Facts: - known for: chemotaxis - ethnicity: german - field: embryology - birth date: january 9 , 1901 - name: johannes holtfreter - image size: 150px - nationality: united states - death place: 1992 - birth place: richtenberg , germany Based on these bullet points, write a short biography describing the life of johannes holtfreter .
johannes holtfreter was a german-american developmental biologist whose primary focus was the '' organizer , '' a part of the embryo essential for the development of the proper body plan .