ANIMAL PEDIGREES 247 



which the advantage of cross-fertilisation can be 

 obtained i.e., constraining every animal to begin 

 its development at its earliest ancestral stage, at the 

 very bottom of its genealogical tree. 



On this view the actual development of any 

 animal is strictly limited at both ends: it must 

 commence as an egg, and it must end in the 

 likeness of the parent. The problem of recapitula- 

 tion becomes thereby greatly narrowed ; all that 

 remains being to explain why the intermediate 

 stages in the actual development should repeat the 

 intermediate stages of the ancestral history. 



Although narrowed in this way, the problem still 

 remains one of extreme difficulty. It is a conse- 

 quence of the theory of Natural Selection that 

 identity of structure involves community of descent ; 

 a given result can only be arrived at through 

 a given sequence of events : the same morphological 

 goal cannot be reached by two independent paths. 

 A negro and a white man have had common 

 ancestors in the past ; and it is through the long- 

 continued action of selection and environment that 

 the two types have been gradually evolved. You 

 cannot turn a white man into a negro merely by 

 sending him to live in Africa: to create a negro the 

 whole ancestral history would have to be repeated ; 

 and it may be that it is for the same reason that the 

 embryo must repeat or recapitulate its ancestral 

 history in order to reach the adult goal. 



I am not sure that we can get much further than 

 this at present. However, be the explanation what 

 it may, there can I think be no doubt as to the 



