Abb. 270: Human blastocyst (above), clearly distinguishable from the blastocyst of a Rhesus monkey (below), at the stage of deposition at the mucous membrane of the uterus (thick green line). The transition of the thick-walled part of the ovum to the thin-walled part is gradual in the upper ovum and abrupt in the lower one.
According to Blechschmidt