THE CENTURY'S PROGRESS IN BIOLOGY 



phosis to the animal kingdom, in the doctrine which 

 Goethe and Oken advanced independently, that the ver- 

 tebrate skull is essentially a modified and developed ver- 

 tebra. These were conceptions worthy of a poet; im- 

 possible, indeed, for any mind that had not the poetic 

 faculty of correlation. But in this case the poet's vision 

 was prophetic of a future view of the most prosaic sci- 

 ence. The doctrine of metamorphosis of parts soon 

 came to be regarded as a fundamental feature in the 

 science of living things. 



But the doctrine had implications that few of its 

 early advocates realized. If all the parts of a flower- 

 sepal, petal, stamen, pistil, with their countless devia- 

 tions of contour and color are but modifications of the 

 leaf, such modification implies a marvellous differentia- 

 tion and development. To assert that a stamen is a 

 metamorphosed leaf means, if it means anything, that in 

 the long sweep of time the leaf has by slow or sudden 

 gradations changed its character through successive 

 generations, until the offspring, so to speak, of a true 

 leaf has become a stamen. But if such a metamorphosis 

 as this is possible if the seemingly wide gap between 

 leaf and stamen may be spanned by the modification of 

 a line of organisms where does the possibility of modi- 

 fication of organic type find its bounds? Why may 

 not 1;he modification of parts go on along devious lines 

 until the remote descendants of an organism are utterly 

 unlike that organism? Why may we not thus account 

 for the development of various species of beings all 

 sprung from one parent stock? That too is a poet's 

 dream; but is it only a dream? Goethe thought not. 

 Out of his studies of metamorphosis of parts there grew 

 in his mind the belief that the multitudinous species of 

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