A system and method for harvesting, storing, and implanting biological units, in particular hair follicular units (FUs). The system is particularly useful to facilitate hair transplant procedures. FUs are harvested from a body surface, either attached to a patient or in a strip of removed tissue, and shuttled into a cartridge having a plurality of receptacles. The receptacles are open in a distal direction toward a removal tool, but a cover over the proximal ends of the receptacles prevents the FUs from continuing out of the cartridge. One way to shuttle the FUs is to provide a pressure differential, such as by applying suction to the proximal end of a receptacle. The shuttle subsystem may be incorporated within an overall automated or robotic system, or the shuttle subsystem may form part of a semi-automated or even manual apparatus.