De Gheyn’s pen and ink drawing of a frog closely resembles an engraving, especially in its hooked strokes and diagonal shading. The frog is shown on its back with its hind legs outstretched to provide the best view of its under side. This detailed study scrutinises its surface appearance and structure. De Gheyn was acquainted with leading natural scientists in Leiden, and this drawing was probably made during his time there. Another closely related drawing is also in the collection of the National Gallery of Scotland.