Comments on a PLC relationship for cepheids and on the comparison between pulsation and evolution masses for cepheids.

It is suggested that a period-luminosity-color (PLC) relationship currently in use for Cepheids in our Galaxy is not a unique summary of the observational facts and may, in fact, be inconsistent with elementary pulsation theory. Consequently, when this PLC relationship is used to estimate Cepheid luminosities and these luminosities are in turn used to estimate Cepheid masses, one obtains a mass-luminosity relationship whose slope may be far from the truth. Alternate PLC relationships that are consistent both with the observational facts and with pulsation theory are presented. We suggest that either (1) the original estimates of luminosity (on which the normalization of the standard PLC relationship is based) be used to establish a mass-luminosity relationship for Galactic Cepheids or (2) the slope of the mass-luminosity relationship given by evolutionary calculations be accepted and be used to estimate relative luminosities. The effect on blue edges of using spline interpolation in new Cox-Stewart opacities is shown for a single mass. It is suggested that, in estimating the pulsation mode and mass of any Cepheid, the location of that Cepheid in the H-R diagram relative to blue edges for pulsation in the fundamental and first harmonic modes be taken into account.