s recognized by
entomologists or ornithologists, for example, would, if subjected to
breeding tests, be immediately proved to be _analytical varieties_,
differing from each other merely in the presence or absence of definite
factors."[19]

The following from David Starr Jordan, the leading American authority on
fishes, will serve to show how numerous have been the new names invented
in recent years, all tending further to confuse and complicate the
problem of what is a species:

"In our fresh-water fishes, each species on an average has been
described as _new_ from three to four times, on account of minor
variations, real or supposed. In Europe, where the fishes have been
studied longer and by more different men, upwards of six or eight
nominal species have been described for each one that is now considered
distinct."[20]

[Footnote 19: "Mendel's Principles of Heredity," p. 284, 1909.]

[Footnote 20: "Science Sketches," p. 99.]

And again:

"Thus the common Channel Catfish of our rivers has been described as a
new species not less than _twenty-five times_, on account of
differences real or imaginary, but comparatively trifling in value."[21]

[Footnote 21: "Science Sketches," p. 96.]

Perhaps the reader will tolerate another somewhat long quotation because
of the light which it sheds on this whole problem.

"Some years ago we had a parasite of a very destructive aphid down in
our books as _Lysiphlebus tritici_. In carrying out our investigations
it became necessary to find out whether this parasite had more than a
single host insect, and whether it could develop in more than one
species of aphid. To this end, recently emerged males and females were
allowed to pair, after which the female oviposited in several species of
aphids. Both parents were then killed and preserved and all of their
progeny not used in further experiments were also preserved, and thus
entire broods or families were kept together. In this way females were
reared out of one host species and allowed to oviposit in others, until,
often after several hosts had been employed, it would be bred back into
the species whence it first originated. In all cases the host was reared
from the moment of birth, while with the parasite both parents and
offspring were kept together.

"The result of this little fragment of work _was to send two genera and
fourteen species to the cemetery_--you may call it Mt. Synonym Cemetery,
if you choose--while the inse