ChitinBased Organic Networks: An Integral Part of Cell Wall Biosilica in the Diatom Thalassiosira pseudonanaFinancial support from the Deutsche Forschungsgemeinschaft is gratefully acknowledged Br 1278123. We thank N. Eichner, R. Hett, G. Lehmann, and Dr. S. Wenzl Regensburg as well as M. Kammer Dresden for excellent experimental assistance.