No. 643] 



ORTHOGENESIS 



135 



ist are alike impressed witli the incessant action of Nat- 

 ural Selection on animal mechanisms and with the now 

 testimonials to this aspect of Danvin's great principle. 



When it comes to the origins either of new characters 

 or of new proportions quite different is the attitude of 

 observers of mechanical evolution ; no evidence whatever 

 has been forthcoming from the same fifty-two years of 

 close observation and research as to the causes of origin, 

 at the same time the modes of origin of all mechanical 

 characters are indubitably orthogenetic. 



To further clarify the bearing of palaeontology on 

 orthogenesis, I desire to point out that all visible me- 

 chanical evolution goes hand in hand with invisible physi- 

 coehemical evolution; and that there are steps in evo- 

 lution which are primarily physical, others wliich are 

 primarily chemical, others which are primarily mechani- 

 cal. Therefore the experimental botanist, zoologist, bio- 

 chemist, biophysicist, or geneticist, has the opportunity 

 to win immortal fame by discovering the causes of me- 

 chanical evolution. 



Meanwhile the palaeontologist enjoys the entirely 

 unique position of being the only competent observer of 

 the Origin of Species so far as specific characters are 

 recorded in the hard parts of animals and the relatively 

 few soft parts which are preserved in a fossil condition. 



2. Oethogenetic Origin of New Characters 

 All agree that sound induction either as to the origin 

 of new characters or their transformation is an exceed- 

 ingly difficult matter. It has taken me thirty-three years 

 of uninterrupted observation in ni;niy groups of mam- 

 mals and reptiles to reach llic conchision that the origin 

 of new characters is invai'iably orthogenetic. 



In 1889 I first observed (Osborn, 18Si).4(;) that now 

 cusps originate on the grinding teeth of Moccno Pri- 

 mates, now recognized as lemuroids, in a dt'finite and 

 adaptive manner from minute shadowy ])oginnin,ii-s which 

 are mechanicjdly adjusted to similar minute shadowy 



