Abstract: A microbiological assay investigatory apparatus has a source of electromagnetic waveform energy, a support and a linear color sensor. The support serves to hold a microbiological assay tray in a predetermined location relative to the source and to the sensor. The assay tray has different reaction chemicals and microorganisms of the same type in respective wells or chambers. The linear color sensor is disposed in a predetermined position relative to the support and concomitantly the assay tray for receiving electromagnetic waveform radiation emanating from a linear array of the wells in response to waveform energy from the source. The linear color sensor generates a signal encoding colorimetric data pertaining to a series of samples lying along a line intersecting the linear array of the wells.