The ornamental design for a mousecage, as shown and described.
FIG. 1 is a perspective view of a mouse cage showing my new design;
FIG. 2 is another perspective view thereof;
FIG. 3 is another perspective view thereof;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a rear elevational view thereof;
FIG. 6 is a left side elevational view thereof;
FIG. 7 is a right side elevational view thereof;
FIG. 8 is a top plan view thereof;
FIG. 9 is a bottom plan view thereof;
FIG. 10 is a perspective view of the mouse cage where the mouse cage is in a configuration of use; and,
FIG. 11 is an exploded perspective view of the mouse cage.
The broken lines in FIG. 10 depict environment that form no part of the claimed design. The broken lines in FIG. 11 depict portions of the mouse cage that form no part of the claimed design.