Symmetric Galactic Nebulae.

Attention is drawn to some recent investigations of nebulae by Shajn and llase. The advantages of a new investigation restricted to nebulae showing quasi-elliptical symmetry are noted. The observations and organization of a catalogue of 152 symmetric nebulae (36 new) are explained. The catalogue contains data of position and distance, of size, orientation, and relative surface brightness, and of involved stars. A galactic pole is derived. About 20 nebulae are associated with clusters, and about 90 have central stars with a wide variety of spectra, including 6 W stars and 6 Be stars. The distribution of size is related to estimated surface brightness, so as to show that the symmetric nebulae are probably density-bounded ellipsoids. The smallest are the densest. The orientations indicate that the ellipsoids tend to stretch parallel to the galactic equator. The need for more stellar spectra and quantitative nebular data is stressed.