The Givreuse Enigma

A man is found mysteriously duplicated in the trenches of World War I. Brilliantly prefiguring the theme of cloning, The Givreuse Enigma (1917) features the "bipartition" of a human being into two totally similar individuals, each naturally believing himself to be the original. Adventure in the Wild (1935) takes place in the savage, unexplored depths of Sumatra where brave explorers encounter the mysterious hidden race of the bestial Carabao Men, creatures with "monstrous heads, eyes as phosphorescent as a leopard's, canines elongated into tusks, and hair the color of iron."