APPLICATION OP THE LAW OF BIOGENY. 349 



likely to lead to groping in the dark ; and it not infrequently leads to the 

 most unfortunate results far inferior to those which might be established 

 beyond question without any study of the history of development." 

 ALEXANDEK BUAUN (1872). 



IN applying to Organogeny the fundamental law of Bio- 

 geny, we have already afforded some conception of the 

 degree in which we may follow its guidance in the study of 

 tribal history. The degree differs greatly in the different 

 organ-systems ; this is so, because the capacity for trans- 

 mission on one side, and the capacity for modification on 

 the other, vary greatly in the different organs. Some parts 

 of the body cling tenaciousl} 7 to the inherited germ-history ; 

 and, owing to heredity, accurately retain the mode of 

 evolution inherited from primaeval animal ancestors ; other 

 parts of the body, on the contrary, exhibit very small 

 capacity for strict heredity, and have a great tendency to 

 assume new kenogenetic forms by adaptation, and to modify 

 the original Ontogeny. The former organs represent, in the 

 many-celled community of the human organism, the con- 

 stant or conservative; the latter, on the contrary, the 

 changeable or progressive element of evolution. The mutual 

 interaction of both elements determines the course of his- 

 torical evolution. 



Only to the conservative organs, in which Heredity pre- 

 ponderates over Adaptation, in the course of tribal evolu- 

 tion, can we directly apply the Ontogeny to the Phylogeny, 

 and can infer, from the palingenetic modification of the 

 germ-forins, the primseval metamorphosis of the tribal forms. 

 In the progressive organs, on the contrary, in which Adap- 

 tation has acquired the ascendency over Heredity, the 

 original course of evolution has, usually, been so changed, 



