Karl Ernst Ritter von Baer, Edler von Huthorn (1792-1876) was a Estonian naturalist, biologist, geologist, meteorologist, geographer, a founding father of embryology, explorer of European Russia and Scandinavia, a member of the Russian Academy of Sciences, a co-founder of the Russian Geographical Society and the first President of the Russian Entomological Society. He studied the embryonal development of animals, discovering the blastula stage of development and the notochord and described the germ layer theory of development (ectoderm, mesoderm, and endoderm) as a principle in a variety of species laying the foundation for comparative embryology.In 1826 Baer discovered the mammalian ovum and established that mammals develop from eggs. In geology the term Baer's law also refers to the proposition that in the northern hemisphere, erosion occurs mostly on the right banks of rivers, and in the southern hemisphere on the left banks. Baer Island in the Kara Sea was named after him for his important contributions to the research of Arctic meteorology between 1830 and 1840. Baer was a pioneer in studying biological time, the perception of time in different organisms or what we now call subjective biology. He died in 1876 at the age of 84.