created in the beginning,"--was at least an attempt to use the term in a
well-defined sense. Of course, this definition assumed the "fixity" of
species; but with the wide prevalence of the views of Darwin and his
followers the term "species" has fallen into disrepute, and is now
regarded by many as only an artificial rank in classification
corresponding to no objective reality in the natural world. Some
writers, as Lankester, have found so much fault with the term as to urge
its complete abandonment in scientific literature. This is logical
enough from the standpoint of Darwinism; for if the latter be true there
ought indeed to be such a swamping of every incipient "species" as to
make one kind blend with others all around it in the classification
series.

But since the term has by no means been discarded, we must endeavor to
determine the sense in which it continues to be used in good scientific
literature.

"A species," says Huxley, "is the smallest group to which distinct and
invariable characters can be assigned." The Standard Dictionary says
that the term is used for "a classificatory group of animals or plants
subordinate to a genus, and having members that differ among themselves
only in minor details of proportion and color, and are capable of
fertile interbreeding indefinitely."

The latter authority also adds:

"In the kingdoms of organic nature species is founded on identity of
form and structure, and specifically characterized by the power of the
individuals to produce beings like themselves, who are in turn
productive."