18 LIFE: ITS NATUEE, OEIGIN AND MAINTENANCE 



It is true that up to the present there is no evidence of such hap- 

 pening : no process of transition has hitherto been observed. But on the 

 other hand, is it not equally true that the kind of evidence which would 

 be of any real value in determining this question has not hitherto been 

 looked for ? We may be certain that if life is being produced from non- 

 living substance it will be life of a far simpler character than any that 

 has yet been observed in material which we shall be uncertain whether 

 to call animate or inanimate, even if we are able to detect it at all, 

 and which we may not be able to visualise physically even after we 

 have become convinced of its existence.* But we can look with the 

 mind's eye and follow in imagination the transformation which non- 

 living matter may have undergone and may still be undergoing to pro- 

 duce living substance. No principle of evolution is better founded than 

 that insisted upon by Sir Charles Lyell, justly termed by Huxley ' the 

 greatest geologist of his time,' that we must interpret the past history 

 of our globe by the present ; that we must seek for an explanation of 

 what has happened by the study of what is happening ; that, given 

 similar circumstances, what has occurred at one time will probably occur 

 at another. The process of evolution is universal. The inorganic 

 materials of the globe are continually undergoing transition. New 

 chemical combinations are constantly being formed and old ones broken 

 up ; new elements are making their appearance and old elements dis- 

 appearing.! Well may we ask ourselves why the production of living 

 matter alone should be subject to other laws than those which have 

 produced, and are producing, the various forms of non-living matter ; 

 why what has happened may not happen. If living matter has been 

 evolved from lifeless in the past, we are justified in accepting the 

 conclusion that its evolution is possible in the present and in the future. 

 Indeed, we are not only justified in accepting this conclusion, we are 

 forced to accept it. When or where such change from non-living to 

 living matter may first have occurred, when or where it may have 

 continued, when or where it may still be occurring, are problems as 

 difficult as they are interesting, but we have no right to assume that 

 they are insoluble. 



Since living matter always contains water as its most abundant 

 constituent, and since the first living organisms recognisable as such 

 in the geological series were aquatic, it has generally been assumed that 

 life must first have made its appearance in the depths of the ocean.]: 



* ' Spontaneous generation of life could only be perceptually demonstrated by filling 

 in the long terms of a series between the complex forms of inorganic and the simplest 

 forms of organic substance. Were this done, it is quite possible that we should be 

 unable to say (especially considering the vagueness of our definitions of life) where life 

 began or ended.' K. Pearson, Grammar of Science, second edition, 1900, p. 350. 



f See on the production of elements, W. Crookes, Address to Section B, Brit. 

 Assoc., 1886 ; T. Preston, Nature, vol. lx., p. 180; J. J. Thomson, Phil. Mag., 1897, 

 p. 311 ; Norman Lockyer, op. cit., 1900 ; G. Darwin, Pres. Addr. Brit. Assoc., 1905. 



I For arguments in favour of the first appearance of life having been in the sea, 



