Huxley was the first man to attack Owen's ideas on the vertebrate skeleton, in his Croonian Lecture to the Royal Society in 1858. He showed from a study of the early stages of lower fish, and also the stickleback and the frog, that the segmentation of the skull in higher vertebrata is a secondary process, and is independent of vertebration. The basis of the work was embryology, but the early history of the skull was known in only a few species.