Ernst Haeckel's Discomedusae.

Ernst Haeckel (1834-1919) was a German biologist who drew beautiful illustrations of weird animals, plants, and micro-organisms in his work Kunstformen der Natur (Art Forms of Nature).

Haeckel's a flamboyant and interesting man: he promoted Charles Darwin's work in Germany, but at the same time he often fudged the details of his work to fit many of his hare-brained theories.

Unfortunately, Haeckel also promoted the idea of "biogenic theory", where he postulated that there are "primitive races" that require the supervision and protection of a more "mature" societies.

Link: Art Forms of Nature | Wikipedia entry on Haeckel (via Mad Professor)