THE APPEARANCE OF LIFE 71 



others, again, are distinguished by the abundance of helium 

 and hydrogen present in their atmosphere, indications of 

 tremendous radio-activity. The bluish-white stars are even 

 hotter ; the ultra-violet portion of their spectra is very 

 extensive, and includes radiation of particular intensity and 

 of unknown origin, and the presence of helium in their 

 atmosphere implies that they are also the seat of important 

 radio-active phenomena. 1 



During the period when the sun was passing through these 

 various stages, the chemical activities taking place on earth 

 under its influence must have been more numerous and 

 emphatically more powerful than they are to-day. The ultra- 

 violet radiation was of greater extent than in our mercury 

 vapour lamps to-day, and the chemical combinations this 

 radiation was capable of stimulating must have been far more 

 varied than those which we can bring about to-day, and which 

 would be a necessary condition for the appearance of life. 

 Ultra-violet radiation emanating from the sun and capable of 

 penetrating our atmosphere was then able to achieve results 

 which the irradiation of the present epoch is no longer capable 

 of accomplishing unaided. Thus it is that we can explain the 

 lack of spontaneous generation in our own day. Moreover, 

 the earth itself, during that far-off period, was at a different 

 stage. It was possessed of greater radio-activity, and its 

 atmosphere contained hydrogen, helium, and perhaps other 

 elements developing from the disintegration of various simple 

 substances, at that particular stage which chemists call the 

 nascent state, during which their chemical affinities were 

 higher ; hence we have another reason why combinations 

 impossible to-day could then have been produced. It must have 

 been from quaternary substances, more complex than the 

 formic amides, that the true albuminoid substances developed. 

 After the simplest of these had been obtained, the formation 

 of the others became a purely chemical phenomenon. The 

 researches of P. Schiitzenberger, A. Kossel, E. Fischer, L. C. 

 Maillard, and others, on the constitution of albuminoid 

 substances, essential factors in chemical life, at any rate, 

 have thrown considerable light on the constitution of the 

 quaternary substances. A preponderating part in their constitu- 

 tion is played by the amino-acids, formed by an acid agent 



1 XIX, 306. 



