The Origin of Species by Large, rather than by 
Gradual, Change, and by Guppy’s Method 
of Differentiation. 
BY 
J. C. WILLIS, M.A., Sc.D., F.R.S., 
Eiiropcan Correspondent of the Botanic Garden , Rio de Janeiro. 
‘ May not the births of new species, like the deaths of old ones, be sudden.’— Lyell. 
I N the days of Special Creation it was of course assumed that each species 
was created de novo in the form in which it was found to occur most 
widely upon the surface of the earth, while varieties were supposed to owe 
their origin to subsequent change. Towards the end of this period, how¬ 
ever, it began to be recognized, e. g. by Lyell and Hooker (8, p. 702, and 
6, p. xxv, quoted in ‘ Age and Area’, p. 3), that all existing species were not 
created simultaneously, but that new ones, which would usually (of necessity) 
occupy less area, were from time to time appearing. Once this was fully 
recognized, it is clear that the way was open for the acceptance of some 
scheme of evolution, so soon as something feasible should be proposed. 
The great difficulty that lay before the ‘special creationists * was to 
explain why species were so obviously grouped by affinities (as they were 
called), a fact which was perceived at a very early date, and was the under¬ 
lying motive of the attempts that were continually being made to group 
plants and animals into genera and families in what was called the ‘ natural ’ 
system 1 of classification. If species were specially created, each for its own 
place, there seemed no reason why they should be so evidently capable of 
arrangement into genera and other groups, and why these groups should 
usually occupy continuous areas. Nothing, evidently, could explain affinity 
but some scheme of evolution. If we imagine species showing affinity to 
have descended from some common ancestor, and therefore suppose that on 
the whole the affinities of species will be more and more pronounced the less 
1 * A genus is called natural not because it exists in nature, but because it comprehends species 
more naturally resembling each other than they resemble anything else ’ (Lindley ( 7 ), p. xvi). 
Annals of Botany, Vol. XXXVII. No. CXLVIII. October, 1923.] 
