Engraving of Karl Ernst von Baer (1792-1876), Estonian embryologist. As was the case with most 19th Century Russians, Baer's higher education was based in Germany. At the University of Konigsberg in 1827, he published his work on the mammalian egg. He then went on to study embryos, showing that the developing egg developed several layers of tissue from which specialised organs grew. He also showed the similarity in the embryology of diverse mammalian species. This was confirmed when he discovered that all mammalian embryos had a notochord at some stage, later developing as a spinal cord. As a result, the phylum Chordata was established as part of animal classification.