210 ANIMAL PEDIGREES 



The elder Agassiz was the first to point out, in 

 1858, the remarkable agreement between the em- 

 bryonic growth of animals and their palaeontological 

 history. He called attention to the resemblance 

 between certain stages in the growth of young fish 

 and their fossil representatives, and attempted to 

 establish, with regard to fish, a correspondence 

 between their palaeontological sequence and the 

 successive stages of embryonic development. He 

 then extended his observations to other groups of 

 animals, and stated his conclusions in these words : 

 " It may therefore be considered as a general 

 fact, very likely to be more fully illustrated as 

 investigations cover a wider ground, that the phases 

 of development of all living animals correspond to 

 the order of succession of their extinct representa- 

 tives in past geological times." 



This point of view is of great importance. If 

 the development of an animal is really a repetition 

 or recapitulation of its ancestral history, then it is 

 clear that the agreement or parallelism which 

 Agassiz insists on between the embryological and 

 palaeontological records must hold good, and a 

 most important field of work is thus opened up to 

 us. It is sometimes urged however that such work 

 is necessarily unfruitful and inconclusive, because of 

 the scantiness of our knowledge concerning life in 

 the earlier geologic periods, or as it is commonly 

 termed, the imperfection of the geological record. 

 I have elsewhere protested against this objection, 

 and would repeat my protest here. The actual 

 number of fossils already obtained, especially from 



