 The modified microscope had a prism which could produce a microscopic spectrum on a microscope slide.The device could also distinguish and measure different wavelengths of light making it a “micro-spectroscope.” Engelmann used this device to illuminate a strand of "Cladophora" (not "Spirogyra") with light from the visible spectrum, exposing different sections to different wavelengths (or colors of light).He added the oxygen seeking bacteria B. termo to this setup and noted where they accumulated (Note