The Doctrine of Evolution. 449 



volumes and essays before the publication of The Origin of 



The clew which Mr. Spencer followed was given him by 

 the great German embryologist Von Baer, and an adumbra- 

 tion 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 simplicity 

 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. 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 Entwickelungsgeschichte, 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 pro- 

 ceeds through a series of differentiations, and the result is a 

 change from homogeneity to heterogeneity. 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 mark the successive differ- 

 entiations in the embryos of a thousand animals was to write 

 a thousand life-histories upon correct principles. 



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

 he was chiefly interested in the study of political govern- 

 ment and in history so far as it helps the study of politics. 

 A philosophical student of such subjects must naturally 

 seek for a theory of evolution. If I may cite my own expe- 

 rience, it was largely the absorbing and overmastering pas- 

 sion for the study of history that first led me to study evo- 

 lution in order to obtain a correct method. When one has 

 frequent occasion to refer to the political and social progress 

 of the human race, one likes to know what one is talking 

 about. Mr. Spencer needed a theory of progress. He could 

 see that the civilized part of mankind has undergone some 

 change from a bestial, unsocial, perpetually fighting stage of 

 savagery into a partially peaceful and comparatively humane 

 and social stage, and that we may reasonably hope that the 

 change in this direction will go on. He could see, too, that 

 along with* this change there has been a building up of 

 tribes into nations, a division of labor, a differentiation of 



