Jules Verne achieved a triumph when his imagination, fired by Rudolph Wyss’ “The Swiss Family Robinson,” was impelled to carry the story a step farther in “The Castaways of the Flag.” An island was ever his spiritual home; and no one was ever happier upon one. “The Castaways of the Flag” is a satisfactory sequel to “The Swiss Family Robinson” because it is the production of Jules Verne, an original genius, set in motion by Rudolph Wyss. Wherever “The Swiss Family Robinson” is heard, “The Castaways of the Flag” should also be heard.