Pallas travelled throughout the Netherlands and to London, improving his medical and surgical knowledge. He then settled at The Hague, and his new system of animal classification was praised by Georges Cuvier. Pallas wrote "Miscellanea Zoologica" (1766), which included descriptions of several vertebrates new to science which he had discovered in the Dutch museum collections. A planned voyage to southern Africa and the East Indies fell through when his father recalled him to Berlin. There, he began work on his "Spicilegia Zoologica" (1767–80).