Deep spectra of the planetary nebula IC 418 were obtained in the wavelength range 4190-5850 A. The data made it possible to map an extended halo about the source, evaluate the variation in halo intensity with radius, and model the results in terms of a radially symmetric dust scatter envelope. It is suggested that the nebula is in a relatively

IAUC 5077 available at Central Bureau for Astronomical Telegrams. IAUC 5077 available at Central Bureau for Astronomical Telegrams.

IAUC 5079 available at Central Bureau for Astronomical Telegrams.

IAUC 5078 available at Central Bureau for Astronomical Telegrams.

The effect of a spiral-like perturbation in the orbits of an axisymmetric galactic potential is studied using surfaces of section. It is found that the perturbation induces stochasticity and diffusion of orbits in phase space.

An aspect of the missing mass problem in galaxies, not easy to address, is whether the dynamical mass distribution is spherical or greatly flattened, following the light. Rotation curves of spirals out of the plane of the disk cannot, by definition, be measured. A way around this problem might be to use satellite galaxies orbiting within a few