Many astronomers have considered the Milky Way itself a nebula. The most common theory doubtless is that it closely conforms to a spiral nebula--an opinion that has found a particularly warm advocate in the Dutch astronomer, Easton (see Figure 1). A few years ago Prof. Bohlin expressed the view that it is most akin to a planetary nebula, or more precisely to a ring nebula which is supposed to grow out of a planetary ellipsoid nebula by the gaseous matter being driven from its poles toward its equator. It is of a certain interest that this theory lends itself to the support of Swedenborg’s--nevertheless improbable--hypothesis about the origin of the planets in the solar system. As we later shall see the Easton conception has the better reasons in its favour. If classified according to age the stars are again distributed with the Milky Way as a reference point. Thus, let us consider their evolution, which for various reasons is assumed to take the following course. We may commence when the star-matter existed on the nebula stage. It then radiated the light characteristic of certain incandescent gases, principally the lightest two, hydrogen and helium, and further of an otherwise unknown gas called nebulium (nebula-substance). These gases were later condensed and dark spectral lines commenced to appear beside the bright lines of the aforesaid gases. Stars on this stage, named after their discoverer Wolf-Rayet stars, occur only in the immediate vicinity of the Milky Way. A later stage in their evolution is represented by the so-called helium stars in whose spectrum the dark helium lines preponderate. They are considerably concentrated around our Galaxy. Somewhat more evenly distributed and yet of decidedly greater frequence in the neighbourhood of the Milky Way, the hydrogen stars appear, characterized by strongly developed hydrogen lines and somewhat retreating helium lines. These stars are more developed than the helium stars and form with them the group of white stars so named after the colour of their light. Next in evolution follow the yellow stars, to which our Sun belongs. Dark metal lines appear in their spectrum. They are more evenly distributed than the groups mentioned before. Still further is this true about the red stars whose spectra contain the characteristic bands of chemical compounds and therefore betray comparatively advanced cooling. They are fairly uniformly spread over the heavens but are still somewhat more numerous in the vicinity of the Milky Way than further therefrom. [Illustration: Fig. 1. The Milky Way, pictured as a spiral nebula by Easton] These facts are demonstrated in the statistics by E. C. Pickering, Director of the Harvard Observatory, who divided the firmament in four equal zones, the first of which is nearest to the Milky Way (and includes it) and the last of which contains the Galactic poles. His table shows the percentages of different stars in each of the four zones.