General Introduction 



Of like mould are the students who have still 

 further broadened the glory of our age by prov- 

 ing evolution to be the law of Nature's history; 

 who have shown that, however structureless 

 the universe may have been in the distant past 

 whether glowing solid, seething liquid, or lam- 

 bent gas yet that within its bosom lay all the 

 possibilities of the worlds around us. Lyell 

 laid the foundation of the theory of development 

 when he established the sufficiency of forces at 

 work in modern times to account for the earth's 

 geological history. Spectroscopy continued the 

 impulse in a new path by giving support to Kant's 

 nebular hypothesis, and by showing the innum- 

 erable host of heaven to be built up of like mater- 

 ials with our globe. Von Baer added suggestive 

 corroboration by his discovery that the history 

 of the development of a race from lower forms is 

 recapitulated in the transformations undergone 

 by every individual before birth. The arch of 

 evidence of evolution arose rapidly under the 

 hands of these men, yet its span required an ex- 

 planation of how species came to be, and how 

 man had ascended from humble forms of life. 

 An arch all but finished may lack only a keystone 

 to complete it; that added, it has strength and 

 sureness; that wanting, it has neither. When 

 Darwin supplied the keystone of evolutionary 

 evidence in the facts of natural selection, then, 

 and then only, did the law of universal develop- 

 ment fairly come into the possession of mankind. 

 A law, surely, of profoundest significance. By 



