ABSTRACT
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.
During the summer of 1937 I had the opportunity of working at the Marine Laboratory of the Carnegie Institution of Washington on Dry Tortugas, Florida.
The “astral lake” or “lake” is the term used by Chambers (1917) for the hyaline region within the aster from which innumerable rays radiate. Its site is the “centrosphere” of cytologists.
The deceleration in the movement of the egg nucleus as it penetrates deep into the aster causes, in itself, a pronounced increase in the curvature of the path of the egg nucleus. However, if no force entered other than that carrying the egg nucleus toward the lake, the path of the egg nucleus would always be directed toward the lake.
