Committee on Publication
Barton W. Evermann
Chairman and Editor
C. Hart Merriam Henry Gannett
A. D. Hopkins Arthur L. Day
PROCEEDINGS
OF THE
Washington Academy of Sciences
Vol. VIII
1906
WASHINGTON
May, 1906-MARCH, 1907
AFFILIATED SOCIETIES.
Anthropological Society of Washington.
Biological Society of Washington.
Botanical Society of Washington.
Chemical Society of Washington.
Columbia Historical Society.
Entomological Society of Washington.
Geological Society of Washington.
Medical Society of the District of Columbia.
National Geographic Society.
Philosophical Society of Washington.
Society of American Foresters.
Washington Society of the Archaeological Institute
of America.
Washington Society of Engineers.
3L1 L
PRE98 OF
The New Eh* Printing Company
Lancaster, Pa.
CONTENTS.
PAGE
Mexican, Central American, and Cuban Cambari ; by A. E.
Ortmann i
The Geodetic Evidence of Isostasy ; by John F. Hayford . . 25
Distribution of the Lymphatics in the Head, and in the Dorsal,
Pectoral and Ventral Fins of Scorpaenichthys marmoratus ; by
Wm. F. Allen 41
Evidences bearing on Tooth-cusp Development; by James
Williams Gidley 91
New Starfishes from the Pacific Coast of North America; by
Walter K. Fisher in
Notes on Japanese Hepaticae ; by Alexander W. Evans . . 141
A Study of Rhus glabra; by Edward L. Greene . . . 167
Aspects of Kinetic Evolution ; by 0. F. Cook . . . . 197
Age of the Pre-volcanic Auriferous Gravels in California ; by
J. S. Diller 405
Aerial Locomotion ; by Alexander Graham Bell . . . 407
On a Collection of Fishes from Buenos Aires; by Carl H. Eigen-
mann ........... 449
Histology and Development of the divided Eyes of certain Insects ;
by George Daniel Shaf er 46 1
Index ........... 487
ILLUSTRATIONS
FACING PAGE
I. Lymphatic System in Scorficenichthys marmoratus 90
II. Portion of same continued 90
III . Portion of same continued 90
IV. Cheek Teeth of Living Insectivores and Bats 108
V. Teeth of Mesozoic Mammals no
VI. Japanese Hepaticae 162
VII. Japanese Hepaticae 164
VIII. Japanese Hepaticae .. 166
IX. LilienthaFs and Chanute's Gliding Machines 448
X. Langley's Aerodrome No. 5 in flight May 6, 1896 448
XL The Accident to Langley's Aerodrome 448
XII. The Wright Brothers' Gliding Machine 448
XIII. Bell Tetrahedral Kites 448
XIV. The Bell Tetrahedral Kite, "Frost King" 44S
XV. The Frost King flying in a Ten-mile Breeze 448
XVI. The Bell Tetrahedral Kite " Siamese Twins," front view. 448
XVII. The Bell Tetrahedral Kite " Siamese Twins," rear view. 448
XVIII. A Floating Kite, adapted to be towed out of the water .. 448
XIX. The Dirigible Airships " Patrie " and " Villede Paris".. 448
XX. Count von Zeppelin's Airship 448
XXI. Placostomus lafilatce Eigenmann 458
XXII. Loricaria vetula Cuvier & Valenciennes 45 S
XXIII. Po?nolobus melanosto?nus, Geophagus australe and
Batrachops scottii 45 8
XXIV. Divided Eyes of Certain Insects 480
XXV. Divided Eyes of Certain Insects 482
XXVI. Divided Eyes of Certain Insects 4S4
XXVII. Microphotographs of Insect Eyes 4S6
WASHINGTON ACADEMY OF SCIENCES
OFFICERS ELECTED JANUARY 17, 1907
Presiden t
Charles D. Walcott
Vice-Presidents
From the Anthropological Society W. H. Holmes
Archceological Society John W. Foster
Biological Society Leonhard Stejneger
Botanical Society David White
Chemical Society F. W. Clarke
Columbia Historical Society A. R. Spofford
Entomological Society A. D. Hopkins
Geological Society C. Willard Hayes
Medical Society D . Kerfoot Shute
National Geographic Society Willis L. Moore
Philosophical Society John F. Hayford
Society of Engineers F. H. Newell
Society of American Foresters Gifford Pinchot
Secretary
Frank Baker
Class 0/1908
Barton W. Evermann
L. O. Howard
O. H. Tittmann
Treasarer
Bernard R. Green
Managers
Class 0/1909 Class of 1910
L. A. Bauer Frederick V. Coville
C. F. Marvin J. S. Diller
C. HartMerriam Geo. M. Kober
Standing Committees for 1907
Committee on Meetings
L. A. Bauer, Chairman
C. W. Hayes
J. D. Morgan
F. V. Coville
E. B. Rosa
Committee on Publication
Barton W. Evekmann, Chairman
C. Hart Merriam
Hfary Gannett
A. D. Hopkins
Arthur L. Day
Vlll
WASHINGTON ACADEMY OF SCIENCES
Committee on Finance
Tiieo. N. Gill, Chairman
Bernard R. Green
E. M. Gallaudet
L. O. Howard
Geo. O. Smith
Committee on Rules
O. H. Tittmann, Chairman
A. K. Fisher
J. H. Gore
Committee on Membership
F. V. Coville, Chair 7na?t
Willis L. Moore
C. K. Wead
Lyman J. Briggs
Geo. W. Littlehales
D. K. Shute
Committee on Building
Geo. M. Kober, Chairman
Lyman J. Briggs
Arnold Hague
Geo. T. Vaughan
David White
Committee on Functions
C. F. Marvin, Chairman
F. W. Clarke
R. A. Harris
Committee on Affiliation
F. W. Clarke, Chairman
Whitman Cross
J. F. Hayford
C L. Marl att
E. W. Nelson
NINTH ANNUAL REPORT OF THE SECRETARY, 1906.
To the Washington Academy of Sciences :
Mr. President and Members of the Academy : During the period
from January iS, 1906, to January 17, 1907, the Academy has held
the following meetings :
January iS, 1906 — Annual meeting for the election of officers,
etc.
February 6, 1906 — Meeting to hear an address by Prof. Harry
Fielding Reid on " The Various Methods of Estimating the Age of the
Earth." This was discussed by Prof. Henry F. Osborn, Prof. Simon
Newcomb and Mr. Bailey Willis.
February 23, 1906 — Meeting to hear a paper on u Old Age, Its
Nature and Cause," by Prof. Chas. Sedgwick Minot. Discussed by
Prof. A. F. A. King, Marshall A. Price and Dr. Harvey W.
Wiley.
February 27, 1906 — Meeting to hear the annual address of the
President of the Anthropological Society, Dr. Geo. M. Kober, on
" The Health of the City of Washington."
April 14, 1906 — Meeting to hear a paper by Mr. John F. Hay-
ford, on " The Recent Geodetic Evidence of Isostasy and its bearing
upon the greater Geologic Problems." Introduced by Mr. O. H. Titt-
mann and dircussed by Major C. E. Dutton, Dr. C. Willard Hayes
and others.
May 17, 1906 — Meeting to hear an address by Prof. Francis Gano
Benedict on "The Respiration Calorimeter and the Factors of Human
Nutrition." Discussed by Dr. J. B. Nichols, Dr. E. B. Rosa, and
Dr. C. F. Langworthy.
November 27, 1906 — Meeting to hear an address by Prof. Chas.
Hubbard Judd on " Visual Perception." Discussed by Prof. G. M.
Stratton.
December 13, 1906 — Meeting to hear an address by Dr. Alexander
Graham Bell on " Aerial Locomotion." Discussed by Mr. C. F.
Manly and Prof. A. F. Zahm.
At the meeting of November 27, amendments to the By-Laws were
adopted providing for a class of life members.
The Board of Managers has held eight meetings for the transaction
of business.
X WASHINGTON ACADEMY OF SCIENCES
Mr. Alexander Graham Bell having resigned the office of Vice-
President, the National Geographic Society nominated in his place
Mr. Willis L. Moore, who was duly elected by the Board.
Delegates were sent to represent the Academy at the celebration of
the 200th anniversary of Franklin's birth held by the American Philo-
sophical Society, April 17-20, 1906.
A Committee of Arrangements has been appointed to prepare for
the reception of the International Zoological Congress which is to
visit Washington in August, 1907.
At the time of the passage by Congress of the bill establishing a
Board of Education in the District of Columbia the Managers sent to
each Justice of the Supreme Court of the District of Columbia a reso-
lution recommending the appointment on the Board of one or more
members of recognized ability and attainment in some of the natural
sciences and who are thoroughly familiar with modern methods of
scientific teaching. Dr. Barton W. Evermann was subsequently
appointed.
Vol. VII of the Proceedings has been completed and issued during
the year and Vol. VIII is well advanced toward completion. A new
catalogue of the members of the Academy and Affiliated Societies has
been projected and is now in course of preparation.
Application having been made by the Washingten Society of Engi-
neers for admission to the group of Affiliated Societies it was favor-
ably considered by the Board. A vote of the Academy is now being
taken by correspondence, as provided by Art. VI, Sec. 2, of the By-
Laws.
The Academy has suffered the following losses by death during the
year :
H. G. Ogden died February 26, 1906.
S. P. Langley died February 27, 1906.
The statistics of membership at this date are as follows :
Patrons :
At date of last report S
Elected during the year o S
Honorary Members :
At date of last report o
Elected during the year 1 1
Life Members :
At date of last report o
Elected during the year 1 1
NINTH ANNUAL REPORT OF THE TREASURER XI
Resident Members :
At date of last report 167
Elected and qualified during the year 10
Transferred from non-resident list 1 178
Deceased 2
Resigned 4
Transferred to honorary list 1 7 171
Non-resident Members :
At date of last report 173
Elected and qualified during the year 13 186
Resigned 9
Transferred to life list 1
Transferred to resident list 1 11 175
356
Counted twice 1
Total membership January 17, 1907 355
Respectfully submitted,
Frank Baker,
Secretary.
January 17, 1907.
NINTH ANNUAL REPORT OF THE TREASURER, 1906.
To the Washington Academy of Sciences :
The Treasurer has the honor to submit the following annual report
of receipts, disbursements, and funds in his hands for the year from
January 1, 1906, to December 31, 1906, when the account was closed
and balanced :
The receipts during the year have been as follows :
Dues of resident members, 1903 $ 5.00
Dues of resident members, 1904 10.00
Dues of resident members, 190^ 65.00
Dues of resident members, 1906 710.00 $ 790.00
Dues of non-resident members, 1904 5-oo
Dues of non-resident-members, 1905 30.00
Dues of non-resident members, 1906 775.20
Dues of non-resident members, 1907 ^.00 S15.20
xii WASHINGTON ACADEMY OF SCIENCES
Sales of Publications and refunds from authors for re-
prints, etc 164.56
Interest on bank deposits and investments 622.97
Cash returned by Committee on Meetings, balance not
used expenses meetings of November 27 and December
13, 1906 9. 84
Total receipts $2,402.57
The amounts and objects of the expenditures were as follows :
Paid on account of expenses incurred in previous year, 1905 :
Secretary's office $ 6.40
Meetings I7'7°
Publishing Vol. VII of Proceedings 441.00
Editor's office, 1905 500.00 965.10
Paid on account of expenses of the past year, 1906 :
Secretary's office $ 33.71
Treasurer's office 101.39
Meetings 291.09
Publishing Vol. VIII of Proceedings 632.07
Greeting to American Philosophical Society
of Philadelphia 15.00 $1,073.26
Total disbursements $2,038.36
Statement of Account.
Balance from last annual statement $ 810.^3
Receipts duringthe year 2,402.57
To be accounted for $3,213.10
Disbursements during the year 2,038.36
Cash balance on hand $1,174.74
Of this balance $195.09 belongs to the permanent fund, leaving
$979.65 available for general expenses.
These funds are on deposit with the American Security and Trust
Company, drawing 2 per cent, interest.
The only outstanding bills within the knowledge of the Treasurer
are :
Editor's office, 1906 $500.00
Expenses of meetings 8.75
Expenses of Secretary's office 27.00
NINTH ANNUAL REPORT OF THE TREASURER Mil
and the completion and binding of Vol. VIII of the Proceedings,
which, it is understood, will not exceed the balance of funds on hand.
Dues remain unpaid as follows :
For 1902, $ 10
*903i x5
i9°4. 35
1905, 60
1906, 250
$37o
The investments are the same as stated in the last annual report,
namely :
Cash on hand belonging to permanent fund $ 195.09
809 shares stock of Washington Sanitary Improvement Co. 8,090.00
1 share stock of Colonial Fire Insurance Co 100.00
2 shares stock Scheutzen Park Land & Building Associa-
tion, par value $100, actual value doubtful, say $44.00 SS.00
2 first trust notes of Laura R. Green, 3 years, 5 per cent.
interest, for $2,000, and $1,500 3,500.00
1 first trust note of Aurelius R. Shands, 3 years, 4^ per
cent, interest 444.44
$12,417.53
The two notes of Laura R. Green are deposited with Thos. J.
Fisher & Co., Washington, D. C, for collection of interest, and the
remainder of the investments are in the Academy's safe deposit box at
the Union Trust Company.
Respectfully submitted,
Bernard R. Green,
Treasurer.
January 5, 1907.
PROCEEDINGS
OF THE
WASHINGTON ACADEMY OF SCIENCES
Vol. VIII, pp. 1-24. May 3, 1906.
MEXICAN, CENTRAL AMERICAN, AND CUBAN
CAMBARI.
By A. E. Ortmann,
Carnegie Museum, Pittsburg, Pa.
The larger part of the material, upon which the following
notes are based, was loaned to the writer by the Museum of
Natural History of Paris through the kindness of Professor E.
L. Bouvier, for which I wish to express my most sincere thanks.
I am also under obligations to the Academy of Natural Sciences
of Philadelphia, where I was granted the privilege of examin-
ing the crawfish-collections ; some of this material has also been
used for the following notes.
I. Subgenus PARACAMBARUS, new subgenus.
Paracambarus, new subgenus of Potamobiidas ( Cambarus
■paradoxus ) .
Sexual organs of male with the two parts in close apposition
to their tips ; in the male of the first form, both tips are shortly
pointed and horny ; in addition there is, on the posterior margin
of Ire inner part, at a short distance from the tip, a long and
strong, horny spine. Anterior margin of sexual organs with-
out shoulder. Male with hooks on the ischiopodite of fourth
perciopods only. Female with a spin form process on the
sternum between the fifth perciopods.
The presence of hooks only on the fourth pereiopods of the
male, and the peculiar spine of the sternum of the female dis-
Proc. Wash. Acad. Sci., May, 1906. 1
2 ORTMANN
tinguish this subgenus at once from all other Cambari} The
male copulatory organs are also different from those of any-
other species of the genus, but they approach, to a certain de-
gree, those of the subgenera Procambarus and Cambarus.
This is the sixth subgenus distinguished by the writer within
the genus Cambartis.2 It may be well to point out here the
most important characters of these six subgenera by arranging
them into a key.
KEY FOR THE SUBGENERA OF CAMBARUS.
a. Outer and inner part of male sexual organs in close apposition up
to their tips ; tips in the male of the first form horny or soft,
with accessory horny spines.
b. Both tips of male organs horny; inner part with a strong acces-
sory spine on posterior margin. Female with a spine on
sternum between fifth pereiopods. Male with hooks on ischi-
opodite of fourth pereiopods Paracantbarus.
bb. Both tips of male organs soft, with accessory horny spines on
one of them. Female without spine on sternum between fifth
pereiopods. Male with hooks on ischiopodite of third, or of
third and fourth pereiopods.
c. Male organs with a small accessory spine, belonging to the
inner part ; anterior margin with a shoulder near the tips ;
male with hooks on third pereiopods Procambarus.
cc. Male organs with one to three horny accessory spines (often
tuberculiform or plate-like), belonging to the outer part;
shoulder generally absent, if present, remote from the tips ;
male with hooks on third, or on third and fourth pereiopods.
Cambarus.
aa. Outer and inner part of male sexual organs distinctly separated
for a more or less considerable distance at the tips; outer part,
in the male of the first form, entirely transformed into a horny
spine, rarely with a soft secondary spine.
d. Outer part of male organs consisting of two rather long spines,
one horny, the other soft, bristle-like ; male with hooks on
second and third pereiopods Cambarellus.
dd. Outer part of male organs formed by one single horny spine;
1 Except Cambarus montezuma; (subgenus Cambarellus).
2 See Proc. Amer. Philos. Soc, XLIV, 1905, 96 and 97, and Ann. Carnegie
Mus., III. 1905, 437.
MEXICAN, CENTRAL AMERICAN, AND CUBAN CAMBARI 3
male generally with hooks on third pereiopods, rarely on third
and fourth pereiopods.
e. The two parts of the male organs shorter or longer, often very
long, straight, divergent, or gently curved Faxonius.
ee. The two parts of the male organs with rather short, sharply
recurved tips, forming about a right angle with the basal
part Bartonius.
Paracambarus stands very isolated within the genus. We
have regarded Procambartis as representing to a degree the old
original stock of the genus. Paracambarus is more closely
related to Procambarns than to any other subgenus, but there
is no direct genetic connection imaginable. Although probably
derived from common ancestors, each has apparently gone its
own way of development, Paracambai'us being rather extreme
and one-sided in certain characters.
The only species, upon which this subgenus is founded, is
new, and the description is as follows :
CAMBARUS (PARACAMBARUS) PARADOXUS,
new species.
Diagnosis : Rostrum subovate, slightly concave above, mar-
gins converging, without marginal spines, contracted into a
short, triangular acumen ; carapace without lateral spines ;
areola wide, slightly longer than half of the anterior section of
the carapace ; first pereiopods with the chela subovate, swollen ;
palm subcompressed, covered with strong, subsquamose tu-
bercles, which form, near the inner margin, two to three irregu-
lar, longitudinal rows ; fingers longer than the palm, with tu-
bercles at the bases, and a longitudinal rib on the outer faces ;
cutting edges with strong, irregular tubercles. Carpopodite
granulated and tuberculated, spinose on inner and lower side.
Only fourth pereiopods hooked in the male. First abdominal
appendages of male with both parts in close apposition to the
tips ; tips horny in the male of the first form, both with a slight
outward and backward curve ; inner part on posterior side, a
short distance from the tip, with a strong and long, spiniform
process. Annulus ventralis, of the female forming an almost
semicircular, transverse elevation, convex anteriorly, depressed
4 ORTMANN
and concave posteriorly. Sternum between fifth pereiopods
with a strong, triangular, anteriorly directed, spiniform process.
Description of adult male of 'Jirsl form :
Rostrum subovate, upper face slightly concave, margins
elevated, converging, without marginal spines, contracted into
a short, triangular acumen, which is shorter than the width of
the rostrum at the base. Postorbital ridges subparallel, ante-
riorly without spines. Carapace rather compressed, covered
with punctations, which are rather large on gastrical region and
base of rostrum ; sides of carapace finely granulated, granules
more distinct on hepatical region. Suborbital angle blunt.
Branchiostegal spine short, tuberculiform ; cervical groove
slightly sinuate ; no lateral spines on the sides of the carapace ;
areola wide, with four to five irregular rows of punctations,
slightly longer than half of the anterior section of the carapace
(including rostrum).
Abdomen as wide as, and longer than, carapace ; basal seg-
ment of telson with three or four spines on each side ; posterior
segment semicircular.
Eftistoma with anterior part broadly triangular, sharply
pointed in the median line ; lateral margins concave anteriorly,
convex posteriorly ; aniennal scale broad, greatest width ante-
rior to the middle ; flagellum rather short, reaching to the second
or third abdominal segment.
First -pcreio-pods rather stout; hand elongated-ovate, slightly
compressed ; surface with strong, subsquamiform tubercles, dif-
fering in color from the surface of the hand, being, in alcoholic
specimens, bluish black, while the rest of the hand is brownish
yellow ; tubercles irregularly distributed, but with the tendency
to form two or three rows near the inner margin, and slightly
more crowded on the rounded outer margin of the hand ; on
under surface of hand, the tubercles are more remote from each
other, and not colored differently from the surface. Fingers
distinctly longer than the palm, slightly gaping at the bases,
each with a smooth longitudinal rib on outer and inner face,
included by rows of punctations ; tubercles of palm extending
upon bases of both fingers, and forming a short row upon prox-
imal part of outer margin of movable finger ; cutting edges with
MEXICAN, CENTRAL AMERICAN', AM) CUBAN CAMBARI 5
irregular, strong tubercles ; tips horny, and generally another
horny tooth a short distance from tip on cutting edge of the im-
movable finger.
Carpopodite short, with a longitudinal sulcus above, granu-
lated and tuberculated ; tubercles forming one or two spines on
distal end of inner margin, and two other spines on lower sur-
face, one on anterior margin, the other at the lower articulation
with the hand. Meropodite granulated, but almost smooth on
the larger portion of outer and inner face ; several strong tuber-
cles at distal end of upper margin ; inner and outer lower
margins each with a row of strong, spiniform tubercles, the
outer row shorter. All the tubercles of the chelipeds appear
squamiform on account of a fringe of short, stiff hairs at their
anterior edges.
Ischioftodite of fourth fierct'oflods with a strong hook ; this
hook has a subcompressed, broad base, and is subcompressed,
but narrower at the tip, and is slightly twisted. The ischiopo-
dite of the third pereiopods is without hook, and there is only
a slight, almost imperceptible elevation at its inferior margin.
Fig. i. Cambarus paradoxus, sp. n. First pleopod (right side) of male (I).
a, outer view; b, inner view. Enlarged about tour times.
First pleopods (see Fig. i) reaching to the middle of the bases
of the third pereiopods, stout, slightly curved backward ; inner
and outer parts subequal, in close apposition to the tips. Both
tips curved gently backward, and slightly outward, horny ;
inner part, on posterior margin, at a short distance from the tip,
with a strong, spiniform process, going off at an acute angle,
and being longer than the two tips of this organ.
Male of the second form : Tips of inner and outer parts of
6 ORTMANN
sexual organs, as well as the spiniform process, not horny ;
hook of fourth pereiopods smaller and weaker.
Female: Similar to the male, but chelae not so strong. An-
nulus ventralis transversely semicircular, anterior margin con-
vex, elevated, with a curved longitudinal fissure ; posterior
margin with a subtriangular depression. Sternum between the
fifth pereiopods with a triangular, spiniform process, directed
forward, which fits into the depression of the annulus.
Aside from the peculiarities offered by the subgeneric charac-
ters, this species is also remarkable for its chelae, which differ
in a number of features from the types of chelae usually seen
in the genus Cambarus.
Measurements :
The following are the dimensions of the three type-speci-
mens : c? (I) : total length 48 mm.; carapace 23; anterior part
15, posterior part 8 ; abdomen 25 ; hand 17, palm 7, fingers 10 ;
width of hand 7. — c? (II) : total length 48.5 mm.; carapace
23.5, anterior part 15.5, posterior part 8 ; abdomen 25 ; hand 16,
palm 6.5, fingers 9.5 ; width of hand 6. — 9 : total length 48
mm. ; carapace 23, anterior part 15, posterior part 8 ; abdomen
25 ; hand 15, palm 6.5, fingers 8.5 ; width of hand 6.
The largest cT (I) measures 51 mm., and the largest 9
54.5 mm.
Locality : Sierra de Zacapoaxtla, State of Puebla, Mexico. —
L. Diguet coll. 1904 (" ruisseaux torrentueux des montagnes, a
le cafiada de Tetela de Ocampo"). (Mus. Paris, numerous
specimens.)
II. CAMBARUS (PROCAMBARUS) PILOSIMANUS,
new species.
Diagnosis : Rostrum subplane, with a marginal spine on each
side ; carapace with two lateral spines on each side ; areola nar-
row, as long as, or longer than, half of the anterior section of
the carapace ; first pereiopods with the chela long, subcylindri-
cal, slightly compressed, covered with tubercle-like granules ;
fingers about as long as the palm, each with a smooth longi-
tudinal ridge on the outer side, for the rest densely pilose on
MEXICAN, CENTRAL AMERICAN, AND CUBAN CAMBARI 7
outer and inner sides, the hairs extending upon the distal part
of the palm. (In young individuals, the pilosity is less marked
or even absent.) Carpopodite and meropodite granulated, and
with a few granules developed into sharp spines on the inner
and lower sides (indistinct in old individuals) ; third pereiopods
hooked in the male ; first abdominal appendages of male with
inner part pointed and straight, longer and much thinner than
the broad and blunt outer part; shoulder of anterior margin
only slightly developed ; inner face flattened and only slightly
dilated. Annulus ventralis of the female conically elevated.
Description of adult male of the first form :
Rostrum subplane, margins elevated, gradually convergent,
slightly convex, chiefly so anteriorly, with a distinct marginal
spine on each side a short distance from the tip ; acumen trian-
gular, rather short, shorter than width of rostrum at base ; mar-
gins of acumen hairy ; postorbital ridges subparallel, ending
in a spine anteriorly ; carapace compressed, thickly and finely
punctate, and finely granulated on the sides ; suborbital angle
blunt ; branchiostegal spine small ; cervical groove sinuate, two
lateral spines on each side behind the cervical groove ; areola
very narrow, but not obliterated, with one irregular row of punc-
tations, longer than half of the anterior section of the carapace
(including rostrum).
Abdomen about as long and as wide as the carapace; basal
segment of telson with two (rarely three) spines on each side ;
posterior segment broadly rounded, short.
Epistoma with anterior part triangular, obtuse ; antcnnal
scale broad, broadest in the middle ; flagellum longer than the
carapace, but shorter than the whole body.
First pereiopods elongated, subcylindrical ; hand elongated,
slightly compressed, with subparallel margins, widest at the base
of the fingers ; surface thickly granulate, granules tuberculi-
form, rounded, a-ery distinct, subequal ; fingers about as long
as the palm, both on outer faces with a smooth longitudinal
ridge ; for the rest, the fingers are thickly pilose on outer and
inner side, the pilosity extending a short distance upon the palm
on both faces ; carpopodite subcylindrical, with an indistinct,
longitudinal sulcus on upper side ; granulated everywhere, gran-
8
ORTMANN
ules largest on inner side ; a granule each at the distal end of
inner margin, on the anterior margin of inner side, and at distal
end of lower margin, more strongly developed and subspini-
form ( often only indistinctly so ) ; meropodite granulated, gran-
ules indistinct on outer and inner faces ; a subspiniform one
near distal end of upper margin, and several subspiniform ones
on lower side (often indistinct).
Ischiopodite of third pair of pcreiopods with a strong hook.
Fig. 2. Cambarus filosimanus, sp. n. First pleopod (right side) of male (I),
a, outer view; l>, inner view. Enlarged about four times.
First pleopods (see fig. 2) rather short, straight ; anterior
margin with an indistinct, blunt shoulder near the tips ; outer
and inner part in close apposition to their tips ; tip of outer part
very blunt and rounded, slightly compressed in the antero-
posterior direction ; tip of inner part straight, thin and pointed,
distinctly longer than outer part ; at its base, on the anterior
side, in front of the shoulder, there is a short, procurved, horny
spine ; inner part flattened on inner face, slightly dilated, with
hairs radiating from an indistinct oblique rib.
Male of second form: The horny spine of the copulatory
organs is replaced by a small, soft, blunt tubercle.
Young males (of first or second form), less than 50 mm. total
length, differ in the areola, which is about as long as the ante-
rior section of the carapace ; chelipeds shorter and weaker,
their granulations indistinct; they have short, scanty hairs, and
the fingers are not pilose; carpopodite with well developed
spines; meropodite also with sharp spines; one near distal
end of upper margin, one at distal end of outer lower margin,
and one or two at distal end of inner lower margin ; besides,
MEXICAN, CENTRAL AMERICAN, AND CUBAN CAMBARI 9
there are one to three more, forming an irregular row in the
middle of the lower side.
Female: Young females are like young males, older indi-
viduals have the pilosity of the fingers well developed, but the
chelipeds are less elongated than in old males, and consequently
comparatively broader. The spines of meropodite and carpop-
odite of the chelipeds also have the tendency to disappear in
very old individuals. Annulus ventralis a blunt, low, sub-
conical tubercle, with an S-shaped longitudinal fissure.
Mcasurc?nents :
The following are the measurements of the two type-speci-
mens : cT (I): total length 72 mm. ; carapace 36, anterior sec-
tion 23, posterior section 13 ; abdomen 36; length of hand 30,
width of hand 8. 9 : total length 62 mm.; carapace 31, an-
terior section 20, posterior section 11 ; abdomen 31 ; length of
hand 19, width of hand 6.
The largest females measure 68 mm. ; the largest male is the
above type.
Localities :
T}rpes and Cotypes : Coche, pres de la riviere de Coban,
Guatemala. — Exped. du Mexique. Bocourt (Mus. Paris, 10
cf(I), 3 c?(II), 9 9).1
Belize, British Honduras. — Exped. du Mexique (Mus. Paris,
id1 (I)).
Remarks: There is quite a difference in the features of old
and young individuals. Generally, in specimens less than 45
mm. long, the pilosity of the fingers is not developed, and merop-
odite and carpopodite of the chelipeds possess sharp spines.
There is a £,45 mm. long, which shows traces of pilosity,
while two males of the first form, of 49 and 50 mm. respectively,
do not show it. The smallest male of the first form that has it,
is 58 mm. long. Upward of this size all specimens have the
fingers densely pilose. The spines of the chelipeds disappear
entirely only in the oldest individuals; the smallest male (first
1 I have not been able to locate this place, nor a river " Coban " ; but Coban
is the well-known capital of the province of Alta Vera Paz. The river at Coban
is called Rio Cahabon. Coban, Alta Vera Paz, is the locality for a species of
Cambarus mentioned by Huxley (1S7S).
IO ORTMANN
form), in which they have disappeared, is 58 mm. long, but in
another, 62 mm. long, they are still recognizable. Three other
males of the first form, 69, 71, 72 mm., have no spines. In
the females, the spines generally persist up to a size of 60 and
62 mm., but they are missing in two females of 62 and 68 mm.
length.
Cambarns pilosimanus is closely allied to C. williamsoni Ort-
mann ' from Los Amates, near Izabal, Guatemala. Indeed, it
may be identical with it. The difference of the pilosity of the
chelse in old individuals of C. pilosimanus is very marked how-
ever, but we are to bear in mind that the largest individual of C.
•williamsoni was rather small (51.5 mm.). Aside from the pilos-
ity of the chelse, the only important difference noted is in the
male copulatory organs, C. filosimanus having the shoulder
less developed, and the tips of the inner and outer part more
strongly contrasted. But this difference is not necessarily spe-
cific, since for the rest the copulatory organs of both species are
built according to the same plan. Other differences are only
slight and apparently unimportant. In the young of C. pilosi-
manus, where the pilosity of the chelse is not developed, the car-
popodite and meropodite always possess a number of sharp
spines, while in C. williamsoni only in the very young are
traces of such spines visible on the meropodite. In specimens
of about the same size, the granulations of the hand are more
distinct in C. williamsoni, although in old individuals of C.
filosimanus the granules are much stronger than in any speci-
mens of C. williamsoni that are known. Further, the hand of
C. pilosimanus is comparativel}' less slender, and is broader
than in C. williamsoni.
The close affinity, if not identity, of these two species is also
borne out by the geographical distribution, but the two known
localities of C. pilosimanus are farther north than that of C.
williamsoni. It is quite possible that additional material will
demonstrate their identity, but for the present I separate them,
since there is no individual among the material from the prov-
ince of Izabal that shows any trace of the pilosity of the chelse.
1 Ann. Carnegie Mus., Ill, 1905, 439.
MEXICAN, CENTRAL AMERICAN, AND CUBAN CAMBARI II
III. CAMBARUS (PROCAMBARUS) MEXICANUS
Erich son.
Literature : see Faxon, Mem. Mus. Harvard, 10, 1885, 50, and :
Camb. mex. Ortmann, Zool. Jahrb. Syst., 6, 1891, 12; —
Faxon, Proc. U. S. Nat. Mus., XX, 1898, 649 ; — Hay,
Amer. Natural., XXXIII, 1899, 959 and 964.
Camb. (Cambarus) mex. Ortmann, Proc. Amer. Philos. Soc,
XLIV, 1905, 101.
Camb. (Procambarus) mex. Ortmann, Ann. Carnegie Mus.,
Ill, 1905, 438.
I have examined the male of the first form of this species pre-
served in the Philadelphia Academy, from Mirador, Mexico
(already mentioned by Faxon). The copulatory organ belongs
to the type of the subgenus Procambarus and is allied to that of
C. williamsoni and flilosimanus. It differs in the very strongly
developed shoulder, and the position of the horny, procurved
spine, which is almost terminal on the inner part. The tips of
inner and outer part resemble those of C. williamsoni.
An additional locality for this species is represented in the
collections of the Philadelphia Academy :
Texolo, State of Vera Cruz, Mexico. — S. N. Rhoads coll.
1899. — 3 c? (II), 2 9. (Texolo is near Xico, on the branch
road from Jalapa, distant about 15 miles from Jalapa.)
In the males of the second form of this set, the shoulder of
the sexual organs is not quite so sharp, and the inner part is
more pointed.
IV. CAMBARUS (PROCAMBARUS) CUBENSIS
Saussure.
Literature: see Faxon, Mem. Mus. Harvard, X, 1885, 51,
pi. 2, f. 1 ; pi. 8, f. 5, and :
Camb. cub. Faxon, Proc. U. S. Nat. Mus. 1885, 358; Hay,
Amer. Natural., XXXIII, 1899, 959-963.
Camb. (Cambarus) cub. Ortmann, Proc. Amer. Philos. Soc,
XLIV, 1905, 101.
!2 ORTMANN
Camb. (Procambarus) cub. Ortmann, Ann. Carnegie Mus., Ill,
1905,438.
Among the material from the Paris Museum, sent to me by-
Professor Bouvier, the following specimens were present :
i. i d (II), 2 9. Cuba; Peters.
2. 4 d (II), i 9. Cuba; Peters. (Nos. i and 2 apparently
from the Berlin Mus.)
3. 2 d (I), 2 d (II), 4 9. "Amerique"; Morelet. (All
badly damaged, but copulatory organs well preserved.)
4. 1 d (I), type of Saussure's C1. consobrinus. (Dry specimen,
mounted upon a piece of pith ; badly damaged, and copulatory
organs not visible.)
The following remarks are to be made :
1. C. consobrinus Saussure l is undoubtedly identical with
C. cubensis. Although in the present type-specimen the male
organs are not visible, it agrees with C. cubensis in all other
respects. It has a very small lateral spine on the carapace.
But such a spine is also present in two specimens (d and 9) in
our first set, while the third (9) has only a trace of it. In the
five specimens of the second set, which are all very young, two
males (II) have a small granule in its place ; the others are
apparently smooth. Of the eight specimens of the third set,
one (a male of the first form) shows a small tubercle, and two
females have none. The rest is too poorly preserved.
2. The male copulatory organs (Fig. 3, a-c) need some dis-
cussion. The description given by v. Martens (Arch. f. Naturg.,
38, 1872, p. 129) is quite correct, disregarding a lapsus calami
or misprint, that renders a certain passage unintelligible. V.
Martens says (translated) : They consist of two parts " an outer
one, which ends in a blunt point, and has the anterior margin
near this point considerably swollen ; and an inner one, which
extends beyond the former posteriorly, and forms on the inner
side a plane, ovate face, -which is adjacent to that of the ap-
pendage of the anterior side (' zvelche sich an die des Anhanges
der vorderen Seite anlegt '). At its end there are two lobes,
one in close apposition to the end of the outer part, the second
one shorter, projecting separately forward, and more rounded."
1 Rev. Mag. Zool. (2), 9, 1857, p. 101, and Mem. Soc. Geneve, 14, 1S5S, 457,
pi. 3, f. 21.
MEXICAN, CENTRAL AMERICAN, AND CUBAN CAMBARI 13
The words emphasized by me cannot be understood as they
stand. But if we conjecture that v. Martens wrote or intended
to write, instead of zwrderen (anterior), anderen (other), every-
thing is clear : he meant to say, that the inner plane face of the
inner part is adjacent to the identical face of the appendage of
the otJicr side.
Thus the whole description is intelligible, and indeed, it is a
correct characterization of the chief features of this organ. It
is very interesting to note, that already v. Martens attributes to
the inner part two lobes, and his second one is clearly the acces-
sorv spine, which is not horny in the male of the second form ;
v. Martens, consequently, describes this organ of the male of
the second form.
He has also correctly interpreted this organ. There is also
in our specimens an outer part, which ends bluntly, and has the
anterior margin slightly swollen just below the tip. The inner
part is dilated and flattened on the inside, and forms, on the
anterior margin, near the tip, a sharp shoulder. Its posterior
margin extends considerably beyond the margin of the outer
part, which is due to the extreme dilatation of the inner face.
Its tip is pointed, and has, in the second form, a rounded, pro-
jecting lobe anteriorly.
In the male of the first form, the tip of the inner part is more
slender and thin, almost setiform, but soft (not horny). The
projecting lobe is replaced by a slightly procurved, horny spine,
which is two-pointed, one point being blunt, the other acute and
thin.
Faxon's figures (1885, pi. 8, f. 5, 5', 5", 5"') are only partly
correct. There is hardly any objection to Fig. 5"', which repre-
sents the inner view of this organ of the left side of the male of
the second form. It shows plainly the pointed tip of the inner
part and the lobiform accessory process, as well as the thickened
anterior margin of the tip of the outer part. Fig. 5" represents
the same organ from the outside. The different parts are recog-
nizable, but the outer part is not marked off at the tip, and the
accessory lobe of the inner part is rendered incorrectly (as a
recurved, blunt hook). Fig. 5' is intended to represent the
inner view of this organ of the left side in the male of the first
14
ORTMANN
form ; the inner part is drawn correctly, showing the setiform
tip and the horny spine ; this spine, however, is drawn triangu-
larly-single-pointed, while it is really slightly procurved and
two-pointed. The outer part is represented in this drawing by
a blunt, conical process, while actually it resembles the con-
dition seen in the male of the second form, being concealed by
the inner part with the exception of the swollen anterior margin,
which projects slightly. Fig. 5 (outer view of same organ) is
Fig. 3. Cambarus cubensis Sauss. a, First pleopod (left side) of male (II),
outer view; b, the same, inner view; c, tip of same organ of male (I), inner
view; d, annulus ventralis of female. All figures enlarged.
quite unintelligible ; the tip of the outer part is not correctly
represented, while the horny process is much too thin and is
recurved, instead of procurved.
That the differences between Faxon's figures and our speci-
mens are due to incorrect rendering of the object by the draughts-
man, is evident from the fact that it is impossible to reconcile
the different views (inner and outer) of the same object. Correct
figures of the organ in question are submitted here.
Thus the copulatory organs of C. cubensis clearly belong to
the type of the subgenus Procambarus ; the outer part has no
terminal horny teeth, but is soft and blunt ; the inner part is flat-
MEXICAN, CENTRAL AMERICAN, AND CUBAN CAMBARI 15
tened and dilated on the inside, with a shoulder on the anterior
margin near the tip ; the end of the inner part has a soft tip,
and, in addition, in the male of the first form, a horny spine,
which is replaced, in the second form, by a blunt tubercle.
C. cubensis is closely allied to the species williamsoni, pi'lo-
simanus, and mexicanus, but differs in the following characters :
(1) The dilatation of the inner face of the male copulatory
organ is much more pronounced ; the tip of the inner part is
more pointed, almost setiform, in the male of the first form ;
the horny spine is two-pointed. (2) The rostrum has marginal
spines ; these are also present in C. williamsoni and filosi-
manus, but are absent in C. mexicanus. (3) The carapace has
a small lateral spine, which is sometimes absent; this spine is
always missing in C. mexicanus, while the other two species
have two distinct lateral spines on each side.
3. Faxon's description of the annulus ventralis of the female
(1. c, p. 52) is correct: " composed of a large anterior bilobed
tubercle, and a smaller posterior tubercle." I only wish to add
that the small posterior tubercle possesses the S-shaped longi-
tudinal fissure commonly seen in Cambarus, and it seems to me
that only this tubercle ought to be regarded as the annulus. I
was able to observe the shape of the annulus only in the largest
female of the first set ; in all other females, which are small, it
is very indistinct, a fact that has also been noticed by Faxon.
For the rest, this species has been well described by Faxon,
but in the figure of the anterior part of the animal [pi. 2, f /),
the marginal spines of the rostrum have been omitted. These
spines are small, but present in all specimens at hand.
V. CAMBARUS (CAMBARUS) WIEGMANNI Erichson.
Camb. wiegm. Faxon, Mem. Mus. Harvard, X, 1885, 38 (liter-
ature). — Hay, Amer. Natural., XXXIII, 1899, 959 anc* 9^4-
Camb. (Cambarus) wiegm. Ortmann, Proc. Amer. Philos.
Soc, XLIV, 1905, 102.
Hagen's female type specimen in the Philadelphia Academy
agrees rather well with a male of the first form present in the
same collection. This latter one is from the Cope collections
and represents a new locality for the species :
1 6 ORTMANN
Lake Xochimilco, south of City of Mexico (Federal District).
— E. D. Cope coll., 1885.
This male has enabled me to draw up the following descrip-
tion :
Rostrum broad, moderately long, plane above ; margins ele-
vated, slightly convergent anteriorly, near the tip more strongly
convergent, and forming a short, subtriangular acumen ; no
marginal spines nor marginal angles at base of acumen, and
the elevated margins continued to the tip, which is bluntly
pointed ; postorbital ridges divergent posteriorly, without spines
anteriorly ; carapace ovate, slightly compressed, punctate,
slightly granulated on the sides ; suborbital angle blunt, branchi-
ostegal spine distinct, but blunt (tuberculiform) ; cervical groove
sinuate ; no lateral spine ; areola longer than half of the anterior
section of carapace, rather narrow in the middle, with two to
three irregular rows of punctations.
Abdomen as wide as, and slightly longer than, the carapace ;
anterior segment of telson with three spines on each side ; pos-
terior segment semicircular.
Ejyistoma with anterior part almost semicircular, a little an-
gular on the sides, and bluntly pointed at the middle ; antennal
scale broad, broadest anterior to the middle ; jlagellum shorter
than carapace (but damaged at end).
Chclipeds with hand rather wide, not much swollen, com-
pressed, with subparallel margins ; surface squamoso-tubercu-
late, tubercles on inner margin more crowded and stronger,
forming an irregular row of serrations ; fingers strong, about as
long as the palm, with longitudinal ribs and punctations on outer
face, and with squamiform tubercles at the bases ; cutting edges
tuberculated, tubercles irregular, a larger one near the base of
each finger, and another large one near the distal end of immov-
able finger ; carpopodite squamoso-tuberculate, inner side with
several spiniform tubercles, upper surface with a slight longi-
tudinal sulcus; meropodite smooth, with a few tubercles near
distal end of upper margin, and two rows of tubercles on lower
margins, the outer ones shorter.
Ischiofodite of third and fourth pereiopods with hooks, those
of the third pereiopod are very small, but distinct and tubercu-
MEXICAN, CENTRAL AMERICAN, AND CUBAN CAMBARI 1 7
liform. Those of the fourth pereiopod very strongly devel-
oped, swollen and inflated, tapering to a blunt point; coxofio-
ditc of third pereiopod with a semicircular, elevated, compressed
tubercle, that of the fourth pereiopod with a strong, triangular
spine, directed outward ; that of the fifth pereiopod with a small,
spiniform tubercle below genital opening, directed downward.
Fig. 4. Cambarus -tuiegmanni Erichson. First pleopod (right side) of male
(I), a, outer view; b, inner view. Enlarged about three times.
First -plcopods (Fig. 4) rather long and slender for the sub-
genus Cambarus, reaching to the coxopodites of the second perei-
opods, almost straight, very slightly curved ; truncated at the
tip, with three horny teeth, of which the outer one is compressed
and truncated, crescentic in shape ; the inner tooth is broadly
triangular, and the anterior is short and spiniform,1 the inner
part of this organ terminating in an almost straight spine, which
is only slightly directed outward, and is slightly longer than the
truncated outer part, and has a distinct horn)' tip.
Measurements : Total length 60 mm. ; carapace 29, anterior
part of carapace 18.5, posterior 10.5; width of areola 1.75;
abdomen 31 ; length of hand 25.5, width of palm 9.5 (Erichson
gives the following figures: total length 52 mm., length of
hand 17 mm., width of hand 6.5 mm. Hagen gives 66 mm.
as total length.)
Comparing the present male with the description of the spe-
1 This latter one seems to belong to the inner part; but I suspect strongly
that such is the case also in other species of the subgenus. The homologies of
the sexual organs of Cambarus are altogether not well understood, and urgently
need a more close study.
Proc. Wash. Acad. Sci., May, 1906.
ORTMANN
cies given by Erichson, and the discription of the female given
by Hagen, there is hardly any difference. Hagen describes
and figures the epistoma as triangular and rather acute, which is
not the case in our individual, and further, Hagen gives only
two lateral spines for the anterior section of the telson. These
differences are of no consequence, variations in these charac-
ters being frequent in other species. I have compared the
female in Philadelphia, which served as the base of Hagen's
description, and which, since the Berlin types of Erichson have
disappeared, must be regarded as the type of the species, and
I find it to agree in all essential characters with our male,
chiefly so in the shape of body and rostrum. Thus I think,
the present male ought to be referred to this species.
As is evident from the characters of the male of the first form
described above, C. wiegmanni belongs to the subgenus Cam-
barns, to the section of C. blandingi, and the group of C.
allem',1 and it has been assigned its correct position already by
Hagen and Faxon (allied to C. barbatus). The sexual organs
are peculiar on account of the crescentic, compressed and trun-
cated outer horny tooth, and do not closely agree with any of
the known species of the subgenus ; but just this feature agrees
with the rt//£«z-group in so far as this group is characterized by
peculiar and aberrant conformations of the tips of the sex-
ual organs.2 In shape of carapace, areola and rostrum, this
species agrees closely with C. evermanni, barbatus and alleni>
and the rostrum represents a rather advanced stage of develop-
ment, being broadly lanceolate, without any traces of marginal
spines or even marginal angles in their place. It resembles to
a certain degree, the rostrum of C. clyfeatus Hay3 from Bay
St. Louis, Hancock Co., Miss., but in the latter form the rostrum
is still broader, and almost rounded off at the apex. I should
1 See Ortmann, Proc. Amer. Phil. Soc. 1905, 98 and 100; Ann. Car. Mus.,
I9°5. 437 and 438.
2 The sexual organs agree most nearly with those of C. hinei Ortm. from Lou-
isiana, with the exception that in the latter species the crescentic and truncated
tooth is absent, and that the distal part of the organ is distinctly curved backward.
See Ortmann in The Ohio Naturalist, VI, 1905, p. 402, fig. 1. Also the rostrum
of C. hinei is transitional toward C. wiegmanni.
3 Proc. U. S. Nat. Mus., XXII, 1S99, 122, fig. 2, no. 1.
MEXICAN, CENTRAL AMERICAN, AND CUBAN CAMBARI 1 9
not be surprised, if this latter species, of which the male is un-
known, should finally prove to belong to this group, and not to
the second group of Faxon (affinity of C. cubcnsis) as Hay is in-
clined to believe.
The hooks of the ischiopodites of the pereiopods are very pecu-
liar, and unlike anything else that is known in the genus. And
further, the development of the spines and processes of the cox-
opodites of the three last pairs of pereiopods is very unique ;
such processes are indeed found in other species in the shape of
tubercles or ridges on the fourth or fifth pereiopods, but they
never assume such proportions as in this species, and the out-
wardly directed spine of the coxopodite of the fourth pereiopod
in C. wiegmanni is without parallel.
Thus it seems that C. wiegmanni is to be regarded as a very
peculiar, and, in certain features, extremely developed form of
the subgenus Cambarus, which belongs to a rather advanced
and modern group of it (a l/cni- group, see 1. c, p. 105) which
is characteristic for those parts of the coastal plain of the south-
ern United States, that are most recent geologically. Its pres-
ence in Mexico is rather interesting, and the specialized char-
acter points to a recent immigration into these parts. But we
are to bear in mind that the a/lcni-gvoup in general is compara-
tively poorly known and needs further study.
VI. Subgenus CAMBARELLUS.
For the species of this subgenus I am only able to add a few
new locality records :
Cambarus (Cambarellus) montczumce Saussure (Faxon, 1885,
121 ; 1898, 660).
Neighborhood of City of Mexico : Laguna de Santa Isabel.
— G. Seurat coll., 1897 (Mus. Paris, 1 c? (I), 1 ?).
Mexico. — Mus. Paris, numerous specimens, collected by
various persons, but without more explicit localities.
Lake Xochimilco, south of City of Mexico (Federal Dis-
trict). E. D. Cope coll., 1885 (Philadelphia Academy, 1 ?).
Most of the specimens seen by the writer belong to the form
tridens v. Mart. With Faxon, I do not believe that this is
worth a varietal name. According to my observations, young
20 ORTMANN
examples generally are tridens, while the typical form is found
only among old individuals, and is comparatively rare.
Cambarus (Cambarellus) montezumce dugesi Faxon (1898,
660,//. 66,/. /).
Guadalajara, State of Jalisco, Mexico. — Diguet coll. (Mus.
Paris ; many specimens).
Same locality. — Duges coll. (Mus. Paris, 4 c?).
State of Guanajuato, Mexico. — Diguet coll. (Mus. Paris,
4^,4?)-
The latter locality is the type-locality recorded by Faxon. The
specimens from Guadalajara have been mentioned by Bouvier
as C. montezumce iridens (Bull. Mus. Paris, 1897, 224), but they
clearly belong to this variety.
Cambarus (Cambarellus) montezumce occidentalis Faxon,
(1898, 661, pi. 66,/. 3, 4).
Hot Springs, Huingo, State of Michoacan, Mexico. — S. N.
Rhoades coll., 1899 (Philadelphia Academy ; many specimens).1
VII. SYNOPSIS OF THE CRAWFISH-FAUNA OF MEXICO, CENTRAL
AMERICA AND THE WEST INDIES.
Our knowledge of the chorology of the genus Ca.abarus,
south of the United States, is rather poor. Crawfish are now
known from Mexico, Guatemala, British Honduras, and Cuba,
but not only is the morphology of these forms not well under-
stood, but also we have only a few and often doubtful or unre-
liable locality-records. In order to call attention to this lack in
our knowledge, I want to condense here the known facts, and
point out the questionable records.
Four subgenera are represented in this southern section of
the range of the genus : Paracambarus, jProcambarus, Cam-
barus, Cambarcllus. The first two are not found in the United
States, while the other two are. Cambarus is largely distrib-
uted in the United States, and has its main range there, only
one species having invaded Mexico. Cambarcllus has its main
abode in Mexico, and only one species is known from a single
locality in Louisiana (New Orleans).
1 Huingo is near Lake Cuitzeo, and site of large salt works by evaporation
from natural springs flowing into the lake. Crawfish were numerous in these
springs and streams (communication from Mr. S. N. Rhoades to the writer).
MEXICAN, CENTRAL AMERICAN, AND CUBAN CAMBARI 21
The following is a list of the known species and their dis-
tribution :
i. Cambarus {Paracambar us) -paradoxus Ortmann.
Tetela, Sierra de Zacapoaxtla, State of Puebla, Mexico.
2. Cambarus {Procambarus) digucti Bouvier.
Tributaries of Rio Santiago, State of Jalisco, Mexico (Bouvier).
Guadalajara, State of Jalisco (Faxon).
Ameca, State of Jalisco (Faxon).
Hacienda de Villachuato, State of Michoacan (Faxon). The
location of this hacienda is unknown.
This species consequently belongs to the Pacific drainage in
western Mexico.
3. Cambarus {Pro cambarus) williamsoni Ortmann.
Los Amates, Province of Izabal, Guatemala (Atlantic drain-
age).
4. Cambarus {Procambarus) pilosimanus Ortmann.
Coche, on river Coban, Guatemala (probably Coban, Prov-
ince of Alta Vera Paz, see above p. 9, footnote).
Belize, British Honduras. (Both localities in Atlantic drain-
age.)
5. Cambarus {Procambarus) mexicanus Erichson.
Mexico (Erichson, Ortmann). Probably the City of Mexico
is meant, since the presence of this species in its neighborhood
is confirmed by other records from the Federal District.
Santa Maria, Mexico (Faxon). There are half a dozen places
of this name in various parts of Mexico. One is close to the
City of Mexico, and thus we may assume that this is intended.
Tomatlan, Mexico, " terres chaudes " (Saussure). Again
there are several places of this name in Mexico : one is south
of the City of Mexico, in the Federal District, another in the
State of Jalisco, not far from the Pacific Ocean ; a third one
about 10 miles south of Huatusco, in the State of Vera Cruz.
Saussure's specification: "terres chaudes" renders it safe to
assume that this latter locality in the State of Vera Cruz was
intended.
Puebla, State of Puebla (v. Martens).
Mirador, Mexico (Faxon). This is an observation station in
the State of Vera Cruz, 190 15' N., 960 40' W., alt. 3,600
feet. I was not able to find it on any of the maps at my disposal.
22 ORTMANN
Texolo, State of Vera Cruz (see above p. u).
Thus this species is known from the states of Mexico (Federal
District), Puebla, and Vera Cruz, that is to say, from the central
plateau and from the Atlantic slope.
6. Cambarns {Procambarus) cubensis Erichson.
Cuba. Saussure gives the interior of this island, and Faxon
creeks in a little town opposite Havana.
7. Cambarus {Cambarus) wiegmanni Erichson.
Mexico (Erichson, Hagen), probably the City of Mexico.
Lake Xochimilco, Federal District (see above, p. 16).
Jalapa, Mexico (Faxon). This is very likely Jalapa in the
State of Vera Cruz, although there are other places of this name
in Mexico.
These localities are on the central plateau and the Atlantic
slope. This species has been recorded with some doubt from
the Isthmus of Tehuantepec (Faxon), but we would better drop
this for the present.
8. Cambarus (Cambarellus) chapalanus Fax.
Lake Chapala, State of Jalisco, Mexico (Pacific drainage).
9. Cambarus {Cambarellus} montezumce Sauss.
a. Typical form (including var. tridens v Mart.).
Chapultepec, Federal District, Mexico (Saussure). West of
City of Mexico.
Lake Texcoco, Federal District (Faxon). East of City of
Mexico.
Lake Xochimilco, Federal District (see above, p. 19). South
of City of Mexico.
Laguna de Santa Isabel, near City of Mexico (see above, p.
19). I have not been able to locate this, but the statement
that it is near the City of Mexico associates this with the first
three records given.
Puebla, State of Puebla, Mexico (v. Martens).
Lake San Roque, Trapuato, Mexico (Faxon). I have not
been able to find this locality designated on any of the maps, or
in any gazetteer consulted by me.
Vera Cruz, Mexico (Ortmann) (Zool. Jahrb. Syst., 6, 1891,
p. 12). This locality should be considered as doubtful till con-
firmed. The specimens upon which this record was founded,
MEXICAN, CENTRAL AMERICAN, AND CUBAN CAMBARI 23
were secured from a dealer, and it was not stated whether the
city or the state of Vera Cruz was meant. Moreover, it is well
known how utterly untrustworthy dealers' localities are.
The presence of this species in its typical form is thus posi-
tively known only on the central plateau, near the cities of
Mexico and Puebla.
b. Cambarus (Cambarellus) monteztnnce dugcsi Faxon.
State Guanajuato, Mexico (Faxon, Mus. Paris).
Guadalajara, State of Jalisco (Bouvier, Mus. Paris, see above,
p. 20).
Pacific drainage.
c. Cambarus (Camba reikis) montczumce areolalus Faxon.
Parras, State of Coahuila, Mexico (Faxon). Northern part
of central plateau.
d. Cambarus (Cambarellus) montezumai occidcntalis Faxon.
Mazatlan, State of Sinaloa, Mexico (Faxon).
Huingo, State of Michoacan, Mexico (see above, p. 20).
Pacific drainage.
It is hard at present to draw any conclusions from these
meagre records. Only a few remarks may be made, but it is
very likely that they will be subject to revision when more in-
formation comes to hand.
The subgenus Procambarus possesses its most primitive form
(C. digueti) in the western extremity of its range (mountainous
region toward the Pacific slope). The most extreme species
(C. cubensis) is found at the eastern extremity of the range, in
Cuba. Intermediate forms are found on the central plateau and
the eastern hot country of Mexico (C. mexicanus), in Guate-
mala, and British Honduras (C williamsoni and fi/'los/mattus),
thus indicating the direction of the dispersal (see Ortmann, Ann.
Cam. Mus., 3, 1905, p. 441).
Thus Procambarus not only points out the original home of
the genus in a general way (Mexico), but indicates especially
the western portions of this country. However, further research
is very desirable.
Cambarus wiegmanni is the only representative of the sub-
genus Cambarus in Mexico ; the bulk of this subgenus being
found in the United States, chiefly in the southern parts (see
24
ORTMAXX
Ortmann, P. Amer. Philos. Soc, 44, 1905, p. 103 f.). Moreover,
it belongs to a rather advanced and modern group of this sub-
genus (alleni-gvoup), which is characteristic for the late Terti-
ary and Post-tertiary plains of the South Atlantic and Gulf bor-
der in the United States. Thus it is very probable, that this
species immigrated into Mexico from the United States, repre-
senting a direction of dispersal opposite to that generally ob-
served in the genus, for which, however, at least one other in-
stance is known (C clarki, 1. c, p. 126). The known habitat
of C. wicgmanni appears rather isolated, and it is much to be de-
sired that northern Mexico and southern Texas should be in-
vestigated with a view to settle this question.
The most primitive species of the subgenus Cambarellus (C
shufeldti) is found in Louisiana. C. chapalanus appears slightly
more primitive compared with C. montezumce and its varieties,
and is found in western Mexico. Of the montezumce forms,
areolatus is the most primitive and the most northern, nearest to
the United States, while occidenlalis is the most advanced (shape
of rostrum), and is western in Mexico. Thus the evidence
is partly contradictory. Leaving out chapalanus, the general
trend of the evidence is to show that the subgenus originated in
the southern United States and immigrated into Mexico, first
into the central plateau, then into the Pacific slope.
This would, consequently, offer a third case of reversed
migration in this region, and my map (1905, pi. 3) should be
changed accordingly (the brown color). This would also not
conflict with the morphological characters of Cambarellus, the
shape of the sexual organs inclining more toward the subgenus
Faxonius of the United States, than toward the Mexican sub-
genera. But I must confess, that the evidence for this assump-
tion appears at present too scanty, so that we can hardly call it
more than a mere theory. It is chiefly with a view to instigate
further research on these questions that I have ventured to ex-
press at all an opinion on this topic.
PROCEEDINGS
OF THE
WASHINGTON ACADEMY OF SCIENCES
Vol. VIII, pp. 25-40 May iS, 1906
THE GEODETIC EVIDENCE OF ISOSTASY, WITH A
CONSIDERATION OF THE DEPTH AND COM-
PLETENESS OF THE ISOSTATIC COMPEN-
SATION AND OF THE BEARING OF
THE EVIDENCE UPON SOME OF
THE GREATER PROBLEMS
OF GEOLOGY.1
Introduction.
By O. H. Tittmann.2
It is my pleasant duty to introduce to you the speaker of the evening,
but I shall ask your indulgence for a few moments while I explain to
you the reasons which lead up to the investigation of which he will give
you an account. You are aware that the governments of the world
maintain an international Geodetic Association under the terms of a
formal convention for the purpose of furthering the admeasurement
of the earth. The countries which are parties to this convention are
Great Britain, whose monumental work in India is of the greatest
importance and which is also conducting geodetic operations in South
Africa ; Germany, the originator of the Association ; France, the
mother of geodesy; Russia, Austria-Hungary, Italy, Spain, The
Netherlands, Norway, Sweden and Denmark. The Orient is repre-
1 Published with the permission of the Superintendent of the Coast and
Geodetic Survey.
2 At a meeting of the Washington Academy of Sciences on the evening of
April 14, 1906, this paper was read by Mr. Ilavford. It has been thought desir-
able to publish in this connection the introductory remarks made by Mr. O. H.
Tittmann, Superintendent of the Coast and Geodetic Survey, and the discussion
by Major Clarence E. Dutton.
Proc. Wash. Acad. Sci., May, 1906. 25
26 HAYFORD
sented by Japan, and this continent by the United States and Mexico.
In South America, Brazil, the Argentine Confederation, Chili and
Peru, are organizing geodetic surveys and will doubtless become
parties to the convention which recognizes the determination of the
earth's figure and size as an international function. As the arc of
Peru, which was recently remeasured by the French, was measured
by a European nation, the United States is the only country among all
the American nations, which has contributed to our knowledge of
the earth's figure. Leaving out of consideration for the present several
minor arcs along the Atlantic seaboard the Coast and Geodetic Survey
published in the year 1900 the results of the measurement of the trans-
continental arc along the 39th parallel. This was followed in the
year 1901 by an account of the oblique arc extending from Eastport,
Maine, to New Orleans, La. Since then it has published the results
of its trigonometric survey extending from the southern boundary of
California to Monterey Bay, California. These great triangula-
tions were begun in many separate localities and when they were
connected it became necessary to adopt a uniform system of coordi-
nates for the whole country. The advantage of doing this was recog-
nized by the engineers of the Army, under whom an extended trigono-
metric survey covering the region of the Great Lakes had been
completed, and their triangulation, 1 aving been connected with that
of the Coast and Geodetic Survey, was, by cooperation between the
Departments having charge of these organizations, referred to the
same datum adopted by the Coast and Geodetic Survey. The earlier
coastwise triangulations of the Coast and Geodetic Survey were pro-
jected upon the Bessel spheroid. As the work progressed it became
evident that the Clark spheroid of 1S66 was in the region of the United
States better adapted for the purpose of a reference spheroid than the
former, and it was substituted for the Bessel spheroid. It also became
clear that for purely geographic purposes the Clark spheroid would
suffice, or at any rate that an attempt to substitute, if it were possible,
a closer osculating spheroid would involve enormous labor without
compensating advantages. This point of view established the policy
of referring all the trigonometric work on the United States to a com-
mon origin of coordinates on the Clark spheroid of 1S66 on which
much of it had already been developed.
Side by side with the computations necessary in this great under-
taking the investigation of the form of the geoid involving the anom-
alies which were developed by the trigonometric and astronomical
operations was carried on, for the adoption of a reference spheroid
THE GEODETIC EVIDENCE OF ISOSTASV 27
for geographical purposes did not relieve us of the duty of trying to
explain the discrepancies between it and the existing geoid.
The discussion of the arcs hitherto published proceeded along the
conventional lines of treating these anomalies, that is, the deflection
of the vertical as though they were accidental errors of observation,
though it was well understood that such is not the case. When,
however, the arcs were all connected it became possible to treat the
triangulations in a much more general way and to have regard to the
surface within the area covered by them, which would most nearly
represent the geoid. To this very difficult task Mr. Hayford addressed
himself. He first devised methods of computation which brought the
investigation within reach of the limited force of computers at his
disposal. What he will tell you to-night in brief, will be submitted
in more detail to the International Geodetic Association as a contribu-
tion from this country to a problem which all are trying to solve.
The results will, I believe, make evident to you the great power of
geometry, using the word in its etymological sense, to disclose facts
which are of the greatest importance to geology and geophysics.
The Paper.
By John F. Hayford, C.E.1
My intention is to present to you a general view of an investi-
gation which is still in progress, to state some of the principal
conclusions reached, and to indicate very briefly some of the
relations of these conclusions to conclusions reached by others
along very different lines of investigation.
At the outset it is necessary to have a clear conception of the
condition called isostasy.
If the earth were composed of homogeneous material, its
figure of equilibrium, under the influence of gravity, and of its
own rotation, would be an ellipsoid of revolution. The earth is
composed of heterogeneous material which varies considerably
in density. If this heterogeneous material were so arranged
that its density at any point depended simply upon the depth of
that point below the surface, that is, if all the material in each
horizontal stratum were of one density, the figure of equilibrium
would still be an ellipsoid of revolution.
1 Chief of Computing Division and Inspector of Geodetic Work, Coast and
Geodetic Survey.
28 HAYFORD
If the heterogeneous material composing the earth were not
arranged in this manner at the outset the stresses produced by
gravity would tend to bring about such an arrangement. But
as the material is not a perfect fluid, as it possesses considerable
viscosity, at least near the surface, the rearrangement will be
imperfect. In the partial rearrangement some stresses will
still remain, different portions of the same horizontal stratum
may have somewhat different densities, and the actual surface
of the earth will be a slight departure from the ellipsoid of
revolution in the sense that above each region of deficient
density there will be a bulge or bump on the ellipsoid, and
above each region of excessive density there will be a hollow,
relatively speaking. The bumps on this supposed earth will be
the mountains, the plateaus, the continents — and the hollows
will be the oceans. The excess of material represented by that
portion of the continent which is above sea level will be com-
pensated for by a defect of density in the underlying material.
The continents will be floated, so to speak, upon the relatively
light material below them and, similarly, the floor of the ocean
will, on this supposed earth, be depressed because it is com-
posed of unusually dense material. This particular condition
of approximate equilibrium has been given the name, isostasy.
Is the earth to-day in this condition? In connection with a
study of this question it is convenient to define two or three
phrases which will be found useful and in defining them to add
precision to our conception of isostasy.
The adjustment of the material toward this condition, which
is produced in nature by the stresses due to gravity, may be
called the isostatic adjustment.
The compensation of#the excess of matter at the surface (con-
tinents) by defect of density below, and of surface defect of
matter (oceans) by excess of density below may be called the
isostatic compensation.
Let the depth within which the isostatic compensation is com-
plete be called the depth of compensation. At and below this
depth the condition as to stress of any element of mass is iso-
static, that is, any element of mass is subject to equal pressures
from all directions as if it were a portion of a perfect fluid.
THE GEODETIC EVIDENCE OF ISOSTASY 29
Above this depth, on the other hand, each element of mass is
subject in general to different pressures in different directions,
to stresses which tend to distort it and to move it.
The idea implied in this definition of the phrase "depth of
compensation," that the isostatic compensation is complete
within some depth much less than the radius of the earth, is not
ordinarily expressed in the literature of the subject, but it is an
idea which it is difficult to dodge if the subject is studied care-
fully from any point of view. The data to be discussed to-night
indicate that all the isostatic compensation occurs within a thin
surface layer of the earth, extending down J^ or possibly ^V of
the depth from the surface to the center.
The geodetic evidence which may be used to test whether or not
the condition called isostasy exists, consists of determinations of
gravity and of determinations of deflections of the vertical.
It is to the evidence furnished by the latter that I wish to call
your attention to-night. Within the limits of the United States
and connected by continuous triangulation, which has all been
reduced to one datum, 507 astronomic determinations have been
made; 265 of latitude, 79 of longitude, and 163 of azimuth.
These furnish that component of the deflection of the vertical
which lies in the meridian at 265 stations, and the prime vertical
component at 232 stations. These astronomic stations are scat-
tered from Maine to southern California, in portions of 33 states.
This triangulation and the astronomic determinations connected
with it are furnished to the world by the Coast and Geodetic
Survey and the Lake Survey and constitute a magnificient
contribution by the United States toward the determination of
the figure and size of the earth.
In deriving the figure and size of the earth from observed
deflections of the vertical the usual practice has been to ignore
the topography around each station, except that occasionally
observed deflections have been rejected because they were in or
near a mountainous region. The effect of a possible systematic
distribution of density in each horizontal stratum of the earth
has also been ignored.
The topographic irregularities are visible and known. The
systematic distribution of density below the surface is invisible
30 HAYFORD
and unknown. The topographic irregularities and the distri-
bution of density each affect the deflections of the vertical.
Therefore, each should be taken into account as far as possible
in any attempt to derive the figure and size of the earth from
geodetic measurements. They are so taken into account in the
investigation now in progress in the Coast and Geodetic Survey.
This investigation seeks to determine not only the figure and
size of the earth but also to determine whether the condition
called isostasy exists with its peculiar distribution of sub-surface
densities, and if so the depth within which the isostatic compen-
sation is complete. Several complete and independent solutions
by least squares of the problem of determining the figure and
size of the earth have been made in this investigation upon
different assumptions as to isostasy and depth of compensation.
The residuals of these different solutions, expressing the
degree of harmony brought about by the different assumptions,
furnish the evidence as to which of the assumptions is nearest
the truth.
One solution was made on the assumption that the condition
called isostasy does not exist, that no isostatic adjustment occurs
when vast masses are eroded from high parts of the earth's
surface, and are transported and deposited on the low parts —
that the earth is so rigid as to support the continents as local
excesses of mass. It is equivalent to the assumption that the
depth of isostatic compensation is infinite.
To make this solution it was necessary to compute the effect
of all the topography for a considerable distance from each
station. The computation was made to cover all topography
within 2,564 miles of each of the 304 stations.
The usual solution was also made. This solution is based
upon the tacit assumption that no relation exists between deflec-
tions of the vertical and the topography. It is equivalent to the
assumption that isostatic compensation exists and is complete at
depth zero — that there exists immediately below every elevation
(either mountain or continent) the full compensating defect of
density, and that at the very surface of the ocean floor there
lies material of the excessive density necessary to compensate
for the depression of that floor. Under no other condition can
THE GEODETIC EVIDENCE OF ISOSTASY 3 1
it be true that the observed deflections of the vertical are inde-
pendent of the known topography. This assumption, tacitly
made in the usual determinations of the figure of the earth,
such for example, as the Clark and Bessel determinations,
represents an impossible condition. It is a limiting case.
If the depth of compensation is finite, the deflections of the
vertical due to topography will be partly counterbalanced by the
contrary deflections due to defects and excesses of density
below the surface. The counterbalancing will be more com-
plete the greater the distance from the station to the partic-
ular topographical features under consideration. Given an as-
sumed depth within which the compensation is complete, and
assuming that the compensation is uniformly distributed through
that depth, it is a simple matter to compute the corresponding
deflections. The computation takes account fully of the amount
by which the plumb line is drawn toward a given mountain
range by the direct attraction of the mass of the range, and
also of the smaller effect of the contrary sign produced upon
the plumb line by the relative defect of density below the range.
Three complete solutions were made in turn upon the assump-
tions that the depth of compensation is 101, 75, and 71 miles.
These particular assumed depths were based upon preliminary
examinations.
A comparison of the five solutions corresponding to assumed
depths of compensation, infinity, 101 miles, 75 miles, 71 miles,
and zero, showed that the sum of the squares of residuals was least
for the 71-mile solution. Therefore, 71 miles is the most probable
of these five assumed values for the depth of compensation.
How strong and clear is the evidence that the actual condi-
tion of the earth is that called isostasy, with the isostatic com-
pensation uniformly distributed within the depth of 71 miles,
rather than that it is an earth in which there is no isostatic
compensation, on which the continents and oceans are main-
tained by rigidity? Compare the 71-mile solution with that for
assumed depth infinity, the last named being the solution cor-
responding to extreme rigidity.
The sum of the squares of the residuals in the former solu-
tion is 8,000 and in the latter is 65,000, more than 8 times as
32 HAYFORD
large. In the former solution there are but 19 per cent, of the
residuals greater than 5" and the maximum residual is 16",
whereas in the latter 66 per cent, of the residuals are greater
than 5" and the maximum residual is 44". In the former solu-
tion the average residual is 3".i and the latter 8". 8.
The evidence shows clearly and decisively that the assump-
tion of complete isostatic compensation within the depth of 71
miles is a comparatively close approximation to the truth, that
the assumption of extreme rigidity is far from the truth — that
the United States is not maintained in its position above sea
level by the rigidity of the earth, but is, in the main, bouyed
up, floated, upon underlying material of deficient density.
The conclusions just stated were based upon the 507 residuals
considered as one group. The residuals have been examined
in separate groups of 25, each group covering a small region.
Not a single group of 25 contradicts the conclusion just stated.
It is certain that for the United States and adjacent regions,
including oceans, the isostatic compensation is more than two-
thirds complete — perhaps much more.
The departure from perfect compensation may be, in some
regions, in the direction of over-compensation rather than
under-compensation but in either case the departure from perfect
compensation is less than one-third.
In terms of stresses, it is safe to say that these geodetic ob-
servations prove that the actual stresses in and about the United
States have been so reduced by isostatic adjustment that they
are less than one-tenth as great as they would be if the con-
tinent were maintained in its elevated position, and the ocean
floor maintained in its depressed position, by the rigidity of the
earth.
In order to secure the greatest possible accuracy in deriving
the figure of the earth it is necessary to determine as accurately
as possible the depth at which the isostatic compensation occurs.
This is also of great importance on account of its bearing on the
greater problems of geology. With what degree of accuracy
does this geodetic investigation fix the depth of compensation?
When all the evidence from the solutions for depths infinity,
101 miles, 75 miles, 71 miles, and zero, is also taken into ac-
THE GEODETIC EVIDENCE OF ISOSTASY 33
count, it appears that, if the compensation is uniformly distrib-
uted with respect to depth, the most probable value of the limit-
ing depth is 71 miles and that it is practically certain that the
limiting depth is not less than 50 miles nor more than 100 miles.
No conclusive evidence has yet developed in the investigation
that the depth of compensation is different for different parts of
the United States.
In all that has been said thus far, and in the corresponding
parts of the investigation, it has been assumed that the compen-
sation is uniformly distributed with respect to the depth. This
assumption is not necessarily true and it must, therefore, be
examined. It was adopted as a working hypothesis because it
happened to be the one reasonable assumption which lends itself
most readily to computation, and because it also seemed to the
speaker to be the most probable simple assumption.
It is probably impossible to determine the distribution of the
compensation with respect to depth from investigations based
simply upon deflections of the vertical. Possibly pendulum
observations combined with deflection observations may detect
the manner of distribution.
All that can be done with deflections of the vertical is to
determine the depth of compensation on various assumptions in
regard to distribution with respect to depth.
Just as the limiting depth of the compensation, if it is uni-
formly distributed with respect to depth, has been determined
by this investigation to be about 71 miles, so it has also been
determined by a later portion of the investigation that if the
compensation is greatest at the surface and diminishes uniformly
with respect to depth until it fades out to zero, the limiting depth
is about 109 miles.
Again, it has been determined by the investigation that if the
compensation all occurs within a stratum ten miles thick the
bottom of the stratum is at a depth of about 37 miles.
My belief is that the depth 71 miles and the corresponding
assumed manner of distribution are nearer the truth than either
the depth 37 or 109 miles with its corresponding assumption.
This belief rests on insecure foundation. If anyone will tell me
the manner of distribution of the compensation with respect to
34 HAYFORD
depth I believe that from the observed deflections of the vertical
now available the limiting depth of compensation can be derived
with reasonable certainty, with an error of less than 25 per cent.
Thus far this talk has been confined to the direct deductions
from the geodetic observations. In this field the speaker en-
joys a peculiar advantage in being in unusually close touch
with the subject. He has no such advantage with respect to
the suggestions which are about to be made on the bearing of
these deductions upon some of the greater problems of geology.
Nevertheless, the suggestions seem to be desirable in order to
indicate some of the important relations of the geodetic investi-
gation to other investigations.
The direct deductions from the geodetic observations, which
have been stated, are a safe and strong foundation which can-
not be shaken. The superstructure of suggestions which I am
about to build upon it is relatively weak and unsafe. Please
remember if you do succeed in knocking down the superstruc-
ture, that the foundation is still in place and awaiting an abler
architect than I am to put a good superstructure upon it.
The fact is established by this geodetic investigation that the
isostatic adjustment brought about by gravity has reduced the
stresses to less than one-tenth of those which would exist if the
continents and oceans were maintained by rigidity. This gives
new and very strong emphasis to the idea that the earth is a
failing structure, not a competent structure. The mechanics of
the two kinds of structures are very different.
Geologists, and others who deal with the mechanics of the
earth, seem to realize only a part of the time that the earth is a fail-
ing structure. Even during the periods of realization it is seldom
that one acts upon the supposition that the earth is so utterly in-
competent to bear the stresses brought upon it as this geodetic
investigation indicates. Let me cite two examples taken from
speakers before this Academy and in this room within a year.
One speaker, in stating the various methods of estimating the
age of the earth, referred to the fact that there is no great excess
of land surface about the equator as compared with the
remainder of the earth. It has been urged that this indicates
THE GEODETIC EVIDENCE OF ISOSTASY 35
that the earth solidified in comparatively recent time. For other-
wise, under the influence of a decreasing rate of rotation, the
water would draw away from the equator and leave it high and
dry. Now if the earth is so weak that it can stand but a small
fraction of the weight of a continent before isostatic readjust-
ment begins to take place, of course the equatorial protuberance
due to decreasing rotation will be leveled down by failure and
isostatic readjustment practically as fast as it develops, even if
no other actions tend to level it down. Hence the study of the
distribution of land with respect to latitude furnishes a measure
of the earth's weakness, not of its age.
Another speaker quoted an article by Mr. G.Johnstone Stoney
in which it is suggested that the permanence of the continents
is due to elastic expansion of all the underlying material when
load is removed by erosion. This idea, viewed in the light of
geodetic evidence, seems to be extremely absurd, for it assumes
the earth to be perfectly elastic — a competent structure — to great
depths, whereas the earth is apparently inelastic to a high degree
even near the surface and is apparently failing continuously
under the stresses brought to bear upon it.
The expression "failing continuously" has been used pur-
posely. It is possible that the continents and oceans are in then-
present positions because light material accumulated at the out-
set in the places now occupied by the continents, and heavier
material accumulated where the deep oceans now lie. This
would constitute an initial isostatic adjustment. But the geologic
evidence is overwhelming that within the interval covered by
the geologic record many thousands of feet of thickness have
been eroded from some parts of the earth and have been trans-
ported to and deposited upon other parts. If isostatic readjust-
ment had not also been in progress during this interval, it would
be impossible for the isostatic compensation to be so nearly
complete as it is at present.
For example, it is estimated by competent authority that a
series of strata from 8 to 10 miles thick have been eroded and
carried away from certain areas in the western part of the
United States, which are now broad and lofty platforms carry-
ing mountain ridges. The present elevation of these areas is
36 HAYFORD
less than three miles — the average elevation, not the elevation
of the summits. Yet the present isostatic compensation, as
already stated, departs not more than one-third from present
perfection. The only reasonable explanation is that the iso-
static readjustment keeps pace approximately with erosion and
deposition.
Upon the basis that the isostatic compensation is complete and
uniformly distributed throughout the first 71 miles of depth,
will the computed variations of density be so great as to raise a
doubt of the validity of the conclusions which have been drawn?
The highest large area within the region covered by this in-
vestigation is the region southwest of Denver, Colorado, with
an elevation of about 11,000 feet or 2.1 miles. This is 3 per
cent, of 71 miles. Hence, on the basis stated, the average
density of the material beneath this region is 3 per cent, less
than that beneath the areas along the coast which lie practically
at sea level. The deepest ocean area of considerable size
within the region of the investigation is in the Atlantic, north-
east of the Caribbean Islands, with a depth of 3,000 fathoms
or 3.4 miles. On the basis stated the average density of the
material underlying this deep spot is only 3 per cent, greater
than that of the material under areas which lie at sea level.
This computed variation in density is small, much smaller
than the variations in density between different rock samples
from different regions. Hence it presents no contradiction to
the supposition that the location of continents and oceans may
be due to initial differences of density in the materials.
But if there is a continuous isostatic readjustment in progress
it is apparently necessary to believe that a given material may
change in density as much as 3 per cent., under the varying
conditions as to pressure (and possibly temperature) to which it
is subjected within the first 71 miles of depth in the earth.
Both laboratory obvervations and geologic observations indi-
cate that this is not only possible but probable.
The elastic effects probably cooperate in producing such
changes of density, but probably play a minor part only.
Laboratory experiments have established as a general law of
chemistry that increase of pressure favors such chemical
THE GEODETIC EVIDENCE OF ISOSTASY 37
changes as are accompanied by decrease of volume, that is, in-
crease of density.
So, too, it is a law well established by laboratory investiga-
tions that the mass of a given gas that will remain in solution
in a given liquid is proportional to the pressure. According to
this law, known as Henry's Law, wherever beneath the surface
of the earth gases and liquids are in contact an increase of pres-
sure will drive more gas into solution and so increase the den-
sity of the mixture. A decrease of pressure will cause apart of
the gas to come out of solution and decrease the density of the
mixture.
Considering solution as a chemical process this law is but a
specific example of the general law stated a moment ago.
Many other specific examples might be given of changes in
pressure producing changes in chemical state and thereby
changes in density.
Very important among these, because it is a process appar-
ently in progress very extensively, is the solution of rock con-
stituents in water and redeposition with a net increase of
density of the rock so modified.
A quantitative study shows that changes of these kinds in a
small part only of the materials in the heterogeneous mixture
which makes up each cubic mile are sufficient to account for a
change of 3 per cent, in the average density, and that isostatic
readjustment brought about in part in this manner is not at all
improbable.
The consensus of geologic evidence also indicates the exist-
ence of this relation of pressure, chemical state and density.
For example, rocks which have been under great pressure be-
cause they have been deep within the crust are, in general,
more dense than those composed of the same proportions of the
elements but which have not been subjected to great pressure.
So, too, it is a general law of metamorphism that changes going
on in rocks which are now near the surface but which formerly
were deep-seated are changes which are accompanied by de-
crease in density.
The indications are, therefore, that when an elevated area
under which there is complete isostatic compensation is un-
38 HAYFORD
loaded by erosion the underlying material to a depth of 71
miles increases in volume mainly because of chemical changes
induced by the decrease in pressure, and partly also because of
changes in the gases from solution to the free state. This in-
crease in volume raises the surface. It also increases the pres-
sure at each level above the 71-mile depth, and tends to bring
it back toward the value which it had at that level before the
unloading.
This expansion process alone is not sufficient, however, to
maintain an isostatic adjustment indefinitely.
As the process progresses — a continuous expansion in the
underlying material keeping pace approximately with continu-
ous unloading by erosion at the surface — the pressure near the
bottom of the expanding column will become considerably less
than it is at the same level in other areas at which no unloading
by erosion is taking place. So, too, near the top of the expand-
ing column the pressures will tend to be somewhat greater than
at the same level in other areas. The result of these differences
in pressure at any given horizontal surfaces will be to set up,
sooner or later, a great slow undertow from the ocean areas
toward the continents, and a tendency to outward creeping at
the surface from the continents toward the oceans.
Let me now emphasize the idea that the theory briefly sketched
in the last few minutes is one which correlates many groups of
observed facts.
It obviously accounts for the marked general tendency for
areas unloading by erosion to rise and those loading by deposi-
tion to subside.
The theory indicates how the changes in density which ac-
company matamorphism are a part of the process of continent
building.
The theory also accounts for the tangential stresses along
the earth's surface of which the crumpled strata, especially of
mountainous areas, are the evidence. For the great undertow
toward the continents is attached to the surface strata by con-
tinuous material and tends to carry them inward. A great con-
test is waged between the shearing stresses developed between
the undertow and the surface strata on the one side, and the
THE GEODETIC EVIDENCE OF ISOSTASY 39
compressive stresses exerted in a horizantal direction in surface
strata, on the other side. The shortening of the surface strata
by bending is a record of the extent to which the surface strata
have suffered in the contest.
According to this theory the undertow should be most power-
ful a short distance inside the continental borders and hence the
mountain building should be most active there. Many geolo-
gists have stated this to be the fact.
Again, according to this theory, such mountain ranges should
be unsymmetrical, thereby indicating that the pressure came
from the ocean side. Again, according to the geologists, many
mountain systems show this effect as, for example, the Alle-
ghenies.
Many other points might be brought out. But the time is
too short.
So, too, the time has been too short to credit ideas to their
originators, some of whom are present here to-night. I have
tried simply to marshall the ideas and facts in such a way that
their relations would become evident.
Discussion.
By Major Clarence E. Dutton.
I have only words of praise for the paper of Mr. Hayford. He
seems to have expressed very accurately the conception of isostasy.
His definitions of isostatic adjustment and isostatic compensation are
very good. The chief point in his paper which makes it a valuable
contribution to science is his determination of the depth at which the
compensation occurs and is probably limited. That determination
proves to be of a greater depth than f had anticipated, but it is none
the less satisfactory on that account. Indeed I think it is more satis-
factory than I had anticipated. It gives a greater concentration to the
isostatic effort and permits us to infer a larger amount of horizontal
displacement in the underlying masses than if it were much deeper.
Also his determination of the amount of strain to which the rocks are
subject is very much less and the amount of outstanding deformation
of the earth is correspondingly less than we could have reasonably
expected.
I have never supposed that isostasy was a force or condition which
produced great elevations and subsidences of the earth. I^have always
40 HAYFORD
been careful to distinguish sharply between the force which tends to
preserve the various elevations and depressions of the earth from the
force which tends to raise the lands and depress the sea bottoms.
Those two classes of forces are at work independently of each other.
The heavy masses of sediment which are formed upon the bottom of
the sea can, I conceive, only be elevated by a positive uplifting force.
Those portions of the land which are being denuded can only have
their profiles depressed by an independent process of subsidence.
Isostasy merely tends to keep the levels of the denuded region on the
one hand, and the loaded regions of the sea bottom on the other, at
constant levels.
PROCEEDINGS
OF THE
WASHINGTON ACADEMY OF SCIENCES
Vol. VIII, pp. 41-90. May iS, 1906.
DISTRIBUTION OF THE LYMPHATICS IN THE
HEAD, AND IN THE DORSAL, PECTORAL,
AND VENTRAL FINS OF SCORP^N-
ICHTHYS MARMORATUS.
By Wm. F. Allen.
CONTENTS.
Page.
Introduction 41
General Survey of the Lymphatics of Scorpienichthys 44
Superficial or Subcutaneous Lymphatics of the Trunk 47
Profundus or Submuscular Lymphatics of the Trunk 58
Facial Lymphatics 65
Lymphatics of the Hyoid Arch 66
Cephalic Sinus • 67
Pericardial Sinuses 71
General Considerations and Summary 78
Synonymy 83
Literature S4
Description of the Figures 87
Abbreviations Used in the Figures 87
I. INTRODUCTION.
In some previous work on the Blood-Vascular System of the
Loricati (2)1 the lymphatics were frequently injected to distin-
guish them from the veins, and, and upon looking over the lit-
erature of the lymphatics of fishes, I was impressed with the
general incompleteness and obscureness that seemed to charac-
terize it. Ophiodon and Scorpcenichthys differ very materially
1 The figures in parentheses refer to a list of the literature at the end of the
paper.
Proc. Wash. Acad. Sci., May, 1906. 41
42 ALLEN
in many important details from the forms that have already-
been studied, namely : Squalus, Raja, Torpedo, Amia
( = Amiatus), Cyprinus, Leuciscus, Salmo, Lucius (= Esox),
Pe?'ca, Lophius, Pleuronectes and Uranoscopus . The lym-
phatics of the Loricati therefore appealed to me as a subject
worthy of study ; hence this paper, which deals with the distri-
bution of the lymphatic vessels in the head, dorsal, and paired
fins of Scorpainichthys.
Two investigators of this subject in selachians, namely,
Robin (23) and Mayer (18) deny the existence of lymphatics in
fishes other than the visceral system. They consider the super-
ficial and profundus vessels of the head and trunk as veins,
and their sinuses they regard as venous sinuses. If this is
true for selachians, it is certainly not true for the teleosts.
In Scorpceuichthys wherever there are blood-vessels and con-
nective tissue there are lymphatics. Strange to say, the
lymph and the plasma of the blood of this group has a green-
ish tinge, so that in an uninjected specimen the lymphatics,
although lighter in color, might readily be taken for veins.
Lymph usually contains some red corpuscles, often sufficient to
give it a red tinge. Whether they have come directly into the
lymphatics through the spleen and lymphatic glands, or through
venous-lymphatic openings, or have transuded through the
walls of the blood-vessels into lymphatic spaces and thence into
the lymphatic vessels is still an open question. If, however,
some lymph be drawn out with a pipette from the myelonal or
superior longitudinal spinal lymphatic trunk, lying in the spinal
canal above the cord, or from any of the lymphatic sinuses, and
ejected into a bottle, and some blood be placed in a second
bottle, the difference can quickly be detected upon the addition
of a little alcohol. Most of the corpuscles of the lymph are color-
less, while those of the blood have a dark brown color. The
entire visceral lymphatic system can often be injected from the
myelonal lymphatic trunk, which would hardly be possible were
it a vein ; and further, the arrangement of what has been desig-
nated as the neural lymphatic vessels, goes to prove that they
are a part of a distinct profundis system. In front of each neu-
ral spine there is a neural lymphatic vessel, which empties into
DISTRIBUTION OF LYMPHATICS IN SCORP/ENICHTHYS 43
the myelonal lymphatic trunk ; also in front of each alternate
neural spine there is a neural artery, coming from the dorsal
aorta, and in front of the other alternate neural spines, a vein
that empties either into the kidney or into the caudal vein. If
the neural lymphatic vessels be regarded as veins, there would
be one artery and vein in front of one set of alternate neural
spines and two veins in front of the other set of alternate neural
spines, a very unlikely arrangement. The same correlation
can be shown in connection with the haemal vessels.
Scor^pcenichthy s sometimes reaches a weight of twenty-five
pounds and is one of the largest, if not the largest, of the Cot-
tidae. It is easily obtained close to shore, is little used as food,
lives out of water for hours, remains hard sometime after death,
and taken all in all, furnishes a most excellent fish for anatom-
ical study. These observations were made at the Hopkins Sea-
side Laboratory, Pacific Grove, California.
The same injecting masses were used that were employed in
my studies on the blood vessels (2), and if only the lymphatics
were to be injected preference was given to the berlin blue
gelatin mass. The fish was severed transversely a little behind
the vent and the body was placed head downward in a dish. A
glass cannula connected with a piece of rubber tubing was
forced forward in the myelonal lymphatic trunk. Usually a
little cotton was placed around the cannula and over the cut
ends of the dorsal, lateral, and ventral longitudinal lymphatic
vessels. The syringe filled with the berlin blue mass was then
connected with the rubber tubing, and with slow steady stroke
the mass was forced into the lymphatics until they were com-
pletely filled, which is usually the case, but should this fail en-
tirely or in part, it can be repeated farther forward, or the lateral
and ventral lymphatics can be injected in a similar manner. In
other species of fishes having a very small myelonal vessel or
none at all, one has to resort mainly to the lateral lymphatic
trunks. The tail can be injected caudad in a similar manner
from the myelonal lymphatic trunk. It is, however, of primary
importance in working with fishes that have been caught with a
hook to cut the line if the hook has been swallowed. To at-
tempt pulling it out would, in all probability, rupture the large
44
ALLEN
sinuses surrounding the heart, which would be fatal to a suc-
cessful injection.
The history of the work done on the lymphatics has been
given by Milne-Edwards (16), Robin (23), Trois (28), and Hop-
kins (8). The general physiology and physiological history is
fully set forth in Schafer (26). A recent paper of unusual in-
terest is that of F. M. Sabin's " On the Origin of the Lymphatic
System from the Veins and the Development of the Lymph
Hearts and Thoracic Duct in the Pig" (27). Anything further on
the history of the lymphatics of Pisces would be simply repetition.
2. GENERAL SURVEY OF THE LYMPHATICS OF
SCORP^ENICHTHYS.
As in the higher vertebrates, Milne-Edwards (16; p. 471-2)
and subsequent investigators, have separated the lymphatics of
fishes into a visceral and a muscular portion, the latter division
having been further subdivided into a superficial or subcutaneous
and a profundus or submuscular system. These three systems
in Scorficenichthys are in close connection. Except in the head
region the principal superficial and profundus vessels are longi-
tudinal trunks that terminate anteriorly in the cephalic and peri-
cardial sinuses, which empty into the jugular near the prootic
process and into one of the branches of the inferior jugular ;
posteriorly they are collected in the neighborhood of the last
vertebra by the right and left forks of the caudal vein.
The superficial or subcutaneous system of the trunk consists
of 4 longitudinal canals, respectively — dorsal, ventral, and
lateral. Both of the lateral lymphatic trunks (Figs. 1, 4, 5 and
6; JL.L.V.) lie in a median plane, directly beneath the skin
in a sheath of connective tissue that separates the dorsal from
the ventral myotomes. Posteriorly they unite with the corres-
ponding forks of the myelonal lymphatic trunk in the region of
the last vertebra, and the combined trunks empty into the right
and left branches of the caudal vein. Anteriorly after passing
under the shoulder-girdle each of these trunks bifurcates, the
lower fork emptying into the pericardial sinus, and the upper
after receiving the corresponding fork of the myelonal lymphatic
trunk, finally terminates in the cephalic sinus situated under
DISTRIBUTION OF LYMPHATICS IN SCORP^ENICHTHYS 45
the hyomandibular bone. Throughout its entire course the
lateral lymphatic trunk receives numerous dorsal and ventral
intermuscular or transverse vessels, which arise from a network
on the surface of the myotomes, and which anastomose with
the dorsal and ventral lymphatic trunks. The dorsal lymphatic
trunk (Figs. I and 4 ; D.L.V.) is found under the skin in the
dorso-median line, but for the most part it is a paired vessel,
running along on each side of the dorsal fin between the super-
ficial and profundus dorsal fin muscles. In the region of the
fins both trunks receive numerous cross-branches from the dorsal
fin or median dorsal lymphatic vessel, that traverses the basal
canal ' of the rays, and which collects the network from the
dorsal fin. Throughout their whole length the dorsal lymphatic
trunks are in connection with the intermuscular and the neural
or interspinal vessels. Posteriorly this trunk is continued into
the basal canal of the caudal fin as the caudal fin sinus, and
when the median line is reached, unites with the corresponding
ventral trunk in forming the hcemal or inferior spinal lymphatic
canal. The ventral lymphatic trunk (Figs. 1, 2, 3, 4 and 6;
V.L. V.) occupies a similar position on the lower side of the
body. In the region of the anal fin it is a paired vessel. Be-
tween the ventrals it expands into a reservoir, which receives
the ventral fin sinuses that collect the lymph from the ventral
fins. A few myotomes in advance of the ventrals it pierces the
ventral fin musculature and follows along the lower side of the
pelvics to empty into the pericardial sinus. Posteriorly it enters
the basal canal of the caudal fin as the caudal fin sinus, and as
described above anastomoses with the dorsal and haemal trunks.
Throughout its entire course it is in connection with the ventral
intermuscular or transverse vessels and the hcemal or interspinal
lymphatic vessels. The most cephalic of the ventral inter-
muscular vessels is much larger than the others and is desig-
nated as the pectoral sinus (Figs. 1, 2, 3, 4, 5 and 6, P.S.).
It receives the common trunk formed by the union of the 2
large sinuses situated on either side and at the base of the pec-
1 Immediately distad to the basal articulation of each raj there is a sort of for-
amen, here designated as the basal foramen of the fin or the fin-ray. Trois
calls it cruna (eye of a needle).
46
ALLEN
toral fin, and each of these sinuses is in communication with
cross-branches from the median pectoral fin sinus, lying within
the basal canal and collecting the pectoral fin network.
Two principal trunks constitute the main profundus or sub-
muscular system. The dorsal one, which is undoubtedly the
largest and most important vessel in Scorpamichlhys, is desig-
nated as the my clonal or superior longitudinal lymphatic trunk
(Figs. 4 and 5, My.L. V.). It runs in the spinal canal directly
above the cord from which it is separated by a septum. Be-
tween the skull and atlas it divides, and both forks after passing
laterad out of this canal unite with the lateral lymphatic trunks
in forming two common vesicles that finally terminate in their
respective cephalic sinuses. In the region of the last vertebra
this trunk again bifurcates to unite with the lateral trunks in
forming joint papillae that undoubtedly empty into the right and
left forks of the caudal vein. Along its entire course it receives
numerous neural or interspinal vessels that communicate above
with the dorsal trunk, and which are often prolonged ventrally to
unite with the longitudinal haemal or inferior spinal lymphatic
trunk and the abdominal sinus. Since the longitudinal hcemal
or inferior spinal lymphatic trunk does not come under the head
of this paper it has not been figured. It travels in the haemal
canal, is continuous posteriorly with the dorsal and ventral
trunks, and anteriorly it appears to empty into the abdominal
sinus. Within the haemal canal it receives the haemal or inter-
spinal vessels, which are also in communication with the ven-
tral lymphatic trunk. The abdominal sinus (Figs. 4, 5 and 6,
Abd.S.), which lies directly under the kidney and empties
anteriorly into the cephalic and pericardial sinuses, receives nu-
merous small lymphatic vessels from the reproductive organs,
the great lymphatic trunk from the viscera, and many inter-
costal vessels that are also connected with the profundus ven-
tral lymphatic trunk. The latter vessel (Figs. 4, 6 and 9,
V.L. V. 1 ) perhaps should have been included as one of the prin-
cipal profundus longitudinal trunks. It pursues a similar course
to the ventral lymphatic trunk along the lower wall of the visceral
cavity and terminates anteriorly in the posterior end of the peri-
cardial sinus. Several interlinking vessels were noticed in the
DISTRIBUTION OF LYMPHATICS IN SCORIVEMCIITHYS 47
region of the ventral fins between this trunk and the main ven-
tral lymphatic trunk.
In the head region there is the same division into superficial
and profundus systems. The superficial facial trunk (Figs. 4
and 5, S.Fac.L. V.) takes its origin in the neighborhood of
the snout, and following along the upper inner edge of the sub-
orbital bones, crosses the prootic process to join the jugular
papilla of the cephalic sinus. The profundus facial trunk
(Figs. 4 and 5, P.Kac.L.V.) could only be found in the orbit;
branches were seen to enter it from the adductor mandibular
muscles, and it was traced to a point in front of the prootic
foramen, where it probably passed under the jugular and entered
the abdominal sinus. This point, however, could not be deter-
mined. There are 2 hyoidean lymphatic trunks, which run
along the upper and lower sides of the arch (Figs. 3 and 4,
A.Hyo. T. and P.Ilyo. T.). Of the 2 the lower is the principal
stem. It collects the lymph from the branchiostegal region, and
after receiving the upper vessel expands into a sinus that empties
into the cephalic sinus.
With Scorpamichlhys nothing has been done in connection
with the lymphatics of the viscera. The main trunk, however,
was often injected from the myelonal trunk, and was seen to
follow the coeliaco-mesenteric artery and empty into the ab-
dominal sinus. The lymph from the reproductive organs was
poured into the abdominal sinus through numerous small vessels.
In an injected specimen of Ophiodon lymphatic vessels were
seen to arise from all the organs and empty into trunks that fol-
lowed the courses of their corresponding blood-vessels, often
nearly surrounding them. These canals were collected ante-
riorly into a main coeliaco-mesenteric trunk that discharged itself
in the abdominal sinus, and posteriorly the principal intestinal
vessels traveled along with the posterior mesenteric vein between
the reproductive organs to culminate in the abdominal sinus.
3. SUPERFICIAL OR SUBCUTANEOUS LYMPHATICS
OF THE TRUNK.
Lateral lymphatic trunk (Figs. 1, 4, 5 and 6, L.L. V.). —
No other of the lymphatic canals of fishes has received the
48 ALLEN
attention that this one has. It is easily located and the one
from which this system has usually been injected. According
to Milne-Edwards (16, p. 473) and Stannius (24, p. 254) this
vessel was briefly described and its connection with the ductus
of Cuvier noted by Hewson (5) and Monro (14). Vogt (33)
however, was the first to show the connection of this trunk with
the caudal vein, but (in 1, p. 134) gives the credit of this dis-
covery to Hyrtl. From the latter (7) one obtains a most excel-
lent account of this vessel. It is represented (p. 233) as arising
from numerous dorsal and ventral transverse vessels (Seitenast-
Parre) into which empty numerous smaller branches that collect
the network coming from the matrix of the scales, and in con-
versely restating the course of these vessels he says that the
longitudinal trunk empties into the blood-vascular system.
Further on (p. 234) he adds that in a successful injection the
sinuses at the base of the pectoral and ventral fins and their
branches were filled, but that no vessels were noted in connection
with the dorsal fins. He also states that the lateral trunk ter-
minates in a caudal sinus which empties into the caudal vein,
and with Acipenser, Cyprinus, Leiiciscus, Esox and Gobio it
ends anteriorly in a thin-walled pear-shaped cephalic sinus
situated at the side of the skull directly behind the orbit, which
empties into the jugular a little forward of the lower jaw and
opercular vein. Shortly before the lateral lymphatic trunk
terminates in the cephalic sinus several vessels coming from the
jaws, the gills, the tongue and branchiostegal membrane are
described as emptying into it. With the salmon and the trout,
Hyrtl notes an entirely different anterior mode of communication
with the venous system. Here the lateral trunk after curving
under the clavicle empties into the sinus of the spermatic vein
(Sinus der Holvenen) at its junction with the ductus of Cuvier,
and this opening is guarded by a valve opening into the vein.
While with Perca luciopei'ca, Tinea c/irysitis, and Cottus gobio
both points of union are said to exist. Vogt (1, p. 134-7) also
describes this trunk in the salmon with great detail. He noticed
the transverse branches emptying into the main trunk, but con-
sidered them as extravasations caused by the rupture of the
thin-walled lateral canal. Posteriorly this canal is said to end
DISTRIBUTION OF LYMPHATICS IN SCORP/ENICIITIIYS 49
in a sinus that empties into the caudal vein (veine cardinale).
Upon reaching the end of the thoracic cavity it expands into a
capacious reservoir, lying directly beneath the clavicle. Within
the sinus there is a slit covered by a strong valve that leads into
a vessel about the diameter of a pi»-head, which passes directly
into the sinus of Cuvier. PI. K (Figs. 7 and 8 ; 64) shows this
cephalic sinus papilla entering the sinus of Cuvier from the
front. Vogt speaks of this trunk as a mucous canal, and since
he could find no lateral mucous canal in the salmon into which
the mucous pores emptied, he inferred that they emptied into
this trunk. Stannius (24, p. 252-4) states that this trunk takes
its source from numerous transverse branches, and following
along with the truncus lateralis N. vagi terminates in caudal
and cephalic sinuses. In addition the latter receives lymph
from the head, gills, and trunk and empties into the precava
(truncus transversus). From footnotes Milne-Edwards gives us
the following additional information : Sihirus has three paral-
lel lateral lymphatic vessels. With some fishes, as for example,
the pike, roach, grudgeon, barb, and sturgeon, the lateral trunk
is prolonged into the head and forms a sinus at the base of the
skull, which empties into the jugular through a transverse canal.
With the salmon, cod, rays, and sharks, the lateral trunks open
into a pair of large cervical sinuses, that descend behind the
center of the scapula and reunite in the median line at the point
where the abdominal sinus joins them. Each of these scapular
reservoirs communicates with the anterior vena cava or ductus
Cuvieri through an orifice guarded by valves. Trois (28, 29,
30 and 31) gives a most excellent account of this vessel in
Lo-phius -piscatoriuS) Uranoscofius scaber, and in several of the
Pleuronectidas. He describes this trunk as ending in cephalic
and caudal sinuses, and has satisfied himself that the transverse
branches are not superfluous injecting mass as Vogt maintains.
These vessels in Lophins are portrayed as sending off branches
between the myotomes, which anastomose with similarly ar-
ranged profundus vessels, forming a sort of ladder network.
The transverse rami are represented as also anastomosing with
the dorsal and ventral lymphatic trunks. Uranoscopus (29, p.
20, and PL on p. 37) furnishes a beautiful example of a fish
50 ALLEN
having 3 longitudinal lateral lymphatic trunks, and since the
middle one is the largest and is connected with the venous
system at either end Trois is right in attributing only secondary
importance to the other two. Trois also noted the knotty ap-
pearance of the main lateral trunk in Uranoscofius (29, p.
21-2) which he thinks is due to rudimentary or imperfect valves
that may have been put out of action by death, and the difficulty
that he has experienced in injecting this trunk he ascribes to the
resistance of these valves. This knotty appearance of the lateral
trunk was also noticed in Scorficenichthys, but since no trace of
valves has been found it seems best to attribute it to the outside
resistance of the body musculature, rather than to the existence
of hypothetical valves. To a considerable extent this arrange-
ment may check the flow of the lymph and also the injecting
mass, but by swelling out in the region of the centers of the
myotomes it considerably increases the capacity of the lymphatic
system. With the carp and pike Sappey (25, p. 41, and PI. XII,
Fig. 2) describes and figures the lateral trunk as bending ventrad
about 15 or 20 mm. in front of the clavicle and emptying directly
into the jugular without forming any sinus. Hopkins (8, p.
371-2) in addition to describing the ordinary termination of the
lateral trunk in cephalic and caudal sinuses says that in Am/a
this trunk receives a branch from the pectoral sinus before pass-
ing under the pectoral arch to open into the cephalic sinus,
which is said to extend from the dorsal end of the clavicle to
the base of the skull, and which empties into the jugular about
1 cm. cephalad and a little ventrad of the dorsal end of the
clavicle.
The lateral lymphatic trunk of Scorfiamichthys (Figs. 1, 4, 5
and 6, L..JL. V.) in the trunk region corresponds in the main
with the descriptions of the previous investigators. As has
already been stated in the general survey of the lymphatics this
vessel lies beneath the skin in the median lateral line, and ex-
cept in the cephalic portion of the trunk follows parallel, but
mesad of the lateral line canal. It is distinctly a superficial
vessel lying in the connective tissue septum that separates the two
halves of the great lateral muscle. Throughout its entire course
it takes up numerous dorsal and ventral intermuscular or trans-
DISTRIBUTION OF LYMPHATICS IN SCO k I'.K \ K UTII YS 5 I
verse branches, the most cephalic of which is a large ventral
sinus to which the name pectoral sinus has been given. Pass-
ing under the pectoral arch it follows along in front of the first
rib across the anterior fork of the kidney. About half way
across the kidney it receives a communication from the pericar-
dial sinus (Figs. 4, 5 and 6, Per.S.), and when the atlas is
reached unites with a fork of the myelonal or longitudinal spinal
lymphatic trunk, the point of junction being marked by quite
a large reservoir, designated as the occipital sinus (Figs. 4 and
5, Oc.S.). From here on the combined trunk thus formed is a
distinct profundus vessel designated as the cranial lymphatic
trunk (Figs. 4 and 5, Cr.L. V.). This vessel finally empties
into the cephalic sinus, and is described in detail further on
under a separate paragraph.
Had the lateral trunk in Scorpcenichlhys, after having passed
under the clavicle, curved downward without expanding into a
sinus and emptied into the jugular, we would have the condi-
tions as described for the carp and pike by Sappey (25). Had
the lobe of the kidney not extended so far cephalad and the
occipital sinus been located in front of the precava a little below its
present position in Scorpcenichlhys, and received the branchial,
hyoidean, and facial trunks, but not the myelonal, it would have
answered to Vogt's description of the anterior termination of the
lateral canal in the cephalic sinus with the salmon (1) ; provided
that this sinus emptied into the precava. Finally, had the
lateral trunk of Scorpcenichthys continued to the base of the
skull, without receiving the myelonal trunk and the pericardial
sinus, but collecting the branchial, facial and hyoidean trunks,
and had sinus (s) emptied into the jugular we would have had
the conditions met with in Cyprinus, Leuciscus, Esox, Acipen-
ser, etc. It is of special interest to note in this connection that
Hyrtl and Milne-Edwards have vaguely described 2 anterior
communications from the lateral lymphatic trunk with the venous
system in Cottus gobio, a species belonging to the same family
as Scorpcenichthys .
The intermuscular or transverse vessels (Figs. 1, 2, 4 and 5,
Intm. V.) described by Hyrtl, Stannius, Milne-Edwards, Trois,
Sappey, Hopkins, and which Vogt took to be extravasations of
52 ALLEX
the injecting mass have certainly been found in Scorpcenichthys,
following along superficially in the septa between the myotomes.
The ventral vessels anastomose with the ventral lymphatic trunk
and the dorsal with the dorsal trunk. These vessels are con-
nected by a lymphatic network, which has its origin from the
surface of the muscles and connective tissue, and branches are
also received that arise from a very rich network on the subcuta-
neous layer of the skin. This network is especially conspicuous
in fresh-water drum, Aplodinotus grunniens, where it can be seen
through the transparent scales. The secondary lateral trunks
described by Trois in Uranoscopus are certainly of only secon-
dary importance in Scorpcenichthys . For not only is the central
vessel much larger and connected at either end with the venous
system, but the secondary lateral vessels are only found in the
cephalic end of the trunk, and the most dorsal one is not a con-
tinuous trunk, but simply a series of regular cross vessels.
Pectoral sinus and lymphatics of the pectoral Jin. — This
sinus (Figs, i, 2, 3, 4, 5 and 6, P.S.) lies directly below the
skin between the base of the pectoral fin and the post-clavicle, or
perhaps to more accurately state it, between the superficial pec-
toral adductor muscle, and the anterior myotomes and the
sterno-hyoideus muscle (see fig. 2). In a well-injected speci-
men it can be traced cephalad between the sterno-hyoideus and
superficial abductor muscles to what has been designated as the
ventral pericardial sinus (Figs. 3, 4 and 6, V.Per.S.). Since
the ventral pericardial sinus receives the ventral lymphatic trunk,
the union of the pectoral sinus with the ventral pericardial sinus
is analogous to the union of the ventral intermuscular or trans-
verse vessels with the ventral lymphatic trunk. In addition to
its dorsal and ventral connections the pectoral sinus is always
in direct communication with the abdominal sinus (Figs. 4 and
6, Abd.S.) In a very large specimen from which Fig. 6 was
drawn an additional connection was also noticed with abdomi-
nal sinus, which received a communicating branch from the
pericardial sinus. Near the termination of the pectoral sinus
in the lateral lymphatic trunk it receives a common trunk formed
from the union of the outer and the inner pectoral fin sinuses
(see figs. 1, 4 and 6). Of these two sinuses the inner is the
DISTRIBUTION OF LYMPHATICS IN SCOK I'. 1. \ K IITII YS 53
larger (Figs, i, 2, ia and 4, I.P.S.). It follows along the
base of the fin between the superficial and profundus adductor
muscles, having blind sacs that pass between the profundus
adductor muscles, but which send up short branches between
the middle rays that soon fork to anastomose with the corres-
ponding branches of its fellow, thus forming a circle over the
bases of the middle rays (Fig. 2). These circular vessels re-
ceive short pectoral-ray vessels (Figs. 2 and 2a, P.F.L. V. 0)),
which run along the inner surface of the rays. They are much
shorter than the main pectoral fin or pectoral fin-ray vessels,
but appear in a well-injected specimen to have communicating
branches with the main pectoral-ray vessels. The outer pec-
toral sinus (Figs. 1 and 2a, O.P.S.) occupies a similar posi-
tion between the superficial and profundus pectoral abductor
muscles. It also sends back little pockets between the bundles
of the profundus muscle, and receives dorsad a large branch
that has its origin from the superficial and profundus abductor
muscles (see Fig. 1). The outer pectoral sinus, after curving
over the most dorsal ray, joins the inner pectoral sinus in form-
ing a common trunk that empties into the main pectoral sinus.
In addition to these 2 pectoral sinuses there is a third or median
pectoral sinus (Fig. 2a, M.P.S.), which traverses the basal
canal of the pectoral rays.1 This trunk receives the main pec-
toral Jin or the main pectoral Jin-ray vessels (Figs. 2 and 2a,
P.F.L. V.). Two such vessels accompany each ray and receive
the network from the pectoral fin membrane. As is shown in
Fig. 2a numerous cross-branches pass between the rays from
the median pectoral sinus to both the inner and the outer pec-
toral sinuses.
Very little is to be found in the literature on the lymphatics
of the pectoral fin. Hyrtl (7, p. 234) says that a pectoral sinus
and its branches are filled in a successful injection of the lateral
trunk. Stannius (24, p. 253) briefly describes a sinus at the
base of the pectoral which receives numerous branches from the
pectoral fin muscles. Hopkins simply states with Amia. (8,
p. 371) that the lateral trunk receives the pectoral sinus. Trois
(28, p. 8, and 29, p. 25) says that in Lophius and Uranoscopus
1 See note, page 45.
54 ALLEN
there are at least 3 pectoral lymphatic trunks emptying into the
cephalic sinus. Secondary branches are noted as anastomosing
with the intercostals, and a sinus (vaso collettore) is spoken of
as lying at the base of the rays and forming a ring about every
ray. Lymphatic vessels are described as running along the
surface of the rays and collecting the rich network from the
skin. It will be seen from Trois' description that the lymphatics
of the fin itself correspond somewhat with the arrangement in
Scorpcenichthys, but as regards their mode of termination there
is nothing in common.
Dorsal lymphatic trunk (Figs. 1 and 4, D.L. V.). — Hyrtl
and Vogt seem to have overlooked this canal. Stannius (24,
p. 253) says that this trunk can be divided into 2 subordinate
stems. First a vessel is described as running along the angle
of the intermuscular septa, and a vessel is noted as passing
along between the upper border of the great lateral muscle and
the longitudinal muscle of the dorsal fin, which would place
it at the base of the dorsal fin. Cross-branches are said to
exist between the 2 trunks, and the second trunk receives
numerous branches that followed along the rays. The first
dorsal trunk of Stannius is undoubtedly the same as that de-
scribed by Trois and myself as the most dorsal of the secondary
lateral lymphatic trunks. Trois (28, p. 6) and Sappey (25,
p. 47) describe the dorsal trunk in Lophius and the pike as a
knotty vessel that separates into 3 distinct trunks upon reaching
the dorsal fin, two of which run laterad to the base of the rays,
while the third, more slender, passes through the holes in the
base of the rays. Two vessels for each ray collect the lymph
from the fin and empty into the median trunk. With Uranoscopus
(29, p. 23) the anastomosis with the neural or interspinal vessels
was noted. Hopkins (8, p. 373) describes this trunk in Amia
as anastomosing with the lateral trunk before terminating in the
caudal sinus, while anteriorly it bifurcates at the base of the
skull, each fork emptying into a cephalic sinus.
The description given of the dorsal longitudinal lymphatic
trunk by Trois for Lophius and Uranoscopus will also answer
very well for Scoj-pcenichthys. In the region of the dorsal fins
this canal separates into three longitudinal trunks, two of which
DISTRIBUTION OF LYMPHATICS IN SCORPvENICHTHYS 55
running along at the base of the fins between the great lateral,
superficial, and profundus dorsal fin muscles are evidently the
main stems, and might be designated as the lateral dorsal lym-
phatic trunks (Figs. I and 4, D.L. V.) ; while the third or
median dorsal lymphatic trunk (Figs. 1 and 4, D.L. V.w)
simply passes through the basal canal of the rays and collects
the dorsal fin lymphatic vessels. Numerous transverse inter-
linking vessels were noticed between the median dorsal and
the 2 lateral dorsal lymphatic trunks, and the dorsal Jin lym-
phatic vessels (Figs. 1 and 4, D.F.L. V.) were merely small
branches of the median lymphatic trunk, that followed along
the cephalic and caudal surfaces of each spine and ray and col-
lected the network from the fin membrane. Some variation,
however, is shown in the anterior region of the first dorsal,
where there is but one dorsal fin lymphatic vessel between the
first and second, and between the second and third spines, both
of which empty directly into the lateral dorsal trunks. In addi-
tion to receiving the dorsal fin vessels the median dorsal lym-
phatic trunk collects numerous small branches from the super-
ficial or extrinsic dorsal fin muscles (Fig. 1). Anteriorly these
2 lateral dorsal lymphatic trunks do not terminate directly into
cephalic sinus as described by Hopkins for Amia, but through-
out their entire course communicate with the lateral lymphatic
trunk through the intermuscular or transverse vessels, and with
the myelonal or longitudinal spinal lymphatic trunk through the
neural or interspinal vessels (Fig. 4, Neu.L. V.). The most ce-
phalic neural or interspinal vessel (Figs. 4 and 5, JVeu.L. V.w)
does not empty into the myelonal trunk, but follows along be-
hind the skull and terminates in the cranial lymphatic trunk.
Ventral lymphatic trunk and lymphatics of the ventral fins
(Figs. 1, 2, 3, 4, 6, 9 and 10, l V.L.V.). — According to
Milne-Edwards (16, p. 473) this vessel has been described by
Monro (14) and Hewson (5) in Gadus, and as was the case with
the dorsal trunk this canal seems to have been overlooked by
Hyrtl and Vogt, although the former states that a ventral fin
sinus is filled from a good injection of the lateral trunk. Stan-
nius (24, p. 253) describes this vessel as unpaired, running
1 Figs. 7 to 10 are text-figs, on pp. 73, 74, 76 and 77.
56 ALLEN
along between the halves of the lateral muscle from the vent to
the shoulder-girdle. Caudad the vessel from the anal fin is dis-
charged into it, and in the rump region it receives transverse
vessels that follow the intermuscular septa. Trois (28, p. 7)
and (29, p. 23) represents the ventral trunk in Lophius and
Uranoscopus as consisting of 2 parallel trunks. With Urano-
scopus they run close together and are connected by numerous
cross-branches. In front of the anal they unite, and the com-
mon trunk receives 3 vessels from the region of the anal fin, of
which the median is the largest and traverses the basal canal of
the rays ; the 2 lateral trunks are found at the base of the fin
and travel toward the tail, and the 3 vessels are said to be con-
nected by transverse rami. With Lophius we are told that the
ventral canals bifurcate at a very acute angle in front of the
ventral fins, and that these branches collect everything at the
base of the ventrals. Sappey (25, p. 47) states with the pike
and carp that this trunk is very similar to the dorsal ; that it is
a single trunk in the region of the anal fin; but in advance of
this, between the ventrals and pectorals, it consists of two par-
allel trunks, which are prolonged to the posterior end of the
skull. With the Pleuronectidse, Sappey (p. 49 and PI. XII,
fig. 4) represents the ventral trunk as consisting of 2 parallel
vessels in the region of the anal fin, but uniting in front of
it in a common trunk that empties into the sinus of Cuvier.
Hopkins (8, p. 372) describes the ventral trunk as beginning
at the base of the caudal fin and extending cephalad to the
heart, where it divides into two branches that merge into peri-
cardial sinus, which communicates with the cephalic sinus and
thence with the veins. On its course it receives the lymph from
the anal and pectoral fins, and the sinus at the base of each of
these is said to be much smaller than the one at the base of the
pectoral.
The ventral longitudinal lymphatic trunk of Scorpcenichthys
(Figs. 1, 2, 3, 4, 6, and 9, V.L. V.) differs very materially
from any of the species described above, although perhaps con-
forming more closely to Hopkins' account for Anita than any
of the others. The course of this trunk through the anal fin
and its prolongation into the basal canal of the caudal fin is left
DISTRIBUTION OF LYMPHATICS IN SCORP^ENICHTHYS 57
for another paper. In contrast to Trois' description this is a
single trunk in Scorjxznichthys, extending from the vent to the
origin of the pectoral fins. It runs along superficially in the
ventro-median line from the vent to the origin of the pectorals,
but pierces the body wall some distance behind its cephalic
end ; the exact position is noted by 7'(Figs. I and 4), which is
a little cephalad to the point of union with the vessels coming
from between the profundus and superficial abductor muscles of
the ventral fin. At this point a slight sinus is formed, which
might be described as receiving an anterior and a posterior
ventral trunk. The combined trunk or main stem thus formed
penetrates obliquely between the 2 ventral fin abductor muscles,
continues cephalad in a median line along the lower surface of
the pelvic bones (Fig. 4), and passing between the clavicles
and the pelvics, curves around the anterior end of the pelvics
to enter the ventral -pericardial sinus (Figs. 4, 6, 9 and 10,
V.JPer.S.) directly below the ventricle from the rear. The con-
nection of this sinus with the veins will be described further on
under a separate paragraph. Between the ventral fins the
ventral trunk expands into a distinct pear-shaped sinus to which
the name ventral sinus has been given (Figs. 1, 2 and 4,
V.L.S.). This sinus receives at least one pair of intermuscular
vessels and two ventral Jin sinuses (Figs. 1, 2 and 4, V.F.L. S.),
which lie on the upper or inner base of the ventral fins. They
receive the ventral Jin or the ventral Jin ray vessels (Figs. 1, 2
and 4, V.F.L. V.) from between each two rays, which soon
bifurcate, each fork running along the adjoining rays and
receiving the network from the membrane between the two.
This is the typical arrangement, but some irregularities are
often found as shown by Fig. 2, where some auxiliary ventral
-fin vessels (Fig. 2, V.F.L. V. (1)) were noticed traversing the
innermost rays, which reunited in a common vessel that passed
over the lowrer side of the fin to empty into the ventral fin sinus
close to its union with the ventral sinus. The ventral fin sinuses
are prolonged cephalad between the external ventral fin abduc-
tor muscles and the great lateral muscle as the ventral Jin muscu-
lature lymphatic vessels (Figs. 1 and 2, V.M.L. V.)> and in
route receive at least three intermuscular or transverse lymphatic
Proc. Wash. Acad. Sci., May, 1906.
58 ALLEN
vessels. Mesad of these ventral fin musculature lymphatic ves-
sels there are still two other ventral fin musculature vessels
(Fig. 2, V.M.L. V.w), which run between the internal and
external ventral fin abductor muscles, and unite with the main
ventral trunk immediately before it penetrates the musculature
to empty into the pericardial sinus.
From the above description of the termination of the ventral
fin vessels into a single sinus outside the fin it will be noticed
that this is a very different arrangement from that found in the
dorsal and pectoral, where these vessels emptied into a median
sinus, which traversed the basal canal of the rays, and having
numerous transverse branches, communicating with the two
lateral sinuses, lying at the base of the fin.
In the paragraph on the lateral lymphatic trunk it was stated
that a typical ventral intermuscular or transverse lymphatic
vessel connected the lateral with the ventral lymphatic trunk.
The most cephalic of these vessels, however, show some devia-
tion from this general plan. The first one connects the pectoral
sinus with the anterior end of the ventral trunk ; the second
interlinks the pectoral sinus with the ventral fin intermuscular
vessel ; the third and fourth communicate with the lateral trunk
and the ventral fin intermuscular vessel ; the fifth unites with
the lateral trunk and the ventral fin sinus ; while the sixth ex-
tends from the lateral trunk to the ventral sinus.
4. PROFUNDUS LYMPHATICS OF THE TRUNK.
The profundus ventral lymphatic tru?ik (Figs. 3 and 4,
V.L. V.(1)), which seems to have escaped the notice of the pre-
vious investigators, pursues a parallel and somewhat similar
course to the main ventral tymphatic trunk between the great
lateral muscles, but follows along the inner or visceral side of
them. So far as could be ascertained it arose near the vent and
passing cephalad along the median line close to the visceral
cavity, terminated in the posterior end of one of the pericardial
sinuses (Figs. 4, 6 and 9). Throughout its course it receives
or gives off numerous intercostal lymphatic vessels (not shown
in any of the figures), which follow along the inner side of
the intermuscular septa, parallel with the intermuscular or trans-
DISTRIBUTION OF LYMPHATICS IN SCORP/ENICIITHYS 59
verse lymphatic vessels and anastomose dorsally with the ab-
dominal sinus. In the region of the ventral fin, and not improb-
ably in other places, interlinking vessels were found between
the profundus and superficial ventral trunks.
Myelonal or superior longitudinal spinal lymphatic trunk
(Figs. 4 and 5, My.L. V.). — This trunk with its neural or inter-
spinal branches has been described by Hyrtl (7) and Stannius
(24) as ending in the caudal sinus, but nothing whatever is said
about its anterior connections. Trois states that this trunk in
Lophius, Uranoscopus, and the Pleuronectidae (28 to 31) runs
along in the spinal canal, receives numerous interspinal branches,
and is connected with the haemal longitudinal trunks by means
of transverse vessels. With Rhombus maximus and R. Icevis (30,
p. 43) an additional longitudinal trunk was described as travel-
ing along at the level of the bases of the interspinal bones. So
far as could be discovered, Sappey (25) is the only one to give
a cephalic ending for this canal. He states that it is a very
important trunk with the pike and flatfish, and with these 2
fishes it is represented as extending from the coccyx of the
last vertebra to the first cervical vertebra — where it turns to
empty into the jugular. He further adds that there appears to
be no caudal connection with the papilla of the lateral canal.
No such trunk was portrayed by Vogt in the salmon or by Hop-
kins in Amia.
In Scorpamichthys the myelonal or super for longitudinal spinal
lymphatic trunk (Figs. 4 and 5, My.L. V.) agrees very well
with the descriptions given it by Trois and Sappey in Lophius,
Uranoscopus, Esox, and the Pleuronectidee, except that its
cephalic termination is very different from what Sappey repre-
sents it for the pike and the flatfish. This trunk seems to be of
different relative importance in different groups. With Scor-
pcenichthys it is the longest and undoubtedly the most important
of the longitudinal canals. It is located in the spinal canal
directly above the myelon or cord, from which it is separated
by a rather tough connective tissue septum. The neural ox inter-
spinal lymphatic vessels (Fig. 4, Neu.L. V.), which have been
described so accurately by Trois and Sappey, are very important
branches of the myelonal trunk in Scorpcenichthys. Their
60 ALLEN
course lies between the neural spines and anastomose dorsad
with the dorsal or the 2 lateral dorsal lymphatic trunks. Since
there is no special anterior connection of the dorsal lymphatic
trunk with cephalic or pericardial sinus in Scorpcenichthys save
through the neural or interspinal and the dorsal intermuscular
or transverse vessels into the lateral or myelon trunks, and since
the neural or interspinal vessels are much the larger, especially
at the junction with the myelonal trunk, it is more than likely
that they convey most of the lymph from the anterior portion of
the dorsal fin region, while the main supply for the dorsal inter-
muscular vessels evidently comes from the surface of the myo-
tomes and the surrounding connective tissue. The main mye-
lonal trunk extends from the last caudal vertebra to the skull.
Its posterior connection with the caudal vein will be described
in a later paper. When the skull is reached it bifurcates, each
fork after passing laterad between the skull and the first vertebra
or atlas empties into a rather large sinus situated at the side of
the atlas, directly in front and a little below the base of the first
rib. This sinus is designated as the occipital sinus (Figs. 4
and 5, Oc.S.) and receives, as has already been stated, the main
lateral lymphatic trunk from the side and rear. Very likely
this sinus should be considered nothing more than a swelling
caused by the union of these 2 important trunks the resultant of
which is the cranial lymphatic trunk.
The course of this sinus-like vessel (Figs. 4 and 5, Cr.L. V.)
is along the lateral base of the skull. Following the upper sur-
face of the head kidney for a short distance, it crosses under
the first spinal nerve and receives from above the Jirst neural or
interspinal lymphatic vessel (Figs. 4 and 5, Neu.L. V.{1^) ; then
continuing along the side of the cranial wall between the great
abdominal lymphatic sinus and the IX and X cranial nerves
expands into a sinus (Figs. 4 and 5, S.), which lies directly
above the jugular vein, on a level with the optic lobes, immedi-
ately behind the prootic process and between the skull and the
first internal branchial levator muscle. This sinus has 2 open-
ings ; the most cephalic one is simply a tapering down of the
sinus into a papilla, which curves outward and downward to
communicate with the abdominal sinus ; while the other opening
DISTRIBUTION OF LYMPHATICS IN SCORP^NICHTHYS 6 1
leads into a lateral vessel or papilla, which curves around the
first internal branchial levator muscle to empty into what has
been designated as the cephalic sinus (Figs. 4 and 5, Ceph.S.).
A full description of this sinus and its connection with the jugu-
lar behind the prootic process will be given under a separate
paragraph.
Longitudinal /nrmal or inferior spinal lymphatic trunk and
the abdominal sinus. — Hyrtl and Stannius seemed to have over-
looked these vessels, but such a canal is represented by Vogt
(1, p. 138) as consisting of 2 large lymphatic trunks that follow
the aorta, and into which the trunk from the viscera and the
vessels from the body wall empty. The posterior connections
of these trunks were not given, but anteriorly they are said to
empty into a branch of the third canal, terminating in the
cephalic sinus. Vogt states (p. 138) that this canal (PL L,
Figs. 1 and 8 ; 64) comes from a common reservoir which fol-
lows the superior plate of the fourth branchial arch, and that it
receives 2 important branches, one coming from the fourth
branchial arch and the other arising at the middle of the body.
The last branch is said to communicate in the median line with
the corresponding branch from the opposite side immediately in
front of the kidney, and at this point receives the 2 longitudinal
trunks which follow the aorta. Two small vessels, which could
not be definitely traced, but which appeared to come from the
brain, are described as emptying into the cephalic ends of these
longitudinal trunks. Milne-Edwards (16, p. 477) says that in
general there are 2 lymphatic canals running parallel with the
aorta, but expresses some doubt about their emptying into the
cervical or cephalic sinuses. He further adds in a footnote that
Fohmann (4) found 2 longitudinal lymphatic vessels traveling
along with the aorta in the eel, which received branches from
the trunk musculature and emptied anteriorly into the cephalic
sinus. With the pike Sappey (25, p. 49) represents the trunk
sous-vertebral 2,$ occupying the same canal as the caudal artery
and vein, being situated below the vein, and receiving branches
which traverse the muscles adjacent to the hasmal spines. With
the Pleuronectidee (p. 50) he states that the inferior spinal trunk
empties into the jugular directly below the superior trunk. It
62 ALLEN
is also of interest to note in this connection that he claims to
have found the minute lymphatic vessels anastomosing with the
blood capillaries in the connective tissue of the muscles and the
skin. Trois' description of this canal in Lofhius, Urano-
scofius, and in the Pleuronectidae (28 to 31) is very similar to
Sappey's, but so far as could be learned he does not give a
cephalic ending for this trunk. With the Pleuronectidas he finds
2 parallel longitudinal vessels, a superior and an inferior longi-
tudinal trunk, having numerous anastomosing cross branches
that form a scale-shaped network on the caudal vein. Hopkins
does not mention any longitudinal haemal trunk, but describes
(8, p. 375) a large abdominal sinus running along the right side
of the air-bladder. Caudad it is said to anastomose with one of
the ducts from the duodenum ; throughout its course it receives
branches from the bladder and the stomach and finally empties
into the right lymphatic sinus, which terminates in the ductus
Cuvieri.
Both the longitudinal haemal lymphatic trunk and the abdom-
inal sinus were found in Scor^pcenichthys. The haemal trunk
was noticed only in the caudal region, and undoubtedly empties
into the abdomidal sinus.
The abdominal sinus in Scoi'-panichthys (Figs. 4, 5 and 6,
Abd.S.) is a very large and important sinus, lying directly
below the kidney and extending from the posterior end of the
abdominal cavity to the orbit. A little behind the precava it
divides, each fork following along under its respective lobe of
the kidney continues cephalad along the ventro-lateral surface
of the skull, and when the prootic process is reached directly
below the jugular, or directly opposite the first internal branchial
levator muscle, it turns inward and downward to end blindly
opposite the parasphenoid behind the orbit. In some specimens
the injecting mass so settled as to give the appearance of 2
abdominal sinuses with numerous cross branches in the visceral
cavity. Throughout the abdominal cavity this sinus receives
many branches from the reproductive organs, urinary bladder,
body wall, and probably from the kidney itself. The body
wall vessels are the intercostals, which follow along the inner
surface of the intermuscular septa and anastomose ventrad with
DISTRIBUTION OF LYMPHATICS l\ SCORP^ENICHTHYS 63
the profundus ventral lymphatic vessel. Numerous interlinking
vessels were also found between this sinus and the myelonal
trunk. With Ophiodon a large posterior mesenteric trunk was
seen to pass between the generative organs with the correspond-
ing vein acid empty into this sinus ; it had its origin from the
posterior end of the intestine, being simply a continuation of the
main intestinal trunk. As has already been stated the abdomi-
nal sinus receives a communication from the pectoral sinus, and
a little in advance of this a connection is received from the peri-
cardial sinus (Figs. 4 and 6) ; while between the two it receives
the large cceliaco-mesenteric lymphatic trunk (Figs. 4 and 6,
Cce. Mes. L. V.), coming from the viscera and following the
course of the corresponding artery. In advance of the head
kidney each cephalic fork of this sinus swells up considerably
upon the receipt of 3 sinuses from the region of the branchial
arches. An important communication, which has already been
mentioned is the papilla from sinus (S) of the cranial lymphatic
trunk (Figs. 4 and 5, S.). Another possible accession is the
profundus facial lymphatic trunk (Figs. 4 and 5, P.Fac.
L. V.).
Branchial or dorsal branchial sinuses (Figs. 4 and 5, Br.L.Si).
These 3 sinuses appear to arise from the dorsal extremities of
the first, second, third and fourth arches respectively, and pass-
ing between the obliqui dorsales muscles, unite with each other
and the abdominal sinus in such a way as to entirely encircle the
2 internal branchial levator muscles. My injections simply
showed these sinuses to be blind pockets off from the ab-
dominal sinus, and no trunks from the branchial arches or
even from the dorsal branchial muscles were seen to empty
into them.
Vogt in the salmon (1, p. 177-8) describes the second canal
emptying into the common cephalic sinus as being composed of
3 different branches, each of which is composed of 2 different
components. These 3 branches come from the first, second,
and third branchial arches, and of their 2 components, one is
very small, arising from the superior part of the arch especially
from the filaments ; while the other is more superficial, continues
along the arch and unites with the inferior jugular (Veine de
64 ALLEN
Duvernoy). Vogt states that he has succeeded in injecting the
inferior jugular from the common branchial canal (Fig. L ; 63).
A somewhat similar arrangement is shown for the fourth arch ;
the two branchial components unite in a common stem that anas-
tomoses with a large trunk coming from the middle <3f the body
and finally ends in the cephalic sinus as described under the
abdominal sinus. Stannius (24, p. 254) says that lymphatic
vessels arise from the branchial arches and empty into a trunk
running in the canal of the arches. Trois (28 and 29) always
found a branchial trunk in the groove of each arch in Lo^phms
and Uranoscoftus, which received branches arising from net-
works in the arches and in the filaments. The filament net-
works are represented as being much finer and necklace-shaped,
while those of the arch are irregular and much coarser. In
connection with Uranoscoptis (29, p. 26) the author states that
Fohman (4) is the only one having described these branchial
lymphatic vessels, and attributes the fact that they have not been
discovered by other investigators to their faulty method of pro-
cedure, namely, of immersing the specimen in alcohol.1
Miiller (15) and Stannius (24) have shown a somewhat similar
arrangementof branchial vessels under the head of vencentitritice,
and in a previous paper of mine (2) both dorsal and ventral
nutrient branchial veins were figured and described ; the former
emptied into the jugular and the latter into the inferior jugular.
These vessels received branches from the arches and the filament
nutrient veins, which arose from a capillary network in the fila-
ments. This network could easily be distinguished from the
regular gill network on account of its different arrangement
and its much coarser meshes.
In not being able to find lymphatic vessels arising from the
gills and the branchial arches I am not disposed to contradict
their existence, for I can see no reason why the gills should
not possess lymphatics.
'In this connection, would state that I see no objection to preserving an
Injected specimen in alcohol or formalin for future reference. I have kept
injected material in formalin for years in as perfect shape as when first injected,
and upon writing up a description find them of greater value than reference
figures or mere memory.
DISTRIBUTION OF LYMPHATICS IN SCORP/ENICIITHYS 65
5. FACIAL LYMPHATICS.
As in the trunk region there is a distinct superficial and pro-
fundus system. Strange to say Vogt (1, p. 137) is the only
anatomist to have definitely described lymphatics arising from
the facial region of Pisces. The first canal emptying into the
cephalic sinus in the salmon is said to originate on the temporal
(pterotic) crest from two trunks coming from the head. The
first branch, which is somewhat similar to the vessel described
below in Scorpa>nic]ithys as the profundus facial lymphatic
trunk, has its source at the anterior angle of the nasal fossa,
and passing through the orbit receives branches from the upper
part of the face and head. The second branch, which is evi-
dently analogous to the superficial facial trunk in Scorpamich-
thys, is represented as following along under the suborbital
bones and collecting numerous branches from the surface of the
cheeks, of which the inferior maxillary vessel is the largest;
this is said to run along in front of the preopercle from which
it receives several branches. Hyrtl (7, p. 236) describes a
swelling of the jugular at the entrance of the optic nerve into
the orbit that is in communication with a similar bulb on the
opposite side as the sinus ophthalmicus (Fig. 8, d), and this
sinus he thinks receives the lymph from the head. In a pre-
vious paper (2) a similar sinus-like vessel was described as cross-
ing the eye muscle canal and connecting the 2 internal jugular
veins ; but with Ophiodon there is no marked swelling of the
jugulars at the junction with the connecting vessel, which is
evidently nothing more than a venous sinus. Stannius (24, p.
254) claims that the connection of the head and trunk lymphatics
has not yet been made clear.
Superficial facial lymphatic trunk (Figs. 4 and 5, S.Fac-
L. V.). — With Scorpatnichthys this trunk has its origin in the
region of the first suborbital bone from a dorsal and a ventral
fork ; the dorsal branch comes from the snout and the space
surrounding the nasal sac ; while the ventral branch follows
along above and behind the maxilla. After uniting the common
stem crosses the orbit between the adductor muscle of the pala-
tine arch and the upper and inner edge of the chain of subor-
bital bones, or suborbital stay as it is in this species. Upon
66 ALLEN
reaching the posterior end of the orbit it crosses over the facialis-
mandibularis nerve and vein, and after passing across the lateral
surface of the prootic process unites with the jugular papilla of
the cephalic sinus (see Figs. 4 and 5) and ultimately reaches
the jugular. Numerous branches were received from the sur-
face of the adductor mandibular muscles, and soon after cross-
ing the facialis-mandibularis vein, is joined from the rear
by a rather large branch, which runs along the dorsal and
inner surface of the opercle. No inferior maxillary branch as
described by Vogt in the salmon was noticed.
Profundus facial lymphatic trunk (Figs. 4 and 5, P.Fac-
L. V.). — In the last specimen dissected the course of this canal
could be followed much better than in any of the others. It
appears to be entirely confined to the region of the orbit. In
this specimen it started from the dorsal side of the orbit, and
passing ventrad across the anterior end of the orbit bifurcates at
the ventro-cephalic corner of the orbit, but soon reunites. The
outer or sinus portion being much the larger, extends some dis-
tance ventrad between the adductor muscles of the palatine arch
and the mandible ; a few branches from the adductor mandibular
were noticed, and after uniting the common stem passes caudad
across the orbit on the surface of the adductor muscle of the
palatine arch, a little mesad of the facialis-maxillaris vein, but
some little distance inward from the superficial facial lymphatic
vessel. This trunk could be traced to a point immediately be-
neath the junction of the internal and external jugular veins,
but no farther. Very likely it continues caudad below the
jugular through the prootic process foramen and empties into
the abdominal sinus. The final ending of the profundus facial
lymphatic trunk could not, however, be determined.
6. LYMPHATICS OF THE HYOID ARCH.
Two distinct lymphatic canals are found running along the
dorsal or anterior and the ventral or posterior edges of the arch.
Of these the -posterior or ventral lymphatic trunk (Figs. 3 and 4,
P.Hyo. T.) appears to be the main stem. It traverses the lower
and posterior edge of the epi- and cerato-hyals, and from be-
tween each 2 branchiostegal rays receives 1 or 2 small branches
DISTRIBUTION OF LYMPHATICS IN SCORPyENICHTHYS 67
(Fig- 3, Hh.S.L. V.) arising from the hyo-hyoideus superior
muscles and the branchiostegal membrane. Directly behind the
inter-hyal the posterior hyoidean trunk expands into a reservoir
designated as the hyoidean sinus (Figs. 3 and 4, Ilyo.S.). This
sinus also receives the anterior or dorsal hyoidean trunk (Figs.
3 and 4, A.Hyo.T.), which runs along the upper and anterior
edge of the epi- and cerato-hyals, and in front of the inter-hyal
swells up into a sort of a sinus from which a papilla crosses the
outer surface of the inter-hyal and empties into the main hyoi-
dean sinus. At about the center of the arch quite an important
branch was seen to join it from the genio-hyoideus muscle.
This vessel (Figs. 2 and 3, Gh.L. V.) after passing along the
inner ventral surface of the muscle, crosses the first and second
branchiostegal rays, and at this point makes a sharp curve to
cross the outer surface of the cerato-hyal and empty into the
anterior hyoidean trunk. The main hyoidean sinus (Fig. 4,
Ilyo.S.) gradually tapers down dorsally into a papilla that
empties into the cephalic sinus from below and to the rear, and
ultimately reaches the jugular through it. This system of
lymphatic vessels appears to have been almost entirely over-
looked. The only reference found is that of Hyrtl (7, p. 237)»
where he represents the lymphatics from the tongue and branchi-
ostegal rays as emptying into the lateral trunk near the cephalic
sinus.
This concludes the description of the distribution of the
lymphatic trunks of the head, dorsal, ventral and pectoral fins
of Scorpcsnichthys, but 2 important sinuses into which they
empty, and which ultimately terminate in the venous system
remain to be described.
7. CEPHALIC SINUS.
With the salmon Vogt (1, p. 136) represents the cephalic
sinus as being an expansion of the lateral lymphatic trunk at
the cephalic end of the thorax, which lies under the clavicle and
has a slit covered by a valve that leads into a vessel about the
diameter of a pin head, which terminates in the sinus of Cuvier
near the jugular. This sinus is said to have 3 other openings
that are also defended by valves. In brief the first comes from
68 ALLEN
the face, the second from the first 3 branchial arches, and
the third from the fourth branchial arch, the viscera, and the
body wall. Hyrtl (7) states that the lateral trunk in Acificn-
ser, Cy-prinns, Leuciscus, Esox, etc., ends in a thin-walled
pear-shaped sinus situated at the side of the skull, a little
behind the orbit, which empties into the jugular a little forward
of the lower jaw and opercular vein. This sinus he believes is
contractile upon electrical or mechanical stimulation. With the
salmon and trout the lateral trunk is said after passing under
the clavicle to end in a sinus that discharges itself in the sinus
of the spermatic vein (Sinus der Holvenen) at its junction with
the ductus of Cuvier. A valve was seen at the point of union,
but no vessels were described in advance of the cephalic sinus ;
doubtless for reasons so fully set forth by Vogt (1), namely, that
the vessels emptying into this sinus were all guarded by valves,
and the injection mass would naturally find its way into the
venous system. With Pcrca lucioferca, Tinea chrysitis and
Cottus gobio both points of union were noticed. Stannius (24, p.
254) speaks of the lymphatics from the head, gills, and trunk as
uniting in a sinus that emptied into the truncus transversus (pre-
cava) near the jugular, and in a footnote states that this com-
munication was noted by Monro (14) and Hewson (5). Milne-
Edwards (16, p. 475) following Hyrtl says that in the pike,
roach, grudgeon, barb and sturgeon, the lateral trunk is pro-
longed into the head and terminates at the base of the cranium
into a sinus that empties into the jugular through a transverse
canal. While in the salmon, cod, rays and sharks he describes
the lateral vessels as opening into a pair of cervical sinuses,
which descend behind the center of the scapula to unite in the
median line at a point where the abdominal sinus joins them,
and each of these scapular reservoirs is said to communicate
with the ductus Cuvieri through an orifice protected by valves.
Also with Perca lucioferca and Cottus Gobio 2 modes of com-
munication with the venous system are vaguely mentioned.
Trois's description in Lophius (28, p. 8) of the termination of
the 2 lateral lymphatic vessels in the cervical or cephalic sinuses
and their union with the abdominal sinus is almost identical
with the descriptions given by Hyrtl and Milne-Edwards,
DISTRIBUTION OF LYMPHATICS IN SCORP.-EMCIITIIYS 69
except that no connection is noted with the venous system.
According to Sappey (25) there are no cephalic sinuses in the
carp or the pike. He states that both the lateral and myelonal
or superior longitudinal spinal lymphatic trunks empty directly
into the jugular, and with the Pleuronectidie the inferior spinal
or longitudinal hcemal trunk likewise terminates in the jugular,
while the ventral trunk empties directly into the ductus Cuvieri.
No other vessels were mentioned from the head region, doubt-
less for the reasons given above. Hopkins represents the lat-
eral lymphatic trunk of Aiuia (8, p. 371) as passing under the
clavicle and opening into a cephalic sinus at the base of the
cranium. This sinus is described as receiving the pericardial
sinus from below ; its opening into the jugular is said to be
about 1 cm. cephalad and a little ventrad of the dorsal end of
the clavicle, and the orifice is guarded by a valve opening into
the vein.
Possibly it might simplify matters somewhat to classify the
cephalic sinuses and their connections described in the previous
paragraph under 5 different heads. Firsts in Acifienscr, Cy-
■prinus Leaciscus, Fsox, etc., the lateral trunk after passing
under the pectoral arch follows the ramus lateralis vagi to the
base of the skull, and there expands into a cephalic sinus that
empties into the jugular. Second, with Lofhius, the salmon,
trout, ray, and shark the lateral trunk immediately after pass-
ing under the shoulder-girdle discharges itself in a cervical or
cephalic sinus that empties into the precava, and which accord-
ing to Vogt in the salmon receives other trunks from the face
and the branchial arches. Third, midway between these two
extremes comes Aw/a with a lateral trunk which after passing
under the clavicle terminates in a cephalic sinus, that also re-
ceives the pericardial sinus, and which ultimately empties into
the jugular instead of the precava. Fourth, Perca, Tinea,
and Cottus are vaguely described as having two communica-
tions with the venous system ; probably the jugular and pre-
cava connections are the ones referred to. Fifth, with the
carp, pike and flatfish there are said to be no cephalic sinuses,
the main lymphatic trunks emptying directly into the jugular
and precava.
170 ALLEN
What is designated as the cephalic sinus in Sco?'pceiiichthys
(Figs. 4 and 5, Cefih.S.) does not fit very well into any of these
classes and seems to constitute one of its own. Here this sinus
is a sort of stomach-shaped reservoir situated between the
hyomandibular bone and the first internal branchial levator mus-
cle, which would make it nearly opposite and a little below the
level of the cerebrum and the optic lobes. Its cephalic dorsal
corner gradually tapers down into a papilla, which passes in-
ward and empties into the jugular directly behind the prootic
process. At this point the jugular itself expands into a sort of
reservoir before greatly diminishing in caliber to pass through
the foramen formed by the prootic bone and its process. In a
large uninjected specimen of Ophiodon from which a portion
of the dorsal wall of the jugular had been removed the orifice
could be distinctly seen from the inside of the vein. It pierced
the ventro-lateral wall a little behind the prootic process, and
was guarded by a strong valve that opened into the vein. This
valve was attached dorsad, but was free three fourths of the
way around. As the cephalic sinus papilla passed behind the
prootic process to empty into the jugular it recieves the super-
ficial facial trunk. In the posterior ventral corner of the cephalic
sinus there is a second opening into which a prolongation of the
hyoidean sinus enters. A third opening remains to be noted in the
posterior dorsal corner, which is in connection with a lateral
papilla from a sinus at the cephalic end of the cranial lymphatic
trunk (Figs. 4 and 5, S). As previously stated this sinus corres-
ponds in position to the cephalic sinus described and figured by
Hyrtl in Leuciscus, however, in Scorjicenichthys this sinus does
not empty directly into the venous system ; anteriorly it tapers
rapidly down into a papilla that passes ventrad between the
cephalic sinus papilla and the first internal branchial levator
muscle to communicate with the cephalic end of the abdominal
sinus, but in no case was any direct connection noticed between
it and the cephalic sinus, the cephalic sinus papilla, or the jug-
ular vein. As stated above the connection of this sinus with the
cephalic sinus comes from its lateral wall. Sinus S in Scorfce-
nichthys (Figs. 4 and 5) is therefore to be regarded as simply an
DISTRIBUTION OF LYMPHATICS IN SCORPyENICIITHYS 7 1
expansion of the cranial lymphatic trunk ; a trunk that is formed
by the union of the lateral and myelonal canals.
8. PERICARDIAL SINUSES.
Strange to say so far as could be determined Hopkins (8, p.
372—3) is the only one to describe such a sinus ; evidently it is
absent in the other species studied or else it has been over,
looked. The ventral lymphatic trunk in „ \111ia is represented as
branching at the level of the heart ; each fork running between
the pericardium and the tough fibrous partition separating the
pericardial from the abdominal cavity, is said to merge into
large pericardial sinuses that communicate with the sinuses of
the lateral trunk (cephalic sinuses). With Scorpcenichthys this
is a very large and extremely important sinus, and appears to
be made up of several divisions or sub-reservoirs, which have
for convenience been designated as the main pericardial, pos-
terior, and ventral pericardial sinuses.
One of the main pericardial sinuses (Figs. 4, 6, 9 and 10,
Per.S.) is perhaps best shown in Fig. 6, which is drawn from
a very large specimen that was well injected and hardened in
formalin. It is a retort-shaped reservoir situated directly behind
the precava or ductus of Cuvier. Its dorsal stem crosses the
corresponding lobe of the kidney to unite with the main lateral
trunk. In this specimen a branch was given off caudad at the
base of the kidney which anastomosed with a branch of the
pectoral sinus that emptied into the abdominal sinus. In no
other specimen was this connection noticed, but a little below
this level and in front there is always some communication with
the abdominal sinus. Here a much larger branch is given off
cephalad (Figs. 4 and 6) which soon expands into 3 large
divisions (Fig. 6 ; a, b and c). The most anterior one (a) passes
cephalad to terminate in the abdominal sinus directly behind
the precava. The middle one (b), which is the largest of the 3,
is a blind sac that extends ventrad directly behind the precava
and rests on the dorsal surface of the sinus venosus. Without
carefully dissecting out sinus (/;) it always has the appearance
of emptying into the sinus venosus. I have, however, carefully
dissected out this sinus in many specimens to make certain that
72
ALLEN
there was no communication with the venous system here, and
have satisfied myself in every case that this is simply a blind
sac. The third division (c) is merely a much smaller blind sac,
lying behind (b). At about this level the pericardial sinus
receives a small lymphatic vessel from the side, which comes
from the center of the clavicle (Figs. 4 and 6, C.L. V.). In
this region it is important to avoid confusing the external
subclavian and anterior gastric or oesophagus veins (Fig. 6,
J?. Sub. V. and A. Gas. V.) with the lymphatics. The external
subclavian vein crosses over the pericardial sinus and its divi-
sions {a, b and c) to discharge itself in the precava ; while the
anterior gastric veins pass under the pericardial sinus, but over
its divisions (a, b and c) and likewise empty into the precava.
There is always quite a prominence in the neighborhood of the
anterior ventral corner of the pericardial sinus which extends
outward and forward some little distance between the external
and internal pharyngo-clavicularis muscles.
From a lateral view what appears to be a separate posterior
pericardial sinus (Figs. 4 and 6, Per.S.m) emptying into the
main pericardial sinus is shown in a ventral view (Figs. 9 and
10, Pcr.S.(Y)) to be nothing more than a posterior continuation
of the main pericardial sinus. Each of these so-called posterior
pericardial sinuses or posterior continuations of the main peri-
cardial sinuses passes at first ventrad behind the sinus venosus
and ventricle, being separated from them only by the pericar-
dium, and when the posterior ventral corner of the ventricle is
reached curves backward at nearly right angles. At this point
in about half of the specimens a connecting branch (Fig. 6 and
10, X) was given off cephalad to anastomose with a papilla of
the ventral pericardial sinus (Figs. 6 and 10, P. V.Pcr.S.) that
communicates with the main pericardial sinus. In an equal
number of specimens connecting vessel (X) was absent (see
Figs. 4 and 9), and possibly it should be noted that in these
specimens the ventral pericardial sinus papilla always followed
very close to the posterior portion of the main pericardial sinus.
Both of the posterior pericardial sinuses or posterior portions of
the main pericardial sinuses continue backward some little dis-
tance, gradually increasing in size as they approach one another,
DISTRIBUTION OF LYMPHATICS IN SCORIM5NICHTII YS
73
until finally they come into contact, but do not anastomose.
Both of them end some little distance in advance of the ventral
fins, and either may receive the profundus ventral lymphatic
trunk.
Ji.l.J.V.
Mut.Kto
Ph.L.V.
Nixt.Vn
V.P?r.S.(r>
Lin. r.
Fig. 7. Shows the branching of the ventral pericardial sinus to the pharynx
region, especially to the bases of the first and second branchial arches and the
thyroid gland. The anterior ventral pericardial sinus has been cut and turned
forward from its natural position. Small Scorpcenichthys. Natural size.
A list of the abbreviations used in text-figs. 7 to 10 will be found in a general
list, p. 87, under 13.
With Scorfcenichthys there is always a distinct and very im-
portant ventral ^pericardial sinus (Figs. 3, 4, 6, 7, 9 and 10,
V. Per. Si). Since there is always a marked depression in the
region of the bulbus arteriosus this sinus might be said to con-
sist of an anterior and a posterior portion. The posterior por-
tion of this sinus (Figs. 3,4, 6, 9 and 10, V.Per.S.) is a somewhat
irregularly-shaped reservoir situated below the anterior end of
the ventricle and the bulbus arteriosus. Its 2 posterior dorsal
corners are prolonged across the posterior half of the ventricle
as papilla? (Figs. 4, 6, 9 and 10, P. V.Per.S.), which com-
municate with the anterior ventral corners of the corresponding
pericardial sinuses. Between these 2 papillae the ventral longi-
tudinal lymphatic trunk curves around the cephalic ends of the
pelvic bones, and empties in the median line into the posterior
end of the ventral sinus. Ventrally this sinus bifurcates and
soon forms 2 conspicuous reservoirs situated on the ventral sur-
Proc. Wash. Acad. Sci., May, 1906.
74
ALLEN
face of the clavicles (see Fig. 3), and into these sinuses the ven-
tral prolongations of the pectoral sinuses terminate. The ante-
rior dorsal corner of the posterior ventral pericardial sinus is con-
tinuous with the anterior portion of the ventral pericardial sinus.
Mut.m
JVntVar
.I.j.r.
Fig. 8. Deeper dissection of the same specimen as Fig. 7 to show the origin
of the inferior jugular from the nutrient branchial veins and its course above
the ventral aorta.
This sinus (Figs. 3, 4, 6, 7, 9 and 10, V.Per.S.{l)) passes cepha-
lad along the lower side of the ventral aorta, and when midway
between the combined trunks of the third and fourth afferent
branchial vessels and the second pair of afferent branchial
vessels, it divides ; each fork, designated as the ^pharynx lym-
phatic vessel (Figs. 3, 6, 7 and 8, Ph.L.V.), passes at first
obliquely across the thyroid gland and the second afferent
branchial trunk. Here it bifurcates, the anterior fork going
along the side of the thyroid to the base of the first branchial
arch ; while the other stem continues along between the afferent
and efferent branchial vessels of the second arch and shortly
sends off a branch which traverses along behind the afferent
branchial trunk. Neither of these branches could be traced
farther than to the origin of the first branchial filaments. They
evidently only receive lymph from the connective tissue lining
the base of the second branchial arch and the thyroid gland.
Since no similar branch was found on any of the other branchial
arches this fork has been designated as a pharynx rather than
a branchial vessel. In well-injected specimens as is shown by
(Fig. 6, Thyr.L. V., and Fig. 3) there was found an additional
DISTRIBUTION OF LYMPHATICS IN SCORIVENICHTHYS 75
stem emptying into the ventral pericardial sinus between the 2
pharynx vessels. It apparently arises solely from the thyroid
gland, and it may have some direct connection with some of the
branches of the inferior jugular that run along the dorsal sur-
face of the gland.
During the early stages of this work I had no inference that
either the pharynx or the thyroid lymphatic vessels had any
communication with the inferior jugular. Later on a specimen
was dissected in which the entire venous system, with the single
exception of the jugular and its branches, was found to be well
filled from an injection of the myelonal lymphatic trunk. This
of course led me to believe that there must be another commu-
nication with the venous system in the head region other than
the cephalic sinus, and most careful search was made of all the
lymphatic vessels surrounding the jugular, precava, sinus
venosus, and especially lobe (b) of the pericardial sinus ; still
no connection whatever was found. Also every opening into
these veins was accounted for. As the work progressed the
lymphatics of several heads was injected from the ventral
lymphatic trunk, and as a rule in these specimens the pericar-
dial lymphatic sinuses, the thyroid, and pharynx lymphatic ves-
sels were well filled, and the mass entered the nutrient branchial
and the inferior jugular veins, but rarely extended in the inferior
jugular as far back as the sinus venosus ; it would first run out
some of the cut lymphatic vessels that were severed in removing
the head. In one specimen I first injected the venous system
from one of the hepatic veins with a blue mass, and after allow-
ing the mass to partially solidify, injected the lymphatics with a
yellow mass from the ventral lymphatic trunk. The lymphatic
sinuses, pharynx, and thyroid lymphatic vessels were found to
be well filled with the yellow mass, as was also the nutrient
branchial veins, and the yellow mass had forced back the blue
a short distance in the inferior jugular vein. Upon further dis-
section the entire venous system, including the jugular and the
dorsal nutrient branchial veins, was found to be filled with the
blue mass, indicating of course that a connection must exist be-
tween either the pharynx or the thyroid lymphatic vessel and one
of the branches of the inferior jugular. By dissection I have
76
ALLEN
been unable to find the exact point of union, but am inclined to
believe that the thyroid vessel is the one that communicates
with the venous system. For a short distance each pharynx
lymphatic vessel runs along the ventral surface of the combined
trunk of the third and fourth nutrient branchial veins, and at
this point several dorsal branches are given off, but they ap-
parently go to the posterior end of the thyroid. The largest of
them, however, leads into the sinus situated at the base of the
second branchial arch.
H.LJ.V,
V.Per.Slrr
P. V.fkrS:
Per.Sr
Fig. 9. Ventral view of the large pericardial lymphatic sinuses surrounding
the heart. Only a portion of the ventral pericardial sinus is figured. In this
specimen the two interlinking arms between the ventral pericardial and the peri-
cardial sinuses had no additional connection with the posterior portion of the
pericardial sinus as it has in some specimens, shown in Fig. 10. Medium large
Scorpcenichthys. Natural size.
It is of interest in this connection to again note that Vogt (i,
p. 138) in the salmon describes one of the 2 dorsal lymphatic
trunks of each branchial arch*, which terminates in the cephalic
sinus, as being prolonged ventrad and anastomosing with the
veine de Duvernoy (inferior jugular), and from Vogt's descrip-
tion it is perfectly clear that he has not confused the nutrient
DISTRIBUTION OF LYMPHATICS IX SCORI'/ENTCHTHYS
77
branchial veins for lymphatics, otherwise they would terminate
in the jugular and not in the lymphatic trunk that emptied into
the cephalic sinus. It will be seen at a glance that this connec-
tion of the dorsal lymphatic trunks with the inferior jugular
described by Vogt in the salmon is very different from the some-
what hypothetical union described above, notwithstanding that
both modes of communication occur in the same vicinity.
KPer.SAO
&r.S.
Per.&W
Fig. io. Same view of another specimen as Fig. 9 in which the interlinking
arms of the pericardial and ventral pericardial sinuses had an additional connec-
tion (JC) with the posterior portion of the pericardial sinus. Medium size
Scorpcznichthys. Natural size.
Possibly at this point a note should be made in connection
with the inferior jugular and its branches. In Scorfamichthys
2 inferior jugulars empty into the sinus venosus, a large right
and a much smaller left inferior jugular (Figs. 3, 6, 7 and 8,
7?. and L.I.J. V.) ; both of which pass along, above and to the
side of the ventral aorta, and unite in a common stem directly
behind the common trunks of the third and fourth afferent
branchial vessels. Perhaps it would have been more accurate
to have conversely stated this arrangement by saying that the
common stem of the inferior jugular bifurcated behind the com-
raoji trunks of the third and fourth afferent branchial vessels,
78 ALLEN
and each fork after passing along the side of the ventral aorta
emptied into the sinus venosus. Following the common stem
of the inferior jugular cephalad it will be seen from (Figs. 6, 7
and 8) that it may branch and each fork receive first the com-
bined sinus-like trunk of the third and fourth nutrient branchial
veins and then in succession the second and first nutrient
branchial veins as shown by Fig. 8, Nut. V.(S4), etc.) or as was
noticed in other specimens may expand into a broad sinus
between the second and third branchial arches, which in like
manner collects the nutrient branchial veins. In either case the
anterior part of the inferior jugular in spreading out over the
thyroid gland took on more the appearance of a lymphatic trunk
than it did a vein. •
9. GENERAL CONSIDERATIONS AND SUMMARY.
Scorficenichtkys has as complete a lymphatic system as is to
be found in any vertebrate ; in general wherever there is con-
nective tissue there are lymphatics. As in the higher Verte-
brata there are distinct superficial and profundus systems. In
the trunk region the main lymphatic canals are longitudinal
trunks that terminate caudad in the caudal vein, and cephalad
empty in one way or another into the cephalic and ventral peri-
cardial sinuses, which ultimately reach the jugular and appa-
rently the inferior jugular veins. These sinuses are simply
non-contractile reservoirs in no way comparable to the lym-
phatic hearts of the Batrachia. In the region covered by this
paper no valves were found except at the orifice of the cephalic
sinus papilla in the jugular.
1. The lateral lymphatic canal in the trunk region very
closely resembles the descriptions already given for other
species. Dorsal and ventral intermuscular or transverse
branches were regularly received ; they arose from a network
in the connective tissue of the myotomes and skin, and anasto-
mosed above with the dorsal lymphatic trunk and below with
the ventral trunk. In the anterior region of the trunk there
are dorsal and ventral lateral lymphatic vessels, which are
merely a series of longitudinal cross-branches, lying above and
below the main lateral trunk, but which give additional support
DISTRIBUTION OF LYMPHATICS IN SCORP/ENICHTHYS 79
to Trois' statement that similar longitudinal trunks in Urano-
scofins are doubtless of only secondary importance. Before
passing under the shoulder-girdle the lateral trunk receives a
large pectoral sinus that collects the lymph from the pectoral
fin region, and from here on its course and connections are very
different from what has been described for any other fish.
Following the first rib inward it receives a communication from
the pericardial sinus, and opposite the atlas unites with a fork
of the myelonal trunk in what is designated as the occipital
sinus, from which the cranial trunk has its source.
2. A large and very important myelonal or superior longi-
tudinal spinal lymphatic trunk is found traversing the spinal
canal above the cord, from which it is separated by a septum.
The neural or interspinal branches noted by previous workers
are very conspicuous in Scorfcenichlhys ; all of which anasto-
mose above with the dorsal lymphatic trunks, and many of
them are prolonged ventrally to connect with the abdominal
sinus or the longitudinal haemal lymphatic trunk. Evidently
this trunk is absent in many species or else it has been over-
looked. So far as could be ascertained Sappey is the only
one to give it a cephalic ending ; he represents it with the pike
and carp as curving outward at the first cervical vertebra and
emptying directly into the jugular. In Scorpcenichthys the
myelonal trunk bifurcates directly behind the skull ; each fork
passing outward between the skull and atlas unites with the
lateral lymphatic trunk in forming the cranial lymphatic trunk,
and as stated above the occipital sinus marks the point of union.
3. The cranial lymphatic trunk follows along the ventro-
lateral wall of the skull above the jugular, and shortly before
the prootic process is reached dilates into sinus (s), which opens
laterally into the cephalic sinus and anteriorly into the abdomi-
nal sinus.
4. Trois' description of the dorsal lymphatic trunk in Lophius
and Uranoscopus will answer equally well for Scor^pcEiiichthys.
In the fin region it splits up into 3 parallel vessels, 2 of which
run along at the side and base of the rays and the third is a
median trunk that traverses the basal canal of the rays ; the
latter trunk receives branches from the fin membrane, there
80 ALLEN
being 2 for each spine or ray, and sends outward numerous
cross-branches to the lateral trunks ; the two lateral dorsal
trunks communicate with the lateral lymphatic trunk through
the intermuscular or transverse vessels, and with the myelonal
trunk through the neural or interspinal vessels. The first neural
vessel passes between the skull and the first neural spine and
empties into the cranial lymphatic trunk.
5. With Scorficenichlhys the ventral lymphatic trunk in front
of the anal fin is not a paired vessel as described by Trois.
Between the ventrals it expands into a large heart-shaped sinus
into which the ventral fin sinuses are discharged. They
receive the lymph from the ventral fins and are prolonged be-
tween the body myotomes and the ventral fin musculature to
end in the ventral lymphatic trunk. Two other branches have
their origin from between the superficial and profundus ab-
ductor muscles of the ventral fin. In the median line the ven-
tral lymphatic trunk penetrates between the superficial and pro-
fundus abductor muscles, and following along the lower side
of the pelvics terminates in the posterior end of the ventral
pericardial sinus. The ventral intermuscular or transverse'
vessels connect this trunk with the lateral lymphatic trunk.
6. A profundus ventral lymphatic trunk was observed run-
ning along the inner surface of the body musculature parallel
with the main ventral lymphatic trunk. Connecting branches
were noticed between the two in the region of the ventral fins,
and it was also in communication with the abdominal sinus
through the intercostal vessels ; while anteriorly it emptied into
one of the pericardial sinuses.
7. A large pectoral sinus is placed at the base of each pec-
toral ; dorsad it unites the lateral trunk and the abdominal sinus,
and ventrad it is prolonged to communicate with the ventral
pericardial sinus. Into the pectoral sinus is discharged a com-
mon trunk formed from the union of the external and internal
pectoral sinuses. These sinuses run along at the base of the fin
and receive connecting branches from the median pectoral sinus,
which traverses the basal canal of the rays and collects the
lymph from the fin. Trois is the only one to describe the pec-
toral lymphatics, and he represents the n>ain trunks in Loph/us
DISTRIBUTION OF LYMPHATICS IN SCORP/ENICHTHYS 8l
and Uranoscopus as emptying directly into the cephalic
sinus.
8. In Scor-p<znichth\$ there are distinct superficial and pro-
fundis facial lymphatic systems. The superficial system arises
in the snout region, follows the upper inner surface of the sub-
orbital stay through the orbit, and after receiving a branch from
the opercular region joins the jugular papilla of the cephalic
sinus directly behind the prootic process ; while the profundus
system takes its origin from a large orbital sinus, and could be
traced to a point directly in front of the foramen formed by the
prootic process with the skull, but no further. Very likely it
passes through this foramen below the jugular and empties into
the abdominal sinus. Vogt describes somewhat similar vessels
in the salmon as uniting in a common trunk that emptied into
the cephalic sinus, which is located under the clavicle.
9. There are in Scorpcenichthys 2 lymphatic canals running
along either side of the hyoid arch. The ventral or posterior
one is evidently the main trunk, since it collects the lymph from
the branchiostegal region and expands into a sinus behind the
interhyal, which receives the dorsal or anterior trunk. This
hyoidean sinus tapers down dorsad into a papilla that empties
into the cephalic sinus.
10. Strange to say, my dissections have revealed no lym-
phatic vessels coming from the cranial cavity ; these doubtless
exist, but the injection mass has failed to reach them. From
the arrangement of the blood vessels one would expect to find
one of the trunks passing out of the cranial cavity near the V and
VII complex, and joining one of the large lymphatic sinuses
attached to the side of the skull. Very likely there is a poste-
rior trunk, which in some way or another unites with the mye-
lonal trunk. In some previous work on the vascular system the
myelonal trunk of a large Ophiodon was injected, and upon
opening up the cranial cavity all of the semi-circular canals of
the ear were found to be filled with injecting mass.
11. An extremely important vesicle in Scorpcenichthys is the
abdominal sinus, which is situated directly below the kidney,
and forking with it is prolonged cephalad to the orbit. It
receives the lymphatics from the reproductive organs, the inter-
82 ALLEN
costal vessels, the coeliaco-mesenteric trunk from the viscera,
the dorsal branchial sinus which could only be traced to the
arches, and more than likely the lymphatic vessels from the
kidney and the profundus facial trunk ; in addition it has inter-
linking branches with the myelonal trunk, and has communica-
tions with the pectoral sinus, the pericardial sinus, and the
cranial trunk.
12. What is designated as the cephalic sinus in Scorflce-
nichthys may be only analogous to the similar sinus of other
fishes that performs the same function, but which has entirely
different connections and very different modes of termination.
With Scor-panichthys this is a non-contractile stomach-shaped
reservoir situated beneath or mesad to the upper portion of the
hyomandibular. Dorsad it tapers down into a sort of a papilla
that empties into the jugular directly behind the prootic process.
The orifice of this papilla is guarded by a valve, which opens
into the vein. In one way or another the lymph from the entire
body can reach this sinus ; the superficial facial lymphatic trunk
unites with its jugular papilla; the hyoidean sinus empties into
it from below ; and a connecting branch from sinus (s) of the
cranial trunk, which is also in direct communication with the
abdominal sinus, is received from above and behind.
13. The pericardial sinuses, which surround the heart in
Scorficenic/ithys have been subdivided into 3 distinct reservoirs.
What has been designated as the main pericardial sinus is situ-
ated between the precava and the shoulder-girdle. It is in con-
nection above with the lateral lymphatic trunk, and sends off a
vecicle anteriorly that soon divides into 3 lobes, the most ante-
rior being in communication with the abdominal sinus and the
other 2 ending blindly. Some little distance below this level
the pericardial sinus is continuous posteriorly into what has been
described as the posterior pericardial sinus, which either ends
blindly or receives the profundus ventral lymphatic trunk. In
addition to all these connections it also receives from below and
in front a prolongation of the ventral pericardial sinus, a sinus of
considerable importance, which can always be separated into a
posterior and an anterior portion. The former receives the
ventral lymphatic trunk and the ventral prolongations of the
DISTRIBUTION OF LYMPHATICS IN SCORP^ENICIITIIYS 83
pectoral sinuses ; while the latter branches anteriorly into what
has been designated as the thyroid and pharynx vessels, one of
the other of which, undoubtedly communicate with the inferior
jugular. As was noted for the cephalic sinus, the lymph from
the entire body can be discharged in one way or another into
the ventral pericardial sinus, and doubtless ultimately into the
inferior jugular.
IO. SYNONYMY.
Abdominal sinus. — Desc. as 2 parallel trunks following the
aorta (?), Vogt (1) ; Vasi longitudinali spinali inferiori (?), Trois
(28) ; Le tronc sous-vertebral (?), Sappey (25) ; Third abdominal
sinus (?), Hopkins (8).
Branchial lymphatic sinuses. — Canaux muciques des
branchies and Canaux muciques du 4me. arc branchial, Vogt
(1) ; Linfatici delle branchie, Trois (28).
Cephalic sinus. — Kopf-Sinus, Hyrtl (7) ; Desc. as spacious
reservoir lying under the clavicle, Vogt (1) ; Desc. Stannius
(24) and Milne-Edwards (16) ; Seni cefalici o cervicali, Trois
(28); Cephalic sinus, Hopkins (8).
Dorsal fin lymphatic vessels. — Tronchetti linfatici delle pinne,
Trois (31); Reseau cutane de la nageoire dorsale, Sappey
(25).
Dorsal lymphatic trunk. — Untergeordnetere oberflachliche
Langsstamme, Stannius (24) ; Desc. Milne-Edwards (16) ;
Tronco linfatico longitudinale dorsale, Trois (28) ; Les troncs
lymphatiques dorsaux, Sappey (25) ; Dorsal lymphatic trunk,
Hopkins (8).
Intermuscular or transverse lymphatic vessels. — Seitenast-
Paare, Hyrtl (7) ; Desc. Stannius (24), Milne-Edwards (16),
and Hopkins (8) ; Tronchetti trasversali, Trois (28) ; Troncules
qui s'etendent au tronc abdominal and Troncules qui relient le
tronc lateral au tronc abdominal, Sappey (25).
Lateral lymphatic trunk. — Seitengefasse, Hyrtl (7); Grand
canal lateral and des canaux muciques, Vogt (1) ; Seitenlangs-
stamme, Stannius (24) ; Les troncs lateraux, Milne-Edwards
(16) and Sappey (25) ; Tronchi linfatici laterali, Trois (28) ;
Lateral lymphatic trunk, Hopkins (8).
84 ALLEN
Secondary lateral lymphatic trunks. — Probably one of
Stannius' dorsal lymphatic trunks ; Desc. Milne-Edwards in
Silurus ; Tronchetti linfatici laterali accessor]' (29).
Median pectoral Jin sinus. — Vaso collettore profondo (?),
Trois (28).
Myelonial or superior longitudinal spinal lymphatic trunk. —
Wassergefasse im Ruckenmarks-Canal, Hyrtl (7) ; Langs-
stammes des Canalis spinalis, Stannius (24) ; Longitudinale
spinale superiore (28) and Tronco linfatico sopravertebrale
(31), Trois ; Tronc lymphatique sus-vertebral ou intrarachidien,
Sappey (25).
Neural or interspinal lymphatic vessels. — Desc. Hyrtl,
Stannius, and Milne-Edwards ; Vasi interspinosi, Trois (28) ;
Troncules lymphatiques qui viennent se jeter dans le grand
tronc sus-vertebral, Sappey (25).
Pericardial sinus. — Pericardial sinus, Hopkins (8).
Profundus facial lymphatic trunk. — Desc. Vogt (1).
Pectoral sinus. — Desc. Hyrtl and Stannius; Trois (28) desc.
three pectoral sinuses emptying into cephalic sinus ; Pectoral
sinus, Hopkins (8).
Superficial facial lymphatic trunk. — Desc. Vogt (1).
Ventral fin lymphatic sinuses. — Desc. Hyrtl, Trois, and
Sappey ; Sinus at the base of the ventral fin, Hopkins (8).
Ventral or abdominal lymphatic trunk. — Ein unpaarer
epigastrischer Langsstamm, Stannius (24); Desc. Milne-Ed-
wards (16) ; Tronchi linfatici abdominali, Trois (28) ; Les troncs
lymphatiques inferieurs ou abdominaux, Sappey (25); Ventral
lymphatic vessel, Hopkins (8).
II. LITERATURE.
1 . Agassiz et Vogt.
1845 Anatomiedes Salmones. Memoires de la Societe des Sciences Naturelles
de Neuchatel.
2. Allen, W. F.
1905 Blood-Vascular System of the Loricati (The Mail-cheeked Fishes).
Proc. Wash. Acad. Sci., Vol. VII.
3. Ecker, A.
1889 Anatomy of the Frog. Trans, by G. Haslam. Oxford.
DISTRIBUTION OF LYMPHATICS IN SCORIVKNICHTHYS 85
4. Fohmann.
1827 Das Saugadersystem der Wirbelthiere, I Heft. Heidelberg.
5. Hewson, W.
1769 An Account of the Lymphatic System in Fishes. Phil. Trans.
6. Hall, M.
1836 A Critical and Experimental Essay on the Circulation of the Blood.
7- Hyrtl.J.
1843 Ueber die Caudal und Kopf-Sinuse der Fische. Arch. f. Anat. u.
Physiol.
8. Hopkins, G. S.
1893 The Lymphatics and Enteric Epithelium of Amia calva. The Wilder
Quarter-Century Book. Ithaca.
9. Jones, T. W.
1868 The Caudal Heart of the Eel a Lymphatic Heart. Phil. Trans.
10. Kilborne, F. L.
1884 Preliminary Note on the Lymphatics of the Common Bull-head, Ameiu-
rus catus. Proc. Amer. Asso. Adv. Sci., Thirty-third meeting. Phila-
delphia.
11. Leeuwenhoek.
1660 Arcana Naturae ditecta. In Epist. LXVI, about 1660, described the
caudal heart of the eel.
12. Leydig, F.
1851 Anatomisch-histologische Untersuchungen iiber Fische und Rep-
tilien. Lehrbuch der Histologic des Menschen und der Thiere. Zur
Anatomie und Histologic der Chimaera monstrosa. Arch. f. Anat. u.
Physiol.
13. Langer, C.
1867 Ueber Lymphgefasse des Darmes einiger Susswasserfische. Du Bois
und Reicherts Archiv.
14. Monro, A.
1785 The Structure and Physiology of Fishes. . London.
15. Miiller, J.
1839 Vergleichende Anatomie der Myxinoiden. M^m. de l'Acad. des Sci.
de Berlin.
16. Milne-Edwards, H.
1859 Lemons sur la Physiologie et l'Anatomie compare'e. Tome IV. Paris.
17. Moreau, E.
1881 Histoire naturelle des Poissons de la France.
18. Mayer, P.
1888 Ueber Eigenthiimlichkeiten in den Kreislaufsorganen der Selachier.
Mitth. Zool. Stat. Neapel. VIII. Bd.
19. Owen, R.
1871 Anatomy of Vertebrates. Vol. I. London.
86 ALLEN
20. Parker, T. J.
1866 On the Blood vessels of Mustelus antarcticus. Phil. Trans.
21. Robin, C.
1845 Note sur le systeme sanguin et lymphatique des Raies et des Squales
Journal lTnstitut.
22. Robin, C.
1845 Sur les vaisseaux lymphatiques des Poissons. Arch. gen. de m^d.
Partie anatomique.
23. Robin, C.
1867 M^moire sur l'anatomie des lymphatiques des Torpilles. Jour, de
l'Anat. et Physiol.
24. Stannius, H.
1854 Handbuch der Anatomie der Wirbelthiere. Vol. II of Siebold und
Stannius. Berlin.
25. Sappey, P. C.
1880 Etudes sur l'appareil mucipare et sur le systeme lymphatique des pois
sons. Paris.
26. Schafer, E. A.
1898 Text-Book of Physiology. Pages 1S1-185 ; 261-285 ; 285-312. London.
27. Sabin, Florence R.
1902 On the Origin of the Lymphatic System from the Veins and the Devel-
opment of the Lymph Hearts and Thoracic Duct in the Pig. Amer.
Jour, of Anat.
28. Trois, E. F.
1878 Ricerche sul sistema linfatico del Lophius piscatorius. Atti del R.
Istituto Veneto di scienze, lettere ed arti. Vol. IV, Ser. 5.
29. Trois, E. F.
1880 Ricerche sul sistema linfatico dell'Uranoscopus scaber. Atti del R.
Istituto Veneto di scienze, lettere ed arti. Vol. VI, Ser. 5.
30. Trois, E. F.
1881 Ricerche sul sistema linfatico dei Pleuronettidi, Rhombus maximus e R.
lsevis. Atti del R. Istituto Veneto di scienze, lettere ed arti. Vol.
VII, Ser. 5.
31. Trois, E. F.
1881 Ricerche sul sistema 'linfatico dei Pleuronettidi, Psettini, Platessini,
Pleuronectini, e Soleidi. Atti del R. Istituto Veneto di scienze, lettere
ed arti. Vol. VII, Ser. 5.
32. Trois, E. F.
1882 Ricerche sul sistema linfatico dei Gadoidei, Motella tricirrata e M. mac-
ulata. Atti del R. Istituto Veneto di scienze, lettere ed arti. Vol.
VIII, Ser. 5.
33- Vogt, C.
1842 Ueber die Schleimgange der Fische. Aemtlicher Bericht iiber die Ver-
sammlung der Gesellschaft "deutscher Naturforscher und Aerzte zu
Mainz.
DISTRIBUTION OF LYMPHATICS IN SCORPyENICIITIIYS 87
12. DESCRIPTION OF THE FIGURES.
Sco rpcen ichthys m a rm 0 rat us .
All of the figures were drawn to a scale from injected specimens. In the col-
ored figures the lymphatics are indicated by yellow and the veins by blue: while
in the other figures the veins are cross-barred and the lymphatics are drawn in
outline or stippled.
Fig. 1. Represents a general lateral view of the head region of a small Scor-
pcenichthys ,' the skin being removed to show the superficial vessels of the body,
dorsal, ventral, and pectoral fins. X^-
Fig. 2. Ventral view of the same specimen as above. Shows the superficial
vessels of the body, ventral, and pectoral tins. The left pectoral superficial ad-
ductor muscle is cut distad and turned toward the body to show the profundus
trunks.
Fig. 2a. Is from a transverse section through a portion of the pectoral fin
near its base to show the termination of the pectoral fin vessels in the pectoral
fin sinus.
Fig. 3. Shows a ventral view of a deeper dissection of a small Scorpcenich-
thys head. Most of the ventral musculature is removed as is also the left hyoid
arch, the left branchial arches, and the left pectoral fin. The right hyoid arch
is turned forward and outward and the branchiostegal rays are cut close to their
bases. In this figure the ventral aorta and its branches are cross-barred with
blue lines. Note especially the anterior branching of the ventral pericardial
sinus to the pharynx and the thyroid gland. There is undoubtedly some com-
munication in the region of the thyroid with a branch of the inferior jugular.
Xxff-
Fig. 4. Deeper dissection of a small Scorpanichthys as seen from the left side.
The shoulder-girdle and pectoral fin are removed, as is also a portion of the
skull, suborbital stay, opercle, and the great lateral muscle. X %•
Fig. 5. Dorsal view of the great superficial and profundus trunks and sinuses
of the right side of the head. Kidney, brain, and walls of the cranium drawn
to show the topography. The entrance of the cephalic sinus into the jugular,
lying in front of the VII nerve and directly behind the prootic process, is dis-
tinctly shown. Same specimen as Fig. 4. Natural size.
Fig. 6. Lymphatic trunks and sinuses in the region of the heart of a very
large Scorpamichthys as seen from the left side. X *A-
Figs. 7 to 10 have been changed to text-figures under S, pp. 73, 74, 76 and 77.
13. ABBREVIATIONS USED IN THE PLATE AND TEXT-FIGURES.
A or P prefixed to an abbreviation signifies anterior or posterior; R or L,
right or left. A series is numbered from cephalad to caudad.
Abd.S. Abdominal sinus.
A.Br.A.(\-i) Afferent branchial trunks.
Add.M. Adductor mandibular.
Add.P.A. Adductor arcus palatini.
A. Gas. V. Anterior gastric or oesophagus veins.
88 ALLEN
A.Hyo.T. Anterior hjoidean lymphatic trunk.
An. Auricle.
B.Art. Bulbus arteriosus.
Br. Branchiostegal rajs.
Br. A. (i-4) Branchial arches.
Br.L.S. Branchial or dorsal branchial lymphatic sinuses.
Car. V. Cardinal vein.
Cefh.S. Cephalic sinus.
Cer. Cerebellum or epencephalon.
CI. Clavicle.
CI. V. Clavicle lymphatic vessel.
Ccc.Mes.L.V. Coeliaco-mesenteric lymphatic trunk.
Cr. Cranial wall.
Crb. Cerebrum or prosencephalon.
Cr.L. V. Cranial lymphatic trunk.
D.Dr.M. Depressor dorsal ray muscles.
D.F.L.V. Dorsal fin lymphatic vessels.
D.L. V. Dorsal lymphatic trunk.
D.L.V.(\) Median dorsal lymphatic trunk.
Dr. Dorsal fin rays or spines.
Dr.Ex.M. Extrinsic muscles of the dorsal fin.
E.J. V. External jugular vein.
E.Sub.V. External subclavian vein.
F.Man.V. Facialis-mandibularis vein.
F.Max. V. Facialis-maxillaris vein.
Gh.L. V. Genio-hyoideus lymphatic vessel.
Gfi.M. Genio-hyoideus muscle.
Gh. V. Genio-hyoideus vein.
HA. I. V. Hyo-hyoideus inferior vein.
Hh.S.L. V. Hyo-hyoideus superior lymphatic vessel.
Hh.S.M. Hyo-hyoideus superior muscle.
Hyo.A. Hyoid arch.
Hyo.S. Hyoidean lymphatic sinus.
I.J. V. Inferior jugular vein.
I. L.Br. A.M. Internal branchial arch levators.
Im.M. Intermandibularis muscle.
Ink. Inter-hyal.
Intm. V. Intermuscular or transverse lymphatic vessels.
I.P.S. Inner pectoral fin sinus.
J. V. Jugular vein.
L.Dr.M. Levator dorsal ray muscles.
Lin. V. Lingual vein.
L.L. Lateral line canals.
L.L. V. Lateral lymphatic trunk.
L.L. V.(2) Secondary lateral lymphatic trunks.
L.Net. Network of minute lymphatic vessels.
Man. Mandible or dentary bone.
Max. Maxilla.
Max. V. Maxillaris vein.
DISTRIBUTION OF LYMPHATICS IN SCORP-dSNICHTHYS 89
Max. V. Truncus maxillaris trigeminior infra-01 bitalis.
M.P.S. Median pectoral tin sinus.
My. Myelon or spin;il cord.
My.L.V. Mjelonial or superior spinal longitudinal lymphatic trunk.
Myo. Myotomes of the great lateral muscle.
Neu.L.V. Neural or interspinal lymphatic vessels.
Neu.S. Neural spines.
No. Nasal opening.
Nut. V.(i) to (*} Nutrient veins (1) to (j).
O.B. Olfactory bulb or rhinencephalon.
Obi. Oblongata or metencephalon.
Oc.S. Occipital sinus.
O.D.M. Obliqui dorsales muscles.
O.L. Optic lobes or mesencephalon.
O.N . V. Orbito-nasal vein.
Op. Operculum or opercular bone.
O.P.S. Outer pectoral fin sinus.
P. Pectoral fin.
P. CI. Postclavicle.
P.C. V. Connecting vessels between the median and the outer and inner
pectoral tin sinuses.
Pel. Pelvic bones.
Per.S. Pericardial sinus.
Per.S.(\) Posterior pericardial sinus or posterior portion of the pericardial
sinus.
P.Fac.L. V. Profundus facial lymphatic trunk.
P.F.L. V. Pectoral fin lymphatic vessels.
P.F.L.V.(\) Extra pectoral fin lymphatic vessels.
Ph.L. V. Pharynx lymphatic vessel.
P.Hyo.T. Posterior or ventral hyoidean lymphatic trunk.
P.P. Add. M. Profundus pectoral adductor muscle.
Pr. Pectoral rays.
Prec. Precava.
Prem. Premaxilla.
Pro. P. Prootic process.
P.S. Pectoral sinus.
P. V.Abd.M. Profundus ventral abductor muscle.
P. V. Per.S. Papilla of the ventral pericardial sinus that joins the main peri-
cardial sinus.
R.Lat.X. Ramus lateralis vagi.
R.My.L. V. Right fork of the myelonal lymphatic trunk.
5\ Lymphatic sinus at the cephalic end of the cranial trunk.
S.Cl. Supraclavicle.
S.Pac.I,. I'. Superficial facial lymphatic trunk.
S.Oc. Supraoccipital.
S.Orb. Chain of suborbital bones or suborbital stay.
S.P.Abd.Af. Superficial pectoral abductor muscle.
S.P.Add.M. Superficial pectoral adductor muscle.
Sp.N. Spinal nerves.
Proc. Wash. Acad. Sci., May, 1906.
9°
ALLEN
Sub. A. Subclavian artery.
5. V.Abd.M. Superficial ventral abductor muscle.
5. Ven. Sinus venosus.
Thyr. Thyroid gland.
Thyr.L. V. Thyroid lymphatic vessel.
V.Ao. Ventral aorta.
Ven. Ventricle.
Ver.w First vertebra or atlas.
V.F.L.S. Ventral fin lymphatic sinus.
V.F.L. V. Ventral fin lymphatic vessels.
V.F.L. V.(\) Auxiliary ventral fin lymphatic vessels.
V.L.S. Ventral lymphatic sinus.
V.L. V. Ventral or abdominal lymphatic trunk.
V.L. V.(i) Profundus ventral lymphatic trunk.
V.M.L.V. Ventral fin musculature lymphatic vessel.
V.M.L.V.(\) Secondary ventral fin musculature lymphatic vessel.
V.Per.S. Ventral pericardial sinus.
V.Per.S.(\) Anterior portion of the ventral pericardial sinus.
Vr. Ventral fin rays.
X. Connection between the ventral sinus papilla and the posterior
part of the pericardial sinus.
Y. Point where the ventral lymphatic trunk pierces the ventral
wall to empty into the ventral pericardial sinus.
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PROCEEDINGS
OF THE
WASHINGTON ACADEMY OF SCIENCES
Vol. VIII, pp. 91-106 pls. iv-v July 10, 1906
EVIDENCE BEARING ON TOOTH-CUSP
DEVELOPMENT.1
By James Williams Gidley,
Department of Geology, U. S. National Museum.
In connection with the work of cataloguing the portion of the
Marsh collection of Mesozoic mammals, obtained under the au-
spices of the U. S. Geological Survey and now deposited in the
United States National Museum, I have made some discoveries
of seeming importance in the form of evidence bearing on the
question of tooth-cusp homologies in the mammalian molars.
This evidence I wish briefly to present in the following pages,
hoping it may throw some added light on the very important
subject of tooth morphology.
Before proceeding, I wish to express my indebtedness to Dr.
George P. Merrill for making possible the arrangements for
this detailed study of material and for his encouragement in the
work ; to Prof. Charles Schuchert, of Yale University, for
submitting to my hand the type material of the Marsh collection
at New Haven ; and to Prof. Henry F. Osborn of the American
Museum of Natural History, for his courtesy in placing the
collection of Mesozoic mammals in that institution at my disposal.
My thanks are also due Mr. G. S. Miller, Jr., for his valuable
aid in selecting study material from the collection of modern
mammals in the National Museum and for a clear translation
of Herluf Winge's paper on tooth-cusp development.
1 Based on a study of the Mesozoic Mammal Collection in the U. S. National
Museum.
Proc. Wash. Acad. Sci., July, 1906. 91
92
GIDLEY
Of the several theories thus far advanced for the evolution of
the teeth, none has been entirely satisfactory, and there is still
a wide disagreement among authorities, especially as regards
the position of the primary cone or " protocone " in the upper
molars. As proposed by the late Prof. E. D. Cope and sup-
ported by Prof. Henry F. Osborn, the primary cone is to be
found invariably on the inner or lingual side of the trigonodont
upper teeth, and is the homologue of the central cone in Tri-
conodon, in which the three main cusps are arranged in an
antero-posterior line, the trigonodont molar having been derived
from this form through the shifting of the two lateral cones to
the outside. The central cone {protocone) remaining on the
inner side, thus forms a triangle {trigori) with the apex pointing
inward. In the meantime, according to this theory, the cusps
of the lower molars are supposed to have moved in the opposite
direction, leaving the central cusps (flrotocoui'd) on the outside,
forming an oppositely directed triangle (trigonid). Thus the
primary cones of the upper and lower molars in shifting have
completely reversed their positions in relation to each other, the
primary cone of the upper molars not only moving to the inner
side of the crown, but taking a position in the series inside the
primary cone of the lower molars as well.
This theory, so skillfully worked out by Osborn, has been
widely accepted as satisfactorily explaining the problem of tooth-
cusp evolution. But recent paleontological and embryological
investigations have thrown a large amount of discredit on the
whole theory. As stated by Wortman, Scott has shown most
conclusively, from paleontological evidence, that in the upper
molariform premolars the primary cone is on the outer side and
the subsequently added cusps have a very different history from
that proposed by the tritubercular theory for the true molars.
The embryological researches of Woodward, Tacker, and others
have not only confirmed Scott's theory for the premolars, but
show also that in all groups of mammals investigated the antero-
external cusp or paracone is first to appear in the permanent
upper molars and milk molars, as it does in the premolars, and
the order of appearance of the other principal cusps is practi-
cally the same as proposed by Scott for the premolars.
EVIDENCE BEARING ON TOOTH-CUSP DEVELOPMENT 93
Woodward1 found that in Ccntctcs and Ericulus the main in-
ternal cusp, usually termed the protocone, was first to develop,
but he believed this cusp to be the paracone, the whole tooth
representing only the antero-external triangle of such a form
as Talpa, the protocone and metacone not having been de-
veloped. This, as stated by Woodward, is a modification of
Mivart's view published in 1868, 2 in which he states his belief
that in Ccntctcs, Chrysocloris* and like forms, the main
portion of the crown represents the union of the two external
prisms of Talpa and like forms. According to Mivart, the
main internal cusp of Ccntctcs, Ericulus, Chrysocloris, etc.,
was derived by the fusion of the paracone and metacone, while
the protocone and hypocone are wanting or rapidly diminishing
in size and importance. According to both Woodward and
Mivart, therefore, in these forms, which have been considered
typical trituberculates, the outer cusps are developments of the
cingulum, while the main internal cusp has been wrongly termed
the protocone and is in reality the paracone, according to
Woodward, or combined paracone and metacone, according to
Mivart, while the inner cusp (protocone) is greatly diminished in
size or has entirely disappeared. These two authorities, there-
fore, are agreed on the two points of principal importance regard-
ing Ccntctcs and Ericulus, viz : (1) the location of the paracone in
the main internal cusp and (2) the ultimate loss of the protocone.
I strongly concur in these views, for in a series of upper molars,
including Potamogalc, Solcnodon, Ccntctcs, Ericulus, Hcmi-
ccntctcs and Chrysocloris (see figs. 1-6, pi. IV), the stages sug-
gesting the gradual diminishing and final disappearance of the
protocone are very complete, amounting almost to demonstration,
and there can be little doubt that the molars of the Ccntctcs and
Chrysocloris type have been derived from forms similar to that
of Potamogalc, involving the loss of the protocone. In conse-
quence of this the paracone, or combined paracone and meta-
cone, comes to be the principal inner cusp. In Potamogalc the
1 Proc. Zool. Soc. London 1S96, 588-589.
2Journ. Anatomy and Physiol., Vol. II, 139, 1S6S.
3 The form figured by Mivart has since been removed to a distinct genus,
Bematiscus Cope, Am. Nat., XXVI, 1S92, 127. The typical Chrysocloris upper
molar has no trace of a protocone.
94
GIDLEY
protocone is quite prominent and still typical in form, while in
Solenodon it is much reduced and is beginning to divide trans-
versely, or more probably is beginning to separate from a like-
wise reducing hypocone. This is in favor of the view held
by Mivart that the simple inner cusp in Potamogale and like
forms is in reality the fused protocone and hypocone. The
reduction is carried still further in Centetes, in which two
inner cingulum-like cusps appear, one on each side of the
enlarged paracone. In Chrysocloris and Hemicentetes the
inner cusp (protocone and hypocone) has entirely disappeared.
Regarding Mivart's " fusion theory," I am inclined to believe
that Woodward has not given due weight to the evidence cited
by Mivart and that there is considerable support for this theory
to be found in the modern bats and insectivores. Mivart con-
sidered the Potamogale molar as an intermediate form between
molars of the Talfa type, having twro external triangular prisms,
and those of Centetes and Ericulus, having only one such
prism. He pointed out that in Potamogale there is " a very
interesting approximation of the triangular prisms," in which
the paracone and metacone, although still remaining distinct,
are in very close juxtaposition. This view is strongly supported
by a series of bat molars to which Mr. G. S. Miller has kindly
called my attention. In this series, which includes Vesfie?-tilio,
Scotophilia and Harpiocefhahis^ are suggested the successive
steps from Talfa to Potamogale in the insectivore group.
Vesfertilio represents the normal or more generalized form,
in which the protocone is large, the paracone and metacone
are widely separated, and the external styles are nearly equal
in size. The mesostyle is much reduced in Scoto-philus and is
drawn inward, the paracone and metacone are more closely
appressed and the protocone is somewhat shortened. In Har-
piocephalus l the mesostyle has disappeared, the parastyle and
1 The skull of Harpiocephalns from which this description was taken was
obtained by Mr. G. S. Miller through the kindness of Oldfield Thomas, of the
British Museum.
Unforunately it came too late to be photographed and figured uniformly
with the series. Its place is taken on Plate III, by an outline drawing from a
figure for Wilhelm Peters' Fledermause des Berlines Museums fiir Naturkunde
(a projected monograph of the bats).
EVIDENCE BEARING ON TOOTH-CUSP DEVELOPMENT 95
metastyle have drawn closer together and compose the entire
outer portion of the crown, while the paracone and metacone
are closely approximated, forming the greater part of the inner
portion of the crown, the protocone being very much reduced.
Thus in Harfioccphalus a stage is reached nearly analogous
to that of Potamogale^ the principal difference being that the
metacone is the dominant cusp instead of the paracone, as in
the latter genus.1
From these comparisons it seems reasonably clear that such
forms as Centctes, Ericulus and Chrysochloris have attained a
secondary or pseudo-tritubercular form by passing through some
such stages of evolution as are suggested by the two series here
selected. Other examples of a fusing paracone and metacone
and reducing protocone may be found in the molars of some of
the creodonts and carnivorous marsupials and in the sectorials
of many of the carnivores.
From the foregoing it now seems to be demonstrated beyond
question that the main inner cone of Centetes and Ericulus is
not the protocone as observed in normal groups, but, if not
entirely made up of the primary cusp (paracone), it at least in-
volves that element and Woodward's contention that the evi-
dence of embryology is in entire harmony for the molars and
premolars is not controverted by these seeming exceptions as
supposed by Osborn.
Wortman of late has strongly opposed what he terms the
"cusp migration theory," and has brought considerable evi-
dence to showr that, in the creodonts and carnivores, at least,
the cusps of the upper molars in general are homologous to
those of the molariform premolars and have had substantially
the same history in their development.
Against this combined evidence Osborn 2 has recently re-
affirmed the tritubercular theory, " as originally proposed,"
resting the whole question on the point of evidence as to
" whether the main reptilian cone, or protocone, of the ances-
1 In the Laramie mammals I find that the metacone equals or is larger than
the paracone in those forms in which the postero-external heel is well developed
in the upper molars.
2 Amer. Journ. Science (4), Vol. 17, 1904, 321-323.
96
GIDLEY
tors of the mammals was found upon the antero-internal side or
on the antero-external side of the upper molars." This evidence,
according to Osborn, is in favor of the tritubercular hypothesis,
and conclusive evidence of the theory is furnished in the Jurassic
mammal molars. However, a study of all the mesozoic mam-
mal material available has led the present writer to exactly
opposite conclusions.
Unfortunately, Osborn's observations were confined to a very
limited amount of material, and from a careful examination of
the teeth of Triconodon and Dryolestcs,1 two forms especially
studied by him, it seems that his conclusions were based on
evident, though perfectly excusable, errors of observation, due
doubtless to the minuteness of the teeth and their dark color,
which make it difficult in many cases to distinguish, between a
fracture and the natural surface of the tooth. Thus, according
to Osborn,2 the upper molars of Dryolestes are " broadly trans-
verse or triangular and upon the internal side of each is a large,
conical, pointed cusp,/r, supported by a large stout fang, . . .
The external portion of the crown is depressed, and bears one
large antero-external cusp ? pa and one smaller postero-external
cusp ? me which is either partially worn away or less pronounced
in development." But there are two important cusps not noted by
Osborn, one an external cusp placed anterior to the main external
cusp, the other a small but well-defined intermediate cusp appear-
ing on the posterior transverse ridge. Thus there are five distinct
cusps instead of three, as stated by Osborn, and these do not form
a trigon in the sense that this term has been used, for the main
external cusp is in the middle of the base of the triangle instead
of forming one of its angles.
In the upper molars of Triconodon the three principal cusps are
arranged in a direct line, and are nearly equal in size and form,
and the two lateral cones are each supplemented by a small but
well-defined internal basal heel-like cusp and an external basal
cingulum. The main cusps are flattened externally into a con-
tinuous wall in one species (see PL V, fig. i), while they are
1 The specimens studied by the present writer and referred to these genera
are from the Atlantasaurus beds of Wyoming. These beds are usually referred
to the upper Jurassic, although they may be lower Cretaceous.
2Amer. Journ. Science (4), Vol. 17, 1904, 322.
EVIDENCE BEARING ON TOOTH-CUS1' DEVELOPMENT 97
much rounded and deeply divided on the inner or lingual side.
Thus, there is not the slightest suggestion of a tendency toward
an outward movement of the lateral pair of cusps, while it is
easily conceivable that the continued development of the two
inner heel cusps and outer cingula wrould early result in a gen-
eral form of tooth very different in pattern from the tritubercular
type which might form the basis for such molars as those of the
diprotodont marsupials and many of the rodents or even of the
manatee and mastodon. I do not wish to be understood here
as implying any relationship between these very diverse forms,
but as especially emphasizing the fact that in Triconodon is sug-
gested an easy and not improbable way in which some complex
molars may have been derived without having passed through
the typical tritubercular stage.
Thus, it is shown by this restudy of the two forms, which
according to Osborn represent successive stages in the evolution
of the mammalian molar, that the gap between them, which
was already great, even according to Osborn's interpretation, is
very greatly increased especially from the tritubercular theory
standpoint. Moreover there is no evidence, in the way of in-
termediate forms, indicating that Dryolestes ever passed through
a stage strictly analogous to that of Triconodon or that the
main internal cusp is in any way homologous to the central
cone in the Triconodon molars. Furthermore, a critical com-
parison of these two forms shows that such an hypothesis is beset
by many difficulties. The following are the principal ones :
(1) The molars of Triconodon are larger and fewer in number
than in Dryolestes indicating a generally higher specialization.
(2) The lateral cones in Triconodon are already comparatively
much specialized, being suplemented by growths of the cingu-
lum externally and heel cusps internally and thus do not es-
pecially resemble, either in form or proportions, any two of the
external cusps in Dryolestes. (3) The external portion of the
upper molar in Dryolestes (see PI. V, figs. 2 and 3) is composed
of three simple connate cusps supported by two fangs, their
general appearance suggesting an arrangement homologous to
the three cusps and two fangs of Triconodon; while (4) the
internal portion of the tooth is a high antero-posteriorly com-
98
GIDLEY
pressed V-shaped cusp supported by a single fang, centrally
placed, and exposed on its inner side for the greater part of its
length, the maxillary bone apparently not yet having formed
a completed socket, or alveolus, for its reception. Thus the
whole construction of the inner cusp, which is highly sugges-
tive of a heel development, differs materially from the central
cone of Triconodon.
A
O O O
B
°-=0— ° °^y=° °=o=°
c
0=0=0 0=0-0
D
VAVAV
E
F
J
Fig. 11. Phyletic History of the Cusps of the Ungulate Molars. A, Reptilian
Stage, Haplodont, Permian. B, Protodont Stage {Dromotherium) , Triassic.
C, Triconodont Stage {Amphilestes). D, Tritubercular Stage (Spalacothe-
rium). E, Tritubercular-tuberculo Sectorial, Lower Jurassic. F, The same, in
Upper Jurassic. G, The same, in Upper Cretaceous. H, The same, Puerco,
Lower Eocene. /, Sexitubercular-sexitubercular, Puerco. J, Sexitubercular-
quadritubercular, Wahsatch. (After Osborn.)
Considering the outer portion of the Diyolestes molar as
homologous to the three cones and two fangs of Triconodon,
EVIDENCE BEARING ON TOOTH-CUSP DEVELOPMENT 99
^ ' o"o
a
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£
3 X^Q^ -Bc^^^
£ 4
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QOOCfcQ©
a 5
Fig. 12. Suggested Phyletic History of T-vo Types of Complex Molars. [As
in Osborn's diagram, the solid black dots represent the cusps of the upper
molars, the circles, those of the lower molars.] 1 to 6, Phyletic history of the
" Tritubercular " type; a to d, Phyletic history of the " Triconodont " type;
e,f, From the brachyodont Triconodont stage to the bilobed hypsodont type of
molar.
A, B, C, E and G compare with A, B, C, E and G in Osborn's diagram, fig.
11 ; ^, Dryolestes type, Atlantosaurus beds (? Upper Jurassic); 5 and 6, Proto-
lambda or Pediomys type, Laramie beds (Upper Cretaceous); d, Triconodon
type, Atlantosaurus beds ( ? Upper Jurassic) ; f Palceolagus type, White River
beds (Oligocene).
IOO GIDLEY
the derivation of this type of tooth is much simplified, it being
not so far removed from the primitive reptilian condition, and
though diverging on different lines, is no more specialized, as
a whole, than the Triconodon type of tooth, the differentiation
being carried on more rapidly in the latter in the special de-
velopment of the anterior and posterior lateral cones and their
accessory cusps, while in Dryolestes the specialization has
apparently been centralized in the development of the high,
narrow, heel-like cusp and its supporting fang on the inner
side of the molar.
This view is strongly supported by the evidence obtained from
still another characteristic Atlantosaurus-beds type of molar
represented by Dicrocynodon. In this form, PL V, fig. 4, the
same primitive arrangement of three cusps and two fangs is
preserved in the outer portion of the tooth, while on the internal
side a large secondary cusp has been developed differing widely
in character from that of Dryolestes. This cusp is a laterally
compressed cone supported by two rudimentary fangs and is
joined to the outer portion of the tooth by a high, wedge-shaped
ridge. The base of the inner cone is greatly expanded antero-
posteriorly, curving gently outward toward the external portion
of the tooth. Thus the crown, as a whole, is greatly constricted
medially with the inner and outer portions superficially resem-
bling each other.
From these observations two important conclusions may be
drawn : First, that, leaving out of consideration the multitu-
berculates, there are among the mammals of the Atlantosaurus
beds at least three distinct forms of upper molars representing
three primitive types of about equal specialization apparently
leading off in entirely independent lines. Probably only one of
these, Dryolestes, represents an ancestral type from which the
Upper Cretaceous and later forms possessing trigonodont molars
may have been derived. Second, that the evidence derived
from the Atlantosaurus beds mammals entirely supports the
evidence of embryology and agrees in general with the "pre-
molar analogy " theory. Thus, the evidence from all sources
points overwhelmingly to the conclusion that the primary cone
is to be found on the outer side in the upper molars of primi-
EVIDENCE BEARING ON TOOTH-CUSP DEVELOPMENT IOI
tive trituberculate forms and in all forms derived from a tritu-
bercular type of tooth as well, except where the main inner cone
(protocone) has been reduced secondarily. The opposite view
held by the tritubercular theory now apparently stands on very
insufficient evidence, and the proposition that the protocone, of
Osborn, represents the primary cusp is entirely without support.
The lower molars of the Atlantosaurus beds mammals fur-
nish abundant additional evidence along the line of conclusions
regarding the shifting of three cusps from a straight line to
form the primitive triangle. In such forms as Dryolcstes and
Paurodon we have trituberculate molars in the primitive or
forming stage, and, what is most significant, the cusps resemble
very closely, both in position and relative proportions, those of
the premolars of later types in their early stages of transition
to the molariform pattern. In the lower molars of Paurodon
the crown consists of a high, pointed cusp (protoconid), centrally
placed, a low posterior heel, a small anlero-internal cusp (para-
conid), and a very small median internal cusp (metaconid).
The last two form the base of the trigonid. In Dryolcstes both
the trigonid and the pimitive heel are somewhat more advanced
in development. In still other forms, such as Manacodon and
Tinodon, the two internal cusps are relatively large and the
trigonid is fullv developed, while the heel, or talonid, is very
small or entirely wanting. In all the paraconid and metaconid
are entirely on the internal side of the crown, and in these and
all the material examined there is not the slightest evidence
of any shifting of the cusps, but they seem to have arisen in the
positions they now occupy.1 In Paurodon the heel is apparently
as much or more developed than either of the internal cusps
and seems to have made its appearance even in advance of the
metaconid. Also the metaconid is still very rudimentary and is
just budding off near the base of the protoconid, but little pos-
terior to its apex and midway of the entire length of the crown,
while the place of origin assigned to it by the tritubercular
hypothesis is already occupied by the comparatively large heel.
'This is in accord svith the general conclusions on tooth cusp development
reached bv Herluf Winge as early as 1882. Widinsk Meddelelsor fn den natur-
hist. Florening e Kjobenhavn. iSS;. p. iS.
102 GIDLEY
From these observations it seems apparent that the trigonid
of the lower molars is not the reverse of the trigon of the upper
molars, as held by advocates of the tritubercular theory, and
the homologues of the elements of the upper and lower molars,
as proposed by this theory, are far from being apparent. (This
also accords with the conclusions of Winge.)
The lower molars of Triconodon differ from any of the forms
just described. They are composed of three nearly equal
cone-like cusps arranged like those in the upper molars of this
genus in an antero-posterior line. There is no cusp corres-
ponding with the metaconid in Dryolestes. There is a continu-
ous basal cingulum on the inner face of the crown, and the
posterior cusp is in no way homologous, except in position, to
the heel in the lower molars of Paurodon and Dryolestes.
The mammals from the upper Cretaceous Laramie beds show
a great advance in development. The molars of the tritubercu-
late forms of this horizon have passed into a second well-defined
stage of specialization which, though varying greatly in detail
in the various types, conforms in general to a distinctive pattern
which may readily have been derived from some Atlantosaurus-
beds form, such as Dryolestes. An upper molar of Pediomys
Marsh, a typical example of the Laramie tritubercular molar,
compared with the corresponding tooth of Dryolestes, presents
the following differences and indicates the principal lines of
progression :
(i) The main internal cusp (prolocone) is much broadened
antero-posteriorly ; (2) a second small V-shaped intermediate
cusp (protoconule) has been added ; (3) the postero-external
cusp (metacone) has greatly increased, nearly equaling, both in
size and importance, the median external, or primary, cone
(paracone), while the antero-external cusp ( parastyle) has re-
mained small and undeveloped. A correspondingly pro-
gressive development marks the trigonid and heel of the
lower molars.
Thus, the " trigonodont " tooth, or a type of molar with three
principal cusps of almost equal importance, arranged in the
form of a triangle, makes its first appearance in the Laramie.
This pattern of tooth Cope early recognized as a general primi-
EVIDENCE BEARING ON TOOTII-CUSP DEVELOPMENT IO3
tive type, and on its representatives in the lower Eocene he
founded the tritubercular theory. That this type is primitive
and many, at least, of the later forms have been derived from
it, have been too conclusively demonstrated by Cope, Osborn,
Scott and others to be seriously questioned ; but this early
trigonodont form, as is now evident, was derived in a totally
different way from that assumed by the tritubercular hy-
pothesis.
An especially interesting feature in these Laramie forms is
the oft-repeated appearance in the upper molars of a back-
wardly extended outer heel-like cusp connected by an elevated
ridge with the postero-external cusp. This portion of the tooth
is thus converted into a more or less perfect sectorial, or cutting,
blade, against which the anterior blade of the trigonid shears,
while the greatly broadened heel or talonid of the lower molar,
extending backward under the antero-posteriorly expanded
protocone of the upper molar, forms a successful crushing
apparatus. Thus, so early as the Cretaceous the prevailing
molar types were about equally equipped for use as cutting or
crushing mechanisms. The creodonts and carnivorous marsu-
pials seem to have early taken advantage of the sectorial blade
to the neglect of the crushing heel which gradully diminished
in relative size and importance, while in many other forms,
using the crushing portion of the tooth most, the sectorial blade
was early lost.
Another special character marking the advance of the upper
Cretaceous mammal molars is the first indication in a few forms
of the postero-internal cusp [hypocone), which forms the fourth
main cusp in the later quadra-tubercular type of molars. This
cusp has apparently been derived, according to the evidence of
these Laramie types, from independent sources in different
groups of mammals. In a form which Marsh has referred to
Tclacodon a strong cone-shaped cusp has developed on the
postero-internal cingulum of the tooth indicating the deriva-
tion of the hypocone from that source. Another form, appar-
ently representing an undescribed genus (PI. V, fig. 7) is
evidently developing a hypocone from the primitive posterior
intermediate cusp. Still another form, represented by Proto-
104
GIDLEY
lambda Osborn, seems to indicate a third source from which the
hypocone may have developed. In Protolambda the internal
heel (protocone) is broadly expanded and flattened posteriori}''
without a cingulum, yet the peculiar shelf-like form of this por-
tion of the tooth suggests the origin of a hypocone budding off
from the protocone independently of either the cingulum or pos-
terior intermediate cusp.
From such a form as that presented in PL V, fig. 7, it is but
a short step to the typical selenodont artiodactyl type of molar
through the progressive development of the V-shaped posterior
intermediate cusp. The addition of a second posterior cusp
budding off from the enlarged postero-intermediate cusp would
readily convert the tooth into a perissodactyl type of molar.
Thus is suggested a fourth possible source of origin for the
hypocone. This does not necessarily imply an actual relation-
ship of this particular form to the ungulates, but indicates a
type closely resembling them which differs widely from the
primitive carnivores and insectivores, in which the hypocone,
when present, was undoubtedly derived from the cingulum.
These observations suggest especially that apparently homol-
ogous elements in the teeth of the more highly complex forms
may often arise from different sources.
The correlation and homologies of the cusps of the lower
molars in comparison with those of the upper series have, for
the most part, been left out of this discussion. One observa-
tion, in this connection, however, of seeming great importance
and significance should be noted here.
In examining a large number of examples of both living and
extinct forms, I have found the following associations between
the heel of the lower molars and the protocone of the upper
teeth to hold constantly true, viz : A functional, broad, crush-
ing protocone is invariably associated with a well-developed
crushing heel in the opposing lower molar. A reduced or vesti-
gial protocone is invariably associated with a correspondingly
reduced or vestigial heel in the opposing lower molar. Since
the heel of the lower molars is admittedly of secondary origin,
this feature alone would seem to argue stroncrlv for a like sec-
ondary origin for the protocone in the upper molars.
EVIDENCE BEARING ON TOOTH-CUSP DEVELOPMENT IO5
SUMMARY AND CONCLUSIONS.
Summing up the evidence derived from this preliminary
study, the following conclusions are suggested :
1. That the evidence obtained from the Mesozoic mammal
teeth furnishes no support to the tritubercular theory in so far
as it involves the position of the protocone and the derivation of
the trigonodont tooth from the triconodont stage through the
shifting of the lateral cones outward in the upper molars and
inward in the lower molars.
2. That it supports entirely the embryological evidence that
the primary cone is the main antero-external cusp, or paracolic,
having retained its position on the outside in most upper molars
(see exceptions above, p. 95).
3. That it agrees in the main with Huxley's " premolar-
analogy " theory, as supported by Scott.
4. That the molars of the Multituberculates, Triconodoti,
Dryolestes and Dicrocynodon, were apparently derived inde-
pendently from the simple reptilian cone ; hence the supposi-
tion follows that the trituberculate type represents but one of
several ways in which the complex molars of different groups
may have been derived.1
5. That in the forms derived from the trituberculate type of
molar the order of succession of the cusps is not the same in all
groups, and apparently homologous elements are sometimes de-
veloped from different sources. Hence it follows that no theory
involving an absolute uniformity of succession in the development
of complex molars zu ill hold true for all groups of mammals.
In the foregoing pages I have restricted the use of Osborn's
tooth-cusp nomenclature for the reason that, in this particular
discussion, there are some cases in which it is not strictly appli-
cable and might lead to confusion.
On similar grounds Dr. Wortman2 has expressed the opinion
that all attempts to establish a tooth-cusp nomenclature founded
on supposed homologies are "foredoomed to failure" and
should be entirely abandoned as " useless and confusing." I
1 Somewhat similar conclusions have been reached from different reasoning
by E. S. Goodrich, M. Tims and others.
2Amer. Journ. Science (4), Vol. 16, 1903, 265-368.
Proc. Wash. Acad. Sci., August, 1906.
106 GIDLEY
agree with the general sentiment expressed {of. ctt., p. 366)
that, owing to the adoption of different plans in different groups
of mammals for increasing the complexity of their molars, no
terminology founded on the basis of cusp homologies can be
made strictly applicable to all the mammalia. I do not, how-
ever, consider this sufficient ground for abandoning absolutely
so convenient a system of nomenclature as that proposed by
Osborn. Granting that many of the terms proposed are founded
on mistaken homologies, it does not necessarily follow that they
need be in the least confusing, as suggested by Wortman. For
in any system used, in order to make that system of greatest
convenience and highest utility, the names once adopted should
be permanent and not subject to transfer or substitution on any
ground of changed conceptions of homologies or history, for
the same reason that generic and specific names are retained
regardless of the fact that they may have been given to denote
some supposed affinity or characteristic which may later have
proved entirely erroneous.
Viewed from the nomenclature standpoint, therefore, the
convenient names proposed by Osborn have come to assume an
individuality which conveys a far more definite meaning than
any purely descriptive terms, be they of relative position or
supposed homologies. Moreover, they have the valuable ad-
vantages of clearness and brevity in description. On these
grounds, in the opinion of the present writer, and for the added
reason that great confusion would inevitably result from any
change in a terminology that has found its way into so many
publications, Osborn's nomenclature should be retained as orig-
inally proposed. Thus the term "protocone" always means
the main antero-internal cusp of a normal upper molariform
tooth, whether that element is regarded as the original primary
cusp or otherwise.
The objection that the terms are not universally applicable is
scarcely worthy of consideration since they are widely appli-
cable to the great majority of mammalian molar types, without
in the least interfering with the use of terms descriptive of " rel-
ative position only," which may be used in any cases where Os-
born's terms do not apply.
EXPLANATION OF PLATE IV.
(All figures except fig. 9, three times natural size.)
Fig. 1. Potamogale — left upper jaw (No. 124327 U. S. N. M.) ; habitat, Africa.
Fig. 2. Solcnodon — left upper jaw (No. 2230, U. S. N. M.) ; habitat, Cuba.
Fig. 3. Centeles — left upper jaw (No. 63316 U. S. N. M.) ; habitat, Mada-
gascar.
Fig. 4. Ericulus — left upper jaw (No. 1224S8 U. S. N. M.) ; habitat, Mada-
gascar.
Fig. 5. Hemicentetcs — left upper jaw (No. 63319 U. S. N. M. ) ; habitat, Africa.
Fig. 6. Chrysochloris — left upper jaw (No. 616S6 U. S. N. M.) ; habitat, Africa.
Fig. 7. Vespertilio fuscus — left upper jaw (No. 62736 U. S. N. M.) ; habitat,
Washington, D. C.
Fig. 8. Scotofhilus huhli — left upper jaw (No. 1 13463 U. S. N. M.) ; habitat,
Philippines.
Fig. 9. Harpiocepfialus — right upper jaw. (Outline drawing taken from a plate
prepared in 1880 by Wilhelm Peters for a monograph of the bats. This
monograph was never published.)
Proc. Wash. Acad. Sci., Vol. VIII.
Plate IV.
CHEEK TEETH OF LIVING INSECTIVORES AND BATS
EXPLANATION OF PLATE V.
Figs, i and la. Triconodon ? bisulcus Marsh (Atlantosaurus beds), left upper
molars, m2 and m3, crown and external views. Six times natural size
(No. 269SU. S. N. M.).
Figs. 2, 2a and 2b. Dryolestes sp. (Atlantosaurus beds), left upper molars;
crown, external, and posterior views. Seven times natural size (No.
2845 U. S. N. M.).
Fig. 3. Dryolestes, first right upper molar, m1 ; crown view. Eight times natural
size (No. 2S39 U. S. N. M.).
Figs. 4 and 4a. Dicrocynodon sp. (Atlantosaurus beds), left upper molars;
crown and external views. Six times natural size (No. 2715 U. S. N.
M.).
Figs. 5, 5a, 5^ and 5c. Paurodon sp. (Atlantosaurus beds), right lower molar,
m2, crown, external, internal and posterior views. Eight times natural
size (No. 2733 U. S. N. M.).
Figs. 6, 6a, 6b and 6c. ? Pediotnys sp. (Laramie beds), left upper molar; crown,
external, posterior, and anterior views. Eight times natural size (No.
5062 U. S. N. M.).
Figs. 7, "ja and "jb. Gen. et sp. indt. (Laramie beds), left upper molar; crown,
external and anterior views. Eight times natural size (No. 5076 U. S.
N. M.).
Proc. Wash. Acad. Sci., Vol. VIM.
Plate V.
TEETH OF MESOZOIC MAMMALS
PROCEEDINGS
OF THE
WASHINGTON ACADEMY OF SCIENCES
Vol. VIII, pp. m-139. August 14, 1906.
NEW STARFISHES FROM THE PACIFIC COAST OF
NORTH AMERICA.
By Walter K. Fisher,
Leland Stanford Junior University.
The United States National Museum recently sent the writer
most of the starfishes in its collections from the west coast of
North America. These collections comprise material dredged
by the Fisheries Steamer Albatross, as well as specimens from
other sources. As it will be some time before the final report
can be completed and published, the following species are
described in advance:
Lepty chaster pacijicus.
Lepty chaster anomalus.
Astropecten ornatissimus.
Ltiidia ludwigi.
Luidia asthenosoma.
Henricia aspera.
Hcnricia polyacantha.
Crossaster alternatus.
Crossaster boreal is.
Rathbunaster calij vrntcus, new genus and species.
In the Bulletin of the Bureau of Fisheries for 1904, Vol.
XXIV, June 10, 1905, pp. 291 to 320, the writer published 1
new genus, 2 new subgenera, and 24 new species, based on
material collected by the Albatross in Alaska in 1903, and off
Proc. Wash. Acad. Sci., August, 1906. v'111)
112 FISHER
California in 1904. Most of these forms are found also in the
National Museum material, collected at an earlier date.
The new forms described below will be figured in the final
report.
Family ASTROPECTINID^) Gray.
Genus Leptychaster l Smith.
Lepty chaster Smith, Ann. and Mag. Nat. Hist., Ser. 4, xvii,
1876, no.
Leptopty chaster Smith, Philos. Trans., Zool. Kerguelen Island,
clxviii, 1879, 27^-
LEPTYCHASTER PACIFICUS Fisher, new species.
Ravs 5. R = 43 mm. ; r = 14 mm. ; R= $r. Breadth of
ray at base 16 mm.
General form similar to that of L. arctfeus (Sars) but disk
rather broader. General form flattened ; rays evenly tapered,
bluntly pointed ; interbrachial angle slightly rounded, but
abrupt ; abactinal surface subplane ; margin of rays defined by
inferomarginal plates, rounded ; superomarginal plates well-
developed, relatively larger than in L. arcticus, forming a
fairly conspicuous margin to abactinal paxillar area ; actinal
surface slightly convex ; actinal interradial areas slightly
smaller, and intermediate plates fewer than in L. arcticus.
Tube-feet pointed, the proximal with a rudimentary subcorneal
disk; superambulacral plates small.
Abactinal paxillar area fairly compact, the paxillee decreas-
ing in size toward center of disk, midradial line, and end of
ray ; smallest paxillar in center of disk, the largest on margin
of area at base of ray. Paxillas similar in character to those of
L. arcticus, but slightly larger, and spinelets a trifle longer.
Base of pedicel flaring into a roundish plate with 4 or 5 short
rather irregular lobes by which the plates touch or imbricate
slightly, and between which the papulse emerge. Larger
paxillar with about 25 peripheral and 30 central slender delicate
1 This is the original spelling, and, as it is very evident that there is no typo-
graphical error, this name should be employed instead of Leftoftychaster.
NEW STARFISHES FROM THE PACIFIC COAST II3
terete blunt spinelets ; spinelets occupying center of tabulum
form a coordinate flat-topped group, usually stand upright and
are crowded; peripheral spinelets usually radiate and are not
equal in length.
Marginal plates short, band-like, but both series more con-
spicuous than in L. a'rcticus; superomarginal plates, 30 in
number from interradial line to extremity of ray much wider
than long on proximal half of ray, the width rapidly decreasing
on outer portion until plates are nearly quadrate. Plates form
an arched bevel to margin of abactinal area, are separated by
deep fasciolar grooves, and are covered with short delicate
terete spinelets which form a close nap all over exposed surface.
Inferomarginals corresponding to superomarginals, beyond
which they extend laterally forming margin of ray; separated
from superomarginals by rather wide groove ; short, band-like,
separated by fasciolar furrows, forming well-arched bevel to
actinal surface ; first plate about twice as wide as corresponding
superomarginal ; all densely covered with small spinelets similar
to those of superomarginals, but a trifle larger, those of trans-
verse median region slightly squamiform and directed outward.
Actinal intermediate areas rather smaller than in L. arcticus;
one series of intermediate plates extending about three-fourths
length of ray or to eighteenth inferomarginal ; a second series
extending to seventh or eighth plate, and a third series con-
fined to angle bounded by adjacent first 2 plates. Intermediate
plates with a low tabulum crowned by a coordinate group of
15 or 20 papilliform spinelets, those in center being slightly
thicker and more clavate than the peripheral ones.
Adambulacral plates about as wide as long with a rounded
furrow margin, but first 2 or 3 plates wider than long and with
more angular margin. Armature consists of (1) a furrowr series
of 4 (more rarely 5) slender, rather long, blunt cylindrical
spinules, the two central being slightly the longest or the 4
subequal ; (2) on actinal surface are 2 or 3 longitudinal series
of about 4 similar spinules which decrease in size toward outer
edge of plate ; third series when present more irregular, its
spinelets distinctly tapered, slenderer, shorter and sharper.
Furrow spinelets usually bent back from furrow, and arma-
ture has a decidedly crowded appearance.
ii4
FISHER
Mouth-plates narrow, the free margin of each being longer
than that adjacent to first adambulacral, and the combined
plates forming a salient angle into actinostome. Margin of
plate with a series of about 15 slender tapering spinules, de-
creasing in length from inner to outer end of plate. About 8
to 10 of these are more regular and occupy the free actinosto-
mial margin, the rest being adjacent to first adambulacral plate,
between which and the mouth-plate there is a fairly wide suture.
A series of numerous similar spinules stands on edge of suture
furrow, and sometimes an incomplete, irregular, intermediate
series is present.
Madreporic body situated about its own diameter from inner
edge of superomarginal plates, fairly large, surrounded and par-
tially obscured by large paxillae ; striations deep, coarse, irreg-
ular, centrifugal.
Type, No. 21925, U. S. Nat. Mus. Type locality, Alba-
tross Station 2862, near north end of Vancouver Island (inside)
in 238 fathoms, on gray sand and pebbles.
This well-marked form has larger superomarginals than any
previously described species. I have compared the type with
a specimen of L. arcticus (No. 17992, U. S. Nat. Mus., " Sta.
21, Cashes Ledge'') having a major radius of 35 mm. In L.
arcticus the proximal superomarginal plates are not conspicu-
ously larger than those of outer third of ray. They are roundish
and resemble large paxillae, but in L. pacijicus the proximal
plates are much wider than those of distal half of ray, and the
plates decrease regularly in width all along ray. The mar-
ginal plates of L. arcticus are shorter, hence more band-like,
than in L. pacificus, there being 36 plates to R = 35 mm.,
while in L. pacijicus, with R 43 mm., there are but 28 to 30
plates. On account of the difference in size of the superomar-
ginals in the 2 species, the abactinal paxillar area is narrower in
L. pacijicus. The actinal interradial areas of L. arcticus are
slightly larger than in L. facijicus and the paxillae are more
crowded. The present species seems to bring Leptychaster
nearer to both Bathybiastcr and Psilastcr, on account of the
larger superomarginal plates. There are, of course, no special
spines on the marginal plates of any Leptychaster.
NEW STARFISHES FROM THE PACIFIC COAST II5
LEPTYCHASTER ANOM ALUS Fisher, new species.
Rays 5. R= 27 mm.; r = 17 mm.; 7?=i.6r. Breadth
of ray at base, 19 mm.
In general form and ornamentation greatly resembling Par-
astropccten inermts Ludvvig. Disk broad, rays short, broad
and blunt ; interbrachial arcs shallow and wide ; abactinal sur-
face subplane, capable of slight inflation ; marginal plates con-
spicuous, devoid of enlarged spines or spinelets, but covered
with granules and granuliform spinelets; actinal intermediate
areas broad ; adambulacral plates with 3 or 4 furrow spines ;
small superambulacral plates present ; a very tiny anal pore
present.
Abactinal paxillar area compact ; paxillas arranged in not very
regular oblique transverse rows at sides of ray ; without order
in median radial area and center of disk. Paxillar largest at
base of ray and in interradial areas decreasing conspicuously
in size toward center of disk and tip of ray ; larger at sides of
paxillar area than in mid-radial region. Paxillas with subcir-
cular bases having 5 or 6 very short irregular lobes, by which
neighboring plates touch, or even imbricate in center of disk and
mid-radial area. Papulae in 5's and 6's (except in center of
disk and along mid-radial lines where they are absent). Column
of paxilla about as high as breadth of base, flaring at summit,
the largest crowned with a coordinate noriform group of about
40 or 45 short, terete, often clavate, round-tipped spinelets ; of
these about one-half form a peripheral series and are a trifle
slenderer and longer. On the smaller paxillas the spinelets de-
crease markedly in size, but only slightly in number.
Supermarginal plates, 15 in number from median interradial
line to extremity of ray form an arched bevel to border of abac-
tinal surface ; plates shorter than wide, but increase in length
on outer half of ray. Plates of both series separated by trans-
verse narrow deep fasciolar grooves and a narrow deep groove
(not so deep as transverse grooves) separates superomarginal
from inferomarginal series. Superomarginal plates covered
with short, terete, blunt granuliform spinelets, similar to but
larger than paxillar spinelets, becoming well-defined slender
Il6 FISHER
spinelets in fasciolar grooves. Superomarginal covering is to
be considered as a spinelet rather than granules.
Inferomarginal plates much wider than long, encroaching
more onto actinal area than do superomarginals onto abactinal,
and corresponding in position to superomarginals. Spinelets,
densely covering surface of plates, larger than those of supero-
marginals, and increasing in size toward outer end of plate
which projects slightly beyond adjacent end of superomarginal,
thus defining the ambitus. Inferomarginal spinelets granuli-
form in middle of plate, often attaining a squamiform appear-
ance at outer end; spinelets in fasciolar furrows, slender. No
enlarged spines of any sort on either marginal series. Termi-
nal plate small, granulose, deeply notched below.
Actinal interradial areas large ; intermediate plates low-pax-
illiform, arranged in chevrons, the series adjacent to adambu-
lacrals extending about three-fourths length of ray or to eighth
inferomarginal. Plates decrease in size toward margin, are
strongly imbricated internally, and the paxillar crowns which are
composed of about 25 to 30 clavate obtuse, not very crowded,
spinelets (slender when dry) surmount a low convex elevation
or tabulum. Well-defined fasciolar channels separate these
tabula.
Adambulacral plates about as wide as long, with a slightly
rounded, angular furrow margin, the angularity being more
pronounced in vicinity of mouth plates. Armature consists of
(1) a furrow series of 4 (sometimes 3) terete or slightly flat-
tened bluntly pointed tapering spinules about as long as plate
and graduated in length orad, the longest spine being on aboral
end of plate ; or the spinules may be disposed like rays of fan
and graduated in length toward either end of series. (2) On
actinal surface are about 3 longitudinal series of smaller spine-
lets, decreasing in length toward outer edge of plate where the
spinelets are like those of actinal intermediate plates. Four
spinelets commonly occur in the inner actinal series and about
3-5 in each of the outer; or the 2 latter series may be wanting,
the spinelets, instead, forming ah irregular group, especially on
outer part of ray where there are frequently upwards to 16 or
20 actinal spinelets.
NEW STARFISHES FROM THE PACIFIC COAST 117
Mouth plates narrow, rather prominent actinally, the free
margins of the combined plates forming a salient angle into
actinostome ; free margin of each plate slightly angular near
inner end and longer than the margin adjacent to first adambu-
lacral. Armature consists of a furrow series of about 6 or 7
tapering spinules decreasing in length from the inner enlarged
tooth, outward, and thence continued along margin adjacent to
first adambulacral in about 9 much smaller spinelets similar to
those of actinal intermediate plates. A superficial series of
similar spinelets follows margin of median suture, increasing in
size toward inner angle of plate, and an incomplete more or less
irregular series often, but not always, occurs between marginal
and superficial series. There is more or less variation in the
details of dental armature.
Madreporic body rather large, about midway between center
and extreme edge of disk. Striations coarse, centrifugal, very
irregular; madreporic body sometimes nearly hidden by 5 or 6
large paxillas.
Type, No. 21926, U. S. Nat. Mus. Type locality, Alba-
tross Station 3310, Bering Sea, in 58 fathoms, on dark sand and
mud.
Remarks. — This species bears a close resemblance to Paras-
tropectcn inermis Ludwig,1 and is probably congeneric with
that form, although anomalus has a minute anal pore. The
presence of an anal pore is, I believe, a character of scarcely
more than specific importance. For instance one species of
Astrofccten has been shown by Verrill to possess a minute
anus. Although I have not yet had an opportunity to make
serial sections of the anal region of anomalus, I have been able
to make out a tiny pore in 2 specimens, and the intestine lead-
ing to the pore is well developed. It may perhaps seem her-
etical to classify the present species with Lefty chaster, but
anomalus differs chiefly from L. facificus in having a larger
disk, shorter rays, broader actinal interradial areas, and a
slightly different ornamentation on paxillre and marginal plates.
'Mem. Mus. Comp. Zool., XXXII, July, 1905, 76, pi. to, fig. 21, 22; pi. xxi,
fig. 117; pi. xxii, fig. 126. (Gulf of Panama and Cocos Id., 1,271 and 1,40s
meters.)
Il8 FISHER
The superomarginals are only a trifle, if any, larger in anomalies
although the inferomarginals are a little longer and not quite
so broad. The chief differences are therefore in proportion.
But pacijicus is an undoubted Le-pty chaster, an evident offshoot
of arcticus, of the circumpolar fauna. It therefore follows in
due course that anomalus is a Leptychaster, although super-
ficially different enough from kcrguelencnsis, perhaps, to war-
rant another generic designation if we did not have the inter-
mediate steps.
Without having examined specimens of Parastropecten iner-
mis I hesitate to further question the validity of the genus,
although frankly I find no generic characters other than the
size of the superomarginals that can separate the form from
Lefty chaster. At any rate, L. anomalus differs from P. iner-
mis in having fewer furrow spines, more paxillae spinelets, 5
and 6 papulae about the very short-lobed roundish plates (instead
of 4), and finally in possessing a minute anal pore. The
general facies of the 2 forms is strikingly alike.
Genus Astropecten Schulze.
Astropecten Schulze, Betrachtung der versteinerte Seesterne u.
ihre Theile, 1760.
There appear to be 3 species of Astropecten off the Cali-
fornia coast. One, which I have provisionally identified as
A. erinaceus Gray, does not range much north of San Diego,
and seems to be a shore form. I have been unable to identify
the other two species with any previously described form. I
have recently described one of these as Astropecten californicns1
and the other is diagnosed below. In order to contrast the
principal characters a synopsis of the 3 forms is added.
a. A series of spines along upper edge of superomarginals, and
usually, also, a second, parallel longitudinal series, spaced from
the above ; size large ; littoral erinaceus.
aa. Superomarginals entirely devoid of enlarged tubercles or spines.
b. Paxillae larger, about 3 transverse series opposite 2 superomar-
ginals at base of ray ; paxillae not irregular and more crowded
along radial lines ; the enlarged spine of actinal surface of
adambulacral plates, slender, tapering and bluntly pointed.
ornatissimus.
'Zool. Anzeiger, Bd. XXX, Nr. 10, June 19, 1906, 299.
NEW STARFISHES FROM THE PACIFIC COAST IIO.
66. Paxilla? smaller, about 4 or 5 transverse series opposite 2 supero-
marginals at base of ray, crowded and more or less irregular
along radial lines; enlarged adambulacra] spine with rounded
or truncate tip, and not conspicuously tapered... ca lifo miens.
ASTROPECTEN ORNATISSIMUS Fisher, new species.
This species differs from its nearest relative, A. californicus,
in having shorter rays, larger paxillae with longer spinelets,
longer and slenderer adambulacral spines, and longer marginal
spines.
R — 56 mm. ; r = 14 mm. ; R = ^r. Breadth of ray at base,
16.5 mm.
The paxillae afford the most evident difference between orna-
tissimus and californicus. In californicus there is a consider-
able area around center of disk in which the paxillae are smaller
and more crowded than on remainder of disk and on rays, and
paxillae of midradial regions are more irregular, at least in
arrangement, than along margins of ray. In the present form
the large paxillae extend nearly to center of disk, there being
only a small area of small paxillae.
The paxillae of sides of rays are not in such regular rows and
are not easily differentiated from the midradial ones. About
3 or 3^ transverse series of paxillae correspond to 2 superomar-
ginal plates at base of ray (usually 5 in californicus), about 5 at
middle of ray, and 6 or 7 near tip. Opposite suture between
second and third superomarginal plates about 12 or 13 paxillae
can be counted across ray to same point on opposite side (18 to
20 in californicus). Large paxillae at base of rays with 15 to
18 peripheral and 10 to 15 central spinelets, which are much
longer than in californicus, terete, with rounded or clavate tips.
Tabulum of paxilla fairly broad so that both central and per-
ipheral spinelets appear spaced, giving the whole an open flori-
form appearance. Farther along ray, 1 to 6 central spinelets
to a paxilla, and upwards to 15 or 18 peripheral. At very end
of ray the paxillae are much smaller.
Superomarginal plates 32 to a ray, without enlarged spine-
lets or tubercles. General surface covered with short spinelets,
delicate except along median transverse line where they are cla-
120 FISHER
vate to thimble-shaped, increasing in size toward upper end of
plate (same spinelets are markedly squamiform in californicus).
Armature of inferomarginal plates very similar to that of cal-
ifornicus, there being usually 2 or 3 marginal spines obliquely
placed, and, in a line, 3 more spaced, smaller, spines along
aboral edge of plate. The auxiliary lateral spines situated just
adorad to the regular lateral spines on each plate are longer
than the same spines of californicus.
Adambulacral furrow spines 3 or 4, similar to those of cal-
ifornicus. First actinal series with 2 spines, the aboral being
much the longer, tapering, slightly flattened, bluntly pointed,
longer and slenderer than the corresponding spine of califor-
nicus. The adoral member is about as long as the furrow
spine which stands vis-a-vis. Outer or second actinal series
usually consists of 3 slender untapered spines somewhat shorter
than furrow spines, and standing in a fairly regular row.
Near base of furrow 2 or 3 very small spinelets sometimes
stand on outer end of plate.
Mouth spines similar to those of californicus, but the mar-
ginal series stand slightly spaced from the intermediate spines,
so that inner end of combined plates is broader and the 3 series,
superficial, intermediate and marginal, are more clearly evi-
dent. All spines are slenderer and a trifle longer than in cal-
ifornicus. Marginal spines, about 7 between tooth and inner
end of first adambulacral plate ; and about 6 or 7 more minute
spinelets continue the series two-thirds distance to outer end of
plate.
Madreporic body concealed by paxillae, situated as in cali-
fornicus and crossed by sinuous strias ; tiny, spiniform knobs on
ridges of californicus apparently lacking.
Color in alcohol, bleached yellowish to whitish ; color in life
unknown.
Type, No. 21927, U. S. Nat. Mus. Type locality, vicinity
of Santa Barbara Islands, in 150 fathoms. The vertical range
is 67 to 162 fathoms, and the species extends south to Lower
California at least, and north to the latitude of Monterey Bay.
Remarks. — This species differs from A. fragilis Verrill in
having numerous actinal adambulacral spines and shorter rays.
NEW STARFISHES FROM THE PACIFIC COAST 121
A. regalis Gray, a short-rayed form, also has but one actinal
adambulacral spine, scarcely longer than longest furrow spine.
A. vcrrilli de Loriol differs from ornatissimus in having a dif-
ferent inferomarginal and adambulacral armature. The supero-
marginal plates of verrilli carry small tubercles forming a single
longitudinal series. A. rubidus de Loriol is allied to articulatus
(Say), having broad supermarginal plates, a smaller disk than
ornatissimus^ and with rays broader at tip, paxillae with shorter
spinelets, and adambulacral plates with much smaller spinelets
— 3 small ones in actinal ser
Family LUIDIID^ (Sladen) Verrill.
Genus Luidia Forbes.
Luidia Forbes, Mem. Wern. Soc, vni, 1839, I23*
There are three species of Luidia occurring off the California
coast. In literature two names occur — Luidia foliolata Grube '
and L. catifornica Perrier.2 According to Ludwig the latter
name is a nomen nudum ; hence it need not further be con-
sidered. Ludwig3 further states that Grube gives California
as the locality of foliolata. I have not been able to consult
Grube's description, but from the fact that Sladen thinks folio-
lata may not be distinct from brcvispina, I have considered
that the name must apply (if not actually to brcvisfina) to a
common, shallow water Luidia (Southern Alaska to San Diego,
and Mazatlan?) which is closely related to brevisfiina. This-
form I have compared with specimens of L. brcvispina, and it
is perfectly distinct. If the name foliolata does not apply to it,
it is a new form.
The other 2 species are evidently new and the more evident
characters of the 3 forms are contrasted in the following
synopsis.
1 L'eber einige neue Seesterne des Breslauer zoologischen Museums < 43
Jahresber. d. Schlesisch. Gesellsch. f. vaterland. Kultur, Breslau, 1S66, 59.
{Fide Ludwig.)
2 Etude sur la repartition geographiques des Asterides. < Xouv. Archiv
Mus. Hist. Nat. Paris, II ser. I, 1S7S, $■;, 91. (Fide Ludwig.)
3 Mem. Mus. Corhp. Zool., XXXII, 1905, So, footnote.
122 FISHER
a. Lateral abactinal paxillae with a quadrate or subquadrate tabulum.
b. No pedicellariae ; abactinal surface drab gray or greenish gray in
life Luidia foliolata .
bb. Pedicellariae (bivalved) on inferomarginal plates (abactinal end)
and on superomarginal paxillae, and trivalved upright pedicel-
lariae on actinal intermediate plates ; abactinal surface reddish
in life, sometimes mottled with lighter Ltiidia ludivigi.
aa. Paxillae with stellate crown ; granuliform abactinal 2-jawed pedi-
cellariae; slender 2-jawed actinal intermediate pedicellariae;
rather prominent lateral spines Luidia asthenosoma.
LUIDIA LUDWIGI Fisher, new species.
Rays 5. jR = 107 mm.; r = 13 mm. 7? = 8.2r. Breadth
of ray at base, 15 mm.
Rays slender, very gradually tapering to a pointed extremity ;
interbrachial arcs acute ; general form depressed as in other
species of genus, but abactinal surface well arched ; sides of
ray rounded ; abactinal area with 3 or 4 regular series of quad-
rate paxillae on each side, the superomarginal with small 2-
and 3-jawed pedicellariae ; inferomarginal plates rather narrow,
arched, with 1 to 3, usually 2, lateral spines, and 3-6 actinal
spinules larger than spinelets of general surface, and on upper
end a pedicellaria similar to that of adjacent paxilla ; actinal
intermediate plates of interradial areas and proximal half of ray
each with a rather prominent 3-jawed pedicellaria ; adambula-
cral plates with a curved furrow spine, 3 actinal spines and 1 or
2 smaller spinules.
Abactinal paxillar area rather crowded ; paxillae of 4 or 5
lateral regular series, quadrate ; fourth, fifth, or sixth series
(according to size of specimen) with many subcircular or not
obviously quadrate paxillae ; superomarginal paxillae slightly
smaller than those of adjacent series ; paxillae thence decreas-
ing in size toward mid-radial area where they are arranged
without regularity and are roundish or irregular in outline. In
some small specimens paxillae are not so obviously quadrate in
lateral series, being subcircular in outline, but nevertheless
arranged regularly. Crown of spinelets not so flat as in folio-
lata but rather convex especially in small examples ; supero-
NEW STARFISHES FROM TIIF PACIFIC COAST 1 23
marginal paxillae with about 35 short clavate spinelets in a
radiating coordinate group, and most of them also with a small
2-jawed valvate pedicellaria, slightly longer than spinelets ;
next series with about 40 spinelets, those in center of tabulum
stouter than the peripheral, as in superomarginal paxillae ;
small mid-radial paxillae with about 20 spinelets.
Inferomarginal plates relatively narrower than in foltolata
(i.e., with reference to transverse axis of plate); fasciolar
grooves deep, and wider (with reference to long axis of ray)
than same dimension of special raised ridges of inferomargi-
nals. Outer or abactinal end of each plate with a 2-jawed
pedicellaria similar to that of adjacent superomarginal paxilla,
and with 1 or 2, usually 2, tapering sharp spines, of which
sometimes the inner, sometimes the outer, is the longer; the
longer (about 4 mm.) equal to about width of its plate; more
rarely 3 shorter subequal spines in transverse series on outer
end of plate ; spines forming a prominent marginal fringe to
ray ; on actinal surface of plate, 3 to 6 much shorter spinules
form a transverse series in line with lateral spines, or a zigzag,
or even double series, while margin of plate bears slender terete
spinelets, becoming more capillary in fasciolar grooves.
Adambulacral armature consisting of a curved sabre-shaped
furrow spine, and on actinal surface 3 tapering bluntly pointed
spines, of which 1, the longest, stands behind furrow spine and
the other 2 forai a slightly oblique longitudinal series just
behind first actinal spine ; or 2 spines, the adoral the shorter,
stand in a longitudinal series just behind furrow spine, and the
third just outside of the aboral (longer) spine of the series ; 1 to
3 small slender spinelets occur on outer part of plate, frequentlv
3 at base of ray forming a longitudinal series, or 1 on adoral
edge of plate, back of outer adoral spine.
Actinal intermediate plates of interradial region and proximal
half of ray paxilliform, surmounted by a prominent 3-jawed
pedicellaria which is surrounded at base by numerous slender
spinelets in a calyx-like whorl. Each pedicellaria is conical
and 1.5 to 2 times as high as its width at base.
Mouth plates narrow, with 6 or 7 marginal spines and 7 or 8
superficial ones, forming together a double series on the raised
124
FISHER
exposed surface of plate parallel with median suture. Inner
spine of superficial series largest, and like the rest, slender,
pointed, tapering. All spines decrease in size toward outer
end of plate. Innermost marginal spine situated nearer peri-
stome than is the enlarged inner superficial spine.
Madreporic body between second and third lateral rows of
paxillse, and hidden by them.
Type, No. 21928, U. S. Nat. Mus. Type locality, Alba-
tross Station 2970, vicinity of Santa Barbara Islands, in 29
fathoms, on fine gray sand and mud.
Remarks. — This species has the general form of L. lorioli
Meissner (Mazatlan), but has longer arms, which are more at-
tenuate distally. L. ludwigi lacks the conspicuous sharp spinules
which are present in many of the lateral abactinal paxillse of
lorioli, and the latter has no abactinal pedicellariae, such as are
very characteric of the present species. Another character
which separates ludwigi from both lorioli and bellonce Lutken
is the presence of prominent pedicellariae on the actinal inter-
mediate plates of interradial region and proximal half of ray.
Details of adambulacral armature differ in all three forms.
L. ludwigi differs from L,. quinaria in having much longer nar-
rower rays, no scattered and abundant abactinal pedicellariae
over the midradial region, and in having 3-jawed, not 2-jawed,
actinal pedicellariae. The abactinal pedicellariae of quinaria
are low, and of the bivalved form of some Goniasteridae. The
adambulacral plates also have 2-jawed pedicellariae in quinaria.
Named for Prof. Hubert Ludwig.
LUIDIA ASTHENOSOMA Fisher, new species.
This fragile creature bears a close resemblance to L. sarsi
Diiben and Koren, of northern Europe and the Mediterranean,
and may be looked upon as a north Pacific representative of
that species. None of the specimens are as large as L. sarsi
is known to grow. The California species differs from sarsi
in having very small, abactinal, 2-jawed (rarely 3-jawed), gran-
uliform pedicellariae scattered along the medioradial area, with
larger ones, sometimes, on the regular lateral paxillae, and on
upper end of inferomarginal plates. The inferomarginal spines
NEW STARFISHES FROM THE PACIFIC COAST 1 25
are longer, the adambulacral armature and minor details of
paxilla? are different.
Rays 5. 7?= 86 mm.; r = 9 mm. ; 7? = 9.5/-. Breadth of
ray at base, 10 to 11 mm.
Rays long, narrow, pointed, very gently tapering, with a
slightly convex abactinal surface usually sunken along mid-
radial line. General form much flattened ; sides of rays
rounded ; inferomarginal plates narrow, not encroaching much
upon actinal area, but forming rather the margin of ray ; ambu-
lacral furrow wide and shallow ; tube feet long, in 2 series ;
actinal and marginal spines rather long and bristling, the ad-
ambulacral armature forming 2 series continuous with that of
inferomarginal plates; actinal intermediate plates usually with
a rather short, 2-jawed, blunt, papilliform pedicellaria.
Abactinal paxilla? with a stellate crown ; those of supermar-
ginal series larger than rest, and each corresponding to an infero-
marginal plate, to upper end of which it is closely juxtaposed.
Crown of superomarginal paxilla longitudinally oval (as in
sarsi), the others subcircular. Adjacent to superomarginal
paxilla? are about 2 regular series of lateral abactinal paxilloe,
about 2 of which correspond to 1 superomarginal paxilla.
Paxillae diminish in size very rapidly toward median line of ray
and become less regular in arrangement as they approach it.
Superomarginal paxilla has slightly convex tabulum armed
with about 30 slender denticulate spinelets, of which about 10
are scattered on surface of tabulum and the remainder about
the periphery, the whole forming a diverging group. The
superomarginal and other lateral paxilla? sometimes have a
blunt 2-jawed pedicellaria similar to but larger than those scat-
tered over the midradial area (see below). The adjacent pax-
illae have about 12 peripheral and 3 to 5 central spinelets, while
those in midradial region have about 10 peripheral and 3 or 4
central, very much smaller, spinelets, the whole paxilla being
notably smaller. Many of small paxilla? of midradial area also
bear in center of tabulum, surrounded usually by a few small
peripheral spinelets, a small obovoid 2-jawed valvate pedicel-
laria, resembling a split granule. Viewed from above, the
pedicellaria is elliptical in shape when closed. Each jaw is
126 FISHER
hollowed on inner face and occasionally is larger, springing
from a very low paxilla and emerging between the others.
Rarely there are 3 jaws. Jaws of pedicellariae much thicker
and more robust than any paxilla spines.
Inferomarginal plates relatively very narrow, transversely
arched, encroaching but slightly upon actinal surface, forming
rounded margin to ray; chord of width equal to 1.5 times that
of adambulacral and actinal intermediate plates combined.
Fasciolar grooves deep and wide, slightly wider (/. e., meas-
ured on long axis of ray) than corresponding dimension of
specialized elevated ridge of plate. Each plate with a trans-
verse series of 3 robust, tapering, sharp spines, of which the
outer is often slightly the longest, but frequently the middle one,
or the 2 are subequal ; inner (actinal) spine of series is some-
times much slenderer than other 2, and only one half or two
thirds length of longest spine ; latter attains a length of 5.5 mm.
or slightly over one half width of abactinal paxillar area, or
nearly twice width of plate (/. <?., chord of width). General
surface of plate covered with slender almost capillary spinelets
which become finer in fasciolar grooves ; and upper end of plate
sometimes bears a pedicellaria similar to those of abactinal
surface.
Adambulacral plates with a slender sabre-shaped furrow
spine, and forming a linear series with it on actinal surface, 2
slender tapering pointed spines, the inner of which is the stouter
and slightly the longer. A couple of very slender spinelets
stand on adoral side of outermost spine, which decreases in size
toward extremity of ray more rapidly than the inner.
On most of the actinal intermediate plates of proximal two
thirds of ray is a small 2-jawed pedicellaria accompanied by 2 or 3
capillary spinelets ; when former is absent its place is taken by
about 3 to 5 capillary spinelets ; jaws of pedicellaria blunt, ob-
long to obovate, 0.5 mm. high ; 3 or 4 pedicellariae in interradial
region, but very few spinelets.
Mouth-plates more like those of Astroficctcn than most spe-
cies of Luidia. Exposed surface of combined plates, ovoid,
prominent; suture between plates fairly wide. Armature con-
sisting of a slightly tapering, bluntly pointed tooth and back of
NEW STARFISHES PROM THE PACIFIC COAST 127
that on margin a large 2-jawed pedicellaria nearly as long as
tooth. Two shorter spines may take the place of the pedi-
cellaria. In line with the tooth a series of about 10 superficial
spinelets follows edge of suture, decreasing in size toward outer
end of plate ; and along curved margin adjacent to first adam-
bulacral are 4 or 5 slender spinelets, the second from inner end
of series often the longest. This series is separated from the
superficial by a shallow groove.
Color in life, reddish brown (burnt Sienna) on abactinal sur-
face; marginal spines lighter, often whitish; actinal surface
whitish.
Type, No. 21929,11. S. Nat. Mus. Type locality, Albatross
Station 3148, off Central California in 47 fathoms, on brown
mud.
Family ECHINASTERIDiE Verrill.
Genus Henricia ' Gray.
Henricia Gray, Ann. and Mag. Nat. Hist., Ser. i, vi, 1840, 184.
Type, Astcrias sanguinolenta O. F. Miiller.
Linckia Forbes, non Nardo, Mem. Wern. Soc. vm, 1839, I2°-
Cribrella Forbes, non Agassiz, Brit. Starfishes, 1841, 106.
Cribrella Liitken, Gronl. Echinod., 1857, 30; and most authors
since then.
Echinaster M. & T. Syst. Ast., 1842, 22 (pars).
Henricia Bell, Ann. and Mag. Nat. Hist., Ser. 6, vi, 1890, 472.
HENRICIA ASPERA Fisher, new species.
Rays 5. R= 100 mm.; r= 15 mm; R=6.6r. Breadth
of ray at base, 14 mm.
Disk small, rays slender, usually not swollen at base. Abac-
tinal skeleton forming an open meshwork, the individual plates
1 Cribrella Ag., the name long used for this genus, is a synonym of Liuckia
Nardo. Forbes appropriated Agassiz's name and transferred it to a different
group, that is, to the genus which Gray had previously named Henricia. Cri-
bella Forbes drops out of nomenclature both because it is a synonym of Henricia
and more especially as it is a homonym of Cribrella Agassiz. The Cribrella
of Agassiz was proposed (Mem. Soc. Sci. Nat. Neuchatel t. 1, 1S35. 191 1 as a
substitute name for Liuckia Xardo, the latter being now in use. Consequently
Cribrella Ag. has no status other than as a synonym of Liuckia.
128 FISHER
indistinguishable and spinelets very short granuliform, not ar-
ranged in evident pseudopaxillae as in levhiscula. Meshes
roundish quadrate, or irregularly polygonal, more open in some
examples than in others, containing sometimes i or 2 small
secondary ossicles with a few granuliform spinelets. Meshes
usually considerably wider than enclosing trabeculas, and with
5 to 12 papulae on proximal two-thirds of ray, 5 to 7 distally
(but fewer in small specimens). Spinelets not crowded, but
spaced, short, sharp, much slenderer, and fewer than in levius-
cula, often reduced to mere granuliform sharp elevations on
plate and more or less obscured by a tight thin skin ; arranged
along ridges irregularly, but in not over three rows, often in
only one irregular series. These rows are interrupted, dividing
the spinelets and granules into groups probably corresponding
to underlying plates, although no divisions are evident. There
are commonly 5 to 15 spinelets in one of these groups, but in
some specimens they are so obscured by the superficial mem-
branes that only the very tips of the spinelets are visible. They
are invisible to the naked eye, and are seen with difficulty under
a strong glass. Division into groups more evident on sides of
ray.
Marginal plates regularly arranged. Superomarginal series
departing from interradial angle about midway between dorsal
center of disk and inner angle of jaw-plates ; occasionally rather
irregular near interbrachial angle ; plates sometimes transversely
elongated, with 10 to 12 spinelets. Inferomarginals slightly
larger or exactly equal to superomarginals ; 1 or 2 rows of in-
termarginal plates on basal fifth of ray ; also 1 or 2 rows of ac-
tinal intermediate plates, 2 extending about one fifth length of
ray, and 1 series for one half length, beyond which point in-
feromarginals and adambulacrals are in contact. Inter- and
inframarginal papula? ; 1 to 6 in an area. Marginal plates
also form fairly regular transverse series with adambulacrals,
although latter are more numerous than former.
Adambulacral plates with 1 small spine deep in furrow ; on
some plates, especially in large specimens, a second may be
present just above it and in line. On actinal surface 2 larger
spines stand in an oblique transverse series on furrow margin
NEW STARFISHES FROM THE PACIFIC COAST 1 29
(frequently a group of 3) ; and behind them 3 or 4 much shorter
graduated spinelets in a single zig-zag series, all more or less
united basally by membrane. Armature varies greatly, some-
times 2 transverse series of spines being present, and the spines
themselves vary in shape from slender cylindrical tapering to
thick, clavate and blunt. Armature generally has appearance
of being in a single series and rather sparse. The outer spine-
lets of some specimens (those which have very minute spinelets
generally) are buried in membrane and all but invisible.
Madreporic body variable — usually subtubercular, roundish,
with coarse striations.
Color in life : Abactinal surface deep chrome yellow ; papu-
lar areas deep saffron yellow ; actinal surface pale Indian
yellow.
Type, No. 21930, U. S. Nat. Mus. Type locality, Alba-
tross Station 3052, off Oregon in 48 fathoms, on " coral,"
broken shells and rocky bottom.
HENRICIA POLYACANTHA Fisher, new species.
Rays 5. R = 66 mm.; r=nmm.; R = 6r. Breadth of
ray at base, 13 mm.
Rays moderately to decidedly slender, very flexible, tapering
gradually to bluntly pointed, upturned tip ; abactinal surface
usually collapsed more or less ; disk rather small ; adambula-
cral plates at base of ray with 30 to 40 actinal spinelets, and in
furrow, instead of the usual single spinelet, 2 to 6 such spine-
lets grouped or in a vertical series ; always more than 1 furrow
spinelet ; at base of ray always more than 3.
Abactinal and lateral surfaces of rays covered with small,
evenly-spaced pseudopaxillge, leaving papular areas consider-
ably larger than the plates; papulae 1 to an area, large.
Without aid of a glass the papular areas appear roundish.
Paxilla? more or less elongated in one direction ; convex, cov-
ered with exceedingly small spinelets, which are numerous, but
vary greatly in number, according to the size of pseudopaxilla ;
10 to 40 is the usual number. Paxillae form a more or less evi-
dent median radial line along ray.
13O FISHER
External to adambulacral plates is a regular series of actinal
intermediate plates, and separated from the latter by a regular
series of papulae is a row of smaller inferomarginals. Some-
times a supermarginal series can be distinguished just above
the inferomarginals, especially on outer part of ray, where the
2 series are fairly regular. At base of ray the serial arrange-
ment is broken up and 2 or 3 additional series of small inter-
mediate plates are interpolated. The "marginal plates " are
larger than dorsolateral pseudopaxillas.
Adambulacral plates separated by a distinct suture. Arma-
ture very dense, consisting of many spinelets, as follows: (1)
on furrow face of plates 2 to 6 small sabre-shaped spinelets in
a vertical series, or more irregularly in 2 series. The number
varies in different individuals. Usually there are 5 or 6 at base
of ray and 2 or 3 to each plate beyond middle. Occasionally
specimens have more than three on plates of distal portion of
arm. (2) On actinal surface of plate are 30 to 40 slender
pointed spinelets arranged in 3 or 4 transverse series on inner
half of plate, but too crowded on outer half to form rows.
Even the inner spinelets are often without regularity. Spine-
lets decrease rapidly in length and calibre from the furrow out-
ward, the outer spinelets being sharper than the inner and
about the same size as those on other actinal plates.
Madreporic body prominent, tubercular, situated midway
between center of disk and interbrachial angle, there being
small spinelets scattered on the surface. Striations coarse,
irregularly radiating.
Type, No. 21931, U. S. Nat. Mus. Type locality, Albatross
Station 2936, off Dan Diego, Cal., in 359 fathoms, on mud.
Family SOLASTERIDiE Perrier.
Genus Crossaster Miiller & Troschel.
Crossasier Miiller & Troschel, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, 1840, 103.
a. Marginal plates of two kinds in a single linear series — conspicuous
transversely oriented, prominently spinous, paxilliform plates
alternating with 1 or 2 low longitudinally placed plates with
NEW STARFISHES FROM THE PACIFIC COAST 131
short spinelets; proximal marginal plates strictly actinal in
position; adambulacral plates with usually four actinal spines.
Papulae very conspicuous; abactinal skeleton more open.
Crossaster alternatus.
aa. Marginal plates of one kind, viz. : conspicuous transversely
oriented paxilliform plates which are strictly marginal in posi-
tion ; adambulacral plates with 2 or 3 actinal spines. Abactinal
skeleton less open Crossaster borealis.
CROSSASTER ALTERNATUS Fisher, new species.
Rays 10. R =63 mm.; r = 24 ; R=2.6r. A larger speci-
men taken between San Diego and San Clemente (500 fathoms)
in 1904 measures as follows: R = 100 mm.; r — 34 mm.;
R= 2.gr. Breadth of ray at base, 23 mm.
General form flattened ; abactinal surface of disk slightly
convex, capable of inflation, but flattened on central part;
abactinal surface of rays slightly rounded ; margins well
rounded ; actinal surface nearly flat ; interbrachial angles rather
acute ; abactinal skeleton open reticulate, the ossicles slenderer
than in Crossaste?' fiafifiosus ; papulae large; paxillas small,
well-spaced ; marginal plates characteristic, more prominently
spinous transversely placed plates alternating with (usually 2)
longitudinally oriented plates with very short spinelets ; marginal
plates actinal in position on basal half of ray ; actinal interradial
areas small, with few plates set fairly close together ; a single
series of very small intermediate plates extending to end of
ray ; adambulacral plates with 4 to 8 furrow spinules and a
transverse series of 4 actinal spinules.
Abactinal integument rather thin but tough and pliable,
parchment-like, quite opaque and obscuring the ossicles unless
dried. Skeleton open and forming a net-work with fairly wide
meshes, which are irregular and largest on disk ; connecting
ossicles slender, often irregular; enclosed within meshes, small
free irregular ossicles ; these often absent, but usually present
on disk and most numerous near its center. Paxillas with a 2-
to 4-slender-lobed base and a low stout pedicel surmounted by
usually 4 or 5 rough, delicate tapering, pointed, spinelets en-
closed in a delicate membraneous sac, which fits tightly about
I32 FISHER
each spinule for about half its length, leaving only its basal
part obscured. In consequence of the open character of skele-
ton, paxillse are well spaced, but are much smaller and more
numerous than in Crossaster papposus. They are largest and
most widely spaced midway between center of disk and margin
on radial areas, thence rapidly diminishing in size toward ex-
tremity of ray and less toward center of disk. A bare sulcus
leads from each interradial angle half way to center of disk.
These bare areas are about 1 mm. wide and are paved solidly
with ossicles which are the upper edge of the incomplete cal-
careous interbrachial partition. At the inner end of this bare
area, in 1 interradius is the madreporic body surrounded by
several paxillae ; in the other radii several slightly larger pax-
illae hold a similar position. Papulae large, partially obscuring
the small paxillae ; absent from bare interradial areas ; 2 to 7 or
8 to each mesh of skeleton on rays and as many as 15 on disk,
or even more where meshes are incomplete. Papulae com-
monly 3 mm. long, pointed. In the interradii a number of the
abactinal plates are actinal in position because the marginal
plates are drawn inward toward the mouth. Thus in the type
the distance between marginal plates and interradial angle is 6
to 8 mm., consequently the dorsal integument with plates and
papulae is drawn onto actinal surface.
Marginal plates conspicuous ; about 14 or 15 prominent,
rather widely spaced, transversely oriented, paxilliform plates
seem to represent the inferomarginal series, and between each
of these, in the same linear series, are 1 to 3, usually 2, longi-
tudinally oriented, much lower and slightly smaller plates,
which may represent the superomarginal series, although now
forming a single series with inferomarginals. Prominent mar-
ginals become more conspicuous toward tip of ray, acquiring a
heavy, compressed pedicel often higher than its width at top,
and very paxilliform in appearance, bearing 2 transverse rows
of about 8 to 16 long, tapering needle-like spinules, which in-
crease in length but decrease in number toward extremity of
ray. Beyond proximal fourth of ray there are two well-de-
fined series of these spinules, of which the adoral spinules are
the shorter, and in the other series about 3 skin-covered spin-
NEW STARFISHES FROM THE PACIFIC COAST 1 33
ules become much larger than the rest and have very fine
points. Distally the spinules form 2 palmate series, but there
is more or less variation in their numbers. The non-prominent
longitudinally oriented plates vary considerably in size, and
decrease markedly in size distad, whereas the others become
more prominent. Except at base of ray, they are not nearly
so high as transverse plates and are rounded to elliptical-ob-
long, bearing upwards to 25 very short spinelets in about 3 or 4
longitudinal series. At tip of ray these plates are very small,
bearing a group of 5 or more delicate spinelets.
Actinal interradial areas small, with small, closely-placed,
paxilliform plates bearing 4 to 10 spinelets, which are more del-
icate than those of abactinal paxillae, although the latter are of
about the same size. Interradial paxillae about 10 to 20 in
number. Proceeding along ray almost to its tip is an incon-
spicuous series of very small actinal intermediate plates, often
rather widely separated, a plate usually opposite each adambu-
lacral plate, and distally bearing only a single small spinelet, or
none at all, proximally with 2 to 5 spinelets.
Adambulacral plates with a palmate furrow series proximally
of 6 to 8, distally of 4 or 5, very delicate, tapering sharp skin-
covered spinules united for about a third their length by a web.
Mesial spinules longest (about one-third width of plate in length)
thence decreasing in length toward either end of series. On
actinal surface of plate a transverse comb of 4 or 5 slender,
needle-like, sharp spines, the 2 or 3 mesial much the longest,
the inner usually slightly longer than furrow spinules, often
much longer ; outermost spine usually nearly equal to the
longest, which exceeds in length width of plate. These
spines, like those of furrow series, invested in membrane,
which forms vane-like lateral expansions (causing the spinule
to appear broad and flat near base) and unites them in a com-
mon web by their bases. On distal part of ray the large adam-
bulacral spines are similar in size and appearance to the larger
inferomarginal spines, already described.
Mouth-plates of the usual shape, rather prominent actinally.
Each plate with 3 long slightly tapering pointed spines at
inner end, these decreasing in size outward, so that third spine is
134 FISHER
about one half length of innermost ; thence series is continued
to end of plate in 7 or 8 much shorter spines resembling those
of first adambulacral plate. All spines skin-covered and united
basally by a web. On actinal surface, parallel with median
suture and slightly nearer it than free margin, is a comb of 2 to 8
skin-covered sometimes basally webbed spinules similar to but
smaller than corresponding series of first inferomarginal.
Madreporic body irregularly circular or oval, situated about
midway between center of disk and margin ; convex, irregu-
larly and centrifugally striated ; about 3 mm. in diameter.
Color in life: " salmon pink."
Young : Young specimens agree very well with the large ex-
amples, except that the papulae are less numerous, and there is a
slight reduction in number of spines of interradial, marginal
and adambulacral plates, as well as fewer itnerradial and mar-
ginal plates. In small specimens there is more often only one
superomarginal plate interpolated between the transversely
oriented inferomarginals, and the former are slightly more
superior in position, at base of ray, than in adults. Adambu-
lacrals commonly with 3 to 5 furrow spinules proximally, and
about 5 actinal. Usually only 1 or 2 large papulae to a mesh ;
abactinal spinelets not fewer in number than in adults.
Type, No. 21932, U. S. Nat. Mus. Type locality, Albatross
Station 2839, Santa Barbara Islands, Cal., in 414 fathoms, on
gray sand.
CROSSASTER BOREALIS Fisher, new species.
Rays 9 to 12. R = 140 mm.; r = 47 mm. R = 3?'-
Breadth of ray at base, 23 mm.
Related to C. australis Perrier. General form much as in
preceding species, but disk usually more arched, and commonly
slightly sunken in middle ; marginal plates prominent, paxilli-
form, transversely oriented, spaced ; not of two kinds as in the
preceding species ; situated on margin of ray and disk, not
proximally encroaching on actinal surface to any great extent;
interradial areas small, paved with small roundish close-set
plates bearing very few spinelets ; a single series of small scat-
NEW STARFISHES FROM TIIF. PACIFIC COAST 135
tered intermediate plates extending nearly to tip of ray ; abac-
tinal skeleton similar to that of preceding species, but slightly
less open, i. c, meshes somewhat smaller; paxillae small,
spaced, typically arranged with more or less regularity on disk,
in series parallel with median radial ; anal aperture prominent.
Abactinal integument entirely obscuring underlying skeleton,
unless dried or treated with caustic potash. Paxillae small,
spaced, with a low tabulum surmounted by i to 6 slender blunt
or pointed, tapering spinelets. In life these spinelets are thick,
short and stubby, owing to a membranous investment, and are
usually 3 or 4 to each paxilla. In center of disk and along
distal half of ray, paxillae irregularly arranged, but between
these two areas an arrangement in longitudinal rows more
or less evident. Base of paxillae with 3 or 4 slender unequal
lobes impinging upon those of neighboring paxillae or connected
by short irregular ossicles ; latter not numerous ; near center of
disk there are 1 or 2 isolated ossicles in many of the meshes.
Anus surrounded by 4 or 5 large paxillae. As in preceding spe-
cies a very narrow bare sulcus extends from interradial angle
about half way to center of disk. Papulae prominent, but
usually not quite so large as in preceding species, about 3 to 10
to a mesh on disk, 1 to 3 in distal half of ray where skeleton
is closer.
Marginal plates, about 30 to each side of a ray, prominent,
confined to side wall of ray, paxilliform with fairly high pedi-
cels (relatively about as in papposits), bearing 2 vertical or
transverse palmate series of 6 to 9 stout tapering pointed skin-
covered spines, the mesial of which are the longest. Some-
times there is 1 main series and 2 or 3 smaller spines stand
adorally out of the series, or there may be a second adoral
series of less conspicuous spinules, but few in number. Spines
of proximal plates shorter than rest, except near tip of ray.
Actinal interradial areas rather small, about 35 to 40 plates
to each area. Plates obscured by integument which has fine
furrows or wrinkles leading from interadambulacral sulcuses
to marginal plates. Plates appear spaced, each bearing 1 to 4
short stubby papilliform spinelets, very delicate when dried.
Plates arranged irregularly in rows, between the wrinkles. A
I36 FISHER
series of very small widely spaced actinal intermediate plates
extends over three fourth length of ray. They bear usually 1
or 2 stumpy spinelets, or are spineless.
Adambulacral plates with (1) a palmate furrow series of 5 or
6 (distally 3 or 4) slender tapering skin-covered spinelets (united
for about half their length by a web) of which the 2 or 3 mesial
are subequal, the laterals much shorter. These spinelets are
of about same length as in preceding species. (2) On actinal
surface a transverse series oi 4 (3 on smaller examples, vary-
ing to 2 and 5) much longer, slender, terete, blunt, skin-covered
spines, the second or third usually longest (exceeding in length
the width of plate), the outer about one half length of inner
(where there are 3 spines) ; when 2 spines only are present they
are subequal and long.
Mouth plates just a trifle narrower than in preceding species.
Free margin with a webbed series of about 11 spinelets increas-
ing in length toward inner end of each plate to 2 or 3 enlarged
spines, the innermost stoutest. On actinal surface of plate near
inner end of each is a stout, though slender, spine. Sometimes
instead of this a small one stands on outer end of plates, or
there may be 2 or 3 small spines.
Madreporic body variable in size, similar to that of preceding
species, and, like it, situated at inner end of an interradial
fasciole. Two or 3 large paxillae stand near it.
Type, No. 21933, U. S. Nat. Mus. Type locality, Albatross
Station 2858, east of Kadiak Island in 230 fathoms, on blue
mud and gravel ; also found in Bering Sea, in 987 fathoms, on
green mud.
Family PYCNOPODIID^E x Stimpson (restr.).
Rathbunaster Fisher, new genus.
Rathbunaster Fisher, new genus of Pycnopodiidas. (Type, R.
californicus Fisher, new species.)
Near Pycnofiodia Stimpson, but differing in having a smaller
disk, with the rays constricted at base and easily detachable ;
1 Used by Stimpson (Proc. Bost. Soc. Nat. Hist., vm,iS62, 261), as synony-
mous with Asteriida.' of modern authors. As here employed it includes Pycho-
fiodia, Rathbunaster and possibly also Anastcrias, although I have not examined
that genus.
NEW STARFISHES FROM THE PACIFIC COAST 137
in the entire absence of rudimentary annular or calcareous
ridges at base of ray, in the abortion of alternate superomar-
ginal plates beyond base of ray, and in the small widely spaced
inferomarginals each bearing a slender spine ; in the greater
prominence of the adambulacral plates which are placed on the
same level with the inferomarginals (and each with a single
spine as in Pycnopodia) ; in the less crowded condition of the
ambulacral ossicles.
The circular isolated plates on abactinal surface of rays are
more numerous than in Pycnopodia and each bears a wreathed
spine, whereas in Pycnopodia spines are rare on abactinal plates
of arm. There are no large bivalved pedicellariae as in Pyc-
nopodia. Tube-feet quadriserial except at extremity and base
of ray where they are biserial. Ambulacral plates being less
crowded, the tube feet are really intermediate in arrangement
between the biserial and quadriserial type. Mouth plates are
more prominent than in Pycnopodia and approach in form
the type common to Brisingidae. Actinostome wide, like the
Brisingidae.
Named for Dr. Richard Rathbun.
RATHBUNASTER CALIFORNICUS Fisher, new species.
Rays 17 (varying from 13 to 17). R = 155 mm. (variable);
r = 23 mm. R = 6.Jr (variable). Breadth of ray at base, 9
to 11 mm.
Disk nearly flat, circular; rays long, slender, Brisinga-like,
deciduous, more or less constricted at base, adjacent to disk.
Abactinal integument thin, transluscent on rays, thicker on disk ;
abactinal skeleton reduced to small circular plates, widely
spaced, each bearing a slenderneedle-like spine heavily wreathed
with pedicellariae; a single superomarginal spine to each plate,
widely spaced ; a single inferomarginal spine to each plate, twice
as numerous as superomarginals ; a single long slender adambu-
lacral spine to each plate. Numerous long vermiform papulae.
Disk resembling that of a Brisinga in general form, only
larger, the rays being very insecurely connected and therefore
readily broken off. Rays in general form suggesting those of
Proc. Wash. Acad. Sci., August, 1906.
I38 FISHER
Freyella. Abactinal surface depressed, collapsed on account
of the utter absence of any sort of rigidity. On disk, small
roundish plates imbedded in membrane are spaced about 2 to 3
mm. apart, each plate being .5 to 1.25 mm. in diameter, and
they are slightly more crowded toward center of disk than near
periphery ; on ray, plates are rather more widely spaced, and
about 4 irregular longitudinal series are sometimes evident,
although often no serial arrangement is present. These small
plates are a trifle convex in center, and bear a single very
delicate needle-like spinule, most of which are encircled about
the middle or nearer tip by a very elegant wreath of minute
crossed pedicellariae. This wreath consists of a circular expan-
sion of membrane, the upper surface being thickly beset with
pedicellarias, the lower naked. These wreaths are a little
larger, and more crowded near center of disk. Scattered be-
tween the primary plates are minute grains. Papular pores
pierce abactinal integument, the papulae being long slender,
vermiform, and arranged in groups of 2 or 3 up to 10 or 12.
On disk they appear very crowded. Intermarginal papulae
present, more or less grouped.
Marginal spines longer and stouter than abactinal and bear-
ing more prominent wreaths of pedicellarias. Inferomarginal
plates small, spaced (not in contact), closely appressed to ad-
ambulacral plates, to every 4 or 5 of which there is 1 inferomar-
ginal. Spine borne on a ventral boss of plate, on about same
level with adambulacral spines, not much more ventrally as in
Pycnofodia helianthoides. Just above each alternate infero-
marginal, a somewhat larger superomarginal bears a single
subequal wreathed spine. These plates touch the inferomar-
ginals and are elongated transversely. Opposite the remaining
inferomarginals they are very small and rudimentary, reduced
to a tiny ossicle devoid of a spinelet, and wholly invisible until
skin is dried. Near base of rav each inferomarginal has a
spiniferous superomarginal adjacent to it, but soon the alternate
superomarginals, as noted above, lose their spine and atrophy.
Comparatively few of the inferomarginal spines have a forfici-
form pointed pedicellaria at their base .75 mm. in length. This
may stand on plate near base of spine.
NEW STARFISHES FROM THE PACIFIC COAST 1 39
Adambulacral plates placed obliquely as in Pycnopodia hclian-
thoidcs, but not so crowded. They are not sunken within fur-
row as in that species, but are on same level with inferomar-
ginal plates and define true margin of furrow. Each plate
bears a single spinule, slightly shorter and much slenderer than
inferomarginal spine. No pedicellarice on either spines or
plates.
Mouth plates small, each with a marginal spine pointing
across mouth of furrow, another over actinostome, and usually
2 upright spines, subequal to furrow spines, on actinal surface
near suture — i placed behind the other. Furrow spines may
bear i or 2 small forficiform pedicellariae but usually they do
not; several, instead, being found on inner angle of plate.
Ambulacral furrow wide and shallow ; ambulacral plates not
so crowded as in Pycnopodia Jielianthoides. Ambulacral pores
in 4 rows, except at very base of furrow, and on terminal third
or fourth of ray, where there are but 2 rows. Tube-feet large,
rather crowded. At base of furrow they are very evidently in
only 2 rows and resemble those of Brisinga. Soon the plates
become a little more crowded and a not very marked quadri-
serial arrangement of the feet then becomes evident. Actino-
stome very wide, 24 mm. on a disk 44 mm. in diameter.
Madreporic body small, situated near interradial angle; dis-
tant about its own diameter from edge of disk. Striations
radial.
In this species the gonads open to the exterior near base of
rays. There is one gonad on either side of ray, much as in
Pycnopodia.
Type, No. 21934, U. S. Nat. Mus. Type locality, Alba-
tross Station 2925, off San Diego, Cal., in 339 fathoms, on
mud.
PROCEEDINGS
OF THE
WASHINGTON ACADEMY OF SCIENCES
Vol. VIII, pp. 141-166 pls. vi-vm August 14, 1906
NOTES ON JAPANESE HEPATIC^.
By Alexander W. Evans.
Yale University.
Schiffner ' has already emphasized the fact that the Hepat-
icee of Japan are of unusual interest. They not only include
a very large number of species for the size of the island, over
250 having already been reported, but among these species are
both northern and southern types, owing to the many degrees
of latitude through which Japan extends and to the varied
atmospheric conditions which are to be found there. The flora
includes at least 2 endemic genera, Cavr'cularia Steph.2 and
Makinoa Miyake,3 both of which, according to our present
knowledge, are monotypic. It also includes a number of
species which, although referable to well-known genera,
present peculiarities so anomalous that they have necessitated
a revision or amplification of the original generic characters.
This, for example, is the case with Ptilidium bisseti (Mitt.)
Evans,4 which differs from all other known members of the
genus in developing a felt of cilia on the outer surface of both
leaves and underleaves and which is further remarkable in bear-
ing water-sacs on some of the smaller branch-leaves.
The present paper is a partial report on 2 collections, one
made by Mr. T. Yoshinaga (formerly Inoue), of Aki-machi,
1 Oesterr. Bot. Zeitschr. 49: 3S5. 1S99.
- Bull, de l'Herb. Boissier 5 : 87. 1S97.
3 Bot. Mag. Tokyo 13 : 21. pi. 3. 1S99.
♦Rev. Brvol. 32: 57. 1905.
Proc. Wash. Acad. Sci., August, 1906. ('41)
i4-
EVAXS
and the other by Mr. S. Okamura, of Kochi. The majority of
the specimens in both collections came from the province of
Tosa. Most of the species noted are additions to the Japan-
ese flora and include 5 which are here proposed as new. Of
these new species 2 have already been named in manuscript
by Herr F. Stephani, of Leipzig, but have not yet been
described. All of the species noted belong to well-known
genera, and more than half are Lejeuneag. Among the latter
is one species which affords an interesting link between the
genera Harpalejeunea and Drepatiolcjeunea. At least 3 other
Lejeuneae, new to Japan and apparently to science, also occur
in these collections. Unfortunately they are represented by
sterile specimens only, and it has therefore seemed wise to post-
pone their description until more complete material can be
examined. The types of the new species are deposited in the
herbarium of the writer, at New Haven, Connecticut.
1. METZGERIA QJJADRISERIATA Evans, new species.
(PI. VI. figs. 1-5.)
Pale yellowish green, growing in depressed mats ; thallus
prostrate, repeatedly dichotomous, occasionally giving rise to
adventitious branches from the margin or from the postical sur-
face of the midrib, well-developed branches about 0.7 mm. wide
and from 1.5 to 3.5 mm. long between the forks, plane or slightlv
convex; midrib 0.08 mm. wide, bounded both antically and
postically by 2 rows of cells, smooth above, bearing a few scat-
tered and simple cilia below ; wing mostly from 5 to 8 cells
broad, smooth on both surfaces but ciliate on the margin, the
cilia scattered and borne singly, usually shorter than the width
of the wing, straight or slightly contorted, blunt at the apex or
irregularly branched ; cells of the wing plane or slightly con-
vex, their walls more or less thickened and sometimes with
indistinct trigones, not varying much in size in different parts
of the thallus, averaging 42 x 28, u; inflorescence dioicous ;
female branch broadly orbicular-obovate, 0.35 mm. long, slightly
emarginate at the apex, rather closely ciliate on the margin and
usually bearing a few cilia on the postical surface, the cilia
similar to those found on the thallus ; remaining parts not seen.
NOTES ON JAPANESE HEPATIC^E I43
Type locality, Ioki-mura, Tosa. Collector, Yoshinaga (no.
11), November, 1903.
In his Hepaticje Japonic^ Stephani ' accredits to Japan the
4 following species of Metzgeria: — M. conjugata Lindb., M.
furcata (L.) Dumort., M. hamata Lindb. and M. -pubescens
(Schrank) Raddi. All of these species have a wide geographi-
cal distribution in temperate regions, and M. hamata is also
common in many tropical countries. Two years later, in his
Species Hepaticarum, Stephani2 throws doubt upon the occur-
rence of M. furcata in Japan but adds a fifth species, M. con-
sanguinea Schiffn.,3 originally described from Java but now
known also from the island of Luzon.
Of these 5 species, M. hamata and M. consanguinea are both
closely related to M. quadriscriata. They agree with it in their
dioicous inflorescence and also in the structure of the costa, which
is bounded both above and below by 2 rows of cortical cells. In
these 2 species, however, the thallus is more robust than in M.
quadriscriata, the marginal cilia are borne in pairs, and some of
the branches at least are strongly convex. M. hamata is further
distinguished by its larger cells, and by its longer, more numer-
ous and more contorted cilia, while in M. consanguinea many
of the ultimate branches are practically wingless and extend
outward from the substratum. Whether this last peculiarity is
to be considered a specific character or not is somewhat ques-
tionable. Stephani implies that it may be due to some unusual
condition in the environment and states that he has seen similar
branches in other species.
Another close ally of M. quadriscriata is M. lindbcrgii
Schiffn.,4 a Javan species, which is now known also from
Sumatra, Tahiti and the Marquesan Islands. M. lindbcrgii
agrees with the new species in the structure of its costa, and also
in the fact that its marginal cilia are borne singly. It is, how-
ever, more robust, its wings being often 15 cells broad, and its
inflorescence is autoicous. From M. conjugata and M. furcata
1 Bull, de l'Herb. Boissier 5 : 81. 1S97.
2 Bull, de l'Herb. Boissier 7 : 941, 947. 1S99.
3Nova Acta Acad. Caes. Leop. -Carol. 60 : 271. 1S93.
4Denkschr. Mat.-Naturw. CI. Kais. Acad. Wiss. Wien 67: 30. 189S.
144 EVANS
the new species differs in the structure of its midrib. Although
in both of these species there are only 2 rows of cortical cells
antically, there are normally 4 rows postically.
2. MYLIA VERRUCOSA Lindb.
Mylia verrucosa Lindb. Acta Soc. Sci. Fenn. 10: 236. 1872.
Locality, Mount Kuishi, Tosa. Collector, Okamura (no.
1 15), October, 1904. This rare species has already been reported
by Yoshinaga l under the name Leioscyphus verrucosus (Lindb.)
Steph. Lindberg first recorded it from Saghalin and Amur,
but it was apparently not collected in any other localities until
it was found in Japan.
3. RADULA OYAMENSIS Stephani.
(PI. VI, figs. 6-10.)
Radula oyamensis Stephani, Hedwigia 23 : 149. 1884.
Loosely tufted, dark and dull green; stems 0.15 mm. in di-
ameter, irregularly pinnate, the branches widely spreading,
similar to the stem but often with smaller leaves ; leaves imbri-
cated, the lobe convex and often reflexed at the apex, widely
spreading, broadly falcate-ovate, 1 mm. long, 0.7 mm. wide,
attached by an almost longitudinal line of insertion, rounded at
the antical base and arching partially or wholly across the axis,
antical margin strongly rounded, apex broad and rounded, pos-
tical margin also rounded, forming an angle of 900 or more with
the keel, margin everywhere entire ; lobule subrhombiform in
outline, 0.45 mm. long, 0.35 mm. wide, more or less inflated
along keel and in basal portion, otherwise appressed to the
lobe, inner margin attached by an almost longitudinal line of
insertion for half its length or more, not dilated, free margin
straight, forming a blunt or rounded angle with the inner
margin, extending almost at right angles to the axis and sub-
parallel with the keel, outer margin straight, subparallel with
the axis, forming a rounded or very obtuse angle, the apex
with the margin free, apex tipped with a hyaline papilla, not
borne in a distinct depression, keel more or less arched,
1 Bot. Mag. Tokyo 17 : (38). 1903.
NOTES ON JAPANESE HEPATIC^E 1 45
scarcely or not at all decurrent ; leaf-cells plane or nearly so,
averaging io/i at the margin of the lobe, 15 /t in the middle and
18 fi at the base, walls thin, trigones small but distinct, cuticle
on both surfaces very minutely verruculose ; inflorescence dioi-
cous ; female inflorescence borne on a leading branch, inno-
vating on both sides, the innovations usually simple ; bracts sim-
ilar to the leaves, but a little smaller, the lobe measuring 0.75 x
0.5 mm. and the lobule 0.45 x 0.25 mm., the latter almost
transversely inserted; perianth long-exserted, strongly com-
pressed in the upper part, narrowly obovate in outline, 2.5
mm. long, 0.9 mm. wide, gradually narrowed to a stalk-like
base, broad and truncate above ; mouth shortly two-lipped,
entire ; male inflorescence terminating a leading branch, bracts
in about three pairs, suberect, strongly inflated, shortly and
unequally bifid with rounded divisions ; mature sporophyte not
seen.
Locality, Hono-Kawa, Tosa ; growing mixed with Lejeunese.
Collector, Okamura (no. 112), July, 1904.
Perhaps the most striking features of Radula oyamensis are
the strongly convex lobes, the verruculose cuticle and the long
and slender perianth. With regard to the peculiarities of the
cuticle in this genus, little mention is to be found in the litera-
ture, but it is probable that roughened cells occur in other spe-
cies. In the genus Scapania, where the cuticle of late has re-
ceived a good deal of attention, it has been found that specific
characters which are derived from it have to be employed with
caution, and it is possible that this same statement will apply to
the present genus.
R. oyamensis belongs to group Tumidae, as defined by
Stephani.1 The original specimens were collected by Dr. C.
Gottsche on Mount Oyama, and the species has since been re-
ported by Yoshinaga from the province of Iyo. The plant was
first described from male material, and no account of the
perianth has subsequently appeared. R. lindbergii Gottsche,
although placed by Stephani a in his group Communes, bears a
certain resemblance to R. oyamensis, the lobes and lobules
1 Hedwigia 23 : 162. 1SS4.
2L. c.? 149.
I46 EVANS
having much the same form in the 2 species. In R. lindbcrgii,
however, the lobe spreads more obliquely and is less convex,
the lobule is less inflated and is attached by nearly its whole
length along the inner margin, the perianth is broader, and the
antheridial spike is very long, sometimes bearing 15 or more
pairs of bracts. ./?. Undbergii is widely distributed in Europe
and has already been reported in Japan from the provinces of
Tosa and Iyo.
4. COLOLEJEUNEA FLOCCOSA (Lehm. & Lindenb.)
Schiffn.
Cololcjcunea floccosa (Lehm. & Lindenb.) Schiffn., Consp.
Hepat. Archip. Indici 243. 1898. *
Locality, on leaves of Acrostichum yoshinagai, Mount Hono-
gawa. Collector, Yoshinaga (no. 1, p. p.), August, 1888. New
to Japan. Originally described from Luzon but since reported
from Java and Sumatra.
5. COLOLEJEUNEA GCEBELII (Gottsche) Schiffn.
Cololejeunea gcebelii (Gottsche) Schiffn., Consp. Hepat. Archip.
Indici 244. 1898.
Locality, on leaf of Trichomanes jaftonicuni, Akinokawa,
Tosa. Collector, Yoshinaga (no. 25, p. p.), October, 1903.
This species was first described from specimens collected in
Java. It is also known from the island of Penang and has
already been reported from Japan by Yoshinaga.
6. COLOLEJEUNEA VENUSTA (S.-L.) Schiffn.
Cololejeunea vcnusta (S.-L.) Schiffn. in Engler & Prantl, Nat.
Pflanzenfam. 1: 122. 1893.
Localitv, on leaves of Plagiogyria euphlcbia, Tokimoto,
Tosa-gun, Tosa. Collector, Okamura (no. 76), January, 1904.
New to Japan. Known also from Java, the type locality, and
from Sumatra.
The Japanese specimens do not agree in all respects with the
figures of Sande Lacoste.2 In these the lobules are represented
1 Full synonymy of the 3 species of Cololejeunea mentioned in the present
paper may be found in this volume.
2 Syn. Hep. Javan. pi. 12. 1856.
NOTES ON JAPANESE HEPATICVE 1 47
as being covered over with slender seta-, similar to those found
on the lobes, and no trace of a false median nerve is shown, the
cells of the lobe being fairly uniform throughout, except that
the basal cells are longer and destitute of set;e. In the speci-
mens from Tosa the lobule is perfectly smooth ; in the outer
portion, close to the end of the keel, the free margin bears a
slender tooth, usually composed of 2 superimposed cells, and
there is commonly a second blunt tooth somewhat nearer the
axis ; the margin is otherwise entire. In well-developed leaves
there is a fairly distinct false nerve, composed of 1 or 2 rows
of elongated cells. Unfortunately the writer has been unable
to secure specimens of C. vcnusta for comparison, so that it has
been impossible to determine whether these differences are real
or simply due to inaccuracies in the figures.
7. LEJEUNEA PLANILOBA Evans, new species.
(PI. VI, figs. 11-16.)
Pale green, not glossy, scattered or in loose depressed mats ;
stems prostrate, loosely adherent to the substratum, 0.08 mm.
in diameter, sparingly and irregularly branched, the branches
widely spreading : leaves loosely imbricated, the lobe obliquely
to widely spreading, slightly convex but not reflexed at the apex,
scarcely falcate, oblong, 0.7 mm. long, 0.4 mm. wide, antical
margin decurrent by a single cell, rounded to subcordate at the
base, arching partially or wholly across the axis, outwardly
curved to the broad and rounded apex, postical margin more
or less outwardly curved, continuous with the keel or forming
with it a very obtuse angle, margin entire throughout ; lobule
ovate-rectangular, 0.25 mm. long, 0.15 mm. wide, inflated in
basal half, keel arched near the base, nearly straight in outer
portion, smooth, free margin appressed to the lobe except at base,
straight or slightly curved, sinus straight or very shallowly lun-
ulate, apical tooth straight and blunt, papilla proximal, usually
in a distinct depression, reflexed and more or less concealed be-
hind the margin ; leaf-cells plane or nearly so, averaging 12 /j.
at the margin of lobe, 21 x 15 ft in the middle and 30 x 18 ;i at
the base, thin-walled but with distinct and rarely confluent tri-
1 48 EVANS
gones and intermediate thickenings, cuticle smooth, ocelli none ;
underleaves distant to subimbricated, orbicular, 0.2 mm. long,
bifid about one half with a narrow and blunt sinus and triang-
ular, erect divisions, rounded to acute at the apex, margin entire
or vaguely and irregularly sinuate on the sides ; inflorescence
autoicous ; female inflorescence borne on a leading branch, in-
novating on one side, the innovation simple or branched, some-
times terminating in a male spike ; bracts obliquely spreading,
complicate and unequally bifid, keel not winged, lobe oblong,
0.6 mm. long, 0.3 mm. wide, rounded at the apex, entire, lobule
oblong to ligulate, 0.4 mm. long, 0.12 mm. wide, rounded at
the apex, entire ; bracteole connate on both sides at base, ovate
to obovate, 0.4 mm. long (to junction with bracts), 0.3 mm. wide,
bifid about one half with a narrow sinus and erect, subacute
divisions, margin irregularly sinuous ; perianth about half ex-
serted, obovoid, 0.65 mm. long, 0.4 mm. wide, narrowed toward
the base, rounded at the apex and with a short but distinct beak,
inflated and with 5 low keels in the upper part, surface smooth ;
male inflorescence occupying a short branch or terminal on a
longer branch, bracts mostly in from 2 to 4 pairs, closely imbri-
cated, shortly and subequally bifid with rounded divisions,
bracteoles present at base of spike, similar to the underleaves,
antheridia borne singly ; capsule brown, spherical, 0.35 mm.
in diameter, spores irregular in form, about 23 {jl wide, minutely
verruculose.
Type locality, Mount Yokogura, Tosa, on bark. Collector,
Okamura (no. 67), March, 1904.
Lejeunea planiloba agrees with other members of the genus
in its delicate texture, in the structure of the apical portion of
the lobule and in the 5-keeled perianth, as well as in other less
important respects. Its subrectangular, relatively large lobule
is perhaps somewhat aberrant and will at once serve to distin-
guish it from L. cavifolia (Ehrh.) Lindb. and L. flava (Sw.)
Nees. Only one other species of the genus has been reported
from Japan, namely, Eulejcunca co7iipacta Steph. In this spe-
cies the leaves are described as acuminate, so that it could hardly
be confused with L. -planiloba.
The new species bears a certain superficial resemblance to
NOTES ON JAPANESE HEPATICyE I49
C/iciloIcjcunca interiexta (Lindenb.) Steph., which has also
been listed as a Japanese plant. The type specimen of this
species was collected by Dr. Mertens in the Caroline Islands,
and has been kindly sent to the writer for examination by Dr.
von Keisslern, of Vienna. The species has a rather wide dis-
tribution in the islands of the Pacific. In well-developed
plants the lobule has almost the same form as in L. -plant-
loba. The apical region, however, is built up on a different
plan and shows the distal hyaline papilla which is character-
istic of the genus Cheilolejeunea} In some cases the proximal
papilla in L. -planiloba cannot be easily demonstrated, because
it bends down behind the apical tooth and is more or less con-
cealed (PI. VI, fig. 14). From the genus Rectolejeunea? which
is also characterized by a proximal papilla, the new species
must be excluded on account of its 5-keeled perianth. At the
same time its close resemblance to certain species of this genus,
such as the West Indian R. fhyllobola (Nees & Mont.) Evans,
should not be overlooked.
8. LEPTOLEJEUNEA SUBACUTA Stephani, new species.
(PI. VII, figs. 1-9.)
Pale yellowish green, often becoming brownish with age or
upon drying, growing scattered or in thin depressed mats ; stem
prostrate, 0.05'mm. in diameter, closely adherent to the sub-
stratum, copiously branched, the branches widely spreading,
often microphyllous toward the extremities ; leaves distant to
loosely imbricated, the lobe widely spreading, plane or slightly
concave, rhomboid-oblong, the antical and postical margins
subparallel, 0.5 mm. long, 0.25 mm. wide, attached by a short
and almost longitudinal line of insertion, antical margin rounded
near base but scarcely reaching the middle of the axis, slightly
curved, or, in the outer part, nearly straight, postical margin
straight or nearly so, forming a continuous line with the keel,
lobe gradually narrowed to a rounded, obtuse or rarely subacute
apex, margin entire throughout; lobule oblong-ovoid, 0.17
mm. long, 0.12 mm. wide, inflated to beyond the middle, keel
1 See Evans, Bull. Torrey Club 33 : 2. pl.i,f.4. 1906.
2 Ibid. 33: 8.
150 EVANS
slightly arched, free margin nearly straight, outer portion (in-
cluding apical tooth) appressed to lobe, inner portion slightly
involute, sinus shallow and lunulate, apical tooth short, blunt,
slightly curved, papilla in a distinct depression, making the
lobule appear bidentate at the apex when flattened ; leaf-cells
plane, averaging 15 /j. at the margin of the lobe, 21 n in the
middle and 30 x 23// at the base, thin-walled, trigones and in-
termediate thickenings minute but distinct, not confluent ; basal
ocellus measuring 55 x 28 ft, strongly inflated, assisting in the
formation of the water-sac, remaining ocelli scarcely larger
than the other cells, sometimes indistinct, variable in number
but sometimes as many as 8, irregularly scattered through lobe
or arranged in from 1 to 3 interrupted and indistinct longitudinal
rows; underleaves distant, 0.05 mm. long, 0.085 mm- wide,
basal portion rectangular or trapezoidal in outline, abruptly con-
tracted to a narrow line of attachment, consisting of a radicellif-
erous portion with or without a rudimentary disc and 6 marginal
cells, the median marginal cell on each side rounded to obtuse,
setae widely to obliquely spreading, 0.07 mm. long, 0.01 mm.
wide, usually composed of 3 cells in a single row, rarely 2 cells
wide at the base ; inflorescence dioicous ; female inflorescence
borne on a simple and very short branch (with one leaf and one
underleaf besides the involucre), bracts and bracteoles in unfer-
tilized flowers suberect ; bracts complicate, unequally to sub-
equally bifid, the lobe oblong, 0.37 mm. long, 0.17 mm. wide
(maximum measurements), rounded to obtuse at the apex, mar-
gin entire, lobule narrower, ligulate-oblong, 0.34 mm. long, 0.09
mm. wide, apex mostly blunt, margin entire ; bracteole some-
what connate on both sides, oblong, 0.37 mm. long, 0.13 mm.
wide, bifid one sixth or less with a sharp sinus and erect, triangu-
lar divisions, acute to rounded at the apex, margin entire or
nearly so, ocelli mostly 2 to 4, scattered ; male inflorescence
terminating the stem or a branch, bracts in 2 to 4 pairs, imbri-
cated, inflated, very shortly and subequally bifid with rounded
divisions, keel strongly arched, minutely crenulate in outer part,
bracteole present at base of spike, similar to the normal under-
leaves but smaller; mature perianth and sporophyte not seen.
Type locality, Akinokavva, Tosa, on leaves of Gymnogramme
NOTES OX JAPANESE HEPATIC<E 151
elliptica and Ptcris cretica. Collector, Yoshinaga (no. 25. p. p.),
October, 1903.
Leafy propagula are produced by this new species in great
abundance and resemble in all essential respects those described
by the writer for L. clliplica, L. exocellata and various species
of Drepanolejeunea? They occur not only on sterile plants
but also on those with sexual organs. In some cases they are
borne here and there behind normal leaves, the branch bearing
them showing no apparent modifications. It is much more
usual, however, to find them on microphyllous branches with
closelv crowded and aborted leaves (fig. 3). In such a case,
each rudimentary leaf gives rise to a propagulum, and the
growth of the branch is ultimately limited, although usually not
until many propagula have been formed. When the propagula
become detached they leave behind them their inflated basal
sheaths. It sometimes happens that an entire plant gives itself
up more or less completely to the production of propagula, and
under these circumstances it becomes difficult to detect upon it
normal leaves and underleaves.
The propagula themselves exhibit no new features. The first
1 or 2 underleaves develop radicelliferous discs in the usual way,
and the first few leaves are more or less sharp-pointed, the first
leaf of all being sometimes but not always reflexed.
L. subacuta is closely related to the widely distributed L.
elliptica (Lehm. & Lindenb.) Schiffn. and also to L. exocellata
(Spruce) Evans, of the American tropics. It agrees with these
species in its general habit, in its entire leaves, in its cell struc-
ture, in its large basal ocelli and in its short and simple female
branch. It differs from both in the more numerous ocelli of its
leaves and in its broader and blunter perichaetial bracts. Its
leaves also are a little broader than in L. elliptica (being usually
from 12 to 14 cells broad, instead of from 8 to 12), and its dioi-
cous inflorescence will further distinguish it from L. exocellata.
Another close ally, judging from the description, is L.folii-
cola Steph.,2 known only from the type locality, the island of
1 Bull. Torrey Club 29 : 507-509. pi. 22,/. 9-13. fl. 24, f. 10. 1902. 30 : 29,
31- 32, 37. 39- fl-5,f-3- 1903-
2 Hedwigia 35 : 106. 1S96.
152 EVANS
Luzon. In this species the inflorescence is also dioicous and
the leaves show 2 or 3 rows of small ocelli in addition to the
large basal ocellus. The underleaves are also characterized
by spreading divisions, each composed of 3 cells. Unfortu-
nately the female inflorescence of L.foliicola is unknown, but
its acuminate, acute or apiculate leaves will at once separate it
from L. subacuta, and its long antheridial spikes, bearing from
10 to 12 pairs of bracts, offer a second distinguishing character.
9. DREPANOLEJEUNEA TENUIS (Reinw. Bl. & Nees)
Schiffn.
(PI. VII, figs. 10-19.)
Drefanolejctmea tenuis (Reinw. Bl. & Nees) Schiffn., Consp.
Hepat. Archip. Indici 280. 1S98.1
Pale yellowish green, not glossy, growing scattered or in
thin depressed mats ; stems prostrate, 0.035 mm- m diameter,
rather loosely adherent to the substratum, sparingly and irregu-
larly branched, the branches widely spreading, usually with
smaller leaves than the stem but otherwise similar ; leaves dis-
tant to subimbricated, the lobe obliquely spreading to suberect,
slightly convex but with the apex usually strongly reflexed,
more or less falcate especially when flattened, ovate-lanceolate,
0.3 mm. long, 0.14 mm. wide, attached by a short and almost
longitudinal line of insertion, antical margin straight or slightly
incurved near the base, then strongly outwardly curved to the
apex, sometimes arching partially or wholly across the axis,
sometimes entirely free from it, postical margin more or less
incurved, apex long-acuminate, usually tipped with from 2 to 4
cells in a single row, margin minutely and irregularly crenu-
late or denticulate from projecting cells, usually but not always
bearing from 1 to 5 more distinct teeth between the antical base
and the apex; lobule strongly inflated throughout, ovoid, 0.17
mm. long, 0.0S mm. wide, keel strongly arched, forming a
continuous line with postical margin of lobe, roughened from
projecting cells, free margin involute to or beyond the apex,
sinus lunulate, apical tooth strongly curved, hyaline papilla in
a distinct depression ; leaf-cells plane to strongly convex, aver-
1 The synonymy of the species is here given in full.
NOTES ON JAPANESE HEPATICiE 153
aging about 16/1 in diameter, a few of the basal cells a little
longer and narrower than the others, walls slightly thickened
with indistinct and often confluent trigones and intermediate
thickenings, ocelli none; underleaves distant, trapezoidal in
general outline from a somewhat narrow base, 0.08 mm. long,
0.07 mm. wide, bifid to about the middle, with obliquely spread-
ing divisions and a lunulate sinus, basal region usually with 6
marginal cells around a central radicelliferous region, divisions
mostly 3 or 4 cells long and 1 or 2 cells wide at the base;
inflorescence dioicous ; female inflorescence on a short branch,
innovating on one side, the innovation short and simple ; bracts
obliquely spreading, complicate, unequally bifid, not winged
along the keel, lobe ovate, 0.5 mm. long, 0.25 mm. wide,
acuminate, margin irregularly dentate or short-ciliate, the
teeth from 1 to 3 cells long, lobule more narrowly ovate, 0.4
mm. long, 0.14 mm. wide, apex variable but usually sharp-
pointed, margin toothed but less strongly than in the lobe ;
bracteole connate at the base on both sides, broadly ovate, 0.4
mm. long, 0.25 mm. wide, bifid about one third with erect,
acute to acuminate divisions and an obtuse sinus, margin as in
the lobule ; perianth about half-exserted, oblong-obovoid, 0.6
mm. long, 0.35 mm. wide, gradually narrowed toward the base,
rounded to truncate at the apex and abruptly contracted into a
short but distinct beak, keels 5, sharp, extending to below the
the middle, very indistinctly roughened from projecting cells ;
remaining parts not seen.
Locality, Takimoto, Tosa, on bark, mixed with Pycnolcjeunca
tosana Steph. Collector, Okamura (no. 103 p. p.), October,
1904. This species has not before been recorded from Japan
but has a wide distribution in Java, Sumatra and the Philippine
Islands. It has also been reported, probably erroneously,
from tropical America.
Since the last published description of this little species ap-
peared over 60 years ago,1 it has seemed advisable to redescribe
it. Unfortunately the male inflorescence seems to be still un-
known, and no organs of vegetative reproduction have as yet
been detected.
'G. L. & N. Syn. Hep. 390. 1S45.
154 EVANS
D. tenuis is a somewhat aberrant member of the genus. In
the majority of the species which have been described the keels
of the perianth are spinose, ciliate or distinctly toothed, some-
times being prolonged as horns. In D. temcis the keels are
rounded in the upper part and are practically smooth (PL VII,
fig. 10). It is not, however, unique in this respect, but agrees
with 2 American species, D. sitbulata Steph. and Lejeuvea
(Drefianolejamea) anoplantka Spruce. This peculiarity, al-
though important, is hardly sufficient to exclude these species
from Di'ejianolejeunea, as it is unsupported by differences in
vegetative structure.
The differential characters which separate D. tc7iuis from the
2 American allies just mentioned have already been noted by
the writer in another connection.1 The marginal teeth which
are there alluded to are exceedingly variable and on many
leaves are absent altogether (PI. VII, fig. 12). On other
leaves they are very pronounced (PI. VII, fig. 11), and there
are all gradations between these 2 extreme conditions. There
is apparently no definite correlation between the size of the leaves
and the length of these marginal teeth. Another variable char-
acter is found in the leaf-cells. These are sometimes plane and
sometimes markedly convex or even papillate.
10. HARPALEJEUNEA INTERMEDIA Evans, new
species.
(PI. VIII, figs, i-ii.)
Pale green, more or less tinged with yellow or brown, grow-
ing in depressed mats ; stems prostrate, 0.045 mm. in diameter,
loosely adherent to the substratum, sparingly and irregularly
branched, the branches widely spreading, similar to the stem ;
leaves contiguous to imbricated, the lobe obliquely spreading to
suberect (widely spreading when flattened out), convex and re-
flexed at the apex, falcate-ovate, 0.28 mm. long, 0.17 mm.
wide, abruptly dilated from a narrow basal region and attached
by a short and almost longitudinal line, antical margin slightly
incurved near base, then strongly outwardly curved to the apex,
■Bull. Torrev Club 30: 25. 1903.
NOTES ON JAPANESE HKI'ATIC/E 155
postical margin somewhat incurved, forming an almost contin-
uous line with keel, apex usually acute, tipped with 1 or 2 cells,
whole margin (except close to the antical base) irregularly
denticulate from projecting cells ; lobule inflated throughout,
ovoid, 0.17 mm. long, 0.1 mm. wide, keel strongly arched,
free margin involute to the apex, curved, sinus (in flattened
leaves) deeply lunulate, apical tooth abruptly curved, papilla in
a slight depression ; leaf-cells plane to somewhat convex, aver-
aging 14// at the margin of the lobe, 18/; in the middle and
28 x 18 u at the base, walls with large, irregular and often con-
fluent trigones and intermediate thickenings, ocelli mostly 1
to 3 at base of lobe, 35 fi long, 23 u wide, often indistinct or
wanting; underleaves distant, broadly obcuneate, 0.05 mm.
long, 0.05 mm. wide, narrowed toward the base, bifid about
one-half with spreading obtuse divisions, separated by a rounded
to obtuse sinus ; divisions mostly 3 cells long (beyond the basal
region) and 2 cells wide, usually tipped by a single blunt cell,
sometimes by 2 cells side by side, more rarely by 2 superimposed
cells, basal region commonly with 6 marginal cells surrounding
a central radicelliferous portion ; inflorescence dioicous ; female
inflorescence usually borne on a leading branch, sometimes on a
short branch, innovating on one side, the innovation long and
often again floriferous ; bracts obliquely spreading, unequally
bifid, complicate, lobe ovate, sometimes falcate and reflexed at
the apex, 0.6 mm. long, 0.3 mm. wide, acute to acuminate, mar-
gin irregularly dentate or denticulate, keel sharp, occasionally
with a narrow, interrupted and entire wing in the upper part,
lobule ovate, 0.5 mm. long, 0.2 mm. wide, apex usually acute,
margin as in the lobe ; bracteole somewhat connate on one side,
ovate from a narrow base, 0.45 mm. long, 0.35 mm. wide, bifid
about one-third with acute divisions and a sharp sinus, margin
crenulate or denticulate, often unidentate on the sides ; remain-
ing parts not seen.
Type locality, Mount Myoken, Tosa, on bark. Collector,
Yoshinaga (no. 7 and no. 6 p. p.), October, 1903. In no. 6 the
new species grows mixed with Odoiitosch/sma denudatum (Mart. )
Dumort. No. 7 may be designated the type.
As a general rule the species of the Lejeuneas in which inno-
I56 EVANS
vations are developed show but a single pair of pericheetial
bracts. In other words there is an abrupt transition between
the bracts with their explanate lobules and the normal leaves
just below them with their well-developed water-sacs. H.
intermedia offers a certain exception to this rule, the leaf below
the innovation being distinctly intermediate between a normal
leaf and a bract (PI. VIII, figs. 1, 2). In this leaf the lobe is
larger than on ordinary leaves and also less convex, while the
lobule is acutely pointed and almost plane. The underleaves
also show a gradual transition toward the bracteole, but this is
a much more usual condition.
The new species is also of interest because in some respects
it is intermediate between the genus to which it has been referred
and Drcpanolcjeunea. The most important differences between
these 2 genera are found in the underleaves. In typical
species of Harpalejeunea these are divided by a shallow sinus
into 2 broad and divergent divisions, rounded at the apex and
usually 3 or 4 cells wide. The radicelliferous region is
commonly indistinct. In Drepanolejeunea the divisions of the
underleaves are setaceous and usually widely spreading ; in
most cases they consist of from 2 to 5 elongated cells in a
single row, but they may be 2 cells wide at the base. These
divisions arise from a basal portion in which the radicelliferous
region is bounded by a distinct margin of larger cells. In H.
intermedia the underleaves show a basal portion with a fairly
distinct border (PL VIII, fig. 7), and the divisions vary at the
apex from rounded and 2 cells wide, to pointed and tipped with
2 superimposed cells (PI. VIII, figs. 8, 9). They therefore
combine the underleaf-characters of the 2 genera. In some
respects these underleaves bear a resemblance to those of H.
pseudoneura Evans,1 of the Hawaiian Islands, which is also a
somewhat aberrant member of the genus.
H. intermedia is apparently the first species of Harpalejeunea
which has been recorded from Asia, and it has no very close
allies among species known from other parts of the earth. H.
pseudoncura, with which its underleaves have just been com-
pared, is at once distinguished by the continuous row of ocelli
■Trans. Conn. Acad. 10 : 427.^/. 50, f. i-g. 1900.
NOTES ON JAPANESE HEI'ATICyE ' 157
running through the lobes of the leaves. More typical members
of the genus, such as H. ovata (Hook.) Schiffn., show a group
of basal ocelli in the same position as in H. intermedia, but of
course their underleaves conform to the normal type. In the
form of its leaves the new Har-palejeunea agrees with certain
species of Drcpanolcjcunca, such as the recently described D.
sctistifa Steph.,1 of Java and Celebes. In this species, however,
the lobes of the leaves are strongly 'dentate and show scattered
ocelli.
11. BRACHIOLEJEUNEA SANDVICENSIS
(Gottsche) Evans.
Brachiolejeunea sandvicensis (Gottsche) Evans, Trans. Conn.
Acad. 10: 419. 1900.
Locality, on bark, Utsutsumai, Tosa. Collector, Okamura
(no. 105, p. p.), September, 1904.
The writer has already pointed out the fact, in the place above
quoted, that B. gottschci Schiffn. is a synonym of the older
Phragmicoma sandvicensis Gottsche. When B. gottschci was
first published it was somewhat doubtful whether Wichura's
type specimens came from Japan or Java. Since this time, how-
ever, it has been twice recorded as a Japanese plant, once by
Schiff ner,3 whose specimens were collected at Tokyo by Miyake,
and once by Yoshinaga. Its occurrence in both Japan and the
Hawaiian Islands would seem to indicate that it has a wide geo-
graphical distribution, but it does not seem to have been reported
from any intermediate localities.
12. FRULLANIA DENSILOBA Stephani, new species.2
(PL VIII, figs. 12-22.)
Brownish red, dull or faintly glossy, growing in depressed
mats ; stems prostrate, rather loosely adherent to the substratum,
0.12 mm. in diameter, at first regularly pinnate with short, ob-
liquely to widely spreading branches, some of the branches
1 Hedwigia 35 : S3. 1S96.
2Oesterr. Bot. Zeitschr. 43 : 390. 1S99.
3Published as a nomen nudum by Yoshinaga in Bot. Mag. Tokyo 15: (92).
1 90 1.
158 • EVANS
remaining short and simple, others becoming themselves pinnate
in the same way as the stem ; stem-leaves contiguous to loosely
imbricated, the lobe widely spreading, somewhat falcate, ob-
long-obovate, 0.4 mm. long, 0.3 mm. wide, slightly convex,
rounded at the antical base and arching partially across the
stem, rounded at the apex, margin entire; lobule clavate, 0.17
mm. long, 0.08 mm. wide, inflated throughout, subparallel with
the stem and separated from it by about half its own width,
mouth obliquely rounded, stylus minute, filiform or subulate,
tipped with a hyaline papilla, mostly 4 or 5 cells long and
1 or 2 cells wide at the base; branch-leaves smaller than
the stem-leaves, relatively narrower and more closely imbri-
cated, 0.35 mm. long, 0.25 mm. wide, lobules similar to those
of the stem but close together and oblique, lying with their
rounded ends upon the axis and forming with it an angle of
about 450; leaf-cells plane or nearly so, averaging about 8 <i
at the margin of the lobe, 9 // in the middle and 18 x 12 it at the
base, walls more or less thickened and with indistinct trigones,
the portion lining the cavity being usually pigmented, ocelli
mostly in a single row of from 3 to 6 cells, running ob-
liquely from the stem between the axis of the lobe and the pos-
tical margin, averaging 28 x 23 jti in size, contents dark red,
ocelli of leaves subtending branches often in 2 rows ; inter-
leaves of stem distant, oblong with subparallel sides, 0.22 mm.
long, 0.17 mm. wide, neither cordate nor rounded at the base,
bifid one-half or less with a narrow, acute sinus and broad,
erect, rounded divisions, margin entire; underleaves of the
branches contiguous to subimbricated, often partially covered
over by the lobules, narrowly ovate or ligulate, 0.14 mm. long,
0.05 mm. wide, with narrow and often acute divisions ; inflores-
cence dioicous ; female inflorescence borne on a leading branch ;
bracts in 2 or 3 pairs, passing by insensible gradations into the
leaves, complicate and unequally bifid, lobes of innermost bracts
ovate to oblong, 0.75 mm. long, 0.35 mm. wide, narrowed
toward the apex but usually obtusely pointed, margin irregularly
sinuate, ocelli usually in 2 rows in lower third of lobe, lobule
ovate-lanceolate, 0.6 mm. long, 0.25 mm. wide, subacute at the
apex, bearing a cluster of short and irregular cilia at the base,
NOTES ON JAPANESE II KPATICK 159
the uppermost one or stylus a little longer than the others, mar-
gin otherwise entire ; innermost bracteole free, ovate, 0.7 mm.
long, 0.4 mm. wide, bifid to about the middle with a narrow
sinus and acute divisions, margin indistinctly short-ciliaie at the
base, otherwise entire ; perianth about half-exserted, obovate in
outline, 1.1 mm. long, 0.7 mm. wide, gradually narrowed
toward the base, rounded to truncate at the apex, beak short,
cylindrical, entire or nearly so at the mouth, perianth com-
pressed, but with a distinct, rounded postical keel, narrowing
toward the apex, surface smooth; spores brownish, 35// in
diameter; male plant not seen.
Type locality, Mount Konomine, Tosa. Collector, Yoshi-
naga (no. 32), November, 1903. Another specimen (cotype)
from Mount Ishidachi, Iyo. Collector, Okamura (no. 119),
August, 1904. Determination made by Stephani.
The specific name of the present species probably refers to
the crowding of the lobules. This peculiarity is not always
apparent on the main stem or on leading branches but is espec-
ially well seen on short branches with limited growth (PI. VIII,
fig. 15). The crowding of the lobules is accompanied by a
change in their position with respect to the axis. Instead of
being erect, they tend to become oblique, the inflated ends being
more or less appressed to the axis. The underleaves on these
branches are sometimes almost hidden by the lobules and are.
much smaller and narrower than when normally developed,.
F. densiloba belongs to the subgenus T/iyopsiclla of Spruce", ■
which includes a large proportion of the tropical Frullaniae.
The row of ocelli in the lobes of its leaves and bracts is a
character which it shares with many other species of the genus.
Of those which occur in Japan, F. appendiculaia Steph., F.
111011 il iata Xees and F. makinoana Steph. may be especiallv
mentioned. The first 2 of these are more robust than F. den-
siloba and are further characterized by their obtusely pointed
to acuminate leaves. The third species is somewhat more
closely allied but differs in the large and semicircular stylus,
which it develops between the lobule and the stem, and also in
the broader underleaves, lunately excised at the apex with broad
and obtuse lobes.
l6o EVANS
The publication of new specific names without descriptions is
a practice which is unfortunately becoming more and more prev-
alent in the literature of hepaticology. In certain cases the
authors of the names are not directly responsible. Collections,
for example, are sent to them for determination and, if they in-
clude new species, these are often named in manuscript, the
authors intending to publish them with descriptions later on.
When a list of the determinations is sent back to the collector
he is very likely to have it printed and to include in it the manu-
script species, as well as those which are already known to
science. In other cases manuscript names without descriptions
are published by the authors themselves, apparently in the vain
hope of securing priority for their species.
Of course such names have no claims whatever to recognition ;
they are nomina nuda, and the species to which they are assigned
cannot be considered published in any sense. At the same time,
without adding to our knowledge, these names increase the
difficulties of the student, who cannot help feeling that they
ought to be investigated. A case in point is with reference to
Scafania brevis Steph. and S.jafonica Steph. Both of these
species were published as nomina nuda by Yoshinaga1 but no
direct reference is made to either of them by Miiller in his mono-
graph of the genus Scapania.2 Under S. stefikanii, however,
he notes the fact that this species, proposed as new, is based on
2 of Stephani's manuscript species, and there is reason to believe
that these 2 species are the S. brevis and S. ja^ponica referred
to above. If the publication of these 2 names had been deferred
until the plants could have been properly described, no such
confusion would have arisen.
Sheffield Scientific School,
Yale University.
>Bot. Mag. Tokyo 15 : (92). 1901. 17: (38). 1903.
2Nova Acta Acad. Cajs. Leop. -Carol. 83. 1905.
EXPLANATION OF PLATE VI.
Metzgeria quadriserzata Evans.
Fig. i. Part of thallus, just beyond a fork, postical view, X 40.
2. Midrib with adjoining cells, antical view, >( F>°-
3. Marginal cilia, X 225.
4. Cross section of midrib with adjoining cells, postical edge below, X -~^-
5. Female branch, X 4°-
The figures were all drawn from the type specimen.
Radirfa oya?ncnsis Stephani.
Fig. 6. Part of female plant with perianth and subfloral innovations, postical
view, X 17-
7. Part of stem, antical view, X *7-
8. Cells from middle of lobe, some of the verrucuhe showing at right,
X3°Q-
9. Apex of lobule, X 225.
10. Pericha;tial bract, X 4°-
The figures were all drawn from Okamura's specimens.
Lcjcunca planiloba Evans.
Fig. 11. Part of female plant with perianth, postical view, the lobule of a bract
lying over the stalk of the capsule, X 40.
12. Part of stem, postical view, X 4°-
13. Cells from middle of lobe, X 300.
14. Apex of lobule, X 225.
15. Bract with connate bracteole, X 4°-
16. Other bract from same involucre, X 4°-
The figures were all drawn from the type specimen.
' [62
Proc Wash. Acad Set., Vol. Vl!l.
Plate VI.
FIGS 1-5, METZGERlA QUAORISERIATA EVANS.
FIGS 6-10. RADULA OYAMENSIS STEPHANI.
CIGS 11-16. LEjEUNcA PLANILOBA EVaNS
EXPLANATION OF PLATE VII.
Leptolejeimea subacuta Stephani.
Fig. i. Part of female stem with two inflorescences, postical view, X 4°-
2. Part of stem with branch, postical view, X 4°-
3. Propaguliferous branch with one propagulum about to be separated
postical view, X 4°-
4. Cells from middle of lobe, the middle cell an ocellus, X 3°°-
5. Apex of lobule, X 225.
6. 7. Underleaves, X 225.
8. Bracts and bracteole with subfloral leaf and underleaf, X 40-
9. Bracts and bracteole from another involucre, X 4°-
The figures were all drawn from the type specimen.
D repanolej eunea tenuis (Reinw. Bl. & Nees) Schiffn.
Fig. 10. Part of female plant with perianth, postical view, X 4°-
11, 12. Parts of stems, antical view, X 4°-
13. Cells from middle of lobe, X 3°°-
14. Cells from antical margin of lobe, X 225-
15. Apex of lobe, X 22S-
16. Apex of lobule, X 225.
17. 18. Underleaves, X 225-
19. Bracts with connate bracteole, X 40.
Figs. 11 and 12 were drawn from specimens collected by Tevsmann in Java
and determined by Gottsche ; the others from Okamura's Japanese specimens.
(164)
Proc Wash. Acad Sci., Vol viii.
Plate vii
FIGS. 1-9. LEPTOLEJEUNEA SUBACUTA STEPHANI.
FIGS. 10-19. DREPANOLEJEUNEA TENUIS (REINW. Bl. & NEES) SCHIFFN.
EXPLANATION OF PLATE VIII.
Uarpalejeunca i?iter?nedia Evans.
Figs. 1,2. Parts of female plants, each with an inflorescence, postical view
X40.
3. Part of stem, antical view, X 4°-
4. Cells from middle of lobe, X 3°°-
5. Cells from antical margin of lobe, X 225-
6. Apex of lobule, X 225.
7. Underleaf, X 225.
8. 9. Apices of underleaf-divisions, X 225-
10. Bract with connate bracteole, X 4°-
11. Other bract from same involucre, X 4°-
The figures were all drawn from the type specimen.
Frtdlania denslloba Stephani.
Fig. 12. Part of female plant with perianth, postical view, X 4°-
13. Part of stem with bases of 2 branches, postical view, X 4°-
14. Part of stem with base of branch, antical view, X 4°-
15. Branch with limited growth and crowded lobules, postical view, X 40.
16. Cells from middle of lobe, including one ocellus and part of another,
X3°°-
17. Stylus of stem-leaf, X 225.
iS. Apex of one division from a stem-underleaf, X 225-
19. Branch-underleaf, X225.
20-22. Innermost bracts and bracteole from a single involucre, X 4°-
Figs. 12, 20, 21 and 22 were drawn from the type specimen ; the others from
Okamura's specimens.
(166)
Proc. Wash. Acad Sci., Vol. VIII.
Plate VIII.
FIGS. 1-11. HARPALEJEUNEA INTERMEDIA EVANS.
FIGS. 12-22. FRULLANIA DENSILOBA STEPHANI.
PROCEEDINGS
OF THE
WASHINGTON ACADEMY OF SCIENCES
Vol. VIII, pp. 167-196. December 18, 1906.
A STUDY OF RHUS GLABRA.
By Edward L. Greene.
INTRODUCTION.
The genus Rhus as Tournefort restricted it two centuries ago,
and as many another systematist since his day has held it, is
clearly marked and easily denned. As to habit — that foremost
indication of a good plant genus — this generic type stands well
aloof from all its allies ; even distinctly apart from each and
every one of those kindred generic groups which, like Cottnus,
Toxicodendron, Metofiium, Lobadium, Rhoeidium, and Styftho-
nia, in another than the Tournefortian school of taxonomy, have
been thought of as preferably constituting mere subgenera of
RInts. But not a species in any of those other genera named
makes the least approach to typical Rhus in habit. Every species
and variety of this appears as a shrub or tree with few stout stag-
horn-like branches, each clothed heavily near its summit with
odd-pinnate leaves, these usually large and of many leaflets.
In our silva the only tree which in aspect recalls the sumachs is
that naturalized alien, the Ailanthus, a genus 01 no near affinity
to Rhus. But between the last and its near relative Schmaltzia
there is no habital resemblance. In this regard they are quite
as unlike as are currant bushes and elder trees ; and, as for
Toxicodendron, its habit is as remote from that of Rhus as the
habit of a grape vine or English ivy is remote from that of wal-
nut trees.
Over and above its marked habit, the characters by which this
Rhus of Tournefort establishes itself as a model genus are, the
Proc. Wash. Acad. Sci., December, 1906. 167
l68 GREENE
terminal origin of its inflorescence, the firmness and compactness
of that inflorescence, concurring with small red velvety or plushy
drupelets for fruits.
Of the genus, in this which seems to me the most reasonable
and natural acceptation of it, there exist in North America, ac-
cording to classic standards, four species, — Rhus glabra,
typhina, ptimila and copallina}
To the last of these there is attributed a geographic range
somewhat incredible for that of any one species of shrub of what-
ever genus ; almost incredible, I say, to any experienced student
of climatology as affecting plant life and the distribution of spe-
cies. But according to the books Rhus copallina occurs as one
and specifically the same in several widely sundered and very
different floral regions. It is said to be common in the hard soil
and severe climate of New England, and as much at home in the
subtropic lowlands of Florida, twelve hundred miles southwest-
ward ; even running away to the arid cactiferous hills of further
Texas that lie westward from Florida another thousand miles ;
and yet again, in a region so extremely different from either of
these as that of the Great Lakes in Minnesota and Wisconsin,
the same Rhus copallinay it is said, recurs.
An European celebrity more than twenty years ago, without
field knowledge of the shrubs, and with no experience in prob-
lems of North American phytogeography, but using the imper-
fect light of European herbarium material only, made out and
named a half dozen varieties and subvarieties of our Rhus copal-
Una;"1 all which work is ignored or suppressed by later Ameri-
can compilers of books ; to whom the following out of the vivid
suggestions of Engler would entail the expenditure of much time
and energy, whereas suppression is of all things the most easily
done.
Rhus copallina is one of many hundreds of North American
phytologic problems awaiting investigation and solution.
Another of our four species, namely Rims pumila, stands in
most marked contrast to the preceding in point of geographic
LTorrey & Gray, Flora of North America i : 217. Gray, Synoptical Flora 1 :
384-
2 Engler, in DC. Monographic Phanerogamarum, 4: 3S3.
A STUDY OF RHUS GLABRA 169
distribution. It is almost local, occurring nowhere but in lower
and middle districts of the Carolinas and Georgia.
Rhus lyphiua, the largest and most tree-like of our species,
ranges widely, at least when compared with R. pumila. It is cata-
logued for all the states from Maine to Georgia and Mississippi,
thence northward to Minnesota and the Dakotas, but is every-
where less common than R. glabra, and more particular than
either that or R. cofalliiia as to its environment. Everywhere
southward it is of the mountains or the hill country only, never
coming down to the lowlands or to the seaboard. Neither at
the northwest does it come out from its woodland habitat to
adorn the copses bordering the prairies where a subspecific ally of
R. glabra is so much in evidence. It seems to have little
adaptability to varying conditions other than those of heat and
cold ; though in this regard its adaptability is very marked.
The climate of Minnesota and the Dakotas, and that of Georgia
and Mississippi are extremely unlike as to temperature. Yet
between the Julius typhina of the most northerly locality and
that of the stations farthest southward, one does not discover
notable differences other than those of the size of the shrub and
the number of the leaflets. In other respects they seem to be
much the same ; so that the type is apparently one of a singular
degree of stability under somewhat varying conditions.
Concerning R/ius glabra, the type species of the genus as to
North America, one may note first of all its nearly universal dis-
tribution. In this regard it is most unlike any of its congeners
here. From beyond the river St. Lawrence northward, down,
to the very shores of the Gulf of Mexico, its range is across the
continent. Within these parallels, into every floral region be-
tween the oceans, however different — excepting only that of
California — there enters that which, according to the books
and lists of plants, is Rhus glabra.
There is no one species of tree or shrub of any continent
that really holds the geographic range which the books and lists
ascribe to Rhus glabra. By all the analogies of things there
ought to be several marked species or subspecies of this type in
the southern Appalachian region between Maryland and Ten-
nessee and Georgia ; another and an equally distinguishable set
iyo
GREENE
between northern New England and the headwaters of the
Mississippi beyond Lake Superior ; another species or two pecu-
liar to that vast empire of the Middle West, the prairie country ;
as many more in that different and equally extensive stretch of
country lying between southern Missouri and the shores of the
Gulf of Mexico. Then, since there is a Rhus glabra all up and
down the two thousand miles' length of the Rocky Mountain
region, this ought to be thoroughly distinct by plenty of charac-
teristics, and to resolve itself naturally into a number of varieties
or subspecies. Just the same should be looked for in the shrub
accredited to another empire, that of the Pacific slope northward
lying between the sources of the Columbia and Puget Sound;
while the scores of isolated mountain ranges rising up out of the
deserts of Nevada, Utah, Arizona and New Mexico — for the
type in question is there also — should furnish another and pre-
sumably the most marked group of Rhus glabra segregates.
Our herbaria cannot to-day be supposed to be well supplied
with specimens representing this type. No author has investi-
gated it, and no special call has been made for the collecting of
these shrubs from different regions. Nevertheless, the mass of
material that has been before me during some months past is
amply sufficient to enable the investigator to point out characters
by which a number of species may be, and reasonably must be,
given recognition ; characters of foliage in abundance, and
characters of the fruiting panicle and the fruit itself.
Perhaps more trying than the task of examining and com-
paring specimens to find out specific characters, is the great
amount of bibliographic work that is necessary in order to
determine which one of the several eastern species ought to
bear the name Rhus glabra; for even this, as indicated —
though never described — by Linnaeus was an aggregate. In
the botanic gardens of Europe several species had been long in
cultivation, had been recognized as species and even described
as such, when Linnaeus in the middle of the eighteenth century
came along, and, bundling all the glabrous kinds together, named
not any one of them, but the whole bundle of species, Rhus
glabra.
If Linnaeus is to be credited with some one particular Rhus
A STUDY OF RHUS GLABRA 1 7 1
glabra that we must if possible segregate from the bundle of
species which bundle he so named, our task is one demanding
the very best skill of both the taxonomist and the historian.
EARLY HISTORY.
Prior to the discovery of America the Rhus of all botany was
a monotypic genus. It began and ended with Rhus carta)/ a,
also by some authors called Rhus obsoiu'oruui, a shrub of the
Mediterranean region, well known in the useful arts from im-
memorial ages.
No second species of Rhus was known until as late as the year
1620, when Caspar Bauhin, publishing an illustrated quarto
containing names and descriptions of more than 600 new plants
from various parts of the world, brought to the notice of bot-
anists what he chose to name Sumach angustifolium} This
was known to have come from the New World, though in an
herbarium specimen only. Historically this is the earliest and
oldest element entering to the confused R. glabra Linn. Bauhin
himself in the year 1620 showed a preference for the Arabic
name Sumach, the exact equivalent of the Greek and Latin
Rhus ; but in his more comprehensive work of three years later,
the Pinax, as if having decided to use the Greek and Latin
rather than the Arabic name of the genus, he adopts Rhus,
renaming his new American species, Rhus augustifolia?
At the time of its publication in 1620, and long afterwards,
the material on which it was founded was believed to have been
derived from some island off the coast of Brazil ; but a century
later, no further specimens of it having been received from any
part of South America, and because of its now having come
to be known as certainly North American, the idea of its being
indigenous to Brazil was abandoned.
In so far as I have been able to examine early records, the
next mention of any American Rhus is in Banister's Catalogue
of Virginian Plants, published in the year 1688. That this was
some member of the group of R. glabra we are assured by his
note that the branches are glabrous. The one with soft hairy
1 Prodromus Theatri Botanici, p. 15S.
2Pinax Theatri Botanici, p. 414.
172
GREENE
branches, R. tyfihina, was by this time well known by Bauhin's
description of it, and had perhaps already appeared in some
gardens in Europe. In 1726 both the hairy and the smooth
sumachs were to be found in some London gardens and parks,
and in 1732 Dillenius published a folio plate and a full descrip-
tion of what must apparently stand for the R. glabra Linn,
of 1753-
CHARACTERS FOR SEGREGATE SPECIES.
Linnaeus' statement of the characters of Rhus glab?'a reads
thus : " Leaflets pinnately arranged, lanceolate, serrate, glabrous
on both faces." This is the same as no description at all. If one
assume said compound leaf to be odd-pinnate rather than equally
pinnate, one does so without any warrant in any word that
author said about either the species or the genus. Equally
without warrant will be any assumption that the leaf is of 7
leaflets, or that it is of 17, or of 27. Linnaeus gives no hint of
its character in these most significant particulars. One will also
reasonably infer that the leaflets are not notably pointed at the
upper end ; and whether at base they be stalked or sessile you
have no means of judging. It must also be assumed that there
is no distinction of coloring noticeable respecting the two faces of
the leaf; also whether of a dark-green, or of a bright-green,
or of a glaucous or blue-green, one is not informed. Such a
description as Linnaeus gives of Rhus glabra might easily apply
to each one of five species, or of fifty, or of five hundred species
in a genus. It is therefore worthless for diagnostic purposes.
Coming down from the middle of the eighteenth century to
near the close of the nineteenth, we shall find that in American
books of American botany the Linnaean diagnosis of R. glabra
has met with a little amendment. That in Gray's Manual in
1890 reads thus : " Smooth, somewhat glaucous ; leaflets 11-31,
whitened beneath, lanceolate-oblong, pointed, serrate." The
expression, " whitened beneath," is one that helps us to fix on
certain shrubs, mostly southern, as representing this author's R.
glabra; but in New England there are at least two different
sumacs which this phrase completely excludes ; one of them,
inhabiting Massachusetts, shows not even a trace of bloom on
the lower face. Both of these, and with them several more
A STUDY OF RHUS GLABRA 1 73
species of the east and south, are excluded as having hardly
half of the " 11-31 " leaflets.
In Britton's Manual of 1901 is that of Gray somewhat ampli-
fied and therefore less safe. Here Gray's evasive term,
" pointed," gives place to the more definitive word " acumi-
nate," but this excludes yet another set of forms in which no
leaves are acuminate. Moreover, leaves and leaflets have dif-
ferent ways of being acuminate, in so much that, in order to be
able to really describe the apex of the leaflet in each segregate
of R. glabra, I find it necessary to use such truly definitive
terms as subulate-acuminate, cuspidate-acuminate, and such
phrases as slenderly acuminate and caudately acuminate. But
more unfortunate still is the Britton's Manual description of the
leaves as being dark-green above. That indeed applies to what
I take for real R. glabra, and to several of its Atlantic slope
allies ; but it holds good in not one of those far-southwestern
species of New Mexico, Arizona and Utah, which said Manual
goes far out of its way to speak of as forming a part of R.
glabra. Even in the middle west and far-northwestern districts
not a tithe of the definable species can be said to have leaves of
other than a dull lightish green.
Finally, the authors of none of the books knew anything of
the differences of fertile inflorescences in this aggregate. That
these in the fruiting and mature state are narrowly oblong in
a few, oblong-fusiform in many, and almost or quite exactly
pyramidal in many more, a discovery the importance of which
will not be disputed, is a fact which is herein first brought to
notice.
It is my belief that even the flowers in some species will be
found to present characters available for the further establish-
ment of species here. Both calyx and corolla are far from
being the same in all ; but I have declined to make any use of
these for the reason that in the herbaria exist such multitudes of
specimens that are in flower only, and of which the fruiting
panicles are yet unknown.
In true Rhus glabra, and also in by far the greater propor-
tion of the segregates herein proposed, both branches and foliage
are wholly glabrous. In the diagnoses I permit this to be taken
1 74 GREENE
for granted, never mentioning such a matter except in the cases
of those two or three of the new species in which there occurs a
trace of pubescence.
Key to the Species.
* Leaves deep or dark green above (except in Xo. 9), usually
white with bloom beneath,
f Panicles of fruit oblong, or oblong-fusiform.
Leaflets very many, 17—21 or more, and large.
Leaflets oblong-lanceolate, obtuse at base and subsessile, at apex
abruptly pointed 1. R. glabra.
Leaflets oblong-lanceolate, sessile, slenderly long-pointed.
2. R. oreophila.
Leaflets linear-lanceolate, sessile and auricled at base, at apex
caudate-acuminate. 3. R. auriculata.
Leaflets less numerous, commonly 13-17.
Leaflets lance-oblong, tapering abruptlv at base and less abruptlv at
apex 4 . R. tthacensis.
Leaflets oval to oblong-lanceolate, merely acute at apex.
5. R. ashei.
tt Fruiting panicles broadest near the base and pyramidal.
Leaflets rather few (except in Nos. 6 and S).
Leaflets 17-21, sessile, oblong-lanceolate, acuminate.
6. R. pyramidata.
Leaflets very large, but only 13-17, subsessile, acute rather than
acuminate 7. R. caroliniana.
Leaflets 19-23, narrowly oblong-lanceolate, obtuse at base, the apex
subulate-linear S . R . atrovirens .
Leaflets 13-17 and small, oblong-lanceolate, coarsely serrate, slend-
erly acuminate 9. R. ptdchella.
Leaflets only 11-15, notably thin, attenuate-acute.
10. R. ladoviciaiia .
Leaflets 11— 13, small but firm, subpetiolulate, abruptly but sharply
acuminate.. 11. R. arbuscula.
Leaflets 13-15, large, petiolulate, subfalcate, sharply acuminate.
12. R. petiolata.
Leaflets 13-17, oblong-lanceolate, subpetiolulate, triangular-subulate
at apex 13. R. valida.
Leaflets 13-15, sessile by a rounded base, the apex short, slenderly
attenuate 14. R. longula.
Leaflets only 11-13 and small, sessile, subulate-acuminate, their
rachis pubescent 1^. R. sandbergii.
A STUDY OF RHUS GLABRA 1 75
* * Leaves ample (except in No. 25), of a lighter green above,
less glaucous beneath. Panicles in almost all pyramidal.
All the species far western and northwestern.
Leaflets 13-17, subsessile, sparsely pilose, subulate-acuminate.
16. J\ . borealis.
Leaflets 1 1— 1 3.
Large, sessile, subfalcate-oblong, abruptly broad-pointed.
17. R. media .
Oblong, subsessile, abruptly acuminate iS. R . cismontana.
Large, acutish at base and subpetiolulate, abruptly short-pointed.
19. R. sambucina.
Leaflets 13-17-
Shining above, sessile by an obtuse base, cuspidately acute.
20. R. miens.
Checkered light and dark green above, subsessile, cuspidatelv acu-
minate 21. R. tcsscllata .
Leaflets 9-15, oblong-lanceolate, sessile, acuminate.
22. R. macrotkyrsa.
Leaflets 17-19, oblong-linear, sessile, acutish at base, long-acuminate.
23. R. arguta.
Leaflets 13-17, oblong, sessile, obtuse at base, the apex merely acute.
24. R. aprica.
Leaflets 11-13, narrowly lanceolate, sessile, acuminate.
25. R. occidentalis .
* * * Leaves smaller, of fewer leaflets, altogether pale, very glau-
cous beneath. Panicles small, less definitely pyramidal.
All of arid southwestern regions (But Xo. 9. A'. pnl-
chclla, of the southern Appalachian mountains is naturally
of this group).
Leaflets 1 1-15.
Sessile, oblong-lanceolate, short-acuminate 26. R. albida.
Petiolulate, subfalcate-lanceolate, slenderly acuminate.
27. R. elegant id a.
Leaflets 9—1 1 , sessile, oval to oblong-lanceolate 2S. R. sorbifolia.
Leaflets 7-9, subsessile, lanceolate, slenderly acuminate deeply incise-
serfate 29. R. asplenifolia.
1. RHUS GLABRA Linnaeus.
Rhus rami's ex stipitc -pullulantibus giabn's, Banist. Catal. in
Ray, Hist. 2 : p. 1928. 1688.
Rhus Virginicum panicula sparsa, rami's patulis glahris,
Dillen., Hort. Elth. p. 323, t. 314. 1732.
176
GREENE
Rhus glabra Linn. Sp. PL, p. 265. 1753, in part, excluding
both the shrub of C. Bauhin and that of Catesby.
Rhus glabrum, Mill. Diet. 1768?
Shrub commonly 2-3 m. high, with very few and stout diver-
gent branches: leaves mostly 5-7 dm. long, the rachis and
petiole very stout, the latter 1-1.5 dm. long; leaflets about
17-21, not crowded, very large, 8-13 cm. long, 3-3.5 cm. wide,
oblong-lanceolate, subsessile, abruptly and not slenderly acumi-
nate, evenly serrate, the serratures 12 or 13 on a side, texture
in maturity rather firm but not subcoriaceous, upper face deep
green and smooth, lower face glaucous but not excessively so :
staminate panicle very large, often 3 dm. high, pyramidal,
almost 2 dm. wide at base in the largest, the pistillate, when in
flower nearly as long but fusiform, less than 1 dm. wide up and
down the middle part, in fruit oblong-fusiform, 6-10 cm. wide
below the middle ; drupelets very many, round-ovate.
This is the common and apparently the only glabrous Rhus
of the Potomac Valley in southern Maryland and eastern Vir-
ginia, ranging eastward and northward through southern
Pennsylvania, to Delaware, New Jersey, and to Connecticut, if
I refer here a flowering specimen in the National Herbarium
from Green's Farms, 1894, by C. L. Pollard. The type from
which the above description is drawn is the shrub as it grows in
the District of Columbia, and up and down the Potomac above
Georgetown.
The choice between this and the next for something to bear
the name R. glabra Linn, is made rather arbitrarily, perhaps ;
for either one may have been that grown in the Eltham garden
and figured by Dillenius. The two are distinct by their fruiting
panicles, and the fruit of the Dillenian type was unknown,
because only the staminate shrub was raised from the seed by
which it was introduced into Europe. As to the size of the
leaves and leaflets, however, the present species alone answers
to the account given by Dillenius ; hence the probability in favor
of this as identical with his.
Since Linnaeus himself did not describe the species ; and
since the one only synonym, quoted by him which carries with
it a description is that of Dillenius, the name R. glabra must be
A STUDY OF RHUS GLABRA 1 77
applied here unless it be left to fall into synonymy altogether.
Philip Miller, as a contemporary of Dillenius and Linnaeus,
and as a cultivator of these shrubs, might have been expected
to identify correctly the A', glabra of Linnaeus when he adopted
the name ; yet to what he so named in his Dictionary, the name
glabra does not really apply, for he describes its branches as
downy, thus awakening a doubt as to whether his R. glabra was
not some possible segregate of Rhus typJiina.
2. RHUS OREOPHILA, sp. nov.
Shrub 2-3 m. high : leaves 3-4 dm. long, the petiole 6-8 cm.
long : leaflets 19-27, closely approximate, not of the largest,
7—9 cm. long, 2.5 cm. wide, narrowly oblong-lanceolate, sessile,
rather slenderly acuminate, lightly and almost obsoletely ser-
rate, the serratures 10-12 on each side, texture firm, almost
subcoriaceous, lower face whitish with a dense bloom, upper
face by no means deep or dark green, of a rugulose-roughened
rather than smooth surface : fruiting panicle large and much
elongated, oblong-fusiform, 18-28 cm. long, only about 5 cm.
wide, very compact, the drupelets subglobose, nearly 5 mm. in
diameter.
Mountain districts of Maryland, Virginia, the Carolinas and
eastern Tennessee ; not in the lower hill country of the Potomac
Valley outside the mountains, nor at all northward. The type
specimen in the National Herbarium is on sheet No. 327800,
from Chapel Hill, North Carolina, by W. W. Ashe, no date of
collecting given, nor any specific locality. Two sheets from
the Biltmore Herbarium, the material gathered at different dates
in 1896 and 1897, without indication of either the collector or
special station, except the name Biltmore, represent the species
beautifully. So does another, from the mountains of Cocke
County, Tenn., by Mr. Thos. H. Kearney, September 14, 1897.
Yet another U. S. Herbarium specimen, in good foliage but
young fruit, is from near Luray, Va., by Mr. and Mrs. Steele,
August 30, 1 901.
The species is in contrast with R. glabra by smaller leaflets,
with denser bloom beneath, and a longer, narrower thyrsus of
larger and more closely compacted drupelets.
I78 GREENE
It may not perhaps be determinable to a certainty that the
preceding rather than this, was grown in London, and formed
the type of Dillenius' figure of leaves and staminate panicle.
But Banister's field, and probably that of Catesby also, by both
of whom seeds were sent to England, was the lower country,
where only what I have here called Rhus glabra is found.
3. RHUS AURICULATA, sp. nov.
More slender than R. glabra, all the parts somewhat smaller,
the fruiting panicles especially only about one-third as large :
leaves 2.5-3.5 dm. long; leaflets about 19, approximate, often
alternate, 7-10 cm. long, never more than 2 cm. in width, often
less, of linear-lanceolate outline, the apex caudately long-atten-
uate, the sessile base showing definite though small auricles,
the serratures light but rather close, 14-18 on a side, texture
subcoriaceous, the upper face light green, transversely rugose,
the somewhat sunken veins correspondingly prominent on the
very glaucous lower face ; fruiting panicles oblong or slightly
verging toward the pyramidal, 10-13 cm' high 5 drupelets com-
paratively few, large.
A remote southwestern ally of R. glabra, with very definite
specific marks. It is known to me only as collected by Mr. C.
L. Pollard, August 11 to 12, 1896, the special locality, Agri-
cultural College, Oktibbeha County, Mississippi. The type
specimen occupies sheet 271931 of the National Herbarium.
There is a duplicate in Herbarium Field Museum which I have
seen. Mr. Pollard's distribution number 1261 is on these two
of his labels that I have seen.
The species must quite surpass R. glabra in beauty. Its
narrow slender-pointed leaflets seem to droop from the rachis
rather than to spread away from it horizontally. This, how-
ever, is characteristic of several other allies of R. glabra belong-
ing to regions lying westward.
4. RHUS ITHACENSIS, sp. nov.
All the parts smaller and more slender than in R. glabra, the
branches not glaucous, seldom glaucescent : leaflets 13-17,
A STUDY OF RHUS GLABRA 1 79
sessile by an abruptly acutisb base, 6-7 cm. long, saliently
serrate, tbe serratures 13-15 on a side, upper face dull deep
green, lower glaucous but less so than in R. glabra, the texture
thinner: fruiting panicle small comparatively, long-peduncled,
12-18 cm. long, oblong fusiform, not very compact, its branches
thinly tomentellous ; drupelets below medium size, notably
smaller than in R. glabra.
Seems to take the place of R. glabra everywhere to the west-
ward of the Alleghenies in western Pennsylvania and New
York, and in northern Ohio. The station for the type is near
Ithaca, New York, as the name might indicate ; the type speci-
men is on sheet No. 225037 U. S. National Herbarium ; was
collected at Fall Creek, September, 1893, by K. M. Wiegand.
Sheet 292227 is the same from Westmoreland County, Penn-
sylvania, 1878, by P. E. Pierron, consisting of uppermost leaves
and a panicle each of staminate and pistillate flowers. It is
also in U. S. Herbarium in flower only, from Elyria, Lorain
County, northern Ohio, as collected in flower only by A. E.
Ricksecker, August 1, 1894.
Excellent specimens, true to the type, are in the Herbarium
of the Geological Survey of Canada as follows : sheet 34165
from Sandwich, Ontario, by John Macoun, July, 1901 ; also
another from Bellville, Ontario, by the same as early as 1867,
this in male flower only.
All the so-called Rhus glabra from the geographic region so
indicated, differs from the southern R. glabra and the New
England R. -pyramidata in points quite sufficient to establish it
in the rank of at least a strong subspecies.
5. RHUS ASHEI (Small).
Rhus Caroliniana Ashe, Bot. Gaz. 20: 548, 1895, not of Mil-
ler, Diet. 1768.
Schmaltzia Ashei Small, Fl. 729.
Shrub erect but low, only 3-5 dm. high ; leaflets 13-17, oval
to oblong lanceolate, 5-7 cm. long, acute, not acuminate, sessile,
rather coarsely subserrate-dentate, the teeth about 10 on each
side, pale beneath but not glaucous : panicle of ovoid outline,
large for the plant, 10-15 cm- l°ng-
I SO GREENE
In old fields and low woods of middle North Carolina, col-
lected by Ashe, who correctly indicated it as a good new species
but under a name long preoccupied.
6. RHUS PYRAMIDATA, sp. nov.
Both the shrub and its foliage smaller than in R. glabra, the
mature leaves firmer, almost subcoriaceous, equally white with
bloom beneath, the whole leaf 3 dm. long or less; leaflets 17-
21, sessile, oblong-lanceolate, acuminate, lightly serrate, the
serratures 12-16 on each side: fruiting panicle large, notably
compound, the primary branches being again widely branched,
the whole subpyramidal, 8-12 cm. wide toward the base and
only 12-18 cm. high ; drupelets very numerous, smaller than in
southern allies, 3 mm. wide, suborbicular inclining to ovate.
This definition I trust may prove to include a large part of
what has been called Rhus glabra in northern New York, New
England and adjacent Canada. That which I wish to cite as
the type specimen is on sheet 312308 of the National Her-
barium, and was collected near Lake Waccabuc, Westchester
County, New York, by Mr. C. L. Pollard, August 12, 1894.
The locality lies easily within the range of Colden's field studies
made in the middle of the eighteenth century or earlier. It
might therefore be guessed that R. -pyramidata also entered into,
and formed a part, bibliographically speaking, of Linnaeus'
aggregate R. glabra. But this cannot be established as a fact ;
nor would it alter the situation in the least if it could be ; for
Colden did not describe the shrub, and his work is of later date
than that of Dillenius, to which we are obliged to resort for any
described and definable thing that may bear the appellation
Rims glabra Linn.
The Rhus glabrum of Philip Miller, which he said was from
New England, and which he reported as cultivated in his time
under the name of New England Sumach, cannot have been the
present species ; for he attributes to that " downy " branches, as
I have already remarked under R. glabra.
There is presumptive evidence in the herbaria of the existence
in southern New England of at least two more species, the diag-
noses of which cannot be safely made for want of fruiting pani-
A STUDY OF RHUS GLABRA 1 8 1
cles. One of these I have seen only in the herbarium of the Field
Museum, sheets 13682 and 185 10. Both specimens were col-
lected and distributed by the late D. C. Eaton, somewhere near
New Haven; no date. Another is from South Hadley, Mass.,
1887 ; the collector's name illegible. This is on sheet 275445
of U. S. National Herbarium. By evident marks of foliage
and detached flowering panicle this is certainly distinct from all
others known, and nearest R. ithacensis, unless the panicle be
pyramidal.
7. RHUS CAROLINIANA Miller.
RJius glabra, -panicula sfiarsa coccinea, Catesby, Carol. App.
4, t. 4.
Rhus glabra Linn. Sp. PI. 2 ed. 380 (1762) in part onlv, and
as to the shrub of Catesby.
Rhus Caroliniana Mill. Diet. ed. 1768.
Rhus elegans Ait. Hort. Kew. 1 : 365. 1789.
Shrub 2-3 m. high: leaves large, but of only 13-17 leaflets,
these not closely approximate but large, commonly 8-1 1 cm.
long, 2-3 cm. wide, subsessile, acute rather than acuminate,
strongly serrate, the serratures about 9 on a side, upper face
deep green, lower glaucous : fruiting panicle large and not com-
pact, exactly pyramidal, 2 dm. long or more, 1.5 dm. wide at
base ; drupelets uncommonly small, bright scarlet rather than
dark-red in maturity.
A South Carolinian species, collected, described and illustrated
by a large folio plate, in the middle of the eighteenth century,
by Catesby, who also was the medium of its introduction into
English parks and gardens at the same time; from which, also,
it is probably long since lost. That it is thoroughly distinct from
R. glabra Catesby's description and figure demonstrate, to all
who know Rhus glabra. Philip Miller also knew it to be distinct,
and in the year 1768 gave it the trivial name of R. caroliniana.
Again, as still grown in Kew Gardens twenty years later than
the date of Miller's work, Aiton, as if ignorant of Miller's
name R. caroliniana, published it again as distinct from R.
glabra under a new name, R. elegans.
From a highly instructive paper on some small trees observed
152 GREENE
in Georgia, published by Mr. Roland M. Harper last year,1 it
appears to me probable that this zealous explorer of southern
fields and woods has, without knowing it, rediscovered this
large scarlet-fruited Rhus of Catesby. Mr. Harper says that
he found what he took for Rhus] glabra "in a cane-brake on
the bank of the Coosa River, in Floyd County, about twelve
miles below Rome, Georgia, a veritable little grove of this
species, in which many of the specimens were as much as seven
inches in diameter and thirty feet tall, with the lowest branches
higher up than I could reach." Mr. Harper describes the
drupelets of this tree as " bright scarlet," just the color men-
tioned by Catesby more than a century ago, as being one among
several marks by which R. caroliniana was to be distinguished
readily from the then well known R. glabra, the fruits of which
are unvaryingly of a dark crimson when mature.
8. RHUS ATROVIRENS, sp. nov.
Stout upright shrub, the young branches and lower face of
foliage not very glaucous : leaves about 3 dm. long, with
unusually stout petiole and rachis, the whole more firm and
ascending than in allied species : leaflets about 23 and closely
approximate, subcoriaceous, of a dark green above, pale but
not white beneath, of only middle size, 5-7.5 cm. long, nar-
rowly oblong-lanceolate, subsessile by an obtuse base, the apex
subulate-linear, entire, the serratures of the margin, though
obscure very numerous, 16-22 on each side : panicle of fruit
narrowly pyramidal, 1.5 dm. long, compact; drupelets larger,
than in the last, quite rotund, 4 mm. wide, deep crimson as in
most species.
Mountain region of northern Alabama ; type in the National
Museum No. 19814, from near Gadsden, 1888, by Gerald Mc-
Carthy. Distinguished from one and all the foregoing by its
narrow and crowded dark green and rather rigid leaflets.
9. RHUS PULCHELLA, sp. nov.
Branches not stout, angular, glaucous, minutely lenticellate :
leaves not large, about 2 dm. long, rather long-petioled, of a
1 Torreya, 5 : 163.
A STUDY OF RHUS GLABRA 1 83
somewhat glaucescent green above, very glaucous beneath ;
leaflets 13-17, small, sessile, drooping on the rachis rather than
spreading away from it on the same plane, oblong-lanceolate,
5-6 cm. long, slenderly acuminate and somewhat irregularly
and coarsely serrate-toothed below the acumination, as well as
more lightly and evenly serrate in the middle : panicle pyram-
idal, small, about 8 cm. long, slender-peduncled, somewhat
recurved or drooping.
Known only from Yellow River, near McGuire's Mill,
Guinnett County, Georgia, July 11, 1893, John K. Small;
type in National Museum, sheet No. 19816. A small and
very graceful species, recalling some of the far-southwestern
forms found in Arizona.
10. RHUS LUDOVICIANA, sp. nov.
Shrub with quite slender branches, the foliage not large
ascending, glabrous except as to the hairy line of the rachis,
about 2.5 dm. long; leaflets 11-15, opposite, of thin texture
even in full maturity, dull green above, moderately glaucous
beneath, 5-8 cm. long, attenuate, acute rather than acuminate,
evenly serrate, the serratures 12-16 on each margin: panicle
small, pyramidal, 8 cm. long, 4 cm. broad toward the base ;
drupelets obliquely orbicular, of a dark red-purple and not
strongly pubescent.
The type specimen is in my own herbarium, from along the
seaboard in southwestern Louisiana, at Cotes Blanches, October
10, 1884, by A. B. Langlois. A strongly-marked, probably
small species, said to form low thickets in a peculiar maritime
region that is still almost unknown botanically.
If the Rhus angustifolia Bauhin, believed to have come from
the coast of Brazil, was derived from some North American
coast by that voyager of nearly or quite three centuries ago, it
would be easy to fancy that the specimen in Burser's herba-
rium, which became Bauhin's type, was from some shore of the
Gulf of Mexico, and even may have been identical with what is
here described as R. ludoviciana, and which is the only known
maritime ally of R. glabra. And that which may elevate this
Proc. Wash. Acad. Sci., February, 1907.
184 GREENE
fancy almost or quite to the rank of a probability is the at least
highly interesting coincidence that my type specimens of R.
ludoviciana bear the only leaves and leaflets known to me that
answer to Bauhin's description of those of Burser's specimen.
He gave the number of the leaflets, their form and dimensions,
the serrated character of their margin, and the narrowly atten-
uate apex, not omitting mention of the darker green upper and
paler lower faces of the leaflets.
This, as I have said before under R. glabra, is the earliest
element, historically speaking, that enters into Linnaeus' aggre-
gate ; and had the latter described his Rhus species as carefully
as Bauhin had described his a hundred and thirty years before
him, the task of the twentieth century botanist at this juncture
would have been much less difficult.
11. RHUS ARBUSCULA, sp. nov.
Shrub low, tree-like in form though commonly less than 1 m.
high : branches of the season glabrous, glaucous, obscurely
angled, not very stout, but foliage large and ample ; largest
leaves 3 dm. long, of 11 to 13 rather remote leaflets, these
lance-oblong, 7 to 9 cm. long, often subfalcate, notably inequi-
lateral at base, never quite sessile, the petiolule definite though
very short, upper face of leaflets light or deep-green, the lower
very glaucous ; serratures moderately salient, 10 to 15 on each
margin, the apex abruptly and sharply acuminate : panicle
pyramidal, very small for the foliage, usually but 7 to 9 cm.
long ; drupelets of the smallest.
Near Culver, Marshall County, Indiana ; collected August 18,
1906, by Mr. H. Walton Clark, of the United States Bureau of
Fisheries.
The type locality, and thus far the only known station, is a
barren hill above the eastern shore of Lost Lake, near Culver,
Indiana. The specimens at hand are two, both of them excel-
lent, but evidently not from the same bush, and, as I suspect,
from somewhat different exposures. One of them has a maturer
foliage beginning to redden for the autumn ; and the branch,
as well as the rachis of the leaves in this all show much bloom.
A STUDY OF RHUS GLABRA 1 85
This I designate as the type specimen. The other differs only
in having foliage of a clear and vivid green, and the stem shows
but little bloom. Both specimens have been presented to, and
will be preserved in, the U. S. National Herbarium.
12. RHUS PETIOLATA, sp. nov.
Branches not stout, glabrous, glaucous, striate, roughened
also by small and very protuberant lenticels : leaves ample, not
long, though long-petioled : leaflets about 13, large, 8-10 cm.
long, oblong-lanceolate and often subfalcate, distinctly petiolu-
late, the base obviously inequilateral, apex sharply acuminate,
the sides sharply but unevenly serrate, the serratures 13 to 15,
upper face of leaflets of a rich deep green, the lower very
glaucous : panicle small for the foliage, pyramidal, 10 cm. high,
compact, the branches thinly and rather stiffly hirtellous ; drupe-
lets rather large.
Prairie region of the interior of Minnesota, the type from
near Spicer, Minn., August, 1892, W. D. Frost, Herb. Field
Mus. sheet No. 140259. Well marked by the large definitely
petiolulate leaflets.
13. RHUS VALIDA, sp. nov.
Branches very stout and robust, upright, at the end of the
first season no longer glaucous but light brown, between cin-
namon and chestnut-color, striate, copiously lenticellate : leaves
not large in proportion, less than 3 dm. long ; leaflets about 15,
approximate, short-petiolulate, oblong-lanceolate, 6-10 cm.
long, with about 11 serratures on each margin and a short tri-
angular-subulate point, texture subcoriaceous, upper face dull
deep green and transverse-rugose, lower fairly glaucous but
not white: panicle rather oblong-pyramidal, large, 12-14 cm*
high, its branches thinly tomentulose-pubescent : drupelets
many, large, little compressed, rather thinly plushy.
Even in the herbarium specimens this impresses one as some-
thing wholly apart from any and all eastern and southern
shrubs that have been called R. glabra. The very stout stri-
ated, lenticellate and upright branches, with smallish foliage
1 86 GREENE
evidently more ascending than is usual in the genus, and the
large rather narrow panicle — all these marks indicate a
species, and one possibly somewhat local about Lake Michigan.
The type specimens, all in Herbarium Field Museum, are from
Hinsdale, a suburb of Chicago, and were collected October 12,
1902, by Ernest C. Smith, his distribution No. 577. I also
refer here without hesitation Mr. O. E. Lansing's No. nil, as
in Herbarium Field Museum, from West Pullman, 111., Septem-
ber 8, 1900.
Later than all these are specimens sent me late in August,
1906, from near Nashotah, Wisconsin, by Dr. H. V. Ogden
of Milwaukee. These came to hand after the above diag-
nosis of J?, valida had been finished, and the type specimens
returned to the Field Museum. But they answer perfectly to
my description of the species in every particular, and therefore
only further confirm it while extending its range.
14. RHUS LONGULA, sp. nov.
Stem and branches not known : leaves about 3 dm. long, with
long stout ascending petiole, and 13 or 15 approximate leaflets,
these 7-9 cm. long, sessile by a rounded base, the apical acumi-
nation short though slenderly attenuate, the margins lightly and
almost subcrenately serrate with about n or 12 serratures, tex-
ture firm, hardly subcoriaceous, color dark dull-green above,
whitish-glaucous beneath : fruiting panicle narrowly oblong and
greatly elongated, 18 cm. long, hardly 5 cm. wide at the widest
part, the short branches hirtellous-tomentulose ; drupelets of
middle size and numerous.
Bluffs of the Mississippi River far northward ; the special
station for the type somewhere near Stockton, Minnesota ; the
type specimen in U. S. Herbarium, No. 19813, collected by
Mr. John M. Holzinger, August 23, 1888. Also on sheet
19811 is aflowering specimen by the same collector, of "May,
1889," which appears to be the same specifically. The station
for this is not named.
That R. longula, away at the western North should flower
in May is noteworthy ; for its ally, R. glabra, so far southward
as the valley of the Potomac does not begin to flower until July.
A STUDY OF RHUS GLABRA 1 87
The eastern analogue, R. ithaccnsis, in Pennsylvania, does
not come into flower before the end of July or early August.
These segregates of R. glabra from the northwest, by their
almost vernal flowering, reassert for themselves a more distant
relationship to the eastern types than that which we should infer
from their visible characters alone.
15. RHUS SANDBERGII, sp. nov.
Rhus glabra var. sandbergii, Vasey & Holzinger in Herbarium
Field Museum.
Very dwarf, flowering and fruiting freely at 1.5-2 dm. high ;
branches of the season 4-5 cm. long, angular, rusty-tomentulose
and with also a few hirsute hairs, older branches glabrate :
leaves small, barely 1.5 dm. long, the slender rachis pubescent
on all sides; leaflets 11-13, sessile, oblong-lanceolate, 4-6 cm.
long, appressed-serrate, the serratures 15-17 on each margin,
apex subulate-acuminate, both faces nearly or quite glabrous,
the upper deep green, the lower glaucous : panicle very small,
seldom exceeding 5 cm. long, subpyramidal, its branches
densely and subtomentosely hirsute : drupelets of the ordinary
size and color.
Said to grow in crevices of rocks, near the head of Lake
Superior at Thompson, Minnesota, where it was collected in
flower in July, and in fruit in August, 1891, by J. H. Sandberg,
who afterwards distributed it under numbers 401 and 921. His
locality for it is the only one known. I would indicate as the
type specimen the fruiting one on sheet 19898 of the National
Herbarium. Happily Mr. Sandberg, unlike most collectors of
Rhus specimens, gathered this in both flower and fruit.
Prof. John M. Holzinger of the Normal School at Winona,
Minnesota, would have proposed this species as new, in his
paper published in the Minnesota Botanical Studies, part 8, in
1896, but was deterred by the opinion of some authority who
would have reduced R. typhina and R. glabra to one species,
with this as a connecting link between them.
I 88 GREENE
16. RHUS BOREALIS, sp. nov.
Shrub evidently large but not stout, at least as to the branches,
these smooth, glabrous, glaucous : leaves ample as to breadth,
but not greatly elongated, 3 dm. long, the usual hairy line of
the rachis quite hirsute, but other parts of the rachis, and also
the midvein of the leaflets on both faces showing a few pilose
hairs ; leaflets 13-17, subsessile, broad and approximate, oblong-
lanceolate, 8-1 1 cm. long, subulate-acuminate, coarsely and
closely subcrenate-serrate, the serratures about 14 on a side,
texture of leaflet uncommonly thin, upper face of a light but
rather lurid green, the lower glaucous almost to whiteness :
panicle not large, 11 cm. long in fruit, narrow-pyramidal, dis-
tinctly pedunculate, the peduncle and branches of panicle hir-
sute, the hairiness more or less distinctly retrorse : drupelets
larger than the average and of a lighter color, being bright
crimson.
Central Michigan near Alma, on dry ridges, collected Au-
gust 12, 1895, by Charles A. Davis, the type specimen in the
Herbarium of the Field Museum, Chicago. A fine species,
perhaps common enough in central Michigan, and probably
beyond the boundaries of the State southward, a region in which
little or no effective collecting has been done in late years. But
there is a poor flowering specimen, or fragment, in the National
Herbarium which, by the one leaf it bears, I can refer here. This
appears to have been sent by Mr. Beale, in 1899 ; but there is
nothing to indicate who collected it, or where. Although pubes-
cent, this bears no relation to R. hirta.
17. RHUS MEDIA, sp. nov.
Branches rather sharply angular in maturity and sparsely
dotted with small lenticels : leaves large but not elongated, only
2 dm. long, rachis not stout, whitish with bloom, glabrous except
as to a tomentulose line ; leaflets about 13, large, sessile, oblong
or subfalcate-oblong, broadly and abruptly pointed rather than
acuminate, appressed-serrate, the serratures 13-15 on a side,
the whole leaflet of firm texture and about 8 cm. long, 2-2.5
cm. wide, of a dull lightish green above, quite glaucous beneath :
A STUDY OF RHUS GLABRA 1 89
fruiting panicle rather lax, slender-peduncled and as if some-
what drooping but of pyramidal outline, its branches rather
finely pubescent ; drupelets of middle size, notably oblique,
acutish.
Inhabits the region of scattered woodlands and small prairies
in southern Michigan and northern Indiana and Illinois, if I
rightly refer to it rather numerous specimens, collected in various
places, all in young leaf and flower only. Such are in the her-
bariafrom Warrenville, 111., by L. M. Umbach, July 2, 1895, and
by Charles C. Deam at Bluffton, Indiana, 1897 ; but the type
sheet, No. 1 24146 of the Field Museum, a perfect fruiting speci-
men, is from Jackson County, Michigan, by S. H. and D. R.
Camp, September 19, 1898. Sheet 6072 of the same herbarium,
from Stark County, Illinois, may or may not be the same. Its
detached fruiting panicle may well belong here, but the one
leaf shown is attached to a flowering branch, and therefore im-
mature.
18. RHUS CISMONTANA, sp. nov.
Shrub doubtless low, all its parts reduced in size and rather
slender as to branches and leaf-rachis, all these pale and
glaucous: leaves 1.5-2 dm. long, ascending; leaflets 11-13,
not crowded, of a pallid green above but only glaucescent
beneath, mostly oblong and abruptly acuminate, 4-6 cm. long,
only subsessile, or some of the more basal leaflets definitely
petiolulate, sharply and rather closely serrate, the serratures
10-12 on each side, even the most mature state of foliage not
subcoriaceous, though firm : fruiting panicle about 9 cm. high,
pyramidal but narrowly so and compact ; outline of drupelets
slightly inclining to ovate, being a trifle longer than broad, not
depressed but rather acutish at summit.
Open hills of the more westerly parts of Nebraska and Kansas,
as well as probably in adjacent Colorado, if not Wyoming. The
type specimens are in U. S. Herbarium No. 210241, collected
by Mr. Rydberg in Thomas County, Nebraska, 1883 ; and Mr.
J. B. Norton's so-called R. glabra from Riley County, Kansas,
collected in 1895, appears to be quite the same; probably even
Mr. Clements' specimens from northeastern Nebraska, 1893,
I9O GREENE
belong here, for, while in these the foliage is larger, the leaflets
seem to have all the marks of R. cismontana, even to the peti-
olules, these being very evident.
19. RHUS SAMBUCINA, sp. nov.
Stem and branches unknown : leaves of few leaflets, the
whole leaf, including the rather long petiole, little more than 2
dm. long, the leaflets 11 or 13, approximate, large, 7-10 cm.
long, oblong-lanceolate, acutish at base and subpetiolulate, the
apical acumination rather abrupt and short, the sides with 11 or
12 quite large and sharp serratures, the texture of mature foliage
not known, color of upper face a pale glaucescent green, of the
lower only paler, with nothing of the white bloom of real R.
glabra: panicle not pyramidal even in flower, but rather oval,
or at most oval-subpyramidal, in fruit oval, decidedly lax, the
branches villous-pubescent ; drupelets of middle size.
Singular species, with broad short leaves made up of few and
much serrated leaflets, all pale green on both faces. The locality
of this is remote and but little known. The type specimens
are in Herbarium Field Museum, sheet 140404, and are from
near Piedmont, South Dakota, by Alice Pratt, June and August,
1895. Unfortunately only the young foliage is present; the
one fruiting panicle was preserved only as detached from the
branch ; yet this matches perfectly, in its peculiar branching
and laxity, the flowering panicles.
In the same herbarium, sheet 123606, are flowering speci-
mens of what seems to be the same, from southern Iowa,
Decatur County, T. J. Fitzpatrick, June 13, 1896.
20. RHUS NITENS, sp. nov.
Shrub stoutish, perhaps low, young branches and also petioles
and lower face of foliage merely glaucescent : leaves short and
short-petioled, the whole leaf barely 2 dm. long, the petiole and
rachis stout, ascending; leaflets 13-17, closely approximate,
seldom opposite, lance-oblong, 4.5-6.5 cm. long, subcoriaceous,
sessile by an obtuse base, the apex cuspidately acute rather than
acuminate, evenly but not deeply serrate, the serratures 10-12
A STUDY OF RHUS GLABRA I9I
on a side, upper face of a lightish green but somewhat polished,
the lower only pale, not whitened : fruiting panicle small, only
about 8 cm. high, definitely pyramidal, its branches short,
sparsely hirtellous : drupelets immature but perhaps full grown,
orbicular, or a little broader than high.
At 6000 feet in the mountains near Provo, Utah, July 10,
1894, as collected by Mr. Marcus E. Jones, his No. 5612 as in
the National Herbarium. This differs from all other far-western
species in that its foliage is almost as highly polished as that of
R. copallina.
21. RHUS TESSELLATA, sp. nov.
Shrub low, copiously and densely leafy, the leaves rigidly
ascending, about 2.5 dm. long, the pinnae approximate; leaflets
about 15, lance-oblong, 5-7 cm. long, not quite sessile, cuspi-
dately acuminate, evenly and quite sharply serrate, the serra-
tures 13-17 on a side, the texture subcoriaceous even at flowering
time, upper face very smooth and somewhat shining, in general
dark green, showing very prominently the fine whitish midvein
and veinlets, but some intervals between veinlets wholly of a
light green, exhibiting the whole surface as notably checkered,
lower face merely pale and glaucescent, not glaucous : panicle
small for the foliage ; fruit not seen.
Foothills of the Rocky Mountains in northern Colorado, at alti-
tudes of 6000 to 7000 feet; type specimen in U. S. Herbarium
No. 257466, collected by J. H. Cowen, July 20, 1895 ; no spe-
cial locality mentioned. The species by leaf characters alone
is a very good one, even if the checkering of dark and light
green be but accidental or occasional. The species here defined
may or may not include all the so-called R. glabra of eastern
Colorado mountains.
22. RHUS MACROTHYRSA Goodding.
Rhus macrothyrsa Good. Bot. Gaz. 37 : 56. 1904.
Shrub 1.5-2.5 m. high, glabrous except as to vigorous young
growing shoots, these at base ferruginous-tomentose : leaves
2-2.5 dm. long; leaflets 9-15, green above, not glaucous be-
neath, oblong-lanceolate, sessile, acuminate, sharply serrate :
I92 GREENE
fruiting panicle open, large, oblong-fusiform, 15-25 cm. long,
recurved, its branches coarsely pubescent : drupelets little com-
pressed, 3 mm. wide.
Calientes, Nevada, 1902, L. N. Goodding. No specimens
seen by the writer, but by the description the species must be
distinct enough, and probably local in southern Nevada.
23. RHUS ARGUTA, sp. nov.
Shrub said to be 1-3 m. high, the branches stoutish, smooth,
glabrous, glaucous even in full maturity ; leaves notably ascend-
ing rather than spreading, 3 dm. long, the petiole uncommonly
elongated and, like the rachis, very glaucous; leaflets 17 or 19,
narrowly oblong-linear or subfalcate, 6-8 cm. long, sessile by
an acutish base, closely, sharply and saliently serrate, the ser-
ratures 15 or 16 on a side, the acumination long and narrow,
upper face deep green but dull, the transverse veins conspicu-
ously paler, lower face very glaucous : panicle not large, 10-12
cm. high, pyramidal, its branches hirsutulous ; drupelets of the
largest.
Species of the Pacific slope, apparently common in the
Columbia River region, at least eastward ; very possibly an
aggregate, resolvable into several ; but the type of the above
diagnosis is from Rhea Creek, Morrow County, Oregon, and
was collected by J. B. Leiberg, September 11, 1894, his No.
893 as in U. S. Herbarium. The following, all from western
Washington, are more or less true to this type : sheet 93075 in
Herbarium Field Museum, from near Spokane, in flower only ;
sheet 93076 of the same, from the same region with lax pyram-
idal panicle very much larger, leaflets larger, greener on both
faces and by no means sharply serrate ; A. D. E. Elmer,
Wawawai, 1897 ; Frank Kreager, Spokane County, 1902 ;
Sandberg & Leiberg, Rock Island, 1893, and Robert Horner,
Waitsburg, 1897, these last all as in U. S. Herbarium, likewise
from Idaho, A. A. Heller, Nez Perces County, 1896, his No.
3421. This is quite true to the type as to foliage, but in flower
only; a fruiting specimen, from Salmon River, Vernon Bailey,
1895, with leaflets not so typical.
A STUDY OF RHUS GLABRA 193
Among all these there is nothing of Torrey's Rhus glabra^
var. occidentals. Nearly all that I have seen of Pacific coast
material which matches that of the Wilkes Expedition, comes
not from Oregon or Washington, but from British Columbia.
24. RHUS APRICA, sp. nov.
Dimensions of shrub, and characters of branches unknown :
leaves as a whole remarkably broad and short, the leaflets being
few and approximate but large, subcoriaceous, deep green
above, light green beneath, but without bloom ; leaflets about
15, oblong, 6-8 cm. long, obtuse at base and sessile, at apex
only cuspidately acute, not acuminate, very evenly and quite
distinctly though not sharply serrate, the serratures 10 or n on
each margin : panicle pyramidal, small, about 8 cm. high, its
branches only sparingly and obscurely villous-pubescent ; drupe-
lets rather large.
Very well marked by its few and large leaflets green on both
faces; but known only as collected by M. W. Gorman, on
Camas Creek in the Washington State Forest Reserve, August
20, 1897. It is said to occupy dry open grassy slopes. The
type specimen is in U. S. Herbarium. Its label bears Mr.
Gorman's collection number 632.
25. RHUS OCCIDENT ALIS (Torrey).
Rhus glabra occidentalis Torr. in Bot. Wilkes' Exp. 257.
1874.
Only flowers and young foliage known : leaflets (in what
should be the type specimen, U. S. Herbarium sheet No. 19819)
11-13, oblong-lanceolate, sessile, notably acuminate, beneath
only glaucescent ; the panicle small and very slender peduncled ;
even the branch slender, but quite glaucous.
The label bears, in the handwriting of Asa Gray, the legend,
"Okanogan, Wash. Territory."
The Okanogan region lies partly in Washington and partly in
British Columbia, and all the more recent specimens seen by the
writer which match the type are from the Canadian part of the
region. Sheet 4471 of the Canadian Survey Herbarium, Arrow
194 GREENE
Head Lake, near Lake Okanogan, is every way true to the
type, except that the leaflets are less numerous ; nine in most of
the leaves and none with a greater number, a few having seven
only. In the same herbarium 4473, from Spence's Bridge, in
the same general region, has mostly 13 leaflets. The like is
true in the case of number 63749, collected at Cascade, B. C,
by Mr. J. M. Macoun in 1902. But all these specimens are in
one and the same unsatisfactory condition of early flowering,
with foliage, of course, not fully grown. They indicate, how-
ever, a northerly species, from which the two Washington spe-
cies herein characterized are sufficiently distinct. Not, however,
until mature foliage and fruiting panicles of it shall be brought
to light can R. occidentalis be properly described.
26. RHUS ALBIDA, sp. nov.
Probably low, the branches not robust, very light-colored
and, with the rachis and lower face of leaves, much whitened
with bloom, even the upper face of foliage of a pale color and
glaucescent : leaves 1.5-2.5 dm. long; leaflets about 13, not
crowded, not deflected but spreading, subsessile, 4-6 cm. long,
oval to oblong-lanceolate, abruptly acute or short-acuminate,
saliently serrate, the serratures 10-14 on each side : fruiting
panicle about 1 dm. high and quite broadly pyramidal, its
branches only very delicately but rather densely velvety : drupe-
lets much compressed and acutish.
As far as known this very beautiful Rhus is local on the San
Francisco Mountain not far from Flagstaff in northern Arizona.
The type specimen, sheet No. 410696 of the National Her-
barium, was collected there, at an altitude of between 6000 and
7000 feet, August 18, 1901, by J. B. Leiberg, his distribution
No. 587 1. A perfect male flowering specimen is in my own
herbarium, as collected by myself at the same station, July 13,
1889. Again, National Herbarium sheet 334404 holds a flower-
ing branch from the same locality by D. T. MacDougal, his dis-
tribution No. 309, July 18, 1898. This, too, from an altitude
of about 7000 feet. The late date of its flowering, as an ally
of Rhus glabra in the generally torrid climate of Arizona, indi-
cates the subalpine character of its habitat.
A STUDY OF RHUS GLABRA 1 95
27. RHUS ELEGANTULA, sp. nov.
Branches slender, glabrous, of a distinctly pinkish brown
underneath a coat of bloom: leaves small, 1.2- 1.8 dm. long,
the slender rachis quite white with bloom, its villous line very
marked; leaflets 11-15, loosely arranged, spreading or slightly
deflected, distinctly petiolulate, 4-6 cm. long, narrowly subfal-
cate-lanceolate, at least the long and slender acumination falcate,
sometimes the whole leaflet, the serratures, about 8 on a side,
more or less sharply prominent, the texture rather firm, color of
upper face pale bluish-green, the lower whitish with bloom :
fruiting panicle large in proportion to the foliage, commonly
more than 1 dm. high, pyramidal but narrowly so, its branches
thinly villous with ascending or spreading hairs : drupelets
small, arranged upon simple racemose branches of the panicle,
compressed, acutish.
Mountains of extreme southern Arizona along the Mexican
boundary, the typical specimens from about Fort Apache, by
Edward Palmer, June, 1890 ; these on sheet 19808 of the
National Herbarium ; others distributed by Dr. Palmer under
his No. 585. Probably the same as a specimen from the Santa
Catalina Mountains, September, 1896 by J. W. Tourney, U. S.
Herbarium sheet 441724. Lastly rather larger specimens, but
otherwise true to the character, have come in this season from
the Huachuca Mountains, sent by Mr. J. C. Blumer, who col-
lected them late in August, 1906.
28. RHUS SORBIFOLIA, sp nov.
Shrub apparently low and not stout, the young branches and
lower face of foliage not whitened, hardly paler than glauces-
cent : leaves small, only 1-2 dm. long, spreading away from
the stem divaricately, or even a trifle deflected, the petiole and
rachis rather slender; leaflets few, only 9 or 11 and loosely
arranged, dull deep green above, glaucescent beneath, of small
size, 2.5-6 cm. long, oval to oblong-lanceolate, sessile by an
abruptly acutish base, at apex subulate pointed rather than
acuminate, rather remotely and sharply serrate, the serratures
only 7-9 on each margin : panicle of staminate flowers pyram-
I96 GREENE
idal, 12 cm. long : sepals triangular, acute; petals twice as
long, oblong, obtuse, the anthers equaling them.
Type from mountains west of Las Vegas, New Mexico, G.
R. Vasey, 1881 ; U. S. Herbarium No. 195 10. Species with
most characteristic habit and foliage.
29. RHUS ASPLENIFOLIA, sp. nov.
Shrub evidently dwarf or at least low, the leafy branches
short, slender, tortuous, glabrous, glaucous : leaves small,
about 1.5 dm. long, the rachis slender, deeply and narrowly
furrowed and the hairy line obvious ; leaflets only 7-9, pale
green above, moderately glaucous beneath, oblong-lanceolate to
lanceolate, 3.5-5.5 cm. long; subsessile, acuminate, very irreg-
ularly and somewhat incisely serrate, even coarsely so, the
serratures now and then so deep and large as to amount to lobes
rather than serratures : only a staminate panicle seen, this
narrowly pyramidal, 5 cm. long.
Type from Wolf Creek, Wyoming, July 12, 1896, A. Nelson,
distributed to U. S. Herbarium, under No. 2303, mounted on
U. S. Herbarium sheet 285144. Manifestly intermediate be-
tween the Nebraskan R. cismontana and the characteristic
species of Arizona ; the foliage peculiar.
PROCEEDINGS
OF THE
WASHINGTON ACADEMY OF SCIENCES
Vol. VIII, pp. 197-403. February 13, 1907.
ASPECTS OF KINETIC EVOLUTION.
By O. F. Cook.
The kinetic theory of evolution finds in the facts of organic
development indications that the characters of species change
spontaneously, or without environmental causation. Evolution-
ary progress is further conceived as accomplished through the
union of the normally diverse individual members of species into
a coherent network of interbreeding lines of descent, rather than
by the isolation of variant individuals or by the selective restric-
tion of descent to individuals possessing particular characters.
Former theories have undertaken to explain the method of
evolution by reference to the dendritic figure of descent as shown
in the ever-branching relationships of species, genera and fami-
lies. The kinetic interpretation of the evolutionary process is
based on what may be called the intraspecific figure of descent,
the relationship of organisms inside the species, which is reticu-
lar or net-like, and not tree-like.
Theories based on the dendritic conception of descent may
also be described as differential ; that is, they have given atten-
tion chiefly to the problems of distinction and separation of
organic groups. The kinetic theory is integral or synthetic,
and conceives the evolutionary process as conducted by the
accumulation and combination of the variations which appear
among the members of the species.
These simple distinctions are fundamental, and will neces-
sitate an extensive readjustment of methods of thought and
investigation in the field of evolution.
I98 COOK
Various aspects of the kinetic theory have been presented in
earlier essays, of which the present chapters are a continuation.
Indeed, it is likely to become apparent to the reader that they
have been written at different times and that they often lack
unity and consistency. The same ground has in some cases
been traversed repeatedly and in different directions, but the
frequent restatement of the same distinctions appears to be
necessary in the development of so large and complicated a
subject. My thanks are due Mr. Walter T. Swingle for much
helpful interest and criticism.
1. KINETIC EVOLUTION AND THE FITNESS PROBLEM.
The theory that evolution is caused by natural selection and
the survival of the fittest is now commonly admitted to be inad-
equate, but our studies tend, as usual, to follow the beaten paths
of thought, and adjust themselves only with reluctance to new
interpretations. The point at which the selection theory becomes
obviously deficient is that it does not account for the fitness to
which the evolutionary progress is ascribed. This has given
rise to the attempt in recent years to penetrate farther into what
has been called " the problem of fitness," on the natural assump-
tion that more light could certainly be reached in the quarter
whence came the first suggestions of evolutionary illumination.
Nevertheless, those who have followed closely on the route of
natural selection have not yet come through into regions of clear
vision.
Fitness is the primary idea of the doctrine of evolution by
selection. Fitness affords the cogs, as it were, by which evolu-
tion is supposed to be worked by the environment. Even if we
were to admit, for the argument, that evolutionary motion could
be caused by selection towards greater fitness, the evolutionary
factory would still lack the very important facility for providing
these cogs of fitness by which the environment could gain a
hold upon the species and roll them along. Some selective
evolutionists have assumed that environment could form the cogs
by impressing itself upon the species, and others that the species
could, as it were, wrinkle itself in response to external stimuli,
and thus give the environment a selective impingement.
ASPECTS OF KINETIC EVOLUTION 1 99
These suggestions have not been able to retain the full con-
fidence of biologists for the selective theory, as witness the
recent remarkable diversions towards Mendelism and muta-
tionism. The prompt acceptance of these doctrines by so many
students of evolution is not justified by any indication of general
pertinence for the facts on which they are based. They met
with immediate welcome because they afforded a suggestion,
at least, of methods by which new characters or character-com-
binations could be produced. They promised, in other words,
the long-needed supplement of the selective theory, the cogs
which selection might turn.
The kinetic theory recognizes that evolution does not depend
upon selection nor upon the environment, and still less upon
mutation and Mendelism. The evolutionary causes are in the
species, not in the environments. They are resident, moreover,
in species as constituted in nature, and are exemplified only
abnormally in the phenomena which become prominent in the
close-bred domesticated plants to which the studies of Mendel
and De Vries were mostly directed.
TWO TYPES OF ORGANIC FITNESS.
The current belief in the environmental causation of evolution
is largely due to the confusion of two different kinds of organic
fitness, (i) The general fitness of the species for the environ-
ments in which they exist ; and (2) the special fitness or power
of adjustment of the individual organisms to particular condi-
tions which they may encounter. An interesting example of
the extent to which these two distinct phenomena have been
confused may be found in so well known a work of reference
as the Standard Dictionary. Adaptation is defined as "an ad-
vantageous conformation of an organism to changes in its envi-
ronments," but the quotation given to illustrate the use of the
word in this sense alludes to the " special adaptations " of deep-
sea organisms. The definition applies to the second type, fit-
ness by individual adjustment, while the example refers only to
the first type, the general fitness of the species, genus or family
as a whole.
No method has been suggested whereby either type of fitness
Proc. Wash. Acad. Sci., December, 1906.
200 COOK
can be caused by the environment, but the fact that individual
adjustments do have definite relations to the environment, has
served to sustain a belief in the environmental causation of evo-
lution. All species have, of course, fitness for their environ-
ments ; otherwise they would not continue to exist. They must
be more fit than other species which have had access to the
same environments, or they would be driven out. Neverthe-
less, inside of the general environment, or place of the species in
the economy of nature, there is still a very great diversity of
individual experience to which each organism must adjust itself.
The environment at all times determines the relation of fitness,
but the characters which afford the fitness are as truly results of
evolution as any other characters. It has not been shown that
they are caused by the environment or that they can be inherited
from it.
The doctrine of environmental causation of evolution supports
one assumption by another equally baseless. It takes for
granted that adjustment differences between individuals of the
same species are caused by the environmental differences which
are met by these same adjustments. It also takes for granted
that the general fitness or adaptation of the species is merely a
product of the fitness of individual adjustment, whereas there
are two phenomena of fitness which are quite distinct in their
relations to the problem of evolutionary causes, though neither
of them affords any special indication regarding the nature of
such causes. The adjustment of individuals to differences of
environment is a form of organic elasticity which permits lateral
vibrations or displacements of characters, while the fitness of a
species or genus as a whole is, obviously, an accomplished result
of evolution instead of being a formative principle or cause.
ADAPTIVE VERSATILITY OF ORGANISMS.
To say, as has been the custom of writers on evolution, that
organisms are plastic or susceptible of environmental influences,
is only half of the truth. Organisms are not merely plastic,
but versatile. Under different conditions they are able to grow
in different ways, and often in ways which qualify them better
for existence in these particular conditions, though not neces-
ASPECTS OF KINETIC EVOLUTION 201
sarily so. A Guatemalan variety of the cotton plant takes on
in Texas a robust, upright habit of growth very distinct from
that of its Central American ancestor. It might be held that
this deviation from the previous type serves a purpose in the
internal economy of the plants, in enabling them to carry on
more efficiently the process of vegetative development. Never-
theless, it cannot be reckoned as a truly adaptive change, since
it does not improve the chances of the survival of the variety in
the new environment. These very large and vigorous plants
are relatively infertile, and ripen their fruits much later than
those which retain the normal low-growing parental form. This
behavior of the cotton plant is not the exception, but accords
with a general tendency of tropical plants toward excessive
vegetative development when first planted in northern latitudes.
The longer days and higher temperatures of our summer seasons
are not utilized for earlier and larger production of fruit, but are
wasted in riotous vegetative expansion often cut short by frost
before a single seed has been formed.
New environments may also throw plants into a condition of
morphological instability* which can scarcely have any relation
to adaptation, since the result is an endless diversity of abrupt
variations or mutations along many different lines, including the
most opposite. The hereditary coherence of the species or
variety is lost, and the individuals scatter, as it were, in all direc-
tions. This explosive type of variation is occasioned, obviously,
by changes of environment, but it is equally obvious that one
and the same change of environment cannot be directly described
as having caused many diverse variations ; it need only be
thought of as having occasioned an abnormal intensification of
normal individual diversity.
In some manner, quite unknown as yet, changes of conditions
do induce changes of methods of development, but to infer that
these changes are always advantageous, or that the external
causes actuate the modified development of the organisms, is
bad logic and worse biology.
Curiously enough, it is only at one particular point that such
reckless conclusions are indulged. When we find a dozen dif-
ferent species of plants growing on the same square yard of soil,
202 COOK
it does not occur to us to suppose that their diversities are due
to the different conditions under which they have grown, for the
conditions are the same. We accept without debate the fact that
the plants are developing each according to the methods of its
own species. It is only when we find plants of the same species
following different methods of growth when under different con_
ditions that we can be betrayed into supposing that the condi-
tions are producing the characters of the organisms. In reality
this reasoning has no more propriety when we compare a plant
or an animal with another member of its own species than when
we compare it with a member of a different species.
As long as the adjustments are physiological only, we do not
find it necessary to marvel, but when they become appreciable
from the morphological standpoint our interest is aroused. And
when accommodations cause taxonomic difficulties by affecting
the characters by which we have described species, some are
ready to believe that environment must be responsible for evo-
lution because it can be alleged to change the characters of
species. To reach this conclusion the amassing of detailed
knowledge of plants and animals was superfluous. It could
have been based quite as logically on the fact that rain " causes "
us to carry umbrellas, and to wear waterproof coats. The
African variety of mankind adopts the reverse policy, but no
less appropriate to the occasion. He discards all of his scanty
wardrobe and gives his naked skin a coat of palm oil. The
birds can not change or take off their feathers, but their own
organization provides a convenient supply of oil, and an instinct
to use it when needed. Plants can neither go in when it rains
nor oil themselves, but many plants grow a water-shedding coat
of wax or of fine hairs on the upper surfaces of their leaves.
All species of plants and animals have, as already remarked,
not only their general specific methods of development, but they
have in addition certain ranges of adjustment to the different
conditions under which they are able to exist. The environ-
mental qualifications of a species are not to be represented by a
single point, but by maximal and minimal boundaries, like the
geographical latitudes and longitudes which may be used to
indicate its position on the earth's surface.
ASPECTS OF KINETIC EVOLUTION 203
It is usually possible to discover somewhere between the pro-
hibitive extremes an optimum condition, or a locality where the
fullest development of the species takes place. Unfavorable
conditions multiply as the boundaries are approached, and
development is variously impeded and restricted, but surely the
ability of the organisms to accept or to avoid a measure of such
restrictions and to achieve an existence in spite of them, is small
warrant for concluding that the conditions afford an adequate
biological explanation of the characters. Still less are we justi-
fied in supposing that the unfavorable peripheral conditions are
any more truly causative than the central optima. Adverse cir-
cumstances, by restricting development, would seem rather to
require the organism to put forth more active energies, not of
development merely, but of accommodation as well. And yet
it is in abnormal features arising under abnormal conditions
that the evidences of environmental causation have been chiefly
found.
If each species wrere restricted to an absolute uniformity of
conditions and materials, the doctrine of environmental causa-
tion would have had at least a partial justification, whereas the
versatility of organisms, instead of demonstrating environmental
causation, renders it highly improbable. The individual mem-
bers of species in nature are different, even under the same con-
ditions ; why should we expect them to be alike under different
conditions?
For some species the range of environmental conditions is
very broad, in others very narrow. The fitness of the latter
type of species may appear to be greater than the former, in the
sense of being more highly specialized. It is not, however, the
extent of narrowly specialized fitness, but the extent of widely
varied adjustment which generally determines the range of dis-
tribution and the numerical prosperity of the species.
In a general way the power of a species to accommodate
itself to different environments might be held to favor evolution,
because it would improve the chances of sustained numerical
prosperity, which is an evolutionary advantage. It does not
appear, however, that " plasticity" wrould be especially helpful
in the evolution of the particular characters which might be
204 COOK
modified in adjustments to the different conditions. The
"plasticity" might hinder, even, as Professor Metcalf has
recently pointed out, for the ability of the species to accom-
modate itself promptly would render unnecessary any perma-
nent progress in the direction of these particular changes.1
Of permanent effects arising from the influence of environ-
ment upon adjustment changes, there would remain only the
possibility that a species which had once possessed a wide range
of accommodation, might lose this by long disuse, and might
thus become more narrowly specialized as a result of environ-
mental influence. Thus an amphibious species, if confined
long enough to a strictly terrestrial habitat, might forget, as it
were, how to grow in water.
That experiments have not yet demonstrated such an effect
does not justify a general denial of the possibility. The phe-
nomenon would be no less real if it took a hundred or a thousand
years to produce it than if it required only five or ten.2 But in
any case the result would be negative rather than positive,
involving a diminution of the powers of the species rather than
an enlargement of them. There would be a loss of characters
instead of an addition, and no occasion to infer that environment
had aided evolution. The case would be quite analogous with
the influence of environment through natural selection, which is
likewise not constructive, but wholly restrictive.
Much of the existing terminology of evolutionary discussion
is calculated to commit us in advance to the doctrine that the
adjustment is caused by the environment, whereas the fact is
that the organisms are active instead of passive, and are able to
put forth their own efforts toward adjustment to the varied
external circumstances. It is only in a loose and figurative
sense that the environment can be said to cause the adaptive
adjustments. The arctic climate "causes" the Esquimaux to
clothe themselves in furs, but it does not skin the fur-bearing
'Metcalf, M. M., 1906. The Influence of Plasticity of Organisms upon Evo-
lution, Science, N. S. 23 : 789.
2 An additional reason for caution in denying the possibility of a loss of the
power of accommodation from disuse is found in the phenomenon of " fixing the
type" of a variety by selection. The normal diversity tends to disappear when
only one carefully selected type of the variety is bred for several generations.
ASPECTS OF KINETIC EVOLUTION 205
animals and sew their pelts together. We say, similarly, that
a desert climate "causes" a plant to become more hairy, but
this is as yet a mere figment of speech. We have no notion of
the chain of biological events coming between the dryness and
the hairs. We can appreciate the advantage of the reduced
transpiration, but we do not know how the plant puts on the
additional protection against the dry atmosphere.
ALTERNATIVE ADJUSTMENT CHARACTERS.
We shall hardly come to understand aright the relation of
fitness to evolution until we accustom ourselves to thinking of
these variations of accommodation or so-called " environmental
reactions " as expressions of the power of the plant or animal to
choose, as it were, between alternative methods of growing and
of conducting the functions of existence.
Organic versatility, plasticity, or whatever it may be called,
does not conduce to the rapid development of specialized char-
acters (adaptation), or to the multiplication of new groups (specia-
tion), but it is undoubtedly of vast practical importance in the
economy of species. Some species have little of this readiness
of adjustment, while others are able to adopt a great variety of
forms and can thus take advantage of opportunities of existence
under a great diversity of natural conditions. By keeping open
a larger number of alternative lines of progress, the power of
accommodation very greatly increases the ability of species to
solve their environmental problems. The environment is unable
to prevent such groups from accumulating many kinds of varia-
tions or from making trial of them, as it were, in a great variety
of combinations. This affords the best of opportunities for the
construction of new types with enlarged environmental resources,
instead of providing merely for the differentiation of narrowly
localized and specialized species.
The different characters assumed by a species in accommodat-
ing itself to different environments are not less characters of the
species because they are shown simultaneously than if they
were developed in successive epochs of evolution. The only
sense in which they are not characters of the species is the nar-
rowly taxonomic one in which species are treated as having
206 COOK
" identity of form and structure." Characters changed when
conditions change are to be reckoned as alternative characters,
no less than sexual differences. Indeed, the sex determination
itself sometimes appears as an incident of environmental adjust-
ment.1
Alternation of generations and dimorphism afford further
analogies. There is no warrant for the supposition that the evo-
lutionary status of any of these kinds of characters is different
from that of characters which appear in all individuals of the
species. Professor Metcalf says :
"A high degree of plasticity hinders evolution b}r selection,
of characters similar to those acquired by plastic response to the
environmental influences."
This seems to imply that alternative characters which appear
responsively have to be acquired over again by selection in order
to become genuine results of evolution. If this were true selec-
tion might indeed be impeded. Such a distinction is not illogical,
but it applies only in the metaphysical systems of evolution
which assume that selection causes evolution and that environ-
ment causes characters.
A character which can be varied readily and which thus
increases the power of the species to accommodate itself to varied
environments is much more valuable than one which is not
capable of such adjustment, and there is no reason to suppose
that selection would favor the development of a non-adjustable
form of the same character. Moreover, both the character itself
and its adjustability or " plasticity" are already genuine evolu-
tionary results reached by the same processes as any other
characters.
It is only when we have allowed our meanings to slip from
harmless abstractions to fictitious concretions that we explain
evolution by selection and characters by plastic response to
environmental influences. However unobjectionable such ex-
pressions may be if used in sufficiently general, literary senses,
they are dangerously misleading as the basis of physiological
inferences, because they take for granted unproved and improb-
able assumptions, such as the causing of characters by environ-
1 See Fink, B., 1906. Plant World, 9 : 183.
ASPECTS OF KINETIC EVOLUTION 20J
ment and the causing of evolution by selection, assumptions
which rest in turn on the still more general and obviously
erroneous assumption that species are normally uniform and
stationary, whereas they are neither. It will some day be
reckoned as one of the paradoxical incidents of biological history
that this static theory, which is simply a relic of pre-Darwinian
doctrine of special creation, should have been cherished most
jealously by the ultra-materialistic school of biology.
ENVIRONMENTAL ADJUSTMENT ANALOGOUS TO LOCOMOTION.
The power of locomotion is a very important adaptive char-
acter of organisms because it gives great freedom of choice of
environment. The hippopotamus, for example, is an aquatic
animal, but the brief nocturnal excursions to the grassy river-
bank or to the neighboring rice farm keep the huge bulk alive.
Being animals ourselves and accustomed to use our powers of
locomotion to change our environments, we fail to appreciate
this form of adaptation and view with much wonder the fact
that organic types have other means of dealing with environ-
mental problems.
Unable to change their environments, they have the alterna-
tive power of changing their characters and of behaving in dif-
ferent ways in different environments. Some of the most
striking instances of this kind are afforded by a series of plants
(belonging to diverse and unrelated natural families) which can
live either in water or on land, and which have two sets of char-
acters appropriate to the alternative habitats. On land they have
the characters of other land plants, in water the characters of
other aquatics. The mystery is that they can change from the
one to the other. Some have imagined that if we could find out
how this change is accomplished we would have penetrated to
the causes of evolutionary changes in general. The analogy
between locomotion and environmental adjustment has been
overlooked, along with the probability that both these methods
of adjustment have been attained by the same evolutionary
processes. They are finished products and not merely charac-
ters in the making.
The elasticity of muscular tissues is onlv one of the many
208 COOK
methods by which organisms are able to place themselves in
more advantageous relations to their environment, and to man-
ifest a power of choice with reference to external circumstances.
Even among the simplest types of organic structure this faculty
is definitely in evidence. The slime-moulds (myxomycetes) pass
the vegetative period of their existence in rotten wood or other
decaying vegetable matter. By simple amoeboid movements
the naked, softly slimy protoplasm, of which these primitive
organisms consist, is able to creep out at maturity to an exposed
surface before giving up its water and separating itself into dry,
wind-blown spores.
To better accomplish the work of dissemination many of the
myxomycetes have the hereditary talent or instinct to subdivide
their colony into small masses, each of which builds itself a
stalk to climb upon. There is then built out from this stalk a
network of threads to hold the spores so that they can be sifted
out and scattered gradually by the wind, instead of falling at
once to the ground. The stalk-building myxomycetes do not
work, however, by any arbitrary or merely mechanical stand-
ards. When the surface of the decaying log over which they
have spread themselves at maturity is uneven, so that a part of
them must stand in wet depressions or chinks of the bark, these
have longer stems than the others. In some species only those
in the wet situations will have stems, while those in exposed
places will remain seated directly on the substratum.
The building of the stem and the climbing up are not two dif-
ferent adaptations, but are merely the two aspects of the same
act of adjustment to environmental conditions. In some con-
nections it may do no harm to say that the wet situation causes
the long stem and causes the slime mould to climb up, but for
biological purposes all such statements must mean very little
until we know something of the chain of events between the
wetness and the building and climbing. Still less defensible is
the policy of saying that the stem is " caused" by the environ-
ment while the motion is "spontaneous" in the organism.
Mechanical biologists would be consistent, at least, in ascribing
both acts to " stimuli."
The myxomycetes have long been objects of special interest in
ASPECTS OF KINETIC EVOLUTION 20O.
the scientific world because they have been thought to combine
the characters of animals and of plants and thus to afford a con-
necting link between the two organic kingdoms. Beginning with
such a primitive and undifferentiated form of life, it is easy to think
of the animals as gradually specializing the power of locomo-
tion, the plants the alternative powers of morphological and
physiological adjustment. The animals excel in seeking their
own environments, the plants in the ability to take what comes.
The purpose of this rehearsal of elementary facts is merely
to convey, if possible, the suggestion of an idea of organic
elasticity, so to speak, of which muscular contractility and loco-
motion are the extreme specializations, but which extends into
all departments of organic activity, morphological as well as
physiological. Some may still prefer to say that the environ-
ment " causes" the adjustments to be made, but it will remain
none the less true that the organisms themselves make the
adjustments.
Zoologists speculate on such questions as whether the eggs of
Vancouver wood-peckers, if transferred to Arizona, would hatch
Arizona wood-peckers, or whether the transferred individuals
would gain Arizona characters in a few generations. What the
wood-peckers might or might not do depends on the amount of
organic elasticity which they may happen to possess, but the ex-
periment is unnecessary for answering the general question,
since plants show a high development of these powers of prompt
adjustment to diverse conditions. It is not even necessary that the
eggs be hatched in Arizona. Many plants, as already noted,
can adjust themselves to such changes at any stage of their ex-
istence, and are regularly accustomed to do so. They are both
fish and flesh. In water they have the form, structure and func-
tions of other strictly aquatic species ; on land they are equally
ready to behave as terrestrial species.
Needless to say, hundreds of plants have been described as
new species which proved afterward to be only land, water,
shade, sun, or other environmental forms of previously known
species, and such unnecessary "species" continue to be de-
scribed. There is no way to ascertain from a few her-
barium specimens whether their differences represent the results
210 COOK
of evolution as isolated groups or are merely adjustments to
different conditions, any more than it could be ascertained with-
out local study whether an individual bird-skin represented a
regular resident, a migrant, or a still more accidental visitor.
In this merely taxonomic or nomenclatorial sense the envi-
ronment can be said to cause species, but such a statement has
no warrant in the field of evolution. If we have undertaken to
diagnose species by characters which represent merely environ-
mental adjustments our only course for the future is to recognize
and rectify our mistakes, and not attempt to utilize them as the
basis of doctrines of environmental causes of evolution.
For physiological and evolutionary purposes the species is not
to be thought of in the mere systematic sense, as represented by
the original specimen or even by the form in which the plant
appears in what are supposed to be its normal conditions. The
■physiological and evolutionary species covers all the forms tinder
zvhich the organism can maintain itself and complete its life-
history, to say nothing of the definitely abnormal results shown
when conditions are too adverse.
Adjustment characters, as such, are not inherited, according
to the usual definition of inheritance, that is, they are not
necessarily repeated in each generation, but are readily recover-
able when needed, even after long periods of time. The plant
or animal if kept for many generations under the same envi-
ronment may continue to show the same adjustment, but this
may be completely changed by transfer to other conditions of
growth. Thus at 4000 feet coffee has a more strict and upright
habit of growth, darker, firmer foliage and larger seeds than
at 2000 feet, but if seedlings from the two altitudes be exchanged
they always grow into trees showing the characters appropriate
to their new situations.
It appears, therefore, that both kinds of fitness, the general
features which adapt the species as a whole to its place in nature,
and the special powers of adjustment which assure to the indi-
vidual a certain latitude of environmental opportunities, are
normal characters of species, quite as much as those which
have no such acute relations to the environment. Unless we
can resume and carry to completion the Darwinian task of
ASPECTS OF KINETIC EVOLUTION 211
proving that all characters have arisen as useful adaptations,
other methods and causes of evolution must be sought. To
question the adequacy of selective and environmental causes is
to admit at least the possibility that such theories are completely
erroneous, for any causes which are adequate to produce and
develop useless characters can produce, a fortiori^ useful ones.
There are enough adaptations to occupy many naturalists for
many life-times. They can, if they prefer, live and die without
hesitating to entertain doubts of the efficiency of enviromental
causation. And yet the fact will remain that the great majority
of the differences between related species and between the indi-
viduals of the same species have no environmental utility at all,
and are quite unlikely to have had any. This is not to be as-
certained by denying or affirming the theoretical utility or use-
lessness of a few selected characters, but by observing whole
orders and classes of organisms to learn the general proportions
between differences of characters and differences of environ-
mental relations, and by perceiving that the former vastly out-
number the latter.
The fitness which the individuals of a species of plants can
attain by adjusting themselves to the special conditions is, as we
have seen, a kind of stepping aside, a morphological motion,
put forth by the organism itself as truly as are the coordinated
muscular acts which enable the higher animals to move
from place to place and thus to choose their own environ-
ments. A perennial plant must arrange to tolerate whatever
extremes of temperature, moisture, and exposure to sunlight its
habitat may provide. Its powers of making such adjustments
may be reckoned as functions of its tissues and organs in quite
the same sense as locomotion and sustained high temperature
are functions of the animal organism. The plant withstands a
temperature range of a hundred degrees and more, but mammals
and birds establish their own temperatures and keep them ad-
justed to tenths of degrees. It is a regular custom for many of
them to travel annually for thousands of miles to find congenial
conditions. The arctic plover is said to fly every year the whole
length of the continent from Greenland to Patagonia and back
again.1
' Knowlton, F. H. 1902. The Journeyings of Birds, Pop. Sci. Mon. 60 : 323.
212 COOK
The power to make or maintain such adjustments, whether
by changes of muscular or other tissues, may well be reckoned
as a character of a species, but there is nothing to show that
morphological powers of adjustment are different in any evolu-
tionary respect from the others, or that they afford any warrant
for the inference that evolutionary changes are due to environ-
mental differences, or that they arise first as adjustments to
external conditions. Any change which increases fitness has
the advantage of selective encouragement, and is thus able to
exert a larger influence in determining the evolutionary course
of the species, so that evolution tends ever toward greater fitness,
though other lines of progress are not excluded. If changes
could take place only in adaptive characters, the difficulty of
maintaining fitness would be greatly increased, because charac-
ters would need to be useful from their very inception, whereas
they have now the possibility of becoming useful at any stage
of their expression. Selection begins to discriminate against a
character only when it has become harmful.
SELECTIVE PERFECTION OF ADAPTATIONS.
It is not intended to imply that there are never any direct
reactions to environmental influences or that such reactions are
never of advantage to the organism. The Washingtonia palm
of the deserts of Southern California has a complete covering
of dead leaves over the whole length of its trunk, and secures,
no doubt, a very desirable protection against the extreme heat
and dryness. The retention of the leaves is made possible
because the climate is dry. Palms native in humid regions
usually drop their dead leaves promptly, but if not they are soon
weakened by decay and fall away. Such coincidences could
scarcely be avoided in any relations so complex as those of
biology, but it does not appear that they are of a nature or fre-
quency to give them more than a very subsidiary importance in
evolution.
A plant or animal that encounters adverse conditions and is
not able to obtain sufficient food will remain stunted. This
small size is an advantage, however, in a region where food is
scarce or uncertain. Nevertheless it is those individuals of the
ASPECTS OF KINETIC EVOLUTION 213
species which are naturally small, that is smaller than most of
their kind, even under favorable conditions, which would be
able to make this reaction most successful, since they would be
less stunted, or less abnormal, than the others. Thus even the
simplest cases of environmental reaction are not to be separated,
for evolutionary purposes, from the phenomena of normal diver-
sity among the members of the species. Selection, as far as it
influences the movement of the species toward adaptation, works
through this intraspecific diversity rather than through the
environmental reactions. The reactions are not selected, but
the individuals which happen to excel in making the reactions.
Another case illustrating the same principles is that of the
inconspicuous colors of the desert animals. Selection is sup-
posed to have produced these inconspicuous colors because they
conceal the animals, and thus give them protection against the
enemies to which they would otherwise be very much exposed.
The insecurity of this assumption becomes apparent as soon as
we consider the equally striking fact of nature that desert plants
also have the same series of dull shades of pale grayish and
brownish colors. It would seem, therefore, that evolutionary
inferences regarding the colors of the desert organisms will
have to provide for the plants as well as for the animals, and
that they must not depend wholly upon the idea of protection
against predaceous foes.
From the plants it is very easy to gain another clue to
causes of the obscure coloration. The vegetative tissues of
desert plants are usually as green as those of species native in
humid regions, but in arid climates the soft, thin-walled, green
cells have to be covered by thick integuments to protect them
from the dry air, and from too great intensity of light and heat.
The modified colors seem to be purely incidental to the modified
integuments which mask the green tissues within. The thick-
ened, specialized outer skins simply protect the plants against
the too rapid loss of water, and enable them to withstand more
severe conditions of drouth. Many other species living under
exactly the same conditions of exposure are nevertheless able to
retain the fresh green colors of plants of humid regions, because
they have solved their transpiration problems in other ways, just
214
COOK
as there are a few bright colored desert animals. The pigments
which determine the color lie in the deeper layers of the skin,
and are readily concealed by a thickening of the superficial
layers, or by the development of darker pigments above to pro-
tect the lower cells from sunlight, as in the human species.
When the color is resident in an outer covering of hairs, feathers,
or scales, a very direct environmental reaction takes place, for
these are no longer actively living, and the strong sunlight can
bleach out the colors as well while the animals are alive as after
they are dead. This is true of many insects and also of the
horned toad, young or recently moulted individuals showing a
bright yellow which is lacking in the old.
Finally, the protective coloration doctrine loses another instal-
ment in the fact that in the brilliant lights of deserts no colors
are very conspicuous. There is no occasion, so to speak, for
the development in desert animals of the brilliant tints which
may enable the members of the same species to more quickly
recognize each other in the sombre depths of tropical forests.
There have been, no doubt, many cases where the protective
colors have been of immense advantage in the severe struggle
for existence to which animals are often exposed. Selection
must have had an immense influence in perfecting the marvel-
lous adjustments which many species have with their environ-
mental conditions. The nicety of some of . these adjustments
cannot be exaggerated — it is already past credence. A little
fish, common in Liberia, is so exactly the color of the water-
covered sandy stream-beds over which it swims that its presence
is often betrayed only by the darting shadows. A little frog
living in the sandy pools of the California desert canyons has
the same elaborately speckled browns and grays, and likewise
becomes invisible, except for the shadows. A slender pale gray
lizard of the Colorado desert of southern California even excels
the fish and the frog, for it seems to have the instinct of always
facing the sun when it stands upon a stone to gain a lookout.
In this position both its color and its shadow coincide with those
of the stone, and the concealment is perfect.
The subject is one of tempting interest of detail, but enough
has been said, perhaps, to make it evident that the dull colora-
ASPECTS OF KINETIC EVOLUTION 2 I 5
tion of desert animals is a very complex phenomenon, not to be
explained merely by coincidence, nor by environmental reac-
tion, nor even by the selection of reactions.
The possibility of developing such elaborate contrivances is
not adequately conceived until we are able to think of the species
as having an active instead of a merely passive evolution, until
we recognize that species have internal as well as external
reasons for continuing to put forth variations of all the charac-
ters they possess, as long as the environment does not forbid.
The endless possibilities of adjustment can then be realized, for
the narrower the environmental road the more definitely adap-
tive must be the evolutionary motion of the species.
ORGANIC UTILITY AND ENVIRONMENTAL FORTUITY.
The utility of new characters is not to be narrowly restricted
to the environmental sense. New characters can be thought of
as having what may well be termed an organic utility, quite
apart from their effects upon environmental relations. They
may afford a desirable stimulation like that commonly shown in
the greater vigor of crosses between organisms not too unlike,
and they may also contribute to the structural perfection and
general efficiency of the organism. Both these effects of new
characters would give the new type environmental and selec-
tional advantages, but indirectly, and not to the exclusion of
other more definitely adaptive contributions to constructive
evolution.
In the recognition of physiological values for new characters
the kinetic theory of evolution diverges widely from the older
doctrine that species are normally constant and stationary until
changes are brought about by environmental influences. Al-
though often misnamed dynamic, this conception was in reality
static, for the organisms were supposed to have no power of
change except as worked upon by the external causes. Never-
theless, variations, even when ascribed to the environment, were
often held to be merely fortuitous in their relations to evolution,
for it was not believed that they would be preserved and accen-
tuated except by natural selection. The development of useless
characters could not be admitted under this theory, although it
Proc. Wash. Acad. Sci., December, 1906.
2l6 COOK
has become increasingly obvious that many of the characters
which differentiate related species and genera are quite lacking
in environmental utility, and probably always have been.
Many characters which are now useful could have had little or
no utility at the time of their inception unless they appeared
suddenly in a highly developed state, as suggested by the now
popular doctrine of mutation.
The kinetic theory enables us to understand that during the
earlier period, while a character has only an organic utility, it
nevertheless tends to be preserved and to become more and
more accentuated, in accordance with the principle of kinesis
or prepotency of new variations and recently acquired characters,
just as though the species were actively concerned to test the
environmental possibilities of each of the new characters it may
be able to develop. In this view there is no period in which
the new character is entirely useless. Its continued develop-
ment is normal and advantageous on the ground of organic
utility, unless it happens to encounter some environmental
obstacle which forbids further advance, or unless an excessive
development is attained which weakens or unbalances the
organism.
In comparatively rare cases an acute natural selection may
intervene and establish a standard for the species by eliminating
all individuals which do not have a certain character developed
to a required degree. If only one course of evolution remains
open, progress in this direction may be greatly accelerated, for
as the normal diversity of descent is eliminated the prepotency
of the remaining variations appears to increase. This is not
because the environment is hastening the perfection of a new
form of fitness, but because it is of the nature of species to
change, and to continue in the direction of further development
of the characters already possessed.
As far as environmental causes are concerned, there appears
to be complete fortuity in the appearance and development of
characters, except as selective specialization intervenes. This
may occur, of course, at any time in the development of the
character, and may lend it an environmental significance not
possessed before, and perhaps not continued except for a limited
ASPECTS OF KINETIC EVOLUTION 2\J
period or stage of development. Thus the monkeys and anthro-
poid apes seem to have secured from their larger brains no
special advantage over other animals. No species of anthro-
poids seems to have become very abundant or widely distributed.
Only one member of the group continued brain-development to
the point of utility in the struggle for existence, and gradually
gained supremacy over the mundane creation. But mental
development has by no means remained restricted to simple
environmental requirements. Cerebral convolutions have con-
tinued to multiply among the more specialized or highly civilized
varieties of mankind until they have become, if recent statistics
are to be trusted, a positive hindrance to the well-being of the
species, like the overgrown plumage of the pheasants and birds-
of-paradise, or the burdensome antlers of the extinct Irish elk.
Civilized man is now facing a crisis in his own evolution. He
must soon decide whether he will make use of his over-developed
intellect for solving the problems which now beset his existence,
or allow it to carry him entirely out of contact with his environ-
ment and compass his destruction. As the supply of barbarous
peoples of high mentality has almost run out, the present experi-
ment of our race with civilization presents an element of histor-
ical finality which adds, if possible, to the natural interest of
such phenomena. All former civilizations of the European or
Mediterranean peoples have proved suicidal. It remains to be
seen whether the modern faith in science will be justified by
the finding of means to avoid another repetition of history.
Capable individuals tend always to assume parasitic habits
and to become infertile, until the race is represented only by the
relatively incapable immunes, upon whom civilization gets no
hold. Science must make plain to capable people the folly of
becoming parasites, or of permitting parasitism. Scientific dis-
coveries have placed civilized man in many new relations with
his environment, but these relations must have complete bio-
logical adjustment if they are to contribute to the evolutionary
progress of the race. Scientific discoveries have transformed
the arts of production and transportation, but they have had no
corresponding influences upon social organization. Luxury,
idleness and over-education are dangers to society, not merely
2l8 COOK
nor principally because they are connected with an unjust divi-
sion of material wealth, but also because they rob the race of its
most capable elements. However cruel and pitiful the fate of
the incapable who are being eliminated in slums and factories,
deterioration is no less real at the other end of the social series,
and the loss to the race is far greater.
Instead of dwelling, as has been customary, upon the fortuity
of variations and of evolution, we might often gain a clearer
insight by reversing the points of view and appreciating the fact
that it is the environment which is fortuitous rather than the
development of species. Whether a character be useful or use-
less depends entirely upon the circumstances in which the
organism is obliged to exist. Nowhere is this better shown
than in man himself. The qualities necessary to a safe and
prosperous existence in barbarism may be thoroughly disad-
vantageous in a member of a civilized community. The only
way in which the development of desirable qualities may be sub-
stantially encouraged is by furnishing conditions in which they
are advantageous, not, perhaps, in the way in which advantage
is commonly reckoned, but in ways which shall conduce to the
biological end of increasing, relatively at least, the better ele-
ments of the race, instead of tending to eliminate them.
The causes and remedies of these conditions are not to be
considered here, the object being merely to illustrate from the
history of man what is no doubt a general experience of species
in nature, the change of the status of a character from useless
to useful and then to harmful, depending upon this fortuitous
relation between the character and the conditions. That only
one species out of the millions which share with us the surface
of our Earth should have developed intelligence, reason, con-
sciousness, and personality, has appeared very strange, but it
seems still more remarkable, when the vicissitudes of the journey
are considered, that even this one should have reached so unique
a distinction, and more mysterious yet that it should continue to
climb the same summit far beyond any environmental or selec-
tive requirements, and even in despite of such requirements.
Nevertheless, we are but doing what other species of organisms
and other races of men have done before, with the single excep-
ASPECTS OF KINETIC EVOLUTION 2 1 9
tion, perhaps, of a better appreciation of the fate that is already
befalling ns.
Another highly specialized animal, the fig insect, affords an
equally instructive illustration of the possibility that a character
may develop past the point of fitness, and become dangerous to
the species. The fig insects are much too highly specialized
to be able to lead a free existence. They live only in the fruits
of fig trees, which may very properly be said to have domesti-
cated them as their only means of securing cross-fertilization.
The two species, the insect and its fig tree, have thus a mutual
interdependence of a very complete kind. In addition to their
physical peculiarities, the female insects have the highly special-
ized instinct to find the young fig fruits and to force their way
into them, often with much difficulty and the loss of their wings,
so that further flight is impossible. The utility of the insect
depends finally upon the fact that it is stupid enough not to dis-
tinguish between the male and female fig trees. The difference
is a fatal one for the individual insect, for those which enter the
female figs are lost. Their eggs never develop, and they leave
no progeny, the perpetuation of the species devolving upon the
relatively few insects which happen to reach male instead of
female trees. Young male flowers are extremely scarce at the
time when the principal generation of insects emerges, as though
to definitely force them to carry pollen to the female trees.
It is evident that the continued success of this method of pol-
lination depends upon a very acute adjustment of the intelli-
gence of the insects. They must know enough to seek, enter
and fertilize the fig flowers, but not enough to distinguish be-
tween those of the male and of the female trees. All of the
insects which are really useful to the fig species in enabling it
to ripen its seed are lost to the insect species, for their eggs have
no chance of development. From the standpoint of the insect
species there is an acute natural selection in favor of those which
go to the flowers of male trees, but if there should anywhere be
developed an instinctive preference for the male trees so that
the fruits of the female trees remained unvisited, the fig would
cease, in that region, to produce seed, and would become ex-
tinct, along with its insect tenant.
220 COOK
The selection which would eliminate the over-wise insects
would not be applied to them directly, but to the trees which
have become completely dependent upon their insect servants.
Their highly specialized flower-receptacles are so tightly closed
that no other insects will enter.1 When once such a delicate
adjustment of structures and instincts breaks down, the parts are
as useless as a watch that will not keep time. The utility de-
pends only on the adjustment, and when the adjustment has
become highly complex changes are far more likely to disturb
than to improve it. Highly specialized types, those upon which
selection has exerted the most successful influence, are ever the
most liable to sudden and complete extinction, as geological
history has already shown.
Close adjustments induced by selective influence are not, in
the long run, truly advantageous. The chances of survival are
not increased by close adjustment, but by the continuation of
development of characters which allow a wide range of possi-
bilities of existence under different environmental conditions.
From the standpoint of the species, changes of the environment
are fortuitous, and the utility of adjustments is also fortuitous
and temporary. Indeed, the study of adaptations alone might
have suggested caution in the acceptance of the doctrine of en-
vironmental causation, for a vast number of adaptations, and
perhaps the majority of them, do not have reference to the en-
vironment, but are devices for keeping the species together, that
is, for facilitating symbasic interbreeding. To this class of sym-
basic adaptations belong the whole series of specializations of
flowers to secure the visits of insects, the group of phenomena
which has probably figured more largely than any other as an
evidence that adaptation is a genuine phenomenon of nature and
not merely an elaborate collection of coincidences. These
cross-fertilizing adaptations are real and wonderful, but the
plants instead of having been acted upon by external influences
have taken advantage of the environment to enable them to
1 A wild species of fig native in the Comitan district of the Mexican state of
Chiapas has its fruits so completely closed that even the fig insects can no longer
emerge by the natural aperture, but are obliged to bore through the wall of the
fruit to let themselves out. Mr. W. T. Swingle informs me that this is true also
of the sycamore-figs of the Old World.
ASPECTS OF KINETIC EVOLUTION 221
maintain and extend the normal organization of the species.
The individual plant gains no advantage from cross-fertilization ;
the advantage appears only when the results are viewed from
the standpoint of the species.
FITNESS BY CORRELATION OF VARIATIONS.
No one has appreciated more keenly than Darwin himself the
limitation of his doctrine of selection in the way of providing
new characters of fitness on which selection could work. He
continued with persistence the search for adaptive significances
of characters, and supplemented his discoveries in that direction
by the hypothesis of the correlation of variations. This assumes
that the characters which are being developed by selection carry
with them the development of other characters, some of which
may remain useless while others attain utility and thus become
in turn the objects of selective education. It is as though charac-
ters were fastened together in groups like chairs and tables so
that they could be hitched along first by one leg and then by
another.
Instances of correlation between characters have been found,
and the suggestion gains somewhat from the fact that mutations
of independent origin often show close similarity although dif-
fering from the parent type in numerous characters instead of in
one only. Such a mutation might receive a selective advantage
for one character, though the others would be preserved at the
same time. Nevertheless, this suggestion would be subject to
the same objection as the mutation theory as a whole, that the
phenomena are abnormal and do not afford a true indication of
the method of evolution in nature, for there the diversity appears
not to be of the mutation type, but shows unlimited intergrada-
tions of all the characters, as though to give absolute freedom
in the making of truly constructive combinations.
Correlations between different parts and tissues undoubtedly
exist, but we may believe that they are brought about by normal
evolutionary processes instead of supposing that characters have
been tied up in arbitrary groups or bundles, which only explains
one difficulty by imagining others still more mysterious. Such
a character-complex would be, in effect, a suborganic organiza-
222 COOK
tion, if such an expression maybe permitted. The hereditary-
instinct or spirit of the species would be subdivided, like the
spirits of the gods of the Japanese mythology. We would then
need to speculate on the nature and relations of these subordi-
nate entities whose only purpose, after all, was to stop a gap in
a theory. While selection appeared as the only method of
actuating evolutionary motion it was justifiable, perhaps, to use
a charitable imagination on this suggestion of fitness by correla-
tion, but in the kinetic interpretation, where it is perceived that
selection is not the cause of evolution, the correlation assump-
tion does not need to be invoked. It is excluded, as the logi-
cians would say, by the law of paucity, a beneficent selection
which eliminates unnecessarily complicated hypotheses.
KINETIC ORIGIN OF ADAPTIVE FITNESS.
Weismann's recognition of the noninheritance of " acquired
characters" or "direct adaptations" destroyed the foundation
of the older selective doctrine of evolution by environmental
causation, and left the means by which adaptation had been
attained a complete mystery, especially for those who continued
to hold the other half of the doctrine of selection, that species
are normally stationary. To logical minds it has appeared
obvious that a new foundation must be found or that the whole
doctrine of evolution must be given up, whence the special atten-
tion given in later years to the " Origin of Fitness," in the hope
of finding some way in which the external conditions can pro-
duce heritable internal changes in organisms. If the present
interpretation of the facts be correct, this is a completely insol-
uble problem, or rather it is a gratuitous and artificial one, for
there is no such relation as that which the selective school of
" Genuine Darwinians" has hoped to ascertain.
The non-inheritance of "acquired characters" proves that
the changes which the environment " causes" are not those on
which evolution proceeds, and forbids us to assert any directly
causal connection between evolution and environment. Progress
toward greater fitness arises and goes forward in quite the same
manner as other forms of evolutionary change. The environ-
ment establishes, however, requirements of fitness, at times very
ASPECTS OF KINETIC EVOLUTION 223
rigorous with regard to some particular faculty or feature, but
generally allowing wide liberty of chance and choice in other
respects. The adaptations are seldom so close that no further
beneficial or indifferent changes can be made. If we attempt,
by artificial selection, to enforce too narrow restrictions and main-
tain a closely uniform type, the effort always fails through the
deterioration of the organism. The total fitness of species to
their environments is simply the summary of their past histories.
It has nothing in particular to do with evolutionary causes.1
The problem of fitness appears to be truly insoluble under the
idea of normally stationary species. The postulates of the older
selective doctrine are in direct logical agreement with each other,
but one without the other is completely inoperative as a working
hypothesis. Some have even denied adaptation because they
despaired of explaining it, but all these difficulties disappear
when the point of view is changed. Kinetic evolution supplies
more abundant materials on which selection can act, and explains
how fitness can come about without environmental causation.
We are not obliged to discredit the evidence of our senses that
adaptations exist, nor to reject the obvious probability that they
are induced, though not caused, by the environment itself. All
the difficulties are surmounted when we appreciate the fact that
the environment works by the restriction and deflection of a
normal evolutionary motion, and not as a direct or actuating
cause. The environment furnishes certain specifications regard-
ing what may be built, but builds nothing itself. Changes of
the environments imply changes of the vital specifications ; they
enable new evolutionary steps to be taken, but the species itself
must originate and develop the appropriate variations before
selection can favor them with its discriminating encouragement.
The strength of the theory called Darwinism, that evolution
is caused by natural selection, lay largely in the fact that it
presented a solution of the problem of fitness, and could then
explain evolution through adaptation. Darwinism was rational
'The word environment is itself the occasion of great ambiguity in evolu-
tionary literature, some writers using it with reference to its supposed power
to cause favorable variations, and others merely as a summary of selective influ-
ences. Between these two extremes there are many gradations of emphasis, so
that two writers may use the same words in expressing contradictory opinions.
2 24 COCK
as a theory, but the facts have refused to sustain it. Subsequent
efforts by Naegeli, Weismann, De Vries, and others to supple-
ment or supplant selection as an evolutionary cause have failed
to command general confidence, largely because they provided
no logical or adequate solution of the fitness problem, and
undertook to deny adaptation or to explain it away as a mere
coincidence. The best that could be done under the static
hypothesis was to suppose that if the new types happened to
differ from the old in characters of greater adaptive utility they
could survive, and, it might be, exterminate their parents. No
means not wholly hypothetical were suggested whereby the
environment could exert a definite influence upon the course of
evolution.
The kinetic theory more than makes good these deficiencies.
It removes all need or temptation to minimize the extent of
adaptation or the obviously very important role of selection in
evolution. Though providing more generously than Darwinism
itself the materials for selection to work upon, it does not carry
us upon the dangerous ground of supposing that selection itself
is an evolutionary cause, or that evolution is limited to adaptive
characters. Darwinism assumed too much and explained too
little. It predicated an important causal relation where none
existed, and could still explain the evolution of adaptive char-
acters only. Kinetic evolution assumes less and explains more.
In recognizing the fact that the species are normally in motion
it allows for the development of useless as well as of useful
characters, and explains also how selection can contribute to
adaptive specialization.
SUMMARY OF INFERENCES REGARDING FITNESS.
The problem of fitness is a crucial defect in the doctrine of
evolution by selection, because in this theory selection does not
become effective until enough fitness has been obtained to give
a character selective value. The fact that organisms are often
able to adjust themselves to different environments has been
taken to prove that the environment causes variations of selective
value. Environmental selection of these adjustment characters
yielded the logically complete idea of an evolution initiated and
actuated by environment.
ASPECTS OF KINETIC EVOLUTION 225
The kinetic theory rejects the hypothesis of environmental
causation of evolution as fatally discordant with the facts of
organic nature. The individual members of species are normally
diverse, even under the same conditions ; the fact that they may
differ under different conditions is not to be accepted as a proof
of environmental causation of evolution.
There are two phenomena of organic fitness : first the adap-
tation to environment afforded by the general characters of the
species ; and second, the power often shown by individual
plants and animals to adjust themselves to varied environmental
conditions. The latter is a form of organic elasticity compara-
ble, in a general evolutionary sense, to muscular contraction
and locomotion, and with no special significance as a factor of
evolution, nor any special pertinence as an example of the
method of evolution.
Both kinds of fitness are results of evolution, instead of being
causes. They are fruits of the tree, not the roots. Fitness is
maintained because evolution continues, not because the environ-
ment works changes in organisms. For the static evolutionist,
fitness becomes an abstract and insoluble problem. Viewed
from the kinetic standpoint, it appears as a natural and neces-
sary consequence of a spontaneous evolutionary motion con-
trolled or deflected by selective influence.
Environments continually change, and with them the relative
utility of characters. A feature useless in one environment may
be of value in another, or a useful character may become use-
less or even detrimental, depending on external circumstances.
There is thus a real and intimate relation between fitness and
environment, but not a relation which can justify recourse either
to natural selection or to direct adaptation, as causes of evolu-
tion. It is not to be taken for granted that all the differences
shown by plants or animals when environments are changed are
in the direction of fitness. With different conditions and mate-
rials, organisms build differently, or they may wander from the
pathway of normal development in unwonted surroundings.
Natural selection encourages fitness by preserving the fittest,
but there are also environmental differences with no adaptive
relation, and upon which selection exerts no influence.
226 COOK
*
To find that organisms differ in different environments is,
after all, only to find that they exist, for where the conditions
of existence differ the organisms must differ. The power of
organisms to form adjustments is a measure of their ability to
exist, for no environments are absolutely constant. Species
strive, as it were, by every artifice at their command to enlarge
their environments, to conquer more opportunities of existence.
Now and then a successful combination is attained.
Causes which can bring characters of selective value into
existence can bring other characters as well, and can carry for-
ward their development. It is no longer necessary to suppose
that natural selection is an evolutionary cause at all, in the strict
sense of the word. Selection may still be recognized as a con-
dition or an influence in evolution, but there is nothing to show
that evolutionary progress is actuated by selection. Fitness, in
last analysis, comes by evolution, not evolution by fitness.
Selection helps to explain adaptation, but it does not explain
evolution ; it enables us to understand why evolution follows
some courses and not others, but it does not show how the evo-
lutionary advance is accomplished, nor how a new character can
develop to the point of utility or harmfulness, so that selection
can encourage or restrict it.
The Lamarckian and the Darwinian theories ascribed evolu-
tion to causes resident in the environment. The kinetic theory
ascribes it to causes resident in the species. The causes of
evolution are not to be ascertained by the solution of the prob-
lem of fitness, but lie rather in the constitution of species and
in the methods of organic descent.
2. INTRASPECIFIC DIFFERENCES AS MATERIALS OF EVOLUTION.
The time has gone by when it was supposed that new knowl-
edge could be gained by the analysis and rearrangement of old
data and deductions. Nevertheless, it remains true that every
advance in science requires, sooner or later, a new and consistent
arrangement of the materials of investigation, and of the lan-
guage to be used in describing them. Words are not things,
but they often control the predisposition of the mind and thus
obscure or illuminate the field of mental vision.
ASPECTS OF KINETIC EVOLUTION 227
Science deals primarily with facts, and only incidentally with
inferences or theories, though the latter are of immense use in
helping to ascertain facts and test their causal relations. Useful
theories arrange facts in what appear to be connected sequences,
and enable us to project ourselves into the realm of the un-
known without hopelessly losing our way in the maze of unre-
lated data which we are otherwise likely to encounter. We
follow the theory until we encounter facts which prove or dis-
prove it, or until a more direct or more coherent theory has
been suggested.
Theories are like legislative enactments; the surest way to be
rid of a bad one is to enforce it. A false theory, if studied with
sufficient care will correct itself, because the places will be found
where it is inapplicable. Moreover, the theories and laws which
are the most difficult to repeal are those which contain a large
measure of truth and justice, and which have been long in force,
so that many vested interests have grown up around them.
They take possession, as it were, of the field of investigation,
divide it up and place on guard a multitude of technical terms
and distinctions which defend the approaches of the citadel of
error by a battery of words, which go far to keep a new idea
unintelligible.
The prevalent doctrine that evolution is caused or actuated by
natural selection is such a theory, containing a large and impor-
tant truth, and at first immensely fertile in scientific results and
practical applications, but essentially erroneous, and in some
fundamental respects dangerous to agriculture and to man
himself.
The basal axioms, the things taken for granted in the selec-
tion theory are (i) that species are normally stationary and con-
stant in their characters and (2) that their evolutionary progress
is caused by the environment, but neither of these assumptions
proves to accord with the facts. It has not been shown that
either environment itself or the selection which it exerts are
true, efficient causes of evolution. Neither has evidence been
found to prove that a species has ever remained stationary in all
its characters, or that the component individuals tend to become
"exactly alike," even under the most uniform conditions.
228 COOK
Nature abounds in striking evidence of the alternative kinetic
view that species are normally in motion, and that the individual
organisms of which they are composed have a normal and
necessary intraspecific diversity, quite independent of environ-
mental influences. Moreover, there is reason to believe, from
the prevalence of sexual and other diversities inside the specific
lines, and from the degeneration which follows attempts at
maintaining a stable and uniform type, that diversity among
individuals of a species is not only universal and normal, but
necessary and advantageous. The prevalent doctrine that evo-
lution is caused or actuated by natural selection has been char-
acterized as a static theory because species are thought of as
normally at rest, that is, as stationary or constant in characters
and tending to be uniform as far as external conditions will
permit. The causes of variation and of evolution were sought
in the environment and not in the species itself. The problem
was to show how the external causes produce the internal effects,
but the task was hopeless from the beginning, for the variations
which the environment causes are not those through which
evolution goes forward.
It is apparent, therefore, that the abandonment of the static
point of view, and the placing of a new interpretation upon a
large class of familiar facts calls for a new plan for the study
and discussion of the phenomena familiarly called variations,
in the older and looser sense of the term, meaning all the differ-
ences to be found among the individuals of a species. Differ-
ences not caused by environmental influences were, of course,
quite unconsidered in static theories and classifications. There
was not even a scientific term for this universal phenomenon of
intraspecific diversit}-.
A complete treatment of the subject would involve the rear-
rangement of a large part of the data which have figured in the
evolutionary literature of the last half-century. The scope of
the present statement permits only a brief and imperfect outline.
It is not possible even to adequately describe and illustrate the
details of the facts of original observation to which reference is
made. Particular instances are not given, therefore, with any
idea that they are adequate to demonstrate the truth of the inter-
ASPECTS OF KINETIC EVOLUTION 2 29
pretation which has been put upon them. They serve only as
samples of groups of facts to which the interpretation is applic-
able, the primary object being, not to demonstrate conclusions by
formal arguments, but to indicate a standpoint, the correct-
ness of which may be judged by other observers from the facts
encountered in their own fields of investigation.
To learn the nature and causes of evolution it has not been
sufficient to explore and explain the barriers between the species.
It is necessary to go inside the species and to ascertain, if pos-
sible, which of the many differences between the component
individuals represent forward steps in organic development, and
which mere lateral diversions or displacements.
DARWIN'S DISCOVERY OF VARIATION.
Much has been written to show that Darwin did not discover
evolution, as popularly supposed, since the idea may be traced
back to the Greek philosophers or to the Hindus, and had been
entertained in modern times by Lamarck and several others
of Darwin's predecessors. And yet, the popular impression,
though perhaps inexact as to technical terms, is more just than
that of many scientific critics. Darwin was able to secure
general interest and confidence in an idea previously indefinite,
intangible and practically useless. If Darwin did not discover
evolution or even invent entirely new arguments in its favor, he
performed a more valuable and unique service in establishing
the fundamental fact of variation, without which all evolutionary
ideas would have remained empty and sterile speculations, as
they had remained during the two thousand years preceding.
Darwin discovered what is still more important to the scien-
tific world than the abstract idea or theory of evolution, namely
the means of evolution, which is variation. Darwin was the
first to adequately appreciate the fact that species do not consist
of individuals identical in form or structure, but of those which
are diverse, each different from the others in a greater or lesser
degree. Upon the fact of variation Darwin also based his
theory of evolution by natural selection and other environmental
causes, a theory which has had great popularity in the general
scientific world, because it afforded the most concrete suggestion
230
COOK
regarding the nature of the causes of evolution. It is desired
therefore, to distinguish clearly at this point between the facts
of variation first adequately recognized by Darwin and the
theory of environmental causes of evolution often called Dar-
winism. Naturalists do not all believe in environmentally
caused evolution, but nearly all are now agreed in thinking of
species, not as single morphological points, but as large groups
of similar individuals.
Since the time of Darwin it has been believed that evolution
has been accomplished by means of variations, but there is still
the widest divergence of scientific opinion regarding the kinds
of variations which cause or contribute to developmental changes.
Some theories depend upon one or another of the different kinds
of variations and ignore the others, and some hold that all varia-
tions are caused by the environment and that evolution itself is
merely a summary of environmental influences.
Many writers have approached the subject from the stand-
point of formal definitions and narrowly technical distinctions,
but the practical divergences between the different views become
most apparent from the types of variation — the kinds of intra-
specific differences — upon which they depend as showing the
nature of evolutionary motion. To correctly fix upon the kind
or kinds of variations which contribute to evolution, is the first
step of progress toward knowledge of the true evolutionary
factors, and brings us by the most direct route to the determina-
tion of the primary question, whether the true, efficient causes
of evolution lie in the environment or in the organisms them-
selves. Are the variations which are induced by the environ-
ment those by which evolutionary progress is accomplished?
In Darwin's original suggestion environment was held to
bring about evolution, first by inducing variations and then by
selecting those which proved to be advantageous. The environ-
ment was considered as at once the cause of variations and of
evolution. This view is still generally accepted as the teaching
of science regarding organic evolution, although many modi-
fications and collateral suggestions have appeared necessary to
Darwin himself and to many of his successors. Some have
approached the Lamarckian idea of direct adaptation, in ascrib-
ASPECTS OF KINETIC EVOLUTION 23 1
ing much to the moulding influence of the environment, and in
requiring correspondingly little of selection. Other writers have
gone to the opposite extreme, making little of environmental
factors and much of natural selection of fortuitous individual
variations. The latter tendency has been dominant since Weis-
mann showed that "acquired characters," the results of direct
environmental influences, are seldom or never inherited.
In the original Darwinism and its various amended forms
there seems usually to have been included the tacit assumption
of a constant of variability. It is taken for granted that a cer-
tain amount of variation shall be manifested by each species, so
that selection by paring off the species on one side can cause it
to grow out on the other, and thus compel a gradual change of
characters. Without selection the average is thought to remain
stationary, and if selection be withdrawn the progress already
made may be lost by retrogression. Selection, in this view, is
the true actuating cause or principle of evolution.
Mivart, and recently many others, have considered that both
the environmental variations and the minute and fluctuating indi-
vidual differences were alike in adequate to accomplish evolution
through selection, and have advocated a return toward the older
doctrine of special creation. They hold still to the evolutionary
idea that species arise one from another, but suppose that the
new types originate suddenly by " extraordinary births," or by
abrupt mutative variations, that is, by individuals which depart
widely from the type of the older species. The occurrence of
many such abrupt variations is a definitely established fact.
Among plants they often come true to seed, and among animals
they are often prepotent when bred with other members of their
own variety or local species. Nevertheless, it does not appear
that this is the method by which species originate in nature.
The prepotency of new variations indicates the probability that
old species are tranformed by this means rather than that new
species are abruptly originated.
Darwin appreciated better than many of his successors in the
field of evolutionary literature the fact that variations are of
many kinds, of very different evolutionary significance, and due
to many different causes. As an evolutionary pioneer it was
Proc. Wash. Acad. Sci., December, 1906.
232 COOK
a sufficient service to have shown that enough variation exists to
make evolution feasible or even plausible. The scholastically
educated public, which often appreciates arguments much better
than facts, was obliged to approach evolution through Darwin's
deductions rather than through his perceptions. Evolution was
accepted or rejected on the merits of natural selection, though
the two ideas have no necessary connection. Natural selection
and evolution are both facts, but in proving that the one is the
adequate practical cause of the other it would be necessary to
show that the variations through which evolution goes forward
are caused by natural selection. No such causation has been
demonstrated. Natural selection does not furnish the variations
nor explain why variations are accumulated and carried for-
ward into evolution. It only explains why some variations are
preserved instead of others. It does not explain evolution, but
shows how the direction of evolution may be influenced by the
environment. The causes of evolution, or, to be more explicit,
the causes of evolutionary variations, are as mysterious to us as
they were to Darwin, and indeed, more so, since the greatest
step in evolutionary investigation since the time of Darwin has
been a negative one, the destruction of the theory of the inher-
itance of characters acquired from the environment. Darwin
sometimes placed much importance on variations induced by
environment, and invented the theory of pangenesis to explain
the inheritance of such, and bring them within the field of nat-
ural selection. Without pangenesis and direct inheritance, nat-
ural selection loses its place as a positive factor in evolution and
becomes purely negative ; it neither causes variations nor
causes them to accumulate. The most that can be claimed is
that it hastens the development of some characters by retarding
others, or by forbidding them entirely. It is apparent in some
groups of organisms that the influence of natural selection has
been very great, in others that it has been very small,1 but its
effects are in all cases dependent upon the underlying facts, that
variations do appear and are accumulated. Natural selection
does not explain evolution, except in a very loose and super-
1 Cook, O. F., 1902. Evolutionary Inferences from the Diplopoda. Proc.
Entomological Society of Washington, 5 : 14.
ASPECTS OF KINETIC EVOLUTION 233
ficial sense ; the first step toward a better solution of the riddle
is to reorganize the vocabulary of variations so that it can be
used to express something more than erroneous deductions from
natural selection. Many words and distinctions of use in pre-
senting the idea that natural selection is a true, actuating cause
of evolution, may be spared, but there are others whose utility
is not destroyed by this change of view.
VARIATIONS AND INTRASPECIFIC DIFFERENCES.
Before entering upon a discussion of a general scheme of
variations it is necessary to notice a fundamental error commonly
attached to the word variation itself. Most of the exponents of
selective theories of evolution have made, either tacitly or
avowedly, the assumption that all the individuals of a species
are normally alike and tend to remain uniform, and that the
differences found among them are of external origin and of the
same nature as the differences between species, and hence of
evolutionary significance. It has been assumed, in other words,
that all the differences to be found among the members of a
species are variations in the evolutionary sense, and hence that
a cause of difference among the members of a species is neces-
sarily a cause of the evolution of species. It is not too much to
say that this assumption of normal specific stability and uni-
formity, either absolute or within constant limits, begs in advance
the whole question of the nature and causes of evolutionary
change. Notwithstanding the popularity it has enjoyed, this
static idea of species is worthy of no more respect than any other
unsupported hypothesis.
For the former purposes it appeared desirable to divide
the variations, that is, the differences to be found among the
individuals of a species, into two classes — (i) those with which
they are endowed at birth, and (2) those which they acquired
later from the external conditions of their existence. Variations
were classified, in other words, as either congenital or acquired.
The distinction is not illogical, but it has proved worse than
useless for evolutionary purposes, because the static theory by
which it was suggested was an erroneous assumption.
Many objections to natural selection, or to evolution as based
234 COOK
upon it, have been raised from the time of Darwin to the pres-
ent day, but a doctrine with so many merits was not to be dis-
placed until another could be found. Furthermore, the alterna-
tive views hitherto presented have shared either one or both of the
false premises of natural selection, or they are built, like that
theory, on some one group of biological phenomena, and leave
out of account other data equally pertinent to the general conclu-
sion, and equally in need of evolutionary explanation.
One of the ways in which the search for evolutionary causes
went far afield was in assuming a close and essential relation
between evolution and the origin of species. It was thought that
if it could be known how new species came into existence the
secret of the diversity of nature would be revealed. As a mat-
ter of fact evolution has very little to do with originating or
multiplying species. The evolutionary process continues, we
may believe, whether the group becomes divided or not. The
two parts become different because evolution continues in both,
but it would also have continued if the separation had not taken
place. Isolation, of one kind or another, is the cause of the
multiplication of species, but not of evolution. We would gain
no special advantage for evolutionary observation by stationing
ourselves at the point of bifurcation of one group into two ; the
only lesson would be that isolation isolates, that segregation
segregates. Evolution, it cannot be repeated too often, does not
take place in the gaps which are left between the species, but
inside of the species, among the interbreeding organisms ; it is
an zWrtfspective phenomenon, not interspecific.
To learn how species differ is only to ascertain what roads
they have traveled over, it is only by canvasing the differences
between the individuals of a species that we can hope to ascer-
tain how the evolutionary progress is accomplished. It will not
suffice, when when we find that the individuals of a species differ
in a certain respect, to assume that this is the line of evolution-
ary advancement. We must be content first to recognize and
describe the several kinds of intraspecific differences before we
can hope to estimate with confidence the contribution of each
form of change to the general and permanent progress of the
species.
ASPECTS OF KINETIC EVOLUTION 235
CLASSIFICATION OF INTRASPECIFIC DIFFERENCES.
Intraspecific differences may be classified by reference to
three considerations ; the nature of the diversity, its origin or
occurrence, and its relation to environmental fitness. Such a
classification is open to the objection that it requires an advance
decision upon the evolutionary bearings of the facts which are
being classified for evolutionary purposes. This objection also
applies, however, to all preceding efforts at classifying vari-
ations. Such classifications have no value, of course, as the
basis of arguments. Their use is purely that of permitting an
orderly arrangement of materials and of illustrating distinctions.
They aid in discrimination, not in demonstration.
The utility of the proposed arrangement may be best appreci-
ated by thinking of it, not as a classification, but as affording
points of view or avenues of approach to the study of the intricate
complexities of evolutionary problems. The purpose of physio-
logical study is not classification, but the comprehension of
causal relations.
Differences oj Growth Stages. — Changes of size, form,
structure, and function shown in the life-history of normal mem-
bers of the species, including metamorphosis and alternation of
generations and structural phases. The forms of diversity
grouped under this head would not be called variations except
in the most general sense of the term, but they must be taken
into account in making a complete outline of intraspecific dif-
ferences.
Differences of Normal Descent (Heterisni). — Individual and
other differences, including those of sex and polymorphism,
which appear among the members of the species under normal
conditions of interbreeding in the same environment, and even
among the simultaneous offspring of the same parents.
Differences of heterism have no relation to accommodational
fitness, though they may assist in the evolution of adaptive
characters. They have sometimes been called fortuitous or
fluctuating variations because they had no apparent utility, the
organic advantage of diversity of descent not having been
recognized.
Differences of Accommodation to Environment (Art ism). —
236 COOK
Differences resulting from the ability of individual organisms
to adjust or accommodate themselves to different environments.
These are the variations which have the most intimate connec-
tion with the environment, though they have no special signifi-
cance as causes of evolution.
Differences of Deficient Accommodation (Topisni) . — Differ-
ences resulting from the inability of organisms to fully adjust
themselves to special conditions. The result is a non-hereditary
divergence from the normal characters of the species.
Differences under New Conditions (NeotoJ>ism) . —Vari-
ations induced by the transfer of organism to new and unwonted
conditions. Three stages of new place effects may be distin-
guished, (1) those in which there is merely a stimulation of
growth, (2) those in which there is also a definite mutative
change of the hereditary characteristics of the variety, (3) those
in which the new conditions call forth a promiscuous mutative
diversity.
Differences of Partial or Recent Interruption of Inter-
breeding {Porrisni). — Differences arising from the unequal
distribution of variations, that is, from a recent or partial inter-
ruption of interbreeding. Such are the differences that exist
between individuals from the remote parts of the range of a
species (geographical differences) and the differences of segre-
gated local varieties of domesticated species. The nature of
these differences is the same as that of the differences between
species. They are the result of divergent tendencies of evolution.
Differences of New Genetic Variations (Neism). — Prepotent
variations which arise under normal conditions of free inter-
breeding, without having existed previously among the ancestors
of the variant individuals. They can be preserved without
isolation, and are the characters which probably contribute most
to heterism, and to the normal evolutionary progress of species
in nature. There is no evidence that the appearance of such
variations has any connection with adjustment or environmental
fitness. Their preservation depends, of course, upon their being
useful, or at least not positively detrimental.
Differences of Aberrant Heredity ( Teratism). — Failure of
the organism to attain the normal form, structure or size of the
ASPECTS OF KINETIC EVOLUTION 237
species. Teratism occurs whenever there is any accidental
deviation from normal developmental processes, whenever con-
ditions change beyond the practicable limits of normal adjust-
ment, and whenever the specific network of descent is abnor-
mally narrowed. Thus there are many kinds of teratisms, and
manj^ gradations between them and the other more normal kinds
of variations.
Mutations are abnormal or teratic neisms which appear
abruptly in inbred or narrowly segregated groups, and which
require isolation in order to be preserved. Even when in-
duced by changes of environment, mutations are to be reckoned
as aberrations rather than as accommodations.
This classification makes no claim to final completeness, since
still other kinds of intraspecific differences may be discovered.
No doubt the schedule will appear to some as already too
extensive and complex, but it will be evident that none of
the alleged kinds of differences can be left out of account with-
out misinterpreting one or more of the other groups of phe-
nomena. To overlook the facts of heterism would make hope-
less confusion under artism, topism and neotopism. To fail to
distinguish between neism and teratism is to mistake degenera-
tive mutations for examples of progressive evolution.
Characters, in the morphological sense, cannot be classified
and catalogued as heterisms, artisms, or teratisms. There is an
intimate and even interchangeable relation between these differ-
ent kinds of differences. An individual may be larger than
others of its species, either as an inheritance or as a new vari-
ation, or because the conditions are favorable, or even because
they are new. Finally its greater size may be abnormal, or of
the nature of a monstrosity. The same character may thus
have great diversity of evolutionary significance.
DIFFERENCES OF GROWTH-STAGES.
Under this class of intraspecific differences it is proposed to
include all the general forms and growth-stages in which the
members of a species normally appear in any part of their life
history. Only in the lowest and most primitive groups do all
the separate, individual organisms belonging to the same
238 COOK
species have even a general similarity of structure and external
appearance.
There have been extensive and not altogether profitable dis-
cussions of the relation of growth-characters to those of the adult
and to the evolutionary history of the species. The older em-
bryologists worked out a doctrine of recapitulation to explain
larval and juvenile characters, but it is evident in some groups,
such as the insects, that preliminary stages may be quite as adap-
tive as the adult form of the species, and sometimes distinctly
more so. The differences of growth-stages are themselves of
very different types in the various natural groups, as a result of
the great diversity of methods by which evolution has been
accomplished.
THREE TYPES OF CELLULAR STRUCTURES.
The most fundamental diversity of form and structure which
exists among the members of the same species is that which
arises from the existence of different types of cell-organization.
In many of the lower groups of plants the vegetative organism,
like a filamentous alga or a moss-plant, is composed of simple
cells which have not conjugated and which have in many cases
no power of conjugation. In the higher types of plants and
animals the body of the organism, in its highest and most com-
plete form, is built up of cells in a double or conjugating condi-
tion. The higher fungi differ from the ferns, flowering plants,
and higher animals in that the cells associate themselves while
in the first stage of conjugation, before the nuclei have fused,
while the cells of the other groups represent the second stage of
conjugation. The nuclei have fused, but the chromatin gran-
ules still remain distinct.1
The great diversity of the cells which compose the bodies of
the higher plants and animals may be viewed as a phenomenon
of social organization. The lower the organism the more alike
are the cells until in the lowest all cells are similar and equal.
Where socialization, the habit of joining together or living in
groups, has not progressed too far, the cells of compound indi-
1 Cook, O. F., and Swingle, W. T., 1905. Evolution of Cellular Structures.
Bulletin 81, Bureau of Plant Industry, U. S. Department of Agriculture.
ASPECTS OF KINETIC EVOLUTION 239
viduals may still be alike ; the organization is still a mere gre-
garious association. Later, there may come about a division of
labor among the cells, and a corresponding diversification of
structure and form. The common pond-scum (Sftirogyra) con-
sists of threads formed of cylindrical cells, joined end to end,
and all alike in their vegetative and reproductive powers.
Another similar organism (CEdogoniuvi) consists, for the most
part, of similar chains of equal cells, but these have only vege-
tative functions. The power of reproduction has been restricted
to two kinds of special sexual cells different from the vegetative
cells.
Advance in the scale of organization not only maintained this
distinction between the reproductive and vegetative cells, but
continued to increase the numbers and differentiate the struc-
tures and functions of the latter, until the immensely complex
bodies of the higher plants and animals had been built up.
The primitive type of cell organization, that which built up
the filaments of the lower algae and the vegetative tissues of the
liverworts and the mosses was not able, however, to reach the
higher possibilities of cellular structure. The cells which com-
pose the bodies of the higher fungi have two nuclei, and those
of the flowering plants and higher animals have two sets of
chromosomes. These double-celled conditions have arisen
through a lengthening out of the process of cell-conjugation as
it occurred in primitive types like CEdogonium. Instead of
conjugating at brief and distant intervals, the cells which com-
pose the bodies of the higher plants and animals are in a condi-
tion of prolonged conjugation, the cell fusion which begins
when the egg-cell is fertilized by the sperm not being completed
until after the whole compound cellular structure has been built.
Several groups of plants have two structural phases, one
built of the primitive simple type of cells, the other of the double
or sexual type. The moss-spore, when it germinates, first
produces a delicate tube like a pond-scum, and the fern-spore a
small plate of simple cells, much like a liverwort. These
diverse stages or phases of structure of the same organism
have usually been described as alternation of generations, but
the case is in reality entirely different from the phenomenon of
alternation found among animals.
24O COOK
ALTERNATION OF GENERATIONS (METAGENESIS).
In many animals and plants the usual method of propagating
new individuals by new sexual conjugations gives place to a
more or less regular alternation with generations which are
propagated vegetatively, or without a new conjugation. Among
the animals, such as the tunicates and plant-lice, the generations
which propagated vegetatively have a form different from those
which propagate by renewed conjugation.
Alternation of generations, in the proper sense of the words,
occurs when the same species exists in two alternative forms,
and especially where the two forms have different methods of
propagation. The plant-lice furnish the most familiar example
of alternation of generations. We may suppose that, like other
insects, they were confined originally to normal sexual repro-
duction, but their evolution has been in the direction of smaller
size and simpler structure, and they have also developed the
power of multiplying for several generations by partheno-
genesis, the parthenogenetic generations being further distin-
guished by the absence of wings, and by being very short-lived.
At the end of the season winged insects of both sexes are pro-
duced, and normal fertilization and egg-laying ensues.
No such alternation of sexual and parthenogenetic generations
is known to have arisen among plants, though a similar interpre-
tation might be placed upon the bamboos, for example, which
propagate vegetatively by the branching of their root-stocks for
a long series of years. Then all the plants of the species blos-
som, bear fruit and die, at the same time. Each sterile shoot
of the bamboo might be interpreted as parthenogenetic genera-
tion if compared with the sexually propagated generations of a
plant like Indian corn.
METAMORPHOSIS.
Among the insects in particular, and to a somewhat less de-
gree in many other animals (mollusca, Crustacea, batrachia,
fishes, etc.). pronounced changes of form and structure, some-
times very abrupt, take place during the life-history of each in-
dividual. Thus caterpillars change by metamorphosis into
butterflies, grubs into beetles, maggots into flies, tadpoles into
frogs, etc.
ASPECTS OF KINETIC EVOLUTION 24I
Metamorphic differences are largely adaptive, but it is none
the less probable that the alternation of bodily forms and the
change of food and environment may contribute something to
the same physiological results as diversity of descent. In the
more specialized insects metamorphosis is accompanied by a
complete disorganization of the larval tissues, the pupae repre-
senting, as it were, a return to the egg stage, the change of ex-
ternal form affording an opportunity for a complete rebuilding
of the cellular structure of the body. It may be that this fact,
viewed in connection with the extremely complex nuclear organs
of the cells of insects, will assist in explaining the unique effi-
ciency of the insect organism.
Metamorphosis is not restricted, however, to animals. In
plants like Eucalyptus and Junificrus there are sudden changes
of form and structure from the juvenile to the adult phase of the
species.
HETERCECISM.
Many plant and animal parasites infest two or more hosts in
different stages of their life-history. Changes of hosts are then
usually coincident with metamorphoses, or with change of gen-
eration or of structural phases. It has been inferred by some
that the abrupt change in the organism is due to the change of
food and other conditions of existence, but this does not find
confirmation in the studies of the life-histories of the parasites.
The indications are more favorable to the opposite suggestion
that the great diversity of conditions has enabled the parasites
to proceed on two or more independent courses of evolution.
The parasites have developed the power of living in two or
three distinct environments at different periods of their life-
history, and the characters which adapt them to this variety of
conditions have been attained, apparently, in quite the same
manner as the characters of other less specialized plants and
animals.
The more primitive simple-celled stage, or haplogamic
phase, of many species of rust-fungi is confined to pines or to
others of the more primitive families of plants, while the more
advanced and efficient double-celled phase of the parasite has
been able to attack plants of more highly developed families,
242 COOK
such as the Leguminosae or Composita?. There can be little
doubt in such cases that the evolution of the later phases of the
parasites have taken place in coincidence with the advancing
development of their host-plants to which they are so strictly
confined.
GROWTH SPECIALIZATIONS ARISING FROM SOCIAL ORGANIZA-
TION (politism).
Just as cells have become diverse by specialization in the build-
ing up of compound cellular structures, so individual organisms
of the same species may become diverse under conditions of
social organization, that is, when the individual organisms do
not live singly and independently, but in groups, colonies or
compound individuals. The bionomic unit of such species is
no longer the individual but the colony, since it is only in the
colony form that it meets its environmental problems or enters
into relations with other species. A good illustration of politism
is to be found among the compound types of higher plants, those
which take the form of shrubs or trees and consist of aggregates
of large numbers of the individual twigs or branches which cor-
respond to whole individuals of simpler types.
The primitive herbaceous types of flowering plants have a
root and a stem, the latter with a series of leaves and a flower
at the top. If this be considered an individual, larger plants
with many stems or branches and many flowers are compound
individuals. Each branch or flowering twig of a tree may be
thought of as corresponding to the small individual herb.
Usually the branch-individuals are all of one kind, or at least
equivalent and able to replace each other, but in some species
such as cacoa, coffee, cotton and the Central American rubber
tree (Castillo.) the branches are strictly dimorphic, that is, of two
or more distinct kinds with different forms, structures and func-
tions, and also taking definite positional relations in the building
up of the compound individual plant or tree.
It is among the animals, however, that specializations of poli-
tism exist in vast variety, and the diversity becomes obvious
and familiar. In many different groups there have grown up
social organizations, so that all stages may be found between the
ASPECTS OF KINETIC EVOLUTION 243
merely gregarious condition in which the individuals are still
equal and alike, to those in which the diversity inside the same
species may be greater than that of genera and families in other
groups. In man himself social organization has scarcely gone
farther than the gregarious state, though some races of man-
kind have more pronounced social instincts than others, and
such instincts have undoubtedly been important factors in their
progress or backwardness in civilization. In some countries
distinct castes exist, but these are racial or historical in origin and
scarcely amount to the attainment of intraspecific diversification.
By far the most compact and highly specialized forms of
social organization are to be found among the insects. Re-
markably similar conditions have been attained independently
in several different families belonging to two very different
orders, the termites and the hymenoptera. In these highly
specialized insects the individuals of a species are no longer
capable of independent existence, but, like the cells of the
higher plants and animals, have no meaning except as parts of
a collective, super-individual organism. The nest or colony
has become the true unit of the species, and its members are
differentiated into numerous castes adapted to particular func-
tions by pronounced differences of size and structure. Among
the hymenoptera only the females have social instincts and take
part in the labors of the nest or the hive, but among the termite
both sexes are equally involved. Reproduction is restricted to
a single royal pair, who do no work beyond burrowing in the
ground after their first and only flight. The king and queen
and their numerous progeny are fed and cared for, and the
architectural and agricultural labors of the state are performed
by hosts of sterile dwarfs, of which in some species there are as
many as four different castes — soldiers, foremen, workers and
nurses, each distinct in form and highly specialized in instincts
for its particular part in the labors of the city.
The body of the termite queen may be hundreds of times the
size of that of a worker, and the head and mandibles of a soldier
twenty times as large as those of a nurse. Termite communities
often contain millions of inhabitants. They build structures far
exceeding, proportionally, anything attempted by man, and
244 COOK
maintain underneath them immense systems of subterranean
fungus gardens and chambers for storing and curing the com-
minuted wood of which the gardens are built. This material is
brought in from long distances by means of tunnels bored
through the earth or covered passages built over rocks and
tree trunks.
Politism is to be classed as a specialization of growth-stages,
because among the bees, at least, it has been found that the
differentiation of the sterile worker from the fertile queen is
determined by the amount and quantity of food given to the
growing larva. It is difficult to believe, however, that this is
true of the termites, for the young are not stationary grubs as
among the bees, but active creatures which circulate to all parts
of the nest, so that a consistent policy of feeding seems quite
impracticable. Moreover, the workers and other sterile castes
of the termites are not undeveloped females alone, as among the
bees, but consist of stunted forms of both sexes.
DIVERSITY OF NORMAL DESCENT (HETERISM).
The individuals of a specific group may appear closely alike
when compared with those of other species, but when compared
with each other their diversity becomes obvious. Many evolu-
tionary writers have believed in a principle of heredity which
would make all the members of a species " exactly alike," and
have then assumed that intraspecific diversity is due to varia-
tion of environmental experiences in one stage or another of the
life-history of the differing individuals. The kinetic theory
depends upon neither of these hypotheses, but recognizes the
diversity of individuals inside the species as a normal and
highly significant evolutionary phenomenon, for which the term
heterism has been proposed. Plants and animals propagated
under the same conditions may appear more similar than others
of the same stock grown under diverse conditions, but they do
not tend to any complete uniformity except as this is brought
about by the abnormal inbreeding to which domesticated vari-
eties are usually subjected.
Heterism might be defined further as the morphological
aspect of symbasis. To support and hold together the organic
ASPECTS OF KINETIC EVOLUTION 245
structure there must be an interweaving of lines of descent
among diverse individuals. This requirement is most conspicu-
ously met by the familiar phenomena of sex-differentiation, but
can be traced upward through all the intermediate stages from
simple heterism, or mere individual diversity.
As manifestations of heterism are to be included all stages of
intraspecific diversity, from individual differences to the extreme
specializations of the sexes and polymorphic forms of the higher
plants and animals. The function of heterism is to afford diver-
sity of descent, under conditions of symbasic interbreeding.
Narrow segregation or selective inbreeding tends to eliminate
heterism, but with the inevitable result of degeneration. Heteric
characters are highly heritable and though sometimes affected
by environmental conditions are in no way dependent upon them
or caused by them.
Purity of stock and uniformity of characters are not syn-
onymous terms, as commonly supposed. A very "pure " inbred
strain may degenerate and become inconstant through mutation,
or there may be the diversity of dimorphism or polymorphism
in a species or variety which has not been crossed with any alien
blood.
Heterism, in its most general and unspecialized sense, is what
has been called by some authors individual variation or fluc-
tuating variation. It includes the regular and normal individual
diversity of the memhers of a species which is not induced by
differences of external conditions. Some writers do not admit
that there is any such diversity, not caused by external conditions.
It is very difficult, of course, to say that any given character
or difference may not be connected with an environmental
change, but it is very easy to ascertain with reference to most
of the so-called individual differences, that the environmental
relation, if any, is not at all constant, and not to be established
on the basis of any form of scientific observation yet suggested.
We are perfectly aware that the children of the same parents,
born and raised under the same roof are often very unlike, while
on the other hand, close family likeness may persist between
children born and bred in remote parts of the earth involving
the completest possible change of climate, food, and other con-
ditions of existence.
246 COOK
Intraspecific differences, or variations, as they have been
called, have been interpreted hitherto either as results of envi-
ronmental influences or as steps toward evolutionary change.
The recognition of heterism, or the diversity of normal symba-
sic descent, is incidental to a third explanation of the value of
variations, that they help to maintain the vital strength or
organic efficiency of the species.
Indeed, the frequency and extent of the differences of sexes,
castes, races and alternating generations show not onlv that
organisms may change without being divided into separate
species, but also that diversity inside the species has an evolu-
tionary as well as an environmental significance.
Heterism has, if this suggestion be well founded, a concrete
physiological value in the economy of the species, quite as real
as food and water, though of a different kind. The fuel and
water are necessary to keep the engine going, but it is also
necessary that the machine be kept in repair and from time to
time replaced by another built on the same plan.
Environmental variability or power of accommodation, en-
ables the species to operate under a variety of external condi-
tions, but heteric variability provides diversity of descent, even
under uniform and favorable conditions, and thus makes it pos-
sible for the species to continue to produce new individual
organisms as good or better than the old.
Theories of evolution by environmental causation have over-
looked heterism and have assumed that the individual members
of species would be alike if there were no environmental in-
equalities to make them different. This assumption is con-
trary, however, to all the pertinent facts observable in nature.
Acquaintance with the members of any wild species of plants
or animals soon shows that individual differences exist, as great,
and often greater, than those recognized everywhere among
men and women, or among horses, dogs, tulips, roses, grape-
vines or apple trees. Definite individual diversity, as of stature,
features, and thumb marks is not confined to the European races,
nor to the human species. Travellers newly arrived in Africa
or China often have the impression that the natives are all
closely alike, but with longer residence they appear as different
as Europeans.
ASPECTS OF KINETIC EVOLUTION 247
Likewise with plants and animals ; it is necessary only to
become personally acquainted with them to appreciate their
individual differences. The shepherd knows all his sheep as
individuals, also the poultry-raiser knows the eggs of the indi-
vidual hens, and the farm boy knows the kind of nuts which
each hickory tree produces.
An instructive instance of natural heterism was observed in a
species of agave which is extremely abundant on the mountains
to the north of Chiantla, in the department of Huehuetenango,
Guatemala. The size, shape, color and spine-development of
plants growing by the hundreds along the roadside varied end-
lessly. Some were pale-green and heavily pruinose, some slightly
pruinose and much darker green. Some tapered rather gradu-
ally to the point, some carried their width to near the end. On
some the spines were very numerous and prominent, on others
scattering and small, and with all grades and combinations of
these and other varying characters. It is not claimed that these
agaves have essentially greater individual differences than other
plants. The phenomenon of heterism is rendered unusually
striking because their large leaves have a very definite form and
are closely alike on the same plant, and thus give unusually
favorable opportunities for observing and comparing the differ-
ences which exist.
SPECIALIZATIONS OF HETERISM.
The recognition of the facts of heterism, the existence of
intraspecific diversity for its own sake, and of its own physio-
logical value to the species might appear to rest on merely theo-
retical ground were it not for the many specializations of heterism
for which no use or meaning has even been imagined, other than
that of maintaining a desirable diversity of descent.
In some species heterism has remained unspecialized. The
individuals are different, but still all equivalent and alike, pos-
sessing all the essential vegetative and reproductive parts. Such
species secure the benefits of heterism only by the introduction
of new characters, for each character can be shared ultimately
by all the members of the species and thus ceases to be of value
as a means of maintaining diversity of descent.
Proc. Wash. Acad. Sci., December, 1906.
248 COOK
Heterism becomes specialized when there are permanently
established differences among the members of the species, as in
the familiar phenomenon of sex. There is also a series of many
gradations between unspecialized heterism of merely individual
differences, and the fully established sex-differentiation. The
separate sexes of the higher animals are so familiar a phe-
nomenon that we have been satisfied to consider them merely as
incidental to the process of reproduction, and have thus over-
looked the additional physiological value of sexual differences
as specializations of heterism, to insure diversity of descent.
In man himself and the higher mammals and birds the prin-
ciple of sexual selection enunciated by Darwin may have had an
influence in the further accentuation of sexual differences such
as beards, wattles, combs, tail-feathers and other means of
rendering one sex or the other conspicuous and thus attracting
their mates, but secondary sexual differences are not confined
to the higher groups or even to animals. Many plants are
unisexual and the two sexes often have differences other
than those of the essential organs. As the two sexes of plants
neither see nor come near each other, the pollen being carried
by the wind or by insects, there can be no question of sexual
selection here. Even types as lowly as the mosses and liver-
worts often have the sexes separate and very unlike. Nature
furnishes, indeed, hundreds and thousands of instances of inde-
pendently acquired sexual diversity without use either in environ-
mental relations or in reproductive processes.
The use lies, we may believe, not in the particular differences
but in the diversity of descent which the species is enabled to
maintain. Diversity is of value to a species not only to enable
it to exist under a variety of conditions, but also because diver-
sity in descent is an important factor in maintaining the organic
strength or vital efficiency of the individual organisms. We may
still believe that all character differences have their uses, but the
use is not confined to environmental or selective considerations.
More fundamental than these is the use of the diversity to the
organisms themselves.
Sexual differences contribute, in other words, to the increased
effectiveness of sexual reproduction, that is, they intensify the
ASPECTS OF KINETIC EVOLUTION 249
effects of fertilization or cell-conjugation in endowing the new
organism with the power of vigorous growth. With this inter-
pretation of sexual differences in mind we are the more ready
to entertain the idea that specializations of heterism would be
beneficial, even apart from the sexual diversification of the
species, and are thus able to recognize and appreciate a group
of phenomena which has hitherto remained meaningless and
neglected.
Since the time of Sprengel and especially since Darwin, it
has been known that many plants, even those which are
bisexual, or provided with both pollen and egg-cells, have many
specialized habits and devices which serve to secure cross-fer-
tilization. Although possessed of pollen of their own the flowers
are often so formed that the pistils receive pollen only from
abroad, and in many species foreign pollen is a necessity, pollen
from the same plant being entirely ineffective. The advantage
of cross-fertilization being admitted, the value of these adapta-
tions for securing it becomes obvious, but the benefits lie, as
Darwin discovered, not in the " crossing by itself" which " does
no good," but in the diversity of parentage which may in this
way be brought about. These specializations have, in other
words, a double function ; they assist in the crossing and
also minister to the diversity of descent which is the object of
the crossing. They have, in other words, the same function
as sexuality, and have been interpreted by naturalists as a simple
or incipient form of sexuality.
Still simpler specializations of heterism have only one of these
two functions, that of maintaining the diversity, but without
assisting in the bringing of the diverse parents together. The
crossing is left, apparently, to chance, but when it takes place
the diversity renders it the more effective. As instances of this
simple type of specialized heterism may be cited such species
as Verbascum blattaria, the flowers of which are pink on some
plants and yellow on others. The two types grow freely inter-
mingled over wide ranges of country but no intermediates are
found.
25O COOK
DIFFERENCES OF ADJUSTMENT TO ENVIRONMENT (ARTISM).
The notion that all of the differences to be found among the
individual members of species are caused by inequalities of en-
vironmental experience finds no warrant in the vast mass of
experimental facts accumulated by agricultural experience with
domesticated plants and animals, nor in observations of species
in undisturbed natural conditions. The differences which can
be ascribed directly to environmental influences are relatively
few and of little importance for evolutionary purposes. Of in-
direct effects of environment there are two principal classes,
those which arise from the ability of organisms to adjust or
accommodate themselves to different environments, and those
which result from a disturbance of heredity by new and unac-
customed conditions.
The individual members of species often differ among them-
selves as a result of the possession of a certain range of organic
elasticity or power of adjustment to different environmental con-
ditions. Such differences are commonly greater among plants
than among animals, for the latter are often able, through the
power of locomotion, to choose or to control the conditions
under which they shall exist, while stationary plants are sub-
ject to much wider ranges of environmental vicissitudes. It has
often been taken for granted that these differences of accommo-
dation are direct results of environmental influences, the or-
ganism being thought of as having a merely passive plasticity.
The fact is, however, that this power of accommodation is as
positive a phenomenon, as truly a form of organic activity, as
growth, locomotion or reproduction, and as worthy of a definite
and appropriate designation in evolutionary literature.
Indeed it is no mere figure of speech to term these differences
accommodations. The word can be used of plants and animals
in their environmental relations in quite the same sense as for
the change of convexity executed by the human eye to enable
objects to be clearly seen at shorter or longer distances.
This group of intraspecific differences has received a large
amount of study from evolutionary specialists, and especially
from ecologists and others who hoped to find the causes of evo-
ASPECTS OF KINETIC EVOLUTION 2$l
lutionary progress in mechanical effects of environmental influ-
ences. A large number of special phenomena of artism have
been named, such as heliotropism, or the power of plants to grow
toward the light or to turn themselves to face the sun. Ge-
otopism is the opposite tendency of the roots to bury themselves
in the soil.
Some writers on " evolutionary mechanics" have gone so far
as to name the tendency of birds to stand or fly facing the wind
as pneumotropism, and of fish to head up stream as rheo-
tropism. Consistent prosecution of this tendency to ascribe
special " forces," and to give technical names to each habit or
instinctive act could result only in confusion, worse, indeed, than
the older practice of ascribing all unexplained organic phe-
nomena to a general "vital force." Even the operations of
agriculture are conducted by many primitive peoples on an in-
stinctive rather than a rational basis. In spite of permanent
employment and a fully assured supply of food, the Indians of
Central America obey an internal compulsion to scatter upon
the land, when the proper season comes, to clear and plant their
corn fields. Owners of mines and plantations have reconciled
themselves to a complete suspension of work during the corn-
planting weeks, having learned by experience that it is useless
to oppose or to reason with this irresistible agricultural impulse.
It would be possible, of course, to describe this agricultural
instinct as a form of geotropism, a turning to the land for food
as the root turns to the soil. The practical point is not, how-
ever, the choice or application of terms, but to note the prob-
ability that the instinctive actions by which man and the higher
animals adapt themselves to environmental needs belong to the
same general class of phenomena as the accommodative changes
of plants. We know why we clear the land and plant our crops,
and if the need or the advantage be not present we have no
difficulty in discontinuing our agricultural labors, but it is not
likely that agriculture arose, in the first place, as a conscious
and deliberate art. Its beginnings are probably to be traced
back by imperceptible stages to the primitive root crops of trop-
ical America which grow readily from cuttings of the stems and
rootstocks, so that the digging and harvesting of one crop plants
and cultivates the next.
252 COOK
We permit ourselves to say that agriculture was learned in
some such accidental way, but we forbear to say that plants
also learn to adapt themselves to take better and better advan-
tage of environmental requirements. We base the distinction
on the fact that we have reasons for our actions, but in the great
majority of comparable cases the reasons have been discovered
long after the arts had been perfected. We have theories of
swimming, but young children often swim quite as instinctively
as animals.
This may appear an entirely irrelevant digression, but a use-
ful purpose may have been served if we are ready to recognize
the essential unity of the phenomena of accommodation or direct
adaptation and cease to demand special explanatory terms and
hypothetical forces for each of the multifarious forms of adap-
tive change. The explanation will come when our knowledge
of protoplasmic organization has sufficiently increased, but in
the meantime we gain nothing by multiplying the mystery or
by giving it a multitude of names.
Under the theory that environment causes evolution a very
real and important relation was supposed to exist between
artisms, or adaptive alternative characters inside species, and
ecology, or the study of the adaptive characters of species.
Artisms or environmental adjustment variations have received
much consideration from those who have held that evolution is
caused by the environment, and who have believed, in accord-
ance with this view, that the environmental variations were true
examples of progressive evolutionary change, carried forward
by external influences.
This doctrine became untenable when Weismann showed that
characters directly " acquired" from the environment are not
inherited, that is, they do not show any tendency to repeat them-
selves unless the inducing conditions are present. Weismann
proposed to explain the possession by the same species of alter-
native characters by his theory of determinants, or internal
" mechanisms of heredity." These determinants were thought
to control in advance the characters of the organism, and alter-
native characters were explained as the work of two or more
sets of determinants which could be brought into action by par-
ASPECTS OF KINETIC EVOLUTION 253
ticular conditions. Where the alternatives are sharply defined
as in the two sexes of man and the higher animals this theory
might appear to be applicable, but where, as in many plants,
there are, even in the same species, all stages of sexual differ-
entiation, or many distinct castes or forms, with or without
reference to the sexes, the theory of determinants becomes im-
practicably complex.
In the experiments of Standfuss with butterflies it has been
found possible, by changes in the temperatures in which the
pupae are kept, to influence the colors of the adults so as to
approximate those of a different geographical variety or seasonal
form. It has been inferred as a consequence that temperature
is a direct evolutionary factor in causing one species to change
into another. In reality, however, this is but one of the many
instances in which failure to distinguish between the taxonomic
and the evolutionary standpoints has permitted confusion to
enter. Some of these seasonal and geographical forms of but-
terflies have been named as distinct species, but if it be found
that the supposedly distinctive characters are merely artisms or
accommodations to temperature, the proper step is to revise our
classification before attempting to use it as a basis of evolu-
tionary inferences. The largest possibility suggested in the
present instance is that abnormal temperatures may induce in one
part of a species a character which another part has reached by
normal evolutionary process. The fact that the different geo-
graphical color races may have been described and named as
species and varieties cannot be made to prove that temperature
is a cause of species-formation.
This power of accommodation to the environment, specific
elasticity or artism, may be thought of for evolutionary purposes
as a general character of the species, but like other characters it
is possessed in different degrees by different individuals, and this
difference of degree is as heritable as any other feature. Some
individuals and strains of a species may have greater range of
elasticity on both ends of the series, while others have greater
freedom of change in one direction than in the other, for example,
they can become very hairy, but not very smooth. Still again,
we find mutative variations toward a restriction of the normal
254 COOK
range of development. Some of the coffee mutants have ex-
tremely short internodes. None of these complications need
obscure the fact that the phenomena of artism can be viewed as
entirely distinct from those of heterism, though neither phe-
nomenon excludes the other.
DIFFERENCES OF USE AND DISUSE.
One of the reasons for the persistence of the belief that
adjustments to external conditions represent direct effects of
environment, lies in the fact that several other kinds of intra-
specific differences have been confused with environmental
adjustments. Most of these additional types of diversity are
rather uncommon, but they are well calculated to confuse
thought and even to vitiate experiments, especially when these
are undertaken without fully considering all the sources of
possible error.
If an animal or a plant be kept in captivity or placed other-
wise under conditions where its normal activities are not called
into use, muscles or other organs may fail to reach their normal
development, or they may actually decline in size and deteriorate
in structure under continued disuse. There are certain senses,
of course, in which it may be said that the environment, by
determining the use of parts, causes them to prosper or decline,
but closer attention will show that these are phenomena of
growth and nutrition rather than of environmental adjustment.
The use of a muscle is as truly a condition of its development
as the food from which the tissue is nourished, and the decline
of such a part may be reckoned as a starvation phenomenon, or
interference with the normal processes of growth.
The fact that so much has to be learned through precept and
practice by the young of the human species has led some to
overlook the existence of definite instincts and muscles which
develop without use, just as the internal organs and functions
develop in the embryo before birth.
The idea that there is a natural and general tendency to
evolutionary motion, to change of organic form and structure,
need not be confused with the predication of a principle of evo-
lutionary perfection by which some writers have thought that
ASPECTS OF KINETIC EVOLUTION 255
organisms might be carried along in an ever-upward direction.
Some species have gone forward or upward, but for each of the
groups which has been able to perpetuate itself by continuing
upward there have been hundreds and thousands which have
not continued in lines of effective progress, but have turned
aside and have been extinguished. This is as true of man and
of human societies as of species. They do not tend to go
upward but they do tend to change and these changes have
carried a few upward to higher levels, where new planes of
development and expansion were possible, but where the prob-
abilities of still further steps were as doubtful as before, and as
truly dependent upon correct, if unconscious choice. One view
is teleological, the other purely causational.
The phenomenon of degeneration, the reduction or elimination
of unused parts or organs, has led to the placing of undue
emphasis upon the utilitarian aspect of evolution. Darwin
attempted to connect the deficient size and strength of the unused
organs of the individual with their reduction in the species by
means of his theory of pangenesis which assumed that all parts
of the body contribute to the reproductive cells. Degeneration
was made a converse of natural selection ; the reduction was
believed to appear first in the adult, and then the negative
acquired character was transmitted to the next generation.
Many characters of adult organisms consist in part of a genetic
or hereditary contribution, which might be called a qualitative
element, to which is added during growth a quantitative reaction
to more or less favorable conditions, depending not only upon
external circumstances but also upon the perfection and effi-
ciency of the remainder of the organism. Disuse undoubtedly
affects the quantitative side of the development of voluntary
muscles and other analogous organs, but it is not easy to under-
stand how a progressive reduction could be brought about on
Darwin's hypothesis.
After the elimination of the quantitative element due to use, a
state of stability might be expected to ensue, unless there be
predicated in addition a principle of organic economy tending
to the gradual and continued elimination of useless characters
and organs. In other words, the effect of pangenesis acting
256 COOK
alone would be limited to comparatively few generations, and
would dispose of superficial and recently acquired characters
only, an inference apparently supported by the persistence of
many rudimentary organs.
The extreme constancy of vestigial characters confirms the a
■priori expectation that selection would have little to do with
them except to eliminate ; but differences, nevertheless, occur,
of which progressive modification without selective influence
must necessarily be predicated.
Weismann's panmixia was intended to represent a view
diametrically opposite to that of Darwin, approaching the
question of reduction from the side of heredity only, and laid
emphasis on the opinion that, selection being discontinued, indis-
criminate crossing without reference to the character previously
at a premium would result ultimately in the reduction of the
selectively developed parts. But even if it be admitted that a
reduced average would be attained within specific limits or
where intercrossing is possible, panmixia remains entirely inad-
equate to explain the progressive elimination of wings, legs,
eyes or other important parts of the body, unless it be extended,
as in the previous case, to an organic law of economy, a prop-
osition logically quite distinct from panmixia. It is of inci-
dental interest to note that both Darwin and Weismann have thus
tacitly admitted a law of organic motion in the direction of the
simplification of organisms, and that this proposition is again
the exact opposite of that of Nageli whose " Vervollkommungs-
jirincij)'''' works from the simple to the complex.
The phenomena of degeneration may appear to militate
against the idea of a spontaneous organic motion. The belief
has been that though organisms are in a sense elastic, in that one
or more characters can be far drawn out by selection, they tend
more or less promptly to return to what might be viewed as the
previous condition of rest or equilibrium. Especially would this
be the case where selection has been very acute and has accen-
tuated one character at the expense of the total efficiency of the
organism with reference to conditions other than that which has
determined the special selection. The removal of the latter
would then involve the loss of the advantage gained by selec-
ASPECTS OF KINETIC EVOLUTION 257
tive response to the special demands. In groups subjected to
an active struggle for existence this would mean a change of
direction rather than a cessation of selection. In many other
instances, notably among parasitic forms, the loss of normal
organs ascribed to disuse is better explainable by selection, since
the apparent degeneration is of decided advantage from the
standpoint of the actual life-history of the animals.
The principle of panmixia seems, indeed, to involve an un-
warrantable extension of the idea of organic elasticity, since it
implies that organic structure is maintained by selection alone,
without which everything would drop back to simple protoplasm.
Of such a general tendency to degeneration there is, however,
no indication. As explained elsewhere, the reversion of inbred
highly selected types to the wild form of the species is not de-
generation, but a recovery of normal structure after restoration
to normal conditions of interbreeding.
DIFFERENCES OF DEFICIENT ACCOMMODATION (TOPISM).
Environmental differences are not all of one kind. Some of
them are the results of the power of accommodation or adjust-
ment (artism), while others represent rather a deficiency in
ability of this kind, so that the organism, though perhaps able
to maintain an existence, fails to attain one or another of the
normal characters of the species. Thus there is a variety of
canary bird which if fed on cayenne pepper during its period of
moulting produces red feathers instead of yellow.
The South American Indians are said to be able to alter the
color of the feathers of their domesticated parrots by inoculating
them with the blood of toads. The colors of certain flowers
can be modified by special conditions or by treatment with
chemicals. The injury of the white pigs from paint-root, while
black pigs escaped, as related by Darwin, would be another
example of the same group of phenomena.
The relations of topism to artism and to teratism are some-
times very intimate. A character assumed by one plant as a
means of accommodation may appear in another as a limitation
of the power of accommodation or as a complete abnormality.
The need of discrimination and the difficulty of exercising it
2 58 COOK
are frequently apparent in the literature of the subject. Thus
it has been inferred from experiments on a spiny New Zealand
plant that the spines, instead of being a means of protection
against grazing animals, of which there were none in New
Zealand, are in reality an adaptation against transpiration,
because they do not appear when the plants are cultivated in a
humid atmosphere.
"After being placed in the moist chamber, the plants devel-
oped no more spines and are now seedling plants in all respects
except for the few spines, which were developed prior to the
culture in moist air. Moreover, it seems evident that such
plants would remain in the seedling form so long as they were
kept in an atmosphere constantly moist and exposed to a feeble
light.
" Even an adult shoot on a full grown plant in the open and
freely producing spines, may have any further production of
such suppressed at once, if the shoot should continue its growth
under slightly more hygrophytic conditions. Thus quite recently,
I observed on the clay hills near Wellington, a shoot creeping
near the ground whose apical portion was covered by grass.
This shoot where fully exposed to the light was spinous as usual,
but where shaded and in a slightly moister atmosphere was quite
without spines.
" From the above it follows that the production of spines in
Discaria Toumatou can be controlled at will by specifically
changing its environment — a plant exposed to a dry atmosphere
and normal light producing spines, whilst one exposed to a moist
atmosphere and a feeble light produces no spines, but in their
place leafy shoots of unlimited growth.
" That spines on xerophytic plants are an adaptation against
the attacks of grazing animals is a matter of such general belief
as to be admitted into certain botanical text-books as a proved
fact.
" It seems, however, to me that my experiment, detailed above,
is a fairly crucial case, and that in Discaria Toumatou, at any
rate, the spines are a direct response to conditions of dryness,
and function as a special contrivance for checking transpiration.
If so, then they have nothing to do primarily with attacks of
ASPECTS OF KINETIC EVOLUTION 259
grazing animals, especially when it is borne in mind that New
Zealand never contained such, excepting the various species of
Mo a."1
That the spines did not develop under conditions of moisture
and feeble light can scarcely be accepted, however, as proving
that they are a special contrivance for checking transpiration,
for many analogous adaptations do not fail to appear in advance
of the conditions which require them. Cacti, and other spiny
plants often make most of their growth in periods of humid
weather, but they do not on that account fail to put on spines.
The possibility that the spines may be a useful form of tissue
for the plant when living in the normal desert habitat is not a
sufficient explanation of the failure to produce the spines under
conditions of humidity and deficient sunlight. The spines might
be an adaptive character and still appear under all conditions of
growth. They might represent an adjustment character or artism
and still be only reduced instead of being eliminated in the shade
form. That the spines disappear entirely indicates that another
factor may need to be recognized, that certain conditions are
necessary for their development, and that without these condi-
tions the plant is unable to make spines, just as the pepper-fed
canary birds may be thought of as no longer able to produce
yellow feathers.
The interest of the Discaria experiment would have been
increased if it had included a test of the behavior of the plants
in shade conditions without excessive atmospheric moisture, to
determine whether deficiency of light might not of itself inhibit
the formation of the spines, simply by restricting the activity of
the cells. The formation of the spines is a specialization which
the seedling plants do not attain until they have grown to con-
siderable size, perhaps not until they have encountered condi-
tions of drought and exposure to strong sunlight. It is, there-
fore, not unreasonable to suppose that these conditions are a
necessity to enable the plant to produce the spines, and hence
that its failure to produce them represents not so much an accom-
modation as a lack of accommodation, that is, topism, instead
of artism.
1 Cockayne, L., 1905. Significance of Spines in Discaria Toumatou Raoul
(Rhamnaceas), New Phjtologist, 4 : 79.
26o COOK
The prompt loss of wool by sheep brought to tropical coun-
tries is one of the most striking instances of response to environ-
mental conditions, but there are several elements which need to
be taken into account in attempting to arrive at a clear under-
standing of the nature of the process. The continuous heat
and excessive humidity may induce an abnormal condition of
the skin and cause the hair to fall out, as often happens in hu-
man fever-patients. On the other hand, the failure of the sheep
raised in the tropics to produce wool may be due to a lack of
sufficiently normal conditions of existence which disturbs the
normal heredity and affects first the most highly specialized
character of the animal. The loss of wool could be explained
in this way as a deterioration or reversion rather than as a new
or adaptive character. The domestic sheep is now supposed
by Lydekker to be descended from wild types which had a
hairy summer coat and produced wool only as cold weather
approached.1
Many animals and plants require the seasonal vicissitudes of
heat and cold as a normal part of the conditions of existence,
and refuse to behave normally in tropical regions where wide
ranges of temperature do not occur.2 Indeed, the changes of
temperature appear to supply to some of them the same kind of
bodily vigor to which diversity of descent contributes. The
plants and animals of. tropical regions appear to have rela-
tively great rapidity of evolutionary progress, as pointed out
by President Jordan, who finds that the tropical fishes are much
more highly specialized than those of extratropical waters.
"The processes of specific change, through natural selection
or other causes, if other causes exist, take place most rapidly
there and produce most far-reaching modifications."3
It has not been shown, however, that natural selection is less
acute in the colder regions of the globe ; in fact, the general
impression has been that the requirements are the more stringent
and exacting.
'Lydekker, R., 1904. The Field, 104: 654.
2 Apples, cherries and many other temperate trees and cultivated plants fail
to reach productive maturity under consistently tropical conditions, just as the
seeds of lettuce may refuse to sprout without alternations of temperature, and
the eggs of some mosquitoes refuse to hatch unless they have been frozen.
3Jordan, D. S., 1901. Science, N. S., 14: 566.
ASPECTS OF KINETIC EVOLUTION 26 1
TEMPORARY EFFECTS OF NEW CONDITIONS (NEOTOPISM).
Experiments to test the effects of different environments upon
plants are often interfered with by a temporary stimulation of
growth, due, apparently, to the fact that the conditions are new,
rather than to any essential superiority of the new place.
Like travelers in foreign countries they may often behave in
a manner very different from their habits at home. Organisms,
as well as men, though not built by their environments, are
often built into them to such a degree that where the accustomed
supports and restrictions are taken away the usual courses of
action are no longer followed. New and unexpected character-
istics assert themselves, not only or chiefly because the new
conditions cause the organism to vary, but because they give it
an opportunity to do so, or strengthen and bring to expression
some tendency or instability of equilibrium. The new
characteristics which have a definite connection with the new
environment and are in the nature of adjustments to it may be
expected to continue, but there is, in addition, a temporary effect,
a temporary lack of adjustment, or a stimulation or aberration
which sooner or later disappears.
This phenomenon may be called neotopism, or the new place
effect. It is often strikingly shown in plants, and is not lack-
ing in animals. The most familiar example of it is, perhaps,
that of the tonic medicines. A vast number of substances,
utterly unlike among themselves and having utterly diverse
specific actions upon the human system when taken in large
quantity, may nevertheless produce the same beneficial effect
of temporarily increasing the efficiency of the organism, when
taken in extremely small doses.
Neotopism is also to be reckoned as one of the factors con-
tributing to the great vigor and rapid distribution of plants and
animals immediately following their introduction into a new
region. It is true that they may also have the advantage of
immunity from diseases or natural enemies to which they were
subject at home, but this is by no means a sufficient explanation
of the unusual vigor and fecundity which they manifest for a time
and which disappears after a series of years. Many plants,
like the Russian thistle, which terrified the agricultural regions
262 COOK
of the Middle West a decade ago, after threatening for a time to
become permanently injurious pests, have taken their places as
comparatively peaceful settlers among the older plant inhabitants.
Neotopism is a phenomenon long known in practical agricul-
ture, but hitherto not explained and generally not accepted in
the scientific world, because the requisite evolutionary viewpoint
was lacking. Having come to appreciate the physiological
functions of heterism in maintaining the vital efficiency of organ-
isms, we are in position to understand that a transfer to new
conditions may also act as a direct stimulant of organic vigor,
an artificial symbasis, as it were, which has probably contrib-
uted much to the sustained vitality of our inbred cultivated
plants.
Likewise the heterism of the species might be thought of as
increased by the extension to the new locality, and the added
neotopic diversity might serve the same purpose as normal
heterism in helping to maintain the organic vigor of the species
as a whole, under conditions of free interbreeding. Thus devices
for securing wide distribution serve the interests of the species
in a variety of ways. They not only tend to increase the
numerical prosperity of the group, but increase the facilities
for interbreeding among the members of the species and also
give it the benefit of as widely different conditions as possible.
The diversity of conditions accentuates diversity of descent and
thus contributes to the vigor of the species. With sedentary
plants in particular we should be prepared to learn that changes
of conditions of growth are as beneficial as changes of diet for
man and the higher animals.
In many crops it has become a regular agricultural practice
to exchange seed between more or less distant localities. Seed
planted in a new locality often produces better and more fertile
plants than in the place where it was grown, and better than
the same stock after it has been planted in the same place for a
series of years. The new conditions afford, for a time, the
same physiological benefits as diversity of descent and new
variations, and constitute, indeed, a striking confirmation of the
physiological relations of these groups of phenomena.
In many other cases neotopism may only bring to the surface
ASPECTS OF KINETIC EVOLUTION 263
and accentuate conditions of degeneration. Many varieties of
domesticated plants and animals have been bred so long and so
narrowly in one particular locality that any change is accom-
panied by notable deterioration. Thus it comes to be believed
that seeds of one particular plant, such as the radish or the
cauliflower, can be grown to perfection only at Erfurt. Trans-
ferred to any other point, neotopic mutation at once appears and
brings diversity and commercial inferiority. In a similar way
many high-bred animals like the Jersey cattle also deteriorate
or show special susceptibility to disease when subjected to new
conditions, even to those in which other less closely adjusted
breeds are able to thrive.
BEARING OF NEOTOPISM UPON ACCLIMATIZATION.
Neotopism must also be taken into account in another depart-
ment of agricultural investigation. The phenomenon is often
very marked in plants introduced from tropical countries into tem-
perate regions, and has had the opposite effect of deceiving
us regarding the possibility of acclimatizing species or varieties
of tropical origin. The popular impression is that the colder
climate of our more northern latitudes will restrict the growth
of plants from the tropics, but this is the reverse of what usually
happens, as a matter of fact. It seems to be a general law that
annual-crop plants, whether of temperate or of tropical origin, are
most vigorous and productive near their northern limit of growth.
The reason for this is that the longer days supply a greater
amount of heat and sunlight than in the tropics themselves.
Plants newly introduced from the tropics commonly misuse
these exceptionally favorable conditions to put forth an abnor-
mal amount of vegetative growth and are often killed by frost
before they commence fruiting. It has been usual to explain
the failure of such experiments on the simple ground that our
northern season has proved too short for these tropical varieties,
but as a matter of fact the time may have been equal to that
required by these same varieties for normal growth and maturity
at home in the tropics. Thus the Kekchi variety of Upland
cotton, which matures seeds in Eastern Guatemala in five months
from planting, required in Texas over six months to produce
Proc. Wash. Acad. Sci., January, 1907.
264 COOK
a much smaller crop the first year after its introduction, and
might have produced no seed at all if the tendency to abnormal
luxuriance of growth had not been checked by a long period of
dry weather. Other tropical varieties of cotton have consistently
refused to produce seed when introduced into Texas, even
though the same length of season would have been sufficient in
their home localities.
With the superior conditions of growth supplied by our north-
ern summers most of the tropical varieties would be able, if
they utilized their opportunities properly, to develop even more
rapidly than they do in the tropics, and this result has been
reached with some of the Mexican varieties of corn. During
their first seasons in the United States they became greatly
overgrown and ripened scarcely any seed, but after a few years
they recovered their short-season qualities and became es-
pecially useful as extra-early varieties, like the " Mexican
June" corn.
The conditions under which such experiments are usually
made are well calculated to intensify neotopism instead of hold-
ing it in check. It has been reasoned after the analogy of our
domestic varieties that fertile soil and thorough cultivation will
conduce to the early maturity so much desired. Moreover, it is
the regular practice to keep testing gardens and experimental
plots in the best of condition. The result is that the newly in-
troduced tropical variety is surfeited with the unwonted supply
of readily available food and moisture, which still further in-
creases the tendency to abnormal vegetative growth.
Many such varieties have entirely failed of acclimatization
because they ripened no seed at all in the localities in which
the first experiment happened to have been made. Neverthe-
less, the inference is not warranted that such varieties cannot
be acclimatized in temperate regions. Experiments in the in-
troduction of new types of Upland cotton from Guatemala have
shown that the tendency to rank and sterile vegetative develop-
ment can be controlled by carrying the new stock far enough
to the north and placing it in comparatively sterile soil. In the
latitude of Washington the Guatemalan varieties of cotton
showed much more normal habits of growth, and made more
ASPECTS OF KINETIC EVOLUTION 265
progress toward fertility and seed-production than in the much
longer growing season of Texas. These experiments afford a
definite intimation, to say the least, that by the proper choice of
conditions for the first planting the neotopic stimulation of trop-
ical varieties can be held sufficiently in check to permit the ma-
turing of at least small amounts of seed. This opens the way
to the practical acclimatization in the United States of useful
varieties of cotton, corn and other important food-plants of
tropical origin.
Further experiments have shown that the second generation
of cotton in the United States is notably earlier and more
productive than the first generation, when grown from seed
of the same origin and planted in adjacent rows. It has also
become evident that there are at least three stages or kinds of
new place effects to be considered in the acclimatization of
different varieties and types of cotton. The changes of hered-
itary behavior which can be induced by the transfer to new
conditions are not limited merely to increased size or vigor, but
have obvious bearing upon the phenomena of mutation, since
the plants may change in a very definite manner in characters
which would usually be considered of varietal or even of specific
importance. The lack of fertility which accompanies the aber-
ration from normal characters affords a further analogy with
mutations. Nor does the interest of the experiment end here,
for it has been proved that this neotopic form of mutation
may supervene in a perfectly definite manner even after the
plants have grown for a time according to the specifications of
normal form and habits of the variety.
When the change takes place early the whole plant may show
the abnormal characters and may be more or less completely
sterile. In another locality plants of the same origin may grow
for a time in a normal manner and remain normally productive,
but may then change suddenly and completely to the abnormal,
infertile, neotopic condition. In this form of neotopism the
behavior of the individual plants grown from the same lot of
imported seed is often remarkably uniform and the result is
closely parallel to that described a few years ago by Dr. C. A.
White in tomatoes. Two lots of seed produced, with much
266 COOK
uniformity, progeny so unlike their parents that Dr. White
described and named them as a new species.1
A third result sometimes reached by transferring plants to
new conditions is to induce a more or less general outbreak of
miscellaneous variations of an abruptly mutative character. In
such instances the stimulation effect may be lacking or very
inconstant. Some individuals may be several times as large as
their parents, while others are as much smaller.
Although the new conditions evidently induce the mutative
variations, they can not be said to cause them, in any definite
evolutionary sense, as proved by the great diversity of the muta-
tions which the same change of conditions may call forth. The
unfavorable conditions unbalance the organisms, but the indi-
vidual lapses from normal heredity take many different direc-
tions, without reference to particular requirements of the
environment.
The practical significance of the new-place-effects is, there-
fore, entirely different in different instances. As long as the
result is an increase of vigor and fertility, the phenomenon is a
useful one ; but if the stimulation be so great as to change the
characters of the plants and render them infertile the crop may
be ruined, and this misfortune may also be reached when many
miscellaneous variations and degenerations appear.
DIFFERENCES ARISING FROM PARTIAL ISOLATION (PORRISM).
Members of the same species are often more or less unlike in
the different parts of their geographical range of distribution.
Some of these differences will be found to have relations to
differences of environment, but others will persist even when
brought into tne same conditions. These geographical diversi-
ties represent, no doubt, the results of partial isolation, and are
of the same nature as the differences between species. If inter-
breeding were adequate, evolutionary progress would be kept
uniform over the whole species, but if the organism is sedentary
or lacking in facilities of dispersion local diversities may accu-
mulate.
1 White, C. A., 1905. The Mutations of Lycopersicum, Popular Science
Monthly, 47 : 151.
ASPECTS OF KINETIC EVOLUTION 267
Individuals from neighboring localities may maintain the usual
amount of similarity, but if specimens from remote parts of the
geographic range of the species be compared they may prove
notably different. If the climatic or other conditions of the two
localities are unlike it is very natural to infer that this is the
cause of the differences between their organic inhabitants.1
That this explanation may prove, in some cases, to be correct,
does not justify us, however, in neglecting to perceive that the
remote members of a species may have opportunities to accu-
mulate diverse characteristics, much as though they belonged
to two distinct species. The extent to which they can do this
will depend upon the habits of the particular plant or animal.
Sedentary species of animals or plants which have no means of
securing wide dissemination of seeds or pollen, tend to manifest
local divergencies. The cause of this is, apparently, that new
characteristics appear in different parts of the range of the
species more rapidly than they can be distributed through the
whole interbreeding group. Thus the quail, or Virginia par-
tridge, a nonmigratory bird extending from New England to
Central America, shows a large number of appreciably different
local varieties or subspecies, which might not exist if the bird
were migatory and there were a more general intermingling of
the members of the species. The differences which charac-
terize such local subspecies may be quite the same, both in
character and amount, as those which distinguish completely
segregated species, but they are treated as subspecies because
the distribution of the whole group still remains continuous, and
provides a complete series of connecting links between the local
forms which happen to be described as subspecies.
1 Engler, A., 1904. Plants of the Northern Temperate Zone in their Transi-
tion to the High Mountains of Tropical Africa. Annals of Botany, iS : 539.
" I am convinced that in such cases the somewhat different climate is the
cause of all or at least of a part of the modifications. Sometimes in connection
with these new variations are also to be observed (cf. Cerastium ccespitosum),
which may become the beginning of other new forms. The constancv of such
climatical adaptations may be a different one and often become fixed through a
geological period. I may add that systematic studies have also convinced me
that many of the xerophytes, and that a good deal (I do not say all) of the quali-
ties of xerophytes, which are usually called adaptations for protection against a
dry climate, are caused by the climate itself."
268 COOK
The essential difference between a species and a subspecies
does not lie, as commonly supposed, in the nature or amount of
the differences as such. The practical question is whether two
groups are actually separate in nature or are still connected.
Subspecies may be more different than other completely segre-
gated species. On the other hand, groups which are really
segregated in nature and thus unable to interbreed, are by that
fact on the road to the acquisition of specific differences. That
they may not have become very different from each other does
not prove that they are not good species or that it is undesirable
to accord them recognition as such.
It does not follow, as some have supposed, that subspecies
are always incipient species, or that there is any inherent force
or tendency which will insure a subsequent separation into
distinct species. The existence of these diverse local forms has
not been shown to be any disadvantage to a species, and may,
indeed, conduce to its greater vigor, since it tends, like heterism,
to insure a certain amount of desirable diversity of descent.
If the habits of a species were to change in the direction of
an increase of its power of dissemination and wide interbreed-
ing, the local differences would tend to disappear, since new
variations could then spread more rapidly throughout the whole
group and render its evolutionary progress more uniform.
Porrism corresponds, inside the species, to many of the dif-
ferences between species. It is true that when species of the
same genus live in different environments and have different
habits they usually have structural difference corresponding to
their respective needs. Examples of such adaptations are fre-
quent among the higher plants and animals, and their super-
ficial similarity to artism inside the species has been the basis of
the doctrine that evolution has been effected by environmental
causes. The best corrective of this misapprehension is a study
of one of the lower groups of plants and animals in which the
same family, order or class has the same habits and the same
place in the economy of nature. Many excellent examples will
be found among the mosses, liverworts and alga? among plants,
and among the myriapoda and lower insects where the number
and character of the diversity of the species is out of all imag-
ASPECTS OF KINETIC EVOLUTION 269
inable proportion with differences of conditions, habits or selec-
tive requirements. Hundreds of species, genera, families, and
even orders, have been differentiated notwithstanding complete
and long-standing adjustment to the same kind of existence.
The multiplication of species under such circumstances has
little reference to environment or to natural selection, and the
characters by which the groups differ are not explainable on the
basis of utility. The diplopod fauna of tropical Africa changes
almost completely every thousand miles, but the tropical forest
conditions under which a large proportion of the species live
are, for their purposes, practically identical the world over.
But with these wingless, slow-moving creatures unable to bear
exposure to daylight and dry atmosphere, the opportunities for
segregation are greater than those for dissemination. The
environment allows a wide freedom of choice, and evolution
by means of useless changes has far outrun the natural selection
of advantageous differences. As far as their external charac-
ters are concerned, these animals appear to have been quite as
well adapted to their environment in the carboniferous age as
they are to-day, but they have not ceased to differentiate species,
although preserving much more than in some groups the same
general form. Indeed, the wealth of definite structural differ-
ences is, if anything, greater than among the higher insects,
where the progress in adaptive structural changes would seem
to have removed the necessity of accentuating the inconse-
quential differences which the diplopoda have utilized as
means of evolutionary motion.
DIFFERENCES OF NEW VARIATIONS (NEISM).
Much of the heterism or normal individual diversity of the
members of a species can be described as resulting from differ-
ent combinations and proportions of what have been called the
unit characters of the species. The interweaving of the lines
of individual descent brings, as we know, an infinite diversity
of form and features, and with these differences accentuated by
environmental influences there is almost an infinity of possibili-
ties of diversified characters in the same species. Nevertheless,
the making of all possible permutations of the characters which
27O COOK
may exist in a species at any particular period would lead, after
all, to no truly progressive change. Nothing is gained for evo-
lutionary purposes by attempting to explain new characters
merely as reversions or as new combinations.
Nor can such assumptions fully account for the facts, since
it is often obvious that absolutely new and unprecedented evo-
lutionary departures sometimes appear, which could not be
accounted for by any combination of characters existing in the
remaining members of the group. Such are the remarkable
crests developed on a few of the anterior segments of East
African millipedes of the family Oxydesmidae, specialized
structures which are entirely without analogy in the remainder
of the order Merocheta or, for that matter, of the entire class
Diplopoda.
It would be altogether presumptuous, of course, to insist that
any particular variation or mutation represented the very first
appearance of its type in the history of the species. It is usual
to ascribe variations to possible admixtures of blood at some
point in the genealogy of the individual, near or remote. But
these suggestions, even if justified for particular cases, should
not be allowed to obscure the more fundamental consideration
that the very idea of a progressive evolution implies the origina-
tion and development of new characters, both of form and of
structure, and the opening of new environmental relations for
the species.
Of the causes of new characters we are, as yet, in ignorance,
but of their uses we need be in no doubt. New characters not
only make evolution possible, but by true symbasic interbreed-
ing they help to maintain the vitality or organic efficiency of the
species. Neism reinforces heterism and contributes to evolu-
tionary progress. New characters are not averaged away and
obliterated by interbreeding, but are prepotent. They tend to
spread throughout the species and to become more and more
accentuated.
That variation may bring an increase of the vegetative vigor
or vital efficiency of the organism could not be more clearly
shown than in the numerous instances where unusual bodily
strength and hardiness accompany reproductive debility or even
ASPECTS OF KINETIC EVOLUTION 27 1
complete sterility, as in the familiar instance of the mule.1
Many similar instances were observed in Guatemala. Coffee
plantations which, owing to unfavorable conditions, were dead
or dying, often showed occasional mutations which remained
healthy and luxuriant. Through some strange internal differ-
ence they were able to carry on their vital functions with con-
spicuous success while all their normal neighbors had completely
failed. If coffee were grown for the leaves like tea or for other
vegetative parts, these mutations would furnish new types of
great economic value, but of thousands of such variants which
have come under the observation of planters not one has proved
to be equal in fertility or normal seed production to the parent
type, under favorable conditions.
PREPOTENCY OF NEW VARIATIONS.
If only a small proportion of the progeny showed the new
character it might still gain a footing in the species, especially
if favored by selection. Those who have relied on the mathe-
matical doctrine of chance have felt it necessary to claim gen-
erous assistance from the principle of selection. Experiments
with new variations seem all to agree, however, that among
their own relatives, or under equal conditions of symbasis, they
have not merely an equal chance of reproducing themselves,
but that probabilities are distinctly in their favor. The variation
is not resisted but welcomed. The majority does not set the
fashion ; it is the few who are able to make pleasing modifica-
tions of style. The new pattern may not be better or more
beautiful than the old, but change is pleasing in itself and may
secure a wide vogue for an ugly or uncomfortable garment.
With organisms as with clothes the essence of beauty is fitness,
as Socrates long ago pointed out. The changes which make a
permanent contribution to evolutionary progress are those which
fit best into the existing structure and increase its fitness to its
surroundings. Our admiration for changes and likewise for
fitness in nature and in art, may be an intellectual reflection
of the evolutionary properties of organisms.
1 Cook, O. F., 1904. The Vegetative Vigor of Hybrids and Mutations. Proc.
of Biological Society of Washington, 17: 83.
272 COOK
DIFFERENCES OF ABERRANT HEREDITY (TERATISM).
There are many biological accidents, so to speak, as when in
the laboratory, or perhaps in the surf of the sea beach, an egg
of one of the simpler animals is shaken apart and develops into
two organisms instead of one. In a similar manner, through
some mistake of division, two-headed monsters and other mal-
formations occur. No less abnormal are many of the freaks
which can be produced by unfavorable conditions of growth.
Another series of abnormalities is caused by violations of the
law of symbasis, that is, through inbreeding which eliminates
heterism and normal diversity of descent.
Teratic characters which are the result of accidents of growth
or environment are not inherited, except as they may give rise
to a general weakness or debility of the organism. Teratic
neisms, on the other hand, are readily heritable.
Teratisms, like accommodational variations, have received
much study, especially from those who hoped to gain from
organic derangements an insight into the nature of the agencies
by which organic structures are built. The field of teratology
affords many interesting and significant data, but the correct
interpretation of them has been hindered, as in other departments
of evolution, by the confusion of issues which are essentially
distinct. There are at least as many kinds of teratisms as there
are of normal differences, and probably more, and endless
gradations of each kind. This is well illustrated by the phe-
nomena of mutation which have received so large an amount of
study in recent years. Mutations show all degrees of abnor-
mality, and they grade imperceptibly into the differences of
normal individual diversity (heterism) as well as into those of
normal and prepotent new characters (neism).
ABNORMAL MUTATIVE DIVERSITY.
That species are not normally constant and stationary in their
characters could not be better proved experimentally than by
the many attempts of breeders of plants and animals to maintain
constancy of characters in domesticated varieties. Selection
conduces at first to such a constancy or uniformity among all
ASPECTS OF KINETIC EVOLUTION 273
the members of the breed, those not conforming to the approved
standard being ruthlessly weeded out. The type having been
once established by this means, the variety remains for a period
of years more or less uniform, generally very much more so
than the members of wild species in nature. It is the experience
of all history, however, that varieties decline after a time from
their original excellence and have to be replaced by other, newer
sorts, which by reason of their more recent origin have been
subjected to shorter periods of inbreeding. The degeneration
of the older variety may be indicated in a number of ways, such
as a decline in fertility or weaker vegetative growth, or suscep-
tibility to fungous and insect parasites, so that it usually dis-
appears from cultivation or husbandry before the final stage of
sterility and extinction is reached, though the tendency in this
direction often becomes very obvious.
One of the symptoms of degeneration is the appearance of
numbers of freaks, sports or mutations, as they are variously
called. These variations of domesticated plants and animals
are often interesting, and sometimes valuable on account of
some special peculiarity, such as long hair, double flowers,
albino color, etc. This is especially true among the plants
cultivated for their flowers, where the never-ending diversity of
garden varieties is obtained by the preservation of the numerous
mutations into which wild species commonly "break" after a
period of domestication and inbreeding.
A general tendency among all such sorts is towards lessening
of seed production, and finally complete sterility may ensue.
The last is not a calamity in species which can be propagated
by cuttings, and many of our cultivated species have reached
this condition. With others, as for example, the " seedless "
green-house or forcing cucumbers, the extreme scarcity of seeds
which renders the variety desirable is at the same time a serious
obstacle to its cultivation.
On the strength of the older static, uniformitarian theory of
life, some writers have insisted that mutations must be caused
by environment, there being, in their opinion, nothing else to
cause them. The diversity of the mutations could be explained,
under this doctrine, only by environmental differences, such as
274 COOK
the variety of chemical compounds which might be found in the
soil of the same seed-bed. But no evidence of any constant
relation between any particular chemical and any particular
mutative character has been adduced. That any will be forth-
coming may well be doubted, in view of the fact that the same
or closely similar mutative characters often appear under very
different conditions of soil and climate, and very diverse muta-
tions under the same conditions.
The diversity of the mutations among themselves shows that
it is not safe as yet to assert more than this general organic in-
stability ; detailed causes are not yet revealed. The necessity
of this caution is rendered still more obvious by the behavior of
neotopic mutations, those induced by changes of environmental
conditions. If in a given environment a plant mutated only in
one direction, we would still be far from knowing adequately
that the environment caused the mutation, but even when we
have reason to believe that a change of environment has induced
mutation we are forbidden to go farther, because of the very
great diversity of the mutations which the same change of envi-
ronment or the same history of selective inbreeding can induce.
It has been shown in the discussion of neotopism that new
conditions may conduce to the appearance of abruptly discon-
tinuous mutative variations. The percentage of mutants is
notably larger in some regions than in others, but even this
does not compel us to believe that the conditions are the true
cause of the mutations, in any detailed sense. They are rather
to be thought of as merely the occasion of the change, by having
brought the coffee, the cotton or the Capsicum the sooner to the
point when it can no longer follow the hereditary road over
which the individuals must travel to attain the ancestral type of
adult form.
The mutative individuals are not to be thought of as the evo-
lutionary pioneers of the species ; they represent rather those
who are falling out by the wayside. They may be classed to-
gether with normal new variations in the sense that they are
outside of the specific norm or average, but the)' have a dif-
ferent position with reference to the evolutionary route of the
species. They represent the criminals and cranks, but not the
ASPECTS OF KINETIC EVOLUTION 275
leaders and reformers of the specific organization. For special
agricultural purposes mutations are often extremely valuable,
but when the desire is for the general improvement of the
species or the race, the essentially degenerate nature of muta-
tions cannot be left out of account.
The kinetic theory, if correct, shows that variations, to be of
evolutionary value, must take place in the species, or in full
contact with society, as it were, and not alone, or in disregard
of the condition, interests, and evolutionary direction of the
species at large.
Mutations are physiological phenomena, just as evolution
itself is a physiological process ; they will undoubtedly be
found to have causes when we are able to appreciate them.
They may be thought of as functional reactions from the re-
striction of normal heterism and diversity of descent. This ab-
normal condition of inadequate symbasis renders the organism
unstable and it falls down, degenerates or mutates.
Inbreeding is to be studied as a condition of existence, and
the manner in which the species reacts may be observed with
the same propriety as any more purely environmental problem.
Mutations may be abnormalities induced by abnormal conditions
of descent, but the reaction which produces them need not be
considered abnormal, since it is evidently the same tendency
which contributes to the maintenance of the normal heterism.
Indeed, the mutations might restore the normal intraspecific
diversity if interbreeding were permitted, as in nature. The
very fact that mutations of plants so frequently tend toward
dioecism might be accepted as another evidence of their value
as a corrective of inbreeding and deficient heterism.
Coffee mutations are often largely or completely unisexual, or
have greatly accentuated proterogyny or proterandry. A condi-
tion entirely analogous to a dioecious species could be obtained
by the crossing of such staminate and pistillate trees. Never-
theless, Professor De Vries has described and named such a
unisexual mutation as a new species, without regard to the tax-
onomic consequences of the application of this policy to sexually
differentiated higher animals.
If similar results justify the predication of similar causes the
2j6 COOK
appearance of similar mutations under diverse conditions may-
be accepted as proof that they were induced by the common
condition of inbreeding. Otherwise it would be necessary to
suppose that different topic factors have produced like results,
all of which shows the hopelessness of connecting mutations
with environment. Mutations represent abnormally accentuated
individual differences, and it seems not unlikely that most of them
follow lines of variation already established within the species.1
It has been found in all the species thus far canvassed that a
few mutative tendencies are much more frequently shown than
the others.
Nevertheless, it is not safe to assume that the same mutation
reappears even twice in identical forms. Whenever two similar
mutations of coffee, cotton, or Capsicum have been brought
together and compared they have always been found to be very
distinctly different, even more so than the unmutated individuals
of the uniform type from which they have arisen.
3. EVOLUTION, SPECIATION AND ADAPTATION.
One of the most frequent causes of confusion and error in
evolutionary thought is the failure to distinguish clearly between
evolution, speciation and adaptation; to distinguish, in other
words, between the process of evolution itself and two of the
relatively incidental results of environmental interference.
As long as a group of organisms remains united so that all
its members interbreed freely with each other, evolution remains
a unit in the sense that the whole group, though it may be chang-
ing any or all of its characters, still keeps together and retains
its specific coherence. But if such a group be split into two or
more parts which do not interbreed, evolution has as many
separate courses, and the isolated parts attain differential char-
acters, or, to use the words of former days, new species origi-
nate. It is obvious, however, that the differentiation of the new
groups, while accomplished by evolution, is occasioned by isola-
tion.2 The multiplication of groups, which as a process may be
'The oranges, lemons and pomelos afford, according to Mr. W. T. Swingle,
many excellent examples of this parallelism of mutative variation.
2 Confusion often creeps in at this point from the field of geology, for the
paleontological species is usually a random sample or section of the network of
ASPECTS OF KINETIC EVOLUTION 277
called speciation, is brought about by isolation, and is not a
necessary cause nor a necessary result of evolution.
In a similar way another group of evolutionary writers have
confused evolution with adaptation. Evolution results, not un-
commonly, in the production of characters which give a species
a specialized fitness for some particular environment. From
such facts it was argued that the increase of fitness or " survival
of the fittest" represented the method of evolution, or in other
words, that evolution is merely a process of adaptation actuated
by the selective power of the environment. The facts of nature
show, however, that evolutionary motion is not at all restricted
to directions of fitness, and it is also obvious that an evolution so
restricted could not produce even the characters of fitness upon
which it would depend for its supposed power to transform
species. Fitness must be attained by evolution before the envi-
ronment can give the character selective specialization by limit-
ing the evolutionary motion and deflecting it into more definitely
adaptive directions.
Evolution is the process of change by which the members of
an organic group become different from their predecessors, or
from other groups of common origin.
Symbasis is the normal evolutionary condition of free and ex-
tended interbreeding among the individual members of natural
species.
Symbasis implies adequate diversity of descent ; it is to be
distinguished on the one side from the narrow inbreeding which
induces abnormal mutations, and on the other from the wide
cross-breeding which produces abnormal hybrids.
The continual interweaving of the lines of descent from diverse
and unrelated ancestors appears to be necessary to sustain the
vitality and evolutionary progress of the higher plants and ani-
mals. The constructive evolution of new organic types does
not take place on simple or narrow lines of descent, but requires
descent. When considered with reference to each other, the contemporaneous
species of a horizon have the same significance as species of the present day, but
species of different horizons may have a relation which two simultaneous species
would never have, that is, one may be the true ancestor of the other. The same
word species is used for several categories of organic groups. See, Four Cate-
gories of Species, American Naturalist, April, 1899.
278 COOK
that large numbers of organisms advance in company, as in
specific groups A species is an organization of diverse, inter-
breeding individuals, dependent for its continued existence upon
its ability to maintain a broad and intricately interwoven net-
work of descent.
Speciation is the attainment of differential characters by seg-
regated groups of organisms, that is, by subdivisions of older
species.
Isolation of an organic group implies such a separation that
interbreeding with members of other groups is excluded.
Isolation is of primary importance in speciation, since isolated
groups of organisms always become different, but there is no
indication that isolation is an evolutionary factor in the sense of
causing or contributing to organic development. Its influence
is negative rather then positive, for small groups of individuals
advance less rapidly then large, and often deteriorate through
inbreeding and inadequate diversity of descent.
The multiplying of species is a process distinct from develop-
mental progress, and constitutes a distinct scientific problem.
Evolution might be explained without explaining speciation,
and speciation without explaining evolution. Recognition of
the diversity of the problems enables the factors to be separated ;
evolution depends upon symbasis, speciation upon isolation.
The segregation of a new group, whether by geographic
barriers or by selective discrimination, merely affords opportu-
nity for a new evolution to go forward. The means by which the
progress is accomplished are to be sought inside the group, and
not in the mere fact of isolation or selection. The multiplica-
tion of the number of evolving groups is a phenomenon distinct
from that of the evolution itself. The evolutionary question is
not how the species become isolated, but how they become dif-
ferent after they have been isolated.
Adaptation is the attainment of characters which place the
species in a more advantageous relation with its environment.
Selection is a form of isolation which eliminates from the spe-
cies individuals lacking in the expression of certain characters.
Under unconscious or natural selection only the most deficient
in these characters are rejected ; under conscious or artificial
ASPECTS OF KINETIC EVOLUTION 279
selection by man only the most proficient are saved. Selection,
by deflecting and confining the evolutionary motion of the
species to particular channels, conduces to the adaptive speciali-
zation of characters, but it is not an actuating cause of their
development.
Symbasis is a primary factor in evolution, an obstacle or neg-
ative factor in speciation. Selection often accounts for the
accentuation of differences between related species, but is not on
this account to be reckoned as an actuating cause or principle
of evolution. It may explain the direction which evolution has
taken with reference to a particular character, but does not show
how the evolution has been accomplished.
Adaptation represents the bionomic aspect of evolution, specia-
tion the taxonomic. Selection strengthens adaptations ; isola-
tion multiplies species; symbasis conducts evolution. Adapta-
tion and speciation have appeared to many writers as causes of
evolution, but in the kinetic or physiological interpretation they
appear only as results, quite incidental to the true evolutionary
process of progressive change in species.
RELATION BETWEEN HETERISM AND SPECIATION.
Recognition of the phenomena of heterism, the normal diver-
sity of the interbreeding members of specific groups, is neces-
sary, perhaps, to a full appreciation of the preceding distinctions
between evolutionary change or vital motion and the subdivi-
sion or multiplication of species. Although commonly treated
together, or even indiscriminately confused, these two processes
are quite distinct. They may even run counter to each other,
for evolutionary progress is not assisted by the subdivision of a
subdivision of a species, but more likely to be hindered. The
larger the number of interbreeding individuals the larger are
the possibilities that desirable variations will appear, and the
wider are the opportunities of a progressive utilization of a new
feature. The group, as a whole, will advance more rapidly
than if the range of transmission be narrowed by subdivision.
Segregation permits the subordinate groups to become dif-
ferentiated, but it does not conduce to the advance of the whole
series. The newly segregated groups become capable of tax-
Proc. Wash. Acad. Sci., January, 1907.
280 COOK
onomic recognition as species, but this is a mere incident of
evolution, not an actuating cause nor a necessary effect.
The recognition of heterism or diverse, alternative descent,
and the frequent development of sexual and other specializations
of heterism inside specific lines, shows that the subdivision of
species is to a very small extent, if any, the direct result of evo-
lutionary advance. Not only can diverse characteristics exist
inside specific lines, but it is an advantage to maintain just such
heterogeneity. The only condition in which heterism would
directly conduce to the formation of a new species would be that
of alternative characters which hindered interbreeding. It is
conceivable, for example, that a species might contain at the
same time variations both toward earlier and later flowering,
and that, instead of counteracting each other, both tendencies
might become gradually more accentuated. The incidental
result would be that interbreeding would cease and two separate
groups would become established.1 In such a case it might
well be claimed that evolution had directly resulted in the multi-
plication of species, but it would still be true that it had done
so only by means of segregation, and would show only that
evolution might result in segregation, not that segregation is a
factor in evolution, as often supposed. Isolation is an important
consideration in phylogeny or historical biology, which under-
takes to tell why the species are in the places we find them.
But isolation and species-subdivision have only a remote aud
incidental connection with evolution ; they do not cause the pro-
gressive change.
The confusion of evolution with speciation has greatly impeded
the progress of evolutionary science by withdrawing attention
from the real issues to relatively unimportant considerations.
It has misled many students of evolution into the belief that
isolation or segregation is an important factor of evolutionary
progress, whereas its influence is negative rather than positive.
The selection doctrine of Darwin and the mutation doctrine of
De Vries are both theories of speciation rather than of evolution.
^he hickory-borer {Clytus f ictus) and the locust-borer {Clytus robinice) are
very similar species, and the females are quite indistinguishable. The perfect
insects of the former emerge however, in June, those of the latter in September.
See Packard, A. S., 1880, Guide to the Study of Insects, p. 497.
ASPECTS OF KINETIC EVOLUTION 28 1
They hold that new groups have to be isolated, that new species
have to be made, in order to originate and preserve new char-
acters.
" Each new variety or species, when formed, will generally
take the place of, and thus exterminate its less well-fitted parent.
This, I believe to be the origin of the classification and affinities
of organic beings at all times ; for organic beings always seem
to branch and sub-branch like the limbs of a tree from a common
trunk, the flourishing and diverging twigs destroying the less
vigorous, the dead and lost branches rudely representing extinct
genera and families."
Evolution, on this basis, would not be a process of transfor-
mation so much as of elimination and substitution. The parental
type remains relatively stationary and unmodified until the new
form can expand and replace it. The same is true of the
mutation theory of De Vries, except that the new variations are
supposed to be larger. The new character can persist only as
it is able to crowd out its parent or neighbor and to conquer for
itself a place in nature. Every new character which has been
preserved, must, under these theories, be environmentally useful,
which a very large proportion of the characters and differences
of plants and animals are not, as even the most pronounced
Darwinians like Professor Lankester now admit.
The kinetic theory does not encounter these difficulties and im-
probabilities. It recognizes speciation and evolution as entirely
distinct problems, and does not require that a new species be
made in order to preserve a new character, or even that char-
acters must be useful. Characters may be preserved even when
they are harmful, and may contribute to the extinction of the
species. Evolution, in the kinetic theory, is definitely a proc-
ess of transformation by the adoption and propagation of new
variations in existing species. New variations are not segre-
gated from the parental type, but interbreed freely with it, and
thus bring about its evolutionary progress.
SELECTION EXPLAINED BY EVOLUTION.
As so often happens, the philosophical abstractions of logic
have yielded very little assistance in the comprehension and
282 COOK
description of the facts of evolution. Numerous attempts have
been made to define the relations of selection and evolution by
means of Aristotle's categories of causation. Perhaps the best
example of this is by Professor Cattell :
" In discussions on the theory of evolution we find Neo-Dar-
winians saying that ' natural selection ' is the cause of the origin
of species, and Neo-Lamarckians saying that the environment
and the movements of the animal are the causes of adaptations.
Now in these cases the word ' cause ' is used ambiguously, igno-
rance of the facts of evolution being concealed by the exhibition
of ignorance of logic.
" I wonder how many men of science have read Aristotle, or
understand his distinctions between material, efficient, formal
and final causes. We are not here concerned with a formal
cause, the idea or plan of a thing, nor with a final cause, the
end for which it is made ; but no student of organic evolution
can afford to ignore the distinction between material and efficient
causes, or between the occasion and the efficient cause of an
event. The material cause is that of which a thing is made,
one of the occasions or necessary conditions of its existence ;
the efficient cause is that which produces a thing and makes it
what it is. When no qualification is used cause should mean
efficient cause or vera causa.
" ' Natural selection ' is no cause of the origin of species, but
may be the cause of the annihilation of unfit species. Whether
or not the environment, or consciousness, or the movements of
animals are causes of hereditary modifications are open ques-
tions. What is called the cause of an adaptation is, however,
usually only its occasion."1
Selection is neither a formal, a final, a material nor an effi-
cient cause of evolution. Evolution goes on without selection.
This shows how poorly adapted the Aristotelian categories are
for the expression of relations so complex as those of evolution.
Those who depend upon systems of abstract formulation for the
comprehension of biology can fit selection and evolution into
these categories only by saying that evolution is the cause of
'Cattell, J. McKeen, 1S96. The Material and Efficient Causes of Evolution.
Science, N. S., 3 : 66S.
ASPECTS OF KINETIC EVOLUTION 283
selection. This, at least, would not wholly misrepresent the
facts of nature, for evolution accomplishes the results which it
has been customary to ascribe to selection.
Unless evolution were going on the selective effects would not
appear. The older writers commonly made the confusion even
worse by assuming that adaptation and evolution are the same.
Adaptation is not evolution, but only a special kind or result of
evolution. Selection aids evolution to produce adaptation.
Translating again into scholastic language, evolution is the
efficient cause of adaptations, while selection is the occasional
cause or condition which conduces to adaptations. Adaptive
characters are brought into existence in the same way as other
characters, by the evolutionary motion of species. Adaptation
can be said to be caused by selection only as a pure abstraction,
when it refers merely to the deflection which environmental
obstacles have induced in the normal motion of the species.
The confusion of ideas has not been limited to advocates of
natural selection, but is shared even by its most active opponents.
Thus Mivart, in a book written to show the inadequacy of the
selective theory of evolution, admits for selection a power which
it does not have :
" ' Natural Selection,' simply and by itself, is potent to explain
the maintenance or the further extension and development of
favorable variations, which are at once sufficiently considerable
to be useful from the first to the individual possessing them.
But Natural Selection utterly fails to account for the conserva-
tion and development of the minute and rudimentary beginnings,
the slight and infinitesimal commencements of structures, how-
ever useful those structures may afterward become."1
As long as we fail to perceive that selection is not a cause of
evolution the issue remains uncertain. If selection is able to
cause even a little evolution it might, with time, cause much.
The " slight individual differences" may suffice for the work,
as Darwin claimed, and the practicability of a selective evolu-
tion appears to turn on such arguments as the amount of time
estimated by geologists and physicists from considerations even
more obscure than those of biology itself. Selection is not
1 Mivart, St. George, 1871. On the Genesis of Species, New York ed., p. 35.
284 COOK
merely inadequate as a cause of evolution ; it is not an evolu-
tionary cause at all, but only a test and an evidence of the effi-
ciency of other causes which reside in the species and enable it
to go forward with persistence, even when obliged to follow a
narrow path between environmental obstacles.
Selection is potent to explain the further extension and devel-
opment of favorable variations only by its ability to influence an
evolution which is already in progress, and not in any sense
which renders it a cause of evolution. The selective potency
of the environment consists only in its ability to restrict evolu-
tion, not in any power to actuate or to carry forward the process
of development. Selection may still be enumerated as an evo-
lutionary factor, but it is wholly a negative factor, restrictive
and not constructive.
DARWINIAN FORMULAE OF EVOLUTION.
Evolution is a name for the process of gradual change by
which the diversity of organic nature has come about. Darwin's
theory of natural selection was based on the indication that some
of the characters of plants and animals have been attained
because individuals possessing these characters had an advan-
tage in the struggle for existence. Many Darwinians " more
Darwinian than Darwin " have made this proposition universal
and say in effect that all characters of plants and animals have
arisen because they give or have given their possessors advan-
tages in the struggle for existence.
Darwin's original proposition points in the direction of an im-
portant truth, that plants and animals are specially adapted to
their various environments. Great emphasis came to be placed
on this point because the adjustment of species to their respec-
tive places in nature had been taken to prove the special crea-
tion of species, so that a theory of gradual development had to
supply a solution for the problem of adaptation before it could
expect to receive general credence or even the serious con-
sideration of the scientific public.
In the course of the discussion which raged in the decades
after the publication of the Origin of Species attention was prin-
cipally directed to the phenomena of adaptation and speciation,
ASPECTS OF KINETIC EVOLUTION 285
and the Darwinian doctrines were crystallized into formulae
which were believed to demonstrate evolution from the facts of
the struggle for existence and the survival of the fittest.
PROVED FACTS. NECESSARY CONSEQUENCES.
Rapid Increase of Organisms. "1 _ . . _ .
m itvt ^ i-r j- -j i ox »• ^Struggle for Existence.
1 otal Number of Individuals stationary. J
Struggle for Existence. "i _ . , . . „. ,
TT b° . , TT . . ^Survival of the Fittest.
Heredity with Variation. J
Survival of the Fittest. \ Changes of Organic
Change of External Conditions. J Form.
The earlier Darwinists were practical men and made the best
use of the facts as they knew them. Whether the facts they
regarded as proved would really be able to bring about evolution
in normally stationary species is a question which might still be
debated on philosophical grounds, like the fourth dimension of
space and other hypothetical problems. But for practical pur-
poses there is no need to reopen the discussion, since it is now
apparent that formulae like those quoted above leave out of
account a very important part of the facts of nature, the very
facts, as it happens, which are most potent in the development
of organic types. The evolution, if any, which the formula
would provide would certainly not be that found in nature.
Scientific progress, at least in biology, does not follow the
lines of formal mathematics or logic, but depends on history and
human nature, like political and economic movements. It could
not be expected that the evidences of evolutionary processes
would be carefully weighed and correctly appreciated at a time
when the very idea of evolution was being assaulted as an im-
moral perversion of intellect.
The best that could be done at the time was to drive the piles
of accepted inferences into the mud of ignorance. The struc-
ture reared on such a foundation could not be a permanent one,
but it has served to shelter a generation of students of nature,
and enabled them to prepare the foundations of a more secure
edifice of evolutionary doctrine based directly on ascertained
facts.
286 COOK
In popular discussions it often happens that the best and most
important data are left in the background because the public is
not ready to appreciate them. Thus Huxley, who rendered the
most valiant service in the defense of Darwinism as a theory of
environmentally caused evolution, also wrote this discriminating
statement :
" It is in the recognition of a tendency to variation apart from
the variation of what are ordinarily understood as external con-
ditions that Darwin's view is such an advance on Lamarck."
To have secured popular appreciation for these nonenviron-
mental variations at that time was manifestly impracticable. Even
after fifty years their existence is still generally unrecognized.
The credit of turning the scientific world to the study of evo-
lution will always belong to Darwin and Huxley, but the fifty-
years canvass which has now been given to the Darwinian
theory of environmental action upon normally stable species has
yielded nothing of moment. Huxley's appreciation of the
advance of Darwin beyond Lamarck has not been shared by
the evolutionary public, and the result has been a general
reaction toward pre-Darwinian conceptions, and even to some
which Darwin himself considered and dismissed.1
Perhaps the time has come to renew the consideration of the
problem from the kinetic standpoint and to take into account
again the normal diversity of descent and the normal inter-
breeding of the members of species. These facts have re-
mained veritable stones of offense for the builders of static
theories of environmental causation, but they can now be util-
ized as foundations of a new and more commodious structure of
evolutionary thought.
4. MODES OF EVOLUTIONARY MOTION.
The law of evolution which declares that organic nature has
come into existence through a connected and gradual process,
and not through millions of separate creations of species, now
commands the practically universal adherence of biologists, and
1 " And again, after mentioning the frequent, sudden appearances of domestic
varieties he speaks of ' the false belief as to the similarity of natural species in
this respect.'" See Mivart, 1S71. Genesis of Species, 36.
ASPECTS OF KINETIC EVOLUTION 287
has also been applied as a philosophical principle in the elucida-
tion of many facts and problems outside the organic series.
After being once adequately presented such an integration of
knowledge could scarcely have failed to command respectful
consideration, and its general acceptance has already become so
much a matter of course that the word evolution is not uncom-
monly used in a much narrower sense and identified with one or
the other of the theories which have been invented to explain
the methods and immediate causes of the process of organic
change, a subject upon which there is still no lack of differing
opinions.
Although the doctrine of the independent creation of species
has been set aside, it has proved much more difficult to elimi-
nate, even from the minds of the biologists themselves, what may
be called the static view of nature. It is not strange that the
stability of species should have first impressed the scientific
mind. When closely similar plants and animals, not distin-
guished by the popular intelligence, were found to differ in
minute particulars which were, nevertheless, invariably trans-
mitted to their offspring, a creative pre-arrangement seemed to
be the only explanation, and the apparently gratuitous variety
of organic forms was very naturally ascribed to causes outside
the reach of human comprehension.
Later, when it was realized that in spite of the wonderful sta-
bility of species the component individuals are never identical
in all particulars, but differ endlessly among themselves, and
that even these minor differences tend to reproduce themselves,
the theory of the gradual transformation and subdivision of spe-
cies became a logical possibility, and the search at once began
for a method by which variations of a certain kind could be
accumulated instead of cancelling each other and disappearing
in a stationary average.
The explanation of evolution is the biological task now re-
ceiving the widest and most earnest attention, and is the subject,
directly or indirectly, of a literature so vast that even a casual
reading of all the books and papers as they come from the press
would be a formidable undertaking. Such multiplicity of pub-
lications betokens, of course, a corresponding diversity of opin-
288 COOK
ions. Not only is there no common point of view from which
evolutionary problems are studied ; there is no agreement re-
garding the nature of the problem or the methods by which a
solution is to be expected, nor even a general evolutionary
language in which discussion may be made intelligible.
Explanations of such a process as evolution are of many dif-
ferent grades or categories. Literary demands were satisfied
by a name and a definition ; theologically it was sufficient to
substitute the idea of a continuous for an intermittent creation.
Philosophy was content with the predication of gradual trans-
formations due to natural causes. Even among biologists there
are those who appear to have rested content with similar gen-
eralities, though some have not failed to appreciate that when
Darwin established the probability of biological evolution he
opened a multitude of other questions regarding the nature,
causes and significance of the process. Realizing at once the
importance of his discovery and the difficulty of securing the
confidence of either the scientific or the general public, he ex-
pended years of labor in the collection of facts and the con-
trivance of theories which should increase the plausibility of the
main proposition, that plants and animals are variable, both in
nature and in domestication, and that the diversity of organic
nature was gradually attained through the medium of variations.
When the causes of a phenomenon are known the sequence of
events can be predicted. Theory may then out-run and assist
observation. On the other hand, if the causes are out of reach
it is obvious that we can not even theorize to advantage without
a correct conception of the externals. We must know what
takes place before we are in a position to ask why it takes
place. In some lines of thought the simple historical concep-
tion of continuous evolutionary change greatly assists in the
causal explanation of events, but in biology, the home of the
evolutionary conception, the sequence is still in doubt and we
are still far from the causal stage of knowledge. It is needless,
perhaps, to add that the application of false and fictitious
biological analogies vitiates much philosophical and sociolog-
ical literature.
Gravitation was not explained by Newton, its behavior was
ASPECTS OF KINETIC EVOLUTION 289
carefully studied and found to be consistent, and mathematically
precise. "Natural laws" are working substitutes for causal
explanations. When we understand the ^>/iy, the ' law ' of
sequence becomes superfluous.
There is a frequent impression that the principal object and
result of scientific study is generalization, but as a matter of fact
the progress of science leads much more often to particulariza-
tion, to the recognition of distinctions between things previously
supposed to be alike. The powers, forces and principles which
formed the subject of abstract discussions in the earlier history
of science are being gradually relegated to the background, as
our acquaintance with the facts improves and yields insight into
the causal connection of events which formerly appeared mere
sequences.
Evolution is not merely a law, but a process. In each species
an evolution is going on, in a manner quite analogous to the
processes of growth, locomotion and reproduction in the indi-
vidual. Certain features of similarity there are, no doubt, in
all evolutions, as there are in digestion and other general forms
of vital activity. These general similarities can be collected, it
may be, and formulated as laws if this method of expression be
desired, though this would be, after all, only a special method of
describing the processes. Laws themselves have to be ex-
plained by resolving them into processes. Only hopelessly
metaphysical minds are satisfied with abstract statements, or
able to imagine that generalizations are explanations.
Evolutionists agree that organisms change, but regarding the
nature and causes of change great diversity of opinion still
exists. The progress thus far is negative. We have learned
that evolution is not a merely mechanical process, or due to
merely environmental causes, and that it is not a merely cyto-
logical process, due to internal mechanisms of descent. It is a
superorganic process accomplished through the association of
organisms into large specific groups.
Evolution is, in short, a process of change in organisms, a
kind of motion by which plants and animals have advanced
from the simple and undifferentiated protoplasm of the lowest
types to the highly specialized and complicated structures of the
29O COOK
highest. For half a century this probability that the world of
organism has come into existence through long series of changes
has been the most prominent idea before the scientific public,
but we have not yet accepted fully the simplest purport of the
idea of evolution and asked ourselves the direct question : By
what mode or manner of motion is evolution accomplished?
Some have assumed that the evolutionary causes are resident
in the environment, and others that they exist in the organisms
themselves. A third alternative is here considered, that evolu-
tion arises from the association of organisms into interbreeding
groups, or species. Species, in this interpretation, appear to
contain the causes of evolution, instead of evolution affording
the explanation of species.1
The first result of Darwin's attempt at establishing the general
idea of evolution on a basis of relation to concrete facts was a
long and bitter controversy with those who clung to the older
theory that the species of nature had arisen by separate creative
acts. Biological science made good its escape from the house
of theological bondage, but its controversial sins have con-
demned it to forty years of wandering in the wilderness of
species-formation and environmental adjustments, desert regions
often very interesting in themselves, but remote enough from
the fertile fields of evolution.
It may well be doubted whether any student of nature, if
asked the direct question, whether species are normally at rest
or normally in motion, would definitely and dogmatically hold
to the static assumption. This appears to have been made quite
unconsciously, in the great majority of cases, or taken entirely
for granted. Nevertheless, all the current theories and methods
of investigating evolutionary problems are based on this assump-
tion of normally stationary species. The influence of the
doctrine of special creation was too strong to be overcome at
once, even by biologists who were very active in opposing its
theological implications.
The idea of environmental causation of evolution has com-
1 Cook, O. F., 1904. Evolution not the Origin of Species, Popular Science
Monthly, for March. Reprinted with additions in the Smithsonian Report for
1904 under the title, The Evolutionary Significance of Species.
ASPECTS OF KINETIC EVOLUTION 20,1
pletely pervaded all our forms of thought and expression ; it has
been the general base and background of evolutionary science.
The average of biological opinion remains very nearly in the
same place as Darwin's original announcement of a theory of
environmental causes of evolution. The environment is sup-
posed to bring about the variations and to select and preserve
those having adaptive value, and thus to cause evolution.
Though Darwin himself appreciated in later years the tentative
character of this inference and sought in every direction for
contributing agencies to strengthen and support it, some of his
followers have had no such reluctance in crystallizing the idea
of environmental causes into definite formulae which are still
the shibboleths of evolutionary orthodoxy. President David
Starr Jordan not long ago quoted an interesting paragraph from
the evolutionary creed of the late Dr. Eliot Coues :
" Every offspring tends to take on precisely the structure or
form of its parents, as its natural physical heritage ; and the
principle involved, or the law of heredity, would, if nothing
interfered, keep the descendants perfectly true to the physical
characters of their progenitors ; they would breed true and be
exactly alike. But counter influences are incessantly operative,
in consequence of constantly varying external conditions of
environment ; the plasticity of organization of all creatures ren-
dering them more or less susceptible of modification by such
means, they become tinlike their ancestors in various ways and
to different degrees. On a large scale is thus accomplished,
by natural selection and other natural agencies, just what man
does in a small way in producing and maintaining different
breeds of domestic animals."1
It should be needless to say that this formula, like many
statements of similar import which might be collected from
biologists of a former generation, and even from those of the
present day, involves a complete misrepresentation of the facts.
No such species has been found in nature, and no species has
been made uniform by an}' refinement of artificial conditions.
It is possible through selective inbreeding to eliminate a large
part of the normal individual diversity of organisms, but at the
'The Popular Science Monthly, May, 1903.
292 COOK
expense of vitality, and at the ultimate cost of extinction, where-
ever such experiments are continued for a sufficient period of
time.
More recently still, a son of Charles Darwin, speaking as
President of the British Association for the Advancement of
Science, has reflected the conclusion which the scientific world
has drawn from his father's doctrine of natural selection, that it
is the cause of evolution.
" The fundamental idea in the theory of natural selection is
the persistence of those types of life which are adapted to their
surrounding conditions, and the elimination by extermination
of the ill-adapted types. The struggle for life amongst forms
possessing various degrees of adaptation to slowly varying con-
ditions is held to explain the transmutation of species."1
It may be doubted whether Charles Darwin himself would
ever have ventured upon so direct and so generalized a state-
ment. He was anxious always that his readers should take a
favorable view of the feasibility of evolution through natural
selection, but at the same time he could not forget the immense
improbability of the claim that all characters are adaptive and
useful. This caution was not shared by Wallace, who has
never hesitated to proclaim selection as the cause of evolution,
alike efficient and sufficient. With Darwin, natural selection
remained a theory, and he never ceased to seek additional evi-
dence to support or supplement it, but with Wallace and many
others it soon became an undoubted fact, or at least an unques-
tioned formula.
" Suffice it to say here that this theory of natural selection —
meaning the elimination of the least fit and therefore the ulti-
mate 'survival of the fittest' — has furnished a rational and
precise explanation of the means of adaptation of all existing
organisms to their conditions, and therefore of their transforma-
tion from the series of distinct but allied species which occupied
the earth at some preceding epoch. In this sense it has actually
demonstrated the ' origin of species,' and, by carrying back this
process step by step into earlier and earlier geological times, we
1 Darwin, G. 11., 1905. Address of President of the British Association for the
Advancement of Science; Nature, 72 : 370. Science, N. S., 22 : 258.
ASPECTS OF KINETIC EVOLUTION 293
are able mentally to follow out the evolution of all forms of life
from one or a few primordial forms. Natural selection has
thus supplied that motive power of change and adaptation that
was wanting in all earlier attempts at explanation, and this has
led to its very general acceptance both by naturalists and by the
great majority of thinkers and men of science."1
But notwithstanding the categorical certitude of these and
many similar statements which might be collected, it is still
very doubtful whether any naturalist, that is, any careful and
experienced student of plant or animal species in nature, would
definitely claim or undertake to prove that isolation or natural
selection is, or could be, a true, actuating cause of evolution.
Nevertheless, many such students have permitted themselves to
use expressions which can be so interpreted, and the philo-
sophical, and especially the unbiological part of the scientific
community, has not hesitated to repeat and elaborate this idea
as though it were an ascertained and undeniable fact.
Primitive peoples are ever ready to personify nature and in-
animate objects and to ascribe to them the ability to grow and
to put forth other spontaneous actions. Modern science has
gone to the other extreme. It has denied to the species of
plants and animals the powers of development which they
really possess, and has sought for the causes of organic evolu-
tion among the inanimate objects of the environment. It has
done this quite gratuitously and as a matter of course, without
taking the trouble to raise the question whether there might be
any alternative worthy of consideration.
The primitive theory of a flat earth, with its various childish
explanations of the sun's whereabouts during the night, endured
for thousands of years, but finally gave place to the conception
of a spherical earth, about which the luminary revolved contin-
uously. Nevertheless, this improved doctrine, while adequate
for the explanation of the phenomenon of days and nights, was
also erroneous, and had to be replaced by a still broader inter-
pretation of astronomical facts.
Astronomers of the Ptolemaic school saw no reason to doubt
that the earth was stationary, and they were able to predict
'Wallace, Alfred Russell, 1900. The History of the Nineteenth Century.
294 COOK
eclipses and planetary movements in spite of this fundamental
misconception. Mysteries and discrepancies remained, how-
ever, until students of the heavenly bodies were willing to
admit that the sun was the center of the system and that the
earth revolved like her sister planets.
If adaptations were the only evolutionary phenomena in need
of explanation, the doctrine of environmental causes might serve
scientific purposes for as many centuries as the Ptolemaic
astronomy, but it has become very apparent that many organic
changes are going on which have no connection with adapta-
tion, and which would not be explained by selection, even if
everything claimed for it were to be admitted.
To think of species as normally in motion will be found very
difficult, no doubt, by those who have been so long accustomed
to take it for granted that they are normally at rest. The dif-
ficulties of readjustment are still further increased by the fact
that the available technical language and customary forms of
expression have been elaborated for the exposition of the static
doctrine of environmental causation, and lend themselves only
with difficulty to the presentation of the opposite doctrine, that
species are normally in motion.1 Many distinctions formerly
considered of value now appear to have little significance.
Many things are readily explainable which seemed utterly
mysterious before, and many new problems can be approached
which have hitherto appeared quite inaccessible.
Since the time of Darwin a long and varied series of amend-
ments and supplements have been proposed for the doctrine
of natural selection, and no end of diversity of individual
opinion has existed among biologists regarding the adequacy
and relative significance of the various factors and forms of
selection. The kinetic theory enables us to look beyond all
this cloud of discussion and to perceive that selection is not
merely inadequate as the cause of evolution ; it is not an evo-
lutionary cause at all, in the concrete physiological sense ; it
does not set evolution in'motion, nor keep it going.
1 Three classes of difficulties attend the progress of science, the concrete diffi-
culties of ascertaining facts, the conceptual difficulties of interpreting them, and
the philological difficulties of describing the new facts and the concepts in terms
of general intelligibility. The problems of expression are often quite as serious
as the others, and quite as worthy of scientific study.
ASPECTS OF KINETIC EVOLUTION 295
The difficulties which attend the presentation of the kinetic
theory arise, no doubt, largely from this fact, that it breaks
with the Darwinian traditions and recants the whole doctrine
of selection as the actuating cause or principle of evolution.
It seeks for the laws and causes of evolution, not in the environ-
ment, nor in a "hereditary mechanism" of the organisms
themselves, but in the association of organisms into specific
groups of interbreeding individuals, which are the units of
evolutionary motion. The reader is therefore duly warned
that, unlike most of the suggestions made since the time of
Darwin, kinetic evolution does not come as an amendment to
natural selection.
Those who may wish to experiment with the new method of
biological locomotion had best unload beforehand all their pre-
possessions regarding natural selection as an evolutionary cause.
This does not mean that selection is to be permanently aban-
doned, but it can be taken up later, and put to a much more
useful purpose than before. Indeed, the material analogy may
be carried a step further by saying that the supposed evolu-
tionary properties of selection have been due to an unsuspected
admixture of kinetic implications, the selection idea in itself
being quite inert, and incapable of actuating even a logical
conception of evolutionary motion.
Theories which located the causes of evolution in natural
selection or other forms of environmental reactions have con-
sidered the species normally stationary until acted upon by the
external forces. Theories which located the causes inside the
organisms have thought of evolutionary motion as proceeding
in definite directions without regard to environmental influences,
except as they might work the extermination of types poorly
fitted to the conditions they happened to encounter. The kinetic
theory, in appreciating the fact that the evolutionary change
goes forward in a network of descent woven by the free inter-
breeding of the individual members of the specific group,
reaches the conception of a highly composite, indeterminate
motion carried along without any environmental causation, but
at the same time capable of being deflected through selective
influence into channels of adaptation.
Proc. Wash. Acad. Sci., January, 1907.
296 COOK
The most feasible way of presenting the kinetic interpretation
and of comparing it with other alternative views has seemed to
be that of canvassing further this question of the nature of the
motion by which evolution is supposed to be accomplished in
accord with the different doctrines. It may be that by so doing
the issue can be made more direct and that there will be less
risk of wandering into the unprofitable side-paths of aimless
discussion. The fact already referred to, that the vocabulary
of evolution has been constructed so largely for the explanation
of static doctrines, makes it necessary to review briefly some of
the primary terms and distinctions. .
PHILOSOPHICAL USES OF EVOLUTIONARY MATERIALS.
Circles can be described through any three points, and new
systems of philosophy can be elaborated out of a few primary
distinctions. As geometry and other speculative sciences of
number and space relations have been called upon to assist in
the measuring of land, the building of machines, the naviga-
tion of the sea, and the exploration of the heavenly bodies, so
have the methods of philosophy been applied to evolution. This
is not only because philosophers have become interested in evo-
lution, but because philosophical systems are the most available
form of mental machinery for dealing with complex miscel-
laneous, hypermathematical problems, like evolution.
It has been the ambition of philosophers to frame general
descriptions of the universe of thought in terms of logical con-
sistency. Indeed, the tendency in philosophy has been to place
by far the greater emphasis upon the logical consistency, each
philosopher assuming the right to choose his own particular
universe for descriptive purposes. Unfortunately for evolu-
tionary philosophers, their systems are confronted, sooner or
later, with the concrete facts of plant and animal life, and then
no amount of logical consistency can atone for a biological over-
sight. Theories may be perfectly logical and yet be utterly
inadequate. But even though not correct or final, philosophical
theories of biology may still amply justify themselves by aiding
in the discovery of relations which might have remained unsus-
pected and hence uninvestigated. The ungrateful facts may
ASPECTS OF KINETIC EVOLUTION 297
refuse to support the theory which has led to their discovery,
but this does not render the facts of less value for practical pur-
poses, nor even for use in other and better theories. It is as
idle to condemn theories as to worship them ; it is the old
counsel of using and not abusing.
Theories of evolution have been made thus far from the facts
of variation, the differences which exist among the members of
the same species. In each of the different systems it has been
assumed that a certain kind or group of variations represented
steps in the evolutionary journey. The philosophical circles of
doctrine have been described in different planes in accordance
with the selection of particular lines of samples from the multi-
tudinous facts of variation.
The theory of natural selection is supported by the facts of
adaptation and geographical distribution. The theory of direct
adaptation was based on variations of accommodation, on the
fact that organisms are often able to adjust themselves to a con-
siderable range of environmental conditions. Nageli's deter-
minant theory was based on the fact that the plants most care-
fully studied by him showed tendencies of variation in definite
directions. The theory of mutation rests on facts of abrupt
modifications in the form and structure.
The kinetic interpretation claims the consideration of believers
in the other doctrines because it affords a larger outlook upon
the facts of nature. Adaptation and mutation no longer appear
as unconnected or contradictory phenomena, but are completely
reconciled under one simple inference.
The kinetic theory differs from its predecessors not merely
nor principally in dependence upon a different series of facts of
variation, but also in the method of combining them. It is not
merely a circle cut in one plane or described on one cross-
section of data, but considers all three dimensions of space. It
permits us to understand that variations are not all of the
same character or of the same evolutionary significance. It
also recognizes that as species are networks of descent and not
mere aggregates of similar organisms, so evolution is not merely
a summary or integration of variations, but is accomplished only
through the normal extension of the specific reticulum.
298 COOK
In pre-evolutionary days there was no need to make special
studies of variation, since it was freely admitted by the scientific
public that the differences of varieties and even of species arose
from environmental influences upon normally stationary types.
The supposition was that genera had been created, rather than
species, though Linnaeus interfered with this view by combining
many of the groups recognized by his predecessors as genera
and by holding then that species also were specially created.
The significance of this history is that the two ideas, first, that
of normally uniform and stationary species, and second, that of
the environmental causation of variations, were inherited from
the pre-evolutionary period and have continued to be used with-
out scientifically critical warrant.
Moreover, the first quest for evolutionary causes was not made
in the direction of more thorough study of the constitution of
species, but was concerned rather with the exploration of the
boundaries and the gaps between species. The issue raised by
Darwin, and more especially by Huxley and other controversial
biologists, was that of proving to the theological public that new
species could be produced by evolution, instead of definitely
investigating the means by which the evolutionary progress of
species is accomplished. The chief interest was directed, not
to evolution itself, but to the two results of evolution, speciation
and adaptation, the generally admitted pre-Darwinian doctrine
of environmental causation of variations serving all the imme-
diate needs of the discussion.
TYPES OF EVOLUTIONARY THEORIES.
Static Theories. — According to the theory to which the
name Darwinism is generally, though unjustly, limited, evolu-
tion is brought about by the influence of environment, which
causes organisms to vary, preserves advantageous modifications,
diminishes or eliminates the relatively unfit, and thus transforms
or subdivides species.1 Such theories may be called static be-
cause they assume that species are normally in a state of rest or
1 "Darwin has left the causes of variation and the question whether it is lim-
ited or directed by external conditions perfectly open." Huxley, Life and
Letters, 2 : 205, 1901.
ASPECTS OF KINETIC EVOLUTION 299
stable equilibrium, so that evolutionary motion appears as the
result of forces external to the organism. Differences among
the individuals of a species are ascribed to environmental
causes ; without such disturbing influences the species is
thought to remain stationary and uniform. Darwin and many
others have believed in spontaneous variations, but it has been
argued that such must be ' swamped ' in the general average by
intercrossing, so that without the external influence of selection
there could be no progressive change.
Darwin himself admitted that in the domestic animals ' man
does not cause variability and cannot even prevent it,' but on
the same page he made the contradictory statement that * the
initial variation is caused by slight changes in the conditions of
life,' and this has served as the cardinal principle of those who
have claimed to be Darwinists, while rejecting the wider per-
ception cited above. Again in the same work (p. 79) Darwin is
ready to admit that ' a somewhat complex, though apparently
useless, structure may be suddenly developed without the result
of selection.'1
Saltatory Theories. — That variations can be preserved by
selection, and are frequently so preserved among domesticated
animals and plants, cannot, of course, be doubted, but the diffi-
culty of believing that natural conditions would provide the
necessary selection or segregation at the right junctures has
led many biologists to look with favor upon the idea that new
species have not arisen by imperceptibly gradual changes, as
Darwin supposed, but by a succession of leaps, as it were.
This view is defended by reference to the so-called ' sports' or
very pronounced variations occurring among domestic plants
and animals.
Mr. Francis Galton has compared the organism to a polygo-
nal body which comes to rest at a point considerably in advance
of its former position when its equilibrium has been sufficiently
disturbed. Professor De Vries has adopted the saltatory view,
as a result of his studies of what he calls mutations, or pro-
nounced and readily transmissible variations of domestic plants.
1 The Variation of Animals and Plants under Domestication, p. 3, New York,
1897.
300 COOK
Instead of slow or gradual changes of the characters of species
there are supposed to occur at remote intervals in the life of a
species relatively brief periods of mutation in which violently
abrupt variations are given off in an explosive manner. Each
of these discontinuous variations is considered as representing
the production of a new species, there being no gradations be-
tween it and the parental type. Unfortunately, the wide appli-
cation of this analogy is prevented by the fact that in many
natural groups descent from a single individual is impossible.
Moreover, the new types or sports studied by Professor De
Vries are, like other closely inbred plants and animals, much
less fertile than their wild progenitors, thus increasing the
probability that the inbreeding or segregation necessary to
secure and preserve these abnormalities would give them a
fatal handicap in the struggle for existence. Finally, the wide
distribution, among both plants and animals, of sexual differen-
tiation and other expedients for securing cross-fertilization, seems
a sufficient warrant for distrusting any theory which disregards
this important group of evolutionary phenomena.
Determinant Theories. — The noninheritance of acquired
characters led Nageli and Weismann to formulate what maybe
termed determinant theories, under which the motion of species
is not thought of as caused or directly influenced by the environ-
ment, but as the function of internal " mechanisms of descent."
Nageli believed that species did not vary in all directions indis-
criminately, as Darwin had held, but that they kept, without
selective influences, a definite direction. He therefore con-
cluded that the organization of living matter contained what he
called a " Vervollkommungsfirinzifi" or principle of perfection,
which carried them ever upward along the road from simplicity
to complexity.
Weismann sought in his doctrine of determinants to render
this conception more concrete regarding the nature of the in-
ternal mechanism, and to provide a means of selective influence.
Determinants may be described as biological atoms, resident in
reproductive cells and able to determine in advance the charac-
ter of the new organism, independent of its environmental rela-
tions. The environment also has no effect on the next genera-
ASPECTS OF KINETIC EVOLUTION 3OI
tion, selection pertaining not to the characters themselves, but
to the determinants which might repeat the characters in the
next generation. Further elaboration of the doctrine of deter-
minants has been made in the belief that the external conditions,
while unable to act through the body of the organisms, might
act directly upon the reproductive cells. Others assume con-
flicts or struggles between determinants (germinal selection) as
possible factors in evolutionary motion.
As a suggestion that evolution might be the result of external
influences, and as a means whereby characters imposed by the
environment could be transmitted, Darwin invented the theory
of pangenesis, to the effect that the germinal material carrying
reproductive influences was assembled from all parts of the body
of the parent organism. Direct evidence for this supposition
has never been found ; indeed, the contrary proposition, that
acquired characters are not and cannot be inherited, has com-
manded the belief of Professor Weismann and his numerous
followers. Having cut loose, as it were, from environment,
which had been the chief resource of static theories, they have
sought the explanation of the evolutionary problem in a so-called
" hereditary mechanism," by which the characters of successive
generations are held to be predetermined in the reproductive
cells. The structure of the living cell has accordingly received
the attention of many earnest investigators and a new science of
cytology has been rapidly built up. But, as in the pursuit of
her somewhat older sister, embryology, no general uniformity
of structure or processes has been discovered. Biology has
been enriched by the addition of a vast number of interesting
facts, but the minute structure and internal organs of plants and
animals, including the structure and organs of the component
cells themselves, have been found to share the general diversity
of nature, and to be as much in need of evolutionary explana-
tion as the external characteristics of the various natural groups.
With an infinity of biological facts to draw upon, no theory
need remain without support, real or apparent. An evolu-
tionary inference warranted in one group may be quite false as
a general law, and in this sense an inadequate theory may be
more misleading than one which is actually erroneous. Thus
302 COOK
each of these types of evolutionary theories may be said to rest
upon certain groups of evolutionary facts which are more or less
completely ignored by the others. The niceties of many adapta-
tions to environment have led Darwin and his followers to
almost exclusive reliance upon that factor. Saltatory theories
provide larger variations, but require even more effective isola-
tion. Determinant theories deny the influence of environment
and must ascribe adaptations to accident or to pre-established
harmony. All three theories antagonize the obvious fact that
a very general tendency of organic development has been
toward the increase of facilities for cross-fertilization. These
have been interpreted as inimical to evolution because they
interfere with the preservation of the abnormally close-bred
variations which have been mistaken for true steps in the
progress of organic series.
KINETIC OR SYMBASIC EVOLUTION.
Somewhat between the doctrines of selection and of deter-
mination, but distinct from both, is another conception of evolu-
tionary motion, that it is caused neither by external environments
nor by internal mechanisms, but goes forward as a necessary
result of the normal specific constitution of living matter. It is
observed that organisms normally exist and make evolutionary
progress only in large groups of interbreeding individuals.
Evolution is, in a word, symbasic ; that is, organisms must
travel together along the evolutionary pathway, and must be
connected with each other by an intricate network of descent
in the weaving of which the diversities of the members of a
species have a definite physiological value. Without diversity
of descent the cellular organization deteriorates. This being
the case, it is easy to understand that new variations are pre-
potent, and that species make more rapid evolutionary progress
in proportion to their numerical size. The larger and more
widely distributed the species, the greater the opportunities of
variation and of evolutionary progress.
Kinetic evolution is thus the reverse of many current theories,
in that it recognizes a normal and necessary movement of change
not caused by environment. It is the reverse of the selective
ASPECTS OF KINETIC EVOLUTION 303
theory of Darwin in holding evolution to be independent of
natural selection. It reverses the panmixia doctrine of Pro-
fessor Weismann, in that it treats the interbreeding of the
numerous and diverse individuals of species as conducive of
biological motion, instead of as hindering it. It is the reverse
of the mutation theory of Professor De Vries, in that evolu-
tion is held to go forward normally in entire species, and not
merely in individuals or in narrow lines of descent.
One of the chief weaknesses of all the static doctrines, both
saltatory and selective, lay in the apparent necessity that new
variations be isolated from their relatives in order to preserve
their new characters and make evolutionary advance possible,
for the fundamental concepts of the static doctrine are the
normally stationary average and the swamping effects of inter-
crossing.
The kinetic theory differs fundamentally from all its prede-
cessors in recognizing the fact that evolution is not a process of
segregation, but of synthesis and integration. The transforma-
tion of species in nature is brought about by the sharing of in-
dividual variations through interbreeding. Conjugation and
cross-fertilization do not hinder evolution, but are essential to
the gradual building up of the intricate coordinations of char-
acters through which adaptations and other desirable changes
go forward. Selection, inbreeding, isolation and other forms of
segregation, reduce the number of accessible variations, narrow
the basis of the vital structure, and result in organic weakness,
sterility and extinction. Selective isolation accentuates par-
ticular variations and has been utilized in the diversification of
domestic varieties of plants and animals useful to man, but
abnormal and weak from the evolutionary standpoint, and
affording no complete analogy with the natural development of
organic types. The sterility of many hybrids and the tendency
of inbred varieties to produce relatively infertile sports may
prove to be explainable by the same fact of inadequate fertili-
zation. For want of better words it may be said that the vital
tension of inbreeding is too little, while that of hybridity is too
great; the normal course of biological evolution lies, obviously,
between the two extremes. Evolution, or biological motion,
304 cook
appears to be necessary as well as universal. Free interbreed-
ing between the members of large organic groups, or species, is
the condition under which biological evolution is going forward
in nature, and we have no reason to seek its cause in any aber-
ration or specialization of structure or function.
The fundamental and truly dynamic causes of evolution still
lie hidden in the equally unknown causes of genetic variation,
but the evolutionary history of a group of organisms is a proc-
ess which a kinetic theory adequately explains by supplying
physiological reasons and methods.
The ultimate theory or stage of evolutionary explanation must
await far more complete knowledge of the nature of the phenom-
ena to which we commonly refer under such abstract terms as
matter and force, expressions which we can neither describe nor
define, except in a purely formal manner. Much is gained,
however, by the recognition of the fact of normal evolutionary
motion, by perceiving that organic development is a kinetic
phenomenon, for the species no less than for the individual.
Individuals and species are conditioned, but not caused, by their
environments ; they descend from other species and from other
individuals in continuous series of ever-changing forms. There
is an inside as well as an outside physiology of evolution, and
it is idle to ignore either the one or the other.
To advance from the static to the kinetic point of view gives
us ready and practical solutions for many problems which on the
static basis bid fair to have required long periods of time and
large expenditure of money. It brings also, as does every
advance of science, a host of new questions which the static
evolutionist could never have asked, such as the rapidity of
evolutionary motion and the means of accelerating, retarding or
deflecting it.
A kinetic theory of evolution does not need to explain varia-
tion any more than it needs to explain symbasis and environ-
ment ; it accepts these three groups of biological facts, and
correlates them as evolutionary factors. Conversely, a theory
of variation is not necessarily a theory of evolution ; the two
questions may be viewed as quite distinct. The recognition of
evolution as a kinetic process does not conflict with a dynamic
ASPECTS OF KINETIC EVOLUTION 305
explanation of variation, but contributes to such an achievement
by rendering the problem more definite. It affords another
conception of how evolution may be accomplished, but a con-
ception more comprehensive than those which have gone before ;
one which does not depend upon any theoretical or doubtful
relation, but upon the well ascertained and universal fact that
organisms exist everywhere in species — groups of diverse indi-
viduals freely interbreeding to form a complex network or fabric
of descent.
To some there may appear to be no practical distinction
between the static and the kinetic views. Not a few naturalists
have entertained truly kinetic conceptions of the facts of organic
nature, even while continuing to misrepresent them by the use
of the static terminology. For descriptive purposes, such as the
tracing of phylogenies, the differences are less important, but
fundamental divergence is obvious in approaching the physio-
logical questions of methods and causes. The probable truth of
a theory does not depend merely upon the number of facts which
can be assembled under it, but also upon the coherence and
practical consistency of the relations alleged. Of two theories
otherwise equal the more simple and direct should receive the
greater confidence. The kinetic theory is not compelled to
ascribe utility to all characters, and can explain useful and use-
less characters by reference to the same facts of organic diversity
and association in species.
SUMMARY OF EVOLUTION THEORIES.
Static theories view the species as normally stationary, and
ascribe evolutionary motion to environmental causes of adapta-
tion. The static theory commonly called Darwinism (though
avoided by Darwin himself) treats adaptations as caused indi-
rectly through natural selection, by the survival of the fittest of
the individual variations. The static theory of Lamarckism
treats adaptations as direct results or responses to environmental
influences.
Saltatory theories view the species as normally stationary
except for rare intervals of sudden transformation or " muta-
tion " caused either by the environment or by internal "forces"
306 cook
of unknown character. Selection can determine the survival
of mutations adapted to environmental conditions, but exerts no
direct adaptive influence.
Determinant theories view species as moving gradually in
definite directions in obedience to internal " principles of per-
fection " or "mechanisms of descent." Adaptation depends
on the coincidence between evolution and environment ; selec-
tion exerts no direct influence.
Kinetic theories view species as normally in motion, but not
in a single or definite direction, and not as a result of environ-
mental causes. The normal evolutionary motion of the species
may be restricted and deflected by the selective action of the
environment, resulting in adaptation.
The adjacent tables may assist in showing the relations be-
tween these different types of evolutionary theories. Table I
indicates the methods by which the various doctrines answer
some of the principal questions regarding evolutionary motion.
Table II brings these questions into relation with the conclu-
sions reached in previous chapters. Discrepancies between dif-
ferent evolutionary doctrines are often explainable by the fact
that some of them are in reality theories of adaptation or of
speciation, rather than of evolution. Thus, as the table shows,
interbreeding is a strongly negative factor in the multiplication
of species (speciation), but at the same time it is a strongly posi-
tive factor in evolution. The chief factors in adaptation and
speciation have only negative or restrictive effects upon evolution.
NORMAL CONDITION OF SPECIES.
The most fundamental diversity of opinion regarding the
nature of evolutionary motion is that of the normal condition of
species. Two assumptions are possible and have equal warrant
for scientific consideration. Under theories of environmental
and selective causation, it has been taken for granted that species
are normally stationary and uniform unless acted upon by some
disturbing external influence. The question of causes, on this
assumption, is a simple one. The difficult problem is to explain
how the external influences produce the organic results which
have been ascribed to them. Fifty years of study have been
ASPECTS OF KINETIC EVOLUTION
307
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308 cook
expended on this phase of the problem, but with no direct results.
For this reason, if for no other, the careful consideration of the
alternative possibility would be justified.
The kinetic theory is not dependent, however, upon merely
abstract or inferential justification, but is supported by the evi-
dence of all observations and experiments which have a bear-
ing upon the question. That groups of organic individuals
become different whenever they have been isolated for any con-
siderable periods of time, may be taken as proof that evolutionary
change is a general and normal condition of the existence of
species. It can be asserted, of course, that divergences be-
tween groups of common origin are due to differences of
environment, but the inadequacy of this explanation is con-
clusively shown by the many instances where groups have pre-
served great similarity of habits and environmental conditions,
but have attained, nevertheless, to a great diversity of form and
structure, as in the conspicuous instance of the animals of the
class Diplopoda, and of various classes of the lower plants, such
as the mosses and hepaticae.
Two modifications of the stationary assumption had been
formulated, previous to the kinetic theory. Under the muta-
tion theory of Professor De Vries, the normal condition of uni-
formity is supposed to give place at rare intervals to periods of
mutation or sudden appearance of new species. In the deter-
minant theory of Nageli, species were held to be normally in
motion, but the motion was supposed to follow a definite direc-
tion as the result of internal physical and chemical adjustments.
The changes predicated as normal for species under the kinetic
theory are of an indeterminate and composite character. The
species is not thought of as changing in one direction merely,
but in many characters at once, the required result being a con-
structive coordination of changes which will increase the vita
efficiency of the organism and enlarge its power of utilizing its
environmental opportunities.
RAPIDITY OF EVOLUTIONARY MOTION.
Static theories, which have agreed in thinking of species as
normally stationary, have also taken it for granted that evolu-
ASPECTS OF KINETIC EVOLUTION 3O9
tionary changes must be gradual, and some writers have dwelt
upon the imperceptible slowness of evolutionary progress. The
mutation theory of Professor De Vries adopts the other extreme,
in holding that evolutionary motion is abruptly discontinuons,
the individual organism leaping, as it were, from one species to
another without any steps or gradations. From the kinetic
standpoint, mutations like those studied by Professor De Vries
are interpreted as abnormal and degenerative phenomena, but
the fact is recognized that the individuals of many species in
nature have very recognized differences, so that the steps of
evolutionary progress may not always be infinitesimally grad-
ual. There are indications that prepotent new characters may
often transform a species or variety in a comparatively short
period of time.
CONTINUITY OF EVOLUTIONARY MOTION.
Theories which ascribe organic changes to selection or to en-
vironmental causes imply that progress is limited to the charac-
ters which happen at the time to have environmental significance.
In this view evolutionary motion, though gradual, must be de-
scribed as occasional, rather than as continuous. After a
period of selective development a species might cease, for a time,
to be affected by selection and remain stationary, or might even
retrograde, as claimed by Weismann and others.
In the mutation theory the idea of occasional change is car-
ried still farther, so that evolutionary motion would need to be
described as intermittent and occurring only at rare intervals.
This is the type of evolutionary theory which comes nearest to
the older doctrine of separate creation of species. It represents
species as arising from single individuals, and denies gradual
or continuous progress. It declares that evolutionary motion
is saltatory or discontinuous ; that there are sudden changes or
jumps from one species into another. Such an evolution could
not be described as taking place in species, but between them,
the species themselves being essentially stationary except when
acted upon by special " forces." Whether the forces are exter-
nal or internal is a matter of opinion which subdivides saltatory
evolutionists into two subordinate schools.
3io
COOK
Saltatory evolution consists of a series of abrupt lateral dis-
placements, each species remaining stationary and unchanged
from the time of its origin by mutation. No forward progress
of the members of interbreeding groups is provided. Mo-
tion takes place only in the individuals which give rise to the
new groups. Selection would thus have no influence upon evo-
lutionary motion in connection with the mutation theory. Its
function would be limited to the determination of the survival
of the new species which might prove to be adapted to their
environments. Motion is conceived only in simple inflexible
lines and not in a network of descent which can bend in adap-
tive directions when environmental obstacles are encountered.
Saltatory theorists do not deny that diversity exists among
the members of species, but they ascribe this to the influence
of external conditions or to a general principle of inconstancy
or fluctuation, without any special evolutionary significance.
Saltatory theories stand in most direct contrast with those
which ascribe continuity to the evolutionary motion of species,
which are thought of not as advancing by leaps or sudden trans-
formation of one species into another, but as going forward by
gradual steps, larger or smaller. Natural selection by the en-
vironment is thought of as changing the average and hence as
causing evolutionary motion. The higher groups of plants and
animals have so many adaptive characters that evolution by
natural selection has been accepted by many biologists as a
demonstrated fact.
Determinant and kinetic theories agree in expecting evolu-
tion to be continuous, the one because the internal mechanisms
would continue to act, the other because the interbreeding of the
ever-diverse individuals of the species is being continued.
MUTATIONS DISTINGUISHED FROM NATURAL SPECIES.
There is a wide and fundamental difference between the kind
of evolutionary motion shown by mutations of inbred domesticated
species and that by which the progressive development of
natural species has been brought about. The condition of in-
breeding under which mutations appear has so far weakened
the organism that the newly modified form is recessive, that is,
ASPECTS OF KINETIC EVOLUTION 3 I I
it tends to disappear when crossed with unrelated groups. Such
variations could not spread or propagate themselves in a nor-
mally symbasic species ; each would need to be carefully iso-
lated in order to be preserved. In the second place, very few,
if any, of the thousands of mutations which have come under
the eyes of planters and experimenters have proved to be more
fertile, in the true reproductive sense, than the parental types.
Nearly all of them are conspicuously deficient in this respect,
and would thus struggle under a fatal selective handicap in
competing with the parent form, if they were not at once wiped
out by interbreeding. Mutations have very great agricultural
importance, but their practical value will not be enhanced by
overlooking this fact of deficient fertility which is fatal to the
view that they represent a genuine condition of progressive
evolution.
Mutations arise sideways, as Professor De Vries explains,
but it does not follow that new species are formed in this
manner. Mutations are frequent in domesticated plants because
varieties in cultivation are separated by inbreeding from the
normal forward progress of the whole interbreeding species.
Each species when once formed is supposed, under the mutation
theory, to remain stationary so that progress can be made only
when new varieties become segregated from the mass.
There is, however, another and very different way in which
variations can contribute to evolutionary progress. Instead of
being recessive mutations, the variations which have practical
evolutionary significance are prepotent, and can work one change
after another in the gradually advancing group. The true evo-
lutionary significance of mutations is not that species arise by
mutation, but that the progressive steps, by which the evolution
of species is gradually accomplished, are not imperceptibly
small. There may be a very appreciable advance between two
successive individuals.
Very acute selection or some other way of separating a new
mutation from its unmodified parent stock must be imagined in
order to account for its preservation, but plants and animals
abound in characters which could scarcely have been perpetu-
ated in this way. With self-fertilized plants a single individual
Proc. Wash. Acad. Sci., January, 1907.
312 COOK
can start a new race or variety, but with sexually differentiated
animals this is much more difficult, since interbreeding is neces-
sary for reproduction. An actual instance will illustrate the
point. In all the millipedes of the world-wide order Merocheta
the olfactory cones of the antennae are four in number, arranged
in a square, with the single exception of a series of closely
related East African genera of the family Gomphodesmidae,1
which are unique in the possession of ten olfactory cones
arranged in a circle. That the four cones in a square is the
ancestral condition, is certain, because it is shared also by all
the other orders of the very ancient class. Diplopoda, many
members of which are known from the carboniferous period.
That the number is invariable in the order Merocheta can not
be claimed, since, obviously, it must have varied at least once,
when the circle of ten cones came into existence. No variation
has been recorded, however, either in the four-coned or the ten-
coned genera, on the many thousands of specimens which have
been examined.
Nor are there any indications that the ten-coned condition is
an advantage which has gained any favors from natural or other
forms of selection. The ten-coned genera as a group show no
other conspicuous peculiarity and have contributed, apparently,
only m average share to the evolutionary diversification and
geographical distribution of the family. Moreover, the habits
and environmental relations of the whole class Diplopoda are
such as to reduce the influence of natural selection to a
minimum.2
Under such circumstances the sidewise origination and pres-
ervation of a ten-coned new species as a mutation seems highly
improbable, but there is, on the other hand, no reason why
a genetic variation to ten cones should not spread through a
species and be carried forward into the other species and genera
into which the ten-coned group might afterward subdivide. If
there had ever been millipedes with the intervening number of
1 Cook, O. F., 1899. African Diplopoda of the Family Gomphodesmidae.
Proc. U. S. National Museum. 21 : 677-739.
2 Cook, O. F., 1902. Evolutionary Inferences from the Diplopoda. Proc.
Entomological Society of Washington. 5 : 14.
ASPECTS OF KINETIC EVOLUTION 3 1 3
cones we have every reason to expect that indications of them
would remain, either in species with such numbers or in occa-
sional individual variations. The facts of mutation may help
us to be reconciled to the probability that millipedes with five,
six, seven, eight or nine cones may never have existed, but they
do not warrant the general inference that evolution goes for-
ward by the origination of species sideways by mutation.
The difficulty is not that the mutations of domesticated plants
and animals are not as different and as readily to be described
and distinguished from each other as natural species. Nor is
it impossible that some of the species named and described in
formal botanical and zoological classifications represent mutative
variations from narrowly segregated wild types. The differ-
ences are not formal or theoretical, but physiological and prac-
tical. The conditions under which the mutations of cultivated
plants and animals arise are not those under which the construc-
tive evolution of nature has gone forward, and the mutations are
deficient in the primary requirements of vigor and fertility.
That discontinuous variations may contribute to the evolu-
tionary progress of species in nature is no part of the mutation
theory of De Vries, which definitely rejects and denies an)' grad-
ual evolution, any continuous change and accumulation of char-
acters. Species once formed by mutation are just as stationary
and immutable, according to De Vries, as Linnaeus said they
were. All the evidences of gradual evolutionary divergence of
organic groups accumulated by Darwin and his successors are
ignored in the mutation theory, because no evolutionary changes
were detected in the original CEnotheras which Professor De
Vries kept in his garden for eighteen years.
The kinetic theory is not thus at odds with the facts of
science. It provides an evolution of species by a thor-
oughly gradual, continuous process, more broadly continu-
ous, indeed, than any suggested before. It recognizes that
new variations are prepotent, and are able to accumulate and to
transform the species in which they appear. Species are nor-
mally in motion and do not depend upon the intermittent inter-
ference of selection, nor upon mutation, for the development
of new characters. Instead of finding the motive power or
314 COOK
active principle of evolution in natural selection or in mutation,
the kinetic theory finds evolutionary causes in normal diversity
and free interbreeding in specific networks of descent.
Both the selection theory and the mutation theory imply that
new characters and new types have to be preserved by isolation.
Under the kinetic theory it is clearly perceived that isolation
explains only the multiplication of species, but is not an evolu-
tionary factor, or even a necessary condition of evolution. The
kinetic theory provides for the first time a consistent outline of
a method of gradual and continuous evolution in normally ex-
tensive, freely interbreeding specific groups, the condition in
which organisms everywhere exist in nature.
PRINCIPAL AGENT OF EVOLUTIONARY CHANGE.
At this point the various theories show, perhaps, their most
obvious divergencies. The doctrine of pure selection, or Dar-
winism, holds that selection is the actual cause or principle of
evolutionary advance, supporting this by various other assump-
tions, such as an environmental causation of variations or a cor-
relation between useful and useless variations.1
The isolation theory of Gulick appreciates the inadequacy of
selection and seeks for special conditions or behavior which can
explain the evolutionary progress of groups of individuals
which have merely been isolated from the parent species with-
out having been placed in appreciably different environments.
The Lamarckian doctrine of direct adaptation finds its greatest ad-
vantage here, in that the environment itself is supposed to cause
the changes directly. Professor De Vries argues, in some of his
writings, that mutations are due to environmental causes, though
frankly admitting that the connection of events is unknown.
1 Belief in correlation of characters as an important adjunct to selective evo-
lution has been reaffirmed very recently by Professor Lank ester.
"For they [correlated characters] enable us to understand how it is that
specific characters, those seen and noted on the surface by systematists, are not
adaptations of selective value. They also open a wide vista of incipient and
useless developments which may suddenly, in their turn, be seized upon by ever,
watchful natural selection and raised to a high pitch of growth and function."
See Lankester, E. Ray, 1906. Inaugural Address before the British Association
for the Advancement of Science. Science, N. S., 24: 228.
ASPECTS OF KINETIC EVOLUTION 3 I 5
It is commonly taken for granted by the advocates of the
selection hypothesis that a certain constant of variation will be
maintained by the species, so that the cutting off of the extremes
on one side will cause a still greater development on the other,
and thus actually move the species along.
This idea may never have been very definitely formulated,
but it is obvious that many writers on selection have relied upon
the unexpressed assumption as affording the means by which
selection could produce evolutionary change in a normally
stationary group of organisms.
The Darwinian doctrine of variation grafted upon the older
idea of stationary species resulted in the conception of a species
composed of variable individuals, but with a stationary specific
average. Experiments with domesticated varieties had shown
that selection could change the center of gravity or character-
average of a group, and this idea applied to nature at large
gave the hypothesis of evolution through selection.
In arguing the inadequacy of selection, Mivart, De Vries and
others have taken the ground that selection could not carry the
specific average beyond the boundary or limit of range of
variation for the original group, and this is the logically correct
inference, unless the idea of a constant of variability be included
as a factor of the problem. But even this is inadequate to
account for the general evolutionary results, for unless the
further notion of a normal tendency to progressive change be
added, the presumption would be that the selectively reduced
species would attempt merely to reproduce its lost members, to
regain its original size and cover again the field from which it
has been excluded by selection.
It may be held, therefore, that both in logic and in fact the
explanation of the ascertained and generally admitted data of
selection depends upon the recognition of a normal and spon-
taneous tendency of species to evolutionary change. It is this
tendency, this specific kinesis or law of motion, which carries
species into close selective contacts with their environments.
The species are travelling by their own motion, in spite of
selective obstacles, and not because environmental selection is
carrying them along.
3 16 cook
The determinant theory of Nageli, as already indicated,
ascribed changes to an internal "principle of perfection" of
heredity, which conducted the evolution of a species in a definite
direction. There was no need, in this view, of showing any
direct connection with the environment. Selection was applied
to a species as a whole, to preserve or to eliminate, but it was
not thought of as actuating evolution or as conducting it in
adaptive directions.
The determinant theories of Weismann and his followers
may be described as hybrids between the doctrines of Nageli
and those of Darwin and Lamarck. They predicated a cel-
lular mechanism of heredity for conducting the process of
evolution, but supposed that this mechanism could be actuated
or affected by environmental influences and compelled in this
way to carry the species in directions of adaptation.
Darwin, in his theory of pangenesis, assumed that all parts
of the body of the parent contribute materials to the germ-cells
and hoped thus to explain how characters acquired from the
environment might be passed on to succeeding generations.
Weismann denied the inheritance of acquired characters, but he
nevertheless repeated Darwin's attempt at providing for the
inheritance of environmental influences, because it appeared
impossible without this to construct a theory of environmental
causation and explain the facts of selection and adaptation.
Weismann was well aware that his theory of determinants
was so complex as to appear improbable, but he defended it
with persistence on the ground that it was the only way in
which heredity could be understood. Unfortunately, the vast
complexity of ideas does not explain the facts of organic descent,
but only adds to them an even more mysterious hypothetical
field. Moreover, the data of environmental relations do not
accord any better with the Weismannian than with the Dar-
winian hypothesis. Experiments have not shown that there is
any close, constant or definite relations between environment
and heredity. The most that can be claimed is that the environ-
ment, in some manner still quite unexplained, may sometimes
induce an instability, or tendency to stumble and fall from the
normal hereditary pathway of the type.
ASPECTS OF KINETIC EVOLUTION 3 17
The theory of determinants afforded, at most, a method of
thinking about the process of organic succession, but it does
not appear that this way of thinking is either correct or neces-
sary. It assumes a complete diversity of nature between ger-
minal and somatic cells, which the facts do not warrant, especi-
ally among plants, and it assumes further that there are definite
mechanical directive relations between the germ-cells and the
resulting organisms, which the facts also refuse to indicate. Of
the real nature of heredity we know, as yet, absolutely nothing,
any more than of analogous phenomena, instinct and memory.
Speculations, even of purely hypothetical character, may some-
times be of service in the treatment of scientific problems, but
no speculation should be cherished which hides or even casts a
shadow over facts.
Under kinetic evolution the symbasic interbreeding of the
diverse individuals of the species is held to be the principal
agent of evolutionary change, since it is in this manner that the
prepotent variations which appear among the component indi-
viduals are transmitted and combined into the complex organic
result. Interbreeding is held to effect an integration of indi
vidual variations inside the species, instead of each variation
being considered a new species, as in the mutation theory.
Symbasis is one of the general conditions of organic exist
ence, but under static theories its evolutionary significance was
so completely overlooked that no term was provided by which
it could be directly and definitely symbolized. The word in-
terbreeding, if used alone, would generally be misunderstood
in one of two opposite and equally unfortunate senses. Some
writers use interbreeding as synonymous with inbreeding or
close-breeding, and some for wide cross-breeding, which are
exactly the conditions to be avoided in the discussion of normal
specific relations. Another term being indispensable, symbasis
was introduced, in allusion to the fact that the individual mem-
bers of species are normally associated in groups. The expres-
sion also lends itself most conveniently to the description of
kinetic interpretations, in view of the fact that the association
of organisms into symbasic groups is looked upon as one of the
principal agencies of evolutionary progress.
318 cook
The introduction of a new term is always to be deprecated,
and may help very little, after all, in the explanation of a new
distinction. The word has to be explained, as well as the idea.
Nevertheless, there are occasions like the present, where progress
in expression is likely to be permanently hampered unless we
can be permitted to place definite labels upon our phenomena
and refer to them by unequivocal word-symbols.
Symbasis, more properly than any other ascertained fact,
can be called a cause of evolution. It may not cause variation,
but it does enable variations to be combined into a general
evolutionary change of type.
UTILITY OF NEW CHARACTERS.
New characters, as mere fortuitous variations, might or might
not be useful, but if selection were the only cause of evolution,
progress would be limited to characters of definite utility.
Every character, therefore, which has attained to any consider-
able degree of expression would have a definite use, or would
have had use at some former time in the evolution of the
species. This logical necessity of predicating the utility of all
characters is the most obvious weakness of the theory of selec-
tion, for there are large numbers of character differences be-
tween species which are not only obviously useless at present
but which were probably equally useless in the past.
Gulick's isolation theory does not insist on the utility of
specific differences, nor do the mutations of De Vries or the de-
terminate changes of Nageli and Weismann follow, of neces-
sity, the course of environmental utility. Selection would
explain the disappearance of types too far lacking in fitness,
but adaptation would remain a mere coincidence, depending on
whether adaptive variations happen to appear.
Under the kinetic theory it is possible to admit that useful
and useless characters have equal possibilities of appearing and
evolving, as long as they do not become actually detrimental,
but at the same time selection is admitted to have a definite and
practical evolutionary function, since the rejection of harmful
tendencies has the power of enforcing more rapid specialization
in useful directions. Selection is, indeed, more effective for
ASPECTS OF KINETIC EVOLUTION 3 19
inducing adaptation under the kinetic theory than under the
purely selective doctrine of Darwinism, because in kinetic evo-
lution a much wider range of characters can be expected to
reach a sufficient development to render them of selective im-
portance. Under a logical static theory, only those characters
could be developed which have selective value from their first
inception.
METHODS OF PRESERVING NEW CHARACTERS.
The great weight given to the various forms of selection,
isolation, and environmental influence as factors of evolution
have been determined largely by the belief that new characters
or variations could not be preserved unless they were in some
way separated from the unmodified parental type. This opinion
has been supported largely by the fact that many of the varia-
tions which have been taken for examples of normal evolution-
ary motion have been in reality more or less abnormal results
of the condition of inbreeding common in our domesticated
varieties of plants and animals. The prepotency of the un-
selected wild type has been insisted upon, as well as the swamp-
ing effects of intercrossing, when the characters of the carefully
selected variety fade away into those of the unspecialized
parental form without leaving any apparent result. Neverthe-
less, the fact seems to be that new characters are prepotent, not
of necessity over the whole taxonomic species to which the
individual may belong, but at least in the particular variety or
group and in the particular stage of interbreeding in which the
variation appears. The recognition of the prepotency of new
variations makes it obvious that the preservation and continued
evolution of new characters does not involve the necessity of
isolating the new form or the extinction of the old, after a period
of struggle for existence.
Mechanical theories of evolution have centered largely about
this question of acquiring characters, but it is still more impor-
tant to know how characters are preserved after having been
acquired. Organisms appear to acquire some characters from
the environment, but it does not follow that the characters are
also preserved by the environment, or even that the characters
320
COOK
acquired from the environment are those which contribute in a
definite manner to evolution. The kinetic interpretation en-
ables us to understand the probability that a character is pre-
served for the same reason for which it appears in the first
place.
The name Darwinism is commonly, though rather unjustly,
limited to the gradual or selective theory under which variations
gained genetic significance only when they were favored by
partial or complete isolation, brought about either by the elim-
ination of the less efficient parental form during the struggle for
existence, or through geographical or other accidents prevent-
ing the swamping effects of intercrossing. This meant that
variations did not tend to be preserved, that they tended only
to continue their fluctuations around the stationary specific
average. This conception was based, as already indicated, on
the choice of the fluctuating variations or unspecialized het-
erism and artism as representing the variations on which evolu-
tion proceeds.
Under the assumption that organisms are normally stationary
it was natural to ascribe variations to new conditions. It may
be found, however, that the facts can be accommodated as well
or better by supposing that new conditions of nutrition and
growth afford more facilities for variation. Variations, once
produced, tend to repeat themselves ; not, it may be, in all of the
offspring, but at least in some of them. The object of varia-
tions, the value of variations for the species, lies not so much in
giving them new characters as in giving them a diversity of
characters. Variations which appear in a part of the offspring,
but not in all, serve most efficiently the purposes of increasing
and maintaining heterism, and of insuring diversity of descent,
after the manner of the many secondary sexual characters which
appear to be quite useless except for this physiological purpose.
The kinetic theory differs from all its predecessors in recog-
nizing physiological reasons for holding that new characters
are prepotent. From the fact that they afford opportunity for
organic readjustment, they enjoy an advantage over the un-
modified type both in accentuation of characters and in vitality
and fecundity of offspring. The evolutionary possibilities of a
ASPECTS OF KINETIC EVOLUTION 321
new character may depend as much or more upon its fitting
into and supplementing the complex of existing characters as
upon any direct utility from the environmental standpoint.
Evolution, in other words, may be viewed as an aspect of the
physiological process of interbreeding by which the vitality of
organisms is sustained.
NATURAL SELECTION AS AN EVOLUTIONARY FACTOR.
The preponderance attained by the selection theory has prob-
ably been due, in large measure, to its logical simplicity and
consistency in holding that selection is the positive, efficient
factor or actuating principle of evolution. The unbiological
public has accepted this interpretation of the causes of evo-
lutionary motion with practical unanimity, but among biologists
themselves there has always been a wide appreciation that the
facts did not warrant the definite generalization which Darwin
himself carefully avoided, but which his friends made for him
and christened with his name.
All other suggestions of methods of evolution are the result
of more or less definite perceptions of the inadequacy of natural
selection as an evolutionary cause. No amendment of natural
selection has the logical consistency of the original, nor has any
gained a comparable popularity in the scientific world. The
mistake has been made, if the present diagnosis is correct, in
attempting to modify or repair the hypothesis of selection as an
evolutionary cause.
Under the kinetic theory selection appears as a negative fac-
tor only ; its power is to inhibit motion, not to cause it. It is
not improbable that selection, by closing other avenues of
change, can induce more rapid progress in a particular direction,
but such an effect of accleration would not prove that selection
can cause evolutionary motion ; it would indicate that a certain
amount of change necessarily takes place as the result of causes
inherent in the species. A variation eliminated by selection
does not help to maintain the needful diversity of descent, and
this may make the surviving variations the more effective for
inducing adaptive specializations. Selection, by thus restricting
the field of change, may be able to focus the evolution upon one
32 2 COOK
variation, but a condenser is not to be reckoned as a source of
light.
The kinetic theory therefore definitely abandons selection as
a cause or positive factor, and perceives that the influence of
selection, powerful though it be in many cases, is of a negative
and restrictive character — an influence which could not be
exerted if the species were not already in motion.
The kinetic theory, though departing radically from the
doctrine of selection as an evolutionary cause, is, in a practical
sense, much nearer to Darwinism than are many other sug-
gestions which, though intended to supplement the selection
hypothesis, would in reality completely nullify it, by denying to
selection any true power to influence the course of evolutionary
progress. The kinetic theory, though denying that selection is
in any proper sense an evolutionary cause, ascribes to it a
definite evolutionary function. The environment does not carry
the species into adaptive specialization, it only deflects the
normal specific motion. The evolution is in the species, the
power of deflection in the environment.
Professor De Vries clearly recognizes that the function of
selection is regulative and not active, though he still refers to it
as a cause of evolution.
" Notwithstanding all these apparently unsurmountable diffi-
culties, Darwin discovered the great principle which rules the
evolution of organisms. It is the principle of natural selection.
It is the sifting out of all organisms of minor worth through the
struggle for life. It is only a sieve, and not a force of nature,
no direct cause of improvement, as many of Darwin's adver-
saries, and unfortunately many of his followers also, have so
often asserted. It is only a sieve, which decides which is to
live, and what is to die. But evolutionary lines are of great
length, and the evolution of a flower, or of an insectivorous
plant is a way with many sidepaths. It is the sieve that keeps
evolution on the main line, killing all, or nearly all that try to
go in other directions. By this means natural selection is the
one directing cause of the broad lines of evolution. "
" Of course, with the single steps of evolution it has nothing to
do. Only after the step has been taken, the sieve acts, elimi-
ASPECTS OF KINETIC EVOLUTION 323
nating the unfit. The problem, as to how the individual steps
are brought about, is quite another side of the question."1
This is in notable contrast with the previously quoted dictum
of Professor Lankester, regarding an " ever-watchful natural
selection " by which characters are " seized upon " and " raised
to a high pitch of growth and function."
INTERBREEDING AS AN EVOLUTIONARY FACTOR.
In full accord with the idea that evolutionary change or motion
is caused by selection or environmental influence, are the opin-
ions, already emphasized, that isolation is necessary to preserve
new characters, and that the sexual phenomena of interbreeding
stand in the way of evolutionary progress by hindering the per-
petuation of new characters. These corollaries of the selection
hypothesis find no place in the kinetic theory. Interbreed-
ing and other phenomena of sexuality have been reckoned
in the present discussion as positive factors in evolutionary
motion.
Evolution, in the kinetic interpretation, represents the work-
ings of no special force, principle or mechanism ; it is carried
forward by the symbasic interbreeding of the diverse individuals
of which species are composed. The final and ultimate expla-
nation of evolution must await an understanding of the constitu-
tion of living matter. We must learn why the prepotent genetic
variations occur, and why the interbreeding is necessary. But
having once appreciated the variations and the interbreeding as
ever-present facts, evolution is no longer mysterious ; it follows
as a natural and obvious consequence.
THE KINETIC FIGURE OF EVOLUNTIONARY MOTION.
It will be apparent from the preceding chapters that the evo-
lutionary motion predicated under the kinetic theory differs
from that of previous doctrines in important respects. In the
first place, it is a highly complex or compound motion instead
of a simple one, not to be typified by a push from the environ-
ment, by a pull by natural selection, by an occasional mutative
leap, nor even by the onward transportation of a determining
"DeVries, H., 1905. Species and Varieties, p. 6.
324
COOK
" hereditary mechanism." The figure of developmental progress
under the kinetic theory is that of the advance of a huge and
intricate network or trestle, built and supported by the inter-
grafting of the lines of descent throughout the species. Envi-
ronmental obstacles can compel the progressive advance of this
specific structure to be accomplished by many lateral bendings,
but these deviations and displacements need no longer be mis-
taken for examples of normal evolutionary motion. That indi-
vidual organisms can step aside, or even fall out of the ranks,
proves, at the most, only that such transverse motions are pos-
sible ; it does not show that they represent the method or the
conditions by which the constructive evolutions of natural species
go forward. The environmental reactions and mutations are
made suddenly and can be readily demonstrated to our impa-
tient eyes, but the coherent advance of the whole specific net-
work has to be inferred from the relations of species as we find
them in nature.
Some are inclined to distrust the results of the cosmic labora
tory and to prefer to explain evolution by the lateral diversions
which can be demonstrated in their own experimental cages
and gardens. After keeping Lamarck's evening primroses in
his garden for eighteen years without detecting any change,
Professor De Vries has concluded that the species is constant
and stationary and that further evolution is accomplished only
by mutative variations, like those which appeared during this
interval.
"There is neither a gradual modification nor a common
change of all the individuals. On the contrary, the main
group remains wholly unaffected by the production of new
species. After eighteen years it is absolutely the same as at
the beginning, and even the same as is found elsewhere in
localities where no mutability has been observed. It neither
disappears nor dies out, nor is it ever diminished or changed in
the slightest degree.
..." My evening primrose, however, produces in the same
locality, and at the same time, from the same group of plants,
quite a number of new forms, diverging from their prototype
in different directions.
ASPECTS OF KINETIC EVOLUTION 325
"Thence we must conclude that new species are produced
sideways by other forms, and that this change only affects the
product, and not the producer. The same original form can in
this way give birth to numerous others, and this single fact at
once gives an explanation of all those cases in which species
comprise numbers of subspecies, or genera large series of
nearly allied forms."1
These inferences were made, of course, without reference to
the kinetic conception of evolutionary motion as a specific struc-
ture or network of descent. Nor is the possibility considered
that a small group of individuals isolated and inbred in a foreign
land might behave in an abnormal manner, or at least in a
manner that would afford small indication of the normal mode
of evolutionary motion. Other parallel cases observed in coffee,
cotton, capsicum, tea and other plants, indicate that mutative
variations like those of the evening primrose are the regular re-
sults of the treatment to which the plants have been subjected
in domestication. Instead of illustrating the method by which
evolutionary advance is accomplished, mutations appear to
represent a stage in the degeneration of organisms which have
been removed from the vital fabric of specific descent ; they do
not show how the evolutionary network is woven, but how the
strands can be unraveled. Conditions of uniformity like those
of inbred domesticated varieties are to be found in nature only
exceptionally, in the relatively few degenerating types which
have become regularly addicted to self-fertilization or to vege-
tative propagation. Nor do we find under normal evolutionary
conditions of symbasic interbreeding and individual diversity
these violent mutative departures from the parental types.
There is a vastly greater range and flexibility of characters
and character-combinations. Nevertheless, it is very doubtful
whether a species as a whole would make an appreciable evo-
lutionary advance in eighteen years. In any event, the fact
could hardly be determined from a few specimens in a foreign
garden.
All kinds of variations can be described as having been pro-
1 De Vries, H., 1905. The Evidence of Evolution. Smithsonian Report for
1904, p. 396.
326 COOK
duced sideways. The doctrine of selection, like that of muta-
tion, looks upon lateral or transverse displacements as the steps
by which evolution is accomplished. From the kinetic stand-
point it appears obvious that only those lateral movements really
contribute to the evolution of the species which make a lasting
addition to the internal diversity of the species and broaden and
strengthen the structural network of descent. Mutations which
arise under conditions of inbreeding do not serve this purpose.
They are loose loups or free ends of the fabric of descent,
torn out by the disarrangement of the tensions of the specific
machinery of development. They do not affect the species, of
course, if they remain isolated from it. On the other hand,
mutations which are allowed to interbreed freely with the wild
type, or even with each other, loose their distinctive peculiarities
and are merged back toward the ancestral form, and [toward
the more normal condition of promiscuous individual diversity.
As evolutionary phenomena the mutations described by Pro-
fessor De Vries have not less of interest and significance than
the facts of adaptation and environmental adjustment which
served as the basis of earlier theories of evolution. And like
the data of the earlier theories, the facts of mutation are capable
of being interpreted in a very different relation to the evolution-
ary motion of specific groups of organisms. Since constructive
evolution is accomplished, as far as we know, only in these
large groups of freely interbreeding individuals, we may well
be cautious in the acceptance of any doctrines which do not
take into account the normal constitution of species, and the
nature of the motion by which their evolutionary progress is
accomplished.
A species is not a merely arbitrary collection or aggregate of
organisms ; it is itself an organization by which organic exist-
ence is maintained and organic evolution is accomplished. It
is customary to think of the higher types of organisms as hav-
ing been made possible by the association of greater and greater
numbers of cells, but this association and specialization of cells
into tissues and organs has not been accomplished without the
meeting of another evolutionary requirement, the association of
the organisms into large interbreeding groups, or species.
ASPECTS OF KINETIC EVOLUTION 327
Organic energy is primarily an integration of cellular energy,
and the energy of cellular development has to be readjusted
and renewed by conjugations between cells of diverse descent.
The answer to the question why this is so must come from a
new department of science, a general cellular biology which
shall study the problems of cellular organization and associa-
tion. It is here, if anywhere, that we must learn why organisms
are normally diverse, why interbreeding is necessary and why
evolution follows as a universal consequence. A species,
viewed as a protoplasmic fabric of interwoven lines of descent,
is different from any other object in nature, but its properties
and potentialities are no less peculiar than its structure and its
modes of motion.
5. THE HEREDITY CONCEPT MODIFIED BY HETERISM.
Questions are debated with the most persistence and the least
profit when diverse opinions are being expressed by means of
the same words. The term heredity has figured largely in evo-
lutionary discussions ever since the time of Darwin, and yet the
ideas which it represents are by no means the same in the minds
of the many investigators who use it. The meanings do not
vary merely in the extent of their application to related ideas.
They differ fundamentally in their standpoints, and in their
conceptions of the nature of the causes of evolution.
The traditional concept of heredity, the supposed production
of like by like, also enters largely into the composition of the
various philosophical systems of evolution, so largely, in fact,
that evolution, descent and heredity are often treated as synony-
mous terms. Indeed, the whole subject of evolution is often
summarized and crystallized into heredity, so that no further
thinking is possible which does not definitely adopt or as defi-
nitely reject the heredity conceptions of the various schools of
evolutionary study. The extreme views are very widely diver-
gent, and perhaps equally remote from the truth.
On the one side is the hypothesis of environmental causation,
or a direct impression or moulding of characters by external
conditions ; on the other side is the hypothesis of prefiguration
or definite predetermination of characters by internal character-
Proc. Wash. Acad. Sci., February, 1907.
328 COOK
unit mechanisms of descent. Some regard heredity as a sum-
mary of environmental influences, and some as the result of an
intracellular mechanism of predetermination, having no relation
to the environment.
The environment does not form organisms, but neither can
organisms be thought of correctly without bearing in mind their
normal diversities and powers of individual accommodation to
different external conditions, powers which are as incompatible
with ideas of complete predetermination from within as they are
with ideas of direct causation from without. Heredity, as signi-
fying the succession of organisms in continuous lines of descent,
is an actual fact, though as yet quite unexplained. Heredity,
in the sense of a normal uniformity of organisms in species,
does not exist. Instead of like producing like, the rule of hered-
ity is that unlike produces unlike. To assist in an understand-
ing of evolution and of the processes of descent the conception
of heredity must be modified, and for some purposes entirely
replaced, by a recognition of the facts of heterism, the normal
inherent diversity shown by the individuals, castes and sexes of
the same species. It is only when the members of a species are
compared with the members of other species that they can be
said to be alike. Compared with the members of their own
species, all organisms are different.
Heredity and variation are not uncommonly personified as two
opposing agents or " forces," the one striving to make organ-
isms alike, the other to make them different. The late Pro-
fessor Hyatt and others have even gone so far as to definitely
locate all the heredity inside the organism and all the variation
outside, holding that the organisms would be identical in form
and structure were it not for variable external influences. The
conception of heredity as an ideal uniformity is more applicable
to some species than to others, but is not completely true of any.
Experiment has everywhere shown that the members of the
species and varieties are alike — as far as they are alike —
because they breed together, not because they live in the same
environments or because their form is definitely predetermined
by an internal mechanism. The network of descent is a part
of the mechanism of heredity, quite as truly as any character-
unit particles can be.
ASPECTS OF KINETIC EVOLUTION 329
The character-unit hypothesis of heredity is one of the corol-
laries of the environmental causation hypothesis of evolution.
It seemed necessary to predicate 'something in addition to the
observed methods and sequences of organic existence, in order to
explain the evolutionary progress of species. How could the
environment change the characters of organisms, and how could
the changes of the characters be inherited and bring about the
transformation of the characters of the species? These are the
questions which Darwin sought to answer by his hypothesis of
pangenesis, a migration of determinant particles from all parts
of the body of the parent to the reproductive cells, so as to
repeat in the offspring the modifications which the parent organ-
ism had experienced. The doctrine of pangenesis never found
any support or justification in fact, since it could not be as-
certained that characters caused by the environment are in-
herited by pangenesis or otherwise. Nevertheless, the doctrine
of determinant character-unit particles has been kept alive by
the speculations of Nageli, Weismann, and many other mathe-
matically inclined students of evolutionary problems.
The kinetic theory does not approach the problem from this
standpoint, for it finds causes of evolution in the facts of sym-
basic interbreeding and normal intraspeciric diversity. The
first significant fact in the direction of an explanation of evolu-
tion is the method of interweaving of the network of descent in
which evolutionary progress is carried forward. In place of
the assumption by static theories of a hypothetical mechanism
of character-determination, with an equally hypothetical result of
ideal uniformity, the kinetic theory presents for our study con-
junctions of lines of diverse descent and results of continued
diversity of offspring.
HEREDITY IN CELL SPECIALIZATION.
The fact that the germ-cells of the higher plants and animals
are so different from those of which the various tissues and
organs of the adult body are composed, has been taken to mean
that they have some special function of heredity. A long series
of exceedingly difficult and detailed investigations have been
made in the hope of discovering these causes of development
330
COOK
which were supposed to lie hidden inside the nuclei of the
reproductive cells.
If we trace back the organic series to their more simple repre-
sentatives we not only find that the body cells become more like
each other, but that the distinction between somatic or body cells
and reproductive cells quite fades out. When the unicellular stage
is reached, the problem of heredity seems largely eliminated,
for here reproduction consists merely in the repeated division of
cells into two equal parts, the close similarity of which appears
in no way mysterious. The difference between the higher
plants and animals and the lower lies in the fact that in the
former the cells do not repeat indefinitely the same size, shape
and structure, but are greatly diversified, though remaining
joined together in colonies or compound individual organisms.
Viewed in this manner it becomes apparent that there is no par-
ticular point at which this mechanical idea of heredity becomes
necessary, no definite stage where the similarity of parts of a
divided cell ceases to explain the facts of organic structure.
Reproduction and growth frequently figure merely as two
names for the same process. Division of cells, which is repro-
duction among the lowest organisms, means growth in the
higher. The process of conjugation of cells commonly termed
sexual reproduction, need not be allowed to complicate the
question of heredity, since the same stages of gradual differ-
entiation can be traced among double- or conjugate-celled
organisms as among simple-celled. Organisms which have
conjugated recently do not divide differently from those which
have not, though they may not be able to continue to divide
indefinitely without conjugation. Among the higher compound
organisms, conjugation takes place only at the unicellular stage.
All the cell divisions necessary to the building up of the plant
or animal body must be carried on without any readjustments
of conjugate relations. To this limitation is doubtless due the
fact that as organisms increase in complexity and in special-
ization of tissues, conjugation becomes a more and more indis-
pensable preliminary to the reproduction of each new cell
colony, or compound individual. If, for example, there could
be one hundred divisions between each conjugation, this would
ASPECTS OF KINETIC EVOLUTION 331
suffice for one hundred generations of unicellular organisms
but might provide only one compound individual. Plants and
lower animals can be grown from cuttings or will regenerate
lost parts, but among the higher animals these powers of
asexual reproduction gradually disappear.
Divergence from the normal may occur at any stage in the
development of the individual, which also varies continuously,
and not merely in the germ-cell. If the life-history of a very
simple animal or plant be considered, the concentration of in-
terest on one point tends to disappear. The processes of growth
and the preparation for spore-formation in such an organism as
Spirogyra do not appear less interesting or less fundamental
from the biological standpoint than conjugation and reproduc-
tion. Moreover, we now know that adaptations arise inside of
cells as well as outside. The chromosomes and centrosomes,
no less than the larval stages of insects, may prove to be re-
sultant phenomena of evolution, rather than causal or truly
primitive.
It is easy to understand how those who have approached
evolution through the study of complex and specialized higher
groups should be led to think of heredity as a mechanism, but
if we take our standpoint at the other end of the organic crea-
tion it becomes apparent that heredity is merely a name for the
fact that cell divisions by which organisms are built up follow
closely similar lines in each successive generation. Organisms
are not different merely because they are built of different
kinds of cells, nor merely by reason of different arrangements
of the same kinds of cells. Both causes of difference are
present together in all the higher groups. Both kinds of dif-
ferentiation have gone forward simultaneously and it need not
be thought more wonderful that the cells of the same compound
individual are different than that different species should be
found among unicellular organisms. Indeed, heredity is most
perfect when the cells formed by successive divisions are all
alike. It maybe deemed a departure from strict heredity when
the)' become diversified, as in higher organisms. But whether
the individual consists of a single cell or of a colony formed
by many cell divisions, we are still dealing with the same
332
COOK
fact of organic repetition, and have no more reason in the one
case than in the other to view heredity as the function of any
special organ. We may define heredity as the property of
organisms with as much propriety as the chemist treats crystal-
lization as a property of sugar. The cells know, as it were,
how to arrange themselves repeatedly into similar colonies or
compound individuals, just as the molecules of a chemical com-
pound take repeatedly the same crystal form.
The causes of crystallization and of heredity are equally
unknown ; we can merely expect for the future that to which
the past has accustomed us. We have no better reasons for
expecting to find that the adult is definitely prefigured in the
germ-cell that we have for supposing that the crystallographic
forms or other properties of inorganic materials can be deter-
mined by microscopical examinations of the substances in solu-
tions or in amorphous states. The germ-cells with their chro-
mosomes and other internal organs do indeed carry the organic
sequence from one generation to another, but this fact gives us
no warrant that they contain any parts or particles which will
afford a general explanation of evolution. And even if the
germ-cells do contain some feature of special bearing upon
heredity, it does not alter the probability that the results of the
agencies operating in the germ-cells are shown to best advantage
in the completed organisms. Sperms and egg-cells are them-
selves organisms, quite as truly as the elephants and whales,
but their infinitesimal size, which kept them unknown and mys-
terious so long, does not warrant us in ascribing to them any
gratuitous mysteries, nor in failing to appreciate that evolution
is a motion of the specific network of descent.
Whatever the nature and functions of nuclear organs may be
in different groups of animals and plants, we may expect that
these organs and functions will find their primary explanation
and relations in the evolutionary network of descent, rather than
as affording an independent basis for theories of heredity.
Neither the relations of individual organisms to environment,
nor the possibility that germ-cells have predetermining relations
to adults, will justify us in leaving out of account the network
of descent in which the evolution of species goes forward.
ASPECTS OF KINETIC EVOLUTION 333
HEREDITY AS A RESULT OF ENVIRONMENT.
The strength of the predisposition toward theories of environ-
mental causes of evolution finds many illustrations in the con-
troversies which have raged about the Lamarckian doctrine of
direct environmental influences. Thus Professor Lankester,
even when opposing Lamarck, assumes environmental influ-
ences of a character which the facts may not justify. It is shown
that Lamarck was illogical in supposing that new environmental
characters could be preserved by heredity and thus replace at
once the effects of the " long-continued response to the earlier
normal specific conditions," but it becomes evident, even while
this excellent chronological distinction is being drawn, that it
rests on a conception of heredity only slightly less objectionable
than that of Lamarck himself. Though making no direct ref-
erence to mechanical theories of heredity, these assumptions are
such as to suggest and to justify such interpretations.
" Normal conditions of environment have for many thousands
of generations moulded the individuals of a given species of
organism, and determined as each individual developed and
grew ' responsive ' quantities in its parts (characters) ; yet, as
Lamarck tells us, and as we know, there is in every individual
born a potentiality which has not been extinguished. Change
the normal conditions of the species in the case of a young indi-
vidual taken to-day from the site where for thousands of gener-
ations its ancestors have responded in a perfectly defined way
to the normal and defined conditions of environment, reduce the
daily or seasonal amount of solar radiation to which the indi-
vidual is exposed ; or remove the aqueous vapor from the atmos-
phere ; or alter the chemical composition of the pabulum access-
ible ; or force the individual to previously unaccustomed muscular
effort or to new pressures and strains ; and (as Lamarck bids us
observe), in spite of all the long-continued response to the ear-
lier normal specific conditions, the innate congenital potentiality
shows itself. The individual under the new quantities of envir-
oning agencies shows new responsive quantities in those parts
of its structure concerned, new or acquired characters."1
lankester, E. Ray, 1906. Inaugural Address before the British Association
for the Advancement of Science. Nature, 74 : 330. Science, N. S., 24 : 607.
334 cook
If the environments controlled the character-units and thus
moulded the characters of organisms we should expect to find
that each environment would have its own organisms, or that
all the individuals of the same species in the same environment
would be alike, or at least more alike than individuals from
different environments, but these results have not been attained.
Sexual and other analogous differences which have been de-
veloped among the members of the same species in the same
environments are vastly greater than any of the diversities
which differences of environments can cause or induce. More-
over, there are nowhere in nature any constant environments
which suppress or tend to extinguish the potential of adjustment.
Vicissitudes are ever at hand, ready to make selections in direc-
tions of adjustability. The highest types of organic life, those
which have been able to travel farthest on the evolutionary road,
are those which have responded most effectively to their oppor-
tunities for learning the arts of adjustment. Neither are these
responses mere passive mouldings ; the powers of individual ad-
justment, no less than the general adaptive characters of the
species have been attained by the putting forth of variations, the
steps by which species travel.
Heredity, the name we have given to the mysterious power
of plants and animals to follow accurately the developmental
pathway of the species, and even to repeat the individual pecu-
liarities of the parents, is more similar to memory than to any
other biological phenomenon. Professor Lankester's concep-
tion of the facts implies that the hereditary memory is imposed
from without, that it is stamped or moulded upon the species by
the environment, and that its strength is, or should be, propor-
tional to the time during which the environmental impression is
continued. It is true that new or recent environmental reac-
tions, or direct adaptations, are not inherited, and do not replace
the older responsive characters of the species, but this fact lends
no support to the doctrine of environmentally moulded heredity,
for other character-modifications do appear suddenly, and do
immediately and definitely replace the earlier type of the
species, as shown in numerous and well established instances
of genetic variation and mutation. These modifications of
ASPECTS OF KINETIC EVOLUTION 335
heredity have no doubt adequate physiological causes resident
in the species, but as far as the environment is concerned they
seem to be thoroughly spontaneous and fortuitous. They ap-
pear without notice and bring their own new and complete
heredity with them ; their very appearance signifies and consists
in an abrupt modification of heredity. The environment may
reject the new character and extinguish all the individuals with
the modified system of heredity ; it may limit heredity through
selection, but it does not mould or modify heredity.
Heredity has been defined, in accordance with Professor
Lankester's view, as the sum of past environments, but this
statement, as usually understood, is only partial and misleading.
It is true only to the extent that it means that the heredity of a
species is a summary of the variations which the environments
have permitted it to retain. The idea, for example, that im-
proved environments will change the inherent characters of
backward races of mankind or of the deficient and criminal
classes of our populations, as often stated by philanthropists, is
founded on teleological inferences, and not on concrete observa-
tions. New environments may permit new and desirable char-
acters to be put forth which the selection of adverse conditions
has forbidden hitherto, but humanitarians seldom have patience
with such time-consuming methods of improvement. Moreover,
if they were to view the subject from a biological standpoint
they would soon appreciate the desirability of selecting the good
stocks for further amelioration instead of wasting their efforts,
relatively, at least, upon unworthy materials, in the vain hope of
realizing an unnatural ideal of equality. Ethical considera-
tions which concern only the relations of individuals and or-
ganized social bodies are often applied to racial and other
questions as purely biological as those of the relations of species
and subspecies in any other department of nature. Our chief
duty with reference to the really backward and deficient races
is to keep them from bringing about the deterioration of our
own, as almost inevitably occurs when a higher race comes in
contact with a lower. The qualities and standards which con-
duce to fitness in a higher civilization are of little or no signi-
ficance in a lower, and rapidly deteriorate. This does not
336 COOK
prove that the higher qualities are caused by the environment,
but only that they require certain conditions in which to develop
and maintain themselves.
Environment is of the first importance to individual organ-
isms, but the inference so widely drawn in scientific and general
literature, that the environment causes and controls evolution, is
essentially fallacious. It controls, in a measure, by limiting
some of the avenues of advance, or by setting higher and
higher requirements for continued progress, but life finds mil-
lions of different ways to solve its environmental problems.
Given a particular environment and a particular selection of
individuals with their hereditary qualities and habits known, and
we may with confidence expect a fairly definite reaction in line
with previous experiments of the same kind. But this does not
mean that evolution is an environmental cul de sac. Changes
are not passive merely, but kinetic. The environmental possi-
bilities are persistently tested by many variations. Species have
retained in this way the power of ameboid motion, and have thus
crept over the whole face of nature, and into all the crevices.
The progress possible in a single life-time or generation may
be small, but the lesson is plain. The largest, most practical,
and most precious factors of amelioration for plants, animals
and men, lie in the discovery and preservation of those indi-
viduals which are in the line of evolutionary advancement for
the breed — those possessing the qualities required by the en-
vironment, and which at the same time strengthen the species
and help to maintain the necessary vital motion in courses of
beneficial change.
THE PURITY OF GERM-CELLS AND CHROMOSOMES.
In the search for causes of natural phenomena an important
step appears to have been taken when definite quantitative re-
lations have been established. It is not strange, therefore, that
the discovery of Mendelian or "disjunctive" hybrids should
have aroused much interest, and even a certain amount of excite-
ment, among biologists. Mathematical considerations have
been allowed to obscure biological facts, and Mendel's "prin-
ciples of inheritance" have been declared to be as fundamental
ASPECTS OF KINETIC EVOLUTION 337
and significant for biology as Dalton's law of definite propor-
tions for chemistry. Deductions from Mendelism followed in
rapid succession, such as the purity of germ-cells, inheritance
by character-units, and the localization of these in chromosomes.
Mendelism as a phenomonon is both interesting and sugges-
tive, but it lacks warrant as a generalization, because the con-
ditions imposed by the experiments are as likely to be the
cause of the results as the general principles of heredity alleged
to have been revealed. There are, in fact, many reasons for
believing that the inbreeding which is deemed an essential pre-
liminary to experiments in Mendelism, induces the "disjunc-
tion " of the hybrids, instead of the purity of the germ-cells
or the antagonism of " dominant " and " recessive " character-
units. It is, perhaps, to be expected that Mendelism can be
found whenever the conditions of the experiment can be met,
but this does not prove that the phenomenon is a normal one.
Still less has it been shown that Mendelism has been a con-
tributing factor in evolution, since in Mendelian hybrids the
more recently derived characters are held not to be dominant,
but recessive, and would thus have the less chance of being
preserved under natural conditions of unrestricted crossing.
Some writers have claimed for Mendelism a practical utility
as determining the methods of procedure in breeding, and many
plants and animals are being bred to learn which characters
are dominant and which recessive, it being taken for granted
that such facts have a fixed and definite value for each species
or variety, thus enabling the results of breeding combinations
to be known in advance. The utility of such knowledge is,
nevertheless, negative rather than positive ; it may keep the
breeder from attempting the impossible, but it seldom gives him
new leverage in attacking practical problems. The danger is
rather that the acceptance of erroneous theories of heredity
may delay his perception of facts and discourage his efforts.
It seems to be agreed by several experimental evolution-
ists that white fur or feathers is a recessive character ; but
no attempt has been made to test the general basis of this
assumption by comparing interbred white mice with inbred
gray mice. Albinism is one of many mutations induced by
338 cook
inbreeding, and this debilitating process has been continued
with white mice ever since the original specimens were caged,
while gray mice have mostly remained at liberty until needed
for breeding experiments. To overlook these historical differ-
ences is to neglect factors of known significance for those
of purely hypothetical meaning.
A second series of pertinent facts commonly ignored is the
frequent and perhaps general dominance or prepotency of muta-
tions when bred upon their own immediate blood-relations.
Commercial white mice are a long standing breed, with no
close and equally inbred gray relatives. To test prepotency
fairly a new mutation would be required. There are numerous
instances in literature, but experimenters naturally attach special
importance to what happens in their own cages.
For a third experiment which might afford conclusive evi-
dence on the pure germ-cell theory, some of the more recently
developed varieties of mice might serve. If two varieties of
independent origin which had been crossed separately with mice
of the ancestral type and found to mendelize, were then crossed
with each other and found to revert to the parental type, experi-
mentalists might admit that the doctrine of pure germ-cells had
been definitely disproven. The mice which in the Mendel
experiments had produced pure white, yellow or black germ-
cells would later have produced gray germ-cells. And yet this
possibility in crosses of selected domesticated varieties has been
known since the time of Darwin's experiments with pigeons.
The arrangement of the chromatin granules into chromo-
somes, to which so much importance is ascribed, is a very tempo-
rary phenomenon. The chromosomes do not appear to retain
their separate identity either during sexual fusion (mitapsis) or
during vegetative growth, when the activities of the cells are
bringing to expression the qualities which have been transmitted
through the gametes. The diversity in number of chromo-
somes in closely allied species, or even in the same species, also
tends to weaken our faith in the idea that chromosomes as such,
or as character groups, play a very definite or determining part
as governors of the form of the organic structure of the indi-
vidual plant or animal. The chromosomes may prove, after
ASPECTS OF KINETIC EVOLUTION 339
all, to be merely crowds of chromatin granules which are being
assembled from the vegetative nucleus for mitapsis, and redis-
tributed after mitapsis to resume the functions of control over
vegetative growth.
Adult organisms, with their various characters, do develop out
of germ-cells, but until we know something more of the nature
of protoplasm, there can be no certainty that the individual char-
acters of the adult are in the germ-cell in any such form that
we can look in and find them. As well might we undertake to
find in human embryos or infants the mental and moral char-
acters of adult persons. All that we can be sure of is that the
potentialities are there, but the nature, form and residence of
these potentialities can be discussed only by means of abstract
inferences, and are not yet accessible to the concrete imagina-
tion. This explains why the theories of hereditary mechanisms
are merely philosophical or mathematical, not biological. Even
if the conception were correct and it were possible to ascertain
by some extension of microscopic vision that chromosomes or
granules are prefigurations of adult organisms, the fact would
still have little use as an explanation of heredity, or even as a
working hypothesis, until we could learn, or at least imagine,
how the models could build the structures. It is as though
some barbarous tribe, on being visited for the first time by a
modern man-of-war, should think to explain the structure by
finding a small model of the ship in a glass case in the saloon.
There would simply be two ships to explain, instead of one.
Indeed, the discovery of the character-unit mechanism has been
so long and so vividly anticipated that it is not altogether unjust
to mention the fact that no very definite uses for such a con-
trivance have been suggested.
The studies of Boveri tend to show that in one group, at
least, there is a definite necessity for the presence of one full
series of chromosomes to make normal development possible,
but this is still very far from showing that individual chromo-
somes or granules correspond to different parts of the animal.
A mutilation or disarrangement of the organs of the germ-cells
might well interfere with their development into normal indi-
viduals, even if the adult organism were not prefigured, pre-
340
COOK
formed, or prefixed, inside the reproductive cell. It is highly
important, of course, that the nature and extent of all determi-
native relations be known, but until the nexus, the modus
operandi of the process has been learned, predetermination by
material particles has no special standing as a theory, especially
where the resulting concept of heredity fails to accord with
concrete, facts, such as the need of normal heterism and free
interbreeding.
To those who view the matter from the mathematical side
only, it is still impossible to -prove that essential changes occur
in mitapsis which make the chromomeres and chromosome
aggregates different from what they were before the fusion took
"place. Nevertheless, there are three facts of nature, universal
and much accentuated among all the higher plants and
animals, which these theories of construction of organisms by
character-unit mechanisms leave entirely out of account, with-
out physiological meaning or explanation, (i) the diversity of
the individual members of species, (2) the elaborate adaptations
for interbreeding, and (3) the conjugation of the granules in
mitapsis. The different assortments of chromosomes or gran-
ules might explain the diversity, but they show no use or reason
in it. They may cause, too, the adaptive characters of inter-
breeding, but still for no purpose. Finally, they perform the
elaborate evolutions of mitapsis, but all without result, accord-
ing to these hypotheses of purity of germ-cells or of chromosomes.
For numerical purposes it may be that all these complexities
of symbasis are useless and unnecessary. The diversity of
genera and species, and of the individuals inside the species,
could all be worked out arithmetically if we could be provided
beforehand with the determinant mechanisms and a system of
permutations for combining them. But from the biological
standpoint it seems equally clear that this is not the way the
organisms were developed in nature. The character-unit plan
might have avoided all these unexplained and apparently un-
necessary complications of heterism and symbasis. The diffi-
culty is that, like its progenitor, the static theory of evolution
by environmental causes, it seems not to be followed in the
organic creation. Organisms are not naturally uniform and
ASPECTS OF KINETIC EVOLUTION 341
they do not tend to stay uniform. Organisms are not naturally
pure-bred, and their tendencies are ever to be mixed more and
more. This is the overwhelming testimony of the facts of
nature, which the inventors of character-unit mechanisms would
do well to canvass before entering upon their labors.
Chromosomes and granules as parts of cells are morpho-
logical entities, in the sense that they exist and can be made
visible by microscopical technique. It does not follow, how-
ever, that they are biological or evolutionary entities, or that
they can properly be thought of as having any general evolu-
tionary significance, except as parts or organs of cells or of or-
ganisms, which are the units of life. Moreover, as already in-
dicated from other considerations, not even organisms can be
considered units of evolution, which requires the coherent net-
work of descent of a normally diverse, interbreeding species.
CONTACTS BETWEEN LINES OF DESCENT.
The fact that the lines of descent are joined only in repro-
ductive cells should not be taken to mean that there is merely
a single or casual contact between them, nor prevent our
recognizing the possibility that the functions of the chromatin
granules may be physiological rather than morphological. It is
through them, evidently, that the reorganization of the proto-
plasm of the cells is accomplished. They represent the citadels
of life, the most vital points of the cell substance. The final
stage and apparent purpose of the process of conjugation is to
bring them into contact with other granules from other lines of
descent. The nature of this contact, whether the granules
exchange particles, or renew their vital energy by molecular or
other adjustments, is still unknown.
The most recent results of cytological investigation are in
accord with the supposition that the ability of the higher plants
and animals to lessen the number of conjugations and prolong
the intervals of vegetative growth, has been attained by the
development of more and more efficient methods of conjuga-
tion. A few years ago the opinion was held that the proc-
ess of synapsis involved only a fusion and reduction of
the number of the chromosomes ; it now appears that the
342 COOK
chromosomes are not the ultimate units of the nuclear structure,
but are merely aggregates of granules of chromatin. In the
final stage of conjugation (mitapsis) the chromosome aggregates
no longer appear distinct, but are subdivided into small clusters
of granules called chromomeres. The chromomeres are strung
out like beads in single file along two slender, protoplasmic
threads which finally lie parallel and close together, so that the
individual chromomeres can be paired off and fused with each
other. Instead, therefore, of thinking of conjugation as a
simple bulk fusion of protoplasm or of nuclei, we must view it
as involving a long line of many scores, hundreds, or even
thousands, of contacts or combinations between the much smaller
granule-groups or chromomeres. Chromomeres appear, there-
fore, to have important physiological functions as specialized
contact points in the fusion and reorganization of the protoplasm,
and do not need to be thought of as bearers of hereditary char-
acter-units.
There remains one other stage of elaboration of mathematical
hypotheses of heredity, to treat the chromomeres as permanent
entities of descent and deduce the infinitely multifarious diver-
sities of individuals in nature from the infinity of combinations
and rearrangements of which the chromomeres may be capable.
This theory is complete and unimpeachable mathematically,
but is as indefensible biologically as its predecessors ; for like
them it rests on the assumption that the bringing of the chro-
matin granules into contact in mitapsis has no significance in
descent. It takes for granted that nothing of importance oc-
curs when the granules appear to fuse, and that they separate
again without mixture, interpenetration, or combination, of the
granular or fluid constituents of the protoplasm.
The character-unit assumption requires us to imagine some way
in which the particular granules could create or bring about the
existence or the accentuation of the particular character, whereas
the other interpretation, by lines of descent, does not needlessly
destroy the unity of the problem of heredity. It avoids the
necessity of elaborate and gratuitous hypotheses in a field which
science is scarcely prepared to enter. As in the adjoining
regions of instinct and memory, it is easy to ascribe the phe-
ASPECTS OF KINETIC EVOLUTION 343
nomena to positional or other relations of molecules or atoms of
the cerebral tissues, but impossible to imagine an adequate nexus
of association with the concrete facts, actions or functions. The
opinion has already been recorded in another place that truly
mechanical solutions of this series of problems are likely to
await the recognition of additional properties of matter, which
physical researches are now revealing with such startling
rapidity.1 As clearly perceived and definitely stated by Lord
Kelvin, the current conceptions of physics are not adequate for
the treatment of the problems of biological evolution.
The wonderful and altogether unexpected results of studies
of the internal structures of cells are but poorly appreciated by
those whose hopes have dwelt on the discovery of mechanisms
of heredity. From the morphological standpoint it may appear
that little has been obtained except to open another chapter in
the vast complexity of nature. The internal organs and proc-
esses of cells have their multifarious similarities and diversities,
like all other phases of organic existence. Reproduction is
carried on by as many different methods as assimilation, res-
piration or locomotion. The great and surprising result of
cytological investigation is not in learning that such diversity
exists, which might have been anticipated, but in ascertaining
that the evolution of the large and complex bodies of the higher
plants and animals has been made possible by the evolution of
superior methods of reproduction. Mechanical theorists have
been so intent on finding a mechanism of heredity that they
have failed to recognize the physiological significance of an
improved process of conjugation.
The older idea was that reproduction, that is, the production
of a new individual plant or animal, followed the conjugation or
complete union of the parental germ-cells, but it has been found
that this is not true of any of the higher types of life. What
has been considered conjugation among the higher groups, that
is, the process in which the characters of the new organism are
determined — as far as they are determined in the germs — is
not a complete conjugation of the germ-cells, but only the begin-
ning of a conjugation which continues throughout the life of the
new individual.
^ook, O. F., 1904. Evolution and Physics. Science, N. S., 20: S7.
344 cook
This fact has bearing upon the conception of heredity, for it
takes us another step away from the older idea of a mechanism
in the cell, and shows us that the intracellular organs, which
some look upon as the mechanisms of heredity, are capable of
change and adaptation like other parts of organisms, and that
the problem of evolution is not to be solved by the supposition
that evolution is determined in advance by mechanisms of
heredity.
In the lower groups the union of the gametes is completed
before vegetative growth is resumed, or before the new genera-
tion begins. But in the remote ancestors of the higher groups
this procedure was abandoned, and the completion of conjuga-
tion was deferred. Vegetative growth began to be carried on
while the cells were still in the double, conjugating condition.
If the form of the adult were strictly predetermined by the inter-
nal organs of the cell, the double-celled organisms could have
existed only as monstrous doubles of the simple-celled organ-
isms which are built up after conjugation is completed. But,
as a matter of fact, the structures which were built up from these
double, conjugating cells proved to be entirely different from
those which had been built previously from simple cells. New
evolutions began on entirely independent lines, without refer-
ence to the character-units or other equipment of heredity
resident in the cells of which the new structures were built.
Moreover, the old form of heredity continued to be transmitted,
even after new and higher types of organic structures had been
intercalated into the life-history of the primitive organism.
All the liverworts, mosses and ferns continue to build up the
two different kinds of cellular structures, one during conjuga-
tion and the other after or between conjugations. The two
kinds of heredity, the conjugate and the post-conjugate, continue
to run peaceably along the same lines of descent, like multiple
telegraphic messages on the same wire.
Such complications do not, of course, dismay the inventors
of hereditary mechanisms. Difficulty only adds zest to their
ingenuity. Having invented one set of determinants, it is easy
to invent another and have them working by turns, as Weis-
mann gravely proposed in explaining the alternative heredity of
ASPECTS OF KINETIC EVOLUTION 345
sexes. For the bees and ants three kinds of mechanisms were
provided, and for the termites four kinds, though in reality up-
wards of a dozen sorts would be needed to account for the
strange diversity of types found in some of the African species.
And the most curious thing about the ants and termites is that
the animals which exhibit the supposed results of these diverse
kinds of mechanisms do not transmit them at all, but are de-
scended independently in each generation from sexual insects.
Here again it is apparent that new methods of development
have been entered upon without requiring any change or dis-
placement of the old. With the bees, at least, the heredity is
not determined when the egg is laid, or even when it hatches.
It is still possible for two or three days to induce the young
larva to develop either into a queen or into a worker, by vary-
ing the nature and amount of food. The environment deter-
mines, evidently, which of the mechanisms shall continue in
play and which retire into desuetude.
There is no need, of course, to continue the discussion in
this direction ; doubtless it is too long already. There are
those who think only in relations of numbers and spaces ; and
for these mechanical forms are a necessity. But for those who
approach from the biological side, who are curious to understand
nature, and yet not so impatient as to accept even scientific fic-
tion at the expense of ascertainable fact, these character-unit
mechanisms of heredity do not appear to help, but rather to
hinder, clear perception and exposition.
ALTERNATIVE OR POLARIZED HEREDITY.
From the standpoint of the kinetic theory it appears possible
to reconcile the proposed character-unit phenomena of Men-
delism with other facts of alternative descent, without invoking
the hypothesis of character-units and pure germ-cells. The
phenomena of heterism and symbasis, that is, normal diversity
and broad-breeding in specific groups, do not necessitate the
character-block assumption. They only require us to suppose
that diversity of descent affords a certain amount of molecular
tension or attraction, a polarity, as it were, between proto-
plasmic elements derived from the different lines of descent.
346 cook
There also appears to be a complete series of stages of accentua-
tion of this polarity of descent. The most primitive condition
is that of indiscriminate or unspecialized heterism, in which a
character shows all degrees of expression from the lowest
minimum to the highest maximum, with a preponderance at
some intermediate or optimum point.
The physiological advantages of diversity of descent not only
prevent the species from concentrating or stagnating on a cen-
tral average or optimum point, but they often favor the develop-
ment of two optima. The connecting series of character-stages
may weaken, or it may entirely disappear, except for rare
abnormalities, the normal form of the species being represented
by the two separated extremes. The typical and most familiar
instances of specialized heterism is to be found, of course, in
the phenomena of sex. The primary sexual characters are
now so intricately involved with the functions of reproduction
that their significance as specializations of heterism is much
obscured, but large numbers of secondary sexual characters
are quite functionless for any purpose thus far detected, except
this of increasing the diversity of descent inside the species.
When once a species has reached the stage of sex-differen-
tiation, and has thus established a polarity of descent, the ten-
dency seems to be for other specializations of heterism to group
themselves with sex. The result is to give each generation
the benefit of full diversity of descent, instead of losing this
advantage in cases where similar individuals might breed
together. No doubt it is easier, too, for a new character to
join with and accentuate an already established polarity than to
establish a new one for itself. Even among the plants which
have not attained differentiation into separate sexes there are
definitely alternative characters, and sometimes there are not
merely two alternatives, or two groups, but several, and in a
variety of combinations, as in the genus Lythrum. In insects
the phenomena of alternative descent reach their highest ac-
centuation and complexity, for there they are superposed upon
the sex-differentiation. There may be two distinct forms of
one of the sexes, as among the bees. In some species of
termites both sexes are capable of specialization in several dif-
ASPECTS OF KINETIC EVOLUTION 347
ferent directions, so that more than a dozen different and dis-
tinct types of individuals may be found in the same colony,
and no intermediate forms.
The equal sharing of the two sexes in these wonderful
specializations of the termites is a reminder of the general fact
of numerical equality between the sexes. Among the bees
where the male sex is completely useless in the social economy
and environmental relations of the colony, the reduction of the
number of males has been accomplished only by the very re-
markable specialization of the reproductive process. The sex
is no longer determined by a polarity or other simple relation
which would give equality of sexes, but by the queen herself,
who has the power of laying at will either fertilized or unferti-
lized eggs, the former developing into females, the latter into
males. This arrangement appears peculiar because it consti-
tutes so radical an exception to the general rule of equality in
the choice by individuals of one or the other of the two routes
of development possible in all sexually differentiated species.
If these relations depended upon merely mechanical arrange-
ments or upon the relative numbers of different kinds of pure
germ-cells, we should expect the frequent occurrence of many
definite deviations from equality of sexes.
Experiments have shown that in some groups of animals and
even in plants the sex-determination may be influenced by the
conditions of existence, and particularly by nutrition and tem-
perature. The changes are supposed, however, to occur in
continuous series of gradations, as though brought about by
general influences upon the constitution of the organism, rather
than by the abrupt changes of adjustment which might be ex-
pected to result from the action of character-unit devices.
The phenomena of Mendelism constitute an extension of the
facts of alternative descent ; for they show that this is not limited
merely to secondary sexual characters and to the form differ-
ences of polymorphic species, but that closely similar effects
can be obtained in a somewhat artificial manner, by com-
bining domesticated varieties with properly opposed characters.
Instead of producing merely averages or miscellaneous grada-
tions of intermediates, well established and contrasted differ-
348 cook
ences are preserved separately, like alternative sexual differ-
ences. Instead, therefore, of considering that Mendel's Laws
explain sexuality, it seems more reasonable to assimilate the
Mendelian phenomena with those of normal alternative descent
as shown generally in sex-inheritance.
If the principle of alternative or polar heredity applies to
Mendelism, the earlier explanations by the special character-
units, segregated in different germ-cells, will be superfluous.
The phenomena would still be abnormal, as are the conditions
under which they appear, but they would no longer need to be
associated with the phenomena of incompatability of chromatin,
described by Guyer in sterile hybrids between diverse species.
" When germ-cells are to be matured, before the real reduc-
tion, there is in most forms a so-called false reduction, in which
the chromosomes fuse in pairs so that there appears to be only
half the normal number present, though in reality each is
double (bivalent) and equivalent to two of the simple (univalent)
type. The doubling of chromosomes which normally occurs
at such times is frequently incomplete, or lacking, in hybrids.
This is especially true if the hybrids are from widely separated
species. Instead of a normal spindle bearing the usual number
of bivalent chromosomes, multipolar spindles, or two separate
spindles may appear, thus apparently permitting the two kinds
of parental chromatin to remain apart. In the most extreme
cases a complete separation may occur subsequently, the entire
chromatin of one parent occupying one cell, that of the other a
different cell. Such visible separations, however, only occur
extensively in sterile hybrids from markedly different parent
species. Fertile hybrids from closely related forms, for the
most part, display spindles normal in appearance. . . .
" In the case of these milder fertile crosses, then, where rever-
sions follow the Mendelian law, the germinal incompatibilities
must be narrowed down to the qualities themselves rather than
confined to the respective germ-plasms as a whole. These
qualities must separate and each take up its abode in a different
germ-cell irrespective of whether the other qualities of that par-
ticular germ-cell are of a different parentage or not. The
cases in which the entire plasmas are segregated are then prob-
ASPECTS OF KINETIC EVOLUTION 349
ably but magnified images of what occurs among the specific
qualities of the milder crosses. The interesting possibility arises
that if fertile hybrids can be secured from widely different
species the plasmas of which must be more incompatible than
those of nearly related forms, such hybrids will give rise to
offspring in which there is reversion, not only of one character,
but of many or all characters in the same individual, due to a
more thorough segregation of the parental germ-plasm as a
whole. In other words, the farther apart the parent species
are, the more complete will be the return in any given offspring
which shows reversion." l
Instead of representing germinal incompatibility, the Men-
delian phenomena may prove to be merely examples of the
preservation of welcome and desirable contrasts. Nor is it
unreasonable to suppose that the polarity or other form of alter-
native reaction is rendered more definite and intense by the
process of inbreeding which is considered a necessary prelimin-
ary for the exhibition of the Mendelian phenomena. Con-
trary to Dr. Guyer's supposition, the " disjunction " of characters
does not appear to depend upon the extent of diversity, but upon
conditions of inbreeding. Experiments with Mendelism seem
to succeed only with closely inbred domesticated varieties, not
with wild species. Indeed, it is only among narrow-bred do-
mesticated varieties that materials for such experiments can be
found, that is, definitely contrasted pairs or small groups of
uniform characters.
SEXUALITY OF CONJUGATE ORGANISMS.
The sexual differentiation of the higher plants and animals
affords another fairly definite indication that sexual and other
alternative characters are determined by some such general
principle as polarity, rather than by specialized character-unit
mechanisms of the reproductive cells. It is now known that the
bodies of higher plants and animals are not the result of a com-
pleted conjugation of the parental sex-cells, but are formed be-
1 Guyer, M. F., 1903. The Germ Cells and the Results of Mendel. Cincinnati
Lancet-Clinic, May 9.
350
COOK
fore the conjugation is completed, and are thus a joint or conju-
gate product of the two germ-cells.
The sexuality of the higher plants, known to the ancients, and
to the aborigines of tropical America, reasserted by Bacon, re-
discovered by Sprengel and substantiated by Muller and Darwin,
has been denied on technical grounds by recent botanical
writers, as a result of the prevalence of certain morphological
theories of alternation of generations. This doctrine has led to
the inference that the bodies of our higher flowering plants
represent an "asexual generation," and it is held to be absurd
to ascribe to such organisms the qualities and specializations of
sexuality.
Some botanists accordingly refuse to call the stamens and
pistils sexual structures, or the staminate and pistillate plants
male and female, because they do not represent the same
kind or stage of sexual differentiation as that shown in male
and female moss-plants or male and female fern-prothallia.
The fact remains, however, that the sexuality of such a plant
as the date palm is completely analogous to the sexuality of the
higher animals and of man himself. In other words, it has
been proposed to deny sexuality to exactly that form of sex-
differentiation to which the word was originally applied.
The significant fact is that the sexual differentiation of
organisms should have taken place on the two different planes
of structural organization, both in the simple-celled lower types
and in the conjugate-celled higher types. Indeed, there are
three grades or stages of development where sexual diversifica-
tion has taken place.
i. Sexual differences of the single gametic cells, as of the
sperms and ova, or the pollen-grains and the egg-cells.
2. Sexual differences of simple-celled gamete-bearing struc-
tures, as of the male and female thalli of liverworts, the male
and female plants of mosses, and the male and female pro-
thallia of ferns, Isoetes, Selaginella and Equisetum.
3. Sexual differences of double-celled or conjugate struc-
tures, as of the male and female individuals of the higher plants
and animals.
Nor does the reckoning end here, for the separation and
ASPECTS OF KINETIC EVOLUTION 35 I
diversification of the sexes has not taken place twice only
among the plants, but probably hundreds of times, independ-
ently, and in different and unrelated natural groups, the ances-
tors of which were bisexual. Separate sexes, though well-nigh
universal among the higher animals, both arthropods and verte-
brates, show, nevertheless, numberless independent specializa-
tions. In short, no tendency of evolution has been so definite
and so general as that leading toward the accentuation of sexual
differences. This can hardly mean anything less than that
diversity of descent, to which sexuality ministers, has a general
physiological importance and is not merely incidental to fortuitous
collocations of character-units. No doubt it will be found that
the details of sex-determination differ much in the different
groups of animals and plants, but this will not diminish the
general significance of the phenomenon.
Sex-determination by purely mechanical means might still
serve the purposes of symbasic interbreeding, but the heredity
which might be due to the existence and operations of such
mechanisms would not afford the basis of a complete theory
of evolution. It would still be in need of an evolutionary
explanation.
VEGETATIVE MODIFICATIONS OF HEREDITY.
Further reasons for preferring this idea of polar or positional
relations of the ancestral hereditary elements to that of charac-
ter units or determinants, is to be found in the fact that the
hereditary attributes of form and structure are apparently ca-
pable of change at any time in the life-history of the organism,
and not merely at the time of conjugation when under the more
mechanical theory the nature of the individual should be deter-
mined, once for all.
As a matter of fact, plants do make extensive and permanent
alterations of their characters during the vegetative period.
Such cases, though relatively rare, are numerous in the aggre-
gate. The best known instances are those of bud varia-
tions or "sports/' as the gardeners call them, where^a single
bud produces a branch as different from the others as seed-
grown individuals, or more so. A bud mutation of coffee found
352
COOK
in Guatemala in 1904 showed characters often approached by-
seedling mutations, but somewhat more accentuated than any
of the similar mutations which have been raised from seedlings.
Fasciation is, perhaps, to be looked upon as a form of bud
variation, but it must rise in some instances, at least, through a
derangement of the apical cells, rather than as a mutating adven-
titious bud. This has been observed very frequently in fascia-
tions of asexually propagated plants like Dioscorea and Ipomcea.
A normally round stem broadens gradually to several times its
normal width, but retains its original thickness or even becomes
thinner than before.
Another instance in which heredity, in the usual sense of the
word, is suspended or set aside during vegetative growth, may
be found in the familiar phenomenon of galls, where the presence
of the insect parasite or the substances secreted by it, is able
to cause the formation of complicated and highly specialized
structures, as though new ingredients of heredity had been
added.
The mutations which often occur in the first generation of
plants when grown in new regions are also to be reckoned as
post-reproductive changes of the hereditary type, for while we
could not be certain in any individual case, that the mutation
could not have occurred if the seed had not been transferred,
the very great difference in the percentage and the range of
mutations which can be secured from the same stock of seed
will prove that the new conditions have been an inducing cause,
able to act after the planting of the seed and long after the
nuclear elements have been arranged on a basis which would
normally have persisted throughout the life of the individual.
The fourth type of interference with heredity during the
vegetative period is that of graft hybridism. The extent to
which this takes place with normal plants has not been ascer-
tained, but the power of communicating diseased conditions has
been well established in a variety of instances ranging from
peach -yellows, peach-rosette, and the mosaic disease of tobacco,
to the only slightly abnormal variegations. Mr. Luther Bur-
bank relates also an instance in which a graft of a red-foliaged
variety of Primus influenced the foliage and the progeny of
the stock.
ASPECTS OF KINETIC EVOLUTION 3 53
RELATION OF HEREDITY TO IIETERISM.
The recognition of normal diversity inside the species neces-
sitates a modification of the older view of heredity which predi-
cated an exact likeness among the members of a species. The
uniformity which the older authors had chiefly in mind was that
of the members of one species compared with those of another
species. This is indeed a wonderful phenomenon, and it is not
surprising that mechanical explanations were suggested. It
was also quite to be expected that when the idea of internal
"mechanisms of heredity" had arisen it should have seemed
necessary to predicate a complete uniformity of individuals as
the normal result of the workings of such a device. The
mechanical inference was carried even to the extent of suggesting
that the diagnostic characters like those enumerated in system-
atic manuals are each represented by one of the chromosomes
or minute masses of infinitesimal granules found in the nuclei
of reproductive cells.
As a matter of fact, natural species do not differ merely by
six or seven formally expressed characters. They are different
throughout, and the diversity does not end with the distinctions
between the species, but extends to the individuals of each of
the groups. Appreciating the necessity of greater flexibility for
the mechanisms of descent, Mr. Walter T. Swingle suggested
several years ago that the expression of characters might not
depend directly or entirely upon the chromosomes or granules
themselves, but upon their positional relations. This sugges-
tion avoids all occasion of resorting to the character-unit hypoth-
esis, and may afford a clue to a cytological explanation of the
phenomena of heterism.1
It is not necessary to think that the granules determine the
characters as such ; they need be considered only as representing
the characteristics of the ancestral lines of descent. It is then
1 Mr. Swingle also calls my attention to the very pertinent fact that the nar-
rowly mechanical character-unit hypotheses, to which objection is taken in the
present paper, have not been proposed or defended by those who have made the
truly important contributions to the science of cytology. Indeed, it is exactly
these investigators with first-hand knowledge of the anatomy of cells who appre-
ciate most keenly the wholly hypothetical nature of the character-unit specula-
tions.
354 COOK
possible to suppose that if the granules derived from a given
ancestor secure a favorable position the characters of that ances-
tor will predominate in the new individual. In this way the
characters of different ancestors might assert themselves in end-
lessly varied degrees, even in the offspring of the same parents,
as they often do. This theory has the advantage of affording
a thinkable connection between facts which otherwise appear
completely mysterious. Two collateral circumstances increase
the warrant for applying the suggestion to the phenomena of
heterism.
It has been indicated by several observers, but most directly
by Prowazek l that the granules of chromatin, which compose
the chromosomes at the period of the conjugation, migrate, dur-
ing vegetative growth, to positions at the knots of the nuclear
network, as though to direct the processes of assimilation and
growth. It was found by Maupas in his experiments with
infusoria that continual inbreeding causes the gradual deterior-
ation and diminution of the nucleus, as though diversity of
descent were necessary to maintain the nuclear network, either
by keeping up the number of granules or by enabling them to
stay at the right distance apart. Such a relation would explain
the known facts, to the extent of indicating a reason for heterism
and a means for bringing it about.2
It is also easier to conceive of the possibility of bud-variations
under the supposition that the influences exerted by the chrom-
atin depend upon position, rather than upon the origination of
new units or upon the making of different combinations. Modi-
fications of hereditary forms and methods of growth do occur
during the vegetative period, as already stated, and may be
quite as pronounced as the mutations obtained from seed.
Changes capable of accounting for bud-variations would also
be adequate for the explanation of mutative variations.
Those who begin with the assumption that evolutionary prog-
ress is actuated by external causes are compelled to argue that
the diversities of individual organisms arise through varied
1 Prowazek, J., 1904. Keimveranderungen in Myxomycetenplasmodium. Oes-
terreich. Bot. Zeitsch., 54: 27S.
2 Cook, O. F. and Swingle, W. T., 1905. Evolution of Cellular Structures.
Bui. 8i, Bureau of Plant Industry, U. S. Dept. of Agriculture.
ASPECTS OF KINETIC EVOLUTION 355
environmental experiences, but the inadequacy of this con-
jecture is made plain by the fact that the greatest of these intra-
specific divergencies, those of sexes, castes and alternating
generations are obviously not subject to such an explanation.
Protoplasmic arrangement, and the specializations of the organs
and processes of reproductive cells, were not, of themselves,
effective for the problems of advancing organization. There
had to be differences, vital tensions, as it were, between the
protoplasms, if organic progress were to be maintained, and con-
jugation were to become adequate for the building up of large,
complex and long-lived organisms.
As fission suffices for the reproduction of only the simplest
types, and haplogamy, apaulogamy and finally paragamy,
have proved necessary to continue the propagation of organisms
of successively higher degrees of complexity, so, for the very
highest, sexual diversity and continuously maintained symbasis
are requisite. The effect of prolonging the process of con-
jugation is to double in each organism the threads of the vital
network. The separation of a species into sexes is a still more
advanced category of specialized descent, since it doubles the
whole specific network, permits accumulation of two sets of
variations, and insures that each individual be descended from
two diverse parents.
But even this provision of interbreeding does not suffice to
maintain the perfection of organic excellence found in man
himself, where the requirement of diverse descent is so acute as
to forbid, on pain of degenerate offspring, the union of indi-
viduals separated by less than four or five generations, or by
two or three strains of alien blood. Human descent is so
difficult and precarious a fabric that the double network cannot
be held in place merely by the joining of adjacent knots.
The structure is likely to totter or fall if the lines of descent
which join in the building of each new individual are not well
braced by meeting each other at broad angles. Neighboring
parallel or only slightly divergent lines do not afford the neces-
sary stability of contrast, the vital tension which enables the con-
jugate cells to build a well-knit body. The intricacies of rela-
tionships which fascinate the genealogist are not gratuitous or
356 cook
accidental, but are a biological necessity in the elaboration of
the framework of symbasic descent which sustains the organic
vigor of the species.
In cytology, no less than in the more general fields of study,
it is the physiological values which need first to be ascertained?
before the morphological considerations can be correctly appre-
ciated. Germ-cells can indeed be viewed as mechanisms of
descent, but speculations regarding them should not be made
the basis of evolutionary thought nor the test of orthodoxy, to
the exclusion of more definite and concrete indications of the
nature of evolutionary processes.
The kinetic theory finds significance and confirmation in the
now rapidly accumulating indications of an extensive series of
fusions between the individual granules of chromatin, which
previous cytological interpretations, based on static views of
evolution, have denied. From the kinetic point of view the
fusions of the chromatin are an important and altogether ac-
cordant part of the whole system of evolution ; they are the ac-
tual knots and junctions of the fabric of descent. Static theories
of cellular determinants, on the other hand, can see in these
evidences of fusion only an elaborate deception, an unnecessary
complexity of the process of reproduction, just as it was for-
merly held that sexual reproduction itself stood in the way of
evolution, because it interfered with the subdivision of species
and the isolation of new variations.
The traditional concept of heredity, the ideal of uniformity in
descent, has furnished the basis of all preceding doctrines of
evolution. Conditions of isolation or of restricted descent have
accordingly been considered typical for evolution, because it was
only in narrow bred groups that the ideal of uniformity could
be approximated in nature. The kinetic theory breaks with all
these traditions, and seeks to substitute for the abstract concep-
tion of a uniform, definite or mechanical heredity, a recognition
of the concrete fact of normal diversity, inside the species.
6. THE CONSTITUTION OF SPECIES.
Astronomy is reckoned as queen among the sciences because
it has demonstrated that definite and orderly relations exist
ASPECTS OF KINETIC EVOLUTION 357
amidst the apparently hopeless disorder of the stars. The
ancients, grouped the stars into constellations, but modern
science shows us systems ruled by laws of mathematical preci-
sion.
Biology has remained longer in the constellation stage. Spe-
cies are still discussed, even by evolutionists, as though they
were mere chance aggregates of organisms, at once too familiar
and too diverse to be formally defined.
It may well be that no coherent definition can be made for
species as mere aggregations or constellations of organisms ;
the idea itself is vague and essentially unscientific. The pri-
mary error was that of treating the species as a morphological
group, whereas the true evolutionary species is a physiological
system. Like a stellar system, it may contain a large number
of different individual members, and even different kinds of
members. The unity of the species does not depend upon
the organisms being all alike. It is necessary only that they
remain within range of mutual influence through interbreeding,
which is the biological analogue of gravitation.
A species, that is, a normal, natural, evolutionary species, is
a large, coherent group of freely interbreeding organisms. But
with species, as with stars, all systems are not alike. There
are suns, satellites, planets, asteroids, nebulae, variable stars,
doubles and comets, in vast diversity of sizes and combina-
tions.
In biology, as in astronomy, the most familiar things have
proved very deceptive. The sun, moon and stars appear alike
to revolve around the earth, from east to west. It was at first
an extremely heterodox idea that the earth revolves around the
sun. Moreover, neither of the apparent motions gave any inti-
mation of the third order of motion, that of the system as a
whole. In a similar way we have taken it for granted that the
evolution of species could be explained by the motions we have
been able to detect among our domesticated plants and animals.
We are now learning that these types of life are not reliable
examples of evolutionary systems, that their motions are often
retrograde or degenerative instead of progressive and construc-
tive. Nor are abnormal evolutionary conditions entirely con-
358 cook
fined to domesticated organisms. Among the millions of biolog-
ical systems many have wandered from the path of progressive
evolution and are on the way to extinction. As with the mo-
tions of the heavenly bodies, nature herself has deceived us, or
rather she has given us new riddles to read.
The motion of species is not like that of the stars, in simple
geometrical figures. The evolutionary progress of species is
accomplished by the weaving of an intricate fabric of lines of
descent through the free interbreeding of the component organ-
isms. The simple, normal and typical constitution of a species
may be thought of as a huge but simple network of uniform
texture. All the organisms are diverse, but the diversity is
merely individual and indiscriminate, so that the network has a
uniform texture.
THE SPECIFIC CONSTITUTION OF LIVING MATTER.
Inorganic matter exists in a variety of conditions or physical
states, gaseous, liquid, colloidal, crystalline, granular or amor-
phous. The properties of matter depend upon these conditions
or states quite as much or more than upon the chemical com-
position or ultimate nature of the materials of which they are
composed. There are laws of gases, liquids and crystals be-
cause the different substances behave very much alike in the
same physical states. Indeed, the same physical states of dif-
ferent substances are generally very much more alike than the
different physical states of the same substance.
In a similar manner the qualities of living matter are to be
associated and described with reference to its various states or
conditions. Chemically it is a mixture of water and of small
quantities of numerous substances and compounds. Physically
it is a jelly or colloid. Biologically it manifests such powers as
growth, digestion, motion and reproduction. Morphologically
it consists of cells or protoplasmic units with a more or less dif-
ferentiated internal structure, and a power to combine or asso-
ciate into organisms.
For evolutionary purposes the chemical, physical and organic
points of view do not suffice. It is necessary to recognize that
living matter shows still another unique property, another kind
ASPECTS OF KINETIC EVOLUTION 359
of constitution, the specific. A species is quite as concrete a
phenomenon as a crystal. Both are collections or aggregates
of smaller units, and the units have in both cases definite and
necessary relations to each other on which the existence and
further development of the crystal or the species depend.
It is true that many valuable evolutionary data have been
secured from captive or domesticated plants and animals, but
the results of this whole class of experiments indicate very
definitely that evolutionary phenomena under these conditions
are degenerative and not constructive. We are driven back to
study the constitution of species in nature, to gain a clear under-
standing of the organic conditions which make possible genuine
developmental progress, a true organic evolution.
No theory or evolutionary interpretation can hope for per-
manence which leaves out of account this primary fact that
organisms normally exist in large groups of freely interbreeding
individuals, the groups commonly called species. Domesticated
varieties of plants exist without interbreeding and a few species
in nature are supposed to propagate only by vegetative methods,
by parthenogenesis or by self-fertilization, but no genus, family
or order appears ever to have developed without the association
of the individual organisms into interbreeding groups or species.
The only exceptions, if any, are among the bacteria and other
extremely simple forms of life which have failed to develop
either a specialized nuclear structure in the cells themselves or
an ability to associate and differentiate to form compound cellu-
lar organisms.
The reigning popularity of laboratory methods of research
may permit small welcome for the suggestion of a method of
evolution which requires the extensive equipment of nature and
can not be demonstrated in cages or gardens, except by negative
results, like those already well known. This disappointment
need not continue, however, any longer than may be necessary
to perceive that while experiments with domesticated species
lose in apparent general significance under the new interpreta-
tion, they gain greatly in definiteness. If they do not show us
how the fabric of normal evolutionary descent is woven, they at
least teach us how it may be unravelled. This knowledge is of
360 COOK
great value, not only to help breeders in the making of useful
domestic types, but also to students of the general problem.
Domesticated plants and animals furnished the most effective
arguments for the theory of organic evolution, for although the
ancestral wild types of many cultural species are still unknown,
and may have become extinct, there can be no doubt that thou-
sands of their varieties have originated in domestication, and
that similar varieties continue to arise under the eyes of the
cultivator and breeder. Domesticated plants and animals have
supplied, too, nearly all the materials for evolutionary experi-
ments, and it is also with them that evolutionary theories must
find, ultimately, their practical application.
A false or inadequate theory, though avowedly based on
studies of domesticated species, may be quite as injurious to
agricultural progress as another drawn from facts ascertained
from useless wild species. Any idea worthy of general credence
will bear the test of application to both classes of phenomena.
A theory is merely a way of thinking about things, and is useful
if it enables us to see, or even to suspect, causal connection
between facts previously unassociated. One theory is better
than another if it brings important facts into relation, and is
considered established as a law or doctrine when it accomodates
all the facts of the field it was designed to cover. The dis-
tinction frequently attempted between " theoretical " and " prac-
tical " investigations of evolution is quite fictitious, as in other
fields of knowledge.
By a curious perversity of language the designation "pure
science" is often applied to accumulations of knowledge not
yet refined enough to be useful for practical purposes. The
talk of discrepancies between theory and practice amounts to a
kind of fiction, a euphemistic way of saying that an inadequate
theory may not be wholly worthless as an indication of relations
not yet adequately understood.
For establishing the general fact of variation and thus dem-
onstrating the possibility of an evolutionary and continuous
creation, the variations which have arisen under domestication
afforded the most pertinent and convincing testimony. No
biologist now doubts that evolution has taken place and still
ASPECTS OF KINETIC EVOLUTION 36 1
continues, but there is, nevertheless, a very wide and very
practical divergence of opinion regarding the nature and causes
of the evolutionary process. In the study of this question
it becomes important to realize that the evolutionary condition
of cultural species differs from that of wild types because of
the much greater degree of inbreeding to which the former
are commonly subjected.
The constitution of species has a practical bearing upon agri-
culture, not because the domesticated plants and animals have
not been studied from an evolutionary standpoint, but for the
very opposite reason, that they have been considered too exclu-
sively, so that the important differences existing between them
and wild species have been overlooked. Ideas drawn from
domesticated varieties have been projected into nature at large,
and this made it only the more impossible to appreciate the fact
that grave differences exist between wild and domesticated
groups of organisms.
Evolutionary science has gained much from the study of do-
mesticated plants and animals, and may gain still more in the
future. The objection is only to the use of such studies and
results as an exclusive basis of interpretation of the facts of
nature. All that happens in domestication may also happen in
nature, for domestication is, after all, only a department of
nature. It does not follow, however, that nature is fully mir-
rored in domestication; the mirror is too small. It shows us
only the conditions in which constructive evolution does not
take place, even in nature.
The recognition of the fact that evolution is a phenomenon
depending upon the specific constitution of living matter has
been delayed, no doubt, by the difficulties which have been en-
countered in the field of taxonomy. In the recent decades nat-
uralists have faltered in the task of nomenclature set by Lin-
naeus. To merely describe and give names to the millions of
evolutionary unit groups of organisms which occupy the sur-
face of our planet is a work much too vast for the present re-
sources of science. The temptation of weariness has been to
shorten it by passing over the apparently useless redundancy
of slightly different groups, or by declaring that all is vanity of
362 COOK
merely abstract conception, that species do not exist, and can
not be defined.1
Those who have not persevered beyond this stage of skepticism
and satisfied themselves of the existence of species in nature,
can have little use for an interpretation based on the recognition
of species as definite entities, consisting not merely of aggre-
gates of individual organisms, but also of fabrics of interwoven
lines of descent.
The difficulty in defining species is the lack of clear percep-
tions, not only of the nature and constitution of species, but also
of the fact that several diverse types of phenomena are being
covered by the word. Under such circumstances a general
definition of species, however framed, could afford only a ficti-
tious unification of expression, the ideas and implications cov-
ered by the term remaining essentially diverse and often quite
contradictory. This confusion affords, however, no justifica-
tion of a failure to use the term in one or another of the explicit
senses of which it is capable, nor of a refusal to define the usage
of the term in any particular connection.
The difficulty of defining the term species has arisen mostly
from the fact that the phenomenon is a physiological one,
whereas the general supposition has been that it is morpho-
logical. The idea that species are " founded on identity of
form and structure," as the dictionaries say, is still widely
prevalent, and is one of the tenets of evolutionary belief upon
which Professor De Vries especially insists.
The impracticability of a morphological definition of species
arises from the fact that it is impossible to set definite limits to
the extent of the variability or diversity which is to be permitted
in the species. Identity of form and structure makes an excellent
definition ; the objection to it is that no such species seem to
exist in nature, or as Professor De Vries says, " * * * purely
uniform species seem to be relatively rare." 2 In some groups
1 Thus a recent defender of the mutation theory of De Vries has declared : " If
it is really true that De Vries does not know what constitutes a species, then,
indeed, we find our faith in his work thereby increased. Who, indeed, except
the makers of dictionaries, does ' know what constitutes a species ' ? "
This method of reasoning was very popular in mediaeval times and was then,
reduced to the neatly pious formula: " Credo quia absurdum."
2De Vries, H., 1905. Species and Varieties, 64.
ASPECTS OF KINETIC EVOLUTION 363
all the members of the species are closely similar, but in others
they may be extremely unlike, as when the specializations of
sex and polymorphism have been developed. There is no need,
however, that we define species as a morphological term, since
species are not caused nor constituted by the likeness or unlike-
ness of the component organisms. Indeed, it is unlikeness rather
than likeness that conduces to the prosperity of the species.
The species in nature is constituted by the fact that the com-
ponent individuals breed together. For evolutionary purposes
a species is a group of interbreeding organisms ; nothing more
is required, nothing less will suffice. Species are units of
organic evolution ; organisms continue to exist and to make evo-
lutionary progress only in large groups of freely interbreeding
individuals. Groups of organisms which do not interbreed are
no longer species ; they no longer have the typical and essential
evolutionary constitution of living matter.
Whether the individuals are alike or different does not in the
least affect the specific unity of a group if the organisms are
associated in nature on a basis of free interbreeding. If the
groups have ceased to interbreed, Avhether by reason of geo-
graphical barriers, or of structural or instinctive incompatibility,
they are no longer a unit of evolution, no matter how close the
external similarity may appear.
Natural species are not the only groups of organisms to which
the name is applied, but since all other so-called species are
mere parts or fragments of natural species, a recognition of
natural species must precede a true appreciation of the more or
less artificial subdivisions of species.
These evolutionary facts are quite independent of the old
taxonomic idea that the limits of species could be determined
by ascertaming whether the animals or plants can interbreed.
The evolutionary question is whether they do interbreed.
Groups able to interbreed perfectly will still follow divergent
courses of evolution, if kept apart. On the other hand, the
failure of the extreme members of the same species to inter-
breed would not destroy the unity and coherence of the group.1
1 Cook, O. F., 1905. The Evolutionary Significance of Species. Smith-
sonian Report for 1904.
364 COOK
The exclusion of the domesticated plants and animals from
use as illustrations of the true methods of evolution may appear
to withdraw the subject from the consideration of all who do
not have intimate acquaintance with' species in nature. There
remains, however, an excellent and very familiar example of
evolutionary conditions, that of man himself. The genus Homo
has achieved in a relatively brief period a wide divergence
from its simian relatives. This progress in development has
been coincident with the achievement of a world-wide distribu-
tion and with free interbreeding throughout the area of distribu-
tion, except as hindered by geographical barriers. Moreover,
a further close analogy is to be found in the development of the
human individual personality by a complex network of contacts
with other members of a social group. Without such social
contacts the intellectual development was limited to automatic
instincts ; with socialization new lines of evolution became pos-
sible, just as conjugation opened the road to the development of
compound organisms, and the further various stages of advance
in prolonged conjugation made possible higher and higher types
of cellular structures.
LONGITUDINAL AND TRANSVERSE SECTIONS OF SPECIES.
Longitudinal sections of species show differences along lines
of descent. They include what are commonly called life-his-
tories, based on studies of the progressive changes of form and
of methods of existence by which individual organisms follow
each other in lines of descent.
Transverse sections of species show differences and relations
between lines of descent, that is, the internal bionomy of the
species. The objects of study are not the methods of develop-
ment or the physiology of individuals as such, but the nature and
relations of the different kinds of individuals which exist in the
species. The individuals of a species which are alive at any
one time may be thought of as affording a cross-section or end
view of the network of descent.
Some of the facts of the constitution of species can be under-
stood best from longitudinal sections, some from cross-sections,
and many can be best thought of by keeping both aspects of the
network in mind.
ASPECTS OF KINETIC EVOLUTION 365
DIVERSITY IN LENGTHS OF CONJUGATE PERIODS.
The patterns of longitudinal sections of the networks of de-
scent of different species are determined by the longevity of the
individual organisms. In popular language it might be said
that the generations of some species overlap while those of other
species do not. Many species, both of animals and of plants,
are strictly annual. All of the adults die in the fall, and the
species exists in the winter only in the form of eggs, spores or
seeds. These hatch or germinate in the spring and all the new
individuals grow to a simultaneous sexual maturity, interbreed,
reproduce and die. All the members of the species are in nearly
the same condition at the same time and the figure of descent
is simple and regular.
A few species, such as the bamboos among the plants, pre-
serve this complete simultaneity, although living through a con-
siderable series of years. Flowers and fruits may be produced
only at rare intervals of two or three decades. All the plants
of the species reproduce at the same time and then die. But in
nearly all groups the lengthening of the life of the individual
organism means the overlapping of the generations and the
simultaneous existence of many different forms or stages of the
species.
Such a statement is not adequate, however, for a scientific
description of the complexities of overlapping descent ; for the
word generation has been used with a great diversity of mean-
ings. In the lowest unicellular organisms each independent
cell-individual is a generation. In the next stage, where the
cells are joined into simple and relatively undifferentiated struc-
tures, the word generation may well denote the interval between
two successive conjugations, or rather the structure which is
built up between the ending of one conjugation and the ending of
the next. But even this definition fails us as we go higher in
the scale of existence and find plants and animals which build
two or more organic structures between successive conjugations.
In some cases there is a succession of two kinds of cellular
structures, one structure being built up before the formation
of the sex-cells, before conjugation commences, and another
structure after conjugation has commenced. The former is
366 COOK
built of simple nonconjugate cells, the latter of double or con-
jugate cells. The nonconjugate structure corresponds to the
" generation" of the simpler types of organization. The con-
jugate structure is a new feature intercalated into the previous
life-cycle, which it often completely overshadows. The con-
jugation period of many organisms, and especially of the highest
groups, both of animals and of plants, is now very much
longer than the part of their life history which corresponds
to a whole generation in the lower groups. For tracing homol-
ogies between the higher and the lower groups it is still pos-
sible to talk of the period between conjugations as a gener-
ation, but most of the generation is now occupied by the
conjugation period, the life-time of the double-celled phase of
organization. This corresponds merely to the fertilized egg-cell
or oospore of the lower algae which do not build up any struc-
tures of conjugate cells.
In other cases, which are properly to be called alternation of
generations, the diversity of the two interconjugational forms has
been brought about by vegetative propagation, which replaces
or supplements the sexual reproduction of the species. Alter-
nation of generations, that is, of two forms of organic individuals
in the same species, may take place either in the conjugate or
in the simple or nonconjugate period of the "generation."
Thus in the mosses and liverworts vegetative propagation is fre-
quent in the simple-celled phase, while in the ferns and flower-
ing plants it appears in the conjugate period. Vegetative pro-
pagation is often described as a purely asexual process, but this
is not true of the higher plants, since the conjugate phase
is wholly a sexual phenomenon, a part of the sexual process of
conjugation.
It may therefore be held that the term generation, as popularly
used with reference to the higher plants and animals, does not
correspond to what is meant by generations among the lower
groups. The period of the life-history which constitutes a gen-
eration among the more primitive types of life is so brief as to
remain practically unnoticed among the highest. Conversely,
the conjugate period which is so short and unimportant as not
to complicate the question of generations in the lower groups is
ASPECTS OF KINETIC EVOLUTION 367
lengthened to cover nearly all the activities of the species in
higher types of life.
Among the lower groups the overlapping of the generations
appears to be a mere coincidence and serves no important evo-
lutionary purpose, but among the higher types it is a condition
of the utmost significance, since it has permitted the develop-
ment of parental instincts and of the numberless devices and
habits by which the eggs or seeds or the young individuals are
protected and nourished through periods of helplessness. The
lengthening of the embryonic and juvenile periods has been
necessary to permit the development of large and highly special-
ized organisms. The overlapping of the generations is also a
prerequisite for the development of social habits and instincts,
and especially in the transmission of the postnatal inheritance
on which the development of human culture and civilization
depends. Civilization has been developed and has persisted
only among those races in which the family unit of social organ-
ization was maintained, so that the children secured the advan-
tage of long and intimate contact with their parents and were
thus able to acquire, transmit and accumulate in the race the
collective experience and progress of the component individuals
and families. Thus the aborigines of tropical America who
live mostly in separate and isolated families have built up
numerous primitive civilizations, while the natives of tropical
Africa who live only in villages have never developed civiliza-
tions. Indian children are the constant associates and helpers
of their parents while the children of an African village are
herded among themselves in little troops or squads like the street
waifs of our slums. Even our highly developed systems of
formal education have this serious defect and danger, that they
tend to disconnect the generations, and to throw the young into
premature and reactionary forms of social organization instead
of permitting them to grow gradually into their normal places
in the general fabric of the community.
DIFFERENT TYPES OF CELLULAR ORGANIZATION.
The complexity of the constitution of species can not be fully
appreciated unless it be kept in mind that each individual of all
368 COOK
the higher types of life is itself a compact system or colony of
cellular organisms, and that these compound units are not only
different as to the aggregate cell-individuals, but there are dif-
ferent kinds of cellular organizations. Not only does endless
diversity exist among the unicellular or single-celled types of
life ; there are also different manners and degrees of cell-asso-
ciation to make up the multicellular types. If the cells of the
colony-individuals are alike, the organism is called isocytic, if
unlike heterocytic.
If the cells which associate have no separating cell-walls the
organism may be described as plasmodial, as in the Myxomy-
cetes and in such alga? as Caulerfia and Acetabularia. If the
cells have the form of long slender filaments the organism is
described as hyphal, as in the fungi ; if built of definite cell
blocks it is called cellular, in the strict sense. The fourth or
highest type, found in the animals, combines the other three.
Some cells remain quite free and unattached, like the red and
white blood corpuscles ; some tissues are still plasmodial, others
hyphal, while still others, and these in the majority, have
definite cellular structure.
Finally, the colony-individuals differ in being built of cells
which are not conjugating (agamic cell-structures) or of those
which are in conjugation (conjugate cell-structures). Of the
latter there are two types, the first is that shown by the higher
fungi which build colony-individuals of binucleate cells, formed
before the nuclei have fused in conjugation (apaulogamic cell-
structures). The second type of conjugate structure is that of
the higher plants and animals whose bodies are built up of cells
with the nuclei fused, but with a double number of chromosomes
(paragamic cell-structures).
These facts are capable of a very definite graphic represen-
tation in our ideal longitudinal sections of specific networks of
descent. Double-celled structures are the conjugate product of
two lines of descent and their existence is to be shown in our
diagram by double, closely parallel lines. The network which
represents the method of descent of intermediate groups, such as
thearchegoniate plants (liverworts, mosses and ferns), may show
single and double lines in almost equal proportions. Primitive
ASPECTS OF KINETIC EVOLUTION 369
groups may show only single lines, higher groups only double
lines, except at the actual points of junction where conjugation
takes place.1
In alternation of generation and metamorphosis the organism
changes its external form without altering the figure of descent.
Alternation of generations, like the differentiation of separate
sexes, exists in simple-celled as well as in double-celled organ-
isms. The phenomena are of an entirely different and minor
order of significance compared with the diversities of the dif-
ferent types of cellular structure. Wonderful as the changes
are, they are still of a merely morphological and adaptive
character and do not indicate new evolutionary departures of the
scope of the double-celled structures.
SPECIFIC CONSTITUTIONS MODIFIED BY SPECIALIZED HETERISM.
There are two principal groups or kinds of specific constitu-
tions which can be studied or thought of as cross-sections of the
networks of descent. These two series of special types of species
arise through two forms of specialization of methods of descent.
Instead of remaining uniform or homogeneous throughout, the
network of descent becomes variously subdivided or separated
into subspecific strands.
The first form of subspecific differentiation consists in special-
izations of heterism, that is, the establishment within the species
of definite forms of diversity of descent, so that individuals are
not merely different individually, but fall into two or more
groups regularly distinguishable by definite characters. These
groups are not formed by isolation, and their existence does not
interfere with interbreeding, but usually has the contrary effect
of encouraging or compelling interbreeding, since the members
of the same group may be unable to interbreed with each other,
but are specially adapted for interbreeding with the members of
the other group or groups of which the species is composed.
SPECIES WITHOUT SPECIALIZATION OF HETERISM (ARROPIC).
The diversity of normal symbasic descent remains miscel-
laneous and unspecialized. The individuals may be more or less
1 Diagrams of networks of descent in the various types of double-celled struc-
tures have been given in another place. Bulletin Si, Bureau of Plant Industry,
U. S. Department of Agriculture.
370 cook
obviously different, but the differences are fluctuating or com-
pletely intergraded, so that no definite alternatives of descent
appear, and no distinct subspecific groups are indicated.
Individuals are all similar, equivalent and bisexual or her-
maphrodite. None of the vertebrate or arthropod animals show
this condition, but it appears to be very common among the
lower animals and among plants. Species in which there are
no specializations of heterism, no differentiated paths of alterna-
tive descent, may be called arropic species.
The arropic condition is not merely synonymous with herma-
phroditism, through all arropic species are bisexual. The her-
maphroditism of the lower groups of animals and of plants is a
normal condition incidental to their more primitive organization.
Among the higher groups which have attained sexual differ-
entiation hermaphroditism has reference more definitely to ab-
normal cases of bisexuality. The arropic condition is also more
definite and restricted than bisexuality, since organisms may be
bisexual and still manifest some of the following forms of alter-
native heterism.
SPECIES WITH SPECIALIZATIONS OF HETERISM (ROPIC).
Specializations of heterism exist, and definitely alternative
routes of descent are followed by different individuals. The
individual members of species fall into distinct groups, but not
as the result of segregation or of differences of environmental
conditions. The group differences are usually such as to facili-
tate or to compel interbreeding between the groups.
The attainment of the ropic condition marks an important
stage in the evolution of a species, very favorable, apparently,
to its further development and to the greater and greater exten-
sion of the heteric specializations. The distinction is entirely
concrete and practical, but there seems to be no suitable and
convenient English word by which to designate it. The expres-
sions alternation and alternative have been used too widely al-
ready, and would increase the confusion now existing as the
result of identifying alternation of generations with phenomena
of entirely distinct nature, such as the different kinds of cellular
structures.
ASPECTS OF KINETIC EVOLUTION 371
Subsexual Species. — A species consisting of bisexual organ-
isms divided into subsexes, that is, into groups differing in one
or more characters, but not showing special adaptations to
secure cross-fertilization.
The first stage of specialized heterism is represented by spe-
cies which include two or more types or forms, merely for the
sake of the diversity, as it were, and with no sexual diversifi-
cation, that is, no adaptations, for securing cross-fertilization
between the two forms. The differences appear to be of the
same nature and to have the same symbasic utility as secondary
sexual characters, but the utilization of them is still left to
chance. Examples of subsexes are probably to be found in
such species as Verbascum blatlaria, Viola hicolor, and others
in which plants of different castes live together indiscriminately.
Antidromous or right-and-left-handed plants like cotton and
Casltlla, might also be recognized as affording instances of
subsexual differentiation.
It often happens in zoology that the sexes of the same animals
are at first described and named as two distinct species, but
after their true relations have been ascertained one of the sup-
posed species is, of course, rejected, no matter how diverse the
sexes may be. Similarly, these subsexual forms need to be
taken into account by the taxonomist. The criteria commonly
applied to determine specific distinctness are not adequate, since
it is possible for constant differences unconnected with sexual
diversity, to exist inside the same species without in any way
justifying the taxonomic subdivision of the group on the usual
basis. There is, however, no reason why any established type
of diversity like these subsexes should not be named and de-
scribed separately, just as the sexes are treated separately when
their characters are different.
Botanists are acquainted with numerous instances of diversity
among the members of species which may prove to be subsexes ;
though it is also possible that the differences may belong to
species which closer study may distinguish. Thus there are
species of Actcea which have the berries either waxy white or
crimson, and in about equal quantities. Numerous species of
Delphinium have the flowers either pink or blue. In species
372 COOK
of Aconitum purple and creamy or greenish white flowers are
described. Pink flowers also appear occasionally as definite
variants of white-flowered species of Achillcea.
Semisexual Species. — A species consisting of bisexual organ-
isms divided into semisexes, that is, into groups differing in
characters which conduce to interbreeding between the groups.
This is the condition reached by many species in which the
individuals are all bisexual, but differ among themselves in char-
acters which insure, or at least facilitate, cross-fertilization. In
the well known instance of Lythrum there are three castes of
plants with short, medium, and long styles and filaments, and
three different kinds of pollen grains and stigmatic papillae. A
long-styled plant produces only short and medium stamens, and
must be fertilized by pollen from long stamens, to be found
only on other plants. The semisexes of the primrose were
described by Darwin. Similar conditions are known in Oxalis,
Houstonia, and many other genera.
Among plants, at least, it might appear that semisexual con-
ditions are more advantageous than the next stage of completely
differentiated sexes. Cross-fertilization is secured, but at the
same time all individuals may produce seed, and not merely
half of them. That complete sexual differentiation has been
attained notwithstanding, and in so many different groups,
affords an intimation of the importance of symbasic heterism in
the structural economy of organisms. The fact loses none of
its significance if we reflect that the complete separation of the
sexes in plants reduces by half the facilities of the species for
producing seeds. All individuals being stationary, the males
can contribute to the welfare of species by none of the accessory
habits which have been so richly developed among the animals.
Indeed, it is by no means unlikely that the tendency of selective
influence on many plants has been to keep them in the semi-
sexual condition, sexually differentiated only far enough to
secure cross-fertilization, but not far enough to preclude the
production of seeds by all individuals.
Sexual Species. — A species consisting of unisexual organ-
isms, or divided into two sexes, male and female, so that inter-
breeding between the sexes is necessary to reproduction.
ASPECTS OF KINETIC EVOLUTION 373
The complete separation of species into two sexes is the con-
dition obtaining in all the higher animals, both vertebrates and
arthropods, as well as in many of the lower animals, and in
numerous plants. It has been found recently that even among
the moulds and other lower fungi the plant body, or mycelium,
is of two kinds, and that spores are produced only when these
are brought together.
Secondary sexual characters are of two kinds, or may be so
considered : (i) Those which are accessory to reproductive
processes, or assist in caring for the seeds, eggs, or young,
such as the mammas of the higher animals ; (2) those which
are merely the result of accumulation of differences which add
to the heterism or internal diversity of the species, such as the
manes, beards, tail-feathers or sexual differences of color or
form which are of no use in reproduction or in the environ-
mental relations of the species.
The environmental uselessness of many sexual differences is
an obvious and well known fact. Not only do the two sexes
generally occupy exactly the same environment with equal suc-
cess, but the presence or absence of many sexual character-
istics may have no practical significance for the individual.
Some varieties of mankind are beardless ; some have beards
only late in life, and some have beards in early manhood, but
cut them off without appreciable detriment. The uselessness
of such characters is shown even more strikingly in certain
species of beetles. Some of the males are scarcely distin-
guishable externally from the females, while others have the
head or thorax fantastically modified by the growth of long,
heavy, antler-like processes. It is easy to understand that for
all the males to be thus encumbered might be a serious handi-
cap to the species.
It may be that selection will help to explain why such fea-
tures commonly pertain to the male sex. Great diversity among
the females would interfere with recognition by males unless
their instincts were modified in a corresponding manner. More-
over, variation is the more practicable in the male sex because
the extent of the coordination necessary among the bodily or-
gans is not so great. Variation, which in the females might
374 COOK
have occasioned serious functional derangements or might have
too greatly increased the difficulties of existence, can be toler-
ated by the males without injury to the species.
That secondary sexual characters are often so completely
without function, in the ordinary sense of the word, does not
mean that they are of no value to the organism. With refer-
ence to the environment they are often worse than useless, but
in the physiology of descent they may have an important func-
tion. The existence of two sexes doubles, as it were, the sym-
basic effect of cross-fertilization, by permitting the accumulation
of two sets of variations, a second reason for the more rapid
progress made by sexually diversified organisms.
What has been called organic evolution has been thought of
too exclusively from the environmental side. Evolution has an
internal as well as an external function ; it has a bearing upon
the quality of organisms, as well as upon quantity. Species are
advantaged not only by characters which give them a wide
range and permit the propagation of large numbers, but it is of
equal importance that the vitality of the species be maintained
through the provision of adequate diversity of descent, as as-
sured by sexual specialization and by the access of new varia-
tions.
The doctrine of sexual selection was invented by Darwin to
explain the so-called secondary characters, differences admit-
tedly useless from the environmental standpoint, the two sexes
of a species being subject, generally, to identical external con-
ditions. And yet there is everywhere manifest a tendency to
the further accentuation of sexual diversities, which are by no
means confined to man, or to the higher animals in which esthetic
instincts have been attained.
Viewed as specializations of heterism, secondary sexual char-
acters have an obvious and general utility, though of an internal
nature. A species with two separated sexes is the stronger
because it can accumulate two lines of variations. Symbasic
interbreeding becomes, as it were, doubly effective, and the
stimulus of diversity can be utilized for a much longer period than
if the character were to spread to all the members of the species.
If the present interpretation of the facts be correct, we have
ASPECTS OF KINETIC EVOLUTION 375
in the familiar phenomenon of sex an example of a fundamental
evolutionary principle which has thus far escaped formal recog-
nition. Heterism is a concrete property or requirement for con-
structive evolution, though left quite out of account in theories
which have thought to explain organic development by external
influences of environment, or by internal "mechanisms of
heredity."
Sex specialization in species corresponds to paragamy in
cells ; the sustained diversity of the associated sexes is curiously
analogous to the prolonged separation of the parental chromo-
somes. Sexuality supplements paragamy, and both serve the
same purpose of increasing the vitality of the individual organ-
isms and the coherence of the specific networks of descent.
Superscxual Species. — A species consisting of organisms of
two sexes, but with one or both sexes again subdivided into
two or more kinds of individuals.
That the uses of the diversities of the sexes are not limited
merely to the reproductive functions, is well shown by the fact
that specializations of heterism are sometimes carried beyond the
stage of definite sexuality. Thus there are, among the sexually
differentiated higher animals and birds, numerous instances of
the existence of two color-forms, indifferently intermingled, but
not intergraded. It has been found, for example, that there
are in eastern North America two kinds of screech-owls, red and
gray, which are not separated geographically or in breeding.
The following reference to the occurrence of leopards of two
colors in the Malay region may serve as a sample of many
similar observations among the mammals.
" Man}" of the hunters I have met, and some of the authors I
have read, appear to consider the black leopard a distinct
species, but it is simply a freak of the ordinary spotted leopard,
just as the silver and the black fox are freaks from the common
red. In a litter from a red vixen I have seen a silver among
red pups ; and I met a man in the jungle where lower Siam
meets the Malay Peninsula who had found a black among the
spotted leopard's cubs, upon which, however, the spots, of course,
are not very clearly defined until they become older."
..." I noticed after I got its pelt off, that in the sun it had
376 cook
a kind of watered silk appearance, as a result of the deeper
black of the spots, which, though invisible, were really there
just the same." l
In a similar case of supersexual dichromatism in a chrysomelid
beetle experiments showed that the two color-forms could be
separated and established as uniform varieties by selective
breeding.2 The mating of black individuals produced only
black offspring in the first generation, while matings of spotted
individuals continued to give a proportion of black offspring
until the third generation.
SPECIFIC CONSTITUTIONS MODIFIED BY RESTRICTED DESCENT.
This is the second form of diversity of constitutions revealed
by cross-sections of networks of descent. Unlike the specializa-
tions of heterism, the members of groups formed by restricted
descent do not, of course, breed together, for it is in this
that the restriction of descent consists. The specializations of
heterism are in accord with the evolutionary advancement of the
species, but the groups formed by restricted descent are removed
from the conditions of free interbreeding and of normal evolu-
tionary progress. They represent, instead, the different stages
of a process of deterioration.
Symbasic Species. — Species with descent unrestricted, con-
sisting of large numbers of diverse individuals freely inter-
breeding in a broad, continuous and regular network of descent.
A species is not merely an aggregation of organisms, whether
alike or different ; the organisms are connected by a completely
interwoven fabric of lines of descent. Such plants as Portulaca
oleracea, Poa pratensis and Ceratodon purpureus, may serve
as examples of very widely distributed symbasic species.
Porric Species. — Species made up of partially segregated
subspecies. The cross-section of the network of descent, instead
of showing a rounded or regular form, is irregular, or partially
subdivided into arms or branches.
Widely distributed species, but locally diversified, like the
1 Whitney, Caspar, 1904. Outing for April, p. 14.
2McCracken, I., 1905. A study of the Inheritance of Dichromatism in Lina
Lapponica. Journal of Experimental Zoology, 2 : 117.
ASPECTS OF KINETIC EVOLUTION m
European Helix hortensis, afford the best examples of this type of
intraspecific diversity. The quail, or Virginia partridge, a non-
migratory bird widely distributed through eastern North America
from New England to Guatamala, shows many local subspecies
connected by series of imperceptible gradations. The sugar
maple of eastern North America has several geographical sub-
species.
Stenic Species. — Species consisting of stens, that is, of nar-
rowly segregated subspecies, domesticated varieties, or breeds,
propagated by sexual reproduction.
As a result of propagation by narrow breeding, the individual
members of a sten are much more nearly uniform than those of
normal symbasic species, or even than those of geographical
subspecies. As purely stenic species may be mentioned those
which do not exist any longer in the wild state, but are made
up of many local domesticated varieties. The domesticated
animals fall here, except as they may represent hybrids of dif-
ferent wild species. Of domesticated plants the Indian corn or
maize is the best example, since it has retained a complete system
of cross-fertilization, which many domesticated plants have lost.
Very small, closely localized natural species, like the remark-
able Hawaiian land-snails upon which Gulick has based his
theory of evolution by isolation, represent essentially the same
condition of restricted descent as domesticated stenic varieties.
Linic Species. — Species composed of separate, parallel or
slightly diverging lines of descent, propagated by autogamy or
parthenogenesis, and not united into a network.
Wheat and barley are perhaps the most conspicuous examples
of linic species among domesticated plants, though many other
species are autogamous, with more or less consistencv- Strict
line breeding is not possible, of course, among the sexually
differentiated higher animals, but is sometimes approached by
what is called in-and-in breeding of closely related individuals.
Line-bred organisms are extremely uniform, even more so
than stens. Self-fertilization involves only the combination
of gametes of the same origin and probably of very nearly
identical nuclear configuration ; at least there is even less varia-
tion. Linic species occur in nature as in the well-known in-
378 cook
stances of Hieracium upon which Nageli based his theory of
evolution in a definite direction. The persistence by partheno-
genesis of the individual differences of transplanted specimens
was accepted as proving that variation held to definite directions.
Likewise De Vries has made use of linic autogamous species
of Draba to illustrate his conception of elementary species.
The uniformity and stability of the line-bred plants has been
taken to represent the normal condition of species, and the in-
ference has been made that the species recognized in nature by
taxonomists are generally composed of similar independent
units, the effect of the method of propagation, to resolve the spe-
cies into separate lines of descent, being left out of consideration.
Clonic Species. — Species consisting of separate lines of de-
scent continued by vegetative propagation alone.
Clones, like lines, are propagated from single individuals,
but by vegetative processes only, so that variation is almost
completely avoided. Nevertheless, even vegetatively propa-
gated plants are not completely uniform. Clonic groups of the
same origin often show fine gradations of diversity, and occa-
sional mutative variations are known.
Clones do not exist, of course, among the higher animals, but
they areexceedingly numerous among plants. Several domes-
ticated species now exist, as far as known, only in this form.
The horse-raddish, sweet-potato, banana, arracacha, yautia and
taro may be mentioned as seedless plants, but large numbers of
others are nearly seedless or have varieties which are seedless.
THEORIES OF EVOLUTION BY RESTRICTED DESCENT.
It is a noteworthy fact that the earlier theories of evolution,
including those of Darwin, Nageli, Gulick and De Vries, have
been based upon one or another condition of restricted descent.
The kinetic theory is the only suggestion of a method of evolu-
tion applicable to conditions of unrestricted descent. The pre-
disposition to see in restricted descent ideal conditions of evolu-
tion has been strengthened, if it has not been wholly supported,
by the fact that it is only in restricted descent that the traditional
ideal of heredity can be applied. Only narrow-bred organisms
afford even an approximate identity of form and structure.
ASPECTS OF KINETIC EVOLUTION 379
De Vries, Gulick and Nageli have given their chief attention
to extreme forms of restriction, like those of Draba, Achatinclla
and Hieracium. Darwin kept much nearer to the consideration
of natural conditions, though his doctrine of selection implies
that evolutionary progress depends entirely upon the plan of
causing species to change by restricting the descent of the com-
ponent individuals. In the kinetic theory, it need scarcely be
repeated, the result of selective restriction is not evolution, but
specialization. The evolutionary motion would still take place
if the selective restrictions of descent were not imposed.
COMBINED FORMS OF SUBSPECIFIC DIVERSITY.
Modifications of the constitution of species by specializations
of heterism do not interfere with the attainment of the other form
of diversity by restricted descent. Thus a sexual species may
be partially segregated into geographical subspecies or may be
narrowed still further into the stenic condition of domesticated
varieties and breeds. Linic and clonic subdivisions of sexually
differentiated species do not occur, of course, among the higher
animals, being limited to the lower groups and to plants which
have the power of sexual propagation or of parthenogenetic de-
velopment. But even among the cultivated plants it does not
appear that any sexually differentiated species has been resolved
completely into the clonic condition. There are large numbers
of clonic female varieties of figs and date-palms, but the male
trees are usually recruited from chance seedlings, so that the
network of descent is not entirely destroyed. The female half
of the species is represented by vegetatively propagated clones,
but on the male side miscellaneous individual diversity remains.
The existence of restricted subspecific groups may not inter-
fere in the least with the maintenance of a normal specific net-
work of descent. A widely distributed symbasic species may
have a few porric subspecies as a result of the partial isolation
of particular localities. Special conditions, such as an alpine
climate, might restrict a part of a species to linic or clonic
propagation while the remainder retained fully symbasic condi-
tions of descent. Through the fabric of broadly diversified
descent there may run narrowly compact strands composed of
380 COOK
linic or clonic individuals, which no longer share the symbasic
interbreeding of the group and afford no true criterion of the
conditions under which evolution goes forward. Just as most
planets are attended by satellites, so species are sometimes
found to be supplemented by small subspecific adjuncts, little
species-like groups of organisms which some have taken for
new or incipient species, but which stand in a permanently sub-
ordinate or retrograde relation to the evolutionary part of the
species.
LIMITATIONS OF CLONIC PROPAGATION.
Vegetative propagation, whether in nature or in domestication,
appears to conduce always to seedlessness. Some have thought
to explain this fact by reference to the superiority of the asexual
over the sexual propagation. This reasoning is scarcely ade-
quate, in view of the fact that much larger numbers of species
have retained their capacity of producing seeds, though regu-
larly supplementing the sexual by the vegetative propagation.
The greater probability is that the decline of sexual fertility in
vegetatively propagated types is a symptom of deterioration,
just as sterility is a frequent characteristic of abnormal vari-
ations or of hybrids.
The formation of the sex-cells, as we now know, is a highly
specialized and complicated process, and it is easy to understand
why it should be the first of the physiological functions to
become deranged and inefficient. It is known also, from the
behavior of hybrids and mutations, that vegetative vigor has no
direct relation or apparent connection with reproductive vigor.
Indeed, sterile hybrids and mutations often show great and
notably superior strength and longevity, due, we may suppose,
to the stimulation which attends new variations. This con-
sideration may also explain why clonic and linic species usually
appear to consist of definite groups of closely similar individuals.
These groups may have originated by individual mutative vari-
ations of notable vegetative vigor, which have on this account
survived or crowded out the weakening survivors of the original
symbasic species or other variations less recent or less vigorous.
The disastrous effects of inbreeding among the higher ani-
mals have been known for centuries, and are taken into account
ASPECTS OF KINETIC EVOLUTION 38 1
by all breeders. That the same principles apply to plants, has
remained in doubt for two reasons : (1) The much less com-
plex organization and less specialized tissues of plants render
many of them less acutely dependent upon cross-fertilization.
(2) The plants which have been longest under cultivation are
not grown for their seeds and are propagated asexually, so
that their decline in reproductive fertility has not diminished
their economic value. No plant valued for its seeds has been
propagated other than from seeds for any considerable period.1
Numerous tropical root-crops and fruits, such as the sweet-po-
tato, yam, agave, sugar-cane, banana, pine-apple, and bread-
fruit have been grown for thousands of years from cuttings, prob-
ably without the interposition of a single seedling generation.
In a sexually propagated species inbreeding would have led
long since to extinction, but these clonic varieties are still ex-
tremely vigorous. Nevertheless, such species do not form a
real exception to the rule of deterioration under inbreeding, since
a very large proportion of them, belonging to many and very
diverse families, have shown this tendency towards seedlessness.
The reduction or elimination of the reproductive parts has
been ascribed by some to selection, and by others to a supposed
biological law of paucity which causes useless parts to disap-
pear. No basis of fact has been shown, however, for either of
these explanations ; unassisted nature supplies us with instances
like Sphagnum and Lunularia to which neither would logic-
ally apply, but which would be well accommodated in the
view that continued asexual propagation, like other forms of
isolation, weakens the reproductive powers. This law would
also explain why the absence of sexual reproduction ap-
pears only as the character of aberrant species or genera, and
has not been able to persist for a period long enough to permit
the differentiation of organic groups of higher systematic rank.
Botanists seem not to have ascertained the existence of any wild
phanerogamous plant which is always and everywhere seedless.
'Apparent exceptions to this rule appear only among trees, such as the
almond and the pistache, where the normal long life of the individual may be
thought of as lessening the period of vegetative propagation, if counted by
generations.
382 COOK
The opinion has long existed among horticulturists that varie-
ties of fruit trees tend to deteriorate, but a biological explana-
tion has been lacking thus far. The most prominent horticul-
tural writer to defend such a view is Burbidge, who holds that
budding and grafting are artificial and unnatural processes, for
which propagation by rooted cuttings should be substituted.
The analogy of the seedless tropical root-crops indicates that
the use of cuttings would afford no protection against the grad-
ual reduction of fertility, though the suppression of seeds in
fruit trees may not be an undesirable symptom, except when it
is accompanied by a deterioradon in quality. Only a few hor-
ticultural varieties have been propagated as clones for more than
a century, but the advance of sterility has already become ap-
preciable to nurserymen, who are careful to plant seeds from
seedling trees, in the belief that these germinate better and pro-
duce more vigorous stocks than the fruit of grafted clonic
varieties.
That superior varieties are commonly deficient in vigor is thus
explainable without reference to any special perversity of nature ;
such varieties may owe their reproductive debility to the fact
that they have been more carefully and persistently propagated
without crossing. Some varieties of peaches, for example,
yield a very small percentage of viable seed. In France many
attempts to secure seedlings of the "Alexander" have failed.
This variety and the very similar " Amsden " appeared about
the same time and are supposed to be seedlings of " Hale's
Early," a variety also notably deficient in reproductive fertility,
since only about ten per cent, of the seeds germinate. The
seedlings of " Hale's Early" are also, as a general rule, very
diverse, without close resemblance to the parent or to each other.
The variety called " Hill's Chili " affords an instructive contrast,
in that practically all the seeds germinate and about ninety per
cent, of the seedlings come true to the parental type, leaving
about ten per cent, of variations.1
Obviously, the evolutionary status of these two varieties is
very different ; one is entering upon the stage of mutative aber-
'For these interesting facts I am indebted to Mr. William A. Taylor, of the
United States Department of Agriculture.
ASPECTS OF KINETIC EVOLUTION 383
ration, while the other is approaching that of complete sterility.
Horticulturists have not uncommonly believed that the longer
the succession of " grafted generations " of tree fruits the greater
the likelihood of deviations from the type of the original seedling,
but this idea seems not to have received scientific consideration
or support, perhaps because it appeared to contradict the opinion
of Darwin1 and many other evolutionary writers who have held
that characters can be permanently " fixed " by inbreeding, or
close selective segregation, of which propagation by cuttings
may be taken to be the extreme form. The kinetic theory of
evolution permits us to understand, however, that the "fixity"
to be secured either by inbreeding or by asexual propagation is
only relative, and that its result in both cases is to predispose
the organism to abrupt variations and reproductive debility.
ORIGIN OF LINIC AND CLONIC CONDITIONS.
The occurrence of self-fertilization , parthenogenesis, and vege-
tative propagation in nature has undoubtedly caused many
writers to suppose that these methods of descent represent
truly normal evolutionary conditions. Indeed, no abnormality
need be charged in the many cases where the species maintains at
the same time the normal network of descent by sexual repro-
duction with free interbreeding. The abnormal condition super-
venes when the species loses its network of symbasic descent
and is resolved into disconnected lines. Such a condition may
result whenever the normally sexual and symbasic reproduction
becomes less effective than autogamous or purely vegetative
methods of propagation. Thus, in such little plants as Draba
and Viola, which have to avoid the competition of larger neigh-
bors by blossoming early in the spring, the non-symbasic
methods of propagation take on great importance, for insects
are scarce and the weather often so inclement as to completely
prevent the transfer of pollen.
Similarly, in alpine and arctic conditions, vegetative propaga-
tion is much safer, and usually much more successful than sex-
ual reproduction. The short and treacherous seasons often pre-
vent the ripening of seed. The formation of apogamic bulblets
'The Effects of Cross and Self-Fertilization in the Vegetable Kingdom, p. 27.
384 COOK
instead of flowers is frequent among the saxifrages and other
Arctic plants, though many similar instances are known in natives
of temperate and tropical regions.
Wheat and barley, and to a less degree several other domes-
ticated plants, have been unconsciously selected towards autog-
amy in a similar manner, by being cultivated far to the north
of their original habitats. In unfavorable seasons only the
autogamously fertilized seeds would ripen. The wild relatives
of all these plants, so far as known, have facilities for cross-
fertilization.
That autogamy and other forms of restricted descent conduce
to the breaking up of species into small subspecific groups, is well
shown among the cereals. The rye plant has retained and even
accentuated its provisions for cross-fertilization, and has kept
its position as a relatively normal coherent species, instead of
falling apart into distinct varieties. Cross-fertilization has also
been fully maintained in the corn plant, but here the large size
of the seeds and their compact grouping on the ears greatly facili-
tate selection, and have favored the establishment of many local
varieties.
RELATION OF LINIC TO CLONIC PROPAGATION.
The fact that reproductive fertility deteriorates more rapidly
than vegetative vigor, when organisms are placed under condi-
tions of restricted descent, is to be correlated with another phe-
nomenon, discovered by Darwin, that autogamous fertilization
is sometimes superior to more miscellaneous methods of narrow
inbreeding. This fact has been generally accepted to mean
that autogamy and heterogamy are both normal evolutionary
conditions. In the kinetic interpretation it does not appear
that autogamy is a truly normal and progressive state. The
superiority of strict autogamy over more miscellaneous inbreed-
ing appears explainable by analogy with parthenogenesis and
vegetative propagation. All three processes can be viewed as
methods of postponing deterioration from restricted descent, by
omitting the nuclear readjustments which are required in normal
sexual reproduction. When diversity of descent is no longer
sufficient for normal readjustments, degeneration begins, in the
form of mutative variations. These usually fall below the
ASPECTS OK KINETIC EVOLUTION 385
parental standards, or.at least diverge from them so seriously as
to injure the commercial value of the crop, as strikingly shown
in the tobacco varieties studied by Mr. A. D. Shamel.1
Seed produced by autogamous fertilization yields plants of
very much greater uniformity, and it is in this fact that their
superiority lies. The plants were not better, as individuals, than
some of those produced by the more miscellaneous breeding, but
the tendency to degenerate variation had been avoided, or at
least postponed.
Such facts do not appear to warrant any general contrast
between cross-fertilization and self-fertilization, but only between
narrow breeding and line breeding, and of these the line breed-
ing appears to be superior because it constitutes an approxima-
tion to vegetative propagation and avoids the need of nuclear
readjustments with inadequate diversity of descent. The union
of two nuclei which are the autogamous progeny of the same
individual organism, can hardly require any new adjustments
to be made. The formalities of sexual reproduction are ob-
served, but diversity of descent, which gives physiological value
and evolutionary significance to the process, has been eliminated.
Self-fertility and parthenogenesis, like vegetative propagation,
have value only as means of avoiding, for a time, the normal
results of restriction of descent, not because they represent
normal evolutionary methods of organic succession.
DIVERSITY REACTIONS IN RESTRICTED DESCENT.
Efforts toward the selective improvement of domesticated
plants and animals have been accompanied everywhere by the
narrowing of the lines of descent, and often by close inbreed-
ing. How far this abnormal condition is responsible for the
results of experiments with domesticated species, and how far
these results are of general evolutionary significance, remains
to be considered. Most of our important food-plants were
domesticated long before the period covered by human history
or tradition, so that the general claim of selective improve-
ment through thousands of years could not be denied, and has
'Shamel, A. D., 1906. The Effect of Inbreeding in Plants. Yearbook of U.
S. Department Agriculture for 1905, p. 3S6.
386 COOK
continued to be accepted as a sufficient cause of the extensive
modifications which have taken place.
The question has been debated at length on theoretical
grounds, but without decisive results, since it appeared to lie
outside the range of experimental determination, owing to the
vast periods of time which have figured in the calculation.
Fortunately, all plant cultures are not the same in method or in
history, and the so-called Arabian coffee furnishes an instructive
contrast with other domesticated species. Coffee has prob-
ably not been in cultivation much more than a thousand years,
and has existed but a few centuries, or often only a few decades,
in its present centers of production. It is not an annual, but a
shrub, or small tree, the selective improvement of which would
require more years than planters generally expect to give to the
business. Plantations are generally large, and experiments
with individual trees are difficult and time-consuming, so that it
is only within recent years that the securing of improved varie-
ties of coffee has received serious attention. The evolutionary
factors of selection and of long periods of local influences of
soils and climates are thus alike absent, and yet there is no lack
of coffee varieties with abundant diversity in form, habit and
color. Their general similarity consists only in being inferior
in fertility to the parent type.
So much has been written upon the improvement of plants by
domestication and selection that this inferiority of coffee varie-
ties may seem exceptional, but the apparent anomaly disappears
if we reflect that fruit trees and other horticultural plants sup-
posed to have been greatly improved in domestication are not
grown for the seeds, and hence complete fertility in the sexually
reproductive sense has been a minor consideration or even a
positive disadvantage ; indeed, with many plants it has been
one of the direct objects of selection to reduce the number of
seeds or to eliminate them completely. More or less seedless
abnormalities are valuable, for example, among the grapes,
plums, and oranges. If coffee were cultivated as an edible
fruit the new sorts would be of use, since thicker pulp and
smaller seeds are frequent characteristics of the berries ; indeed,
a coffee which did not produce any normally developed seeds
ASPECTS OF KINETIC EVOLUTION 387
was found in 1903 in Costa Rica. As ornamentals, some
variations offer new colors and greater abundance of flowers,
and the foliage and habit of the trees sometimes deviate strik-
ingly from the normal or parent form. Unfortunately, the
planters would find an advantage only in the direction of increas-
ing the number, size, or weight of the seeds themselves, and
they accordingly pronounce the new varieties worthless.
Similar abrupt variations of many cultivated plants and animals
were studied and described by Darwin as "sports," but it was
also known to him that such variations are relatively infertile
and do not persist in the presence of the normal or less closely
inbred types, so that it has remained for Professor De Vries to
base upon such variations a general theory of evolution. The
variations, or sports, chiefly studied by Professor De Vries are
those of an evening primrose native in North America and
escaped from cultivation in Holland, and thus accidentally seg-
regated from the wild stock of its species. It belongs, like
the coffee, to a family in which there are specialized provisions
to assist cross-fertilization, so that the early manifestation of ihe
effects of inbreeding might be expected.
The variations of (Enothera described by Professor De Vries
seem to be closely parallel to those of coffee ; most of them are
conspicuously deficient in reproductive fertility, and some are
quite sterile. This relative or complete sterility of sports, or
variations secured by inbreeding, warns us that evolutionary
inferences founded on this class of facts must be carefully
revised, since it is obvious that organisms notably deficient in
the power of reproduction can not be expected to have played
a large role in the process of organic evolution. Nature, like
the coffee-plantevs, requires seeds ; reproductive efficiency is the
first requisite of survival.
A general evolutionary significance of the phenomena of muta-
tions becomes apparent when the facts are interpreted from
the standpoint of normal heterism, that is, as reactions from
the abnormal uniformity which is the first result of restricted
descent. The diversity of mutations is greater than the diver-
sity of normal heterism, but this is in entire accord with what
we know of other physiological reactions of organisms. Muta-
388 COOK
tions are at once degenerative and reconstructive, just as the high
temperature which attends many diseases of the human organ-
ism is at once an evidence of illness and an indication of con-
structive systemic reaction. Indiscriminate crossing of muta-
tive varieties tends to restore the wild type of the species.
Mongrel dogs are wolfish ; mongrel pigeons, even of white
ancestry, are blue ; mongrel roosters become red in approxi-
mating the primitive game breeds ; mongrel flowers are single
and small.
Stronger evidence could scarcely be demanded for proving
that the interbreeding of the members of a species is a measure
of organic stability, not a stationary or uniform stability, but a
stability of coherent symbasic motion.
EXAGGERATED HETERISM OF CLONIC HYBRIDS.
Further evidence that mutations are reactions from abnormally
restricted descent may be drawn from the results of sexual re-
production among clonic varieties. The sexual offspring of
plants which have been subjected to considerable periods of
vegetative propagation always show a very large amount of in-
dividual diversity. This has caused them to be reckoned as
hybrids, though in reality they represent a very distinct type
of evolutionary phenomena. Each clonic variety is, after all,
only an individual member of its species, and as such varieties
have not been selected or bred to uniformity, in the sense of
coming true to seed, they and their offspring might be expected
to retain the original amount of heterism or normal individual
diversity of the wild type of the species. As a matter of fact
the sexual offspring of clones have an individual diversity of
the order of mutations. The only difference appears to be that
all the individuals may be mutants, instead of the relatively
small percentages usually appearing in species which have been
subjected to courses of selective inbreeding for the elimination of
heterism.
DIVERSITY RELATIONS BETWEEN SUBSPECIES WITH
RESTRICTED DESCENT.
As long as the diversity of the members of species appears
either as the merely accidental or arbitrary result of environ-
ASPECTS OF KINETIC EVOLUTION 389
mental influence or of mechanisms of heredity, both the theory
and practice of evolution remain mysterious and contradictory.
It is only after the physiological value of diversity in the con-
stitution of species has been recognized that we begin to gain
a definite appreciation of the practical bearings of evolutionary
facts. With nature wrongly interpreted, the results of domesti-
cation and breeding were likewise obscured and distorted. As
long as our reckoning was based on the false ideal of unifor-
mity and stability of species, it was not possible to gain an orderly
concept of even the simplest of evolutionary relations, or to
escape from the confusion and contraditions which have left
even the most concrete investigators in hopeless disaccord.
Among breeders of plants there exists the greatest possible
diversity of opinion regarding the value of hybridizing as a
means of securing new organic forms of superior agricultural
utility. Some breeders have secured very valuable hybrids,
while others have found hybrids of no use at all as a means of
increasing the desirable characters of the species which they
were seeking to ameliorate. To explain and reconcile this
apparent contradiction is not only a matter of scientific interest
in its bearing upon the general subject of evolution ; it is also of
much practical importance to be able to distinguish between
the different kinds and combinations of subspecific groups and
to avoid a waste of efforts upon methods and materials which do
not promise useful results.
The time has not yet come for the establishment of absolute
standards and criteria, if indeed such a time is ever to come.
There are unforseen accidents, not only in the best regulated
families, but in nature as well. It is the rarely unusual cir-
cumstance, the exception to all known rules, which may have
great interest and potential value. The sterility of mules is one
of the most invariable of the phenomena of hybridization, and
yet fertile mules are not altogether unknown, nor is it certain
that such an animal might not be a means of securing new and
desirable variations of our equine stocks. Hybrids between the
different species of bovine animals are generally fertile and
readily made, but the establishment of a breed combining the
blood of the buffalo and the domestic cow has proved difficult.
390 cook
For the practical breeder, as for the scientific investigator,
nothing should be taken for granted until verified by actual ex-
periment, but it is, nevertheless, useful to have, if possible, a
system of interpretation by which results once attained can be
understood, and proper discrimination made between the rela-
tive prosoects of alternative fields of investigation. Selections,
mutations, crosses and hybrids, have entirely different impor-
tance in different groups, depending upon the nature of the
characters which it is desired to secure, and upon the adapta-
bility of the species to different methods of propagation. In the
amelioration of coffee, for example, mutations promise little be-
cause of their smaller production of seeds, but if the flowers or
pulp of the berries were the valuable part, mutations would be
as valuable as among other horticultural species.
Selection and hybridization have been thought of as two alter-
native methods by which evolution might be brought about, and
the debate has continued as to which is the better. The question
could never be answered in this form, for the assumption on
which it is asked is a false one. The normal species, the unit
of evolution, is neither stationary nor uniform. It not only
makes a slow and gradual advance, as a whole, but it manifests
all the time a vast diversity among the different individuals.
Some of this diversity is induced by the environment, but much
of it is quite spontaneous and continues to appear even in a
uniform environment.
The value of selection does not lie in any power to cause
these inherent differences ; it can only preserve them and pre-
vent, as it were, the swinging back of the pendulum of normal
diversity. The alert breeder seeks to catch it at its highest and
to hold it steadily there. It cannot be held forever, as is now
generally recognized. Sooner or later the selected type deterio-
rates, and shows itself inferior to some more recent selection
which has lost less of the normal vigor of the species.
To hybridize selected varieties may serve merely to release
the pendulum and allow it to swing back along the curve of
normal diversity. The vast majority of the progeny are likely
to be inferior to the parents in the special qualities which have
made them valuable. Some of them may approach the standard,
ASPECTS OF KINETIC EVOLUTION 39I
but they seldom or never surpass it. The breeder concludes
that hybridizing is a mistake and finds that much more can be
accomplished by selection. This conclusion is quite correct if
he is dealing only with long-domesticated strains of plants and
animals, and if he wishes to obtain from them the greater ac-
centuation of some character already specialized by selection.
If the varieties are not too unlike, or too long selected, the result
of crossing will be to restore the more normal but less desirable
diversity. If the varieties crossed are somewhat more remote,
the diversities may balance each other into a somewhat uniform
intermediate average. Still longer selection may establish the
specialized characters as definitely alternative, in the Mendelian
sense, so that they do not combine again into a single hereditary
pattern, but separate regularly into the two original components,
as in the pea hybrids studied by Mendel, and the many other
instances discovered by more recent investigators.
In none of these three cases or types of hybrids is there any
reason to expect an increase of characters beyond the range of
accentuation to be reached by selection ; they all involve, instead,'
a lessening of the amplitude of diversity obtainable through
selection. If the selective specialization of characters of a va-
riety were a true step in the evolution of the species, these kinds
of hybrids could be called reversions or retrogressions, since
they appear to go backward and undo the results of selection.
To call them reversions is very misleading, however, from the
evolutionary standpoint, since the closely selected type, however
useful, represents only a temporary and abnormal phenomenon,
a holding of the pendulum of variation to one side, instead of
permitting it to describe its normal vibrations, or to change its
general position and point of support.
The simple analogy of the pendulum proves entirely in-
adequate as a means of illustrating the normal conditions and
requirements of true evolutionary advances of specific groups,
for we are not dealing then with vibrations of single characters,
but with a complicated network, a veritable fabric of descent
and of character-combinations. The pendulum analogy is ap-
propriate only for the single lines or narrow strands of descent
which selection separates from the web of the species, and
Proc. Wash. Acad. Sci., February, 1907.
392 COOK
holds for a time at a point of high expression a character which
averages much lower in the species at large.
MUTATIVE VARIATION OF SELECTED VARIETIES.
The only way in which the accentuation of such a narrowly
selected character can be still further increased, beyond the
range of normal variation of the species, is by abnormal varia-
tion ; that is, by mutation. The narrow selection may be said
to induce the mutations because it weakens and unbalances the
hereditary tendencies of the variety, but the mutations are by
no means limited to the character or quality for which the
variety has been selected ; they are likely to take any or all
directions. Some of them are generally found to carry the
breeder along the lines he desires to follow.
Are hybrids between selected varieties of the same plant or
animal of no practical breeding utility? Yes, if it is desired to
preserve or strengthen the vitality of the organism or to secure in-
termediate characters, or new combinations of characters already
existing.
The general answer must be negative, if the purpose is to
obtain new characters, or higher degrees for accentuation of
characters already specialized by selection. Instead of securing
a larger range of diversity, the contrary results are much more
likely to be reached. It may even happen, if the varieties have
been subjected to narrow selection, that the hybrid offspring,
instead of being more variable than their parents, will actually
be more uniform, the hybridization bringing them back, as it
were, to the hereditary road from which they were beginning to
wander towards mutative degeneration.
The mutations are as abnormal, of course, in the strictly evo-
lutionary sense, as the narrow descent which induces them, but
for agricultural purposes they may be very valuable, and often the
abrupt change of form seems to lend them a remarkable vegeta-
tive vigor which greatly increases their productive capacity.
This is notably the case among plants, and especially among
those cultivated for their vegetative parts instead of for their
seeds.1
'Cook, O. F., 1904. The Vegetative Vigor of Hybrids and Mutations. Proc.
Biological Society of Washington, 17 : 83.
ASPECTS OF KINETIC EVOLUTION 393
The facility with which many plants can be propagated from
cuttings or by grafting often permits sterile mutations and
crosses to be preserved and utilized for long periods of time.
Among animals, on the other hand, mutations are of relatively
small value. The higher organization of animals renders them
liable to earlier and more serious deterioration from inbreeding,
though there is great difference in the susceptibility of different
kinds of animals.
BEHAVIOR OF DISCRIMINATE MUTATIONS.
When mutations are crossed with other members of their own
immediate group of related individuals they are generally pre-
potent. They do not tend to average away and disappear, but
are repeated, or even accentuated, in a considerable proportion
of each successive generation, and sometimes in all of them.
Plant mutations which can be propagated by self-fertilization
are often constant from the first, and have been thought by some
to represent the formation of genuine new species.
When mutations are bred outside of their own group, and
especially when they are crossed with the wild type of the
species or with the variety which has not been long or closely
selected, they are not prepotent, but recessive. The new muta-
tive characters appear weaker than the others and may fade out
and disappear entirely. The same result may be reached by
indiscriminate interbreeding among the representative of two or
more mutations or selective varieties. The ancestral characters
of the wild type of the species reassert themselves, and may
even reappear in crosses between varieties from which they
have long been lost.
All these and other similar phenomena can be understood,
or at least brought into rational relations, if we keep in mind
the fact that crosses between the narrowly selected varieties or
mutations of the same species tend to restore the original and
normal conditions of free interbreeding. They tend, in other
words, to repair and reconstruct the normal fabric of symbasic
descent, and to reduce the strains and deteriorations caused by too
close segregation, too little diversity, and too much inbreeding.
Instead of being monstrous or unnatural, these crosses are
394
COOK
more normal, more vigorous, and more fertile, than their parents.
Why, then, are they called hybrids? Because we have been
led astray by the theory of normally uniform and stationary
species, in which it was made to appear that anything which
interfered with identity of form and structure was essentially
unnatural, like a cross between members of species which do
not normally breed together, and which produce, when so bred,
abnormal progeny. There are many groups in nature which
are reckoned as species, but which are no farther apart than
some of the varieties of cultivated plants, and which can breed
together without difficulty or abnormality. For systematic
purposes it is desirable to recognize each separate natural
group of organisms as a species, and this can also be justified
from evolutionary standpoints, for segregated groups are able
to make evolutionary progress on distinct lines, and eventually
to become different from other groups of common origin.
It often happens, however, that evolutionary progress is not
consistent in the vegetative and reproductive parts of the organ-
isms. Species which appear very distinct externally may, when
brought together, breed freely and normally, while others whose
bodily differences are difficult to detect may refuse to mingle
or may produce only sterile or otherwise abnormal hybrids.
While it is thus difficult or, it may be, impossible, to draw an
absolute line of definition, or to restore the old distinction be-
tween hybrids and crosses, this does not justify us in ignoring
the very wide and very practical differences between the ex-
treme conditions of this series of phenomena.
ANALOGIES OF HYBRIDS AND MUTATIONS.
The phenomena which have the nearest and most genuine
relations with hybrids are not crosses, but mutations. Hybrids
and mutations can both be described in the same words, as
aberrations from normal heredity. Both are due to the same
cause, inadequate fertilization, which unbalances the organic
equilibrium and gives rise to abrupt variation, usually in many
directions at once. Mutations and hybrids show also a general
deficiency of fertility. This is carried, very often, to the ex-
treme of complete sterility, though there may be present at the
ASPECTS OF KINETIC EVOLUTION 395
same time unusual vegetative vigor, analogous, in all probability,
to the stimulation of energy of growth which appears in normal
crosses and in prepotent new variations. Though no experi-
ments are known to have been made with the idea of such a test
directly in mind, the indications are that results of mutation and
hybridization might prove in the same species almost identical,
for many so-called false hybrids do not appear to be the results
of a genuine and effective interbreeding, but seem rather to
involve an approach to the phenomenon of artificial partheno-
genesis, somewhat similar to the parthenogenetic development
through chemical and mechanical stimuli, described by Loeb
and others. The two nuclei of the supposed parents of the
false hybrid do not appear to have united and combined the
parental qualities, since the progeny shows no definite indication
of the traits of one of the supposed parents, either in the first or
in subsequent generations. The facts discovered by Guyer in
sterile hybrid pigeons, that the parental chromatin elements
remain separate and do not undergo a normal mitapsis, illus-
trates the possibility of false hybrids, especially in plants and
in lower types of animals where parthenogenesis can take place.
Such an abnormal and inadequate method of fertilization would
explain extensive variations of the progeny, which well deserve
to be called false hybrids. Nor is it unlikely that the same
explanation may be found to apply to variable hybrids, even
when they share the characters of the parents. The indications
are that in different cases there are all possible gradations in
the extent and efficiency of the combination of the parental ele-
ments, from that which affords mere stimulation to that which
gives a fully intermediate result.
It does not follow, however, that the combination is normal
or complete when the first generation is intermediate. The first
generation may be intermediate under two nearly opposite con-
ditions, as already noted. Crosses are intermediate when the
parental elements are thoroughly congruous. Their combina-
tion merely restores a normal condition of symbasis, that is,
provides a normal amount of diversity of descent. The first
generation of hybrids is also intermediate when the parental
elements are very diverse and antagonistic. Hybrids which
396 COOK
appear quite uniformly intermediate in the first generation may-
prove, nevertheless, to be completely sterile, as in the mule,
whereas intermediate crosses between narrow varieties are always
completely fertile, more so, it may be, than their more inbred
parents. No distinction is to be drawn between crosses and
hybrids which are uniformly intermediate and at the same time
fertile, but there is a wide range of phenomena between an inter-
mediate, fertile cross between narrow varieties and an inter-
mediate sterile hybrid between diverse species. Next to the
hybrids which are intermediate, but sterile, are those which are
intermediate and fertile, but show diversity and partial sterility
in the second generation, proving that the parental elements did
not combine in a manner to afford a stable equilibrium of hered-
ity. In another stage of hybridity, with less diversity of parents,
the first generation is variable, which may be taken to mean that
the parental elements are sufficiently similar to influence each
other, instead of exerting a uniform degree of repulsion.
Nevertheless, they do not combine readily, but form uncertain
and extremely varied combinations.
The purpose of this enumeration is to show that with hybrids,
as with crosses, there is a series of phenomena which can be
described and interpreted in terms of diversity, using as a stand-
ard the normal diversity of the individuals of species in nature.
In this way it is possible to avoid the ambiguities which have
attended the use of the false and artificial standard of uniformity.
From normal diversity there may be departures on either side,
on the one to abnormal uniformity, on the other to abnormal
diversity, and both of these can be reached, as we have seen,
in several ways. Uniformity appears :
1. In closely selected varieties (stens).
2. In varieties or individuals propagated from cuttings or by
other asexual methods (clones).
3. In the progeny of inbred saltatory variations (mutations).
4. In crosses between moderately inbred stenic varieties.
5. In first generation hybrids between species so remote as to
combine with difficulty.
Likewise diversity greater than the normal may appear :
1. Among mutations from narrowly inbred varieties.
ASPECTS OF KINETIC EVOLUTION 2>9l
2. Among crosses between individual clonic types, long sub-
jected to vegetative propagation.
3. In a species or variety which has been placed in new and
unwonted conditions (neotopic mutations).
4. Among crosses between narrowly inbred varieties (Mende-
lian hybrids).
5. Among hybrids between species not too remote to combine
at all, but not sufficiently related to combine in a regular and
uniform manner.
THE NATURE OF STERILE HYBRIDS.
A further distinction of fundamental significance remains to
be added to the preceding, before the full range of the phenom-
ena of interbreeding can be made apparent. The general im-
pression has been that the development of a new individual
represented the result of a combination of the two parental sex-
cells, but this is only partially true, especially among the higher
plants and animals. The fusion of the parental sex-cells is
carried through only two of the three stages of conjugation.
Fertilization unites the outer, unspecialized protoplasms (plas-
mapsis) and also the nuclei (karyapsis), but the chromatin,
the most highly specialized cell-substance, the citadel, as it
were, of the life of the cells, remains distinct until after the new
individual has developed, so that the body is not composed of
simple, post-conjugational cells, but of double cells in a condi-
tion of prolonged conjugation.
The fusion of the chromatin granules, or ultimate sex-ele-
ments (mitapsis), may not take place until the new individual
is mature and about to form new sex-cells of its own. The
other cells of the body never reach mitapsis. The sterility
of hybrids arises, it is now believed, from the inability of the
sex-elements to pass this third and final stage of conjugation.
It was always mysterious that hybrid combinations which could be
made for one generation could not continue for a second or a third
generation. This new appreciation of the nature of the process
of conjugation makes it apparent, however, that hybrids are
sterile because the parental elements do not make even one
complete conjugation. There is thus a definite difference
398 COOK
between a sterile hybrid and a fertile combination, one which
might have restricted the use of the term hybrid to the former.
Sterile hybrids, like false hybrids, are scarcely to be reckoned
as forms of conjugation. They are rather to be looked upon
as more nearly allied to parthenogenesis, a development through
stimulation merely, but without the possibility of forming new
relations of heredity or of making new combinations of charac-
ters. Sometimes there is not even enough cooperation between
the mismated partners of the cell-units to carry the organism
through even the normal cycle of individual existence. Hybrids
often refuse to grow up, or they may die suddenly and without
apparent external cause.
The building up of each cellular organism involves a contin-
ued cooperation between the parental sex-elements, which may
be thought of as persisting in all the cells of which the body is
composed. Whenever this cooperation breaks down, or proves
inadequate, the further development of the conjugate organism
becomes impossible.
PAPERS RELATING TO KINETIC EVOLUTION.
i 895. An Arrangement of the Geophilidae, a Family of Chilopoda. Proc. U. S.
Nat. Museum, 18: 63.
1896. Note on the Classification of Diplopoda. American Naturalist, 30: 681.
i8gg. Four Categories of Species. American Naturalist, 33 : 287.
1901. Duoporus, a New Diplopod from Mexico. Proc. Ent. Soc. of Washing-
ton, 4 : 402.
1901. A Kinetic Theory of Evolution. Science, N. S., 13 : 969.
1902. Evolutionary Inferences from the Diplopoda. Proc. Entomological Soc.
of Washington, 5 : 14.
1902. The Earwig's Forceps and the Phylogeny of Insects. Proc. Ent. Soc. of
Washington, 5 : 84.
1902. Kinetic Evolution in Man. Science, N. S., 15 : 927.
1902. A Deciduous Tropical Tree. Plant World, 5 : 171.
1903. Stages of Vital Motion. Popular Science Monthly, 63 : 14.
1903. Evolution, Cytology and Mendel's Laws. Pop. Sci. Mon., 63 : 219.
1904. Evolution not the Origin of Species. Pop. Sci. Mon., 64: 445.
1904. Professor Metcalf's Evolution Catechism. Science, N. S., 19: 312.
1904. Natural Selection in Kinetic Evolution. Science, N. S., 19: 594.
1904. The Vegetative Vigor of Hybrids and Mutations. Proc. Biological Soc.
of Washington, 17 : 83.
1904. Evolution and Physics. Science, N. S., 20: 87.
1904. The Biological Evolution of Language. The Monist, 14: 4S1.
1904. Evolution of Weevil-Resistance in Cotton. Science, N. S., 20: 666.
1905. The Social Organization and Breeding Habits of the Cotton-Protecting
Kelep of Guatemala. Bull. 10, Technical Series, Bureau of Entomology,
U. S. Department of Agriculture.
1905. Evolution of Cellular Structures. Bull. 81, Bureau of Plant Industry, U.
S. Department of Agriculture. (W. T. Swingle, joint author.)
1905. The Evolutionary Significance of Species. Smithsonian Report for
1904. P- 397-
igo6. Weevil-Resisting Adaptations of the Cotton Plant. Bull. 8S, Bureau of
Plant Industry, U. S. Department of Agriculture.
1906. The Vital Fabric of Descent. Proc. Washington Academy of Sciences,
7: 301.
1906. Factors of Species-Formation. Science, N. S., 23: 506.
1906. The Nature of Evolution. Science, N. S., 24: 303.
399
INDEX.
acclimatization 263
accommodation differences 202, 235, 236
Achillea 372
Aconitum 372
acquired characters 222, 319
Actcza 371
adaptation 211, 276, 283
defined 199, 278
adaptations, symbasie 220
adaptive fitness 222
versatility 200
adjustment of locomotion 207
characters 205
African diplopods 269, 312
agamic cell-structures 368
Agave, heterism of 247
agents of evolution 314
agricultural instincts 251
agriculture, primitive 251
albinism 337
alternation of generations 240, 366
alternative adjustment characters 205
heredity 345
anthropoids 217
antidromous plants 371
apaulogamic cell-structures 368
apogamic bulblets 383
Arctic plants, apogamous 384
plover, migrations of 211
Aristotle's categories 282
arropic species 369
artism 235, 250
astronomy and biology 356
autogamy 377, 384
barley, linic species 377
bees, sex-determination of 347
biology, compared to astronomy 356
human 218
bionomy of species 364
bovine hybrids 389
branch dimorphism 242
bud mutations 351
variations 354
Burbank on Prunus 352
cacao, dimorphic branches of 242
Castillo., dimorphic branches of 242
categories of causation 282
Cattell, quoted 282
cell differentiation 239, 329
cellular organization 367
structures, three types 238
Ceratodon 376
cerebral development 217
change of seed 262
character-unit assumption 339, 342, 353
chromomeres 342
chromosome purity 337
chromosomes 336
positional relations of 353
temporary 338
chromatin of hybrids 348
chrysomelid beetles, dichromatism of 376
civilizations suicidal 217
clones, definition of 378
clonic conditions 383
hybrids 388
propagation 380
species 378
varieties, limitations of 382
Cockayne, reference to 259
coffee, accommodations 210
amelioration of 390
dimorphic branches of 242
mutations 253, 271, 275, 325, 386
colors of desert animals 213
combined forms of diversity 379
conjugate cell-structures 368
heredity 344
organisms 330, 349
periods 365
conjugation, evolution of 330
nature of 343
conscious selection 278
conspicuous colors in forests 214
constant of variation 315
constitution of species 356
continuity of evolution 309
corn, Indian 264
correlation of variations 221
cotton acclimatization 201, 263
dimorphic branches 242
variations 201
Coues, on uniformity 291
cross-fertilizing adaptations 220
crystallization compared to heredity 332
Darwin, G. H., on natural selection 292
Darwin, Charles, on variation 229
on substitution 281
Darwinia, N. formulae 284
Darwinism 223, 230, 320
degeneration 255, 273
Delphinium 371
dendritic conception of descent 197
descent differences 235
desert colors 213
plants 213
deterioration of varieties 382
under inbreeding 381
determinant theories 300, 316
defined 306
DeVries, elementary species 378
on mutations 314, 324
on selection 322
on uniform species 362
theory of 387
dichromatism 375
dimorphic branches 242
diplopods, African 269, 312
Discaria experiment 258
discontinuous motion 309
variations 300
400
ASPECTS OF KINETIC EVOLUTION
401
discriminate mutations 393
disjunction 337
diversity, conditions of 396
of hybrids 388
reactions 385
domesticated species 359
domestication of food plants 385
dominant characters 337
double-celled organisms 344
Draba 378, 383
dynamic causes 304
educational danger 367
elementary species 378
elimination 281
elk, antlers burdensome 217
Engler, on mountain plants 267
environment, definitions 223
environmental fortuity 215
influence 335
reactions 213
ethics of race 335
Eucalyptus, metamorphosis 241
evening-primrose mutations 387
evolution a process 289
by restricted descent 378
defined 277
theories compared 307
evolutionary species 210
exaggerated heterism 388
explanations of evolution 288
expression problem 294
false hybrids 395
fasciation 352
Ficus 220
fig insect 219
fish with protective color 214
fitness by correlation 221
origin of 222
problem 198
forces of evolution 328
formulae of evolution 285
fortuity 215
of environment 218
frog with protective color 214
galls, heredity of 352
genetic variations 236
germinal incompatibility 348
selection 301
Gomphodesmidae 312
graft-hybridism 352
growth defined 330
stages 235, 237
Gulick isolation theory 314, 318, 377
Guyer on hybrids 348
Hawaiian snails 377
Helix 377
heredity, alternative or polar 345
and crystallization 332
and environment 333
and heterism 353
concept 327
in cell-specialization 329
hermaphroditism 370
heterism 244, 279, 327
and heredity ,353
and sex 374
heterism defined 235
functions of 248, 346
of clonic hybrids 388
specialization of 247, 369
hetercecism 241
heterogamy 384
Hieracium, linic species 378
Houslonia 372
human descent 355
evolution 363
Huxley, quoted 286
Hyatt's evolutionary forces 328
hybrids, diversity of 388
of clones 388
like mutations 394
sterile 397
various kinds 395
hybridization, limits of 394
versus selection 390
inbreeding, effects of 382
inconspicuous colors 213
infusoria, nuclei of 354
integral theory 197
intellect over-developed 217
interbreeding as evolutionary factor 323
intermittent evolution 309
intraspecific differences 226, 235
figure of descent 197
isolation defined 278
theory 314
Jordan, on selection 260
Juniperus, metamorphosis 241
karyapsis 397
Kelvin, opinion of 343
kinetic figure of evolution 323
theory defined 295, 302, 306
Knowlton, on bird migration 211
Lamarckian adaptations 230
L,amarekian theory 314, 333
Lankester, on heredity 333
on selection 323
on useless differences 314
laws and processes 289
leopard, black 375
Liberian fish 214
limitations of clonic propagation 380
line-bred organisms 377
lines, definition of 377
linic conditions 383
species 377
living matter specific 358
lizard with protective habits 214
Lydekker, on sheep 260
Ly thrum, heterism of 346, 372
maize varieties, 377, 384
mathematical heredity 339
Maupas, on nuclei of infusoria 354
mechanical theories 319
Mendelisni and sex 348
Mendelian heredity 336
Merocheta 312
metamorphosis 240
metagenesis 240
Metcalf, on plasticitity 204, 206
mice experiments 337
402
COOK
millipeds 270, 312
mitapsis 338, 397 _ _
Mivart. on abrupt variations 231
on natural selection 283
modes of evolutionary motion 286
mongrel reversions 388
monkeys 217
mules sometimes fertile 385
mutation theory 308, 313
mutations 274
degenerative 309, 310
discriminate 393
diversity of 387
of tomato 265
like hybrids 394
parallel 221
post-reproductive 352
prepotency of 393
teratic neisms 236
versus species 310
mutative variation 392
myxomycetes, accommodation in 208
chromatin of 354
Naegeli's theory 256, 300, 316, 378
natural selection 227, 232
selection negative 321
neism 236, 269
neotopism 236, 261
network motion 323
new characters prepotent 319
place effects 236
variations 269
nuclear deterioration 354
(Edogonium 239
olfactory cones of millipeds 312
organic elasticity 200
utility 215
overlapping of generations 367
Oxalis 372
Oxydesmidse 270
paint-root 257
pangenesis 316, 329
panmixia 256
paragamic cell-structures 368
parasitic fungi 241
tendencies 217
parthenogenesis 398
particularization 289
pendulum analogy 390
pheasants, plumage over-developed 217
philosophical systems 296
physiological species 210
physiology of cells 356
of evolution 304
of species 362
pigeon experiment 337
plasmapsis 397
plasticity in evolution 203
Poa 376
polar heredity 345, 348
politism 242
porric species 376
porrism 2^6, 266
Portulaca 376
positional relations of chromosomes 353
post-conjugate heredity 344
predetermination hypothesis 327
prefiguration hypothesis 327
premature socialization 367
prepotency 231, 271
of variations 319
preservation of characters 319
protective colors 213
proterandry in coffee 275
proterogyny in coffee 275
Prowazek, on chromatin 354
Prunus, graft-hybrid 352
Ptolemaic astronomers 293
pure science 360
purity of germ-cells 336
quail, subspecies of 267, 377
race evolution 335
rapidity of evolutionary motion 308
recessive characters 337
reproduction defined 330
restricted descent 376, 385, 388
descent, theories of 378
reticular descent 197
reversions 388, 391
root-crops, tropical 381
ropic species 370
Russian thistle 261
rust fungi 241
rye, a coherent species 384
saltatory evolution 299, 305, 309
screech-owls, supersexes of 375
secondary sexual characters 346
sections of species 364
seedless plants 273, 378
species unknown 381
segregation 278
selection defined 278
function of 389
inadequate 198
induces mutation 392
in mutation theory 310
preserves variations 390
versus hybridization 390
selective perfection of adaptations 212
restriction of descent 379
self-fertilization 377
semisexes, definition of 372
semisexual species 372
sex and Mendelism 348
-determination 347, 351
-differentiation 350, 355
sexual characters 373
selection 374
species 372
sexuality of conjugate organisms 349
of plants 350
Shamel, on tobacco 385
sheep in tropics 260
social organization 217, 242
of cells 238
socialization, premature 367
speciation 205, 276, 279
defined 278
theories of 279
species and subspecies 268
constitution of 356, 369, 376
in motion 294, 306
meaning of 359, 362
physiology 362
specific organization 327
ASPECTS OF KINETIC EVOLUTION
403
spiny plants 258
Spirogyra 331
spring-blossoming plants 383
Standfuss, experiments of 253
static theories defined 233, 298, 305
stenic species 377
stens, definition of 377
sterile hybrids 348, 397
structure of species 357
subsexes, definition of 371
subsexual species 371
subspecifie diversity 379
substitution 281
supersexes, definition of 375
supersexual species 375
Swingle, on positional heredity 353
symbasic adaptations 220
evolution 302
species 311, 376
symbasis, function of 323
symbasis defined 277, 317
synthetic theory 197
tables comparing theories 307
taxonomy inadequate 361
temperature range of plants and animals
211
teratic neisms 236
teratism 236, 272
termite organization 243
termites, heredity of 345
tobacco experiments 385
tomato mutations 265
topism 236, 257
unconscious selection 278
uniformity, conditions of 396
uniformity by autogamy 385
unisexual coffee mutations 275
use and disuse phenomena 254
utility, environmental and organic 215
of new characters 318
of sex characters 373
variation, discovery of 229
variations under domestication 360
vegetative propagation 366, 381
variations 351
vigor 380
Verbascum 249, 371
versatility of organisms 200
Viola 371, 383
Virginia partridge 267
vital tension 303, 355
network 355
Wallace, on natural selection 292
Washington palm 212
wealth and deterioration 218
Weismann on heredity 256, 300, 316
wheat, linic species 377
White on tomatoes 265
PROCEEDINGS
OF THE
WASHINGTON ACADEMY OF SCIENCES
Vol. VIII, pp. 405-406. February 13, 1907.
AGE OF THE PRE-VOLCANIC AURIFEROUS
GRAVELS IN CALIFORNIA.
By J. S. Diller.
GENERAL STATEMENT.
The age of the auriferous gravels of the Sierra Nevada in
California is generally given as late Miocene or Pliocene and is
based chiefly on fossil plants and a few animal forms. The
auriferous gravel period in all probability was a long one and
no considerable part of its flora has yet been connected directly
with its contemporaneous marine fauna of the same region.
On physiographic and stratigraphic grounds and the general
relations of the Sierra Nevada to sedimentation, it has long been
supposed by some geologists that the oldest auriferous gravels,
the deep gravels of Lindgren, are probably Eocene, but the
evidence assigned is problematic rather then positive.
EOCENE FLORA OF SOUTHWEST OREGON
While studying the Eocene deposits of the Roseburg, Coos
Bay, and Riddles quadrangles in Oregon, fossil leaves were
found in the same strata with marine shells, thus affording an
opportunity definitely to connect the land flora with its contem-
poraneous marine fauna.
The following list of ten species embraces the Eocene plants
identified by Dr. F. H. Knovvlton with more or less certainty
from a number of localities within the area noted above :
Magnolia lanceolata Lesq.
Magnolia californica ? Lesq.
Laurus californica ? Lesq.
Sabalites calif ornicus ? Lesq.
Aralia whitneyi Lesq.
Proc. Wash. Acad. Sci., February, 1906. ( 405 )
406 DILLER
Pofiulus zaddachi Heer.
Aralia angustiloba ? Lesq.
Juglans califomica P Lesq.
Ulmus califomica Lesq.
Ficus tilicBfolia ? Al Branner.
Among the shells found with or very near the fossil leaves,
Dr. Wm. H. Dall has recognized over 20 genera, and remarks :
"The fossils are Eocene. They contain a number of inter-
esting things, particularly the Orbitolites, which is usually char-
acteristic of the Oligocene on the Atlantic coast and is now for
the first time recognized from the Pacific coast."
The fossil leaves were found near the southeast border of the
Eocene where shells are not abundant, but a short distance far-
ther northeast they become very abundant locally with such
characteristic forms as Venericardia planicosta and Turritella
nvasana, and there is no doubt concerning the Eocene age of
the strata containing the fossil leaves.
Of the 10 species of plants identified seven are somewhat in
doubt, but three, Magnolia lanceolata, Aralia zvhitneyi, and
Populus zaddachi, are completely satisfactory. They all occur
in the auriferous gravels of Independence Hill, on the western
slope of the Sierra Nevada, as well as on the summit of the
northern end of the range, 7^ miles southwest of Susanville.
The last species occurs at many other localities among which
may be mentioned the lone formation of Kosk Creek and Little
Cow Creek of Shasta County, Cal., and the auriferous gravels
of Moonlight, Chalk Bluff, and Volcanic Hill.
Eight of the 10 species reported from the Eocene of Oregon,
occur, according to Mr. Lindgren, in the "bench gravels" of
Independence Hill, in California. It seems probable therefore
that not only the " deep gravels " but also the " bench gravels,"
both of which belong to the pre-volcanic gravels, may be of
Eocene age.
PROCEEDINGS
OF THE
WASHINGTON ACADEMY OF SCIENCES
Vol. VIII, pp. 407-448. pls. IX-XX March 4, 1907.
AERIAL LOCOMOTION.
With a Fe<v Notes of Progress in the Construction
of an Aerodrome.1
By Alexander Graham Bell.
The history of aerial locomotion is full of tragedies ; and
this is specially true where flying machines are concerned.
Men have gone up in balloons and most of them have come
down safely. Men have launched themselves into the air on
wings, and most have met with disaster to life or limb. There
have been centuries of effort to produce a machine that should
fly like a bird, and carry a man whithersoever he willed through
the air; and previously to 1783, the year sacred to the memory
of the brothers Montgolfier, all experiments at aerial locomo-
tion had this end exclusively in view\
Then came a period when the conquest of the air was sought
through the agency of balloons. For more than one hundred
years the efforts of experimenters were chiefly directed to the
problem of rendering the balloon dirigible ; and the earlier
experiments with gliding machines, and artificial wings — and
the proiects of men to drive heavy bodies through the air by
means of propellers, were largerly forgotten. The balloon was
changed from its original spherical form to a shape better
adapted for propulsion ; and at last through the efforts of San-
tos Dumont we have arrived at the dirigible balloon of to-day.
But in spite of the dirigibility of the modern balloon, it has so
1 An address presented before the Washington Academy of Sciences, Decem-
ber 13, 1906.
Proc. Wash. Acad. Sci., March, 1907. 407
408 BELL
far been found impracticable to impart to this frail structure a
velocity sufficient to enable it to make headway against any-
thing but the mildest sort of wind. The character of the bal-
loon problem has therefore changed. Velocity of propulsion
rather than dirigibility is now the chief object of research. l
It has long been recognized by a growing school of thinkers,
that an aerial vehicle, in order to cope with the wind, should be
specifically heavier than the air through which it moves. This
position is supported by the fact that all of Nature's flying
models, from the smallest insect to the largest bird, are speci-
fically heavier than the air in which they fly, most of them
many hundreds of times heavier, and that none of them adopts
the balloon principle in flight. It is also significant in this con-
nection that some of Santos Dumont's most celebrated exploits
were accomplished with quite a small balloon so ballasted as to
sink in the air instead of rise. He was then enabled, under the
influence of his motive power, to steer his balloon upwards with-
out the expenditure of ballast, and to descend without the loss
of gas. This probably typifies — for the balloon — the direc-
tion of change in the future. A reduction in the volume of gas,
coincidently with an increase in motive power, will lead to
greater velocity of propulsion — now the main desideratum.
Then, dependence upon velocity for support rather than gas,
may gradually lead to the elimination of the gas-bag altogether :
in which case the balloon will give birth to a flying machine of
the heavier-than-air type.
However this may be it is certainly the case that the tendency
of aerial research is to-day reverting more and more to the old
lines of investigation that were pursued for hundreds of years
before the invention of the balloon diverted attention from the
subject. The old devices have been reinvented. The old ex-
periments have been tried once more. Again the birds are rec-
ognized as the true models of flight ; and again men have put
on wings — but this time with more promise of success.
Lilienthal boldly launched himself into the air in an apparatus
of his own construction having wings like a bird and a tail for a
rudder. Without any motor he ran down hill against the wind.
1 Some of the latest forms of dirigible balloon are shown in Plates XIX and XX.
AERIAL LOCOMOTION 4O9
Then, upon jumping into the air, he found himself supported
by his apparatus, and glided down hill at an elevation of a few
feet from the ground, landing safely at a considerable distance
from his point of departure. This exhibition of gliding ilight
fairly startled the world, and henceforth the experiments of
Lihenthal were conducted in the public eye. He made hun-
dreds of successful flights with his gliding machine, varying its
construction from time to time, and communicating to the world
the results of his experiments with practical directions how to
manage the machine under circumstances of difficulty. So
that, when at last he met with the usual fate of his predecessors
in this line, the experiments were not abandoned. They were
continued in America by Chanute of Chicago, Herring, arid
other Americans, including the Wright brothers of Dayton,
Ohio. (See Plate IX.)
Hargrave, of Australia, attacked the flying machine problem
from the standpoint of a kite, communicating his results to the
Royal Society of New South Wales. It is to him we owe the
modern form of kite known as the " Hargrave Box Kite," which
surpasses in stability all previous forms of kites. He also con-
structed successful flying machine models on a small scale using
a store of compressed air as his motive power. He did not at-
tempt to construct a large sized apparatus, or to go up into the
air himself — so he still lives, to carry on researches that are of
interest and value to the world.
No one has contributed more to the modern revival of interest
in flying machines of the heavier-than-air type than our own
Professor Langley, the late Secretary of the Smithsonian In-
stitution. The constant failures and disasters of the past had
brought into disrepute the whole subject of aerial flight by man ;
and the would-be inventor, or experimenter, had to face — not
only the natural difficulties of his subject, but the ridicule of a
sceptical world. To Professor Langley is due the chief credit
of placing this subject upon a scientific basis, and of practicallv
originating what he termed the art of " Aerodromics." In his
epoch-making work on " Experiments in Aerodynamics," pub-
lished in 1891 among the Smithsonian Contributions to Knowl-
edge, he prepared the world for the recent advances in this art
410
BELL
by announcing that: "The mechanical sustention of heavy
bodies in the air, combined with very great speeds, is not only
possible, but within reach of mechanical means we actually
possess."
He also attempted to reduce his principles to practice, by the
construction of a large model of an aerodrome driven through
the air by a steam engine under the action of its own propellers.
I was myself a witness of the memorable experiments made by
Professor Langley on the 6th of May, 1896, with this large
sized model, which had a spread of wing of about 14 feet. No
one who witnessed the extraordinary spectacle of a steam engine
flying with wings in the air, like a great soaring bird, could
doubt for one moment the practicability of mechanical flight.
I was fortunate in securing a photograph of this machine in
full flight in the air, so that an automatic record of the achieve-
ment exists. (See Plate X). The experiment realized the utmost
hopes and wishes of Professor Langley at that time : "I have
brought to a close," he says, "the portion of the work which
seemed to be specially mine — the demonstration of the practica-
bility of mechanical flight ; and for the next stage, which is the
commercial and practical development of the idea, it is prob-
able that the world may look to others. The world, indeed,
will be supine if it does not realize that a new possibility has
come to it, and that the great universal highway over-head is
now soon to be opened."
But the world was not satisfied with this position. It looked
to Professor Langley himself to carry on the experiments to the
point of actually transporting a human being through the air
on an aerodrome like his model ; and so, with the aid of an ap-
propriation from the War Department of the United States, Pro-
fessor Langley actually constructed a full sized aerodrome, and
found a man brave enough to risk his life in the apparatus —
Mr. Manly, of Washington, D. C.
Great public interest was aroused ; but Professor Langley did
not feel justified in giving information to the public, and there-
fore to foreign nations, concerning experiments undertaken in
the interests of the War Department. His own dislike to pre-
mature publicity cooperated with his conscientious scruples, to
AERIAL LOCOMOTION 4II
lead him to deny the newspapers the opportunity of witnessing
the experiments. But the newspapers insisted upon being rep-
resented. The correspondents flocked to the scene, and camped
there for weeks at considerable expense to their papers. They
watched the house-boat containing the aerodrome by day and
by night; and, upon the least indication of activity within, news-
paper reporters were on hand in boats. After long delay in hopes
of securing privacy it was at last decided to try the apparatus ;
but the newspaper representatives, embittered by the attempts to
exclude them, were bringing the experiments into public con-
tempt. They nicknamed the apparatus " The Buzzard," and
were all ready to presage defeat.
Two experiments were made ; but on both occasions the
apparatus caught in the launching ways, and was precipitated
into the water without having a chance to show what it could
do in the air. The newspapers immediately announced to the
world the failure of Professor Langley's machine, and ridiculed
his efforts. The fact of the matter is, that the machine was
never tried ; and that there was no more reason for declaring it
a failure than for deciding that a ship would not float that has
never been launched. After having witnessed the successful
flight of the large sized model of 1896, I have no doubt that
Professor Langley's full sized aerodrome would have flown had
it been safely launched into the air. (See Plate XI.)
When the machine was for the second time precipitated into
the water it was not much damaged by the accident. Pro-
fessor Langley, of course, was more anxious about the fate
of his intrepid assistant than of his machine, and followed
Mr. Manly into the house-boat to ascertain his condition.
During this temporary withdrawal from the scene of the
catastrophe, the crew of a tug-boat grappled the frail frame-
work of the submerged aerodrome ; and in the absence of any
one competent to direct their efforts, they broke the machine to
pieces, thus ending the possibility of further experiments without
the expenditure of much capital. The ridicule of the news-
papers however effectually prevented Professor Langley from
securing further financial aid; and, indeed, broke his heart.
There can be little doubt that the unjust treatment to which he
412
BELL
was exposed contributed materially to the production of the
illness that caused his death.
He lived long enough however to know of the complete frui-
tion of his hopes by others ; and, only two days before his
death, he had the gratification of receiving a communication
from the newly formed Aero Club of America, recognizing and
appreciating his efforts to promote mechanical flight. This
communication read as follows :
RESOLUTIONS OF THE AERO CLUB OF AMERICA, ADOPTED
JANUARY 20, I906.
"Whereas, Our esteemed colleague, Dr. S. P. Langley,
Secretary of the Smithsonian Institution, met with an accident
in launching his aerodrome, thereby missing a decisive test of
the capabilities of this man-carrying machine, built after his
models which flew successfully many times ; and
"Whereas, In that difficult experiment, he was entitled to
fair judgment and distinguished consideration because of his
important achievements in investigating the laws of dynamic
flight, and in the construction of a variety of successful flying
models : Therefore be it
"Resolved, That the Aero Club of America, holding in high
estimation the contributions of Dr. Langley to the science of
Aerial Locomotion, hereby expresses to him its sincerest ap-
preciation of his labors as a pioneer in this important and
complex science ; and
"Be it further resolved, That a copy of these resolutions be
sent to the Board of Regents of the Smithsonian Institution,
and to Dr. Langley."
Professor Langley was on his death bed when these resolu-
tions were brought to his attention, and when asked what should
be done with the communication his pathetic answer was " Pub-
lish it." To all who knew his extreme aversion to publicity in
any form this reply indicates how keenly he felt the misrepre-
sentation of the press.
Both in the case of Lilienthal and Langley their efforts have
not been in vain. Others have continued their researches ; and
today the world is in possession of the first practical flying-
AERIAL LOCOMOTION 413
machine — the creation of the brothers Orville and Wilbur
Wright, of Dayton, Ohio. Indeed we have news from France
that a second has just appeared constructed by the same Santos
Dumont to whom the world already owes the first practical
dirigible balloon.
The Wright brothers began by repeating the gliding experi-
ments of Lilienthal with improved apparatus of the Hargrave
type as modified by Chanute. (See Plate XII.) After having
made many successful glides through the air without a motor,
they followed in the footsteps of Langley and propelled their
machine by means of twin screws operated by engine power.
They were successful in launching their apparatus into the air,
and it flew, carrying one of them with it. Their machine has
flown not once simply, but many times, and in the presence of
witnesses ; so that there can be no doubt that the first successful
flying-machine has at last appeared. Specially successful flights
were made on the third and fourth of October 1905, which were
referred to by the Wright brothers in a letter to the Editor of
L'Aerophile published in that journal, January, 1906. They
have-also made a communication upon the subject to the Aero
Club of America ; and have received the formal congratulations
of that organization upon their success.
Each of the Wright brothers, in turn, has made numerous
flights over their testing field near Dayton, Ohio, sometimes at
an elevation of about 80 feet, at other times skimming over the
field at a height of about ten feet from the ground. They have
been able to circle over the field of operation, and even to
describe in the air the figure eight, thus demonstrating their
perfect control over their apparatus both in the vertical and hori-
zontal directions. They have succeeded in remaining continu-
ously in the air for more than half an hour — thirty-eight min-
utes in fact — and only came down on account of the exhaustion
of their fuel supply. They state that the velocity attained was
one kilometer per minute, or about 37 miles an hour. The ma-
chine has not only sustained its own weight in the air during
these trials, but has also carried a man, and a gasoline engine
weighing 240 lbs., exerting a force of from 12 to 15 horse
power, and in addition an extra load of 50 lbs. of pig-iron. The
4H
BELL
apparatus complete with motor weighed no less than 925 lbs.
while the supporting surfaces consisted of two superposed aero-
planes each measuring six by 40 feet ; so that the machine as a
whole had a flying-weight of nearly two lbs. per square foot
(1.9 lbs.).
Thanks to the efforts of the Wright brothers the practicability
of aerial flight by man is no longer problematical. We can no
longer consider as impossible that which has already been
accomplished. America may well feel proud of the fact that
the problem has been first solved by citizens of the United States.
A FEW NOTES OF PROGRESS IN THE CONSTRUCTION OF AN
AERODROME.
For many years past, in fact from my boyhood, the subject
of aerial flight has had a great fascination for me. Before the
year 1896 I had made many thousands of still unpublished ex-
periments having a bearing upon the subject ; and I was there-
fore much interested in the researches of Professor Langley
relating to aerodynamics. We were thrown closely together in
Washington and although we rarely conversed upon aerody-
namics we knew that we had a subject of mutual interest and
showed the greatest personal confidence in one another. I did
not hesitate to show him my experiments, he did not hesitate to
show me his. .At least as early as 1894, Professor Langley
visited me in my Nova Scotia home and witnessed some of my
experiments ; and in May, 1896, he reciprocated by inviting me
to accompany him to Quantico, Virginia, and witness a trial of
his large sized model. The sight of Langley's steam aerodrome
circling in the sky convinced me that the age of the flying ma-
chine was at hand. Encouraged and stimulated by this remark-
able exhibition of success, I quietly continued my experi-
ments in my Nova Scotia laboratory in the hope that I too
might be able to contribute something of value to the world's
knowledge of this important subject.
Warned by the experience of others, I have sought for a safe
method of approach — a method that should risk human life as
little as possible during the earlier stages of experiment. Ex-
periments with aerodromes must necessarily be fraught with
AERIAL LOCOMOTION 415
danger, until man, by practical experience of the conditions to
be met with in the air, and of the means of overcoming them,
shall have attained skill in the control of aerial apparatus. A
man cannot even ride a bicycle without practice ; and the birds
themselves have to learn to fly. Man, not having any inherited
instincts to help him in this matter, must first control his flight
consciously, guided by knowledge gained through experiment.
Skill can only be obtained by actual experience in the air ; and
this experience will involve accidents and disasters of various
sorts before skill can be obtained. If these disasters should, as
so often in the past, prove fatal to the experimenter, the knowl-
edge obtained by the would-be aviator will be lost to the world,
and others must begin all over again, instead of pursuing the
subject where he left off, with the benefit of his knowledge and
his experience. It is therefore of the utmost consequence to
progress in the art of aviation, that the first attempts to gain
experience in the air should be made under such conditions of
safety as to reduce to a minimum the liability to fatal results.
The Wright brothers' successful flying machine travels at the
rate of about thirty-seven miles an hour; and, judging from its
great flying weight (nearly two pounds per square foot of sup-
porting surface), it is unlikely that it could be maintained in the
air if it had very much less velocity. But should an accident
happen to a body propelled through the air with the velocity of
a railroad train, how about the safety of the occupants? Acci-
dents will happen, sooner or later, and the chances are largely
in favor of the first accident being the last experiment. While
therefore we may look forward with confidence to the ultimate
possession of flying machines exceeding in speed the fastest
railroad trains, it might be the part of wisdom to begin our first
experiments at gaining experience in the air, with machines
travelling at such moderate velocities as to reduce the chances
of a fatal catastrophe to a minimum. This means that they
should be light-flying machines ; that is, the ratip of weight
to supporting surface should be small.
While theory indicates that the greater the weight in propor-
tion to supporting surface consistent with flight, the more inde-
pendent of the wind will the machine be, yet it might be advis-
416 BELL
able to begin, if possible, with such a moderate flying-weight
as to permit of the machine being flown as a kite. There would
be little difficulty then in raising it into the air ; and, should an
accident happen to the propelling machinery, the apparatus
would descend gently to the ground ; or the aviator could cast
anchor, and his machine would continue flying — as a kite — if
the wind should prove sufficient for its support. If it could fly,
as a kite, in a ten-mile breeze, then a velocity of only ten miles
an hour would be sufficient for its support as a flying maching
in calm air, while a less speed would suffice in heading into a
moderate wind.
Such velocities would be consistent with safety in experi-
ments, especially if the flights should be made over water in-
stead of land, and at moderate elevations above the surface.
Under such circumstances the inevitable accidents which are
sure to happen during first experiments are hardly likely to be
followed by more serious consequences than a ducking to the
man, and the immersion of the machine. If the man is able to
swim, and the machine to float upon water, little damage need
be anticipated to either.
There are two critical points in every aerial flight — its be-
ginning and its end. A flying machine adapted to float upon
water not only seems to afford a safe means of landing, but
also promises a solution of that most difficult of problems — a
safe method of launching the apparatus into the air. If the
supporting floats are so formed as to permit of the machine be-
ing propelled over the surface of the water like a motor boat,
then, if sufficient headway can be gained under the action of
her aerial propellers, the machine can be steered upwards into
the air, rising from the water, after the manner of a water bird,
in the face of the wind. This seems to be the safest method of
gaining access to the air ; but, of course, its practicability de-
pends upon possibilities of lightness and speed yet to be demon-
strated.
In any event, if the machine, man and all, is light enough to
be flown as a kite, it can be towed out of the water into the air
through the agency of a motor boat ; and, upon land, it would
not even be necessary for it to gain headway before rising, for,
AERIAL LOCOMOTION 417
in a supporting wind, it would rise of itself into the air, if re-
lieved of the weight of the man, and fly as a kite. It would
then be a comparatively simple matter to lower the kite to a
convenient height from the ground, and to hold it steadily in
position by subsidiary lines, while the aviator ascends a rope
ladder to his seat in the machine. In this way the man would
not be exposed to danger during the critical operation of launch-
ing the apparatus into the air ; and, by a converse process, a
safe landing could be effected without bringing the machine to
the ground. The chance of injury to the machine itself would
also be much lessened by relieving it of the weight of the man
during the initial process of launching, and the final process of
bringing the machine down to the ground.
Such speculations as these of course are only justifiable upon
the assumption that it is possible to construct an aerial vehicle
large enough and strong enough to support a man and an engine
in the air, and yet light enough to be flown as a kite in a moderate
breeze with the man and engine and all on board. My experi-
ments in Nova Scotia have demonstrated that this can be done ;
and I now therefore find myself seriously engaged in the attempt
to reduce these ideas to practice by the actual construction of an
aerodrome of the kite variety. The progress of experiment may
be divided into three well marked stages — the kite stage, the
motor boat stage, and the free flying-machine rising from the
water.
THE KITE STAGE.
In April, 1899, I made my first communication on the subject
of kites to the National Academy of Sciences in a paper entitled,
" Kites with Radial Wings," which was reviewed, with illustra-
tions, in the Monthly Weather Review for April, 1899 (Vol-
XXVI, pp. 154-155, Plate XI). I made another communica-
tion to the National Academy on the 23rd of April, 1903, upon
"The Tetrahedral Principle in Kite Structure," which was
published, with 91 illustrations and an appendix, in the National
Geographic Magazine for June, 1903 (Vol. XIV, pp. 220-251).
The substance of the present address was presented, in
part, to the National Academy of Sciences at their recent
418 BELL
meeting in Boston, Mass., November 21, 1906. The experi-
ments referred to, which were undertaken at first for my
own pleasure and amusement, have gradually assumed a serious
character from their bearing upon the flying-machine problem.
The word "kite" unfortunately is suggestive to most minds
of a toy — just as the telephone at first was thought to be a toy
— so that the word does not at all adequately express the nature
of the enormous flying structures employed in some of my ex-
periments. (See Plates XVI, XVII, XVIII.) These structures
were really aerial vehicles rather than kites, for they were capable
of lifting men and heavy weights into the air. They were flown
after the manner of kites, but their flying cords were stout manilla
ropes. They could not be held by hand in a heavy breeze ; but
had to be anchored to the ground by several turns of the ropes
around stout cleats like those employed on steamships and men-
of-war.
One of the great difficulties in making a large structure light
enough to be flown as a kite, has been pointed out by Professor
Simon Newcomb in an article in McClure's Magazine published
in September, 1901, entitled " Is the Air-Ship Coming?"; and
this difficulty had so much weight with him at that time as to
lead him to the general conclusion that — " The construction of
an aerial vehicle which could carry even a single man from place
to place at pleasure, requires the discovery of some new metal,
or some new force."
This conclusion the Wright brothers, and now Santos
Dumont, have demonstrated to be incorrect ; but Professor New-
comb's objections undoubtedly have great force, and reveal the
cause of failures of attempts to construct large-sized flying-ma-
chines upon the basis of smaller models that actually flew. Pro-
fessor Newcomb shows that where two aerial vehicles are made
exactly alike, only differing in the scale of their dimensions, the
ratio of weight to supporting surface is greater in the larger one
than in the smaller ; the weight increasing as the cube of the
dimensions, whereas the supporting surfaces only increase as the
squares. From this the conclusion is obvious that if we make
our structure large enough it will be too heavy to fly even by
itself — far less be the means of supporting an additional load
AERIAL LOCOMOTION 419
like a man, and an engine for motive power. This conclusion
is undoubtedly correct in the case of structures that are " exactly
alike, excepting in their dimensions," but it is not true as a
general proposition.
A small bird could not sustain a heavy load in the air ; and
while it is true that a similar bird of double the dimensions would
be able to carry a less proportionate weight because it is itself
heavier in proportion to its wing surface than the smaller bird
— eight times as heavy in fact, with only four times the wing
surface — still it is conceivable that a flock of small birds could
sustain a heavy load divided equally among them, and it is
obvious that in this case the ratio of weight to wing surface
would be the same for the whole flock as for the individual
bird. If then we build our large structure by combining together
a number of small structures each light enough to fly, instead of
simply copying the small structure upon a larger scale, we
arrive at a compound or cellular structure in which the ratio of
weight to supporting surface is the same as that of the individual
units of which it is composed, thus overcoming entirely the really
valid objections of Professor Newcomb to the construction of
large flying-machines.
In my paper upon the tetrahedral principle in kite structure, I
have shown that a framework having the form of a tetrahedron
possesses in a remarkable degree the properties of strength and
lightness. This is especially the case when we adopt as our
unit structure the form of the regular tetrahedron, in which the
skeleton frame is composed of six rods of equal length as this
form seems to give the maximum of strength with the
minimum of material. When these tetrahedral frames or cells
are connected together by their corners they compose a struc-
ture of remarkable rigidity, even when made of light and fragile
material — the whole structure possessing the same properties of
strength and lightness inherent in the individual cells them-
selves.
The unit tetrahedral cell yields the skeleton form of a solid,
and it is bounded by four equal triangular faces. By covering
two adjoining faces with silk or other material suitable for use
in kites, we arrive at the unit "winged cell " of the com-
420
BELL
pound kite ; the two triangular surfaces, in their flying position,
resembling a pair of wings raised with their points upward, the
surfaces forming a dihedral angle. (A, Plate XIII.) Four of
these unit cells, connected together at their corners, form a four-
celled structure, having itself the form of a tetrahedron contain-
ing in the middle an empty space of octahedral form, equal in
volume to the four tetrahedral cells themselves. (B, Plate XIII.)
In my paper I showed that four of these four-celled structures
connected at their corners resulted in a sixteen-celled structure
of tetrahedral form, containing, in addition to the octahedral
spaces between the unit cells, a large central space equivalent
in volume to four of the four-celled structures. (C, Plate XIII.)
In a similar manner four of the sixteen-celled structures con-
nected together at their corners form a sixty-four-celled structure.
(D, Plate XIII. ) Four of the sixty-four-celled structures form a
two hundred and fifty-six-celled structure, etc., etc., and in
each of these cases an empty space exists in the center, equiva-
lent to half of the cubical contents of the whole structure, in
addition to spaces between the individual cells, and minor groups
of cells.
Kites so formed, exhibit remarkable stability in the air under
varying conditions of wind, and I stated in my paper that the
kites which had the largest central spaces seemed to be the most
stable in the air. Of course these were the structures that were
composed of the largest number of unit cells ; and I now have
reason to believe that the automatic stability of these kites de-
pends more upon the number of unit cells than upon the pres-
ence of large empty space in the kites ; for I have found, upon
filling in these empty spaces with unit cells, that the flying
qualities of a large kite have been greatly improved. The
structure, so modified, seems to fly in as light a breeze as be-
fore but with greatly increased lifting power ; while the gain in
structural strength is enormous.
I had hitherto supposed that if cells were placed directly be-
hind one another, without providing large spaces between them,
comparable to the space between the two cells of a Hargrave
box kite, the front cells would shield the others from the action
of the wind, and thus cause them to lose their efficiency ; but no
AERIAL LOCOMOTION 42 1
very marked effect of this kind has been observed in practice.
Whatever theoretical interferences there may be, the detrimental
effect upon the flying qualities of a kite are not, practically,
obvious ; while the gain in structural strength and in lifting
power outweigh any disadvantages that may exist. I presume,
that there must be some limit to the number of cells that can be
placed in close proximity to one another without detrimental
effect ; but so far my experiments have not revealed it.
To test the matter, I put together into one structure all the
available winged cells I had in the laboratory — 1300 in num-
ber. These were closely attached together without any other
empty spaces in the structure than those existing between the
individual cells themselves when in contact at their corners.
The resulting kite, known as "The Frost King," consisted of
successive layers, or strata of cells, closely superposed upon
one another. (See Plate XIV.) The lowest layer, or floor of
the structure, consisted of 12 rows of 13 cells each. The cells
forming each row were placed side by side attached to one an
other by their upper corners ; and the 12 rows were placed one
behind the other, the rear corners of one row being attached to
the front corners of the row immediately behind. The next
stratum above the floor had 11 rows of 14 cells; the next, 10
rows of 15 cells; etc., — each successive layer increasing in
lateral dimensions and diminishing in the fore and aft direc-
tion ; so that the top layer, or roof, consisted of a single row of
24 cells placed side by side. One would imagine that a closely
packed mass of cells of this kind — 1300 in number — would
have developed some difficulty in flying in a moderate breeze if
the cells interfered with one another to any material extent : but
this kite not only flew well in a breeze estimated at not more
than about 10 miles an hour because it did not raise white-caps,
but carried up a rope-ladder, several dangling ropes 10 and 12
meters long, and more than 200 meters of manilla rope used as
flying lines, and in addition to all this, supported a man in the
air. (See Plate XV.)
The whole kite, impedimenta and all, including the man,
weighed about 131 kgs. (288 lbs.) ; and its greatest length from
side to side was 6 meters at the top and three meters at the
422
BELL
bottom. The sloping sides measured 3 meters and the length
from fore to aft at the square bottom was 3 meters. It is obvious
that this kite might be extended laterally at the top to twice its
length without forming an immoderately large structure. It
would then be 12 meters on the top (39 ft.) and 9 meters on the
bottom from side to side, without changing the fore and aft
dimensions, or the height. It would then contain more than
double the number of cells and so should be able to sustain in
the air more than double the load ; so that such a structure
would be quite capable of sustaintng both a man, and an engine
of the weight of a man, and yet be able to fly as a kite in a
breeze no stronger than that which supported the " Frost
King."
An engine of the weight of a man could certainly impart to
the structure a velocity of 10 miles an hour, the estimated veloc-
ity of the supporting wind, and thus convert the kite into a free
flying-machine. The low speed at which I have been aiming
— for safety's sake — is therefore practicable.
In the "Frost King" and other kites composed exclusively
of tetrahedral winged cells, there are no horizontal surfaces (or
rather surfaces substantially horizontal as in ordinary kites), but
the framework is admirably adapted for the support of such
surfaces. Horizontal aeroplanes have much greater lifting-
power than similar surfaces obliquely arranged as in the tetra-
hedral construction, and I have made many experiments to com-
bine horizontal surfaces with winged cells, with greatly im-
proved results so far as lifting-power is concerned. But there
is always an element of instability in a horizontal aeroplane,
especially if it is of large size ; whereas kites composed exclu-
sively of winged cells are wonderfully steady in the air under
varying conditions, though deficient in lifting-power ; and the
kites composed of the largest number of winged cells seem to
be the most stable in the air.
In the case of an aeroplane of any kind the center of air-pres-
sure rarely coincides with the geometrical center of surface, but
is usually nearer the front edge than the middle. It is liable to
shift its position, at the most unexpected times, on account of
some change in the inclination of the surface or the direction of
AERIAL LOCOMOTION 423
the wind. The change is usually small in steady winds ; but
in unsteady winds great and sudden changes often occur.
The extreme possible range of fluctuation is, of course, from
the extreme front of the aeroplane to the rear, or vice versa, and
the possible amount of change, therefore, depends upon the
dimensions of the aeroplane — especially in the fore and aft
direction. With a large aeroplane the center of pressure may
suddenly change to such an extent as to endanger the equilibrium
of the whole machine. Whereas, with smaller aeroplanes,
especially those having slight extension in the fore and aft
direction, the change, though proportionally as great, is small
in absolute amount. Where we have a multitude of small sur-
faces well separated from one another, as in the tetrahedral con-
struction, it is probable that the resultant center of pressure for
the whole kite can shift to no greater extent than the centers of
pressure of the individual surfaces themselves. It is, therefore
extremely unlikely that the equilibrium of a large kite could be
endangered by the shifting of the centers of pressure in small
surfaces within the kite. This may be the cause of the auto-
matic stability of large structures built of small tetrahedral cells.
If so, one principle of stability would be: Small surfaces —
well separated — and many of them. The converse proposition
would then hold true if we desired to produce instability and a
tendency to upset in a squall — namely : Large surfaces —
continuous — and few of them.
Another source of danger with large continuous surfaces is
the fact that a sudden squall may strike the kite on one side,
lifting it up at that side and tending to upset it. But the com-
pound tetrahedral structure is so porous, that a squall passes
right through and lifts the other side as well as the side first
struck ; so that the kite has not time to be upset before the blow
on one side is counterbalanced by a blow on the other. I have
flown a Hargrave box kite simultaneously with a large kite of
many tetrahedral cells in squally weather for the purpose of
comparing them under similar conditions. The tetrahedral
structure often seemed to shiver when struck by a sudden squall,
whereas the box kite seemed to be liable to a swaying or tipping
motion that would be exceedingly dangerous in a structure of
large size forming part of a flying machine.
424
BELL
Another element of stability in the tetrahedral structure lies
in the fact that the winged surfaces are elevated at a greater
angle above the horizon than 45 °.
Supposing the wings of a cell to be opened out until they are
nearly flat — or at least until they each make a comparatively
small angle with the horizon — say 200 — then if, from any
cause, the cell should tip so as to elevate one wing (say to 25 °)
and depress the other (say to 15 °) then the lifting-power of the
wind will be increased upon the elevated wing and diminished
on the depressed wing, so that there would be no tendency to a
recovery of position, but the very reverse. The pressure of the
wind would tend to increase the tipping action, and favor the
production of oscillation and a tendency to upset. The lifting-
power of the wind upon a surface inclined at io° is less than at
200 ; and greater at 250 than 200. The more the wings are
opened out, and the flatter they become, the more essentially
unstable is the arrangement in the air.
Now suppose the wings to be raised until they are nearly
closed, or at all events until they make a small angle with the
vertical (say 700 from the horizontal), then if from any cause
the cell should tip so as to elevate one wing (say to 75 °) and
depress the other (say to 65 °), the lifting-power of the wind will
be increased upon the depressed wing and diminished on the
elevated wing ; for the lifting-power of the wind is greater at
65 ° than at 700 and less at 75 °. Thus the moment a tipping
action begins the pressure of the wind resists it, and an active
force is invoked tending to restore the structure to its normal
position. The more the wings are raised, and the more they
approach the perpendicular position the more stable essentially
is the arrangement in the air.
The dividing line between these two opposite conditions seems
to be drawn about the angle of 45 °. As the tetrahedral wing-
surfaces make a greater angle than this with the horizontal they
constitute an essentially stable arrangement in the air ; whereas
a horizontal surface represents the extreme of the undesirable
unstable condition.
These considerations have led me to prefer a structure com-
posed of winged tetrahedral cells alone, without horizontal sur-
AERIAL LOCOMOTION 425
faces either large or small, although the lifting-power is less
than when horizontal surfaces are employed, because the factor
of safety is greater. One of the chief causes that have led to
disasters in the past has been lack of stability in the air. Auto-
matic stability under varying conditions is surely of the very
first consequence to safety, for what would it profit a man were
he to gain the whole world and lose his own equilibrium in the
air? A kite composed exclusively of multitudinous winged-cells
seems to possess this property of automatic stability in a very
marked degree. If then its lifting-power is sufficient for our
purpose there is no necessity for the introduction of a factor of
danger by the addition of horizontal surfaces. Of course the
addition of such surfaces would enable us to secure the desired
lifting-power with a smaller and therefore lighter structure, and
this would be of advantage if we could be sure of its stability in
the air.
In employing tetrahedral winged-cells alone, upon the hollow
plane of construction in which large empty spaces occurred
within the kite, a practical difficulty was encountered arising
from the enormous size of the structure required for the support
of a man, combined with the increasing weakness of the struc-
ture as it increased in size. The discovery that the cells may
be closely massed together without marked injurious effects has
completely remedied this difficulty ; for upon this plan, not only
is the structural strength improved by an increase of size, but
the lifting-power increases with the cube of the dimensions, so
that a very slight increase in the dimensions of a large kite in-
creases very greatly its lifting-power. We now have the possi-
bility of building structures composed exclusively of tetrahedral
winged-cells that will support a man and an engine in a breeze
of moderate velocity, without the necessity of constructing a
kite of immoderate size. The experiments with the " Frost
King" made in December, 1905, satisfied me upon this point,
and brought to a close my experiments with kites.
Conclusion.
Since December, 1905, my attention has been directed to other
points necessary to be considered before an aerodrome of the
426 BELL
kite variety can be made ; and to the assembling of the ma-
terials for its manufacture.
I have had to improve and simplify the method of making
the winged-cells themselves. Through the agency of Mr.
Hector P. McNeil, Superintendent of the Volta Laboratory,
Washington, D. C, who is now taking up the manufacture of
tetrahedral cells as a new business, I am now able to obtain
cells constructed largely by machinery, and with stamped-metal
corners to hold the rods together. The process of tying the
cells and parts of cells together had proved to be very labori-
ous and expensive ; and the process was not suited to unskilled
persons. By the new process most of the work is done by ma-
chinery, and no skill is required to connect the cells together.
I have also had to go into the question of motor construction,
a subject with which I am not familiar ; and while waiting for
the completion of the material required for the aerodrome I have
been carrying on experiments to test the relative efficiency of
various forms of aerial propellers. I have also been occupied
with the details of construction of a supporting float adapted for
propulsion over the water as a motor boat, and also adapted to
form the body of the flying-machine when in the air.
Of course it would be premature for me to enter into any
description of experiments that are still in progress, or to submit
plans for an aerodrome which are still under discussion. I shall
therefore simply say in conclusion that I have recently been
making experiments in propelling, by means of aerial propellers,
a life-raft supported, catamaran fashion, on two metallic cyl-
inders. The whole arrangement, with a marine motor on board,
is exceedingly heavy, weighing over 2,500 pounds; and it is
sunk so low that the water level rises at least to the middle of
the supporting cylinders, so that the raft is not at all adapted for
propulsion, and cannot attain great speed. The great and
unnecessary weight of this machine has led to an interesting
and perhaps important discovery that might have escaped atten-
tion had the apparatus been lighter and better adapted for pro-
pulsion.
Under the action of her aerial propellers, this clumsy raft is
unable to attain a higher speed than four miles an hour; and yet
AERIAL LOCOMOTION 427
she is able to face a sixteen-mile white-cap breeze, and make
headway against it, instead of drifting backwards with the wind.
Under such circumstances her speed is materially reduced ; but
the point I would direct attention to is this, that she is not stopped
by a current of air moving with very much greater velocity than
her maximum possible speed in a calm. Of course there would
be nothing remarkable about this if her propellers were acting
in the water instead of the air, but they were not. They acted
exclusively in the air, and the water was only an additional
resistance to be overcome.
It is worthy of note in this connection that the rapid rotation
of the propellers yield a theoretical efficiency of thirty or forty
miles an hour, and that the mass of the machine and the resis-
tance of the water drag this down to an actual performance of
only four miles, so that at first sight it appears probable that the
effect noted may be a result of the greater slip of the propellers
acting in a calm. I am inclined to think however that this
explanation is insufficient ; and would suggest the following as
more probable.
The enormous mass of the moving body enables it to acquire
very considerable momentum with slight velocity ; whereas, the
opposing current of air has such slight mass, that it cannot
acquire an equal momentum with a very much higher velocity.
If two bodies of unequal mass, moving with equal but oppo-
site velocities, come into collision with one another, then the
heavier body will not be completely stopped by the lighter. It
will make headway against the resistance of the other even
though the lighter should possess superior velocity, provided,
of course, that it has a sufficient superiority of mass. We are
here dealing with momentum (»/;■), not velocity (v) alone. The
body having the greatest momentum will be the victor in the
struggle whatever the actual velocities may be.
The suggestiveness of this result lies in its application to the
flying machine problem. A balloon, on account of its slight
specific gravity, must ever be at the mercy of the wind. In
order to make an)' headway against a current of air it must itself
acquire a velocity superior to the wind that opposes it. On the
other hand it is probable that a flying machine of the heavier-
428 BELL
than-air type, at whatever speed it moves, will be able to make
headway against a wind of much greater velocity, provided
its momentum is greater than the momentum of the air that op-
poses it.
DISCUSSION OF DR. BELL'S ADDRESS BY CHARLES M. MANLY.
It is a notable sign of the kind of attention aeronautical work is now
attracting , that one who has to his credit the accomplishment of such
big things as Dr. Bell has, should become so actively engaged in it.
As Dr. Bell has already pointed out, the world owes much to Mr.
Langley for taking hold of the subject when it was looked upon as the
wild dream of cranks and enthusiasts and by putting it on a scientific
basis made it seem worthy of serious attention. It is no less fortunate
that we have to-day such men as Dr. Bell actively engaged in the con-
struction of large man-carrying machines, for the influence of their
example causes the work to be looked on by the public more and more
seriously all the time.
Dr. Bell has pointed out that one of the advantages possessed by
such a slow speed aerodrome as he will be able to construct by util-
izing his important invention of tetrahedral cells, is the possibility of
anchoring such a machine and having it maintained at a height through
its ability to fly as a kite. This suggests the superiority which such a
machine will possess not only as regards safety in case of a break-down
of the machinery, but also as regards its use as a war machine. The
ability to anchor and remain steadily over a given point will enable
the operator or operators to thoroughly study and map out fortifications
and the disposition of field forces, as there is very slight probability of
so small an object as an anchor rope being discovered by the enemy,
and even if it should be, the ability of the operator to cut the rope
would render him comparatively free from capture.
As a war machine Dr. Bell's tetrahedral plan of cellular construction
for the surfaces would also I think present another very great advantage.
Such a machine might be badly riddled with shot and yet be able to
maintain very good equilibrium, while a machine having large units of
surface with large parts in the frame work of its surfaces, would be
very seriously crippled should a chance shot disable one of the main
supports on one side.
It may not be amiss to call attention also to the fact that the operator
on any aerodrome or balloon when at a considerable height can plainly
see submarine boats at any depth in the water. Such machines can
therefore be used for determining the number of submarine craft in
AERIAL LOCOMOTION 429
the enemy's force of harbor defenses, and by keeping the machine
circling above a battleship or a fleet of ships, the possibility of attack
by submarine boats would be very greatly lessened. In fact I should
think that with Dr. Bell's multicellular machine there would be no great
difficulty in maintaining the operator in the air for hours by simply
flying the machine as a kite anchored to the ship.
I trust that Dr. Bell will pardon me for not agreeing with the
explanation he suggested of the very interesting fact noted in regard to
the propulsion of the " Catamaran Life Raft " by means of aerial pro-
pellers, namely that the raft advanced against a 16-mile breeze,
although in a calm it was able to make only something like four miles
an hour.
It seems to me that this ability of the raft to advance against a 16-mile
wind is not due to the difference between the momentum of the raft
and the momentum of the air, but to the fact that the raft presents
very little resistance to the wind, while the propeller, being revolved
at a high rate of speed by the engine, tends to advance in the air at a
speed proportionate to its pitch multiplied by its number of revolutions
in a given time ; and I have no doubt that the raft would have advanced
against any wind of a velocity less than that which would be created
by the slip of the propeller revolving in still air at the same speed as
when driving the raft. In other words, if the propeller had a pitch,
let us suppose, of one foot (that is, tended to advance through the air
one foot for each revolution, or forced the air backwards one foot for
each revolution), such a propeller revolving at the rate of a thousand
revolutions a minute would in a calm create a back wind of a thousand
feet per minute, and of course a propeller of two feet pitch would
create a back wind of two thousand feet per minute when revolving at
the same speed. Such a propeller, then, of two feet pitch, revolving
at this speed, when mounted on a raft should be able to prevent the
raft being blown backwards in a wind of somewhere near two thousand
feet per minute. I have no doubt that the back wind due to the pro-
peller in Dr. Bell's experiment was of an even higher velocity than
two thousand feet per minute.
Few of us can conceive of the affairs of the world being very differ-
ent from what we are accustomed to. But there are certain definite
effects which we can be fairly confident will follow definite changes.
I am not a prophet nor the son of a prophet, but I feel safe in ventur-
ing a conservative prediction in regard to one of the effects of aero-
dromic work in the next few years. We may not be able to make it
a general vehicle of transportation, as some enthusiasts predict; I my-
43°
BELL
self, indeed, while unwilling to define the limits of the possible, cer-
tainly do not expect such results very soon. But I have no hesitation
in asserting that the attainment of the ability to fly say three hundred
miles, — a degree of success now practically certain to be attained
within five years — will, at whatever risk of danger to the aeronaut,
have as important an effect on warfare as the advent of wireless teleg-
raphy, and a far greater one than the perfecting of the submarine boat
or the Whitehead torpedo, both of which even now are causes of the
greatest concern to the officers of even the last, and largest, and most
expensive battleship.
It is interesting in this connection to learn, what I have just been
told on good authority, that a prominent admiral of the navy who
has just retired is planning to devote his time to a thorough study of
aerodromics, foreseeing as he probably does the early advent of the
flying war machine, which there seems ample ground for believing
will prove to be the most important single step in the progress of the
art of war.
I am pleased to hear Dr. Bell state publicly his confidence in the
accuracy of the reports of the success of the Wright brothers, fori my-
self have had every confidence in them and have thoroughly appreciated
the motives which have prompted them to withhold a public demon-
stration of their machine until business arrangements can be completed
which will enable them to reap the financial profits which their suc-
cess so richly deserves.
I trust that I shall be pardoned for emphasizing Dr. Bell's statement
as to the importance of the fact that the "Wright brothers have flown
not only once but many times. The fact that a machine has flown
successfully and carried a man not only a few hundred feet but some-
thing like twenty-five miles, will, when its significance is realized, have
the greatest effect on the future progress of the work.
I have always wondered why it is that the more prominent polar
explorers have been able to secure very large sums of money for use in
their attempts to reach the north pole, yet no public benefactor has
seemed ready to render substantial financial assistance in the solution
of this problem of opening up for mankind the great aerial highway,
which to me at any rate, seems of such vast importance to the
world. The only reason I could assign for this has been, that while
the existence of such a point as the pole is capable of mathematical
demonstration, the possibility of a successful flying machine has seemed
a subject not for science but for dreams.
It seems to me however, that the fact that success has already been
AERIAL LOCOMOTION 43 1
achieved by the Wright brothers should put the whole problem on a
very different footing and convince even the skeptical that the question
of success is now merely a question of degree. As people of means
who wish to perpetuate their name can do it in no better way than by
assisting in a substantial manner in the progress of scientific investiga-
tion, they will surely now be ready to furnish the funds necessary to
ensure more rapid progress in this work.
We must remember that in these days work of this kind progresses
by leaps and bounds. It is barely seven years ago that the first annual
automobile show was held in Madison Square Garden, New York.
No attempt was made to utilize the galleries of the Garden and practi-
cally the entire area of the main floor was given over to a track which
was used for demonstrating to the audience the fact that an automobile
could be stopped in a very much shorter distance than a horse-drawn
vehicle going at the same speed. The management in charge of this
show, in order to fill up space, even provided seats which were ar-
ranged for the convenience of the visitors. Last winter, just six years
after that date, instead of one show occupying only a small portion of
the Garden, there were two shows of about equal size held simultan-
eously in New York, and the one which was held in the Garden not
only filled it from cellar to roof, but the streets all around were filled
with demonstrating machines, and instead of seats being provided, it
was necessary to have policemen to see that the people followed the
proper circuit of the building so that the crowd should be kept moving
and all might have a chance to view the exhibition. As the outcome
of industry which six years ago amounted to nothing, we have in the
United States to-day something like ten million dollars invested in
approximately 75 manufacturing establishments which, during the
year which is just closing, have produced more than fifty thou-
sand machines, and instead of the automobile being ridiculed by the
cartoonist as a chimerical dream it has become the chariot of the mil-
lionaire and the freight truck of the industrial world, hauling goods
and ore from the steamship piers and the mines.
Realizing that this enormous progress has been made in the short
period of less than a decade, it is only a pessimist of the deepest dye
who would dare predict that the next decade will not see not only
enormous strides in the progress of aerodromics, but also the aero-
drome itself an important factor in human affairs.
For thousands of years man was content to travel no faster than his
ancestors, but the advent of the steam locomotive followed by that of
the electric car has quickened the inventive genius of the world to its
43 2
BELL
very core ; and man, not content with being confined to travel at a
high speed on a definite route marked by parallel steel rails, has
quickly taken up the automobile which can follow not only the multi-
tudinous roadways, but, if necessary, blaze out its own way through
the fields and woods. Instead of having his ambition satisfied by this
multiplication of his possible paths, he still thirsts for more freedom
and will not be satisfied until he has opened up for himself access to
the highways of the air, which are limitless in all directions and on
which speed laws enforced through police traps, if not impossible,
will at least be most difficult to maintain and enforce.
While for many years I have felt the deepest interest in aeronautical
matters, it was only in 1898 that I first became actively engaged in the
work. I had the pleasure and the honor of being associated for some
seven years with the lamented Secretary Langley as his assistant in
direct charge of the experiments which he conducted at the Smith-
sonian Institution. Dr. Bell has already referred to the fact that this
later work which Mr. Langley conducted was carried on for the Board
of Ordnance and Fortification of the War Department. As you are
all no doubt aware, it is the custom of the War Department in con-
ducting important tests to exclude not only the general public but also
the representatives of the newspapers ; and in undertaking this work
for the War Department, Mr. Langley made a very definite agreement
that the public should be excluded from witnessing the construction of
the aerodrome and the tests of it, though in the interests of science he
retained the privilege of later publishing whatever part of the work he
might deem of importance to the scientific world. It could not be
foreseen at that time that the carrying out in good faith of this agree-
ment would bring upon him the bitter animosity of the whole corps of
American newspaper writers who would vent their ill will in ridicule
and in censure for failure to achieve complete success.
As those of you who followed the newspaper reports during the ex-
periments in the summer and fall of 1903, will recall, the large house-
boat, on which were stored both the large machine and a duplicate of
it on a smaller scale, was carried down the Potomac River in July and
anchored at a point about forty miles from Washington. The first
experiments which were made were conducted with this model which
was an exact duplicate of the larger machine but of exactly one quarter
the linear dimensions. The object of the tests with this model was to
determine whether the balancing of the large machine had been cor-
rectly calculated from the results of the many previous tests of the
steam driven models of approximately the same size but embodying
AERIAL LOCOMOTION 433
important differences in certain details. I will not burden you with
an account of the long series of exasperating delays encountered, de-
lays almost entirely brought about by the very unusual weather condi-
tions which could not be foreseen and provided against ; I will only
say that the several newspaper representatives who went down the
river early in July and remained stationed there for several months in
a malarial district on the Virginia shore, and who had to row some-
what over a mile and a half in order to get within close range of the
house-boat which was anchored in the middle of the river, were nat-
urally not very favorably influenced either by the fogs and high winds
or by their necessary exclusion from all real knowledge of the work
going on within the house-boat.
I cannot emphasize too strongly that there was neither fault in design
nor inherent weakness in any part of this large aerodrome. The
whole machine had been subjected to the most severe tests and strains
in the Institution shops in the endeavor to find any possible points of
weakness and had shown itself able to withstand any strain it would
meet in the air.
The experiments themselves convinced both Mr. Langley and myself
that it would have been better to have conducted them over land rather
than over water and we should thereby have avoided a great deal of
expense and the major part of the delays and accidents which were
encountered ; yet it must be remembered that in work of this kind
experiment is the only sure guide and that aftersight is always much
clearer than foresight. It is my personal opinion that had the experi-
ments been conducted over the land instead of over the water, not
only would the funds which proved inadequate have been more than
ample, but success would have been achieved as early as 1902 instead
of what the public has judged to be failure in 1903.
Dr. Bell has told you that in the last experiment the aerodrome was
broken to pieces through the ignorance and carelessness of the tugboat
men in getting it out of the water. It was almost heart-breaking to
look at the wreck that they made of it ; but although Mr. Langley
found himself without funds for making further experiments with the
machine, vet at my earnest solicitation he allotted sufficient money to
enable the frame to be repaired so that it is practically as good as new
and stands to-day completely assembled with its engine and everything
to enable it to fly except a new set of supporting surfaces.
It has been generally supposed that the work has been abandoned and
this idea has been strengthened by Mr. Langley's death, but I think I
can assure you that the work is not abandoned but merely temporarily
434
BELL
suspended, for it is my purpose, at the earliest moment that I can
possibly spare the time for it, to reequip the aerodrome with proper
supporting surfaces and using the same launching apparatus, to give
the aerodrome a fair trial, this time over the land instead of over the
water, when I feel very certain that it will fully demonstrate the
correctness of its design and construction and crown Mr. Langley's
researches with the success which they so richly deserve, and I trust
that the day that this will be achieved is very near at hand. It was
the launching apparatus, all will remember, which in both of the
experiments caused the accidents that prevented any test of the aero-
drome itself. These accidents were not due to defects in the design or
fundamental construction of the launching apparatus, for the smaller
apparatus of exactly the same design had been used more than thirty
times for launching the smaller machines and without a single failure.
Certain minute defects in the releasing mechanism were the sole cause
of the trouble.
It has been very generally supposed that in his experiments Mr.
Langley used exclusively what maybe called " single tier " surfaces
and that he did not recognize that the superposing of the lifting sur-
faces presented certain great advantages not only as regards ease of
construction and strength, but also in reducing the size of the machine.
This general impression is due to the fact that all of the photographs
of the machines in flight which he published officially, and also those
published by the newspapers, have shown the machine as equipped
with " single tier" surfaces. I may say however that as early as 1S90
and constantly from that time until the work was temporarily suspended
in 1903, Mr. Langley experimented with superposed surfaces, the first
experiments of course being with very small models having their motive
power furnished by means of stretched or twisted rubber. The same
large steam driven models which flew so successfully in 1S96, the first
flight of which Dr. Bell has just spoken of having witnessed, were in
1899 equipped with superposed surfaces and were tested in free flight
during the months of July and August.
The quarter-size model of the large aerodrome driven by a gasolene
engine which was first tested in 1901 and later in the summer of 1903,
was also equipped with superposed surfaces, but in the test of August,
1903, which was witnessed by the newspaper representatives, the
a single tier " surfaces were used. The prime reason that the large
aerodrome was equipped with the " single tier" surfaces was that the
best flights of the models were with such surfaces, and although in the
beginning it was planned to build superposed surfaces for the large
AERIAL LOCOMOTION 435
machine later, the early depletion of the funds provided by the Board
of Ordnance and Fortification made it imperative to utilize what had
already been constructed, as it was with the greatest reluctance that
Mr. Langley continued the work with the funds of the Institution, and
all expense which could be avoided was carefully guarded against. I
have thought it well to mention this fact as I have had many inquiries
as to why it was that Mr. Langley never realized that the superposed
type of construction for the supporting surfaces presented important
advantages.
It was my duty while connected with the Smithsonian Institution to
prepare answers to the large number of letters on aeronautical subjects
which were constantly received. While some of the writers sought
advice, others offered it ; and a large number of the letters indicated
that the writers believed that the problem of constructing a successful
machine required the discovery of some " secret." In view of this
experience, I have thought that it might not be amiss to emphasize,
that there is no " secret " which needs to be discovered in order to build
a successful machine, but that success is to be achieved by laying out a
good design based on a proper knowledge of the laws of aerodromics
as at present known, next by giving the greatest care to constructing
the parts as strong as possible for the permissible weight, and then
trying the machine, not once only, but again and again under condi-
tions presenting the least possible danger to the operator.
In this connection attention may be called to the fact that when a
machine is planned and the weight of the different parts is allotted, so
that the total weight shall not exceed a certain proportion relative to
the supporting area, the experimenter need not be surprised to find,
when he has completed his machine that it weighs forty or fifty per
cent, more than he has calculated ; for in carrying out the innumerable
details of construction small increases in weight at almost every point
finally increase the total weight surprisingly.
In all of the accounts which I have lately seen of the experiments of
the Wright brothers, no mention has been made of the fact that the
success of the Wrights has been built on the very valuable work of
Mr. Chanute, who for many years carried on at his own expense work
in the construction and testing of gliding machines, and who I under-
stand, not only furnished the Wright brothers with the design for their
first gliding machine, but also placed at their disposition his own
machines with which they made their initial gliding experiments.
There is perhaps no one who has made a closer study and has a more
thorough understanding of the whole subject of aerodromics than Mr.
436 BELL
Chanute, and I should like very much to see him given due credit for
the very important work which he has done.
DISCUSSION BY PROF. A. F. ZAHM, OF THE CATHOLIC UNIVERSITY
OF AMERICA.
I fully concur with Dr. Bell in the opinion that aerial locomotion is
practicable, and is likely soon to be of great moment in the affairs of
the world. For the progress of this science, during the past decade or
two, has been as positive, as continuous, as substantial as that of any
branch of engineering or of architecture. Constantly and quietly, in
various parts of the world, men have grappled with the difficulties of
this apparently hopeless enterprise, and now, I believe, we are about
to enjoy the fruitful and splendid issue of their labors.
The subject of aerial locomotion may be divided into four main
branches : first, the science of captive and free balloons ; second, the
science of motor balloons ; third, the science of gliding and soaring
machines; fourth, the science of dynamic flying-machines. Each of
these has had its ardent advocates, and each is, I believe, practically
feasible.
The first branch, or that of captive and free balloons, is already a
practical science, inasmuch as such balloons perform substantially the
functions for which they are designed. The captive balloon can be
sent aloft safely in all kinds of weather for taking observations, and
making maps of the neighboring region, even in winds of upwards of
forty miles an hour. The free balloon, likewise, is comparatively safe
when made by an experienced manufacturer and managed by a properly
trained pilot. Such balloons may be kept aloft for days, or even
weeks, traversing, in that time, hundreds of miles, or possibly the
width of a continent, if the wind be favorable. But, though we grant
the practicability of balloons of this type, it must be said also that their
functions are limited ; their chief usefulness thus far being for the study
of the atmosphere, for observations of the land beneath, for military ope-
rations, for public exhibitions, and now recently, for racing and sport.
The ideal of the motor balloon is more important and more difficult,
though it also seems about to be realized. The function of such craft
is to go forth in all kinds of ordinary weather, to run in all directions,
with or against the wind, scores of miles at a stretch, and to remain
under perfect control. Salverda has shown, by reference to the yearly
wind records at Paris, that aerial navigation may be practically real-
ized, for that locality, when a vessel can be driven twenty-eight miles
an hour. Is such achievement possible? More than a decade ago
AERIAL LOCOMOTION 437
theorists demonstrated mathematically that this speed, and even higher,
was attainable by appliances then known. Now apparently the inven-
tors, taking a lesson from Santos Dumont, have caught up with the
computers, and are producing the high speed balloons. On the third
of this month, an eye witness told me that he saw Count von Zeppelin's
air-ship fly about Lake Constance at a speed of twenty -eight miles an
hour, independently of the wind, and that she obeyed her rudder as
perfectly as a boat on the water. It is reported that the inventor has
deduced from these experiments that a larger vessel will operate still
more effectively, that an air-ship of this type can be made to carry fifty
passengers at a speed of more than thirty miles an hour. Count von
Zeppelin writes that his present balloon, which is 410 feet long and 38
feet in diameter, has attained a speed of 33.5 miles an hour, and is
able to go 1,860 miles through the air at a speed of 31 miles an hour,
or 3,000 miles at a speed of 25 miles an hour, without stopping for sup-
plies. To match this achievement in Germany, let me add that the
French Government has just accepted the second Lebaudy motor-
balloon, and has ordered one more like it, thus adding three modern
air-ships to her aerial equipment. Such facts may give us at least a
little faith in aerial locomotion of the second kind.
The goal of the gliding and soaring machines is to travel through
the air on motionless wings, without the aid of gas or motive power,
by the sole aid of wind and gravitation ; not only to glide downward,
but also to soar up to the clouds, and sweep over vast territories, as do
the condor and the albatross. To some people this seems absurd ; but
there are the vultures and the gulls performing the impossible every
day. Humboldt assures us that the condor can soar from the Pacific
to the heights of Cotopaxi and Aconcagua without wing-beat. Here
is a splendid field of research which thus far has remained practically
unexplored.
Unfortunately, I can not quote an instance of real soaring by man ;
that is to say, gliding to an indefinite height and distance, without the
use of motive power. Still, from the mechanical nature of the per-
formance, I believe it is feasible. Dr. Langley was so convinced of
the possibility of this kind of flight that he looked forward to the time
when men would soar over vast distances, and possibly circumnavi-
gate the globe without the expenditure of motive power, save in those
regions of the atmosphere where there might be an extended calm or
downward trend of the wind.
Two years ago the Wright brothers compared their power of aerial
gliding with that of a vulture in North Carolina, among the Kill-Devil
438 BELL
sand hills. On a day when there was little or no wind, they observed
a buzzard tobogganning down the atmosphere parallel to the sloping
sand and very near to it. Where the slope was steep enough the bird
could glide indefinitely without wing-beat, but where the incline was
too gentle, say seven degrees or less, the buzzard had to flap a little to
maintain its flight. Having carefully noted a considerable stretch of
sand where the bird could barely sail without flapping, they mounted
their glider and skimmed over the same slope without motive power.
From such experiments they concluded that they could glide fully as
well as the buzzard, and possibly a trifle better. In other words, if
they were placed on a perch with the bird in competition, in a large
closed room, they would probably win the prize for long distance
gliding.
In one other feat, also, they imitated the vulture. They hovered
motionless above a sand slope for 59 seconds, neither rising nor fall-
ing, nor advancing nor receding. In this case, of course, the wind
had a slightly upward trend, say of seven or more degrees, just as
must be the case when any bird floats fixed and motionless in the air.
I put this question to them recently : " After beating the buzzard in
the art of gliding, did you try to beat him in the art of soaring up to
the clouds? " They replied that nothing would have given them more
pleasure ; but their power machine, on which they had worked so
arduously, and so long, was ready for its first test, and Christmas was
just at hand. So they went out in a bitter gale, launched their motor
flying machine in the teeth of a tumultuous thirty-mile wind, and flew
half a mile through the air, or three hundred and some feet over the
ground. Thus ended their gliding and thus began their dynamic flight.
But they still envy that feathered professor of the atmosphere, and
still have confidence that they may, to some extent, acquire his fasci-
nating art. If they could dispose of their present power machine,
doubtless they would return again to the sand-hills and plunge pell-
mell into the soaring business.
As to the fourth type, or the motor flying-machine, I need add little
to the excellent summary given by Dr. Bell. Without radical improve-
ment, such machines may be driven through the air with the speed of
the eagle, and made to carry several hundred pounds burden. The
Wright brothers, in their recent communication to the Aero Club of
America, conclude with these words : " It is evident that the limits
of speed have not as yet been closely approached in the flyers already
built, and that in the matter of distance the possibilities are even more
encouraging. Even in the existing state of the art, it is easv to design
AERIAL LOCOMOTION 439
a practical and durable flyer that will carry an operator and supplies
of fuel for a flight of over 500 miles at a speed of 50 miles an hour."
In a great conflict like the recent oriental war, one such machine
could do more reconnoitering than ^0,000 armed men. For, in a few
hours, it could completely survey and snap-shot the enemy's main field
of operations, though covering hundreds of square miles. A fleet of
such machines, armed with bombs and fire pellets, could devastate the
whole of an enemy's border, both towns and villages, unless opposed
by other flyers. Possibly, also, a fleet of this kind could protect a
nation's seaboard against the attack of battleships, unless the latter were
accompanied by an aerial squadron. Therefore, if one great nation
keep flyers, all the world-powers must have them.
But this seems like hunting for trouble with a search light just before
daybreak. Whatever be the mission of the flying-machine, I think we
may say of it as the English do: "The thing is bound to come,
whether we like it or not." "And damned be he who first cries
hold !"
As to Dr. Bell's researches in this interesting and now popular field
of inquiry, I would say, first, that every earnest friend of science
should be very grateful to him for lending his illustrious name to a
much ridiculed pursuit, at a time when it jeopardized one's peace and
good name publicly to promote mechanical flight. I well remember
with what apprehension Mr. Chanute consented to become chairman
of the first international conference on aerial navigation in this country.
And we all too well remember the attitude of many people toward
Dr. Langley's painstaking and unobtrusive investigations. The Wright
brothers, also, experienced hostile treatment in certain quarters before
their success was known. Even after the news of their splendid flights
of last year had been circulated privately among their friends, we
heard many apparently intelligent dogmatists assert that it is not the
design of Providence, or of Nature, that a human being should fly;
and that, furthermore, the performance is manifestly impossible.
This is another illustration of the value of public opinion in matters of
technical import. But fortunately, the destinies of science are not
dominated wholly by the vote of the majority, nor yet by grand officials,
whether legislative or executive, else, I fear we never should have
either a science or an art of aerial locomotion.
Another service for which we may thank Dr. Bell is his having met
publicly, both by model and by argument, a profound objection of the
mathematicians, based on that ancient Euclidean theorem connecting
the surfaces and volumes of similar figures with certain powers of their
Proc. Wash. Acad. Sci., March, 1907.
44°
BELL
homologous linear dimensions. Dr. Bell did not deny the law, as a
chagrined or an angry person might ; but, like a shrewd man of affairs,
he admitted the law, and discovered a way to evade it.
Now that his reply is familiar to us, it may seem amusing that
people urged the Euclidean objection so strongly ; but the fact is that
many persons, besides Professor Newcomb, advanced it as an argument
against the practicability of mechanical flight. In the middle eighties
an eminent geologist made it the basis of a magazine article, in which he
proved, with fine eloquence, that it is impossible for a human being
ever to fly. He further supported his contention by a vigorous biolog-
ical argument, and possibly also by a theological or teleological one, I
do not remember. He asserted that nature had tried for centuries to
produce a flying creature as heavy as a man, but had failed ; therefore,
it is utterly impossible for man to achieve mechanical flight. By
diligent experimentation she had tested and adopted the strongest
possible materials, she had developed the most powerful motor for a
given weight, she had employed the most favorable shapes and the
most efficient mode of propulsion. But what was the outcome ? Her
largest flyer weighs hardly so much as a human dwarf. The ostrich
is the limit. The ostrich is the living witness of nature's failure. And
that picturesque old reptile, with the twenty-foot wings, that soared so
grandly over the Cretacean seas, remains to-day the fossil proof of
nature's utmost capacity, and therefore also of man's. Such argumentst
such prettily woven sophistries, such quaint immemorial cobwebs, have
Dr. Bell and his associates brushed reverently from the pages of science.
There are many features of Dr. Bell's remarkable kites, both struc-
tural and aerodynamic, that merit most careful attention ; more parti-
cularly the relation of the forward resistance to the total upward lift,
the effectiveness of the provision for automatic stability and equilibrium
in all kinds of tumultuous winds, the distribution of stresses in the frame,
and of the impulsive pressures over the sustaining surfaces. But these
topics seem to me more suitable for experimentation than for abstrac,
analysis.
One interesting phenomenon, however, I will notice in closing.
Dr. Bell relates that his floating kites, which in calm weather, could
advance but four miles an hour, still continued to make headway
against a sixteen-mile wind. The momentum of the craft might main-
tain this forward motion for a few seconds, but not for a considerable
period. For the total momentum in any direction is equal to the initial
momentum plus the impulse of the resultant force in the line of pro-
gression. Or, in the language of algebra,
AERIAL LOCOMOTION 44I
mz = mQv9 -f (F — F')t
in which mv is the momentum at the time /, wQv0 the initial momentum,
F — F' the resultant of the average propulsive and opposing forces.
If mv is positive for large values of /, the equation shows that F must
at least equal F' . But Dr. Bell observed, that the kites continued al-
ways to advance, or that mv remained positive. Therefore the pro-
pulsive force continued, on the average, at least equal to the resistance.
In other words, it was the propeller thrust, rather than the momentum,
that maintained the indefinite forward progression.
But how, it may be asked, could the propeller thrust maintain head-
way against a sixteen-mile wind, if, in calm weather, it could support a
speed of only four miles an hour ? I would answer : first, that the water
resistance was not greater in the sixteen-mile wind, but probably less ;
second, that the propeller thrust might be not very different in a calm
and in a sixteen-mile wind, as Maxim found. This latter point Mr.
Manly can elucidate readily from his extensive study of both the theory
and actual working of screw-propellers.
It is well for the world when a man of Dr. Bell's fertility espouses
some favorite science. He took up the kite as a toy, and now presents
these wonderful structures; light and beautiful as butterflies, yet strong
and stable enough for human life. If next he incline to magnificence,
what lovely air-castles will follow ! Serenely, one day, may he soar
in a gossamer palace, when the blue waves blossom, and the wind sings
over the sea !
Appendix A.
Details Concerning the Kite "Frost King."
Number of Cells in
the " Frost
King."
Layers of Number of
Number of cells
Number of cells
cells. rows.
in each row.
in each layer.
1st layer 1
24
24
2d layer 2
23
46
3d layer 3
22
66
4th layer 4
21
84
5th layer 5
20
100
6th layer 6
19
114
7th layer 7
18
126
8th layer S
17
136
9th layer 9
16
144
10th layer 10
15
150
nth layer n
M
154
1 2 th layer 12
13
156
Total number of cells, 1,300
442
BELL
Dimensions. — Each cell had a side of 25 centimeters, so
that the roof, or ridge pole, measured 6 meters extending later-
ally across the top of the structure. The oblique sides were 3
meters in length ; and the bottom, or floor, formed a square hav-
ing a side of 3 meters. The whole structure constituted a sec-
tion of a tetrahedral kite — the upper half in fact, of a kite,
having the form of a regular tetrahedron with a side of 6 meters.
Weight. — The winged cells composing this structure weighed
on the average 13.84 gms. apiece, so that the whole cellular
part of the structure which supported all the rest — consisting
of 1,300 winged-cells — weighed 17,992 gms.
In addition to this, the kite carried as dead load stout sticks
of wood which were run through the structure to distribute the
strain of the pull upon the strong parts of the framework —
that is, upon the junction points of the cells. The outside edge
of the kite was also protected by a beading of wood. The whole
strengthening material weighed 9,702 gms., and the kite, as a
whole, weighed 27,694 gms. (61 lbs.).
Surface. — I estimate the surface of an equilateral triangle
having a side of 25 centimeters, as about 270.75 square centi-
meters. In which case the silk surface of a single winged-cell,
consisting of two triangles, amounts to 541.5 square centime-
ters ; and the actual silk surface employed in 1,300 cells equals
70.3950 square meters (757-7 sq. ft.).
The surfaces are all oblique ; and if we resolve the oblique
surfaces into horizontal and vertical equivalents (supporting sur-
faces and steading surfaces) we find that the resolved horizontal
equivalent (supporting surface) of a single winged cell forms a
square of which the diagonal measures 25 centimeters, and this
is equivalent to a rectangular parallelogram of 25 x 12.5 cm.,
having an area of 312.5 square centimeters.
Thus an actual silk surface of 541.5 square centimeters
arranged as the two wings of a winged cell, yields a supporting
surface of 312.5 square centimeters.
In kites, therefore, composed exclusively of tetrahedral winged
cells, each having a side of 25 centimeters, the area of support-
ing surface bears the same proportion to the actual surface as
the numbers 3,125 to 5,415 ; or 1 to 1.7328.
AERIAL LOCOMOTION 443
Supporting surface i
Actual surface ~ 1.7328
A simple way of calculating the amount of supporting surface
in such structures is to remember that there are 32 cells to the
square meter of supporting surface. Therefore, the 1300 cells
of the kite " Frost King" had a supporting surface of 40.6250
square meters (437.3 sq. ft.).
Ratio of Weight to Surface. — The actual silk surface em-
ployed in the " Frost King" was 70.3950 square meters (757-7
sq. ft.), the weight of the kite was 27,694 gms. (61 lbs.), so that
on the basis of the actual surface, the flying weight was 393.4
gms. per square meter (0.08 lbs. per sq. ft.).
But for the purpose of comparing the flying weight of a tetra-
hedral kite with that of other kites in which it is usual to estimate
only the aeroplane surfaces that are substantially in a horizontal
plane, it would be well to consider the ratio of weight to hori-
zontal or supporting surface in this kite.
The weight was 27,694 gms. (61 lbs.); the resolved horizontal
or supporting surface was equivalent to 40.6250 square meters
(437.3 sq. ft.), and the flying weight for comparison with other
kites was 681.7 gms« Per square meter of supporting surface
(0.14 lbs. per sq. ft.).
The kite, in addition to its own weight, carried up a mass of
dangling ropes and a rope-ladder, as well as two flying cords of
manilla rope. The impedimenta of this kind weighed 28,148
gms. (62 lbs.). It also supported a man, Mr. Neil McDermid,
who hung on to the main flying rope at such a distance from the
cleat attached to the ground that when the rope straightened
under the strain of the kite he was carried up into the air to a
height of about 10 meters (over 30 ft.). The weight of this
man was 74,910 gms. (about 165 lbs.). Thus, the total load
carried by the kite, exclusive of its own weight, was 103,058
gms. (or 227 lbs.).
The whole kite, load and all, including the man, therefore,
weighed 130,752 gms. (288 lbs.), and its flying weight was
1857.4 gms. per square meter of actual surface (0.38 lb. per
sq. ft.) ; or 3218.5 gms. per square meter of supporting surface
(0.66 lb. per sq. ft.).
444
BELL
Appendix B.
Partial Bibliography Relating to Aerial Locomotion, prepared,
through the courtesy of the smithsonian institution,
by Dr. Cyrus Adler, Assistant Secretary, in
Charge of Library and Exchanges.
Dr. Adler says : " In accordance with your request, I am authorized to send
you herewith a list of the writings of S. P. Langley, Octave Chanute, Otto
Lilienthal, Lawrence Hargrave, and A. M. Herring, to be used in connection
with your recent paper on aerial locomotion. I ought to explain that, excepting
in the case of Mr. Langley's writings, I am not at all sure that the lists are
complete, since the time afforded for bringing together the references was very
short, and of course there may be publications in out-of-the-way journals which
would only be revealed by a more extended inquiry. I have also appended a list
of papers on the subject published by the Smithsonian Institution, as the Smith-
sonian publications are accessible in all libraries throughout the country, whereas
many of the publications cited in the other lists are not readily to be found"
Langley, S. P.
1891 Experiments in Aerodynamics. Smithsonian Contributions to Knowl-
edge, Washington, D. C.
1891 Experiences d'Aerodynamique. Revue de PAeronautique, Paris, pages
77-124.
1891 Recherches Experimentales Aerodynamiques et Donnees d'Experience.
Extrait des Comptes rendus des Seances de l'Academie des Sciences t.
CX1II. Stance du 13 Juillet, Paris.
i89i-'g2 Recherches Experimentales Aerodynamiques et Donnees d'Expe-
rience. " L'Adronaute," vol. 24-25, pages 176-180, Paris.
1891 The Possibility of Mechanical Flight. Century Magazine, New York,
September, pages 783-785.
1892 Mechanical Flight. The Cosmopolitan, New York, May.
1893 The Internal Work of the Wind. Smithsonian Contributions to Knowl-
edge, Washington, D. C.
1893 La Travail Interieur du Vent. Revue de l'Aeronautique, Paris.
1894 The Internal Work of the Wind. American Journal of Science, New
Haven, Conn., vol. XLVII, January.
1894 Die innere Arbeit des Windes. (American Journal of Science, 1894,
ser. 3. vol. XLVII, p. 41.) Naturwissenschaftliche Rundschau Braun-
schweig, 31 Marz, No. 13, pp. 157-160.
1895 Langley's Law. Aeronautical Annual, Boston, No. 1, pp. 127-128.
1896 Description du vol m^canique, Extrait des Comptes rendus des Stances
de l'Academie des Sciences t. CXXII, Seance du 26, Mai, pp. 1-3.
1896 Description du vol mechanique. Comptes Rendus, cxxii, May 26.
1896 A Successful Trial of the Aerodrome. Science, New York, May 22, p.
753-
1896 Experiments in Mechanical Flight. Nature, London, May 2S, p. 80.
1896 L' Aeroplane de M. Samuel Pierpont Langley. L'Aeronaute, 29 Ann^e,
No. 7, Juliet, Paris.
1897 Story of Experiments in Mechanical Flight. The Aeronautical Annual,
Boston, No. 3, pp. 11-25.
AERIAL LOCOMOTION 445
1897 The New Flying Machine. Strand Magazine, London, June, pp. 701-
718.
1897 The " Flying Machine." McClure's Magazine, June, pp. 647-660.
1897 Story of Experiments in Mechanical Flight. Smithsonian Report,
Washington, D. C.
1900 The Langley Aerodrome : Note prepared for the Conversazione of the
American Institute of Electrical Engineers, New York, April 12, 1901.
Smithsonian Report, Washington, pp. 197-216.
1901 The Greatest Flying Creature. Smithsonian Report, Washington.
1902 Note of the Aerodrome of Mr. Langley. Published in Scientific Ameri-
can Supplement of November 29 and December 6.
rgo4 Experiments with the Langley Aerodrome. Smithsonian Report, Wash-
ington.
Chanute, Octave
1890 Aerial Navigation : A lecture delivered to the students of Sibley College,
Cornell University, May 2. (Reprint.) The Railroad and Engineering
Journal.
1891 Progress in Aerial Navigation. The Engineering Magazine, New York,
October, vol. 2, No. 1.
1893 Aerial Navigation. Transportation, New York, October, vol. 1, No. 2,
pp. 24-25.
i8gi-'93 Progress in Flying Machines. The Railroad and Engineering
Journal, New York, continued from October, 1891, to March, 1893, and
from May, 1893, to December, 1893.
i8g3-'94 Progress in Flying Machines. L'Aeronaute, Paris, 26-27, PP- 221-
224.
i8g6-'g7 Sailing Flight, parts 1 and 2. The Aeronautical Annual, Boston,
Nos. 2 and 3, pp. 60-76, 9S-127.
1898 American Gliding Experiments. Separate- Abdruck, Heft 1, der Illus-
trirten Aeronautischen Mittheilungen, pp. 1-8.
i8gg Progress in Flying Machines. New York, pp. i-vi, 1-308.
1900 Aerial Navigation. The Independent, New York, pp. 1006-1007, 1058-
1060.
1900 Experiments in Flying. McClure's Magazine, New York, vol. XV, No.
2, June.
1901 Aerial Navigation : Balloons and Flying Machines from an Engineering
Standpoint. Cassier's Magazine, New York, June, vol. 20, No. 2, pp.
111-123.
igo3 La Navigation Aerienne aux Etats-Unis. L'Aerophile, Aotit, 11 Ann^e,
No. 8, pp. 171-183.
igo3 L'Aviation en Amerique. Revue GeneVale des Sciences, pures et ap-
pliqu^es, Paris, 14 Annee, No. 22, November 30, pp. 1133-1142.
igo4 Aeronautics. Encyclopaedia Brittannica Supplement, London, pages
100-104, with 3 plates.
igo4 Aerial Navigation. Scientific American Supplement, New York, vol.
57» PP- 23598-23600.
igo3-'o4 Aerial Navigation. Smithsonian Institution Report, pp. 1 73-181.
1904 Aerial Navigation. Popular Science Monthly, New York, vol. 64, pp.
385-393-
446 BELL
1906 Aerial Navigation. Engineering World. Chicago, August 10, vol. 4.
No. 9, p. 222. i
Lilienthal, Otto
1889 Der Vogelflug als Grundlage der Fliegekunst. Berlin, pp. i-viii,
1-187, plates I-VIII.
1891 Ueber Theorie und Praxis des freien Fluges. Zeitschrift fiir Luftschif.
fahrt. Berlin, X, Heft 7 u. 8, pp. 153-164.
i8gi Ueber meine diesjahrigen Flugversuche. Zeitschrift fiir Luftschif-
fahrt. Berlin, X, Heft 12, pp. 286-291.
1892 Ueber die Mechanik im Dienste der Flugtechnik. Zeitschrift fiir Luftt
schiffahrt und Physik der Atmosphare. Berlin, XI, Heft 7 u. 8, pp.
180-186.
1892 Ueber den Segelflug und seine Nachahmung. Zeitschrift fiir Luft-
schiffahrt und Physik der Atmosphare. Berlin, XI, Heft 11, pp. 277-281.
1893 Die gewolbten Flugelrlachen vor dem oestreichischen Ingenieur- und
Architekten Verein. Zeitschrift fiir Luftschiffahrt und Physik der At-
mosphare. Berlin, XII, Heft 3/4, pp. 8S-90.
1893 Die Flugmaschinen des Mr. Hargrave. Zeitschrift fiir Luftschiffahrt
und Physik der Atmosphare. Berlin, XII, Heft 5, pp. 114-118.
1893 Ein begeisterter Flugtechniker in Chile. Zeitschrift fiir Luftschiffahrt
und Physik der Atmosphare. Berlin, XII, Heft 5, p. 126.
1893 Zur zweiten Auflage Buttenstedts " Flugprincip." Zeitschrift fiir Luft-
schiffahrt und Physik der Atmosphare. Berlin, XII, Heft 6, pp. 143-145.
1893 Ueber Schraubenflieger. Zeitschrift fiir Luftschiffahrt und Physik der
Atmosphare. Berlin, XI, Heft 9, pp. 228-230.
1893 Die Tragfahigkeit gewdlbter Fliichen beim praktischen Segelrluge.
Zeitschrift fiir Luftschiffahrt und Physik der Atmosphare. Berlin, XII,
Heft 11, pp. 259-272.
1893 Die Tragfahigkeit gewdlbter Flachen beim praktischen Segelfluge. Sep-
aratabdruck aus Nr. 11 der Zeitschrift fiir Luftschiffahrt und Physik der
Atmosphare. November, pp. 259-272.
1894 Allgemeine Gesichtspunkte bei Herstellung und Anwendung von Flug.
apparaten, Zeitschrift fiir Luftschiffahrt und Physik der Atmosphare.
Berlin, XIII, Heft 6, pp. 143-155.
1894 Maxim's Flugmaschine. Zeitschrift fiir Luftschiffahrt und Physik der
Atmosphare. Berlin, XIII, Heft 10, pp. 272-273.
1894 Wellner's weitere luftschrauben-Versuche. Zeitschrift fiir Luftschiffahrt
und Physik der Atmosphare. Berlin, XIII, Heft 12, pp. 334-336.
1895 Resultate der praktischen Segelradversuche Prof. Wellner's. Zeitschrift
fiir Luftschiffahrt und Physik der Atmosphare. Berlin, XIV, Heft 1,
pp. 25-26.
1895 Die Profile der Segelflachen und ihre Wirkung. Zeitschrift fiir Luft-
schiffahrt und Physik der Atmosphare. Berlin, XIV, Heft 2/3, pp. 42-57.
1895 Ueber die Ermittelung der besten Flugelformen. Zeitschrift fiir Luft-
schiffahrt und Phystkder Atmosphare. Berlin, XIV, Heft 10, pp. 237-245.
1894 Lilienthal's Experiments in Flying. Nature, London, December 20,
vol. 51, No. 1312, pp. 177-179.
1894 Deux Lettres de M. Otto Lilienthal. L'Aeronaute, Paris, 27 Annee,
No. 12, December, pp. 267-270.
AERIAL LOCOMOTION 447
1894 Principes GeneVaux a Considerer dans la Construction et l'emploi des
appareils de vol de M. Otto Lilienthal. L'AeYonaute, Paris, 27 Anne>,
No. 12, December, pp. 270-274.
1894 Die Flugapparate, Berlin, Sonderabdruck aus Nr. 6 der Zeitschrift fiir
Luftechiffahrt und Physik der Atmosphare. Berlin, pp. 3-15.
1895 Les Experiences de M. Lilienthal par M. P. Lauriol. Revue de L'Aero-
nautique, 8 Annee, ire Livraison, pp. 1-10.
i8g6 Practical Experiments for the Development of Human Flight. The
Aeronautical Annual, No. 2, Boston, pp. 7-22.
1897 At Rhinow. The Aeronautical Annual, No. 3, Boston, pp. 92-94.
1897 The Best Shapes for Wings. The Aeronautical Annual, Boston, No. 3,
PP- 95-97-
1897 Der Kunstrlug. In : Taschenbuch f. Flugtechniker 2.
1894 Aurl., Berlin (313-321).
Hargrave, Lawrence
1889 Flying Machine Memoranda. Journal and Proceedings of the Royal
Society of New South Wales, Sydney, vol. XXIII, part 1, pages 70-74.
1890 On a Compressed-air Flying-machine. Journal and Proceedings of the
Royal Society of New South Wales, Sydney, vol. XXIV, part 1, pages
52-57-
1892 Flying-Machine Work and the 1/6 I. H. P. Steam Motor Weighing 2>lA
lbs. (Reprint). Journal and Proceedings of the Royal Society of New
South Wales, vol. XXVI, pages 170-175.
1892 Flying-Machine Work and the 1/6 I. H. P. Steam Motor Weighing 3%
lbs. Journal and Proceedings of the Royal Society of New South Wales,
Sydney, vol. XXVI, pages 170-175.
1896 On the Cellular Kite. (Reprint.) Journal and Proceedings of the
Royal Society of New South Wales, vol. XXX, pages 1-4.
1898 "Aeronautics." (Reprint.) Journal and Proceedings of the Royal
Society of New South Wales, vol. XXXII, pages 55-65.
1903 Hargrave's Versuche, 111. aeron. Mitt., Strassburg, 7, (366-370).
Herring, A. M.
1896 Dynamic Flight. Aeronautical Annual, Boston, No. 2, pp. 89-101.
1897 Recent Advances Toward a Solution of the Problem of the Century.
Aeronautical Annual, Boston, No. 3, pp. 54-74.
1899 Die Regulirung von Flugmaschinen. Zeitschrift fiir Luftschiftahrt
und Physik der Atmosphare. Berlin, XVIII, Heft 9, pp. 205-211.
1899 Einige sehr leichte Benzin- und Dampfmotoren. Zeitschrift fiir Luft-
schiffahrt und Physik der Atmosphare. Berlin, XIX. Heft 1, pp. 1-4.
44»
BELL
List of Articles Relating to Aeronautics Published by the
Smithsonian Institution.
No.
Author.
Arago, Francis...
789
8oi
Glaisher, James...
Wenham, F. H. ..
Langley, S. P. ...
884
Langley, S. P. ...
938
Lilienthal.Otto...
"34
"35
Huffaker, E. C...
1 149
1 197
1248
Bacon, John M ...
1267
1268
Janssen, J
1269
1270
1352
Curtis,Thomas E.
Lyle, E. P., Jr....
1358
1379
Baden-Powell,
Maj. B. F. S.
1380
H43
Wright, Wilbur...
Pettigrew, Jas.
Bell
1494
M95
1496
1597
Baden-Powell,
Maj. B.
Langley, S. P ,,,
1598
von Lendenfeld,
R
Title.
Aeronautic Voyages performed with a
view to the advancement of science.
An Account of Balloon Ascensions.
On Aerial Locomotion
Experiments in Aerodynamics
The Internal Work of the Wind
Where Published.
The Problem of Flying and Prac-
tical Experiments in Soaring.
Story of Experiments in Mechan-
ical Flight
On Soaring Flight
Letters from the Andr^e Party ,
Scientific Ballooning
Count Von Zeppelin's Dirigible Air
Ship ,
The Progress of Aeronautics
Lord Rayleigh on Flight ,
The Langley Aerodrome (Note pre-
pared for the conversazione of the j
Amer. Inst, of Elec. Engineers,
New York City, April 12, 1901).
The Zeppelin Air Ship
Santos-Dumont Circling the Eiffel
Tower in an Air Ship
The Greatest Flying Creature
Recent Aeronautical Progress, and
Deductions to be drawn therefrom
regarding the Future of Aerial
Navigation.
Some Aeronautical Experiments
On the Various Modes of Flight in
Relation to Aeronautics
Progress with Air Ships
Aerial Navigation
Graham Bell's Tetrahedral Kites
Experiments with the Langley Aero-
drome
Relation of Wing Surface to Weight. Report, 1904
Report, 1863.
Report, 1863.
Report, 1889.
Cont. to knowl-
edge, Vol. 27.
Cont. to knowl-
edge, Vol. 27.
Report, 1893.
Report, 1897.
Report, 1897.
Report, 1897.
Report, 1898.
Report, 1899.
Report, 1900.
Report, 1900.
Report, 1900.
Report, 1900.
Report, 1901.
Report, 1 901.
Report, 1902
Report, 1902
Report, 1867
Report, 1903
Report, 1903
Report, 1903
Report, 1904
Proc. Wash. Acad. Sci.. Vol. VIII
Plate IX.
I.ilienthal Gliding Machine as reproduced in America for Chanute by Herring.
Gliding through the air on Chanute's Multiple-winged Glider.
Proc. Wash. Acad. Sci., Vol. VIII.
Plate X.
Langley's Aerodrome No. 5 in flight, May 6, 1896.
From instantaneous photograph by Alexander Graham Bell.
Proc. Wash. Acad. Sci., Vol. VIII.
Plate XI.
* 5?
» 3
ft fl*
< O
5'c
5-i f
r 3- (0
8 t B
?3 =2.
° s> n>
3-3* ^.
O J U)
^ n >
* 2 rt:
Proc. Wash. Acad. Sci., Vol. VIII.
PlatejXII.
o
kLf „ i^^^
i
'^i*000*
M.
A
V
1
Si
^1
• i^ii
It
Proc. Wash. Acad. Sci., Vol. VIII.
Plate XlH.
n W
2. crq
5 K
r» **
Proc. Wash. Acad. Sci., Vol. VIII.
Plate XIV.
Proc. Wash. Acad. Sci., Vol. VIM
Plate XV.
The Frost King in the air, flying in a ten-mile breeze, and supporting a man on the flying rope.
During the experiment the rope straightened under the pull of the kite, and the man was raised to a height nfM ™-
&&£s^^S^SSS^&Sff. brought doWD safely- »«££<ff&S2££*&£i&
Proc. Wash. Acad. Sci.. Vol. VIII.
Plate XVI.
r,
P5P C/5
52 3
5'
35 2
m
Proc. Wash. Acad. Sci., Vol. VIII.
Plate XVII.
~ ">
to
•O c
3-1
° 2 —
2. O
He °
3 ">
Proc. Wash. Acad. Sci., Vol. VIII.
Plate XVIII.
A Floating Kite, adapted to be towed out of the water.
Kite consistsof a bridge, ortruss, of tetrahedral celN with wings of Japanese waterproof piper upon two floats of
light framework covered with oilcloth. A stint towing pole extends laterally across the lower part of the wing-
piece at the front. Photograph by Douglas McCurdy. Illustration from the National Geographic Society.
Proc. Wash. Acad. Sci., Vol. VIII.
Plate XIX.
1
The French Military Dirigible, " Patrie," in flight.
The latest French airship. " La Patrie," is ,i,v, feet in diameter by 196 feet long, and has a capacity ot 111,195 cubic feet.
Driven by a 70-horsepower motor and two propellers, this dirigible has recently made about 30 miles an hour. Its
lifting capacity is 2,777 pounds. Illustration from the Scientific American.
The New Deutsch Airship, " Ville de Paris," the latest dirigible balloon.
The peculiar arrangement of twin, hydrogen-filled cylinders forms a sort of balancing tail. This airship has a length
of 60 meters (196.85 feet) and a diameter of 10. S meters (35.43 feet) while its capacity is 3,000 cubic meters (105,943 cubic
feet). Its propellers are placed on either side of the body framework, or " nacelle," and at about the center of the
latter, which is boat-shaped. The weight which can be carried, outside of the equipment and the fuel sufficient for
a ten hours' run, is about 1,100 pounds. A 70-horsepower Panhard motor is used. Illustration from the Scientific
A merican.
Proc. Wash. Acad. Sci.. Vol. VIII.
Plate XX.
Count Von Zeppelin's Airship— the largest and fastest thus far constructed — coming out of its shed
and performing various evolutions above Lake Constance.
{.This airship, which is 38 feet in diameter by 410 feet in length and which lias a capacity of 367,120 cubic feet, held itself
., stationary against a 33'2-mile-an-hour wind in January last, by means ol two 35-horsepower gasoline motors driv-
ing four propellers. The airship can lift three tons additional to its own weight, which gives it a radius of 3,0:0
miles at 31 miles an hour. On October 11, 1906, Count Zeppelin maneuvered this dirigible balloon above Lake
Geneva, ascending to a height of 2.500 feet and steering the huge cigar-shaped ai'-rostat very nicelv. The airship
is mounted on floats, so that it works equally well on the water. During one flight it remained in the air an hour
_^ and twenty minutes, although the steering-gear was caught in the skeleton framework and became partly unman-
i J ageable. The attempts proved also that the airship was dirigible in spite of its great size, as several complete
t .. circles were made while in the air. Illustrations from the Scientific American.
PROCEEDINGS
OF THE
WASHINGTON ACADEMY OF SCIENCES
Vol. VIII, pp. 449-458. Plates XXI-XXIII March 4, 1907.
ON A COLLECTION OF FISHES FROM
BUENOS AIRES.1
By Carl H. Eigenmann.
The present paper is a report on a collection of fishes obtained
near Buenos Aires, Argentina, by Prof. W. B. Scott, of Prince-
ton University. The collection adds several species to the La
Plata fauna. These are marked*. Four of these species are
new. The types are in the Museum of Princeton University, and
a series of cotypes and duplicates is in the Museum of Indiana
University.
The fresh-water fish fauna of Buenos Aires is essentially
Amazonian and in striking contrast to the fresh-water fauna of
North America of corresponding latitude and equally remote
from the mouth of the Amazon which lies on the equator.
None of the Amazon genera has passed much beyond the
borders of the United States. Most of them do not reach
beyond Panama. The Paraguay, whose sources are in contact
with those of the Tapajos and Madeira, southern tributaries of
the Amazon, has provided an easy and open road for the
Amazon fauna to the Lower Parana and La Plata. But few
Amazon types extend south of Buenos Aires.
silurid^:.
Luciopimelodus pati Valenciennes.
One specimen.
Pseudaplatystoma coruscans Agassiz.
One specimen.
* Contributions from the Zoological Laboratory of Indiana University, No.
80.
Proc. Wash. Acad. Sci., March, 1907. 449
450 EIGENMANN
Rhamdia quelen Qiioy & Gaimard.
One specimen.
Pimelodus clarias macrospila Giinther.
Two specimens, each with 3 series of large spots.
Pimelodus albicans Valenciennes.
One specimen.
Pimelodus valenciennis Kroyer.
Four specimens.
Iheringichthys labrosus (Kroyer).
Several specimens.
Doras granulosus Valenciennes.
A single specimen, 470 mm. long.
Lateral line 22, the hooks of the lateral plates beginning
under the end of the dorsal.
LORICARIID^
Plecostomus commersoni Cuvier & Valenciennes.
Four specimens.
* Plecostomus laplatae Eigenmann, new species. (Plate XXI.)
Depth 5 in length; head 3.4 (3.28 in cotype) ; D. 1, 7 (not
counting the fulcrum); A. 1, 4 ; scutes 31 -f 1 caudal scute;
depth of head 1.75 (1.66) ; width of head 1.2 in its length (1 + ) ;
length of snout equaling depth of head (1.5 in head); inter-
orbital 2.8 in head (2.66); length of mandibular ramus 3 in
interorbital (2 + ) ; barbel more than half length of eye; snout
spatulate, rounded ; supraorbital margin not raised ; supraoccip-
ital ridge very feeble, temporal plates not carinate ; scutes of
sides little keeled, spinulose, 7 between dorsal and adipose, 14
to 16 between anal and caudal ; supraoccipital bordered by a
median and two or three lateral scutes. Lower surface of head
and belly entirely granulose in the type, partly naked between
the base of pectoral and ventral. First dorsal ray about equal
to length of head, last ray .66 (.5) length of head ; base of dor-
sal equal to its distance from end of second scute beyond tip of
adipose spine ; pectoral extending to second sixth of the ventrals ;
caudal distinctly emarginate ; caudal peduncle a little more than
3 times as long as deep.
COLLECTION OF FISHES FROM BUENOS AIRES 45 1
Color of type : Sides, ventral surface and head profusely
spotted, the spots largest on the belly, minute on the head ;
lightish streaks along the lateral keels ; dorsal dusky with one
or two rows of spots between every two rays ; caudal unspotted,
the lower part dusky ; anal dark, unspotted ; ventrals and pec-
torals dusky, the former with large spots, the basal two thirds
of the latter with very numerous minute spots similar to those
of head.
Color of cotype : Ventral surface plain ; sides with obscure
large spots, the light streaks along the keels much more evi-
dent ; head profusely covered with spots much larger than those
in the type ; dorsal with a series of large spots on the posterior
half of each interradial membrane ; caudal sooty, anal obscurely
spotted ; entire upper surfaces of ventrals and pectorals spotted,
the spots of the pectoral more numerous and smaller, but not as
small as those of the head.
Apparently related to Plecostomus carinatus vaillanti and
tietensis.
Type in Mus. Princeton Univ., a specimen 410 mm. long,
from Buenos Aires; coll. Prof. W. B. Scott. Cotype, no.
11351, Mus. Ind. Univ., a specimen 214 mm. long, from same
place.
Loricaria vetula Cuvier & Valenciennes. (Plate XXII.)
One specimen.
Loricaria anus Cuvier & Valenciennes.
Six specimens.
These specimens have the lateral keels separate to the last 3
or 4 scutes ; the dorsal without spots but with the second half
of the membrane dark.
CHARACID^.
Curimatus platanus Giinther.
One specimen.
Curimatus gilberti Quoy & Gaimard.
Two specimens.
Prochilodus lineatus (Valenciennes).
Six specimens, the largest 430 mm.
45 2
EIGENMANN
Leporinus obtusidens (Valenciennes).
One specimen. Depth 3.5; head 4.33; interorbital equals
snout ; snout conical ; teeth short, truncate ; lateral spots ob-
scure, vertical, the caudal spot most prominent; anal concave,
the second and third ray reaching much beyond the tip of the
last, nearly to caudal.
Astyanax rutilus (Jenyns).
Five specimens.
D. 11 ; A. 28 in one, 30 in the others; scales 6 or 7-37 to
39-5 to 7.
* Acestrorhamphus brachycephalus (Cope).
One specimen. D. 10; A. 26 ; head 3.75 ; depth 3.33 ; eye
4 in head; scales 1 1-55-9.
Acestrorhamphus hepsetus (Cuvier).
One specimen.
* Acestrorhamphus ferox (Giinther).
One specimen.
Salminus maxillosus (Cuvier & Valenciennes).
Three specimens.
In the older ones the dark lateral lines are much more con-
spicuous than in the younger.
Serrasalmo marginatus Valenciennes.
Two specimens.
Hoplias malabaricus (Bloch).
Two specimens.
clupeid^:.
Pomolobus ? melanostomus Eigenmann, new species. (Plate
XXIII, Fig. 6.)
I am not sure of the identification of this species. It differs
from the other American relatives of Clufea in having the
dorsal inserted behind the ventrals.
D. 13 to 16 ; A. 17 to 20 ; head 4.5 to 5 ; depth 3.33 to 3.66 ;
ventral serrae strong, beginning near posterior margin of pre-
opercle, 26-29. -^ye a ntt^e longer than snout, 3 to 3.5 in head ;
mouth oblique, the lower jaw included ; maxillary extending a
little beyond front of eye ; gillrakers about two thirds as long
as eye ; no teeth on vomer ; alimentary canal short, peritoneum
COLLECTION OF FISHES FROM BUENOS AIRES 453
white ; dorsal short, its origin over some part of the last third of
the ventrals, a little nearer caudal than tip of snout. Scales
caducous, crenulate.
A dark band along the entire back, median predorsal line
free from pigment ; a faint dusky streak along the upper part
of the side to the middle of caudal ; no humeral spot ; upper
lip black, tip of snout and lower jaw dusky ; sides of head and
body without pigment cells.
The reproductive organs indicate that the larger specimens
are mature.
Type in Mus. Princeton Univ., a specimen 85 mm. long,
from Buenos Aires; coll. Prof. W. B. Scott. Cotypes in the
collections of Princeton and Indiana Universities (No. 11364,
Mus. Ind. Univ.), 14 specimens 58 to 85 mm. long, from same
place.
STOLEPHORID^).
Ilisha flavipinnis (Valenciennes).
Two specimens.
Stolephorus olidus Gtinther.
Seven specimens.
Upper margin of silvery band well denned, the lower margin
not, the silvery area in the adult covering the entire sides. Anal
about 26; depth about 5.5 (4.5 in the types).
MUGILID^.
Mugil platanus Giinther.
Five specimens. These agree with Giinther's description,
except that in the three better preserved specimens and the
smallest the upper half of the base of the pectoral is black, the
rest of the fin uniform.
ATHERINID^.
Atherinichthys bonariensis Cuvier & Valenciennes.
Four specimens.
Atherinichthys argentinensis Cuvier & Valenciennes.
Origin of spinous dorsal behind anus. A. 1, 15 ; scales 50,
8 between dorsal and anal ; depth 6.5 to base of caudal ; head
4.33 ; scales rounded behind; pectorals equal head less mouth ;
lateral band one sixth depth of body.
454 EIGENMANN
sci^nid^:.
Pachyurus bonariensis Steindachner.
Many specimens.
cichlid^:.
Heros autochthon Giinther.
Two specimens.
Geophagus australe Eigenmann, new species. (Plate XXIII,
Fig. 7-)
Closely related to G. duodecimspinosum = balzanii, from the
Paraguay. It differs from that species in the more pointed
snout, less steep profile, more rapidly descending dorsal slope,
longer, more slender caudal peduncle, narrower interorbital,
etc. It differs from its next nearest relative, G. gymdogenys, in
the scales of the cheek and in the color.
Head 3 to 3.16; depth 2 to 2.4; D. xn to xiv, 10 or 11;
A. in, 8 ; lateral line 28 to 30 (16 to 18 + 10 to 12) ; 25 to 27
scales along the middle of the side.
Subrhomboidal ; dorsal outline unequally arched, the highest
point at the origin of the dorsal. In G. balzanii the dorsal profile
is much more regularly arched from the tip of snout to end of
dorsal ; anterior profile convex in front of dorsal, nearly stra'ght
on head ; caudal peduncle rather long and slender, its depth 1
to 1.33 in its length ; interorbital very convex, the bony portion
3.5 in the head (2.5 in balzanii) ; cheeks with 3 series of scales
on their upper part, the lower portion naked (about 7 series in
balzanii) ; 7 or 8 tubercular gillrakers on lower half of arch ;
a single complete series of scales on the subopercle with a few
scales forming an imperfect second series below them. Eye 4
to 4.5 in head ; nares half way between tip of snout and eye
(distance of nares from tip of snout 1.6 in their distance from
eye in balzanii).
Ventrals reaching the anal papilla or slightly beyond origin
of anal ; pectoral reaching to first anal spine or first anal ray ;
soft dorsal and anal high, reaching considerably beyond base of
caudal ; caudal lunate or but slightly emarginate, its base much
less densely scaled than in G. balzanii ; bases of dorsal and anal
with few scales ; fold of the lower lip not continuous.
A dark area across back in front of the dorsal ; bases of some
COLLECTION OF FISHES FROM BUENOS AIRES 455
of the scales of the back frequently very dark brown ; side with
about 6 cross-bands, each of those on middle of side composed
of double dark lines with a band of light of equal width between
them ; no dark spot on side ; pectoral light ; ventrals blue-
black ; dorsal dusky, with ascending light stripes which are
largely replaced by light spots on the soft dorsal ; caudal dusky,
with round hyaline spots on the rays similar to those on soft
dorsal ; anal with similar but smaller and less distinct spots ; no
spot or ocellus on the caudal.
Type in Mus. Princeton Univ., a specimen 155 mm. long,
from Buenos Aires ; coll. Prof. W. B. Scott. Cotypes in
Princeton and Indiana Universities (no. 11352, Mus. Ind.
Univ.), 6 specimens 100 to 150 mm. long, from same locality.
Batrachops scottii Eigenmann, new species. (Plate XXIII,
Fig. 8).
? Crenicichla semifasciata Pellegrin (not Heckel) Cichlides,
339, 1904 (Buenos Aires; Montevideo).
This species is closely related to semifasciata of Heckel, from
which it differs conspicuously in color. B. semifasciatus was
described from specimens collected in the Paraguay River
at Caigara in Matto Grosso. No other specimens have been
found unless those recorded by Pellegrin belong to semifasciatus.
The two species may be distinguished as follows :
a. D. xxii, 10; A. in, 7 ; lateral line 25+ 12; scales 56 or 57;
greatest thickness 1.25 in greatest height which is 5 in the
total length ; depth of caudal peduncle equals five eights of
the greatest depth ; eye 1.5 diameters behind tip of lower jaw,
5.5 in head ; suborbital one third the diameter of eye ; peroper-
cular margin turned forward ; a dark band from eye to opercle,
7 or S dark lines from base of dorsal to middle of side, darkest
below lateral line and fading out below; a dark ocellus on
base of caudal ; each scale of the side yellow, with a dark
brown margin ; fins without spots, semifasciatus.
aa. D. xxi or xxn, 13; A. in, S or 9; lateral line 25 + 14; scales
57; head 3.4 to 3.5 ; depth 4 to 4.5; greatest thickness 1.5
in greatest depth ; depth of caudal peduncle 2 in greatest
depth; eye 2.5 diameters behind tip of lower jaw, 5.5 to 7
in the head ; preorbital 1 (in adult) to 2 (in youngest) in
the eye ; peropercular margin slanting obliquely backward ;
Proc. Wash. Acad. Sci., March, 1907.
456 E-IGENMANN
tips of dorsal and anal reaching caudal ; a dusky shade from eye
to edge of opercle continued faintly in the young to the caudal ;
very conspicuous markings extending from eye down and
' back ; they consist first of a black blotch followed by two or
four parallel black lines, these followed after an interval by
one to 5 similar ones and these again in some specimens by
other similar ones ; back to the lateral line in the young with
very obscure cross shades ; side, and in the adult the back
also, with light stripes along the middle of the scales and
prominent zigzag dark stripes between each two rows of
scales ; entire dorsal and base of anal spotted ; caudal ob-
scurely spotted ; pectorals and ventrals plain.
The black markings below the eye are so unique and con-
spicuous that they attract the attention at once and give the
impression of India ink pen strokes.
I take great pleasure in dedicating this species to the collector,
Prof. W. B. Scott, of Princeton University.
Type in Mus. Princeton Univ., a specimen 280 mm. long,
from Buenos Aires ; coll. Prof. W. B. Scott. Cotypes in
Princeton and Indiana Universities (No. 11420, Mus. Ind.
Univ.), 145 to 165 mm. long, from same place.
PLEURONECTID^.
Achirus lineatus (Linnaeus).
Two specimens.
458 COLLECTION OF FISHES FROM BUENOS AIRES
EXPLANATION OF FIGURES.
1-3. Plecostomns la f lata Eigenmann, type.
4-5. Loricaria vetula Cuvier & Valenciennes.
6. Pomolobus 7nelanostomus Eigenmann, type.
7. Geophagus australe Eigenmann, type.
S. Batrachofs scotti Eigenmann, type.
Proc. Wash. Acad. Sci., Vol. VIII.
Plate XXI
FIGS. 1-3. PLACOSTOMUS LAPLAT/E EIGENMANN, NEW SPECIES.
Proc. Wash. Acad. Sci., Vol. VIII.
Plate XXII.
FIGS. 4 & 5. LORICARIA VETULA CUVIER & VALENCIENNES.
Proc. Wash. Acad. Sci.. Vol. VIM.
Plate XXI
FIG 6. POMOLOBUS MELANOSTOMUS EIGENMANN, NEW SPECIES.
W*^"^^^
w cms ,
fi&iS^r -^*»>
_grf
ax^^r
1£1-
KhK^M^i
FIG. 7. GEOPHAGUS AUSTRALE EIGENMANN, NEW SPECIES.
FIG. 8. BATRACHOPS SCOTTII EIGENMANN, NEW SPECIES.
PROCEEDINGS
OF THE
WASHINGTON ACADEMY OF SCIENCES
Vol. VIII, pp. 459-486. pls. xxiv-xxviii March 6, 1907.
HISTOLOGY AND DEVELOPMENT OF THE DIVIDED
EYES OF CERTAIN INSECTS.
By George Daniel Shafer.
Exner, 1891, Zimmer, 1897, and Kellogg, 1898, 1900, and
1903, have discussed the divided-eye condition of certain crus-
taceans and insects. It is the purpose of the following paper:
1. To describe the histological structure of the divided com-
pound eyes of Sympetriim corrupta, Anax Junius, Dibio hirtus,
two species of Blepharoceridaj and two species of CaHibcetis.
2. To describe the development of the large-facetted area of
the eye in CaHibcetis and Sympctrum corrupta.
3. To refer briefly to the significance of the divided-eye con-
dition in these eyes.
This investigation was made in the Entomological Laboratory
of Stanford University, under the direction of Prof. V. L.
Kellogg. I wish here to thank Professor Kellogg, Mr. Doan
and Miss McCracken for help in the laboratory ; also Professor
Aldrich, Dr. Needham and Mr. Grinnell for identifying some
of the material used.
SYMPETRUM CORRUPTA Hagen.
The compound eyes of Sympctrum corrupta, as shown in
Fig. 1, Plate XXIV, are divided by a curved line into almost
equal upper and lower parts. The lower half of the eye is
dark and a good hand lens shows it to be made up of very
small facets. The upper half is lighter in color and made up
Proc. Wash. Acad. Sci., March, 1907. 459
46O SHAFER
of larger facets. Longitudinal sections of the ommatidia of
both these parts of the eye may be obtained by making vertical
cross-sections, or by making longitudinal sagittal sections of
the head. Fig. 2 shows a vertical section passing through both
the upper and the lower portions of the eye. Most of the eye
elements are cut longitudinally. A few in the region a, of the
upper part of the eye are represented in diagonal cross-section.
A glance at the figure makes clear the deeply pigmented condi-
tion of the narrow eye elements of the lower half as contrasted
with the less pigmented larger elements of the upper half of
the eye. There is no gradual transition in the pigmentation or
in the size of the eye elements. The line of division is as
sharp within the eye as it appears in the outside facet view.
No septum marks the division ; but with the first larger orama-
tidial element, passing toward the upper part of the eye, the
deep black iris pigment stops and a brownish less dense iris
pigment begins. This is true also of the deeper seated pig-
ments, but these are a little darker in color in the large element
half of the eye than in the iris pigment in the same part. Figs.
3 and 4 show some of the details of structure of the upper and
lower parts of the same eye. The corneal region is made up
of hexagonal lens-like segments each of which maybe called a
corneal lens. In vertical section each lens is seen to consist of
a thin cuticular portion and a thicker stratified layer just beneath.
The cuticular portion takes and retains nuclear stains well. The
under portion takes stains readily enough but gives them up easily.
No hypodermal cells or nuclei have been observed in the eye, but
the bases of the pseudocones lie close to the under portion of the
lens. The cells which compose these pseudocones have lost their
identity entirely in the lower portions, and nearly so in the
upper, outer, larger portion of the cones. However, in the
extreme upper ends, the cone cells have each secreted a denser
curved plate-like body within itself, and this stains deeply.
Four of these may be found in each pseudocone. Two are
shown in the longitudinal sections at en. Each plate appears
to surround a cell nucleus. In the case of the pseudocones of
the small ommatidial elements, cross-sections made just below
the little plates mentioned show four cells as represented in
DIVIDED EYES OF CERTAIN INSECTS 46 1
Fig. 3, B. Two of these cells are always larger than the
other two. Two of the plates of the pseudocones are always
larger when four are seen — sometimes only 2 can be found.
The pseudocones of the large ommatidia are wider, longer and
farther apart than those of the small ommatidia. Both have
relatively the same shape. The inner portion of each pseudo-
cone tapers nearly but not quite to a point. Each inner end is
really truncate and appears to have a funnel-like opening.
Extending along the line of the longitudinal axis of the pseudo-
cone and beginning immediately beneath the truncate cone tip
is the retinula. This has a darker rhabdome portion along the
axis from the tip of the pseudocone to the basement membrane.
The axis itself, however, is occupied by a very narrow light
band. Often, if the sections are jammed a little in the cutting,
the rhabdome portion takes a wavy form as shown in the frag-
ment at iv (Fig. 4, A). The retinulae of the large ommatidia
are wider, but no longer than those of the small ommatidia.
Immediately beneath the basement membrane, in all parts of
the eye is a network of tracheal vessels, 2 of which are shown
in cross-section at tr (Figs. 3, A, and 4, A). Under the tracheal
network is a narrow layer of retinular-like bodies rb (Figs. 3
and 4, A). These bodies have their long axes parallel with
each other, but not always exactly parallel to the retinular axes
above them. Some sections show a definite fibrous or continu-
ous cell connection between the ends of the retinula at the base-
ment membrane bm, and the upper outer ends of these retinular-
like bodies. These connecting strands are always narrower
than either the retinula or the retinular-like bodies, and they
curve around the tracheae, often, in order to make the connec-
tion. It seemed impossible to demonstrate the presence of
retinular nuclei satisfactorily in old adult eyes used, but they
were easily shown at rn (Fig. 4, A), in the eye of a young insect
dissected from an old nymph case when the adult was just
ready to issue.
Here and there along the upper part of some cells of the
retinular-like bodies large nuclei have been found («, Figs. 3
and 4, A). These nuclei appear larger than the ordinary pig-
ment cell nuclei. Whether they have any special significance
462 SHAFER
has not been determined. Cross-sections of the retinular-like
bodies under the large ommatidia are shown in Fig. 4, B.
Regularly, they appear as shown, with 4 cells — one large, 2
smaller and 1 very small cell. Cross-sections of the corre-
sponding retinula above show that the separate cells there have
almost lost their identity in the adult eyes ; but in the very
young teneral adult 4 nucleated cells may be seen (Fig. 4, C)
in cross-section. From the lower part of the retinular-like bodies
extend branching tree-like nerve fibers which break up into
brushes of fibrils at their inner ends.
The pigment of the region of the small ommatidia may be
described under 4 heads :
1. That grouped in dense black masses around the pseudo-
cones and already named the iris pigment. It is contained in 2
kinds of cells called by Grenacher, 1879, primary and secondary
pigment cells. The secondary cells are long, narrow and
closely packed around and among the pseudocones — their axes
lying parallel with the cone axes. Around cross-sections of
the upper parts of the cones 20 to 22 of these pigment cells may
be counted in a circle touching the outer boundary of the cone
(Fig. 3, B, sip). In the sections near the inner tapering tip of
the cone as few as 14 pigment cells have been counted touching
the cone. Below that the separate cells could not be counted,
but they are packed all the way between the different pseudo-
cones, being densest on the middle plane of the cone. There
are 2 chief pigment cells for each eye element. They are
short and thin and the 2 encircle the cone tip (Figs. 3 and 4, A).
2. Pigment occupies the retinula and the cells between the
retinula from the apex of the cones to the basement membrane.
Beginning near the distal ends of the retinula this pigment
becomes denser and denser toward the basement membrane
until a plane (ee, Fig. 3, A), is reached a little below the mid-
dle of the retinula. From this plane to the basement membrane
the pigment is again less dense.
3. A band of dense black pigment lines the basement mem-
brane and on the inner side of this membrane, extends down to
the distal ends of the retinular-like bodies. It is densest immedi-
ately beneath the basement membrane, around the trachea and
DIVIDED EYES OF CERTAIN INSECTS 463
in a thin band, /, which marks its lower boundary along the dis-
tal ends of the retinular-like bodies.
4. A black pigment similar to that along the retinula sur-
rounds the retinular-like bodies, and ends at the proximal ends
of these bodies in a narrow densely black band of pigment, gp
(Figs. 3 and 4, A). This in Sicyonia sculpa, has been named the
pigment or tapetum sheath of the optic ganglion by Exner, 1891.
The same description of pigment holds for the large omma-
tidial part of the eye except that the iris pigment and retinular
pigment in this case are brownish yellow and everywhere in
this part of the eye the pigment is very much less dense than
in the small ommatidial region.
ANAX JUNIUS Drury.
The facets of the compound eyes of the male of Anax Junius
are not all of the same size. Facets may be found that differ
as much in size as those of the different areas on the eye of
Sympetriim, but no line divides the eye of Anax into 2 regions.
In this case the larger facets are found on the upper and inner
surfaces of the eyes, and the smaller facets on the outer lower
margins. The 2 sizes grade into each other. It was not until sec-
tions were made of the eye that this condition was noticed. Fig.
12 was made from a cross-section of the head of a male Anax,
cut in a plane passing through the ocellus and perpendicular to
the facet area of the compound eye. The figure shows clearly
this gradation of the large facets on the upper inner part of the
eye into the smaller ones at the outer margin. As is shown also,
along with this gradation in the size of facets, the elements of
the ommatidia pass through a like gradation in size and length.
Moreover, a similar but reverse condition holds for the pigmen-
tation in this eye. Around the smaller shorter elements at the
outer margin of the eye the pigment is densest and occupies the
whole length of the retinula?. Passing toward the inner part of
the eye, the pigment becomes less and less dense around the
proximal ends of the retinula; until in the region of the largest
ommatidia almost no pigment is present except the iris pigment.
Other than this difference in size and pigmentation, the large
and small ommatidia are very similar as may be seen in Figs.
464 SHAFER
13, A, and 14, A. Beneath the corneal lenses and lying above
the distal ends of the pseudocones is a distinct hypodermal
layer. In longitudinal section, two apparent nuclei are present
above each pseudocone, sn (Figs. 13 and 14, A). The pseudo-
cone itself has a structure similar to that of Sympetrium, its upper
part showing still the boundaries of 4 cells which may be seen
in cross-section (Fig. 13, C).
Each retinula is made up of 4 retinular cells which enclose a
single rod-like rhabdome, rb (Figs. 13, A and B, and Figs.
14, A and B). The retinular cells of the ommatidia from the
2 extreme parts of the eye described vary, somewhat in shape (as
seen in Figs. 13, B, and 14, B) but there are always the 4 cells
present, each with its nucleus (Fig. 13, B). Extending up be-
tween the different retinulas and lying parallel with them are
many open spaces or lumina (Fig. 13, A, I). The smaller ends
of these extend even between the distal parts of the pseudocones
and their surrounding pigment cells (Fig. 13, C, I). The iris
pigment of this eye occupies cells of 2 types called by Grenacher
and others the primary or chief pigment cells and the secondary
pigment cells. Two primary pigment cells surround the small
proximal end of each pseudocone (Figs. 13 and 14, A, cifi).
These cells are shown as they appear in cross-section in Fig.
13, D, cfi. The nuclei of these cells have not been satisfactorily
seen although the nuclei of the retinular cells and secondary pig-
ment cells in the same sections were deeply stained and easily
seen. Eight to 10 pigment cells have been counted around
each pseudocone. They are longer and more slender than the
primary cells around which they lie, and they extend down a
little between the distal ends of the retinulas (Figs. 13 and 14
A, nsp). As has already been said, the pigmentation of the
smaller outer elements of the eye occupies the whole length of
the retinulge. This pigment lies in the retinular cells themselves,
and it is densest always in the distal half of the cells.
BIBIO HIRTUS Goef.
The compound eyes of the male Bibio are much larger than
those of the female. They nearly touch along the narrow front
and occupy almost the entire head. The whole facet area is
DIVIDED EYES OF CERTAIN INSECTS 465
thickly covered with slender hairs ' and the remarkable double
character of the eyes may be easily overlooked.
Indeed, it is only upon careful observation that the densely
black, small, facetted area is seen at all. If the head of the fly
is tilted back by lifting up the proboscis, a hand lens will show
the narrow black small facetted area on the extreme ventral
surface of the compound eye. This area is scarcely one sixth
that of the entire eye and is separated from the large facetted
upper surface by a narrow groove or offset. Fig. 11 shows the
position of the small facetted part of the eye. Fig. 8, perhaps,
shows better the relative extent of the 2 kinds of elements as
seen in longitudinal sagittal section. As shown in this Fig. 8,
the elements beneath the small facetted region are little more
than half the length of those under the large facets. Moreover,
the part occupied with small elements is densely pigmented.
The rest of the eye has but little pigment.
The elements of a large ommatidia consist of a thin cuticular
hexagonal facet, a pseudocone, a retinula, and iris pigment cells
surrounding the pseudocone. The cells of a pseudocone cannot
be distinguished from each other in the outer large part of the
cone. The lower truncate or slightly rounded apex of the cone
is a little denser than its upper part and this denser portion stains
more readily. Here the 4 cells making up the cone can be dis-
tinguished, each having its nucleus (Figs. 9 and 10, c«, and
Fig. 9, B). Cross-sections of the distal ends of 3 neighbor-
ing retinula? are shown in Fig. 9, C. Each retinula is made
up of 6 cells arranged in a circle around a seventh cell in the
center. The inner borders of each of the 6 cells has a rounded
deeply stained rhabdomere (as this part of the eye was named
by Grenacher, 1879). The rhabdomere of the seventh cell oc-
cupies the axis of the retinula. At their distal ends the 6 retin-
ular cells overlap entirely the rounded denser apex of the pseu-
docone, d (Figs. 9, A, and 10). The seventh cell, together
with its rhabdomere and those of the other 6 cells, stop snugly
against the inner end of the pseudocone. Near the middle part
1 Whether these apparent tactile hairs, which cover the eve of Bibio so densely
and are found on the eye of Blephorocera less abundantly, are really supplied
with tactile sense organs has not been determined bv me.
466 SHAFER
of the retinula this seventh cell, which is entirely surrounded at
its distal end, is found squeezed out between the other 6 retinular
cells and is not here completely surrounded by them (Fig. 9, £).
This condition holds for the retinula for its entire proximal half.
It is true also that this seventh cell crops out in every case on
the same side of the retinula, namely, on that side of the re-
tinula turned toward the inner ventral angle of the eye. Fig.
9, D, shows 3 adjacent retinulae in cross-section in the region
of the nuclei. These nuclei are long-elliptical in shape (Fig.
9, A, rn), and in cross-section they are not all the same size,
since some are cut near the middle and some near their ends.
In the cross-section of every retinula, however, the nucleus of
the narrow seventh cell may be found near its outer margin
(Fig. 9, Z>, 7«). The rhabdomeres are all smaller at the prox-
imal end of the retinula, but they are always 7 in number, the
odd one occupying the axial position at the inner part of the
narrow seventh cell. These facts, taken with that of the con-
stant presence of the seventh nucleus, make it certain that this
peculiar seventh structure is truly a retinular cell whose distal
end is entirely surrounded by the corresponding ends of its 6
companions. The proximal ends of the retinulae are bounded
by a very thin basement membrane, bm (Figs. 9, A, and 10).
A little beneath this membrane spreads a somewhat thicker
granular tapetum, tp (Figs. 9 and 10), and immediately under
this is a network of tracheae, tr. Leading from the inner prox-
imal end of each retinula through the basement membrane, the
tapetum, and between the tracheae is a narrow bundle of nerve
fibers, which are soon lost in a fine granular layer, gr (Figs.
9, A, and 10), just within the trachial network.
The iris pigment of the large element part of the eye is com-
paratively slight. It is contained in narrow pigment cells, nsp
(Figs. 9 and 10), which surround the pseudocones and extend a
little way down between the retinulae. Fig. 9, C, sip shows
the arrangement of these cells between the retinulae. The
proximal three fourths of the retinulae have no pigment cells
around them at all and the retinulae themselves touch each other
(Fig. 9, D).
The conditions described above also hold for the small eye
DIVIDED EYES OF CERTAIN INSECTS 467
elements with the following exceptions. The cuticular facets
of this portion of the eye are much denser than those above the
large elements. The iris pigment is black and extremely dense.
A heavy black pigment occupies the retinular cells throughout
their entire length. Drawing 10 was made from a section
that had been depigmented with cone, nitric acid and absolute
alcohol, equal parts. The tapetum and the basement mem-
brane in this part of the eye are always a little farther apart
than in the large element region. Under the trachea and
between the nerve strands that lead down from the retinulse of
both the large and the small elements are numerous large round
or oval nuclei which stain deeply {gn, Figs. 9 and 10, A). No
pigment is present around these nuclei. It might be added
here that cross-sections of the retinulae of the small ommatidia
did not show the number of retinular cells present so clearly as
those cut across the large ommatidia. Judging from the num-
ber of retinular nuclei however, the number of retinular cells is
the same in the retinular of both regions of the eye.
'BLEPHAROCERA CAPITATA Loew.
Kellogg, 1903, has called attention to the fact that both males
and females of the Blepharoceridas have divided compound eyes.
In all the genera described by Kellogg the large facetted area
of the eye is dorsal, and the small facetted deeply pigmented
area of the eye is lateral. Moreover, the dorsal area of the
female eye is greater than that of the male. Males and females
of species representing 2 genera (Blcpharocera capitata and
Bibioccfihala elcgantulus) were studied by me. The histolog-
ical structure of the eye elements in the 2 genera and in both
sexes is practically the same. The description and drawings
given here are taken from Blefiharocei'a capitata. Fig. 30 is a
microphotograph showing the optic ganglion, as well as the dorsal
and the lateral eyes of the right side of the head of this species.
It will be convenient hereafter to speak of the two areas as the
dorsal and the lateral eyes since they are separated from each
other by a narrow but distinct groove and the outer lobes of the
1 1 am glad to make reference to a recent preliminary note on the " Morphol-
ogy and Development of the Divided Eyes of Blepharocerca tenuipes'1'' by Dr.
Wm. A. Riley, in Science, Sept. 7, 1906.
468 SHAFER
optic ganglion beneath each area are distinct. The corneal
lenses over the greater part of the dorsal eye have been torn
from this section. The remaining 2 entire elements, however,
show the ommatidia in this dorsal eye to be about two and a
half times the length of those in the lateral eye. The lens and
the pseudocone of a dorsal ommatidia are continuous. That is,
the inner surface of the corneal lens is not noticeably separated
from its adjoining cone beneath. This is easily seen in micro-
photograph 29 and Fig. 15. The rounded apex of each of the
pseudocones is denser than the rest of the cone and stains
readily. Cross-sections through this denser apex show the
cone to be made of 4 cells and the nucleus of each cell is found
in this denser part (Fig. 15, A). In the outer larger part of
the cone the cell walls cannot be distinguished. Surrounding
the tip of each one are 2 very thin primary iris pigment cells
(Fig. 15, A, ci-fi). Outside of these, sheathing the distal part of
each cone and extending down between the retinulae are 22 to
24 slender secondary pigment cells (Fig. A, sip, and Fig. 29,
sip). A retinula in this eye is composed of 7 cells — 6 entirely
surrounding the seventh for its entire length. The rhabdomere
of each cell is distinct (Fig. 15, C, rb). The distal ends of the
retinular cells abut closely against the rounded cone tip and in
their extreme proximal ends just above the basement membrane,
lie the 7 large retinular nuclei (Fig. 15, A, rn). A definite
bundle of nerve fibers leads from the base of each retinula
through the basement membrane (Figs. 15, A and 29, nj).
The number and position of the cells in the ommatidia of the
lateral eye of this fly is the same as that just described for the
dorsal eye. The corneal lenses of the lateral eye are more
distinctly formed and the retinular cells as well as the iris pig-
ment cells (primary and secondary) are densely packed with
pigment. In the dorsal eye the pigmentation in the iris is very
slight and it is absent in the retinular cells of this eye.
CALLIByETIS HAGENI Etn.
Several references have already been made by different
investigators to the condition of the compound eyes of certain
mayflies (Pictet, 1845; Ciaccio, 1880; Carriere, 1893; and
DIVIDED EYES OF CERTAIN INSECTS 469
Zimmer, 1897). The large facetted dorsal eyes have been
called turban eyes and the smaller deeply pigmented eyes, the
lateral eyes. The females have only the small lateral pigmented
eyes. Zimmer, 1897, has given the histological structure of the
eyes of 7 genera of mayflies according to Pictet's classification
and he discussed also the physiological significance of the turban
eyes of these insects.
The structure of the eyes of Callibatis hageni differs in only
a few points from that given by Zimmer for Cloe fuscata Pict.
It will be well, however, to describe briefly the structure of the
eye in the adult male of Callibcetis hageni before taking up the
development of the turban eye in that species. Microphoto-
graph 24 (a cross-section through the head) shows the relative
size, position, pigmentation and the general structure of the
right turban and lateral eyes. The large and small eye ele-
ments are entirely separated here by a deep, rather wide, groove.
A single partly divided optic ganglion lies beneath the right
turban and lateral eyes and a similar ganglion beneath the left
eye o-pg in Figs. 23, 25 and 26. Drawings in Fig. 16 show
more clearly the structure of 2 entire elements of the turban eye.
The light-gathering or dioptric apparatus consists of a corneal
lens, 16 Ac, a cone, Aco, and a hypodermal space between the
lens and the cone, 16 Ahs. The cornea is made up of rather
distinct convex lenses, Ac, which are continuous with each other.
The outer third of each of these lenses appears to be denser
than the inner two thirds. The cone is composed of 4 crystaline
bodies so closely associated along their inner faces that they
appear in all except cross-sections as one solid cone body with
its slightly convex base facing the cornea. This is the eucone
type of Grenacher, 1879. The outer faces of each crystaline
body are surrounded by the less dense protoplasm of the mother
cone cell and in this protoplasm just distal to the base of the
cone are the cone cell nuclei (Fig. 16, A, en). The cross-sec-
tion made just distal to the cone base B, shows the 4 cone cells
and their nuclei. The hypodermal space contains no nuclei,
and it is filled by transparent fluid only. Zimmer demonstrated
2 nuclei in this space for Cloe. He did not figure the nuclei in
this space for the eye of Bcetis cerea Pict., or for that of Chiro-
470 SHAFER
tonetes ignotus Walk., but speaks of the space nevertheless as
being formed by 2 hypodermal cells.
Closely surrounding the entire length of the cone cells and
the hypodermal space are 20 to 22 secondary pigment cells
(Figs. 16, A, nsfi and B, sip). No primary pigment cells are
present. The distal ends of the secondary pigment cells touch
the cornea and their proximal ends are in contact with the
outer or distal retinula (Fig. 16, A, dm). It is proper to speak
of a distal retinula in this eye because there is also an inner or
proximal retinula -prn in each ommatidia — the 2 retinular parts
being connected by a very delicate strand (rs, Fig. 16, A).
Both proximal and distal retinulse are composed of 7 retinular
cells. Fig. 16, C, shows the 7 short distal retinular cells and
their nuclei. These cells surround the tip of the cone rosette
fashion. The proximal retinula is of about the same length as
the connecting strand. Fig. 16, D, shows the 7 nucleated cells
of this part in cross-section, and Fig. 16, E, is a similar section
near the middle part of a proximal retinula. The rhabdome in
its cross-section here is seen to be a 7-pointed star within a
circle which bears on its circumference 7-knobbed projections,
zv, radiating along the same lines as the points of the star and
lying between the boundaries of the retinular cells. The knobbed
parts, zv, are the secondary rods of Zimmer, 1897. This large
surfaced rhabdome terminates a little short of the outer end of
the proximal retinula in a single blunt rod tip as shown in Fig.
16, D. The outer end of the retinula therefore appears filled
with transparent liquid. Zimmer has described these transparent
ends in Cloe as " bladder trachea," and he figures no nuclei in
them. My sections of the turban eye of Callibcetis show the 7
nuclear structures present always, as represented in Fig. 16, D.
The inner faces of the distal retinular cells bear an extremely
thin rhabdome plate next to the tip of the cone (Fig. 16, C, drb).
Near the distal ends of the proximal retinula the connecting
strand, rs, breaks up, Fig. 16, A, into smaller strands which
seem to be continuous with the 7 secondary rods, zv of Fig. 16,
E. The connecting rods may be seen in the photograph no. 27.
The space around the rods, between the distal and proximal ret-
inulce, appears to be filled with an almost transparent liquid —
DIVIDED EYES OF CERTAIN INSECTS 47 1
tiny pigment granules being present in some sections. But these
may have been carried there by the razor. Upon the basement
membrane are short pigment cells which are sometimes above
the membrane between the proximal ends of the retinulae ; some-
times beneath the membrane between the nerve fibers, nf\ and
sometimes partly above, partly beneath the membrane. A
second delicate membrane k marks the lower limit of migration
of this pigment.
Fig. 17, A and B, show the structure of two ommatidiae in
the lateral pigmented eye of Callabcctis. One of the elements
is represented in its normal pigmented condition, the other de-
pigmented so that the position of nuclei maybe seen. The cor-
neal lenses in this eye are thin as compared with the turban eye
and their inner faces fit snugly upon the distal bases of the cones.
These cones are not as dense as those of the large elements
just described. They are 4 in number, however, and appear
to have the same density throughout. The cone cell nuclei en,
are found in the extreme distal base of the cone. In depig-
mented sections the nucleated distal ends of the retinular cells
may be seen touching the tip of the cone. There are 7 of these
retinular cells surrounding the rod-like rhabdome as represented
in Fig. 17, B. No primary iris pigment cells are present, and
there are but half the number of secondary pigment cells found
in the turban eye. The 11 cells (Fig. 17, B), which are present,
however, are densely pigmented, and they overlap the cones
and the upper retinular. The retinular cells are deeply pig-
mented through their entire length. Just beneath the basement
membrane is a narrow almost transparent granular tapetum and
under that an irregular broader band of pigment. So far, this
pigment has not been observed above the basement membrane
in the lateral eye. Nerve fibers «/"(Fig. 17, A) lead from the
inner ends of the retinula through the tapetum and the under-
lying pigment.
Another species of Callibcet/'s (probably californica) was
studied in connection with hageni. The latter is the larger of
the 2 species but the eye structure of the male of this smaller
form differs from that just described for hageni in but two par-
ticulars that are worth attention :
Proc. Wash. Acad. Sci., March, 1907.
472 SHAFER
1. The cornea of the turban eye of the smaller species is
thinner and its lenses less convex than those in C. hageni.
2. The retinular connecting strands in the eye of the smaller
species are about one and one third times longer than the prox-
imal retinulee. That is, the strands in this species are relatively
a third longer than they are in the eye of C. hageni.
DEVELOPMENT OF THE LARGE FACETTED EYE
AREA (TURBAN EYE) IN CALLIB^STIS Etn.,
AND IN SYMPETRUM CORRUPTA Hagen.
As is well known, the young of dragonflies and mayflies
pass through incomplete metamorphoses in their post-embry-
onic development, and the young of both live in fresh water.
Young nymphs of both species of Callibcetis and of S. cor-
rufita were collected from still or slowly running water near
Stanford University in March and reared to the adult stage in
the laboratory. In this way material was obtained representing
different stages in the development of the large facetted-eye
areas. Carriere, 1886, first briefly called attention to the origin
of the elements of the turban eye of mayflies from elongated
epithelial cells near the dorsal edge of the lateral eye. His
observations in the main agree with the following account.
All nymphs of Callibcztis under 4 mm. in length have only
lateral pigmented eyes. When the nymphs are 4 to 5 mm. long
however, the lateral eyes have about completed their develop-
ment. Then a narrow yellowish or light brown band appears
above the dorsal edge of each lateral eye of the male nymphs.
This marks the first noticeable beginning of the large facetted
eye, and cross-sections made of the head of such a nymph show
the hypodermis, just beneath the light brown band, to be made
up of modified long slender hypodermal cells with a second
layer of much shorter cells lying against their inner bases.
Already 2 membranes very close together are forming here.
One of these membranes (Fig. 21, A, k), marks the inner bound-
ary of the second layer of cells A, 2J111. The other membrane
A, dm, marks the inner boundary of the outer layer of modified
long hypodermal cells. The nuclei of some of the cells of the
second layer are above the membrane A, bm, and some are
DIVIDED EYES OF CERTAIN INSECTS 473
below it. These 2 membranes were found also beneath the
developing unpigmented ommatidia in the upper eye of young
S. corruptee (Fig. 7, A, bm and k, and Fig. 6). The upper
membrane is found throughout the further development of the
eye and corresponds to the basement membrane of the adult.
The lower membrane, k, seems to be identical with the limiting
membrane, l\ of the lower pigment cells in the adult eye (Fig.
16, A). This second layer of cells (Fig. 21, A, 2/in), then, ap-
pears to be that from which developed the lower pigment cells
of the adult eye. If that is true, it is clear how it is possible
for those pigment cells to migrate up and down through the
basement membrane in the adult eye since that membrane is
formed, in the beginning, at the inner ends of the outer hypo-
dermal layer of cells (Fig. 21, A, ihn), around these developing
pigment cells A, zhn, not as an entire or closed membrane above
them.
In cross-sections of the head made at a little later stage of de-
velopment, cells of this upper modified hypodermal layer just de-
scribed are found to be differentiating into an outer and an inner
layer so that 2 rows of nuclei may be seen above those which lie
along the basement membrane (Fig. 21, B, if a). Long undi-
vided hypodermal cells may still be seen, however, at the edges
of this developing turban eye, Fig. 21, B, x, next to the normal
hypodermis, and at y, next to the dorsal edge of the lateral pig-
mented eye. In a still later stage of development (Fig. 22) the
cone cells and the secondary iris pigment cells are found occu-
pying the position of the outer row of nucleated cells described
in Fig. 21, B, opposite x. The retinulae, each already definitely
formed of its 7 cells occupies the position of the second row of
nucleated cells in Fig. 21, B, opposite o. Here again the ele-
ments in the middle of the developing eye (Fig. 22, ifa) are
easily recognized as the older elements. Younger elements at
the edges, x andjy, are seen much below the cornea. At each
molt of the growing nymph these newer elements at the margin
of the eye rise to their normal position under the cornea and
thus increase the size of the eye. Fig. 22 represents the stage
of development of the turban eye when the nymph is 8 to 9 mm.
long. The pigmented eye has practically the same size as that
in the 5 mm. nymph.
474 SHAFER
None of the sections offers definite proof as to how the group
of 7 retinular cells or, of the 4 cone cells, in a single element
arise — whether by multiplication of a single mother cell to form
each retinula for example, or by association of the original
mother cells into groups of cells. The secondary pigment cells
however, seem to be homologous or identical with some of the
original long hypodermal cells of the first upper hypodermal
layer (Fig. 21, A, ihn). The evidence for this is very strong
at least, in the young nymph eye of S. corrupta. Fig. 7, A,
shows a single developing ommatidia from the unpigmented
area of the eye of a young nymph. In this eye, some of the
cells of the first hypodermal layer separate into upper and lower
parts, the latter giving rise to the retinular layer as in C. hageni.
The upper part then becomes two-layered again and cells of the
lower of these layers (Fig. 7, A, nfic) become chief pigment cells ;
the upper, gives rise to the cone cell layer A, en. Other cells
of the first hypodermal layer appear simply to elongate. They
grow very little and are seen surrounding the cone, chief pigment
cells and retinular elements at A, nsfl. These elongated dor-
mant cells lie in the position of the secondary pigment cells in
the adult eye. Fig. 7, B, shows 2 elongated hypodermal cells
from the developing margin of the eye (Fig. 6, x). They are
almost identical in size and shape with what are evidently sec-
ondary pigment cells in Fig. 7, A, nsj>. As development goes
on, the young short retinulas lengthen rapidly.
In the 9 mm. stage of development of the Callibaztis nymph,
the rhabdomes are found as round rod-like bodies in all the
older middle retinulas. By the time the sub-imago is ready to
issue, the cones have all practically finished development. A
few very small undeveloped cones are found around the outer
margin, but most of these remain still undeveloped in the adult.
Photographs 23 and 25 are made from cross-sections of the
heads of sub-imagoes. The turban and lateral eyes are so
definitely formed here that one might suppose development
complete. Fig. 18, A, shows the structure of 2 ommatidia in a
turban eye of a sub-imago of C. hageni. The corneal lens is
definite but thin. The retinulas are slightly constricted just
beneath the tips of the cones. In the cross-section (Fig. 18, B)
DIVIDED EYES OF CERTAIN INSECTS 475
the rhabdome is seen to be star-shaped with the " secondary
rods " beginning to develop between the boundaries of the
retinular cells. Fig. 19 shows the structure of the turban eye
elements of an old sub-imago of C. caltfornica — i. e.y just
before time for the adult to issue. The cornea is still thin, but
the secondary pigment cells have pushed it up a little and the
distal ends of these cells may be seen overlapping the bases of
the cones between c and en (Fig. 19). The retinula is now more
nearly pinched into two. I was unable however, to demonstrate
the presence of any nuclei in this retinula of the sub-imago
below the constriction (d, Fig. 19) as might perhaps be expected.
Otherwise the preparation for the separation of the distal and
proximal retinulas and for the formation of the hypodermal
space seems complete in this stage of the development.
It is wonderful to see the rapid enlargement of the turban
eyes as the adult issues from its sub-imago stage. Sub-imagoes
issue from the nymphs in less than 3 seconds. The process for
the adults is longer — 40 to 60 seconds — but the head enlarges
immediately upon breaking through the chitin, and the turban
eyes expand almost to bursting with a liquid. When photo-
graphs 24 and 26 of the adult eye are compared with 23 and 25
of the sub-imago or drawing 16, A, with drawing 19, it is clear
what happened to permit the enlargement. The secondary
pigment cells which overlapped the bases of the cones have
straightened up. The cornea has been lifted to permit this and
thus the hypodermal space is formed — being bounded by the
cornea, the cone and the surrounding secondary pigment cells.
The liquid contents of this space and the secondary pigment
cells together, undoubtedly secrete the thicker corneal lens of
the adult eye. That is to say, the hypodermal space is anal-
ogous to a cell in this eye, but it is in no sense homologous to
a cell as is shown by its origin. Furthermore, the space between
the distal and proximal retinulae is to be directly associated with
the rapid expansion of the eye of the issuing adult. The narrow
connecting portion of the retinula of the old sub-imago (Fig. 19)
has been stretched to form the connecting strands of the adult.
It must be observed here also that the proximal retinulse out-
number the distal in the old sub-imago and in the adult. The
476
SHAFER
extra retinulae are found in a ring around the outer margin of
the eye. This has been noted by Pictet, and figured by
Zimmer, 1897, and named by them the " abkonical ring" in
the adult eye.
Fig. 20 shows the structure of 2 ommatidia from the turban
eye of an unidentified mayfly. It has primary pigment cells.
No adults of this species were reared, but the development of
the eye up to the sub-imago stage is, in general, identical with
the development of the eyes just described.
TABLE OF MEASUREMENTS OF DIVIDED-EYE ELEMENTS.
Small pigmented
Ommatidia.
Length.
Greatest
Diameter.
Greatest
Thick-
ness.
Large Ommatidia.
Length.
_ , ! Greatest
Greatest Thick.
Diameter.
Corneal lens
Hypodermal space.
Cone
Entire retinula
Proximal retinula.
0.348
1.268
I 0.07 I
measured along the cone axis.
0.095
0.44
.07
2-73
1. 18
0.125
ness.
mm.
1. Symfetrum corrupta Hagen.
0.728
4
0.546
0-273 1
o-395 1
0.728
1.82 I 0.546
4 -5
2. Anax Junius Drury.
Pseudocone
0.32
1.09 0.205
4-5
0.36
i-5 0.45
6
3. Bibio hirtus Goef.
Retinula
0.348
0.65
0.19
.18
0.507
i-54
0.327
o-3
4. Blefharocera capitata Loew.
Lens and pseudocones —
Retinula
0.3
•507
0.2
,18
0.7
i-33
0.42
•39
5. CallibcBtis /lagetn' E,tn.
0.158
0.19
6. Callibcetis calif or?iica Banks.
Cornea
Hypodermal space.
Cone
Entire retinula
Proximal retinula..
measured <
0.07
ilong the
cone axis.
°-35
0.9
0.-568
0.124
1.23
•05
3-8
1.26
.11
0.09
.126
DIVIDED EYES OF CERTAIN INSECTS 477
In an eye like that of Anax where the large elements in one
part of the eye pass gradually over into smaller elements in
another part of the eye, both kinds of elements seem to develop
from the same center — the smaller elements being the last
formed.
As has been shown in the 2 divided eyes studied {Callibcetts
and Synvpetrum) the large ommatidial elements begin develop-
ment after the pigmented lateral eye is complete. In this case
the optic ganglion which has already been formed for the pig-
mented eye appears to bud or enlarge to receive the nerve fibers
of the new eye elements. To support statements already made
and for further reference the accompanying table of measure-
ments of the eye elements of the different eyes studied is given.
SIGNIFICANCE OF THE DIVIDED EYE CONDITION.
Exner, 1891, has shown that an eye with a structure like that
of the turban eye of Callibcetis (adult) is capable of forming an
image of superposition upon the proximal retinulas as well as
an image of apposition upon the distal retinulae. By means of
this repeated formation of images upon the retina, the eye with
the superposition image is enabled to see, even if somewhat
indistinctly, in dim light where the small facetted deeply pig-
mented eye could not see at all. Zimmer has shown that this
is of advantage to the mayflies in mating, since the males seek
the females on the wing in the twilight.
In the case of all the other large facetted eyes discussed in
this paper, an image of superposition would be impossible, since
the retinulae in every case lie rather close together and are not
divided into proximal and distal parts. In everv eye however,
the increase in the size of the dioptric apparatus accompanies
the decrease in pigmentation. Both of these conditions favor
the admission of more light. This would admit of a better appo-
sition image being formed in dim light. The small dioptric ap-
paratus and dense pigmentation accompany each other and both
favor the formation of a distinct apposition image in extremely
bright light. Whatever the special adaptation then, the divided
condition of the eyes may be regarded as an adaptation of dif-
ferent parts of the eye to suit different intensities of light.
478 SHAFER
Moreover, it would be of as much advantage to increase the
sensitive receiving surface (rhabdome surface) in the eye used
in dim light as to increase the dioptric or light gathering sur-
face. The complicated rhabdome surface of the turban eye of
Callibcetts shows this increased sensitive surface and further-
more, the retinulae of the " abkonical ring " each have well de-
veloped rhabdomes. The rhabdomes of the larger ommatidia of
all the divided eyes are larger than those of the small ommatidia.
Stanford University,
April 28, 1906.
LITERATURE CITED.
Exner, S.
1891 Die Physiologie der Facettirten Augen von Krebsen und Insecten.
Leipzig u. Weine
Grenadier
1879 Untersuchungen iiber das Sehorgan der Arthropoden, Insbesondere der
Spinnen, Insecten und Crustacean. Gottingen.
Zimmer, C.
1897 Die Facetten Augen der Ephemeriden Zeit. f. Wiss. Zool.. Bd. LXIII,
pp. 236-262.
Kellogg, V. L.
1898 The Divided Eyes of Arthropods. Zoolog. Anzeig., Vol. 21, pp. 280-
281.
1900 Notes on the Structure and Life-history of Blepharocera capitata Loew.
Ent. News, Vol. II, pp. 305-318.
1903 Net Winged Midges of North America (Blepharoceridse). Proceedings
Cal. Association of Science, 3 series, Zool., Vol. Ill, No. 6.
Pictet
1843 Histoire naturelle des Insects NeVropteres. Famille des Ephemerines.
Geneve, 1845.
Eaton
1888 Monograph of recent Ephemeridae or Mayflies. Trans. Linn. Soc.
London, 2 series, Vol. Ill, Zool.
Carriere, J.
1893 Kurze Mittheilungen aus Fortgesetzten Untersuchungen liber die Se-
horgen. Zool,, Anz. IX.
Ciaccio, G. V.
1880 Sopra la Notomia Minuta Degli Occhi Delia Cloe diptera. Reviewed in
Journal of the Royal Mic. Soc, 1882, II, p. 609.
EXPLANATION OF FIGURES.
The sections from which the following drawings and microphotographs
were made were cut 3 to 6 microns in thickness. They were stained either
with Haedenheim's iron hematoxylin or by a modified Weigert's hematoxylin
method. Some sections were cross-stained with good results by safranin in
DIVIDED BYES OF CERTAIN INSECTS 479
analin. Depigmentation was done with absolute alcohol and C. P. nitric acid,
equal parts, mixed. Killing of live material was done with best results in hot
Gilson's fluid. The drawings were outlined with a camera lucida.
Abbreviations not found in the following list are explained in the text itself.
c. Corneal lens (cornea).
en. Cone-cell nucleus.
tr. Trachea.
Bm. Basement membrane.
rn. Retinular nucleus.
nsp. Nuclei of secondary iris pigment cells.
sip. Secondary iris pigment cell.
Ifa. Large facetted area (dorsal eye).
sfa. Small facetted area.
tp. Tapetum.
opg. Optic ganglion.
cip. Chief iris pigment cell.
up. Dorsal part of the head.
rb. Rhabdome (rhabdomere).
sn. Semper's nuclei in hypodermis.
co. Cone or pseudocode.
nf. Nerve fibers leading from retinula.
Its. 1 lypodermal space.
dm. Distal retinula nuclei.
prn. Proximal retinula nuclei.
rs. Connecting retinular strand.
h. Tactile hair.
ce. (Esophagus.
tb. Turban or dorsal large facetted eye.
la. Lateral pigmented eye.
/Is. Transparent liquid space around the connecting strands.
drb. Rhabdome of the distal retinula.
PLATE XXIV.
Figs, i to 7. Male of Sympetrum corruption Hagen.
Fig. 1. Head of adult showing relative size and shape of the large and small
facetted areas, X 8.
Fig. 2. Cross-section of the right eye of adult, X 34-
Fig. 3. A. A few elements from the small facetted deeply pigmented part of
the eye (adult), X I4I-
B. Cross-section of a cone and its surrounding secondary pigment
cells from A, X 500.
Fig. 4. A. Ommatidia from the large facetted part of the eye of 6". corrupta,
XHi-
B. Cross-section of three of the rhabdome-like bodies, rb of 4, A,
X 5°°-
C. Cross-section of the retinula in the region of the nuclei from Fig.
4, -4, X 385-
Fig. 5. Head of a male nymph 51. corrupta, showing the triangular large
facetted area forming.
Fig. 6. Cross-section of one eye of Fig. 5.
Fig. 7. A. A single ommatidial element from the developing large facetted
area of a nymph of S. corrupta, X 3^5-
B. Two of the upper modified hypodermal cells from the margin x
of Fig. 6, X 3S5-
Figs. 8 to 11. Eye of male Bibio hirtus Goef.
Fig. 8. Longitudinal sagittal section of right eye, X4i«
Fig. 9. A. Three ommatidia from the large facetted area, X 2°5-
B. Cross-section of cone tip through cone nuclei and surrounding
secondary pigment cells.
C. Cross-section of three retinulae near their distal ends.
E. Cross-section of a retinula near its middle.
D. Cross-section of three retinula; in region of retinular nuclei.
4S0
Proc. Wash. Acad. Sci., Vol. VIII.
Plate XXIV.
PLATE XXV.
Fig. io. Ommatidia from the small facetted pigmented area of male Bibio
eye, X 9°o-
Fig. ii. Head of male Bibio hirtus.
Figs. 12 to 14. Eye of Anax Junius, Drury.
Fig. 12. Cross section of a single eye of adult, X 4T-
Fig. 13. A. Two ommatidia from the upper largest facetted part of the eye,
X102.
B. Cross-section of the retinula through the nuclei.
C. Cross-section of cone and surrounding secondary pigment cells
and lumina.
D. Cross-section of cone tip showing surrounding primary or chief
pigment cells and secondary pigment cells.
E. Cross-section of three retinula? and enclosed lumina.
Fig. 14. Two ommatidia from the smallest facetted part of the eye, X I02-
Fig. 15. Eye of Blepharocera capitata Loew.
A. Two ommatidia from the large facetted division of the eye (dor-
sal), X 205.
B. Cross-section through tip of cone showing four cone cells with
their nuclei and the surrounding secondary pigment cells.
C. Cross-section of a retinula showing the rhabdomeres.
Fig. 16. Adult eye of a male Callibcetis hageni Etn.
A. Two entire ommatidial elements from the turban or dorsal eye
and parts of two proximal retinulse whose corresponding cone
elements are not shown, X 385-
B, C, D, and E. Cross-sections of corresponding parts of Fig. A as
indicated by the lines.
48 2
Proc. Wash. Acad. Sci., Vol. VIII.
Plate XXV.
yl it'"''
i f
s
14
-Mf-
■ :■■■
r
.
PLATE XXVI.
Fig. 17. A. Two ommatidia from the lateral pigmented eye of adult male C.
hageni Etn. One element is represented as depigmented, X
385.
B. Cross-section of retinula of A.
Fig. 18. A. Two ommatidia of a turban eye of a male subimago of C. hageni
Etn.
B. Cross-section of retinula of A.
Fig. 19. Two ommatidia from the turban eye of a male subimago of C. cali-
fornica Banks. An old subimago just before adult was ready to
issue, X38.S-
Fig. 20. Two ommatidia from the turban eye of male subimago of a mayfly
of unknown species showing chief pigment cells. Adult of this
species was not reared.
Figs. 21 to 22. Eye of nymph of C. hageni Etn.
Fig. 21. A. A small part of the earliest developmental stage of the turban
eye of C. hageni observed.
B. Entire eye of a young male nymph at a little later stage of develop-
ment than A, i. e., nymph 5 mm. long, X 120.
Fig. 22. Entire eye (turban and lateral) of a male C. hageni nymph S to 9
mm. long, X I2°-
4S4
Proc. Wash. Acad. Sci., Vol. VIII.
Plate XXVI.
18
■
V
wm *
17
y k
■ -
' -
i -
PLATE XXVII. MlCROPHOTOGRAPHS.
Fig. 23. Cross-section of head of subimago of male C. hageni.
Fig. 24. Cross-section of a head of adult male C. hageni.
Fig. 25. Cross-section of head of subimago of male C. calif ornica.
Fig. 26. Cross-section of male adult of C. califomica.
Fig. 27. Cross-section of part of large turban eye of an adult male C. hageni,
showing the connecting strands between the proximal and distal
retinula;.
Fig. 28. Microphotograph of cross-section of head of an old nymph of .S.
corrupta, the adult of which was about to issue. The section
passes through the edge, only, of the pigmented part of the eye
which in its largest part was about equal to the upper large facetted
area as is shown by the size of the optic ganglion.
Fig. 29. A few ommatidia from the dorsal eye of a female B. capitata.
Fig. 30. Left dorsal and lateral eyes of a female B. capitata showing optic
ganglion also. Most of the cornea of the dorsal eye is torn away.
See Fig. 29.
486
Proc. Wash. Acad. Set., Vol. VIII
Plate XXVII.
QD.8.
INDEX.
Note. — New names in black-face type, synonyms in Italics.
For index to paper on "Aspects of Kinetic Evolution " by O. F. Cook, see pp.
400-403.
Acestorliampbus brachycephalus 454
ferox 454
hepsetus 454
Achirus lineatus 458
Acipenser 48
Acrostichum yoshinagai 146
Aerial Locomotion 407
Age of the Pre-volcanic Auriferous Grav-
els in California 405
albicans. Pimelodus 452
albida, Rhus 194
Allen, Wm. F. 41
alleni, Cambarus 18
alternatus, Crossaster 131
Ami a 42
Amiatus 42
Amphilestes 98
Anasterias 136
Anaxjunius, compound eye of 463
angustiloba, Aralia 406
anomalus, Leptychaster 115
anus, Loricaria 453
Aplodinotus grunniens 52
pppendiculata, Frullania 159
aprica, Rhus 193
Aralia angustiloba 406
whitneyi 405
arbuscula, Rhus 184
arcticus, Leptychaster 112
areolatus, Cambarus (Cambarellus) mon-
tezumae 23
argentinensis, Atherinichthys 455
arguta, Rhus 192
ashei, Rhus 179
aspera, Henricia 127
asplenifolia, Rhus 196
Asterias sanguinolenta 127
asthenosoma, Luidia 124
Astropecten 118
Astropecten californicus 118
erinaceus 118
fragilis 120
ornatissimus 119
regalis 121
rubidus 121
verrilli 121
Astropectinidce 112
Astyanax rutilus 454
Atherinichthys argentinensis 455
bonariensis 455
Atherinidse 455
atrovirens, Rhus 182
auriculata, Rhus 17S
Auriferous Gravels in California, Age of
the Pre-volcanic 405
australe, Geophagus 456
autochthon, Heros 456
Ba;tis cerea 469
balzanii Geophagus 456
Barb 68
barbatus, Cambarus 18
Bathybiaster 114
Batrachops scottii 457
semifaseiatus 457
Bell, Alexander Graham 407
bellona?, Ludwigia 114
Bematiscus 93
Bibio hirtus, compound eye of, 464
Bibiocephalus elegantulus 461
Bilobed hypsodont stage of molars 99
bisseti, Ptilidium 141
blandingi, Cambarus 18
Blepharocera capitata, compound eye of,
467
tenuipes, compound eye of, 467
bonariensis, Atherinichthys 455
borealis, Crossaster 134
borealis, Rhus 188
Brachiolejeunea gottschei 157
sandvicensis 157
brachycephalus, Acestorhampus 454
Brachyodont tricodont stage of molars 99
brevis, Scapania 160
brevispiua, Luidia 121
Buenos Aires, On a Collection of Fishes
from, 451
californica, Calliba?tes 471
Laurus 405
Luidia 121
Juglans 406
Magnolia 405
Ulmus 406
californicus, Astropecten 118
californicus, Rathbunaster 137
californicus, Sabalites 405
Callibaetes californica 471
hageni 468
Cambarellus 19
Cambari, Mexican, Central American
and Cuban 1
Cambarus alleni 18
barbatus 18
blandingi 18
clarki 24
4S7
488
INDEX
Cambarus clypeatus 18
consobrinus 12
evermanni 18
hinei 18
montezumae 2
shufeldti 24
tridens 19
williamsoni 10
(Cambarellus) chapalanus 22
montezumae 19
areolatus 23
dugesi 20
occidentalis 20
tridens 20
(Cambarus) wiegmanni 20
(Paracambarus) paradoxus 3
(Procambarus) cubensis 11
digueti 21
mexicanus 11
pilosimanus 6
capitata, Blepharoeera, compound eye of
467
caroliniana, Rhus 181
Carp 69
Cavicularia 141
cavifolia, Lejeunea 148
Centetes 93
cerea, Baetus 469
chapalanus, Cambarus (Cambarellus) 22
Characidae 453
Cheilolejeunea 149
intertexta 149
Chirotonetes ignotus 469
Chloe fuscata 469
chrysitis, Tinea 48
Chrysochloris 93
Cichlidae 456
cismontana, Rhus 189
clarki, Cambarus 24
Clupea 454
Clupeidae 454
clypeatus, Cambarus 18
Cod 68
Cololejeunea floccosa 146
goebeli 146
venusta 146
commersoni, Plecostomus 452
compacta, Eulejeunea 148
complex molars, Phyletic history of 99
tritubercular type of 99
triconodont type of 99
conjugata, Metzgeria 143
consanguinea, Metzgeria 143
consobrinus, Cambarus 12
corrupta, Sympetrum, compound eye of
459. 472
coruscans, Pseudoplatystoma 451
Cottus 69
gobio 48
Crenicichla semifasciala 457
Cretica, Pteris 151
Cribrella 127
Crossaster 130
alternatus 131
borealis 134
papposus 132
cubensis, Cambarus (Procambarus) 11
Curi matus gilberti 453
platanus 453
Cyprinus, 42
densiloba, Frullania 157
denudatum, Odontoschisma 155
Dicrocynodon 100
digueti, Cambarus (Procambarus) 21
Diller, J. S. 405
Divided Eyes of Certain Insects, Histol-
ogy and Development of 459
Doris granulosus 452
Drepanolejeunea 151
setispina 157
tenuis 152
Dromotherium 98
Dryolestes 96
dugesi, Cambarus (Cambarellus)
montezumae 20
duodecimspinosum, Geophagus 456
Dutton, Maj. Clarence E. 39
Echinaster 127
Echinasteridae 127
Eel 61
Eigenmann, Carl H. 451
elegantula, Rhus 195
elegantulus, Bibiocephalus, compound
eye of 467
elliptica, Gymnogramme 151
Eocene Flora of Southwest Oregon 405
Ericulus 93
erinaceus, Astropecten 118
Esox 42
Eulejeunea compacta 148
euphlebia, Plagiogyria 146
Evans, Alexander W. 141
evermanni, Cambarus 18
exocellata, L,eptojeunea 151
Faxonius 24
ferox, Acestorhamphus 454
Ficus tiliaefolia 406
Fisher, Walter K. in
Fishes from Buenos Aires, On a Collec-
tion of 451
fiava, Lejeunea 148
flavipinnis Ilisha 455
floccosa, Cololejeunea 146
foliicola, Leptolejeunea 151
foliolata Luidia 121
fragilis, Astropecten, 120
Freyella 138
Frullania appendiculata 159
densiloba 157
makinoana 159
moniliata 159
furcata, Metzgeria 143
fuscata, Chloe 469
Fusion theory of tooth cusp development
94
Gadus 55
Geodetic Evidence of Isostasy 25
Geophagus australe 456
balzanii 456
duodecimspinosum 456
gymdogenys 456
Gidley, James Williams 91
gilberti, Curimatus 453
glabra, Rhus 175
Gobio 48
gobio, Cottus 48
goebelii, Cololejeunea 146
INDEX
489
gottschei, Braehiolejeunea 157
granulosus, Doris 452
Greene, Edward L. 167
grunniens, Aplodinotus 52
Gudgeon 68
gymdogenys, Geophagus 456
Gymnogramnie elliptica 151
hageni, Callibaetis, compound eye of 468
hamata, Metzgeria 143
Harpalejeunea 156
Harpalejeunea intermedia 154
ovata 157
pseudoneura 156
Harpioeephalus 94
Hay ford, John F. 27
helianthoides, Pycnopodia 138
Hemieentetes 93
Henri cia 127
Henricia aspera 127
polyacantha 129
Hepatica?, Notes on Japanese 141
hepsetus, Acestorhauiphus 454
Heros autochthon 456
hinei, Cambarus 18
hirtus, Bibio, Compound eye of 464
Histology and development of Divided
eyes in Certain Insects 454
Hoplias malabaricus 454
hypocone 103
ignotus, Chironectes 469
Iheringichthys labrosus 452
Ilisha flavipinnis 455
inermis, Parastropecten 115
intermedia, Harpalejeunea 154
intertexta, Cheilolejeunea 149
Isostasy, Geodetic Evidence of 25
ithacensis, Rhus 178
Japanese Hepaticse, Notes on 141
japonica, Scapania 160
japonicum, Trichomanes 146
Juglans californica 406
Junius, Anax, compound eye of 463
kerguelensis, Leptyehaster 118
labrosus, Iheringichthys 452
loevis, Rhombus 59
lanceolata, Magnolia 405
laplatse, Plecostomus 452
Laurus californica 405
Leioscyphus verrucosus 144
Lejeunea cavifolia 148
flava 148
planiloba 147
Leptojeunea exocellata 151
foliicola 151
Leptolejeunea subacuta 149
Leptopty chaster 112
Leptychaster 112
Leptychaster anomalus 115
arcticus 112
kerguelensis 118
pacificus ii2
Leuciscus 42
Linckia 127
lindbergii, Metzgeria 143
Radula 145
lineatus, Archirus 458
Prochilodus 453
Lobadium 167
longula, Rhus 186
Lophius 42
I,ophius piscatorius 49
Loricaria anus 453
vi' tul a 453
Loricariida;4£2
lorioli, Ludwigia 124
Luciopimelodus pati 451
lucioperca, Perca 48
Lucius 42
ludoviciana, Rhus 183
Ludwigia bellonce 124
lorioli 124
quinaria 124
ludwigi, Luidia 122
Luidia 121
asthenosoma 124
brevispina 121
californica 121
foliolata 121
ludwigi 122
sarsi 124
Lymphatics of Scorpcrnichlhys viarmo-
ratus 41
macrospila, Pimelodus clarus 452
macrothyrsa, Rhus 191
Magnolia californica 405
lanceolata 405
Makinoa 141
makinoana, Frullania 159
malabaricus, Hoplias 454
Manly, Charles M. 428
marginatus, Serrasalmo 454
maxillosus, Salminus 454
maximus, Rhombus 59
media, Rhus 188
melanostomus, Pomolobus 454
metacone 102
Metopium 167
Metzgeria conjugata 143
consanguinea 143
furcata 143
hamata 143
lindbergii 143
pubescens 143
quadriseriata 142
Mexican, Central American and Cuban
Cambari 1
mexicanus, Cambarus (Procambarus) 11
moniliata, Frullania 159
montezutnoe, Cambarus 2
Cambarus (Cambarellus) 19
Mugil platanus 455
Mugilidae455
Mylia verrucosa 144
nitens, Rhus 190
Notes on Japanese Hepaticse 141
obtusidens, Leporinus 454
occidentalis, Cambarus (Cambarellus)
montezumae 20
Rhus 193
Odontoschisma denudatum 155
olidus, Stolephorus 455
49°
INDEX
On a Collection of Fishes from Buenos
Aires 451
Ophiodon 41
Orbitolites 406
oreophila, Rhus 177
ornatissimus, Astropecten 119
Ortmann, A. E. 1
ova, Harpalejeunea 157
oyamensis, Radula 144
paciricus, Leptychaster 112
Paleolagus 99
papposus, Crossaster 132
Paracambarus 1
paracone 102, 105
paradoxus, Cambarus (Paracambarus) 3
Parastropecten inermis 115
parastyle 102
pati, Luciopimelodus 451
Paurodon 101
Pediomys 99
Perca 42
lucioperca 48
petiolata, Rhus 185
Phragmicoma sandvicensis 157
Phyletic History of Complex Molars 99
Ungulate Molars 98
phyllobola, Rectolejeunea 149
Pike 61
pilosimanus Cambarus (Procambarus) 6
Pimelodus albicans 452
clarias macrospila 452
valenciennis 452
piscatorius, Lophius 49
Plagiogyria euphlebia 146
planicosta, Venericarda 406
planiloba, L,ejeunea 147
platanus, Curimatus 453
Mugil 455
Plecostomus carinatus vallanti 453
commersoni 452
laplatse 452
tietensis 453
Pleuronectes 42
Pleuronectidae 56
polyacantha, Henriciai29
Pomolobus melanostomus 454
Populus zaddachi 406
Potamogale 93
Pre-volcanic Auriferous Gravels in Cali-
fornia, Age of, 405
Procambarus 2
Prochilodus lineatus 453
protocone 92, 102
protoconule 102
Protodont stage of ungulate molars 98
Protolambda 99
pseudoneura, Harpalejeunea 156
Pseudoplatystoma coruscans 451
Psilaster 114
Pteris cretica 151
Ptilidium bisseti 141
pubescens, Metzgeria 143
pulchella, Rhus 182
Pycnolejeunea tosana 153
Pycnopodia 136
helianthoides 138
Pycnopodiidae 136
pyramidata, Rhus 180
quadriseriata, Metzgeria 142
quelen, Rhamdia 452
quinaria, Ludwigia 124
Radula lindbergii 145
oyamensis 144
Raja 42
Rathbunaster 136
californicus 137
Rays 68
Rectolejeunea 149
Rectolejeunea phyllobola 149
regalis, Astropecten 121
Reptilian stage of ungulate molars 98
Rhamdia quelen 452
Rhceidium 167
Rhombus laevis 59
maximus 59
Rhus 167
Rhus, albida 194
aprica 193
arbuscula 184
arguta 192
ashei 179
asplenifolia 196
atrovirens 182
auriculata 178
borealis 188
caroliniana 181
cismontana 189
elegantula 195
glabra, a study of 167
glabra 175
ithacensis 178
longula 186
ludovicianus 183
macrothrysa 191
media 188
nitens 190
occidentalis 193
oreophila 177
petiolata 185
pulchella 182
pyramidata 180
sambucina 190
sandbergii 187
sorbifolia 195
tessellata 191
valida 185
rubidus, Astropecten 121
rutilus, Astyanax 454
Sabalites californicus 406
Salminus maxillosus 454
Salmo42
Salmon 59
sambucina, Rhus 190
sarsi, Luidia 124
sandbergii, Rhus 187
sandvicensis Phragmicoma 157
Brachiolejeunea 157
sanguinolenta, Asterias 127
scaber, Uranoscopus 49
Sciaenidae 456
Scapania 145
brevis 160
japonica 160
stephanii 160
Seorpaenichthys marmoratus, Lymphatics
of 41
INDEX
49]
Scotophilia 94
Scott, Prof. W. B. 451
scottii, Batrachops 457
sculpta, Sicyona 463
setispina, Drepanolejeunea 157
se»u'fasciatus, Crenicichla 457
semifasciatus, Batrachops 457
Serrasalmo marginatus 454
sexitubercular-quadritubercular stage of
teeth 98
Sharks 68
shufeldti, Carabarus 24
Sicyona sculpta 463
Silurus 49
Sol aster idee 130
Solenodon 93
sorbifolia, Rhus 195
South-west Oregon, Eocene Flora of 405
Spalacotherium 98
Squalus 42
stephanii, Scapania 160
Stolephorus olidus 455
Study of Rhus glabra, A 167
Styphonia 146
Sturgeon 68
subacuta, Leptolejeunea 149
Sympetrum corrupta, compound eye of
459. 472
Talpa 93
Telacadon 103
tenuipes Blepharocera 467
tenuis, Drepanolejeunea 152
tessellata, Rhus 191
Thyopsiella 159
tietensis, Plecostomus 453
tiliaefolia, Ficus 406
Tinea 69
chrysitis 48
Tinodon 101
Tittmann, O. H. 25
Tooth-cusp Development 91
Torpedo 42
tosana, Pycnolejeunea 153
Trichomanes japonicum 146
Toxicodendron 167
tridens, Cymbarus montezumae 20
tridens, Cambarus 19
Triconodon 92
Triconodont stage of ungulate molars 98
of complex molars 99
Turritella uvasana 406
trigon 92
trigonid 92
trigonodont tooth 102
tritubercular-tuberculo sectorial 98
Tritubercular stage of ungulate molars
98
of complex molars 99
Trout 69
Tumidse 145
Ulmus californica 49
Ungulate molars, Phyletic History of, 98
Protodont stage of, 98
Reptilian stage of, 98
Triconodont stage of, 98
Tritubercular stage of, 98
Uranoscopus 49
scaber 49
uvasana, Turritella 406
valenciennis, Pimelodus 452
valida, Rhus 185
vallanti, Plecostomus carinatus 453
Venericardia planicosta 406
venusta, Cololejeunea 146
verrilli, Astropecten 121
verrucosa, Mylia 144
verrucosus, Leioscyphus 144
Vespertilio 94
vetula, Loricaria 453
whitneyi, Aralia 405
wiegmanni, Cambarus 15
cambarus (Cambarus) 15
williamsoni, Cambarus 10
yoshinagai, Acrostichum 146
zaddachi, Populus 406
Zahm, Prof. A. F. 436
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