DOG, cow chosen as a friend by a, 78; laughter in, 90; fondness for certain musical keys in the, 112; author's experiments with the, 113; origin of musical discrimination in the, 114; knowledge of the echo in the, 115; author's observations of an echo-loving, 115; parental affection in the, 141; abstract idea of numbers in the, 173, 174; phenomenon of dreaming in the, 218; medication by sick, 220.
DROSERA ROTUNDIFOLIA, insectivorous, 208.
DUCK, friendship between bantam cock and, 78; hawk attacked and killed by, 78; sense of direction in, 199.
DYTICUS MARGINALIS, auditory rods of, 30; death-feigning in a fresh-water annelid when approached by, 204.
EAGLE, recognition of individuals by, 76.
EAR, Dyticus, 30; corydalis, 30; grasshopper's, 31; Tabanus, 34.
EARWIG, method of incubation practised by, 105; care of young by, 105; M. Geer's experiment with, 105; love of offspring in, 106; author's experiments in testing parental affection in the, 136.
ECITON HAMATA, ants of the same species rescue an imprisoned, 100; Belt's experiments in testing the sympathy of, 101.
ELEPHANT, abstract ideation in the, 217; Conklin's testimony as to abstract ideation in, 218; mud used to stop bullet holes by, 220; a branch of a bush used as a fan by, 221.
EPIPONE SPINIPES, method of supplying larva with fresh food used by, 104; differentiation in the amount of food for male and female grub, 104.
EUPLOCINÆ, length of life in tropical, 137.
EYE, flounder's, 9; plaice's, 9; sole's, 9; mole's, 10; fresh-water _Cymothoe's_, 13; OEquorea's, 15; sea-urchin's, 16; oyster's, 17; _Alciope's_, 17; snail's, 19; crayfish's, 21; _Gyrinus'_, 23; _Periophthalmus'_, 25; _Onchidium's_, 26; calotis', 27.
FISH, phosphorescent and pigmented, 13; parental affection in, 138; sense of direction in, 200.
FLEA, memory in the, 86; dancing and military evolutions by, 86; method of educating the, 87.
FLOUNDER, the origin of unilateral eyes in, 9.
FORMICA FUSCA, sympathy in, 100; species of _Podura_ domesticated by, 126.
FORMICA RUFESCENS, pet beetles in the nest of, 126.
FORMICA SANGUINEA, slave-making habit in, 155; sympathy evinced by, 102; Lubbock's observations of a sick, 102.
FROG, tinctumutation in the, 182; chromatophores of, 182; Heincke's observations, 183; location of color-changing sense in, 190.