Hans Driesch

In 1891 Driesch separated the blastomeres of two-cell sea-urchin embryos. Individual cells could produce smaller but complete larvae. In this material and stage, a cell’s developmental potential therefore exceeded the portion it normally contributed within an intact embryo.

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Driesch investigated separation at further stages and fused blastulae to produce larger larvae. These manipulations examined how embryos adjusted when cell number, arrangement and relationships changed, contributing to the study of regulative development.

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Much of Driesch’s embryological research took place at the Naples zoological station. He later taught and wrote philosophy, interpreting biological organization through vitalism. The observable outcomes of his separation and fusion experiments can be distinguished from that philosophical interpretation.

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