DARWIN AND PALEONTOLOGY 231 



in single characters; they are the nuances, or 

 shades of difference, which are the more gradual 

 the more finely we dissect the geologic column; 

 bit by bit the Waagen mutations are added to 

 each other in different single characters until the 

 sxrni or degree of mutations is reached which no 

 zoologist would hesitate to assign specific or ge- 

 neric rank. The essence of Waagen's mutation 

 is orthogenesis or variation in determinate direc- 

 tions, as distinguished from the indefinite varia- 

 tion imphed in Darwin's theory.^ This law re- 

 ceived the powerful support of our countryman 

 Hyatt, of the Austrian paleontologist Neumayr, 

 and many others. 



In 1889 Osborn," in observing the teeth of large 

 numbers of Eocene mammals, chiefly of the 

 smaller monkeys, horses, tapirs, and other forms, 

 first noticed that new elements here also arise def- 

 initely and can only be measured after long in- 

 tervals of time. He first applied (1890) the 

 term " definite variations " ^ to these characters, 

 but many years later, on observing that many 

 such characters were destined to become adaptive, 

 he gave the same elements the name " rectigrada- 



^ Professor Poulton maintains that determinate variation is 

 precisely what Natural Selection would show, namely direction 

 through the accumulation of favorable variations. 



" Osborn, H. F. : " The Paleontological Evidence for the Trans- 

 mission of Acquired Characters," British Association Reports, 

 Newcastle-upon-Tyne meeting, September, 1889. London, 1890. 



""Are Acquired Variations Inherited? Opening a Discussion 

 upon the Lamarckian Principle in Evolution." American Society 

 of Naturalists, Boston, December 31, 1890. American Naturalist, 

 Vol. XXV, No. 291, March, 1891, pp. 191-216. 



