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 by which this is effected, and
the Duke of Argyll admits the accuracy of his observations. In our
British species, such as Orchis pyramidalis, it is not necessary that
there should be any exact adjustment between the length of the nectary
and that of the proboscis of the insect; and thus a number of insects of
various sizes are found to carry away the pollinia and aid in the
fertilization. In the Angraecum sesquipedale, however, it is necessary
that the proboscis should be forced into a particular part of the
flower, and this would only be done by a large moth burying its
proboscis to the very base, and straining to drain the nectar from the
bottom of the long tube, in which it occupies a depth of one or two
inches only. Now let us start from the time when the nectary was only
half its present length or about six inches, and was chiefly fertilized
by a species of moth which appeared at the time of the plant's
flowering, and whose proboscis was of the same length. Among the
millions of flowers of the Angraecum produced every year, some would
always be shorter than the average, some longer. The former, owing to
the structure of the flower, would not get fertilized, beca