36 ON GOETHE'S SCIENTIFIC RESEAECHES. 



him of the universality of his newly-discovered principle, 

 so that in 1795 and 1796 he was able to define more 

 clearly the idea that had struck him in 1786, and to 

 commit it to writing in his ' Sketch of a General Intro- 

 duction to Comparative Anatomy.' He there lays down 

 with the utmost confidence and precision, that all differ- 

 ences in the structure of animals must be looked upon as 

 variations of a single primitive type, induced by the 

 coalescence, the alteration, the increase, the diminution, 

 or even the complete removal of single parts of the 

 structure ; the very principle, in fact, which has become 

 the leading idea of comparative anatomy in its present 

 stage. Nowhere has it been better or more clearly ex- 

 pressed than in Goethe's writings. Subsequent authorities 

 have made but few essential alterations in his theory. 

 The most important of these is, that we no longer under- 

 take to construct a common type for the whole animal 

 kingdom, but are content with one for each of Cuvier's 

 great divisions. The industry of Goethe's successors has 

 accumulated a well-sifted stock of facts, infinitely more 

 copious than what he could command, and has followed 

 up successfully into the minutest details what he could 

 only indicate in a general way. 



The second leading conception which science owes to 

 Goethe enunciated the existence of an analogy between 

 the different parts of one and the same organic being, 

 similar to that which we have just pointed out as sub- 

 sisting between corresponding parts of different species. 

 In most organisms we see a great repetition of single 

 parts. This is most striking in the vegetable kingdom ; 

 each plant has a great number of similar stem leaves, 

 similar petals, similar stamens, and so on. According to 

 Goethe's own account, the idea first occurred to him while 

 looking at a fan-palm at Padua. He was struck by the 

 immense variety of changes of form which the sue- 



