It was on a visit to Bognor collecting sand that he encountered Polyzoa and Foraminifera, which he sorted, mounted and studied. Parker became one of the greatest authorities on the Foraminifera, a group containing microscopic single-celled amoeboid protists with calcareous tests (shells). Had he not met Rupert Jones and Crawford Williamson he might have remained an unpublished amateur. It was Jones, mainly, who taught him how to present his considerable knowledge, and together they wrote 34 papers on the forams. At the same time, Parker worked on his dissections, preparations and skeletons of vertebrates, especially birds. He developed, for example, about 300 preparations of bird wings and many complete skeletons. This work resulted in 24 papers on birds, including one on Archaeopteryx. There is a general article on birds in Encyclopædia Britannica, 9th ed.  Richard Owen was one of Parker's teachers, yet Parker came to overthrow the master's ideas. Owen's view on anatomy did not derive from evolution, but from German philosophical notions of idealism. These ideas, associated in biology with Goethe and Kant, and developed in anatomy by Oken and Cuvier, were used by Owen in his theoretical expositions. Vertebrate anatomy, in this scheme, was to be seen as variations on an archetype. From an idea of Goethe's in 1790, Oken developed a theory that the bones of the skull were four modified vertebrae. Oken's exaggeration "The entire man is only a vertebra" was memorable. Oken's ideas were revived and expanded by Owen, and presented to the British Association meeting in 1846. The weak point in Owen's theory was its basis solely on the more derived and specialised skulls, and even so it took no notice of their embryological development. For example, Owen made no reference to the work of Rathke, who had shown in 1839 that there was no sign of the four vertebrae in the early embryo of snakes. 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.