In the cosmic space there is no water vapour, no atmosphere, and a low temperature, and there is hence no reason why spores should lose appreciably more of their germinating power in ten thousand years than in six months. We must therefore admit the possibility that spores may move for an almost infinite length of time through cosmic space and yet be ready for germination when they fall upon a planet in which all the conditions for germination and development exist, _e. g._, water, proper temperature, and the right nutritive substances dissolved in the water (inclusive of free oxygen). While thus everything is favourable to Arrhenius’s hypothesis, Becquerel raises the objection that the spores going through space would yet be destroyed by ultraviolet light. This danger would probably exist only as long as the germ is not too far from a sun. The difficulty is a real one since the ultraviolet rays have a destructive effect even in the absence of oxygen. It is possible, however, that there are spores which can resist this effect of ultraviolet light. Arrhenius’s theory can not of course be disproved and we must agree with him that it is consistent not only with the theories of cosmogony but also with the seeming potential immortality of certain or of all cells. The alternative to Arrhenius’s theory is that living matter did originate and still originates from non-living matter. If this idea is correct it should one day be possible to discover synthetic enzymes which are capable of forming molecules of their own kind from a simple nutritive solution. With such synthetic enzymes as a starting point the task might be undertaken of creating cells capable of growth and cell division, at least in the apparently simple form in which these phenomena occur in bacteria; viz., that after the mass has reached a certain (still microscopic) size it divides into two cells and so on. If Arrhenius is right that living matter has had no more beginning than matter in general, this hope of making living matter artificially appears at present as futile as the hope of making molecules out of electrons. The problem of making living matter artificially has been compared to that of constructing a _perpetuum mobile_; this comparison is, however, not correct. The idea of a _perpetuum mobile_ contradicts the first law of thermodynamics, while the making of living matter may be impossible though contradicting no natural law.