The pictures illustrate Ernst Haeckel's biogenetic law. In the beginning embryos of different species look remarkable similar, later different characteristics develop. The images initiated controversies and charges of fraud.
<bdi><a href="https://en.wikipedia.org/wiki/en:Ernst_Haeckel" class="extiw" title="w:en:Ernst Haeckel"><span title="German biologist, naturalist, philosopher, physician, and artist (1834-1919)">Ernst Haeckel</span></a>
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1868
Ernst Haeckel: <i>Natürliche Schöpfungsgeschichte</i>, Georg Reimer, Berlin 1868.