1874 illustration from Anthropogenie showing "very early", "somewhat later" and "still later" stages of embryos of ﬁsh (F), salamander (A), turtle (T), chick (H), pig (S), cow (R), rabbit (K), and human (M)
Source: Wikipedia - Ernst Haeckel
Haeckel's embryo drawings are something of embarrassment for biology, but how they have been used to mislead their dupes should be an even bigger embarrassment for creationist pseudoscientists, if it were even remotely possible to embarrass them with evidence of false claims, that is.
Haeckel produced his set of drawings intending to show how vertebrate embryology supported Darwinian evolution by pointing to a common ancestor and because the stages of development represented a replay of the evolution which led to their final adult forms. Unfortunately, he not only 'enhanced' his drawings to support this 'Recapitulation theory' but then