lO THE HISTORY OF CEEATLON. 



unscientific idea of a creator existing outside of matter, and 

 changing it, may easily creep in, it will perhaps be better in 

 future to substitute for it the more accurate term, develop- 

 vient 



The great value which the History of Development pos- 

 sesses for the scientific understanding of animal and vege- 

 table forms, has now been generally acknowledged for many 

 years, and without it it would be impossible to make any 

 sure progress in organic morphology, or the theory of forms. 

 But by the history of development, only one part of this 

 science has generally been understood, namely, that of 

 organic individuals, usually called Embryology, but more 

 correctly and comprehensively, Ontogeny. But, besides this, 

 there is another history of development of organic species, 

 genera, and tribes (phyla), which has the most important 

 relations to the formet. 



The subject of this is furnished to us by the science of 

 petrifactions, or palaeontology, which shows us that each 

 tribe of animals and plants, during different periods of the 

 earth's history, has been represented by a series of entirely 

 different genera and species. Thus, for example, the tribe 

 of vertebrated animals was represented by classes of fish, 

 amphibious animals, reptiles, birds, and mammals, and each 

 of these groups, at different periods, by quite different kinds. 

 This palseontological history of the development of organ- 

 isms, which we may term Phylogeny, stands in the most 

 important and remarkable relation to the other branch of 

 oi^ganic history of development, I mean that of individuals, 

 or Ontogeny. On the whole, the one runs parallel to the 

 other. In fact, the history of individual development, or 

 Ontogeny, is a short and quick recapitulation of palaeonto- 



