Nageli

NAGELI Karl (Carl Wilhelm von Naegeli, 1817-91), outstanding German botanist and biological theorist of the 19th century. Nageli received his education in Zurich, first worked in Berlin and Jena, where with Schleiden he founded the journal "Zeitschrift f. wissenschaftliche Botanik" (Zurich, 1844-46), then in Italy and England, where he studied algae. Nageli first obtained a professorship in Zurich, then in Freiburg, where he conducted major studies on the structure of starch grains, which led him to the theory of idioplasm (see). He ended his life in Munich as a professor and director of the botanical institute. In addition to the works mentioned, Nageli's remarkable discoveries include the discovery of spermatozoa in ferns, works on the structure and growth of cell walls (theory of intussusception), a number of morphological-physiological works, and especially works of a purely theoretical nature, which played a largely reactionary role in the history of biological thought. Assigning a negligible role to Darwinian theory of selection, N. put forward a number of other factors of evolution. The improvement of organisms depends, in his opinion, on internal causes lying in the molecular forces of the hereditary substance (idioplasm). Of external influences, some produce only non-hereditary modifications; others, acting on the idioplasm, cause new properties of an adaptive nature in the organism. N. is distinguished by the characteristic tendency of German natural philosophers to develop his purely speculative doctrine down to the smallest details. His fascination with his speculative theories may be the reason that N., while working on the problem of heredity, could overlook the remarkable experiments of Mendel, who was in correspondence with him. Nageli's most important works: "Die Stärkekorner, morphologische, physiologische, chemisch-physikalische und systematisch-botanische Monographie" (Munich, 1858); "Entstehung u. Begriff der naturhistorischen Art" (Lpz., 1865); "Mechanisch-physiologische Theorie der Abstammungslehre" (Munich-Leipzig, 1884).