Carl Wilhelm von Nageli (1817-1891), Swiss botanist. Nageli studied cell division and pollination. He is best known for his unproductive and discouraging correspondence with Gregor Mendel concerning the latter's celebrated work on Pisum sativum, the garden pea. He was an advocate of orthogenesis and an opponent of Darwinism. He developed an inner perfecting principle which he believed directed evolution. He wrote that many evolutionary developments were non-adaptive and variation was internally programmed.