574 Ridley . — On Endemism and the Mutation Theory . 
Summary. 
Dr. Willis bases his arguments on the number of plants marked VC, 
VR in Trimen’s ‘Flora of Ceylon’, and states that a VC plant cannot 
disappear without a geological catastrophe. It is shown that the rarity or 
commonness of plants in Ceylon, as based on this book, is unreliable for 
practical purposes, and that the VC species can and do disappear without 
any catastrophe. 
Endemic species in Ceylon and elsewhere are nearly all the relics 
of an old flora rapidly disappearing, and in most cases cannot be evolu- 
tions of a later date, as there is nothing in the land from which they 
can have evolved, and therefore they must be the oldest, not the youngest 
part of the flora. 
The mutation theory that new characters arise at a step, and that once 
they have appeared they remain hereditary and do not revert, is not in 
accordance with the facts. The theory fails to account for the adaptation 
of plants to their surroundings, and no theory yet proposed, except that 
of Natural Selection, does so. 
The struggle for existence (more correctly the struggle for continuous 
reproduction) is not confined to the seedling, but is continuous throughout 
the life of the plant, and a mutation, however apparently trivial, of any organ 
in the plant may be adapted for this end. 
It has been of course impossible in this paper to do more than give 
illustrative examples on any one point ; the amount of evidence against the 
mutation theory and the various points controverted above is too enormous 
for even one book. This class of work can only be done in the field. 
Arguments based on calculations made from a book, however well written, 
are unreliable and misleading. 
Dr. Trimen’s Flora, on which Dr. Willis bases his arguments, is a good 
Flora for its date, but a great deal of research work has been since done 
on the countries adjacent to Ceylon, and from which the Ceylon flora took 
its origin. Most of the Ceylon species require critical examination again. 
There have been many misidentifications and errors in the geographical 
distribution, and very many of the species are but little known at present. 
With this work the study of the Ceylon flora commences, but the story 
is by no means complete yet, nor will it be till all the plants have been 
carefully and completely studied, one by one, in their relations to all 
conditions in which they occur in their natural wild state. 
