I have two small embryos preserved in alcohol, that I forgot to label. At present I am unable to determine the genus to which they belong. They may be lizards, small birds, or even mammals. Karl von Baer (1828) The changes undergone by a developing embryo forms an hourglass: early on embryos from different species vary significantly, later on, they converge to be similar, and finally, they...
Phylotypic stage
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