  By extrapolating the accumulated low-redshift data on the absorption radius
of galaxies and its luminosity scaling, it is possible to predict the total
absorption cross-section of the gas associated with collapsed structures in the
universe at any given epoch. This prediction can be verified observationally
through comparison with the well-known spatial distribution of the QSO
absorption systems. In this way, it is shown that HDF, NTT SUSI Deep Field and
other such data give further evidence for the plausibility of origin of the
significant fraction of the Ly$\alpha$ forest in haloes of normal galaxies.
