ancers of, 33.

DIPTERA, ears of, 33;
love of pastime in, 125.

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.

E

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.

ETIOLATION, definition of, 184, 185.

EUPLOCINAE, 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.

F

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 RUFA, sympathy evinced by, 102.

FORMICA RUFESCENS, pet beetles in the nest of, 126.

FORMICA SANGUINEA, slave-making habit in, 155;
sympathy evinced by, 102;
Lubbock's obse