The Movement of the Egg Nucleus in Relation to the Sperm Aster in the Echinoderm Egg

The names of O. Hertwig, H. Fol, E. Selenka, W. Roux, H. E. Ziegler, E. B. Wilson, and E. G. Conklin are associated with the classic observations on the migration of the male and female pronuclei in the inseminated egg. These workers advanced several interpretations to account for the migration. Later R. Chambers (1917) presented evidence that the aster is a gelated body and that the astral centre is the centre of centripetally directed cytoplasmic currents. On the basis of this interpretation of the aster, a reinvestigation was made of the movements of the pronuclei.