The ‘cells of Rauber’ are

The blastomeres in the blastocyst are arranged into an outer layer called trophoblast and an inner group of cells attached to trophoblast called the inner cell mass. Inner cell mass looks like a small knob at one pole which gives rise to the embryo and is called the embryonal knob. The trophoblast does not take part in the formation of the embryo proper. It remains external to the embryo and gives rise to the extraembryonic membranes, namely, chorion and amnion, for the protection and nourishment of the embryo. The trophoblast cells in contact with the embryonal knob are known as cells of Rauber.