EVOLUTION IN BIOLOGY. 289 



der, Yon Bar, Rathke, and Remak in Germany, founded 

 modern embryology; while, at the same time, they 

 proved the utter incompatibility of the hypothesis of 

 evolution, as formulated by Bonnet and Haller, with 

 easily demonstrable facts. 



Nevertheless, though the conceptions originally de- 

 noted by "evolution" and "development" were shown 

 to be iitenable, the words retained their application to 

 the process by which the embryos of living beings gradu- 

 ally make their appearance; and the terms "Develop- 

 ment," " Eiitwickelung," and " Evolutio," are now indis- 

 criminately used for the series of genetic changes ex- 

 hibited by living beings, by writers who would emphatic- 

 ally deny that "Development" or " Entwickelung " or 

 " Evolutio," in the sense in which these words were usu- 

 ally employed by Bonnet or by Ilaller, ever occurs. 



Evolution, or development, is, in fact, at present em- 

 ployed in biology as a general name for the history of 

 the steps by which any living being has acquired the 

 morphological and the physiological characters which 

 distinguish it. As civil history may be divided into 

 biography, which is the history of individuals, and uni- 

 versal history, which is the history of the human race, 

 so evolution falls naturally into two categories, the evo- 

 lution of the individual, and the evolution of the sum of 

 living beings. It will be convenient to deal with the 

 modern doctrine of evolution under these two heads. 



