Wilhelm Roux on embryonic axes, sperm entry and the grey crescent

Abstract

In the very year, 1883, when Wilhelm Roux was pondering on the meaning of mitosis (see Sander 1991), he started experimenting on amphibian eggs. The first problem he set out to solve — or rather, the first question he discussed in writing — was the orientation of the prospective embryo in the egg. In amphibians this is a formidable problem, partly owing to the highly complex gastrulation movements, which in some respects have remained enigmatic to this day. Indeed, on trying to ascertain dorsoventral and antero-posterior polarity in the frog’s egg, Roux was confused by aberrant gastrulation movements in quite a spectacular way. Irrespective of this, he gained remarkable and still valid insights concerning the prospective median plane in frog eggs and the epigenetic factors that bring about its orientation — the latter study (Roux 1887) being adorned with further speculations on equal and unequal mitoses during early cleavage.