APPLICATION OF THE LAW OF BIOGENY. 349 



likely to lead to p:ropin^ in the dark ; and it not infrequently loads to the 

 most unfortunate results — far inferior to those which might be established 

 beyond question w'thout any study of the history of development." — 



ALEXA.NDER 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 tenaciously 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 progi-essive 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-forms, the primaeval metamorphosis of the tribal forms. 

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

 tation has acquired the ascendency over Heredity, the 

 oiiginal course of evolution ha«, usually, been so chano-ed. 



