156 INORGANIC EVOLUTION. [CHAP. XIX. 



speak, with regard to these different forms. In that way, then, the 

 geologist has been able to bring before us the continuity of life in 

 various forms, from the most ancient geological strata to the most 

 recent. The record may be incomplete, but is complete enough for my 

 purpose. 



But that is not the only evidence of evolution to which I can refer. 

 The teachings of embryology confirm the argument based upon the 

 study of geology, and suggest that the life-history of the earth is 

 reproduced in the life-history of individuals. The processes of organic 

 growth or embryonic development present a remarkable uniformity 

 throughout the whole of the zoological series ; and although knowledge 

 is still limited, some authorities hold that there is the closest possible 

 connection between the development of the individual and the develop- 

 ment of the whole series of animal life. There are others, however, 

 who do not regard the argument derived from embryology as a very 

 convincing one. However this may be, if we study the embryos of the 

 tortoise, fowl, dog, and man, we find that there is a wonderful simi- 

 larity between them at a certain stage. At a further stage of develop 

 ment the similarity is still borne out. This does not mean that a 

 vertebrate animal during its development first of all becomes a tortoise, 

 and then the various animals which are represented by these embryos ; 

 it simply means that they are all related, inasmuch as there is con- 

 tinuity. 



After these references to plants and animals it should be clear 

 what organic evolution really is, and therefore what evolution is 

 generally. 



