MOUSE, love of music in, 116; musical discrimination in, 117; Quigley's observations, 117; Benedick's experiments with, 117; author's observations and analysis of the song of "singing," 118; Ada Sterling's observations of music-loving, 118, 119. MULE, idea of time evinced by a, 175, 176. MYRIANIDA, eyes of, 17; reproduction in, 18. MYRMECA RUGINODIS, memory of friends (kindred) in, 68; experiments with, 68. MYRMECOCYSTUS, the honey-making, 157; natural history of, 158; author's experiments in testing the reasoning powers of, 158, 159; division of labor in a colony of, 161. N NECTOCALYX, marginal bodies in jelly-fish's, 51. NERVE, transmission of impressions through, 41; the power of discrimination in, 41; the association of ideas (impressions) in, 43; memory in, 43. NEWT, tinctumutation in, 186; author's experiments with, 186. O OEQUOREA, eyes of, 15. OESTRUS EQUI, selection of foreleg of horse for oviposition by, 103. ONCHIDIUM, cephalic eyes of, 26; dorsal eyes of, 26. OPOSSUM, letisimulation in the, 202, 212. ORANG-UTAN, laughter in the, 89; use of missiles by, 222. OX, homing sense in the, 199, 200. OYSTER, eyes of, 16. P PAPILIONINÆ, length of life in tropical, 137. PERCH, love of offspring in the white, 138. PERIOPHTHALMUS, habitat of, 25; peculiar mode of life of, 25; eyes of, 25; food of, 26. PIGEON, love of music in the, 122; Lockman's account of a music-loving, 122; musical discrimination in, 122. PIPE-FISH, parental affection in the, 139; Risso's observations, 139. PLAICE, the origin of unilateral eyes in the, 9; absence of color-changing faculty in blind, 188; Pouchet's demonstration of the color-changing function of the sympathetic nerves in, 189. PODURA, _F. fusca_ and _F. rufescens_ make pets of, 126; author's observations of, 126. POLYERGUS, lowering tendency of slavery shown by, 155, 156. PRIONUS, author's experiments in locating organs of hearing in, 36. Q QUAIL, domesticated, 111; love of caresses in, 111; love of instrumental music in, 111; fondness for the singing voice in, 112. R RAT, fondness for instrumental music in, 116; power of musical discrimination in, 116. REASON, definition of, 147; difference between instinct and, 148. RHIZOPOD, sense of direction in, 48; Carter's observations of, 49; memory in, 60. ROBIN, homing sense in, 199. S SAND-WASP, memory of locality in, 62; author's experiments with, 63. SARCOPTES HOMINIS, death-feigning in, 209. SATIN BIRD, æstheticism in the male, 128; author's observations of, 128. SEA-URCHIN, eyes of, 16. SNAIL, eyes of, 19; visual powers of, 19; courtship of, 20; location of sense of direction in, 194; author's experiments with, 194; author's experiments in demonstrating homing sense in the, 194.