Gibbon, 163.
Gills, 58, 62.
Gill-slits, bars, clefts, 61, 62, 64; in embryos of lizards, birds, mammals, 69; 171.
Giraffe, 133.
Glaciers, alterations made by, 87.
Goats, 157.
Gorilla, 163, 165, 195.
Grand Cañon of the Colorado, 85, 90.
Gravitation, 155.
Guinea-pigs, Brown-Séquard's, 148.