76 DOCTRINE OF EVOLUTION 



securely founded upon the basic principles of anatomy 

 and embryology. Science must treat the data of this 

 category by different methods and must view them in 

 different ways. Therefore we are interested in palaeon- 

 tology because of the way it tells the story of evolution 

 in its own words, and because we are justified in expect- 

 ing that its account should include a description of some 

 such Order of events as that revealed by the developing 

 embryos of modern organisms and that demonstrated 

 by the comparative anatomy of the varied species of 

 adult animals. 



It is true that palaeontology gives direct testimony 

 about the evolutionary succession of animals in geo- 

 logic time. But we now know that embryology is 

 even more direct in its proof that organic transformation 

 is natural and real ; while at the same time there is a 

 completeness in the full series of developmental stages 

 connecting the one-celled egg with the adult creature 

 that must be forever lacking in the case of the fossil 

 sequence of species. If paragraphs and pages are 

 missing from the brief embryonic recapitulation, whole 

 chapters and volumes of the fossil series have been lost 

 for all time. The investigators whose task it has been 

 to decipher the story of the earth's evolution have had 

 to meet numerous and exasperating difficulties which 

 do not confront the embryologist and anatomist who 

 study living materials. Nevertheless the library of 

 palseontological documents is one which has been 

 founded for over a century, and it has grown fast dur- 

 ing recent decades, so that consistent accounts may now 

 be read of the great changes in organic life as the earth 

 has altered and grown older. And in all this record, 



