872 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 1915. 



effects its oxidation. On such lines I think we may with great con- 

 fidence interpret all those intergrading forms which breed trne and 

 are not produced by factorial interference. 



It is to be inferred that these fractional degradations are the con- 

 sequence of irregularities in segregation. We constantly see irregu- 

 larities in the ordinary meristic processes and in the distribution of 

 somatic differentiiition. We are familiar with half segments, with 

 imperfect twinning, with leaves partially petaloid, with petals par- 

 tially sepaloid. All these are evidences of departures from the 

 normal regularity in the rhythms of repetition or in those waves of 

 differentiation by which the qualities are sorted out among the parts 

 of the bod}^ Similarly, when in segregation the qualities are sorted 

 out among the germ cells in certain critical cell divisions, we can not 

 expect these differentiating divisions to be exempt from the imper- 

 fections and irregularities which are found in all the grosser divi- 

 sions that we can observe. If I am right, we shall find evidence of 

 these irregularities in the association of unconformable numbers 

 with the appearance of the novelties which I have called fractional. 

 In passing let us note how the history of the sweet pea belies those 

 ideas of a continuous evolution with wliich we had formerly to con- 

 tend. The big varieties came first. The little ones have arisen later, 

 as I suggest, by fractionation. Presented with a collection of modern 

 sweet peas, how prettily would the devotees of continuity have 

 arranged them in a graduated series, showing how every intergrade 

 could be found, passing from the full color of the wild Sicilian 

 species in one direction to white, in the other to the deep purple of 

 " Black Prince," though happily we know these two to be among the 

 earliest to have appeared. 



Having in viev/ these and other considerations which might be 

 developed, I feel no reasonable doubt that, though we may have to 

 forego a claim to variations by addition of factors, yet variation both 

 by loss of factors and by fractionation of factors is a genuine phe- 

 nomenon of contemporary nature. If then we have to dispense, as 

 seems likely, with any addition from without we must begin seri- 

 ously to consider whether the course of evolution can at all reasonably 

 be represented as an unpacking of an original complex which con- 

 tained within itself the whole range of diversity which living things 

 present. I do not suggest that Vve should come to a judgment as to 

 what is or is not probable in these respects. As I have said already, 

 this is no time for devising theories of evolution, and I propound 

 none. But, as we have got to recognize that there has been an 

 evolution, that somehow or other the forms of life have arisen from 

 fewer forms, we may as well see whether we are limited to the old 

 view that evolutionary progress is from the simple to the complex, 

 and whether after all it is conceivable that the process was the other 



