A Group of Peculiar Shell Stars.

Spectrographic observations of the stars AX Mon, lID 50138, lID 31648, lID 218393, and lID 236031, made in 1952 and 1953, are described. The various features which these stars have in common are discussed. These are principally the occasional appearance and rapid variations of displaced absorption components in the hydrogen lines. It is suggested that the infall of material from the shell may occur, in addition to outward surges, like prominence activity, previously suggested by Struve.