This paper deals with the adiabatic pulsations of a homogeneous prolate spheroid subject to the tidal action of a secondary rigid body. It is shown that the presence of an external mass partially removes the degeneracy of the fundamental modes belonging to the first spheroidal harmonics. The p-modes are strongly affected but remain always stable when the adiabatic exponent is greater than unity. The gmodes, on the contrary, are nearly independent of the tidal force, except for values of the eccentricity e close to unity. In any case, the tidal action cannot entirely remove the convective instability of a homogeneous spheroid. The third-order virial equations also exhibit the existence of an f-mode belonging to the third spheroidal harmonics which, in agreement with previous works, becomes unstable if e is greater than the critical value 0.94774. This mode is almost independent of the compressibility of the system.