uccessive steps that have led to our present state of knowledge. I began
with Aristotle, and showed that this great philosopher, though he prepared
a digest of all the knowledge belonging to his time, yet did not feel the
necessity of any system or of any scientific language differing from the
common mode of expression of his day. He presents his information as a man
with his eyes open narrates in a familiar style what he sees. As
civilization spread and science had its representatives in other countries
besides Greece, it became indispensable to have a common scientific
language, a technical nomenclature, combining many objects under common
names, and enabling every naturalist to express the results of his
observations readily and simply in a manner intelligible to all other
students of Natural History.

Linnaeus devised such a system, and to him we owe a most simple and
comprehensive scientific mode of designating animals and plants. It may at
first seem no advantage to give up the common names of the vernacular and
adopt the unfamiliar ones, but a word of explanation will make the object
clear. Perceiving, for instance, the close relations between certain
members of the larger groups, Linnaeus gave to them names that should be
common to all, and which are called generic names,--as we speak of Ducks,
when we would designate in one word the Mallard, the Widgeon, the
Canvas-Back, etc.; but to these generic names he added qualifying
epithets, called specific names, to indicate the different kinds in each
group. For example, the Lion, the Tiger, the Panther, the Domestic Cat
constitute such a natural group, which Linnaeus called _Felis_, Cat,
indicating the whole genus; but the species he designates as _Felis
catus_, the Domestic Cat,--_Felis leo_, the Lion,--_Felis tigris_, the
Tiger,--_Felis panthera_, the Panther. So he called all the Dogs _Canis_;
but for the different kinds we have _Canis familiaris_, the Domestic
Dog,--_Canis lupus_, the Wolf,--_Canis vulpes_, the Fox, etc.

In some families of the vegetable kingdom we can appreciate better the
application of this nomenclature, because we have something corresponding
to it in the vernacular. We have, for instance, one name for all the Oaks,
but we call the different kinds Swamp Oak, Red Oak, White Oak, Chestnut
Oak, etc. So Linnaeus, in his botanical nomenclature, called all the Oaks
by the generic name _Quercus_, (characterizing them by their fruit, the
acorn, comm