has a similar cuckoo-like habit, and which is most closely
allied in every respect to the species from the Plata, even in
such trifling peculiarities as standing on the backs of cattle;
it differs only in being a little smaller, and in its plumage
and eggs being of a slightly different shade of colour. This
close agreement in structure and habits, in representative
species coming from opposite quarters of a great continent,
always strikes one as interesting, though of common
occurrence.

Mr. Swainson has well remarked, [8] that with the exception
of the Molothrus pecoris, to which must be added the
M. niger, the cuckoos are the only birds which can be called
truly parasitical; namely, such as "fasten themselves, as it
were, on another living animal, whose animal heat brings
their young into life, whose food they live upon, and whose
death would cause theirs during the period of infancy." It
is remarkable that some of the species, but not all, both of
the Cuckoo and Molothrus, should agree in this one strange
habit of their parasitical propagation, whilst opposed to each
other in almost every other habit: the molothrus, like our
starling, is eminently sociable, and lives on the open plains
without art or disguise: the cuckoo, as every one knows,
is a singularly shy bird; it frequents the most retired thickets,
and feeds on fruit and caterpillars. In structure also
these two genera are widely removed from each other.
Many theories, even phrenological theories, have been advanced
to explain the origin of the cuckoo laying its eggs in
other birds' nests. M. Prevost alone, I think, has thrown
light by his observations [9] on this puzzle: he finds that the