No. 643] 



ORTHOGENESIS 



137 



about; it sharpens your powers of observation and 

 makes you much more cautious about your inductions. 

 My original observations on the Primates required cor- 

 roboration, and this I have sought through the observa- 

 tion of the origin of new characters in many other kinds 

 of mammals traced in their evolution over very long 

 periods of time, especially the horses, the rhinoceroses, 

 and recently the proboscideans, but most profoundly and 

 exhaustively the titanotheres, an extinct family remotely 

 related to the horses, which I have studied monographi- 

 cally for twenty-one years.^ 



Even by trying to keep an absolutely open eye and 

 mind, entirely uninfluenced by any theory, or preconcep- 

 tion, or opinion, I have been unable to find a single ex- 

 ception among these many different kinds of mammals 

 to the observations made on the Primates in 1888 and 

 1889; not a single new organ is observed to arise for- 

 tuitously or indefinitely ; it always arises gradually, con- 

 tinuously, and adaptively from its minute shadowy 

 beginnings. This continuous reciprocal, mechanical co- 

 adaptation seems to be an established fact in evolution, 

 and is established most strongly where explanation or 

 search for causes seems to be most difficult. 



I am not enthusiastic about the adoption of the term 

 orthogenesis, admirably significant as it is in its Greek 

 derivation, first, because Eimer connected it with La- 

 marck's and Buff on 's principles of inheritance of ac- 

 quired modifications, and, second, because it does injus- 

 tice to the first great observer of direct adaptive origins 

 in nature, namely, the G-erman palaeontologist Wilhelm 

 Heinrich Waagen, whose observations in 1869 laid the 

 foundation of all subsequent work both among the in- 



lOsborn, H. F., " The Titanotheres of Ancient Wyoming, Dakota, and 

 Nebraska. Life and Geography of the Central Kocky Mountain Region in 

 Eocene and Oligocene Times. Evohition of the Titanothere Family. The 

 Causes of Development and Extinction of Mammals," U. S. Geol. Survey 

 Monograph No. 55. [UnpubUshed.] Completed for the Survey June 30, 

 1920. This monograph is the most complete and exhaustive analysis that 

 has thus far been made of the evolution of any family of organisms. 



