The embryo is thus left almost unaffected, and serves as a record of the past condition of the species.
Hence it is that existing species during the early stages of their development so often resemble ancient and extinct forms belonging to the same class.
On this view of the meaning of embryological resemblances, and indeed on any view, it is incredible that an animal should have undergone such momentous and abrupt transformations as those above indicated, and yet should not bear even a trace in its embryonic condition of any sudden modification, every detail in its structure being developed by insensibly fine steps.