ng, 19, 126;
nest-building, gradation in, 18, 120, 121, 122;
instincts, complex, difficulty in believing in their evolution, 20, 121

Intermediate forms, _see_ Forms

Island, _see_ Elevation, Fauna, Flora

Island, upheaved and gradually colonised, 184

Islands, nurseries of new species, 33, 35 _n._, 185, 189

Isolation, 32, 34 _n._, 64, 95, 183, 184

Lepidosiren, 140 _n._, 212

Limbs, vertebrate, of one type, 38, 216

MAMMALS, arctic, transported by icebergs, 170;
distribution, 151, 152, 193;
distribution of, ruled by barriers, 154;
introduced by man on islands, 172;
not found on oceanic islands, 172;
relations in time and space, similarity of, 176;
of Tertiary period, relation of to existing forms in same region, 174

MAMMALS, NAMES OF:--
Antelope, 148;
Armadillo, 174;
Ass, 79, 107, 172;
Bat, 38, 123, 128 _n._, 131, 132, 214;
Bear, sterile in captivity, 100;
--whale-like habit, 128 _n._;
Bizcacha, 168, 203, 212;
Bull, mammae of, 232;
Carnivora, law of compensation in, 106;
Cats, run wild at Ascension, 172;
--tailless, 60;
Cattle, horns of, 75, 207;
--increase in S. America, 90;
--Indian, 205;
--Niata, 61, 73;
--suffering in parturition from too large calves, 75;
Cheetah, sterility of, 100 and _n._;
Chironectes, 199;
Cow, abortive mammae, 232;
Ctenomys, _see_ Tuco-tuco;
Dog, 106, 114;
--in Cuba, 113 and _n._;
--mongrel breed in oceanic islands, 70;
--difference in size a bar to crossing, 97;
--domestic, parentage of, 71, 72, 73;
--drooping ears, 236;
--effects of selection, 66;
--inter-fertile, 14;
--long-legged breed produced to catch hares, 9, 10, 91, 92;
--of savages, 67;
--races of resembling genera, 106, 204;
--Australian, change of colour in, 61;
--bloodhound, Cuban, 204;
--bull-dog, 113;
--foxhound, 114, 116;
--greyhound and bull-dog, young of resembling each other, 43,
44 _n._, 225;
--pointer, 114, 115, 116, 117, 118;
--retriever, 118 _n._;
--setter, 114;
--shepherd-dog and harrier crossed, instinct of, 118, 119;
--tailless, 60;
--turnspit, 66;
Echidna, 82 _n._;
Edentata, fossil and living in S. America, 174;
Elephant, sterility of, 12, 100;
Elk, 125;
Ferret, fertility of, 12, 102;
Fox, 82, 173, 181;