uired by a true land-bird.

That such habits might be acquired under stress of need is rendered
highly probable by the facts stated by the well-known American
naturalist, Dr. Abbott. He says that "the water-thrushes (Seiurus sp.)
all wade in water, and often, seeing minute mollusca on the bottom of
the stream, plunge both head and neck beneath the surface, so that
often, for several seconds, a large part of the body is submerged. Now
these birds still have the plumage pervious to water, and so are liable
to be drenched and sodden; but they have also the faculty of giving
these drenched feathers such a good shaking that flight is practicable a
moment after leaving the water. Certainly the water-thrushes (Seiurus
ludovicianus, S. auricapillus, and S. noveboracensis) have taken many
preliminary steps to becoming as aquatic as the dipper; and the
winter-wren, and even the Maryland yellow-throat are not far
behind."[40]

Another curious example of the way in which species have been modified
to occupy new places in nature, is afforded by the various animals which
inhabit the water-vessels formed by the leaves of many epiphytal species
of Bromelia. Fritz Mueller has described a caddis-fly larva which lives
among these leaves, and which has been modified in the pupa state in
accordance with its surroundings. The pupae of caddis-flies inhabiting
streams have fringes of hair on the tarsi to enable them to reach the
surface on leaving their cases. But in the species inhabiting bromelia
leaves there is no need for swimming, and accordingly we find the tarsi
entirely bare. In the same plants are found curious little Entomostraca,
very abundant there but found nowhere else. These form a new genus, but
are most nearly allied to Cythere, a marine type. It is believed that
the transmission of this species from one tree to another must be
effected by the young crustacea, which are very minute, clinging to
beetles, many of which, both terrestrial and aquatic, also inhabit the
bromelia leaves; and as some water-beetles are known to frequent the
sea, it is perhaps by these means that the first emigrants established
themselves in this strange new abode. Bromeliae are often very abundant
on trees growing on the water's edge, and this would facilitate the
transition from a marine to an arboreal habitat. Fritz Mueller has also
found, among the bromelia leaves, a small frog bearing its eggs on its
back, and having some other peculiarities of st