288 DARWINISM TO-DAY. - 



of some factor or factors besides that of natural selection 

 to explain evolution lines as revealed by palgeontological 

 study is shared by a large majority of the recognised 

 American palaeontologists. Osborn of Columbia, Williston 

 of Chicago, Hyatt of Boston, Smith of Stanford, studying 

 respectively the fossil mammals, the reptiles, and the 

 molluscs, all voice their belief in the existence of evidence in 

 the history of the evolution of these animal groups for 

 orthogenetic variation and descent. 



Recently Whitman, the Nestor of American zoologists, 



has declared himself strongly as an adherent of the actuality 



of orthogenetic evolution. For many years 



expression in Whitman has been studying the variations and 



favour of ortho- inheritance in pigeons, and through this work 



in particular he has become convinced that 

 species-forming variation does advance in a definite direc- 

 tion as well as in various directions. He says, 22 "natural 

 selection, orthogenesis, 23 and mutation appear to present 

 fundamental contradictions ; but I believe that each stands 

 for truth, and reconciliation is not distant. The so-called 

 mutations of (Enothera are indubitable facts ; but two lead- 

 ing questions remain to be answered. First, are these muta- 

 tions now appearing, as is agreed, independently of varia- 

 tion, nevertheless a production of variations that took place 

 at an earlier period in the history of these plants? Sec- 

 ondly, if species can spring into existence at a single leap, 

 without the assistance of cumulative variations, may they 

 not also originate with such assistance? That variation 

 does issue a new species, and that natural selection is a 

 factor, though not the only factor, in determining results, 

 is, in my opinion, as certain as that grass grows although 

 we cannot see it grow. Furthermore, I believe I have 

 found indubitable evidence of species-forming variation 

 advancing in a definite direction (orthogenesis), and like- 

 wise of variations in various directions (amphigenesis). If 



