INDEX 



327 



Respiration, 7. 



Resting spore, 28. 



Reticulura, 67. 



Rhizocrinus loxotensis (illus.), 305. 



Rivalry, adaptations for, 185. 



Rookeries, fur-seal (illus.), 169. 



Rumen, 67. 



Sacculina (illus.), 187. 



Sacculina, adult and larva (illus.), 

 195. 



Salamander, embryonic stages of 

 (illus.), 87. 



Saliva, 67. 



Salmon leaping (illus.), 289. 



Salmo viridens (illus.), 145. 



Sarcoptes (illus.), 192. 



Sauba, ant mimicked by Membra- 

 cidce (illus.), 220. 



Scale, red orange (illus.), 196. 



Schilbeodes furiosus (illus.), 132. 



Schistocerca (illus.), 280. 



Scorpion (illus.), 127. 



Scorpion-fish (illus.), 132. 



Sea, a barrier to distribution, 288. 



Sea, faunal areas of, 304. 



Sea-anemone, 37; with algas in 

 body (illus.), 178. 



Sea-cow (illus.), 277. 



Sea-cucumber, alimentary canal of 

 (illus.), 70. 



Sea-squirt (illus.), 194. 



Sea-urchin, metamorphosis of (il- 

 lus.), 96. 



Sea-urchins (illus.), 259. 



Seal, fur (illus.), 136; pups killed 

 by parasite (illus.), 186; rook- 

 eries (illus.), 169. 



Selection,artificial,120;natural,117. 



Self-defense, adaptations for, 128 ; 

 instincts of, 245. 



Sensation, 8. 



Senses, special, 224 ; of the simplest 

 animals, 225. 



Sensorium, 241. 



Serphus (illus.), 141. 



Sex, 57 ; object of, 57 ; dimorphism, 

 58. 



Shark-clinging fish (illus.), 125. 



Sheep, bighorn (illus.), 167 ; Rocky 

 Mountain (illus.), 167. 



Sight, sense of, 237. 



Simplest animals, life of, 1. 



Siphonophora, 46. 



Skate, egg case of California barn- 

 door (illus.), 140 ; egg of (illus.), 

 79. 



Skin of man, tactile papilla of 

 (illus.), 227. 



Smell, sense of, 229. 



Smelling organs, 229. 



Smelling pits of leaf-eating beetle 

 (illus.), 230. 



Social life, 149. 



Sound-making, 235 ; organs, 235. 



South American realm, 301. 



Specialization, 66 ; of organs, 66. 



Special senses, 224. 



Species, altered by adaptation to 

 new conditions, 276; debarred 

 by barriers, 274 ; debarred by in- 

 ability to maintain their ground, 

 275 ; definition of, 279 ; relation 

 of, to habitat, 283. 



Sperm cell, 35, 56. 



Sphinx moth, larva of (illus.), 215. 



Spicules, sponge, 33. 



Spiders (illus.), 212; nest-making 

 habits of, 259. 



Sponges, 32. 



Spongin, 36. 



Spontaneous generation, 51. 



Spore, 15, 52 ; resting, 28. 



Sting-ray (illus.), 133. 



