EMBRYOLOGY OF FROG-Grey Crescent

1. Grey crescent is a crescent-like and grey coloured area developing on the surface of amphibian egg opposite to thepoint of sperm entry.
2. lt is a surface feature developing as a result of cytoplasmic movements stimulated by sperm entry in the egg.
3. It appears just above the margin where the yellow-white vegetal pole material merges with the darkly pigmented animal pole material. '

4. It appears on the surface of the egg opposite to the point of sperm entry.
5. Grey crescent marks the fiiture dorsal side of the embryo.
6. The first cleavage bisects the grey crescent into two equal halves and this plane represetyhe future median plane of the embryo.
7. The formation of grey crescent, thus fixes up the final symmetry of the egg and the future embryo.
8. In the gastrula, the grey crescent materials are located on the dorsal lip of the blastopore.
9. The grey crescent materials function as the organizer because, when it is removed from the embryo, the embryo fails to develop further. At the same time when a normal embryo is grafted with another grey crescent, two embryos develop.
10.In later gastrula grey crescent materials are incorporated with the chorda mesoderm.