English: Gerhard Heilmann's comparative illustrations of the embryos and adult life drawings of a crocodile (C), common fowl (F), lizard (L) and tern (T).
Датум
Извор
The Danish book Vor Nuvaerende Viden om Fuglenes Afstamming
{{Information
|Description = Gerhard Heilmann's comparative illustrations of the embryos and adult life drawings of a crocodile (C), common fowl (F), lizard (L) and tern (T).
|Source = The Danish book ''Vor Nuvaerende Viden om Fuglenes Afstam