The paper reviews former contentions of the writer to the effect that in the realm of classical physics, at any rate, the Michelson-Morley experiment has an illusory significance in relation to the theory of restricted relativity, and that in this realm there would be sense to the useful part of the theory involving, as it does, the invariance of the equations under the Lorentzian transformation, even though the Michelson-Morley experiment should give a positive effect and rods and clocks should fail to partake of the Lorentzian contraction and time changes when set in motion with velocity $v$ in the system $S$. It is shown, however, that the existence of a relativistically invariant quantum theory provides for the Lorentzian contraction and allied phenomena cited above and calls for them as necessities. Without such a theory, the invariance of the equations alone would have nothing to say on these matters.

A general classification of novae in terms of integral parameters is proposed. It is shown in particular that the distribution of novae in dependence on the intrinsic luminosity at maximum brightness reveals the existence of two distinct classes, designated as common novae and supernovae. In Section (A) the usefulness of the study of temporary stars in comparison with the study of permanent stars is discussed. Sections (B) and (C) give a tentative classification of novae in terms of integral parameters as well as a brief tabulation of some of the observational data on these parameters. In the course of this discussion a number of interesting problems suggest themselves. Among them the problems of the primary and secondary images of novae and of supernovae and the investigation of the final states of temporary stars are of particular interest. In (D) some approximate relations among the integral parameters are described. In (E) the frequency of occurrence $n\left(M\right)\mathrm{}$ of novae in dependence on their absolute magnitude $M$ is explicitly established and graphically represented. The fundamental significance of the fact is emphasized that the function $n\left(M\right)\mathrm{}$ has two pronounced maxima. In (F) the importance of the fact is analyzed that supernovae preferably appear in those parts of nebulae whose surface brightness is low. Two outstanding cases of supernovae which are located in points of excessively low surface brightness are reproduced in Fig. 3. In Section (G) it is shown that the average frequency of occurrence of supernovae in different types of nebulae does not depend essentially on the type. In Section (H) a number of reasons are advanced which appear to be sufficient to rule out the assumption of collisions between luminous stars as a cause for supernovae. Finally in Section (I) a review is given of the decisive observations and considerations which have resulted in the recognition of supernovae as a separate class of temporary stars.