Contributions to the theory of natural selection. A series of essays ... By Alfred Russel Wallace ...

CREATION BY LA W. 271
A Case of Orchis-structure explained by NcLatural
Selection.
There is a Madagascar Orchis-the Angrmcum sesquipedale-with an immensely long and deep nectary.
How did such an extraordinary organ come to be
developed? Mr. Darwin's explanation is this. The
pollen of this flower can only be removed by the base
of the proboscis of some very large moths, when trying
to get at the nectar at the bottom of the vessel. The
moths with the longest probosces would do this most
effectually; they would be rewarded for their long
tongues by getting the most nectar; whilst on the other
hand, the flowers with the deepest nectaries would be
the best fertilized by the largest moths preferring
them. Consequently, the deepest nectaried Orchids
and the longest tongued moths would each confer on the
other an advantage in the battle of life. This would
tend to their respective perpetuation, and to the constant lengthening of nectaries and probosces. Now
let it be remembered, that what we have to account
for, is only the unusual length of this organ. A nectary is found in many orders of'plants and is especially
common in the Orchids, but in this one case only is
it more than a foot long. How did this arise? We
begin with the fact, proved experimentally by Mr.
Darwin, that moths do visit Orchids, do thrust their
spiral trunks into the nectaries, and do fertilize them
by carrying the pollinia of one flower to the stigma of
another. He has further explained the exact mechanism