A HISTORY OF SCIENCE 



compound receptacles would be explained as being 

 several leaves which, being united above one centre, 

 keep their inward parts separate and are joined on 

 their margins. We can convince ourselves of this by 

 actual sight when such composite capsules fall apart 

 after becoming ripe, because then every part displays 

 an opened pod." l 



The theory thus elaborated of the metamorphosis of 

 parts was presently given greater generality through 

 extension to the animal kingdom, in the doctrine which 

 Goethe and Oken advanced independently, that the 

 vertebrate skull is essentially a modified and developed 

 vertebra. These were conceptions worthy of a poet 

 impossible, 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 of fundamental importance. 



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 metamorpho- 

 sis as this is possible if the seemingly wide gap be- 

 tween leaf and stamen may be spanned by the modifica- 



