Scope and Purport of Evolution 41 



trine of evolution. The clue was not given by 

 Mr. Darwin. Darwinism was not yet born. Mr. 

 Spencer's theory was worked out in all its parts, 

 and many parts of it had been expounded in vari- 

 ous published volumes and essays before the publi- 

 cation of the " Origin of Species." 



The clue which Mr. Spencer followed was given 

 him by the great embryologist, Karl Ernst von 

 Baer, and an adumbration of it may perhaps 

 be traced back through Kaspar Friedrich Wolf 

 to Linnaeus. Hints of it may be found, too, in 

 Goethe and in Schelling. The advance from sim- 

 plicity to complexity in the development of an 

 egg is too obvious to be overlooked by any one, 

 and was remarked upon, I believe, by Harvey ; 

 but the analysis of what that advance consists 

 in was a wonderfully suggestive piece of work. 

 Baer's great book was published in 1829, just at 

 the time when so many stimulating ideas were 

 being enunciated, and its significant title was 

 Entwickelungsgeschichte, or " History of Evolu- 

 tion." It was well known that, so far as the 

 senses can tell us, one ovum is indistinguishable 

 from another, whether it be that of a man, a fish, 

 or a parrot. The ovum is a structureless bit of 

 organic matter, and, in acquiring structure along 

 with its growth in volume and mass, it proceeds 



