Sleep, alternation of night and day in its bearing upon periodic, 157-158, 159, 167, 168 animals’ winter, 165, 166 artists’ varied portrayal of, 156, 157 definition of term, varied, 157-161 irregularities and abnormal manifestations of, 164-166 length and duration of, conditions affecting, 166-167 man’s, compared with repose or quiescence of other living things, 159-161 salient feature connected with, 161-164 Shakespeare on, 155, 156 (quotations) Snails, whelks and propagation of, 137, 138 protection of young, 137, 138 Snakes, dragons and, connection between, 120-123 winged serpents, and probable origin of, 121-125 Solar system, comparative distance from “fixed stars,” 221-222 Sound, rate at which it travels, 221 Sparrows— hedge and house, distinction between, 267 differences between, 266-268 cuckoo eggs laid in nests of, 266, 267 use to agriculturists, 267 house and tree, close connection between, 268 harm done by, 267, 268 hidden or latent capacity in, 268 probable effects of destroying, 268 various species related to, 268 _Spectator, The_, case of poisoning by _Rhus toxicodendron_ recorded in, 96 Spiders, garden, use made by astronomers of thread of, 262, 263 gossamer threads of minute autumn, 287-289 spinnerets of, 289-291 threads produced by, various uses made of, 289-292 various species of, 289 Spurges (_Euphorbiaceæ_), various species of, 301 Star-fishes, propagation of, 329-330 Stars, early superstitions with regard to, 227, 228 fixed, comparative distance of solar system from, 221 estimated number of, 222 measurement of, 225 “photographic,” estimated distance of, 223 shape of, 231, 233 “Vega,” position of, 224, 225 _Stegomyia_ Gnat, 2, 3 Stings, poisonous, American plants possessing, 104 comparison between plants and animals possessing, 97, 106 nettles and other plants provided with, 103, 104 Stone-borers, shell-fish and worm, 347-349 “Suspended animation,” examples of, 168, 169 Symbolism, legendary monsters in relation to, 125, 127 Tadpoles, food of, 211, 212 growth and development of, 210,211 gigantic, 218 Tait, discoveries of, with regard to ozone, 252 Tapestry, Bayeux, representation of Halley’s comet in, 231 Tertiaries, the, sand and clay deposits termed, 83 Thayer, Abbott, colour-protection and invisibility of animals as demonstrated by, 306-312 Troughton, use of spider’s lines in telescopes introduced by, 292 Tissue, explanation of term, 174 Toads, English species, 216 European species, various, 216-219 gigantic tadpoles of spur-heeled, 216-218 method of catching prey, 219 Tolstoi, Metchnikoff’s meeting with, 43, 44 “Toxin,” conversion into “anti-toxin,” 102 Trees, English, derivation of various, 57 Tree-sparrows, 268 Trout, “natural selection” theory in relation to increased caution of, 269, 270