  We investigate collapse of magnetic protostellar clouds of mass $10$ and $1
M_{\odot}$. The collapse is simulated numerically using the two-dimensional
magnetohydrodynamic (MHD) code `Enlil'. The simulations show that protostellar
clouds acquire a hierarchical structure by the end of the isothermal stage of
collapse. Under the action of the electromagnetic force, the protostellar cloud
takes the form of an oblate envelope with the half-thickness to radius ratio
$Z/R \sim (0.20-0.95)$. A geometrically and optically thin primary disk with
radius $0.2-0.7 R_0$ and $Z/R \sim (10^{-2}-10^{-1})$ forms inside the
envelope, where $R_0$ is the initial radius of the cloud. Primary disks are the
structures in magnetostatic equilibrium. They form when the initial magnetic
energy of the cloud exceeds $20 \%$ of its gravitational energy. The mass of
the primary disk is $30-80 \%$ of the initial mass of the cloud. The first
hydrostatic core subsequently forms in the center of the primary disc. We
discuss the role of primary disks in the further evolution of clouds, as well
as possible observational appearance of the internal hierarchy of the
collapsing cloud from the point of view of the features of the magnetic field
geometry and the distribution of angular momentum at different levels of the
hierarchy
