40 THE ORIGIN OF LIFE 



I was formerly not as fully alive to this fact 

 as I ought to have been, or I should have pro- 

 vided myself in 1906 with a good supply of this 

 substance from the same stock as that with which 

 my experiments were then made. As it was, I 

 had to get a new supply last summer; and, hav- 

 ing obtained it from the same house, at first sup- 

 posed that I was dealing with just the same kind 

 of ingredient as had been previously used. It 

 proved, however, to be somewhat different in 

 strength and composition; and the sequel has been 

 that in these new experiments positive results were 

 only obtained after periods three or four times as 

 long as those which sufficed in the trials made in 

 1906. 



I had found then that in spring and summer 

 weather (and the latter happened to be specially 

 warm and bright) the diffuse daylight experiments 

 were much more successful than those made in the 

 autumn and early winter of the same year, when 

 both light and heat were much less. And as all 

 the new experimental vessels were this time to be 

 exposed to diffuse daylight, 1 and half the summer 

 was over before the first batch of tubes was ex- 



1 Owing to my residence in the country, and having no means 

 of making proper use of an incubator. 



