282 EVOLUTION IN BIOLOGY. [LECT. 



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 

 denoted by "evolution" and "development" were 

 shown to be untenable, the words retained their 

 application to the process by which the embryos of 

 living beings gradually make their appearance; and 

 the terms "Development/' " Entwickelung," and 

 "Evolutio," are now indiscriminately used for the 

 series of genetic changes exhibited by living beings, 

 by writers who would emphatically deny that " De- 

 velopment" or "Entwickelung" or "Evolutio," in 

 the sense in which these words were usually em- 

 ployed by Bonnet or by Haller, ever occurs. 



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

 employed 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 universal history, which is the history of the 

 human race, so evolution falls naturally into two 

 categories, the evolution of the individual, and the 

 evolution of the sum of living beings. It will be 

 convenient to deal with the modern doctrine of evolu- 

 tion under these two heads. 



I. The Evolution of the Individual. 

 No exception is, at this time, known to the 

 general law, established upon an immense multitude 



