  Rapidity distributions for $\Lambda$ and $\bar{\Lambda}$ hyperons in central
Pb-Pb collisions at 40, 80 and 158 A$\cdot$GeV and for ${\rm K}_{s}^{0}$ mesons
at 158 A$\cdot$GeV are presented. The lambda multiplicities are studied as a
function of collision energy together with AGS and RHIC measurements and
compared to model predictions. A different energy dependence of the
$\Lambda/\pi$ and $\bar{\Lambda}/\pi$ is observed. The $\bar{\Lambda}/\Lambda$
ratio shows a steep increase with collision energy. Evidence for a
$\bar{\Lambda}/\bar{\rm p}$ ratio greater than 1 is found at 40 A$\cdot$GeV.
