PRESIDENT’S ADDRESS. 15 
without concluding that the origin of life must have been due to the 
same process, this process being, without exception, continuous, and 
admitting of no gap at any part of its course. Looking therefore at the 
evolution of living matter by the light which is shed upon it from the 
study of the evolution of matter in general, we are led to regard 
it as having been produced, not by a sudden alteration, whether 
exerted by natural or supernatural agency, but by a gradual process 
of change from material which was lifeless, through material on the 
borderland between 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 con- 
ditions, 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 
hypothetical 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 
70 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. 
