos, PL 38; illustration of mutation, 

 19; illustration of natural selection, 15; 

 protective coloration not explicable by 

 the inheritance of effects of use and dis- 

 use, 75; signal, white rump patch, 146. 



Radiolaria, skeletons, PL 21. 



Recognition marks, 146-147. 



Regeneration and inheritance of parental 

 modification, 71. 



Relationship, key to classification, 91. 



"Relations concerning Ireland" (Giraldus), 



3- 



Religion, a cause of segregation, 169. 



Reproduction, among unicellular organ- 

 isms, 68, 69; and length of life, 20, 22, 

 23, 24; asexual, and inheritance of 

 parental modifications, 71; birth-rate, 

 n, 12; easily disturbed, 66; effects of 

 destroying organs of, 34; evolution 

 centres in, 82 ; germ cells in higher 

 organisms, 69; increase in, aids in 

 struggle for existence, 17; organs of, 

 in flowering plants, 752, 153, PL 86; 

 regeneration of organs, 71. 



Ring-necked plover, recognition marks, 

 PL 82. 



Robin, illustration of species, 88; rate of 

 increase, n; sexual coloration, 150. 



Robinson, Louis, PL 100. 



Rock-rose, 752. 



Rocky Mountains, cause of segregation, 61. 



Romanes, G. ]., 17,94, 10=5, 197, 199, PI- 17, 

 PL 36-38, PL 43, PL 44, PI- 75, PI- 

 93-99; sexual selection in birds, 53; 

 physiological selection, 66. 



Rosacea, 90. 



Rostellum of orchid, 156, PL 89. 



Roux, \Vilhelm, 192. 



Royal Society of London, goose barnacle, 5. 



Ruffed grouse, PL 23. 

 "Ruth," 176. 



Sacculina, 184, 185, PL 1 01. 



Sacrum, human, with tail muscles, PL 95; 



of man and apes, 164, PL 91. 

 Saitis pulex, PI. 28. 

 Salamander, embryos, PI. 38; tadpole, 



98; warning color, 133. 

 Salamandra maculosa, 133. 

 Salvia, 157; glutinosa, PL 88. 

 Sand-flounder, PL 48. 

 Sandpiper, protective color, 119. 

 Sargassum fish, 124, 126, PL 65. 

 Savage, illustration of social progress, 173 



et seq. 



Savoy cabbage, PL 6, PL 8. 

 Sceloporus undulatus, PI. 52. 

 Scepastus pachyrhynchoides, PL 73. 

 Schistocerca, 62. 

 Sclater, mimicry of leaf-cutting ants, 137, 



145, PI- 75- 



Sea-horse, 124. 



Sea-lion, nictitating membrane, PL 36. 



Seasonal change of color, 121, 126, 129, 

 PL 57, PL 67. 



Secondary sexual characters, see Sexual 

 selection ; more developed in female, 58. 



Seeds, spiny, not evolved through inherit- 

 ance of the effects of use, 76. 



Segregation, 60-67, J 68; see also 42-47, 48. 



Selection, artificial, 28-31; germinal, 96; 

 natural, 3-47; organic, 27, 28, 177, 192; 

 physiological, 66; "selection value," 17, 



37; 



Selenia tetralunaria, 122. 



Sesia culicijormis and tipulijormis, PL 70. 



Seventeen-year cicada, 51, PL 29. 



Sexual coloration, 149-151. 



Sexual selection, Intro, xi, 47-60, 168, 169, 

 172, 173, 175, 178, 179-183; a cause 

 of segregation, 44; objections to, 56-60. 



Sheep, Ancon, segregation, 65 ; Faroe 

 Islands, segregation, 65 ; merinos and 

 heath sheep do not interbreed, 48; 

 protective color of wild, 120. 



Shore birds, protective color, 119. 



Siberia, former warm climate, 62. 



Signals and recognition marks, 146-147. 



Silurian fossils, 106. 



Simiid(F, 164. 



Simplification ("degeneration"), 183-187. 



Siphonophores, transparency, 117. 



Sitana minor, PL 34. 



