256 ERNST HAECKEL AND CARE GEGENBAUR 



real species at the present day ; they might or might not 

 be discoverable as fossils. That they had real existence 



j 



either now or at some past epoch Haeckel never doubted. 

 In his construction of phylogenetic trees he was so confident 

 in the truth of his biogenetic law that he largely disregarded 

 and consistently minimised the importance of the evidence 

 from palaeontology. 



The biogenetic law differed from the Meckel-Serres law 

 chiefly in the circumstance that many of the adult lower 

 forms whose organisation was supposed to be repeated in 

 the development of the higher animals were purely hypo- 

 thetical, being deduced directly from a study of ontogeny 

 and systematic relationships. The hypothetical ancestral 

 forms which the theory thus postulated naturally took their 

 place in the natural system, for they were merely the con- 

 crete projections or archetypes of the classificatory groups. 



The transcendentalists, of course, conceived evolution, 

 whether real or ideal, as a uniserial process, whereas Haeckel 

 conceived it as multiserial and divergent It is here that the 

 superficial agreement of the biogenetic law with the law of 

 von Baer comes in. 



We might almost sum up the relation of the biogenetic 

 law to the laws of von Baer and Meckel-Serres by saying 

 that it was the Meckel-Serres law applied to the divergent 

 differentiation upheld by von Baer instead of to the uniserial 

 progression believed in by the transcendentalists. 



How near in practice Haeckel's law came to the 

 recapitulation theory of the transcendentalists may be seen 

 in passages like the following, with its partial recognition of 

 the /:>//<//< idea : l " As so high and complicated an 

 organism as that of man . . . rises upwards from a simple 

 cellular state, and as it progresses in its differentiating and 

 perfecting, it passes through the same series of transforma- 

 tions which its animal progenitors have passed through, 

 during immense spaces of time, inconceivable ages ago. . . . 

 Certain very early and low stages in the development of 

 man, and other vertebrate animals in general, correspond 

 completely in many points of structure with conditions which 



1 The Ilitlory of Creation, vol. i., p. 310, 1876. Translation of the 

 Natitrlichc ScMpfttngSgeschii htc, 1868. 



