Roux
                experiment

Roux's experiment on frog eggs (1888)

    Roux pierced one cell [here, the right side] of a two-cell frog embryo with a hot needle. This cell continued to divide through the blastula stage [top row: large cells on the right, while the other [left] side continued to develop essentially normally. The blastocoel (F) is apparent in both pictures. A sagittal section through the left side (below, left] shows normal cell movement expected for a gastrula, including epiboly of the dorsal lip (Ee) inward, giving rise to the production of the three cell layers. However, subsequent development produced only the left side of a frog, as shown by a cross-section through the embryo, where neurulation has produced the folds of the neural plate (Md) on the left side, and the right side remains undifferentiated.

    Roux concluded that development was mosaic, and that already at the two-cell stage determinants in the single fertilized eggs determined left- vs right-side development. Subsequent divisions further divided determinants so as to determine the fate of the daughter cells. Thus embryonic development is a consequence of factors internal to the embryo being partitioned and gradually manifesting themselves.

    Roux operated without knowledge of Mendelian Genetics, and neglected the possibility that presence of the 'killed' right-hand cell might affect development of the un-operated left side. His results contrast with those of Hans Driesch's experiment.



All text material ©2021 by Steven M. Carr