False-colour scanning electron micrograph (SEM) of the centric, brackish water diatom Cyclotella meneghiniana. Diatoms are a type of single-celled algae distinguished by an intricate, glassy, silica-based cell wall or frustule. The frustule consists of two valves, which fit together like the halves of a box; one valve is slightly larger than the other & acts as the lid". The micrograph shows one valve, & the surrounding girdle band which binds it to the other valve. When diatoms divide, each valve produces a new half inside itself. Diatoms are an important component of the marine & freshwater plankton. Magnification: x950 at 35mm size. Yellow tint. Original is BW print B305/19M. Reference: MICROCOSMOS, figure 5.29. page 103."