When we look at the matter in this light, it is very evident that there
are multitudes of long recognized specific distinctions that ought to
be discarded. For instance, there are some twenty odd "species" of wild
pigs scattered over the Old World, which Flower and Lydekker assure us
would probably "breed freely together."[16] The yak and the zebu of
India, and the bison of America, would on this basis have to be
surrendered, for it is well known that they will all breed freely with
the common domestic cattle, as well as with one another. Perhaps all or
nearly all of the dozen or more "species" of the genus _Bos_ would thus
be included together. All of the dogs, wolves, and others of the
_Canidæ_ might thus be considered as fundamentally a unit. The cats
(_Felidæ_) are well known to breed freely together, Karl Hagënbeck of
Hamburg having crossed lions and tigers as well as others of the family.
Practically all of the bears have been crossed repeatedly, and the
progeny of these and other crosses are quite familiar sights at the
London Zoölogical Gardens. Among the lower forms of life even more
surprising results have been attained by Thomas Hunt Morgan and others.
[Footnote 16: "Mammals Living and Extinct," pp. 284-285.]
It would, however, be a very hasty conclusion to say on the basis of
these facts that there are no natural limitations to groups of animals
and plants. But we are entirely warranted in concluding from these facts
that in very many cases, perhaps in most, our system of taxonomic
classification of animals and plants has gone altogether too far, and
that scientists have erected specific distinctions which are wholly
uncalled for and which confuse and obscure the main issues of the
species problem. Among the workers in botany and in every department of
zoölogy there have always been the "splitters" and the "lumpers," as
they are familiarly called; the former insisting on the most minute
distinctions between their "species," thus multiplying them; the latter
being more liberal and tending to diminish the number of species in any
given group. For a generation or more in the recent past the "splitters"
had things pretty much their own way; but of late there is a growing
tendency to frown down the mania for creating new names. Even yet it is
with the utmost reluctance that long established specific distinctions
are surrendered, as is illustrated in the case of the mammoth, which is
acknowledged by some of the very best authorities to be really
indistinguishable from the modern Asiatic elephant. Several fossil bears
were long listed in scientific books; but they are all acknowledged now
to be identical with the modern grizzly, and as we have already
intimated all the modern ones ought to be put together. These modern
rationalizing methods have made but a slight impression on the vast
complex of the fossil plants and animals, affecting the names of only a
few of the larger and better known forms. In the realm of invertebrate
palæontology, however, the "splitters" are still holding high carnival,
in spite of the efforts of some very prominent scientists in the
opposite direction. For palæontologists still follow the irrational
course of inventing a new name, specific or even generic, for a form
that happens to be found in a kind of rock widely separated as to "age"
from the other beds where similar forms are accustomed to be found. As
Angelo Heilprin expresses it, "It is practically certain that numerous
forms of life, exhibiting no distinctive characters of their own, are
constituted into distinct species _for no other reason than that they
occur in formations widely separated from those holding their nearest
kin_."[17]
As a result of these methods this same author declares: "It is by no
means improbable that many of the older _genera_, now recognized as
distinct by reason of our imperfect knowledge concerning their true
relationships, have in reality representatives living in the modern
seas."[18]
[Footnote 17: "Geographical and Geological Distribution of Animals," pp.
183, 184.]
[Footnote 18: _Id_., pp. 207, 208.]
But the situation is very little better when we come to deal with plants
and animals of our modern world. Because, with the many thousands of
students of natural science all over the world, each anxious to get into
print as the discoverer of some new form, the systematists have a dead
weight of names on their hands that by a rational and enlightened
revision could doubtless be reduced to but a fraction of their present
disheartening array. For as the result of the extensive breeding
experiments now being carried on under the study of what is called
Mendelism (a term that will be explained in the next chapter), it has
been found that great numbers of the "species" of the systematists or
classificationists will not stand the physiological test of breeding,
that is, they are found to breed freely together according to the
Mendelian Law. As William Bateson remarks:
"We may even be certain that numbers of excellent species 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 insect involved is now _Aphidius testaceipes_.
The systematist who studies only dried corpses will soon be out of
date."[22]
[Footnote 22: F.M. Webster, of the U.S. Dept. of Agriculture, in
_Science_, April 12, 1912, p. 565.]