ar combination of features is in direct relation to its habits,
for it does not lie in wait and spring upon its prey like the Cat, but
hunts it like the Dog.

While Genera themselves are, like Families, easily distinguished, the
characters on which they are founded, like those of Families, are
difficult to trace. There are often features belonging to these groups
which attract the attention and suggest their association, though they
are not those which may be truly considered generic characters. It is
easy to distinguish the Genus Fox, for instance, by its bushy tail, and
yet that is no true generic character; the collar of feathers round the
neck of the Vultures leads us at once to separate them from the Eagles,
but it is not the collar that truly marks the Genus, but rather the
peculiar structure of the feathers which form it. No Bird has a more
striking plumage than the Peacock, but it is not the appearance merely
of its crest and spreading fan that constitutes a Genus, but the
peculiar structure of the feathers. Thousands of examples might be
quoted to show how easily Genera may be singled out, named, and entered
in our systems, without being duly characterized, and it is much to be
lamented that there is no possibility of checking the loose work of this
kind with which the annals of our science are daily flooded.

It would, of course, be quite inappropriate to present here any
general revision of these groups; but I may present a few instances to
illustrate the principle of their classification, and to show on what
characters they are properly based. Among Reptiles, we find, for
instance, that the Genera of our fresh-water Turtles differ from each
other in the cut of their bill, in the arrangement of their scales,
in the form of their claws, etc. Among Fishes, the different Genera
included under the Family of Perches are distinguished by the
arrangement of their teeth, by the serratures of their gill-covers, and
of the arch to which the pectoral fins are attached, by the nature and
combination of the rays of their fins, by the structure of their scales,
etc. Among Insects, the various Genera of the Butterflies differ in the
combination of the little rods which sustain their wings, in the form
and structure of their antennae, of their feet, of the minute scales
which cover their wings, etc. Among Crustacea, the Genera of Shrimps
vary in the form of the claws, in the structure of the parts of the
mouth, in the artic