48 THE ORIGIN OF LIFE 



similar phenomena in a gradually diminishing or 

 simplifying manner through various grades, although 

 we do not see the change take place one into the 

 other, is evidence of the same nature as that on which 

 the Nebular Theory is actually based. 



A nebula has never been seen to change from one 

 stage into another ; but different nebulae are seen in 

 different stages of development. 



We say we do not see them change because 

 no change has yet been seen from one such grade up 

 to another, next it in the scale, by purely physical 

 or chemical reactions ; so also no change occurs from 

 highly organic bodies not bacterial into bacteria. 

 Such a change may require countless ages to be accom- 

 plished in. But changes have been found, however, 

 which would entitle us to regard some of them as 

 ancestors of others, and to regard the transformations 

 actually obtained artificially, although highly unstable, 

 as in a certain sense sufficient to fill the gap between 

 the complex bacillus and the simpler bodies in the 

 scale of chemical and physical efiects. 



The word Life is therefore used here in a sense 

 which, if not necessarily a new one, is at least an 

 extension, and perhaps a considerable extension, of 

 that in which it is already employed. It is used in 

 such a manner as to include within its scope many 

 phenomena hitherto regarded as belonging to the 

 lifeless world, but really of a kind which would 

 entitle us to look upon them as similar, though 

 simpler, phenomena in the scale of being. The unity 

 underlying these is that for which we plead, and the 



