Frog development. 17th century artwork comparing the development of a frog (left) to that of a carnation (Dianthus sp.) plant (right). Plate 12 from 'Historia Insectorum Gerneralis' (1669) by the Dutch entomologist Jan Swammerdam (1637-1680). Swammerdam was the first to demonstrate that the different life stages of insects were developmental stages of the same animal, not changes of animal type, as believed at the time.