2O2 



INDEX 



Reproduction, among unicellular organisms, 

 68, 69; and length of life, 20, 22, 23, 24; 

 asexual, and inheritance of parental 

 modifications, 71; birth-rate, II, 12; 

 easily disturbed, 66; effects of destroying 

 organs of, 34; evolution centres in, 82; 

 germ cells in higher organisms, 69; in- 

 crease in, aids in struggle for existence, 

 17; organs of, in flowering plants, 152, 

 153, PI. 86; regeneration of organs, 71. 



Ring-necked plover, recognition marks, PI. 

 82. 



Robin, illustration of species, 88; rate of 

 increase, II; sexual coloration, 150. 



Robinson, Louis, PI. 100. 



Rock-rose, 152. 



Rocky Mountains, cause of segregation, 61. 



Romanes, G. J., 17, 94, 105, 189, 191, PI. 17, 

 PL 36-38, PL 43, PL 44, PL 75, PL 93-99; 

 sexual selection in birds, 53; physiologi- 

 cal selection, 66. 



Rosaces, go. 



Rostellum of orchid, 156, PI. Sg. 



Royal Society of London, goose barnacle, 5. 



Ruffed grouse, PL 23. 



"Ruth," 176. 



Saccnlina, 184, 185, PL 101. 



Sacrum, human, with tail muscles, PL gj ; 



of man and apes, 164, PL gi. 

 Saifis pill ex, PL 28. 

 Salamander, embryos, PI. jS ; Tadpole, gS ; 



warning color, /y. 

 Salamandra maculosa, /??. 

 Salvia, 157; glutiuosa, PL SS. 

 Sand-flounder, /'/. yv_v. 

 Sandpiper, protective color, 119. 

 Sargassum fish, 124, 126, PL 65. 

 Savage, illustration of social progress, 173 



et sey. 



Savoy cabbage, PL 6, PL S. 

 Sceloforus undulatus, PL J2. 

 Sn'/'iistiis pachyrhynchoides, PL 73. 

 Schistocerca, 62. 

 Sclater, mimicry of leaf-cutting ants, 137, 



US, PI- 75. 

 Sea-horse, 124. 



Sea-lion, nictitating membrane, PL j(~>. 

 Seasonal change of color, 121, 126, 129, PL 



57, PL ^7- 



Secondary sexual characters, see Sexual 

 selection; more developed in female, jS. 



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; physiological, 66; "selec- 

 tion value," 17, 37. 



Selenia tctralunaria, 122. 



Sc's/a ciiliciforniis and tipuliformis, PL jo. 



Seventeen-year cicada, 51, /'/. 29. 



Sexual coloration, 149-151. 



Sexual selection, Intro, xi, 47-60, 1 68, 169, 

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

 segregation, 44; objections to, 5660. 



Sheep, Ancon, segregation, 65; Faroe 

 Islands, segregation, 65; merinos and 

 heath sheep do not interbreed, 48; 

 protective color of wild, 1 20. 



Shore birds, protective color, 119. 



Siberia, former warm climate, 62. 



Signals and recognition marks, 146-147. 



Silurian fossils, 106. 



Simiidce, 164. 



Simplification ("degeneration"), 183-187. 



Siphonophores, transparency, 1 1 7. 



Si tana minor, PL 34. 



Skeletons of unicellular organisms, 32, PI, 

 21 ; of arm of vertebrates, gs. 



Skin muscles in man, 94. 



Skunk, 133, 134, /'/. 12. 



Skunk-cabbage, 154. 



Slavonia, fossil Paliidina, 107. 



Small pox, 171. 



Smelting ore, 176. 



Si/ierinf/n/s tiliic, PL 55 ; ocellata, 142. 



Snail, development of pond, 97. 



Snails of Oahu, segregation, 63. 



Snakes, aggressive color, 126; behavior of 

 poisonous, 143 ; hind limbs, 93, 94; 

 mimicry, 139, PL 79 ; protective color, 

 120. 



Snipe protective color, 119. 



Snow grouse seasonal color change, 121, 



PL 57- 



Snowy-owl, 126. 



Socialism, control of marriage, 182; na- 

 ture socialistic, 187. 



Social progress, an end in itself, 176; vs. 

 evolution, 173-1 77. 



Soil, relation to segregation, 63. 



concolor, 89, go, 91. 



i, distinguished from germ cells, 70; 

 relation to processes of reproduction, 



74- 

 Sparrow, aggressive color, 126; protective 



color, 1 1 8, PL 49. 

 SpatJiura solstitialis, PL 26. 



