Greater than Gods and Trysts in Time — C.L. Moore

This volume collects two of her longer short works with the theme of time travel. In "Greater than Gods," a scientist and inventor working on a way to select the sex of unborn children opens up two possible futures for the human race. But when both potential futures begin to communicate with him, he finds his choice will determine the future of the whole human race in ways he never anticipated. In "Trysts in Time," a bored adventurer sets off through time . . . and finds more than he bargained for in a beautiful woman who keeps reappearing throughout all of history!