THE DOCTRINE OF EVOLUTION. 589 



so many people mix up Darwinism with the doctrine of evolu- 

 tion, and have but the vaguest and haziest notions as to what it 

 is all about. As I explained above, Mr. Darwin's great work was 

 the discovery of natural selection and the demonstration of its 

 agency in effecting specific changes in plants and animals ; and in 

 that work he was completely original. But plants and animals 

 are only a part of the universe, though an important part, and 

 with regard to universal evolution or any universal formula for 

 evolution Darwinism had nothing to say. Such problems were 

 beyond its scope. 



The discovery of a universal formula for evolution, and the 

 application of this formula to many diverse groups of phenomena, 

 have been the great work of Mr. Spencer, and in this he has had 

 no predecessor. His wealth of originality is immense, and it is 

 unquestionable. But as the most original thinker must take his 

 start from the general stock of ideas accumulated at his epoch, 

 and more often than not begins by following a clew given him by 

 somebody else, so it was with Mr. Spencer when about forty years 

 ago he was working out his doctrine of evolution. The clew was 

 not given him by Mr. Darwin. Darwinism was not yet born. 

 Mr. Spencer's theory was worked out in all its parts, and most 

 parts of it had been expounded in various published volumes and 

 essays before the publication of The Origin of Species. 



The clew which Mr. Spencer followed was given him by the 

 great German embryologist 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 Schel- 

 ling. The advance from simplicity to complexity in the develop- 

 ment 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. Von 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 Entwickelungsgeschiclite , or History 

 of Evolution. 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 through a series of differ- 

 entiations, and the result is a change from homogeneity to hetero- 

 geneity. Such was Von Baer's conclusion, to which scanty justice 

 is done by such a brief statement. As all know, his work marked 

 an epoch in the study of embryology, for to observe and mark the 

 successive differentiations in the embryos of a thousand animals 

 were to write a thousand life-histories upon correct principles. 



Here it was that Mr. Spencer started. As a young man he was 



