Colon, 68.

Dead-leaf butterfly (illus.), 211.

Colonial jelly-fishes, 45; Protozoa, Death, 103.

Cottony cushion scale (illus.), 142. Diodon hystrix (illus.), 134.
Courtship, instincts of, 248.
Crab, metamorphosis of (illus.), 97;

with sea-anemone (illus.), 177.
Cray-fish, auditory organ of (illus.),
233.

Cricket, auditory organ of (illus.),
234.

Cricket, mole (illus.), 146.

Crinoid (illus.), 305.

Crop, 71.

Crowd of animals, 114.

Crustaceans, adults and larvæ
(illus.), 195.

Dismal Swamp fish (illus.), 282.
Distribution, character of barriers,
to, 288; geographical, 272; in-
fluenced by climate, 291; laws
of, 274; modes of, 296; moun-
tains a barrier to, 293; of Cana-
dian Skipper butterfly (illus.),
273; of clouded Skipper butter-
fly (illus.), 273; of Erynnis mani-
toba (illus.), 273; sea a barrier
to, 288; temperature a barrier
to, 290.
Diverticula, 74.

Cteniza californica, nest of (illus.), Division of labor, 22, 168.

261.

Cyanocitta cristata (illus.), 138.
Cycle, life, 78.

Cypselurus (illus.), 131.
Cytoplasm, 3.

Dog, pointer (illus.), 256.
Dragon-fly, eye of (illus.), 239.
Duck, family (illus.), 137.
Duodenum, 68.

Duration of life, 101.

Earthworm, alimentary canal of | Fish, egg of (illus.), 79; embry-

(illus.), 71.

Ectoblast, 82.

Ectoderm, 33.

Egg case of Californian barn-door
skate (illus.), 140; cockroach (il-
lus.), 140.

Egg cell, 21, 56.

Egg, fertilized, 35; of bird (illus.),
79; of butterfly (illus.), 79; of
fish (illus.), 79; of katydid (il-
lus.), 79; of skate (illus.), 79; of
toad (illus.), 79.
Electric ray, (illus.), 135.
Embryology, 64.

Embryonic development, 80; of
the pond snail, 81.

onic stages of (illus.), 87; -louse
(illus.), 188.

Fishes, man-of-war (illus.), 175;
nest-making habits of, 264.
Fission, 9; binary, 54.
Flagella, 25.
Flagellata, 24.

Flatworm, alimentary canal of
(illus.), 70.

Flounder, development of (illus.),
100; wide-eyed (illus.), 100.
Flying fishes (illus.), 131.
Food, adaptations for securing,
125; necessary to animal life,
106.

Form, primitive, 20.

Gapes, worm which causes, 60.

Eye of dragon-fly (illus.), 239; of Gastrula, 82.

jelly-fish (illus.), 238.

Gemmule, 35.

Generalization, 66.

Fauna, 296; bassalian, 305; littoral, Generation, spontaneous, 51.

306; pelagic, 304.
Faunal areas of the sea, 304.
Feeding habit of Californian wood-
pecker (illus.), 128, 129; of Mela-
nerpes formicivorus bairdii
(illus.), 128, 129; instincts of,

244.
Female, 57.

Generations, alternation of, 51.
Geographical distribution, 272.
Geometrical larva on branch (illus.),
209.

Gerrhonotus scincicauda (illus.),

204.

Giraffe (illus.), 126.
Gizzard, 71.

Grasshopper, auditory organ of Icerya and Vedalia, 121.

Gregarina polymorpha (illus.), 14. | Indo-African realm, 301.

Habitat, relation of species of, 283. | Instincts, altruistic, 243; classifi-

Jack-rabbits, showing variation
(illus.), 281.

Jay, Canada (illus.), 138.
Jejunum, 68.

of Jelly-fish, eye of (illus.), 238.
Jelly-fishes, 37; colonial, 45.

Kallima (illus.), 211.

nest of rufus Kangaroo (illus.), 139.

Katydid, egg of (illus.), 79.
Lady-bird beetles (illus.), 214.

Lady-fish, metamorphosis of (illus.), | Marks, recognition, 22, 129, 223.

98.

Larva, 92; of the mosquito, 93;
of butterfly pupating (illus.), 94;
of the honey-bee, 152.
Leaf-cutting ant mimicked by tree-
hoppers (illus.), 220.
Lemur (illus.), 302.
Lemur varius (illus.), 302.
Lemurian realm, 302.

Lepas, adult and larva (illus.), 195;

metamorphosis of (illus.), 101.
Lerema accius, distribution of
(illus.), 273.

Lernæocera (illus.), 188.
Life cycle, 78.

Life, communal, 168; duration of,
101; primitive, 21; processes,
21; social, 149.

Light, influence of, on animals,

237.

Lipeureus densus (illus.), 188.

Littoral fauna, 306.

Lizard, alligator (illus.), 204.

Lizzia koellikeri, eye of (illus.),

238.

Medusæ, 41.
Megalops, 97.

Melanerpes formicivorus bairdii,
feeding habit of (illus.), 128, 129.
Membracidæ mimicking Sauba
ant (illus.), 220.
Mesoderm, 33.

Metamorphosis, 90; of Albula vul-
pes (illus.), 98; of Anosia plex-
ippus (illus.), 92; of barnacle
(illus.), 101; of butterfly (illus.),
92; of crab (illus.), 97; of in-
sects, 90; of lady-fish (illus.),
98; of Lepas (illus.), 101; of
mosquito (illus.), 93; of sea-ur-
chin (illus.), 96: of sword-fish
(illus.), 99; of toad, 94, (illus.),
95; of Xiphias gladius (illus.),

99.
Metazoa, 32.

Metridium dianthus (illus.), 43.
Micro-organism, 16.

Migration of lemming, 118; of lo-
cust, 118.
Mimickry, 218.

Locust, post-embryonic develop- Mind, 255.

ment of (illus.), 91.
Locusts of Galapagos
(illus.), 280.

Mining-bee, nest of (illus.), 160.

Islands | Molt, 91.

Louse, sucking (illus.), 188.

Macropus rufus, 139.

Mad Tom (illus.), 132.

Male, 57.

Mammals, care of young of, 268.

Manatee (illus.), 277.

Monarch butterfly (illus.), 219;
mimicked by Viceroy butterfly
(illus.), 219.
Monogamy, 135.

Mosquito, auditor organ of (illus.),
235; head of (illus.), 127; meta-
morphosis of (illus.), 93; young
stages of (illus.), 147.

Man-of-war, Portuguese (illus.), Moth, cankerworm (illus.), 59.

175.

Mantis (illus.), 127.

Many-celled animal, 2.

Marine Protozoa, 15.

Mountains as barriers to distribu-

tion, 293.

Mouth parts of mosquito (illus.),

127.

Mouse-fish in gulf-weed (illus), 208.
Mt. Orizaba (illus.), 300.
Multiplication, 50; of animals,
114; simplest method of, 53;
slightly complex methods of, 54.
Murres, Pallas's (illus.). 165.
Mussel, alimentary canal of (illus.),
72.

Mutual aid, 163.

234; of grasshopper (illus.), 234;
of mosquito (illus.), 235; of mol-
lusk (illus.), 233.
Organic matter, 112.
Organs, auditory, 232; of smell,
229; of sound-making, 235; of
taste, 228; of touch, 226; spe-
cialization of, 66; vestigial, 147.
Oriole, Baltimore, nest of (illus.),
267.

Ornithotomous sutorius, nest of,
268.

Osprey Falls (illus.), 285.
Otolith, 232.

Ox, alimentary canal of (illus.) 67.
Oxygen, necessary to animal life,
107.

Pagurus (illus.), 176.
Pandorina, 26.

Narcine brasiliensis (illus.), 135.
Natural selection, 117.
Neotropical realm, 301.
Nerve cells, 240.
Nerve fibers, 240.
Nest-making habits of birds, 264;
of fishes, 264; of insects, 262;
of invertebrates, 258; of spiders,
259; of vertebrates, 264.
Nest of Baltimore oriole (illus.),
267; of beavers (illus.), 269; of
Californian bush-tit (illus.), 270;
of Cleniza californica (illus.),
261; of pocket - gopher (illus.), | Papilla, tactile, of skin of man
271; of rufus humming - bird
(illus.), 265, 266; of tailor-bird
(illus.), 268; of trap-door spider
(illus.), 261; of turret - spider
(illus.), 262.

Nokee (illus.), 132.

Nomeus gronovii (illus.), 175.
North Temperate realm, 299.
Nuclear membrane, 3.
Nucleus, 3.

Pandorina sp. (illus.), 26.
Pandorina morum (illus.), 27.
Papilio, chrysalid of (illus.), 205.

(illus.), 227.
Papillæ, 67.
Paramecium, 9.

Paramecium aurelia (illus.), 10.
Paramecium caudatum (illus.), 11.
Paramecium plutorinum (illus.),

11.

Parasite of caterpillar (illus.), 190;
relation to host, 179.

Parasites, simple structure of, 181.
Parasitism, 179; kinds of, 180.

Obelia, alimentary sac of (illus.), | Parthenogenesis, 60.

69.

Esophagus, 67.

Omasum, 67.

One-celled animals, 2.

Patagonian realm, 302.

Pediculus (illus.), 188.

Pelagic fauna, 304.

Pelican, brown (illus.), 125.

Organ, 63; auditory, of cray-fish | Peneus, adult and larva (illus.),