CHAPTER XII 
CRITIQUE OF THE RECAPITULATION THEORY? 
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 phylogeny, 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. 
1. 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 
«From W. B. Scott, The Theory of Evolution (copyright 1917). Used by 
special permission of the publishers, The Macmillan Company. 
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