W. B. Scott — Variations and Mutations. 



6i 6 



.Charaktere regellose Abiinderungen und jede Mutation ent- 

 wickelt denselben Varietatenkreis."* 



All this might have been written of mammalian phyla, to 

 which it exactly applies. Another fact of general application is 

 that there is no necessary proportion between the variability 

 of a group and the amount of mutation through which it passes. 

 On the contrary, such groups may exist substantially unchanged 

 through long periods of time, but being nevertheless extremely 

 variable in all stages of their history. Others again may show 

 little variation at any one stage and yet by steady advance 

 experience complete transformation. 



This mode of viewing the facts of development may be ex- 

 pressed by an analogy. The track of a cyclonic storm is deter- 

 mined by the path of the storm center, around which the winds 

 circulate, blowing in every direction. These circulating winds 

 would represent the variations which occur at every stage in the 

 history of a phylum, while the course of the storm-center 

 would represent the phylogenetic change, or mutations. Thus 

 the cycles of variation tend to repeat themselves, though the 

 center around which they revolve has a course of its own, de- 

 pendent, not on the accumulation of these winds which happen 

 to be blowing in the right direction, but upon factors of a much 

 wider significance. 



I am very well aware that any such view as that here sug- 

 gested is opposed to many facts which appear to show that the 

 distinction between individual variation, variety, species, 

 genus, etc. is one only of degree and not of kind, the incon- 

 stant differences between variants being very much the same, 

 and often greater in amount, as the more or less stable differ- 

 ences between species. As every one knows, it is often most 

 difficult to determine the bounds of a natural group and sys- 

 tematists differ radically on such questions. But the problem 

 is one as to factors of change. The distinction between var- 

 iation and mutation does not necessarily imply an objective 

 reality for species which does not extend to variations ; there may 

 be such a difference, but it cannot be demonstrated. What is 

 meant is that the march of transformation is the resultant of 

 forces both internal and external which operate in a definite 

 manner upon a changeable organism and similarly affect large 

 numbers of individuals. That phylogenetic advance does not 

 consist in the selection of a few favorable variations out of a 

 large number of haphazard changes, is irresistibly born in upon 

 the student of real phyla. This view in no way impugns the 

 importance of natural selection as enunciated by Darwin, 

 though of course it is irreconcilable with the omnipotence of 



*Neumayr, M. Die Statmne des Thierre'ches. Bd. I, pp 60-61. 



