THE PROBLEM OF THE ORIGIN OF SPECIES. 11 



I am aware that orthogenesis is held by many to be utterly incompatible with 

 both natural selection and mutation. De Vries says (vol. 1, page 40): 



The Darwinian principle demands that species-forming variability and mutability be 

 indeterminate in direction. Deviation in all senses must arise, without favor to any par- 

 ticular 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. 



Again (page 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 appearance of adaptive modifications 

 lies outside the pale of the natural science of to-day. In fact, the great advantage of Dar- 

 win's doctrine of selection lies in this, that it strives to explain the whole evolution of the 

 animal and plant kingdoms without the aid of supernatural presuppositions. According 

 to this doctrine, species-forming variability goes on without regard to the qualification of 

 the new species for maintaining themselves in life. It simply supplies the struggle for 

 existence with the material for natural selection. Whether this selection takes place 

 between individuals, as Darwin and Wallace supposed, or decides between whole species, 

 as the mutation-theory demands, ultimately it is, in either case, simply the ability for 

 existence under given external conditions that decides upon the permanence of the new form. 



I take exception here only to the implication that a definite variation-tendency 

 must be considered to be teleological because it is not "orderless." I venture to 

 assert that variation is sometimes orderly and at other times rather disorderly, 

 and that the one is just as free from teleology as the other. In our aversion to the 

 old teleology, so effectually banished from science by Darwin, we should not forget 

 that the world is full of order, the organic no less than the inorganic. Indeed, what 

 is the whole development of an organism if not strictly and marvelously orderly? 

 Is not every stage, from the primordial germ onward, and the whole sequence of 

 stages, rigidly orthogenetic? If variations are deviations in the directions of the 

 developmental processes, what wonder is there if in some directions there is less 

 resistance to variation than in others? What wonder if the organism is so balanced 

 as to permit of both unifarious and multifarious variations? If a developmental 

 process may run on throughout life (e.g., the lifelong multiplication of the surface- 

 pores of the lateral-line system in Amid), what wonder if we find a whole species 

 gravitating slowly in one or a few directions? And if we find large groups of species 

 all affected by a like variation, moving in the same general direction, are we com- 

 pelled to regard such "a definite variation-tendency" as teleological, and hence 

 out of the pale of science? If a designer sets limits to variation in order to reach a 

 definite end, the direction of events is teleological; but if organization and the laws 

 of development exclude some lines of variation and favor others, there is certainly 

 nothing supernatural in this, and nothing which is incompatible with natural selec- 

 tion. Natural selection may enter at any stage of orthogenetic variation, preserve 

 and modify in various directions the results over which it may have had no pre- 

 vious control. 



It should be noted in this connection that the difficulty of incipient stages is 

 not what it is so generally presumed to be. The advocates of natural selection 



