Conkin (Nov. 24, 1963 - Nov. 21, 1952) was an American biologist and embryologist. In 1905 he discovered that the contents of a tunicate's egg weren't uniform.
Different parts of it were differently colored. When the mother egg began to divide, the new daughter cells that came from different colored areas became, as they split away, different types of tissue. The yellow stuff in the egg produced muscle cells, for instance, and the grayish stuff became the gut.
In addition to his work in embryology, he published a number of works on evolution. He estimated he made a thousand public lectures interpreting evolution to religious and lay groups. He was a leading critic of society's response to advanced technology. From Today in Science History