44 PHYLOGENY 



What does it mean that a few mutants keep on reappearing year 

 after year, and that even the mutants themselves mutate, not in new 

 lines, but in the same old ones? Persuaded as deeply as I am that 

 we can never draw from a species anything for which no ancestral 

 foundations preexist, I anticipate that our wild evening primroses 

 have revelations to make. 



Whatever revelations may await future investigation in this field, 

 the work done in the Primrose Garden of Amsterdam will stand as 

 a classical contribution to the new biology, and as one of the very 

 best models in method of research that we have yet seen. 



Natural selection, orthogenesis, and mutation appear to present 

 fundamental contradictions; but I believe that each stands for truth, 

 and that reconciliation is not distant. 



The so-called mutations of Mnotlnera are indubitable facts; but 

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

 tions, now appearing, as is claimed, independently of variation, never- 

 theless the products of variations that took place at an earlier period 

 in the history of these plants? Secondly, if species can spring into 

 existence at a single leap, without the assistance of cumulative varia- 

 tions, may they not also originate with such assistance? That varia- 

 tion does issue in 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 (ortho- 

 genesis), and likewise of variations in various directions (amphi- 

 genesis). If I am not mistaken in this, the reconciliation for natural 

 selection and orthogenesis is at hand. 



I am aware that orthogenesis is held by many to be utterly incom- 

 patible with both natural selection and mutation. "The Darwinian 

 principle demands," says De Vries, "that species-forming variability 

 and mutability be indeterminate in direction. Deviation in all senses 

 must arise, without favor to any particular direction, and especially 

 without partiality for the direction proceeding from the theory to 

 be explained. Every hypothesis which departs from this principle 

 must be rejected as teleological, and therefore unscientific." (Vol. i, 

 p. 140.) 



Again (p. 180) the same point is amplified: "Again and again, and 

 by authors of different aims, it has been insisted upon that species- 

 forming variability must be orderless. The assumption of a definite 

 variation-tendency which would condition, or even favor, the appear- 

 ance of adaptive modifications, lies outside the pale of the natural 

 science of to-day. In fact, the great advantage of Darwin's doctrine 

 of selection lies in this, that it strives to explain the whole evolution 

 of the animal and plont kingdoms without the aid of supernatural 



