LIFE: ITS NATUKE, OEIGIN AND MAINTENANCE 17 



inanimate and animate, to material which has all the characteristics to 

 which we attach the term ' life.' So far from expecting a sudden leap 

 from an inorganic, or at least an unorganised, into an organic and 

 organised condition, from an entirely inanimate substance to a completely 

 animate state of being, should we not rather expect a gradual procession 

 of changes from inorganic to organic matter, through stages of gradually 

 increasing complexity until material which can be termed living is 

 attained ? And in place of looking for the production of fully formed 

 living organisms in hermetically sealed flasks, should we not rather search 

 Nature herself, under natural conditions, for evidence of the existence, 

 either in the past or in the present, of transitional forms between living 

 and non-living matter? 



The difficulty, nay the impossibility, of obtaining evidence of such 

 evolution from the past history of the globe is obvious. Both the hypo- 

 thetical transitional material and the living material which was originally 

 evolved from it may, as Macallum has suggested, have taken the form of 

 diffused ultra-microscopic particles of living substance * ; and even if they 

 were not diffused but aggregated into masses, these masses could have 

 been physically nothing more than colloidal watery slime which would 

 leave no impress upon any geological formation. Myriads of years may 

 have elapsed before some sort of skeleton in the shape of calcareous or 

 siliceous spicules began to evolve itself, and thus enabled ' life,' which 

 must already have possessed a prolonged existence, to make any sort of 

 geological record. It follows that in attempting to pursue the evolution 

 of living matter to its beginning in terrestrial history we can only expect to 

 be confronted with a blank wall of nescience. 



The problem would appear to be hopeless of ultimate solution, if 

 we are rigidly confined to the supposition that the evolution of life has 

 only occurred once in the past history of the globe. But are we justified 

 in assuming that at one period only, and as it were by a fortunate and 

 fortuitous concomitation of substance and circumstance, living matter 

 became evolved out of non-living matter life became established? Is 

 there any valid reason to conclude that at some previous period of its 

 history our earth was more favourably circumstanced for the production of 

 life than it is now ? f I have vainly sought for such reason, and if none 

 be forthcoming the conclusion forces itself upon us that the evolution 

 of non-living into living substance has happened more than once and we 

 can be by no means sure that it may not be happening still. 



* There still exist in fact forms of life which the microscope cannot show us (E. A. 

 Minchin, Presidential Address to Quekett Club, 1911), and germs which are capable of 

 passing through the pores of a Chamberland filter. 



f Chalmers Mitchell (Art. Life,' Encycl. Brit., eleventh edition) writes as 

 follows : ' It has been suggested from time to time that conditions very unlike those 

 now existing were necessary for the first appearance of life, and must be repeated if 

 living matter is to be reconstituted artificially. No support for such a view can be 

 derived from observations of the existing conditions of life.' Cf. also J. Hall-Edwards, 

 op. cit. 



