14 The Recapitulation Theory and Human Infancy 



8. The Developmental-Ancestral Correspondence Clearly Enunciated: 



Fritz Miiller. 



It has been noted that Darwin had profited by the contribu- 

 tion to his theory made by Miiller in his book, "Fur Darwin," 

 published in 1864. Torn between the claims of the rival theories, 

 Miiller determined rigidly to apply the principles of Darwin to 

 one group, the Crustacea, in order to discover whether lines of 

 descent and a genetic classification could in this manner be 

 determined within it. In concluding his study Miiller general- 

 ized upon the facts of resemblance between the developmental 

 history of descendants and the adult state of ancestors in a more 

 precise manner than Darwin had in his first edition. His con- 

 clusions are as follows: 



"Descendants, therefore, reach a new goal, either by deviat- 

 ing sooner or later whilst still on the way towards the form of 

 their parents, or by passing along this course without deviation, 

 but then, instead of standing still, advance still further. 



"In the second case the entire development of the progenitors 

 is also passed through by the descendants, and, therefore, so far 

 as the production of a species depends upon this second mode of 

 progress, the historical development of the species will be mir- 

 rored in its developmental history. 



"The historical record preserved in developmental history is 

 gradually effaced as the development strikes into a constantly 

 straighter course from the egg to the perfect animal, and it is 

 frequently sophisticated by the struggle for existence which the 

 free-living larvae have to undergo. 



"Which of the different modes of development at present 

 occurring in a class of animals may claim to be that approach- 

 ing most nearly to the original one, is easy to judge from the 

 above statements." 18 



9. "Ontogeny is a Short and Rapid Recapitulation of Phylogeny:" 



Haeckel. • 



In the statement of principles quoted above from Fritz Miiller 

 it will be observed that there is no disposition to weight the cases 

 of recapitulation in very great disproportion to those of embry- 

 onic or larval deviation. Two possible courses of development 

 are shown, recapitulation being the second. And there is little 

 disposition, if any, to make the second class of cases the more 

 prevalent or the more characteristic in any fundamental way 



18 Facts and Arguments for Darwin, pp. Ill, 112, 114. 



