Energy transfer processes at 10 K in the water-soluble bacteriochlorophyll a-protein complex (FMO complex) from the green bacterium Prosthecochloris aestuarii have been studied by femtosecond one- and two-color pump-probe measurements. Decay-associated spectra have been obtained for different excitation wavelengths. From these we conclude that energy relaxation occurs via a stepwise, cascading process down the Q(y) manifold of energy states in the FMO complex. Observed time constants for these steps are 500 fs and 1.7, 5.5, and 30 ps and are correlated with the position in the Q(y) manifold, becoming shorter with increasing energy. Anisotropy decay functions at different wavelengths exhibit two major components : one of similar to 100 fs and one of similar to 1 ps.