An improved motorized transfer mechanism for use in a continuous ambulatory peritoneal dialysis apparatus (CAPD) is provided for automatically transferring a piercing pin from the clamped port of a used container of used dialysis solution to the clamped port of a container of fresh dialysis solution. The transfer mechanism is characterized by a track member extending between opposed aligned port mountings, an upstanding guideway adjacent to each port mounting and a rack formation located midway between the opposite ends of the track member. The rack formation is rotatably engageable with a circular gear sector secured to the spike carrier disposed within the guideways of the track member. The linear movement between the opposed ports of the spike carrier is performed by a motor-driven drive screw. The intermediate 180 degree rotational movement of the spike occurring when the rack formation of the track member engages the circular gear sector of the spike carrier, both inverts the spike and positions it adjacent an ultraviolet bulb for sterilization thereof.