The nematic liquid crystalline state is characterized by long-range orientational order of the average direction of the long molecular axis. Similar to the case of a Heisenberg ferromagnet it is a state of a spontaneously broken continuous orientational symmetry of the high temperature phase, that is, of the isotropic liquid phase. As a consequence, the spectrum of collective excitations of the nematic director field is expected to be gapless in the long-wavelength limit and the so-called Goldstone mode should exist [ 1-31.For finite wavelengths, the collective dynamics of bulk nematics can be described within the hydrodynamic equations of motion introduced by Ericksen [4-81 and Leslie [9-111. A number of alternate formulations of hydrodynamics [12-181 leads essentially to the equivalent results [19]. The spectrum of the eigenmodes is composed of one branch of propagating acoustic waves and of two pairs of overdamped, nonpropagating modes. These can be further separated into a low-and high-frequency branches. The branch of slow modes corresponds to slow collective orientational relaxations of elastically deformed nematic structure, whereas the fast modes correspond to overdamped shear waves, which are similar to the shear wave modes in ordinary liquids.In the long-wavelength limit, the relaxation rates for both modes are proportional to q2 which is characteristic of hydrodynamic modes. Here q is the wave-vector of the overdamped mode.