CHAPTER XH 

 CRITIQUE OF THE RECAPITULATION THEORY 1 



W. B. SCOTT 



Embryology is the study of the development of the individual 

 organism from its beginning in the egg to the attainment of the adult 

 condition. This individual development is called ontogeny and the 

 question of the relation of ontogeny to the ancestral history of the 

 species, or phytogeny, constitutes one of the main problems of embry- 

 ology. Around this problem many controversies have raged, contro- 

 versies which have by no means arrived at a definite solution, even 

 to-day. Thirty years ago the "recapitulation theory" was well-nigh 

 universally accepted, according to which the individual development, 

 or ontogeny, was regarded as an abbreviated repetition of the ances- 

 tral history of the species, or phylogeny. Haeckel called this theory 

 the "fundamental biogenetic law" and upon it he established his 

 whole "History of Creation." Nowadays, that "fundamental law" 

 is very seriously questioned and by some high authorities is altogether 

 denied. However, even those who take this extreme position con- 

 cerning the recapitulation theory see in the facts of embryology one 

 of the strongest supports of the doctrine of evolution. 



It was very early recognized that the recapitulation theory could 

 not be applied with literal exactness, but was subject to certain 

 important exceptions and qualifications. 



i. That the history must have been enormously abbreviated. 

 After three weeks of incubation the tiny speck of protoplasm, which 

 forms a circular mark on the yolk of a hen's egg, is developed into a 

 fully formed chick, ready for hatching and able in large degree to take 

 care of itself. On the other hand, the evolution of birds from their 

 invertebrate ancestors, through the fishes, amphibians, and reptiles, 

 the separation of the gallinaceous stock from other birds and the 

 differentiation of this particular species were extremely slow processes, 

 extending through unnumbered millions of years. Admitting reca- 

 pitulation to the fullest extent, it is evidently a physical impossibility 



1 From W. B. Scott, The Theory of Evolution (copyright 1917). Used by 

 special permission of the publishers. The Macmillan Company. 



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