The spectra of helium stars are peculiar and suggestive. Those belonging to Miss Maury's earliest groups--many of them visibly nebulous--bear next to no traces of metallic absorption, showing instead lines of oxygen, of nitrogen, and of hydrogen in all its three series. The conditions, accordingly, needed to produce the 'cosmic' modification of hydrogen are realized in these inchoate bodies. What those conditions actually are we cannot tell, yet it may be confidently surmised that they will prove to be of an electrical nature. Hydrogen resembles the metals in being electro-positive; it collects at the negative pole during the electrolytic decomposition of water. There is, however, an unmistakable tendency in primitive sidereal objects to display absorption rays of electro-negative rather than of electro-positive elements. It is conceivable that hydrogen may be capable of altering its behaviour in this respect, and that the molecules radiating the Pickering and Rydberg series, in addition to the more familiar Huggins series, have, in fact, through some corpuscular re-arrangement, assumed the electro-negative quality properly characterizing a non-metallic substance. The association of this form of hydrogen with oxygen and nitrogen in early helium stars would thus be naturally related to the simultaneous quasi-disappearance from them of the spectral badges of metals. The helium-line most distinctive of this stellar family is situated well up in the blue. It appertains to the same vibrational sequence with D3, which is also represented in Rigel, one of the more 'advanced' Orion stars. In Rigel, too, we meet a fairly prominent magnesium ray, lying below the blue helium emanation, while as yet iron is unapparent. Numerous fine, faint streaks, due to its absorption, only emerge when the Sirian type is fully reached, and they are mostly of the 'enhanced' kind. When the spark discharge is substituted for the arc as the source of illumination, certain lines in the resulting spectrum brighten relatively to the others, and these have been distinguished by Sir Norman Lockyer as 'enhanced.' Now, the rule is strikingly prevalent that the absorption rays in white stars are of this class; yet it can no longer be interpreted as indicating for them an excessively high temperature. Rather, it would seem that electrical conditions still imperfectly defined are in question, and their gradual removal or subsidence is, beyond doubt, largely instrumental in bringing about the transition to the solar stage. The effacement of helium-absorption is even more perplexing. No sooner does iron begin to show than it vanishes. There is still a faint trace of its 'blue' line in Vega; none survives in Sirius.