The Recapitulation Theory in Biology 59 



logical record or recapitulation of the evolution of the race 

 through descent. Several biologists believe that the origin of 

 embryonic traces of adult ancestral forms is due to an extension 

 of the embryonic period to include characters once functional in 

 larvae, these characters having been retained by the larvae when 

 no longer needed by the modified adult. The genuineness of 

 ancestral resemblance has been impugned on physiological 

 grounds, but the justification for this seems questionable when 

 the facts are carefully described. 



Conclusions Regarding Recapitulation. 



The above account of the biological discussion of recapit- 

 ulation seems to lead to the following conclusions: 



1. Ontogeny denotes the sequence of events in the life-history 

 of the individual beginning with the maturation and fertiliza- 

 tion of the egg, and progressing, under the stimulation of the 

 environment and the mutual relation of parts, through a series 

 of structures to senility and death. 



2. A proper conception of an animal involves the entire life- 

 history and should not be based upon its adult condition alone. 

 There has been some kind of life-history from the beginning. 

 " Development and life are coextensive." 98 



3. Heredity denotes the persistence of characteristics through 

 descent, whereby the life-history tends to be preserved in its 

 original form. 



4. But the several phases or periods of ontogeny (embryonic, 

 larval, adolescent, adult, senile) are all subject to variation, 

 and selection (when they are such as to be affected by biolog- 

 ical utility) and have varied in unlike degrees, whether one 

 compares stages in one line of descent or homologous stages 

 in different lines of descent. 



5. These variations, whether small or greater, have appeared 

 in, upon, and around old structures, so that any phase of on- 

 togeny undergoing revision tends to preserve in some degree 

 the character of the original basic structure. Because of this 

 fact any ontogeny is likely to give some indication of its past, 

 and to this extent constitutes a " record." 



6. Resemblances between comparable ontogenetic periods 

 will therefore tend to be closest between descendants and im- 



98 Of. Sedgwick, in Darwin and Modern Science. 



