The early stages of development in Carcharhinus plumbeus

Six embryos of the sandbar shark, Carcharhinus plumbeus , were found in a gravid female caught at Ras Muhammad, southern tip of Sinai peninsula, in October 1975. Their external morphology, internal organs, and the structure of the egg case and the uterus are described. Embryos were estimated to be two months old and all were in a stage of development between the end of the external-gill phase and before the beginning of the pseudoplacenta formation. The foetomaternal interrelation is based on oxygen supply from the maternal uterus mucosa and some mucus is produced by tubular glands also in the uterus mucosa. The compartments formation and the septum generation are described. An embryonic-membrane-storage chamber has been found for each embryo and we assume that this structure is common, at least, to all the genus Carcharhinus .