Karl Ernst von Baer – Wikipedia, the free encyclopedia
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von Baer studied the embryonic development of animals, discovering the blastula stage of development and the notochord. Together with Heinz Christian Pander and based on the work by Caspar Friedrich Wolff he 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 the book Über
Entwickelungsgeschichte der Thiere (1828). In 1826 Baer discovered the mammalianovum. The first human ovum was described by Edgar Allen in 1928. In 1827 he completed research Ovi Mammalium et Hominis genesi for Saint-Petersburg’s Academy of Science (published at Leipzig[7][8]) and established that mammals develop from eggs.
He formulated what became known as Baer’s laws of embryology:
General characteristics of the group to which an embryo belongs develop before special characteristics.
General structural relations are likewise formed before the most specific appear.
The form of any given embryo does not converge upon other definite forms, but separates itself from them.
The embryo of a higher animal form never resembles the adult of another animal form, such as one less evolved, but only its embryo.
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