it is but rarely covered by the water; the other, Melita insatiabilis, a
little lower; both species live together in numerous swarms. We cannot
therefore suppose that the loving couples are threatened with
disturbance more frequently than those of other species, nor would it be
more difficult for the male, than for those of other species, in case of
his losing his female, to find a new one. Nor is it any more easy to see
how the contrivance on the body of the female for insuring the act of
copulation could be injurious to other species. But so long as it is not
demonstrated that our species are particularly in want of this
contrivance, or that the latter would rather be injurious than
beneficial to other species, its presence only in these few Amphipoda
will have to be regarded not as the work of far-seeing wisdom, but as
that of a favourable chance made use of by Natural Selection. Under the
latter supposition its isolated occurrence is intelligible, whilst we
cannot perceive why the Creator blessed just these few species with an
apparatus which he found to be quite compatible with the "general plan
of structure" of the Amphipoda, and yet denied it to others which live
under the same external conditions, and equal them even in their
extraordinary salacity. Associated with, or in the immediate vicinity of
the two species of Melita, live two species of Allorchestes, the pairs
of which are met with almost more numerously than the single animals,
and yet their females show no trace of the above-mentioned processes of
the coxal lamellae.

These cases, I think, must be brought to bear against the conception
supported with so much genius and knowledge by Agassiz, that species are
embodied thoughts of the Creator; and, with these, all similar instances
in which arrangements which would be equally beneficial to all the
species of a group are wanting in the majority and only conferred upon a
few special favourites, which do not seem to want them any more than the