LECTURE IH 

 EVIDENCE FROM EMBRYOLOGY AND BLOOD TESTS 



JEmbryology .is the- study of the development of 



the individual organsim from its beginning in the 

 egg to the attainment of the adult condition. This 

 individual development is called ontq^er^/ and flip 

 question of the relation of ontogeny to the ancestral j- 

 history of the species, or ?>ht/7sKiftiy t jyj|irtitfftTT?m : ' 

 of the main problems of embryology. Around this 

 problem many controversies have raged, contro- 

 versies which have by no means arrived at a definite 

 solution, even to-day. Thirty years ago the "re- 

 capitulation theory" was well-nigh universally ac- 

 cepted, according to which the individual develop- 

 ment, or ontogeny^ was regarded as an abbreviated 

 repetition of the ancestral history of the species, or 

 phylogeny. Haeckel called this theory the "fun- 

 damental biogenetic law" and upon it he established 

 his whole "History of Creation." Nowadays, that 

 "fundamental law" is very seriously questioned and 

 by some high authorities is altogether denied. How- 

 ever, even those who take this extreme position con- 

 cerning the recapitulation theory see in the facts of 

 embryology one of the strongest supports of the 

 doctrine of evolution. 



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