INDEX 



235 



Protohippus, 67 

 Protopterus, 167, 177 

 Protozoa, fossils of, 60 

 Protozoan ancestry of Metazoa, 



in 

 Ptarmigan, colour of, 125 

 Pterodactyl, 66 

 Pteropus, 165 

 Pterygotus, 57 

 Pupa stage, of barnacle, 82 



of Sacculina, 83 

 Pupse of insects, change of colour 

 in, 120 



Rabbit, rapid increase of num- 

 bers, 40 



recognition markings in, 140 

 Radiolaria, fossils of, 60 

 Rana temporaria, development of, 



100 

 Rate of increase of an animal, 39 

 Recapitulation theory, 84 



causes hindering, 97 



tests of, 106 

 Recognition markings, 123, 140 

 Regnum, and words derived from 



it, 63 

 Reindeer, fossils of, 56 



variation in, 43 

 Reptilia, 177 



fossils of, 65 



relation to birds, 180 

 Retrograde development, 159 

 Reversion, examples of, 52, 194 

 Rhinoceros, fossils of, 56 

 Rock-pigeon, 29 

 Rudimentary organs, 95, 161 



Sacculina, affinities, development 

 and degeneration of, 81, 83, 

 160 



Salinella, 113 



Schizopod, stage of prawn, 81 



Sea-urchin, metamorphosis in, 105 

 pluteus larva of, 102 



Secondary period, 56 



Sematic colours, 122 



Sheep, variation in, 43 



Sigillaria, 57 



Silk fowl, 35 



Siren, 177 



Size, influence of, 68 



Skunk, warning colour of, 134 



Sloth, colour of, 125 



Snails, variation in, 44 



Snakes, mimicry in, 140 



Sole, see Flounder, 86 



Solen, eye of, 107 



Solomon, classification of ani- 

 mals, 1 



Somerville, Lord, on breeding 

 sheep, 36 



Spanish fowl, 35 



Species, extinction of, 68 

 illustrations of, 4 



Spencer, Herbert, 17 



Spencer, Lord, on breeding 

 cattle, 36 



Spiders, alluring resemblance in, 

 132 



Splint bones of horse, 67, 96, 161 



Squirrels, flying, 168 



Stenorhynchus, 132 



Stick caterpillars, 126 



Stick insect, 129 



Stigmaria, 57 



Stoat, colour of, 124 



Structural modifications, 38 



Struggle for existence, 41 



Sturgeon, 167 



Survival of the fittest, 47 



Swimming bladder of fish, 167 



Tapirs, fossils of, 56 



geographical distribution of, 75 

 Ternate, 212 

 Tertiary period, 56 

 Theromorpha, 187 

 Thomisus decipiens, 132 

 Thrush,epigamic coloration in, 141 



