DARWIN AND PALEONTOLOGY 237 



new, definite, orthogenetic characters whicli could 

 not have been acquired in ontogeny arise at birth, 

 among them the cusps of the teeth. Since the 

 Lamarckian doctrine either fails or need not be 

 invoked to explain these definite adaptive origins 

 in the teeth, and apparently also in the horns, 

 why invoke it for other adaptive phenomena? 

 This does not preclude the constant operation of 

 the law of organic selection ^ or the " selection 

 of coincident variations " advocated by Morgan, 

 Baldwin, and myself, which I still regard as a 

 useful supplementary hypothesis to Natural Se- 

 lection, explaining many of the alleged instances 

 of the inheritance of acquired characters. 



Unknown causes of certain adaptive origins. 

 In 1890 I pointed out that, since the Lamarckian 

 principle gave us a working hypothesis of direc- 

 tion in these adaptive origins, in abandoning the 

 Lamarckian principle we would be left without 

 any explanation, and in developing this idea I 

 came to the conclusion in 1895 ^ that we must 

 appeal to the existence of some unknown factor 



' Osborn H. F.: "A Mode of Evolution Requiring Neither 

 Natural Selection nor the Inheritance of Acquired Characters 

 (Organic Selection)," Trans. N. Y. Acad. Sci., March and April, 

 1896, pp. 141-48. 



See also: " Ontogenic and Phylogenic Variation,'' Science, 

 Vol. IV, 1896, November 27, pp. 786-90; "Organic Selection," 

 Science, N. S., Vol. VI, No. 146, October 15, 1897, pp. 583-87; 

 " The Limits of Organic Selection," American Naturalist, Vol. 

 XXI, November, 1897, pp. 944-51 ; " Modification and Variation, 

 and the Limits of Organic Selection; A Joint Discussion with 

 Professor Edward B. Poulton of Oxford University," Proc. Amer. 

 Assoc. Adv. Science, Vol. 46, 1897, p. 239. 



' " The Hereditary Mechanism and the Search for the Unknown 

 Factors of Evolution," Biol. Led. Marine Biol. Lab. 1894, Ginn & 

 Co., Boston, 1895. 



