TRANSFORMATION OF MORPHOLOGY 313 



him to reconstruct probable lines of descent ; from the 

 standpoint of the student of development and heredity the 

 fact of recapitulation is a difficult problem whose solution 

 would perhaps give the key to a true understanding of the 

 real nature of heredity. 



To make full use of the conception of the organism as an 

 historical being it is necessary then to understand the causal 

 nexus between ontogeny and phylogeny. 



We shall see in the next chapter that the transformation 

 of morphology from a comparative to a causal science did 

 take place towards the end of the century, and that some 

 progress was made towards an understanding of the relation 

 between individual development and ancestral history, par- 

 ticularly by Roux and Samuel Butler, working with the 

 fruitful Lamarckian conception of the transforming power of 

 function. 



