The design is defined by the visual features of the INK CARTRIDGE shown in the drawings, whether those features are features of shape, configuration, ornament or pattern, or a combination of any of those features. Drawings of the design are enclosed. The drawings show two variants of the design. Figures 1 through 9 show a first variant. Figures 10 through 18 show a second variant. In the drawings: FIG. 1 is a front plan view of the INK CARTRIDGE according to the first variant; FIG. 2 is a top plan view of the INK CARTRIDGE according to the first variant; FIG. 3 is a right side view of the INK CARTRIDGE according to the first variant; FIG. 4 is a left side view of the INK CARTRIDGE according to the first variant; FIG. 5 is a rear plan view of the INK CARTRIDGE according to the first variant; FIG. 6 is a bottom plan view of the INK CARTRIDGE according to the first variant; FIG. 7 is a left front top perspective view of the INK CARTRIDGE according to the first variant; FIG. 8 is a right rear top perspective view of the INK CARTRIDGE according to the first variant; FIG. 9 is a bottom right rear perspective view of the INK CARTRIDGE according to the first variant; FIG. 10 is a front plan view of the INK CARTRIDGE according to the second variant; FIG. 11 is a top plan view of the INK CARTRIDGE according to the second variant; FIG. 12 is a right side view of the INK CARTRIDGE according to the second variant; FIG. 13 is a left side view of the INK CARTRIDGE according to the second variant; FIG. 14 is a rear plan view of the INK CARTRIDGE according to the second variant; FIG. 15 is a bottom plan view of the INK CARTRIDGE according to the second variant; FIG. 16 is a left front top perspective view of the INK CARTRIDGE according to the second variant; FIG. 17 is a right rear top perspective view of the INK CARTRIDGE according to the second variant; and FIG. 18 is a bottom right rear perspective view of the INK CARTRIDGE according to the second variant.