THE GROWTH OF GROUPS 3 



common conception of that agency. In its new role 

 it does not appear as a creative process. 



Several writers have urged the importance of sudden 

 and obvious variations such as are called sports, or 

 mutants. Huxley expressed his belief that races were 

 occasionally derived from sports. In 1892 Bateson 

 pointed to the discontinuity of species and explained it 

 as the natural outcome of discontinuous variation. If 

 by species we mean those groups which are being denned 

 as such at the present day, and if by discontinuous 

 variation we mean obvious differences which may be 

 seen, exceptionally, when comparing offspring with their 

 parents ; then it seems to me that Bateson 's proposition 

 is indisputable. The evidence to be described in this 

 book is in support of it. 



In the Mutation Theory of De Vries we find the same 

 opinions in a more decided shape, amply supported by 

 evidence from the vegetable kingdom, indeed so com- 

 plete is the evidence that botanists more generally than 

 zoologists regard mutation as the method of evolution. 

 Above all, through Mendel's work and all that has fol- 

 lowed from it in the last decade, we have gained an 

 insight into the nature of living things, compelling us to 

 recognize that the change which comes over them is not 

 comparable to a gliding movement, but to a series of 

 little steps, not always of the same width but often wide 

 enough to be appreciated with certainty. 



DIFFICULTIES ARISING FROM THE USE OF THE WORD 

 SPECIES. 



Discussions on the origin of species are usually un- 

 satisfactory because the term species has no decided 



