(5) Division of the spindle into two halves, one remaining in the egg, the other in the prominence. The prominence becomes at the same time nearly constricted off from the egg as a polar cell.
(6) Formation of a second polar cell in same manner as first, part of the spindle still remaining in the egg.
(7) Conversion of the part of the spindle remaining in the egg after the formation of the second polar cell into a nucleus—the female pronucleus.
(8) Transportation of the female pronucleus towards the centre of the egg.
(9) Entrance of one spermatozoon into the egg.
(10) Conversion of the head of the spermatozoon into a nucleus—the male pronucleus.
(11) Appearance of radial striæ round the male pronucleus which gradually travels towards the female pronucleus.
(12) Fusion of male and female pronuclei to form the first segmentation nucleus.
List of important recent Publications on the Maturation and Impregnation of the Ovum.
1. Auerbach. Organologische Studien, Heft 2.