In Hans Spemann’s 1928 salamander experiment, what process did the transplanted tissue help organize?

Hans Spemann’s 1928 salamander experiment showed that transplanted tissue could organize embryonic development.

Spemann and Hilde Mangold transplanted a small region from one amphibian embryo to another. The transplanted tissue induced nearby cells to form a second embryonic body axis, including structures associated with a nervous system and supporting tissues.

They called the influential region the organizer. The experiment demonstrated that embryonic cells are guided by signals from neighboring tissues, rather than developing entirely independently according to their own fixed destinies.

The work became central to experimental embryology and developmental biology. Spemann received the 1935 Nobel Prize in Physiology or Medicine. The organizer is now understood through molecular signaling pathways, including factors in the Chordin and BMP systems, although those molecular details were unknown in 1928.