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In his Gastraea studies Ernst Haeckel characterized the initial stages of the animal embryo, describing complete and incomplete cleavages in various groups, until the gastrula stage. Thereby, he was able to point out various degrees of developmental diversification in these initial stages of development. As the functional meaning of such cleavages was not clear however, it was difficult to argue about...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.