A fluid dispenser pumps fluid in increments. The dispenser includes a computer which, on command, determines the volume of fluid dispensed per increment, the determined value constituting a calibration value which is stored in the memory of the computer. A controller which may include the computer as a component provides for dispensing a selected number of doses, each of a selected volume. The controller can also specify a time interval between the delivery of successive doses. The dispenser is particularly useful in combination with apparatus for charging petri dishes with agar.