  We present UBVJHKHalpha and HI data of the irregular galaxy NGC 2366. It is a
normal boxy-shaped disk seen at high inclination angle. We do not see any
unambiguous observational signature of a bar. There is an asymmetrical
extension of stars along one end of the major axis of the galaxy, and this is
where the furthest star-forming regions are found, at 1.3R_Holmberg. The HI is
normal in many respects but shows some anomalies: 1) The integrated HI shows
two ridges running parallel to the major axis that deproject to a large ring.
2) The velocity field exhibits several large-scale anomalies superposed on a
rotating disk. 3) The inclination and position angles derived from the
kinematics differ from those dervied from the optical and HI mor- phology. 4)
There are regions in the HI of unusually high velocity dispersion that
correlate with deficits of HI emission in a manner suggestive of long-range,
turbulent pressure equilibrium. Star-forming regions are found where the gas
densities locally exceed 6 Msolar/pc^2. NGC 2366, like other irregulars, has
low gas densities relative to the critical gas densities of gravitational
instability models. Because of the lack of shear in the optical galaxy, there
is little competition to the slow gravitational contraction that follows energy
dissipation. However, the peak gas densities in the star-forming regions are
equal to the local tidal densities for gravitational self-binding of a rotating
cloud. Evidently the large scale gas concentrations are marginally bound
against background galactic tidal forces. This condition for self-binding may
be more fundamental than the instability condition because it is local,
three-dimensional, and does not involve spiral arm generation as an
intermediate step toward star formation.
