THE ORIGIN OF LIFE 167 



as it is termed." Dr Saleeby considers this 

 supposition of former more favourable conditions 

 not only unjustifiable, but unwarrantable. "Now 

 it happens to be true," he says, " that every differ- 

 ence between past and present conditions which 

 physics and geology and chemistry can assert tends 

 to the probability that if spontaneous generation 

 is impossible now, it must have been a hundredfold 

 more impossible a hundred million years ago. 

 Yet, for some three decades, the great majority of 

 biologists have been content to believe that spon- 

 taneous generation is impossible now, even though 

 land, and sea, and sky are packed with organic 

 matter under the very conditions which obviously 

 favour life, as the all but omnipresence of life 

 abundant to-day demonstrates, but that spontaneous 

 generation was possible in the past when, by the 

 hypothesis, there was no organic matter present at 

 all, and when life had to arise in the union and 

 architecture of such simple substances as inorganic 

 carbonates." 



This criticism seems fair, and yet life un- 

 doubtedly did arise from the inorganic ; and if it 

 did^ and if it does not do so now, there must have 

 been some favourable condition present then which 

 is not present now, and of which we know nothing. 

 It is quite true that we sterilise by heat, but it is 

 also true that we incubate by heat ; and what the 



