The Recapitulation Theory in Biology 61 



12. It is obvious that recapitulation in the sense of a chrono- 

 logical repetition of a succession of adult forms in phylogeny is 

 very unlikely. It may have happened in the earliest evolu- 

 tion of organic form as suggested by the very general 

 similarity in early ontogenetic development of the Metazoa, 

 a development which has a somewhat general corre- 

 spondence to what is believed by many to be the evolu- 

 tionary sequence among existing lower forms. It has happened 

 somewhat conspicuously among many animals with larvae, 

 for a certain part of the life-history, and also with particular 

 characteristics and organs in some degree, more noticeably in 

 shells and bony structures. 



13. But where such recapitulation has occurred, there has 

 been coincidently an alteration of the ancient structures, so that 

 the original form of the latter is often made out with great 

 difficulty, the alteration having had the effect of obscuring the 

 older pattern to some degree, often radically. As a conse- 

 quence life-history has been very much more altered than it 

 has been extended through descent. 



14. If by recapitulation is meant any traces of adult features 

 in early ontogeny, there is considerable evidence for it, although 

 not a large amount comparatively. But this is not recapitu- 

 lation in the proper meaning of the term. If by recapitulation 

 is meant any ancestral reference whatever in early ontogeny, 

 there is much of this, especially to more recent ancestral life- 

 history, but this is even a farther remove from the meaning of 

 the word. It is practically synonymous with heredity. If 

 ontogeny is a " record" at all, it is more particularly a record 

 of antecedent ontogenies, to the degree these are not effaced 

 by subsequent variational or mutational changes. 



