A sampling of x-ray images of natural subjects on Earth. Weighed towards plants and seashells, but also includes animals and fungi. 750 images cover 500 species. They are sorted into 25 Forms by the Universal Radiographic Forms Society, which ends the book giving a stern warning to Earthlings. Correction: The Zig-Zag section snails thought to be in Vertigo genus are really somewhere in the Urocoptoidea superfamily.