Ridley .—On Endemism and the Mutation Theory. 561 
Dr. Willis’s theory of mutation is described in the ‘Annals of the Roy. 
Bot. Gard., Peradeniya/ as that new characters are supposed to arise 
at one step : once they have appeared the new characters are hereditary 
and the new form does not go back to the old one. 
In other words, all mutations are at once fixed. This is easily shown 
not to be the case. Nor does the theory in the least explain the adap- 
tations to surroundings, e. g. why Calophyllum inophyllum , adapted as its 
fruits are for sea dispersal, occurs only on the sea-shore, or why Crinum 
asiaticum , with long-tubed white fragrant flowers only fertilizable by a 
crepuscular sphingid, only opens its flowers at exactly the time of the 
appearance of the moth. In fact, the theory is the old special creation 
hypothesis with the creator left out, and no substitute given. 
Every gardener and field botanist of ordinary observing powers knows 
that very many variations (or mutations as Dr. Willis prefers to call them) 
occur in plants which do not appear again in their offspring. 
Many years ago in Singapore we obtained a variety of Antigonon 
leptopus in which the normally pink flowers were pure white. This variety, 
though it came true from cuttings, did not come true from seeds. All 
its seedlings gave pink flowers for a considerable period. After some 
years (the mutation not being fixed till then) we obtained a few white- 
flowered seedlings. Zinnias grown in the garden at Singapore from culti- 
vated plants from Europe in three years reverted to the form of the 
original small-flowered wild plant. The same thing happened with the 
garden Balsam and other cultivated plants. But this is well known to 
every gardener. Very striking cases in a natural state will be shown later 
on in this paper. 
The argument that specific differences which plants possess have never 
been shown to be of practical use now or of some use in the past, does 
not hold good in view of the extensive literature on fertilization and 
dissemination, and on the relations of plants to their surroundings. 
The whole life-history of any single plant is not at present really 
known — its physiology and habits ; its insect, fungal, or other enemies ; its 
requirements due to the action of light, heat, electricity, rain, dew, frost 
or drought ; its food and water-supply ; its means of fertilization, protec- 
tion, and reproduction ; in fact, the whole physiological and ecological 
history of the plant from the seed to its reproduction and death by day 
and night, in normal and abnormal weather, at all seasons of the year, and 
in all geological or climatic changes for the period of its existence as 
a species. Until this is known, it is impossible to give the cause of 
all specific differences. I do not believe this is known of any common 
English plant, still less of any tropical one. 
In Ann. Roy. Bot. Gard., Perad., vol. iv, p. 2, Dr. Willis writes : ‘ A point 
that has so far escaped attention is, that the characters that distinguish genera 
i 
