Karl Ernst von Baer

Karl Ernst von Baer (February 17 1792 - November 26 1876) was a Prussian-Estonian naturalist.

Born in Piibe (Piep), Estonia. Educated at the Cathedral School in Reval (Tallinn) and the University of Dorpat (Tartu). He became a professor at Königsberg University (Kaliningrad) in 1817 and full professor of zoology in 1821. He studied the embryonal development of animals, discovering the blastula stage of development and the notochord, with Christian Pander described the germ-layer theory of development (ectoderm, mesoderm, and endoderm) and discovered the mammalian ovum in 1827. He laid the foundations of the science of comparative embryology with his book Über Entwickelungsgeschichte der Thiere (1828) and formulated what would later be called the Baer laws:

1. The general characters of the group to which an embryo belongs appear in development earlier than the special characters.
2. The less general structural relations are formed after the more general, and so on, until the most specific appear.
3. The embryo of any given form, instead of passing through the state of other definite forms, on the contrary, separates itself from them.
4. Fundamentally the embryo of a higher animal form never resembles the adult of another animal form, but only its embryo.

In 1834 Baer joined the St Petersburg Academy of Sciences, first in zoology (1834-46) and then in comparative anatomy and physiology (1846-62). His interests while there were ichthyology, ethnography, anthropology and geography. The last years of his life (1867-76) were spent in Tartu, where he became the one of the leading critics of the theories of Charles Darwin.