 Wheeler was stimulated by recent late nineteenth-century debates, themselves provoked by a flood of new discoveries. August Weismann and Oscar Hertwig provided particularly strong and contrasting positions. Weismann had begun from an epigenetic viewpoint and initially rejected the idea that individual form emerges through the unfolding, or evolution, of pre-existent form in the inherited germ. But by the time his Das Keimplasm appeared in 1892 (translated into English in 1893), Weismann had changed his mind. As Weismann wrote: