Hans Driesch experiment on Sea Urchins (1902)
Driesch tested Wilhelm Roux's theory of
development, with sea urchins instead of frogs.
Instead of destroying one blastomere, he agitated sea urchin
embryos at the two- & four-cell stage until they
disassociated into separate cells. Each cell developed as a
complete larval sea urchin, somewhat smaller than normal. This
Driesch took as evidence for a totipotent or pluripotent
capacity of embryonic cells, meaning that each cell
retained the capacity to develop normally. [Contrast
'retained the capacity" with "retained all the information
necessary ...."]. In Driesch's interpretation, this
implied that development was a consequence of external
factors operating on the cells. This
conclusion was opposite to that of Roux, who argued that
development was the manifestation of internal properties.
At the latter blastula stage of
development, Driesch showed that separation of the upper ('animal')
from the lower ('vegetal') halves allowed the 'animal'
portion to development substantially to maturity, whereas the
'vegetal' half remained essentially undifferentiated.
© 2021 by Steven M. Carr