  The entropy change $\Delta S$ between the high-temperature cubic phase and
the low-temperature tetragonally-based martensitic phase of
Ni$_{2+x}$Mn$_{1-x}$Ga ($x = 0 - 0.20$) alloys was studied. The experimental
results obtained indicate that $\Delta S$ in the Ni$_{2+x}$Mn$_{1-x}$Ga alloys
increases with the Ni excess $x$. The increase of $\Delta S$ is presumably
accounted for by an increase of magnetic contribution to the entropy change. It
is suggested that the change in modulation of the martensitic phase of
Ni$_{2+x}$Mn$_{1-x}$Ga results in discontinuity of the composition dependence
of $\Delta S$.
