For the assumption of eternity of life only the transference of germs from one solar system to another would have to be considered and the question arises whether or not germs can keep their vitality so many thousands of years. Arrhenius thinks that this is possible on account of the low temperature (which must be below -220° C.) at which no chemical reaction and hence no decomposition and deterioration are possible in the spores; and on account of the absence of water vapour. The question then arises: Have we any facts to warrant the assumption that spores may remain alive for thousands of years under such conditions and retain their power of germination? We know that seeds have a very limited vitality, and the statement that grain found in the Egyptian tombs was still able to germinate has long been recognized as a myth. Miss White[27] found that in wheat grains, there appeared a well-marked drop in their germinating power after about the fourth year, reaching zero in eleven to seventeen years. In a drier climate they last longer than in a moist climate. It is of importance that the hydrolyzing enzymes in the seeds, such as diastase, erepsin, remained unimpaired even after the germinating power of the seeds had disappeared. The seeds were able to resist for two days the temperature of liquid air, though the subsequent germination was delayed by this treatment. Macfadyen[28] exposed non-sporing bacteria, viz., _B. typhosus_, _B. coli communis_, _Staphylococcus pyogenes aureus_, and a _Saccharomyces_ to liquid air. The experiments showed that a prolonged exposure of six months to a temperature of about -190° has no appreciable effect on the vitality of micro-organisms. To judge by the results there appeared no reason to doubt that the experiment might have been successfully prolonged for a still longer period. [27] White, J., _Proc. Roy. Soc._, 1909, B, lxxxi., 417. [28] Macfadyen, A., _Proc. Roy. Soc._, 1903, lxxi., 76. Paul Becquerel[29] found that seeds which possess a very thick integument may live longer than the grain in Miss White’s experiments. The thickness of the integument prevents the exchange of gases between air and seed. Thus seeds of leguminoses (_Cassia bicapsularis_, _Cytisus biflorus_, _Leucæna leucocephala_, and _Trifolium arvense_) had retained their power of germination for eighty-seven years. Becquerel has shown that the dryness of the membrane is very essential for such a duration of life, since when dry it is impermeable for gases and the slow chemical reactions inside the grain become impossible. [29] Becquerel, P., _Revue générale des Sciences_, 1914, xxv., 559.