Plankton diatoms, North Sea (with quite a few Rhizosolenia sp.). Mountant has yellowed. Prepared by Watson and Sons Ltd. Olympus BHB microscope using 450nm LED light. 10x Nikon Plan Apo NA 0.45 objective. Leitz Heine condenser, set to dark ground. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. Single unstacked image.