202 ANIMAL PEDIGREES 



us that as individual animals arise, not spon- 

 taneously, but by direct descent from pre-existing 

 animals, so also is it with species, with families, 

 and with larger groups of animals, and so also has 

 it been for all time ; that as the animals of 

 succeeding generations are related together, so also 

 are those of successive geologic periods ; that all 

 animals living or that have lived are united 

 together by blood relationship of varying nearness 

 or remoteness; and that every animal now in 

 existence has a pedigree stretching back, not 

 merely for ten or a hundred generations, but 

 through all geologic time since the dawn of life on 

 this globe. 



The study of Development, in its turn, has 

 revealed to us that each animal bears the mark of 

 its ancestry, and is compelled to discover its 

 parentage in its own development ; that the phases 

 through which an animal passes in its progress 

 from the egg to the adult are no accidental freaks, 

 no mere matters of developmental convenience, but 

 represent more or less closely, in more or less 

 modified manner, the successive ancestral stages 

 through which the present condition has been 

 acquired. Evolution tells us that each animal has 

 had a pedigree in the past. Embryology reveals to 

 us this ancestry, because every animal in its own 

 development repeats its history, climbs up its own 

 genealogical tree. Such is the Recapitulation 

 Theory, hinted at by Agassiz, and suggested more 

 directly in the writings of Von Baer, but first 

 clearly enunciated by Fritz Mttller, and since 



