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THE PALEONTOLOGICAL SOCIETY

CONFERENCE ON THE ASPECTS Of
PALEONTOLOGY

*

FIRST ANNUAL MEETING,
CAMBRIDGE, MASS., DECEMBER 29, 1909.

Reprinted from the POPULAR SCIEHCB MONTHLY, June to November, 1910.

WASHINGTON, D. C.
1910

MATTHEW
LIBRARY

THE PALEONTOLOGIC EECORD
THE PALEONTOLOGICAL SOCIETY CONFERENCE PAPERS

BY PROKESSOB JOHN M. CLARKE

STATE MUSEUM, ALBANY, N. Y.

Introductory. — The birth of a new society devoted to special scien-
tific aims counts but little for the advancement of knowledge and cul-
ture in these days of multiplex organizations if it fails to come into
being and before the world with an adequate excuse and a clean-cut
purpose. The Paleontological Society, which was conceived a year
ago and born last winter in Boston at the meetings of the American
Association, is the outcome of a conviction on the part of workers in
this science that there is a common bond of interest among them all,
in spite of the peculiar conditions which have stamped paleontology
with their diversity and kept its devotees asunder. Students of this
science have approached it along different avenues. Some, and chiefly
those dealing with the vertebrates, have laid the foundations of their
work in the living world; others, and here chiefly the students of
invertebrates, have made their entry as geologists and have worked
their way from beneath upward to the earth's surface. Among the
paleobotanists good men have arrived through both approaches. As
an equipment for trustworthy and lasting work, both of these lines of
preparation have proved their efficiency and so all arguments bent to
demonstrate the superiority of the one over the other schooling resolve
themselves to a conclusion that both are essential to the best result.

Diversity in training and in the field of activity has led to diversity
of sympathy, and it seemed, even to those who had long hoped for a
unification of these interests, that it might hardly be practicable to
obliterate these cleavage planes. The governing principles of the sci-
ence are common, the bearings of paleontologic researches and results
are the widest conceivable in their relation to the problems of life,
whether past, present or future, and it is not likely that the magnitude
of the science can be unduly stated. From some such considerations as
these, the writer, chosen as first president of the new society, endeavored
to bring into the foreground of the society's first meeting, by a " Con-
ference on the Aspects of Paleontology," an introductory presentment
of some of the broader factors and principles of the science, and the
articles that follow herewith are the partial outcome of this conference.
In every case where practicable, the themes were presented by two

763058

2 THE PALEONTOLOGIC RECORD

sneakers making their approach from different fields of interest. The
an effort to define and emphasize the common platform

^ ... on. which the 'paleontologists must stand together; even more than this,
•*i /*: it-'wfti otyitrp'ose to declare at the outset that the organization, though

the patron of detailed researches and patient endeavor, recognizes that
the sole impulse which can guarantee its usefulness and maintain its
integrity is its devotion to a standard which touches close on human
interests.

ADEQUACY OF THE PALEONTOLOGIC RECORD

BY PROFESSOR SAMUEL CALVIN

UNIVERSITY OF IOWA

WHEN or how life began on our planet no one may be able to
tell us; but that life has been present and has been an impor-
tant factor in the world's geological development since before the be-
ginning of the Cambrian is known to the most callow of embryo geol-
ogists taking his first course at the village high school. So far as
relates to the skeleton-bearing, marine invertebrates which have lived
on floors of epicontinental seas, there are remarkably complete records
of this long history of living things, the order of their succession, their
migrations, their geographic distribution during any given portion of
geologic time, as well as of the progressive and orderly modifications
which resulted in the extermination of decadent or unfit types, on the
one hand, or resulted, on the other hand, in the advancement of certain
types and their adaptation to the conditions prevailing in the living
world to-day.

The zoologist, confining attention to living forms, gets a view of the
animal creation as it exists, after ages of development and modification,
during a fraction of a single faunal stage. The paleontologist, while
unable to see the beginnings of life, gets the broader view which comes
from a study of the organic world as it has appeared during numberless
successive stages. He may trace the origin of forms and note the trend
and tendency of variations in ways denied the zoologist. Neither the
depth of the water nor the distance from the shore at the points where
the objects of his study lived interferes with the thoroughness of his
explorations. He is not limited to what he may learn by taking
samples of the old sea bottom, here and there, with a dredge; he
traces his life zones with practical continuity over areas of continental
extent.

The faithfulness with which the paleontological record has been
kept since the beginning of the Cambrian is a matter of constant sur-
prise. No organism was too small for preservation, if only its soft

THE PALEONTOLOGIC RECORD 3

parts were supported or protected by a stony skeleton of some kind;
no parts of the skeletal structure were too minute to be kept practically
unaltered to the smallest microscopic detail; no period of time has
been so long that the records of the large or the small things of life
were necessarily obliterated. The shells of such minute and delicate
things as radiolaria and foraminifera, on the one han'd, and that king
of invertebrates, the giant Camaroceras, on the other, have all been
kept through the ages with equal fidelity. The hinge characters of
the brachiopods, their internal arm supports, their spires and loops, the
distribution of the ramifying bloocl channels in the mantle, the surface
markings of every rank and grade down to the smallest which can be
observed only with the lens, and the microscopic structure of the shell
itself, are other examples of the faithfulness with which details, how-
ever insignificant in point of magnitude, have been guarded, protected,
preserved. Strangely enough, in respect to a very large proportion of
the animal remains buried in the ancient sediments it looks as if time
had been standing still; it has neither marred nor destroyed. The
organic remains from the Ordovician formations are quite as perfectly
preserved as those from the Tertiary.

The profusion of the life of the ancient seas is as much a source of
surprise as the detailed perfection of the record. In the Mississippi
Valley limestones constitute a very large proportion of the sedimentary
rocks, and it is unnecessary to say that these limestones record the life
and death of countless myriads of organisms. In some cases the waters
of the old seas were comparatively quiet, and the shells or other hard
parts, undisturbed and unbroken, remain in the positions they occu-
pied when the individuals they represent were alive. There is a bed
of marly shale carrying many thin lenses of limestone, lying between
the Platteville and the Galena, from 60 to 70 feet above the base of
the Mohawkian, and these lenses are made up in large part of un-
broken brachiopod shells. On the surface of one of these slabs, in an
area measuring 35 square inches, one may count more than 60 perfect
specimens of Dalmanella subcequata and Orthis tricenaria. The rate
is about 290 individuals to the square foot. The number on a square
mile of such sea bottom runs up into the billions. The number of
individuals of the species Pentamerus ollongus that swarmed on the
bottom of the Niagaran sea is strikingly demonstrated in every paleon-
tological museum. The wide geographic range of this species is well
known; its range in time was such as to make possible the accumula-
tion of beds of limestone, 70 feet in thickness, from the detritus of
its broken shells. Like other persistent or widely ranging species, it
gave rise to a very large number of varietal forms, some of which have
been described as specifically distinct.

The Devonian formations furnish similar evidence of the wonder-

4 THE PALEONTOLOGIC RECORD

ful profusion of the ancient life and help us to appreciate the wealth
of material that the paleontologist has at his command. In the quarries
at Independence, Iowa, there are beds crowded with beautifully pre-
served forms, mostly brachiopods, as perfect to-day in every detail of
shell structure and ornamentation as when the currents of life pul-
sated within. A coral reef, no species lost, has been cut into by a small
intermittent stream near Littleton, Iowa; and perfect coralla, wagon
loads of them, are strewn along the sandy channel a quarter of a mile
or more. A successor to the reef just noted, composed of different
species, the corals still in place, may be seen and studied on the west
side of the river opposite the village of Littleton. The state quarry
beds near North Liberty are simply cemented masses of brachiopods;
they illustrate the remarkable prodigality of the Devonian life, but the
individuals are not in good condition for study. It is a different case
that is presented by the fossils in the marly beds of the Lime Creek
shales at the exposures between Mason City and Eockford. A very
large proportion of the specimens here are as perfect as when the
animals lived; and there is a beauty and delicacy and exquisite refine-
ment about most of them that is scarcely matched, certainly not sur-
passed, anywhere among fossils of any age or time. More than 65
species occur in the Lime Creek fauna, and thousands of individuals
of some of the species, illustrating wide ranges of variation, enrich the
museums of the world.

Along the Aux Sables River at many points near Thedford and
Arkona, Ontario, there are calcareous shales containing a marine fauna,
or rather a succession of faunas which once flourished in wonderful
profusion and is still preserved in equally wonderful perfection. Sta-
tistics and computations would fail to give an adequate conception
of the abundance and character of the material here offered for study.
No detail of the skeletal parts has been lost ; and as for the number of
individuals, they are simply uncountable. There lies before me a
small fragment of this old sediment having a surface of less than 15
square inches and it shows 51 identifiable individual specimens, not
counting stem segments of crinoids. The 51 individuals are distrib-
uted among eleven species, and these represent eleven genera — namely,
Phacops, Platyceras, Tentaculites., Spirifer, CTionetes, Hederella,
Ortliopora, Chcetetes, Arthracantha,, Striatopora and Aulopora. Can
any bit of modern sea bottom of similar size make a better showing?
Above and below the Rocky Glen, near Arkona, from which this speci-
men came, there are opportunities to study continuous sections ap-
proximately 100 feet in thickness, the successive beds crowded with
organic remains and revealing the historic sequence of varying organic
types as the life responded to slight changes of environment. Here,
as at countless other localities, the paleontologist gets a view of

THE PALEONTOLOGIC RECORD 5

changes, of movements, of trend and tendency among living things
ranging over a period of time equal to many millenniums.

Another life record of especial interest, typical of many scattered
up and down the land areas of the globe, is furnished by the Osage
division of the Mississippian at Burlington and Keokuk. Of one group
of crinoids, the Camerata, these Mississippian limestones have yielded
about 250 species, and of other groups a number about equally as great.
The beauty and perfection of the individual specimens can be ap-
preciated only by those who have had the good fortune to see the superb
collections of Wachsmuth and Springer. Crinoids flourished here in
such numbers that beds of limestone 150 feet in thickness are built
practically of crinoidal remains and nothing else. The time repre-
sented was long enough to allow of a series of modifications of such ex-
tent that the crinoid fauna of the Upper Burlington is very distinct
from that of the lower beds of the same formation, while the fauna of
the Keokuk differs from both. Here again the paleontologist is
favored, not only with a wealth of material, but with an opportunity to
note the trend and tendency of things. This was the time of greatest
development, of highest prosperity, among camerate crinoids. But in
the midst of this prosperity the trained paleontologist may discover
signs of degeneration, the prophecy of speedy extinction. The law
enunciated by Beecher and quoted by Professor Woodward in his ad-
dress before the geological section of the British Association at its
meeting in Winnipeg last summer, is well exemplified in the Missis-
sippian history of this particular group of crinoids. The tendency
among any division of skeletal-bearing animals to run to extravagant
ornamentation in the way of ribs, nodes, spines or other excesses of
dead, useless, skeletal matter, is something that precedes and presages
the decline and death of the race. Even in the Upper Burlington the
skeleton of the crinoids is heavier than in the Lower; stronger nodes
on the plates are produced; more arm plates are incorporated in the
dorsal cup; the animals are weighted down with useless matter. This
tendency is carried to extremes in the Keokuk limestone, a fact well
exemplified by the species figured on plate 15 of Hall's " Geology of
Iowa," Volume I., part II. In these species the development of
massive spines and heavy nodose plates reaches its maximum. The
race has come to the end of its career. When the Keokuk closes, only a
few of the simpler forms of the Camerata survive, and even these
shortly disappear. The paleontologist sees the operation of the same
law, the same trend and tendency, among the Cretaceous Ammonoids;
in many other groups of animals it is as clearly manifest ; but it would
not be profitable, before such a body as this, to carry the discussion
farther, even if the limits of the paper permitted. Let me close by

6 THE PALEONTOLOGIC RECORD

quoting from the address of Professor Woodward, to which reference
has already been made :

Geology and paleontology in the past have furnished some of the grandest
contributions to our knowledge of the world of life; they have revealed hidden
meanings which no study of the existing world could even suggest; and they
have started lines of inquiry which the student of living plants and animals
alone would scarcely have suspected to be profitable.

ADEQUACY OF THE PALEONTOLOGIC KECOED

BY R. S. BASSLER

U. S. NATIONAL MUSEUM

THE imperfection or inadequacy, instead of the adequacy of the
paleontologic record, has long been a favorite subject of discus-
sion, and it is only within recent years that this heresy of an imperfect
record is being abandoned by paleontologists in general. However, as
many of our biologic, and even a few of our paleontologic, friends still
have doubts regarding the matter, the present conference upon this and
allied subjects is very opportune.

I have a vivid recollection of the joy experienced in my school days,
when, during an examination in geology, the subject of an impromptu
essay was announced as "The Imperfection of the Paleontologic
Kecord." Here was a subject in which I was well grounded from text-
book reading, and I remember distinctly the telling points made. The
lack of hard parts causing the absence of many classes of animals ; the
great amount of unrepresented time in the geologic column; the meta-
morphism and consequent disappearance of fossils, and, when present,
the frequent imperfectness of the specimens themselves, were dwelt on
in great detail. Since that time, my experience in invertebrate paleon-
tology has compelled me to unlearn every one of these supposed facts,
and to come to the conclusion that, considered both biologically and
stratigraphically, the paleontologic record is sufficiently adequate for
all reasonable purposes.

Professor Calvin's paper tells us (1) of the detailed perfection of
the record, (2) of the profusion of the material, and (3) of the broad
view as to trend and tendency of biologic characters which the study
of paleontology gives. His presentation of the subject is such that we
must all agree with him. It therefore seems best for me to confine my
remarks to the reasons usually advocated for the imperfection, namely,
the lack of hard parts in many animals, metamorphism, the frequent
imperfect preservation of fossils, and the unrepresented time in the
geologic column.

The lack of hard parts in many animals is a serious, although not
fatal, objection to their preservation as fossils. For the best results as

THE PALEONTOLOGIC RECORD 7

fossils, a stony framework of some kind is desirable, as we all know,
but horny, or even the most perishable materials may be preserved under
favorable conditions. Mr. Walcott's work on the Medusas, and the
researches of Euedemann on the graptolites, as well as the work of
others whom we can call to mind, are examples of excellent results from
material of the latter nature, not to mention the hairs of the worm so
carefully described by the Cincinnati paleontologist!

The metamorphism and apparently complete obliteration of all
fossil remains in the rocks of certain large areas is likewise an appar-
ently serious objection to the adequacy of the record, but here careful
searching with the structural relations in mind will reveal the fossils,
if present at all. The greatly folded and cleaved slates, schists and
volcanic tuffs of the Piedmont area have long been the despair of both
paleontologist and geologist, but at this meeting of the Geological
Society of America, the State Geologist of Virginia will tell of Cin-
cinnatian fossils in the so-called Algonkian and other schists and vol-
canics of the easternmost Piedmont of that state. In this case the dis-
covery of well-preserved fossils was quite simple. It consisted merely
in finding a place where the cleavage and stratification coincided, and
then working hard.

Professor Calvin has spoken of the richness and beautiful preserva-
tion of certain Paleozoic faunas. While the beauty and occasional
richness of such faunas is not to be gainsaid, we must not forget the
many horizons and localities affording, in comparison, specimens so
poorly preserved that they might readily furnish an argument for the
inadequacy of the record. Nor must we forget that in quite a portion
of the geologic column organic remains are not only poorly preserved,
but are, as known at present, very rare. However, these lean spots can
be made most productive of paleontologic results by careful search and
by methods of preparation. Several years ago the number of lower
Paleozoic fossils found in the Ozarks could almost be counted on one's
fingers, but we now have in the National Museum, from this formerly
almost barren spot, several hundred drawers of beautiful material.

Fortunately the preparation and methods of study of paleontologic
material has progressed to such a point that a poor fossil is no longer a
bugbear. A specimen may be considered inadequate for study because
it is covered with refractory clay. The application of caustic potash
solves this difficulty. Certain limestone bands in the New York
Niagaran and Cayugan are crowded with fossils, although often few of
the species can be determined because of a hard, clayey covering. In
preparing some specimens for exhibition, the treatment with caustic of
a single slab, about three inches wide and five inches long, enabled me
to bring out over a hundred species on one surface alone, not including
the ostracods and other microscopic organisms. How often will the
present sea bottom furnish such results?

8 THE PALEONTOLOGIC RECORD

Nature is very kind in preparing fossils for us. The Onondaga
limestone, at the Falls of the Ohio, although only a few feet in thick-
ness, has yielded seven hundred or more species of exquisitely preserved
fossils. Examine the freshly quarried limestone and you may be able
to crack out perhaps two dozen species of poorly preserved material,
but go to the neighboring field where solution of the limestone and
silicification of its contained fossils has occurred, and a host of beautiful
forms awaits you. Strata, which under ordinary circumstances would
yield very poor fossils, can, if silicification has commenced, be made to
afford excellent specimens. By exposure to the weather for a year or
so, the silicification can be advanced to such a stage that etching with
acid will free the fossils. The beautiful etched material from the
New Scotland of New York is a familiar example of this style of
preparatory work. Most of the Cambrian and Ordovician formations
of the Appalachian Valley yield shells which, as they occur in the lime-
stone, are almost impossible as subjects for study, but as silicified
pseudomorphs, all the beauty and detail of the original shell are
reproduced.

Thin sections are a valuable aid in identifying the merest fragment
of certain classes of organisms, and their use here is indispensable.
A thin section of an otherwise undeterminable fragment of a Cambrian
protremate brachiopod will distinguish the horizon. Other methods of
preparation and study might be mentioned, but time forbids, although
I can not refrain from speaking of the several whitening processes.
The use of a coating of ammonium chloride or anilin chloride on fossils
for photographic purposes is well known, but the excellent results
obtained from the use of the same process in the study of poor material
may not be so apparent to all. A trilobite indistinctly outlined in the
rock under ordinary circumstances, flashes into bold relief when covered
with the ivory white film of ammonium chloride. Casts and molds of
fossils too indistinct to show any structure ordinarily, will reveal many
characters when so whitened. Recently occasion arose to study a
species of Cambrian phyllopod which had already been described and
figured. The specimen was practically nothing but a film upon the
rock, and apparently the last word had been said upon it. It was sug-
gested that the specimen be whitened and then photographed with the
sun's rays nearly parallel to its surface. The result was most gratifying
as structures which could not be proved to exist by the aid of the eye
alone, came into plain view in the negative. All these various methods
of preparation and study make available a vast amount of material
which formerly was thought too imperfect to be fully considered in
determining the adequacy of the record, hence the great value of such
methods to the paleontologist is obvious.

The real adequacy of the record, if it might be so called, lies in the

THE PALEONTOLOGIC RECORD 9

imperfections or gaps in the stratigraphic column. Measured accord-
ing to the sections of twenty-five years ago, the number of these gaps is
growing greater and greater, yet with the discovery and intercalation
of new formations, the aggregate of which at the present day has almost
doubled the thickness of Paleozoic rocks in the last decade, manifestly
the great breaks are being reduced. It was not so many years ago that
the Potsdam sandstone was supposed to be the oldest fossiliferous sedi-
mentary rock, yet now we know that many thousands of feet of much
more highly fossiliferous strata intervene between this formation and
the Azoic, and that other thousands occur above the Potsdam and
below the Ordovician as then recognized.

With the intercalation of new formations and the consequent
diminution in the size of the stratigraphic gaps, it is then probably
only a matter of time before the complete faunal succession can be
established. The break in stratigraphy at one point will be bridged
over in another area, and it is possible that in only a few regions, such
as on the borders of the continent, will permanent gaps exist. Faunas
are and will be traced from one area to another until in time we shall
know their complete geologic history. With these data in hand, the
study of their correlation will not only be greatly simplified, but also
will not be hampered by time breaks in the record. While imperfect,
or possibly irretrievably lost at the dawn, the faunas of succeeding times
are ample for all purposes.

INTEKDEPENDENCE OF STEATIGEAPHY AND
PALEONTOLOGY

BY DB. W. J. SINCLAIR

PRINCETON UNIVERSITY

IN discussing this subject from the view-point of a vertebrate paleon-
tologist, I am disposed to lay stress on what I believe ought to be,
rather than what has been, the degree of interdependence of these two
branches of geology. Vertebrate paleontology has been studied very
largely from the morphological and genealogical side, a study of struc-
ture, adaptation and the evolution of phyla. Stratigraphic geology has
been invoked only when it became necessary to know the order of super-
position of the various horizons, to determine the true evolutionary
succession of a phylum or development of an adaptation.

I have purposely presented this extreme view, not because I believe
that such studies may not be classed legitimately as paleontological, but
because I wish to emphasize, by contrast, the view-point which we
should ever keep before us as paleontologists — the use of our materials
as Leitfossilien. The two correlative conceptions of the faunal unit
and the zone, a more or less restricted association of animals and the

io THE PALEONTOLOGIC RECORD

rock layer in which it occurs and which it characterizes, long and suc-
cessfully employed by the invertebrate paleontologist, must be recog-
nized and used by us also.

I need hardly refer to the fact that the determination of the geolog-
ical age and the successful correlation of many North American forma-
tions, ranging from Mesozoic to Pleistocene, depend in large measure, if
not entirely, on vertebrate fossils. I need only contrast the American
series of Pleistocene glacial and interglacial stages, determinable at
present only by the strictly stratigraphic method of superposition, with
the carefully worked-out series in Europe, where each epoch of ice
advance and retreat is characterized by its particular fauna and flora.
That even the beginnings of stratigraphic paleontology, as contrasted
with the morphological, will lead to immediate and valuable results, is
strikingly shown by Professor Calvin's1 recent paper in the Bulletin
of our parent society, the Geological Society, in which he describes the
Aftonian mammal fauna from the earliest of American interglacial

While readily admitting that the slow-moving invertebrate, living,
it may be, in the very mud which is destined to become the matrix of
its fossil remains, enjoys advantages as a prospective horizon-deter-
miner which the agile vertebrate can more readily, and does most will-
ingly, escape, still the short life of vertebrate species, and their com-
paratively rapid evolution, fit them for use as index fossils quite
admirably. The localization of mammalian faunas, their inability to
cross barriers such as ocean basins and great mountain ranges, their
dependence on temperature, etc., are comparable to similar conditions
circumscribing the free migration of invertebrates. We should not
expect to find in the distribution of vertebrate faunas the analogues of
the cosmopolitan graptolite zones of the Ordovician or the ammonite
zones of the Trias, but we can work out our major zones as recognized
by the great migrational movements among vertebrates, expressed in
changes in the faunas and the rock succession, which will give us a
world scale, and then, by interpolation, fill in the minor and local sub-
divisions which we probably shall not be able to correlate at once, but
which there is every reason to believe we may be able to do later.

The attempt will be accompanied by difficulties which are not appre-
ciated by the invertebrate paleontologist, and I speak feelingly and from
experience, for there is a difference between collecting, on the one hand,
from a layer a few inches thick, crowded with shells, and, on the other,
tramping miles up hill and down over beds hundreds of feet thick, to
be rewarded by a few teeth, a lot of useless bone fragments or nothing.
Horizons based on vertebrates must include larger stratigraphic units

1 Bulletin of the Geological Society of America, Vol. 20, pp. 341-356, Pis.
16-27, October, 1909.

THE PALEONTOLOGIC RECORD n

than are recognized for invertebrates, because of the scattered nature of
the material and the additional probability that continental deposits, in
which alone vertebrates have their chief importance as guide fossils,
have accumulated more rapidly than marine beds. Similarly, condi-
tions peculiar to their mode of deposition make it difficult, perhaps
impossible, to define lithologically the limits of the zones we are at-
tempting to characterize. And here another trouble confronts us, for
the faunas are incompletely known, and we are not yet in a position to
dogmatize too freely on the subject of vertebrate index fossils. But
that the method of zonal studies is the correct one is very clearly shown
in Dr. Matthew's2 recent monograph on the Carnivora and Insectivora
of the Bridger Eocene, and will be demonstrated with equal force when
Professor Osborn's volume on the titanotheres is published.

Various attempts have been made at the correlation of European
and American mammal horizons, their measure of success depending
entirely on the degree of closeness with which these correspond to
true zones. At present, we are attempting to correlate subdivisions,
both faunal and stratigraphic, of all orders of magnitude, the majority
including many faunules and many zones. Evidently, this tendency
must be corrected by careful zonal studies, if vertebrate paleontology
is to have any standing as an aid to stratigraphy in the correlation of
our non-marine formations.

BIOLOGIC PRINCIPLES OF P ALE 0 GEOGRAPHY

BY PBOFESSOR CHARLES SCHUCHERT

YALE UNIVERSITY

IN" deciphering the ancient geography as to the position of the marine
waters and the land masses, we as pioneers in this work must be
controlled primarily by the known fossilized life and secondarily by
the character and place of deposition of the geologic formations. This
record is most extensive and best preserved in the deposits of the con-
tinental and the littoral region along the continental shelves of the
oceanic areas. Back of these two principles, however, there is another
that eventually will become the primary guiding factor. It is the prin-
ciple of diastrophism — one seeking to explain the causes for the
periodic movements of the lithosphere.

In our study of the ancient seas with their sediments and entombed
life we have safe guidance in the phenomena of the present. Ludwig
in 1886 estimated the species of animals then known to naturalists as
upwards of 312,000, and in 1905 Stiles thought this great total had
increased to about 470,000 forms. Of this sum fully 60 per cent, are
insects, and of the remainder, the writer concludes that about 25 per
a Memoirs American Museum of Natural History, Vol. IX., Part VI., 1909.

12 THE PALEONTOLOGIC RECORD

cent., or 115,000 species, live in the sea, and 71,000 have their habitat
on the land or in the waters of the land. Of the 115,000 kinds of
known animals inhabiting the seas nearly 70 per cent, are Ccelenterata,
Echinodermata, Molluscoidea and Mollusca, the types of organisms
most often found by the stratigrapher and on which he is largely de-
pendent in deciphering the ancient geography.

Let us now examine into the number of available fossil forms made
known by the paleontologists. As early as 1868, Bigsby in his
"Thesaurus Siluricus " listed 8,897 species from the strata beneath
the Devonic, and in his " Thesaurus Devonico-Carbouiferous " of
1878, he further enumerated about 5,600 Devonic and 8,700 Carbonic
forms. In 1889 Neumayr concluded that there were then known about
10,000 Jurassic species. We may therefore estimate that the paleontol-
ogists of to-day have access to at least 100,000 species of fossils. Their
numbers in the geologic scale are about as follows: Cambric 2,000,
Ordovicic 8,000, Siluric 8,000, Devonic 9,000, Lower Carbonic 7,000,
Upper Carbonic 8,000, Permic 4,000, Triassic 6,000, Jurassic 15,000,
Cretacic 10,000 and Tertiary 25,000. The end of species-making is
not at all in sight, and the day will come when paleontologists will deal
with ten times as many species as are now known.

Stiles tells us that zoologists know but from 10 to 20 per cent, of
the living forms, and there should therefore be from 3,760,000 to
4,700,000 different kinds of animals alive to-day, ranging from the
protozoa to man. Now let us compare the abundance of living ani-
mals with those of the geologic ages, and especially with the Jurassic
period, of which life we have probably a better knowledge than of any
time back of the Tertiary. The European Jurassic has long been
divided into 33 zones (Buckman hints at a probable 100), and if we
hold that each one of these times had only one quarter as many species
as in the lowest estimate of the present world, there must have lived
during the entire Jurassic something like 31,000,000 kinds of animals.
Yet paleontologists have described not more than 15,000 Jurassic
forms. The great imperfection of the extinct life record is thus forcibly
brought to our attention, and we learn from these estimates that for
each krnd of animal preserved in the rocks more than 2,000 other kinds
are utterly blotted out of the geologic record.

Much of this more apparent than real imperfection, however, is
due to the vast number of insect species now living — animals that must
have been comparatively few in the Jurassic, due in the main to the
absence of flowering plants. From these figures, however, we must not
conclude that the geologic record is equally imperfect throughout; for
the paleontologist studying marine fossils well knows that he can not,
as a rule, hope to study other than those kinds of animals that have
hard and calcareous or siliceous external or internal skeletons. Of

THE PALEONTOLOGIC RECORD 13

such there may be in the present seas about 250,000 kinds, of which
about 25,000 have been named. Therefore on this basis we can say
that the student of Jurassic faunas knows 1 species in every 54 of
shelled animals that lived during this period.

This admittedly great imperfection of the life record needs to be
further explained so that the reader will not arrive at the erroneous
conclusion that modern stratigraphy rests upon very insecure founda-
tions. The stratigrapher in determining the age of a given deposit,
and in the identification of it from place to place and from country to
country, and even across the great oceans, deals in his work not with
quantity of species, but with comparatively small numbers of con-
stantly recurring hard parts of certain species that are more often of
marine than of land origin. Many of these forms have but local value
but others have spread thousands of miles, and some of the long en-
during species range over the greater part of the earth. Some of the
best guide fossils in the Paleozoic are the brachiopods because they
are present in nearly all the strata of this era. The writer in 1897
listed 1,859 forms then known from these rocks of North America.
Of these about 28 per cent., or 537 species, had great geographic dis-
tribution. 117 species are found in the Rocky Mountain area, the
Mississippi valley and the Appalachian region, and of these 36 are also
known to occur in foreign countries. The number of species common
to North America and other continents, however, is 121. It is upon
faunal assemblages of this quantity and nature that the stratigrapher
relies most in deciphering the former extent of the continental seas.

In the making of paleogeographic maps or in the determination of
geologic time, using fossils as the essential basis, we have guidance in
those of marine faunas, and the floras and faunas of the land and its
fresh waters. Of these widely differing realms or habitats we now
know that the fossils of the marine faunas are the more reliable not
only because there are so many more of them than of the land dwellers,
but more especially because their geologic succession is far more com-
plete. The conditions of preservation, that is, appropriate burial in
sediments, are always at hand in marine waters, but on the land en-
tombment occurs only exceptionally, whereas the life of fresh waters
is very meager and almost unchanging during geologic time. Then,
too, marine life is "less affected by meteorologic factors, and more
dependent upon conditions which affect the whole hydrosphere rather
than small areas of it. The struggle for life is less intense, the food
supply generally more adequate, enemies less vigorous, and dangerous
fluctuations of temperature far less frequent, in the sea than on land.
The same features make the land fauna more clearly indicative of
minor divisions of the scale, and of the progress of organic evolution

i4 THE PALEONTOLOGIC RECORD

in the general region concerned; while less conclusive as to the con-
temporaneity of widely separated though analogous faunas."1

In regard to the probable geographic position of the shore lines we
rarely have safe guidance in the fossils, and for this depend on the
nature of the deposits. Greatest dependence is placed upon the geo-
graphic position of sandstones and especially on conglomerates to indi-
cate the probable former shores. Limestones of uniform character
and wide distribution are indicative of greater distance from land.
Shallowness of the continental seas is proved by a rapid change in
the character of the sediments both laterally and vertically, and by
the oolite and dolomite deposits. Intraformational conglomerates,
coral reefs, ripple marks, and shrinkage cracking furnish further evi-
dence to the same conclusion. Storm waves are known to plough the
present sea-bottom to depths of 160 feet. Calcareous muds are now
forming in tropical and subtropical waters at sea-level around coral
reefs, and elsewhere in these latitudes at depths from 200 to 600
meters. It is probable that all of the ancient great limestone deposits
are of warm waters, and, if so, are an additional aid in discerning the
geologic times and regions of milder climates.

Phosphatic concretions form in the littoral region where the tem-
perature changes are rapid, as off the coast of the New England states,
and periodically cause much destruction of the individual life. The
carcasses decompose at the bottom of the sea, making nuclei for the
accretion of phosphate of lime, and because of the irregular periodicity
of accumulation come to be arranged in definite stratigraphic zones.
Old Eed sandstone fishes are also usually found in clay nodules but
abundantly only in limited zones (Scaumenac, Canada and Wildungen,
Germany). Have these also been killed by rapid changes in the tem-
perature of these waters ? In any event the fish-bearing beds are always
found near the shore lines of Devonic seas.

Scour of sea bottom is met with in the present seas where great
streams of water are forced through narrow passages, as the Gulf
Stream in the Meridian area; or where such streams impinge against
the continental shelf, as north of Cape Hatteras, or flow across sub-
merged barriers " a few miles broad," as the Wyville-Thomson ridge
connecting the British and Faeroese plateaus (Johnstone, 1908, 31).
Strong currents preventing sedimentation also occur in long and narrow
bays, as that of Fundy, where the undertow caused by the very high
tides of this region sweeps the bottom clean. These exceptional and,
after all is said, rather local occurrences can not be the explanation for
the many known breaks in the geological sedimentary record, the dis-
conformities of stratigraphers. These breaks are at times as extensive
as the North American continent (post Utica break), and are usually

1 Ball, Jour. GeoL, 1909, 494.

THE PALEONTOLOGIC RECORD 15

of very wide extent. Scour of the bottom by the currents of the an-
cient continental seas will not explain away the presence of these truly
land times, but it is to be sought in the oscillatory nature of the seas
of all time which is probably caused by the periodic unrest of the
earth's crust due to earth shrinkage. We agree with Suess that " Every
grain of sand which sinks to the bottom of the sea expels, to however
trifling a degree, the ocean from its bed," and every movement of the
sea-bottoms and the periodic down fracturing of the horsts causes the
strand lines to tremble in and out, be they of a positive or transgres-
sive or of a negative or land-making character.

The ancient marine life had similar zoogeographic arrangement to
that of the present. It can be grouped into local faunas and these
combined into subprovinces, provinces and realms. Their distribution
is governed primarily by the presence or absence of land barriers, and
secondarily by temperature and latitude. In the present seas tempera-
ture is one of the main factors controlling the distribution of the
species, but during the geologic ages the climate was, as a rule, far more
uniform than now, as we are living under the influence of polar ice
caps and a passing glacial period, or possibly even an Interglacial
period.

The faunas with which the stratigraphic paleontologist works appear
in many instances as suddenly introduced biotas. Our collaborators
of half a century ago explained them as Special Creations, but since
their time we have learned that the suddenly appearing faunas are not
such in reality but only seem to appear rather quickly due to the slow-
ness of sedimentary accumulation. Ulrich estimates that the American
Paleozoic has less than 100 mapable units or formations, each with a
duration of probably not less than 175,000 years. Accordingly, each
foot of average sedimentary rock has taken not less than 833 years to
accumulate. Our knowledge regarding the average rate of sedimentary
marine accumulation is, however, as yet very insecure, and to make
this clear some of the remarks made by Sollas, President of the Geo-
logical Society of London (1910), will be quoted. He was led to make
these remarks after the reading of a paper by Buckman correlating
the Jurassic sections of South Dorset. He said, " The correlation of
thin seams with thick deposits was a matter of great importance. . . .
It might afford some hints as to the order of magnitude of the scale of
time. If we assumed that one foot of sediment might accumulate in
a century, in an area of maximum deposition, then in the case of the
seam two inches thick, which was represented by 250 feet in the Cottes-
wolds, the rate of formation would be less probably than 1 foot in
150,000 years." What Ulrich's estimate of time necessary for the
accumulation of one foot of average sediment means to migratory faunas
may be illustrated by the spreading of Littorina littorea. In the last

THE PALEONTOLOGIC RECORD

century this edible European gastropod was introduced at Halifax,
Nova Scotia, and in 50 years attained the Delaware Bay and north to
Labrador. Taking this dispersion as the basis for calculating f aunal mi-
grations, we learn that they may spread 500 miles, while one sixteenth
of an inch of average sediment is depositing, or 8,000 miles during
the time of one foot of sedimentary accumulation. If, therefore, Paleo-
zoic faunas migrated " only one fiftieth as fast as this living shell, then
we may reasonably assert essential contemporaneity for stratigraphic
correlations extending entirely across the continent." We have here
an explanation for the apparently sudden distribution of the Ordovicic
brachipod Rhynchotrema capax, that everywhere holds an identical
geologic horizon from Anticosti to the Big Horns and from El Paso,
Texas, to Arctic Alaska. Spirifer hungerfordi spreads during the first
half of Upper Devonic time from the Urals to Iowa, and another
brachiopod, String ocephalus burtoni, migrates during the last third of
Middle Devonic time from western Europe to Manitoba.

The life of the present seas extends from the strand-line to the
deepest abj^ss, but by|£ar the greatest quantity and variety lives in the
upper sunlight, photic or diaphanous region. Photographically the
light of the sun is detectable in exceptionally clear-water tropical seas
to a depth of about 2,000 feet, but Johnstone places the average depth
for all waters at 650 feet, beyond which there is more or less of total
darkness, the aphotic realm.

Sunlight is the first essential for the existence of life. Where it
penetrates, there plant life is possible, and this life is the substratum
on which all animal life is ultimately dependent for food. Near the
surface of the sea lives the plankton, sometimes referred to as the
"pastures of the sea" and compared with the "grass of the fields."
Most of this plankton consists of diatoms that at present are by far
more prolific in the cooler polar waters. At times of greatest abun-
dance in Kiel Bay as many as 200 of these " jewels of the plant world "
are contained in a drop of water, and in the Antarctic seas there is
an area of ten and one half million square miles where diatom ooze is
accumulating. They are the principal food supply for most of the ses-
sile benthos, or bottom life, among which the mollusca and brachiopods
are of the greatest importance in paleogeography.

Geologic deposits rich in diatoms are sometimes regarded as those
of the deep sea, at least as of deeper waters than those of continental
seas. The English Carbonic deposits, rich in diatoms, have a fauna
whose species are all of the shallow water kinds. The vast Miocene
diatom deposits of California, described by Arnold, have living bottom
types of foraminifera that, according to Bagg, do not indicate a depth
of over 500 fathoms.

From the present distribution of marine life we learn that the

THE PALEONTOLOGIC RECORD 17

greatest bulk of invertebrates are restricted to the bottom of the shal-
low seas within the depth to which sunlight readily penetrates, that is,
a depth on the average not over 600 feet. The value of this observa-
tion to the paleogeographer and the student of fossil marine life lies
in the confirmation of paleontologists that continental seas are shallow
seas, to the bottom of which in most places sunlight permeates. These
seas are to be compared with the littoral regions of the present oceans,
and they are the areas that are most exposed to climatic and physical
changes, due to their proximity to the atmosphere and the lands. The
life of these waters is, therefore, subject to an environment that is
more or less changeable, and one of the basic causes underlying or-
ganic change. It is the invertebrates of the littoral and shallow seas
that the paleontologist studies.

In the tropical and subtropical shallow seas one meets with the
greatest variety of life and with the brighter colored and more orna-
mental shelled animals, but we are much surprised when told that the
greatest number of individuals occur in the colder shallow waters of
the temperate and polar regions. Johnstone states, "There is little
doubt that the distribution of life in the sea is exactly opposite to that
on the land. The greatest fisheries are those of the temperate and
arctic seas. . . . Nowhere are sea birds so numerous as in polar
waters. The benthic fauna and flora are also most luxuriant." The
Bay of Naples has a " richly varied, but (in mass) a scanty fauna and
flora," and " at the very least the amount of life in polar seas is not
less than in the tropics."2

Marine life is also more prolific near river mouths of the tem-
perate zones, probably because of the great quantities of dissolved
" salts of nitrous and nitric acid and ammonia, and other substances
which are the ultimate food-stuffs of the plankton." Just outside of
the estuary of the Mersey in Lancashire there were "not less than
twenty, and not more than two hundred animals varying in size from an
amphipod (one fourth inch long) to a plaice (eight to ten inches long)
on every square meter of bottom" (Johnstone, 1909: 149, 176, 195-6).
Finally the quantity of life in the shallow waters of the sea is not
directly governed by favorable habitat, such as shallow sunlight waters
in constant circulation and of equable temperature, but seems to be
primarily controlled by the amount of the minimal food elements.
Sea-water may be regarded as a dilute food-solution having the essen-
tial materials on which life is dependent. Of these nitrogen and the
compounds of silica and phosphoric acid are present in the smallest
amount. Johnstone tells us that " The density of the marine plants
will therefore fluctuate according to the proportions of these indispen-
sable food-stuffs" (234). "It is only the protophyta among the

'"Life in the Sea," 1908, 201-205.

1 8 THE PALEONTOLOGIC RECORD

plankton which can utilize the C02 and the nitric acid compounds,
and so we see that upon these rest the greater part of the task of
elaborating the dissolved food-stuff of the sea" (239).

Undoubtedly much of the land-derived nitrogen, estimated at 38
million tons per annum, is used up in the shallow areas by the plants.
We therefore arrive at the conclusion that shallow seas bordering
naked, cold, or arid lands should have the smallest amount of life,
and that those of temperate regions adjacent to low lands under pluvial
climates should have the greatest number of individuals. This con-
clusion, however, may be decidedly altered by the oceanic currents in
that they distribute far and wide the salts of the sea.

These factors also suggest that during " critical periods " the
faunas should be least abundant and varied, and that at the times of
extreme base levels and sea transgressions they ought to be at their
maximum development. These suggestions are borne out by the small
Cambric, Permic and earliest Eocene faunas and the large cosmopolitan
biotas of the Siluric, Jurassic and Oligocene times.

Sessile algae are not common on muddy or sandy grounds, and these
areas in the present seas have been compared with the desert areas of
the lands. That muddy grounds are now nearly devoid of algous
growth has particular significance in stratigraphy, because in the geo-
logic column at many levels and in nearly, all regions occur black shale
formations that are not only devoid of plant fragments but are also
usually very poor in fossils of the sessile benthos. When the latter are
present it is seen that they are usually thin-shelled and small forms,
or are types of organisms that live in the upper sunlight realm and
are either of the swimming plankton or the floating nekton. As ex-
amples of such deposits may be cited the widely distributed Utica for-
mation of the Ordovicic extending from southern Ohio -to Lake Huron
and east to Montreal, and the Genesee (Devonic) of New York. In
these cases what appears to be of the sessile benthos is thought to be-
long to the nekton attached to floating seaweeds or other floating ob-
jects, and eventually all of the life of the nekton and the plankton
sinks to the bottom of the sea. Therefore the carbonaceous matter of
the black shales may be of algous origin like that of the New York
Genesee, but it is far more probable that it is largely of animal origin,
as the crude petroleum of such deposits usually has the optical proper-
ties of animal oil and especially those of fish oil.3 Plants may be torn
from rocky bottoms of the shallow areas by the action of the storms and
then carried by the currents into eddying areas like the present Sar-
gossa Sea, which has among its algae a very characteristic assemblage
of animals. It is probable, however, that black shales having wide dis-
tribution were more often the deposits in closed arms of the sea (cul

'Dalton, Economic Geology, 1909, 627.

THE PALEONTOLOGIC RECORD 19

de sacs), or when of small areal extent, as the result of fillings of holes
in the sea bottom. In all such places there is defective circulation and
lack of oxygen resulting in foul asphixiating bottoms.

These are the " halistas " of Walther and the " dead grounds " of
Johnstone. To-day such are the Black Sea and the Bay of Kiel, where
sulphur bacteria abound in greatest profusion. These decompose the
dead organisms that rain from the photic region into such suffocating
areas, or the carcasses which are drawn there by the slow undertow from
the higher ground. These bacteria in the transforming process deposit
in their cells sulphur that ultimately combines with the iron that is pres-
ent and replaces the calcareous skeletons of invertebrates by iron pyrite
or marcasite. In this way are formed the wonderfully interesting
pseudomorphs of Triarthrus becki, the Utica trilobite preserving the
entire ventral limbs, and of the other well preserved but small inverte-
brates from the Coal Measures black shale of Danville, Illinois.

Brackish-water and especially deep-sea shelled animals tend to have
thin shells, while increase of salinity tends towards the thickening and
roughening of the calcareous shells. It is a well known fact that in the
dolomite-depositing continental seas like that of the Guelph (Siluric).
all of the molluscs have ponderous thick shells. These have been in-
terpreted as reef-living species but actual reefs in the Guelph are un-
known. The molluscs are often common but corals are represented by
but a few species. Similar conditions are known to occur in other
dolomite faunas. Further, the Guelph was of a time of decided progres-
sive emergence and restrictional seas under an arid climate, and there-
fore the waters must have been abnormally salty.

Rivers constantly discharge into the sea great quantities of plant
material, but as a rule little of it other than the wood is swept far out
to sea. At present the rivers of northern Siberia float into the sea
vast numbers of logs that drift with the currents to Spitzbergen, East
and West Greenland and Arctic America. This wide dispersal of
wood by the sea is met with only in the cold regions, whereas in trop-
ical waters the wood is rapidly decomposed. Single leaves are rarely
transported far from their place of origin, and when of good preserva-
tion in geologic deposits, give decisive evidence of the nearness of the
shore. On the other hand, tough palm leaves have been seen in the
sea 70 miles from land and rafts of leaves are often met with 200 or
more miles beyond the mouths of the Kongo and the Amazon. Prox-
imity to shore is also indicated by the presence in marine faunas of
land molluscs, insects and bones of land vertebrates.

With tillites now known in the Lower Huronian of Canada, in the
Lower Cambric of northern Norway, China, South Africa and Aus-
tralia, and in the Permic of India, South Africa, Australia and Brazil,
we observe the recurrence of glacial climates. The Siluric and Devonic

20 THE PALEONTOLOGIC RECORD

coral reefs occurring in Arctic regions, the sponge, coral and bryozoa
reefs in the Jurassic of northern Europe, the rudistid and other
cemented pelecypods in reefs of wide distribution in the Cretaceous,
and the almost world- wide distribution of the Nummulitidae (north of
Siberia) in the late Eocene and Oligocene point as clearly to warm
waters and mild polar climates. Further the widely distributed Car-
bonic foraminifers of the family Fusulinidae that swarmed in temper-
ate and tropical regions are unknown to Arctic and Antarctic regions.
In other words, long before we have a fossil record the earth had cli-
matic zones, and for long periods the climate was mild to warm,
punctuated by shorter intervals of cold to mild climates.

The volume of sea water to-day is very great, but we must ask our-
selves: Has this quantity always been such or was it even greater, as
some geologists still hold? We no longer agree with Laplace and
Dana that the earth passed through an astral stage, but rather agree
with Chamberlin that it always has had a more or less cold exterior.
Through volcanic activity much juvenile water from the interior of the
earth was extruded in geologic time and was added to the vadose waters
of the surface. Suess states that " the body of the earth has given forth
its oceans and is in the middle phase of its gas liberations." Accord-
ingly, the Paleozoic oceans must have been quantitatively smaller than
those of the present, and the gradual increase in the volume of vadose
waters has been accommodated by the periodic increase of oceanic
depth.

We also agree with Walther that the oceans of Paleozoic and earlier
time did not have the great abyssal depths they now have. The ac-
centuated deepening of the permanent oceanic basins did not begin
until the Triassic, for in none of the great depths of the present oceans
are found traces of Paleozoic organisms, and all here are of Mesozoic
or Tertiary origin. In the shallow regions, however, are still found
a few Paleozoic testaceous-bearing genera of brachiopods, tubicular
annelids, pelecypods, gastropods, Nautilus, and Limulus. The deepen-
ing of the Pacific, the Indian, and especially the Atlantic oceans has
been at the expense of the lands or horsts, for the ancient continents,
Gondwana and Laurentia, have each towards the close of the Mesozoic
been broken into several masses. We may therefore speak of permanent
oceans, and transgressed, fractured, and partially down faulted, con-
tinents or horsts.

These are some of the factors that control the making of some of
the modern paleogeographic maps.

THE PALEONTOLOGIC RECORD 21

BIOLO.GIC PRINCIPLES OP P ALE 0 GEOGRAPHY

BY DE. F. H. KNOWLTON

U. S. GEOLOGICAL SUBVEY

/CONSIDERING the breadth and intricacy of the subject assigned
^^ me, and the limited time that can be given to its consideration,
it has seemed best to me to restrict my remarks to two or three of the
obviously more important phases of the problem.

Aside from the study of the rock-masses themselves — which are
often difficult of interpretation — relianceifor an interpretation of paleo-
geography must be placed in the former life found entombed, and of
the two biologic elements, plants undoubtedly hold a very high — prob-
ably the highest — place.

In making use of plants in the study of paleogeography we may
first consider distribution. If we find two fossil floras identical or
similar in all essential or important details, we feel justified in re-
garding them for all practical geologic purposes as contemporaneous.
In order that we may be certain that the two floras are identical, they
must be composed of types that are readily identifiable, that is, forms
so well characterized that they may be easily and certainly recognized.
As examples of such floral elements mention may be made of many
ferns and fern allies, most cycads, conifers and peculiar, well-marked
or characteristic dicotyledons. Having settled the contemporaneity of
the floras, inquiry may next be made as to the probable manner in
which the separated or isolated areas were reached by these floras.
Here again we must carefully consider the character of the flora and
the means for its natural dispersal. The living flora, and for that
matter probably the floras from at least the beginning of the Tertiary
progressively to the present time, has developed in many ways means
for the comparatively rapid and wide-spread dissemination of their
reproductive parts (seeds, etc.). For example, a large percentage of
the members of the dominant living family of seed-plants — the Com-
posite— have developed seeds with an attachment of soft, fluffy hairs
which serve to float them in the air, often to great distances. In many
other living groups there are similar, or at least as effective, devices
for dissemination, but as we go back in time adaptations calculated to
be of aid in distribution grow less and less, and soon even seeds of any
kind are unknown, or known but imperfectly, and reproduction is
normally by means of spores, that is, reproductive bodies in which there
is no embryo already formed when they leave the parent plant. It is
obvious that plants that are reproduced by seeds, in which there is
both an embryo and a supply of food for use during germination, must
possess a decided advantage over those reproduced by means of spores.

22 THE PALEONTOLOGIC RECORD

In the groups of spore-bearing plants ordinarily found fossil, the
spores are not known to have developed any particular devices for their
wide dissemination, such as flotation in air, attachment to animals, etc.
They are produced in vast quantities, and depend upon a few reach-
ing situations favorable for successful germination. Their vitality is
also of apparently exceedingly limited duration, and it is doubtful if
they could long survive immersion in salt water.

The bearing of the above digression is apparent. Given a fossil
flora made up of ferns or fern allies, exclusive of what are known to
belong to the cycadofilices, and when such flora is found in two or more
separated areas, we are justified, in my opinion, in arguing a practically
continuous land connection. They were incapable of crossing very wide
reaches of open water, particularly salt water. Fresh-water streams
have been to some extent avenues of distribution, but many fossil
floras — and living floras as well — are too widely spread to be explained
by this means. "When, as is usually the case, identical floras occupying
different areas are mixed floras, the bearing on the means of reaching
the various areas is more complicated. An example may better serve
to bring this out. Thus, the Jurassic flora is practically world-wide
in its distribution, ranging from Franz Josef Land, 82° N"., to Louis
Philippe Land, 63° S. It is composed of ferns, fern-allies, cycads and
conifers, a large percentage being true ferns. The probability of a
close land connection argued on the basis of the true ferns, has already
been alluded to. The cycads — the Jurassic is called the age of cycads
— were abundant in individuals and numerous in forms. On the basis
of our knowledge of living types, it may be stated that cycad seeds
germinate immediately on falling from the cone without any necessary
resting period. They are not known to retain their vitality for a
longer period than three years, and usually but two years. They sink
promptly in fresh water and as the stony coat is easily penetrated by
water, they either germinate or rot at once. In salt water they will
probably sink and decay even more quickly. Therefore, the probability
of their being transported for any great distance over open water is
reduced to a minimum. The conifers of the Jurassic were reproduced
by seeds. They belong to types not known to enjoy any special means
for transportation, nor is it probable they could better withstand fresh-
or salt-water immersion than the cycads. All classes of vegetation
present in the Jurassic, therefore, argue for a practically continuous
land connection.

In considering the bearing of any flora on the paleogeographic
problem the process is similar to that outlined above. That is, an
analysis of the composition of the flora, a study of the means of nat-
ural dissemination which includes duration of vitality, and finally a
judgment as to its probable means or avenues of transportation, in-
volving a land connection or otherwise.

THE PALEONTOLOGIC RECORD 23

A word may be said as to the presence of land plants in marine de-
posits. That the trunks of trees may float for a considerable time and
to great distances is undeniably possible, but unfortunately the study
of fossil wood has not yet reached that degree of refinement in most
cases that will permit of its general use, and reliance in identification
must be placed largely in foliar and reproductive organs. The delicate
fronds of ferns, leaf-clad branchlets of conifers and the leaves of seed-
bearing plants are incapable of long withstanding the immersion and
wave action of salt waters. In my judgment, therefore, the presence
of fronds, leaves and similar organs in marine deposits argues very
near-by land.

The only other point I shall consider is the bearing of plants on the
interpretation of climate. Since it is generally acknowledged that
plants furnish the most reliable data for this phase of the subject, an
inquiry as to the kinds of plants that have been found most valuable
in this connection may be of interest. Obviously our interpretation of
the probable conditions under which the plants of past geological ages
grew, must be on a basis of a knowledge of present conditions found
to obtain for similar or closely related groups. That we may occasion-
ally err in this is possible, especially if reliance is based on too few
forms, but when all the various elements of a flora are considered, the
results are thought to be within a close approximation of the truth.
Thus, since Artocarpus — the bread-fruit tree — only grows at the pres-
ent day within 20° of the equator, it follows that when Artocarpus is
found fossil in Greenland, 72° N., the conditions at the time it
flourished there must have been tropical or subtropical, and this con-
clusion is confirmed by the tree ferns and cycads associated with it.
Palms can not flourish with a temperature below 40°; a fossil flora,
rich in palms of well-defined types, could hardly have grown under
very much cooler conditions. Tree-ferns are practically confined to
within 30° of the equator and a temperature of approximately 60°. A
fossil flora, such, for example, as the Triassic of Virginia, that contains
numbers of tree-ferns, must have grown under tropical or subtropical
conditions. A fossil flora rich in types, the living representatives of
which can withstand a temperature of — 40° to — 60°, or even lower,
must have been at least cool-temperate. Cycads are now found only
within 30° of the tropics; a rich cycad flora argues then for a tropical
or at least a subtropical climate.

Examples of this kind could be multiplied almost indefinitely. In
interpreting geological climate selection is made so far as possible of
the plants or groups of plants, that are confined at the present day
within relatively narrow limits of temperature, be this high, medium
or low.

24 THE PALEONTOLOGIC RECORD

PALEONTOLOGIC EVIDENCES OF CLIMATE

BY T. W. STANTON

U. S. GEOLOGICAL SURVEY

nnO every one climate is an interesting theme. The climates of the
-L past, especially when they can be shown to differ in character
or distribution from those of the present, attract the attention of the
general public, and they are of importance to the special student of
geologic history whether his researches deal with the purely physical
aspects of the subject or include some branch of paleontologic study.

The evidence as to former climates comes from many sources. The
records of deposition and denudation in themselves sometimes give
more or less definite indications concerning variations in temperature
or moisture or both; the land floras when compared with those now
living by their general characters and by the details of their structure,
show more or less clearly the climatic conditions under which they
lived ; the land animals, especially the higher vertebrates, afford a good
basis for inferring their habits and hence indirectly their environment,
including climate; marine invertebrates give trustworthy evidence of
differences in temperature of oceanic littoral waters at least in the later
periods. It is obvious, however that the data furnished by any one of
these lines of evidence will make only unconnected fragments of the
history of past climates and that the evidence on the climate of any
particular epoch, if derived from a single source, is seldom so complete
or so convincing that corroborative testimony from other sources is not
desirable. The subject is one in which general cooperation is essential.

It should be stated at the outset that the most abundant and most
definite evidence comes from paleobotany, and will be outlined in Mr.
White's paper. The discussion of the data derived from fossil verte-
brates must also be left for some one who is qualified to present it, and
the whole Paleozoic era may be passed over with the statement that so
far as indications from the animal life are concerned the climate of
the whole earth was mild and equable. The proof of local exceptions
to this statement comes from other sources.

All inferences from paleontologic evidence as to former climatic
conditions rest in the final analysis on a comparison with the present
distribution of animals and plants with reference to climate. Such
comparisons may be general or specific, direct or indirect, and the con-

THE PALEONTOLOGIC RECORD 25

elusions that may be drawn from them vary greatly in positiveness.
To take a familiar example, the reef-building corals are now restricted
to shallow waters in which the mean temperature during the coldest
month in the year is not less than 68° F., and such conditions are not
found in the northern hemisphere north of latitude 32°. Since late
Tertiajy corals differ but little from those of the present time it is
justifiable to assume that coral reefs in late Tertiary rocks indicate
waters of about the temperature stated. But when Jurassic coral reefs
are found as far north as latitude 53° it is by no means so certain that
they indicate a minimum monthly mean temperature of 68° F., and
concerning Devonian and Silurian coral reefs in high latitudes the
doubt must be still greater. At the present time large reptiles are
mainly confined to hot moist climates, but that fact alone can not be
considered proof that the Mesozoic dinosaurs required the same kind
of a climate.

The impress of climate on the present fauna is shown in various
ways. A tropical fauna contains the greatest number of species and
exhibits its luxuriance in other ways. Thus, taking shell-bearing
marine mollusks to illustrate the general law, Dall has shown in Bul-
letin 84, U. S. Geological Survey, that the average tropical fauna in
shallow waters consists of over 600 species, while the temperate fauna
has less than 500 species, and the boreal fauna only 250. Again, there
are certain genera that are characteristic of particular zones, and as-
semblages of forms that are recognized as belonging only to frigid, or
temperate, or tropical waters, and in genera that have a wide range
many of the species are restricted to certain limits of temperature.

In the late Tertiary faunas which contain a large proportion of
living genera and many living species justifiable inferences as to climate
may be made from direct comparison with living faunas. By one or
another of the tests just indicated, or by a combination of them, Dall
has produced convincing evidence that the Oligocene fauna of the
Atlantic states was subtropical and that the Oligocene maintains its
subtropical character even as far north as Arctic Siberia. He has also
shown that the Miocene fauna of Maryland indicates a temperate
climate and that a similar cool-water fauna extended at that time as
far south as Florida.1 The fossils of the raised Pliocene beaches at
Nome, Alaska, according to the same investigator, furnish evidence of
warmer climate during Pliocene time even at that high latitude. By
similar methods, in a paper published in the Journal of Geology, Vol.
XVII., Arnold has recently argued for a series of climatic changes in
the late Tertiary and Pleistocene of California.

When the investigation is carried back to the Mesozoic and earlier

1 See especially Dall's " Contributions to the Tertiary Fauna of Florida,"
published as Vol. III. of the Transactions of the Wagner Free Institute of
Science, Philadelphia, and a chapter in the Miocene volume of the Maryland
Geological Survey.

26 THE PALEONTOLOGIC RECORD

faunas in which few of the genera and none of the species are identical
with those now living the problem becomes more difficult and the con-
clusions are much less definite, as the comparisons must be more gen-
eral. Proofs of actual temperatures as measured in degrees should not
be expected unless the botanists can furnish data. There is, however,
great local differentiation of faunas and it is fair to ask the question
to what extent this is due to differences in climate. One of the earliest
discussions of this question was by Ferdinand Roemer, who more than
fifty years ago in " Die Kreidebildungen von Texas " noted the fact
that the Cretaceous of the highlands in Texas is lithologically and
faunally much like the Cretaceous of southern Europe and the Medi-
terranean region, that it differs from the Cretaceous of New Jersey in
about the same way that the southern European Cretaceous differs from
that of England and northwestern Germany, and that in each case the
European deposit is approximately 10° farther north than its American
analogue. He concluded that the differences between the northern and
southern facies were due to climate and that the climatic relations be-
tween the two sides of the Atlantic were about the same in Cretaceous
time as they are now. Roemer's conclusion that there were climatic
zones in the Cretaceous may be true, but his reasoning was based on
false premises so far as the American deposits are concerned, for the
New Jersey type of marine Cretaceous extends with little change all
the way from New Jersey to the Rio Grande, and the " Cretaceous of
the highlands " with which he contrasted it, now known as the
Comanche series, is not represented by marine beds on the Atlantic
coast. This shows the necessity for careful stratigraphic and areal
work as well as for good paleontology before such broad conclusions
can be safely made.

The more general work of Neumayr2 recognized in the Jurassic
and Cretaceous of Europe three fauna! provinces designated as boreal,
central European, and alpine or equatorial, which on account of their
zonal distribution he regarded as indicating climatic differences. He
believed that these zones are recognizable throughout the northern
hemisphere and cited evidence to show that similar zones exist south of
the equator. In recent years Neumayr's conclusions have been ques-
tioned by many because in so many instances genera supposed to be
characteristic of one zone have been found mingled with those of
another. For example, the alpine ammonite genera Lytoceras and
Phylloceras occur in Alaska (lat. 60°) associated with the boreal
Aucella, and Aucella itself ranges from the Arctic Ocean to the torrid
zone. Still, in spite of such exceptions and anomalies in distribution,
there is much evidence for a real distinction between boreal and south-
ern faunas in the Jurassic and in the Cretaceous which may indicate
a zonal distribution of temperature in Mesozoic time. It should be

2 " Erdgeschichte," Vol. II., p. 330 et seq.

THE PALEONTOLOGIC RECORD 27

remembered, however, that a boreal climate probably did not then mean
a frigid climate,, and that the differences in temperature were probably
not so great as at the present time.

The conclusions justified by the evidence from fossil invertebrates
are:

1. In the Paleozoic there is practically no faunal evidence of cli-
matic zones comparable with those that now exist.

2. In the Mesozoic there is a more or less definite zonal distribution
of faunas which may be in part due to differences in climate but this
conclusion in each case should be checked by the study of the floras and
all other available lines of evidence.

3. From the middle of the Tertiary on through the Pleistocene trust-
worthy conclusions as to climatic conditions and changes can be made
by direct comparisons with the distribution of living faunas.

THE MIGRATION AND SHIFTING OF DEVONIAN FAUNAS

BY PKOFESSOR HENRY S. WILLIAMS

CORNELL UNIVERSITY

IN the year 1881 I presented before the American Association for
the Advancement of Science the first definite announcement of
the theory of recurrent faunas, applying it to the fauna of the Mar-
cellus, Genesee and Ithaca black shales of New York, which I then
conceived to be represented by the continuous fauna of the black shales
of Ohio, Indiana, Kentucky and Tennessee ; and also in the same paper
the theory of shifting of faunas was applied to the Hamilton and Che-
mung faunas of central New York.1 Since that time a large amount of
evidence has been accumulated confirming these hypotheses.

The two hypotheses are correlated. Recurrence, or the departure of
a fauna, its replacement by another and its final reappearance in the
same section at a higher level, become the facts upon which the hypoth-
esis of shifting of the faunas is based; and only on the assumption of
the continuance and shifting of a fauna without losing its character-
istics can we satisfactorily explain its recurrence.

The following facts are among the more important which have come
to light in the course of my studies :

§ 1. The Catskill sedimentation was shown to be thicker and to start
lower down in the geological column in eastern New York than in
middle and western New York. In eastern New York it began while
the Hamilton marine fauna was still present and cut it off, bringing in
estuarian conditions with a brackish water and land fauna and flora.
In middle New York no Catskill sedimentation is present until after

1 Proo. American Association for the Advancement of Science, Vol. XXX.,
p. 186, etc.

28 THE PALEONTOLOGIC RECORD

the arrival of the Chemung fauna ; and in western New York no trace
of the Catskill type of sediments appears till after the close of the
Devonian.

These facts are direct evidence of shifting of the environmental
conditions of the edge of the continent westward as the deposits of the
middle and upper Devonian were being laid down. With this shifting
westward of the off-shore conditions of the sea, there went on a corre-
sponding shifting of several faunas that were adjusted to each phase of
those conditions.

These facts were stated in a paper on the classification of the upper
Devonian published in 1885. 2

§ 2. The Appearance of Dominant Species of a General Fauna in
Reversed Order of Succession at the Close of a Fossiliferous Zone. —
The case of Spirifer Icevis in the Ithaca Zone and of the frequent ap-
pearance of Leiorhynchus at the opening and close of a fossiliferous
zone were among the earliest observed facts suggesting the actual shift-
ing of the body of the fauna entering the area in one order of succession
and its departure in the reverse order. In the Ithaca section there
occurs at the base of the fossiliferous zone of the Ithaca member a bed
containing abundance of Spirifer (Reticularia) Icevis. The discovery
of the same species at the top of the fossiliferous zone as the normal
Ithaca fauna become sparse gave the first suggestion that the faunas
were moving or shifting. The Eeticularia zone marked the first trace
of the fauna to enter and the last to leave the area. Confirmatory evi-
dence was also found in the order of succession of the dominant species
of the Ithaca fauna. These facts were reported in 1883.3

§ 3. The study of the mode of occurrence of Leiorhynchus still fur-
ther drew attention to the definite order in which series of species came
in and went out of any given area. The species of the genus were
generally found abundantly at the base or at the top of the fossiliferous
zones rich in the brachiopods in the midst of which Leiorhynchus was
rare.4

§ 4. The reappearance in a single or few strata of several represen-
tatives of an earlier fauna long after the formation to which they were
normal had ceased.

Slight traces of this fact were observed in the first survey of the
Devonian section passing through Ithaca, reported in 1883, Bull. 3,
U. S. G. S., and the fauna No. 14 N (p. 15) was called a recurrent
Hamilton fauna because of the appearance there of such species as
Spirifer fimbriatus, S. augustus, Pleurotomaria capillaria and others;

2Proc. American Association for tJie Advancement of Science, XXXIV.,
p. 222.

8 Bull. 3, U. S. G. S., p. 20, and 1885 Proc. A. A. A. 8., Vol. XXXIV., p.
222, etc.

4 See Bull. 3, U. S. G. S., pp. 16 and 17, 1883.

THE PALEONTOLOGIC RECORD 29

and higher up in the midst of the Chemung section at Chemung nar-
rows Tropidoleptus carinatus and Cypricardella bellistriata, Phacops
bufo and Dalmanites calliteles were found.

The discovery of such traces of an earlier fauna led to further
search; and as the evidence accumulated an elaboration and definite
formufotion of the theory of recurrence of faunas was made which has
been set forth in several papers, and is illustrated in detail in the folio
of the Watkins Glen-Catatonk quadrangles, which is now in press, for
the U. S. Geological Survey (December, 1909).

The facts there brought out are substantially as follows : There are
exhibited in the sections mapped for the quadrangles two series of fos-
siliferous zones; the separate zones of the two series alternate in suc-
cession; the zones of one series dominate the western sections of the
area and thus thin out or disappear on tracing them eastward ; the zones
of the second series dominate the eastern sections and particularly the
whole eastern New York sections, but thin out westward and in some
cases are entirely wanting in sections west of the Watkins Glen quad-
rangle. The first set of faunal zones includes the faunas of the Gene-
see shale, the Portage formation and the several divisions of the
Chemung formation.

The second set of zones includes the Hamilton fauna proper and
recurrent representatives of that fauna which I have named the Para-
cyclas lirata zone, the Spirifer mesistrialis zone, the LeiorJiynchus
globuliformis or Kattel Hill zone. These zones are represented by the
typical Ithaca group of Hall in its typical sections at Ithaca ; and above
them appear the first, second and third recurrent Tropidoleptus faunas
(which I originally named the Van Etten, the Owego and the Swart-
wood Tropidoleptus zones, respectively). All of these several fossilifer-
ous zones of the second set become decidedly thin on passing westward
across the region. The Ithaca fauna is, occasionally, detected west of
the Watkins Glen quadrangle, but is confined to less than 100 feet thick-
ness at Watkins, is recognized for three hundred feet at Ithaca and
ranges through at least 600 feet along Tioughnioga Eiver.

Only a slight trace of the Paracyclas zone is seen as far west as
Ithaca, but it is well expressed in the section on the east side of the
area. The Van Etten, Owego and Swartwood Tropidoleptus zones
appear in thin tongues of strata as far west as the Waverly quadrangle
and are seen in occasional traces as far west as the Elmira quadrangle.
When followed eastward they appear to blend together as a modified
Hamilton fauna sparsely appearing in the strata up to the income of
the Catskill type of sedimentation.

Where the Hamilton recurrent zones are seen in sharpest expression
the recurrent species range through only a foot or a few feet of strata,
hold in abundance four or five characteristic Hamilton species such as

30 THE PALEONTOLOGIC RECORD

Tropidoleptus carinatus, Cypricardella ~bellistriata, Rhipidomella van-
uxemi, Spirifer marcyi and Delthyris mesacostalis (=D. consobrinus)
and others; and the Owego and Swartwood zones appear in the midst
of a characteristic Chemung fauna both above and below them. In the
Owego recurrent zone both Phacops rana and Dalmanites calliteles
occur.

The Van Etten recurrent zone lies entirely below the range of
Spirifer disjunctus and associated species of the Chemung formation.
On following the sections eastward from the Waverly quadrangle the
species of the Chemung fauna become scarce, and east of the Chenango
Eiver very few species of the typical Chemung fauna have been detected
— although they are still abundant in the Chemung rocks to the south-
east and southward across Pennsylvania, Maryland and Virginia.

§ 5. These facts have been interpreted as evidence not only of a
general shifting of faunas coincident with a rising of the land along
the eastern edge of the present continent, but of oscillation of condi-
tions and alternate occupation of the area by two sets of faunas coming
from opposite directions and temporarily living in abundance in the
area of central New York.

§ 6. The lithologic changes in the sediments containing the different
faunas are not sufficient to account for the change in fauna. In quite
a number of sections there is no appreciable difference in lithologic
constitution between the strata which for a hundred feet thickness
have been filled with characteristic Chemung species and the imme-
diately following thin zone (of a foot or two) with scarcely a trace of
the Chemung species, but holding, in great number, species which if
found by themselves would be undisputed evidence of the Hamilton
formation.

§ 7. It becomes necessary therefore to suppose that the controlling
cause determining the presence of one or other fauna is not the char-
acter of the bottom on which the sediments which preserved the fauna
were laid. We are thus led to conclude that the qualities of the ocean
water have determined the shifting or migration of the faunas. The
conditions to which the faunas were adjusted were evidently those of
depth, salinity or temperature of the waters in which the species lived ;
and their change of habitation was occasioned by change in the direc-
tion, path or extent of flow of oceanic currents.

This leads us to consider the principles of migration as affecting
marine organisms.

§ 8. Migration of Species and Shifting of Faunas. — Migration as
commonly applied in natural history means the movement of large
numbers of the same species from one place to another in a general
definite direction at more or less regular periodic times. So birds mi-
grate northward with the advance of warm weather; some fish migrate

THE PALEONTOLOGIC RECORD ~ 31

from sea up rivers in breeding seasons; pigeons fly eastward or west-
ward in great flocks, or grasshoppers invade a rich country devouring
the vegetation in their path, or lemmings migrate across country in
great quantities.

The term in these cases has to do with movements of one kind of
animal in relation to the comparatively stable range of feeding-ground
for the remainder of the fauna inhabiting the areas concerned. The
term is rarely if ever applied to the slower movement of the whole body
of animals of a fauna, coincident with great changes of climate, such
as the advance of the glacial cover over the northern parts of Europe
or America produced during the glacial age, or the advance of an
Asiatic fauna across the Bering Straits and down the west coast of
North America at some Pleistocene time when an ice bridge furnished
means of communication by land from one continent to the other.
Perhaps there is no impropriety in extending the application of the
term migration to these latter cases in which the whole fauna and
flora of a region is affected instead of single or a few species; and in
which the change of position of habitat is slow and spread over a great
period of time instead of being coincident with annual change of sea-
sons. The term may equally well be applied to movements in the
seas and movements on the lands.

There is, however, one reason for choosing a separate name for the
movements of the latter kind to distinguish their, from typical migra-
tions.

In the first class of cases the migration is voluntary and is per-
formed by those organisms which have the power of more or less rapid
locomotion. They may be said to do* the migrating themselves. In
the second case the movements are ./ involuntary and the movement is
forced upon all the living organises of the region and the change in
position may be supposed to take place by the contracting on one side
of the area of the conditions of possible existence for the species and
the extension on the other side c>f favorable conditions of environment.
The movements extend over marjy generations of life so that relatively
sedentary species may gradually -adjust their locus hdbitans to a given
direction of migration. To this letter process of migration I have been
accustomed to apply the term " shifting of faunas."

Migration of species is an expression of the ability of some organ-
isms to appreciate slight changes o^ favorable conditions of environ-
ment and to take advantage of the letter conditions during the life-
time of an individual. Shifting of faunas is an expression of the
necessity for the perpetuation of the rac a of certain conditions of en-
vironment and the dying out of the w'hole fauna in the areas from
which the favorable conditions are remo ved with corresponding spread
of the fauna into new areas into whichi the favorable conditions have
been shifted.

32 THE PALEONTOLOGIC RECORD

Shifting of faunas is an expression of the inability of the species
of the fauna to survive under the changed conditions of environment
which have overwhelmed them in the original habitat; but of an abil-
ity on the part of all those which migrate to follow the favorable con-
ditions as they shift from one area to another.

In both typical migration of species and shifting of faunas change
in the environmental conditions of life constitute the stimulus to change
of habitat on the part of the organisms; and the movement of the or-
ganisms is a direct response to the stimulus — those organisms in the
first case which migrate showing their greater vitality compared with
their neighbors who stay at home; while those who stay at home show
a greater power of endurance and organic adjustment to wider range
of environmental conditions.

In the case of the shifting faunas those which endure without
change of characters exhibit an acquired closeness of adjustment to
some particular combination of environmental conditions which they
are forced to follow or die and suffer annihilation. The evidence of
their endurance is indicated by return and reoccupation of the same
area at a later geological stage when by their reappearance, the orig-
inal condition of environment may be assumed to have recurred.

In the case of living organisms evidence of migration is found in
the actual presence of the species at one time in a region at a consider-
able distance from its ordinary locus hdbitans; and in some cases by see-
ing the species in the process of migration, as for instance the temporary
alighting in fatigued condition of flocks of northern land birds on
Bermuda Island on their migration southward.

In the case of fossil species the shifting of a fauna is expressed by
the presence of a number of species representing an earlier fauna in a
stratum in the midst of rocks containing a different and dominantly
later set of species.

The fauna is then said to recur and it is the recurrence of the
fauna which forms the basis for the inference that the fauna has
shifted its locus liabitans during the period of time represented by the
sedimentary deposits separating the formation in which the fauna is
dominant from the zone in the higher formation in which the recur-
rent species are found.

This theory of the shifting of place and the recurrence in time of
the same fauna involves certain conceptions as to the nature of species
and the laws of evolution which it is important to consider.

§ 9. Evidence of Continuity. — To establish evidence of motion in
migration as in any other kind of motion it is all important to know
that the body or bodies to which the motion is ascribed is continuously
the same.

In the Devonian case I have been studying the moving body is a

THE PALEONTOLOGIC RECORD 33

fauna; not only have I found it necessary to establish identity of the
species in the recurrent zones with those of the initial zones, but it is
essential to show that the faunas as a whole are the same.

To put this in another form of statement we must establish the fact
that not only the individual species have retained their specific char-
acters, but the further fact that the equilibrium of adjustment to each
other in the faunal community has not been changed, in order to prove
that the recurrent fauna is the direct successor of a fauna represented
in the rocks at a lower horizon.

This has led to such distinction as rare and dominant species of the
fauna, and only as some such comparative frequency of the species in
the faunal combination is apparent can we be sure that we are not
considering an accidentally accumulated sample of a general fauna.

The presence of occasional associated species belonging to the
normal fauna of the formation in which the recurrent zone appears is
not antagonistic to the theory, because the theory proposes' an invading
of the territory occupied by the normal fauna, and whatever were the
causes which brought about the shifting of the fauna they were not
so completely different as to annihilate all evidence of the fauna previ-
ously occupying the ground. Hence it is only necessary to find an
abrupt change of the grand majority of species to make the induction
that the faunas have shifted their habitat.

The theory involves the further conception of grand general faunas
which have their center of habitat and distribution in permanent
oceanic basins, as distinguished from the special and (in geological
strata) temporarily expressed faunas such as we are accustomed to as-
sociate with individual geologic formations.

In the case before us two such general faunas are in evidence, one
of which in its dominant characteristics is traced westward into Iowa,
Idaho and Arizona and up the Mackenzie Eiver valley to the north and
across the polar regions to Russia and northern Europe. The other
is traced eastward and southward into central and southern Europe
and also dominantly into South America.

Although, with our present knowledge, it is not possible to deter-
mine in any temporary expression of marine faunas those particular
species which were derived from one from those derived from the other
grand source, it is possible to recognize numerous species which belong
to one center of distribution and others that belong normally to the
other.

§10. Interpretation of the Facts. — It is also important to keep our
heads clear in interpreting the facts.

It is only by close examination and comparison of the fossils them-
selves that identity of species or identity of faunas can be established.

The fixed characters of species are not only the characters by which

34 THE PALEONTOLOGIC RECORD

one species is distinguished from another, but they are of generic,
ordinal and even class value, and they may be of immense age in the
race and mark no special, narrow stage of its history.

It is a question of interpretation whether each particular phase of
expression of fluctuating characters is a matter of time or of environ-
ment.

I have reached the conclusion that it is those species which have
the greater degree of normal and persistent fluctuation of character
which migrate and follow the shifting conditions of environment, and
their life period is correspondingly longer.

On the other hand species whose plasticity of characters is narrow,
are more closely adjusted to their environment, are local in their range
of habitat, and temporary in their geological life-period.

Interpreting the facts on this basis it is the phases of continuously
fluctuating characters in species of wide geographic distribution and
long geologic range which furnish the most satisfactory evidence of
temporary stages in the life history of faunas.

Another question of interpretation arises when we attempt to re-
construct the physical condition of the environment at successive
stages of time.

In a single vertical section we have positive evidence of succession
in time. If we were sure that no recurrence of the same fauna could
take place we could correlate two vertical sections strictly upon the
fauna contained in the strata, on the basis of the supposition that the
single fauna appeared but once in the section and that when it ceased
in a given section its whole life period was expressed. But the facts
show us that this is not the case in nature. In geological times as in
the present, we know that many distinct faunas are living on the face
of the earth at the same- time, even for very similar conditions of en-
vironment. It becomes therefore a very complex matter to correlate
two sections in which the order of faunas and the character of the
sediments differ; which is generally the case for any two sections sepa-
rated by fifty miles from each other, although on stratigraphic evi-
dence they may be properly interpreted as covering the same interval
of time.

PALEONTOLOGIC EVIDENCES OF ADAPTIVE EADIATION

BY PROFESSOR HENRY FAIRPIELD OSBORN

AMERICAN MUSEUM OF NATURAL HISTORY

rjlHE law of adaptive radiation1 is an application of paleontology
-•- of the idea of divergent evolution as conceived and developed
successively in the studies of Lamarck, Darwin, Huxley and Cope. It

1 Osborn, H. F., " The Law of Adaptive Radiation," Amer. Naturalist, Vol.
XXXVI., No. 425, pp. 353-363.

THE PALEONTOLOGIC RECORD

35

is more than divergence because it implies evolution in every direction
from a central form. The idea of radii, or radiations from a central
form greatly assists the imagination, because a distinctive feature of
paleontology is that we are constantly dealing with fragments of his-
tory. The radiations which have been discovered must be supple-
mented by those which remain to be discovered, and it is very remark-
able how in group after group of animals these missing " radii " have
turned up.

Eadiation actually begins in certain single organs, and the first
principle to be observed, as shown in the accompanying diagram, is

LIMBS AND FEET

VOLANT

FOSSORIAL

ARBOREAL

Short-limbed, plantigrade, 1 AMBULATORY
pentadactyl, unguicu- I OB

late Stem J TERRESTRIAL

NATATORIAL
Amphibious

CURSORIAL
Digit igrade

Aquatic

Unguligrade

TEETH

OMNIVOROUS

(Fish
Flesh
Carrion

HERBIVOROUS ^

Grass

Herb

Shrub

Fruit

Root

MYRMECOPHAGOUS
Dentition reduced

Stem INSECTIVOROUS
MAIN LIKES OF ADAPTIVE RADIATION OF (a) limbs and feet, (6) teeth among mammals.

36 THE PALEONTOLOGIC RECORD

that radiation of different parts of the body is not necessarily cor-
related ; that is, that the adaptive divergence of the feet and limbs may
take one direction, while that of the teeth and skull may take another
direction. Thus great variety in combinations of characters may arise,
bringing about the very antithesis of Cuvier's supposed "law of cor-
relation " ; for we find that while the end results of adaptation are such
'that all parts of an animal conspire to make the whole adaptive, there
is no fixed correlation either in the form or rate of development of
parts, and that it is, therefore, impossible for the paleontologist to
predict the anatomy of an unknown animal from one of its parts only,
unless the animal happen to belong to a type generally familiar. For
example, among the land vertebrates the feet, which are associated with
the structure of the limbs and trunk, may take one of many lines of
adaptation to different media or habitats, either aquatic, terrestrial,
arboreal or aerial; while the teeth, which are associated with the struc-
ture of the skull and jaws, also may take one of many lines of adapta-
tion to different kinds of food or modes of feeding, whether herbivorous,
insectivorous or carnivorous. Through this independent adaptation of
different parts of animals to their specific ends there have arisen among
vertebrates almost unlimited numbers of combinations of food and tooth
structure.

Alternations of Habitat. — In the long vicissitudes of time and
procession of continental changes animals have been subjected to alter-
nations of habitat either through their own migrations or through the
"migration of the environment itself," to employ Van den Broeck's
epigrammatic description of the profound and sometimes sudden en-
vironmental changes which may take place in a single locality. The
traces of alternations of anatomical adaptation corresponding with
these alternations of habitat are recorded both in paleontology and
anatomy. For example, Huxley in 1880 briefly suggested the arboreal
origin of all the marsupials, a suggestion which has been confirmed
abundantly by the detailed studies of Dollo and Bensley, according to
which we may imagine that the marsupials have passed through a series
of phases, as follows: (1) a very early "terrestrial or ambulatory"
phase, (2) a "primary arboreal" phase as exemplified by the tree
phalangers of the present day, (3) a "secondary terrestrial" phase
as exemplified by the kangaroos and wallabies, (4) a " secondary ar-
boreal " phase as exemplified by the tree kangaroos.

Each one of these phases has left its anatomical record in the struc-
ture of the feet and limbs, although this record is often obscured by
adaptation.

Louis Dollo especially has contributed most brilliant discussions of
this theory of "alternations of habitat" as applied not only to the
interpretation of the anatomy of the marsupials but of many kinds of

THE PALEONTOLOGIC RECORD 37

fishes, and to such reptiles as the herbivorous dinosaurs of the Upper
Cretaceous.

This brief consideration of the external features of adaptation leads
us to glance at groups of animals. We here observe the influence of
geographic distribution; we observe the adaptive radiation of groups
botfa continental and local.

Continental Adaptive Radiation. — Among the Tertiary mammals
we can actually trace the giving off of radii in several, sometimes in all,
directions for the purpose of taking advantage of every opportunity to
secure food, to escape enemies, and to reproduce kind, the three phe-
nomena of the struggle for existence. Among such well-known quad-
rupeds as the horses, rhinoceroses and titanotheres the modifications
involved in these radiations can be clearly traced. Thus the history of
the life of continents presents a picture of contemporaneous radiations
in different parts of the world. We observe the contemporaneous and
largely independent radiations of the hoofed animals in South America,
in Africa and in the great continent comprising Europe, Asia and
North America.

Through the laws of parallelism and convergence each of these
radiations produced a greater or less number of analogous groups.

While originally independent, the animals thus evolved separately as
autochthonous types in many cases finally mingled together as migrant
or invading types.

We may thus work out gradually the separate contributions of the
great land masses of North America, South America, etc., to the mam-
malian fauna of the world. As a rule the greater the continents the
more important and fundamental the orders or larger groups of mam-
mals which have radiated in them; the lesser land masses and conti-
nental islands, like Australia, have been less favorable to wide adaptive
radiation. One of the most interesting features of adaptive radiation is
that it may also occur locally.

Local Adaptive Radiation. — On a smaller scale are the local adaptive
radiations which occur through segregation of habit and local isolation
in the same general geographic region wherever physiographic and
climatic differences are sufficiently great to produce local differences in
food supply or other local factors of change. This principle is well
known among living animals, and it is now being demonstrated among
many of the Tertiary mammals, remains of four or five distinct genetic
series having been discovered in the same geologic deposits.

The existence of multiple phyla of related animals, as of the rhi-
noceroses, horses and titanotheres in the same localities is due partly
to the operation of the law of local adaptive radiation.

This is conspicuously the case among the titanotheres, for example,
the chief evolution of which can be traced in the Eocky Mountain

38 THE PALEONTOLOGIC RECORD

region. In the Eocene we discover four or five independent local
phyla; again in the Oligocene we discover five or six independent local
phyla. The evolution of these animals appears to have been chiefly
American.

In other cases, however, the polyphyletic condition appears to have
been through the mingling with local phyla of phyla evolved in other
countries. This is illustrated in the case of the Middle Miocene rhi-
noceroses of America, which are invaded by rhinoceroses of Eurasiatic
or European origin.

In studying the herbivorous quadrupeds, therefore, we must keep
in the imagination constantly the production of local phyla through
local radiation and the intermingling of foreign phyla through migra-
tion. There are a few very striking and profound differences between
quadrupeds which recur so frequently that where we discover one form
we may surely anticipate the discovery of the opposite or antithetic
form: in other words, there are extremes of structure shown in the
proportions of the skull, of the teeth, of the limbs, and groups of
quadrupeds are constantly tending through adaptive radiation to reach
these extremes. Some of the contrasting extremes are the following:
brachyodonty vs. hypsodonty, dolichocephaly vs. brachycephaly, dolicho-
pody vs. brachypody.

For example, a local adaptive radiation observed in the horses is
that the forest-living types are brachyodont, or possess short-crowned
teeth, while the desert-living horses are hypsodont, typically grazers,
with long-crowned teeth.

Extremes of long-headedness and short-headedness, of long-foot-
edness and of short-footedness, comprise a very large part of the mech-
anism of adaptive radiation; but we have to do also with long-necked
and short-necked types, and with many other chances of proportion
which are correlated with different feeding habits.

THE PALEONTOLOGIC RECORD 39

ANATOMY AND PHYSIOLOGY IN INVERTEBRATE EX-
TINCT ORGANISMS

BY RUDOLF RUEDEMANN

STATE MUSEUM, ALBANY, N. Y.

THE inquiry into the position of anatomy and physiology in in-
vertebrate paleontology seems very appropriate at present, since
paleontology is steadily becoming more closely affiliated to zoology, and
the sphere of zoology is at present dominated by comparative anatomy
and physiology.

Since, however, invertebrate paleontology has only the hard parts,
mostly outer shells, at its disposal, the view still prevailing among
zoologists that little is to be expected from it in regard to the solution
of the problems of anatomy and physiology of the lower animals seems
natural. Nevertheless, the results already attained prove that if paleon-
tologists do not approach their material with a geological knowledge
only, as has been done in the past altogether too often, most gratifying
results may be obtained, at least in some classes, for it must be con-
ceded that the connection of the hard parts with the fleshy parts is very
unlike in different classes; it is very intimate in some, as the crinoids
and brachiopods, and again more indifferent, as in the gastropods.

But it is not claiming too much for invertebrate paleontology if we
say that where the hard parts are of great structural importance,
paleontology has earlier taken cognizance of this fact and consequently
gone ahead of zoology. As an instance I may cite Zittel's investigations
of the skeleton of the hexactinellid sponges which have taught the
fundamental importance of the form of the spicules and the structure
of the skeleton in that class and whose results have been readily
adopted by zoologists. In classes which, as the brachiopods and crinoids,
are to-day mere shadows of their former greatness, paleontology has its
greatest chance, and it would fail in its task if it would there not be-
come the instructor of the affiliated science; and it is gratifying to see
that this fact is finding recognition, as, for instance, in Ray Lankester^s
"Treatise of Zoology," where the chapter on the crinoids has been
entrusted to Bather, a paleontologist and one of the best authorities on
crinoids.

It is apparent that in such classes as those just mentioned, of which
only the last ends of the branches are still alive, the origin and nature

40 THE PALEONTOLOGIC RECORD

of many structures can not be elucidated, even by the embryology and
comparative anatomy of the recent forms, but only by paleontology.
Such a structure is, for instance, the mystifying stem of the crinoids
which, by a study of the primitive ancestors of the crinoids among the
cystids, is, readily recognized as a dorsal evagination of the body.
Likewise, to cite another example, the siphuncle of the recent Nautilus,
which is obscure as a wholly rudimentary organ, is in such primitive
Paleozoic cephalopods as Nanno and Piloceras, still seen in its original
form and thereby recognized in its nature.

Since that which has already been accomplished in fossil anatomy
is proof that there are still larger fields to be ploughed and harvested,
it is proper to inquire into the best methods of this work before us.

We first need more extensive and more intensive or more detailed
purely descriptive anatomical researches of the invertebrate fossils.
There are many species that, when investigated in their smallest detail,
are bound to give important results.* I may cite here, as examples of
such accomplishments, Hudson's minute study of the strange Blas-
toidocrinus of our Chazy rocks with its 90,000 ossicles, or that of the
Eurypterus fischeri by Holm. Of this archaic fossil marine arachnoid,
a relative of the scorpion and of the king crab, it can be fairly said that,
as far as its chitinous integument is concerned, it is as well known as
any recent species. "We know, through Holm, its gills, its complex
genital appendages of both sexes, and even its fine hairs and bristles.
Dr. Clarke and myself have lately continued these investigations in
the American eurypterids, and there observed the structure of the com-
pound eyes, the pore system of the segments, the genital apertures, the
mode of moulting, the arrangement of some of the principal muscles
and other anatomical facts of interest.

It can be said that this field of detailed descriptive anatomy has
been merely touched thus far, as far as our fossil invertebrates are con-
cerned, and altogether too much neglected. This is not only true as to
the gross anatomy, but still more so as to the microscopic structure.
It must be conceded that owing to the secondary changes in the rocks,
this latter line of investigation meets with great obstacles not fully ap-
preciated by the zoologist, and that it is only in its infantile stage in
some classes. But the results obtained by the microscopic research of
the Paleozoic bryozoans in this country may be considered as a striking
example of what persistency and enthusiasm may still accomplish. In
microscopic anatomy of the fossils the training of a geologist is as
much required as that of a zoologist and the history of these investi-
gations shows that a zoologist without geologic training may be badly
misled by the deceptive states of preservation of the fossils.

The main object of anatomical research is to result in comparative
anatomy and to determine what parts are fundamental or primary and

THE PALEONTOLOGIC RECORD 41

what have undergone modifications due to functional changes. It is
obvious that here invertebrate paleontology is in a position to answer a
host of questions that could not be successfully approached by compar-
ative anatomy of recent forms, by the direct observation of successive
changes. Its methods of investigation have already been applied with
wonderful success to large parts of our Paleozoic crinoids, brachiopods,
bryozoans and cephalopods. And I do not doubt that the time has
come when the preliminary stage of mere description of fossils is passed,
and a monographic treatment of each class that would fully enter into
the comparative anatomy of all structures preserved, could be profitably
undertaken.

It is only by this work that paleontology can hope to make those
contributions to philosophical anatomy in revealing the causes of the
different structures which it is especially fitted and called upon to
furnish by its ability to study the gradual development of the struc-
tures. Wherever a class of fossils has been thus thoroughly treated, it
has given a fruitful crop of new hypotheses and principles, as is in-
stanced by Hyatt's investigation of the fossil cephalopods. Most
classes, and especially the corals, echinoids and trilobites, await such
treatment by competent investigators.

Since physiology is that branch of biology that treats of the laws of
phenomena of living organisms, it might seem hopeless to expect any
information from the fossil world. This is apparently the more true
in regard to the invertebrates, since a special physiology exists thus far
only for men and the higher invertebrates and the recent invertebrates
are largely a virgin field. For this reason also, only the most general
foundations of comparative physiology have been laid, and an inverte-
brate fossil physiology would get as yet but little support from that
side. Moreover, the main source of exact information in recent physi-
ology is the experimental method, and this is wholly inapplicable to
the fossil world.

And yet it seems to us that the empiric method upon which physi-
ology has so long flourished promises also rich fruit in paleontology.
I can do no more now than briefly mention the problems that most
readily suggest themselves here. Invertebrate paleontology will be
especially competent to furnish contributions to the mechanics of
physiology by throwing light on the development of the means and
modes of locomotion. In connection with this problem invertebrate
paleontology also shows most clearly the deep-reaching influence of
secondary fixation on the structure of the organism, as in the case of
the strange Richtfiofenia among the brachiopods and the EudistaB
among the lamellibranchs. It can not fail that the progress in recent
invertebrate physiology will stimulate inquiry into the physiology of
the fossils ; and further that, as invertebrate fossil anatomy progresses,
the data for such inquiry will also come forth.

42 THE PALEONTOLOGIC RECORD

Another problem closely connected with that of the mode of loco-
motion is that of the origin of the organs of sense, and also upon this,
as far as tl^e organs of seeing at least are concerned, the fossil inverte-
brates are able to throw some light, as in the trilobites and eurypterids.

Another line of inquiry is that of the mode of nutrition as recog-
nizable by the appendages, and its influence upon the general structure
Under this heading such interesting minor problems as that of the
origin of parasitism arise and may be solved, as indicated by a recent
publication as to the time of beginning, causes and gradual changes of
parasitism, to^its very complex present conditions.

Probably also the physiology of respiration will in time receive
important additions as far as the echinoderms, crustaceans, scorpions
and eurypterids are concerned.

The widest scope, however, will have those problems that are con-
nected with the reactions of the organisms to their physical and chem-
ical surroundings. The invertebrate paleontologist meets forever, in
sight of the ever-changing faunules, the question, what exterior influ-
ences caused these changes ? Often they can be directly recognized, as
in the dwarfed faunules of the Devonic pyritiferous Tully limestone or
of the bituminous Marcellus and Genesee shales or the eurypterid
faunas of the Salina lagoons. The systematic investigation of these
reactions through the series of formations is an inviting task.

A special problem of singular interest connected with the reaction
of the organisms to the chemical surroundings is that of the composi-
tion of the shell of the invertebrates. There is good evidence for the
view that the shells were at first chitinous and that but gradually they
became calcareous or siliceous. This important question again is
intimately connected with that of the original composition of the ocean,
and this line of inquiry again leads us to the highly fascinating paleo-
physiological problem, lately so happily dealt with by Professor Lane,
as to the geological evidence on the original composition and origin
of the vital liquid, the original body temperature and the physiological
origin of the hard parts of the invertebrates in general.

CONTRIBUTIONS TO MORPHOLOGY FROM
PALEONTOLOGY

BY PROFESSOR WILLIAM BULLOCK CLARK

THE JOHNS HOPKINS UNIVERSITY

OUR knowledge of the morphology both of the animal and plant
kingdoms has been largely extended by the work of the paleon-
tologist. Mention needs only to be made of the many species, genera
and families, even orders and classes, established solely for fossil forms

THE PALEONTOLOGIC RECORD 43

to show how much we owe to paleontology. There is not a single sub-
kingdom but has been immensely enriched from this source.

Some of the fossil species possess morphological characters so closely
allied, on the one hand to earlier, and on the other to later, forms as to
indicate that they occupy a position in the line of descent, and phylo-
genetic series have been established frequently on this basis. As ex-
amples we have the well-known developmental series of the horse and
the camel. Other illustrations may be found in the Paludinas of the
Slavonian Pliocene and in the Planorbis types of Steinheim.

Still other fossil forms combine in the same species several morpho-
logical features which later become segregated and characterize different
types. Such " synthetic types" serve to show the common origin of
the forms in question if not their actual ancestors and have greatly
enlarged our knowledge of the morphology of the several groups in-
volved. These early forms are, for the most part, highly generalized,
while their descendents are variously specialized. Take, for example,
the mammalian Condylartha, small, generalized TJngulata with an
astragalus shaped almost as in the Carnivora; or the reptilian Anomo-
dontia with intermediate skeletal characters between the highest
labyrinthodonts and the lowest mammals; or again, the early Paleozoic
cystoids with generalized characters in their calyx plates which appear
in more specialized forms in later crinoids and blastoids. An almost
indefinite number of such illustrations might be cited.

Still other fossil forms present morphological characters so dif-
ferent from other fossil or living species that the genetic relationships
may not be determined accurately. Some of these are possible of refer-
ence to already defined orders, while others present so many diverse
morphological characters as to require the establishment of new divi-
sions for their reception.

A survey of the known fossil and living forms shows that not only
have old species constantly become extinct during the progress of
geological time, but new species have been as frequently appearing.
This is equally true of genera, families, orders or even classes. Some
forms have appeared and disappeared, as the case may be, suddenly;
others slowly. The great group of the Ammonites, for example, dis-
appeared suddenly at the close of the Cretaceous after showing many
degenerate characters, while the Trilobites gradually declined during
late Paleozoic time before their final extinction. One of the most
striking features in the developmental history of plants and animals is
found in the great number of fossil types which have left no descendants.

Both the animal and plant kingdoms furnish a wealth of material
with which to demonstrate the aid which paleontology has rendered to
morphology.

The contributions of invertebrate paleontology are numerous and
striking :

44 THE PALEONTOLOGIC RECORD

The Protozoa afford in the Carboniferous FusulinidaB and in the
Tertiary NummulinidaB forms with very different morphological char-
acters from those living to-day, while the numerous extinct species of
the Lituolidas and Textularidse in the Cretaceous and of the Miliolidae
and Globigerinidag in the Tertiary have greatly widened our knowledge
of the entire subkingdom.

The Ccelenterata in the Paleozoic Tabulata and Graptoloidea show
types so different from living forms that the systematist has never
been able to satisfactorily assign them to a position within the limits
of the phylum. Many external and internal characters appear that are
quite unknown in later forms. On the other hand, the paleontological
subclass of the Tetracoralla long imperfectly understood is now re-
garded with a fuller knowledge of the "morphology as affording the
probable ancestors of the later Hexacoralla.

The Echinodermata have furnished two classes, the Cystoidea and
the Blastoidea, unknown after the Paleozoic, whose morphology aids
very materially in an interpretation of later and more highly differen-
tiated forms among the Pelmatozoa. Thus the cystoids, which have
been regarded as the ancestral type from which the crinoids have
sprung, afford forms like the Camarocystites, in which the arms are
similar to those of the crinoids although the calyx plates are irregularly
arranged and thus cystoidean in character. Both the Asterozoa and
Echinozoa are represented in the fossil state by many species that greatly
widen our knowledge of the morphology of this group. Take for
example, the Echinocystites, regarded as belonging to the Palechinodea
which has a valvular pyramid of calcareous anal plates so highly char-
acteristic of the cystoids.

The Molluscoidea, to which phylum belong the Bryozoa and Brachio-
poda, would be but imperfectly understood from a morphological stand-
point but for the vast number of fossil forms. The Brachiopoda have
been estimated to have less than 150 living species, while probably more
than 6,000 fossil species have been described. Of the 31 families only
7 have living representatives. We are dependent, therefore, largely on
the fossil forms for our knowledge of the morphology of this class.

The Mollusca with their varied forms, although so well represented
to-day, have furnished in the fossil state one of the most interesting
and important orders in the animal kingdom, the Ammonoidea with
its 5,000 and more species ranging from the Devonian to the Cretaceous.
Even the allied Nautiloidea, although containing living forms, attained
its chief development in the Paleozoic, and it is from these ancient forms
that we obtain our chief knowledge of the morphology of this group
with their early straight and irregularly coiled types.

The Arthropoda afford in the Paleozoic the important groups of the
trilobites and euripterids, forms that have aided greatly in the inter-

THE PALEONTOLOGIC RECORD 45

pretation of the entire phylum. The trilobites from their morpholog-
ical features have been generally regarded as entomostracous crusta-
ceans with relationships on the one hand to the Phyllopoda and on the
other to the Merostomata, while the coalescing of the caudal segments
suggests also a relationship to the Isopoda.

Vertebrate paleontology has also furnished much to morphology.

The Fishes would be but imperfectly known in their wonderful
variety but far the fossil types. The problematical group Agnatha
found only in the Silurian and Devonian affords no certain evidence
of a lower jaw or paired limbs,, and in some of the genera of the Ostra-
coderma mimic in a curious way the contemporaneous euripterids,
which has led some to erroneously ally them with the Merostomata.
The dermal armor of most of these forms is also a striking morpholog-
ical feature.

Woodward divides the fishes proper into Elasmobranchii, Holo-
cephali, Dipnoi and Teleostomi, and considers that the common an-
cestors of all were Elasmobranchs. Numerous fossil forms among the
Elasmobranchs and Dipnoids as well as the Crossopterygians which
have been thought by many to bridge the gap between the Telelostomi
and Dipnoi have added largely to our knowledge of the phylum.

The Batrachians which consist to-day largely of diminutive forms
were represented in the later Paleozoic and early Mesozoic by the Stego-
cephalia which contain the giant labyrinthodonts with their highly
complex infolding of the walls of the teeth.

The Reptilians which began their existence toward the close of the
Paleozoic became so numerous and diversified during the Mesozoic that
this division of geological time has been referred to as the age of
reptiles. Several orders of Saurians containing many giant types
flourished during this time, but became practically extinct before the
close of the period. With the adaptation of some for walking on their
hind legs, of others for swimming, and still others for flight we have
developed a great variety of morphological features that would never
have been suspected from a study of living forms.

The Birds which are recognized as possessing certain dinosaurian
relationships and were doubtless derived from one of the reptilian orders
are unknown prior to the Jurassic. The Mesozoic forms are general-
ized, the tail at first not being atrophied and the pelvis imperfectly
developed as in later forms. The vertebras also had not acquired their
saddle-shaped articulation while teeth were present in the jaws of the
adults. Such forms certainly add greatly to our knowledge of the
morphology of this class.

The Mammals which began in the early Mesozoic were represented
throughout the Cenozoic time by highly diversified forms, many of
which have left no descendants. The gradual evolution of the mam-

46 THE PALEONTOLOGIC RECORD

malian skeleton has brought about many morphological modifications
from those shown in the Batrachia and Eeptilia. We find the skull
loses the prefrontal and postfrontal bones, the mandible is simplified,
the limb bones show a development of terminal epiphyses with ossifica-
tion to the center of the vertebras and the bones of the pelvic arch are
ossified. From the beginning of the Tertiary time a marvelous variety
of morphological characters appears, and without the fossil types we
should have but an inadequate conception of this great phylum.

The contributions of paleobotany to morphology are in some re-
spects quite as striking as those of paleozoology.

The fossil Thallophytes have not furnished any very striking varia-
tions from their present morphological features, while the Bryophytes
are scarcely represented as fossils except in very recent deposits.

The remaining phyla, the Pteridospermatophytes, the Pteridophytes
and the Spermatophytes have their oldest known beginnings as far
back as the Devonian and their study has enormously widened the
bounds of plant morphology.

The Pteridospermatophytes, which are confined to the Paleozoic,
are in habit and vegetative morphology ferns — in methods of repro-
duction and in the morphology of their reproductive organs typical seed
plants. They alter our whole conception of ferns and seed plants and
in their significance are comparable to archetypal vertebrata, the acqui-
sition of the seed habit in plants and the vertebral column in animals
probably marking the culmination of the transfer of vital activity from
aquatic to terrestrial conditions.

In the Pteridophytes the extinct Paleozoic class, the Sphenophyllales,
is significant, since the morphology of the distinct lycopod and Equi-
setum lines seems to merge in this group. The lycopod type, itself
represented in the existing flora by six or seven genera of herbaceous
plants, monotonously uniform in their morphology, is found in the
Paleozoic to constitute one of the chief units in the arborescent flora
with numerous species of complex organization, whose stem, foliar and
reproductive morphology was quite unknown to botanists (Lepido-
dendron, Sigillaria, etc.). The Equisetum type furnishes a like
case. With few existing species of minor importance and uniform
morphology we find in the Paleozoic a host of forms, many of them
arborescent and of varied and complex structure (Catamites, Archceo-
calamites, etc.). Similar examples could be drawn from the fossil
representatives of the true ferns.

In the Spermatophytes another wholly extinct class, the Cordaitales,
embraces a curiously organized group of conifers extending back to the
oldest horizons from which land plants are found, and continuing to
the close of the Paleozoic as one of the most abundant as well as the
highest type of pre-Mesozoic r>lant. In the older Mesozoic we find t\TO

THE PALEONTOLOGIC RECORD 47

groups of plants which have made similar great contributions to
morphology. The Cycadales or cycad-like plants, which to-day are an
inconspicuous group, were one of the dominant Mesozoic types, and any
understanding of the modern forms rests entirely upon a study of their
immensely abundant Mesozoic ancestors. The other group, the Gink-
goales, represented in the existing flora by a single species, the ginkgo,
is found in the Mesozoic to have been represented by many genera and
species of great diversity.

The dominant plants of to-day, the conifers on the one hand, and
the angiosperms on the other, have each afforded many extinct genera,
the former with more fossil than recent species, and only understand-
able in the light of their fossil ancestors. Vegetable morphology based
only upon existing plants abundantly demonstrated its sterility before
the relative recent study of fossil plants placed it upon an altogether
new basis.

EELATION OF EMBEYOLOGY AND VBETEBEATE
PALEONTOLOGY

BY PBOFESSOB RICHARD SWANN LULL

UNIVERSITY

THE problem of recapitulation among vertebrates gives by no means
as accurate results as among invertebrate forms, for while a single
adult shell, if perfectly preserved, will often display the entire life
history or ontogeny of the individual, a bone, or even a ^complete
skeleton, is rarely retrospective and if at all only in some minor detail.
The vertebratist, therefore, in his study of ontogeny, for comparison
with racial history must needs follow either the entire growth of one
animal, a thing manifestly impossible when the embryonic stages are
considered, or study a long series of individuals in various stages of de-
velopment, the securing of which in the great majority of cases is largely
the result of a number of happy accidents. When one comes to weigh
the evidence offered by the actual embryos of fossil vertebrates he will
find a very great dearth of material, for fossil embryos — that is, the
stages in the life history before birth or hatching — are extremely rare.
Eecent embryology, on the other hand, is more productive of results
and the earlier stages of certain organs often suggest those of equivalent
development in animals of the past. In his interpretation of a given
structure, however, one has to bear in mind whether it may not have
been modified to suit some modern need in the life history of the indi-
vidual, and thus no longer give us a true image of bygone structure.
These coenogenetic organs are not historic, but as Wilder says, " have
to do with such immediate environmental problems as nutrition or
protection." Again, if the organ has approximately the same form

48 THE PALEONTOLOGIC RECORD

and character in the ancestral type at the same stage of its development,
it represents an actual repetition of past history and is therefore palm-
genetic. Sometimes it is not quite clear, however, under which caption
the embryonic structure comes, and its interpretation must be attempted
with caution.

0 shorn in his lectures to his students speaks of the three-fold evi-
dence for evolution which stands firmly like a tripod, the legs of which
are comparative anatomy, embryology and paleontology; and the evi-
dence of each should correspond, provided the interpretation be correct.
Of these, however, embryology is manifestly the weakest member, while
paleontology is a tower of strength !

The reptiles are so rare as embryos and withal so ancient a group
that their ontogeny throws but little light upon paleontology. Among
the fossil forms a number of specimens of Ichthyosaurus have been
found with young contained within the body of the adult. Many of
these are in the normal position for f ceti-in-utero ; others are displaced,
with the head directed forward. These latter Branca thinks may be
young that have been eaten. There is also, at times, a very great
difference in the size of the contained young. Aside from a slight dif-
ference in proportions, especially that of head to trunk, and a less degree
of hardness of the embryonic bones, as indicated by their being crushed
over the parent's ribs, the young teach us nothing as to ancestral struc-
ture as they are in every way perfect ichthyosaurs. They do prove,
however, when the evidence of viviparity which they offer is taken in
connection with the supreme degree of aquatic adaptation indicated,
that the ichthyosaurs were high sea-forms, never coming ashore even
for egg-laying.

That certain of the dinosaurs were also viviparous may be proved
by an embryo contained in the unique specimen of Compsognathus
longipes from the Jurassic of Bavaria. So far as I am aware this
embryo gives no other evidence of ontogenetic value.

The turtles have been made the subject of exhaustive study by Hay
and from the embryological point of view by Clark under L. Agassiz.
Anatomically they are the most remarkable of reptiles, having under-
gone during their career an extreme modification in many directions
while retaining a number of very primitive characters. The most
remarkable feature is the development of the shield or carapace, which
contains what are generally considered as the homologues of the ribs of
other vertebrates, but, strangely enough, here lying outside of the
shoulder girdle, a feature wherein the turtles are utterly unique. The
embryology, which is well known, ought to throw some light upon the
origin of this important feature. In their earlier stages of develop-
ment the Chelonia resemble the Lacertilia, the chief pecularity being
caused by the development of this carapace which appears in the form

THE PALEONTOLOGIC RECORD 49

of two longitudinal folds extending above the line of insertion of the
fore- and hind-limbs which have already made their appearance. Hence
the carapace grows outward and over the limb-girdles which come to lie
within the rib-like osseous supports. This ontogeny shows us clearly
how the ancestral carapace may have been formed. Paleontology has
not as yet confirmed this, but doubtless will do so.

< Among birds one of the most interesting features is the occurrence
of vestigial tooth papillae in the jaws of certain embryo parrots and owls
— reminiscent of Mesozoic days when birds were toothed in their adult
state.

Mammalian evidence is very striking in many details and much of
it has recently been summarized by Hubrecht, who makes much of the
character of the placentation and derives from it and other features
some remarkable conclusions. Hubrecht abandons the idea of the
derivation of the mammalia from the reptilian-insectivorean stem, but
on the contrary derives them from amphibia-like animals of the Car-
boniferous. The character of the placentation, moreover, places man,
the Anthropomorphse and the hedgehog among the most archaic of
living mammalian types, an idea also borne out by comparative anatomy
and one which paleontology may some day confirm.

The most primitive mammals, the Prototheria, are still very sug-
gestive of their old reptilian ancestry in many ways, especially in the
method of producing the young inclosed within an eggshell. The posi-
tion of the Marsupials is surely low in the scale of mammalian life,
although they show in many respects remarkable specializations. Wilder
compares them with the Prototheria in that they also bring forth their
young at a very early state of development, though not protected by an
eggshell. The period during which they are permanently attached to
the nipples within the pouch is actually post-embryonic and properly
larval. Vestiges of placentation have been found in at least one mar-
supial, a fact which gives color to the belief that in this respect they
may be degenerate rather than primitive. Broom has shown that the
modern marsupial shoulder girdle passes through a prototherian stage
implying a relationship which is strongly supported in other ways.

The foetal Sirenia and Cetacea, so far as known, show no greater
development of hind-limbs than do the post-natal individuals. They
do show a marked neck construction and the head bent at right angles
with the trunk in a normal quadrupedal posture. The head of the
foetal manatee is very suggestive of the modern ungulate. Eyder has
tried to prove the homology of the caudal flukes in the Sirenia and
Cetacea with the integument of the hind feet, drawing his evidence
largely from comparison with the seals. In the embryo the flukes
appear as lateral expansions near the end of the tail, giving it a lance-
like form when viewed from above. These flaps by transverse expan-

50 THE PALEONTOLOGIC RE COED

sion develop into the powerful swimming flukes of the adult. They
may be compared with lateral flanges on the tail of the sea otter
Enhydris, but in the latter the flaps are elongate, while in the Cetacea
they are short and situated toward the end of the tail. Nevertheless,
the homology of the two types of flange structures appears true, the
posterior position and concentration in the whale being a mechanical
adaptation which has become accelerated in its appearance so as to be
embryonic. The presence of hair on the body of the foetal whale and
of distinct calcareous tooth germs in both upper and lower jaws of the
unborn young of whalebone whales are both reminiscent.

The horses, our knowledge of which is so complete owing to the
pioneer work of Marsh and later of Osborn, show some interesting
points of comparison between foetus and ancestor. The skulls of pre-
natal modern horses resemble those of Mesohippus or even of Eohippus
in the proportions of face and cranium, the short-crowned grinding
teeth, lesser angle between basi-cranial and basi-facial axes and the fact
that the orbit is incompletely ringed with bone. The feet of the unborn
foal are also somewhat reminiscent of old-time conditions.

One of the most difficult points to be reconciled in the acceptance
of the Cope-Osborn theory of the origin of molar cusps was the apparent
non-agreement of cusp ontogeny with the interpreted phylogeny which
this theory upheld. The difficulty has been met in two ways: by the
supposition that coenogenesis has entered into the embryogeny, or that
the paleontological record as shown by the trituberculists is open to a
different interpretation. The present great exponent of the idea claims
that the matter is still sub judice and thus the problem stands.

In conclusion, the paleontological student of the higher vertebrates
can hope to find in embryology a host of valuable suggestions, much
verification of his work and sundry apparent inconsistencies which must
in some way be reconciled. He should ever bear in mind the influence
of nature and nurture, the latter often giving rise to perplexing con-
flicts between the two records. He will on the whole have in embry-
ology a fair mirror of the past wherein, even though the image be some-
what distorted and the more remote reflections dimmed by time, he can
view the striking features of the long procession of the ages.

THE PALEONTOLOGIC RECORD 51

ONTOGENY: A STUDY OF THE VALUE OF YOUNG FEA-
TUEES IN DETERMINING PHYLOGENY

BY PROFESSOR F. B. LOOMIS

AMHERST COLLEGE

IN this paper I want to study what value is to be given to the prin-
ciple that ontogeny is a brief recapitulation of phylogeny, when it
comes to the concrete determination of the ancestry of a given genus.
For the purpose three types have been studied carefully and several
more for confirmations, the principal study being between the young
and adult of the pig, cat and man, the differences being noted to see if
they suggested the forms considered ancestral.

First let us consider the skull of a six weeks' pig in comparison with
that of the adult, the two having been drawn to the same length. The
first and most marked variation is in the brain case, that of the young
being relatively vastly larger. The same is especially true of the sense
capsules of the ear and eye. The later growth is much greater in those
parts of the skull designated as facial, or having to do with the jaws and
their supports. Then there is a change in the axis of the skull, this
being due to the growth of the maxilla region, and lastly where there
is any cellular bone or bone spaces they are developed in later life.
This factor is especially well shown in the development of the elephant
skull and in ruminants. It is coincident with high crests and marked
protuberances.

While most of the features have been indicated in the pig, the same
comparison in the cat reveals the same excessive development of the
brain case and sense organs, the same weakness of the jaws and change
in the axial relations, and this may be further confirmed in looking at
the contrast between a three-year-old child's skull and that of an adult.

The conclusions then to be drawn from this hasty comparison of
the two skulls are, first, that the shape of the skull in the young shows
the excessive development of the brain and sense capsules, so that the
appearance is not that of a primitive animal, but exactly the contrary,
the appearance which the genus would assume were its mental or
nervous development carried to a much higher degree than is the case.
The embryonic development of the brain and sense organs is pushed
far toward the beginning, and is matured, as far as size is concerned,
the earliest of any of the systems. The skull is first an envelope for
the brain and sense organs and is therefore profoundly modified by this
embryonic peculiarity, and the younger the individual the less like the
adult or ancestor the skull is shaped.

52 THE PALEONTOLOGIC RECORD

Secondly, the change of axis is not in the ancestral direction, the
excessive weak condition of the jaws being again an embryonic adapta-
tion and not an ancestral one.

Lastly, in the development of cancellous tissue is a condition which
more nearly approximates the phylogenetic development, but here even
the use of young features is deceptive, for it is seldom that this cellu-
lar bone is developed in the immediate ancestor but is rather found in
several genera back, being usually an accompaniment of the develop-
ment of the heavy facial portion of the skull. So much for form.

Turning to the dentition. The milk set of the pig and those of the
adult are drawn side by side, and it is seen that while the front teeth
of the young approximate those of the adult, the comparison is between
the complicated premolar and molar sets. Briefly, of the four pre-
molars, if all present, in the young (and often but three are developed)
the two in front resemble the premolars to succeed them in the perma-
nent set, while the two rear milk premolars resemble the permanent
molars, the last milk premolar being especially like the last molar.
This granted, the interest centers around whether the pattern of the
milk teeth is such as to indicate the ancestry. A glance at the pig and
its young will show that while the detail is not exactly the same in young
and old, yet they are so alike that no one would identify a single milk
molar as Hyotherium or any other suine genus, but would have to put
it in the genus Sus. Taking other cases among the Ungulata, the his-
tory of the naming of the Miocene genera of horses gives a good ex-
ample. There are, according to Gidley, four genera, Hyohippus, Para-
hippus, Merychippus and Protohippus; of these, three were founded on
young teeth, i. e., the first three named. When it was recognized that
they were young teeth, they were by Cope assigned to Protohippus, but
when the adult teeth were found it was clear that the distinctive features
of these young teeth were the distinctive features of the adult. For the
genus Merychippus there is a difference in that the young teeth are not
cemented, while the adult are. That is ancestral. In analyzing the
descriptions of several genera of horses usually some feature can be
found in the milk tooth which is ancestral.

In the Carnivora there is the carnassial tooth which is specialized;
in the upper jaw it is the third milk premolar and the fourth in the
adult; in the lower jaw it is the fourth milk premolar, and the first
molar of the adult. Thus it is clear that it is a different dental follicle
which forms the young and the adult carnassial. In the case of the dog
the permanent and milk carnassials are approximately alike, but in the
case of the cat the inner lobe or protocone occupies a very different
place in the young from that of the adult, a position characteristic of
none of the Felidae and suggests some of the apparently unrelated
Creodonts.

THE PALEONTOLOGIC RECORD 53

In the matter of the succession of teeth the follicles which form the
last two — the milk premolars — form teeth in the first set of a totally
different and usually more advanced character than the teeth to be
formed from the same follicles in the permanent set. As a general
thing then the conclusion would be that the milk teeth tend to have
the^same characters as mark the permanent set, but when they vary
they often retain characters of the phylogenetically ancestral form.
Weber adds that the later the succession the less the difference between
the milk and permanent sets.

Turning to the limbs, there are again several distinctly ontogenetic
characters, which are by no means ancestral. First, the formation of
epiphyses, so that a bone ossifies from three or more centers. This is
purely an ontogenetic adaptation and has no phylogenetic significance.
Then the articular ends of all the limb bones are greatly enlarged as
compared with adults. This again is not phylogenetic but an adapta-
tion, the joints and their ligaments being early approximated to their
permanent conditions. Then the length of limbs seems to be ef-
fected as an embryonic adaptation. First take the case of man born
with disproportionately short arms and legs. The legs have been inter-
preted as representing a phylogenetic condition, but the same rule does
not apply to the arms which were ancestrally long. This feature of
short limbs is also characteristic of carnivora and I feel that it is an
embryonic adaptation; certainly the ancestral limb can not be deduced
from the young condition. Quite the reverse of conditions obtains
among the Ungulata where the young at birth have disproportionately
long limbs, which with equal certainty does not represent any ancestral
condition recapitulated, for the ancestral limb in ancestral forms is
shorter. Again, I believe the anomalous legs are adaptations to either
the necessity for speed on the part of the young, or for height to reach
the teats, suckling being while the parent is standing.

In the cases of the reduction of digits, greater portions of the re-
duced digits are usually found in the young animals than in the adults,
but in the case of the entire loss of a digit it is also lacking in the
young and embryo.

The general conclusion of the whole matter would then be that the
young give us very little which is not deceptive in reconstructing an-
cestral forms. In certain cases, namely in the teeth and in reduction
of digits, confirmatory points may be obtained, but these must be
used with care, the valuable constructive evidence being rather found
in adult skeletons, and in morphological comparisons. While allowing
that many stages are recapitulated in the development of an individual,
the vast number of adaptations impressed on the young to be used after
birth, make their skeletons specialized even from birth, and such dif-
ferences as exist are seldom reminiscent.

54 THE PALEONTOLOGIC RECORD

PALEONTOLOGY AND ONTOGENY

BY PKOFESSSOR A. W. GRABAU

COLUMBIA UNIVERSITY

ONTOGENY, or the life history of the individual, is commonly
interpreted by zoologists as its embryology, the later stages of
development, from infancy to old age, being deemed of little or no
importance. This was the case fifty years ago; this is largely the case
to-day. From the days when Agassiz first called the attention of zool-
ogists to their one-sided attack of the problem of ontogeny, and urged
them to pay attention to the important post-embryonic stages, down to
our own time, students of recent animals have for the most part been
content to follow the beaten path. They have left to the paleozoologist
the study of the later stages in the life history of the individual, and
the latter's endeavors in this direction have developed the science of
zoontogeny as to-day understood. There" was, perhaps, a natural cause
for this separation, in the fact that the student of soft tissues finds few
changes which he deems worthy of attention, between the embryo and
the adult; whereas the student of hard structures generally sees an
abundance of such changes. This is especially true of invertebrates,
more particularly of such as build external hard structures in which
successive additions are marked by the lines of growth. Vertebrates,
and invertebrates without permanent hard parts, such as the Crustacea,
require series of individuals showing the successive steps in develop-
ment. But mollusks, brachiopods and corals show, by their incremental
lines, the steps in the life history during the post-embryonic period, so
that one perfect individual suffices to present these later stages in
development.

It is not infrequently urged that the hard parts of invertebrates,
especially the shells of mollusks, are not reliable indices of ontogenetic
development, since they represent only the integument, which is subject
to ready modification under the influence of the environment. Such an
argument is based on a total ignorance of the relation of the shell or
other hard structure to the soft parts of the animal. The paleontolo-
gist is convinced that the hard parts of animals are the best indices of
its development, since they record in a permanent form all the minute
modifications which are not even recognizable in the soft parts. More
than this, I believe that shells, those of mollusks at any rate, furnish
us with a record of changes wholly independent of the environment, and
referable entirely to an inherited impulse towards progressive modifica-
tion, along definitely determinable lines. I am well aware that I am
not expressing the opinion of all paleontologists in this statement, and
that this view, moreover, is strongly opposed by some of our ablest
European conchologists. But here again I contend that this difference

THE PALEONTOLOGIC RECORD 55

of opinion is due to a difference of method. When the student of shells
directs his attention chiefly to adult characters, this definitely directed
variation, independent of environment, is not recognized by him. But
no one can study the details of shell ontogeny, especially in the earlier
stages, without quickly realizing that ontogenetic development is ortho-
genetic, and that the inherited impulse towards determinate modifica-
tions is the most powerful controlling factor of the animal's life history.

So far as invertebrates are concerned, the study of post-embryonic
development was first seriously undertaken by the immortal Hyatt, in
his work on the ammonites. To be sure, others before him — notably
d'Orbigny — noticed that a distinct series of changes was recognizable in
the shell of ammonites, but no one before Hyatt actually employed this
method. He himself once told me that when, in the early sixties, he
first realized the importance of this method of study when actually
applied to shelled organisms, and its value as a guide in phylogeny,
it seemed so marvelously simple that he felt sure that the method and
its application must be fully understood by all working naturalists.
" But," he added, " I soon found that I practically stood alone, and I
have spent my life since in the endeavor to convert them to my point
of view/'

This misunderstanding, on the part of many zoologists, of the onto-
genetic method has given rise to their false attitude towards the doc-
trine of the recapitulation of ancestral characters. This subject will
be adequately treated by some of my successors, but I can not forbear
to anticipate them to the extent of pointing out this fact: When the
embryologist seeks for proof or disproof of this concept in the enor-
mously condensed record of the stages between the ovum and birth, he
is bound to be grievously disappointed; for this record, necessarily
modified by eliminations, can only furnish general resemblances of the
embryo to earlier types, and can not be said to actually recapitulate the
life history of the entire race. When, however, the student of post-
embryonic ontogeny compares the youthful stages of an individual with
the adult of immediately preceding species of the same genetic series,
the fact of recapitulation becomes at once apparent.

The post-embryonic life history of an individual falls readily into
stages, of which four major ones have been recognized and named,
chiefly by Hyatt. These are: (1) the infant or nepionic stage; (2)
the adolescent or neanic stage; (3) the adult or ephebic stage, and
(4) the senile or gerontic stage, followed by death. These onto-stages,
as they may be called, are further divided into substages, designated by
the prefixes ana, meta and para, and they may be observed in the ontog-
eny of all individuals. Moreover, in closely related members of one
genetic group, the duration of these stages and substages is approxi-
mately uniform. Change in form, however, may vary greatly, and have

5 6 ^THE PALEONTOLOGIC RECORD

no necessary relation to the onto-stages, even if they coincide with them.
We have thus a second group of stages, which we may designate form
stages, or morphic stages, and there will be required distinct designa-
tions in each case. The best method of naming these stages is to refer
them to the adult ancestral type which they represent.

Thus, in all species of the gastropod shell Fusus, the earliest morphic
stages are a close recapitulation of the adult of Fusus porrectus of the
Eocenic. These stages may therefore be called the F. porrectus stage.
It may be continued for a considerable period of the early life history,
covering several onto-stages, or it may be condensed into a short por-
tion of one stage or substage, in accelerated individuals.

It is of considerable importance that onto-stages and morphic stages
should be discriminated, so I will introduce another illustration.

In the Miocenic of the Atlantic coast we have the gastropod genus
Fulgur well represented. Fulgur fusiformis is normally characterized,
in the adult, by the possession of a pronounced flat shoulder, which is
separated from the body of the shell by an angulation carrying rounded
tubercles. Some of the more specialized individuals lose the angula-
tion and tubercles in the last whorl and become rounded. Thus, while
normally the species is tuberculated in the ephebic onto-stages, special-
ized individuals acquire a new morphic stage through the loss of orna-
mentation. This morphic stage is prophetic of the normal adult of
Fulgur maximum, and hence may be called the F. maximum stage.
F. maximum itself has in its nepionic onto-stage the characters of
adult F. fusiformis; hence it may be designated the F. fusiformis stage.
Some individuals acquire a new stage, namely, a spinous stage, char-
acteristic of the adult of F. carica. In the type designated as F.
tritonis, the nepionic stage is characterized by a fusiformis morphic
stage, the neanic largely by the maximum stage, though some of the
later neanic stages may actually acquire the carica stage. In less
specialized individuals the maximum stage may continue into the early
ephebic in more specialized ones it ceases early in the neanic, the carica
stage taking its place. Finally, Fulgur carica is characterized by the
elimination of the maximum morphic stage, so that the neanic as well
as the ephebic onto-stages are characterized by the spines of the carica
stage, which may even begin in the late nepionic.

In the foregoing, the different morphic stages are shown to be
telescoped with the onto-stages, appearing either earlier and earlier in
the ontogeny of successive individuals, through the operation of the
law of acceleration or tachygenesis ; or later and later, through the
operation of the complementary law of retardation or bradygenesis.
These laws are, of course, only applicable to an orthogenetic series, but
in such a series they are competent to produce, by interaction, all
conceivable combinations of characters.

THE PALEONTOLOGIC RECORD 57

The paleontologist, more than any other naturalist, is concerned
with the product of these interactions, and to him, oftener than to
others, has come the question, Are these results species ? and, if so, what
are the criteria for the separation of species? The student of hard
structures appreciates the difficulty of drawing sharp lines, and one of
his most trying tasks is to satisfy the idiosyncrasies of his colleagues in
the making of species, subspecies, varieties, etc. The student of hard
parts finds transitional forms the rule, and he dare not grind them to
powder under his heel with the remark credited to Stimpson, that
" that is the proper way to dispose of those damned transitional forms."

The philosophic paleontologist recognizes more readily than any one
else the truth of the dictum that nature knows only individuals, and
that species are special creations, called into being by the fiat of the
naturalist. He is concerned not so much with the origin of species as
with the origin of individuals; and while he makes use of the artificial
divisions called species, and sometimes finds his chief joy in multiplying
and subdividing them, he still recognizes their non-existence, and turns
to individuals. He may, perhaps, prefer to speak of mutations, mean-
ing individuals, nevertheless.

But individuals are complex entities, and the paleontologist can not
investigate their genesis before he has thoroughly investigated the origin
of the parts composing it. As Professor Osborn has said, the paleo-
zoologist is concerned primarily with the origin of structures. He
alone is able to trace their development, for he is present at their birth,
he follows their whole history, and will be present also at their extinc-
tion, for the paleontologist alone is immortal.

PALEONTOLOGY AND THE EECAPITULATION THEORY

BY E. R. CUMINGS

INDIANA UNIVERSITY

I

BATHER once said that " If the embryologists had not forestalled
them, the paleontologists would have had to invent the theory
of recapitulation." This may be considered as a fair sample of the
attitude of at least the Hyatt school of paleontologists toward the theory.
It is doubtful if any paleontologist could be found who wholly rejects it.

In violent contrast with the more or less complete acceptance of
the theory by paleontologists, is the attitude of many embryologists
and zoologists. Montgomery and Hurst have perhaps put the case
against recapitulation more strongly than any one else. The former
says, for example,

The method is wrong in principle, to compare an adult stage of one organism
with an immature stage of another.

58 THE PALEONTOLOGIC RECORD

And again:

Therefore we can only conclude that the embryogeny does not furnish any
recapitulation of the phylogeny, not even a recapitulation marred at occasional
points by secondary changes.

Hurst is even more emphatic. He says:

The ontogeny is not an epitome of the phylogeny, is not even a modified
or " falsified " epitome, is not a record, either perfect or imperfect of past
history, is not a recapitulation of evolution.

It would seem as though two statements could scarcely be more
flatly contradictory than those of Bather and Hurst, just quoted.
Nevertheless, I venture to make the assertion that both parties to the
recapitulation controversy are right, for the simple reason that they are
not talking about the same thing. Grabau has called attention to this,
by implication, in one of his papers on gastropods. He states that the
recapitulation theory has been placed in an evil light by the habit of
embryologists of comparing embryonic stages with the adults of exist-
ing representatives of primitive types, and that they have commonly
neglected to compare the epembryonic stages with the adults of geolog-
ically older species. In other words, paleontologists have usually dealt,
in their comparisons, with epembryonic stages, and embryologists with
embryonic stages.

There arises here a question of definition: does the biogenetic law
mean that the ontogeny is a recapitulation of the phylogeny, or does
it mean that the embryogeny is a recapitulation of the phylogeny?
If we take the general consensus of opinion, we shall find for the former
definition; and if we take the words of Haeckel, whose statement of
the law is the one usually quoted, we shall again find for the former
definition.

It is certainly true, at any rate, that the epembryonic stages may
and do show recapitulation, even when the embryonic stages do not, or
when the embryogeny is so obscured by secondary adaptations as to be
untrustworthy. There are many reasons why adaptations should occur
in intra-uterine or larval life to obscure the ancestral record. These
have often been stated and discussed, and I shall pass them with this
mere mention. That the record of remote ancestors, contained in the
embryogeny, may be lost or obscured, while the record of nearer ances-
tors, contained in the epembryogeny, is still clear and convincing, is
my contention; and I hold that this contention is substantiated by the
studies of a host of paleobiologists.

While contrasting the views of biologists and paleobiologists, I do
not wish to create the impression that all of the former have turned
against the theory of recapitulation. Several recent studies of the
development of extant forms seem to afford very satisfactory evidence
that the theory is not wholly rejected in the house of its fathers. Of

THE PALEONTOLOGIC RECORD 59

these I may mention the very interesting papers by Griggs on juvenile
kelps, Zeleny on the development and regeneration of serpulids, and
Eigenmann on the blind vertebrates of North America.

Griggs especially criticizes the views of such critics of recapitula-
tion as His, who holds that the reason why ontogeny seems to recapitu-
late pbylogeny is because the developing organism must from physiolog-
ical necessity pass from less to more complex stages, more or less
resembling ancestral forms; and the views of Morgan, who holds that
only embryonic stages of ancestors are repeated. This is the so-called
" Repetition Theory." To both of these critics Griggs objects that
they confuse physiology and morphology. " The recapitulation the-
ory," he says, " has nothing to do with physiology ; it is purely a matter
of morphology."

On the first point, that the developmental stages are merely the
physiologically necessary steps in the development of the adult organ-
ism, the conclusions of Eigenmann and Zeleny are of especial interest.
Eigenmann shows that in the blind fish, Amblyopsis, the development
of the foundations of the eye is normal, and is phylogenic, while the
stages beyond the foundations are direct. Zeleny concludes that the
ontogenesis of the opercula of serpulids is phylogenic, and recapitulates
ancestral characters; but the regeneratory development of the organ is
direct, and may be very different from the ontogenetic development.
We may ask, therefore, if development takes a certain course only be-
cause that is the physiologically necessary way in which the individual
or the organ must develop, why should a condition of perfect blindness,
with almost total loss of all the eye structures, be attained only by the
round-about method of first developing the foundations of a normal
eye? Why, again, if there is any physiologically necessary course of
development, should the serpulid be able to regenerate the opercula in
a manner entirely different from their ontogenesis ?

Hatschek, Hurst, Montgomery and others maintain that, if two
individuals differ in the adult, they must also differ in the egg, and
consequently must be different at all stages between. From this thesis
they draw the conclusion that organisms can not recapitulate adult
ancestral characters, because any change in the adult stage of an indi-
vidual, causing it to be different from its parents, involves a change in
the entire ontogeny — " the entire row of cells " from the egg to the
adult. That there is some sort of change in the entire row of cells we
grant; but that this change necessarily affects the morphology of the
individual or of its organs, up to the adult stage, we do not grant.
We have here again a confusion of morphology and physiology. The
cell energies may indeed be changed ; but unless a change in the cell
energies inevitably necessitates a change in the morphology of all the
cells or of all the organs which they compose, the argument of Mont-
gomery proves nothing.

60 THE PALEONTOLOGIC RECORD

If inheritance were perfect, the individual would take exactly the
same course in development as its ancestors. That it does not do this
in all cases is a more remarkable fact than that in so many cases it
follows the ancestral mode of development so closely. This loss of
inheritance is due to a progressive condensation of ontogeny, or as it is
commonly called, acceleration. Most embryologists misconceive the law
of acceleration, limiting it to the omission of characters or stages.
With the classic formulation of the law by Hyatt we are all familiar.
According to Hyatt, acceleration involves not only omission, but con-
densation without omission, through the earlier inheritance of char-
acters acquired in the adult or adolescent stages of life. By the un-
equal acceleration of characters an overlapping, or telescoping, as
Grabau calls it, may be introduced. It follows, therefore, that accel-
eration may be by elimination, by condensation without change in the
order of appearance of characters, and by condensation with change in
the order of appearance, or telescoping. As conceived by the paleo-
biologist, the law of acceleration is an explanation of recapitulation, as
well as an explanation of the failure to recapitulate.

Another factor in inheritance is retardation, so named by Cope.
By the operation of this law, characters that appear late in the ontogeny
may disappear in the descendents, because development terminates
before the given characters are reached. In this way the ontogeny
may be shortened and simplified, and many ancestral characters may be
lost entirely. The result of the continued operation of retardation is
retrogression, since the loss of the characters of nearer ancestors, with
the continued repetition in early ontogeny of the characters of remote
ancestors, must eventually cause the species to resemble the remote,
rather than the nearer, ancestors.

II

Of the numerous cases adduced by paleontologists, in which there
is clear evidence of recapitulation, I shall mention a few only.

Probably the best known examples of recapitulation are those made
known by the researches of Hyatt, Branco, Wiirtenburger, Buckman,
Smith and others among the Cephalopoda. It is shown that Ammon-
ites pass through a goniatite stage, and that, as phrased by Zitttel,
" The inner whorls of an ammonite constantly resemble in form, orna-
ment and suture line the adult condition of some previously existing
genus or other." The nautilus grows at first straight or orthocera-
form, then arched or cyrtoceraform, and finally at the close of the first
volution of the shell, becomes close coiled. The impressed zone appears
in ancient nautiloidea in the neanic stage, where the whorls first come
into contact, and is indeed a result of contact. In modern nautilus,
and in Mesozoic and Tertiary nautilus the impressed zone appears in

THE PALEONTOLOGIC RECORD 61

the nepionic stage, before the whorls come into contact. It has been
carried back in the ontogeny by acceleration. Smith concludes from a
study of the development and phylogeny of Placenticeras, an Upper
Cretaceous ammonoid, that "the development of Placenticeras shows
that it is possible, in spite of dogmatic assertions to the contrary, to
decipher the race history of an animal in its individual ontogeny."

'Among the Gastropoda, Grabau and Burnett Smith have pointed
out numerous beautiful cases of recapitulation. In Fusus and its allies,
the higher forms quite constantly resemble in their earlier stages the
adults of ancestral forms. Even in profoundly modified gerontic types,
the young resemble the ancestors. Smith has brought to light in
Athleta (Volutilithes) of the Eocene, an almost perfect example of even
and regular acceleration, with its correlative, the recapitulation in the
young of the Upper Eocene forms of the adult characters of the Lower
Eocene forms. The stages passed through by this group of shells are,
beginning with the earliest, a smooth, curved rib, cancellated, spiny
and sometimes a senile stage. In the ancestral species (A. limopsis)
the curved rib stage comes in at the close of the fourth whorl, whereas
in the Upper Eocene form (A. petrosa), this stage comes in at the
beginning of the third whorl.

Among the Pelecypoda the classic researches of Jackson are familiar
to all. He shows that the modern Pecten passes through, in its on-
togeny, a series of stages resembling adult Rhombopteria, Pterinopecten
and Aviculopecten, and that the geologic order of these genera is the
same as the ontogenetic order in Pecten. In such monomyarian genera
as Ostrea, the initial shell, or prodissoconch, is dimyarian, and resembles
the primitive Nucula. Again, in various more or less widely separated
genera, the condition of complete cemented fixation has produced the
ostreaform shape. Each one of these genera, however, except where
the modification of shape due to fixation appears very early in ontogeny,
recapitulates the adult characters of its respective ancestor. The ex-
amples of this are Mulleria, a member of the Unionidae — like Anodon
in the young; Hinnites, a member of the Pectinacea — like Pecten in
the young; Spondylus, another member of the Pectinacea — like Pecten
in the young.

Beecher's various studies of the Brachiopoda not only brought out
the fact that the initial shell or protegulum of the brachiopod is remark-
ably similar to the most primitive known Lower Cambrian brachiopods,
but have supplied in addition numerous other remarkable examples of
recapitulation. One of the most striking of these is the case of the
Terebratellidae. In both the boreal and austral subfamilies a very com-
plete series of genera correspond to the ontogenetic stages of the ter-
minal or highest genera. Another interesting case is that of Orbicu-
loidea. This discoid shell has at first a straight hinge like Iphidea.

62 THE PALEONTOLOGIC RECORD

It next resembles Obolella, then at a later stage it is like Schizo crania,
and finally adult growth brings in the characters of Orbiculoidea.
Raymond has shown the remarkable similarity of the neanic stage of
Spirifer mucronatus to the adult 8. crispus of the Niagara. Shinier
and Grabau found in the upper Hamilton of Thedford, Ontario, a
variety of Spirifer mucronatus that is very mucronate in the young
and not at all so in the adult. The derivation of this form from
8. mucronatus is beyond question. I have pointed out a precisely
similar case in Platystrophia acutilirata var. senex. This variety,
which occurs in the upper Whitewater beds of Indiana and Ohio, has
a hinge angle of nearly 90° in the adult. In the young, however, the
outlines of the shell are exactly like the typical P. acutilirata, from
which it is beyond any question descended. Greene has shown that
Clionetes granulifer of the Carboniferous is, in the neanic stage, like
the Devonian Chonetes, and that the hinge-spines come in at a consid-
erably earlier stage in the Carboniferous than in the Devonian and
Silurian forms, showing the acceleration of this character.

In the Bryozoa I have pointed out the fact that the colony behaves
as an individual, and like an individual recapitulates in its ontogeny
(astogeny) ancestral characters. This is beautifully shown in Fenes-
tella, in which the earlier zocecia are strikingly like the adult zocecia of
the Cyclostomata. The adolescent zooecia of Devonian Fenestella are
similar to the adult zooecia of Niagara forms. Lang has brought
together numerous cases of recapitulation among Jurassic and Creta-
ceous Stomatopora and Proloscina. The method of dichotomy in the
earlier portions of the colony is constantly more like the normal dichot-
omy of ancestral species.

In graptolites the remarkable researches of Ruedemann clearly
indicate that the graptolite colony recapitulates ancestral characters,
the proximal thecae being similar to ancestral adult thecae. He says:

The rhabdosomes in toto and their parts, the branches, seem also to pass
through stages which suggest phylogenetically preceding forms.

Among the trilobites the studies of Beecher, Walcott and Matthew
are classic. Beecher has shown that there is a common larval form,
the protaspis, and that in higher genera characters appear in the pro-
taspis that are known only in the adults of more primitive genera.
For example, the " main features of the cephalon in the simple protaspis
forms of Solenopleura, Liostracus and Ptychoparia are retained to
maturity in such genera as Carausia and Acontheus" Larval Sao has
characters that occur in the adult of Ctenocephalus. The larval stages
of Dalmanites and Proetus have characters that appear only in the adult
of ancient genera.

Among the corals Beecher and Girty show that such genera as
Favosites have early stages that suggest Aulopora. Lang, in a recent

THE PALEONTOLOGIC RECORD 63

paper, records very interesting cases of recapitulation in the genus
Parasmilia of the Cretaceous. - Bernard concludes that the coral colony,
like the graptolite colony and the bryozoan colony, behaves as an
individual.

In the echinoderms the likeness of the stem ossicles and the devel-
opment of the anal plate of Antedon, to Paleozoic and Mesozoic forms
has become one of the stock illustrations of recapitulation. Jackson
has found interesting examples of recapitulation in the development of
the ambulacral and inter-ambulacral plates of echinoids. Miss Smith
has shown that the young Pentremites is exactly similar in form to the
adult Cadaster. This is an extremely interesting case, for Bather has
independently, and from quite different data, come to the conclusion
that Pentremites is derived from Cadaster.

The idea of recapitulation has been one of the most fertile in the
whole realm of biology, and its usefulness to the paleobiologist has been
almost incalculable. But while there can be no doubt that recapitula-
tion is a fact, the paleontologist should observe all due care not to
assume too much for it. That there are various sorts of adaptations,
arising at all stages of life, and that these may greatly obscure the
ancestral record, is a fact too well known to require more than mention.
There is also always acceleration, sometimes affecting different char-
acters very unequally ; and there may be retardation. All of these fac-
tors complicate the record of ontogeny. Nevertheless, after all of these
have been taken duly into consideration, the parallel between ontogeny
and phylogeny remains a powerful aid to investigation for the pale-
ontologist.

VERTEBRATE PALEONTOLOGY AND THE EVIDENCES
FOR RECAPITULATION

BY L. HUSSAKOF

AMERICAN MUSEUM OF NATURAL HISTORY

AFTER the careful papers of Professors Loomis and Lull in which
the doctrine of recapitulation was so fully set forth from the
standpoint of vertebrate paleontology, I can perhaps do no better than
devote part of the time allotted me to showing how certain leading
vertebrate paleontologists have viewed this question. Then I will cite
one or two illustrations of this principle drawn from among the lower
vertebrates.

Passing over the period of pre-Darwinian paleontology — the pale-
ontology of Cuvier, Owen and Louis Agassiz — we come to the time of
Leidy, who, as Professor Osborn has recently shown,1 was one of the first,

1 In his address on " Darwin and Paleontology " printed in " Fifty Years
of Darwinism." Centennial addresses in honor of Charles Darwin, New York,
1909, p. 209.

64 THE PALEONTOLOGIC RECORD

if not the first, to bring the fruits of paleontology to the support of
evolution. But Leidy, as far as a hasty search through his writings
could reveal, nowhere expressly advocated the doctrine of recapitula-
tion. Indeed, he gave but little attention to the philosophical bearings
of paleontology, generally partly because of temperament and partly
because in those pioneer days material to serve as a basis for generaliza-
tion was still scanty.

Gaudry, one of the first European paleontologists to champion the
cause of evolution,2 likewise did not specially advocate the doctrine
of recapitulation. An examination of his " Philosophic Paleontolo-
gique " fails to reveal any definite belief in this doctrine.

Huxley, as far as I can gather from his papers and essays, be-
lieved in this doctrine, though with certain implied reservations as to its
general applicability. In his presidential address to the Geological
Society of London on " Paleontology and the Doctrine of Evolution "
delivered in 1870, we find some interesting comment on the signifi-
cance of the splints of the living horse, which he regards as indicative
of the presence of three complete digits in the horse ancestor. But
Huxley was never an out-and-out advocate of the biogenetic law.

Cope and Marsh, as we all know, were staunch upholders of evolu-
tion ; and Cope, at least, was also a staunch upholder of the doctrine of
recapitulation. In his " Primary Factors of Organic Evolution," his
last contribution to philosophical paleontology, he devotes considerable
space to proving this doctrine. He says :3

The representatives of each class passed through the stages which are
permanent in the classes below them in the series.

And he backs up this proposition with evidence derived from the
ontogeny and phylogeny of batrachia, the antlers of deer and the blood
trunks of vertebrates generally. For all that, Cope recognized the
justice of certain criticisms which had been brought against the doc-
trine of recapitulation and urged caution in its application.

An example or two of recapitulation may now be cited from the
field of the lower vertebrates.

The mode of development of the teeth in Neoceratodus has some-
times been adduced as an illustration of recapitulation. It is well
known that the Devonic dipnoans (e. g., Dipterus) had teeth com-
posed of rows of denticles, those in each row being more or less fused
at their bases. During the history of the dipnoans since the Devonic
period, the separate denticles have merged more and more until in
Ceratodus and the living Neoceratodus, the rows of denticles are, in

2 According to a letter from Darwin to Gaudry dated Jamury 21, 1868.
"The Life and Letters of Charles Darwin," edited by his son Francis Darwin,
New York, 1899, Vol. II., p. 269.

8 " Primary -Factors of Organic Evolution," Chicago, 1896, p. 195.

THE PALEONTOLOGIC RECORD 65

the adult, replaced by almost smooth ridges. Now, Semon in his
beautiful studies on the development of Neoceratodus* has shown that
the teeth of this fish at one stage in ontogeny, are represented by rows
of denticles even more discrete than the denticles in the Devonic Dip-
terus; then the denticles gradually merge at their bases, the separate
cusps, however, still showing — a stage comparable with the Carbonifer-
ous Ctenodus; then they merge still more and assume the ridge-like
form seen in the adult Neoceratodus.

Another example: In many sharks the alimentary canal is
longer in the embryo than in the adult, the anal opening being situ-
ated near the posterior end of the trunk. From such cases one is in-
clined to believe that in the ancestral sharks this must have been the
condition in the adult form; that is to say, the anal opening probably
was near the posterior termination of the trunk. We may therefore
ask: are there any early fossil sharks which show such a condition?
Eecently Professor Dean has described5 a remarkable specimen of
Cladoselache from the Upper Devonic of Ohio which seems to indicate
such a condition. In this specimen remnants of both kidneys are pre-
served. They extend in the posterior half of the fish and by their direc-
tion indicate that they were drawn together, toward their external
opening, not far from the posterior termination of the trunk. This
shows that the anal opening in this ancestral shark was very much as in
the early shark embryo to-day.

In conclusion perhaps I may venture to make one other point
in regard to this question. A vast amount of skepticism concern-
ing the doctrine of recapitulation is to be found in the literature
of to-day; and if we study the reasons for this skepticism we find
that it is in some measure justified. It is clearly established that among
vertebrates as well as among invertebrates there are many examples of
structures appearing during embryonic growth which are identical
with structures found in the adult of some remote ancestor. But
when we reflect on the amount of adaptation which any embryo
has undergone in its long evolutional history; when we remember
how palingenetic characters are on every hand overlaid by ceno-
genetic ones; who will say that recapitulation is a principle of gen-
eral application, or that it is safe to draw conclusions from all em-
bryos concerning their long extinct ancestors? Who will believe that
a bony fish which runs through its embryonic development in a few
days repeats its ancestral history, when we see at every 'stage of its
ontogeny how it has been adaptively modified for this and for that
special need? Only when series of related forms have certain onto-

4 " Die Zahnentwickelung des Ceratodm forsteri," " Zool. Forsch. in Austral,
u. Malay. Archipel.," 1899, pp. 115-135, pis. xviii-xx.

5 Mem. Amer. Hus. Nat. Hist., Vol. IX., p. 232.

66 THE PALEONTOLOGIC RECORD

genetic stages in common are we justified in inferring that their
racial ancestor may have had such characters in the adult state. But
it should never be lost sight of that this inference is only a provi-
sional hypothesis which may or may not be verified when the paleonto-
logic record is more complete. It is no surprise that the efforts of
some earnest paleontologists have been discredited in some quarters,
especially among zoologists. Some of them have invoked recapitula-
tion as a sort of magic spell by which they can conjure up ancestral
forms from almost any embryonic series, forgetting the limitations of
this doctrine. As far as the attitude of vertebrate paleontologists is
concerned, their view has been aptly summarized by Professor Charles
Deperet in his book " Les Transformations du Monde Animal " and I
can do no better than close with a quotation from him :

If we appeal to paleontology, it must be recognized that this hypothesis
[recapitulation] is by no means verified. There do exist here and there certain
fossil genera, which all their lives have retained certain youthful characteristics
apparent in their living descendants ; but when it comes to reconstructing whole
series chronologically continuous, grave contradictions are met with, and it is
only in the groups of the mammals and perhaps of the reptiles [and, we may
add, fishesl that it becomes possible to present a few examples sufficiently
demonstrative.6

6 "Les Transformations du Monde Animal," Paris, 1907, p. 117.

THE PALEONTOLOGIC RECORD 67

THE KELATION OP PALEOBOTANY TO PHYLOGENY

BY PBOFESSOR D. P. PENHALLOW

MCGILL UNIVERSITY

THE history of plant life has been the central idea in all botanical
studies from the very earliest times, whether expressed in the
imperfect methods of the early German and Dutch botanists who de-
sired simply to establish natural affinities on the basis of external re-
semblances, or in the ambitions of Csesalpino to arrive at a classifica-
tion of plants which should satisfy the conditions of relationship
through the structure of all parts, and especially of the reproductive
organs. For nearly four hundred years the external organs have been
employed as the chief basis of those numerous systems of classification
which have appeared from time to time. The idea that the reproduc-
tive organs and the minute interior structure of plants were of primary
importance as first advocated by Caesalpino, was for a long time lost to
view, although it reappeared now and then in the works of later writers.
Eventually it gained recognition and became a factor of increasing im-
portance, until the most advanced systems now employed involve an
acceptance of both the external parts and the internal anatomy as es-
sential factors.

From the time of Malpighi and Grew, to Goeppert and Corda, our
knowledge of the interior structure of plants made great and rapid
progress, and was later applied successfully by various investigators in
the direction of establishing relationships. To no one are we more
fully indebted for an elaboration of this idea than to Williamson, whose
researches into the structure of fossil plants from the Coal Measures
of Great Britain, during the latter part of the last century, laid the
real foundation of modern paleobotany.

In so brief a treatment as that which is now employed, it is impos-
sible to more than touch upon some of the salient features in the rela-
tions of paleobotany to the course of phylogeny, but it is, nevertheless,
tforth while to give special emphasis to the now well-recognized fact
that a thorough knowledge of the interior structure of the plant, and
especially of the stem, leads to a more comprehensive and exact ac-
quaintance with relationships than that of any other part. This arises
from the fact that the minute anatomical details have a greater degree
of stability than any other portion of the body, doubtless due to the fact
that in its adjustment to the land habit, the environmental influences

68 THE PALEONTOLOGIC RECORD

present the least variable features in those factors which determine re-
lations to mechanical stress and physiological needs.

External organs are notoriously subject to variation, even under
slight alterations of surrounding conditions, within the limits of the
species or even within various stages of development of the same indi-
vidual. From this it is clear that organs such as leaves must be very
unreliable for phylogenetic purposes. It is, unfortunately, true that
much of the paleobotanical work based upon a study of such parts must
be of inferior value, and the conclusions drawn will require extensive
revision when the more rigid tests to be applied through a knowledge
of the stem structure are brought to bear.

The value of paleobotanical evidence consists in its ultimate corre-
lation with known types of plants, and it is obvious that all such studies
should be prosecuted with direct reference to the broader require-
ments of plant biology. This involves a comprehensive knowledge of
the history of plant life from its earliest development; that the data
derived from a study of living species should be correlated with the evi-
dence obtained from fossilized remains. Existing vegetation shows a
very incomplete record of plant life as a whole. Its history as known
until very recent times, and even now to a very large extent, is dis-
played only through the medium of detached groups, and relates chiefly
to the most highly organized types. Through the perspective afforded
by paleobotany, it becomes possible to not only supply missing facts,
but to establish what theory has for so long a time required a satisfac-
tory demonstration of — a more or less continuous series of phenomena
from the rudimentary forms to the most advanced organisms.

Until a very recent date the Linnsean division of plant life into two
great phyla, the cryptogams and the phanerogams, was the prevailing
conception of the constitution of the plant kingdom. This division
recognized no connection between the two great groups, but regarded
them as wholly distinct in origin as in character. But the rapid ad-
vances in a knowledge of plant anatomy, developed toward the middle
of the last century, and especially the remarkable and epoch-making
observations of Hofmeister respecting the process of reproduction,
enabled him to break down the old barriers erected by the doctrine of
the constancy of species, and prove a genetic connection between the
primary divisions of Linnaeus. With this starting-point, the crypto-
gams and the phanerogams were subjected to a severe scrutiny from an
entirely new point of view, with the result that each underwent a re-
vision which led to such a rearrangement of subdivisions as to present
an entirely fresh conception of their relations to one another. The
logical result was finally expressed in the subdivision of the plant world
into four great phyla, which, in their evolutional sequence, came to be
known as I., Thallophyta; II., Bryophyta; III., Pteridophy ta ; IV.,
Spermatophyta.

THE PALEONTOLOGIC RECORD 69

Admirable as this scheme is, and scientifically acceptable as it has
proved to be, it nevertheless presents certain well-recognized defects
with respect to the requirements of theory, although at the time of its
formulation and as late as 1899 it represented the sum of available
knowledge. It was just at this time that paleobotany became available
as p, means of meeting those deficiencies which a knowledge of living
^plants could not overcome. For a long time botanists have been famil-
iar with certain Paleozoic remains having a fern-like aspect which were
generally accepted as ferns; but because of their want of direct con-
nection with stems or fruit, there remained a serious doubt as to their
real character. In the same horizons, detached fragments of stems
were also observed with increasing frequency. The study of their
anatomy disclosed a structure which, in some respects, was curiously
like that of ferns, while in other respects it approximated to the anat-
omy of the higher plants as presented in some of the gymnosperms.
This combination of filicinean and cycadean characters was noted by
Potonie, who succeeded in correlating them and expressing their phylo-
genetic position in the name of a new order which he called the Cyca-
dofilices.

There yet remained to be considered certain remarkable fruits for
which no relationship has as yet been determined until, through the
work of Scott, Oliver, Kidston and others, it was shown that they were
of the nature of seed-bearing organs which could be correlated with the
Cycadofilices. It thus became evident that there was a hitherto un-
known group of plants combining the characters of ferns in their foli-
age and stem structure with those of primitive gymnosperms as pre-
sented in their stems and fruits. On the whole, however, these plants
approached most nearly to the pteridophytes in their external features.
To this new phylum, of which the Cycadofilices formed the most con-
spicuous member, Scott and Oliver in 1904 assigned the most appropri-
ate name, Pteridospermae. This result was based entirely upon paleon-
tological evidence through comparative anatomy, and it compels us to
recognize the existence of five, instead of four great phyla. The far-
reaching significance of this achievement can not be overestimated. It
is not only of the utmost importance as proving the general course of
evolution and bringing into the realm of proved facts what had previ-
ously been a working hypothesis only, but it offers an entirely new point
of departure for the botanist of the future. Attention may also be
directed to one other effect. The tendency of this discovery is to co-
ordinate, unify and strengthen all branches of botanical knowledge,
bringing to us the conviction that the more extended and thorough our
knowledge of the earlier forms of vegetation becomes, the more satis-
factory will be our knowledge of the science as a whole; for while the
example selected is probably the most important for our special pur-
poses, the general utility of paleontological research in relation to the

70 THE PALEONTOLOGIC RECORD

history of development is enforced upon our consideration in a great
many subordinate ways.

Recognizable plant remains first occur in the Silurian in the form
of certain highly organized algae, the ancestral forms of which are un-
known. Nevertheless, the history of NematopJiycus shows that in the
Silurian and extending through the Devonian, members of the brown
algae directly comparable with the modern kelps, both in general char-
acter and in detailed structure, had attained to a development unknown
to any of the marine algae of to-day. Arborescent forms with stems two
feet in diameter and a corresponding height lead to the inference that
they not only represent the culmination of the phylum at that time,
but that they must have been preceded by a long line of ancestral forms,
extending far back into the earlier horizons, possibly into the Eozoic
itself. t

Parka decipiens from the old Red Sandstone of Scotland affords
striking illustration of the very early period at which heterospory was
developed among vascular plants, which, according to the evidence now
available, are comparable with the genus Marsilea among existing types.
In these remains we meet with prostrate stems often one to two inches
in diameter, from which slender, upright branches are produced, bear-
ing in turn conceptacles containing both micro- and mega-sporangia.
Some of these latter further contain prothalli in various stages of de-
velopment.

The earliest form of gymnosperm is that which we recognize in the
genus Cordaites from the Devonian. The highly developed and dicoty-
ledonous character of the stem affords abundant evidence that the
ancestral type must be looked for in some remote and earlier horizon,
but, taken as an isolated case, it affords no clue whatever to the origin
of that particular phylum, although the subsequent course of develop-
ment may be traced with considerable certainty to comparatively recent
times.

The obvious conclusion to be drawn from the geological relations
presented by such illustrations as those recited, is, that the evolution of
even very simple forms from the most primitive plants must have
called for enormously lengthy periods of time. Even the most liberal
application of the law of mutation would fail to adequately account for
the extensive gaps which are recognized as occurring between the
simpler types and those which lie in the same general line of succes-
sion, but with greatly advanced organization.

We are now led to ask, how far have paleontological studies carried
us in our knowledge of plant life from the earliest times, that is, do
they enable us to trace an unbroken series of steps from the first to the
last? To this the answer must be that, while paleobotany has been of
the greatest service in supplying missing data, in filling great gaps in a
supposed sequence and in giving the fullest support to the law of evo-

THE PALEONTOLOGIC RECORD 71

lution, it is as yet by no means adequate with respect to meeting all that
theory demands. For this there is an intelligible explanation based in
part upon the fact that the necessary material is available only under
conditions of great difficulty; and that the character of the remains
upon which research is based is conditioned by the original nature of
the t structure and its ability to survive in an unaltered form, the re-
markable conditions of decay, infiltration, compression, upheaval and
often of volcanic influences to which it has been subjected. The earliest
type of vegetation was that which we now find in hot springs, continued
with the algae found in cool or cold waters, all of which possessed a deli-
cacy of structure which permitted speedy decay. The great abundance
of such organisms probably afford an adequate explanation of the
Laurentian and later forms of graphite which is regarded by many as
the remains of former vegetation. While this hypothesis may be ac-
cepted provisionally, paleobotany is nevertheless wholly unable to fur-
nish any clue to the life history of the individuals, or even to inform
us as to the specific types. Such knowledge as we possess in this direc-
tion is the result of inference from parallel conditions and structures
as now found.

It might be assumed that with an increasing perfection in the pres-
ervation of fossil remains, as found especially in the later formations,
it should be possible to trace the course of descent with accuracy and
completeness. This is, in a measure, true, but although the general re-
quirements of theory may be verified, yet the haphazard conditions
involved in the collection of plant remains make it a very difficult mat-
ter to secure a complete narrative, and there remain many gaps which
it is difficult to fill. The evolutional position of the Bryophytes de-
mands that the origin of these plants should lie somewhere in the early
Silurian or even in the Eozoic age, but we have no certain knowledge
of them until the middle Mesozoic, and their remains do not become
familiar or abundant until the later Tertiary. So important a devia-
tion from what theory demands should lead us to caution in drawing
conclusions from the direct testimony which is thus presented. Unless
otherwise disposed of through paleontological evidence, it would be
more correct to infer that the delicacy of the plants, and the conditions
of their fossilization, have not admitted of their preservation in a recog-
nizable condition ; while there is also the further probability that many
of their remains have been overlooked through resemblance to certain
Pteridophyta for which they might well be mistaken.

In spite of such apparent contradictions, the evidence everywhere
points with great force to the idea that each of the lesser phyla had its
origin in some ancestral form, followed by growth and culmination.
This latter was, in some cases, abrupt, as in many of the Pteridophytes ;
in other instances there was a- gradual decline, as in the lycopods or the
horsetails, which attained their highest development in the later Paleo-

72 THE PALEONTOLOGIC RECORD

zoic, but have since been in a state of degeneracy, their present repre-
sentatives being few in number and of a depauperate character. The
application of this law throughout the enormously lengthy periods re-
quired for the evolution of existing species, has led to the survival of
some of the most ancient types until the present day; to the absolute
obliteration of others which at one time gained great prominence; and
to the gradual dying out of yet others, some of which are now found in
the last stages of their existence. But through the entire course of
change, the evolution of higher and yet higher forms has been the most
conspicuous fact. Furthermore, it is undoubtedly true that the general
course of evolution is in progress to-day as in the past, since all the
potentialities of such evolution exist now as always, though conditioned
by the fact that owing to continued changes in the physical character
of the earth's atmosphere as well as of its crust, the possibilities of evolu-
tion are steadily diminishing and will eventually cease.

There is one direction in which paleobotany gives well-defined as-
surance that the evidence derived from existing species leads to correct
conclusions. In tracing the succession of types, we are led to the belief
that there is no direct sequence. Conterminous evolution is in accord
with neither theory nor ascertained facts, and it is, therefore, impossible
to conceive of a figure which shall in any way represent a single and
unbroken line of succession. If paleontology teaches us anything, it is
that each great phylum, as well as its various subdivisions, finally reaches
its culmination in a terminal member from which no further evolution
is possible. But that from some inferior member, possessing high
potentialities, a side line of development arises. There is thus, in the
early life of each member of the series, a certain recapitulation of
ancestral characters. This conception of a continuance of the main
line of descent through a succession of lateral members is both logical
and fully in accord with the evidence derived from both recent and
extinct forms of plant life, as well as with our present theory of
evolution.

PALEONTOLOGY AND ISOLATION

BY DR. JOHN M. CLARKE

STATE MUSEUM, ALBANY, N. Y.

THE notion of isolation as a factor in variation, as I am using the
term, is that of geographic separation exclusively, the concep-
tion expressed most clearly by Wallace, Moritz Wagner and Jordan.
I take it that while this influence has been carefully estimated in the
geographical distribution of living species, it has not often been ex-
pressed in its own terms in the analysis of extinct faunas. With in-
creasing accuracy in the record of ancient continental lines and bar-

THE PALEONTOLOGIC RECORD 73

riers, we are coining to a point where the efficiency of this factor can
be safely taken into account. The outcome of free interbreeding, as
Jordan has pointed out, is to unify species and obliterate variations.
Per contra, isolation checks this process and gives freer play to tend-
encies arising from other factors in variation. The effect is thus, as
a general rule, negative, but expresses itself freely enough in geo-
graphic provinces severed by some barrier or condition which has the
effect of a barrier. Among existing species the formative effects of
segregation have been very largely illustrated from restricted areas
such as the subdivisional valleys and forests of Hawaii with its dis-
tinctive forms of the Helicidae and other terrestrial snails — a case that
is paralleled in paleontology by the snails of Steinheim. But the effect
is to be reckoned with in larger or continental areas between which
there has been at one time opportunity of interchange, especially in
the case of marine species, with which we chiefly deal, along the epi-
continents.

I have particularly in mind phenomena which have been brought
to my notice by a somewhat extended study of the Devonian faunas
of the southern hemisphere and the broader application of the factor
is best enforced and illustrated by this instance. I may say that this
broader notion seems to be that entertained by Darwin so far as he
specified the conception of geographic segregation as an element in
natural selection and it was his work in South America that formed
the basis of his conclusions.

With other students we recognize the existence during the Devon-
ian of austral continental lands which have been variously designated
and variously outlined. By some this land has been posited as a north
and south Atlantis lying in the meridional axis of the present ocean,
by others a broken land mass partly crossing the southern Atlantic
from east to west. But now we begin to see its continuity and the ex-
tent of its strands, with something of its changes in outline during
its early history. It was the precursor and the nucleus of Gondwana-
land. With it began, so far as we now know, the long history of that
continental land and the successive records of life developing under
continued conditions of geographic isolation from the northern strands.

From Argentina, Bolivia and northern Brazil we have very lucid
evidence, on the basis of paleontology, that in the late Silurian the
shore lines were continuous with those of the north. We have no de-
pendable knowledge of these earlier faunas at the east and indeed
their entire absence is indicated by stratigraphy; but with the sub-
mergence of the Silurian at the west, there entered from the African
east upon this south Atlantic field, a positive diastrophism whose axis
was well nigh normal to that of the present Atlantis, and along the
shores of this growing land bridge entered an invasion of marine life

74 THE PALEONTOLOGIC RECORD

at the opening of the Devonian time. It seems to have come west-
ward from a dispersion area in Africa and it evidently disseminated
itself without interruption of continuity from the strands which now,
as the Bokkeveld beds of Cape Colony, constitute the only evidence
of marine life in the South African Paleozoic, to those of the Falkland
Islands, two far distant regions which have much more of organic
content in common than do the Falklands and the nearer regions of
Parana, Argentina and Bolivia.

This fauna with its special and peculiar features is, however, spread
through Bolivia, western Argentina, southern Brazil, including Parana
and as far north as Matto Grosso, thence eastward by way of the Falk-
lands to South Africa. From the boreal strands of the period it was
separated by a barrier, often narrow and constituted only of deeper
water, so that of the boreal Devonian we find no evidence much south
of the equator in Brazil nor of the austral Devonian north of that line.
This barrier I believe to have been overpassed at times during the early
part of the Devonian by species which are of wider distribution south
and north but these passages seem to have become rarer as time passed
and as more complete geographic isolation was effected.

There are many evidences in this southern fauna that the land
bridge was accompanied by insular strands which are evidenced by
varying percentages in community of species and by bathymetrical
variations. Apart from these possible island masses, there was clearly
a Devonian land bridge extending from South Africa to the Falklands,
westward into Argentina and northward into Bolivia, embracing also
as continental or island lands parts of the states of Parana, Matto
Grosso and even of Para.

By virtue of the evident derivation of the fauna of this time from
the east along newly forming strands which were, throughout the
period of the Devonian, kept asunder from the Atlantic-European
lands at the north, and by its further development under conditions
of isolation, the fauna presents fundamental contrasts to any develop-
ment of the Devonian elsewhere in the world. It is in itself a unit and
a unit also in relation to the sediments in which it is involved. There
is no earlier Devonian in this southern region nor is there any later
Devonian, for wherever the succession has been determined this austral
fauna, bearing no evidence in itself of a later time stamp than early
Devonian, is overlain by Carboniferous deposits without demonstrated
unconformities between. Deposits and faunas which at the north we
are accustomed to regard as of later Devonian age, are absent at the
south, either because this austral land was broadly above the sea dur-
ing these stages and its strands now lie buried or, as seems much more
probable, this sedimentation represents the total Devonian sedimenta-
tion and this fauna the total Devonian fauna at the south.

TEE PALEONTOLOGIC RECORD 75

I can not in this place analyze the peculiarities which give the
austral fauna of these " Falklandia " strands their special impress but
I may specially cite the trilobites which are astonishingly developed.
I presume any competent student of northern faunas, being shown a
series of these without knowledge of their origin, would pronounce
them' of early Devonian age and yet they are neither northern species
nor, in any large degree, northern genera. While they bear the im-
press of boreal genera and resort to morphologic equivalencies thereto
in fugitive epidermal structures which so richly characterize the boreal
trilobites at this time, they are on the whole constructed on a series of
modified types which hold their fundamental expression while de-
veloping minor details with the chronology normal to their succession
at the north. The Phacopes are seldom true PJiacopes, the Dalma-
nites seldom true Dalmanites, yet the same structural decorations and
extravagances we are familiar with at the north, are distributed freely
through the group. This is all equally true, in qualifying terms, of
the other groups of this fauna, save for the fact that in these -we can
hardly venture to insist so entirely on generic distinctions south and
north. The species differences declare themselves on every hand and
taken as a whole the fauna presents fairly conclusive evidence of hav-
ing derived its distinctiveness through its isolation from the boreal
fauna from which it ancestrally took origin. Yet while it has de-
veloped this character it has also proceeded to maintain a faunal com-
position which declares its age, and a morphological stamp which
shows that it developed all its parts in the proper time and place in the
series.

In predicating geographic isolation as the prime factor in this
regional development of the Devonian fauna, its efficiency should not
be made to seem qualified by an illustration which is striking by
virtue of its contrast with the already well known. There are evi-
dences in plenty that geographic isolation has played a similar role
with even more diverse effect in the development of the boreal faunas
of the same geologic stage. The north Atlantic land bridge was con-
tinuous at this time, as evidenced not alone by the presence of the
Coblentzian fauna in the Atlantic coast rocks but by an array of addi-
tional facts; and it seems very probable that the primary movement of
these northern faunas was from the same African dispersion area as
that of the south.

76 THE PALEONTOLOGIC RECORD

THE CONTINUITY OF DEVELOPMENT

BY DB. W. D. MATTHEW

AMERICAN MUSEUM OP NATURAL HISTORY

/CONTINUITY of development in a broad sense hardly calls for
\-# discussion here. The paleontologic evidence in its favor is so
extensive and so universal that the perfection of the proof is merely a
question of the completeness of the evidence. The question for dis-
cussion is rather as to the method of race development and specific
change — whether continuous, by the slow accumulation of minute in-
dividual variations, definite or indefinite, through the influence of
natural selection or of other causes — or discontinuous by the sudden
appearance of distinct mutations or sports, usually of subspecific or
specific value, sometimes of generic value. This question is much de-
bated nowadays, and it would seem that the evidence from paleontology
ought to be of the first importance in deciding it.

It is very commonly asserted that this evidence is strongly in favor
of discontinuous development. This would mean that new species and
even genera appear, as a rule, suddenly at certain levels, and that the
record of a phylum is not usually a slow continuous change from one
species into another as we pass upward from stratum to stratum; but
that one species has a certain vertical range and is then supplanted by
another species, this in turn by a third, and so on, each successive
stage being an advance over the preceding, but the species overlapping
instead of grading.

I think that there is no question but that in vertebrate paleontology
the evidence taken at its face value does appear to be very distinctly
in favor of discontinuous development. Where we are able to follow a
phylum of Tertiary mammalia through a series of strata in one locality,
we find that the successive stages appear, as a rule, full formed at cer-
tain levels, supplant and replace the more primitive stages, and are in
turn supplanted and replaced by more advanced stages. In former
years, when the records of locality and level were less exact, it was
possible to arrange a series of gradations from one stage to another
among the specimens pertaining to a particular phylum, and to assume
that this gradation corresponded to the levels in the formation at
which the specimens had been collected, and that the specific change
was through continuous gradation. The more exact records of locality
and level and the more extensive and complete collections in recent
years have in general failed to confirm this arrangement. In the great
majority of cases, so far as the record shows, new species appear already

THE PALEONTOLOGIC RECORD 77

distinct, at first sporadically along with the more primitive ones, then
more abundantly, finally replacing the older ones altogether. The
intermediate gradations occur along with the more typical individuals,
but without much definite relationship to intergradation in the succes-
sion of strata.1

We may illustrate from the evolution of the oreodonts, as these are
the most abundant and most completely known of American fossil
mammals.

The earliest known representatives of the phylum are Protoreodon
and Protagrioclicerus from the Upper Eocene Uinta beds of Utah. Both
have very short crowned teeth with five crescents on the upper molar, the
fifth crescent quite distinct. The fourth premolar is not molariform.
For the next stage we have to shift to another formation, 400 miles
away, the White Eiver. In the lowest strata of this formation, the
Titanotherium beds, we find Oreodon, Bathygenys and Agriochcerus,
all with decidedly longer crowned teeth, and no trace of the fifth cres-
cent in the molars. In Oreodon and Bathygenys the fourth premolar
is non-molariform, composed of one inner and one outer crescent, as
usual among Artiodactyls. In Agriochcems it has become imperfectly
molariform with two outer crescents and one inner one. Between the
Uinta and White River oreodonts a sharp break intervenes and no
intermediates are known. From this point we can trace the subphyla
of oreodonts up through a considerable succession in the Big Badlands
of South Dakota and the adjoining region. Oreodon culbertsoni, 0.
bullatus, Eucrotaphus, Eporeodon, Mesoreodon and Merychyus appear
to be approximately successive stages in specialization. The skull is
shortened, the teeth become longer crowned, the tympanic bullse are
enlarged, lachrymal vacuities appear, the limbs are lengthened, the
feet lengthened and compacted and the thumb is lost. But there is
not a continuous intergradation in any of these features as we pass
upward in the beds. Oreodons with small bullse are abundant in the
lower and middle White Eiver, the bullae varying very little in size.
A species with medium-sized bullse occurs occasionally associated with
them. In the Upper White River all the oreodons that I have seen have
bullae of large size. The size of the bulla, then, does not increase con-
tinuously as we go up through the formation. Another and much
more specialized genus of oreodonts, Leptauclienia, suddenly appears
in abundance in the Upper White River. I have seen a single specimen
of this genus from the Middle beds, but it shows no more primitive
features than those of the Upper beds. In the Lower Rosebud, immedi-
ately overlying the White River, species of Eporeodon are common, like
1 The statements of fact herein contained are based partly upon field experi-
ence, chiefly upon the records of some 20,000 specimens of fossil mammals and
reptiles in the American Museum collections, most of which the writer has had
occasion to examine and identify and to post the field records of level and
locality, in the course of cataloguing work.

78 THE PALEONTOLOGIC RECORD

those of the underlying beds except that some of them have well-de-
veloped lachrymal vacuities while others have none. Another new race
also makes its appearance suddenly, and in great abundance, in the
genus Promerycochcerus — structurally derivable perhaps from some
of the older oreodons, but not connected with them by intergrada-
tions. Agriochcerus has disappeared. In the Upper Rosebud the
Oreodon-Merycliyus phylum shows a distinct and marked advance in
the length of the crowns of the teeth; lachrymal vacuities are always
present, the feet are decidedly more compact and elongate. Promery-
cochoerus disappears entirely and is replaced by a very distinct and
more advanced genus Merycochoerus. The Leptauchenia series has dis-
appeared temporarily, to re-appear in the Middle Miocene in a more
specialized genus, Cyclopidius, the last known member of this race.

The Middle Miocene (which should follow the Upper Rosebud) is
unrepresented at the locality under consideration (Pine Ridge, South
Dakota), but elsewhere overlies beds with an equivalent fauna, and
contains Merycochoerus in one locality with Merychyus (both repre-
sented by more specialized species) ; in another locality it contains
instead, Promerycochcerus with Ticholeptus (allied to Merychyus) ; in a
third is found the most highly specialized member of the Merycochoerus
line, Pronomotherium. In the Upper Miocene and Lower Pliocene the
oreodonts become much scarcer, and the skulls and skeletons are known
only in two or three instances. Pronomotherium certainly occurs in
Montana; in Nebraska the Merychyi are more advanced in dentition,
belonging to a distinct subgenus Metoreodon; but whether the skulls
and skeletons are equally different we do not yet know, nor are we in
a position to say whether the change is gradual or saltatory.

But the sum of results in regard to the changes from one stage to
another in this best known group of fossil mammals is either that the
changes are abrupt, constituting clean-cut faunal divisions marked by
the sudden appearance in abundance of a more advanced stage; or else
that the new form replaces the older one little by little, but on the
whole can not be fairly said to be gradually converted into it by
infinitesimal gradations.

This general observation applies, in my opinion, equally well to any
abundant group of fossil vertebrates whose phylogeny is sufficiently
known to make them worth considering.

If, therefore, we consider that the record is continuous where there
is no apparent stratigraphic break, and that the known record really
represents what was going on over the entire continent of North
America, I do not see that we can fairly escape from the conclusion that
new species, new genera and even larger groups have appeared by salta-
tory evolution, not by continuous development.

But — and here lies the crux of the whole question — we have no

THE PALEONTOLOGIC RECORD 79

right whatsoever to make either of these assumptions. And without
them the argument from paleontology for discontinuous development
is almost or quite worthless.

If we consider the general conditions controlling evolution and
migration among land mammals, it will be evident, I think, that —

1. The external conditions favoring the evolution and progress of a
given phylum will not be uniformly developed all over the world or
all over one continent, but will appear first, and be at all times more
advanced, in some circumscribed region in one or another continent, or
simultaneously in limited areas of two or more continents, similarly
situated as to climate, temperature, etc.

2. The animal best able to take advantage of these conditions will
be existing at the time (a) in one continent or (&) in more than one,
or (c) different animals in different continents may be equally able to
adapt themselves to the new conditions.

3. As a result, the new stages of any progressive race will first appear
in a limited area and will spread out from that region as the favoring
environment spreads, the race at the same time continuing its progress
further within that area. This area will be the center of dispersal of
the race. Its location will be conditioned by two factors, the early
appearance of the new environmental conditions, and the existence of
species most able to take advantage of these conditions. Parallelism
and convergence in racial evolution will be conditioned by 2b and 2c

4. Progressive change from uniformly warm to zonal climates dur-
ing the Tertiary must needs have been a great factor in controlling the
progress and distribution of Tertiary mammals. As the new conditions
appeared first at the poles, the chief centers of dispersal of the animals
adapted to them must have been in the northern parts of one or another
of the great northern continents.2 The exact location of the dispersal
center for each race would be variously decided by the complex of
environmental and faunal relations of each, and might be shifted from
time to time by changes in these relations.

5. In the regions distant from the center of dispersal the geological
record, if complete, should show the successive appearance of progres-
sively higher types in a phylum, arriving in successive waves of migra-
tion, and each new type suddenly or gradually displacing the previous
stages. Whether the evolution of a race at its center of diffusion was
continuous or discontinuous, the geological record of its progress pre-
served in any other region would be apparently that of a discontinuous
development. It would be not the actual history of its evolution but

2 To a minor extent in the southern parts of the southern continents, whose
restricted area and isolation prevailed in the writer's opinion throughout the
Tertiary. There is some evidence, however, along the lines indicated in para-
graphs 5 and 6, that Patagonia was the chief center of dispersal of South
American Tertiary mammals.

8o THE PALEONTOLOGIC RECORD

an approximation to it. The closeness of the approximation would be
largely measured by the nearness and accessibility of the region in
question to the center of dispersal of the race.

6. If the evolution at the center of dispersal was sharply discon-
tinuous this discontinuity would be merely emphasized elsewhere. If
on the other hand it was continuous, we should get a near approach
to continuity in a complete evolutionary series from a region not remote
from the center of diffusion of the race, while the evolutionary series
from the same region, of a race whose center of dispersal was remote,
would be sharply discontinuous.

7. Applying these principles to some of our American Tertiary
phyla, we find that certain phyla which we can be sure were of North
American origin, such as the camels, oreodonts and peccaries, do present
a much nearer approach to continuity of development than do other
phyla which we can be sure were of old world origin, such as the deer,
the antelopes or the proboscideans.

I assume that since the oreodonts and peccaries never reached the
old world, and the camels did not reach it till the Pliocene, their centers
of dispersal were well to the south of the Bering Sea connection with
the old world. I assume that since the horses are represented by a
double evolutionary series, one in Europe, a closer one in North America,
their center of dispersal lay far enough north to spread into Europe
on one hand, North America on the other, but that the latter was
nearer or more accessible, i. e., their center of dispersal was north-
eastern Asia or Alaska. On similar grounds the center of dispersal of
most of the Tertiary ruminants might be located in northwest Asia, of
proboscideans in central Asia, of tapirs in northeastern Asia, of rhi-
noceroses northeast Asia and Alaska, of dogs in northwest Canada, and
so on — a series of indefinite guesses which a careful study of the present
geographic distribution, with these principles and the imperfect geologic
data in mind, might serve to fix more definitely.

The point at present to be considered is that in such series as the
camels, oreodonts and peccaries, we do have a sufficiently close approach
to a continuous series to warrant our believing that the true process of
their evolution in the center of their dispersal was a gradual one as
regards the evolution of genera and higher groups, but for aught that
paleontology tells to the contrary, it may have been partly, though not
wholly, discontinuous and saltatory so far as the evolution of new species
is concerned. But the larger and more complete the series of speci-
mens studied, the more perfect the record in successive strata, and the
nearer is the hypothetic center of dispersal of the race, the closer do
we come to a phyletic series whose intergrading stages are well within
the limits of observed individual variation in the race. The known
facts in vertebrate paleontology are, in my opinion, utterly inadequate

THE PALEONTOLOGIC RECORD 81

to prove whether the development of races was or was not wholly con-
tinuous. But I think that the evidence, considered in relation to the
imperfection of our knowledge, goes to show that the gaps were not
normally wide. In exceptional cases I think we have reason to believe
that they were wide (Otocyon, for instance), but in these instances the
evidence is not that of the paleontological record.

THE CONTINUITY OF DEVELOPMENT

BY DB. T. WAYLAND VAUGHAN

U. S. GEOLOGICAL SURVEY

AS nearly every one now admits the validity of the arguments in
favor of the derivations of the existing groups of organisms from
previous somewhat different organisms through the operation of nat-
ural causes, I will not enter upon a discussion of the truth of the
theory of organic evolution, nor will I present the results of phylo-
genetic studies. We will assume evolution to be true, and having made
this assumption, the theories of the process and the underlying causes
may be discussed.

Only two theories of the process of evolution seem to me possible:
(1) Darwin's theory of gradual transformation, or the origin of new
species by the gradual augmentation through successive generations of
the difference between progeny and ancestors; (2) that brought par-
ticularly into prominence by de Yries, the theory of saltation, called by
him mutation, according to which the progeny differs definitely, with-
out intergradation, from the parents, and the difference is perpetuated
by heredity. There are two theories of the cause of evolution. Accord-
ing to the first, that of "Weismann, the cause is within the organisms
themselves, new kinds being produced by an inherent tendency to vary,
this tendency being due to differences in the germ cells of the two
parents; the second theory attributes the cause to the action of the
environment on the organisms inhabiting it.

The fundamental problems of evolution can then be resolved into
two questions. Is evolution through gradual divergence from the
parental type, or by saltation ; and is it caused merely by the differences
in the parental germ-plasms or is heritable variation produced by the
environment acting on the organisms ?

As we are all paleontologists, the question may appropriately be
put, what light can paleontology throw on these problems? It may
perhaps render some assistance in deciding between gradual transforma-
tion and saltation, when superimposed conformable beds contain suffi-
ciently abundant faunas, and perhaps the Tertiary marine formations
of our southern states will yield important results when studied in

82 THE PALEONTOLOGIC RECORD

proper detail. Dr. Dall has already traced more or less completely the
genealogy of some of the species, and I have noticed certain series of
species — the group of Corbula fossata, C. oniscus, C. wailesiana, etc.,
being one of them — deserving thorough study, but the paleontologic
work known to me has not as yet been done with the requisite detail to
form the basis of an opinion. The principal contribution to our gen-
eral knowledge of the evolution of organisms that paleontology can
make, however, is, I believe, in tracing out phylogenetic lines, and I
believe the discovery of the processes and causes of evolution must rest
with the experimental biologist. During the past few years very im-
portant experimental investigations have been made by several men,
and I venture to refer to their results, as I regard paleontology as only
an aspect of biology, and think the students in that field should utilize
the information gleaned in others.

In the study of variation it has been shown that the selection of
fluctuating variations does not carry the species beyond a certain limit,
or the extent of the variation is limited, leading to the conclusion that
new species can not be produced by this method. I may here refer to
ecological surveys and the unreliability of conclusions reached by such
researches. Dr. Merriam several years ago presented a paper " Is Mu-
tation a Factor in the Evolution of the Higher Vertebrates ?" in which
he announced the conclusion that it was not. A critical examination of
Dr. Merriam's data showed he had not sufficient information on which
to base such a conclusion. His data possess value for the study of evo-
lution in that they indicate material that may be profitably investigated
by the experimental method. Attention should also be called to the
probable insufficiency of conclusions reached by studying material from
successive geologic horizons. For instance, suppose that two usually
distinct forms are connected by intermediates. There are no means of
ascertaining whether the intermediates represent transition stages be-
tween the two forms or are examples of blended hybridism.

That new species may originate through saltation is rather definitely
proved ; but that it is the only process is not established.

To consider the causes of the origin of new forms : That new forms
should originate from the old without the action of some new influence
seems to me impossible. The circle of possible combinations of already
existent characters could not be transcended, and there would result by
crossing only all the combinations possible within definite limits; this
would be especially obvious if the de Vries hypothesis of unit-characters
be true. Many experiments to determine the influence of various phys-
ical factors on individuals showed only somatic changes not of heritable
nature and the data accumulated seem definitely to prove that somatic
changes, or acquired characters induced through the soma, are not in-
herited.

THE PALEONTOLOGIC RECORD 83

Weismann made a great contribution to the progress of biology by
focusing attention on the germ cells, and although many of his specula-
tions may be discarded, he was a great stimulator of thought. The work
of MacDougal and Tower seems to show how the environment may act
on the individual through the germ-cells and induce permanent changes
in the progeny.

MacDougal has experimented with species of evening-primroses, by
injecting salt solutions into the seed capsules, and summarizes his con-
clusions in two paragraphs i1

The action of reagents having an osmotic and a chemical effect has resulted
in the induction of mutants in the progeny of Raimannia odorata and (Enothera
biennis. The mutants thus induced have been tested to the second and third
generation and found to come true to their newly assumed characters.

The induction of mutants by the action of reagents is a conclusive demon-
stration of the fact that hereditary characters may be altered by external forces
acting directly upon the reproductive mechanism. The action of the reagents
used experimentally is simulated by many conditions occurring in nature.

Tower has conducted a series of experiments on species of beetles
belonging to the genus Leptinotarsa. He endeavored to influence de-
velopment by the conditions of moisture and temperature during the
germinal stages, and induced changes that were perpetuated in the off-
spring, the changed offspring at least in some instances mendelizing
with the parent species. He presents his conclusions in the following
words :2

A careful consideration of the various lines of experimentation recorded
and of the pedigree cultures and the data from observations in nature irre-
sistibly forces one to the conclusion that in these beetles the only variations of
permanence are germinal, and that evolution is through germinal variations.
Those germinal variations which arise in nature are permanent and the same
variations, of the same degree of permanence, are produced in experiment. The
diverse kinds of evidence produced in this and in preceding chapters all go to
show that under varying conditions of their surroundings these beetles vary,
and that as they become more and more extreme an increasing percentage of
striking, permanent variations is found; and as I have just shown, it is possible
in experiment to produce in this same way a variety of permanent modifications.
From all this evidence, however, there nowhere appears the least trace of a
suggestion of any specific action of the conditions of existence, but everywhere
there appears only the action of environment as a stimulus, while the response
is entirely determined by the organism. All of these variations of purely tem-
porary and of permanent kinds resolve themselves into responses of the organism
to the stimuli of its environment, but the nature of the response is entirely
determined within the organisms. It is true that different intensities of the
same stimuli call forth different responses, but, as is shown in the chapter on

^'Mutations, Variations and Relationships of the (Enotheras," Carnegie
Institution of Washington, No. 81, p. 90, 1907.

a"An Investigation of Evolution in Chrysomelid Beetles of the Genus
Leptinotarsa," Carnegie Institution of Washington, Publication No. 48, p. 295,
1906.

84 THE PALEONTOLOGIC RECORD

coloration, the response is entirely determined within the organism, which is
adjusted to different intensities of stimuli and reacts according to its own
method and on the basis of its own constitution, there being no specific reaction
called forth by a given stimulus.

I conclude in the light of these experiments that the production of heritable
variations, slight or extreme, represents in these beetles the response of the
germ plasm to stimuli. In my experiments these stimuli were external, but
there is no a priori reason why they might not also be internal.

I desire also to call your attention to some remarks by Loeb :3

It is obvious that no theory of evolution can be true which disagrees with
the fundamental facts of heredity. It is the merit of de Vries to have shown
that a mutation of species can be directly observed in certain groups of plants,
and he has further shown that the changes occur by jumps, not gradually. This
fact harmonizes with the consequence to be drawn from Mendel's experiments
that each individual characteristic of a species is represented by an individual
determinant in the germ. This determinant may be a definite chemical com-
pound. The transition or mutation from one form into another is therefore
only possible through the addition or disappearance of one or more of the
characteristics of determinants. If this view can be applied generally, it is
just as inconceivable that there should be gradual variation of an individual
characteristic and intermediary stages between two elementary mutations, as
that there should be gradual transitions between one alcohol and its next
neighbor in a chemical series.

To summarize my own opinions on this subject :

1. I think it very doubtful if paleontology can make any especially
valuable contribution to our knowledge of the process or causes of the
evolution of organisms, and that this field must be surrendered to the
experimental biologist.

2. The results of experimental work indicate that the process is not
by the gradual transformation of species, but by saltation. However,
the former method has not been shown impossible.

3. Experimental investigations also indicate that the cause of evo-
lution is by the environment acting on an organism capable of respond-
ing to it.

4. The causes of evolution are chemical in their nature, and the aid
of the chemist is necessary for their thorough elucidation.

« " The Dynamics of Living Matter," p. 3, 1906.

THE PALEONTOLOGIC RECORD 85

THE BIRTHPLACE OF MAN

BY PBOFBSSOB S. W. WILLISTON

THE DNIVEKSITT OP CHICAGO

ARIOUS writers, from Le Conte to Smith Woodward, have spoken
V of critical or rhythmical periods in evolution, periods when evo-
lutionary forces have acted more vigorously than at others, with inter-
vals of relative quiescence. What these forces are and have been we
are not yet sure, whether extrinsic, that is, environmental or Lamarck-
ian, or intrinsic, that is, orthogenetic, teleological or what not. Per-
haps we shall sometime be more certain of the basal causes of evo-
lution, for the paleontologist at least is not satisfied with the crass
ignorance of our Weismannian friends who impute the beginning of all
things to mere chance. Perhaps when we do know these fundamental
causes we shall understand better why evolution has been rhythmical,
if such was really the case, as some of us believe with Woodward.

But, whether there have been internal forces which have had
chiefly to do with the rhythm of evolution, or whether such critical
periods in the evolution of organic life have been due solely to the
larger cosmic forces, I think we shall all admit that there have been
critical places of organic evolution, places upon the earth where evolu-
tion has advanced with more rapid pace than in others, places per-
haps where environmental conditions have conspired to hasten the de-
velopment of life, or of particular groups, classes or kingdoms of life.

Such a critical period, at least for the higher organisms, it seems to
me, was the early Pliocene ; such a critical place was central Asia ; and
both together resulted in the birth of man.

It is a curious fact that nearly all our domestic animals had their
origin in Asia. It is also a curious fact that the domestic animals are,
almost without exception, the crowning ends of their respective lines
of descent, the most highly specialized of their kinds. The genus Bos,
the most highly developed of the even-toed ungulates began, to the
best of our present knowledge, in the Lower Pliocene of India. And
its four distinctive types likewise first appeared there: the Bubalus
group, including the domestic buffalo of India, and its untamable kin
of Africa; the group that is represented by the domesticated humped
oxen of India and their wild relatives of Africa ; the bison strain which
spread in Pleistocene times almost to the remote corners of the earth;

86 THE PALEONTOLOGIC RECORD

and the true oxen, the most useful of all creatures to man, which
spread to Europe as Bos primigenius, the ancestor of Bos taurus.

The sheep also found their expression point in India, and their
home to-day is central Asia. So too the domestic goat yet lives wild in
western Asia, a less plastic type, but purely Asiatic in origin. Indeed,
of the whole family of Bovidse, Asia was the origin and dispersal center,
and it is a curious fact that it still remains the home of the higher
types while others of lower degree have wandered afar to find their
homes in Africa, Europe and America. The camelids after long ages
of exclusive development in North America migrated to Asia to find
their highest evolution in the true camels, the highest and probably
final stage in the evolution of the family, while their kin, of lower de-
gree, went southward to terminate in the llama and alpaca, the only
mammals among all man's servants which we can say with tolerable
certainty have been entirely beyond the influence, direct or indirect, of
Asiatic environment. The reindeer, the highest of all the cervid fam-
ily, doubtless arose in northern Asia; certainly its home is in part
there, though some of its early kin migrated to America and have left
their descendants in the caribous. And India was the birthplace, as it
is the home, of the pig, whence came originally our domesticated swine.
Whether or not we give to Sus the highest place among the non-rumi-
nant, even-toed ungulate mammals, or to the Babirussa, matters not,
for both are of Asiatic origin.

Of the odd-toed ungulates our domestic horse, Equus cdballus,
stands on the very summit; and Equus caballus arose in Asia, where
its ancestors yet have their wild progeny. And I believe that eventually
we must give to Asia the honor of the birthplace of the genus itself.
And the next lower type of the Equidse, the asses, are of Asiatic an-
cestry, though our domestic species comes from Arabia and Africa,
while the most primitive of the horses yet living found their refuge in
Africa.

Southern or central Asia was the birthplace in early Pliocene times
of the elephants, and was their dispersal center; and, in Elephas indi-
cus, the only domesticated species, we have the last and highest stage in
the evolution of the Proboscidea, and, as is the case with the cape
buffalo, the zebras, wart hogs and others, we find in Africa their only
living kin, of more primitive form and untamable.

Of all the great order of Carnivora the genus Felis admittedly oc-
cupies the highest place. The home of the cats is southern Asia and
there doubtless was their birthplace and the center of their dispersal.
The known paleontological record of the true cats is very meager in-
deed, and doubtless always will be till we know more of the Pliocene
and Pleistocene faunas of Asia. Two of the domesticated cats, the
Siamese and the cheetah, are of immediate Asiatic origin, and our fire-

THE PALEONTOLOGIC RECORD 87

Bide pet, while coming from northern Africa, doubtless arose from
Asiatic forebears in Pliocene or Pleistocene times. What the origin of
the various strains of dogs was we know not, though the wild forms
most nearly allied are living in Asia to-day, and the greyhound and
mastiff almost surely were domesticated in Africa thousands of years
ago. I believe that we may safely give to Asia the honor of the birth-
place of most of the domesticated species in Pliocene or Pleistocene
times.

Nor does it seem that this remarkable evolutional acceleration dur-
ing Pliocene times in central Asia was confined to the mammals alone.
The ostrich, the highest type of ratite birds, arose in central Asia. The
jungle fowl, the highest of the gallinaceous birds and the ancestral
stock of our most valued domestic fowls, arose in India and is still at
home there. The peacock is exclusively Asiatic; the gray goose, the
parent of our domestic geese, has its home in part at least in Asia; and
the same may be said of the ancestors of the domestic doves; while the
domestic duck may have originated there for aught we yet know. The
guinea fowls only are exclusively African, and the turkey American.

Of the reptiles I will venture to say less. But is it not a significant
fact that the highest specialization of the reptilian class appeared dur-
ing Pliocene times in the gigantic extinct ga vials of central Asia?
Certainly the cobra is entitled to a high but unenviable distinction
among the snakes. And Megalobatrachus, the largest of all recent
amphibians, lives in Japan and China. Finally, of the domestic plants
by far the majority come directly or indirectly .from the Asiatic flora.

Have all these and doubtless many other facts of their kind no
significance ? Has man been an exception among so many branches of
vertebrate evolution? The common inference has been that so many
of our domesticated animals and plants come from India because man
first reached civilization there, but the inference is, I believe, quite un-
justifiable. Man was born and attained elemental civilization in Asia
because there was the place of all others upon the earth where evolu-
tion in general of organic life reached its highest development in late
Cenozoic times. No mammals and few other creatures have been do-
mesticated by man in thousands of years, for the simple reason that he
had eliminated all but the most advanced and most adaptable long be-
fore, and none were left to compete with them.

That man originated in the western continent is quite impossible.
There is not a particle of evidence in support of such an hypothesis,
for there is no evidence that either man OB any of his ancestry ever
inhabited the western continent till late in Pleistocene times. Indeed,
so far as North America is concerned, there is much to justify the as-
sertion that the Pliocene and Pleistocene were a period of evolutional
depression here, of relative quiescence when the rhinoceroses, tapirs,

88 THE PALEONTOLOGIC RECORD

and later the camels and horses, found conditions uncongenial and
migrated to Asia, a more favored region.

It has often been assumed that man must have originated in a
warm or tropical climate, to account for the loss of his hairy covering.
But I quite agree with Dr. Matthew, that the loss of hair is almost
conclusive evidence of his origin in a temperate or cold climate where
he found clothing necessary to protect himself from the inclemencies
of the weather. We know of no mammals or birds losing their pelage
or plumage because of tropical conditions, though some may have lost
their hair because of vermin.

Taking all these facts and conclusions into consideration it seems
to me that such evidence as paleontology can at the present time offer
points toward central Asia as the birthplace of Homo, and that the
time of his origin, as a family, was late Miocene or early Pliocene.
If Pithecanthropus be really a true hominid, then we already have evi-
dence of his origin in the Asiatic region. Be it as it may, I confidently
believe that within a very few years the discovery of indubitable links
in man's ancestry will be made in central Asia, in China or northern
India. Perhaps to no region of the world does the paleontologist look
with more eager expectation for the solution of many profound prob-
lems in the phylogenies and migrations of the mammals than to central
and eastern Asia. That there are remains of many extinct vertebrates
awaiting discovery there in the late Tertiary and Pleistocene deposits
has been made evident by the many fragments brought to light by
explorers and travelers.

A field second to none other in the importance and richness of the
results to be expected awaits the paleontologist in Asia.

THE RELATION OF PALEONTOLOGY TO THE HISTORY

OP MAN, WITH PARTICULAR REFERENCE TO

THE AMERICAN PROBLEM

BY PROFESSOR JOHN C. MERRIAM

UNIVERSITY OF CALIFORNIA

CONSIDERED in its broadest aspect, the most important relation
Vy of paleontology to the study of man concerns the support which
it gives to the general theory of evolution of the organic world. If it
be held that we have reason to believe man, with all his highest
qualities, a product of evolution out of so-called lower animal^ types,
then it becomes necessary to have a full knowledge of the history of
man and of the forms preceding him, in order to understand the origin
and the true nature of man's fundamental characteristics as they exist
to-day. On the other hand, if there is reason to believe that man as

THE PALEONTOLOGIC RECORD 89

represented in his highest attributes is entirely apart from nature, the
importance of paleontology, as offering a part of the explanation of the
fundamental characteristics of man, is very greatly diminished. The
value of paleontology would then lie largely in an interpretation of the
setting or environment in which man is developing.

, With these considerations in mind, it appears of the greatest impor-
tance for us to obtain as full a history of the organic world, and as
satisfactory an interpretation of the processes therein concerned, as it
is possible to secure. Particularly is it desirable to have before us a
clear statement of that portion of the paleontological record which
leads from the higher vertebrates through the primate division to man.

One of the important phases of general paleontological work which
must receive special attention is the early history of the primate order
with particular reference to the development of those characteristics
which are most prominent in the human family. We have, as yet,
accumulated too little evidence in this field. Among the characters
which must be followed would be ( 1 ) extraordinary brain development,
(2) the tendency to development of an upright position, (3) the free-
ing of the anterior limbs from the work of locomotion and the develop-
ment in them of extraordinary adaptability. Whatever other interests
one may have, there is certainly no more alluring problem than tracing
from the primitive mammalia into the early primate those peculiar
characters through which later on primitive man began the process of
making nature subservient to himself. We may never know whether
the brain actually grew large first and requisitioned the hands, so that
the animal became bipedal and therefore finally erect in position, or
whether a tendency to erect position was directed by the frequent as-
suming of a vertical position in a tree-climbing ancestor; but it is not
beyond reason to presume that a thoroughly satisfactory paleontological
record might give us an explanation of the origin of these characters.

The later primate history, or that which leads directly to the
human type, is also unfortunately incomplete, though most remarkable
advances have been made in the last few years. More missing links
have already been furnished than science was supposed to require a
few decades ago, but we can hardly be said to have one tenth of the
material that it is desirable to have in order to show the transition from
anthropoid to human, or from pithecanthropoid to the type of Spy or
Neanderthal. European paleontologists are at the present time making
rapid strides in filling the gaps of that portion of our ancestral chain
which falls in the Quaternary system, and we may look for other
important discoveries within the next decade.

It is to be presumed that the greater part of the work on the late
Tertiary and Quaternary history of man will be carried on in the old
world. The writer sees no reason why in this important work Amer-

90 THE PALEONTOLOGIC RECORD

ican paleontologists should not interest themselves to some extent in
investigations now in progress in Europe and Asia, just as American
archeologists have contributed to the success of work on the later his-
tory of man. Whether American paleontologsits, working in their own
field, are to have a part in interpreting the Pleistocene history of man
is a burning question at the present time.

"Whether we find that man was in North America in Pleistocene
time or not, it is certainly true that one of the most important prob-
lems in the general history of the human race concerns the date of
occupation of the western hemisphere by the human family. Discussion
of the numerous finds reported to represent Pleistocene man in North
America are too well known to every one to require particular mention.
It should only be noted in passing, that as yet no specimens represent-
ing either skeletal remains or implements of man found in North
America are generally recognized by geologists and paleontologists as
of Pleistocene age. A careful search through the literature, and the
investigation of many of the actual occurrences, lead the writer to the
conclusion that we have, as yet, nothing in North America which can
be considered as unquestionably representing Pleistocene man.

Also in South America there has been serious discussion of many
interesting finds. The evidence on the whole seems to be more dis-
tinctly in favor of Pleistocene occupation there than is the case in
North America. The discoveries made in recent years in the cave at
Last Hope Inlet, and the numerous remains found in the Pampean
formation at levels very far below the surface, seem difficult to interpret
excepting on the supposition that man was present in South America
before the beginning of the recent epoch.

It is to be presumed that any occupation of South America would
necessarily be through migration by way of the northern continent, and
proof of the presence of man in South America in Pleistocene time
would be tantamount to proof that he was in North America at least
as early. This suggestion does not, of course, take into account the
theories of Ameghino to the effect that man is possibly derived from
some of the South American monkey forms. Another suggestion made
by Ameghino would give us an immigration of old world forms, pos-
sibly with ancestral man, coming into the southern continent in com-
paratively late time, by some other route than North America.

In the consideration of man's history in America, it is particularly
important to notice the probable relation of migrations of the human
family to migrations of other groups of mammals. The presumption
is that the migrations of primitive man were caused or occasioned
largely by influences of the same sort as have produced the spreading
out or migration of many other mammalian types. It becomes then
particularly necessary to discover exactly when the more recent migra-

THE PALEONTOLOGIC RECORD 91

tions of mammals into the North American continent have taken place,
and, so far as possible, the exact routes of migration. This problem is
in a large part paleontological, requiring for its interpretation a satis-
factory account of the paleontology of vertebrates, invertebrates and
plants of North America and of Asia, with particular reference to the
relations of adjacent areas. We must also have, associated with this
information, a full statement of the crustal movements in these regions
as interpreted by the stratigraphic geologists and the physiographers.

Through the accumulated efforts of paleontologists in this country
particularly, we have already a considerable mass of evidence bearing
on the general relationships of the faunas of North America and Asia
in comparatively recent geological time, but the detail of the problem
is, as yet, scarcely indicated. Particularly for Pleistocene and Pliocene
time our knowledge of the faunal succession is exceedingly meager, and
we can scarcely expect to know anything satisfactorily until the Pleisto-
cene mammalian paleontology of America has been worked out in
detail. This work must be followed or accompanied by similar studies
of the mammalian faunas of western and southern Asia. When this is
completed we shall know the time of the various migratory movements,
the nature of the faunas which migrated, the character of the land areas
over which they have passed, and the climatic conditions which obtained
along the routes of migration. The presumption is, that when this is
done we shall have actual evidence of the time of man's occupation of
North America.

Viewed in the large, and without regard to the detail which has
just been indicated, it seems possible to present several reasonable
conclusions with reference to the probable period of migration of man
to America. It is shown by study of a map of linguistic stocks of the
western hemisphere that the northern and southern continents taken
together may be divided into between one hundred and two hundred
provinces, based on the number of stocks represented. These lan-
guages vary greatly in their structure, and are not similar to the
languages of other parts of the world. There is every reason to
believe that a large percentage of them have been developed by lin-
guistic differentiation which occurred since man first occupied this con-
tinent, and that measured in years the time required for this differentia-
tion has been long. On the other hand, considering the American con-
tinent as a' whole, we find that the greatly differing physical environ-
ments are not reflected to any extent in different physical types of people
occupying this region. That the human family is not exempt from
physical differentiation, such as is almost universally indicated in mam-
mals which have for some time been distributed over large areas with
varying environments, is clearly shown by the map of the old world.
In that region the human race is known to have been spread over a wide

92 THE PALEONTOLOGIC RECORD

area for a long period, and we find several greatly differing human
physical stocks in different geographic regions, just as we find differing
stocks of mammals and birds.

With the lack of physical diversity among the people of the western
hemisphere, there is also noticeable a resemblance of the whole group
to the people of the adjacent region of Asia. Judged by the standards
of differentiation which we obtain through a study of the history of
geographical distribution of other mammalian groups, we have every
reason to think that the people of America are immigrants who came
from the Asiatic region and spread themselves over America after the
period of the first great physical differentiation of the race, and so
recently that a second stage of physical differentiation has not yet had
time to develop. On the other hand, the time measured in years has
been long enough so that linguistic differentiation could take place.

Inasmuch as a large part of human history falls within the Quater-
nary period, the question naturally arises as to whether the principal
migrations of man to the American continent occurred before, during
or after the Glacial epoch.

As primates are naturally animals of a warm or temperate zone,
it is hardly to be presumed that primitive man came to America during
the ice age, though there is a possibility of immigration in some of the
interglacial epochs. Judging from what is suggested through study of
physical differentiation, it appears improbable that man came over as
early as the epoch preceding the ice age. In other groups of animals
spread over large areas, marked physical differentiation has ordinarily
taken place in a space of time comparable to the Glacial epoch. Had
man been present in America during this long period, widely differing
physical types would almost certainly have developed. On the whole it
seems most probable that he arrived after the end of the last division
of glacial time, or very near the beginning of the present epoch.
Whether his arrival is shown to have occurred just before or just after
the beginning of this epoch remains to be determined.

In conclusion it seems desirable to call the attention of paleontolo-
gists once more to the important part which their work must play in
obtaining the information which we need with reference to the history
of man and his antecedents. Only a small beginning has been made,
and the results which must come are of great importance in the large
problem of man's relation to nature. It is necessary that paleontolo-
gists keep the subject before them, in order to make certain that all
information bearing upon it may be recognized as it becomes available,
and be given its proper place in relation to other evidence now at hand.

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